NPDES Stormwater Permit


The National Pollutant Discharge Elimination System (NPDES) is a federal permit program that regulates the discharge of stormwater and wastewater to waters of the State. In Washington State, the Department of Ecology implements the NPDES program on behalf of the federal government through issuance of the Western Washington Phase II Municipal Stormwater Permit. The intent of the permit is to reduce or eliminate water quality problems in our streams, rivers and lakes by controlling pollution at its source. Stormwater is a significant source of pollution in Puget Sound, and municipal stormwater systems are one of the main ways in which stormwater is discharged to water bodies.

The Western Washington Phase II Municipal Stormwater Permit was re-issued on August 1, 2013, and will be in effect until July 31, 2019.  This permit authorizes the City of Sammamish to discharge stormwater from its MS4 into waters of the State (i.e. Lake Washington) if the city takes certain actions to prevent stormwater pollution. The full permit can be viewed at the Department of Ecology’s website: NPDES Western Washington Phase II Municipal Stormwater Permit

The permit requires the City to take action in each of the following areas:

  • Public education and outreach
  • Public involvement and participation
  • Illicit discharge detection and elimination
  • Controlling stormwater run-off from construction sites
  • Operations and maintenance of stormwater facilities after construction

Planned actions are documented each year in a Stormwater Management Program: 2023 Stormwater Management Program

The documents and links listed below are provided as part of Sammamish’s compliance with the Western Washington Phase II Municipal Stormwater Permit:

View previous annual reports.

Stormwater Development Regulations

See more information at on the Public Works Development Review, Permitting, and Engineering Resources page.

Effective on June 29, 2022 the City adopted the 2021 King County Surface Water Design Manual and City of Sammamish Addendum. The updated code requirements applies to new applications submitted beginning on July 1, 2022 in accordance with the City's NPDES Permit requirements.

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