Frequently Asked Questions

What is the East Waterway Cleanup?

The East Waterway is one of the most active commercial waterways in the Pacific Northwest, supporting shipping and water-based industries. Most vessel traffic consists of shipping container vessels and tugboats.

In addition, the East Waterway serves ecological functions as a deep-water estuary at the mouth of the Duwamish River. It is part of the Muckleshoot Indian Tribe’s and Suquamish Tribe’s usual and accustomed area, with treaty-protected uses including a commercial fishery for salmon as well as ceremonial and subsistence uses. The general public also fishes the waterway from the Spokane Street Bridge.

The East Waterway is part of the larger Harbor Island Superfund Site. The cleanup area stretches one mile and covers 157 acres. It is located immediately downstream and north of the Lower Duwamish Waterway Superfund Site, along the east side of Harbor Island.

Who is the East Waterway Group?

The East Waterway Group, or EWG, is composed of three public entities: the City of Seattle, Port of Seattle and King County. The EWG has worked collaboratively under the direction of the U.S. Environmental Protection Agency (EPA) since 2006 to collect hundreds of sediment, tissue and water samples; perform human health and ecological risk assessments; perform sediment transport modeling; and develop and compare potential cleanup actions for addressing contaminated sediment.

Why is the East Waterway being cleaned up?

The East Waterway is being cleaned up due to unacceptable risks to human health and to the environment. Sediments at the bottom of the waterway contain contaminants that include polychlorinated biphenyls (PCBs), arsenic, dioxins/furans and carcinogenic polycyclic aromatic hydrocarbons (cPAHs) that pose risk to human health. There are 29 contaminants, including PCBs and mercury, which pose risks for benthic invertebrates that are the base of the food chain. PCBs also pose risk to fish within the waterway.

What are the sources of contamination?

Most of the sediment contamination in the East Waterway is from historical releases during more than 100 years of industrial and commercial activity along and upstream of the waterway.

The Port, City and the County have spent decades reducing sources of contamination and continue to take actions in the storm water drainage system, and to control combined sewer overflows, to further reduce contamination.

What remediation option is EPA proposing?

EPA’s Preferred Alternative would actively remediate 121 acres of the East Waterway. It includes dredging 99 acres of contaminated sediment in the open water portions of the East Waterway and capping 7 acres in the nearshore areas, which may require some dredging to accommodate navigation and habitat elevation requirements. EPA’s Preferred Alternative also includes placement of approximately 3 acres of a 9-inch Enhanced Natural Recovery layer under the Spokane Street, West Seattle, and railroad bridges and placement of in situ treatment for contaminated sediments on over 12 acres of limited access in under-pier areas. The remaining 36 acres of the East Waterway would be addressed through Monitored Natural Recovery. Contaminated dredged materials will be transported to a landfill for disposal.

The EWG supports EPA’s Preferred Alternative of a modified version of Alternative 3B(12) as the cleanup remedy for the East Waterway. EPA’s Preferred Alternative provides for a comprehensive sediment cleanup that will substantially reduce risks to human health and the environment. The Preferred Alternative achieves this through active remediation of the vast majority of the waterway, most of which is by removal actions, followed by natural recovery for the rest of the waterway. This will result in a substantially cleaner urban waterway that will continue to be a backbone of our regional economy while also playing a significant role in improving ecological function of the Green/Duwamish Watershed.

Monitoring will be conducted during construction to ensure construction meets design requirements. Monitoring will also occur after construction to measure the remedy’s performance and effectiveness.

How much will the cleanup cost?

Based on EPA’s Proposed Plan, the Preferred Alternative is estimated to cost $290 million. However, costs presented in the Proposed Plan are in 2016 dollars (as calculated in the Feasibility Study); therefore, today’s cost of the cleanup is higher. For example, using a standard national inflation index, $290M becomes $370M in 2022 dollars.

How long will it take to complete this cleanup?

As outlined in the Feasibility Study, clean up alternatives would take 3-5 years to design. As outlined in the Proposed Plan, construction is estimated to take 10 years, assuming a 4.5-month in-water work window each year. The in-water work window is in place to reduce the risk of impacts to salmon at sensitive life stages.

Will the cleanup affect shipping and trade activities?

The cleanup may affect shipping and trade activities. As is customary with cleanups in other areas, and to the extent possible, activities will be scheduled to allow shipping and trade activity to continue.

How will the cleanup affect fish and wildlife?

The Preferred Alternative outlined in the EPA’s Proposed Plan will protect fish and wildlife and will substantially reduce risk to human health. It should be noted that the Washington State Department of Health currently advises people not to eat resident fish and shellfish caught in the Lower Duwamish Waterway and the East Waterway.

After the cleanup, there will be extensive monitoring to confirm that the remediation is performing as designed. This monitoring data will be used by the Washington State Department of Health to re-evaluate seafood advisories.

What’s next?

The public comment period on the EPA’s Proposed Plan is closed. The EPA will finalize its decision on the East Waterway cleanup after considering public comments received on the plan. The EPA will respond to public comments in a Responsiveness Summary in the anticipated Record of Decision (ROD).