June 2002 Off-post GW Monitoring Report Section 4 - Summary and Recommendations

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June 2002 Off-Post Quarterly Groundwater Monitoring Report

Section 4 - Summary and Recommendations

	PCE and TCE concentrations decreased in June 2002 in wells HS-2, LS-2, LS-3, LS-4, LS-5, LS-6, OFR-3, RFR-11 and RFR-12, but PCE concentrations increased in LS-1 and RFR-10.
	No post GAC confirmation samples were collected in June 2002 from wells with GAC treatment systems installed (LS-2, LS-3, LS-6, LS-7, OFR-3, RFR-10, and RFR-11). In accordance with the Plan, post-GAC confirmation samples will be collected every 6 months. The next scheduled event for post-GAC sampling is September 2002.
	All objectives listed in Table 1-1, Sampling Rationale for June 2002, were accomplished. All wells scheduled to be sampled for the June event were sampled. The rationale for recommending wells to be re-sampled in September 2002 is provided in Table 4.1.
	Wells where PCE has not been detected, but other VOCs have been detected, include RFR-12 (TCE and chloromethane) and JW-9 (cis-1,2-DCE). Well FO-J1 had detections of cis-1,2-DCE only, but PCE was eventually detected in this well, also. These data will continue to be evaluated since they may provide key evidence for identifying the source of the contamination in the groundwater and in understanding the movement of PCE to off-post wells.

4.2 - Recommendations

	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 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.
	Wells FO-J1, LS-1, LS-4, LS-5, OFR-1, OFR-2 and RFR-12 had low concentrations of PCE, TCE, chloroform, chloromethane, and/or cis-1,2-DCE above the MDL, but below the RL, and less than 80 percent of the laboratory MCL. Based on the Plan these wells should be retained for future quarterly sampling events, including the September 2002 quarterly sampling event.
	I10-2 and JW-9 reported �M� flags for 1,3,5-trimethylbenzene and chloromethane. All non-compliant analytes were recovered only slightly above tolerance and were non-detect in the associated samples. The parent sample results for the non-compliant analytes were flagged �M� per the AFCEE QAPP. No additional corrective action was necessary since each well represents a unique sample matrix.
	Monitored natural attenuation (MNA) testing should be conducted as part of on-post groundwater sampling in September 2002 to establish a baseline for future comparisons following removal actions at SWMU B-3 and AOC 65. If field data show that the biological component of the MNA extends off-post, additional off-post samples will be collected for MNA testing.
	Post-GAC confirmation samples will be collected at all off-post wells with GAC systems during the September 2002 sampling event. This includes LS-2, LS-3, LS-6, LS-7, OFR-3, RFR-10, and RFR-11.
	For future sampling events wells where no VOCs were detected will have a reduced sampling frequency. Additional wells located to the west and southwest of AOC-65 will be added to future sampling events. Future sampling events will continue to include wells to the west of CS-D and CS-16 (Fair Oaks and Jackson Woods) to confirm any detections.