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AMW-13 exhibited an increasing trend according to the Sen's Slope analysis. The second • quarter 2006 concentration of cis-l,2-dichloroethene at AMW-13 (8.2 ug/L) is higher than concentrations previously observed at that well, but is well below the National Primary Drinking Water Standard (70 ug/L). Tetrachloroethene and trichloroethene at AMW-14 exhibited a statistically significant decreasing trend according to the Sen's Slope analysis. 2.2 Corrective Action Monitoring Groundwater samples were collected by Bryan A. Stirrat & Associates from the corrective action monitoring wells (AMW-1, AMW-3, AMW-4, AMW-10, and AMW-11) during the second quarter 2006 monitoring event. Corrective action monitoring well AMW-5 was not sampled during the second quarter 2006 monitoring event. Bryan A. Stirrat & Associates reported that the sample at AMW-5 was not collected due to a nonfunctional pump. The field and laboratory results provided by BC Laboratories, Inc. for the second quarter 2006 corrective action sampling are summarized on Table 2.3. VOCs have been consistently detected in samples from corrective action monitoring wells AMW- 1, AMW4, AMW-10, and AMW-11. AMW-5 has previously exhibited sporadic VOC detections. No VOCs have been detected in samples from AMW-3 since 1990. The historical groundwater data for the corrective action monitoring wells are presented in Appendix F. The data are graphed on time series concentration plots, included in Appendix G. For VOCs, only those VOCs that exhibited detections for the second quarter 2006 monitoring event were plotted. Historical data from the corrective action monitoring wells from March 1994 to the present were analyzed for temporal trend using Sen's Slope trend analysis. Graphs of the Sen's Slope analyses for corrective action monitoring wells are included in Appendix G. Table 2.4 summarizes the results of the corrective action monitoring well trend analysis. The following inorganic constituents exhibited an increasing trend according to the Sen's Slope analysis: bicarbonate at AMW-1, chloride at AMW-3 and AMW-5, nitrate at AMW-3 and AMW-5, field pH at AMW-5, field specific conductance at AMW-1, AMW-3, AMW-5, and AMW-10, sulfate at AMW-5 and AMW-10, and total dissolved solids (TDS) at AMW-5. The second quarter 2006 concentration of bicarbonate at AMW-1 (1100 mg/L) is comparable to concentrations observed at that well intermittently since August 2003. The second quarter 2006 concentration of chloride at AMW-3 (92 mg/L) is comparable to concentrations observed at that well consistently since August 2003. The second quarter 2006 concentration of chloride at AMW-5 (99 mg/L) is comparable to concentrations observed at that well consistently since July 2001. The chloride concentration at both AMW-3 and AMW-5 is well below the National Secondary Drinking Water Standard (250 mg/L). The second quarter 2006 concentration of nitrate at AMW-3 (15 mg/L) is comparable to concentrations observed at that well consistently since August 2003. The second quarter 2006 concentration of nitrate at AMW-5 (13 mg/L) is comparable to concentrations observed at that well consistently since July 2001. The concentration of nitrate at both AMW-5 and AMW-10 during the second quarter 2006 is below the concentration observed in background well AMW-2 (40 mg/L). The second quarter 2006 field specific conductance value at AMW-1 (1,300 umhos/cm) is comparable to values observed at that well consistently since March 2003. The second quarter 2006 field specific conductance value at AMW-3 (1,700 umbos/cm) is the highest value observed at that well since March 1994. The second quarter 2006 field specific conductance value at 4