Underground storage tanks

Underground storage tanks (USTs) may be encountered during construction. The location of these tanks may be known by the Washington State Department of Transportation (WSDOT) prior to construction, or the tanks may be discovered during earthwork.

Notify Ecology of releases from USTs within 24 hours.

Follow the instructions below to ensure all USTs are handled properly:


Tank discovery

If you find an tank during construction, immediately notify the Project Engineer (PE) who will initiate the Environmental Compliance Assurance Procedure (ECAP) (pdf 104 kb). This document also describes steps for notifying WSDOT management and regulatory agencies.

You must then notify Ecology of releases from underground storage tanks (USTs) within 24 hours (per 177-340-450 WAC).

WSDOT HazMat staff or consultant must follow up with a status report to Ecology within 20 days

Find more information about reporting spills and USTs on our Hazardous materials spill prevention and reporting page.


Identifying USTs

If your project site includes an underground storage tank, it must be assessed by a Washington (WA) State-certified UST Site Assessor. WSDOT’s Hazard Materials Program has staff who are certified and can assist projects requiring UST removal.

When removing USTs, WSDOT follows the Model Toxics Control Act (MTCA) Cleanup Regulations from the Washington State Department of Ecology (Ecology). This document details Ecology’s guidance for cleaning up hazardous waste sites, establishing cleanup standards, selecting cleanup actions, and updating the site register.

WSDOT requires that all UST removals, including those exempt from Ecology’s UST Regulations (173-360 WAC), are overseen by a WA State-certified UST site assessor. 


Tank removal

Removing a tank requires that the WSDOT HazMat Program or a qualified contractor complete the following steps and notifications:

  • If the tank is regulated, submit a 30-Day Notice to Ecology or contact the Regional Ecology Office for a waiver if necessary to avoid project delays.
  • Contact the local fire marshal, health department, and planning department to determine local permits or requirements. A WA State-certified UST Site Assessor must be present during removal to conduct an appropriate site assessment or site characterization and to document UST closure activities. The WSDOT HazMat Program has WA State-certified Site Assessors available.
  • Provide the appropriate report(s) to Ecology: