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ANNUAL SUMMARY Groundwater General Water Quality Parameters Monitoring data shows that all constituents were within interwell tolerance limits except for: Well MW-3, at which Chloride concentration limits were slightly exceeded in the first semester. Chloride was recorded at 11 mg/l,which slightly exceeds the tolerance limit of 9.8 mg/l. • Well MW-4, at which Turbidity concentration limits were slightly exceeded in the second semester. Turbidity was recorded at 48.1 mg/l,which slightly exceeds the tolerance limit of 48 mg/l. However, this turbidity exceedence should be discounted because of the insignificant difference between the detected value and the tolerance limit and because this was the first analysis from this well. 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 positives for Acetone in the January samples, VOCs were not detected in wells MW-1,MW-2R and MW-3 during the first semester 2007 sampling event. Acetone was also reported in wells MW-1, MW-2R, and MW-3 during the second semester sampling event conducted on July 23, 2007. Trichloroethene(TCE)was detected in well MW-3 during the second semester sampling event at 0.60 mg/l. No further VOCs were detected in any of the remaining wells during first and second semester 2007. COCs Samples for COC analysis were collected from the new wells MW-4 and MW-5 on July 23, 2007. Other than trace concentrations of Di-n-butyl Phthalate in wells MW-4 and MW-5, no semi-volatiles were reported. Di-n-butyl Phthalate is a common laboratory contaminant(as identified in the WDRs)that was found in a laboratory control blank during the second semester sampling event. Other than trace concentrations of Fensulfothion in well MW-5,no Organophosphate Pesticides were reported during the second semester sampling event. The metals reported are typically found in groundwater and there were no exceedences of concentration limits during the second semester sampling event. Surface Water Surface water samples were retrieved on February 11 2007. All concentrations of monitoring and field P Y � g parameters were below established concentration limits where the limits could be determined in the First Semester of 2007. No surface water samples were collected during the second semester of 2007. Foothill Sanitary Landfill 12 Department of Public Works/Solid Waste 2nd Semester and Annual 2007 Groundwater Monitoring County of San Joaquin—January 31,2008