TM 5-814-9
Tracked vehicle lanes. The recommended center-
(1)
filling of the bath and movement of dirt and debris
to-center flexor spacing is 5.5 feet (1.7 meters). The
to the outlet structure when the bath is drained,
flexors are offset (fig 5-6) to allow the vehicle's
flushed and cleaned. A flusher supply discharge
running gear to achieve the maximum flexing
should be placed into the uppermost end of each u-
motion possible. Outer lanes of the bath should
drain. The flushers will provide increased flow in
have the flexors extended to the side walls to
the u-drains to prevent sediment deposition. The
prevent dirt from building up between the ends of
recommended flushing rate is 600 gpm (2280 liters
the flexors and the walls. Each flexor in a tracked
per second) for the lateral u-drains and 900 gpm
vehicle lane should be 9 inches (22.8 centimeters)
(3420 liters per second) for the primary u-drains
high. The method of connecting or imbedding the
and should be set to provide 5 fps (2.4 meters per
flexors to the bottom of the bath must be able to
second) velocity in the u-drain. Flushing time is
withstand the impact of all types of vehicles using
arbitrarily set at 15 to 25 minutes, depending on
the bath.
soiling conditions. The flow rate for filling may be
increased in order to fill the bath in a reasonable
Dual-purpose lanes. The design of flexors in dual-
(2)
amount of time; a fill time of 30 minutes or less is
purpose lanes will be similar to those in the tracked
recommended. The fill/flush procedures are con-
lanes. The flexors should be spaced 18 inches (45.7
trolled by the wash facility operator (see chap 4.)
centimeters) apart. The flexors shall be installed at
The system of pumps and supply piping is designed
right angles to the lane and extend from the edge of
to be independent of other systems. The source of
lateral trench drain in the lane to the side walls of
fill/flush water is the equalization basin.
the bath. This design prevents dirt from collecting
Design. U-drains are to be designed to handle the
between the wall and the flexor. The flexors are not
(3)
offset (fig 5-7) in order to allow better vehicle
peak solids and hydraulic loadings that occur in
control. Each flexor shall be 3 inches (7.6 centi-
moving wastewater to the effluent structure. A
meters) above the floor level and constructed in
minimum grade of 2 percent is required in the
such a way to withstand the impact of both tracked
drains along with 5 fps velocity to prevent settling.
and wheeled vehicles.
Materials. U-drains should be lined with concrete
(4)
i. Entrance ramp. The slope of the entrance ramp is
or other impervious material such as plastic, metal,
measured from the top of the first flexor in the bath lane. The
or vitrified clay. The liner should have a smooth,
maximum allowable slope into the bath is 1:7 (14 percent).
circular finish to reduce roughness in the trench.
j. Exit ramp. The maximum allowable slope for the bath
m. Outlet control structure. A moveable weir on the outlet
exit ramp is 1:11(9 percent).
structure is used to regulate the depth of water in the bath (fig
5-11). This weir is located at the interface of the structure and
k. Ramp Slope. Slopes selected will affect the volume of
the bottom of the bath and is designed to be raised or lowered
water required to fill the bath and the resulting amount of
to vary the water depth. A valve or gate is located in the
wastewater to be treated. Therefore, the maximum slopes
structure at the intersection with the transverse u-drain to allow
allowable should be selected except where local conditions
wastewater to discharge into the structure. Weirs, valves and
require flatter slopes.
gates may be motorized or manually operated. The structure
should be designed to minimize solids deposition.
1. U-Drains. Open u-drains shall be used to move soil-laden
5-3. Vehicle spray stands
wastewater from the bath area to the collection system (fig 5-8).
The bottom of the bath should slope toward these drains at a
A spray stand operates much as a commercial car wash in that
minimum of 2 percent to help move mud and debris into the
the vehicle is driven into the facility and sprayed by high-
collection system (fig 5-9).
pressure water from many small nozzles. This method is not
suited, nor recommended, for the irregular-shaped tactical
Configuration. A lateral u-drain is installed along
(1)
vehicles, because M-1 tanks and other vehicles with heavy side
the centerline of each bath lane. Each lateral drain
skirts cannot be cleaned effectively. The spray does not
is connected to the transverse u-drain that runs
effectively remove dirt from the treads, under the skirts, and
perpendicular to the lanes. This transverse drain
other places that are difficult to reach. Spray stands also require
discharges directly into the bath outlet control
larger amounts of water than comparably sized bath prewash
structure. Figure 5-10 shows how these drains are
facilities. Therefore they are not recommended for use at
arranged.
CONUS installations.
Fill/flush system. A fill/flush system with motorized
(2)
valves is provided in the bath to allow for timed
5-7
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