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monitoring of existing groundwater monitoring wells and soil-pore gas probes through <br /> May 2008 to evaluate the significance of LFG at the site. <br /> Concentration Limits <br /> For DMP monitoring wells at the French Camp Landfill, concentration limits (CLs) are <br /> used for the water quality protection standards PS). The CLs shown in Table 2 were <br /> calculated by Herst&Associates using Sanitas , a state-approved statistical software <br /> program,using historical data from background wells MW-6A and MW-7A, and are <br /> presented in Appendix D. Based on a comparison of the data obtained during the first <br /> quarter 2007 monitoring period,the following analytes were found to exceed a CL: <br /> CONSTITUENTConcentration DMP Monitoring Wells <br /> Limit MW-6A* MW-7A* MW-8A MW-9A MW-9B MW-10A <br /> GENERAL CHEMISTRY(mg/l,except as noted) <br /> H 6.798—7.933 6.72 <br /> Barium 0.5243 0.65 <br /> Calcium 143.1 210 <br /> Chloride 370 520 <br /> Magnesium 1 75 110 <br /> VOLATILE ORGANIC COMPOUNDS(pg/1) <br /> Trichlorofluoromethane 1 0.50 1 1.3 <br /> NOTES: (*)—Background Well. <br /> Trend Analysis <br /> In order to evaluate changes in water quality in DMP wells at the French Camp Landfill, <br /> historical groundwater data were evaluated using Sen's Slope trend analyses to determine <br /> if significant increasing or decreasing trends were evident. Trend analyses,performed by <br /> Herst &Associates, are presented in Appendix D and summarized below. <br /> Well Number Increasing Trends Decreasing Trends <br /> MW-6A None Apparent pH <br /> MW-7A None Apparent Specific Conductance,Sulfate <br /> MW-8A None Apparent Nitrate-N <br /> MW-9A Barium None Apparent <br /> MW-9B Sulfate Barium <br /> MW-10A Chloride Nitrate-N <br /> As shown above, CLs were exceeded for inorganic constituents in the samples collected <br /> from wells MW-9A, MW-913 and MW-10A, and with the exception of the chloride <br /> concentration measured in well MW-10A; none of the constituents that exceeded a CL <br /> exhibited a significant increasing trend during the first quarter 2007 monitoring period. <br /> In response to statistical exceedances of chloride and TDS identified in samples from <br /> well MW-l0A during the second quarter 2004, a No Release Demonstration(NRD) for <br /> groundwater monitoring well MW-10A was performed (Herst, 2005). The NRD <br /> concluded that French Camp Landfill, located within the central Stockton area, has been <br /> impacted by saltwater intrusion and the elevated chloride and TDS concentrations <br /> measured in well MW-l0A are believed to be the result of this condition and not the <br /> result of landfill-related impacts. <br /> D:0003_021\FC_w07.doc <br /> 4 Geologic Associates <br />