Human and Ecological Risk Assessment - Earthjustice

Section 2.0Problem Formulationused as the basis for a national-scale site-based Monte Carlo assessment of risks posed by theonsite disposal of CCW at utility power plants across the United States. Figure 2-1 maps theCCW disposal sites modeled in this analysis against long-term average precipitation levels forthe country.Figure 2-1. Coal combustion plants with onsite waste disposal modeledin CCW risk assessment.2.2.1 Conceptual Site ModelFigure 2-2 depicts the conceptual site model for CCW disposal that was the basis for thenational CCW risk assessment, including contaminant sources, exposure pathways, andreceptors. The CCW conceptual site model includes the following exposure pathways:Human Health:• Groundwater to drinking water (drinking water ingestion)• Groundwater to surface water (fish consumption)Ecological Risk:• Groundwater to surface water and subsequent direct contact with contaminated surfacewater and sediments• Groundwater to surface water and subsequent ingestion of contaminated aquatic fooditems.April 2010–Draft EPA document. 2-7