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' Environmental <br /> Mr Harlin Knoll Resources <br /> 14 August 1998 Management <br /> Page 9 <br /> represents weathered product For the purpose of this discussion, TPH-g <br /> refers to this tentatively-identified weathered gasoline <br /> TPH-g occurs in all samples collected beneath the former tank location, <br />' and generally decreases in concentration with depth This is consistent <br /> with the analytical results from the Phase II investigation (Table 1) in that <br />' the maximum TPH-g concentration of 17,000 mg/kg was detected at a <br /> depth of 16 5 feet bgs, and the remaining TPH-g concentrations at boring <br /> B-2 were much lower (1 3 mg/kg or less) Analytical results from both <br />' investigations suggest that soil beneath the former tank location is <br /> impacted by TPH-g from a depth below 115 feet bgs to the water table <br /> Although TPH-g is present in the soil at the former tank location, <br /> benzene appears to be absent The former UST was removed in 1979, <br />' therefore, the potential TPH-g release had to occur prior to this removal <br /> The TPH-g has undergone weathering since the time of release as <br /> indicated by the analytical results regarding its uncharacteristic gasoline <br /> profile Due to the age and weathered condition of the TPH-g, it is <br /> unlikely that benzene, a major component of gasoline that is susceptible <br /> to volatization and degradation, would still be present at detectable <br />' concentrations The only benzene detection in soil has a low <br /> concentration of 0 017 mg/kg and occurs approximately 20 feet above <br /> the water table in a Phase II soil sample collected from a depth of <br />' 215 feet bgs at boring B-2 <br />' Based on field observations and chemical analyses, the soil at boring <br /> B-6 is not impacted with TPH-g Soil samples were analyzed at 31 and <br /> 36 feet bgs. at this location to investigate the zone directly above the <br />' water table TPH-g, BTEX, and TBA analyses all reported low or <br /> nondetectable concentrations In addition, no visible hydrocarbon <br /> impact was noted in the soil during drilling activities <br /> CHEMICAL CONSTITUENTS IN GROUND WATER <br /> TPH-g, BTEX, and TBA were all detected in ground water at the site As <br /> with soil, although TPH-g was detected in ground water from borings <br /> B-5 and B-6, the chromatograms did not match the gasoline profile and <br /> likely represent weathered product, therefore, in this discussion, TPH-g <br /> refers to this tentatively identified weathered gasoline product As a <br />