Phase I Permit Modification - 2016

On July 20, 2016 Ecology modified the Phase I Municipal Stormwater Permit to incorporate, in Appendix 10 of the permit, the stormwater programs that Phase I municipalities adopted to provide equal or similar protection of receiving waters and pollutant control as compared to Appendix 1 of the permit. Visit our Phase I Equivalent Stormwater Manuals for Western Washington webpage for list of the proposed preliminary approved equivalent programs, preliminary approval letters, and associated documents.

The proposed modification also includes a new appendix, Appendix 13, which describes adaptive management plan requirements for pollutants that discharge from the City of Seattleā€™s municipal separate storm sewer system outfalls to the Lower Duwamish Waterway. Related documents and background information can be found on Seattle's Lower Duwamish Waterway webpage and Ecology's Lower Duwamish Waterway cleanup and source control webpage.

Final Permit Modification Documents

Proposed Permit Modification Documents

Ecology posted the documents below on May 18, 2016 for public review and comment.

Public Comments on the Proposed Permit Modification

Ecology accepted written and oral comments on the modified draft permit from May 18 until June 30, 2016. Ecology also held two workshops and public hearings on the modification. One in Seattle on June 23, 2016 and one in Lacey on June 29, 2016. At the workshops we explained the modification and answered questions. The hearings provided the opportunity for people to give formal oral testimony and comment on the proposed modified draft permit.

Ecology Received the Following Comments on the Proposed Permit Modification:


You may direct questions about the permit modification, workshops and hearings, and requests for printed copies of the draft permit modifications to Abbey Stockwell, 360-407-7221 or

For more information:
Seattle Public Utilities - Lower Duwamish Waterway
Lower Duwamish Waterway Cleanup and Source Control
Phase I Municipal Stormwater Permit
Phase II Western WA Municipal Stormwater Permit
Phase I Equivalent Stormwater Manuals for Western Washington
Western Washington Phase II Stormwater Manuals
Stormwater Management Manual of Western Washington 

Last updated July 2016