TCEQ Air Quality Modeling Guidelines

Transcript

1 Air Quality Modeling Guidelines APDG 6232 Air Permits Division Texas Commission on Environmental Quality September 2018 - (APDG 6232v2, Revised 09/ i Page 18) Air Quality Modeling Guidelines TCEQ

2 Table of Contents ... Summary of Changes 1 ... 2 Glossary of Acronyms and Symbols Definitions ... 4 Section I – Introduction ... 10 Section II – Authority for Requesting Air Quality Impacts Analyses ... 11 Section III – Air Quality Analysis ... 11 Air Dispersion Modeling ... 12 Ambient Air Monitoring 12 ... Air Quality Analysis Process ... 13 Section IV – Conducting the Air Quality Analysis ... 13 Screening Modeling 14 ... Refined Modeling ... 14 Modeling Emissions Inventory ... 14 14 Preliminary Impact Determination ... Minor NSR ... 16 Minor NAAQS Analysis ... 16 18 ... State Property Line Standard Analysis ... 19 Health Effects Analysis ... 19 PSD Air Quality Analysis ... 19 PSD NAAQS Analysis -application Analysis ... 21 PSD Pre ... PSD Increment Analysis 22 Additional Impacts Analysis ... 25 Class I Area Analysis 26 ... Sectio n V – Preferred Air Dispersion Models and Associated Inputs ... 27 Preferred Air Dispersion Models ... 28 Source Data ... 28 Downwash Applicability ... 28 29 Recept or Design ... Surface Characteristics of the Modeling Domain 30 ... 31 ... Meteorological Data - (APDG 6232v4, Revised 09/18) Air Quality ii Page Modeling Guidelines TCEQ

3 Section VI Reporting Requirements ... 31 ... Justifying the Use of the Significant Impact Levels 32 Appendix A – 32 Historic Use of SILs ... ... 32 ng the Air Quality Analysis Conducti hour Nitrogen Dioxide and 1 -hour Sulfur Dioxide ... 32 Interim SILs for 1- -2.5 and Ozone 33 ... Recommended SILs for Particulate Matter Federal and State Air Quality Standards ... 35 Appendix B - Appendix C - Requesting Information from the Air Permits Allowable Database ... 38 What the requestor will receive: ... 39 ... 39 What data are in APAD: What data gaps exist in APAD: ... 40 What to do about data gaps in APAD: ... 41 Appendix D – ... 42 Representative Background Monitoring Concentrations Existing Ambient Monitoring Data for the County ... 42 No Existing Ambient Monitoring Data for the County ... 43 46 Monitoring Background Refinement ... Minor and Prevention of Significant Deterioration National Ambient Air Appendix E - Quality Standards ... 48 ... 48 Preliminary Impact Determination Full NAAQS Analysis ... 50 Appendix F - State Property Line Standard Analysis ... 54 Preliminary Impact Determination 54 ... Site -wide Modeling ... 55 Appendix G - Health Effects Analysis ... 56 ... Appendix H – Prevention of Significant Deterioration Pre- application Analysis 58 Appendix I - Prevention of Significant Deterioration Increment 60 ... ... Terms 60 Conducting the Analysis ... 62 Appe ndix J - Preferred Air Dispersion Models ... 66 Refined Models 66 ... Screening Models ... 66 Appendix K - Source Characterizations ... 68 ... 68 Operation or Process Limitations ... Source Types 69 - (APDG 6232v4, Revised 09/18) Air Quality iii Page Modeling Guidelines TCEQ

4 Equivalency of S ource Types ... 72 ... 74 Downwash Applicability Appendix L - Appendix M – Receptor Design ... 76 ... 77 Special cases to consider when developing a receptor grid -property receptors over water ... 77 Off Following are some receptor placement examples ... 78 80 Surface Characteristics of the Modeling Domain ... Appendix N - LULC Analysis for ISC, ISC- PRIME, and SCREEN3 80 ... Use Analysis ... Simplified Auer Land- 81 LULC Analysis for AERMOD and AERSCREEN ... 82 Terrain ... 83 Appendix O - logical Data ... 85 Meteoro Appendix P - Reporting Requirements ... 87 Project Identification Information ... 87 ... 87 Project Overview Type of Perm it Review 87 ... ... Constituents Evaluated 87 Plot Plan ... 87 Area Map ... 88 Air Quality Monitoring Data 89 ... Modeling Emissions Inventory ... 89 Table Correlating the Emission Inventory Source Name and Emission Point Number (EPN) with the Source Number in the Modeling Output ... 90 ... Stack Parameter Justification 90 Scaling Factors ... 90 ... 90 Models Proposed and Modeling Techniques Selection of Dispersion Option ... 90 Building Wake Effects (Downwash) ... 91 Receptor Grid 91 ... Meteorological Data ... 91 Modeling Results ... 91 Electronic Information (Model Input/Output and Associated Computer or Electronic 92 Files) ... ... Conducting an Ambient Ozone Impacts Analysis Appendix Q - 93 - (APDG 6232v4, Revised 09/18) Air Quality iv Page Modeling Guidelines TCEQ

5 Secondary Formation of Particulate Matter (PM ) ... 98 Appendix R - 2.5 Terms ... 98 Overview ... 98 99 Two -tiered Approach ... ... Tier 1 99 ... 107 Tier 2 Appendix S – Additional Guidance for evaluating Nitrogen Dioxide and 1- hour Sulfur ... Dioxide 108 Approval and Application of a Tiering Approach for NO ... 108 2 109 and 1- NAAQS ... hour SO Treatment of Intermittent Emissions for 1- hour NO 2 2 - (APDG 6232v4, Revised 09/18) Air Quality v Page Modeling Guidelines TCEQ

6 Summary of Changes 2015: April • Minor updates to text in various sections in relation to comments provided on the Draft Guidelines during the comment period. Justifying the Use of the Significant Impact Levels, Added in Appendix A – • guidance for justifying the PM SILs for the Increment Analysis. 2.5 • – Conducting a Removed Appendix Q n Ambient Ozone Impacts Analysis. This appendix is under further review. September 2018 : • Minor updates to text in various sections. Updates to numerous sections based on the EPA finalizing revisions to the • Guideline on Air Quality Models (January 2017). dates to numerous sections based on EPA memorand • Up a. - Conducting an Ambient Ozone Impacts Analysis. • Addition of Appendix Q Updates to Appendix R - Secondary Formation of Particulate Matter (PM • ), 2.5 updated based on draft EPA guidance. 0 - (APDG 6232v2, Revised 09 TCEQ /18) Air Quality Modeling Guidelines Page 1 of 11

7 Glossary of Acronyms and Symbols ActualBD Actual emissions at the applicable minor source baseline date ActualMD Actual emissions as of the date of the modeling demonstration ADMT Air Dispersion Modeling Team AOI Area of Impact APD Air Permits Division AQA Air Quality Analysis AQRV Air Quality Related Value Air Quality System AQS CAMS Continuous Ambient Monitor Station CAS Chemical Abstract Service Code of Federal Regulations CFR CTM Chemical Transport Model EPA Environmental Protection Agency EPN Emission Point Number Effects Screening Level ESL FCAA Federal Clean Air Act Federal Land Manager FLM GAQM EPA’s Guideline on Air Quality Models GEP Good Engineering Practice Level Concentration Ground- GLC Structure Height H HGEP GEP Stack Height IRD Information Resources Division L Lesser of the structure height or maximum projected width Use/Land- LULC Land- Cover MERPs Modeled Emission Rates for Precursors Material Safety Data Sheet MSDS National Ambient Air Quality Standard(s) NAAQS New Source Review NSR 2 of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 110

8 Glossary of Acronyms and Symbols ( continued ) PBR Permit By Rule Parts Per Billion PPB PSD Prevention of Significant Deterioration SER Significant Emission Rate Significant Impact Level SIL SIP State Implementation Plan SMC Significant Monitoring Concentration SPLD Single Property Line Designation TAC Texas Administrative Code TAD Technical Assistance Document Texas Clean Air Act TCAA TCEQ Texas Commission on Environmental Quality Toxicology Division TD THSC Texas Health and Safety Code Tons Per Year TPY USGS United States Geological Survey Universal Transverse Mercator UTM 3 of - (APDG 6232v4 , Revised 09 /18) TCEQ Air Quality Modeling Guidelines Page 110

9 Definitions s convenience; they The following explanations of terms are included solely for the reader’ definition in state or federal laws, rules, or regulations. Al l do not take the place of any section references are to Title 30 of the Texas Administrative Code ( TAC ) unless specified otherwise. Particulate matter, radioactive materials, dust, fumes, gas, mist, Air contaminant. smoke, vapor, or odor, including any combination of those items, produced by processes other than natural ( Texas Health and Safety Code [T HSC] Section 382.003). May also be referred to by staff as constituent , chemical , compound , or pollutant . Air dispersion model. A simplification of the physical laws governing the dispersion and transport of contaminants in the atmosphere. The simplification is represented as a set of mathematical equations that require information describing a physical situation before the equations can be solved. Air pollution. One or more air contaminants in such concentration and of such duration that they could cause injury; adversely affect human health or welfare, animal life, vegetation, or property; or interfere with the normal use and enjoyment of animal life, vegetation, or property ( THSC 382.003). that federal land managers A term used by . (AQRV) Value include Air Quality Related visibility, odor, flora, fauna; geological resources; archeological, historical, and other cultural resources; and soil and water resources. Ambient air. That por tion of the atmosphere, external to buildings, to which the general 30 TAC 101.1). public has access ( Area of Impact (AOI) . All locations where the significant increase in the potential emissions of a pollutant from a new source, or significant net emissions increase from a impact (i.e., equal or exceed th modification, will cause a significant e applicable de ). The highest modeled pollutant 101.1 30 TAC impact lev minimis el, as shown in concentration for each averaging time is used to determine whether the source will have a impact for that pollutant. significant Attainment a dary ambient air Any area that meets the national primary or secon rea. quality standard for an applicable criteria pollutant. ontaminant concentrations present in the ambient air that are not Background. Air c attributed to the source or site being evaluated. e atmospheric chemical and Chemical Transport Model (CTM). Models that simulat physical processes such as gas and particle chemistry, deposition, and transport. There are two types of chemical transport models which are differentiated based on a fixed frame of reference (Eulerian) or a frame of reference that moves with parcels of air between the source and receptor point (Lagrangian). 110 - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 4 of TCEQ

10 Class I area. An area defined by Congress that is afforded the greatest degree of air quality protection. Class I areas are deemed to have special natural, scenic, or historic value. The Prevention of Significant Deterioration ( PSD ) regulations provide special protection for Class I areas. Little deterioration of air quality is allowed. degree of emissions An area defined by Congress where a Class II area. moderate growth is allowed. A pollutant for which a National Ambient Air Quality Standard Criteria pollutant. (NAAQS) has been defined. De minimis impact. A change in ground level concentration of an air contaminant as a result of the operation of any new major stationar y source or of the operation of any the existing source that has undergone a major modification that does not exceed significance levels as specified in 40 Code of Federal Regulations (CFR) §51.165(b)(2). [30 TAC 101.1] . Effects Screening Level (ESL). deline concentrations derived by the Texas Gui Commission on Environmental Quality ( ) and used to evaluate ambient air TCEQ concentrations of constituents. Based on a constituent’s potential to cause adverse health effects, odor nuisances, vegetation effects, o r materials damage. Health- based screening levels are set at levels lower than those reported to produce adverse health effects, and are set to protect the general public, including sensitive subgroups such as children, the elderly, or people with existing respiratory conditions. If an air concentration of a constituent is below the screening level, adverse effects are not expected. If an air concentration of a constituent is above the screening level, it is not indicative that an adverse effect will occur, but rather that further evaluation is warranted. Point of constituent emissions release into the air. Emission point. Facility. A discrete or identifiable structure, device, item, equipment, or enclosure that ncluding appurtenances other than emission constitutes or contains a stationary source, i control equipment. A mine, quarry, well test, or road is not considered to be a facility TAC 116.10). For the purpose of emissions inventory, the term does not refer to the (30 entire site but to individual proces s units at the site. Fugitive emission. Any gaseous or particulate contaminant entering the atmosphere that could not reasonably pass through a stack, chimney, vent, or other functionally equivalent opening designed to direct or control its flow. (30 TAC 1 01.1) . An area of agricultural or forest land, or some other undeveloped site Greenfield site. earmarked for commercial development or industrial projects. Level Concentration (GLC). Ground- in The concentration, commonly provided 3 micrograms per cubic meter ( μg/m ), as predicted by modeling. May also be observed by ambient air monitoring. 5 of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 110

11 Hazardous Air Pollutant (HAP). Any pollutant subject to a standard promulgated under 112 (relating t the Federal Clean Air Act ( FCAA ) section o hazardous air pollutants). Major. The term major may refer to the total emissions at a stationary source or to a specific facility. For PSD review, once a site or project is major for one pollutant, all other . 116.12(17) and (18) 30 TAC cance levels in pollutant’s emissions are compared to signifi • A named major stationary source is any source belonging to a list of 28 source categories in 40 CFR 52.21(b)(1) which emits or has the potential to emit 100 tons per year (tpy) or more of any pollutant regulated by the FCAA. major stationary source is any source not belonging to the 28 named -named An un • source categories which emits or has the potential to emit such pollutants in amounts of 250 tpy or more. any single HAP or 25 tpy • A major source is any source that emits 10 tpy or more of or more of any combination of HAPs under FCAA section 112(b). Used in the context of a PSD or Major modified stationary source or facility. major modified stationary source or facility Nonattainment permit application, the phrase refers to a change in operation that results in a significant net increase of emissions for pollutant. New sources at an existing major stationary source are treated as any regulated modifications to the major stationary source. and source Also, see the definitions of facility . The major NSR program contained in parts Major New Source Review (NSR) Program. C and D of title I of the FCCA is a preconstruction review and permitting program applicable to new major sources and major modifications at such sources . In areas meeting the NAAQS ( attainment areas ) or for which there is insufficient information to determine whether they meet the NAAQS ( unclassifiable a reas ), the NSR requirements under part C of title I of the FCA A apply. The Environmental Protection Agency (EPA) or calls this portion of the major NSR program the Prevention of Significant Deterioration ( ), the major NSR nonattainment areas PSD program. In areas not meeting the NAAQS program is implemented under the requirements of part D of title I of the FCCA. The EPA calls this program the "nonattainment" major NSR program. The EPA has promulgated rules in 40 CFR 52.21 to implement PSD in portions of the country that do not have approved state or tribal PSD programs. Major source baseline date. This is th e date after which actual emissions associated with physical changes or changes in the method of operation at a major stationary source affect the available increment. Changes in actual emissions occurring at any stationary source after this date contribut e to the baseline concentration until the minor source baseline date is established. minor may refer to the total emissions at a stationary source or to a Minor. The term for specific facility. To be minor for PSD review, the emissions must be less than 250 tpy named source and 100 tpy for a named source . To be minor for Nonattainment an un- review, the emissio ns must be less than the major source emission thresholds in 30 TAC 116. To be minor for HAPs review, the emissions must be less than 10 tpy for a single . (30 TAC 116) HAP or 25 tpy for multiple HAPs 6 of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 110

12 trigger fter the PSD increment This is the earliest date a Minor source baseline date. date on which a PSD application for a new major source or a major modification to an existing source is considered complete. The minor source baseline date is pollutant and geographically -specific. Modified stationary source or facility. • modified stationary source or When used in the context of modeling, the phrase facility refers to a change in the location or stack parameters of an emission point, including emission rate. phrase • When used in the context of a permit application, the modified stationary source or facility physical change in, or change in method of operation, refers to a that results in an increase of emissions. Levels of air quality to protect the National Ambient Air Quality Standards (NAAQS). d welfare (40 CFR 50.2). public health an Primary standards are set to protect public sensitive health, including the health of “ ” populations such as asthmatics, children, and the elderly from the effects of “criteria air pollutants” and certain non -criteria pollutants. Secondary standards are set to protect public welfare, including protection against decreased visibility, damage to animals, crops, vegetation, and buildings. A facility for which construction started after August 30, 1971, and no New facility. r construction was executed on or before August 30, 1971, and that contract contract fo 116.10). 30 TAC specified a beginning construction date on or before February 29, 1972 ( New source. Any stationary source, the construction or modification of which is started 116.10). r March 5, 1972 (30 TAC afte • When used in the context of modeling, the phrase new source refers to a proposed emission point. refers to a • When used in the context of a permit application, the term new source (30 TAC dified after March 5, 1972 stationary source that was constructed or mo 116.10). • When used in the context of a PSD or Nonattainment permit application, the term new source refers to the total proposed emissions for a greenfield site when the new source increase in emissions will be major. Or, refers to emissions at a minor stationary source when the increase in emissions will be major. . Nonattainment area Any area that does not meet (or that contributes to ambient air quality in a nearby area that does not meet) the national primary or secondary ambient air quality standard for a criteria pollutant. Project. An operational and/or physical change that may affect air emission rates at a site. Property. All land under common control or ownership coupled with all improvements on such land, and all fixed or movable objects on such land, or any vessel on the waters of 30 TAC this state ( 101.1). 7 of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 110

13 of an air pollutant that is allowed to PSD Increment. The maximum allowable increase occur above the applicable baseline concentration for that pollutant . in the Receptor. A location where the public could be exposed to an air contaminant ambient air. For the health effects evaluation process, receptors are classified as industrial or non- industrial. oducts or handling of raw . A receptor relating to the manufacturing of pr Industrial • materials or finished products without any associated retail product sales on property. • Non -industrial . A receptor type such as residential, recreational, commercial, or church. Other business, agricultural, or a school, hospital, day -care center, types include rights -of-way, waterways, or the like. In addition, receptors in unzoned or undeveloped areas may be treated as non- industrial. Refined model. An analytical technique that provides a detailed treatment of physical and chemical atmospheric processes and requires detailed and precise input data. Specialized estimates are calculated that are useful for evaluating source impact relative to air qualit y standards and allowable increments. The estimates are more representative than those obtained from conservative screening techniques. A relatively simple analysis technique to determine whether a Screening technique. given source is likely to pose a thre at to air quality. Concentration estimates from screening techniques are conservative. Significant Monitoring Concentration (SMC). EPA A de minimis level of impact that the has concluded does not justify collecting pre- oses of construction monitoring data for purp an air quality analysis. Single Property Line Designation (SPLD) . A legal agreement that allows two or more property owners to claim a single property line for consideration of their off -property impact for purposes of minor NSR analyses . Site. The area that encompasses all emission sources of constituents. Includes all entity facilities and other emission sources associated with the regulated number TAC 122.10). (30 Site -wide modeling. Modeling (refined or screening) of all emission points on a h the regulated Emissions from all entity number. contiguous property or associated wit , and authorization types except de minimis are included: permit by rule, standard permit new source review permit . Source. • A point of origin of air contaminants, whether privately or publicly owned or (30 TAC 116.10). Upon request of a source owner, the executive director operated shall determine whether multiple processes emitting air contaminants from a single ion will be treated as a single source point of emiss or as multiple sources 101.1). TAC (30 8 of - (APDG 6232v4 , Revised 09 /18) TCEQ Air Quality Modeling Guidelines Page 110

14 • For PSD and Nonattainment permit applications , source may refer to all emission points on a site or to a facility. refers t source When used in the context of modeling, the term • , o the release point volume, or area of emissions. Stationary source. refers to stationary source When used in the context of modeling, the term • emission points that are fixed and not mobile. For example, exhaust from a stack or baghouse is from a fixed point, and exhaust from a car is from a mobile source because the exhaust moves as the car does. • When used in the context of PSD and Nonattainment permit applications, the term refers to any building, structure, facility, or installation t stationary source hat emits or may emit any air pollutant subject to regulation under the FCAA (30 TAC 116.12). major modified stationary source and • Also see modified stationary source or facility or facility . min Trigger date. This is the date after which the PSD increment or source baseline date may be established. rea. Unclassifiable a Any area that cannot be classified on the basis of available information as meeting or not meeting the national primary or secondary ambient air quality standard for the pollutant. UTM is a widely used map projection Transverse Mercator projection (UTM). Universal that employs a series of identical projections around the world in the mid- latitude areas, each spanning six degrees of longitude and oriented to a meridian. This projection preserves angular relationships and scale plus it easily allows a rectangular grid to be superimposed on it. Many worldwide topographic and planimetric maps at scales ranging between 1:24,000 and 1:250,000 use this projection. 9 of - (APDG 6232v4 , Revised 09 TCEQ /18) Air Quality Modeling Guidelines Page 110

15 – Introduction Section I The Texas Commission on Environmental Quality (TCEQ or commission) manages air quality in the state of Texas by regulating the release of air contaminants through the Texas Clean Air Act (TCAA), located in Chapter 382 of the Texas Health and Safety Code (THSC), develops rules, including those in Title 30 of the Texas Administrative Code (TAC), and implements provisions of the Federal Clean Air Act (FCAA) and Code of Federal Regulations (CFR). Applications for projects subject to air quality impact s analyses are those with new and/or modified facilities or sources of emissions of air contaminants. The applicant must fully document the basis for air quality impact analysis determinations as it is the applicant’s responsibility to demonstrate that the permit should be issued. This document provides permit reviewers and air dispersion modeling staff with a process s analysis requirements for case- to evaluate and determine air quality impact by-case the focus of the document is on While permit reviews for new and/or modified facilities. the technical review process, it is available to the regulated community and the public to s analysis requirements and processes that provide an understanding of air quality impact affect air permit applications. During the c ourse of the technical review of an air permit application, the permit reviewer s analysis requirements and and air dispersion modeling staff evaluate air quality impact s analysis and confirm that the applicant has conducted an appropriate air quality impact properly determined off -property impacts for the project facilities and associated sources. The applicant’s air quality impacts analysis, along with the permit reviewer and air dispersion modeling staff’s evaluation and final recommendation, provide a record that demonstrates that the operation of a proposed facility will not cause or contribute to a condition of air pollution and will comply with all applicable federal and state rules and regulations, as well as with the intent of the TCAA. ocument provides a general process and defines minimum criteria for agency While this d staff’s consideration of air quality impacts analysis requirements, this document is not regulatory and does not limit the permit reviewer’s ability to require the applicant to This additional information could be related to comments ide additional information. prov received during the public notice or meeting process, coordination with Environmental o Protection Agency (EPA) or TCEQ staff on known areas of interest, or issues related t -property impacts (protection of public health). Permit reviewers and air dispersion off modeling staff may deviate from this guidance with approval from their supervisors or from the Air Permits Division (APD) director. ferences in term usage and term definitions between the Be aware that there are often dif state and federal regulatory agencies. Please refer to “Glossary of Acronyms and Symbols” and “Definitions” for additional clarification. of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 10 110

16 lyses II – Authority for Requesting Air Quality Impacts Ana Section The policy of the state of Texas and the purpose of the TCAA is “to safeguard the state's air resources from pollution by controlling or abating air pollution and emissions of air welfare, and contaminants, consistent with the protection of public health, general physical property, including the esthetic enjoyment of air resources by the public and the maintenance of adequate visibility” (THSC 382.002(A)). The TCEQ receives its authority for an air quality impacts analysis review through the TCAA and The TCAA requires air permit authorizations for new and/or the FCAA. modified facilities, including a demonstration that the operation of a proposed facility will not cause or contribute to a condition of air pollution and comply with federal requirements under the FCAA. , all construction permits and amendments for facilities require an Under 30 TAC 116.111 In addition, e air quality impacts analysis. ach proposed new major source or major sifiable area shall comply wit h 30 TAC 116.160. modification in an attainment or unclas The EPA has approved the Texas State Implementation Plan (SIP), making the TCEQ the The permitting authority for regulation of air emissions generated in the state of Texas. ource Review (NSR) Texas SIP, which is federally enforceable, includes Texas’ New S permitting programs for both major and minor sources, and these programs implement both the FCAA and the TCAA. The required permits are commonly referred to as -by-case,” or “NSR” permits and must be issued prior to construction. “construction,” “case Additional requirements Facilities must, at a minimum, comply with TCAA requirements. apply if a facility is subject to the permitting programs established in the FCAA. o receive any state Facilities must meet all applicable state rules and federal regulations t or federal air authorization. The applicant must address each of the air quality rules and If any regulations for applicability and explain the basis for expected compliance. particular rule or regulation is not applicable, the applicant must provide the basis for applicability. non- III – Air Quality Analysis Section in the that the proposed operation, as represented An applicant must demonstrate air permit application, would not cause or contribute to a National Ambient Air Quality dard (NAAQS) or Prevention of Significant Deterioration (PSD) Increment violation Stan and would be protective of public health, general welfare, and physical property. This red to as a protectiveness or impacts review or demonstration is commonly refer on. An air quality analysis (AQA) is the means for the applicant to make the evaluati demonstration. The AQA is an evaluation of the potential impact on the environment associated with increased emissions from a new and/or modified facility and can contain ation of air dispersion modeling and ambient air monitoring data. a combin Additional analyses required by federal rule would also be included in the AQA. of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 11 110

17 The AQA is a stand- alone report. Results from the report should be sufficient for staff to Staff evaluate the impact of the proposed operation without input from other reports. not refer to other documents or reports for data required to be in the report. In should without coordination with not exclude items normally required applicants should addition, the ), unless the items are clearly not applicable to ADMT Air Dispersion Modeling Team ( the project. Air Dispersion Modeling As stated above, an AQA may include air dispersion modeling (30 TAC 116.111(J)). Air dispersion models are tools to approximate concentrations from one or more facilities or When an air contaminant is emitted into the atmosphere, it is sources of air contaminants. transported and dispersed by various atmospheric processes. Algorithms and equations e atmospheric processes and have have been developed to approximate (model) thes been incorporated into various computer codes (computer models). Agency staff use the permit applications. A modeled results from these computer models in their review of air prediction alone does not mean that there will be a condition of air pollution, but it is one in the air permit application review process. of many indicators that agency staff considers However, a modeled prediction exceeding a standard or guideline value may be used as or allowable emission rates, stack parameters, the basis to modify proposed/existing rom the operation in order to demonstrate that the predicted impact f operating conditions is acceptable. Ambient Air Monitoring Occasionally, modeled predictions may not clearly indicate whether emissions from a site or individual facility could cause or contribute to a condition of air pollution. In those cases, the use of ambient air monitoring data in the technical review process may be an n to supplement modeled predictions. With few exceptions, the monitoring optio demonstration must be conducted before a permit is issued to ensure that permit conditions and allowable emissions are protective. An ambient air monitor captures a sample of air from the atmosphere. The sample is then analyzed to determine the amount (concentration) of air contaminants contained in the sample. The sample can be automatically analyzed at the monitor location (continuous ambient monitor station or CAMS) or taken to a laboratory to be analyzed (canister or filter sample). The air contaminants contained in a sample from an ambient air monitor come from air contaminant sources that are upwind of the monitor location, both manmade and natural. ay be immediately upwind, such as a combustion engine Some air contaminant sources m exhaust stack, or thousands of miles away, such as the Sahara Desert. The farther the upwind distance from the monitor, the longer the transport time from the source to the monitor, and the more the contaminants are dispersed before reaching the monitor. Ambient air monitoring is used to give an idea of what the air quality is at a specific location during a specific time period. Many samples over an extended period of time estimate ity to each other can provide a reasonable from many locations in proxim of the air quality over a region. of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 12 110

18 Air Quality Analysis Process The AQA process may involve a number of agency staff, depending on the complexity of the application and the potential impact of the proposed facilities or sources on air quality. The permit reviewer determines the scope of the AQA to be performed by the applicant t of other agency staff. Therefore, the applicant should contact the permit and involvemen ving other agency staff in the AQA process. reviewer for guidance before invol For all minor NSR AQAs, management recommends that a modeling protocol be submitted or a guidance meeting be held detailing the proposed approach to demonstrate For al l federal AQAs, a modeling protocol is compliance with all applicable requirements. A modeling required, and a copy of the modeling protocol must be sent to EPA Region 6. protocol or guidance meeting should include as many details, specifics, and support documents as applicable . Ideally, the AQA modeling protocol or guidance meeting When minutes would be identical to the final AQA report without any modeling results. provide as much detail to agency setting up a guidance meeting, the applicant should staff before or staff to prepare for the meeting. the meeting to allow sufficient time f Next, the applicant prepares and submits an AQA to the agency as part of an air permit conduct a technical ADMT application. Frequently, the permit reviewer requests that the he technical quality review, or audit, of an AQA. The purpose of the review is to evaluate t of the AQA to ensure the information and results can be used by agency staff in the that the technical review process. A key part of the review is ADMT ’s assessment predicted concentrations represent potential impacts and demonstrate compliance with . federal and state regulations evaluate the If the ADMT staff finds errors and/or discrepancies during the review, they errors and/or discrepancies to determine whether they would cause a significant change That is, whether the predicted in the magnitude or location of predicted concentrations. be representative and usable by agency staff to determine concentrations would still The ADMT should whether the permit should be issued. work closely with the permit reviewer and the applicant’s modeler to resolve omissions, unclear documentation, or other deficiencies. If the ADMT cannot resolve a modeling -related deficiency, then the modeling submittal is not accepted, and the ADMT forwards recommended corrective actions to the permit Then, the permit reviewer contacts the applicant to provide the deficiencies and reviewer. schedule to resolve them. Section IV – Conducting the Air Quality Analysis The AQA is an evaluation of the impact on the environment associated with increased emissions from a new and/or modified facility and is usually based on the predicted There are two levels of modeling used in the concentrations obtained through modeling. refined. Modeling results from either level, as appropriate, process: screening and AQA may be used to demonstrate compliance with standards or guidelines. of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 13 110

19 Screening Modeling The first level of modeling involves the use of screening procedures or models. Screening algorithms and conservative techniques to indicate whether more models use simple detailed modeling is necessary. Screening models are usually designed to evaluate a single source. Multiple sources can concentration from each source is then The maximum predicted be modeled individually. concentration. This technique summed for an overall estimate of the maximum predicted is conservative since the predicted concentrations from each source are added without regard to time and space . Refined Modeling The second level of modeli ng, refined modeling, requires more detailed and precise input data and more complex models in order to provide refined concentration estimates. The permit reviewer may determine that refined modeling is necessary if the screening analysis indicates that the predicted concentrations from the evaluated sources could exceed a standard, a guideline (such as an effects screening level), a de minimis level, or an agency staff -identified percentage of a standard or guideline. Modeling Emissions Inventory eling emissions inventory consists of the emissions from facilities to be The mod -property emissions. These emissions and off permitted, as well as other applicable on- are identified by emission point numbers (EPNs) but are usually referred to as sources in air d ispersion modeling guidance documents. Preliminary Impact Determination It is important to understand that individual facilities may be subject to different requirements depending on the contaminants and proposed emission rates of each There are facility. NSR two general categories of permits: major and minor NSR. The is often referred to as a federal permit or PSD permit. major NSR A PSD permit can be pollutants (those with NAAQS and PSD increments) and selected issued for criteria (those with significant emission rates but no NAAQS criteria pollutants non- ). Technically, permitting all TCEQ permits are federal in that the state must implement a minor NSR program to ensure the NAAQS and increments are attained. NSR The AQAs for major The purpose of a and minor NSR permits begin with a preliminary impact determination. preliminary impact determination is to determine whether a new and/or modified facility, or a combination of the two, could cause a significant off Either screening -property impact. or refined modeling can be used as appropriate. Below are general steps for identifying emissions to include in the preliminary impact determination. Identify All Sources of Emissions. Step 1: Include emissions from all new and/or modified facilities associated with the project. of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 14 110

20 Step 2: Determine Whether There Is a Net Emissions Increase. Determination of the ). project emissions may vary depending on the type of permit (minor NSR or major NSR The determination of the level of federal applicability is the first step in the technical review process and is performed by the permit reviewer . The federal applicability process While the steps of the modeling process determines whether a project is minor or major. are consistent, requirements vary based on the type of permit and contaminant. Note that the discussion below in terms of actual emissions refers to emissions used in modeling (the two years before the modeling demonstration) and may not be the same as that used in the federal applicability process. proposed allowable emissions from new Minor NSR: The permit reviewer e valuates facilities and allowable emissions increases and decreases from existing facilities directly associated with the permit application or project. emissions from new allowable Major NSR : The permit reviewer evaluates proposed facilities and emissions increases and decreases at any facility site- wide over a (minimum five -year period) . contemporaneous period Evaluate Modifications to Existing Sources Step 3: Carry out this step . at the Site NSR modeling, major For both minor and even if there is no net increase in emissions. include these sources in the preliminary impact determination if there is a change in operating hours or stack parameters, and previous modeling demonstrations were limited . T hat is, the permit was ed on those bas parameters to those operating hours or stack limits. In general, the statements below Step 4: Develop the Emission Inventory . for the Site are valid; however, the applicant should consult with the permit reviewer to verify that the appropriate emission rates were developed. New Facility: Minor NSR: The emission rate is the proposed allowable emission rate. Major NSR: The emission rate is the proposed allowable emission rate. Modified Facility: The emission rate is the difference between the proposed allowable NSR: Minor the current allowable emission rate. emission rate and For modified facilities that have not had a change in location or source parameters, this emission rate is the difference between the proposed allowable emission rate and the current allowable emission rate. For modified facilities that have a proposed change in location or source parameters, model the current allowable emission rates as a negative value with the current location and source parameters and the proposed allowable emission rates with the proposed location a nd source parameters. Include facilities that will be shut down permanently, not operating, or operating at a reduced rate as represented in the air permit application. These representations will be incorporated as enforceable permit limits. The NSR: Major emission rate is the difference between the proposed allowable For facilities identified in the emission rate and the actual emission rate. of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 15 110

21 he emission rate is the difference between the allowable contemporaneous period, t emission rate and the actual emis sion rate. For modified facilities that have not had a change in location or source parameters, this emission rate is the difference between the proposed allowable emission rate change in and the actual emission rate. For modified facilities that have a proposed location or parameters, model the actual emission rates as a negative value source parameters and the proposed allowable with the current location and source emission rates with the proposed location and source parameters. Include facilities that will be shut down permanently, not operating, or operating at a reduced rate as represented in the air permit application. These representations will be incorporated as enforceable permit limits. -term emission rat If the applicant has data on actual short es, then these data can be used to determine short -term emission rates over the representative appropriate averaging time period. If these data are not available, the short -term actual annual emission rat es. Using the emission rates can be derived from the derived short result in larger emission rates to model, -term emission rates may reasonable approach. which is a Step 5: Conduct Modeling. Carry out the preliminary impact determination modeling as discussed b indicated for the applicable modeling analysis elow. Minor NSR When a project does not trigger major NSR review or emits an air contaminant not subject to major NSR review, the minor NSR air quality analysis consists of the following elements and modeling as applicable: • NAAQS analysis; • State Property L ine Standard analysis; and Health Effects analysis. • Also known as effects screening level (ESL) analysis and includes consideration of welfare effects. Minor NAAQS Analysis The purpose of the Minor NAAQS analysis is to demonstrate that proposed emissions of criteria pollutants from a new facility or from a modification of an existing facility that does not trigger PSD review will not cause or contribute to an exceedance of the NAAQS. The demonstration may consist of both air dispersion modeling predictions and ambient air monitoring data. The person conducting the modeling should follow the basic procedure described in the following paragraphs. Minor NAAQS Step 1: Conduct a preliminary impact determination to predict whether hat is, the impact on existing air quality. T the proposed source(s) could make a significant model predicts concentrations at one or more receptors in the modeling grid greater than or equal to a NAAQS de minimis level (note for this document, the term de minimis and he use It should be noted that t icant impact level (SIL) are synonymous). the phrase signif SILs of interim or recommended will need to be justified. Refer to Appendix A for additional guidance . on justifying the use of the SILs of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 16 110

22 • Model all new and/or modified sources. Compare the predicted high concentration at or beyond the property line for each criteria pollutant and each averaging time to . The predicted high the appropriate NAAQS de minimis level in Appendix B concentration may be related to the form of the NAAQS (exceedance- or statistically -based) and the nu mber of years of meteorological data used. • If the sources do not make a significant impact for a pollutant of concern, the If there is a significant impact, then the significant demonstration is complete. an area of impact (AOI), and a full NAAQS analysis is required. ors define recept Go to Step 2. Minor NAAQS Step 2: Determine the AOI for each criteria pollutant and averaging period subject to the NAAQS analysis. • The AOI is the set of receptors that have predic ted concentrations at or greater than the de minimis level for each applicable averaging time and criteria pollutant. • The full NAAQS analysis is carried out for each criteria pollutant and averaging time separately and need only include the AOI for the ass ociated criteria pollutant and averaging time combination. -property sources will need to be evaluated. Off Minor NAAQS Step 3: One method is to sources and associated parameters from the TCEQ to obtain a listing of applicable . The Information Resources Division (IRD) should be contacted to AQA in the evaluate It is the responsibility this listing. request of the person conducting the modeling to obtain these data and ensure their accuracy. Any changes made to the data must be documented and justified. In a ddition, if the person conducting the modeling is aware of source data not provided by the IRD, such as recently issued permitted facilities or facilities in other states applicable within the distance limits of the model , the data should be included as applicable. Refer to Appendix C for additional guidance for requesting data from the IRD . Determine predicted concentrations over the AOI from all Minor NAAQS Step 4: sources and sources to be permitted using the same meteorological data set obtained in the preliminary impact determination modeling. Model allowable emission rates used ) PBR for all sources that emit the criteria pollutant. Use a certified limit for permit -by-rule ( authorizations. For PBRs without a certified limit, use an estimate of allowable emissions based on actual emissions. Use allowable emissions for standard permit authorizations. Minor NAAQS Step 5: Determine a representative monitored background concentration. As defined by the EPA, background air quality includes pollutant concentrations due to natural sources, nearby sources other than the one(s) under consideration, and for additional guidance Refer to Appendix D on determining a unidentified sources. representative monitored background concentration. Minor NAAQS Step 6: e the predicted concentration plus representative Compar monitored background concentration for each criteria pollutant and averaging time to the ). If the maximum concentrations are at or below the appropriate NAAQS (Appendix B If not, review the demonstration for conservatism complete. NAAQS, the demonstration is and determine if any refinements can be made, or demonstrate that the project’s impact will not be significant. of - (APDG 6232v4 , Revised 09 /18) TCEQ Air Quality Modeling Guidelines Page 17 110

23 Appendix E for additional guidance on conducting the Minor NAAQS analys is. Refer to State Property Line Standard Analysis The purpose of the state property line standard analysis is to demonstrate compliance with state standards for net ground- level concentrations. This analysis must demonstrate that resulting air concentrations from all on-property facilities and sources that emit the will regulated pollutant not exceed the applicable standard. property facilities should be evaluated, in many cases the proposed Although all on- emissions or changes in emissions may not be substantial when compared to the total emissions from the site. The person conducting the modeling should follow the basic procedure described in the following paragraphs. State Property Line Step 1: Conduct a preliminary impact determination by modeling the allowable em ission rates for all new and/or modified facilitie s that emit the applicable contaminant . with no other sources on site. I For new sources f the predicted high concentration • than the standard, the demonstration is complete. is equal to or less at the site . If the predicted high modified or only modified sources For new and • concentration is less than technical justification for two percent of the standard, demonstrating compliance may require additional information such as project emissions increases, total site emissions, results from previous site- wide modeling, or ambient air monitoring data. Refer to Appendix F for further discussion to determine if site- wide modeling is needed. • If the predicted high concentration is equal to or greater than two percent o f the standard, coordinate with the permit reviewer to determine if site- wide modeling is needed. Staff will consider factors such as project emissions increases, total site wide modeling, or ambient air monitoring emissions, results from previous site- dat for further discussion a. Refer to Appendix F to determine if site- wide modeling is needed. If site -wide modeling is required, go to Step 2. Model the allowable emission rates for all sources on the State Property Line Step 2: ified limit for PBR . Use a cert minant authorizations. For PBRs property that emit the conta without a certified limit, use an estimate of allowable emissions based on actual emissions. Use allowable emissions for standard permit authorizations. Compare the ). to the applicable state standard (see Appendix B predicted high concentration • If the predicted high concentration is less than or equal to the standard, the demonstration is complete. If the predicted high concentration is greater than the standard, review the • demonstration for conservatism and determine if any refinements can be made. F for additional guidance Refer to Appendix on conducting the State Property Line . analysis Standard of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 18 110

24 Health Effects Analysis The purpose of the Health Effects analysis is to demonstrate that emissions of non- criteria pollutants from a new facility or from a modification of an existing facility w ill be protective of the public’s health and welfare. toxicologists use the results from the Health Effects analysis to evaluate the Agency -by-contaminant basis. The objectives of the effects of emissions on a contaminant analysis are to: -property ground- level concentrations (GLCs) of contaminants Establish off • resu lting from proposed and/or existing emissions, and • Evaluate these GLCs for their potential to cause adverse health or welfare effects. Toxicology Division (TD) staff compare the GLC to an effects screening level (ESL). An ESL is a guideline, and not a standard. This format provides the flexibility required to easily revise the value to incorporate the newest toxicity data. Consult with the TD to used, to obtain additional information concerning ensure that the most recent ESLs are in the Toxicity Factor the basis for ESLs, or to obtain ESLs for contaminants not database , provide the chemical Toxicity Factor database the . For contaminants not in abstract service (CAS) registry number and a material safety data sheet (MSDS) to the itively identify the contaminant and derive an ESL. TD staff so that they can pos G for additional guidance on conducting the Health Effects analysis. Refer to Appendix PSD Air Quality Analysis The PSD program applies when a major source, that is located in an area that is designated as attainment or unclassifiable for any criteria pollutant, is constructed and/or criteria undergoes a major modification. The PSD program also applies to select non- pollutants. The air quality analysis consists of the following elements: • PSD NAAQS analysis; PSD pre • -application analysis; • increment analysis; PSD Additional impacts analysis; and • • Class I area analysis. PSD NAAQS Analysis The purpose of the PSD NAAQS analysis is to demonstrate that emissions of criteria pollutants from a new major source or major modification of an existing source will not cause or contribute to an exceedance of the NAAQS. The demonstration may consist of person both air dispersion modeling predictions and ambient air monitoring data. The conducting the modeling should follow the basic procedure described in the following paragraphs. PSD NAAQS Step 1: Conduct a preliminary impact determination to predict whether the the hat is, n existing air quality. T proposed source(s) could make a significant impact o of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 19 110

25 entrations at one or more receptors in the modeling grid greater than model predicts conc or equal to a NAAQS de minimis level for this document, the term de minimis and (note . It should be noted that the use the phrase SIL are synonymous) of interim or . Refer to Appendix A for additional guidance need to be justified will recommended SILs . on justifying the use of the SILs Model all new and/or modified sources. Compare the predicted high concentration • at or beyond the fence line for each criteria pollutant and each averaging time to the appropriate NAAQS de minimis level in Appendix B . The predicted high concentration may be related to the form of the NAAQS (exceedance- or statistically -based) and the number of years of meteorological data used. If the sources do not make a si • gnificant impact for a criteria pollutant of concern, the demonstration is complete. If there is a significant impact, then an AOI is defined, and a full NAAQS analysis is required. Go to Step 2. PSD NAAQS Step 2: Determine the AOI for each criteria pollutant and averaging period subject to the NAAQS analysis. • at or greater The AOI is the set of receptors that have predicted concentrations than the de minimis level for each applicable averaging time and criteria pollutant. arried out for each criteria pollutant and averaging The full NAAQS analysis is c • time separately and need only include the AOI for the associated criteria pollutant and averaging time combination. Off PSD NAAQS Step 3: -property sources will need to be evaluated. One method is to a listing of applicable sources and associated parameters from the TCEQ to obtain to re evaluate in the AQA . The IRD should be contacted this listing. quest It is the responsibility of the per son conducting the modeling to obtain these data and ensure their accuracy. Any changes made to the data must be documented and justified. In addition, if ce data not provided by the IRD , is aware of sour the person conducting the modeling facilities in other states such as recently issued permitted facilities or applicable within the distance limits of the model Refer to , the data should be included as applicable. Appendix C for additional guidance for requesting data from the IRD . PSD NAAQS Step 4: Determ ine predicted concentrations over the AOI from all obtained sources and sources to be permitted using the same meteorological data set used in the preliminary impact determination modeling. Model allowable emission rates for all sources that emit the regulated criteria pollutant. orizations. For Use a certified limit for PBR auth PBRs without a certified limit, use an estimate of allowable emissions based on actual emissions. Use allowable emissions for standard permit authorizations. PSD NAAQS Step 5: Determine a representative monitored background concentration. As defined by the EPA, background air quality includes pollutant concentrations due to natural sources, nearby sources other than the one(s) under consideration, and unidentified sources. for additional guidance on determining a Refer to Appendix D representative monitored background concentration. Compare the predicted concentration plus representative PSD NAAQS Step 6: monitored background concentration for each criteria pollutant and averaging time to the ). If the maximum c appropriate NAAQS (Appendix B below the oncentrations are at or of - (APDG 6232v4 , Revised 09 TCEQ /18) Air Quality Modeling Guidelines Page 20 110

26 NAAQS, the demonstration is complete. If not, review the demonstration for conservatism and determine if any refinements can be made, or demonstrate that the project’s impact will not be significant. Refer to Appendix E for additional guidance on conducting the PSD NAAQS analysis. -application Analysis PSD Pre application analysis is to provide an analysis of the existing The purpose of the PSD pre- ould affect. ambient air quality in the area that the major source or major modification w The analysis must be based on continuous air quality monitoring data. The person should follow the basic procedure described in the following conducting the analysis . Note that pre- construction and/or post paragraphs -construction monitoring could be required by the TCEQ. PSD Pre Compare the predicted concentration obtained from high -application Step 1: the applicable preliminary impact determination to the significant monitoring concentration (SMC) in Appendix B . • high concentrations obtained from For criteria pollutants, compare the predicted the NAAQS preliminary impact determination modeling demonstration to the SMC the SMC, the for the pollutant of interest. If the maximum concentration is less than the s or exceeds demonstration is complete. If the maximum concentration equal SMC, go to Step 2. For non- criteria pollutants, use the preliminary impact determination results from • demonstration. If the maximum concentration the appropriate minor NSR modeling is less t han the SMC, the demonstration is complete. If the maximum concentration the SMC, go to Step 2. equals or exceeds -application Step 2: PSD Pre Provide an analysis of the ambient air quality in the area that the project emissions would affect able averaging periods . for all applic For criteria pollutants, collect representative monitoring background concentrations • to establish the existing air quality for the area that the project emissions would affect. Refer to Appendix D for additional guidance on determining representative monitoring background concentrations. wide modeling from the minor NSR modeling criteria pollutants, site- For non- • demonstration may be sufficient for the pre- application analysis. If existing monitoring data are not available, or are judged not to be representative or conservative, go to Step 3. specific monitoring network. The applicant -application Step 3: PSD Pre Establish a site- should coordinate with the permit reviewer for determining the scope of monitoring and for preparation of a monitoring quality assurance plan. assistance in the pre-application H for additional guidance on conducting the PSD Refer to Appendix analysis. of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 21 110

27 PSD Increment Analysis The purpose of the PSD increment analysis is to demonstrate that emissions of applicable criteria pollutants from a new major source or major modification of an existing source will not cause or contribute to an exceedance of an increment. The PSD increment is the maximum allowable increase in concentration that is allowed to occur above a The person conducting the modeling should follow baseline concentration for a pollutant. the basic procedure described in the following paragraphs . The following discussion introduces and explains several terms that are specific to PSD increment analyses followed by the basic procedure for conducting the analysis. There are several dates that are used in the increment Baseline and Trigger Dates. analysis: This is the date after which actual emissions • Major source baseline date. associated with physical cha nges or changes in the method of operation at a major stationary source affect the available increment. Changes in actual emissions occurring at any stationary source after this date contribute to the baseline date is established. After the minor concentration until the minor source baseline source baseline date, new and modified major and minor stationary sources in the baseline area consume increment. • This is the date after which the minor source baseline date may be Trigger date. established. This is the earliest date after the trigger date on which source baseline date. Minor • a PSD application for a new major source or a major modification to an existing source is considered complete. - and The minor source baseline date is pollutant geographically -specific. minor Baseline area. The baseline area is established f or each applicable pollutant’s source baseline date by the submission of a complete PSD application and subsequent e areas and source impact analysis. The extent of a baseline area is limited to intrastat includes all portions of the attainment or unclassifiable area in which the PSD applicant would propose to locate, as well as any attainment or unclassifiable area in which the annual averaging proposed emissions would have a significant ambient impact for the period. The ambient concentration level that existed in the baseline Baseline concentration. area at the time of the applicable minor source baseline date. The baseline concentration is the reference point for determining air quality deter ioration in an area. The baseline concentration level is not based on ambient monitoring because ambient measurements reflect emissions from all sources, including those that should be excluded from the measurements. Increment does not need to be obtained to The baseline concentration calculation. determine the amount of PSD increment consumed or the amount of increment available. Instead, the amount of PSD increment that has been consumed in an attainment or unclassified area is determined from the emissions increases and decreases that have occurred from stationary sources in operation since the applicable baseline date. Modeled increment consumption calculations reflect the change in ambient pollutant concentration of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 22 110

28 sions. Increment consumption (or expansion) -affecting emis attributable to increment calculations are determined by evaluating the difference between the actual emissions at the applicable baseline date (Actual ) and actual emissions as of the date of the BD modeling demonstration (Actual ). MD -year average for long Actual -term emission rates, • . This is the representative two BD -year period immediately -term emission rate in the same two or the maximum short If little or no operating data are available, as in before the applicable baseline date. case of permitted sources not yet in operation at the time of the applicable the baseline date, the permit allowable emission rate as of the applicable baseline date is used. • Actual -year average for long . This is the most recent, representative two -term MD -term emission rate in the same emi ssions rates, or the maximum short two -year period immediately before the modeling demonstration. If little or no operating data are available, as in the case of permitted sources not yet in operation at the time of the incre is used. ment analysis, the permit allowable emission rate this analysis to limit the amount of research needed to A tiered approach is suggested for The person conducting the modeling should follow the determine actual emission rates. basic procedure desc ribed in the following paragraphs. PSD Increment Step 1: concentration (excluding high Determine whether the predicted background concentration) obtained in the PSD full NAAQS analysis is equal to or less the applicable increment. If yes, the demonst than ration is complete because all sources Note that Step 1 does not were modeled at allowable emission rates. If not, go to Step 2. apply for criteria pollutants with NAAQS that are statistically -based (i.e., multi -year average). PSD Increment Step 2: Determine the AOI for each criteria pollutant and averaging period subject to the PSD increment analysis. The AOI will be the same one used in the PSD NAAQS analysis, except for those criteria pollutants with NAAQS that are statistically -based. For criteri a pollutants with NAAQS that are statistically -based, determine the AOI following the convention of exceedance- based NAAQS (i.e., maximum predicted concentration). SILs It should be noted that the use of interim or recommended to determine the AOI will nee d to be justified. Refer to Appendix A for additional guidance on justifying the use of the SILs. Obtain a listing of applicable PSD Increment Step 3: -affecting sources and increment associated parameters from the TCEQ to evaluate in the AQA . The IRD should be to re of the person conducting the this listing. quest It is the responsibility contacted to obtain these data and ensure their accuracy. Any changes made to the data modeling is modeling In addition, if the person conducting the must be documented and justified. aware of source data not provided by the IRD, such as recently issued permitted facilities applicable within the distance limits of the model or facilities in other states , the data Refer to Appendix C should be included as applicable. for for additional guidance requesting data from the IRD . Adjust the emission inventory. PSD Increment Step 4: Omit any source from the inventory that has a negative emission rate unless the • source existed and was in operation at the applicable baseline date. A source must of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 23 110

29 have existed and been in operation on or before the applicable baseline date to be considered for increment expansion. • Omit any source permitted after the applicable baseline date that has shut down or that will be shut down as part of the current project . A source that did not exist or was not operating on or before the applicable baseline date would not have contributed to the air quality at that time, and there would be no need to model the source with an emission rate of zero. PSD Increment Step 5: Conduct the modeling demonstration using the same meteorological data set used in the determinat ion of the AOI using the following tiered approach, as applicable. Increment Modeling Tier I. Model all sources using their allowable emission rates. This approach is conservative since the increment is based on the entire allowable consumed emission rate. Compare the predicted high concentration to the appropriate increment B). If the increment is not exceeded, the demonstration is complete. Otherwise, (Appendix go to Tier II. Model selected sources with Actual Increment Modeling Tier II. emission rates and all MD other sources at allowable emission rates. The selected sources are usually the -property sources. applicant’s, since actual emission rates may be difficult to obtain for off consumed for the selected sources is based on This process assumes that the increment and the entire allowable emission rate for all other sources . the entire actual emission rate If the increment is not exceeded, the demonstration is complete. Otherwise, go to Tier III. Increment Modeling Tier III. Model selected sources that existed and were in operation at . and Actual between Actual the applicable baseline date with the difference BD MD • the applicable major source baseline date For major sources permitted at or before but not in operation as of the applicable minor source baseli ne date or for minor permitted at or before the applicable minor source baseline date but sources not in operation as of the applicable minor source baseline date, use the difference and the allowable emission rate. between Actual MD • For sources that existed at the applicable baseline date, where a change in actual emission rates involved a change in stack parameters, use the emission rates associated with both the applicable baseline date and the current and/or proposed as negative numbers along with the Actual source configuration. That is, enter BD the applicable baseline source parameters, and enter Actual for the same MD source as positive numbers along with the current and/or proposed source parameters. Use emission rates found in Tiers I or II for other • sources, as applicable. If the increment is not exceeded, the demonstration is complete. Otherwise, continue to refine increment emission rates or demonstrate that the project’s impact will not be significant. I for additional guidance on conducting the PSD increment analysis. Refer to Appendix of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 24 110

30 Additional Impacts Analysis The purpose of the Additional Impacts Analysis is to show that additional impacts from a new major source or major modification of an existing source will not im pair visibility, soils, and vegetation as a result of the emissions associated with the source or modification. Also, an analysis of the air quality impact projected for the area due to he existing source n of t growth associated with the new major source or major modificatio is required. The person conducting the modeling should follow the basic procedure described in the following paragraphs . The Additional Impacts Analysis consists of the following elements: Growth Analysis; • Visibility Impairment Analysis; and • Soils and Vegetation Analysis. • Each of these analyses is described in detail below. Growth Analysis • The analysis consists of estimating how much new growth (residential, industrial, commercial, and/or other growth) is likely to occur within the in the area (i.e. modeling domain) to support the major source or major modification under review, The and then estimate the emissions which will result from that associated growth. growth analysis shall also include an analysis of the air quality impact project ed for the area as a result of general residential, industrial, commercial, and/or other - An in growth associated with the major source or major modification under review. depth growth analysis is only required if the project would result in a significant shift in population and associated activity into the area (i.e. a population increase on the order of thousands of people). Visibility Impairment Analysis • The analysis consists of evaluating visual impairment from the project emissions within the modeling domain) . This analysis is distinct and within the area (i.e. analysis. The applicant can meet the separate from the Class I area visibility requirement for the Class II visibility impairment analysis by acknowledging compliance with the visibility and opaci ty requirements in 30 TAC Chapter 111. • Soils and Vegetation Analysis The analysis consists of evaluating the impact of the project emissions on soils and vegetation within the area . A good faith effort (i.e. within the modeling domain) site and verify with must be made to unde rstand the area surrounding the project other agencies (National Park Service, U.S. Forest Service, Texas Parks and Wildlife, etc.) the existence of sensitive soils and vegetation. For most types of soils and vegetation, ambient concentrations of criteria pollutants below the secondary NAAQS will not result in harmful effects. The impact on vegetation having no significant commercial or recreational value need not be addressed. of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 25 110

31 Class I Area Analysis A Class I area is an area defined by Congress that is afforded the greatest degree of air quality protection. Class I areas are deemed to have special natural, scenic, or historic value. The PSD regulations provide special protection for Class I areas. Little Maps deterioration of air quality is allowed. of all Class I areas , as well as other location information, are www.nps.gov/subjects/air/class1.htm located at the following link: The purpose of the Class I area analysis is to demonstrate that the project emissions will not have an adverse impact on any Class I area and not exceed Class I increments. The FCAA specifically addresses the prevention of visibility impairment and protect ion of air quality related values (AQRVs) regarding Federal Class I areas. The AQRVs are all those values possessed by an area that may be affected by changes in air quality, and include all those assets of an area whose visibility, significance, or integr ity are dependent upon the environment. Examples of AQRVs include: • visibility, odor, flora, fauna, and other geological resources; archeological, historical, and other cultural resources; and • soils and water quality resources. • criteria pollutants A Class I area analysis is required for all applicable criteria and non- from any new major source or major modification located within 10 kilometers (km) of a 3 hour average impact greater than 1 μg/m Class I area and would have a 24- . In addition, urce or major modification located within 100 km of a Class I area is any new major so required to perform an impacts analysis for the affected Class I areas. A Class I area analysis could be required for sources located more than 100 km from a Class I area if there is concern that the project emissions could cause an adverse impact on a Class I The person conducting the modeling should follow the basic procedure described in area. the following paragraphs . The Class I area analysis consists of the following elements: Class I area increment analysis; and • • Visibility and AQRV analysis. Each of these analyses is described in detail below. Class I Area Increment Analysis • -range transport (distances beyond 50 km) for An approach to address long purposes of assessing PSD increments can be used to determine if a significant ambient impact will occur on a Class I area. The person conducting the analysis should follow the basic procedure described in the following paragraphs. the near from predicted concentrations Use -field Class I Area Increment Step 1: application of the appropriate screening and/or preferred model to determine the significance of ambient impacts at or about 50 km from the new or modified t, If the new or modified source does not make a significant ambient impac source. the demonstration is complete. If the analysis indicates there may be significant ambient impacts at this distance, further analysis is necessary. Go to Step 2. of - (APDG 6232v4 , Revised 09 TCEQ /18) Air Quality Modeling Guidelines Page 26 110

32 For further analysis of assessing significance of Class I Area Increment Step 2: ambient impacts for PSD increments on a Class I area, there is not a preferred Therefore, consultation with the ADMT and model for distances beyond 50 km. EPA is needed to develop an approach for assessing ambient impacts. Chemical transport models (CTMs) can be used at this step and the model setup will need to be based on conservative techniques (e.g., do not include plume depleting processes) . If the new or modified source does not make a significant ambient impact, the demonstration is complete. If the analysis indicates there may be significant ambient impacts, go to Step 3. Class I Area Increment Step 3: Conduct a cumulative PSD increment analysis. For this analysis, the selection and use of an alternative model shall occur in oval from EPA following the requirements of agreement with the ADMT and appr paragraph 3.2.2(e) of the Guideline on Air Quality Models (GAQM). he demonstration of compliance with Class I area increment values is Note that t similar in procedure to the Class II area increment compliance dem onstration; several differences: however, there are The Class I increment analysis considers only the impact on Class I areas. • • The preliminary impact determination is performed with respect to the Class I area SILs. • The Class I area is the center point for the development of the emissions Class I area inventory for the cumulative s. increment analysi • increment values. The modeled results are compared to the Class I area Visibility and AQRV Analysis • coordinate with the appropriate Federal Land Manager (FLM) to Be sure to The FLM is the federal agency or the federal determine the scope of the analysis. official charged with direct responsibility for management of an area designated as the -application meetings between the applicant, TCEQ, and Pre a Class I area. affected FLM to discuss air quality concerns for a specific Class I area are encouraged. Given preliminary information, such as the source’s location and the types and quantity of projected air emissions, the FLM can discuss specific AQRVs, including visibility, for an area and advise the applicant of the analyses needed to assess potential impacts on these resources. Preferred Air Dispersion Models and Associated Inputs Section V – An air dispersion model is a simplification of the physical laws gover ning the dispersion and transport of contaminants in the atmosphere. The simplification is represented as a set of mathematical equations that require information describing a physical situation before the equations can be solved. The required information describing the physical situation is the source data, downwash applicability, receptor design, surface characteristics of the modeling domain, and meteorological data. When the model is run, the required information is read into the set of mathematical equations and then the of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 27 110

33 calculations are performed. The result would be the types of values the user desired to see, such as ambient air ground- level concentrations. person conducting the modeling should select the model that is appropriate for the The ion being conducted, as well as develop/acquire the input data associated with the evaluat . The basic procedure is described in the following paragraphs selected model . Preferred Air Dispersion Models In general, use the models and follow the modeling procedures i dentified in the GAQM. Although the GAQM was developed to address PSD and SIP modeling issues, the ADMT applies the general guidance contained in the GAQM to other modeling demonstrations in order to maintain a consistent approach for all projects. Refer t o Appendix J for additional guidance on preferred air dispersion models. Source Data Begin by clearly identifying and documenting all sources of emissions associated with the modeling analysis. are For each identified source, evaluate and discuss how emissions This discussion will be the supporting basis for the source generated and emitted. characterization used in the modeling analysis. Then determine and document the appropriate source parameters associated with the source characterization. ndix Refer to Appe K for additional guidance on characterizing sources. Downwash Applicability Downwash is a term used to represent the potential effects of a building on the dispersion of emissions from a source. Downwash is considered for sources characterized as poin t sources. The stack height and proximity of a point source to a structure can be used to determine the applicability of downwash. Downwash does not apply to s ources . Downwash is indirectly considered for volume sources by characterized as areas adjusting the initial dispersion factors. Point sources with stack heights less than good engineering practice (GEP) stack height should consider dispersion impacts associated with building wake effects (downwash). GEP stack height is the greater of (40 CFR § 51.100(ii)): ; level elevation at the base of the stack (1) 65 meters, measured from the ground- (2)(i) For stacks in existence on January 12, 1979, and for which the owner or operator , had obtained all applicable permits or approvals requir ed under 40 CFR parts 51 and 52 = 2.5H H g provided the owner or operator produces evidence that this equation was actually relied on in establishing an emission limitation; (ii) For all other stacks, H = H + 1.5L g Air Quality Modeling Guidelines TCEQ , Revised 09 /18) - (APDG 6232v4 Page of 28 110

34 , measured from the ground H -level elevation at the base is the GEP stack height where g of the stack ; H is the structure height , measured from the ground- level elevation at the L is the lesser of the structure height or maximum dimension ; and base of the stack projected width (the width as seen from the sour ce looking towards either the wind direction or the direction of interest) of the structure. ese s define the stack height above which building wake effects on the stack formula Th gas exhaust may be considered insignificant. A structure is considered suffic iently close to a stack to cause downwash when the minimum distance between the stack and the building is less than or equal to five times the lesser of the structure height or maximum projected width of the structure (5L). This ed to as the structure's region of influence. If the source is distance is commonly referr located near more than one structure, assess each structure and stack configuration separately. Once downwash applicability is determined, provide documentation to support that L for Appendix e for the modeling analysis, refer to If downwash is applicabl determination. additional guidance on developing downwash parameters. Receptor Design For modeling, receptors are locations where the model calculates a predicted concentration. Design a receptor grid with sufficient spatial coverage and density to determine the maximum predicted ground- level concentration in an off -property area or For NAAQS and PSD increment modeling, an area not controlled by the applicant. ea of de minimis impact. For example, if the model receptors should cover the entire ar predictions at the edge of the receptor grid are greater than de minimis, extend the receptor grid until the model predictions are less than de minimis. When designing a receptor grid, consider such factor s as: Results of screening analyses; • A source's release height; • • Proximity of sources to the property line; industrial receptors and ambient air monitors; and • Location of non- • Topography, climatology, and other relevant factors. In addition, the location of ambient air receptors should guide the design of the receptor grid. Ambient air for minor NSR modeling starts at the applicant's property line. If a single property line designation (SPLD) exists, then ambient air for minor NSR modeling starts y to federal ngle property line boundary. Note that the SPLD does not appl at the si reviews. For PSD modeling, ambient air starts at the applicant's fence line or other physical barrier to public access. Also, no receptors are required on the applicant's property because the air over an applicant's property is not ambient; therefore, in a regulatory sense, applicants cannot cause a condition of air pollution on their property from their own sources. of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 29 110

35 Generally, the spacing of receptors increases with distance from t he facilities being evaluated. Consider the following types of receptor spacing: • Spaced 25 meters apart. Tight receptors could extend up to Tight receptors . 200- 300 meters from the facilities being evaluated. Consider the distance between the facility and the property or fence line. • km one Spaced 100 meters apart. Fine receptors could extend . Fine receptors from each facility being modeled. . • ed 500 meters apart. Medium receptors could cover the Medium receptors Spac km from each facility. area that lies between one and five Coarse receptors . Spaced one km apart. This spacing could cover the area that • lies beyond the medium receptors out to 50 km. ations into air dispersion models in Universal Transverse Mercator Enter receptor loc (UTM) coordinates, in order to be consistent with on- and off -property source locations permit application, and other reference material, such as United represented in the air States Geolog ical Survey (USGS) topographic maps. Provide the datum used for UTM coordinates. Applicable UTM zones in Texas are either 13 (from the west border to 102 degrees longitude), 14 (between 102 and 96 degrees longitude), or 15 ( east of 96 degrees longitude to the east border). Do not use coordinate systems based on plant -developed coordinate systems. coordinates or other applicant Refer to Appendix M for additional guidance on developing receptor grids. Surface Characteristics of the Modeling Domain The modeli ng domain is the region that will influence the dispersion of the emissions from the facilities under review. Surface characteristics for the modeling domain should be Air dispersion models evaluated when determining representative dispersion coefficients. Dispersion utilize dispersion coefficients to determine the rate of dispersion for a plume. coefficients are influenced by factors such as land- use / land -cover (LULC), terrain, averaging period, and meteorological conditions. he modeling domain is an integral component to air Evaluating the LULC within t dispersion modeling. The data obtained from a LULC analysis can be used to determine The selection of representative dispersion representative dispersion coefficients. use types. coefficients may be as simple as selecting between rural or urban land- For more complex analyses, representative dispersion coefficients can be determined by parameters that are directly related to the LULC within the modeling domain. Evaluate the geography within the Dispersion coefficients are also influenced by terrain. modeling domain to determine how terrain elevations should be addressed. N for additional guidance on conducting a LULC analysis and terrain. Refer to Appendix of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 30 110

36 Meteorological Data The ADMT has prepared meteorological data sets for modeling demonstrations in order These data to establish consistency among modeling demonstrations across the state. sets are available by county for download from the ADMT Internet page. use of one year of meteorological data may be For minor NSR permit applications, the sufficient. However, if five years of meteorological data are used, then use the same five -year meteorological data for all applicable averaging periods for consistency. For recent, readily available five years of meteorological PSD demonstrations, use the most Provide an ASCII version of the data with the AQA submittal. data. Applicants may request to use other available meteorological data not available from the ADMT. If the request is approved, the applica nt is responsible for obtaining, preparing, Before these data sets are used in any modeling demonstration, and processing the data. the applicant should submit them to the ADMT. The ADMT should review and approve the data sets and all the data used to develop the specific meteorological parameters required. O for additional guidance on meteorological data. Refer to Appendix Section VI Reporting Requirements Include in the AQA a written discussion covering the project, the modeling performed, and . . This analysis should contain at least the items in Appendix P the results alone report. Results from the report should be sufficient to make a The AQA is a stand- decision without input from other reports. Do not refer to other documents or reports for to be in the report. In addition, do not exclude items without coordination data required with the ADMT, unless the items are clearly not applicable to the project. Follow the reporting requirements to expedite the technical review of the AQA and to eliminate unnecessary modeling. Send the AQA to the permit reviewer that requested the analysis. In addition, for PSD applications send a copy of the AQA to EPA Region 6. of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 31 110

37 – Justifying the Use of the Significant Impact Levels Appendix A ovide guidance for conducting an air quality analysis The purpose of this appendix is to pr SILs Significant Impact Levels ( ). The interim or recommended (AQA) when relying on tools that can be used to determine whether proposed emissions SILs are screening a National Ambient Air Quality Standard (NAAQS) or cause or contribute to a violation of a Prevention of Significant Deterioration (PSD) increment. Historic Use of SILs -specific The Environmental Protection Agency (EPA) has historically used pollutant , known as SILs , to i concentration levels dentify the degree of air quality impact that A proposed source causes or contributes to a violation of a NAAQS or PSD increment. can demonstrate that they do not cause or contribute to a violation by showing that the from the proposed source’s emissions would be less ambient air quality impacts resulting than the SIL concentration levels. These SIL values have served as a compliance demonstration tool to make the required demonstration in the PSD program. Conducting the Air Quality Analysis The AQAs for PSD and minor New Source Review (NSR) permits begin with a preliminary impact determination. The preliminary impact determination is an evaluation of the project emissions and the results are used to determine whether the project gnificant ambient air impact. If the project emissions do not emissions could cause a si make a significant impact for a pollutant of concern, the demonstration is complete. The EPA has codified several SILs into regulations at 40 Code of Federal Regulation (CFR) 51.165(b). However, criteria pollutants/averaging times that do not have there are The EPA has developed interim and recommended SILs, and has a SIL codified. provided guidance on their use until formal rulemaking can be pursued. -hour Nitrogen Dioxide and 1 Interim SILs for 1 -hour Sulfur Dioxide ) that became effective The EPA promulgated a 1- hour NAAQS for nitrogen dioxide (NO 2 ) sulfur dioxide (SO NAAQS for on April 12, 2010. The EPA also promulgated a 1-hour 2 that became effective on August 23, 2010. e for the The EPA provided guidanc implementation of these two standards for the PSD program (see memoranda titled, NAAQS for the Prevention “Guidance Concerning the Implementation of the 1- hour NO 2 of Significant Deterioration Program,” dated June 29, 2010 and “Guidance Concerning the NAAQS for the Prevention of Significant Deterioration Implementation of the 1- hour SO 2 Program,” dated August 23, 2010). The guidance set forth interim SILs that could be used when conducting the required air quality analyses. SILs were derived using an impact equal to four percent of the respective The interim . The EPA used a threshold of four percent in order to be consistent with NAAQS 1-hour (SERs) how were defined for pollutant s subject to PSD significant emission rates (45 particulate The EPA defined SERs for Register 52676, August 7, 1980). Federal of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 32 110

38 matter ( PM ) and SO as the emission rate that resulted in an ambient impact equal to four 2 interim The values are: SIL 1-hour percent of the applicable short -term NAAQS. 3 ) • NO : 4 ppb (7.5 μg/m 2 3 SO ) : 3 ppb (7.8 μg/m • 2 To support the use of the interim SILs, the documentation associated with the AQA should include a discussion on why it is reasonable to use the interim SILs in the analysis, t set forth the interim SILs. along with copies of the EPA guidance memoranda tha Recommended SILs for Particulate Matter -2.5 and Ozone The EPA promulgated SILs for PM in 2010 (75 Federal Register 64864, 2.5 October 2010). However, the U.S. Court of Appeals vacated and remanded 40 CFR 20, 51.166(k)(2) and 52.21(K)(2) based on EPA’s lack of authority to exempt sources from the requirements of the Federal Clean Air Act (FCCA) when it established SILs for PM 2.5 Following (Sierra Club v. U.S. EPA, Docket No. 10- 1413, D.C. Circuit, January 22, 2013). , but for ozone litigation, the EPA conducted further evaluations for not only PM ) as (O 2.5 3 well given a need, expressed by multiple stakeholders, for the EPA to develop SIL values to . As a result of these evaluations, the EPA developed a new analytical approach for O 3 identify a SIL for each he PSD increments (see t NAAQS and the PM and PM O 2.5 3 2.5 guidance memorandum from EPA titled, “Guidance on Significant Impact Levels for Ozone and Fine Particles in the Prevention of Significant Deterioration Permitting 201 Program,” dated April 17, 8). The new analytical approach is referred to as the air quality variability approach and is based on identifying and quantifying an insignificant impact on air pollutant concentrations based on an assessment of the variability of air quality using data from the ambient PM 2.5 and O monitoring network. Due to fluctuating meteorological conditions and changes in 3 day -to-day source operations, there is an inherent variability in the air quality in the area of a monitoring site. Using a sta tistical framework , the EPA quantified the variability and a value for a concentration difference that is meaningful in the context of determined inherent variability. Changes of less than the value may be considered to be in the noise gn values. The analysis provides a basis to conclude that of the observed desi concentration increases below the value (or SIL ) do not cause or contribute to violations The recommended SIL values are: of the relevant NAAQS or PSD increments. 3 ; : 24 -hour – 1.2 μg/m • PM 2.5 3 Annual – 0.2 μg/m 3 ) : 1 ppb (1.96 μg/m O • 3 3 . The derived is 1.2 μg/m hour PM he recommended SIL value for 24- As noted above, t 2.5 3 air quality variability approach value from the μg/m is 1.5 . However, 40 CFR ambient 3 as the SIL value for the 24- Pending NAAQS. hour PM 51.165(b)(2) lists 1.2 μg/m 2.5 3 further evaluation by EPA, the value of 1.2 μg/m is recommended in order to be consistent with the rule. of - (APDG 6232v4 , Revised 09 TCEQ /18) Air Quality Modeling Guidelines Page 33 110

39 3 is less than the SIL value of 0.3 μg/m The recommended SIL value for annual PM 2.5 an impact memorandum, listed in 40 CFR 51.165(b)(2). As noted in the EPA guidance 3 less than 0.2 μg/m , based on the ambient air quality variability approach, is insignificant and should be considered to not cause or contribute to a violation of the annual PM 2.5 e the discretion to NAAQS. The memorandum also notes that permitting authorities hav 3 3 determine on a case- by-case basis whether an impact between 0.2 μg/m and 0.3 μg/m Be sure to discuss with NAAQS. will cause or contribute to a violation of the annual PM 2.5 3 3 the ADMT if an impact between 0.2 μg/m , prior to submitting an AQA, will and 0.3 μg/m determine significance of the project emissions. be proposed to be used to SILs, the documentation associ To support the use of the recommended ated with the SILs in AQA should include a discussion on why it is reasonable to use the recommended the analysis, along with a um that set forth the y of the EPA guidance memorand cop recommended SILs. of - (APDG 6232v4 , Revised 09 /18) TCEQ Air Quality Modeling Guidelines Page 34 110

40 Appendix B - Federal and State Air Quality Standards The tables below list contaminants that are specifically regulated by federal or state rules by a limit on the concentration in ambient air. The table lists the pollutant name, applicable averaging time, the type of standard, and the threshold concentration. When performing an air quality analysis (AQA), all applicable standards are to be addressed. The source of the information for the tables is as follows: Texas Commission on for this document, the term Environmental Quality (TCEQ) de minimis levels (note minimis and the phrase significant impact level (SIL) are synonymous) are listed in de Code of Federal Regulation ( 40 CFR) 51.165(b)(2); Significant Monitoring Concentrations CFR 52.21(i)(5)(i); Primary and Secondary National Ambient Air are listed in 40 (SMCs) Quality Standards (NAAQS) and form of the standard are listed in 40 CFR 50; Prevention of Significan s for Class I and Class II areas are listed in t Deterioration (PSD) Increment Texas Administrative 40 CFR 52.21(c); and State Property Line Standards are listed in 30 -1 (see SILs are included in table B Interim and recommended 112. ) Chapter TAC Code ( footnotes b and c) and the source of information for these values are from Environmental references are noted emoranda to the EPA m Protection Agency (EPA) memoranda. The beneath table B -1. of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 35 110

41 Table B -1. Criteria Pollutants Secondary Class I Class II Primary Averaging SIL SMC Pollutant 3 3 Increment NAAQS NAAQS Increment Time (μg/m ) (μg/m ) 3 3 3 3 (μg/m (μg/m ) (μg/m ) ) (μg/m ) Carbon 40,000 2,000 - 1-Hour - - - Monoxide Carbon 8-Hour 500 575 10,000 - - - Monoxide - Rolling 3 a - - 0.1 Lead month 0.15 0.15 - average Nitrogen b - 1-Hour 7.5 - - 188 - Dioxide Nitrogen 2.5 25 Annual 1 100 100 14 Dioxide 137 137 1.96 Ozone - - - 8-Hour c 70 ppb) (1 ppb) ( 70 ppb) ( Particulate Matter 8 30 150 24-Hour 5 10 150 (PM ) 10 Particulate 4 Matter 17 - - - Annual 1 (PM ) 10 Particulate c Matter 9 35 35 - 24-Hour 1.2 2 ) (PM 2.5 Particulate c Matter 4 15 12 - 1 0.2 Annual (PM ) 2.5 Sulfur b - - 1-Hour 7.8 - - 196 Dioxide Sulfur 25 512 3-Hour 25 - - 1,300 Dioxide Sulfur d - 13 365 5 5 24-Hour 91 Dioxide Sulfur d - 1 2 - 20 Annual 80 Dioxide month average and not a rolling 3-month average a - The SMC for lead is based on a 3- b - Interim SIL ( www.tceq.texas.gov/assets/public/permitting/air/memos/guidance_1hr_no2naaqs.pdf for 1 -hour NO 2 for 1 www.tceq.texas.gov/assets/public/permitting/air/memos/appwso2.pdf and -hour SO ) 2 c - Recommended SIL d - EPA revoked both the existing 24-hour and annual standards; however, they will remain in effect until one year after the effective date of the 1-hour SO for 1 . Refer to 40 CFR 81.344 designations designations. -h our SO 2 2 36 - (APDG 6232v4 Page 110 Air Quality Modeling Guidelines /18) of , Revised 09 TCEQ

42 -Criteria Pollutant s with a Significant Monitoring Concentration -2. Non Table B SMC Pollutant Averaging Time 3 ) (μg/m a Fluorides 24 - Hour 0.25 Hydrogen Sulfide 1 - Hour 0.2 10 Hour - Reduced Sulfur Compounds 1 10 1 - Hour Total Reduced Sulfur a - Fluorides does not include hydrogen fluoride Table B -3. State Property Line Standards Value Pollutant Averaging Time County Land Use 3 (μg/m ) Residential, business, or commercial a Hydrogen Sulfide 30-Minute 108 All Counties purposes (in general, industrial areas) - non a - Minute Hydrogen Sulfide All Counties 30 All other land uses 162 a 30 - Minute Sulfur Dioxide Galveston and Harris All land uses 715 a Jefferson and Orange 817 All land uses Sulfur Dioxide 30 - Minute a 30 - Minute Remaining Counties All land uses 1,021 Sulfur Dioxide Sulfuric Acid 1 - Hour All Counties All land uses 50 15 All Counties All land uses Sulfuric Acid 24 - Hour a - The 1-hour averaging time is used given that the shortest averaging time for the preferred models typically used for averaging time. regulatory demonstrations is the 1-hour of - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines TCEQ Page 37 110

43 Requesting Information from the Air Permits Allowable Appendix C - Database If staff or applicants need emissions data for an air quality analysis (AQA), they should request this information from the Information Resources Division (IRD) by filling out and submitting an Air Permits Allowable Database (APAD) Modeling Retrieval Request Form. This form may be obtained at the following link: www.tceq.texas.gov/permitting/air/guidance/newsourcereview/nsr_mod_guidance.html Allow ten business days for the IRD to provide the retrieval information. Provide the following information with the request: ignificant ) and Prevention of S For National Ambient Air Quality Standard (NAAQS Deterioration (PSD) i ncrement retrievals, provide the center point, in Universal Transverse Mercator (UTM) coordinates in North American Datum of 1983 (NAD83), of the radius of impact (ROI); UTM easting • UTM northing • • UTM zone The coordinates include the UTM easting (meters), UTM northing (meters), and UTM zone. The retrieval program will automatically take care of any overlap from one zone to another. For the UTM zone, use either 13 (from the west border to 102 degrees de), 14 (between 102 and 96 degrees longitude), or 15 (east of 96 degrees longitu longitude to the east border). For the requested pollutant, this information is used by the retrieval program to locate all sources that are within 50 kilometers (km) of the specified center point. A radius of 50 km -state assumptions are appropriate. is based on transport distances over which steady Steady -state assumptions are fundamental to Gaussian air dispersion models used for regulatory purposes. Check the type of reports desired; • By pollutant By averaging time • • By review type (NAAQS or PSD i ncrement) For Particulate Matter (PM • ) or less, also request a retrieval for Particulate Matter 2.5 (PM ) or less 10 review type. For NAAQS or PSD i ncrement, as The selection of pollutant depends on the NO applicable, identify the pollutant using carbon monoxide (CO), nitrogen oxides ( ), x ), PM sulfur dioxide (SO , or lead (Pb). , PM 2 10 2.5 Indicate the averaging time of interest. The averaging times to select from depend on the review type and pollutant combination. For example, for NO , the relevant averaging x 1-hour and annual and for PSD i times for NAAQS are ncrement, annual only. If you do not specify an averaging time, the retrieval will include all relevant averaging times. of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 38 110

44 Indicate the type of req uest: NAAQS and/or PSD i ncrement. , The term NAAQS pertains to criteria pollutants and indicators, e.g. CO, SO , PM , NO 2 10 x PM . , PM , and PM , and Pb. PSD i ncrement retrievals are available for NO , SO 2.5 10 2.5 x 2 For each pollutant, averaging time, and review t ype combination, the retrieval program generates an electronic file with data for all sources, including area sources, meeting the search criteria with the modeling parameters placed in the proper format for use with certain Environmental Protection Agency PRIME, (EPA) models including AERMOD, ISC- and ISCST3. Submit the APAD Modeling Retrieval Request F orm: • Mail the form to: Information Resources Division, MC 197 Attn: Open Records & Reporting Services TCEQ PO Box 13087 3087 Austin TX 78711- Submit request and form through online Open Records Request Form • Call 512/239- DATA (3282) • What the requestor will receive: -ready text file • Model for each pollutant, averaging time, and review type combination requested. o All sources (POINT and AREA) listed in APAD within 50 km of a UTM coordinate provided in the request are included. Source identifiers are the unique source identifier listed in AP AD. o • listing all sources included in the retrievals with their associated Summary Report number, regulated entity number (RN), emission point number (EPN), permit source location, source emission rate by pollutant, and source parameters. AD: What data are in AP Data were migrated into APAD in three phases: Source IDs (EPNs), source parameters (including locations), permit allowable • emission rates (by pollutant), and permit number for effective permits from the point source database (PSDB); • Source IDs and sour ce parameters for active sources from the State of Texas Air Reporting System (STARS); and • For active sources that reported emissions of criteria pollutants, if there was no an allowable record of an allowable emission rate, those sources were assigned ssion rate of 0 emi pounds per hour (lb/hr) and 0 tons per year (tpy) for the reported pollutants. of - (APDG 6232v4 , Revised 09 TCEQ /18) Air Quality Modeling Guidelines Page 39 110

45 Now that the data migration is complete, data in APAD are currently being supplemented through data entry of permit information listed in Maximum Allowable Emiss ion Rate Tables (MAERTs), with priority given to permits for major sources of criteria pollutants. What data gaps exist in APAD: As it was not initially possible to populate APAD with all allowable emission rates for all sources, some cases of missing or i nconsistent data have been encountered in the database. The issues related to the data gaps are: • EPNs on MAERTs not matching the source identifiers listed in PSDB or STARS; • Pollutant names on MAERTs not matching pollutant names listed in PSDB or STARS; • EPNs with no associated permit number; EPNs with missing or invalid source parameters; and • EPNs with missing or invalid coordinates. • The supplemental data entry continues to eliminate many of the data gaps, but some data are still missing. Indicators of missing data are: • -.” These indicate that a dummy permit number Permit numbers beginning with “D was assigned to the EPN. • Allowable emission rate being 0 lb/hr or 0 tpy. These indicate that actual emissions of this pollutant were reported for the EPN, but there is no record of an allowable emission rate. It is the applicant’s responsibility to research and determine the appropriate emission rate values for these sources. (See What to do about data gaps in APAD below) . Missing or invalid source parameters have been filled in the following way. For missing or invalid parameters for type “STACK”: • o Height = 1.0 meter Temperature = 0 Kelvin o o Velocity = 0.001 meters/second Diameter = 0.001 meters o • For missing or invalid parameters for type “FLARE”: o Height = 1.0 meter o meters Diameter = 0 of - (APDG 6232v4 , Revised 09 /18) TCEQ Air Quality Modeling Guidelines Page 40 110

46 For missing or invalid parameters for type “FUGITIVE”: • Height = 1.0 meter o o Length = 1.0 meter Width = 1.0 meter o o Degree = 0 • These sources have been assigned the Missing or invalid source coordinates. coordinate of the site centroid or coordinate provided on the agency Core Data Form for the site. What to do about data gaps in APAD: to As was the case with data retrievals from PSDB, it is the applicant’s responsibility correct any data in error and provide any supplementary data that may be necessary in performing their AQA. Any corrections to the data must be accompanied with documentation that Air Permits Division (APD) staff can validate. Much of the data y to fill in data gaps are contained in the paper files located in Central Records at necessar the Texas Commission on Environmental Quality (TCEQ). However, there are on- line data sources applicants are encouraged to use: • Site emission inventory data access by Reg ulated Entity reference number at www15.tceq.texas.gov/crpub/index.cfm?fuseaction=regent.RNSearch to access permit documents, like the MAERTs, at • Central Records search records.tceq.texas.gov/cs/idcplg?IdcService=TCEQ_SEARCH Validated data corrections will be loaded in APAD as appropriate. As corrections are made, the data quality will improv e. Staff and applicants are not limited to using only APAD as a data source. If the applicant is aware of data not contained in APAD, such as recently issued permitted facilities, shut down facilities, or facilities in other states, the data should be incl uded as applicable. All changes to data must be documented. 1250 if you have Contact the Air Dispersion Modeling Team (ADMT) at (512) 239- questions about how to use the retrievals for the AQA. of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 41 110

47 ons Representative Background Monitoring Concentrati Appendix D – The purpose of representative background monitoring concentrations is to account for sources not explicitly modeled in an air dispersion modeling analysis. Most air dispersion modeling analyses only account for industrial stationary emission sources; t herefore, additional information needs to be used to account for other emission sources such as natural sources, nearby sources other than the one(s) under consideration, and tive unidentified sources. Ambient air quality monitors are used to provide representa entrations for a project site. background conc Ideally, a network of monitors would be available to provide concentrations near the site of the permit application. The term “near” means within about one kilometer (km) of the ons from existing sources or the area of the combined area of maximum concentrati maximum impact from existing and proposed sources. However, existing monitors within 10 km of the proposed sources can also be used. Unfortunately, data from nearby monitors are rarely available; furthermore, time and cost constraints usually prohibit the . Applicants and staff should use the following establishment of site- specific networks guidance to determine an appropriate monitor to represent air quality at the project site. This procedure can be us ed for National Ambient Air Quality Standards (NAAQS) and -application analyses. pre Existing Ambient Monitoring Data for the County -specific ambient air monitoring data are not available and an ambient air monitor is If site located in the same county as t he project site, use the most recent data from the nearest ambient air monitor. Justify why the monitoring data are representative for the air quality in the area of the project site. or selected is If there are multiple monitors in the same county, justify why the monit conservative or representative of the area the project would affect. For example, if the nearest monitor is located in an urban area surrounded by many industrial sources but the project sources are located in a rural area with no surrounding sources, the argument could be made that the air quality by the nearest monitor is indicative of a pollutant “hot spot” and not of the regional air quality around the project sources. The use of this monitor may be considered conservative and the type of documentation to support this claim could be aerial photography of the two locations. However, if the use of the nearest monitor in the example above is too conservative, a more representative monitor from the same county may be used. The type of document ation to support the use of the selected monitor could be aerial photography of the two locations. of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 42 110

48 The documentation to support the selected monitors in the above examples was based sessment on a qualitative assessment. Some cases may require a more quantitative as that could include an analysis of the source of emissions surrounding the two locations (project sources and monitor). For example, the types of sources in the vicinity of each c. An assessment location, the magnitude of reported emissions, allowable emissions, et out to 10 km from each location should be sufficient. Detailed actual emissions data from the Point Source Emissions Inventory may be obtained at the following link: -source -ei/psei.html www.tceq.texas.gov/airquality/point No Existing Ambient Monitoring Data for the County If there are no existing monitoring data for the county where the projec t is located, monitoring data from an adjacent county may be used. Justify why the reported concentrations are conservative or representative of the area the project would affect. If there are no existing monitoring data for an adjacent county, then monitoring data from another county may be used. Justify why the reported concentrations are representative of the area the project would affect. For example, the nearest ambient air monitor is located over 80 km and two counties over from the project. The project is the only major source in its county. The monitor over 80 km away is in close proximity to several major sources. The monitoring data from this monitor may be used provided the justification ces would be no higher in an would be the air quality in the area near several major sour area that only has one major source. The type of documentation to support this claim include comparing county emissions, county population, categories of source emissions ons surrounding the location of for each county, and a quantitative assessment of emissi monitor compared to the project site, etc. Emissions data can be obtained at the following url: -inventories/national www.epa.gov/air -emissions and -emissions -inventory -nei -inventories -emissions www.epa.gov/air Population data can be obtained at the following url: www.census.gov/programs -surveys/popest.html Once an appropriate monitor has been selected to represent the air quality of the project Begin by obtaining site, the representative background concentration is determined. ambient monitoring data and corresponding documentation from the Environmental Protection Agency (EPA) AirData website at the following url: www.epa.gov/outdoor -air -quality -data is a good source to obtain representative background concentrations The EPA AirData since it contains current monitoring data and reports both the exceedance and -based values. statistically Monitoring data may also be obtained from the Texas Commission on Environmental Quality’s (TCEQ’s) Texas Air Monitoring Information System (TAMIS) Web Interface located at the following url: www17.tceq.texas.gov/tamis/ The monitoring data from TAMIS are the same monitoring data that are in the EPA -based values are not readily available. AirData; however, the statistically of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 43 110

49 A third option is to obtain monitoring data from the TCEQ’s yearly summary reports at the following url: -bin/compliance/monops/select_year.pl www.tceq.texas.gov/cgi Depending on the pollutant and averaging time being evaluated, the representative background concentration may be in the form of the standard (exceedance- or statistically -based). Note that any higher monitor rank may be used as a background concentration. That is, the high, first high (H1H) monitored concentration could be used instead of the high, second high (H2H) monitored concentration, since the H1H monitored on would be higher and thus more conservative: concentrati • Carbon Monoxide (CO) - Select the H2H monitored concentration from the most recent complete year for the 1- hour and 8- hour averaging times. o A year meets data completeness criteria if at least 75 percent of th e hours in a year are reported. month average value that encompasses the Lead (Pb) - Select the highest rolling 3- • most recent 38- month period of complete data for a monitori ng site (i.e., the most . recent three- year calendar period plus two previous months) rolling 3 o The -month average is considered complete if the 3-month data capture rate is greater than or equal to 75 percent. Nitrogen Dioxide (NO • ) 2 o 1-hour averaging time - Select the most recent three -year average of the annual 98th percentile daily maximum 1 -hour values that encompasses three consecutive calendar years of complete data for a monitoring site.  A year meets data completeness criteria when all four quarters are complete. A quarter is complete when at least 75 percent of the sampling for each quarter have complete data. A sampling day has complete days -flagged data if 75 percent of the hourly concentration values, including State data affected by exceptional events which have been approved for exclusion by the Administrator, are reported. Annual averaging time o - Select the annual monitored concentration from the most recent complete year for the annual averaging time.  A year meets data completeness criteria when 75 percent of the hours in a year are reported. ) - Select the most year average of the annual fourth- three- recent Ozone (O • 3 highest daily maximum 8- hour average that encompasses three consecutive calendar years of complete data for a monitoring site. The completeness criteria is met for the three o f -year period at a monitoring site i daily maximum 8- hour average concentrations are available for at least 90% of -year monitoring season, on average, for the three the days within the O 3 period, with a minimum data completeness criteria in any one year of at least monitoring season. 75% of the days within the O 3 Air Quality Modeling Guidelines TCEQ , Revised 09 /18) - (APDG 6232v4 Page of 44 110

50 o Years with concentrations greater than the level of the standard shall be included even if they have less than complete data. Thus, in computing the hour average three- year average fourth highest daily maximum 8- concentration, calendar years with less than 75% data completeness shall be included in the computation if the three -year average fourth- highest daily maximum 8 -hour concentration is greater than the level of the standard. • Particulate Matter (PM ) - Select the H2H monitored concentration for the 24- hour 10 averaging time that encompasses the most recent three consecutive calendar years of complete data for a monitoring site. o A year meets data completeness criteria if at least 75 percent of the scheduled PM samples per quarter are reported. 10 Particulate Matter (PM • ) 2.5 24- Select the most recent three- year average of the o hour averaging time - hour values that encompasses three annual 98th percentile of the 24- consecutive calendar years of complete data for a monitoring site.  A year meets data completeness criteria when at least 75 percent of the scheduled sampling days for each quarter have valid data. o -year average of the - Select the most recent three Annual averaging time annual monitored concentrations that encompasses three consecutive calendar years of complete data for a monitoring site.  A year meets data completeness criteria when at least 75 percent of the scheduled sampling days for each quarter have valid data. ) • Sulfur Dioxide (SO 2 - Select the mos 1-hour averaging time -year average of the t recent three o annual 99th percentile daily maximum 1- hour values that encompasses three consecutive calendar years of complete data for a monitoring site.  A year meets data completeness criteria when all four quarters are complete. A q uarter is complete when at least 75 percent of the sampling days for each quarter have complete data. A sampling day has complete -flagged data if 75 percent of the hourly concentration values, including State data affected by exceptional events which have been approved for exclusion by the Administrator, are reported. 3-hour averaging time o - Select the H2H monitored concentration for the 3- hour averaging time from the most recent complete year. A year meets data completeness criteria provided that at least 75 percent of  the hourly data are complete in each calendar quarter. Select the H2H monitored concentration for the o hour averaging time - 24- 24- hour averaging time from the most recent complete year. A year meets data completeness criteria provided that at  least 75 percent of the hourly data are complete in each calendar quarter. of - (APDG 6232v4 , Revised 09 /18) TCEQ Air Quality Modeling Guidelines Page 45 110

51 - Select the annual monitored concentration from the Annual averaging time o most recent complete year for the annual averaging time. A year meets data completeness criteria provided that at least 75 percent of  the hourly data are complete in each calendar quarter. If the monitoring data do not meet the completeness criteria described above, there are procedures in the Appendices to 40 CFR Part 50 that provide methods for validating incomplete data for several pollutants and averaging times . For those pollutants and averaging times where procedures are not provided, the applicant can propose methods for using monitoring data with incomplete data. Monitoring Background Refinement e monitored background concentration used in an analysis is too conservative, then it If th may be necessary to refine the monitored background concentration in order to remove or limit contributions from the modeled point sources. Several methods are provided below. The goal is to obtain a representative background concentration using an appropriate amount of time and effort. Therefore, the options do not need to be followed in sequence and may be combined as appropriate. For isolated sources located in the general area of the monitors. Isolated means • there are no other point sources within the 90 -degree sector, or whose emissions would interact within the 90- degree sector with the same meteorological conditions. A source could impact a monitor within a 90- sector downwind of degree the source. Determine the average background concentration at each applicable monitor for the year under review by excluding values when the source(s) in question impacts the monitor. Obtain hourly or daily concentrations and corresponding meteorological data from the TCEQ. Exclude concentrations caused by transport from the source toward the monitor within the 90-degree sector. Average the remaining concentrations for each separate averaging time to determine the average background value. • Identify the location of the receptors with significant predicted concentrations from the project. Determine the meteorological conditions associated with these predicted concentrations. Obtain hourly or daily monitored concentrations and corresponding meteorological data from the TCEQ. Find meteorological conditions that are similar to those that caused the predicted concentrations and identify applicable monitoring data with the same meteorological conditions. Use this monitored concentration as the background concentration. Find a monitor that is not affected by the background point sources included in the • modeling demonstration. This could be done by modeling the background point ns or by sources to identify those that contribute to the monitored concentratio analyzing wind flow patterns. prescribed For particulates, determine if the concentration was caused by a non- • , wind speed in excess of the monthly average, etc fire . If so, use the next highest concentration that would not be affected by these events. of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 46 110

52 For any method of refinement of monitoring background concentrations, all documentation and technical justification must be provided. For example, when excluding onale hourly data, be sure to clearly identify all excluded hourly data and discuss the rati for excluding the data. TCEQ 110 47 Page Air Quality Modeling Guidelines /18) , Revised 09 - (APDG 6232v4 of

53 Minor and Prevention of Significant Deterioration National Appendix E - Ambient Air Quality Standards The purpose of the National Ambient Air Quality Standards (NAAQS) analysis is to demonstrate that proposed emissions of cr iteria pollutants from a new facility or from a modification of an existing facility will not cause or contribute to an exceedance of the NAAQS. The demonstration may consist of both air dispersion modeling predictions and person conducting the modeling should follow the basic ambient air monitoring data. The procedure described in the following paragraphs. Preliminary Impact Determination The procedure begins with a preliminary impact determination to predict whether the proposed emissions could make a sig nificant impact on existing air quality. That is, the model predicts concentrations at one or more receptors in the modeling grid greater than for this document, the term de minimis and or equal to a NAAQS de minimis level (note t should be noted that the use the phrase significant impact level (SIL) are synonymous). I will need to be justified. Refer to Appendix A for interim or recommended SILs of additional guidance on justifying the use of the SILs. Model all new and/or modified sources using the appropriate length of meteorological data. For Minor NAAQS, one year of National Weather Service (NWS) meteorological However, if five years of meteorological data are used, then use the data is sufficient. same five year meteorological data for all applicable averaging periods for consistency. For Prevention of Significant Deterioration (PSD) NAAQS, five years of NWS or at least one year of meteorological data, three years of prognostic meteorological data, -specific meteorological data are required. site dicted high concentration for each criteria pollutant and each averaging time are The pre then compared to the appropriate NAAQS de minimis level. For Minor NAAQS, the predicted high concentration is located at or beyond the property line. For PSD NAAQS, the predi cted high concentration is located at or beyond the fence line. The predicted high concentration may be related to the form of the NAAQS (exceedance- or statistically -based) and the number of years of meteorological data used: Repor t the maximum high, first high (H1H) predicted • Carbon Monoxide (CO) - concentration from all receptors across the applicable meteorological data set for and 8- 1-hour the hour averaging times. A de minimis level has not been established. Proceed to the full • Lead (Pb) - NAAQS anal ysis. ) • Nitrogen Dioxide (NO 2 1-hour averaging time - When using one year of meteorological data, report the o maximum H1H predicted concentration from all receptors. When using five five -year average of the H 1H years of meteorological data, report the highest years of When using three predicted concentrations from all receptors. meteorological data, report the highest three- prognostic year average of the of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 48 110

54 H1H predicted concentrations from all receptors. For additional guidance hour NO regarding the evaluation of 1- , see Appendix S. 2 - Report the maximum predicted concentration from all o Annual averaging time receptors across the applicable meteorological data set. Ozone (O • ) - Any net emissions increase of 100 tons per year (tpy) or more of 3 ) subject to PSD would volatile organic compounds (VOCs) or nitrogen oxides (NO x require an ambient impact analysis. See Appendix Q for guidance on conducting an ozone ambient impact analysis. • Particulate Matter (PM ) - Report the maximum H1H predicted concentration from 10 all receptors across the applicable meteorological data set for the 24- hour averaging time. Particulate Matter (PM • ) 2.5 24- o hour averaging time - When using one year of meteorological data, report the maximum H1H predicted concentration from all receptors. Wh en using five -year average of the H1H five years of meteorological data, report the highest predicted concentrations from all receptors. years of When using three meteorological data, report the highest three- year average of the prognostic ncentrations from all receptors. H1H predicted co Annual averaging time o - When using one year of meteorological data, report the maximum predicted concentration from all receptors. When using five years of meteorological data, report the highest five -year average of the pr edicted concentrations from all receptors. years of When using three prognostic meteorological data, report the highest three -year average of the predicted concentrations from all receptors. Environmental Protection Agency ( ) – The EPA) revoked both • Sulfur Dioxide (SO 2 the existing 24- hour and annual average standards with the promulgation of the 1-hour standard; however, these averaging times will remain in effect until one designations. hour SO year after the effective date of the 1- 2 o 1-hour averaging time - When using one year of meteorological data, report the maximum H1H predicted concentration from all receptors. When using five years of meteorological data, report the highest five -year average of the H1H predicted concentrations from all receptors. When years of three using prognostic meteorological data, report the highest three- year average of the H1H predicted concentrations from all receptors. For additional guidance , see Appendix S. regarding the evaluation of 1- hour SO 2 - Report the maximum H1H predicted 3-hour and 24- times o hour averaging concentration from all receptors across the applicable meteorological data set. Annual averaging time - Report the maximum predicted concentration from all o receptors across the applicable meteorological data set. of - (APDG 6232v4 , Revised 09 TCEQ /18) Air Quality Modeling Guidelines Page 49 110

55 Be aware of model limitations when using a concatenated meteorological data set with with a multiple averaging times in the same model run. For example, when modeling NO 2 hour and annual averaging -year meteorological data set and both the 1- five concatenated five times are selected, the model may compute -year average concentrations for both averaging times. This is not appropriate for the annual averaging time. If the sources do not make a significant impact for a pollutant of concern, the demonstration is complete. If there is a significant impact, then an area of impact (AOI) is defined, and a full NAAQS analysis is required. The AOI is the set of receptors that have ns at and above the de minimis level for each applicable averaging predicted concentratio time and pollutant. Please note that when evaluating emissions of PM , secondary 2.5 formation must be addressed. Refer to Appendix R for additional information regarding secondary formation of PM . 2.5 Full NAAQS Analysis The full NAAQS analysis is carried out for each pollutant using the AOI results from the preliminary impact determination and applicable averaging time. For multiple AOIs for the same pollutant, the person conducting the model ing can use one receptor grid that combines all significant receptors from each averaging time. The full NAAQS analysis considers all emissions at the site under review, as well as ducting emissions from nearby sources and background concentrations. The person con the modeling can receive a listing of all sources and associated parameters from the Texas Commission on Environmental Quality (TCEQ) to include in the air quality analysis (AQA). The person conducting the modeling should contact the Information Resources Division (IRD) to request this listing. Refer to Appendix C for additional guidance on source retrievals. It is the responsibility of the person conducting the modeling to obtain these data and ensure their accuracy. Any changes made to the data must be documented and justified. In addition, if the person conducting the modeling is aware of source data not provided by the IRD, such as recently issued permitted facilities or applicable facilities in other states within the distance limits of the model, the data should be included as applicable. Model allowable emission rates for all sources that emit the pollutant. Use a certified limit for -by-rule ( ) authorizations. For PBRs without a certified limit, use an estimate PBR permit of allowable emissions based on actual emissions. Use allowable emissions for standard permit authorizations. Use the same meteorological data set used in the preliminary impact determination modeling. The predicted concentrations may be related to the form of the NAAQS (exceedance -based) and the number of years of - or statistically meteorological data used: - When using one year of meteorological data, report the maximum H1H • CO predicted concentration from all receptors for the 1- hour averaging hour and 8- times. When using five years of meteorological data, three years of prognostic meteor specific meteorological data, report the , or one year of site- ological data maximum high, second high (H2H) predicted concentration from all receptors for hour averaging times. hour and 8- the 1- of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 50 110

56 month average. For a conservative - The NAAQS for Pb is based on a rolling 3- Pb • representation, the Air Dispersion Modeling Team (ADMT) recommends reporting the maximum H1H monthly predicted concentration from all receptors across the applicable meteorological data set. Or a post -processing tool is available from EPA (LEADPOST) that will compute the maximum predicted concentration in the form of the standard from all receptors across the applicable meteorological data set. To download LEADPOST and the corr esponding documentation, refer to: -dispersion- -preferred -and- modeling https://www.epa.gov/scram/air -quality recommended- models#aermod • NO 2 - When using one year of meteorological data, report the 1-hour averaging time o maximum H1H predicted concentration from all receptors. When using five years of meteorological data, report the maximum five -year average of the 98th percentile of the annual distribution of the maximum daily 1- hour predicted concentrations (or high, eighth high (H8H) predicted concentration) determined for each receptor. years of When using three meteorological data, prognostic report the maximum three -year average of the 98th percentile of the annual hour predicted concentrat ions (or H8H distribution of the maximum daily 1- one year of When using tration) determined for each receptor. predicted concen site -specific meteorological data, report the maximum 98th percentile of the annual distribution of the maximum daily predicted concentrations (or H8H predicted concentration) determined for eac h receptor. Annual averaging time - Report the maximum predicted concentration from all o receptors across the applicable meteorological data set. subject to - Any net emissions increase of 100 tpy or more of VOCs or NO • O 3 x PSD would be required to perform an ambient impact analysis. Refer to Q for additional guidance on conducting an ozone ambient impact Appendix analysis. - When using one year of meteorological data, report the maximum H1H • PM 10 hour averaging time. When predicted concent ration from all receptors for the 24- using five years of meteorological data, report the maximum high, sixth high (H6H) predicted concentration for the concatenated five- year period. When using three years of prognostic meteorolog ical data, report the maximum high, fourth high year period. When using (H4H) predicted concentration for the concatenated three- specific meteorological data, report the maximum H2H predicted one year of site- concentration for the 24- hour averaging time. • PM 2.5 24- When using one year of meteorological data, report hour averaging time - o the maximum H1H predicted concentration from all receptors. When using five five years of meteorological data, report the maximum -year average of the 98th hour predicted nual distribution of the maximum 24- percentile of the an concentrations (or H8H predicted concentration) determined for each receptor. prognostic e years of When using thre meteorological data, report the maximum three- year average of the 98th percentile of the annual distribution of the of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 51 110

57 -hour predicted concentrations (or H8H predicted concentration) maximum 24 e year of site determined for each receptor. When using on -specific meteorological data, report the maximum 98th percentile of the annual distribution of the -hour predicted concentrations (or H8H maximum 24 This is consistent with predicted concentration) determined for each receptor. EPA guidance provided secondary formation of PM is sufficiently addressed. 2.5 Refer to Appendix R for additional information concerning secondary formation of PM . 2.5 o Annual averaging time - When using one year of meteorological data, report the maximum predicted concentration from all receptors. When using five years of meteorological data, report the highest five the predicted -year average of concentrations from all receptors. prognostic years of When using three meteorological data, report the highest three -year average of the predicted concentrations from all receptors. SO • 2 - When using one year of meteorological data, report the 1-hour averaging time o maximum H1H predicted concentration from all receptors. When using five five -year average of the years of meteorological data, report the maximum 99th percentile of the annual distribution of the maximum daily 1- hour predicted conc entrations (or H4H predicted concentration) determined for each receptor. years of prognostic When using three meteorological data, report the maximum year average of the 99th percentile of the annual distribution of the three- maximum daily 1 -hour predicte d concentrations (or H4H predicted concentration) determined for each receptor. When using on e year of meteorological data, report the maximum 99th percentile of the site -specific annual distribution of the maximum daily 1- hour predicted concentrations (or H4H predicted concentration) determined for each receptor. 3-hour and 24- o When using one year of meteorological hour averaging times - data, report the maximum H1H predicted concentration from all receptors for the 3- hour averaging times. When using five years of hour and 24- meteorological data, three years of prog nostic meteorological data, or one year -specific meteorological data, report the maximum H2H predicted of site concentration from all receptors. - Report the maximum predicted concentration from all Annual averaging time o eorological data set. receptors across the applicable met Note that for any demonstration a higher concentration rank may be used to compare with a standard. That is, the maximum H1H predicted concentration could be used instead of 1H would be higher and the maximum H2H predicted concentration, since the maximum H thus more conservative. Determine a representative monitored background concentration to add with the predicted concentrations. Refer to Appendix D for additional guidance on determining representative monitoring concentrations. Compare the predicted concentration plus representative monitored background concentration for each pollutant and averaging time to the appropriate NAAQS. If the maximum concentration is at or below the NAAQS, the of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 52 110

58 demonstration for conservatism and demonstration is complete. If not, review the determine if any refinements can be made (operating limitations, conservative emissions estimates, etc.), or demonstrate that the project’s impact will not be significant. One refinement could be the use of the most recent two years of actual emissions data -term -property sources. However, actual emissions data available for short for select off averaging periods may be limited or not available. The EPA developed technical assistance documents (TADs) for implementing the 2010 SO standard . See the following 2 webpage: -2010- - sulfur pollution/technical -documents -assistance -implementing www.epa.gov/so2- e-standard dioxid The SO modeling TAD provides recommendations on how an air agency could model 2 ambient air in proximity to or impacted by an SO ce to assess compliance emission sour 2 with the SO NAAQS for designation purposes only. There are recommendations in the 2 that differ from guidance contained in the Guideline on Air Quality Models (GAQM) TAD he and these recommendations should not be used in permit modeling. With that said, t modeling TAD does provide a discussion on developing actual emissions data for SO 2 data, and could be used to help estimate actual modeling based on available operational emissions data. Keep in mind that dividing the annual emissions by the number of hours hat in the year is not an accurate representation of actual emissions for sources t experience emission rate variability throughout the year and should not be used. Be sure to coordinate with the ADMT on developing actual emissions data for modeling prior to submitting the AQA. pact will not be significant may A possible demonstration to determine if the project’s im consist of comparing the project’s impact to the applicable NAAQS de minimis level. If the project’s impact is less than the applicable NAAQS de minimis level, then the project’s This demonstration should be completed once all refinements impact is not significant. have been considered. of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 53 110

59 State Property Line Standard Analysis Appendix F - The purpose of the state property line standard analysis is to demonstrate compliance with state standards for net ground- level concentrations for sulfur dioxide (SO ), hydrogen 2 S), and sulfuric acid (H SO ). This analysis must demonstrate that resulting air sulfide (H 4 2 2 concentrations from all on- property facilities and sources that emit the regulated pollutant will not exceed the applicable state standard. Although all on- property facilities should be evaluated, in many cases the proposed emissions or changes in emissions may not be substantial when compared to the total emissions from the site. The basic procedure is described in the following paragraphs. Preliminary Impact Determination The procedure begins by conducting a preliminary impact determination by modeling the proposed allowable emission rates for all new and/or modified facilities that emit the regulated pollutant. Modeling with one year of National Weather Service (NWS) state property meteorological data is sufficient. If conducting an analysis for both the SO 2 National Ambient Air Quality Standards (NAAQS), and the hour SO line standard and 1- 2 s is based on five years of meteorological data, be aware of NAAQS analysi 1-hour SO 2 model limitations when using a concatenated meteorological data set. For example, when modeling SO year meteorological data set in AERMOD, with a concatenated five- 2 -year average concentrations. This is not appropriate for the AERMOD will compute five state property line standard. In addition, the Environmental Protection Agency (EPA) has provided modeling guidance related to the treatment of emissions from facilities that operate intermittently. T he techniques described in EPA’s modeling guidance are based on the form of the 1- hour . NAAQS, and they do not apply to the state property line standard analysis for SO SO 2 2 or each For new sources with no other sources on site, the predicted high concentrations f pollutant and averaging time at or beyond the property line are then compared against the applicable state standard. If the predicted high concentrations are equal to or less than state standard depends the standard, the demonstration is complete. Note that the SO 2 on the county. Galveston, Harris, Jefferson, and Orange counties have a more stringent S state standard depends on the land usage of the In addition, the H state standard. 2 esidential, business, or downwind property affected. If the downwind property is used for r commercial purposes (in general, non- industrial areas), the state standard is more stringent: minute averaging time. Report is based on a 30- - The state standard for SO SO • 2 2 the maximum high, first high (H1H) predicted concentratio n from all receptors for hour averaging time is used given that the the 1- hour averaging time. The 1- shortest averaging time for the preferred models typically used for regulatory hour averaging time. demonstrations is the 1- minute averaging time. Report S is based on a 30- S - The state standard for H H • 2 2 the maximum H1H predicted concentration from all receptors for the 1- hour hour averaging time is used given that the shortest averaging time. The 1- of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 54 110

60 averaging time for the preferred models typically used for regulatory demonstrations is the 1- hour averaging time. • - Report the maximum H1H predicted concentration from all receptors for H SO 2 4 the hour averaging times. 1-hour and 24- For new and modified or only modified sources at the site, the predicted high conc entrations for each pollutant and averaging time at or beyond the property line are then compared against two percent of the applicable state standard. If the predicted high concentration is less than two percent of the state standard, technical justificat ion for demonstrating compliance may require additional information such as project emissions increases, total site emissions, results from previous site- wide modeling, or ambient air monitoring data. For example, a nearby H kilometers (km) of the site S ambient monitor (within 8- 10 2 property line) has recorded a concentration just below the state standard. The site S. The project seeking an authorization has never conducted site- wide modeling for H 2 e emissions. Even though the emissions increase is a small percentage of the overall sit project emissions increase has a model prediction less than two percent of the state standard, modeling only the project emissions increase may sufficient to be not demonstrate compliance with the standard. However, if the predicted high concentration is equal to or greater than two percent of the wide modeling is state standard, coordinate with the permit reviewer to determine if site- needed. Staff will consider factors such as project emissions increases, total site wide modeling, or ambient air monitoring data. results from previous site- emissions, S, which results in For example, an applicant models the project emissions increase of H 2 a predicted concentration equal to or greater than two percent of the state standard. S has been previously conducted using the same model and the Site -wide modeling for H 2 site -wide modeling results were only a small fraction of the state standard. Even though model predictions associated with the project emissions increase is greater than two percent of the state standard, adding the predicted concentration from the project to the previous site- wide predicted concentration may be sufficient to demonstrate compliance wide modeling including the project emissions incr ease may with the state standard. Site- not be necessary. Site- wide Modeling -wide modeling is required, model the allowable emission rates for all sources on the If site property that emit the regulated pollutant using the same meteorological data set used in -by-rule the preliminary impact determination modeling. Use a certified limit for p ermit (PBR) authorizations. For PBRs without a certified limit, use an estimate of allowable emissions based on actual emissions. Use allowable emissions for standard permit predicted high concentration to the applicable state authorizations. Compare the standard. If the predicted high concentration is equal to or less than the state standard, the demonstration is complete. If the predicted high concentration is greater than the state standard, review t he demonstration for conservatism and determine if any refinements can be made. of - (APDG 6232v4 , Revised 09 /18) TCEQ Air Quality Modeling Guidelines Page 55 110

61 Health Effects Analysis Appendix G - The purpose of the health effects analysis is to demonstrate that emissions of non- criteria pollutants from a new facility or from a modif ication of an existing facility will be protective of the public’s health and welfare. Agency toxicologists use the results from the health effects analysis to evaluate the effects of emissions on a contaminant -by-contaminant basis. The objectives of the analysis are to: • level concentrations (GLCs) of contaminants -property ground- Establish off resulting from proposed and/or existing emissions, and Evaluate these GLCs for their potential to cause adverse health or welfare effects. • The Air Permits Division (APD) has developed a guidance document to assist with conducting a health effects analysis. This guidance document is titled, Modeling and Effects Review Applicability: How to Determine the Scope of Modeling and Effects (MERA), and can be found at the following url: Air Permits Review for www.tceq.texas.gov/assets/public/permitting/air/Guidance/NewSourceReview/mera.pdf The MERA document establishes a process to determine the scope of the modeling and health effects review. The MERA document also provides information on the toxicology health effects evaluation procedure typically performed by the Toxicology Division (TD). tiered approach. health effects evaluation procedure is based on a three- -wide site The Tiers I, II, and III represent progressively more complex levels of review: • Tier I - The maximum off -property short - and long -term GLCs are compared to the effects screening lev els (ESLs) for the contaminants under review. An ESL is a guideline—not a standard. This format provides the flexibility required to easily revise the value to incorporate the newest toxicity data. Consult with the TD to ensure that the most recent ESLs ar e used, to obtain additional information concerning the basis for ESLs, or to obtain ESLs for contaminants not i n the Toxicity Factor database. For contaminants not on the published list, provide the chemical abstract service (CAS) registry number and a material safety data sheet (MSDS) to the TD staff so that they can positively identify the contaminant and -property short -term GLCs are equal to - and long derive an ESL. If the maximum off or less than the ESLs for the contaminants under review, adverse heal th or welfare effects would not be expected. Information on the Toxicity Factor database can be found at the following url: www.tceq.texas.gov/toxicology/esl/ESLMain.html • Tier II - For contaminants with GLCs predicted to exceed their applicable ESL, determine whether the locations are industrial or non- industrial (residences, recreational areas (land or water), day care centers, hospitals, schools, unzoned . For industrial receptors, if the maximum and/or undeveloped areas, etc.) -property short -term GLCs are equal to or less than two times the - and long off ESLs for the contaminants under review, adverse health or welfare effects would industrial receptors, if the maximum off not be expected. For non- - short -property of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 56 110

62 -term GLCs are equal to or less than the ESLs for the contaminants under and long review, adverse health or welfare effects would not be expected. • While Tiers I and II are reviews based solely on predicted concentratio ns, Tier III - specific factors that have a bearing on Tier III incorporates additional case- by-case review may exposure. The factors the TD considers in a Tier III case- include surrounding land use, magnitude of predicted concentrations, frequency of predicted exceedance, toxic effect caused by the contaminant, etc. Consideration of all these factors together provides additional information about the potential for exposure and occurrence of adverse health and welfare effects. For additional information on the frequency of predicted exceedance, refer to the guidance memo at the following url: www.tceq.texas.gov/assets/public/permitting/air/memos/effeval.pdf of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 57 110

63 Appendix H – Preventio n of Significant Deterioration Pre -application Analysis The purpose of the Prevention of Significant Deterioration (PSD) pre- application analysis is to provide an analysis of the existing ambient air quality in the area that the major source or major modif ication would affect. The analysis must be based on continuous air quality monitoring data. The basic procedure is described in the following paragraphs. Note that pre- construction and/or post -construction monitoring could be required by the on on Environmental Quality (TCEQ). Texas Commissi Compare the predicted high concentration obtained from the applicable preliminary impact determination to the significant monitoring concentration (SMC): Carbon Monoxide (CO) - Report the maximum high, first high (H1H) predicted • hour averaging time. concentration from all receptors for the 8- month average. For a Lead (Pb) - The SMC for Pb is based on a three- • conservative representation, the Air Dispersion Modeling Team ( ADMT ) recommends reporting the maximum H1H monthly predicted concentration from all receptors. • Nitrogen Dioxide (NO ) - Report the maximum predicted concentration from all 2 receptors for the annual averaging time. ) - A SMC has not been established for O . However, any net emissions • Ozone (O 3 3 tons per year (tpy) or more of volatile organic compounds (VOCs) 100 increase of ) subject to PSD would be required to perform an ambient or nitrogen oxides (NO x impact analysis, including the gathering of ambient air quality data. e maximum H1H predicted concentration from ) - Report th Particulate Matter (PM • 10 all receptors for the 24 -hour averaging time. was vacated on January 22, 2013. • Particulate Matter (PM ) - The SMC for PM 2.5 2.5 • Sulfur Dioxide (SO ) - Report the maximum H1H predicted concentration from all 2 receptor s for the 24 -hour averaging time. Fluorides - Report the maximum H1H predicted concentration from all receptors for • hour averaging time. the 24- - Report the maximum H1H predicted concentration from S) • Hydrogen Sulfide (H 2 all receptors for the 1- hour averag ing time. Reduced Sulfur Compounds - • Report the maximum H1H predicted concentration hour averaging time. from all receptors for the 1- . However, SO SO • Sulfuric Acid Mist (H ) - A SMC has not been established for H 2 2 4 4 -wide modeling from the minor New Sour site ce Review (NSR) modeling application analysis. demonstration may be sufficient for the pre- Total Reduced Sulfur Compounds - • Report the maximum H1H predicted concentration from all receptors for the 1- hour averaging time. of - (APDG 6232v4 , Revised 09 /18) TCEQ Air Quality Modeling Guidelines Page 58 110

64 s than the SMC, the demonstration is complete. If the If the maximum concentration is les maximum concentration equals or exceeds the SMC, provide an analysis of the ambient air quality in the area that the project emissions would affect for applicable averaging periods. nalysis of the ambient air quality in the area that the project When conducting an a emissions would affect, collect representative monitoring background concentrations to establish the existing air quality in that area. Refer to Appendix D for additional guidance ng representative monitoring background concentrations. Please note that on determini when conducting an analysis of the ambient air quality in the area that the project application analysis is required for all averaging periods emissions would affect, the pre- h there is a National Ambient Air Quality Standards (NAAQS); not just the for whic averaging period associated with the SMC. If existing monitoring data are not available, or are judged not to be representative, then the applicant should establish a site- specific m onitoring network. The applicant should coordinate with the permit reviewer for determining the scope of monitoring and for assistance in the preparation of a monitoring quality assurance plan. of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 59 110

65 Appendix I - Prevention of Significant Deterioration Increme nt The purpose of the Prevention of Significant Deterioration (PSD) increment analysis is to demonstrate that emissions of applicable criteria pollutants from a new major source or exceedance of major modification of an existing source will not cause or contribute to an an increment. The PSD increment is the maximum allowable increase in concentration that is allowed to occur above a baseline concentration for a pollutant. The following discussion introduces and explains several terms that are specific to P SD increment analyses followed by the basic procedure for conducting the analysis. Terms There are several dates that are used in the increment . Baseline and Trigger Dates analysis: • Major source baseline date . This is the date after which actual emissions associated with physical changes or changes in the method of operation at a major stationary source affect the available increment. Changes in actual emissions e contribute to the baseline occurring at any stationary source after this dat concentration until the minor source baseline date is established. After the minor source baseline date, new and modified major and minor stationary sources in the baseline area consume increment. Applicable major source baseli ne dates are listed below: ) - February 8, 1988 o Nitrogen Dioxide (NO 2 Particulate Matter (PM ) - January 6, 1975 o 10 ) - October 20, 2010 Particulate Matter (PM o 2.5 ) - January 6, 1975 o Sulfur Dioxide (SO 2 This is the date after which the minor source baseline date may be • Trigger date . established. Applicable trigger dates are listed below: o NO - February 8, 1988 2 PM - August 7, 1977 o 10 - October 20, 2011 PM o 2.5 o SO - August 7, 1977 2 Minor source baseline date • . This is the earliest date after the trigger date on which a PSD application for a new major source or a major modification to an existing source is considered complete. The minor source baseline date is pollutant - and -specific. geographically , and SO , PM The minor source baseline dates have been established for NO 10 2 2 , the minor source baseline date was established for all areas of the state. For NO 2 , the minor source baseline and SO as a single date for the entire state. For PM 2 10 dates were established by air quality control regions (AQCRs). The minor source of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 60 110

66 for all areas of the state. The baseline dates have not been established for PM 2.5 minor source baseline dates for PM are established by county. 2.5 Please contact the Air Dispersion Modeling Team (ADMT) for information on minor source baseline dates. The baseline area is established for each applicable pollutant’s minor Baseline area . source baseline date by the submission of a complete PSD application and subsequent source impact analysis. The extent of a baseline area is limited to intrastate areas and includes all portions of the attainment or unclassifiable area in which the PSD applicant would propose to locate, as well as any attainment or unclassifiable area in which the proposed emissions would have a signifi cant ambient impact for the annual averaging period. The following are three examples for determining the extent of the baseline area: 1. If the annual predicted concentrations associated with proposed emissions of 3 PM are less than 0.3 μg/m for all recept ors, then the extent of the baseline area 2.5 is limited to the county in which the PSD applicant would propose to locate. 2. If the receptors with annual predicted concentrations associated with proposed 3 ed to the county in which or greater are limit equal to 0.3 μg/m emissions of PM 2.5 the PSD applicant would propose to locate, then the extent of the baseline area is limited to that county. 3. If the receptors with annual predicted concentrations associated with proposed 3 equal to 0.3 μg/m ater extend into one or more adjacent or gre emissions of PM 2.5 counties. counties, then the extent of the baseline area encompasses all of those . The ambient concentration level that existed in the baseline Baseline concentration eline date. The baseline concentration area at the time of the applicable minor source bas is the reference point for determining air quality deterioration in an area. The baseline concentration level is not based on ambient monitoring because ambient measurements ng those that should be excluded from the reflect emissions from all sources, includi measurements. . An applicant does not need to obtain the baseline ambient Increment calculation concentration to determine the amount of PSD increment consumed or the amount of increment available. Instead, the amount of PSD increment that has been consumed in an attainment or unclassified area is determined from the emissions increases and decreases that have occurred from stationary sources in operation since the applicable baseline date. Modeled increment consumpt ion calculations reflect the change in ambient pollutant concentration attributable to increment -affecting emissions. Increment consumption (or expansion) calculations are determined by evaluating the difference ) and actual between the actual emissions at the applicable baseline date (Actual BD ). emissions as of the date of the modeling demonstration (Actual MD • -year average for long Actual . This is the representative two -term emission rates, BD od immediately -year peri -term emission rate in the same two or the maximum short before the applicable baseline date. If little or no operating data are available, as in the case of permitted sources not yet in operation at the time of the applicable of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 61 110

67 baseline date, the permit allowable emission rate as of the applicable baseline date is used. -term • Actual -year average for long . This is the most recent, representative two MD emissions rates, or the maximum short -term emission rate in the same two -year operating data period immediately before the modeling demonstration. If little or no are available, as in the case of permitted sources not yet in operation at the time of the increment analysis, the permit allowable emission rate is used. Conducting the Analysis The ADMT suggests a tiered approach to this analysis to limit the amount of research needed to determine actual emission rates. The person conducting the modeling should follow the basic procedure described in the following paragraphs. Determine whether the predicted high concentration (excluding background concentr ation) obtained in the PSD full National Ambient Air Quality Standards (NAAQS) analysis is at or below the applicable increment . This procedure does not apply for criteria pollutants with NAAQS that are statistically -based (i.e., multi -year average). NO • - Report the maximum annual average concentration at any receptor for each 2 year modeled. PM • 10 hour averaging time - o 24- Report the maximum high, second high (H2H) concentration at any receptor from each year modeled. mum annual average concentration at - Report the maxi Annual averaging time o any receptor for each year modeled. NAAQS results are based on the maximum high, sixth high If the 24 -hour PM 10 (H6H) predicted concentration, then do not compare the results with the increment. Although there is no annu al NAAQS for PM , follow the procedure to determine 10 the area of impact (AOI) for the annual NAAQS. The AOI is the set of receptors that have predicted concentrations equal to or greater than the de minimis level. increment analysis. Also, be aware of Use this AOI to conduct the annual PM 10 model limitations when using a concatenated meteorological data set. For -year meteorological data with a concatenated five example, when modeling PM 10 ions that set for the annual averaging period, the model may compute concentrat -year period. This is not appropriate for the have been averaged over the five annual averaging time. Compare the highest average concentrations from each year modeled to the increment to determine compliance. PM • 2.5 24- o Report the maximum H2H concentration at any hour averaging time - receptor from each year modeled. Annual averaging time - Report the maximum annual average concentration at o any receptor for each year modeled. of - (APDG 6232v4 , Revised 09 TCEQ /18) Air Quality Modeling Guidelines Page 62 110

68 -year average five NAAQS results are based on a -hour and annual PM If the 24 2.5 of the maximum predicted concentrations, then do not compare the results with the Please note that when evaluating emissions of PM increments. , secondary 2.5 formation must be addressed. Refer to Appendix R for additional information y formation of PM . regarding secondar 2.5 SO • 2 3-hour and 24- hour averaging times - Report the maximum H2H concentration o at any receptor from each year modeled. o - Report the maximum annual average concentration at Annual averaging time any receptor for each year modeled. If the predicted concentration (excluding background concentration) obtained in the PSD full NAAQS analysis for the pollutants listed above is at or below the applicable increment, then the demonstration is complete because all sources were modeled at allowable emission rates. If not, then an AOI is defined, and further analyses are required. The increment analysis is carried out for each criteria pollutant and averaging time separately and need only include the AOI for the associated criteria pollutant and averaging time combination. The AOI will be the same one used in the PSD NAAQS -based. analysis, except for those criteria pollutants with NAAQS that are statistically While the significant impact levels (SILs) for both NAAQS and increment are identical, the procedures to determine significance (that is, predicted concentrations to compare to the SIL) are different. This difference occurs because for those NAAQS that are statistically - utants with based, the corresponding increments are exceedance- based. For criteria poll NAAQS that are statistically -based, determine the AOI following the convention of based NAAQS (i.e., maximum predicted concentration). exceedance- • For example, when modeling PM , use the maximum predicted concentrations 2.5 hour and annual averaging times from all receptors to determine the AOI for the 24- -year average of the maximum predicted concentrations from the five instead of the NAAQS analysis. It should be noted that the use of interim or recommended SILs to determine the AOI will need to be justified. Refer to Appendix A for additional guidance on justifying the use of the SILs. -affecting emissions at the site under The increment analysis considers all increment -affecting emissions from nearby sources. The person review, as well as increment conducting the modeling can receive a listing of all increment -affecting sources and associated parameters from the Texas Commission on Environmental Quality (TCEQ) to include in the air dispersion modeling. The person conducting the modeling should cont act the Information Resources Division (IRD) on how to receive this listing. Refer to Appendix C for additional guidance on source retrievals. It is the responsibility of the person conducting the modeling to obtain these data and ensure their accuracy. Any t be documented and justified. In addition, if the person changes made to the data mus conducting the modeling is aware of source data not provided by the IRD, such as recently issued permitted facilities or applicable facilities in other states, the data should be included as applicable. of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 63 110

69 Adjust the emission inventory. • Omit any source from the inventory that has a negative emission rate unless the source existed and was in operation at the applicable baseline date. A source must have existed and been in operation on or before the applicable baseline date to be considered for increment expansion. Omit any source permitted after the applicable baseline date that has shut down or • . A source that did not exist or as part of the current project that will be shut down was not operating on or before the applicable baseline date would not have contributed to the air quality at that time, and there would be no need to model the source with an emission rate of zero. Conduct the modeling demonstration using the same meteorological data set used in the determination of the AOI using t he following tiered approach, as applicable. Increment Modeling Tier I . Model all sources using their allowable emission rates. This in increment is based on the entire approach is conservative since the difference allowable emission rate. • NO - Report the maximum annual average concentration at any receptor for each 2 year modeled. PM • 10 24- hour averaging time - Report the maximum H2H concentration at any o receptor from each year modeled. - Report the maximum annual average concentration at o Annual averaging time any receptor for each year modeled. PM • 2.5 o 24- hour averaging time - Report the maximum H2H concentration at any receptor from each year modeled. o - Report the maximum annual average concentration at Annual averaging time any receptor for each year model ed. • SO 2 o 3-hour and 24- hour averaging times - Report the maximum H2H concentration at any receptor from each year modeled. o - Report the maximum annual average concentration at Annual averaging time any receptor for each year modeled. ations when using a concatenated meteorological data set. For Be aware of model limit five with a concatenated -year meteorological data set for example, when modeling NO 2 five the annual averaging period, the model may compute -year average annual concentrations. This is not appro priate for the annual averaging time. Please note that , secondary formation must be addressed. Refer to when evaluating emissions of PM 2.5 . Appendix R for additional information regarding secondary formation of PM 2.5 Compare the predicted concentration to the appropriate increment. If the increment is not exceeded, the demonstration is complete. Otherwise, go to Tier II. of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 64 110

70 Increment Modeling Tier II . Model selected sources with Actual emission rates and all MD other sources at allowable emission rates. The selected sources are usually the -property sources. applicant’s, since actual emission rates may be difficult to obtain for off This process assumes that the difference the selected sources is based in increment for on the entire actual emission rate. Report the model predictions following the same conventions listed in Tier I. Compare the predicted high concentration to the appropriate increment. If the increment is not exceeded, the dem onstration is complete. Otherwise, go to Tier III. . Model selected sources that existed and were in operation at Increment Modeling Tier III the applicable baseline date with the between Actual difference and Actual . MD BD • efore the applicable major source baseline date For major sources permitted at or b but not in operation as of the applicable minor source baseline date or for minor sources permitted at or before the applicable minor source baseline date but not in e baseline date, use the difference operation as of the applicable minor sourc between Actual ). and the allowable emission rate (Actual MD BD For sources that existed at the applicable baseline date, where a change in actual • emission rates involved a change in stack parameters, use the emission rates associated with both the applicable baseline date and the current and/or proposed source configuration. That is, enter the Actual as negative numbers along with BD the applicable baseline source parameters, and enter Actual for the same MD e numbers along with the current and/or proposed source source as positiv parameters. • Use emission rates found in Tiers I or II for other sources, as applicable. Report the model predictions following the same conventions listed in Tier I. Compare the predicted high concentration to the appropriate increment. If the increment is not exceeded, the demonstration is complete. Otherwise, continue to refine increment This emission rates or demonstrate that the project’s impact will not be significant. be completed once all refinements have been considered. demonstration should of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 65 110

71 Appendix J - Preferred Air Dispersion Models The Environmental Protection Agency (EPA) has adopted the American Meteorological Society/EPA Regulatory Model (AERMOD) as the preferred air dispersion m odel for major New Source Review (NSR) permits. The model is used for refined modeling of criteria pollutants within approximately 50 kilometers (km) of a site. Beyond 50 km, the EPA does not have a preferred model for long The -range transport. ed a screening approach to address long EPA codifi -range transport for purposes of g NAAQS and/or PSD increments assessin . The first step of the screening approach relies -field application of the appropriate screening and/or preferred model to upon the near from the new or modified determine the significance of ambient impacts at or about 50 km . If the analysis indicates there may be significant ambient impacts at this distance, source . For further assessment of the significance of ambient further analysis is necessary impacts for NAAQS and/or PSD increments, approaches (models and modeling parameters) must be established on a case- by-case basis in consultation with the Air Dispersion Modeling Team ( ) and EPA Region 6. ADMT Refined Models OD or the most recent version of the Industrial Source An applicant can use either AERM -PRIME) model until a federal Complex (ISC) with Plume Rise Model Enhancements (ISC NSR review is required. The most recent version of the ISC model can also be used if the s could not be affected by building downwash at a site. dispersion of air contaminant Once an applicant has used AERMOD for a major NSR permit, AERMOD should be used for minor NSR permits as well. In addition, if AERMOD has been relied upon for a minor e to be used at that site (this includes single NSR permit, AERMOD should continu ). This guidance will ensure consistency in the property line designations [SPLDs] technical review process as modeled concentrations will be calculated under the he ISC -PRIME model or the ISC model requirements of the same modeling system. If t has been used previously, engineering judgment must be used to reconcile emissions limits and controls based on predicted differences in contaminant concentrations between modeling systems until all authorizations at the site are evaluated under the same modeling system. Screening Models An applicant can use either AERSCREEN or the SCREEN3 model until a federal NSR review is required. AERSCREEN is a screening version of AERMOD, and SCREEN3 is a screening version of the IS C model. Once an applicant has used AERSCREEN for a major NSR permit, AERSCREEN should be used for minor NSR permits as well. In addition, if AERSCREEN has been relied upon ed -wide analysis for a minor NSR permit, AERSCREEN should continue to be us for a site ). This guidance will ensure consistency in the technical at that site (this includes SPLDs review process as modeled concentrations will be calculated under the requirements of the same modeling system. If the SCREEN3 model has been used previously, of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 66 110

72 ineering judgment must be used to reconcile emissions limits and controls based on eng predicted differences in contaminant concentrations between modeling systems until all authorizations at the site are evaluated under the same modeling system. 67 TCEQ 110 Page Air Quality Modeling Guidelines /18) , Revised 09 - (APDG 6232v4 of

73 Source Characterizations Appendix K - -directed It is important that the applicant, or staff developing scenarios for agency modeling, completely and accurately describes the operating factors and conditions of the facilities undergoing permit review. The following is a list of the type of factors that should be considered before emissions can be characterized and model parameters developed. Operation or Process Limitations The applicant, or Texas Commission on Environmental Quality (TCEQ) staff as applicable, should address the following factors in the permit application and modeling protocol or checklist, if the facilities do not operate continuously: -case and reasonable worst -case operational • Operational scenarios. Provide worst -case scenario to occur. ould be for the worst scenarios, and discuss how likely it w In addition, describe the operational processes in enough detail to justify all source type characterizations. For example, for a blasting operation, provide the minimum and maximum size of a blasting area and the details of how the blasting operation will be conducted. That is, describe such operational factors as whether the operation will be done manually or by machine; on a single side at a time or multiple sides; or on one level at a set height or multiple levels with a varying height. Hours of operation. For each facility under permit review, identify the hours of • operation. If the hours of operation are less than 8760 hours per year, provide any time -of-day or seasonal restrictions, and whether the emissions are the same for . each hour or if they are reduced for some hours Type of emissions. Identify all facilities that could be operated simultaneously. For • example, for a site with coating and blasting facilities, indoor coating and outdoor blasting could occur at the same time. If the emissions are not continuous, the applicant should identify any batch process or a process that must occur before another process can occur. In addition, the applicant should include the frequency , for example, one hour out of every three hours or and duration of the emissions one hour per day. -term emissions for a single specific facility often vary • Emission rates. Short significantly with time because of such factors as fluctuations in process operating conditions; control device operating conditions; type of raw materials being handled or processed; and ambient conditions. Provide the basis used to determine the maximum allowable emission rate. For example, is the emission rate an hour, or are the emissions based on the potential for a single spike during uniform throughout an hour? Alternatively, are the emissions linked to wind speed, such as wind- generated emissions originating from a standing stockpile? /18) Air Quality Modeling Guidelines TCEQ Page 68 of - (APDG 6232v4 , Revised 09 110

74 Controls. Describe any best management practice that will be used in addition to • controls that must be used to meet best available control technology requirements, such as shrouds, bunkers, or fixed enclosures. The use of partial or full obstructions to airflow will affect the way a fugitive emission is characterized for input into the air dispersion model. The characterization will depend on factors such as the height of release; height of the enclosure; particle size; and the duration of the operation. For example, if shrouds will be used to contain emissions from the outdoor blasting or painting of small equipment, the characterization will be different if two- -sided sided shrouds are used compared to the use of four shrouds. The height of release that will be used in the model for the two- sided -sided shroud. In addition, shroud will be lower than the height of release for a four if particle size was not considered in the development of the emission rate, the modeled emission rate might be reduced to account for lower expected emissions due to impact with all sides of the shroud and release of emissions at the top of the shroud. Source Types The source characterizations used in a modeling analysis will depend on the model being used. The guidance discussed in this section addresses some, but not all, possible ways point sources. Ensure that applicants are to characterize certain types of point and non- aware of any new procedures before final modeling is conducted. In addition, applicants, or staff if applicable, should include a complete description of how a source is characterized and how the applicable modeling parameters were developed in the air quality analysis (AQA). The description is important because several characterizations for the same source could be appropriate depending upon the potential impact of building and other structures and meteorological conditions. The following is a brief discussion of different source characterizations: • Point. Use the point source characterization to simulate emissions that are emitted from a stack. For the point source characterization, such as a vent pipe, use the actual stack diameter, exit gas velocity, and exit gas temperature in the modeling demonstration. Use the actual height of release unless the height of release varies due to the operational process. In those cases, use the average height of release. For example, if a vent pipe is located on the deck of a marine vessel, the height of the top of the pipe will vary during the loading or unloading process, as the vessel height of release and rises or falls in the water. Therefore, determine an average use that height in the model. Pseudo- point. This source type is a point source characterization using default o stack parameters, and the emissions are treated as if they are released from a stack. Default parameters for stack diameter , exit gas velocity, and exit gas temperature are used to prevent the stack plume from having any buoyancy or points momentum flux. Examples of sources that might be treated as pseudo- are individual pipe connections; flanges; small vents and ducts (a few f eet in diameter); small stockpiles; and covered, obstructed, or horizontal stacks. , Revised 09 /18) Air Quality Modeling Guidelines - (APDG 6232v4 Page 69 of TCEQ 110

75 Use the following default stack parameters when using SCREEN3 or ISC: Stack diameter: 0.001 meter  Exit gas velocity: 0.001 meters per second  Exit gas temperature: 0 Kelvin (the ISC model will use the ambient  temperature as the exit gas temperature)  Height of release: use the actual release height When using AERSCREEN or AERMOD, follow the appropriate guidance contained in the AERMOD Implementation Guide for determining the default parameters: -preferred- modeling www.epa.gov/scram/air -dispersion- -quality -recommended- and models#aermod have options for covered/capped D also Note that AERSCREEN and AERMO and/or horizontal stacks. Use POINTCAP for covered/capped stacks and POINTHOR for horizontal stacks. For each of these options, the user specifies height of release, stack diameter, exit g as velocity, the actual stack parameters ( and exit gas temperature) as if the release were from a non- capped vertical point source. Volume. Use the volume source characterization to simulate emissions that initially • issions from disperse in three dimensions with little or no plume rise, such as em vents on a building roof; multiple vents from a building; and fugitive emissions from pipes, stockpiles, and conveyor belts . Parameters used to characterize volume sources are location, height of release, and initial horizontal and vertical dimensions. The height of release is the center of the volume source above the ground. The initial horizontal and vertical dimensions are used to determine the applicable dispersion parameters. The length of the side of the volume source, the vertical height of the source, and whether the source is on or adjacent to a structure or building must be identified in order to determine the applicable Volume dispersion parameters (see section 1.2.2 of the ISC Model User’s Guide - ed for estimating the initial horizontal and II for suggested procedures to be us vertical dimensions for various types of volume sources). For example, if the length and width of a piping structure is 10 meters and the e from piping extends from the surface to 20 meters, and the emissions could com multiple locations throughout the entire piping structure, then the initial horizontal dimension would be 10 meters divided by 4.3, the initial vertical dimension would be 20 meters divided by 2.15, and the height of release would be 10 meters. ver, if emissions could only come from the upper portions of the piping Howe structure (from 10 to 20 meters), then the initial horizontal dimension would be 10 meters divided by 4.3, the initial vertical dimension would be 10 meters divided by 4.3, and the hei ght of release would be 15 meters. The base of the volume source must be square. If the base is not square, model the source as a series of adjacent volume sources, each with a square base. For relatively uniform sources, determine an equivalent square by taking the square root of the area of the length and width of the volume base. of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 70 110

76 • Area. Use the area source characterization to simulate emissions that initially level or disperse in two dimensions with little or no plume rise, such as ground- . emissions from a storage pile, slag dump, landfill, or holding pond -level low Parameters used to characterize area sources are location, geometry, and release height. The geometry of an area source may be characterized as a rectangle, circle . If the source is not at ground level, then a irregularly shaped polygon, or height of release must be entered into the model. The emission “rate” is unique for an area source in that emissions are entered in units of mass per unit time per unit area; an emission flux rather tha n a rate. Use an emission rate per unit area instead of total emissions; that is, divide the total emissions in grams per second by the total area in square meters. Also, the model integrates over the portion of the area that is upwind of a receptor so rec eptors may be placed within the area and at the edge of the area. The model does not integrate for portions of the area that are closer than one meter upwind of a receptor. from Open Pit. Use the open pit source characterization to simulate emissions • -grade open pit. Parameters used are the open that originate from a below facilities and pit emission rate, the average release height, the initial lengths of the X Y sides of the open pit, the volume of the open pit, and the orientation angle in degrees from 360 degrees (north). While detailed guidance is contained in section Volume II, some factors to consider follow. 1.2.4 of the ISC Model User’s Guide - As with the area source characterization, an emission rate per unit area is o used; that is, the total emissi ons in grams per second divided by the total area in square meters. o The average release height above the base of the open pit cannot exceed the pit’s effective depth, which is calculated by the model based on the pit’s length, release height of zero indicates emissions that width, and volume. An average are released from the base of the pit. o The length- to-width aspect ratio for open pit sources should be less than 10 to 1. Unlike the area source characterization, the open pit cannot be subdivided because the assumption used to develop the algorithm is that the emissions are mixed throughout the pit before being dispersed. Characterize irregularly shaped pit areas by a rectangular shape of equal area. o Unlike the area source characterization, receptors cannot be placed within the boundaries of the pit. Flare. Flares are a special type of elevated source that may be modeled using a • point source characterization or a flare source characterization. It may be difficult to obtain the necessary input parameters for air dispersion modeling based on the design and operation of a flare. A large open flame radiates a significant portion of the heat of combustion associated with a flaring gas stream. The buoyancy of the combustion gases will be related to the remaining sensible heat of the flare gas. There are two methods for modeling emissions from a flare. One method uses a traditional point source characterization with user -provided exit gas velocity, exit gas temperature, height of release, and effective stack diameter to determine the of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 71 110

77 amount of buoyancy flux. In this method, the heat release of the flared gas is used to derive an equivalent stack diameter while the exit gas temperature and exit gas velocity are fixed. Use the following default parameters: o Exit gas veloc ity: 20 meters per second o Exit gas temperature: 1273 Kelvin o Height of release: use the actual height of the flare tip The effective stack diameter (D) in meters is calculated using the following equations: −6 � = 10 퐷퐷 푞푞 푛푛 and − (1 푞푞 = 푞푞 0.048 ) 푀푀푀푀 √ 푛푛 where: = gross heat release in calories per second q = net heat release in calories per second q n MW = weighted (by volume) average molecular weight of the compound being flared Note that enclosed vapor combustion units should not be modeled with the ameters but instead with stack parameters that reflect the physical preceding par characteristics of the unit. The second method for modeling emissions from a flare was developed for the flare source characterization. In this method, the user provides the height of ase and the gross heat release from the flare. The height of release is the rele actual height of the flare tip. The model uses the gross heat release from the flare together with a fixed exit gas temperature and exit gas velocity to internally calculate the ef fective diameter. Equivalency of Source Types There is no direct equivalency or relationship between the types of source characterizations . Many factors must be considered to determine if a source characterization is conservative or representative. A conservative characterization is one that will result in a higher concentration than a representative characterization would in a specific area of concern. In addition, a conservative concentration would not be expected permitted facility. In general, use a screening to occur based on actual operation of the model to determine whether a characterization would be conservative and under what meteorological conditions. This information will make the processes of model result led predictions easier. Factors to consider when -processing of mode clarification or post choosing a source characterization include: of - (APDG 6232v4 , Revised 09 /18) TCEQ Air Quality Modeling Guidelines Page 72 110

78 Type of compliance demonstration. National Ambient Air Quality Standards • (NAAQS), Prevention of Significant Deterioration (PSD) Increment, and state property line standard compliance demonstrations are directly related to the highest concentrations predicted in ambient air. For these demonstrations, a characterization does not have to be representative if it results in a conservative prediction. However, for a healt h effects review, the type of receptor and magnitude and frequency of exposure must be considered. Therefore, a source should be characterized in the most representative way to ensure that the health effects review is based on realistic data, and to prevent costly or unnecessary process changes. • Distance from the source to the property line or area of concern. At great distance (on the order of thousands of feet), and other factors such as height of release being equal, source type is not as important as when the distance to a property line or area of concern is short. At great distance, predicted concentrations will begin to converge as horizontal and vertical dispersion parameters increase and differences between them for a given source type decrease. However, for short distances there can be significant differences between horizontal and vertical dispersion parameters and thus between predicted concentrations of different source types. • the height of Height of release. While the height of release from a stack is obvious, release from a fugitive source may not be obvious and is important because the height of release for a fugitive source is the plume centerline and the height of maximum concentration. With no plume rise, the maximum concentration in the plum e will stay at the same height and concentrations can only reach the ground through vertical dispersion. For a pseudo- point and usually any point within an area, there is no initial vertical dispersion; however, a volume source has initial efore, a volume source with the same level of emissions as a dispersion. Ther point source can have a greater impact than a pseudo- pseudo- point source within short distances because the plume reaches the ground more quickly. point source will directly affect point source. The shape of a non- Shape of a non- • the model’s prediction of the magnitude and location of maximum concentrations. In addition, the predicted frequency of occurrence will also be affected. Therefore, it would not be appropriate to represent the base of a long and narrow source of emissions as a single equivalent square, unless there were other mitigating factors such as great distance from the source to the property line or receptors of concern. Either multiple volumes, single area, or several areas may be an appropriate choice. Keep in mind that a justification for any choice of source type based on the specific factors for the project is required. of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 73 110

79 Downwash Applicability Appendix L - Downwash is a term used to represent the potential effects of a building on the dispersion of emissions from a source. Downwash is considered for sources characterized as point sources. The stack height and proximity of a point source to a structure can be used to to sources determine the applicability of downwash. Downwash does not apply characterized as areas. Downwash is indirectly considered for volume sources by adjusting the initial dispersion factors. Point sources with stack heights less than good engineering practice (GEP) stack height should consider dispersion impact s associated with building wake effects (downwash). : 51.100(ii)) GEP stack height is the greater of (40 Code of Federal Regulation ( CFR) (1) 65 meters, measured from the ground- level elevation at the base of the stack ; (2)(i) For stacks in existence on January 12, 1979, and for which the owner or operator had obtained all applicable permits or approvals required under 40 CFR parts 51 and 52, H = 2.5H g provided the owner or operator produces evidence that this equation was actually relied blishing an emission limitation; on in esta (ii) For all other stacks, = H + 1.5L H g level elevation at the base is the GEP stack height, measured from the ground- H where g level elevation at the of the stack; H is the structure height, measured from the ground- base of the stack; and L is the lesser of the structure height or maximum dimension ected width (the width as seen from the source looking towards either the wind proj direction or the direction of interest) of the structure. s define the stack height above which building wake effects on the stack formula ese Th ignificant. gas exhaust may be considered ins A structure is considered sufficiently close to a stack to cause downwash when the minimum distance between the stack and the building is less than or equal to five times the lesser of the structure height or maximum projected width of the structure (5L). This distance is commonly referred to as the structure's region of influence. If the source is located near more than one structure, assess each structure and stack configuration separately. For SCREEN3, include the building with dimensions that result in the highest GEP stack height for that source, to evaluate the greatest downwash effects. Be aware that when screening tanks, the tank diameter should not be used. The SCREEN3 model uses the square root of the sum of the individual squares of both the width and length for a structure in order to calculate the projected width. Because most tanks are round, the projected width is constant for all flow vectors. However, using the ted width that is too actual tank diameter for both width and length will result in a projec large. Therefore, when screening tanks, the diameter of the tank should be divided by the square root of 2. of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 74 110

80 For refined models, there are tools available for assessing each structure and stack configuration if a source is located near more than one structure. The Building Profile -building Input Program - -PRIME) is a multi Plume Rise Model Enhancements (BPIP dimensions program incorporating the GEP technical procedures for PRIME applications, parameters for use with air dispersion which calculates direction- specific downwash models. For more information on the user’s guide and the program documentation, see modeling -dispersion- -quality www.epa.gov/scram/air the following url: - model -related- -programs#bpipprm support Once downwash applicability is determined, provide documentation to support that determination. The documentation may include, but is not limited to, a plot plan with all sources and structures clearly labeled, a table of structure heights used in the downwash analysis, recent aerial photography, etc. Note that for solid structures surrounded by porous structures, only include the dimensions for the solid structure. For example, if a building is surrounded by condensed piping, include the dimensions of the enclosed building in the downwash analysis and do not base the dimensions on the total size of the enclosed building and condensed piping. of - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 75 TCEQ 110

81 or Design – Recept Appendix M For modeling, receptors are locations where the model calculates a predicted concentration. Design a receptor grid with sufficient spatial coverage and density to determine the maximum predicted ground- level concentration in an off -property area or an area not controlled by the applicant. For NAAQS and PSD increment modeling, receptors should cover the entire area of de minimis impact. For example, if the model predictions at the edge of the receptor grid are greater than de minimis, extend the receptor grid until the model predictions are less than de minimis. When designing a receptor grid, consider such factors as: • Results of screening analyses; • A source's release height; Proximity of sources to the property line; • industrial r eceptors and ambient air monitors; and • Location of non- Topography, climatology, and other relevant factors. • In addition, the location of ambient air receptors should guide the design of the receptor grid. Ambient air for minor New Source Review (NSR) modeling starts at the applicant's property line. If a single property line designation (SPLD) exists, then ambient air for minor NSR modeling starts at the single property line boundary. Note that the SPLD does not apply to federal reviews. For Prevention of Significant Deterioration (PSD) modeling, ambient air starts at the applicant's fence line or other physical barrier to public access. Also, no receptors are required on the applicant's property because the air over an applicant's property is not ambient; therefore, in a regulatory sense, applicants cannot cause a condition of air pollution on their property from their own sources. Generally, the spaci ng of receptors increases with distance from the sources being evaluated. Consider the following types of receptor spacing: • . Spaced 25 meters apart. Tight receptors could extend up to Tight receptors 300 meters from the sources being evaluated. Consider the distance between 200- the source and the property or fence line. Spaced 100 meters apart. Fine receptors could extend one . • Fine receptors kilometer (km) from each source being modeled. • . Spaced 500 meters apart. Medium receptors could cover the Medium receptors area that lies between one and five km from each source. . Spaced one km apart. This spacing could cover the area that Coarse receptors • lies beyond the medium receptors out to 50 km. of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 76 110

82 al Transverse Mercator Enter receptor locations into air dispersion models in Univers -property source locations and off (UTM) coordinates, in order to be consistent with on- represented in the air permit application, and other reference material, such as United the datum used for UTM States Geological Survey (USGS) topographic maps. Provide coordinates. Applicable UTM zones in Texas are either 13 (from the west border to 102 102 and 96 degrees longitude), or 15 (east of (between ees longitude), 14 degr ems based on plant degrees longitude to the east border). Do not use coordinate syst 96 coordinates or other applicant -developed coordinate systems. Special cases to consider when developing a receptor grid In most cases, the property line is well defined and all sources of emissions are on property. However, for some activ ities, such as marine loading, sources may be located -property and emitting directly into ambient air. For these cases, the following guidance off for determining the points of evaluation is appropriate for the technical review process, the analysis is for a standard or effects screening level (ESL), with and applies whether one exception. The Texas legislature enacted Section 382.066 in the Texas Health and Safety Code (THSC) [House Bill (HB) 3040] for shipyard facilities. This section exempts criteria or ship repair operations from modeling and effects review for non- shipbuilding pollutants over coastal waters. Therefore, for these facilities, the following guidance only eptors applies to reviews concerning criteria pollutants. For non- criteria pollutants, no rec are required over water. Off-property receptors over water There are three basic approaches that could be used to determine where receptors -property in ambient air. These could be should be placed when a source is located off used individually or in combination. These distances would apply for technical review purposes only. The applicant must still comply with all the Agency’s rules and regulations. : A fixed distance for modeled receptor grid points of 25 meters is Set distance • -level fugitive normally used for low -type emissions and for emissions from stacks that could be affected by downwash. The points start at the property line and -200 meters before the suggested grid spacing changes. If extend from about 100 the activity is located off in the water, the source of emissions is -property considered to be part of the property during actual operations. Since the general public would not be present at the source, receptors should be placed starting at a distance 25 meters from the edge of the source instead of on the actual property line. : There are two general distance limit scenarios. Controlled or restricted distance • Controlled: If the applicant can limit access to an area near the source of o emissions for the duration of the operation such that the general public and -site workers would not be exposed, the modeled receptor grid points could off begin at the edge of the control area, as well as, on the property line in the uncontrolled areas. Use of buoys would be an example of a way to limit access. of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 77 110

83 o Restricted: If the applicant can show that access is restricted, the modeled receptor grid points could begin at the edge of the restricted area, as well as, on the property line in the unrestricted areas. For the purposes of modeling and a restricted area is accessible only to the applicant’s employees, effects review, including personnel associated with marine vessel operations. If other individuals have access to the area, then the area is not restricted, and receptors would be placed in the area. Exam ples of restricted areas could be a coastal easement agreement with the General Land Office that allows the applicant to restrict access, or any other authority that allows the applicant to post signs that prohibit access to anyone other than the applicant ’s personnel. The applicant should provide documentation for restricted areas, including specific coordinates and any applicable specified conditions for the area, to the permit reviewer. Note that a restricted area could be a water area, shore area, or both. Model limitation distance • : There is another consideration, in addition to the set or controlled distance consideration. The model may not be able to calculate a concentration immediately adjacent to the source. In that case, the modeled receptor grid points should begin at the closest point that the model can calculate a concentration from the source at or beyond 25 meters from the edge of the source. The distance of the grid points from the edge of the source would be linked to the limiting algorithm in the model. This distance could be a minimum of one meter for meters from the center of a , or an area source to about 47 a point, pseudo- point volume source with about a 91- meter base. Note that a model’s limitation is not related to a “property line” but to an algorithm in the model. Therefore, there may be sources that are located on a property at a distance that would prevent the model from calculating a concentration on a property line or on a grid receptor placed on a land location off the property. Following are some receptor placement examples : Consider a site that has emissions from a stack on a Receptor Placement Example 1 ship that is moored at a dock in the water off the actual property of the applicant. distance of 25 meters from the edge of the ship Receptors should be placed starting at a in the water and out a sufficient distance to record the highest predicted concentrations and to demonstrate that concentrations are declining with distance. ucts blasting operations in at cond : Consider a site th Receptor Placement Example 2 locations at a site: a dock, located in the water off the applicant’s actual property; and, two outside a building located in the center of the property. Operations are such that the (a criteria pollutant) should be evaluated per permit reviewer determines that PM 10 HB3040. During blasting at the dock, the applicant can control access out to a distance of 40 meters over water from all sides of the ship. For the controlled area, receptors should be placed at the start of the area. Normal receptor placement procedures would be used -line receptors over land, and away from the controlled area over the for the property water. Receptors over both land and water should extend out a sufficient distance to record the highest predict ed concentrations and to demonstrate that concentrations are declining with distance. of - (APDG 6232v4 , Revised 09 TCEQ /18) Air Quality Modeling Guidelines Page 78 110

84 If the dock and building operations can occur at the same time, then the controlled area owever, if for the dock operation will drive the creation of the receptor grid over water. H the operations can occur independently, and the area near the dock will not be controlled during operations at the building, then a separate model run may be required for this tance from the scenario depending on factors such as the amount of emissions and dis water. In this case, the receptors should start at the property line and extend directly over water. Receptor Placement Example 3 : Consider a site where the applicant unloads container ships at a dock. Assume that the width of the ship is 20 meters. In addition, assume that the operation can be represented by a volume created by the movement of a multiple scoop conveyor lifting material out of a compartment and onto another conveyor. The length and width of the volume are 16 meters based on the size of the compartment. With no other adjustments to the initial dimensions, receptors over water could be placed starting at a distance of about 9 meters from the center of the volume. However, since this distance is less than 25 meters from the edge of the ship, the greater distance should be used. In this case, the receptors over water would begin at a distance of 45 meters from the dock (25 meters from the edge of the ship) and should continue out a sufficient distance over the water to record the highest predicted concentrations and to demonstrate that concentrations are declining. Normal receptor placement would be used for the -line receptors away from the water. If the distance from the center of the volume property s less than 9 er property line i wat meters, the recep tors over land would start at to a non- 9 meters from the center of the volume. of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 79 110

85 Surface Characteristics of the Modeling Domain Appendix N - The modeling domain is the region that will influence the dispersion of the emissions from the facilities under review. Surface characteristics for the modeling domain should be evaluated when determining representative dispersion coefficients. Air dispersion models ispersion utilize dispersion coefficients to determine the rate of dispersion for a plume. D coefficients are influenced by factors such as land- -cover (LULC), terrain, use / land averaging period, and meteorological conditions. Evaluating the LULC within the modeling domain is an integral component to air dispersion modeling. The data ob tained from a LULC analysis can be used to determine representative dispersion coefficients. The selection of representative dispersion use types. For coefficients may be as simple as selecting between rural or urban land- ive dispersion coefficients can be determined by more complex analyses, representat parameters that are directly related to the LULC within the modeling domain. LULC Analysis for ISC, ISC-PRIME, and SCREEN3 For the ISC, ISC -PRIME, and SCREEN3 models, the dispersion coefficients are based on whether the area is predominately rural or urban. The classification of the land use in the vicinity of sources of air pollution is needed because dispersion rates differ between rural sion because of and urban areas. In general, urban areas cause greater rates of disper -induced mixing. This mixing is due to the increased turbulent mixing and buoyancy combination of greater surface roughness caused by more buildings and structures and greater amounts of heat released from concrete and similar surfaces. Environmental Protection Agency (EPA) guidance provides two procedures to The determine whether the character of an area is predominantly rural or urban. One use typing and the other is based on population density. Both procedure is based on land- kilometer radius from a procedures require an evaluation of characteristics within a three- use typing method is based on the work of August Auer (Auer, 1978) source. The land- and is preferred because it is more directly related to the surface characteristics of the luated area that affects dispersion rates. eva -intensive to apply. A While the Auer land- use typing method is more direct, it can be labor -use designation is clear; . If the land simplified technique can be used as a screening tool that is, about 70 percent or more of the total land use is either rural or urban, then further refinement is not necessary. of - (APDG 6232v4 , Revised 09 TCEQ /18) Air Quality Modeling Guidelines Page 80 110

86 Simplified Auer Land-Use Analysis use types: Industrial (I), The Auer land- use approach considers four primary land- Commercial (C), Residential (R), and Agricultural (A). Within these primary types, subtypes are identified in Table N -1. Table N -1. Land Use Types and Corresponding Dispersion Classification Class Type Description Urban Heavy Industrial I1 Urban I2 Light/Moderate Industrial Commercial C1 Urban Common Residential R1 Rural (Normal Easements) Compact Residential R2 Urban (Single - Family) Compact Residential R3 Urban - (Multi Family) Estate Residential Rural R4 (Multi - Acre) A1 Metropolitan Natural Rural A2 Agricultural Rural (Grass/Weeds) Undeveloped A3 Rural Undeveloped A4 Rural (Heavily Wooded) Rural Water Surfaces A5 use analysis is to estimate the percentage of the area The goal in a simplified Auer land- within a three- kilometer radius of the source to be evaluated that is either rural or urban. Both land use types do not need to be evaluated since the land use type that has the greatest percentage will be the representative type. The primary assumption for the simplified procedure is based on the premise that many facilities should have clear -cut rural or urban designations; that is, the percentage of the use designation primary designation should be greater than about 70 percent. If the land- represents less than 70 percent of the total, supplement the analysis with current aerial through photography of the area surrounding the sources or with a detailed drive- use designation to be used in the modeling demonstration. summary to support the land- of - (APDG 6232v4 , Revised 09 TCEQ /18) Air Quality Modeling Guidelines Page 81 110

87 LULC Analysis for AERMOD and AERSCREEN are determined by parameters For AERMOD and AERSCREEN, dispersion coefficients that are directly related to the LULC within the modeling domain. For example, albedo, use types and all Bowen ratio, and surface roughness length all vary for different land- the surface boundary layer. three parameters affect processes that take place in • - defined as the ratio of reflected flux density to incident flux density, Albedo referenced to some surface. A high albedo value is associated with a greater reflection of amount of reflection of incoming solar radiation. An increase in the incoming solar radiation will result in less energy available for sensible or latent heat loss and thus a decrease in convective turbulence. • Bowen Ratio - defined as the ratio of sensible heat flux to latent heat flux from the e up into the air. A low Bowen ratio is associated with a surface that earth’s surfac has a larger latent heat flux than sensible heat flux. A large latent heat flux means less energy is available for sensible heat loss, and will result in a decrease in convective turbul ence. - defined as the height above the displacement plane Surface Roughness Length • at which the mean wind becomes zero when extrapolating the logarithmic wind speed profile downward through the surface layer. A high surface roughness length will result in greater mechanical turbulence and increased vertical mixing. There are numerous field studies and references that document different values for these surface characteristic parameters based on LULC, as well as for different seasons of the year. In addition, a tool has been developed by the EPA (AERSURFACE) that can be used to process land cover data to determine the surface characteristic values of the modeling domain. To download AERSURFACE and the corresponding documentation, - model -support -related- modeling refer to: www.epa.gov/scram/air -quality -dispersion- programs#aersurface ed, including any references for Provide the technical justification for model options select parameter values in the air quality analysis (AQA). AERMOD and AERSCREEN also include an urban option so that the model can be run using urban algorithms. The urban option used in AERMOD and AERSCREEN is not the same as urban dispersion coefficients used with ISC, ISC -PRIME, and SCREEN3. The urban option in AERMOD and AERSCREEN is used to account for the dispersive nature like” boundary layer that forms during nighttime conditions due to the of the “convective- urban heat isl and effect. The urban heat island effect is due to industrial and urban development. In rural areas, a large part of the incoming solar energy is used to evaporate water from vegetation and soil. In cities, where less vegetation and exposed e majority of the sun’s energy is absorbed by urban structures and asphalt. soil exists, th At night, the solar energy (stored as vast quantities of heat in city buildings and roads) is les and slowly released into the city air. Additional city heat is given off at night by vehic factories, as well as by industrial and domestic heating and cooling units. The slow release of heat tends to keep nighttime city temperatures higher than those of the faster cooling rural areas. The magnitude of the urban heat island effect is dri ven by the rural temperature difference that develops at night. urban- of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 82 110

88 The urban option is used to enhance the turbulence for urban nighttime conditions over that which is expected in the adjacent rural, stable boundary layer. For most applications, the Lan d Use Procedure described in Section 7.2.1.1 of the Guideline on Air Quality Models (GAQM) is sufficient for determining the urban/rural status. However, there may be sources located within an urban area, but located close enough to a body of water or ther non- urban land- use categories to result in a predominately rural land use to o classification within three kilometers of the source following that procedure. Users are therefore cautioned against applying the Land Use Procedure on a source- by-source but should also consider the potential for urban heat island influences across the basis, full modeling domain. This is consistent with the fact that the urban heat island is not a localized effect, but is more regional in character. bout the urban option and the corresponding required input For additional information a parameters for the urban option, see the guidance contained in the AERMOD : Implementation Guide www.epa.gov/scram/air -recommended- and -preferred- modeling -dispersion- -quality models#aermod Terrain Much of Texas can be characterized as having relatively flat terrain; however, some areas Air Dispersion Modeling Team (ADMT) to-complex terrain. The of the state have simple- defines flat terrain as terrain equal to the elevation of the stack base; simple terrain as terrain lower than the height of the stack top; and, complex terrain as terrain above the height of the plume center line (for s creening modeling, complex terrain is terrain above the height of the stack top). Terrain above the height of the stack top but below the height of the plume center line is known as intermediate terrain. determine how terrain elevations Evaluate the geography within the modeling domain to should be addressed. There are many sources of terrain elevation data that can be used in air dispersion modeling demonstrations. However, the sources of terrain elevation data eference system, areas covered, and may differ in sampling interval, geographic r accuracy of data. For example, Universal Transverse Mercator (UTM) is just one of many map projections used to represent locations on a flat surface. Also, be aware that there are several horizontal data coordinate systems or datum (North American Datum (NAD) 27, World Geodetic System (WGS) 72, NAD83, and WGS84) that are used to represent locations on the earth’s surface in geographic coordinates (latitude and longitude). When ocations in UTM coordinates, make certain representing receptor, building, and source l that all of the coordinates originated in, or are converted to, the same horizontal datum. -PRIME models, use both the simple and complex For modeling with the ISC and ISC lat terrain applies. That is, if terrain elevations for terrain calculation options if other than f receptors are used, activate both simple and complex options. In cases where multiple sources with varying heights of emissions must be evaluated, use the ISC or ISC -PRIME N3 model. Since the SCREEN3 model can only evaluate models rather than the SCREE one source at a time, combined results for sources in intermediate- to-complex terrain might not be representative. of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 83 110

89 If other than flat terrain is modeled, use appropriate receptor elevations. Ensure that t he higher terrain is always included in any direction from the source, not just the highest terrain. For example, if the highest terrain is to the north of the property, but the second highest terrain is to the south, include receptors at and in the general vicinity of each location. Conservative options may be used to reduce the effort of determining specific receptor heights for dense grid networks. For example: • Omit terrain if only ground- Terrain is generally level fugitive sources are modeled. not a consideration when modeling releases from fugitive sources. Releases from these sources are typically neutrally buoyant and are essentially at ground level. Maximum concentrations from fugitive releases are thus expected to occur at the nearest downwind receptor location. However, include terrain near a property or fugitive point sources are fence line for elevated fugitive releases, or if non- included in the modeling demonstration. Set receptors to the stack base elevation, if some elevations are below stack base. • If the terrain is all below stack base, choose the FLAT terrain height option • -PRIME models, which will keyword in the Control pathway of the ISC and ISC cause the model to ignore terrain heights. Note: do not select the elevated terrain without including receptor elevations in the Source pathway. height option For modeling with AERMOD and AERSCREEN, the model treats the plume as a combination of two limiting cases: a horizontal plume (terrain impacting) and a terrain- following plume. In flat terrain t . In complex terrain, AERMOD he two states are equivalent -stratified conditions. incorporates the concept of the dividing streamline for stably Generally, in stable flows, a two- layer structure develops in which the lower layer remains . Since the plume is modeled horizontal while the upper layer tends to rise over the terrain following plume), the as a combination of two limiting cases (horizontal plume and terrain- model handles the computation of pollutant impacts in both flat and complex terrain within the same modeling framework thereby obviating the need to differentiate between the formulations for simple and complex terrain. The model’s total concentration is calculated as a weighted sum of the concentrations associated with these two limiting cases or plume states. -processor program, AERMAP, has been developed to process terrain data in A pre conjunction with a layout of receptors and sources to be used in AERMOD. Using gridded terrain data, AERMAP first determines the base elevation at each receptor and source. AERMAP then calculates a representative terrain- influence height for each receptor (hill height scale) with which AERMOD computes receptor -specific dividing streamline values. For more information on AERMAP and the corresponding documentation, re fer to: -related- modeling www.epa.gov/scram/air -dispersion- -quality - -support model programs#aermap If there are significant problems with the resolution of the terrain data, that is, a mix of scales that could result in the omission of terrain features or significant changes in elevation, additional discrete receptors with appropriate elevations should be included in the receptor grid. of - (APDG 6232v4 , Revised 09 TCEQ /18) Air Quality Modeling Guidelines Page 84 110

90 Meteorological Data x O - Appendi The Air Dispersion Modeling Team (ADMT) has prepared meteorological data sets for modeling demonstrations in order to establish consistency among modeling demonstrations across the state. These data sets are available by county for download from the ADMT Internet page as follows: -PRIME For ISC/ISC www.tceq.texas.gov/permitting/air/modeling/admtmet.html For AERMOD www.tceq.texas.gov/permitting/air/modeling/aermod- datasets.html . In addition to the meteorological data sets, the Internet pages above include information on how the meteorological data sets were developed, as well as the file naming conventions of the meteorological data sets. For AERMOD, meteorological data sets have been developed using three surface roughness categories (low, medium, and high). Refer to Appendix N for additional appropriate surface roughness category. guidance on determining the For minor New Source Review (NSR) permit applications, the use of one year of National meteorological data may be sufficient. However, if five years of Weather Service (NWS) meteorological data are used, then us data for NWS year meteorological e the same five- applicable averaging periods for consistency. For Prevention of Significant all Deterioration (PSD) demonstrations, use the most recent, readily available five years of NWS meteorological data. The Guideline on Air Quality Models (GAQM) also provides an option to use prognostic meteorological data for a regulatory modeling application where there is no representative NWS station, and it is prohibitive or not feasible to collect spec ific data. The Environmental Protection Agency (EPA) adequately representative site- released the Mesoscale Model Interface Program (MMIF) that converts the prognostic meteorological data (Mesoscale Model 5 or Weather Research and Forecasting) into a format suitable for dis persion modeli ng applications. When processing prognostic meteorological data for AERMOD, the MMIF should be used to process data to generate AERMET inputs and the data subsequently processed through AERMET for input into The GAQM also notes that at least three years of prognostic meteorological AERMOD. data are required, and an operational evaluation of the meteorological modeling data for all model years (i.e., statistical or g raphical) should be completed. The use of these data will need to be coordinated with the ADM T. -ready model Provide an ASCII version of the data with the air quality analysis (AQA) submittal. of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 85 110

91 Applicants may request to use other available meteorological data not available from the btaining, preparing, ADMT. If the request is approved, the applicant is responsible for o and processing the data. Before these data sets are used in any modeling demonstration, the applicant should submit them to the ADMT. The ADMT should review and approve ological parameters the data sets and all the data used to develop the specific meteor required. Provide the following information: Surface and upper -air data. Provide how these data were obtained (e.g., National • Climatic Data Center [NCDC], Support Center for Regulatory Atmospheric Modeling [SCRAM], or other source). • cedures for replacing missing data. Replacement of missing data must follow Pro Procedures for Substituting Values standard procedures. Follow the guidance in for Missing NWS Meteorological Data for Use in Regulatory Air Quality Models ace missing values before processing them. Document and 1992) to repl (Atkinson, submit all occurrences of missing data and proposed replacement values. Technical justification and supporting documentation for all model selections • albedo, Bowen ratio, surface roughness leng th, etc.). (e.g., • Documentation for how these data will be processed, including quality quality control procedures. assurance/ of - (APDG 6232v4 , Revised 09 /18) TCEQ Air Quality Modeling Guidelines Page 86 110

92 Appendix P - Reporting Requirements The air quality analysis (AQA) submitted to the Texas Commission on Environmental Quality (TCEQ) in support of an air permit application becomes an addendum to the air permit application. The analysis should include the items below, as appropriate. Project Identification Information Provide the following information to clearly identify the analysis: • icant Appl o Facility o o Permit Application Number o Regulated Entity Number o Nearest City and County o Applicant's Modeler Project Overview • Include a brief discussion of the plant process(es), and types and locations of emissions under consideration. Type of Permit Revi ew Indicate the type of permit review required by the permit reviewer. • Constituents Evaluated List all constituents that were evaluated. Be sure to provide all relevant information • for each constituent evaluated (standard/effects screening level (ESL), che mical abstract service (CAS) number, etc.). Plot Plan Depending on the scope of the project, several plot plans may be needed to • present all requested information. • Include a plot plan that includes: A clearly marked scale. o All property lines. For Prevention of Significant Deterioration (PSD) Analyses, o include fence lines. A true o -north arrow. o Universal Transverse Mercator (UTM) coordinates along the vertical and horizontal borders. Please do not use plant or other coordinates. of - (APDG 6232v4 , Revised 09 TCEQ /18) Air Quality Modeling Guidelines Page 87 110

93 Include the datum of your coordinates. o o Reference UTM coordinates and locations of all emission points including fugitive sources modeled. Labels/IDs and coordinates for emission points on the plot plan should correlate o with the information contained in the AQA. o Buildings and structures on- -property which could cause property or off downwash. Include length, width, and height. Area Map • For minor New Source Review (NSR) Analyses, o Include a copy of the area map submitted with the air permit application. The 1.9 mile (three kilometer) radius of the map should cover the area within a use analysis. facility if used for the Auer land- o The area map should include all property lines . For sites with a single property line designation (SPLD), include all property lines associated with the SPLD . agreement with the AQA. and order Also include a copy of the SPLD o Add UTMs to the horizontal and vertical dimensions of the map section, as well as the date and title of the map. Include the datum of your coordinates. Annotate schools within 3,000 feet of the so urces nearest to the property line. o For the Health Effects Review, annotate the nearest non- o industrial receptor of any type. Include any additional non- industrial receptors requested by the Toxicology Division. • For PSD Analyses, o Include a copy of the area map submitted with the air permit application. The map should cover the area within a 1.9 mile (three kilometer) radius of the use analysis. facility if used for the Auer land- o The area map should include all fence lines. o Add UTMs to the horizontal and vert ical dimensions of the map section, as well as the date and title of the map. Include the datum of your coordinates. Include maps that show the location of: o  PSD Class I areas within 10 kilometers (6.2 miles) or 100 kilometers (62 miles). attainment areas, and  topographic features within Urban areas, non- kilometers (31 miles) or the distance to which the source has a 50 significant impact, whichever is less.  site or local meteorological stations, both surface and upper air. Any on- air monitoring sites used for background site ambient State/local/on-  concentrations. of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 88 110

94 Air Quality Monitoring Data For minor NSR and PSD National Ambient Air Quality Standards (NAAQS) • Analyses, o Provide the monitor ID, county, and address for each monitor. background concentrations were obtained. o Discuss how ambient o Include a summary of observations for each constituent and averaging time, if available. Provide all calculations, including electronic spreadsheets and substitution o data. For the Health Effects Review, identify monitored data that was used to • supplement or substitute for modeling. Demonstrate that the data represent near worst -case operational and meteorological conditions. Modeling Emissions Inventory • -Property Sources to be Permitted, On Include a copy of the Table 1(a) that was submitted with the air permit o application and subsequently approved by the permit reviewer. Ensure additional entries are provided on the Table 1(a) if stack parameters for any averaging period or load level could be different. o Identify spec ial source types or characterizations such as covered stacks, horizontal exhausts, fugitive sources, area sources, open pit sources, volume sources, stockpiles, and flares. Include all assumptions and calculations used to determine as appropriate the o size, sides, rotation angles, heights of release, initial dispersion coefficients, effective stack diameter, gross heat release and weighted (by volume) average molecular weight of the mixture being burned. Specify particulate emissions as a function of particl o e size; mass fraction for each particle size category; and particle density for each particle size category, as applicable. • Other On -Property Sources, -Property and Off Include the Air Permits Allowable Database (APAD) retrieval for each o constituent. Includ o e an additional list for each constituent for any sources modeled but were not included in the APAD retrieval. This list should contain all the information required by the Table 1(a). For PSD Analyses, include a list of secondary emissions, if applicable. o Secondary emissions occur from any facility that is not a part of the facility being reviewed, that would only be constructed or would have an increase of emissions as a result of the permitted project. of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 89 110

95 Table Correlating the Emission Inventory Source Name and Emission Point Number (EPN) with the Source Number in the Modeling Output • -references the source identification numbers used in the Include a table that cross modeling if they are different from the EPNs in the Table 1(a) or from any additional list of sources. Stack Parameter Justification Include the basis for using the listed stack parameters (flow rates, temperatures, • stack heights, velocities). This should include the calculations used to determine the parameters. If the production or load levels could be less than 100 percent, demonstrate how • the modeled emission rates and stack parameters were obtained to produce the -case impacts (in certain cases lower production levels may result in higher worst predicted impacts). percent, 75 percent and 100 percent production or Include at least 25 percent, 50 • load levels analyses, if the source could be operated at these reduced levels. Scaling Factors • Discuss how emission scalars were developed and used in the modeling e scalars that should be included in an demonstration. In addition, identify thos enforceable permit provision, such as restricted hours of operation. Models Proposed and Modeling Techniques • Include a detailed discussion of the models that were used, model version options such as the regulatory default option numbers, and the model entry data and the period option. • Discuss any specialized modeling techniques such as screening, collocating ing ratio sources, and . Include assumptions and sample calculations. • Selection of Dispersion Option ection of urban or rural dispersion coefficients on the Auer land- Base the sel • use analysis. • Include a detailed discussion and sufficient technical justification to support the selection of the dispersion option. of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 90 110

96 Building Wake Effects (Downwash) Discuss how downwash st • ructures were determined and include applicable information required to use the EPA's BPIP -PRIME. Submit all input files and files generated by the BPIP -PRIME program, and any computer assisted drawing files. • used in the ated building IDs and associ Provide a table of structure heights downwash analysis. Receptor Grid • Discuss how the receptor grids were determined for each type of analysis. Include the datum of your coordinates. • eptors Discuss if terrain was applicable. If so, discuss how terrain for individual rec • was determined. Meteorological Data • Indicate the surface station, surface station anemometer height, surface station -air station, and period of record, as applicable. profile base elevation, upper • Include the meteorological data files used for all demonstrations. Discuss how meteorological data were determined or replaced. Include • Air ) approval of replacement data. ADMT Dispersion Modeling Team ( In addition, submit all the supplementary data used to develop the specific input • meteorological parameter s required by the meteorological pre- processor programs. Modeling Results Summarize and compare the modeling results relative to all applicable de minimis • values, standards, guidelines, or reference air concentrations. Tabulated results are preferred. For the Health Effects Review, present the maximum concentrations predicted for • industrial receptors separately and include the location of the receptor. non- Provide the predicted frequency of exceedance if applicable. For the Additional Impacts Analysis (for PSD Analyses), include the results of the • additional impacts analysis for growth, visibility, and soils and vegetation. • For the Class I Area Impacts Analysis (for PSD Analyses), include the results of the Class I area impacts analysis, as applicable. of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 91 110

97 Electronic Information (Model Input/Output and Associated Computer or Electronic Files) • Include: All input and output files for each air dispersion model run, including data, grid o and plot files. All files produced by a software entry program. o ed downwash program input and output files and any computer All automat o assisted drawing files. All meteorological data files in ASCII format. o o All boundary files, including computer assisted drawing files, specifying coordinates for property lines. ll boundary files, including computer assisted drawing files, For PSD Analyses, a o specifying coordinates for fence lines. o Include all spreadsheet files used for comparison of predicted concentrations with standards or guidelines. This includes, but is not limited to, spreadsheet files used for ratio techniques. of - (APDG 6232v4 , Revised 09 TCEQ /18) Air Quality Modeling Guidelines Page 92 110

98 Conducting an Ambient Ozone Impacts Analysis Appendix Q - For a Prevention of Significant Deterioration (PSD) application, if a project will emit 100 or more of volatile organic compounds (VOCs) or nitrogen oxides tons per year (tpy) (NO ) emissions, an ozone impact analysis to demonstrate predicted compliance with the x 8-hour ozone standard is required, including the gathering of ambient air quality data. The person conducting the analysis should follow the basic procedure described in the following paragraphs: specific monitoring data or representative monitoring Step 1. Determine whether site- data will be used to obtain an ozone background concentration. -specific monitoring program must last a minimum of at l east four to six A site • months up to twelve months during the ozone season (an ozone season can vary highest daily maximum based on the location being evaluated). Use the fourth- 8-hour average ozone concentration monitored during a single ozone season or up three- hour ozone highest daily maximum 8- year average of the annual fourth- to a concentrations if data are available. Representative monitoring data may be available from the ozone network in Texas. • Refer to Appendix D for additional guidance on determining a representative ozone background concentration. If the background concentration equals or exceeds 70 parts per billion (ppb), Step 2 cannot be used and approaches such as the applicant providing emissions offsets or reducing proposed VOC or NO or the project below 100 tpy would be emissions f x considered. Step 2. Determine the potential impacts on ozone levels associated with the proposed project emissions. As part of the revisions made to the Guideline on Air Quality Models (January 17, 2017), Environmental Protection Agency (EPA) promulgated a two- tiered demonstration the approach for addressing single- source impacts on ozone. The first tier involves the use of technically credible relationships between precursor emissions and a source’s impact (th at may be published in literature; developed from modeling that was previously conducted for an area by a source, a governmental agency, or some other entity that is deemed sufficient; or generated by a reduced form model) in combination with other ive information and analysis for the purpose of estimating secondary impacts from support a particular source. The second tier involves application of more sophisticated case -specific chemical transport models (e.g., photochemical grid models). The appropriate tier for a given application should be selected in consultation with the Air Dispersion Modeling Team (ADMT) and be consistent with applicable EPA guidance. Tier 1 The EPA developed a tier 1 demonstration tool for ozone precursor emissions called Modeled Emis sion Rates for Precursors (MERPs). The development of the tool and 2, 201 December dated related guidance is summarized in a memorandum from EPA 6 with a subject, “Guidance on the Development of Modeled Emission Rates for Precursors of - (APDG 6232v4 , Revised 09 TCEQ /18) Air Quality Modeling Guidelines Page 93 110

99 nstration Tool for Ozone and PM under the PSD Permitting (MERPs) as a Tier 1 Demo 2.5 Program.” The basic idea behind the MERPs is to use technically credible air quality modeling to relate precursor emissions and peak secondary pollutant impacts from specific or hypothetical sourc es. To derive a MERP value, the model predicted relationship between precursor emissions from hypothetical sources and their downwind maximum impacts can be combined with a significant impact level (SIL) using the following equation: 푓푓푟푟푀푀푒푒 푟푟푟푟푟푟 푒푒 푒푒푒푒푒푒푒푒푒푒푒푒 푀푀푒푒 푒푒푀푀 푠푠푟푟푒푒푒푒 ℎ푦푦푦푦 푀푀푟푟ℎ푒푒푟푟푒푒푒푒푟푟푒푒 푀푀푀푀푀푀 푒푒푒푒푒푒푀푀 푆푆푆푆푆푆∗ 푀푀푀푀푀푀푀푀 = 푒푒푀푀 푠푠푟푟푒푒푒푒 ℎ푦푦푦푦 푀푀푟푟ℎ푒푒푟푟푒푒푒푒푟푟푒푒 푒푒푒푒푦푦푟푟푒푒푟푟푓푓푟푟푀푀푒푒 푞푞푠푠푟푟푒푒푒푒푟푟푦푦 푀푀푀푀푀푀 푒푒푒푒푒푒푀푀 푟푟푒푒푟푟 The ADMT used the air quality modeling results presented in Appendix A of the EPA MERPs memorandum to derive MERPs for the hypothetical sources located in Texas -case derived MERPs for using the EPA recommended SIL for ozone (1 ppb). The worst the hypothetical Texas sources are presented below in Table Q -1: Table Q -1. Worst -case MERP Val ues (in tons per year) - 8 hour Ozone Precursor NO 250 x VOC 2290 To use the MERP values in Table Q -1 as a tier 1 demonstration, an analysis will need to be provided that shows that the emissions characteristics of the project source and the chemical and physical environment in the vicinity of the project source are adequately represented by the various hypothetical Texas sources modeled by the EPA (and documented in the EPA MERPs memorandum). are both precursors to ozone For the ozone impacts, VOC and NO formation, and the x contributions to ozone formation are considered together. The proposed ozone precursor emissions increase can be expressed as a percent of the lowest MERP for each will not be precursor and then summed. A value less than 100% indicates that the SIL exceeded: 푒푒푒푒푒푒푒푒푒푒푒푒 푀푀푒푒푒푒 푉푉푁푁푉푉 푦푦푟푟푀푀 푝푝푒푒푒푒푟푟 푒푒푒푒푒푒푒푒푒푒푒푒 푀푀푒푒푒푒 푦푦푟푟푀푀 푝푝푒푒푒푒푟푟 푁푁푁푁 푥푥 + �∗ < 100% 100 � 푉푉푁푁푉푉 푀푀푀푀푀푀푀푀 푁푁푁푁 푀푀푀푀푀푀푀푀 푥푥 and 120 tpy of VOC. For example, a project with proposed emissions of 200 tpy of NO x precursors to ozone formation, the contributions to 8- and VOC are both Since NO hour x daily maximum ozone are considered together. The proposed emissions increase can be expressed as a percent of the lowest MERP for each precursor and then summed: 200 푟푟푦푦푦푦 푟푟푦푦푦푦 120 �∗ � 100 + 푟푟푦푦푦푦 250 2290 푟푟푦푦푦푦 [ ] ∗ 100 0.05 0.8 + = = 85% of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 94 110

100 Since the value is less than 100%, this example shows the source impact is less than the SIL and a cumulative analysis would not be needed. -1 are too conservative, then MERP If the worst- case MERP values listed in Table Q values for a specific hypothetical source may be used provided a demonstration is shown -2 that the identified hypothetical source is representative for the project source. Tables Q -3 show the derived MERPs for all of the hypot hetical Texas sources for precursors and Q NO and VOC, respectively. The ADMT used the air quality modeling results presented in x Appendix A of the EPA MERPs memorandum (also provided in Tables Q -3 as -2 and Q the Max Impact) to derive MERPs for the hypothetical sources located in Texas using the EPA recommended SIL for ozone: Table Q -2. NO MERP Values for Hypothetical Texas Sources x Height Max Impact Source Emissions (tpy) MERP (tpy) (ppb) 500 H 5 (Terry) 1.17 427 5 (Terry) 500 L 1.2 416 5 (Terry) H 2.04 490 1000 5 (Terry) 3000 H 4.29 699 19 (Henderson) 500 H 1.93 259 19 (Henderson) 500 L 2 250 1000 H 3.46 289 19 (Henderson) 19 (Henderson) 356 8.42 H 3000 20 (Harris) H 0.78 641 500 20 (Harris) 500 L 0.79 632 20 (Harris) 1000 H 1.35 740 20 (Harris) 3000 H 2.81 1067 24 (Parker) 500 H 1.3 384 L 24 (Parker) 500 1.29 387 24 (Parker) H 2.31 432 1000 24 (Parker) 3000 H 5.14 583 25 (Guadalupe) 500 H 0.72 694 25 (Guadalupe) 500 L 0.73 684 1000 H 1.34 746 25 (Guadalupe) H 3000 25 (Guadalupe) 980 3.06 of - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines TCEQ Page 95 110

101 Table Q -3. VOC MERP Values for Hypothetical Texas Sources Max Impact Height Emissions (tpy) Source MERP (tpy) (ppb) 0.03 H 5 (Terry) 16666 500 500 L 5 (Terry) 0.03 16666 5 (Terry) 1000 H 0.06 16666 3000 H 0.22 13636 5 (Terry) 19 (Henderson) 500 L 0.05 10000 19 (Henderson) H 0.15 6666 1000 19 (Henderson) 1000 L 0.1 10000 19 (Henderson) 3000 H 0.51 5882 20 (Harris) 500 L 0.14 3571 1000 H 0.29 3448 20 (Harris) 0.27 L 1000 20 (Harris) 3703 20 (Harris) H 1.09 2752 3000 500 L 0.17 2941 24 (Parker) 24 (Parker) 1000 H 0.33 3030 24 (Parker) 1000 L 0.33 3030 2290 24 (Parker) 3000 H 1.31 3125 0.16 L 500 25 (Guadalupe) H 1000 25 (Guadalupe) 0.34 2941 L 2777 0.36 25 (Guadalupe) 1000 3000 H 1.29 25 (Guadalupe) 2325 The sources are identified by number and county. The numbers are the same numbers used to identify sources in the EPA MERP memorandum. For source height, a value of H represents an elevated release (90 meters) and a value of L represents a surface release (1 meter). and 310 tpy of VOC As an , a project with proposed emissions of 800 tpy of NO example x is proposed to be located in Caldwell County. Caldwell County is adjacent to Guadalupe County and the MERP values from source 25 (Guadalupe) will be used. An analysis is compare the chemical and physical environment in the vicinity of the first conducted to project source (Caldwell County) relative to the hypothetical source modeled in Guadalupe County. Information used in the analysis may include average and peak temperatures, humidity, terrain, rural/urban nature of the area, regional sources of pollutants (biogenic, industrial, etc.), and ambient concentrations of relevant pollutants. Based on this analysis, and the proposed emissions associated with the project, the NO x MERP value associ ated with the 1000 tpy source and the VOC MERP value associated with the 500 tpy source will be used. As with the previous example, the proposed 110 - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 96 of TCEQ

102 emissions increase can be expressed as a percent of the MERP for each precursor and then summed: 800 푟푟푦푦푦푦 310 푟푟푦푦푦푦 �∗ � + 100 3125 푟푟푦푦푦푦 푟푟푦푦푦푦 746 [ ] = 0.1 1.07 + 100 ∗ 117% = value is greater than 100 percent, a cumulative analysis is needed since Given that the the source impact is greater than the SIL. The cumulative analysis for a NAAQS demonstration includes contributions from background concentrations and impacts associated with ozone precursor emissions. The following equation is used: + 푉푉푠푠푒푒푠푠푒푒푟푟푟푟푒푒 퐶퐶푒푒 푒푒푀푀푒푒푒푒푒푒푒푒푟푟푟푟푟푟푟푟푒푒푀푀푒푒 = 퐵퐵푟푟푒푒 퐵퐵퐵퐵 푟푟푀푀푠푠푒푒푀푀 푒푒푀푀푒푒푒푒푒푒푒푒푟푟푟푟푟푟푟푟푒푒푀푀푒푒 푁푁푁푁 푉푉푁푁푉푉 푒푒푒푒푒푒푒푒푒푒푒푒 푀푀푒푒푒푒 푦푦푟푟푀푀 푝푝푒푒푒푒푟푟 푒푒푒푒푒푒푒푒푒푒푒푒 푀푀푒푒푒푒 푦푦푟푟푀푀 푝푝푒푒푒푒푟푟 푥푥 � + �∗푆푆푆푆푆푆 푁푁푁푁 푀푀푀푀푀푀푀푀 푀푀푀푀푀푀푀푀 푉푉푁푁푉푉 푥푥 Continuing with the Caldwell County project example, the 8- hour background concentration for the project area is determined to be 60 ppb. The cumulative concentration would be: 310 푟푟푦푦푦푦 푟푟푦푦푦푦 800 �∗ + 푦푦푦푦푝푝 1 + 푦푦푦푦푝푝 60 = � 푟푟푦푦푦푦 3125 푟푟푦푦푦푦 746 푦푦푦푦푝푝 + = 60 푦푦푦푦푝푝 1.17 61 = 푦푦푦푦푝푝 .17 hour NAAQS (70 ppb) and the is less than the 8- The cumulative concentration -site demonstration is complete. The contributions to the formation of ozone from off sources are generally accounted for through the use of background concentrations. For been recently permitted and are not yet operating, -site sources that may have nearby off their contribution towards ozone formation may need to be determined since background concentrations will not include their contribution. Tier 2 Tier 2 assessments are intended for impact assessments that are not able to be satisfied with a tier 1 demonstration in that pre- existing information is not available or representative of the situation such that more refined modeling is necessary. For these situations, application of more sophisticated case- specif ic chemical transport models source impacts. (e.g., photochemical grid models) should be performed to address single- - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines TCEQ Page 97 of 110

103 ) Secondary Formation of Particulate Matter (PM Appendix R - 2.5 The purpose of this appendix is to provide guidance for addressing secondary formation of PM must be addressed even if the . Please note that secondary formation of PM 2.5 2.5 predicted concentration for direct PM is less than the significant impact levels (SILs). 2.5 Furthermore, secondary formation of PM for p must be addressed rojects that trigger 2.5 , including cases where the project PM minor or federal New Source Review (NSR) for 2.5 )) are ) and nitrogen oxides (NO emissions of precursor emissions ( sulfur dioxide (SO x 2 less than the significant emission rates (SERs). Terms Direct Solid particles emitted directly from an air emissions source or PM emissions. activity, or gaseous emissions or liquid droplets from an air emissions source or activity which condense to form particulate matter at ambient temperatures. Direct PM 2.5 ons include elemental carbon, directly emitted organic carbon, directly emitted emissi sulfate, directly emitted nitrate, and other inorganic particles (including but not limited to crustal materials, metals, and sea salt). Those air pollutants other than PM Secondary PM Emissions. direct emissions that 2.5 PM precursors . For NSR permitting pu rposes, contribute to the formation of PM 2.5 2.5 . and NO include SO x 2 Overview is well documented and has The complex chemistry of secondarily formed PM 2.5 esented significant challenges with the identification and establishment of historically pr particular models for assessing the impacts of individual stationary sources on the formation of this air pollutant. For example, the current preferred air dispersion model emissions but does not (i.e. AERMOD) can be used to simulate dispersion of direct PM 2.5 explicitly account for secondary formation of PM . As part of the revisions made to the 2.5 tiered Guideline on Air Quality Models (January 17, 2017), the EPA promulgated a two- . A demonstration approach for addressing single -source impacts on secondary PM 2.5 detailed discussion on the tiered approach, including examples, is provided below. Keep t impacts are determined as par in mind that the appropriate methods for assessing PM 2.5 of the normal consultation process with the Texas Commission on Environmental Quality (TCEQ). of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 98 110

104 Two -tiered Approach tiered demonstration approach for As noted above, the EPA promulgated a two- source impacts on secondary PM addressing single- . The first tier involves the use of 2.5 technically credible relationships between precursor emissions and a source’s impact (that may be published in literature; developed from modeling that was previously other entity that is conducted for an area by a source, a governmental agency, or some deemed sufficient; or generated by a reduced form model) in combination with other supportive information and analysis for the purpose of estimating secondary impacts from a particular source. The second tier involves application of m ore sophisticated case- specific chemical transport models (e.g., photochemical grid models). The appropriate tier for a given application should be selected in consultation with the Air Dispersion Modeling Team (ADMT) and be consistent with applicable EPA guidance. Tier 1 The EPA developed a tier 1 demonstration tool for secondary PM precursor emissions 2.5 called Modeled Emission Rates for Precursors (MERPs). The development of the tool and dated December 2, 201 6 related guidance is summarized in a memorandum from EPA with a subject, “Guidance on the Development of Modeled Emission Rates for Precursors under the PSD Permitting (MERPs) as a Tier 1 Demonstration Tool for Ozone and PM 2.5 Program.” The basic idea behind the MERPs is to use technically credi ble air quality modeling to relate precursor emissions and peak secondary pollutant impacts from specific or hypothetical sources. To derive a MERP value, the model predicted relationship between precursor emissions from hypothetical sources and their downwind maximum impacts can be combined with a significant impact level using the following equation: 푟푟푟푟푟푟 푒푒 푒푒푒푒푒푒푒푒푒푒푒푒푀푀 푒푒 ℎ푦푦푦푦 푀푀푟푟 ℎ푒푒푟푟푒푒푒푒 푟푟푒푒 푒푒푀푀 푠푠푟푟푒푒푒푒 푓푓푟푟푀푀푒푒 푀푀푀푀푀푀 푒푒푒푒푒푒 푀푀 = ∗ 푀푀푀푀푀푀푀푀 푆푆푆푆푆푆 푒푒푀푀 푠푠푟푟푒푒푒푒 ℎ푦푦푦푦 푀푀푟푟 ℎ푒푒푟푟푒푒푒푒 푟푟푒푒 푒푒 푒푒푒푒푦푦푟푟푒푒푟푟푓푓푟푟푀푀 푀푀푀푀푀푀 푒푒푒푒푒푒 푀푀 푟푟푒푒푟푟 푞푞푠푠푟푟푒푒푒푒푟푟푦푦 The ADMT used the air quality modeling results presented in Appendix A of the EPA MERPs memorandum to derive MERPs for the hypothetical sources located in Texas 3 using the EPA recommended SILs for PM (1.2 μg/m for the 24- hour averaging time 2.5 3 for the annual averaging time). The worst -case derived MERPs for the and 0.2 μg/m hypothetical Texas sources are presented below in Table R -1: Table R -1. Worst -case MERP Values (in tons per year) hour PM Annual P M - 24 Precursor 2.5 2.5 NO 2500 10000 x 1801 343 SO 2 -1 as a tier 1 demonstration, an analysis will need to To use the MERP values in Table R be provided that shows that the emissions characteristics of the project source and the uately chemical and physical environment in the vicinity of the project source are adeq represented by the various hypothetical Texas sources modeled by the EPA (and documented in the EPA MERPs memorandum). , Revised 09 110 of 99 Page Air Quality Modeling Guidelines /18) TCEQ - (APDG 6232v4

105 emissions and secondary PM includes both direct PM An evaluation of PM 2.5 2.5 2.5 s, modeling is conducted following emission precursor emissions. For the direct PM 2.5 applicable guidance to determine impacts associated with the direct PM emissions. The 2.5 impacts can be expressed as a percent of the SIL and summed with the secondary PM 2.5 impacts. For the secondary PM and SO impacts, NO are both precursors to 2 2.5 x secondary PM formation, and the contributions to secondarily formed PM are 2.5 2.5 considered together. The proposed secondary PM precursor emissions increase can be 2.5 expressed as a percent of the lowest MERP for each precursor and then summed. A will not be exceeded when considering the SIL value less than 100% indicates that the hour and combined impacts of the direct and secondary precursor emissions on 24- annual PM : 2.5 푁푁푁푁 푆푆푁푁 푒푒푒푒푒푒푒푒푒푒푒푒 푀푀푒푒푒푒 푦푦푟푟푀푀 푝푝푒푒푒푒푟푟 푀푀푀푀푀푀 푒푒푒푒푒푒푀푀 퐶퐶푟푟푒푒푠푠푒푒 푒푒푒푒푒푒푒푒푒푒푒푒푀푀푒푒푒푒 푦푦푟푟푀푀 푝푝푒푒푒푒푟푟 푥푥 2 + �∗ 100 < 100% + � 푀푀푀푀푀푀푀푀 푁푁푁푁 푆푆푆푆푆푆 푀푀푀푀푀푀푀푀 푆푆푁푁 2 푥푥 and For example, a project has proposed emissions of 200 tons per year (tpy) of NO x 80 and modeling of those tpy of SO emissions . The project also has emissions of PM 2.5 2 3 3 . Using this and an annual prediction of 0.03 μg/m hour prediction of 0.4 μg/m gives a 24- -1 gives: -case MERPs listed in Table R information, along with the worst 3 80 푟푟푦푦푦푦 푟푟푦푦푦푦 200 0.4 휇휇퐵퐵 / 푒푒 + 100 �∗ + ℎ 푀푀푠푠푟푟 � : 24 3 푟푟푦푦푦푦 푒푒 1.2 휇휇퐵퐵 343 푟푟푦푦푦푦 2500 / [ ] 0.33 + 0.08 + 0.23 = ∗ 100 = 64% 3 푟푟푦푦푦푦 200 80 푟푟푦푦푦푦 푒푒 0.03 휇휇퐵퐵 / + �∗ 100 + � : 퐴퐴푒푒푒푒푠푠푟푟푒푒 3 푒푒 1801 휇휇퐵퐵 0.2 푟푟푦푦푦푦 10000 푟푟푦푦푦푦 / [ ] 100 ∗ = 0.15 + 0.02 + 0.04 = 21% hour and annual aver Since the values for both the 24- aging times are less than this example shows the source impact is less than the SILs and a cumulative 100%, analysis would not be needed. Keep in mind that this exercise may need to be performed separately for the NAAQS and increment analyses based on the output metric used with , the maximum predicted ions. When modeling PM emiss the modeling of the direct PM 2.5 2.5 hour and concentrations from all receptors are used in the increment analysis for the 24- year averages of the maximum predicted annual averaging times instead of the five- concentrations used in a NAAQS analy sis. The example above follows the same procedure described in the EPA MERPs memorandum. The example is taken a step further in order to quantify the secondary impacts in impacts using the same MERP concept. Quantifying the secondary PM PM 2.5 2.5 the air quality analysis is necessary in order to determine the total predicted concentration for the increment analysis since public notice requires the degree of increment of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 100 110

106 consumption that is expected from the new source or modification. The estimated concentratio n from the secondary impacts can be determined from the following equation: 푦푦푟푟푀푀 푝푝푒푒푒푒푟푟 푒푒푒푒푒푒푒푒푒푒푒푒 푀푀푒푒푒푒 푦푦푟푟푀푀 푝푝푒푒푒푒푟푟 푆푆푁푁 푒푒푒푒푒푒푒푒푒푒푒푒 푀푀푒푒푒푒 푁푁푁푁 푥푥 2 � = �∗푆푆푆푆푆푆 + 푉푉푀푀푒푒푒푒푒푒푒푒푟푟푟푟푟푟푟푟푒푒푀푀푒푒 푀푀푀푀푀푀푀푀 푀푀푀푀푀푀푀푀 푁푁푁푁 푆푆푁푁 푥푥 2 -case MERPs from Table Using the project information provi ded in the example, the worst R-1, and the SILs, the total predicted concentrations can be determined based on the following: 푆푆푒푒푒푒푀푀푒푒푀푀 푟푟푟푟푦푦 + 푒푒푀푀푒푒푒푒푒푒푒푒푟푟푟푟푟푟푟푟푒푒푀푀푒푒푒푒 푒푒푀푀푒푒푒푒푒푒푒푒푟푟푟푟푟푟푟푟푒푒푀푀푒푒푒푒 푇푇푀푀푟푟푟푟푒푒 푒푒푀푀푒푒푒푒푒푒푒푒푟푟푟푟푟푟푟푟푒푒푀푀푒푒 = 푀푀푀푀푀푀 푒푒푒푒푒푒푀푀 푀푀푒푒푟푟푒푒푒푒푟푟 푟푟푦푦푦푦 80 푟푟푦푦푦푦 200 3 3 / : 0.4 휇휇퐵퐵 ℎ푀푀푠푠푟푟 푒푒 24 + 휇휇퐵퐵 �∗ / + 1.2 푒푒 � 푟푟푦푦푦푦 2500 푟푟푦푦푦푦 343 3 3 0.372 / 휇휇퐵퐵 / 푒푒 + 0 .4 휇휇퐵퐵 = 푒푒 3 = 0.772 휇휇퐵퐵 / 푒푒 푟푟푦푦푦푦 200 80 푟푟푦푦푦푦 3 3 : 0.03 휇휇퐵퐵 / 푒푒 퐴퐴푒푒푒푒푠푠푟푟푒푒 + � �∗ 0.2 휇휇퐵퐵 + 푒푒 / 푟푟푦푦푦푦 10000 푟푟푦푦푦푦 1801 3 3 + = 휇휇퐵퐵 / 푒푒 푒푒 0 .03 0.012 휇휇퐵퐵 / 3 / 휇휇퐵퐵 푒푒 0.042 = -1 are too conservative, then MERP If the worst- case MERP values listed in Table R values for a specific hypothetical source may be used provided a demonstration is shown that the identified hypothetical source is representative for the project source. Tables R -2 hour and annual MERPs, respectively, for the hypothetical -3 show the derived 24- and R -5 show the derived 24- hour and . Tables R -4 and R Texas sources for precursor NO x al Texas sources for precursor SO annual MERPs, respectively, for the hypothetic . The 2 ADMT used the air quality modeling results presented in Appendix A of the EPA MERPs -2 thru R memorandum (also provided in Tables R -5 as the Max Impact) to derive MERPs ing the EPA recommended SILs for for the hypothetical sources located in Texas us : PM 2.5 of - (APDG 6232v4 TCEQ , Revised 09 /18) Air Quality Modeling Guidelines Page 101 110

107 Table R -2. NO 24- hour MERP Values for Hypothetical Texas Sources x Max Impact Source Emissions (tpy) Height MERP (tpy) 3 ) (μg/m 500 5 (Terry) 0.038 15789 H 5 (Terry) 500 L 0.082 7317 5 (Terry) 1000 H 0.072 16666 5 (Terry) H 0.205 17560 3000 19 (Henderson) 500 L 0.12 5000 19 (Henderson) 1000 H 0.08 15000 19 (Henderson) 1000 L 0.23 5217 3000 H 0.26 13846 19 (Henderson) 4615 0.13 L 500 20 (Harris) 20 (Harris) H 0.09 13333 1000 1000 L 0.24 5000 20 (Harris) 20 (Harris) 3000 H 0.33 10909 24 (Parker) 500 L 0.21 2857 24 (Parker) 1000 H 0.16 7500 2500 0.48 L 24 (Parker) 1000 24 (Parker) 3000 H 0.6 6000 5454 500 L 0.11 25 (Guadalupe) 25 (Guadalupe) 1000 H 0.12 10000 25 (Guadalupe) 1000 L 0.24 5000 0.41 8780 H 25 (Guadalupe) 3000 of - (APDG 6232v4 , Revised 09 TCEQ /18) Air Quality Modeling Guidelines Page 102 110

108 Table R -3. NO Annual MERP Values for Hypothetical Texas Sources x Max Impact Source Emissions (tpy) Height MERP (tpy) 3 ) (μg/m 500 H 0.0011 90909 5 (Terry) 5 (Terry) 500 L 0.0037 27027 1000 H 0.0021 95238 5 (Terry) 5 (Terry) 3000 H 0.0056 107142 19 (Henderson) L 0.005 20000 500 19 (Henderson) 1000 H 0.003 66666 19 (Henderson) 1000 L 0.012 16666 19 (Henderson) 3000 H 0.012 50000 20 (Harris) 0.009 11111 L 500 20 (Harris) H 0.004 50000 1000 1000 L 0.02 10000 20 (Harris) 20 (Harris) 3000 H 0.015 40000 24 (Parker) 500 L 0.004 25000 24 (Parker) 1000 H 0.003 66666 20000 0.01 L 24 (Parker) 1000 24 (Parker) 3000 H 0.013 46153 500 L 0.005 20000 25 (Guadalupe) 25 (Guadalupe) 1000 H 0.003 66666 25 (Guadalupe) 1000 L 0.012 16666 0.014 42857 H 25 (Guadalupe) 3000 of - (APDG 6232v4 , Revised 09 /18) TCEQ Air Quality Modeling Guidelines Page 103 110

109 Table R -4. SO 24-hour MERP Values for Hypothetical Texas Sources 2 Max Impact Source Emissions (tpy) Height MERP (tpy) 3 ) (μg/m 500 H 0.068 8823 5 (Terry) 5 (Terry) 500 L 0.277 2166 1000 H 0.122 9836 5 (Terry) 5 (Terry) 3000 H 0.356 10112 19 (Henderson) L 0.37 1621 500 19 (Henderson) 1000 H 0.52 2307 19 (Henderson) 1000 L 1.06 1132 19 (Henderson) 3000 H 2.04 1764 20 (Harris) 363 1.65 L 500 20 (Harris) H 0.89 1348 1000 1000 L 3.49 343 20 (Harris) 20 (Harris) 3000 H 2.86 1258 24 (Parker) 500 L 0.55 1090 1463 24 (Parker) 1000 H 0.82 1000 585 2.05 L 24 (Parker) 24 (Parker) 3000 H 3.55 1014 1052 500 L 0.57 25 (Guadalupe) 25 (Guadalupe) 1000 H 0.74 1621 25 (Guadalupe) 1000 L 1.41 851 2.71 1328 H 25 (Guadalupe) 3000 of - (APDG 6232v4 , Revised 09 TCEQ /18) Air Quality Modeling Guidelines Page 104 110

110 Table R -5. SO Annual MERP Values for Hypothetical Texas Sources 2 Max Impact Source Emissions (tpy) Height MERP (tpy) 3 ) (μg/m 500 H 5 (Terry) 0.0019 52631 500 5 (Terry) 0.0039 25641 L 5 (Terry) 1000 H 0.0037 54054 5 3000 H 0.0102 58823 (Terry) 19 (Henderson) 500 L 0.006 16666 19 (Henderson) H 0.007 28571 1000 19 (Henderson) 1000 L 0.019 10526 19 (Henderson) 3000 H 0.039 15384 20 (Harris) 500 L 0.04 2500 1000 H 0.022 9090 20 (Harris) 20 (Harris) 1000 1801 0.111 L 20 (Harris) H 0.1 6000 3000 500 L 0.008 12500 24 (Parker) 24 (Parker) 1000 H 0.009 22222 24 (Parker) 1000 L 0.026 7692 24 (Parker) 3000 H 0.043 13953 500 7692 0.013 L 25 (Guadalupe) 1000 H 0.014 14285 25 (Guadalupe) 5000 25 (Guadalupe) 1000 L 0.04 H 3000 8955 0.067 25 (Guadalupe) The sources are identified by number and county. The numbers are the same numbers used to identify sources in the EPA MERP memorandum. For source height, a value of H represents an elevated release (90 meters) and a value of L represents a surface release (1 meter). is As an example, a project with emissions of and 150 tpy of SO 800 tpy of NO x 2 and proposed to be located in Hood County. The project also has emissions of PM 2.5 3 and an annual r prediction of 1.1 μg/m hou modeling of those emissions gives a 24- 3 . Hood County is adjacent to Parker County and the MERP values prediction of 0.1 μg/m from source 24 (Parker) will be used. An analysis is first conducted to compare the chemical and physical environment in the vici nity of the project source (Hood County) relative to the hypothetical source modeled in Parker County. Information used in the analysis may include average and peak temperatures, humidity, terrain, rural/urban and ambient ants (biogenic, industrial, etc.), nature of the area, regional sources of pollut concentrations of relevant pollutants. Based on this analysis, and the proposed emissions associated with the project, the 1000 tpy NO MERP values (low height) and the 500 tpy x , Revised 09 /18) Air Quality Modeling Guidelines - (APDG 6232v4 Page 105 TCEQ of 110

111 SO MERP values (low height) from source 24 (Parker) will be used. As with the previous 2 example, emissions can be expressed as a the impacts associated with the direct PM 2.5 percent of the SIL and summed with the secondary PM impacts, which are based on 2.5 expressing the proposed emissions increase as a percent of the MERP for each precursor and then summed. A value less than 100% indicates that the SIL will not be exceeded when considering the combined impacts of the direct and secondary precursor emissions on 24- hour and annual PM : 2.5 3 휇휇퐵퐵 / 150 1.1 푟푟푦푦푦푦 800 푟푟푦푦푦푦 푒푒 24 ℎ푀푀푠푠푟푟 : + � 100 �∗ + 3 푟푟푦푦푦푦 2500 푟푟푦푦푦푦 1090 / 푒푒 1.2 휇휇퐵퐵 [ ] 0.32 = + 0.92 + ∗ 100 0.14 = 138% 3 휇휇퐵퐵 푒푒 / 0.1 800 푟푟푦푦푦푦 150 푟푟푦푦푦푦 : 퐴퐴푒푒푒푒푠푠푟푟푒푒 � 100 �∗ + + 3 푟푟푦푦푦푦 휇휇퐵퐵 0.2 20000 / 푒푒 12500 푟푟푦푦푦푦 ] [ + 100 ∗ 0.04 0.5 + 0.01 = 55% = Since the value for the annual averaging time is less than 100%, this shows the source impact is less than the SIL and a cumulative analysis would not be needed. For reporting purposes in the air quality analysis, the total annual predicted concentration would be determined following the steps in the previous example (total annual predicted 3 concentration of 0.11 μg/m ). Given that the value for the 24- hour averaging time is greater than 100 percent, a cumulative analysis is needed since the source impact is . greater than the SIL When determining significant receptors to include in the cumulative analysis, add the impacts to the modeling results contributions associated with the secondary PM 2.5 Then identif associated with the direct PM emissions on a receptor -by-receptor basis. y 2.5 receptors with total predictions greater than or equal to the SIL and use these receptors in the cumulative modeling analyses. The cumulative analysis for a NAAQS demonstration includes contributions from emissions (from the project source background concentrations, modeling of direct PM 2.5 precursor and nearby off -site sources), and impacts associated with secondary PM 2.5 emissions. The following equation is used: 퐵퐵푟푟푒푒 퐵퐵퐵퐵 푟푟푀푀푠푠푒푒푀푀 푒푒푀푀푒푒 + + 퐶퐶푟푟푒푒푠푠푒푒 푀푀푀푀푀푀 푒푒푒푒푒푒푀푀 푉푉푠푠푒푒푠푠푒푒푟푟푟푟푒푒 퐶퐶푒푒 푒푒푀푀푒푒푒푒푒푒푒푒푟푟푟푟푟푟푟푟푒푒푀푀푒푒 = 푒푒푀푀푒푒푒푒푒푒푒푒푟푟푟푟푟푟푟푟 푁푁푁푁 푦푦푟푟푀푀 푝푝푒푒푒푒푟푟 푒푒푒푒푒푒푒푒푒푒푒푒 푀푀푒푒푒푒 푦푦푟푟푀푀 푝푝푒푒푒푒푟푟 푆푆푁푁 푒푒푒푒푒푒푒푒푒푒푒푒 푀푀푒푒푒푒 2 푥푥 � �∗푆푆푆푆푆푆 + 푀푀푀푀푀푀푀푀 푁푁푁푁 푀푀푀푀푀푀푀푀 푆푆푁푁 푥푥 2 - (APDG 6232v4 110 of 106 Page Air Quality Modeling Guidelines /18) , Revised 09 TCEQ

112 hour background concentration Continuing with the Hood County project example, the 24- 3 for the project area is determined to be 24 μg/m and the 24- hour modeled value, which 3 includes the project source and nearby off -site sources, is 4.6 μg/m . The 24- hour cumulative concentration would be: 150 푟푟푦푦푦푦 푟푟푦푦푦푦 800 3 3 3 4.6 휇휇퐵퐵 / 푒푒 = + � 24 휇휇퐵퐵 / 푒푒 / 휇휇퐵퐵 + 푒푒 + 1.2 �∗ 푟푟푦푦 푦푦 1090 푟푟푦푦푦푦 2500 3 3 3 0.55 푒푒 / 휇휇퐵퐵 + 푒푒 휇휇퐵퐵 4.6 + / / 24 = 푒푒 휇휇퐵퐵 3 푒푒 / 휇휇퐵퐵 .15 29 = 3 The cumulative concentration is less than the 24- ) and the hour NAAQS (35 μg/m from off demonstration is complete. The contributions to secondarily formed PM -site 2.5 ly accounted for through the use of background concentrations. For sources are general -site sources that may have been recently permitted and are not yet operating, nearby off their contribution towards secondarily formed PM may need to be determined since 2.5 background concentrations will not include their contribution. increment A similar type of demonstration can be performed for the 24- hour PM 2.5 analysis. However, background concentrations would not be included, as they are with a hour modeled value of the direct emissions would be NAAQS analysis, and the 24- different as well. The differences in the modeled value are related to using an inventory of hour PM increment affecting sources and the form of the model output. For the 24- 2.5 would be the highest, high- second high 24- hour increment analysis, the model output NAAQS analysis, the model year period. For the 24- prediction over a five- hour PM 2.5 output would be a five- year average of the 98th percentile of the annual distribution of the ntrations. -hour predicted conce maximum 24 Tier 2 Tier 2 assessments are intended for impact assessments that are not able to be satisfied existing information is not available or with a tier 1 demonstration in that pre- representative of the situation such that more refined modeling is n ecessary. For these specific chemical transport models situations, application of more sophisticated case- source impacts. (e.g., photochemical grid models) should be performed to address single- , Revised 09 110 of 107 Page TCEQ Air Quality Modeling Guidelines /18) - (APDG 6232v4

113 Appendix S – Additional Guidance for evaluating Nitrogen Dioxide and 1-hour Sulfur Dioxide The purpose of this appendix is to provide additional guidance for addressing the nitrogen ) National Ambient Air Quality Standards hour sulfur dioxide (SO dioxide (NO ) and 1- 2 2 A) issued a memorandum on (NAAQS). The Environmental Protection Agency (EP March 1, 2011 with a subject, “Additional Clarification Regarding Application of Appendix hour NO W Modeling Guidance for the 1- National Ambient Air Quality Standard.” This 2 m issued memorandum is meant to supplement the memorandu by the EPA on 29, June 2010 with a subject, “Guidance Concerning the Implementation of the 1- hour NO NAAQS for the Prevention of Significant Deterioration Program.” The March 1 2 ppendix memorandum provides further clarification and guidance on the application of A hour NO W guidance for the 1- standard. 2 ) chemistry options in the March 1 While the discussion of nitrogen oxides (NO x standard, the discussion of other topics in hour NO memorandum is exclusive to the 1- 2 -hour SO standard, accounting for the the memorandum should apply equally to the 1 2 differences in the form of the two standards. The memorandum does not apply to the and SO , nor does it apply to other pollutants with a other averaging periods of NO 2 2 standard based on a multiyear average. The EPA also issued a memorandum on September 30, 2014 with a subject, “Clarification on the Use of AERMOD Dispersion Modeling for Demonstrating Compliance with the NO 2 National Ambient Air Quality Standard.” This memorandum is meant to supplement the The sued by the EPA on June 29, 2010 and March 1, 2011. memoranda is September 30 memorandum discusses the Ambient Ratio Method 2 (ARM2) as a tier 2 ratios to NO screening approach. ARM2 is based on hourly measurements of the NO 2 x and provides more detailed estimates o f this ratio based on the total NO present. The x memorandum also discusses the Ozone Limiting Method (OLM) and Plume Volume associated Molar Ratio Method (PVMRM) tier 3 screening approaches and the in-stack /NO ratios used in the tier 3 applications. NO x 2 Approval and Application of a Tiering Approach for NO 2 There are different approaches to demonstrate compliance with the NO NAAQS: 2 . 100 percent conversion of NO 1. Tier 1 – to NO x 2 2. Tier 2 – multiply the tier 1 results by the ARM2, which provides estimates of /NO values based on ambient levels of NO representative equilibrium ratios of NO 2 x 2 and NO derived from national data from the EPA’s Air Quality System. The national x ratio of 0.5 and a maximum ratio of /NO default for ARM2 will include a minimum NO 2 x /NO Alternative default minimum NO 0.9. values may be established based on the 2 x -stack emissions ratio, with alternative minimum values reflecting the source’s in ratios. These should be based on source- /NO specific data, -stack NO source’s in 2 x which satisfies al l quality assurance procedures that ensure data accuracy for both NO within the typical range of measured values. However, manufacturer test and NO x 2 -reviewed literature, or the EPA’s NO data, state or local agency guidance, peer /NO x 2 used as sources of data. ratio database may be If another minimum value is used, of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 108 110

114 sufficient justification and documentation will need to be provided prior to submitting the Air Quality Analysis. Note that the source code for AERMOD has been edited to include the ARM2 method; therefore, AERMOD will internally compute the ambient ratios using the ARM2 equation when modeling with applicable NO emission rates and using the ARM2 x model option keyword. For model platforms that do not have the ARM2 method coded or when conducting modeling using generic emission rates (e.g., 1 pound per hour or an ambient ratio of 0.9 for simplicity since 0.9 is the 1 gram per second), use RM2. maximum ambient ratio used with A use of the regulatory OLM and PVMRM options within AERMOD to determine 3. Tier 3 – the amount of conversion of NO to NO . The key input variables for these model 2 x options are in- stack NO /NO ratios and background ozone concentrations. 2 x In-stack NO /NO • : ratios 2 x The EPA established a general acceptance of 0.50 as a default in- o stack ratio of for input to the OLM and PVMRM model options within AERMOD . NO /NO 2 x stack NO When conducting a cumulative modeling analysis, a default in- /NO 2 x for more distant sources (sources located greater than ratio of 0.2 can be used three kilometers from the primary source). ratio other than the default, sufficient /NO stack NO If proposing an in- o 2 x justification and documentation will need to be provided to support the source- speci fic data on the in- ratio. /NO stack NO x 2 Background ozone concentrations: • o There are many options for utilizing the background ozone data in the OLM and PVMRM model options. Be sure to provide sufficient justification and documentation to support the use of the ozone data (representativeness of the monitor, filling in missing data, etc.). Even though the OLM and PVMRM tier 3 screening techniques are considered part of the regulatory version of AERMOD, prior approval (submitting modeling protocols to Air ts Division (APD) and the EPA) is required for any applicant proposing to use a t ier Permi given the additional input data requirements and complexities associated with 3 approach the tier 3 screening options . Sufficient documentation and justification must be provided when developing the modeling protocol. -hour SO Treatment of Intermittent Emissions for 1 -hour NO and 1 2 2 NAAQS An assumption of continuous operation for intermittent emissions using the maximum umption and could result in them allowable emissions may be an overly conservative ass becoming the controlling emission scenario for determining compliance with the 1- hour hour SO standards. To account for this, the March 1 memorandum discusses NO and 1- 2 2 sions: different approaches for evaluating intermittent emis • Excluding certain types of intermittent emissions from the compliance demonstrations for the 1- standards. The most hour SO and 1- hour NO 2 2 /18) Air Quality Modeling Guidelines TCEQ - (APDG 6232v4 of Page 109 , Revised 09 110

115 and appropriate data to use for compliance demonstrations for the 1- hour NO 2 NAAQS are those based on emissions scenarios that are continuous 1-hour SO 2 enough or frequent enough to contribute significantly to the annual distribution of maximum 1 -hour concentrations. daily • Using model scalars to limit the hours modeled to account for meteorological are more repres conditions that entative of actual operations. A permit condition can be used to restrict operation to certain hours of the day. • Modeling the impacts from intermittent emissions based on an average hourly rate, rather than the maximum hourly emission rate. The March 1 memorandum is limited to what intermittent emissions are related to. An emergency generator is provided as an example of an intermi ttent emissions unit, and up/shutdown operations are provided as examples of intermittent emissions start on os. The memorandum does not have a discussion regarding a specific duration scenari the number of hours of operation per year that constitutes intermittent or infrequent. Furthermore, there is no discussion on the frequency of intermittent emissions needed to be considered to contribute significantly to the annual distribution of daily maximum 1-hour concentrations. Also important for determining and evaluating intermittent emissions is the distinction between intermittent emissions that can be scheduled with some degree of flexibility and intermittent emissions that cannot be scheduled. The recommendation is that compliance demonstrations for the 1- hour NO hour and 1- 2 NAAQS be based on emission scenarios that can logically be assumed to be SO 2 relatively continuous or which occur frequently enough to contribute significantly to the hour concentrations. There are unique annual distribution of daily maximum 1- case -by-case factors, as it relates to determining whether or not emissions are ct the application of the guidance in the March 1 memorandum. intermittent, that can affe The proposed operation of the unit or operating scenarios will need to be fully explained and documented in order to determine the appropriateness of following the guidance in the memorandum. Th e ADMT recommends providing sufficient justification and documentation for intermittent use prior to submitting the Air Quality Analysis. For example: How many units are there; • • How often will the unit operate per year; • What is the duration of operation once the unit is operating; Will the unit be operated on a known schedule or will it operate randomly; • • What are the magnitude of the emissions for the source(s); • Does the unit operate simultaneously with other sources? of TCEQ - (APDG 6232v4 , Revised 09 /18) Air Quality Modeling Guidelines Page 110 110

Related documents

2017 NJ Air Monitoring Report

2017 NJ Air Monitoring Report

2017 New Jersey Air Quality Report New Jersey Department of Environmental Protection ber 30 , 2018 Octo New Jersey Department of Environmental Protection Bureau of Air Monitoring Mail Code: 401 - 02E ...

More info »
2020 ANP draft

2020 ANP draft

Wisconsin Department of Natural Resources 2020 Air Monitoring Network Plan June 2019 DRAFT

More info »
untitled

untitled

AIR QUALITY EXPERT GROUP Particulate Matter in the United Kingdom Summary Prepared for: Department for Environment, Food and Rural Affairs; Scottish Executive; Welsh Assembly Government; and Departmen...

More info »
Policy and Action Standard

Policy and Action Standard

Policy and Action Standard An accounting and reporting standard for estimating the greenhouse gas effects of policies and actions

More info »
Spatial Data Analysis with R

Spatial Data Analysis with R

Spatial Data Analysis with R Robert J. Hijmans and Aniruddha Ghosh May 03, 2019

More info »
NRDC: Where There’s Fire, There’s Smoke   Wildfire Smoke Affects Communities Distant from Deadly Flames (PDF)

NRDC: Where There’s Fire, There’s Smoke Wildfire Smoke Affects Communities Distant from Deadly Flames (PDF)

NRDC: Where There’s Fire, There’s Smoke - Wildfire Smoke Affects Communities Distant from Deadly Flames (PDF) october 2013 DC R N iSSUE bRiEF ib:13-09-b Where There’s Fire, There’s Smoke: Wildfire Smo...

More info »
Slide 1

Slide 1

Particulate Matter (PM) Emission Calculations Presented by: Evan Shaw Mecklenburg County Land Use and Environmental Services Agency Air Quality Division

More info »
Categories

Categories

Categories Cisco constantly the relevance of websites within a particular category to ensure the industry’ s evaluates accuracy . The categories classifications used by Cisco Cloud Web Security are su...

More info »
Smoke Health Statement Extended2 Camp Fire 111618.docx

Smoke Health Statement Extended2 Camp Fire 111618.docx

16 , November 2018 Sac Metro Air District Communications Office (916) 874 - 4888 Contact: (916) 874 - 7798 Sacramento County Public Health Advisory Continues Through Wildfire Smoke Monday, November 19...

More info »
606 PCAP 3 0 Draft  9 26 17

606 PCAP 3 0 Draft 9 26 17

City of Pittsburgh CLIMATE ACTION PLAN Version 3.0

More info »
Air Pollution and School Activities   Public Health Recommendations for Schools

Air Pollution and School Activities Public Health Recommendations for Schools

Air Pollution and School Activities Public Health Recommendations for Schools on Fine Particle Air Pollution Air Quality Conditions* First, check local air conditions at https://fortress.wa.gov/ecy/en...

More info »
School Indoor Air Quality Best Management Practices Manual

School Indoor Air Quality Best Management Practices Manual

School Indoor Air Quality Best Management Practices Manual November 2003 Office of Environmental Health and Safety Indoor Air Quality Program DOH 333-044 November 2003

More info »
UL White Book

UL White Book

GUIDE INFORMATION FOR ELECTRICAL EQUIPMENT THE WHITE BOOK 2015-16 UL PRODUCT CATEGORIES CORRELATED TO THE 2011 AND 2014 NATIONAL ELECTRICAL CODE® UL’s General Guide Information is updated daily. To co...

More info »
Best Available Techniques for Preventing and Controlling Industrial Pollution

Best Available Techniques for Preventing and Controlling Industrial Pollution

Best Av AilABle techniques for Preventing And controlling industriAl Pollution Activity 2: Approaches to establishing Best Available t echniques (BA t) Around the World

More info »
Energy Efficiency in Local Government Operations

Energy Efficiency in Local Government Operations

LOCAL GOVERNMENT CLIMATE AND ENERGY STRATEGY SERIES Energy Efficiency in Local Government Operations A Guide to Developing and Implementing Greenhouse Gas Reduction Programs Energy Efficiency U.S. ENV...

More info »
NRDC: Air Pollution from Hydraulic Fracturing Threatens Public Health and Communities (PDF)

NRDC: Air Pollution from Hydraulic Fracturing Threatens Public Health and Communities (PDF)

december 2014 I SS BRIEF N R DC E u I p:14-10-a Fracking Fumes: Air Pollution from Hydraulic Fracturing Threatens Public Health and Communities p Just off Interstate Highway 25, Drill Rig in front of ...

More info »
Minnesota Climate and Health Profile 2015

Minnesota Climate and Health Profile 2015

MINNESOTA CLIMATE AND HEALTH PROFILE REPORT 2015 An Assessment of Climate Change Impacts on the Health & Well-Being of Minnesotans Minnesota Department of Health MINNESOTA CLIMATE & HEALTH PROGRAM, EN...

More info »
USDA Rural Development

USDA Rural Development

Select a state to see the income limits for the counties in that state. Rural Development Single Family Housing Guaranteed Loan Program ME WA VT ND MT RI NH CT NY MN OR MA WI ID SD MI WY PA NJ IA DE O...

More info »