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:

  • File Online with My DOR. My DOR works best with Google Chrome or Mozilla Firefox.

    1. Log in using your Secure Access Washington (SAW) user ID. If you don’t have a user ID or aren’t sure, see if you have an account first before signing up.
    2. Click Getting Started on the Business Licensing and Taxes service page.
    3. Follow the steps below based on your business status.

      If you do not yet have an existing business

        1. Click File New Business License Application. Be sure to select the endorsements for which you wish to apply.


      If you already have an existing business

        1. If you haven’t already, add access to your business. You’ll need a UBI number and letter ID.
        2. Click on the business you want to apply for a license/endorsement under, then click on the location.
        3. Click File New Business License Application.


      You can pay using an E-check or a major credit card (gift cards can't be used).

      Find more help using My DOR, including video tutorials.


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