NPL Site Remedial Design for Municipal Water Supply Wausau, Wisconsin


Chlorinated solvent spills at a bulk chemical station and seepage from an abandoned municipal landfill had contaminated soils and a shallow aquifer. The depth to the aquifer, the primary drinking water supply for the city of Wausau, Wisconsin, was only 10 feet from the major source area of contamination. Hydro Geo Chem was retained to:

      • develop a conceptual design for a soil vapor extraction (SVE) system,
      • calculate performance standards for the SVE system, and
      • present design to EPA and State of Wisconsin.

    Hydro Geo Chem's Approach

    Predesign field investigations included soil-gas surveys, soil permeability surveys, and SVE pilot tests. Based on the results, numerical models of alternative system configurations were developed and used to optimize the system design. In addition, a vadose zone mass-flux model was created and used to calculate performance standards for the SVE system. The model considered aqueous-phase VOC transport from the vadose zone into the aquifer. Model results were used to negotiate final clean-up standards. Complicating remedial design was the proximity of the shallow aquifer and municipal water supply to the source of contamination. The SVE system was designed to minimize water entrainment and maximize sweeping efficiency through the use of a proprietary SVE well configuration.


    Hydro Geo Chem provided technical support, represented the client and potentially responsible parties before regulatory agencies, and represented the client at a news conference involving both television and print media. Our final design was accepted by EPA and by the State of Wisconsin. Closure was achieved within the time frame predicted by the numerical simulations.

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