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4 <br /> SOIL MASS BALANCE CALCULATIONS <br /> ASSUMPTIONS: <br /> I, k <br /> BTEX constituents and TPHg were detected in soil samples collected from SB3, MW 1, and VEW3. Ethyl benzene, <br /> xylenes, and TPHg were detected in a soil sample colledted from MW2. Based on results of selected soil samples <br /> collected and analyzed during drilling activities and flame ionization detector or photo ionization detector readings <br /> measured in the field, there appears to be two distinct areas of impacted soil beneath the site. The first area is located <br /> immediately beneath the former UST excavation and appears to be limited to depths between approximately 13 and 23 <br /> feet below ground surface as depicted on Figure 4. The second impacted area is larger in size and is located closer to <br /> the water table (Figure 4). ;The estimated lateral extent of BTEX constituents and TPHg in soil samples collected from <br /> the vadose zone is is depicted on Figure 3. <br /> Area 1 <br /> For the purpose of obtaining a conservative estimate of the mass of BTEX and TPHg in the vadose zone, the lateral <br /> extent of petroleum impacted soil were assumed to be the shape of an ellipse. 'The vertical extent of petroleum <br /> impacted soil was assumed,to extend from 13 feet bgs to 23 feet bgs. The highest concentration of BTEX and TPHg <br /> detected in soil samples is 48.02 milligrams per kilogram (mg/kg) and 1,900 mg/kg, respectively. Average <br /> concentrations of 22.03 mg/kg and 970 mg/kg of BTEX and TPHg, respectively, were used in mass balance <br /> calculations to provide a conservative estimate of the mass'of BTEX and TPHg in the upper vadose zone. <br /> Area of ellipse(A)=II('/:a)'( '/2b) <br /> a=short axis of ellipse = 10' <br /> b=long axis of ellipse = 15' A x dr, v Uolu�G <br /> Volume(V) =Ad <br /> d=depth interval = 10' IC <br /> n= soil porosity=40% � C��t`e�t'� "" ' ��"�""` <br /> w.�ss <br /> k <br /> A=I1('/z x 10')( '/z x 15) <br /> 118W <br /> V 118 ft2. 10' <br /> 1,180 ft petroleum impacted soil <br /> Average BTEX concentration (Avbtex) Average TPHg concentration (Avtphg) <br /> =22.03 mg/kg =970 mg/kg <br /> 28.3 liters (1) = 1 W 28.3 liters= 1 W <br /> 1.7 kg= 1 liter(1) 1.7 kg= 1 liter(1) <br /> lmg= 1E-6 kg lmg= 1E-6 kg <br /> Mass (M)=V x n x Avbtex Mass (M)=V x n x Avtphg <br /> L M=(1,180 ft)(.40)(22.03 mg/kg) M=(1,180 ft3)(.40)(970 mg/kg) <br /> 10,398 Wmg/kg =457,840 ft3mg/kg <br /> (10,398 if mg/kg)(28.3 Uft)(1.7 kg/1)( IE-6 kg) (457,840 W mg/kg)(28.3 Uft3)(1.7 kg/1)( 1E=6 kg) <br /> 0.5 kg BTEX =22 kg TPHg <br /> i <br />