Chehalis River Flood Retention Mitigation

The Chehalis River Basin Flood Control District was evaluating the potential of constructing a flood retention facility and temporary reservoir near Pe Ell, Washington to reduce flooding impacts from the Willapa Hills in southwest Washington. The flood retention facility is expected to have significant impacts to natural resources that will require mitigation under state and federal law. Mr. Gorman served as a subconsultant to Kleinschmidt Associates to prepare mitigation and management plans for various natural resources, including vegetation, wetlands and wetland buffers, streams and stream buffers, fish and aquatic species habitat, riparian habitat surface water quality, and large woody material. The primary objective of the project was to provide Chehalis River flood retention mitigation for impacted fish and wildlife species. Mr. Gorman was the lead ecological engineer to establish critical mitigation parameters, develop a slate of mitigation candidate sites, prepare mitigation site screening criteria and list by mitigation type, develop conceptual mitigation design examples and plans, develop example project cost estimates to be extrapolated across a 573,000-acre watershed, and prepare a mitigation assessment report. Mr. Gorman was the lead author on a white paper on hyporheic exchange and its potential to mitigate increasing stream temperatures that impact native salmonids.