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MONITORING RESULTS Sampling and analysis procedures are in Appendix A and the field data sheets are in Appendix B. The laboratory reports are in Appendix C. Statistical Analysis The FSL has been approved to use interwell tolerance limits methods,with an upgradient well providing background data(Tables 2 & 3). MW-4 was located directly up-gradient of the landfill based on groundwater elevations from the previously-installed wells. This well has been sampled ten times since installation. Concentration limits have been established based on Sanitas software calculations using data for MW-4. Groundwater The water at all groundwater wells meet drinking water standards. Monitoring and Field Parameters A review of the third and fourth quarter general water quality parameters (Tables 2 & 3) indicates compliance with concentration limits where limits could be determined with the exception of Nitrate as Nitrogen detected at a concentration of 2.0 mg/L at cross-gradient well MW-1, and at 2.9 mg/L in wells MW-2R, and MW-3. These values slightly exceeded concentration limit of 1.8 mg/L calculated from MW-4 data,however,these concentrations are below the US EPA and California Maximum Contaminant Level(MCL) and the California Public Health Goal of 10 mg/L. VOCs One VOC (trichloroethene)was reported in MW-3 in the August 2010 sampling event at a trace concentration of 0.3 ug/L in MW-3. The well was resampled in November 2010, and trichloroethene was reported in a concentration of 0.56 ug/L. These concentrations are below the these concentrations are far below the Maximum Contaminant Level (MCL) of 45 ppm and the US EPA and California Public Health Goal. However,the County is planning to increase the corrective action(landfill gas collection)to remove this contaminant. VOCs were not detected in any other well during the August or November 2010 sampling events. Surface Water Surface water samples were not taken this semester. Surface water samples were last taken from the creek flowing along the eastern property boundary during the first semester 2010. These results were discussed in the First Semester 2010 Report. Note that the creek receives contribution from the ground surface and several smaller creeks on the neighbor's properties east of the creek, and that these surfaces and the creek itself are subject to cattle grazing. Surface water from these properties also enter the stream, and is included in the samples taken. Foothill Sanitary Landfill 8 Department of Public Works/Solid Waste 2nd Semester and Annual 2010 Groundwater Monitoring County of San Joaquin—January 31,2011