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_ a'a r 1 Results of Initial Investigation and Work Plan December 18, 1990 ARCO Service Station No.760, Lodi, California AGS 38048-4 indicate concentrations e: fPHg and BTEX compounds are less than 10 and 1.0 ppm, respectively, the soil will be used to backfill the former gasoline tank cavity. If laboratory e� results of the composite soil samples indicate concentrations of TPHg and BTEX compounds are greater than 10 and 1.0 ppm respectively, the soil will be disposed of properly. The disposal of stockpiled soil is ARCO's responsibility. estimate of Fxcavated Soi ' The approximate limits of the proposed excavation are based on information gathered r+ during our October 1990 investigation and are shown on Plate P-2. The actual size of the excavation will depend on site conditions and the concentration of hydrocarbons encountered during excavation. We estimate 1000 cubic yards of soil may be excavated. The estimate of the volume of soil is based on(1)the amount of backfill surrounding the existing gasoline tanks and excavating the existing tank cavity to approximately 18 feet below grade, (2) an evaluated amount of soil excavated from pipeline trenches excavated 5 feet deep, 2 feet wide for a total linear distance of 130 feet, (3) excavating the proposed tank cavity to 12 feet below grade and(4) the amount of backfill in the fonner waste-oil tank cavity and excavating the former cavity to approximately 15 feet below grade. This estimate of excavated soil will vary depending on the final depths of the excavations. r Methods of Collecting Soil Samples The soil will be brought to the ground surface in an excavator bucket,and the outer soil will be scraped away. A clean,6-inch-long,2-inch-diameter, clean brass tube will be driven into the soil using a percussion sampler. The brass tube will be removed and the ends covered 16 Applied GeOSYSAMs