National Pollutant Discharge Elimination System

Snohomish County has operated under a National Pollutant Discharge Elimination System (NPDES) municipal stormwater permit since 1995. This permit, which is required to comply with the federal Clean Water Act, details the actions the county must perform to minimize or prevent stormwater pollution. 

New! #1

The 2023 Stormwater Management Program (SWMP) Plan is now available. It describes the activities and programs the county plans to carry out to meet the requirements of the 2019-2024 NPDES stormwater permit.

New! #2

The county’s 2022 NPDES Annual Report is also available. It describes the actions the county took to meet NPDES permit requirements during the preceding calendar year.

Additional Information

The links below will help you find out more about the county’s NPDES municipal stormwater permit, what the county does to meet permit requirements and how you can get involved:

In addition to the NPDES municipal stormwater permit, the county also operates under NPDES industrial stormwater permits (applicable to some county solid waste facilities and Paine Field) and NPDES construction stormwater permits (applicable to some county construction projects). This web page and its subpages focus on the municipal stormwater permit.