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.
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