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An underground storage tank (UST) 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 apply only to underground tanks and piping storing either petroleum or certain hazardous substances.
EPA estimates that there are over one-half million federally regulated USTs buried at thousands of sites nationwide. Nearly all USTs at these sites contain petroleum. These sites include marketers who sell gasoline to the public (such as service stations and convenience stores), and nonmarketers who use tanks solely for their own needs (such as fleet service operators and local governments).
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 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.
Exemptions from the UST regulation
The following USTs are excluded from regulation and, therefore, do not need to meet federal requirements for USTs: