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Thurston County, Washington

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Thurston County government received a grant from the U.S. Environmental Protection Agency to study ways to translate data about local waters into land use planning policies. The project evaluated current conditions in areas of Totten, Eld, Budd/Deschutes, Henderson, and Nisqually Reach watersheds. It also conducted hydrological modeling of various management practices to identify what worked best for each water area. Finally, the group recommended next steps for continued work to Thurston's Board of County Commissioners. 

Date of Grant 2013 

Regulatory Reasons for the Study The Washington State Legislature's Growth Management Act (RCW 36.70a.020) requires Counties to plan for population growth in a way that preserves and protects area waters, natural resources and Puget Sound.

Completed Work

​Reports (PDFs)
Final Report (Hydrological Modeling / Watershed-Based Land-Use Planning)
Summary of Recommendations 
Vulnerable Lands Report 
Basin Evaluation Report (Current Conditions & Best Management Practices) 
Basin Evaluation Report Appendices   
​Maps (PDFs)
Map of project area  ​​Map 10: Estimated Increase in Total Impervious Area: 2006 to Buildout
Basin map ​​Map 11: 1991 Forest Canopy by Basin
Map 1: Thurston County Watersheds Map 12: 2006 Forest Canopy by Basin
Map 2: Thurston County Basins Map 13: Forest Lands Vulnerable to Conversion
Map 3: Puget Sound Watershed Characterization Analysis Units in WRIAs 13 & 14 Map 14: Thurston County Wetlands
Map 4: Benthic Index of Biotic Integrity (B-IBI) Sample Site Locations Map 15: Stream Riparian Buffers
Map 5: General Water Quality, Thurston County’s Streams – 2007-2009 Water years ​​Map 16: Puget Sound Watershed Characterization Landscape Groups
Map 6: 1991 Total Impervious Area by Basin Map 17: Basin Current Conditions
Map 7: 2010 Total Impervious Area by Basin Map 18: Importance of Water Flow: Surface Water
Map 8: 2035 Estimated Total Impervious Area by Basin ​​Map 19: Importance of Water Flow: Groundwater Recharge
Map 9: Total Impervious Area Estimate at Buildout by Basin Map 20: Importance of Water Flow: Groundwater Discharge


Recommendations for Future Basin Studies  This study recommended a further study of three basins that represent a range of current ecological conditions. The Black Lake which relects the impacts of rural neighborhoods, McLane Creek which reflects impacts from a mostly undeveloped forest area, and Woodard Creek which reflects impacts from a commercial/industrial area near densely populated neighborhoods. 

Project partners  

Thurston County collaborated with Thurston Regional Planning Council on this project. 

County codes or regulations affected by this project

The results of this study may be applied to existing development regulations, transfer or purchase of development rights, low impact development, or long-term protection of sensitive lands.


According to population studies, Thurston County is one of the fastest growing regions in Washington State. The area is expecting about 140,000 new people by 2040. 

This growth will bring economic benefit to the unincorporated areas of Thurston County which are served by the County government. It will also bring demand for new homes and new County roads and services. Growth in a very rainy place like Thurston County affects the ability of undeveloped land to provide valuable services. Heavy rains drain into areas called wetlands, which reduces flooding.  Soils of undeveloped land filter runoff, helping clean it as it seeps into drinking water aquifers (most Thurston County residents drink untreated water from local aquifers).  Development in rural areas means the land no longer provides these free services. It also means more pollution gets caught in rainwater runoff as it flows into in area waters, which may make them unsafe for people and pets to play in, fish from and drink. 

Thurston County government wants to meet the requirements of the State Legislature's Growth Management Act by accommodating growth in a way that preserves the health of area waters and the quality of life for current and future residents. That is the goal of this project: To understand where the threats to our natural resources are greatest, and to identify ways to prevent the degradation of those resources, preserving them for future generations.