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second quarter 2006 monitoring event. The analytical results from samples collected at these q g Yt p wells are used to determine potential landfill-related impacts. The well screens for MW-lA and MW-2 are located in waste material. The analytical results from MW-IA and MW-2 are used to evaluate the changes in water quality within the landfill. During the second quarter 2006 monitoring event, analysis for field parameters (pH, specific conductance, temperature, and turbidity) and monitoring parameters (barium, bicarbonate, calcium, carbonate, chloride,magnesium, nitrate,potassium, sodium, sulfate, and total dissolved solids [TDS]) was performed for the background monitoring wells, detection monitoring wells, and evaluation monitoring wells. 2.1 Results for Detection Monitoring Wells Second quarter 2006 field and laboratory sampling results from background and detection monitoring wells are summarized on Table 2.2, along with the concentration limits determined from background monitoring well data. Bryan A. Stirrat did not report a field turbidity result for monitoring well MW-9A during the second quarter 2006. The historical groundwater data for the background and detection monitoring wells are presented in Appendix D. The data are graphed on time series concentration plots in Appendix E. For VOCs, only those VOCs with second ' quarter 2006 detections in background or detection monitoring wells were plotted. The concentration limits were developed using data collected through the second quarter 2006. The statistical analysis calculations are presented in Appendix E. A copy of the statistical analysis methodology is presented in Appendix C. As presented on Table 2.2, the following constituents exceeded their respective concentration limits: barium at MW-8A and MW-9B, calcium at MW-8A, chloride at MW-9B, potassium at MW-8A and MW-9B, and temperature at MW-9A and MW-9B. Monitoring well MW-8A exhibited a pH value higher than the concentration limit range. The chloride concentrations(with high specific conductance values) could indicate a saltwater intrusion to the groundwater. The , French Camp Landfill is within the central Stockton area impacted by saltwater intrusion (Fourth Quarter/Annual 1999 Monitoring Report, French Camp Landfall, CH2MHILL,January 2000). Historical data from the background and detection monitoring wells were evaluated for temporal t trend using Sen's Slope trend analysis. Graphs of the Sen's Slope analyses are included in Appendix E. There were no constituents that both exceeded their concentration limits and exhibited increasing trends according to Sen's Slope analysis. The following constituents exhibited an increasing trend,but did not exceed their respective concentration limits. chloride at MW-10A and sulfate at MW-9B. Sen's Slope analysis identified decreasing trends in the following constituents: nitrate at MW-8A and MW-10A, pH at MW-6A, sulfate at MW-7A, and turbidity at MW-6A, MW-7A, MW-9A, and MW-10A. As noted above, MW-6A and MW-7A are background monitoring wells, and trends in the groundwater quality at these wells are not indicative of an impact from the facility. There were no VOC detections at background or detection monitoring wells during the second quarter 2006 monitoring event. 2.3 Results for Evaluation Monitoring Wells Groundwater samples were collected during the second quarter 2006 monitoring event from ' evaluation monitoring wells MW-lA and MW-2. The field and laboratory results from the second quarter 2006 sampling event are summarized on Table 2.3. The historical groundwater data for the evaluation monitoring wells are presented in Appendix F. The field and monitoring 2