North Boeing Field Georgetown Steam Plant
7370 E Marginal Way S, Seattle, WA 98108


Updated February 2020

Ecology has reviewed a first draft of the Remedial Investigation Report (see definition below) and a new draft is expected in 2017.
In 2008, Ecology entered into a legal agreement called an Agreed Order with the Boeing Company, King County, and the City of Seattle (collectively the potentially liable parties or PLPs) to investigate contamination at this site.
Under the Agreed Order, the PLPs are required to complete the following:

  • Remedial Investigation (RI). The purpose of the RI is to define the nature and extent of contamination at the site and to determine if it is contributing to the sediment contamination in the Lower Duwamish Waterway.
  • Feasibility Study (FS). The FS will use the results of the Remedial Investigation to evaluate and choose measures to clean up contamination and minimize recontamination of the sediment.

To view site reports and fact sheets, click on the "View Electronic Documents" link to the right.
What happens next?

Ecology is working with the PLPs to complete the RI and move forward with FS. The next opportunity for public comment will be when the Draft Final FS Report is ready for review, although Ecology may also decide to hold a public comment period for the Draft Final RI Report. 
Why this cleanup matters

This site is part of Ecology’s Lower Duwamish Waterway source control efforts, because it is located near the Lower Duwamish Waterway (LDW) Superfund Site. The 5-mile stretch of the Duwamish River that flows north into Elliot Bay was added to the Superfund National Priorities List by the U.S. Environmental Protection Agency (EPA) in 2001.

The sediments (mud) in the river contain a wide range of contaminants due to decades of industrial activity and runoff from urban areas. EPA is leading efforts to clean up the river sediments.

Ecology is leading efforts to control sources of contamination from the surrounding land area. The long-term goal is to minimize recontamination of the river sediment and restore water quality in the river. 
North Boeing Field is one of several sites that will be cleaned up as part of Ecology’s Source Control Strategy – controlling sources of pollution to the river. Contaminants in the soil and groundwater around the river pose a risk to human health and the environment. They can also find their way into the river through storm runoff and other pathways. For more information, visit our Source Control page.

Approximate site boundary is in orange. Click on image to enlarge it.
Please click on the photo for a larger view


Site location

The North Boeing Field and Georgetown Steam Plant Site is located in an industrial area on the east side of the Lower Duwamish Waterway. It is bordered to the southwest by East Marginal Way South, to the east by King County International Airport, and to the northwest by Ellis Avenue South. On the other side of Ellis Avenue South is a residential neighborhood.

The Lower Duwamish Waterway drainage basin is divided into source control areas. This site is located within the Slip 4 Early Action Area (river mile 2.8) source control area along the east bank of the river.

Site history

Georgetown Steam Plant

In 1906, Seattle Electric Company built the Georgetown Steam Plant (GTSP) along the Duwamish River to provide power during periods of high electricity use.  After 1912, use of the steam plant decreased under Puget Power ownership. The City of Seattle acquired the plant in 1951 and operated it on standby until it was fully decommissioned in 1973.
The GTSP is a National Historic Landmark. The City still owns the 7.29-acre property and operates a historical museum there.
When built, the GTSP was next to the Duwamish River. When that part of the river was straightened in 1913 to form the Duwamish Waterway, the GTSP Flume was constructed to carry cooling water to Slip Four.

North Boeing Field

King County owns most of North Boeing Field (NBF). Boeing leases about 117 acres from King County, and owns the improvements it has built on the property. Boeing has operated at North Boeing Field since the 1940s for aircraft and aerospace manufacturing, maintenance, and research.


Contamination at the site is most likely the result of industrial operation and maintenance activities performed on this site since the 1940’s.
In soil, the contaminants of concern are:

Polychlorinated biphenyls (PCBs)
Total petroleum hydrocarbons (TPH)
Polynuclear aromatic hydrocarbons (PAHs)
Metals (Antimony, arsenic, cadmium, chromium, copper, lead, mercury, and zinc)

In groundwater, the contaminants of concern are:

Total petroleum hydrocarbons (TPH)
Volatile and semi-volatile organic compounds (VOCs and SVOCs)
Metals (Antimony, arsenic, chromium, and lead)

In stormwater solids, the contaminants of concern are:

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

In Slip 4 sediments, the contaminants of concern are:

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

Previous cleanup work

EPA’s Early Action cleanup in Slip 4 was completed in 2012. As part of this project, Boeing and the City removed debris and cleaned up sediments in the Slip. Boeing also installed a stormwater treatment system to remove solids from the stormwater draining off the northern portion of the site. This area had very high levels of PCBs, due to the historical handling of electrical transformer oil and aircraft hydraulic oil. Controlling this runoff made a significant difference in the amount of PCBs reaching the river.
In 1985 and 2006, the City independently removed PCB-contaminated soil from the southwest portion and southern boundary of the GTSP property. This portion of the site is referred to as the low-lying area because surface water historically flowed into this region from portions of the GTSP and offsite areas.
In 2009, the City independently cleaned up and replaced the GTSP Flume, which was known to be a source of contamination to the river.
2011, Boeing conducted an Interim Action to remove accessible PCB-contaminated soil along the fence line adjacent to the Steam Plant.
Also In 2011, the City and Boeing conducted an Interim Action under the direction of Ecology to remove soil contaminated with PCBs and petroleum from the low-lying area near the GTSP, which had the potential to move offsite and contaminate Slip 4. They also capped areas where the soil was contaminated with other chemicals.
Boeing continues to make progress on a large scale effort to remove PCB-contaminated materials such as caulk, paint, building materials, and surface debris. EPA regulated this action is under the federal Toxic Substances Control Act.
Since 2010, Boeing has removed thousands of linear feet of PCB-contaminated concrete joint material from the site, and re-sealed the joints. They have also cleaned, repaired, and replaced many of the storm drains on the north end of the property.


The Model Toxics Control Act (MTCA; Chapter 70.105D RCW is Washington’s environmental cleanup law). It provides requirements for contaminated site cleanup and sets standards that protect human health and the environment. Ecology enacts the MTCA and oversees cleanups. The MTCA site cleanup process is completed in steps (see graphic below) over a variable timeline.

Please click on the photo for a larger view


Map showing site location as King County, WA SITE INFORMATION


View Electronic Documents

Cleanup Site Details Report

Facility Site ID: # 2050

Cleanup Site ID: 4765

Seattle, King County

Status: Cleanup Started   Get definitions of Status terminology

Mark Adams
Site Manager
(425) 649-7107

Brad Petrovich
Project Planner and Public Involvement Coordinator
(425) 649-4486

Document Repositories:

Northwest Regional Office
3190 160th Ave SE
Bellevue, 98008-5452

South Park Branch / Seattle Public Library
8604 Eighth Avenue South
Seattle, 98108