2021 Surface Water Design Manual
King County, Washington
The Department of Natural Resources and Parks has adopted a public rule (PUT 8-3-6) revising the King County Surface Water Design Manual (SWDM). In accordance with King County Code, Chapter 2.98, Rules of County Agencies and Executive Policy INF 7-6-1-EP “Drafting and Implementing Rules”, this public rule was adopted June 23, 2021. The 2021 SWDM is effective as of July 23, 2021.
Printed copies of the 2021 SWDM are not being provided. Interested parties can download the electronic version of the manual and then print and bind their own manual. Contact David Batts at firstname.lastname@example.org for further information on suggested printing specifications.
The entire 2021 SWDM including Chapters 1-6, Appendices A through D, Definitions, and Reference sections is available for download in Adobe Acrobat PDF format. The electronic version of the manual is searchable and the bookmarks function within the navigation pane allows for quickly moving through document. Note that although some of the materials in the Reference section of the 2021 SWDM may have been adopted by administrative rule or ordinance, the administrative rule that adopted the SWDM has not formally adopted any of the materials in this section.
Important notice about projects permitted under earlier versions of the SWDM
Per requirements in King County’s Phase 1 Municipal Stormwater Permit (effective date August 1, 2019), projects permitted under the 2016 SWDM that have not started construction by July 1, 2026, and projects permitted under earlier versions of the SWDM that have not started construction by July 1, 2021, must be revised to comply with the requirements of the 2021 SWDM, or subsequent versions as directed by state regulations. Revisions will need to be approved by the Permitting Division of the King County Department of Local Services (DLS-PD), or its successor agency prior to construction.
*“Started construction” means, the site work associated with, and directly related to the approved project is at a stage where rough grading is complete or utilities are installed. For rough grading to be considered complete, elevations are within 1 foot of final design elevations.
2021 Surface Water Design Manual documents
Combined SWDM including all chapters, appendices, definitions, and reference sections (19.3 MB)
The combined SWDM PDF is markup capable; the individual Chapters and other sections are not at this point in time.
SWDM errata edits
Errata and edits log (2021/10/05) (110 KB)
Chapter 2- Drainage Plan Submittal (351 KB)
Chapter 5-Flow Control Design (1.5 MB)
Definitions (457 KB)
Design Manual drawings:
Standard drawings from the 2021 King County Design Manual can be downloaded individually in AutoCAD DWG format. Additionally, the AutoCAD DWG drawings can be downloaded as a single file or chapters can be downloaded individually.
Select a group of drawings to download and extract:
Standard drawings in AutoCAD DWG format
- Chapter 4 in AutoCAD format (zip file, 5.3 MB)
- Chapter 5 in AutoCAD format (zip file, 10.6 MB)
- Chapter 6 in AutoCAD format (zip file, 17.5 MB)
- Appendix C in AutoCAD Format (zip file, 15.6 MB)
- Appendix D in Auto CAD format (zip file,13.7 MB)
- All AutoCAD drawings (zip file, 62.8MB)
New as of 9/1/2022
Declarations of Covenant for use in unincorporated King County for residential single family properties (zip file, 164 KB)
Reference 8-H, Site Improvement Bond Quantities Worksheet:
- The web links on full SWDM pdf file pages 979 and 1030 are incorrect
- The web link on the separate References pdf file page 56 is incorrect.
- The web link on full SWDM pdf file page 149 is correct as it is here.
2021 SWDM cover pages
Full Manual binder cover (2.8 MB)
Appendix C and D covers (2.3 MB)
Surface Water Design Manual application maps
SWDM maps in PDF format:
Flow Control Application Map (1.4 MB)
Water Quality Application Map (1.4 MB)
Landslide Hazard Drainage Areas Map (1.5 MB)
SWDM signed public rule and 2016-2021 summary of changes
SWDM Public Rule PUT-8-3-6 (297 KB)
SWDM Summary of Changes (95.3 KB)
Blanket adjustments and clarifications
None at the present time.
If you have questions about these changes, contact Mark Wilgus at email@example.com.
Information on key provisions of King County Drainage Code Title 9
For questions about the stormwater services website, please contact Mark Wilgus, Engineer, King County Stormwater Services Section.