Underground Storage Tank (UST) Program

Underground storage tank system illustration

What is a Regulated UST?

According to Arizona Revised Statutes (ARS), a UST is a tank or a combination of tanks and connected underground pipes and impact valves used or once used to contain regulated substances. These systems must have at least 10 percent of the total volume of the tank and connected pipes underground to be considered USTs.

USTs do not include any of the following:

  • A farm or residential tank with 1,100 gallons or less capacity used for storing motor fuel for noncommercial purposes
  • A tank used for storing heating oil for consumptive use on the premises where stored
  • A septic tank
  • A pipeline facility, including gathering lines, regulated under either The Natural Gas Pipeline Safety Act of 1968 (49 United States Code, Sections 1671 – 1686) or The Hazardous Liquid Pipeline Safety Act of 1979 (49 United States Code, Section 2001)
  • An intrastate pipeline facility regulated under a state law comparable to the provisions of law referred to in Subdivision D, Item i or ii
  • A surface impoundment, pit, pond or lagoon
  • A stormwater or wastewater collection system
  • A flow-through process tank
  • A liquid trap or associated gathering lines directly related to oil or gas production and gathering operations
  • A storage tank situated in an underground area, such as a basement, cellar, mine working, drift, shaft or tunnel, if the storage tank is situated on or above the surface of the floor
  • Pipes connected to any of the structures described in the bullets above

Learn more about keeping your regulated UST(s) in compliance with new State and Federal Laws | Learn More >