Gas Works Park

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Last Updated July 2023

2023 fact sheet

2023 Response to Comments

From June 20 – July 20, 2023, Ecology invited review of a cleanup action plan and associated documents for the cleanup of remaining contamination at the Gas Works Park site. The plan calls for removing and capping shoreline soil, treating shoreline groundwater, dredging sediment, capping sediment, monitoring, and administrative site use controls.

The plan is part of a legal agreement between Ecology, the City of Seattle (City), and Puget Sound Energy (PSE).

The following documents were available for review:   

• Cleanup Action Plan: describes Ecology’s selected cleanup action to address remaining contamination.
• Consent Decree (legal agreement): requires the City and PSE to develop detailed design documents and construct the cleanup action described in the cleanup action plan.
• State Environmental Policy Act-Determination of Non-Significance: Ecology determination that the cleanup action is not likely to have a significant adverse environmental impact.

Next Steps
Ecology has reviewed and considered the public comments received on the documents, and no edits to the documents are necessary.  Ecology is finalizing the documents.

From 2023 – 2027, engineering design and permitting will continue, including additional investigations and evaluations to refine the cleanup action and enable detailed design work. Construction is planned to begin in 2027.

The Gas Works Park site consists of two units, a 21-acre Upland Unit and a 56-acre in-water Sediment Unit.  Multiple previous cleanup actions have addressed contamination in the Upland Unit, except for bank soil and arsenic-contaminated groundwater along the shoreline.

Sediment throughout the Sediment Unit is contaminated.  

Contaminants present are from former upland industrial operations and include polycyclic aromatic hydrocarbons, arsenic, nickel, carbazole and dibenzofuran.  Additional contaminants associated with other sources in Lake Union are also present in 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.

• June 20 - July 20, 2023:  Public comment period
• June 28, 2023:  Online public meeting (Download presentation PDF)
• Fall 2023: Public comments addressed, and cleanup action plan finalized
• 2023 to 2027: Engineering design and permitting, including additional investigations and evaluations to refine the cleanup action and enable detailed design work
• 2027: Begin construction

Current Gas Works 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.

Background
Formerly territory occupied by three indigenous communities (the Duwamish, Hachooabsh, and Shilsholes), the area surrounding the northern portion of Lake Union was settled by non-natives in the mid- to late 1800s. In 1907, construction of a manufactured gas plant was completed on the upland area of the Gas Works Park site to supply fuel for the growing population of Seattle. The plant operated until 1956.  Other industries (e.g., tar refining, bulk fuel storage, shipbuilding) also historically operated in the upland area.  These past industrial activities resulted in contamination of soil, groundwater and sediment.
Contamination in the upland area has been largely addressed through multiple cleanup actions completed between 1971 and 2020.  

Location
The Gas Works Park site is located at 2101 N Northlake Way, Seattle, Washington on Lake Union. It consists of approximately 21 upland acres (Upland Unit) and approximately 56 in-water acres (Sediment Unit). 

The City of Seattle owns the majority of the Upland Unit and the State of Washington owns the majority of the Sediment Unit.