An underground storage tank system is a tank and any underground piping connected to the tank that has at least 10 percent of its combined volume underground. The federal UST regulations are designed to reduce the chance of releases from USTs, detect leaks and spills when they do occur, and secure a prompt cleanup.

UST owners and operators are responsible for reporting and cleaning up any releases and, in the event of a leak or spill, are responsible for paying the costs associated with cleaning up releases and compensating third parties.
The greatest potential hazard from a leaking UST is that the petroleum or other hazardous substance can seep into the soil and contaminate groundwater, the source of drinking water for nearly half of all Americans. A leaking UST can present other health and environmental risks, including the potential for fire and explosion.

Until the mid-1980s, most USTs were made of bare steel, which is likely to corrode over time and allow UST contents to leak into the environment. Faulty installation or inadequate operating and maintenance procedures also can cause USTs to release their contents into the environment.

The UST regulations apply only to underground tanks and piping storing either petroleum or certain hazardous substances. In practice, nearly all USTs contain petroleum and are used by marketers who sell gasoline to the public (such as service stations and convenience stores) and non-marketers who use tanks solely for their own needs (such as fleet service operators and local governments).

State UST programs approved by the U.S. EPA are allowed to operate in lieu of the federal program and EPA’s state program approval regulations set standards for state programs to meet. States may have more stringent regulations than the federal requirements.

For more information, visit EPA’s Office of Underground Storage Tanks Web site.

Published: April 1, 2002

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