Revised Seattle Stormwater Code and Seattle Stormwater Manual Effective July 1, 2026

The revised Seattle Stormwater Code and Seattle Stormwater Manual became effective July 1, 2026. That means, projects with a completed application on July 1, 2026, or later, must comply with the 2026 code. If this applies to your project, please download and use the updated submittal documents from the  SDCI Stormwater Code website.  

Projects with a completed SDCI permit application submitted prior to July 1, 2026, may choose to comply with either the 2021 code or the 2026 code. An application is complete when intake has been approved and all intake fees have been paid.

The final versions of the 2026 Stormwater Code, Seattle Stormwater Manual, and many of the supporting documents have been posted to the Stormwater Code page,    

Here are the main changes to the SDCI stormwater review submittal documents:

• Projects with less than 5,000 square feet of new and replaced hard surface or land disturbance no longer require a custom Construction Stormwater Control (CSC) plan! The new Small Construction Stormwater Control Soil Management (CSC/SOIL) Standard Plan is made to be submitted as is, without edits.

  Note: For projects with 5,000 square feet or more of new and replaced hard surface or demolition permits with 5,000 square feet or more of land disturbance, a custom construction stormwater control and soil management plan sheet is required. Use the updated Standard Notes and Standard Details on your stamped plans.

• The Stormwater Plan replaces the Drainage and Wastewater Construction Plan (DWC).  This plan may be used for all projects that require stormwater review. Contact SPU at sidesewerinfo@seattle.gov for more information regarding wastewater review and side sewer permitting.

  Note: If your project has 5,000 square feet, or greater, of new plus replaced hard surface area or 10,000 square feet, or greater, of land disturbing activity, your plan must be stamped by a professional engineer.

There have been many helpful updates made to the stormwater details and standard notes:  

The stormwater review team is available to answer questions. Follow the instructions on SDCI’sthe SDCI Contact Us page or use the chat icon on the lower right corner of  SDCI’s home page. Both of these paths get you to a reviewer from the stormwater team. 

We’ll have training and virtual Q&A sessions starting in early July. Keep an eye on our Stormwater Codes website!