Underground Storage Tank (UST) public record

We collect data on the sources and causes of underground storage tank (UST) leaks and spills in Washington. The federal Energy Policy Act of 2005 requires us to report sources and causes of these underground storage tank releases.

The federal fiscal year runs from the beginning of October to the end of September. We last updated the data on this page on Jan. 10, 2024.

Site inspections by federal fiscal year

year active sites active USTs sites inspected sites in full compliance
2021 3419 8762 1380 56 percent
2022 3395 8701 979 36 percent
2023 3377 8633 993 46 percent

Unless otherwise noted, sites were inspected by Ecology staff. Compliance includes release detection and release prevention requirements.

Tank facility and onsite inspection information is based on USTs that are regulated under federal Subtitle I that satisfy the definition of UST in 40 CFR 280.12, except for those identified in 40 CFR 280.10(b) and (c) as excluded USTs. Emergency power generator USTs are included. Onsite compliance inspections measure technical compliance rate as defined by the EPA.

Confirmed releases from USTs

Most of these releases were found when old tanks were being removed. Sampling the soil in the tank area revealed contamination. These “legacy releases” may have occurred years ago, but contamination was only discovered during the marked fiscal year. It is difficult to determine the source or cause of a legacy release. That's why most of the sources and causes in the charts below are “unknown.” This is in contrast to releases discovered due to leak detection, tank gauging systems, UST operator discoveries, unusual operating conditions, etc., as part of ongoing operation of the USTs.

Release sources by federal fiscal year

year dispenser piping tank submersible turbine pump area other unknown total
2021 0 0 8 0 0 11 19
2022 3 2 3 1 1 4 14
2023 0 1 2 0 0 18 21

Release causes by federal fiscal year

year corrosion overfill physical or mechanical damage other unknown total
2021 7 0 1 0 11 19
2022 2 0 2 2 8 14
2023 1 2 1 0 17 21