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 Feb. 20, 2025.
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 |
| 2024 | 3361 | 8597 | 1165 | 42 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 |
| 2024 | 0 | 3 | 4 | 1 | 1 | 23 | 32 |
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 |
| 2024 | 3 | 3 | 1 | 0 | 22 | 29 |