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TM 10-3835-231-13
(4)
Tank Pad and Berm Construction. Proper tank pad and berm construction are most important to provide for
tank operation and protection from spill or a fire resulting from the spill. (See figure 4-3, 4-4, and 4-5.) Sites for tanks and
their berms should be carefully selected, giving consideration to space, terrain, soil consistency, and accessibility.
(a)
Berms are normally constructed of earth from the surrounding area. The more impermeable the soil
the better, such as high clay content is desirable to avoid leakage and keep the berm in shape. Adding some rock and
gravel will tend to avoid washout.
(b)
Tank pads are preferably constructed of a loamy or clay soil containing some sand so that a smooth
area can be graded and hold its shape. (See figure 4-5.) The longest slope should be approximately 1° (degree) from
horizontal. Other shorter slopes will be greater. The low point should be where the tank drain will end up when the tank is
unrolled. A small ditch and a basin for the tank drain line and drain valve can be excavated by hand at the time the tank is
unrolled. The low point described is to permit maximum pump out of the tank and drainage through the drain line. The
base of the tank pad area must be virgin soil, cut soil, or well compacted. To avoid damage to the tank bottom sticks,
stones, or sharp objects must be removed prior to installing the tank.
(c)
Tank berms are constructed as shown on figures 4-3 and 4-4. They may be constructed before, after,
or simultaneously with tank pad construction, depending on job conditions. In any case, it is necessary that the tank pad
be cleared of any rocks, clumps, etc, that roll on during berm construction. It is recommended that tank pad rough grading
be completed before berm construction. The preferred materials are soils containing a fairly high clay content to hold
shape and provides sealing. The berm should be compacted as it is constructed.
(d)
Berms may be constructed of sandbags if site conditions preclude earth construction, however,
sandbag berms will not hold a tank spill very well unless action is taken to seal the gaps between bag ends. Heavy clay
packing between joints will help. Nevertheless considerable leakage can take place. Sandbags are supplied with the
TPT.
(e)
To install a berm drain, hand cut a trench in the first layer of the berm. Lay the drain line in the trench
and cover. Finish constructing the berm. Install valve on drain line and be sure valve is closed.
(f)
If the installation authority decides to install construction grade polyethylene sealing sheets, they
should be installed after the pad and berm are completed. After the joints of the sheeting are sealed, a light layer of soil
(without rocks) may be spread to protect the sheeting and hold it in place.
4-7
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