policy [memo]

Transcript

1 Department of Environmental Management Office of Water Resources (OWR) SEWER/WATER LINE SEPARATION POLICY FOR DESIGN OF SANITARY SEWERS 1 sewers and water lines A. Lateral placement of ge-to-edge. Sewers shall be laid at least 10 feet horizontally from any existing or proposed water line. The distance shall be measured ed There is no minimum vertical separation required provided the 10 foot horizontal separation is maintained. Structures, other t han pipelines or conduits, through which sanitary wastewater flows such as, but not limited to, manholes, valve vaults, meter pits and pump station wet wells shall also be constructed at least 10 feet horizontally from any existing or proposed water line, measured ed ge-to-edge. sis, if In cases where it is not possible to maintain a 10 foot horizontal separation, the OWR may allow deviation on a case-by-case ba supported by data from the design engineer. Such deviation may a llow installation of the sewer pipelines and/or structures clo ser to a water line, provided that: 1. The sewer pipeline and/or structures and water line are laid in separate trenches, or The sewer pipeline and/or structures and water line may be installed in the sa 2. nch of me trench with the water line placed on a be undisturbed earth, and In either case, the crown of th e sewer pipeline shall be at least 18 inches below the invert of the water line. 3. In situations where it is impossible to obtain proper horizontal tection shall be and vertical separation as stipulated above, the following pro provided: 1. thickness) or a carrier pipe for at least 10 feet either side of the area Encasement of the sewer pipeline in concrete (min. 6 inch not complying with the minimum horizontal and vertical separation, or 2. The design and construction of the sewer pipeline must meet the requirements applicable to water lines (any AWWA-approved material for potable water conveyan ce), and pressure tested in accord ance with AWWA specifications, or 3. foot In instances of conflict with sanitary wastewater structur es mentioned above, relocate the water line to achieve either a 10 horizontal or 18 inch vertical separation. B. Sewers crossing water lines Sewers crossing over water lines should be a voided, but if conditions warrant this situ ation, then adequate structural support shall be provided for the sewer to maintain line and grade. Sewers cro al ssing under water lines shall be laid to provide a minimum vertic separation of 18 inches between the invert of the water line and may be the crown of the sewer. Relocation of an existing water line r lines shall be constructed of an AWWA-approved material for pot able necessary to achieve this vertical separation. Relocated wate the required water service pressu re for a distance of 10 feet on each side of the crossing, m easured water conveyance and designed for perpendicular to the sewer. The crossing shall be arranged so that the sewer joints will be equidistant and as far as possible from the water line joints. Where conditions prevent an 18 inch vertical separation from being maintained, the following methods shall be specified: 1. quirements applicable to water lines (any AWWA-approved material The design and construction of the sewer must meet the re of 10 feet on each side of the crossing, for potable water conveyance) for a distance and measured perpendicular to the water line pressure tested in accordance w ith AWWA specifications, or 2. Either the water line or the sewer ma y be encased in concrete (min. 6 inch thickness) or a carrier pipe for a distance of 10 feet on each side of the crossing, measured perpe pe shall be designed and constructed of ndicular to the water line. The carrier pi materials which are satisfactory to the OWR, or 3. Any other methods, if supported by data from the design e ngineer, which ensure adequate watertightness and are satisfactor y to the OWR. 1 Water lines shall be defined as any conduits or pipelines that convey potable water. 10/96 (rev. 5/01)

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