Puget Sound Olympia

Municipal Stormwater

Washington State Department of Transportation NPDES Municipal Stormwater Permit

Current permit

Ecology issued a new modified permit to the Washington State Department of Transportation (WSDOT) on March 6, 2014.

Public Comments and Appeal Record

Previous Permits, Focus Sheets, and Additional Resources

Purpose of the Permit

State and Federal regulations require WSDOT to have National Pollutant Discharge Elimination System (NPDES) permit coverage in the urbanized  areas covered by Phase I and Phase II of the municipal stormwater permit program. This permit also covers stormwater discharges to any water body in Washington State for which there is an Environmental Protect Agency approved Total Maximum Daily Load with load allocations and associated implementation documents specifying actions for WSDOT stormwater discharges. Discharges covered include stormwater runoff from state highways, rest areas, park and ride lots, ferry terminals, and maintenance facilities. The permit addresses these legal requirements and regulates the discharge of pollutants to protect water quality in Washington State.

Permit Modification

Ecology issued a permit originally to WSDOT on February 4, 2009. A minor modification was made to this permit on May 1, 2009, to correct minor, non-substantive errors found after permit issuance. The permit covers discharges from its municipal separate storm sewer system (MS4). MS4s are conveyances or a system of conveyances including roads with drainage systems, streets, catch basins, ditches, man-made channels, and storm drains.

A second modification added substantive language to the permit as a result of a settlement agreement between the Departments of Ecology and Transportation and Puget Soundkeeper Alliance. Permit sections modified include: S6.C, S7. E.2.d., S8.E., Appendix 7, Stormwater Management Program Plan, Sections 3 and 3.1, 5.4, 6.2, and Appendix 3, Applicable TMDL Requirements.

The second permit modification required Ecology to modify or issue an administrative order establishing new TMDL-related permit requirements for WSDOT at least every eighteen months. The proposed draft modifications make substantive changes to the permit including adding new TMDL-related permit requirements in Appendix 3, making references to the 2011 updated Highway Runoff Manual (HRM) instead of 2008 HRM, and updating the Stormwater Management Program Plan (SMPP) in Appendix 7.