The commencement of permanent and final repairs of flood-damaged Skagit River levees has turned the once quiet Skagit River Basin into a bustling construction scene of dump trucks, excavators and workers spanning five work sites and three diking districts simultaneously.
The estimated eight-week long repairs kicked off in late July and will address a half-mile stretch of levees at a combined cost of $4,622,400. Additional levee rehabilitation work is planned for Skagit Diking Districts 17 and 22 in the coming weeks.
Under a cost-share agreement, the U.S. Army Corps of Engineers (USACE) will cover 80% of the project cost, while the Skagit Diking Districts funds the remaining 20%.
In response to levee damages resulting from consecutive floods in 2020 and 2021, 2,400 feet of riverward banks will be repaired. In the damaged state the levees flood defense is significantly reduced. Repairs to slope failures, bank stabilization, scoured riprap armor, and cracking of riverward benches will restore the levees to their originally designed and built 50-year level of protection, or a 2% chance of flooding annually.
The impact on recreation and traffic is expected to be minimal and temporary at most work sites. The most noticeable impact will be on a heavily-used walkway for cyclists and pedestrians that connects Lions Park to downtown Mount Vernon.
Like other levee repair projects, the riverbank work will be carried out within the designated "fish window" period between June 15 and August 31, which allows construction crews to operate in the water with the least interference to salmon populations.
Janet Curran, USACE levee program manager, highlighted the significance of the Skagit River and lower Skagit Valley as critical habitats for threatened salmon species. "We are implementing several measures to mitigate impacts on salmon habitat, including the use of anchored root wads to enhance aquatic habitat."
Curran also mentioned that the planting of two rows of willow tree bundles along the repair sites. As the planted willows mature, they will provide shade, cover, and a source of terrestrial insects for juvenile salmon to eat as the young migrate to sea.
Throughout the planning process USACE officials coordinated, consulted and worked with federal, tribal and state agencies, including: Environmental Protection Agency, National Marine Fisheries Services, U.S. Fish & Wildlife Service, Sauk-Suiattle Indian Tribe, Swinomish Indian Tribal Community, Samish Indian Tribe, Upper Skagit Indian Tribe, Tulalip Tribes of Washington, Washington State Department of Ecology, State Historic Preservation Office and Skagit County.