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VOCs Two VOCs (1,1-Dichloroethene and Trichloroethene) were reported in samples collected from well MW-3 during the 1St semester sampling,but not in the retest that followed. They were again reported in the 2n semester sampling events. These detections will continue to be scrutinized in the future. Due to the size of the pipes serving the LFG wells in the western part of the landfill(near MW-3), it is likely that LFG is not adequately collected from that portion of the landfill. To address this potential, the County intends to improve the piping to the two wells in this portion of the landfill in 2010. The County continues to be concerned that installation of impermeable liner over refuse decreases the potential venting of LFG in spite of the presence of a LFG collection system. Sealing the refuse from the air can increase the potential for contamination of groundwater by LFG entering the soil beneath the landfill. Semi-Volatile Organic Compounds (SVOCs) Eight SVOCs were reported in samples collected from wells MW-3 and MW-4 during the COC sampling event collected during the 3rd Quarter 2009,but were not reported in these well when re- sampled during the 4th quarter 2009. Therefore, the first reports were erroneous,probably due to laboratory contamination. Metals • Well MW-1: Groundwater samples were unable to be obtained during 2009 sampling events due to low water levels. • Well MW-2R: Five metals were observed during the COC sampling event collected during the 3rd Quarter 2009. Two of the metals were observed at trace concentrations. However,the presence of these metals are not an indication of impact from the landfill, because these same metals were detected in MW-4 which is up gradient of the landfill. • Well MW-3: Seven metals were observed during the COC sampling event collected during the 3rd Quarter 2009. Five of the metals were observed at trace concentrations. However,the presence of these metals are not an indication of impact from the landfill, because these same metals were detected in MW-4 which is up gradient of the landfill. • Well MW-4: Six metals were observed during the COC sampling event collected during the 3rd Quarter 2009. Three of the metals were observed at trace concentrations. However,because MW-4 is up gradient of the landfill the presence of these metals are not an indication of impact from the landfill. • Well MW-5: Five metals were observed during the COC sampling event collected during the 3rd Quarter 2009. Two of the metals were observed at trace concentrations. However, the presence of these metals are not an indication of impact from the landfill, because these same metals were detected in MW-4 which is up gradient of the landfill. Foothill Sanitary Landfill 14 Department of Public Works/Solid Waste 2nd Semester and Annual 2009 Groundwater Monitoring County of San Joaquin—January 31,2010