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Toxics Cleanup Program

Underground Storage Tanks (USTs)

Laws and Rules

State Program Approval

Washington State has a federally-approved state Underground Storage Tank (UST) program.  This means that state law, not federal law, applies to UST systems in this state.
To obtain such approval, the state UST program must meet minimum federal requirements.

Federal Requirements

For information about the federal UST program, and the minimum requirements for state program approval,  visit:

State Laws and Rules

The following laws and rules apply to UST systems in this state:

  • Statute: Chapter 90.76 RCW (last revised May 2013)  

    Statutes are passed by the legislature or by the people through a citizens’ initiative. Statutes establish the legal authority for state agency programs. Statutes are codified as the Revised Code of Washington (RCW).

  • Rule: Chapter 173-360 WAC (last revised August 2012)
    The terms rule and regulation are used interchangeably. Rules are laws issued by a state agency providing instructions on how to comply with a statute. Rules are issued under the authority granted to the agency by the statute. The Washington Administrative Code (WAC) codifies the rules and arranges them by subject or agency.

For your convenience, Ecology has published the following document that contains both the UST statute and rule:

Ecology has published documents that answer frequently asked questions (FAQ) about the UST regulations:

  • Regulatory Interpretations
  • Regulatory Interpretation Manual for UST Regulations (Publication No. 04-09-088)  (last revised May 2004)
    (Not available at this time, undergoing revision.)

Regulatory History

To read a brief history of the regulation of underground storage tanks, visit

Current Rulemaking

Ecology plans to amend Chapter 173-360 WAC, Underground Storage Tank (UST) Regulations. As part the rulemaking, Ecology plans to:

  1. Incorporate federal rule changes needed to maintain state program approval, as specified in 40 CFR Parts 280 and 281 and adopted in June 2015.
  2. Incorporate changes to the state’s UST program specified in the authorizing state statute, Chapter 90.76 RCW.
  3. Make other selective changes to the requirements governing the state’s UST program (such as updating UST service provider requirements).
  4. Streamline rule requirements, improve rule clarity, and improve consistency within the rule and with other state and federal laws and rules.

For more information about the rulemaking and how to get involved, visit:

Ecology Laws and Rules Page

To find information about other agency laws and rules, or the status of other agency rule making, go to