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2.1 Detection Monitoring During the third quarter 2010 monitoring event, Del-Tech collected groundwater samples from the background well (AMW-2) and detection monitoring wells (AMW-6, AMW-7, AMW-12, AMW-13, and AMW-14). The field results provided by Del-Tech and laboratory results provided by TestAmerica for the third quarter 2010 groundwater detection monitoring event are summarized on Table 2.2. The historical groundwater data for the detection monitoring wells are presented in Appendix D. Times series concentration plots of 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 third quarter 2010 monitoring event were plotted. The concentration limits presented on Table 2.2 were calculated by Herst & Associates, Inc. from data collected through the third quarter 2010 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 CH2M Hill in January 2000. A copy of the statistical analysis methodology is presented in Appendix C. During the third quarter 2010 monitoring event, the following constituents exceeded their concentration limits: barium at AMW-13 and AMW-14, chloride at AMW-14, and temperature at AMW-7 and AMW-14. The hexavalent chromium concentrations at AMW-6 (0.0068 mg/L) and AMW-7 (0.0068 mg/L) exceeded the concentration limit of 0.005 mg/L, but the observed concentrations are trace(estimated)values below the laboratory reporting limit(RL). The third quarter 2010 barium concentration at AMW-13 (0.263 mg/L) is comparable to concentrations observed at that well since November 2005, and is well below the National Primary Drinking Water Standard (2 mg/L). The third quarter 2010 barium concentration at AMW-14 (0.263 mg/L) is comparable to historical concentrations observed at that well, and is well below the National Primary Drinking Water Standard (2 mg/L). The third quarter 2010 chloride concentration at AMW-14 (81.4 mg/L) is comparable to historical concentrations observed at that well, and is well below the National Secondary Drinking Water Standard (250 mg/L). The third quarter 2010 field temperature value at AMW-7 (23.1 °C) is comparable to historical values observed at that well. The third quarter 2010 field temperature value at AMW- 14(22.3 °C) is comparable to historical values observed at that well. During the third quarter 2010 monitoring event,no VOCs were detected above the 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. Tetrachloroethene was detected above the RL at AMW-14. The third quarter 2010 concentration of tetrachloroethene at AMW-13 (5.0 ug/L)is comparable to historical concentrations observed at that well, and does not exceed the National Primary Drinking Water Standard (5 ug/L). The third quarter 2010 concentration of tetrachloroethene at AMW-14 (1.8 ug/L) is the lowest concentration observed at that well since November 2004, and is below the National Primary Drinking Water Standard (5 ug/L). The third quarter 2010 concentration of trichloroethene at AMW-13 (1.4 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 Mann-Kendall / Sen's Slope trend analysis. Graphs and summary tables of the Mann-Kendall / Sen's Slope analyses for detection monitoring wells are presented in Appendix E. The following 2