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the former Mobil bulk plant. Ground water data from B-5 (approximately 13 feet west of the <br /> site, near Grantline Road), although not collected according to standard protocol, indicates that <br /> no detectable concentrations of gasoline or diesel-range hydrocarbons are present in ground <br /> water in the vicinity of B-5. Soil data collected in 1989 for diesel-range constituents indicates <br /> that with the exception of soil samples collected in the northeast corner of the property (EB6 at <br /> 5 and 10 fbg), diesel-range hydrocarbon concentrations do not exceed 10 ppm. Field <br /> instrumentation capable of detecting gasoline-range hydrocarbons, did not respond to soil <br /> samples collected from AW-1 (also in the northeast corner of the site). These data indicate the <br /> adequacy to which the lateral extent of hydrocarbons have been characterized. <br /> Sixth Bullet Item <br /> Alton Geoscience does not agree with the statement "Because the severity of contamination left <br /> beneath the site and adjacent to the site has not been adequately characterized, the risk <br /> evaluation presented in the report is flawed." As stated above, the lateral extent of <br /> hydrocarbons has been adequately characterized to the north, south, east, and qualitatively to the <br /> west. The risk assessment is based on the upper 95% confidence interval chemical concentration <br /> in soil detected during the March 25, 1993, supplementary boring installation. Furthermore, <br /> it is assumed that the upper 95% confidence interval chemical concentrations are present 10 feet <br /> beneath the entire footprint of a hypothetical building located on the site. These assumption are <br /> conservative and serve to overestimate actual vapor migration and human health risks. <br /> Seventh Bullet Item <br /> As stated previously, Alton Geoscience does not agree that "separate-phase" hydrocarbons are <br /> present. There is no evidence that separate-phase hydrocarbons are present. This is supported <br /> by the ground water monitoring and sampling results compiled since October 1990. No <br /> "separate-phase" hydrocarbons have been detected in any monitoring wells. The ground water <br /> monitoring and sampling results do not support the presence of "separate-phase" hydrocarbons <br /> beneath the site. Rather, the ground water monitoring and sampling results support the absence <br /> of "separate-phase" hydrocarbons beneath the site, evidenced by low to non detectable <br /> concentrations. <br /> Eighth Bullet Item <br /> Geomatrix states that "active remediation of separate phase hydrocarbons at this site and <br /> additional investigation of the lateral extent of contamination are necessary. " There is no <br /> evidence which suggests that separate-phase hydrocarbons are present either in soil or ground <br /> water at this site. Conversely, sufficient information, particularly the comprehensive ground <br /> water database established for this site, is available which supports the assertion that there are <br /> no liquid-phase hydrocarbons in soil or ground water at the site. <br /> 3 <br />