Willamette River Stormwater Outfalls

For the City of Wilsonville, OR

projects-WilsonvilleW2r is working with a team of civil and geotechnical consultants to address channel erosion at stormwater outfalls to the Willamette River. Our role is to conduct the hydrologic and hydraulic analysis, provide natural systems design engineering elements, conduct the wetland delineation, and complete State and Federal permitting requirements for in water work. This is a complex project requiring integration of natural channel design and traditional civil engineering strategies to reduce erosion while enhancing both habitat and water quality along the banks of the Willamette River. We have approached the design alternatives with an understanding of what the regulatory agencies will require and what could be covered under various programmatic permitting tools. This saves considerable time and money in the design iterations and alternatives assessment. Our in depth hydraulic analysis addressed the implications of potential permitting requirements such as the use of rounded rock or large wood within weak soils along a large river. This facilitated negotiation of a design that minimized impact to habitat and water quality while stabilizing and enhancing eroded channels.