South Lake Washington Shoreline Restoration Project
The shores of Lake Washington are a vital nursery for young salmon. However, most of this shoreline habitat has been altered with piers and other overwater structures, bank armoring, and reduced native vegetation that would protect fish and wildlife. Now, 1,300 feet of shorelands and a three-acre waterfront property will be restored at an important point along the south end of the lake.
This top priority area under the WRIA 8 Chinook Salmon Conservation Plan is in a migratory and rearing corridor for the young salmon, which migrate from the Cedar River between January and April each year. Studies by the US Fish & Wildlife Service have shown that the juvenile Chinook salmon tend to rear along shorelines close to the mouth of the Cedar River. Juvenile salmon need shallow water areas with overhanging vegetation to spend time feeding and growing, protected from predators, before heading out to the marine waters.
This three-acre property, next to Boeing’s Renton Plant, is near the mouth of the Cedar River—in the critical migratory corridor. The property was created in 1965 when 150,000 cubic yards of fill was placed into the lake. The fill was placed alongside a 20-foot-wide flume, or channel, made of two sheet-pile walls. The channel formerly was used to release water into Lake Washington from the Shuffleton Steam Plant.
Restoration Project and Partners
The restoration project site includes the 650-foot derelict flume, and the shore area overgrown with Himalayan blackberry and other invasive plants. The shoreline—both above and below the water line—is littered with concrete and other debris. Three ‘dolphins’, made up of grouped creosote-treated piles, are located on the eastern side of the property.
DNR and partners designed this project to restore about 1,300 linear feet of shoreline habitat and three acres of upland habitat to improve and restore the water quality of the lake and nearshore habitat. The restoration will increase native trees, plants, and other overhanging vegetation to shade the shoreline. Bank hardening will be reduced and shallow-water habitat expanded closest to the mouth of the Cedar River—habitat heavily used by juvenile Chinook salmon.
South Lake Washington site before restoration.
This project is the result of a public private partnership between Washington State Departments of Natural Resources, Transportation, and Ecology, along with US Fish and Wildlife Service and Boeing. With $154,000 from the Salmon Recovery Funding Board (SRFB) to initiate the project and pay for design, the partnership is providing roughly $3 million to complete restoration, and carry out monitoring studies before and after completion. Each entity achieves program goals through this shoreline enhancement. For example, in addition to state and federal agencies achieving environmental goals, Boeing will gain new infrastructure when their stormwater outfalls are moved into deeper water in order to improve the shallow water habitat for salmon. The state Department of Transportation will receive mitigation credit for helping fund the project, and DNR—in collaboration with USFWS—will have the opportunity to carry out project effectiveness monitoring. And the reward to the community from this partnership will be the completion of the largest shoreline enhancement project in South Lake Washington.
This project strives to be an example of successful partnerships and encourage future collaborative restoration efforts between public and private entities.
The planning, design and permitting of a restoration project at the site, Phase 1, is complete. It included a feasibility study, conceptual design, final design of the project, and initial monitoring studies.
Beginning after the spring 2014 migration of young salmon moving to marine waters, the following actions are to take place (beginning in late June):
- Remove 921 linear feet of inner and outer flume sheet pile walls and associated cross beams
- Remove non-native invasive plants from the 3-acre upland property and re-plant native vegetation
- Remove three derelict dolphins from the lake consisting of 21 creosote-treated grouped piles
- Remove rip rap and other debris from the shoreline
- Place 9,000 cubic yards of fine gravel, sand, round cobble, and sediment along the shoreline to create shallow water habitat
- Plant native vegetation that will hang over the shoreline
- Restore a 0.29 acre wetland
- Place three log groupings along the shoreline as habitat
- Extend two stormwater outfalls into deeper waters
DNR has worked with US Fish and Wildlife Service to complete salmon monitoring along the project shoreline. The monitoring is occurring before construction and once the shoreline is restored. The data will allow us to report pre- and post-project fish counts at the project site and two control sites in the lake.
Final Lake Washington/Cedar/Sammamish Watershed (WRIA 8) Chinook Salmon Conservation Plan. 2005.
Tabor, A. Roger, Howard A. Gearns, Charles M. McCoy III, and Sergio Camacho. 2006. Nearshore Habitat Use by Juvenile Chinook Salmon in Lentic Systems of the Lake Washington Basin. U.S Fish and Wildlife Service Annual Report, 2003 and 2004.