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The organic chemicals in the subsurface may be leached to the groundwater. To <br /> estimate the potential chemical loading rate from the subsurface soil to groundwater for <br /> the four chemicals of concern (Section 3.1), the Jury et al. (1983) Behavior Assessment <br /> :. Model was used (Section 4.4.3.1). The loading rate of contaminants from the subsurface <br /> leaching to groundwater was used as input to the saturated zone model, AT123D (Yeh <br /> 1981). Details of the models and parameters used are described in Section 4.4.3.1. <br /> The organic chemicals in the subsurface may be released to .the atmosphere by <br /> volatilization. To estimate the airborne concentrations of the five chemicals of concern, <br /> the volatilization flux component of the Jury Behavior Assessment Model was used. The <br /> site is currently paved which reduces the volatilization flux. The paving acts as a <br /> relatively impermeable layer. Although there are no current development plans to <br /> remove the paving, this pathway was modeled with the current occupational populations. <br /> To be protective of human health in the event that the paving would be removed in the <br /> future, the site was also modeled to represent residents living on the site. The <br /> emissions from the model were used as input to a simple box model to calculate <br /> exposure concentrations in air at the site. Site-specific characteristics along with <br /> applicable chemical information which influence fate and transport were used for <br /> modeling whenever possible. <br /> 4.2.3 Exposure Points <br /> An exposure point is a specific location where human receptors can come in contact with <br /> ..• site-related chemicals. Exposure points are usually selected so that the greatest and <br /> most reasonable potential exposures will be quantitatively evaluated. Evaluation of <br /> receptor risks at these points is the most conservative and therefore provides an upper <br /> bound on the potential risks for receptors at other exposure points not selected for <br /> quantitative evaluation. <br /> The exposure points for the YFS site include groundwater for ingestion, dermal contact, <br /> and inhalation during showering and air above the site (for inhalation of volatile <br /> emissions). <br /> S:\LDC\YPLLO.RPT May 4, 1995 4-4 <br /> 1 <br />