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City of Seattle

October 6, 4:02 PM click here to comment > 2

Major Duwamish Waterway hotspot cleanup effort begins this week

The decade-long effort to clean up the Lower Duwamish Waterway takes a major step forward this week as the City of Seattle begins work on one of the hotspots on the Superfund mega-site.

The cleanup of Slip 4, about three miles upstream from Harbor Island, near the Georgetown community, comes as the U.S. Environmental Protection Agency considers how to clean up the rest of the five-mile portion of the river. EPA’s cleanup plan is expected to be issued next year.

One of five major lower Duwamish hotspots, which collectively account for about half the chemical contamination on the river, Slip 4 is a 6.4-acre navigational slip on the east bank of the waterway, about 1400 feet long and 200 feet wide.

In his remarks today at a press event at Slip 4, Mayor McGinn said “We’re not waiting to take action on contamination in the Duwamish. We are attacking hot spots now so we can get ahead of the problem.”

James Rasmussen, Duwamish River Cleanup Coalition, speaks to the press at Slip 4 with Mayor McGinn and Dennis McLerran, EPA Region 10 Administrator

McGinn said the effort to clean up the river will begin to restore a part of Seattle that needs help to once again provide healthy habitat for fish, birds, and people.

“We’re not just cleaning up contamination in this process, we are also creating new habitats for fish and other wildlife” McGinn said.

Working with its partners — The Boeing Company, the Port of Seattle, and King County — Seattle is making cleanup progress on Slip 4 and the other hot spots in advance of the main Superfund process which will address cleanup of the entire river.

A pier and berthing area for industrial vessels at Slip 4 have been used over the years, and storm drains and emergency sewer overflows historically were routed into the slip. The slip is full of debris — logs, piling, bulkheads, and other derelict material. About 3.5 acres of the slip’s sediment is contaminated with polychlorinated biphenyls or PCBs, along with some metals, organic compounds, and petroleum products.

Controlling ongoing pollution sources to Slip 4 has been an important part of planning the cleanup. Source control actions led by Ecology and EPA have been completed at a number of properties and other efforts will continue to ensure that the cleanup of Slip 4 is not re-contaminated.

An important part of the cleanup is restoring habitat for fish and wildlife; this cleanup will add habitat in shallow water and the intertidal area. New aquatic habitat on the banks will also be created. The cleanup will include a net gain of over an acre of shallow and riparian habitat for threatened Puget Sound Chinook and Coastal/Puget Sound bull trout.

The City purchased the land in the cleanup area so the land use could be converted from industrial vessel berthing to habitat; and in-water cleanup work is only allowed between October and mid-February to protect migrating juvenile salmon.

A combination of proven technologies is being used to clean the sediments while improving habitat. The project includes stringent requirements for best management practices and monitoring of water quality. About 800 tons of debris will be removed from the slip. The most contaminated sediments will be removed from the slip bottom, and the banks will be excavated back to create stable slopes and expand habitat.

Contaminated sediment being removed

The removed sediments and soils will be drained and shipped by barge and rail, for disposal in a permitted landfill. Engineered multi-layer caps of clean sand, gravel, and rock will then be placed to cover the sediments and banks. The old concrete pier on the northwest bank will be demolished to improve habitat. Both land-based excavators and floating equipment will be used for the cleanup work.

Total costs for Slip 4 cleanup are about $8 million. The project is expected to be completed in early 2012.

Detailed information on Slip 4 is posted at:

Posted by: Words: April Thomas, Pictures: Jen Nance


Comment from Donna Moriarty
Time October 14, 2011 at 2:10 pm

So happy to see this important work is beginning!

Comment from Tjreally hurts the people
Time September 9, 2013 at 10:39 pm

this is really hurtinig thee people that have that as thier only know sleeping resource. the people have been camil]ng in numbers providing the saftey they can in the area, they need places they can take the garbage to so that it doesnt pile up. and most of them are willing to woek with clean up crew when they come if they ask.. its hard for most of to adapt to any other place..; and dontr want to try to make it where they have no clue how hings can turn out. i have family in there who knows nothing else and is not able to understand how, cant be told go here hasd to be shown kindly by hand where to go and be introduced to the new place. otherwise has no clue at all, i cant help him and the Greenbelt is all he knows..;