ICF collaborated with the CCNRD to obtain a 2006 Salmon Recovery Funding Board grant to develop project alternatives, 35-percent design plans, and a construction cost estimate. As part of the alternatives analysis and design process, ICF conducted a wetland and stream delineation and collected baseline geomorphic, streambed sediment size, water temperature, geotechnical, and sediment contaminant data.
ICF surveyed river cross-sections along a 1.5-mile reach of Nason Creek and developed a Hydrologic Engineering Centers River Analysis System (HEC-RAS) model to support an analysis of project alternatives. We worked with stakeholders, including Washington State Department of Transportation (WSDOT), U.S. Forest Service (USFS), and the Upper Columbia Regional Technical Team, to select the preferred alternative.
The preferred alternative proposed the installation of a 90-foot-long, 12-foot-diameter culvert, countersunk six feet at inlet and outlet locations along SR 207, an innovative solution to protecting the existing highway infrastructure while maintaining the current Nason Creek alignment and sediment-transport regime, which would allow year-round flows and fish passage to the disconnected oxbow habitat. Both culverts were designed to meet the Washington Department of Fish and Wildlife (WDFW) fish passage criteria for culverts. Review of the hydraulic modeling results and site conditions led to the development of 35-percent grading and planting plans for the preferred alternative, and award of Bonneville Power Administration Independent Scientific Review Panel (ISRP) funds.
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