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MW -6 (Down -gradient): All constituents were within the tolerance limits in 2013, with the exception of chloride, nitrate and nitrogen, sulfate, TDS, and Magnesium which exceeded their respective concentration limits in the 1st Quarter 2013. Trend analysis indicates an increasing trend in TDS. No VOCs were reported in well MW -6 this year. iMW -7 (Up -gradient): F11 fl u H_ All constituents were within the tolerance limits in 2013. No VOCs were reported in well MW -7 this year. Surface Water Surface water samples were not collected this year due to lack of surface water flow. Surface water was last collected on January 27, 2011. All concentrations of field parameters and constituents of concern were below established concentration limits. VOCs were not detected during the 1st Quarter 2011 sampling event. HISTORICAL TIME SERIES PLOTS AND STIFF DIAGRAMS Historical Time Series Plots are presented in Appendix F. Note that constituents not detected are plotted at a value of half their respective detection limits. Outliers were included in the plots as directed by RWQCB staff. Stiff diagrams are submitted annually with the fourth quarter and annual report. The stiff diagrams submitted for the fourth quarter indicate a sodium -sulfate water type for deep zone wells, MW -6 and MW -7. The shallow zone wells exhibit four uniquely different water types; SB -1 and MW -11 A are a sodium -bicarbonate type, MW -4 is a sodium/calcium-sulfate type, MW -5, and MW -8 are calcium -bicarbonate type and MW -9A, and MW -10A are a sodium -chloride type (Appendix F). An interpretation of zonation of water types in the shallow groundwater zone is presented on Figure 2. A comparison of water quality values between upgradient and downgradient wells in both the shallow and deep zone do not indicate a significant increase in mineralization. Although bicarbonate ions are sometimes assumed to indicate the influence by LFG and that LFG is the carrier mechanism for VOC impact to groundwater, relatively high bicarbonate milliequivalent levels are present in well SB -1 where VOCs are generally not detected. In addition, at well MW -8 where many VOCs have been detected, the bicarbonate milliequivalent levels have been relatively low. Corral Hollow Sanitary Landfill 21 Department of Public Works/Solid Waste 4th Quarter and Annual 2013 Groundwater Monitoring County of San Joaquin — January 15, 2014