Mill Creek RM 1.75 Design

The Walla Walla County Conservation District has developed a preliminary engineered design to restore instream, floodplain,and riparian habitat for portions of Mill Creek located in Walla Walla County, Washington. This reach includes Segments 1 and 2 as identified in the Lower Mill Creek Fish Habitat and Passage Assessment and Strategic Action Plan (Confederated Tribes of the Umatilla Indian Reservation, 2017) and are located between river mile (RM) 1.75 and RM 4.0 downstream of the cities of College Place and Walla Walla. The site is within the Mill Creek major spawning area, which has experienced significant erosion and loss of riparian vegetation from high flow events. The engineered design includes a series of engineered log structures, floodplain reconnections and riparian plantings to benefit mid-Columbia summer steelhead, bull trout and reintroduced spring Chinook salmon. Large wood, by reducing erosion and fine sediment input, will reduce impacts on salmonid redds. Large wood structures will provide pools for adult holding, prey habitat, and juvenile rearing.

The Project design goal is to restore natural processes In Mill Creek, Walla Walla County WA, while maximizing habitat improvement. When implemented, the project would increase stream cplexity with large wood placements, and reconnect floodplain and side channels, and enchance the riparian area with native plantings to benefit mid-Columbia summer steelhead, bull trout and reintroduced spring Chinook salmon.