Photo courtesy of King County [enlarge] Dennis Clark, watershed stewardship coordinator for King County, said the 2.5-acre site will be “an ecological treasure on the Duwamish.”

July 30, 2009

Duwamish habitat work in final stage

By Katie Zemtseff
Journal Staff Reporter

The final stage of a $3.7 million major habitat restoration project on the Duwamish River got underway this week. The project, called the North Wind's Weir, has been in the works since 1991.

Dennis Clark, watershed stewardship coordinator for King County, said it is good to see the project moving forward. “We've all worked on this for so long and to actually see it happen is really rewarding.”

The project is a partnership between a number of groups and public agencies: King County, the U.S. Army Corps of Engineers, the cities of Seattle and Tukwila, the Washington State Salmon Recovery Funding Board, the Washington State Department of Natural Resources' Aquatic Lands Enhancement Account, the Elliott Bay/Duwamish Restoration Program and the King Conservation District.

Noel Gilbrough of the corps said a contractor has not yet been selected though bids should be opened in the next couple of weeks.

The site is at a “transition zone,” a critical point where freshwater from the Green/Duwamish River mixes with saltwater from Puget Sound.

When complete in 2010, the restoration will provide federally protected chinook salmon with shallow water habitat, feeding opportunities and hiding spaces as they move from freshwater to saltwater. The work is expected to boost survival rates for salmon.

Clark said the 2.5 acres will be “an ecological treasure on the Duwamish because its going to (become) high quality habitat and it's pretty substantial (in size).”

The site was likely used as light industrial space in the past, Clark said, though when he first started working on the project automobiles were stored there.

In 1991, the site was ranked first on a list of restoration sites. In 1998, it was included in a 45-project list called the Green/Duwamish Ecosystem Restoration Project, developed by the corps, local government and the Muckleshoot Indian Tribe.

It was purchased in 2001 for $1.9 million. After the purchase, teams found there was soil contaminated with hydrocarbons on the property. The partnership did soil remediation in both 2004 and 2008.

Teams did further soil cleanup this spring. Clark said it was tricky to clean up soil without spreading contamination into the river so the team used a PortaDam to do the job. The PortaDam is a system of scaffolding combined with a tarp that protects work space from water. Any water that does get into the work space is pumped out.

Now the partnership is beginning final construction, which the corps is leading. It will remove additional soil and sculpt the space to benefit salmon.

The river will have shallow grades that are gently sloping or flat where salmon can rest and predators cannot follow them. Construction will also provide space for salmon to rest and feed. The team will create a marsh along the river, and an upland area with trees and shrubs.

Clark said the city is hoping to recruit some of the 2,000 workers at the Boeing Customer Service Center across the street to volunteer to help maintain the property after the work is done.

The project will help with future restoration of the lower Duwamish River. Contaminated sediments downstream are being cleaned up through federal Superfund work now under way.

For more information, visit www.govlink.org/watersheds/9/plan-implementation/SRFB-northwinds.aspx.