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APPENDIX A <br /> CALCULATIONS FOR ESTIMATION OF VOC <br /> MASS AND CONCENTRATION <br /> Described below are procedures employed for estimation of volatile organic <br /> chemicals (VOC) vapor mass and concentration in Tracy Yard soil. <br /> VOC Soil Mass Estimate <br /> Mass of VOC present within the target area of dual phase remediation system <br /> was estimated from site characterization information on VOC distribution. <br /> Attached Figures A-1 through A-4 summarize VOC distribution data. <br /> VOC distribution data was broken down into sub-areas to ease volume <br /> estimation in conjunction with concentration distribution. VOC mass within <br /> each sub-area was then estimated by multiplying volume of impacted soil with <br /> density and then with VOC concentration. Table A-1, attached, presents <br /> information pertaining to VOC mass estimation calculation. <br /> VOC Vapor Concentration Estimate <br /> VOC concentration in vapor phase for the dual phase extraction process was <br /> determined by estimating contribution from soil and ground water separately. <br /> Following is a description of the estimation process. <br /> I Vapor Phase VOC Contribution from Soil <br /> ERM used the model outlined in Jury Model (Behavior Assessment Model for <br /> Trace Organics in Soil,Jury et a1, 1983,Journal of Environmental Quality, Vol. 12, <br /> No. 4) to estimate soil vapor concentrations based on soil concentrations of <br /> volatile organic chemicals (VOC). The Jury model states that the total soil <br /> concentration of a compound, Ctotal, equals the sum of the adsorbed phase, <br /> aqueous phase, and gaseous phase: <br /> Ctotal =Csoil + Cliquid + Cvapor <br /> = Cvapor (a * Kd/H + b/H + c) <br /> and <br /> Csoi1 = Kd * Cliquid: <br /> A-1 <br />