All objectives listed in Table 1.1, Sampling Rationale for March 2003, were accomplished. All wells scheduled to be sampled for the March event were sampled.

Twenty-two wells reported detections of VOCs in March 2003. Of the wells with VOC detections, two wells had concentrations above the MCL for PCE and/or TCE. Wells RFR-10 and RFR-11 had detections of PCE above the MCL of 5.0 �g/L and well RFR-10 had a detection of TCE above the MCL of 5.0 �g/L. Both of these wells were previously equipped with GAC filtration systems.

Eight wells had detections of VOCs reported at concentrations above the RL for one or more of the following analytes: PCE, TCE, chloroform, dichlorodifluoromethane, dibromochloromethane, methylene chloride, and toluene. Chloroform was detected in JW-14, JW-14-NP, and LS-1; PCE in LS-2, LS-3, LS-6, LS-7 and OFR-3; TCE and dichlorodifluoromethane in OFR-3; toluene in JW-14-NP; and dibromochloromethane in LS-1. Toluene is believed to be associated with tape used to secure sample labels to the bottles. Wells LS-2/LS-3, LS-6, LS‑7, and OFR-3 were previously equipped with GAC filtration systems.

Twenty-one wells reported concentrations of VOCs above the MDL, but below the RL (F-flagged) for one or more of the following analytes: bromodichloromethane, bromoform, PCE, TCE, cis-1-2-dichloroethene, chloroform, and toluene. These analytes were detected in wells FO-17, FO-8, FO-J1, HS-2, I10-2, JW-9, JW-26, JW-30, LS-1, LS-2, LS-3, LS-4, LS-5, LS-6, LS-7, LS-7-NP, OFR-1, OFR-2, RFR-10, RFR-11 and RFR-12.

PCE concentrations decreased in March 2003 in wells HS-2, JW-14, LS-1, LS-2, LS-3, LS-5, LS-6, LS-7, OFR-2, OFR-3, RFR-10, and RFR-11

TCE concentrations decreased in wells I10-2, LS-1, LS-2, LS-5, LS-6, LS-7, RFR-11, and RFR-12.

PCE concentrations increased in wells I10-2, JW-26, OFR-1, and RFR-12.

TCE concentrations increased in wells LS-3 and RFR-10.

In the March 2003 event, post-GAC confirmation samples were collected from wells equipped with GAC filtration systems (LS-2, LS-3, LS-6, LS-7, OFR-3, RFR-10, and RFR-11). The results from post-GAC sampling confirm that the wellhead treatment systems are reducing VOCs to below the applicable MCLs for drinking water. Detections occurring in post-GAC samples in March 2003 were: PCE at a concentration of 0.07 mg/L in RFR-11 and toluene at concentrations of 0.07 mg/L in RFR-11, 0.12 �g/L in RFR-10, 0.52 �g/L in LS-7-A2, 0.86 �g/L in LS-2/LS-3-A2. Toluene is believed to be associated with tape used to secure sample labels to the bottles.

Comparison of samples collected with and without prior purging shows that concentrations were similar in two wells; however at LS-7, the non-purged sample had a reduced concentration of PCE.

Wells with detections above 90% 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 June 2003 event in accordance with Plan requirements.

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

Wells with detections of VOCs at less than 80% of the MCL (FO-8, FO-17, FO-J1, HS-2, I10-2, I10-4, JW-9, JW-14, JW-14-NP, JW-26, JW-30, LS-1, LS-4, LS-5, LS-7-NP, OFR-1, OFR-2, and RFR-12) will continue to be sampled on a quarterly basis, including the June 2003 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 September 2003 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 June 2003, wells where no VOCs were detected may be sampled as needed. March 2003 wells where no VOCs were detected, which can be sampled annually, include DOM-2 and I10-7.

If, in the future, additional wells are located to the west and southwest of AOC‑65, 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 June 2003 is provided in Table 4.1.

Toluene-free tape will be used to secure sample labels to sample bottles during future groundwater monitoring events.