[Home] [Master Table of Contents]
Section 4 - Summary and Recommendations
All objectives listed in Table 1.1, Sampling Rationale for March 2004, were accomplished. All wells scheduled to be sampled for the March event were sampled.
Twenty-one of the thirty-two wells sampled reported detections of VOCs in March 2004. Of the wells with VOC detections, one well had concentrations above the MCL for PCE and TCE. Well RFR-10 had detections of PCE and TCE above the MCLs of 5.0 �g/L. RFR-10 also had a detection of cis-1,2-DCE at a concentration 0.44 �g/L, below the RL. This well has been equipped with a GAC filtration system.
Five wells had detections of VOCs reported at concentrations below the MCL, but above the RL for one or both of PCE and TCE; PCE was detected above the RL in I10-4, LS‑6, LS-7, and OFR-3; and TCE above the RL in OFR-3 and RFR-11. Wells LS-2/LS-3, LS-6, LS‑7, RFR-11, and OFR-3 have been equipped with GAC filtration systems. Well JW-14 and the JW-14 duplicate sample had concentrations of chloroform above the RL and bromodichloromethane below the RL. These concentrations were below the applicable MCLs.
Fourteen 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, chloroform, dichlorodifluoromethane, and toluene. These analytes were detected in samples FO-J1, HS-2, JW-7, JW-8, JW-9, JW-28, JW-30, LS-1, LS-2, LS-3, LS-2/LS-3-A1, LS-2/LS-3-A2, LS-4, LS-5, OFR-1, OFR-2, and OFR-2 FD.
Six wells had no detections from the short list of VOCs: DOM-2, JW-26, JW-29, RFR-3, RFR-4, and RFR-5.
Five wells had a detection of 1,1-DCE which was �M� flagged (see �M� flag discussion in Section 3.0): FO-8, I10-2, JW-12, OFR-4, and RFR-12.
PCE concentrations decreased between December 2003 and March 2004 in wells JW‑7, JW-26, JW-30, LS-1, LS-2, LS-4, LS-6, OFR-1, OFR-3, RFR-3, RFR-10, and RFR-12. These decreases ranged in magnitude from 0.01 mg/L (JW-30) to 9.68 mg/L (OFR-3).
TCE concentrations decreased in wells LS-7, OFR-3, RFR-11, and RFR-12. These decreases ranged from 0.01 mg/L (LS-7) to 5.90 mg/L (OFR-3).
PCE concentrations increased in wells FO-J1, HS-2, I10-4, JW-8, JW-9, LS-3, OFR-2, and RFR-11. The increases ranged from 0.02 mg/L (HS-2) to 2.16 mg/L (I10-4).
TCE concentrations increased in wells I10-4, LS-1, LS-2, LS-3, and RFR-10. The increases ranged from 0.05 mg/L (JW-12) to 2.0 mg/L (RFR-10).
Two new wells (RFR-4 and RFR-5) were added to the quarterly monitoring in March 2004. No VOCs were detected in these wells.
| 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 June 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 March 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, I10-4, JW-7, JW-8, JW-9, JW-14, JW-28, JW-30, LS-1, LS-2, LS-3, LS-4, LS-5, LS-6, LS-7, OFR-1, OFR‑2, OFR-3 and RFR-11) in March 2004 will continue to be sampled on a quarterly basis, including the June 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 September 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 June 2004, wells where no VOCs were detected may be sampled as needed, depending on historical detections. March 2004 wells with no VOCs detected include DOM-2, JW-26, JW-29, RFR-3, RFR-4, and RFR-5. Five wells had a detection of 1,1-DCE which was �M� flagged (see �M� flag discussion in Section 3.0): FO-8, I10-2, JW-12, OFR-4, and RFR-12. | |
| 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 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 June 2004 is provided in Table 4.1. |