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1� <br /> Contaminant Mass Calculation Estimates <br /> Total Petroleum Hydrocarbons as Gasoline (TPHG) - Capillary Fringe Soil <br /> Affected soil column (capillary fringe), assumed 3' thick in the plume area, hence <br /> (100' x 20' x 3') + (125' x 80' x 3') = 36,000 ft-3 <br /> 36,000 ft3 x 0 028 ft3/m3 = 1 ,008 m3 <br /> Total TPHG concentration (1996 data) = 21600 mg/kg or, 0 0216 kg/I <br /> Soil Type - Silty Clay (assumed 108 Ib/ ft3 , at 17 3% optimum moisture content) <br /> Effective Porosity Clay - 40%, 40% - 17% = 23% soil open pore space <br /> Residual Mass TPHG = density x porosity <br /> "Mass TPHG = 114 23 kg/m3 x 0 23 = 26 27 kg/m3 <br /> Mass TPHG = 26 27 kg/m3 x 0 0216 kg/I = 0 567 kg/m3 <br /> Total TPHG = 0 567 kg/m3 x 1008 m3 = 571 kg in capillary soil column <br /> or, 151 gallons TPHG estimated <br /> Benzene - Soil Total of observed concentrations = 0 988 mg/kg <br /> *"Mass Benzene = 114 23 kg/m3 x 0 23 = 26 27 kg/M3 <br /> Mass Benzene = 26 27 kg/m3 x 0 000000988 kg/l = 0 0000259 x 10 6 kg/m3 <br /> Total Benzene = 0 0000259 kg/m3 x 1,008 m3 = 0 0026 kg in soil column <br /> or, 0 0069 gallons Benzene estimated <br />• <br /> Page 12 <br />