WA State Licensing: Underground storage tank

Underground storage tank

An Underground Storage Tank endorsement is required for owners of storage tanks with all of the following:

  • Capacity greater than 110 gallons.
  • At least 10% of volume (including piping) below the surface of the ground.
  • Contain petroleum or other hazardous substances.

Note: Some tanks may be exempt.


  • The owner must file an application within 30 days after a new installation is complete, or upon modification or purchase of existing tanks.
  • A Notice of intent to install must also be filed directly with the Department of Ecology at least 30 days before new installation work begins.
  • All owners of regulated UST's, other than state or federal government agencies, must provide proof of ability to pay costs of a release from their tanks at the liability minimums set in WAC 173-360A 1000 through 1015.

Note: If using insurance, attach the complete insurance policy from the provider, which includes the certificate as set forth in WAC 173-360A-1083. The certificate holder should be:

Business Licensing Service
PO Box 9034
Olympia WA 98507-9034

If you are not using liability insurance, attach a Certificate of Financial Responsibility as set forth in WAC 173-360A-1096.

See also:

Post your license

A license must be posted at each location where the licensee operates. You may not begin this business activity until you receive a Business License listing the required endorsement(s).

How to apply

Apply by using one of the following options:


Specialty endorsement Fee
Underground Storage Tank $173.80 per tank
Weighing and measuring device Variable
Other fees that may apply Fee
Registering your business name as a trade name $5
Business License Application $19 (non-refundable)


Regulatory questions

Department of Ecology
Phone: 360-407-7037 or 1-800-917-0043