Site Description
The Site is located along East Marginal Way on the east shore of the Lower Duwamish Waterway (LDW) on approximately 20 acres of property,. The Site address is 4525 Diagonal Avenue South, Seattle, Washington. The Site consists of 2 parcels owned and managed by the Port: the West Parcel (9 acres) and the East Parcel (11 acres). The East Parcel is currently leased to ConGlobal Industries. The primary activities on the ConGlobal lease property include container storage, repair, and chassis storage. The West Parcel is currently not occupied by a tenant but is used for material storage. A Port public access and habitat mitigation area (sbəq̓ʷaʔ Park and Shoreline Habitat) is located along the southern shoreline of the West Parcel, adjacent to the LDW.
Site History
Prior to the channelization of the Duwamish River in the early 1900s the Site was an undeveloped tidal marsh. In 1972 the City sold the property to Chiyoda Corporation International for construction of a chemical manufacturing plant. Chiyoda’s manufacturing plant was never constructed; however, Chiyoda did complete Site preparation work including dredging along the shoreline and removal of previously abandoned sewage treatment plant structures. Chiyoda also leased the property to the Army Corps of Engineers to store and treat approximately 10 million gallons of hydraulically dredged sediment slurry from the cleanup of a 1974 polychlorinated biphenyl (PCB) transformer fluid spill in the LDW.
The Port acquired the property from Chiyoda in 1984 and divided the property into two parcels in 1985. Chevron USA Products Company (Chevron) purchased the East Parcel from the Port in 1985 with plans to construct a petroleum distribution terminal. Chevron’s terminal was never constructed; however, Chevron did use the property to stockpile and land farm petroleum-contaminated soil. Chevron owned the East Parcel until 1992, when it was conveyed back to the Port.
The Port leased the West Parcel to Lafarge Cement Company for use as a bulk cement terminal from 1989 to 1998. In the early 1990s, the Port redeveloped the East Parcel for use as a container storage yard.
Contamination Issue
The Site is the historic location of one of the City’s first wastewater treatment plants, serving the residential and industrial areas of several south Seattle neighborhoods including SoDo, Beacon Hill and Georgetown. The plant closed in 1970, and their structures were demolished soon after; however, several acres of sewage sludge was left as fill across much of the Site. Following the plant closure, the Site supported a few other owners and site uses until the Port purchased the property in the 1900s. In 1996, the Port redeveloped the entire east parcel of the property into its current layout and use – off-dock container terminal storage and repair for empty shipping containers. The primary contaminants of concern are related mainly to the use of sewage sludge as fill, and include PCBs, heavy metals, and petroleum.
Why is the Port Doing this Cleanup?
The site’s history of industrial operations led to the significant contamination of the Site’s shallow soil and groundwater. This cleanup will not only protect human health for site and utility repair workers but also prevent recontamination of the adjacent waterway.
This cleanup is being conducted under an Administrative Settlement Agreement and Order on Consent (ASAOC) between the U.S. EPA and the Port of Seattle, City of Seattle, and King County. The ASAOC requires an Engineering Evaluation and Cost Analysis (EE/CA) investigation and report for the Site.
Status
The EE/CA investigation was completed in late 2024. We are currently working on the EE/CA report and expect to have that completed by the summer of 2026.
Contact Information
Roy Kuroiwa | Environmental Program Manager | [email protected]
Additional Resources
Visit the Terminal 108 project page for more information.
