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Soil Boring Results and VEG/ISCO Work Plan <br />Field Maintenance Shop #24, Stockton, California October 2016 <br />2.1.1. Soil Boring SB-4 <br />TPH-g ranged from a concentration of 3,800 milligrams per kilogram (mg/kg) at 9-10 feet <br />bgs (silt) to 9.2 mg/kg at 22-23 feet bgs (clay). <br />TPH-d ranged from a concentration of 560 mg/kg at 9-10 feet bgs (silt) to 49 mg/kg at 22- <br />23 feet bgs (clay). <br />Benzene and toluene were not detected above the laboratory method detection limits <br />(MDLs). <br />Ethylbenzene ranged from a concentration of 3.6 mg/kg at 14-15 feet bgs (silt with sand) <br />to below method detection limits at 22-23 feet bgs (clay). <br />Total Xylenes ranged from a concentration of 51 mg/kg at 9-10 feet bgs (silt) to 0.052 <br />mg/kg at 22-23 feet bgs (clay). <br />Naphthalene ranged from a concentration of 63 mg/kg at 14-15 feet bgs (silt with sand) to <br />0.63 mg/kg at 22-23 feet bgs (clay). <br />Impacts appear to be concentrated in the upper portion of the soils beneath the former dispenser <br />island in the vicinity of SB-4. <br />2.1.2. Soil Boring SB-5 <br />TPH-g ranged from a concentration of 890 mg/kg at 20-21 feet bgs (silty sand) to 12 mg/kg <br />at 16-17 feet bgs (poorly graded sand with silt). <br />TPH-d ranged from a concentration of 2,200 mg/kg at 20-21 feet bgs (silty sand) to 10 <br />mg/kg at 16-17 feet bgs (poorly graded sand with silt). <br />Benzene was detected in only one sample with a concentration of 0.0055 mg/kg at 25-26 <br />feet bgs (clay). <br />Toluene was not detected above the laboratory MDL. <br />Ethylbenzene ranged from a concentration of 17 mg/kg at 20-21 feet bgs (silt with sand) <br />to 0.021 mg/kg at 16-17 feet bgs (poorly graded sand with silt). <br />Total Xylenes ranged from a concentration of 19 mg/kg at 20-21 feet bgs (silt with sand) <br />to below the laboratory MDL at 30-31 feet bgs (clay). <br />Naphthalene ranged from a concentration of 31 mg/kg at 20-21 feet bgs (silt with sand) to <br />0.080 mg/kg at 30-31 feet bgs (clay). <br />2.1.3. Soil Boring SB-6 <br />TPH-g ranged from a concentration of 19 mg/kg at 31-32 feet bgs (clay) to 0.22 mg/kg at <br />14-15 feet bgs (poorly graded sand with silt). <br />TPH-d ranged from a concentration of 250 mg/kg at 14-15 feet bgs (Poorly graded sand <br />with silt and gravel) to 4.1 mg/kg at 31-32 feet bgs (silt). <br />Benzene was detected in only one sample with a concentration of 0.041 mg/kg at 31-32 <br />feet bgs (silt). <br />Toluene was not detected above the laboratory MDL. <br />Page 4