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• <br /> • Benzene and Total Petroleum Hydrocarbons as Gasoline (TPH-G) were used to <br /> calculate the total mass in groundwater prior to remediation. Benzene is a known <br /> carcinogen and a priority risk assessment constituent. Concentrations of TPH-G are <br /> the largest at this Site and therefore, would calculate the largest mass. <br /> • Impacted groundwater volumes were calculated using best fit cylinders, based on the <br /> ranges specified in Table D-2. Each mass was calculated using the maximum <br /> concentration within the range, except for the range which contained the maximum <br /> concentration of the data set. The maximum concentration was used in calculating <br /> the mass for the last range. <br /> • A typical porosity of 0.30 was used based on a mixed soil of sandy to silty clay. <br /> • Thickness of impacted groundwater is equal to 20 feet or the water column length in <br /> extraction well E-1 in October 1992. <br /> Table D-2. Groundwater Mass Balance Calculation Results <br /> Concentration Calculated Total Mass'-- <br /> Impacted <br /> ass-Impacted Soil Well Ranges Concentration Mass Removed <br /> Volume (ft) Constituent ID (m/L/) (m/L) (lbs) (a) (lbs) <br /> 6,000 Benzene W-3 0.5-5 5 0.001 <br /> 300 Benzene W-3 >5 5.2 0.00003 <br /> 6,300 Benzene W-10 >0.5 3.5 0.0004 <br /> 0.001 0.0003 <br /> 3,100 TPH-G W-3 50-500 500 0.03 4 <br /> 3,100 TPH-G W-3 >1,000 1,000 0.06 <br /> 6,300 TPH-G W-11 >50 59 0.01 <br /> 0.10 0.01 <br /> (a) Mass (lbs) = Impacted Groundwater Volume (ft) * Porosity * Water density <br /> (L/ft3) * Concentration(mg/L) * 10-3 g/mg * 0.002203 lb/g <br /> r.• <br /> I <br />