Secondary Containment of Dangerous Waste
State law requires liquid dangerous wastes to have secondary containment which will prevent spills or leaks of liquid dangerous wastes from reaching the environment.
Secondary containment for drums storing dangerous wastes often consists of concrete floors with curbing or lined diked areas. Apply a protective coating or sealant to the interior of a concrete structure used for secondary containment. Build it with as few joints as possible. Commercially available portable units, such as totes and containment pallets, typically accommodate one to four drums.
Put incompatible wastes in separate containment systems so that the wastes cannot mix if there is a spill or leak.
The base of the secondary containment system must be free of cracks or gaps. It must be impervious so that it contains leaks, spills, and accumulated rainfall until the collected material can be found and removed. Protect containers or tanks from contact with liquid accumulated from leaks, spills or rainfall. The containment base can be sloped to allow easier drainage and removal, or the containers can be elevated. For container storage, inspect the containment system at least once a week forspills and deterioration Tank storage systems are inspected on a daily basis.
To protect from rain and snow, it is recommended that containers and the secondary containment be inside a building or under some type of protective covering. The cover must allow for adequate inspection. Covered secondary containment must be large enough to contain ten percent of the free liquid in all containers or 100 percent of the free liquid in the largest container.
Uncovered secondary containment must have capacity to hold the additional precipitation resulting from a maximum 25-year storm lasting 24 hours. That is, the containment system must hold the volume of water resulting from a 24-hour rainfall with an average rainfall intensity (in inches/hour) of a storm that should occur only once in every 25 years. Uncovered secondary containment systems must have positive drainage control, such as a locked drainage valve, to prevent releasing contaminated liquids while allowing ready drainage of uncontaminated rainfall.
Tanks often have concrete vault structures as secondary containment. Other methods include installing external liners and using double-walled tanks.
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