TM 5-814-9
Section VI. OTHER TREATMENT SYSTEM COMPONENTS
6-35. Water source
evaporation and vehicle carry-off will need to be
replaced from the water source. Treatment systems
All treatment Systems will require a reliable water source for
with basins that have large surface areas may have
charging the CVWF initially for make-up, regardless of the
greater water losses due to evaporation than basins
form of secondary treatment. The volume of water required will
with smaller surface areas. This loss will increase
depend on the type of wash facility constructed, type and
the volume of makeup water required, as discussed
configuration of the treatment system, frequency of use, losses,
below.
and the local climate. If a recycle system is provided, the
designer must determine the most feasible and economical
c.
Climate. The evaporation rate at the installation
method of filling the system initially and then maintaining the
must be considered when calculating the volume of
water level in the system by adding makeup water from the
make-up water needed to maintain the total demand.
water source. Makeup water will be required to restore the
The volume of rainfall at the installation as well as
system to a working level as water to carried off by the vehicles
the amount lost to evaporation should be calculated
or lost to evaporation and overspray. All original source and
to determine the volume of water needed from the
makeup water should be added at the water supply basin, if
water source. Water balance computations should
provided. This water should be uncontaminated, reasonably
be performed by the designer to assure adequate
clean, and should not require treatment before being introduced
supplies of water throughout the entire washing
into the system. All sources of water available at the installation
season.
should be considered for use, singly or in combination, as
sources of water at a CVWF including dedicated wells, surface
6-36. Piping
water, tapping into the existing potable water supply or
captured rainwater.
Wastewater should be conveyed by gravity whenever possible
for economy. Pumping should be avoided because residual oils
a.
Type of facility. A wash facility that has a prewash
may become emulsified and difficult to remove, solids cause
will require more makeup water than a facility with
wear on pumps and pumps add significant capital and operating
only wash stations because of increased water lost
cost to the facility. Conveyances, whether gravity sewers or
by vehicle carry-off, overspray, and evaporation.
open channel, must be constructed to grades which will provide
Water losses from carry-off can be as high as 160
adequate scouring velocity to prevent solids deposition. All
gallons per vehicle. Losses due to overspray and
pipes must be designed for peak hydraulic and solids loadings,
evaporation can be as high as 10% from water
including that contribution from storm water runoff from
cannons and 5% from hoses at wash stations.
hardstands. Open-channel flow should be used whenever
possible for ease of maintenance. If siting problems or severe
b.
Type and configuration of treatment system. The
slopes make open-channel flow impractical, the designer should
type and configuration of the treatment system is
use large-diameter pipes. Locate manholes at each change in
another factor to consider when estimating the vol-
slope or direction and at each pipe intersection. Design long,
ume of makeup water required. A discharge system
straight sections of conduit to minimize the number of manholes
will require that the total water demand including
required. All frequently operated, buried valves should be
makeup be taken from the developed water source.
accessible through pits or manholes.
In a recycle system, only the water lost to overspray,
6-28
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