ARCHIVED REPORTS_2012_7 - Laserfiche WebLink

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well was installed in 2003, but quickly reduced to "trace" in three quarters. Excluding probable contamination during well construction and compounds also found the QC blanks, no VOC has been reported in this well. Therefore, there has been no indication of impact from the landfill at this well. MW-7(Up gradient): Concentrations of all parameters were within established concentration limits where the limits could be determined(Table 2). A comparison of general water quality parameters between MW-7 (up-gradient) and MW-6 (downgradient)indicates better water quality downgradient of the landfill. This indicates 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, a decreasing trend is reported in the concentration of Chloride(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, but were not available this quarter. 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 last collected on April 5, 2012, and is included in this second 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 was operated until a steady-state gas composition indicated that the well was purged and ready for sampling. Soil gas samples were collected in 1-liter Summa canisters and sent for VOC analysis by EPA method TO-14. The concentrations of major gasses were recorded during the second quarter 2012 TO-14 sampling event, and a sample was collected from the probe most likely to have the highest VOC concentration: the sample was taken from the probe with the highest methane content, but if methane was not detected,the sample was collected from the deepest probe. The probe selected in the first TO-14 sampling event conducted in 2006 has been used thereafter for this analysis. Methane concentrations were zero in all perimeter migration monitoring wells during this quarter 40 with the exception of SG-6M and SG-6D. Corral Hollow Sanitary Landfill 14 Department of Public Works/Solid Waste 2n°Quarter 2012 Groundwater Monitoring County of San Joaquin—July 30,2012