Facility Site ID: 2218 Cleanup Site ID: 1944

Current Status - February 2024

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We held a public comment period from November 2023 - January 2024 on a Remedial Investigation and Feasibility Study. 

View a summary of the most recent comment period, the comments we received, and our responses here.

Documents available for review and comment during the most recent comment period:

Download the fact sheet to read a summary of the latest information about this cleanup site.

Learn more about this cleanup and others along the LDW! Join us at Community Office Hours - new in 2024! 

View the office hours schedule.

We are offering monthly community office hours in 2024 at different locations in Georgetown and South Park. Drop-in to talk with cleanup site managers, outreach, and technical staff about the Lower Duwamish Waterway cleanup. Phone interpretation available in Spanish, Chinese, Vietnamese, and Khmer. All ages welcome!

Site Information

Aerial view of the Site in relation to the historic and current path of the Duwamish River.
Aerial view of the Site in relation to the historic and current path of the Duwamish River.

Site background

The Boeing Isaacson Thompson cleanup site is located in an industrial area of Tukwila on the east bank of the Lower Duwamish Waterway (LDW). The cleanup site is comprised of two properties owned by The Boeing Company and one property owned by the Port of Seattle. 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 early 1900s. After dredging, the area was used as farmland and then for a variety of industrial purposes. The former Duwamish River channel (later Slip 5) in the middle of the site was filled over time with contaminated materials from unknown sources.

The Isaacson Property (northern portion)

  • Prior to 1945: The Mineralized Cell Wood Preserving Company used a solution of arsenic and sulfate salts of copper and zinc to treat lumber. Sludge and chemicals remaining in the tanks were reportedly drained directly to the ground during tank cleaning. 
  • 1984: Boeing purchased the 9.84-acre property from Isaacson Steel Company, which had owned the property since 1943.

The Port of Seattle Property (northwestern portion)

  • 1960s: A wall, called a bulkhead, was built along the LDW and filled to reclaim about 50 ft of land between the waterway and the Isaacson property. This ½-acre parcel of land is owned by the Port of Seattle.

The Thompson Property (southern portion) 

  • 1920s-1930s: Bissel Lumber Company operated on the property. 
  • 1930s-1966: The inlet partially dividing the Isaacson and Thompson property, called Slip 5, was filled in over time with contaminated materials including smelter slag and fire brick material. 
  • 1956: Boeing purchased the 19.35-acre property.

Nearby cleanup sites and source control information

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.

Investigating contamination (Remedial Investigation)

A variety of soil and groundwater investigations occurred at this Site from 1983 through 2009.  In 2010, Boeing and Ecology entered into an Agreed Order which required Boeing to perform a Remedial Investigation and Feasibility Study and to develop a Cleanup Action Plan for the Site. Boeing conducted the Remedial Investigation between 2011 and 2012. It focused on further investigating soil, groundwater, soil vapor, storm drain solids, stormwater, and sediment at the Site to adequately understand the locations and types of contamination. The investigation also looked at the Site’s potential for recontamination of the sediments in the LDW. The table at the bottom of the webpage lists the contaminants found at this Site. 

Consider options (Feasibility Study)

To address the contamination found at the Site, Boeing prepared a Feasibility Study, which evaluated five different cleanup alternatives. The costs and environmental benefits of the alternatives were then compared, leading to a preferred cleanup alternative.

Cleanup Alternatives

  • Alternative 1: Containment and Hydraulic Control via Capping and Groundwater Extraction
  • Alternative 2: Containment and Hydraulic Control via Capping and Vertical Barrier
  • Alternative 3: In Situ Groundwater Treatment, Containment, and Shoreline Excavation 
  • Alternative 4: Focused Excavation and Containment, and In Situ Groundwater Treatment
  • Alternative 5: Site-Wide Excavation of Contaminated Soil

Preferred Cleanup Alternative: Alternative 3

Alternative 3 consists of the following activities:

  • In Situ Treatment: This type of treatment uses physical, biological, and/or chemical mechanisms to transform or destroy specific contaminants. At this Site, a Permeable Reactive Barrier is being planned to treat groundwater contamination. First, a trench will be excavated and backfilled with engineered materials that are reactive with Site contaminants. Then, as contaminated groundwater flows through these materials, the contaminants will break down and/or be trapped in place, preventing them from flowing into the LDW. 
  • Excavation: Contaminated soil will be removed from the Port property between the waterway and permeable reactive barrier alignment, and in the Observed Tar-Like Substance area (Shown in Figure 2).
  • Bulkhead replacement: The wooden bulkhead on the Port of Seattle’s property will be replaced with a new steel bulkhead or other engineered shoreline that will be stabilized or armored to protect against erosion. The bulkhead along the Boeing Thompson property may be replaced at a different time as part of a separate infrastructure project. 
  • Containment: Pavement at the Site will be maintained or repaired to provide a barrier, called a cap, to prevent human contact with contaminated soil and groundwater. The cap will also limit precipitation/stormwater from coming into contact with contamination in the ground. This will help keep contamination from moving into the LDW.
  • Institutional controls: Legal or administrative measures will be put in place to restrict or prohibit activities that could result in exposure to contaminants that are above acceptable health risk levels or interfere with the integrity of the cleanup action. 
  • Long-term groundwater monitoring: The groundwater will be monitored to make sure the cleanup alternative continues to protect the LDW. 
Cleanup actions planned for the Boeing Isaacson Thompson Site include In Situ treatment, excavation, and bulkhead replacement.
Cleanup actions planned for the Boeing Isaacson Thompson Site include In Situ treatment, excavation, and bulkhead replacement.

Site Details

8701 E. Marginal Way S., Tukwila, WA
8701 E. Marginal Way S., Tukwila, WA

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 a remedial investigation, feasibility study, and cleanup action plan. As of February 2024, we are finalizing the remedial investigation and feasibly study and working on the draft Cleanup Action Plan. This document and a future legal agreement will be available for review during a future public comment period in 2024.

Why this cleanup matters

This Site is along the Lower Duwamish Waterway Superfund Site, which consists of a 5-mile stretch of the Duwamish River. The U.S. Environmental Protection Agency (EPA) added the LDW Superfund Site to the Superfund National Priorities List in 2001. Ecology is working to stop or reduce sources of contamination to the LDW Superfund Site, an effort known as “source control,” so that the EPA can proceed with the cleanup of the river sediment. Although this site is located in the Upper Reach, the area of the river that will begin sediment cleanup as early as 2024, the sediments adjacent to the Site have been deferred to align with the uplands cleanup to ensure the sources are sufficiently controlled.

General Cleanup Process

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.
Legal 1
Document Title Document Date Document Type
Boeing Isaacson Thompson - Final Agreed Order 4/23/2010 Agreed Order
Public Information 7
State Environmental Policy Act 1
Document Title Document Date Document Type
Boeing Isaacson Thompson Final SEPA Checklist CAP 12/13/2023 SEPA Documents
Technical Reports 15
Document Title Document Date Document Type
Feasibility Study Report, Final – For Public Review, Appendix A, Isaacson-Thompson Site Tukwila, Washington 7/5/2023 Feasibility Study
Feasibility Study Report, Final – For Public Review, Isaacson-Thompson Site Tukwila, Washington 7/5/2023 Feasibility Study
Boeing Isaacson Thompson - Port of Seattle Sliver Data Summary Report 11/12/2015 Site Specific Technical Document - other
Boeing Isaacson Thompson - Final - For Public Review - Remedial Investigation Report (2 - Appendices) 4/21/2014 Remedial Investigation Report
Boeing Isaacson Thompson - Final - For Public Review - Remedial Investigation Report (1 - Text, Tables, Figures) 4/21/2014 Remedial Investigation Report
Boeing Isaacson Thompson - Final RI/FS Work Plan 9/16/2011 Remedial Investigation Work Plan
Boeing Isaacson Thompson Initial Investigation Report—LUST 2557 4/14/2011 Initial Investigation Report
Boeing Isaacson Thompson - Property Boundary Investigation 9/9/2009 Remedial Investigation Report
Boeing Isaacson Thompson - Data Summary Report - Appendix B 9/2/2009 Site Specific Technical Document - other
Boeing Isaacson Thompson - Data Summary Report - Appendix A 9/2/2009 Site Specific Technical Document - other
Boeing Isaacson Thompson - Data Summary Report 9/2/2009 Remedial Investigation Report
Boeing Isaacson Thompson - Independent Action Redevelopment Update 3/29/2009 Site Specific Technical Document - other
Boeing Isaacson Thompson - Site Hazard Assessment 8/1/2008 Site Hazard Assessment Report
Boeing Isaacson Thompson - Investigation Building 14-09 Data Report 5/4/1988 Site Specific Technical Document - other
Boeing Isaacson Thompson - Evaluation of Potential Soil and Groundwater Contamination 12/21/1983 Site Specific Technical Document - other
There may be more documents related to this site. To obtain documents not available electronically, you will need to make a public records request.

Places to see print documents

  • Northwest Regional Office
    15700 Dayton Ave N
    Shoreline, 98133
    Please schedule an appointment to view print documents at this location.

Contaminants 11

Contaminant Type
Soil
Groundwater
Surface Water
Air
Sediment
Bedrock
Metals - Metals - Other C C
Halogenated Organics - Polychlorinated biPhenyls (PCB) C C
Non-Halogenated Organics - Polycyclic Aromatic Hydrocarbons C
Halogenated Organics - Halogenated Solvents C
Metals - Arsenic C C
Metals - Lead C
Metals - Mercury C C
Non-Halogenated Organics - Other Non-Halogenated Organics C
Non-Halogenated Organics - Petroleum-Diesel C
Non-Halogenated Organics - Petroleum-Gasoline C
Non-Halogenated Organics - Petroleum-Other C
S
Suspected
C
Confirmed Above Cleanup Levels
B
Below Cleanup Levels
RA
Remediated-Above
RB
Remediated-Below
R
Remediated
This contaminant list was based on our best information at the time it was entered. It may not reflect current conditions at the site.