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Hazardous Waste Cleanup: Boeing Plant 2, Tukwila, Washington

EPA accepted public comments on the Corrective Measures Study and Statement of Basis from June 17 through August 1, 2019. EPA will consider all comments received regarding the proposed corrective action and the Statement of Basis in making our final corrective action decision. If you have questions, please contact RCRA Project Coordinator Dave Bartus (, 206-553-2804.

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Site History and Cleanup Status

Boeing Plant 2 is located on the east bank of the Duwamish Waterway in Seattle and Tukwila, Washington.

Plant 2 was built in the late 1930s and was a major aircraft manufacturing facility during World War II. PCBs from transformers and related electrical equipment, as well as from paints, caulk, and hydraulic fluids were released at Plant 2 and into the Lower Duwamish Waterway. A wide range of other hazardous chemicals are found in certain areas of soil and groundwater, including metals, cyanide, petroleum products, and chlorinated solvents.

When the Lower Duwamish Waterway became a Superfund site, several "hot spot" areas of sediment contamination were targeted for cleanup before the larger Superfund cleanup could proceed. Boeing Plant 2 is one of these hot spot cleanups, also called Early Action Areas, or EAAs.

The Boeing Plant 2 is a Resource Conservation and Recovery Act (RCRA) hazardous waste facility. Metals, solvents, PCBs and other contamination remain in certain areas of the facility. The Boeing Company is under a RCRA Order from EPA to investigate and clean up Plant 2.

Boeing completed cleanup of sediments (mud) and shoreline soils next to the facility in 2015. They removed 163,000 cubic yards of sediment and replaced it with clean soil. Boeing continues to monitor the quality of the sediment at the site as required by the post-construction monitoring plan.

In the upland area of the facility, Boeing completed the majority of interim soil cleanups and installed stormwater treatment systems to prevent contaminants from entering the waterway. Boeing is addressing groundwater contamination through interim measures that reduce the source of contaminants and by monitoring a series of shoreline wells.

Boeing provided EPA with their plan to complete cleanup at the remaining uplands areas, including final corrective actions for areas where interim measures have been completed. EPA accepted comments on the Corrective Measures Study as well as EPA’s tentative decision, known as a Statement of Basis, from June 17 through August 1, 2019.

The Corrective Measures Study considers a number of cleanup methods to complete cleanup of soils and groundwater in the uplands area of the facility. Final proposed remedies documented in the Statement of Basis include enhanced reductive dechlorination (ERD), ERD and excavation with off-site disposal, excavation with off-site disposal, and bioventing. In addition to these specific remedial technologies, EPA is also proposing long- and short-term groundwater monitoring, as well as engineering and institutional controls. EPA proposes to use an adaptive management strategy where additional data or revisions to a cleanup approach may be needed.

Boeing has also prepared a draft environmental covenant and a pavement and subsurface management plan that will ensure the proposed remedies, when finalized, are fully protective of human health and the environment.

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Site Description

Uplands Source Control Corrective Measures

Uplands source control work is focused on nine remediation areas, and on associated groundwater. The various remediation areas are described below:

RA 1 – 2-10 North Sheetpile Area: RA 1 is in the paved industrial area within the 2-10 Building, with a small portion extending into the unpaved shoreline area below the 2-10 Building overhang. The original source of contamination to soil and groundwater at RA 1 was a TCE degreaser. RA 1 has been the subject of several IMs. Areas of groundwater with chlorinated VOC (cVOC) concentrations exceeding proposed FMCLs were identified as the primary issue in RA 1.

RA 2 – 2-10 South Sheetpile Area: RA 2 is in the paved industrial area within the 2-10 Building with a small portion of the RA extends into the unpaved shoreline area below the 2-10 Building overhang. The original source of contamination to soil and groundwater at RA 2 was a TCE degreaser. RA 2 has been the subject of several interim measures. Areas of groundwater with cVOC concentrations exceeding proposed FMCLs were identified as the primary issue in RA 2.

RA 3 – 2-31 Area: RA 3 is an area previously covered by a portion of the 2-31 Building that was demolished as part of the 2010-2012 demolition/redevelopment project and extends a bit into the Plant 2 stormwater management area. The original source of contamination to soil and groundwater at RA 3 was a TCE degreaser, which was located within the footprint of the un-demolished portion of the 2-31 Building, and TCE supply piping that was removed in 2011. Areas of groundwater with cVOC concentrations exceeding proposed FMCLs were identified as the primary issue along with the presence of crushed concrete used to backfill tunnel excavations and placed above the water table in this area during the 2010-2012 demolition/redevelopment project.

RA 4 – 2-66 Sheetpile and Surrounding Area: RA 4 encompasses the 2-66 paved industrial area and unpaved shoreline area and the western portion of the 2-60 paved industrial area. It consists of groundwater with COC concentrations exceeding the proposed FMCLs for cVOCs, BTEX (benzene, toluene, ethylbenzene, xylene) and naphthalene as surrogates for TPH, various metals, cyanide, gasoline-range petroleum hydrocarbons (GRPH), diesel-range petroleum hydrocarbons (DRPH), and PCBs. The original sources of cVOC contamination at RA 4 are believed to have been a TCE degreaser and a leaking TCE storage tank that was decommissioned in the late 1980s.

RA 5 – South Yard Area: RA 5 is an area within the paved industrial area along the southern boundary of Plant 2 (see Figure 2). The area contains groundwater with concentrations of cVOCs, BTEX as surrogates for TPH, arsenic, zinc, and DRPH that exceed their proposed FMCLs. In soil, PCBs and motor-oil-range petroleum hydrocarbons (MoRPH) are the only constituent groups detected in RA 5 at concentrations greater than the proposed FMCLs. The main source of cVOCs in RA 5 were cisterns and contaminated soil which have been removed or excavated, respectively.

RA 6 – OA 18 Area: RA 6 is an area within the greater paved industrial area that is centered on RCRA Unit OA 18 and includes the Building 2-40 East Parking Lot Area (see Figure 2). The primary issue in RA 6 is the presence of SVOCs, total petroleum hydrocarbons (TPH), naphthalene, and cyanide in soil at concentrations greater than their respective proposed FMCLs.

RA 7 – Unpaved Shoreline Area: RA 7 is the unpaved shoreline area located to the west of the paved industrial area and adjacent to the habitat restoration area that runs along most of the length of Plant. North of the South Park Bridge, RA 7 consists of the unpaved shoreline area fronting the LDW, the habitat restoration area, and Slip 4. South of the bridge, RA 7 fronts the LDW. From 2010 through 2012, Boeing completed a demolition and redevelopment project - as part of the redevelopment project, stormwater bioswales and stormwater treatment vaults were installed in the unpaved shoreline area. The primary issue in RA 7 is the presence of TCE, GRPH, DRPH, and MoRPH in soil in the stormwater area at concentrations exceeding proposed soil FMCLs (TMCLs for TPH).

RA 8 – Paved Industrial Area: RA 8 includes all portions of the paved industrial area not contained within the other RAs. RA 8 is primarily covered by concrete and asphalt paving, buildings, parking, roadways, and small landscape strips. A large portion of the paved industrial area south of the bridge was remediated as part of the 2010-2012 demolition/redevelopment project referenced above during which impacted soil was removed and tunnel excavations were backfilled above the water table with crushed concrete. The backfill contains residual PCBs and other contaminants. The primary issue in RA 8 is the presence of groundwater exceedances associated with cVOCs, benzene, naphthalene, arsenic, copper, zinc, nickel, cyanide, and PCBs.

RA 9 – OA 11 Area: This area includes both former Building 2-72 and the former fenced West Bank Substation due to the presence of PCBs, TPH, and inorganics in soil and groundwater. Subsequent investigations defined the geographic extent of PCBs in OA-11 present in the transformer area on Plant 2 and a small portion of the neighboring Jorgensen Forge property. Remediation of the OA-11 area has been completed as a stand-alone Focused Corrective Measures Study (FMCS). Under this process, investigation and remediation of the area was completed in various phased through September 20, 2016. Additional characterization work focusing on remaining contamination on the neighboring Star Forge, LLD property (formerly the Jorgensen Forge property) was completed in the spring of 2017. Boeing has finalized its plan to compete corrective action at the remaining uplands sites, including final corrective actions where interim measures have been completed or are underway.

Sediments and Shoreline Soils

In August 2011, EPA released a Final Decision and Response to Comments for the cleanup of the sediments and shoreline at Boeing Plant 2. Boeing began implementation of the sediment cleanup in January 2013, completing this work over three construction seasons in 2017.

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Contaminants at this Facility

General classifications of Contaminants Constituents of Concern (COCs) that require corrective actions for soil or groundwater include polychlorinated biphenyls (PCBs), inorganics (metals), volatile organic carbons compounds (VOCs), semi-volatile organic compounds (SVOCs), and petroleum hydrocarbons.

Based on currently-available data, certain constituents have been detected but cannot be conclusively eliminated as constituents of concern requiring corrective action, Bis(2 ethylhexyl) phthalate (BEHP), cadmium, nickel, and free cyanide have data or analytical issues, but are retained as COCs for groundwater with specific additional sampling and data evaluation requirements to determine if they will remain COCs (refer to the CMS Volume X, Section 2.2 and Attachment S2B). These constituents are addressed through short term monitoring or an adaptive management approach within the context of corrective measures, as described in greater detail in the SB.

Arsenic, copper and zinc are COCs in groundwater but are generally the result of geochemical conditions in the groundwater associated with VOC contamination in soil. As discussed further in the SB, as geochemical conditions in soils and groundwater return to more normal conditions as corrective measures for organics progress, the impact of these COCs on groundwater is expected to diminish. Subject to obtaining the advanced approval of EPA, an Adaptive Management approach will be used if these metals persist above the applicable cleanup levels in groundwater.

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Institutional and Engineering Controls

Soil cleanup levels have been developed based on the long-held understanding that Plant 2, located in the industrial corridor of Seattle, is and will remain an industrial facility and that Boeing would place an environmental covenant on the site deed to document and ensure this current and future land use. Proposed Final Media Cleanup Levels (FMCLs) have been developed that engineering and institutional controls will include, but not be limited to pavement maintained to reduce infiltration and direct contact with soil, and restricted access to industrial areas.

The following assumptions are made in the development of soil FMCLs:

  • The site will remain an industrial facility with the industrial areas of the site remaining under controlled access.
  • The industrial areas of the site will remain paved and/or covered by buildings with slab-on-grade foundations. In Volume X, the industrial area is referred to as the paved industrial area.
  • The area along the shoreline will consist of unpaved, landscaped areas that transition to the North and South Habitat Areas built in from 2012 through 2015. This unpaved area has limited access and is referred to in Volume X as the unpaved shoreline area.

Engineering controls include pavement or buildings over the entire facility except for the unpaved shoreline area to reduce infiltration and prevent direct contact with underlying soils. Institutional controls will include restrictive covenants for each of the parcels comprising the Plant 2 facility, and a Pavement and Subsurface Management Plan that will ensure that the selected remedies remain protective during routine non-cleanup-related constructive activities.

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Land Reuse Information

The Boeing Plant 2 facility is, and is expected to remain, an industrial facility in active use. FMCLs for soil at the facility are protective of this current and future land use. EPA will require Boeing to establish institutional controls in the form of environmental covenants for the various parcels that comprise the Plant 2 facility.

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Regulatory Authority

RCRA Corrective Action

Corrective action at Plant 2 is being conducted under the authority of the Resource Conservation and Recovery Act (RCRA) § 3008(h). The governing document is the 1994 Administrative Order on Consent, RCRA Docket # 1092-01-22-3008(h).


Given the presence of PCBs, cleanup of this site is also subject to the requirements of the Toxic Substances Control Act. EPA has issued several cleanup approvals for various phases of work at Plant 2, including building demolition, sediment cleanup, and soil cleanup. Most of these approvals have been in the form of risk-based disposal approvals under authority of 40 Code of Federal Regulations §761.61(c). For copies of PCB approvals supporting the Plant 2 cleanup, contact Julie Congdon, 206-553-2752.

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Community Involvement Plan: Community Involvement Plan for Lower Duwamish Waterway Cleanup (including Boeing Plant 2)(PDF)(88 pp, 17 MB, October 2016). Outlines how, when and where EPA will provide information the public needs to understand our work, and how the community can be actively involved in the cleanup process.

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