Underground storage tank (UST) program
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:
- If more than 10% of an AST’s volume is buried or flows through underground piping, we regulate it as an underground storage tank.
- Above-ground petroleum tanks with a capacity of 10,000 gallons or more at Class 1 oil handling facilities are overseen by our Spills Prevention, Preparedness, and Response program.
Certain ASTs are subject to federal regulations, including:
- ASTs that qualify as “bulk storage containers”. See EPA’s Aboveground Storage Tank webpage for details.
- ASTs located near navigable waters, which may be subject to additional federal regulations and oversight.
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).
Related links
Contact information
tanks@ecy.wa.gov
UST Hotline: 800-826-7716