Frequent Questions

Secondary containment for tanks must include one of more of the following: a liner external to the tank, a vault, a double-walled tank, or an equivalent device as approved by the Regional Administrator (40 CFR §264.193(d)). What is a vault?

While there is no regulatory definition of a vault, vaults are described, on page 7-37 of the "Technical Resource Document for the Storage and Treatment of Hazardous Waste in Tank Systems" (December 1986, EPA530-SW-86-044), as "...generally contruced of concrete, is typicall an underground chamber with a roof that will contain any released tank contents." 

In addition, it is important to note that this guidance represents clarification of the Federal regulations. Most states are authorized to implement the Federal regulations. We recommend that you also contact your state's implementing agency to acquire additional information on hazardous waste tank secondary containment. The Office of Resource Conservation and Recovery  (ORCR) has compiled a list of waste program Web sites maintained by EPA Regional offices and state environmental agencies to help users locate the appropriate agency within their states.

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