Human and Ecological Risk Assessment - Earthjustice

Section 1.0Introduction1.2 Purpose and Scope of the Risk AssessmentThe purpose of this risk assessment was to identify CCW constituents, waste types,exposure pathways, and receptors that may produce risks to human and ecological health, and toprovide information about those scenarios that EPA could use to develop management optionsfor CCW management.The scope of this risk assessment was utility CCWs managed onsite at utility powerplants. EPA’s Report to Congress: Wastes from the Combustion of Fossil Fuels (U.S. EPA,1999a) reports that there are 440 coal-fired utility power plants in the United States. Althoughthese plants are concentrated in the East, they are found in nearly every state, with facilitysettings ranging from urban to rural. The large volumes of waste generated by these plants aretypically managed onsite in landfills and surface impoundments. This risk assessment wasdesigned to develop national human and ecological risk estimates that are representative ofonsite CCW management settings throughout the United States.1.3 Overview of Risk Assessment MethodologyTo estimate the risks posed by the onsite management of CCW, this risk assessmentestimated the release of CCW constituents from landfills and surface impoundments, theconcentrations of these constituents in groundwater and surface water near coal-fired utilitypower plants, and the risks that these concentrations pose to human and ecological receptors.1.3.1 Contaminant SourcesThe size, design, and locations of the onsite CCW landfills and surface impoundmentsmodeled in this risk assessment were based on data from a national survey of utility CCWdisposal conducted by the Electric Power Research Institute (EPRI) in 1995 (EPRI, 1997). Datafrom this survey on facility area, volume, and liner characteristics were used in the CCW riskassessment because they were the most recent and complete data set available at the time the riskassessment was conducted (2003). However, as shown in Table 1-1, the EPA/DOE studyconducted since then (U.S. DOE, 2006) shows a much higher proportion of lined facilities thando the 1995 EPRI data (see further discussion in Section 4.4.1).Table 1-1. Liner Prevalence in EPRI and DOE SurveysLiner Type1995 EPRI Survey a – 181 facilitiesLandfillsSurfaceImpoundmentsUnlined 40% 68%Lined (compacted clay or composite[clay and synthetic])2004 DOE Survey b – 56 facilities60% 32%Unlined 3% 0%Lined (compacted clay or composite[clay and synthetic])aEPRI (1997)bU.S. DOE (2006)97% 100%April 2010–Draft EPA document. 1-2