2019-2024 Stormwater Update/Public Comment Opportunity

The National Pollutant Discharge Elimination System (NPDES) permit program addresses water pollution by regulating point sources that discharge pollutants to waters of the United States. Created in 1972 by the Clean Water Act (33 USC § 1251), the NPDES permit program authorizes state governments to perform many permitting, administrative, and enforcement aspects of the program. In July 2019, the Washington State Department of Ecology issued a new Phase I Municipal Stormwater Permit as authorized under RCW 90.48 and the Clean Water Act. This Phase I Permit is valid until mid-2024 at which time Ecology will issue an updated permit. The 2019-2024 Phase I Municipal Stormwater Permit, including appendices, can be reviewed on Ecology’s website here.


In compliance with the Phase I Permit, the County has:

  • Submitted drafts of the County’s enforceable documents to Ecology. The draft documents (provisions of county code and sections of the Stormwater Drainage Manual) are revisions of existing program regulations to reflect new permit requirements. Ecology issued a preliminary consistency determination in November of 2020.
  • Undertaken a distinct code project to implement the started construction requirement of Special Condition S5.C.5.a of the Phase I Municipal Stormwater Permit, including clarification of the Ecology definition of “started construction.” These proposed code amendments will be reviewed by County Council at a public hearing scheduled for April 7,2021, and were reviewed by the Snohomish County Planning Commission at a hearing on December 15, 2020 (agenda here).
  • Periodically notified affected applicants of approved projects and applications subject to a pre-January 22, 2016, version of the County’s drainage regulations that they are impacted. If those projects/applications have not started construction by July 1, 2021, PDS must reevaluate them for compliance with updated drainage regulations the County must adopt by July 1, 2021. This is a requirement dictated by the County’s Phase I Municipal Stormwater Permit, issued to the County by the Washington State Department of Ecology under federal and state law.

Revised draft enforceable documents available for public review and comment: 

SCC 30.91 Definitions

SCC 30.63A  Drainage

SCC 30.63B  Land Disturbing Activity

Stormwater Drainage Manual Volume I – Minimum Technical Requirements

Stormwater Drainage Manual Volume II – Construction Stormwater Pollution Prevention BMPs

Stormwater Drainage Manual Volume III – Hydrologic Analysis and Flow Control BMPs

Stormwater Drainage Manual Volume IV – Source Control BMPs

Stormwater Drainage Manual Volume V – Runoff Treatment BMPs

Stormwater Drainage Manual Volume VI – Stormwater Facility Maintenance


NPDES Determination of Nonsignificance 


Next Steps – Additional Public Comment Opportunities

The stormwater documents were considered by the Planning Commission at a briefing on February 23, 2021, and at a public hearing on March 23, 2021. The County Council will review the stormwater documents in May and June of 2021. You can access a listing of county council meetings on their Meetings & Webcasts page at: https://snohomishcountywa.gov/2288/Meetings-Webcasts-Archives. The required effective date for the updated regulations is July 1, 2021. If you have any questions, please contact Terri Strandberg:


Attn: Terri Strandberg, Principal Planner

Snohomish County Planning and Development Services

3000 Rockefeller Ave., M/S 604

Everett, WA 98201