Washington Department of Transportation Municipal Stormwater Permit

This permit specifically covers the Washington State Department of Transportation (WSDOT). Through this permit, we require the agency to manage and control polluted stormwater runoff to protect downstream waters from pollution.

Besides covering state highways and transportation-related facilities, this permit also covers stormwater discharges from rest areas, park and ride lots, ferry terminals, and maintenance facilities within urban areas of Washington.

The current permit went into effect April 5, 2014, and expires April 5, 2019.

Why does WSDOT need to control stormwater?

Statewide, WSDOT oversees more than 7,000 miles of highway. When rest areas, ferry terminal holding lots, and park and ride lots are included, they manage over 40,000 acres of paved surfaces. Paved surfaces do not allow water to penetrate into the ground where it can be naturally filtered and treated before entering streams or underground water supplies. This lack of infiltration results in excess stormwater running off state highway facilities each year.

Current permit and related documents

Permit reissuance - 2019

The current permit expires on April 5, 2019. We reissued the updated general permit on March 6, 2019. The permit becomes effective on April 5, 2019, and expires on April 5, 2024.

What's changing

We updated the current permit language to improve consistency with the Phase I and Phase II Municipal Stormwater permits. We also proposed the organizational change of removing the WSDOT Stormwater Management Program Plan (SWMP) from the permit. The SWMP would instead be a stand-alone document, required by the permit, that WSDOT will update annually through a public process.

Permit reissuance documents 

Public notice process and comments

Ecology accepted public comment on the draft permit from December 5, 2018 until February 5, 2019. Ecology held a webinar and public workshop and hearing in Lacey, Washington on January 11, 2019. We received oral and written comments during the public comment period and responded to these comments in Appendix A of the fact sheet.


Formal draft release for public comment: Dec. 5, 2018
Issue final permit: March 6, 2019
Permit effective: April 5, 2019

WSDOT permit compliance

See the WSDOT water resources and erosion control page for information on permit-related activities such as:

  • Stormwater research
  • Annual reports
  • Monitoring reports
  • Total Maximum Daily Load (TMDL) implementation reports

Previous permit documents

Permit (effective March 7, 2012)
Permit Statement of Basis