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26.9 *Q. As discussed above, field temperature at MW-10A does not exhibit a significant <br /> upward statistical trend. A Wilcoxon rank-sum test comparing the field temperature data at <br /> background wells MW-6A and MW-7A to the data at MW-l0A(a= 0.05) indicates that the field <br /> temperature data at MW-l0A are statistically distinct from those at the background wells. The <br /> Wilcoxon rank sum plot is presented in Appendix E. The presence of stable field temperatures at <br /> MW-10A that are statistically distinct from background temperatures indicates that the <br /> concentration limit exceedance for field temperature at MW-l0A in the first quarter 2012 is likely <br /> due to spatial variation in the natural groundwater temperatures at the site. <br /> The first quarter 2012 chloroform concentration at upgradient well MW-6A (2.8 ug/L) is greater <br /> than the range of concentrations observed at MW-6A since the beginning of background in March <br /> 1997 (<0.5 ug/L to 1.5 ug/L). However, as discussed above, chloroform at upgradient well MW- <br /> 6A does not exhibit a significant upward statistical trend. <br /> The first quarter 2012 trichlorofluoromethane concentration at well MW-9A (2.5 ug/L) is within <br /> the range of concentrations observed at MW-9A since the beginning of background in March <br /> 1997 (<0.5 ug/L to 8.3 ug/L). As discussed above, trichlorofluoromethane at MW-9A exhibits a <br /> significant downward statistical trend. <br />