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The Monitoring and Reporting Program requires that soil gas be monitored semi-annually. Samples are Ianalyzed by a certified laboratory per EPA test method TO-14A. MONITORING RESULTS Sampling and analysis procedures are in Appendix A and the field data sheets are in Appendix B. The p g Y p Pp pp laboratory reports are in Appendix C. Statistical Analysis The FSL has been approved to use interwell tolerance limits methods (up-gradient well provides the background data). Analytical results from this monitoring period were compared to the concentration limits (Table 2). Tolerance limits for five of the general water quality parameters were determined using statistical analysis. The other limits shown were taken from the WDRs. The statistical analysis is described in Appendix D. Groundwater Monitoring and Field Parameters The concentration of Chloride (11 mg/L) slightly exceeded the concentration limit(9.8 mg/L)in MW-3. Historically, the Chloride concentration has consistently been approximately at this low concentration. The Chloride concentration was 10 mg/L when this well was first sampled in 1995, and the highest concentration (13 mg/L) was reported in April 1999 (Appendices E and F, which also contain the results of the analysis of the on-site water supply well, although this is not a compliance point). This concentration is well below drinking water standards (California DHS). VOCs One VOC (Acetone)was reported in samples collected from wells MW-1, MW-2R, and MW-3 on January 31, 2007. Acetone was not reported in these wells when re-sampled for Acetone on April 4, 2007; therefore, the first reports were erroneous,probably due to laboratory contamination. Other than these false positive for Acetone in the January samples, VOCs were not detected in wells MW-1, MW-2R and MW-3 1 this semester. No analytes were detected in any of the laboratory control blanks this semester. Surface Water Surface water samples were retrieved on February 11, 2007. All concentrations of monitoring and field parameters were below established concentration limits where the limits could be determined in the First Semester of 2007 (Table 3). Leachate Waste Discharge Requirements require monitoring leachate flow rate,pH, and Electrical Conductivity on a monthly basis (Table 5). Foothill Sanitary Landfill 8 Department of Public Works/Solid Waste 1e Semester Groundwater Monitoring County of San Joaquin—July 31,2007