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During excavation of the former waste-oil tanks approximately 150 cy of soil were <br /> removed and disposed of at a Class II landfill The total pounds of petroleum hydrocarbons <br /> as gasolene removed have been estimated using an average concentration of 100 ppm and <br /> assuming a bulk density for soil of 122 IWO The total pounds of petroleum hydrocarbons as <br /> diesel removed have been estimated using an average concentration of 820 ppm and assuming <br /> a bulk density for sod of 1221bs/ft3 The average concentrations used were obtained from <br /> analytical results of soil samples collected from samples beneath the former waste-oil USTs <br />' Analytical results of soli samples are presented in Table 7 <br /> Petroleum hydrocarbons as gasoline removed = 100 mg/kg x I x 10-6 kg/mg x <br /> 122 lb/ft3 x 150 cy x 27 ft3/cy <br /> 49 lbs ofetroleum hydrocarbons drocarbons as TPHG removed <br /> P <br /> Petroleum hydrocarbons as diesel removed = 820 mg/kg x 1 x I06 kg/mg x 122 lb/ft3 <br /> x 150 cy x 27 ft'/cy <br />' =405 lbs of petroleum hydrocarbons as TPHD removed <br /> 6.2 Petroleum Hydrocarbons Remaining in Soil <br /> Based on analytical results of soil samples collected from the soil borings and samples collected <br /> beneath the UST excavations, residual petroleum hydrocarbons remain beneath the site The <br /> highest concentrations were detected beneath the product lines and former waste-oil tanks <br /> T9 and T10 Figures 5 through 8 depict the extent of residual petroleum hydrocarbons that <br /> remain beneath the site from 0 to 29 feet bgs and 30 to 615 feet bgs The area impacted was <br /> estimated using a planumter (instrument that measures plan view area within contour lines) <br /> The mass of petroleum hydrocarbons remaining as TPHG and TPHD was estimated using the <br /> following parameters and equations <br />' From 0 to 29 feet bgs and 30 to 615 feet bgs petroleum hydrocarbons as gasoline were <br /> detected in three areas (former gasoline UST, former product lines, and near the former <br /> waste-od tanks) Concentrations within 0 to 29 feet bgs ranged from below laboratory <br /> detection limits to 5,700 ppm (beneath the former product lines) Figure 5 shows the location <br /> of the soil samples The total pounds of petroleum hydrocarbons as gasoline that remain <br /> between 0 to 29 feet have been estimated using an average concentration of 383 ppm, and <br /> assuming a bulk density for soil of 122 lb/ft' Concentrations within 30 to 615 feet ranged <br /> from below laboratory to 160 ppm (near the former waste-oil tank T8) Figure 6 shows the <br /> location of the soil samples The total pounds of petroleum hydrocarbons as gasoline that <br /> remain between 30 and 615 feet bgs have been estimated using an average concentration of <br /> 16 ppm, and assuming a bulk density for soil of 145 Ib/ft3 (silty sand and sand sediment)for the <br /> deeper sod interval The average concentrations used were obtained from analytical results <br /> of soil samples collected from the soil borings, soil samples collected beneath the former USTs <br /> W-\N\PJO11805\D8051420 4 B5-97\pra 1 Rev 0 3112/97 <br /> 20905-142 004 C-2 <br />