AQUA TERRA Consultants
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Modeling Study of PCB Contamination in the Housatonic River, MA


  • U.S. EPA Office of Water,Office of Science and Technology,Washington, DC
  • U.S. EPA Region I, Boston, MA
  • Weston Solutions, Inc., West Chester, PA
  • Since 1998, AQUA TERRA's principals and staff have been involved in a modeling study of PCB contamination in the Housatonic River in western Massachusetts. Initial work efforts focused on the development of a modeling framework to represent the fate, transport, and bioaccumulation of polychlorinated biphenyls (PCBs) within the river system. PCBs historically were released to the Housatonic River from the General Electric facility in Pittsfield, MA. Over a period of decades, starting in the 1930s, these compounds have accumulated in the river's bed and floodplain sediments and impoundments both in Massachusetts and further downstream in Connecticut. As part of a comprehensive agreement among the various governmental agencies and GE, signed in 1998, EPA is conducting detailed modeling of PCB fate, transport, and bioaccumulation to support both human health and ecological risk assessments from PCB exposures in the area.

    AQUA TERRA supported EPA's efforts in this investigation by developing the integrated modeling framework to address both current conditions and projected impacts of alternative future conditions, including a 'no-action' alternative and various remediation measures. Since the study is designed to support EPA's regulatory decision-making related to a major remediation effort, the production of scientifically-defensible results is mandated.

    The primary study area (PSA) extends from the confluence of the East and West Branches of the River below Pittsfield, MA to the Woods Pond Dam, a distance of approximately 10 miles; the contributing watershed area extends an additional 24 miles downstream to the USGS gage at Great Barrington, MA, with a total drainage area of 282 square miles. A modeling framework was needed because no single model is capable of representing all the physical, chemical, and biological processes critical to PCB fate, transport, and bioaccumulation over the wide range of spatial and temporal scales needed to address the contamination issue. To support the exposure and risk assessment efforts, the PCB modeling involves Total PCBs, and selected congeners.

    AQUA TERRA Consultants directed the development of the initial modeling framework design (MFD) involving three separate, but linked, component models to represent the watershed loadings, hydrodynamics, sediment transport, water quality and bioaccumulation processes needed to analyze the historical and current PCB contamination in the Housatonic River system. A team of modeling experts in these disciplines was assembled to meet the challenges of the study. The watershed analysis is being performed by AQUA TERRA using the U. S EPA Hydrological Simulation Program - FORTRAN (HSPF); the results obtained from using HSPF quantify the hydrologic and sediment source loadings from the contributing watershed to the river segment. HydroQual will perform instream modeling of sediment and PCB fate and transport using the Environmental Fluid Dynamics Code (EFDC), and EVS Environmental will use the outputs of the HSPF and EFDC models to simulate PCB bioaccumulation and uptake using an aquatic food chain model FCM.

    The project has demonstrated several innovative software tools and capabilities designed and/or used by AQUA TERRA Consultants to facilitate watershed modeling. Development of the watershed model involved the use of the following modern computational techniques: model segmentation, land use, soils-related parameters, and precipitation patterns were developed \ characterized from a Geographic Information System; the hydrology calibration was performed using an "Expert Advisor" program designed for HSPF by the U.S. Geological Survey and Visual Basic scripts to automate calibration output; The Housatonic watershed model is operated by an interactive graphical interface ("Scenario Generator") that facilitates simulation of the calibrated model to represent a range of scenarios. The interface includes a map of the basin and capabilities to modify the model inputs, execute the model, and display graphical and statistical results.

    A pilot application on a test reach located in the primary study area was performed to develop and test the model linkage components between and among HSPF, EFDC and FCM. The pilot application produced a sound methodology for linking the models. Concurrent with the hydrology and sediment calibration for the entire watershed, AQUA TERRA is working jointly with the other modeling groups to fully implement the linkage of HSPF with the EFDC and FCM models. The linked modeling system will be used to calibrate to current/historical conditions, assess historical PCB accumulation over time, and project impacts of alternative future conditions, including remediation needs and plans.

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