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Vapor Transport From Groundwater <br /> by Raoult's Law (they cannot exceed the "effective vapor concentration") Using <br /> Raoult's Law or calculating the effective solubility and multiplying by Henry's Law <br /> will result in the same equilibrium vapor concentration for a given TPH mixture <br /> I <br /> E 4 9 Effective Diffusion Coefficient r ` <br /> The overall effective diffusion coefficient is calculated as a depth-weighted average of <br /> the effective diffusion coefficients in the capillary fringe, the vadose zone above the <br /> capillary fringe, the lens and the building foundation The reason for considering the <br /> capillary fringe in the calculation is that the moisture content in the capillary fringe is <br /> usually much higher than the moisture content in the unsaturated zone The smaller <br /> air-filled porosity in the capillary fringe will reduce the overall diffusion coefficient <br /> significantly Following the approach in ASTM (1995) the overall diffusion <br /> coefficient is given by <br /> Deli =(d cv +d,+dl,,,, +d bldg) d p + d v + diem + d bldg (E-3) <br /> • Dcffcap Dery Defflens 17D. <br /> Cap <br /> where <br /> D,ff = overall effective gaseous diffusion coefficient from water <br /> table to the building foundation [cm2/s] <br /> Def-sap — effective gaseous diffusion coefficient in the capillary <br /> fringe [cm2/s] <br /> Defib — effective gaseous diffusion coefficient in the vadose zone <br /> between the capillary fringe and the building foundation <br /> [cm2/s] <br /> Defflens = effective gaseous diffusion coefficient in the lens <br /> [cin2/S] <br /> Deffbldg = effective gaseous diffusion coefficient in the building <br /> foundation [cm2/s] <br /> dip = thickness of the capillary fringe [cm] <br /> dy — thickness of the vadose zone above the capillary fringe <br /> and below the building foundation [cm] <br /> dle,,,. — thickness of the lens [cm] <br /> dbtdg = thickness of the building foundation [cm] <br /> E-5 <br />