The US Environmental Protection Agency (EPA) and the Boeing Company have signed an agreement to construct a new stormwater treatment system at North Boeing Field in Seattle to reduce the amount of toxic polychlorinated biphenyls (PCBs) discharge into the Duwamish River.

The North Boeing Field storm drain system, which carries stormwater to the Duwamish River through more than seven miles of catch basins, drains, inlets, and oil-water separators, is claimed to deposit high quantity of PCBs to the river sediments in Slip 4 on the lower Duwamish waterway.

Boeing has designed an initial stormwater treatment system, which has already begun treating stormwater from the highly contaminated areas of North Boeing Field and over the course of the next year a long-term system will be put in place at the site.

With the installation of this stormwater treatment system, the cleanup of several acres of contaminated sediments in Slip 4 under an EPA settlement agreement with the City of Seattle and King County will proceed in 2011.

EPA associate director of superfund cleanup office in Seattle Lori Cohen said that Boeing’s investment in stormwater treatment will pay dividends in cleaning up the lower Duwamish River and Puget Sound.

“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,” Cohen said.