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RISC Manual Version 4 4 <br /> In this equation, the vapor phase concentration in the soil at the building foundation, <br /> Cvr, is assumed to be negligible (CYf<<C,) in comparison to the concentration in <br /> vapor at the water table <br /> r U, _ '`= a - �s r' - ✓rte_ . n.' '3: `*�,�.._4� -� #. y3 s,�> <br /> rSOURCE TERMx ,,, �, . �N S -e -, <br /> E a r <br /> The vapor phase concentration at the water table is calculated using Henry's Law <br /> partitioning from the groundwater into the vapor phase concentration <br /> ( L g E-2 <br /> C = CB,V 1000cm3 1000mg ( ) <br /> where <br /> C,,S = vapor phase concentration dust above the water table in <br /> the capillary fringe [g/cm3] <br /> Cg,,. = dissolved phase concentration at the top of the <br /> groundwater aquifer(water table-capillary fringe <br /> interface) [mg/l] <br /> KH = Henry's law constant [(mg/])/(mg/1)] <br /> If this model is linked with the Dissolved Phase Transport model (Appendix B)or the <br /> Saturated Soil Model (Appendix C) then the vapor flux in g/d is calculated for each <br /> time step If this model is run in a stand-alone mode the user will be asked to specify <br /> a constant concentration in groundwater (Cg,.,)that is assumed to be directly under the <br /> house <br /> This model does not check to see if the dissolved phase concentration entered by the <br /> user (in a stand-alone mode) exceeds the effective solubility for the chemical It is <br /> important that the user enter a concentration in groundwater that does not exceed the <br /> chemicals' effective solubility This also applies to groundwater with non-aqueous <br /> phase liquids(NAPL) on the surface because the vapor concentrations are also limited <br /> E-4 <br />