Of the 20 wells sampled, 17 reported detections of VOCs. Of these detections, two wells reported concentrations above the MCL. Wells RFR-10 and RFR-11 had detections of PCE above the MCL. 

Of the 17 wells with detections of VOCs, ten wells reported results that were above the MDL, but below the RL (F-flagged) for one or more of the following analytes, bromodichloromethane, chloromethane, dibromochloromethane, dichlorodifluoro-methane, cis-1-2-dichloroethene, 4-isopropyltoluene (p-cymene), and methylene chloride.

Seven wells had detections at concentrations above the RL for one or more of PCE, TCE and chloroform. PCE was detected above the RL in all seven wells, two of which were above the MCL (RFR-10 and RFR-11). TCE was detected above the RL in two wells, but not above the MCL. Chloroform was detected above the RL in three wells, but not above the MCL.

PCE concentrations decreased in September 2002 in wells FO-J1, LS-1, LS-6, LS-7, OFR-2, OFR-3, and RFR-10, but PCE concentrations increased in HS-2, I10-2, LS-2, LS-3, LS-4 and RFR-11.

TCE concentrations decreased in September 2002 in wells LS-2, LS-6, OFR-3, RFR-10, and RFR-11.

Post GAC confirmation samples were collected in September 2002 from wells with GAC treatment systems installed (LS-2, LS-3, LS-6, LS-7, OFR-3, RFR-10, and RFR-11). The results from post-GAC sampling confirmed that the wellhead treatment systems are removing VOCs to non-detectable levels in the drinking water. 

All objectives listed in Table 1.1, Sampling Rationale for September 2002, were accomplished. All wells scheduled to be sampled for the September event were sampled. 

Wells HS-2, I10-2, JW-14, LS-4, LS-5, OFR-1, OFR-2 and RFR-12 had low concentrations of PCE, TCE, chloroform, chloromethane, bromodichloromethane, dibromochloromethane, dichlorodifluoromethane, isoproppyltoluene-4-(cymene, p-), and/or cis-1,2-DCE above the MDL, but below the RL, and less than 80 percent of the laboratory MCL. 

Wells with detections that approached or exceeded MCLs (OFR-3, RFR-10, RFR-11, LS-2, LS-3, LS-6, and LS-7) will continue to be sampled and monitored on a quarterly basis, including the December 2002 event, until they meet DQO requirements of four consecutive quarterly events with no detection of contaminants. Depending on concurrence by regulatory agencies, the sampling frequency may then be reduced.

Based on the Plan these wells should be retained for future quarterly sampling events, including the December 2002 event, until they meet DQO requirements of four consecutive quarterly events with no detection of contaminants. Depending on concurrence by regulatory agencies, the sampling frequency may then be reduced.

OFR-1 reported a �B� flag for methylene chloride. The analyte was recovered in the sample as well as the associated blank. The parent sample results for the analyte was flagged �B� per the AFCEE QAPP. No additional corrective action was necessary since each well represents a unique sample matrix. 

Post-GAC confirmation samples will be collected at all off-post wells with GAC systems during the March 2003 sampling event. This will include LS-2, LS-3, LS-6, LS-7, OFR‑3, RFR-10, and RFR-11. 

For future sampling events including December 2002 wells where no VOCs were detected may have a reduced sampling frequency. Additional wells located to the west and southwest of AOC-65 may be added to future sampling events. For the December 2002 event, a new well (I10-5) will be sampled if access to the well is received from the well owner. Future sampling events will continue to include wells to the west of CS-D and CS-MW16-LGR (Fair Oaks and Jackson Woods) to confirm any detections. 

In accordance with the Plan, post-GAC confirmation samples will be collected every six months. The next scheduled event for post-GAC sampling is March 2003.

The rationale for recommending wells to be sampled in December 2002 is provided in Table 4.1.