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historical groundwater data for the detection monitoring wells are presented in Appendix E. For VOCs, only those compounds that exhibited detections at detection monitoring wells during the fourth quarter 2009 monitoring event were plotted. The concentration limits presented on Table 2.2 were calculated by Herst & Associates, Inc. from data collected through the fourth quarter 2009 monitoring event. The statistical analysis calculations for detection monitoring wells are presented in Appendix E. Information on the development of the concentration limits can be found in the Fourth Quarter/Annual 1999 Monitoring Report, Austin Road Landfill, prepared by C112M Hill in January 2000. A copy of the statistical analysis methodology is presented in Appendix C. During the fourth quarter 2009 monitoring event, barium at AMW-13 and AMW-14, hexavalent chromium at AMW-6 and AMW-7, and gasoline -range petroleum hydrocarbons at AMW-12 exceeded their respective concentration limits. The fourth quarter 2009 barium concentration at AMW-13 (0.26 mg/L) is comparable to concentrations observed at that well since May 1995, and is well below the National Primary Drinking Water Standard (2 mg/L). The fourth quarter 2009 barium concentration at AMW-14 (0.25 mg/L) is comparable to concentrations observed at that well since August 2006, and is well below the National Primary Drinking Water Standard (2 mg/L). The fourth quarter 2009 hexavalent chromium concentration at AMW-6 (0.0055 mg/L) is comparable to historical concentrations observed at that well, and is well below the National Primary Drinking Water Standard for chromium (0.1 mg/L). The fourth quarter 2009 hexavalent chromium concentration at AMW-7 (0.0057 mg/L) is comparable to historical concentrations observed at that well, and is well below the National Primary Drinking Water Standard for chromium (0.1 mg/L). The fourth quarter 2009 detection of gasoline -range petroleum hydrocarbons at AMW-12 (180 ug/L) is the first detection of this constituent above the reporting 4Plimit (50 ug/L) since monitoring for the constituent began in August 2003. During the fourth quarter 2009 monitoring event, no VOCs were detected above the laboratory reporting limit (RL) in samples collected from detection monitoring wells AMW-2, AMW-6, AMW-7, or AMW-12. Tetrachloroethene and trichloroethene were detected above the RL at AMW-13. Dichlorofluoromethane, tetrachloroethene, and trichloroethene were detected above the RL at AMW-14. The fourth quarter 2009 concentration of dichlorofluoromethane at AMW-14 (0.68 ug/L) is comparable to historical concentrations observed at that well. The fourth quarter 2009 concentration of tetrachloroethene at AMW-13 (4.2 ug/L) is comparable to historical concentrations observed at that well, and is below the National Primary Drinking Water Standard (5 ug/L). The fourth quarter 2009 concentration of tetrachloroethene at AMW-14 (8.0 ug/L) is comparable to historical concentrations observed at that well, and is greater than the National Primary Drinking Water Standard (5 ug/L). The fourth quarter 2009 concentration of trichloroethene at AMW-13 (1.1 ug/L) is comparable to historical concentrations observed at that well, and is below the National Primary Drinking Water Standard (5 ug/L). The fourth quarter 2009 concentration of trichloroethene at AMW-14 (0.63 ug/L) is comparable to historical concentrations observed at that well, and is below the National Primary Drinking Water Standard (5 ug/L). Historical data from the detection monitoring wells were analyzed for temporal trends using Sen's Slope trend analysis. Graphs and summary tables of the Sen's Slope analyses for detection monitoring wells are presented in Appendix E. The following inorganic constituents exhibited an increasing trend according to the Sen's Slope analysis: barium at AMW-6 and AMW-14, bicarbonate alkalinity at AMW-2, AMW-6, AMW-7, and AMW-13, calcium at AMW-7 and AMW-14, chloride at AMW-6 and AMW-7, magnesium at AMW-7 and AMW-14, nitrate at 2