EPA Issues Woonasquatucket River Cleanup Decision (USA)

EPA has selected its cleanup plan for addressing contaminated sediment, soil, surface water and groundwater at the Centredale Manor Restoration Project Superfund Site in North Providence, R.I.

Residents living along the Woonasquatucket River, recreational visitors, including anglers, and construction workers as well as wildlife are potentially exposed to site contamination and these exposures may present an unacceptable human health or ecological risk. EPA’s selected cleanup plan will prevent direct contact with contaminated soil and sediment that presents an unacceptable risk; allow fish consumption from and contact and additional non-contact recreational use of the Woonasquatucket River; prevent movement of contaminants into the Woonasquatucket River that could result in exceedances of water quality criteria; comply with federal drinking water standards at the Source Area; and reduce risk to wildlife.

Dioxins and Polychlorinated Biphenyals (PCBs) are the most wide-spread contaminants found at the site; other contaminants include furans, metals, volatile organic compounds, semi-volatile organic compounds, and pesticides.

The cleanup actions will address the contaminated sediment, soil, surface water and groundwater, and the overall protectiveness of the cleanup will be assessed at least every 5 years. The selected cleanup plan generally requires:

• Removal and off-site treatment and/or disposal of buried waste material from the Source Area (where contamination releases originally occurred) and installation of a Resource Conservation and Recovery Act (RCRA) Subtitle C cap over remaining contamination in the Source Area;

• Excavation of the majority of contaminated Woonasquatucket River sediment and floodplain soil in the Allendale and Lyman Mill reaches of the River and placement into an upland Confined Disposal Facility (CDF) with off-site treatment and/or disposal of dewatered sediment and floodplain soil that have the highest contamination levels;

• Placement of soil cover over the remaining contamination in the Oxbow to facilitate enhanced natural recovery and preserve valuable habitat;

• Implementation of Institutional Controls to prevent exposure and preserve the integrity of components of the selected cleanup plan and long-term monitoring and maintenance to protect the integrity of the RCRA cap, upland CDF, Allendale Dam and thin-layer wetland cover; and

• Mitigation of wetlands and floodplains.

Two changes were made to EPA’s proposed cleanup plans after considering the comments received during the two formal comment periods:

1. EPA continues to believe the upland Confined Disposal Facility disposal option –with the highest levels of contaminated material taken off-site for treatment– is the best approach to address contaminated sediment/soil; however, EPA has expanded the area where an upland CDF could be located to beyond what is in close proximity to the site, including locations outside the Town of Johnston. With this expansion, EPA believes a location can be identified that addresses most or all of the concerns raised by the public.

2. In response to concerns about the effectiveness of the proposed alternative, the selected cleanup plan for the Oxbow Area was modified and expanded to allow for additional removal of contaminated soil and sediment.

The R.I. Dept. of Environmental Management has concurred with the selected cleanup plan.

EPA will soon begin a mediation process with a number of the potentially responsible parties for performance of the cleanup work. The estimated cost for this cleanup is $104 million. EPA will work closely with the towns of North Providence and Johnston, interested citizens, and state officials as the project progresses.

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Press Release, October 11, 2012