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MONITORING RESULTS Groundwater Summary Groundwater was sampled on April 16, 2007. Concentrations of parameters in all wells were within established concentration limits. In January 2006, all wells were resurveyed based on the NAVD88 control rather than MSL. Top of Casing(TOC) elevations have been changed on Tables 1 and 2 to correspond with the new surveyed elevations at that time. Six VOCs were reported in impacted well MW-5, one of which in"trace"concentrations. No VOCs reported in MW-5 appeared in any of the laboratory control blanks. No VOCs were reported in the other two shallow aquifer wells. No VOCs were reported in any of the deep aquifer wells. No parameter appeared in any of the laboratory control blanks. Shallow Aquifer SB-1 (Up-gradient): Concentrations of all the parameters analyzed were within established concentration limits (Table 1). The concentration limits of Nitrate as Nitrogen and Total Dissolved Solids (TDS) could not be established due to statistically significant increasing trends. In addition, there is a decreasing trend present for turbidity this quarter(Table 3). Concentration limits for Nitrate and TDS were taken from WDRs. No VOCs were reported this quarter at this well. MW-4 (Down-gradient): Concentrations of all parameters were within established concentration limits. Decreasing trends in Chloride, TDS, Sulfate, Turbidity, and EC continue this quarter. A review of the data indicates that decreasing trends for these parameters were first apparent during the following quarters: • Chloride in first quarter 2003 • TDS in first quarter 2001 • Sulfate in third quarter 2004 • EC in second quarter 2004 This indicates a relatively long trend of improving general water quality conditions at this well. Corral Hollow Landfill 7 Department of Public Works/Solid Waste 2nd Quarter 2007 Groundwater Monitoring County of San Joaquin—July 31,2007