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Stormwater services

Managing stormwater and waterborne pollution

Find comprehensive services, data and information related to stormwater and non-point source pollution in King County, Washington.

To offer a suggestion or report an error on the King County stormwater services and information website, please contact Fred Bentler, webmaster.

Stormwater Services and Information for King County, Washington

Proposed Updates
Surface Water Design Manual

The King County Department of Natural Resources and Parks is declaring its intent to adopt an update to the 2009 Surface Water Design Manual by public rule in accordance with King County Code Chapter 2.98 Rules of County Agencies.

The 2016 Surface Water Design Manual (SWDM) for the purposes of public review consists of the following draft chapters, appendices, and maps.  The Summary of Changes document provides a chapter by chapter guide to the most significant revisions. Redlined versions tracking all changes made are available upon request.  The proposed public rule is also provided below.

Written comments on these proposed changes are due by COB on January 18, 2016.  Email written comments to Mark Wilgus of King County Water and Land Resources Division, Stormwater Services Section at  Oral comments may be provided in person between the hours of 8:30 am to 4:30 pm from Monday, December 14th through Friday, December 18, 2015 at the Water and Land Resources Division offices on the 6th floor of the King Street Center, 201 South Jackson Street, in Seattle.

  2016 Surface Water Design Manual Draft Documents

 PDF Size

 SWDM Summary of Changes

 221 KB

 Entire SWDM including appendices and references

 24,530 KB


SWDM Chapters


 Chapter 1-Drainage Review and Requirements


1,193 KB

 Chapter 2- Drainage Plan Submittal 

 642 KB

 Chapter 3-Hydrologic Analysis and Design 

 762 KB

 Chapter 4-Conveyance System Analysis and Design 

4,334 KB

 Chapter 5-Flow Control Design 

3,167 KB

 Chapter 6-Water Quality Design 

 4,233 KB


 331 KB




 Appendix A-Maintenance Requirements for Flow Control, Conveyance, and Water Quality Facilities


401 KB

 Appendix B-Master Drainage Plan Objective, Criteria, Components, and Review Process

46 KB

 Appendix C-Simplified Drainage Review Requirements

3,567 KB

 Appendix D-Construction Stormwater Pollution Prevention Standards

4,277 KB


Surface Water Design Manual Application Maps

 Flow Control Application Map (no proposed changes from 2009 version)

898 KB

 Water Quality Application Map (no proposed changes from 2009 version

948 KB

 Landslide Hazard Drainage Areas Map (no proposed changes from 2009 version

1,288 KB


SWDM Proposed Public Rule


SWDM Proposed Public Rule PUT-8-3-5




35 KB

If you have questions about the proposed changes, contact Mark Wilgus at

2009 King County Surface Water Design Manual (SWDM)

Pursuant to King County Council adoption of Ordinance 16264, the Department of Natural Resources and Parks adopted a public rule revising the King County Surface Water Design Manual (SWDM). In accordance with King County Code, Chapter 2.98, Rules of County Agencies, this public rule was adopted on January 9, 2009.

The hard copy of the 2009 SWDM is available for purchase at the Water and Land Resources Division office at 201 S. Jackson Street, 6th floor reception. The manual costs $145 plus tax and can be ordered by calling 206-477-4800 and paying an additional $13 for shipping.

Need a copy of the 2005 SWDM? It is now on sale at the special discounted price of $51 plus tax and shipping. Call 206-477-4800 to order or come to 201 S Jackson Street 6th floor reception and save shipping.

Files are available for download in Adobe Acrobat PDF format.

The entire manual is available for download. One great benefit of having the SWDM as one electronic document is the search function. It is only necessary to take the time to download it once. Save it to your desktop for convenient access.

2009 King County SWDM (18 MB)

Here the SWDM is provided in sections.

This document contains the main body of the SWDM, which includes Chapters 1-6 and the Definitions Section.

2009 SWDM Main Body (7.8 MB)

This next section includes the SWDM Appendices.

Appendix A Maintenance Requirements for Flow Control, Conveyance, and WQ Facilities (140 Kb)

Appendix B Master Drainage Plan Objective, Criteria and Components, and Review Process (25 Kb)

Master Drainage Planning for Large Site Developments - Process and Requirements   details the Process and Requirements to submit  a Master Drainage Plan to the Department of Permitting and Environmental Review 

Appendix C Small Project Drainage Requirements (2.2 MB)

Appendix D Erosion and Sediment Control (ESC) Standards (2.2 MB)

The Reference section is the final part of the SWDM. Although some of the materials in this Reference section may have been adopted by administrative rule or by ordinance, the administrative rule that adopted the SWDM has not formally adopted any of the materials in this section.

References (2.3 MB)


2009 Design Manual Errata:

The printed version of the Manual does not include the errata. If you have a printed version of the Manual, you can download the errata from the page linked here.

2009 SWDM Errata

Application of the Manual's targeted protection levels is determined from the following three application maps of King County. The maps are available here to view or download. This pdf format was chosen to allow the user to zoom in and out, pan the map in any direction, and print the map at the best resolution possible. Click the icon below if you need to download Adobe Acrobat.
Get Adobe Acrobat

Other than the website listed on the maps, the content of the 2009 maps is the same as the 2005 maps.

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2009 Flow Control Applications Map, PDF file







2009 Water Quality Applications Map, PDF file







2009 Landslide Hazard Drainage Areas Map, PDF file




SWDM Summary of Changes (14 KB)

SWDM Public Rule (20 KB)

Previous versions: 2005 Design Manual and other archived documents.

2009 Design Manual Drawings:

Standard drawings from the 2009 King County Design Manual can be downloaded individually in AutoCAD DWG format. Additionally the AutoCAD DWG drawings can be downloaded as a single 9.0 Mbyte file or chapters can be downloaded individually.


Select a group of drawings to download and extract:





Standard Drawings in AutoCAD DWG format


Large ZIP file of all chapters
Download ZIP files of individual chapters:





(9.1 MB)

For questions about the stormwater services website, please contact Dale Nelson, Engineer, King County Stormwater Services Section.