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Drainage Manual 

The Thurston County Drainage Design and Erosion Control Manual (DDECM) spells out regulatory standards for reducing and managing stormwater runoff on new development and redevelopment projects. It applies in unincorporated Thurston County, and in cities and urban growth areas that adopt it. 

Current Manual  |  Past Manuals  |  Subscribe to our email list for updates 

2022 Drainage Manual Update

We’re updating the Drainage Design and Erosion Control Manual. The updated version will become effective on June 30, 2022. Stay tuned to this page for updates or if you'd like updates emailed to you, subscribe using the link above.