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calcium at MW -913 in the third quarter 2011 is likely due to spatial variation in the natural groundwater geochemistry at the site. The third quarter 2011 field temperature value at well MW -9A (22.4 °C) is within the range of temperatures observed at MW -9A since the beginning of background in March 1997 (19.6 °C - 27.6 °C), and is the lowest temperature observed at that well since February 2009. As discussed above, field temperature at MW -9A does not exhibit a significant upward statistical trend. A Wilcoxon rank -sum test comparing the field temperature data at background wells MW -6A and MW -7A to the data at MW -9A (a = 0.05) indicates that the field temperature data at MW -9A are statistically distinct from those at the background wells. The Wilcoxon rank sum plot is presented in Appendix E. The presence of stable field temperatures at MW -9A that are statistically distinct from background temperatures indicates that the concentration limit exceedance for field temperature at MW -9A in the third quarter 2011 is likely due to spatial variation in the natural groundwater temperatures at the site. The third quarter 2011 field temperature value at well MW -913 (22.9 °C) is within the range of temperatures observed at MW -913 since the beginning of background in March 1997 (20.0 °C - 28.0 °C), and is the lowest temperature observed at that well since February 2009. As discussed above, field temperature at MW -913 does not exhibit a significant upward statistical trend. A Wilcoxon rank -sum test comparing the field temperature data at background wells MW -6A and MW -7A to the data at MW -913 (a = 0.05) indicates that the field temperature data at MW -913 are statistically distinct from those at the background wells. The Wilcoxon rank sum plot is presented in Appendix E. The presence of stable field temperatures at MW -913 that are statistically distinct from background temperatures indicates that the concentration limit exceedance for field temperature at MW -913 in the third quarter 2011 is likely due to spatial variation in the natural groundwater temperatures at the site. The third quarter 2011 field temperature value at well MW -10A (22.9 °C) is within the range of temperatures observed at MW- l0A since the beginning of background in March 1997 (13.5 °C - 26.9 °C), and is the lowest temperature observed at that well since February 2009. As discussed above, field temperature at MW- l0A does not exhibit a significant upward statistical trend. A Wilcoxon rank -sum test comparing the field temperature data at background wells MW -6A and MW -7A to the data at MW-l0A (a = 0.05) indicates that the field temperature data at MW -10A are statistically distinct from those at the background wells. The Wilcoxon rank sum plot is presented in Appendix E. The presence of stable field temperatures at MW-l0A that are statistically distinct from background temperatures indicates that the concentration limit exceedance for field temperature at MW-l0A in the third quarter 2011 is likely due to spatial variation in the natural groundwater temperatures at the site. The third quarter 2011 chloroform concentration at upgradient well MW -6A (1.2 ug/L) is within the range of concentrations observed at MW -6A since the beginning of background in March 1997 (<0.5 ug/L to 1.5 ug/L). As discussed above, chloroform at upgradient well MW -6A does not exhibit a significant upward statistical trend. The third quarter 2011 trichlorofluoromethane concentration at well MW -9A (0.53 ug/L) is within the range of concentrations observed at MW -9S since the beginning of background in March 1997 (<0.5 ug/L to 8.3 ug/L). As discussed above, trichlorofluoromethane at MW -9A exhibits a significant downward statistical trend.