Underground storage tank regulations

Washington’s Underground Storage Tank (UST) regulations, or UST rule, are in place to prevent the release of petroleum or other hazardous substances from underground storage tank systems and ensure any leaks or spills are found and cleaned up.

The UST rule sets requirements for tank construction, maintenance, and inspections. Owners or operators must do regular walk-through inspections. Ecology staff inspect tank systems at least every three years.

Ecology doesn’t regulate tanks used only for home heating oil, or most aboveground storage tanks.

2018 updates to UST rule

In July 2018, we repealed the old rule, Chapter 173-360, and adopted a new rule, Chapter 173-360A. The new rule went into effect Oct 1, 2018.

Who is affected?

The changes to the UST rule may impact people who:

  • Own or operate UST systems.
  • Provide services to tank owners and operators,
  • Deliver product to, or collect waste oil from, UST systems,
  • Provide pollution liability insurance for UST systems,
  • Train UST system operators,

Help with following the law

Our resources for UST owners and operators include a video, checklist, and thorough guidance document to help people follow the updated law.

What changed

The new UST regulation:

  • Incorporates federal rule updates, including:
    •  new operation and maintenance requirements
    • requirements for field-constructed tanks and airport hydrant systems
  • Integrates changes to the state statute that authorizes the program, Chapter 70A.355 RCW (such as licensing requirements for UST systems).
  • Updates other requirements governing the program (such as UST service provider requirements).
  • is clearer and more consistent with other state and federal laws

Highlights of the 2018 UST Rule Revisions goes into more detail.

Why we updated the UST regulations

Washington has a federally-approved Underground Storage Tank program. This means that state law, not federal law, applies to regulated UST systems in the state (except for systems on Native American lands). To keep this approval our laws must meet federal requirements.

In October 2015, the Environmental Protection Agency (EPA) adopted changes to the federal UST program rules (40 Code of Federal Regulations [C.F.R.] Part 280) and state program approval (40 C.F.R. Part 281). These are the first major changes to the federal rules since 1988.

The changes enact the requirements in the UST Compliance Act of 2005, add new operation and maintenance requirements for UST systems, and establish requirements for certain types of UST systems that were deferred in 1988. States with federally-approved programs had to incorporate the changes by October 2018 to maintain program approval.