June 99
8.2
Design all components of storm sewerage system on
basis of not less than 10-year storm frequency for one
hour.
8.3
Comply with the requirements of off-site receptor of storm
water. Provide retention, if required.
8.4
Do not connect storm drainage system to sanitary
sewerage systems.
8.5
To extent feasible, do not locate sewer pipes and manholes
under pavement. Provide manholes at junctions, changes
in direction, changes in slope, and changes in invert
elevations of sewers 200 mm (8-inch) and above.
[Cleanouts are required for 100 and 150 mm (4 and 6-inch)
sewers]. Limit spacing between manholes to 90 m (300
feet), except 150 m (500 foot) spacing is permitted in
straight runs of long outfall sewers.
8.6
Indicate on drawings where extra strength pipe is required
to support anticipated trench and superimposed loads.
Include adequate pipe bedding and, if necessary, provide
structural supports for sewer pipes, manholes, inlets, and
other appurtenances.
8.7
Limit sanitary trunk sewers to not less than 200 mm
(8-inch) diameter and sanitary sewer building connections
to not less than 100 mm (4-inch) diameter. Establish
sanitary sewer slopes to provide minimum velocity of 0.6
mm per second (two feet per second) when pipe is flowing
full; maximum slope shall be ten percent, unless there are
unusual circumstances.
8.8
Limit storm sewers serving drainage inlets to not less than
200 mm (8-inch) diameter and building connections to not
less than 100 mm (4-inch) diameter. Establish storm
sewer slopes to provide minimum velocity of 0.6 mm per
second (two feet-per-second) when pipe is flowing full.
Maximum storm sewer design velocity shall be in
non-erosive range for specified pipe material.
8.9
Storm drainage curb and gutter inlets shall be designed to
match the profile of the curb and/or curb and gutter. No
part of the inlet shall be behind the curb. Grating for inlets
shall be selected based on drainage capacity, ability to
screen out harmful debris, ability to pass unobjectionable
debris, strength, and permanency.
8.9
Use State or local standard details for manholes, inlets,
endwalls and pipe cradles. Adjust master specification as
VA Design Guide -- National Cemetery Administration
Page 5 -90
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