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1 <br /> !ITE CLOSURE EVALUATION REPORT <br /> Ultramar Station No. 696 <br /> 2448 West Kettleman Lane <br /> Lodi, California <br /> Delta Project No. D093-916 <br /> Page 5 <br /> ' During August 31 through September 8, 1994, six soil confirmation borings were advanced at locations <br /> indicated on Figure 3. Laboratory analysis of samples submitted indicate TPH as gasoline to be below <br /> ' the laboratory's limit of detection of 1 mg/kg in all samples except those collected from confirmatica <br /> borings CB-4, CB-5 and CB-6. A very conservative assumption would be that 400 cubic yards of soil <br /> impacted with a volume weighted average of 300 mg/kg of TPH as gasoline in the vicinity of CB-4, <br /> CB-5, and CB-6 would amount to approximately 60 gallons of gasoline remaining in the soil matrix. <br /> Given that approximately 1 600 gallons of gasoline were removed from the soil matrix utilizing the SVE <br /> pP Y � g <br /> system and that a conservative estimate indicates that approximately 60 gallons of gasoline may remain <br /> in the soil matrix, it appears that greater than 96 percent of the gasoline in the subsurface has been <br /> ' removed through active remediation. This figure does not account for the removal of liquid-phase <br /> hydrocarbons and hydrocarbon-impacted ground water from January 1986 to late 1988. <br /> f� <br /> 6.0 DISCUSSION <br /> Environmental investigations conducted at the_site indicate that petroleum_hydrocarbons leaked from the <br /> ' north end of a former underground fuel storage tank and moved downward through soil to the ground <br /> water table. Remediation efforts at the site appear to have reduced the extent of petroleum hydrocarbons <br /> ' in soil to a narrow column directly beneath the former tank pit. The concentration of petroleum <br /> hydrocarbons in ground water has been reduced to non-detect levels. <br /> 1 <br /> t <br /> RPTl34.SJS <br /> 1 <br />