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2.0 Groundwater Monitoring Program
<br /> During the third quarter 2010 monitoring event, groundwater monitoring was performed at the
<br /> French Camp Landfill by Del-Tech. Groundwater samples were collected from two background
<br /> monitoring wells(MW-6A and MW-7A)and four detection monitoring wells(MW-8A, MW-9A,
<br /> MW-9B, and MW-10A) during the third quarter 210 monitoring event. The analytical results
<br /> from samples collected at these wells are used to determine potential landfill-related impacts.
<br /> The WDRs stipulate semi-annual sampling of the background monitoring wells and detection
<br /> monitoring wells for field parameters (pH, specific conductance, temperature, and turbidity) and
<br /> monitoring parameters (bicarbonate, calcium, carbonate, chloride,magnesium, nitrate, potassium,
<br /> sodium, sulfate,TDS,and VOCs).
<br /> The field results provided by Del-Tech and the laboratory results provided by TestAmerica for
<br /> the third quarter 2010 groundwater monitoring event are summarized on Table 2.2. The
<br /> historical groundwater data for the background and detection monitoring wells are presented in
<br /> Appendix D. Times series concentration plots of historical groundwater data for the monitoring
<br /> wells are presented in Appendix E. For VOCs, only those compounds that exhibited detections
<br /> at groundwater monitoring wells during the third quarter 2010 monitoring event were plotted.
<br /> The concentration limits presented on Table 2.2 were calculated from data collected through the
<br /> third quarter 2010 monitoring event. The statistical analysis calculations for groundwater
<br /> monitoring wells are presented in Appendix E. A copy of the statistical analysis methodology is
<br /> presented in Appendix C.
<br /> As presented on Table 2.2, the following constituents exceeded their respective concentration
<br /> limits during the third quarter 2010: calcium at MW-8A; chloride at MW-10A; magnesium at
<br /> MW-8A; potassium at MW-8A, MW-9A, and MW-913; field specific conductance at MW-10A;
<br /> and field temperature at MW-9A, MW-913, and MW-10A. Elevated chloride concentrations
<br /> (with elevated specific conductance values) could indicate a saltwater intrusion to the
<br /> groundwater. The French Camp Landfill is within the central Stockton area impacted by
<br /> saltwater intrusion (Fourth Quarter/Annual 1999 Monitoring Report, French Camp Landfill,
<br /> CH2M HILL,January 2000).
<br /> Historical data from the groundwater monitoring wells were analyzed for temporal trends using
<br /> Mann-Kendall / Sen's Slope trend analysis. Graphs and summary tables of the Mann-Kendall /
<br /> Sen's Slope analyses for groundwater monitoring wells are presented in Appendix E.
<br /> Chloride at MW-10A, potassium at MW-7A and MW-9B, field specific conductance at MW-
<br /> 10A, and sulfate at MW-913 exhibited increasing trends. Of these constituents, chloride at MW-
<br /> 10A, potassium at MW-913, and field specific conductance at MW-10A exceeded their
<br /> concentration limits. Mann-Kendall / Sen's Slope analysis identified decreasing trends in the
<br /> following constituents: bicarbonate alkalinity at MW-8A, calcium at MW-6A, chloride at MW-
<br /> 7A, magnesium at MW-6A and MW-8A, nitrate at MW-8A and MW-10A, field pH at MW-6A
<br /> and MW-913, field specific conductance at MW-7A, sulfate at MW-7A, TDS at MW-7A and
<br /> MW-8A, and field turbidity at MW-7A, MW-9A, and MW-10A. As noted above, MW-6A and
<br /> MW-7A are background monitoring wells, and trends in the groundwater quality at these wells
<br /> are not indicative of an impact from the facility.
<br /> Chloride at MW-10A, potassium at MW-913, and field specific conductance at MW-10A
<br /> exceeded their concentration limit and also exhibited a significant increasing statistical trend.
<br /> The third quarter 2010 concentration of chloride at MW-10A (627 mg/L) is consistent with
<br /> historical concentrations observed at that well. The third quarter 2010 concentration of potassium
<br /> at MW-913 (40.2 mg/L) is higher than historical concentrations observed at that well and may
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