R309-550-7. Separation of Water Mains and Transmission Lines from Sewers.
(1) Basic Separation Standards.
(a) The horizontal distance between water lines and sanitary sewer lines shall be at least 10 feet. Where a water main and a sewer line must cross, the water main shall be at least 18 inches above the sewer line. Separation distances shall be measured edge-to-edge (i.e. from the nearest edges of the facilities).
(b) Water mains and sewer lines shall not be installed in the same trench.
(c) Where local conditions make it impossible to install water or sewer lines at separation distances required by subsection (a), the sewer pipes are in good condition, and there is not high groundwater in the area, it may be acceptable if the design includes a minimum horizontal separation of 6 feet and a minimum vertical clearance of 18 inches with the waterline being above. In order to determine whether the design is acceptable, the following information shall be submitted as part of the plans for review.
(i) reason for not meeting the minimum separation standard;
(ii) location where the water and sewer line separation is not being met;
(iii) horizontal and vertical clearance that will be achieved;
(iv) sewer line information including pipe material, condition, size, age, type of joints, thickness or pressure class, whether the pipe is pressurized or not, etc.;
(v) water line information including pipe material, condition, size, age, type of joints, thickness or pressure class, etc.;
(vi) ground water and soil conditions; and,
(vii) any mitigation efforts.
(d) If the basic separation standards as outlined in subsections (a) though (c) above cannot be met, an exception to the rule can be applied for with additional mitigation measures to protect public health, in accordance with R309-105-6(2)(b).
(3) Special Provisions.
The following special provisions apply to all situations:
(a) The basic separation standards are applicable under normal conditions for sewage collection lines and water distribution mains. More stringent requirements may be necessary if conditions such as high groundwater exist.
(b) All water transmission lines that may become unpressurized shall not be installed within 20 feet of sewer lines.
(c) In the installation of water mains or sewer lines, measures shall be taken to prevent or minimize disturbances of the existing line.
(d) Special consideration shall be given to the selection of pipe materials if corrosive conditions are likely to exist or where the minimum separation distances cannot be met. These conditions may be due to soil type, groundwater, and/or the nature of the fluid conveyed in the conduit, such as a septic sewage which produces corrosive hydrogen sulfide.
(e) Sewer Force Mains
(i) When a new sewer force main crosses under an existing water main, all portions of the sewer force main within 10 feet (horizontally) of the water main shall be enclosed in a continuous sleeve.
(ii) When a new water main crosses over an existing sewer force main, the water main shall be constructed of pipe materials with a minimum rated working pressure of 200 psi or equivalent pressure rating.
(4) Water Service Laterals Crossing Sewer Mains and Laterals.
Water service laterals shall conform to all requirements given herein for the separation of water and sewer lines.
R309-550-8. Installation of Water Mains.
The specifications shall incorporate the provisions of the manufacturer's recommended installation procedures or the following applicable standards:
(a) For ductile iron pipe, AWWA Standard C600-10, Installation of Ductile Iron Water Mains and Their Appurtenances;
(b) For PVC pipe, ASTM D2774, Recommended Practice for Underground Installation of Thermoplastic Pressure Piping and PVC Pipe and AWWA Manual of Practice M23, 2003;
(c) For HDPE pipe, ASTM D2774, Recommended Practice for Underground Installation of Thermoplastic Pressure Piping and AWWA Manual of Practice M55, 2006; and,
(d) For Steel pipe, AWWA Standard C604-11, Installation of Buried Steel Water Pipe- 4 inch and Larger.
A continuous and uniform bedding shall be provided in the trench for all buried pipe. Stones larger than the backfill materials described below shall be removed for a depth of at least 6 inches below the bottom of the pipe.
Backfill material shall be tamped in layers around the pipe and to a sufficient height above the pipe to adequately support and protect the pipe. The material and backfill zones shall be as specified by the standards referenced in Subsection (1), above. As a minimum:
(a) for plastic pipe, backfill material with a maximum particle size of 3/4 inch shall be used to surround the pipe; and,
(b) for ductile iron pipe, backfill material shall contain no stones larger than 2 inches.
(4) Dropping Pipe into Trench.
Under no circumstances shall the pipe or accessories be dropped into the trench.
(5) Burial Cover.
All water mains shall be covered with sufficient earth or other insulation to prevent freezing, unless they are part of a non-community system that can be shut-down and drained during winter months when temperatures are below freezing.