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ENDPOINT:CALCULATION OF EFFECTIVE DIFFUSIVITY IN SOIL <br /> P <br /> ( EQUATIONS: age 2 of 3 <br /> t,. * De = (Da*Pa"3.33)IPt"2 (Millington-Quirk, 1961) <br /> SYMBOLS AND DESCRIPTIONS UMTS VALUE RATIONALE <br /> Da = Diffusion Coefficient of Air cm2/second see below (EPA, 1990) <br /> i Pa = Air-Filled Porosity dimensionless 0.106 (by previous equation) <br /> Pt = Total Soil Porosity dimensionless 0.276 (Alton, 1990) <br /> De = Effective Diffusion Coefficient of Chemical in Soil cm2/second see below (by equation) <br /> Chemical Da De <br /> i <br /> Benzene 8.90E-02 6.55E-04 <br /> Toluene 8.70E-02 6.40E-04 <br /> Ethylbenzene 7.50E-02 5.52E-04 <br /> Xylenes 7.00E-02 5.15E-04 <br /> ENDPOINT:CALCULATION OF CHEMICAL FLUX TO SOIL SURFACE <br /> EQUATIONS: <br /> ' F = (De*Csg)/L <br /> SYMBOLS AND DESCRIPTIONS UMTS VALUE RATIONALE <br /> ' De Effective Diffusion Coefficient of Chemical in Soil cm2/second see below (by previous equation) <br /> Csg = Concentration of Chemical in Soil Gas g/cm3 see below (by previous equation) <br /> L= Depth to Impacted Soil cm see below (minimum depth to groundwater) <br /> F = Flux to Ground Level g/cm2-second see below (by equation) <br /> Chemical De Csa L F <br /> Benzene 6.55E-04 2.05E-05 304 4.42E-1I <br /> Toluene 6.40E-04 SA2E-06 304 1.77E-11 <br /> Ethylhenzene 5.52E-04 6.20E-05 304 1.13E-10 <br /> Xylenes 5.15E-04 2.47E-05 304 4.18E-11 <br /> ENDPOINT:CALCULATION OF INDOOR AIR CONCENTRATION FROM FLUX THROUGH FOUNDATION <br /> EQUATIONS: <br /> Ci(s) = F* A*b*(I/VR)*cfl <br /> VR. = A*CH*E+02 <br /> SYMBOLS AND DESCRIPTIONS UMTS VALUE RATIONALE <br /> F = Flux of Chemical to Ground Level g/cm2-second see below (by previous equation) <br /> A = Surface Area of Building Floor cm2 7.43E+05 (estimated "footprint" of building 40x20 sq.ft.) <br /> CH = Ceiling Height of Building cm 305 (assumes tailing height of 10 ft.) <br /> b = Attenuation Factor for Foundation dimensionless 1E-03 (OCHCA, 1991) <br /> E = Air Exchange Rate volume/hour 2 (personal communication) <br /> cfl = Conversion Factor (mg/m3)/(g/cm3) 1.00E+09 (by definition) <br /> ct2 = Conversion Factor hour/second 2.78E-04 (by definition) <br /> VR = Building Ventilation Rate cm3/second 1.26E+05 (by equation) <br /> Ci(s) = Concentration of Chemical in Indoor Air mg/m3 see below (by equation) <br /> i <br /> Chemical F Ci s <br /> Benzene 4.42E-11 2.61E-04 <br /> Toluene 1.77E-I 1 1.05E-04 <br /> Ethylbenzene 1.13E-10 6.651`04 <br /> Xylenes 4.18E-11 2.47E-04 <br /> RSKCALC4 <br /> i <br /> I <br />