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5.0 SOIL-PORE GAS MONITORING In accordance with WDR Order No. R5-2007-0046, soil-pore gas probes are monitored semiannually using a field screening protocol, and soil-pore gas samples are only collected if field screening indicates methane concentrations greater than 2.5 percent. During the monitoring period, field screening of soil-pore gas probes was conducted on February 16, 2009. As shown on Table 6, no methane was detected in any of the soil- pore gas probes, and as a result, no samples were collected. 6.0 SUMMARY Groundwater quality conditions beneath the French Camp Landfill during the monitoring period are generally similar to those observed in previous monitoring periods. CLs were exceeded for one or more constituents in the samples collected from background well MW-6A, and compliance wells MW-9A, M -913 and MW-10A. With the exception of the chloride concentration measured in the sample collected from well MW-10A,none of the constituents that exceeded a CL exhibited a statistically significant increasing trend during the monitoring period. Previous statistical exceedances for chloride and TDS have been identified in samples from well MW-l0A and a NRD for groundwater monitoring well MW-l0A (Herst, 2005) concluded that the French Camp Landfill has been impacted by saltwater intrusion and the elevated chloride and TDS concentrations measured in well MW-l0A are believed to be the result of this condition and not the result of landfill-related impacts. Organic constituent results indicate chloroform was measured above the PQL in the sample collected from wells MW-6A. In response to the detection of chloroform, retest samples were collected from this well on June 30, 2009. The results of the retest samples indicate that chloroform was confirmed in both of the retest samples at similar concentrations above the PQL. Review of the historical database indicates that since 1995 chloroform has only been detected three times at three different sample points in on-site wells, while low levels of chloroform have been intermittently detected in background well MW-6A. Since chloroform is also a constituent used to treat drinking water and has been rarely detected in on-site wells, and given the fact that background well MW-6A is located approximately 1200 feet from the landfill and was completed in a traffic box in a residential street,the detection of chloroform in background well MW-6A is not believed to the result of a release from the landfill. The results of water quality analyses completed for surface-water monitoring stations are generally consistent with previous results. During the current monitoring period, one VOC (carbon disulfide) was measured above the PQL in the sample collected from station SW-1. In response to the detection of chloroform in station SW-1,retest samples were collected on June 30, 2009. The results of the retest samples indicate that no VOCs were detected and the carbon disulfide concentration measured in the primary sample is concluded to be a false positive. With the exception of turbidity in all three surface-water samples, no statistically significant increasing trends were noted. Since turbidity exhibits a statistically significant increasing trend at background surface water stations SW-1 and DA2009-0018TC_t SA09.doc 6 Geologic Associates