Duwamish Waterway Park

Last Updated:  October 2024

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Blog | "Cleaning Up: Fieldwork starting in the Duwamish Waterway Park” (Oct. 28, 2024)

Comments | Response Summary

Cleanup moves forward with Remedial Investigation
Sampling fieldwork will begin in November 2024. You can expect to see a small drill rig, support vehicles, and staff working as we sample the soil, groundwater, surface water, and sediment in the riverbed.

We’ll use the results of our sampling to understand what and where the contaminants are, as well as how they might affect human health, plants, and wildlife. We’ll compile this information into a report called a remedial investigation, which will help us to evaluate possible options for cleaning up the contamination.

Community Outreach
Ecology held a 45-day public comment period (January 30 – March 15, 2023) on a Public Participation Plan and a legal agreement called an Agreed Order with the City of Seattle, the Potentially Liable Person, for the Duwamish Waterway Park cleanup site at 7900 10th Avenue South in Seattle. The Agreed Order requires the City to address contamination at the site. 

Ecology has reviewed and considered the public comments received on the documents and will finalize both documents. 

Based on Ecology’s evaluation of the comments, no updates were made to the Agreed Order. 

Ecology has also reviewed and considered the comments on the Public Participation Plan (PPP) and based on public comments regarding the Duwamish Valley community, Ecology will continue to refine our public outreach planning.

Ecology will finalize the PPP. We will continue to evaluate the community’s use of our adjusted LDW site outreach planning for future comment periods and will amend the PPP, as needed, based on community engagement. 

The Duwamish Waterway Park is continuing the cleanup process. Ecology will make the future Remedial Investigation, Feasibility Study, and Cleanup Action Plan available for public review and comment.

See Response Summary for details.

The Duwamish Waterway Park site is adjacent to the Lower Duwamish Waterway Superfund Site, which includes 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. 

The Model Toxics Control Act (MTCA) 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.

Ecology will consider all comments received during this public comment period and may make changes to the Agreed Order or Public Participation Plan. If the documents require significant changes, we will hold another public comment period. 

If no significant changes are made, Ecology will finalize the documents and the City will proceed with the Remedial Investigation, Feasibility Study, and create a Draft Cleanup Action Plan for public review.

Each of those steps will require a public comment period. The graphic above shows these different stages of cleanup. Sometimes multiple stages occur in one public comment period.

Current Duwamish Waterway Park cleanup site Public Participation Plan

This plan includes information for the public regarding opportunities to get involved in the Site cleanup process. The outreach activities and mechanisms presented reflect Ecology’s current plans for keeping the public informed and for receiving information and comments from the public. 

Location
The Duwamish Waterway Park is on the west side of the Lower Duwamish Waterway (LDW) in the South Park neighborhood of Seattle. The site is approximately 1.7 acres and includes a play area, picnic area, and beach with river access. Seattle Parks and Recreation owns and manages the park.

Site discovery and Initial Investigation
Preliminary soil investigations occurred at the site in 2014 and 2019, documenting soil contamination of lead and arsenic.  Ecology was notified of the discovery of contamination in spring of 2019, and an Initial Investigation was completed in January 2020.  During the Initial Investigation, Ecology evaluated environmental conditions at the property and reviewed all available data. The goal of the Investigation was to determine if the release may pose a threat to human health or the environment, and if further cleanup actions are needed.  Ecology tracks any site that is suspected or confirmed to be contaminated with hazardous materials, as required by the state’s cleanup law, the Model Toxics Control Act (MTCA), created by a 1989 voter initiative.

Ecology’s Confirmed and Suspected Contaminated Sites List
Following the Initial Investigation process the site was listed on the Confirmed and Suspected Contaminated Sites List in February 2020.  

The Voluntary Cleanup Program (VCP) enables owners of contaminated sites to meet state cleanup standards under MTCA independently and to receive technical guidance from Ecology during the process.  The VCP enables owners to work on a contractual basis rather than under an Ecology legal order.  Participants in the VCP pay fees to Ecology to cover the department’s costs for guidance and review.  VCP sites must meet the same cleanup standards as properties formally managed by Ecology under MTCA.

In July 2020 City of Seattle Parks and Recreation (SRP) entered into the VCP (VCP Project Number NW3279) and requested a review and opinion on a Remedial Investigation (RI) of the Duwamish Waterway Park in July 2020.  Ecology requested additional information from SRP in August 2020 to draft our opinion letter.  SRP started renovation work at the site in October 2020.  Ecology received a revised RI in August 2021 which included additional information on interim actions.  Interim actions at the site included selective soil excavation, removal, and replacement with clean fill; construction of concrete pathways, placement of vegetation and laying of sod material, and installation of various capping technologies throughout the park.   

In October 2021, Ecology’s issued an opinion letter to SRP for the independent interim cleanup actions at the site.  The opinion letter documented several concerns about the potential impacts to human health and the environment.  Ecology’s opinion also described several information gaps regarding the components of an RI and Feasibility Study (FS)—site characterization and the establishment of cleanup standards for the selection and implementation of a cleanup action under MTCA.  Ecology’s opinion offered guidance and a path forward for SRP to address contamination at the site under MTCA, with the potential goal for a No Further Action determination.  

After Ecology’s opinion letter, SPR conducted beach sampling independently and agreed to address Ecology’s information gaps identified in the Opinion letter by drafting and seeking Ecology’s opinion on an RI/Feasibility Study (FS) work plan.  In April 2022 Ecology received SPR’s draft RI/FS workplan. 

Based upon the findings of the draft RI/FS workplan and the growing complexity of the Site cleanup, Ecology decided to terminate the VCP project and move the Site into a formal process under an Agreed Order.  Under the formal process, Ecology will have more oversight over the cleanup than the independent VCP cleanup process, including consistent and proactive community involvement and outreach.