Updating Stormwater Regulations - What & Why

What’s Happening Now?

The 2021 Stormwater Code and Manual have been finalized and will become effective July 1, 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.

The final 2021 Stormwater Code and Manual, as well as summaries of changes, are posted on the Project Documents page.

In addition, the SPU Public Drainage System Requirements Director's Rule DWW-210 is now posted. This new director's rule includes Storm Mainline Extension rules, requirements to ensure sufficient capacity, and the Public Drainage System design requirements that were in SPU CAM 1180. It replaces SDCI's Small Project Point of Discharge protocol and prohibits 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.

We've held four public meetings as part of the public review process. Recordings of the meetings are available in the links as indicated below.

  • January 28, 2021 (Completed): This meeting, associated with Public Review Period #3, focused on changes to the full revised draft of the Stormwater Manual (all volumes and appendices) since the spring 2020 public review period. In addition, it covered associated changes to the Grading Code and introduced the new SPU public drainage system Director's Rule. If you missed this meeting, watch our recording and take a look at the PowerPoint. (Note: the PowerPoint presentation also includes topics covered in November. Also, the following is an important clarification about the recording.)

    Important Note: during the Public Meeting, you asked if the information on a SDCI preliminary assessment report would "vest" a project based on the information provided (e.g. approved point of discharge, flow control requirements, etc.). We would like to clarify that preliminary assessment reports or preliminary applications do not vest any projects to a certain code or director's rule. SDCI permit applications will not be vested to the 2016 Stormwater Code and associated rules unless there is a complete permit application (i.e. the full permit submittal is screened, accepted, and fees paid) prior to July 1, 2021.
  • 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.

  • 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!

Also, we published a Determination of Non-Significance (DNS) Public Notice about this project in December 2020. 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 becomes 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. They will be effective on July 1, 2021.