Human and Ecological Risk Assessment - Earthjustice

Section 2.0Problem FormulationWaste TypeWaste StreamTable 2-1. Waste Streams in CCW Constituent DatabaseLandfillLeachateLandfillsTotalWaste bSurfaceImpoundmentsPoreWaterConventional CCW 97 62 13Ash (not otherwise specified) 43 30 0Fly ash 61 33 2Bottom ash and slag 24 23 3Combined fly and bottom ash 7 4 4FGD sludge 4 5 6Codisposed Ash & Coal Refuse 9 1 5FBC Waste 58 54 0abAsh (not otherwise specified) 18 10 0Fly ash 33 32 0Bottom and bed ash 26 25 0Combined fly & bottom ash 20 22 0For waste types (shaded rows) the table gives the number of sites; for waste streams(unshaded rows), the table gives the number of samples.Whole waste concentration data.Along with the type of WMU (landfill or surface impoundment), the three waste types inTable 2-1 defined the basic modeling scenarios to be addressed in the full-scale analysis. Tocharacterize these waste types, the CCW constituent database was queried by waste type todevelop the waste concentration data for the constituents and the major ion and pH conditionsused to develop waste-type-specific metal sorption isotherms (see Appendix D for a moreextensive discussion of the development of CCW waste chemistries and metal sorptionisotherms).2.1.1.2 CCW Constituents of Potential ConcernThe CCW constituent database contains data on more than 40 constituents. During thehazard identification step of the CCW risk assessment, constituents of potential concern wereidentified from this list of constituents by searching EPA and other established sources forhuman health and ecological benchmarks (e.g., Agency for Toxic Substances and DiseaseRegistry [ATSDR]; see Section 3.1 and Appendices G and H for a full list of sources). Table 2-2 shows the results of that search for each constituent. Benchmarks were found for 24 chemicalsin the constituent database. The 16 constituents without human health or ecological benchmarkswere not addressed further in the risk analysis. 22 The CCW constituents without human health benchmarks are limited to common elements, ions, and compounds(e.g., iron, magnesium, phosphate, silicon, sulfate, sulfide, calcium, pH, potassium, sodium, carbon, sulfur).These measurements were used to determine overall CCW chemistries modeled in the risk assessment (seeSection 3). Although some of these chemicals or parameters (e.g., pH, sulfate, phosphate, chloride) can pose anecological hazard if concentrations are high enough, they were not addressed in this risk assessment.April 2010–Draft EPA document. 2-3