tanks (welded steel or fiberglass reinforced plastic (FRP)).
Ensure that contract requires the design and installation in
accordance with 40 CFR 280 or any more stringent state or
local criteria. Require separation of exterior tank walls from
the interior walls with standoffs, thus creating an open
space, or interstitial, for monitoring of leaks. This is
called a Type II tank. Do not exceed 12 feet (3.7 m) in
diameter for tanks. Limit tank length to six times the
diameter. Ensure that factory-fabricated tanks comply with UL
a) Install tanks in accordance with NFPA 30 and also
in strict accordance with the manufacturer's installation
b) Install the tank so that the bottom slopes
downward toward one end at a slope of 1 percent. Locate
transfer pumps and suction piping at the low end of the tank.
c) Provide straps and anchors designed to prevent
flotation of tanks located in areas with high groundwater
levels or subject to flooding. Provide electrical isolation
strips between hold-down straps and metal tanks. Anchors may
be a concrete anchor slab under the tank or concrete deadmen.
d) Place tanks on a uniform bed of homogeneous
granular material at least 6 inches (150 mm) thick for steel
tanks and 12 inches (300 mm) thick for fiberglass tanks. If a
concrete anchor slab is used, place a minimum of 12 inches
(300 mm) of bedding between the tank and the concrete anchor
slab. Do not use blocks, chocks, or rocks.
e) Ensure that tank is installed by state-certified
UNDERGROUND VERTICAL STORAGE TANKS.
Cut and cover.
General Design Considerations. Underground vertical
storage tanks are steel-lined reinforced concrete with an
interstitial space and leak monitoring capability. These
tanks may be completely buried, surface-constructed and then
covered with embankment, or any variation in between;
containment must be provided for the volume of the tank above