Four rivers, four counties and nine levees. The busy emergency levee repair season meant to safeguard life and property in Western Washington is nearing its end, but work remains before the start of the fall flood season.
Repairs to the King County Mason Thorson Ells levee on the Middle Fork Snoqualmie River began September 12 near the popular “Blue Hole” recreation site in North Bend, Washington. The estimated two-week-long project will repair a 60-foot-long segment damaged in a 2020 flood event.
The $108,400 project is safeguarding a mix of property with an estimated value of $158 million. Under a cost-share agreement, the U.S. Army Corps of Engineers (USACE) pays 80% of the project, and the King County Flood Control District covers the remaining 20%.
In the damaged state, the levee’s flood defense is reduced to a one-year flood level protection or a 99% chance of flooding any year. USACE will remove a portion of the damaged area and then add embankment material and rock armor to restore the levee to its originally designed and built 10-year level of protection, or a 10% chance of flooding annually.
“The Middle Fork Snoqualmie River has a recent flood history, so it’s imperative we tackle this repair quickly, ensuring people at risk of a levee breach are protected,” stressed Janet Curran, USACE levee program manager. “The fully restored levee will reduce risk to homes, private agricultural and public infrastructure in the area protected by the levee.”
According to Curran, an aquatic biologist, construction is taking place during the in-water work window of July 15 to October 31 to minimize impacts on local fish populations and follow best-managed practices. This project area is above Snoqualmie Falls, so there are no anadromous and federally listed salmonid species in the area. The local fish populations include mountain white fish, cutthroat, and rainbow trout.
While construction impacts are expected to be minimal, access to the downstream end of the levee and the “Blue Hole” beach will be closed during the repair. The river will remain accessible for boating use during construction.
Passing boaters are advised to be aware of their surroundings and stay to the right. A memorial bench will also be temporarily moved and placed in its original location when repairs are complete.
The project includes environmental measures meant to enhance and protect the surrounding natural wildlife and vegetation. USACE will remove invasive species and retain as much existing native vegetation as possible while planting ten native willow tree bundles every six feet. Nine Douglas fir trees will also be planted to compensate for removing one sequoia and two deciduous trees on the levee’s landward side.
Throughout the planning process, USACE officials coordinated, consulted and worked with federal, tribal and state agencies, including the Environmental Protection Agency, National Marine Fisheries Services, U.S. Fish & Wildlife Service, Yakima Nation, Muckleshoot Indian Tribe, Snoqualmie Indian Tribe, Tulalip Tribes of Washington.
[Information provided by the US Army Corp of Engineers-Seattle District]
