Ecology NPDES Permit

Mill Creek's Surface Water Utility (SWU) operates under a permit issued by the Washington State Department of Ecology called the National Pollutant Discharge Elimination System (NPDES) Phase 2 municipal stormwater permit. The NPDES permit is primarily based on the Federal Clean Water Act, but also the Endangered Species Act for protection of salmon habitat.

Clean Water Act
The Clean Water Act requires municipal agencies across the United States to take steps toward reducing polluted stormwater runoff. The law was applied in two phases:

  • Phase 1 was for larger agencies with a population over 100,000
  • Phase 2 was for agencies under 100,000

Mill Creek is a Phase 2 agency, and the Phase 2 permit for western Washington covers approximately 80 cities and portions of 5 counties. The latest version of the permit became effective August 1, 2019, and will expire in 2024.

Permit Coverages
The permit covers a wide range of required activities, including operation and maintenance, education and outreach, illicit discharge detection, and enforcing development standards. The new Phase 2 permit took effect on August 1, 2019, with enhanced requirements on education and outreach, training, system mapping, and control of sources of pollution.

Surface Water Management Program
One of the permit requirements is to post the city's 2021 Surface Water Management Program (SWMP) document (by March 31, 2021) and the 2020 Annual Report for public review (by April 30, 2021). The SWMP is designed to reduce the discharge of pollutants and meet water quality requirements to the maximum extent practicable, and is updated every year for submittal with the city's Annual Report to the Department of Ecology. The Draft 2021 plan is available to view in the menu to the right.

The public is welcome to review the relevant documents and make comments regarding the Draft 2021 Storm Water Management Plan.  Send comments to

 • Department of Ecology Construction permit, select here
Department of Ecology  Industrial permit, select here.