Facility Site ID: 49919 Cleanup Site ID: 15139

  • Site Status

  • Cleanup Started

Current Status

Aerial map of Duwamish Waterway Park, 2021
Aerial map of Duwamish Waterway Park, 2021
Last Updated:  November 2022

Site Hazard Assessment

Washington State Department of Ecology (Ecology) has completed a Site Hazard Assessment (SHA) for the site. Ecology’s purpose in conducting an SHA is to identify the hazardous substance(s) and environmental characteristics associated with the site. In addition, Ecology evaluates the potential threat to human health and the environment, assigning a rank from 1 to 5, with 1 being most hazardous and 5 being the least. The rank is relative to other assessed sites in Washington. An SHA was conducted at this site on October 10, 2022, and it was assigned a rank of 2.


Agreed Order
Ecology is in the process of drafting and negotiating an Agreed Order with the Potentially Liable Persons (PLPs). The Agreed Order is a legal document that requires the PLPs to address contamination at the site.

Why This Site Matters

View of Lower Duwamish Waterway
View of Lower Duwamish Waterway
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. 

General Cleanup Process

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.
Click image to enlarge
Click image to enlarge

What Happens Next?

Ecology is moving the Site into the formal MTCA process. Notification letters have been issued to PLPs and negotiations to enter into an Agreed Order are underway.

Site Information

View of Lower Duwamish Waterway from Duwamish Waterway Park, August 2022
View of Lower Duwamish Waterway from Duwamish Waterway Park, August 2022
Location
The Duwamish Waterway Park (Site) is located 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.  

Duwamish Waterway Park - Voluntary Cleanup Program: July 2020 Through May 2022

Duwamish Waterway Park playground area, September 2022
Duwamish Waterway Park playground area, September 2022
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 (Parks) 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 Parks in August 2020 to draft our opinion letter.  Parks 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 Parks 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 Parks 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. 
Legal 3
Document Title Document Date Document Type
DWP Final PLP Status Letter 10/19/2022 Final Potentially Liable Person Status Letter
Duwamish Waterway Park Addition - Early Notice Letter 12/21/2021 Early Notice Letter
Duwamish Waterway Park - Early Notice Letter 2/5/2020 Early Notice Letter
Technical Reports 25
Document Title Document Date Document Type
Duwamish Waterway Park - SHA Rank Letter 10/28/2022 Site Specific Administrative Document - other (Administrative correspondence)
Duwamish Waterway Park - Site Hazard Assessment 10/10/2022 Site Hazard Assessment Report
Duwamish Waterway Park - SHA Notification Letter 6/15/2022 Site Specific Administrative Document - other (Administrative correspondence)
Duwamish Waterway Park—NW3279 Draft RI/FS Workplan 4/26/2022 Remedial Investigation Work Plan
Duwamish Waterway Park—NW3279 Remedial Investigation Report Version 3 Additional Information 10/8/2021 Remedial Investigation Report
Duwamish Waterway Park—NW3279 Email Correspondence RI V3 Request for Additional Information 10/8/2021 Site Specific Administrative Document - other (Administrative correspondence)
Duwamish Waterway Park—NW3279 Soil Sampling Report Park Bench Sliver Area 9/30/2021 Site Specific Technical Document - other
Duwamish Waterway Park—NW3279 Email Correspondence Confirmation Sampling Questions 9/29/2021 Site Specific Administrative Document - other (Administrative correspondence)
Duwamish Waterway Park Addition - Initial Investigation Field Report 9/14/2021 Initial Investigation Report
Duwamish Waterway Park—NW3279 Project Meeting, Progress, Next Steps Sept07 2021 9/7/2021 Progress Report
Duwamish Waterway Park—NW3279 Remedial Investigation Report Version 3 Appendices 8/20/2021 Remedial Investigation / Feasibility Study
Duwamish Waterway Park—NW3279 Remedial Investigation Report Version 3 8/20/2021 Remedial Investigation / Feasibility Study
Duwamish Waterway Park Addition - Phase II ESA Soil Sampling Report 6/24/2021 Site Specific Technical Document - other
Duwamish Waterway Park—NW3279 Project Meeting, Progress, Next Steps Mar22 2021 3/22/2021 Progress Report
Duwamish Waterway Park—NW3279 Project Meeting, Progress, Next Steps Jan27 2021 1/27/2021 Progress Report
Duwamish Waterway Park—NW3279 Email Correspondence Preliminary Feedback 4 10/30/2020 Site Specific Administrative Document - other (Administrative correspondence)
Duwamish Waterway Park—NW3279 Email Correspondence Preliminary Feedback 3 10/8/2020 Site Specific Administrative Document - other (Administrative correspondence)
Duwamish Waterway Park—NW3279 Email Correspondence Preliminary Feedback 2 9/15/2020 Site Specific Administrative Document - other (Administrative correspondence)
Duwamish Waterway Park—NW3279 Email Correspondence Preliminary Feedback 1 8/10/2020 Site Specific Administrative Document - other (Administrative correspondence)
Duwamish Waterway Park—NW3279 Terrestrial Ecological Evaluation form 7/1/2020 Terrestrial Ecological Evaluation
Duwamish Waterway Park—NW3279 Remedial Investigation Report 6/23/2020 Site Specific Technical Document - other
Duwamish Waterway Park - Initial Investigation Field Report 1/28/2020 Initial Investigation Report
Duwamish Waterway Park - March 2019 Soil Sample Results 3/1/2019 Site Specific Technical Document - other
Duwamish Waterway Park - January 2019 Soil Sample Results 1/28/2019 Site Specific Technical Document - other
Duwamish Waterway Park - July 2014 Soil Sample Results 7/20/2014 Site Specific Technical Document - other
Voluntary Cleanup Program 3
Document Title Document Date Document Type
Duwamish Waterway Park—NW3279 VCP Termination letter 9/21/2022 VCP Administrative Document
Duwamish Waterway Park—NW3279 VCP Opinion Letter 10/27/2021 VCP Opinion on Site Cleanup – Other
Duwamish Waterway Park—NW3279 Electronic VCP Application Acceptance Package 7/15/2020 VCP Administrative Document
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.
  • South Park Branch / Seattle Public Library
    8604 Eighth Avenue South
    Seattle, 98108
    This location may only have print documents available during open comment periods.

Contaminants 8

Contaminant Type
Soil
Groundwater
Surface Water
Air
Sediment
Bedrock
Metals - Metals - Other C S S
Halogenated Organics - Polychlorinated biPhenyls (PCB) C S S
Non-Halogenated Organics - Polycyclic Aromatic Hydrocarbons C S S
Metals - Arsenic C S S
Metals - Lead C S
Metals - Mercury C S S
Halogenated Organics - Other Halogenated Organics C S S
Non-Halogenated Organics - Other Non-Halogenated Organics C S S
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.