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intermittently since August 1991, and is within the National Secondary Drinking Water Standard range (6.5 - 8.5). During the fourth quarter 2006 monitoring event, no VOCs were detected above the laboratory PQL in samples collected from detection monitoring wells AMW-12. Bromoform and dibromochloromethane were detected above the PQL at AMW-2 during the fourth quarter 2006. Bromoform was detected above the PQL at AMW-6 during the fourth quarter 2006. Bromoform and dibromochloroemethane were detected above the PQL at AMW-7 during the fourth quarter 2006. Tetrachloroethene was detected above the PQL at AMW-13 during the thrid quarter 2006. 1,2-Dichloropropane, dichlorodifluoromethane, tetrachloroethene, and trichloroethene were detected above the PQL at AMW-14 during the fourth quarter 2006. The fourth quarter 2006 concentration of 1,2-dichloropropane at AMW-14 (0.54 ug/L) is comparable to concentrations observed at that well intermittently since February 1997 and consistently since August 2005. The fourth quarter 2006 concentrations of bromoform at AMW- 2 (0.78 ug/L), AMW-6 (1.2 ug/L), and AMW-7 (1.8 ug/L) are the second detections of bromoform at these wells. The fourth quarter 2006 concentration of dibromochloromethane at AMW-2 (0.56 ug/1) and AMW-7 (1.2 ug/L) are the second detections of dibromochloromethane at these wells. The fourth quarter 2006 concentration of dichlorodifluoromethane at AMW-14 (0.54 ug/L) is comparable to concentrations observed at that well intermittently since May 1996. The fourth quarter 2006 concentration of tetrachlorothene at AMW-13 (1.5 ug/L) is comparable to concentrations observed at that well intermittently since March 1994, and is below the National Primary Drinking Water Standard (5 ug/L). The fourth quarter 2006 concentration of tetrachloroethene at AMW-14 (8.8 ug/L) is comparable to concentrations observed at that well intermittently since March 1996. The fourth quarter 2006 concentration of trichloroethene at AMW-14 (1.1 ug/L) is comparable to concentrations observed at that well intermittently since March 1996, and is below the National Primary Drinking Water Standard (5 ug/L). Historical data from the detection monitoring wells were analyzed for temporal trend using Sen's Slope trend analysis. Graphs of the Sen's Slope analyses for detection monitoring wells are included in Appendix E. The following inorganic constituents exhibited an increasing trend according to the Sen's Slope analysis: barium at AMW-6, bicarbonate at AMW-6, AMW-7, AMW-12, and AMW-13, calcium at AMW-14, chloride at AMW-6 and AMW-7, hexavalent chromium at AMW-12, magnesium at AMW-14, nitrate at AMW-2, AMW-6, and AMW-7, potassium at AMW-14, sodium at AMW-14, field specific conductance at AMW-2 and AMW-7, strontium at AMW-14, and total dissolved solids (TDS) at AMW-7. Of the constituents that exhibited a statistically significant increasing trend during the fourth quarter 2006, only hexavalent chromium exceeded its concentration limit. Although there were increasing trends for nitrate at AMW-6 and AMW-7 and field specific conductance at AMW-7, background well AMW-2 also exhibited increasing trends for nitrate and field specific conductance during the fourth quarter 2006 monitoring event. Sen's Slope analysis identified decreasing trends in the following inorganic parameters: arsenic at AMW-2 and AMW-7, calcium at AMW-12, chloride at AMW-12 and AMW-14, magnesium at AMW-12, nitrate at AMW-13, potassium at AMW-13, field specific conductance at AMW-14, sulfate at AMW-6 and AMW-14, total dissolved solids (TDS) at AMW-14, and field turbidity at AMW-2.