The PCE concentration in Well LS-7, located near the southwestern corner of CSSA and downgradient of the Building 90/AOC 65 source area, continued an overall increasing trend during this monitoring event. The PCE concentration increased from 4.0 mg/L in June 2001 to 4.5 mg/L in September 2001. These concentrations were approaching the PCE MCL and triggered installation of a GAC filtration system. The TCE concentration in LS-7 remained below the RL at 0.43 mg/L in June 2001 but increased to 0.81 mg/L in September 2001, which is above the MDL but still below the RL and MCL.

Well RFR-10 had PCE concentrations of 14.0 mg/L and TCE concentrations of 7.5 mg/L, both of which are above the MCL. CSSA immediately responded in accordance with the Plan by supplying bottled water and evaluating RFR-10 for a GAC filter treatment system. The GAC filtration treatment system was installed in October 2001.

Wells I10-2, RFR-10, JW-14, LS-6, and LS-7 had low concentrations of PCE and/or TCE above the MDL, but below the RL and less than 90 percent of the laboratory MCL. These wells should be retained for future quarterly sampling events, including the December 2001 quarterly sampling event.

Wells DOM-2, FO-22, FO-J1, JW-12, JW-13, JW-6, JW-9, RFR-6, RFR-7, RFR-8, and RFR-9 did not have any VOC concentrations detected above the MDL. These wells should be re-evaluated for possible sampling depending on the needs of the groundwater investigation and project DQOs. Most of these wells should be removed from the December 2001 quarterly sampling list so that additional off-post private wells can be tested to the southwest and west of AOC 65, where the lateral extent of the contaminant plume has not been sufficiently delineated.