Figure 2-2. Checking grade of tank foundation.
(3) After the tank is erected, stabilize the
outer slopes with an asphalt base material to prevent
(1) Concrete Foundation Ring. Where tanks
washout of the soil material.
must be sited on alluvial deposits, flood banks, or in low
wet areas, build a concrete foundation ring (fig. 2-3) of
Purpose of the foundation is to provide
the same diameter as the tank. Pour a continuous
drainage of water away from the tank so
concrete ring 12 inches thick and 2 feet high with its
that moisture will not accumulate and
base 18 inches below the ground surface. Provide drain
corrode the tank bottom.
pipes below the top of the ring but above ground level.
d. Surfacing. If the foundation materials or ground
Fill the ring with suitable foundation material. Compact
the fill to provide stable support for the tank bottom.
water contain alkali salts which will corrode the tank
Surfacing will be required in wet areas, especially if the
bottom, surfacing is required. Use a bituminous seal
water is salty or brackish. The side staves of the tank
coat, or work bituminous material into the top layer of
bear on the concrete ring when tank is erected.
foundation material. Tarpaper or roofing felt may be
used. It is a good practice to apply surfacing even when
the foundation material is not corrosive in order to
prevent seepage of water from the subsoil. Concrete
slab foundations are desirable if time, labor, and
material are available.
e. Special Foundations. Occasionally, tanks must
be built on sites which would not be used under ideal