On September 29, the U.S. Environmental Protection Agency signed an agreement with The Boeing Company to construct a new stormwater treatment system at North Boeing Field in Seattle. The treatment system will greatly reduce the amount of toxic polychlorinated biphenyls (PCBs), which are an on-going source of pollution to the Duwamish River.

The North Boeing Field storm drain system carries stormwater to the Duwamish River through more than seven miles of catch basins, drains, inlets, and oil-water separators. Studies by the Washington State Department of Ecology (Ecology), the City of Seattle, and Boeing showed the North Boeing Field storm drain system is the biggest source of PCBs to the river sediments in Slip 4, one of the most highly contaminated sites on the lower Duwamish waterway.

Goal is to reduce PCB discharge to Duwamish River

According to Lori Cohen, Associate Director of EPA’s Superfund cleanup office in Seattle, Boeing’s stormwater treatment work will significantly reduce PCBs discharge to the Duwamish River and better protect Puget Sound.

“Boeing’s investment in stormwater treatment will pay dividends in cleaning up the lower Duwamish River and Puget Sound,” said Cohen. “By reducing the volume of PCBs released to the river from North Boeing Field, we’re taking a major step forward in controlling one of the biggest PCBs pollution sources on the Duwamish and allowing us to move forward with our cleanup work.”

With the installation of this stormwater treatment system, cleanup of Slip 4 – one of several hot spot cleanups on the waterway – will proceed in 2011. Several acres of contaminated sediments in Slip 4 will be cleaned up under an EPA settlement agreement with the City of Seattle and King County.

PCBs are toxic pollutants that stay in the environment for a long time and can build up in fish and shellfish. PCBs are found at unsafe levels in the sediments and fish of the Lower Duwamish River. Concerns about PCBs in fish prompted the state to issue a health advisory warning people not to eat any crab, shellfish, or fish (except salmon) from the Lower Duwamish River.

Earlier this summer, Boeing agreed to design an initial stormwater treatment system with EPA oversight during the negotiation of today’s agreement. The initial system began operating last week treating stormwater from the most highly contaminated areas of North Boeing Field. The initial system will be managed under today’s agreement, and over the course of the next year, a long-term system will be put in place at the site. The treatment system is part of a broader effort to locate and contain or treat contamination in the North Boeing Field drainage area that flows into the stormwater outfall at Slip 4.

Background on Slip 4 & Lower Duwamish Waterway Superfund site:

Today’s stormwater treatment agreement enables the cleanup of Slip 4 to proceed while Ecology’s overall site investigation and cleanup continues at North Boeing Field. The Slip 4 cleanup was delayed when Ecology found high levels of PCBs in North Boeing Field storm drains discharging to Slip 4. The agencies agreed to delay cleanup until the on-going sources of PCBs were reduced, lessening the potential for recontamination of clean areas.

Slip 4 is part of the Lower Duwamish Waterway Superfund site, which was added to EPA’s National Priorities List in 2001. The contaminants in the river sediments include PCBs, polyaromatic hydrocarbons (PAHs), mercury and other metals, and phthalates. Sediments (mud and sand on the river bottom) in and along the lower river contain a wide range of contaminants from years of industrial activity and from stormwater pollution.

EPA and Ecology jointly oversee the Lower Duwamish Waterway cleanup. EPA is the lead agency for the investigation and cleanup of contaminated sediments throughout the lower river. As the lead agency for controlling the sources of pollution to the lower river, Ecology works with the City of Seattle and King County to investigate and control sources throughout the Duwamish drainage basin.

EPA’s investigation of the contamination and cleanup options for the Lower Duwamish Waterway sediments, the Remedial Investigation/Feasibility Study, is moving toward completion. The Remedial Investigation was completed earlier this year, which identified the contaminants, where they are located, and which are the most dangerous.

A second draft of the Feasibility Study, which looks at alternatives for cleanup, will be available for public review on Oct. 12. EPA and Ecology will host public meetings on Dec. 7 and Dec. 9. EPA expects the cleanup plan to be completed by 2012.

For more information about the Slip 4 cleanup, visit: http://yosemite.epa.gov/r10/cleanup.nsf/ldw/slip+4

For more information about the Lower Duwamish Waterway cleanup, visit: http://yosemite.epa.gov/r10/cleanup.nsf/ldw/