Underground storage tank (UST) program
Updated Underground Storage Tank rule takes effect Nov. 24, 2023
The legislature recently passed a law directing the Pollution Liability Insurance Agency (PLIA) to establish and run a new state financial assurance program for UST owners and operators. Ecology updated our underground storage tank regulations to allow for this new program. The changes take effect Nov. 24, 2023.
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 conduct compliance inspections and provide technical assistance to help tank owners prevent leaks and spills.
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. We are federally required to inspect tanks at least every three years.
Find it fast
- Checklists & Forms
- Tank Closures
- Guidance and Focus Sheets
- Operator Training
- New Owner/New Tank
- Service Providers
The fee for each underground storage tank is:
- $216.09 beginning July 1, 2023
2023 fee increase focus sheet
- $228.58 beginning July 1, 2024
2024 fee increase focus sheet
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).