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' Y <br /> necessary information to make risk management decisions (EPA 1992c). Conservative <br /> assumptions (i.e., assumptions that generally overestimate risk) were used in this r <br /> assessment when site-specific data were lacking or incomplete. <br /> r <br /> 1.2 SCOPE <br /> The scope of this risk assessment is limited to the evaluation of potential health risks <br /> and groundwater impacts associated with residual contaminants in soil associated with <br /> the former gasoline tanks under existing conditions and projected future land use. <br /> Future site development will most likely be a trucking terminal that will result in the <br /> continuation of the site being paved with asphalt or concrete. <br /> The approach used for the analysis of the risks posed by the concentrations of the <br /> chemicals in soil and groundwater is based on EPA guidance for the evaluation of <br /> human health risks at Superfund sites. Specifically, this risk assessment is consistent with <br /> referenced EPA guidance provided in the following EPA documents: ExQosure Factors <br /> Handbook (EPA 1989a), Risk Assessment Guidance for Superfund. Volume I: Human <br /> Health Evaluation Manual (EPA 1989b), Superfund Exposure Assessment Manual (EPA <br /> 1988c). Health Effects Assessment Summary Tables (HEAST) (EPA 1994). The <br /> r <br /> Integrated Risk Information System (IRIS), a computer database containing up-to-date <br /> human health risk and EPA regulatory information for numerous chemicals was used to <br /> obtain toxicity values. EPA cautions that these documents are intended to provide y <br /> guidance only in the conduct of health risk assessments and that considerable <br /> professional judgement must be used in their application (EPA 1989b). <br /> Fate and transport modeling was conducted to estimate the potential concentrations in <br /> groundwater that could result from the existing residual soil contamination. Unsaturated <br /> zone modeling was used to estimate loading rates of chemicals to groundwater. The _ <br /> unsaturated zone modeling also calculated air emission rates because the chemicals may <br /> volatilize (evaporate) into the air posing a potential human health risk to workers on <br /> site. Groundwater modeling was used to estimate potential groundwater chemical <br /> concentrations at the existing water supply well. <br /> SALDC\YELLO.FPr May 4,1995 1-2 <br />