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® Monitoring Parameter Concentration Limits <br /> Interwell concentration limits were established from background monitoring well G-l. No <br /> concentration limits were exceeded this semester in any wells. However, since there is an indication of <br /> possible changes in the background water quality, it is possible that higher levels of constituents may <br /> begin to be reported in the downgradient wells at the site. A careful review of the future monitoring <br /> results will be undertaken to try to segregate the influence to increasing background conditions from <br /> influences from the landfill. <br /> VOCs <br /> VOCs were not reported in any wells during this semester. <br /> With the exception of recently-installed G-1, all wells have been free of VOCs since January 2003. At <br /> G-1, Acetone, Chloroform, and Toluene were occasionally observed when the well was first installed in <br /> 2010 and reported during the 2nd Semester 2010, but have not been reported since that time. This <br /> confirms our conclusion that these detections were due to slight contamination of that well during <br /> construction. We 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 November <br /> 2012 (Appendix Q. Results were unremarkable. <br /> 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 second 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 August 7, 2012. All of the wells sampled were free of methane. <br /> VOCs were detected in all soil gas samples that were collected. The highest VOC concentration was <br /> found in well SG03-D (Table 5 and Appendix H). Continued lack of groundwater impact indicates that <br /> the presence of VOCs in the soil does not threaten groundwater quality. <br /> North County RC&SL Public Works/Solid Waste <br /> 2"d Semester and Annual 2012 Groundwater Monitoring 7 County of San Joaquin—January 15,2013 <br />