The term applied to devices used in storage-tank systems to contain the liquid that might accidentally escape from the primary storage vessel.
One common secondary-containment system is represented by double wall tanks or double wall piping. If the interior (primary tank or pipe) fails, the released liquid will be contained by the outer wall until the situation can be remedied.
A secondary-containment system may also consist of an impervious liner, installed in the tank earthen excavation, or an impervious liner installed in the piping trench.
Impervious geosynthetic liner systems can use various types of material for the walls of the secondary containment system. These include but are not limited to concrete walls, galvanized steel walls, stainless steel walls and earthen berm walls all with an earthen subgrade.
Some jurisdictions allow compacted clay liners (CCLs) for secondary containment system floors and walls but this normally is not a viable choice when fuel is being stored since gasoline can penetrate the CCL.