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0 <br />0 <br />11 <br />I 1 <br />i] <br />1� <br />[7 <br />1) In background well G-1 the concentration limit for Electrical Conductivity was exceeded in <br />the fourth quarter. The exceedence is not an indication of a release because the well is up - <br />gradient from the landfill. The concentration is below the DHS Maximum Contaminant <br />Levels for drinking water. <br />Monitoring Parameter Concentration Limits <br />Interwell concentration limits were established from background monitoring well G-1. <br />VOCs <br />Acetone (trace concentration) was reported in wells G-31), G-5, and G-6 in the third quarter. A <br />trace of Methylene Chloride was reported in G-31) in the third quarter. <br />Acetone (trace concentration) was reported in well G-5 in the fourth quarter. <br />Other than "false positives" no VOCs were reported in G-1, and G-4 <br />Surface Water <br />Surface water samples could not be collected in the second semester due to insufficient rainfall. <br />Unsaturated Zone <br />During the second semester, the lysimeters did not yield enough water for sampling, indicating <br />no detectable leaks from the liner in those areas. Unsaturated zone monitoring will continue in <br />accordance with the WDRs. <br />Unsaturated Zone Soil Pore Gas <br />Soil gas samples were collected on September 29 and 30, 2005. Before sampling, the methane <br />content was measured using a CES-LANDTEC GEMTm500 portable gas detector. The <br />GEMTm500 was operated until a steady-state gas composition indicated that the well was purged. <br />After purging, gas samples were collected in 6 -liter Summa canisters and sent to Atmospheric <br />Analysis and Consulting, Inc. for analysis by EPA method TO -14A. <br />Test Results <br />Methane concentrations were zero percent in all but two of the wells. The concentration varied <br />from 2.3 percent in SG -7 to 50.3 percent in SG -6. <br />VOCs were detected in ten of the seventeen air samples. The highest VOC concentration was <br />found in well SG -6 (Table 6, Appendix I). The County plans to install a LFG extraction system <br />in 2006 in accordance with the Engineering Feasibility Study. <br />North County RCSL 7 Public Works/Solid Waste <br />2nd Semester and Annual 2005 Groundwater Monitoring County of San Joaquin — January 24, 2006 <br />