TM 5-814-9
Section V. WATER SUPPLY BASIN
6-29. Introduction
effluent volume to the wash facility. If the basin is too small,
there will not be enough wash water, but if it is too large, it will
Filtered water from the secondary treatment facility (sand filter
not be cost-effective. The effective depth of the water supply
or lagoon) flows by gravity into the wash water supply basin.
basin should be 5 to 8 feet (1.5 to 2.5 meters). Deeper basins
This is a lined basin which stores the filtered wash water supply
should be considered in arid regions to reduce water surface
for the vehicle wash area. Maximum and minimum operating
areas, thereby minimizing evaporation.
levels are monitored by level sensors in the wash water
pumping station. The basin is sized to store, at a minimum, the
6-31. Liner
quantity of water required to wash the maximum number of
vehicles for which the facility is designed during the design
The water supply basin may be lined with concrete, clay, or a
wash period. Makeup water for the CVWF is added into the
synthetic material, if required, such as those described for the
water supply basin. If necessary, excess water can be
equalization basin (para 6-26 above). In areas with high
discharged from this basin; however, the basin should be sized
evaporation rates, light-colored basin liners might be considered
to hold the water demand volume plus storm water from a one-
to lower solar heat gain and decrease the evaporation rate.
hour duration 10-year storm event.
6-32. Influent structure
6-30. Capacity
An energy dissipation device or treatment should be installed at
The effective water volume of the basin should be based on Vave
the inlet to dissipate the energy of the influent water and prevent
for a one week wash period or Vmax for a peak use period,
liner erosion. The inlet should be close to the maximum water
whichever is greater. A safety factor ranging from 1.25 to 2.0
elevation in the basin to prevent water from backing up into the
times Vave or V max, should be incorporated to help insure ad-
pipe and surcharging the sand filter drain system.
equate water volume at all times. The basin should include 3
6-33. Service
feet (1.0 meter) of freeboard above the highest water level,
including an allowance for stormwater. There is no need to
There should be little, if any, solids deposition in this basin, so
provide for sediment storage in this basin since the water in the
there is no need for a ramped service entrance into it. There
basin should not contain sediment. A depth of 2 to 4 feet should
should also be no oil in this basin, so no oil removal equipment
be allowed for dead storage at the bottom of the basin. This
is needed.
additional volume allows for submergence of the effluent
control structure. Figures 6-22 and 6-23 show different views
6-34. Security
of a water supply basin. The designer must ensure that the size
Fences may have to installed around the basin to prevent
of the water supply basin is compatible with the influent volume
animals from entering the area to drink or bathe.
from the secondary treatment or water source and with the
6-25
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