Current through Reg. 49, No. 52; December 27, 2024
The following rules apply to separation distances between
potable water and wastewater treatment plants, and waterlines and sanitary
sewers.
(1) Waterline/new sewer line
separation. When new sanitary sewers are installed, they shall be installed no
closer to waterlines than nine feet in all directions. Sewers that parallel
waterlines must be installed in separate trenches. Where the nine-foot
separation distance cannot be achieved, the following guidelines will apply.
(A) Where a sanitary sewer parallels a
waterline, the sewer shall be constructed of cast iron, ductile iron, or
polyvinyl chloride (PVC) meeting American Society of Testing and Materials
specifications with a pressure rating for both the pipe and joints of 150 per
square inch (psi). The vertical separation shall be a minimum of two feet
between outside diameters and the horizontal separation shall be a minimum of
four feet between outside diameters. The sewer shall be located below the
waterline.
(B) Where a sanitary
sewer crosses a waterline and the sewer is constructed of cast iron, ductile
iron, or PVC with a minimum pressure rating of 150 psi, an absolute minimum
distance of six inches between outside diameters shall be maintained. In
addition, the sewer shall be located below the waterline where possible and one
length of the sewer pipe must be centered on the waterline.
(C) Where a sewer crosses under a waterline
and the sewer is constructed of ABS truss pipe, similar semi-rigid plastic
composite pipe, clay pipe, or concrete pipe with gasketed joints, a minimum
two-foot separation distance shall be maintained. The initial backfill shall be
cement stabilized sand (two or more bags of cement per cubic yard of sand) for
all sections of sewer within nine feet of the waterline. This initial backfill
shall be from one quarter diameter below the centerline of the pipe to one pipe
diameter (but not less than 12 inches) above the top of the pipe.
(D) Where a sewer crosses over a waterline,
all portions of the sewer within nine feet of the waterline shall be
constructed of cast iron, ductile iron, or PVC pipe with a pressure rating of
at least 150 psi using appropriate adapters. In lieu of this procedure the new
conveyance may be encased in a joint of 150 psi pressure class pipe at least 18
feet long and two nominal sizes larger than the new conveyance. The space
around the carrier pipe shall be supported at five feet intervals with spacers
or be filled to the spring line with washed sand. The encasement pipe should be
centered on the crossing and both ends sealed with cement grout or manufactured
seal.
(2) Waterline
manhole separation. Unless sanitary sewer manholes and the connecting sewer can
be made watertight and tested for no leakage, they must be installed so as to
provide a minimum of nine feet of horizontal clearance from an existing or
proposed waterline. Where the nine-foot separation distance cannot be achieved,
a carrier pipe as described in paragraph (1)(D) of this section may be used
where appropriate.
