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Thurston County Stormwater Utility

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.

 

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2016 Drainage Design and Erosion Control Manual Revision for Thurston County

The Thurston County Drainage Design and Erosion Control Manual (DDECM) was adopted by the Thurston County Board of Commissioners on October 18, 2016. The 2016 DDECM takes effect on December 31, 2016. Projects submitted for permitting after December 31, 2016 will be subject to the 2016 DDECM. The 2016 DDECM is available for download below. There are several policies and Administrator Memos that apply to the 2009 DDECM and they will apply to the 2016 DDECM as well. The policies and memos are available for download below as well. The stormwater utility staff is currently preparing a policy to apply the 2009 policies and memos to the 2016 manual. This policy will be posted as soon as it is signed.

 

2016 Thurston County Drainage Design and Erosion Control Manual

Summary of Changes

Maintenance Checklist


2009 Drainage Design and Erosion Control Manual for Thurston County

The 2009 DDECM was approved by Thurston County commissioners on August 17, 2009 and took effect November 16, 2009. It is applicable to projects submitted for permitting between November 16, 2009 and December 30, 2016. It is equivalent to the 2005 Department of Ecology Stormwater Manual for Western Washington.

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

Related Items


1994 Manual


 

Contact Us

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

 

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