Seattle Stormwater Problem Engages All Levels of Government

BELLEVUE, Washington (ENS) – The City of Seattle, King County and the Boeing Company have signed an agreement with the state of Washington to investigate and propose solutions for cleanup of soil, stormwater, and groundwater contamination in the North Boeing Field/Georgetown Steam Plant area of south Seattle.

Signed Thursday, the agreement will pave the way for a cleanup of contaminated sediment at the bottom of Slip 4, a nearby inlet of the Duwamish Waterway, that is planned by the U.S. EPA.

Polychlorinated biphenyls and other pollutants have been found in storm drains that empty to Slip 4 from city, county and Boeing property in the study area.

A cleanup in the 137 acre North Boeing Field/Georgetown Steam Plant area will help prevent re-contamination of the inlet.

The Washington state Department of Ecology will conduct an investigation and work with the three property owners, who will pay the estimated $2.5 million cost of the study and analysis.

The area to be studied includes northern portions of King County International Airport, which is commonly known as Boeing Field as well as property owned by King County and currently leased by Boeing to the west, and the city-owned Georgetown Steam Plant site to the north.

North Boeing Field has a complex storm drain system that includes over 400 catch basins, 400 manholes, up to 16 oil water separators and lift stations, parking lot ditches, and roof drains. The system connects with seven to eight miles of piping ranging from four to 48 inches in diameter.

Stormwater from the Steam Plant flume and from North Boeing Field flows into Slip 4, which is part of the Early Action Area with the Lower Duwamish Waterway Superfund Site.

The Lower Duwamish Waterway (Photo
courtesy Dept. of Ecology)

A five-mile reach of the Duwamish River – upstream of Harbor Island – is the federal Lower Duwamish Superfund cleanup site, jointly administered by the EPA and the state Department of Ecology. Slip 4 is part of that larger sediment cleanup effort.

The Lower Duwamish Waterway site is a 5.5 mile portion of the Lower Duwamish River which flows into Elliott Bay, a part of Puget Sound.

Cleanup of the waterway is part of Ecology’s effort to reduce and prevent toxic threats to the environment and to support the governor’s Puget Sound Initiative – a cooperative effort among state, local, federal and tribal governments, businesses and organizations to protect and restore Washington’s inland marine waters.

In the solids from the stormwater drainage system, contaminants of concern are:

* Polychlorinated biphenyls (PCBs)
* Polynuclear aromatic hydrocarbons (PAHs)
* Semi-volatile organic compounds (SVOCs)
* Arsenic, copper, lead, mercury, and zinc

In Slip 4 sediments, contaminants of concern are:

* Polychlorinated biphenyls (PCBs)
* Semi-volatile organic compounds (SVOCs)

The three parties have conducted several cleanup and storm drain improvement projects over the past 25 years, all aimed at cleaning up soil and groundwater contamination from past industrial activities.

Still, PCBs and other contaminants continue to appear in storm drain sediments.

“Before cleaning Slip 4, we must find how to prevent its re-contamination,” said Jim Pendowski, who leads Ecology’s toxic cleanup program.

“The agreement by Seattle, King County and Boeing to undertake a single, unified investigation makes sense, given the area’s complex contamination problems,” he said. “This approach may serve as an effective model for other challenging parts of the Lower Duwamish.”

An Agreed Order between the Department of Ecology and the city, the county and Boeing is online here [].

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