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

The current permit expires on April 5, 2019. We plan to reissue the updated general permit in the spring of 2019.

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.

Formal Draft Documents 

Public Comment Period

We held a public comment period on the draft WSDOT Municipal Stormwater from Dec. 5, 2018  to Feb. 5, 2019. We will reissue the final permit after we consider all public comments and make final changes to the draft permit. We will publish a Response to Comments as an appendix to the fact sheet to address comments submitted during the public comment period.

Workshop and hearing

We held one workshop immediately followed by a public hearing on January 11, 2019 at the Department of Ecology Headquarters in Lacey. The workshop and hearing was also available as a webinar. During the workshop, we explained the proposed changes to the permit and answered questions. You may view the presentation.


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