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quarter 2006 and TCE was last detected in this well in 3`d quarter 2007. These are sporadic low concentration VOC detections that are generally not persistent at the well. 5 Year COCs Groundwater samples were analyzed for the Five-year Constituent of Concern this semester during the 3`d Quarter 2009. Results were unremarkable with one exception. Eight Semivolatile Organic Compounds(SVOCs)were observed in both MW-3 and background well MW-4. When retested during the 4th Quarter 2009 sampling event, these SVOCs were not observed in either MW-3 or MW-4, which indicates that the first reports were erroneous, probably due to laboratory contamination. None of the other 5-year COC monitoring parameters suggested that the water from the monitoring wells had been impacted by landfill activities. Surface Water Surface water samples were taken from the creek flowing along the eastern perimeter of the property during the first semester 2009. The results of analyses of the upstream and downstream samples were similar. The downstream sample was less in both total dissolved solids and electrical conductivity than the upstream sample, indicating that the landfill did not contribute to the surface water in these respects. No surface water samples were collected during the second semester due to lack of flowing water. Note that the creek receives contribution from the ground surface and several smaller creeks on the property east of the creek, and that these surfaces and the creek itself are subject to cattle grazing. The County and landfill operator cannot control constituents that may be carried into the creek from the other property. Leachate Waste Discharge Requirements require monitoring leachate flow rate, pH, and Electrical Conductivity on a monthly basis (Table 5). Leachate volumetric data for several months indicates reasonable average flow rates. Vadose Zone Soil Gas First Semester Results Soil gasses were sampled on July 15, 2009. Samples were collected by first measuring the methane content using a CES-LANDTEC GEMTM 500 portable gas analyzer. The GEMTM 500 was operated until a steady-state gas composition indicated that the well was purged. After purging, gas samples were collected in stainless steel Summa canisters and sent to Atmospheric Analysis &Consulting, Inc. for analysis by EPA method TO-14A (Appendix I). Second Semester Results VOCs were detected in all soil gas samples (Table 6). The highest concentration of any VOC was found in SG-l. Freon 12 was most often reported with the highest concentration in a sample. The Foothill Sanitary Landfill 9 Department of Public Works/Solid Waste 2'a Semester and Annual 2009 Groundwater Monitoring County of San Joaquin—January 31,2010