Updating Stormwater Regulations - Project Documents

A Chinook salmon spawning in the reconstructed reach of the Thornton Confluence Floodplain project site. Courtesy Chapin Pier, Seattle Public Utilities, October 2018.
  • What & Why
    We're working on our 2021 Stormwater Code and Manual Update.
  • Get Involved
    We're working on our 2021 Stormwater Code and Manual Update.
  • Project Documents
    We're working on our 2021 Stormwater Code and Manual Update.
  • Background
    We're working on our 2021 Stormwater Code and Manual Update.
  • Timeline
    We're working on our 2021 Stormwater Code and Manual Update.

Project Documents

Draft Documents for Notice of Rulemaking - March 23 through April 9, 2021

  • Summary of Changes
  • Stormwater Code (Seattle Municipal Code)
  • Draft of new SPU Public Drainage System Director's Rule (SPU DWW-210): This new rule includes Storm Mainline Extension, Approved Point of Discharge, and ensuring sufficient capacity requirements as well as the Public Drainage System Design Requirements that are currently in SPU CAM 1180. This rule will replace SDCI's Small Project Point of Discharge protocol and will prohibit any new drainage discharges to the "formerly combined" public sanitary sewers and require mainline extensions for certain projects in the combined sewer and ditch and culvert areas.
  • Draft 2021 Stormwater Manual (Joint Director's Rule SPU DWW-200/SDCI 10-2021)
    • Volume 1- Project Minimum Requirements
    • Volume 2- Construction Stormwater Control
    • Volume 3- Project Stormwater Control
    • Volume 4- Source Control
    • Volume 5- Enforcement (no change at this time)
    • Appendix A- Definitions
    • Appendix B- Additional Submittal Requirements
    • Appendix C- On-site Stormwater Management BMP Infeasibility Criteria
    • Appendix D- Subsurface Characterization and Infiltration Testing for Infiltration BMPs
    • Appendix E- Additional Design Requirements and Plant Lists
    • Appendix F- Hydrologic Analysis and Design
    • Appendix G- Stormwater Control Operations and Maintenance Requirements
    • Appendix H- Financial Infeasibility Documentation for Vegetated Roofs and Rainwater Harvesting
    • Appendix I- Landscape Management Plans and Integrated Pest Management Plan

If you wish to submit a comment, please complete the comment template and email it to SPUStormwaterCodeRev@seattle.gov or mail your comments to:

Sherell Ehlers
Seattle Public Utilities
700 Fifth Ave, Suite 4400
PO Box 34018
Seattle, WA 98124-4018

Email correspondence is preferred.

Draft Documents for Public Review #3 - January 11 through February 19, 2021

If you wish to submit a comment, please complete the comment template and email it to SPUStormwaterCodeRev@seattle.gov or mail your comments to:

Sherell Ehlers
Seattle Public Utilities
700 Fifth Ave, Suite 4400
PO Box 34018
Seattle, WA 98124-4018

Email correspondence is preferred.

Note: The actual Stormwater Code and Manual changes are still to be determined. However, our regulations must be equivalent to Ecology's NPDES 2019 Stormwater Permit (Ecology Permit).

SEPA Determination of Non-Significance December 10-24, 2020

We have conducted a State Environmental Protection Act (SEPA) environmental review of the City of Seattle's proposed 2021 Stormwater Code and Rule Update. The lead agency, Seattle Public Utilities (SPU), has issued a Determination of Non-Significance (DNS). This proposal involves the adoption of ordinances amending the City of Seattle's Stormwater Code and associated Directors' Rule. 

You can see all of the documents related to the SEPA review and DNS listed under the headings below.

Draft Documents for Public Review #2 - November 2 - November 20, 2020

Draft Documents for Public Review #1 - April 1 through May 16 20, 2020

These documents were posted for the review period of April 1 through May 16 2020.