Underground storage tank (UST) program

Information for underground storage tank owners and operators

Our Underground Storage Tank (UST) program is one of the largest pollution prevention programs at Ecology. Every year, just over 3 billion gallons of fuel are stored underground. We inspect tank systems at least every three years. We also provide technical assistance to help tank owners make sure their systems are installed, managed, and monitored correctly to prevent leaks or spills.

Program overview

We regulate more than 8,500 tanks at more than 3,400 facilities, including gas stations, industrial and commercial properties, and government-owned properties. We make sure these tanks and their associated piping systems are installed, managed, and monitored to prevent releases into the environment.

Washington’s UST program is federally-approved. This means that state law, not federal law, applies to UST systems in this state. Washington's underground storage tank regulations are in Chapter 173-360A WAC.

Sources and causes of releases

View our data on the sources and causes of releases from UST systems in Washington. 

Other storage tanks

You must report any spills or leaks of petroleum or hazardous substances to Ecology, whether or not we regulate the tank. Report releases affecting water or spills of dangerous materials immediately.

Aboveground storage tanks

Ecology does not regulate most above-ground storage tanks (ASTs). These tanks typically hold petroleum products (like heating oil, propane, or diesel) or other potentially hazardous chemicals. Local fire agencies, counties, and/or cities, regulate and permit ASTs, with two exceptions:

Certain ASTs are subject to federal regulations, including:

Home heating oil tanks

We do not regulate any home heating oil tanks, underground or aboveground. For information about home heating oil tanks, contact the Pollution Liability Insurance Agency (1-800-822-3905).