The objectives listed in Table 1.1 were accomplished with the exception of one well. All wells scheduled to be sampled for the December event were sampled with the exception of HS‑1. This well has not been put online yet.

Twenty-one of the thirty-one wells sampled reported detections of VOCs in December 2004. Of the wells with VOC detections, two wells had concentrations above the MCL for PCE and/or TCE. Well RFR‑10 had a detection of 11.7 �g/L PCE, which exceeds the MCL of 5.0 �g/L. Well RFR‑10 also had a detection of TCE at a concentration of 5.55 �g/L, also above the MCL, and cis-1,2-DCE at a concentration 0.25 �g/L, below the RL. Well RFR‑11 has detections of PCE (5.32 �g/L) above the MCL of 5.0 �g/L, and TCE (0.58 �g/L) below the MCL. Both RFR-10 and RFR-11 were previously equipped with GAC filtration systems.

Five wells had detections of VOCs reported at concentrations below the MCL but above the RL for one or more of PCE and TCE. PCE and TCE were detected above the RL in OFR‑3; PCE was detected above the RL in wells LS‑2, LS‑3, LS‑6, and LS‑7. Wells LS‑2/LS‑3, LS‑6, LS‑7, and OFR‑3 have been equipped with GAC filtration systems.

Thirteen wells reported concentrations of VOCs above the MDL, but below the RL for one or more of the following analytes: PCE, TCE, cis-1‑2‑DCE, dichlorodifluoromethane, chloroform, and toluene. These analytes were detected in samples FO‑J1, HS‑2, I10‑2, I10‑4, JW‑7, JW‑8, JW‑14, JW‑14 FD, JW‑28, JW‑30, LS‑4, LS‑5, OFR‑1, and RFR‑12.

Well RFR-13 was sampled for the first time this quarter. Initial results reported chloroform (54.1 mg/L), bromodichloromethane (5.0 mg/L), and dibromochloromethane (1.55 mg/L). These COCs are regulated as total trihalomethanes with a combined MCL of 80 mg/L. The well owner was interviewed and reported a self-performed disinfection using household bleach. A follow up sample was collected on January 11, 2005, with similar results: chloroform (64.52 mg/L), bromodichloromethane (8.74 mg/L), and dibromochloromethane (2.94 mg/L). The concentrations of combined trihalomethanes increased in the second sampling event. The well owner was informed of the results and directed to TCEQ guidance for the public on well disinfections.

Eleven wells had no detections from the short list of VOCs: FO‑22, I10‑5, I10‑7, JW‑9, JW‑26, JW‑28 FD, JW‑29, OFR‑2, OFR‑2 FD, RFR‑3, RFR‑6, and RFR‑7.

PCE concentrations decreased between September 2004 and December 2004 in nine wells: HS‑2, I10‑4, JW‑8, JW‑14, LS‑3, LS‑7, OFR‑1, OFR‑2, and RFR‑10.

TCE concentrations decreased in two wells: RFR‑10 and RFR‑11.

PCE concentrations increased in eight wells: FO‑J1, JW‑7, JW‑30, LS‑2, LS‑4, LS‑6, OFR‑3, and RFR‑11.

TCE concentrations increased in 10 wells: FO‑J1, JW‑8, JW‑30, LS‑2, LS‑3, LS‑5, LS‑6, LS‑7, OFR‑3, and RFR‑12.

Post GAC samples were not collected from wells (LS‑2/LS‑3, LS‑6, LS‑7, OFR‑3, RFR‑10, and RFR‑11) this quarter. Post-GAC samples will be collected again in March 2005.

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 March 2005 event.

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 2004 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, I10‑4, JW‑7, JW‑8, JW‑14, JW‑28, JW‑30, LS‑2, LS‑3, LS‑4, LS‑5, LS‑6, LS‑7, OFR‑1, OFR‑3, RFR‑10, RFR‑11, RFR‑12 and RFR‑13) in December 2004 will continue to be sampled on a quarterly basis, including the March 2005 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 2005 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 2005, wells where no VOCs were detected may be sampled as needed, depending on historical detections. December 2004 wells with no VOCs detected include FO‑22, I10‑5, I10‑7, JW‑9, JW‑26, JW‑29, OFR‑2, RFR‑3, 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 Subdivision areas) to confirm they continue to meet drinking water standards.

In accordance with project DQOs, the rationale for selection of wells to be sampled in March 2005 is provided in Table 4.1.