UNDERGROUND STORAGE TANK

An Underground Storage Tank (UST), in United States environmental law, is a tank and any underground piping connected to the tank that has at least 10 percent of its combined volume underground. USTs, used to store petroleum, are regulated in the United States to prevent release of petroleum and contamination of groundwater.
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(Water Quality) (1) Any one or combination of underground tanks and any connecting underground pipes used to contain an accumulation of regulated substances. (2) A tank located at least partially underground and designed to hold gasoline or other petroleum products or chemicals.

A tank located at least partially underground and designed to hold gasoline or other petroleum products or chemicals.

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For purposes of Subtitle I of the Resource Conservation and Recovery Act, this is any tank used to store petroleum or hazardous substances regulated under the Comprehensive Environmental Response, Compensation, and Liability Act, the volume of which is 10% or more beneath the surface of the ground. This does not include, among other things, any farm or residential tank of 1,100 gallons or less capacity used for storing motor fuel for noncommercial purposes, tanks used for storing heating oil for consumptive use on the premises, or septic tanks.
  

A tank located at least partially underground and designed to hold gasoline or other petroleum products or chemicals.