8701 E Marginal Way S, Tukwila, WA 98108

Maps data @ 2019 Google
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Updated February 2020

The Feasibility Study (see below) is underway.

In 2010, Ecology entered into an Agreed Order with the Boeing Company (the Potentially Liable Person or PLP) to investigate and develop a cleanup action plan for the site.  

The Agreed Order describes the work that the PLP agrees to perform on the site. Under this legal agreement, Boeing is 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. During the RI, the PLPs will collect data necessary to adequately characterize the contamination in soil, groundwater, stormwater, and sediments.
  • Feasibility Study (FS). The FS will use the results of the RI to evaluate and choose measures to cleanup contamination and prevent recontamination of the sediment.
  • Draft Cleanup Action Plan (DCAP). Ecology will identify a preferred cleanup action based on the results of the FS.

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 Boeing Company to move forward with the FS. The next opportunity for public comment will be when the Draft Final RI and FS Reports are ready for review.

 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 clean up 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. 
The Boeing Isaacson Thompson site 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.

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Site location

This site is located in an industrial area of Tukwila, on the east bank of the Lower Duwamish Waterway. The site includes two adjacent properties owned by the Boeing Company, the Isaacson (Boeing Isaacson) property on the north and the Thompson (Boeing Thompson) property on the south.

The site is bordered to the east by East Marginal Way S, to the north by the Jorgensen Forge cleanup site, to the south by the 8801 E. Marginal Way S cleanup site. It is bordered to the east by East Marginal Way S and the King County Regional Airport, and to the west by the Lower Duwamish Waterway.

The Lower Duwamish Waterway drainage basin is divided into source control areas. This site is located within the Boeing Isaacson/ Central King County International Airport (river mile 2.8-3.7) source control area along the east bank of the river.

Site history

The site is a former tidal marsh area which was reclaimed when the Duwamish River was straightened and channelized to form the current Duwamish Waterway in the late 1800s and early 1900s.  After dredging, the area was used as farmland.

Boeing Isaacson Property

The Boeing Company purchased the northern portion of the site (Boeing Isaacson Property) from the Isaacson Steel Company in 1984.

Around 1941, the United States Navy used the property just north of Boeing Isaacson and constructed steel melting, forging, and fabricating facilities that were known as Isaacson Iron Works Plant No. 2. The Isaacson Steel Company purchased the plant in the 1950s and expanded the steel fabrication facility to what is now the Boeing Isaacson property during the 1950s-1960s.

Boeing Thompson Property

The Boeing Company purchased this property (what is now the southern portion of the site) in January 1957. It is approximately 19.35 acres in size.

In the 1920’s-1930’s Bissel Lumber Company occupied the Boeing Thompson site to the south of former Slip 5. At that time Slip 5, an inlet on the LDW, was located between the Isaacson property and the Thompson property. From the 1930’s to the mid-1960’s portions of Slip 5 were filled with various materials, including slag and fire brick material.

In the 1960s, a bulkhead was constructed along the LDW and backfilled to reclaim about 50 feet of land between the waterway and the Isaacson property line. This strip of land is identified in King County ownership records as part of the waterway and therefore is under Port control.

By about 1966, Slip 5 was completely filled as part of site development at Boeing Thompson.


Contamination at this site is due to industrial operations and facility development. In soil, the contaminants of concern are:

•Metals - arsenic, cadmium, chromium, lead, mercury, nickel, zinc 
•Polychlorinated biphenyls (PCBs)
•Petroleum hydrocarbons

In groundwater, the contaminants of concern  are:

•Metals - arsenic, barium, chromium, lead

In stormwater, the contaminants of concern are:

•Metals - antimony, arsenic, lead
•Petroleum hydrocarbons

In sediments, the contaminants of concern are:

•Metals - arsenic
•Polychlorinated biphenyls (PCBs)
•Polycyclic aromatic hydrocarbons (PAHs)
•Volatile organic compounds (VOCs) - benzyl alcohol
•Benzoic acidPhthalates


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.

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Map showing site location as King County, WA SITE INFORMATION


View Electronic Documents

Cleanup Site Details Report

Facility Site ID: # 2218

Cleanup Site ID: 1944

Tukwila, King County

Status: Cleanup Started   Get definitions of Status terminology

Erin Hobbs
Site Manager
(425) 649-7231

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

Document Repositories:

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