Harbor Island is a 420-acre island located in the Duwamish River delta in Elliott Bay in the City of Seattle, Washington. The man-made island was constructed on the Duwamish River delta with the addition of bulkheads and fill placed in the early 1900s.
The Harbor Island site has evolved from an industrialized upland area into a complex cleanup site involving both the upland area and the offshore sediment. Contaminated media included soils, sediments, and groundwater.
Cleanup for the various Operable Units (OUs) of the site has included contaminated soil removal and upland capping, dredging of contaminated sediment, capping contaminated material that remains in place, enhanced natural recovery, and groundwater monitoring. The cleanup goals are defined in the various Harbor Island formal decision documents (Records of Decision (RODs), Explanations of Significant Differences (ESDs), and state Cleanup Action Plans (CAPs)) for each OU.
The site is heavily industrialized and is expected to remain industrialized in the future. There are currently no residences on the island. The entire island and associated sediments are designated as the Superfund site.
The site is not yet "construction complete." Ongoing activities include long-term groundwater monitoring, IC implementation, cap inspections and maintenance, and design and construction of air sparging and soil vapor extraction systems in the Tank Farm OU. Additionally, a supplemental remedial investigation and feasibility study is underway at the East Waterway OU.
The Harbor Island Site began as an investigation of a secondary lead smelter located on the island. The distribution of lead and other metals occurred over the entire island and, therefore, the investigation became island-wide.
Operable Units (OUs)
After the investigation began, it was realized that creating separate "Operable Units," or OUs, would be advantageous for managing the cleanup processes. The following is a list of the operable units in current use:
- Soil and Groundwater OU (S&G-OU1)
- Tank Farms OU (TF-OU2)
- Lockheed Upland OU (LU-OU3)
- Lockheed Shipyard Sediments OU (LSS-OU7)
- West Waterway Sediments OU (WW-OU8)
- Todd Shipyards Sediments OU (TSS-OU9)
- East Waterway Sediments OU (EW-OU10)