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Morita Brothers 15 May 6, 1992 0, 4.0 CONCLUSIONS AND RECOMMENDATIONS ' The data obtained from the tank removal operations suggest that soil impacted with gasoline hydrocarbons at concentrations in excess RWQCB recommended guidelines ' exist at the subject site in an area beneath the former location of the 5,000 gallon underground unleaded gasoline tank as well as the product pipeline associated with ' the northern gasoline dispensers The subsequent soil drilling activities indicate that gasoline hydrocarbons in excess of 10 mglkg are confined to a depth of less than 25 feet below surface at the location of the former 5,000 gallon unleaded gasoline ' tank, and less than 20 feet at the location of the product pipeline associated with the northern gasoline dispensers, and less than 10 feet laterally from the former tank, ' and less than 10 feet laterally from the former location of the product pipeline associated with the northern gasoline dispensers There is a single anomolous laboratory result of benzene detected at a concentration of 10 mg/kg, and toluene detected at 1 3 mg/kg at a depth of 30 feet in boring TH-4, which was positioned 15 feet west of the west side of the former 5,000 gallon unleaded gasoline tank However TPH as gasoline was detected at a concentration of only 5 85 mg/kg in this sample, and the concentration of benzene at a depth of 20 feet was only 0 021 mg/kg, and ' 0 052 mg/kg at a depth of 40 feet in this boring This indicates a very limited volume of impacted soil in the vicinity of the 30 foot sample Laboratory analysis of soil ' samples from the two vertical assessing borings detected total lead at what appears to be a background concentration of 19 to 20 mg/kg Soluble lead was analyzed for in ' these samples and none was detected Therefore, no lead impacted soil has been observed Based on the field information and analytical data, it appears that if ' remediation measures are undertaken, they would involve less than 300 cubic yards of soil in the area of the former 5,000 gallon unleaded gasoline tank, less than 200 cubic yard of soil in the area of the product pipeline associated with the northern ' gasoline dispensers 4. 1 Remedial Action Alternatives At least four options for remediation of the soil are applicable to the site, 1) no action, ' 2) excavation and transportation of soil to an approved landfill, and 3) in-situ vapor, and 4) excavation and surface btoremediation ' EB-8101-2 9204-EO44 RPT ■