Underground Storage Tank (UST)
A tank and connected piping with at least 10% of volume underground, used for storing petroleum or hazardous substances.
An underground storage tank (UST) is a tank and any underground piping connected to the tank that has at least 10 percent of its combined volume underground. USTs are commonly found at gas stations, industrial facilities, and military bases where they store petroleum products like gasoline, diesel fuel, and heating oil, as well as hazardous substances.
The U.S. EPA regulates approximately 542,000 active USTs across the country. Federal regulations require UST owners and operators to prevent releases, detect leaks, and take corrective action when releases occur. Modern USTs must have corrosion protection, spill prevention, overfill prevention, and leak detection equipment.
UST systems that are improperly managed pose a significant environmental risk. Leaking USTs can contaminate groundwater, soil, and nearby waterways with petroleum and other hazardous chemicals. The EPA's UST program works with state and territorial regulatory agencies to ensure proper management of UST systems throughout their lifecycle.
Related Terms
A UST that has confirmed or suspected releases of petroleum or hazardous substances into the environment.
UST ComplianceAdherence to federal and state regulations governing the installation, operation, and closure of underground storage tank systems.
Tank ClosureThe process of properly decommissioning an underground storage tank, either by removal or closure in place.
Petroleum ContaminationEnvironmental pollution caused by the release of petroleum products such as gasoline, diesel, and heating oil from UST systems.