Tuesday, September 8, 2015

SR 520 Program helps keep the salmon swimming

By Olivia Rother

Few things are as widely revered in the Pacific Northwest as the salmon. The fish's esteem here runs deep, from the Native Americans who for millennia thrived on salmon to the tourists who delight in watching fishmongers hurl an ice-bathed sockeye at Seattle's Pike Place Market. Given the fish's iconic status, it's no surprise that improving salmon habitat is a high priority for our agency when we look for ways to mitigate the environmental effects of our construction projects. 

Juvenile Chinook salmon (photo by Roger Tabor)
In the SR 520 Bridge Replacement and HOV Program, for example, we are pursuing a number of projects to improve and restore salmon-bearing streams and shorelines. Many of these projects are
located in or around Lake Washington, including:
  • A restored section of Yarrow Creek
    and a new, fish-friendly culvert
    built beneath SR 520.
    The Cedar River Elliott Bridge Reach project, which involves aquatic-habitat improvements, floodplain restoration and wetland establishment aimed at boosting the river's Chinook stocks. 
  • The East Approach project, where we'll enhance spawning habitat for sockeye salmon beneath and alongside the SR 520 floating bridge's east approach. Key elements involve supplementing lake-bed gravel along the shoreline, removing an existing bulkhead and rubble, and restoring and replanting the shoreline.
  • The Yarrow Creek project, where we made channel improvements to this urban creek and adjoining Eastside streams, and installed larger culverts under the roadway to eliminate potential barriers to fish migration. We also upgraded numerous culverts and stream channels.
  • The Evans Creek project, which included substantial improvements to the creek and its wetland floodplain. Evans Creek contains three distinct Chinook salmon populations.
  • The Bear Creek project, where we improved salmon habitat by restoring portions of this Redmond creek through realignment and reconstruction of the channel, riparian and floodplain restoration, and planting of native riparian vegetation.
Our most recently completed project is the south Lake Washington shoreline restoration project. This effort re-established about a quarter mile of nearshore and upland habitat on a three-acre property next to Boeing's Renton Plant, near the mouth of the Cedar River.

The shores of Lake Washington are a vital nursery for young salmon. Most of the shoreline at this location, however, had been altered by fill and man-made structures that destroyed the shallow near-shore habitat small salmon require. This shoreline restoration project not only removed many of those structures but also planted native trees and shoreline vegetation, and removed invasive vegetation from the site. In addition, we established more suitable juvenile salmon habitat by regrading nearshore areas and re-establishing critical shallow areas, and extended two stormwater outfalls to avoid disturbing the restored shallow habitat. 

These steps will help re-establish vital rearing habitat for migrating salmon; improve water quality with a healthy upland habitat of native trees, bushes and grasses; and provide essential shallow-beach habitat in the lake that supports many other wildlife species. The project also involves pre- and post-project monitoring that will provide information about the success of the restoration and use of the site by juvenile salmon over time.
The south Lake Washington site before restoration.
The south Lake Washington site after restoration.
The south Lake Washington shoreline restoration project has been a highly successful collaboration between the Washington State Department of Natural Resources (DNR), WSDOT, and The Boeing Company. We supported the restoration project as partial mitigation for the environmental impacts of constructing the new SR 520 floating bridge across Lake Washington — the SR 520 Bridge Replacement and HOV Program. As part of an ongoing effort to enhance Lake Washington, DNR received a grant for the planning, design and permitting of a restoration project at this south Lake Washington site. Boeing provided funding to DNR to replace stormwater outfalls and extend them to deeper water.

Our agency works on a variety of mitigation projects to improve the region's parks, natural areas, and historic and cultural resources.  These mitigation projects are part of our overall commitment to environmental stewardship. For more information on the additional 14 SR 520 mitigation projects, check out the SR 520 website.