c) Within the dike wall, consider a hybrid,
primary/secondary system for large area dike containments.
The primary containment consists of a concrete work area
around the tank, curbed with independent, curbed concrete
drainage leading to the main dike area drain. Experience has
shown that such an area could probably handle 99.9 percent of
all spills. The surrounding secondary containment area would
be made up of less expensive systems that would provide
impervious containment in the rare event of a catastrophic
tank failure but where the curbing would prevent smaller, more
common type spills from reaching and causing
gravel/impervious liners or coated asphalt. The secondary
contained area would also drain to the main dike collection
drain and oil/water separator.
d) Do not use Bentonite or a Bentonite composite
material in the construction of dikes or basins.
Reinforced Concrete Dikes. Design reinforced
concrete (prefabricated or cast-in-place) dikes and their
foundations to resist and contain the full hydrostatic load
when filled to capacity. Consider the use of reinforced
concrete blocks with or without exterior earth mounding. Use
vertical reinforced concrete dikes where space is a premium.
Seal all concrete surfaces with a flexible, UV-resistant,
fuel-resistant coating if required by local or State
regulations. As a minimum, spray all concrete surfaces with a
Combination Dikes. A vertical concrete wall backed
by an external earthen berm may be used. Design the combined
earthen and concrete unit and its foundation to resist and
contain the full hydrostatic load when filled to capacity.
The dike floor could be either concrete or liner as described
Remote Containment/Impoundment Spill Collection
Systems. As an alternative to dike enclosures, use a spill
collection system consisting of a series of drains leading
from storage tank areas to a remote containment or impoundment
designed to prevent the accidental discharge of petroleum.
This is not the preferred method and requires approval of
Service Headquarters. Generally, this system is used for