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King County Stormwater Management Program Annual Reports

Our Phase I Municipal Stormwater National Pollutant Discharge Elimination System (NPDES) Permit (Phase I Permit) requires us to submit an Annual Report to the Washington State Department of Ecology (Ecology). The Annual Report is submitted on or before March 31st and provides information for our previous year’s work.

The Stormwater Management Plan (SWMP), also attached to the Annual Report, provides our plan for complying with the Phase I Permit for the year to come.

Our Stormwater Planning program informs and assists in the development of policies and strategies to protect stormwater, which is described in our Stormwater Action Management Plan (SMAP).

You are invited to participate in the decision-making processes involving the development, implementation, and update of our Stormwater Management Plan (SWMP) and Stormwater Action Plan (SMAP). If you have questions or feedback about our Annual Report, SWMP, or SMAP please email us at

Download current document here:

2023_Annual Report