Client: Wasco County Soil and Water Conservation District
Mill Creek is a moderately-sized tributary to the Columbia River that originates on the eastern slope of Mt. Hood and flows northeast through the City of The Dalles, Oregon. Urbanization along the lower two miles of Mills Creek in the City of The Dalles resulted in the simplification of the aquatic and riparian habitats. In 2011, The Dalles Watershed Council (DWC) commissioned an evaluation of the urbanized reach to assess land use impacts and identify opportunities for habitat restoration. Following the initial assessment, a preliminary engineering design was developed for the Honald/Buyers property. The preliminary design included excavation and connection of a historic side channel that had been partially filled, utilization of an existing side channel as a backwater alcove, installation of a precast spanning bridge across the reconnected side channel, and installation of large wood structures along the channels and floodplain to increase roughness and improve habitat conditions.
After receiving initial feedback from the permitting agencies in 2015, the Wasco County Soil and Water Conservation District and DWC contracted with Waterways Consulting to complete the final design and oversee construction. Waterways incorporated agency comments and completed a value engineering analysis to bring the projected construction cost within the available budget. Waterways also built a hydraulic model to fulfill FEMA No-Rise requirements and to analyze the timing and frequency of flow accessing the restored side channel. The final restoration design included excavation and connection of the historic side channel, installation of a multi-plate pipe arch culvert embedded with streambed material, and installation of large wood structures along the side channel and floodplain. The project was constructed during summer/fall 2015.