Human and Ecological Risk Assessment - Earthjustice

Section 2.0Problem FormulationToxicity Assessment of CCW Constituents (continued)Constituent CAS ID HHB a EcoB bMeasurementsTotal Dissolved SolidsnoneTotal Organic CarbonnoneDissolved Organic CarbonnoneaHHB = human health effect benchmarkbEcoB = ecological benchmarkcKnown carcinogen (for chromium VI, inhalation only); although arsenic can act asboth a carcinogen and a noncarcinogen, the cancer risk exceeds the noncancer risk atany concentration, so the more protective cancer benchmark for human health wasused throughout this assessment.dProbable carcinogeneSafe Drinking Water Act Action Level only2.1.2 Waste Management ScenariosThe full-scale CCW risk assessment modeled landfills and surface impoundmentsmanaging wastes onsite at coal-fired utility power plants. Because EPA selected a site-basedmodeling approach for the full-scale analysis, it was necessary to locate these disposal sitesacross the country to provide the spatial foundation for this analysis. It was also necessary tocharacterize CCW WMUs to define the scope for source modeling.Two primary sources of data on these were used to characterize this population:• 1998 Energy Information Agency (EIA) data on coal-fired power plants, which identifiesapproximately 300 coal-fired power plants with onsite waste management• The 1995 EPRI waste comanagement survey (EPRI, 1997), which contains detailedWMU data (i.e., area, capacity, liner status, and waste type) for 177 of those facilities.Because of the completeness of the WMU data from the EPRI survey, the EPRI datawere used to establish the plant locations and WMU data for the full-scale modeling effort forconventional CCW 3 and CCW codisposed with coal refuse, as well as to help define protectivewaste management settings for the screening analysis.Note that although there is overlap, the 140-site CCW constituent database described inAppendix A and the EPRI survey used to characterize CCW landfills and surface impoundmentswere assembled under separate efforts and represent different populations of disposal sites. Asdescribed in Section 3.1.3, these data sets were sampled independently during the Monte Carloanalysis, and constituent data were not assigned to particular sites except by waste type.Although there is a good amount of FBC data in the constituent database (58 sites; seeTable 2-1), there were only 3 FBC landfill sites in the EPRI database and 4 additional sites addedby EPA, for a total of 7 FBC sites with data on onsite WMUs. Because EPA believes that this3 Fly ash, bottom ash, boiler slag, and FGD sludge.April 2010–Draft EPA document. 2-5