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Investigation and Remedial Action Planning – Quinnipiac River

Southington, Connecticut

Services: Sediment & Ecosystems
Clients Served: Industrial

The site, which was formerly a large-scale overhaul and repair facility in Southington, Connecticut, is located along the banks of the Quinnipiac River. Loureiro conducted a phased characterization investigation of river bottom sediments. The predominant contaminant identified was nickel. The nickel contamination was primarily confined along the southern bank of the river downstream of the former outfalls.

Pore water sampling was performed through the placement of equilibrators to assess the bioavailability of nickel. The data obtained on the pore water and sediment indicated that natural geochemical factors were resulted in low metal solubilities. The majority of nickel in the sediments was in the form of inert solid phases, most predominantly of which is bulk nickel metal. Other nickel phases were in the form of non-bioavailable precipitates, which are expected to remain insoluble in the future. A benthic survey was performed utilizing upstream and downstream reference stations to evaluate the condition of the benthic macroinvertebrate community. Each experimental station was found to have physical habitat characteristics that were comparable to the reference station and were unaffected by the metals contamination present.

While the data indicated no discernable impact, the presence of nickel in bottom sediment at concentrations above ecological benchmarks was a concern to the regulatory agency and remedial action was being required. Loureiro negotiated a remedial action goal utilizing statistical analysis wherein sediment exhibiting concentrations in excess of 4 times the remedial action goal were the target. Using this approach, the existing dataset was the basis for the remedial action and we successfully demonstrated confirmatory sampling was not necessary.

As the work was to be performed in the Quinnipiac River, a myriad of permits or approvals were necessary. Prior to initiation of work, Loureiro completed permit and approval applications and successfully negotiated the authorizations from the following agencies: State of Connecticut Commission on Culture & Tourism, Town of Southington Conversation Commission and Planning and Zoning Department, State of Connecticut Department of Energy and Environmental Protection, and the Army Corps of Engineers. The remediation project was implemented by Loureiro Contractors, Inc.


  • Performance of comprehensive characterization of river bottom sediments including pore water sampling to demonstrate bioavailabity and benthic survey of the macroinvertebrate community.
  • Successful use of statistical analysis in the development of remedial action objective
  • Successful negotiation with the State of Connecticut for a remediation approach where confirmatory sampling was not necessary
  • Evaluation of numerous remediation alternatives to address sediment impacts.
  • Successful negotiation of 7 individual permits or approvals from 5 different regulatory agencies with jurisdiction over the project