A U.S. Army Corps of Engineers contractor removed pilings today that will let the tides return to Union Slough in Everett, Wash., for the first time in 40 years as part of an environmental restoration project.
The return of the tides to the Snohomish River delta is made possible by a Seattle District, U.S. Army Corps of Engineers restoration project, with the City of Everett as the sponsor and is authorized under Section 1135 of Water Resource Development Act of 1986.
Originally designed as a federal navigation project in 1910, the initial navigation project included dredging, construction of dikes and a settling basin, and was completed in 1963.
The fish and wildlife habitat in the Snohomish estuary, including Union Slough, had been significantly degraded as a result of the modifications made to the navigation channel. An estimated 75 percent of the wetlands in the lower Snohomish basin have been altered due to local flood control, agricultural conversion and, to a lesser extent, filling. Union Slough has been almost entirely diked.
The areas behind the levees are predominantly freshwater wetlands dominated by reed canary grass, and agricultural fields providing no access for fish. In recent years the farms behind the levees have ceased to operate and the land has passed into public ownership. In two other locations on Union Slough, the levees have been breached to re-create habitat areas, and one location has been preserved as a fresh water wetland.
The Union Slough project includes set back levees along a distributary channel of the Snohomish and will open 35 acres to tidal influence. This project builds on successful restorations nearby, and will be further enhanced by a City of Everett mitigation project that will be built along with this project. The two projects will combine to open nearly 100 acres of contiguous land to tidal influence. The nearby Spencer Island project built by the Washington State Department of Fish and Wildlife is the model for this project.
Construction was initiated in 2004 and will be completed this year. Work consisted of construction of a new set-back levee, filling the old borrow ditches, and breaching the old levee in three locations. Bridges to maintain the existing public-access trail span the levee breaches. The entire site will flood and drain completely twice a day with the tide.
The goal of the project was to restore natural habitat forming processes to create a dynamic and self-maintaining environment that is hospitable to fish and wildlife. The levee along Union Slough was replaced and breached, in order to:
* Create and maintain tidal inundation in estuarine habitat
* Maintain existing level of flood damage reduction
* Maintain existing public access
The project site covers approximately 93 acres. The project was formulated as a whole. However, the local sponsor dedicates 50 acres of the project to mitigation for other work. Therefore, the Corps is cost-sharing approximately 46 acres of the project, and the local sponsor is funding 50 acres. The cost of the restoration project is approximately $7.5 million dollars.
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