The East Waterway, an operable unit of the Harbor Island Superfund Site in Seattle, Washington, is one of the most active commercial waterways in the Pacific Northwest. After more than 20 years of study, the U.S. Environmental Protection Agency is proposing a cleanup remedy for this 1.5-mile-long (2.4-kilometer-long), 157-acre (63.5-hectare) waterway. The remediation of large, complex, urban contaminated sediment sites presents a unique set of technical and administrative challenges. This paper presents the key challenges for implementing cleanup, including: 1) controlling recontamination during dredging in an active waterway that may take up to 10 years to complete; 2) cleaning up 12 acres (4.9 hectares) of sediment in limited-access underpier areas; and 3) understanding the unique physical processes that affect long-term site concentrations following cleanup. Because these three elements will substantially affect project performance, they must be considered during remedial design and construction efforts.
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