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;CV\YA1rC • <br /> A S S O C I A T E S I N C . <br /> ' SOIL MASS BALANCE CALCULATIONS <br /> ' Assum tip •ons: <br /> The estimated lateral extents of TPHg and benzene from 40 feet bgs to 60 feet bgs are generally similar in areal <br /> size, and the estimated lateral extents of TPHg and benzene from 60.5 feet bgs to 75 feet bgs are generally similar, <br /> with the estimated lateral extent of benzene being slightly larger in both depth intervals. Consequently, the <br /> ' isoconcentration shown on Figure 9 was used to perform mass balance calculations to estimate the area of TPHg <br /> and benzene in soil from 40 feet bgs to 60 feet bgs, and the isoconcentration shown on Figure 10 was used to <br /> perform mass balance calculations to estimate the area of TPHg and benzene in soil from 60 feet bgs to 75 feet bgs. <br /> ' The estimated lateral extent of TPHg and benzene in both intervals is generally in the shape of an ellipse. <br /> 40'-60' interval: 60'-75' interval: <br /> Area of ellipse(A)=II('/�a)( %2b) Area of ellipse(A)=II(%za)( %b) <br /> a=short axis of ellipse a=short axis of ellipse <br /> b=long axis of ellipse b=long axis of ellipse <br /> ' Volume(V)=Ad Volume(V)=Ad <br /> d=depth interval d=depth interval <br /> ' A=II('/2 x 43')( %2 x 58') A=II(%2 x 46')( '/2 x 98') <br /> = 1,959 ft2 =3,541 ftz <br /> ' V=(1,959 ftz)(20') V=(3,541 ft2)( 15') <br /> =39,176 ft3 petroleum impacted soil =53,107.5 ft3 petroleum impacted soil <br /> ' Average benzene concentration(Avb) Average benzene concentration(Avb) <br /> Avb calculated using sample results Avb calculated using sample results from <br /> from borings B1,B2, and VE1 borings B1, 132,MW2, MW6,B101,and B103 <br /> ' (8.1+4.0+19+0.56+0.005+0.036+0.032)/7= (9.6+0.057+0.097+0.015+5.2+0.008+0.013)/7= <br /> =4.5 mg/kg =2.1 mg/kg <br /> 28,3 liters(1)= 1 ft3 28.3 liters= 1 ft3 <br /> 1.7 kg= I liter(1) 1.7 kg= 1 liter(1) <br /> lmg= IE-6 kg lmg= IE-6 kg <br /> Mass(M)=V x Avb Mass(M)=V x Avb <br /> M=(39,176 ft3)(4.5 mg/kg) M=(53,107.5 ft3)(2.1 mg/kg) <br /> = 176,292 ft3mg/kg = 111,529 ft3mg/kg <br /> (176,292 ft mg/kg)(28.3 1/ft3)(1.7 kg/1)( IE-6 kg) =(111,529 ft3mg/kg)(28.3 1/ft)(1.7 kg/I)( IE-6 kg) <br /> =8.5 kg benzene =5.4 kg benzene <br /> 1 <br /> ' s:\enviromnewl\25291\reporMirp.doc <br />