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indication of possible changes in the background water quality, it is possible that higher levels of <br /> constituents may begin to be reported in the downgradient wells at the site. A careful review of the <br /> future monitoring results will be undertaken to try to segregate the influence to increasing background <br /> conditions from influences from the landfill. <br /> VOCs <br /> VOCs were not reported in any wells during this semester. <br /> With the exception of newly-installed G-1, all wells have been free of VOCs since January 2003. At <br /> G-1, Acetone Chloroform, and Toluene were occasionally when the well was first installed in 2011 <br /> reported during the 2nd Semester 2010, but have not been reported since that time. This confirms our <br /> conclusion that these detections were due to slight contamination of that well during construction. We <br /> expect that this well will remain "non-detect status" in the future. <br /> With the exception of the detections at G-1, VOCs have not been confirmed at the North County <br /> Sanitary Landfill since January 2003, over nine years ago. <br /> Storm Water <br /> Storm water was sampled from discharge point SW-4 at the north west corner of the Unit in February <br /> 2012 (Appendix Q. Results were unremarkable. <br /> AML Surface Water <br /> Surface water was not available for sampling this semester. Surface water samples were last collected <br /> January 31, 2011. Samples are taken if sufficient water is flowing at sampling points during the wet <br /> season. <br /> Unsaturated Zone (Lysimeters) <br /> During the first semester,the lysimeters did not yield enough water for sampling, indicating no <br /> detectable leaks from the liner in those areas. Unsaturated zone monitoring will continue in accordance <br /> with the WDRs. <br /> Soil Gas <br /> Soil gas samples were collected on May 17, 2012. With the exception of SG-6, all of the wells sampled <br /> were free of methane. Methane was observed in SG-6 at 26.7%. <br /> VOCs were detected in all soil gas samples that were collected. The highest VOC concentration was <br /> found in well SG-6 (Table 5 and Appendix H). Continued lack of groundwater impact indicates that the <br /> presence of VOCs in the soil does not threaten groundwater quality. <br /> Leachate <br /> Waste Discharge Requirements require monthly monitoring of leachate flow rate,pH, and Electrical <br /> Conductivity (Table 2). In addition,the County is monitoring the quantity of liquid in the secondary <br /> sump below Modules 3 and 4. <br /> North County RC&SL Public Works/Solid Waste <br /> 151 Semester 2012 Groundwater Monitoring 7 County of San Joaquin—July 26,2012 <br />