Updating Stormwater Regulations - What & Why

What’s Happening Now?

Our proposed 2021 Stormwater Code and Manual update is scheduled to be effective in July 2021. Our new rules will replace the current Stormwater code and Directors' Rules, which are administered jointly by SDCI and Seattle Public Utilities (SPU). For more information, visit our background page.

Draft documents of the 2021 Stormwater Code and Manual, supporting documentation, and other related code changes are posted now on the Project Documents page and will be posted from January 11 through February 19, 2021 for the third and final Public Review Period #3.

We'll post the following:

  • Revised Draft of the Stormwater Manual (all Volumes and Appendices)
  • Revised Draft of the Stormwater Code (Seattle Municipal Code Chapters 22.800-22.808)
  • New Related Draft SPU Public Drainage System Director's Rule (includes Storm Mainline Extension rules and the Public Drainage System design requirements that are currently in SPU CAM 1180)
  • Related Grading Code and Land Use Code Revisions

Public Review Period #3 is the last opportunity for the public to comment on the draft Codes and Manual and supporting documents before the Stormwater Code is sent to City Council in the Spring of 2021 and the Stormwater Manual will be sent to the Director's for final approval.

  • As part of this process, we will be holding an online public meeting to highlight the revisions on January 28, 2021: This meeting will focus on changes to the full revised draft of the Stormwater Manual (all volumes and appendices) since the spring 2020 public review period.

To make comments, see the instruction on the Get Involved page.

There have already been three previous public meetings and recordings of the meetings are available in the links as indicated below.

  • Spring of 2020 (Completed): Prior to submittal of the Draft Stormwater Code and Manual to Ecology (Two2 online public meetings were held on: April 26 and May 6, 2020. If you missed them, watch our recording of the April 26 meeting and take a look at the PowerPoint!

  • November 12, 2020 (Completed): This meeting focused on changes to the Stormwater Code, Volume 1 of the Stormwater Manual, Appendix B (Additional Submittal Requirements) and Appendix I (Landscape Management Plan and Integrated Pest Management). If you missed this meeting, watch the recording and take a look at the PowerPoint. Please note: the graphs of the Peak Flow Control Standard changes on pages 37 and 38 were incorrect in the meeting presentation and are corrected in the files posted here.

Also, we published a Determination of Non-Significance (DNS) Public Notice about this project. See the Project Documents page for the SEPA Checklist and SEPA DNS.

Project Benefits

Our stormwater code protects people, property, and the environment by controlling how rain that beomes stormwater runoff flows off of streets, buildings, and parking lots. Stormwater runoff can cause flooding, landslides, and erosion that can damage our homes, businesses, and property. Stormwater runoff carries oil and grease, fertilizers, pesticides and other toxic chemicals to our creeks, lakes, bays, rivers, and other waterways.

The End Result

Our regulations will be equivalent to Ecology's 2019 Stormwater Manual and address concerns and topics identified by internal and external stakeholders.