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® Table 2.2 presents the VOC detections at background and detection monitoring wells during the fourth quarter 2006 monitoring event. 1,2-Dichloroethane was detected in detection monitoring well MW-913 at a concentration (0.25 ug/L) below the laboratory practical quantitation limit (PQL). Bromodichloromethane was detected in background monitoring well MW-6A and detection monitoring wells MW-9A and MW-l0A at concentrations (0.38 ug/L, 0.19 ug/L, and 0.22 ug/L, respectively) below the laboratory PQL. Bromoform was detected in background monitoring well MW-6A and detection monitoring wells MW-9A and MW-l0A at concentrations of 2.8 ug/L, 1.4 ug/L, and 1.2 ug/L, respectively. Chloromethane was detection in background monitoring wells MW-6A and MW-7A at concentrations (0.19 ug/L and 0.35 ug/L) below the laboratory PQL. Dibromochloromethane was detected in background monitoring well MW-6A at a concentration of 1.4 ug/L, and in detection monitoring wells MW-9A and MW-l0A at concentrations of 0.86 ug/L and 0.97 ug/L,respectively. Trichlorofluoromethane was detected in detection monitoring well MW-9A at a concentration of 1.7 ug/L. None of these VOCs exhibit an increasing trend according to Sen's Slope analysis. The bromodichloromethane detections at MW-6A, MW-9A, and MW-l0A during the fourth quarter 2006 are the first detections of these constituents at these wells. The bromoform detections at MW-9A and MW-l0A during the fourth quarter 2006 are the first detections of this constituent at these wells. The chloromethane detections at MW-6A and MW-7A during the fourth quarter 2006 are the first detections of this constituent at these wells. The dibromochloromethane detection at MW-9A during the fourth quarter 2006 is the first detection of this constituent at this wells. 2.3 Results for Evaluation Monitoring Wells ® Groundwater samples were collected during the fourth quarter 2006 monitoring event from evaluation monitoring well MW-2. ATC and Associates reported that evaluation monitoring well MW-IA was dry during the fourth quarter 2006. The field and laboratory results from the fourth quarter 2006 sampling event are summarized on Table 2.3. The historical groundwater data for the evaluation monitoring wells are presented in Appendix F. The field and monitoring parameter data are presented on time series concentration plots in Appendix G. Historical data from the evaluation monitoring wells were evaluated for temporal trend using Sen's Slope trend analysis. Graphs of the Sen's Slope analyses are included in Appendix G. There were no constituents that exhibited an increasing trend according to Sen's Slope analysis. Sen's Slope analysis identified decreasing trends in barium at MW-2, chloride at MW-IA and MW-2,and temperature at MW-IA. There were no VOC detections at evaluation monitoring well MW-2 during the fourth quarter 2006 monitoring event. 3