FINAL REMEDIAL INVESTIGATION REPORT FOR CONSTRUCTION ...

FINAL

FINAL REMEDIAL INVESTIGATION REPORT FOR CONSTRUCTION DEBRIS SITES CC-IAAP-001 AND CC-IAAP-002 ADDENDUM

IOWA ARMY AMMUNITION PLANT MIDDLETOWN, IOWA November 19, 2020

Prepared for: U.S. Army Corps of Engineers, Louisville District 600 Dr. Martin Luther King Jr. Place Louisville, KY 40202-2232

Prepared by: Leidos, Inc. 13397 Lakefront Drive, Suite 100 Earth City, MO 63045

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STATEMENT OF INDEPENDENT TECHNICAL REVIEW

Environmental Services at Iowa Army Ammunition Plant Middletown, Iowa

U.S. ARMY CORPS OF ENGINEERS

LOUISVILLE DISTRICT The Leidos, Inc., team has completed the Final submittal of the Remedial Investigation Report for Construction Debris Sites CC-IAAP-001 and CC IAAP 002 Addendum Iowa Army Ammunition Plant, Middletown, Iowa. Notice is hereby given that an independent technical review (ITR) has been conducted that is appropriate to the level of risk and complexity inherent in the project, as defined in the Project Management Plan and Contractor Quality Control Plan. During the ITR, compliance with established policy principles and procedures, utilizing justified and valid assumptions, was verified. This included review of assumptions; methods, procedures and material used in analyses; the appropriateness of data used and level of data obtained; and reasonableness of the results including whether the product meets the USACE’s needs consistent with the law and existing USACE policy.

Leidos Project Manager Leidos ITR Team Leader

11/19/2020

11/19/2020

Signature Date Signature Date

Matthew Vest Matthew Bange

Remedial Investigation Report for Construction Debris Sites CC-IAAP-001 and CC-IAAP-002 Addendum Iowa Army Ammunition Plant, Middletown, Iowa

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TABLE OF CONTENTS SECTION PAGE LIST OF TABLES ........................................................................................................................ ii LIST OF FIGURES ..................................................................................................................... iii LIST OF APPENDICES ............................................................................................................. iii ACRONYMS AND ABBREVIATIONS .................................................................................... iv

EXECUTIVE SUMMARY .................................................................................................... ES-1

1.0 INTRODUCTION..............................................................................................................1

1.1 SITE OPERATIONAL BACKGROUND ...............................................................1 1.1.1 Installation....................................................................................................1 1.1.2 CC-IAAP-001 ..............................................................................................2 1.1.3 CC-IAAP-002 ..............................................................................................2

1.2 PURPOSE OF THE REMEDIAL INVESTIGATION REPORT ADDENDUM ..........................................................................................................2

1.3 BASIS OF THE REMEDIAL INVESTIGATION REPORT ADDENDUM ..........................................................................................................4

2.0 SUMMARY OF THE REMEDIAL INVESTIGATION REPORT ..............................5

2.1 NATURE AND EXTENT OF CONTAMINATION ..............................................5

2.2 2014 BASELINE HUMAN HEALTH RISK ASSESSMENT AND SCREENING LEVEL ECOLOGICAL RISK ASSESSMENT ..............................7

3.0 RESIDENTIAL BASELINE HUMAN HEALTH RISK ASSESSMENT FOR CC-IAAP-001 AND CC-IAAP-002 ................................................................................11

3.1 CONCEPTUAL EXPOSURE MODELS FOR THE RESIDENTIAL LAND USE SCENARIOS AT CC-IAAP-001 AND CC-IAAP-002 ....................12 3.1.1 CC-IAAP-001 Conceptual Exposure Model .............................................12 3.1.2 CC-IAAP-002 Conceptual Exposure Model .............................................14

3.2 IDENTIFICATION OF SITE-RELATED CONTAMINANTS OF POTENTIAL CONCERN .....................................................................................17 3.2.1 Chemicals and Radionuclides of Potential Concern in Surface Soil

and Soil ......................................................................................................18 3.2.2 Chemicals and Radionuclides of Potential Concern in Groundwater ........19 3.2.3 Indoor Air (Vapor Intrusion Pathway) .......................................................21

3.3 EXPOSURE ASSESSMENT ................................................................................21 3.3.1 Exposure Setting ........................................................................................22 3.3.2 Identification of Exposure Pathways for Quantitative Risk

Evaluations .................................................................................................22 3.3.3 Quantification of Exposure ........................................................................22

3.4 TOXICITY ASSESSMENT ..................................................................................25 3.4.1 Chemical Toxicity Assessment ..................................................................25 3.4.2 Radiological Toxicity Assessment .............................................................27


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TABLE OF CONTENTS (Continued) SECTION PAGE

3.5 RISK CHARACTERIZATION .............................................................................28 3.5.1 Determination of Chemical Cancer Risk ...................................................28 3.5.2 Determination of Chemical Non-Cancer Hazards .....................................28 3.5.3 Determination of Radiological Cancer Risk ..............................................29 3.5.4 Additivity of Chemicals and Radiological Cancer Risks ..........................30 3.5.5 Risk Characterization .................................................................................30 3.5.6 CC-IAAP-001 Residential Risk Characterization Results .........................33 3.5.7 CC-IAAP-002 Risk Characterization Results ............................................48

3.6 CONCLUSIONS OF THE RESIDENTIAL BASELINE HUMAN HEALTH RISK ASSESSMENT ...........................................................................62

3.7 UNCERTAINTY ANALYSIS ..............................................................................62 3.7.1 Data Evaluation and COPC Identification Uncertainties ...........................62 3.7.2 Exposure Assessment Uncertainties ..........................................................65 3.7.3 Toxicity Assessment Uncertainties ............................................................66 3.7.4 Risk Characterization Uncertainties ..........................................................68

4.0 SUPPLEMENTAL SCREENING LEVEL ECOLOGICAL RISK ASSESSMENT .................................................................................................................71

5.0 REFERENCES .................................................................................................................75

LIST OF TABLES

Table ES-1. Residential BHHRA COPCs and ROPCs ................................................................5 Table 2-1. 2014 BHHRA COPCs .............................................................................................7 Table 3-1. Carcinogenic Risks and Noncarcinogenic Hazards for Exposures to

Combined Area-Related COPCs/ROPCs and Naturally Occurring Constituents at CC-IAAP-001 ...............................................................................35

Table 3-2. Background Comparisons of CC-IAAP-001 Media Concentrations, Carcinogenic Risks and Noncarcinogenic Hazards to Determine Naturally Occurring Constituents ..........................................................................................40

Table 3-2a. Estimation of Hexavalent Chromium Background Concentrations in Unfiltered Groundwater Based on Maximum and Mean Concentrations of Hexavalent Chromium and Total Chromium at CC-IAAP-001 ............................43

Table 3-3. Residential Carcinogenic Risks and Noncarcinogenic Hazards for Exposures to Remaining Site-Related COPCs and ROPCs in CC-IAAP-001 Unfiltered Groundwater ..........................................................................................45

Table 3-4. Weight of Evidence Evaluation of Total Uranium as a Final COC and Uranium Isotopes as Final ROCs in CC-IAAP-001 Unfiltered Groundwater ..........................................................................................................46

Table 3-5. Carcinogenic Risks and Noncarcinogenic Hazards for Exposures to Combined Area-Related COPCs/ROPCs and Naturally Occurring Constituents at CC-IAAP-002 ...............................................................................49


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LIST OF TABLES (Continued)

Table 3-6. Background Comparisons of CC-IAAP-002 Media Concentrations, Carcinogenic Risks and Noncarcinogenic Hazards to Determine Naturally Occurring Constituents ..........................................................................................55

Table 3-6a. Estimation of Hexavalent Chromium Background Concentrations in Unfiltered Groundwater Based on Maximum and Mean Concentrations of Hexavalent Chromium and Total Chromium at CC-IAAP-002 ............................57

Table 3-7. Residential Carcinogenic Risks and Noncarcinogenic Hazards for Exposures to Remaining Site-Related COPCs and ROPCs in CC-IAAP-002 Unfiltered Groundwater ..........................................................................................58

Table 3-8. Weight of Evidence Evaluation of Hexavalent Chromium as a Final COC and Uranium Isotopes as Final ROCs in CC-IAAP-002 Unfiltered Groundwater ..........................................................................................................60

LIST OF FIGURES

Figure 1. CC-IAAP-001 Layout and Location Figure 2. CC-IAAP-002 Layout and Location Figure 3. CC-IAAP-001 Conceptual Exposure Model Figure 4. CC-IAAP-002 Conceptual Exposure Model

LIST OF APPENDICES

APPENDIX A* RISK ASSESSMENT TABLES (USEPA RAGS PART D) FOR THE CC-IAAP-001 RESIDENTIAL BHHRA AND SUPPORTING CALCULATIONS

APPENDIX B* RISK ASSESSMENT TABLES (USEPA RAGS PART D) FOR THE CC-IAAP-002 RESIDENTIAL BHHRA AND SUPPORTING CALCULATIONS

APPENDIX C* RADIOLOGICAL PRELIMINARY REMEDIATION GOAL CALCULATIONS

BACK COVER

*CD-ROM Appendices A, B, and C; Attachments A-1 through A-7, B-1 through B-6, and C-1 and C-2


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ACRONYMS AND ABBREVIATIONS

95% UCL 95 percent upper confidence limit 2017 UFP-QAPP Uniform Federal Policy-Quality Assurance Project Plan for Remedial

Investigation at Iowa Army Ammunition Plant, Middletown, Iowa τevent lag time per event µg/-cm2-event microgram(s) per square centimeter(s)-event µg/L microgram(s) per liter µg/dL microgram(s) per deciliter µg/m3 microgram(s) per cubic meter µg/mg microgram(s) per milligram ABS absorption fraction ACCLPP Advisory Committee on Childhood Lead Poisoning Prevention ACF area correction factors ACM asbestos-containing material ADAF age-dependent adjustment factor AF adherence factor ARAR applicable or relevant and appropriate ASL above the screening level ASL-NUT above the macronutrient screening level AT averaging time atm-m3/mole atmospheres-cubic meter per mole ATSDR Agency for Toxic Substances and Disease Registry AWQC ambient water quality criteria B dimensionless ratio for dermal permeability BERA Baseline Ecological Risk Assessment bgs below ground surface BHHRA Baseline Human Health Risk Assessment BLL blood lead level BSL below the screening level BTV background threshold value BW body weight CaCO3 calcium carbonate CalEPA California Environmental Protection Agency CAS Chemical Abstracts Service CC critical concentration CBD cannot be determined CDC Centers for Disease Control and Prevention CDI chronic daily intake CEM conceptual exposure model CERCLA Comprehensive Environmental Response, Compensation, and

Liability Act CF conversion factor Cgw chemical concentration in groundwater cm centimeter(s) cm2 square centimeter(s) cm2/day square centimeters per day cm/hr centimeter(s) per hour


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ACRONYMS AND ABBREVIATIONS (Continued)

cm2/s square centimeters per second cm2-yr/kg square centimeter(s)-year per kilogram CNS central nervous system COC chemical of concern COPC chemical of potential concern COPEC chemical of potential ecological concern Cr(III) trivalent chromium Cr(VI) hexavalent chromium CSF cancer slope factor CSFd dermal cancer slope factor CSFi inhalation cancer slope factor CSFo oral cancer slope factor CSM conceptual site model DA dose absorbed DAD dermally absorbed dose days/yr days per year DFS dermal contact factor for soil DFSM dermal contact factor for soil, mutagenic DFW dermal contact factor for water DFWM dermal contact factor for water, mutagenic Dia diffusivity in air Diw diffusivity in water DU depleted uranium EC exposure concentration ECO ecological-based Eco-SSL ecological soil screening level ED exposure duration EF exposure frequency ELCR excess lifetime cancer risk ELCRderm excess lifetime cancer risk (dermal) ELCRing

ELCRinh

excess lifetime cancer risk (ingestion) excess lifetime cancer risk (inhalation)

EM Engineer Manual EPC exposure point concentration ERA ecological risk assessment ESL ecological screening level ET exposure time EV event frequency FA fraction absorbed FFA Federal Facility Agreement FFS Focused Feasibility Study FI fraction ingested FS Feasibility Study ft feet g gram(s) g/cm3 gram(s) per cubic centimeter


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g/mole gram(s) per mole GIABS gastrointestinal absorption factor H’ Henry’s Law Constant, unitless HEAST Health Effects Assessment Summary Tables HH human health HHRA human health risk assessment HI hazard index HLC Henry’s Law Constant HQ HQderm HQing

HQinh

hazard quotient hazard quotient (dermal) hazard quotient (ingestion) hazard quotient (inhalation)

hr/event hour(s) per event IAAAP Iowa Army Ammunition Plant IAEA International Atomic Energy Agency IAC Iowa Administrative Code IDNR Iowa Department of Natural Resources IEUBK Integrated Exposure Uptake Biokinetic IFS ingestion factor for soil IFSM ingestion factor for soil, mutagenic IFW ingestion factor for water IFWM ingestion factor for water, mutagenic IRIS Integrated Risk Information System IRP Installation Restoration Program IRS ingestion rate of soil IRW ingestion rate of water IUR inhalation unit risk K Andelman volatilization factor Kd soil to water distribution coefficient kg kilogram(s) kg/mg kilograms per milligram KM Kaplan-Meier Koc organic carbon partition coefficient Kow octanol-water partition coefficient Kp dermal permeability coefficient L liter(s) LAP load, assemble, and pack L/cm3 liter(s) per cubic centimeter L/day liter(s) per day LEL lowest effects level L/kg liter(s) per kilogram L/m3 liter(s) per cubic meter LOAEL lowest-observed-adverse-effect-level L-yr/kg-day liter-year per kilogram-day m3 cubic meter(s) m3/kg cubic meter(s) per kilogram


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MBV mean background value MCL maximum contaminant level mg milligram(s) mg/μg milligram(s) per microgram mg/cm2 milligram(s) per square centimeter mg/day milligram(s) per day mg/kg milligram(s) per kilogram mg/kg-day milligram(s) per kilogram-day mg/L milligram(s) per liter mg/m3 milligram(s) per cubic meter mg-yr/kg-day milligram-year per kilogram-day mmHg millimeters of mercury MOA mode of action MP melting point MW molecular weight NA not available or not applicable NCP National Oil and Hazardous Substances Contingency Plan NE not established NFA No Further Action NJDEP New Jersey Department of Environmental Protection NOAEL no-observed-adverse-effect-level NPL National Priority List NRWQC National Recommended Water Quality Criteria NSL no screening level NV not volatile OEHHA Office of Environmental Health Hazard Assessment OMOE Ontario Ministry of the Environment ORNL Oak Ridge National Laboratory OSWER Office of Solid Waste and Emergency Response OU operable unit PAH polycyclic aromatic hydrocarbon PAL project action limit PCB polychlorinated biphenyl pCi picocurie(s) pCi/g pCi/µg

picocurie(s) per gram picocurie(s) per microgram

pCi-yr/g picocurie(s)-year per gram pCi/L picocurie(s) per liter pCi-yr/L picocurie(s)-year per liter PEF particulate emission factor PP Proposed Plan PPRTV Provisional Peer-Reviewed Toxicity Values PRG Preliminary Remediation Goal QA/QC quality assurance/quality control QAPP quality assurance project plan


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RAGS Part A

Risk Assessment Guidance for Superfund, Volume I, Human Health Evaluation Manual (Part A)

RAGS Part D Risk Assessment Guidance for Superfund: Volume I Human Health Evaluation Manual (Part D, Standardized Planning, Reporting, and Review of Superfund Risk Assessment)

RAIS Risk Assessment Information System RAO remedial action objective RDX royal demolition explosive RfC reference concentration RfD reference dose RfDd dermal reference dose RfDi inhalation reference dose RfDo oral reference dose RI remedial investigation RI Report Remedial Investigation Report for Construction Debris Sites

CC-IAAP-001 and CC-IAAP-002 RI Work Plan Final Work Plan, Remedial Investigation of Construction Debris

Sites CC-IAAP-001 and CC-IAAP-002 RME reasonable maximum exposure ROC radionuclide of concern ROPC radionuclide of potential concern RSL Regional Screening Level S solubility SA surface area SCV secondary chronic value SLERA Screening Level Ecological Risk Assessment SSL soil screening level SVOC semivolatile organic compound T&E threatened and endangered t* time to reach steady state TBC to be considered TEC threshold effects concentrations UFP-QAPP Uniform Federal Policy-Quality Assurance Project Plan USACE U.S. Army Corps of Engineers USDA U.S. Department of Agriculture USEPA U.S. Environmental Protection Agency USFWS U.S. Fish and Wildlife Service UTL95-95 95% upper tolerance limit with 95% coverage UU/UE unlimited use and unrestricted exposure VF volatilization factor VISL vapor intrusion screening level VOC volatile organic compound VP vapor pressure WOE weight of evidence yr year(s)


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EXECUTIVE SUMMARY

This Remedial Investigation (RI) Report Addendum (“Addendum”) presents the Residential Baseline Human Health Risk Assessment (BHHRA) and Supplemental Screening Level Ecological Risk Assessment (SLERA) for Construction Debris Site #1 (CC-IAAP-001) and Construction Debris Site #2 (CC-IAAP-002) at the Iowa Army Ammunition Plant (IAAAP), Middletown, Iowa. The Residential BHHRA and Supplemental SLERA presented in this document addends the BHHRA and SLERA that were prepared as part of the Remedial Investigation Report for Construction Debris Sites CC-IAAP-001 and CC-IAAP-002 (RI Report) (PIKA 2014a) (“2014 BHHRA” and “2014 SLERA”). The 2014 BHHRA evaluated potential risks from exposure to residual contamination under the Commercial/Industrial Land Use scenario (the current and Reasonably Anticipated Future Land Use for IAAAP). The 2014 BHHRA concluded that there were no adverse carcinogenic risks or noncarcinogenic hazards above U.S. Environmental Protection Agency (USEPA) target limits for chemicals of potential concern (COPCs) for all evaluated exposure media, at both areas, under Commercial/Industrial Land Use. However, as noted in the RI Report, a visual inspection conducted as part of the RI field investigation identified the presence of asbestos-containing material (ACM) associated with roofing material found in three distinct locations of the CC-IAAP-002 debris piles. No such finding was made at CC-IAAP-001. The results of soil sampling and analysis indicate that concentrations of asbestos fibers in core samples were reported to be non-detect for both CC-IAAP-001 and CC-IAAP-002. During the visual inspection, it was noted that the ACM observed in the CC-IAAP-002 debris piles exhibited disintegration from weathering. This finding indicates that asbestos in the debris piles is becoming increasingly friable. Increased friability increases the potential for releases of microscopic fibers into the air, thereby increasing the potential for human and environmental exposures. A subsequent Focused Feasibility Study (FFS) Report (i.e., “Focused Feasibility Study Report for Construction Debris Sites CC-IAAP-001 and CC-IAAP-002”) (PIKA 2014b) and subsequent Proposed Plan (PP) (i.e., “Final Proposed Plan for Construction Debris Sites CC-IAAP-001 and CC-IAAP-002”) (PIKA 2015) identified the removal of ACM in the CC-IAAP-002 debris piles as a component of the preferred remedial alternative (i.e., Remedial Alternative #4). Because removal of ACM from the debris piles at CC-IAAP-002 has been determined to be necessary, CC-IAAP-002 does not meet the conditions for unlimited use and unrestricted exposure (UU/UE) or no further action (NFA). This finding also applies regardless of the results of the Residential BHHRA in this Addendum, until the removal action has occurred. Because the 2014 BHHRA did not include an evaluation of the Residential Land Use scenario, an evaluation of the Residential Land Use scenario is necessary to determine if COPCs and radionuclides of potential concern (ROPCs) identified and evaluated during the Residential BHHRA are retained as final contaminants of concern (COCs) or radionuclide of concern (ROC) requiring additional evaluations in a Feasibility Study (FS) to determine if a remedial action(s) is warranted. In this Residential BHHRA, a COC or ROC is a site-related contaminant in a medium present at concentrations resulting in excess lifetime cancer risks (ELCRs) and/or noncarcinogenic hazard indices (HIs) that are greater than the respective target limits of ELCR of 1E-04 and a HI of 1 under the Residential Land Use scenario. These target limits are the same as those used in the 2014 BHHRA. The target ELCR of 1E-04 represents the upper limit of the USEPA’s National Oil and Hazardous Substances Contingency Plan (NCP) target risk range of 1E-06 to 1E-04


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(USEPA 1990). An ELCR of 1E-06 represents the probability of one additional cancer case resulting from potential exposure to the site that could occur within a population of one million people, over a lifetime. Similarly, an ELCR of 1E-04 represents the probability of one additional cancer case above baseline that could occur within a population of ten thousand people, over a lifetime. A finding of UU/UE leads to a determination of NFA. According to USEPA guidance in Office of Solid Waste and Emergency Response (OSWER) Directive 9355.7-04 (i.e., “Land Use in the CERCLA Remedy Selection Process”) (USEPA 1995), the presence of contaminants in media at concentrations protective of residential exposures allow for Unrestricted Land Use. Under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), an area meeting UU/UE does not require remedial action (i.e., including land use controls) and five-year reviews. Generally, in order for an area to meet UU/UE, all media must be shown to have no identified COCs or ROCs at concentrations resulting in ELCRs and HIs that are less than or equal to the respective target limits of ELCR of 1E-04 and a HI of 1 under the Residential Land Use scenario. Therefore, this Addendum presents the Residential BHHRA in order to facilitate future decision-making regarding determinations of UU/UE and possible NFA status for CC-IAAP-001 under current conditions, as well as for CC-IAAP-002 under future conditions, subsequent to ACM removal per Remedial Alternative #4. In other words, because ACM was not identified at CC-IAAP-001 for removal, if no chemical COCs are identified under the Residential Land Use (considered the most conservative/ protective and representative of UU/UE), then the determination of UU/UE and NFA is warranted for CC-IAAP-001. However, for CC-IAAP-002, a final determination of NFA and UU/UE cannot be achieved until the removal of the ACM from that area is completed. Additionally, this Addendum presents the Supplemental SLERA. By their nature, SLERAs are intended to be conservative and protective and often overestimate potential ecological risks. Despite the conservative evaluation, risks to ecological receptors were not anticipated in the RI Report (PIKA 2014a). However, as agreed with the USEPA, the SLERA was updated to consider potential ecological risks to federally-listed species that have been listed since the 2014 SLERA was completed. While these sites are very small and offer little habitat, the updated SLERA included herein is proactive and further protective. The Supplemental SLERA evaluated updated ecological receptor information and ecological screening levels to facilitate future decision-making regarding determinations of NFA status for CC-IAAP-001 and CC-IAAP-00 from an ecological perspective. The Residential BHHRA methods applied in this Addendum are consistent with those established in the Uniform Federal Policy-Quality Assurance Project Plan for Remedial Investigation at Iowa Army Ammunition Plant, Middletown, Iowa (2017 UFP-QAPP) (CH2M Hill 2017). Additionally, the methods established in the 2017 UFP-QAPP are consistent with the following:

• RI Report (PIKA 2014a) • USEPA’s Risk Assessment Guidance for Superfund, Volume I, Human Health Evaluation

Manual (Part A) (RAGS Part A) (USEPA 1989) • and the U.S. Army Corps of Engineers (USACE) Engineering Manual entitled Risk

Assessment Handbook, Human Health Evaluation, Volume I: Human Health Evaluation, EM 200-1-4 (USACE 1995).


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Residential Baseline Human Health Risk Assessment

During the RI that was conducted in 2013, analytical data were acquired for the following media: surface soil (0 to 0.5 feet [ft] below ground surface [bgs]), subsurface soil (0.5 to 10 ft bgs), groundwater (unfiltered and filtered), surface water, and sediment (0 to 0.5 ft bgs). Although filtered groundwater samples were collected, only evaluations of exposures to unfiltered groundwater are used to characterize potential health risks in this Residential BHHRA. The results of risk evaluations of filtered groundwater data are presented in Appendices A and B for CC-IAAP-001 and CC-IAAP-002, respectively, and are only discussed during weight of evidence (WOE) discussions in the risk characterization. No surface water samples were collected from CC-IAAP-002 because of the absence of surface water at the time of sampling. For this Residential BHHRA, surface water exposure pathways are determined to be incomplete because surface water does not exist in the drainage ways in either construction debris area year-round, but rather, occurs intermittently, only during storm events. Because of the absence of a continuous presence of surface water, sediment data is considered to be similar to soil data and are combined with surface soil data in this Residential BHHRA for the evaluation of residential soil exposures. ACM-related exposure pathways are incomplete for CC-IAAP-001 and potentially complete via release and air transport mechanisms at CC-IAAP-002. The residential receptors evaluated in this Addendum are a young child (0 to 6 years old) and an adult. For the purpose of this evaluation, the adult is assumed to be an individual ages 6 to 26 years old. Exposure media of concern for these receptors include surface soil, subsurface soil and unfiltered groundwater. During Residential Land Use, soil exposures can potentially occur at all three of the aforementioned depth intervals; however, for the purposes of the Residential BHHRA, exposures to surface soil (0 to 0.5 ft bgs) and combined surface and subsurface soil (0 to 10 ft bgs) are evaluated. Separate evaluations of exposures to only subsurface soil are not performed for the following reasons: 1) contaminant profiles are similar between surface and subsurface soil at both areas; thus migration of contaminants in surface soil does not impact subsurface soil; 2) there are no volatiles present in the subsurface soil to which residential receptors could be exposed via inhalation; and 3) evaluation of the 0-10 ft soil depth interval is consistent with requirements of the 2017 UFP-QAPP (CH2M Hill 2017). Following applicable CERCLA policy and guidance, groundwater at the operable unit (OU)-9 areas is classified as Class IIb, a potential source of drinking water. For this reason, and because land use is not considered during the groundwater classification process, this Residential BHHRA evaluated residential exposures to groundwater in the shallow overburden. Future residents were evaluated for exposures to groundwater COPCs and ROPCs through the ingestion of groundwater used as drinking water and dermal contact with groundwater while bathing/showering. When volatiles are present in groundwater, inhalation exposures were evaluated during use of groundwater as tap water for common household purposes. For groundwater, USEPA guidance recommends once groundwater is determined to be suitable for drinking, risk-based concentrations should be based on residential exposures in order to restore the aquifer to beneficial use (e.g., drinking water standards) wherever practicable (USEPA 2009). Therefore, only the Resident Receptor representing Unrestricted (Residential) Land Use was evaluated in this RI Addendum. The assumption of the potable use of overburden groundwater represents only a hypothetical scenario utilized for the purpose of determining the UU/UE status of the construction debris areas. Typically, exposures to groundwater are evaluated utilizing only data acquired for unfiltered groundwater samples. Both unfiltered and filtered groundwater samples were collected from CC-IAAP-001 and CC-IAAP-002 and analyzed for total and dissolved metals, respectively.


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Concentrations of uranium isotope were calculated from measured concentrations of total and dissolved uranium in unfiltered and filtered groundwater, respectively. The filtered groundwater results for metals and radionuclides were only considered and discussed in the WOE evaluations in this BHHRA to provide additional area-specific information and decision-making. The potable use of overburden groundwater is considered as a hypothetical scenario utilized for the construction debris areas to facilitate a determination of NFA versus a determination that groundwater is impacted and requires additional remedial action(s). Based on the data and pathway analyses in the conceptual exposure models (CEMs), the following exposure media and routes are evaluated for all residential receptors at CC-IAAP-001 and CC-IAAP-002 in this Addendum:

• Surface Soil (0 to 0.5 ft) o Incidental ingestion (COPCs and ROPCs), o Dermal contact (COPCs), o Inhalation of fugitive dusts in air (COPCs and ROPCs), o Inhalation of volatile decay progeny of uranium isotopes, and o External radiation

• Soil (0 to 10 ft) o Incidental ingestion (COPCs and ROPCs), o Dermal contact (COPCs), o Inhalation of fugitive dusts in air (COPCs and ROPCs), o Inhalation of volatile decay progeny of uranium isotopes, and o External radiation.

• Groundwater (Unfiltered) o Ingestion of groundwater used as drinking water (COPCs and ROPCs), o Dermal contact during bathing/showering (COPCs), o Inhalation of volatiles emitted from groundwater used for potable household purposes

(COPCs and ROPCs), and o External radiation (water immersion, e.g., during bathing).

Following the selection of exposure media, COPCs and ROPCs were identified in soil and groundwater through data comparisons to the USEPA’s Regional Screening Levels (RSLs) (USEPA 2020a) and USEPA’s Radiological Preliminary Remediation Goals (PRGs) (USEPA 2020c), respectively, for residential soil and tap water, along with other project action limits (PALs). The RSLs were obtained from the most recent version of the generic tables available on the USEPA’s RSL website and are presented in the USEPA’s Risk Assessment Guidance for Superfund: Volume I Human Health Evaluation Manual (Part D, Standardized Planning, Reporting, and Review of Superfund Risk Assessment), Final (RAGS Part D) tables in Appendices A and B for CC-IAAP-001 and CC-IAAP-002, respectively (USEPA 2001). The radiological PRGs were calculated using the USEPA’s online PRG and risk calculator (USEPA 2020c), the outputs of which are presented in Appendix C. The radiological PRGs are also presented in Appendices A and B. During this process, the vapor intrusion pathway (i.e., from groundwater into indoor air) was removed from further evaluations because all groundwater concentrations at both areas are less than the USEPA’s Vapor Intrusion Screening Levels (VISLs) (USEPA 2020b). Both the USEPA’s RSLs and VISLs used in the selection of COPCs are based on a target ELCR of 1E-06 and a target non-cancer hazard quotient (HQ) of 0.1. The radiological PRGs used in the selection of ROPCs are based on a target ELCR of 1E-06. Table ES-1 presents the soil and groundwater COPCs and ROPCs identified for CC-IAAP-001 and CC-IAAP-002.


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Table ES-1. Residential BHHRA COPCs and ROPCs

Medium CC-IAAP-001 CC-IAAP-002 Surface Soil (0 to 0.5 ft bgs)

Arsenic Arsenic Hexavalent Chromium Benzo(a)pyrene

Uranium-234 Hexavalent Chromium Uranium-235 Uranium-234 Uranium-238 Uranium-235

Uranium-238 Soil (0 to 10 ft bgs)

Arsenic Arsenic Hexavalent Chromium Benzo(a)pyrene

Uranium-234 Hexavalent Chromium Uranium-235 Uranium-234 Uranium-238 Uranium-235

Uranium-238 Groundwater (Total)

Arsenic Arsenic Barium Barium

Hexavalent Chromium Bromomethane Lead Hexavalent Chromium

Uranium Uranium Uranium-234 Uranium-234 Uranium-235 Uranium-235 Uranium-238 Uranium-238

Reasonable maximum exposures were then quantified through the calculations of medium-specific exposure point concentrations (EPCs) for the COPCs that represent the lesser of the 95 percent upper confidence limit (95% UCL) of the arithmetic mean concentration and the maximum concentration. Additionally, residential exposure assumptions consistent with reasonable maximum exposure scenario were defined as input values for chemical intake equations. Separate intake calculations were performed for the residential receptors based on non-cancer and cancer effects. For evaluating the potential for non-cancer effects, chemical intakes were calculated separately for the young child and adult assuming exposure durations of 6 years and 26 years, respectively. For evaluating the potential for cancer effects, the chemical intakes were calculated over an age-adjusted exposure duration of 26 years, representing the combined young child (ages 0 to 6 years) adult (ages 6 to 26 years) age groups (i.e., 6 years for the child plus 20 years for the adult). The intakes were combined with the appropriate toxicity values in mathematical algorithms for calculating ELCRs for the age-adjusted resident and non-cancer HIs for the young child resident and the adult resident. Risk characterization was performed for CC-IAAP-001 and CC-IAAP-002 by combining the receptor/exposure pathway-specific chemical intakes calculated based on the EPCs and assumptions determined during the exposure assessment, with the corresponding COPC-specific and ROPC-specific toxicity criteria determined during a toxicity assessment to calculate cumulative (total) ELCRs and non-cancer HIs for each residential receptor, over all evaluated exposure media at each area. During calculations of cumulative, receptor ELCRs, chemical and radiological ELCRs are summed together in accordance with USEPA’s directive entitled: “Radiation Risk Assessment at CERCLA Sites: Q&A” (USEPA 1999). The risk characterization evaluations and results for CC-IAAP-001 and CC-IAAP-002 are presented in several steps.

• The first step is to calculate receptor-specific ELCRs and HIs that include concentration contributions from both site-related COPCs/ROPCs and naturally-occurring constituents that have been identified as COPCs/ROPCs. COPCs/ROPCs with ELCRs and/or HIs exceeding


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target limits are retained for further evaluations in the risk characterization (i.e., second through fourth steps as applicable). COPCs and ROPCs with ELCRs and/or HIs less than target limits are eliminated from further evaluations.

• The second step is to determine those COPCs (i.e., metals) and ROPCs that are naturally-occurring based on concentration comparisons with IAAAP-specific background threshold values (BTVs), as well as comparisons of area-specific residential ELCRs and HIs with ELCRs and HIs calculated for the BTVs. Chemicals determined to be naturally occurring are removed from further evaluations.

• Following removal of the naturally-occurring chemicals in the second step, the third step presents and discusses the remaining ELCRs and HIs from the site-related COPCs and ROPCs.

• The fourth step determines and presents the final COCs and ROCs. This step includes a WOE evaluation of the site-related COPCs and ROPCs to determine those that will be retained as final COCs and ROCs, if any, for further evaluation in the feasibility study. The identification of no COCs or ROCs results in no further evaluations.

This RI Report Addendum reflects certain procedural departures from the standard USEPA human health risk assessment (HHRA) process that the Army routinely applies at its installations (USEPA 1989). The soil background values for metals were obtained from the “Baseline Ecological Risk Assessment” (BERA) (MWH 2004). Soil background values for radionuclides (uranium isotopes) were obtained from sample data presented in the “Iowa Army Ammunition Plant FUSRAP Remedial Investigation Report for Firing Sites Area, Yards C, E, F, G, and L, Warehouse 3-01 and Area West of Line 5B, Middletown, Iowa, Final” (USACE 2008). Groundwater background values were obtained from the Technical Memorandum entitled “Evaluation of Background Concentrations of Metals in Groundwater, Iowa Army Ammunition Plant, Middletown, Iowa. Final” (CH2M Hill 2020). This background comparison method is consistent with the 2017 UFP-QAPP (Worksheet #14). Although inconsistent with the process the Army uses for the evaluation of background in the HHRA for their installations, this method complies with the requests from the USEPA in a memorandum from Mr. Danny O’Connor, USEPA Region 7 Remedial Project Manager, to Ms. Jennifer Busard, IAAAP Project Manager (no subject, dated June 10, 2019) (USEPA 2019). The overall results of the characterization of ELCRs and non-cancer HIs under the Residential Land Use scenario indicate that residential exposures surface soil, soil (0 to 10 ft bgs) and unfiltered groundwater (assuming the potable use scenario) at both CC-IAAP-001 and CC-IAAP-002 fail to meet the target ELCR limit of 1E-04 and/or the target HI limit of 1, even after removal of ACM from the CC-IAAP-002 debris piles is completed. The subsections below summarize the residential risk characterization results and conclusions for CC-IAAP-001 and CC-IAAP-002.

CC-IAAP-001 Risk Characterization Results and Conclusions Based on the results of the risk characterization of CC-IAAP-001, residential ELCRs for exposures to surface soil and soil (0 to 10 ft bgs) exceed the NCP’s target ELCR limit due to ingestion of uranium-234 and uranium-238. However, because the concentrations of these isotopes are less than the soil BTVs and therefore, consistent with background conditions, uranium-234 and uranium-238 in surface soil and soil are not attributed to IAAAP-related processes. The ELCRs and HIs calculated for the ingestion of unfiltered groundwater exceed target limits under the


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Residential Land Use scenario due predominantly to concentrations of arsenic, hexavalent chromium, uranium, uranium-234, and uranium-238. The inhalation pathway for uranium-234 and uranium-238 contributes even more predominantly to the receptor ELCR than ingestion, due to decay chain progeny (i.e., radium-226). The maximum concentration of lead also exceeded the USEPA’s benchmark for blood lead levels in young children. However, because arsenic and lead concentrations are less than the groundwater BTVs and therefore, consistent with background conditions, arsenic and lead are not attributed to IAAAP-related processes. Arsenic and lead are identified as a naturally-occurring chemicals and not area-related COPCs. Therefore, arsenic and lead were not retained for further evaluations in the Residential BHHRA for CC-IAAP-001. An IAAAP-specific groundwater BTV was not developed for hexavalent chromium. Therefore, additional analysis was completed to determine if hexavalent chromium concentrations reported in unfiltered CC-IAAP-001 groundwater are consistent with background. There is no known historical record of IAAAP processes or operations involving the use of hexavalent chromium being conducted at CC-IAAP-001. An estimated background level of hexavalent chromium was determined for CC-IAAP-001 unfiltered groundwater based on the IAAAP-specific groundwater BTV for chromium and area-specific ratios of hexavalent chromium to chromium concentrations reported for CC-IAAP-001 unfiltered groundwater. As a result of comparative analyses, hexavalent chromium was determined to be present in unfiltered groundwater at CC-IAAP-001 at concentrations comparable to the estimated background levels. Based on this finding, hexavalent chromium is not an area-related COPC. In addition, if hexavalent chromium was considered to be a site-related COPC, it would not be identified as a final COC since both chromium and hexavalent chromium concentrations reported for CC-IAAP-001 unfiltered groundwater are less than the maximum contaminant level (MCL). Therefore, hexavalent chromium was not identified as a final COC in unfiltered groundwater at CC-IAAP-001. IAAAP-specific groundwater BTVs are not available for uranium, uranium-234 or uranium-238. There is no known historical record of IAAAP processes or operations involving the use of uranium or uranium isotopes ever having been conducted at CC-IAAP-001, though uranium has been used in processes and operations conducted in other areas of the IAAAP. However, comparisons of unfiltered groundwater concentrations of uranium with the USEPA’s MCL show that the uranium concentrations in unfiltered groundwater at CC-IAAP-001 are less than the MCL. Similarly, comparisons of unfiltered groundwater concentrations of total uranium isotopes (i.e., the sum of the uranium isotope concentrations) at CC-IAAP-001 with the radiological activity equivalent to the USEPA’s MCL for uranium show that the uranium isotope concentrations are less than the activity equivalent concentration to the MCL. Therefore, uranium was not identified as a final COC, and uranium-234 and uranium-238 were not identified as final ROCs in unfiltered groundwater at CC-IAAP-001.

CC-IAAP-002 Risk Characterization Results and Conclusions Based on the results of the risk characterization of CC-IAAP-002, residential ELCRs for exposures to surface soil and soil (0 to 10 ft bgs) exceed the NCP’s s target ELCR limit due to ingestion of uranium-234 and uranium-238. However, because the concentrations of these isotopes are less than the soil BTVs and therefore, consistent with background conditions, uranium-234 and uranium-238 in surface soil and soil are not attributed to IAAAP-related processes. However, the ELCRs and HIs calculated for the ingestion of unfiltered groundwater exceed target limits under the Residential Land Use scenario due predominantly to concentrations of arsenic, hexavalent chromium, uranium-234, and uranium-238. The inhalation pathway for uranium-234 and uranium-238 contributes even more


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predominantly to the receptor ELCR than ingestion, due to decay chain progeny (i.e., radium-226). Because arsenic concentrations are consistent with background conditions and are not attributed to IAAAP-related processes, arsenic was not identified as a final COC. An IAAAP-specific groundwater BTV was not developed for hexavalent chromium. Therefore, additional analysis was completed to determine if hexavalent chromium concentrations reported in unfiltered CC-IAAP-002 groundwater are consistent with background. There is no known historical record of IAAAP processes or operations involving the use of hexavalent chromium being conducted at CC-IAAP-002. An estimated background level of hexavalent chromium was determined for CC-IAAP-002 unfiltered groundwater based on the IAAAP-specific groundwater BTV for chromium and area-specific ratios of hexavalent chromium to chromium concentrations reported for CC-IAAP-002 unfiltered groundwater. As a result of comparative analyses, hexavalent chromium was determined to be present in unfiltered groundwater at CC-IAAP-002 at concentrations comparable to the estimated background levels. Based on this finding, hexavalent chromium is not an area-related COPC. In addition, if hexavalent chromium was considered to be a site-related COPC, it would not be identified as a final COC since both chromium and hexavalent chromium concentrations reported for CC-IAAP-002 unfiltered groundwater are less than the MCL. Therefore, hexavalent chromium was not identified as a final COC in unfiltered groundwater at CC-IAAP-002. IAAAP-specific groundwater BTVs are not available for uranium-234 and uranium-238. There is no known historical record of IAAAP processes or operations involving the use of uranium or uranium isotopes ever having been conducted at CC-IAAP-002, though uranium has been used in processes and operations conducted in other areas of the IAAAP. However, comparisons of unfiltered groundwater concentrations of total uranium isotopes (i.e., the sum of the uranium isotope concentrations) at CC-IAAP-002 with the radiological activity equivalent to the USEPA’s MCL for uranium show that the uranium isotope concentrations are less than the activity equivalent concentration to the MCL. Therefore, uranium-234 and uranium-238 were not identified as final ROCs in unfiltered groundwater at CC-IAAP-002.

Conclusions of the Residential BHHRA No COCs or ROCs were identified in soil or groundwater at both CC-IAAP-001 and CC-IAAP-002 under the Residential Land Use scenario in the Residential BHHRA. CC-IAP-001 and CC-IAAP-002 can move forward to the next phase in the CERCLA to facilitate the removal of the ACM at CC-IAAP-002 followed by a NFA determination once the ACM removal action is completed.

Supplemental Screening Level Ecological Risk Assessment

The 2014 SLERA concluded that risks to ecological receptors from chemicals in CC-IAAP-001 surface soil, surface water, and sediment and in CC-IAAP-002 surface soil and sediment are not anticipated and that no further remedial action from an ecological perspective was required. However, the northern long‐eared bat (Myotis septentrionalis) and the rusty patched bumble bee (Bombus affinis) were added to the federally threatened and endangered species list subsequent to the completion of the SLERA. Per the request from the USEPA and the 2017 UFP-QAPP (CH2M Hill 2017), the 2014 SLERA was updated to evaluate these newly added species. A review of the federally listed threatened and endangered species in Iowa (USFWS 2018a) indicated that the rusty patched bumble bee is endangered in portions of four counties. However,


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Des Moines County, where the IAAAP is located, is not one of the four counties of concern. As a result, no further evaluation of the rusty patched bumble bee at IAAAP is required. The northern long-eared bat was also added to the federally endangered species list for Des Moines County after the 2014 SLERA was completed. However, the Indiana bat was evaluated in the 2014 SLERA (PIKA 2014a) and potential ecological risks from exposure to media at both construction debris sites was determined to be negligible. In particular, the forging range of Indiana bats is so large compared to the size of CC-IAAP-001 and CC-IAAP-002 that the evaluation is not spatially relevant. Because no new chemical data have been collected and the ecology and life history is similar for the northern long-eared and Indiana bats, it is reasonable to conclude that risks to the northern long-eared bat also would be negligible. This Supplemental SLERA was also updated from the 2014 SLERA (PIKA 2014a) for applicability to current benchmarks and ecological risk assessment methods. The 2014 SLERA (PIKA 2014a) focused on the screening of maximum detected concentrations against screening benchmarks. This is a standard component of a SLERA. For the 2014 SLERA, screening benchmarks were used to assess the potential for risks to ecological receptors to occur from exposure to chemical constituents in surface soil, surface water, and sediment. Screening benchmark values were based on conservative assumptions and represent, where possible, no-observed-adverse-effects-levels (NOAELs) for chronic exposures. A review of the screening benchmarks indicated that very few benchmarks have changed since the 2014 SLERA was completed. In the limited instances where a few of the surface water benchmarks could change, no significant changes to previously determined risk results would occur. Based on the evaluation of the rusty patched bumble bee and northern long-eared bat along with an assessment of the chemical screening in the 2014 SLERA, the conclusion of the Supplemental SLERA is the same as that for the 2014 SLERA (PIKA 2014a), i.e., no ecological risks at CC-IAAP-001 from exposure to surface soil, surface water, and sediment and no ecological risks at CC-IAAP-002 from exposure to surface soil and sediment are anticipated. It bears noting that the USEPA ecological risk assessment (ERA) process (USEPA 1997a, 1998) is readily applied for CERCLA remedial investigations independent of considerations of the size, ecological relevance, or ecological significance of contaminated sites. Often however, a site may not need an ecological assessment based on the actual site features. In general, a SLERA is not required at terrestrial sites that only occupy a very few acres. Many areas on IAAAP such as CC-IAAP-001 and CC-IAAP-002 had SLERAs previously completed on them, and these efforts arguably were unnecessary. Where spatially relevant receptors of the sort that could form the basis of remedial action (i.e., receptors other than small rodents or earthworms) are present, the initial step in the SLERA is a comparison of concentrations of chemicals detected in site media to those of ecotoxicological-based screening values. This screening step does not account for ecological features or natural resource assets on the site. Importantly, considerations for an animal’s home range, population density, or other metrics that are readily available in the open literature, are not addressed in this screening step; if they were, relatively smaller sites would likely not be found to need ecological assessments. Such small sites generally do not support enough receptors that remedial actions would be required to provide for their protection and any protection provided would not be measurable. Caution should be exercised when reviewing the results of a SLERA completed for small sites that have no ecologically significant resources and more specifically, where the results of such SLERAs are not readily translatable to realistic site conditions.


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Procedurally, the SLERA for areas CC-IAAP-001 and CC-IAAP-002 were completed to update the original SLERA per the request of the USEPA. The update included(s) a re-evaluation of potential receptors that could occur on the areas to address if new federally-listed threatened and endangered (T&E) species could potentially use the areas for any purpose, and to re-evaluate the comparison of area concentrations to current ecological screening values that may have changed since the last SLERA was completed. This type of update does not consider spatial or temporal characteristics of the receptors and how they relate to the area. Both areas evaluated in this RI Addendum are very small and would not support the Northern long-eared bat spatially or ecologically and there is no risk evaluation method that has been developed for the rustic bumble bee. Site CC-IAAP-001 is approximately 1.3 acres and CC-IAAP-002 is approximately 0.63 acres. As stated, there is limited habitat and ecological resources on these areas.

Results Summary of the Remedial Investigation Addendum Report

Based on the results of the Residential BHHRA, no COCs or ROCs requiring further evaluations in a Feasibility Study and/or additional remedial action(s) were identified for either site. All media at CC-IAAP-001 achieve UU/UE, as well as NFA. Although no COCs or ROCs were identified in soil or groundwater at CC-IAAP-002, this site does not achieve UU/UE or NFA until after the ACM removal action has occurred. The conclusion of the Supplemental SLERA is the same as that for the 2014 SLERA (PIKA 2014a), i.e., no ecological risks at CC-IAAP-001 from exposure to surface soil, surface water, and sediment and no ecological risks at CC-IAAP-002 from exposure to surface soil and sediment are anticipated.


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1.0 INTRODUCTION

This document presents the Remedial Investigation (RI) Report Addendum (Addendum) for Construction Debris Site #1 (CC-IAAP-001) and Construction Debris Site #2 (CC-IAAP-002) at the Iowa Army Ammunition Plant (IAAAP) located in Middletown, Iowa. This focus of this Addendum is to supplement the Baseline Human Health Risk Assessment (BHHRA) and update the Screening Level Ecological Risk Assessment (SLERA) prepared in 2014 as part of the Remedial Investigation Report for Construction Debris Sites CC-IAAP-001 and CC-IAAP-002 (RI Report) (PIKA 2014a). This Addendum includes a human health risk evaluation of the Residential Land Use scenario and additional ecological risk evaluations. To avoid reader confusion between the BHHRAs and SLERAs prepared as part of the RI Report (PIKA 2014a) and those prepared in this Addendum, the BHHRA and SLERA that were prepared as part of the RI Report are referred to as the “2014 BHHRA” and the “2014 SLERA.” The BHHRA and the SLERA performed as part of this Addendum are referred to as the “Residential BHHRA” and the “Supplemental SLERA,” respectively. The following subsections to this Introduction present brief background summaries of the purpose of this Addendum, information regarding the basis for the risk assessment methods, and current regulatory guidance.

1.1 SITE OPERATIONAL BACKGROUND

In accordance with the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), the U.S. Environmental Protection Agency (USEPA) added the IAAAP to the National Priority List (NPL) of Superfund sites, on August 30, 1990 (Site Identification IA7213820445), based on the presence of known and suspected releases of hazardous contaminants to the environment and on hazard ranking. CC-IAAP-001 and CC-IAAP-002 are areas located within the boundary of the IAAAP Installation that were used for disposal of construction and demolition debris. CC-IAAP-001 and CC-IAAP-002 have been added, as a health-protective measure, to the list of IAAAP areas being investigated and/or remediated in accordance with the CERCLA process, under the U.S. Army’s Installation Restoration Program (IRP). Sections 1.1.1, 1.1.2, and 1.1.3 briefly describe the operations and physical features of the IAAAP Installation, CC-IAAP-001, and CC-IAAP-002, respectively.

1.1.1 Installation The IAAAP is a military facility located in the southeastern part of Iowa in Des Moines County, near the town of Middletown, approximately 10 miles west of the Mississippi River. The IAAAP is an active, government-owned, contractor-operated facility, the mission of which has been load, assemble, and pack (LAP) operations involving large-scale ammunition, including projectiles, mortar rounds, mines, and warheads. The IAAAP has several LAP operations lines and ammunition storage yards (along with other miscellaneous operations) spread across more than 19,000 acres. All of the IAAAP land is currently owned and under the control of the U.S. Army, although portions of the facility were previously under control of other tenant organizations, including the Atomic Energy Commission. Use restrictions and outgrants administered by the U.S. Army as part of its land management responsibilities limit the IAAAP, which operates as a military installation, to Commercial/Industrial Land Use. Currently, American Ordinance, LLC is the government contractor at IAAAP and manufactures a wide variety of artillery and tank munitions for the United States. Less than one-third of the IAAAP property is occupied by active or formerly active munitions production or storage facilities. Per the RI Report (PIKA 2014a),


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approximately 7,750 acres are currently leased for agricultural use, 7,500 acres are forested land, and the remaining area is used for administrative and industrial operations. Past munitions production at the IAAAP has resulted in contamination of soil and ground water and discharges of waste water containing explosives and their byproducts to surface water (USACE 1998).

1.1.2 CC-IAAP-001 CC-IAAP-001 is not an active area and was not used as part of any of the IAAAP processes or LAP operations, nor did it receive wastes from any IAAAP processes. CC-IAAP-001 was discovered in October 2007 at the intersection of Roads H and I, during work on a water line along Road H. The area shown on Figure 1 is bounded by a curving railroad spur that crosses Road H at the south end of the site and Road I at the northeast end of the area. CC-IAAP-001 covers approximately 1.34 acres and was used to discard construction and demolition debris. Debris is visible in several eroded areas along the steep embankment adjacent to Road H. Surface debris also exists along the drainage located at the base of the embankment along Road H. Visible debris includes scattered bricks, corrugated metal, metal parts, wire, and metal banding. Due to the presence of the debris, a visual inspection was performed of the area, during the RI, that focused on the presence of asbestos-containing material (ACM). The visual inspection of the CC-IAAP-001 identified no suspect ACM in site debris, surface soil, or boring cores. More detailed information regarding the ACM survey and results are discussed in Section 2.1.

1.1.3 CC-IAAP-002 CC-IAAP-002 is not an active area and was not used as part of any of the IAAAP processes or LAP operations, nor did it receive wastes from any IAAAP processes. CC-IAAP-002 was discovered by recreational users in March 2009 along an intermittent tributary to Brush Creek in a forested area south of Line 2. The area shown on Figure 2 covers approximately 0.625 acres and was used to discard construction and demolition materials, including sheets of metal, bricks, corrugated transite roofing/siding, wire, buckets, and wood. The debris appears to have been placed along the banks of a drainage feature which discharges to Brush Creek. The end of the debris lies approximately 100 to 200 feet (ft) from the confluence with Brush Creek. Due to the presence of the debris, a visual inspection was performed of the area, during the RI. The visual inspection focused on the presence of ACM that could be associated primarily with asbestos-cement (transite), and pieces of thermal insulation possibly from past building demolition and disposal activities. The inspection identified three areas along Brush Creek that contained significant quantities of asbestos-containing cement panels/roofing material, which exhibit disintegration due to exposure to the elements. No ACM was visually identified in soil boring cores collected from CC-IAAP-002. More detailed information regarding the ACM survey and results are discussed in Section 2.1.

1.2 PURPOSE OF THE REMEDIAL INVESTIGATION REPORT ADDENDUM

This Addendum was completed to evaluate the potential risks to resident receptors in a BHHRA and to update the 2014 SLERA (PIKA 2014a). The 2014 BHHRA evaluated receptors under the Commercial/Industrial Land Use scenario and determined that there are no potentially unacceptable health risks for those receptors, based on the available data (i.e., for soil, groundwater, surface water, and sediment) and the exposure assumptions that were described therein. The results of the 2014 BHHRA for CC-IAAP-001 and CC-IAAP-002 formed the basis of a Focused Feasibility Study (FFS) Report (i.e., “Focused Feasibility Study Report for Construction Debris Sites CC-IAAP-001


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and CC-IAAP-002”) (PIKA 2014b) and subsequent Proposed Plan (PP) (i.e., “Final Proposed Plan for Construction Debris Sites CC-IAAP-001 and CC-IAAP-002”) (PIKA 2015). The results of the FFS were used to identify the preferred remedial alternative in the PP, (i.e., “Alternative 4 – Removal and Disposal of ACM Debris Piles”). The 2014 BHHRA did not include an evaluation of Residential Land Use which is necessary to determine if additional remedial actions are warranted and if unlimited use and unrestricted exposure (UU/UE) conditions are met for the two areas. Because the IAAAP is still an active facility, assumptions regarding residential exposures at CC-IAAP-001 and CC-IAAP-002 should be considered as hypothetical and are applied for the purposes of supporting a determination of status of relative to NFA and UU/UE conditions for all media. For each of the construction debris areas, a determination of UU/UE applies only if no chemicals of concern (COCs) or radionuclides of concern (ROCs) are identified under the Residential Land Use scenario. COCs and ROCs are identified as potentially site-related contaminants with concentrations that result in excess lifetime cancer risks (ELCRs) and/or noncarcinogenic hazard indices (HIs) that exceed the respective target limits established in the USEPA’s National Oil and Hazardous Substances Contingency Plan (NCP) (USEPA 1990). The target ELCR is 1E-04, which represents the upper limit of the NCP’s target risk range of 1E-06 to 1E-04. An ELCR of 1E-06 represents the probability of one additional cancer case above baseline that could occur within a population of one million people, over a lifetime. Similarly, an ELCR of 1E-04 represents the probability of one additional cancer case above baseline that could occur within a population of ten thousand people, over a lifetime. The target noncarcinogenic HI is 1. HIs less than or equal to the target limit indicate that no adverse systemic health effects are considered likely following exposures, as evaluated in a BHHRA. According to USEPA’s Office of Solid Waste and Emergency Response (OSWER) Directive 9355.7-04 entitled “Land Use in the CERCLA Remedy Selection Process” (USEPA 1995), the presence of contaminants in media at concentrations protective of residential exposures allow for Unrestricted Land Use. A decision of UU/UE for CC-IAAP-001 and CC-IAAP-002 would mean that no COCs or ROCs were identified that warrant additional remedial actions. If no COCs or ROCs are identified, then no additional remedial action (i.e., including land use controls) and five-year reviews are required. A determination of no further action (NFA) is made and the site proceeds to the next phase in the CERCLA process (i.e., PP). However, a visual inspection conducted as part of the RI field investigation identified the presence of ACM associated with roofing material found in three distinct locations of the CC-IAAP-002 debris piles. No such finding was made at CC-IAAP-001. The results of soil sampling and analysis indicate that concentrations of asbestos fibers in core samples were reported to be non-detect for both CC-IAAP-001 and CC-IAAP-002. During the visual inspection, it was noted that the ACM observed in the CC-IAAP-002 debris piles exhibited disintegration from weathering. This finding raised concerns that asbestos in the debris piles is becoming increasingly friable with time. Increased friability increases the potential for releases of microscopic fibers into the air, thereby increasing the potential for human and environmental exposures. A subsequent FFS Report (i.e., “Focused Feasibility Study Report for Construction Debris Sites CC-IAAP-001 and CC-IAAP-002”) (PIKA 2014b) and PP (i.e., “Final Proposed Plan for Construction Debris Sites CC-IAAP-001 and CC-IAAP-002”) (PIKA 2015) identified the removal of ACM in the CC-IAAP-002 debris piles in the preferred remedial alternative (i.e., Remedial Alternative #4). Because removal of ACM from the debris piles at CC-IAAP-002 has been determined to be necessary, CC-IAAP-002 cannot be deemed as NFA regardless of the results of this Addendum until the removal action is completed. The PP indicates that “NFA will be recommended after the ACM is removed and subsequent site sampling verifies the site as not having unacceptable risk levels”


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(PIKA 2015). Achievement of UU/UE is consistent with the third remedial action objective (RAO) presented in the PP (PIKA 2014b) for CC-IAAP-002. According to the PP

• “Prevent direct media contact with human and ecological receptors; • Prevent migration of friable asbestos through wind, surface water runoff, and erosion

pathways; and • Remove all ACM debris from CC-IAAP-002 to prevent exposure and allow for unlimited

use and unrestricted exposure. After removal of the ACM debris, NFA is recommended.” According to the PP (PIKA 2015), no RAOs were considered necessary for CC-IAAP-001 because no unacceptable risk was identified during the 2014 BHHRA, which evaluated non-residential exposure scenarios. Therefore, this Addendum presents the Residential BHHRA in order to determine NFA status for CC-IAAP-001 under current conditions, as well as for CC-IAAP-002 under future conditions, subsequent to ACM removal per Remedial Alternative #4. Additionally, this Addendum also presents the Supplemental SLERA. By their nature, SLERAs are intended to be conservative and protective and often overestimate potential ecological risks. Despite the conservative evaluation, risks to ecological receptors were not anticipated in the RI Report (PIKA 2014a). However, as agreed with the USEPA, the SLERA was updated to consider potential ecological risks to federally-listed species that have been listed since the 2014 SLERA was completed. While these sites are very small and offer little habitat, the updated SLERA included herein is proactive and further protective. The Supplemental SLERA updated ecological receptor information and ecological screening levels to facilitate future decision-making regarding determinations of NFA status for CC-IAAP-001 and CC-IAAP-002 from an ecological perspective. Results of the Residential BHHRA and the Supplemental SLERA will be used to support future decision-making regarding UU/UE and NFA. This Addendum makes recommendations, as needed, relative to whether or not further remedial actions are warranted in a future CERCLA decision document(s).

1.3 BASIS OF THE REMEDIAL INVESTIGATION REPORT ADDENDUM

The basis for the methods and technical approaches applied to the Residential BHHRA is the approved 2017 Uniform Federal Policy-Quality Assurance Project Plan for Remedial Investigation at Iowa Army Ammunition Plant, Middletown, Iowa (2017 UFP-QAPP) (CH2M Hill 2017), as well as USEPA and USACE risk assessment guidance. The conceptual exposure model (CEM) information, data screening and risk assessment methods applied in this Addendum are consistent with those established in the 2017 UFP-QAPP, which was prepared separate from and subsequent to the Final Work Plan, Remedial Investigation of Construction Debris Sites CC-IAAP-001 and CC-IAAP-002 (RI Work Plan) (PIKA 2013) that established the objectives, scope, procedures, and methods for the RI conducted in 2014 at CC-IAAP-001 and CC-IAAP-002. The risk assessment methods and approaches described in IAAAP-wide Worksheet #14 of the 2017 UFP-QAPP, as well as those previously applied in the RI Report (PIKA 2014a), provide the primary basis for those applied in this Addendum. For the Residential BHHRA, those methods are also consistent with the USEPA’s Risk Assessment Guidance for Superfund, Volume I, Human Health Evaluation Manual (Part A) (RAGS Part A) (USEPA 1989) and the U.S. Army Corps of Engineers (USACE) Engineering Manual entitled Risk Assessment Handbook, Human Health Evaluation, Volume I: Human Health Evaluation (i.e., “Risk Assessment Handbook EM 200-1-4”) (USACE 1995). The ecological risk assessment methods previously applied in the RI Report (PIKA 2014a) are the primary basis for the Supplemental SLERA.


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2.0 SUMMARY OF THE REMEDIAL INVESTIGATION REPORT

The RI Report (PIKA 2014a) documents activities performed to characterize the nature and delineating the horizontal and vertical extent of contamination potentially resulting from construction debris, evaluate the fate and transport of contaminants in the environment, and to assess potential risks to human health and the environment at CC-IAAP-001 and CC-IAAP-002. The RI was performed in accordance with CERCLA and the IAAAP Federal Facility Agreement (FFA) (U.S. Army and USEPA 1990). No investigations were conducted at CC-IAAP-001 or CC-IAAP-002 prior to the 2014 RI, nor have there been any other investigations since the RI. This section briefly summarizes the nature and extent of contamination and the BHHRA and SLERA that were presented in the RI Report (PIKA 2014a). In an effort to maintain document streamlining of this Addendum, the reader is referred to the specified sections of the RI Report for detailed information related to the following: study area investigation activities (Section 3.0), physical characteristics (i.e., climate, ecology, topography, hydrology, geology, and hydrogeology) (Section 4.0), and contaminant fate and transport (Section 6.0).

2.1 NATURE AND EXTENT OF CONTAMINATION

In order to fulfill the above-stated objectives of the RI, surface soil (0 to 0.5 ft below ground surface [bgs]), subsurface soil (0.5 to 10 ft bgs), unfiltered and filtered groundwater, surface water, and sediment (0 to 0.5 ft bgs) samples were collected during a field investigation that was conducted in June 2013. No surface water samples were collected from CC-IAAP-002 due to the absence of surface water at the time of the investigation. Samples were submitted for laboratory analyses of the following target analytes: explosives, semivolatile organic compounds (SVOCs), polynuclear aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), pesticides, polychlorinated biphenyls (PCBs), herbicides, metals, hexavalent chromium, and asbestos. Dissolved and total metals analyses were performed on filtered and unfiltered samples, respectively, of groundwater and surface water. In the evaluation of nature and extent of contamination in the RI Report (i.e., Section 5.0 and Appendix D), sample concentrations of all analytes were compared to project action limits (PALs), which were defined in the RI Report (PIKA 2014a) as “The numerical value the decision-maker uses as the basis for choosing a remedial action at a Site. It may be a regulatory threshold such as a maximum contaminant level (MCL), a risk-based concentration level, a reference-based standard, or a technological limitation.” Specific screening levels and standard used to determine PALs for the RI Report were specified in the RI Work Plan. The PALs used for assessing nature and extent for each medium represented the lowest of the human health (HH) PALs versus ecological-based (ECO) PALs. In addition to the lower of the HH and ECO PALs, soil and sediment metals concentrations were compared to area-specific, mean background values (MBVs) determined for soil. Comparisons of CC-IAAP-001 and CC-IAAP-002 media concentrations to PALs and MBVs for determining nature and extent of contamination were done only for characterization purposes, and were not used for eliminating chemicals from further evaluations in the 2014 BHHRA or 2014 SLERA. The results of the nature and extent of contamination of investigated media at CC-IAAP-001 indicated that seven metals (arsenic, barium, cadmium, total chromium, hexavalent chromium, lead, and selenium) and one pesticide (endrin aldehyde) exceeded their respective PALs or background value. These exceedances are described as follows (PIKA 2014a).


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• Soil – metals (arsenic, barium, cadmium, total chromium, lead, and selenium) and one pesticide (endrin aldehyde) exceeded their respective PALs or soil background values.

• Groundwater – metals (total and dissolved arsenic, total chromium, total hexavalent chromium, and total lead) exceeded their respective PALs.

• Sediment – metals (arsenic, barium, total chromium, and selenium) exceeded their respective PALs.

• Surface Water – metals (total and dissolved arsenic; total and dissolved barium; total hexavalent chromium, and total selenium) exceeded their respective PALs.

At CC-IAAP-002, seven metals (arsenic, barium, cadmium, total chromium, hexavalent chromium, lead, and selenium) and twelve SVOCs (acenaphthene, acenaphthylene, benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(g,h,i)perylene, chrysene, dibenzo(a,h)anthracene, fluoranthene, indeno(1,2,3-cd)pyrene, phenanthrene, and pyrene) exceeded their respective PALs or background values. These exceedances are described below (PIKA 2014a).

• Soil – metals (arsenic, barium, total chromium, lead, and selenium) exceeded their respective PALs or soil background values.

• Groundwater – metals (total and dissolved arsenic, total chromium, and total hexavalent chromium) exceeded their respective PALs.

• Sediment – metals (arsenic, barium, total chromium, lead, and selenium) and twelve SVOCs (acenaphthene, acenaphthylene, benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(g,h,i)perylene, chrysene, dibenzo(a,h)anthracene, fluoranthene, indeno(1,2,3-cd)pyrene, phenanthrene, and pyrene) exceeded their respective PALs or soil background values.

The concentrations of metals in surface and subsurface soils at both sites are within the range of the background samples collected across the installation, with the exception of selenium (PIKA 2014a). In addition to determining the nature and extent of chemical contamination at CC-IAAP-001 and CC-IAAP-002, soil and surface water samples were collected and analyzed for asbestos; however, no air samples were collected. Asbestos fibers were not detected in any of the samples from either area. Additionally, a visual inspection of both CC-IAAP-001 and CC-IAAP-002 was conducted by an Iowa licensed Asbestos Inspector, by physically walking the work areas and performing a visual inspection of the surface. The inspection focused primarily on asbestos-cement panels (transite), and pieces of thermal insulation possibly remaining after building demolitions or disposal. The visual inspection of CC-IAAP-001 identified no suspect ACM. However, the visual inspection of CC-IAAP-002 identified three distinct areas of suspect ACM along the creek that contained significant quantities of asbestos containing cement panels. Four samples were collected that included the cement panels and a very small quantity of a tar like substance (likely a roofing adhesive or sealant). Asbestos fibers (chrysotile) were detected in all four samples. No suspect material was visually identified in any of the soil boring cores collected during the inspections at CC-IAAP-001 or CC-IAAP-002. Asbestos was not detected in any of the soil and water samples collected. Therefore, the extent of ACM is limited to the roofing material within the debris piles located within CC-IAAP-002. Several areas within the debris piles were observed to contain roofing material that has disintegrated due to prolonged exposure to the elements.


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2.2 2014 BASELINE HUMAN HEALTH RISK ASSESSMENT AND SCREENING LEVEL ECOLOGICAL RISK ASSESSMENT

The 2014 BHHRA evaluated the potential for health risks to human and ecological receptors, at both areas, assuming baseline conditions (i.e., no remediation has occurred), under the Commercial/Industrial Land Use scenario. This land use scenario is consistent with the current and foreseeable future land use of the IAAAP, though CC-IAAP-001 and CC-IAAP-002, which are inactive areas, cannot be designated into any formal land use category since no such category exists for construction debris. The 2014 BHHRA evaluated potential exposures to chemicals of potential concern (COPCs) in soil, sediment, groundwater, and surface water at CC-IAAP-001 and CC-IAAP-002. The COPCs for CC-IAAP-001 and CC-IAAP-002 were selected based on comparisons of the maximum detected concentrations in each evaluated medium with the corresponding HH PALs for Commercial/Industrial Land Use. USEPA Industrial Regional Screening Levels (RSLs) for soil applied during COPC selection targeted an ELCR of 1E-06 and a hazard quotient (HQ) of 0.1. The resulting lists of COPCs for the Commercial/Industrial Land Use Scenario at CC-IAAP-001 and CC-IAAP-002 are presented in Table 2-1. Although maximum soil and sediment concentrations were also compared to background values, none of the exceeding metals were eliminated from the 2014 BHHRA.

Table 2-1. 2014 BHHRA COPCs Medium CC-IAAP-001 CC-IAAP-002

Surface Soil (0-1 ft bgs)

Arsenic Arsenic Dimethylphthalatea

Surface and Subsurface Soil (0-10 ft bgs)

Arsenic Arsenic Dimethylphthalatea

Groundwater (Filtered)

Dissolved Arsenic Dissolved Barium Dissolved Manganese

Dissolved Arsenic Bromomethane

Groundwater (Unfiltered)

Total Arsenic Total Barium Total Hexavalent Chromium Total Lead Total Uranium

Total Arsenic Total Barium Total Cadmium Total Hexavalent Chromium

Surface Water (Filtered) Dissolved Arsenic NA Surface Water (Unfiltered)

Total Arsenic Dissolved Hexavalent Chromium

NA

Sediment Arsenic Arsenic Benzo(a)pyrene Dimethylphthalatea

a Dimethylphthalate was retained as a COPC based on the absence of screening level and toxicity criteria. NA – Data are not available for determining COPCs because surface water was absent from CC-IAAP-002 at the time of sampling.

Following the identification of COPCs at CC-IAAP-001 and CC-IAAP-002, exposure point concentrations (EPCs) were calculated for each of the media of concern for input into the calculations of ELCRs and non-cancer HQs, along with receptor/medium-specific exposure assumptions. The following receptor scenarios were evaluated for ELCRs and HIs at CC-IAAP 001 and CC-IAAP-002:


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Current Adolescent (Ages 12 – 18 Years) and Adult Hunter Exposures: • Surface Soil/Sediment

o Ingestion o Dermal Contact o Dust Inhalation

• Unfiltered Surface Water (Evaluated Only for CC-IAAP-001) o Ingestion o Dermal Contact

Future Adolescent (Ages 12 – 18 Years) and Adult Hunter Exposures: • Soil (Surface and Subsurface Soil, 0 – 10 ft bgs)/Sediment


• Unfiltered Surface Water (Evaluated Only for CC-IAAP-001) o Ingestion o Dermal Contact

Future Commercial/Industrial Worker Exposures: • Soil (Surface and Subsurface Soil, 0 – 10 ft bgs)


• Unfiltered Groundwater o Ingestion

Future Construction Worker Exposures: • Soil (Surface and Subsurface Soil, 0 – 10 ft bgs)


Descriptions of the previously listed receptor scenarios are evaluated and provided in Sections 7.1.3.1 and 7.2.3.1 for CC-IAAP-001 and CC-IAAP-002, respectively, in the RI Report (PIKA 2014a). COPC-specific ELCRs and HQs were summed over all exposure routes and media to calculate the total ELCRs and non-cancer HIs associated with each area. The 2014 BHHRA concluded that the ELCR and non-cancer HI estimates for all evaluated human receptors at both CC-IAAP-001 and CC-IAAP-002 are below the USEPA’s target risk range (1E-06 to 1E-04) and target HI of 1, respectively. Additionally, predicted blood lead levels (BLL) for the future commercial/industrial worker at CC-IAAP-001 were below the USEPA’s benchmark criterion (i.e., a less than 5 percent probability that the BLL would ever exceed 10 micrograms per deciliter [μg/dL]). No EPCs or ELCRs were calculated for asbestos at either CC-IAAP-001 or CC-IAAP-002. No ACM was observed at CC-IAAP-001. Although ACM was observed and chrysotile was detected in three areas of the CC-IAAP-002 debris piles, no air samples were collected from either area and there were no detections of asbestos in soil cores or water samples collected from either area. The 2014 SLERA evaluated exposures of terrestrial and aquatic species to contaminants of potential ecological concern (COPECs) identified in surface soil, surface water, and sediment at CC-IAAP-001 (i.e., endrin aldehyde, arsenic, barium, cadmium, hexavalent chromium, lead, and selenium) and in surface soil and sediment at CC-IAAP-002 (i.e., 14 semivolatile organic compounds, arsenic, barium, hexavalent chromium, lead, selenium, and uranium). While there


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were HQs greater than 1.0 (ranging from 1.2 to 14 at CC-IAAP-001 and 1.6 to 19 at CC-IAAP-002), the 2014 weight-of-evidence evaluation indicated that risks to all ecological receptors at both areas are not anticipated and no additional remedial action is required from an ecological perspective.


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3.0 RESIDENTIAL BASELINE HUMAN HEALTH RISK ASSESSMENT FOR CC-IAAP-001 AND CC-IAAP-002

The Residential BHHRA for CC-IAAP-001 and CC-IAAP-002 was developed using current USEPA risk assessment guidance documents that are cited, as applicable, throughout this document. Risk assessment tables and supporting calculations for CC-IAAP-001 and CC-IAAP-002 are presented in Appendices A and B, respectively. In both appendices, and in a manner consistent with the 2014 BHHRA, the risk assessment tables supporting the text are those that follow the information and formatting requirements established in the USEPA’s Risk Assessment Guidance for Superfund: Volume I Human Health Evaluation Manual (Part D, Standardized Planning, Reporting, and Review of Superfund Risk Assessment), Final (RAGS Part D) (USEPA 2001). The supporting calculations (i.e., EPC and lead model calculations) are contained in Attachments A-1, A-2, and B-1 of the respective appendices. All current information available for CC-IAAP-001 and CC-IAAP-002, including analytical data, as well as other pertinent information related to the conceptual site model (CSM) (i.e., environmental setting, previous investigations, understanding of nature and extent of contamination, upgradient and downgradient vicinity groundwater plumes, contaminant fate and transport, and potential environmental migration and exposure pathways) are presented in the RI Report (PIKA 2014a) and in area-specific Worksheet #3.110 for CC-IAAP-001 and CC-IAAP-002 of the 2017 UFP-QAPP (CH2M Hill 2017). The analytical data collected during the 2013 RI and that were used in the 2014 RI Report (PIKA 2014a) are the same data applied in this Residential BHHRA. All data collected from both areas are organic and inorganic chemical data. Included in the inorganic analytical data sets for metals in soil and groundwater was elemental uranium, which was identified as a COPC in CC-IAAP-001 unfiltered groundwater during the 2014 BHHRA (see Table 2-1). No soil or groundwater samples were collected for analysis of the radiological isotopes of uranium (i.e., uranium-234, uranium-235 and uranium-238) during the 2013 RI; therefore, the isotopic concentrations have been calculated in this Residential BHHRA, for both areas, from the reported concentrations of elemental uranium in soil and groundwater, along with all decay chain prodigy, assumed to be in secular equilibrium with the parent isotopes. Although depleted uranium (DU) has been used at the IAAAP, and that DU fragments have been visibly observed in soil and investigated at other portions of the IAAAP (e.g., the Firing Sites Areas), there is no information to suggest that DU should be present in the OU-9 construction debris areas. Therefore, calculations of the isotopic concentrations were performed by incorporating the weight percentages of uranium-234 (0.0057%), uranium-235 (0.72%) and uranium-238 (99.28%) that correspond to natural uranium, along with the specific activities of each isotope. The percent weights for natural uranium were applied rather than those for DU for two reasons. 1) Risks calculated for natural uranium are more health-conservative. This is because DU is considerably less radioactive than natural uranium because not only does it have less uranium-234 and uranium-235 per unit mass than natural uranium, but essentially all traces of decay products beyond uranium-234 and thorium-231 have been removed during extraction and chemical processing of the uranium prior to enrichment. 2) Natural uranium is conservatively assumed because the source of the uranium detected in soil and groundwater at both areas (i.e., area-related process or natural occurrence) is unknown. The calculations of the uranium isotopes are presented for CC-IAAP-001 and CC-IAAP-002 in Appendix A, Attachment A-1 and Appendix B, Attachment B-1, respectively.


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3.1 CONCEPTUAL EXPOSURE MODELS FOR THE RESIDENTIAL LAND USE SCENARIOS AT CC-IAAP-001 AND CC-IAAP-002

The CEMs for the Residential Land Use scenario assumed for CC-IAAP-001 and CC-IAAP-002 provide the basis for COPC selection; identification of hypothetically exposed residential receptors and potentially complete exposure pathways; and calculations of EPCs, chemical intakes, ELCRs, and HIs. Only the analytical data collected during the 2013 RI, as summarized in Section 2.1 of this Addendum, were used as the basis for developing the CEMs and this Residential BHHRA. The CEMs for CC-IAAP-001 and CC-IAAP-002 are described in Sections 3.1.1 and 3.1.2, respectively. Additionally, the CEMs for CC-IAAP-001 and CC-IAAP-002 are both presented schematically in Figures 3 and 4, respectively, and show all elements of complete and incomplete migration and exposure pathways, from sources to the receptors.

3.1.1 CC-IAAP-001 Conceptual Exposure Model The media investigated for CC-IAAP-001 during the RI Report (PIKA 2014a), as shown on Figure 1, included collection of seven surface soil samples (0 to 0.5 ft bgs), fifteen subsurface soil samples (0.5 to 10 ft bgs), three groundwater samples, three surface water samples, and four sediment samples (0 to 0.5 ft bgs). Based on available analytical data, environmental setting, and conservative exposure assumptions a CEM (Figure 3) is presented for CC-IAAP-001 that shows a scenario in which a resident is potentially exposed to chemical and radiological contaminants via dust and volatiles inhalation from soil, volatiles inhalation from groundwater (i.e., used for potable household purposes), ingestion of and dermal contact with surface soil, subsurface soil and groundwater during residential activities, and external radiation from soil and groundwater (i.e., water immersion). Appendix A, Table A-1, shows an expanded and more detailed evaluation of receptors and exposure pathways presented in the CEM, as well as the selection and exclusion of medium/receptor/pathway combinations. Selected pathways are used as the basis for the development of all components of the Residential BHHRA for CC-IAAP-001. The residential receptors are identified to be a young child (0 to 6 years old) and an adult. An adult resident is an individual who is assumed to live for a total of 26 years at one residence, 6 years as a child plus 20 years as an adult. In the receptor analysis, the child and adult receptors are considered separately, as exposures can occur to each age group individually, and also as one residential receptor who lives at the same residence as both a child and an adult for a total duration of 26 years. Evaluations of these age groups in this manner are consistent with USEPA’s Human Health Evaluation Manual, Supplemental Guidance: Update of Standard Default Exposure Factors (USEPA 2014). Table A-1 shows that the exposure media considered for the residential receptor are surface soil, subsurface soil, groundwater, surface water, and sediment. Surface water is not a considered to be an exposure medium associated with complete pathways in the CEM because surface water does not exist in the stream bed year-round, but rather, occurs intermittently during storm events. Although not evaluated in this Residential BHHRA, exposures to surface water and sediment were conservatively evaluated in the 2014 BHHRA for current and future adolescent and adult hunters. The evaluation of the hunter scenario, which represents a bounding scenario for similar surface water/sediment exposures that might occur to a resident, resulted in no unacceptable cancer risks or non-cancer hazards. In this Residential BHHRA, Table A-1 shows that the absence of a continuous surface water flow has resulted in the exclusion of all surface water pathways from further evaluations. Additionally, because of the absence of a continuous flow of surface water at


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CC-IAAP-001, sediment is considered to be similar to surface soil. Therefore, for the purposes of the Residential BHHRA, the sediment data that were acquired for samples collected from the 0 to 0.5 ft depth interval, are treated as surface soil data and are henceforth referred to as “surface soil” data. Table A-1 shows that exposures to the following soil depth intervals were considered for evaluations of residential exposures at CC-IAAP-001: surface soil (0 to 0.5 ft bgs), subsurface soil (0.5 to 10 ft bgs), and combined surface and subsurface soil (0 to 10 ft bgs). During Residential Land Use, exposures can potentially occur at all three of the aforementioned depth intervals; however, for the purposes of the Residential BHHRA, exposures to only surface soil (0 to 0.5 ft bgs) and combined surface and subsurface soil (0 to 10 ft bgs) are evaluated. Under a hypothetical residential scenario, surface soil is the medium assumed to be the more readily available of the two media for exposures. Incidental ingestion, dermal contact, and external radiation exposures can occur during a variety of activities that require little or no intrusion into the surface, which can include, though not be limited to the following: outdoor home recreational activities, gardening, routine lawn maintenance, and landscaping. Inhalation of dusts containing chemical and/or radiological contaminants, as well as volatilized chemicals and/or radiological decay progeny from the uranium isotopes, emanating from surface soil can occur during any of these activities more readily than from subsurface soil (i.e., from depths greater than 0.5 ft bgs), assuming that subsurface soil is not mechanically disturbed or brought to the surface. However, under a hypothetical land redevelopment scenario, it is assumed for the purpose of evaluation in this Residential BHHRA that subsurface soil within the 0.5 to 10 ft bgs depth interval, can be brought to the surface (e.g., during land redevelopment) and made available for exposures that could occur during any of the residential activities just discussed for surface soil. Because the contaminant profiles between surface and subsurface soils are similar, with no vertical migration being evident from surface to subsurface soil, surface soil (including dry sediment) and subsurface soil are combined and evaluated as one exposure medium (i.e., soil within the 0 to 10 ft bgs depth interval) in this Residential BHHRA for CC-IAAP-001. Evaluation of potential residential exposures to soil (0 to 10 ft bgs) is consistent with the approach established in the 2017 UFP-QAPP (CH2M Hill 2017). The CEM is based on conservative assumptions that under the Residential Land Use scenario, groundwater exposures could occur during usage of overburden groundwater (with depths ranging from 13 to 32 ft bgs) as a potable source. Given the land use of the IAAAP, the potable use of the overburden is highly unlikely. However, following applicable CERCLA policy and guidance, groundwater at the IAAAP, including CC-IAAP-001, is classified as Class IIb, a potential source of drinking water and as such, must be evaluated in this Residential BHHRA. For this reason, and because land use is not considered during the groundwater classification process, this Residential BHHRA evaluates residential exposures to groundwater in the shallow overburden. This evaluation will support future decision-making relative to a determination of the UU/UE status of CC-IAAP-001 or a determination of additional remedial actions at CC-IAAP-001 that may be warranted to address any identified COCs, based on evaluations during a Feasibility Study. Table A-1 shows that residential exposure pathways to chemicals and radionuclides in groundwater (unfiltered and filtered) used as drinking water, as well as for bathing/showering and other household purposes, have been selected for further evaluation in this Residential BHHRA. Typically, exposures to groundwater are evaluated utilizing only data acquired for unfiltered groundwater samples. Groundwater was also selected for further evaluation of the indoor vapor intrusion pathway.


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In summary, Table A-1 shows that the following media and exposure routes (with applicable contaminant types shown in parentheses) are selected for further evaluation in this Residential BHHRA for CC-IAAP-001:

• Surface Soil (0 to 0.5 ft bgs) o Incidental ingestion (chemicals and radionuclides) o Dermal contact (chemicals) o Inhalation of fugitive dusts in air (chemicals and radionuclides) o Inhalation of volatilized contaminants (chemicals and radionuclides) o External radiation (exposures based on soil volume).

• Soil (0 to 10 ft bgs) o Incidental ingestion (chemicals and radionuclides) o Dermal contact (chemicals) o Inhalation of fugitive dusts in air (chemicals and radionuclides) o Inhalation of volatilized contaminants (chemicals and radionuclides) o External radiation (exposures based on soil volume).

• Groundwater (Unfiltered) o Ingestion of groundwater used as drinking water (chemicals and radionuclides) o Dermal contact during bathing (chemicals) o Inhalation of volatiles emitted from groundwater used for potable household purposes

(chemicals and radionuclides) o Inhalation of volatiles in indoor air following vapor intrusion (chemicals and radionuclides) o External radiation (water immersion).

3.1.2 CC-IAAP-002 Conceptual Exposure Model The UFP-QAPP CEM for CC-IAAP-002 is similar to that presented for CC-IAAP-001, with the exception being that no surface water samples were collected from the CC-IAAP-002. The media investigated for CC-IAAP-002 during the RI Report (PIKA 2014a), as shown on Figure 2, included collection of 6 surface soil samples (0 to 0.5 ft bgs), 13 subsurface soil samples (0.5 to 10 ft bgs), 3 groundwater samples, and 3 sediment samples (0 to 0.5 ft bgs). At the time of sampling, surface water samples could not be collected because surface water was not present at CC-IAAP-002. Based on available analytical data, environmental setting, and conservative exposure assumptions a CEM (Figure 4) is presented for CC-IAAP-002 that shows a scenario in which a resident is potentially exposed to chemical and radiological contaminants via dust and volatiles inhalation from soil, volatiles inhalation from groundwater (i.e., used for potable household purposes), ingestion of and dermal contact with surface soil, subsurface soil and groundwater during residential activities, and external radiation from soil and groundwater (i.e., water immersion). The CEM also presents potential soil and air migration pathways of friable asbestos released from ACM observed in the source debris piles at CC-IAAP-002 during the visual inspection conducted as part of the 2014 RI. Based on the findings of the inspection, the ACM to soil pathway is considered to be incomplete because no asbestos fibers were detected in soil. However, the deteriorating condition of the ACM is indicative of the presence of a potentially complete release and migration pathway of friable asbestos fibers to the air. Because a decision has been made to remove ACM from the debris piles at CC-IAAP-002, no air samples have been or will be collected. Because there are no residents currently living within the CC-IAAP-002 area, and it is assumed that Remedial Alternative #4 will have been implemented (i.e., all ACM at CC-IAAP-002 is removed) prior to any redevelopment, the inhalation of airborne asbestos fibers is considered to be


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incomplete as a exposure route for residential receptors for future scenario as the removal action is already been determined necessary and the preferred alternative has been chosen. Therefore, exposures to asbestos fibers did not need to be quantitatively evaluated in this Residential BHHRA. Table B-1 shows an expanded and more detailed evaluation of receptors and exposure pathways that are presented in the CEM, as well as the selection and exclusion of medium/receptor/pathway combinations. Selected pathways are used as the basis for the development of all components of the Residential BHHRA for CC-IAAP-002. The residential receptors are identified to be a child (0 to 6 years old) and an adult. An adult resident is an individual who is assumed to live for a total of 26 years at one residence, 6 years as a child plus 20 years as an adult. In the receptor analysis, the child and adult receptors are considered separately, as exposures can occur to each age group individually, and as one residential receptor who lives at the same residence as both a child and an adult for a total duration of 26 years. Evaluations of these age groups in this manner are consistent with USEPA’s Human Health Evaluation Manual, Supplemental Guidance: Update of Standard Default Exposure Factors (USEPA 2014). Appendix B, Table B-1, shows that the exposure media considered for the residential receptor are soil, groundwater, and sediment. Surface water is not a considered to an exposure medium associated with complete pathways in the CEM because surface water does not exist in the stream bed year-round, but rather, occurs intermittently during storm events. As previously stated, no surface water was present on the area at the time of sampling. Because surface water is present infrequently, the sediment that was sampled at CC-IAAP-002 is considered to be more consistent with being soil. Although not evaluated in this Residential BHHRA, exposures to sediment were conservatively evaluated in the 2014 BHHRA for current and future adolescent and adult hunters. The evaluation of the hunter scenario, which represents a bounding scenario for similar sediment exposures that might occur to a resident, resulted in no excess lifetime unacceptable cancer risks or non-cancer hazards. Additionally, because of the absence of a continuous flow of surface water at CC-IAAP-002, sediment is considered to be similar to surface soil. Therefore, for the purposes of the Residential BHHRA, the sediment data that were acquired for samples collected from the 0 to 0.5 ft depth interval, are treated as surface soil data and are henceforth referred to as “surface soil” data. Table B-1 shows that exposures to the following depth intervals were considered for evaluations of residential exposures at CC-IAAP-002: surface soil (0 to 0.5 ft bgs), subsurface soil (0.5 to 10 ft bgs), and combined surface and subsurface soil (0 to 10 ft bgs). During Residential Land Use, exposures can potentially occur at all three of the aforementioned depth intervals; however, for the purposes of the Residential BHHRA, exposures to only surface soil (0 to 0.5 ft bgs) and combined surface and subsurface soil (0 to 10 ft bgs) are evaluated. Under a hypothetical residential scenario, surface soil is the medium assumed to be the more readily available of the two media for exposures. Incidental ingestion, dermal contact and external radiation exposures can occur during a variety of activities that require little or no intrusion into the surface, which can include, though not be limited to the following: outdoor home recreational activities, gardening, routine lawn maintenance, and landscaping. Inhalation of dusts containing chemical and/or radiological contaminants, as well as volatilized chemicals and/or radiological decay progeny from the uranium isotopes, emanating from surface soil can occur during any of these activities more readily than from subsurface soil (i.e., from depths greater than 0.5 ft bgs), assuming that subsurface soil is not mechanically disturbed or brought to the surface. However, under a hypothetical land redevelopment scenario, it is assumed for the purpose of evaluation in this Residential BHHRA that subsurface soil within the 0.5 to 10 ft bgs depth interval, can be brought to the surface (e.g., during land redevelopment) and made available for exposures


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that could occur during any of the residential activities just discussed for surface soil. Because the contaminant profiles between surface and subsurface soils are similar, with no vertical migration being evident from surface to subsurface soil, surface soil (including dry sediment) and subsurface soil are combined and evaluated as one exposure medium (i.e., soil within the 0 to 10 ft bgs depth interval) in this Residential BHHRA for CC-IAAP-002. Evaluation of potential residential exposures to soil (0 to 10 ft bgs) is consistent with the approach established in the 2017 UFP-QAPP (CH2M Hill 2017). The CEM conservatively assumes that under a Residential Land Use scenario, groundwater exposures could occur during usage of overburden groundwater (determined to be at a depth of approximately 12 ft bgs) as a potable source. Given the land use of the IAAAP, the potable use of the overburden is highly unlikely. However, following applicable CERCLA policy and guidance, groundwater at the IAAAP, including CC-IAAP-002, is classified as Class IIb, a potential source of drinking water and as such, must be evaluated in this Residential BHHRA. For this reason, and because land use is not considered during the groundwater classification process, this Residential BHHRA evaluates residential exposures to groundwater in the shallow overburden. This evaluation will support future decision-making relative to a determination of the UU/UE status of CC-IAAP-002 or a determination of additional remedial actions at CC-IAAP-002 that may be warranted to address any identified COCs, based on evaluations during a Feasibility Study. Table B-1 shows that residential exposure pathways to groundwater (unfiltered and filtered) used as drinking water, as well as for bathing/showering and other household purposes, have been selected for further evaluation in this Residential BHHRA. Typically, exposures to groundwater are evaluated utilizing only data acquired for unfiltered groundwater samples. Groundwater was also selected for further evaluation of the indoor vapor intrusion pathway. In summary, Table B-1 shows that the following media and exposure routes (with applicable contaminant types shown in parentheses) were selected for further evaluation in this Residential BHHRA for CC-IAAP-002:

• Surface Soil (0 to 0.5 ft bgs) o Incidental ingestion (chemicals and radionuclides) o Dermal contact (chemicals) o Inhalation of fugitive dusts in air (chemicals and radionuclides) o Inhalation of volatilized contaminants (chemicals and radionuclides) o External radiation (exposures based on soil volume).

• Soil (0 to 10 ft bgs) o Incidental ingestion (chemicals and radionuclides) o Dermal contact (chemicals) o Inhalation of fugitive dusts in air (chemicals and radionuclides) o Inhalation of volatilized contaminants (chemicals and radionuclides) o External radiation (exposures based on soil volume).

• Groundwater (Unfiltered) o Ingestion of groundwater used as drinking water (chemicals and radionuclides) o Dermal contact during bathing (chemicals) o Inhalation of volatiles emitted from groundwater used for potable household purposes

(chemicals and radionuclides) o Inhalation of volatiles in indoor air following vapor intrusion (chemicals and radionuclides) o External radiation (water immersion).


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3.2 IDENTIFICATION OF SITE-RELATED CONTAMINANTS OF POTENTIAL CONCERN

Surface soil, soil and groundwater (unfiltered and filtered) data collected and used during the 2014 RI Report (PIKA 2014a) are used in this Residential BHHRA in order to identify COPCs and radionuclides of potential concerns (ROPCs) for the media and pathways selected in Sections 3.1.1 and 3.1.2 for CC-IAAP-001 and CC-IAAP-002, respectively. Chemicals included in the evaluation to determine COPCs are the VOCs, SVOCs, PAHs, explosives, pesticides, and metals (including elemental uranium) detected in surface soil, soil and groundwater at CC-IAAP-001 and CC-IAAP-002. Although metal COPCs are determined for both unfiltered (total metals) and filtered (dissolved metals) groundwater in Appendices A and B for CC-IAAP-001 and CC-IAAP-002, respectively, only the risk evaluations of unfiltered metals are presented in this Residential BHHRA. Radionuclides included in the evaluation are uranium-234, uranium-235 and uranium-238, the concentrations of which were calculated from the measured concentrations reported for elemental uranium in surface soil, soil (0 to 10 ft bgs) and groundwater, as described in Section 3.0 and presented in Attachments A-1 and B-1 for CC-IAAP-001 and CC-IAAP-002, respectively. COPCs and ROPCs are chemical and radiological constituents detected in soil and groundwater that are selected for quantitative risk evaluations based on exceedances of risk-based screening levels by maximum reported concentrations. Because the processes of identifying COPCs and ROPCs do not include data comparisons with background threshold values (BTVs), the lists of constituents selected to be COPCs and ROPCs for each medium of interest include both area-related contaminants and naturally-occurring chemical and/or radionuclides. Further evaluations in the risk characterization section are later performed that identify which of the identified COPCs and ROPCs are area-related versus those that are naturally occurring. Those COPCs and ROPCs determined to be naturally occurring are then eliminated from further risk evaluations, as described in Sections 3.5.6.2 and 3.5.7.2 for CC-IAAP-001 and CC-IAAP-002, respectively. This Residential BHHRA document reflects certain procedural departures from the standard USEPA human health risk assessment (HHRA) process that the Army routinely applies at its installations (USEPA 1989). An example is the inclusion in the HHRA of onsite detected chemicals and radionuclides with concentrations that are either the same or less than those of their respective site-specific background concentrations (naturally occurring constituents). Such an approach adds extraneous information into the HHRA process. The intent of COPC and ROPC screening is to minimize the scope of risk assessments by eliminating constituents that will have no bearing on risk and hazard outcomes and per 40 Code of Federal Regulations 300.400(b)(1) CERCLA, background (naturally-occurring) substances are not subject to remedial actions. The Army considers that initially computing risks and hazards for all detected constituents, only to secondarily re-compute risks and hazards without the risks from the naturally occurring constituents (background) is not useful and makes the risk assessment results confusing to the public. The knowledge of risks associated with naturally occurring constituents does not contribute to the determination of remedial actions that may be required to address an impact from former DOD activities. Importantly, computing risks and hazards for constituents without having first conducted background screening is not a conservative gesture. The soil background values for metals were obtained from the “Baseline Ecological Risk Assessment” (BERA) (MWH 2004). Soil background values for radionuclides (uranium isotopes) were obtained from sample data presented in the “Iowa Army Ammunition Plant FUSRAP Remedial Investigation Report for Firing Sites Area, Yards C, E, F, G, and L, Warehouse 3-01 and Area West of Line 5B, Middletown, Iowa,


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Final” (USACE 2008). Groundwater background values were obtained from the Technical Memorandum entitled “Evaluation of Background Concentrations of Metals in Groundwater, Iowa Army Ammunition Plant, Middletown, Iowa. Final” (CH2M Hill 2020). This background comparison method is consistent with the 2017 UFP-QAPP (Worksheet #14). Although inconsistent with the process the Army uses for background in the HHRA for their installations, this method complies with the requests from the USEPA in a memorandum from Mr. Danny O’Connor, USEPA Region 7 Remedial Project Manager, to Ms. Jennifer Busard, IAAAP Project Manager (no subject, dated June 10, 2019) (USEPA 2019). Sections 3.2.1 through 3.2.3 describe the methods applied to initially identify COPCs (site-related contaminants and naturally-occurring chemicals/radionuclides) for these media/pathways under the Residential Land Use scenario.

3.2.1 Chemicals and Radionuclides of Potential Concern in Surface Soil and Soil In this Residential BHHRA, a detected chemical was retained as a COPC (area-related contaminant or naturally-occurring chemical) in surface soil or soil (0 to 10 ft bgs) if the maximum reported concentration exceeds the corresponding USEPA RSL for residential soil (USEPA 2020a). The residential soil RSLs are available in tables online and address direct contact exposures via ingestion, dermal contact, and inhalation (i.e., in airborne fugitive dusts and/or as volatilized chemicals). The residential soil RSLs were derived by the USEPA for protection of cancer and non-cancer effects and are applicable to determining both surface soil and soil COPCs in this Residential BHHRA. If exposure to a chemical exhibits both cancer and non-cancer effects, then the lower of the two values is the RSL used for data comparisons. Cancer risk-based RSLs target protection of a resident at the 1E-06 ELCR (i.e., representing the occurrence of one additional incident of cancer risk over baseline in a population of one million people). Generally, RSLs have been published that are protective of non-cancer effects to a resident based on a target HQ of 1 or 0.1. For this analysis, non-cancer RSLs targeting the HQ of 0.1 was applied for additional health conservatism. For detected metals that are considered to be essential macronutrients (i.e., calcium, magnesium, and sodium) for which USEPA RSLs are not available due to the lack of toxicity criteria, RSLs were applied that were calculated in the RI Report (PIKA 2014a) based on U.S. Department of Agriculture (USDA) Tolerable Upper Intake Levels (USDA 2014). Other detected chemicals with no established USEPA RSLs are retained as COPCs for qualitative discussion in the Uncertainties Analysis section (Section 3.7). The uranium isotopes were individually evaluated for determination of ROPCs in surface soil and soil (0 to 10 ft bgs) for the Residential Land Use scenario through comparisons of the maximum calculated concentrations of uranium 234, uranium-235 and uranium-238 (i.e., calculated from measured concentrations of elemental uranium) with preliminary remediation goals (PRGs) calculated using the USEPA’s online Radiological PRG Calculator (USEPA 2020c). Radiological PRGs were calculated for the uranium isotopes in surface soil and soil (0 to 10 ft bgs) for the ingestion, inhalation and external radiation pathways based on default inputs, and included contributions from decay chain progeny assumed to be in secular equilibrium with the parent isotopes. PRG contributions from the external radiation pathway assumed infinite soil volume and area correction factors (ACFs) based on the default calculator area size. Inputs and outputs from the Radiological PRG Calculator for soil are presented in Appendix C, Attachment C-1. Risk-based and USEPA maximum contaminant level (MCL)-based soil screening levels (SSLs) for protection of groundwater are also available in the USEPA’s RSL tables for data comparisons.


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However, applications of the SSLs to soil data comparisons are not necessary because actual groundwater data are used in this Residential BHHRA. Based on the data comparisons to residential soil RSLs and radiological PRGs presented in Appendix A, Tables A-2.1 through A-2.4 (as indicated below), the following chemicals and radionuclides are identified as COPCs and ROPCs, respectively, for CC-IAAP-001 surface soil and soil (0 to 10 ft bgs), for quantitative risk evaluations:

• Surface Soil (0 to 0.5 ft bgs) - Tables A-2.1 and A-2.2 o Arsenic o Hexavalent Chromium o Uranium-234 o Uranium-235 o Uranium-238

• Soil (0 to 10 ft bgs) - Tables A-2.3 and A-2.4 o Arsenic o Hexavalent Chromium o Uranium-234 o Uranium-235 o Uranium-238.

Similarly, Appendix B, Tables B-2.1 through B-2.4 show that the following chemicals and radionuclides are identified as COPCs and ROPCs, respectively, for CC-IAAP-002 surface soil and soil (0 to 10 ft bgs), for quantitative risk evaluations :

• Surface Soil (0 to 0.5 ft bgs) - Tables B-2.1 and B-2.2 o Arsenic, o Benzo(a)pyrene, and o Hexavalent Chromium o Uranium-234 o Uranium-235 o Uranium-238.

• Soil (0 to 10 ft bgs) - Tables B-2.3 and B-2.4 o Arsenic, o Benzo(a)pyrene, and o Hexavalent Chromium o Uranium-234 o Uranium-235 o Uranium-238.

3.2.2 Chemicals and Radionuclides of Potential Concern in Groundwater Analytes detected in groundwater at CC-IAAP-001 and CC-IAAP-002 generally include organics and total (unfiltered) and dissolved (filtered) metals (including elemental uranium). Although the 2017 UFP-QAPP (i.e., Worksheet #14) (CH2M Hill 2017) approach for evaluating metals in groundwater is to include only total metals, dissolved metals have also been evaluated for informational purposes in Appendices A and B. In the 2014 BHHRA, total metals concentrations were used to evaluate exposures and risks to a future commercial/industrial worker utilizing groundwater (unfiltered) as a potable source. For consistency with the UFP-QAPP and the 2014 BHHRA, evaluations of organic chemicals and only total metals in unfiltered groundwater, used as a potable source, are presented in the main report sections of this Addendum.


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Selection of groundwater COPCs was conducted primarily through comparisons of maximum concentrations to USEPA’s risk-based tap water RSLs (USEPA 2020a). In this Residential BHHRA, if the maximum concentration of a chemical was above the RSL, then that chemical was identified as a groundwater COPC. For detected metals that are considered to be essential macronutrients (i.e., calcium, magnesium, and sodium) for which USEPA RSLs are not available due to the lack of toxicity criteria, RSLs were applied that were calculated in the RI Report (PIKA 2014a) based on USDA Tolerable Upper Intake Levels (USDA 2014). Other detected chemicals with no established USEPA RSLs are retained for qualitative discussion in the Uncertainties Analysis section (Section 3.7). The uranium isotopes were individually evaluated for determination of ROPCs in groundwater, used for potable purposes under the Residential Land Use scenario, through comparisons of the maximum calculated isotopic concentrations (i.e., calculated from measured concentrations of elemental uranium) with radiological PRGs for tap water. The tap water PRGs were calculated using the USEPA’s online Radiological PRG Calculator (USEPA 2020c) for the ingestion, inhalation and external radiation (water immersion) pathways based on default exposure inputs, and included contributions from decay chain progeny assumed to be in secular equilibrium with the parent isotopes. Inputs and outputs from the Radiological PRG Calculator for groundwater are presented in Appendix C, Attachment C-2. Based on the data comparisons to RSLs and radiological PRGs for tap water presented in Appendix A, Tables A-2.6 and A-2.7, respectively, the following chemicals and radionuclides are identified as COPCs and ROPCs, for CC-IAAP-001 groundwater, for quantitative risk evaluations:

• Arsenic (total), • Barium (total), • Hexavalent chromium, • Lead (total), • Uranium (total) • Uranium-234 (total) • Uranium-235 (total), and • Uranium-238 (total).

Data for hexavalent chromium included only unfiltered data. No dissolved hexavalent chromium data are available for groundwater at C-IAAP-001. Similarly, based on the data comparisons to RSLs and radiological PRGs for tap water presented in Appendix B, Tables B-2.6 and B-2.7, respectively, the following chemicals and radionuclides are identified as COPCs and ROPCs, for CC-IAAP-002 groundwater, for quantitative risk evaluations:

• Arsenic (total), • Barium (total), • Bromomethane, • Hexavalent chromium (total), • Uranium (total), • Uranium-234 (total), • Uranium-235 (total), and • Uranium-238 (total).


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Bromomethane data, which are not reported as being either total or dissolved, are evaluated for unfiltered groundwater. Data for hexavalent chromium included only unfiltered data. No dissolved hexavalent chromium data are available for groundwater at C-IAAP-002.

3.2.3 Indoor Air (Vapor Intrusion Pathway) Vapor intrusion occurs when there is a migration of vapor-forming chemicals from any subsurface source into an overlying building. Generally, in order to characterize the potential for vapor intrusion to occur at a site, near-source subsurface soil gas, sub-slab soil gas, and/or groundwater samples are typically collected. If a building exists at the site, indoor air samples are collected. Currently, no buildings exist within the CC-IAAP-001 or CC-IAAP-002 areas; however, for the sake of assessing the potential for risks under a Residential Land Use scenario, this BHRRA Addendum assumes that a house with a basement will be constructed at each site in the future. For CC-IAAP-001 and CC-IAAP-002, vapor-forming chemicals detected in overburden groundwater samples are being evaluated. Generally, vapor-forming chemicals could include volatile and some semivolatile organic compounds, elemental mercury, and polychlorinated biphenyls. One indicator of the potential for a chemical to volatilize is the Henry’s Law Constant (HLC). Typically, a chemical with a HLC value greater than 1E-05 atmospheres-cubic meter per mole (atm-m3/mole) is considered to be potentially volatile. USEPA’s RSL Tables also indicate chemicals that are considered to be volatile. Table A-2.8 shows three potentially volatile chemicals detected in groundwater beneath CC-IAAP-001 were identified for evaluation of indoor air vapor intrusion. These include 2-butanone, fluoranthene, and fluorene. Similarly, Table B-2.8 shows that groundwater detections of 2-hexanone, bromomethane, phenanthrene, and pyrene were identified for evaluation of indoor air vapor intrusion at CC-IAAP-002. For evaluation in this Residential BHHRA, if at least one COPC is identified for the indoor air vapor intrusion pathway for an area, then the pathway is considered to be complete and a quantitative evaluation of health risks is warranted. In order to identify COPCs, the maximum groundwater concentrations of the aforementioned chemicals in both areas were compared to the USEPA’s residential Vapor Intrusion Screening Levels (VISLs) (USEPA 2020b) for groundwater, which are also presented in Tables A-2.8 and B-2.8. The VISLs applied are generic values representing concentrations in groundwater derived based on a default residential exposure scenario. The VISLs applied target an ELCR of 1E-06 for carcinogens and an HQ of 0.1 for noncarcinogens. The data comparisons in Tables A-2.8 and B-2.8 show that all maximum concentrations of chemicals detected in groundwater at CC-IAAP-001 and CC-IAAP-002, respectively, are below the corresponding VISLs. Therefore, none of the volatile chemicals detected in groundwater are retained as COPCs for the indoor air vapor intrusion pathway analysis. This also indicates that potential contributions to health risk from this pathway are likely to be insignificant at both areas.

3.3 EXPOSURE ASSESSMENT

The exposure assessment evaluates potential exposure for receptor populations reasonably anticipated to be exposed to surface soil, soil and groundwater COPCs (identified in Section 3.2). The exposure assessment is performed in three steps: evaluation of exposure setting (Section 3.3.1), identification of exposure pathways for quantitative risk evaluations (Section 3.3.2), and quantification of exposure (Section 3.3.3).


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3.3.1 Exposure Setting As the first step in the exposure assessment, the exposure setting is characterized in terms of the physical characteristics of each area, as well as land use and potentially exposed populations using available area-specific information. Physical descriptions of each of the construction debris areas were summarized in Section 1.1 of this Residential BHHRA, with more detailed descriptions provided in Section 2.1 of the RI Report (PIKA 2014a). Descriptions of land use and potentially exposed populations for each area were provided in Sections 1.0 and 2.1 of this Residential BHHRA. More detailed discussions of the exposure setting are provided in the 2014 RI Report (PIKA 2014a), as well as in area-specific Worksheet #10 for CC-IAAP-001 and CC-IAAP-002 in the 2017 UFP-QAPP (CH2M Hill 2017).

3.3.2 Identification of Exposure Pathways for Quantitative Risk Evaluations In the second step of the exposure assessment, the exposure setting information is used to construct a CEM (see Figures 3 and 4 for CC-IAAP-001 and CC-IAAP-002, respectively) that provides the basis for the identification of medium-specific COPCs and ROPCs (previously discussed in Section 3.2 and presented in Tables A-2.1 through A-2.8 and Tables B-2.1 through B-2.8), as well as potentially complete exposure pathways between chemical sources and potential receptors (previously presented in Tables A-1 and B-1). All of the potentially complete pathways were initially presented as part of the CEMs in Section 3.1. However, with the elimination of surface water exposure pathways in the CEMs and the subsequent elimination of the indoor air vapor intrusion pathway relative to detected groundwater concentrations of potentially volatile organic chemicals during COPC identification (Section 3.2 and Tables A-2.8 and B-2.8), the following pathways are selected for quantitative evaluations of the Residential Land Use scenario in the Residential BHHRA for both CC-IAAP-001 and CC-IAAP-002:

• Surface Soil (0 to 0.5 ft) o Incidental ingestion (COPCs and ROPCs), o Dermal contact (COPCs), o Inhalation of fugitive dusts in air (COPCs and ROPCs), o Inhalation of volatile decay progeny of uranium isotopes, and o External radiation

• Soil (0 to 10 ft) o Incidental ingestion (COPCs and ROPCs), o Dermal contact (COPCs), o Inhalation of fugitive dusts in air (COPCs and ROPCs), o Inhalation of volatile decay progeny of uranium isotopes, and o External radiation.

• Groundwater (Unfiltered) o Ingestion of groundwater used as drinking water (COPCs and ROPCs), o Dermal contact during bathing/showering (COPCs), o Inhalation of volatiles emitted from groundwater used for potable household purposes

(COPCs and ROPCs), and o External radiation (water immersion, e.g., during bathing).

3.3.3 Quantification of Exposure In the third step of the exposure assessment, doses or intakes of COPCs and ROPCs (area-related contaminants and naturally-occurring chemicals or radionuclides) for each receptor resulting from contact with contaminated media are calculated.


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3.3.3.1 Calculations of Exposure Point Concentrations The first step in quantifying chemical and radiological exposures is the calculation of EPCs for each COPC and ROPC identified for each area and medium of concern. In this Residential BHHRA, EPCs were calculated for each of the construction debris areas using methods consistent with those applied in the 2014 RI Report (PIKA 2014a), as well as those described in installation-wide Worksheet #14 of the 2017 UFP-QAPP (CH2M Hill 2017), the USACE’s Risk Assessment Handbook EM 200-1-4 (USACE 1995) and the USEPA’s RAGS Part A (USEPA 1989). The methods applied to calculating soil and groundwater EPCs in this Residential BHHRA are also consistent with USEPA’s approximation of the reasonable maximum exposure (RME) scenario applied to the calculations on chemical intakes, ELCRs and non-cancer HQs/HIs as established USEPA guidance documents Calculating the Concentration Term (USEPA 1992) and Calculating Upper Confidence Limits for Exposure Point Concentrations at Hazardous Waste Sites (USEPA 2002). As part of the RME scenario, a medium-specific EPC is calculated to be the lesser of the 95 percent upper confidence limit (95% UCL) of the arithmetic mean concentration or the maximum reported concentration for that COPC. The 95% UCL was calculated using the most recent version of ProUCL (Version 5.1.002), in accordance with the USEPA’s ProUCL Version 5.1.002 User Guide (USEPA 2015). It is recommended by USEPA (USEPA 2015) that as a rule of thumb, a data set with a minimum of eight to ten samples is needed to compute the UCLs. This is because the UCLs for small data sets are mainly driven by the critical value, which becomes large and unstable for data sets comprised of fewer than eight to ten samples. Therefore, in this Residential BHHRA, the maximum concentration is selected as the EPC for any data set with less than eight to ten samples. For each field duplicate pair, the maximum reported concentration of the pair was conservatively incorporated into the calculation of the 95% UCL, as well as into the determination of the maximum concentration for the data set, in order to determine the EPC. Calculations of EPCs for surface soil, soil and groundwater COPCs and ROPCs at CC-IAAP-001 are presented in Attachments A-1 through A-6. Calculations of EPCs for surface soil, soil and groundwater COPCs and ROPCs at CC-IAAP-002 are presented in Attachments B-1 through B-6. The resulting surface soil, soil and groundwater EPCs calculated for CC-IAAP-001 are presented in Tables A-3.1 through A-3.6. Likewise, the surface soil, soil and groundwater EPCs calculated for CC-IAAP-002 are presented in Tables B-3.1 through B-3.6. Because the groundwater data sets for both CC-IAAP-001 and CC-IAAP-002 contain less than the USEPA-recommended minimum of eight to ten samples for a 95% UCL calculation, all groundwater EPCs are represented by the respective maximum concentrations.

3.3.3.2 Calculations of Chemical Intakes In addition to calculating EPCs, input values for chemical and radionuclide intake equations were selected from current guidance. The equation input values represent assumptions about exposures to COPCs and ROPCs in environmental media via the applicable exposure pathways. These values are entered into equations used to quantify exposure to contaminated media as chemical/radiological intakes. A chemical intake occurs when a chemical is taken in to the body via a route of exposure (i.e., ingestion, dermal absorption, or inhalation), then is subsequently absorbed into the bloodstream. Depending on the exposure route, chemical intakes are calculated as chronic daily intakes (CDIs) based on the appropriate guidelines. Chemical intakes via all routes are calculated in accordance with the USACE’s Risk Assessment Handbook Engineer Manual (EM) 200-1-4 (USACE 1995) and USEPA’s RAGS Part A (USEPA 1989). Additionally, dermally absorbed doses (DADs) are calculated for dermal exposures in accordance with USEPA’s Risk


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Assessment Guidance for Superfund, Volume I: Human Health Evaluation Manual (Part E, Supplemental Guidance for Dermal Risk Assessment) (USEPA 2004), and air exposure concentrations (ECs) are calculated for inhalation exposures in accordance with USEPA’s Risk Assessment Guidance for Superfund, Volume I: Human Health Evaluation Manual (Part F, Supplemental Guidance for Inhalation Risk Assessment) (USEPA 2009). The input values are selected for consistency with the RME scenario for the evaluations of potential residents at CC-IAAP-001 and CC-IAAP-002. If available, area-specific values are applied as equation inputs. In the absence of area-specific values, default values are obtained or calculated based on values provided in current USEPA guidance such as the Exposure Factors Handbook, 2011 Edition (USEPA 2011) and Human Health Evaluation Manual, Supplemental Guidance: Update of Standard Default Exposure Factors (USEPA 2014). Noncarcinogenic exposures to chemicals are calculated separately for child (0 to 6 years) and adult residents as average daily intakes. For carcinogenic exposures, daily intake rates are age-adjusted based on child (0 to 6 years) and adult parameters (e.g., intake rates, exposure duration, and body weights) and averaged over lifetime (i.e., 70 years). For some carcinogenic chemicals, cancer effects occur via a mutagenic mode of action (MOA). Of the construction debris area COPCs, the mutagenic MOA for carcinogenicity is applicable to hexavalent chromium in surface soil, soil and unfiltered groundwater at both CC-IAAP-001 and CC-IAAP-002, as well as to benzo(a)pyrene in surface soil and soil at CC-IAAP-002. Therefore, in the carcinogenic evaluations of hexavalent chromium and benzo(a)pyrene, intake rates are age-adjusted over several life stages (i.e., 0 to 2 years of age, 2 to 6 years of age, 6 to 16 years of age, and 16 to 26 years of age, in accordance with USEPA’s Supplemental Guidance for Assessing Cancer Susceptibility from Early Life Exposures to Carcinogens (USEPA 2005a). Appendix A Tables A-4.1, A-4.3 and A-4.5 of this Residential BHHRA present input values used for all chemical intake equations and associated rationale and reference citations, as well as all of the equations and supporting equations used to calculate intakes, for surface soil, soil and groundwater receptor/exposure pathway scenarios for CC-IAAP-001, respectively, that were selected for quantitative risk evaluations. Similarly, Appendix B Tables B-4.1, B-4.3, and B-4.5 present input values used for all chemical intake equations and associated rationale and reference citations, as well as all of the equations and supporting equations used to calculate intakes, for surface soil, soil and groundwater receptor/exposure pathway scenarios for CC-IAAP-002, respectively, that were selected for quantitative risk evaluations.

3.3.3.3 Calculations of Radiological Intakes The quantification of internal and external radiological exposures are performed based on similar information regarding exposure setting and assumptions (i.e., equation input factors) that describe chemical exposures. USEPA’s RAGS Part A states: The pathways of exposure and the mathematical models used to evaluate the potential health risks associated with radionuclides in the environment are similar to those used for evaluating chemical contaminants. Many of the radionuclides found at Superfund sites behave in the environment like trace metals. Consequently, the types of data needed for a radiation risk assessment are very similar to those required for a chemical contaminant risk assessment. For example, the environmental, land use, and demographic data needed and the procedures used to gather the data required to model fate and effect are virtually identical. The primary differences lie in the procedures used to characterize the radionuclide contaminants (USEPA 1989).


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Radiological exposures were calculated in accordance with information and equations presented in the USEPA’s RAGS Part A (USEPA 1989) and in the USEPA’s Radiological PRG Calculator User’s Guide (USEPA 2020c). Appendix A Tables A-4.2, A-4.4 and A-4.6 of this Residential BHHRA present input values used for all radiological intake equations and associated rationale and reference citations, as well as all of the equations and supporting equations used to calculate intakes, for surface soil, soil, and groundwater receptor/exposure pathway scenarios for CC-IAAP-001, respectively, that were selected for quantitative risk evaluations. Similarly, Tables B-4.2, B-4.4, and B-4.6 present input values used for all radiological intake equations and associated rationale and reference citations, as well as all of the equations and supporting equations used to calculate intakes, for surface soil, soil, and groundwater receptor/exposure pathway scenarios for CC-IAAP-002, respectively, that were selected for quantitative risk evaluations.

3.4 TOXICITY ASSESSMENT

The toxicity assessment describes the relationship between the magnitude of exposure to a constituent and the possible severity of adverse effects and weighs the quality of available toxicological evidence. Where possible, this assessment provides a numerical estimate of the increased likelihood and/or severity of adverse effects associated with chemical and radiological exposures. Both chemical and radiological toxicities have been assessed for CC-IAAP-001 and CC-IAAP-002. Toxicity assessment approaches for both COPCs and ROPCs are discussed in the paragraphs below.

3.4.1 Chemical Toxicity Assessment The toxicity assessment in this Residential BHHRA identifies current toxicity values established based on cancer effects (i.e., oral and dermal cancer slope factors [CSF] and inhalation unit risks [IUR]) and toxicity values established based on non-cancer effects (i.e., oral and dermal reference doses [RfD] and inhalation reference concentrations [RfC]) for COPCs identified at CC-IAAP-001 and CC-IAAP-002. Detailed discussions of the toxicity assessment portion of the BHHRA relative to CC-IAAP-001 and CC-IAAP-002 are provided in Sections 7.1.4 and 7.2.4, respectively, of the RI Report (PIKA 2014a), and are applicable to this Addendum. The oral and inhalation toxicity values used in the HHRAs are obtained from the USEPA standard hierarchy of toxicity value sources (USEPA 2003a):

• Tier 1 Source: Integrated Risk Information System (IRIS). Database available online through the National Center for Environmental Assessment in Cincinnati, Ohio. IRIS is maintained by USEPA (USEPA 2020e).

• Tier 2 Source: USEPA Provisional Peer‐Reviewed Toxicity Values (PPRTV). Provisional peer‐reviewed toxicity values generated for interim use and available from USEPA.

• Tier 3 Sources: Other Peer‐Reviewed Toxicity Values.

These toxicity values are applied to the estimated intakes (described in Section 3.3.3) in order to quantify carcinogenic ELCRs and noncarcinogenic HQs and HIs in Section 3.5. The toxic effects of a chemical generally depend not only upon the inherent toxicity of the chemical and the level of exposure (intake), but also on the route of exposure (oral, inhalation, or dermal) and the duration of exposure. Thus, a full description of toxic effects of a chemical includes a listing of what adverse health effects the chemical may cause, and how the occurrence of these effects depend upon intake, route, and duration of exposure.


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Toxicity values provided by USEPA typically reflect administered‐dose values; that is, they represent concentrations that are protective following ingestion or inhalation. However, the dermal route of exposure represents concentrations absorbed into the blood. Therefore, the absorbed‐dose concentrations identified for dermal exposure are compared to absorbed‐dose toxicity values derived by applying gastrointestinal absorption (GIABS) factors to administered‐dose toxicity values (USEPA 2004). If a GIABS factor is not available for a specific COPC, the corresponding oral CSF or RfD is used by default when evaluating dermal exposures. Detailed discussions of the chemical toxicity assessment portion of the BHHRA are provided in Sections 7.1.4 and 7.2.4 of the RI Report (PIKA 2014a) relative to CC-IAAP-001 and CC-IAAP-002, respectively.

3.4.1.1 Noncarcinogenic Effects Tables A-5.1, A-5.2, B-5.1, and B-5.2 present oral/dermal and inhalation non-cancer toxicity values, respectively, for each COPC, along with corresponding GIABS factors, primary target organs affected following exposures and/or critical effects, combined uncertainty/modifying factors, and sources of the toxicity data presented for each COPC. In this Residential BHHRA, chronic toxicity RfDs and RfCs are applied to all residential receptor evaluations. In this Residential BHHRA, Tables A-5.1 and A-5.2 present non-cancer toxicity values for all COPCs identified at CC-IAAP-001, and Tables B-5.1 and B-5.2 present non-cancer toxicity values for all COPCs identified at CC-IAAP-002.

3.4.1.2 Carcinogenic Effects Tables A-6.1 and A-6.2 and Tables B-6.1 and B-6.2 present oral/dermal and inhalation cancer toxicity values, respectively, for each COPC, along with corresponding GIABS factors, USEPA cancer weight of evidence (WOE) classifications, and sources of the toxicity data presented for each COPC. Descriptions of each WOE classification are provided in Sections 7.1.4.1 and 7.2.4.1 of the RI Report (PIKA 2014a). In this Residential BHHRA, Tables A-6.1 and A-6.2 present cancer toxicity values for all COPCs identified at CC-IAAP-001, and Tables B-6.1 and B-6.2 present cancer toxicity values for all COPCs identified at CC-IAAP-002. Definitions of WOE classifications are provided in the table footnotes.

3.4.1.3 Lead Lead was identified as a COPC in unfiltered groundwater beneath CC-IAAP-001. Exposures to lead can result in both carcinogenic and systemic health effects; however, there are currently no toxicity values available that define carcinogenic or systemic endpoints for lead. Therefore, health risks due to lead exposures under Residential Land Use scenarios are typically evaluated using the Integrated Exposure Uptake Biokinetic (IEUBK) Model, which assesses potential risks to young children, ages 0 to 84 months. Children are evaluated as they are considered to be more sensitive to the effects of lead exposures than are adults. In this Residential BHHRA, IEUBK Model (Version 1.1, Build 11) is used to evaluate potential exposures by potential residential children, ages 12 to 72 months at CC-IAAP-001 per USEPA’s “Recommendations for Default Age Range in the IEUBK Model Transmittal Memorandum and Document” (USEPA 2017a). Age-specific data for time spent outdoors, ventilation rate, dietary intake, water intake and incidental soil/dust ingestion rates were provided for use as inputs into the IEUBK model, in a memorandum sent from Mr. Daniel O’Connor, USEPA Region 7 Remedial Project Manager, to Ms. Jennifer Busard, IAAAP Project Manager on September 24, 2020 (USEPA 2020d). In 2012, the Advisory


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Committee on Childhood Lead Poisoning Prevention (ACCLPP) conducted a critical review of available lead toxicity studies, and reported that the overall WOE substantiates that neurocognitive decrements (as well as other adverse systemic effects, such as cardiovascular, immunological, and endocrine effects) can occur in children, even when BLLs are below 10 μg/dL (ACCLPP 2012). Based on the conclusion that BLLs below 10 μg/dL can harm children, the ACCLPP and Centers for Disease Control and Prevention (CDC 2007) have recommended that a revised reference value of 5 μg/dL blood lead be used to identify children with elevated BLLs. Therefore, in this the Residential BHHRA, the blood lead reference level of 10 μg/dL has been replaced with the updated reference level of 5 μg/dL in the IEUBK Model. Additionally, in this Residential BHHRA, the default maternal blood lead concentration at childbirth has been updated in the IEUBK Model from 1 μg/dL to 0.6 μg/dL, as recommended in USEPA’s May 2017 memorandum entitled Transmittal of the Update of the Adult Lead Methodology’s Default Baseline Blood Lead Concentration and Geometric Standard Deviation Parameters (USEPA 2017b). These updated default parameter values, which differ from the former default values that were used in the 2014 BHHRA, are based on the most recent 6 years of blood lead concentration data (2009 to 2014) from the National Health and Nutrition Examination Survey.

3.4.2 Radiological Toxicity Assessment Health impacts from exposure to radiation and radionuclides are expressed as the risk of developing cancer. Cancer risks from ingestion, inhalation, and external radiation (soil volume and water immersion) exposures to ROPCs and decay chain progeny in soil and groundwater were estimated using USEPA’s most recent internal and external radiation CSFs developed for these exposure routes. The most recent CSFs for morbidity were obtained from Oak Ridge National Laboratory’s (ORNL) Calculation of Slope Factors and Dose Coefficients (ORNL 2014a) that were derived for morbidity. The same CSFs are also incorporated into the USEPA’s online radiological PRG calculator (USEPA 2020c). The CSFs were used to convert exposures to radionuclides to carcinogenic risk. The morbidity radiological CSFs for all parent uranium isotopes and associated decay chain progeny are presented in the RAGS Part D risk tables in Appendices A and B for CC-IAAP-001 and CC-IAAP-002, respectively. The soil radiological CSFs used to evaluate exposures to ROPCs in soil via ingestion, inhalation and external radiation (soil volume) are presented in Tables A-6.3 and B-6.3 for CC-IAAP-001 and CC-IAAP-002, respectively. The 2014 ORNL document provides soil ingestions CSFs for “Soil Population” and “Soil Worker”, which are described as follows (ORNL 2014a): “Population” refers to morbidity CSFs for ingestion of soil averaged over all ages in a population. Examples of soil ingestion include a child consuming soil, touching a soil covered surface and then ingesting food without washing hands, and dust ingestion. “Soil Worker” refers to adult-specific CSFs coefficients for soil ingestion and incorporates a different ingestion rate compared to that used for the general population. In this residential BHHRA, the “Soil Population” CSFs are used for evaluating soil ingestion exposures to hypothetical residential receptors. The water radiological CSFs used to evaluate exposures to ROPCs in groundwater via tap water ingestion, inhalation, and external radiation (immersion) are presented in Tables A-6.4 and B-6.4 for CC-IAAP-001 and CC-IAAP-002, respectively.


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3.5 RISK CHARACTERIZATION

The objective of risk characterization is to integrate the information developed in the exposure assessment and the toxicity assessment into a calculation and evaluation of the potential ELCRs and non-cancer HQs associated with the site-related contaminants COPCs and naturally-occurring chemicals. Once the combined total risk from COPCs (site-related contaminants) and naturally-occurring chemicals are calculated, then background comparisons are performed to identify the naturally-occurring chemicals, in conjunction with calculations and presentations of potential ELCRs and non-cancer HQs from naturally–occurring chemicals. Next, naturally-occurring COPCs are removed from the risk characterization and only the ELCRs and non-cancer HIs are presented for site-related COPCs. In the final step of the risk characterization, weights of evidence are evaluated in conjunction with the ELCRs and HQs calculated for the site-related COPCs to determine whether or not they are final COCs. The risk characterization methods used in this Residential BHHRA are consistent with those established in the 2017 UFP-QAPP (CH2M Hill 2017).

3.5.1 Determination of Chemical Cancer Risk The potential for carcinogenic effects are characterized in terms of the incremental probability of an individual developing cancer over a lifetime as a result of site-related exposure to a potential carcinogen, for chronic exposures. The ELCR is estimated from the projected lifetime daily average intake and the CSF, the latter of which represents an upper bound estimate off the dose-response relationship. To summarize the calculation process, the ELCR associated with an ingestion (ELCRing) or dermal (ELCRderm) exposure to a carcinogenic COPC is calculated for a given medium by multiplying the pathway-specific lifetime average daily chemical intake (i.e., expressed as the ingestion CDI [milligram(s) per kilogram-day (mg/kg-day)] or dermal DAD [mg/kg-day]) by the corresponding oral CSF (CSFo) ([mg/kg-day]-1) or dermal CSF (CSFd) ([mg/kg-day]-1). The generalized equations for calculating the ingestion and dermal ELCRs are as follows.

𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝑖𝑖𝑖𝑖𝑖𝑖 = 𝐸𝐸𝐶𝐶𝐶𝐶 × 𝐸𝐸𝐶𝐶𝐶𝐶𝑜𝑜 𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 = 𝐶𝐶𝐷𝐷𝐶𝐶 × 𝐸𝐸𝐶𝐶𝐶𝐶𝑑𝑑

The ELCR associated with the inhalation (ELCRinh) of a carcinogenic COPC (i.e., as being adsorbed onto dust particulates emanating from soil or as a volatilized chemical) is calculated by multiplying the lifetime average EC (microgram[s] per cubic meter [μg/m3]) by the IUR ([μg/m3]-1).

𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝑖𝑖𝑖𝑖ℎ = 𝐸𝐸𝐸𝐸 × 𝐶𝐶𝐼𝐼𝐸𝐸

The ELCRs resulting from exposure to multiple carcinogens are assumed to be additive. The total ELCR is estimated by summing the ELCRs estimated over all COPCs and over all pathways. In the National Contingency Plan (USEPA 1990), USEPA states that for known or suspected carcinogens, acceptable exposure levels are generally concentration levels that represent an ELCR between 1E-06 and 1E-04. All ELCRs calculated for individual COPCs, or summed over multiple COPCs, are compared to USEPA’s acceptable target risk range. This is because generally, total ELCRs at or below 1E-04 do not warrant a response action. Total ELCRs estimated to be greater than 1E-04 may warrant further action.

3.5.2 Determination of Chemical Non-Cancer Hazards The potential for noncarcinogenic health effects is evaluated by the calculation of HQs for individual COPCs, which are then summed to yield the HI. An HQ is the ratio of the daily intake averaged over the exposure duration for a given exposure route (i.e., ingestion CDI [mg/kg-day],


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dermal DAD [mg/kg-day], or inhalation EC [milligram(s) per cubic meter (mg/m3)]) to the corresponding chemical-specific oral RfD (RfDo) (mg/kg-day) or dermal RfD (RfDd) (mg/kg-day) inhalation RfC (mg/m3). The generalized equations for calculating the ingestion HQ (HQing) and dermal HQ (HQderm) are as follows.

𝐻𝐻𝐻𝐻𝑖𝑖𝑖𝑖𝑖𝑖 = 𝐸𝐸𝐶𝐶𝐶𝐶 ÷ 𝐸𝐸𝑅𝑅𝐶𝐶𝑜𝑜 𝐻𝐻𝐻𝐻𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 = 𝐶𝐶𝐷𝐷𝐶𝐶 ÷ 𝐸𝐸𝑅𝑅𝐶𝐶𝑑𝑑

Similarly, the inhalation HQ (HQinh) is calculated per the equation as follows. 𝐻𝐻𝐻𝐻𝑖𝑖𝑖𝑖ℎ = 𝐸𝐸𝐸𝐸 ÷ 𝐸𝐸𝑅𝑅𝐸𝐸

The assumption of additive effects reflected in the HI is most properly applied to substances that induce the same effect by the same biological mechanism (USEPA 1989). Consequently, summing HQs for substances that are not expected to induce the same type of toxic effect will overestimate the potential for adverse health effects. The HI provides a measure of the potential for adverse effects, but it is conservative and dependent on the quality of experimental evidence. If a receptor is assumed to be exposed via multiple exposure routes and/or pathways, the HIs from all relevant exposure routes and/or pathways are summed to obtain the total HI for that receptor. If the total HI is less than or equal to one, multiple-pathway exposures to COPCs at the site will be judged unlikely to result in an adverse effect. If the sum is greater than one, further evaluation of exposure assumptions and toxicity, including consideration of specific target organs affected and mechanisms of toxic actions of COPCs is warranted to ascertain if the cumulative exposure would in fact be likely to harm exposed individuals. If the results of the further evaluations still indicate potential health effects in exposed individuals, then the development and evaluation of remedial alternatives may be warranted.

3.5.3 Determination of Radiological Cancer Risk Potential ELCRs associated with ingestion, inhalation, and external radiation (i.e., based on soil volume and water immersion) exposures to individual radionuclides were calculated using CSFs and intake estimates, calculated in a manner similar to that which is done for assessing chemical ELCRs. The general equation used to estimate the potential radiological ELCRs is as follows:

𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸 = 𝐸𝐸𝐶𝐶𝐶𝐶 × 𝐸𝐸𝐶𝐶𝐶𝐶

For the ingestion and inhalation exposures routes for soil and groundwater, the CDI is expressed in units of picocuries (pCi). For external radiation exposures to soil (i.e., based on soil volume) and groundwater (immersion), the CDIs are expressed in units of picocuries-year per gram (pCi-yr/g) and picocuries-year per liter (pCi-yr/L), respectively. The CSFs for all pathways are expressed as the inverse of the respective CDI units such that multiplication of the CDI and CSF yields a unitless ELCR. Therefore, the units for the ingestion/inhalation CSFs, the external radiation CSF for soil volume and the external radiation CSF for water immersion are (pCi)-1, (pCi-yr/g)-1 and (pCi-yr/L)-1, respectively. Similar to the COPCs, the theoretical probability of developing cancer from exposure to two or more ROPCs and by two or more exposure pathways was calculated by summing the ELCRs for each ROPC. The total ELCR for each parent uranium isotope (uranium-234, uranium-235 and uranium-238) was calculated by summing the ELCRs for the uranium isotope with those of all decay chain progeny, assuming secular equilibrium. The total radiological ELCR for the receptor or pathway was calculated by summing over the total parent isotope ELCRs (i.e., including contributions from decay progeny). Similar to the COPCs, all ELCRs calculated for individual


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ROPCs, or summed over multiple ROPCs, are compared to USEPA’s acceptable target risk range. This is because generally, total ELCRs at or below 1E-04 do not warrant a response action. Total ELCRs estimated to be greater than 1E-04 may warrant further action.

3.5.4 Additivity of Chemicals and Radiological Cancer Risks CSFs for radionuclides are defined differently than CSFs for a chemicals. USEPA outlines these differences in USEPA’s Radiation Exposure and Risk Assessment Manual (USEPA 1996) that are considered. Major differences include the following:

• The radiological endpoint is fatal cancer – the chemical endpoint is tumorigenic cancer or non-carcinogenic risk

• Radiological risk estimates are based primarily on human data – chemical risk estimates are based primarily on animal studies

• Radiological risk estimates are based on the central estimate of the mean – chemical risk estimates are based on 95% upper confidence limit of the mean.

Because CSFs for radionuclides and chemicals are specific to distinct models incorporating different assumptions (as indicated above), Section 10.7.3 of USEPA’s RAGS Part A (USEPA 1989) had initially cautioned against combining radiological and chemical risks. In addition, natural background radiation is ubiquitous at levels exceeding typical risk targets and natural variability may preclude the ability to quantify small incremental risks due to contamination (USEPA 1996). However, USEPA has updated this position in the “Radiation Risk Assessment at CERCLA Sites: Q&A” (see Q28, page 11) (USEPA 1999):

“...Excess cancer risk from both radionuclides and chemical carcinogens should be summed to provide an estimate of the combined risk presented by all carcinogenic contaminants. An exception would be cases in which a person reasonably cannot be exposed to both chemical and radiological carcinogens. Similarly, the chemical toxicity from uranium should be combined with that of other site-related contaminants.” While there are differences between slope factors for radionuclides and chemicals, similar differences also occur between different chemical slope factors. In the absence of additional information, it is reasonable to assume that excess cancer risks are additive when evaluating the total incremental cancer risk associated with contaminated sites. EPA continues to recommend that risk estimates for radionuclides and chemical contaminants also be tabulated and presented separately in the risk characterization report.”

In this Residential BHHRA, chemical and radiological ELCRs are calculated and presented separately prior to identification of site-related COPCs and ROPCs, after which, they are presented and summed together.

3.5.5 Risk Characterization The risk characterization combines the receptor/exposure pathway-specific chemical and radiological intakes with the corresponding toxicity criteria to calculate ELCRs for COPCs and ROPCs as well as non-cancer HIs for COPCs, as discussed previously in Sections 3.5.1 through 3.5.4. ELCRs and HQs have been calculated for site-related COPCs/ROPCs and naturally occurring constituents (i.e., chemicals or radionuclides) in surface soil, soil, and unfiltered groundwater. ELCRs and HQs have also been calculated for filtered groundwater, for informational purposes, and are tabulated in this section, but only the ELCRs and HQs for unfiltered groundwater are characterized. Filtered


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groundwater ELCRs and HQs are only discussed during WOE evaluations for determination of final COCs. As stated in Sections 3.5.1 through 3.5.3, site ELCRs and HIs are compared to the USEPA’s target limits of 1E-04 and 1, respectively during the risk characterization. The risk characterizations for CC-IAAP-001 and CC-IAAP-002 were conducted in four separate steps, as presented in Sections 3.5.6 and 3.5.7, respectively. The purpose of the four steps is characterize risks from all site-related contaminants (COPCs/ROPCs) and naturally-occurring constituents and to determine which of the site-related COPCs/ROPCs are ultimately retained as final COCs/ROCs that require additional remedial actions. Only site-related COPCs/ROPCs are carried through to the final step of the risk characterization (i.e., for determination of final COCs/ROCs). These include COPCs/ROCs that exceed the target ELCR and/or HI limits of 1E-04 and 1, respectively, as well as IAAAP-specific BTVs if available. COPCs/ROPCs identified as naturally-occurring constituents with concentrations consistent with that of corresponding BTVs are only presented as part of the total risks and then presented separately. However, once COPCs/ROPCs are determined to be naturally-occurring, they are removed from the risk characterization. As indicated previously, background data are not available for all COPCs/ROPCs and exposure media being evaluated at the IAAAP. COPCs/ROPCs for which no background data are available and associated with ELCRs and HIs exceeding target limits, are retained in the risk characterization as being potentially site-related and may or may not be retained as final COCs/ROCs based on other weights of evidence. The four steps of the risk characterization process are described in greater detail in Sections 3.5.3.1 through 3.5.3.4.

3.5.5.1 Total Combined Risks from Site-Related and Naturally Occurring COPCs and ROPCs

First, an initial risk characterization is performed by calculating ELCRs and HIs for chemicals and radionuclides originally identified as COPCs and ROPCs in Section 3.2 that represent the combined contributions from both site-related concentrations and naturally occurring concentrations (i.e., “total risks”). All COPCs and ROPCs evaluated in this step are those determined from exceedances of USEPA’s RSLs and USEPA’s Radiological PRGs, respectively, as previously described in Section 3.2. This approach of presenting total risks including risks associated with naturally-occurring chemicals, is only done for informational purposes per the request of the USEPA via a memorandum from Mr. Daniel O’Connor, USEPA Region 7 Remedial Project Manager, to Ms. Jennifer Busard, IAAAP Project Manager (no subject, dated June 10, 2019) (USEPA 2019). No remedial decisions for future actions are based on these total risk estimates. As stated by USEPA (i.e., USEPA 1988 and 1989), the risk characterization should be conducted to determine the risks from contamination, since naturally-occurring as well as anthropogenic constituents such as those from vehicle exhaust (non-site related chemicals) are not considered or evaluated as contamination. Therefore, this first step of the risk characterization process presents and discusses receptor-/COPC-/ROPC-specific ELCRs and HIs that include contributions from both potentially site-related sources and natural occurrence. All COPCs and ROPCs with ELCRs and/or COPCs with HIs exceeding target limits (i.e., ELCR>1E-04 and HI>1, respectively) are retained for further evaluations (i.e., for the second through fourth steps) in the risk characterization to determine if they are naturally occurring constituents or site-related COPCs/ROPCs. COPCs/ROPCs for which ELCRs and HIs calculated in the first step of the risk characterization that are within target limits are not evaluated or discussed further and are not used to determine final COCs/ROCs.


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3.5.5.2 Risk Characterization of Naturally-Occurring Constituents During the second step of the risk characterization, only detected metals for which ELCRs and/or HIs, as well as detected radionuclides for which ELCRs were determined to exceed target limits during the first step of the risk characterization, and for which IAAAP-specific background data are available, are evaluated to determine if they are to be retained as site-related COPCs/ROPCs or naturally-occurring constituents. This is done by comparing the maximum concentrations for the detected metals/radionuclides at CC-IAAP-001 and CC-IAAP-002, associated with ELCRs and HIs exceeding target limits, with corresponding IAAAP-specific BTVs established for the applicable exposure media. At the operable unit (OU)-9 construction debris areas, the background evaluation applies only to metals in surface soil, soil, and unfiltered groundwater, as well as to radionuclides in surface soil and soil. Soil BTVs for metals were obtained from the BERA (MWH 2004). Groundwater BTVs for the metals were obtained from the technical memorandum entitled Evaluation of Background Concentrations of Metals in Groundwater, Iowa Army Ammunition Plant, Middletown, Iowa. Final (CH2M Hill 2020). No background data are available for organic constituents in any media or for dissolved metals in filtered groundwater. Soil background values for radionuclides were determined from a data set consisting of seven samples that were analyzed for uranium-234, uranium-235, and uranium-238, which were presented and used in the "Iowa Army Ammunition Plant FUSRAP Remedial Investigation Report for Firing Sites Area, Yards C, E, F, G, and L, Warehouse 3-01 and Area West of Line 5B, Middletown, Iowa, Final" (USACE 2008). Because the background data set consisted of only seven samples, the maximum concentrations were selected for use as soil BTVs for the OU-9 areas. The soil background data and BTV selections for the uranium isotopes are presented in Tables A-2.5 and B-2.5 for CC-IAAP-001 and CC-IAAP-002, respectively. There are no IAAAP-specific background data for the uranium isotopes in groundwater. This background risk evaluation is consistent with the 2017 UFP-QAPP (Worksheet #14), as well as the USEPA’s request presented in their memorandum from Mr. Danny O’Connor, USEPA Region 7 Remedial Project Manager, to Ms. Jennifer Busard, IAAAP Project Manager (no subject, dated June 10, 2019) (USEPA 2019). Based on the data comparisons, metals and radionuclides with maximum concentrations less than the respective BTVs are considered to represent background. In this step of the risk characterization, ELCRs and HIs are then presented for both the naturally-occurring constituents and those constituents that cannot be determined as being naturally occurring (i.e., due to no available background data and BTVs). Beyond this step of the risk characterization, naturally-occurring constituents are removed from the evaluation. Therefore, ELCRs and HIs associated with naturally-occurring constituents are not used in the identification of final COCs/ROCs or in evaluations to determine if remedial actions are warranted. Metals and radionuclides with ELCRs and/or HIs that exceed target limits (i.e., per the first step of the risk characterization) for which no IAAAP-specific background data are available, are retained for further analyses in the third and fourth steps of the risk characterization to determine if they should be retained as final COCs/ROCs for the feasibility study. To summarize, comparisons with background in this step of the risk characterization produces the following findings:

• Area-specific maximum concentrations for metals and radionuclides exceeding target ELCR and HI limits (per the first step of the risk characterization process) that are less than their corresponding background BTVs, indicate that the concentrations of those constituents are


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consistent with background conditions and are considered to be naturally occurring constituents (i.e., not site-related COPCs or ROPCs). The ELCRs and HIs calculated for naturally-occurring constituents are removed from further consideration in the BHHRA.

• COPCs/ROPCs with maximum concentrations that exceed corresponding BTVs are retained as site-related COPCs/ROPCs for further evaluation in the risk characterization (i.e., third and fourth steps) to assess whether or not they are to be retained as final COCs/ROCs for the feasibility study.

3.5.5.3 Residential Risk Characterization of Site-Related COPCs and ROPCs In the third step of the risk characterization, total receptor ELCRs and HIs calculated for only site-related COPCs/ROPCs are presented and discussed. Site-related COPCs/ROPCs from this step are retained for the fourth and final step of the risk characterization, as described in Section 3.5.3.4.

3.5.5.4 Final COC and ROC Determination In this final step of the risk characterization, all site-related COPCs and ROPCs are evaluated quantitatively and qualitatively, as appropriate, to determine if they are final COCs and ROCs that warrant additional evaluation in a feasibility study and possible remedial actions, or if there are no final COCs/ROCs identified, which would thereby qualify the area for a decision of NFA. However, as previously discussed, NFA for CC-IAAP-002 can only be attained following removal of ACM observed in the debris piles.

3.5.6 CC-IAAP-001 Residential Risk Characterization Results As described in the Section 3.5.5, the risk characterization of hypothetical future Residential Land Use at CC-IAAP-001 is conducted in four steps, the results of which are presented in four subsections. The purpose of the risk characterization is to present and discuss receptor-specific and COPC-/ROPC-specific ELCRs and HIs, and to ultimately determine those COPCs and ROPCs (previously identified in Section 3.2), if any, that are to be retained as final COCs/ROCs for further evaluations in a feasibility study. All COPCs and ROPCs not retained as final COCs and ROCs are eliminated from evaluations in a feasibility study because ELCRs and HIs are within target limits and/or they are determined to be naturally occurring constituents based on background comparisons. The first step of the risk characterization of CC-IAAP-001, Section 3.5.6.1, presents and discusses receptor-/COPC-/ROPC-specific ELCRs and HIs that include contributions from both potentially site-related sources and natural occurrence. All COPCs/ROPCs with ELCRs and/or HIs exceeding target limits (i.e., 1E-04 and 1, respectively, are retained for further evaluations in the risk characterization (i.e., in the second through fourth steps) to determine if they are either naturally occurring constituents or site-related COPCs/ROPCs. During the second step of the risk characterization, Section 3.5.6.2, maximum concentrations for metal COPCs and ROPCs (i.e., retained from the first step) are compared to corresponding BTVs. Metal COPCs and ROPCs with maximum concentrations less than BTVs are determined to be naturally occurring. Also in the second step of the risk characterization, ELCRs and HIs are presented for the naturally occurring constituents, which are not retained for further evaluations in the risk characterization. Metal COPCs and ROPCs with maximum concentrations greater than BTVs, along with constituents for which no BTVs are available, are retained as site-related COPCs and ROPCs for further evaluations in the third and fourth steps of the risk characterization. Section 3.5.6.3 (third risk characterization step) presents and discusses the ELCRs and HIs for the site-related COPCs and ROPCs. In Section 3.5.6.4 (the fourth and final step of the risk characterization), the site-related COPCs and ROPCs are further


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evaluated quantitatively and qualitatively to determine if they are final COCs and ROCs that warrant additional remedial actions under CERCLA, or if there are no final COCs and ROCs identified, which would thereby qualify CC-IAAP-001 for a decision of NFA.

3.5.6.1 Risk Characterization of Site-Related COPCs/ROPCs and Naturally Occurring Constituents at CC-IAAP-001

The receptor-specific discussions below, along with Table 3-1, summarize the COPC- and ROPC-specific EPCs, ELCRs and non-cancer HIs calculated over all exposure routes for residential receptors at CC-IAAP-001. Although identified as COPCs and ROPCs in Section 3.2, the ELCRs and HIs presented include contributions from site-related COPCs and ROPCs, as well as from and naturally occurring constituents. For this step of the risk characterization, ELCRs associated with COPCs and ROPCs are presented and discussed separately. For chemical exposures at CC-IAAP-001, supporting calculations of COPC/chemical intakes, ELCRs, and HIs are presented in Appendix A. ELCR calculations for the age-adjusted young child/adult resident are presented in Tables A-7.1a (surface soil and unfiltered groundwater) and A-7.1b (soil and unfiltered groundwater). HI calculations for the young child resident are presented in Tables A-7.2a (surface soil and unfiltered groundwater) and A-7.2b (soil and unfiltered groundwater). HI calculations for the adult resident are presented in Tables A-7.3a (surface soil and unfiltered groundwater) and A-7.3b (soil and unfiltered groundwater). For radiological exposures at CC-IAAP-001, supporting calculations of radiological intakes and ELCRs are also presented in Appendix A. Tables A-8.1 through A-8.6 present medium-specific ELCR calculations for the age-adjusted young child/adult resident, showing ELCRs for parent uranium and decay chain isotopes. Table A-8.7 shows cumulative ELCRs summed over surface soil plus unfiltered groundwater for the parent uranium isotopes (i.e., with decay chain contributions included but not shown). Similarly, Table A-8.8 shows cumulative ELCRs summed over soil (0 to 10 ft bgs) plus unfiltered groundwater for the parent uranium isotopes. Summaries of COPC-/ROPC-specific and pathway-specific ELCRs and non-cancer HIs for CC-IAAP-001 are presented in Appendix A, Table A-9.1 for surface soil plus unfiltered groundwater exposures. Similarly, summaries of COPC-specific ELCRs and non-cancer HIs are presented in Table A-9.2 for soil plus unfiltered groundwater exposures.

Resident Young Child/Adult ELCRs Table 3-1 shows that the cumulative ELCR calculated for age-adjusted resident (i.e., young child/adult) combined exposures to surface soil and unfiltered groundwater (3E-02) exceeds the upper limit of the USEPA’s target risk range. The surface soil and unfiltered groundwater ELCRs contributing to the total receptor ELCR are 4E-03 and 3E-02, respectively. Table A-9.1 shows that the total receptor exceedance is due predominantly to the ingestion of uranium-234 and uranium-238 in surface soil, as well as the ingestion and inhalation of uranium-234 and uranium-238 isotopes (i.e., parents and progeny) in unfiltered groundwater. Table A-8.5 shows that an inhalation ELCR of 3E-02 for unfiltered groundwater contributes the most predominantly to the receptor risk, which is due to radium-226 in the uranium-234 (1E-02) and uranium-238 (1E-02) decay chains. In addition to the radiological risks, Table 3-1 also shows that total arsenic (3E-04) and hexavalent chromium (3E-04) in unfiltered groundwater also contribute significantly to the cumulative receptor ELCR. Table A-9.1 shows that this in turn, is due to the ingestion of arsenic (3E-04) and hexavalent chromium (3E-04) in unfiltered groundwater.


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Table 3-1 also shows that cumulative the ELCR calculated for age-adjusted resident (i.e., young child/adult) combined exposures to soil and unfiltered groundwater (3E-02) exceed the upper limit of the USEPA’s target risk range. The soil and unfiltered groundwater ELCRs contributing to the total receptor ELCR are 4E-03 and 3E-02, respectively. Table A-9.2 shows that the total receptor exceedance is due predominantly to the ingestion of uranium-234 and uranium-238 in soil, as well as the ingestion and inhalation of uranium-234 and uranium-238 isotopes (i.e., parents and progeny) in unfiltered groundwater. Table A-8.5 shows that an inhalation ELCR of 3E-02 for unfiltered groundwater contributes the most predominantly to the receptor risk, which is due to radium-226 in the uranium-234 (1E-02) and uranium-238 (1E-02) decay chains. In addition to the radiological risks, Table 3-1 also shows that total arsenic (3E-04) and hexavalent chromium (3E-04) in unfiltered groundwater also contribute significantly to the cumulative receptor ELCR. Table A-9.2 shows that this in turn, is due to the ingestion of arsenic (3E-04) and hexavalent chromium (3E-04) in unfiltered groundwater.

Table 3-1. Carcinogenic Risks and Noncarcinogenic Hazards for Exposures to Combined Area-Related COPCs/ROPCs and Naturally Occurring Constituents at CC-IAAP-001

Exposure Medium

Residential Receptor

COPC/ROPCa

(EPC Units) CC-IAAP-001b Retain for

Further Evaluations? EPC ELCR HI

Surface Soil (0-0.5 ft bgs), Soil (0-10 ft bgs), and Unfiltered Groundwater Exposures Surface Soil (0-0.5 ft bgs)

Young Child (Ages 0-6 Years)

Arsenic (mg/kg) 9.56 NA 0.3 No Hexavalent Chromium (mg/kg) 0.997 NA 0.004 No

Uranium-234 (pCi/g) 0.32 NA NA No Uranium-235 (pCi/g) 0.014 NA NA No Uranium-238 (pCi/g) 0.30 NA NA No

Total HI: NA 0.3 NA Adult Arsenic (mg/kg) 9.56 NA 0.03 No

Hexavalent Chromium (mg/kg) 0.997 NA 0.0004 No


Total HI: NA 0.03 NA Resident (Age-Adjusted Child/Adult)

Arsenic (mg/kg) 9.56 1E-05 NA No Hexavalent Chromium (mg/kg) 0.997 3E-06 NA NA

Uranium-234 (pCi/g) 0.32 2E-03 NA Yes Uranium-235 (pCi/g) 0.014 2E-05 NA No Uranium-238 (pCi/g) 0.30 2E-03 NA Yes

Total ELCR: 4E-03 NA NA Soil (0-10 ft bgs)


Arsenic (mg/kg) 10.6 NA 0.3 No Hexavalent Chromium (mg/kg) 0.665 NA 0.002 No


Total HI: NA 0.3 NA


36 FINAL


(Continued)

Exposure Medium

Residential Receptor

COPC/ROPCa

(EPC Units)

CC-IAAP-001b Retain for Further

Evaluations? EPC ELCR HI

Surface Soil (0-0.5 ft bgs), Soil (0-10 ft bgs), and Unfiltered Groundwater Exposures (Continued) Soil (0-10 ft bgs)

Adult Arsenic (mg/kg) 10.6 NA 0.03 No Hexavalent Chromium (mg/kg) 0.665 NA 0.0003 No



Arsenic (mg/kg) 10.6 2E-05 NA No Hexavalent Chromium (mg/kg) 0.665 2E-06 NA No

Uranium-234 (pCi/g) 0.32 2E-03 NA Yes Uranium-235 (pCi/g) 0.014 2E-05 NA No Uranium-238 (pCi/g) 0.30 2E-03 NA Yes

Total ELCR: 4E-03 NA NA Unfiltered Groundwater


Arsenic, Total (µg/L) 13 NA 2 Yes Barium, Total (µg/L) 1,200 NA 0.3 No Hexavalent Chromium (µg/L) 11 NA 0.2 No Lead, Total (µg/L)c 16 NA NA Yes Uranium, Total (µg/L) 17 NA 4 Yes Uranium-234 (pCi/L) 6.0 NA NA No Uranium-235 (pCi/L) 0.26 NA NA No Uranium-238 (pCi/L) 5.7 NA NA No

Total HI: NA 7 NA Adult Arsenic, Total (µg/L) 13 NA 1 No

Barium, Total (µg/L) 1,200 NA 0.2 No Hexavalent Chromium (µg/L) 11 NA 0.2 No Lead, Total (µg/L)c 16 NA NA NA Uranium, Total (µg/L) 17 NA 3 Yes Uranium-234 (pCi/L) 6.0 NA NA No Uranium-235 (pCi/L) 0.26 NA NA No Uranium-238 (pCi/L) 5.7 NA NA No

Total HI: NA 4 NA Resident (Age-Adjusted Child/Adult)

Arsenic, Total (µg/L) 13 3E-04 NA Yes Barium, Total (µg/L) 1,200 NA NA NA Hexavalent Chromium (µg/L) 11 3E-04 NA Yes Lead, Total (µg/L)c 16 NA NA NA Uranium, Total (µg/L) 17 NA NA No Uranium-234 (pCi/L) 6.0 1E-02 NA Yes Uranium-235 (pCi/L) 0.26 4E-06 NA No Uranium-238 (pCi/L) 5.7 1E-02 NA Yes

Total ELCR: 3E-02 NA NA


37 FINAL


(Continued)

Exposure Medium Residential Receptor

COPC/ROPCa

(EPC Units)



Surface Soil (0-0.5 ft bgs), Soil (0-10 ft bgs), and Unfiltered Groundwater Exposures (Continued) Total Young Child HI Based on Surface Soil + Unfiltered Groundwater: NA NA 7 NA

Total Young Child HI Based on Soil + Unfiltered Groundwater: NA NA 7 NA Total Adult HI Based on Surface Soil + Unfiltered Groundwater: NA NA 4 NA

Total Adult HI Based on Soil + Unfiltered Groundwater: NA NA 4 NA Total Resident ELCR Based on Surface Soil + Unfiltered Groundwater: NA 3E-02 NA NA

Total Resident ELCR Based on Soil + Unfiltered Groundwater: NA 3E-02 NA NA Filtered Groundwater Exposuresd

Filtered Groundwater (µg/L)


Arsenic, Dissolved (µg/L) 4.1 NA 0.7 NA Barium, Dissolved (µg/L) 590 NA 0.2 NA Uranium, Dissolved (µg/L) 1.4 NA 0.4 NA Uranium-234 (pCi/L) 0.50 NA NA No Uranium-235 (pCi/L) 0.022 NA NA No Uranium-238 (pCi/L) 0.47 NA NA No

Total HI: NA 1.2 NA Adult Arsenic, Dissolved (µg/L) 4.1 NA 0.4 NA

Barium, Dissolved (µg/L) 590 NA 0.1 NA Uranium, Dissolved (µg/L) 1.4 NA 0.2 NA Uranium-234 (pCi/L) 0.50 NA NA No Uranium-235 (pCi/L) 0.022 NA NA No Uranium-238 (pCi/L) 0.47 NA NA No


Arsenic, Dissolved (µg/L) 4.1 8E-05 NA NA Barium, Dissolved (µg/L) 590 NA NA NA Uranium, Dissolved (µg/L) 1.4 NA NA NA Uranium-234 (pCi/L) 0.50 1E-03 NA NA Uranium-235 (pCi/L) 0.022 3E-07 NA NA Uranium-238 (pCi/L) 0.47 1E-03 NA NA

Total ELCR: 2E-03 NA NA Notes: a All chemicals and radionuclides presented in this table were identified as COPCs and ROPCs in Section 3.2; however, the EPCs, ELCRs and HIs presented include contributions from potentially site-related sources combined with contributions from background (i.e., naturally-occurrence). The units for the EPCs (presented in adjacent column) are presented in parentheses after the COPC/ROPC. b The ELCR and HI corresponding to the site (CC-IAAP-001) EPC presented for each COPC and ROPC represents the sum of the pathway-specific ELCRs and HIs calculated in Appendix A for each receptor/exposure medium scenario. The ELCRs for the uranium isotopes include contributions from all of the associated decay chain progeny, over all of the exposure pathways evaluated. Although correct, the total HIs may not appear to have been summed correctly because both the chemical-specific and total HIs are rounded to one significant figure. c ELCRs and HIs are not calculated for lead. Rather, the IEUBK model was run to determine the risk to young children, ages 12 to 72 months, due to exposures to drinking water containing 16 micrograms per liter (µg/L) of lead. The risk benchmark is a 5% probability of exceeding a BLL of 5 µg/dL. Because the results of the modeling indicate that there is a 7.9% probability of the BLL to exceed 5 µg/dL, there is a risk for potential health effects. Please refer to the results of the modeling described in the "Lead Risk Calculation" subsection of Section 3.5.6. IEUBK model inputs and output are presented in Appendix A, Attachment A-7. d Residential ELCRs and HIs are presented for filtered groundwater exposures for informational purposes and possible use in weight of evidence evaluations. pCi/g = picocurie(s) per gram pCi/L = picocurie(s) per liter NA - Calculation of the ELCR or HI value is either not applicable to receptor group or not able to be calculated due to toxicity criteria not being available.


38 FINAL

Resident Young Child Non-Cancer HIs Table 3-1 shows that the cumulative non-cancer HIs calculated for resident young child combined exposures to surface soil plus unfiltered groundwater (7), exceed the USEPA’s target HI of 1. Tables A-9.1 and A-9.2 show that upon analysis of target organs, the total receptor HI is driven mainly by the HI calculated for the cardiovascular system and skin (HI = 2.5 due to ingestion of total arsenic in groundwater), as well as for the kidney (HI = 4.6 due mostly to ingestion of total uranium in groundwater). Therefore, this receptor scenario fails to meet the USEPA’s target HI of 1 at CC-IAAP-001 due to exposures to unfiltered groundwater used as a potable source.

Resident Adult Non-Cancer HIs Table 3-1 shows that cumulative non-cancer HIs calculated for resident adult combined exposures to surface soil plus unfiltered groundwater (4), as well as for combined soil plus unfiltered groundwater (4), exceed the USEPA’s target HI of 1. Tables A-9.1 and A-9.2 show that upon analysis of target organs, the total receptor HI is driven mainly by the HI calculated for the cardiovascular system and skin (HI = 1.3 due to ingestion of total arsenic in groundwater), as well as for the kidney (HI = 2.8 due mostly to ingestion of total uranium in groundwater). Therefore, this receptor scenario fails to meet the USEPA’s target HI of 1 at CC-IAAP-001, due to exposures to unfiltered groundwater used as a potable source.

Lead Risk Calculation Total lead was identified as a COPC in unfiltered groundwater at CC-IAAP-001. Therefore, in accordance with USEPA risk assessment guidance, the potential health risk to a young child resident due to exposures to lead in groundwater used as a drinking water source has been calculated using the IEUBK Model (Version 1.1), as described in Section 3.4.1.3. For this evaluation, the IEUBK Model provides an estimate of the risk (i.e., probability) that cumulative exposures to area-specific lead concentrations in combined media (in this case, outdoor soil and groundwater used as drinking water), as well as exposures to model-calculated concentrations assumed from other sources (i.e., dust resulting from outdoor soil concentrations and dietary sources), could result in a BLL that exceeds the benchmark BLL. As described in Section 3.4.1.3, the benchmark BLL applied in this evaluation is 5 μg/dL. Current USEPA guidance for the IEUBK Model (USEPA 1994) recommends the use of the mean concentration as the EPC. However, because data are available from three groundwater samples, the maximum concentration of 16 micrograms per liter (μg/L) reported for monitoring well CC-IAAP-01-SB01-GW-14A is used as the groundwater EPC in the model calculations. The EPC of 16 μg/L slightly exceeds the USEPA action level for lead in tap water (15 μg/L), which is also the RSL for lead that was used in COPC selection (see Table A-2.1). Similarly, for area-specific soil contributions of lead, the maximum detected soil concentration of 28 milligrams per kilogram (mg/kg), which was reported for location CC-IAAP-01-SF01-SS-00A, was entered into the model as the continuous outdoor soil concentration. The IEUBK Model output presented in Attachment A-7 shows that a geometric mean BLL of 2.6 μg/dL could result following lead exposures at CC-IAAP-001, with an estimated probability that 7.9 percent of the exposed population of potential resident children could have BLLs greater than the 5 μg/dL benchmark. This probability is greater than the USEPA target of 5 percent, which represents an elevated risk of potentially adverse health effects following hypothetical child exposures to unfiltered lead in CC-IAAP-001 groundwater used as tap water, based on the model assumptions.


39 FINAL

Summary The risk characterization of ELCRs and HIs as a result of residential exposures to concentrations from both potentially site-related sources and natural occurrence in surface soil, soil, and groundwater at CC-IAAP-001 indicate the following:

• ELCRs for surface soil and soil exceed the target limit of 1E-04 due ingestion of the ROPCs uranium-234 and uranium-238. There are no ELCRs exceeding the USEPA’s target limit due to residential exposures to COPCs in surface soil and soil. ELCRs calculated for unfiltered groundwater exceed the USEPA’s target limit of 1E-04 due to ingestion of total arsenic, hexavalent chromium, uranium-234, and uranium-238. The ROPCs contribute the most predominantly to the surface soil, soil and unfiltered groundwater ELCRs.

• There are no non-cancer HI exceedances of the USEPA’s target limit of 1 by COPCs in surface soil or soil. However, non-cancer HIs calculated for unfiltered groundwater exceed the USEPA’s target limit of 1 for both the resident child and adult receptors due to ingestion of total arsenic (cardiovascular system and skin) and total uranium (kidney).

• Based on the IEUBK model results showing an exceedance of the USEPA’s benchmark BLL, there is an increased risk of adverse health effects expected for a young child (ages 12 to 72 months) from the maximum lead concentration of 16 µg/L in unfiltered groundwater.

Because the concentrations of arsenic, hexavalent chromium and uranium-235 in both surface soil and soil, as well as the concentrations of total barium and uranium-235in unfiltered groundwater, result in ELCRs and HIs less than target limits, these constituents are eliminated from further evaluations in the remaining three steps of the risk characterization. The COPCs and ROPCs listed below for CC-IAAP-001 exceed target risk and/or HI limits due to contributions from combined site-related and naturally occurring concentrations. Therefore, they are retained for comparative evaluations with background in Section 3.5.6.2 to determine if they are site related or naturally occurring.

• Surface Soil (0 to 0.5 ft bgs) o Uranium-234 o Uranium-238

• Soil (0 to 10 ft bgs) o Uranium-234 o Uranium-238

• Unfiltered Groundwater o Total arsenic o Hexavalent chromium o Total Lead o Total uranium o Uranium-234 o Uranium-238

3.5.6.2 Risk Characterization of Naturally-Occurring (Background) Constituents at CC-IAAP-001 In Section 3.5.6.1, two radionuclides in surface soil and soil (uranium-234 and uranium-238) and three metals in unfiltered groundwater (total arsenic, hexavalent chromium and total uranium) were identified as ROPCs and COPCs for evaluation in this second step of risk characterization


40 FINAL

evaluation to determine if they are naturally occurring constituents or site-related COPCs and ROPCs at CC-IAAP-001. IAAAP facility-wide BTVs have been established for metals in soil, which were first applied in the BERA (MWH 2004) and for metals in unfiltered groundwater (CH2M Hill 2020). Additionally, IAAAP-specific uranium isotope data for soil background is available, from which BTVs were determined in Appendix A, Table A-2.5 based on maximum concentrations. No IAAAP-specific radiological background data are available for groundwater. Residential receptor-specific ELCRs and HIs have been calculated for the BTVs for all CC-IAAP-001 surface soil/soil and groundwater COPCs and ROPCs. Supporting calculations of receptor-specific chemical intakes, ELCRs, and HIs due to background are presented in Appendix A. ELCR calculations for age-adjusted young child/adult resident exposures to COPCs in background soil and unfiltered groundwater are presented in Table A-7.1d. HI calculations for young child resident and adult resident exposures to background soil and unfiltered groundwater are presented in Tables A-7.2d and A-7.3d, respectively. For radiological exposures at CC-IAAP-001, supporting calculations of radiological intakes and ELCRs for soil BTVs are also presented in Appendix A, Table A-8.3 for the age-adjusted young child/adult resident, showing contributions from parent uranium and individual decay chain isotopes. Table A-8.11 also shows calculations of ELCRs for background soil for the parent uranium isotopes (i.e., with decay chain contributions included but not shown). The Appendix A summary of pathway-specific background ELCRs and non-cancer HIs for CC-IAAP-001 COPCs and ROPCs are presented in Table A-9.5 for soil plus unfiltered groundwater. Table 3-2 shows a comparison of site maximum concentrations with BTVs for unfiltered groundwater, as well as comparisons of CC-IAAP-001 ELCRs and HIs with corresponding background ELCRs and HIs.

Table 3-2. Background Comparisons of CC-IAAP-001 Media Concentrations, Carcinogenic Risks and Noncarcinogenic Hazards to Determine Naturally Occurring

Constituents

Exposure Medium

Residential Receptor COPC/ROPCa

Background Comparisons and Determination of Naturally

Occurring Constituents

Risk Characterization of Naturally Occurring

Constituentsb Retain as Site-Related COPC/ ROPC?

Maximum Conc. (µg/L)

Area EPC

(µg/L)

BTVc (µg/L)

Naturally Occurring?

ELCR HI

Area Bkgd. Area Bkgd.

Surface Soil (0-0.5 ft bgs)

Resident (Age-Adjusted Child/ Adult)

Uranium-234 (pCi/g) 0.39 0.32 1.50 Yes 2E-03 1E-02 NA NA No


Soil (0-10 ft bgs)





41 FINAL


Constituents (Continued)

Exposure Medium







Area EPC

(µg/L)

BTVc (µg/L)


ELCR HI


Unfiltered Groundwater


Arsenic, Total (µg/L) 13 13 33.3 Yes NA NA 2 6 No

Hexavalent Chromium (µg/L)d

11 J 11 21 Yes NA NA 0.2 0.5 No

Chromium, Total (µg/L)e 16 16 31 Yes NA NA NA NA NA

Lead, Total (µg/L)f 16 16 18.1 Yes NA NA NA NA No

Uranium, Total 17 17 NA CBDg NA NA NA NA NA Uranium-234 (pCi/L) 6.0 6.0 NA CBDd NA NA NA NA NA

Uranium-238 (pCi/L) 5.7 5.7 NA CBDd NA NA NA NA NA

Adult Arsenic, Total (µg/L) 13 13 33.3 Yes NA NA 1 3 No


11 J 11 21 Yes NA NA 0.2 0.3 No



Uranium, Total 17 17 NA CBDg NA NA NA NA NA Uranium-234 (pCi/L) 6.0 6.0 NA CBDd NA NA NA NA NA

Uranium-238 (pCi/L) 5.7 5.7 NA CBDd NA NA NA NA NA

Resident (Age-Adjusted Child/Adult)

Arsenic, Total (µg/L) 13 13 33.3 Yes 3E-04 6E-04 NA NA No


11 J 11 21 Yes 3E-04 6E-04 NA NA No



Uranium, Total 17 17 NA CBDg NA NA NA NA Yes Uranium-234 (pCi/L) 6.0 6.0 NA CBDd 1E-02 NA NA NA Yes


42 FINAL



Exposure Medium







Area EPC

(µg/L)

BTVc (µg/L)


ELCR HI


Unfiltered Groundwater (Continued)

Resident (Age-Adjusted Child/Adult) (Continued)

Uranium-238 (pCi/L)

5.7 5.7 NA CBDd 1E-02 NA NA NA Yes

Notes: a All chemicals and radionuclides presented in this table were identified as COPCs and ROPCs, respectively, in Section 3.2 and were retained for further evaluations based on exceedances of target ELCR and/or HI limits as reported in Table 3-1. The evaluations in this table determines those COPCs and ROPCs that are more likely due to natural occurrence. ELCRs and HIs from the naturally occurring constituents are not retained for further analyses beyond this step of the risk characterization process. b ELCRs and HIs corresponding to CC-IAAP-001 medium-specific EPCs and IAAAP-specific BTVs are presented in the "Area" and "Bkgd." columns, respectively. The ELCR and HI corresponding to the site (CC-IAAP-001) EPC presented for each COPC and ROPC represents the sum of the pathway-specific ELCRs and HIs calculated in Appendix A for each receptor/exposure medium scenario. The ELCRs for the uranium isotopes include contributions from all of the associated decay chain progeny, over all of the exposure pathways evaluated. Although correct, the total HIs may not appear to have been summed correctly because both the chemical-specific and total HIs are rounded to one significant figure. c The sources of all IAAAP-specific BTVs are discussed in Section 3.5.5.2. d The valued entered as the BTV for hexavalent chromium is an estimated value based on site-specific data (see Section 3.5.6.2 hexavalent chromium discussion and Table 3-2a). e Although total chromium is not a COPC in any media, the unfiltered groundwater maximum concentration, EPC and groundwater BTV are presented as supplemental information relative to the risk characterization of hexavalent chromium. The entry for total chromium in the remaining columns is "NA" (not applicable). f ELCRs and HIs are not calculated for lead. Rather, the IEUBK model was run to determine risk, i.e., the percent probability that the BLL in young children, ages 12 to 72 months, could exceed the BLL benchmark level of 5 µg/dL. Please refer to the results of the modeling described in the "Lead Risk Calculation" subsection of Section 3.5.6.1. IEUBK model inputs and output are presented in Appendix A, Attachment A-7. g Cannot be determined (CBD) - A determination of the constituent as being naturally occurring (or not) cannot be determined due to no available IAAAP-specific background data or calculated BTV. ELCRs and HIs for metals and radionuclides that cannot be determined as being naturally occurring are presented along with ELCRs and HIs for the naturally occurring constituents. NA - Calculation of the ELCR or HI value is not applicable due to any of the following: inconsistency with receptor group scenario, no established BTV, or no available toxicity criteria.

The following paragraphs discuss evaluations of each of the COPCs (arsenic, hexavalent chromium lead, and uranium) and ROPCs (uranium-234 and uranium-238) relative to IAAAP-specific BTVs.

Arsenic Based on the Table 3-2 comparisons, it is evident that the maximum concentration (EPC), ELCRs and HIs calculated for total arsenic in unfiltered groundwater are less than the corresponding values determined for the groundwater BTVs. Consequently, total arsenic is considered to be naturally occurring in unfiltered groundwater at CC-IAAP-001 and is therefore, removed from further evaluations and discussions in this risk characterization.

Hexavalent Chromium Hexavalent chromium was initially identified as a COPC in unfiltered groundwater at CC-IAAP-001 in Section 3.5.6.1. No IAAAP-specific groundwater BTVs have been established for hexavalent chromium; however, an IAAAP-specific BTV of 31 µg/L has been established for total chromium. Because hexavalent chromium is typically present as a fraction of the total chromium, background comparisons between total chromium in CC-IAAP-001 groundwater and


43 FINAL

the BTV can be conducted in a manner that allows for inferences to be made regarding the natural occurrence of hexavalent chromium at CC-IAAP-001. This can done by application of area-specific ratios of hexavalent chromium concentrations to chromium concentrations in groundwater, as discussed in the following paragraphs and presented in Table 3-2a. At CC-IAAP-001, the maximum total chromium concentration reported for unfiltered groundwater, 16 µg/L, is less than the BTV of 31 µg/L. Since hexavalent chromium concentrations are typically present as a fraction of the total chromium concentrations, then it may be inferred that hexavalent chromium concentrations in unfiltered groundwater at CC-IAAP-001 should also be within background levels expected for hexavalent chromium. This can be demonstrated by consideration of the area-specific ratios of hexavalent chromium concentrations to total chromium concentrations present in CC-IAAP-001 groundwater, as presented in Table 3-2a. The ratio of the maximum concentrations of hexavalent chromium (11 µg/L) to total chromium (16 µg/L) is 0.7. The ratio of the arithmetic mean concentrations of hexavalent chromium (10.5 µg/L) to total chromium (11.4 µg/L) is 0.9. As a conservative area-specific approach, multiplication of the lesser of the two ratios (i.e., 0.7) by the BTV yields an estimated background concentration of 21 µg/L for hexavalent chromium. By comparison, the maximum reported concentration of hexavalent chromium in CC-IAAP-001 (11 µg/L) is less than the estimated background level for hexavalent chromium in groundwater (21 µg/L) at CC-IAAP-001. Although this approach applies an area-specific ratio of hexavalent chromium to total chromium concentrations, it provides only an estimate because of inherent uncertainties associated with potential variations in ratios between CC-IAAP-001 and the background groundwater well locations due to differences in physical (e.g., hydrogeologic characteristics) and chemical conditions (e.g., pH and the presence of organics in the overburden). Uncertainties associated with this approach are discussed in Section 3.7.4.3 of the Uncertainties Analysis section of this Residential BHHRA. Therefore, based on consideration of area-specific ratios of hexavalent chromium to chromium per the unfiltered groundwater data for CC-IAAP-001, in conjunction with the groundwater BTV, it is likely that hexavalent chromium detected in CC-IAAP-001 groundwater is associated with naturally-occurring conditions. The historical absence of IAAAP process-related activities and sources at CC-IAAP-001 further supports this finding. Therefore, hexavalent chromium is not retained as a site-related COPC in unfiltered groundwater at CC-IAAP-001.

Table 3-2a. Estimation of Hexavalent Chromium Background Concentrations in Unfiltered Groundwater Based on Maximum and Mean Concentrations of Hexavalent Chromium and

Total Chromium at CC-IAAP-001

Maximum/Mean Hexavalent

Chromium and Chromium

Concentrations

Total Chromium

BTVa

CC-IAAP-001 Hexavalent Chromium

Conc.

CC-IAAP-001 Chromium

Conc. Ratiob

Estimated Hexavalent Chromium

Background Conc.c

Is CC-IAAP-001 Hexavalent Chromium

Concentration Less Than Estimated

Background Level? (Yes/No)

Maximum (µg/L) 31 11 16 0.7 21 Yes Mean (µg/L) 31 10.5 11.4 0.9 29 Yes Notes: a BTV – Background threshold value b Ratio = Hexavalent chromium concentration / chromium concentration. c Estimated hexavalent chromium background concentration = chromium BTV x Ratio.


44 FINAL

Lead Total lead was identified as a COPC in unfiltered groundwater at CC-IAAP-001. As discussed in Section 3.5.6.1, the result of IEUBK modeling for young children (ages 12 to 72 months) exposed to the maximum detected concentration of 16 µg/L in groundwater used as drinking water indicate that there is a risk of potential adverse health effects. However, based on the Table 3-2 comparisons, the maximum concentration (EPC) of 16 µg/L for total lead in unfiltered groundwater is less than the BTV of 18.1 µg/L. Consequently, total lead is considered to be naturally occurring in unfiltered groundwater at CC-IAAP-001 and is therefore, removed from further evaluations and discussions in this risk characterization.

Uranium Total uranium was identified as a COPC in unfiltered groundwater at CC-IAAP-001 in Section 3.5.6.1. An IAAAP-specific groundwater BTV has not been established for uranium. While there is no historical record of IAAAP processes or operations ever having been conducted at CC-IAAP-001, uranium was part of processes and operations conducted at the IAAAP. Therefore, uranium is retained as a potential site-related COPC in unfiltered groundwater for further evaluations in this risk characterization.

Uranium Isotopes Based on the Table 3-2 comparisons, it is evident that the maximum concentrations of uranium-234 and uranium-238, along with the ELCRs calculated for total arsenic in surface soil and soil, are less than the corresponding values determined for the soil BTVs. Consequently, uranium-234 and uranium-238 are considered to be naturally occurring in surface soil and soil and are therefore removed from further evaluations in this risk characterization. Because no IAAAP-specific BTVs are available for radionuclides in groundwater, uranium-234 and uranium-238 in unfiltered groundwater at CC-IAAP-001 are retained for further evaluations and discussions in this risk characterization.

Summary Based on the risk characterization discussion in Section 3.5.6.1 and following evaluations of naturally occurring constituents, the following constituents are retained as a possible site-related COPCs and ROPCs at CC-IAAP-001 for further evaluations in this risk characterization:

• Uranium (unfiltered groundwater) • Uranium-234 (unfiltered groundwater) • Uranium-238 (unfiltered groundwater)

3.5.6.3 Risk Characterization of Site-Related COPCs and ROPCs at CC-IAAP-001 Based on the analysis in Section 3.5.6.2, only uranium in unfiltered groundwater has been retained as a site-related COPC at CC-IAAP-001. Table 3-3 presents the receptor-specific HIs for total uranium, as well as the ELCRs for uranium-234 and uranium-238 in unfiltered groundwater at CC-IAAP-001.


45 FINAL

Table 3-3. Residential Carcinogenic Risks and Noncarcinogenic Hazards for Exposures to Remaining Site-Related COPCs and ROPCs in CC-IAAP-001 Unfiltered Groundwater


CC-IAAP-001b EPC ELCR HI


Uranium, Total (µg/L) 17 NA 4 Uranium-234 (pCi/L) 6.0 NA NA Uranium-238 (pCi/L) 5.7 NA NA

Total HI: NA 4 Adult Uranium, Total (µg/L) 17 NA 3

Uranium-234 (pCi/L) 6.0 NA NA Uranium-238 (pCi/L) 5.7 NA NA

Total HI: NA 3 Resident (Age-Adjusted Child/Adult)

Uranium, Total (µg/L) 17 NA NA Uranium-234 (pCi/L) 6.0 1E-02 NA Uranium-238 (pCi/L) 5.7 1E-02 NA

Total ELCR: 3E-02 NA Notes: a The ELCRs and HIs corresponding to the CC-IAAP-001 EPCs presented for the uranium isotopes and total uranium, respectively, in unfiltered groundwater each represent the sum of the pathway-specific ELCRs and HIs calculated in Appendix A for each receptor scenario. The ELCRs for the uranium isotopes include contributions from all of the associated decay chain progeny, over all of the exposure pathways evaluated. NA - Calculation of the ELCR or HI value not applicable.

The following paragraphs discuss the noncarcinogenic hazards associated with residential exposures to total uranium in unfiltered groundwater.

Resident Young Child/Adult ELCRs Table 3-3 shows that the total receptor ELCR (3E-02) from uranium-234 and uranium-238 exceeds the USEPA’s target limit of 1E-04. Table A-10.1 shows that the total receptor exceedance is due predominantly to the ingestion and inhalation of uranium-234 and uranium-238 isotopes (i.e., parents and progeny) in unfiltered groundwater. Therefore, this receptor scenario fails to meet the USEPA’s target ELCR for due to ingestion exposures to unfiltered groundwater at CC-IAAP-001 used as a potable source.

Resident Young Child Non-Cancer HIs The cumulative non-cancer HI calculated for resident young child exposures to unfiltered groundwater (4) exceeds the USEPA’s target HI of 1. Table A-10.1 shows that upon an analysis of target organs, the total receptor HI is driven mainly by the HI calculated for the kidney (HI = 4.3 due mostly to ingestion of total uranium in groundwater). Therefore, this receptor scenario fails to meet the USEPA’s target HI of 1 at CC-IAAP-001, due to ingestion exposures to unfiltered groundwater used as a potable source.

Resident Adult Non-Cancer HIs The cumulative non-cancer HI calculated for resident adult exposures to unfiltered groundwater (3) exceeds the USEPA’s target HI of 1. Table A-10.1 shows that upon an analysis of target organs, the total receptor HI is driven mainly by the HI calculated for the kidney (HI = 2.6 due mostly to


46 FINAL

ingestion of total uranium in groundwater). Therefore, this receptor scenario fails to meet the USEPA’s target HI of 1 at CC-IAAP-001, due to ingestion exposures to unfiltered groundwater used as a potable source.

Summary The risk characterization of ELCRs and HIs associated with residential exposures to site-related concentrations of total uranium and uranium isotopes in unfiltered groundwater at CC-IAAP-001 results in exceedances of the respective USEPA’s target limits. Therefore, total uranium in unfiltered groundwater are identified as a site-related COPC and is retained for further evaluation in Section 3.5.6.4 to determine if it should be identified as a final COC. Also, uranium-234 and uranium-238 in unfiltered groundwater are identified as site-related ROPCs and are retained for further evaluation in Section 3.5.6.4 to determine if they should be identified as final ROCs.

3.5.6.4 Evaluation of Total Uranium and Uranium Isotopes to Determine Final COC and ROC Status in CC-IAAP-001 Unfiltered Groundwater

Based on the results of the risk characterization Sections 3.5.6.1 through 3.5.6.3, total uranium in unfiltered groundwater was determined to be the only site-related COPC at CC-IAAP-001 due to ingestion exposures to a resident adult and child resulting in noncarcinogenic HIs exceeding the target HI limit. The exceedance is based on a maximum concentration detected in one groundwater sample. Uranium-234 and uranium-238 were identified as site-related ROPCs in unfiltered groundwater due to ingestion and inhalation exposures to a resident resulting in ELCRs exceeding the target limit of 1E-04. In order to determine if total uranium is a final COC in unfiltered groundwater, and if the uranium isotopes are final ROCs in unfiltered groundwater for further evaluation in a feasibility study, the following paragraphs and Table 3-4 present evaluations of lines of evidence other than the health risks that have been calculated and presented throughout this risk characterization.

Table 3-4. Weight of Evidence Evaluation of Total Uranium as a Final COC and Uranium Isotopes as Final ROCs in CC-IAAP-001 Unfiltered Groundwater

Remaining Site-Related

COPC/ ROPC

Unfiltered Groundwatera Weight of Evidence Evaluations Filtered Groundwatera

USEPA MCL

Radiological Activity

Equivalent to MCLb

Is Unfiltered Groundwater

EPC < MCL?

Is Site-Related COPC/

ROPCa Final COC/ ROC?

Rationale EPC (Max. Conc.)

Child/ Adult

Resident ELCR

Child Resident

HIa

EPC (Max. Conc.)

Child/ Adult

Resident ELCR

Child Resident

HIa

Site-Related COPCs Uranium, Total (µg/L) 17 NA 4 1.4 NA 0.4 30 NA Yes No

Max. Conc. <

MCL Site-Related ROPCs

Uranium-234 (pCi/L) 6.0 1E-02 NA 0.50 1E-03 NA NA NA NA No Sum of

Max. Isotope Conc. <

MCL Activity

Equivalentc

Uranium-238 (pCi/L)

5.7 1E-02 NA 0.47 1E-03 NA NA NA NA No


47 FINAL

Table 3-4. Weight of Evidence Evaluation of Total Uranium as a Final COC and Uranium Isotopes as Final ROCs in CC-IAAP-001 Unfiltered Groundwater (Continued)

Remaining Site-

Related COPC/ ROPC


USEPA MCL


Equivalent to MCLb


EPC < MCL?




Child/ Adult

Resident ELCR

Child Resident

HIa

EPC (Max. Conc.)

Child/ Adult

Resident ELCR

Child Resident

HIa

Site-Related ROPCs (Continued) Uranium Isotopes (Total) (pCi/L) 11.7 3E-02 NA 0.96 2E-03 NA NA 27 Yes No

Sum of Max.

Isotope Conc. <

MCL Activity

Equivalentc Notes: a The EPCs for uranium and the uranium isotopes are based on the maximum detected concentrations in unfiltered groundwater. The ELCRs and HIs corresponding to the CC-IAAP-001 EPCs presented for total uranium and the uranium isotopes represent the sum of the pathway-specific ELCRs and HIs calculated in Appendix A for the child/adult resident and child residential scenarios, respectively. The resident child HI is presented because it represents the greater of the child versus adult HIs. The ELCRs for the uranium isotopes include contributions from all of the associated decay chain progeny, over all of the exposure pathways evaluated. b An activity equivalent of the USEPA's MCL is presented in accordance with USEPA's OSWER Directive 9283.1-14 entitled "Use of Uranium Drinking Water Standards under 40 CFR 141 and 40 CFR 192 as Remediation Goals for Groundwater at CERCLA Sites" (USEPA 2001), which states: "The 2000 MCL rule established an MCL for uranium of 30 μg/L. For the MCL rulemaking, EPA assumed a typical conversion factor of 0.9 picocurie(s) per microgram (pCi/μg) for the mix of uranium isotopes found at public water systems, which means that an MCL of 30 μg/L will typically correspond to 27 pCi/L. EPA considered the 30 μg/L level (which corresponds to a 27 pCi/L level) to be appropriate since it is protective for both kidney toxicity and cancer." c The sum of the maximum concentrations of site-related uranium isotopes in unfiltered groundwater include only uraniums-234 and -238. However, even if the maximum concentration of uranium-235 (0.26 pCi/L) were included, the sum of the maximum concentrations of all three isotopes (12.0 pCi/L) in unfiltered groundwater is still less than the MCL activity equivalent of 27 pCi/L. NA - Not applicable.

Uranium One line of evidence to consider is the filtered versus unfiltered data that is available for CC-IAAP-001 groundwater. Based on filtered groundwater data, dissolved uranium exposures result in residential HIs that are less than the target limit. Of the three groundwater well locations that were sampled for total and dissolved uranium at CC-IAAP-001, total and dissolved uranium collected from one location, 01-GW1, exhibited a greater total result (17 µg/L) than the corresponding dissolved result (1.4 µg/L). However, the total and dissolved results from the other two well locations were nearly similar. From this comparison, it could be inferred that total uranium concentrations reported for unfiltered groundwater could be due to sedimentation in the samples that were collected. Another line of evidence to consider is comparisons to the MCL for uranium, 30 µg/L. Both the maximum total and maximum dissolved uranium concentrations reported for groundwater samples collected from CC-IAAP-001 (i.e., 1.4 µg/L and 17 µg/L, respectively) are less than the MCL. Since uranium is present in groundwater at concentrations less than the promulgated standard considered to be protective of human health, total uranium in unfiltered groundwater should not be identified as a COC at CC-IAAP-001. Additionally, depleted uranium has been used in processes and operations in other areas of the IAAAP installation, though there is no historical record to suggest that any such processes or operations were ever conducted at CC-IAAP-001. Uranium concentrations in unfiltered groundwater are less than the USEPA’s MCL, which is established as an enforceable drinking water standard. Therefore, total uranium is not identified as a COC in unfiltered groundwater at CC-IAAP-001.


48 FINAL

Uranium Isotopes Table 3-4 shows that the concentrations of uranium-234 (6.0 µg/L) and uranium-238 (5.7 µg/L) are summed to determine a concentration of 11.7 µg/L of total uranium isotopes. This concentration is compared to an activity equivalent concentration (27 pCi/L) of the elemental uranium MCL (30 µg/L). The activity equivalent of the USEPA's MCL was determined in accordance with USEPA's OSWER Directive 9283.1-14 entitled "Use of Uranium Drinking Water Standards under 40 CFR 141 and 40 CFR 192 as Remediation Goals for Groundwater at CERCLA Sites” (USEPA 2001), which states:

"The 2000 MCL rule established an MCL for uranium of 30 micrograms per liter (μg/L). For the MCL rulemaking, EPA assumed a typical conversion factor of 0.9 pCi/μg for the mix of uranium isotopes found at public water systems, which means that an MCL of 30 μg/L will typically correspond to 27 pCi/L. EPA considered the 30 μg/L level (which corresponds to a 27 pCi/L level) to be appropriate since it is protective for both kidney toxicity and cancer."

The comparison shows that the total concentration of uranium isotopes in unfiltered groundwater at CC-IAAP-001 is less than the activity equivalent concentration of the MCL. Therefore, uranium-234 and uranium-238 are not identified as ROCs in unfiltered groundwater at CC-IAAP-001.

Summary Based on the results of the Residential BHHRA for CC-IAAP-001, no additional remedial actions are warranted and the site can proceed to the next phase in the CERCLA process, as a NFA area in a PP.

3.5.7 CC-IAAP-002 Risk Characterization Results As described in the Section 3.5.5, the risk characterization of hypothetical future Residential Land Use at CC-IAAP-002 is conducted in four steps, the results of which are presented in four subsections. The purpose of the risk characterization is to present and discuss receptor-specific and COPC-/ROPC-specific ELCRs and HIs, and to ultimately determine those COPCs and ROPCs (previously identified in Section 3.2), if any, that are to be retained as final COCs or ROCs for further evaluations in a feasibility study. All COPCs and ROPCs not retained as final COCs and ROCs are eliminated from further evaluations in a feasibility study because ELCRs and HIs are within target limits and/or they are determined to be naturally occurring chemicals based on background comparisons. The first step of the risk characterization of CC-IAAP-002, Section 3.5.7.1, presents and discusses receptor-specific and COPC-/ROPC-specific ELCRs and HIs that include contributions from both potentially site-related sources and natural occurrence. All COPCs and ROPCs with ELCRs and/or HIs exceeding target limits (i.e., 1E-04 and 1, respectively, are retained for further evaluations in the risk characterization (i.e., in the second through fourth steps) to determine if they are either naturally occurring constituents or site-related COPCs or ROPCs. During the second step of the risk characterization, Section 3.5.7.2, maximum concentrations for metal COPCs and ROPCs (i.e., retained from the first step) are compared to corresponding BTVs. Metal COPCs and ROPCs with maximum concentrations less than BTVs are determined to be naturally occurring. Also in the second step of the risk characterization, ELCRs and HIs are presented for the naturally occurring constituents, which are not retained for further evaluations in the risk characterization. Metal COPCs and ROPCs with maximum concentrations greater than BTVs, along with constituents for which no BTVs are available, are retained as site-related COPCs and ROPCs for further evaluations in the third and fourth steps of the risk characterization. Section 3.5.7.3 (third risk characterization step) presents and discusses the ELCRs and HIs for the


49 FINAL

site-related COPCs and ROPCs. In Section 3.5.7.4 (the fourth and final step of the risk characterization), the site-related COPCs and ROPCs are further evaluated quantitatively and qualitatively to determine if they are final COCs and ROCs that warrant additional remedial actions under CERCLA, or if there are no final COCs and ROCs identified, which would thereby qualify CC-IAAP-002 for a decision of NFA following removal of the ACM.

3.5.7.1 Risk Characterization of Site-Related COPCs/ROPCs and Naturally Occurring Constituents at CC-IAAP-002

The receptor-specific discussions below, along with Table 3-5, summarize the COPC- and ROPC-specific EPCs, ELCRs and non-cancer HIs calculated over all exposure routes for residential receptors at CC-IAAP-002. Although identified as COPCs and ROPCs in Section 3.2, the ELCRs and HIs presented include contributions from site-related COPCs and ROPCs, as well as from and naturally occurring constituents. For this step of the risk characterization, ELCRs associated with COPCs and ROPCs are presented and discussed separately. For chemical exposures at CC-IAAP-002, supporting calculations of site chemical intakes, ELCRs, and HIs are presented in Appendix B. ELCR calculations for the age-adjusted young child/adult resident are presented in Tables B-7.1a (surface soil and unfiltered groundwater) and B-7.1b (soil and unfiltered groundwater). HI calculations for the young child resident are presented in Tables B-7.2a (surface soil and unfiltered groundwater) and B-7.2b (soil and unfiltered groundwater). HI calculations for the adult resident are presented in Tables B-7.3a (surface soil and unfiltered groundwater) and B-7.3b (soil and unfiltered groundwater). For radiological exposures at CC-IAAP-002, supporting calculations of radiological intakes and ELCRs are also presented in Appendix B. Tables B-8.1 through B-8.6 present medium-specific ELCR calculations for the age-adjusted young child/adult resident, showing ELCRs for parent uranium and decay chain isotopes. Table B-8.7 shows cumulative ELCRs summed over surface soil plus unfiltered groundwater for the parent uranium isotopes (i.e., with decay chain contributions included but not shown). Similarly, Table B-8.8 shows cumulative ELCRs summed over soil (0 to 10 ft bgs) plus unfiltered groundwater for the parent uranium isotopes. Summaries of COPC-/ROPC-specific and pathway-specific ELCRs and non-cancer HIs for CC-IAAP-002 are presented in Appendix B Table B-9.1 for surface soil plus unfiltered groundwater exposures Similarly, summaries of COPC-specific ELCRs and non-cancer HIs are presented in Tables B-9.2 for soil plus unfiltered groundwater exposures.


Exposure Medium



Evaluations? EPC ELCR HI Surface Soil (0-0.5 ft bgs), Soil (0-10 ft bgs), and Unfiltered Groundwater Exposures

Surface Soil (0-0.5 ft bgs) (mg/kg)


Arsenic (mg/kg) 10.2 NA 0.3 No Benzo(a)pyrene (mg/kg) 0.57 NA 0.03 No Hexavalent Chromium (mg/kg) 1.1 NA 0.005 No Uranium-234 (pCi/g) 0.33 NA NA No Uranium-235 (pCi/g) 0.014 NA NA No Uranium-238 (pCi/g) 0.31 NA NA No

Total HI: NA 0.3 NA


50 FINAL


(Continued)

Exposure Medium




Surface Soil (0-0.5 ft bgs), Soil (0-10 ft bgs), and Unfiltered Groundwater Exposures (Continued) Surface Soil (0-0.5 ft bgs) (mg/kg) (Continued)

Adult Arsenic (mg/kg) 10.2 NA 0.03 No Benzo(a)pyrene (mg/kg) 0.57 NA 0.004 No Hexavalent Chromium (mg/kg) 1.1 NA 0.0004 No Uranium-234 (pCi/g) 0.33 NA NA No Uranium-235 (pCi/g) 0.014 NA NA No Uranium-238 (pCi/g) 0.31 NA NA No


Arsenic (mg/kg) 10.2 2E-05 NA No Benzo(a)pyrene (mg/kg) 0.57 5E-06 NA No Hexavalent Chromium (mg/kg) 1.1 4E-06 NA No Uranium-234 (pCi/g) 0.33 2E-03 NA Yes Uranium-235 (pCi/g) 0.014 2E-05 NA No Uranium-238 (pCi/g) 0.31 2E-03 NA Yes

Total ELCR: 5E-03 NA NA Soil (0-10 ft bgs) (mg/kg)


Arsenic (mg/kg) 12 NA 0.3 No Benzo(a)pyrene (mg/kg) 0.21 NA 0.01 No Hexavalent Chromium (mg/kg) 0.64 NA 0.003 No Uranium-234 (pCi/g) 0.30 NA NA No Uranium-235 (pCi/g) 0.01 NA NA No Uranium-238 (pCi/g) 0.29 NA NA No

Total HI: NA 0.4 NA Adult Arsenic (mg/kg) 12 NA 0.04 No

Benzo(a)pyrene (mg/kg) 0.21 NA 0.001 No Hexavalent Chromium (mg/kg) 0.64 NA 0.0003 No Uranium-234 (pCi/g) 0.30 NA NA No Uranium-235 (pCi/g) 0.01 NA NA No Uranium-238 (pCi/g) 0.29 NA NA No


Arsenic (mg/kg) 12 2E-05 NA No Benzo(a)pyrene (mg/kg) 0.21 2E-06 NA No Hexavalent Chromium (mg/kg) 0.64 2E-06 NA No Uranium-234 (pCi/g) 0.30 2E-03 NA Yes Uranium-235 (pCi/g) 0.01 2E-05 NA No Uranium-238 (pCi/g) 0.29 2E-03 NA Yes

Total ELCR: 4E-03 NA NA Unfiltered Groundwater (µg/L)


Arsenic, Total (µg/L) 18 NA 3 Yes Barium, Total (µg/L) 390 NA 0.1 No Bromomethane (µg/L) 1.5 NA 0.08 No Hexavalent Chromium (µg/L) 11 NA 0.2 No Uranium, Total (µg/L) 3.8 NA 0.9 No Uranium-234 (pCi/L) 1.3 NA NA No Uranium-235 (pCi/L) 0.1 NA NA No Uranium-238 (pCi/L) 1.3 NA NA No

Total HI: NA 4 NA


51 FINAL


(Continued)

Exposure Medium




Surface Soil (0-0.5 ft bgs), Soil (0-10 ft bgs), and Unfiltered Groundwater Exposures (Continued) Unfiltered Groundwater (µg/L) (Continued)

Adult Arsenic, Total (µg/L) 18 NA 2 Yes Barium, Total (µg/L) 390 NA 0.06 No Bromomethane (µg/L) 1.5 NA 0.04 No Hexavalent Chromium (µg/L) 11 NA 0.1 No Uranium, Total (µg/L) 3.8 NA 0.6 No Uranium-234 (pCi/L) 1.3 NA NA No Uranium-235 (pCi/L) 0.1 NA NA No Uranium-238 (pCi/L) 1.3 NA NA No

Total HI: NA 3 NA Resident (Age-Adjusted Child/Adult)

Arsenic, Total (µg/L) 18 3E-04 NA Yes Barium, Total (µg/L) 390 NA NA NA Bromomethane (µg/L) 1.5 NA NA NA Hexavalent Chromium (µg/L) 11 3E-04 NA Yes Uranium, Total (µg/L) 3.8 NA NA NA Uranium-234 (pCi/L) 1.3 3E-03 NA Yes Uranium-235 (pCi/L) 0.1 8E-07 NA No Uranium-238 (pCi/L) 1.3 3E-03 NA Yes

Total ELCR: 7E-03 NA NA Total Young Child HI Based on Surface Soil + Unfiltered Groundwater: NA NA 5 NA

Total Young Child HI Based on Soil + Unfiltered Groundwater: NA NA 5 NA Total Adult HI Based on Surface Soil + Unfiltered Groundwater: NA NA 3 NA

Total Adult HI Based on Soil + Unfiltered Groundwater: NA NA 3 NA Total Resident ELCR Based on Surface Soil + Unfiltered Groundwater: NA 1E-02 NA NA

Total Resident ELCR Based on Soil + Unfiltered Groundwater: NA 1E-02 NA NA Filtered Groundwater Exposuresc

Filtered Groundwater (µg/L)


Arsenic, Dissolved (µg/L) 1.2 NA 0.2 NA Bromomethane (µg/L) 1.5 NA 0.08 NA Uranium, Dissolved (µg/L) 3.0 NA 0.8 NA Uranium-234 (pCi/L) 1.06 NA NA No Uranium-235 (pCi/L) 0.047 NA NA No Uranium-238 (pCi/L) 1.00 NA NA No

Total HI: NA 1 NA Adult Arsenic, Dissolved (µg/L) 1.2 NA 0.1 NA

Bromomethane (µg/L) 1.5 NA 0.04 NA Uranium, Dissolved (µg/L) 3.0 NA 0.5 NA Uranium-234 (pCi/L) 1.06 NA NA No Uranium-235 (pCi/L) 0.047 NA NA No Uranium-238 (pCi/L) 1.0 NA NA No

Total HI: NA 0.6 NA


52 FINAL


(Continued)

Exposure Medium




Filtered Groundwater Exposuresc (Continued) Filtered Groundwater (µg/L) (Continued)


Arsenic, Dissolved (µg/L) 1.2 2E-05 NA NA Bromomethane (µg/L) 1.5 NA NA NA Uranium, Dissolved (µg/L) 3.0 NA NA NA Uranium-234 (pCi/L) 1.06 2E-03 NA NA Uranium-235 (pCi/L) 0.047 7E-07 NA NA Uranium-238 (pCi/L) 1.0 2E-03 NA NA

Total ELCR: 5E-03 NA NA Notes: a All chemicals and radionuclides presented in this table were identified as COPCs and ROPCs in Section 3.2; however, the EPCs, ELCRs and HIs presented include contributions from potentially site-related sources combined with contributions from background (i.e., naturally-occurrence). The units for the EPCs (presented in adjacent column) are presented in parentheses after the COPC/ROPC. b The ELCR and HI corresponding to the site (CC-IAAP-002) EPC presented for each COPC and ROPC represents the sum of the pathway-specific ELCRs and HIs calculated in Appendix B for each receptor/exposure medium scenario. The ELCRs for the uranium isotopes include contributions from all of the associated decay chain progeny, over all of the exposure pathways evaluated. Although correct, the total HIs may not appear to have been summed correctly because both the chemical-specific and total HIs are rounded to one significant figure. c Residential ELCRs and HIs are presented for filtered groundwater exposures for informational purposes and possible use in weight of evidence evaluations. NA - Calculation of the ELCR or HI value is either not applicable to receptor group or not able to be calculated due to toxicity criteria not being available.

Resident Young Child/Adult ELCRs Table 3-5 shows that the cumulative ELCR calculated for age-adjusted resident (i.e., young child/adult) combined exposures to surface soil and unfiltered groundwater (1E-02) exceeds the upper limit of the USEPA’s target risk range. The surface soil and unfiltered groundwater ELCRs contributing to the total receptor ELCR are 5E-03 and 7E-03, respectively. Table B-9.1 shows that the total receptor exceedance is due predominantly to the ingestion of uranium-234 and uranium-238 in surface soil, as well as the ingestion and inhalation of uranium-234 and uranium-238 isotopes (i.e., parents and progeny) in unfiltered groundwater. Table B-8.5 shows that an inhalation ELCR of 6E-03 for unfiltered groundwater contributes the most predominantly to the receptor risk, and is due to radium-226 in the uranium-234 (3E-03) and uranium-238 (3E-03) decay chains. In addition to the radiological risks, Table 3-5 also shows that total arsenic (3E-04) and hexavalent chromium (3E-04) in unfiltered groundwater also contribute significantly to the cumulative receptor ELCR. Table B-9.1 shows that this in turn, is due to the ingestion of arsenic (3E-04) and hexavalent chromium (3E-04) in unfiltered groundwater. Table 3-5 also shows that cumulative the ELCR calculated for age-adjusted resident (i.e., young child/adult) combined exposures to soil and unfiltered groundwater (1E-02) exceed the upper limit of the USEPA’s target risk range. The soil and unfiltered groundwater ELCRs contributing to the total receptor ELCR are 4E-03 and 7E-03, respectively. Table B-9.2 shows that the total receptor exceedance is due predominantly to the ingestion of uranium-234 and uranium-238 in soil, as well as the ingestion and inhalation of uranium-234 and uranium-238 isotopes (i.e., parents and progeny) in unfiltered groundwater. Table B-8.5 shows that an inhalation ELCR of 6E-03 for unfiltered groundwater contributes the most predominantly to the receptor risk, and is due to radium-226 in the uranium-234 (3E-03) and uranium-238 (3E-03) decay chains. In addition to the radiological


53 FINAL

risks, Table 3-5 also shows that total arsenic (3E-04) and hexavalent chromium (3E-04) in unfiltered groundwater also contribute significantly to the cumulative receptor ELCR. Table B-9.2 shows that this in turn, is due to the ingestion of arsenic (3E-04) and hexavalent chromium (3E-04) in unfiltered groundwater.

Resident Young Child Non-Cancer HIs Table 3-5 shows that the cumulative non-cancer HIs calculated for resident young child combined exposures to surface soil plus unfiltered groundwater (5), as well as for combined soil plus unfiltered groundwater (5), exceed the USEPA’s target HI of 1. Tables B-9.1 and B-9.2 show that upon an analysis of target organs, the total receptor HI is driven mainly by the HI calculated for the cardiovascular system and skin (HI = 3.3 due to ingestion of total arsenic in groundwater), as well as for the kidney (HI = 1 due mostly to ingestion of total uranium in groundwater). Therefore, this receptor scenario fails to meet the USEPA’s target HI of 1 at CC-IAAP-002, due to exposures to unfiltered groundwater used as a potable source.

Resident Adult Non-Cancer HIs Table 3-5 shows that the cumulative non-cancer HIs calculated for resident adult combined exposures to surface soil plus unfiltered groundwater (3), as well as for combined soil plus unfiltered groundwater (3), exceed the USEPA’s target HI of 1. Tables B-9.1 and B-9.2 show that upon an analysis of target organs, the total receptor HI is driven mainly by the HI calculated for the cardiovascular system and skin (HI = 1.8 due to ingestion of total arsenic in groundwater. Therefore, this receptor scenario fails to meet the USEPA’s target HI of 1 at CC-IAAP-002, due to exposures to unfiltered groundwater used as a potable source.

Summary The risk characterization of ELCRs and HIs as a result of residential exposures to concentrations from both potentially site-related sources and natural occurrence in surface soil, soil, and groundwater at CC-IAAP-002 indicate the following:

• ELCRs for surface soil and soil exceed the target limit of 1E-04 due ingestion of the ROPCs uranium-234 and uranium-238. There are no ELCRs exceeding the USEPA’s target limit due to residential exposures to COPCs in surface soil and soil. ELCRs calculated for unfiltered groundwater exceed the USEPA’s target limit of 1E-04 due to ingestion of total arsenic, hexavalent chromium, uranium-234, and uranium-238. The ROPCs contribute the most predominantly to the surface soil, soil and unfiltered groundwater ELCRs.

• There are no non-cancer HI exceedances of the USEPA’s target limit of 1 by COPCs in surface soil or soil. However, non-cancer HIs calculated for unfiltered groundwater exceed the USEPA’s target HI limit of 1 for both the resident child receptor due to ingestion of total arsenic (cardiovascular system and skin) and total uranium (kidney), and for the resident adult due to ingestion of total arsenic (cardiovascular system and skin). However, because the resident child HI calculated for the kidney includes contributions from both total uranium (0.95) and barium (0.097), and the total uranium HI is actually less than 1 for the young child resident, as well as for the adult resident, total uranium in unfiltered groundwater at CC-IAAP-002 is not retained for further evaluations in this risk characterization.


54 FINAL

Because the concentrations of arsenic, benzo(a)pyrene, hexavalent chromium, and uranium-235 in both surface soil and soil, as well as the concentrations of bromomethane, total barium, total uranium, and uranium-235 in unfiltered groundwater, result in ELCRs and HIs less than target limits, these COPCs are eliminated from further evaluations in the remaining three steps of the risk characterization. The COPCs and ROPCs listed below for CC-IAAP-002 exceed target risk and/or HI limits due to contributions from combined site-related and naturally occurring concentrations. Therefore, they are retained for comparative evaluations with background in Section 3.5.7.2 to determine if they are site related or naturally occurring.

• Surface Soil (0 to 0.5 ft bgs) o Uranium-234 o Uranium-238

• Soil (0 to 10 ft bgs) o Uranium-234 o Uranium-238

• Unfiltered Groundwater o Total arsenic o Hexavalent chromium o Uranium-234 o Uranium-238

3.5.7.2 Risk Characterization of Naturally-Occurring Constituents at CC-IAAP-002 In Section 3.5.7.1, two radionuclides in surface soil, soil and unfiltered groundwater (uranium-234 and uranium-238) and two metals in unfiltered groundwater (total arsenic and hexavalent chromium) were identified as ROPCs and COPCs for evaluation in this second step of risk characterization evaluation to determine if they are naturally occurring constituents or site-related COPCs and ROPCs at CC-IAAP-002. IAAAP facility-wide BTVs have been established for metals in soil, which were first applied in the BERA (MWH 2004) and for metals in unfiltered groundwater (CH2M Hill 2020). Additionally, IAAAP-specific uranium isotope data for soil background is available, from which BTVs were determined in Appendix B, Table B-2.5 based on maximum concentrations. No IAAAP-specific radiological background data are available for groundwater. Residential receptor-specific ELCRs and HIs have been calculated for the BTVs for all CC-IAAP-002 surface soil/soil and groundwater COPCs and ROPCs. Supporting calculations of receptor-specific chemical intakes, ELCRs, and HIs due to background are presented in Appendix B. ELCR calculations for age-adjusted young child/adult resident exposures to background soil and unfiltered groundwater are presented in Table B-7.1d. HI calculations for young child resident and adult resident exposures to background soil and unfiltered groundwater are presented in Tables B-7.2d and B-7.3d, respectively. For radiological exposures at CC-IAAP-002, supporting calculations of radiological intakes and ELCRs for soil BTVs are also presented in Appendix B, Table B-8.3 for the age-adjusted young child/adult resident, showing contributions from parent uranium and individual decay chain isotopes. Table B-8.11 also shows calculations of ELCRs for background soil for the parent uranium isotopes (i.e., with decay chain contributions included but not shown).


55 FINAL

The Appendix B summary of pathway-specific background ELCRs and non-cancer HIs for CC-IAAP-002 COPCs and ROPCs are presented in Table B-9.5 for background soil plus unfiltered groundwater. Table 3-6 shows a comparison of site maximum concentration with BTVs for unfiltered groundwater, as well as comparisons of area ELCRs and HIs with corresponding background ELCRs and HIs.


Constituents

Exposure Medium

Residential Receptor COPCa

Background Comparisons and Determination of Naturally Occurring

Constituents




Area EPC

(µg/L)

BTVc (µg/L)


ELCR HI


Surface Soil (0-0.5 ft bgs)




Soil (0-10 ft bgs)




Unfiltered Groundwater


Arsenic, Total (µg/L) 18 18 33.3 Yes NA NA 3 6 No


11 J 11 9 No NA NA 0.2 0.1 Yes

Chromium, Total (µg/L)e 39 39 31 No NA NA NA NA NA

Uranium-234 (pCi/L) 1.3 1.3 NA CBDf NA NA NA NA NA


Adult Arsenic, Total (µg/L) 18 18 33.3 Yes NA NA 2 3 No


11 J 11 9 No NA NA 0.1 0.09 Yes





56 FINAL



Exposure Medium

Residential Receptor COPCa

Background Comparisons and Determination of Naturally Occurring

Constituents




Area EPC

(µg/L)

BTVc (µg/L)


ELCR HI

Area Bkgd. Area Bkgd. Unfiltered Groundwater (Continued)


Arsenic, Total (µg/L) 18 18 33.3 Yes 3E-04 6E-04 NA NA No


11 J 11 9 No 3E-04 3E-04 NA NA Yes


Uranium-234 (pCi/L) 1.3 1.3 NA CBDf 3E-03 NA NA NA Yes

Uranium-238 (pCi/L) 1.3 1.3 NA CBDf 3E-03 NA NA NA Yes

Notes: a All chemicals and radionuclides presented in this table were identified as COPCs and ROPCs, respectively, in Section 3.2 and were retained for further evaluations based on exceedances of target ELCR and/or HI limits as reported in Table 3-5. The evaluations in this table determines those COPCs and ROPCs that are more likely due to natural occurrence. ELCRs and HIs from the naturally occurring constituents are not retained for further analyses beyond this step of the risk characterization process. b ELCRs and HIs corresponding to CC-IAAP-002 medium-specific EPCs and IAAAP-specific BTVs are presented in the "Area" and "Bkgd." columns, respectively. The ELCR and HI corresponding to the site (CC-IAAP-002) EPC presented for each COPC and ROPC represents the sum of the pathway-specific ELCRs and HIs calculated in Appendix B for each receptor/exposure medium scenario. The ELCRs for the uranium isotopes include contributions from all of the associated decay chain progeny, over all of the exposure pathways evaluated. Although correct, the total HIs may not appear to have been summed correctly because both the chemical-specific and total HIs are rounded to one significant figure. c The sources of all IAAAP-specific BTVs are discussed in Section 3.5.5.2. d The valued entered as the BTV for hexavalent chromium is an estimated value based on site-specific data (see Section 3.5.7.2 hexavalent chromium discussion and Table 3-2a). e Although total chromium is not a COPC in any media, the unfiltered groundwater maximum concentration, EPC and groundwater BTV are presented as supplemental information relative to the risk characterization of hexavalent chromium. The entry for total chromium in the remaining columns is "NA" (not applicable). f CBD - A determination of the constituent as being naturally occurring (or not) cannot be determined due to no available IAAAP-specific background data or calculated BTV. ELCRs and HIs for metals and radionuclides that cannot be determined as being naturally occurring are presented along with ELCRs and HIs for the naturally occurring constituents. NA - Calculation of the ELCR or HI value is not applicable due to any of the following: inconsistency with receptor group scenario, no established BTV, or no available toxicity criteria.

The following paragraphs discuss evaluations of each of the COPCs (arsenic and hexavalent chromium) and ROPCs (uranium-234 and uranium-235) in unfiltered groundwater relative to IAAAP-specific BTVs.

Arsenic Based on the Table 3-6 comparisons, it is evident that the maximum concentration (EPC), ELCRs and HIs calculated for total arsenic in unfiltered groundwater are less than the corresponding values determined for the groundwater BTVs. Consequently, total arsenic is considered to be naturally occurring in unfiltered groundwater at CC-IAAP-002 and is consequently, removed from further evaluations and discussions in this risk characterization.

Hexavalent Chromium Hexavalent chromium was initially identified as a COPC in unfiltered groundwater at CC-IAAP-001 in Section 3.5.7.1. No IAAAP-specific groundwater BTVs have been established for hexavalent


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chromium; however an IAAAP-specific BTV of 31 µg/L has been established for total chromium. Because hexavalent chromium is typically present as a fraction of the total chromium, background comparisons between total chromium in CC-IAAP-002 groundwater and the BTV can be conducted in a manner that allows for inferences to be made regarding the natural occurrence of hexavalent chromium at CC-IAAP-002. This can done by application of area-specific ratios of hexavalent chromium concentrations to chromium concentrations in groundwater, as discussed in the following paragraphs and presented in Table 3-6a. At CC-IAAP-002, the maximum total chromium concentration reported for unfiltered groundwater, 39 µg/L, is greater than the BTV of 31 µg/L. Since hexavalent chromium concentrations are typically present as a fraction of the total chromium concentrations, then it may be inferred that hexavalent chromium concentrations in unfiltered groundwater at CC-IAAP-002 should also be above background levels expected for hexavalent chromium. This can be demonstrated by consideration of the ratios of hexavalent chromium concentrations to total chromium concentrations present in CC-IAAP-002 groundwater, as presented in Table 3-6a. The ratio of the maximum concentrations of hexavalent chromium (11 µg/L) to total chromium (39 µg/L) is 0.28. The ratio of the arithmetic mean concentrations of hexavalent chromium (7.75 µg/L) to total chromium (15.5 µg/L) is 0.50. As a conservative area-specific approach, multiplication of the lesser of the two ratios (i.e., 0.28) by the BTV yields an estimated background concentration of 9 µg/L for hexavalent chromium. By comparison, the maximum reported concentration of hexavalent chromium in CC-IAAP-002 unfiltered groundwater (11 µg/L) is greater than the estimated background level for hexavalent chromium in groundwater (8.7 µg/L) at CC-IAAP-002. However, if the ratio based on the arithmetic mean concentrations is applied (i.e., 0.5), the estimated background level would be 16 µg/L, which is greater than the maximum hexavalent chromium concentration at CC-IAAP-002 (11 µg/L). Taken together, the use of ratios based on the maximum and mean concentrations indicate that hexavalent chromium concentrations in CC-IAAP-002 unfiltered groundwater approximate estimated background levels. Although this approach applies area-specific ratios of hexavalent chromium to total chromium concentrations, it provides only estimates because of inherent uncertainties associated with potential variations in ratios between CC-IAAP-002 and the background groundwater well locations due to differences in physical (e.g., hydrogeologic characteristics) and chemical conditions (e.g., pH and the presence of organics in the overburden). These uncertainties associated with this approach are discussed in Section 3.7.4.3 of the Uncertainties Analysis section of this Residential BHHRA.

Table 3-6a. Estimation of Hexavalent Chromium Background Concentrations in Unfiltered Groundwater Based on Maximum and Mean Concentrations of Hexavalent Chromium and

Total Chromium at CC-IAAP-002

Maximum/Mean Hexavalent

Chromium and Chromium

Concentrations

Total Chromium

BTVa

CC-IAAP-002 Hexavalent Chromium

Conc.

CC-IAAP-002 Chromium

Conc. Ratiob

Estimated Hexavalent Chromium

Background Conc.c

Is CC-IAAP-002 Hexavalent Chromium

Concentration Less Than Estimated

Background Level? (Yes/No)

Maximum (µg/L) 31 11 39 0.28 9 No Mean (µg/L) 31 7.75 15.5 0.50 16 Yes

Notes: a BTV – Background threshold value b Ratio = Hexavalent chromium concentration / chromium concentration. c Estimated hexavalent chromium background concentration = chromium BTV x Ratio.


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Therefore, based on consideration of groundwater data for CC-IAAP-002, in conjunction with the groundwater BTV, hexavalent chromium detected in CC-IAAP-002 groundwater approximates concentrations consistent with naturally occurring conditions. The absence of records indicating the occurrence of any historical IAAAP process-related activities and sources at CC-IAAP-002 further supports this finding. However, as a conservative measure, hexavalent chromium is retained as a site-related COPC in unfiltered groundwater at CC-IAAP-002 for further evaluations in this risk characterization. This is because of uncertainties inherent in the method used for calculating representative background levels for CC-IAAP-002 unfiltered groundwater, which does not preclude the possibility that hexavalent chromium could exceed the estimated background levels (i.e., based on levels calculated using the lower, more conservative ratio of 0.28).

Uranium Isotopes Based on the Table 3-6 comparisons, it is evident that the maximum concentrations of uranium-234 and uranium-238, along with the ELCRs calculated for uranium-234 and uranium-238 in surface soil and soil, are less than the corresponding values determined for the soil BTVs. Consequently, uranium234 and uranium-238 are considered to be naturally occurring in surface soil and soil and are therefore removed from further evaluations in this risk characterization.

Because no IAAAP-specific BTVs are available for radionuclides in groundwater, uranium-234 and uranium-238 in unfiltered groundwater at CC-IAAP-002 are retained for further evaluations and discussions in this risk characterization.

Summary In summary, based on the risk characterization discussion in Section 3.5.7.1 and following evaluations of naturally occurring constituents, the following constituents are being retained for further evaluations in this risk characterization:

• Hexavalent chromium (unfiltered groundwater) • Uranium-234 (unfiltered groundwater) • Uranium-238 (unfiltered groundwater)

3.5.7.3 Risk Characterization of Site-Related COPCs and ROPCs at CC-IAAP-002 Based on the analysis in Section 3.5.7.2, hexavalent chromium, uranium-234, and uranium-238 in unfiltered groundwater have been retained as a site-related COPCs and ROPCs at CC-IAAP-002. Table 3-7 presents the receptor-specific ELCR and HIs for hexavalent chromium and the uranium isotopes, in unfiltered groundwater at CC-IAAP-002.



CC-IAAP-002b EPC ELCR HI


Hexavalent Chromium (µg/L) 11 NA 0.2 Uranium-234 (pCi/L) 1.3 NA NA Uranium-238 (pCi/L) 1.3 NA NA

Total HI: NA 0.2


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(Continued)

Residential Receptor COPC/ROPCa CC-IAAP-002b

EPC ELCR HI Adult Hexavalent Chromium (µg/L) 11 NA 0.1

Uranium-234 (pCi/L) 1.3 NA NA Uranium-238 (pCi/L) 1.3 NA NA

Total HI: NA 0.1 Resident (Age-Adjusted Child/Adult)

Hexavalent Chromium (µg/L) 11 3E-04 NA Uranium-234 (pCi/L) 1.3 1E-02 NA Uranium-238 (pCi/L) 1.3 1E-02 NA

Total ELCR: 3E-02 NA Notes: a The ELCRs and HIs corresponding to the CC-IAAP-002 EPCs presented for hexavalent chromium and the uranium isotopes in unfiltered groundwater each represent the sum of the pathway-specific ELCRs and HIs calculated in Appendix B for each receptor scenario. NA - Calculation of the ELCR or HI value not applicable.

The following paragraphs discuss the risk characterization of residential exposures to hexavalent chromium in unfiltered groundwater.

Resident Young Child/Adult ELCRs The ELCR (3E-04) calculated for the age-adjusted resident (i.e., combined young child/adult) exposures to hexavalent chromium in unfiltered groundwater at CC-IAAP-002, exceeds the upper limit of the USEPA’s target risk range. Additionally, the ELCRs for uranium-234 (1E-02) and uranium-238 (1E-02) exceeds the USEPA’s target limit of 1E-04. Table B-10.1 shows that the total receptor exceedance is due predominantly to the ingestion and inhalation of uranium-234 and uranium-238 isotopes (i.e., parents and progeny) in unfiltered groundwater. Because the total receptor ELCR associated with unfiltered groundwater use as a potable source is 3E-02, this scenario fails to meet the target limit of 1E-04.

Resident Young Child Non-Cancer HIs The cumulative non-cancer HI (0.2) calculated for resident young child exposures to hexavalent chromium in unfiltered groundwater at CC-IAAP-002 is less than the USEPA’s target HI of 1.

Resident Adult Non-Cancer HIs The cumulative non-cancer HI (0.1) calculated for resident adult exposures to hexavalent chromium in unfiltered groundwater at CC-IAAP-002 is less than the USEPA’s target HI of 1.

Summary The risk characterization of ELCRs and HIs associated with residential exposures to site-related concentrations of hexavalent chromium, uranium-234, and uranium-238 in unfiltered groundwater at CC-IAAP-002 result in the exceedance of the target ELCR limit of 1E-04. Therefore, hexavalent chromium in unfiltered groundwater is identified as a site-related COPC and is retained for further evaluation in Section 3.5.7.4 to determine if it should be identified as a final COC. Similarly, uranium-234 and uranium-238 in unfiltered groundwater are identified as a site-related ROPCs and are retained for further evaluation in Section 3.5.7.4 to determine if they should be identified as final ROCs.


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3.5.7.4 Evaluation of Hexavalent Chromium and Uranium Isotopes to Determine Final COC and ROC Status in CC-IAAP-002 Unfiltered Groundwater

Based on the results of the risk characterization (Sections 3.5.7.1 through 3.5.7.3), hexavalent chromium in unfiltered groundwater is the only area-related COPC at CC-IAAP-002 due to ingestion exposures to a resident resulting in an ELCR exceeding the USEPA’s target ELCR range. The exceedance is based on a maximum concentration detected in one groundwater sample. Uranium-234 and uranium-238 were identified as site-related ROPCs in unfiltered groundwater due to ingestion and inhalation exposures to a resident resulting in ELCRs exceeding the target limit of 1E-04. In order to determine if hexavalent chromium is a final COC in unfiltered groundwater, and if the uranium isotopes are final ROCs in unfiltered groundwater for further evaluation in a feasibility study, the following paragraphs and Table 3-8 present evaluations of lines of evidence other than the health risks that have been calculated and presented throughout this risk characterization.

Table 3-8. Weight of Evidence Evaluation of Hexavalent Chromium as a Final COC and Uranium Isotopes as Final ROCs in CC-IAAP-002 Unfiltered Groundwater

Remaining Site-Related

COPC/ ROPC


USEPA MCL


Equivalent to MCLb


EPC < MCL?




Child/ Adult

Resident ELCR

Child Resident

HIa

EPC (Max. Conc.)

Child/ Adult

Resident ELCR

Child Resident

HIa

Site-Related COPCs Hexavalent Chromium (µg/L)

11 0 0 ND NA NA 100 NA Yes No Max. Conc. < MCL

Chromium, Totalc (µg/L) 39 NA NA ND NA NA 100 NA Yes NA

Not Quantitatively

Evaluated Site-Related ROPCs

Uranium-234 (pCi/L) 1.3 3E-03 NA 1.06 2E-03 NA NA NA NA No

Sum of Max. Isotope

Conc. < MCL Activity

Equivalentd

Uranium-238 (pCi/L) 1.3 3E-03 NA 1.00 2E-03 NA NA NA NA No

Uranium Isotopes (Total) (pCi/L)

2.6 6E-03 NA 2.06 5E-03 NA NA 27 Yes No

Notes: a The EPCs are based on the maximum detected concentrations. The ELCRs and HIs corresponding to the CC-IAAP-002 EPCs presented for hexavalent chromium and the uranium isotopes represent the sum of the pathway-specific ELCRs and HIs calculated in Appendix B for the child/adult resident and child residential scenarios, respectively. The resident child HI is presented because it represents the greater of the child versus adult HIs. b An activity equivalent of the USEPA's MCL is presented in accordance with USEPA's OSWER Directive 9283.1-14 entitled "Use of Uranium Drinking Water Standards under 40 CFR 141 and 40 CFR 192 as Remediation Goals for Groundwater at CERCLA Sites (USEPA 2001)", which states: "The 2000 MCL rule established an MCL for uranium of 30 μg/L. For the MCL rulemaking, EPA assumed a typical conversion factor of 0.9 pCi/μg for the mix of uranium isotopes found at public water systems, which means that an MCL of 30 μg/L will typically correspond to 27 pCi/L. EPA considered the 30 μg/L level (which corresponds to a 27 pCi/L level) to be appropriate since it is protective for both kidney toxicity and cancer." c Although total chromium is not a COPC in any media, the unfiltered groundwater EPC (i.e., based on the maximum detection) and groundwater BTV are presented as supplemental information relative to the risk characterization of hexavalent chromium. The entry for total chromium in the remaining columns is "NA" (not applicable). d The sum of the maximum concentrations of site-related uranium isotopes in unfiltered groundwater include only uraniums-234 and -238. However, even if the maximum concentration of uranium-235 (0.06 pCi/L) were included, the sum of the maximum concentrations of all three isotopes (2.7 pCi/L) in unfiltered groundwater is still less than the MCL activity equivalent of 27 pCi/L. NA - Not applicable.


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Hexavalent Chromium In Section 3.5.7.2, hexavalent chromium was determined to be present in unfiltered groundwater at CC-IAAP-002 at concentrations that are comparable to estimated background levels. However, uncertainties exist in the ratios of hexavalent chromium to chromium concentrations used to estimate representative background concentrations of hexavalent chromium in groundwater, as well as in the possibility that hexavalent chromium in CC-IAAP-002 unfiltered groundwater could actually exceed estimated background levels. Therefore, hexavalent chromium was conservatively retained for further evaluations to determine whether or not it should be identified as a COC in unfiltered groundwater. In order to facilitate this determination, data comparisons to the USEPA MCL are applied as a WOE. Currently, no MCL exists for hexavalent chromium. However the USEPA has promulgated a MCL of 100 µg/L for chromium. Table B-2.6 in Appendix B shows that the maximum concentrations of both hexavalent chromium (11 µg/L) and total chromium (39 µg/L) in unfiltered groundwater at CC-IAAP-002 are less than the MCL. Although the MCL for chromium does not differentiate between hexavalent and trivalent chromium, and is not a risk-based value, both hexavalent and trivalent chromium are covered under the total chromium drinking water standard. This is because these forms of chromium can convert back and forth in water and in the human body, depending on environmental conditions. Therefore, in order to ensure that the greatest potential risk is addressed, the USEPA's regulation assumes that a measurement of total chromium is 100 percent hexavalent, i.e., the more toxic form (USEPA 2020f). Based on the results of the background evaluation of hexavalent chromium (Section 3.5.7.2) and the absence of records indicating the occurrence of any historical IAAAP process-related activities and sources at CC-IAAP-002, along with the MCL comparisons as a WOE, hexavalent chromium is not retained as a COC in unfiltered groundwater at CC-IAAP-002.

Uranium Isotopes Table 3-8 shows that the concentrations of uranium-234 (1.3 µg/L) and uranium-238 (1.3 µg/L) are summed to determine a concentration of 2.6 µg/L of total uranium isotopes. This concentration is compared to an activity equivalent concentration (27 pCi/L) of the elemental uranium MCL (30 µg/L). The activity equivalent of the USEPA's MCL was determined in accordance with USEPA's OSWER Directive 9283.1-14 entitled "Use of Uranium Drinking Water Standards under 40 CFR 141 and 40 CFR 192 as Remediation Goals for Groundwater at CERCLA Sites” (USEPA 2001), which states:

"The 2000 MCL rule established an MCL for uranium of 30 micrograms per liter (μg/L). For the MCL rulemaking, EPA assumed a typical conversion factor of 0.9 pCi/μg for the mix of uranium isotopes found at public water systems, which means that an MCL of 30 μg/L will typically correspond to 27 pCi/L. EPA considered the 30 μg/L level (which corresponds to a 27 pCi/L level) to be appropriate since it is protective for both kidney toxicity and cancer."

The comparison shows that the total concentration of uranium isotopes in unfiltered groundwater at CC-IAAP-002 is less than the activity equivalent concentration of the MCL. Therefore, uranium-234 and uranium-238 are not identified as ROCs in unfiltered groundwater at CC-IAAP-002.

Summary Based on the results of the Residential BHHRA for CC-IAAP-002, no COCs or ROCs were identified in any of the evaluated media. Although no COCs or ROCs were identified and no


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additional remedial actions are required to address the chemicals at the site, the ACM removal action must occur before this site can be wholly considered as NFA.

3.6 CONCLUSIONS OF THE RESIDENTIAL BASELINE HUMAN HEALTH RISK ASSESSMENT

No COCs or ROCs were identified in soil or groundwater at both CC-IAAP-001 and CC-IAAP-002 under the Residential Land Use scenario in the Residential BHHRA. CC-IAP-001 and CC-IAAP-002 can move forward to the next phase in the CERCLA to facilitate the removal of the ACM at CC-IAAP-002 followed by a NFA determination once the ACM removal action is completed.

3.7 UNCERTAINTY ANALYSIS

Uncertainties are inherent in all components of the Residential BHHRA process for the two construction debris areas (i.e., data evaluation, exposure assessment, and toxicity assessment), as well as in the procedures that are used in calculating and characterizing health risks to potential residents. A qualitative assessment of these uncertainties and the resulting impacts of potentially overestimating or underestimating ELCRs and non-cancer HIs associated with both areas is discussed in this section.

3.7.1 Data Evaluation and COPC Identification Uncertainties The 2014 BHHRA discusses the uncertainties associated with the data evaluation, as well as characterization of the nature and extent of contamination within each construction debris area. Because the same data used in this Addendum were used in the 2014 BHHRA, those uncertainties discussed in the 2014 BHHRA apply to this Addendum. Other uncertainties noted during the data evaluation and identification of COPCs for this Residential BHHRA are discussed in Sections 3.7.1.1 through 3.7.1.3.

3.7.1.1 Sampling Strategy Uncertainties The first step in acquiring data is sampling; therefore, sampling strategy can affect data evaluation and the calculations of EPCs, ELCRs and non-cancer HIs. Because much of the sampling conducted within both areas were biased toward areas of likely contamination, the EPCs calculated in this Residential BHHRA based on the biased datasets are likely to be higher than those that would be calculated based on a non-biased sampling strategy (e.g., random sampling, systematic random sampling from grid, etc.). Consequently, the human health risks are considered to be higher and more health-conservative. Therefore, applications of datasets based on biased sampling strategies have likely resulted in an over-estimation of the ELCR and non-cancer HIs calculated in this Addendum.

3.7.1.2 Analytical Uncertainties Some unavoidable uncertainty is associated with the contaminant concentrations detected and reported by the analytical laboratory. The quality of the analytical data used in the risk assessment depends on the adequacy of the set of procedures that specifies how samples are selected and handled and how strictly these procedures are followed. QA/QC procedures within the laboratories are used to minimize uncertainties; however, sampling errors, laboratory analysis errors, and data analysis errors can occur.


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Some current analytical methods are limited in their ability to achieve detection limits at or below risk-based screening levels (i.e., RSLs [USEPA 2020a] and VISLs [USEPA 2020b]). Under these circumstances, it is uncertain whether the true concentration is above or below the screening levels, which are protective of human health. For detected chemicals in soil samples collected from both areas, the RSL for hexavalent chromium is exceeded by some reporting limits. For detected chemicals in CC-IAAP-001 groundwater, the RSLs for arsenic (dissolved), and hexavalent chromium (total) are exceeded by some reporting limits. Similarly for detected chemicals in CC-IAAP-002 groundwater, the RSLs for 2-hexanone, arsenic (dissolved), bromomethane, and hexavalent chromium (total) are exceeded by some reporting limits. However, because all of these chemicals were retained as COPCs for quantitative evaluations of health risks, it is likely that the health risks are not underestimated. Finally, the quality and usability of analytical data reported by the laboratory could potentially introduce uncertainties into the BHHRA process. All analytical data collected from CC-IAAP-001 and CC-IAAP-002 were subjected to third-party review and validation, in accordance with the USEPA’s guidelines, in order to determine the quality and usability of the data relative to project data quality objectives. Data validation reports were prepared from this review and included into the RI Report (PIKA 2014a) as Appendix E (“Data Quality Review and Validation Report”). The results of the analytical data validation concluded that 99.9 percent of the data collected from both areas should be considered valid, meeting the quality assurance project plan (QAPP)-specified minimum completeness goal of 98 percent. Some qualifications were made due to minor quality issues observed during the review. Data that were considered to be not valid/usable, i.e., that were qualified “R” (“rejected) during validation included semivolatile organic compounds, PCBs, and royal demolition explosive (RDX) in CC-IAAP-001 soil; semivolatile organic compounds, explosives, and herbicides in CC-IAAP-001 groundwater; several pesticides and herbicides in CC-IAAP-002 soil; and PAHs, SVOCs, explosives, pesticides, herbicides, and metals in CC-IAAP-002 groundwater. These R-flagged data were removed from the data sets prior to calculations of EPCs. Given that only approximately 2 percent of the data were removed, with all of the rejected results being at or near the respective levels of detection, there are no significant impacts expected that would result in over- or underestimating ELCRs and non-cancer HIs.

3.7.1.3 COPC and ROPC Identification Uncertainties Although the HHRA deviates from standard practice in COPC and ROPC screening, it is important to document here, the established procedural process for arriving at the list of chemicals and radionuclides that are to be carried through an HHRA. Typically, the very first screen, applicable to all categories of chemicals (e.g., inorganic, anthropogenic, etc.) is for frequency of detection. In brief, chemicals or radionuclides that occur in 5% or less of samples for a given medium, are usually eliminated because it is evident up front, that these constituents might play an insignificant role. In this Risk Assessment, no chemicals or radionuclides were screened out based on frequency of detection. The second screen is typically a background screen, and it would be for naturally occurring constituents only (principally inorganic compounds, such as metals). Organic chemicals such as pesticides or solvents should not be present in site background, and if they are, an alternate site background location must be sought. In this screening, the maximum onsite metal or radionuclide detection is typically compared with a value that is twice the mean concentration in site background. Where the maximum onsite concentration is less than ‘the two-times-the-background-mean’ concentration, the metal/radionuclide is typically removed from all other consideration in the HHRA. In this Risk Assessment, the background screen was not done before the risk-based screening. The third screening task is risk-based screening and was completed for


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this HHRA. The maximum detected onsite concentration or the 95% UCL of a chemical was compared to their current USEPA RSL table (USEPA 2020a), wherein the values reflect a cancer risk level of 1E-06 (for carcinogens), and a HQ of 0.1 in the case of systemic toxicants. The process used for identifying COPCs and ROPCs in this BRRHA requires making decisions and developing assumptions on the basis of historical information, process knowledge, and best professional judgment about the data. However, the decisions and assumptions applied in the data evaluation process and subsequently, the COPC/ROPC identification process, were made in a manner that errs in favor of not underestimating health risks. The USEPA’s residential RSLs, VISLs and radiological PRGs were used to screen analyte data are also subject to uncertainty. The RSLs, VISLs and PRGs are derived based on health-conservative assumptions regarding exposure, employing upper-bound values used in calculating chemical intake, and target an ELCR of 1E-06 and a HI of 0.1. The screening process involved comparing maximum contaminant concentrations of chemicals/radionuclides in each of the evaluated media with the RSLs, VISLs and PRGs, as appropriate. Therefore, if at least one detected concentration of a chemical/radionuclide in a medium (i.e., soil or groundwater) exceeded the corresponding screening level, the chemical was retained as a COPC. This selection process maximizes the probability that the ELCRs and HIs calculated in the residential BHHRA reflect any chemical/radionuclide that could contribute to the risks and hazards, so that these endpoints are not underestimated. Regarding data comparisons with the VISLs, application of VISLs to current groundwater concentrations of volatile chemicals is considered likely to be health conservative in representing potential indoor air vapor intrusion into a residential dwelling each at CC-IAAP-001 and CC-IAAP-002. Although the groundwater data comparisons to VISLs for both areas indicated no exceedances of the VISLs and therefore, no significant potential for indoor vapor intrusion, comparisons to the VISLs introduce health conservatism into the data evaluation process because current concentrations of chemicals in the groundwater are likely to decrease in the future due to natural fate and transport processes. Another source of uncertainty is the evaluation of chemicals without established RSLs and toxicity criteria. All chemicals presented in Tables A.2-1 and B.2-1 without RSLs and toxicity criteria are retained as COPCs, but qualitatively evaluated in Section 3.7.4 to determine if potential health risks associated with these chemicals could result in the total ELCRs and HIs calculated for CC-IAAP-001 and CC-IAAP-002 as being potentially underestimated. In this Residential BHHRA, RSLs were applied to the essential nutrients (i.e., calcium, magnesium, and sodium) that were calculated in the RI Report (PIKA 2014a) based on USDA Tolerable Upper Intake Levels (USDA 2014). The calculation methods used to derive the RSLs for essential nutrients were designed to result in the lowest representative “reference dose” that would maximize health conservatism and minimize the potential for underestimating possible health risks. Based on this method, and the detected essential nutrients, only dissolved magnesium in CC-IAAP-001 groundwater was retained as a COPC. Total magnesium in groundwater samples collected from CC-IAAP-001 monitoring wells was not retained as a COPC. Typically, it would be anticipated that the total concentration of magnesium would be greater than the corresponding dissolved concentration, so this calls into question possible uncertainties related to analytical and sampling procedures. Nonetheless, because magnesium has no USEPA-approved toxicity criteria, no quantitative health risks were calculated as part of the risk characterization. Therefore, addressing magnesium as a COPC in groundwater, though not quantitatively evaluating magnesium for health risks, represents the most health-conservative approach available.


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The USEPA’s SSLs (USEPA 2020a) that are protective of groundwater from contaminants in soil were not applied in the determination of soil COPCs, as discussed in Section 3.2.1. Applications of the SSLs to soil data comparisons is considered overly conservative, because based on the evaluation of the soil to groundwater pathway in Section 6.3.1 of the RI Report (PIKA 2014a), this pathway is unlikely to be a significant pathway for the following reasons: (1) metal concentrations in soil approximate ranges of background concentrations detected at the installation, and (2) immobilization due to adsorption and precipitation, in conjunction with the effects of dilution, dispersion and other natural mechanisms, would likely prevent the migration of any significant chemical concentrations from soil into groundwater. However, not identifying soil COPCs based on data comparisons with the SSLs may result in a slight underestimation of ELCRs and non-cancer HIs relative to soil exposures under a Residential Land Use scenario. Overall, the screening method used to identify COPCs introduces uncertainties designed to overestimate health risks for potential residential receptors in this Residential BHHRA.

3.7.2 Exposure Assessment Uncertainties Uncertainties in the exposure assessment are inherent in assumptions made regarding future land uses and receptors, estimation of magnitude, frequency, and duration of exposures, and input values used to calculate chemical intakes. These are discussed in the following subsections (Sections 3.7.2.1 and 3.7.2.2).

3.7.2.1 Future Land Use and Potential Receptors As stated in the 2014 BHHRA (PIKA 2014a), there is little uncertainty associated with future land use and receptors. The U.S. Army is the current owner of the IAAAP property and has indicated that there are no plans to redevelop any land for residential use in the foreseeable future. Therefore, it is important to note that all assumptions regarding future residential developments of the CC-IAAP-001 and CC-IAAP-002 areas, as well as subsequent potential exposures to residents, are evaluated only for informational and decision-making purposes relative to a determination of UU/UE and NFA status. Although the Land Use of the IAAAP is Industrial, the Residential (Unrestricted) Land Use is evaluated as a means to fully assess baseline conditions. Because Residential (Unrestrictive) Land Use is considered protective for all potential receptors without limitations or use restrictions preventing exposure, the two construction debris areas were also evaluated using the Resident Receptor Exposure Scenario to determine UU/UE conditions, based on chemicals, with the knowledge that additional remedial actions are needed to remove the residual ACM before UU/UE conditions can be met for CC-IAAP-002. Evaluations of the Residential Land Use scenario at CC-IAAP-001 and CC-IAAP-002 tend to overestimate actual ELCRs and non-cancer HIs for soil when considering that the actual current and expected future use of these areas for disposal of construction debris. However, this uncertainty does not apply to groundwater because according to applicable CERCLA policy and guidance, groundwater at the OU-9 areas is classified as Class IIb, a potential source of drinking water. For this reason, and because land use is not considered during the groundwater classification process, this Residential BHHRA evaluated residential exposures to groundwater in the shallow overburden. For groundwater, USEPA guidance recommends once groundwater is determined to be suitable for drinking, risk-based concentrations should be based on residential exposures in order to restore the aquifer to beneficial use (e.g., drinking water standards) wherever practicable (USEPA 2009).


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3.7.2.2 Exposure Quantification Uncertainties Uncertainty is introduced through the process of estimating representative exposure concentrations for the evaluated exposure media. Analytical results were used to calculate a 95% UCL concentration. The lesser of the maximum detected concentration and the 95% UCL was used as the EPC for in this Residential BHHRA. This practice is designed to not underestimate EPCs, especially when considering that (1) surface soil and subsurface soil in the current configuration at CC-IAAP-001 and CC-IAAP-002 is assumed to be excavated, mixed, and used for grading of under the Residential Land Use scenario, and (2) a potential residential receptor is assumed to move randomly about his/her property and could become exposed to soil COPCs at any location on the property. Moderate uncertainty can be introduced in the data aggregation process for estimating a representative exposure concentration in the exposure media. USEPA’s ProUCL program (Version 5.1.002) applied statistical tests to determine the distribution that best describes the dataset for each chemical, within each area of concern. For each COPC, ProUCL then reports the 95% UCL associated with the distribution type that best describes the dataset of interest. The 95% UCLs are calculated both with and without detection limits. This method may moderately overestimate the exposure concentration. In addition, when the resulting individual contaminant risks are summed to provide a total ELCR or HI, the compounding conservatism of this method for estimating EPCs will likely result in an overestimation of the total risk. Additionally, it is conservatively assumed that chemical concentrations detected under current site conditions that existed several years ago will remain constant for evaluations of future exposure scenarios. In other words, the measured concentrations (and resulting EPCs) are not reduced by loss due to natural removal processes such as volatilization, leaching, and/or biodegradation. This assumption is a source of uncertainty that tends to overestimate exposure concentrations under a Residential Land Use scenario. Quantification of exposure provides an estimate of the chemical intake for various exposure pathways identified at the site. Aside from assumptions regarding land use scenarios and EPC calculations, uncertainties are also inherent in equations used to calculate intake for the evaluated exposure pathways, as well as within the exposure assumptions defined by the input values assigned to the equation exposure parameters. For each primary exposure pathway chosen for analysis in this Residential BHHRA, health-conservative assumptions were made concerning the routes of exposure and the input parameters governing intake rates. In the absence of area-specific data, the assumptions used are consistent with current USEPA-approved default values representing the RME scenario, so that upper bound estimates of chemical intakes, ELCRs, and HIs are calculated to ensure a health-conservative evaluation of the two construction debris areas.

3.7.3 Toxicity Assessment Uncertainties The method used to develop a non-cancer toxicity criterion (RfD or RfC) involves identifying a threshold level below which critical health effects are not expected to occur. The RfD and RfC values are generally based on studies of the sensitive animal species tested (unless adequate human data are available) and certain endpoints that can readily be measured. Uncertainties exist in the experimental data set for such animal studies. These studies are used to derive the experimental exposure representing the highest dose level tested at which no critical effects are measured (i.e., the no-observed-adverse-effect level [NOAEL]); in some cases, however, only a lowest-observed-adverse-effect level (LOAEL) is available. As noted by Tannenbaum and Comaty (2019) “It is not known that the critical effect of the animal study that supports the RfD is adverse


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(i.e., harmful), and it is unclear at what dose higher than an RfD, truly health compromising effects are triggered.” Further, for other than reproductive compromise (e.g., reduced litter size) and neurotoxic effects, the animal studies from which RfDs and RfCs derive do not (even) test for adversity. They instead only report on somatic differences observed, for which there was a statistically significant increase or decrease in incidence relative to the response of control animals. By way of example, should treated animals display a statistically enlarged liver, there is no information to say that the animals with that condition are any less healthy than control animals that did not display this change. In the same way, observed hydropic renal pelvis, hemosiderin deposition in the liver, or renal tubular epithelial vacuolation are not known to be adverse critical effects, and likely are not (Tannenbaum 2020). The RfD and/or RfC is derived from the NOAEL (or LOAEL) for the critical toxic effect by dividing the NOAEL (or LOAEL) by uncertainty factors. These factors usually are in multipliers of 10, with each factor representing a specific area of uncertainty in the extrapolation of the data. For example, an uncertainty factor of 100 is typically used when extrapolating animal studies to humans. Additional uncertainty factors are sometimes necessary when other experimental data limitations are found. Because of the large uncertainties (10 to 10,000) associated with some RfD or RfC toxicity values, safe levels of exposure for humans are not known. As in the critical effect from the toxicity studies, the application and the actual value of uncertainty factors to the NOAEL or LOAEL has not been verified or validated. It is likely these arbitrary values do not correlate to actual effects and are not measurable. For noncarcinogenic effects, the amount of human variability in physical characteristics is important in determining the risks that can be expected at low exposures and in determining the NOAEL (USEPA 1989). The toxicological data for dose response relationships of chemicals are frequently updated and revised, which can lead to overestimation or underestimation of risks. These values are often extrapolations from animals to humans, and this can also cause uncertainties in toxicity values because differences can exist in chemical absorption, metabolism, excretion, and toxic response between animals and humans. The USEPA considers differences in body weight, surface area, and pharmacokinetic relationships between animals and humans to minimize the potential to underestimate the dose-response relationship; as a result, more conservatism is usually incorporated into these steps. In particular, toxicity factors that have high uncertainties may change as new information is evaluated. Therefore, COPCs associated with high uncertainties in toxicity studies may be subject to regulatory change in the future. Finally, the toxicity of a contaminant may vary significantly with the chemical form present in the exposure medium. For example, risks from metals may be overestimated because they are conservatively assumed to be in their most toxic forms (e.g., chromium is assumed to be in the hexavalent form). The carcinogenic potential of a chemical can be estimated through a two-part evaluation involving (1) a WOE assessment to determine the likelihood that a chemical is a human carcinogen, and (2) a slope factor assessment to determine the quantitative dose-response relationship. Uncertainties occur with both assessments. The CSF for a chemical is a plausible upper-bound estimate of the probability of a response per unit intake of a chemical over a lifetime. It is used to estimate an upper-bound lifetime probability of an individual developing cancer as a result of exposure to a particular level of a potential carcinogen. The slope factor is derived by applying a mathematical model to extrapolate from a relatively high, administered dose to animals to the lower exposure levels expected for humans. The slope factor represents the 95% UCL on the linear component of the slope (generally the low-dose region) of the tumorigenic dose-response curve. A number of low-dose extrapolation


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models have been developed, and USEPA generally uses the linearized multi-stage model in the absence of adequate information to support other models. Therefore, methods used to derive SFs result in an overestimation of ELCRs in this Residential BHHRA.

3.7.4 Risk Characterization Uncertainties Risk assessment, as a scientific activity, is subject to uncertainty. This is true even though the method used in this HHRA follows USEPA guidelines. As noted previously, the risk characterization in this Residential BHHRA is subject to uncertainty pertaining to sampling and analysis, selection of COPCs, exposure estimates, and availability and quality of toxicity data. The subsections below describes risk characterization uncertainties encountered in this Residential BHHRA.

3.7.4.1 Risk Additivity for Chemicals Uncertainties related to the summation of HQs and ELCRs across chemicals and pathways are a primary uncertainty in the risk characterization, specifically, during the first step of the risk characterization of site-related COPCs and naturally occurring chemicals. In the absence of information on the toxicity of specific chemical mixtures, it is assumed that ELCRs and HQs are additive (i.e., cumulative) (USEPA 1989). The limitations of this approach for noncarcinogens are (1) the effects of a mixture of chemicals are generally unknown in that it is possible that the interactions could be synergistic, antagonistic, or additive, and (2) the RfDs and RfCs have different accuracy and precision and are not based on the same severity or effect. Limitations of the additive risk approach for multiple carcinogens are (1) according to the USEPA (USEPA 1989) the chemical-specific slope factors represent the upper 95th percentile estimate of potency, and because upper 95th percentiles of probability distributions are not strictly additive, the summing individual ELCRs can result in an excessively conservative estimate of total lifetime cancer risk; and (2) the target organs of multiple carcinogens may be different, so the risks would not be additive. In the absence of data, additivity for ELCRs over multiple chemicals is assumed for this Residential BHHRA, and is consistent with USEPA risk assessment guidance.

3.7.4.2 Chemicals without Available Toxicity Criteria Another uncertainty inherent with the characterization of total ELCRs and HIs for CC-IAAP-001 and CC-IAAP-002 are the presence of chemicals in soil and groundwater for which no toxicity criteria are established. These chemicals are retained as soil COPCs in Tables A-2.1 and B-2.1 for evaluation as part of this uncertainties analysis in order to determine if the presence of these chemicals could in a potential underestimation or health risks. These chemicals, not including the macronutrient metals, are presented below for CC-IAAP-001 and CC-IAAP-002, accordingly.

• Acenaphthylene (CC-IAAP-001 surface soil and soil; CC-IAAP-002 surface soil and soil), • Dimethyl phthalate (CC-IAAP-002 surface soil and soil), • Endrin aldehyde (CC-IAAP-001 surface soil and soil), • Benzo(g,h,i)perylene (CC-IAAP-001 surface soil and soil; CC-IAAP-002 surface soil and

soil), and • Phenanthrene (CC-IAAP-001 surface soil and soil; C-IAAP-002 surface soil, soil and

groundwater).


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Given that none of the above chemicals have established toxicity criteria for performing quantitative risk evaluations, typically, it is standard industry practice to apply surrogate values in order to provide some assessment as to the potential impacts regarding the uncertainty associated with the ELCRs and HIs calculated for COPCs for which toxicity criteria do exist. Typically, the surrogate chemicals selected for application of toxicity values should be similar in some key properties, (e.g., structure, toxicity and toxicological mechanisms, molecular weight, chemical properties, etc.). For the PAHs acenapthylene, benzo(g,h,i)perylene, and phenanthrene, other PAHs are selected based primarily on structure and number of aromatic rings comprising the molecules. Though the above-listed chemicals were retained as COPCs due to a lack of risk-based screening levels, for consistency with the 2014 BHHRA, no surrogate toxicity values were applied in order to calculate ELCRs and HIs for these chemicals during risk characterization. If toxicity criteria and risk-based screening levels were available for the above chemicals, it is possible that some of these chemicals would still have been retained as COPCs, while others would be eliminated. Hypothetically, assuming this to be the case, then the lack of available toxicity criteria for the above chemicals has resulted in an underestimation of the total receptors ELCRs and HIs, the magnitude of which is not known.

3.7.4.3 Estimation of Background Levels for Hexavalent Chromium Hexavalent chromium was identified as a COPC in unfiltered groundwater at both CC-IAAP-001 and CC-IAAP-002. As part of the risk characterization, maximum concentrations, ELCRs and HIs calculated for COPCs (i.e., metals) at both areas are compared to IAAAP-specific background BTVs, as well as ELCRs and HIs calculated for the BTVs, to determine if the presence of concentrations of COPCs are consistent with background conditions. Those COPCs with concentrations above background are retained as being potentially area-related COPCs for further evaluations. Those COPCs with concentrations below background are considered to be naturally occurring and not retained for further evaluations. The actual impacts of the previously described uncertainties on the estimation of area-specific groundwater BTVs are unknown, but cumulatively, they could result in either an over- or under-estimation of actual background levels that naturally occur under ambient conditions at each OU-9 area.


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4.0 SUPPLEMENTAL SCREENING LEVEL ECOLOGICAL RISK ASSESSMENT

A SLERA (2014 SLERA) was previously conducted at CC-IAAP-001 and CC-IAAP-002 in the RI Report (PIKA 2014a). By their nature, SLERAs are intended to be conservative and protective and often overestimate potential ecological risks. Despite the conservative evaluation, risks to ecological receptors were not anticipated in the RI Report (PIKA 2014a). However, as agreed with the USEPA, the SLERA was updated to consider potential ecological risks to federally-listed species that have been listed since the 2014 SLERA was completed. While these sites are very small and offer little habitat, the updated SLERA is proactive and further protective. The supplemental SLERA evaluated updated ecological receptor information and ecological screening levels to facilitate future decision-making regarding determinations of NFA status for CC-IAAP-001 and CC-IAAP-002 from an ecological perspective. The 2014 SLERA evaluated exposures of terrestrial and aquatic species to COPECs identified in surface soil, surface water, and sediment at CC-IAAP-001 (i.e., endrin aldehyde, arsenic, barium, cadmium, hexavalent chromium, lead, and selenium) and in surface soil and sediment at CC-IAAP-002 (i.e., 14 semivolatile organic compounds, arsenic, barium, hexavalent chromium, lead, selenium, and uranium). While there were HQs greater than 1.0 (ranging from 1.2 to 14 at CC-IAAP-001 and 1.6 to 19 at CC-IAAP-002), the weight-of-evidence evaluation indicated that risks to all ecological receptors at both areas are not anticipated and no additional remedial action is required from an ecological perspective.

However, the northern long‐eared bat (Myotis septentrionalis) and the rusty patched bumble bee (Bombus affinis) were added to the federally threatened and endangered species list subsequent to the completion of the SLERA. These species were not evaluated in the 2014 SLERA. A review of the federally listed threatened and endangered species in Iowa (USFWS 2018a) indicated that the rusty patched bumble bee is endangered in portions of four counties. However, Des Moines County, where IAAAP is located, is not one of the four counties of concern. As a result, no further evaluation of the rusty patched bumble bee at IAAAP is required. The northern long-eared bat is listed as threatened throughout the state of Iowa (USFWS 2018a). While the northern long-eared bat was not previously evaluated in the 2014 SLERA, the endangered Indiana bat was evaluated at both construction debris areas in the 2014 SLERA. The Indiana bat is listed as endangered in a number of counties in Iowa including Des Moines. Based on information presented by the U.S. Fish and Wildlife Service (USFWS) (USFWS 2018b), these species are fairly similar in ecology and life history. For example, USFWS (USFWS 2018b) notes that “the northern long-eared bat and Indiana bat are both temperate, insectivorous, migratory bats that hibernate in mines and caves in the winter and spend summers in wooded areas.” Both species typically hibernate mid-fall through mid-spring each year. Suitable summer habitats for both species include a wide variety of forested/wooded habitats where they roost, forage, and travel. Some adjacent and interspersed non-forested habitats such as emergent wetlands and adjacent edges of agricultural fields, old fields, and pastures could occur in the forested habitats. The main habitat difference between the two bats appears to be that northern long-eared bats are typically associated with upland forests with generally more canopy cover than Indiana bats. They prefer upland, mature forests (Caceres and Pybus 1997) with occasional foraging over forest clearings, water, and along roads (Jong 1985). However, most foraging occurs on forested hillsides and ridges, rather than along riparian areas preferred by the Indiana bat (Brack and Whitaker 2001; LaVal et al. 1977).


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Based on a qualitative evaluation, the 2014 SLERA (PIKA 2014a) concluded that potential risk to individual Indiana bats from COPECs detected in media at CC-IAAP-001 and CC-IAAP-002 was not anticipated. In particular, the forging range of Indiana bats is so large compared to the size of CC-IAAP-001 and CC-IAAP-002 that the evaluation is not spatially relevant. No additional sampling since the RI Report (PIKA 2014a) has been conducted so there is no new chemical data with which to revise the Indiana bat evaluation previously conducted in the 2014 SLERA. Based on their similar ecology and life history, similar negligible risks would be estimated for the northern long-eared bat. In fact, risks might even be lower for the northern long-eared bat than the Indiana bat because they do not preferentially forage along the riparian corridors like the Indiana bat. Bioaccumulation can be more appreciable in the aquatic versus terrestrial habitat (e.g., mercury) so contaminant uptake might be reduced in the terrestrial habitats where the northern long-eared bats prefer to forage. In summary, the northern long-eared bat was added to the federally endangered species list for Des Moines County after the 2014 SLERA was completed (PIKA 2014a). The Indiana bat was qualitatively evaluated in the 2014 SLERA (PIKA 2014a) and risks from potential exposure to media at both construction debris areas was determined to be negligible. Because no new chemical data have been collected and the ecology and life history is similar for the northern long-eared and Indiana bats, it is reasonable to conclude that risks to the northern long-eared bat also would be negligible. This Supplemental SLERA was also updated from the 2014 SLERA (PIKA 2014a) for applicability to current benchmarks. The 2014 SLERA (PIKA 2014a) focused on the screening of maximum detected concentrations against screening benchmarks. This is a standard component of a SLERA. For the 2014 SLERA, screening benchmarks were used to assess the potential for risks to ecological receptors to occur from exposure to chemical constituents in surface soil, surface water, and sediment. Screening benchmark values were based on conservative assumptions and represent, where possible, NOAELs for chronic exposures. From a chemical results perspective, the screens do not need to be updated because no new chemical data have been collected. The screening benchmarks in the 2014 SLERA were obtained following the selection hierarchy in the order presented as follows by medium:

Soil 1. USEPA Ecological Soil Screening Levels (Eco-SSLs) (USEPA 2003-2007). 2. USEPA Region V Ecological Screening Levels (ESLs) (USEPA 2003b). 3. Final selected NOAEL-based Critical Concentrations (CCs) for Terrestrial Receptors from

the Site-Wide Baseline Ecological Risk Assessment (MWH 2004) where CCs are lower than screening benchmarks identified from the previously listed sources, as specified in the RI Work Plan (PIKA 2013).

Surface Water 1. Iowa Water Quality Standards (Iowa Administrative Code [IAC] 2012). 2. USEPA Freshwater Chronic Ambient Water Quality Criteria (AWQC) (USEPA 2013). 3. ORNL Secondary Chronic Values (SCVs) for aquatic life (Suter and Tsao 1996). 4. USEPA Region V ESLs (USEPA 2003b). 5. Final selected NOAEL-based CCs for Aquatic Receptors from the Site-Wide Baseline

Ecological Risk Assessment (MWH 2004) where CCs are lower than screening benchmarks identified from the previously listed sources, as specified in the RI Work Plan (PIKA 2013).


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Sediment 1. Consensus-based threshold effects concentrations (TECs) (MacDonald et al. 2000). 2. Ontario Ministry of the Environment (OMOE) Lowest Effects Levels (LELs) (OMOE 1993). 3. ORNL Sediment SCVs (Jones, Suter, and Hull 1997). 4. USEPA Region V ESLs (USEPA 2003b). 5. Final selected NOAEL-based CC’s for Aquatic Receptors from the Site-Wide Baseline

Ecological Risk Assessment (MWH 2004) where CCs are lower than screening benchmarks identified from the previously listed sources, as specified in the RI Work Plan (PIKA 2013).

With the exception of the first two sources for surface water, the benchmarks in these sources do not typically change. The first two sources in the surface water screening benchmark hierarchy (Iowa Water Quality Standards from the IAC and the USEPA freshwater chronic aquatic life National Recommended Water Quality Criteria [NRWQC]) were checked for updates and compared against the screening benchmarks from these sources found in the RI Report Appendix G, Table G-3, “Selection of Surface Water COPECs from the Draft RIR for Construction Debris Sites” (PIKA 2014a). The current IAC (Chapter 61) is dated January 17, 2018; the USEPA NRWQC is not dated. Based on this comparison, there are no significant changes to surface water screening values. However, there are three minor findings:

1. The 2016 freshwater chronic criterion continuous concentration is 0.72 μg/L dissolved cadmium, based on a hardness of 100 milligrams per liter (mg/L) as calcium carbonate (CaCO3), and is an increase (i.e., less stringent) from the 2001 criteria of 0.25 μg/L dissolved cadmium, based on a hardness of 100 mg/L as CaCO3. This increase is primarily due to use of EC20s over maximum acceptable toxicant concentrations, new data for existing species, and the inclusion of a new sensitive genus (Cottus). Because the current benchmark in the SLERA (0.45 μg/L) is more conservative than the 2016 updated value of 0.72 μg/L the results of the SLERA would not change.

2. USEPA has conversion factors for hardness-dependent dissolved metals, so these benchmarks could be made specific to dissolved metals. However, with the current list of COPECs, this conversion would only apply to lead and use of the conversion factor does not result in an exceedance.

3. The IAC and USEPA have criteria for some water quality parameters (chloride, pH, and sulfide) which could be added to the table; however; none of these area-specific parameters exceed the criteria.

In summary, in order to determine the potential for ecological risk, the maximum detected concentrations were compared against screening benchmarks in the 2014 SLERA (PIKA 2014a). No additional chemical data have been collected subsequent to the completion of the 2014 SLERA (PIKA 2014a). A review of the screening benchmarks indicated that very few benchmarks have changed since the 2014 SLERA was completed. In the limited instances where a few of the surface water benchmarks could change, no significant changes to previously determined risk results would occur. As a result, no further updates of the 2014 SLERA are required. Based on the evaluation of the rusty patched bumble bee and northern long-eared bat along with an assessment of the chemical screening in the 2014 SLERA, the conclusion of the Supplemental SLERA is the same as that for the 2014 SLERA (PIKA 2014a), i.e., no ecological risks at


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CC-IAAP-001 from exposure to surface soil, surface water, and sediment and no ecological risks at CC-IAAP-002 from exposure to surface soil and sediment are anticipated. It bears noting that the USEPA ERA process (USEPA 1997a, 1998) is readily applied for CERCLA remedial investigations independent of considerations of the size, ecological relevance, or ecological significance of contaminated sites. Often however, a site may not need an ecological assessment based on the actual site features. In general, a SLERA is not required at terrestrial sites that only occupy a very few acres. Many areas on IAAAP such as CC-IAAP-001 and CC-IAAP-002 had SLERAs previously completed on them, and these efforts arguably were unnecessary. Where spatially relevant receptors of the sort that could form the basis of remedial action (i.e., receptors other than small rodents or earthworms) are present, the initial step in the SLERA is a comparison of concentrations of chemicals detected in site media to those of ecotoxicological-based screening values. This screening step does not account for ecological features or natural resource assets on the site. Importantly, considerations for an animal’s home range, population density, or other metrics that are readily available in the open literature, are not addressed in this screening step; if they were, relatively smaller sites would likely not be found to need ecological assessments. Such small sites generally do not support enough receptors that remedial actions would be required to provide for their protection and any protection provided would not be measurable. Caution should be exercised when reviewing the results of a SLERA completed for small sites that have no ecological significant resources and more specifically, where the results of such SLERAs are not readily translatable to realistic site conditions. Procedurally, the SLERA for areas CC-IAAP-001 and CC-IAAP-002 were completed to update the original SLERA per the request of the USEPA. The update included(s) a re-evaluation of potential receptors that could occur on the site to address if new federally-listed threatened and endangered (T&E) species could potentially use the areas for any purpose, and to re-evaluate the comparison of area concentrations to current ecological screening values that may have changed since the last SLERA was completed. This type of update does not consider spatial or temporal characteristics of the receptors and how they relate to the area. Both areas evaluated in this RI Addendum are very small and would not support the Northern long-eared bat spatially or ecologically and there is no risk evaluation method that has been developed for the rustic bumble bee. Area CC-IAAP-001 is approximately 1.3 acres and CC-IAAP-002 is approximately 0.63 acres. As stated, there is limited habitat and ecological resources on these areas.


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5.0 REFERENCES

ACCLPP 2012. Advisory Committee on Childhood Lead Poisoning Prevention. 2012. Low Level Lead Exposure Harms Children: A Renewed Call for Primary Prevention. Atlanta, GA. Centers for Disease Control and Prevention Available online at http://www.cdc.gov/ nceh/lead/ACCLPP/Final_Document_030712.pdf.

ATSDR 2013. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Uranium. Department of Health and Human Services, Public Health Service, Atlanta, GA. February.

Brack Jr., V. and J.O. Whitaker Jr. 2001. Foods of the northern myotis, Myotis septentrionalis, from Missouri and Indiana, with notes on foraging. Acta Chiropterologica 3:203–210.

Caceres, M.C. and M.J. Pybus 1997. Status of the northern long-eared bat (Myotis septentrionalis) in Alberta. Alberta Environmental Protection, Wildlife Management Division, Wildlife Status Report No. 3, Edmonton, AB, 19pp.

CalEPA 2020. California Environmental Protection Agency. Toxicity Criteria Database. Office of Environmental Health Hazard Assessment and Air Resources Board. Available online at https://oehha.ca.gov/air/general-info/oehha-acute-8-hour-and-chronic-reference-exposure-level-rel-summary. Accessed October 2020.

CDC 2007. Centers for Disease Control and Prevention. Interpreting and Managing Blood Lead Levels<10 μg/dL in Children and Reducing Childhood Exposures to Lead. Recommendations of CDC’s 13 Advisory Committee on Childhood Lead Poisoning Prevention. Morbidity Mortality Weekly Report, 14 2007. 56.

CH2M Hill 2017. Uniform Federal Policy-Quality Assurance Project Plan for Remedial Investigation at Iowa Army Ammunition Plant, Middletown, Iowa. Final. December.

CH2M Hill 2020. Evaluation of Background Concentrations of Metals in Groundwater, Iowa Army Ammunition Plant, Middletown, Iowa. Final. February.

IAC 2012. Iowa Administrative Code. Chapter 61: Water Quality Standards. May 16, 2012. IAEA 2020. International Atomic Energy Agency. “Depleted Uranium.” Obtained from IAEA

website at: https://www.iaea.org/topics/spent-fuel-management/depleted-uranium. Accessed October 2020.

Jones, D.S., G.W. Suter II, and R.N. Hull 1997. Toxicological Benchmarks for Screening Contaminants of Potential Concern for Effects on Sediment Associated Biota: 1997 Revision. Oak Ridge National Laboratories (ES/ER/TM-95/R4). November 1997.

Jong, C.G. Van Zyll De 1985. Handbook of Canadian Mammals: Bats. Univ. of Chicago Press. 212 pp. LaVal, R.K., R.L. Clawson, M.L. LaVal, W. Caire 1977. Foraging behavior and nocturnal activity

patterns of Missouri bats, with emphasis on the endangered species Myotis grisescens and Myotis sodalis. Journal of Mammalogy, 58(4):592-599.

MacDonald, D.D., C.G. Ingersoll, and T.A. Berger 2000. Development and Evaluation of Consensus-Based Sediment Quality Guidelines for Freshwater Ecosystem. Archives of Environmental Contamination and Toxicology 39:20-31.

MWH 2004. Draft Final Baseline Ecological Risk Assessment, Iowa Army Ammunition Plant. October.


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NJDEP 2009. New Jersey Department of Environmental Protection. Derivation of Ingestion-Based Soil Remediation Criterion for Cr+6 Based on the NTP Chronic Bioassay Data for Sodium Dichromate Dihydrate. Prepared for the Risk Assessment Subgroup of the NJDEP Chromium Workgroup. April 8.

OMOE 1993. Ontario Ministry of the Environment. Guidelines for the Protection and Management of Aquatic Sediment Quality in Ontario. ISBN 07729-9248-8. August, 1993.

ORNL 2014a. Oak Ridge National Laboratory. Calculation of Slope Factors and Dose Coefficients. ORNL/TM-2013/00. September.

ORNL 2014b. Oak Ridge National Laboratory. Area Correction Factors for Contaminated Soil for Use in Risk and Dose Assessment Models. ORNL/TM-2013/00. September.

ORNL 2020. Oak Ridge National Laboratory. Risk Assessment Information System (RAIS). Online Database found on the worldwide web at: http://rais.ornl.gov/home/about.html. Accessed October 2020.

PIKA 2013. PIKA International, Inc. Final Work Plan, Remedial Investigation of Construction Debris Sites CC-IAAP-001 and CC-IAAP-002. May.

PIKA 2014a. PIKA International, Inc. Remedial Investigation Report for Construction Debris Sites CC-IAAP-001 and CC-IAAP-002, Iowa Army Ammunition Plant, Middletown, Iowa. Volumes I and II. Prepared for Army Contracting Command–Rock Island. Final Report. March.

PIKA 2014b. PIKA International, Inc. Focused Feasibility Study Report for Construction Debris Sites CC-IAAP-001 and CC-IAAP-002. Prepared for Army Contracting Command–Rock Island. Final Report. August.

PIKA 2015. PIKA International, Inc. Final Proposed Plan for Construction Debris Sites CC-IAAP-001 and CC-IAAP-002. Prepared for Army Contracting Command–Rock Island. Final Report. January.

Suter, G.W., and C.L. Tsao 1996. Toxicological Benchmarks for Screening Potential Contaminants of Concern for Effects of Aquatic Biota: 1996 Revision. Prepared for the U.S. Department of Energy. ES/ER/TM-96/R2. June 1996.

Tannenbaum 2020. Personal communication: email dated August 25, 2020. From Lawrence Tannenbaum, Senior Health Risk Assessor, U.S. Army Public Health Center, to Jeffrey Leach, Chief Environmental Assessment Branch, U.S. Army Public Health Center. Subject: Draft RI Report IAAAP OU-9 RTCs (UNCLASSIFIED). August 2020.

Tannenbaum, L.V., and S.J. Comaty 2019. “A path forward for improved noncancer assessment: the truly adverse dose (the TAD).” Human and Ecological Risk Assessment: An International Journal. January 3, 2019.

U.S. Army and USEPA 1990. U.S. Army and U.S. Environmental Protection Agency. Iowa Army Ammunition Plant Federal Facility Agreement Under CERCLA Section 120, Administrative Docket Number: VII-F-90-0029.

USACE 1995. U.S. Army Corps of Engineers, Engineering and Design, Washington, D.C. Risk Assessment Handbook, Human Health Evaluation, Volume I: Human Health Evaluation. EM 200-1-4. June 30.


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USACE 1998. U.S. Army Corps of Engineers, Omaha District, Omaha, NE. Record of Decision, Soils Operable Unit #1, Iowa Army Ammunition Plant, Middletown, Iowa. Revision 1, September 29.

USACE 2008. U.S. Army Corps of Engineers, St. Louis District Formerly Utilized Remedial Action Program (FUSRAP). Iowa Army Ammunition Plant FUSRAP Remedial Investigation Report for Firing Sites Area, Yards C, E, F, G, and L, Warehouse 3-01 and Area West of Line 5B, Middletown, Iowa, Final. October 8.

USDA 2014. U.S. Department of Agriculture, Online Database Found at: http://fnic.nal.usda.gov/dietary-guidance/dietary-reference-intakes/dri-tables.

USEPA 1986. U.S. Environmental Protection Agency, Risk Assessment Forum, Washington, D.C. Guidelines for Carcinogen Risk Assessment. EPA/630/R-00-004. September.

USEPA 1988. U.S. Environmental Protection Agency, Office of Emergency and Remedial Response, Washington, D.C. Guidance for Conducting Remedial Investigations and Feasibility Studies under CERCLA. Interim Final. EPA/540/G-89/004; OSWER Directive 9355.3-01. October.

USEPA 1989. U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, Washington, D.C. Risk Assessment Guidance for Superfund, Volume I, Human Health Evaluation Manual (Part A). Interim Final. EPA/540/1-89/002. December.

USEPA 1990. U.S. Environmental Protection Agency. National Oil and Hazardous Substances Contingency Plan. Final Rule. 40 CFR Part 300.

USEPA 1991. U.S. Environmental Protection Agency, Office of Emergency and Remedial Response, Washington, D.C. Risk Assessment Guidance for Superfund, Volume I, Human Health Evaluation Manual (Part B, Development of Risk-Based Preliminary Remediation Goals). Interim. EPA/540/R-92/003; Publication 9285.7-01B. December.

USEPA 1992. U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, Washington, D.C. Supplemental Guidance to RAGS: Calculating the Concentration Term. Publication 9285.7-08I. May.

USEPA 1994. U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response (OSWER), Washington, D.C. Guidance Manual for the IEUBK Model for Lead in Children. PB93-963510; OSWER #9285.7-15-1. February.

USEPA 1995. U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response (OSWER), Washington, D.C. Land Use in the CERCLA Remedy Selection Process. OSWER Directive No. 9355.7-04. May 25.

USEPA 1996. U.S. Environmental Protection Agency, Office of Air and Radiation, Washington, D.C. Radiation Exposure and Risks Assessment Manual (RERAM), Risk Assessment Using Radionuclide Slope Factors. EPA 402-R-96-016. June.

USEPA 1997a. U.S. Environmental Protection Agency, Washington, D.C. Ecological risk assessment guidance for Superfund: Process for Designing and Conducting Ecological Risk Assessments. Interim Final. EPA 540-R-97-006.

USEPA 1997b. U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, Washington, D.C. Health Effects Assessment Summary Tables (HEAST), FY 1997 Update. EPA-540-R-97-036 and PB97-92119. July.


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USEPA 1998. U.S. Environmental Protection Agency, Washington, D.C. Guideline for Ecological Risk Assessment. USEPA. EPA/630/R-95/002F.

USEPA 1999. U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, Washington, D.C. Radiation Risk Assessment at CERCLA Sites: Q&A. Directive 9200.4-31P; EPA 540/R/99/006. December.

USEPA 2001. U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, Washington, D.C. Risk Assessment Guidance for Superfund, Volume I: Human Health Evaluation Manual (Part D, Standardized Planning, Reporting, and Review of Superfund Risk Assessments). Final. OSWER 9285.7-47. December.

USEPA 2002. U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, Washington, D.C. Calculating Upper Confidence Limits for Exposure Point Concentrations at Hazardous Waste Sites. OSWER 9285.6-10. December.

USEPA 2003a. U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, Washington, D.C. Human Health Toxicity Values in Superfund Risk Assessments. OSWER Directive 9285.7-53. December 5.

USEPA 2003b. U.S. Environmental Protection Agency, Region V. RCRA Ecological Screening Levels. August 22, 2003.

USEPA 2003–2007. U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, Washington, DC. Ecological Soil Screening Levels (Eco-SSLS). Various Interim Publications. OSWER Directive 9285.7-73.

USEPA 2004. U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, Washington, D.C. Risk Assessment Guidance for Superfund, Volume I: Human Health Evaluation Manual (Part E, Supplemental Guidance for Dermal Risk Assessment). Final. EPA/540/R/99/005; OSWER 9285.7-02EP; PB99-963312. July.

USEPA 2005a. U.S. Environmental Protection Agency, Risk Assessment Forum, Washington, D.C. Supplemental Guidance for Assessing Cancer Susceptibility from Early Life Exposures to Carcinogens. EPA/630/R-03/003F. March.

USEPA 2005b. U.S. Environmental Protection Agency, Risk Assessment Forum, Washington, D.C. Guidelines for Carcinogen Risk Assessment. EPA/630/P-03/001B. March.

USEPA 2009. U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, Washington, D.C. Risk Assessment Guidance for Superfund, Volume I: Human Health Evaluation Manual (Part F, Supplemental Guidance for Inhalation Risk Assessment). Final. EPA-540-R-070-002; OSWER 9285.7-82. January.

USEPA 2011. U.S. Environmental Protection Agency, Office of Research and Development, National Center for Environmental Assessment, Washington, D.C. Exposure Factors Handbook: 2011 Edition. EPA/600/R-09/052F. September.

USEPA 2013. U.S. Environmental Protection Agency, Office of Water and Office of Science Technology. National Recommended Water Quality Criteria. February 8.

USEPA 2014. U.S. Environmental Protection Agency. Human Health Evaluation Manual, Supplemental Guidance: Update of Standard Default Exposure Factors. OSWER Directive 9200.1-120, Washington, D.C. February 6.


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USEPA 2015. U.S. Environmental Protection Agency, Office of Research and Development, Washington, D.C. ProUCL Version 5.1.002 User Guide, Statistical Software for Environmental Applications for Data Sets with and without Nondetect Observations. EPA/600/R-07/041. October.

USEPA 2017a. U.S. Environmental Protection Agency, Office of Land and Emergency Management, Washington, D.C. Recommendations for Default Age Range in the IEUBK Model Transmittal Memorandum and Document. OLEM Directive 9200.2-177. November 15.

USEPA 2017b. U.S. Environmental Protection Agency, Office of Land and Emergency Management. Transmittal of the Update of the Adult Lead Methodology’s Default Baseline Blood Lead Concentration and Geometric Standard Deviation Parameters. OLEM Directive 9285.6-56. May 17.

USEPA 2019. U.S. Environmental Protection Agency. Memorandum (No Subject) from Mr. Danny O’Connor, USEPA Region 7 Remedial Project Manager, to Ms. Jennifer Busard, IAAAP Project Manager. June 10.

USEPA 2020a. U.S. Environmental Protection Agency. Regional Screening Levels (May 2020). Available online at https://www.epa.gov/risk/regional-screening-levels-rsls-generic-tables. Accessed May 2020.

USEPA 2020b. U.S. Environmental Protection Agency. Vapor Intrusion Screening Level Calculator. Available online at https://www.epa.gov/vaporintrusion/vapor-intrusion-screening-level-calculator. Accessed April 2019.

USEPA 2020c. U.S. Environmental Protection Agency. Radiological Preliminary Remediation Goal Calculator and User Guide. Available online at https://www.https://https://epa-prgs.ornl.gov/radionuclides/users_guide.htmll. Accessed October 2020.

USEPA 2020d. U.S. Environmental Protection Agency. Memorandum (No Subject) from Mr. Danny O’Connor, USEPA Region 7 Remedial Project Manager, to Ms. Jennifer Busard, IAAAP Project Manager. Signed September 24.

USEPA 2020e. U.S. Environmental Protection Agency. Integrated Risk Information System. Available online at https://www.epa.gov/iris. Accessed February 2020.

USEPA 2020f. U.S. Environmental Protection Agency. Chromium in Drinking Water. Available online at https://www.epa.gov/sdwa/chromium-drinking-water. Accessed May 2020.

USFWS 2018a. Iowa County Distribution of Federally Threatened, Endangered, Proposed and Candidate Species. Available online at https://www.fws.gov/midwest/endangered/lists/ iowa_cty.html. Species Table listed as revised on May 18, 2017, while web page last updated on March 12, 2018.

USFWS 2018b. Programmatic Biological Opinion for Transportation Projects in the Range of the Indiana Bat and Northern Long-Eared Bat. Midwest Regional Office, Bloomington, MN. February.


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FIGURES


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SCO<ACP> W:\IAAAP IRP\GIS\OU-9 Residential & Eco Risk Assessment\Projects\Figure 1 Construction Debris Site #1 CC-IAAP-001.mxd lawsond 4/17/2019 10:41:00 AM</ACP>

I

H

CC-IAAP-001

LEGENDRailroadTributary/Drainage DitchArea Boundary

Figure 1. CC-IAAP-001 Layout and LocationIowa Army Ammunition PlantMiddletown, Iowa

0 100Feet$

Skunk RiverWatershed

Long CreekWatershed

Brush CreekWatershed

Spring CreekWatershed

AreaLocation

Esri World Imagery Basemap

SCO<ACP> W:\IAAAP IRP\GIS\OU-9 Residential & Eco Risk Assessment\Projects\Figure 2 Construction Debris Site #2 CC-IAAP-002.mxd caseltona 11/28/2018 7:04:29 AM</ACP>

Brush CreekCC-IAAP-002

LEGENDCreekTributary/Drainage DitchArea BoundaryRailroad

Figure 2. CC-IAAP-002 Layout and LocationIowa Army Ammunition PlantMiddletown, Iowa

0 50Feet

Skunk RiverWatershed

Long CreekWatershed

Brush CreekWatershed

Spring CreekWatershed

AreaLocation

Esri World Imagery Basemap

Primary

Source

Release

MechanismMedia

Transport and

MigrationMedia Exposure Routes

Ecological

Receptors

Figure 3. CC‐IAAP‐001 Conceptual Exposure Model

SOURCE INTERACTION

Human Receptors

(Current / Future)

RECEPTORS

Resident

Terrestrial

Biota

Inhalation of Dust ○/●

Ingestion ○/○ ○

Dermal Contact ○/○ ○

Ingestion ○/○ ●

Ingestion/Inhalation 4 ○/● ●Dermal Contact 5 ○/● ○External Radiation ○/● ○

Ingestion/Inhalation 4 ○/● ○Dermal Contact 5 ○/● ○External Radiation ○/● ○


1 Surface water occurs only during storm events. Therefore, for exposure evaluations, dry sediment is treated as surface soil.2 For exposure evaluations, surface soil also includes dry sediment treated as surface soil.3 Depth to water ranges from 13 to 32 feet bgs.4 Ingestion and inhlation are exposure routes considered for chemicals and radionuclides.5 Dermal contact is an exposure route considered for only chemicals.

Flow Chart Continues

Insignificant Pathway

● Potentially Complete Pathway

○ Incomplete Pathway

Complete but Significance Unknown

LEGENDReceptor Potential Exposure Activity Exposure Media/Pathway

Terrestrial Biota Birds and mammals foraging Surface Soil (Ingestion), Biota (Ingestion)

Resident Residential activities Dust Inhalation (chemicals and radionuclides),

Soil/Groundwater (Ingestion and Inhalation (chemicals and

radionuclides), Dermal (chemicals), and external radiation

Discarding of construction and

demolition debris (scattered

bricks, corrugated metal, metal

parts, wire, and metal banding)

Runoff

Leaching/ Infiltration

Fugitive Dust

Soil

Air

Surface Water/ Sediment 1

Biota

Subsurface Soil

Uptake

Groundwater 3

SurfaceDebris

Surface Soil 2

IRP Activities:

•No buildings present at or near the site

•Nature and extent of soil, sediment, surface water, and groundwater were adequately characterized during the 2014 RI

•Visual inspection and soil sampling for asbestos during 2014 RI indicated no ACM in debris piles or asbestos fibers in soil; no air samples collected

•2014 HHRA indicated no unacceptable risk to current and future hunters (adolescent and adult), future outdoor site workers, and future construction workers

•2014 SLERA indicated an acceptable risk to ecological receptors and no further evaluation of risk was required

Primary

Source

Release

MechanismMedia

Transport and

MigrationMedia Exposure Routes

Ecological

Receptors

Figure 4. CC‐IAAP‐002 Conceptual Exposure Model

SOURCE INTERACTION

Human Receptors

(Current / Future)

RECEPTORS

Resident

Terrestria

l Biota

Inhalation of Fibers ○/○

Inhalation of Dust ○/●

Ingestion ○/○ ○

Dermal Contact ○/○ ○

Ingestion ○/○ ●

Ingestion/Inhalation 5 ○/● ●Dermal Contact 6 ○/● ○External Radiation ○/● ○


Ingestion/Inhalation 5 ○/● ○

Dermal Contact 6 ○/● ○External Radiation ○/● ○

2 There is no surface water on the site. Dry sediment is considered surface soil.3 For exposure evaluations, surface soil also includes dry sediment treated as surface soil.4 Depth to water was approximately 12 feet bgs.5 Ingestion and inhlation are exposure routes considered for chemicals and radionuclides.

LEGEND 6 Dermal contact is an exposure route considered for only chemicals.

Flow Chart Continues

Insignificant Pathway

● Potentially Complete Pathway

○ Incomplete Pathway

Complete but Significance Unknown

Terrestrial Biota Birds and mammals foraging Surface Soil (Ingestion), Biota (Ingestion)

Receptor Potential Exposure Activity Exposure Media/Pathway

Resident Residential activities Dust Inhalation (chemicals and radionuclides), Soil/ Groundwater

(Ingestion and Inhalation (chemicals and radionuclides), Dermal

(chemicals), and external radiation

1 Although non‐detects were reported as the results of all ACM soil sample analyses and air samples were not collected, the ACM pathway to both soil and to are considered to be

potentially complete to a hypothetical future resident due to the continued presence of friable ACM that was observed in the debris piles. However, the expected implementation of

Remedial Alternative #4, which includes the removal of ACM from debris piles at CC‐IAAP‐002 as described in the Focused Feasibility Study (PIKA 2014), will mitigate all ACM

exposure pathways.

Discarding of construction

and demolition debris

(scattered bricks,

corrugated metal, metal

parts, wire, and metal banding)

Runoff

Leaching/ Infiltration

Fugitive Dust

Soil

Air

Sediment 2

Biota

Subsurface Soil

Uptake

Groundwater 4

SurfaceDebris

Surface Soil 3

IRP Activities:

•No buildings present at or near the site

•Nature and extent of soil, sediment, surface water, and groundwater were adequately characterized during the 2014 RI

•Visual inspection during 2014 RI found roofing material‐based ACM (chrysotile) in three areas of the debris piles that exhibited disintegration due to prolonged weathering; no asbestos fibers were detected in soil; no air samples were collected

•2014 HHRA indicated no unacceptable risk to current and future hunters (adolescent and adult), future outdoor site workers, and future construction workers

•2014 SLERA indicated an acceptable risk to ecological receptors and no further evaluation of risk was required

Friable ACM 1

Airborne Air


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APPENDIX A

RISK ASSESSMENT TABLES (USEPA RAGS PART D) FOR THE CC-IAAP-001 RESIDENTIAL BHHRA AND SUPPORTING CALCULATIONS

(On the CD-ROM on the Back Cover of this Report)


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ATTACHMENT A-1

CALCULATIONS OF ISOTOPIC URANIUM CONCENTRATIONS IN SOIL AND GROUNDWATER AT CC-IAAP-001



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ATTACHMENT A-2

CALCULATIONS OF EXPOSURE POINT CONCENTRATIONS FOR CHEMICALS OF POTENTIAL CONCERN IN SURFACE SOIL (0 TO 0.5 FT BGS) AT CC-IAAP-001



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ATTACHMENT A-3

CALCULATIONS OF EXPOSURE POINT CONCENTRATIONS FOR RADIONUCLIDES OF POTENTIAL CONCERN IN SURFACE SOIL (0 TO 0.5 FT BGS)

AT CC-IAAP-001



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ATTACHMENT A-4

CALCULATIONS OF EXPOSURE POINT CONCENTRATIONS FOR CHEMICALS OF POTENTIAL CONCERN IN SOIL (0 TO 10 FT BGS) AT CC-IAAP-001



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ATTACHMENT A-5

CALCULATIONS OF EXPOSURE POINT CONCENTRATIONS FOR RADIONUCLIDES OF POTENTIAL CONCERN IN SOIL (0 TO 10 FT BGS) AT CC-IAAP-001



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ATTACHMENT A-6

CALCULATIONS OF EXPOSURE POINT CONCENTRATIONS FOR CHEMICALS AND RADIONUCLIDES OF POTENTIAL CONCERN IN SHALLOW

GROUNDWATER AT CC-IAAP-001



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ATTACHMENT A-7

OUTPUT FOR INTEGRATED EXPOSURE UPTAKE BIOKINETIC MODEL FOR ASSESSING POTENTIAL CHILD HEALTH RISKS FOLLOWING LEAD EXPOSURES

AT CC-IAAP-001



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APPENDIX B

RISK ASSESSMENT TABLES (USEPA RAGS PART D) FOR THE CC-IAAP-002 RESIDENTIAL BHHRA AND SUPPORTING CALCULATIONS



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ATTACHMENT B-1

CALCULATIONS OF ISOTOPIC URANIUM CONCENTRATIONS IN SOIL AND GROUNDWATER AT CC-IAAP-002



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ATTACHMENT B-2

CALCULATIONS OF EXPOSURE POINT CONCENTRATIONS FOR CHEMICALS OF POTENTIAL CONCERN IN SURFACE SOIL (0 TO 0.5 FT BGS) AT CC-IAAP-002



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ATTACHMENT B-3

CALCULATIONS OF EXPOSURE POINT CONCENTRATIONS FOR RADIONUCLIDES OF POTENTIAL CONCERN IN SURFACE SOIL (0 TO 0.5 FT BGS)

AT CC-IAAP-002



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ATTACHMENT B-4

CALCULATIONS OF EXPOSURE POINT CONCENTRATIONS FOR CHEMICALS OF POTENTIAL CONCERN IN SOIL (0 TO 10 FT BGS) AT CC-IAAP-002



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ATTACHMENT B-5

CALCULATIONS OF EXPOSURE POINT CONCENTRATIONS FOR RADIONUCLIDES OF POTENTIAL CONCERN IN SOIL (0 TO 10 FT BGS) AT CC-IAAP-002



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ATTACHMENT B-6

CALCULATIONS OF EXPOSURE POINT CONCENTRATIONS FOR CHEMICALS AND RADIONUCLIDES OF POTENTIAL CONCERN IN SHALLOW

GROUNDWATER AT CC-IAAP-002



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APPENDIX C

RADIOLOGICAL PRELIMINARY REMEDIATION GOAL CALCULATIONS



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ATTACHMENT C-1

CALCULATIONS OF RADIOLOGICAL PRELIMINARY REMEDIATION GOALS FOR RESIDENTIAL SOIL



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ATTACHMENT C-2

CALCULATIONS OF RADIOLOGICAL PRELIMINARY REMEDIATION GOALS FOR RESIDENTIAL TAP WATER



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