3.06.2 Post Construction Stormwater BMP Standards and Specifications

Transcript

1 3.06.2 Post Construction Stormwater BMP Standards and Specifications March 2013

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3 3.06.2 Post Construction Stormwater BMP Standards and Specifications Specifications: Infiltration 3.06.2.1 Bioretention 3.06.2.2 Permeable Pavement Systems 3.06.2.3 3.06.2.4 Vegetated Roofs 3.06.2.5 Rainwater Harvesting 3.06.2.6 Restoration Practices 3.06.2.7 Rooftop Disconnection 3.06.2.8 Vegetated Channel s 3.06.2.9 Sheet Flow to Filter Strip or Open Space 3.06.2.10 Detention Practices 3.06.2.11 Stormwater Filtering Systems 3.06.2.12 Constructed Wetlands 3.06.2.13 Wet Ponds 3.06.2.14 Soil Amendments 3.06.2.15 Proprietary Practices 3.06.2.16 Source Controls Appendices: 3.06.2. A -1 Soil Investigation Procedures 3.06.2. A -2 Landscaping Guidelines 3.06.2. A -3 Compost Material Properties 3.06.2. A-4 Stormwater Hotspots Guidelines 3.06.2. A -5 Design of Stormwater Conveyance Systems -6 Design of Flow Control Structures 3.06.2. A 1 3.06.2- 03/2013

4 Infiltration BMP Standards and Specifications 1.0 Storm water Infiltration Practices that capture and Definition: temporarily store the design storm volume before allowing it to infiltrate into the soil over a two day period. Design variants include: 1- A Trench Infiltration  Infiltration  1- B Basin Infiltration practices use temporary surface or underground storage to allow incoming stormwater runoff to exfiltrate into underlying soils. Runoff first passes through multiple pretreatment mechanisms to trap sediment and organic matter before it reaches the practice. As the stormwater penetrates the underlying soil, chemical and physical adsorption processes remove pollutants. measured Infiltration practices are suitable for use in residential and other urban areas where soil nch per hour. To prevent possible groundwater contamination, infiltration permeability rates exceed 1 i care shall be taken to should not be utilized at sites designated as stormwater hotspots. Extraordinary rmance bonds, post -term infiltration rates are achieved through the use of perfo assure that long -term maintenance. construction inspection and long 03/2013 1 3.06.2. 1 -

5 BMP Standards and Specifications Infiltration Infiltration Stormwater Credit Calculations 1.1 receive 100% retention Infiltration practices volume credit (R ) for the volume stored and v ( Table 1.1 ) additional pollutant removal credit is awarded. by the practice infiltrated . No Table 1.1 Infiltration Performance Credits Runoff Reduction Retention Allowance 100% RPv 100% of Retention Storage of Retention Storage Cv 10 0% Fv 100% of Retentions Storage Pollutant Reduction 100% TN Re duction of Load Reduction of Load Reduction TP Reduction 100% 100% of Load Reduction TSS Reduction Section The practice must be sized using the guidance detailed in Design Criteria Infiltration 1.5. 03/2013 2 3.06.2. 1 -

6 Infiltration BMP Standards and Specifications Figure Trench. 1.1 . Infiltration Figure 1.2. Infiltration Section with Supplemental Pipe Storage . 1 3 03/2013 - 3.06.2.

7 BMP Standards and Specifications Infiltration . 1.3 . Infiltration Basin Figure 4 3.06.2. 1 - 03/2013

8 BMP Standards and Specifications Infiltration 1.2 Infiltration Design Summary Table 1.2 summarizes design criteria for infiltration practices, and Table 1.3 summarizes the materials specifications for these practices. For more detail, consult Sections 1.3 through 1. 1.8 7. Section describes practice construction and maintenance criteria. Table 1.2 Infiltration Design Summary Basins Trenches Feasibility Minimum soil infiltration of 1”/hr • (Section 1.3) strictions for treating hotspots, high loads, or dry weather flows Re • seasonal high groundwater for infiltration without • 2 foot separation from underdrain For infiltration with underdrain, invert of underdrain must be above • season al high groundwater • Setback s from wells, buildings and utilities Conveyance • Must safely convey the Conveyance Event (Cv) (Section 1.4) Pretreatment retention volume in pretreatment, depending on soil 25% to 50% of • (Section 1.5) infiltration rate • All runoff must be treated pretreatment options may be used Several • Sizing (Maximum 1 1 ) ( × i t d i t = × d max d 2 2 d = Depth) max η r (Section 1.6) Maximum depth limits as well, based on practice size and CDA (See Table 1.4) Sizing (Surface Area) x x η SA = Sv/ (d + ½ i x t Sv ) f SA = / ( t ) d + ½ i r f (Section 1.6) - t days Variables: maximum drawn down time ( 2) = d -verified infiltration rate for the native soils (ft./day) i = field 4) = available porosity of the stone reservoir (assume 0. η r treated by the Sv = Retention volume practice d = Infiltration depth (ft.) t typically 2 hours, or = Time to fill the infiltration facility (days – f 0.083 days) Geometry • • Wider than they are deep to avoid Flat trench or basin bottom (Section 1.6) injection well status 4:1 or flatter internal side slopes • for basins ponding maximum • 2’ or lower dept h for basins Maintain vegetation in the buffers and practice drainage area to minimize Landscaping erosion and debris (Section 1.7) 5 1 3.06.2. - 03/2013

9 BMP Standards and Specifications Infiltration 1.3. Infiltration Material Specifications Table ation Specific Material Notes Topsoil and grass layer Surface Layer (optional) .5 inches and a minimum diameter of .5 0 2 Clean, aggregate with a maximum diameter of Layer Stone inches . (Delaware #3) Install one per 50 feet of length of inch Schedule 40 PVC - Install a vertical 6 , minimum 1 well per infiltration practice e, with a lockable cap and perforated pip Observation Well anchor plate practice inch rigid schedule 40 PVC pipe, with 3/8” perforations at 6 inches on - 6 inch or - 4 Use Overflow collection pipe er cent (optional ) ) II - GD Use poly propylene geotextile with a flow rate of > 110 gallons/min./sq. ft. (e.g., Filter Fabric (sides only) 1.3 Infiltration Feasibility Criteria high storage and retention ed Infiltration practices have very ies when sited and design capabilit appropriately . Designers should evaluate the range of soil properties during initial site layout and seek to configure the site to conserve and protect the soils with the greatest recharge and infiltration rates. soils shown on NRCS soil surveys should be In particular, areas of Hydrologic Soil Group A or B considered as primary locations for infiltration practices. Additional information about soil and infiltration are described in more detail later in this section. During initial design phases, designe rs should carefully identify and evaluate constraints on infiltration, as follows: EPA Requirements for Class V Injection Wells. Certain types of practices in this category may be classified as a Class V Injection Wells, which are subject to regulations under the Federal In general, if the facility allows stormwater Underground Injection Control (UIC) program. Facilities with a runoff to come in direct contact with groundwater it would meet this criterion. ndwater table would not meet the criterion. minimum 2’ vadose zone separation from the grou Designers are advised to contact the DNREC Groundwater Discharges Section for additional information regarding UIC regulations and possible permitting requirements. Contributing Drainage Area. To be most effect ive minimize the contributing drainage area (CDA). The CDA should be as close to 100% impervious as possible to minimize organic capping and maintenance concerns . The facility specific design, pretreatment and maintenance requirements will differ dependin practice. infiltration g on the size of the Infiltration shall not be located on slopes greater than nless slope Further, u 5%. Site Topography. stability calculations demonstrate otherwise, infiltration practices should be located a minimum -gradient slopes greater than 20%. The average slope of the distance of 200 feet from down horizontal contributing drainage areas should be less than 15%. 03/2013 6 3.06.2. 1 -

10 BMP Standards and Specifications Infiltration A minimum vertical distance of 2 feet must be Minimum Depth to Water Table or Bedrock. provided between the bot tom of the infiltration practice and the seasonal high water table or bedrock . The minimum vertical distance of 2 feet is relaxed for layer for systems without an underdrain invert of the underdrain systems with an underdrain; the design hat the seasonal must be set such t high groundwater does not encroach into system through the underdrain. Soils. Native soils in proposed infiltration areas must have a minimum infiltration rate of 1 inch per hour (typically Hydrologic Soil Group A and B soils meet this cr it erio n). Init ially, soil infiltration rates can be estimated from NRCS soil data, but -site designers must verify soil permeability by using the on . Soils investigation must be in the Soil Investigation Procedures soil investigation methods provided soils or geotechnical engineer. perfor med by a qualified Sites that have been previously graded or disturbed Soils/Redevelopment Sites. Use on Urban Fill retain their original soil permeability due to compaction. Therefore, such sites are do not typically oft not good candidates for infiltration practices en unless the geotechnical investigation shows that in/hr. the soil infiltration rate exceeds 1.0 -weather Infiltration practices should not be used on sites receiving regular dry Dry Weather Flows. flows fro . stormwater flows other non- , or -water m sump pumps, irrigation water, chlorinated wash Setbacks. Infiltration practices should not be hydraulically connected to structure foundations or pavement, in order to avoid harmful seepage. Setbacks to structures v ary based on the size of the : infiltration facility Table 1.4 Minimum Setbacks Minimum Setback Size of Infiltration Facility Septic Well Structure is Up -Grade Structure is Down-Grade System 100' 25' 5' 250 to 2,500 square feet 150' 50' 150' 100' 10' 2,500 to 20,000 square feet 25' 100' 100' 150' 20,000 to 100,000 square feet Proximity to Utilities. No Infiltration facility shall be built within five feet horizontally of an existing underground utility without prior authorization from the utility owner. A proposed underground utility may be built within five feet, horizontally, of an infiltration facility as long as protective measures are in place accounting for future maintenance of the underground utility and meeting the design requirements of the utility owner. Infiltration practices are not intended to treat sites with Hotspots and High Loading Situations. 03/2013 7 3.06.2. 1 -

11 BMP Standards and Specifications Infiltration high sediment or trash/debris loads, because such loads will cause the practice to clog and fail. Infiltration practices should be avoided at potential stormwater hotspots that pose a risk of operations, groundwater contamination. For a list of potential stormwater hotspot consult Appendix 4. 1.4 Infiltration Conveyance Criteria The nature of the conveyance and overflow to an infiltratio n practice depends on the scale of infiltration and whether the facility is on -line or off -line. Where possible, conventional infiltration practices should be designed offline to avoid damage from the erosive velocities of larger design If runoff i s delivered by a storm drain pipe or along the main conveyance system, the storms. -line practice. Pretreatment shall be provided for storm infiltration practice shall be designed as an off drain pipes systems discharging directly to infiltration systems. Off- lin e infiltration : Overflows can either be diverted from entering the infiltration practice or dealt overflow methods include the following: . Optional with via an overflow inlet  gn volume Utilize a low to enter -flow diversion or flow splitter at the inlet to allow only the desi opening sized for the target flow, in the facility. This may be achieved with a weir or curb combination with a bypass channel. Using a weir or curb opening helps minimize clogging and (further guidance on determining the peak flow rate will be reduces the maintenance frequency necessary in order to ensure proper design of the diversion structure). Use landscaping type inlets or standpipes with trash guards as overflow devices.  infiltration : An overflow structure should always be incorporated into on -line designs to -line On infiltration area. The following criteria apply to overflow safely convey larger storms through the structures:  An overflow mechanism such as an elevated drop inlet or overflow weir should be used to direct , stabilized water course, or storm sewer high to a non -erosive down -slope overflow channel flows system designed to convey the Conveyance Event (Cv) . 1.5 Infiltration Pretreatment Criteria long term integrity of the to protect the Every infiltration system shall have pretreatment mechanisms of the following techniques must be installed to pretreat 100% o f the inflow in infiltration rate. One every facility: Specification  Vegetated C hannel (see 8. Vegetated Channel )  Grass Filter Strip (see Specification 9. Sheet flow to Open Space ) volume ) etention  Forebay (minimum 25% of the r ) ing Systems Filter Stormwater Specification 12. (see Filter Sand  03/2013 8 3.06.2. 1 -

12 BMP Standards and Specifications Infiltration  Proprietary Practices (see Specification 15. Proprietary Practices) A minimum pretreatment volume of at least 25% of the des ign retention volume shall be provided for any infiltration facility which serves a CDA greater than 20,000 sq. ft. Exit velocities from the pretreatment shall be non- 4 fps) during the largest above typically erosive ( design storm that is connected to the facility and flow from the pretreatment chamber should be d across the width of the practice (e.g., using a level spreader). evenly distribute Design 1.6 Infiltration Criteria should be flat (i.e., 0% longitudinal and lateral Facility Slope. The bottom of an infiltration facility s) to enable even distribution and infiltration of stormwater slope , however the bottom may be stepped . internally per design specifications ver an The maximum vertical depth to which runoff may be ponded o : Infiltration Basin Geometry side is 24 inches. The basin infiltration -slopes should be no steeper than 4H:1V Surface Cover (optional) : Designers may choose to install a layer of topsoil and grass above the practice. infiltration s must consist of Stone Layer : Stone layer 2.5 clean, washed aggregate with a maximum diameter of (Delaware #3 stone) . inches and a minimum diameter of 0.5 inches Underground Storage (optional) In the underground mode, runoff is stored in the voids of the : stones, and infiltrates into the under lastic, concrete, or comparable material lying soil matrix. P structures can be used in conjunction with the stone to increase the available temporary underground storage. In some instances, a combination of filtration and infiltration cells can be install ed in the floor of a dry extended detention (ED) pond See Specification 12. Detention Practices . : to convey collected optional Overflow Collection Pipe overflow collection pipe can be installed An runoff from larger storm events to a downstream conveyan ce system. Trench Bottom: To protect the bottom of an infiltration trench from intrusion by underlying soils , a be used. by a 6 The underlying native soils should be separated from the stone layer sand layer must M C 33, 0.02- , AST to 8 inch layer of coarse sand (e.g. 0.04 inch). : a geotextile fabric with a flow rate of > 110 gal./min./sq. ft. (e.g., Delaware Use Filter Fabric II). GD- areas are shown in Recommended material specifications for infiltration Material Specifications: 03/2013 9 3.06.2. 1 -

13 BMP Standards and Specifications Infiltration Table 1.3 in Section 1.2. Sizing: Practice The proper approach for designing infiltration practices is to avoid forcing a large amount of infiltration into a small area. Therefore, individual infiltration practices that are limited in size due to soil permeability and availa ble space need not be sized to capture the entire design volume for the contributing drainage area, as long as other stormwater treatment practices are applied at the site to meet the remainder of the design storm volume . Several equations are needed to size infiltration practices. The first equations establish the maximum 1.1 trench ) or Equation depth of the infiltration practice, depending on whether it is a surface basin ( Equation ). 1.2 with an underground reservoir ( (for Infiltration Basins) n Depth Equation 1.1. Maximum Surface Basi 1 × = i d t max d 2 Equation 1.2. Maximum Underground Reservoir Depth (for Infiltration Trenches) 1 ( ) × i t d 2 = d max η r Where: d = maximum depth of the infiltration practice (feet) max i = field -verified infiltration rate for the native soils(ft./day) - 2) days = maximum drawn down time ( t d = available porosity η 4) of the stone reservoir (assume 0. r This equation makes the following design assumptions: • soil infiltration subgrade ation Rates. tested For design purposes, the field- Conservative Infiltr rate (i) is divided by 2 as a factor of safety to account for potential compaction during construction and to approximate long term infiltration rates . On -site infiltration inve stigations should always be conducted to establish the actual infiltration capacity of underlying soils, using the methods presented in the Soil Investigation Procedures . • Stone Layer Porosity. servoirs, 4 shall be used in the design of stone re A porosity value of 0. although a larger value may be used if underground retention chambers are installed within the . reservoir Rapid Drawdown. Infiltration practices should be sized so that the target runoff reduction • isance ponding conditions. volume infiltrates within 48 hours, to prevent nu (for Infiltration Basins) 1.3. Surface Basin Surface Area Equation ) x SA = Sv t / (d + ½ i f 1.4. Underground Reservoir Surface Area Equation (for Infiltration Trenches) 03/2013 10 3.06.2. 1 -

14 BMP Standards and Specifications Infiltration x x Sv η t d + ½ i / ( SA = ) r f Where: = SA Surface area (sq. ft.) = Design retention volume treated by the practice Sv η 4) = available porosity of the stone reservoir (assume 0. r d = Infiltration depth (ft.) (maximum depends on the scale of Equation 1.1 or 1.2 ) infiltrat ion and the results of -verified infiltratio field = i /day) n rate for the native soils (ft t Time to fill the infiltration facility (days – = typically 2 hours, or 0.083 f days) can also be designed to address, in whole or in part, the detention storage needed Infiltration practices to comply with channel protection and/or flood control requirements. The designer can model various expected infiltration approaches by factoring in storage chambers within the stone aggregate layer and as part of the design. Routing calculations can also be used to provide a more accurate solution of the peak discharge and required storage volume. Infiltration Landscaping Criteria 1.7 site plan and aesthetically designed with Infiltration trenches can be effectively integrated into t he adjacent native landscaping or turf cover . Vegetation associated with the infiltration practice buffers should be regularly mowed with clippings removed and maintained to keep organic matter out of the infiltratio n device and maintain enough vegetation to prevent soil erosion from occurring. Infiltration 1.8 Construction Sequence Infiltration practices are particularly vulnerable to failure during the construction phase for two reasons. First, if the constructi on sequence is not followed correctly, construction sediment can clog the practice. In addition, heavy construction can result in compaction of the soil, which can then eeds to be reduce the soil’s infiltration rate. For this reason, a careful construction sequence n followed. During site construction, the following steps are absolutely critical: compaction by preventing construction equipment and vehicles from traveling over the Avoid • tection” using “Sensitive Area Pro proposed location of the infiltration practice during guidelines . construction line” until construction is complete “off- should remain trenches Infiltration to prevent • construction sediment from clogging the stone reservoir layer . Prevent sediment from entering the 03/2013 11 3.06.2. 1 -

15 BMP Standards and Specifications Infiltration uper silt fence, diversion berms or other means. In the erosion and infiltration site by using s n sediment control plan, indicate the earliest time at which stormwater runoff may be directed to a trench c methods erosion and sediment control plan must also indicate the specifi . The infiltration . to be used to temporarily keep runoff from the infiltration facility should basins Infiltration serve as the sites for temporary sediment control devices (e.g., not • on methods are unless extensive design and constructi sediment traps, etc.) during construction ation facilities employed to protect the infiltr . Examples of these design ’ ability to infiltrate considerations are the need to remove choking sediment from the facility, tilling the basin, and performing additional geological site investig ations to determine that the infiltration rate has been maintained. • Upland drainage areas need to be completely stabilized with a thick layer of vegetation prior to commencing excavation for an infiltration practice. installation of an infiltration practice is done using the following The actual Infiltration Installation. steps: 1. Excavate the infiltration practice to the design dimensions using a backhoe or , from the side excavator. 2. Install geotextile per design on the trench sides. Large tree roots should be trimmed flush with the sides of infiltration trenches to prevent puncturing or tearing of the filter fabric during subsequent procedures. When laying out the geotextile, the width should include sufficient installation material to compensate for perimeter irregularities in the trench and for a 6 -inch minimum overlap at the top of the trench. The filter fabric itself should be tucked under the sand layer on the bottom of the infiltration trench . Stones or other anchoring objects should be placed o n the fabric at the trench sides, to keep the trench open during windy periods. Voids may occur between the fabric and the excavated sides of a trench. Natural soils should be placed in all voids, to ensure the fabric conforms smoothly to the sides of excavation. 3. Scarify the bottom of the infiltration practice, and spread 6 inches of sand on the bottom as a filter per design . layer 4. Anchor the observation well(s), and add stone to the practice in 1 -foot lifts. side s of to establish a dense turf cover for at least 10 feet around the 5. Use sod , where applicable the infiltration practice, to reduce erosion and sloughing. . Review Construction needed during construction to ensure that the infiltration Review is proved design and this specification. Qualified practice is built in accordance with the ap individuals should use detailed inspection checklists to include sign -offs at critical stages of construction, to ensure that the contractor’s interpretation of the plan is consistent with the designer’s inte ntions. Infiltration Maintenance Criteria 1.9 03/2013 12 3.06.2. 1 -

16 BMP Standards and Specifications Infiltration The -term performance of infiltration practices. Maintenance is a crucial element that ensures the long most frequently cited maintenance problem for infiltration practices is clogging of the stone by organi c matter and sediment. The following design features can minimize the risk of clogging: CDA. Stabilized Infiltration systems may not receive runoff until the entire contributing drainage area has been completely stabilized , unless a design and constructio n method can be shown to remove . all clogging sediment prior to site completion Observation Well Infiltration practices should include an observation well, consisting of an . flush with the -inch diameter perforated PVC pipe fitted with a lockable cap installed anchored 6 ground surface, to facilitate periodic inspection and maintenance. No Filter Fabric on Bottom. Avoid installing geotextile filter fabric along the bottom of infiltration practices. Experience has shown that filter fabric is prone to cloggi ng. However, permeable filter fabric must be installed on the trench sides to prevent soil piping. Infiltration systems must be covered by a common open space to allow Direct Maintenance Access. Access must be provided to allo w personnel and heavy equipment to inspection and maintenance. ce tasks, such as reconstruction or rehabilitation. While a turf cover is -routine maintenan perform non scale infiltration practices, the surface must never be covered by an impermeable permissible for small- as asphalt or concrete. material, such Effective long -term operation of infiltration practices requires an Operation and Maintenance Plan, maintenance inspection schedule with clear guidelines and schedules, as 1.5 Table shown in including possible, facility . Where below maintenance should be integrated into routine landscaping maintenance tasks. 03/2013 13 3.06.2. 1 -

17 Infiltration BMP Standards and Specifications ractices activities for infiltration p aintenance 1.6. Typical m Table Maintenance Activity Schedule • Replace topsoil and top surface filter fabric (when clogged). As needed d filter strips as necessary and remove the clippings. • Mow vegetate • . Ensure that the contributing drainage area, inlets, and facility surface are clear of debris -reseeding if where Perform spot • Ensure that the contributing drainage area is stabilized. ed. need Quarterly Remove sediment and oil/grease from inlets, • flow diversion structures, pre -treatment devices, and overflow structures. • Repair undercut and eroded areas at inflow and outflow structures. xcess of 1/2 inch in depth. Standing Check observation wells 3 days after a storm event in e • water observed in the well after three days is a clear indication of clogging. treatment devices and diversion structures for sediment build- up and structural Inspect pre- • Semi -annual damage. inspection that may drop leaf • Remove trees that start to grow in the vicinity of the infiltration facility litter, fruits and other vegetative materials that could clog the infiltration device . Annually - treatment cell. • Clean out accumulated sediments from the pre Maintenance Plan for the project will be approved by DNREC or the Delegated An Operation and Agency prior to project closeout. The Operation and Maintenance Plan will specify the property staff to owner’s primary maintenance responsibilit ies and authorize DNREC or Delegated Agency or corrective action in the event that proper maintenance access the property for maintenance review is not performed. Infiltration facilities that are, or will be, owned and maintained by a joint ownership t be located in common areas, community open space, such as a homeowner’s association mus -owned property, jointly owned property, or within a recorded easement dedicated to community public use. Operation and M ty and should clearly outline how vegetation in the Infiltration facili Plans aintenance its buffer will be managed or harvested in the future. Periodic mowing of the Infiltration facility is , unless it is managed as a meadow (mowing every other year) or forest. The maintenance required . plan should schedule a cleanup at least once a year to remove trash and debris Maintenance of an that evaluate the is driven by annual maintenance reviews Infiltration facility results, specific ion and performance of the Infiltration facility. Based on maintenance review condit . required maintenance tasks may be References 1.10 No references. 03/2013 14 3.06.2. 1 -

18 BMP Standards and Specifications Bioretention 2.0 Bioretention Definition: Practices that capture and store stormwater runoff and pass it through a filter bed of engineered soil media comprised of sand, and organic lignin matter. Filtered runoff may be collected and returned to the conveyance system, or allowed to infiltrate into the soil. Design variants include: 2- A Traditional Bioretention  In-Situ Bioretention (including Rain Gardens)  2- B 2- C Streetscape Bioretention   2- D Engineered Tree Boxes  2- E Stormwater Planters  2- F Advanced Bioretention Sys tems Bioretention systems are typically designed to manage stormwater runoff from frequent, small of larger storms (e.g., 10 -yr) in magnitude storm events, but may provide stormwater detention some circumstances. Bioretention practices shall generally be designed such that larger storm events bypass the system into a separate facility where site conditions allow. For each of the design variants above, t here are two basic configurations: Underdrain • : Practices with a positive discharge using perforated pipe ; Designs pollutant reduction occurs through a combination of runoff reduction and treatment by the filtering media. Addition of an infiltration sump is required to maximize runoff reduction performance. Advanced systems may provide greater pollutant r emoval capabilities through the use of improved media components and/or internal modifications that encourage partial anaerobic conditions. • Infiltration Designs : Practices with no underdrains that can infiltrate the design storm volume ; pol lutant reduction is based solely on the load reduction in 48 hours with provided by the design retention storage volume. The particular design configuration to be implemented on a site is typically dependent on specific site conditions and the characteristics of the underl ying soils. These criteria are discussed in more detail below. 7/3/2014 3.06.2.2- 1

19 BMP Standards and Specifications Bioretention Figure 2.1. Traditional Bioretention Underdrain Design Figure 2.2. Traditional Bioretention Infiltration Design 7/3/2014 3.06.2.2- 2

20 Bioretention BMP Standards and Specifications Figure 2.3. Rain Garden Figure 2.4. Streetscape Bioretention 7/3/2014 3.06.2.2- 3

21 BMP Standards and Specifications Bioretention Figure 2.5. Engineered Tree Box 7/3/2014 3.06.2.2- 4

22 Bioretention BMP Standards and Specifications Figure 2.6. Stormwater Planter 5 3.06.2.2- 7/3/2014

23 BMP Standards and Specifications Bioretention 2.1 Bioretention Stormwater Credit Calculations The retention volume credit for Bioretention practices depends on the volume of runoff that is infiltrated from this pra ). In addition, Bioretention systems using an ctice (Table 2.1a & b underdrain receive a removal efficiency credit for filtering pollutants as they pass through the soil media. 2.1(a) Bioretention With Underdrain Performance Credits Runoff Reduction R etention Allowance 50% - A/B Soil 5 0% of Retention Storage RPv - C/D Soil 5 0% of Retention Storage RPv % of Retention Storage Cv 5 1 % of Retention Storage Fv Pollutant Reduction * 100% of Load Reduction + TN Reduction 30% Removal Efficiency 100% of Load Reduction + TP Reduction 40% Removal Efficiency 100% of Load Reduction + TSS Reduction 80% Removal Efficiency *Advanced systems may provide higher removal efficiencies With Infiltra tion Performance Credits 2.1(b) Bioretention Runoff Reduction 100% Retention Allowance - RPv 100% of Retention Storage A/B Soil RPv - C/D Soil 100% of Retention Storage Cv Retention Storage 100% of Fv Retention Storage 100% of Pollutant Reduction TN Reduction 100% of L oad Reduction TP Reduction 100% of Load Reduction TSS Reduction 100% of Load Reduction 7/3/2014 3.06.2.2- 6

24 BMP Standards and Specifications Bioretention 2.2 Bioretention Design Summary Table 2.2 summarizes design criteria for bioretention practices, and Table 2.3 summarizes the materials specifications for thes e practices. For more detail, consult the appropriate sections referenced in column 1. tion Design Summary Table 2 .2 Bioreten Infiltration Designs Standard Underdrain Designs Feasibility IAW Appendix Can treat hotspots if designed with an rate • inimum soil infiltration M • 1 (Section 2.3) impermeable liner, but cannot treat high • loads, or Restrictions for treating hotspots, high sediment loads or dry weather flows dry weather flows • ust not intersect Invert of underdrain m groundwater • 2 foot separation from seasonal high seasonal high groundwater table 3-4 feet of head (unless Minimum • for internal water storage designed ) • (Table 2.4) Small CDA, varying based on practice type 2.5) • Setbacks from wells, buildings and utilities (Table Conveyance • Can be designed off - line or on - line 2.4) (Section -year storm event (Cv) and 100- year storm event (Fv) unless designed to • Must safely convey the 10 bypass these larger storm events Pretreatment • All runoff directed to a bioretention practice must recei ve pretreatment (Section 5) 2. Sizing ( ) [ ] ( ) Sv d SA SA + × d + d + SA Sv η / × 2 η ) + × ( = × (Total Storage) nt pretreatme p ponding gravel p gravel media media filter − − 2 1 (Section 2.6) Sizing Sv d × media (Min . Surface Area) SA ≥ filter (Section 2.6) d   ponding k d t × × +   f media 2   Sizing (Ponding ) / 2 = + × Sv d ( SA SA + V ponding p − − ponding pretreatme p 1 2 nt Volume) d = depth of the filter media ( typically 2 ft) Variables: media η = effective porosity of the filter media (typically 0. 4) media = depth of the underdrain and underground storage gravel layer(ft) d gravel = effective porosity of the gravel layer (typically 0.4) η gravel = surface area at the lowest elevation of the ponding area (sq. ft.) SA p-1 may be no greater than 2X ] SA SA [Note p-1 filter surface area at the depth of ponding = SA p-2 the maximum ponding depth of the practice (ft). = d ponding = volume stored in pretreatment practices Sv pretreatment = filtering media permeability (ft/day; typically assume 5.7 ) k = drawdown time within the filter (2 days maximum) t d Geometry and R P v: 12”; Cv: 18”, Fv: 24” Ponding Depth: gravel layer to extend into (varies Media Depth: Minimum 24” Dimensions for s mall -scale practices) ; may require (Section 2.6) more permeable soil profile 3:1 side slopes Side Slopes: ; for “curb drop” designs (e.g., streetscape bioretention), in ponding area maximum drop of 12” Lands caping ) 2 - Plant in zones based on elevation within the filter ( see Appendix A 2. (Section Maintain vegetation in the drainage area to limit sediment loads to the practice. 7) 7 3.06.2.2- 7/3/2014

25 BMP Standards and Specifications Bioretention Table 2.3. Bioretention Material Specifications Material Specification Notes • for in - may be less situ Minimum depth of 24” ( : (by volume) Media to contain 14 Biosoil- practices) Bioretention 75 60% concrete sand; fineness modulus > 2. • Filter Media • ume of filter media used should be The vol 14) (Biosoil- -shredded hardwood mulch 30% triple • based on 110% of the calculated design • certified 10% aged, STA compost volume, to account for settling Between 7 and 2 mg/kg of P in the soil media be procured from approved 3 The media must ; Filter Media CECs greater than 10 biosoil media vend ors Testing Use aged, shredded hardwood bark mulch 3 ” layer on the surface of the biosoil media bed Mulch Layer Use of river stone or pea gravel, coir and jute Alternative uppress weed growth matting, or turf cover may be acceptable with prior 3” layer to s Surface Cover approval Loamy sand or sandy loam texture, with less than Top Soil 3 inch tilled into surface layer 5% clay content, pH corrected to between 6 and 7, For Turf Cover and an organic matter content of at least 2% sump below ’ 2 ” cover on underdrain; min. Rice Gravel ( 1 / 4 ” stone ) shall be double - washed 3 Min. Underdrain and free of all fines invert of underdrain stone (as needed) ble To increase storage for larger storm events, chambers, perforated pipe, stone, or other accepta Storage Layer material can be incorporated below the filter media layer (optional) Impermeable Use a 30 mil (minimum) PVC Geomembrane liner covered by 8 to 12 oz./sq. yd. non- woven geotextile. Liner (NOTE: THIS IS USED ONLY FOR HOTSPOTS AND SMALL PRACTICES NEAR BUILDING (optional) FOUNDATIONS, OR IN FILL SOILS AS DETERMINTED BY A GEOTECHNICAL INVESTIGATION) flat, be no more laid drains shall be - Under • than 20 -ft apart and daylight to point of corrugated • 4- or 6 -inch perforated Underdrains, adequate conveyance. for underdrains pipe (CPP) polyethylene Cleanouts, and • -outs shall be provided at all terminal Clean Observation • -inch SDR 35 (min.) PVC for 4- or 6 ends and every 100 -ft. Wells cleanouts and observation wells • An observation well shall be provided for every 500 sq.ft. of f ilter media surface area. - Establish plant materials as specified in the Appendix 2, Stormwater BMP Landscaping See landscaping plan and the recommended plant list Plant Materials Criteria 7/3/2014 3.06.2.2- 8

26 BMP Standards and Specifications Bioretention 2.3 Bioretention Feasibility Criteria ied in most soils or topography, since runoff simply percolates through Bioretention can be appl returned to the stormwater system via an underdrain . an engineered soil bed and is infiltrated or Key constraints with B ioretention include the following: EPA Requirements for Class V Injection Wells. Certain types of practices in this category may be classified as Class V Injection Wells, which are subject to regulations under the Federal Underground Injection Control (UIC) program. In general, if the facility allows stormwater runoff to come in direct contact with groundwater it would meet this criterion. Facilities with a minimum 2’ vadose zone separation from the groundwater table would not meet the criterion. tion for additional Designers are advised to contact the DNREC Groundwater Discharges Sec information regarding UIC regulations and possible permitting requirements. Space. Designers can assess the feasibility of using bioretention facilities based on a Required simple relationship between the contributing drainage area and the corresponding required be between 3% to 6% of the contributing surface area. The bioretention surface area will usually (CDA), depending on the imperviousness of the CDA and the desired bioretention drainage area ponding depth. When a bioretention fa cility is installed on a private residential lot, its existence and purpose should be noted on the deed of record. A sample Record Plan note is as follows: “This lot contains practices that are intended to meet State regulations related to the management of stormwater runoff. It is the responsibility of the owner to maintain these practices in proper working condition in order fulfill this requirement ”. Site Topography. Bioretention is best applied when the grade of contributing slopes is greater than 1% and less than 5%. Available Hydraulic Head. Bioretention is f undamentally constrained by the invert elevation of the existing conveyance system to which the practice. In general, 4 to 5 feet of elevation above . If an this invert is needed to accommodate the required ponding and filter media depths or elevated underdrain design is used to accommodate an internal water storage (IWS) inverted design , less hydraulic head may be adequate. Water Table. Bioretention should always be separated from the water table to ensure that groundwater does not intersect the filter bed. This could otherwise lead to possible groundwater contamination or failure of the Bioretention facility. A separation distance of 2 feet is required between the bottom of the excavated Bi oretention facility and the seasonally high ground water table . for infiltration designs Soils and Underdrains . Soil conditions do not typically constrain the use of Bioretention , although they do determine whether an underdrain is needed. Underdrains ar e required if the measured permeability of the un derlying soils does not meet the requirements for infiltration practices in accordance with Appendix 1, Soil Investigation Procedures for Stormwater BMPs . 7/3/2014 9 3.06.2.2-

27 BMP Standards and Specifications Bioretention A stone sump can be used to extend an infiltrating facility to a more permeable layer, as needed. When designing a Bioretention practice, designers should verify soil permeability by using the . methods provided in Appendix 1, Soil Investigation Procedures for Stormwater BMPs hnical investigations are required to determine if the use of an In fill soil locations, geotec . impermeable liner and underdrain are necessary Contributing Drainage Area. Bioretention facilities work best with smaller contributing drainage areas, where it is easier to achieve flow dis tribution over the filter bed. Typical size for traditional Bioretention facilities ( acres and drainage area 2- A) can range from 0.1 to 5 practices ( consist of up to 100% impervious cover. Drainage areas to smaller Bioretention 2- B, 2- C, 2- D, and 2- E) typ ically range from 0.5 acre to 1.0. The maximum recommended area to a single bioretention basin or single cell of a Bioretention facility is 2.5 acres impervious due to limitations in the ability of bioretention to effectively manage large volumes and peak However, if hydraulic considerations are adequately addressed to manage the rates of runoff. -flow diversions, potentially large peak inflow of larger drainage areas (such as off -line or low by-case instances where these forebays, etc.), there may be case- recommended maximums can be adjusted. 2. 4 . Maximum Table CDA to Bioretention Recommended Traditional Small - scale and Urban Bioretention Bioretention Design Variants 2 - A, 2 - F 2 - B , 2 - C , 2 - D , and 2 - E Maximum CDA 10.0 acres 1.0 a cre s impervious) (2.5 ac. impervious) (0.25 ac. An impermeable bottom liner and an underdrain system must be employed Hotspot Land Uses. a Bioretention hotspot runoff. However, will receive untreated when Bioretention can facility still be used to treat “non s of the site . For a list of potential stormwater hotspots, -hotspot” part see Appendix 4, Stormwater Hotspots Guidance . Floodplains. Bioretention facilites should be constructed outside the limits of the 100- year floodplain. should not receive baseflow, irrigation Bioretention facility No Irrigation or Baseflow. The -water or other non- stormwater flows. water, chlorinated wash Setbacks . To avoid the risk of seepage, Bioretention facilities should not be hydraulically connected to structure foundations. The designer should check to ensure footings and foundations of adjacent buildings do not encroach within an assumed 4:1 phreatic zone drawn from the maximum design water elevation in the B ioretention facility. The setback for buildings from Table 2.5 can be used in l ieu of a phreatic zone analysis. 7/3/2014 3.06.2.2- 10

28 BMP Standards and Specifications Bioretention Table 2.5. Setbacks for Bioretention Practices Buildings Contributing Drainage Area/ Septic Systems Facility Facility Design Variant Wells Gradient - Up Down gradient - 50’ 10’ 0 to 0.5 Acre CDA 1 00’ 25’ 0.5 to 5 Acre CDA 50’ Any Practice With a Liner 100’ Any Practice Without a Liner 1 50’ 100’ Interference with underground utilities should also be avoided, Proximity to Utilities. or agency is com utility from the applicable particularly water and sewer lines. Approval pany required if utility lines will run below or through the bioretention area. C onflicts with water and sewer laterals (e.g., house connections) may be unavoidable, and the construction sequence must be altered, as necessary, to avoid impact s to existing service. Additionally, designers should ensure that future tree canopy growth in the B facility ioretention will not interfere with existing overhead utility lines. Urban Minimizing External Impacts. Bioretention o higher public practices may be subject t visibility, greater trash loads, pedestrian traffic, vandalism, and vehicular loads. Designers should design these practices in ways that prevent, or at least minimize, such impacts. In addition, designers should clearly recognize the need to perform frequent landscaping maintenance to remove trash, check for clogging, and maintain vigorous plant growth. The urban landscape context may feature naturalized landscaping or a more formal des When urban Bioretention ign. is used in sidewalk areas of high foot traffic, designers should not impede pedestrian movement or create a safety hazard. Designers may also install low fences or other measures to prevent damage from pedestrian short -cutting across the practices. 2.4 Bioretention Conveyance Crit eria There are two basic design approaches for conveying runoff into, through, and around Bioretention practices: enters the 1. Off -line: Flow is split or diverted so that only the runoff from the design storm facility . Bioretention area. Larger flows by -pass the Bioretention 2. On- line: All runoff from the drainage area flows into the practice. Flows that exceed the design capacity exit the practice via an overflow structure or weir. overflow : -line Bioretention Off Optional methods include the follow ing:  Create an alternate flow path at the inflow point into the structure such that when the maximum ponding depth is reached, the incoming flow is diverted past the facility. In this 7/3/2014 3.06.2.2- 11

29 BMP Standards and Specifications Bioretention case, the higher flows do not pass over the filter bed and through the f acility , and additional . flow is able to enter as the ponding water filters through the soil media -flow diversion or flow splitter at the inlet to allow only the design storm Utilize a low  volume ( e.g., the RP or a fracti ) to enter the facility. This may be achieved with the RP on of v v a weir or curb opening sized for the target flow, in combination with a bypass channel. Using a weir or curb opening helps minimize clogging and reduces the maintenance frequency . ary in order to ensure proper design of the Determining the peak flow rate will be necess diversion structure . On -line Bioretention : An overflow structure should always be incorporated into on -line to safely convey larger storms through the B facility designs . The following criteria ioretention to overflow structures: apply An overflow shall be provided within the practice to pass flows not treated by the practice  to an adequate conveyance system . Larger events (e.g., the C or F ) may be partially or fully v v ioretention facility managed by the B as the maximum depth of ponding in the as long and 24” for F . bioretention cell does not exceed 18” for the C v v Common overflow systems within bioretention practices consist of an outlet structure, where  the maximum ponding depth within the the top of the structure is set so as to control bioretention facility. The crest of the outlet structure is therefore typically set at 6 to 18 inches above the surface of the filter bed. The overflow capture device should be scaled to the application –  this may be a landscape for small practices -type structure for larger installations. te or yard inlet or a commercial gra The maximum design discharge should be checked  erosive condition at the outlet for a non- . Outlet protection should be provided as necessary. point Bio 2.5 Pretreatment Criteria retention Pre Bioretention facilities is necessary to trap coarse sediment -treatment of runoff entering Ideally, p re-treatment measures particles before they reach and prematurely clog the filter bed. be designed to evenly spr ead runoff across the entire width of the bioretention area. should Several pre -treatment measures are feasible, depending on the type of the bioretention practice and whether it receives sheet flow, shallow concentrated flow or deeper concentrated flows. The fol lowing are appropriate pretreatment options: For Traditional Bioretention (2- -F): A, 2 -treatment Cells (channel flow): Similar to a forebay, this cell is located at piped inlets  Pre may include an energy d or curb cuts leading to the bioretention area and issipater sized for the expected rates of discharge. It has a storage volume equivalent to at least 15% of the total storage volume (inclusive) with a recommended 2:1 length- to-width ratio. The cell may be formed by a wooden or stone check dam or an earthe n berm . Pretreatment cells do not need underlying engineered soil media, in contrast to the main bioretention cell.  Grass Filter Strips (sheet flow): Grass filter strips that are perpendicular to incoming sheet flow extend from the edge of pavement (with a slight drop at the pavement edge) to the 7/3/2014 3.06.2.2- 12

30 BMP Standards and Specifications Bioretention bottom of the bioretention basin at a 5:1 slope or flatter. Alternatively, if the Bioretention oot has sides slopes that are 3:1 or flatter, a 5 f grass filter strip at a maximum 5% facility (20:1) slope . can be used  (sheet flow). A gravel diaphragm located at the edge of the Gravel or Stone Diaphragms pavement should be oriented perpendicular to the flow path to pre -treat lateral runoff, with a 2 to 4 inch drop one must be sized from the pavement edge to the top of the stone . The st according to the expected rate of discharge. Gravel or Stone Flow Spreaders (concentrated flow). The gravel flow spreader is located at  curb cuts, downspouts, or other concentrated inflow points, and should have a 2 to 4 inch elevation d rop from a hard- edged surface into a gravel or stone diaphragm. The gravel should extend the entire width of the opening and create a level stone weir at the bottom or treatment elevation of the basin. Proprietary Practices : Structures that meet the pre -treatment requirements of Specification  may be used for pre 15.0, Proprietary Practices -treatment. -Scale Bioretention ( 2- B, 2- C, 2- D, 2- E): For Small  as part of the gutter system serve to keep the heavy loading of organic debris Leaf Screens ating in the bioretention cell. from accumul Grass Filter Strips (for sheet flow), applied on residential lots, where the lawn area can  serve as a grass filter strip adjacent to a rain garden.  Gravel or Stone Diaphragm (for either sheet flow or concentrated flow); this is a gravel diaphragm at the end of a downspout or other concentrated inflow point that should run perpendicular to the flow path to promote settling. Trash Racks eet flow or concentrated flow) between the pre- treatment cell and  (for either sh se will allow trash to collec t in specific locations the main filter bed or across curb cuts. The and create easier maintenance. Pre -treatment Cell (see below) located above ground or covered by a manhole or grate.  This type of pretreatment is not recommended for re -5). sidential rain gardens (B Bioretention Design Criteria 2.6 Geometry: Bioretention facilities must be designed with an internal flow path geometry Design such that the treatment mechanisms provided by the bioretention are not bypassed or short - circui ted . In order for these B ioretention facilities during the Resource Protection Event (RPv) to have an acceptable internal geometry, the “travel time” from each inlet to the outlet should be ible. In addition, incoming flow maximized by locating the inlets and outlets as far apart as poss must be distributed as evenly as possible across the entire filter surface area. Inlets and Energy Dissipation: Where appropriate, t he inlet(s) to Streetscape B ioretention (2- C), Engineered Tree Boxes ( 2- E) should be stabilized using DE 2- D) and Stormwater Planters ( No. 3 stone, splash block, river stone or other acceptable energy dissipation measures. Iinlet protection practices that could be considered include : 7/3/2014 3.06.2.2- 13

31 BMP Standards and Specifications Bioretention o . Downspouts to stone energy dissipaters Sheet flow over a depressed curb with a 3 -inch drop. o o Curb cuts allowing runoff into the bioretention area. o Covered drains that convey flows across sidewalks from the curb or downspouts. Grates or trench drains that capture runoff from a sidewalk or plaza area. o The h: surface ponding depth is 12” for the RPv . Ponding depths can Ponding Dept maximum be increased to a maximum of 18” for management of the Cv and a maximum of 24” for the Fv. However, if these greater are used, the design must carefully consider i ssues such ponding depths as safety, aesthetics, the viability and survival of plants, and erosion and scour of side slopes. ”. Shallow er ponding The depth of ponding in the bioretention area should never exceed 24 treetscape Bioretention (2- C), depths (typically 6 to 12 inches) are recommended for S T ree B 2- D), and S tormwater P lanters ( 2- E). Engineered oxes ( Traditional Bioretention faciliti es (2- A, 2 -F) and R ain Gardens (2- B) should be Side Slopes: or space constrained areas, a constructed with side slopes of 3:1 or flatter. In highly urbanized s. For safety drop curb design or a precast structure can be used to create stable, vertical side wall purposes, drop curb designs should not exceed a vertical drop of more than 12 inches. Media and Surface Cover: The filter media and surface cover are the two most Biosoil ioretention facility in terms of long -term performance. The following important elements of a B are key factors to consider in determining an acceptable soil media mixture.  General Biosoil Media Compositi on. The Biosoil -14 soil mixture has the following volumetric composition: 60% coarse concrete sand (Fineness Modulus > 2. o 75) 30% triple shredded hardwood mulch o 10% aged, STA certified compost o media must For systems intended to meet regulatory requirements, biosoil be obtained from an approved conformance with the media composition and standards vendor that can certify in this specification. Phosphorus Content The recommended range for phosphorus content for the soil . component is between 7 mg/kg and 23 mg/kg .  Compost. Compost used for Bioretention facilities shall meet the requirements Appendix 3, . Compost Material Properties  Cation Exchange Capacity (CEC). The CEC of a soil refers to the total amount of positively charged elements that a soil can ho ld; it is expressed in milliequivalents per 100 grams (meq/100g) of soil. For agricultural purposes, these elements are the basic cations of +1 +2 +1 +2 calcium (Ca ), potassium (K ) and sodium (Na ) and the acidic cations ), magnesium (Mg 7/3/2014 14 3.06.2.2-

32 BMP Standards and Specifications Bioretention +1 +3 of hydrogen (H ). The CEC of the soil is determined in part by the uminum (Al ) and al nic matter present. Soils with CECs exceeding 10 are amount of clay and/or humus or orga preferred for pollutant removal. matter content of any soil will help to Increasing the organic increase the CEC. Biosoil Infiltration Rate. The  media must meet the minimum infiltration rate biosoil testing protocol for B ioretention soil . established in the Department’s Biosoil Depth. The biosoil media bed depth should be a minimum of 24 inches although th is  can be reduced for small bioretention practices (practices 2-B, 2- C, 2- D and 2-E) as -scale . A rice gravel layer may be added below the filter noted elsewhere in this specification . If media if a greater depth is required to reach a more permeable layer in the soil profile trees are included in the bioretention planting plan, tree planting holes in the filter should be deep enough to provide enough soil volume for the root structure of the selected mature trees. systems. Native grasses , perennials or shrubs Trees are not recommended for underdrain and underdrain systems . should be used instead of trees to landscape shallower filter beds  Mulch. A 2 to 3 inch layer of mulch on the surface of the filter bed enhances plant survival, and pre -treats runoff before it reaches the filter media. Shredded suppresses weed growth, , makes a very good surface cover, as it hardwood bark mulch, aged for at least 6 months retains a significant amount of pollutants and typically will not float away.  Alternative to Mulch Cover. In some situations, designers may consider alternative surface covers such as turf, native groundcover, river rock , or pea gravel. Use of such alternative covers require prior approval from the appropriate approval authority. Section For tention designs Underdrain require an underdrain (see Biore 2.3 ) , the s: that shall be a 4- or 6 -inch underdrain corrugated polyethylene pipe (CPP) . The perforated underdrain be sized so that the bioretention practice fully drains within 48 hours. The must shall 4” bank- ” (nominal 1/ underdrain run be encased in a layer of clean, washed “rice gravel ) with a minimum of 3” of cover. The gravel layer should be extended a minim um of 2’ gravel below the invert of the underdrain to enhance the infiltration capabilities of th e system. This may also serve as an aerobic/anaerobic zone for situations in which the water table fluctuates below the invert. Each underdrain should be located no more than 20 feet from the next pipe. traditional Bioretention practices All ude at least one observation well and/or cleanout should incl pipe . The observation wells /cleanouts should be appropriately sized PVC tied into any T’s or Y’s in the underdrain system, and should extend slightly above -on or the surface, with a screw locking cap. Un derground Storage Layer (optional): For Bioretention facilities with an underdrain, an 7/3/2014 3.06.2.2- 15

33 BMP Standards and Specifications Bioretention underground storage layer consisting of chambers, perforated pipe, stone, or other acceptable to increase stora ge for larger storm material can be incorporated below the filter media layer and volume . The depth events of the storage layer will depend on the target treatment and storage volumes needed to meet water quality, channel protection, and/or flood protection criteria. Impermeable L This material should be used only for appropriate hotspot designs , small iner: scale practices (i.e. , B-4) that do not meet the necessary separation requirements from buildings , fill applications where deemed necessary by a geotechnical investigation . Designers should or in ty mil (minimum) PVC Geomembrane liner covered by 8 to 12 oz./sq. yd. non- woven use a thir geotextile. Recommended material specifications for Bioretention facilities are Material Specifications: shown in Table 2.3. Bioretention Signage: in highly urban ized areas may be stenciled or permanently facilities marked to designate them as a stormwater management facility in order to avoid potential complaints about an otherwise properly functioning system . The stencil or plaque should indicate (1) its water quality purpose, (2) that it may pond briefly after a storm, and (3) that it is not to be disturbed except for required maintenance. Specific Design Issues for In -Situ Bioretention, including Rain Gardens (2 -B): In some cases, the native soil profile may be adequate to support infiltration of the RPv without -type system. may also be the need for a more elaborate traditional Certified yard waste compost mixed with the native soils instead of biosoil media. It is generally recommended that this and/or outlying areas within larger pr ojects approach be used for projects with small CDAs that cannot be easily captured by a primary facility . For some residential applications, front, side, acceptable captures and/or rear yard bioretention may be an option. This form of bioretention - to medium roof, lawn, and driveway runoff from low - density residential lots in a depressed area (6 to 12 inches) between the home and the primary stormwater conveyance system (roadside ditch or pipe system). The planting media must be deep en ough to extend below the topsoil and into the more permeable subsoil. If the permeable soil layer is relatively close to the surface, it may be possible to simply excavate to provide the necessary design storage volume and incorporate 3” - ard waste compost 4” of certified y into the native soil. Although this type of system is particularly conducive to the inclusion of trees in the planting plan, tree planting holes should be deep enough to provide enough soil volume for the root structure of the selected m . ature trees Shredded hardwood mulch is added as a top dressing to complete the installation. It is preferred that this category of bioretention be designed as an infiltration practice. However, if an underdrain is required to ensure adequate function or to retro -fit a failing system, it may be connected to a storm drain or open channel conveyance system . 7/3/2014 3.06.2.2- 16

34 BMP Standards and Specifications Bioretention 2- C): Streetscape Bioretention is installed Specific Design Issues for Streetscape Bioretention ( or in the road itself. In many cases, -of-way either in the sidewalk area in the road right areas can also serve as a traffic calming or street parking control Streetscape Bioretention devices . The basic design adaptation is to move the raised concrete curb closer to the street or in the street, and then create inlets or curb cuts that divert street runoff into depressed vegetated areas within the expanded right of way . Roadway stability can be a design issue where streetscape bioretention practices are installed. Designers should c onsult design standards pertaining to roadway drainage. It may be necessary to provide a n impermeable liner on the road ioretention facility to keep water from saturating the road’s sub- base. side of the B Specific Design Issues for Tree Boxes ( 2- D): Engineered Tree Boxe s are installed Engineered . The soil in the sidewalk zone near the street where urban street trees are normally installed is increased and used to capture and treat stormwater. Treatment is volume for the tree box g areas together in a row. The surface of the increased by using a series of connected tree plantin enlarged planting area may be mulch, grates, permeable pavers, or conventional pavement. The large and shared rooting space and a reliable water supply increase the growth and survival rates arsh planting environment. in this otherwise h When designing Engineered Tree Boxes , the following criteria should be considered:  The bottom of the soil layer must be a minimum of 4 inches below the root ball of plants to be installed.  Engineered Tree Box designs sometimes c over portions of the filter media with pervious pavers or cantilevered sidewalks. In these situations, it is important that the filter media is connected beneath the surface so that stormwater and tree roots can share this space. n Engineered Tree Box grate over filter bed media is one possible solution to  Installing a prevent pedestrian traffic and trash accumulation. Low, wrought iron fences can help restrict pedestrian traffic across the tree box bed and serve  from the pavement to the micro as a protective barrier if there is a dropoff -bioretention cell. A removable grate may be used to allow the tree to grow through it.  Each tree needs a minimum of 400 cubic feet of root space.  Specific Design Issues for Stormwater Planters (2- E): Stormwater Planters are a useful option to disconnect and treat rooftop runoff, particularly in ultra -urban areas. They consist of confined planters that store and/or infiltrate runoff in a soil bed to reduce runoff volumes and pollutant loads. Stormwater P combine an aesthetic landscaping feature with a functional form of lanters Stormwater stormwater treatment. generally receive runoff from adjacent rooftop Planters downspouts and are landscaped with plants that are tolerant to periods of both drought and inundation. The two ba sic design variations for stormwater planters are the infiltration Stormwater P lanter and the filter Stormwater P lanter. infiltration Stormwater P lanter filters rooftop runoff through soil in the planter followed by An infiltration into soils below the planter. The recommended minimum depth is 30 inches, with the 17 3.06.2.2- 7/3/2014

35 BMP Standards and Specifications Bioretention shape and length determined by architectural considerations. The planter should be sized to treat -inch of runoff from the contributing rooftop area. Infiltration planters should be at least 1/2 placed at least 10 feet away from a building to prevent possible flooding or basement seepage damage. Stormwater Planter A watertight filter does not allow for infiltration and is constructed with a to pr event seepage. Since a filter concrete shell or an impermeable liner on the bottom lanter is self -contained and does not infiltrate into the ground, it can be installed Stormwater P right next to a building. The minimum planter depth is 18 inches, with the shape and length determined by architectural considerations. Runoff is captured and temporarily ponded above the planter bed. Overflow pipes are installed to discharge runoff when maximum ponding depths are exceeded. In addition, an underdrain is used to carry runoff to the storm sewer system. All planter s should be placed at or above finished grade elevation. Plant materials should be capable of withstanding moist and seasonally dry conditions. Planting media should have an infiltration rate of at least 2 inches per hour. The sand and gravel on the bottom of the planter should have a minimum infiltration rate of 5 inches per hour. The planter can be constructed of stone, concrete, brick, wood or other durable material. Specific Design Issues for Advanced Systems (2- F): Recent research on Bioretention has led to more advanced systems that are capable of greater reductions of certain targeted pollutants. One promising technology for reducing phosphorus levels in stormwater runoff involves the use of water treatment residuals (WTR) in the media mix. Other media supplements such as activated charcoal, sawdust and even shredded paper have also been shown to improve removal Another approach of certain constituents from stormwater runoff. employs modifications to the configuration of the bioretention system t o retain a portion of the accumulated stormwater. This so-called internal water storage (IWS) design has been shown to reduce soluble nitrogen levels ioretention facility by inducing an anaerobic condition within the B itself. While this research looks pr omising, design specifications have not been developed to date. However, the Department recognizes that the technology in this field is evolving rapidly and encourages the use of the latest advances in science. Advanced systems will be evaluated on a cas e-by-case basis and assigned performance credits as deemed appropriate by the Department until formally adopted into these Standards and Specifications. Practice Sizing : Bioretention will typically be sized to treat a ll or a portion of the RP , and can v through volume contained in the surface ponding area, soil media, and also partially meet the C v gravel reservoir layers of the practice. The following equations are provided to assist designers in determining an optimal sizing for the facility. However traditional sizing approaches using design volume, void ratio of the stone and biosoil media, etc. are also acceptable. 7/3/2014 18 3.06.2.2-

36 BMP Standards and Specifications Bioretention Equation 2.1 First, designers should calculate the total storage volume of the practice using Equation 2.1 ( ) [ ] ( ) = + d SA Sv η η × + × × d Sv d SA SA + × + 2 / ) ( p media filter − − nt pretreatme ponding p 2 1 gravel gravel media Where: Sv = total storage volume of practice (cu. ft.) surface area of the top of the filter media (sq. ft.) = SA filter depth of the filter media ( typically 2 ft) = d media η = effective porosity of the filter media (t ypically 0. 4) media d = depth of the underdrain and underground storage gravel layer (ft) gravel of the gravel layer (typically 0. = effective porosity η 4) gravel SA = surface area at the lowest elevation of the ponding area (sq. ft.) p-1 [Note SA may be no greater than 2X SA ] filter p-1 SA surface area at the depth of ponding = p-2 = the maximum ponding depth of the practice (ft). d ponding volume stored in pretreatment practices = Sv pretreatment 2.1 can be modified if the storage depths of the biosoil media, gravel layer, or ponded Equation water vary in the actual design or with the addition of any surface or subsurface storage components (e.g., additional area of surface ponding, subsurface storage chambers, etc.). The n the B ioretention facility should not exceed 24 inches. If storage maximum depth of ponding i -line or in series with the bioretention area , the storage practices practices will be provided off S pecification should be sized using the guidance in Detention Practices 10.0, Minimum Filter Surface Area The filter should be designed with sufficient surface a rea to dewater within 48 hours (Equation 2.2). If the surface area used in Equation 2.1 is insufficient to allow for this drawdown time, the designer should increase the surface area of the practice, or adjust the value of Sv to reflect a volume that can be drawn down in this time. Equation 2.2 Sv × d media ≥ SA filter d   ponding × × + d t k   d media 2   Where: k = filtering media permeability (ft/day; typically assume 5.7) thin the filter (2 days maximum) = drawdown time wi t d 7/3/2014 3.06.2.2- 19

37 BMP Standards and Specifications Bioretention Infiltration Volume : The amount of stormwater that enters the stormwater practice can either be filtered and discharge through an underdrain, or be infiltrated. The volume infiltrated depends on the design variation and is calculated using Equations 2.3 or 2.4. Infiltration Designs with an Underdrain and Sump practices must include a sump (i.e., storage below For designs with an underdrain, Bioretention infiltrate within 48 is assumed to the underdrain, see figure 2.2). The volume stored in the sump hours for the purposes of Equation 2.3. Equation 2.3 ( ) ] [ η i 2 , min Sv × × = d SA infiltrati gravel sump filter on Where: = volume infiltrated through from the practice (cu. ft.) Sv infiltration n(ft) = depth of underground storage gravel layer below the underdrai d sum p i = field -measured infiltration rate for the native soils (ft./day) Infiltration Designs For practices without an underdrain, the volume infiltrated is equal to the entire storage volume, provided that the soil’s infiltration rate is sufficient to infiltrate this volume within 48 hours (equation 2.4). Equation 2.4 ( ) Sv 2 i Sv , min = infiltrati on Filtering Volume: The volume treated by filtration (i.e., filtered through the practice medium and discharged , an d is calculated using equation 2.5. Filtering through an underdrain), is defined as Sv filtering alone is only acceptable for small -scale bioretention variants. For such designs , the filtering volume is equal to the total storage . However, the filter must be sized to achieve the volume minimum treatment volume. Equation 2.5 = − Sv Sv Sv filtering on infiltrati 7/3/2014 3.06.2.2- 20

38 BMP Standards and Specifications Bioretention Ponding Volume : will fill up faster than the collected During high intensity storm events, the bioretention practice nsure that stormwater is able to filter through the soil media. Consequently, it is critical to e sufficient volume is ponded, or stored prior to the filter. The ponding volume is calculated in equation 2.6. Equation 2.6 ( ) / 2 + = × V + SA SA d Sv 1 2 − − ponding p p ponding nt pretreatme can be designed to address, in whole or in part, the detention storage needed to Bioretention conveyance and/or flood control requirements. The comply with can be dis counted from the Sv 10- yr or 100- yr runoff volumes to satisfy stormwater quantity control requirements. Bioretention Landscaping Criteria 2.7 Landscaping is critical to the performance and function of bioretention areas. Therefore, a landscaping plan shall be provided for ioretention facilities . all B imum plan elements should include the proposed bioretention template to be used, Min delineation of planting areas, the planting plan, including the size, the list of planting stock, sources of plant species, and the planting sequence, including post -nursery care and initial Planting plans must be prepared by a qualified professional . maintenance requirements. preferred over non- native species, but some ornamental species may be Native plant species are used for landscaping effect if they are not aggressive or invasive. Some popular native species that work well in bioretention areas and are commercially available can be found in Appendix 2, Stormwater BMP Landscaping Criteria . The degree of landscape maintenance that will determine some of the be provided will also s for urban bioretention areas. Plant selection differs if the area will be frequently planting choice weeded, in contrast to a site which will receive minimum annual mowed, pruned, and maintenance. In areas where less maintenance will be provided and where trash accumulation in shrubbery or herbaceous plants is a concern, consider a “turf and trees” landscaping model where the turf is mowed along with other turf areas on the site . Spaces for herbaceous flowering plants can be included 21 3.06.2.2- 7/3/2014

39 BMP Standards and Specifications Bioretention 2.8 Bioretention Construction Sequence Controls Bioretention facilities should be fully protected by sil t fence Erosion and Sediment . facilities should remain undisturbed or construction fencing. Ideally, B ioretention during Large Bioretention facilities may construction to prevent soil compaction by heavy equipment. be used as small sediment traps or basins during construction. However, these must be accompanied by notes and graphic details on the Sediment & Stormwater Plan specifying that (1) of the trap or basin at the construction stage must be at least 1 the maximum excavation depth higher than -construction foot (final) inver t (bottom of the facility) , and (2) the bottom of the post f the facility is the facility shall be ripped, tilled or otherwise scarified upon final excavation. I -measured infiltration rate must be verified through designed for infiltration, the original field retes ting . The plan must also show the proper procedures for converting the temporary sediment Bioretention facility , including dewatering, cleanout and control practice to a permanent stabilization. Bioretention Installation . The following is a typical const ruction sequence to properly install a (also see Figure 2.3 ). The construction sequence for small- scale Bioretention facility Bioretention is more simplified. These steps may be modified to reflect different Bioretention applications or expected site condi tions: Step 1 ioretention facility may only begin after the entire contributing . Construction of the B drainage area has been stabilized with vegetation. It may be necessary to block certain curb or cted. The proposed site should be checked other inlets while the bioretention area is being constru for existing utilities prior to any excavation. Step 2. The designer and the installer should have a preconstruction meeting, checking the boundaries of the contributing drainage area and the actual inlet elevations to ensure they conform to original design. Since other contractors may be responsible for constructing portions of the site, it is quite common to find subtle differences in site grading, drainage and paving elevations that can produce hydraulically imp ortant differences for the proposed B ioretention . The designer should clearly communicate, in writing, any project changes determined facility during the preconstruction meeting to the installer and the plan review/inspection authority. Step 3. Temporary erosion and sediment controls (e.g., diversion dikes, reinforced silt fence) are needed during construction of the B ioretention to divert stormwater away from the facility facility until it is completed. Special protection measures such as ero Bioretention sion control fabrics may be needed to protect vulnerable side slopes from erosion during the construction process. Step 4 . Any pre -treatment cells should be excavated first . . Excavators or backhoes should work from the sides to excavate the Bioret ention facility Step 5 to its appropriate design depth and dimensions. Excavating equipment should have adequate 7/3/2014 3.06.2.2- 22

40 BMP Standards and Specifications Bioretention reach so they do not have to sit inside the footprint of the B . Contractors ioretention facility etention basins, whereby the basin is split should use a cell construction approach in larger bior into 500 to 1,000 sq. ft. temporary cells with a 10- 15 foot earth bridge in between, so that cells can be excavated from the side. Step 6. or till the bottom soils to a depth of 6 to 12 inches to promote It may be necessary to rip if a bucket without teeth is used for excavation . greater infiltration . for an underdrain design, place the appropriate depth Step 7 If a stone storage layer will be used rice gravel on the bottom, install the perforated underdrain pipe, pack rice gravel to 3 inches of . A layer of rice gravel may also be necessary for an infiltrating design above the underdrain pipe media does not reach a permeable layer in the soil profile. if the 24” biosoil T he biosoil media must come from an approved Step 8. . If not used upon delivery, store supplier it on an adjacent impervious area or plastic sheeting. Apply the media in 12- inch lifts until the desired top elevation of the Bioretention facility is achieved. Wait a few days to check for settlemen t, and add additional media , as needed, to achieve the design elevation. Sprinkling with water between lifts may reduce the amount of settling that occurs. Step 9. Prepare planting holes for any shrubs and plants , install the vegetation, and water accord ingly. Install any temporary irrigation. . Place the surface cover in Step 10 ), depending on the design. both cells (mulch, river rock, etc. If matting will be used in areas that will be planted , the matting will need to be stabilization installed prior to Step 9 ), and holes or slits will have to be cut in the matting to install planting ( the plants. Step 11. Install the plant materials as shown in the landscaping plan, and water them during weeks of no rain for the first two months. Step 12. If curb cuts or inlets are blocked during bioretention installation, unblock these after the drainage area and side slopes have good vegetative cover. It is recommended that unblocking ea includes newly curb cuts and inlets take place after two to three storm events if the drainage ar installed asphalt, since new asphalt tends to produce a lot of fines and grit during the first several storms. Step 1 3 . Conduct the final construction inspection (see below ), then log the GPS coordinates for each bioretention facility and submit them for entry into the local maintenance tracking database. 7/3/2014 3.06.2.2- 23

41 BMP Standards and Specifications Bioretention Construction Sequence Figure 2.3. Typical Bioretention An example construction phase inspection checklist is available in the Construction Inspection. hnical Document. appropriate section of the Tec The following items shall be included in the Post Construction Verification Documentation. Post Construction Verification Documentation for Practices: Bioretention • Surface dimensions of biosoil bed. • Depth of biosoil media. • ions of any pre -treatment component. Volume dimens Elevations of any structural components, including inverts of pipes, weirs, etc. • 2.9 Bioretention Maintenance Criteria An Operation and Maintenance Plan for the project will be approved by the Department or the Delega The Operation and Maintenance Plan will specify ted Agency prior to project closeout. the property owner’s primary maintenance responsibilities and authorize the Department or 24 3.06.2.2- 7/3/2014

42 BMP Standards and Specifications Bioretention Delegated Agency staff to access the property for maintenance review or corrective action in the that are, or will be, Practices event that proper maintenance is not performed. Bioretention owned and maintained by a joint ownership such as a homeowner’s association must be located ned property, jointly owned property, in common areas, community open space, community -ow or within a recorded easement dedicated to public use. Operation and Maintenance Plans should clearly outline how vegetation in the Bioretention Practice will be managed or harvested in the future. The Operation and M aintenance Plan should schedule a cleanup at least once a year to remove trash and debris. Practices Maintenance of Bioretention is driven by annual maintenance reviews that evaluate the Based on maintenance rev and performance of the practice. condition iew results, specific maintenance tasks may be required. Table 2.6. Typical Bioretention Maintenance Items and Frequency Frequency Maintenance Items s of Inspect the site after storm event that exceed s 0.5 inche • rainfall. Stabilize any bare or eroding areas in the contributing • perimeter area drainage area including the Bioretention During establishment, as needed (first • Water trees and shrubs planted in the Bioretention planting year) during the first growing season. In general , water bed every 3 days f or first month, and then weekly during the remainder of the first growing season (April - October), depending on rainfall. Quarterly or after major storms Remove debris and blockages • (>1 inch of rainfall) Repair undercut, eroded, and bare soil areas • vegetated perimeter area and Mowing of the Bioretention • ce a year Twi banks (as directed in approved O&M plan) • Cleanup to remove trash, debris and floatables • A full maintenance review Annually Check condition of outlet structure • • Repair broken mechanical compo nents, if needed – during the One time • Bioretention planting bed replacement/ reinforcement second year following construction plantings (as applicable) Forebay sediment removal • Every 5 to 7 years • Flush underdrain system (as applicable) and spillway, as needed • Repair pipes, outlet structure From 5 to 25 years • Remove any accumulated sediment within facility, as needed 7/3/2014 3.06.2.2- 25

43 BMP Standards and Specifications Bioretention 2.10 References National Pollutant Removal Performance Database, Version 3.0 . Center for CWP. 2007. Watershed Protection, Ellicott City, M D. Hirschman, D., L. Woodworth and S. Drescher. 2009. Technical Report: Stormwater BMPs in An Assessment of Field Conditions and Programs . Center for Virginia’s James River Basin – Watershed Protection. Ellicott City, MD. Hunt, W.F. III and W.G. Lord. 2006. “Bioretention Performance, Design, Construction, and North Carolina Cooperative Extension Service Bulletin. Maintenance.” Urban Waterways Series. AG- 588- 5. North Carolina State University. Raleigh, NC. Saxton, K.E., W.J. Rawls, J.S. Romberger, and R.I . Papendick. 1986. “Estimating generalized soil -water characteristics from texture.” Soil Sci. Soc. Am. J. 50(4):1031- 1036. Maryland Department of the Environment. 2001. Maryland Stormwater Design Manual . http://www.mde.state.md.us/Programs/WaterPrograms/SedimentandStormwater/stormwater_design/index.asp Prince George’s Co., MD. 2007. . Available online at: Bioretention Manual http://www.princegeorgescountymd.gov/Government/AgencyIndex/DER/ESG/Bioretention/pdf/Bioretent ion%20Manual_2009%20Version.pdf Schueler, T. 2008. Technical Support for the Baywide Runoff Reduction Method. Chesapeake www.chesapeakestormwater.net Stormwater Network. Baltimore, MD. Smith, R.A. and Hunt, W.F. III. 1999. “Pollutant Removal in Bioretention Cells with Grass Cover” Smith, R. A., and Hunt, W.F. III. 2007. “Pollutant removal in bioretention cells with grass cover.” Pp. 1- 11 In: Proceedings of the World Environmental and Water Resour ces Congress 2007 . Virginia DCR Stormwater Design Specification No. 9: Bioretention Version 1.8. 2010 . Wisconsin Department of Natural Resources. Stormwater Management Technical Standards . http://www.dnr.state.wi.us/org/water/wm/nps/stormwater/techstds.htm#Post 7/3/2014 3.06.2.2- 26

44 BMP Standards and Specifications Permeable Pavement 3.0 Permeable Pavement Systems Definition: Paving surfaces that capture and temporarily by store stormwater runoff through filtering voids in the pavement surface into an underlying reservoir . Filtered runoff may be collected and returned to the ce system, or conveyan nfiltrate into allowed to i the soil. Design variants include: 3- A Porous  (PA) Asphalt  3- B Pervious Concrete (PC) avers (CP) Concrete grid P or (PP) avers Permeable interlocking concrete P  3- C 3- D Plast ic Grid Pavers (GP)  Other variat ions of permeable pavement that are DNREC approved permeable pavement surface materials are also encompassed in this section. Permeable pavement systems may be designed to provide stormwater detention for all design storm events are actices . Permeable pavement pr that are unable to infiltrate all design storms . for larger runoff events often combined with a separate facilit ies to provide controls Regardless of which design variant is chosen, the runoff reduction credit applied to the practice eservoir is the volume of runoff that is being stored in the r layer underneath the permeable hours. It is recommended that an underdrain and pavement and infiltrated over a period of 48- control structure be constructed within the reservoir for long term maintena nce and facilit y inspections. The particular design configuration to be implemented on a site is typically dependent on soils. specific site conditions and the characteristics of the native 3.06.2. 03/2013 3- 1

45 BMP Standards and Specifications Permeable Pavement 2 3.06.2.3- 03/2013

46 BMP Standards and Specifications Permeable Pavement Permeable Pavement Stormwater Credit Calcul ations 3.1 The retention volume credit for permeable pavement depends on the volume of runoff that is infiltrated from this practice (Table 3.1). 3 .1 Permeable Pavement Performance Credits Runoff Reduction Retention Allowance 100% A/B Soil - RPv Storage Retention 100% of Retention - C/D Soil 100% of RPv Storage Storage Cv 100% of Retention Storage Retention Fv 100% of Pollutant Reduction TN Reduction 100% of Load Reduction 100% of Load Reduction TP Reduction TSS Reduction 100% of Load Reduction Section The practice must be sized using the guidance detailed in 3.6. Permeable Pavement Design Criteria. 3 03/2013 3.06.2.3-

47 BMP Standards and Specifications Permeable Pavement 3.2 Permeable Pavement Design Summary Table 3.2 summarizes design criteria for permeable pavement, and Tables 3.3 and 3.4 summarize pecifications for this practice. For more detail, consult Sections 3.3 through 3.7. the materials s Sections 3.8 and 3.9 describes practice construction and maintenance criteria. Design Table 3 .2 Permeable Pavement Summary Feasibility Minimum soil • infiltration of 1”/hr, unless an underdrain is used (Section 3.3) External drainage close to 100% impervious • Pavement surface < • 3% slope , unless an underdrain is used. If • Minimum 2’ separation to seasonal high groundwater water shall not enter into the reservoir an underdrain is used the seasonal high ground Cannot treat hotspots or areas with high pollutant loads • • Cannot treat high speed roads • Setbacks from wells, buildings and utilities (Table 3.5) Conveyance and Safely convey Cv design storms • Fv (Section 3.4) eatment Pretr • Not needed (Section 3.5) Sizing (Reservoir Layer 1 { } P ( ) ( × + − ) d × R t i f c 2 Depth ) d = p (Section 3.6) η r Depth of the reservoir layer (ft.) d = Variables: p d Depth of runoff from the contributing drainage area (not including the = c ce) for the design storm (ft.) permeable pavement surfa R = A /A = The ratio of the contributing drainage area (A ) (not including c c p the permeable pavement surface) to the permeable pavement surface area ) (A p = The rainfall depth for the design storm (ft.) P native -verified i = The field infiltration rate for the soils (ft./day). If an impermeable liner is used in the design then i = 0. = The time to fill the reservoir layer (day) – assume 1 day t f = The effective porosity for the reservoir layer (0. 4) η r Landscaping (Section Not applicable .7) 3 4 03/2013 3.06.2.3-

48 BMP Standards and Specifications Permeable Pavement Material Specifications : Permeable pavement material specifications vary according to the specific pavement product selected. A general comparison of different permeable pavements is Table provided in manufacturer’s technical specifications for , but designers should consult 3.3 specific criteria and guidance. Table 3.3. Different Permeable Pavement Specifications Material Notes Specification Surface open area: 5% to 15%. Permeable Must conform to specifications. ASTM C936 inches for vehicles. Thickness: 3.125 Interlocking Reservoir layer required to support the Compressive strength: 55 Mpa. Concrete Pavers structural load. Open void fill media: aggregate (PP) Open void content: 20% to 50%. Must conform to ASTM C 1319 Thickness: 3.5 inches. specifications. Concrete Grid Compressive strength: 35 Mpa. Reservoir layer required to support the (CP) Pavers Open void fill media: aggregate, topsoil structural load. and grass, coarse sand. depends on fill material. Void content: Compressive strength: varies, depending Reservoir layer required to support the Plastic Reinforced on fill material. structural load. (GP) Grid Pavers Open void fill media: aggregate, topsoil and grass, coarse sand. %. Void content: 15% to 25 May not require a reservoir layer to support Thickness: typically 4 to 8 inches. Pervious Concrete the structural load. Compressive strength: 2.8 to 28 Mpa. (PC) Open void fill media: None Void content: 15% to 20 %. ing Thickness: typically 3 to 7 in. (depend Reservoir layer required to support the Porous Asphalt on traffic load). structural load. (PA) Open void fill media: None. eneral material specifications for the component structures installed describes g 3.4 Table beneath the permeable pavement. Note that the size of stone materials used in the reservoir and filter layers may differ depending on the type of surface material. 5 03/2013 3.06.2.3-

49 BMP Standards and Specifications Permeable Pavement Table 3.4. Material Specifications for Underneath the Pavement Surface Specification Notes Material e over PP: 2 in. depth of No. 8 ston ASTM D448 size No. 8 stone (e.g. , 3/8 to 3/16 3 to 4 inches of No. 57 stone -washed and free inch in size). Should be double Bedding Layer PC: None of all fines. PA: 2 in. depth of No. 8 stone ASTM D448 size No. 57 stone (e.g. 1 1/2 to 1/2 inch in size); No. 2 Stone (e.g. 3 inch to 3/4 inch PP: No. 57 stone in size). Depth is based on the pavement PC: No. 57 stone Reservoir Layer structural and hydraulic requirements. Should be PA: No. 2 stone double -washed and clean and free of all fines. servoir layer shall be at least 6” deep. The re Use 4 to 6 inch diameter perfor (or equivalent corrugated HDPE may be used pipe ated PVC forations at 6 inches on center. for smaller load inch per -bearing applications), with 3/8- - Perforated pipe installed for the full length of the permeable pavement cell, and non Underdrain perforated pipe, as needed, is used to connect with the storm drain system. T’s and Y’s installed as needed, depending on the underdrain configuration. Extend cleanout pipes to the ented caps at the Ts and Ys. surface with v An aggregate The depth of the reservoir layer storage layer below the underdrain invert. above the invert of the underdrain must be at least 12 inches. The material specifications are Infiltration Sump the same as Reservoir Layer . may require The underlying native soils The choker stone layer should be a minimum of separation from the stone reservoir by a Filter Layer m of 1” per foot of 1” thick, and a minimu thin layer of choker stone as determined (optional) reservoir depth. by geotechnical investigation . woven, polypropylene geotextile with a Flow Rate greater than 125 - Use a needled, non Non - woven gpm/sq. ft. (ASTM D4491), and an Apparent Opening Size (AOS) equivalent to a US # 70 Geotextile STM D4751). or # 80 sieve (A (optional) Use a perforated 4 to 6 inch vertical PVC pipe (AASHTO M 252) with a lockable cap, Observation Well or just beneath P installed flush with the surface P. 3.3 Permeable Pavement Feasibility Criteria Since permeable pavement has a very high r unoff reduction capability, it should always be considered as an alternative to conventional pavement. Permeable pavement is subject to the same feasibility constraints as most infiltration practices, as described below. Required Space. A prime advantage of permeable pavement is that it does not normally require additional space at a new development or redevelopment site, which can be important for tight sites or areas where land prices are high. Soils. Soil conditions do not typically constrain the use o f permeable pavement , although they do determine whether an underdrain is needed. Underdrains are required if the measured , per the in/hr 1.0 soils is less than native on-site soil investigation methods permeabilit y of the in . 1 provided Appendix Exter Any external drainage area contributing runoff to permeable nal Drainage Area. 6 03/2013 3.06.2.3-

50 BMP Standards and Specifications Permeable Pavement the surface pavement should never exceed five times area of the permeable pavement (two times is recommended) , and it should be as close to 100% impervious as possible. nt pavement surface slopes can reduce the stormwater storage Steep Slope. Paveme Surface capability of permeable pavement and may cause shifting of the pavement surface and base materials. Designers should use a terraced design for permeable pavement when the local slope is 3 percent or greater. Pavement Bottom Slope. The bottom slope of a permeable pavement installation should be as slope s) to enable even distribution and flat as possible (i.e., 0% longitudinal and lateral infiltrat ion o f stormwater. On sloped s terraces ites, internal check dams or can be incorporated into the subsurface to encourage infiltration. If an underdrain is used, low -grade l ongitudinal slope . by-case basis on a case- s are permissible Minimum Hydraulic Head. The elevation difference needed for permeable pavement to function properly is generally nominal . A minimum vertical distance of 2 feet must be provided Minimum Depth to Water Table. between the bottom of the permeable pavement installation (i.e., the bottom invert of the reservoir if an underdrain system is not used. If an layer) and the seasonal high water table underdrain is used, the seasonal high groundwater may not encroach . into the reservoir layer not be To avoid the risk of seepage, permeable pavement practices should Setbacks. hydraulically connected to structure foundations. Setbacks to structures vary based on the size of the permeable pavement installation (Table 3.5) Table 3.5. Setbacks for Permeable Pavement Buildings Wells/ Utilities Pavement Area Up - Gradient D own - Gradient 100’ from wells ’ 5 2 250 to 1,000 sf 5 ’ -gradient from 5’ down 0’ ’ 1,000 to 10,000 sf 1 0 5 utility lines >10,000 sf 100 25 ’ ’ *Note: In some cases, the use of an impermeable liner along the sides of the g from the surface to the bottom of permeable pavement practice (extendin the reservoir layer) may be used as an added precaution against seepage, and by-case may be removed or relaxed on a case- the setback requirements . basis not be used to t reat hotspot runoff. For a list Hotspot Land Uses. ould Permeable pavements sh 4 Appendix , consult . of potential stormwater hotspot operations 7 03/2013 3.06.2.3-

51 BMP Standards and Specifications Permeable Pavement intended to treat sites with not Permeable pavement is High Pollutant Loading Situations. sediment or trash/debris loads, since such loads will cause the practice to clog and fail. Sites wit h significant pervious area (newly established turf and landscaping) are considered high loading sites and the pervious areas should be diverted from the permeable pavement area. If unavoidable, an increased maintenance sch edule to check for clogging may be required on a . by-case basis case- Permeable pavement is recommended for sidewalks, driveways, residential High Speed Roads. streets, parking areas, shoulders, and gutter sections. Permeable pavement should not be used for high speed roads with prior approval from DelDOT or other applicable roadway agency. 3.4 Permeable Pavement Conveyance Criteria Permeable pavement designs should include methods to convey larger storms (e.g., Cv , Fv ) to other stormwater management . The following is a list of methods that can be used to facilities accomplish this: • Place an underdrain in the bottom of the reservoir layer and attached to a control structure, designed to pass excess flows after water has filled the reservoir layer. , to Place a n over flow pipe; a perforated pipe horizontally near the top of the reservoir layer • water has filled the reservoir layer pass excess flows after storm . Increase the thickness of the reservoir layer to increase storage (i.e., create freeboard) to • accommodate the Cv and Fv events . addit ional • Create underground detention within the reservoir layer of the permeable pavement system using structural void space. Reservoir storage may be augmented by plastic or concrete arch structures, etc. • Route excess flows to another detention or conveyance system that is designed for the flows. greater event management of Set the storm drain inlets flush with the elevation of the permeable pavement surface to • The design should also make effectively convey excess stormwater runoff past the syste m. allowances for relief of unacceptable ponding depths during larger rainfall events . 3.5 Permeable Pavement Pretreatment Criteria Pretreatment for most permeable pavement applications is not necessary, since the surface acts as pretreatment to the reservoir layer below. Pretreatment - if the pavement receives run is necessary on from adjacent pervious areas can be placed strip grass buffer or gravel . For example, a adjacent to pervious (landscaped) areas to trap coarse sediment particles before they reach the clogging. pavement surface, in order to minimize Permeable Pavement Criteria Design 3.6 Type of Surface Pavement: The type of pavement should be selected based on a review of the 8 03/2013 3.06.2.3-

52 BMP Standards and Specifications Permeable Pavement pavement specifications and properties , a nd designed according to the product manufacturer’s recommendations. Internal Geometry and Drawdowns:  Rapid Drawdown. Permeable pavement should be designed so that the target storage - before is detained in the reservoir for as long as possible – up to 48 hours vo lume attached to a control structure n underdrain infiltration. A through ing completely discharg a minimum orifice size of 0.5” ( recommended regardless of the calculated drawdown with will only be based off of time) may also be emplo yed. Runoff Reduction retention volumes runoff infiltrated . To promote greater runoff reduction for permeable pavement located on  Infiltration Sump. infiltration sump can be installed marginal soils, an storage layer below the to create a underdrain invert. ve Infiltration Conservati Rates.  Designers should always decrease the measured infiltration rate by a factor of 2 during design, to approximate long term infiltration rates. reservoir layer consists of the stone underneath the pavement section and Reservoir layer: The total . The thickness of the reservoir layer is above the bottom filter layer or underlying soils soils, structural requirements of determined by runoff storage needs, the infiltration rate of native the seasonal high wat base, depth to the pavement sub- er table and bedrock, and frost depth conditions. A geotechnical engineer should be consulted regarding the suitability of the soil subgrade. The reservoir layer should be composed of clean, double -washed stone aggregate and sized  to be treated and the structural requirements of the expected traffic for both the storm event loading. The  reservoir layer should consist of clean double -washed Delaware No. 3 stone, unless a specific site constraint or structural concern requires different stone sizing.  The bott om of the reservoir layer should be completely flat so that runoff will be able to infiltrate evenly through the entire surface. For sites with native slope that do not allow for a . flat bottom, the bottom should either be terraced or check dams should be installed ). 3.3 Most permeable pavement designs will require an underdrain (see Section Underdrains: Underdrains can also be used to keep detained stormwater from flooding permeable pavement of permeable pavement designs, . Flat terrain may affect proper drainage during extreme events so underdrains should have a minimum 0.5% slope . Underdrains should be located 20 feet or less . The underdrain should be perfo rated schedule 40 PVC pipe, with 3/8 -inch from the next pipe perforations at 6 inches on center , or corrugated HDPE depending on load -bearing application . The underdrain should be encased in a layer of clean, washed No.57 stone with a minimum of 2” of stone below the underdrain pipe . The underdrain system should include a flow control to hours. ensure t hat the reservoir layer drains slowly; however it should completely drain within 48  -reduction orifice within a weir or other easily The underdrain outlet can be fitted with a flow inspected and maintained configuration in the downstream manhole as a means of regulating The the stormwater detention time. The minimum diameter of any orifice should be 0.5 inch. hours verify that the volume will draw down completely within 48 will designer 9 03/2013 3.06.2.3-

53 BMP Standards and Specifications Permeable Pavement  For infiltration designs, an underdrain(s) can be installed into a c ontrol structure that has an full outlet higher than the underdrain inlet in order to promote infiltration vo lume, while the still allowing for overflow within the system. In this scenario, a lower capped drain should also be installed for future maintena nce.  downstream structure for Alternatively , an underdrain(s) can be installed and capped at the future use if maintenance observations indicate a reduction in the soil permeability. All permeable pavement practices should include observation wells. The observation well is used to observe the rate of drawdown within the reservoir layer following a storm event and to facilitate periodic inspection and maintenance. The observation wells should consist of a well - anchored, perforated 4 to 6 inch (diameter) P VC pi pe that is tied into the underdrain system. The well should extend vertically to the bottom of the reservoir layer and extend upwards to be flush with with the surface (or just under pavers) a lockable cap . In addition, cleanout pipes should be pro vided if the pavement surface area exceeds 1,000 sq. ft. Infiltration Sump (optional): A n optional upturned elbow , elevated underdrain , or other control structure configuration can be used t o promote greater runoff reduction for permeable pavement ils (see 3.2) . The Infiltration Sump allo w s for the design of Figure located on marginal so invert above the . The depth of the reservoir layer infiltration reservoirs even in marginal soils of be at least 12 inches. The depth of th infiltrat ion sump is sized so that the the underdrain must in a 48 hour period. design storm can infiltrate into the native soil with If no underdrain is emplo yed, t he bottom of infiltration sump must be at least 2 feet above the seasonal high water table. The inclusio n of an infiltra tion sump is not permitted for designs with an impermeable liner. (optional) To protect the bottom of the reservoir layer from intrusion by Filter Layer : , a filter layer is underlying soils required in marginal soils . The native soils should be separated from the stone reservoir by a thin, (minimum 1”, or 1”/foot of reservoir) layer of choker stone . (No. 8 or approved equal) ilter fabric is not recommended for the bottom -woven Geotextile (optional): Non -woven f Non . of the reservoir layer as filter fabric can become a future plane of clogging within the system filter fabric is still recommended to protect the excavated sides of the Permeable woven non- polypropylene geotextile reservoir layer, in order to prevent soil piping. A needled, non -woven, with a Flow Rate greater than 125 gpm/sq. ft. (ASTM D4491), and an Apparent Opening Size (AOS) equivalent to a US # 70 or # 80 sieve (ASTM D4751). The geotextile AOS selection is based on the percent passing the No. 200 sieve in “A” s oil subgrade, using FHWA or AAS HTO selection criteria. (optional) Impermeable Liner This material should be used only for appropriate : fill where deemed necessary by a geotechnical investigation . Use a thirty mil applications The -woven geotextile. (minimum) PVC Geomembrane liner covered by 8 to 12 oz./sq. yd. non usage of an impermeable liner precludes any runoff reduction from the permeable pavement. However, the system may still be employed as a stormwater capturing and routing facility 10 03/2013 3.06.2.3-

54 BMP Standards and Specifications Permeable Pavement particularly in densely urban areas. Perme able Pavement Sizing: The thickness of the reservoir layer is determined by both a aul structural and hydr ic design analysis. The reservoir layer serves to retain stormwater and also Permeable pavement st supports the design traffic loads for the pavement. ructural and hydraulic sizing criteria are discussed below: Structural Design. The pavement surface must be able to support the maximum anticipated traffic load. The structural design process will vary according to the type of pavement selected, anufacturer’s specific recommendations . The thickness of the permeable pavement and the m and reservoir layer must be sized to support structural loads and to temporarily store and then infiltrate the design storm volume (e.g., the water quality, channel protection , and/or flood control volumes). On most new development and redevelopment sites, the structural support requirements will dictate the depth of the underlying stone reservoir. The structural design of permeable pavements involves consideration of four mai n site elements: Total traffic; • • soil strength; Native Environmental elements; and • • Bedding and Reservoir layer design. The resulting structural requirements may include, but are not limited to, the thickness of the pavement, filter, and reservoir layer. Designers should note that if the native soils have a California Bearing Ratio (CBR) less than 4%, they may need to be compacted to at least 95% of the Standard Proctor Density, which generally rules out their use for infiltration. As such, if the underlying soils are found to be sub -standard an additional amount of subsoil may need to be excavated and replaced to increase the structural capacity of the system. Designers should determine structural design requirements by consulting transportation design gui dance sources, such as the following: AASHTO Guide for Design of Pavement Structures (1993); and, • AASHTO Supplement to the Guide for Design of Pavement Structures (1998). • Permeable pavement is typically sized to store stormwater runoff in the Hydraulic Design. reservoir layer . The storage volume in the permeable pavement system must account for the or overflow structure . The design underlying infiltration rate and flow through any underdrain required reservoir depth. is routed through the pavement to accurately determine the storm The depth of the reservoir layer needed to store the design storm or infiltration sump can be . 3.1 Equation determined by using 11 03/2013 3.06.2.3-

55 BMP Standards and Specifications Permeable Pavement Equation 3.1 1 } { × + − ( × ) ( ) R d P i t c f 2 = d p η r Where: d (ft.) = Depth of the reservoir layer p d = Depth of runoff from the contributing drainage area (not including the c permeable pavement surface) for the design storm (ft.) R = A /A = The ratio of the contributing drainage area (A ) (not including the c p c ) permeable pavement surface) to the permeable pavement surfa ce area (A p P = The rainfall depth for the design storm (ft.) i soils (ft./day). If an = The field -verified infiltration rate for the native impermeable liner is used in the design then i = 0 . t day hours or 1 24 assume = The time to fill the reservoir layer (day) – f η for the reservoir layer (0. = The effective porosity 4) r This equation makes the following design assumptions: • The contributing drainage area (A ) does not contain pervious areas. c For design purposes, the field- tested subgrade soil infiltrat ion rate (i) is divided by 2 as a • factor of safety to account for potential compaction during construction . If the nat i ve so i l will be compacted to meet structural design requirements of the pavement section, the design infiltration rate of the subgrade soil shall be b ased o n m easur em ent o f t he infiltration rate of the subgrade soil subjected to the compaction requirements. For design with underdrains, calculate s using the hydrological routing or the drawdown time modeling procedures used for detention systems with th r the e depth and head adjusted fo ensure that the practice will draw down within 48 hours. to porosity of the aggregate The depth of the reservoir layer cannot be less than the depth required to meet the pavement T increased structural requirement. to meet he depth of the reservoir layer may need to be structural or larger storage requirements , and shall always be a minimum of 6” deep. For crediting purposes (see Section ), 3.1 Permeable Pavement Stormwater Credit Calculations Equation 3.2. the total storage volume pro vided by the practice, Sv , should be determined using Equation 3.2. η = × × Sv d A p r p Depending on the design option, all or a portion of the design volume will be designed to equation also ensures that the volume credited infiltrate, as calculated using Equation 3.3. This with infiltration will draw down within 48 hours. This equation also assumes that the measured soil infiltration rate is divided by 2 due to compaction during construction. 03/2013 3.06.2.3- 12

56 BMP Standards and Specifications Permeable Pavement Equation 3.3. × A , Sv η ) × min( i d = p iltration r s inf Where: Sv = Volume designed to infiltrate through the porous pavement section. infiltration d = depth of the sump or, for designs without an underdrain, depth of the s reservoir Some of the volume stored in the infiltration p ractice is not designed to infiltrate, but is contained within the reservoir, during which time a portion of the volume is evaporated, or detained for a long period . Although the volume calculated as filtering can be equal to the entire storage volume min us the amount infiltrated, no more than 1” of storage within this reservoir can using equation 3. This volume is calculated 4. be considered in crediting this practice. 3.4. Equation ( ) 630 , , 3 min − = × Sv A Sv Sv inf p iltration filtering Detention Storage Design : Permeable pavement can also be designed to address, in whole or in and/or Various requirements. Fv part, the detention storage needed to comply with Cv can be modeled by factoring in storage within the stone aggregate layer, expected approaches tructures used as part of the design. Routing calculations can also be infiltrat ion, and any outlet s used to provide a more accurate solution of the peak discharge and required storage volume. Once runoff passes through the surface of the permeable pavement system, designers should calculate outflow pathways to handle subsurface flows. Subsurface flows can be regulated using underdrains, the volume of storage in the reservoir layer, the bed slope of the reservoir layer, e Pavement Conveyance 3.4 Permeabl and/or a control structure at the outlet (see Section Criteria ). Permeable Pavement 3.7 Landscaping Criteria arge- Permeable pavement does not have any landscaping needs associated with it. However, l scale permeable pavement applications should be carefully planned to integrate the t ypical lot (such as trees and islands) in a manner that maximizes landscaping features of a parking runoff treatment and minimizes the risk that sediment, mulch, grass clippings, leaves, nuts, and fruits will inadvertently clog the paving surface. Permeable Pavement Construction Sequence 3.8 Experience has shown that proper installation is absolutely critical to the effective operation of a permeable pavement system. 13 03/2013 3.06.2.3-

57 BMP Standards and Specifications Permeable Pavement Erosion and Sediment Controls . The following erosion and sediment control guidelines must be followed during construction: • All permeable pavement areas should be fully protected from sediment intrusion by silt fence to prevent construction traffic tracking . or construction fencing • Permeable pavement areas should remain outside the limit o f disturbance during construction to prevent soil compaction by heavy equipment. Permeable pavement areas should be clearly marked on all construction documents and grading plans. To prevent soil compaction, heavy out of permeable pavement areas during and vehicular and foot traffic should be kept immediately after construction. If compaction occurs, an additional geotechnical investigation may be required to determine that the native soils are still capable of infiltrating. All stormwater calculations wi ll need to be revised to match the revised compacted native soil infiltration capacity. be taken to avoid tracking must permeable • During construction, care sediments onto any pavement surface to avoid clogging. • not be used as a temporary sediment basin. permeable pavement shall s intended to be Area ocating a sediment basin on an area intended for permeable pavement is unavoidable, When l the invert of the sediment basin must be a minimum of 1 above the final design elevation foot of the bottom of the reservo ir course. All sediment deposits in the excavated area sh all be carefully removed prior to installing the subbase. The installation of permeable pavement systems should Permeable Pavement Installation. e following is a typical construction follow the manufacturers recommended guidelines. Th sequence, which will be modified per manufacturer’s recommendations: Construction of the permeable pavement shall only begin after the entire contributing . Step 1 hould be checked for existing utilities prior drainage area has been stabilized. The proposed site s to any excavation. Do not install the system in rain or snow, and do not install frozen bedding materials. As noted above, temporary erosion and sediment controls are needed during installation Step 2. rt stormwater away from the permeable pavement area until it is completed. Addit ional to dive protecti ve measures such as erosion control fabrics may be needed to protect vulnerable side slopes from erosion during the excavation process. The proposed permeable pav ement area must be kept free from sediment during the entire construction process. Construction materials contaminated by sediments must be removed and replaced with clean materials. should work from the sides to excavate the reser Heavy equipment . Step 3 vo ir layer to its . For small appropriate design depth and dimensions to minimize compaction of the subsoil pavement applications, excavating equipment should have arms with adequate extension so they e pavement area. For larger pavement do not have to work inside the footprint of the permeabl applications, contractors can utilize a cell construction approach, whereby the proposed permeable pavement area is split into 500 to 1000 sq. ft. temporary cells with a 10 to 15 foot earth bridge in between, so cells can be excavated from the side. Excavated material should be 14 03/2013 3.06.2.3-

58 BMP Standards and Specifications Permeable Pavement placed away from the open excavation so as to not jeopardize the stability of the side walls. Step 4. The native soils along the bottom of the permeable pavement system should be scarified led to a depth of 3 to 4 inches . or til 5. Provide a minimum of 2 inches of aggregate above and below the underdrain. The Step underdrain should slope towards the outlet at a grade of 0.5% or steeper. The up -gradient end s of the underdrain should be capped. Wher e an underdrain pipe is connected to a structure, there shall be no perforations within 1 foot of the structure. T the no perforations in to be here are -outs and observation wells within 1 foot of the surface. clean No. Step 6. Spread 6 -inch lifts of the appro priate washed stone aggregate ( Delaware 3 or approved equal inches of additional aggregate cover above the underdrain, and ). Place at least 2 then compact until there is no visible movement of the aggregate, but do not crush the aggregate with the comp action equipment . , per manufacturer’s recommendations. 7. layer Step Install the bedding , or , industry Paving materials shall be installed in accordance with manufacturer 8. Step specifications for the particular type of pavement. Examples as shown below: engineer’s Installation of Porous Asphalt. • The following has been excerpted from various documents, most notably Jackson (2007). o Install porous asphalt pavement similarly to regular asphalt pavement. The pavement course. The laying temperature should be should be laid in a single lift over th e bedding o o o between 230 F. F and 260 F, with a minimum air temperature of 50 Complete compaction of the surface course when the surface is cool enough to resist a o uired for proper compaction. More ton roller. One or two passes of the roller are req 10- rolling could cause a reduction in the porosity of the pavement. o The mixing plant must provide certification of the aggregate mix, abrasion loss factor, and asphalt content in the mix. Test the asphalt mix for its resistan ce to stripping by water using ASTM 1664. o Transport the mix to the site in a clean vehicle with smooth dump beds sprayed with a non- petroleum release agent. The mix shall be covered during transportation to control cooling. ement surface by application of clean water at a rate of at Test the permeability of the pav o least five gallons per minute over the entire surface. All water must infiltrate directly, without puddle formation or surface runoff. Inspect the facility 18 to 30 hours after a rainfall greater o than 1/2 inch, to determine if the facility is draining properly. • The basic installation sequence for pervious concrete is Installation of Pervious Concrete. outlined by the American Concrete Institute (2008). It is strongly recommended that concrete allers successfully complete a recognized pervious concrete installers training program, inst 15 03/2013 3.06.2.3-

59 BMP Standards and Specifications Permeable Pavement such as the Pervious Concrete Contractor Certification Program offered by the NRMCA. The installation procedure is as follows: basic o Drive the concrete truck as close to the project site as possible. o Water the underlying aggregate (reservoir layer) before the concrete is placed, so the aggregate does not draw moisture from the freshly laid pervious concrete. o After the concrete is placed, approximately 3/8 to 1/2 inch is struck off, using a vibratory screed to allow for compaction. o Compact the pavement with a steel pipe roller per manufacturer’s recommendation. o Cut joints for the concrete to a depth of 1/4 inch. o The curing process is very important for pervious concrete. Cover the pavement with plastic sheeting within 20 minutes of the strike -off, and keep it covered for at least seven (7) days. Do not allow traffic on the pavement during this time period. o the facility 18 to Remove the plastic sheeting only after the proper curing time. Ins pect 30 hours after a rainfall greater than 1/2 inch, to determine if the facility is draining properly . . The basic installation process is Permeable Interlocking Concrete Pavers • Installation of greater detail by Smith (2006). described in Place edge restraints for open -jointed pavement blocks before the bedding layer and o pavement blocks are installed. Permeable interlocking concrete pavement (IP) systems require edge restraints to prevent vehicle loads from moving the paver blocks. Edge restraints may be standard curbs or gutter pans, or precast or cast -in- place reinforced concrete borders a minimum of 6 inches wide and 18 inches deep, constructed with Class A3 concrete. Edge restraints along the traffic side of a permeable pavement bloc k system are recommended. o Place the No. 57 stone in a single lift. Level the filter course and compact it into the reservoir course beneath with at least four (4) passes of a 10 -ton steel drum static roller until there is no visible movement. The first two (2) passes are in vibratory mode, with the final two (2) passes in static mode. The filter aggregate should be moist to facilitate movement into the reservoir course. o Place and screed the bedding course material (typically No. 8 stone). o Fill gaps at the edge of the paved areas with cut pavers or edge units. Cut pavers no -third (1/3) of the full unit size. smaller than one o Fill the joints and openings with stone. Joint openings must be filled with ASTM D No. 8 stone, although No. 8P or No. 9 stone may be used where needed to fill 448 narrower joints. o Compact and seat the pavers into the bedding course with a minimum low -amplitude Hz plate compactor. 5,000- to 95- lbf, 75- o Do not compact within 6 feet of the unrestrained edges of the pavers. o The system must be thoroughly swept by a mechanical sweeper or vacuumed or excess aggregate. immediately after construction to remove any sediment o Inspect the area for settlement. Any blocks that settle must be reset and re- inspected. o r a rainfall greater than 1/2 inch, to determine the facility 18 to 30 hours afte Inspect if the facility is draining properly . 16 03/2013 3.06.2.3-

60 BMP Standards and Specifications Permeable Pavement Inspections before, during and after construction are needed to ensure Construction Inspection. permeable pavement is built in accordance with these specifications. Use detailed inspection checklists that require sign -offs by qualified individuals at critical stages of construction, to ensure the contractor’s interpretation of the plan is consistent with the designer’s intent. An ecklist for permeable pavement practices can be found example construction phase inspection ch in Article 4 . Some common pitfalls can be avoided by careful construction supervision that focuses on the following key aspects of permeable pavement installation: • Store materials in a protected area t o keep them free from mud, dirt, and other foreign materials. • The contributing drainage area should be stabilized prior to directing water to the permeable pavement area. is • Check the aggregate material to confirm it is double washed, meets specifications and installed to the correct depth. Check elevations (e.g., the invert of the underdrain, inverts for the inflow and outflow points, • etc.) and the surface slope. Make sure the permeable pavement surface is even and the storage bed drains within 48 • hours. Ensure caps are placed on the upstream end of the underdrain. • pretreatment structures to make sure they are properly installed and working • Inspect any effectively. • Once the final construction inspection has been completed, log the GPS coordinates for each facility and submit them for entry into the local BMP maintenance tracking database. to divert the runoff from the first few runoff It is recommended -producing storms away from -gradient conventio nal asphalt larger permeable pavement applications, particularly when up areas drain to the permeable pavement. This can help reduce the input of fine particles often produced shortly after conventional asphalt is laid down. 3.9 Permeable Pavement Maintenance Criteria -term performance of permeable pavement. Maintenance is a crucial element to ensure th e lo ng The most frequently cited maintenance problem is surface clogging caused by organic matter and sediment. Periodic street sweeping will remove accumulated sediment and help prevent clogging, however, it is als o critical to ensure that surrounding land areas remain stabilized. The following tasks must be avoided on ALL permeable pavements: sanding   re-sealing re-surfacing   power washing 17 03/2013 3.06.2.3-

61 BMP Standards and Specifications Permeable Pavement  storage of snow piles containing sand  storage of mulch or soil materials construction staging  An Operation and Maintenance Plan for the project sha ll be approved by DNREC or the The Operation and Maintenance Plan will specify Delegated Agency prior to project closeout. and authorize DNREC or Delegated the property owner’s primary maintenance responsibilities Agency staff to access the property for maintenance review or corrective action in the event that proper maintenance is not performed. Permeable Pavement p that are, or will be, owned ractices and maintained by a joint owne rship such as a homeowner’s association mu st be located in common areas, community open space, community -owned property, jointly owned property, or within a recorded easement dedicated to public use. Maintenance of Permeable Pavement p is driven b y annual maintenance reviews that ractices and performance of the practice. Based on maintenance review results, evaluate the condition specific maintenance tasks may be required. Recommended maintenance tasks are outlined in Table 3.6 . Table 3.6. Recommended ma intenance tasks for permeable pavement practices. 1 Maintenance Tasks Frequency  For the first 6 months following construction, the practice and CDA and after storm events that exceed After installation should be inspected at least twice ded repairs or stabilization. 1/2 inch of rainfall. Conduct any nee As needed in grid paver applications grass Mow  during the growing season Stabilize the contributing drainage area to prevent erosion  Remove any soil or sediment deposited on pavement.  As needed that are Replace or repair an y necessary pavement surface areas  degenerating or spalling  Vacuum pavement with a standard street sweeper to prevent clogging 2 - 4 times per year (depending on use) Conduct a maintenance inspection  Annually  Spot weeding of grass applications sediment in pre - Remove any accumulated  treatment cells and inflow Once every 2 to 3 years points  Conduct maintenance using a regenerative street sweeper If clogged Replace any necessary joint material  1 end on pavement use, traffic loads, and surrounding land use. Required frequency of maintenance will dep on permeable pavements is similar Winter maintenance Maintenance Considerations: Winter to standard pavements, with a few additional considerations: Large snow storage piles should be located in adjacent grassy areas so that sediments and  before they reach the permeable pavement. pollutants in snowmelt are deposited Sand or cinders should never be applied for winter traction over permeable pavement or areas  of impervious pavement that drain t oward permeable pavement.  When plowing plastic reinforced grid pavements, snow plow blades should be lifted 1/2 inch to 1 inch above the pavement surface to prevent damage to the paving blocks or turf. Porous 18 03/2013 3.06.2.3-

62 BMP Standards and Specifications Permeable Pavement PICP) can pavers ( concrete interlocking able asphalt (PA), pervious concrete (PC) and perme be plowed similar to traditional pavements, using similar equipment and settings.  Owners should be judicious when using chloride products for deicing over all permeable e the salts will most assuredly be transmitted into the pavements designed for infiltration, sinc groundwater. Salt can be applied but environmentally sensitive deicers are recommended. Permeable pavement applications will generally require less salt application than traditional pavements. s are installed on private residential lots, homeowners will need to (1) permeable pavement When -term maintenance be educated about their routine maintenance needs, (2) understand the long plan, and (3) be subject to a maintenance agreement as described above. It is highly recommended that a spring maintenance inspection and cleanup be conducted at each permeable pavement site Example maintenance , particularly at large- scale applications. Article 5 inspection checklists for permeable pavements can be found in . 3.10 References . “Permeable Pavement: Research Update and Design Hunt, W. and K. Collins. 2008 Urban Waterways Series. Implications.” North Carolina Cooperative Extension Service Bulletin. . Jackson, N. 2007. Design, Construction and Maintenance Guide for Porous Asphalt Pavements National Asphalt Pavement Association. Information Series 131. Lanham, MD. Smith, D. 2006. -selection design, construction and Permeable Interlocking Concrete Pavement . Interlocking Concrete Pavement Institute. Herndon, VA. maintenance. Third Edition 19 03/2013 3.06.2.3-

63 BMP Standards and Specifications Vegetated Roofs 4.0 Vegetated Roofs Definition: , on top a building, that capture and Practices store rainfall in an engineered growing media , which is designed to support plant growth. A portion of the captured rainfall evaporates or is taken up by plants, which reduce runoff volumes, peak runoff helps rates, and pollutant loads on development sites. Vegetated Roof s, also known as green typically contain a layered system of roofs, roofing, which is designed to support plant growth and retain water for plant uptake preventing ponding on the roof while surface. The roofs are designed so that water drains vertically through the media and then horizontally along a waterproofing layer Two types of vegetated towards the outlet. © Bethany Blues Restaurant, Lewes roofs exist: extensive or intensive. They vary based on the depth of soil and type of plants. Design variants include: wit h  drought resistant 4- A Extensive Vegetated Roof s: S hallow growing media succulent plants, such as sedums  4- B Intensive Vegetated Roof s: Deep growing media with traditional p lantings and irrigat ion provide runoff reduction and water quality treatment for small storms, Vegetated Roofs they are ypically including the Resource Protection event (RPv). T not designed to provide stormwater detention of Cv and Fv storms alt ho ugh some intensive vegetated roof systems larger may be designed to meet or partially meet these criteria, or the vegetated roof could be integrated with a rainwater harvesting system . However, m ost vegetated roof designs generally are acility combined with a separate f located away from the building to provide large storm controls. This specification is intended for situations where the primary design objective of the Vegetated Roof is stormwater management . Green roof benefits go beyond just stormwater manag ement, but the ancillary benefits are not covered within this specification. 3.06.2. 03/2013 4- 1

64 BMP Standards and Specifications Vegetated Roofs . ypical Layers for a Vegetated Roof 4. 1. T Figure 2 3.06.2.4- 03/2013

65 BMP Standards and Specifications Vegetated Roofs Stormwater Credit Calculations 4.1 Vegetated Roof annual runoff reduction Extensive Vegetated Roofs receive 50% credi t (RR) for the contributing . Intensive 4.1 below able roof area, along with associated pollutant removals identified in T oofs exhibit greater annual runoff reduction at 75% capture rate. Vegetated R 4.1(a) Extensive Vegetated Roof Performance Credits Run off Reduction Retention Allowance 0% RPv - A/B Soil * 50% RPv - C/D Soil * N/A Cv 5% Fv 1% Pollutant Reduction 100% of Load Reduction TN Reduction 100% of Load Reduction TP Reduction TSS Reduction N/A Retention Allowance 0% 4.1(b) Intensive Vegeta ted Roof Performance Credits Runoff Reduction 0% Retention Allowance A/B Soil - * RPv 75% N/A RPv C/D Soil * - Cv 8% Fv 2% Pollutant Reduction TN Reduction 100% of Load Reduction TP Reduction 100% of Load Reduction TSS Reduction N/A Retention Allow ance 0% *The growing m used for vegetated roofs is classified as an A/B soil for calculation edia purposes. Therefore, the vegetated roof performance is not dependent on the existing soil conditions and the credit for C/D soils is not applicable (N/A) . The practice must be designed using the guidance detailed in Section 4.6 Vegetated Roof Design . in order to receive the above performance credits Criteria 4.2 Summary Vegetated Roof Design 3 03/2013 3.06.2.4-

66 BMP Standards and Specifications Vegetated Roofs Table 4.2 summarizes design criteria for Vegetated Roofs .3 summarizes the , and Table 4 materials specifications for this practice. For more detail, consult Sections 4.3 through 4.7. Sections 4.8 and 4.9 describe practice construction and maintenance criteria. Table 4.2 Vegetated Roof Design Summary to conform with local building codes s Need • • Needs to have r oof access for maintenance and construction • Structural capability of the roof must be assessed by a qualified licensed professional Feasibility • Setbacks : 2’ plant setback from building edge; 1’ from roof penetrations; Do not locate (Section 4.3) electrical and HVAC components within the drainage system. (1/4” per foot); slope • Roof Slope, Extensive: Minimum 1% (1/8” per foot); Preferred 2% Maximum ). 21% (2.5 ” per foot Roof Slope, Intensive: Minimum 1%; Maximum 2% slope ( 1/4” per foot) • Conveyance • Drainage layer needs to convey overflow capacity of the downspout system without (Section 4 .4) backing up the green roof. • Designed to prevent the media from clogging the conveyance system Pretreatment • Not needed (Section 4 .5) S izing of contributing drainage area. • Surface area of the vegetated roof must be at least 3/4 (Section 4 .6) Landscaping required. Landscape plan • 7 (Section 4. ) . Only intensive roofs may have plants other than • drought resistant succulents Material Specifications Vegetated Roof 4. 3. Table Material Specification ply rubber is typically used EPDM single , but any manufacturer recommended - • Waterproof waterproofing layer for roofs can be used so long as it meets local, state and federal Membrane for waterproofing . building codes Root Barrier Impermeable liner that impedes root penetration of the membrane. • Depth of the drainage layer is generally 0.25 to 1.5 inches thick for extensive designs. • The drainage layer should consist of synthetic or i • norganic materials (e.g., gravel, provid e efficient drainage. recycled polyethylene, etc.) that can • Designers should consult the material specifications as outlined in ASTM E2396 and Drainage Layer E2398. • Roof drains and emergency overflow should be designed in accordance with state and local building codes woven, polypropylene geotextile • Needled, non - . Density (ASTM D3776) > 16 oz./sq. yd., or approved equivalent. • Filter Fabric • Puncture resistance (ASTM D4833) > 220 lbs., or approved equivalent. combine with the drainage layer. • Some manufacturers may Extensive: Media depth between 3 and 6 inches ; 90% lightweight inorganic materials and • 10% organic matter (e.g. well Growth Media -aged compost). Intensive: Media depth upwards of 6 inches ; Organic content can increase up to 40%. • sustaining, and - - that are shallow Extensive: Succulent plants, such as sedums, rooted, self • tolerant of direct sunlight, drought, wind, and frost. Plant Materials d media depth must satisfy selecte Intensive: Any non -invasive plantings, though the • planting s , and the building ’ s height and sun and wind exposure should be accounted for. st / watering irrigation recommended. permanent year required; Extensive: Watering for 1 • Irrigation Intensive: Irrigation required. • 4 03/2013 3.06.2.4-

67 BMP Standards and Specifications Vegetated Roofs 4. 3 Vegetated Roof Feasibility Criteria -family Vegetated roof s are ideal for use on commercial, institutional, municipal and multi residential buildings . , although they can also be incorporated on single family residential homes -urban -suited for use on ultra They are particularly well development and redevelopment sites. Key constraints with vegetated roof s include the following: Structural Capacity of the Roof. Vegetated roof s can be limited by the additional weight of the fully saturated soil and plants, in terms of the physical cap acity of the roof to bear structural to ensure that the professional licensed loads. The designer must consult wit h a qualified The structural building will be able to support the additional live and dead structural load. capability and verification shall comply with local building codes. T he maximum depth of the system or the need structural reinforcement must be determined during this vegetated roof . consultation In most cases, fully /sq. ft., lbs. s have loads of about 15 to 30 vegetated roof -saturated extensive which is fairly similar to traditional new rooftops that have a waterproofing layer anchored with (12 to 15 lbs./sq. ft.) . Intensive systems vary widely depending on the soil depth and stone ballast landscape features, and may be upwards of 100 l bs/sq.ft. For a discussion of vegetated roof ASTM E structural design issues, consult Chapter 9 in Weiler and Scholz- Barth (2009) and - 2397- 05, Standard Practice for Determination of Dead Loads and Live Loads Associated with Green ( Vegetated ) Roof Systems . In addition, use standard test methods ASTM E2398- 05 for Water Capture and Media Retention of Geocomposite Drain Layers for Green (Vegetated) Roof , and ASTM E2399- . Maximum Media Density for Dead Load Analysis 05 for Systems Roof Pitch. storage vol Vegetated roof ume is maximized on relatively flat roofs. Some pitch is needed to promote positive drainage and prevent ponding and/or saturation of the growing , so the minimum slope is 1% (1/8” per foot), while the preferred slope is 2% (1/4” per media ay be pitched up to 21% for stormwater management (2.5” per foot) . Extensive roofs m foot) . purposes, while intensive roofs must remain relatively flat , at maximum 2% (1/4” per foot) Roof Access. Access to the roof must be available to deliver construction materials and perform routine maintenance. Designers must also consider how they will get construction and maintenance materials up to the roof (e.g., by elevator or crane) and how materials will be Access requirements shall comply with local building codes. stockpiled in the confined space. When the Vegetated Roof occurs on a private residential lot, its existence and purpose should be A sample Record Plan note could be as follows: “A Vegetated Roof noted on the deed of record. is located on the residence as part of the overall stormwater management system. This Vegetated by the owner and access for maintenance reviews shall be made Roof shall be maintained available to the Delaware Department of Natural Resources and Environmental Control, assigned agent tormwater Program, or its .” Sediment and S 5 03/2013 3.06.2.4-

68 BMP Standards and Specifications Vegetated Roofs Roof Type. The roof deck layer is the foundation of a vegetated roof . It may be Deck composed of concrete, wood, metal, plastic, gypsum or a composite material. The type of deck material determines the strength , load bearing capacity, longevity and potential need for vegetated roof system. In general, concrete decks are preferred for vegetated insulation in the roof s, although other materials can be used as long as the appropriate system components are matched t o them. Certain roof materials, such as exposed treated wood and galvanized metal, may not be appropriate for vegetated roof tops due to pollutant leaching through the media (Clark et al, 2008). The roof deck type should be coordinated with the building’s designers , only requirement is that it complies with the applicable building codes . Buffers . Rooftop electrical and HVAC systems must not be located within the drainage way of the vegetated roof . A 2 -foot wide vegetation -free zone is re quir ed along the perimeter of the roof, with a 1 -free zone around all roof penetrations, to act as a firebreak. -foot vegetation Local Building Codes. Building codes often differ in each municipality, and local planning and zoning authorities should be consulted to obtai n proper permits. In addition, the vegetated roof to with respect state and local building codes federal, all wit h comply structural design must loadings, roof drains, waterproofing, and all other building related requirements. 4. 4 Vegetated Roof Conveyan ce Criteria (refer to 4. The vegetated roof drainage layer 6: Functional Elements of a Vegetated Roof System) should convey flow from under the growing media directly to an outlet or overflow system such as a tradit ional rooftop downspout drainage system . Any collection systems near the soil media must be protected to prevent clogging; either by filter fabric and stone surround, or by raising the drains above the media by 3”. Any drains that are raised shall only be considered emergency flow, and suffici ent drainage should be utilized in other areas to prevent their use under normal rain conditions. Pretreatment Criteria 4. 5 Vegetated Roof Pretreatment is not necessary for vegetated roof s. 4. 6 Vegetated Roof Criteria Design Functional Elements of a vegetated roof A : is composed of up to System Vegetated Roof different systems or layers seven that are combined together to protect the roof and provide soil and plant conditions that can reduce the impervious effects of the building . These components are placed on top the roof deck layer, as mentioned in Section 4.3. Designers can employ a wide range of materials for each layer, which can differ in cost, performance, and structural load. The entire system as a whole must be assessed to meet design requi rements. Some manufacturers which contain many of the below elements offer proprietary systems , or in other cases the Weiler and components are installed individually. Additional information can be found in 6 03/2013 3.06.2.4-

69 BMP Standards and Specifications Vegetated Roofs Scho lz -Barth (2009), Snodgrass and Snodgrass (2006) and Dunnett and Kingsbury (2004). The design layers include: vegetated roof Waterproofing Layer : All 1. systems must include an effective and reliable waterproofing layer to prevent water damage to the building structure . A wide range of waterproofing ma terials can be used, including built up roofs, modified bitumen, single - , and liquid EPDM rubber waterproofing layer must be 100% -applied methods). The ply waterproof and have an expected life span as long as any other element of the vegetated roof system. The waterproofing layer must be designed in accordance to local, state and federal building codes – the only requirement of this specification is to include waterproofing. : 2. Insulation Layer Many vegetated roof tops contain an insulation layer, usually l ocated above, but sometimes below, the waterproofing layer. The insulation increases the energy efficiency of the building , and can protect the roof deck , p articularly for metal roofs. Whether to use insulation and its location if installed should be coord inated with the building designers, and is not a requirement of this specification. The next layer of a system is a root barrier that protects the vegetated roof 3. Root Barrier : waterproofing membrane from root penetration ange of . A wide r and ultimately failure root barrier options are available , but are typically high density polyethylene . Chemical root barriers or physical root barriers that have been impregnated with pesticides, metals or other chemicals that could leach into stormwater runoff be avoided. Some must waterproofing layers may also serve as a root barrier, but should only be used in if recommended by the manufacturer. combination 4. Drainage Layer and Drainage System : A drainage layer placed between the root barrier and the growing media is used to quickly remove excess water from the vegetation root zone . The depth of the drainage layer is generally 0.25 to 1.5 inches thick with the deeper depths for intensive designs. The drainage layer should consist of synthetic or inorganic materials ( e.g. , clean, washed granular material , such as ASTM D 448 size No. 8 stone , or polyethylene drainage mats ) that are capable of providing efficient drainage. The drainage layer should convey the runoff to a tradit ional system o f condu ctors and roof leader s. American Society for Testing and protected roof drains, Materials ( ) E2396 and E2398 can be used to evaluate alternative material ASTM specifications. 5. Root -Permeable Filter Fabric: A semi -permeable , non- woven polypropylene filter fabric is normally plac ed between the drainage layer and the growing media to prevent the media from migrating into the drainage layer and clogging it , but allowing the roots to penetrate through . Many manufactured drainage layers come with a filter fabric attached, which is ac ceptable. is the growing media Vegetated Roof The next layer in a : Growing Media 6. . For an 7 03/2013 3.06.2.4-

70 BMP Standards and Specifications Vegetated Roofs Extensive syste m, the media ranges from 3 to 6 inches deep , with 3 to 4 inches being the standard depth . The recommended growing media for E xtensive Vegetated Roo fs is composed of approximately 90% lightweight inorganic materials, such as expanded slates, shales or clays, pumice, scoria or other similar materials that are synthetically produced. The remaining media should contain no more than 10% organic matter, Amendments – Soil Specification 14 see -aged compost ( normally well ). The percentage of organic matter should be limited, since it can leach nutrients into the runoff from the roof and clog the permeable filter fabric. The growing media should have a maximum water retention capacity of 30%. It is advisable to mix the media in a batch facility prior to delivery to the roof , or opt for a proprietary engineered green roof growing media. More -Barth (20 09) and information on growing media can be found in Weiler and Scholz Snodgrass and Snodgrass (2006). ntensive The composition of growing media for I Vegetated Roof s may be different, and it vegetated is often much greater in depth (e.g., 6 to 48 inches). If trees are included in the media must be at least 4 feet deep to provide enough roof , the growing landscape plan A higher composition of organic soil volume for the root structure of mature trees. matter may be needed to support the larger shrubs and trees, and should be altered per the recommendations of a Landscape Architect . , up to 40% maximum organic content Minimum 75% plant coverage must be planted and maintained on the : Plant Cover 7. vegetated roof. The plant coverage is increased to minimum 90% for pitched roofs above 5%. For ther succulent plants must be planted or o Extensive systems, sedums , or in pre individually -planted trays . Though non- native, , supplied in a rolled mat format these slow -growing, shallow -rooted, perennial plants can withstand harsh conditions at the roof surface. See Section 4. 7 Vege tated Roof Landscaping Criteria for addit ional Intensive For plant informat ion. succulent fs, the plant type can be oo Vegetated R though the plants survivability on the roof top must broadened to any non -invasive plant, be accounted for. The plants for bo th types of systems should be per the recommendations of a qualified professional. : vegetated roof Standards specifications for North American s continue Material Specifications to evolve, and no universal material specifications exist that cover the wid e range of roof types ASTM and system components currently available. The has recently issued several overarching Table vegetated roof standards, which are described and referenced in 4. 3 (See Section 4.2) . tand manufacturer specifications for each Designers and reviewers should also fully unders particularly if they choose to install proprietary “complete” vegetated roof component, system systems or modules. Vegetated Roofs shall be designed and constructed with the minimum Vegetated Roof Sizing: materia mum l specifications stated above. In addition, the size of the Vegetated Roof, or maxi both Extensive and Intensive, must be minimum 75% of the total contributing drainage area. 8 03/2013 3.06.2.4-

71 BMP Standards and Specifications Vegetated Roofs Specific volume requirements are not required. If the guidance is followed, Vegetated Extensive Roofs have been shown to reduce the annual runoff by 50% (Berghage et al, 2009), and I ntensive Vegetated R oofs by 75% (Mentens et al, 2005). Roof s, especially I ntensive systems, can have Vegetated n dramatic rate attenuation effects o larger storm events, and and 1 00- year may be used, in part, to manage a portion of the 10- events can model the higher storm events by factoring in storage within the drainage . Designers . The er’s stated porosity) layer , using a porosity of 0. 30 for the soil media (or manufactur drainage layer can also be accounted for and varies depending on type (ie, modules with storage cups versus stone drainage; the manufacturer’s recommendations on sizing or the standard porosity per stone type should be used to ca lculate the storage in the drainage layer) . 4. 7 Vegetated Roof Landscaping Criteria , placement Plant select ion and maintenance are critical to the performance and function of Vegetated Roof The landscape plan must be s. Therefore, a landscaping plan shall be provided. prepared for a Vegetated Roof by a licensed design professional experienced with vegetated roof s, and it must be reviewed and approved by the local development review authority. Plant select ion for vegetated roof tops is an integral de sign consideration, which is governed by Vegetated Roof installations local climate and design objectives. The ground cover for E xtensive are or Sedum, Delosperma, Talinum, Semperivum s, such as -growing succulent hardy, low , Hieracium difficult growing conditions found on building rooftops . See that can tolerate the 06, Guide for Selection, Installation and Maintenance of Plants for Green ASTM E2400- uidance on selecting the appropriate vegetated roof plants (Vegetated) Roof Systems . Addit io nal g for hardiness can be found in Snodgrass and Snodgrass (2006). zones in the Delaware region egetated Roof plant species that work well the Delaware A list of so me co mmon Extensive V region can be found in 4. 4 below. Table Vegetated Table Exten sive 4. 4. Ground Covers appropriate Roof s in Delaware. for Moisture Light Plant Requirement Notes Delosperma cooperii Dry Pink flowers; grows rapidly Full Sun Delosperma 'Kelaidis' Full Sun Dry Salmon flowers; grows rapidly Delosperma nubigenum 'Basutoland' Full Sun Moist - Dry Y ellow flowers; very hardy Sedum album Full Sun Dry White flowers; hardy Yellow flowers; native to U.S. Dry Full Sun Sedum lanceolatum 9 03/2013 3.06.2.4-

72 BMP Standards and Specifications Vegetated Roofs Moisture Light Plant Requirement Notes Sedum oreganum Part Shade Moist Yellow flowers; native to U.S. Pink flowers; drought tole rant Sedum stoloniferum Sun Moist Sedum telephiodes Sun Dry Blue green foliage; native to region - Moist Sedum ternatum Part Shade - Shade Dry White flowers; grows in shade Talinum calycinum Sun Dry Pink flowers; self sows e, ability to sow or not, foliage height, should choose species based on shade toleranc Note: Designers plants, and spreading rate. See Snodgrass and Snodgrass (2006) for definitive list of vegetated roof including accent plants. orbs, systems. Herbs, f Vegetated Roof Intensive Plant choices can be much more diverse for grasses, shrubs and even trees can be used, but designers should understand they have higher watering, weeding and landscape maintenance requirements . than an Extensive system Addit io nal Landscaping Criteria and Notes: • The species and layout of the landscape plan shall reflect the location of building, in terms of its height, exposure to wind, snow loading, heat stress, orientation to the sun, and shading by surrounding buildings. In addition, plants should be selected that are fire resistant and mus t be , cold and high winds. able to withstand heat • Designers must also match species to the expected rooting depth of the growing media, which can also provide enough lateral growth to stabilize the growing media surface. The landscape plan should usually i nclude several accent plants to provide diversity and seasonal color. For a comprehensive resource on vegetated roof plant selection, consult Snodgrass and Snodgrass (2006). vegetated roof It is also important to note that most Extensive be native not plant species will • to the Delaware region (which contrast s with native plant recommendations for other stormwater practices, such as bioretention and constructed wetlands). plant nurseries in the region, le to it is advisab • Given the limited number of vegetated roof to have the plant materials contract -grown . determine the lead time for delivery and • When appropriate species are selected, most E xtensive Vegetated Roof s in Delaware will not first year of during the require supplemental irrigation, except for temporary watering t is recommended to have a permanent watering or irrigation system . I establishment for especially dry conditions , but watering is only a requirement for the first year after planting. art of the drainage layer that stores Some proprietary systems contain water storage cups as p additional runoff which the plant roots can utilize in dry periods. These systems can help reduce watering needs and increase plant survivability. 10 03/2013 3.06.2.4-

73 BMP Standards and Specifications Vegetated Roofs • For Intensive Vegetated Roofs, irrigation is a permanent requirement . It is recommended to explore Specification 5.0 Rainwatering Harvesting , for irrigation needs to increase water reuse and stormwater credit. as it is important to allow plants to -fall, mid The planting window extends from the spring to • ore the first killing frost. root thoroughly bef Plants can be established using cuttings, plugs, and • mats. Several vendors also sell mats, rolls, or proprietary pre -vegetated roof planting modules. For the pros and cons of each e minimum plant coverage must be method, see Snodgrass and Snodgrass (2006). Th achieved after planting and maintained throughout the life of the greenroof. design should include non • The vegetated roof -vegetated walkways to allow for easy access to the roof for weeding and making spot repairs (howev er, the vegetated roof portion must be -quarters of the total drainage area). minimum three Construction Sequence Vegetated Roof 4. 8 designs, there is no typical step . Given the diversity of V egetated Roof Installation -by-step construction sequence for proper installation. The following general construction considerations are noted: • Construct the roof deck with the appropriate slope and material. mbrane Install the waterproofing me , according to manufacturer’s specifications. • nsure the system is water tight by placing at least 2 inches of water Conduct a flood test to e • over the membrane for 48 hours to confirm the integrity of the waterproofing system. Add additional system components (e.g., insulation, root barrier, drainage layer and interior • drainag e system, and filter fabric), taking care not to damage the waterproofing. Drain collars and protective flashing should be installed to ensure free flow of excess stormwater. The growing media should be mixed prior to delivery to the site. Media should be spread • evenly over the filter fabric surface. The growing media should be covered until planting to prevent weeds from growing. Sheets of exterior grade plywood can also be laid over the traffic should be growing media to accommodate foot or wheelbarrow traffic, although the n. limited over the growing media to reduce compactio The growing media should be moistened prior to planting, and then planted per the landscape • plan, or in accordance with ASTM E2400. Plants should be watered immediately after installa tion and routinely during establishment. It generally takes 12 to 18 months to fully establish the vegetated roof. An initial fertilization • 14) with adequate minerals using slow release fertilizer (e.g., 14 -14- is often needed to a second application the second growing year , followed by support growth . Temporary watering may also be needed during the first summer, if drought conditions persist. Hand -Barth, Weiler and Scholz weeding is also critical in the first two years (see Table 10.1 of for a photo guide of common rooftop weeds) 2009, . 11 03/2013 3.06.2.4-

74 BMP Standards and Specifications Vegetated Roofs Warranty that specif ies Replacement are and a Most construction contracts should contain a C • 75% minimum survival after the first growing season of species planted and a minimum effective vegetative ground cover of 75% for fl at roofs and 90% for pitched roofs. s during construction are needed to ensure that the vegetated roof Review Review . Construction is built in accordance with these specifications. Detailed review checklists should be used that ed individuals at critical stages of construction and confirm that the include sign -offs by qualifi contractor’s interpretation of the plan is consistent with the intent of the designer and/or manufacturer. installer should be retained to construct the vegetated roof s An experienced ystem. The vegetated roof should be constructed in sections for easier inspection and maintenance access to the membrane and roof drains. Careful construction oversight is needed during several steps of vegetated roof installation, as follows: • ement of the waterproofing layer, to ensure that it is properly installed and During plac watertight; , to prevent future ponding During placement of the drainage layer and drainage system • water ; During placement of the growing media, to confirm that it meets the ; • • Upo n installation of plants, to ensure they conform to the landscape plan ; • /or Before issuing use and occupancy approvals; and • At the end of the first or second growing season, to ensure desired surface cover specified in the Care and Replacement Warranty has been achieved. Vegetated Roof practices . Reference the example Construction Review Checklist for Vegetated Roof 4. 9 Maintenance Criteria An Operation and Maintenance Plan for the project shall be approved by the Department or the Delegated Agency prior to project closeout. The Operation and Maintenance Plan will specify or the property owner’s primary maintenance responsibilities and authorize the Department Delegated Agency staff to access the property for maintenance review in corrective action , or for the event that proper maintenance is not performed. Vegetated Roofs that are, or will be, owned and maintained by a joint ownership such as a homeowner’s association must be located in common areas, community open space, community -owned property, jointl y owned property, or When the Vegetated Roof occurs on a within a recorded easement dedicated to public use. private residential lot, its existence and purpose must be noted on the deed of record. The with a si mple document that explains the developer shall provide subsequent h omeowners purpose and routine maintenance needs for the Vegetated Roof. Maintenance of Vegetated Roofs is driven by annual maintenance reviews that evaluate the condition and performance of the practice. Based on maintenance review results, specific 12 03/2013 3.06.2.4-

75 BMP Standards and Specifications Vegetated Roofs maintenance tasks may be required. Since Vegetated Roofs are living systems on top of a building, it is recommended to perform two reviews per year, though only one is required. must during the growing season reviewed be Vegetated Roofs to assess vegetative cover, and to look for leaks, drainage problems and any rooftop structural concerns (see In below). 4. 5 Table should be hand addit ion, the vegetated roof -weeded to remove invasive or volunteer plants, and ). (ASTM, 2006) plants/media should be added to repair bare areas (refer to ASTM E2400 If a roof leak is suspected, it is advisable to perform an electric leak survey (i.e., Electrical Field Vector Mapping) to pinpoint the exact location, make localized repairs, and then reestablish system components and ground cover. be avoided, since their presence could The use of herbicides, insecticides, and fungicides are to hasten degradation of the waterproof membrane. Also, power -washing and other exterior maintenance operations should be a voided so that cleaning agents and other chemicals do not plant vegetated roof s. harm the , and the inspection checklist Maintenance by a qualified reviewer shall be performed reviews Both the Department or or the appropriate Delegated Agency. the Department should be sent to the appropriate Delegated Agency shall have the right to inspect the Vegetated Roof should the . need arise, on all commercial, institutional, residential buildings Checklist Maintenance Review ofs. for Vegetated Ro Reference the example Table Associated with Vegetated Roof s 4. 5. Typical Maintenance Activities Frequency Maintenance Items Water to promote plant growth and survival. As Needed • eplace any dead or dying vegetation. • R • Inspect the waterproof membrane for le aking or cracks. two first for Annual fertilization ( ). only years • • Weeding to remove invasive plants (no digging or using pointed tools). -Annually Semi • roof drains, scuppers and gutters to ensure they are Check not overgrown or have organic matter deposits. Remove any ac cumulated organic matter or debris. eplace any dead or dying vegetation. R • 13 03/2013 3.06.2.4-

76 BMP Standards and Specifications Vegetated Roofs References 4. 10 ASTM International. 2006. Standard Guide for Selection, Installation and Maintenance of Plants . Standard E2400- national. West 06. ASTM, Inter for Green (Vegetated) Roof Systems Conshohocken, PA. available online: http://www.astm.org/Standards/ E2400.htm. Standard Test Method for Water Capture and Media Retention of ASTM International. 2005. . Geocomposite Drain Layers for Green Roof Systems 05. ASTM, International. Standard E2398- West Conshohocken, PA. available online: http://www.astm.org/Standards/ E2398.htm. -life runoff quality: green versus Clark, S., B. Long, C. Siu, J. Spicher and K. Steele. 2008. “Early e, WA. American Society of Civil Seattl Low Impact Development 2008. traditional roofs.” Engineers. . Timber Press. Planting Green Roof s and Living Walls Dunnett, N. and N. Kingsbury. 2004. Portland, Oregon. Northern Virginia Regional Commission (NVRC). 2007. Low Impact Development Manual. airfax, VA. “Vegetated Roofs.” F Green . Plants: a resource and planting guide Roof Snodgrass, E. and L. Snodgrass. 2006. Timber Press. Portland, OR. Green Systems: A Guide to the Planning, Design, and Roof -Barth 2009. Weiler, S. and K. Scholz Wiley Press. Construction of Landscapes over Structure. New York, NY. Green roofs as a tool for solving the rainwater Mentens, J., D. Raes, and M. Hermy. 2005. st runoff problem in the urbanized 21 Landscape and Urban Planning, KULeuven, century? Belgium. Berghage, R., D. Beattie, A. Jarrett, C. Thuring, F. Razaei, and T. O’Connor. 2009. Green Roofs for Stormwater Runoff Control. Office of Research and Development, United States Environmental Protection Agency. 14 03/2013 3.06.2.4-

77 Specifications Rainwater Harvesting BMP Standards and 5.0 Rainwater Harvesting systems Rainwater Harvesting Definition: intercept, divert, store and release rainfall for impervious future use. Rainwater that falls onto surfaces is collected and conveyed into an above - ferred to as a or below -ground storage tank (also re cistern or rain tank) - , where it can be used for non -site stormwater potable water uses and on -potable uses may disposal/infiltration. Non include landscape irrigation, exterior washing (e.g. car washes, building facades, sidewalks, street eepers, fire trucks, etc.), flushing of toilets and sw urinals, fire suppression (sprinkler) systems, supply for chilled water cooling towers, replenishing and operation of water features , distribution to a green wall or living wall system, Photo courtesy of Lake County (IL) Stormwater Management Commission Rainwater any instances, . In m and laundry can be combined with a secondary stormwater Harvesting practice to enhance stormwater and/or provide treatment of overflow from the Rainwater Harvesting retention system. Rainwater Harvesting systems are separated into two categ ories. Design variants include:  5- A Seasonal Rainwater Harvesting Systems  5- B Continuous Rainwater Harvesting Systems By providing a renewable source of water to end users, Rainwater Harvesting systems can have environmental and economic benefits beyond stormwater management (e.g., increased water conservation, water supply during drought and mandatory municipal water supply restrictions, decreased demand on municipal or groundwater supply, decreased water costs for the end -user, potential for increased groundwater recharge, etc .). 1 03/2013 3.06.2.5-

78 Rainwater Harvesting BMP Standards and Specifications 5.1 Rainwater Harvesting Stormwater Credit Calculations performance credit s for Rainwater Harvesting systems are based upon a design The in prepared accordance with the guidelines of Section 5. s 5.1 (a) and 5. 6. Table list the credits for 1(b) retention and pollutant reduction . Rainwater Harvesting Seasonal (a) 5.1 Performance Credits Runoff Reduction Retention Allowance 50 % 50 RPv - A/B Soil Storage % of Retention Storage RPv - C/D Soil 50 % of Retention Cv 0% Fv 0% ollutant Reduction P TN Reduction 100% of Load Reduction TP Reduction 100% of Load Reduction 100% of Load Reduction TSS Reduction 5.1(b) Continuous Rainwater Harvesting Performance Credits Runoff Reduction Retention Allowance 75% RPv - A/B Soil 75% o f Retention Storage 75% of Storage Retention RPv - C/D Soil Cv 0% Fv 0% Pollutant Reduction TN Reduction 100% of Load Reduction 100% of Load Reduction TP Reduction 100% of Load Reduction TSS Reduction 5.2 Rainwater Harvesting Design Summary , and Table 5. 3 summarizes the le 5. 2 summarizes design criteria for Rainwater Harvesting Tab materials specifications for this practice. For more detail, consult Sections 5.3 through 5.7. Sections 5.8 and 5.9 describes practice construction and maintenance criteria. 2 03/2013 3.06.2.5-

79 BMP Standards and Specifications Rainwater Harvesting 2 Rainwater Harvesting Design Summary Table 5. • Harvested rainwater may be used for non - potable uses; pipes and spigots conveying harvested rainwater labeled as non -potable with local plumbing codes • Conform Harvested water separated from main water supply • Risk assessment conducted • if reuse will include human contact or affect human health • Adequate space provided for storage tank and overflow Backflow from the discharge point into the storage tank not allowed • Feasibility ied above the groundwater table • uld be bur Tanks sho ; if the tank is in groundwater it (Section 5.3) must be secured from floating • Bearing capacity of soil must be considered for a full storage tank • pH of the soil must be considered in relation to interaction with tank material • Un derground components setback from utilities in accordance with setback requirements of the utility • Underground storage tanks recommended being at least 10 ft. from building foundations • Often used to separate rooftop runoff from hotspots ; evaluate risk of c ollecting runoff from industrial roofs that themselves may be considered hotpots slope of 1.5% • Pipes connecting downspouts to storage tank must have min imum Conveyance • Overflow must be provided with capacity equal to or greater than inflow pipe (Section 5.4) • Overflow capacity sufficient to drain the tank while maintaining freeboard and birds • Overflow must be screened to prevent rodents from entering the tank Pretreatment - treatment is required for all tanks • Pre (Section 5.5) Small tank systems must have le af screens or gutter guards at a minimum • Large tank systems requires full capture pretreatment • • Aboveground tanks UV and impact resistant Underground tanks designed to support overlying soil and any vehicle or other loads • round tanks fully accessible for entry to perform maintenance and repair. • Underg Standard size manhole for access must be secured or locked s Storage Tank • Sealed using a water -safe, non -toxic material (Section 5.6) • Aboveground tanks must be opaque • Openings screened • Foundation to support full tank • Backflow prevention if hooked up to a municipal backup water supply Distribution Systems Include appropriately sized pump that produces sufficient pressure for all intended end • (Section 5.6) uses • ground pipes insulated or heatwrapped Distribution lines buried beneath frost line; above if system will be in continuous use. Include a drain plug or cleanout sump to empty the tank • Criteria Seasonal Rainwater Harvesting Systems Sizing : (Section 5.6) • Weekly irrigation demand must be at least 50% of the st ored volume Continuous Rainwater Harvesting Systems : • Minimum of 50% of demand is met through non -irrigation needs • Weekly water demand during the growing season must be 50% of stored volume • Weekly water demand during the non -growing season must be 25% of st ored volume • Designed to withstand freezing conditions Alternative: • Evaluate water needs and runoff volumes on a daily basis for at least a 15-year modeling period to demonstrate that the volume retained is as large as volume credited for RPv C Landscaping riteria Plan showing area to be irrigated, plants to be used, and expected water demand • (Section 5.7) necessary to maintain plants 3 03/2013 3.06.2.5-

80 BMP Standards and Specifications Rainwater Harvesting 3. Material S systems Table 5. pecifications for Rainwater Harvesting Specification Item • Commo n conveyance materials for non - roof runoff include concrete, HDPE, PVC, aluminum and galvanized steel Common roof runoff conveyance materials: polyvinylchloride (PVC) pipe, vinyl, • Pipes, Gutters aluminum and galvanized steel s and Downspout Recommended aluminum, round - bottom gutters roof runoff conveyance materials: • and round downspouts Lead should not be used as gutter and downspout solder, since rainwater can dissolve • the lead and contaminate the water supply • Aboveground tank material UV and impact resistant • Storage tan ks water tight and sealed using a water -safe, non -toxic substance Storage Tanks • Tanks must be opaque to prevent the growth of algae -grade products for potable water or food acceptable be -used tanks must Re • Note: This table does not address indoor systems or pumps. 5. 3 Rainwater Harvesting Feasibility Criteria Rainwater Harvesting systems are designed A number of site -specific features influence how and/or utilized. These should not be considered comprehensive and conclusive considerations, but rather some recommendations that should be considered during the process of planning to systems into the site design. The f incorporate Rainwater Harvesting ollowing are key considerations for Rainwater Harvesting feasibility: non- potable uses. This specification does Plumbing Code. Harvested rainwater may be used for s and plan reviewers should consult not address indoor plumbing or disinfection issues. Designer building codes to determine the allowable indoor uses and required treatment for harvested local rainwater. systems where a municipal backup supply is used, Rainwater Harvesting In cases must have backflow preventers or air gaps to keep harvested water separate from the main water supply. Pipes and spigots using rainwater must be clearly labeled as non -potable. Water R euse. Harvested rainwater may be used for non -potable uses; however, w hen harvested will be reused where human contact and human health should be considered, rainwater documentation o f a risk assessment for the reuse of stormwater design the that outlines assumptions and evaluation process must be submitted to the Department . . Available Space Adequate space is needed to house the storage tank and any overflow. Space uring Rainwater Harvesting limitations are rarely a concern with systems if they are considered d the initial building design and site layout. Storage tanks can be placed underground, indoors, on rooftops that are structurally designed to support the added weight, and adjacent to buildings. and to creatively site the tanks. Designers can work with architects landscape architects Underground utilities or other obstructions should always be identified prior to final determination of the tank location. When the rainwater harvesting system occurs on a private should be noted on the deed of record. residential lot, its existence and purpose 4 03/2013 3.06.2.5-

81 Rainwater Harvesting BMP Standards and Specifications Site Topography. Site topography and storage tank location should be considered as they relate to all of the inlet and outlet invert elevations in the Rainwater Harvesting system. The final invert of the outlet pipe from the storage tank must be at an elevation that will not allow water from the discharge point to backflow into the storage tank. The elevation drops the resulting and associated with the various components of a Rainwater Harvesting system elevations should be considered early in the design, in order to ensure that the Rainwater invert Harvesting system is feasible for the particular site. . Locating Site topography and storage tank location will also affect pumping requirements areas will make it easier to convey runoff from impervious surfaces and storage tanks in low roofs of buildings to cisterns. However, it will increase the amount of pumping needed to distribute the harvested rainwater back into the building or to irrigated areas situated on h igher ground. Conversely, placing storage tanks at higher elevations may require larger diameter conveyance systems wit h flatter slopes. However, this will also reduce the amount of pumping , ensuring impervious source needed for distribution. I t is often best to locate a cistern clos e to the minimal that . needed are conveyance lengths Available Hydraulic Head . The required hydraulic head depends on the intended use of the water. For residential landscaping uses, the cistern should be sited up -gradient of t he landscaping areas or on a raised stand. Pumps are commonly used to convey stored rainwater to the end use in order to provide the required head. When the water is being routed from the cistern to the inside of a building for non -potable use, often a pum p is used to feed a much smaller pressure tank inside the building which then serves the internal water demands. Cisterns can also use gravity to accomplish indoor residential uses (e.g., laundry) that do not require high water pressure. Und . Water Table erground storage tanks are most appropriate in areas where the tank can be the water table. The tank should be located in a manner that will not subject it to above buried flooding. In areas where the tank is to be buried partially below the water table, s pecial design features must be employed, such as sufficiently securing the tank (to keep it from “floating”), conducting buoyancy calculations when the tank is empty. The tank may need to be secured and appropriately with fasteners or weighted to avoid upl ift buoyancy. The tank must also be installed according to the tank manufacturer’s specifications. Soils . Storage tanks should only be placed on native soils or on fill in accordance with the manufacturer's guidelines. The bearing capacity of the soil upo n which the cistern will be placed must be considered, as full cisterns can be very heavy. This is particularly important for above- ground cisterns, as significant settling could cause the cistern to lean or in some cases to potentially topple. A suffici ent aggregate, or concrete base, may be appropriate depending on the soils. The pH of the soil should also be considered in relation to its interaction with the cistern material. into consideration . All underground utilities must be taken Proximity of Underground Utilities systems, treating all of the Rainwater during the design of underground Rainwater Harvesting system components and storm drains as typical stormwater facilities and pipes. The Harvesting 5 03/2013 3.06.2.5-

82 BMP Standards and Specifications Rainwater Harvesting underground utilities must be marked and avoided during the installation of underground tanks Underground Rainwater Harvesting system components and piping associated with the system. must be set back from other underground utilities in accordance with the setback requirements of the other utilities. Contributing Drainage Area. The contributing drainage area (CDA) to the cistern is the impervious area draining to the tank. Areas of any size, including portions of drainage areas , can be used based on the sizing guidelines in this design specification. R unoff should be routed direct ly fro m impervious surfaces to Rainwater Harvesting systems in closed roof drain systems or storm drain pipes, avoiding surface drainage, which could allow for increased contamination of the water. The quality of the harvested rainwater will vary Rainwater . Water Quality of Harvested according to the impervious surface over which it flows. Water harvested from certain types of rooftops, such as asphalt sealcoats, tar and gravel, painted roofs, galvanized metal roofs, sheet met al or any material that may contain asbestos may leach trace metals and other toxic compounds. In general, harvesting rainwater from such roofs should be avoided. If a sealant or paint roof surface is desired, it is recommended to use one that has been certified for such purposes by the National Sanitation Foundation (ANSI/NSF standard). Chemicals, sealants, salts or other potential pollutants that may be applied to impervious surfaces Collection systems from ater. should be considered prior to reuse or irrigation of harvested rainw non- -treatment to remove sediment and hydrocarbons that rooftop sources should include pre may result in leaching of metals from the may be present on driving surfaces. Acidic rainfall roof surface, tank lining or water later als to interior connections. Limestone or other materials may be added in the tank to buffer acidity , following the results of a pH test , if desired. Hotspot Land Uses . Harvesting rainwater can be an effective method to prevent contamination of rooftop r unoff that would result from mixing it with ground- level runoff from a stormwater hotspot operation. In some cases, however, industrial roof surfaces may also be designated as not be stormwater hotspots. Runoff from roof surfaces that may be contaminated should collected for reuse without first evaluating the effect that the pollutants in the runoff will have on the reuse system. Storage tank Setbacks from Buildings . overflow devices should be designed to avoid causing ponding or soil saturation within 10 feet of building foundations. Tanks must be designed to be watertight to prevent water damage when placed near building foundations. In general, it is recommended that underground tanks be set at least 10 feet from any building foundation. g. systems should be Vehicle Loadin Rainwater Harvesting Whenever possible, underground placed in areas without vehicle traffic or be designed to support live loads from heavy trucks, a requirement that may significantly increase construction costs. l. Storage Tank Materia Rainwater Harvesting systems may be ordered from a manufacturer or can be constructed on site from a variety of materials. below 4 Table 5. compares the advantages and disadvantages of different storage tank materials. 6 03/2013 3.06.2.5-

83 BMP Standards and Specifications Rainwater Harvesting Table 5.4. Advantages and Disadvan tages of Various Cistern Materials ( Source: Cabell Brand Center, 2007; Cabell Brand Center, 2009) Tank Material Advantages Disadvantages Commercially available, alterable and Must be installed on smooth, solid, level moveable; durable with little maintenance; -ground footing; pressure proof for below Fiberglass light weight; integral fi ttings (no leaks); installation; expensive in smaller sizes broad application Commercially available, alterable, Can be UV - degradable; must be painted or - ground installations; moveable, affordable; available in wide tinted for above Polyethylene - range of sizes; can install above or below ground -proof for below pressure installation ground; little maintenance; broad application Can modify to topography; can alter Longevity may be less than other materials; Modular footprint and create various shapes to fit site; higher risk of puncturing of water tight Storage relatively inexpensive membrane during construction e capacity (20 to 50 gallons); Low storag Commercially available; inexpensive Plastic Barrels limited application Commercially available; designs for above and below ground applications; aluminum May need to be lined for potable use; soil Aluminized alloy layer protects from corrosion; long pH may reduce service life Steel service life Small storage capacity; prone to corrosion, and rust can lead to leaching of metals; Commercially available, alterable and Steel Drums moveable verify prior to reuse for toxics; water pH and soil pH may also limit applications Durable and immoveable; suitable for above Potential to crack and leak; expensive or below ground installations; ncrete FerroCo neutralizes acid rain Potential to crack and leak; permanent; will Durable, immoveable, versatile; suitable for Cast in Place need to provide adequate platform and above or below ground installations; Concrete zes acid rain design for placement in clay soils neutrali Durable and immoveable; keeps water cool Stone or Difficult to maintain; expensive to build in summer months oncrete Block C Commercially available; can create very large cisterns (greaterh than 100,000 Steel Reinforced Not available for above ground applications gallons); long service life; can support high Polyethylene cove r and shallow burial depths 5.4 Rainwater Harvest ing Conveyance Criteria Collection and Conveyance. The collection and conveyance system con sists of the gutters, downspouts and pipes that channel rainfall into storage tanks. Roof g utters and downspouts should be designed as they would for a building wit hout a Rainwater Harvesting system. Aluminum, round -bottom gutters and round downspouts are generally recommended for Rainwater Harvesting . Minimum slopes of gutters must be specified on the Sediment and Stormwater Management Plan . If the system will be us ed for management of larger storm events, must conveyance system storm intensit ies. the be designed to convey the appropriate Conveyance p be at a minimum slope of 1.5% and sized/designed to must ipes to the cistern tank convey the intended design stor m, as specified above. In some cases, a steeper slope and larger sizes may be recommended and/or necessary to convey the required runoff, depending on the 7 03/2013 3.06.2.5-

84 Rainwater Harvesting BMP Standards and Specifications design objective and design storm intensity. All conveyance pipes to the storage tank, including gutt ers and downspouts , must be kept clean and free of sediment, debris and rust. system design Overflow. An overflow mechanism must be included in the Rainwater Harvesting in order to handle an individual storm event or multiple storms in succession that e xceed the must have a capacity equal to or greater than the inflow capacity of the tank. Overflow pipes pipe(s) and have a diameter and slope sufficient to drain the cistern while maintaining an adequate freeboard height. The overflow pipe must be screened to prevent access to the tank by rodents and birds. 5.5 Rainwater Harvesting Pretreatment Criteria Pre -treatment is required to keep sediment, leaves, contaminants and other debris from the ll and large tank systems. All requirements differ between sma -treatment system. Minimum pre -treatment pre -free. The purpose of pre- -maintenance or maintenance devices should be low is to significantly cut down on maintenance by preventing organic buildup in the tank, treatment thereby decreasing microbial food sources. Small Tank Rainwater Harvesting Systems. Leaf screens and gutter guards meet the minimal requirement for pre -treatment of small tank systems (less than 2,500 gallons) collecting roof , although direct water filtration is preferred. Leaf screens are mesh screens installed over runoff either the gutter or downspout to separate leaves and other large debris from rooftop runoff. Leaf screens must be regularly cleaned to be effective; if not maintained, they can become clogged -up debris can also harbor wing into the storage tanks. Built and prevent rainwater from flo treatment bacterial growth within gutters or downspouts (TWDB, 2005). Other acceptable pre- devices for small tank systems include: • First Flush Diverters: First flush diverters direct the init ial pulse of rainfall away fro m the storage tank. While leaf screens effectively remove larger debris such as leaves, twigs and blooms from harvested rainwater, first flush diverters can be used to remove smaller contaminants such as dust, pollen and bird and rodent feces ( Figure ). Simple first 5.2 flush diverters require active management, by draining the first flush water volume to a pervious area following each rainstorm. Roof washers are placed just ahead of storage tanks and are used to filter • Roof Washers: small debris from rainwater ). Roof washers Figure 5.3 ( harvested from roof surfaces consist of a tank, usually between 25 and 50 gallons in size, with leaf strainers and a filter microns. The filter functions to remove very small with openings as small as 30- particulate matter from harvested rainwater. All roof washers must be cleaned on a regular basis. 8 03/2013 3.06.2.5-

85 Rainwater Harvesting BMP Standards and Specifications First Flush Diverter Figure 5.3. Roof Washer Figure 5.2. (Source: TWRB, 2005) (Source: T WRB, 2005) Large Tank Rainwater Harvesting Systems. Large tank systems (greater than 2,500 gallons) should include a full -capture pretreatment system capable of treating and conveying the flow rate ibuting impervious surface drainage generated by the Resource Protection event from the contr area. A design intensity of 1.2 /hour is necessary to capture the Resource Protection event . inches This design intensity captures a significant portion of the total rainfall during a large majority of rainfall events ( NOAA, 2004). • Proprietary Devices : For large scale applications, proprietary vortex devices and filters can proprietary A areas. rainwater from larger impervious harvested provide filtering of vortex filter may serve as an effective pre- tank filt ration device. device or 5.6 Rainwater Harvesting Design Criteria : System Components compose system: a Rainwater Harvesting The following  Impervious surface  , storm drain Collection and conveyance system (e.g., gutter and downspouts )  Pre -Treatment s  Storage tank  Distribution system  practice Overflow, filter path or secondary stormwater retention 9 03/2013 3.06.2.5-

86 Rainwater Harvesting BMP Standards and Specifications The system components are discussed below: 1. Impervious Surface: Only runoff from impervious surfaces should be collected for reuse on the site. Collection of runoff from roofs and sidewalk areas are preferred over roads, driveways and parking lots because runoff from these areas requires less pre - treatment prior to reuse on the site. Runoff from impervious surfaces that are treated with salt or other chemicals detrimenta l to plant health should not be reused on site for landscape irrigation. When collecting runoff from roofs, t he rooftop should be made of porous material with efficient drainage either from a sloped roof or an smooth, non- efficient roof drain system. Slow drainage of the roof leads to poor rinsing and a prolonged first flush, which can decrease water quality. Collection and Conveyance System: Runoff collected from impervious areas should 2. be conveyed to the storage tank in a closed pipe conveyance system to prevent further contamination of the runoff. Roof g utters and downspouts should be designed as they would for a building without a Rainwater Harvesting system. If the system will be used for management of larger storm events, the conveyance pipes d be designed to shoul convey the appropriate storm intensities. Pipes connecting downspouts to the cistern tank should be at a minimum slope of 1.5% and sized/designed to convey the intended design ting Conveyance See Section 5.4. Rainwater Harves storm, as specified above. Criteria. is required to keep sediment, leaves, contaminants and -treatment Pre -Treatment: Pre 3. -treatment requirements differ between . Minimum pre other debris out of the storage tank small and large tank systems. All pre -treatment devices should be low -maintenance or maintenance -free. The purpose of pre- treatment is to significantly cut down on maintenance by preventing organic buildup in the tank, and decrease microbial food sources , thereby improving the quality of the stored water resour ce. Leaf screens and -treatment gutter guards meet the minimal requirement for pre of small tank systems (less than 2,500 gallons), although direct water filtration is preferred. For large tank systems capture pretreatment system capable of (greater than 2,500 gallons), should include a full- treating and conveying the flow rate generated by the Resource Protection event from the A design intensity of 1.2 contributing impervious surface drainage area. inches /hour is necessary to capture the Resource Protect ion event. See Section 5.5. Rainwater Harvesting Pretreatment Criteria. Storage Tanks: The storage tank is the most important and typically the most 4. expensive component of a Rainwater Harvesting system. Cistern capacities range from llons. Multiple tanks can be placed adjacent to each other and 250 to over 30,000 ga connected with pipes to ba lance water levels and increase overall storage on -site as system capacities for residential use range from needed. Typical Rainwater Harvesting 1,500 to 5,000 gallons . Storage tank volumes are calculated to meet the water demand detail below in further and stormwater storage volume credit objectives, as described in this specificat ion. 10 03/2013 3.06.2.5-

87 Rainwater Harvesting BMP Standards and Specifications While many graphics and photos depict cisterns with a cylindrical shape, the tanks can be made of many materials and configured in various shapes, depending on the type used and the site conditions where the tanks will be installed. For example, configurations can be rectangular, L -shaped, or step vertically to match the topography of a site. The be considered when designing a Rainwater Harvesting system following factors that must and selecting a storage tank: Aboveground storage tanks must  be UV and impact resistant.  Underground storage tanks must be designed to support the overlying soil and any other anticipated loads (e.g., vehicles, pedestrian traffic, etc.). have a standard size manhole or  Rainwater Harvesting systems must Underground and repair equivalent opening to allow access for cleaning, inspection, maintenance locked to prevent unwanted access. s access point should be secured or purposes. Thi must  All Rainwater Harvesting systems be sealed using a water -safe, non -toxic substance. systems may be ordered from a manufacturer or can be  Rainwater Harvesting constructed on site fr 5.3 Rainwater in 5.4 Table om a variety of materials. Harvesting Feasibility Criteria compares the advantages and disadvantages of different storage tank materials.  Aboveground s must be opaque or otherwise protected from direct torage tanks sunlight to inhibit algae growth  Storage tanks must be screened to discourage mosquito breeding and reproduction.  A suitable foundation must be provided to support the storage tank when it is filled to capacity.  Dead storage below the outlet to the distribution system a nd an air gap at the top of the tank must be added to the total volume. For gravity -fed systems, a minimum of 6 inches of dead storage should be provided. For systems using a pump, the dead storage depth will be based on the pump specifications. must to a municipal backup water supply Any hookup  have a backflow prevention device to keep municipal water separate from stored rainwater; this may include incorporating an air gap to separate the two supplies. quire a pump to convey harvested Most distribution systems re Distribution Systems: 5. orage tank to its final destination, whether inside the building, an rainwater from the st automated irrigation system, or gradually discharged to a secondary stormwater treatment practice. The Rainwater Harvesting -sized system mu st be equipped with an appropriately intended pump that produces sufficient pressure for all -uses. end -stage centrifugal The typical pump and pressure tank arrangement consists of a multi into the pressure tank, pump, which draws water out of the storage tank and sends it where it is stored for distribution. When water is drawn out of the pressure tank, the pump activates to supply additional water to the distribution system. The backflow e main potable water preventer is required to separate harvested rainwater from th distribution lines. 11 03/2013 3.06.2.5-

88 Rainwater Harvesting BMP Standards and Specifications Rainwater Harvesting system must be buried beneath the frost Distribution lines from the line. Lines from the -off Rainwater Harvesting system to the building should have shut valves that are accessible when snow co ver is present. A drain plug or cleanout sump, also draining to a pervious area, must be installed to allow the system to be completely -wrapped to emptied, if needed. Above -ground outdoor pipes must be insulated or heat upted operation during winter. prevent freezing and ensure uninterr be included in the Rainwater Harvesting Overflow: An overflow mechanism must 6. system design in order to handle an individual storm event or multiple storms in succession that exceed the capacity of the tank. Overflow pipes mu st have a capacity equal to or greater than the inflow pipe(s) and have a diameter and slope sufficient to drain the cistern while maintaining an adequate freeboard height. The overflow pipe must ds. See Section 5.4. be screened to prevent access to the tank by rodents and bir Harvesting Conveyance Criteria. Rainwater Rainwater Harvesting Material Specifications : Gutters and downspouts used to convey roof runoff to the storage tank may be composed of polyvinylchloride (PVC) pipe, vinyl, aluminum and galvanized steel. Lead may not be used as gutter and downspout solder, due to the possibility of contamination of runoff. roof runoff Common conveyance materials for non- include concrete, HDPE, PVC, aluminum and galvanized steel. -toxic -safe, non turally sound, watertight, and sealed using a water Storage tanks must be struc material. Re -purposed tanks used to store rainwater for reuse must be acceptable for potable -grade products. Above -ground storage tanks must be opaque to prevent the water or food of algae in the tank. Underground storage tanks should have 18 to 24 inches of soil cover growth and be located below the frost line. The basic material specifications for Rainwater Harvesting systems are presented in Table 5.3 . Designers should consult with e xperienced Rainwater Harvesting system and irrigation installers on the choice of recommended manufacturers of prefabricated tanks and other system components. Objectives system variations Rainwater Harvesting : and System Configuration Design Many can be designed to meet user demand and stormwater objectives. This specification focuses on providing a design framework for addressing the resource protection volume (RPv) credit ing objectives and achieving compliance with the regulations. From a Rainwater Harvest standpoint, there are numerous potential configurations that could be implemented. However, in , this specification adheres to the following terms of the goal of addressing the design storm ls: concepts in order to properly meet the stormwater retention goa to use rainwater as a resource to meet on is designed -site demand System  System is designed to manage rainwater  in conjunction with other stormwater treatment practices (especially those that promote groundwater recharge). Peak flow reduction is realized through reduced volume and temporary storage of runoff.  12 03/2013 3.06.2.5-

89 BMP Standards and Specifications Rainwater Harvesting Rainwater Harvesting system design configurations may be targeted for seasonal or continuous treatment in a , and/or (year -round) use of rainwater through (1) internal use , (2) irrigation (3) ondary practice. sec Sizing of Rainwater Harvesting Systems Size the cistern to meet the required runoff reduction volume generated from the contributing drainage area based on the Resource Protection Event. However, any storage provided in a esting system, either not meeting or exceeding the RPv volume, will be Rainwater Harv accounted. In addition, the designer needs to consider both the water supply (i.e., runoff volume) and the demand (i.e., the irrigation and other water use needs). The water demand co mponent is critical, and the designer needs to determine both how much water is needed, and whether that demand is seasonal or throughout the year. Even though more intense rainfall typically occurs during the growing season, it is desirable to use at lea st a portion of the volume in the cistern throughout the year. Seasonal Rainwater Harvesting Systems : In the Seasonal Rainwater Harvesting System design, water demand is for landscape irrigation, and occurs only during the growing season. For this desi weekly irrigation demand must be at gn, of the stored least 50% . volume Continuous Rainwater Harvesting Systems : In the Continuous Rainwater Harvesting System design, the demand is spread throughout the through non- irrigation needs, such as year, so that a minimum of 50% of the demand is met plumbing, process water, car washing, or other uses that are present throughout the year. In addit ion, the Rainwater Harvesting System must be designed to withstand freezing temperatures without incurring damage to t he system. Alternative Sizing: As an alternative to these sizing options, the designer may complete daily modeling analyses to the runoff volume for the determine RPv event. This modeling would evaluate both water needs and runoff volumes on a daily ba -year modeling period, based on local rainfall sis for at least a 15 data, and would provide output to demonstrate that the volume retained in the cistern for the RPv event over the modeling period is at least as large as the volume credited in Section 5.1. Rainwater Landscaping Criteria 5.7 Harvesting If the harvested water is to be used for irrigation , the design plan must include the delineation of , the planting plan, and quantification of the expected the proposed planting areas to be irrigated demand water . Native plants based upon the area to be planted and the types of plants selected are recommended for the planting plan as they will best tolerate dry periods and will not require supplemental irrigation from another water source. Calculations to determine expected irrigation demand may be completed in accordance with the procedure provided in U.S. Green Building Council’s document “LEED for Homes Rating System”, January 2008. 13 03/2013 3.06.2.5-

90 Rainwater Harvesting BMP Standards and Specifications Rainwater Harvesting Construction Sequence 5.8 ng Installation. Rainwater Harvesti It is advisable to have a single contractor to install the system, outdoor irrigation system and secondary runoff reduction Rainwater Harvesting practices. The contractor should be familiar with Rainwater Harvesting system sizing, installa tion, and placement. A licensed plumber is required to install the Rainwater Harvesting system components connecting to the internal plumbing system. A standard construction sequence for proper system installation is Rainwater Harvesting provided below. T system his can be modified to reflect different Rainwater Harvesting applications or expected site conditions. 1. Properly install the storage tank at the design location . devices 2. Route all downspouts , roof drains , and conveyance pipes to pre treatment . . 3. Rou te all pipes from pretreatment devices to the storage tank 4. Install the pump (if needed) and piping to end -uses (indoor, outdoor irrigation, or tank dewatering release) . Test system for proper function. Flush roof drains, downspouts , conveyance pipes and storage tank. 5. 6. ntil the overflow filter path has been Stormwater should not be allowed to overflow u stabilized with vegetation. The following items should be inspected prior to final sign -off and Construction Inspection. acceptance of a Rainwater Harves ting system: Collected • impervious area matches plans • Diversion system is installed in accordance with the plan • Pretreatment system is installed openings Mosquito screens are installed on all tank • • Overflow device is directed as shown on plans vesting • Rainwater Har system foundation is constructed as shown on plans Catchment area and overflow area are stabilized • Landscape / lawn irrigation system and/or secondary • stormwater treatment practice(s) is installed as shown on plans Piping to reuse system constructe • d as designed on the plan Rainwater 5.9 Maintenance Criteria Harvesting Maintenance Agreements An Operation and Maintenance Plan for the project will be approved by the Department or the Delegated Agency prior to project closeout. The Operation and Mai ntenance Plan will specify the property owner’s primary maintenance responsibilities and authorize the Department or Delegated Agency staff to access the property for maintenance review or corrective action in the rmed. event that proper maintenance is not perfo 14 03/2013 3.06.2.5-

91 Rainwater Harvesting BMP Standards and Specifications Operation and Maintenance Plans should clearly outline how Rainwater Harvesting Systems will be managed. Maintenance of a Rainwater Harvesting Systems is driven by annual maintenance reviews that evaluate the condition and performance of the syst em . Based on maintenance review results, specific maintenance tasks may be required. It is highly recommended that self -inspections and maintenance periodic as well . be conducted for each system Rainwater Harvesting S ystem Maintenance Schedule Maintenan ce requirements for Rainwater Harvesting systems vary according to use. Systems that are used to provide supplemental irrigation water have relatively low maintenance requirements, while systems designed for indoor uses have much higher maintenance require ments. Table 5.5 describes routine maintenance tasks to keep Rainwater Harvesting systems in working condition. Inspections of proprietary components of the Rainwater Harvesting system should be conducted by a qualified inspector as determine by the manuf acturer. 5.5. Suggested maintenance Table for Rainwater Harvesting systems items Frequency Maintenance Items downspouts Twice a year Keep gutters , , and conveyance pipes free of leaves and other debris treatment Inspect and clean pre Four times a year ices dev Once a year Inspect and clean storage tank lids, paying special attention to vents and screens on inflow and outflow spigots. Check mosquito screens and patch holes or gaps immediately Inspect condition of overflow pipes, overflow filte Once a year r path and/or secondary stormwater treatment practices Every third year Inspect tank for sediment buildup Every third year Check integrity of backflow preventer Every third year Inspect structural integrity of tank, pump, pipe and electrical system As needed Replace damaged or defective system components surface impervious As needed Clear overhanging vegetation and trees over In some situations, poorly designed Rainwater Harvesting Mosquitoes. s can create system and reproduction. S creens on above- and below -ground habitat suitable for mosquito breeding tanks are required to prevent mosquitoes and other insects from entering the tanks. However, i f screening is not sufficient in deterring mosquitoes, dunks or pellets containing larvicide can be added t o cisterns when water is intended for landscaping use. Cold Climate Considerations systems have a number of components that can be impacted by freezing Rainwater Harvesting winter temperatures. Designers should give careful consideration to these conditio ns to prevent system damage and costly repairs. For above -ground systems, winter -time operation may be more challenging, depending on tank size and whether heat tape is used on piping. If not protected from freezing, these Rainwater systems mus Harvesting t be taken offline for the winter and stormwater treatment credit may not -line period. At the start of the winter season, be granted for the practice during that off ions -ground systems that have not been designed to incorporate special precaut vulnerable above should be disconnected and drained. It may be possible to reconnect the former roof leader systems for the winter. 15 03/2013 3.06.2.5-

92 Rainwater Harvesting BMP Standards and Specifications For underground and indoor systems, downspouts and overflow components should be checked for ice blockages during snowmelt events. 5.10 References Virginia Rainwater Harvesting Manual Cabell Brand Center. 2007. . Salem, VA. http://www.cabellbrandcenter.org . Sal Virginia Rainwater Harvesting Manual, Version 2.0 Cabell Brand Center. 2009. em, VA. (Draft Form) http://www.cabellbrandcenter.org -Carson, , McKee Cistern Design Spreadsheet é, J. Alex and Lawson, Sarah. 2009. Forast Rainwater Management Systems, Inc., and Center for Watershed Protection, Inc. NOAA Atlas 14 National Oceanic and Atmospheric Administration (NOAA). 2004. . Revised 2006. Silver -Frequency Atlas of the United States, Volume 2, Version 3.0 Precipitation Spring, MD. Texas Regional Water Board (TWDB). 2005. The Texas Manual Rainwater Harvesting. Third Ed. Austin, TX. U. S. Green Building Council. 2008. LEED for Homes Rating System January 2008. 16 03/2013 3.06.2.5-

93 BMP Standards and Specifications Restoration Practices Restoration Practices 6.0 Restoration Practices Definition: include Regnerative Stormwater Conveyance , also known as Systems Coastal Plain Outfalls, and other practices that restore existing degraded natural systems to their former functional condition. Streambank stabilization is also included in this category. Photo: Hala Flores, Anne Arundel Co., MD -channel conveyance structures are open SCS) Regenerative Stormwater Conveyance Systems (R that convert, through attenuation ponds and a sand seepage filter, surface storm flow to shallow hese systems safely convey, attenuate, and treat the quality of groundwater flow. In doing so, t These structures utilize a series of constructed shallow aquatic pools, riffle storm water runoff. The chip mix filter bed media. grade control, native vegetation, and an underlying sand/wood S channel are best characterized by the Rosgen A or B stream SC physical characteristics of the R classification types, where “bedform occurs as a step/pool, cascading channel which often stores The e pools associated with debris dams” (Rosgen, 1996). large amounts of sediment in th pretreatment, recharge, and water quality sizing criteria presented in these guidelines are similar to These structures feature surface/subsurface criteria for a typical stormwater filtering device. runoff storage seams and an energy dissipation design that is aimed at attenuating the flow to a desired level through energy and hydraulic power equivalency principles. Streambank stabilization includes bioengineering techniques as well as structural solutions to . Despite the name, many of abate the mass wasting of soil as a result of the movement of water these practices can be used to stabilize shorelines as well as streambanks. Design variants for Restoration Practices include: 6- A. Step Pool RSCS   S 6- B. Seepage Wetland RSC  6- C. Streambank Stabilization 3.06.2.6- 03/2013 1

94 BMP Standards and Specifications Restoration Practices Figure 6.1 S a Step Pool RSC Example of Figure S a Seepage Wetland RSC Example of 6.2 2 03/2013 3.06.2.6-

95 BMP Standards and Specifications Restoration Practices 6.1 Restoration Practices Credit Calculations The performance of Restoration Practices from both a runoff reduction and pollutant reduction standpoint is highly dependent on the design and site characteristics for a given application . For this reason, performance credits will be determined by the Department on a case- by-case basis until more data becomes available. Restoration Practices Performance Credits 6.1 Runoff Reduction Retention Allowance TBD on Case - by - Case Basis - by - TBD on Case A/B Soil - RPv Case Basis TBD on Case Case Basis C/D Soil - - by - RPv Cv TBD on Case - by - Case Bas is Fv Case Basis - TBD on Case - by Pollutant Reduction by TN Reduction TBD on Case - - Case Basis - Case Basis TP Reduction TBD on Case - by TBD on Case TSS Reduction Case Basis - by - 03/2013 3 3.06.2.6-

96 BMP Standards and Specifications Restoration Practices Design Summary Restoration Practices 6.2 and Streambank Stabilization Practices Conveyance Systems The design of Regenerative Stormwater requires specialized knowledge and skills. However, some general awareness of these systems and how they function may be helpful in evaluating potential applications for this practice. date, As of this have been the best available design criteria for Regenerative Stormwater Conveyance Systems developed by Anne Arundel County, Maryland. Therefore, the Department is recommending this s in Delaware. The Anne Arundel document to serve as the primary design tool for RSCS application County guidance has been included for reference as Appendix 6- 1 of this document. This document is frequently updated. Therefore, designers are advised to check Anne Arundel County’s Website to see if a newer version has been released prior to initiating a proposed design. The USDA Natural Resources Conservation Service (NRCS) has developed design guidance for bioengineering and other streambank stabilization techniques in Chapter 16 of its Engineering Field Handbook. The Department is recommending this document to serve as the primary design tool for these practices in Delaware. This chapter is included as Appendix 6- 2 of this document. 03/2013 4 3.06.2.6-

97 BMP Standards and Specifications Restoration Practices 6.3 References Anne Arundel County, Dept. of Public Works, Bureau of Engineering. “Design Guidelines for Rev. 4, November 2011. Regenerative Step Pool Storm Conveyance (SPSC)”. USDA, Natural Resource Conservation Service, Part 650, Engineering Field Handbook, Chapter 16, “Streambank and Shoreline Protection”. 1996. 03/2013 5 3.06.2.6-

98 BMP Standards and Specifications Restoration Practices -1 APPENDIX 6 MD ANNE ARUNDEL COUNTY, DESIGN GUIDELINES FOR OL STORM CONVEYANCE (SPSC) REGENERATIVE STEP PO 03/2013 -1- 1 3.06.2.6.A

99 Regenerative Step Pool Storm Conveyance (SPSC) – also known as Coastal Plain Outfalls Design Guidelines - Immediately after Home Port Farms construction Home Port Farms - One year after construction Homeport Farms Six years after construction - Original : June 2009 Revision 1: August 2010 Revision 2: November 2010 Revision 3: July 2011 Ron Bowen, P.E. Revision 4: November 2011 mber 2012 Revision 5: Dece

100 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering Technical Advisory Committee This document was prepared by Hala Flores, P.E., Dennis McMonigle, and Keith Underwood ; and updated by Ken Pensyl . This document is maintained on the Anne Arundel County website and can be . http://www.aacounty.org/DPW/Watershed/StepPoolStormConveyance.cfm accessed through Updates and revisions to this document are reviewed by the Technical Advisory Committee as follows. Hala Fl ores, P.E., WSSC, Principal Engineer, Water Analysis Unit Earl Reaves, I&P, County Forester Christopher Soldano, OPZ, Deputy Director Elizabeth Burton, OPZ, Chief Engineer Administrator Code Enforcement John Peacock, I&P, ard Olsen, DPW, Infrastructure Rich Management Division , Chri Jim Stein, Vernon Murray SCD s Maex, and Charles Henney, AA Keith Underwood, Underwood and Associates Erik Michelsen, Executive Director, South River Federation onigle, DPW, Environmental Restoration Project Manager M Dennis Mc s Markusic, DPW, NPDES MS4 Coordination/Ecosystem Assessment Program Manager - Jani Ken Pensyl, DPW, Environmental Restoration Project Manager See last page for summary of revisions. 2 of 36 Page vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines – Re

101 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering Important Note This document features design guidelines and procedural steps to aid design engineers in sizing a Regenerative Step Pool Storm Conveyance (SPSC) system. It is the responsibility of the design engineer to check the feasibility and acceptability for using these systems at their project site. s can be used in lie u of stormdrains as roadside conveyance/attenuation systems. SPSC SPSC s may be used for peak flow management or steep slope stability treatment and are considered Stormwater Best Management Practices ( if they are sized to accommodate the ) structural BMPs volum 2000 Maryland Storm w ater Design e control requirements specified in Chapter 2 of the Manual, Volumes I and II (the St ate M anual ) . In general, SPSC s may be used as a structural stormwater management device to provide water quality treatment as part of the treatment train or at the downstream outfall after all Environmental Site Design (ESD) techniques have been exhausted to the Maximum Extent Practical (MEP) as dictated in the State anual. Under M SD when the design conforms to the special circumstance, the SPSC may be used as part of the E criteria found in Chapter 5 for microbioretention or bio - swale and the of the State Manual general configuration co nforms to the principles of ESD: using small - scale practices distributed uniformly around the site to capt While SPSC systems can be ure runoff close to the source. implemented on steep slopes, in no circumstance can water quality credit be claimed for SPSC segments with a longitudinal profile slope that exceeds 5 percent. Introduction channel conveyance structures that - are open s SPSC surface pools through , convert Regenerative These and a sand seepage filter, surface storm flow to shallow groundwater flow . subsurface systems are designed to safely convey and treat the quality of storm flow and may have d iffering to accommodate design configuration s various site implementation conditions . The three design configurations for SPSC systems are as follows: - A series of constructed shallow aquatic pools, riffle grade control s , native vegetation, and . medium istics of this sand/woodchip mix filter bed The physical character underlying SPSC channel are best characterized by the Rosgen A or B stream classification types, where “bedform occurs as a step/pool, cascading channel which often stores large This is iment in the pools associated with debris dams” (Rosgen, 1996). amounts of sed the typical SPSC configuration , historically known as the coastal plain outfall, and is best suited for ephemeral and perennial entrenched gully systems with moderate to steep percent . 2 channel and valley slopes , larger than - A series of riffle grade controls aimed at diverting flow from the main channel to created d on the adjacent floo plain. hip mix filter is placed lateral to A sand/woodc shallow moats these shallow pools w from the channel to allow the flo to filter back to the main channel. Typically, the main channel is limited in capacity to the baseflow and all storm flow is plain where wetland areas form and flourish. directed to the floo The physical d SPSC channel are best characterized by the Rosgen DA stream characteristics of this classification type, where streams are “highly interconnected channel systems developing in gentle relief terrain areas consisting of cohesive soil materials and exhibiting wetland environments w ith stable channel conditions.” (Rosgen, 1996). This configuration is best 3 of 36 Page vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines – Re

102 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering suited for perennial moderately entrenched systems with gentle channel and valley smaller than 2 percent. Th is gradients, SPSC configuration is also known as a wetland seepage sys tem . riffles rock instream - in an entrenched strategically placed A series of one or more perennial stream to encourage upstream sedimentation and connection of the channel instream only t riffle he with the adjacent floo d plain. The is ideally set such that cess to the baseflow is contained in the channel and all storm flow has unimpeded ac time, a Rosgen DA channel is formed and the floodplain adjacent floodplain. Over or This configuration is best suited f storage and pollutant removal actions are restored. onfiguration is also known as a constructed . This SPSC c entrenched perennial channels instream . riffle The pretreatment, recharge, and water quality sizing criteria presented in these guidelines follow closely the State of Maryland’s criteria for a ty pical stormwater filtering device. These structures feature surface/subsurface runoff storage seams and an energy dissipation design that aulic power is aimed at attenuating the flow to a desired level through energy and hydr equivalency princip s. e l SPS C structures can be designed to provide energy dissipation and extreme flood conveyance/attenuation functions, as well as recharge and water quality treatment in excess of inked through ESD. The inherent energy dissipation achieved in the step pool design is directly l hydraulic design computations to reduced stream power and bank shear stresses in the receiving streams. The reduced energy and velocity at the downstream end of these structures result in conventional stormwater practice reduced channel erosion impacts commonly seen between outfalls and ultimate receiving waters. SPSC structures are generally best suited in natural ravines and are the preferred method of ESD techniques su ch as . storm water conveyance throughout the water train on a developed site alternative pavement, greenroofs, rooftop disconnections, vegetated swales, etc., should be considered and utilized to the MEP in the upstream area of a proposed SPSC system. A secondary benefit provided by the pools and plant material is to reduc e flow velocity and enhance the removal of suspended particles and their associated nutrients and/or pollutants. Additionally, uptake of dissolved nutrients and adsorption of oils and greases by the plant ove and beyond the benefits achieved through material yield secondary water quality benefits ab the primary water quality sand/woodchip mix filter. ave been adapted to the Anne The design material and plant list featured within this document h Arundel County coastal plain environment. The materials used within the SPSC, to the extent medium is quarried throughout the region possible, are taken from the coastal plain. The sand and can be readily obtained. The boulders found in these systems are sandstone (e.g., bog iron, ne’s porosity, as well as its ability to retain water, allows it to ferracrete). Sandsto iron stone, naturalize quickly, providing habitat for ferns, moss, and other organisms that persist in these s, systems. While sandstone is the preferred material for use as boulders within these system Further, granite may be substituted if sandstone availability is demonstrated to be of a concern. 4 of 36 Page vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines – Re

103 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering broken sandstone boulders that meet the hydraulic sizing criteria maybe used in lieu of silica cobbles in the riffle construction. The use of other alter native boulder and cobble material must be approved by the Anne Arundel County reviewer and/or project manager Maintenance of the . pH abitat systems; thus, the use of limestone levels is profound in ensuring the survival of these h pr stone is prohibited. oducts or cement - based General Design Situations SPSC structures consist of an open channel conveyance with alternating riffles and pools. These systems are best suited for ditches, outfalls, ephemeral and intermittent channels with longi . However, the design can be easily tudinal profile s lopes that are less than 10 percent adapted for sites where the slope exceeds 10 percent. For these sites, the size and quantity of the les and rows of boulders inherent in the design computations are increased to m cob b itigate for the stability issues associated with steep slopes. It is noted that the utilization of two or more (larger than rows of boulders typically will result in a water cascade. In extreme slope situations to safely 50 percent ), the designer may elect to use specially designed retaining structures traverse the grade. tidal wetlands and streams, the - In order to preserve the integrity and habitat functions of non . This designer is encouraged to minimize to the extent possible changes to the drainage pattern within the site following the native drainage is achieved by placing proposed SPSC systems construction impacts, in the long run it will preserve paths. While this may result in temporary - non f habitat functions within the hydraulic input which is crucial to the survivability o tidal streams and wetlands. It should be noted though that the computations presented in this document are minimum design guidelines to ensure that the constructed system will not degrade . However, if over des igned these systems may trap sediment . Sediment trapping in the pools are energy balancing the pools is a natural phenomena and is generally not cause for concern, unless this is clearly interfering with the project design goals and in that case undesired sediment sition should be removed as part of a routine maintenance plan . depo "The current condition of single gravel - bedded channels with high, fine grained banks and relatively dry valley - flat surfaces disconnected from groundwater is in stark contrast to the pre - scrub) and shallow branching streams." set tlement condition of swampy meado ws (shrub - (Walter, R., & Merritts, D. 2008). Current stormwater management regulations require that proposed development plans include appropriate mitigation measures and be continge nt on the presence of a stable outfall. According to the Anne Arundel County Watershed Master Plans, problem area inventories such as erosion, buffer deficiencies, headcuts, infrastructure impacts, and suboptimal habitats are notable in varying degrees in more than 90 percent of the surveyed stream segments. For projects that drain to stream channels with active incisions, it is imperative that proper tie - in design be established between the SPSC system and the connecting at the proper downstream channel. This could b e accomplished by installing an instream riffle elevation to promote upstream connection and prevent headcut erosion from floodplain unraveling the proposed SPSC systems . It is noted that each case should be evaluated carefully and that desi gn engineer s propose appropriate solutions based on the individual circumstance notifying and engineer is responsible for case . Additionally, the designer/ surrounding each State and Federal authorities. Local, approvals from the all required obtaining 5 of 36 Page vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines – Re

104 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering t is important to acknowledge that each site has unique and defining features that require site I - specific design and analysis. The guidance provided below is intended to provide the fundamentals for sizing the facility to meet the regulatory requirements b ut is not intended to - substitute engineering judgment regarding the validity and feasibility associated with site specific implementation. Designers need to be familiar with the hydrologic and hydraulic e design and they should also enlist the engineering principles that are the foundation of th expertise of qualified individuals in stormwater management and stream restoration plantings with respect to developing appropriate planting plans and habitat improvement features. Hydraulic Design of SPSC System s SPSC systems can be used to reduce a surface water discharge. This is accomplished by converting surface discharge to subsurface flow/spring head seep. The design up to the 10 0 year specific established restoration goals of the SPSC should be based on for the project. The sand/woodchip mix filter medium is specifically required for retrofit projects with water quality restoration goals. The depth and quantity of the pool structures are linked to water quality, energy dissipation, and flow attenuation /peak management requirements. Additionally the SPSC ded may be based on the specific needs to retrofit an existing ero design parameters determined channel outfall . The dimensions of the riffle and pool segments are designed in a manner to - in to the receiving e and safe conveyance of the design flow. ensure adequat The downstream tie - deficiency, such as incision and erosion, and promote long s to correct an existing channel aim ments. The term stable outfall conditions. This is a requirement for all proposed develop - downstream tie in design may result in additional water quality benefit for the contributory water quality mitigation for new drainage area, however, this may not be claimed as ather this benefit development related impacts. R may be claimed fo r select redevelopment Public Works for projects and will be evaluated by the Anne Arundel County Department of consideration as credits toward the County’s National Pollution Discharge Elimination System ) p ermit (NPDES - MS4 Municipal Separate Storm Sewer System conditions . The construction engineer to carefully target the specific es it imperative for the design/ cost of these systems mak restoration goals prior to providing a design solution. The following steps have been formulated ineer in preparing the minimum design elements for the SPSC. to aid the designer eng 1. Develop the hydrologic design parameters for the project The drainage area should be delineated to the outfall point of the SPSC and the connecting channel tie in location if applicable . In new development projects, - ESD shall be used to the MEP such as to minimize alterations to the existing drainage patterns for the site. Using - NRCS TR 55, determine the flow path, time of concentration, the USDA and weighted runoff curve numbers for all points o f investigations and required landuse scenarios. Using USDA - NRCS TR20, determine the 1, 10, and 100 year peak discharges for all points of investigations and required landuse scenarios. pertinent model input and output points of hydrology parameters for Include all required landuse scenarios on the construction plans. investigations and 6 of 36 Page vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines – Re

105 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering Establish and quantify the restoration goals for the project 2. Establish the goals for the SPSC. The goals may include, but are not limited, to the following: □ e open channel surface conveyance in lieu of stormdrains. Providing saf □ Providing structural water quality mitigation in excess of ESD to the MEP. □ Providing slope and outfall stabilization . □ Subwatershed retrofit s as outlined in local comprehensive watershed assessment and Chesapeake Bay TMDL Watershed studies Implementation Plan . (WIP) The restoration goal for the project and the provided quantities of water quality treatment shall be listed on the construction plans. Map the horizontal alignment for the project 3. p a geometric plan sheet showing the SPSC alignment with stations and Develo tabulated coordinates. The SPSC will be placed in the landscape following a curvilinear flow path whenever possible that generally follows the shape of the ravine or localized drainage path. Special attention should be followed to minimize impacts to natural features. This could be accomplished through innovative/adaptive construction phasing and tree protection plans. inear designs of Special effort shall be made by the designer to avoid entrenched l the step pool structure. Storage opportunities on the floodplain lateral to the structure should be utilized to the maximum extent possible. Measure the length of the reach along the plan view alignment from its input to the discharge loc ation. This length shall be described in the design formulas as . In the event that channel hall be at the receiving . The discharge location s L design instream the receiving channel is incised/disconnected from the floodplain, an be utilized to may riffle A connect the receiving channel with the floodplain. work. Design horizontal alignment shall be established for the instream guidelines for the - in are included in this document. instream riffle tie 7 of 36 Page vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines – Re

106 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering 1+50 0+50 1+00 1+50 L design 1+00 2+00 0+00 In - stream Flow SPSC Flow +50 0 0+00 Map a preliminary vertical alignment for the project 4. Me asure the elevation difference “ E” between the top and the bottom of the proposed SPSC. In the event that the proposed SPSC connects downstream channel, the n incised to a instream elevation of the floodplain terrace shall be used as the downstream elevation. An design with a to set at the floodplain terrace in riffle - is required at the tie p of weir elevation location. Compute the average outfall slope, S, by dividing E by L design. in longitudinal percent SPSC segments utilized for water quality shall not exceed 5 for boulder cascades will be needed percent l slope exceeds 5 slope. If the overal , traversing the grade. Boulder cascades may be placed at a maximum of 50 percent 5 (1V:2H) . A maximum slope feet of vertical drop from the top of the cascade to the 50 percent lowest point in the downstr eam pool shall be permitted for cascades with a slope be required along the length of the project to traverse . Multiple cascades may Longer cascades at a flatter slope maybe used in accordance with the steeper grades. w. The location of the cascade shall be selected to minimize cascade design chart belo site disturbances and environmental impacts. Use a minimum 4 foot cobble apron at the rising limb of the pool. Refer to schematic drawings. th of the pools must be at least and could be twice the le T he leng ngth of the riffles maximum length of riffle . The selected longer to reduce the number of structures used “excluding the cobble apron length on the rising limb of the shall not exceed feet 8 energies excessive . pool” so as not to build unarmored sides of the pool shall be laid at no steeper than 3H:1V. All Page 36 of 8 Re Step Pool Storm Conveyance (SPSC) Guidelines vision 5: December 2012 –

107 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering For an SPSC system with a 6 foot long cobble riffle, a 14 foot long pool, a 1 foot elevation drop over the riffle and pool combined segment s is used . The overall slope is 1/20 or 5 percen t. . is required A inch fixed pool depth minimum 18 Alternate pool and riffle channels. Three consecutive pools separated by boulder weir grade control structures shall be used following a cascade. above the information Using and not considering the nee d for cascades , the number of / (L + L ) . ) = L riffle and associated pools (N esign d riffle pool pools/riffles In the event the connecting stream is incised, Boulders shall be used to construct an in - stream weir. Minimum Maximum Cascade Required Allowable Cascade length Height Cascade Slope (ft/ft) (ft) (ft) 4 0.5 8 0.5 10 5 0.4 6 15 0.3 7 23 8 0.2 40 0.1 9 90 >10 >100 0.1 The cascade height is measured f rom the top of the cascade to the low est point in the subsequent pool. Three f ull size pools are required at the bottom of a cascade. – Typical Profile Alternating Pools and Riffles 36 Page 9 of vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines – Re

108 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering Cascade @ 50% Slope Pool #2 Pool #1 Pool #3 Max. Height from top of cascade to bottom of p ool = 5 ft. Boulders Silica Cobbles h f Cascade ( special design h (Typical) Height f following the h (Typical) f cascade ) Filter Fabric Cascade Boulders shall Sand/Wood Chip be double lined Mix Existing Ground Three p Cascade Profile Cascade ools following – - cascade and pool channel segments Design the typical cross section for the riffle/ weir/ 5. weir/ The riffle/ cascade and pool channels shall be parabolic in shape. for the Design the riffle/ cascade and pool channels to carry the Q weir/ design ye unmanaged 100 ar storm flow in a parabolic shape. The area and hydraulic radius of a parabola are computed as follows: 2 WD Area Mathematic al Solution 3 2 2 D W , Hydraulic 1959 Chow Radius 2 2 D 8 3 W min.) . W (8 ft ontal 10 Horiz 10 Horizontal Anchor Rock Anchor Rock = (1 Vertical) D Riffle Section through Boulder 10 Horizontal 10 Horizontal D = (1 Vertical) d 2 x 50 Riffle Section through Cobble 36 of 10 Page vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines Re –

109 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering feet The minimum freeboard for lined waterways or outlets shall be 0.25 above design high wate r in areas where erosion - resistant vegetation cannot be grown and maintained. No freeboard is required if vegetation can be grown and maintained. (USDA, 2006.) /weir Select a trial constructed riffle channel width (W). The width is the and shall be minimum 8ft dimension perpendi cular to the flow . channel depth (D). The side slopes of the Select a trial constructed riffle /weir For retrofit projects with parabolic channel shall not be steeper than 10H:1V. limited right of way and/or floodplain constraints, the engineer may increase the cross sectional entrenchment up to 5H:1V if it can be demonstrated that the - section will remain stable for the design storm. The dead storage depth within the pool shall not be considered when checking for nce adequacy of conveya . The calculated Design using a trial cobble with a d of 6 inches. d shall be the 50 50 stone size diame and shall be rounded up median ter to be used in riffle channels he density of the stone . T to the D50 Median stone sizes shown on the table below l be specified. The depth of the cobble material is equal to 2 x shal (MDSHA, d 50 Show the cobble gradation table below . Highway Drainage Manual, 1981 clearly on the plans. Cobble Gradation Table 11 of 36 Page vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines – Re

110 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering Calculate the Manning’s n roughnes pth, s coefficient based on the constructed de D, associated with the 100 year ultimate flow conditions and the cobble size: 1/6 d = D n / (21.6 log (D/ )+14), (USDA, 2006). 50 Where: Manning’s n, use 0.05 for cascades. n = D depth of water in the riffle channel associated with unmanaged = 100 year Q , feet , design = d Median cobble size, f ee t 50 Use the Manning formula to calculate the flow and velocity associated with the trial parameters D, W, and year 00 . The design fl ow shall meet or exceed the 1 d 50 ultimate flow conditions. 1/2 2/3 (S) ) (1.49/n) (A) (R Q = h Where: Q = 100 year ultimate flow (cfs) = conversion factor 1.49 n = Manning’s n, determined by USDA, 2006 equation A = cross - section area of a riffle channel, which for a parabola = 2/3(W)(D), feet ) where W is top constructed width ( feet ) and D is the constructed depth ( = R ), calculated using Chow 1959 relationship for parabolas feet hydraulic radius ( h S = average slope over entire length of project ( feet / feet ) ), V = Q/A ond /sec feet locity in the riffle channel ( ve = V ), develop a hydraulic rating curve/table feet Using small incremental depths (0.1 for the channel to ensure that subcritical flow conditions prevail to the greatest alculating the Froude n c . A Froude umber extent possible. This is achieved by Froude number exceeding 1 indicates that the flow is supercritical , while a number of less than 1 indicates that the flow is subcritical in nature. The Isbash coefficient for high turbulence should be used when sizi ng the cobble stones to accommodate supercritical conditions. Increasing the cobble size or the width depth ratio of the riffle channel can increase roughness and reduce velocity. This can further assist in meeting subcritical flow conditions . V Fr gD 36 12 Page of – vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines Re

111 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering he design velocity shall be checked to ensure that it is below the maximum T allowable velocity estimated from the Isbash formula below (NRCS, 2007). A graphical solution of the Isbash formula is also shown. This will be an iterative dsheets can be used to streamline the calculations. design process. Sprea 0 . 5 0 5 . w s Allowable Velocity C 2 g D Isbash Formula Maximum 50 w Where: C = 0.86 for prevailing supercritical flow and 1.2 for prevailing subcritical flow 2 /sec t f = 32.2 g 3 ) = stone density (lb/ft s 3 = water density (lb/ft ) w d is a median size of cobble stone diameter ( feet ) . = For the purpose of SPSC design, D 50 50 36 of 13 Page Re – Step Pool Storm Conveyance (SPSC) Guidelines vision 5: December 2012

112 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering Graphical Solution for Isbash technique VI 4 Figure TS14C - 6, (210 - - - NEH, August 2007, TS14C (ft) meter, d Spherical dia Average velocity (ft/s) 50 of 36 14 Page Step Pool Storm Conveyance (SPSC) Guidelines Re vision 5: December 2012 –

113 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering Ineffective Cascade Flow Areas 5 ft. elevation drop (max.) Followed by 3 consecutive A A’ pools Flow Anchor Rock B B ’ Riffle Pool Sequence (Typical) – Cascade Sequence . W (8 ft min.) D 2 x d 0 (18 in min.) D f Sand/Woodchip Mix d (riffle) f . W ( 4 ft min.) sand - A’ Section A Riffle Weir Cross Section through Cobble h (18 in. min.) f Sand/Woodchip Mix (pool) d f min. 18 in. Section B - B’ Pool Cross Section Page 15 of 36 vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines – Re

114 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering The constructed depth of the typical pools (h ) and the pool directly f ) shall not be less than 18 inches and shall not following a cascade (h f cascade exceed 3 feet . Floodplain storage should be sought in the event that additional volume of storage is required. This will result in a pool geometric design with less than 3 feet of embankment and will meet the exemption criteria he State as specified in Appendix B.1 of t Code 378 the SPSC system from the Soil Conservation s Manual. This exempt District small pond approval . The minimum design depth of the pools shall be estimated based on the use of the solved form of the Bernoulli ow. The Bernoulli equation conservation of energy equation shown bel . D and V feet was solved to achieve a pool channel velocity of 4 second / correspond to the riffle/cascade channel design depth and velocity respectively. 2 V . h or h D 0 25 f cascade f 2 g ide To ensure stability, the pools shall be constructed with a minimum s slope of 3H:1V. The minimum width depth ratio for the pools is 10H:1V. medium shall meet the AASHTO - M - 6 or The sand/wood chip filter C - ASTM - 33, 0.02 inches to 0.04 inches in size. Sand substitutions such #10 are not as Diabase and Graystone ( acceptable. No calcium AASHTO) carbonate or dolomitic sand substitutions are acceptable. No “rock dust” can be used for sand. The woodchips are added to the sand mix, percent by volume, to increase the organic content and approximately 2 0 lant growth an promote p d sustainability. medium , below The minimum depth of the sand/woodchip mix filter , d f the invert of the pools, shall be 18 inches. Filter fabric shall be placed under all boulders. Refer to design figures for To prevent undercutting , a continuous sheet of filter placement location. section. Filter fabric shall not be fabric shall be used along the cross - placed in the pools so as not to impede filtration. The sandstone boulders serve as the weir component of the riffle grade lders should be arranged in a curved manner as control structure. The bou shown on the riffle pool sequence schematic and the sandstone weir elevation view. This arrangement is intended to encourage flow deflection s near the to the center of the pool and the creation of ineffective flow area channel banks. To achieve this, the sandstone boulders shall be arranged horizontally in the center of the channel and the arms on either side of the / approximately 20 channel shall be extended parabolically degree angle enter of the pool The sandstone boulders should be . longitudinally to the c 36 of 16 Page Re – vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines

115 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering sized by the engineer to be at least three to four times heavier than the riffle channel cobble . Typically, the diameter of sandstone boulders shall The typical bould in length. feet er size shall be designed not be less than 2 and specified on the plans by the enginee r to best fit the channel shape, i.e., smaller cross - sections will require smaller boulders, while larger channel cross - sections may require larger boulders. The sand stone interlocking Boulders maximize in shape to boulders should be tabular . shall be used to line cascade segments. The footer rocks provide added stability to the sandstone boulder in the event that excessive erosion is experienced in the energy dissipation pools. er rocks may not be necessary in the event that the utilized The foot sandstone boulders size is adequately anchored ( 2 feet below the lowest elevation point in the pool). The footer rocks shall be equivalent in size to the sandstone boulders and should be tabular in shape to allow for maximum interlocking. Boulders shall be stacked as a double layer when used to armor a cascade. All f ooter rocks shall be anchored 2 feet below the lowest . excavated elevation in the pool Further, all boulder weir structures shall be anchored by a minimum of 2 ft to existing soils in the bank 6. Design the instream riffle tie - in s tructure (i f applicable) of the riffle shall be set approximately 30 feet downstream The instream in location. The top elevation of the weir shall be - tie set at the as determined appropriate by the desired floodplain elevation /historic engineer and approval authority. This is intended such as to impede headcut through the SPSC and inundate the floodplain for all flows above nhance the water quality conditions the base - flow conditions , thus e . instream riffle shall be connected longitudinally to the upstream and The slope boulder existing grade through a maximum 4 percent downstream gradual transition and . This will ensure ot that flow velocities do n channel impede the fish passage. Sand Sand shall be used for filling the stream bed to the desired elevation. for creating as part of the erosion and sediment control plan bags utilized instream diversion may be left in place. Geotextile shall be used to sepa rate the sand fill and the overlay boulders that l ine the channel . The boulders shall ext end in cross - section to the 2 - year storm. boulders shall be sized t The instream o remain in place under the 100 year velocity and shear stress, and shall be placed in a manner to create maximum hydraulic friction. The last two structure s within the SPSC system may be inundated by the instream 100 year flood elevations. year water surface RAS shall be used to estimate - HEC instream 100 the RAS sect - elevation. The HEC ions shall be extended upstream to the ed 100 point where the existing and propos . The year floodplains converge 17 of 36 Page vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines – Re

116 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering degradation to the hydraulic design shall not result in instream proposed flooding ivate adequacy of upstream public facilities or in increased on pr . properties C stream Flow In Max. 3 ft. Sand Fill “Sandbags from stream diversion left in place” C may be Existing Ground longitudinal profile Instream riffle Silica Cobbles stream In Boulders floodplain 0 yea stream 10 r In Width of Instream Riffle = 2 yr Storm Existing Ground Geotextile Sand Fill Sandbags from stream Sand/Wood Chip left may be diversion Mix in place Most downstre am SPSC riffle/pool Main Channel structure C: Cross section at constructed instream riffle tie in with SPSC - Section C 7. Check and adjust the design parameters based on the project goals The provided sand/woodchip mix filter bed area can be computed by multiplying the average width of the sand/woodchip mix medium , where the provided , , Chapter 3.4 of the State Manual inches mix depth is at least 18 nd/woodchip sa , L woodchip mix medium , in the direction of the by the length of the sand/ sand flow. 36 of 18 Page – Step Pool Storm Conveyance (SPSC) Guidelines vision 5: December 2012 Re

117 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering Where, x d WQ f v Sizing Criteria MDE , 2000 A Filtering f h ) ( t d K f f f 2 = required sand/woodchip mix filter bed area (ft A ) f 2 ) provided sand/woodchip mix filter bed area (ft = A provided feet = width of sand/woodchip mix filter bed ( W feet ), minimum = 4 sand ) ) along the project (L feet L = length ( pre sand 3 = prescribed Water Quality Volume (ft WQ ) v ), use minimum 24 inches feet d = sand/woodchip mix f ilter bed dept h ( f (Average of d (riffle) (pool) and d f f K = coefficient of permeability of filter medium ( feet /day), use K = 3.5 for sand/woodchip mix = Depth of Pool ( feet ), minimum 18 inches h f t = design filter bed drain time (days), use 1.67 days as recommended by MDE for f sand mix filters and retrofit outfall or For SPSC systems that meet the ESD criteria and f projects, the stream restoration for the contributing drainage required WQ v ing the depth of pools, width of sand/woodchip by adjust area may be met to increase the filtering capacity mix filter, or length of the facility Partial . treatment credit may be claimed for outfall retrofit and stream restoration projects SPSC systems proposed as part of a new development or . not designed as an ESD device may not claim any redevelopment that is water quality credit. In situations where the existing soil, underlying the proposed SPSC, is confirmed through “borings” to be highly infiltratable, and the SPSC meets the designer may utilize the the ESD criteria or is a retrofit project, State Manual’s water quality sizing criteria for an infiltration basin in lieu of filtration. This is prescribed so the designer engineer is not forced, under certain circumstances, t o replace highly infiltratable native soil with non - native filter bed material. In order to claim water quality credit, the design ponding depth/head , h , intended to drive the seepage through the f filter shall be entirely above the seasonal high groundwat er elevation. The proposed SPSC will satisfy peak management flow requirements if two conditions are met: □ First, adequate storage volume within the pools and sand/woodchip voids shall be provided to meet the required r the project . storage volume/quantity management fo it must be demonstrated that the design renders the □ Second, development/desired hydraulic power equivalent to the pre - hydraulic power through the proposed energy dissipation pools. Page 36 of 19 Re vision 5: December 2012 – Step Pool Storm Conveyance (SPSC) Guidelines

118 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering e the required To achieve the conditions above, the designer must compar peak management storage volume with the combined volume within the n the sand/woodchip mix. A 30 pools and the volume in the voids withi porosity percent shall be used for the sand/woodchip mix to (n=0.3) calculate the volume within the void s. The total provided storage shall exceed the required storage volume for the design peak management storm. Second, the selected design for the SPSC must be checked using the conservation of energy principles to ensure that the hydraulic power is tely reduced to design/ pre - adequa development levels. This is achieved by equating the pre - development or reference condition hydraulic power to the post development hydraulic power and solving for the equivalent ender this power to the added stream length/volume of storage needed to r desired condition. The conservation of energy principles are then utilized to convert the energy loss within this horizontal length to an equivalent vertical drop. The vertical drop is then converted to multiple drops that are dis tributed along the system in a manner that result in the least site disturbances. The provided quantity/volume of pools is then compared with the calculated quantity/volume of pools. If the provided pool storage is less than the computed/required pool st orage, then additional SPSC design measures or additional upland management strategies must be taken to reduce the inflow and in turn the hydraulic power. Refer to the figure below for a demonstration of the SPSC - provided volume of storage and input para meters for the conservation of energy computations. It should be noted that equating the geometric configuration of a multiple pool system to one pool with an area equal to the cumulative areas within used to simplify the the individual pools is a conservative measure and is hydraulic power routing computations. It is expected that cumulative roughness and headloss within the multiple pool configuration to be much higher than the individual pool configuration. 20 of 36 Page vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines – Re

119 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering Storage Volume in Pools = Q V in post /A in D i n D out 1 D out 2 D riffl D out e 3 D poo l L Storag e Volume in Voids x L x W D x Porosity f sand Design Water Surface Sand/Woodchip mix ~ Elevation ~ Porosity = 30% Df (Average filter bed area= (D riifle +D )/2 pool = Q V in post /A in D V = Q i post out /A n out D = out + D + D D out3 out2 out1 D riffl e D poo l The se s teps should be followed in checking the before/after hydraulic power: pre -  development/design and post development Compute the - pre hydraulic powers by substituting the development and post development discharges in terms of Q in the hydraulic power n. The hydraulic power is expressed in the units of equatio second . lb/ Hydraulic Power = x Q x S, where 3 is the unit weight of water = 62.4 lb/ft Q corresponds to CPV discharge Chapter 2 of State Manual S is the slope of the outfall channel in percent  Equate the pre - development/design and post development hydraulic powers and solve for the needed added stream length. x Q  E/L x Q )= ) E/L x ( x ( pre post post pre  The elevation difference between the top and bottom of the project and the unit w eight of water will remain constant, 36 of 21 Page – Step Pool Storm Conveyance (SPSC) Guidelines vision 5: December 2012 Re

120 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering therefore, the channel protection requirement could be expressed in terms of a required additional stream channel length L , add needed to render the post development hydraulic power equivalent to the pre - development hydr aulic power. L - ) /Q x (Q = L L add pre Post Pre pre The required headloss due to friction through the Step Pool  - Storm Conveyance system can be calculated using the Darcy Weisbach equation. By substituting L for L, this headloss add ergy loss within an added stream becomes equivalent to the en channel of length L . The friction factor can be calculated add - using established relationships between Darcy Weisbach friction factor and the Manning friction coefficient listed in Chow, 1959. Weisbach headloss – The Darcy equation is as follows: 2 V fL out add Friction loss head 2 g D out By substituting the required headloss term in the Bernoulli  conservation of energy equation, the total combined design depth ” feet of all proposed pools shall be at least equal to the “D in out term embedded in the Bernoulli conservation of energy equation of all depicted below. If the total combined depth in feet proposed pools is less than the calculated “D ” term, then out additional pools are required or alternatively the pools could be ” term using trial and error for the “D made deeper. Solve out techniques or available commercial solver functions/calculators, (i.e., Microsoft Excel). The general and solved forms of the Bernoulli conservation of energy equation are shown below. lli Equation General Form of the Bernou (Potential + Kinetic + Static) Energies = (Potential + SPSC entrance Kinetic + Static) Energies loss + Head within SPSCsystem SPSC outlet orm of the Bernoulli Equation Solved F 2 2 2 fL Q 9 9 9 Q Q add D E D out in 3 2 2 2 2 2 gD 4 4 4 W gD W gD W out out in in out out Page 36 of 22 – Step Pool Storm Conveyance (SPSC) Guidelines vision 5: December 2012 Re

121 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering Where, = f Darcy - Weisbach friction factor, the Chow 1959 equations below may be used to relate the friction factor to a manning roughness: 1 / 3 2 8 , 1959 Chow n gRh f http://www.water.tkk.fi/wr/kurssit/Yhd - 12.121/www_book/runoff_6.htm L additional channel length ( feet ) required to render the post = add deve pre - development conditions lopment power to Design velocity at entrance riffle = V = V in D = Design depth at entrance riffle = D in Design width of riffle = W = W in W feet Width of the pool ( = ) out V this term is ) in the pool, second / feet typical velocity of flow ( = out unknown in the Bernoulli equation. Using flow continuity principals, this term could be expressed in terms of the CP V design discharge, D . , and W out out 2 = g acceleration due to gravity = 32.174 f t /sec = D Solve for combined dept h of flow in all pools ( feet ) and out compare to the total provided pool depth section and profile design for the project - Finalize the cross 8. section Develop a grading plan based on the preliminary profile and cross - typical design. Adjust the preliminary profi le dimensions to accommodate site specific concerns/impacts. Minimum design parameters for hydraulic, water quality, and quantity management criteria should be rechecked based on adjustments to the riffle/pool channels to ensure that safe and adequate veyance is still maintained. con The sand/woodchip mix filter bed shall have a minimum depth of 18 inches under the riffle channel and a minimum width of 4 feet and shall be placed as the substrate drainage material along the entire project length. dimensions of the sand/woodchip mix filter bed will be The actual determined based on the required water quality volume. Typically, construction of the SPSC system shall begin at the downstream end and proceed upstream to the project outfall. The outlet pool is igned to be placed at the lowest point in the project reach. This is often des floodplain, but can also be located in in t he receiving wetland or stream/ upland settings where the SPSC system discharges to another stormwater BMP or adequate storm conveyance sys tem. Footer boulders shall be placed at the interface of the pools and riffles as shown below. Additional boulders shall be placed on top of the footer at the weir elevation upstream of the footer boulders to form the boulders Boulders shall pe. exceed the dimensioning riffle channel parabolic sha the Maryland State Highway and unit weight requirements for Administration ( riprap. Class 3 ) SHA 23 of 36 Page vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines – Re

122 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering Pool Riffle Footer Boulders (Parabolic Cross - Weir Section) Boulders extend 6 in. . below bottom of pool Boulders shall exceed dimensioning and unit weight requirements for SHA Class 3 riprap Sand/ Wood Chip Mix Existing Ground Continue the process of alternating pools and riffles /weirs up through the ool. If the entry pool ties to an existing pipe outfall, system to the entry p additional armoring or scour protection of the pool may be needed to address the pipe exit velocities associated with supercritical hydraulic pool at the project conditions. The designer may elect to use a larger size entry to dissipate the outfall velocity and/or to address pretreatment concerns. If the SPSC is proposed below a pipe system, it is desirable that the top invert of the weir associated with the entry pool is set at or above the of the discharge pipe or culvert. It is the responsibility of the design invert engineer to check the adequacy of the upstream drainage system and drainage area. Vegetative stabilization must comply with Anne Arundel Soil Conservation/MDE stabilization specific Kentucky 31 tall fescue is ations. . not to be used in wetlands or wetland buffer systems should be used 8 inch thick) – (4 inch Course woodchips and compost provided that throughout the limit of disturbance for site stabilization lled during the first available planting season. plantings will be insta - All areas should be hydro seeded. At the end of each day, exposed dirt shall be stabilized immediately. be placed It is advisable that e xcess materials, i.e., cobbles and boulders, the cross the maintenance phase to section for use during at the edge of - . correct any physical instability . A direct maintenance access shall be provided to the system All public systems must be fully contained within public right of way or easement with sufficient width to allo w future maintenance and retrofit activities as needed. 9. equirements Setback r The minimum setback from the 10 0 year water surface elevation of the . system to structures on slabs is 10 feet valuated Systems located uphill of an existing house or structure shall be e for possible adverse effects to the structure. 36 of 24 Page Re – Step Pool Storm Conveyance (SPSC) Guidelines vision 5: December 2012

123 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering water surface elevation of a system located uphill of a 0 year The 10 building or structure that has a basement shall be no closer than 20 feet from the structure or the intersection of the structure foundation footing and the phreatic line associated with the overflow depth of the device, whichever is greater. The 10 0 year water surface elevation of a system located downhill of a building or structure that has a basement shall be no closer than 10 fe et from the structure foundation or the intersection of the structure foundation footing and the phreatic line associated with the overflow depth of the device, whichever is greater. water surface elevation of a system shall be located a 0 year The 10 mum of 1 foot below the structure floor or basement floor. mini Certification to this effect from a professional engineer shall be shown on the plan. The 10 0 year water surface elevation of a system shall not be located within 25 feet of a retaining wall or th percent e top of a slope that is 25 or greater. In no case shall the phreatic line associated with the overflow depth of the system intersect the existing or final ground surface of the retaining wall or slope. The 10 water surface elevation of a system shall not be located 0 year within 50 feet of any residential water supply well. The designer shall consider the proximity of sanitary septic drain fields when locating a new system. These systems can raise the localized e impact existing septic drain fields. groundwater elevation and therefor ensure that constructed SPSC systems pose no impact The designer shall to primary and secondary septic drain fields and shall consult the Anne Arundel County Health Department regulations in these instances. The 10 0 year water surface elevation of a system shall not be located within 10 feet horizontally from any public sanitary sewer manhole and clean out s tructure s Sewer manholes, clean outs, or house connection s . located 1 foot above the pump stations, and other sewer structures shall be 100 year storm elevation within the SPSC system. otes n ontrol uence of construction and erosion and sediment c Seq 10. It is preferred that the SPSC system be installed at the end of the construction phase (when the upstream area is st abilized) so as not to if the site contaminate the SPSC during upstream construction. However , is constricted and the SPSC system needs to be installed earlier on in the sequence, then upstream flows must be directed around the SPSC system to avoid contam ination. Under no circumstance c an the SPSC system be used as a sediment control the Anne Arundel Soil device during construction unless approved by SCD Conservation District ) (AA . Upstream controls such as diversion arounds are required dur - and pump pipes ing construction so as not to contaminate the SPSC system. 25 of 36 Page vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines – Re

124 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering The SPSC system shall not be finalized until all upstream construction is and erosion and sediment and all disturbed areas stabilized complete . control measures have been removed f the inspector at the discretion o reinforced or Special attention shall be paid to the application of perimeter super silt fence along the SPSC system so as not overwhelm the silt fence with concentrated flow and develop erosion within the SPSC floodplain and behind the st one structures. If erosion from sheet flow to the system is observed during construction, a plan revision to address the upstream drainage area and an adequate design of the conveyance channel should be the problem location. submitted for SPSC sediment co ntrols when possible shall have reinforced silt fence along the toe of the outlet for the bottom pool. A bypass for upstream runoff around the SPSC is needed until the drainage area is permanently end of each work stabilized. Riffles and pools shall be stabilized at the day. Draft a planting plan 11. The planting plan and proposed species must be reviewed and approved by the County project manager/reviewer prior to installation. Additionally, any plant substitutions must be approved by the project manager/r eviewer before the substitute species are installed. the Maryland For projects within the airport zone, a sample list of MAA Aviation Administration ( approved native plants is attached at the ) end of this document. A selection of approved ved trees with appro understory of shrubs and herbaceous materials should be provided. Pay special attention to use of native material, diversity, and dense placement of plant material within appropriate wetness zones throughout the site (MDE, 2000). zation measure, s eed and mulch (compost) the entire As a temporary stabili site with annual rye throughout construction. Spray down a minimum 4 - 8 inch layer of compost throughout the site avoiding areas of ponding water . The compost shall be derived from the natural compostin g process of plant material with no lime additives. The PH acceptable range shall be between 5 and 8. Red As a permanent stabilization measure, s eed the entire site with may be ed Fescue alternatively used. Chewing R Fescue. Existing trees to be protected shall be marked clearly on the project plan view and planting plan. i The designer has the option to use nverted root wads, in the pool areas to enhance the soil porosity and create habitat for the biological community. Root wads shall be embedded 6 feet b elow the invert of the pool and their not exceed 10 percent of the pool volume. Root wads shall not size shall be used in the two pools directly upstream of a cascade. The root wads shall be placed in the center of the pool in a vertical alignment. It is noted that the is not a requirement and is an option. Root wads root wads use of 26 of 36 Page vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines – Re

125 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering are not intended to serve any bed or bank stabilization purpose and are primarily used to enhance habitat and increase roughness. 12. Prepare a monitoring plan and schedule o f completion Prior to release of certification of completion, inspectors must ensure that adequate vegetative stabilization has occurred. Adequate vegetative cover. percent ground stabilization requires 95 In addition, all sediment accumulation having re sulted from upstream construction must be removed to design elevations. A monitoring plan must be prepared to address the specific restoration - 3 per Article 16 205(a). Clearly show the erosion - goals for the project control monitoring device on the sedime nt and erosion control plan . Structural stability and plants survivability are the two most pertinent components to monitor for private/developer built projects. These components shall be monitored for three years or as established in the plan cess. Enforcement of the monitoring conditions shall be tied to review pro roval process and release of the stormwater management the asbuilt app bond. The monitoring plan for SPSC shall include annual vegetation survey to nt nt that planted species have 80 perce docume survivability and a biannual physical stability assessment. At the discretion of the project manager, annual benthic macro invertebrate monitoring using the Anne Arundel County approved protocols and storm event chemical monitoring for nutrients and se diments may be required. The monitoring plan shall also address all permit required project monitoring. owned SPSC systems is Routine/biannual maintenance of County - prescribed for a period of three years. This includes, but is not limited to, mulching an d seeding of devoid areas, diseased plant replacement and replanting if necessary, removal of excessive debris and invasive species. This is done to ensure plant survivability, and to monitor and ensure the by performing any routine structural integrity of the construction project structural maintenance necessary. accumulation exceeds ediment In the event that s inches in the first year, 6 the contractor shall spray down an additional layer of compost and replant pected in the pools to balance the pool bottoms. Sediment deposition is ex the energies within the system ( nput versus stable sediment i upstream geomorphic design). Removal of accumulated sediment should be limited integrity of the to when the accumulated sediment threatens the structural system . Unless encountered with natural groundwater perch, the filtering capacity shall be physically checked. If the filtering capacity diminishes substantially (e.g 72 the design ponding depth is not recovered after . terial within the pools shall be hours), the top few inches of discolored ma removed and shall be replaced with fresh material. The removed sediments should be disposed in an acceptable manner ( . landfill). i.e 27 of 36 Page vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines – Re

126 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering Direct all sandstone weirs and maintenance access shall be provided to pools . - t is required for all privately maintenance agreemen A recorded owned SPSC systems. The operation and maintenance design detail and schedule shall be shown owned structures, the maintenance - he asbuilt plan. For privately on t d the recordation number shall be agreement shall be officially recorded an included on the approved grading plans. , At a minimum, a maintenance plan shall include removal of exotic native plant species identified in the annual invasive, and/or non - County and by the vegetation survey using methods approved by the Maryland Department of Agriculture. 28 of 36 Page vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines – Re

127 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering 13. Design c hecklist Reviewer Comments SPSC Item Check Yes/No most , landcovers, and soil to the Delineate drainage area of the SPSC system. downstream point - Develop TR55/TR20 model run to calculate the pre - development and post development peak discharges. Hydrology to calculate the required TR55 Utilize MDE standards and and other overbank quantity volume of channel protection storage to be controlled within the system. Conduct a downstre am investigation to check the adequacy of the outfall system. Check the conveyance design (width, depth, slope) to ensure storm over the 0 year safe conveyance of the 10 riffle/weir/cascade channels and that stable design dimensions for the co bbles and sandstone boulders are provided. Check the calculated minimum pool depth to ensure that sufficient pool depth is provided to dissipate the upstream energies properly. Hydraulics 0 year development stream power for the 10 - Check the post - e that it is rendered equal to the pre storm to ensur ( development stream power. Note: this requires that sufficient SPSC length and number of pools be provided) Does the storage volume within the pools and voids meet the rescribed for required quantity management storage volume p the project and calculated using the MDE standards and TR55 ? follow the natural drainage path and alignment Does the Alignment efforts are made to avoid impacts to natural resources such as trees and wetlands? Tree Have speci men trees been identified and a tree protection plan Protection been developed? Does the SPSC system extend downstream to a point where the outfall is considered stable? Downstream Has adequate downstream tie in/transition been provided to - ie in T - address dow nstream instability and to ensure the outfall remains stable? the riffle segments been pla ced with a slope flatter than Have 5 percent ? Have the pool segments been placed with a slope flatte r than 1 Longitudinal ? percent Slope Have placed at no more than 1H:1V slope with cascades been double - lined boulders , and the height of any single cascade does not exceed 5 ? feet ) Do the side slopes for the pool (from all unarmored segments exceed 3 :1 ? V H Does the depth of the pool exceed t he minimum calculated depth based on the upstream velocities? Pool Design The design of the riffle and weir shall be modified such as not to result in feet pool depth exceeding 3 . Does the length of the pool exceed the minimum required 10 length to accommodate the 3 V :1 H feet and allow sufficient slope on unarmored sides? Is the length of the pool at least twice as long as the length of the riffle? 29 Page 36 of – vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines Re

128 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering Reviewer Comments Yes/No Check SPSC Item Is the channel parabolic in shape? Does the width, depth, and slope meet the design requi rement minimal entrenchment and safe conveyance of the and allow Riffle ? 0 year storm 10 Channel Design Are the cobble size adequate for accommodating the 10 0 d 50 velocities ? year Did the designer include a cobble gradation table on the plan? Are the boulders forming the weir 3 - 4 times larger than the calculated d ? 50 Are the footer boulders extended/anchored at least 2 feet Design Weir below the lowest point of the scour pool? - section for the weir safely convey the 10 0 year Does the cross ? storm Is filter fab ric placed under the sandstone boulders? Are the cascades armored with sandstone weir over filter at any given fabric and the height does not exceed 5 feet location? Cascade Design Are three pools provided following the cascade, with adequate weirs separating each pool structure and designed in a manner storm? to safely convey the 10 0 year ovided a typical detail sections for the Has the designer pr - cross actual riffle, stone weirs and pools where needed and sections along the alignment at frequent intervals to reflect changes in the grading shall be developed s section - he cross ? Note: t - Cross , based on the geometric alignment and shall show the station numbers existing grade, proposed grade, and sand mix/stone structure detail . section 0 year Has the designer shown the 10 storm water surface Drawings ? s section cross elevation on the typical and actual - Has the designer provided a longitudinal profile along the centerline of the alignment and shown invert and top Profile Drawings and the 10 water surface 0 year elevation s of all structures elevation ? Has proposed grading been provided , and are minimum/maximum dimensioning requirements met? water surface elevation been plotted on the Has the 10 0 year Plan Sheets plan? Is the 10 wa ter surface elevation sufficiently contained 0 year within easements and is below all habitable structures? approved erosion and sediment control plan by Has an been implemented upstream and downstream of the AASCD system prior to excavation clear SPSC and channel ing E&S shaping? Have flows from traps and basins been bypassed around the newly constructed SPSC system? Provide documentation from MDE/Army Corps of Engineers Wetlands, ll County Agencies. for approval of all impacts to a S treams, B uffers, and 100 year F loodplain and public a permanent and direct maintenance access Have right of way been provided to ? all public facilities Maintenance Has a maintenance agreement been signed and recorded for ? private SPSC structures 30 of 36 Page Step Pool Storm Conveyance (SPSC) Guidelines – Re vision 5: December 2012

129 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering Check SPSC Item Reviewer Comments Yes/No for Has a monitoring /maintenance plan been developed Monitoring - owned systems as prescribed in the design guidelines County Plan and is clearly shown on the plan? Have mulching and hydro - seeding been pres cribed for the entire system ? Planting use of native the cial attention to spe Has the designer paid material, diversity, and dense placement of plant material throughout the site? within appropriate wetness zones 14. Inspection c hecklist Comments Inspector SPSC Item Check Yes/No system match the alignment Alignment Does the alignment of the specified on the plan? Length Has the contractor provided sufficient SPSC length to meet the minimum requirement on the plan? Does the elevation difference from structure to structure Elevation and from top to bo Difference ttom of system match the design plan profile? and Number of Does the number of weirs match the number specified on the plan and profile? Weirs Is the connecting outfall physically stable with no signs Outfall C of erosion and is t he structure properly t ied in to the onditions and outfall as specified on the plans? ie - in T Does the number of pools match the number specified on the plan and profile? Pools Does the depth in any given pool exceed the minimum plans? required pool depth as shown on the design in vertical height at any feet Cascades shall not exceed 5 given location. Cascades shall be parabolic in shape with adequate width and depth to accommodate safe conveyance of the 10 0 Cascades year storm as specified on the plan. shall be followed by three consecutive pools. Cascades Cascades shall be underlined by filter fabric. i.e. curvilinear in the direction of the flow? , Are the weirs similar to a cross - are the boulders placed in a manner rect the flow to the center of the pool vane that would di and away from the banks? section parabolic with adequate depth and Is the cross - conveyance as specified on the 0 year width for safe 10 W eir C ross - plans? section Are the sandstone boulders forming the weir 3 to 4 times an the larger th underlined by filter for the cobbles and d 50 fabric as specified on the plans? Are footer boulders provided and extend to a depth that is 2 feet below the lowest point in the pool? stone gradation d Does the cobble size meet the 50 Cobbles req uirements indicated on the gradation table ? Are the cobbles rounded? Are they silica/bank run 31 of 36 Page vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines – Re

130 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering Check Yes/No Inspector Comments SPSC Item gravel? Has the contractor placed the required volume of filter sand mix below the system? Filter Sand M ix Do 0 percent es the filter sand mix include 2 wood chips by volume? filter fabric been applied under Has all sandstone boulder Filter F abric structures and as required on the plans? all the upstream erosion and sediment control Have measures been removed? Have adequate conveyance system s been provided to E&S (Note: The presence of erosion address all lateral drainage ? lateral to the system suggests poor grading and the need for lateral conveyance systems to intercept the flow.) Has mulch/compost been applied on the entire site? - seeded with Red Fescue ? Has the entire site been hydro Has the site been planted with adequate number of shrubs Plantings and trees as specified in the plan? (Note: Pay special attention to use of native material, diversity, and dense placement of plant ma terial within appropriate wetness zones throughout the site .) main tenance access been provided Has a direct vehicular Maintenance ? as an entry location to the site Access Are public facilities located within a deeded public parcel or a perpetual nt? easeme For Private Has a maintenance agreement been prepared, signed, and S recorded? tructures For Public Structures: built is The following items must be verified before the structure as - accepted by DPW and the bond is released SPSC Item Check Yes/No Inspector Comments For water quality ephemeral systems, do the pools drain Filtering to an acceptable level where the design ponding head for Capacity the filter is fully recovered in 72 hours after a rain event? oved sedimentation (exceeding 6 Has the contractor rem Sedimentation inches) from the pools? Has the structure been monitored for at least 3 years? Specifically physical stability and plant survivability. Monitoring Have annual monitoring reports been submitted to I&P they favorable? If not, were and IMD and were deficiencies addressed? Plant Has at least 80 percent of the planted shrubs and tree s Survivability ? survive d 3 years after installation Physical Are all sandstone boulders in place with no sign of bank erosion throughout the length of the project? stability or bed d from the Have all invasive plant species been remove Invasive ? seeded - Species system and the entire system re 32 of 36 Page vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines – Re

131 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering References Rosgen, D., 1996, Applied River Morphology, Wildland Hydrology. . Hill - , McGraw Chow, V.T. , 1 959, Open Channel Hydraulics . Water Management, Jarrett, A.R. , Pennsylvania State University 1994, ecember 1981, H ighway Administration, D Maryland Department of Transportation, State anual, December 1981. Highway Drainage M partment of Agriculture (USDA) Natural Resources Conservation United States De - VI - Service (NRCS), (210 st 2007), Stone Sizing Criteria. NEH, Augu Maryland Department of the Environment (MDE), Ellicot t City, MD, 2000 Maryland Stormwater Design Manual, Volumes I & II. Unit ed States Department of Agriculture (USDA) Natural Resources Conservation W . aterway Standard Code 468 Lined Service (NRCS), 2006, United States Department of Agriculture (USDA) Natural Resources Conservation - Ponds Service (NRCS), 1997, Construction: Agricultural Handbook Planning, Design, . 590 , page 12 United States Department of Agriculture (USDA) Natural Resources Conservation - , Chapter 16, Appendix 16 Engineering Field Handbook Part 650 Service (NRCS), 1996, . A, Figure 16A - 1 - Walter, R., & Merritts, D. Powered (2008). Natural Streams and the Legacy of Water - 304. Mills, Science, 319, 299 City of Wheat Ridge, Colorado, Department of Public Works, Engineering Division, A02 Detail Code - Rock and Riprap Gradation, E 33 of 36 Page vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines – Re

132 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering Abbreviated List of Native Plants Ste p Pool Storm Conveyances are designed with the intention that they will mimic natural processes. Vegetation plays an important role in these processes. It is highly encouraged on all projects and required on those in Anne Arundel County to use native veg etation appropriate for the conditions of the site. The following is a sample, abbreviated list of native plants that may be used on SPSC structures within the airport zone. The list has been cross - checked for consistency with the Maryland Aviation Admin may be istration (MAA) approved plant list. This list subject to expansion to accommodate other native plant species and future updates to the MAA guidelines. It is the responsibility of the designer to check and propose native plant species that are co nsistent with MAA regulations for projects within the airport zone. Common Name Name Comments Latin Ilex opaca (Male Only) American Holly Bald Cypress Taxodium distichum Bayberry Myrica pensylvanica Blue Flag Iris Iris versicolor Christm as Ferns Polystichum acrostichoides Cinnamon Fern Osmunda cinnamomea Fringe Tree Chionanthus virginiana (Male Only) Ilex glabra (Male Only) Inkberry Schizachyrium scoparium Little Bluestem Mountain Laurel Kalmia latifolia Pitch Pine P inus rigida Panicum virgatum Switchgrass Clethra alinifolia Summersweet Sweetbay Magnolia Magnolia virginiana Tussock Sedge Carex stricta Virginia Sweetspire Itea virginica For SPSC projects outside of the airport zone, the designer shall util ize the list of native plants as listed below: Common Name Latin Name Ilex opaca American Holly Atlantic White Cedar Chamaecyparis thyoides Bald Cypress Taxodium distichum Northern Bayberry Morella pensylvanica Blue Flag Iris Iris v ersicolor Broomsedge Andropogon virginicus Christmas Fern Polystichum acrostichoides Osmunda cinnamomea Cinnamon Fern Common Winterberry Ilex laevigata 34 of 36 Page vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines – Re

133 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering Common Name Latin Name Cranberry Vaccin i um macrocarpon Lowbush lueberry v accin ium Anguaticolium B Water Lily Nymphea odorata Fringe Tree Chionanthus virginiana Orontium aquaticum Golden Club Highbush Blueberry Vaccinum cory m bosum Inkberry Ilex glabra Little Bluestem Schizachyrium scoparium Mountain Laurel Kalmia latifolia Redhead Grass Potamogeton perfoliatus Eastern Red c edar Juniperus virginiana Royal Fern Osmunda regalis Amelanchier canadensis Serviceberry Panicum virgatum Switchgrass Smooth Alder Al nus serrulata Black Gum N y ssa sylvatica Sweet P epperbush Clethra alinifolia Swamp Azalea Rhododendron viscosum S outhern Bayberry Morella canotiniensis Sweetbay Magnolia Magnolia virginiana Carex stricta Tussock Sedge Woodwardia virgini Virginia Chain Fern ca Itea virginica Virginia Sweetspire Wax Myrtle cerifera M orella Yellow Pond Lilly Nuphar advena Riverbirch Batala Nigna American Hornbean Carpinus caroliniana A complete list of native plants ca under n be found The list above is not a complete list. . Special attention shall be placed www.aacounty.org/IP/Resources/AANativePlants.pdf on diversity and dense placement of plant material within appropriate wetness zones throughout the site (MDE, 2000). Additional information on native plants for the Chesapeake Bay region can be found at . For www.nps.gov/plants/pubs/chesapeake information concerning Native Plant Nur series, please visit and scroll down to the "Forestry Forms and Fact www.aacounty.org/IP/Forms.cfm Sheets" section. 35 of 36 Page vision 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines – Re

134 Design Guidelines for Step Pool Storm Conveyance Anne Arundel County Government Department of Public Works, Bureau of Engineering Summary of Revisions: SPSC system can and cannot be used as August 2010 Revision 1: (a) Added language to clarify when an part of the ESD treatment train. definition indicating November 2010 Revision 2: (a) Replaced the d50 cobble size definition with the d 100 that the cobble design size is the minimum allowable cobble size to be used r ather than median stone size. (b) Added a clarification on the minimum and maximum allowable length of pools and riffles. (c) Added a design checklist. (d) Added an inspection checklist. (e) Added guidance pertaining to sequence of construction and erosio n and sediment control measures. groundwater April 2011 Revision 3: The 2000 Maryland Stormwater Design Manual does not prescribe a for filtering systems as is done with infiltration systems . Due to this, revision 3 separation requirement requirement for groundwater separation from the filtering system. However, to ensure that eliminates the the filtering mechanism works as designed, the design water quality filter ponding depth in the pools, also known as seepage head, shall be available for storage du ot inundated by seasonal ring storm events and n Further, construction inspection shall verify that pools do ground water. drain down within 72 hours to their design levels. Added horizontal and vertical setback requirements for SPSC systems. Added Width/Depth “Regen erative” to the practice name for consistency with EPA TMDL/WIP publications. t. ee ratio for Riffle/Weir section shall not be less than 10W:1D. Further, pool depths shall not exceed 3 f riteria. Modified the Erosion and Sediment Control and planting c Comstock, Debbie Cappuccitti, and Richard Trickett, MDE. Comments received t Reviewed by Stewar Comstock on 7/15/2011. Comments were addressed as part of revision 3. t from Stewar October 2011, Revision 4. Some of the minimum and maximum all owable dimensions were changed to allow more energy dissipation and better channel connection with the floodplain. The changes were as follows: Pool length shall be at least two times longer than the riffle length. - et no steeper than 10H:1V slope to allow for better - The weir/riffle cross - section shall be s connection with the floodplain Root wads may float and cause a debris jam that can undermine the stability of the stone - ft in the structures. The use of r oot wads is optional and if used must be anchored at least 6 Root wads shall not be used in ground. the two pools directly upstream of a cascade. - Added a cascade maximum height versus allowable slope design table. The footer rocks shall be anchored 2 feet below the lowest point in the pool. - the Changed is instream riffle. The instream riffle slope constructed instream weir to the name of - set to a maximum of 4% or 1H:25V. December 2012 Revision 5: (a) A cobble stone gradation table was added to assist in defining the d design 50 requirements. (b) Added section entrenchment up to 5H:1V. This - allowance for increasing cross regarding (c) Drawing schematics updated with additional detail allowance is limited to retrofit projects. um allowable slope. ) Text corrections pertaining to the instream riffle maxim d . ( cobble placement 36 of 36 Page 5: December 2012 Step Pool Storm Conveyance (SPSC) Guidelines – Revision

135 BMP Standards and Specifications Restoration Practices -2 APPENDIX 6 -NRCS ENGINEERING FIE LD HANDBOOK USDA PART 650, CHAPTER 16 MBANK AND SHORELINE PROTECTION STREA 3.06.2.6.A 03/2013 -2- 1

136 United States Engineering Department of Agriculture Field Natural Resources Handbook Conservation Service Streambank and Chapter 16 Shoreline Protection

137 Streambank and Shoreline Protection Part 650 Chapter 16 Engineering Field Handbook Issued December 1996 Cover: Little Yellow Creek, Cumberland Gap National Park, Kentucky (photograph by Robbin B. Sotir & Associates) The United States Department of Agriculture (USDA) prohibits discrimina- tion in its programs on the basis of race, color, national origin, sex, religion, age, disability, political beliefs, and marital or familial status. (Not all pro- hibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (braille, large print, audiotape, etc.) should contact the USDA Office of Communications at (202) 720-2791. To file a complaint, write the Secretary of Agriculture, U.S. Department of Agriculture, Washington, DC 20250, or call 1-800-245-6340 (voice) or (202) 720-1127 (TDD). USDA is an equal employment opportunity employer. 16–ii (210-vi-EFH, December 1996)

138 Chapter 16 Preface Chapter 16, Streambank and Shoreline Protection, is one of 18 chapters of the U.S. Department of Agriculture, Natural Resources Conservation Ser- vice, Engineering Field Handbook, previously referred to as the Engineer- ing Field Manual. Other chapters that are pertinent to, and should be refer- enced in use with, Chapter 16 are: Chapter 1: Engineering Surveys Chapter 2: Estimating Runoff Chapter 3: Hydraulics Chapter 4: Elementary Soils Engineering Chapter 5: Preparation of Engineering Plans Chapter 6: Structures Chapter 7: Grassed Waterways and Outlets Terraces Chapter 8: Chapter 9: Diversions Chapter 10: Gully Treatment Chapter 11: Ponds and Reservoirs Chapter 12: Springs and Wells Chapter 13: Wetland Restoration, Enhancement, or Creation Chapter 14: Drainage Chapter 15: Irrigation Chapter 17: Construction and Construction Materials Chapter 18: Soil Bioengineering for Upland Slope Protection and Erosion Reduction This is the second edition of chapter 16. Some techniques presented in this text are rapidly evolving and improving; therefore, additions to and modifi- cations of chapter 16 will be made as necessary. 16 i – (210-vi-EFH, December 1996)

139 Chapter 18 Acknowledgments This chapter was prepared under the guidance of Ronald W. Tuttle, na- tional landscape architect, United States Department of Agriculture, Natu- ral Resource Conservation Service (NRCS), and Richard D. Wenberg, national drainage engineer (retired). Robbin B. Sotir & Associates, Marietta, Georgia, was a major contributor to the inclusion of soil bioengineering and revision of the chapter. In addi- tion to authoring sections of the revised manuscript, they supplied original drawings, which were adapted for NRCS use, and photographs. Walter K. Twitty, drainage engineer (retired), NRCS, Fort Worth, Texas, and Robert T. Escheman, landscape architect, NRCS, Somerset, New Jersey, Carolyn served a coordination role in the review and revision of the chapter. A. Adams, director, Watershed Science Institute, NRCS, Seattle, Washington; design engineer; Gary E. Formanek, agricultural engi- Leland M. Saele, neer; and Frank F. Reckendorf, sedimentation geologist (retired), NRCS, Portland, Oregon, edited the manuscript to extend its applicability to most geographic regions. In addition these authors revised the manuscript to reflect new research on stream classification and design considerations for riprap, dormant post plantings, rootwad/boulder revetments, and stream barbs. H. Wayne Everett, plant materials specialist (retired), NRCS, Fort Worth, Texas, supplied the plant species information in the appendix. Mary editor, John D. Massey, visual information specialist, and R. Mattinson, Wendy R. Pierce, illustrator, NRCS, Fort Worth, Texas, provided editing assistance and desktop publishing in preparation for printing. 16 ii – (210-vi-EFH, December 1996)

140 Chapter 16 Streambank and Shoreline Protection 650.1600 Introduction 16–1 Contents: Purpose and scope ... 16 – (a) 1 – 1 Categories of protection ... 16 (b) Selecting streambank and shoreline protection measures ... 16 – 1 (c) Streambank protection 16–3 650.1601 (a) General ... 16 3 – Planning and selecting stream-bank protection measures ... 16 3 (b) – Design considerations for streambank protection ... 16 – (c) 6 (d) Protective measures for streambanks ... 16 – 10 650.1602 Shoreline protection 16–63 (a) General ... 16 – 63 (b) Design considerations for shoreline protection ... 16 63 – Protective measures for shorelines ... 16 64 (c) – References 16–81 650.1603 Size Determination for Rock Riprap 16A–1 Appendix A Appendix B Plants for Soil Bioengineering and Associated Systems 16B–1 Tables Table 16–1 Live fascine spacing 16 – 16 Table 16–2 16 – 49 Methods for rock riprap protection Figures Figure 16–1 Appropriate selection and application of streambank 16 – 2 or shoreline protection measures should vary in response to specific objectives and site conditions Vegetative system along streambank 16 9 – Figure 16–2 16 iii – (210-vi-EFH, December 1996)

141 Streambank and Shoreline Protection Part 651 Chapter 16 National Engineering Handbook Figure 16–3a – 12 Eroding bank, Winooski River, Vermont, June 1938 16 16 – 12 Figure 16–3b Bank shaping prior to installing soil bioengineering practices, Winooski River, Vermont, September 1938 Three years after installation of soil bioengineering Figure 16–3c – 12 16 practices, 1941 Soil bioengineering system, Winooski River, Vermont, 16 – 12 Figure 16–3d June 1993 (55 years after installation) Figure 16–4 Live stake details 16 – 13 Figure 16–5 16 – 15 Prepared live stake Figure 16–6 Growing live stake 16 – 15 Figure 16–7 Live fascine details 16 – 17 Figure 16–8 Preparation of a dead stout stake 16 – 18 Figure 16–9a Placing live fascines 16 – 18 18 – Figure 16–9b Installing live stakes in live fascine system 16 Figure 16–9c 16 – 18 An established 2-year-old live fascine system Figure 16–10 Branchpacking details 16 – 20 Figure 16–11a Live branches installed in criss-cross configuration 16 – 21 Figure 16–11b 16 – 21 Each layer of branches is followed by a layer of compacted soil Figure 16–11c A growing branchpacking system 16 – 21 Vegetated geogrid details Figure 16–12 – 16 23 Figure 16–13a 16 – 24 A vegetated geogrid during installation Figure 16–13b A vegetated geogrid immediately after installation 16 – 24 Figure 16–13c Vegetated geogrid 2 years after installation 16 – 24 Figure 16–14 Live cribwall details 16 – 26 Figure 16–15a Pre-construction streambank conditions 16 – 27 27 – Figure 16–15b A live cribwall during installation 16 iv (210-vi-EFH, December 1996)

142 Streambank and Shoreline Protection Part 651 Chapter 16 National Engineering Handbook Figure 16–15c – 27 An established live cribwall system 16 16 – 28 Figure 16–16 Joint planting details Live stake tamped into rock joints 16 Figure 16–17a 29 – Figure 16–17b 16 – 29 An installed joint planting system An established joint planting system 16 – 29 Figure 16–17c Figure 16–18 Brushmattress details 16 – 31 Figure 16–19a 16 – 32 Brushmattress during installation Figure 16–19b An installed brushmattress system 16 – 32 Figure 16–19c Brushmattress system 6 months after installation 16 – 32 Figure 16–19d Brushmattress system 2 years after installation 16 – 32 Figure 16–20 Tree revetment details 16 – 34 – 35 Figure 16–21a Tree revetment system with dormant posts 16 Figure 16–21b Tree revetment system with dormant posts, – 35 16 2 years after installation Log, rootwad, and boulder revetment details 16 – 36 Figure 16–22 Figure 16–23 Rootwad, boulder, and willow transplant 16 – 37 revetment system, Weminuche River, CO Dormant post details 16 – 38 Figure 16-24 Figure 16–25a Pre-construction streambank conditions 16 – 39 Figure 16–25b – Installing dormant posts 16 39 Figure 16–25c 16 – 39 Established dormant post system Figure 16–26 Piling revetment details 16 – 41 Figure 16–27 Slotted board fence details (double fence option) 16 – 42 Figure 16–28 Slotted board fence system 16 – 43 Figure 16–29 Concrete jack details 16 – 44 45 – Figure 16–30 Wooden jack field 16 v (210-vi-EFH, December 1996)

143 Streambank and Shoreline Protection Chapter 16 Part 651 National Engineering Handbook Figure 16–31 – 46 Concrete jack system several years after installation 16 16 47 Rock riprap details Figure 16–32 – 16 – 48 Figure 16–33 Rock riprap revetment system Concrete cellular block details – 50 Figure 16–34 16 Figure 16–35a Concrete cellular block system before backfilling 16 – 51 Concrete cellular block system several years 16 Figure 16–35b 51 – after installation Coconut fiber roll details – 52 Figure 16–36 16 Figure 16–37a Coconut fiber roll 16 – 53 Coconut fiber roll system 16 Figure 16–37b 53 – Figure 16–38 16 – 55 Stream jetty details Stream jetty placed to protect railroad bridge 16 – 56 Figure 16–39a 16 56 Figure 16–39b Long-established vegetated stream jetty, with – deposition in foreground Figure 16–40 16 – 58 Stream barb details Stream barb system 16 – 59 Figure 16–41 Figure 16–42 Vegetated rock gabion details 16 – 61 Figure 16–43 16 – 62 Vegetated rock gabion system Figure 16–44 Timber groin details 16 – 65 Timber groin system Figure 16–45 – 16 66 Figure 16–46 16 – 67 Timber bulkhead system Figure 16–47 Timber bulkhead details 16 – 68 Figure 16–48 Concrete bulkhead details 16 – 69 Figure 16–49 Concrete bulkhead system 16 – 70 Figure 16–50 Concrete revetment (poured in place) 16 – 71 71 – Figure 16–51 Rock riprap revetment 16 vi (210-vi-EFH, December 1996)

144 Streambank and Shoreline Protection Chapter 16 Part 651 National Engineering Handbook Figure 16–52 16 – 74 Live siltation construction details Live siltation construction system 16 Figure 16–53 75 – Figure 16–54 Reed clump details 16 – 77 78 – Figure 16–55a Installing dead stout stakes in reed clump system 16 Completing installation of reed clump system 16 – 78 Figure 16–55b Established reed clump system Figure 16–55c 78 16 – Figure 16–56 Coconut fiber roll details 16 – 79 – 80 Figure 16–57 Coconut fiber roll system 16 vii (210-vi-EFH, December 1996)

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146 Chapter 16 Streambank and Shoreline Protection (c) Selecting streambank and shoreline protection measures 650.1600 Introduction This document recognizes the need for intervention into stream corridors to affect rehabilitation; however, (a) Purpose and scope it is also acknowledged that this should be done on a selective basis. When selecting a site or stream reach Streambank and shoreline protection consists of for treatment, it is most effective to select areas within restoring and protecting banks of streams, lakes, relatively healthy systems. Projects planned and estuaries, and excavated channels against scour and installed in this context are more likely to be success- erosion by using vegetative plantings, soil bioengineer- ful, and it is often critically important to prevent the ing, and structural systems. These systems can be used decline of these healthier systems while an opportu- alone or in combination. The information in chapter 16 nity remains to preserve their biological diversity. does not apply to erosion problems on ocean fronts, Rehabilitation of highly degraded systems is also large river and lake systems, or other areas of similar important, but these systems often require substantial scale and complexity. investment of resources and may be so modified that partial success is often a realistic goal. (b) Categories of protection After deciding rehabilitation is needed, a variety of remedies are available to minimize the susceptibility The two basic categories of protection measures are of streambanks or shorelines to disturbance-caused those that work by reducing the force of water against erosive processes. They range from vegetation- a streambank or shoreline and those that increase oriented remedies, such as soil bioengineering, to their resistance to erosive forces. These measures can – engineered grade stabilization structures (fig. 16 1). In be combined into a system. the recent past, many organizations involved in water resource management have given preference to engi- Stormwater reduction or retention methods, grade neered structures. Structures may still be viable op- reduction, and designs that reduce flow velocity fall tions; however, in a growing effort to restore sustain- into the first category of protection. Examples include ability and ensure diversity, preference should be permeable fence design, tree or brush revetments, given to those methods that restore the ecological jacks, groins, stream jetties, barbs, drop structures, functions and values of stream or shoreline systems. increasing channel sinuosity, and log, rootwad, and boulder combinations. The second category includes As a first priority consider those measures that channels lined with grass, concrete, riprap, gabions, • are self sustaining or reduce requirements for cellular concrete, and other revetment designs. These future human support; measures can be used alone or in combination. Most use native, living materials for restoration; • designs that employ brushy vegetation, e.g., soil • restore the physical, biological, and chemical bioengineering, either alone or in combination with functions and values of streams or shorelines; structures, protect from erosion in both ways. improve water quality through reduction of • temperature and chronic sedimentation Revetment designs do not reduce the energy of the problems; flow significantly, so using revetments for spot protec- • provide opportunities to connect fragmented tion may move erosion problems downstream or riparian areas; and across the stream channel. retain or enhance the stream corridor or shore- • line system. – (210-vi-EFH, December 1996) 1 16

147 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook ives and Less coefficient " . e s i w r e h s=channel slope n= roughn t o s d n e t t i n e h w g n o r w s i t I . y t i n u m m o c c i t o i b e h t f o y t u a e b d n a y t i l i b a t s , y t i r g e t n i e h t e v r e s e r p o t s d n e t t i (Aldo Leopold) n e h w t h g i r s a=cross sectional flow area a=cross sectional flow area V=average velocity r = hydraulic radius i g n i h t Appropriate selection and application of streambank or shoreline protection measures should vary in response to specific object site conditions A " /n where 1/2 s 1 2/3 – V=1.49r Figure 16 2 – 16 (210-vi-EFH, December 1996)

148 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Projected development over anticipated project • life. 650.1601 Streambank protection (2) Causes and extent of erosion problems If bank failure problems are the result of wide- • spread bed degradation or headcutting, deter- (a) General mine what triggered the problem. • If bank erosion problems are localized, deter- The principal causes of streambank erosion may be mine the cause of erosion at each site. classed as geologic, climatic, vegetative, and hydraulic. These causes may act independently, but normally (3) Hydrologic/hydraulic data work in an interrelated manner. Direct human activi- Flood frequency data (if not available, estimate • ties, such as channel confinement or realignment and using regional equations or other procedures). damage to or removal of vegetation, are major factors • Estimates of stream-forming flow at 1- to 2-year in streambank erosion. recurrence interval and flow velocities. • Estimates of width and depth at stream-forming Streambank erosion is a natural process that occurs flow conditions. when the forces exerted by flowing water exceed the • Channel slope, width, depth, meander wavelength, resisting forces of bank materials and vegetation. and shape (width/depth, wetted perimeter). Erosion occurs in many natural streams that have • Sediment load (suspended and bedload). vegetated banks. However, land use changes or natu- • Water quality. ral disturbances can cause the frequency and magni- tude of water forces to increase. Loss of streamside (4) Stream reach characteristics vegetation can reduce resisting forces, thus stream- • Soil and streambank materials at site. banks become more susceptible to erosion. Channel • Potential streambank failures. realignment often increases stream power and may Vegetative condition of banks. • cause streambeds and banks to erode. In many cases Channel alignment. • streambed stabilization is a necessary prerequisite to • Present stream width, depth, meander amplitude, the placement of streambank protection measures. belt width, wavelength, and sinuosity to deter- mine stream classification. Identification of specific problems arising from • (b) Planning and selecting stream- flow deflection caused by sediment buildup, bank protection measures boulders, debris jams, bank irregularities, or constrictions. The list that follows, although not exhaustive, includes based on a pebble count. Bed material d • 50 data commonly needed for planning purposes. • Quality, amount, and types of terrestrial and aquatic habitat. (1) Watershed data Suspended load and bedload as needed, to • When analyzing the source of erosion problems, con- determine if incoming sediment load can be sider the stream as a system that is affected by water- transported through the restored reach. shed conditions and what happens in other stream When selecting protective measures, analyze the • reaches. An analysis of stream and watershed condi- needs of the entire watershed, the effects that tions should include historical information on land use stream protection may have on other reaches, changes, hydrologic conditions, and natural distur- surrounding wetlands, the riparian corridor, bances that might influence stream behavior. It should terrestrial habitat, aquatic habitat, water quality, anticipate the changes most likely to occur or that are and aesthetics. Reducing runoff and soil loss planned for the near future: from the upland portions of the watershed using • Climatic regime. sound land treatment and management measures Land use/land cover. • normally makes the streambank protection History of land use, prior stream modifications, • solution less expensive and more durable. past stability problems, and previous treatments. – (210-vi-EFH, December 1996) 3 16

149 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook (6) Soils (5) Stream classification A particular soil's resistance to erosion depends on its Stream classification has evolved significantly over the cohesiveness and particle size. Sandy soils have low past 100 years. William Davis (1899) first divided streams into three stages as youthful, mature and old cohesion, and their particles are small enough to be entrained by velocity flows of 2 or 3 feet per second. age. Streams were later classified by their pattern as Lenses or layers of erodible material are frequent straight, meandering, or braided (Leopold & Wolman, sources of erosion. Fines are selectively removed from 1957) or by stability and mode of sediment transport soils that are heterogeneous mixtures of sand and (Schumm, 1963 and 1977). Although all these systems served their intended purposes, they were not particu- gravel, leaving behind a layer of gravel that may pro- larly helpful in establishing useful criteria for stream- tect or armor the streambed against further erosion. Rosgen (1985) developed a bank protection and design. However, the hydraulic removal of fines and sand stream classification system that categorizes essentially from a gravel matrix may cause it to collapse, resulting in sloughing of the streambank and its overlying all types of stream channels on the basis of measured material. morphological features. This system has been updated several times (Rosgen, 1992) and has broad applicability for communication among users and to predict a The resistance of cohesive soils depends on the physi- stream's behavior based on its appearance. cal and chemical properties of the soil as well as the chemical properties of the eroding fluid. Cohesive soils often contain montmorillonite, bentonite, or Predicting a stream's behavior based on appearance is other expansive clays. Because unvegetated banks also a feature of the Schumm, Harvey, and Watson made up of expansive clays are subject to shrinkage (1984) channel evolution model developed for during dry weather, tension cracks may develop paral- Oaklimeter Creek in Mississippi. This model discusses lel to and several feet below the top of the bank. These channel conditions extending from total disequilib- rium to a new state of dynamic equilibrium. Such a cracks may lead to slab failures on oversteepened banks, especially in places where bank support has model is useful in stream restoration work because been reduced by toe erosion. Tension cracks can also streams can be observed in the field and their domi- nant process determined in the reach under consider- contribute to piping and related failures. ation (i.e., active headcutting and transport of sedi- ment, through aggradation and stabilization of alter- (7) Hydrologic, climatic, and vegetative nate bars, and approaching a stage of dynamic equilib- conditions Stream erosion is largely a function of the magnitude rium). and frequency of flow events. Flow duration is of Rosgen's (1992) stream classification system goes secondary importance except for flows that exceed stream-forming flow stage for extended periods. A beyond the channel evolution model as it is based on determining hydraulic geometry of stable stream streambank's position (outside curve or inside) can also reaches. This geometry is then extrapolated to un- be a major factor in determining its erosion potential. stable stream reaches to derive a template for poten- tial channel design and reconstruction. Watershed changes that increase magnitude and frequency of flooding, such as urbanization, deforesta- The present version of Rosgen's stream classification tion, and increased surface runoff, contribute to streambank erosion. Associated changes, such as loss has several types (A, B, C, D, DA, E, F, and G), based of streamside vegetation from human or animal tram- on a hierarchical system. The first level of classifica- pling, often compound the streambank erosion effect. tion distinguishes between single or multiple thread channels. The streams are then separated based on degrees of entrenchment, width-to-depth ratio, and In cold climates where streams normally freeze or stream sinuosity. They are further subdivided by slope partly freeze during winter, erosion caused by ice is an additional problem. Streambanks are affected by ice range and channel materials. Several stream subtypes are based on other criteria, such as average riparian scour in several ways: vegetation, organic debris and channel blockages, flow Streambanks and associated vegetation can be • forcibly damaged during freezing or thawing regimes, stream size, depositional features, and mean- der pattern. action. 16 4 (210-vi-EFH, December 1996) –

150 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Grade control structures should be designed to main- • Floating ice can cause gouging of streambanks. • Acceleration of flow around and under ice rafts tain low channel width-to-depth ratios, maintain the sediment transport capacity of the channel, and pro- can cause damage to streambanks. vide for passing a wide range of flow velocities with- Erosion from ice may be minimized or reduced by out creating backwater and causing sediment deposi- tion. Vortex rock weirs, "W" rock weirs, and other vegetation for the following reasons: rock/boulder structures that protect the channel • Streambank vegetation reduces damaging cycles of freeze-thaw by maintaining the temperature of without creating backwater should be considered bank materials, thus preventing ice from forming instead of small rock and log dams. and encouraging faster thawing. Vegetation tends to be flexible and absorbs much Local obstructions to flow, channel constrictions, and • bank irregularities cause local increases in the energy of the momentum of drifting ice. slope and create secondary currents that produce • Vegetation helps protect the bank from ice accelerations in velocity sufficient to cause localized damage. Woody vegetation has deeply embedded roots • streambank erosion problems. These localized prob- that reinforce soils. lems often are treated best by eliminating the source • Deeply rooted, woody vegetation helps to control of the problem and providing remedial bank protec- erosion by adding strength to streambank materi- tion. However, secondary cross currents are also a als, increasing flow resistance, reducing flow natural feature around the outside curves of meanders, and structural features may be required to modify velocities in the vicinity of the bank, and retard- these cross currents. ing tension crack development. Streamflows that transport sustained heavy loads of (8) Hydraulic data sediment are less erosive than clear flows. This can Stream power is a function of velocity, flow depth, and easily be seen where dams are constructed on large slope. Channelization projects that straighten or enlarge channels often increase one or more of these sediment-laden streams. Once a dam is operational, the sediment drops out into the reservoir pool, so the factors enough to cause widespread erosion and associated problems, especially if soils are easily water leaving the structure is clear. Several feet of erodible. degradation commonly occurs in the reach below the dam before an armor layer develops or hydraulic parameters are sufficiently altered to a stable grade. In Headcuts often develop in the modified reach or at the watersheds that have high sediment yields, conserva- transition from the modified reach to the unaltered tion treatments that significantly reduce sediment reach. They move upstream, causing bed erosion and loads can trigger stream erosion problems unless bank failure on the main stream and its tributaries. runoff is also reduced. Returning the stream to its former meander geometry is generally the most reliable way to stop headcuts or prevent their development. Installing grade control (9) Habitat characteristics structures that completely cross a stream and act as a The least-understood aspect of designing and analyz- ing streambank protection measures is often the very low head dam may initiate other channel instabili- impact of the protective measures on instream and ties by: inducing bank erosion around the ends of the riparian habitats. Commonly, each stage of the life • structure; cycle of aquatic species requires different habitats, each having specific characteristics. These diverse • raising flood levels and causing out-of-bank habitats are needed to meet the unique demands flows to erode new channels; imposed by spawning and incubation, summer rearing, • trapping sediment, thus decreasing channel capacity, inducing bank erosion and flood plain and overwintering. The productivity of most aquatic scour; and systems is directly related to the diversity and com- increasing width-to-depth ratio with subsequent • plexity of available habitats. lateral migration, increased bank erosion, and increased bar deposition or formation. 16 – 5 (210-vi-EFH, December 1996)

151 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Fish habitat structures are commonly an integral part (11) Social and economic factors Initial installation cost and long-term maintenance are of stream protection measures, but applicability of factors to be considered when planning streambank habitat structures varies by classified stream type. and shoreline protection. Other factors include the Work by Rosgen and Fittante (1992) resulted in a suitability of construction material for the use in- guide for evaluating suitability of various proposed tended, the cost of labor and machinery, access for fish habitat structures for a wide range of morphologi- equipment and crews at the site, and adaptations cal stream types. They divide structures into those for needed to adjust designs to special conditions and the rearing habitat enhancement and those for spawning local environment. habitat enhancement. The structures for rearing habi- tat enhancement include low stage check dam, me- dium stage check dam, boulder placement, bank- Some protection measures seem to have apparent advantages, such as low cost or ease of construction, placed materials, single wing deflector, channel con- but a more expensive alternative might best meet strictor, bank cover, floating log cover, submerged planned objectives when maintenance, durability of shelter, half log cover, and migration barrier. U-shaped material, and replacement costs are considered. Effect gravel traps, log sill gravel traps, and gravel placement upon resources and environmental values, such as are for spawning habitat enhancement. aesthetics, wildlife habitat, and aquatic requirements, are also integral factors. Since a multitude of interrelated factors influence the productivity of streams, the response of fish and wildlife populations to changes in habitat is often The need for access to the stream or shoreline and the difficult to predict with confidence. effects of protection measures upon adjacent property and land uses should be analyzed. (10) Environmental data Minor protective measures can be installed without Environmental goals should be set early in the plan- using contract labor or heavy equipment. However, ning process to ensure that full consideration is given to ecological stability and productivity during the many of the protective measures presented in this chapter require evaluation, design, and implementa- selection and design of streambank protection mea- sures. Special care should be given to consideration of tion to be done by a knowledgeable interdisciplinary team because precise construction techniques and terrestrial and aquatic habitat benefits of alternative costly construction materials may be required. types of protection and to maintenance needs on a site specific basis. In general, the least disturbance to the existing stream (c) Design considerations for system during construction and maintenance produces streambank protection the greatest environmental benefits. Damages to the environment can be limited by: (1) Channel grade The channel grade may need to be controlled before Using small equipment and hand labor. • Limiting access. any permanent type of bank protection can be consid- • • ered feasible unless the protection can be safely and Locating staging areas outside work area boundaries. economically constructed to a depth well below the Avoiding or altering construction procedures • anticipated lowest depth of bed scour. Control can be by natural or artificial means. Reconstructing stream during critical times, such as fish spawning or bird nesting periods. channels to their historical stream type (i.e., stream • Coordinating construction on a stream that geometry) has been successfully used to achieve grade control. Artificial measures typically include rock, involves more than one job or ownership. gabions and reinforced concrete grade control struc- Adopting maintenance plans that maximize • riparian vegetation and allow wide, woody tures. vegetative buffers. Scheduling construction activities to avoid • expected peak flood season(s). (210-vi-EFH, December 1996) 6 – 16

152 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook (2) Discharge frequency (4) Freeboard Freeboard should be provided to prevent overtopping Maximum floods are rarely used for design of stream- of the revetment at curves and other points where high bank protection measures. The design flood frequency should be compatible with the value or safety of the velocity flow contacts the revetment. In these areas a potential supercritical velocity can set up waves, and property or improvements being protected, the repair the climb on sloping revetments may be appreciable. cost of the streambank protection, and the sensitivity and value of ecological systems within the planning Because an accurate method to determine freeboard unit. Bankfull discharge (stream-forming flow) of requirements is not available for sloping revetments in natural streams tends to have a recurrence interval of critical zones, the allowance for freeboard should be 1 to 2 years based on the annual flood series (Leopold based on sound judgment and experience. Under and Rosgen, 1991). The discharge at this frequency is similar conditions, the freeboard required for a sloping commonly used as a design discharge for stream revetment is always greater than that for a vertical revetment. restoration (Rosgen, 1992). For modified streams, the 1- to 2-year frequency discharge is also useful for design discharge because it is the flow that has the most impact (5) Alignment upon the stability of the stream channel. Changes in channel alignment affect the flow charac- teristics through, above, and below the changed reach. Straightening without extensive channel hardening (3) Discharge velocities does not eliminate a stream's tendency to meander. An Where the flow entering the section to be protected erosion hazard may often develop at both ends of the carries only clay, silt, and fine sand in suspension, the maximum velocity should be limited to that which is channel because of velocity increases, bar formations, nonscouring on the least resistant material occurring and current direction changes. Changes in channel in any appreciable quantity in the streambed and bank. alignment are not recommended unless the change is to reconstruct the channel to its former meander The minimum velocity should be that required to geometry. transport the suspended material. The depth-area- velocity relationship of the upstream channel should be maintained through the protected reach. Where the Alignment of the reach must also be carefully consid- flow entering the section is transporting bedload, the ered in designing protective measures. Because of minimum velocity should be that which will transport major changes in hydraulic characteristics, stream- banks for channels having straight alignment generally the entering bedload material through the section. require a continuous scour-resistant lining or revet- ment. To prevent scour by streamflow as the stream The minimum design velocity should also be compat- ible with the needs of the various fish species present attempts to recreate its natural meander pattern, most banks must be sloped to a stable grade before the or those targeted for recovery. Velocity changes can lining is applied. For nonrigid lining, the slope must be reduce available habitat or create physical barriers that restrict fish passage. Further information on fish flat enough to prevent the lining material from sliding. habitat is available in publications cited in the refer- Curved revetments are subjected to increased forces ence section. because of the secondary currents acting against them. Streambank protection measures on large, wide chan- More substantial and permanent types of construction may be needed on curved channel sections because nels most likely will not significantly change stream- flow velocity. On smaller streams, however, the pro- streambank failures at these vulnerable points could result in much greater damage than that along unob- tective measures can influence the velocity throughout structed straight reaches of channel. the reach. n s values In calculating these velocities, the Manning ’ selected should represent the stream condition after the channel has matured, which normally requires several years. Erosion or sedimentation may occur if this is not anticipated. 7 16 – (210-vi-EFH, December 1996)

153 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Methods used to provide protection against undermin- (6) Stream type and hydraulic geometry Stream rehabilitation should be considered in the ing at the toe are: context of the historically stable stream type and its Extending the toe trench down to a depth below • geometry. If stream modification has caused short- the anticipated scour and backfilling with heavy ened meander wavelength, amplitude, and radius of rock. • Anchoring a heavy, flexible mattress to the curvature, the stream being treated might be best bottom of the revetment, which at the time of stabilized by restoring the historical geometry. The width-to-depth ratio of the stream being treated may installation will extend some distance out into be too high to transport the sediment load, and a lower the channel. This mattress will settle progres- sively as scour takes place, protecting the revet- ratio may be needed in the design channel. ment foundation. Installing a massive toe of heavy rock where • (7) Sediment load and bed material To determine the potential for stream aggradation, the excavation for a deep toe is not practical. This sediment load (bedload and suspended) for storm and allows the rock forming the toe to settle in place snowmelt runoff periods must frequently be deter- if scour occurs. However, because of the forces of flow, the settlement direction of the rock is mined before reconstruction. The size distribution of not always straight down. the streambed and bar material also should be deter- Driving sheet piling to form a continuous protec- mined. These measurements are important above and • tion for the revetment foundation. Such piling below the reconstruction reach under consideration as should be securely anchored against lateral well as in the main tributary streams above the reach. This information is used with appropriate shear stress pressures. To provide for a remaining embed- ment after scour, piling should be driven to a equations to determine the size of material that would be entrained at bankfull discharge (stream-forming depth equal to about twice the exposed height. flow) for both the tributary streams and in the re- • Installing toe deflector groins to deflect high velocity currents away from the toe of the stored reach. The sediment transport rate must be sufficient to prevent aggradation of the newly restored revetment. • Installing submerged vanes to control secondary channel. As shown by studies in Colorado (Andrews, currents. 1983) on gravelbed rivers, it is anticipated that par- ticles as large as the median diameter of the bed Since most of these measures have direct impacts on surface will be entrained by discharge equal to the bankfull stage (stream-forming flow) or less. aquatic habitat and other stream functions and values, their use should be considered carefully when plan- ning a streambank protection project. (8) Protection against failure Measures should be designed to provide against loss of support at the revetment s boundaries. This includes ’ (10) Ends of revetment upstream and downstream ends, its base or toe, and The location of the upstream and downstream ends of revetments must be selected carefully to avoid flank- the crest or top. ing by erosion. Wherever possible, the revetment should tie into stable anchorage points, such as bridge (9) Undermining Undermining or scouring of the foundation material by abutments, rock outcrops, or well-vegetated stable sections. If this is not practical, the upstream and high velocity currents is a major cause of bank protec- tion failure. In addition to protecting the lowest ex- downstream ends of the revetment must be positioned pected stable grade, additional depth must be provided well into a slack water area along the bank where bank erosion is not a problem. to reach a footing that most likely will not be scoured out during floods or lose its stability through satura- tion. Deep scour can be expected where construction is on an erodible streambed and high velocity currents flow adjacent to it. (210-vi-EFH, December 1996) 8 – 16

154 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Sediment bars, snags, trees, and other debris drifts (11) Debris removal Streambank protection may require the selective that create secondary currents or deflect flow toward removal or repositioning of debris, such as fallen trees, the banks may require selective removal or relocation in the stream channel. The entire plant structure does sediment bars, or other obstructions. Because logs and other woody debris are the major habitat-forming not always need to be dislodged when considering the components in many stream systems, a plan for debris removal of trees and snags; rooted stumps should be left in place to prevent erosion. Isolated or single logs removal should be developed in consultation with that are embedded, lodged, or rooted in the channel qualified fish and wildlife specialists. Small accumula- tions of debris and sediment generally do not cause and not causing flow problems should not be dis- turbed. Fallen trees may be used to construct bank problems and should be left undisturbed. protection systems. Trees and other large vegetation When planning streambank stabilization work, select are important to aquatic, aesthetic and riparian habitat access routes for equipment that minimize disturbance systems, and removal should be done judiciously and with great care. to the flood plain and riparian areas. All debris re- moval, grading, and material delivery and placement should be accomplished in a manner that uses the (12) Vegetative systems smallest equipment feasible and minimizes distur- Vegetative systems provide many benefits to fish and bance of riparian vegetation. Excavated material wildlife populations as well as increasing the stream- bank's resistance to erosive forces. Vegetation near should be disposed of in such a way that it does not interfere with overbank flooding, flood plain drainage, the channel provides shade to help maintain suitable water temperature for fish, provides habitat for wild- or associated wetland hydrology. In high velocity life and protection from predators, and contributes to streams it may be necessary to remove floating debris aesthetic quality. Leaves, twigs, and insects drop into selectively from flood-prone areas or anchor it so that it will not float back into the channel. the stream, providing nutrients for aquatic life 2). (fig. 16 – 2 – Vegetative system along streambank Figure 16 16 9 (210-vi-EFH, December 1996) –

155 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Although woody brush is preferable for habitat rea- • Protection and maintenance requirements are sons, suitable herbaceous ground cover can provide often high during plant establishment. desirable bank protection in areas of marginal erosion. Woody vegetation, which is seeded or planted as Perennial grasses and forbes, preferably those native to the area, should be used rather than annual grasses. rooted stock, is used most successfully above base- Woody vegetation may also be used to control undesir- flow on properly sloped banks and on the flood plain adjacent to the banks. Vegetation should always be able access to the stream. used behind revetments and jetties in the area where sediment deposition occurs, on the banks above base- Associated emergent aquatic plants serve multiple flow, and on slopes protected by cellular blocks or functions, including the protection of woody stream- similar type materials. bank or shoreline vegetation from wave or current wave action, which tend to undercut them. Many species of plants are suitable for streambank Vegetation protects streambanks in several ways: protection (see appendix 16B). Use locally collected native species as a first priority. Exotic or introduced Root systems help hold the soil particles together • increasing bank stability. species should be used only if there is no alternative. • Vegetation may increase the hydraulic resistance They should never be invasive species. Locally avail- to flow and reduce local velocities in small able erosion-resistant species that are suited to the channels. soil, moisture, and climatic conditions of a particular • Vegetation acts as a buffer against the hydraulic site are desirable. Aesthetics may also play an impor- tant role in selecting plants for certain areas. forces and abrasive effect of transported materials. • Dense vegetation on streambanks can induce sediment deposition. In many instances streambank erosion is accelerated by overgrazing, cultivating too close to the banks, or • Vegetation can redirect flow away from the bank. by overuse. In either case the treated area should be protected by adequate streamside buffers and appro- priate management practices. If the stream is the (d) Protective measures for source of livestock drinking water, access can be streambanks provided by establishing a ramp down to the water. Protective measures for streambanks can be grouped Such ramps should be located where the bank is not steep and, preferably, in straighter sections or at the into three categories: vegetative plantings, soil bioengi- neering systems, and structural measures. They are inside of curves in the channel where velocities are often used in combination. low. Providing watering facilities out of the channel (i.e., on the flood plain or terrace) for the livestock is often a preferred alternative to using ramps. (1) Vegetative plantings Conventional plantings of vegetation may be used The visual impact, habitat value, and other environ- alone for bank protection on small streams and on locations having only marginal erosion, or it may be mental effects of material removal or relocation must also be considered before performing any work. used in combination with structural measures in other situations. Considerations in using vegetation alone Protective measures reduce streambank erosion and for protection include: • prevent land losses and sediment damages, but do not Conventional plantings require establishment time, and bank protection is not immediate. directly stabilize the channel grade. However, if the • Maintenance may be needed to replace dead channel is restored to a stable stream type, vegetative plants, control disease, or otherwise ensure that protective measures, such as soil bioengineering, can materials become established and self-sustaining. be used to stabilize the streambanks. Vegetation • assists in bank stabilization by trapping sediment, Establishing plants to prevent undercutting and bank sloughing in a section of bank below reducing tractive stresses acting on the bank, redirect- baseflow is often difficult. ing the flow, and holding soil. The boundary shear • stress provided by vegetation, however, is much less Establishing plants in coarse gravely material may be difficult. than that provided by structural elements. 16 – (210-vi-EFH, December 1996) 10

156 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Many sites require some earthwork before soil bio- (2) Soil bioengineering systems Properly designed and constructed soil bioengineering engineering systems are installed. A steep undercut or systems have been used successfully to stabilize slumping bank, for example, may require grading to a – – 3b, 16 – 3c, and 16 3d). streambanks (figs. 16 3:1 or flatter slope. Although soil bioengineering – 3a, 16 systems are suitable for most sites, they are most successful where installed in sunny locations and Soil bioengineering is a system of living plant materials constructed during the dormant season. used as structural components. Adapted types of woody vegetation (shrubs and trees) are initially installed in specified configurations that offer immedi- Rooted seedlings and rooted cuttings are excellent ate soil protection and reinforcement. In addition, soil additions to soil bioengineering projects. They should bioengineering systems create resistance to sliding or be installed for species diversification and to provide habitat cover and food for fish and wildlife. Optimum shear displacement in a streambank as they develop establishment is usually achieved shortly after earth roots or fibrous inclusions. Environmental benefits derived from woody vegetation include diverse and work, preferably in the spring. productive riparian habitats, shade, organic additions to the stream, cover for fish, and improvements in Some of the most common and useful soil bioengineer- aesthetic value and water quality. ing structures for restoration and protection of stream- banks are described in the following sections. Under certain conditions, soil bioengineering installa- tions work well in conjunction with structures to provide more permanent protection and healthy func- tion, enhance aesthetics, and create a more environ- mentally acceptable product. Soil bioengineering systems normally use unrooted plant parts in the form of cut branches and rooted plants. For streambanks, living systems include brushmattresses, live stakes, joint plantings, vegetated geogrids, branchpacking, and live fascines. Major attractions of soil bioengineering systems are their natural appearance and function and the economy with which they can often be constructed. As discussed in chapter 18 of this Engineering Field Handbook, the work is normally done in the dormant months, generally September to March, which is the off season for many laborers. The main construction materials are live cuttings from suitable plant species. Species must be appropriate for the intended use and adapted to the site's climate and soil conditions. Consult a plant materials specialist for guidance on plant selection. Ideally plant materials should come from local ecotypes and genetic stock similar to that within the vicinity of the stream. Species that root easily, such as willow, are required for measures, such as live fascines and live staking, or where unrooted cuttings are used with structural measures. Suitable plant materials are listed in appendix 16B. They may also be identified in Field Office Technical Guides for specific site conditions or by contacting Plant Materi- als Centers. (210-vi-EFH, December 1996) 11 – 16

157 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Bank shaping prior to installing soil 3b – Figure 16 Figure 16 – 3a Eroding bank, Winooski River, Vermont, June 1938 bioengineering practices, Winooski River, Vermont, September 1938 3d – 3c Soil bioengineering system, Winooski Figure 16 – Figure 16 Three years after installation of soil bioengineering practices, 1941 River, Vermont, June 1993 (55 years after installation) (210-vi-EFH, December 1996) 16 – 12

158 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Applications and effectiveness (i) Live stakes— Live staking involves the insertion and tamping of live, rootable vegetative cuttings into • Effective streambank protection technique 4 and 16 – the ground (figs. 16 – where site conditions are uncomplicated, con- 5). If correctly prepared, struction time is limited, and an inexpensive handled, and placed, the live stake will root and grow method is needed. 6). (fig. 16 – • Appropriate technique for repair of small earth A system of stakes creates a living root mat that stabi- slips and slumps that frequently are wet. lizes the soil by reinforcing and binding soil particles Can be used to peg down and enhance the per- • formance of surface erosion control materials. together and by extracting excess soil moisture. Most Enhance conditions for natural colonization of willow species root rapidly and begin to dry out a • bank soon after installation. vegetation from the surrounding plant commu- nity. • Stabilize intervening areas between other soil bioengineering techniques, such as live fascines. • Produce streamside habitat. Figure 16 Live stake details 4 – Cross section Not to scale Streambank 2 to 3 feet Erosion control fabric ° 90 Dead stout stake 2 to 3 feet (triangular spacing) Stream-forming flow Baseflow Live cutting 1/2 to 1 1/2 inches in diameter Streambed Toe protection Note: Rooted/leafed condition of the living Geotextile fabric plant material is not representative of the time of installation. 16 13 – (210-vi-EFH, December 1996)

159 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Placement may vary by species. For example, • Construction guidelines along many western streams, tree-type willow Live material sizes — The stakes generally are 0.5 to 1.5 inches in diameter and 2 to 3 feet long. The specific species are placed on the inside curves of point bars where more inundation occurs, while shrub site requirements and available cutting source deter- willow species are planted on outside curves mine sizes. where the inundation period is minimal. • Live material preparation The buds should be oriented up. • Four-fifths of the length of the live stake should • The materials must have side branches cleanly removed with the bark intact. be installed into the ground, and soil should be The basal ends should be cut at an angle or point firmly packed around it after installation. • Do not split the stakes during installation. Stakes • for easy insertion into the soil. The top should be that split should be removed and replaced. cut square. An iron bar can be used to make a pilot hole in • Materials should be installed the same day that • they are prepared. firm soil. • Tamp the stake into the ground with a dead blow hammer (hammer head filled with shot or sand). Installation • Erosion control fabric should be placed on slopes subject to erosive inundation. • Tamp the live stake into the ground at right angles to the slope and diverted downstream. The installation may be started at any point on the slope face. • The live stakes should be installed 2 to 3 feet apart using triangular spacing. The density of the installation will range from 2 to 4 stakes per square yard. Site variations may require slightly different spacing. (210-vi-EFH, December 1996) 14 – 16

160 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook (Robbin B. Sotir & Associates photo) Prepared live stake 5 – Figure 16 Figure 16 – 6 Growing live stake (210-vi-EFH, December 1996) 15 – 16

161 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Dead stout stakes used to secure the live fascines Live fascines are long bundles of (ii) Live fascines— branch cuttings bound together in cylindrical struc- should be 2.5-foot long, untreated, 2 by 4 lumber. Each tures (fig. 16 – 7). They should be placed in shallow length should be cut again diagonally across the 4-inch contour trenches on dry slopes and at an angle on wet 8). face to make two stakes from each length (fig 16 – Only new, sound lumber should be used, and any stakes slopes to reduce erosion and shallow sliding. that shatter upon installation should be discarded. Applications and effectiveness Apply typically above bankfull discharge Installation • (stream-forming flow) except on very small • Prepare the live fascine bundle and live stakes drainage area sites (generally less than 2,000 immediately before installation. • acres). Beginning at the base of the slope, dig a trench Effective stabilization technique for stream- on the contour approximately 10 inches wide and • deep. banks. When properly installed, this system does not cause much site disturbance. • Excavate trenches up the slope at intervals • Protect slopes from shallow slides (1 to 2 foot 1. Where possible, place one – specified in table 16 depth). or two rows over the top of the slope. • Offer immediate protection from surface • Place long straw and annual grasses between erosion. rows. Install jute mesh, coconut netting, or other • • Capable of trapping and holding soil on a stream- acceptable erosion control fabric. Secure the bank by creating small dam-like structures, thus fabric. reducing the slope length into a series of shorter Place the live fascine into the trench (fig. 16 – 9a). • slopes. Drive the dead stout stakes directly through the • • Serve to facilitate drainage where installed at an live fascine. Extra stakes should be used at con- angle on the slope. Enhance conditions for colonization of native • nections or bundle overlaps. Leave the top of the dead stout stakes flush with the installed bundle. vegetation by creating surface stabilization and a microclimate conducive to plant growth. Live stakes are generally installed on the • downslope side of the bundle. Tamp the live Construction guidelines stakes below and against the bundle between the — Live materials Cuttings must be from species, such previously installed dead stout stakes, leaving 3 inches to protrude above the top of the ground as young willows or shrub dogwoods, that root easily 9b). Place moist soil along the sides of – (fig. 16 and have long, straight branches. the bundles. The top of the live fascine should be slightly visible when the installation is Live material sizes and preparation – completed. Figure 16 9c shows an established • Cuttings tied together to form live fascine bundles normally vary in length from 5 to 10 feet live fascine system 2 years after installation is or longer, depending on site conditions and completed. limitations in handling. The completed bundles should be 6 to 8 inches in • – Table 16 Live fascine spacing 1 diameter, with all of the growing tips oriented in the same direction. Stagger the cuttings in the bundles so that tops are evenly distributed - - - - - - - - - - - - Soils - - - - - - - - - - - - Slope steepness throughout the length of the uniformly sized live Erosive Non-erosive Fill fascine. (feet) (feet) (feet) Live stakes should be 2.5 feet long. • 1/ 3 – 73 5 3:1 or flatter 55 – – Inert materials — String used for bundling should be 1/ 2/ Steeper than 3:1 3 3 – 5 untreated twine. (up to 1:1) 1/ Not recommended alone. 2/ Not a recommended system. – (210-vi-EFH, December 1996) 16 16

162 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Live fascine details Figure 16 – 7 Top of live fascine slightly exposed Cross section after installation Not to scale Moist soil backfill Prepared trench Erosion control fabric & seeding Stream-forming flow Baseflow Streambed Live fascine bundle Live stake Geotextile fabric (2- to 3-foot spacing between dead stout stakes) Toe protection Note: Dead stout stake Rooted/leafed condition of the living (2- to 3-foot spacing along bundle) plant material is not representative of the time of installation. Live branches (stagger throughout bundle) Bundle Twine (6 to 8 inches in diameter) 17 16 – (210-vi-EFH, December 1996)

163 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook 8 – Preparation of a dead stout stake Figure 16 Installing live stakes in live fascine system 9b – Figure 16 (Robbin B. Sotir & Associates photo) 2 1/2' Figure 16 An established 2-year-old live fascine 9c – (Robbin B. Sotir & Associates photo) system Saw a 2" by 4" diagonally to 2" by 4" lumber produce two dead stout stakes Not to scale Placing live fascines (Robbin B. Sotir & Figure 16 – 9a Associates photo) 16 – 18 (210-vi-EFH, December 1996)

164 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Wooden stakes should be 5 to 8 feet — Inert materials (iii) Branchpacking— Branchpacking consists of alternating layers of live branches and compacted long and made from 3- to 4-inch diameter poles or 2 by backfill to repair small localized slumps and holes in 4 lumber, depending upon the depth of the particular – 11b, and 16 – 11c). 10, 16 streambanks (figs. 16 – slump or hole being repaired. – 11a, 16 Installation Applications and effectiveness Effective and inexpensive method to repair holes • Starting at the lowest point, drive the wooden • in streambanks that range from 2 to 4 feet in stakes vertically 3 to 4 feet into the ground. Set height and depth. them 1 to 1.5 feet apart. Produces a filter barrier that prevents erosion • • Place an initial layer of living branches 4 to 6 and scouring from streambank or overbank flow. inches thick in the bottom of the hole between the vertical stakes, and perpendicular to the Rapidly establishes a vegetated streambank. • slope face (fig. 16 10). They should be placed in • Enhances conditions for colonization of native – a criss-cross configuration with the growing tips vegetation. • Provides immediate soil reinforcement. generally oriented toward the slope face. Some Live branches serve as tensile inclusions for of the basal ends of the branches should touch • the undisturbed soil at the back of the hole. reinforcement once installed. As plant tops begin • to grow, the branchpacking system becomes Subsequent layers of branches are installed with increasingly effective in retarding runoff and the basal ends lower than the growing tips of the branches. reducing surface erosion. Trapped sediment Each layer of branches must be followed by a • refills the localized slumps or hole, while roots layer of compacted soil to ensure soil contact spread throughout the backfill and surrounding with the branches. earth to form a unified mass. • Typically branchpacking is not effective in slump • The final installation should conform to the areas greater than 4 feet deep or 4 feet wide. existing slope. Branches should protrude only slightly from the filled installation. Water must be controlled or diverted if the Construction guidelines • Live branches may range from 0.5 to 2 — Live materials original streambank damage was caused by inches in diameter. They should be long enough to water flowing over the bank. If this is not done, touch the undisturbed soil of the back of the trench erosion will most likely occur on either or both and extend slightly from the rebuilt streambank. sides of the new branchpacking installation. 16 19 (210-vi-EFH, December 1996) –

165 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Branchpacking details 10 Figure 16 – Cross section Not to scale Existing vegetation, plantings or soil bioengineering systems Max. depth 4' Max. depth 4' Streambank after scour Live branches (1/2- to 2-inch diameter) Compacted fill material Stream-forming flow Wooden stakes (5- to 8-foot long, 2 by 4 lumber, driven 3 to 4 feet into undisturbed soil) Baseflow Streambed 1 to 1 1/2 feet Geotextile fabric Toe protection Note: Root/leafed condition of the living plant material is not representative of the time of installation . 20 – 16 (210-vi-EFH, December 1996)

166 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook 11b – Each layer of branches is followed by a – 11a Live branches installed in criss-cross Figure 16 Figure 16 (Robbin B. Sotir & (Robbin B. Sotir & Associates layer of compacted soil configuration photo) Associates photo) – (Robbin B. Sotir & Associates photo) A growing branchpacking system 11c Figure 16 – 21 (210-vi-EFH, December 1996) 16

167 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook (iv) Vegetated geogrids— Installation Vegetated geogrids are similar to branchpacking except that natural or syn- • Excavate a trench that is 2 to 3 feet below thetic geotextile materials are wrapped around each streambed elevation and 3 to 4 feet wide. Place soil lift between the layers of live branch cuttings the geotextile in the trench, leaving a foot or two 13b, and 16 – 13c). overhanging on the streamside face. Fill this area (figs. 16 – 12, 16 – 13a, 16 – with rocks 2 to 3 inches in diameter. Applications and effectiveness Beginning at the stream-forming flow level, place • a 6- to 8-inch layer of live branch cuttings on top Used above and below stream-forming flow • of the rock-filled geogrid with the growing tips at conditions. right angles to the streamflow. The basal ends of Drainage areas should be relatively small • (generally less than 2,000 acres) with stable branch cuttings should touch the back of the streambeds. excavated slope. • The system must be built during low flow Cover this layer of cuttings with geotextile leav- • ing an overhang. Place a 12-inch layer of soil conditions. • Can be complex and expensive. suitable for plant growth on top of the geotextile Produce a newly constructed, well-reinforced • before compacting it to ensure good soil contact streambank. with the branches. Wrap the overhanging portion Useful in restoring outside bends where erosion of the geotextile over the compacted soil to form • is a problem. the completed geotextile wrap. • • Capture sediment, which rapidly rebuilds to Continue this process of excavated trenches with further stabilize the toe of the streambank. alternating layers of cuttings and geotextile • wraps until the bank is restored to its original Function immediately after high water to height. rebuild the bank. • • Produce rapid vegetative growth. This system should be limited to a maximum of 8 Enhance conditions for colonization of native • feet in total height, including the 2 to 3 feet below the bed. The length should not exceed 20 vegetation. feet for any one unit along the stream. An engi- Benefits are similar to those of branchpacking, • but a vegetated geogrid can be placed on a 1:1 or neering analysis should determine appropriate dimensions of the system. steeper slope. The final installation should match the existing • slope. Branch cuttings should protrude only Construction guidelines Live materials slightly from the geotextile wraps. Live branch cuttings that are brushy — and root readily are required. They should be 4 to 6 feet long. Natural or synthetic geotextile Inert materials — material is required. (210-vi-EFH, December 1996) 22 – 16

168 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Figure 16 – 12 Vegetated geogrid details Dead stout stake used to secure geotextile fabric Cross section Not to scale Install additional vegetation such as live stakes, rooted seedlings, etc. Eroded streambank Compacted soil approximately 1-foot thick Live cuttings Geotextile fabric Height varies 8 foot maximum Stream-forming flow Baseflow Streambed Rock fill 2 to 3 feet Note: Rooted/leafed condition of the living plant material is not representative 3 to 4 feet of the time of installation. (210-vi-EFH, December 1996) 23 – 16

169 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook 13b – Figure 16 – 13a A vegetated geogrid during installation A vegetated geogrid immediately after Figure 16 (Robbin B. Sotir & Associates (Robbin B. Sotir & Associates photo) installation photo) Vegetated geogrid 2 years after installation (Robbin B. Sotir & Associates photo) 13c – Figure 16 24 16 – (210-vi-EFH, December 1996)

170 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Installation A live cribwall consists of a box- (v) Live cribwall— Starting at the base of the streambank to be like interlocking arrangement of untreated log or • timber members. The structure is filled with suitable treated, excavate 2 to 3 feet below the existing streambed until a stable foundation 5 to 6 feet backfill material and layers of live branch cuttings that wide is reached. root inside the crib structure and extend into the • Excavate the back of the stable foundation slope. Once the live cuttings root and become estab- lished, the subsequent vegetation gradually takes over (closest to the slope) 6 to 12 inches lower than the front to add stability to the structure. the structural functions of the wood members (fig. Place the first course of logs or timbers at the • 16 – 14). front and back of the excavated foundation, approximately 4 to 5 feet apart and parallel to the Applications and effectiveness slope contour. Effective on outside bends of streams where • Place the next course of logs or timbers at right strong currents are present. • Appropriate at the base of a slope where a low • angles (perpendicular to the slope) on top of the previous course to overhang the front and back wall may be required to stabilize the toe of the slope and reduce its steepness. of the previous course by 3 to 6 inches. Each course of the live cribwall is placed in the same • Appropriate above and below water level where manner and secured to the preceding course stable streambeds exist. with nails or reinforcement bars. • Useful where space is limited and a more vertical • Place rock fill in the openings in the bottom of structure is required. Effective in locations where an eroding bank the crib structure until it reaches the approxi- • may eventually form a split channel. mate existing elevation of the streambed. In • Maintains a natural streambank appearance. some cases it is necessary to place rocks in front Provides excellent habitat. of the structure for added toe support, especially • • Provides immediate protection from erosion, in outside stream meanders. Place the first layer of cuttings on top of the rock • while established vegetation provides long-term material at the baseflow water level, and change stability. the rock fill to soil fill capable of supporting • Supplies effective bank erosion control on fast flowing streams. plant growth at this point. Ensure that the basal Should be tilted back or battered if the system is • ends of some of the cuttings contact undisturbed soil at the back of the cribwall. built on a smooth, evenly sloped surface. When the cribwall structure reaches the existing • • Can be complex and expensive. ground elevation, place live branch cuttings on the backfill perpendicular to the slope; then Construction guidelines Live branch cuttings should be 0.5 to Live materials — cover the cuttings with backfill and compact. Live branch cuttings should be placed at each • 2.5 inches in diameter and long enough to reach the course to the top of the cribwall structure with back of the wooden crib structure. growing tips oriented toward the slope face. — Logs or timbers should range from 4 Follow each layer of branches with a layer of Inert materials to 6 inches in diameter or dimension. The lengths will compacted soil. Place the basal ends of the re- vary with the size of the crib structure. maining live branch cuttings so that they reach to undisturbed soil at the back of the cribwall with growing tips protruding slightly beyond the front Large nails or rebar are required to secure the logs or of the cribwall (figs. 16 timbers together. 15c). – – 15a, 16 – 15b, and 16 • The live cribwall structure, including the section below the streambed, should not exceed a maxi- mum height of 7 feet. An engineering analysis should determine appropriate dimensions of the system. The length of any single constructed unit should • not exceed 20 feet. 25 16 – (210-vi-EFH, December 1996)

171 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Live cribwall details 14 Figure 16 – Existing vegetation, plantings or soil bioengineering systems Cross section Not to scale Erosion control fabric Compacted fill material Stream-forming flow 3 to 4 feet Baseflow Live branch cuttings Streambed 2 to 3 feet Rock fill 4 to 5 feet Note: Rooted/leafed condition of the living plant material is not representative of the time of installation. 26 – 16 (210-vi-EFH, December 1996)

172 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook A live cribwall during installation 15b – Figure 16 Figure 16 – 15a Pre-construction streambank conditions Figure 16 – 15c An established live cribwall system (210-vi-EFH, December 1996) 27 – 16

173 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Joint planting or vegetated (vi) Joint planting— Construction guidelines The stakes must have side riprap involves tamping live stakes into joints or open Live material sizes — branches removed and bark intact. They should be 1.5 spaces in rocks that have been previously placed on a – 16). Alternatively, the stakes can be inches or larger in diameter and sufficiently long to slope (fig 16 tamped into place at the same time that rock is being extend well into soil below the rock surface. placed on the slope face. Installation Applications and effectiveness • Tamp live stakes into the openings of the rock • Useful where rock riprap is required or already during or after placement of riprap. The basal ends of the material must extend into the backfill in place. or undisturbed soil behind the riprap. A steel rod • Roots improve drainage by removing soil moisture. • or hydraulic probe may be used to prepare a hole Over time, joint plantings create a living root mat in the soil base upon which the rock has been through the riprap. placed. These root systems bind or reinforce the • Orient the live stakes perpendicular to the slope soil and prevent washout of fines between and with growing tips protruding slightly from the 17b, – – 17a, 16 below the rock. finished face of the rock (figs. 16 and 16 Provides immediate protection and is effective in • – 17c). • Place the stakes in a random configuration. reducing erosion on actively eroding banks. • Dissipates some of the energy along the streambank. Figure 16 – 16 Joint planting details Cross section Not to scale Stream-forming flow Baseflow Streambed Riprap Dead stout stake used to secure geotextile fabric Live stake 28 16 – (210-vi-EFH, December 1996)

174 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook An installed joint planting system 17b – Figure 16 – 17a Live stake tamped into rock joints (joint Figure 16 (Robbin B. Sotir & Associates photo) (Robbin B. Sotir & Associates photo) planting) Figure 16 – 17c An established joint planting system (Robbin B. Sotir & Associates photo) (210-vi-EFH, December 1996) 29 – 16

175 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook A brushmattress is a combi- Installation (vii) Brushmattress— nation of live stakes, live fascines, and branch cuttings Grade the unstable area of the streambank • installed to cover and stabilize streambanks (figs. uniformly to a maximum steepness of 3:1. – 16 – 18, 16 • Prepare live stakes and live fascine bundles – 19a through 16 19d). Application typically starts above stream-forming flow conditions and immediately before installation, as previously described in this chapter. moves up the slope. • Beginning at the base of slope, near the stream- Applications and effectiveness forming flow stage, excavate a trench on the contour large enough to accommodate a live • Forms an immediate, protective cover over the fascine and the basal ends of the branches. streambank. • Useful on steep, fast-flowing streams. • Install an even mix of live and dead stout stakes at 1-foot depth over the face of the graded area Captures sediment during flood conditions. • using 2-foot square spacing. Rapidly restores riparian vegetation and stream- • • Place branches in a layer 1 to 2 branches thick side habitat. vertically on the prepared slope with basal ends • Enhances conditions for colonization of native located in the previously excavated trench. vegetation. • Stretch No. 16 smooth wire diagonally from one dead stout stake to another by tightly wrapping Construction guidelines Live materials — wire around each stake no closer than 6 inches Branches 6 to 9 feet long and approxi- from its top. mately 1 inch in diameter are required. They must be flexible to enable installations that conform to varia- Tamp and drive the live and dead stout stakes • tions in the slope face. Live stakes and live fascines into the ground until branches are tightly secured to the slope. are previously described in this chapter. • Place live fascines in the prepared trench over Untreated twine for bundling the live — Inert materials the basal ends of the branches. fascines and number 16 smooth wire are needed to tie Drive dead stout stakes directly through into soil • down the branch mattress. Dead stout stakes to secure below the live fascine every 2 feet along its length. the live fascines and brushmattress in place. • Fill voids between brushmattress and live fascine cuttings with thin layers of soil to promote root- ing, but leave the top surface of the brush- mattress and live fascine installation slightly exposed. – 16 30 (210-vi-EFH, December 1996)

176 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook – 18 Brushmattress details Figure 16 Live and dead stout stake spacing Cross section 2 feet o.c. Not to scale Branch cuttings 16 gauge wire Live stake Stream-forming flow Baseflow Streambed Live fascine bundle Live stake Geotextile fabric Dead stout stake driven on 2-foot centers each way. Dead stout stake Minimum length 2 1/2 feet. Wire secured to stakes Brush mattress Note: Rooted/leafed condition of the living 2 ft plant material is not representative at the time of installation. – 31 (210-vi-EFH, December 1996) 16

177 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Figure 16 – 19b An installed brushmattress system 19a – Brushmattress during installation Figure 16 (Robbin B. Sotir & Associates photo) (Robbin B. Sotir & Associates photo) Brushmattress system 2 years after – Figure 16 19c 19d – Figure 16 Brushmattress system 6 months after installation installation (Robbin B. Sotir & Associates (Robbin B. Sotir & Associates photo) photo) (210-vi-EFH, December 1996) 32 – 16

178 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Construction guidelines (4) Structural measures Structural measures include tree revetments; log, Lay the cabled trees along the bank with the • rootwad and boulder revetments; dormant post basal ends oriented upstream. • Overlap the trees to ensure continuous protec- plantings; piling revetments with wire or geotextile fencing; piling revetments with slotted fencing; jacks tion to the bank. Attach the trunks by cables to anchors set in the or jack fields; rock riprap; stream jetties; stream barbs; • bank. Pilings can be used in lieu of earth anchors and gabions. in the bank if they can be driven well below the point of maximum bed scour. The required cable A tree revetment is constructed (i) Tree revetment— size and anchorage design are dependent upon from whole trees (except rootwads) that are usually cabled together and anchored by earth anchors, which many variables and should be custom designed 20, 16 are buried in the bank (figs. 16 – to fit specific site conditions. 21a, and – 16 – Use trees that have a trunk diameter of 12 inches • 21b). or larger. The best type are those that have a Applications and effectiveness brushy top and durable wood, such as douglas Uses inexpensive, readily available materials to fir, oak, hard maple, or beech. • • form semi-permanent protection. Use vegetative plantings or soil bioengineering • systems within and above structures to restore Captures sediment and enhances conditions for colonization of native species. stability and establish a vegetative community. Has self-repairing abilities following damage • Tree species that will withstand inundation after flood events if used in combination with should be staked in openings in the revetment soil bioengineering techniques. below stream-forming flow stage. • Not appropriate near bridges or other structures where there is high potential for downstream damage if the revetment dislodges during flood events. • Has a limited life and may need to be replaced periodically, depending on the climate and dura- bility of tree species used. • May be damaged in streams where heavy ice flows occur. • May require periodic maintenance to replace damaged or deteriorating trees. (210-vi-EFH, December 1996) 33 – 16

179 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Tree revetment details 20 Figure 16 – Plan view Not to scale Flow Piling may be substituted for earth anchors Existing vegetation, plantings or soil bioengineering systems Stabilize streambank to top of slope where appropriate Earth anchors (8-inch dia. by 4-foot min.) Two-thirds of bank height covered Stream-forming flow Second row applied Cross section Baseflow Not to scale Bank toe Earth anchors 6 feet deep 34 16 – (210-vi-EFH, December 1996)

180 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Tree revetment system with dormant posts 21a – Figure 16 Figure 16 – 21b Tree revetment system with dormant posts, 2 years after installation (210-vi-EFH, December 1996) 35 – 16

181 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook (ii) Log, rootwad and boulder revetments— Applications and effectiveness Used for stabilization and to create instream • These revetments are systems composed of logs, rootwads, and boulders selectively placed in and on structures for improved fish rearing and spawn- 22 and 16 – 23). These revet- ing habitat streambanks (figs. 16 – ments can provide excellent overhead cover, resting • Effective on meandering streams with out-of- bank flow conditions. areas, shelters for insects and other fish food organ- • isms, substrate for aquatic organisms, and increased Will tolerate high boundary shear stress if logs stream velocity that results in sediment flushing and and rootwads are well anchored. • deeper scour pools. Several of these combinations are Suited to streams where fish habitat deficiencies described in Flosi and Reynolds (1991), Rosgen (1992) exist. Should be used in combination with soil bioengi- • and Berger (1991). neering systems or vegetative plantings to stabi- Log, rootwad, and boulder revetment details Applied fluvial geomorphology short course) – Figure 16 — 22 (adapted from Rosgen 1993 Existing vegetation, plantings or Cross section soil bioengineering systems Not to scale 8- to 12-foot Length Stream-forming flow Rootwad Baseflow Streambed Thalweg channel Diameter of log = 16-in min. Boulder 1 1/2 times diameter of log Footer log 16 – 36 (210-vi-EFH, December 1996)

182 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Install a footer log at the toe of the eroding bank lize the upper bank and ensure a regenerative • by excavating trenches or driving them into the source of streambank vegetation. bank to stabilize the slope and provide a stable Enhance diversity of riparian corridor when used • in combination with soil bioengineering systems. foundation for the rootwad. • Place the footer log to the expected scour depth Have limited life depending on climate and tree • species used. Some species, such as cottonwood at a slight angle away from the direction of the or willow, often sprout and accelerate natural stream flow. • colonization. Revetments may need eventual Use boulders to anchor the footer log against flotation. If boulders are not available, logs can replacement if natural colonization does not take be pinned into gravel and rubble substrate with place or soil bioengineering methods are not 3/4-inch rebar 54 inches or longer. Anchor rebar used in combination. to provide maximum pull out resistance. Cable Construction guidelines and anchors may also be used in combination with boulders and rebar. Numerous individual organic revetments exist and Drive or trench and place rootwads into the many are detailed in the U.S. Forest Service publica- • streambank so that the tree's primary brace roots tion, Chap- Stream Habitat Improvement Handbook. ter 16 only presents construction guidelines for a are flush with the streambank. Place the root- wads at a slight angle toward the direction of the combination log, rootwad, and boulder revetment. • Use logs over 16 inches in diameter that are streamflow. crooked and have an irregular surface. Backfill and combine vegetative plantings or soil • Use rootwads with numerous root protrusions bioengineering systems behind and above • and 8- to 12-foot long boles. rootwad. They can include live stakes and dor- Boulders should be as large as possible, but at a • mant post plantings in the openings of the revet- minimum one and one-half the log diameter. ment below stream-forming flow stage, live They should have an irregular surface. stakes, bare root, or other upland methods at the top of the bank. Figure 16 – 23 Rootwad, boulder, and willow transplant revetment system, Weminuche River, CO (Rosgen, Wildland hydrology) – 16 37 (210-vi-EFH, December 1996)

183 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Dormant post (iii) Dormant post plantings— Construction guidelines Select a plant species appropriate to the site plantings form a permeable revetment that is con- • structed from rootable vegetative material placed conditions. Willows and poplars have demon- strated high success rates. along streambanks in a square or triangular pattern – 25b, 16 – 25c). Cut live posts approximately 7 to 9 feet long and • (figs. 16 – 24, 16 – 25a, 16 3 to 5 inches in diameter. Taper the basal end of Applications and effectiveness the post for easier insertion into the ground. Install posts into the eroding bank at or just • Well suited to smaller, non-gravely streams • where ice damage is not a problem. above the normal waterline. Make sure posts are • installed pointing up. Quickly re-establishe riparian vegetation. • • Reduce stream velocities and causes sediment Insert one-half to two-thirds of the length of post below the ground line. At least the bottom 12 deposition in the treated area. inches of the post should be set into a saturated Enhance conditions for colonization of native • soil layer. species. Are self-repairing. For example, posts damaged • • Avoid excessive damage to the bark of the posts. • by beaver often develop multiple stems. Place two or more rows of posts spaced 2 to 4 feet apart using square or triangular spacing. • Can be used in combination with soil bioengi- • neering systems. Supplement the installation with appropriate soil Can be installed by a variety of methods includ- • bioengineering systems or, where appropriate, ing water jetting or mechanized stingers to form rooted plants. planting holes or driving the posts directly with machine mounted rams. Unsuccessfully rooted posts at spacings of about • 4 feet can provide some benefits by deflecting higher streamflows and trapping sediment. Figure 16-24 Dormant post details Cross section Existing vegetation, plantings Not to scale or soil bioengineering systems Dormant posts Streambank Stream-forming flow 2:1 to 5:1 slope 5 ft Baseflow Streambed 2 ft 2 to 4 feet triangular spacing 38 16 – (210-vi-EFH, December 1996)

184 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Pre-construction streambank conditions 25a – Figure 16 25b Figure 16 – Installing dormant posts (Don Roseboom photo) (Don Roseboom photo) 25c – (Don Roseboom photo) Established dormant post system Figure 16 39 16 – (210-vi-EFH, December 1996)

185 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook (iv) Piling revetment with wire or geotextile Installation Piling revetment is a continuous single or fencing— • Beginning at the base of the streambank, near double row of pilings with a facing of woven wire or stream-forming flow stage, drive pilings 6 to 8 feet apart to a depth approximately half their – geogrid material (fig. 16 26). The space between length and below the point of maximum scour. If double rows of pilings is filled with rock and brush. the streambed is firm and not subject to appre- ciable scour, the piling should be driven to re- Applications and effectiveness Particularly suited to streams where water next • fusal or to a depth of at least half the length of the piling. to the bank is more than 3 feet deep. Additional rows of pilings may be installed at Application is limited to a flow depth (and height • • higher elevations on the streambank if required of piling) of 6 feet. More economical than riprap construction in • to protect the bank and if using vegetation or deep water because it eliminates the need to other methods is not practical. build a stable foundation under water for holding • Fasten a heavy gauge of woven wire or geotextile material to the stream side of the pilings to form the riprap in place. • Is easily damaged by ice flows or heavy flood a fence. The purpose of this material is to collect debris while serving as a permeable wall to debris and should not be used where these conditions occur. reduce velocities on the streambank. Double row piling revetment is typically con- • Do not use where the stream has fish or an • abundance of riparian wildlife. structed with 5 feet between rows. Fill the row Do not use without careful analysis of its long- space with rock and brush. • term effects upon aesthetics, changes in flows • If the streambed is subject to scour, extend the where large amounts of debris will be collected, woven wire or geotextile material horizontally toward the center of the streambed for a dis- habitat damage caused by driving or installing pilings with water jets, and possible dangers for tance at least equal to the anticipated depth of recreational uses (boating, rafting, swimming, or scour. Attach concrete blocks or other suitable weights at regular intervals to cause the fence to wading). settle in a vertical position along the face of the Construction guidelines pilings after scouring occurs. Inert materials — • Used material, such as timbers, logs, Place brush behind the piling to increase the railroad rails, or pipe, may be used for pilings. Logs system's effectiveness. Where piling revetments should have a diameter sufficiently large to permit extend for several hundred feet in length, install permeable groins or tiebacks of brush and rock driving to the required depth. Avoid material that may produce toxicity effects in aquatic ecosystems. at right angles to the revetment at 50 foot inter- vals. This reduces currents developing between the streambank and the revetment. – 40 (210-vi-EFH, December 1996) 16

186 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Piling revetment details Figure 16 – 26 Front elevation Heavy woven wire or geogrid fencing Not to scale Piling 6 to 8 feet Stream-forming flow Baseflow Streambed Weight Existing vegetation, plantings or soil bioengineering systems Cross section Not to scale Piling (8- to 12-in dia.) Heavy woven wire or Streambank geogrid fencing 5 to 6 feet Stream-forming flow Baseflow Sloped bank Brush Streambed Concrete block weight ground than height above Equal to or greater 16 – 41 (210-vi-EFH, December 1996)

187 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook May be vulnerable to damage by ice or heavy • (v) Piling revetment with slotted board fencing — This type of revetment consists of slotted board flood debris; should not be used where these fencing made of wood pilings and horizontal wood conditions occur. • Usually complex and expensive. timbers (figs. 16 – 27 and 16 – 28). Variations include Most effective on streams that have a heavy • different fence heights, double rows of slotted fence, sediment load of sand and silt. and use of woven wire in place of timber boards. The • Can withstand a relatively high velocity attack size and spacing of pilings, cross members, and verti- cal fence boards depend on height of fence, stream force and, therefore, can be installed in sharper curves than jacks or other systems. velocity, and sediment load. • Useful in deeper stream channels with large flow depths. Applications and effectiveness • • Low slotted board fences, which do not control Most variations of slotted fencing include some bracing or tieback into the streambank to in- the entire flood flow, can be very effective for crease strength, reduce velocity against the streambank toe protection where the toe is the weak part of the streambank. streambank, and to trap sediment. Should not be constructed higher than 3 feet • • May not be appropriate where unusually hard materials are encountered in the channel bottom. without an engineering analysis to determine sizes of the structural members. Figure 16 – 27 Slotted board fence details (double fence option) Existing vegetation, plantings Cross section or soil bioengineering systems Not to scale 5 ft. Brace Piling Boards Brush & rock fill optional Stream-forming flow Baseflow Streambed Equal to or greater than height above ground – 42 16 (210-vi-EFH, December 1996)

188 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Installation Should not be used without careful consideration • See (iv) Piling revetment with wire or of its long-term effects upon aesthetics, changes • for general construction geotextile fencing in flows where large amounts of debris are guidelines. collected, habitat damage caused by driving or Drive the timber piling to a depth below the • installing pilings with water jets, and possible channel bottom that is equal to the height of the dangers for recreational uses (boating, rafting, slotted fence above the expected scour line when swimming, or wading). stream soils have a standard penetration resis- Construction guidelines tance of 10 or more blows per foot. Increase the Inert materials — Slotted fencing is constructed of piling depth when penetration resistance is less wood boards, wood pilings, and woven wire. Avoid than 10 blows per foot. Take great care during layout to tie in the up- materials that may produce toxicity effects in aquatic • ecosystems. stream end adequately to prevent flanking and unraveling. Figure 16 – 28 Slotted board fence system 43 16 – (210-vi-EFH, December 1996)

189 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Do not use on high velocity, debris-laden Jacks are individual • (vi) Jacks or jack fields— structures made of wood, concrete, or steel. The jacks streams. • are placed in rows parallel to the eroding streambank Somewhat flexible because of their physical configuration and installation techniques that and function by trapping debris and sediment. They are often constructed in groups called jack fields allow them to adjust to slight changes in the – – 31). (figs. 16 30, and 16 channel grade. 29, 16 – Most effective on long, radius curves. • Not an effective alternative for redirecting flow • Applications and effectiveness May be an effective means of controlling bank • away from the streambank. erosion on sinuous streams carrying heavy Do not use without careful analysis of its long- • term effects upon aesthetics, changes in flows bedloads of sand and silt during flood flows. This where large amounts of debris are collected, fish condition is generally indicated by the presence habitat damage, and possible dangers for recre- of extensive sandbar formations on the bed at low flow. ational uses (boating, rafting, swimming, or wading). Are complex systems requiring proper design • and installation for effective results. • Collect coarse and fine sediment, when function- ing properly, and naturally revegetate as the systems, including cable, become embedded in the streambank. – Figure 16 Concrete jack details 29 Front elevation Concrete, wood, or steel jack Not to scale Cable - 3/8 inch wire strands Anchor piling Notch Cable clamps Staples 6 feet Streambed 1 foot 4 feet Baseflow Streambed 5 to 20 feet Upstream anchor Downstream & inline anchor (210-vi-EFH, December 1996) – 44 16

190 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Steel jacks are used in a manner similar to that of Construction guidelines wood jacks; however, leg assemblies, cable size, Inert materials — Jacks may be constructed of wood, anchor blocks, and anchor placement details vary. steel, or concrete. Wooden jacks are constructed from three poles 10 to 16 feet long. They are crossed and Concrete beams may be substituted for steel, but wired together at the ends and midpoints with No. 9 engineering design is required to determine different attachment methods, anchoring systems, and assem- galvanized wire. Cables used to anchor the wood jack systems should be 3/8-inch diameter or larger with a bly configurations. minimum breaking strength of 15,400 pounds. Wooden jack systems dimensioned in this chapter are limited to shallow flow depths of 12 feet or less. 30 – Wooden jack field Figure 16 Note: For streams of high velocity, a sturdy construction would be to tie all ends together. Bank to be protected Rock placed at base of jack to prevent floating. Floodplain Stream channel Cable Deadman anchor Note: Supplemental anchors should be used to tie (timber log) individual jacks into the streambank. 16 – 45 (210-vi-EFH, December 1996)

191 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Bury anchors or drive anchor pilings to the • Installation design depth determined by an engineer. Depths Jack rows can be placed on a shelf 14 feet wide • for one line and on two shelves, each 14 feet may vary from 5 to 20 feet and must be specified based on individual site characteristics. wide, for a double jack row. Grade the shelf to On long curves, anchor jack rows at intermediate slope from 1 foot above the streambed at the side • points along the curve to isolate damages to the nearest the stream to 3 feet above the streambed jack row. Two 3/8-inch diameter wire cables tied at the side nearest the slope. This encourages a to timber or steel pilings provide adequate an- dry surface for construction and provides some chors. Place anchors up the streambank rather additional elevation for protection from greater than in the streambed. depths of flow. Alternatively, jacks can be con- Consider pilings if streambed anchors are re- • structed on the streambed or on the top of the quired. Space pilings 75 to 125 feet apart along bank and moved into place. • Space jacks closely together with a maximum of the jack row, with closer spacing on shorter curves. one jack dimension between them to provide an almost continuous line of revetment. • Attach an anchored 3/8-inch diameter wire cable • Anchor the jacks in place by a cable strung to one leg of each jack to prevent rotation and improve stability. through and tied to the center of the jacks with • cable clamps. The cable should be tied to a Place jack rows perpendicular to the bank at buried anchor or pilings, thereby securing all the regular intervals where jack rows are not close to existing banks. This prevents local scour. jacks as a unit. Wooden jacks are weighted by rocks, which should be wired onto the jack Extend bank protection far enough to prevent flanking action. Ensure the jack row is anchored poles. The first two pilings at the upstream end of the jack line should be driven no more than 12 to a hardpoint at the upstream end. feet apart to reduce the effect of increased water • Supplement the jack string or field with vegeta- force from trash buildup. tive plantings. Dormant posts offer a compatible component in the system. 31 – Concrete jack system several years after installation Figure 16 46 16 – (210-vi-EFH, December 1996)

192 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Rock riprap, properly designed Construction guidelines (vii) Rock riprap— Inert materials Cobbles and gravel obtained from the and placed, is an effective method of streambank — protection (figs.16 – 32 and 16 – 33). The cost of quarry- stream bed should not be used to armor streambanks ing, transporting, and placing the stone and the large unless the material is so abundant that its removal will quantity of stone that may be needed must be consid- not reduce habitat for benthic organisms and fish. ered. Gabion baskets, concrete cellular blocks, or Material forming an armor layer that protects the bed – – 35b; and similar systems (figs. 16 – 35a, 16 34, 16 from erosion should not be removed. Use of stream – 42, 16 – 43) can be an alternative to rock riprap cobble and gravel may require permission from state 16 and local agencies. under many circumstances. Removing streambed materials tends to destroy the Applications and effectiveness diversity of physical habitat necessary for optimum • Provides long-term stability. fish production, not only in the project area, but up- • Has structural flexibility. It can be designed to stream and downstream as well. Construction activi- self-adjust to eroding foundations. Has a long life and seldom needs replacement. ties often create channels of uniform depth and width • • Is inert so does not depend on specific environ- in which water velocities increase. Following disrup- tion of the existing streamflow by alteration of the mental or climatic conditions for success. • stream channel, further damage results as the stream May be designed for high velocity flow conditions. seeks to reestablish its original meander pattern. 32 Figure 16 – Rock riprap details Cross section Existing vegetation, plantings Not to scale or soil bioengineering systems Erosion control fabric Stream-forming flow Top of riprap minimum thickness = maximum rock size 1 1.5 (max.) Baseflow Gravel bedding, geotextile fabric, as needed Streambed Bottom of riprap minimum thickness = 2 x maximum rock size (210-vi-EFH, December 1996) 47 – 16

193 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Numerous methods have been developed for designing Upstream, the stream may seek to adjust to the new gradient by actively eroding or grading its banks and rock riprap. Nearly all use either an allowable velocity or tractive stress methodology as the basis for deter- bed. The eroded material may be deposited in the channel downstream from the alteration causing 2 lists several – mining a stable rock size. Table 16 additional changes in flow pattern. The downstream accepted procedures currently used in the NRCS. The table provides summary information and references channel will then also adjust to the new gradient and increased streamflow velocity by scour and bank where appropriate. Two of the more direct methods of obtaining a rock size are included in appendix 16A. All erosion or further deposition. four methods listed in the table provide the user with a design rock size for a given set of input parameters. Rock riprap on streambanks is affected by the hydro- dynamic drag and lift forces created by the velocity of The first time user is advised to use more than one method in determining rock size. Availability of rock flow past the rock. Resisting the hydrodynamic effects are the force components resulting from the sub- and experience of the designer continue to play impor- merged weight of the rock and its geometry. These tant roles in determining the appropriate size rock for forces must be considered in any analytical procedure any given job. for determining a stable rock size. Channel alignment, surface roughness, debris and ice impact, rock grada- tion, angularity, and placement are other factors that must be considered when designing for given site conditions. Figure 16 – 33 Rock riprap revetment system (210-vi-EFH, December 1996) 48 – 16

194 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook A well graded rock provides the greatest assurance of The transition zone can be designed as a filter, bed- ding, or geotextile. The bank soils, bank seepage, and stability and long-term protection. Poorly graded rock rock gradation and thickness are factors to consider results in weak areas where individual stones are when determining the transition material. subject to movement and subsequent revetment fail- ure. Satisfactory gradation limits and thickness of the rock riprap can be determined from the basic stone Bedding material is generally a pit run sand-gravel – 3 in appendix 16A can help determine mixture. Bedding is suitable for those sites where size. Figure 16A rock gradation limits for any calculated basic rock size bank materials are plastic and forces can be consid- , D ered external, that is, forces acting on the bedding (D , and so forth). 50 75 result only from the action of flow past or over the rock riprap. Bedding is not recommended for condi- The void space between rocks in riprap is generally tions where flow occurs through the rock (as on steep many times greater than the void space in existing slopes), where subject to wave action, or where flow bank materials. A transition zone serves two purposes: Distributes the weight of rock to the underlying • velocity exceeds 10 feet per second. soil. • Prevents movement and loss of fine grained soil into the large void spaces of the riprap. Table 16 – 2 Methods for rock riprap protection Method (reference) Basis for rock size Procedure Comments Isbash Curve Allowable velocity — Use design velocity and Use judgment to factor Appendix 16A (reprint Curve developed from curve to determine basic in site conditions. The rock size (D Isbash work. basic stone weight is ). from SCS Engineering 100 Field Manual, chapter often doubled to account for debris. 16, 1969). Tractive stress — Enter monograph with FWS-Lane Easy to use procedure. Appendix 16A (reprint Monograph developed channel hydraulic and Generally results in a from SCS Engineering from Lane's work. physical data to solve conservative rock size. Design Standards Far for basic rock size (D ). — 75 West States, 1970). COE Method Allowable velocity — Use equation or graphs Detailed procedure can Corps of Engineers, be used on natural or Basic equation developed and site physical and EM 1110-2-1601, 7/91, by COE from study of prismatic channels. hydraulic data to models and comparison determine basic rock Hydraulic Design of to field data. size (D ). Flood Control Channels. 30 Federal Highway Tractive Force Theory — Use equation with known Stability factor requires Administration Uses velocity as a primary site data and user user judgment of site Hydraulic Engineering design parameter. determined stability conditions. factor to solve for basic Circular No. 11, Design of Riprap Revetment (1989). ). rock size (D 50 49 16 – (210-vi-EFH, December 1996)

195 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook A nonwoven geotextile may be used in lieu of a • A filter is a graded granular material designed to prevent movement of the bank soil. A filter is recom- bedding or filter layer under the rock riprap. The geotextile material must maintain intimate con- mended where bank materials are nonplastic, seepage forces exist, or where bedding is not adequate protec- tact with the subsurface. Geotextile that can move with changes in seepage pressure or exter- tion for the external forces as noted above. The site should be evaluated for potential seepage pressures nal forces permits soil particle movement and from existing or seasonal water table, rapid fluctua- can result in plugging of the geotextile. A 3-inch tions in streamflow (rapid drawdown), surface runoff, layer of bedding material over the geotextile prevents this movement. or other factors. In critical applications or where experience indicates problems with the loss of bank Hand-placing all rock in a revetment should • material under riprap, use chapter 26, part 633 of the seldom, if ever, be necessary. While the revet- NRCS National Engineering Handbook, January 1994, ment may have a somewhat less finished look, it for guidance in designing granular filters. is adequate to dump the rock and rearrange it with a minimum of hand labor. However, the Nonwoven geotextiles are widely used as a substitute rock must be dumped in a manner that will not separate small and large stones or cause damage for bedding and filter material. Availability, cost, and to the filter fabrics. The finished surface should ease of placement are contributing factors. For guid- ance in selection of the proper geotextile, refer to not have pockets of finer materials that would flush out and weaken the revetment. Sufficient NRCS Design Note 24, Guide to Use of Geotextile. hand placing and chinking should be done to provide a well-keyed surface. Installation • Minimum thickness of the riprap should at least The Engineering Field Handbook, Chapter 17, Con- equal the maximum rock size at the top of the revetment. The thickness is often increased at struction and Construction Materials, has additional information on riprap construction and materials. the base of the revetment to two or more times the maximum rock size. The toe for rock riprap must be firmly estab- • Manufacturers have developed design recommenda- lished. This is important where the stream bot- tions for various flow and soil conditions. Their rec- tom is unstable or subject to scour during flood ommendations are good references in use of gabions, flows. cellular blocks, and similar systems. Banks on which riprap is to be placed should be • sloped so that the pressure of the stone is mainly against the bank rather than against the stone in Figure 16 Concrete cellular block details 34 – the lower courses and toe. This slope should not be steeper than 1.5:1. The riprap should extend up the bank to an elevation at which vegetation Revegetate will provide adequate protection. 6 in above design wave height or top of slope • A filter or bedding must be placed between the riprap and the bank except in those cases where Steepest slope of block placement 3:1 the material in the bank to be protected is deter- 12 in min. mined to be a suitable bedding or filter material. The filter or bedding material should be at least 6 Stream-forming flow inches thick. Baseflow Geotextile fabric Streambed Cross section 18 in min. Not to scale – 50 (210-vi-EFH, December 1996) 16

196 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Concrete cellular block system before backfilling 35a – Figure 16 Figure 16 – 35b Concrete cellular block system several years after installation (210-vi-EFH, December 1996) 51 – 16

197 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook • Prefabricated materials can be expensive. (viii) Coconut fiber rolls— Coconut fiber rolls are cylindrical structures composed of coconut husk Manufacturers estimate the product has an • effective life of 6 to 10 years. fibers bound together with twine woven from coconut 36, 16 – (figs. 16 – 37a, and 16 – 37b). This material is most commonly manufactured in 12-inch diameters and Construction guidelines lengths of 20 feet. It is staked in place at the toe of the • Excavate a shallow trench at the toe of the slope slope, generally at the stream-forming flow stage. to a depth slightly below channel grade. • Place the coconut fiber roll in the trench. • Applications and effectiveness Drive 2 inch x 2 inch x 36 inch stakes between Protect slopes from shallow slides or undermin- • the binding twine and coconut fiber. Stakes should be placed on both sides of the roll on 2 to ing while trapping sediment that encourages plant growth within the fiber roll. 4 feet centers depending upon anticipated veloci- ties. Tops of stakes should not extend above the Flexible, product can mold to existing curvature • top of the fiber roll. of streambank. • Produce a well-reinforced streambank without In areas that experience ice or wave action, • much site disturbance. notch outside of stakes on either side of fiber roll and secure with 16-gauge wire. Figure 16 – 36 Coconut fiber roll details Cross section Not to scale Existing vegetation, plantings or soil bioengineering systems Herbaceous Erosion control fabric plugs Stream-forming flow Baseflow Coconut fiber roll Streambed 2 in. by 2 in. by 36 in. oak stakes (210-vi-EFH, December 1996) – 52 16

198 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Coconut fiber roll 37a – Figure 16 Figure 16 – 37b Coconut fiber roll system (210-vi-EFH, December 1996) 53 – 16

199 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Backfill soil behind the fiber roll. • Construction guidelines Rock filled jetties are the most com- If conditions permit, rooted herbaceous plants — Inert materials • mon, however, other materials are used including may be installed in the coconut fiber. timber, concrete, gabions, and rock protected earth. • Install appropriate vegetation or soil bioengineer- ing systems upslope from fiber roll. Installation • Use a D size rock equal to 1.5 to 2 times the d Jetties are short dike-like struc- (ix) Stream jetties— 50 50 tures that project from a streambank into a stream size determined from rock riprap design methods for bank full flow condition. channel. They may consist of one or more structures placed at intervals along the bank to be protected. Most Size and space jetties so that flow passing • around and downstream from the outer end will are constructed to the top of the bank and can be ori- ented either upstream, downstream, or perpendicular to intersect the next jetty before intersecting the eroding bank. The length varies but should not the bank (figs. 16 – 38 and 16 39). – unduly constrict the channel. Rock jetties typi- Jetties deflect or maintain the direction of flow cally have 2:1 side slopes with an 8 to 12-foot top width and 2:1 end slope. through and beyond the reach of stream being pro- Space jetties to account for such characteristics as tected. In function and design, jetties change the • direction of flow by obstructing and redirecting the stream width, stream velocity, and radius of curva- streamflow. Their design and construction require ture. Typical spacing is 2 to 5 times the jetty length. specialized skills. A fluvial geomorphologist, engineer, Construct jetties with a level top or a downward • slope to the outer end (riverward). The top of the or other qualified discipline with knowledge of open jetty at the bank should be equal to the bank channel hydraulics should be consulted for specific considerations and guidelines. height. • Orient jetties either perpendicular to the stream- bank or angled upstream or downstream. Per- Applications and effectiveness Used successfully in a wide variety of applica- • pendicular and downstream orientation are the tions in all types of rivers and streams. most common. Effective in controlling erosion on bends in river • Tie jetties securely back into the bank and bed to • and stream systems. prevent washout along the bank and undercut- ting. Place rock a short distance on either side of • Can be augmented with vegetation or soil the jetty along the bank to prevent erosion at this bioengineering systems in some situations; i.e., deposited material upstream of jetties. critical location. The base of the jetty should be keyed into the bed a minimum depth equal to the May develop scour holes just downstream and • rock size. D off the end of the jetties. 100 Can be complex and expensive. • 16 54 (210-vi-EFH, December 1996) –

200 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Stream jetty details Figure 16 – 38 Cross section Not to scale Length of jetty (varies) Stream-forming flow Existing bank 2:1 Baseflow Streambed Rock riprap 1:1 Front elevation Not to scale 8-12 feet, top width 2:1 2:1 Key into streambed, 1:1 approx. D 100 1:1 – 55 (210-vi-EFH, December 1996) 16

201 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Stream jetty placed to protect railroad bridge 39a – Figure 16 Figure 16 – 39b Long-established vegetated stream jetty, with deposition in foreground (210-vi-EFH, December 1996) 56 – 16

202 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Installation Stream barbs are low rock sills (x) Stream barbs— size rock equal to two times the d size projecting out from a streambank and across the Use a D • 50 50 stream's thalweg to redirect streamflow away from an determined from rock riprap design methods for 40 and 16 – – eroding bank (figs.16 41). Flow passing bank full flow condition. The maximum rock size ) should be about 1.5 to 2 times the D size. over the barb is redirected so that the flow leaving the (D 50 100 The minimum rock size should not be less than barb is perpendicular to the barb centerline. Stream .75D barbs are always oriented upstream. . 50 Key the barb into the stream bed to a depth • below the bed. Application and effectiveness approximately D 100 Construct the barb above the streambed to a • Used in limited applications and range of applica- • rock, but height approximately equal to the D bility is unclear. 100 • generally not over 2 feet. The width should be at Effective in control of bank erosion on small , but not less than a streams. least equal to 3 times D 100 typical construction equipment width of 8 to 10 Require less rock and stream disturbance than • jetties. feet. Construction of barbs can begin at the • streambank and proceed streamward using the Improve fish habitat (especially when vegetated). • barb to support construction equipment. Can be combined with soil bioengineering practices. • Align the barb so that the flow off the barb is • Can be complex and expensive. directed toward the center of the stream or away from the bank. The acute angle between the barb Construction guidelines and the upstream bank typically ranges from 50 to 80 degrees. — Stream barbs require the use of large Inert materials rock. • Ensure that, at a minimum, the barb is long enough to cross the stream flow low thalweg. • Space the barbs apart from 4 to 5 times the ’ s length. The specific spacing is dependent barb on finding the point at which the streamflow leaving the barb intersects with the bank. – (210-vi-EFH, December 1996) 57 16

203 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Stream barb details Figure 16 – 40 Plan view Not to scale 8 ft min. (L) C ° ° 50 to 80 C of stream barb Vegetative bank between barbs Flow Cross section Not to scale Existing Length determined 8 ft. min. grade by design (L) Stream-forming flow Slope Baseflow Geotextile fabric Streambed Key into streambed approx. D 100 (210-vi-EFH, December 1996) 58 – 16

204 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook 41 – Stream barb system Figure 16 (210-vi-EFH, December 1996) – 16 59

205 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Construction guidelines (xi) Rock gabions— Rock gabions begin as rectangu- lar containers fabricated from a triple twisted, hexago- When constructing vegetated Live material sizes — rock gabions, branches should range from 0.5 to 2.5 nal mesh of heavily galvanized steel wire. Empty inches in diameter and must be long enough to reach gabions are placed in position, wired to adjoining gabions, filled with stones, and then folded shut and beyond the back of the rock basket structure into the wired at the ends and sides. NRCS Construction Speci- backfill or undisturbed bank. fication 64, Wire Gabions, provides detailed informa- Galvanized woven wire mesh or tion on their installation. Inert materials — galvanized welded wire mesh baskets or mattresses Vegetation can be incorporated into rock gabions, if may be used. The baskets or mattresses are filled with sound durable rock that has a minimum size of 4 desired, by placing live branches on each consecutive – 42 and Gabions can be layer between the rock-filled baskets (fig. 16 inches and a maximum of 9 inches. 43). These gabions take root inside the gabion – 16 coated with polyvinyl chloride to improve their service baskets and in the soil behind the structures. In time life where subject to aggressive water or soil conditions. the roots consolidate the structure and bind it to the Installation slope. Remove loose material from the foundation area • and cut or fill with compacted material to pro- Applications and effectiveness • Useful when rock riprap design requires a rock vide a uniform foundation. • size greater than what is locally available. Excavate the back of the stable foundation (closest to the slope) slightly deeper than the Effective where the bank slope is steep (typically • greater than 1.5:1) and requires structural support. front to add stability to the structure. This pro- vides additional stability to the structure and Appropriate at the base of a slope where a low • ensures that the living branches root well for wall may be required to stabilize the toe of the vegetated rock gabions. slope and reduce its steepness. Place bedding or filter material in a uniformly • Can be fabricated on top of the bank and then • graded surface. Compaction of materials is not placed as a unit, below water if necessary. • Lower initial cost than a concrete structure. usually required. Install geotextiles so that they lie smoothly on the prepared foundation. Tolerate limited foundation movement. • • • Have a short service life where installed in Assemble, place, and fill the gabions with rock. Be certain that all stiffeners and fasteners are streams that have a high bed load. Avoid use where streambed material might abrade and properly secured. cause rapid failure of gabion wire mesh. • Place the gabions so that the vertical joints are • Not designed for or intended to resist large, staggered between the gabions of adjacent rows lateral earth stresses. Should be constructed to a and layers by at least one-half of a cell length. Place backfill between and behind the wire maximum of 5 feet in overall height, including • baskets. the excavation required for a stable foundation. • For vegetated rock gabions, place live branch • Useful where space is limited and a more vertical structure is required. cuttings on the wire baskets perpendicular to the • slope with the growing tips oriented away from Where gabions are designed as a structural unit, the effects of uplift, overturning, and sliding must the slope and extending slightly beyond the be analyzed in a manner similar to that for grav- gabions. The live cuttings must extend beyond ity type structures. the backs of the wire baskets into the fill mate- rial. Place soil over the cuttings and compact it. Can be placed as a continuous mattress for slope • protection. Slopes steeper than 2:1 should be Repeat the construction sequence until the • structure reaches the required height. analyzed for slope stability. • Gabions used as mattresses should be a mini- mum of 9 inches thick for stream velocities of up to 9 feet per second. Increase the thickness to a minimum of 1.5 feet for velocities of 10 to 14 feet per second. (210-vi-EFH, December 1996) 60 – 16

206 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook • Where abrasive bedloads or debris can snag or many applications, however, when drainage is tear the gabion wire, a concrete cap should be critical, the fabric must maintain intimate con- used to protect those surfaces subject to attack. tact with the foundation soils. A 3-inch layer of sand-gravel between the gabions and the filter A concrete cap 6 inches thick with 3 inches material assures that contact is maintained. penetration into the basket is usually sufficient. • At the toe and up and downstream ends of ga- The concrete for the cap should be placed after bion revetments, a tieback into the bank and bed initial settlement has occurred. should be provided to protect the revetment • A filter is nearly always needed between the gabions and the foundation or backfill to prevent from undermining or scour. soil movement through the baskets. Geosyn- thetics can be used in lieu of granular filters for Figure 16 Vegetated rock gabion details 42 – Existing vegetation, plantings or soil bioengineering systems Cross section Not to scale Compacted fill material Live branch cuttings (1/2- to 1-inch diameter) Erosion control fabric Stream-forming flow Geotextile fabric Baseflow Gabion baskets Streambed 2 to 3 feet Note: Rooted/leafed condition of the living plant material is not representative of the time of installation. – 16 61 (210-vi-EFH, December 1996)

207 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Vegetated rock gabion system 43 (H.M. Schiechtl photo) – Figure 16 (210-vi-EFH, December 1996) – 16 62

208 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook (b) Design considerations for shoreline protection 650.1602 Shoreline protection (1) Beach slope Slopes should be determined above and below the waterline. The slope below waterline should be repre- (a) General sentative of the slope for a distance of at least 50 feet. Shoreline erosion results primarily from erosive forces (2) Offshore depth and wave height in the form of waves generally perpendicular to the Offshore depth is a critical factor in designing shore- shoreline. As a wave moves toward shore, it begins to line protection measures. Structures that must be drag on the bottom, dissipating energy. This eventually constructed in deep water, or in water that may be- causes it to break or collapse. This major turbulence come deep, are beyond the scope of this chapter. stirs up material from the shore bottom or erodes it Other important considerations are the dynamic wave from banks and bluffs. Fluctuating tides, freezing and height acting in deep water (roughly, the total height thawing, floating ice, and surface runoff from adjacent of the wave is three times that visible) and the de- uplands may also cause shorelines to erode. creased wave action caused by shallow water. Effec- tive fetch length also needs to be considered in deter- (1) Types of shoreline protection mining wave height. Methods for computing wave Systems for shoreline protection can be living or height using fetch length are in NRCS Technical Re- nonliving. They consist of vegetation, soil bioengineer- leases 56 and 69. ing, structures, or a combination of these. (3) Water surface (2) Planning for shoreline protection The design water surface is the mean high tide or, in measures nontidal areas, the mean high water. This information The following items need to be considered for shoreline may be obtained from tidal tables, records of lake protection in addition to the items listed earlier in this levels, or from topographic maps of the reservoir site chapter for planning streambank protection measures: in conjunction with observed high and normal water • Mean high and low water levels or tides. lines along the shore. Potential wave parameters. • • Slope configuration above and below waterline. (4) Littoral transport • Nature of the soil material above and below The material being moved parallel to the shoreline in water level. the littoral zone, under the influence of waves and • Evidence of littoral drift and transport. currents should be addressed in groin design. It is • Causes of erosion. important to determine that the supply of transport • Adjacent land use. material is not coming from the bank being protected • Maintenance requirements. and the predominant direction of littoral transport. This information is used to locate structures properly with respect to adjacent properties and so that groins can fill most quickly and effectively. Another factor to be considered is that littoral transport often reverses directions with a change in season. The rate of littoral transport and the supply are as important as the direction of movement. No simple ways to measure the supply are available. For the scope of this chapter, supply may be determined by observation of existing structures, sand beaches, auger samples of the sand above the parent material on the beach, and the presence of sandbars offshore. Other 63 16 – (210-vi-EFH, December 1996)

209 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook considerations are existing barriers, shoreline configu- (c) Protective measures for ration, and inlets that tend to push the supply offshore shorelines and away from the area in question. The net direction The analysis and design of shoreline protection mea- of transport is an important and complex consideration. sures are often complex and require special expertise. For this reason the following discussion is limited to (5) Bank soil type revetments, bulkheads, and groins no higher than 3 Determining the nature of bank soil material aids in feet above mean high water, as well as soil bioengi- estimating the rate of erosion. A very dense, heavy neering and other vegetative systems used alone or in clay can offer more resistance to wave action than combination with structural measures. Consideration noncohesive materials, such as sand. A thin sand lens must be given to the possible effects that erosion can result in erosion problems since it may be washed out when subjected to high tides or wave action for control measures can have on adjacent areas, espe- extended periods of time. The resulting void will no cially estuarine wetlands. longer support the bank above it, causing it to break away. (1) Groins Groins are somewhat permeable to impermeable finger-like structures that are installed perpendicular (6) Foundation material to the shore. They generally are constructed in groups The type of existing foundation may govern the type of called groin fields, and their primary purpose is to trap protection selected. For example, a rock bottom will littoral drift. The entrapped sand between the groins not permit the use of sheet piling. If the use of riprap is acts as a buffer between the incoming waves and being considered on a highly erodible foundation, a shoreline by causing the waves to break on the newly filter will be needed to prevent fine material from washing through the voids. A soft foundation, such as deposited sand and expend most of their energy there 44 and 16 dredge spoil, may result in excessive flotation or 45). – – (figs. 16 movement of the structure in any direction. Applications and effectiveness • Particularly dependent on site conditions. Groins (7) Adjacent shoreline and structures Structures that might have an effect on adjacent shore- are most effective in trapping sand when littoral line or other structures must be examined carefully. drift is transported in a single direction. End sections need to be adequately anchored to exist- • Filling the groin field with borrowed sand may be ing measures or terminated in stable areas. necessary, if the littoral transport is clay or silt rather than sand. • Will not fill until all preceding updrift groins have (8) Existing vegetation The installation of erosion control structures can have been filled. a detrimental effect upon existing vegetation unless Construction guidelines steps are taken to prevent what is often avoidable site — The most common type of structural disturbance. Existing vegetation should be saved as an Inert materials groin is built of preservative-treated tongue and integral part of the erosion control system being groove sheet piling. installed. (210-vi-EFH, December 1996) 16 – 64

210 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook 44 – Timber groin details Figure 16 Top of bank 6-inch diameter poles - spacing varies Mean high water 24 in. or elevation key to bulkhead Sheet piling Ground surface 3 1/2 ft min. Cross section STD placement of galvanized 2 by 8 stringers 24 in. 20d nails min. Bank Mean high 2 in. by 8 in. or 2 in. by 10 in. treated T&G sheet piling water elevation 6 in. polepiles Varies Plan 65 (210-vi-EFH, December 1996) – 16

211 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook • Key the shoreward end of the groins into the Installation Groins must extend far enough into the water to shoreline bank for at least 2 feet or extend them • retain desired amounts of sand. The distance to a bulkhead. between groins generally ranges from one to • Measure the groin height on the shoreline so that it will generally be at high tide or mean high three times the length of the groin. When used in water elevation plus 2 or 3 feet for wave surge conjunction with bulkheads, the groins are height. Decrease the height seaward at a gradual usually shorter. • rate to mean high water elevation. Groins are particularly vulnerable to storm damage before they fill, so initially only the first three or four at the downdrift end of the system should be constructed. Install the second group of groins after the first • has filled and the material passing around or over the groins has again stabilized the downdrift shoreline. This provides the means to verify or adjust the design spacing. 45 Timber groin system – Figure 16 16 – (210-vi-EFH, December 1996) 66

212 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Installation (3) Bulkheads Bulkheads are vertical structures of timber, concrete, Use environmentally compatible treated timber. • Thickness and spacing of pilings, supports, cross • steel, or aluminum sheet piling installed parallel to the shoreline. member, and face boards must be engineered on a site-by-site basis. Applications and effectiveness • Pilings can be drilled, driven, or jetted depending • on the foundation materials. Depth of piling must Generally constructed where wave action will not cause excessive overtopping of the structure, be at least equal to the exposed height below the which causes bank erosion to continue as though point of maximum anticipated scour. the bulkhead were not there. • Place stones or other appropriate materials at Scour at the base of the bulkhead also causes the base of the bulkhead to absorb wave energy. • In salt water environments, use noncorrosive • failure. The vertical face of the bulkhead re- materials to the greatest extent possible. directs wave action to cause excessive scour at the toe of the structure unless it is protected. Construction guidelines — Inert materials The most common materials used for 46 and bulkhead construction are timber (figs. 16 – 49), and masonry. 48 and 16 – 47), concrete (figs. 16 – 16 – Timber bulkhead system 46 – Figure 16 16 – 67 (210-vi-EFH, December 1996)

213 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook – 47 Timber bulkhead details Figure 16 Existing vegetation, plantings Cross section Not to scale or soil bioengineering systems Backfill and slope to meet site conditions Erosion control fabric 2 in x 6 in cap Existing bank 7/16 galvanized bolt 2 in x 8 in x 16 in wale 6 in x 6 ft anchor pile 5 ft min. 3/8 in cable Geotextile fabric 3 ft Mean high 2 in x 8 in x 16 in wale water elevation 5 ft Note: Locate bottom wale near ground line, not more than 3 inches on center from 7 ft top wale. 2 in x 8 in or 2 in x 10 in T&G sheet piling 6 in x 10 in fender pile Existing vegetation, plantings or soil bioengineering systems Cross section Berm - min. 2 x wave height Not to scale Backfill and slope to meet site conditions Erosion control fabric 3:1 or flatter Mean high water elevation Gravel drain Max. 4 feet Geotextile fabric Coarse gravel or riprap Weep holes 11/2 dia. (as needed) 10' O.C. Wave height or 18" (whichever is least) 2 x H or 2 x wave height (whichever is greater) 68 – (210-vi-EFH, December 1996) 16

214 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook – 48 Concrete bulkhead details Figure 16 Cross section Existing vegetation, plantings Poured in place concrete wall Berm - min. 2 x wave height or soil bioengineering systems Not to scale 8 in. min. Backfill and slope to meet site conditions Erosion control fabric 3:1 or flatter Gravel drain No. 4 bars at 12 in. o.c. Max. 4 ft. No. 4 bars at 16 in. o.c. Mean high water elevation Geotextile fabric Coarse gravel or riprap as needed Weep holes 1.5 in. dia. at 10 ft. o.c. Wave height or 18 in. (whichever No. 4 bars at 16 in. o.c. is least) 1 ft.-2 in. No. 4 bars at 12 in. o.c. 8 in. 8 in. 1 ft.-3 in 1 ft.-2 in 2 ft.-1 in. 4 ft.-6 in. Existing vegetation, plantings Cross section or soil bioengineering systems Concrete block wall Berm - min. 2 x wave height Not to scale 8 in. min. Erosion control fabric 3:1 or flatter Gravel drain Geotextile fabric No. 4 bars at 16 in. o.c. Backfill and slope to meet site conditions Horizontal joint reinforcement Mean high Max. 4 ft. 2 - no. 4 bars in bond beams at water elevation 16 in. o.c. or joint reinforcement at 8 in o.c. Coarse gravel or riprap as needed Weep holes 1.5 in. dia. at 10 ft. o.c. Wave height or 18 in. whichever No. 4 bars at 16 in. o.c. is least 10 in. No. 4 bars at 12 in. o.c. 6 in. 6 in. 14 in. 3 ft.-8 in. 16 – (210-vi-EFH, December 1996) 69

215 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook 49 – Concrete bulkhead system Figure 16 (210-vi-EFH, December 1996) – 16 70

216 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Construction guidelines (4) Revetments Revetments are protective structures of rock, con- • The size and thickness of rock revetments must crete, cellular blocks, or other material installed to fit be determined to resist wave action. NRCS – Technical Release 69, Rock Riprap for Slope 50 and the slope and shape of the shoreline (figs. 16 Protection Against Wave Action, provides guid- 16 51). – ance for size, thickness, and gradation. The base of the revetment must be founded below • Applications and effectiveness the scour depth or placed on nonerosive material. Flexible and not impaired by slight movement • caused by settlement or other adjustments. • Angular stone is preferred for revetments. If • Preferred to bulkheads where the possibility of rounded stone is used, increase the layer thick- ness by a factor of 1.5. extreme wave action exists. Use a minimum thickness of 6-inch filter material Local damage or loss of rock easily repaired. • • No special equipment required for construction. under rock. • • Subject to scour at the toe and flanking, thus • If geotextile is used in place of granular filter, filters are important and should always be cover the geotextile with a minimum of 3inches considered. of sand-gravel before placement of rock. Complex and expensive. • – Figure 16 Concrete revetment (poured in place) 50 – 71 (210-vi-EFH, December 1996) 16

217 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook 51 – Rock riprap revetment Figure 16 (210-vi-EFH, December 1996) – 16 72

218 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook (ii) Live fascine— The live fascines previously de- (5) Vegetative measures scribed in this chapter work best in shoreline applica- If some vegetation exists on the shoreline, the shore- line problem may be solved with more vegetation. tions where the ground between them is also pro- Determine if the vegetation disappeared because of a tected. Natural geotextiles, such as those manufac- single, infrequent storm, or if plants are being shaded tured from coconut husks, are strong, durable, and work well to protect the ground. out by developing overstory trees and shrubs. In either case revegetation is a viable alternative. Consult local Construction guidelines technical guides and plant material specialists for Live materials appropriate plant species and planting specifications. Live cuttings as previously described — Vegetative Control of for fabrication of live fascine bundles. Fabricate live NRCS Technical Release 56, fascine bundles approximately 8 inches in diameter. Wave Action on Earth Dams, provides additional Live stakes should be about 3 feet long. guidance. Dead stout stakes approximately 3 Inert materials — (6) Patching A shoreline problem is often isolated and requires only feet long to anchor well in loose sand. Jute mesh with a simple patch repair. Site characteristics that would long straw for low energy shorelines. Natural geo- indicate a patch solution may be appropriate include textile with long straw for higher energy shorelines. good overall protection from wave action, slight un- dercutting in spots with an occasional slide on the Installation bank, and fairly good vegetative growth on the shore- The installation methods are similar to those dis- line. The problems are often caused by boat wake or cussed for live fascines, with the following variations: excessive upland runoff. Fill undercut areas with stone Excavate a trench approximately 10 inches wide • sandbags or grout-filled bags and repair with a grass and deep, beginning at one end of and parallel to the shoreline section to be repaired and extend- transplant, reed clumps, branchpacking, vegetated ing to the other end. geogrid, or vegetated riprap. • Spread jute mesh or geotextile fabric across the Slides that occur because of a saturated soil condition excavated trench and temporarily leave the are best alleviated by providing subsurface drainage or remainder on the slope immediately above the trench. a diversion. Leaning or slipping trees in the immediate slide area may need to be removed initially because of Place a live fascine bundle in the trench on top of • the fabric and anchor with live and dead stout their weight and the forces they exert on the soil; stakes. however, once the saturated condition is remedied, Spread long straw on the slope above the trench disturbed areas should be revegetated with native • to the approximate location of the next trench to trees, shrubs, grasses, and forbs to establish cover. be constructed upslope. • Pull the fabric upslope over the long straw and (7) Soil bioengineering systems Soil bioengineering systems that are best suited to spread in the next excavated trench. Trenches reducing erosion along shorelines are live stakes, live should be spaced 3 to 5 feet apart and parallel to fascines, brushmattresses, live siltation, and reed each other. • Repeat the process until the system is in place clump constructions. over the treatment area. Live stakes offer no stability until (i) Live stake— they root into the shoreline area, but over time they provide excellent soil reinforcement. To reduce failure until root establishment occurs, installations may be enhanced with a layer of long straw mulch covered with jute mesh or, in more critical areas, a natural geotextile fabric. Refer to streambank protection section of this chapter for appropriate applications and construction guidelines. (210-vi-EFH, December 1996) 73 – 16

219 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Live siltation (iv) Live siltation construction— Brushmattresses for shore- (iii) Brushmattress— construction is similar to brushlayering except that the lines perform a similar function as those for stream- orientation of the branches are more vertical. Ideally banks. Therefore, effectiveness and construction guidelines are similar to those given earlier in this live siltation systems are approximately perpendicular chapter, with the following additions. to the prevailing winds. The branch tips should slope upwards at 45 to 60 degrees. Installation is similar to Applications and effectiveness brushlayering (see Engineering Field Handbook, chapter 18 for a more complete discussion of a • May be effective in lake areas that have fluctuat- ing water levels since they are able to protect the brushlayer). shoreline and continue to grow. Able to filter incoming water because they also Live siltation branches that have been installed in the • trenches serve as tensile inclusions or reinforcing establish a dense, healthy shoreline vegetation. units. The part of the brush that protrudes from the Installation ground assists in retarding runoff and surface erosion from wave action and wind (figs. 16 52 and 16 – – After the trench at the bottom has been dug and • 53). the mattress branches placed, the trench should be lined with geotextile fabric. Applications and effectiveness Live siltation systems provide immediate erosion • Secure the live fascine, press down the mattress control and earth reinforcement functions, including: brush, and place the fabric on top of the brush. At this point, install the live and dead stout • • Providing surface stability for the planting or stakes to hold the brush in place. A few dead establishment of vegetation. stout stakes may be used in the mattress branch Trapping debris, seed, and vegetation at the • and partly wired down before covering the shoreline. • Reducing wind erosion and surface particle fabric. This helps in the final steps of covering movement. and securing the brush and the fabric. • Drying excessively wet sites through transpira- tion. • Promoting seed germination for natural colonization. Reinforcing the soil with unrooted branch • cuttings. Reinforcing the soil as deep, strong roots • develop and adding resistance to sliding and shear displacement. Construction guidelines — Live branch cuttings 0.5 to 1 inch in Live material diameter and 4 to 5 feet long with side branches intact. Installation • Beginning at the toe of the shoreline bank to be treated, excavate a trench 2 to 3 feet deep and 1 to 2 feet wide, with one vertical side and the other angled toward the shoreline. • Parallel live siltation rows should vary from 5 to 10 feet apart, depending upon shoreline condi- tions and stability required. Steep, unstable and high energy sites require closer spacing. – (210-vi-EFH, December 1996) 74 16

220 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Live siltation construction details 52 Figure 16 – Plan Not to scale Littoral Shoreline transport AA Toe of shoreline bank Live siltation constructions 5 to 10 ft Section A-A Littoral transport Live brush Excavated trench 2 to 3 ft Fill material Live 1 to 2 ft siltation branches Note: Rooted/leafed condition of the living plant material is not respresentative of the time of installation. (210-vi-EFH, December 1996) 75 – 16

221 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Live siltation construction system 53 (Robbin B. Sotir & Associates photo) – Figure 16 (210-vi-EFH, December 1996) – 16 76

222 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Reed clump installations consist of (v) Reed clump— Installation root divisions wrapped in natural geotextile fabric, Reed root clumps are either placed directly into • placed in trenches, and staked down. The resulting fabric-lined trenches or prefabricated into rolls 5 root mat reinforces soil particles and extracts excess to 30 feet long. With the growing tips pointing up, moisture through transpiration. Reed clump systems space clumps every 12 inches on a 2- to 3-foot- are typically installed at the water's edge or on shelves wide strip of geotextile fabric to fabricate the – – 55). in the littoral zone (fig. 16 rolls. The growing buds should all be oriented in 54 and 16 the same upright direction for correct placement Applications and effectiveness into the trench. Reduces toe erosion and creates a dense energy- • • Wrap the fabric from both sides to overlap the dissipating reed bank area. top, leaving the reed clumps exposed and bound • with twine between each plant. Offers relatively inexpensive and immediate protection from erosion. • Beginning at and parallel to the water's edge, • Useful on shore sites where rapid repair of spot excavate a trench 2 inches wider and deeper damage is required. than the size of the prefabricated reed roll or reed clumps. • Retains soil and transported sediment at the • shoreline. To place reed clumps directly into trenches, first line the trench with a 2- to 3-foot-wide strip of • Reduces a long beach wash into a series of shorter sections capable of retaining surface geotextile fabric before spreading a 1-inch layer soils. of highly organic topsoil over it at the bottom of Enhances conditions for natural colonization and the trench. Next, center the reed clumps on 12- • establishment of vegetation from the surround- inch spacing in the bottom of the trench. Fill the ing plant community. remainder of the trench between and around Grows in water and survives fluctuating water reed clumps with highly organic topsoil, and • compact. Wrap geotextile fabric from each side levels. to overlap at the top and leave the reed clumps exposed before securing with dead stout stakes Construction guidelines spaced between the clumps. Complete the instal- — The reed clumps should be 4 to 8 Live materials inches in diameter and taken from healthy water- lation by spreading previously excavated soil around the exposed reed clumps to cover this dependent species, such as arrowhead, cattail, or water iris. They may be selectively harvested from staked fabric. existing natural sites or purchased from a nursery. • To use the prefabricated reed clump roll, place it in the excavated trench, secure it with dead stout stakes, and backfill as described above. Wrap reed clumps in natural geotextile fabric and bind Repeat the above procedure by excavating addi- • together with twine. These clumps can be fabricated several days before installation if they are kept moist tional parallel trenches spaced 3 to 6 feet apart and shaded. toward the shoreline. Place the reed clumps from one row to the next to produce a staggered Natural geotextile fabric, twine, and — Inert materials spacing pattern. 3- to 3.5-foot-long dead stout stakes are required. 16 – (210-vi-EFH, December 1996) 77

223 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Reed clump details 54 Figure 16 – Cross section Not to scale Natural geotextile fabric wrap Backfill Mean high water elevation Backfill Lakebed Coconut fiber roll Organic soil (optional to reduce Dead stout wave energy) stakes Plan Not to scale 3-6 feet Aquatic plant Dead stout stake 12-18 inches Optional coconut fiber roll 12-18 inches Mean water level Trench (filled with organic soil) 78 – 16 (210-vi-EFH, December 1996)

224 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Completing installation of reed clump 55b Figure 16 – 55a Installing dead stout stakes in reed clump Figure 16 – (Robbin B. Sotir & Associates photo) (Robbin B. Sotir & Associates photo) system system Figure 16 – 55c Established reed clump system (Robbin B. Sotir & Associates photo) (210-vi-EFH, December 1996) 79 – 16

225 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Applications and effectiveness (8) Coconut fiber roll Coconut fiber rolls are cylindrical structures com- • Effective in lake areas where the water level posed of coconut fibers bound together with twine fluctuates because it is able to protect the shore- 56 and 16 line and encourage new vegetation. – 57). This woven from coconut (figs. 16 – material is most commonly manufactured in 12-inch Flexible, can be molded to the curvature of the • shoreline. diameters and lengths of 20 feet. The fiber rolls func- Prefabricated materials can be expensive. tion as breakwaters along the shores of lakes and • Manufacturers estimate the product has an • embayments. In addition to reducing wave energy, this effective life of 6 to 10 years. product can help contain substrate and encourage development of wetland communities. Figure 16 – 56 Coconut fiber roll details Cross section Vegetative Not to scale plantings Coconut fiber roll Mean high water elevation Eroded Lakebed shoreline 2 in. x 2 in. x 36 in. oak stakes 80 16 (210-vi-EFH, December 1996) –

226 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Installation Fiber roll should be located off shore at a dis- • tance where the top of the fiber roll is exposed at low tide. In nontidal areas, the fiber roll should be placed where it will not be overtopped by wave action. • Drive 2 inch x 2 inch stakes between the binding twine and the coconut fiber. Stakes should be placed on 4-foot centers and should not extend above the fiber roll. • If desired, rooted cuttings can be installed be- tween the coconut fiber roll and the shoreline. 57 – Coconut fiber roll system Figure 16 81 16 – (210-vi-EFH, December 1996)

227 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Naiman, Robert J. 1992. Watershed management. Springer-Verlag, NY. 650.1603 References Rosgen, David L. 1985. A stream classification sys- — tem riparian ecosystems and their Andrews, E.D. 1983. Entrainment of gravel from natu- management. First North American Riparian rally sorted riverbed material. Geological Society Conference, Tucson, AZ. of America 94:1225-1231. Rosgen, David L. 1992. Restoration. Pages E-1 through Bell, Milo C. Fisheries handbook of engineering re- E-28 in Applied Fluvial Geomorphology, and quirements and biological criteria. pages E-29 through E-36 in Wildland Hydrology Consultants (Rosgen) Short Course, September Berger, John. 1991. Restoration of aquatic ecosystems: 28-October 2, 1992, Pagosa Springs, CO. science, technology, and public policy. Report for national research council committee on Rosgen, Dave, and Brenda Fittante. 1992. Fish habitat restoration of aquatic ecosystems in applied structures: a selection using stream classifica- fluvial geomorphology. Wildland Hydrology tion. Pages C-31 through C-50 in Applied Fluvial Consultants (Rosgen) Short Course, September Geomorphology, and pages E-29 through E-36, 28-October 2, 1992, Pagosa Springs, CO, pp. E-29 Wildland Hydrology Consultants (Rosgen) Short through E-36. Course, September 28-October 2, 1992, Pagosa Springs, Colorado. Coppin, N.J., and I.G. Richards. 1990. Use of vegetation in civil engineering. Butterworths, London, Schumm, Stanley A. 1963. A tentative classification of England. alluvial rivers. U.S. Geologic Survey Circular 477, Washington, DC. Davis, William M. 1889. The geographical cycle. Geo- graphical Journal 14: 481-504. Schumm, Stanley A. 1977. The fluvial system. John Wiley and Sons, NY, 338 pp. Flosi, Gary, and Forrest Reynolds. 1991. California salmonid stream habitat and restoration manual. Schumm, Stanley A., Mike D. Harvey, and Chester A. California Department of Fish and Game. Watson. 1984. Incised channels: morphology, dynamics and control. Water Resources Publica- Gray, Donald H., and Andrew T. Leiser. 1982. tions, Littleton, CO, 200 pp. Biotechnical slope protection and erosion con- trol. Van Nostrand Reinhold, New York, NY. The Pacific Rivers Council. 1993. Entering the water- shed. Washington, DC. Leopold, Aldo. 1949. A sand county almanac and sketches here and there. U.S. Army Coastal Engineering Research Center. 1975. Shore protection manual, volumes I and II. Leopold, Luna B., and David L. Rosgen. 1991. Move- ment of bed material clasts in gravel streams. U.S. Army Corps of Engineers. Help yourself — A Proceedings of the Fifth Federal Interagency discussion of erosion problems on the Great Sedimentation Conference, Las Vegas, NV. Lakes and alternative methods of shore protec- tion. A General Information Pamphlet. Leopold, Luna B., and M. G. Wolman. 1957. River channel patterns; braided, meandering, and U.S. Army Corps of Engineers. 1981. Main report, final straight. U.S. Geologic Survey Professional Paper report to Congress on the Streambank Erosion 282-B. Washington, DC. Control Evaluation and Demonstration Act of 1974, Section 32, Public Law 93-251. Malanson, George P. 1993. Riparian landscapes. Cam- bridge University, Great Britain. (210-vi-EFH, December 1996) 82 – 16

228 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook U.S. Army Corps of Engineers. 1983. Streambank U.S. Department of Agriculture, Soil Conservation protection guidelines. Service. Agricultural Information Bulletin 460. U.S. Department of Agriculture, Forest Service, South- U.S. Department of Agriculture, Soil Conservation Service. Vegetation for tidal shoreline stabiliza- ern Region. 1992. Stream habitat improvement handbook. tion in the Mid-Atlantic States, U.S. Government Printing Office S/N001-007-00906-5. U.S. Department of Agriculture, Soil Conservation Service. 1977. Design of open channels. Techni- U.S. Department of Transportation. 1975. Highways in the river environment-hydraulic and environmen- cal Release 25. tal design considerations. Training and Design U.S. Department of Agriculture, Soil Conservation Manual. Service. 1974. A guide for design and layout of vegetative wave protection for earth dam em- U.S. Department of Transportation. Use of riprap for bankments. Technical Release 56. bank protection. (need date) U.S. Department of Agriculture, Soil Conservation Waldo, Peter G. 1991. The geomorphic approach to channel investigation. Proceedings of the Fifth Service. 1983. Riprap for slope protection against wave action. Technical Release 69. Federal Interagency Sedimentation Conference. Las Vegas, NV, pp. 3-71 through 3-78. U.S. Department of Agriculture, Soil Conservation Service. 1994. Gradation design of sand and gravel filters. Natl. Eng. Hdbk, part 633, ch. 26. (210-vi-EFH, December 1996) 83 – 16

229 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook 16 – 84 (210-vi-EFH, December 1996)

230 Glossary Bankfull discharge — The discharge that fills the channel without overflowing Natural streams onto the flood plain. — The streamflow volume and depth that is Modified or entrenched streams the 1- to 3-year frequency flow event. The discharge that determines the stream's geomorphic planform dimen- sions. Bar A streambed deposit of sand or gravel, often exposed during low-water periods. Baseflow The ground water contribution of streamflow. Bole Trunk of a tree. Branchpacking Live, woody, branch cuttings and compacted soil used to repair slumped areas of streambanks. A combination of live stakes, fascines, and branch cuttings installed to Brushmattress cover and protect streambanks and shorelines. Bulkhead Generally vertical structures of timber, concrete, steel, or aluminum sheet piling used to protect shorelines from wave action. Channel A natural or manmade waterway that continuously or intermittently carries water. Cohesive soil A soil that, when unconfined, has considerable strength when air dried and significant strength when wet. Current The flow of water through a stream channel. Dead blow hammer A hammer filled with lead shot or sand. A log or concrete block buried in a streambank to anchor revetments. Deadman Deposition The accumulation of soil particles on the channel bed, banks, and flood plain. Discharge The volume of water passing through a channel during a given time, usually measured in cubic feet per second. The time of year when plants are not growing and deciduous plants shed Dormant season their leaves. Duration of flow Length of time a stream floods. Erosion control fabric Woven or spun material made from natural or synthetic fibers and placed to prevent surface erosion. – (210-vi-EFH, December 1996) 85 16

231 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Erosion The wearing away of the land by the natural forces of wind, water, or gravity. Erosive (erodible) A soil whose particles are easily detached and entrained in a fluid, either air or water, passing over or through the soil. The most erodible soils tend to be silts and/or fine sands with little or no cohesion. Failure Collapse or slippage of a large mass of streambank material. Filter A layer of fabric, sand, gravel, or graded rock placed between the bank revetment or channel lining and soil to prevent the movement of fine grained sizes or to prevent revetment work from sinking into the soil. Fines Silt and clay particles. Streamflow between a structure and the bank that creates an area of scour. Flanking Volume of flow per unit of time; usually expressed as cubic feet per Flow rate second. A log placed below the expected scour depth of a stream. Foundation for a Footer log rootwad and boulders. Gabion A wire mesh basket filled with rock that can be used in multiples as a structural unit. Geotextile Any permeable textile used with foundation soil, rock, or earth as an inte- gral part of a product, structure, or system usually to provide separation, reinforcement, filtration, or drainage. A structure built perpendicular to the shoreline to trap littoral drift and Groin retard erosion. Water contained in the voids of the saturated zone of geologic strata. Ground water Headcutting The development and upstream movement of a vertical or near vertical change in bed slope, generally evident as falls or rapids. Headcuts are often an indication of major disturbances in a stream system or watershed. Joint planting The insertion of live branch cuttings in openings or interstices of rocks, blocks, or other inert revetment units and into the underlying soil. Littoral drift The movement of littoral drift either transport parallel (long shore trans- port) or perpendicular (on-shore transport) to the shoreline. The sedimentary material of shorelines moved by waves and currents. Littoral Littoral zone An indefinite zone extending seaward from the shoreline to just beyond the breaker zone. 86 16 – (210-vi-EFH, December 1996)

232 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Live branch cuttings Living, freshly cut branches from woody shrub and tree species that readily propagate when embedded in soil. Live cribwall A rectangular framework of logs or timbers filled with soil and containing live woody cuttings that are capable of rooting. Live fascine Bound, elongated, cylindrical bundles of live branch cuttings that are placed in shallow trenches, partly covered with soil, and staked in place. Live branch cuttings that are placed in trenches at an angle from shoreline Live siltation construction to trap sediment and protect them against wave action. Live stake Live branch cuttings that are tamped or inserted into the earth to take root and produce vegetative growth. Noncohesive soil Soil, such as sand, that lacks significant internal strength and has little resistance to erosion. Strips or sheets of metal or other material connected with meshed or P iling (sheet) interlocking members to form an impermeable diaphragm or wall. iling P A long, heavy timber, concrete, or metal support driven or jetted into the earth. Piping The progressive removal of soil particles from a soil mass by percolating water, leading to the development of flow channels or tunnels. A section of a stream's length. Reach Reed clump A combination of root divisions from aquatic plants and natural geotextile fabric to protect shorelines from wave action. A facing of stone, interlocking pavers, or other armoring material shaped to Revetment (armoring) conform to and protect streambanks or shorelines. Riprap A layer, facing, or protective mound of rubble or stones randomly placed to prevent erosion, scour, or sloughing of a structure of embankment; also, the stone used for this purpose. Rootwad A short length of tree trunk and root mass. Scour Removal of underwater material by waves or currents, especially at the base or toe of a streambank or shoreline. Sediment deposition The accumulation of sediment. ediment load The amount of sediment in transport. S Sediment Soil particles transported from their natural location by wind or water. 87 16 – (210-vi-EFH, December 1996)

233 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook The movement of water through the ground, or water emerging on the face Seepage of a bank. Slumping (sloughing) Shallow mass movement of soil as a result of gravity and seepage. Stream-forming flow The discharge that determines a stream ’ s geomorphic planform dimen- sions. Equivalent to the 1- to 3-year frequency flow event (see Bankfull discharge). Streambank The side slopes within which streamflow is confined. Streambed (bed) The bottom of a channel. Streamflow The movement of water within a channel. Submerged vanes Precast concrete or wooden elements placed in streambeds to deflect secondary currents away from the streambank. Thalweg The deepest part of a stream channel where the fastest current is usually found. Toe The break in slope at the foot of a bank where it meets the streambed. Vegetated geogrid Live branch cuttings placed in layers with natural or synthetic geotextile fabric wrapped around each soil lift. Porous revetments, such as riprap or interlocking pavers, into which live Vegetated structural revetments plants or cuttings can be placed. Vegetated structures A retaining structure in which live plants or cuttings have been integrated. 88 16 – (210-vi-EFH, December 1996)

234 Size Determination for Rock Riprap Appendix 16A Isbash Curve The Isbash Curve, because of its widespread accep- tance and ease of use, is a direct reprint from the previous chapter 16, Engineering Field Manual. The curve was developed from empirical data to determine 1. The – a rock size for a given velocity. See figure 16A rock size (100 percent of riprap user can read the D 100 ≤ this size) directly from the graph in terms of weight (pounds) or dimension (inches). Less experienced users should use this method for quick estimates or comparison with other methods before determining a final design. Rock size based on Isbash Curve 1 – Figure 16A 60 15,000 10,000 5,000 3 40 1,000 20 500 Diameter of stone (in) 250 Weight of stone at 165 lb/ft 100 50 0 14 12 4 16 20 10 8 6 18 2 0 Velocity (ft/s) Based on Isbash Curve Procedure 1. Determine the design velocity. 2. Use velocity and fig. 16A-1 (Isbash Curve) to determine basic rock size. size. 3. Basic rock size is the D 100 – (210-vi-EFH, December 1996) 1 16A

235 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook (nominal diameter in inches). Size of rock for which 25% by weight is larger D s 40 30 20 0 10 Side slope 9 - 12 2:1 1 1/2:1 3:1 6 - 9 Straight channel Ratio of curve radius to water surface width 4 - 6 = 0.52 c = 10 = 0.72 = 0.90 = 0.75 K = 0.87 size. = 0.60 75 6 2 4 8 10 characteristics to determine basic rock size. 0.020 Procedure 3. Basic rock size is the D 1. Determine the average channel grade or energy slope. 2. Enter fig. 16A-2 with energy slope, flow depth, and site physical K .63 .87 .80 .52 .72 0.015 3:1 2:1 2 1/2:1 1 3/4:1 1 1/2:1 Slide slope at maximum s at the base. s Channel slope S (ft/ft) 0.010 size rock in inches C 1.0 0.6 75 0.75 0.90 = D s D Rock size based on Far West States (FWS)-Lane method Depth of flow D (ft) 2 0.005 – s 3.5 CK Mechanics Note 1. grading in accordance with cirteria in NRCS Soil (normal to slope) not less than D foundation, and minimum section thickness include fairly well graded rock, stable (D) greater than 4. water surface elevation and 3 D /W =Water surface width = w D S =Curve radius s c s c R 4. Where a filter blanket is used, design filter material 2. Specific gravity of rock not less than 2.56. 3. Additional requirements for stable riprap Notes: 1. Ratio of channel bottom width to depth 4-6 9-12 6-9 straight channel D R S=Energy slope or channel grade w=62.4 W Figure 16A (210-vi-EFH, December 1996) 2 16A –

236 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook 10 9 8 27 in 24 in 21 in 18 in 14 in upper 7 =1.18 6 D 8 in 17 in 16 in 15 in 13 in lower K 5 5.0 d 75 60 40 20 100 4 K 4.0 etc. ) D K etc. 3 100, 75 100 16A-2 D ––––––––—— , D Rock Riprap Gradation =calculated basic rock size from one 75 , D etc. 50 w/high=lower or upper size limit of riprap ow/high= =K from lower gradation limits curve for the 2 100, 75 D d l d lo D D of the rock riprap design methods K from lower curve D =16 in. (from figure 75 1.18 16 in. =1.18 D Example: Calculate basic rock size from one of the design methods. For this example assume D K Determine K Determine gradation limits d= (K) 1 1.0 9 8 0.8 100 75 7 D D 6 0.6 50 5 Size D Reference 4 30 0.4 D (K) 3 0.25 2 0.2 Gradation limits curve for determining suitable rock gradation 3 – 0 90 80 70 60 50 40 30 20 10 100 % Passing (by weight) 1 Figure 16A 16A – 3 (210-vi-EFH, December 1996)

237

238 Plants for Soil Bioengineering Appendix 16B and Associated Systems The information in appendix 16B is from the Natural Growth rate — Subjective rating of the speed of Resources Conservation Service's data base for Soil growth of the plant: slow, medium, fast, etc. Bioengineering Plant Materials (biotype). The plants Establishment speed are listed in alphabetical order by scientific name. — Subjective rating of the speed Further subdivision of the listing should be considered of establishment of the plant. to account for local conditions and identify species Subjective rating of the potential suitable only for soil bioengineering systems. Spread potential — for the plant to spread: low, good, etc. Table header definitions (in the order they occur on — the tables): Plant materials The type of vegetation plant parts that can be used to establish a new colony of the Genus and species name of the — species. Scientific name plant. Notes — Other important or interesting characteristics Common name of the plant. — Common name about the plant. — Soil preference Indication of the type of soil the Region(s) of occurrence — Region of occurrence plant prefers: sand, loam, clay, etc. using the regions of distribution in PLANTS (Plant List of Attributes, Nomenclature, Taxonomy, and Symbols, — Lists the pH preference(s) of the pH preference 1994). Region code number or letter: 1 plant. Northeast — ME, NH, VT, MA, CT, RI, WV, KY, NY, PA, NJ, MD, DE, VA, OH Subjective rating of the ability — Drought tolerance 2 Southeast — NC, SC, GA, FL, TN, AL, MS, LA, AR North Central — MO, IA, MN, MI, WI, IL, IN 3 of the plant to survive dry soil conditions. 4 North Plains — ND, SD, MT (eastern) WY (eastern) Shade tolerance — Subjective rating of the ability of the plant to tolerate shaded sites. Central Plains 5 NE, KS, CO (eastern) — South Plains 6 TX, OK — Southwest — Subjective rating of the 7 Deposition tolerance — AZ, NM — ability of the plant to tolerate deposition of soil or 8 Intermountain NV, UT, CO (western) organic debris around or over the roots and stems. 9 Northwest — WA, OR, ID, MT (western) WY (western) Flood tolerance Selective rating of the ability of the 0 California — Ca — plant to tolerate flooding events. Alaska A — AK C Caribbean PR, VI, CZ, SQ — Hawaii Flood season HI, AQ, GU, IQ, MQ, TQ, WQ, YQ Time of the year that the plant can — — H tolerate flooding events. — Commercial availability Answers whether the — The minimum water depth Minimum water depth plant is available from commercial plant vendors. required by the plant for optimal growth. — Plant type Short description of the type of plant: The maximum water depth — tree, shrub, grass, forb, legume, etc. Maximum water depth the plant can tolerate and not succumb to drowning. Root type — Description of the root of the plant: tap, A national indicator from Na- — Wetland indicator fibrous, suckering, etc. tional List of Plant Species that Occur in Wetlands: Subjective rating of 1988 National Summary. Rooting ability from cutting — cut stems of the plant to root without special hormone and/or environmental surroundings provided. – (210-vi-EFH, December 1996) 1 16B

239 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Use in sun & part Branches often Notes touch& root at east of the 95th pH sites. Occurs on Plants occur mostly occurs with conifer usually dioecious, overstory. Occurs British Columbia to CA. grows in poor soils. ground level. Often with a high water table and/or an annual flooding event. years of flooding in MS. one season in shade. Survived Pacific NW. Not tolerant of high and prefers sites parallel. Survived 2 plants, cuttings deep flooding for materials plants rooted Plant plants plants type plants fair good good fair potential Spread fast slow medium medium lishment speed Estab- fast when when slow fast fast young young Growth rate good fair to poor cutting from poor poor ability poor Rooting ly deep, rooting at nodes fibrous fibrous, spreading, suckering Root type shrub to fibrous, medium moderate- tree tree small small to small tree tree medium shallow tree medium shallow, yes, yes yes ability but yes in limited quant- ities yes Commer- Plant type cial avail- 9,0 1,2,3, occur- ence 1,2,3, 8,9,0, A 4,5,6, Region 7,8,9, 0 6 4,5,6, 8 Woody plants for soil bioengineering and associated systems vine maple dwarf maple 4,5,7, boxelder red maple silver maple 1,2,3, Common name 1 – Table 16B Scientific name Acer circinatum Acer glabrum Acer negundo Acer rubrum Acer saccharinum 16B – (210-vi-EFH, December 1996) 2

240 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook A species for Usually grows west forested wetland Notes Survived 2 years of northwest. Plant on 10- to 12-foot spacing. of the Cascade milesof the ocean & below 2,400 feet elevation. A nitro- gen source. Short lived species. May be seedable. Sus- ceptible to caterpillers. flooding in MS. Roots have relation with nitrogen-fixing actinomycetes, susceptible to ice damage, needs full sun. sites in the Pacific Mtns, within 125 Thicket forming. plants materials plants Plant type plants good fair potential Spread fast medium lishment speed Estab- most fast alders are fast slow Growth rate Continued — poor to poor fair cutting from ability poor Rooting shallow, spreading, spreading suckering shallow, Root type medium tree shrub tree large yes ability Commer- Plant type cial avail- yes 9,0,A occur- ence Region 5,6 Woody plants for soil bioengineering and associated systems pacific alder red alder smooth alder 1,2,3, Common name 1 – Table 16B Scientific name Alnus pacifica Alnus rubra Alnus serrulata 16B (210-vi-EFH, December 1996) 3 –

241 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Occurs in southeast UT. Rhizomatous. May Notes Usually seed propagated. Occurs in eastern WA, northern ID, & eastern OR. A different variety is Pacific serviceberry A. alnifolia var semiintegrifolia. Host to several insect & disease pests. seeded directly on roadside cut and fill sites in MD. second year. suckers. Has been produce fruit in Supposedly root Occurs AK to CA. A nitrogen source. OR, south ID, NV, & materials plants plants seed plants, seed Plant type plants, plants good fair to potential Spread poor fast medium fast lishment speed Estab- fast medium medium medium rapid moderate thereafter first year, medium Growth rate Continued — cutting from poor poor poor ability poor Rooting Root type shrub small to small tree shrub shrub large shrub yes, but shrub to shallow ability very yes limited quan- tities Commer- Plant type yes cial avail- yes occur- ence 9 Region 4,5,6, 7,8,0 9 1,2,3, 6 9,0,A 1,2,3, s ’ Woody plants for soil bioengineering and associated systems sitka alder serviceberry cusick utah serviceberry false indigo red chokeberry Common name 1 – Table 16B Scientific name Alnus viridis ssp.sinuata alnifolia var cusickii Amelanchier Amelanchier utahensis Amorpha fruitcosa Aronia arbutifolia 16B – 4 (210-vi-EFH, December 1996)

242 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Does produce Thicket forming, native & can be Thicket forming. Notes many forms propagated by prostrate & spread- layering & root cuttings. Occurs NY to FL & TX. plants. Occurs MA to FL & TX. high in CA coastal bluffs. ing. May be seed- forming to 1 foot unisexual plants. root brush cuttings, thickets where materials cuttings, spray; unisexual fascines, Pioneer in gullies, brush plants, mats, layering, able. Colony- cuttings layering, plants cuttings Plant plants mats, stakes, stakes, fascines, Resistant to salt type fascines, Was B. glutinosa. poor fair potential Spread fair fair fast lishment speed Estab- fast fair Growth rate Continued — poor to good good fair good good cutting from ability Rooting tap and root deep & fibrous fibrous deep, wide- suckers spreading spreading, fibrous wide- fibrous, Root type medium medium shrub small medium tree shrub evergreen shrub ever- green shrub medium yes yes yes ability Commer- Plant type cial avail- 1,2,3, 1,2,6 9,0 6,7,8, occur- ence 5,6 0 Region 0 6,7,8, Woody plants for soil bioengineering and associated systems pawpaw seepwillow eastern baccharis coyotebush water wally Common name 1 – Table 16B Scientific name Asimina triloba Baccharis glutinosa Baccharis halimifolia Baccharis pilularis Baccharis salicifolia (210-vi-EFH, December 1996) 5 – 16B

243 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Occurs Newfound- 1 year of flooding in than a few days Notes land to NJ & MN. when cut. Survived Occurs on the Pacific Coast to CO. MS. Hybridizes with B papyrifera. inundation in a New England trial. Short lived but the most resistant to borers of all birches. salicifolia. Plants coppice Not tolerant of more fascines, May be B. materials plants mats, layering, cuttings brush stakes, Plant plants type plants plants potential Spread poor poor lishment speed Estab- young young fast when fast fast when fast Growth rate Continued — good cutting poor from ability poor Rooting poor fibrous fibrous spreadin fibrous fibrous, shallow, Root type medium tree to large green shrub tree tree shrub large ever- small to medium medium medium ability Commer- Plant type yes yes yes cial avail- 6,7,8, occur- ence 5,6 Region 8,9,0, Ag 5,9,A 8,9 0 1,3,4, 1,3,4, 1,2,3, 4,5,7, Woody plants for soil bioengineering and associated systems mulefat baccharis river birch water birch paper birch low birch Common name 1 – Table 16B Scientific name Baccharis viminea Betula nigra Betula occidentalis Betula papyrifera Betula pumila – (210-vi-EFH, December 1996) 16B 6

244 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Not tolerant of sites. Notes flooding in TN tolerate flooding in Hard to transplant. coppice. Not Roots & stumps Valley trial. Occurs MD to FL & west to southern IL & east TX. A northern form occurs from New forested wetland England to NC & west to MN & AR. Occurs Quebec to a MO trial. Occurs Quebec to FL & LA. Transplants with difficulty. A species for FL & TX. LA; naturalized in New England, OH, MI, & TX. Occurs in SW GA to plants materials plants Plant plants plants type plants poor potential Spread poor poor poor poor slow fast slow fair lishment speed Estab- slow slow slow slow fair Growth rate Continued — poor cutting from ability poor poor poor poor Rooting shallow lateral laterals dense tap tap & Root type tap to small tree medium tall tree tree tree ability sources limited tree yes, Commer- Plant type yes cial avail- yes yes yes occur- ence 1,2,3, 5,6,7 6 6 Region 1,2,3, 5,6 4,5,6 1,2,3, 1,2,3, Woody plants for soil bioengineering and associated systems american hornbeam water hickory 1,2,3, bitternut hickory shagbark hickory southern catalpa Common name 1 – Table 16B Scientific name Carpinis caroliniana Carya aquatica Carya cordiformis Carya ovata Catalpa bignonioides (210-vi-EFH, December 1996) 7 – 16B

245 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Very resistant to Survived 2 years of Notes roots will root. tolerate more than a Occurs FL, west to TX & southern IN. Also in Mexico. Leaf fall allelopathic. Occurs TX to witches-broom. few days inundation in a MO trial. Susceptible to witches-broom. Occurs Quebec to NC & AL. Juvenile wood & shade. southern CA & into Mexico. 'Barranco,' flooding in MS. Not 'Hope,' & 'Regal' cultivars were releasedin New Mexico. flooding in MS. Will Survived 3 years of plants materials plants layering, grow in sun or plants mats, Plant plants plants type brush low potential Spread low poor slow slow slow medium poor lishment speed Estab- to fast medium medium medium medium low slow Growth rate slow Continued — good cutting poor from ability poor fair to Rooting poor shallow to deep relatively fibrous medium fibrous tap Root type shrub medium tree tree tree medium shrub large small yes ability Commer- Plant type yes yes cial avail- yes yes 1,2,3, occur- ence 5,6,7, 9,0 1,2,3, 4,5,6, 8 Region 5,6,7, 8,0 5,6,7, 8 0 1,2,3, 1,2,3, Woody plants for soil bioengineering and associated systems sugarberry hackberry buttonbush redbud desert willow 6,7,8, Common name 1 – Table 16B Scientific name Celtis laevigata Celtis occidentalis Cephalanthus occidentalis Cercis canadensis Chilopsis linearis (210-vi-EFH, December 1996) 8 – 16B

246 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook tolerates partial Susceptible to severe browsing & in sandy soils at 7- Notes shade. 'Indigo' plants from layering wan to KS & NE, scale. Occurs PA to FL & west to TX. Pith usually brown. to 8-inch precip & 1,000-foot elevation. tolerant on coastal sites. Occurs ME to FL. cultivar was south to MS, LA, & Has rhizomes; salt Produces new stakes, fascines, Pith brown, plants materials fascines, Root suckers too. brush mats, layering, released by MI cuttings, PMC. plants brush mats, cuttings, TX. plants Plant stakes, type layering, Occurs Saskatche- plants plants fair poor potential Spread good fast medium poor lishment speed Estab- slow fast fast slow Growth rate Continued — fair fair cutting poor from ability poor poor Rooting root shallow, fibrous suckering, & fibrous spreading shallow Root type shrub shrub large tree small small vine shrub yes ability yes yes Commer- Plant type yes cial avail- yes 1,2,3, 4,5,6 4,5,6 1,2,3, 1,2,3, occur- ence 5,6,7, 6 8,9,0 Region 1,2,4, 1,2,6 Woody plants for soil bioengineering and associated systems fringetree western clematis sweet pepperbush silky dogwood roughleaf dogwood Common name 1 – Table 16B Scientific name Chionanthus virginicus Clematis ligusticifolia Clethera alnifolia Cornus amomum Cornus drummondii (210-vi-EFH, December 1996) 9 – 16B

247 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook as bare root; Hard to transplant Notes species with coppices freely. Not tolerant of flooding in TN Valley trial. VA to FL & west to TX. Pith white. root_abil = good to excellent. Occurs Nova Scotia to VA & ND. tolerates city usually brown, racemosa Occurs thickets. Pith plants cuttings, combination with materials fascines, Forms dense fascines, Formerly C. plants mats, layering, smoke. Occurs ME cuttings, & MN to NC & OK. plants brush Plant plants type stakes, fascines, Pith white. Use in poor fair potential Spread fair lishment speed Estab- fair fast medium Growth rate Continued — good fair fair poor cutting from ability fair to Rooting fibrous fibrous shallow, shallow, shallow, fibrous Root type to small tree medium medium small shrub shrub shrub to small medium yes yes ability Commer- Plant type cial avail- 5,6 1,2,3, occur- ence 4,5,6 4,5,6 Region 1,3 Woody plants for soil bioengineering and associated systems flowering dogwood stiff dogwood 1,2,3, gray dogwood 1,2,3, roundleaf dogwood Common name 1 – Table 16B Scientific name Cornus florida Cornus foemina Cornus racemosa Cornus rugosa 10 – 16B (210-vi-EFH, December 1996)

248 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook rootstocks & root- Semievergreen, a thickets on moist Occurs Ontario & Notes good honey plant. partial shade. For- May be same as C. ing of branches. merly C. stolonifera. 'Ruby' cultivar was released by NY PMC. foemina. sites. Grown from seed or grafted. Occurs British Columbia to CA & MN. Survived 6 years of 'Homestead' cultivar was released by ND PMC. Occurs VA to FL & on to South America. Prefers organic sites. MN to AL, AR & MS. cuttings, Forms dense stakes, plants materials plants plants brush mats, layering, flooding in MS. Pith cuttings, white, tolerates plants plants Plant fascines, Forms thickets by type poor potential Spread medium fair lishment speed Estab- slow fast Growth rate Continued — fair poor to poor good cutting poor to poor fair from ability Rooting tap shallow fibrous tap to Root type shrub medium shrub tree tree tree small small yes ability yes Commer- Plant type yes cial avail- 5,7,8, 1,3,4, 1,2,3, occur- ence 9,0,A 1,2,6, Region C 3,8,9, 4,5,6 0,A Woody plants for soil bioengineering and associated systems red-osier dogwood swamp dogwood douglas hawthorn downy hawthorn titi Common name 1 – Table 16B Scientific name Cornus sericea ssp sericea Cornus stricta Crataegus douglasii Crataegus mollis Cyrilla racemiflora – 11 16B (210-vi-EFH, December 1996)

249 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Grows well in May be grown from Thicket forming. limestone & alkaline thickets on dry Occurs in swamps Survived 3 years of flooding in MS. Notes seed but usually flooding in MS. sites. Stoloniferous & tap rooted. Occurs CT toFL & TX. soils. VA to TX. occurs west of the Cascade Mtns. 'Cardan' cultivar was released by ND PMC. grafted. Usually Forms dense Survived 3 years of Easily transplanted. plants plants materials plants Plant type plants plants plants fair potential Spread poor good poor fast fast fast fair medium fair lishment speed Estab- fast fast when young fast slow fast Growth slow rate Continued — poor to fair cutting fair from ability poor poor Rooting poor shallow, fibrous shallow, moderately poor fibrous fibrous shallow, fibrous tap Root type small tree shrub to medium tree small tree tree tree tree large medium large medium yes yes ability Commer- Plant type yes yes cial avail- yes 1,3,4, 9,0 6 occur- ence 5,6 1,2,3, 8,9,A Region 4,5,6, 8,9 1,2,3, 1,2,3, 1,2,6 Woody plants for soil bioengineering and associated systems persimmon silverberry swamp privet carolina ash oregon ash green ash Common name 1 – Table 16B Scientific name Diospyros virginiana Elaeagnus commutata Forestiera acuminata Fraxinus caroliniana Fraxinus latifolia Fraxinus pennsylvanica 12 – 16B (210-vi-EFH, December 1996)

250 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook burned areas. flooding for 100 Notes Was H. militaris. Columbia to CA to years. Has been used in reg_occ 7,8,9. Native ecotypes have thorns! days 3 consecutive Often pioneers on Occurs from British ID. Usually grown from seed or cuttings. Evergreen. Survived deep materials Plant plants plants plants plants plants type plants plants potential Spread poor medium fast fast lishment speed Estab- to rapid medium fast Growth rate Continued — fair fair cutting from ability poor to poor poor poor poor poor to poor Rooting wide- spread deep & Root type tree shrub medium large shrub shrub shrub shrub shrub small to ability Commer- Plant type yes from contract yes growers. yes yes, yes yes cial avail- yes 5,6,7, occur- ence 4,5,6, 7,8,9 Region 2,6 0 9,0 1,2,3, 1,2,6, C Woody plants for soil bioengineering and associated systems honeylocust hibiscus halberd-leaf marshmallow common rose 1,2,3, mallow hibiscus oceanspray sweet gallberry Common name 1 – Table 16B Scientific name Gleditsia triacanthos Hibiscus aculeatus Hibiscus laevis Hibiscus moscheutos Hibiscus moscheutos ssp.lasiocarpos Holodiscus discolor Ilex coriacea (210-vi-EFH, December 1996) 16B 13 –

251 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Easy to transplant flooding in TN when young. flooded sites. Notes Evergreen, sprouts Survived 3 years of Prefers seasonally Plants dioecious. tolerate flooding in Root suckers. Valley trial. Stoloniferous! Occurs eastern US & Canada. flooding in MS. tolerant, will not TN Valley trial. Though drought soil sites. Not after fire. grow on poor or dry Not tolerate plants materials plants plants plants Plant plants plants type plants potential Spread poor fair medium poor medium good lishment speed Estab- slow slow slow slow slow fair Growth rate Continued — poor cutting poor poor from poor poor ability poor poor Rooting & prolific deep & dense tap root laterals wide- spread laterals fibrous laterals tap & Root type tree shrub to small tree to large shrub shrub tree large tree tap & shrub large small small medium large small ability yes yes Commer- Plant type yes yes yes cial avail- yes yes 6 1,2,3, 1,2,3, occur- ence 4,5,6 5,6 1,2,3, Region 1,2,3, 6 4,5,6 1,2,6 1,2,6 Woody plants for soil bioengineering and associated systems possomhaw bitter gallberrry american holly winterberry yaupon black walnut 1,2,3, eastern redcedar Common name 1 – Table 16B Scientific name Ilex decidua Ilex glabra Ilex opaca Ilex verticillata Ilex vomitoria Juglans nigra Juniperus virginiana (210-vi-EFH, December 1996) 14 – 16B

252 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook forested wetland Evergreen. Occurs Notes Trees from the wild east TX & OK, east A species for Dioecious. sites. Prefers acid soils. Evergreen. do not transplant from MA to FL and west to east TX. to FL & north to NJ. well. Hard to transplant. Evergreen. Occurs in swamps fascines, materials plants plants cuttings, Plant plants plants plants plants type plants stakes, plants plants poor to slow fair fair potential Spread fast fast slow lishment speed Estab- fast medium slow fast slow slow Growth slow rate slow Continued — good cutting from poor poor poor ability poor poor poor Rooting poor poor fibrous fibrous wide- shallow spreading deep & & fibrous fibrous tap to Root type small to large shrub tree shrub tree shrub to large shrub to large large tree shallow, large shrub small small small tree large small yes ability yes Commer- Plant type yes yes cial avail- yes yes yes yes 3,7,8, occur- ence 5,6 6 c 1,2,3, 5,6 Region 1,2,3, 1,2,6 1,2,3, 6 1,2,6, 1,2,3, 9,0,A 1,2 1,2 Woody plants for soil bioengineering and associated systems leucothoe spicebush sweetgum tulip poplar black twinberry fetterbush sweetbay southern waxmyrtle swamp tupelo Common name 1 – Table 16B Scientific name Leucothoe axillaris Lindera benzoin Liquidambar styraciflua Liriodendron tulipifera Lonicera involucrata Lyonia lucida Magnolia virginiana Myrica cerifera Nyssa aquatica – 15 (210-vi-EFH, December 1996) 16B

253 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Usually grown from transplant. Nyssa. Vegetative noted. Only grows reproduction not Difficult to Notes in sun or shade on forested wetland Largest fruit of all transplant but plant close to perennial wetland sites. 10- to 12-foot spacing. Tolerated flooding for up to 30 days during 1 growing season. sites. Difficult to seed. A species for plants materials plants plants plants Plant type plants fair potential Spread medium medium slow slow medium poor to fast lishment speed Estab- fast slow slow slow medium slow Growth rate Continued — poor cutting poor from poor poor ability Rooting poor sparse, fibrous fibrous fibrous, very long, decending sparse, Root type tree large to small large tree shrub to large evergreen tree shrub small tall tree small yes ability yes Commer- Plant type yes yes cial avail- 9,0 2 1,2,3, 4,5,6 occur- ence 6 Region 1,2,6 1,2,3, Woody plants for soil bioengineering and associated systems ogeeche lime blackgum hophorn- beam redbay lewis mockorange Common name 1 – Table 16B Scientific name Nyssa ogeeche Nyssa sylvatica Ostrya virginiana Persea borbonia Philadelphus lewesii – (210-vi-EFH, December 1996) 16 16B

254 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Occurs KY to FL, with other species Notes west of the Cascade west to IL & TX. Cascade Mtns. Mtns. with rooting ability occurs east of the or cuttings. Usually cuttings, Propagated by seed plants brush materials plants brush mats, layering, cuttings, plants mats, layering, good to excellent. cuttings, plants fascines, Usually occurs Plant fascines, Use in combination type plants poor poor potential Spread fast slow lishment speed Estab- fast fairly fast Growth slow rate Continued — fair good cutting poor from poor ability fair Rooting shallow tap fibrous rhizomes changes to shallow spreading laterals lateral but with shallow, short Root type small shrub tree shrub tree shrub large small medium medium yes ability Commer- Plant type yes yes yes cial avail- 8,9 occur- ence A Region 8,9 4,5,6, 6 8,9,0, 5,6 1,2,3, 1,2,3, 1,2,3, Woody plants for soil bioengineering and associated systems pacific ninebark mallow ninebark common ninebark loblolly pine water elm Common name 1 – Table 16B Scientific name Physocarpus capitatus Physocarpus malvaceus Physocarpus opulifolius Pinus taeda Planera aquatica 16B 17 (210-vi-EFH, December 1996) –

255 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook A species for forested wetlands A species for Notes forested wetland city smoke & alkali sites. Plant on 10- to12-foot in ID for riparian spacing. Trans- plants well. sites. sites in CA. sites. Tolerates fascines, plants materials poles, brush mats, layering, cuttings, plants poles, brush mats, layering, cuttings, plants Plant plants stakes, stakes, fascines, Under development type medium potential Spread fast fast lishment speed Estab- fast fast Growth rate Continued — poor v good cutting v good from ability Rooting wide- fibrous, spreading shallow deep, fibrous Root type tall tall tree tree large large tree tree yes yes ability Commer- Plant type cial avail- 1,2,3, 1,2,3, occur- ence 0 5,6 Region 0 9,O,A 4,5,8, 4,5,6, 7,8,9, Woody plants for soil bioengineering and associated systems sycamore California sycamore narrowleaf cottonwood balsam poplar Common name 1 – Table 16B Scientific name Platanus occidentalis Platanus racemosa Populus angustifolia Populus balsamifera 18 16B – (210-vi-EFH, December 1996)

256 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Survived over 1 Notes Endures heat & May be sensitive to year of flooding in aluminum in the soil. soils. Dirty tree. inundation in a New propagation is by England trial. Use rooted plant pioneer species on materials. root cuttings. Not than a few days sunny sites. poplars. Plant roots tolerant of more materials root brush mats, layering, MS. Hybridizes with stakes, cuttings, several other root suckers, may be invasive. plants poles, poles, brush mats, layering, cuttings, plants Plant layering, Short lived. A fascines, Tolerates saline stakes, type cuttings, sunny sites. Normal plants fascines, Short lived. fair poor potential Spread fast fast lishment speed Estab- fast fast fast Growth rate Continued — to fair v good cutting from poor v good ability Rooting profuse shallow, suckering shallow, suckers, vigorous under- ground runners fibrous, shallow, fibrous Root type tree tall medium tree tree yes ability yes Commer- Plant type cial avail- 1,2,3, 4,5,7, 1,2,3, occur- ence 7,8,9 Region 8,9,0, A 6,7,8, 4,5,6, 0 Woody plants for soil bioengineering and associated systems eastern cottonwood fremont cottonwood quaking aspen Common name 1 – Table 16B Scientific name Populus deltoides Populus fremontii Populus tremuloides 19 – 16B (210-vi-EFH, December 1996)

257 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook forested wetland forested wetland Notes for riparian sites. trichophora. Usu- Plant on 10- to 12- foot spacing. May be P. balsimifera City, TX, PMC. sites. Has hydro- cyanic acid in most parts, sites. Was P. especially the seeds. Usually ally grown from grown from seed. Thicket forming. Plant on 5- to 8-foot spacing. Reportedly poisonous to cattle. 'Rainbow' cultivar released by Knox Thicket forming. A species for materials brush stakes, root poles, mats, layering, cuttings. Under cuttings, development in ID plants Plant cuttings fascines, A species for type plants, plants good good potential Spread fast lishment speed Estab- fast medium fast Growth rate medium medium fair Continued — v good cutting from ability poor Rooting poor suckering deep & wide- spreading, spread, fibrous suckering fibrous, Root type shallow, shrub large shrub tree small large yes ability Commer- Plant type cial avail- yes yes 4,7,8, occur- ence 5,6 Region 7,8,9, 0,A 9,0,A 1,2,3, 1,2,3, Woody plants for soil bioengineering and associated systems black cottonwood wild plum common chokecherry 4,5,6, Common name 1 – Table 16B Scientific name Populus trichocarpa Prunus angustifolia Prunus virginiana (210-vi-EFH, December 1996) 20 – 16B

258 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook more than a few Did not survive Usually grows west Mtns, in the Colum- flooding in MS. Survived 2 years of days flooding in a trial in New Eng- Notes of the Cascade land. Difficult to lumber species. bia River Gorge to 'Boomer' cultivar Often used as a released by TX transplant larger specimens. the Dalles & to Yakima, WA. Propa- gated from seed sown in fall. street tree in the southeast US. Survived 2 years of PMC. flooding in MS. Often worthless as a plants plants materials plants Plant plants plants type plants fair slow slow poor potential Spread slow slow medium fair fast slow lishment speed Estab- slow slow fast fast medium fast slow Growth rate Continued — poor cutting poor poor from poor ability poor Rooting poor shallow & well- deep, developed iorates to tap & well- well- developed fibrous deep tap laterals somewhat dense shallow laterals developed laterals tap to deep tap tap deter- Root type to large tree tree tree shrub tree tree medium tree large medium large yes yes ability Commer- Plant type yes cial avail- yes yes 9,0 5,6 1,2,3, occur- ence 5,6 Region 1,2,6 6 1,2,3, 4,5,6, 9 1,2,3, 1,2,3, Woody plants for soil bioengineering and associated systems white oak swamp white oak oregon white oak swamp laurel oak overcup oak bur oak Common name 1 – Table 16B Scientific name Quercus alba Quercus bicolor Quercus garryana Quercus laurifolia Quercus lyrata Quercus macrocarpa – (210-vi-EFH, December 1996) 16B 21

259 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook forested wetland Easily transplanted. 12-foot spacing. Easily transplanted. Notes A species for Mat forming from years of flooding in sites. Survived 2 suckers & stolons. Occurs from DE to SC. MS. Plant on 10- to plants materials plants plants plants plants Plant plants type plants good by fair poor stolons low poor potential Spread fast medium fair slow fair lishment speed Estab- fast fast good fast sites fast on fair medium slow Growth rate Continued — poor poor cutting from poor poor ability poor poor poor Rooting spreading developed laterals well- fibrous laterals after taproot disinte- grates shallow, deep fibrous shallow & shallow tap & Root type tree tree to large tree shrub medium medium medium tree tree large small large tree ability yes yes Commer- Plant type yes cial avail- occur- ence 1,2,3, 1,2,3, 6 5,6 1,2,3, Region 1,2,3, 6 5,6 6 1,2 Woody plants for soil bioengineering and associated systems swamp chestnut oak water oak cherrybark oak pin oak willow oak shumard oak 1,2,3, coast azalea Common name 1 – Table 16B Scientific name Quercus michauxii Quercus nigra Quercus pagoda Quercus palustris Quercus phellos Quercus shumardii Rhododendron atlanticum 22 – 16B (210-vi-EFH, December 1996)

260 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Has stoloniferous Notes Normal propagation or seed. Not Thicket forming. forms. Occurs from ME to SC. Highly susceptible to Thicket forming. insects & diseases. tolerant of flooding in TN Valley trial. Escaped in regions 5,7,8,9,0. Reported toxic to livestock. cuttings, is by root cuttings root plants cuttings, A browsed species. root root materials root suckers, plants root suckers, plants plants cuttings, Plant cuttings, type plants cuttings, A browsed species. plants good fair to fair good potential Spread fast fast lishment speed Estab- fast medium fast to fast fast slow Growth rate Continued — poor to fair to poor to poor good fair poor cutting good from fair to fair ability Rooting fibrous, shallow suckering fibrous, suckering Root type shrub large medium tree shrub medium shrub shrub shrub yes yes yes ability Commer- Plant type cial avail- 1,2,3, 7,8,9, 1,2,3, 1,2 occur- ence 1,2,3, Region 7,8,9 4,5,6, 7,8,9, 0 0,A 4,5,6, 9,0 4,5,6 Woody plants for soil bioengineering and associated systems swamp azalea flameleaf sumac smooth sumac black locust baldhip rose nootka rose Common name 1 – Table 16B Scientific name Rhododendron viscosum Rhus copallina Rhus glabra Robinia pseuodoacacia Rosa gymnocarpa Rosa nutkana – 16B 23 (210-vi-EFH, December 1996)

261 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Normal propagation Was R. strigosus. Normal propagation Notes Normal propagation is by root cuttings. is by root cuttings. Use in combination with other species. Rooting ability is good to excellent. is by root cuttings. plants plants materials plants fascines, plants Plant plants plants cuttings, A browsed species. type fair potential Spread fast lishment speed Estab- fair Growth rate Continued — good good good good good cutting to good fair from ability Rooting fibrous shallow fibrous fibrous rhizomat- ous & fibrous Root type small small small small shrub shrub shrub shrub small shrub shrub yes ability Commer- Plant type cial avail- 1,2,3, 1,2,3, 1,2,3 occur- ence 5 6,7,8, 9,0,A Region 4,5,6, 7,8,9, A 3,4,5, 5,6,0 Woody plants for soil bioengineering and associated systems swamp rose virginia rose woods rose allegheny blackberry red raspberry 1,2,3, salmonberry 9,0,A Common name 1 – Table 16B Scientific name Rosa palustris Rosa virginiana Rosa woodsii Rubus allegheniensis Rubus idaeus ssp. strigosus Rubus spectabilis (210-vi-EFH, December 1996) 24 – 16B

262 Chapter 16 Part 650 Streambank and Shoreline Protection Engineering Field Handbook ’ Bankers ‘ callus cut. May be short-lived. Under east of the Cascade species. Plant development in ID Notes Mtns & in ID & MT. plants on 2' to 6' suckers. Usually with several other willow species. spacing. for riparian sites. when young. fascines, Often roots only at stakes, poles, cuttings, Does not form brush stakes, materials fascines, Eaten by livestock poles, fascines, Not a native brush mats, layering, cultivar released by cuttings, Kentucky PMC. plants mats, layering, Not tolerant of cuttings, shade. Hybridized plants brush mats, layering, cuttings, plants Plant plants type stakes, poor potential Spread fast lishment speed Estab- fast medium fast Growth rate Continued — v good v good v good cutting from ability Rooting shallow shallow fibrous fibrous Root type large shrub to to deep large shrub small shrub to tree tree large tree shrub to small medium small yes ability yes yes Commer- Plant type cial avail- 1,2,3, not 4,5,6, occur- ence 7,8,9 5,7,8, Region native 7 9,A 1,3,4, Woody plants for soil bioengineering and associated systems dwarf willow peachleaf willow bebb's willow pussy willow Common name 1 – Table 16B Scientific name Salix X cottetii Salix amygdaloides Salix bebbiana Salix bonplandiana (210-vi-EFH, December 1996) 25 – 16B

263 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Under development partial shade sites. for riparian sites. Notes discrepancy in the Under development livestock. Under released by OR in Idaho for riparian sites. in ID for riparian sites. 'Curlew' cultivar released by WA PMC. PMC. development in ID 'Silvar' cultivar name, it may be S. fascines, A botanic fascines, Use on sunny to brush materials poles, stakes, poles, layering, cuttings, plants stakes, cuttings, Cascade Mtns. plants fascines, Usually east of the poles, layering, ligulifolia! cuttings, 'Placer' cultivar plants mats, layering, released by WA cuttings, PMC. Plant plants stakes, type fascines, Relished by potential Spread fast lishment speed Estab- rapid Growth rate fast Continued — v good v good good cutting from ability good Rooting fibrous shallow, ous suckering, spreading fibrous, rhizomat- shallow, Root type large shrub shrub large shrub shrub shrub medium yes yes yes ability Commer- Plant type yes cial avail- 7,8,9, 8,9 occur- ence 1,2,3, 0 Region 4,9 4,5,6, 0 7,8,9, 0,A 1,2,3, Woody plants for soil bioengineering and associated systems booth willow pussy willow drummond's 7,8,9, willow erect willow coyote willow Common name 1 – Table 16B Scientific name Salix boothii Salix discolor Salix drummondiana Salix eriocephala Salix exigua 16B (210-vi-EFH, December 1996) 26 –

264 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Cascade Mtns at alkaline sites. Some grasses. 'Clatsop' Notes black willow. higher elevations. say this is western Relished by livestock. Under development in ID for riparian sites. tolerance. Can cultivar was compete well with fascines, Not tolerate cuttings, Occurs east of the fascines, Thicket forming. fascines, May have salt poles, plants brush materials brush mats, stakes, poles, mats, layering, cuttings, plants cuttings, PMC. plants poles, brush mats, layering, cuttings, Plant plants layering, released by OR stakes, stakes, type potential Spread fast medium medium lishment speed Estab- fast young, rapid medium there- after when Growth rate Continued — good to good v good excel cutting from ability Rooting shallow fibrous, spreading fibrous, Root type small small to medium shrub to to deep shrub shrub to dense large tree large shrub small tree large ability Commer- Plant type yes cial avail- 6,7,8, 7,8,9, occur- ence 0 Region 0 1,2,3, 4,5,6 9,0 Woody plants for soil bioengineering and associated systems geyer's willow goodding willow hooker willow prairie willow Common name 1 – Table 16B Scientific name Salix geyeriana Salix gooddingii Salix hookeriana Salix humilis (210-vi-EFH, December 1996) 27 – 16B

265 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook ’ Palouse ‘ cultivar released by exigua. Use in Notes to excellent. Under development This species has elevations, east of WA PMC. combination with OR PMC. in ID for riparian callus. 'Rogue' been changed to S. the Cascade Mtns. 1/3 of cutting or at fascines, Thicket forming. fascines, Occurs at high brush materials mats, poles, poles, brush mats, layering, species with cuttings, rooting ability good plants poles, cuttings, plants stakes, poles, brush mats, layering, sites. stakes, cuttings, cultivar released by plants brush mats, fascines, layering, cuttings, Plant plants layering, fascines, Roots only on lower stakes, type stakes, potential Spread fast medium lishment speed Estab- medium medium fair young, medium rapid there- after rapid when Growth rate Continued — v good exce v good v good cutting from ability Rooting shallow fibrous fibrous, spreading to deep fibrous Root type medium large medium tall to small tree to tall shrub shrub shrub shrub yes yes yes ability Commer- Plant type cial avail- 8,9,0 1,3,4, 1,3,4, 6,7,8, occur- ence 9,A Region 5,7,8, 5,7,8, 9,0 9,0 Woody plants for soil bioengineering and associated systems sandbar willow arroyo willow lemmon's willow shining willow Common name 1 – Table 16B Scientific name Salix interior Salix lasiolepis Salix lemmonii Salix lucida (210-vi-EFH, December 1996) 28 – 16B

266 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook ’ Nehalem ‘ sites. There are several subspecies forested wetlands Notes flooding in MS. Susceptible to for riparian sites. Survived 3 years of cultivar released by several diseases OR PMC. and insects. Plant on 10- to 12-foot spacing. livestock. Under Needs full sun. of S. lucida. Under Susceptible to development in ID poles, poles, brush materials fascines, A species for poles, fascines, May be short lived. stakes, mats, layering, development in ID cuttings, for riparian sites. plants brush mats, layering, cuttings, plants brush mats, layering, several diseases cuttings, & insects. root cuttings, plants Plant fascines, Usually browsed by stakes, stakes, type good potential Spread fast to slow lishment speed Estab- fast to slow medium medium Growth rate Continued — good to v good v good cutting excel from ability Rooting sprouts dense, fibrous shallow, fibrous readily Root type shrub to small tree to large shrub tree medium to tall large small ability Commer- Plant type yes yes cial avail- occur- ence 5,6,7, 0 Region 9,0,A 4,7,8, 8 7,8,9, 1,2,3, 1,4,5, Woody plants for soil bioengineering and associated systems pacific willow yellow willow black willow Common name 1 – Table 16B Scientific name Salix lucida ssp. lasiandra Salix lutea Salix nigra – 16B 29 (210-vi-EFH, December 1996)

267 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook sites. Occurs on may defoliate it Cascade Mtns in Notes both sides of the shade. 'Streamco' the East. Insects NY PMC. sparingly escaped in regularly. low to high eleva- cultivar released by fascines, Tolerates partial fascines, Pioneers on burned brush stakes, poles, brush materials poles, mats, layering, stakes, cuttings, plants poles, brush mats, layering, cuttings, plants mats, layering, tions. Often roots cuttings, only at callus. plants Plant stakes, fascines, From Europe, type poor potential Spread fast medium poor lishment speed Estab- fast fast fast Growth rate Continued — excel v good good cutting from ability Rooting shallow shallow spreading fibrous, Root type medium shrub shrub to small tree large to small tree tree large yes ability Commer- Plant type yes cial avail- 1,2,3, not occur- ence Region native 9,0,A 4,7,8, 5 Woody plants for soil bioengineering and associated systems laural willow purpleosier willow scouler's willow Common name 1 – Table 16B Scientific name Salix pentandra Salix purpurea Salix scouleriana (210-vi-EFH, December 1996) 30 – 16B

268 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Notes spring or summer. in trials. 'Plumas' freely; lends itself to shoots branch Evergreen. Soft- cultivar released by OR PMC. Pith white. wood cuttings root easily in spring or summer. sides of the Cascade spring or summer. Mtns. Vigorous root easily in fascines, Occurs on both plants fascines, Was S. mexicana. materials mats, cuttings, excellent survival plants brush fascines, Softwood cuttings plants layering, bioengineering uses; mats, layering, Pith brown. This cuttings, may be S. callicarpa. plants Plant cuttings, root root easily in plants poles, stakes, type brush fascines, Softwood cuttings poor poor potential Spread medium v fast fast lishment speed Estab- rapid v fast young, medium there- after when medium slow Growth rate fast Continued — v good good cutting good poor from ability good Rooting erous fibrous & fibrous stolonif- Root type very large large shrub medium medium shrub shrub shrub large shrub yes yes ability yes Commer- Plant type yes cial avail- 9,0,A 6,7,8, 1,2,3, occur- ence 8,9 Region 1,2,3, 9,0 9,0,A 6,7,8, 4,7,8, 4,5,6, 0,H Woody plants for soil bioengineering and associated systems sitka willow american elder blue elderberry mexican elder red elderberry Common name 1 – Table 16B Scientific name Salix sitchensis Sambucus canadensis Sambucus cerulea Sambucus cerulea ssp. mexicana Sambucus racemosa (210-vi-EFH, December 1996) 31 – 16B

269 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook cuttings in mid- Usually grown from lific sprouter (forms Notes usually within 10 miles of the ocean & on the coastal bays & estuaries. Soft- wood cuttings root Propagation by easily in spring or summer. Pith brown. Use in com- bination with species with rooting ability good to excellent. summer under mist. seed. Occurs east of the Cascade Mtns at midsummer under medium to high thickets). Propaga- elevations. WA PMC. leafy softwood Cascade Mtns, mist. 'Bashaw' cul- fascines, Occurs west of the materials brush mats, plants layering, tion by leafy soft- cuttings, wood cuttings in division of Plant suckers, tivar released by plants plants type plants potential Spread excellent fascines, Resists fire & pro- medium fast lishment speed Estab- rapid Growth rate Continued — fair to good good good fair to cutting from ability Rooting deep suckering lateral laterals shallow, fibrous, dense Root type medium shrub dense tree dense shrub shrub small short ability Commer- Plant type yes yes cial avail- 1,2,3, 0 occur- ence 4,9,A Region 4 9 1,2,3, 2,3,9, 1,2,4, Woody plants for soil bioengineering and associated systems red elder meadow- sweet spirea shinyleaf spirea douglas spirea Common name 1 – Table 16B Scientific name Sambucus racemosa ssp. pubens Spiraea alba Spiraea betulifolia Spiraea douglasii 16B (210-vi-EFH, December 1996) 32 –

270 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook leafy softwood foot spacing. Toler- Notes Plant on 10- to 12- shade, especially on wet sites. cuttings in mid- summer under mist. A weed in New England pastures. Use rooted materials. Propagation by rainfall. ates upland sites in region 6 with 32" materials mats, plants brush fascines, Plant in sun to part plants plants Plant layering, plants plants cuttings, type poor low fair potential Spread slow fast slow lishment speed Estab- rapid medium slow Growth rate Continued — fair good cutting from poor to poor ability poor poor Rooting shallow, shallow freely laterals suckering for knees for aeration fibrous, tap with fibrous shallow dense, Root type shrub dense small shrub colony forming medium tree shrub, large large tree small yes yes ability Commer- Plant type yes yes cial avail- 1,3,4, 5 1,2,3, 5,6 occur- ence 1,2,3 5,7,8, Region 9,0,A 5,6 1,2,3, 1,2,3, Woody plants for soil bioengineering and associated systems hardhack spirea Japanese snowbell snowberry baldcypress eastern hemlock Common name 1 – Table 16B Scientific name Spiraea tomentosa Styrax japonica Symphoricarpos albus Taxodium distichum Tsuga canadensis (210-vi-EFH, December 1996) 33 16B –

271 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook A species for sites. Survived near forested wetland smoke. Use rooted Notes Thicket forming. in MS. Plant on smoke. Tolerates full shade. Older Branch tips root at full shade. plant materials. 10- to 12-foot branches often root when they touch soil. Use in combination with species with rooting ability good to excellent. 2 years of flooding soil. spacing; tolerates cuttings, tolerates city plants materials stakes, plants brush mats, layering, cuttings, plants stakes, plants Plant cuttings, tolerates city layering, Thicket forming; fascines, Thicket forming; type fascines, Was V. alnifolium. potential Spread medium poor fast slow lishment speed Estab- medium fast fast Growth rate Continued — fair to good good cutting poor from ability good Rooting fibrous shallow shallow, dry fibrous sites to shallow fibrous on moist sites tap on shallow, Root type medium shrub large tree shrub to tall shrub large medium yes yes ability Commer- Plant type yes cial avail- 1,2,3, 1,2,3, 4,5,6, occur- ence 8 1,2,3, 6 Region 4,5,9 1,2,3 Woody plants for soil bioengineering and associated systems american elm arrowwood hubblebush viburnam nannyberry Common name 1 – Table 16B Scientific name Ulmus americana Viburnum dentatum Viburnum lantanoides Viburnum lentago 16B – (210-vi-EFH, December 1996) 34

272 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook D. Wymann says it materials. Fruits Notes is more adapted to the South than V. cassinoides. are edible. plants materials plants Plant layering, Use rooted plant type potential Spread slow lishment Estab- speed medium Growth rate Continued — poor cutting from ability poor Rooting Root type shrub shrub large medium ability Commer- Plant type yes cial avail- 5,9 occur- ence Region 1,3,4, 1,2,6 Woody plants for soil bioengineering and associated systems swamp haw american bush cranberry- Common name 1 – Table 16B cientific name Viburnum nudum Viburnum trilobum (210-vi-EFH, December 1996) 35 16B –

273 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook Woody plants with fair to good or better rooting ability from unrooted cuttings 2 – Table 16B Scientific name Common mame Scientific name Common name Acer circinatum pussy willow Salix bonplandiana vine maple Salix discolor seepwillow Baccharis glutinosa pussy willow Salix drummondiana drummond's willow Baccharis halimifolia eastern baccharis erect willow Salix eriocephala Baccharis pilularis coyotebush coyote willow Salix exigua Baccharis salicifolia water wally goodding willow mulefat baccharis Baccharis viminea Salix gooddingii Cephalanthus occidentalis Salix hookeriana buttonbush hooker willow Salix humilis prairie willow Cornus amomum silky dogwood sandbar willow Salix interior Cornus drummondii roughleaf dogwood Salix lasiolepis stiff dogwood arroyo willow Cornus foemina lemmon Salix lemmonii ’ s willow Cornus racemosa gray dogwood roundleaf dogwood shining willow Cornus rugosa Salix lucida Salix lucida ssp. lasiandra Cornus sericea ssp sericea pacific willow red-osier dogwood Salix lutea yellow willow black twinberry Lonicera involucrata Salix nigra Physocarpus capitatus pacific ninebark black willow laural willow Salix pentandra Physocarpus opulifolius common ninebark Salix purpurea Populus angustifolia purpleosier willow narrowleaf cottonwood Populus balsamifera ’ s willow Salix scouleriana scouler balsam poplar sitka willow eastern cottonwood Populus deltoides Salix sitchensis Populus fremontii Sambucus canadensis american elder fremont cottonwood Sambucus cerulea Populus trichocarpa black cottonwood mexican elder ssp. mexicana baldhip rose Rosa gymnocarpa Sambucus racemosa red elderberry nootka rose Rosa nutkana Sambucus racemosa red elder swamp rose Rosa palustris ssp. pubens virginia rose Rosa virginiana Spiraea alba meadowsweet spirea Rosa woodsii woods rose douglas spirea Spiraea douglasii allegheny blackberry Rubus allegheniensis snowberry Symphoricarpos albus Rubus idaeus red raspberry Viburnum dentatum arrowwood ssp.strigosus hubblebush viburnam Viburnum lantanoides Rubus spectabilis salmonberry Viburnum lentago nannyberry Salix X cottetii dwarf willow peachleaf willow Salix amygdaloides 16B – 36 (210-vi-EFH, December 1996)

274 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook Woody plants with poor or fair rooting ability from unrooted cuttings Table 16B – 3 Scientific name Common name Scientific name Common mame dwarf maple Fraxinus pennsylvanica green ash Acer glabrum boxelder Gleditsia triacanthos honeylocust Acer negundo hibiscus Acer rubrum red maple Hibiscus aculeatus halberd-leaf Hibiscus laevis Acer saccharinum silver maple marshmallow pacific alder Alnus pacifica common rose mallow Hibiscus moscheutos red alder Alnus rubra hibiscus Hibiscus moscheutos Alnus serrulata smooth alder ssp. lasiocarpos sitka alder Alnus viridis ssp.sinuata Holodiscus discolor oceanspray cusick's serviceberry Amelanchier alnifolia Ilex coriacea sweet gallberry var cusickii possomhaw Ilex decidua false indigo Amorpha fruitcosa Ilex glabra bitter gallberrry red chokeberry Aronia arbutifolia Ilex opaca american holly Asimina triloba pawpaw Ilex verticillata winterberry river birch Betula nigra yaupon Ilex vomitoria Betula papyrifera paper birch Juglans nigra black walnut Betula pumila low birch Juniperus virginiana eastern redcedar Carpinis caroliniana american hornbeam leucothoe Leucothoe axillaris Carya aquatica water hickory spicebush Lindera benzoin Carya cordiformis bitternut hickory Liquidambar styraciflua sweetgum shagbark hickory Carya ovata Liriodendron tulipifera tulip poplar Catalpa bignonioides southern catalpa Lyonia lucida fetterbush sugarberry Celtis laevigata sweetbay Magnolia virginiana hackberry Celtis occidentalis southern waxmyrtle Myrica cerifera Cercis canadensis redbud Nyssa aquatica swamp tupelo fringetree Chionanthus virginicus Nyssa ogeeche ogeeche lime Clematis ligusticifolia western clematis blackgum Nyssa sylvatica Clethera alnifolia sweet pepperbush Ostrya virginiana hophornbeam Cornus florida flowering dogwood redbay Persea borbonia Cornus stricta swamp dogwood Philadelphus lewesii lewis mockorange Crataegus douglasii douglas' hawthorn Physocarpus malvaceus mallow ninebark Crataegus mollis downy hawthorn common ninebark Physocarpus opulifolius Cyrilla racemiflora titi Pinus taeda loblolly pine Diospyros virginiana persimmon Planera aquatica water elm silverberry Dlaeagnus commutata Platanus occidentalis sycamore swamp privet Forestiera acuminata Populus tremuloides quaking aspen Fraxinus caroliniana carolina ash wild plum Prunus angustifolia Fraxinus latifolia oregon ash (210-vi-EFH, December 1996) 37 – 16B

275 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook – Woody plants with poor or fair rooting ability from unrooted cuttings — Continued Table 16B 3 Common name Scientific name Common mame Scientific name common chokecherry coast azalea Rhododendron atlanticum Prunus virginiana Quercus alba white oak Rhododendron viscosum swamp azalea flameleaf sumac Quercus bicolor swamp white oak Rhus copallina Quercus garryana oregon white oak Rhus glabra smooth sumac black locust Quercus laurifolia swamp laurel oak Robinia pseuodoacacia blue elderberry overcup oak Sambucus cerulea Quercus lyrata hardhack spirea Spiraea tomentosa Quercus macrocarpa bur oak Quercus michauxii Styrax americanus Japanese snowbell swamp chestnut oak Quercus nigra bald cypress Taxodium distichum water oak cherrybark oak Quercus pagoda Tsuga canadensis eastern hemlock american elm pin oak Quercus palustris Ulmus americana Viburnum nudum Quercus phellos swamp haw willow oak Quercus shumardii american shumard oak Viburnum trilobum cranberrybush 16B 38 (210-vi-EFH, December 1996) –

276 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook 1/ 1,fac 1,facu indicator 2,upl 3,upl* 1,facw- 2,fac 3,fac- 4,facu 5,fac- 6,facu 7,fac- 8,facu 9facu 1,facu- 2,facw 3,facw 6,fac+ 7,facw 8,facw 0,facw C,ni H,ni 1,facu- Wetland o 2 1" Max. oh 2 h 0 0 0 0 0 Min. 0 season Flood good fair fair ance toler- Flood poor poor good fair tion tol- erance poor poor Deposi- poor good poor good ance toler- Shade poor poor poor good fair fair tolerance good good Drought good 6.5 5.5 6.0 prefer- ence 6.0 7.0 6.0 pH sands prefer- ence loams sandy loams sands Soil season yes or non- compe- titive yes yes Warm noncompetitive loams noncompetitive name redtop American beachgrass big bluestem giant reed wildrye sand lovegrass red fescue Common Grasses and forbs useful in conjunction with soil bioengineering and associated systems 4 – Table 16B Scientific name Agrostis alba Ammophila breviligulata Andropogon gerardii Arundo donax Elymus virginicus Eragrostis trichodes Festuca rubra 39 – 16B (210-vi-EFH, December 1996)

277 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook 1/ 2,facu+ 1,facw indicator 2,facw 6,facw 1,fac 2,fac 6,facu- 2,fac+ 3,fac+ 4,fac 5,fac 6,facw 7,fac+ 8,fac 9,fac+ H,ni 6,facw* C,ni H,ni C,ni H,ni 1,facu- Wetland 2,obl o 2 2' 1' Max. 1' oh 2 0 0 h 0 0 Min. 1/2' season all Flood Continued — good good good ance toler- good Flood poor fair fair tion tol- erance Deposi- poor poor ance toler- poor poor Shade poor good good tolerance poor Drought 5.5 prefer- 6.0 ence pH prefer- sandy sands to ence loams to sands loams Soil sandy yes season yes yes or non- compe- titive Warm name limpograss coastal panicgrass deertongue switchgrass seashore paspalum elephant- grass Common Grasses and forbs useful in conjunction with soil bioengineering and associated systems 4 – Table 16B Scientific name Hemarthria altissima Panicum amarulum Panicum clandestinum Panicum virgatum Paspalum vaginatum Pennisetum purpureum (210-vi-EFH, December 1996) – 16B 40

278 Part 650 Chapter 16 Streambank and Shoreline Protection Engineering Field Handbook 1/ 1,facu 1,facu 1,upl 1,obl indicator 2,obl 3,facw+ 4,facw 5,facw 6,facw+ 7,facw 8,obl 9,obl 2,obl 3,obl 6,obl 1,obl Wetland o 2 1" 2' Max. oh 2 0 0 0 h 0 Min. 1/2' all season Flood Continued — fair ance good toler- fair poor poor Flood poor tion tol- erance fair poor poor Deposi- poor ance toler- fair poor Shade poor poor tolerance poor good Drought good fair 6.5 prefer- 6.0 4.3-6.0 poor ence 6.5 6.5 pH loams prefer- loam ence sands to loams loam sands to sands to Soil season yes or non- compe- titive Warm yes yes name Kentucky bluegrass little bluestem Indiangrass prairie cordgrass giant cutgrass Common Grasses and forbs useful in conjunction with soil bioengineering and associated systems 4 – Table 16B Scientific name Poa pratensis Schizachyrium scoparium Sorghastrum nutans Spartina pectinata Zizaniopsis miliacea 41 – 16B (210-vi-EFH, December 1996)

279 Part 650 Streambank and Shoreline Protection Chapter 16 Engineering Field Handbook 1/ ` ̨ 'e ̨ indicator Wetland DGed- ” h Û o QpC 2 ̨ Max. regioK ̨ B æ oh 2 Q ̨ h Min. season Flood Continued — ance toler- Flood tion tol- erance Deposi- ance toler- Shade tolerance Drought prefer- ence pH prefer- ence Soil season or non- compe- titive Warm Usually occur in wetlands (67-99%), but Usually occur in nonwetlands (67-99%), but occasionally found in wetlands (1-33%) — Occur almost always (99%) under naturl conditions in wetlands. — Occur in wetlands in another region, but occur almost always (99%) under natural conditions in nonwetlands im — — Equally likely to occur in wetlands or nonwetlands — name Common Grasses and forbs useful in conjunction with soil bioengineering and associated systems 4 Facultative (34-66%). Facultative upland Facultative wetland occasionally found in nonwetlands. Obligate wetland Obligate upland Qpec%Cs BMeQ nMt Mccur %n wetlands in any region, it is not on the National List. ecological information. determine an indiator status. – Northeast (ME, NH, VT, MA, CT, RI, WV, KY, NY, PA, NJ, MD, DE, VA, OH) Southeast (NC, SC, GA, FL, TN, AL, MS, LA, AR) North Central (MO, IA, MN, MI, WI, IL, IN) North Plains (ND, SD, MT (eastern), WY (eastern)) Central Plains (NE, KS, CO (eastern)) South Plains (TX, OK) Southwest (AZ, NM) Intermountain (NV, UT, CO (western)) Northwest (WA, OR, ID, MT (western), WY (western)) California (Ca) Alaska (AK) Caribbean (PR, VI, CZ, SQ) Hawaii (HI, AQ, GU, IQ, MQ, TQ, WQ, YQ) (negative sign) indicates less frequently found in wetlands. (positive sign) indicates more frequently found in wetlands. (asterisk) indicates wetlands indicators were derived from limited (no indicator) indicates insufficient information was available to 1 2 3 4 5 6 7 8 9 0 A C H fac facu facw obl upl – + * ni Region code number or letter: Indicator categories (estimated probability): Frequency of occurrence: Table 16B Scientific name 1/ Wetland indicator terms (from USDI Fish and Wildlife Service's National List of Plant Species That Occur in Wetlands, 1988): – 42 (210-vi-EFH, December 1996) 16B

280 BMP Standards and Specifications Rooftop Disconnection 7. 0 Rooftop Disconnection Definition: Rooftop Disconnection involves managing runoff close to its source by intercepting, infiltrating, filtering, treating to or reusing it as it mo ves fro m the rooftop the drainage system. Rooftop D isconnection practices can be used to reduce the volume of runoff that enters the combined or separate storm sewer systems. Rooftop a portion of Disconnection reduces the v). In (RP Resource Protection Volume order to meet requirements for larger storm Photo courtesy of Montgomery County, M aryland events , Rooftop Discon nection must be combined with additional practices. Rooftop impervious areas may be disconnected from the drainage system and flow to other BMPs for management, including: • Sheet flow to a filter strip or open space (see Specification 9. ) y small infiltration practices such as dry wells or french drains (see Infiltrat ion b • 1. ) Specification 2. • Filtration by rain gardens or stormwater planters (see S pecification ) • Storage and reuse with a rain barrel, cistern or other storage system (see Specifica tion 5 . ) 3.06.2. 03/2013 7- 1

281 BMP Standards and Specifications Rooftop Disconnection . Roof Figure Disconnection with Alternative Runoff Reduction Practices top . 7.1 3.06.2. 03/2013 7- 2

282 BMP Standards and Specifications Rooftop Disconnection 7.1 Rooftop Disconnection Stormwater Credit Calculations soil Rooftop Disconnection receives a variable retention volume credit (Rv) depending upon t he Table 7.1 ) . R etention volume credit for R ooftop Disconnection directed toward a compost type ( will be determined based upon the soil type adjustment after soil amendments. amended soil area Pollutant reduction credits are based upon the load redu ced through retention. Table 7.1 Rooftop Disconnection Performance Credits Runoff Reduction 0% Retention Allowance or A/B Soil - RPv Compost Amended C Soil 2 5 % Annual Runoff Reduction RPv - C/D Soil 10 % Annual Runoff Reduction Cv 10% of RPv Allowance 1% of RPv Allowance Fv Pollutant Reduction TN Reduction 100% of Load Reduction TP Reduction 100% of Load Reduction TSS Reduction 100% of Load Reduction To receive the credits above, Rooftop Disconnection must be designed in accordance with the Section Design Criteria. Disconnection 7. 6 Rooftop cri teria detailed in 3.06.2. 03/2013 7- 3

283 BMP Standards and Specifications Rooftop Disconnection 7.2 Rooftop Disconnection Design Summary Table 7.2 summarizes design criteria for Rooftop Disconnection. For more detail, consult Sections 7.3 through 7.7. Sections 7.8 and 7.9 desc ribe Rooftop Disconnection construction and maintenance criteria . Table 7.2 Rooftop Disconnection Design Summary Minimum disconnection area dimensions = 15ft. x 15 ft. • • Unreinforced grade <2%; turf reinforced grade <5% Feasibility • All soil t ypes eligible (Section 7.3) • Maximum 1,000 sq.ft. rooftop per disconnection • Grade <1%, setback from foundation minimum of 5 ft. Conveyance • Safely convey RPv, Cv, Fv (Section 7.4) Provide turf reinforcement as necessary • Pretreatment r required prior to at • e Downspout energy dissip (Section 7.5) disconnection area Maximum 1,000 sq.ft. rooftop per disconnection • • Maximum rooftop = twice disconnection area Design Dimensions • Disconnection area trapezoidal (Section 7.6) • Minimum width at point of discharge to disconnection area = 15 ft. No impervious areas within disconnection area • Other Design Elements • Use sensitive area protection to prevent compaction during (Section 7.6) construction Landscaping (Section 7.7) • Disconnection area must be vegetated Feasibility Criteria 7.3 Rooftop Disconnection family , mult i- is ideal for use on commercial, institutional, municipal isconnection Rooftop D resident ial -family residential buildings. Key constraints with Rooftop Disconnection and single include available space, soil permeability, and soil compaction. For Rooftop D isconnection the following feasibility criteria exist: To account for runoff reduction, t area at disconnection he available pervious Space. Required feet long the point of discharge must be at least 15 feet wide and 15 for any downspout, area regardless of rooftop area collected disconnection length may be increased as pervious . The credit, but the width must be kept at a minimum of 15 needed to increase the runoff reduction ate residential lot, its existence and purpose should feet. When the disconnection occurs on a priv is as follows: “A minimum be noted on the deed of record. A sample Record Plan note unobstructed pervious, vegetated area of fifteen feet wide by fifteen feet long be provided should ”. to allow for runoff reduction at each downspout conveying roof runoff 7- 4 3.06.2. 03/2013

284 BMP Standards and Specifications Rooftop Disconnection is best applied when the grade of the receiving Site Topography. Rooftop D isconnection . The slope of the receiving pervious area is less than 2% , or less than 5 % with turf reinforcement orcement may include Turf reinf be graded away from any building foundations. areas must appropriate reinforcing materials that are confirmed by the designer to be non -erosive for the specific characteristics and flow rates anticipated at each individual application, and acceptable to the plan approving authority. Soils. Rooftop D isconnection can be used on any post -construction Hydrologic Soil Group. For soil amendments such as compost sites in Hydrologic Soil Group (HSG) C or D, may be used to upgrade the HSG and increase the runoff reduction credit . Also, the erodibility of soils must be considered when designing disconnection practices . may not area exceed rooftop treated Contributing Drainage Area. The maximum impervious . 1,000 sq. ft. per disconnection Setba If the grade of the receiving area is less than 1%, downspouts must be e xtend ed 5 ft. cks. . Note that the downspout extension of 5 feet is intended for simple away from building foundations. The use of a dry well or french drain adjacent to an in -ground ba sement or finished floor area should be carefully designed and coordinated with the design of the structure’s water - proofing system (foundation drains, etc.), or avoided altogether. 7.4 Rooftop Disconnection Conveyance Criteria areas disconnection Rooftop design storm events (RPv, be designed to safely convey all must Cv, Fv) over the receiving area without causing erosion. In some applications, turf reinforcement matting or other appropriate reinforcing materials may be needed to prevent during larger design storms. erosion of the pervious area anticipated 7.5 Pretreatment Criteria Rooftop Disconnection Pretreatment is not needed for Rooftop Disconnection ; however, a transition area must be provided between the downspout discharge point and the disco A downspout nnection area. energy dissipater shall be located at the discharge point of the downspout. If the grade of the xtend . ed 5 ft. away from building receiving area is less than 1%, downspouts must be e 3.06.2. 03/2013 7- 5

285 BMP Standards and Specifications Rooftop Disconnection 7.6 Disconnection Design Crite ria Rooftop rooftop a rea treated may not The maximum impervious 1,000 sq. ft. per disconnection . exceed The contributing roof area may be no more than twice the disconnection area top (i.e. disconnection of a 1,000 square foot rooftop requires at least 500 square feet of pervious disconnection area). The disconnection area must be trapezoidal. The minimum width at the point of discharge from the downspout to the disconnection area is 15 feet. Table 7.3 Rooftop Disconnection Area Design Dimensions Pervious Pervious Rootop Area Pervious (sq.ft.) Disconnection Width Disconnection Width Disconnection Length (ft.) (ft.) (ft.) at at point of discharge downstream 15 15 15 Up to 250 15 16 16 250 - 500 500 750 15 - 21 21 1,000 750 - 15 25 25 Impervious areas m ay not be constructed within the area designated as the pervious disconnection area. The pervious disconnection area must be stabilized from erosion with vegetation (see Table 7.3 Recommended vegetation for pervious disconnection areas). must be taken not to compact the receiving pervious area. To help During site cons truction, care prevent soil compaction, heavy vehicular and foot traffic should be kept out of the receiving pervious area both during and after construction. This can be accomplished by cl early delineating to receive disconnected runoff on all development plans and protecting them the pervious areas sensitive area protection details prior to the start of land disturbing activities. in accordance wit h must be amended or aerated post -construction to increase If compaction occurs, the soils permeabilit y. Rooftop Disconnection Landscaping Criteria 7.7 All pervious disconnection areas receiving rooftop runoff must be stabilized to prevent erosion or transport of sediment to receiving practic es or drainage systems. Several types of grasses Designers should ensure 7.3. listed in appropriate for Rooftop D isconnection areas are Table that the maximum flow velocities do not exceed the values listed in the table for the selected the specific site slope. and grass species 3.06.2. 03/2013 7- 6

286 BMP Standards and Specifications Rooftop Disconnection Table 7.4. Recommended vegetation for pervious disconnection areas. Maximum Velocity (ft/s) Vegetation Type Slope (%) Erosion resistant soil Easily Eroded Soil Kentucky 0 - 5 7 5 Bluegrass 5 - 10 6 4 >10 3 5 Tall Fescue - 5 6 4 0 Grass Mixture 5 10 - 4 3 Annual and Perennial Rye 0 - 5 4 3 Sod 3 4 61, 1954; - Source: USDA, TP Stormwater Design City of Roanoke Virginia Manual, 2008 . Rooftop Disconnection Construction Sequence 7.8 Construction Sequence for Rooftop Disco nnection. For Rooftop D isconnection to a pervious area, the pervious area can be within the limits of disturbance during construction; however, t he following procedures be followed during construction: must • Before site work begins, the receiving pervious disconnection area boundaries must be clearly marked and protected in accordance with sensitive area protection details . • Construction traffic in the disconnection area must be limited to avoid compaction. The n the disconnection area. material stockpile area shall not be located i Construction runoff be directed away from the proposed disconnection area. • must If existing topsoil is stripped during grading, it shall be stockpiled for later use. • • The disconnection area may require light grading to achieve desired elevations and slopes. This grading must be done with tracked vehicles to prevent compaction. be incorporated evenly across the disconnection Topsoil and or compost amendments • must biodegra area, stabilized with seed, and protected from erosion with dable erosion control ting . mat Stormwater • may not be diverted into any compost amended areas until the turf cover is well established and no longer subject to erosion . is c rit ical to review ensure compliance with design Construction Review . Construction standards . Construction reviewers should evaluate the performance of the disconnection after the first big storm to look for evidence of gullies, undercutting or sparse vegetative cover. Spot repairs should be made, as needed. 3.06.2. 03/2013 7- 7

287 BMP Standards and Specifications Rooftop Disconnection Post Construction Verification. Post construction verification may be provided through visual inspection by the construction reviewer. When proper construction of the disconnection area is at the questioned, the construction reviewer may request for s pot grade elevations to be surveyed delineated beginning and end of the s spot grades at interval disconnection area, including necessary to determine that the design criteria has been met. Verify that no impervious surface exists within the pervious disconnection area. Disconnection Maintenance Criteria Rooftop 7.9 ooftop involves the regular lawn or landscaping Maintenance of R areas Disconnection maintenance in the filter path from the roof to the street. In some cases, runoff from a Rooftop Disconnection may be directed to a more natural, undisturbed setting (i.e., where lot grading and clearing is “fingerprinted” and the proposed filter path is protected). or the An Operation and Maintenance Plan for the project will be approved by the Department Delegated Agency prior to project closeout. The Operation and Maintenance Plan will specify or and authorize the Department the property owner’s primary maintenance responsibilities Delegated Agency staff to access the property for maintenance review or corrective action in the event that proper maintenance is not performed. The Operation and Maintenance Plan must ensure that downspouts remain disconnected and pervious filtering/infiltrating areas are not converted to impervious surface or disturbed. Rooftop Disconnection areas that are, or will be, owned and maintained by a joint ownership such as a homeowner’s association must be located in common areas, community open space, -owned property, jointly owned property, or within a recorded easement dedicated to community public use. Whe n the disconnection occurs on a private residential lot, its existence and purpose must be noted on the deed of record. The developer shall provide subsequent h omeowners wit h oftop for Ro a simple document that explains the purpose and routine maintenance needs . Disconnection Operation and Maintenance Plans should clearly outline how vegetation in the Rooftop will be managed in the future. Maintenance of Rooftop Disconnection pervious area Disconnection is driven by annual maintenance reviews that evalua te the condition and performance of the practice. Based on maintenance review results, sp ecific maintenance tasks may be required. Sample Operation and Maintenance Plan Notes include: 1. The [OWNER/HOMEOWNER/LOT OWNER/PROPERTY MAINTENANCE CORPORATION] is re sponsible for maintaining the Rooftop Disconnection area in a pervious, vegetated state having minimum dimensions as shown on the approved Sediment and Stormwater Plan, but in no case less than fifteen feet wide by fifteen feet Turf vegetation shall be maintained at a minimum height of three inches. lo ng. 2. Rooftop disconnection areas shall not be converted to an impervious surface. 3.06.2. 03/2013 7- 8

288 BMP Standards and Specifications Rooftop Disconnection at each downspout discharge point. blocks) shall be maintained (splash dissipaters Energy 3. or its Delegated Age 4. The Department ncy shall have access to private property for the Disconnection area ooftop purposes of maintenance reviews of the R References 7.10 Cit y o f Roanoke Virginia . 2007. Stormwater Design Manual. Department of Planning and nline at: Building and Development. Available o http://www.roanokeva.gov/85256A8D0062AF37/vwContentByKey/47E4E4ABDDC5DA16852 577AD0054958C/$File/Table%20of%20Contents%20%26%20Chapter%201%20Design%20Ma nual%2008.16.10.pdf District Department of Transportation ngineering and E Design (DDOT). In preparation . Manual: Chapter 5- Low Impact Development. Hathaway, J.M. and Hunt, W.F. 2006. Level Spreaders: Overview, Design, and Maintenance. Urban Waterways Design Series. North Carolina Cooperative Extension Service. Raleigh, NC. Available online: http://www.bae.ncsu.edu/stormwater/PublicationFiles/LevelSpreaders2006.pdf United States Department of Agriculture (USDA). 1954. Handbook of channel design for soil and water conservation. SCS -TP -61. Washington, DC. Available online: http://www.wsi.nrcs.u sda.gov/products/w2q/h&h/docs/TRs_TPs/TP_61.pdf Level Spreader Design Guidelines. North Carolina Division of Van Der Wiele, C.F. 2007. Water Quality. Raleigh, NC. Available online: http://h2o.enr.state.nc.us/su/documents/ -3.pdf LevelSpreaderGuidance_Final_ Virginia DCR Stormwater Design Specification No. 1: Rooftop (Impervious Surface) Disconnection, Version 1.9, March 1, 2011 3.06.2. 03/2013 7- 9

289 BMP Standards and Specifications Vegetated Channels Channels 8.0 Vegetated Vegetated open channels Definition: that are designed to convey design storm the volume d Cv, may also (RPv an ). convey the Fv as designed Design variants include:  8- A Bioswale  8- B Grassed Channel Vegetated s systems sh all n ot be designed to provide storm water detention. Vegetated channel can provide a modest amount of runoff filtering and volume attenuation within the channels stormwater conveyance system resulting in the delivery of less runoff and pollutants than a al system of curb and gutter, storm drain inlets and pipes. The performance of vegetated tradition channels will vary depending on the underlying soil permeability. Their runoff reduction performance can be boosted when compost amendments are a dded to the bottom of the channel . Vegetated channels are a preferable alternative to both curb and gutter and storm drains as a stormwater conveyance system, where , topography , soils , and water table development density permit. 12/18/2014 3.06.2.8- 1

290 BMP Standards and Specifications Vegetated Channels Figure 8.1. Typical Section for Bioswale / Grassed Channel Figure 8.2. Example Check Dam 2 12/18/2014 3.06.2.8-

291 BMP Standards and Specifications Vegetated Channels 8.1 Vegetated Channel Stormwater Credit Calculations Vegetated channels receive a variable annual runoff reduction volume credit depending upon the Table 8.1 ). No additional pollutant removal credit is awarded. specific type employed ( Table 8.1 Vegetated Channel Performance Credits Runoff Reduction 0% Retention Allowance A/B Soil or RPv - Bioswale : 50% Annual Runoff Reduction Compost Amended C Soil Grassed Channel: 20% Annual Runoff Reduction Bioswale: 25% Annual Runoff Reduction C/D Soil RPv - Grassed Channel: 10% Annual Runoff Reduction Cv 10% of RPv Allowance Fv 1% of RPv Allowance Pollutant Reduction TN Reduction 100% of Load Reduction TP Reduction 100% of Load Reduction TSS Reduction 100% of Load Reduction 3 12/18/2014 3.06.2.8-

292 BMP Standards and Specifications Vegetated Channels 8.2 Vegetated Channel Design Summary channels, and Table 8.3 summarizes the materials Table 8.2 summarizes design criteria for vegetated specifications for these practices. For more detail, consult Sections 8.3 through 8.7. Section 6.8 describes practice construction and maintenance criteria. Table 8.2 Vegetated Channel Design Summary Feasibility , but does not qualify as hotspot treatment • Can hotspots convey runoff from (Section 8.3) Must not int ersect groundwater table • Recommended l ongitudinal slopes <4% • Longitudinal slope <1% on C/D soils should be designed as Wet land Swale • Conveyance Must safely convey the Cv storm event . • 8.4) (Section lculated and its impact to the • The area of inundation from the Fv storm event must be ca v egetated c hannel accounted for in the design. Pretreatment from source areas where sediment loading is anticipated • All runoff directed to the practice 8.5) (Section must receive pretreatmen t • Sediment forebay required for co ncentrated flow into vegetated channels • Several pretreatment options may be used. Sizing (Total izing is based upon the conveyance of the design storm flow at a depth of For a Bioswale s • Storage) 4” or less and a residence time of 9 minutes (see Equations 8.1 -8.5 ) (Section 8.6) For a Grassed Channel a maximum design storm depth of 4” is required , and the hydraulic • residence time for concentrated flow entering the Grassed Channel should be a minimum of 5 minutes cluded from . Lateral flow entering the Grassed Channel as sheet flow may be ex residence time calculations Design storm flow depth • based on 50% of RPv peak flow rate and residence time Geometry and for the Resource Protection Volume (RPv) ” 4 • Design Flow Depth: Dimensions • Width : 2’ Minim um width 8.6) (Section • 3:1 or flatter side slopes Side Slopes: Longitudinal slopes <4% unless using check dams • Landscaping • Plant based on velocity limits (Tables 8.5 ) (Section 8.7) • Maintain vegetation in the drainage area to limit sediment loads to the practice. 12/18/2014 4 3.06.2.8-

293 BMP Standards and Specifications Vegetated Channels Ta ble 8.3. Vegetated Channel Materials Specifications Specification Component tolerant, erosion resistant grass. The selection of an appropriate species - - A dense cover of water or mixture of species is based on several factors including climate, soil t ype, topography, and sun or shade tolerance. Grass species should have the following characteristics: Deep root system to resist scouring • Grass branched top growth High stem density with well- • Water ce -toleran • Resistance to being flattened by runoff • recover growth following inundation An ability to • Salt tolerant for any channel receiving runoff from roadways • Check dams • be constructed of a non - erosive material such as wood, gabions, riprap, or must (or other support material concrete. All check dams should be underlain with filte r fabric such as stone) conforming to local design standards. Check Dams - • Wood used for check dams should consist of pressure treated logs or timbers, or water resistant tree species such as cedar, hemlock, swamp oak or locust. • Computation o f check dam material is necessary, based on the surface area and depth used in the design computations . tandard allowances, an energy s When conveyance velocity within the v egetated c hannel exceeds Energy Dissipation t commonly, energy dissipation will be required at the dissipation device must be placed. Mos outlet of a piped stormwater conveyance system. Erosion Control B iodegradable erosion control netting or mats that are durable enough to last at least 12 months must be used, conforming to Fabric aware Erosion and Sediment Control Handbook . Del Vegetated Channel Feasibility Criteria 8.3 Vegetated s are primarily applicable for land uses such as roads, highways, and residential channel i nclude the following: development. Some key feasibility issues for vegetated channels The maximum contributing drainage area to a Contributing Drainage Area. channel vegetated should be 10 acres, and preferably less . The design criteria for maximum channel velocity and depth are applied along the entire length (See Section 8.6) . It is this criteria that will determine the maximum drainage area to a specific vegetated channel. Available Space. Vegetated channel footprints can fit into relatively narrow corridors between utilities, roads, parking areas, or other site constraints. Vegetated channels can be incorporated into linear development applications (e.g., roadways) by utilizing the space typically required for an open section drainage feature. The footprint required will likely be greater than that of a typical conveyance channel, but the benefit of the runoff reduction may reduce the footprint requirements for stormwater management elsewhere on the development site. Site Topography. Vegetated channel s should be used on sites with long itudinal slopes of less th an 4% and lengthen the contact . Check dams can be used to reduce the effective slope of the channel time to enhance filtering and/or infiltration. Longitudinal slopes of less than 2% are ideal and may eliminate the need for check dams. However, channels d esigned with longitudinal slopes of less than 12/18/2014 3.06.2.8- 5

294 BMP Standards and Specifications Vegetated Channels 1% should be monitored carefully during construction to ensure a continuous grade, in order to avoid flat areas with pockets of standing water. Sites with longitudinal slopes less than 1% on HSG ‘C’ or ‘D’ soi W etland Swale . ls should be designed as a Land Uses. Vegetated channels can be used in residential, commercial, or institutional development settings. The linear nature of vegetated channels makes them well -suited to treat highway or low - and -den sity residential road runoff, if there is adequate right -of-way width and distance between medium channels include , as long as drainage area driveways. Typical applications of vegetated the following limitations and design criteria can be met: ght -of-way • Within a roadway ri • Along the margins of small parking lots Oriented from the roof (downspout discharge) to the street • • Disconnecting small impervious areas Vegetated channels are not recommended when residential density exceeds more than 4 dwelling due to a lack of available land and the frequency of driveway crossings along the units per acre, channel. Vegetated channels may provide pre -treatment for other stormwater treatment practices. Hotspot Land Use. Vegetated channels can typically be used to convey runof f from stormwater but do not qualify as a hotspot treatment mechanism. ter hotspots, For a list of designated stormwa hotspot operations , consult Appendix 4 . A minimum amount of hydraulic head is needed to implement Available Hydraulic Head. channels in order to ensure positive drainage and conveyance through the channel. The vegetated channels is measured as the elevation difference between the channel hydraulic head for vegetated inflow and outflow point. Hydraulic Capacity Vegetated channels are t ypically designed as on -line practices which must be . designed with enough capacity to (1) convey runoff from the Conveyance Event (Cv) and Flooding Event (Fv) design storms at non- erosive velocities, and (2) contain the Cv flow within the banks of e. This means that the ’s surface dimensions are more often determined by the need the swal channel , which can be a constraint in the siting of to pass the Cv storm event channels within vegetated existing rights -of-way (e.g., constrained by sidewalks). Depth to Water Table. Designers should ensure that the bottom of vegetated channels is above the seasonally high groundwater table. 12/18/2014 6 3.06.2.8-

295 BMP Standards and Specifications Vegetated Channels vegetated channels . However, vegetated channels Soils. Soil conditions do not constrain the use of oils may incorporate compost amendments in order to improve -permeability s situated on low performance. Interference with underground utilities should be avoided, particularly water and sewer Utilities. lines. from the applicable utility company or agency is required if utili ty lines will run Approval below the vegetated channel. Vegetated channels should be constructed outside the limits of the 100- Floodplains. year floodplain. . Vegetated should be located so as to avoid inputs of Avoidance of Irrigation or Baseflow channels -water, or other dry weather flows. gs, irrigation systems, chlorinated wash sprin 8.4 Vegetated Channel Conveyance Criteria • vegetated channel should be designed such that the design The bottom width and slope of a storm flow inches. V egetated channels shall convey the Cv and Fv depth does not exceed 4- at non- erosive velocities (less than 3 feet -per -second) for the soil and vegetative cover provided. Additionally tractive force calculations may be provided to show that a channel is capable of supporting veloc erosive condition. ities in excess of 3 fps in a non- Check dams may be provided to reduce flow velocities. If check dams are employed, flow depths should inches is be calculated through the check dams to ensure that the maximum flow depth of 4- not violat ed for the RPv. • The bottom width and slope of a Bioswale should be designed such that the design storm 50% of RPv peak flow rate , does not exceed 4 -inches, and the residence time of flow depth, es shall and Fv at the flow within the channel must exceed 9 minutes. Bioswal convey the Cv erosive non- (less than 3 fps) for the soil and vegetative cover provided. velocities Additionally tractive force calculations may be provided to show that a channel is capable of supporting velocities in excess of 3 fps in a non- erosive condition. The analysis should evaluate the flow profile through the channel at normal depth, as well as the flow depth over top of the check dams. Vegetated Channel Pretreatment Criteria 8.5 Pretreatment is required for vegetated chann els to dissipate energy, trap sediments and slow down the runoff velocity to below maximum allowable velocity . The selection of a pre- treatment method depends on whether the channel will experience sheet flow or concentrated flow. Several options are as f ollows: 7 12/18/2014 3.06.2.8-

296 BMP Standards and Specifications Vegetated Channels Grass Filter Strip (sheet flow): Grass filter strips extend from the edge of the pavement to the • flatter. channel at a slope of 5:1 or Alternatively, provide a combined 5 bottom of the vegetated feet of grass filter strip at a maximum 5% (20:1) cro ss slope and 3:1 or flatter side slopes on the vegetated channel. Gravel or Stone Flow Spreaders • located (concentrated flow). The gravel flow spreader may be at curb cuts, downspouts, or other concentrated inflow points, and should have a 2 to 4 inch elev ation drop from a hard- edged surface into the gravel or stone flow spreader . The gravel should extend the entire width of the opening and create a level stone weir at the bottom or treatment elevation of the channel. • (channel flow) . This reinforced or otherwise stabilized cell is located Initial Sediment Forebay channel at the upper end of the vegetated segment with a 2:1 length to width ratio and a storage volume equivalent to at least 15% of the Resource Protection event volume (RPv). Typically a concentrated flow from a pipe or other conveyance system enters a vegetated used when channel. Vegetated Channel Design Criteria 8.6 Channel Geometry . Design guidance regarding the geometry and layout of vegetated channels is provided below : • channels should be designed with a trapezoidal or parabolic cross section. A parabolic Vegetated shape is preferred for aesthetic, maintenance, and hydraulic reasons. • feet wide to ensure that an The bottom width of the channel should be at a minimum of 2 for filtering. adequate surface area exists along the bottom of the channel If a channel will be wider than 8 feet, the designer should incorporate benches, check dams, level spreaders or multi - level cross sections to prevent braiding and erosion along the channel bottom. Veg • channel side slopes should be no steeper than 3H :1V for ease of mowing and routine etated maintenance. Flatter slopes are encouraged, where adequate space is available, to pre - enhance treatment of sheet flows entering the channel. Channel Slope. Design guidance regarding the channel slope of vegetated channels is provided below : • channels with slopes greater than 4% require special design considerations, such as Vegetated inch high check dams (and therefore a drop structures to accommodate greater than 12- flatter effective slope), in order to ensure non- erosive flows. • Longitudinal slopes of less than 2% may eliminate the need for check dams. • Vegetated channels designed with longitudinal slopes of less than 1% should be monitored carefully during construction to ensure a continuous grade, in order to avoid fl at areas with pockets of standing water. Sites with longitudinal slopes less than 1% on HSG ‘C’ or ‘D’ soils should be designed as a • Wetland Swale . 12/18/2014 3.06.2.8- 8

297 BMP Standards and Specifications Vegetated Channels -treatm ent, to break up slopes, and to increase the Check dams. Check dams may be used for pre hydraulic residence time in the channel. Design requirements for check dams are as follows: • In typical spacing, the ponded water at a downhill check dam should not touch the toe of the upstream check dam. • The maximum desired check dam height is 12 inches (for maintenance purposes). Design with check dams with a height greater than 12 inches may be submitted with design calculations showing that the surrounding soils can withstand the tractive forces applied from the increased hydraulic pressure head. Armoring may be needed at the downstream toe of the check dam to prevent erosion. • • Check dams must be firmly anchored into the side -slopes to prevent outflanking; check dams must also be anchored into the channel bot tom so as to prevent hydrostatic head from pushing out the underlying soils. Cv design storm peak flow . • Check dams must be designed with a center weir sized to pass the Each check dam should have a weep hole or similar drainage feature so it can dewater after • storms. Check dams should be composed of wood, concrete, stone, or other non- erodible material . • , however an underdrain (or configured with elevated driveway culverts Check dams may be similar physical structure) must be provided to meet the weep hole requirement above . Check dams for vegetated channels • to reduce the effective slope to less than should be spaced 2%, as indicated below in Table 8.4. Table 8.4. Typical Check Dam (CD) Spacing to Achieve Effective Channel Slope 1 1 of 12 of 12 - inch High Spacing Spacing - inch High 3, 4 (max.) Check to (max.) Check Dams Channel Longitudinal 3, 4 to Create Create an Effective Dams an Slope Effective Slope of 0 to 1% Slope of 2% 200 ft. to 0.5% – – to 1.0% 100 ft. – – 1.5% – 67 ft. to 200 ft. 2.0 % – 50 ft. to 100 ft. 40 ft. to 67 ft. 2.5% 200 ft. 100 ft. 33 ft. to 50 ft. 3.0% 3.5% 30 ft. to 40 ft. 67 ft. to 4.0% 25 ft. 50 ft. 33 ft. 2 4.5% 20 ft. to 30 ft. 40 ft. 2 40 ft. 5.0% 20 ft. to 30 ft. Notes: 1 The spacing dimension is half of the above distances if a 6 -inch check dam is used. 2 Vegetated channels with slopes greater than 4% require special design considerations, such -inch high check dams (and therefo re a flatter as drop structures to accommodate greater than 12 effective slope), in order to ensure non -erosive flows. 3 All check dams require a stone energy dissipater at the downstream toe. 4 Check dams require weep holes at the channel invert. Channels with slopes less than 2% will require multiple w eep holes (at least 3) in each check dam. 9 3.06.2.8- 12/18/2014

298 BMP Standards and Specifications Vegetated Channels All vegetated channels shall require a biodegradable erosion control Material Specifications . that is durable enough to Delaware Erosion and Sediment Control Handbook matting conforming to Recommended material specifications for vegetated channels are shown in last at least 12 months. Table 8.3 . Enhancement using Soil Amendments . Soil compost amendments serve to increase the runoff hen channel. The following design criteria apply w reduction capability of a vegetated soil amendments are used: The soil amend ments should extend over the length and width of the channel bottom, and the • Post Construction Stormwater BMP compost should be incorporated to a depth as outlined in nts . Standards and Specifications for Soil Amendme The amended area will need to be rapidly stabilized with perennial, salt tolerant grass species • if . adjacent to a roadway • vegetated channels on steep slopes, it may be necessary to install a protective biodegradable For t the compost -amended soils. Care must be taken to consider the to protec stabilization matting appropriate erosive characteristics of the amended soils when selecting turf reinforcement matting . Sizing vegetated channels are designed based on a peak rate of . Unlike other stormwater practices, flow . Designers must demonstrate channel conveyance and treatment capacity in accordance with the following guidelines: • Hydraulic capacity should be verified using Manning’s Equation or an accepted equivalent method, such as tractive forces and veg etal retardance. o should be maintained at 4 Design storm flow depth based on 50% of RPv peak flow rate inches or less. Manning’s “n” value for vegetated channels should be 0.2 for flow depths up to 4 inches, o decreasing to 0.03 above 4 inches of flow depth. Peak flow rates for the Cv and Fv storms must be non- erosive (less than 3 fps) , or subject to o -specific analysis of the channel lining material and vegetation. a site - Examples of site 8.7 8.5 below specific analysis ranges can be found in Section Table Vegetated (see Channel Landscaping Criteria ) ; o The Cv peak flow rate must be contained within the channel banks. o If the Fv storm event is not contained within the channel, the area of inundation must be shown. • Calculations for peak flow depth and velocity should reflect any increase in flow along the length of the channel, as appropriate. If a single flow is used, the flow at the outlet should be used. Hydraulic residence times (the time for runoff to travel the full length of the channel) • for both Bioswales and Grassed Channels are computed based upon 50% of the RPv peak flow rate. o For Bioswales, t he hydraulic residence time should be a minimum of 9 minutes for the design storm (Mar et al., 1982; Barrett et al., 1998; Washington State Department of Ecology, 2005). If flow enters the channel at several locations, a 9 minute minimum 10 3.06.2.8- 12/18/2014

299 BMP Standards and Specifications Vegetated Channels hydraulic residence time should be demonstrated for each entry point, using Equations 8.1 – 8.5 below . o For Grassed Channels, the hydraulic residence time for concentrated flow enteri ng the Grassed Channel should be a minimum of 5 minutes for the design storm. Lateral flow entering the Grassed Channel as sheet flow may be ex o from residence cluded , but should be accounted for in the channel depth and velocity time calculations calculat ions. For Grassed Channels, in- line culverts (such as driveway crossings) that do not introduce o -treatment requirements and any new flow can be excluded from concentrated flow pre residence time calculations. For Grassed Channels, pipe length should not be included in residence time calculations. o -line culverts , the proportion of grassed channel flow length o For Grassed Channels with in should be a minimum of 80% of the total flow length. The bottom width of the vegetated ntain the appropriate flow channel is therefore sized to mai geometry as follows: Equation 8.1: Manning’s Equation Where: V = flow velocity (ft./sec.) n = roughness coefficient (0.2, or as appropriate) D flow depth (ft.) (NOTE: D approximates hydraulic radius for shallow flows) = channel slope (ft./ft.) s = Equation 8.2: Continuity Equation = V(WD) Q Where: = design storm peak flow rate (cfs) Q V = design storm flow velocity (ft./sec.) W = channel width (ft.) D = flow depth (ft.) (NOTE: channel width ( ) x depth ( D ) approximates the cross sectional flow area for W shallow flows.) Combining Equations 8.1 and 8.2 , and re -writing them provides a solution for the minimum width: Equation 8.3: Minimum Width 11 3.06.2.8- 12/18/2014

300 BMP Standards and Specifications Vegetated Channels Equation 8.2 for the corresponding velocity provides: Solving Equation 8.4: Corresponding Velocity = Q / WD V The width, slope, or Manning’s “ value can be adjusted to provide an appropriate channel design n” n” for the site conditions. However, if a higher density of grass is used to increase the Manning’s “ value and decrease the resulting channel width, it is important to provide material specifications and Equation 8.5 can construction oversight to ensure that the denser vegetation is actually established. then be used to ensure adequate hydraulic residence time. Equation 8.5: Bioswale Length for Hydraulic Residence Time of 9 minutes (540 seconds) L = 540 V Where: = minimum swale length (ft.) L = flow velocity (ft./sec.) V 8.7 Vegetated Channel Landscaping Criteria All vegetated channels must be stabilized to prevent erosion or transport of sediment to receiving practices or drainage systems. Several appropriate types of grasses appropriate for vegetated channels are listed in Table 8.5. Designers should choose plant species that can withstand both wet and dry periods and relatively high velocity flows for planting within the channel. Designers should ensure that the maximum flow velocities do not exceed the values listed in the table for the selected grass species and the specific site slope. 12/18/2014 3.06.2.8- 12

301 BMP Standards and Specifications Vegetated Channels Table 8.5. Recommended vegetation for vegetated channels . Slope (%) Maximum Velocity (ft/s) Vegetation Type Erosion resistant soil Easily Eroded Soil Bermuda Grass 0 - 5 8 6 - 10 7 5 5 4 >10 6 Kentucky Bluegrass 5 0 5 - 7 - 10 6 4 5 >10 3 5 s Tall Fescue Gras 0 - 5 4 6 Mixture 5 - 10 4 3 Annual and Perennial Rye - 5 4 3 0 - Source: USDA, TP 61, 1954 Vegetation not contained in Table 8.5 will be evaluated on a case -by-case basis. chan nels If roadway salt will be applied to the contributing drainage area, vegetated should be planted with salt- tolerant plant species. Landscape design shall specify proper grass species based on specific site, soils and hydric the channel. conditions present along channels should be seeded at Vegetated 70% vegetated cover for project such a density to achieve a completion and 90% vegetated cover after the second growing season. Taller and denser grasses are preferable, although the species is less important than good stabilization and dense vegetative cover. Vegetated hould be seeded and not sodded. Seeding establishes deeper roots and sod may channels s Vegetated have muck soil that is not conducive to infiltration. channels should be protected by a biodegradable erosion control matting to provide immediate stabilization of the c hannel bed and banks. 8.8 Vegetated Channel Construction Sequence Design Notes. Channel invert and tops of banks are to be shown in plan and profile views. A cross sectional view of each configuration shoul d be shown. Completed limits of grading shoul d be shown. T he transition at the entrance and outfall is to be clearly shown on plan and profile views. The following is a typical construction sequence to properly install Vegetated Channel Installation. vegetated channels, although steps may be modifi ed to reflect different site conditions or design 12/18/2014 3.06.2.8- 13

302 BMP Standards and Specifications Vegetated Channels channels should be installed at a time of year that is best to establish turf cover variations. Vegetated without irrigation. Protection during Site Construction . Step 1: vegetated channels shoul d remain outside the Ideally, . However, limit of disturbance during construction to prevent soil compaction by heavy equipment this is seldom practical, given that the channels are a key part of the drainage system at most sites. In these cases, temporary erosion a controls such as dikes, silt fences and other erosion nd sediment control measures should be integrated into the swale design throughout the construction sequence. atting Specifically, barriers should be installed at key check dam locations, and erosion control m d be used to protect the channel . shoul . Installation may only begin after the entire contributing drainage area has been stabilized with Step 2 vegetation. Any accumulation of sediments that does occur within the channel must be removed during the final stages of grading to achieve the design cross -section. Erosion and sediment controls for construction of the channel should be installed as specified in the erosion and sediment control plan. Stormwater flows must not be permitted into the channel until the bottom and side slopes are fully stabilized. Step 3. Grade the vegetated channel to the final dimensions shown on the plan. Excavators or backhoes should work from the sides to grade and excavate the vegetated appropriate channels to the dimensions. Excavating equipment should have scoops with adequate reach so they do not design area. have to sit inside the footprint of the vegetated channel 4 (Optional). Apply soil amendments in accordance with Post Construction Stormwater BMP Step Standards and Specification for Soil Amendments , if specified. . Install check dams and internal pre -treatment features as shown on the plan The top of each Step 5. check dam should be constructed level at the design elevation. Step 6. Seed the bottom and banks of the vegetated channel, and install erosion control matting . 7. Plant landscaping materials as shown in the landscaping plan, and water them weekly during Step the first 2 months. The construction contract should include a care and replacement warranty to ensure that vegetation is properly established and survives during the first growing season following . construction Step 8 . Conduct the final construction inspection and develop a punch list for facility acceptance. 12/18/2014 14 3.06.2.8-

303 BMP Standards and Specifications Vegetated Channels tion . Inspections during construction are needed to Vegetated Channel Construction Inspec channel is built in accordance with these specifications. ensure that the vegetated Some common pitfalls can be avoided by careful construction supervision that focuses on the following key aspects of vegetated channel installatio n: Make sure the desired coverage of turf or erosion control matting has been achieved following • -slopes. construction, both on the channel beds and their contributing side Inspect check dams and pre -treatment structures to make sure they are at correct elevations, are • properly installed, and are working effectively. • Check that outfall protection/energy dissipation measures at concentrated inflow and outflow points are stable. vegetated The real test of a occurs after its first big storm. The post -storm inspection should channel focus on whether the desired sheet flow, shallow concentrated flows or fully concentrated flows assumed in the plan actually occur in the field. Minor adjustments are often needed as part of this post -stor m inspection (e.g., spot re -seeding, gully repair, added armoring at inlets, or realignment of outfalls and check dams). Vegetated Channel Maintenance Criteria 8.9 ted An Operation and Maintenance Plan for the project will be approved by DNREC or the Delega The Operation and Maintenance Plan will specify the property Agency prior to project closeout. owner’s primary maintenance responsibilities and authorize DNREC or Delegated Agency staff to access the property for maintenance review or corrective actio n in the event that proper maintenance is not performed. Vegetated channels that are, or will be, owned and maintained by a joint ownership such as a homeowner’s association must be located in common areas, community open space, community -owned property, j ointly owned property, or within a recorded easement dedicated to public use. Operation and Maintenance Plans should clearly outline how vegetation in the v egetated channel will be managed or harvested in the future. The Operation and Maintenance Plan should schedule a cleanup at least once a year to remove trash and debris. Maintenance of vegetated is driven by annual maintenance reviews that evaluate the channels condition and performance of the practice. Based on maintenance review results, specific maintenance tasks may be r equired. 12/18/2014 15 3.06.2.8-

304 BMP Standards and Specifications Vegetated Channels Channels Table 8.6. Suggested Maintenance Activities and Schedule for Vegetated Maintenance Activity Schedule Mow v egetated channels during the growing season to maintain minimum grass heights • needed As in the 4" to 6" range. . • Ensure that the contributing drainage area, inlets, and facility surface are clear of debris • erform spot -reseeding if where Ensure that the contributing drainage area is stabilized. P needed. Quarterly Remove accumulated -treatment devices, flow sediment and oil/grease from inlets, • pre diversion structures, and overflow structures. Repair undercut and eroded areas at inflow and outflow structures. • Add reinforcement planting to maintain 90% turf cover. Reseed any salt - killed vegetation. • accumulated sand or sediment deposits behind check dams. Remove any • • Inspect upstream and downstream of check dams for evidence of undercutting or erosion, holes. and remove and trash or blockages at weep Examine channel bottom for evidence of erosion, braiding, excessive ponding or dead • Annual inspection grass. Check inflow points for clogging and remove any sediment. • Inspect side slopes and for evidence of any rill or gully erosion and • pretreatment areas repair. Look for any bare soil or sediment sources in the contributing drainage area and stabilize • immediately. Annual inspections are used to trigger maintenance operations such as sediment removal, spot re - vegetation and inlet stabilization. Example maintenance inspection checklists for vegetated channels can be found in Article 5 . 16 12/18/2014 3.06.2.8-

305 BMP Standards and Specifications Vegetated Channels References 8.10 Barrett, Michael E., Michael V. Keblin, Partrick M. Walsh, Joseph F. Malina, Jr., and Randall J. Charbeneau. 1998. Evaluation of the Performance of Permanent Runoff Controls: Summary and portation Research Bureau of Engineering Research. The Conclusions. Center for Trans University of Texas at Austin. Available online at: http://www.utexas.edu/research/ctr/pdf_reports/2954_3F.pdf Haan, C.T., Barfield, B.J., and Hayes, J.C. Design Hydrology and Sedimentology for Small Catchments . Academic Press, New York, 1994. Mar, B.W., R.R. Horner, J.F. Ferguson, D.E. Spyridakis, E.B. Welch. 1982. Summary ̈C Highway . Runoff Water Quality Study, 1977 ̈C 1982. WA RD 39.16. September, 1982 ginia, Stormwater Design Manual. Roanoke Vir 2008. Stormwater Management Design Manual. Department of Planning Building and Development. Roanoke, Virginia. USDA. 1954. Handbook of Channel of Design for Soil and Water Conservation. Stillwater Outdoor Experiment Station. SCS Hydraulic Laboratory and the Oklahoma Agricultural -61, Washington, -TP DC. Washington State Department of Ecology. 2005. Stormwater Manual for Western Washington. State of Washington Department of Ecology. Available online at: http://www.ecy.wa.gov/programs/wq/stormwater/manual.html 17 12/18/2014 3.06.2.8-

306 ions BMP Standards and Specificat Sheet Flow to Filter Strip or Open Space 9. 0 Sheet Flow to Filter Strip or Open Space Definition: vegetated areas that treat Filter strips are adjacent delivered from sheet flow impervious and managed turf areas by runoff velocities and allowing ing slow tle to set sediment and attached pollutants and/or be filtered by the vegetation. The two design variants o f filter strips are and Vegetated Filter Strips Conserved Open Space . The design, installation, and management of these design variants are quite different, as outlined in this specificat ion. In both instances, stormwater must enter the filter strip or conserved open space as sheet flow. If the inflow is from a pipe or channel, an engineered level spreader must be designed in accordance with the criteria contained herein to convert the co ncentrated flow to sheet flow. Applicable practices include:  9- A. Sheet Flow to Vegetated Filter Strip  Conserved Open Space 9- B. Sheet Flow to Vegetated v). In order to (RP Sheet flow practices reduce a portion of the Resource Protection Volume , sheet flow req practices must be combined with uirements for larger storm events meet addit ional pract ices. 3.06.2. 03/2013 9- 1

307 BMP Standards and Specificat Sheet Flow to Filter Strip or Open Space ions or Conserved Open Space Figure 9. 1. Sheet Flow To Vegetated Filter Strip 3.06.2. 03/2013 9- 2

308 BMP Standards and Specificat Sheet Flow to Filter Strip or Open Space ions Sheet Flow Stormwater Credit Calculations 9.1 Sheet flow p ractices receive varying retention volume credit (Rv) depending upon the specific type employed ( Table 9.1 ) . No additional pollutant removal credit is awarded. 9.1(a) Sheet Flow to Vegetated Filter Strip Performance Credits Runoff Reduction 0% Retention A llowance Turf: 25% Annual Runoff Reduction - A/B Soil or RPv Compost Amended C Soil Forest: 40% Annual Runoff Reduction Turf: 10% Annual Runoff Reduction - Forest: 20% Annual Runoff Reduction C/D Soil RPv Cv 10% of RPv Allowance 1% of RPv Allowance Fv Pollutant Reduction 100% of Load Reduction TN Reduction (max. 20% Removal Efficiency) 100% of Load Reduction TP Reduction (max. 20% Removal Efficiency) 100% of Load Reduction TSS Reduct ion (max. 80% Removal Efficiency) 9 .1(b) Sheet Flow to Vegetated Open Space Performance Credits Runoff Reduction Retention Allowance 0% A/B Soil or RPv - Turf: 50% Annual Runoff Reduction Forest: 65% Annual Runoff Reduction Compost Amended C Soi l Turf: 20% Annual Runoff Reduction - C/D Soil Forest: 40% Annual Runoff Reduction RPv Cv 10% of RPv Allowance Fv 1% of RPv Allowance Pollutant Reduction TN Re duction 100% of Load Reduction 100% of Load Reduction TP Reduction 100% of Load Reduction TSS Reduction 3.06.2. 03/2013 9- 3

309 BMP Standards and Specificat Sheet Flow to Filter Strip or Open Space ions *For annual reduction practices, the annual reduction percentage is converted to an event runo ff must be designed The sheet flow practices described above using the guidance detailed in Design Criteria. 9. 6 Sheet Flow Section 9.2 Sheet Flow Design Summary . For more detail, consult Sections Table 9.2 summarizes design criteria for sheetflow practices 9.7. Sections 9.8 and 9.9 describe 9.3 through practice construction and maintenance criteria. Summary 9 .2 Sheet Flow Design Table Filter Strips Sheet Flow to Open Space Typically < 5 ,000 sf impervious cover Hydrologically Connected areas • Max. 1% slope • Max. 8% slopes all soils except • Appropriate for all soils • Appropriate for fill, but runoff reduction except fill, but runoff Feasibility dependent on soil type. reduction dependent on (Section 9.3) soil type. Cannot receive hotspot runoff • pot Cannot receive hots • • Does not include jurisdictional runoff wetlands • Does not include jurisdictional wetlands Must receive sheet flow. • Can be achieved by receiving a relatively short flow path (<150’ • Conveyance pervious or pervious surfaces), or im <75’ (Section 9.4) Can use an engineered level spreader for concentrated flows (Section • 9.6) Pretreatment Not required .5) (Section 9 Minimum Area dependent on slope and Length d ependent on slope and practice Dimensions impervious cover in CDA option (See Tables 9.3 and 9.4) .6) (Section 9 Gravel • diaphragm at the top of the slope for sheet flow applications. Other Design Engineered level spreader for concentrated flow • Elements Permeable berm at the toe of slope of filter strips • n 9 (Sectio .6) • Compost amendments when applied on C soils to increase soil permeability vegetated filter Achieve 90% coverage with herbaceous materials for • open space. vegetated strips and • Create an invasive species plan, and damage no native species for all conservation areas. dscaping Lan 9.7) (Section ed open conserv • Requires 80% tree canopy for forested fi lter strips and space. • Specific criteria for reforestation. • Maximum velocity versus species type in Table 9. 5. 3.06.2. 03/2013 9- 4

310 BMP Standards and Specificat Sheet Flow to Filter Strip or Open Space ions Sheet Flow Feasibility Criteria 9.3 Open Space can be employed Sheet Flow to a Filter Strip or on commercial, institutional, Key constraints buildings. municipal , mult i- family residential and single -family residential oil compaction. available space, soil permeability, s include Filter Strips Vegetated Filter strips are best suited to treat runoff from small segments of impervio us cover (usually less than 5 ,000 s q. ft.) adjacent to road shoulders, small parking lots and rooftops. Filter strip s may also be used as pretreatment for swale, bioretention , or another stormwater practice such as a bio infiltration areas. If sufficient pervious area is available at the site, larger areas of impervious cover can be treated by filter strips, using an engineered level spreader to recreate sheet flow. Filter s trips are also well suited to treat runoff from turf -intensive land uses, such as the managed turf areas of sports fields, golf courses, and parkland. Filter strips tend to have more linear greater and configurations cross -slopes than areas that qualify as “Conserved Open Space”. Strips Filter Forested t of Forested strips are a subse filter Vegetated Filter Strips in which the vegetation cover consists mostly of established tree species with an organic duff layer having greater hydrologic storage non- capacity than a forested filter strip. Runoff through a forested filter strip would be more likely to occur as interflow than as true surface runoff. Conserved Open Space The most common design applications of Conserved Open S pace are on sites that are hydrologically connected to a protected stream buffer, wetland buffer, floodplain, fores t component of the is an ideal conservation area, or other protected lands. Conserved Open Space flow. Care should be , which normally receives runoff as sheet "outer zone" of a stream buffer taken to locate all energy dissipaters or flow spreading devices outside of the protected area. cross a less linear configuration and flatter Conserved Open Space generally has -slope than Vegetated Filter Strips . Runoff reduction in Conserved Open Space is achieved mainly through storage and/or extended residence time. These areas therefore require minimal slope or even Similar to Vegetated Filter Strips slight sump conditions to allow shallow ponding to occur. , Conserved Open Space can be either in the form of turf vegetation or preserved forested areas. Both Vegetated Filter Strips and Conserved Open Space must meet the following requirements: Maximum slope for Vegetated is 8%, in order to maintain sheet flow Filter Strips Slopes . • Maximum slope for Conserved Open Space is 1%. he In addit io n, t through the practice. overall contributing drainage area must likewise be relatively flat to ensure sheet flow draining into the filter. Where this is not possible, alternative measures, such as an engineered level spreader, can be used. 3.06.2. 03/2013 9- 5

311 BMP Standards and Specificat Sheet Flow to Filter Strip or Open Space ions • Soils . Vegetated Filter Strips and C onserved Open Space are appropriate for all soil types , material except fill . As it applies to this practice, fill is defined as any placed soil that The runoff reduction rate, however, requires compaction to meet a design grade or elevation. is dependent on the underlying Hydrologic Soil Groups (see 9.1 above) and whether Table soils receive compost amendments . • Hotspot Land Uses . Vegetated Filter Strips and Conserved Open Space should not receive hotspot runoff, since the infiltrated runoff could c ause gr oundwater contamination. . Underground pipes and conduits that cross a Vegetated • Proximity of Underground Utilities Strip or Filter Conserved Open Space are acceptable. • Jurisdictional Wetlands. Restrictions may apply when these practices are located adjacent to jurisdictional wetlands that are sensitive to increased inputs of stormwater runoff (e.g., bogs and fens). 9.4 Sheet Flow Conveyance Criteria Vegetated Filter Strips and Conserved Open Space are used to treat very small drainage areas of a few acres or less. The limiting design factor is the length of flow directed to the filter . As a rule, flow for impervious surfaces, and 150 feet feet of flo w length 75 after concentrate tends to for pervious surfaces (Claytor, 1996). ves too rapidly to be When flow concentrates, it mo effectively treated , unless an engineered level spreader is used. 9.5 Sheet Flow Pretreatment Criteria Conserved Open Space. Pretreatment is not needed for Sheet Flow to Vegetated Filter Strips or Sheet Flow Design Criteria 9.6 Fo r Vegetated Filter Strips , the following minimum lengths apply (length is measured in direction of flow) : Minimum Length of Filter Strips Table 9. 3 Slope of Filter Strip Minimum Length - 3% 25 feet < 50 feet 3% - 8 % The first 10 feet of filter must be 2% or less in all cases. For Conserved Open Space, the following minimum area a Table 9.4 Minimum Area of Conserved Open Space Slope of Area Minimum Open Space 1% 1:1 equivalent to impervious Max area in CDA 3.06.2. 03/2013 9- 6

312 BMP Standards and Specificat Sheet Flow to Filter Strip or Open Space ions be necessary or required as part of a filter strip or The following accessory structures may conserved open space: Gravel Diaphragms A gravel diaphragm at the top of the slope is required for both filter strips and conserved open space. The gravel diaphragm is created by excavating a 2 -foot w ide and 1- foot deep trench that runs on the same contour at the top of the filter strip. The diaphragm serves two purposes. First, it acts as a pretreatment device, settling out sediment particles before they reach the practice. ilter strip. Second, it acts as a level spreader, maintaining sheet flow as runoff flows over the f The flow should travel over the impervious area and to the practice as sheet flow and then • drop at least 3 inches onto the gravel diaphragm. The drop helps to prevent runoff from running laterally along the pavement edge, where grit and debris tend to build up (thus allowing by -pass of the Filter Strip). A layer of filter fabric should be placed between the gravel and the underlying soil trench. • If the contributing drainage area is st eep (6% slope or greater), then larger stone should be • used in the diaphragm. If the contributing drainage area is solely turf (e.g., sports field), then the gravel diaphragm • may be eliminated. Engineered Level Spreaders following design criteria based The design of engineered level spr eaders should conform to the recommendations of Hathaway and Hunt (2006) on -erosive sheet flow , in order to ensure non At times, it may be necessary to include a bypass structure (see Figure into the vegetated area. 9.1 above ) that diverts the design storm to the level spreader, and bypasses the larger storm Open Space events around the Vegetated Filter Strip or Conserved through an improved channel. An alternative approach would be to direct th e entire flow through a stilli ng basin energy dissipat or and then a level spreader such that the entire Conveyance Event (Cv) storm for the) is discharged as sheet flow through the buffer. 9.4 , Key design elements of the engineered level spreader, as provided in Figures 9.3 and inclu de the following: The length of the level spreader should be determined by the type of filter area and the design • flow: o 13 feet of level spreader length per every 1 cubic foot per second (cfs) of inflow for discharges to a f strip or n area; turf conservatio ilter o 40 feet of level spreader length per every 1 cfs of inflow when the spreader discharges to a forested conservation area (Hathaway and Hunt, 2006). o The minimum level spreader length is 13 feet and the maximum is 130 feet. o preader length, the peak discharge shall be ning the level s For the purposes of determi inch/hour. determined using the Rational Equation with an intensity of 2.7- 3.06.2. 03/2013 9- 7

313 BMP Standards and Specificat Sheet Flow to Filter Strip or Open Space ions The level spreader lip should be concrete, wood or pre- fabricated metal, with a well - • anchored footer, or other accepted rigid, non -erodible material. The ends of the level spreader section should be tied back into the slope to avoid scouring • around the ends of the level spreader; otherwise, short -circuiting of the facility could create erosion. der channel on the up -stream side of the level lip should be three The width o f the level sprea • times the diameter of the inflow pipe, and the depth should be 9 inches or one- half the culvert diameter, whichever is greater. Figure 9.3: Example Level Spreader 3.06.2. 03/2013 9- 8

314 BMP Standards and Specificat Sheet Flow to Filter Strip or Open Space ions Permeable Berm Veg etated Filter Strip s should be designed with a per meable berm at the toe of the filter strip to create a shallow ponding area. Runoff ponds behind the berm and gradually flows through outlet pipes in the berm or through a gravel lens in the berm with a per forated pipe. During larger et al., overtop the berm (Cappiella The permeable berm should have 2006). storms, runoff may the following properties: A wide and shallow trench, 6 to 12 inches deep, should be excavated at the upstream toe of • the berm, paralle l with the contours. • Media for the berm should consist of 40% excavated soil, 40% sand, and 20% pea gravel. • The berm 6 to 12 inches high should be located downgradient of the excavated depression and should have gentle side slopes to promote easy mowing (C appiella et al ., 2006). • Stone may be needed to armor the top of berm to handle extreme storm events. berm is not needed when vegetated filter strips are used as pretreatment to A permeable • another stormwater practice. Compost Soil Amendments Compost soil amendments enhance the runoff reduction capability of a Vegetated Filter Strip can or Conserved Open Space when located on hydrologic soil group C, subject to the following design requirements: The compost amendments should extend over the full length and width of the vegetated area. • The amount of approved compost material and the depth to which it must be incorporated is • Specification 14 , Soil Amendments outlined in . • The amended area must be raked to achieve the most level slope possible without using hea vy construction equipment, and stabilized with perennial grass and/or herbaceous species prior to receiving runoff discharges.. • If slopes exceed 3%, an erosion control matting should be installed in accordance with the Delaware ESC Handbook to assist with stabilization of the site. and/or gravel diaphragm • Compost amendments should not be incorporated until the ). engineered level spreader are installed (see below 9.7 Impermeable Surface Disconnection Landscaping Criteria should Vegetated Filter Strips be Vegetated Filter Strips. planted at such a density to achieve a 90% grass/herbaceous cover after the second growing season. Vegetated Filter Strips should be establishes deeper roots seeded , not sodded. Seeding , and sod may have muck soil that is not consist of turf grasses, may vegetation cive to infiltration (Wisconsin DNR, 2007). The condu , as long as the primary goal of at meadow grasses, other herbaceous plants, shrubs, and trees . Designers should least 90% coverage with grasses and/or other herbaceous plants is achieved choose vegetation that stabilizes the soil and is salt tolerant. Vegetation at the toe of the filter, where temporary ponding may occur behind the permeable berm, should be able to withstand both wet and dry periods. The planting areas can be divided into zones to account for differences 3.06.2. 03/2013 9- 9

315 BMP Standards and Specificat Sheet Flow to Filter Strip or Open Space ions in inundation and slope. grading or clearing of native vegetation is allowed within the Forested Filter Strips . No Forested An Strip . Forested Filter Strips must have at least 80% tree canopy cov erage. Filter invasive species management plan should be developed and approved as part of plan review. Conserved Open Space . No grading or clearing of native vegetation is allowed within the developed and Conserved Open Space. An invasive species management plan should be approved as part of plan review. Conservation Area. In addit ion to the constraints listed for C onserved Open Space Vegetated in section 9.3 above, turf conservation areas must have at least 90 % coverage with grasses and/or other herbaceous plants, although tree coverage in portions is acceptable. Forested Conservation Area. In addit ion to the constraints listed for Conserved Open Space in section 9. 3 above, Forested Conservation Areas must have at least 80 % tree canopy coverage. Open Space ma y At some sites, the proposed Conserved Re -veget ated Conserved Open Space . be not meet the coverage requirements above, may previously disturbed, or may be overrun with invasive plants and vines. In these situations, a landscape architect or horticult uralist should -vegetation or restoration plan for the C onserved Open S prepare a re to achieve the coverage pace forested conservation area. The entire area can be planted with requirements for a turf or a conservation area, for a or with native trees and shrubs herbaceous cover for a vegetated n aforested conservation area. For aforested conservation areas: • Trees and shrubs with deep rooting capabilities are recommended for planting to maximize soil infiltration capacity (PWD, 2007). • Over -plant with seedli ngs for fast establishment and to account for mortality. • Plant larger stock at desired spacing intervals ( 25 for large trees) using random 40 feet to et al ., 2006) . spacing (Cappiella • Plant ground cover or a herbaceous layer to ensure rapid vegetative co ver of the surface area. -vegetated Conserved Open Space shall be ( NOTE: The runoff reduction allowance for Re determined on a case -by-case basis following Departmental review of the proposed landscaping ) plan. Filter Strips a Stabilization. All Vegetated nd re-vegetated Conserved Open Space must be stabilized to prevent erosion or transport of sediment to receiving practices or drainage systems. listed in Table areas are Several types of grasses appropriate for filter strips or turf conservation Des igners should ensure that the maximum flow velocities do not exceed the values listed in 9. 5. the table for the selected grass species and the specific site slope. 3.06.2. 03/2013 9- 10

316 BMP Standards and Specificat Sheet Flow to Filter Strip or Open Space ions Table 9. 5. Recommended vegetation for filter strips and turf conservation areas . Type Vegetation Slope (%) Maximum Velocity (ft/s) Erosion resistant soil Easily Eroded Soil Bermuda Grass - 8 6 0 5 5 10 7 5 - >10 6 4 Kentucky 0 - 5 7 5 Bluegrass 5 - 10 6 4 >10 5 3 Tall Fescue 0 - 5 6 4 Grass Mixture 5 - 10 4 3 Annual and Perennial Rye 3 4 5 - 0 Sod 4 3 Source: USDA, TP - 61, 1954; City of Roanoke Virginia Stormwater Design Manual, 2008 . 9.8 Sheet Flow Construction Sequence Sequence for Vegetated Filter Strips Construction Vegetated Filter Strips can be within the limits of disturbance during construction. The following procedures should be followed during construction: boundaries should be clearly marked. • Before site work begins, filter s trip • construction should be allowed within the filter filter strip Only vehicular traffic used for strip boundary . • If existing topsoil is stripped during grading, it shall be stockpiled for later use. • Construction runoff should be directed away from the proposed f ilter strip site , using perimeter silt fence, or, preferably, a diversion dike. uctio n of the gravel diaphragm or engineered level spreader shall not commence until Constr • erosion and sediment (E&S) the contributing drainage area has been stabilized and perimeter controls have been removed and cleaned out. chieve desired elevations • Filter strips require light grading to a and slopes. This should be done with tracked vehicles to prevent compaction. Topsoil and or compost amendments should be incorporated evenly across the filter strip area, stabilized with seed, and protected by biodegradable erosio n control mat ting or blankets. • Stormwater should not be diverted into the filter strip until the turf cover is dense and well established. Conserved Open Space Construction Sequence for Vegetated onserved Space Open during or after construction No major disturbance may occur within the C (i.e., no clearing or grading is allowed except temporary disturbances associated with incidental 3.06.2. 03/2013 9- 11

317 BMP Standards and Specificat Sheet Flow to Filter Strip or Open Space ions utility construction, restoration operations, or management of nuisance vegetation). The Co nserved Open Space area shall not be stripped of topsoil. Some light grading may be needed at the boundary using tracked vehicles to prevent compaction. must be fully protected during the construction stage of development Conserved Open S pace The and kept outside the limits of disturbance on the Sediment & Stormwater Plan. The perimeter of the Conserved Open Space shall be protected by super silt fence, chain link • sediment discharge. compaction and fence, orange safety fence, or other measures to prevent The limits of disturbance should b e clearly shown on all construction drawings and identified • and protected in the field by acceptable signage, silt fence, snow fence or other protective barrier. Construction of the gravel diaphragm or engineered level spreader shall not commence until • the contributing drainage area has been stabilized and perimeter E&S controls have been removed and cleaned out. until the gravel diaphragm Stormwater should not be diverted into the co nserved open space • and/or level spreader are installed and stabilized. Co ensure compliance with design rit ical to Construction inspection is c nstruction Inspection. standards. Inspectors should evaluate the performance of the filter strip or open space after the rcutting or sparse vegetative first big storm to look for evidence of gullies, outflanking, unde cover. Spot repairs should be made, as needed. The following items shall be included in the Post Construction Verification Documentation. Post Construction Verification Documentation for Sheet Flow Practices: • Dimensions of V egetated Filter Strips (length and width). • Area of Conserved Open Space. • Cross- slope. • -treatment component. Volume dimensions of any pre • Elevations of any structural components, such as gravel diaphragms or engineered level spreaders. Sheet Flow Main 9.9 tenance Criteria An Operation and Maintenance Plan for the project will be approved by the Department or the Delegated Agency prior to project closeout. The Operation and Maintenance Plan will specify or the property owner’s primary maintenance responsibili ties and authorize the Department Delegated Agency staff to access the property for maintenance review or corrective action in the that are, or will be, owned event that proper maintenance is not performed. Sheet Flow Practices and maintained by a joint ownership such as a homeowner’s association must be located in common areas, community open space, community -owned property, jointly owned property, or within a recorded easement dedicated to public use. 3.06.2. 03/2013 9- 12

318 BMP Standards and Specificat Sheet Flow to Filter Strip or Open Space ions Operation and Maintenance Plans should clearly out line how vegetation in the Sheet Flow Practice will be managed or harvested in the future. Maintenance of Sheet Flow Practices is driven by annual maintenance reviews that evaluate the condition and performance of the ecific maintenance tasks may be required. w results, sp practice. Based on maintenance revie 9.6. Sheet Flow to Filter Strip or Open Space Maintenance Items and Frequency Table Frequency Maintenance Items s 0.5 es of inch exceed Inspect the site after storm event that • rainfall. • Stabilize any bare or eroding areas in the contributing perimeter area Wet Pond drainage area including the During establishment, as needed (first Water trees and shrubs planted in the Wet Pond vegetated • year) perimeter area during the first growing season. In general , every 3 days for first month, and then weekly during water the remainder of the first growing season (April - October), depending on rainfall. Quarterly or after major storms • Remove debris and blockages (>1 inch of rainfall) • Repair undercut, eroded, and bare soil areas • Mowing of the Wet Pond vegetated perimeter area and Twice a year embankment • Shoreline cleanup to remove trash, debris and floatables review • A full maintenance Annually Open up the riser to access and test the valves • Repair broken mechan ical components, if needed • One time –during the • Wet Pond vegetated perimeter and aquatic bench second year following construction reinforcement plantings Every 5 to 7 years • Forebay sediment removal • , as needed Repair pipes, the riser and spillway From 5 to 25 years • Remove sediment from Wet Pond area outside of forebays 3.06.2. 03/2013 9- 13

319 BMP Standards and Specificat Sheet Flow to Filter Strip or Open Space ions 9. 10 References Cappiella, K., T. Schueler, and T. Wright. 2006. Urban Watershed Forestry Manual, Part 2. Conserving and Planting Trees at Development Sites . Center for Watershed Protection. Prepared for United States Department of Agriculture, Forest Service. City of Portland, Environmental Services. 2004. Portland Stormwater Management Manual . Portland, OR. Available online at: http://www.portlandonline.com/bes/index.cfm?c=dfbbh Claytor, R. and T. Schueler. 1996. Design of Stormwater Filtering Systems . Center for Watershed Protection. Ellicott City, MD. CWP. 2007. National Pollutant Removal Performance Database Ver . Center for sion 3.0 Watershed Protection, Ellicott City, MD. Hathaway , J. and B. Hunt. 2006. Level Spreaders: Overview, Design, and Maintenance . . Raliegh, Department of Biological and Agricultural Engineering. NC State University edu/stormwater/PublicationFiles/LevelSpreaders2006.pdf . http://www.bae.ncsu. NC. . Available online at: Henrico County Environmental Program Manual Henrico County, Virginia. http://www.co.henrico.va.us/works/eesd/ rolina State University . Level Spreader Design Worksheet . Available online at: North Ca http://www.bae.ncsu.edu/cont_ed/main/handouts/lsworksheet.pdf North Carolina Department of Envir onment and Natural Resources, Division of Water Quality. “Level Spreader Design Guidelines.” January 2007. Available online at: http://h2o.enr.state.nc.us/su/Manuals_Factsheets.htm Low Impact Development Supplement to the Nor thern Virginia Regional Commission. 2007. Northern Virginia BMP Handbook . Fairfax, Virginia. . Available online at: Philadelphia Stormwater Management Guidance Manual http://www.phillyriverinfo.org/Programs/SubprogramMain.aspx?Id=StormwaterManual Schueler, T., D. Hirschman, M. Novotney and J. Zielinski. 2007. Urban Stormwater Retrofit Practices . Manual 3 in the Urban S . Center for ubwatershed Restoration Manual Series Watershed Protection, Ellicott City, MD. Schueler, T. 2008. Technical Support for the Baywide Runoff Reduction Method. Chesapeake Stormwater Network. Baltimore, MD . www.chesapeakestormwater.net Virginia Stormwater Virginia Department of Conservation and Recreation (DCR). 1999. . Management Handbook. Volumes 1 and 2 of Soil and Water Conservation. Richmond, VA. Div. 3.06.2. 03/2013 9- 14

320 BMP Standards and Specifications Detention Practices Practices Detention 10.0 Definition: torage Detention Practices are s practices that are explicitly designed to provide stormwater detention for the Conveyance Event, Cv (10- year) and Flooding Event, Fv ). Design variants include: (100- year Dry Detention P A ond • 10- • Detention Basin Extended Dry B 10- Detention • 10- C Underground Facilities Extended Dry Dry Detention P onds and Detention Basins are widely applicable for most land uses and are best suited for larger drainage areas . An outlet structure restri cts stormwater flow so it backs up and is stored within the basin. The temporary ponding reduces the maximum peak discharge to the downstream channel, thereby reducing the effective shear stress onds receive some credit for bed and banks of the receiving stream. Dry the Detention P on pollutant removal , while Dry Extended Detention Basins receive both runoff reduction and pollutant removal credits. is that, in The key difference between Dry Detention Ponds Dry Extended Detention Basins and ement of the Cv and Fv, a Dry Extended Detention Basin addit ion to manag up to a 24- provides -sized . An under hour detention of all or a portion o f the Resource Protection Volume (RPv) The outlet structure restricts stormwater flow so it backs up and is stored within the basin. temporary ponding enables particulate pollutants to settle out and reduces the maximum peak discharge to the downstream channel, thereby reducing the effective shear stress on banks of the ’s stormwater detention, on Pond Extended detention differs from a receiving stream. Dry Detenti since it is designed to achieve a minimum drawdown time, rather than a maximum peak rate of , which are designed only to manage the larger Conveyance Event . Dry Detention Ponds flow er storm events for only a few minutes or hours. and Flooding Event will often detain small Facilities include vaults and tanks. Underground Detention V Detention Underground aults are shaped underground stormwater storage facilities typically constructed with reinforced box- Detention concrete. Tanks are underground storage facilities typically constructed Underground with large diameter metal or plastic pipe. Both serve as an alternative to surface dry detention for ot adequate land -limited areas where there is n stormwater quantity control, particularly for space -purpose detention area. Prefabricated concrete vaults are for a dry detention basin or multi commercial vendors. In addition, several pipe manufacturers have developed available f rom Underground detention vaul packaged detention systems. ts do not receive any runoff reduction or pollutant removal credit, and should be considered only for management of larger storm events. 03/2013 1 3.06.2. 10 -

321 Detention Practices BMP Standards and Specifications Example of a Dry Detention Pond 1. 10. Figure A) (10- 10 3.06.2. 03/2013 2 -

322 BMP Standards and Specifications Detention Practices Example of a Dry Extended Detention Basin (10 Figure 10.2. -B) 03/2013 3 3.06.2. 10 -

323 BMP Standards and Specifications Detention Practices 10. Figure -C) Example of an Underground Detention Facility (10 3. 4 10 03/2013 3.06.2. -

324 BMP Standards and Specifications Detention Practices Detention Practices Stormwater Credit Calculations 10.1 Dry Detention Ponds Both and Dry Extended Detention Basin s receive a pollutant removal credit, while Dry Extended Detention Basin s receive partial runoff reduction credit as well. Underground Detention Facilities receive no credit for runoff reduction or pollutant removal. Table 10.1 Dry Detention Pond Performance Credits eduction Runoff R 0% Retention Allowance RPv - A/B Soil 0% C/D Soil - 0% RPv 0% Cv 0% Fv Pollutant Reduction 5% TN Reduction 10% TP Reduction TSS Reduction 10% Tab le 10.2 Dry Extended Detention Basin Performance Credits Runoff Reduction 0% Allowance Retention RPv - A/B Soil 10% - RPv 10% C/D Soil 1% Cv 0% Fv Pollutant Reduction 20% TN Reduction 20% TP Reduction 60% TSS Reduction Practices are designed for larger storm events, rather than the Detention Since , the credits RPv they are not based on the relative size of the practice. To receive ed” credits – above are “fix Section these credits, t 6. 10. he practice must be designe d using the guidance detailed in Design Criteria Detention Practices . 03/2013 5 3.06.2. 10 -

325 BMP Standards and Specifications Detention Practices 10.2 Detention Practices Design Summary For more detail, consult Sections Practices. etention 3 summarizes design criteria for D 10. Table practice construction and maintenance 10.3 through 10.7. Sections 10.8 and 10.9 describe criteria. -A) Table 10.3 Dry Detention Pond (10 and Dry ED Basin (10 -B) D esign Summary 3% of CDA for footprint 1% - • inimum CDA = 10 acres Recommended m • Setbacks • in accordance with local codes • Minimum 2’ separation to groundwater or bedrock Geotechnical investigations required • Feasibility (Section 10.3) • soils to determine infiltration rates Soil tests on HSG A and B • No utilities within embankments • 10’ horizontal clearance from utilities Permit required if located on perennial streams • • Community and environmental concerns Designed in accordance with NRC S Small Pond Code 378 Appendix B • • Use accepted hydrologic and hydraulic routing computations • Principal spillway designed to release flow rates from Cv Principal spillway must be accessible by dry land, include anti -floatation, anti-vortex • ks, and contain watertight joints. devices, trash rac • -hours - to 24 Dry ED design must include an orifice to drain the Rpv over 12 Conveyance (Section 10.4) Minimize tree clearing at outlets • -clogging outlets (>3” or internal orifice control) Non • • Outlets non -erosive for the Fv (100 -year storm) event. • Emergency spillway cut in fill must be lined • If no emergency spillway, 3 square feet minimum for principal spillway • Provide inlet protection Pretreatment • those contributing >10% runoff volume – Forebays at major inlets (Section 10.5) • Forebays sized for 10% of RPv • Exit velocity from forebay non -erosive • Direct maintenance access provided Sizing - year, 2.7”) Store volume equivalent to RPv (1 • (Section 10.6) Detain RPv minimum 24 hours, not to exceed 48 hours • Flow evenly distri buted across the pond bottom • longitudinal slope: HSG A/B – • – 2% Geometry/ Features Minimum 1%, HSG C/D (Section 10.6) • Side slopes no steeper than 3:1 • Irregular shape and long flow path increase performance • by small children to principal spillway entry Prevent • to principal spillway and lock maintenance access points Safety ct entry Restri (Section 10.6) 1’ freeboard above the Fv elevation; 2’ freeboard if no emergency spillway • • • Accessible for annual maintenance Maintenance • Minimum 15’ wide maintenance access provided (Section 10.6) • nance set aside area provided Mainte • No woody vegetation within 15’ of toe of embankment or 25’ of pipes Landscaping (Section Landscaping plan required • 10.7) 6 03/2013 3.06.2. 10 -

326 BMP Standards and Specifications Detention Practices -C) Design Summary Table 10.4 Underground Detention Facilities (10 classified as Class V Injection Well Could be • • 1%-3% of CDA for footprint Sufficient head room to facilitate maintenance • in accordance with local codes Setbacks • Feasibility • Minimum 2’ separation to groundwater or bedrock (Section 10.3) • -flotation analysis for watertight systems Anti • ical investigations required Geotechn Structural analysis required • • 10’ horizontal clearance from utilities • Use accepted hydrologic and hydraulic routing computations -clogging outlets (>3” or internal orifice control) Non • Conveyance Outlets non • -eros ive for the Fv (100-year storm) event. (Section 10.4) • Minimize tree clearing at outlets year storm) event. • Internal or external high flow bypass to safely pass the Fv (100 - Pretreatment • Pretreatment structure to capture debris, trash, and coarse sediment (Section 10.5) eparate vault to capture minimum 0.1” of runoff per impervious acre S • Sizing Store volume equivalent to RPv (1 - • year, 2.7”) (Section 10.6) • Prevent access by small children Safety/ Maintenance • Restrict access to principal spillway and lock maintenance access points Access • 1’ freeboard above the Fv elevation (Section 10.6) • Maintenance access provided over the inlet pipe and outflow structure • Watertight joints Materials -place wall sections designed as retaining walls -in • Cast (Section 10.6) • floatation an - Anti alysis required using FS=1.2 Detention Practices Feasibility Criteria 3 10. ractices The following feasibility issues need to be evaluated when Detention P : are considered Certain types of practices in this category, EPA Requirements for Class V Injection Wells. particularly Underground Detention Facilities, may be classified as Class V Injection Wells, which are subject to regulations under the Federal Underground Injection Control (UIC) come in direct contact with program. In general, if the facility allows stormwater runoff to groundwater it would meet this criterion. Facilities with a minimum 2’ vadose zone separation from the groundwater table would not meet the criterion. Designers are advised to contact the DNREC Groundwater Discharges Section for additional information regarding UIC regulations and possible permitting requirements. Space Required. A typical Detention Practice requires a footprint of 1% to 3% of its ry Extended contributing drainage area, depending on the depth of the Dry Detention Pond, D the Detention Basin, or Underground Detention Facility (i.e., the deeper practice, the smaller footprint needed). 03/2013 7 3.06.2. 10 -

327 BMP Standards and Specifications Detention Practices A minimum contributing drainage area of 10 acres is Contributing Drainage Area. in order to Dry Detention Ponds keep the required orifice size from becoming recommended for a maintenance problem . Designers should be aware that small “pocket” ponds will typically (1) have very small orifices that will be prone to clogging, (2) experience fluctuating water levels , and (3) generate more significant bilization with vegetation is very difficult such that proper sta When the contributing drainage area of the Detention Practice is less than maintenance problems. sibility of clogging 10 acres, alternative outlet configurations should be used to eliminate the pos of the outlet. be located downstream of other structural stormwater Underground Detention Systems can controls providing treatment of the design storm. For treatment train designs where upland curve number adjusted f the RPv , d esigners can use a site- practices are utilized for treatment o (CN) that reflect s the volume reduction of upland practices and likely reduce the size and cost of Design Criteria Section ). Practice 6. Detention detention (see 10. Dry Detention Pond or Dry ED Basin epth of a is usually The d Available Hydraulic Head. (dimension between the surface available at the site determined by the amount of hydraulic head . The bottom elevation is normally the invert of the drainage and the bottom elevation of the site) discharges. ing downstream conveyance system to which the Detention Practice exist needed The Dry Detention Pond or Dry ED Basin to function properly will be hydraulic head for a size of the developed drainage area a determined by the nd the available surface area of the basin . An Underground Detention Facility will require sufficient head room to facilitate maintenance of the underground facility. Minimum Setbacks. Local ordinances and design criteria should be consulted to determine minimum setbacks to prope rty lines, structures, and wells. When not specified in local code, 20 should be set back at least -gradient down 5 feet feet from property lines, 2 Detention Practices public o feet from feet from septic system fields, and 150 100 from building foundations, r wells. water supply private and Bedrock. -to-Water Table Depth or s Dry Extended Detention Basin Dry Detention Ponds water table or bedrock will be within 2 feet of the floor of the seasonal high are not allowed if the tention Facilities must also maintain a separation of two -watertight Underground De Non pond. feet from the bottom of the facility to the elevation of seasonal high water or bedrock. For watertight ti-flotation analysis is required to check for , an an Underground Detention Facilities y problems in seasonal high water table areas. buoyanc At least one soil boring must be taken at a low point within the footprint of Geotechnical Tests. detention practice proposed to establish the water table and bedrock elevations and evaluate any A g ilit y. soil suitab eotechnical investigation is required for all underground BMPs, including storage underground systems. 03/2013 8 3.06.2. 10 -

328 BMP Standards and Specifications Detention Practices . Soil is seldom a design constraint for Detention Practices The permeability of soils Soils. investigation must Department Soil Investigation Procedures at wit h in accordance be conducted and sites to determine soil Dry Extended Detention Basin Dry Detention Pond ed propos may . Infiltration through the bottom of the pond is typically suitabilit y encouraged unless it or impair the integrity of the embankment lly thorough a soil layer and potentially migrate latera . other structure Underground must meet structural requirements for Facilities Detention Structural Stability. support and traffic loading as determined by a licensed desig overburden n professional, and based upon manufacturer’s recommendations where applicable. Utilities. For a Dry Detention Pond or Dry ED Basin , no utility lines shall be permitted to cross clearance from embankment. All utilities must have a minimum 10 ' horizontal any part of an Detention Practices unless protective measures are provided for the utility line. Locating on perennial streams will require both a Perennial Streams. Dry Detention Ponds Section 401 and Section 404 permit from the appropriate state or fede ral regulatory agency. Dry Detention Pond Community and Environmental Concerns. can s and Dry ED Basins generate the following community and environmental concerns that need to be addressed during design: nd maintained Dry Detention Ponds Properly designed, constructed a Aesthetic Issues. • and Dry ED Basins can serve as usable active open space in a community. It is important that the design include necessary cross slope on the pond bottom, and the pond is constructed in accordance with that design so that the bottom can be maintained free of . Dry Detention Ponds and Dry ED Basins may also be landscaped with native wet areas vegetation to become an attractive habitat within a community. Existing Forests. may involve or Dry ED Basin Construction of a Dry Detention Pond • extensive clearing of existing forest cover. Designers can expect a great deal of neighborhood opposition if they do not make a concerted effort to save mature trees design and construction. and Dry ED Basin Pond during Dry Detention Safety Risk • Because Dry Detention Ponds and Dry ED Basins do not maintain a . permanent pool of water, they can be very attractive during runoff event when they are holding water. uld be provided to avoid Gentle side slopes and personnel grating sho ous potentially danger , especially where Dry Detention Ponds and Dry ED situat ions . are located near residential areas Basin Improperly functioning Dry Detention Ponds and Dry ED Basins that do Mosquito Risk. • not completely drain or take greater than 48 hours to drain, have the potential to breed mosquitoes. Mosquito problems can be minimized through simple design features and maintenance operations described in MSSC (2005). 03/2013 9 3.06.2. 10 -

329 Detention Practices BMP Standards and Specifications Detention Practice Conveyance Criteria 4 10. Dry Detention Ponds and Dry ED Basins, including thei r conveyance systems, constructed to meet regulatory stormwater management requirements in the State of Delaware shall be designed and constructed in accordance with the USDA NRCS Small Pond Code 378 and this document. USDA NR Designers must use accepted routing calculations to and hydraulic hydrologic CS Detention Practices . determine the required storage volume and an appropriate outlet design for For both Dry Detention Ponds and Dry Extended Detention Basins, the Principal Spillway. control structure must include orifices or outlets designed to release the required flow rates from -pipe the Cv (10 -year frequency storm). The principal spillway may be composed of a structure be designed with spillway shall -pipe -channel configuration. A structure configuration or a weir . The outfall pipe and all on the structure -vortex and trash rack devices -flotation, anti anti connections to the outfall structure shall be made watertight. When reinforced concrete pipe is -ring” gaskets (ASTM C361) e its longevit y, “O used for the principal spillway pipe to increas shall be used to create watertight joints. When the principal spillway is composed of a weir wall discharging to a channel, the channel below the weir must be reinforced (with riprap, for cour of the channel. example) to prevent s For Dry Extended Detention Basins, the control structure Non -Clogging Low Flow Orifice. -flow orifice that will slowly release the RPv over a 24 -hour period. A lo w must include a low flow orifice must be provided that is adequately pr otected from clogging by either an acceptable external trash rack or by internal orifice protection that may allow for smaller diameters. Orifices less than 3 inches in diameter may require extra attention during design, to minimize the potential for clogg ing. . Adequate Outfall Protection ll that will be stable for the The design must specify an outfa flooding event (Fv). The channel immediately below the Dry Detention Pond or Dry ED Basin dimensions in the shortest outfall must be modified to prevent erosion and conform to natural possible distance. This is accomplished by placing appropriately sized riprap over stabilization geotextile in accordance with HEC and -14 Hydraulic Design of Energy Dissipators for Culverts 3.3.11 Riprap ment Control Handbook Specification Channels and Delaware Erosion and Sedi 3.3.10 Riprap Outlet Protection, which can reduce flow velocities from the Stilling Basin or principal spillway to non based upon the channel lining material . -erosive levels (3.5 to 5.0 fps) When the disc harge is to a manmade pipe or channel system, the system must be adequate to Care should be taken to minimize tree clearing convey the required design storm peak discharge. hortest possible along the downstream channel, and to reestablish a forested riparian zone in the s The final release rate of the facility shall distance. Excessive use of rip -rap should be avoided. be modified if any increase in flooding or stream channel erosion would result at a downstream ricted structure, highway, or natural point of rest streamflow . 03/2013 10 3.06.2. 10 -

330 BMP Standards and Specifications Detention Practices Emergency Spillway . Dry Detention Ponds and Dry ED Basins must be constructed with overflow capacity to pass the maximum design storm event (Fv) if the Fv is being routed through emergency spillway the pond or basin rather than bypassing. An designed to convey the Fv or, if c cut in natural ground should be must be lined with stabilization geotextile and ut in fill, riprap. When the maximum design storm will be passing through the principal spillway , the principal spillway outlet pip e must have a minimum cross sectional area of 3 square feet. Inflow points into the Dry Detention Pond or Dry ED Basin . Inflow Points Stabilization must -erosive conditions exist during storm events up to the be stabilized to ensure that non (See orm (i.e., the 10 -year storm event). A forebay conveyance st Detention Practices 10.5 ) shall be provided at each inflow location, unless the inlet provides less Pretreatment Criteria n. than 10% of the total design storm inflow to the Dry Detention Pond or Dry ED Basi Dam Safety Permits. The designer should determine whether or not the embankment meets the In the event that the criteria to be regulated as a dam by the Delaware Dam Safety Regulations. embankment is a regulated dam, the designer should verify that t he appropriate Dam Safety Dam Safet y Program. Permit has been approved by the Department’s or high flow bypass Facilities, an internal or external Detention Underground For Bypass. overflow shall be included in the design to safely pass the Flooding even t (Fv). 5 Detention Practices Pretreatment Criteria 10. A forebay must be Pretreatment Forebay . located at each major inlet to a Dry Detention Pond or Dry Extended Detention Basin to trap sediment and preserve the capacity of the main The following criteria apply to forebay design: treatment cell. • A major inlet is defined as an individual storm drain inlet pipe or open channel serving at . least 10% of the Dry Detention Pond or Dry ED Basin’s contributing runoff volume The of a separate cell, formed by an acceptable consists configuration forebay preferred • gabion baskets, etc. Riprap berms are the a concrete weir, riprap berm, barrier such as preferred barrier material. runoff from the the volume of be sized to contain ten percent of The forebay must • . The relative size from the Resource Protection event area impervious contributing drainage Dry of individual forebays will be proportional to the percentage of the total inflo w to the included in Detention Pond or Dry ED Basin. The storage volume within the forebay may be the calculated required storage volume for the Dry Detention Pond or Dry ED Basin. • The forebay should be designed in such a manner that it acts as a level spreader to distribute cell. torage runoff evenly across the entire bottom surface area of the main s • -erosive or an armored overflow shall be Exit velocit ies from the forebay shall be non provided. Direct maintenance access for appropriate equipment shall be provided to the each forebay 03/2013 11 3.06.2. 10 -

331 BMP Standards and Specifications Detention Practices cture to capture sediment, coarse A pretreatment stru . Pretreatment Underground Detention Detention nderground be placed upstream of any inflow points to U must trash and debris a minimum of 0.1 inches separate sediment sump or vault chamber sized to capture . A Facilities inage area per impervious acre of contributing dra Underground at the inlet for be provided shall Detention . Facilities Detention 6 10. Criteria Design Practices Detention In order to receive the credits outlined in Section 10.1, Detention Practice Sizing. must be sized to store a vo Practices lume equivalent to the Resource Protection storm (i.e., the -year, 2.7” Type II storm event). Further, Dry Extended Detention runoff volume from the 1 Basins must also be sized to detain the RPv for a minimum period of 24 hours , not to exceed 48 hours . Detention Practices can be designed to capture and treat the remaining stormwater discharged from upstream practices to improve water quality . Detention Practices should be sized to equired control peak flow rates from the Conveyance Event and Flooding Event as r in accordance with the Delaware Sediment and Stormwater Regulations and accompanying . Technical Document For treatment train designs where upland practices are utilized for treatment of the RPv, s the designers can use a site- adjusted CN that reflect volume reduction of upland practices to compute the Cv and Fv that must be treated by the D etention Practice. . Dry Detention Pond and Dry Extended Detention Ba sin Internal Design Features The design: ention Basin Dry Extended Det and following apply to Dry Detention Pond • Dry Detention Ponds and Dry ED Basin shall be constructed in a Flow Distribution. manner whereby flows are evenly distributed across the pond bottom, to avoid scour, and, where possible, infiltration , filtering, promote attenuation . a pond constructed on HSG longitudinal slope through minimum • Internal Slope. The A/B soils should be 1% . The minimum longitudinal slope through a pond constructed on HSG C/D soils should be 2%. • or Dry ED Basin should have a Dry Detention Pond Side slopes within the Side Slopes. gradient of 3H:1V to 4H:1V. The mild slopes promote better establishment and growth of In no case vegetation and provide for easier maintenance and a more natural appearance. shall the side slopes be designed and constructed steeper than 3H:1V. designs should have Flow Path. and Dry ED Basin an Long • Dry Detention Pond from inlet to outlet to increase water residence time, irregular shape and a long flow path rms of flow . In te -cutting eliminate short , and to treatment pathways, pond performance path geometry, there are two design considerations: (1) the overall flow path through the pond, and (2) the length of the shortest flow path (Hirschman et al., 2009): 03/2013 12 3.06.2. 10 -

332 BMP Standards and Specifications Detention Practices can be the OR -to-width rat io represented as the length o The overall flow path flo w path ratio. These ratios must be at least 2L:1W ( preferred). Internal berms, 3L:1W baffles, or topography can be used to extend flow paths and/or create multiple pond cells. represents the distance from the closest inlet to the outlet . o The shortest flow path 4. In some The ratio of the shortest flow to the overall length must be at least 0. cases – due to site geometry, storm sewer infrastructure, or other factors – so me inlets may not be able to meet these ratios. However, the drainage area served by these “closer” inlets should constitute no more than 20% of the total contributing drainage area. orifice shall be The low flow ED -clogging Low Flow (Extended Detention) Orifice . • Non The preferred adequately protected from clogging by an acceptable external trash rack. method is a hood apparatus over the orifice that reduces gross pollutants such as floatables and trash, as well as oil and grease and sediment. Orifices less than 3 inches in diameter may require extra attention during design, to the potential for clogging. minimize may be internal orifice protection As an alternative, (i.e., an orifice internal to a perforated vertical stand pipe with 0.5 -inch orifices or used slots that are protected by wirecloth and a stone filtering jacket). etention Safety F eatures. The following safety features apply to D Practices: • The principal spillway opening as well as all inlets and outlets must be designed and constructed to prevent entry by small children. Personnel safety grates shall be installed on the i nlets of all stormwater pipes 12” in diameter or larger that are not straight from the inlet to the open outlet, regardless of the length of the pipe. practices incorporate an additional 1 foot of freeboard above the emergency must • Detention spillway, or 2 maximum the feet of freeboard if the design has no emergency spillway, for water elevation for the Fv , unless more stringent Dam Safety requirements apply . • The emergency spillway must be located so that downstream structures will not be impacted by spillw ay discharges. Fencing of the perimeter of Dry Detention Pond . The is discouraged • s and Dry ED Basins preferred method to reduce risk is to manage the contours of the pond to eliminate drop -offs or other safety hazards. • The should be locked at all times. Maintenance access to Underground De tention Facilit ies Operation and Maintenance Plan will specify how access to the Underground Detention Facility will be accomplished. shall be designed so as to be accessible to annual Detention Practices All Maintenance Access. A minimum 15’ wide maintenance access shall be provided from public open maintenance. space or public right -of-way to the Detention Practice and around the perimeter of the Detention be provided for also Adequate maintenance access must Practice. Detention Underground all 03/2013 13 3.06.2. 10 -

333 BMP Standards and Specifications Detention Practices . with access steps . Access must be provided over the inlet pipe and outflow structure Facilities consist of a standard 30” diameter frame, grate and solid cover, or a hinged Access openings can removable panel. door or Adequate land area adjacent to the Dry Detention Pond or Dry . Maintena nce Set -Aside Area should be provided for in the Operation and Maintenance Plan as a location for ED Basin when maintenance is performed disposal o f sediment removed fro m the pond • The maintenance set -aside area shall accommodate the volume of 0.1 inches of runoff from contributory drainage area. Dry Detention Pond or Dry ED Basin’s the The maximum depth of the set aside volume shall be one foot. • The slope of the set aside area shall not exceed 5 %; and • • The area and slope of the set aside area may be modified if an alternative area or method of disposal is approved by the Department or Delegated Agency. Designers should consider longevity in selecting : Materials ion Vault and Tank Detent jo ints All construction ls for construction of Underground Detention Facilities. materia and pipe -in-place wall sections must be designed as retaining walls. The Cast joints shall be water tight. feet. finished grade to the vault invert should be 20 Manufacturer’s maximum depth from specifications should be consulted for proprietary Underground Detention Facilities . Analysis for Underground Detention: Anti -floatation For watertight Underground Detention Facilities, a or buoyancy problems in the high water -flotation analysis is required to check f nti table areas. Anchors shall be designed to counter the pipe and structure buoyancy by at least a 1.2 factor of safety. Detention Practices 7 10. Landscaping Criteria Facilities No landscaping criteria apply to U nderground Deten t ion . around the perimeter of the should be provided area A vegetated Perimeter . Vegetated of the Dry Detention Practice that extends at least 25 feet outward from the top of bank Detention Pond or Dry ED Basin. Permanent structures (e.g., buildings) should not be constructed within the vegetated perimeter area. Where possible, existing trees should be area during construction. The full width of the vegetated preserved in the vegetated perimeter ace, not within recorded lots. perimeter should be located in common open sp area are often severely compacted during the construction perimeter vegetated The soils in the process, to ensure stability. The density of these compacted soils can be so great that it effectively prevents root penetration and, therefore, may lead to premature mortality or loss of vigor. As a rule of thumb, planting holes should be three times deeper and wider than the diameter of the root ball for ball - -burlap stock, and five times deeper and wider for container -and 03/2013 14 3.06.2. 10 -

334 BMP Standards and Specifications Detention Practices ock. Organic matter such as locally generated compost may be used to amend grown st compacted soil to improve soil structure, help establish vegetation, and reduce runoff. lla et , consult Cappie perimeter areas For more guidance on planting trees and shrubs in vegetated al (2006). Woody Vegetation Woody vegetation may not be planted or allowed to grow within 15 feet of . the toe of the embankment. Woody vegetation may not be planted or allowed to grow within 25 o w pipes. feet of the principal spillway structure or any infl For and Dry Detention Ponds Dry Extended Detention Landscaping and Planting Plan. plan landscaping s, a Basin be provided that indicates the methods used to establish and must maintain vegetative coverage within the Detention Practice and its vegetated The perimeter area. to mature into a native forest in the right places, but yet keep planting plan should allow the pond plant mowable turf along the embankment and all access areas. species that require full Avo id shade, or are prone to wind dam age. Minimum elements of a plan include the following: perimeter area and vegetated • Delineation of pondscaping zones within the pond • Selection of corresponding plant species The planting plan • • Sources of native plant material 10.8 Detention Construction Sequence Practices Underground Detention Construction of proprietary Underground Detention Facilities. Facilities must be in accordance with m anufacturer’s specifications . All runoff into the system until the site is stabilized. The system must be inspected and cleaned of should be blocked sediment after the site is stabilized. Use of Dry Detention Pond or Dry Extended Detention Basin for Erosion and Sediment A Dry Detention Pond may serve as a sediment basin during project construction. Control. tallation of the permanent riser should be initiated during the construction phase, and design Ins - elevations should be set with final cleanout of the sediment basin and conversion to the post or Dry Extended Detention Basin Dry Detention Pond construction nd. The bottom mi in a minimum of six higher than the inches elevation of the temporary sediment basin must be proposed bottom elevation of the Dry Detention Pond or Dry ED Basin to allow for accumulated g conversion from sediment basin to sediment to be removed with the remaining material durin When the sediment basin is being converted into a permanent pond. Dry Detention Pond or Dry , the sediment basin must be dewatered in accordance with the approved plan and Basin ED 03/2013 15 3.06.2. 10 -

335 BMP Standards and Specifications Detention Practices osion and Sediment Control Handbook prior to appropriate details from the Delaware Er . removing accumulated sediment and regrading the pond bottom Review . Mult iple Dry Detention Pond and Dry Extended Detention Basin Construction construction reviews are critical to ensure that stormwater ponds are properly constructed. A checklist for construction phase review should be used to verify that all Detention Practices required items have been completed. Construction reviews are required during the following stages of construction: Pre eting -construction me • • Initial site preparation (including installation of E&S controls) principal the Construction spillway and the of the embankment, including installation of • outlet structure Excavation/Grading (interim and final elevations) • aping plan and vegetative stabilization Implementation of the pondsc • list for facility acceptance) Final inspection (develop a punch • Dry or The following is a typical construction sequence to properly install a Dry Detention Pond reflect different designs, site . The steps may be modified to Extended Detention Basin conditions, and the size, complexity and configuration of the proposed facility. s Dry Detention Ponds or Dry Extended Detention Basin Step 1: Stabilize the Drainage Area . rainage area is completely stabilized. If the should only be constructed after the contributing d site will be used as a sediment trap or basin ed Dry Detention Pond or Dry ED Basin propos during the construction phase, the construction notes should clearly indicate that the facility will be dewatered, dred ged and re -graded to design dimensions after the original site construction is complete. , Step 2: Assemble Construction Materials on-site, make sure they meet design specifications Ensure that appropriate compaction and dewatering equipment is and prepare any staging areas. available. Locate the project benchmark and if necessary transfer a benchmark nearer to the Wet Pond location for use during construction. Step prior to construction, including temporary de Controls Erosion and Sediment Install - 3: wat ering devices and stormwater diversion practices. All areas surrounding the pond or basin that are graded or denuded during construction must be planted with turf grass, native plantings, or other approved methods of soil stabilization. the Clear and Strip 4: -grade. Step embankment area to the desired sub in accordance with Spillway Pipe Principal Excavate the Core Trench and 5: Step Install the construction specification of NRCS Small Pond Code 378 . 03/2013 16 3.06.2. 10 -

336 BMP Standards and Specifications Detention Practices ure the top invert of the overflow weir is and ens Step 6: Install the Riser or Outflow Structure . constructed level at the design elevation using acceptable material 7: Construct the Embankment and any Internal Berms Step 8 to in Construction the embankment inch lifts and compact the lifts with appropriate equipment. 12- allowing for 10% settlement of the embankment. are achieved for the until the appropriate elevation and desired contours 8: Excavate/Grade Step bottom and side slopes of the Dry Detention Pond . Construct forebays at the or Dry ED Basin proposed inflow points. 9: Construct the Emergency Spillway Step in cut or structurally stabilized soils. 10: Install Outlet Pipe - , including any flared end sections, headwalls, and downstream rip s Step . tile underlain by stabilization geotex rap apron protection the approved with Step 11: Stabilize Exposed Soils seed mixtures in accordance with the vegetative stabilization specifications on the approved Sediment and Stormwater Management Plan. or Dry ED Basin Step 12: Plant the Dry Detention Pond ated and Veget Perimeter Area , ). Landscaping Criteria Detention Practices 10.7 following the pondscaping plan ( see Section depth of each forebay and Post Construction Verification. Following construction, the actual geo ed, must be measured, mark the pond or basin itself, the post construction on -referenced to verification survey document . This simple data set will enable maintenance reviewers determine sediment deposition rates in order to schedule sediment cleanouts. a Practices 10. 9 Detention Maintenance Criteri 10. 5. Practices are outlined in M aintenance Typical maintenance activities for Table Detention requirements for Underground Storage Facilities will generally require quarterly visual standing water or excessive inspections from the manhole access points to verify that there is no sediment buildup. Entry into the system for a full inspection of the system components (pipe or vault joints, general structural soundness, etc.) should be conducted annually. Confined space entry credentials are required for t his inspection. 03/2013 17 3.06.2. 10 -

337 BMP Standards and Specifications Detention Practices for 10. Table 5 Typical maintenance items Practices Detention Frequency Maintenance Items During establishment, Water Dry Detention Pond and Dry ED Basin side slopes and • as needed (first year) nd survival bottom area to promote vegetation growth a inlets, pre - treatment Remove sediment and oil/grease from • flow diversion structures, storage practices and devices, overflow structures. Quarterly or • Ensure that the contributing drainage area, inlets , and facility after major storms . surface are clear of debris (>1 inch of rainfall) Ensure that the contributing drainage area is stabilized. • Perform spot where needed. -reseeding Repair undercut and eroded areas at inflow and outflow • structures. • n forebay. Remove Measure sediment accumulation levels i sediment when 50% of the forebay capacity has been lost. • Inspect the condition of stormwater inlets for material damage, erosion or undercutting. Repair as necessary. Inspect the banks of upstream and downstream channels for • sloughing, animal burrows, boggy areas, woody evidence of growth, or gully erosion that may undermine pond embankment integrity. • -rap Inspect outfall channels for erosion, undercutting, rip displacement, woody growth, etc. iser for evidence Inspect condition of principal spillway and r • of spalling, joint failure, leakage, corrosion, etc. Annually • Inspect condition of all trash racks, flashboard risers , and other for evidence of clogging, leakage, debris appurtenances accumulation, etc. Inspect maintenance access to ensure it is free of debris or • woody vegetation, and check to see whether valves, manholes and locks can be opened and operated. Inspect internal and external side slopes of Dry Detention • for evidence of sparse vegetative cover, erosion, or Ponds ded repairs immediately. slumping, and make nee • Monitor the growth of trees and shrubs planted in Dry Detention Ponds. Remove invasive species and replant vegetation where necessary to ensure dense coverage. y the Department or the An Operation and Maintenance Plan for the project will be approved b Operation and Maintenance Plan will The Delegated Agency prior to project closeout. specify ies primary maintenance responsibilit owner’s the property or and authorize the Department or corrective action in the Delegated Agency staff to access the property for maintenance review that proper maintenance is not performed event . Detention Practices that are, or will be , owned and maintained by a joint ownership such as a homeowner’s association must be located in common areas, community open space, community -owned property, jointly owned property, or within a recorded easement dedicated to public use. 03/2013 18 3.06.2. 10 -

338 Detention Practices BMP Standards and Specifications aintenance Operation and M Plans should clearly outline how vegetation in the Dry Detention eter will be managed or harvested in the future. and its vegetated perim Pond or Dry ED Basin Periodic mowing of the vegetated perimeter area is only required within the maintenance access and the embankment. The remaining perimeter can be managed as a meadow (mowing every lan should schedule a shoreline cleanup eration and Maintenance P Op other year) or forest. The . at least once a year to remove trash and debris is driven by annual maintenance reviews that evaluate the Practices etention Maintenance of D . Based on ice condition and performance of the Detention Pract results, maintenance review specific maintenance tasks may be required . References 10.10 Urban Watershed Forestry Manual. Part 1: Cappiella, K., Schueler, T., and T. Wright. 2005. -TP-04- 05. USDA Forest Service, Methods for Increasing Forest Cover in a Watershed . NA Northeastern Area State and Private Forestry. Newtown Square, PA. Technical Report: Stormwater BMPs in Hirschman, D., L. Woodworth and S. Drescher. 2009. . Center for rams Virginia’s James River Basin: An Assessment of Field Conditions & Prog Watershed Protection. Ellicott City, MD. 03/2013 19 3.06.2. 10 -

339 BMP Standards and Specifications Stormwater Filtering Systems Storm water Filtering Systems 11. 0 Definition: Practices that capture and temporarily store the design storm t through a filter volume and pass i . Filtered runoff media or material may be collected and returned to the conveyance system, or allowed rtially infiltrate into the soil. to pa Design variants include: 11- -Structural Sand Filter  A Non 11-  Sand Filter B Surface  11- C Three -Chamber Underground Sand Filter Filter) Sand odular (including “Delaware” M D Perimeter  11- Sand Filter Bioretention also tormwater Filtering System ; however, since it also requires a functions as a S vegetative component is included as in a separate specification (see Specification 2.0 , , Bioretention Bioretention ). Filtering System s are a useful practice to treat stormwater runoff from small, highly Stormwater impervious sites. Stormwater Filtering System s capture, temporarily store, and treat stormwater runoff by passing it through an engineered filter media, collecting the filtered water in an underdrain, and then returni ng it back to the storm drainage system. The filter consists of two chambers: the first is devoted to settling, and the second serves as a filter bed consisting of a sand f ilter media. Stormwater System s are a versatile option because they consu Filtering me very little surface land and have few site restrictions. They provide moderate pollutant removal performance at small sites where space is limited. However, filters have limited or no runoff volume reduction capability, so designers should consider usin g up- gradient runoff reduction practices, which have the effect of decreasing the design storm volume (and size) of the filtering practices. Filtering practices are also suitable to special treatment at designated stormwater hotspots . A list of pot ential stormwater hotspots provide applications can be found in Appendix 4, Stormwater Hotspots Guidelines . Stormwater System Filtering Cv s are typically not to be designed to provide stormwater detention ( 11- 03/2013 3.06.2. 1

340 BMP Standards and Specifications Stormwater Filtering Systems s shall generally be and Fv), but they may in some circumstances. Stormwater Filtering System Three combined with a separate facility to provide those controls. However, the -Chamber Underground Filter can be modified by expanding the first or settling chamber, or adding an Sand extra chamber between the filter chamber and the clear well chamber to handle the detention volume, determined rate through an orifice and weir combination. which is subsequently discharged at a pre- Proprietary filters must be verified for adequate performance, sizing, and longevity. (see 15, Specification Practices Proprietary ). Filter 1. Non Sand -Structural Figure 11. 11- 03/2013 3.06.2. 2

341 BMP Standards and Specifications Stormwater Filtering Systems Surface S 11.2. Filter and Figure 11- 03/2013 3.06.2. 3

342 BMP Standards and Specifications Stormwater Filtering Systems Three Chamber Underground 11.2. Filter Sand Figure 11- 3.06.2. 03/2013 4

343 Stormwater Filtering Systems BMP Standards and Specifications Figure 3. Perimeter Sand Filter 11. 03/2013 3.06.2. 5 11-

344 BMP Standards and Specifications Stormwater Filtering Systems Filtering Practices Stormwater Credit Calculations 11.1. Filtering practices receive no runoff reduction credit, but are credited for pollutant filtering (see Table lined in 11.1). In order to receive this credit, the practice must be sized according to the criteria out Section 11.6 . 11.1 Filtering Practices Performance Credits Runoff Reduction 0% Retention Allowance A/B Soil RPv - 0% - C/D Soil 0% RPv 0% Cv Fv 0% Pollutant Reduction 40% TN Reduction TP Reduction 60% 80% TSS Reduction r Filtering Systems Design Summary 11.2 Stormwate summarizes design criteria for S tormwater Filtering System s , and Table 11 .3 summarizes Table 11.2 the materials specifications for these practices. For more detail, consult Sections 11.3 through 11.7. 11.9 describe practice construction and maintenance criteria. Sections 11.8 and 11.2 Stormwater Filtering Systems Design Summary * Table Surface and Non - Structural Filters Underground and Perimeter Filters ) ( 11 - A D and 11 - B ) - 11 ( 11 - C and <5 Acre CDA, near 100% impervious • • <5 A cre CDA, near 100% impervious Consume <1% of CDA • Consume 2% -3% of CDA • to 10’ head requirement, with lowest requirement for Perimeter Filters (F 4) • 10” - Feasibility • Ideally suited to treat stormwater hotspots and parking lots. 11.3) (Section e CDA, near 100% impervious • <5 Acr Slopes <6% • 5’ clearance for utilities. • Typically designed off • -line Conveyance -line; designer needs to ensure safe passage of the 10 In some cases, underground filters designed off - • 11.4) (Section year storm in these cases. Pret reatment • Sediment Chamber designed to capture 25% of or Sediment chamber, • 5) . 1 1 (Section the design volume. • A series of options including grassed 11- 03/2013 3.06.2. 6

345 BMP Standards and Specifications Stormwater Filtering Systems 11.2 Stormwater Filtering Systems Design Summary * Table Surface and Non - Structural Filters Underground and Perimeter Filters - A and 11 - ) ( 11 ( 11 - C and 11 - D ) B channels, filter strip, check dam, and gravel diaphragm. Sizing: Filter Area [ ] SA DesignVolu me = ( ) )( )( + / ) )( ( d k h d t filter f f f avg .6) 1 (Section 1 Design Volume = design storm volume, typically the water quality storm (cu. ft.) d = Filter media depth (thickness) = minimum 1 ft. (ft.) f ft./day partially clogged sand (ft./day) = 3.5 = Coefficient of permeability – k Variables = Average height of water above the filter bed (ft.), with a maximum of 5ft./2 h f t = Allowable drawdown time = 1.67 day f Sizing: Ponding Minimum Ponding Volume of 75% of Design Volume (Section 11.6) o dewater within 48 hours • Design designed t Geometry/ Features • Sufficient head to allow gravity feeding 11. (Section 6) Preferred filter depth of 18”, 12” minimum • Minimum 30” diameter manholes (for ) C - 11 • • Observation wells and clean - outs Safety/ with steps • Safe maintenance access Maintenance C may Confined space considerations for 11- • Clearly visible (signs or markings for • Features apply under ground practices) (Section 11. 6) • Minimum 5’ headroom for 11 - C in the CDA • Dense, vigorous vegetation for pervious areas Landscaping Grass cover can be used for designs 11- B • 11- A and 7) 11. (Section *Note: While proprietary filters are discussed in this document, they are highly variable in design, and consequently are not included in this table. Specification 15 outlines a process for acceptance of proprietary practices . Material Specifications Table 11.3. Stormwater Filtering Systems Material Specification Non geotextile woven - - structural and surface sand filter s : 3 - inch layer of topsoil on top of a non DE #57 laid above the sand layer. The surface may also have gravel inlets in the topsoil layer to promote filtration. Surface Cover Underground sand filters: DE #57 gravel layer on top of a coarse non- woven geotextile laid over the sand layer. - ticle size range of 33 medium aggregate concrete sand with a par - 6/ASTM C Clean AASHTO M Sand 0.02 to 0.04 inch in diameter. High Density Polyethylene (HDPE) smooth or corrugated The underdrain should consist of -wall pipe. Pipes must comply with ASHTO M252 and ASTM F405. flexible be perforated with slots that have a maximum width of Underdrains meeting ASTM F758 should 3/8 inch and provide a minimum inlet area of 1.76 square inches per linear foot of pipe. Underdrain Underdrains meeting ASTM F949 should be perforated with slots with a maximum width of 1/8 inch that provide a minimum inlet area of 1.5 square inches per linear foot of pipe. machined slots provides greater intake capacity and Underdrain pipe supplied with precision- - resistant drainage of fluids, as compared to standard round - hole perforated pipe. superior clog 11- 7 3.06.2. 03/2013

346 BMP Standards and Specifications Stormwater Filtering Systems d underdrain reduces entrance velocity into the pipe, thereby reducing the possibility that Slotte solids will be carried into the system. Slot rows can generally be positioned symmetrically or asymmetrically around the pipe circumference, depending upon the appl ication. polypropylene geotextile meeting the following specifications: woven, Use needled, non- woven Non- Flow Rate (ASTM D4491) 110 gpm/sq. ft. ≥ Geotextile Apparent Opening Size (ASTM D4751) = US #70 or #80 sieve NOTE: Heat - set or heat - calendared fabrics are not recommended. Underdrain Stone Use DE #57 stone or the ASTM equivalent (1 inch maximum). mum) PVC Geomembrane liner covered by 8 to 12 oz./sq. yd. non - woven Use a thirty mil (mini Impermeable Liner geotextile. 11. 3 Filtering Feasibility Criteria Stormwater Filtering System s can be applied to most types of urban land. They are not always cost - effective, given their high unit cost and small area served, but there are situations where they may clearly be the best option for stormwater treatment (e.g., hotspot runoff treatment, small parking lots, ultra -urban areas etc.). The following criteria apply to filtering practices: System Filtering Stormwater The principal design constraint for s is Available Hydraulic Head. available hydraulic head, which is defined as the vertical distance between the top elevation of the filter and the bottom elevation of the discharge pipe ed for Stormwater Filtering . The head requir System up to 10 feet, depending on the design variant. I t is difficult to employ filters in s ranges extremely flat terrain, since they require gravity flow through the filter. The only exception is the Perimeter Sand Filter , whi ch can be applied at sites with as little as 10 inches of head. The designer must assure that the seasonally high groundwater Depth to Water Table and Bedrock. table and/or bedrock layer does not intersect the bottom invert of the filtering practice. Con tributing Drainage Area. Stormwater Filtering System s are best applied on small sites where in order to reduce the contributing drainage (CDA) area is as close to 100% impervious as possible the risk that eroded sediments will clog the filter. A maximum CD A of 5 acres is recommended for surface sand filters, and a maximum CDA of 2 acres is recommended for perimeter or underground . Stormwater Filtering System s have been used on larger drainage areas in the past, but greater filters clogging problems have typ ically resulted. Space Required. The amount of space required for a S tormwater Filtering System depends on the design variant selected. S urface Sand Filters typically consume about 2% to 3% of the CDA , while Perimeter Sand Filters typically consume less than 1%. Underground S tormwater Filters generally consume no surface area except their manholes. System Filtering s are particularly well suited to treat runoff Land Use. As noted above, S tormwater from stormwater hotspots and smaller parking lots. Other a pplications include redevelopment of 11- 03/2013 3.06.2. 8

347 BMP Standards and Specifications Stormwater Filtering Systems tormwater Filtering commercial sites or when existing parking lots are renovated or expanded. S s can work on most commercial, industrial, institutional or municipal sites and can be located System underground if surface area is not available. Stormwater Filtering Site Topography. s shall not be located on slopes greater than 6%. System All utilities shall have a minimum 5' horizontal clearance from the filtering practice Utilities. . Facility Access. All Stormwater Filtering System s shall be located in areas where they are accessible for inspection and for maintenance (by vacuum trucks). Soils. Soil conditions do not constrain the use of S tormwater Filtering System s. At least one soil boring must be taken at a l ow point within the footprint of the proposed filtering practice to establish the water table and bedrock elevations and evaluate soil suitability. A g eotechnical filtering systems. investigation is required for all underground BMPs, including underground 1, Soil Investigation Procedures for Appendix Geotechnical testing requirements are outlined in Stormwater BMPs. 11. 4 Filtering Conveyance Criteria Most Stormwater Filtering System s are designed as off -line systems so that all flows enter the filter storage chamber until it reaches capacity, at which point larger flows are then diverted or bypassed around the filter to an outlet chamber and are not treated. Runoff from larger storm events should be bypassed using an overflow structure or a flow splitt er. Claytor and Schueler (1996) and ARC (2001) provide design guidance for flow splitters for filtering practices . these cases, designers Some underground filters will be designed and constructed as on -line BMPs. In y pass larger storm events year event) to a (e.g., the 10- must indicate how the device will safel stabilized water course without resuspending or flushing previously trapped material. All Stormwater Filtering System s should be designed to drain or dewater within 4 8 hours after a storm event to reduce the potential for nuisance conditions . 11. 5 Filtering Pretreatment Criteria Adequate pre -treatment is needed to prevent premature filter clogging and ensure filter longevity. Dry or wet pretreatment shall be provided prior to filter media. Pre -treatment devices are subject to the following criteria: Sedimentation chambers are typically used for pre- treatment to capture coarse sediment particles • before they reach the filter bed. 11- 03/2013 3.06.2. 9

348 BMP Standards and Specifications Stormwater Filtering Systems Sedimentation chambers may be wet or dry but must be sized to accommod ate at least 25% of the • design storm volume (inclusive). total • Sediment chambers should be designed as level spreaders such that inflows to the filter bed have near zero velocity and spread runoff evenly across the bed. Non • and Surface Sand Filters may use alternative pre- treatment measures, such as a -Structural grass filter strip , forebay, gravel diaphragm, check dam, level spreader, or combination. The grass filter strip must be a minimum length of 15 feet and have a slope of 3% or less. The check dam y be wooden or concrete and must be installed so that it extends only 2 inches above the filter ma strip and has lateral slots to allow runoff to be evenly distributed across the filter surface. treatment measures should contain a non- Alternative pre- flow path that distributes the erosive flow evenly over the filter surface. If a forebay is used it should be designed to accommodate at least 25% of the total design storm volume (inclusive) . 6 Filtering Design Criteria 11. storm All Stormwater Filte ring System s should be designed to drain the design Detention time: after each rainfall event. hours from the filter chamber within 48 volume Structural Requirements : If a filter will be located underground or experience traffic loads, a . licensed structural engineer should certify the structural integrity of the design S tormwater Filtering System s are gravity flow systems that normally require 2 to 5 Geometry. feet of driving head to push the water through the filter media through the entire maintenance cycle; therefore, sufficient vertical clearance between the inverts of the inflow and outflow pipes is required . The normal filter media consists of clean, washed AASHTO M -6/ASTM C -33 Type of Filter Media. medium aggregate concrete sand with individual grains b etween 0.02 and 0.04 inches in diameter. Depth of Filter Media. The depth of the filter media plays a role in how quickly stormwater moves through the filter bed and how well it removes pollutants. 18 The recommended filter bed depth is inches. An absol ute minimum filter bed depth of 12” above underdrains is required, although designers should note that specifying the minimum depth of 12” will incur a more intensive maintenance schedule and possibly result in more costly maintenance. -woven Geotextil e. A non- woven geotextile should be placed beneath the filter media and above Non should meet criteria provided in the the underdrain gravel layer. The geotextile Table 11. 3 . Underdrain and Liner. Stormwater Filtering System s are normally designed with an impermeable . liner and underdrain system that meet the criteria provided in Table 11. 3 . The underdrain should be covered by a minimum 6 Underdrain Stone gravel layer consisting of -inch 11- 03/2013 3.06.2. 10

349 BMP Standards and Specifications Stormwater Filtering Systems clean, washed #57 stone. There are several design vari ations of the basic filter that enable designers to use Type of Filter. Filtering System s at challenging sites or to improve pollutant removal rates. The choice Stormwater of which filter design to apply depends on available space and hydraulic head and the level of tant removal desired. In ultra- pollu urban situations where surface space is at a premium, Sand Filters are often the only design that can be used. Surface and P erimeter Sand Underground Filters are often a more economical choice when adequate surface area is av ailable. The most common design variants include the following: The • -Structural Sand Filter (11- A). Non Non-Structural Sand Filter is applied to sites less than 2 acres in size, and is very similar to a Bioretention practice (see Specification 2 . Bioreten tion ), with the following exceptions: o The bottom is lined with an impermeable liner and always has an underdrain. o The surface cover is sand, turf or pea gravel. o The filter media is 100% sand. us materials. The filter surface is not planted with trees, shrubs or herbaceo o o The filter has two cells, with a dry or wet sedimentation chamber preceding the sand filter bed. Non-Structural Sand Filter is the least expensive filter option for treating hotspot runoff. The The ioretention areas is generally preferred at most other sites. use of B Surface • Surface Sand Filter (11- B). The Sand Filter is designed with both the filter bed and sediment chamber located at ground level. The most common filter media is sand; however, a In most cases, peat/sand mixture may be used to increase the removal efficiency of the system. Surface Filters are Sand the filter chambers are created using pre- cast or cast -in-place concrete. normally designed to be off -line facilities, so that only the desired water quality or runoff reduction v olume is directed to the filter for treatment. However, in some cases they can be installed on the bottom of a Dry Extended Detention (ED) Pond ( see Specification 10. Detention Practices ). C). • Three -Chamber Underground Sand Filter ( 11- The Three -Chamber Underground Sand Filter is a gravity flow system. The facility may be precast or cast -in-place. The first chamber acts as a pretreatment facility removing any floating organic material such as oil, grease, and tree leaves. It should have a submerged orifi ce leading to a second chamber and it should be designed to minimize the energy of incoming stormwater before the flow enters the second chamber (filtering or processing chamber). material consisting of at the filter The second chamber is the filter chamber. It should contain gravel, geotextile fabric, and sand, and should be situated behind a weir. Along the bottom of the structure should be a subsurface drainage system consisting of a parallel PVC pipe system in a 11- 03/2013 3.06.2. 11

350 BMP Standards and Specifications Stormwater Filtering Systems e installed at the top of the filter layer for safety release in gravel bed. A dewatering valve should b cases of emergency. A by -pass pipe crossing the second chamber to carry overflow from the first chamber to the third chamber is required. uld also receive the overflow from the first The third chamber is the discharge chamber. It sho chamber through the bypass pipe when the storage volume is exceeded. Water enters the first chamber of the system by gravity or by pumping. This chamber removes most of the heavy solid particles, floatable tras h, leaves, and hydrocarbons. Then the water flows to the second chamber and enters the filter layer by overtopping a weir. The filtered stormwater is then picked up by the subsurface drainage system that empties it into the third chamber. Whenever there i s insufficient hydraulic head for a T hree -Chamber Underground Sand Filter , a well pump may be used to discharge the effluent from the third chamber into the receiving storm For Three -Chamber Underground Sand Filter s in combined -sewer areas, a or combined sewer. water trap shall be provided in the third chamber to prevent the back flow of odorous gas. also includes the basic design elements Perimeter Sand Filter ( 11- • The Perimeter Sand Filter D). typically consists of two parallel Filter Sand Perimeter of a sediment chamber and a filter bed. The trenches connected by a series of overflow weir notches at the top of the partitioning wall, which allows water to enter the second trench as sheet flow. The first trench is a pretreatment chamber removing heavy sedim ent particles and debris. The second trench consists of the sand filter layer . A subsurface drainage pipe must be installed at the bottom of the second chamber to facilitate the filtering process and convey filter water into a receiving system. In this d esign , flow enters the system through grates, usually at the edge of a parking lot. The Perimeter Sand Filter is usually designed as an on -line practice (i.e., all flows enter the system), but larger events bypass treatment by entering an overflow chamber. One major advantage of the Filter Sand design is that it requires little hydraulic head and is therefore a good option Perimeter . for sites with low topographic relief The Delaware Modular Sand Filter was specifically developed to meet these conditions u sing a pre -cast structure. The Standard Detail & Specifications for the Delaware Modular Sand Filter 1 of this document. are included as Appendix 11- on-Structural s should consist of a 3 - Surface Cover. The surface cover for N Filter and Surface Sand inch l ayer of topsoil on top of a non -woven filter fabric laid above the sand layer. The surface may also have pea gravel inlets in the topsoil layer to promote filtration. The pea gravel may be located where sheet flow enters the filter, around the margins of t he filter bed, or at locations in the middle of the filter bed. 11- 03/2013 3.06.2. 12

351 BMP Standards and Specifications Stormwater Filtering Systems Sand Filters should have a pea gravel layer on top of a coarse non -woven fabric laid Underground gravel helps to prevent bio ce. The over the sand layer. The pea- -fouling or blinding of the sand surfa fabric serves to facilitate removing the gravel during maintenance operations. Maintenance Reduction Features. The following maintenance issues should be addressed during filter design to reduce future maintenance problems: • Observation Wells and C leanouts. Non -Structural and Surface Sand Filter s should include an observation well consisting of a 6 -inch diameter non -perforated PVC pipe fitted with a lockable and cap. It should be installed flush with the ground surface to facilitate periodic inspection maintenance. In most cases, a cleanout pipe will be tied into the end of all underdrain pipe runs. The portion of the cleanout pipe/observation well in the underdrain layer should be perforated. At 0 square feet of filter surface area. least one cleanout pipe must be provided for every 200 • Access. Good maintenance access is needed to allow crews to perform regular inspections and maintenance activities. “Sufficient access” is operationally defined as the ability to get a vacuum truck or similar equipment close enough to the sedimentation chamber and filter to enable cleanouts. Direct maintenance access shall be provided to the pretreatment area and the filter bed. For underground structures, sufficient headroom for maintenance should be provided. A minimu m head space of 5 feet above the filter is recommended for maintenance of the structure. However, if 5 feet headroom is not available, manhole access should be installed. f Access to the headbox and clearwell o Filters). Manhole Access (for Underground Sand • Underground Sand Filters must be provided by manholes at least 30 inches in diameter, along with steps to the areas where maintenance will occur. Visibility. Stormwater filters should be clearly visible at the site so inspectors and maintenance • easily find them. Adequate signs or markings should be provided at manhole access crews can points for Underground Sand Filters. • Confined Space Issues. Underground Sand Filters are often classified as a confined space . Consequently, special OSHA rules apply, and tr aining may be needed to protect the workers that access them. These procedures often involve training about confined space entry, venting, and the use of gas probes. Filter Material Specifications . that utilize The basic material specifications for filtering practices sand as a filter media are outlined in 3 . Proprietary filters, including those being utilized 11. Table -treatment for rainwater harvesting systems, infiltration, and other applications that utilize for pre 15. alternative media must be evaluated as noted in Specification Filter Sizing . Stormwater Filtering System s are sized to accommodate a specified design storm volume. The volume to be treated by the device is a function of the storage depth above the filter and the surface area of the fil ter. The storage volume is the volume of ponding above the filter. For a given design volume , Equation 11. 1 is used to determine the required filter surface area: 1. Minimum Filter Surface Area for Filtering Practices 11. Equation 11- 03/2013 3.06.2. 13

352 BMP Standards and Specifications Stormwater Filtering Systems [ ] = DesignVolu me d + SA k d h t ( )( ) / )( ( ) )( filter f avg f f Where: SA = area of the filter surface (sq. ft.) filter * (cu. ft.) DesignVolume = design storm volume, typically the water quality storm d = Filter media depth (thickness) = minimum 1 ft. (ft.) f k = Coefficient of permeability – partially clogged sand (ft./day) = 3.5 ft./day h = Average height of water above the filter bed (ft.), with a maximum of 5 f ft./2 able drawdown time = 1.67 day = Allow t f *The minimum design volume to receive credit for filt ering is the runoff volume from the 2.7” NRCS Type II storm event. The coefficient of permeability (ft./day) is intended to reflect the worst case situation (i.e., the condition of the sand media at the point in its operational life where it is in need of replacement or maintenance). Stormwater Filtering System s are therefore sized to function within the desired constraints at the end of the media’s operational life cycle. least 75% of the The entire filter treatment system (including pretreatment) shall temporarily hold at design storm volume prior to filtration ( Equation 11. 2 ) . This reduced volume takes into account the varying filtration rate of the water through the media, as a function of a gradually declining hydraulic head. Storage for Filtering Practices of 2. Required Volume 11. Equation = me 75 . 0 ) V DesignVolu ( ponding Where: required prior to filtration (cu. ft.) = storage volume V ponding Filtering Landscaping Criteria 11. 7 A dense and vigorous vegetative cover shall be establi shed over the contributing pervious drainage areas before runoff can be accepted into the facility. Native plants should be used where possible. landscaping to increase their aesthetics ncorporated site s should be i Stormwater Filtering System into lic appeal. and pub 03/2013 14 11- 3.06.2.

353 BMP Standards and Specifications Stormwater Filtering Systems Surface and Non- Structural Sand Filters can have a grass cover to aid in the pollutant adsorption. The grass should be capable of withstanding frequent periods of inundation and drought. 11. 8 Filter Construction Sequence Erosion and Sediment Control. Stormwater Filtering No runoff shall be allowed to enter the System prior to completion of all construction activities, including revegetation and final site stabilization. Construction runoff shall be treated in separate sedimentation bas ins and routed to bypass the filter system. Should construction runoff enter the filter system prior to final site stabilization, all contaminated materials must be removed and replaced with new clean filter materials its completion before a regulatory inspector approves . The approved Sediment & Stormwater Plan shall include specific measures to provide for the protection of the filter system before the final stabilization of the site. Filter Installation . The following is the typical construction sequence to properly install a System Filtering . This sequence can be modified to reflect different filter designs, site Stormwater conditions, and the size, complexity and configuration of the proposed filtering application. Filtering practices should only be constructed after the contributing 1: Stabilize Drainage Area . Step drainage area to the facility is completely stabilized, so sediment from the CDA does not flow into and clog the filter. If the proposed filtering area is used as a sediment trap or basin d uring the construction phase, the construction notes should clearly specify that, after site construction is complete, the sediment control facility will be dewatered, dredged and regraded to design dimensions for the post -construction filter. Step 2: Install E&S Controls for the Filtering Practice. Stormwater should be diverted around filtering practices as they are being constructed. This is usually not difficult to accomplish for off -line ilter filtering practices. It is extremely important to keep runoff and eroded sediments away from the f throughout the construction process. Silt fence or other sediment controls should be installed around the perimeter of the f ilter, and erosion control fabric may be needed during construction on exposed side -slopes wi th gradients exceeding 4H:1V. Exposed soils in the vicinity of the filtering practice should be rapidly stabilized by hydro -seed, sod, mulch , or other method . Step on-site, make sure they meet design specifications, and 3: Assemble Construction Materials prepare any staging areas. the project area to the desired subgrade. Step 4: Clear and Strip Step 5: Excavate/Grade until the appropriate elevation and desired contours are achieved for the bottom and side slopes of the filtering practice. 11- 03/2013 3.06.2. 15

354 BMP Standards and Specifications Stormwater Filtering Systems 6: Insta ll the Filter Structure and check all design elevations (concrete vaults for surface, Step underground and perimeter sand filters). Upon completion of the filter structure shell, inlets and er to the brim to demonstrate outlets should be temporarily plugged and the structure filled with wat water tightness. Maximum allowable leakage is 5% of the water volume in a 24 -hour period. If the structure fails the test, repairs must be performed to make the structure watertight before any sand is placed into it. . layer of the filter Step 7: Install the gravel, underdrains, and geotextile Step 8: Spread Sand Across the Filter Bed in 1 foot lifts up to the design elevation. Backhoes or other equipment can deliver the sand from outside the filter structure. Sand should be m anually raked. Clean water is then added until the sedimentation chamber and filter bed are completely full. The layers. After 48 hours of drying, facility is then allowed to drain, hydraulically compacting the sand refill the structure to the final top el ilter bed. evation of the f add a 3 -inch Step 9 (Surface Sand Filters Only) : Install the Permeable Filter Fabric over the sand, topsoil layer and pea gravel inlets, and immediately seed with the permanent grass species. The grass facility should not be switched on -line until a vigorous grass cover has should be watered, and the become established. 0: Stabilize Exposed Soils on the perimeter of the structure with temporary seed mixtures Step 1 appropriate for a buffer. All areas above the normal pool should be permanently stabilized by hydroseed , sod, or seeding and mulch. Step 1 1 : Conduct the final construction inspection . Construction Inspection. Multiple construction inspections are critical to ensure that S tormwater Filtering System s are properly const ructed. Inspections are recommended during the following stages of construction: Pre -construction meeting. • • Initial site preparation (including installation of project E&S controls). • Excavation/grading to design dimensions and elevations. • Installation of th e filter structure, including the water tightness test. • Installation of the underdrain and filter bed. • Check that stabilization in contributing area is vigorous enough to switch the facility on -line. • Final Inspection (after a rainfall event to ensure that it drains properly and all pipe connections are watertight. Develop a punch list for facility acceptance. Log the filtering practice’s GPS coordinates and submit them for entry into the local BMP maintenance tracking database. The following items shall be included in the on Documentation. Post Construction Verificati 11- 03/2013 3.06.2. 16

355 BMP Standards and Specifications Stormwater Filtering Systems Post Construction Verification Documentation for S tormwater Filtering System s: • Surface dimensions of filter bed. • Depth of filter media. -treatment component. Volume dimensions of any pre • • Elevat ions of any structural components, including inverts of pipes, weirs, etc. 11.9 Stormwater Filtering Systems Maintenance Criteria An Operati or the on and Maintenance Plan for the project will be approved by the Department oseout. The Operation and Maintenance Plan will specify the Delegated Agency prior to project cl or Delegated property owner’s primary maintenance responsibilities and authorize the Department Agency staff to access the property for maintenance review or corrective action in the event that s that are, or will be, owned and proper maintenance is not performed. S tormwater Filtering System st be located in common areas, maintained by a joint ownership such as a homeowner’s association mu -owned property, jointly owne d property, or within a recorded community open space, community easement dedicated to public use. Operation and Maintenance Plans should clearly outline how vegetation in the Filtering Practice will le a be managed or harvested in the future. The Operation and Maintenance Plan should schedu cleanup at least once a year to remove trash and debris. Maintenance of Stormwater Filtering Systems is driven by annual maintenance reviews that evaluate the condition and performance of the practice. Based on maintenance review results, specific maintenance tasks may be required. Table 11.4. Typical Stormwater Filtering System Maintenance Items and Frequency Frequency Maintenance Items • Inspect the site after storm event that exceed s 0.5 inches of nfall. rai • Stabilize any bare or eroding areas in the contributing the drainage area including Wet Pond perimeter area During establishment, as needed (first • Water trees and shrubs planted in the Wet Pond vegetated year) perimeter area during the first growing season. In general , water every 3 days for f irst month, and then weekly during the remainder of the first growing season (April - October), depending on rainfall. Remove debris and blockages Quarterly or after major storms • (>1 inch of rainfall) Repair undercut, eroded, and bare soil areas • 11- 03/2013 3.06.2. 17

356 BMP Standards and Specifications Stormwater Filtering Systems Frequency Maintenance Items Mowing of the Wet Pond vegetated perimeter area and • Twice a year embankment • Shoreline cleanup to remove trash, debris and floatables A full maintenance • review Annually • Open up the riser to access and test the valves • Repair broken mechanical components, if needed – One time during the Wet Pond vegetated perimeter and aquatic bench • second year following construction reinforcement plantings Every 5 to 7 years • Forebay sediment removal • Repair pipes, the riser and spillway, as needed From 5 to 25 years Remove sedimen t from Wet Pond area outside of forebays • 11- 03/2013 3.06.2. 18

357 BMP Standards and Specifications Stormwater Filtering Systems References 11. 10 Atlanta Regional Commission (ARC). 2001. Georgia Stormwater Management Manual, First Edition . Available online at: http://www.georgiastormwate r.com Design of Stormwater Filtering Systems Claytor, R. and T. Schueler. 1996. . Chesapeake Research Consortium and the Center for Watershed Protection. Ellicott City, MD. http://www.cwp.org/PublicationStore/special.htm Shaver, E and R. Baldwin, Sand Filter Design for Water Quality Treatment , Delaware DNREC, 1991. 11- 03/2013 3.06.2. 19

358 BMP Standards and Specifications Stormwater Filtering Systems -1 APPENDIX 11 STANDARD DETAIL & SPECIFICATIONS FOR DELAWARE MODULAR SAND FILTER 11- 03/2013 3.06.2. 20

359 BMP Standards and Specifications Stormwater Filtering Systems 11- 03/2013 3.06.2. 21

360 BMP Standards and Specifications Stormwater Filtering Systems 11- 3.06.2. 03/2013 22

361 BMP Standards and Specifications Constructed Wetlands Wetlands Constructed 12.0 Definition: mimic natural Practices that by areas to treat urban stormwater wetland incorporating permanent pools with shallow Wetlands are . Constructed storage areas explicitly designed to provide stormwater above Cv and Fv) er storms ( detention for larg Design variants include: storage. RPv the A Traditional  Constructed 12- s Wetland Swales land B Wet 12-  © Google Earth 2010 meral Constructed Wetlands  12- C Ephe D Submerged Gravel Wetland 12-  (to be added at a later date) Constructed Wetland s are shallow depressions that receive stormwater inputs for water quality surface area is covered by shallow (<1’ deep) wetland area, The majority of the wetland treatment. variable with greater depths in the forebay and pools within the wetland. Wetlands possess ense and diverse wetland cover . Runoff from each new storm displaces microtopography to promote d runoff from previous storms, and the long residence time allows multiple pollutant removal processes ideal environment for gravitational settling, to operate. The wetland environment provides an biological uptake, and microbial activity. , but are also unique in their Wetlands Constructed The design variants all share commonalities performance credits. None of the design variants receive any retentio n allowance, though they all have pollutant reduction capabilities. Traditional Constructed Wetlands (12 -A), should be considered for use after all other upland runoff reduction opportunities have been exhausted and there is still a 10- 00- year, 1 year or flood control remaining treatment vo lume or runoff from larger storms (i.e. to manage. events) land -C) can -B) and Ephemeral Constructed Wetlands (12 Swales (12 Both Wet in well drained soils. Submerged Gr provide some runoff reduction credits, particularly avel Wetlands are to be added at a later date, and will only provide pollution reduction credits. Wetlands Wetla Constructed nd Feasibility Section (see criteria have both community and siting 12.3 Criteria the stormwater practice onsite. ing ) that should be considered before incorporat 1 12 3.06.2. - 03/2013

362 BMP Standards and Specifications Constructed Wetlands 12. Wetland Plan View Figure Constructed Traditional 1. Typical 3.06.2. - 03/2013 2 12

363 BMP Standards and Specifications Constructed Wetlands Wetland 12.1 Stormwater Credit Calculations Stormwater wetla nds receive 0% retention credit (R outlined in pollutant removals are ) and v . As a treatment practice, the wetland Ta ble 12 .1 must be sized according to the standards outlined in Section 12 .6 to receive full pollutant removal credit. A Traditional - Table Constructed Wetlands 12.1 P erformance Credits Runoff Reduction Retention Al 0% lowance RPv 0% A/B Soil - C/D Soil 0% - RPv 0% Cv 0% Fv Pollutant Reduction TN Reduction 3 0% Removal Efficiency 4 0 % Removal Efficiency TP Reduction TSS Reduction 8 0% Removal Efficiency Table 12.1 - B Wet land Swale Performance Credits Reduction Runoff 0% Retention Allowance Annual % 15 - RPv A/B Soil Runoff Reduction C/D Soil 10% Annual Runoff Reduction RPv - Cv of RPv Allowance % 1 0% Fv Pollutant Reduction 100% of Load Reduction + TN Reduction 2 0% Removal Efficiency 100% of Load Reduction + ion TP Reduct 30 % Removal Efficiency 100% of Load Reduction + TSS Reduction % Removal Efficiency 60 03/2013 3 3.06.2. 12 -

364 BMP Standards and Specifications Constructed Wetlands Table 12.1 - C Ephe m er al Constructed Wetland Performance Credits Runoff Reduction Retention Allowance 0% RPv A/B Soil 40% Annual Runoff Reduction - RPv 10% Annual Runoff Reduction C/D Soil - Cv 1 % of Rpv Allowance Fv 0% Pollutant Reduction 100% of Load Reduction + TN Reduction 2 0% Removal Efficiency 100% of Load Reduction + TP Reduction 30 Removal Efficiency % 100% of Load Reduction + TSS Reduction 6 0% Removal Efficiency 12.2 Stormwater Wetlands Design Summary Table 1 s. For more detail, consult Sections 2.2 summarizes design criteria for stormwater wetland through 1 2.8 and 12.9 describe practice construction and maintenance criteria. tions 1 2.7. Sec 12.3 d Design Stormwater Wetlan .2 Table 12 Summary for drainage areas less than 5 acres Requires a water balance calculation • . • Consumes about 10% of CDA. ntributing slopes <8%. • Co Feasibility Setbacks from property lines, buildings, septic fields, and wells. • 3) (Section 12. • Typically located in HSG C and D soils, or in areas of high groundwater. • Avoid construction within jurisdictional wetlands . Juris dictional determinations and permi ts maybe required. E valuate impacts to downstream waters, including existing wetlands. . 1% slope within wetland cells. Max • Conveyance • Max . 1 foot drop between wetlands cells. 4) (Section 12. Removable flashboard risers recommended to set pool elevation. • Pretreatment (Reference Wet Pond specification for additional information). Sediment Forebay at Piped Inlets • 5) 12. (Section ” above the normal pool elevation - (no more than 6” after 48hrs, except 12 12 C) • RPv event: Max. • . 2.5 ft above the normal pool elevation. Fv event: Max Sizing Min. 1 ft of freeboard from the design high water surface elevation to the nearest structure, roadway, etc • (Section 12.6) ). (can be outside the extents of the facility 15% to 35% of the total • A only). - n the permanent pools (12 water storage must be provided withi 03/2013 4 3.06.2. 12 -

365 BMP Standards and Specifications Constructed Wetlands .2 Stormwater Wetlan d Design Summary Table 12 B) : Wet land - (12 Swale , max 6 ’ bottom width • ’. Min. 1 -A) Constructed Wetland (12 Traditional Min bench set at 1 • -yr . 4’ wide • 2:1 overall flow path to linear length ratio . elevation. • 0.5:1 est flow path to overall length. short Side slopes 3:1 or flatter. • • Max. 20% of the contributing may enter with less than a 1:1 • Max. 1% avg. slope (increased if h to overall length. ratio of flow pat Geometry checkdams are used) Side slopes 4:1 or flatter .. • Seasonal high groundwater may • . ; 22” if no groundwater source epth minimum 18” Deep Pool d • intersect the low flow channel to Create microtopography within the wetland • promote aquatic vegetation. • Min. 100’ length D) - Submerged Gravel Wetland (12 C) - Ephemeral Constructed Wetland (12 • Side slopes 4:1 or flatter. • To be added at a later date. (seasonal high r below bottom of wetland Groundwate • groundwater may intersect). Landscaping planted. Native Species • Min. 75% (Section 12. 7 Zones . • Match Plants to Inundation and Integrate trees into design • land (not for Wet -B). Swale, 12 Landscaping • aggressive colonizer species. Min. 4 Criteria • Reference Landscape Criteria Specification for additional information. ) Specification 12.3 nd Feasibility Criteria Wetla the following site constraints: Constructed wetland designs are subject to (12- must have enough water Adequate Water Balance. Traditional Constructed Wetlands A) are designed to not go supplied from groundwater, runoff or baseflow so that the permanent pools dry a fter a 30 -day summer drought. A si mple water balance calculation must be performed using the Section . for drainage areas less than 5 acres Water Balance Testing 12.6. equation provided in The contributing drainage area must be large enough to Contributing Drainage Area (CDA). sustain a permanent water level within the stormwater wetland. If the only source of wetland needed to hydrology is stormwater runoff, then typically more than 2 to 3 acres of drainage area is e if the bottom of the wetland maintain constant water elevations. Smaller drainage areas are acceptabl the groundwater table or if the designer and willing to accept periods of the landowner are intercepts (i.e., Ephemeral Constructed Wetlands, 12 -C), and the plant species are chosen to relative dryness variable accommodate this design . Space Requirements. Constructed Wetlands normally require a footprint that takes up about 10% of the contributing drainage area, depending on the average depth of the wetland. Wetlands are Site Topography. ributing slopes is less than 8%. best applied when the grade of cont 03/2013 5 3.06.2. 12 -

366 BMP Standards and Specifications Constructed Wetlands Reference 6.0 for additional information on a step pool Specification . Restoration Practices approach to Constructed Wetlands that can be applied on steep sloped areas. Available Hydraulic Head. The permanent pool elevat ion is typically fixed by the elevation of the Because existing downstream conveyance system to which the wetland will ultimately discharge. the Constructed rm events in needed for sto is shallow, the amount of head needed is storage Wetlands . typically les s than for W et Ponds , usually a minimum of 2 to 4 feet Minimum Setbacks. Local ordinances and design criteria should be consulted to determine minimum setbacks to property lines, structures, utilities, and wells. As a general rule, the edges of C ed onstruct should be located at least 20 Wetlands feet away from property lines, 25 feet from building 100 water supply feet from public and private 150 feet from septic system fields, and foundations, wells. Depth to Water Table. Constructed le is not a major constraint for depth to the groundwater tab The Wetlands . However, , since a high water table can help maintain the permanent pool elevation , designers should keep in mind that high groundwater inputs may reduce pollutant removal rates increase excavation cost s and reduce the storage volume. For Ephemeral Constructed Wetlands, 12 - C, the normal groundwater elevation shall be below the bottom of the wetland, though the seasonal high groundwater may fluctuate within the storage area. Soils. Soil onducted to determine the infiltration rates and other subsurface properties tests must be c make it difficult to maintain of the soils underlying the proposed wetland. Highly permeable soils will a healthy permanent pool. Underlying soils of Hydrologic Soil Group (HSG) C or D should be A soils and HSG B soils are only suitable for adequate to maintain a permanent pool. Most HSG -C. variants 12 -B or 12 Constructed wetland should be constructed off -line Natural Wetlands. , or Discharges to, Use of from and designed to avoid impacts to federal or state jurisdictional waters, including perennial and intermittent streams and ditches, and tidal and non s may not be -tidal wetlands. Constructed wetland t first obtaining a located within or otherwise impact federal or state jurisdictional waters withou permit from the appropriate agency. Designers should request a jurisdictional determination from the 6728) and federal -656- agency (U.S. Army Corps of Engineers, Philadelphia District, 215 regulatory e Department of Natural Resources and Environmental Control, the state regulatory agency (Delawar 9943) to ensure that all federal and state 739- , 302- Wetland and Subaqueous Lands Section jurisdictional areas are identified. An environmental consultant can be hired to assist with the ation. determin . In addition to the community and environmental Community and Environmental Concerns , Constructed Wetlands exist for Wet , which concerns that can can generate the following Ponds addressed during design: must be 03/2013 6 3.06.2. 12 -

367 BMP Standards and Specifications Constructed Wetlands Wetlands ed Construct  can create wildlife habitat and can also become Aesthetics and Habitat. an attractive community feature. Designers should think carefully about how the wetland plant community will evolve over time, since the future plant community may not resemble the one lanted. initially p A management plan must be put in place to help control noxious weeds and invasive species from colonizing the wetlands. threatening Existing Forests.  Given the large footprint of a Constructed Wetland, there is a chance that the construction process may result in extensive tree clearing. The designer should preserve mature trees during the facility layout, and he/she should consider creating a wooded wetland (see Cappiella et al ., 2006) to reduce clearing . Any felled trees, including the root wad, can be placed in the Constructed Wetland to provide wildlife habitat, bank stabilization, and shade. Constructed safer than Wet Ponds due to their reduced Safety Risk. generally are Wetlands  , although forebays and deep d with aquatic benches to reduce micropools should be designe depth safety risks. - if they are under Wetlands Constructed Mosquito control can be a concern for Mosquito Risk.  sized or have a small contributing drainage area. Deepwater zones serve to keep mosquito iding habitat for fish and other pond life that prey on mosquito populations in check by prov larvae. - -sized and frequently Few mosquito problems are reported for well designed, properly maintained Constructed Wetlands ; however, no design can eliminate them completely. Simple precautio ns can be taken to minimize mosquito breeding habitat within constructed wetlands (e.g., constant inflows, benches that create habitat for natural predators, and constant pool Wet –MSSC, 2005). elevations ave higher Swales, due to the lack of deeper pools, may h land mosquito populations, and should have limited residential applicability. Wetla 12.4 nd Conveyance Criteria slope profile within individual wetland cells should generally be flat from inlet to longitudinal The , at 1% maximum. The recommended maximum elevation drop between wetland cells should be outlet 1 foot or less. While many different options are available for setting the normal pool elevation, it is strongly onal flexibility to recommended that removable flashboard risers be used, given their greater operati or spillway can be A weir adjust water levels following construction (see Hunt et al, 2007). also designed to accommodate passage of the larger storm flows at relatively low ponding depths. Wetla 12.5 nd Pretreatment Criteria Wetlands Sediment . Consequently, a forebay shall be regulation is critical to sustain Constructed located at the inlet, and a micropool pool shall be located at the outlet . Forebays are designed in the . same manner as Wet P onds . Reference the design criteria belo w for additional information 03/2013 7 3.06.2. 12 -

368 Constructed Wetlands BMP Standards and Specifications Criteria Design nd Wetla 12.6 A, Traditional Constructed Wetlands: Variant 12- Constructed Traditional Wetland Sizing. provide water quality enhancement for Wetlands d runoff reduction. Additionally, stormwater volumes remaining after upstream practices have provide be sized to control flows stormwater from the Cv and Fv storage . The available wetland s can storms of storm events in volume the Constructed Wetlands is equal to the volume provided above normal water surface elevation , or the volume permanent pool , or the . The permanent pool volume the total must account for a minimum of 15 to 35% of below the normal water surface elevation, to maintain a healthy system. storage volume be sized s o that the 1 -year RPv event has a maximum ponding The Constructed Wetland must depth of 12” above the normal water surface elevation, in order to reduce impact on the aquatic plantings. In addition, the RPv must be attenuated for a minimum of 24 -hours, although no more er can be ponded for more than 48 hours than 6” of wat year Fv event has a maximum . T he 100- 1 foot ponding depth of 2.5 feet above the normal water surface elevation. Additionally, of ed to the freeboard above the Fv or largest design storm water surface elevation must be provid surrounding roadways and structures requiring a Certificate of Occupancy. The extents of the Fv or highest design storm must be clearly denoted on the Sediment and Stormwater Management Plans. Internal Design Geometry. Traditional Constructe d Wetlands can be design ed in several ways, all of which promote diverse emergent and aquatic vegetation, as well as anaerobic and aerobic conditions within the water to promote pollutant removal. In all cases , varied topography within he wetland is encouraged to provide diverse ecology (e.g., hummocks, each component of t . Research and experience have shown ed peninsulas, horizontal tree stumps, boulders, etc) forest t removal pollutan that the internal design geometry and depth zones are critical in maintaining the capability and plant diversity of stormwater wetlands. Wetland performance is enhanced when the wetland has multiple cells, longer flowpaths, and a high ratio of surface area to volume. Whenever possible, constructed wetlands should be irregularly shaped with long, sinuous flow paths. The total length of the flow path compared to the linear length through the wetland area, must be a minimum ratio of 2:1. In addition, the ratio of the shortest flow path through the ed near the outlet) to the overall length must be at least 0.5:1. The system (due to an inlet locat constitute no more than 0.5:1 ratio shall drainage area served by any inlets located less than a 20% of the total contributing drainage area. at distributes the runoff through wetland igned th areas One continuous winding system can be des 1% be limited to maximum of and deeper permanent pools. The flow through the system shall excluding any drops or riffles slope . At area and one least one shallow wetland average permanent pool area must be provided, but there is no maximum on how many times the systems 03/2013 8 3.06.2. 12 -

369 BMP Standards and Specifications Constructed Wetlands can be alternated. See below for more detailed information on the various components. If a more varied range in elevation is desired, a more step pool approach can be taken, where the different cells can be separated in elevation by bio or compost logs, sand berms anchored with rocks/boulders, or other stabilized protection. Forested peninsulas can also be extended across 95% of the width of the wetland, creating two separate zones . Riffles, or rock lined slopes of maximum 8%, can also be used to adjust the grades. The maximum elevation difference between cells sh all be 1 foot. the various Inundation Zones . RPv= 12 ” Normal Pool 1 2 3 4 5 12.4. Figure -36 Traditional Constructed Wetland Inundation Z ones: ( 1) Deep Pool (depth , (2) Transition Zone Low to -18 inches) -6 (depth -18 to - 6 inches) , (3) (depth Marsh Zone , and ( 5) inches to normal pool ), (4) High Marsh Zone (normal pool to + 12 inches) to +30 inches) (+12 Floodplain (adapted from Hunt et al,. 2007). Zone 1: • Forebays. For all designs a forebay must be included at all pipe inlets to provide sedimentation prior to the runoff entering the main wetland system. The forebay must be 3 to 4 foot deep and follow the forebay specifications as described in Specification 13 – Wet Ponds . The forebay will allow for easier access of accumulated sediments rather than being dispersed throughout the wetland syste m. In some instances, it might be desired to direct water from a Wet Pond to a wetland system, in which case a specified forebay is not necessary since one is provided in the Wet Pond. • Deep Pools . The volume of water stored in the deep pools, also referred to as micropools, must be at least 15% of the total water storage volume. At least two s in addition deep pool to the forebay must be provided , one of which must be located prior to the outlet location to provide for additional sediment deposition. D eep pools can help to provide fish habitat , cooler water temperatures, energy dissipation, and sedimentation . These interior deep pools 3.06.2. 9 12 03/2013 -

370 BMP Standards and Specifications Constructed Wetlands be range from - 18 inches to - 36 inches in depth below the normal pool elevation , and must designed to remain permanentl y saturated. If groundwater will not support the permanent pool elevation in the summer months, then the minimum deep pool elevation should be connected within the water flow . The deep pools must be hydraulically 22 inches ed to - lower ls shall be designed with a slope not steeper than 3:1. path. The deep poo Zone 2: Transition Zone. Zone 2 is only allowed as a short transition zone between the deeper pools 6 to - and the low , and ranges from - marsh zone 18 inches below the normal pool elevation. In gener have a maximum slope of 3:1, or flatter, from the deep pool to the al, this transition zone must low marsh zone. It is advisable to install biodegradable erosion control fabrics or similar materials during construction to prevent erosion or slumping of thi s transition zone. s, Marsh Zone. Most of the wetland surface area will exist between the two marsh zone Zone 3: Low vation the normal pool ele below 6 inches s from range zones 3 and 4. The low marsh zone to the should therefore normally be saturated , and planted with species that thrive . It normal pool elevation in this wet condition . Since this . The slope within the low marsh zone shall not be steeper than 4:1 event function in wetland ea between storm s, it should have a surface ar s essential zone provide surface area. between 75 and 125% of the high marsh zone . Zone 4: High Marsh Zone The upper end of the marsh zone is the high marsh zone, which ranges from the normal pool elevation to + 12 , allowing the RPv to inundate to the top of the high inches marsh zone. Where conditions allow, the RPv ponding depth should be reduced to be closer to 6”, which will increase the plant survivability. The slope within the high marsh zone shall not be steeper than 4:1, and typically much flatter marsh zones are designed to increase storage. Any storm events above the RPv event, should inundate into the floodplain Zone 5: Floodplain. 18 inches above the normal water surface and + area. A low floodplain should range between +12 elevation, and be planted with plant , depending on to temporary saturations s suited for infrequent provides storage inches 30 to + weather patterns . An upper floodplain of elevations ranges +18 for the higher storm events, including the Fv. The two floodplains areas can be combined for smaller drainage areas less than 10 acres. Also, i f the Constructed Wetland is connected to a Wet Pond then the Wet Pond can be utilized for the storage of the higher storm events , and the he slope within the . T floodplain storage within the Constructed Wetland can be reduced floodplain shall not be steeper than 4:1, and typically much flatter floodplains are designed to increase storage. Vegetated Perimeter around the wetland area must A minimum 50 foot wide vegetated perimeter . be planted with app spillway shall either be grass or ropriate grasses, trees and shrubs (the emergency in the perimeter riprap). Existing vegetation can and should remain species area, so long as noxious . are eradicated and invasive species are controlled 03/2013 10 3.06.2. 12 -

371 BMP Standards and Specifications Constructed Wetlands . esting Water Balance T Traditional Constructed Wetlands can be scaled to accommodate small drainage areas, although it is necessary to calculate a water balance when the contributing drainage area is less than 5 acres (Refer to Specification 13. Wet Ponds ). is not supplied by groundwater or dry weather Similarly, if the hydrology for the permanent pools flow inputs, a simple water balance calculation must be performed, using Equation 12.2 (Hunt et al., , to assure the deep pools will not go completely dry during a 30 day summer drought. 2007) Equation 2. The Hunt Water Balance Equation for Acceptable Water Depth in a 12. Stormwater Wetland DP = RF * EF * WS/WL – ET – INF – RES m , inches = Depth of pool Where: DP me 1 inch, or use historically RF = Monthly rainfall during drought , inches (assu m data) Rational runoff = Fraction of rainfall that enters the stormwater wetland ( EF coefficient ) WS/WL = Ratio of contributing drainage area to the normal pool wetland surface area (assume ET = Summer evapotranspir ation rate, inches 7 inches ) INF = Monthly infiltration loss (assume 7.2 inches , or 0.01 inch/hour for 30 days, unless a higher infiltration rate is known ) = Reservoir of water for a factor of safety 6 inches) (assume RES , inches iant 12- Var land Swales: B, Wet Wet swales are designed similar to traditional vegetated swales in that land . Sizing Swale land Wet they should convey the Cv and Fv events with non- erosive velocities and should fully contain the Cv event (no freeboard required). If the Fv event is not contained within the swale top of bank, then the not pond all area of inundation or alternate route shall be noted. The RPv water surface elevation sh There is no minimum or maximum more than 6 inches above the normal water surface elevation. drainage area, though typically swales are designed for less than 5 acres of contributing area. land Internal Geometry. swales should be designed as a two stage system. The low flow Wet ld be designed with a permanent to semi t, and shou requires a minimum width of 1 foo - channel permanent water elevation of 4 to 6 inches. This can be accomplished through inception with the seasonal high groundwater or through the use of check dams or other control structures that back the water up to that l . The low flow channel should support plants that evel during wet conditions tolerate mostly wet conditions. The width of the low flow channel should be maximum 6 feet to within (or braiding); very large drainage areas may prevent additional low flow channels from forming require increased widths, but typically the low flow channel will fall in the 2 to 4 foot width range. To increase functionality, the low flow channel should be meandered within the total confines of the Swale (i.e., the top of b land Wet ank does not need to meander, but the low flow channel should). 03/2013 11 3.06.2. 12 -

372 BMP Standards and Specifications Constructed Wetlands +/- 0.1’), a shallow floodplain bench shall be within At the water surface elevation of the RPv event ( dth should be provided, which alleviates shear stress on the sides of the banks. The total bench wi minimum 4 feet and is generally split on either side of the low flow channel, though the dimensions can alter as the low flow channel meanders through the swale section, with increased bench widths on the inside of a curve. Vegetation planted on the benches should also support wet periods, though will be inundated less frequently then the plants in the low flow channel. land Deep pools should not be incorporated into the Wet Swales for safety purposes, as most people The average groundwater assume swales are traversable and would not suspect a deep portion. elevation must be below the bottom of the Wetland Swale; only the seasonal high groundwater may intersect the bottom. land Swales shall not have a steeper slope than 3:1. The Side Slopes. Wet Longitudinal Grade breaks similar to is an average of 1%. The maximum longitudinal slope Slope: -A can be used as necessary. variant 12 Vegetated Perimeter the wetland on both sides of foot wide vegetated perimeter A minimum 10 . be planted with appropriate grasses, trees and shrubs. Existing vegetation can and should swale must remain in the perimeter area, so long as invasive species are eradicated and invasive species are . controlled Variant 12- C, Ephemeral Constructed Wetlands: Sizing. Wetland Ephemeral Constructed Wetlands are designed without a permanent pool, since the be only in the spring and fall months. The Fv water surface shall intent is for them to be wet pond 0 inches maximum 3 above the ground surface, and the RPv event must - -inches and 1 between 6 be provided for the 100- year and larger events, but . An emergency spillway must of water foot traditionally no other outlets are provided. If freezing in the winter is a concern, or for maintenance Wetland should only be purposes, a drain pipe can be pr ovided, but the Ephemeral Constructed drained in late November after amphibian breeding seasons. The wetland can be modeled with the design infiltration rate, and is allowed to hold the RPv event for greater than 48 hours. Geometry. Internal Ephemeral Constructed Wetlands should mimic those found naturally, which typically are ponded low areas. These shallow areas fill up with runoff during wet conditions, and will dry up during periods of little to no rain. These fluctuations typ ically provide more diversity in be planted with a variety of vegetation that must vegetation and animals. The shallow ponded area . can tolerate both wet and dry conditions The seasonal high groundwater may fluctuate into the bottom of the Ephemeral Con structed Wetland, but the average groundwater shall be below the wetland bottom. The wetland shall be elevation 03/2013 12 3.06.2. 12 -

373 BMP Standards and Specifications Constructed Wetlands . al high groundwater if it does intersect the wetland bottom modeled with the season equired to contain the wetland pool. If Depending on the existing grades , an embankment may be r so, a core trench shall extend down to a limiting layer or minimum 4 feet below ground surface, which of water through the embankment, compromising the construction will help prevent lateral migration . The side slopes of the buffer area and within the wetland should be 4:1 or flatter. Side Slopes . around the wetland area must . A Vegetated Perimeter minimum 50 foot wide vegetated perimeter be planted with appropriate grasses, trees and shrubs (the llway shall either be grass or spi emergency rip species so long as noxious Existing vegetation can and should remain in the perimeter area, rap). are eradicated . and invasive species are controlled : Constructed Wetland Material Specifications -site, except for the plant materials, constructed with materials obtained on Wetlands are generally inflow and outflow devices (e.g., piping and riser materials), possibly stone for inlet and outlet fabric for lining banks or berms. In some ins tances clay may need stabilization, and stabilization to be imported to provide a permanent pool elevation in certain areas of the constructed wetland that may not otherwise support a permanent pool. Plant stock should be nursery grown, unless otherwise approved by the local regulatory authority, and should be healthy and vigorous native species free from defects, decay, disfiguring roots, sun -scald, injuries, abrasions, diseases, insects, pests, and all forms of infestations or objectionable disfigurements, as determined by the local reg ulatory authority. nd Landscaping Criteria Wetla 12.7 must be prepared by a licensed etland s and A landscaping plan is required for all Constructed W . The plan sh professional knowledgeable in wetland species outline a detailed schedule for the care, all , particularly for the of vegetation in the wetland and its buffer maintenance and possible reinstallation first 10 years of establishment. The plan should outline a realistic, long -term planting strategy to establish and maintain desired The plan should indicate how wetland plants will be established within each wetland vegetation. -mixes, volunteer colonization, and tree and shrub stock) e.g., wetland plants, seed inundation zone ( Reference the L andscaping Criteria and whether soil amendments are needed to get plants started. for additional Constructed Wetland landscaping specifications. Appendix . Wetla nd Construction Sequence 12.8 depends on site conditions, design complexity, variants wetland the The construction sequence for and the size and configuration of the proposed facility. The following two -stage construction wetland facility and establishing vigorous plant cover. sequence is recommended for installing a 03/2013 13 3.06.2. 12 -

374 BMP Standards and Specifications Constructed Wetlands Stage 1 Construction Sequence: Wetland Facility Construction. wetlands should only be constructed after the Constructed Step 1: Stabilize Drainage A . rea contributing drainage area to the wetland is completely stabilized. If the proposed wetland site will be hould clearly used as a sediment trap or basin during the construction phase, the construction notes s -watered, dredged and re- graded to design dimensions after the indicate that the facility will be de original site construction is complete. Step 2: Assemble Construction Materials on-site, make sure they meet design specifications, and prepa re any staging areas. temporary prior to construction, including 3: Install Erosion and Sediment (E&S) Controls Step dewatering devices, sediment basins, and stormwater diversion practices. All areas surrounding the wetland that are graded or denuded duri ng construction of the wetland are to be planted with turf grass, native plant materials or other approved methods of soil stabilization. In some cases, a phased or staged E&S Control plan may be necessary to divert flow around the stormwater wetland area until installation and stabilization are complete. (if and Construct the Embankment 4: Excavate the Core Trench for the Embankment Step and Emergency Spillway . Pipe . Install the Outlet required) 5: Install the Riser or Outflow Structure and ensure that the top invert of the overflow weir is Step (flashboard risers are strongly recommended by constructed level and at the proper design elevation Hunt et al, 2007). Step 6: Clear and Strip wetland project area to the desired sub -grade. the 8 to 12- inch lifts and compacted with appropriate in ct any Internal Berms Step 7: Constru equipment. are achieved for the until the appropriate elevation and desired contours Step 8: Excavate/Grade g up” the interim elevations . This is normally done by “roughin bottom and side slopes of the wetland with a skid loader or other similar equipment to achieve the desired topography across the wetland. Spot surveys should be made to ensure that the interim elevations are 3 to 6 inches below the final elevations for the wetland. -Topographic Features and Soil Amendments Step 9: Install Micro within wetland area. Since most -soil, they often lack the nutrients and organic matter stormwater wetlands are excavated to sub efore essential to add compost, topsoil needed to support vigorous growth of wetland plants. It is ther or wetland mulch to all depth zones in the wetland. The importance of soil amendments in excavated plant wetland survival and sparse -emphasized; poor plant coverage are likely wetlands cannot be over ts are not added if soil amendmen planting soil should be a high organic content loam or sandy . The 03/2013 14 3.06.2. 12 -

375 BMP Standards and Specifications Constructed Wetlands loam, placed by mechanical methods, and spread by hand. Planting soil depth should be at least 4 inches for shallow wetlands. No machinery should be allowed to traverse over the planting soil during or after construction. Planting soil should be tamped, but it should not be overly compacted. permanent above the normal pool elevation with 10: Stabilize Exposed Soils seed mixtures Step appropriate for a wetland environment by hydro -seeding or seeding under straw per the Landscape . Temporary seed, such as annual rye or winter wheat, can be used to stabilize the soil but Plan permanent species must then be planted or seeded at a later date. Stabilization matting shall be utiliz ed in Wet land Swales, 12 -B, and in all areas of concentrated flow and/or slopes at 3:1 or steeper. Step 11: Post Construction Verification: After soil stabilization, but prior to planting individual species, perform a post construction verification of the constructed wetland. This will confirm the planting zones and normal pool elevation based on the outlet elevation. Three cross -sections ed, ) shall be measured, mark principal spillway the prior to and -wetland, (forebay, mid - and geo referenced on the p ost construction verification survey document . This will enable maintenance reviewers Any to determine sediment deposition rates in order to schedule sediment cleanouts. . embankments shall be verified per the requirements in Specification 13. Wet Ponds Stage 2 Construction Sequence: Establishing the Wetland Vegetation. 12: Open Up the Wetland Connection Step (if desired) . Once the final grades are attained, the pond and/or contributing drainage area connection can be opened to allow the wetland cell to f ill up to the to minimize erosion of unplanted features. If normal pool elevation. Gradually inundate the wetland the wetland area is connected than it will need to be dewatered to the lowest planting elevation (i.e., the low marsh zone) prior to planting. 13: Finalize the Wetland Landscaping Plan At this stage the engineer, landscape . (if needed) Step after architect, and wetland expert work jointly to refine the initial wetland landscaping plan the Constructed Wetland has been constructed and the normal pool elevation has been established if there have been any changes to the planting zones from the initial design . This can allow the designer to select appropriate species and additional soil amendments, based on field confirmation of soils , and also properties and the actual depths and inundation frequencies occurring within the wetland confirm plant availability at the onset of the planting season. Depths in the 14: Measure and Stake Planting Depths Step wetland should be measured to the nearest inch to confirm the original planting depths of the planting , and their zone. Surveyed planting zones should be marked on the post construction verification If necessary, dewater to the locations should also be identified in the field, using stakes or flags. bott om of the low marsh zone prior to staking and planting. 03/2013 15 3.06.2. 12 -

376 BMP Standards and Specifications Constructed Wetlands Three techniques are used in combination to . Step 15: Propagate the Constructed Wetland propagate the emergent community over the wetland bed: k. -Grown Wetland Plant Stoc Initial Planting of Container 1. The transplanting window extends -June. Planting after these dates is quite chancy, since emergent wetland from early April to mid plants need a full growing season to build the root reserves needed to get through the winter. If at all possible, the plan ts should be ordered at least 6 months in advance to ensure the availability time delivery of desired species. and on- . The higher wetland elevations should be established by Broadcasting Wetland Seed Mixes 2. se emergent wetlands. Seeding of wetland seed broadcasting wetland seed mixes to establish diver mixes as a ground cover is recommended for all zones above 3 inches below the normal pool elevation. Hand broadcasting or hydroseeding can be used to spread seed, depending on the size of the wetland cell. . The wing “Volunteer Wetland Plants to Establish. Allo establishment of volunteer species should 3. . Typically if properly managed, be encouraged with the exception of noxious weeds and invasives the constructed wetland will fill out with volunteer species and es tablishment of the planted and seeded species within 3 to 5 years. This is . 16: Install Goose Protection to Protect Newly Planted or Newly Growing Vegetation Step a Canad plants, as predation by particularly critical for newly established emergent and herbaceous wetland vegetation. Goose protection can consist of netting, webbing, or geese can quickly decimate string installed in a criss -cross pattern over the surface area of the wetland , above the level of the emergent plants. Step 17: Plant the Wetlan d Floodplain and Buffer Area . This zone generally extends from 1 to 3 inundated less feet above the normal pool elevation. Consequently, plants in this zone are frequently can be but still must be able to tolerate periods of flooding and soil saturation . The buf fer area planted with species that do not need wet conditions , and can be planted in the spring or fall. reviews Construction . Construction Reviews etlands are critical to ensure that the Constructed W and established. Multi are recommended during the ple site visits and reviews are properly installed following stages of the wetland construction process: -construction meeting Pre • Initial site preparation (including installation of project E&S controls) • Excavation/Grading (e.g., interim/final elevatio • ns) Wetland installation (e.g., microtopography, soil amendments and staking of planting zones) • • Planting Phase (with an experienced landscape architect or wetland expert) Review Final • (develop a punch list for facility acceptance) 03/2013 16 3.06.2. 12 -

377 Constructed Wetlands BMP Standards and Specifications nd Maintenance Criteria Wetla 12.9 An Operation and Maintenance Plan for the project will be approved by the Department or the Delegated Agency prior to project closeout. The Operation and Maintenance Plan will specify the primary maintenance responsibilit and authorize the Department owner’s property ies or Delegated Agency or corrective action in the event that staff to access the property for maintenance review Constructed Wetlands that are, or will be, owned and proper maintenance is not performed. rship such as a homeowner’s association must be located in common areas, maintained by a joint owne -owned property, jointly owned property, or within a recorded community open space, community easement dedicated to public use. aintenance Operation and M how vegetation in the Constructed Wetland should clearly outline Plans and its buffer will be managed or harvested in the future. Periodic mowing of the Constructed buffer is only required along and the embankment. The remaining access maintenance Wetland the a meadow (mowing every other year) or forest. The maintenance plan buffer can be managed as should schedule a shoreline cleanup at least once a year to remove trash and floatables. that evaluate the is driven by annual maintenance reviews Maintenance of a Constructed Wetland results, cond ition and performance of the Constructed Wetland. Based on maintenance review specific maintenance tasks may be required . Additional reviews are required during the first two years of establishment. First Two Years: ust be reviewed twice a year, once in the spring The Constructed Wetland m and once in the fall after a storm event that exceeds 1/2 inch of rainfall. This should be done for the first two years. Additional trips to the project site will be needed for watering, maintenance, etc w hich is described below. should look for bare or eroding areas in the contributing Spot Reseeding. Maintenance personnel  drainage area, around the wetland buffer, and make sure they are and in the wetland cells, immediately stabilized with grass cover. Trees and shrubs planted in the buffer and on wetland islands and peninsulas need Watering.  watering during the first growing season. In general, consider watering every three days for first tober), depending on rainfall. - Oc month, and then weekly during the first growing season (April In the summer months, and times of prolonged drought, all of the plantings may need watering to ensure survival.  Reinforcement Plantings. Regardless of the care taken during the initial planting of the wetland and buffer, it is probable that some areas will remain non- vegetated and some species will not survive. Poor survival can result from many unforeseen factors, such as predation, poor quality drought. Thus, it is advisable and to budge plant stock, water level changes, t for an additional round of reinforcement planting after one or two growing seasons. Construction contracts should include a care and replacement warranty extending at least two growing seasons after initial planting Close -out on , to selectively replant portions of th e wetland that fail to fill in or survive. the project will not occur until a minimum of 70% of the wetland area is permanently vegetated, 03/2013 17 3.06.2. 12 -

378 BMP Standards and Specifications Constructed Wetlands which may take several growing seasons and additional plantings. Designers should ex Invasive Species.  pect significant changes in wetland species composition to occur over time. Reviews should carefully track changes in wetland plant species distribution over nvasive plants should be dealt with as soon as they begin to Noxious plants and undesired i time. invasive species colonize the wetland. As a general rule, control of noxious weeds and undesirable their ) should commence as soon as they are spotted and before (e.g., cattails and Phragmites must be applied by a Certified coverage exceeds more than 5% of a wetland cell area. Herbicides through the Department of Agriculture and be aquatic safe (i.e., aquatic pesticide applicator -based products) Glyphosate . Extended periods of dewatering may also work, since early manual removal provides only short -term relief from invasive species. While it is difficult to exclude invasive species completely from stormwater wetlands, their ability to take over the entire wetland can be reduced if the designer creates a wide range of depth zones and a complex internal structu re within the wetland. Managing vegetation is an important ongoing maintenance task at going Maintenance: Annual, On- and for each inundation zone. Wetland Constructed every  eded Vegetation Management. Thinning or harvesting of excess forest growth will be ne and prevent it from becoming periodically to guide the forested wetland into a more mature state overgrown. Thinning or harvesting operations should be scheduled to occur approximately 5 and 10 years after the initial wetland construction. Removal of woody species on or near the , structural components such as inflow and outflow pipes, and maintenance access embankment areas should be conducted every 2 years.  Regular mowing operations only need to occur along maintenance accessways, and Mowing. occur at minimum twice a year. Reference the Landscape Plan for additional should requirements; some upland meadow areas may also require occasional mowing.  Sediment removal in the pretreatment forebay must occur when 50% of Sediment Removal. total forebay cap acity The owner can plan for this maintenance activity to occur has been lost. every 5 to 7 years.  Sediment Deposits. Sediment removed from the forebay should be deposited in the designated enance set aside area for dewatering, prior to leveling and stabilization or removal from the maint Sediments excavated from Constructed Wetlands site. are not usually considered toxic or hazardous. They can be safely disposed of by either land application or land filling. Sediment testing may be needed prior to sed iment disposal if the contributing area serves a hotspot land use. 12. 10 References A Guide to Creating Vernal Ponds: All the Information You Need to Build and Biebighauser, T., Maintain an Ephemeral Wetland. USDA Forest Service. Cappiella, K., T. Schueler and T. Wright. 2006. Urban Watershed Forestry Manual: Part 2: 03/2013 18 3.06.2. 12 -

379 Constructed Wetlands BMP Standards and Specifications . USDA Forest Service. Center for Watershed Conserving and Planting Trees at Development Sites City, MD . Ellicott Protection. Urban Hunt, W., C. Apperson, and W. Lord. 2005. “Mosquito Control for Stormwater Facilities.” . North Carolina State University and North Carolina Cooperative Extension. Waterways , NC. Raleigh Hunt, W., M. Burchell, J. Wright and K. Bass. 2007. “Stormwater Wetland Design Update: Zones, Urban Waterways . North Carolina State Cooperative nce.” Vegetation, Soil and Outlet Guida , NC. Extension Service. Raleigh Ladd, B and J. Frankenburg. 2003. Management of Ponds, Wetlands and Other Water Reservoirs . -41- Purdue Extension. WQ W. Lenhart, H., W. Hunt. 2011. “ -Water Performance Metrics with a North orm Evaluating Four St Carolina Coastal Plan Storm Vol 137, No.2. Journal of Environmental Engineering ” -Water Wetland. Mallin, M. 2000. Effect of human development on bacteriological water quality in coastal watersheds. 10(4):1047- Ecological Applications 1056. Mallin, M.A., S.H. Ensign, Matthew R. McIver, G. Christopher Shank, and Patricia K. Fowler. 2001. Demographic, landscape, and meteorological factors controlling the microbial pollution of coastal waters. 460(1- 3):185- 193. Hydrobiologia Messersmith, M.J. 2007. Assessing the hydrology and pollutant removal efficiencies of wet detention ponds in South Carolina. MS. Charleston, S.C. College of Charleston, Master of Environmental Studies. . Emmons Minnesota Stormwater Manual C). 2005. Minnesota Stormwater Steering Committee (MSS & Oliver Resources, Inc. Minnesota Pollution Control Agency. St. Paul , MN. Metropolitan Minnesota Urban Small Sites BMP Manual. Constructed Wetlands: Wet Swales. Council/Barr Engineering Co. Santana, F., J. Wood, R. Parsons, and S. Chamberlain. 1994. Control of Mosquito Breeding in . Southwest Florida Water Management District. Brooksville, FL. Permitted Stormwater Systems . Metropolitan Washington Counci Design of Stormwater Wetland Systems Schueler, T, 1992. l of Governments. Washington, DC. VA Department of Conservation and Recreation (VA DCR) . 1999. Virginia Stormwater Management Handbook, first edition. 03/2013 19 3.06.2. 12 -

380 Wet Ponds BMP Standards and Specifications Ponds Wet 13.0 are stormwater Ponds Wet Definition: storage practices that consist of a combination shallow or , micropool, of a permanent pool that promote a good marsh environment for gravitational settling, biological uptake and microbial activity. t Ponds are widely We applicable for most land uses and are best suited for larger drainage areas. Runoff from and each new storm enters the wet pond partially displaces pool water from previous storms. The pool also acts as a barrier to re- suspension of sedi ments and other pollutants et Ponds have a residence time that ranges deposited during prior storms. When sized properly, W from many days to several weeks, which allows numerous pollutant removal mechanisms to operate. above the permanent pool to help meet stormwater management can also provide storage Ponds Wet for larger storms. requirements Design variants include: A Wet Pond 13-  B Wet Extended Detention (ED) Pond  13- hour provides 24- in that a Wet ED Pond differs from a typical Wet Pond A Wet ED Pond detention Wet ED of all or a portion of the Resource Protection Volume (RPv). Optional internal baffles in the n Pond extend the flow path through the pond from the inflow point to the outlet. In addition, a er flow so it backs up and is stored within the Wet ED undersized outlet structure restricts stormwat particulate pollutants to settle out and reduces . The temporary ponding enhances the ability of Pond the maximum peak discharge to the downstream channel, thereby reducing the effective shear stress on banks of the receiving stream. Wet Pond s should be considered for use after all other upland runoff reduction opportunities have treatment exhausted and there is still a remaining been (i.e. Cv volume or runoff from larger storms an Fv) to manage. pollutant for s do not receive any stormwater retention credit and should be considered only Pond Wet and to manage flood events removal efficiency . Wet Pond s have both community and environmental 13. ) that need to be considered before applying concerns (see 3 Wet Pond Feasibility Criteria Section them . 03/2013 1 3.06.2. 13 -

381 Wet Ponds BMP Standards and Specifications 13. A) Design Schematics . 13- 1. Wet Pond ( Figure 03/2013 3.06.2. 13 - 2

382 Wet Ponds BMP Standards and Specifications 13- Extended Detention Pond ( Wet 2. Typical 13. Figure . B) Details 03/2013 3.06.2. 13 - 3

383 BMP Standards and Specifications Wet Ponds Credit Calculations Pond 13.1 Wet As a . Table 13.1 pollutant removals outlined in ) and s receive 0% retention (R Wet Pond credit v must be sized according to the standards outlined in Section treatment practice, the Wet Pond 13.6 to receive full pollutant removal credit . Table 13.1 Wet Pond and Wet ED Pond Performance Credits Runoff Reduction Retention Allowance 0% RPv A/B Soil 0% - RPv 0% C/D Soil - Cv 0% 0% Fv Pollutant Reduction 20% TN Reduction 45% TP Reduction 60% TSS Reduction 03/2013 4 3.06.2. 13 -

384 BMP Standards and Specifications Wet Ponds Summary Design Pond Wet 13.2 Wet Pond in the State of requirements s constructed to meeting regulatory stormwater management Delaware shall be designed and constructed in accordance with the USDA NRCS Small Pond Code for Wet Pond s. For more detail, Table 13.2 summarizes design criteria 378 and this document. consult Sections 13.3 through 13.7. Sections 13.8 and 13.9 describe practice construction and maintenance criteria. Summary e 13.2 Wet Pond Design Tabl • baseflow to support permanent pool Adequate groundwater, runoff or • Recommended minimum Contributory drainage area (CDA) of 10 to 25 acres • Wet Pond surface area size allowance of 1% to 3% of CDA Contributing slopes <15% • • Wet Pond discharge point allows for gravity discharge Feasibility in accordance with local codes Setbacks • Criteria • No utility may cross the embankment (Section 13.3) • Seasonal high water table < design permanent pool elevation • HSG C and D soils; HSG A and some HSG B soils may require a liner Not located within jurisdictional waters, including wetlands or on p • erennial streams Consider community and environmental concerns such as aesthetics, forests, safety, • pollutants, mosquitoes and waterfowl • Principal spillway must be accessible by dry land • Principal spillway must include t rash racks and watertight joints must be protected from clogging • Small low flow orifices Conveyance Outfall channel designed to be stable for the Cv • Criteria to safely convey the Fv spillway designed Emergency • (Section 13.4) • Emergency spillway must be in cut material or reinforced • Inflow points and forebays stable for the Cv • necessary dam safety permits Secure those volume conveying >10% of runoff – Forebays at major inlets • Pretreatment • Forebays sized for 10% of RPv Criteria • erosive discharge from forebay to pond pool Non- (Section 13.5) ect access provided to facilitate forebay maintenance Dir • within the perman ent pool and extended detention • Store RPv (2.7”) Design Criteria Storage >5’ above permanent pool requires design enhancements • Storage (Section 13.6) • Water balance calculation necessary Minimum length to width ratio = 1.5:1 • • Maximum depth of permanent pool = 4.0 feet Design Criteria • Side slopes no steeper than 3H:1V Geometry (Section 13.6) Ten foot wide safey bench constructed 1’ above permanent pool • • cted 1’ below permanent pool Ten foot wide aquatic bench constru • Soil borings / geotechnical tests will confirm need for a liner • Low Flow ED orifice protected from clogging Design Criteria • Riser structure must be accessible for maintenance Appurtenances enclosed structure openings Trash racks provided on • (Section 13.6) • Outlet pipe and pond drain equipped with adjustable gate valve • Materials meet Small Pond Code 378 specifications 13 3.06.2. - 03/2013 5

385 BMP Standards and Specifications Wet Ponds Tabl e 13.2 Wet Pond Design Summary Restrict to principal spillway entry • Design Criteria levation (2’ if no emergency spillway) freeboard above the Fv e One foot of • Safety • Emergency spillway located to not impact downstream structures (Section 13.6) Safety and aquatic benches landscaped to prevent access • tlet structure Provide access to forebays, safety bench, riser and ou • Design Criteria • Access roads built to withstand the expected frequency of use Maintenance Minimum width of access roads = 15’, profile grade < 5:1 • (Section 13.6) Maintenance set aside area provided • • principal spillway or inflow or 25’ of nt the embankme No woody vegetation within 15’ of Landscaping pipes Criteria Detailed landscaping plan required • (Section 13.7) 3 13. Wet Pond Feasibility Criteria s are considered a final storm The following feasibility issues need to be considered when Wet Pond water management practice of the treatment train. Adequate Water Balance. s must have enough water supplied from groundwater, runoff Wet Pond pools or baseflow so that the wet -day summer t after a 30 will not draw down by more than 2 fee drought. A simple water balance calculation must be per E quation s 13.1 and 13.2 formed using the provided in . Water Balance Testing Contributing Drainage Area. A contributing drainage area of 10 to 25 acres is typically ion with recommended for Wet Pond s to maintain constant water elevations. Wet Pond s can still funct drainage areas less than 10 acres, but designers should be aware that these “pocket” ponds will be prone to clogging, experience fluctuating water levels, and generate more nuisance conditions. When the contributing drainage area of the Wet Pond is less than 10 acres, alternative outlet configurations should be used to eliminate the possibility of clogging of the outlet. % of its % to 3 will normally be at least 1 The surface area of a Wet Pond . ments Space Require ding on the pond’s depth. contributing drainage area, depen Wet Pond s are best applied when the grade of contributing slopes is less than Site Topography. 15%. should be used to Available Hydraulic Head. The ultimate discharge point from the Wet Pond e permanent pool. The permanent pool elevation must be determine the minimum elevation of th higher than the outlet elevation in order to have a gravity discharge. In situations where there is little discharge relief on the parcel and the head differential between the permanent pool elevation and the outlet is a weir and outlet channel configuration. n option for the Wet Pond elevation is small, a Local ordinances and design criteria should be consulted to determine minimum Minimum Setbacks. setbacks to property lines, structures, and wells. When not specified in local code, Wet Pond s should be set back at least 20 feet from property lines, 25 feet from building foundations, and 100 feet from 03/2013 6 3.06.2. 13 -

386 BMP Standards and Specifications Wet Ponds water supply wells. septic system fields and 150 feet from public or private system, no utility lines shall be permitted to cross any For an open Wet Pond Proximity to Utilities. part of the embankment of a wet pool. Depth -to-Water Table. The depth to the seasonal high water table is an important consideration in planning of a Wet Pond . When the seasona l high water table elevation exceeds the proposed , the capacity planned for management of the Cv and Fv in permanent pool elevation of the Wet Pond Wet Pond f the water table is close to the surface, it Further, i taken up by groundwater. be the may e excavation difficult and expensive. may mak Highly permeable soils will permanent pool. Underlying Soils. make it difficult to maintain a healthy soils of Hydrologic Soil Group (HSG) C or D should be adequate to maintain a permanent pool. not support a permanent pool without the use of a liner (See Most HSG A and B soils will Table 13.3 Geotechnical must be conducted to determine the suitability of the soils to investigations below). ation test should be support a permanent pool. When soil borings confirm HSG A/B soils, an infiltr inch/hour at the tion rate greater than 1.0 If the infiltration test results in an infiltra conducted. Wet Pond proposed feet or more below the invert, and the seasonal high groundwater table is two Wet ED Pond proposed Wet Pond invert, a stormwat er management BMP other than a Wet Pond or gned. should be desi Use of or Discharges to Natural Wetlands. Wet Pond s may not be located within jurisdictional waters, including wetlands, without obtaining a section 404 permit from the appropria te state or . In addition, the designer should investigate the wetland status of adjacent federal regulatory agency will change the hydroperiod of a downstream areas to determine if the discharge from the Wet Pond natural wetland (see Cappiella et al., 2006 , for guidance on minimizing stormwater discharges to existing wetlands). Perennial Locating perennial streams will require both a Section 401 and s within Wet Pond . Streams Section 404 permit from the appropriate state or federal regulatory agency. Commu s can generate the following community and Wet Pond nity and Environmental Concerns. environmental concerns that nee d to be addressed during design: Many residents feel that Wet Pond Aesthetic Issues. • s are an attractive landscape feature, promote a greater sense of community and are an attractive habitat for fish and wildlife. s are under Wet Pond Designers should note that these benefits are often diminished where - sized or have small contributing drainage areas. Construction of a Wet Pond Existing Forests. • may involve extensive clearing of existing forest cover. Designers can expect a great deal of neighborhood opposition if they do not design and construction. make a concerted effort to save mature trees during Wet Pond ortant community concern, since both young children safety is an imp Safety Risk. • Wet Pond Wet Pond and adults have perished by drowning in s through a variety of accidents, including falling through thin ice cover. Gentle side slopes and safety benches should be provided to 03/2013 7 3.06.2. 13 -

387 BMP Standards and Specifications Wet Ponds s are located near offs, especially where Wet Pond ngerous drop- avoid potentially da . residential areas Pollutant Concerns. s collect and store water and sediment to increase residence Wet Pond • tralized. time that will increase the likelihood for contaminated water and sediments to be neu Wet Pond s can export contaminated However, poorly sized, maintained, and/or functioning and/or water to receiving waterbodies (Mallin, 2000; Mallin et al., 2001; sediments Wet Pond esigners are cautioned that recent research on ). Further, d Messersmith, 2007 s has shown that some Wet Pond s can be hotspots or incubators for algae that generate harmful algal blooms (HABs). Mosquitoes are not a major problem for larger Wet Pond et al Mosquito Risk. • ., s (Santana al, 2005). However, fluctuating water levels in 1994; Ladd and Frankenburg, 2003, Hunt et s could pose some risk for mosquito breeding. Mosquito Wet Pond -sized smaller or under problems can be minimized through simple design features and maintenance operations described in MSSC (2005). s with extensive turf and shallow shorelines can attract Geese and W aterfowl. Wet Pond • nuisance populations of resident geese and other waterfowl, whose droppings add to the nutrient and bacteria loads, thus reducing the removal efficiency for those pollutants. Severa l s much less attractive to geese, such as design and landscaping features can make Wet Pond allowing the perimeter of the Wet Pond to grow up in tall grass and planting shrubs and grasses around the pond ( see Schueler, 1992). 13. teria Pond Conveyance Cri Wet 4 Wet Pond s, including their conveyance systems, constructed to meet regulatory stormwater management requirements accordance in the State of Delaware shall be designed and constructed in with the USDA NRCS Small Pond Code 378 and this document. bottom should be at least 0.5% to facilitate The longitudinal slope of the Wet Pond ernal Slope. Int maintenance. pipe configuration or a The principal spillway may be composed of a structure- Spillway. Principal weir - . A structure spillway must be accessible from dry land principal -channel configuration. The spillway shall be designed with anti- on the structure . flotation, anti -vortex and trash rack devices pipe The outfall pipe and all connections to the outfall structure shall be made watertight. When forced concrete pipe is used for the principal spillway pipe to increase its longevity, “O -ring” rein gaskets (ASTM C361) shall be used to create watertight joints. -seep collars will decrease Anti the principal spillway is composed of movement of water along the outside of the outfall pipe. When , for with riprap a weir wall discharging to a channel, the channel below the weir must be reinforced ( . ) to prevent scour of the channel example Non -Clogging Low Flow Orifice. A low flow orifice must be provided that is adequately protected from clogging by either an acceptable external trash rack or by internal orifice protection that may 03/2013 8 3.06.2. 13 -

388 BMP Standards and Specifications Wet Ponds allow for smaller diameters. Orifices less than 3 inches in diameter may require extra attention during ntial for clogging. design, to minimize the pote Adequate Outfall Protection The design must specify an outfall that will be stable for the . outfall must be modified to . The channel immediately below the Wet Pond conveyance storm (Cv) in the shortest possible distance. This is prevent erosion and conform to natural dimensions by placing appropriately sized riprap over stabilization geotextile in accordance with accomplished HEC -14 Hydraulic Design of Energy Dissipators for Culverts and Channels and Delaware Erosion or 3.3.11 Riprap and Sediment Contro l Handbook Specification 3.3.10 Riprap Outlet Protection -erosive levels (3.5 , which can reduce flow velocities from the principal spillway to non Stilling Basin on the channel lining material based up . Flared pipe sections, which discharge at or near the to 5.0 fps) stream invert or into a step pool arrangement, should be used at the spillway outlet. When the discharge is to a manmade pipe or channel system, the system must be adequate to convey are should be taken to minimize tree clearing along the the required design storm peak discharge. C downstream channel, and to reestablish a forested riparian zone in the shortest possible distance. if The final release rate of the facility shall be modified -rap should be avoided. Excessive use of rip any increase in flooding or stream channel erosion would result at a downstream structure, highway, . or natural point of restricted streamflow Wet Pond Emergency Spillway. maximum s must be constructed with overflow capacity to pass the An design storm event (Fv) if the Fv is being routed through the Wet Pond rather than bypassing. emergency spillway designed to convey the Fv should be cut in natural ground or, if c ut in fill, must be lined with design storm will be passing stabilization geotextile and riprap. When the maximum a minimum cross sectional , the principal spillway outlet pipe must have through the principal spillway area of 3 square feet . Inflow Points Stabilization . - be stabilized to ensure that non must Inflow points into the Wet Pond -year storm erosive conditions exist during storm events up to the conveyance storm (i.e., the 10 event). Inlet pipe inverts should generally be located at or slightly below the permanent pool Wet Pond 13.5 A forebay elevation. (See ) shall be provided at each inflow Pretreatment Criteria location, unless the inlet is submerged or inflow provides less than 10% of the total design storm . inflow to the Wet Pond Dam Safety Permits. The designer should determine whether or not the embankment meets the In the event that the criteri a to be regulated as a dam by the Delaware Dam Safety Regulations. embankment is a regulated dam, the designer should verify that the appropriate Dam Safety Permit Dam Safety Program. has been approved by the Department’s Pond Pretreatment Criteria Wet 5 13. Sediment forebays are considered to be an integral design feature to maintain the longevity of all Wet Pond s. A forebay must be located at each major inlet to trap sediment and preserve the capacity of the 03/2013 9 3.06.2. 13 -

389 BMP Standards and Specifications Wet Ponds main treatment cell. Th e following criteria apply to forebay design: • A major inlet is defined as an individual storm drain inlet pipe or open channel conveying at least ’s contributing runoff volume 10% of the Wet Pond forebay preferred The • formed by an acceptable barrier consists of a separate cell, configuration such as a concrete weir, riprap berm, gabion baskets, etc. Riprap berms are the preferred barrier material. to 4 feet deep . A safety bench is required at the pond shoreline The forebay should be 3 for • forebay depths gr eater than 3 feet. The safety bench need not continue around the entire forebay. • The forebay must be sized to contain ten percent of the volume of runoff from the contributing from the Resource Protection event area impervious . The relative size of individual drainage forebays to the Wet Pond be proportional to the percentage of the total . The storage will inflow volume within the forebay may be included in the calculated required storage volume for the Wet Pond. eet. The forebay should have a length to width ratio of The minimum length of the forebay is 10 f • . L 2:1 or greater . is measured with the direction of flow into the Wet Pond ength The forebay should be equipped with a metered rod in the center of the pool (as measured • lengthwise along the low f low water travel path) for long -term monitoring of sediment Metered wooden stakes will need to be replaced frequently in Wet Pond forebays; accumulation. alternative materials should be considered for longevity. • Vegetation should be included within foreba ys to increase sedimentation and reduce resuspension and erosion of previously trapped sediment. Exit velocities from the forebay shall be non • . or an armored overflow shall be provided -erosive Direct maintenance access for appropriate equipment shall be provided to the each forebay. Criteria Design Wet 6 13. Pond he permanent pool must In order to receive the credits outlined in Section 13.1, t : Wet Pond Sizing be sized to store e from a volume equivalent to the Resource Protection storm (i.e., the runoff volum -year 2.7” Type II storm event ). Further, Wet Ponds must provide 24 hours extended detention the 1 ny remaining treatment volume up to of a the full water quality volume . arged from Wet Ponds can be designed to capture and treat the remaining stormwater disch to improve water quality. Additionally, Wet Ponds should be sized to control upstream practices peak flow rates from the Conveyance Event and Flooding Event as required in accordance with the Delaware Sediment and Stormwater Regulations and accompanying Technical Document. For treatment train designs where upland practices are utilized for treatment of the resource Pv), d or CN that reflect s the volume reduction esigners can use a site- adjusted R protection storm (R v . that must be treated by the Wet Pond ute the Cv and Fv of upland practices to comp 03/2013 10 3.06.2. 13 -

390 BMP Standards and Specifications Wet Ponds Water Balance Testing : A water balance calculation is required to document that sufficient inflows - exist to compensate for combined infiltration and evapo Wet Ponds and Wet ED Ponds to transpiratio (see day summer drought without creating unacceptable drawdowns n losses during a 30- Equation adapted from Hunt et al., 2007). The recommended minimum pool depth to avoid 13.1, nuisance conditions may vary; however, it is generally recommended that the wat er balance maintain a minimum 24 -inch reservoir. 13.1. Water Balance Equation for Acceptable Water Depth in a Wet Pond Equation MB DP > ET + INF + RES – Where: DP = Average design depth of the permanent pool (inches) = Summer evapo ET -transpiration rate (inches) (assume 8 inches) = Monthly infiltration loss (assume 7.2 @ 0.01 inch/hour) INF = Reservoir of water for a factor of safety (assume 24 inches) RES , if any (convert to inches) = Measured baseflow rate to the Wet Pond MB lter this equation are the measurements of seasonal base flow and infiltration Design factors that will a rate. The use of a liner could eliminate or greatly reduce the influence of infiltration. Similarly, land (e.g., ons over time use changes in the upstream watershed could alter the base flow conditi . urbanization and increased impervious cover) . Therefore, Translating the baseflow to inches refers to the depth within the Wet Pond 13.2 Equation 3 /s), to pond -inches: can be used to convert the baseflow, measured in cubic feet per second (ft Baseflow Conversion Equation 13.2. Equation 3 2 Pond inches = (MB in ft ) /s) * (2.592E6) * (12”/ft) / SA of Pond (ft Where: 3 3 /s to ft /month. 2.592E6 = Conversion factor: ft 2 in ft surface area of Wet Pond = SA Storage Design: , plus extended detention must permanent pool he Wet Pond T Wet Pond the store Type II storm ” rainfall 2.7 year, (i.e., the runoff volume from the 1- volume Resource Protection may be provided in multiple cells. Performance is enhanced when multi ple event torage . Volume s paths, high surface area to treatment pathways are provided by using multiple cells, longer flow volume ratios, complex microtopography, and/or redundant treatment methods (combinations of ED extended detention [ pool, ], and marsh). : tention Levels The maximum extended detention volume associated with Maximum Extended De Resource Protection volume should occur within the storage for the Conveyance storm (Cv). The the total storage, including any ponding for larger flooding events (100- year storm) should not extend above the permanent pool more than 5 feet unless specific design enhancements to ensure side slope stability, safety, and maintenance are identified and approved. 03/2013 11 3.06.2. 13 -

391 BMP Standards and Specifications Wet Ponds low path from should have an irregular shape and a long f designs Wet Pond Wet Pond Geometry : Greater flow paths and performance. to outlet, to increase water residence time and Wet Pond inlet irregular shapes are recommended. The total length of the flow path compared to the linear length through the Wet Pond from inlet to outlet, m Internal berms, baffles, ust be a minimum ratio of 2:1. or vegetated peninsulas can be used to extend flow paths and/or create multiple pond cells. In addition, the ratio of the shortest flow path through the system (due to an inlet located near the et) to the overall length must be at least 0.5:1. The drainage area served by any inlets located outl less than a 0.5:1 ratio shall constitute no more than 20% of the total contributing drainage area. : Permanent Pool Depth feet. pool should not exceed four The maximum depth of the permanent ild slopes promote better Side slopes for Wet Pond s must be no steeper than 3 H:1V. M : Side Slopes establishment and growth of vegetation and provide for easier maintenance and a more natural appearance. Wet Pond Benches : side slopes above permanent pool are steeper than 4H:1V, a W . Safety Bench Wet Pond • hen 10 foot wide safety bench shall be constructed one foot above the permanent pool. The safety safety risks. The max s for maintenance access and reduces allow bench imum slope of the safety bench is 5%. pool that promotes permanent the is a shallow area below An aquatic bench . Aquatic Bench • growth of aquatic and wetland plants. The bench also serves as a safety feature, reduces aquatic bench one a 10 foot wide , and conceals floatable trash. Incorporate shoreline erosion foot below permanent pool . Liners : Highly permeable soils will make it difficult to maintain a healthy permanent pool. When a geotechnical investigation recommends a liner, acceptable options include the following: (1) a clay liner following the specifications outlined in Table 13. 3 below; (2) a 30 mil poly -liner; (3) bentonite; (4) use of chemical additives; or (5) other acceptable measures as recommended by a qualified geotechnical professional lay liner should have a minimum thickness of 12 inches with an . A c additional 12 inch layer of compacted soil above it, and it must meet the specifications outlined in Table 13. 3 . Other synthetic liners can be used if the designer can supply supporting documen tation that the material will achieve the required performance. Table 13.3. Clay Liner Specifications Specification Test Method Property Unit 6 - Cm/sec 2434 - ASTM D Permeability 1 x 10 - Plasticity Index of Clay ASTM D Not less than 15 423/424 % Not less than 30 it of Clay Liquid Lim ASTM D - 2216 % Not less than 30 Clay Particles Passing ASTM D - 422 % ASTM D % 95% of standard proctor density Clay Compaction - 2216 DCR (1999). VA Source: 03/2013 12 3.06.2. 13 -

392 BMP Standards and Specifications Wet Ponds if Soil borings should be taken below the proposed embankment, : Required Geotechnical Testing in the vicinity of the proposed outlet area, and in at least two locations within the applicable, Wet Pond proposed . Soil boring data is needed to (1) determine the physical characteristics of bottom the excavated material, (2) determine its adequacy for use as structural fill or spoil, (3) provide data for structural designs of the outlet works (e.g., bearing capacity and buoyancy), (4) determine and compaction/composition needs for the embankment (5) determine the depth to groundwater bedrock and (6) evaluate potential infiltration losses (and the potential need for a liner). orifice shall be The low flow ED -clogging Low Flow (Extended Detention) Orifice Non : The preferred method is a trash rack. adequately protected from clogging by an acceptable external hood apparatus over the orifice that reduces gross pollutants such as floatables and trash, as well as oil and grease and sediment. the Orifices less than 3 inches in diameter may require extra attention during design, to minimize an orifice used As an alternative, internal orifice protection may be potential for clogging. (i.e., -inch orifices or slots that are protected by internal to a perforated vertical stand pipe with 0.5 wirecloth and a stone filtering jacket). he riser must be located such that it is accessible from the pond side slope or safety bench T : Riser be located within the embankment for for the purposes of inspection and maintenance. The riser may is to be provided by lockable manhole cess to the riser Ac maintenance access, safety, and aesthetics. covers, and manhole steps within easy reach of valves and other controls. openings. Trash Ra cks : Trash racks shall be provided for low -flow pipes and for all structure riser Open weirs without an upper enclosure w ill not require trash racks. Synthetic trash rack materials options are available and should be considered. All metal trash racks shall be coated with a rust inhibitor to increase longevity of the device. Wet Pond : hat can completely or partially drain the permanent s should have a drain pipe t Pond Drain ), the pool. In cases where a low level drain is not feasible (such as in an excavated Wet Pond Operation and Maintenance Plan should include requirements for dewatering the Wet Pond . to • The drain pipe shoul d have an upturned elbow or protected intake within the Wet Pond help within 24 Wet Pond sediment deposition, and a diameter capable of draining the keep it clear of hours. • drain must be equipped with an adjustable valve located within the riser, where it Wet Pond The will not be normally inundated and can be operated in a safe manner. drawdowns to prevent downstream discharge of sediments Care should be exercised during Wet Pond or the Delegated Agency Department shall be notified or anoxic water and rapid drawdown. The . is drained before a Wet Pond outlet pipe the oth pool elevation, b If desired to adjust the pond permanent : Adjustable Gate Valve 03/2013 13 3.06.2. 13 -

393 BMP Standards and Specifications Wet Ponds eel wh drain should be equipped with an adjustable gate valve (typically a hand and the Wet Pond and be sized one pipe size greater than the calculated design or pump well knife gate valve) activated Valves should be located inside of the riser at a point where they (a) will not normally be diameter. wheel should be vent vandalism, the hand inundated and (b) can be operated in a safe manner. To pre chained to a ringbolt, manhole step or other fixed object. All materials used in construction of a Wet Pond or Wet ED Pond shall : Material Specifications meet the material specifications in USDA NRCS Small Pond Cod e 378. : Safety Features The principal spillway opening must be designed and constructed to prevent entry by small • children. Wet Ponds must incorporate an additional 1 foot of freeboard above the emergency spillway, or 2 • feet of freeboard if design has no emergency spillway, for the maximum design storm (e.g., Fv) unless more stringent Dam Safety requirements apply. • The emergency spillway must be located so that downstream structures will not be impacted by channel must be designed to direct runoff to a The emergency spillway exit spillway discharges. point of discharge without impact to downstream structures. Fencing of the perimeter of Wet Pond • . The preferred method to reduce risk is to s is discouraged manage the contours of the Wet Pond p- offs or other safety hazards. to eliminate dro Wet Pond side slopes • above permanent pool shall be no steeper than 3H:1V. When Wet Pond -foot wide safety bench must be side slopes above permanent pool are steeper than 4H:1V a 10 provided. The steepness of Wet Pond side slopes below permanent pool will be determined by soil type and • -foot wide aquatic bench located one foot below permanent influence of groundwater. The 10 pool is a requirement for all Wet Ponds and may not be waived. access to • Both the safety bench and the aquati be landscaped to prevent personnel c bench must Perimeter l the pool. andscaping shall be designed so as to not hinder maintenance access by equipment. • be posted. Warning signs may nce issues can be maintena The following Wet Pond s: Maintenance Reduction Feature -going maintenance easier: addressed during the design, in order to make on s must be designed so as to be accessible to annual Wet Pond All Maintenance Access. • maintenance. Good access is needed so crews can remove sediments, make repairs and preserve Wet Pond treatment capacity. o Adequate maintenance access must extend to the forebay, safety bench, riser, and outlet structure and must have sufficient area to allow vehicles to turn around. o be located within the embankment for maintenance access, safety and The riser may aesthetics. Access to the riser should be provided by lockable manhole covers and manhole steps within easy reach of valves and other controls. 03/2013 14 3.06.2. 13 -

394 BMP Standards and Specifications Wet Ponds hstand the -bearing materials or be built to wit Access roads must (1) be constructed of load o 5 feet, and (3) have a profile grade expected frequency of use, (2) have a minimum width of 1 5:1. that does not exceed -of-way or easement must from a public or extend to the Wet Pond A maintenance right o private road. • should be provided Adequate land area adjacent to the Wet Pond -Aside Area: Maintenance Set for in the Operation and Maintenance Plan as a location for disposal of sediment removed from Wet Pond -aside area is necessary on all when maintenance is performed. The maintenance set the to adequately dewater sediment removed from the pond prior to sites adjacent to the Wet Pond spreading and seeding or transporting from the site. -aside area shall accommodate the volume of 0.1 inches of runoff from o The maintenance set utory drainage area. ’s contrib Wet Pond the The maximum depth of the set aside volume shall be one foot. o o The slope of the set aside area shall not exceed 5%; and o The area and slope of the set aside area may be modified if an alternative area or method of Department disposal is approved by the or Delegated Agency. Wet Pond Landscaping Criteria 13.7 be provided around the perimeter of the Wet Pond should A vegetated : Perimeter Vegetated area that extends at least 25 feet outward from the maximum water surface elevation of the Wet Pond . vegetated perimeter provides enhanced water quality management of runoff through filtering, This Wet provides adequate setback from structures to allow for Wet Pond maintenance, and when the Pond perimeter is allowed to grow up into meadow, this area aids in deterring waterfowl from inhabiting the Wet Pond. Permanent structures (e.g., buildings) should not be constructed within the Where xisting trees should be preserved in the to do so, e it is possible area. vegetated perimeter vegetated perimeter area during construction. should be The full width of the vegetated perimeter located in common open space, not within recorded lots. The soils in the Wet Pond vegetated perimeter area are often severely compacted during the construction process, to ensure stability. The density of these compacted soils can be so great that it effectively prevents root penetration and, therefore, may lead to premature mortality or loss of vigor. than the diameter of the As a rule of thumb, planting holes should be three times deeper and wider root ball for ball- -grown stock. -burlap stock, and five times deeper and wider for container and Organic matter such as locally generated compost may be used to amend compacted soil to improve soil structure, help establish vegetation, and reduce runoff. , consult vegetated perimeter areas For more guidance on planting trees and shrubs in Wet Pond . Cappiella et al (2006) Woody vegetation may not be planted or allowed to grow within 15 feet of the Woody Vegetation: toe of the embankment . Woody vegetation may not be planted or allowed to grow within 25 feet of . or any inflow pipes the principal spillway structure 03/2013 15 3.06.2. 13 -

395 BMP Standards and Specifications Wet Ponds be provided that indicates the methods A landscaping plan must Landscaping and Planting Plan: . The perimeter and its vegetated tain vegetative coverage in the Wet Pond used to establish and main landscaping plan should provide elements that promote diverse wildlife and waterfowl use within the Wet Pond, wetland and vegetated perimeter areas . Avoid species that require full shade, or are prone to wind damage. Extra mulching around the base of trees and shrubs is strongly recommended as a means of conserving moisture and suppressing weeds. Minimum elements of a plan include the following: landscaping • perimeter area vegetated and ng zones within both the Wet Pond Delineation of pondscapi Selection of corresponding plant species • The planting plan • bench (including soil amendments, if needed) • The sequence for preparing the aquatic Sources of native plant material • Construction Wet Pond 13.8. may serve as a sediment basin A Wet Pond Use of Wet Pond s for Erosion and Sediment Control . during project construction. If this is done, the volume of the sediment basin must be based on the more stringent sizing rule (erosion and sediment c . storage volume ontrol requirement vs requirement). Installation of the permanent principal spillway should be initiated during the construction phase, and design elevations should be set with final cleanout of the sediment basin and conversion to the post -construction Wet Pond in mind. The bottom elevation of the temporary than the design bottom elevation sediment basin should be set elevation minimum of six inches higher of the final Wet Pond to allow for maintenance cleanout of accumulated sediment durin g pond be implemented to prevent discharge of turbid waters when conversion. Appropriate procedures must basin is being converted into a Wet Pond sediment the . must be obtained before any Approval from the Department or the appropriate Delegated Agency planned Wet Pond or Wet ED Pond can be used as a sediment basin . The Sediment and Stormwater Plan must include conversion steps from sediment basin to permanent Wet Pond in the construction sequence. The Department or Delegated Agency must be notified and provide approval prior to conversion from sediment basin to the final configuration of the Wet Pond or Wet ED Pond. Multiple Review s are are critical to ensure that Wet Pond . construction reviews Construction properly constructed. Construction reviews are , during the following stages of construction required and noted on the plan in the sequence of construction : -construction meeting Pre • Initial site preparation (including installation of E&S controls) • Construction • spillway and the outlet principal of the including installation of the embankment, structure • Excavation/Grading (interim and final elevations) 03/2013 16 3.06.2. 13 -

396 BMP Standards and Specifications Wet Ponds Implementation of the pondscaping plan and vegetative stabilization • • list for facility acceptance) Final inspection (develop a punch quence to properly install a The following is a typical construction se . Construction Sequence designs, site conditions, and Wet Pond . The steps may be modified to reflect different Wet Pond the size, complexity and configuration of the proposed facility. s should only be constructed after the Wet Pond Step 1: Stabilize the Drainage Area . is completely stabilized. If the proposed Wet contributing drainage area to the Wet Pond Pond site will be used as a sediment trap or basin during the construction phase, the construction no tes should clearly indicate that the facility will be de- watered, dredged and re-graded to design dimensions after the original site construction is complete. 2: Assemble Construction Materials Step on-site, make sure they meet design prepare any staging areas. , and specifications Ensure that appropriate compaction and dewatering equipment is available. Locate the project benchmark and if necessary transfer a benchmark nearer to the Wet Pond location for use during construction. 3: Install Erosion and Sediment Controls prior to construction, including Step temporary de- watering devices and stormwater diversion practices. All areas surrounding that are graded or denuded during construction must be planted with turf the Wet Pond grass, native plantings, or other approved methods of soil stabilization. Step 4: Clear and Strip the embankment area to the desired sub -grade. Principal Spillway Pipe 5: Excavate the Core Trench and Install the in Step . accordance with construction specification of NRCS Small Pond Code 378 Step 6: Install the Riser or Outflow Structure, and ensure the top invert of the . overflow weir is constructed level at the design elevation using acceptable 7: Construct the Embankment and Any Internal Berms Step in 8- to 12- Construct the compact the lifts with appropriate equipment. material ts, inch lif embankment allowing for 10% settlement of the embankment. are until the appropriate elevation and desired contours 8: Excavate/Grade Step ond achieved for the bottom and side slopes of the Wet P . Construct forebays at the proposed inflow points. in cut or structurally stabilized soils. 9: Construct the Emergency Spillway Step 10: Install Outlet Pipe Step any flared end sections, headwalls, and including s, 03/2013 17 3.06.2. 13 -

397 BMP Standards and Specifications Wet Ponds downstream rip -rap outlet protectio n underlain by stabilization geotextile . the approved Step 11: Stabilize Exposed Soils with seed mixtures appropriate for the be permanently All areas above the normal pool elevation must perimeter area. Wet Pond stabilized ve stabilization specifications on the approved in accordance with the vegetati Sediment and Stormwater Management Plan. following the 12: Plant the Wet Pond Benches and Vegetated Perimeter Area , Step pondscaping plan ( see Section 13.7 Wet Pond Landscaping Criteria ). Post Construction Verification. Following construction, the constructed Wet Pond depth at three ) must be the prior to principal spillway areas within the permanent pool (forebay, mid -pond , and and geo ed, , mark measured . This y document the post construction verification surve on -referenced to determine sediment deposition rates in order to simple data set will enable maintenance reviewers schedule sediment cleanouts. Maintenance Criteria Wet Pond 13.9 Maintenance is needed so Wet Pond s continue to operate as designed on a l ong -term basis. Wet s normally have fewer routine maintenance requirements than other stormwater control Pond maintenance activities vary regarding the level of effort and expertise required to Wet Pond measures. perform them. Routine Wet Pond maintenance, such as mowing and removing debris and trash, is More significant maintenance (e.g., removing needed several times each year (See Table 13. 4 ). accumulated sediment) is needed less frequently but requires more skilled labor and special equipment. Inspection and repair of critical structural features (e.g., embankments and risers) needs to be performed by a qualified professional who has experience in the construction, inspection, and repair of these features. rebay Sediment removal in the Wet Pond pretreatment fo 50% of total forebay when occur must The owner can plan for this maintenance activit y to occur every 5 to 7 years. capacity has been lost. Sediment removed from the Wet Pond should be deposited in the designated maintenance set aside prior to leveling and stabilization or removal from the site . Sediments excavated ering, area for dewat Wet Pond s are not usually considered toxic or hazardous. They can be safely disposed of by from ed prio r t o sediment disposal if the either land application or land filling. Sediment testing may be need serves a hotspot land use. pond wet Community awareness can contribute to a properly maintained Wet Pond. Signs describing the t Pond function and/or minimum maintenance requirements for the Wet Pond may be posted at the We location to increase community awareness. 03/2013 18 3.06.2. 13 -

398 BMP Standards and Specifications Wet Ponds and Frequency Items Table 13. 4. Typical Wet Pond Maintenance Frequency Maintenance Items • of inches s 0.5 Inspect the site after storm event that exceed rainfal l. Stabilize any bare or eroding areas in the contributing • perimeter area Wet Pond the drainage area including During establishment, as needed (first vegetated • Water trees and shrubs planted in the Wet Pond year) perimeter area during the first growing season. In general , month, and then weekly during the water every 3 days for first remainder of the first growing season (April - October), depending on rainfall. • Quarterly or after major storms Remove debris and blockages (>1 inch of rainfall) Repair undercut, eroded, and bare soil areas • • Mowing of the Wet Pond vegetated perimeter area and Twice a year embankment Shoreline cleanup to remove trash, debris and floatables • • review A full maintenance Annually • Open up the riser to access and test the valves • Repair broken mechanical components, if needed – On e time during the • Wet Pond vegetated perimeter and aquatic bench second year following construction reinforcement plantings Every 5 to 7 years • Forebay sediment removal • Repair pipes, the riser and spillway, as needed From 5 to 25 years Remove sediment fr om Wet Pond area outside of forebays • An Operation and Maintenance Plan for the project will be approved by the Department or the Delegated Agency prior to project closeout. The Operation and Maintenance Plan will specify the and authorize the Department or Delegated ies primary maintenance responsibilit owner’s property or corrective action in the event that staff to access the property for maintenance review Agency , owned and maintained or will be proper maintenance is not p erformed. Wet Pond s that are, by a joint ownership such as a homeowner’s association must be located in common areas, community open space, community -owned property, jointly owned property, or within a recorded easement dedicated to public use. clearly outline how vegetation in the Wet Pond Operation and M and its should Plans aintenance vegetated perimeter area will be managed or harvested in the future. Periodic mowing of the Wet Pond the maintenance access and the embankment. The is only required along vegetate perimeter area can be managed as a meadow (mowing every other year) or forest. Wet Pond perimeter ing remain The maintenance plan should schedule a shoreline cleanup at least once a year to remove trash and floatables. 03/2013 19 3.06.2. 13 -

399 BMP Standards and Specifications Wet Ponds that evaluate the condit ion and reviews is driven by annual maintenance Maintenance of a Wet Pond may . Based on maintenance review performance of the Wet Pond results, specific maintenance tasks . be required 13. References 10 Cappiella, K., T. Schueler and T. Wright. 2006. Urban Watershed Forestry Manual: P art 2: Conserving and Planting Trees at Development Sites . USDA Forest Service. Center for Watershed Protection. Ellicot City, MD . Hirschman, D., L. Woodworth and S. Drescher. 2009. Technical Report: Stormwater BMPs in Virginia’s James River Basin: An Ass . Center for essment of Field Conditions & Programs Watershed Protection. Ellicott City, MD. Urban Hunt, W., C. Apperson, and W. Lord. 2005. “Mosquito Control for Stormwater Facilities.” . North Carolina State University and North Carolina Coopera , NC. tive Extension. Raleigh Waterways Hunt, W., M. Burchell, J. Wright and K. Bass. 2007. “Stormwater Wetland Design Update: Zones, . North Carolina State Cooperative Urban Waterways Vegetation, Soil and Outlet Guidance.” Extension Service. Raliegh, NC. Ladd, B an d J. Frankenburg. 2003. Management of Ponds, Wetlands and Other Water Resorvoirs. Purdue Extension. WQ -41- W. Mallin, M. 2000. Effect of human development on bacteriological water quality in coastal watersheds. 1056. 10(4):1047- Ecological Applications Mal lin, M.A., S.H. Ensign, Matthew R. McIver, G. Christopher Shank, and Patricia K. Fowler. 2001. Demographic, landscape, and meteorological factors controlling the microbial pollution of coastal waters. Hydrobiologia 3):185- 460(1- 193. Messersmith, M.J. 2007 . Assessing the hydrology and pollutant removal efficiencies of wet detention ponds in South Carolina. MS. Charleston, S.C. College of Charleston, Master of Environmental Studies. Minnesota Stormwater Steering Committee (MSSC). 2005. . Emmons Minnesota Stormwater Manual , MN. & Oliver Resources, Inc. Minnesota Pollution Control Agency. St. Paul Control of Mosquito Breeding in Santana, F., J. Wood, R. Parsons, and S. Chamberlain. 1994. . Brooksville, FL. . Southwest Florida Water Management District Permitted Stormwater Systems Schueler, T, 1992. . Metropolitan Washington Council of Design of Stormwater Wetland Systems 03/2013 20 3.06.2. 13 -

400 BMP Standards and Specifications Wet Ponds Governments. Washington, DC. . 1999. Virginia Stormwater Management VA Department of Conservation and Recreation (VA DCR) n. Handbook, first editio - 21 03/2013 3.06.2. 13

401 BMP Standards and Specifications Soil Amendments Soil Amendment s 14.0 Definition: Amendment Soil (also called soil restoration) is a technique applied after construction to till compacted soils and restore their porosity by amending them with compost. These soil amendments can reduce the generation o f runoff from compacted urban lawns and may also be used to enhance the performance of impervious cover disconnections and grass channels. Soil Amendment 14.1 Stormwater Credit Calculations Amendment does not receive a retention allowance. However, the use of soil amendments Soil in accordance with this specification allows disturbed areas to receive a reduction credit for the . The adjustment varies depending on the soil’s Hydrologic Soil Group . Pollutant annual runoff y the equivalent reduction in runoff. loads are assumed to be reduced b summarizes Table 14.1 the runoff and pollutant reduction credits for this practice. Soil amendments can also enhance the performance of other runoff reduction practices that rely on surface infiltration. Runoff and pollutant reduction credits for these types of applications are discussed in the respective specifications for those practices. 14.1 Soil Amendment Performance Credits Runoff Reduction 0% Retention Allowance – 38% Annual Runoff Reduction HSG A HSG B – 50% Annual Runoff Reduction RPv HSG C - 29% Annual Runoff Reduction 13% Annual Runoff Reduction HSG D – Cv 10% of RPv Allowance Fv 1% of RPv Allowance Pollutant Reduction 100% of Load Reduction TN Reduction TP Reduction 100% of Load Reduction 100% of Load Reduction Reduction TSS NOTE: Runoff reduction allowances are for amendment area only. 14- 03/2013 3.06.2. 1

402 BMP Standards and Specifications Soil Amendments Soil Amendment Design Summary 14.2 Table 14. 2 summarizes design criteria for soil amendments, For more detail, consult Sections 14. 3 through 14. 7. Sectio ns 14. 8 and 14.9 describe practice construction and maintenance criteria. Table 14. 2 Soil Amendment Design Summary Restrictions Best Applications/ Purposes The water table or bedrock • Reduce runoff from compacted • 2.0 ≤ feet fr om soil surface lawns • • Enhance performance of Slopes > 10% impervious cover disconnections Saturated or seasonally wet soils • on poor soils tree drip line existing Wit hin • Feasibility Increase runoff reduction within a • • Slopes running toward an existing (Section 14.3) grass channel or proposed building foundation • Increase runoff reduction within a • Contributing impervious surface vegetated filter strip area exceeds the surface area of the • Increase the runoff reduction amended soils function of a reforested area of • Snow storage areas the site Soil Testing Test at two points, including: Before amendment is incorporated, to estimate amount needed (Section 14.6) 1) One week after, to determine if additional amendments are needed 2) incorporation depth outlined in Table 14.4 Cut method to determine Incorporation - Short Depth 14 .6) (Section Compost Volume Need C = A * D * 0.0031 (Section 14.6) C = compost needed (cu. yds.) Where: A = area of soil amended (sq. ft.) D = depth of compost added (in .) 03/2013 2 14- 3.06.2.

403 BMP Standards and Specifications Soil Amendments 14. 3 Soil Amendment Feasibility Criteria Amend ed soils are suitable for any pervious area where soils have been or will be compacted by the grading and construction process. They are particularly well suited when existing soils have be used to filter runoff low infiltration rates (HSG C and D) and when the pervious area will ). The area or strip of amended soils should be (downspout disconnections and grass channels hydraulically connected to the stormwater conveyance system. Soil is particularly Amendment grading of more than a foot of cut and fill recommended for sites that will experience mass across the site. Soil Amendments are not recommended where: • The water table or bedrock is located within 2.0 feet of the soil surface. • Slopes exceed 10%. • Existing soils are saturated or seasonally wet (includin g some soils in HSG D) . • They would harm roots of existing trees (keep amendments outside the tree drip line). The downhill slope runs toward an existing or proposed building foundation. • he amended soils. The contributing impervious surface area exceeds the surface area of t • • Areas that will be used for snow storage. Soil Amendments can be applied to the entire disturbed pervious area of a development or be applied only to select areas of the site to enhance the performance of runoff reduction practices. Som e common design applications include: • Reduce runoff from compacted lawns. • Enhance performance of impervious cover disconnections on poor soils. • Increase runoff reduction within a grass channel. • Increase runoff reduction within a vegetated filter strip. • Inc rease the runoff reduction function of a reforested area of the site. 14. 4 Soil Amendment Conveyance Criteria There are no conveyance criteria for soil amendments. Soil Amendment Pretreatment Criteria 14. 5 ents. There are no conveyance criteria for soil amendm 6 14. Soil Amendment Design Criteria Soil Testing. process. The first Soil tests are required during two stages of the Soil Amendment testing is done to ascertain pre- construction soil properties at proposed amendment areas. The initial testing is u sed to determine soil properties to a depth 1 foot below the proposed amendment area, with respect to bulk density, pH, salts, and soil nutrients. These tests should be and at sufficient density to accurately characterize t he conducted every 5000 square feet then heterogeneity of the site. These testing results are used to characterize potential drainage problems and determine what, if any, further soil amendments are needed. 14- 03/2013 3.06.2. 3

404 BMP Standards and Specifications Soil Amendments The second soil test is taken at least one week after the compost has been incorp orated into the soils. This soil analysis should be conducted by a reputable laboratory to determine whether any further nutritional requirements, pH adjustment, and organic matter adjustments are necessary for plant growth. This soil analysis should be do with the final construction ne in conjunction inspection to ensure tilling or subsoiling has achieved design depths. Determining Depth of Compost Incorporation. The depth of compost incorporation is based on the relationship of the surface area of the So il Amendment to the contributing area of impervious 3 presents some general guidance derived from soil modeling by cover that it receives. Table 14. Holman -Dodds (2004) that evaluates the required depth to which compost must be incorporated. Some adjust ment s to the recommended incorporation depth were made to reflect alternative recommendations of Roa- Espinosa (2006), Balousek (2003), Chollak and Rosenfeld (1998) and others. Table 14. 3. Short -Cut Method to Determine Compost and Incorporation Depths Contri buting Impervious Cover to Soil Amendment Area 1 Ratio 2 3 IC/SA = 0 IC/SA = 0.5 IC/SA = 0.75 IC/SA = 1.0 5 5 4 5 5 4 to 8 2 to 4 3 to 6 Compost (in) 6 to 10 Incorporation Depth 5 5 5 5 15 to 18 6 to 10 18 to 24 8 to 12 (in) Excavation + Excavation + Incorporation Method Tille r Tiller Mixing Mixing Notes: 1 IC = contrib. impervious cover (sq. ft.) and SA = surface area of compost amendment (sq. ft.) 2 -site impervious cover runoff For amendment of areas that do not receive off 3 In general, IC/SA rat ios greater than 1 should be avoided 4 Average depth of compost added 5 B soils, higher end for C/D soils A/ Lower end for Compost Incorporation . Incorporation depths up to 12” can generally be achieved by placing the recommended depth of compost material over the proposed amendment area and tilling down to the specified incorporation depth using appropriate equipment. Incorporation depths greater than 12” require actual removal of the existing soil mantle down to the incorporation depth and physicall Section y mixing with compost in accordance with the recommended procedures in . 14.8 14- 03/2013 3.06.2. 4

405 BMP Standards and Specifications Soil Amendments Once the area and depth of the compost amendments are known, the designer can estimate the by TCC, (1997): total amount of compost needed, using an estimator developed C = A * D * 0.0031 Where: C = compost needed (cu. yds.) A = area of soil amended (sq. ft.) .) D = depth of compost added (in Compost Specifications Compost used to fulfill regulatory requirements shall meet the criteria set forth in Appendix 3, erial Properties Compost Mat provided by a member of the U.S. . In addit ion, it must be . Composting Seal of Testing Assurance (STA) program 14. 7 Soil Amendment Landscaping Criteria what would be other than landscaping criteria for Soil Amendments specific There are no necessary to provide adequate stabilization. 14. 8 Soil Amendment Construction Sequence whether the practice will The construction sequence for Soil Amendments differs depending on be applied to a large area or a narrow area such as a filter strip or g rass channel. Construction techniques also differ depending on the specified incorporation depth. The following typical sequences are provided as general guidance. Incorporation Depth Up to 12”: -soiler The proposed area should be deep tilled to a depth of 2 t o 3 feet using a tractor and sub 1. with two deep shanks (curved metal bars) to create rips perpendicular to the direction of flow. (This step is usually omitted when compost is used for narrower filter strips.) 2. It is important to have dry conditions a t the site prior to incorporating compost. to the Place a layer of an approved compost mix on surface of proposed 3. amendment area 3 depth specified in Table 14. . . Compost -tiller or similar equipment 4. mix is then incorporated into the soil using a roto Incorporation Depth Greater Than 12”: Excavate proposed amendment area to recommended incorporation depth, as follows: 1. 1.1. Scrape off topsoil and stockpile for use in 2.2. 14- 03/2013 3.06.2. 5

406 BMP Standards and Specifications Soil Amendments 1.2. Excavate subsoil working in strips perpendicular to the slope/flowpath, using multiple lift s. Separate and remove 25% - 1.3. 30% of the subsoil, taking the most densely compacted soils for removal. Stockpile remaining subsoil next to excavated area, separately from topsoil, for use in 2.1. 1.4. Scarify bottom of excavated area. Replace subsoil, followed by topsoil and compost amendment, loosening/aerating, and 2. mixing subsoil layers, as follows, to achieve a final settled grade at three months post - installation that matches original grade: 2.1. Replace subsoils by loosening/aerating, and mixing subsoil as multiple lifts are dropped into place. Replace stockpiled topsoil, breaking up and mixing in any grass/soil clumps. 2.2. Table 14. 3 , such that compost is Incorporate recommended amount of compost from uniformly incorporated throughout. 2.3. Number of lifts may vary depending on the capabilities Repeat above steps for each lift. of the equipment being used, but a minimum of 2 lifts is required. 3. Rake to level and remove surface woody debris and rocks larger than 1” d topsoil should be approx. 4” 4. The finished grade of the combination of replaced subsoils an above the existing grade to account for settlement, but must be adjusted to account for field conditions and soil texture, such that a final settled grade at three months post -installation matches the original grade. Once the compost has been incorporated, vegetative stabilization should be initiated immediately. Lime and irrigation may be necessary to ensure adequate germination and quick compaction, The amended area should be protected from re- establishment of vegetation. particularly following the first 3 months of completion as settlement occurs. of Soil Areas Amendment exceeding 5000 square feet should employ simple erosion control measures, such as silt fence, to reduce the potential for erosion and trap sediment. Co Construction inspection involves digging a test pit to verify the depth of nstruction Inspection. mulch, amended soil and scarification. A rod penetrometer should be used to establish the depth of uncompacted soil at one location per 10,000 square feet. 14. 9 Soil Amendment Maintenance Criteria When are applied on private residential lots, Soil Amendments Maintenance Agreements. homeowners will need to be educated on their routine maintenance needs, understand t - he long to a deed restriction or other mechanism enforceable by term maintenance plan, and be subject to ensure that infiltrating areas are not converted or disturbed. The the qualifying local program should, ideally, grant authority for local agencies to access the property for mechanism r corrective action. In addition, the GPS coordinates for all amended areas should be inspection o 14- 03/2013 3.06.2. 6

407 Soil Amendments BMP Standards and Specifications provided upon facility acceptance to ensure long term tracking. simple maintenance agreement should be provided if the Soil Amendment is associated with A more than 10,0 00 square feet of reforestation. A conservation easement or deed restriction, which also identifies a responsible party, may be required to make sure the newly developing forest cannot be cleared or developed management is accomplished (i.e., thinning, inv asive plant removal, etc.). Soil compost amendments within a filter strip or grass channel should be located in a public right -of-way, or within a dedicated stormwater or drainage easement. First Year Maintenance Operations. of Soil Amendments , the In order to ensure the success following tasks must be undertaken in the first year following soil restoration: • Initial inspections. For the first six months following the incorporation of soil amendments, -inch of the site should be inspected at least once after each st orm event that exceeds 1/2 rainfall. • Spot Reseeding. Inspectors should look for bare or eroding areas in the contributing drainage area or around the soil restoration area and make sure they are immediately stabilized with grass cover. Depending on the amended soils test, a one -time, spot fertilization may be • Fertilizatio n. needed in the fall after the first growing season to increase plant vigor. • first eekly during the once every three days for the first month, and then w Water Watering. year ober ), depending on rainfall . -Oct (April There are no major on Ongoing Maintenance. -going maintenance needs associated with Soil Amendments , although the owners may want to de -thatch the turf every few years to increase permeability. The owner should also be aware that there are maintenance tasks needed for filter strips, grass channels, and reforestation areas. Table 14.4. Typical Soil Amendment Maintenance Items and Frequency Maintenance Items Frequency • Inspect es of inch s 0.5 the site after storm event that exceed rainfall. Stabilize any bare or eroding areas in the contributing • the drainage area including perimeter area Wet Pond During establishment, as needed (first vegetated • Water trees and shrubs planted in the Wet Pond year) perimeter area during the first growing season. In general , every 3 days for first month, and then weekly during water the remainder of the first growing season (April - October), depending on rainfall. ges • Remove debris and blocka Quarterly or after major storms (>1 inch of rainfall) • Repair undercut, eroded, and bare soil areas 14- 03/2013 3.06.2. 7

408 BMP Standards and Specifications Soil Amendments Frequency Maintenance Items • Mowing of the Wet Pond vegetated perimeter area and Twice a year embankment • Shoreline cleanup to remove trash, debris and floatables review • A full maintenance Annually Open up the riser to access and test • the valves Repair broken mechanical components, if needed • during the One time – Wet Pond vegetated perimeter and aquatic bench • second year following construction reinforcement plantings Every 5 to 7 years • Forebay sediment removal r pipes, the riser and spillway, as needed Repai • From 5 to 25 years Remove sediment from Wet Pond area outside of forebays • 14. 10 References Quantifying decreases in stormwater runoff from deep- planting and tilling, chisel- Balusek. 2003. compost amendments . Dane County Land Conservation Department. Madison, Wisconsin. Chollak, T. and P. Rosenfeld. 1998. -Amended Soils. Guidelines for Landscaping with Compost City of Redmond Public Works. Redmond, WA. Available online at: http://www.ci.redmond.wa.us/insidecityhall/publicworks/environment/pdfs/compostamendedsoil s.pdf Development of a Landscape Architect Specification for The Composting Council (TCC). 1997. Compost Uti lization . Alexandria, VA. http://www.cwc.org/organics/org972rpt.pdf Holman . PhD -Based Stormwater Practices Chapter 6. Assessing Infiltration -Dodds, L. 2004. ce and Engineering. University of Iowa. Iowa City, IA. Dissertation. Department of Hydroscien Guideline for Soil Amendments Low Impact Development Center. 2003. . Available online at: 03/soilamend.htm http://www.lowimpactdevelopment.org/epa Roa An Introduction to Soil Compaction and the Subsoiling Practice. Technical -Espinosa. 2006. Dane County Land Conservation Department. Madison,Wisconsin. Note. 14- 03/2013 3.06.2. 8

409 BMP Standards a Proprietary Practices nd Specifications Proprietary Practices 15.0 are Definition: Proprietary Practices manufactured stormwater treatment settling, filtration, practices that utilize absorptive/adsorptive materials, vortex separation, vegetative components, and/or manage the other appropriate technology to impacts caused by stormwater runoff . Proprietary Practices may be eligible Certain for some amount of treatment credit, provided Department they have been approved by the and meet the performance criteria outlined in prietary practices will this specification. Pro generally not be eligible for retention volume credit unless the practice can demonstrate the occurrence of runoff reduction processes . Proprietary Practice Stormwater Credit Calculations 15.1 ) unless explicitly approved by the Proprietary o retention credit (R will receive n Practices v . However, they may be credited as treatment practices, provided they meet the Department 15.5, Section Design Criteria Proprietary Practice performance criteria outlined in . 15.1 Proprietary Pract ices Performance Credits Runoff Reduction Retention Allowance 0% 0% RPv - A/B Soil RPv 0% - C/D Soil 0% Cv 0% Fv Pollutant Reduction See DURMM TN Reduction documentat i on See DURMM TP Reduction documentation DURMM See documentation TSS Reduction 3.06.2.15- 03/2013 1

410 BMP Standards a Proprietary Practices nd Specifications 15.2 Proprietary Practice Design Summary Individual proprietary practices will have different site constraints and limitations. Manufacturer’s specifications should be consulted to ensure that proprietary practices are feasible for application on a site -by-site basis. Proprietary Practice Conveyance Criteria 15.3 All proprietary practices must be designed to safely overflow or bypass flows from larger storm events to downstream drainage systems. The overflow associated with the 10- yr storms should be controlled so that velocities are non -erosive at the outlet point (i.e., to prevent downstream erosion) . Manufactured treatment devices may be constructed on -line or off -line. On -line systems receive quality design storm tment for the water upstream runoff from all storms, providing runoff trea and conveying the runoff from larger storms through an overflow. In off -line devices, most or all of the runoff from storms larger than the stormwater quality design storm bypass the device through an upstream diver sion. 15.4 Proprietary Practice Pretreatment Criteria Individual Proprietary may require pretreatment, or may be appropriate for use as Practices pretreatment devices. Manufacturer’s specifications should be consulted to determine the device- specific p retreatment requirements. Proprietary Practice Design Criteria 15.5 The basic design parameters for a P roprietary Practice will depend on the techniques it employs to control stormwater runoff and remove particulate and dissolved pollutants from runof f. In general, the design of devices that treat runoff with no significant storage and flow rate attenuation must be based upon the peak design flow rate. However, devices that do provide storage and flow rate attenuation must be based, at a minimum, on t he design storm runoff volume and, in some instances, on a routing of the design runoff hydrograph. The Department shall verify performance criteria for all proprietary practices proposed for use in Delaware. The removal efficiencies used for P roprie tary Practices are included in the DURMM model documentation. Performance criteria for Proprietary Practices shall be based on the EPA’s by for inclusion in (CBP) Chesapeake Bay Program pollutant removal efficiencies assigned 3.06.2.15- 03/2013 2

411 BMP Standards a Proprietary Practices nd Specifications Chesapeake Bay Model . Ma nufacturers who feel that the performance of their particular the product exceeds the CBP performance criteria as currently assigned may request a formal review of their product following the procedures developed by the Scientific and Technical Advisory tee Commit In order to be considered for improved (STAC) for evaluating stormwater BMPs. performance criteria, the manufacturer shall notify the Department in writing of its intention to esults from the proceed with such formal review and shall forward subsequent findings and r STAC. 15.6 Proprietary Practice Landscaping Criteria Proprietary Practices may or may not require landscaping considerations. Manufacturer’s specifications should be consulted to determine any landscaping requirements for the device. Construction Sequence Proprietary Practice 15.7 ndividual Proprietary Practices will vary based on the specific The construction and installation of i proprietary practice. Manufacturer’s specifications should be consulted to determine the device specif ic construction sequencing requirements. Post Construction Verification Documentation. Documentation shall be provided to the Department or its appropriate Delegated Agency verifying that the Proprietary Practice has been installed in accordance with manufacturer’s recommendations. Proprietary Practice Maintenance Criteria 15.8 In order to ensure e ffective and long -term performance of a Proprietary Practice, regular maintenance tasks and inspections are require d. All Proprietary Practices should be i nspected and maintained in accordance with the manufacturer’s instructions and/or recommendations and any maintenance requirements associated with the device’s certification by the Department . 15. 9 References No references. 3.06.2.15- 03/2013 3

412 Stormwater BMP Design Criteria Source Controls 16.0 Source Controls Control Definition: Source consists of measures to prevent pollutants from coming into contact with stormwater runoff. Preventing pollutant exposure to rainfall and runoff is an important management technique that can reduce the amo unt of pollutants in runoff and the need for stormwater treatment. Control Source practices and pollution prevention can include a wide variety of management techniques that address nonpoint sources of pollution. These practices are typically non -struct ural, require minimal or no land area, and involve moderate effort and cost to implement, when compared to structural treatment practices. Therefore, project planning and design should consider measures to minimize or prevent the they are not available for mobilization by runoff. release of pollutants so Design variants include: 16-  A Nutrient Management 16- B Street Sweeping  involves the reduction of fertilizer to grass lawns and other urban Urban Nutrient Management areas down to the minimum required to sustain adequate vegetative cover . The implementation of urban N utrient Management is based on public education and awareness, targeting suburban Although the residences and businesses, with emphasis on reducing excessive fertilizer use. availability of “Lo -P” or “No -P” fertilizer formulations have improved the situation, managing excess nutrient applications in urban settings will continue to be an important element in the overall goal to minimize impacts from urban stormwater runoff. Sweeping and storm drain cleanout practices rank among the oldest practices used by Street communities for a variety of purposes to provide a clean and healthy environment, and more (NPDES) recently to comply with their National Pollutant Discharge Elimination System rmwater permits. The ability for these practices to achieve pollutant reductions is uncertain sto given current research findings. Only a few S Sweeping studies provide sufficient data to treet in cleanouts on water quality statistically determine the impact of street sweeping and storm dra and to quantify their improvements. Fewer studies are available to evaluate the pollutant reduction capabilities due to storm drain inlet or catch basin cleanouts. Nevertheless, the use of d program has been shown to yield measurable benefits -manage modern equipment under a well and thus this practice should be considered for inclusion in any source control program. 16- 03/2013 3.06.2. 1

413 Source Controls Stormwater BMP Design Criteria 16.1 Source Control s Stormwater Credit Calculations Source controls do not typically receive runoff reduction cr edits. The ability of these practices to reduce nutrients and particulates varies. Table 16.1(a) summarizes the stormwater performance credits for Nutrient Management. Table 16.1(b) summarizes the stormwater performance credits for street sweeping. 16 .1(a) Nutrient Management Performance Credits Runoff Reduction Retention Allowance 0% 0% RPv - A/B Soil 0% RPv C/D Soil - Cv 0% Fv 0% Pollutant Reduction TN Reduction 17% 22% TP Reduction TSS Reduction 0% 16.1(b) Street Sweeping Performance Credits Runoff Reduction Retention Allowance 0% A/B Soil - RPv 0% RPv - C/D Soil 0% 0% Cv Fv 0% Pollutant Reduction TN Reduction 3% 3% TP Reduction 9% TSS Reduction 16- 03/2013 3.06.2. 2

414 Stormwater BMP Design Criteria Source Controls 16.2 Source Controls Design Summary al design criteria. Instead, these practices are usually Source Controls do not have tradition based on guidance documents, or in some cases, formal regulations. implemented The “Urban Nutrient Management Handbook” published by the Virginia Cooperative Extension Service, included as Appendix 16- 1 of this document, is an example of the former. The Delaware ( 3 Del. C. Nutrient Management Law Ch. 22 ) is an example of the latter. The Delaware Nutrient Management Law requires any person who owns, leases, or otherwise h nutrients are applied to develop a nutrient management plan for those controls 10 acres to whic lands. Nutrient management plans must be updated every three years or when significant anyone who applies alterations to the nutrient application occurs. In addition the Law requires nutrients to lands or water in excess of 10 acres to have certification endorsed by the Delaware Nutrient Management Commission. Sweeping to measurably reduce pollutant loadings is highly dependent on its treet The ability of S eductions shown in Table 16.1(b) are based on the values used in the frequency. The pollutant r Phase 5.3 Chesapeake Bay Model. These values are based on the following assumptions ( from personal correspondence, Ms. Olivia Devereux): The assumption is that there is a nitrogen, phos phorus, and sediment reduction when the same section of a street is swept approximately every two weeks, or 25 times a year. When a street is swept periodically and less than every two weeks, the accumulated matter can be mobilized and moved into the strea m system with any rainfall. Therefore, less regularly swept streets are given credit solely for the sediment removed. There are three ways to track street sweeping: 1. Streets swept 25 times a year: track the acres that were swept this number of times, not the acres swept once times 25. 2. Streets swept 25 times a year: track as percent of land area. This is the percent of the land area that received this treatment 25 times a year. mply Street sweeping lbs. Enter the lbs of sediment removed. The number entered is si 3. subtracted from the total sediment load. This requires weighing the sweeper before it goes out and when it returns to determine the lbs of material removed. ED reduction. The N and P reductions are 3% and the For option 1 and 2, there is a N, P, and S Sed reduction is 9%. 16.3 References Goatley, Michael, Jr. and Kevin Hensler, “Urban Nutrient Management Handbook”, Virginia Cooperative Extension Service. May 2011. 16- 03/2013 3.06.2. 3

415 Source Controls Stormwater BMP Design Criteria -1 APPENDIX 16 EXTENSION SERVICE VIRGINIA COOPERATIVE URBAN NUTRIENT M ANAGEMENT HANDBOOK 03/2013 3.06.2.16.A -1- 1

416 U r b a n n U t r i e n t a n a g e M e n t M H a n d b o o k

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418 U r b a n U t r i e n t n a n a g e M M e n t H a n d b o o k Content Coordinators: Michael Goatley Jr., Professor, Crop and Soil Environmental Sciences, Virginia Tech Kevin Hensler, Research Specialist Senior, Crop and Soil Environmental Sciences, Virginia Tech Published by: Virginia Cooperative Extension Project funded by: Virginia Department of Conservation and Recreation Produced by: Communications and Marketing, College of Agriculture and Life Sciences, Virginia Polytechnic Institute and State University Director: Thea Glidden Copy Editor: Bobbi A. Hoffman Assistant Editor: Liz Guinn Layout: Christopher Cox This material is based upon work supported by the Virginia Department of Conservation and Recreation, under Agreement 50301-2009-01-SF. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the Virginia Department of Conservation and Recreation. May 2011

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420 Table of Contents Chapter 1. The Objectives of Turf and Landscape Nutrient Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 1-1 What Is Nutrient Management? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 1-4 Improving Water Quality Through Turf and Landscape Nutrient Management ... 1-4 Literature Cited ... Chapter 2. General Soil Science Principles Soil Formation and Soil Horizons ... 2-1 Soil Physical Properties ... 2-3 Soil Organic Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6 Soil-Water Relationships ... 2-7 Essential Elements for Plant Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11 Soil Survey ... 2-11 Literature Cited ... 2-13 Chapter 3. Managing Urban Soils What Is an Urban Soil? ... 3-1 Urban Soil Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1 Types of Urban Soil Materials and Their Variability ... 3-1 Common Soil Limitations in the Urban Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2 3-5 Managing Urban Soils and Their Limitations ... 3-7 Acid Sulfate Soil Conditions and Management ... Soil Conditions in Highway Rights-of-Way ... 3-9 3-10 Manufactured Soils ... ... 3-11 Modified Soils and Mulches Literature Cited ... 3-12 Chapter 4. Basic Soil Fertility Plant Nutrition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1 Soil pH, Nutrient Availability, and Liming ... 4-3 Nitrogen ... 4-6 Phosphorus ... 4-8 Potassium ... 4-10 Secondary Plant Nutrients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11 Micronutrients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12 Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14 Urban Nutrient Management Handbook I

421 Table of Contents Chapter 5. Soil Sampling and Nutrient Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction 5-1 Soil Test Interpretation and Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1 5-2 Soil Sampling ... 5-5 Understanding Soil Test Reports ... Plant Analysis as a Diagnostic Tool ... 5-7 Nutrient Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7 Sampling Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8 Interpreting a Plant Analysis Result ... 5-8 Literature Cited ... 5-8 Chapter 6. Mid-Atlantic Turfgrasses and Their Management Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1 Primary Cool-Season Grasses of Importance ... 6-1 Primary Warm-Season Grasses of Importance ... 6-4 Native Turfgrasses and Specialty Use Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5 Turfgrass Establishment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7 Maintenance Fertility Programs ... 6-14 Mowing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-18 6-19 Literature Cited ... Chapter 7. The Ornamental Landscape Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1 7-1 Site Assessment and Environmental Design ... Correct Plant Selection and Planting ... 7-2 Determining the Need to Fertilize ... 7-2 Soil Tests ... 7-3 Factors Affecting Nutrient Uptake ... 7-3 Fertilizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3 Specific Fertility Needs 7-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fertilizer Calculations ... 7-7 Fertilizer Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7 Organic and Other Soil Amendments ... 7-10 Nutrient Deficiencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-10 Literature Cited ... 7-11 Appendix 7-A ... 7-13 Appendix 7-B ... 7-15 Urban Nutrient Management Handbook II

422 Table of Contents Chapter 8. Fertilizer and Lime Sources for Turf and Landscapes 8-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction ... 8-1 Defining Fertilizers Nitrogen Sources ... 8-2 8-7 Phosphorus Fertilizer Sources and Fertility Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Potassium Fertilizer Sources and Fertility Guidelines Calcium, Magnesium, and Sulfur Fertilizer Sources and Fertility Guidelines ... 8-9 Micronutrient Fertility Sources and Fertility Guidelines ... 8-10 8-10 Liming Materials and Chemical Composition ... 8-12 Best Management Practices for Water Quality Protection ... 8-13 Literature Cited ... Chapter 9. Organic and Inorganic Soil Amendments Introduction to Organic Amendments ... 9-1 Sources of Organic Amendments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1 Processes for Generating Organic Amendments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-2 Composition of Organic Amendments Factors That Affect Nutrient Availability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-6 Uses of Organic Amendments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-7 Organic Byproduct Summary With Regard to Water Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Inorganic Materials for Amending Soils 9-13 Inorganic Amendment Use Strategies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-14 9-15 Topdressing With Inorganic Amendments ... 9-16 Literature Cited ... Chapter 10. Equipment Calibration and Fertilizer Application Methods Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1 Dry Fertilizer and Application Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1 Broadcast (Rotary) Spreader Calibration 10-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Liquid Fertilizers and Sprayer Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-7 Literature Cited ... 10-10 Chapter 11. Soil-Water Budgets and Irrigation Sources and Timing Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1 The Hydrologic Cycle and Soil-Water Budgets ... 11-1 Watering Basics for Turf and Landscape Plantings ... 11-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Water Reuse: Using Reclaimed Water for Irrigation 11-4 Literature Cited ... 11-7 Urban Nutrient Management Handbook III

423 Table of Contents Chapter 12. Principles of Stormwater Management for Reducing Nutrients From Urban Landscaped Areas Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-1 Introduction to Stormwater Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-1 Managing Urban Stormwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-8 Managing Stormwater on a Residential Lot ... 12-9 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-13 Literature Cited ... 12-13 Appendix 12-A ... 12-15 Appendix 12-B ... 12-19 Chapter 13. Turf and Landscape Nutrient Management Planning Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1 Assessment of Planned Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-3 Initial Client Visit Components of a Nutrient Management Plan ... 13-5 Sample Nutrient Management Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-9 Plan Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-24 Plan Revision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-25 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-25 Literature Cited ... 13-25 Urban Nutrient Management Handbook IV

424 Chapter 1. The Objectives of Turf and Landscape Nutrient Management Chapter 1. The Objectives of Turf and Landscape Nutrient Management Steven Hodges, Professor, Crop and Soil Environmental Sciences, Virginia Tech Michael Goatley Jr., Professor and Extension Specialist, Crop and Soil Environmental Sciences, Virginia Tech Rory Maguire, Associate Professor, Crop and Soil Environmental Sciences, Virginia Tech 1. - The overall climate (rainfall patterns) of a particu Introduction lar location and the variability in topography, such - The locations of many towns and cities in the mid-Atlan as aspect, slope, elevation, etc. tic region are closely linked to a clean, readily available, An understanding of the plant material’s periods of 2. and abundant water resource. The water source must be active growth and its inherent growth rate. sufficient in size and quality to meet the daily life needs of the general population at home (e.g., drinking, cook- 3. The physical and chemical characteristics of the ing, cleaning, leisure, etc.) and its industrial base (e.g., soil as determined by soil testing (an absolute - transportation/shipping, cooling/heating, manufactur requirement for an NMP) and/or review of soil ing applications as a solvent/diluent, etc.). maps (where appropriate). By nature, urban areas are frequently undergoing either The intended use of the plant material. 4. expansion and/or renovation in both commercial and/ The selection and application of the nutrient 5. or residential development. Expansive development in source. rolling topography requires significant soil disturbance. Soils that took millions of years to form are quickly 6. Consideration of the surrounding environment altered and/or removed during construction, eliminating and how it can either impact or be impacted by sod cover and forested areas that are naturally occurring fertilization. water filtration and soil stabilization systems. Expan - An NMP considers each of these factors and presents a sions in roof area and paved surfaces increase the need recommendation for the selection and timing of nutri- for comprehensive stormwater management planning. ent applications that meets the needs of the plant and - By law, soil disturbance, therefore, must be accompa minimizes the loss of nutrients to the environment. nied by appropriate stormwater management strategies (e.g., silt fences, compost berms, natural and synthetic erosion-control mats, etc.) that are designed to protect What Is Nutrient Management? water quality and minimize soil erosion and sediment Nutrient management plans serve two primary pur - loss. poses: (1) ensuring that plants have optimum soil nutri- ent availability for good productivity and quality, and In the final stages of both commercial and residential (2) ensuring minimum movement of nitrogen and phos- development, an urban ecosystem intermingles grasses, phorus from the specified area of application to surface groundcovers, shrubs, ornamental plants, and trees with and groundwaters where they can potentially have a the structural and hardscape (e.g., sidewalks, parking detrimental effect on water quality. Although NMPs lots, driveways, streets, etc.) components. This myriad cover more than nitrogen and phosphorus, only these - of urban landscape components results in many recom two nutrients are considered a risk for impairing water - mendations regarding appropriate plant material selec quality. Other nutrients are essential for plant growth tion and management protocol. Due to the complexity but do not cause water quality problems in the mid- of plant materials, the abundance of hardscapes, and Atlantic region. the proximity of water sources, urban ecosystems have great potential to negatively impact water quality if Most soils in the mid-Atlantic are highly weathered and managed inappropriately. All plant materials have nutri- low in plant-available nutrients, particularly nitrogen, ent requirements, but the levels and timing of applica - phosphorus, and potassium. Some form of fertiliza - tions of nutrients are highly variable and plant-specific. tion is required for even the lowest quality turfgrass, The following factors are a few of the most important if only to maintain a functioning turfgrass population to consider in the development and implementation of a that will protect the soil from erosion. Turf stands sub- nutrient management program (NMP): jected to high traffic and intensive use require regular Urban Nutrient Management Handbook 1-1

425 Chapter 1. The Objectives of Turf and Landscape Nutrient Management fertilization to maintain functionally adequate levels of Knowledge of the physical and chemical characteris - - leaf density, vigor, recuperative potential, stress toler tics of nutrient sources can prove invaluable in calcu - ance, and color. Similarly, ornamental landscape plants lating application rates, reducing fertilizer costs, and - require appropriate fertilization and cultural manage managing applications to minimize potential for losses ment strategies in order to optimize their aesthetic and through volatilization, runoff, and leaching. Most soil functional uses. The challenge of nutrient management test reports will provide specific recommendations is to consider the characteristics of the turfgrass and regarding appropriate fertilizer and/or liming materials landscape plants being grown on each specific site and to address soil limitations. However, a greater under - then make appropriate decisions regarding the timing, standing of fertilizer sources, their characteristics, and material, and application method of required nutrients. their appropriate use (information presented in chapters 8 and 9) is invaluable in optimizing nutrient manage - Nutrient management plans also have economic con- ment strategies. For instance, knowing that prilled urea siderations, because there are both savings and costs can volatilize under existing conditions may lead you - involved in the process. One cost may be hiring a certi - to choose another nitrogen source, a different applica fied nutrient management planner to write a plan. Some tion method, or a best management practice (e.g., irri- lawn care companies and other consultants may offer gating immediately after application) to reduce volatile free nutrient management planning as part of their ser - nitrogen losses. In other situations, a slow-release vice. Making extra trips to apply nitrogen, purchasing nitrogen source might be most appropriate because of - different fertilizer materials to meet specific recommen an anticipated rainy season or the inability to deliver dations, setting aside buffer areas along water bodies, suitable levels of readily available nitrogen sources on etc., could all potentially increase a client’s budget. By a frequent basis. implementing an NMP, savings accrue from avoiding the purchase and application of unnecessary fertilizer There is a great deal of interest in expanding the use of and lime. There may also be savings from greater plant organic compounds (both fertilizers and soil amend - survival because nutrient deficiency will be avoided. ments), and information in this handbook will detail Nutrient management planning is also expected to how to properly utilize these materials in responsible have a societal economic benefit by maintaining high- - plant management programs. Organic sources are per quality water for drinking, ecological, and recreational ceived by most to be “environmentally friendly,” and purposes. generally speaking, this is true. Organic fertilizers and amendments are often an effective way of recycling A brief overview of the basic components of nutrient waste products and they also can improve the physical, management planning and implementation follows. chemical, and biological aspects of soils. However, consider that organic sources almost always contain Selection of Nutrient Sources phosphorus, and if a soil test shows that no phospho- rus is needed, then an organic fertilizer does not fit There are substantial differences in nutrient require - the requirements of an NMP. Instead, an inorganic ments between plants and also in the time nutrients are - fertilizer containing no phosphorus would be a bet required. For example, legumes can produce their own ter fertilizer selection. Knowledge of nutrient sources nitrogen and therefore do not require nitrogen fertiliza - will greatly improve your management options and tion, making them a popular component of highway capabilities. rights-of-way vegetation where there is no desire to sup- ply additional nitrogen after establishment. However, cool- and warm-season grasses (discussed in chapter 6) Nutrient Application Rates require nitrogen, but their periods of maximum growth Nutrient needs for turfgrasses and landscape materials differ, resulting in different timing of optimal nitrogen are based on Virginia Cooperative Extension and land- applications. grant university research. Nutrient application rates for plan development are determined differently for nitro- The age of plants is also important because mature gen compared to phosphorus and potash. Nitrogen rates plants with well-developed root systems require fewer are determined on an annual basis and are specific to nutrients than young plants. This is often realized for the plant species, the use of the plant material, and the phosphorus recommendations when they are typi- - management area. For turf, nitrogen rates are often spe cally greater for plant establishment than they are for maintenance. cific to the plant species; for instance, whether it is a Urban Nutrient Management Handbook 1-2

426 Chapter 1. The Objectives of Turf and Landscape Nutrient Management Sound fertility programs are obviously not based on heavy or light nitrogen feeder. In cool-season grasses, nitrogen alone, because any excess or deficiency of Kentucky bluegrass has a higher seasonal nitrogen other nutrients can negatively affect plant health and requirement than does fine-leaf fescue. In warm-season survival. The annual requirements of most other macro - grasses, bermudagrass responds to aggressive nitrogen nutrients (those required in large quantities) such as programs whereas zoysiagrass requires much smaller phosphorus, potassium, calcium (Ca), and magnesium - amounts annually. The use of the turf is also an impor (Mg) are applied based on current soil test results. In tant factor in seasonal application rates, with lawns conjunction with an appropriate pH, soil levels of these - often utilizing a simple nitrogen program involving rel nutrients are maintained within a range that assures atively low annual nitrogen rates and a limited number an adequate supply of these nutrients to provide good of applications per growing season. turf growth and quality. Similar to nitrogen, excessive On the other hand, athletic fields and golf courses will applications can be damaging to the plant, resulting in have higher annual nitrogen application rates with nutrient imbalances and, particularly for phosphorus, more frequent applications. Higher rates are often the potential to negatively impact water quality. - required due to the foot and vehicular traffic associ ated with areas of concentrated play at these facilities. Nutrient Application Timing Intensive management of these areas enables the turf - Ideally, nutrient applications should be timed to maxi to recover from constant, and, in some cases, dam- mize use efficiency by the targeted plants (VDCR aging use and often includes the practice of “spoon 2005). To minimize losses, it is important to closely - feeding” (very low, but frequent applications) nitro match growth cycles and nutrient demands. Proper tim - gen over the course of the growing season as a key ing is especially important to prevent losses on soils component in maintaining acceptable turf. Experi- with high leaching or runoff potential. From the view - enced turf professionals are constantly evaluating point of the plant, appropriate timing of the first and last their nitrogen programs as the turf they manage reacts applications in the growing season is crucial to plant and responds to daily use and seasonal changes. The health, survivability, disease, stress tolerance, and so relationship between nutrient application and overall forth. turf and landscape plant quality (and often density for grasses) is used to make the appropriate adjustments Nutrient Placement and Application in their fertility programs. Methods Is it possible for turf to negatively impact the environ- For turfgrass, a variety of application methods may be ment if it is inadequately fertilized? Certainly. Inade - - used, depending on the situation. For turf establish quately fertilized turfgrass can be too weak to recover ment, broadcast application followed by incorporation from environmental stress or pest attack. Turf that is is commonly used for lime and fertilizer amendments. thin, weak, and spindly due to lack of adequate nitrogen Surface applications of granular fertilizers on new levels is considered to be “hungry” and can experience plantings and established turf may be made using truck- soil loss due to inadequate soil cover. Experienced turf mounted, push-type rotary, or drop spreaders, depend- managers identify a “hungry turf” not just by its color, ing on the size of the area to be covered. In addition, but also by its growth rate and its ability to recover from liquid fertilizers and foliar nutrients may be sprayed. pest or environmental stress. New equipment can even vary the rate of application in conjunction with global positioning systems (GPS) However, the part of turfgrass management that gets the and preprogrammed application maps. Each method most attention when it comes to environmental impact has advantages, such as increased labor efficiency, - is excessive fertilization. Excessive nitrogen applica improved application precision, and reduced potential tions increase plant succulence, making the turf more for nutrient losses. susceptible to environmental stress (e.g., heat, cold, and moisture extremes) and pest attack, and overall, A nutrient management plan should also include the less wear-tolerant. Overfertilization of nitrogen leads to detailing of site characteristics that require changes in excessive shoot and stem growth at the expense of root management from place to place. Considerations should growth. And of course, excessive applications of nitro- include environmentally sensitive areas such as buffers gen increase the potential that it enters a water source and water bodies and significant differences in soils, and becomes a pollution hazard. vegetative cover, management intensity, and potential Urban Nutrient Management Handbook 1-3

427 Chapter 1. The Objectives of Turf and Landscape Nutrient Management This handbook provides a series of chapters devoted to - nutrient loss pathways. Finally, best management prac the challenges associated with water quality protection tices to prevent or reduce losses of soil, nutrients, and in an urban environment. It presents extensive informa - plant protection chemicals should be identified for each tion on the basic principles in soil and plant sciences, of these areas and the site as a whole. fertility and fertilizers, plant management, soil amend - ments, equipment calibration for fertilizer delivery, Improving Water Quality - irrigation sources and quality, and stormwater manage ment. A standard NMP format is provided in the chap- Through Turf and Landscape ter 13. A certified nutrient management planner will Nutrient Management combine the information from a soil test with extensive - A primary goal of turf and landscape nutrient manage agronomic knowledge of plants, soils, fertilizers, nutri - ment is water quality protection. Appropriate product tion, and the climate in developing the NMP. Incor - selection, delivery rate and timing, and method of appli - porating this information into the design, installation, cation are by far the most important variables in water and management of urban soils and plant materials will quality protection in urban landscape management. The greatly improve water quality. development and implementation of a nutrient man- agement plan also provides potentially significant eco - Literature Cited nomic savings as applications are made based on soil test recommendations. Similarly, since soil test data are Virginia Department of Conservation and Recreation used in developing the plan, plant health and perfor - (VDCR), Division of Soil and Water Conservation. mance will also be enhanced on the basis of scientific Virginia Nutrient Management Standards 2005. data. Nutrient management plans allow for informed , 96-107. and Criteria decisions to be made regarding fertilization such that - plant health and function are optimized in an environ mentally responsible manner. Urban Nutrient Management Handbook 1-4

428 Chapter 2. General Soil Science Principles Chapter 2. General Soil Science Principles W. Lee Daniels, Professor, Crop and Soil Environmental Sciences, Virginia Tech Kathryn C. Haering, Research Associate, Crop and Soil Environmental Sciences, Virginia Tech discussed below) can form in several months to years. Soil Formation and Soil Horizons More detail on parent material and soil relationships in our area can be found at www.mawaterquality.org/pub- Introduction and Soil Composition lications/pubs/manhcomplete.pdf . Soil covers the vast majority of the exposed portion of - The rate and extent of parent material and soil weather the earth in a thin layer. It supplies air, water, nutrients, ing depends on: and mechanical support for the roots of growing plants. The productivity of a given soil is largely dependent 1. The chemical composition of the minerals that make on its ability to supply a balance of these factors to the up the rock or sediment. plant community. 2. The type, strength, and durability of the material that A desirable surface soil in good condition for plant holds the mineral grains together. growth contains approximately 50 percent solid mate - The extent of rock flaws or fractures. 3. rial and 50 percent pore space (figure 2.1). The solid material is composed of mineral material and organic The rate of leaching through the material. 4. matter. Mineral material comprises 45 to 48 percent of The extent and type of vegetation at the surface. 5. the total volume of a typical mid-Atlantic soil. About 2 to 5 percent of the volume is made up of organic matter, Physical weathering is a mechanical process that occurs which may contain both plant and animal residues in during the early stages of soil formation as freeze-thaw varying stages of decay or decomposition. Under ideal processes and differential heating and cooling break up moisture conditions for growing plants, the remaining rock parent material. After rocks or coarse gravels and 50 percent soil pore space would contain approximately sediments are reduced to a size that can retain adequate - equal amounts of air (25 percent) and water (25 per water and support plant life, the rate of soil formation cent) on a volume basis. increases rapidly. As organic materials decompose in the surface soil, the evolved carbon dioxide dissolves in water to form carbonic acid — a weak acid solu- tion that constantly bathes weatherable minerals below. The carbonic acid reacts with and alters many of the primary minerals in the soil matrix to chemically alter and etch the sand and silt fractions and to produce sec- ondary clay minerals. The decomposing organic matter also releases other organic acids (e.g., oxalic, citric, and tartaric) that further accelerate weathering (Brady and Weil 2008). As soil-forming processes continue, some of the fine Figure 2.1. Volume composition of a desirable surface soil. clay soil particles (smaller than 0.002 mm) are carried, - or leached, by percolating water from the upper por tions of the soil (topsoil) down into the lower or subsoil Soil Formation layers. As a result of this leaching action, the surface The mineral material of a soil is the product of the soil texture becomes coarser and the subsoil texture weathering of underlying rock in place or the weathering becomes finer as the soil weathers. of transported sediments or rock fragments. The mate - rial from which a soil has formed is called its “parent Soil Horizons material.” The weathering of residual parent materials to form soils is a slow process that has been occurring Soils are layered because of the combined effects of for millions of years in most of the mid-Atlantic region. organic matter additions to the surface soil and long- term leaching. These layers are called “horizons.” The However, certain soil features (such as “A horizons,” Urban Nutrient Management Handbook 2-1

429 Chapter 2. General Soil Science Principles - vertical sequence of soil horizons found at a given loca The subsoil (B horizon) is typically finer in texture, tion is collectively called the “soil profile” (figure 2.2). denser, and firmer than the surface soil. Organic mat - ter content of the subsoil tends to be much lower than The principal master soil horizons found in managed that of the surface layer, and subsoil colors are often soil systems are: stronger and brighter, with shades of red, brown, and yellow predominating due to the accumulation of iron- A horizon • or mineral surface soil. (If the soil has coated clays. Subsoil layers with high clay accumula - been plowed, this is called the “Ap horizon.”) tion relative to their overlying A horizon are described or subsoil. • B horizon as Bt horizons. If the B is still observed based on color or structural development but not enriched in clay, it is or partially weathered parent material, • C horizon labeled “Bw” by default. which is also part of the subsoil. The C horizon is partially decomposed and weathered or unconsolidated parent materials Rock (R layer) • parent material that retains some characteristics of the similar to that from which the soil developed. parent material. It is more like the parent material from Unmanaged and relatively undisturbed forest soils also which it has weathered than the subsoil above it. By commonly contain an organic O horizon (litter layer) definition, C horizons are “diggable” with a spade or on the surface and a light-colored, acid-leached zone (E soil auger, while R layers cannot be excavated with horizon) just below the A horizon. hand tools. Images with horizon designations for soils typical of our region (Ultisols), along with distribution In addition to the master soil horizons that are noted by maps and information links can be found at http://soils. capital letters (e.g., A and B), soil scientists also assign cals.uidaho.edu/soilorders/ultisols.htm . lowercase letters called “subscripts” (e.g., Ap) to describe the nature of the master horizon (U.S. Department of Agriculture (USDA) 1993). There are several dozen commonly used subscripts, but the most common ones in urbanized areas of the mid-Atlantic are Ap (plowed topsoil), “Bt” (clayey subsoil), and “Cd” (very dense, compacted subsoil). Another important combination to recognize is “Btg,” which indicates a clayey subsoil with color fea- tures (gleying or gray coloration) indicative of poor internal drainage, as discussed later in this chapter.The surface soil horizon(s) or “topsoil” (the Ap or A plus E horizons) is often coarser than the subsoil layer and contains more organic matter than the other soil layers. The organic matter imparts a tan, dark-brownish, or black color to the topsoil. Soils that are high in organic mat- ter (more than 3 percent) usually have very dark surface colors. The A or Ap horizon tends to be more fertile and have a greater concentration of plant roots than any other soil horizon. In unplowed soils, the “elu - viated” (E) horizon below the A horizon is often light-colored or gray, coarser-tex- tured, and more acidic than either the A horizon or the horizons below it because of acid leaching over time. Graphic by Kathryn Haering. Figure 2.2. Soil profile horizons. Urban Nutrient Management Handbook 2-2

430 Chapter 2. General Soil Science Principles As discussed in greater detail in chapter 3, soils in the Silt particles range in size from 0.05 mm to 0.002 mm. urban landscape are frequently highly disturbed and When moistened, silt feels smooth but is not slick or - often contain distinct layering due to cut/fill and grad sticky. When dry, it is smooth and floury and if pressed ing practices that are quite dissimilar from the natural between the thumb and finger, it will retain the imprint. soil horizons discussed above. It is also quite common Silt particles are so fine they cannot usually be seen for the native topsoil (A horizon) layers to be absent by the unaided eye and are best seen with the aid of a and for deeper subsoil materials (Bt) to appear at the strong hand lens or microscope. surface. Graded and layered urban soils also com- is the finest soil particle size class. Individual Clay monly contain highly compacted subsoil layers (Cd particles are finer than 0.002 mm. Clay particles can horizons). be seen only with the aid of an electron microscope. They feel extremely smooth or powdery when dry and Soil Physical Properties become plastic and sticky when wet. Clay will hold the form into which it is molded when moist and will form The physical properties of a soil are the result of soil parent materials being acted on by climatic factors a long ribbon when extruded between the fingers. (such as rainfall and temperature), and being affected There are 12 primary classes of soil texture defined by relief (slope and direction or aspect) and by vegeta - by the USDA (1993). The textural classes are defined tion over time. A change in any one of these soil-form- by their relative proportions of sand, silt, and clay as ing factors usually results in a difference in the physical shown in the USDA’s “textural triangle” (figure 2.3). properties of the resulting soil. The important physical - Each textural class name indicates the size of the min properties of a soil are texture, aggregation/structure, eral particles that are dominant in the soil. Regardless porosity, and bulk density. of textural class, all soils in the mid-Atlantic region contain sand-, silt-, and clay-sized particles, although Texture the amount of a particular particle size may be small. The relative amounts of the different soil-sized particles (smaller than 2 mm), or the fineness or coarseness of the mineral particles in the soil, - is referred to as soil “tex ture.” Mineral grains that are larger than 2 mm in diame - ter are called rock fragments and are measured separately. Soil texture is determined by the relative amounts of sand, in the fine- silt, and clay earth fraction (smaller than 2 mm). Sand particles vary in size from very fine (0.05 mm) to very coarse (2.0 mm) in average diameter. Most sand particles can be seen without a magnifying glass. Sands feel coarse and gritty when rubbed between the thumb and fingers, except for mica flakes, which tend to smear when rubbed. Figure 2.3. The USDA textural triangle (USDA 1993). Urban Nutrient Management Handbook 2-3

431 Chapter 2. General Soil Science Principles Texture can be estimated in the field after a moderate Effects of Texture on Soil Properties amount of training by manipulating and feeling the soil The clay fraction in soils is charged and relatively minor between the thumb and fingers. However, for precise amounts (10 to 15 percent) of clay can significantly measurement and/or prescriptive use, texture should be increase net charge that directly influences both water- quantified by laboratory particle-size analysis. holding and nutrient retention in soils. Water infiltrates To use the textural triangle: more quickly and moves more freely in coarse-textured or sandy soils, which increases the potential for leach - 1. First, you will need to know the percentages of sand, ing of mobile nutrients. Sandy soils also hold less total silt, and clay in your soil, as determined by labora - water and fewer nutrients for plants than finer-textured tory particle-size analysis. soils like clays or clay loams. In addition, the relatively Locate the percentage of clay on the left side of the 2. low water-holding capacity and the larger amount of air triangle and move inward horizontally, parallel to present in sandy soils allow them to warm faster than the base of the triangle. fine-textured soils. Sandy and loamy soils are also more easily tilled than clayey soils, which tend to be denser. 3. Follow the same procedure for sand, moving along the base of the triangle to locate your percentage of In general, fine-textured soils hold more water and plant sand. nutrients and therefore require less frequent applica - tions of water, lime, and fertilizer. Soils with high clay 4. Then, move up and to the left until you intersect the content (more than 40 percent clay), however, actually line corresponding to your clay percentage value. hold less plant-available water than loamy soils. Fine- At this point, read the “textural class” written within 5. textured soils have a narrower range of moisture con- the bold boundary on the triangle. For example, a ditions under which they can be worked satisfactorily soil with 40 percent sand, 30 percent silt, and 30 than sandy soils. Soils high in silt and clay may puddle percent clay will be a clay loam. With a moderate or form surface crusts after rains, impeding seedling amount of practice, soil textural class can also be emergence. High-clay soils often break up into large reliably determined in the field. clods when worked while either too dry or too wet. When soil textures fall very close to the boundary Aggregation and Soil Structure between two adjacent classes, it is appropriate to name both (e.g., sandy clay loam to sandy clay). Also, within - ” is the cementing of several soil par Soil “aggregation a given textural class, soils with high clay contents are ticles into a secondary unit or aggregate. Soil particles often referred to as “heavy” versus those low in clay are arranged or grouped together during the aggregation content that are called “light.” Thus, a “heavy clay process to form structural units (known to soil scientists loam” indicates a soil texture in the upper portion of as “peds”). These units vary in size, shape, and distinct - that textural class, close to being clay. This latter con- ness (also known as strength or grade). In topsoils, soil vention is not defined or formally accepted by the - organic matter is the primary material that cements par USDA but is commonly used by field practitioners. ticles together into water-stable aggregates. In subsoil, - aluminum and iron oxides play a major role in cement If a soil contains 15 percent or more rock fragments ing aggregates, as do finer clay particles which — due (larger than 2 mm), a rock fragment content modifier is to their charge (discussed later in this chapter) — can - added to the soil’s texture class. For example, the tex - also bind and stabilize much larger sand and silt par ture class designated as “gravelly silt loam” would con- ticles together. The types of soil structure found in most tain 15 to 35 percent gravels within a silt loam (smaller mid-Atlantic soils are described in table 2.1 and illus- than 2 mm), fine-soil matrix. A sample with more than trated in figure 2.4. 35 percent gravel would be described as “very gravelly silt loam,” etc. More detailed information on USDA particle-size classes and other basic soil morphological Effects of Soil Structure on Soil Properties - http://soils.usda.gov/techni descriptors can be found at - The structure of the soil affects pore space size and dis or in the USDA Soil Sur - cal/handbook/download.html tribution, and therefore, rates of air and water move- vey Manual (USDA 1993). ment and overall root proliferation. Well-developed structure allows favorable movement of air and water, Urban Nutrient Management Handbook 2-4

432 Chapter 2. General Soil Science Principles Table 2.1. Types of soil structure. Structure type Description Soil particles are arranged in small, Granular rounded units. Granular structure is very common in surface soils (A horizons) and is usually most distinct in soils with relatively high organic matter content. Soil particles are arranged to form Blocky block-like units, which are about as wide as they are high or long. Some blocky peds are rounded Figure 2.4. Types of soil structures. Graphic by Kathryn Haering. on the edges and corners; others are angular. Blocky structure is while poor structure retards movement of air and water. commonly found in the subsoil, Because plant roots move through the same channels in although some eroded fine-textured the soil as air and water, well-developed structure also soils have blocky structure in the surface horizons. encourages extensive root development. With respect to rooting, the size of the pores and their degree of Soil particles are arranged in plate- Platy interconnection are also critically important. In general, like sheets. These plate-like pieces the penetration of air, water, and roots through soils is are approximately horizontal in the soil and may occur in either the favored by “macropores” (larger than or equal to 0.05 surface or subsoil, although they are mm, or sand-sized) that are physically interconnected, most common in the subsoil. Platy particularly vertically. In general, soil productivity is structure strongly limits downward favored when water, air, and roots can move readily movement of water, air, and roots. through the soil. It is also important that soil metabolic It may occur just beneath the plow gasses (e.g., carbon dioxide) be able to diffuse back layer, resulting from compaction into the atmosphere. by heavy equipment, or on the soil surface when it is too wet to work Water can enter a surface soil that has well-developed satisfactorily. (strong) granular structure (particularly fine-textured Soil particles are arranged into Prismatic soils) more rapidly than one that has relatively weak large peds with a long vertical axis. structure. Surface soil structure is usually granular, but Tops of prisms may be somewhat such granules may be indistinct or completely absent if indistinct and normally angular. the soil is continuously tilled, the soil is very coarse, or Prismatic structure occurs mainly if organic matter content is low. in subsoils, and the prisms are typically much larger than other The size, shape, and strength of subsoil structural peds typical subsoil structure types such are particularly important to soil productivity. Sandy as blocks. soils generally have poorly developed structure relative Massive, with no definite structure Structureless - to finer-textured soils because of their lower clay con or shape, as in some C horizons or tent. When the subsoil has well-developed blocky struc - compacted material. ture, there will usually be good air and water movement - or - in the soil. If platy structure has formed in the subsoil, downward water, air movement, and root development Single grain, which is typically in the soil will be slowed. Distinct prismatic structure is individual sand grains in A or C horizons not held together by often associated with subsoils, but those larger prisms organic matter or clay. will usually break down into primary blocky peds. Very large and distinct subsoil prisms are also commonly (Bx horizons), which are associated with “fragipans” massive and dense subsoil layers. Urban Nutrient Management Handbook 2-5

433 Chapter 2. General Soil Science Principles The loosening and development and microbial activity. Porosity and Bulk Density granulation of fine-textured soils promote aeration (gas Soil “porosity,” or pore space, is the volume percentage exchange) by increasing the number of macropores. of the total soil that is not occupied by solid particles. Pore space is commonly expressed as a percentage: Soil Organic Matter bulk density x 100 % pore space = 100 − ( ) Soil organic materials consist of plant and animal resi- particle density dues in various stages of decay. Primary sources of “Bulk density” is the dry mass of soil solids per unit vol- organic material inputs are dead roots, root exudates, ume of soils, and “particle density” is the density of soil litter and leaf drop, and the bodies of soil animals such solids, which is assumed to be constant at 2.65 grams as insects and worms. Earthworms, insects, bacteria, 3) . Bulk densities of mineral per cubic centimeter (g/cm fungi, and other soil organisms use organic materials 3 . A soil soils are usually in the range of 1.1 to 1.7 g/cm as their primary energy and nutrient source. Nutrients 3 will generally with a bulk density of about 1.32 g/cm released from the residues through decomposition are possess the ideal soil condition of 50 percent solids and then available for use by growing plants. 50 percent pore space. Bulk density varies depending Soil “humus” is fully decomposed and stable organic on factors such as texture, aggregation, organic matter, matter that is primarily derived from the bodies of soil compaction/consolidation, soil management practices, microbes and fungi. Humus is the most reactive and and soil horizon. In general, root penetration through important component of soil organic matter and is the soils will be limited in sandy soils when the bulk den- form of soil organic material that is typically reported 3 and in clayey soils at 1.40 sity approaches 1.75 g/cm as “organic matter” on soil testing reports. Soil organic 3 (Brady and Weil 2008). However, water, air, and g/cm matter in Virginia soils typically ranges between 0.5 and roots can penetrate high bulk-density soils that have 2.5 percent in A horizons and can approach 5 percent in - well-developed structure with interconnected macropo heavily enriched garden soils or soils with poor drain- res, as discussed above. age. Higher levels are typically found only in wetlands. Macropores (larger than 0.05 mm) allow the ready Soil organic matter is so reactive (charged) that when movement of air, roots, and percolating water. In con- it exceeds 12 to 20 percent by weight, it dominates soil trast, micropores (smaller than 0.05 mm) in moist soils properties and we refer to it as “organic soil material.” - are typically higher in water content and poorly inter connected, and this does not permit much air move- Factors That Affect Soil Organic Matter ment into or out of the soil. Internal water movement Content is also very slow in micropores. Thus, the movement The organic matter content of a particular soil will of air and water through a coarse-textured sandy soil depend on: can be surprisingly rapid despite its low total porosity because of the dominance of macropores. : Soils that have been in grass for Type of vegetation long periods usually have a relatively higher percent- Under field conditions, the total soil pore space is filled age of organic matter in their surface. Soils that develop with a variable mix of water and air. If soil particles are under trees usually have a low organic matter percentage packed closely together, as in well-graded surface soils in the surface mineral soil but do contain a surface lit- or compact subsoils, total porosity is low and bulk den- ter layer (O horizon). Organic matter levels are typically sity is high. If soil particles are arranged in porous aggre- higher in a topsoil that supports perennial hay, pasture, or gates, as is often the case in medium-textured soils high forest than in a topsoil used for cultivated crops. in organic matter, the pore space per unit volume will be high and the bulk density will be correspondingly low. Tillage: Soils that are tilled frequently are usually - lower in organic matter. Plowing and otherwise till Fine-textured clay soils, especially those without a ing the soil increases the amount of oxygen in the soil, stable blocky (Bt) or granular (Ap) structure, may which increases the rate of organic matter decomposi - have reduced movement of air and water even though tion. This detrimental effect of tillage on organic matter they have a large volume of total pore space. In these is particularly pronounced in very sandy, well-aerated fine-textured soils, micropores are dominant. Because - soils because of the tendency of frequent tillage to pro these small pores often stay full of water, aeration — mote organic matter oxidation to carbon dioxide. especially in the subsoil — can be inadequate for root Urban Nutrient Management Handbook 2-6

434 Chapter 2. General Soil Science Principles : Soil organic matter is usually higher in poorly Drainage Field Capacity and Permanent Wilting drained soils because of limited oxidation, which slows Percentage down the overall biological decomposition process. The term “field capacity” defines the amount of water Soil texture : Soil organic matter is usually higher in remaining in a soil after downward gravitational drain- fine-textured soils because soil humus forms stable age has stopped. This value represents the maximum complexes with clay particles and fine-textured soils amount of water that a soil can hold against gravity fol- - limit the penetration of atmospheric oxygen in and car lowing saturation by rain or irrigation. Field capacity is bon dioxide out of surface soils. usually expressed as percentage by weight (for exam - ple, a soil holding 25 percent water at field capacity Effect of Organic Matter on Soil contains 25 percent of its dry weight as retained water). On a volumetric basis, values for field capacity range Properties from 8 percent in a sand to 35 percent in a clay (Brady Adequate soil organic matter levels benefit soils in and Weil 2008). several ways. The addition of organic matter improves soil physical conditions, particularly aggregation and The amount of water a soil contains after plants are macropore space. This improvement leads to increased wilted beyond recovery is called the “permanent wilt- water infiltration, improved soil tilth, and decreased ing percentage.” Considerable water may still be pres- soil erosion. Organic matter additions also improve soil ent at this point, particularly in clays, but it is held so fertility because plant nutrients are released to plant- tightly that plants are unable to extract it. The amount available mineral forms as organic residues are decom - field capacity and the between of water held by the soil posed (or “mineralized”), and soil humus is highly permanent wilting point is the “plant-available water” charged and retains nutrients against leaching, as dis- - and is maximized in loamy-textured soils. The volumet cussed later. ric plant-available water for sand is typically less than 5 percent but may approach 25 percent volumetric water A mixture of organic materials in various states of for a well-aggregated, loamy soil (see figure 2.1). decomposition helps maintain a good balance of air and water components in the soil. In coarse-textured soils, Tillage and Moisture Content organic material bridges some of the space between - sand grains, which increases water-holding capac Soils with a high clay content are sticky when wet and - ity. In fine-textured soil, organic material helps main form hard clods when dry. Therefore, tilling clayey tain porosity by keeping very fine clay particles from - soils at the proper moisture content is extremely impor packing too closely to one another, thereby enhancing tant. Although sandy soils are inherently droughty, macroporosity. they are easier to till at varying moisture contents because they do not form dense clods or other high- strength aggregates. Sandy soils are also far less likely Soil-Water Relationships than clays to be compacted if cultivated when moist or wet. However, soils containing high proportions of Water-Holding Capacity very fine sand or coarse silts may be compacted by Soil water-holding capacity is determined largely by tillage when moist. the interaction of soil texture, bulk density/pore space, and aggregation. Sands hold little water because they Soil Drainage have little net charge and their large intergranular The overall hydrologic balance of soils — including pore spaces allow water to drain freely from the soils. infiltration and internal permeability — is discussed Clays adsorb a relatively large amount of water, and in greater detail in chapter 11. However, soil scientists their small pore spaces retain it against gravitational commonly use the term “soil drainage” to describe the forces. However, clayey soils hold water much more rate and extent of vertical or horizontal water move - tightly than sandy soils so that much of the water ment and internal soil saturation during the growing retained (more than 40 percent) is unavailable to grow- season. ing plants. As a result, moisture stress can become a problem in fine-textured soils despite their high total water-holding capacity. Urban Nutrient Management Handbook 2-7

435 Chapter 2. General Soil Science Principles support hydrophytic vegetation typical of wetlands, Important factors affecting soil drainage class are: and exhibit redoximorphic features are designated as • Slope (or lack of slope). Further information on mid-Atlantic “hydric soils.” hydric soils and redox features can be found online at • Depth to the seasonal water table. www.epa.gov/reg3esd1/wetlands/hydric.htm . Texture of surface and subsoil layers and of underly - • ing materials. Interpretation of soil redox features can be highly com- plicated in an urban environment due to the effects of Type and strength of soil structure. • soil layer mixing via the cut/fill and grading processes • Problems caused by improper tillage or grading, and changes in internal soil drainage due to ditching such as compacted subsoils or lack of surface soil and pavement interception of normal infiltration. structure. Drainage Classes Another definition of drainage refers to the removal of excess water from the soil to facilitate agriculture, The “drainage class” of a soil defines the frequency of forestry, or other higher land uses. This is usually soil wetness as it limits agricultural practices and is usu- accomplished through a series of surface ditches or the ally determined by the depth in soil to significant gray installation of subsoil drains. redox depletions. The soil drainage classes in table 2.2 - are defined by the USDA Natural Resources Conser vation Service (USDA 1993). They refer to the natural Soil Drainage and Soil Color drainage condition of the soil without artificial drainage. The nature of internal soil drainage in relatively undis- turbed soils is usually indicated by soil color patterns Table 2.2. Soil drainage classes. and color variations with depth. Clear, bright red, and/or yellow subsoil colors indicate well-drained conditions Soil Drainage class characteristics Effect on cropping where iron and other compounds are present in their oxidized forms. A soil is said to be well-drained when Will probably Water is removed Excessively the “solum” (A plus E plus B horizons) exhibits strong require drained rapidly from soil. red/yellow colors without any gray coloration (mottles supplemental Somewhat irrigation. or redox depletions). The term “mottle” is used generi - excessively cally to describe any differences in coloration within drained - a given soil horizon. When those differences in color Well-drained No drainage Water is removed ation are due to wetness, however, the correct term is required. readily, but not “redoximorphic features.” rapidly. When soils become saturated for significant periods of May require Water is removed Moderately time during the growing season, these oxidized (red/ supplemental well-drained somewhat slowly drainage if crops at some periods yellow) forms of iron are biochemically reduced to of the year. that require good soluble forms and can be moved with drainage waters. drainage are This creates a matrix of drab, dominantly gray colors grown. that are described as “redox depletions.” The iron that Water is removed Will probably Somewhat is mobilized is typically reprecipitated locally into so slowly that poorly drained require contrasting red/yellow features that are called “redox supplemental soil is wet at concentrations.” Subsoil zones with mixtures of bright drainage for shallow depths red/yellow and gray colors are indicative of seasonally satisfactory use periodically Poorly drained fluctuating water tables, where the subsoil is wet during during the in production of the winter/early spring and unsaturated in the summer/ growing season. most crops. early fall. Poorly drained soils also tend to accumulate large amounts of organic matter in their surface hori- Very poorly Free water is zons because of limited oxidation and may have very drained present at or near thick and dark A horizons. the surface during the growing Soils that are wet in their upper 12 inches for consid- season. erable amounts of time during the growing season, Urban Nutrient Management Handbook 2-8

436 Chapter 2. General Soil Science Principles minerals and organic matter that typically possess neg- Soil Chemical Properties ative electrical surface charges. These negative charges The plant root obtains essential nutrients almost entirely are present in excess of any positive charges that may by uptake from the soil solution. The chemistry and exist, which gives soil a net negative charge. nutrient content of the soil solution is, in turn, controlled Negative surface charges attract positively charged by the solid material portion of the soil. Soil chemical cations and prevent their leaching. These ions are held properties, therefore, reflect the influence of soil miner - against leaching by electrostatic positive charges but als and organic materials on the soil solution. are not permanently bound to the surface of soil par - ticles. Positively charged ions are held in a “diffuse Soil pH cloud” within the water films that are also strongly Soil pH defines the relative acidity or alkalinity of the attracted to the charged soil surfaces. Cations that are soil solution. It is important to note that pH can only be retained by soils can thus be replaced, or “exchanged,” 2+ measured in soil solution that has equilibrated with soil by other cations in the soil solution. For example, Ca 3+ + solids; you cannot measure the pH of a solid. The pH and/or K and vice versa. The can be exchanged for Al scale in natural systems ranges from 0 to 14. A pH value higher a soil’s CEC, the more cations it can retain. of 7.0 is neutral. Values below 7.0 are acidic and those There is a direct and positive relationship between the above 7.0 are alkaline, or basic. Many agricultural soils relative abundance of a given cation in solution and in the mid-Atlantic region have a soil pH between 5.5 the amount of this cation that is retained by the soil and 6.5. Any soil pH value less than 4.0 is indicative of CEC. For example, if the predominant cation in the acid-sulfate influenced soils (see chapter 3). 3+ 3+ soil solution is Al , Al will also be the predominant + ) activity Soil pH is a measurement of hydrogen ion (H exchangeable cation. Similarly, when large amounts of 2+ in soil solution or effective concentration in a soil and are added to soil solution by lime dissolving over Ca 2+ 3+ water solution. Soil pH is expressed in logarithmic terms, will displace Al from the exchange com- time, Ca which means that each unit change in soil pH amounts to plex and allow it to be neutralized in solution by the a tenfold change in acidity or alkalinity. For example, a alkalinity added with the lime. + (or soil with a pH of 6.0 has 10 times as much active H The CEC of a soil is expressed in terms of moles of is 10 times more acidic) as one with a pH of 7.0. + charge per mass of soil. The units used are “cmol /kg” Soils become acidic when basic cations (positively (centimoles of positive charge per kilogram) or “meq/100 2+ + ) held by soil charged ions such as calcium, or Ca /kg = 1.0 g” (milliequivalents per 100 grams; 1.0 cmol colloids are leached from the soil and replaced by alu- meq/100 g). Soil scientists have used the former unit in 3+ ), which then hydrolyze to form alu - minum ions (Al publications since the early 1980s, while meq/100 g is ) solids, which then liberate minum hydroxide (Al(OH) commonly used in other disciplines. Numerically, they 3 + + ions to solution as water hydrolyzes (splits into H H are the same. Soil CEC is calculated by adding the charge - + + 3+ 2+ 2+ + + ions). This long-term acidification process is and OH , Mg , Ca , NH , , Al , Na and H equivalents of K 4 accelerated by the decomposition of organic matter that that are extracted from a soil’s exchangeable fraction. also releases acids to soil solution. Most soils in the mid-Atlantic region were formed under high rainfall Sources of Negative Charge in Soils with abundant vegetation and are considerably more The mineralogy of the clay fraction and the soil’s acidic than soils of the midwestern and western United humus content greatly influence the quantity of nega - States. In fact, very few soils in Virginia were above pH tive charges present. One source of negative charge is 6.0 when settlers first arrived in the 17th century. “isomorphous substitution,” which is the replacement 3+ 4+ or Al cation in the clay mineral structures of a Si Cation Exchange Capacity: Our with a cation that has a lower surface charge. For exam - 3+ 3+ 4+ Measure of Soil Charge and Reactivity might be might be replaced with Al , or Al ple, Si 2+ 2+ or Fe . Clay minerals with replaced with either Mg The net ability of a soil to hold, retain, and exchange 2+ 2+ a repeating layer structure of two silica sheets sand- ), ), magnesium (Mg cations such as calcium (Ca + + + wiched around an aluminum sheet (two-to-one clays, ), ammonium (NH ), ), sodium (Na potassium (K 4 3+ + such as vermiculite or smectite), typically have a higher ), and hydrogen (H ) is called “cation aluminum (Al exchange capacity,” or CEC. All soils contain clay total negative charge than clay minerals with one silica Urban Nutrient Management Handbook 2-9

437 Chapter 2. General Soil Science Principles If cations are present in equal amounts, the general sheet and one aluminum sheet (one-to-one clays, such strength of adsorption that holds cations in the soil is in as kaolinite). Soil humus is also highly charged due to a the following order: large number of chemically reactive sites called “func- tional groups.” 2+ 2+ 3+ + + + Al > Na > K >> Ca > Mg = NH 4 Soil pH also has a direct relationship to the quantity of negative charges contributed by organic matter and, to a Effect of CEC on Soil Properties lesser extent, from mineral surfaces such as iron oxides. A soil with a low CEC value (1-10 meq/100 g) may As soil pH increases, the quantity of negative charges have some, or all, of the following characteristics: increases due to the reactions of exposed organic matter functional groups and similar reactions that occur on • High sand and low clay content. the surfaces of iron and aluminum oxides and the edges • Low organic matter content. of clays. This pH-dependent charge is particularly important in highly weathered topsoils where organic • Low water-holding capacity. matter dominates overall soil charge. • Low soil pH. It is important to point out that while we use CEC as - • Not easily resistant to changes in pH or other chemi our measure of net charge or reactivity in soils, all cal changes. soils contain a certain amount of positive charges as well. These positive charges are important in retaining • Enhanced leaching potential of plant nutrients such - 2- - + 2+ . + , Cl , or SO anions (negatively charged ions) like NO as Ca , K . , NH 4 3 4 against leaching in certain soils as well. In particular, • Low productivity. highly weathered soils that are high in aluminum and - iron (very red) and low in pH (less than 5.5) may actu (11-40 meq/100 g) higher CEC value A soil with a ally have more positive charges on their surfaces than may have some or all of the following characteristics: negative charges. These soils also have a very strong • Lower sand and higher silt plus clay content. affinity to bind (or fix) phosphorus in very tight com - plexes that will be discussed in chapter 4. • Moderate-to-high organic matter content. • High water-holding capacity. Cation Retention and Leaching in Soils Ability to resist changes in pH or other chemical • The negatively charged surfaces of clay particles and properties. organic matter strongly attract cations. However, the retention and release of these cations, which affects • Less nutrient losses to leaching than low CEC soils. their mobility in soil, is dependent on several factors. Two of these factors are the relative retention strength Base Saturation of each cation and the relative amount or mass of each + 2+ 2+ , and , K Of the common soil-bound cations, Ca , Mg cation present. + Na are considered to be basic cations. The base satura- For a given cation, the relative retention strength by tion of the soil is defined as the percentage of the soil’s soil is determined by the charge of the ion and its size CEC (on a charge-equivalent basis) that is occupied (or diameter). In general, the greater the positive charge by these cations. A high base saturation (more than 50 and the smaller the ionic diameter of a cation, the more percent) enhances calcium, magnesium, and potassium tightly the ion is held (i.e., higher retention strength) availability and prevents soil pH decline. Low base sat- and the more difficult it is to remove that cation and uration (less than 25 percent) is indicative of a strongly 3+ leach it down through the soil profile. For example, Al 3+ acidic soil that may maintain Al activity high enough has a positive charge of three and a very small ionic to cause phytotoxicity. diameter and thus moves through the soil profile very + ), on the other hand, has a charge slowly. Potassium (K Buffering Capacity of one and a much larger ionic radius, so it leaches much more readily. This difference in cation retention The resistance of soils to changes in the pH of the soil has important soil fertility implications that will be dis- solution is called “buffering.” In practical terms, buffer - ing capacity for pH increases with the amount of clay and cussed in chapter 4. Urban Nutrient Management Handbook 2-10

438 Chapter 2. General Soil Science Principles hold and supply sufficient plant-available water, be organic matter. Thus, soils with high clay and organic able to moderate extreme air temperatures, and allow matter content (high buffer capacity) will require more for adequate exchange of gasses between the root zone lime to increase pH than sandy soils with low amounts of - and the atmosphere. Chemically, the soil must main organic matter (low or weak buffer capacity). tain an adequate pH and soluble-salt environment for One laboratory measure of the acid buffering capacity locally adapted plants and supply all of the soil nutri- (or lime demand) of a given soil is called “buffer pH” ents detailed above in adequate amounts to meet the and will be discussed in more detail in chapters 4 and 5. plant’s demand. The overall productivity of the plant It is very important to realize, however, that buffer pH community will be controlled by the soil factor that is is quite different from conventional soil-to-water pH, present in the lowest relative amount, regardless of the as discussed above. adequacy/availability of the rest of the important soil physical and chemical factors. This concept is known as the “the law of the minimum.” For example, over - Essential Elements for Plant Growth all plant growth in urban soils is commonly directly Higher plants and the microbial biomass in soils need limited by compaction and associated lack of rooting a wide array of essential elements to sustain them and volume, regardless of the adequacy of soil pH and build biomass. The soil biota take carbon, hydrogen, nutrient levels. Once you loosen these soils to provide and oxygen from soil, air, and water, so these are not adequate rooting depth, plant growth will increase until - considered soil-supplied nutrients. Six essential ele it becomes limited by the next limiting factor (e.g., low - ments (nitrogen, phosphorus, potassium, sulfur, cal soil pH or phosphorus). Therefore, the overall guiding cium, and magnesium) are taken up by plants from the principle underpinning appropriate soil management is soil in relatively large amounts; these are referred to as that we must manage all important plant growth factors “macronutrients.” All of the essential elements are taken together to maintain adequate plant growth over time. up primarily as dissolved ions from solution; table 2.3 lists their common forms and sources. The ionic form (i.e., cation versus anion) of each nutrient and its spe- Soil Survey cific charge characteristics directly control its relative The soils of all counties have been mapped by the sorption and availability from the soil. Higher plants USDA-NRCS soil survey (1993), and these maps are also require a wide range of other elements (boron, available in soil survey reports, although some county chlorine, cobalt, copper, iron, molybdenum, manga - reports are quite old and in need of modern recorrela - nese, nickel, and zinc) in much smaller amounts and tion. A soil survey report reveals the kinds of soils that these are referred to as “micronutrients.” More detail exist in the county (or other area) covered by the report on the specific forms and supply of plant nutrients can at a level of detail that is usually sufficient for agricul - be found in chapters 4, 5, 7, 8, and 9. tural interpretations. The soils are described in terms of their location on the landscape, their profile charac - Limiting Factors to Plant Growth teristics, their relationships to one another, their suit- - Higher plants rely on the soil for a wide range of ser ability for various uses, and their needs for particular vices in support of their growth. Physically, the soil types of management. Each soil survey report contains must be deep and strong enough to support the plant, information about soil morphology, soil genesis, soil Table 2.3. Soil-supplied macronutrients, sources, and ionic forms for plant uptake. Nutrient Primary sources Dominant form in soil solution + : low pH or wet Organic matter, manures, fertilizers (N-P-K), legumes Nitrogen (N) NH 4 - : moderate pH and oxidized NO 3 - : between pH 5 and 7 PO Phosphorus (P) Organic matter, fertilizers H 4 2 + Potassium (K) Plant litter, fertilizers, soil minerals (micas and feldspars) K 2+ Calcium (Ca) Limes, plant litter, soil minerals (feldspars and carbonates) Ca 2+ Mg Magnesium (Mg) Dolomitic limes, soil minerals 2- Sulfur (S) Atmospheric and gypsum additions, soil sulfides SO 4 Urban Nutrient Management Handbook 2-11

439 Chapter 2. General Soil Science Principles Map units are the actual units that are delineated on conservation, and soil productivity. Soil survey reports the soil map and are usually named for the dominant are available from county and state USDA-NRCS http://soils. cooperative Extension offices and online at soil series and slope phase. Map units generally contain . usda.gov/survey/online_surveys/ more than one soil series. Units are given the name of the dominant soil series if 85 percent or more of the area is correlated as a single soil series (or similar soils Parts of a Soil Survey in terms of use and management). Soil complexes are There are two major sections in a soil survey report. used to name the map unit if the dissimilar inclusions One section contains the soil maps. In most reports, exceed 15 percent. Each map unit is given a symbol the soil map is printed over an aerial photographic base (numbers or letters) on the soil map that designates the image. In the past, soil mapping was done at scales name of the soil series or complex being mapped and ranging from 1-to-10,000 to 1-to-50,000, with 1-to- the slope of the soil. More details on how soil map- 15,840 being the most common scale used before the ping units are developed and named can be found in the 1980s. Current USDA-NRCS mapping is published Soil Survey Manual at http://soils.usda.gov/technical/ at 1-to-24,000 to match U.S. Geologic Survey topo- . manual/ graphic quadrangle maps. Each soil area is delineated by an enclosing line on Using a Soil Survey - the map. Soil delineation boundaries are drawn wher A user interested in an overall picture of a county’s soils ever there is a significant change in the type of soil. should probably turn first to the soil association section The boundaries often follow natural contours, but they of the soil survey report. The general soil pattern of the may also cross and incorporate multiple portions of county is discussed in this section. A user interested in the landscape if the soils are similar across local topo- the soils of a particular farm must first locate that farm graphic variations. on the soil map and determine what soils are present. The other section of a soil survey report is the narra- Index sheets located with the soil maps help the user tive portion. Without it, the soil maps would have little find the correct section of the map. The map legend meaning. Symbols on each map are keyed to a list of gives the soil map the unit names for each symbol and soil mapping units. The nature, properties, and clas- assists with the location of descriptive and interpretive sification and use potentials of all mapping units are material in the report. described in detail. Detailed soil descriptions that provide information to those who are primarily interested in the nature and Terminology Used in Soil Surveys - properties of the soils mapped are located in the nar - is a basic unit of soil classification, consist Soil series rative portion of the soil survey report. The section ing of soils that are essentially alike in all main pro- concerned with the use and management of the soils file characteristics. Most soil mapping units in modern (soil interpretations is helpful to farmers and others ) cooperative soil surveys are named for their dominant who use the soil or give advice and assistance in its component soil series. use (e.g., soil conservationists, cooperative Extension agents). Management needs and estimated yields are Soil phase is a subdivision of a soil series or other unit - included in this section. Newer reports have engineer of classification having characteristics that affect the ing properties of soils listed in tables that are useful to use and management of the soil but do not vary enough highway engineers, sanitary engineers, and others who to merit a separate series. These include variations in design water storage or drainage projects. slope, erosion, gravel content, and other properties. It is important for the urban user of soil surveys to Soil complexes are naturally soil associations and understand that very few soil surveys recognize and occurring groupings of two or more soil series with appropriately interpret the drastically disturbed nature different use and management requirements that occur - of their landscape. Where the soil survey shows map in a regular pattern across the landscape but cannot ping units named for soil series, they represent the be separated at the scale of mapping that is used. Soil dominant undisturbed soils in that landscape that complexes are used to map two or more series that are existed predevelopment. Some older soil surveys sim- commonly intermixed on similar landforms in detailed ply mapped previously developed areas as “made land” county soil maps. Soil associations are utilized in more general and less detailed regional soil maps. or “urban lands.” Virginia soil surveys produced after Urban Nutrient Management Handbook 2-12

440 Chapter 2. General Soil Science Principles 1980 often map disturbed soils as “Udorthents,” which simply indicates that they are dominantly young soils due to their native profiles being largely destroyed. Literature Cited Brady, N. C., and R. R. Weil. 2008. The Nature and Properties of Soils . 14th ed. Upper Saddle River, N.J.: Pearson Prentice Hall. U.S. Department of Agriculture (USDA). Natural Resources Conservation Service. Soil Service Division Staff. 1993. Soil Survey Manual . Hand- book No. 18. Washington: U.S. Government http://soils.usda.gov/technical/ Printing Office. manual/. Urban Nutrient Management Handbook 2-13

441 Chapter 2. General Soil Science Principles 2-14 Urban Nutrient Management Handbook

442 Chapter 3. Managing Urban Soils Chapter 3. Managing Urban Soils Crop and Soil Environmental Sciences, Virginia Tech W. Lee Daniels, Professor, • Presence of anthropic materials (e.g., wood, rags, What Is an Urban Soil? cement) and other contaminants (e.g., oil, metals). More often than not, the soils we manage for plant • Higher temperature variability due to lack of natural growth in urban and suburban areas have been signifi - litter layer or vegetation. cantly altered from their natural state by excavation (cut and fill), grading, topsoil return, or other operations that Figure 3.1 depicts a number of these plant-growth lim - fundamentally alter their morphological, physical, and iting soil factors that we commonly encounter around chemical properties (Brown et al. 2000; Scheyer and building sites, particularly (1) high variability, (2) lay- Hipple 2005). In rural areas, similar disturbances asso- ering, (3) presence of acidic and infertile clayey mate - - ciated with road construction, mining, and utility cor rials at the surface, and (4) issues related to excessive ridors generate similar soil conditions that frequently compaction (high bulk density). Recognizing and deal - limit plant growth (Booze-Daniels et al. 2000). Simply ing with these limitations will therefore be the primary put, urban soils do not contain the natural sequence of focus of this chapter, but other issues and their remedies intact soil horizons that was described in chapter 2. will be addressed as well. Therefore, many of our underlying assumptions about soil testing results, plant growth response and overall soil-plant relations may not apply to these materials, and they must be modified to overcome their inherent limitations for plant growth. Urban Soil Properties When we compare these urban soils materials with nearby natural soil profiles (see chapter 2), a number of Figure 3.1. Diagram of urban soils and important plant growth limiting differences are usually readily apparent (adapted from features. Note that the soil limitations in one portion of a home lot Craul 1992): may be quite different from those encountered in another location of Diagram by Kathryn Haering. the same lot. • Highly variable in all directions. • Abrupt differences in soil texture and density (layer - Types of Urban Soil Materials and ing) with depth. Their Variability • Presence of high-clay materials at the surface/lack of The entire process of site development for housing, topsoil. construction, or landscape development results in large Soil structure that has been degraded, leading to loss of • amounts of soil disturbance, movement, and mixing. The large pores (macropores) and their vertical continuity. degree of impact ranges from limited surface soil com- paction to complete removal of the native soil profile and • High bulk density due to mechanical compaction and its replacement with mixed and dissimilar fill materials lack of structure/macropores. (figures 3.1 and 3.2). Thus, while predevelopment native • Common occurrence of surface crusts on finer-tex - soil properties will be fairly uniform and predictable on a tured materials. given site due to the long-term effect of the soil-forming factors (see chapter 2) the postdevelopment site will be • Soil pH may be higher or lower than normal. much more variable and extreme short-range differences • Restricted aeration and water drainage. in important plant-growth related properties such as com- paction, texture, and pH will be common. While there • Interrupted nutrient cycles and associated microbial is an almost endless variety of mechanisms and expres- populations. sions of soil disturbance, the most common types are (1) exposed subsoil materials, (2) exposed cut materials, and Very low organic matter and nutrient levels compared • (3) filled materials that are compacted and layered. to natural topsoils. Urban Nutrient Management Handbook 3-1

443 Chapter 3. Managing Urban Soils 3. Fills 1. Exposed Subsoil Materials Overall site development and final land shaping and The simplest urban soil scenario to recognize and deal grading generate extensive areas of filled materials with is where the topsoil (A plus E horizons) has been at most sites (figure 3.1). These fills may range from removed. Subsoil materials (B and C horizons) are fre - relatively shallow lifts of returned topsoil over intact quently encountered at the surface of the ground as a subsoils to very thick, multi-layered fills of strongly result of erosion of the native topsoil or severe soil dis- contrasting materials. Fills can often be recognized due turbance associated with earthmoving and construction to their long linear and uniform slopes or “unnatural” activities. In most instances, these materials will be red slope shapes and configurations. However, competent or yellow in color, but they may range from white to - grading and landscaping can make fills virtually indis gray in certain instances. Unlike topsoil, this material is tinguishable from natural landforms. Fills are typically often quite clayey and dense, devoid of organic matter, much more difficult to manage than either exposed sub - and generally resists plant growth. Subsoils in the mid- soils or cuts for a variety of reasons that are discussed Atlantic region are usually highly leached, acidic, and in more detail below. Fill materials tend to be highly infertile and may also be gravelly or rocky. variable and layered and compacted, all of which limit plant growth and water movement. Common Soil Limitations in the Urban Environment Compaction Simple soil compaction (high bulk density) is the most common plant growth and water movement limitation in urban soils (see figure 3.3). Dense layers in soils are commonly called “pans” and may result from a variety Figure 3.2. Typical soil disturbance in subdivision during construction. of natural long-term soil processes (e.g., dense Bt hori- Each lot is graded out (cut and filled) to approximately level the area zons), but are most commonly formed by site develop - immediately surrounding the house. Note large amounts of sand and ment and grading machinery. These compacted zones other construction debris that will more than likely be graded out and incorporated into fills. may occur at the surface or deep in the subsoil but are often denser than natural pans or subsoil layers. Arti- ficially induced pans are particularly common where 2. Cut Slopes and Banks several layers of soil have been disturbed, such as Cut materials are commonly encountered on sites where when topsoil is returned to a regraded lawn after house the natural topography is rolling or sloping and must be construction, or where cut-and-fill operations have reshaped to accommodate yards, driveways, landscap - reshaped an area for landscaping. Natural soil structure ing, and/or drainage features. Cuts are usually a rela - is usually destroyed by these activities; not only are tively minor component of subdivision developments soils made abnormally dense, but there are no longer but are a dominant feature on highway rights-of-way, any natural channels or planes of weakness for roots, - as discussed in more detail later. In general, cut mate water, and air to penetrate. It is also important to point rials expose subsoil and/or deeper geologic strata and out that normal foot traffic, game playing, or infrequent may therefore be very clayey and/or quite coarse and tire traffic can also cause compaction of the immedi - - rock-like. One limitation of these materials is that dur ate surface soil, particularly when the soil is moist and ing grading, cut clays will smear and seal and thereby readily compressible. limit water and root penetration. The lower sections of cut materials may also be subject to the limitations The ability of a growing root tip to penetrate soil is directly dependent on soil strength. Soil strength — described above for exposed subsoils such as clayey which essentially is its resistance to deformation or textures and acidic pH. However, due to the fact that shearing — is controlled primarily by a soil’s bulk den- they are much less variable, less compacted, and tend to sity and moisture content. Workable, loose soils have retain their native soil structure, cut slopes are usually bulk densities of 1.0 to 1.4 grams per cubic centimeter superior to fill materials as described next. Urban Nutrient Management Handbook 3-2

444 Chapter 3. Managing Urban Soils 3 ). In a clayey soil, root penetration is greatly (g/cm retarded during dry conditions when bulk density 3 . The same soil when moist, how- exceeds 1.5 g/cm ever, may not impede rooting because soil strength is then decreased. Sandy soils resist compaction due to their larger packing voids between particles and can support adequate rooting at bulk densities approaching 3 1.8 g/cm , but will still be limiting at higher levels of compaction. Soils that are compacted also resist water movement and gas exchange, which can seriously hinder plant growth. Compacted soils also lack macropore space, Figure 3.4. Turf growth limited by compaction. The bare soil on the left was pH 6.5 and fertile but heavily compacted and therefore, not which lessens water-holding capacity and rooting depth. capable of supporting viable turf after seed germination. The turf in Due to their lack of large pore spaces, water passes very the rest of this photo is also growing in moderately compacted soil as slowly; therefore, dense soils often alternate between evidenced by its “clumpy” appearance. being very wet in the winter and very dry in the summer. Compacted soils also perch wet spots in unexpected Soil Layering and Associated Problems locations and enhance runoff over infiltration. Finally, When downward percolating water encounters a com - a compacted soil can severely limit plant growth, even - pacted zone or a zone of strongly contrasting soil tex if other physical and chemical characteristics such as ture (such as sand over clay or vice versa), water will texture and pH are optimal (see figure 3.4). Thus, soil back up or “perch” just above the contact and saturate compaction cannot be recognized by conventional soil - the zone above it. The nature and quantity of poros testing and is often a “hidden limitation.” ity, particularly the amount of large, continuous pores and channels in the soil, is the primary factor control - ling the rate of water movement. Temporarily perched water tables may persist close to the soil surface from several days to months, depending on local soil and cli - matic conditions. A similar perching occurs when water passes through a coarse-textured soil layer with many large pores and then encounters a finer-textured soil layer (even if noncompacted) with much smaller pores. Perching also occurs — but for an altogether different reason — when water passing through a fine-textured layer encounters a coarser sand or gravel stratum. In this case, the finer-textured clay soil actually holds on to its water so tightly (due to capillary forces or suction) that it significantly slows its movement into the coarser material below. Saturated conditions within the root- ing zone cause a number of problems for plant growth, including lack of oxygen, loss of available nitrogen, and potential heavy-metal toxicities. Adverse Soil Texture or Rock Content As discussed in detail in chapter 2, loamy textures are optimum for plant growth, and most native A horizons 3 ) traffic pan on a mining site Figure 3.3. High bulk density (2.0 g/cm (topsoil) are within this texture class. However, sub- under loose spoil materials. Similar traffic pans are routinely found soil layers (B horizons) are commonly quite clayey, and in home construction and highway environments. Roots cannot pen- etrate or loosen zones that are packed to a bulk density greater than deeper C horizons may be very sandy or rocky. Because 3 3 approximately 1.5 g/cm for a clay or 1.9 g/cm for a sandy-textured of the very fine texture and small pore size of clayey soil. soils, water is so tightly held that uptake by plant roots Urban Nutrient Management Handbook 3-3

445 Chapter 3. Managing Urban Soils is limited. Clayey soils also limit plant growth due to Low Organic Matter and Microbial higher soil strength, their tendency to dry and crack, Activity their tendency to form crusts after rain events, and other Unless topsoil layers are properly salvaged, stored, and adverse chemical properties as discussed below. On the returned, newly constructed urban soils are much lower other hand, very coarse-textured (sandy) or rocky soils in their organic matter content and microbial biomass are also prone to drought and do not retain added fertil - than nearby natural soil profiles. This particularly affects izer and lime elements. surface soil aggregation, infiltration, and water-holding capacity. The lack of microbial activity may also limit Adverse pH and Nutrient Status the soils’ nitrogen, phosphorus, and sulfur cycles, which Most subsoils (B and C horizons) in our region are are highly dependent on the active microbial biomass low in pH (4.0 to 6.0) due to long-term acid-leach- - for important mineralization transformations. Reveg ing processes and are very low in available nutrients etated urban soils will accumulate stable organic matter because they formed well below the zone of active levels and microbial communities over time, but their nutrient cycling and/or fertilization and liming. This development may also be strongly limited by the com- acidic condition greatly increases the solubility of nat- bined adverse soil properties discussed above. urally occurring phytotoxic metals like aluminum and manganese. In certain instances (e.g., Piedmont sap- Inclusion of Mixed and Foreign Materials rolites), however, deep subsoil materials may actually One of the unique diagnostic features of most urban be quite moderate in pH and nutrient cations (calcium, soils is their inclusion of a wide array of dissimilar nat- magnesium, potassium), but they will still be very low ural and man-made (anthropogenic) materials. This is in plant-available nitrogen and phosphorus. The red particularly true of soils on residential lots where con- and yellow colors commonly seen in subsoil materi- tractors are unlikely to remove excess sand, gravel or als are due to coatings of iron-oxides, which tend to other materials due to the cost of loading and hauling. be ubiquitous in regional subsoils. These amorphous By definition, these materials usually are found in the iron coatings along with associated aluminum oxides fill portions of urban soils, but they may also occur in (which are not readily visible) have the ability to scattered pockets or thin veneers over exposed subsoils adsorb large amounts of applied phosphorus fertiliz - or cut areas. Following is a summary of a few of the ers via a process called phosphorus-fixation (see chap - more problematic materials: ter 4), particularly when the soil pH is less than 6.0 (Brady and Weil 2008). are commonly found in layers or Gravel and sand pockets related to mortar mix areas, temporary roads, In certain instances — particularly where high pH or storage areas. These are usually capped with finer- mortar mix or quick lime (see discussion later) have textured fill or topsoil layers, generating a very strong been added to the soil in excessive amounts — the textural discontinuity that limits water drainage. soil pH may be abnormally high (more than 8.2). This can lead to a variety of plant nutrient deficiencies and Cement and mortar mix are usually found in localized toxicities and soil physical problems (Brady and Weil areas but may be mixed throughout a given fill layer 2008). If the soil is alkaline (pH more than 8.2) but when materials are bulldozed or moved during final weakly buffered, the pH can be readily reduced via site grading. Mortar mix will impart very high soil pH ) (SO ) or by add- addition of aluminum sulfate (Al 3 4 2 (9.0 or more) to localized areas for long periods of time ing acid-forming organic matter like pine needles and until it fully reacts with natural soil acidity. Poorly cured leaves and allowing natural decomposition to reacid- waste concrete can also cause locally high soil pH. ify the soil. However, if the soil alkalinity is highly - buffered (i.e., more than 5 to 10 tons of calcium car Waste wood, drywall, nails, rags, etc. tend to be dis- bonate equivalence; CCE) it will be necessary to add carded or to fall into the open excavation next to home elemental sulfur (flowers of sulfur) to quickly form foundations and block walls and are commonly mixed sulfuric acid in soil solution to neutralize the excess into the soils that constitute the backfill. As waste wood alkalinity. This must be done very carefully because, or rags decompose, they generate locally anaerobic as discussed later, reduced sulfur is highly reactive in zones that are adverse to the roots of many native and the soil and even a minor over-application can drive ornamental plants. Drywall, on the other hand, is pri- the soil pH below 4.0. marily gypsum and paper and is actually used as an approved soil amendment (after grinding) in several Urban Nutrient Management Handbook 3-4

446 Chapter 3. Managing Urban Soils southeastern states. Nails, wire, metal flashing, and Managing Dense Soils glass are also commonly encountered in this zone and Field determination of bulk density is difficult for an pose more of a safety hazard to the home gardener than untrained person, but a general identification of com - a plant growth limitation. pacted or dense soils can be estimated via the “calibrated - shovel” technique discussed above. Tillage (e.g., roto Managing Urban Soils and Their tilling) or deep ripping (via a ripper or chisel plow) is the only practical way to improve soil porosity but may Limitations be too expensive or impractical for many home lawns or confined urban situations. Hollow-tine aerification can Soil Sampling, Testing, and Fertilizer also be effective for surface compaction in home lawns. Plus Lime Prescriptions However, care must be taken to avoid excessive tillage, Appropriate soil sampling and testing is critical to manag- which can lead to destruction of large aggregates. Too ing urban soils. First of all, you need to take some time to much tillage also decreases organic matter content by try to understand the nature of your local urban soil land- speeding its oxidation and decomposition. Addition of scape. Start by looking for areas of obvious cut slopes compost and/or other organic amendments into surface and fills. Using a shovel or a tiling spade, try to discern if soil layers will promote aggregation and macroporosity you have topsoil return over cut subsoils or exposed cut and thereby decrease bulk density over time. and fill materials. With a little investigation and thought Gypsum and other soil amendments and conditioners about how your landscape’s soil materials were moved are commonly advertised as being able to “cure com- around, you should be able to discern a pattern. As you paction.” While these products may improve soil aggre - do this, pay attention to whether or not the soil is readily gation they will have virtually no effect on soil bulk “diggable” or dense and resists penetration. Remember density unless they are actively tilled and mixed into the that soils are much stronger and resistant to digging and loosened soil zone. Similarly, certain plants (e.g., switch - penetration when they are dry, so try to do this evaluation grass and alfalfa) are widely touted as being able to root when the soil is moist (but not too wet). deeply into compacted soils and “loosen” them. This is Next, follow the soil sampling instructions outlined not a viable solution for highly compacted soils that lack in chapter 5, but try to separate areas of cut, fill, and structure and vertical continuous macropores, because exposed subsoil where possible into different soil - the growing root tip of these plants is actually quite pli sampling zones. Once a competent lab analyzes the able and must find an open soil pore to exploit before it samples, follow the fertilizer and lime prescriptions. If - can subsequently enlarge and open it further as it pene areas of strongly contrasting vegetation patterns occur trates downward and subsequently expands in diameter. (see figure 3.4), sample them separately. When pos - sible, resample and retest problematic areas in future Managing Clayey Subsoils years to confirm that soil conditions are improving. First, problems of acidity and infertility must be solved It is important to note that the soil testing procedures - through appropriate soil liming and fertilization strat and fertilizer/lime recommendation systems used by egies as discussed above. Usually, another factor to - the majority of university and private-sector laborato correct immediately is the low organic matter con- ries were developed and correlated for use on natural tent. Appropriate amounts of compost or other organic weathered surface soils and therefore may not accu- materials (see chapter 9) should be repeatedly mixed rately predict amendment needs for newly disturbed in (6 inches or more, if possible). Over time, deeply urban soils. This is not to say that soil testing is not the organic matter decomposes and stabilizes the new appropriate for urban soils, but the results of a given surface soil, aiding in essential soil particle aggrega- test need to be specifically interpreted for their applica - tion and building nutrient supplies. Remember that tion to these types of materials. This is particularly true the establishment and maintenance of organic matter when unweathered sediments or soft rocks are being in the soil does much to aid long-term fertility as well revegetated or the road cut exposes unusually reactive as physical properties like aggregation, infiltration, and materials (e.g., sulfidic soils) as discussed later. Once water-holding capacity. these urban soils have been managed and equilibrated Most subsoils are dense and/or clayey, so particular to support vegetation for several years, however, inter - attention must be paid to the problems of poor drainage pretation of soil testing results is more straightforward. Urban Nutrient Management Handbook 3-5

447 Chapter 3. Managing Urban Soils and water saturation as discussed next. Even the addi- tion of trucked-in topsoil usually will not solve poor drainage problems caused by clayey or compacted subsoils. Before new topsoil is added or created by the addition of organic matter, poorly drained exposed sub- soils should be deeply ripped or tilled. In many situa- tions the use of raised beds greatly eases the required modification of surface soil properties. Preserving and Maintaining Native Shrubs and Trees Most of our native woody trees and shrubs in the mid- Atlantic region are adapted to acidic soil conditions but Figure 3.5. Inappropriate addition of topsoil over native trees: The also rely on the maintenance of a litter layer (O horizon) topsoil material was added too thickly (12 inches) and then com- and its provision of essential nutrients as it decomposes pacted (as seen at left) to a point that gas exchange by the living tree over time. Thus, a large majority of the tree’s fine feeder roots was limited. Most of these white oaks died within two years of this application. roots exist in the upper 6 inches or so of soil and are generally adapted to a loose and well-aerated surface. Unfortunately, the urban soil development process fre- A Common Combination of Problems quently removes the litter layer and compacts the soil. and a Prescription Furthermore, typical home lawn liming targets (i.e., pH Dense, clayey, acidic soils are commonly found 6.5 to 7.0) can drive the soil pH to levels where the throughout the urban and roadside environment and trees become deficient in critical micronutrients, par - these materials are usually quite low in plant-available ticularly iron and manganese. To protect these valuable phosphorus when they are freshly graded or exposed in trees during the construction process, it is important cuts. Because of this, it is always important to sample to keep all heavy traffic and fill placement off the soil and soil test these materials. Based on soil tests, it is not immediately around and under the tree’s canopy. This uncommon to see recommendations calling for appli - will usually require placing a temporary fence around cations of lime at 2 to 4 tons per acre, coupled with the tree (to the extent of the canopy drip line) and con- enhanced phosphorus fertilization (150 pounds or more tinued vigilance by the homeowner or an informed con- per acre as phosphorus oxide (P )) to address fertility O 5 2 struction supervisor. issues. The addition of high-quality compost (1 inch) After construction is completed, it is best to leave and tillage of all amendments to 6 inches will rapidly natural litterfall on these areas where possible and to remediate these problems for turf establishment and avoid the addition of excess lime or fertilizers to the growth. This treatment will not correct deeper com- - soil. Unfortunately, many homeowners and landscap paction problems, however, so other soil modification ers desire to establish turfgrass on these areas, which procedures may be necessary for deeper-rooted land- are often undulating due to shallow roots and other scape plantings or to solve problems with water perco- manifestations of the formerly forest soil profile. One lation, as discussed below. It is also important to point particularly damaging practice is the placement of thick out that older established home lawns may actually be (more than 4 inches) lifts of topsoil over the roots in quite high in plant-available phosphorus due to long- an effort to smooth the surface soil out and establish term fertilization, so phosphorus fertilizer rates should viable turf. This frequently leads to soil compaction, always be based on an appropriate soil test. - inadequate gas exchange, and a soil chemical environ ment that is not suitable for the long-term survival of Managing Wet Soils the native trees or shrubs (see figure 3.5). Compacted and/or clayey soils cause numerous water - ing problems. The most obvious is surface ponding caused by slow water penetration into the ground. When dense or high-clay layers limit downward water move- ment, the soil becomes saturated and oxygen — which Urban Nutrient Management Handbook 3-6

448 Chapter 3. Managing Urban Soils moves very slowly through water — cannot reach plant here. Sulfidic soil and geologic materials occur through - out the mid-Atlantic region, but are particularly com- roots. If the saturated condition persists, roots will die mon in the Middle and Upper Coastal Plain region from oxygen starvation. Highly compacted soils, even between Richmond and Stafford County, Va. (Orndorff when dry, cause the same problem. Extended periods and Daniels 2004). of water saturation also lead to increased availability of heavy metals such as iron and manganese, which in Acid sulfate soils are earthen materials that have been some soils may actually be phytotoxic. Saturated con- ) to degraded by oxidation of sulfides (like pyrite, FeS 2 ditions can also accelerate soil nitrogen losses due to produce unusually low soil pH conditions (less than denitrification (see chapter 4). 3.9) when they are excavated from nonoxygenated zones below the surface and exposed to atmospheric There are a number of ways to manage saturation prob- conditions. As they oxidize, a wide array of acidity and - lems in soil. One is to increase internal water move soluble-salt-related plant growth and material damage ment by improving aggregation and pore space. There problems are common. Essentially, these materials con- are several ways to do this: increasing and maintaining tain sulfidic minerals that react with water and oxygen organic material levels, changing or keeping pH in the to form sulfuric acid. This active set of processes is range between 5.5 and 6.5, adding a soil conditioner - called “sulfuricization.” The vast majority of acid sul such as very coarse sand, cultivation only when mois- fate soils is the result of land-disturbing activities that ture levels are ideal, and remediating compaction. How- bring previously unoxidized (reduced) materials up to ever, the addition of organic material and associated the surface and allow them to react. mixing and tillage is probably the single most-effective action you can take, assuming the underlying soil zone The normal maximum range of pH for soils in the mid- is well-drained and can accept percolating water. Atlantic region is between 4.0 and 7.5. In the absence of liming, the great majority of these soils are naturally Another way to increase internal water movement in acidic with a pH between 4.5 and 5.5. In almost all wet soils is to shatter subsoil pans. If just a few deep instances, any soil with a pH less than 3.9 in Virginia is cracks for water percolation are made down through indicative of active or historic acid sulfate soil condi- the subsoil, large amounts of saturated water will flow - tions and is quite toxic to plant growth and local receiv through them (assuming the underlying layers will ing streams. In worst-case instances, soil pH values as accept the water). Alternatively, subsurface drainage low as 1.8 have been measured at locations such as the can be installed beneath the soil to carry away excess Stafford Airport in Virginia (Fanning et al. 2004). water. This is usually expensive, but may be the only alternative in many situations. Still another approach is Where Do Sulfidic Materials Come to limit the amount of water entering the soil by divert - ing surface water away from the poorly drained area From and What Do They Look Like? or by digging interceptor trenches just uphill from it. - Sulfides precipitate naturally in tidal marshes, accumu Plastic mulch can also be used to decrease total water - late in sediments, and are enriched in certain metamor penetration. phic and igneous rocks. Thus, they occur naturally in many of the sediments underlying our Coastal Plain and in other rock types throughout the mid-Atlantic region. Acid Sulfate Soil Conditions and For example, most of the soils in the Fredericksburg/ Management Stafford County, Va., area formed out of parent materi - Over the past decade, many highway, commercial, als that originally contained sulfides, but they oxidized and home residential construction activities in the and weathered out of the surface soil horizons (layers) mid-Atlantic region have exposed what are known as tens of thousands of years ago. These subsoil horizons “sulfidic materials” that quickly react to produce “acid are usually bright yellow to red in color and are usu- sulfate soil conditions” (Wagner et al. 1982). Without ally quite acidic (pH 4.0 to 5.5). However, many deeper question, these materials and their associated effects on cuts (more than 10 to 20 feet) can reveal unoxidized - plant growth, water quality, and construction materi sulfidic materials that are typically gray, steel blue, or als pose the greatest risk of any materials managed in sometimes black in color but still have a high pH (more the urban soil environment (Fanning et al. 2007). Even in situ. Once exposed at the surface, however, than 6.5) though they are not routinely encountered, their affects the pH of these materials can drop below 4.0 within several months. are so catastrophic that they deserve detailed coverage Urban Nutrient Management Handbook 3-7

449 Chapter 3. Managing Urban Soils 1,000 tons of material, which handily also happens to How Do I Recognize Acid Sulfate be the average weight of 1 acre of soil, 6 inches deep. Materials? Reduced sulfur is very reactive and every 1.0 percent of Because fresh, unreacted, sulfidic materials have a sulfidic sulfur, if fully reacted, generates enough acidity near-neutral pH, the only way to identify them before to require approximately 32 tons of agricultural lime - disturbance is appropriate testing and lab analyses as )) per stone (finely ground calcium carbonate (CaCO 3 described later. Once they react to become “active acid 1,000 tons of soil to fully neutralize! Thus, even 0.3 sulfate” soils, distinctive indicators include (1) dead percent sulfidic sulfur in these materials can generate a vegetation, (2) red iron staining on concrete and block lime demand of 10 tons per acre (6 inches deep), which walls, (3) concrete etching and dissolution, (4) rapid is much higher than we ever apply to “normal” soils. corrosion of iron and galvanized metal, and (5) strong Occasionally, Coastal Plain sediments do contain suf - sulfurous odor from rubbed hand samples. ficient lime (as fine shell fragments, etc.) to completely or partially offset their acid-forming potential, but this is a rare occurrence. What Is the Potential Risk and Damage From Acid Sulfate Soil Processes? At Virginia Tech, we use a similar technique to ABA for potential acidity called the peroxide potential acidity Acid sulfate soil conditions and associated sulfuriciza - (PPA) technique. In this method, we use strong hydro - tion reactions generate a number of extreme soil and O ) to force the complete reaction of gen peroxide (H water quality challenges. First of all, plants are killed 2 2 the sulfides and their internal neutralization by carbon - by the direct effects of low pH, high heavy-metal sol- ates. In our experience, it correlates very well with ABA ubility, and soluble sulfate salt stress. The extremely for a wide range of Virginia materials. For example, acidic (pH 1.8 to 3.8) soil solutions and percolates our long-term research results indicate that acid sulfate directly degrade concrete, iron, and galvanized metal materials in the Fredericksburg/Stafford County region via a number of mechanisms. Finally, acid runoff and average between 10 and 20 tons of lime demand per seepage from these materials can seriously degrade acre (or per 1,000 tons of soil) in their fresh/unoxidized local receiving streams. Thus, it is critically important state. On occasion, we have tested small pockets of that these materials be isolated or treated to remediate materials that exceeded 50 tons of lime per 1,000 tons their acid-producing potential and limit damage. - of soil or per acre net acid demand! Once these materi - als have fully reacted and oxidized, however, they typi How Do I Confirm Whether or Not I cally require only 4 to 6 tons of lime per acre to bring Have Acid Sulfate Materials in My Soil? their low pH (less than 4.0) up to 7.0. In addition to the visual symptoms described above, active acid sulfate materials will usually exhibit a com- What Can I Do to Remediate Acid bination of low pH (less than 3.9) and high levels of Sulfate Soil Conditions? potential acidity (total lime demand) relative to native First of all, the only way to prevent these reactions soils. Fresh, unoxidized, sulfidic materials may have a from occurring in disturbed cut/fill materials is to keep normal pH but will have high levels of potential acidity them out of contact with the oxidizing atmosphere and (see below). water. However, once they are placed and graded on a home site, the only practical way to remediate them What Is Potential Acidity and How Is It is to bulk blend sufficient agricultural limestone (or Expressed? other approved liming materials) with them to offset the full amount of acidity that will be produced over Potential acidity is estimated by several lab techniques extended periods of time (i.e., their potential acidity). that have been used and refined by the mining industry We also recommend applying 25 percent more lime to since the 1970s to prevent the formation of “acid mine ensure long-term alkaline buffering in the system. For drainage” from coal and metal mines. The most widely example, let’s assume the soil in your backyard has a used technique is called “acid-base accounting” (ABA), net potential acidity of 10 tons per acre of lime demand. which assumes that all sulfides in the material will fully With the 25 percent buffer factor added to it, you need react to form sulfuric acid and then balances that against to add the equivalent of 12.5 tons of lime per acre, 6 the material’s inherent lime or neutralizing capacity. inches deep. Usually, your yard will be much less than The results are expressed in tons of lime demand per Urban Nutrient Management Handbook 3-8

450 Chapter 3. Managing Urban Soils color, and any gray, blue-gray, or black strata should an acre in size, so we need to convert this to a more practical liming rate per 1,000 square feet. As a matter be tested for total sulfur. If total sulfur is more than of convenience, one 50-pound bag of agricultural lime 0.25 percent, those same strata should be tested for per 1,000 square feet is approximately equivalent to 1 acid-base-accounting or peroxide potential acidity. Any ton per acre. So, the basic liming requirement for your materials with a net lime demand of more than 5 tons of back yard would be 12.5 x 50 pounds = 625 pounds of lime per 1,000 tons of material (or soil) should be iso- agricultural lime per 1,000 square feet. These materi - lated from the surface and either heavily compacted in als would need to be well-mixed (with a rototiller or - place to limit permeability or bulk limed before place air knife) to a depth of 6 inches to ensure full reaction ment to offset acidity production over time. and remediation of the surface rooting zone. Once this material is allowed to react following several rainfall Where Can I Get More Information? or irrigation events, you should be able to use normal We maintain current information and reports on this - plant/lawn establishment procedures, but we recom subject posted to our research website at Virginia Tech mend adding compost to the surface soil mix whenever ). Addi- www.cses.vt.edu/revegetation/remediation.html ( possible. It is important to note that the deeper soil lay- tionally, the most sophisticated program in the world ers will not be affected by this treatment, so planting for recognition and remediation of acid sulfate materi - holes for deep-rooted vegetation (e.g., trees) require als is carried out in Queensland, Australia, due to its deeper treatment. preponderance of acid-forming parent materials. Their We also recommend a similar remedial treatment for all website ( ) is www.nrw.qld.gov.au/land/ass/index.html soils in direct contact with uncoated concrete or foun- quite comprehensive and informative, with numerous dations, block walls, or metal conduits and pipes. The links to their reports, methods, and regulations. exception would be where those materials (concrete, metal, etc.) are under the water table or buried deeply Soil Conditions in Highway enough in the soil that they are beyond the depth of oxygen diffusion. Rights-of-Way In a typical highway construction corridor, materials What Kind of Lime Should I Use? lying above the grade of the proposed road are removed The “lime” that we refer to above is “agricultural (cut) by a variety of earthmoving techniques and hauled lime” (CaCO ) and not hydrated lime or Ca/MgCaCO - to adjacent lower areas for disposal. Whenever possi 3 3 (Ca(OH) - ) or burnt lime (CaO). These two latter mate ble, the cut materials are utilized as subgrade materials 2 rials are commercially available and occasionally used for the roadbed or as fill to span depressions and valleys by the geotechnical engineering community for soil beneath the corridor. Excess fill materials are usually cementation or waste treatment. They do have advan- - disposed of in compacted fills as near to the road cor tages of being more concentrated and quicker to react. ridor as possible to minimize hauling costs. The com - However, they are more expensive, can burn your eyes, bination of cut and fill activity generates fundamentally and can rapidly drive soil pH to very high values that different surfaces for revegetation as the road-building are also toxic to plants. Therefore, we only recommend project progresses across the landscape. Cut slopes will the use of certified agricultural lime for this purpose. frequently expose a surficial weathered soil profile and The use of pelletized lime products is acceptable and then extend well down into the underlying rock or sedi- may make application of the very high rates easier with - ments. These materials will therefore vary consider minimal dusting issues. ably in fundamental chemical and physical properties with depth, particularly in regions like the mid-Atlantic United States, where the geochemical weathering pro- Ideally, How Can We Avoid These files are deep and soil horizonation is strong. These gra - Problems in the First Place? dations with depth are predictable, however, and will Based on our work with the Virginia Department - tend to recur in a prescribed sequence as the cuts pro of Transportation and others (see website below for ceed through the landscape. details), we have developed a statewide map layer that - Fill materials, on the other hand, tend to be quite dif - indentifies all geologic strata that have documented sul ferent from road cuts due to the mixing effects of - fide risk. Predisturbance geologic drill cores by devel oper’s consultants in these units should be evaluated for the earthmoving operations and the fact that they are Urban Nutrient Management Handbook 3-9

451 Chapter 3. Managing Urban Soils typically heavily compacted in place to meet stability imperative to minimize water flow and sediment losses and strength specifications. Fill materials may be more from the initial stages of grading operations. Uncon- or less variable than adjacent cut areas, depending on - trolled erosion also can severely degrade the site qual how they are handled and placed, but they are typically ity of the eroded area, particularly if applied topsoil, - quite compact and lack the well-developed aggrega lime, and fertilizers are lost or a less-hospitable sub - tion or structure that undisturbed soils usually possess. strate is exposed. Therefore, soils in highway fill materials as a rule will be less permeable to air, water, and roots than their nat- Manufactured Soils ural precursors. Fills and fill slopes also are plagued In certain high-value situations like landscape planting by inclusions of aggregate, rock, concrete, and other - beds and constructed athletic fields, the use of manufac construction debris that seriously limit their water- tured topsoil materials is a viable alternative to having retention characteristics. In contrast, soils on cut slopes to manage the pre-existing urban soils (Puhalla et al. generally retain the physical and chemical properties 2010). This is particularly true when we consider what of the original soil/geologic profile, but their surfaces is typically available and marketed as topsoil in rap- are often compacted to some extent by the earthmoving idly developing areas of the mid-Atlantic. The majority equipment, and the soil is often “smeared” and sealed, of materials that are marketed and sold as topsoil are particularly in fine-textured soils. generated by the land development and construction Regardless of whether you are dealing with cut or fill process and may or may not be true topsoil as defined materials, it is critically important to understand that earlier (A plus E horizons). Additionally, these natural the vast majority of materials that will be revegetated topsoils are highly variable over time as they are hauled are composed primarily of subsoil or deeper geologic from differing sites with different soil properties, soil- materials that will be very low in organic matter and removal depths, and handling/storage procedures. Very associated macronutrients, particularly nitrogen and few of these materials are offered with any guarantee phosphorus. When highly weathered subsoils are of pH, texture, or nutrient-supplying ability relative to exposed, we are often left with a very clayey and highly established soil testing standards. acidic substrate that will require significant inputs of The “ideal” soil for most turf establishment and land- - lime and phosphorus fertilizers before its basic chemi scaping applications is loamy in texture to ensure ade- cal properties begin to resemble native topsoils. Deeper quate water-holding capacity and aeration without being cuts that extend below the weathered soil zone will fre - sticky and plastic when handled and graded. Beyond quently contain large amounts of fresh, unweathered that, the soil should be moderate in pH (between 6.5 rocks and sediments that can be significant sources of and 7.5) to ensure maximum beneficial biological calcium, magnesium, potassium, and other nutrient ele - activity and moderate to high in plant-available nutri- ments as they rapidly weather in their newly exposed ents such as calcium (Ca), magnesium (Mg), potassium - geochemical environment. Acid-forming sulfidic mate (K), and phosphorus (P). Good topsoils also contain rials (as discussed earlier) are also commonly encoun- - small but adequate amounts of plant-essential micronu tered in deeper road cuts in a variety of geologic settings trients like iron (Fe) and copper (Cu), but should also and can generate extremely harsh soil chemical condi- be low in soluble salts and sodium (Na), which can dis- tions and associated runoff water quality complications perse soil structure and harm plants. Finally, the ideal as they oxidize. soil would contain approximately 3 to 5 percent organic The cut/fill and site development operations for new matter that serves as a long-term source of plant nutri- highways or other construction activities may cause ents (especially nitrogen), maintains biological activity, uncontrolled water flows and sediment loss from bare and greatly enhances physical properties such as water- soil areas. Many small, localized, disturbed areas with holding capacity. Perhaps most importantly, the ideal seemingly insignificant losses of water and soil will soil for turf and landscaping applications would be con- often coalesce into massive and rapid flows of water sistent over time in all of the above properties so that with high sediment loads, causing severe damage in the user will not have to “fine-tune” establishment and - highway corridors as well as flooding and contamina management protocols for each batch of soil received. tion of receiving streams. Even the initial slow flows of clear water from numerous small areas of disturbance There are currently a number of manufactured topsoils within a highway development corridor can cause - available in the region. One example of a manufac progressively larger erosive flows of water. Thus, it is tured soil developed cooperatively by Luck Stone and Urban Nutrient Management Handbook 3-10

452 Chapter 3. Managing Urban Soils Virginia Tech (Greene premium topsoil) is described Due to the inherent fertility of the Greene topsoil, use below. This description is not intended as an endorse- of initial or starter fertilizers (especially phosphorus - ment of this particular product, but simply as an exam and potassium) is probably not necessary or warranted, ple of one of many commercially viable products. particularly in light of current concerns over minimiz - ing losses of nutrients to surface waters. However, ini- The Greene topsoil product is manufactured from tially high levels of available nutrients will be depleted native soil saprolite, compost, and mineralized igne - over time by plant uptake, and like any soil, subsequent - ous rock dust to produce loamy topsoil that is well-bal fertilization will be required. The Greene topsoil prod - anced in organic matter, available plant nutrients, and uct is not recommended for root zone use with acid- pH. This product was developed cooperatively with the loving plants such as blueberries, azaleas, and native Department of Crop and Soil Environmental Sciences pines unless it is blended with naturally acidic (pH less at Virginia Tech, and as seen in table 3.1, is equal to than 6.0) soil materials. or exceeds natural topsoils in productivity potential for - most horticultural, landscaping, and gardening applica tions. The Greene topsoil is high in organic matter (5 to Modified Soils and Mulches 7 percent), moderate in pH (6.0 to 7.5) and soluble salts Another approach to mitigate the adverse properties of (up to 2.0 millimhos per centimeter (mmhos/cm)), and urban soils is via “soil modification” or “conditioning,” low in sodium. Plant-available phosphorus is more than a process that generally involves the incorporation 70 parts per million (ppm), potassium and magnesium of inorganic or organic amendments into bulk soil to are both more than 100 ppm, and calcium is more than fundamentally alter important soil physical properties 1,000 ppm. This topsoil also provides balanced levels - (Wallace and Terry 1998). Certain inorganic amend of plant-available micronutrients (e.g., boron, copper, ments (e.g., sand or bottom ash) can be added to clayey iron, manganese, and zinc). soils to reduce their stickiness and plasticity, but the volumes required to generate a loamy texture (10 to 40 The Greene topsoil is higher than natural topsoils in percent), coupled with the costs and logistics involved organic matter content and available nutrients because limit this approach to high-value locales. Similarly, it is carefully blended with fresh, unweathered primary waste clays from sand mining operations (e.g., slimes) mineral fines and compost to generate the characteris - can be added into extremely coarse-textured soils to tics displayed in table 3.1. Perhaps most importantly, the convert them to loamy textures but similar issues of cost Greene topsoil product has been tested and proven to be and logistics apply. Other inorganic amendments (e.g., quite consistent over time and has been proven effec - gypsum and lime) can be added to clayey or dispersed tive in a wide range of plant growth uses in research at soils to promote aggregation, but this usually involves Virginia Tech and on-site applications by the producer’s much lower loading rates than textural modification client base of landscapers and developers. Table 3.1. Important soil properties for the Greene topsoil compared to highly productive prime farmland topsoil from Dinwiddie County, Va., and the range of typical topsoil properties found in Virginia. Soil property Greene topsoil Prime farmland Average Virginia topsoil Texture Sandy loam Sandy loam Sandy loam to clay loam pH (acidity) 6.6-7.2 6.0-6.5 4.5-7.5 1-2% Organic matter 5-7% 0.5-3% 300-600 ppm <50-600 ppm >1,200 ppm Available* calcium (Ca) 30-60 ppm >250 ppm <20-80 ppm Available potassium (K) Available phosphorus (P) 75-150 ppm 20-30 ppm <5-30 ppm 0.2-0.7 ppm Available copper (Cu) 1.5 ppm 0.6 ppm Data compiled from research reports by W. Lee Daniels, Virginia Tech. Available soil nutrients are those contained in an acid-extractable form that would be expected to contribute to plant uptake needs over * the growing season and are typically expressed in parts per million (ppm) of total soil weight. For a common-sense conversion, 100 ppm of available Ca in a soil would equate to approximately 200 pounds of calcium in the upper 6 inches of topsoil over 1 acre. Urban Nutrient Management Handbook 3-11

453 Chapter 3. Managing Urban Soils and really differs little from conventional liming prac- Craul, P. J. 1992. Urban Soil in Landscape Design . tice. Certain inorganic soil conditioners (e.g., fly ash New York: John Wiley & Sons. or waste gypsum) may also contain significant levels Fanning, D. S., Cary Coppock, Z. W. Orndorff, W. of soluble salts or potentially phytotoxic elements like L. Daniels, and M. C. Rabenhorst. 2004. Upland boron, so their use must be carefully considered and active acid sulfate soils from construction of new controlled.A wide array of organics (e.g., composts, Austra- Stafford County, Virginia, USA, Airport. biosolids, animal manures, and paper sludges) are also lian Journal of Soil Resources 42:527-36. routinely utilized to enhance aggregation, porosity, and water-holding capacity in urban soils. Usually, these Orndorff, Z. W., and W. L. Daniels. 2004. Evaluation of materials are most effective when incorporated or bulk acid-producing sulfidic materials in Virginia high - blended with surface soil layers, which may require up way corridors. Environmental Geology 46:209-16. to 25 percent volumetric addition rates. One potential , J. V. Krans, and J. M. Goatley Jr. 2010. , J. C . Puhalla drawback of many organic amendments (e.g., biosolids - Sports Fields: Design, Construction, and Mainte and manures) is that addition at these rates may pose nance . 2nd edition. Hoboken, N.J.: John Wiley & - significant nutrient runoff or leaching risks (see chap Sons. ters 2, 9, 10, and 12). Another long-term management factor to consider is that organic amendments will natu- Urban Soil Scheyer, J. M., and K. W. Hipple. 2005. rally decompose with time, and their “bulking effect” Primer - . USDA-NRCS, National Soil Survey Cen on porosity will thereby decline as well. However, the ter. Lincoln, Neb.: USDA. http://soils.usda.gov/ humus fraction they leave behind will make a very valu- /urban/primer.html . use able and long-lived contribution to urban soil quality. - Wagner, D. P., D. S. Fanning, J. E. Foss, M. S. Pat Finally, surface mulches can also be utilized to buffer terson, and P. A. Snow. 1982. Morphological and - soil temperature, enhance water infiltration and reten mineralogical features related to sulfide oxida - tion, limit traffic-related soil compaction, and reduce tion under natural and disturbed land surfaces in weed competition (Brady and Weil 2008). More detail Maryland. In , ed. J. A. Acid Sulfate Weathering on use of organic mulches is found in chapter 9. , D. S. Fanning, and L. R. Hossner, 109-25. Kittrick Soil Science Society of America Special Publica - A more thorough discussion of the full array of soil tion No. 10. Madison, Wis.: Soil Science Society - amendments, conditioners, and mulches and their rela of America. tive advantages and management is beyond the scope of this book. However, greater detail on these topics Handbook of Wallace, A., and R. E. Terry, eds. 1998. can be found in the various resources cited below. Soil Conditioners: Substances That Enhance the . New York: Marcel Physical Properties of Soil Dekker. Literature Cited Booze-Daniels, J. N., J. M. Krouse, W. L. Daniels, D. L. Wright, and R.E. Schmidt. 2000. Establishment of low maintenance vegetation in highway corridors. In Reclamation of Drastically Disturbed Lands , ed. R. I. Barnhisel, W. L. Daniels, and R. G. Darmody, 887-920. Agronomy Monograph No. 41. Madison, Wis.: American Society of Agronomy, Crop Sci - ence Society of America, and Soil Science Society of America. Brady, N. C., and R. R. Weil. 2008. The Nature and Properties of Soils . 14th ed. Upper Saddle River, N.J.: Pearson Prentice Hall. Brown, R. B., J. H. Huddleston, and J. L. Anderson, eds. 2000. Managing Soils in an Urban Environ- ment . Agronomy Monograph No. 39. Madison, Wis.: American Society of Agronomy. Urban Nutrient Management Handbook 3-12

454 Chapter 4. Basic Soil Fertility Chapter 4. Basic Soil Fertility Greg Mullins, Former Professor and Extension Specialist, Crop and Soil Environmental Sciences, Virginia Tech Kathryn C. Haering, Research Associate, Crop and Soil Environmental Sciences, Virginia Tech David J. Hansen, Associate Professor, Plant and Soil Sciences, University of Delaware Plant Nutrition Table 4.1. Eighteen essential elements for plant growth and the chemical forms most Essential Elements commonly taken up by plants. An essential mineral element is one that is required for Form absorbed Symbol Element by plants - normal plant growth and reproduction. With the excep CO C Carbon tion of carbon (C) and oxygen (O), which are supplied 2 + - from the atmosphere, the essential elements are obtained H , OH H Hydrogen , H O 2 from the soil. The amount of each element required by O O Oxygen 2 the plant varies; however, all essential elements are + - , NO NH N Nitrogen 3 4 - equally important in terms of plant physiological pro - 2- HPO P , H PO Phosphorus 4 2 4 cesses and plant growth. + Potassium K K 2+ The exact number of elements that should be considered Calcium Ca Ca “essential” to plant growth is a matter of some debate. 2+ Mg Magnesium Mg For example, cobalt (Co), which is required for nitrogen 2- Sulfur S SO 4 (N) fixation in legumes, is not considered to be an essen - 3+ 2+ Fe Iron , Fe Fe tial element by some researchers. Table 4.1 lists 18 ele- 4+ 2+ Manganese Mn Mn , Mn ments that are considered essential by many scientists. 2- - Boron B H BO , BO , B 0 Other elements that are sometimes listed as essential are 3 4 3 7 3 2+ sodium (Na), silicon (Si), and vanadium (V). Zinc Zn Zn 2+ Cu Cu Copper 2- Categories of Essential Elements MoO Molybdenum Mo 4 - Cl Cl Chlorine - Essential elements can be grouped into four catego 2+ ries, based on their origin or the relative amount a plant Co Co Cobalt 2+ needs in order to develop properly (table 4.2). Nickel Ni Ni Nonmineral essential elements are derived from the 1. air and water. Table 4.2. Essential elements, their relative 2. Primary essential elements are most often applied in uptake, and sources where plants obtain commercial fertilizers or in manures. them. Macronutrients 3. Secondary elements are normally applied as soil Secondary Micronutrients Nonmineral Primary amendments or are components of fertilizers that carry primary nutrients. (Mostly (Mostly (Mostly from (Mostly from soil) from soil) air from soil) and water) Nonmineral, primary, and secondary elements are Nitrogen Calcium Iron Carbon also referred to as “macronutrients,” because they Phosphorus Manganese Magnesium Hydrogen are required in relatively large amounts by plants. Oxygen Potassium Boron Sulfur Zinc 4. “Micronutrients” are required in very small, or Copper “trace,” amounts by plants. Although micronutrients Molybdenum are required by plants in very small quantities, they Chlorine are equally essential to plant growth. Cobalt Nickel Urban Nutrient Management Handbook 4-1

455 Chapter 4. Basic Soil Fertility Sulfur (S) Functions of Essential Elements in Plants • Required for the synthesis of the sulfur-containing Carbon (C), Hydrogen (H), and Oxygen (O) amino acids cystine, cysteine, and methionine, which are essential for protein formation. • Directly involved in photosynthesis, which accounts for most plant growth. • Involved with development of enzymes and vita - mins, chlorophyll formation, and formation of sev- Nitrogen (N) eral organic compounds that give characteristic odors to garlic, mustard, and onion. • Found in chlorophyll, nucleic acids, and amino acids. Iron (Fe) • Component of protein and enzymes, which control • Serves as a catalyst in chlorophyll synthesis. almost all biological processes. - • Involved in many oxidation-reduction reactions dur Phosphorus (P) ing respiration and photosynthesis. • Essential component of adenosine triphosphate (ATP) — which is directly responsible for energy transfer Manganese (Mn) reactions in the plant — and of DNA and RNA. • Functions primarily as a part of the enzyme systems in plants. • Essential component of phospholipids, which play critical roles in cell membranes. Activates several important metabolic reactions. • - • Important for plant development — including devel • Plays a direct role in photosynthesis. opment of a healthy root system, normal seed devel - Along with iron, serves as a catalyst in chlorophyll • opment, and photosynthesis — respiration, cell synthesis. division, and other processes. Boron (B) Potassium (K) • Essential for germination of pollen grains and growth • Responsible for regulation of plants’ water usage, of pollen tubes, seed, and cell wall formation. disease resistance, and stem strength. • Essential for development and growth of new cells in • Involved in photosynthesis, drought tolerance, winter meristematic tissue. hardiness, and protein synthesis. • Sugar/borate complexes associated with translocation of sugars, starches, nitrogen, and phosphorus. Calcium (Ca) • Essential for cell elongation and division. • Important in protein synthesis. • Specifically required for root and leaf development, Zinc (Zn) function of cell membranes, and formation of cell wall compounds. • Essential for promoting certain metabolic/enzymatic reactions. • Involved in the activation of several plant enzymes. • Necessary for the production of chlorophyll, carbo - hydrates, and growth hormones. Magnesium (Mg) • Primary component of chlorophyll, and therefore, Aids in the synthesis of plant growth compounds and • actively involved in photosynthesis. enzyme systems. • Structural component of ribosomes, which are Copper (Cu) required for protein synthesis. • Necessary for chlorophyll formation. • Involved in phosphate metabolism, respiration, and • Serves as a catalyst for several enzymes. the activation of several enzyme systems. Urban Nutrient Management Handbook 4-2

456 Chapter 4. Basic Soil Fertility Elements can be either “mobile” or “not mobile” within Molybdenum (Mo) plants. This determines where symptoms of an element • Required for the synthesis and activity of the enzyme deficiency will first appear in a plant. A mobile element system that reduces nitrate to ammonium in the is one that is able to “translocate” (move) from one part plant. of the plant to another depending on its need. Mobile elements generally move from older (lower) plant parts • Essential in the process of symbiotic nitrogen fixation to the meristem, or growing point. bacteria in legume root nodules. Rhizobia by Chlorine (Cl) Soil pH, Nutrient Availability, and • Involved in energy reactions in the plant, breakdown Liming - of water, regulation of stomata guard cells, mainte nance of turgor, and rate of water loss. Effect of pH on Nutrient Availability Many soil elements change form as a result of chemical • Involved in plant response to moisture stress and reactions in the soil. Plants may or may not be able to use resistance to some diseases. elements in some of these forms. Because pH influences • Activates several enzyme systems. the soil concentration and, thus, the availability of plant nutrients, it is responsible for the solubility of many nutri- • Serves as a counter ion in the transport of several ent elements. Figure 4.1 illustrates the relationship between cations in the plant. soil pH and the relative plant availability of nutrients. Cobalt (Co) • Essential in the process of symbiotic nitrogen fixation Rhizobia bacteria in legume root nodules. by • Not proven to be essential for the growth of all higher plants. Nickel (Ni) • Component of the urease enzyme. • Essential for plants in which ureides are important in nitrogen metabolism. Nutrient Deficiency Symptoms Visual diagnosis of plant deficiencies can be very risky. There may be more than one deficiency symptom expressed, which can make diagnosis difficult. Both soil and tissue samples should be collected, analyzed, Figure 4.1. Relationship between soil pH and nutrient availability. and interpreted before any recommendations are made Graphic by Kathryn Haering. concerning application of fertilizer. Phosphorus solubility and plant availability are con- Terminology used to describe deficiency symptoms trolled by complex soil chemical reactions, which are (table 4.3) includes: - often pH-dependent. Plant availability of P is gener ally greatest in the pH range of 5.5 to 6.8. When soil Yellowing or lighter shade of green. Chlorosis pH falls below 5.8, P reacts with Fe and Al to produce Browning or dying of plant tissue. Necrosis insoluble iron and aluminum phosphates that are not readily available for plant uptake. At high pH values, Between the leaf veins. Interveinal phosphorus reacts with Ca to form calcium phosphates Growing point of a plant. Meristem that are relatively insoluble and have low availability Distance of the stem between the leaves. Internode to plants. Urban Nutrient Management Handbook 4-3

457 Chapter 4. Basic Soil Fertility Table 4.3. Element mobility and specific deficiency symptoms. Mobility Element Deficiency Symptoms and Occurrence Nitrogen Mobile within plants; lower leaves Stunted, slow-growing, chlorotic plants; reduced yield; plants more show chlorosis first. susceptible to weather stress and disease. Some plants may mature earlier. Mobile within plants; lower leaves Overall stunted plant and a poorly developed root system. Can cause Phosphorus purple or reddish color associated with the accumulation of sugars. show deficiency first. Difficult to detect from visual symptoms. Potassium Mobile within plants; lower leaves Scorching or firing along leaf margins, slow growth, poorly show deficiency first. developed root systems, weak stalks, small and shriveled seeds and fruit, and low disease-resistance. Deficiencies most common on acidic sandy soils or soils that have received large applications of Ca and/or Mg. Calcium Poor root growth and failure of terminal buds of shoots and apical Not mobile within plants; upper leaves and the growing point show tips of roots to develop, causing plant growth to cease. deficiency symptoms first. Most often occurs on very acidic soils where Ca levels are low but other deficiency effects such as high acidity usually limit growth before Ca deficiency becomes apparent. Magnesium Mobile within plants; lower leaves Yellowish, bronze, or reddish color in leaves while leaf veins remain show deficiency first. green. Chlorosis of the longer leaves and possible chlorosis and stunting of Somewhat mobile within plants, Sulfur entire plant with severe deficiencies. Symptoms resemble those of N but upper leaves tend to show deficiency; can lead to incorrect diagnoses. deficiency first. Reduced leaf size and deformation of new leaves, interveinal Boron Not mobile within plants; upper chlorosis, distorted branches and stems, possible flower and/or fruit leaves and the growing point show abortion, stunted growth. deficiency symptoms first. May occur on very acidic, sandy-textured soils or alkaline soils. Reduced leaf size, uniformly pale yellow leaves, leaves may lack Copper Not mobile within plants; upper turgor and can develop a bluish-green cast, become chlorotic, and/or leaves and the growing point show curl. Flower production fails to take place. deficiency symptoms first. Interveinal chlorosis that progresses over the entire leaf. With severe Not mobile within plants; upper Iron deficiencies, leaves turn entirely white. leaves show deficiency symptoms first. Factors contributing to Fe deficiency include imbalance with other metals, excessive soil P levels, high soil pH, wet and cold soils. Manganese Not mobile within plants; upper Interveinal chlorosis, brownish-black specks. leaves show deficiency symptoms Occurs most often on high-organic-matter soils and soils with first. neutral-to-alkaline pH and low native Mn content. Shortened internodes between new leaves, death of meristematic Zinc Not mobile within plants; upper tissue, deformed new leaves, interveinal chlorosis. leaves and the growing point show deficiency symptoms first. Occurs most often on alkaline (high pH) soils or soils with high available P levels. Not mobile within plants; upper Interveinal chlorosis, wilting, marginal necrosis of upper leaves. Molybdenum leaves show deficiency symptoms Occurs principally on very acidic soils because Mo becomes less first. available with low pH. Chlorine Mobile within plant, but deficiency Chlorosis in upper leaves; overall wilting of plants. symptoms usually appear on the Deficiencies may occur in well-drained soils under high rainfall upper leaves first. conditions. Causes N deficiency, chlorotic leaves, and stunted plants. Cobalt Used by symbiotic N-fixing bacteria in root nodules of legumes Occurs in areas with soils deficient in native Co. and other plants. Urban Nutrient Management Handbook 4-4

458 Chapter 4. Basic Soil Fertility - • Hydrogen is released into the soil by plants’ root sys are most present Potassium, calcium, and magnesium tems as a result of respiration and ion uptake pro- in soils with pH levels greater than 6.0. They are gen- cesses during plant growth. erally not as available for plant uptake in acidic soils because they may have been partially leached out of • Nitrogen fertilization speeds up the rate at which the soil profile. acidity develops, primarily through the acidity gen- erated by nitrification: At pH values less than 5.0, Al, Fe, and Mn may be sol - uble in sufficient quantities to be toxic to the growth of + - + . + 2NO O + 4H → 2H + 4O 2NH 2 4 3 2 some plants. Aluminum toxicity limits plant growth in most strongly acidic soils. Aluminum begins to solu- - Liming is a critical management practice for maintain bilize from silicate clays and Al hydroxides below a ing soil pH at optimal levels for plant growth. Liming - pH of approximately 5.3, which increases the activ supplies the essential elements Ca and/or Mg, reduces 3+ ity of exchangeable Al . High concentrations of the solubility and potential toxicity of Al and Mn, and exchangeable Al are toxic and detrimental to plant root increases the availability of several essential nutrients. development. - Liming also stimulates microbial activity (e.g., nitri fication) in the soil, and improves symbiotic nitrogen In general, most micronutrients are more available in fixation by legumes. However, over-liming can induce - acidic than in alkaline soils. As pH increases, micronu micronutrient deficiencies by increasing pH above the trient availability decreases, and the potential for defi - optimum range. ciencies increases. An exception to this trend is Mo, which becomes less available as soil pH decreases. In Most plants grow well in the pH range 5.8 to 6.5. Legu- addition, B becomes less available when the pH is less minous plants generally grow better in soils limed to than 5.0 and again when the pH exceeds 7.0. - pH values of 6.2 to 6.8. Some plants, such as blueber ries, mountain laurel, rhododendron, and others, grow Soil organisms also grow best in near-neutral soil. In best in strongly acidic (pH less than 5.2) soils. general, acidic soil inhibits the growth of most organ- isms, including many bacteria and earthworms. Thus, Determining Lime Requirements acidic soil slows many important activities carried on by soil microbes, including nitrogen fixation, nitrifica - Soil pH is an excellent indicator of soil acidity; how - Rhizobia tion, and organic matter decay. bacteria, for ever, it does not indicate how much total acidity is pres- instance, thrive at near-neutral pH and are sensitive to ent, and it cannot be used to determine a soil’s lime solubulized Al. requirement when used alone. The “lime requirement” for a soil is the amount of agri - Soil Acidification and Liming cultural limestone needed to achieve a desired pH range Acidification is a natural process that occurs continu - for the plants that are grown. Soil pH determines only + ously in soils throughout the mid-Atlantic region and is in the soil solution active acidity — the amount of H caused by the following factors: at that particular time — while the lime requirement determines the amount of exchangeable or reserve acid - - • The breakdown of organic matter can cause acidifi ity held by soil clay and organic matter (figure 4.2). cation of the soil as amino acids are converted into acetic acid, hydrogen gas, dinitrogen gas, and carbon Most laboratories use soil pH in combination with dioxide by the reaction: “buffered” solutions to extract and measure the amount of reserve acidity, or “buffering capacity” in a soil. → 2HC + 2CO NO H H O + O + 3H . + N 2C 2 2 2 2 3 2 2 3 7 3 The measured amount of exchangeable/reserve acidity is then used to determine the proper amount of lime • The movement of acidic water from rainfall through needed to bring about the desired increase in soil pH. soils slowly leaches basic essential elements such as Ca, Ma, and K, below the plant root zone and The rate of limestone applied to any area should be increases the concentration of exchangeable soil Al. based on soil test recommendations. A soil test every 3+ reacts with water to form hydrogen ions, Soluble Al two to three years will reveal whether or not lime is which make the soil acidic. needed. Sandy soils generally require less lime at any one application than silt loam or clay soils to decrease • Soil erosion removes exchangeable cations adsorbed soil acidity by a given amount. Sandy soils, however, to clay particles. Urban Nutrient Management Handbook 4-5

459 Chapter 4. Basic Soil Fertility usually need to be limed more frequently because their Nitrogen buffering capacity is low. The Nitrogen Cycle Nitrogen is subject to more transformations than any other essential element. These cumulative gains, - losses, and changes are collectively termed the “nitro gen cycle” (figure 4.3). The ultimate source of N is N 2 gas, which comprises approximately 78 percent of the gas, however, is unavail - earth’s atmosphere. Inert N 2 able to plants and must be transformed by biological or industrial processes into forms that are plant-available. As a result, the turf and landscape industry is heavily dependent on commercial N fertilizer. Some of the more important components of the N cycle are dis- Figure 4.2. Relationship between residual, exchangeable, and active cussed below. acidity in soils. Graphic by Kathryn Haering. ). www.ppi-ppic.org Figure 4.3. The nitrogen cycle (modified from the Potash & Phosphate Institute website at Urban Nutrient Management Handbook 4-6

460 Chapter 4. Basic Soil Fertility amino sugars, and other complex nitrogen compounds. Nitrogen Fixation Inorganic forms of soil nitrogen include ammonium “Nitrogen fixation” is the process whereby inert N - - + 2 (NH ), nitrite (NO ), nitrate (NO ), nitrous oxide 2 4 3 gas in the atmosphere is transformed into forms that (N O ), nitric oxide (NO ), and elemental nitrogen gas 2 gas + are plant-available, including ammonium (NH ) and 4 (N ). Ammonium, nitrite, and nitrate are the most 2 gas - nitrate (NO ). Fixation can take place by biological or 3 important plant nutrient forms of N and usually make by nonbiological processes. up 2 to 5 percent of total soil N. Biological nitrogen-fixation processes include: Nitrogen “mineralization” (figure 4.4) is the conversion + of organic nitrogen to NH . This is an important pro- 4 Symbiotic Nitrogen Fixation cess in the N cycle because it results in the liberation of plant-available, inorganic nitrogen forms. This process is mediated by bacteria with the ability to convert atmospheric N to plant-available N while Nitrogen “immobilization” is the conversion of inor - 2 - + growing in association with a host plant. Symbiotic ganic, plant-available nitrogen (NH or NO ) by soil 4 3 Rhizobium bacteria fix N in nodules present on the microorganisms to organic N forms (amino acids and 2 roots of legumes. Through this relationship, the bacteria proteins). This conversion is the reverse of mineraliza - make N from the atmosphere available to the legume tion, and these immobilized forms of N are not readily 2 as it is excreted from the nodules into the soil. available for plant uptake. Nonsymbiotic Nitrogen Fixation -fixation process that is performed by free- This is a N 2 living bacteria and blue-green algae in the soil. The amount of N fixed by these organisms is much lower 2 Figure 4.4. Mineralization and immobilization of soil nitrogen. than that fixed by symbiotic N fixation. 2 Graphic by Greg Mullins. Nonbiological N-fixation processes include: Carbon-to-Nitrogen Ratios Atmospheric additions Mineralization and immobilization are ongoing pro - Small amounts of N in the order of 5 to15 pounds per cesses in the soil and are generally in balance with one acre per year can be added to the soil in the form of rain another. This balance can be disrupted by the incorpora- or snowfall. This includes N that has been fixed by the tion of organic materials that have high carbon to nitro- electrical discharge of lightning in the atmosphere and gen ratios (C:N). The ratio of %C to %N, or the C:N industrial pollution. ratio, defines the relative quantities of these elements in residues and living tissues. Whether N is mineralized or immobilized depends on the C:N ratio of the organic Industrial Nitrogen Fixation material being decomposed by soil microorganisms. The industrial fixation of nitrogen is the most impor - tant source of N as a plant nutrient. The production of - Wide C:N ratios of more than 30-to-1: Immobiliza • N by industrial processes is based on the Haber-Bosch tion of soil N will be favored. Materials with wide process where H gases react to form ammonia and N C:N ratios include bark mulch, straw, pine needles, 2 2 (NH ). Hydrogen gas for this process is obtained from dry leaves, and sawdust. 3 natural gas and N comes directly from the atmosphere. 2 • C:N ratios of 20-to-1 to 30-to-1: Immobilization and The NH produced can be used directly as a fertilizer 3 mineralization will be nearly equal. or as the raw material for other N fertilizer products, - including ammonium phosphates, urea, and ammo • Narrow C:N ratios of less than 20-to-1: Favor rapid nium nitrate. mineralization of N. Materials with narrow C:N ratios include manure and biosolids. Forms of Soil Nitrogen The decomposition of an organic material with a high Soil N occurs in both inorganic and organic forms. Most C:N ratio is illustrated in figure 4.5. Shortly after incor - of the total N in surface soils is present as organic nitro- poration, high C:N ratio materials are attacked and used as an energy source by soil microorganisms. As these gen. Organic soil N occurs in the form of amino acids, Urban Nutrient Management Handbook 4-7

461 Chapter 4. Basic Soil Fertility Nitrate-N can be also be lost through denitrification, the - is reduced to gaseous nitrous oxide process where NO 3 (N O) or elemental nitrogen (N ) and lost to the atmo - 2 2 + sphere. During nitrification, 2 H ions are produced + + for every NH ion that is oxidized. These H cations 4 will accumulate and significantly reduce soil pH; thus, any ammonium-containing fertilizer will ultimately decrease soil pH due to nitrification. Phosphorus Figure 4.5. Nitrogen immobilization and mineralization after material Graphic by Kathryn Haering. with a high C:N ratio is added to soil. The Phosphorus Cycle Soil P originates primarily from the weathering of soil - organisms decompose the material, there is competi minerals, such as apatite, and from P additions in the tion for the limited supply of available N because the form of fertilizers, plant residues, manure, or biosolids material does not provide adequate N to form proteins -2 - (figure 4.6). Orthophosphate ions (HPO and H PO ) in the organisms. 4 2 4 are produced when apatite breaks down, organic resi- During this process, available soil N is decreased and the dues are decomposed, or fertilizer P sources dissolve. carbon in the decomposing material is liberated as CO These forms of P are taken up by plant roots and are 2 gas. As decomposition proceeds, the material’s C:N ratio present in very low concentrations in the soil solution. narrows and the energy supply is nearly exhausted. At Many soils contain large amounts of P, but most of that this point, some of the microbial populations will die and P is unavailable to plants. The types of P-bearing min- the mineralization of N in these decaying organisms will erals that form in soil are highly dependent on soil pH. result in the liberation of plant-available N. The timing Soluble P, regardless of the source, reacts very strongly of this process will depend on such factors as soil tem- with Fe and Al to form insoluble Fe and Al phosphates perature, soil moisture, soil chemical properties, fertility in acid soils and with Ca to form insoluble Ca phos- status, and the amount of organic material added. phates in alkaline soils. Phosphorus in these insoluble forms is not readily available for plant growth and is Nitrification said to be “fixed.” “Nitrification” is the biological oxidation of ammonium + - + ) to nitrate (NO ) in the soil. Sources of NH (NH 4 3 4 Phosphorus Availability and Mobility for this process include both commercial fertilizers and As discussed earlier, plant roots take up P in the forms the mineralization of organic residues. Nitrification is a - -2 + - of orthophosphates: HPO . The predomi- PO and H , is converted first to NO two-step process where NH 4 2 4 4 2 - nant ionic form of P present in the soil solution is pH- by two autotrophic bacteria in the soil and then to NO 3 dependent. In soils with pH values greater than 7.2, the Nitrobacter ( Nitrosomonas and ). These bacteria get -2 HPO form is predominant, while in soils with a pH their energy from the oxidation of nitrogen and their 4 - between 5.0 and 7.2, the H form predominates. PO . carbon from CO 2 4 2 Phosphorus has limited mobility in most soils because it Nitrification is important to N fertility because nitrate- reacts strongly with many elements and compounds and nitrogen (NO -N) is readily available for uptake and 3 - the surfaces of clay minerals. Unlike nitrate, P anions is an use by plants and microbes. However, NO 3 - 2- (HPO , H ) do not easily leach through the soil pro- PO “anion,” or negatively charged ion. Anions usually 4 2 4 file because of their specific complexing reactions with leach more readily than cations because they are not soil components. The release of soil P to plant roots and attracted to the predominantly negative charge of soil its potential movement to surface water is controlled by colloids. Because of its negative charge and relatively several chemical and biological processes (figure 4.6). large ionic radius, nitrate is not readily retained in the Phosphorus is released to the soil solution as P-bearing soil and is easily leached to groundwater and surface minerals dissolve, as P bound to the surface of soil min- waters. Nitrate losses can be minimized through proper erals is uncoupled or “desorbed,” and as soil organic N management, including the proper rate and timing of matter decomposes or mineralizes (figure 4.7). N fertilizer applications. Urban Nutrient Management Handbook 4-8

462 Chapter 4. Basic Soil Fertility Figure 4.6. The phosphorus cycle (modified from the Potash & Phosphate Institute website at www.ppi-ppic.org ). Most of the P added as fertilizer and organic sources is rapidly bound by soil minerals in chemical forms that are not subject to rapid release; thus, soil solution P concentrations are typically very low (less than 0.01 to 1.00 ppm). The supply of adequate P to a plant will depend on the soil’s ability to replenish soil solution P throughout the growing season (figure 4.7). Phosphorus availability and mobility is influenced by several factors: Soil pH In acidic soils, P precipitates as relatively insoluble iron and Al phosphate minerals. In neutral and calcare - Figure 4.7. Phosphorus content of the soil solution. ous soils, P precipitates as relatively insoluble Ca phos- Graphic by Greg Mullins. phate minerals. As illustrated in figures 4.1 and 4.8, soil P is most available in the pH range of 5.5 to 6.8, where the availability of soluble Al and Fe is low. Urban Nutrient Management Handbook 4-9

463 Chapter 4. Basic Soil Fertility contribute to excessive growth of aquatic organisms, Movement of Soil Phosphorus to Plant Roots which can have detrimental environmental impacts. Phosphorus moves from soil solids to plant roots Soils have a finite capacity to bind P. When a soil through the process of “diffusion.” Diffusion is a slow and short-range process with distances as small as 0.25 becomes saturated with P, desorption of soluble phos- inch. This limited movement has important implications phorus can be accelerated, with a consequent increase because soil P located more than 0.25 inch from a plant in dissolved inorganic P in runoff. Thus, if the level root will never reach the root surface. Dry soils reduce of residual soil phosphorus is allowed to build up by the diffusion of P to roots; therefore, plants take up repeated applications of phosphorus in excess of plant P best in moist soils. needs, a soil can become saturated with P and the poten- tial for soluble phosphorus losses in surface runoff will increase significantly. Residual Fertilizer Phosphorus Recovery A plant uses only 10 to 30 percent of the P fertilizer Research conducted in the mid-Atlantic shows that the applied during the first year following application. The potential loss of soluble P will increase with increasing rest goes into reserve and can be used by plants in later levels of soil test P. Very high levels of soil-test P can years. result from over-application of manure, biosolids, or commercial phosphate fertilizer. Soils with these high soil-test P levels will require several years without P Timing and Placement of Phosphorus Fertilizer additions to effectively reduce these high P levels. New plants need a highly available P source in order to establish a vigorous root system early in the season. Once the root system begins to explore the entire soil Potassium volume, there should be adequate amounts of residual P to maintain plant growth. The Potassium Cycle Potassium is the third primary plant nutrient and is absorbed by plants in larger amounts than any other nutrient except nitrogen. Plants take up K as the mon- + . Potassium is present in relatively ovalent cation K large quantities in most soils, but only a small per - centage of the total soil K is readily available for plant uptake. The K cycle is illustrated in figure 4.9. In the soil, weathering releases K from a number of common min- + erals, including feldspars and micas. The released K can be taken up easily by plant roots, adsorbed by the Figure 4.8. Effect of pH on phosphorus availability to plants. cation exchange complex of clay and organic matter, Graphic by Kathryn Haering. or “fixed” in the internal structure of certain two-to- one clay minerals. Potassium that is fixed by these clay Phosphorus Transport to Surface Waters minerals is very slowly available to the plant. Transport of soil P occurs primarily via surface flow (runoff and erosion), although leaching and subsurface Potassium Availability and Mobility lateral flow may also be possible in soils with high Although mineral K accounts for 90 to 98 percent of the degrees of P saturation and artificial drainage systems. total soil K, readily and slowly available K represent Water flowing across the soil surface may dissolve and only 1 to 10 percent of the total soil K. Plant-available K transport soluble P, and erode and transport particulate (K that can be readily absorbed by plant roots) includes P. Virtually all soluble P transported by surface run- the portion of the soil K that is soluble in the soil solu- off is biologically available, but particulate phospho- tion and the exchangeable K held on the soil’s exchange rus that enters streams and other surface waters must complex. Exchangeable K is that portion of soil K that undergo solubilization before becoming available for is in equilibrium with K in the soil solution. Potassium aquatic plants. Thus, both soluble and sediment-bound P are potential pollutants of surface waters and both can is continuously made available for plant uptake through Urban Nutrient Management Handbook 4-10

464 Chapter 4. Basic Soil Fertility ). www.ppi-ppic.org Figure 4.9. The potassium cycle (modified from the Potash & Phosphate Institute website at the cation exchange process. There can be a continuous, - is held by cation exchange, it is less mobile in fine-tex tured soils and most readily leached from sandy soils. but slow, transfer of K from soil minerals to exchange- Most plant uptake of soil K occurs by diffusion. able and slowly available forms as K is removed from the soil solution by plant uptake and leaching. Potassium fertilizers are completely water-soluble and - have a high salt index, so they can decrease seed ger Potassium applied as fertilizer can have various fates mination and plant survival when placed too close to in the soil. seed or transplants. The risk of fertilizer injury is most • Potassium cations can be attracted to the cation- severe on sandy soils, under dry conditions, and with - exchange complex where it is held in an exchange high rates of fertilization. A convenient and usually able form and readily available for plant uptake. - effective method of applying K fertilizers is by broad casting and mixing with the soil before planting. Fertil - • Some of the K+ ions will remain in the soil solution. izer injury is minimized by this method, but on sandy soils, leaching may cause the loss of some K. • Exchangeable and soluble K may be absorbed by plants. Secondary Plant Nutrients • In some soils, some K may be fixed by the clay fraction. • Applied K may leach from sandy soils during periods Introduction of heavy rainfall. Secondary macronutrients Ca, Mg, and S are required Potassium moves more readily in soil than phosphorus in relatively large amounts for good crop growth. These nutrients are usually applied as soil amendments does, but less readily than nitrogen. Because potassium Urban Nutrient Management Handbook 4-11

465 Chapter 4. Basic Soil Fertility organic matter. Inorganic sulfur is usually present in the or applied along with materials that contain primary 2- nutrients. Secondary nutrients are as important to plant sulfate (SO ) form, which is the form of S absorbed by 4 nutrition as major nutrients, because deficiencies of plant roots. secondary nutrients can depress plant growth as much 2- Both soluble SO in the soil solution and adsorbed 4 as major plant nutrient deficiencies. 2- represent readily plant-available S. Elemental SO 4 sulfur is a good source of S, but it must first undergo 2- Calcium and Magnesium , driven by Thiobacillus biological oxidation to SO 4 bacteria, before plants can assimilate it. thiooxidans Calcium and magnesium have similar chemical proper - This oxidation can contribute to soil acidity by produc- ties and behave very similarly in the soil. Both of these 2+ 2+ ing sulfuric acid. elements are cations (Ca , Mg ), and both cations have the same amount of positive charge and a similar 2- form of Several fertilizer materials contain the SO 4 - ionic radius. The mobility of both Ca and Mg is rela ), potassium sulfate sulfur, including gypsum (CaSO 4 tively low, especially compared to anions or to other ), and potassium SO ), magnesium sulfate (MgSO (K 4 2 4 cations such as Na and K; thus, losses of these cations magnesium sulfate (K-Mag or Sul-Po-Mag). These fer - via leaching are relatively low. tilizer sources are neutral salts and will have little or no Total Ca content of soils can range from 0.1 percent effect on soil pH. - in highly weathered tropical soils to 30 percent in cal 2- -containing compounds, In contrast, there are other SO 4 careous soils. Calcium is part of the structure of sev- ) SO ), aluminum including ammonium sulfate ((NH 4 2 4 eral minerals and most soil calcium comes from the ), that con- ), and iron sulfate (FeSO ) SO sulfate ((Al 4 4 2 3 weathering of common minerals, which include dolo- 2- in these materi - tribute greatly to soil acidity. The SO 4 mite, calcite, apatite, and calcium-feldspars. Calcium is als is not the source of acidity. Ammonium sulfate has a present in the soil solution and because it is a divalent - strong acidic reaction primarily because of the nitrifica cation, its behavior is governed by cation exchange, as + , and aluminum and iron sulfates are very tion of NH 4 are the other cations. Exchangeable Ca is held on the 3+ 3+ . and Fe acidic due to the hydrolysis of Al negatively charged surfaces of clay and organic matter. 2- Calcium is the dominant cation on the cation exchange Sulfate, a divalent anion (SO ) is not strongly 4 complex in soils with moderate pH levels. Normally, adsorbed and can be readily leached from most soils. 2- it occupies 70 to 90 percent of cation exchange sites often In highly weathered, naturally acidic soils, SO 4 above pH 6.0. accumulates in subsurface soil horizons, where posi - tively charged colloids attract the negatively charged Total soil Mg content can range from 0.1 percent in 2- 2- resulting from long-term ion. Residual soil SO SO 4 4 coarse, humid-region soils to 4 percent in soils formed applications of S-containing fertilizers can meet the S from high-magnesium minerals. Magnesium occurs requirements of plants for years after applications have naturally in soils from the weathering of rocks with ceased. Mg-containing minerals such as biotite, hornblende, dolomite, and chlorite. Magnesium is found in the soil 2+ ), its solution and because it is a divalent cation (Mg Micronutrients behavior is governed by cation exchange. Magnesium is held less tightly than calcium by cation exchange Introduction sites, so it is more easily leached and soils usually con- Eight of the essential elements for plant growth are tain less Mg than calcium. In the mid-Atlantic region, called micronutrients or trace elements: B, Cl, Cu, Mg deficiencies occur most often on acidic and coarse- Fe, Mn, Mo, Ni, Zn. Cobalt has not been proven to be textured soils. essential for higher plant growth, but nodulating bac- teria need cobalt for fixing atmospheric nitrogen in Sulfur legumes. Although micronutrients are not needed in large quantities, they are as important to plant nutri - Soil sulfur is present in both inorganic and organic tion and development as the primary and secondary forms. Most of the sulfur in soils comes from the nutrients. A deficiency of any one of the micronutrients - weathering of sulfate minerals such as gypsum; how in the soil can limit plant growth, even when all other ever, approximately 90 percent of the total sulfur in the surface layers of noncalcareous soils is immobilized in essential nutrients are present in adequate amounts. Urban Nutrient Management Handbook 4-12

466 Chapter 4. Basic Soil Fertility Recommended rates of B fertilization depend on such Micronutrients can exist in several different forms in factors as soil-test levels, plant-tissue concentrations, - soil: within structures of primary and secondary miner plant species, weather conditions, soil organic matter, als, adsorbed to mineral and organic matter surfaces, and the method of application. incorporated in organic matter and microorganisms, and in the soil solution. Many micronutrients combine with organic molecules in the soil to form complex Copper molecules called chelates, which are metal atoms sur - In mineral soils, Cu concentrations in the soil solution rounded by a large organic molecule. Plant roots absorb are controlled primarily by soil pH and the amount of soluble forms of micronutrients from the soil solution. - Cu adsorbed on clay and soil organic matter. A major + in surface soils is complexed ity of the soluble Cu A micronutrient deficiency, if suspected, can be identi - 2 with organic matter, and Cu is more strongly bound to - fied through soil tests or plant analysis. Total soil con soil organic matter than any of the other micronutri - tent of a micronutrient does not indicate the amount ents. Sandy soils with low organic matter content may available for plant growth during a single growing sea- become deficient in Cu because of leaching losses. son, although it does indicate relative abundance and Heavy, clay-type soils are least likely to be Cu-deficient. potential supplying power. Micronutrient availability The concentrations of Fe, Mn, and Al in soil affect the decreases as soil pH increases for all micronutrients availability of Cu for plant growth, regardless of soil except Mo and Cl. type. Specific soil-plant relationships for B, Cu, Fe, Mn, Mo, Like most other micronutrients, large quantities of Cu and Zn are discussed in the next sections. can be toxic to plants. Excessive amounts of Cu depress Fe activity and may cause Fe deficiency symptoms to Boron appear in plants. Such toxicities are not common. Boron exists in minerals, adsorbed on the surfaces of clay and oxides, combined in soil organic matter, and in Iron the soil solution. Organic matter is the most important Iron is the fourth-most abundant element, but the solu- potentially plant-available soil source of B. bility of Fe is very low and highly pH-dependent. Iron Factors that affect the availability of B to plants solubility decreases with increasing soil pH. It can include: react with organic compounds to form chelates or iron- organic complexes. Soil Moisture and Weather Iron deficiency may be caused by an imbalance with Boron deficiency is often associated with dry or cold other metals, such as Mo, Cu, or Mn. Other factors that weather, which slows organic matter decomposition. may trigger iron deficiency include excessive phospho - Symptoms may disappear as soon as the surface soil rus in the soil; a combination of high-pH, high-lime, receives rainfall or soil temperatures increase and root wet, cold soils and high bicarbonate levels; and low soil growth continues, but yield potential is often reduced. organic matter levels. Reducing soil pH in a narrow band in the root zone can Soil pH correct iron deficiencies. Several S products will lower Plant availability of B is maximized between pH 5.0 and soil pH and convert insoluble soil iron to a form the 7.0. Boron availability decreases with increasing soil plant can use. pH, which means that B uptake is reduced at high pH. Manganese Soil Texture - Availability of Mn to plants is determined by the equi Coarse-textured (sandy) soils, which are composed librium among solution, exchangeable, organic, and largely of quartz, are typically low in minerals that mineral forms of soil Mn. Chemical reactions affecting contain boron. Plants growing on such soils commonly - Mn solubility include oxidation reduction and compl show boron deficiencies. Boron is mobile in the soil exation with soil organic matter. “Redox” or oxidation- and is subject to leaching. Leaching is of greater con- reduction reactions depend on soil moisture, aeration, and microbial activity. cern on sandy soils and in areas of high rainfall. Urban Nutrient Management Handbook 4-13

467 Chapter 4. Basic Soil Fertility Manganese solubility decreases with increasing soil compounds to form soluble complexes. Organically pH, so Mn deficiencies occur most often on high - complexed, or chelated, Zn is important for the move organic-matter soils and on those soils with neutral-to- ment of Zn to plant roots. Soils can contain from a few alkaline pH that are naturally low in Mn. Manganese to several hundred pounds of Zn per acre. Fine-textured deficiencies may also result from an antagonism with soils usually contain more Zn than sandy soils do. other nutrients, such as Ca, magnesium, and Fe. Soil Total Zn content of a soil does not indicate how much moisture also affects Mn availability. Excess moisture Zn is available. The following factors determine its in organic soils favors Mn availability because reduc- availability: ing conditions convert Mn4+ to Mn2+, which is plant- available. • Zinc becomes less available as soil pH increases. Coarse-textured soils limed above a pH of 6.0 are Manganese deficiency is often observed on sandy particularly prone to develop Zn deficiency. Soluble Coastal Plain soils under dry conditions that have pre- Zn concentrations in the soil can decrease three-fold viously been wet. for every pH unit increase between 5.0 and 7.0. • Zinc deficiency may occur in some plant species on Molybdenum soils with very high P availability and marginal Zn - Molybdenum is found in soil minerals as exchange - concentrations due to Zn/P antagonisms. Soil pH fur able Mo on the surfaces of iron/aluminum oxides and ther complicates Zn/P interactions. bound soil organic matter. Adsorbed and soluble Mo is - ). an anion (MoO • Zinc forms stable complexes with soil organic matter. 4 A significant portion of soil Zn may be fixed in the Molybdenum becomes more available as soil pH organic fraction of high organic-matter soils. It may increases, so deficiencies are more likely to occur on also be temporarily immobilized in the bodies of soil acidic soils. Since Mo becomes more available with microorganisms, especially when animal manures increasing pH, liming will correct a deficiency if the are added to the soil. soil contains enough of the nutrient. Sandy soils are deficient in Mo more often than finer-textured soils are, At the opposite extreme, much of a mineral soil’s • and soils high in Fe/Al oxides tend to be low in avail - available Zn is associated with organic matter. Low - able Mo because Mo is strongly adsorbed to the sur organic-matter levels in mineral soils are frequently faces of Fe/Al oxides. Heavy P applications increase indicative of low Zn availability. Mo uptake by plants, while heavy S applications Zinc availability is affected by the presence of certain decrease Mo uptake. soil fungi, called mycorrhizae, which form symbiotic relationships with plant roots. Removal of surface soil Zinc in land leveling may remove the beneficial fungi and limit plants’ ability to absorb Zn. The various forms of soil Zn include soil minerals, organic matter, adsorbed Zn on the surfaces of organic matter and clay, and dissolved Zn in the soil solution. Acknowledgement Zinc released from soil minerals during weathering can This chapter is dedicated to the memory of Greg Mullins - be adsorbed onto the Cation Exchange Complex, incor (1955-2009). porated into soil organic matter, or react with organic Urban Nutrient Management Handbook 4-14

468 Chapter 5. Soil Sampling and Nutrient Testing Chapter 5. Soil Sampling and Nutrient Testing Rory Maguire, Associate Professor, Crop and Soil Environmental Sciences, Virginia Tech Steven Hodges, Professor, Crop and Soil Environmental Sciences, Virginia Tech Steve Heckendorn, Laboratory Manager, Crop and Soil Environmental Sciences, Virginia Tech Very low: A plant response is most likely if the indi- Introduction cated nutrient is applied. A large portion of the nutrient Soil testing is a fundamental management practice for requirement must come from fertilization. turfgrass and the ornamental landscape. A soil analy - A plant response is likely if the indicated nutrient Low: sis provides essential information on relative levels of is applied. A portion of the nutrient requirement must organic matter, pH, lime requirement, cation exchange come from fertilization. capacity (CEC), and levels of plant-available nutrients (nitrogen, phosphorus, potassium, and specific micro - Medium: A plant response may or may not occur if nutrients) contained in the soil. the indicated nutrient is applied. A small portion of the nutrient requirement must come from fertilization. The goals of soil testing are to determine existing nutri- ent levels, predict additional lime and nutrient needs, High: Plant response is not expected. No additional fer - and evaluate potential excesses or imbalances within a tilizer is needed. given soil. A soil test report usually includes suggested Plant response is not expected. The soil can Very high: lime and fertilizer treatments for turf and landscape supply much more than the turf requires. Additional areas being maintained. Note that soil tests do not mea - - fertilizer should not be added to avoid nutritional prob sure nitrogen (N), because it is a highly mobile nutrient. lems and adverse environmental consequences. Suggested nitrogen rates are general recommendations based on years of research on the nitrogen needs of the turf species or ornamental plant present. While soil testing has been around for nearly 50 years, soil test results and recommendations may vary from lab to lab. To understand this, you need to understand how labs use chemical extraction procedures to predict nutri- ent needs and the amounts required to avoid deficien - cies. The chemical extraction must be calibrated, that is, tested and proven under actual growing conditions using replicated nutrient response field trials with the plant species of interest. These trials should be conducted Figure 5.1. A typical plant response curve as influenced by varying levels of soil nutrients. under a wide range of soils, water regimes, and climatic conditions. The calibration process is an essential com- ponent relating laboratory results to field performance; Soil Test Interpretation and thus, the quality of the calibration data determines the Recommendations accuracy of the resulting recommendations. Soil test results must be related to the expected level Soil testing laboratories may also vary in the chemical of plant response and the appropriate rate of fertilizers methods they use to assess soil nutrient levels and the required to eliminate nutrient deficiency. Soil testing manner in which they report data. Many mid-Atlantic labs may disagree with the manner in which results are states use the Mehlich-1 extractant, while other labora- interpreted and recommendations are made. tories use the newer Mehlich-3. Some states have not adopted the Mehlich-3 extractant because new calibration Sufficiency Level Approach - data are required to relate soil test levels to field perfor mance. Some labs report their results in parts per million, - Most land-grant universities base their recommenda tions on the “sufficiency level” concept. Basically, this some in pounds per acre, and others as a predictive index. extensively tested approach says “fertilize the crop, not Regardless, most laboratories report a rating indicating the soil” by ceasing to recommend nutrient additions the relative status for each nutrient (figure 5.1). Urban Nutrient Management Handbook 5-1

469 Chapter 5. Soil Sampling and Nutrient Testing The following sections will describe proper soil sam- when test levels exceed proven responsive levels. It is pling and interpretation of soil test reports. also the most conservative approach, and as such, it has been attacked at times as being too conservative. This philosophy is difficult for the home landscape because Soil Sampling no yield is taken. However, this philosophy has the greatest potential for producing the most favorable General Sampling Considerations results and is in harmony with the concepts of nutri- Soil sampling should be done every one to five years, ent management planning. In areas of the mid-Atlantic depending on the soil type and management. Com- with highly weathered, low CEC soils, this philosophy pletely modified, sand-based soils used on golf greens, minimizes losses of potassium (K), magnesium (Mg), tees, and athletic fields should likely be tested on an and the more mobile nutrients via leaching. annual basis. For naturally occurring, coarse-textured (i.e., sandy) soils, a typical sampling frequency is Buildup and Maintenance Approach every two to three years. On fine-textured (i.e., loamy The “buildup and maintenance” approach recommends or clayey) soil, sampling likely does not need to be that soil test levels be built to the “high” or nonrespon- done more than every four to five years. If clippings sive level. Soil levels are then maintained by annual are removed, sample more frequently according to the replacement of nutrients to be removed as clippings or soil type. sod, regardless of soil test level. This method assumes When submitting soils for analysis, it is common to that all soils can hold high levels of nutrients, which is request recommendations for specific plants, i.e., turf not the case for soils having relatively low CEC (less or ornamentals. As nutrient requirements vary by plant than 10). type, separate soil samples should be submitted for each recommendation that is required — even if the Cation Saturation Ratio Approach soil looks the same and is in a similar location. The final approach, the “cation saturation ratio” method, For fine-turf maintenance, divide the property into logi - focuses on the ratio of nutrients on the soil exchange cal areas. For example, it is logical to divide a single sites. Most often, these labs suggest that 5 percent of hole on a golf course into green, tee(s), fairway, and the CEC be occupied by potassium, 10 to 20 percent rough categories and to conduct a test on each of these by magnesium, and 70 to 85 percent by calcium (Ca). areas as a unique entity. Again, this approach assumes that the soil has suf- ficient exchange capacity to support these ratios and The turf of a football or baseball field should be divided stay above sufficiency level. For low CEC soils, this - into two to four areas for separate sampling. It is impor approach can result in nutrient additions for the sake tant to remember that the quality of the test report is of adjusting the soil ratio that are unnecessary for high- only as good as the sample submitted; simply testing a quality turf production and could result in inadequate single sample that was gathered from a large area does levels of potassium for some soils. not provide sufficiently detailed information regarding that soil. Keep in mind that regardless of the approach to fertil - ization, in a few cases, soil-testing may not accurately Soil samples can be taken at any time of the year but, in predict a response or lack of response in any given situ- general, it is recommended to take samples in advance ation. Because recommendations are based on many of planting or the time of regular fertilization. Fall sam - years of data, they may not predict needs in a specific pling is most common, as this allows time to get results situation because of unique climatic or soil conditions, and apply lime and nutrients in advance of spring management practices, or pest pressure. growth. Limestone takes months to fully react with soil, so liming should be done well in advance of spring Regardless of the lab used, familiarize yourself with growth, while nutrients are more reactive and should the reporting system and be especially sure the lab has be applied closer to the time of plant growth. Soil sam- calibrated their recommendations for the plant material pling should not be done for at least two months after - being grown. Unverified recommendations or recom fertilization or liming. mendations based on forages or row crops may prove inadequate for intensively managed turfgrass and other Undisturbed areas need to be sampled separately from disturbed areas. Because soils vary with their location landscape plants. Urban Nutrient Management Handbook 5-2

470 Chapter 5. Soil Sampling and Nutrient Testing in the landscape, they should at the very least be sepa- - rated into upland, side slopes, and lowland or bottom land positions. Disturbed soil areas should be separated into smaller units based on amount of disturbance, soil removal, or soil addition. These soil variations are often visible as different soil colors or as differences in soil texture (sand versus clay). The upper diagram in figure 5.2 shows how landscape position affects soil properties; the lower diagram shows how soil color can vary. Each soil type, colored differently in these figures, should ideally be sampled separately. Soil samples should accurately represent the Figure 5.3. Example of a soil probe, mixing bucket, and soil box filled area being sampled. with soil. A representative soil sample consists of a well-mixed The best way to collect a soil sample is with a soil probe, composite of many subsamples. A soil sample from which is fast and easy and collects an even amount of a single spot, instead of the representative sample - soil down to the depth sampled. Soil probes can be pur described here, could result in inaccurate nutrient and chased from many locations, such as garden centers or lime recommendations. Collect at least 10 subsamples online, but it is acceptable to sample using a shovel or from the uniform area you have identified and mix trowel if you are not going to soil-test frequently. Soil them together in a clean plastic bucket. It is important sample containers and information sheets are available the bucket is clean because small amounts of nutrients from laboratories that analyze the samples. or lime in the bucket could contaminate your sample. Once you select uniform areas to sample, the next step Push the soil probe into the soil to the desired depth and is to collect a representative sample from the correct remove any surface plant material such as turf thatch depth. The depth of sampling depends on the land use: before placing it in the bucket. Collect the subsamples It should be 2 to 4 inches for established turf, 6 to 8 from random spots within the sample area by following inches for vegetable and flower beds, and 6 inches for a zigzag pattern as you walk across the landscape (figure trees and shrubs, excluding any mulch (Hunnings and 5.4). When you have collected the necessary number of Donohue 2009). For any land that is going to be tilled, subsamples in your bucket, break up any aggregates or such as vegetable gardens or during turf establishment, clumps and mix thoroughly. It is this thoroughly mixed take the sample to the depth you intend to till. composite of your subsamples that you will submit for testing. There are several private and public soil testing labora - tories and each has its own system for submitting sam- ples. Virginia Cooperative Extension also has offices Figure 5.4. Example of soil sampling locations for a homeowner. Yel- Upper : Changes in soils by landscape position. Lower : Figure 5.2. low dots indicate individual sampling points, and lines collecting dots How soil type and soil color can change spatially. indicate samples that are pooled and mixed. Urban Nutrient Management Handbook 5-3

471 Chapter 5. Soil Sampling and Nutrient Testing particular, favor thatch development. Because thatch is located throughout the state where you can pick up soil almost all organic and very lightweight, it becomes a testing boxes appropriate for submitting soil samples to misleading component of a normal soil sample. the Virginia Tech Soil Testing Laboratory ( www.soilt- est.vt.edu ). These soil boxes hold about a cup or 0.5 In turfgrass areas where thatch thickness exceeds 0.5 pound or more of soil, and you should try to fill them inch, the thatch should be removed before taking any to ensure you submit sufficient soil. An acre contains soil sample used to measure soil pH or other nutrients, about 2 million pounds of topsoil, so the importance such as phosphorus and potassium. This suggests that of collecting a representative subsample cannot be turfgrass areas with thick thatch covers should have overemphasized. two samples taken for analysis to more correctly reflect maintenance nutrient needs. Areas with a thatch thick - - The sample identification should be placed on the labo ness of 0.5 inch or less can be analyzed for nutrient ratory container and placed on a corresponding map or needs with the thatch either mixed in as part of the sam- identification sheet for the areas to be sampled. More ple or removed before taking the sample cores. information on the appropriate steps in sampling soils, submitting the sample, and inte