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Stormwater Code & Rules Update

An Example of Stormwater Control Methods
Our Stormwater Code protects people, property, and the environment by controlling how rain water runs off of streets, buildings, and parking lots.


In May 2014, we published the Draft 2015 City of Seattle Stormwater Manual, Volumes 1 through 5, and the appendices. They are available on the project documents page.

Originally, we anticipated making all the changes at one time in 2015, as we had stated in handouts and at various public meetings throughout 2014. However, the Washington State Department of Ecology (Ecology) was delayed in sending their comments to us on our draft proposal. We received over 150 separate comments from Ecology in February 2015. Therefore, due to the delay, we postponed most of our proposed Stormwater Code changes until January 2016.

In the meantime, in April 2015, the City Council and Mayor approved to revise three sections of the 2009 Stormwater Code (SMC 22.800-22.808). Effective by May 24, 2015. These changes are not the focus of Ecology's review. The changes are:

  • Changing water quality thresholds for roadway projects
  • Exempting Seattle Public Utilities (SPU) water utility projects from flow control, water quality treatment, and green stormwater requirements
  • Granting the Director of SPU discretion to not require flow control requirements for certain combined sewer basins through a Directors' Rule

We posted an addendum to the Stormwater Code and Rule Update SEPA Environmental Checklist on June 25, 2015. We identified a need to propose related revisions to the 2012 Seattle Building Code, the 2012 Seattle Residential Code, and those Seattle Municipal Code titles regulating land use and grading to incorporate the new ecology requirements. These proposed revisions relate largely to the timing of how the Stormwater Code and Rule Update would be imposed (generally referred to as "applicability.") In addition, we identified two additional proposed revisions in the Stormwater Code and Rule Update. 

A public hearing on the 2016 Stormwater Code and related code changes (CB 118465, CB 118466) was held at the Seattle Public Utilities and Neighborhoods Committee on September 11, 2015. The code changes are available on the project documents page. The City Council approved the revisions outlined in the council bills in September 2015. Refer to our timeline page for further information on the effective date of the 2016 Stormwater Code and Manual.


Draft documents for the 2016 City of Seattle Stormwater Code and Manual (submitted to Washington State Department of Ecology April 23, 2014):

The following documents outline the April 2014 summary of changes we made to the code and manual:

Codes & Directors' Rules

Previous Public Meetings

Public Meeting: June 10, 2015

We hosted a public meeting on June 10, 2015 about the 2016 Stormwater Code Update. The draft documents of the 2016 Stormwater Code and the other related code changes are available on the project documents page

Here are the documents from the meeting:

People who attended the meeting represented various engineering and architecture firms, as well as City of Seattle staff. The attendees provided valuable feedback and questions for us to evaluate during the comment period.

Public Meeting: June 3, 2014

We hosted a public meeting on June 3, 2014 about the Stormwater Code and Manual Update. Here are the documents from that public meeting:


Meetings & Events


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