Comprehensive Remedial Investigation/Feasibility Study (RI/FS)

EHS Support is leading a comprehensive Remedial Investigation/Feasibility Study (RI/FS) of a 280-acre explosives manufacturing facility as part of the New York State Superfund Program (SSF). As a result of historical site operations, waste disposal or discharges occurred within an approximately 100-acre main plant area and an approximately 50-acre area in and around a wetland and stream complex to the east of the main plant area. Primary constituents of concern associated with site-related wastes include mercury, inorganics (metals), volatile organic compounds (VOCs), and energetic materials. The scope of the RI includes multi-media investigations of upland soil and groundwater quality, including overburden and bedrock groundwater investigations, and investigations of surface water and sediment quality in streams and wetlands.

As part of the RI, a New York State Department of Environmental Conservation (NYSDEC) Fish and Wildlife Resources Impact Analysis (FWRIA) is being conducted to evaluate potential site-specific ecological effects on fish and wildlife resources associated with exposure to mercury and other metals within the on-site wetland and stream complex and downstream areas. In addition to characterizing the nature and extent of site-related constituents, the multi-pathway FWRIA includes key investigation elements to assess the site-specific bioavailability and toxicity of mercury and other metals:

  • Sediment quality triad (SQT): An SQT investigation integrating sediment chemistry, sediment toxicity testing data, and benthic community analyses was designed and implemented to evaluate potential impacts to benthic invertebrate communities exposed to sediments within the wetland and stream complex.
  • Biological tissue sampling and analysis: Mercury and other metals were analyzed in benthic invertebrate and fish tissue samples collected within the stream and wetland complex to evaluate bioaccumulation pathways to benthic invertebrates and fish, and dietary exposure to semi-aquatic wildlife.

Investigations were also conducted downstream of the wetland and stream complex to characterize the potential off-site transport and deposition of mercury and other metals in sediments and floodplain soils. Based on substrate mapping and systematic sediment delineation sampling, a conceptual site model was developed to describe the migration and disposition of mercury and other metals in sediments within the off-site stream reach. Based on this conceptualization, a phased FWRIA investigation, that includes an SQT assessment and biological tissue sampling, is being implemented to evaluate the site-specific bioavailability and toxicity of mercury and other metals in off-site sediments. In addition to instream investigations, concentrations of mercury and other metals were systematically characterized in floodplain soils in the off-site reach using an elevation-based sampling design to represent variable flood frequencies and potential overbank transport and deposition.

The findings of the FWRIA conducted as part of the RI/FS will support the development of a Proposed Remedial Action Plan (PRAP) that will recommend protective remedial alternatives to mitigate ecological risks, if identified, in on-site or off-site exposure areas. The conceptual remedial approach for the site includes the construction of an on-site consolidation unit to manage contaminated soils and sediments, and to minimize the disturbance of potentially energetic wastes within an existing landfill. The conceptual ecological restoration approach includes re-alignment of the stream and wetland complex to divert flows away from the consolidation unit and the restoration of wetland and riparian habitats along the re-aligned channel. The efficiencies gained by on-site consolidation of soils and sediments requiring remediation are projected to provide major operational and cost savings during construction.

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