Frequently Asked Questions

A remedial action is the steps taken to clean up contamination found at a site.

At the Terminal 115 Plant 1 Site, remedial actions are overseen by the Washington State Department of Ecology under the Model Toxics Control Act.

A remedial investigation involves collecting data to understand the types, volumes, and severity of contamination at a site and where that contamination is located.

A feasibility study explores options for removing or containing contamination and compares the outcomes, costs, and impacts of each cleanup alternative.

The final Remedial Investigation/Feasibility Study document is used by the Washington State Department of Ecology to create a draft Cleanup Action Plan, which identifies the selected cleanup alternative and describes the plan for remediation.

For this type of fieldwork, crews collect soil samples by driving hollow rods into the ground with a drill machine. Samples are taken from the removed soil to test for contamination at different depths.

Groundwater monitoring wells are installed using a sonic drill and water is pumped out for sampling. At Terminal 115, testing for groundwater contamination was performed in both shallow and deep wells.

Fish and wildlife are not impacted by this type of fieldwork.

The team collected samples of groundwater and soil at locations across the site in 2024 and 2025 to collect information on site conditions and fill data gaps from previous studies. These samples were sent to a laboratory to test for the presence of a range of chemicals and metals.

The Washington State Department of Ecology has developed standard cleanup levels. Any substances the lab finds at concentrations less than those cleanup levels are considered safe for human health and the environment. Any found with concentrations greater than those cleanup levels must be remediated.

During the remedial investigation process, the team will use the data collected to create a map showing the types and extent of contamination at the site and begin planning any required cleanup activities.

The results of the remedial investigation will indicate if cleanup is needed. The Port of Seattle and the Boeing Company will work with the Washington State Department of Ecology to make this decision.

In any remedial investigation, there is a possibility there is no contamination found, or only low levels that are within the acceptable range for human and environmental health. In this case, no further actions would be required.

Depending on the specific situation at the site, remedial actions might include work such as removing contaminated soil and replacing it with clean fill, capping or covering contamination to create a barrier between the contamination and human use, treating groundwater to remove contamination, or other types of cleanup methods.

The T-115 Site is next to the lower section of the Lower Duwamish Waterway, which is a U.S. Environmental Protection Agency (EPA)-designated Superfund Site.

Remedial actions on the T-115 Site align with cleanup work in the Lower Duwamish Waterway because they include efforts to control sources of pollution from potentially draining to the Superfund Site. This is part of Washington State Department of Ecology’s Lower Duwamish Waterway Source Control Strategy.

A comprehensive cleanup plan for the Lower Duwamish Waterway Superfund Site is in progress. Cleanup is scheduled to take place over the next decade, beginning in the upper reach and progressing downstream through the middle and lower sections.

Both the Port of Seattle and the Boeing Company are supporting the EPA and Department of Ecology with cleanup efforts along the Duwamish Waterway.

The goal of source control is to minimize or stop the spread of contamination from existing sources. This is done by locating and removing existing contamination and creating management and safety standards to reduce the potential for new contamination.

The formal cleanup project is currently funded by the Port of Seattle and the Boeing Company. The Washington State Department of Ecology is also providing grant funding through the Remedial Action Grant Program. 

Yes, there will be opportunities to engage with the project team during public meetings or via email throughout the project.

The Washington State Department of Ecology will hold Public Comment Periods for the draft Remedial Investigation/Feasibility Study and draft Cleanup Action Plan before documents are finalized. All public comments submitted during these comment periods will be included in a project summary report that the Washington State Department of Ecology creates.

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