Human and Ecological Risk Assessment - Earthjustice

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Section 4.0Risk Characterizationfacilities, including liner leakage rate for landfills and the number of liner perforations forsurface impoundments (TetraTech, 2001). Because data on CCW liner leakage rates were notavailable, there is some uncertainty in applying these Industrial D Guidance liner performancedata to CCW disposal units. Still, these rates do reflect actual performance data from liners underreal WMUs. They demonstrate that composite liners can be effective in reducing leaching fromCCW WMUs and suggest that there will be a decrease in risk from CCW disposal if morefacilities line their WMUs with composite or clay liners. Information from the more recentDOE/EPA study (U.S. DOE, 2006) indicates that composite liners are becoming more prevalentin newly constructed facilities, so the risks from CCW disposal should be lower for newer CCWlandfills and surface impoundments.4.1.4 Constituents Not Modeled in the Full-Scale AssessmentAs described in Section 3.2.4, full-scale modeling was not conducted for all 21constituents that were above the screening criteria in the initial screening analysis; onlyconstituents that were judged likely to have generally higher risks to human health andecological health were modeled in the full-scale risk assessment. 8 Five chemicals (chromium,fluoride, manganese, vanadium, and nickel) had drinking water pathway HQs in the screeninganalysis ranging from 1 to less than 6 for surface impoundments, and three (chromium, fluoride,and vanadium) had screening HQs of 2 for landfills.To address these unmodeled constituents, EPA developed surrogate risk attenuationfactors by dividing the screening risk results by the full-scale risk results, across all unit (liner)types combined, for the constituents modeled in the full-scale assessment. This comparison wasdone only for the drinking water exposure pathway, the only human health exposure pathway forwhich the risks for these constituents were above the screening criteria. Table 4-15 shows therisk attenuation factor statistics for the modeled constituents, and Table 4-16 shows the resultsof applying the median and 10th percentile attenuation factors to the screening risk results for themarginal constituents. Differences in attenuation among the modeled constituents reflectdifferences in contaminant sorption and mobility. To be conservative, the 10th percentileattenuation factor was selected as a high-end value representing the more mobile constituents,such as arsenic, selenium, and molybdenum. The 50th percentile (or median) risk represents acentral tendency value.Table 4-15. Risk Attenuation Factor a Statistics for Modeled Constituents—Groundwater to Drinking Water PathwayStatistic Landfill Surface Impoundment10th percentile 7 1.650th percentile 12 2.6Average 16 3.3Maximum 40 9.3(continued)8 These constituents of concern had human health HQs greater than 6 or both ecological HQs greater than 100 at the90th percentile.April 2010–Draft EPA document. 4-20
Section 4.0Risk CharacterizationRisk Attenuation Factor a Statistics for ModeledConstituents—Groundwater to Drinking Water Pathway (continued)Statistic Landfill Surface ImpoundmentNumber of data points 9 8aThe risk attenuation factor is the ratio of the full-scale analysis risk andscreening analysis risk for a constituent modeled in the full-scale analysis.Table 4-16. Summary of Risk Screening Values for Unmodeled Constituents Using RiskAttenuation Factors—Groundwater-to-Drinking-Water PathwayWMU/PathwayScreeningHQLandfillHQ withMedianAttenuationHQ with10thPercentileAttenuationScreeningHQSurface ImpoundmentHQ withMedianAttenuationHQ with10thPercentileAttenuationChromium VI 2.3 0.2 0.3 4.2 1.6 2.6Fluoride 1.8 0.2 0.3 5.2 2.0 3.3Manganese 1 0.1 0.1 5.6 2.2 3.5Vanadium 2.2 0.2 0.3 2.3 0.9 1.4Nickel - - - 1.3 0.5 0.8For landfills, the risk attenuation factors ranged from 6 to 40, with the lower attenuationfactors mainly representing the more mobile constituents (i.e., those with lower soil sorptionpotential). Both the median and 10th percentile risk attenuation factors were adequate to reducerisks for all nine constituents below an HQ of 1.For surface impoundments, risk attenuation factors were considerably lower, rangingfrom 1 to 9, reflecting higher contaminant mobility due to the higher hydraulic head in surfaceimpoundments (as compared to landfills) and a lower proportion of liners. For the same reason,the screening HQs for surface impoundments were higher than the landfill HQs. As a result ofthis combination of higher HQs and lower risk attenuation factors, only the HQ for nickel wasreduced to below 1 by applying the attenuation factors. The other constituents (chromium,fluoride, manganese, and vanadium) still show risks slightly above an HQ of 1, with HQsranging from 1.4 to 3.5 at 10th percentile attenuation. This is consistent with the general trend inthis analysis of surface impoundments showing higher risks than CCW landfills.4.1.5 Human Health (Groundwater and Fish Consumption) Damage Case ReviewTable 4-17 summarizes the proven damage cases from U.S. EPA (2007) that showed animpact on groundwater, usually through an exceedence of an MCL or state groundwater standardfor one or more metals. As detailed in U.S. EPA (2007), these facilities represent worst-casedisposal conditions: all are unlined, several represent fills in old quarries, and many have wastesdisposed of below the water table. Groundwater standard exceedences are usually onsite orclosely offsite. As one can see in the table, the same metals showing risk exceedences forunlined facilities (arsenic, boron, cadmium, lead, molybdenum, and selenium) in this analysiswere reported as exceedences in the groundwater damage cases. Other incidents of groundwaterApril 2010–Draft EPA document. 4-21
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This draft document has been prepar
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CCWTable of ContentsTable of Conten
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CCWTable of ContentsList of Figures
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CCWTable of Contents4-22. Summary o
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CCWList of AcronymsAcronymDefinitio
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CCWList of AcronymsApril 2010-Draft
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Executive SummaryHuman and Ecologic
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Section 1.0Introduction1.0 Introduc
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Section 1.0Introduction1.3.2 Exposu
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Section 1.0IntroductionThis methodo
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Section 1.0Introduction1.4 Document
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Section 2.0Problem Formulationdata
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Section 2.0Problem FormulationTable
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Section 2.0Problem Formulationsmall
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Section 2.0Problem FormulationFigur
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Section 2.0Problem Formulationonsit
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Section 2.0Problem Formulation2.3 S
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Section 2.0Problem Formulationand C
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Section 2.0Problem Formulationof dr
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Section 3.0Analysisscale analysis.
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Section 3.0Analysis• The RfD is a
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Section 3.0Analysis3.1.2 Ecological
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Section 3.0AnalysisEcological Risk
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Section 3.0Analysisfor the screenin
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Section 3.0AnalysisTable 3-5. Scree
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Section 3.0Analysisapproximately 30
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Page 157 and 158: Section 5.0ReferencesFinkelman, R.B
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Appendix AConstituent DataA.1 Data
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Appendix AConstituent DataA.2.1 Sel
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Appendix AConstituent Data2. Select
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Appendix AAttachment A-1: Sources o
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April 2010-Draft EPA document.[This
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Appendix AAttachment A-2: CCW Const
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Appendix A Attachment A-3Table A-3-
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Appendix A Attachment A-3Cr IIIHgAg
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Appendix A Attachment A-3NO3CNCd, C
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Appendix BWaste Management UnitsWas
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Appendix BWaste Management Units•
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Appendix BWaste Management Units(e.
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Log(capacity, cubic yards)Log(area,
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Appendix BWaste Management UnitsB.7
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Appendix BAttachment B-1: CCW Dispo
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Appendix BAttachment B-1: CCW Dispo
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Appendix BAttachment B-2: CCW WMU D
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Appendix CSite DataWMU and the wate
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Appendix CSite DataFigure C-1. Exam
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Appendix CSite Dataeach site, eithe
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Appendix CSite DataBecause EPACMTP
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Appendix CSite DataHydrogeologic Se
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Appendix CSite DataFigure C-2. EPAC
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Appendix CSite DataEPACMTP Climate
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Appendix CSite DataRF1 Reach Types
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Appendix CSite DataTable C-9. Regio
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Appendix CSite DataHydrologicRegion
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Appendix CSite DataClawges, R.M., a
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Appendix CAttachment C-1: Soil Data
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Appendix CAttachment C-3: Climate C
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Appendix CAttachment C-4: Waterbody
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Appendix DMINTEQA2 Nonlinear Sorpti
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Appendix EEquationsIf Cwctot > Csol
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Appendix EAttachment E-1: Surface W
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Appendix EAttachment E-2: Fish Conc
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Appendix EAttachment E-3: Intake Ra
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Appendix FHuman Exposure Factorswer
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Appendix FHuman Exposure FactorsBec
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Appendix FHuman Exposure FactorsF.1
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Appendix GHuman Health BenchmarksG.
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Appendix GHuman Health BenchmarksHu
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Appendix GHuman Health BenchmarksU.
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Appendix HEcological BenchmarksRisk
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Appendix HEcological BenchmarksH.1.
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Appendix HEcological BenchmarksCons
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Appendix HEcological BenchmarksU.S.
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Appendix ICalculation of Health-Bas
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Appendix JChemical-Specific Inputs
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Appendix JChemical-Specific Inputs
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Appendix KScreening Analysis Result
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Appendix LTime to Peak Concentratio
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