Underground Storage Tank (UST) public record

We collect data on the sources and causes of underground storage tank (UST) releases in Washington.

The data displayed on this page is for federal fiscal year 2020 (Oct. 1, 2019, to Sept. 30, 2020).

General information as of November 2020:

  • Total number of active UST sites — 3,419 sites
  • Total number of active USTs — 8,778 tanks

Summary information for onsite inspections for federal fiscal year 2020: 932

  • Total number of UST site compliance inspections conducted: 932 inspections (926 by Ecology inspectors and 6 by Environmental Protection Agency (EPA) inspectors).
  • Percent of sites in compliance with the UST regulation on the day of inspection: 64 percent of sites in full compliance (a combined measure of 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 or deferred USTs. Emergency power generator USTs are included. Onsite compliance inspections measure significant operational compliance as defined by the EPA.

Summary information on UST contamination found (releases) for federal fiscal year 2020:

  • Number of confirmed releases: 16 sites with confirmed contamination.

The majority of the reported releases were found when old tanks were being removed. Sampling the soil revealed contamination. These are called “legacy releases.” They may have occurred years ago, but contamination was only found during this fiscal year. It is difficult to determine the source or cause of a legacy release. That's why a large percentage of the sources and causes in the chart 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.

Confirmed releases found during fiscal year 2020

Release Source #
Dispenser 1
Piping 3
Tank 2
Unknown 11


Cause of Release #
Overfill 1
Physical or mechanical damage 2
Other 2
Unknown 12

Information posted February 19, 2021.

We are required to report sources and causes of underground storage tank releases, according to the federal Energy Policy Act of 2005.