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.

Licensing requirements and additional supporting documents

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 the Underground Storage Tanks – Business Bulletin.

State endorsement


Underground Storage Tank

$216.09 per tank

Weighing and Measuring Device

Variable fee

Additional fees

State tax registration $0
Registering your business name as a trade name $5
Business License Application fee Variable fee

How to apply


Add a state endorsement to your business

Apply for a new business license

Online assistance
Setting up your business licensing and tax account
How to add a state endorsement

By mail

Complete the licensing requirements above and mail to:

Business Licensing Service
P.O. Box 9034
Olympia, WA 98507-9034