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Investigation and Alternatives Evaluation

East Hartford, Connecticut

Services: Sediment & Ecosystems
Clients Served: Industrial

The site, which is the location of an industrial wastewater treatment facility in East Hartford, Connecticut, is located along the banks of the Connecticut River and Willow Brook, a tributary to the Connecticut River. Loureiro conducted a phased characterization investigation of bottom sediments within Willow Brook. The predominant contaminants identified were semi-volatile organic compounds. Other contaminants including petroleum hydrocarbons, metals, and polychlorinated biphenyls were also identified.

Loureiro performed numerous in-stream sampling events with each event building from the data from the prior event. The outcome of the efforts was the development of a defensible conceptual model regarding contaminant sources and contaminant fate and transport within the system. The conceptual model had to accommodate the significant impacts associated with the reworking of the majority of the channel during the construction of Connecticut Route 2 in 1959. Once the distribution of contamination was adequately defined, Loureiro lead a team of experts in the development of a defensible remedial action approach.

During the development of the remedial action approach, a detailed human health and ecological risk assessment was performed. The risk assessment involved the performance of foodweb modeling for both benthic invertebrates as well as higher trophic-level receptors. Metal bioavailability and risks to benthic invertebrates were estimated using US EPA's AVS/SEM method. Bioavailability and risks to benthic invertebrates of PCBs and PAHs were estimated using organic carbon normalization of data to account for binding to organic carbon in the sediment. While the risk assessment indicated impacts were within acceptable levels, the presence of contaminants in bottom sediment at concentrations above ecological benchmarks was a concern to the regulatory agency.

The proposed remedial action plan involves the excavation and offsite disposal of select areas of bottom sediment and the construction of an engineered control to address abutting floodplain soils. The engineered control consists of a high-density polyethylene geocell membrane filled with 1.5-inch minus gravel and topsoil /riprap that would be stable even under flooding conditions.

Highlights

  • Collection and analysis of over 200 samples to characterize the nature and three-dimensional extent of river bottom sediment impacts
  • Development of defensible conceptual site mode in a complex environment including significant reworking of bottom sediments and stream channel.
  • Involved in the performance of human health and ecological risk assessments utilizing AVS/SEM and OC normalization methods for estimating bioavailability and risk.
  • Use of statistical analysis in the development of remedial action objective.
  • Lead role in numerous technical presentations and discussions with regulatory agency.
  • Development and evaluation of numerous remediation alternatives to address sediment impacts.