Current through Register Vol. 41, No. 3, September 23, 2024
A. Design
integrity. The tops of all sewers entering or crossing streams shall be at a
sufficient depth below the natural bottom of the streambed to protect the sewer
line. In general, one foot of suitable cover shall be provided where the stream
is located in rock and three feet of suitable cover in other material. Less
cover will be considered if the proposed sewer crossing is encased in concrete
and will not interfere with future improvements to the stream channel. Reasons
for requesting less cover shall be given in the application. Below paved
channels, the crown of the sewer lines should be placed under the channel
pavement. Sewers shall remain fully operational during the 25-year flood/wave
action. Sewers and their appurtenances located along streams shall be protected
against the normal range of high and low water conditions, including the
100-year flood/wave action. Sewers located along streams shall be located
outside of the streambed wherever possible and should be sufficiently removed
therefrom to provide for future possible channel widening. Reasons for
requesting sewer lines to be located within streambeds shall be given in the
application.
1. Sewers entering or crossing
streams shall be constructed of watertight pipe. The pipe and joints shall be
tested in place and shall exhibit zero infiltration. Sewers laid on piers
across ravines or streams shall be allowed only when it can be demonstrated
that no other practical alternative exists. Such sewers on piers shall be
constructed in accordance with the requirements for sewers entering or crossing
under streams. Construction methods and materials of construction shall be such
that sewers will remain watertight and free from change in alignment or grade
due to anticipated hydraulic and physical loads, erosion, and impact.
2. Depressed sewers or siphons shall have not
less than two barrels, with a minimum pipe size of six inches and shall be
provided with necessary appurtenances for convenient flushing and maintenance;
the inlet and outlet chambers shall be designed to facilitate cleaning; and, in
general, sufficient head shall be provided and pipe sizes selected to secure
velocities of at least three feet per second for average flows. The inlet and
outlet details shall be arranged so that normal flow is diverted to one barrel
and so that either barrel may be removed for service or cleaning.
B. Water supplies. No general
requirement can be made to cover all conditions. Sewers shall meet the
requirements of the appropriate reviewing agency with respect to minimum
distances to structures and pipelines utilized for drinking water supplies.
There shall be no cross connection between a drinking water supply and a sewer,
or appurtenance thereto.
1. The requirements
of the Virginia Waterworks Regulations (12VAC5-590) shall be
satisfied.
2. The requirements of
the Virginia Sewage Handling and Disposal Regulations (12VAC5-610) shall be
satisfied.
3. No sewer line shall
pass within 50 feet of a drinking water supply well, source, or structure
unless special construction and pipe materials are used to obtain adequate
protection. The proposed design shall identify and adequately address the
protection of all drinking water supply wells, sources, and structures up to a
distance of 100 feet of the sewer line installation.
4. Sewers shall be laid at least 10 feet
horizontally from a water main. The distance shall be measured edge-to-edge.
When local conditions prohibit this horizontal separation, the sewer may be
laid closer provided that the water main is in a separate trench or an
undisturbed earth shelf located on one side of the sewer and the bottom of the
water main is at least 18 inches above the top of the sewer. Where this
vertical separation cannot be obtained, the sewer shall be constructed of water
pipe material in accordance with AWWA specifications and pressure tested in
place without leakage prior to backfilling. The hydrostatic test shall be
conducted in accordance with the most recent edition of the AWWA standard
(ANSI/AWWA C600-82) for the pipe material, with a minimum test pressure of 30
psi.
5. Sewers shall cross under
water mains such that the top of the sewer is at least 18 inches below the
bottom of the water main. When local conditions prohibit this vertical
separation, the sewer shall be constructed of AWWA specified water pipe and
pressure tested in place without leakage prior to backfilling, in accordance
with the provisions of this chapter. Sewers crossing over water mains shall:
a. Be laid to provide a separation of at
least 18 inches between the bottom of the sewer and the top of the water
main.
b. Be constructed of AWWA
approved water pipe and pressure tested in place without leakage prior to
backfilling, in accordance with the provisions of this chapter.
c. Have adequate structural support to
prevent damage to the water main.
d. Have the sewer joints placed equidistant
and as far as possible from the water main joints.
6. No water pipe shall pass through or come
into contact with any part of a sewer manhole. Manholes shall be placed at
least 10 feet horizontally from a water main whenever possible. The distance
shall be measured edge-to-edge of the pipes or structures. When local
conditions prohibit this horizontal separation, the manhole shall be of
watertight construction and tested in place.
