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Mr. Wes Johnson Project 16038-700.000 June 29, 1999 Page 3 The results in Table 1 show that 11 VOCs were detected in the soil vapor sample from well CH-2. Of these, only four have been detected in the groundwater in nearby well MW-5. Also, one VOC (chloromethane) detected in groundwater was not detected in the soil vapor. This indicates that landfill gas may be the source of the VOCs in groundwater. The results in Table 1 show that, with the exception of chloromethane, the equilibrium concentration in groundwater (Cw) predicted from the soil vapor concentration is greater than the measured concentrations of these VOCs in the groundwater. These results are consistent with landfill gas as the source of VOCs in the groundwater. This interpretation is also consistent with the fact that seven VOCs, which were detected in soil vapor, were not detected in groundwater. If groundwater had been the source of the VOCs detected in the soil vapor, then more VOCs would have been detected in groundwater and the measured concentrations of VOCs in the soil vapor would have been higher. Another factor that strongly suggests that landfill gas is the source of VOCs in the groundwater is the fact that VOCs are always associated with methane. Landfill gas monitoring probe adjacent to wells MW-4 and SB-1 did not detect the presence of methane, and these wells are not impacted with VOCs. The only location where VOCs are detected in groundwater (MW-5) is the same location where methane is detected in the soil vapor above the groundwater. With the exception of methylene chloride and chloromethane, all the compounds detected in the soil vapor appear to be present at sufficiently high concentrations to impact groundwater. The fact that only some of these VOCs were detected in groundwater suggests that, despite the close proximity of the soil vapor and groundwater monitoring points, equilibrium have not been established. It should be noted that methylene chloride and chloromethane have been detected only once (in the case of chloromethane) or sporadically (in the case of methylene chloride). The presence of these compounds may be anomalous or due to lab error. The importance of this correlation is the selection of the methods of exploration of the extent of methane and VOC migration from the landfill, and the methods of remediation. Because of the strong correlation between methane and VOCs the logical exploration method would focus on detection methane in the soil vapor above the groundwater with the use of landfill gas monitoring probes. EMC®/I SAC:\J:\PROJECTS\P16\60387000.AS-98\cbell:I Rev.0,06/29/1999 16038-700.000