Seven wells had no detections of the short list of VOCs: FO-22, I10-2, I10-5, JW-9, JW-29, RFR-6, and RFR-7.

PCE concentrations decreased in December 2003 in wells JW-30, LS-2, LS-3, LS-7, OFR-1, and RFR-11. These decreases ranged in magnitude from 0.04 mg/L (JW-30) to 0.63 mg/L (LS-2).

TCE concentrations decreased in wells LS-3, LS-5, and RFR-10. These decreases ranged from 0.03 mg/L (LS-3) to 1.82 mg/L (RFR-10).

PCE concentrations increased in wells JW-7, JW-26, LS-1, LS-6, OFR-2, OFR-3, RFR-3, RFR-10, and RFR-12. The increases ranged from 0.07 mg/L to 1.73 mg/L in OFR-3. December 2003 was the first time that target VOCs were detected in RFR-3.

TCE concentrations increased in wells LS-2, LS-6, OFR-3, RFR-11, and RFR-12. The increases ranged from 0.04 mg/L (RFR-12) to 1.46 mg/L (OFR-3).

No new wells were added to the quarterly monitoring in December 2003.

Historical off-post detections of chloroform have rarely been above the RL. The detections that have occurred do not correlate with those wells which have exceedances of the MCL for PCE or TCE, the COCs at CSSA. Chloroform is a common disinfection by-product and laboratory contaminant. For the December 2003 event, chloroform was detected above the RL at concentrations ranging from 0.13 �g/L to 53.0 �g/L in three of the twenty-nine wells that were sampled.

In accordance with Plan requirements, wells with historical detections above 90 percent of the applicable MCL (LS‑2, LS-3, LS-6, LS-7, OFR‑3, RFR-10, and RFR‑11) will continue to be sampled on a quarterly basis, including the upcoming March 2004 event. Prior to GAC installation, these wells were sampled on a monthly basis. Because a GAC system has been installed, the wells will be sampled quarterly.

Wells with detections above 80 percent of the applicable MCLs are required to be sampled on a monthly basis in accordance with the Plan. No wells sampled during the December 2003 event will be sampled monthly. All wells with VOC detections greater than 80 percent of the applicable MCLs have GAC filtration systems installed and are already included in the quarterly monitoring.

Wells with detections of VOCs at less than 80 percent of the MCLs (FO-J1, HS-2, I10-2, JW-7, JW-8, JW-14, JW-26, JW-28, JW-29, JW-30, LS-1, LS-2, LS-4, LS-5, OFR-1, OFR‑2, RFR-3, and RFR-12) in December 2003 will continue to be sampled on a quarterly basis, including the March 2004 event in accordance with Plan requirements. Depending on concurrence by regulatory agencies, the sampling frequency may then be reduced.

Post-GAC confirmation samples will be collected at all off-post wells with GAC systems during the March 2004 sampling event. This will include wells LS-2, LS‑3, LS-6, LS-7, OFR‑3, RFR-10, and RFR-11.

For future sampling events, including March 2004, wells where no VOCs were detected may be sampled as needed. December 2003 wells with no VOCs detected include FO-22, I10-2, I10-5, JW-9, JW-29, RFR-6, and RFR-7.

In the event additional wells are located to the west and southwest of CSSA, they may be added to future sampling events. 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 they meet drinking water standards.

In accordance with project DQOs, the rationale for selection of wells to be sampled in March 2004 is provided in Table 4.1.