The hydrogeology is a low permeability glacial till over a shale system characterized by shallow depths to ground water and a moderately low average linear ground water flow velocity. The seasonally high water table condition occurs immediately following melt off of the snow pack in the early spring and results in depths to water in monitoring wells of less than two feet below ground surface.
Targeted Environmental Media:
 Dense Non-aqueous Phase Liquids (DNAPLs) - Fractured Bedrock
A shallow plume 200' by 400'.
Major Contaminants and Maximum Concentrations:
- Tetrachloroethene (10,000 µg/L)
No technologies selected.
No technologies selected.
Comments:
A PRB was installed during 2001 to treat ground water impacted by PCE and its decay products. Monitoring of water levels subsequent to construction of the wall has revealed and anomalous ground water sink in the vicinity of the western edge of the PRB. One effect of the sink is the formation of longitudinal flow paths within the PRB. Although there is some variation between monitoring events, the PRB has also received inflows from areas presumed to be both upgradient and downgradient to the wall. The longitudinal flow paths within the PRB and the transient discharge of ground water to the PRB across its presumed upgradient and downgradient boundries both appear to be created by the ground water sink around the sewer.
Containment by plum treatment
Water quality data indicate that the wall has been effective in treating ground water. VOCs are rarely, if ever detected within the wall despite continued detectable concentrations in the former source area upgradient of the PRB. The longitudinal flow paths are apparently extending the residence time of impacted ground water within the wall further enhancing the system's overall effectiveness.
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