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2009 Thurston County Drainage Design and Erosion Control Manual

The Thurston County Drainage Design and Erosion Control Manual sets standards for reducing and managing stormwater runoff on new development and redevelopment projects in the unincorporated areas of Thurston County. The manual also applies to projects within incorporated and urban growth areas that adopt the Thurston County manual.

red arrowThe drainage manual you see on this page was approved by Thurston County commissioners on August 17, 2009 and took effect November 16, 2009.  To view the adopting ordinance, click here. To see the previous, 1994 version, click here.

manual coverThe new manual is consistent with the 2005 Department of Ecology Stormwater Manual for Western Washington. The updates were required under Thurston County's NPDES Phase II permit.

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2016 Drainage Design and Erosion Control Manual for Thurston County

The Water Resources Division is currently revising the 2009 Drainage Design and Erosion Control Manual (DDECM) to be consistent with the 2012 Ecology Stormwater Management Manual for Western Washington. The Thurston County Resource Stewardship Department will be holding public outreach meetings during the spring and summer on the changes to the DDECM and the Thurston County Codes which must also be updated to comply with the current NPDES permit. There will be educational classes to cover the changes in the DDECM this fall. The manual is scheduled to be completed and adopted by December of 2016.

2009 Drainage Design and Erosion Control Manual for Thurston County

Policies

Administrator Memo's

Errata

Modeling Information

  • The 2009 Drainage Design and Erosion Control Manual for Thurston County requires the use of the Western Washington Hydrologic Model, Version 3 (WWHM3) with Thurston County enhancements for BMP design. The Thurston County enhancements include the use of additional rain gage stations and 15-minute time steps and also include a recharge calculator to demonstrate minimum infiltration requirements for projects. The program is available for download by clicking here.
  • Guidance for Using the Recharge Calculation in WWHM3 with Thurston County Enhancements (PDF)
  • Department of Ecology memo approving Western Washington Hydrologic Model with Thurston County Enhancements (PDF)

Design Guides for 2009 Drainage Manual Best Management Practices

Fact Sheets

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Contact Us

 Staff contact: Pat Allen (360) 867-2078.  E-mail: AllenP@co.thurston.wa.us

 

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