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the landfill. This would appear to indicate that the landfill has no affect on the deep aquifer.No primary MCLs were exceeded this quarter in MW-7. Secondary MCLS for EC, Sulfate and TDS were exceeded in MW-7 this quarter. However,the EC, Sulfate, and TDS levels are consistent with the general historical conditions at this well. Based on output from the Sanitas statistical software, an increasing trend is reported in Bicarbonate Alkalinity, whereas a decreasing trend is reported in the concentration of Chloride, and Sulfate (Table 3). No VOCs were reported at this well this quarter. VOCs were last detected in this well on April 23, 2004;these detections are believed to have been introduced during well construction, and do not indicate groundwater impact from the landfill. Surface water Surface water samples were last collected on January 27, 2011. All concentrations of field parameters and constituents of concern were below established concentration limits where the limits could be determined. Unsaturated Zone Soil Pore Gas The Monitoring and Reporting program for the landfill requires semi-annual VOC testing by TO-14 analysis. Soil Gas samples were not collected this quarter,but will be collected and analyzed during the 2nd Quarter 2012. Soil gas samples were last collected on July 28, 2011. This information was included in the third quarter report. Before sampling,the concentration of major gasses (Methane, Carbon Dioxide, and Oxygen) and pressure were measured using a CES-LANDTEC GEMTm2000 portable gas detector. The GEMTm2000 is operated until a steady-state gas composition indicated that the well was purged and ready for sampling. Soil gas samples are collected in 1-liter Summa canisters and sent for VOC analysis by EPA method TO-14. The probes for TO-14 sampling were selected in 2006, with samples collected from the probe most likely to have the highest VOC concentration: the sample was.taken from the probe with the highest methane content. If methane was not detected, then the sample was collected from the deepest probe. The probes selected in 2006 continue to be sampled. VOCs were detected in all seven soil gas well probes during this third quarter monitoring event. The highest VOC concentration was found in well SG-6D. No "upwind" air sample was taken. Groundwater Direction and Flow Rate Shallow Aquifer Groundwater elevations at wells SB-1, MW-4, MW-5, and MW-8 indicate that the groundwater flow gradient in the shallow perched aquifer continues to be to the southwest and into the landfill from SB-1 location(Figure 2 and Appendix G). The average groundwater velocity is calculated to be 2.27 ft/yr based on a gradient of 0.0081 feet per foot. The current water levels are similar Corral Hollow Sanitary Landfill 12 Department of Public Works/Solid Waste 1s`Quarter 2012 Groundwater Monitoring County of San Joaquin—April 16,2012