MIL-HDBK-1005/9A
c) Carry out washing and maintenance operations in
designated areas (which should be as compact as conveniently
possible). Consider the use of non-emulsifying degreasers.
d) Use dry absorbent materials to clean up oil and
gasoline spills on pavements served exclusively by storm water
sewers.
2.5.6.2
Appurtenances
a)
Diversion Chamber
(1) Construction. Construct a manhole with
conventional inflow and outflow storm sewer pipe, incorporating
a small gated outflow to allow diversion of dry weather flows
and the first increment of runoff during storms (see Figure 2).
This also prevents flushing of oil and sediment from the trap
during storm conditions.
(2) Hydraulic design. Design the main inflow and
outflow pipes to pass storm flows, taking care to ensure that
velocities of dry weather flows are sufficient to prevent solids
deposition. Design the gated outflow pipe to pass dry weather
flows. Pipe diameter should not be less than 6 inches (152 mm).
b) Grit Removal. Provide for gravity separation,
washing, and removal of grit where load may block sewer. Use
velocity control channel type, either manually or mechanically
cleaned, with screw type agitated grit washer.
(1) Selection Basis. Use manually cleaned units
for applications where grit load is less than 1 cubic ft (0.0283
cubic m) per day and use mechanically cleaned units for
application where grit load is greater than 1 cubic ft/day.
(2) Design Basis. Provide at least two units
sized to give 95 percent removal of P10 grit size at peak flow
with units in service. Limit variations in flow velocity to a
narrow range and use high values of V/Vs (maximum 70). Refer to
WEF MOP No. 8, Wastewater Treatment Plant Design.
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