draft source areas, soil, and facility · table of contents (continued)...

DRAFT SOURCE AREAS, SOIL, AND FACILITY

STRUCTURES HUMAN HEALTH RISK ASSESSMENT Phoenix-Goodyear Airport-North Superfund Site

Goodyear, Arizona

Submitted to: United States Environmental Protection Agency

Submitted by: AMEC Environment & Infrastructure

Scottsdale, Arizona

July 2012

Project 0146820004

SDMS DOCID#1142156

DRAFT SOURCE AREAS, SOIL, AND FACILITY STRUCTURES HUMAN HEALTH RISK ASSESSMENT

Phoenix–Goodyear Airport–North Superfund Site Goodyear, Arizona July 9, 2012 Project No. 014682.012

This Draft Report was prepared by the staff of AMEC under the supervision of the Engineers and/or Geologists whose seals and signatures appear hereon.

The findings, recommendations, specifications, or professional opinions are presented within the limits described by the client, in accordance with generally accepted professional engineering and geologic practice. No warranty is expressed or implied.

DRAFT Ann Holbrow-Verwiel Principal Toxicologist

DRAFT Stephanie L. Koehne, MBA Project Manager

DRAFT Paul Jeffers, PG Senior Hydrogeologist

DRAFT Caryn A. Kelly Senior Toxicologist

.

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TABLE OF CONTENTS

Page

EXECUTIVE SUMMARY .............................................................................................. 1 1.0 INTRODUCTION ................................................................................................ 1

1.1 OBJECTIVES .............................................................................................. 1 1.2 APPROACH ................................................................................................ 1 1.3 REPORT ORGANIZATION ............................................................................. 2

2.0 SITE CHARACTERIZATION .............................................................................. 3 2.1 SITE DESCRIPTION AND HISTORY ................................................................ 3 2.2 OPERATIONAL HISTORY .............................................................................. 3 2.3 PREVIOUS INVESTIGATIONS ......................................................................... 4 2.4 ON-SITE REMEDIATION SYSTEMS ................................................................ 7 2.5 GENERAL GEOLOGY/HYDROGEOLOGY ......................................................... 8

2.5.1 Upper Alluvial Unit ........................................................................ 9 2.5.1.1 Subunit A ........................................................................ 9 2.5.1.2 Subunit B ........................................................................ 9 2.5.1.3 Subunit C ........................................................................ 9

2.5.2 Middle Alluvial Unit ........................................................................ 9 2.5.3 Lower Alluvial Unit ...................................................................... 10

3.0 DATA EVALUATION AND SELECTION OF CHEMICALS OF POTENTIAL CONCERN .................................................................................................................. 10

3.1 DATA QUALITY ......................................................................................... 10 3.2 DATA USED IN RISK ASSESSMENT ............................................................. 12

3.2.1 Groundwater ............................................................................... 12 3.2.2 Soil Vapor ................................................................................... 13 3.2.3 Soil .............................................................................................. 14 3.2.4 Duplicate Samples ...................................................................... 15

3.3 CHEMICAL CHARACTERIZATION ................................................................. 15 3.3.1 Groundwater ............................................................................... 15 3.3.2 Soil Vapor ................................................................................... 16 3.3.3 Soil .............................................................................................. 16

3.4 SELECTION OF CHEMICALS OF POTENTIAL CONCERN .................................. 16 3.4.1 Groundwater ............................................................................... 17 3.4.2 Soil Vapor ................................................................................... 17 3.4.3 Soil .............................................................................................. 17

3.4.3.1 Comparison to Background .......................................... 17 4.0 EXPOSURE ASSESSMENT ............................................................................ 19

4.1 CHARACTERIZATION OF EXPOSURE SETTING .............................................. 20 4.1.1 Physical Setting .......................................................................... 20 4.1.2 Land and Water Use ................................................................... 21 4.1.3 Potential Receptors ..................................................................... 21 4.1.4 Exposure Areas .......................................................................... 21

TABLE OF CONTENTS (Continued)

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4.2 IDENTIFICATION OF EXPOSURE PATHWAYS ................................................. 22 4.2.1 Sources, Mechanisms of Releases, and Mechanisms of Transport23 4.2.2 Exposure Points and Routes....................................................... 24 4.2.3 Exposure Pathways .................................................................... 24

4.3 EXPOSURE QUANTIFICATION ..................................................................... 25 4.3.1 Exposure Point Concentrations ................................................... 26

4.3.1.1 Groundwater ................................................................. 26 4.3.1.2 Soil Vapor ..................................................................... 27 4.3.1.3 Soil ................................................................................ 28 4.3.1.4 Ambient Air ................................................................... 28 4.3.1.5 Indoor Air ...................................................................... 28

4.3.2 Exposure Equations .................................................................... 29 4.3.3 Exposure Parameters ................................................................. 29

4.3.3.1 Trespasser .................................................................... 29 4.3.3.2 Outdoor and Indoor Commercial/Industrial Worker ....... 30 4.3.3.3 Construction Worker ..................................................... 31 4.3.3.4 Tap Water ..................................................................... 31

5.0 TOXICITY ASSESSMENT ............................................................................... 32 5.1 TOXICITY CRITERIA FOR NONCARCINOGENIC HEALTH RISKS ........................ 33 5.2 TOXICITY CRITERIA FOR CARCINOGENIC HEALTH RISKS .............................. 34

5.2.1 Early Life Susceptibility to Mutagens .......................................... 34 5.3 TOXICITY CRITERIA USED IN HEALTH RISK ASSESSMENT ............................. 35

6.0 RISK CHARACTERIZATION ............................................................................ 35 6.1 NONCARCINOGENIC HEALTH EFFECTS ....................................................... 35 6.2 CARCINOGENIC EFFECTS .......................................................................... 41

7.0 UNCERTAINTY ANALYSIS ............................................................................. 45 7.1 DATA EVALUATION AND SELECTION OF CHEMICALS OF POTENTIAL CONCERN 46 7.2 EXPOSURE ASSESSMENT .......................................................................... 46 7.3 TOXICITY ASSESSMENT ............................................................................ 49 7.4 UNCERTAINTY ASSOCIATED WITH RISK CHARACTERIZATION ........................ 51 7.5 CONCLUSIONS OF UNCERTAINTY ANALYSIS ................................................ 52

8.0 EVALUATION OF POTENTIAL LEACHING FROM SOIL TO GROUNDWATER52 9.0 CONCLUSIONS ............................................................................................... 53

9.1 SUMMARY OF RESULTS BY RECEPTOR ....................................................... 53 9.2 SUMMARY OF RESULTS BY EXPOSURE AREA .............................................. 57 9.3 SUMMARY OF RESULTS BY ENVIRONMENTAL MEDIA .................................... 58

10.0 REFERENCES ................................................................................................. 60


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TABLES

Table 1 Groundwater Analytical Results Used in Risk Assessment Table 2 Soil Vapor Analytical Results Used in Risk Assessment Table 3 Soil Analytical Results Used in Risk Assessment – Volatile Organic Compounds

(VOCs) Table 4 Soil Analytical Results Used in Risk Assessment – Metals Table 5 Soil Analytical Results Used in Risk Assessment – Nitrate, Perchlorate, and

Bis-(2-ethylhexyl) phthalate Table 6 Soil Analytical Results Used in Risk Assessment – Explosives Table 7 Soil Analytical Results Used in Risk Assessment – Pesticides Table 8 Occurrence, Distribution, and Selection of Chemicals of Potential Concern –

Groundwater Table 9 Occurrence, Distribution, and Selection of Chemicals of Potential Concern –

Soil Vapor Table 10 Occurrence, Distribution, and Selection of Chemicals of Potential Concern –

Soil Table 11 Selection of Exposure Pathways Table 12 Exposure Point Concentration Summary – Groundwater Table 13A Exposure Point Concentration Summary – Soil Vapor – Exposure Area A Table 13B Exposure Point Concentration Summary – Soil Vapor – Exposure Area B Table 13C Exposure Point Concentration Summary – Soil Vapor – Exposure Area C Table 13D Exposure Point Concentration Summary – Soil Vapor – Exposure Area D Table 13E Exposure Point Concentration Summary – Soil Vapor – Exposure Area E Table 14A Exposure Point Concentration Summary – Surface Soil – Exposure Area A Table 14B Exposure Point Concentration Summary – Surface Soil – Exposure Area B Table 14C Exposure Point Concentration Summary – Surface Soil – Exposure Area C Table 14D Exposure Point Concentration Summary – Surface Soil – Exposure Area D Table 14E Exposure Point Concentration Summary – Surface Soil – Exposure Area E Table 15A Exposure Point Concentration Summary – Subsurface Soil – Exposure Area A Table 15B Exposure Point Concentration Summary – Subsurface Soil – Exposure Area B Table 15C Exposure Point Concentration Summary – Subsurface Soil – Exposure Area C Table 15D Exposure Point Concentration Summary – Subsurface Soil – Exposure Area D Table 15E Exposure Point Concentration Summary – Subsurface Soil – Exposure Area E Table 16 Values Used for Daily Intake Calculations – Trespasser Table 17 Values Used for Daily Intake Calculations – Outdoor Commercial/Industrial

Worker Table 18 Values Used for Daily Intake Calculations – Indoor Commercial/Industrial

Worker Table 19 Values Used for Daily Intake Calculations – Construction Worker Table 20 Values Used for Daily Intake Calculations – Tap Water Table 21 Non-Cancer Toxicity Data – Oral/Dermal Table 22 Non-Cancer Toxicity Data – Inhalation Table 23 Cancer Toxicity Data – Oral/Dermal Table 24 Cancer Toxicity Data – Inhalation


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Table 25 Summary of Receptor Risks and Hazards for COPCs – Source Area Groundwater

Table 26A-1 Summary of Receptor Risks and Hazards for COPCs – Exposure Area A - Indoor Commercial/Industrial Worker, Pre-Remediation Soil Vapor (Prior to May 2004)

Table 26A-2 Summary of Receptor Risks and Hazards for COPCs – Exposure Area A - Indoor Commercial/Industrial Worker, Ongoing Remediation Soil Vapor (After 2007)

Table 26B-1 Summary of Receptor Risks and Hazards for COPCs – Exposure Area B - Indoor Commercial/Industrial Worker, Pre-Remediation Soil Vapor (Prior to May 2004)

Table 26B-2 Summary of Receptor Risks and Hazards for COPCs – Exposure Area B - Indoor Commercial/Industrial Worker, Ongoing Remediation Soil Vapor (After 2007)

Table 26C-1 Summary of Receptor Risks and Hazards for COPCs – Exposure Area C - Indoor Commercial/Industrial Worker, Pre-Remediation Soil Vapor (Prior to May 2004)

Table 26C-2 Summary of Receptor Risks and Hazards for COPCs – Exposure Area C - Indoor Commercial/Industrial Worker, Ongoing Remediation Soil Vapor (After 2007)

Table 26D-1 Summary of Receptor Risks and Hazards for COPCs – Exposure Area D - Indoor Commercial/Industrial Worker, Pre-Remediation Soil Vapor (Prior to May 2004)

Table 26D-2 Summary of Receptor Risks and Hazards for COPCs – Exposure Area D - Indoor Commercial/Industrial Worker, Ongoing Remediation Soil Vapor (After 2007)

Table 26E-1 Summary of Receptor Risks and Hazards for COPCs – Exposure Area E - Indoor Commercial/Industrial Worker, Pre-Remediation Soil Vapor (Prior to May 2004)

Table 26E-2 Summary of Receptor Risks and Hazards for COPCs – Exposure Area E - Indoor Commercial/Industrial Worker, Ongoing Remediation Soil Vapor (After 2007)

Table 27A Summary of Receptor Risks and Hazards for COPCs – Exposure Area A - Trespasser

Table 27B Summary of Receptor Risks and Hazards for COPCs – Exposure Area B - Trespasser

Table 27C Summary of Receptor Risks and Hazards for COPCs – Exposure Area C - Trespasser

Table 27D Summary of Receptor Risks and Hazards for COPCs – Exposure Area D - Trespasser

Table 27E Summary of Receptor Risks and Hazards for COPCs – Exposure Area E - Trespasser

Table 28A Summary of Receptor Risks and Hazards for COPCs – Exposure Area A -Commercial/Industrial Worker

Table 28B Summary of Receptor Risks and Hazards for COPCs – Exposure Area B - Commercial/Industrial Worker


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Table 28C Summary of Receptor Risks and Hazards for COPCs – Exposure Area C -Commercial/Industrial Worker

Table 28D Summary of Receptor Risks and Hazards for COPCs – Exposure Area D -Commercial/Industrial Worker

Table 28E Summary of Receptor Risks and Hazards for COPCs – Exposure Area E - Commercial/Industrial Worker

Table 29A Summary of Receptor Risks and Hazards for COPCs – Exposure Area A - Construction Worker

Table 29B Summary of Receptor Risks and Hazards for COPCs – Exposure Area B - Construction Worker

Table 29C Summary of Receptor Risks and Hazards for COPCs – Exposure Area C - Construction Worker

Table 29D Summary of Receptor Risks and Hazards for COPCs – Exposure Area D - Construction Worker

Table 29E Summary of Receptor Risks and Hazards for COPCs – Exposure Area E - Construction Worker

Table 30 Site-wide Summary of Receptor Risks and Hazards for COPCs

FIGURES

Figure 1 Site Location Map Figure 2 Known Waste Locations and Potential Source Areas Figure 3 Groundwater Monitoring Locations Figure 4 Soil Vapor Sampling Locations Figure 5a Soil Sampling Locations Figure 5b Soil Sampling Locations – Source Areas Figure 6 Site Conceptual Model

APPENDICES

Appendix A Soil Vapor Analytical Results Appendix B Soil Analytical Results Appendix C Radionuclide Investigation Appendix D Background Evaluation for Metals in Soil Appendix E ProUCL Output Appendix F Estimation of Air Concentrations and Particulate Emission Factors Appendix G Weight-of-Evidence Comparison for Vapor Intrusion Appendix H Calculation of Chemical Cancer Risks and Non-Cancer Hazards - Groundwater Appendix I Calculation of Chemical Cancer Risks and Non-Cancer Hazards – Soil Vapor to

Indoor Air Appendix J Calculation of Chemical Cancer Risks and Non-Cancer Hazards - Soil Appendix K Evaluation of Potential Leaching from Soil to Groundwater

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LIST OF ACRONYMS AND ABBREVIATIONS

ADAF age-dependent adjustment factors

ADD average daily dose

AADD annual average daily dose

AMEC AMEC Environment & Infrastructure, Inc.

ATSDR Agency for Toxic Substances Disease Registry

BEHP bis-2-ethylhexyl phthalate

bgs below ground surface

CalEPA California Environmental Protection Agency

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act

ROD COC contaminant of concern identified in the Record of Decision

COPC constituent of potential concern

CTE central tendency exposure

ESA environmental site assessment

HHRA human health risk assessment

IRIS Integrated Risk Information System

LADD Lifetime Average Daily Dose

LAU Lower Alluvial Unit

LOAEL lowest-observed adverse effect level

MAU Middle Alluvial Unit

MDWSA Main Drywells Source Area

MRL Minimal Risk Level

MTS Main Treatment System

OEHHA Office of Environmental Health Hazard Assessment

PCE tetrachloroethene

PEF particulate emission factor

PM10 particulate matter less than 10 microns

PPRTV Provisional Peer-Reviewed Toxicity Value

PSA potential source area

ROD Record of Decision

QAPP Quality Assurance Project Plan

Q-Q quantile-quantile


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RAGS Risk Assessment Guidance for Superfund

RfC reference concentration

RfD reference dose

RI/FS remedial investigation/feasibility study

RME reasonable maximum exposure

RSL Regional Screening Level

SASFS Source Areas Soil and Facility Structures

SCM site conceptual model

SF slope factor

SQL sample quantitation limit SVE soil vapor extraction

SVM soil vapor monitoring

SVOC semivolatile organic compound

TCE trichloroethene

UAU Upper Alluvial Unit

UCL upper confidence limit

UPI Unidynamics Phoenix Inc.

URF unit risk factor

EPA United States Environmental Protection Agency

VOC volatile organic compound

WMW Wilcoxon-Mann-Whitney

WSRV West Salt River Valley

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DRAFT SOURCE AREAS SOIL, AND FACILITY STRUCTURES HUMAN HEALTH RISK ASSESSMENT

Phoenix-Goodyear Airport-North Superfund Site Goodyear, Arizona

EXECUTIVE SUMMARY

This Draft Source Areas, Soil and Facility Structure Human Health Risk Assessment (HHRA) has been prepared by AMEC Environment & Infrastructure, Inc. (AMEC) on behalf of Crane Co., for the Phoenix Goodyear Airport-North Superfund Site (PGA-North Site), in Goodyear, Arizona. This HHRA was prepared in support of the Unilateral Administrative Order (United States Environmental Protection Agency [EPA], 2003) and the Notice of Lodging of Partial Consent Decree under the Comprehensive Environmental Response, Compensation and Liability Act (Consent Decree) (USEPA, 2006).

The purpose of this baseline HHRA is to provide an analysis of the potential for adverse health effects as a result of potential exposure to chemicals in soil, groundwater, and soil vapor at the PGA-North Site. As a baseline HHRA, it presents an assessment of potential adverse human health effects assuming no further remedial action of the PGA-North Site were to take place. This HHRA follows standard and customary practice as specified in EPA guidelines for the performance of risk assessments.

Background

In 1981, the Arizona Department of Health Services identified industrial solvent impacts to drinking water wells in the PGA-North Site area, specifically trichloroethene (TCE). The EPA added the Site to the National Priorities List in September 1983. Investigation, evaluation, and remediation have been ongoing since that time.

The PGA-North Site is located in Goodyear, Maricopa County, Arizona, approximately 17 miles west of downtown Phoenix. The PGA-North Site includes the former Unidynamics Phoenix Inc. (UPI) facility (the Site), which is located on approximately 58 acres and was the focus of the Source Areas, Soil and Facility Structures Investigation (AMEC, 2011a and b). With the exception of equipment related to remediation activities, the Site is currently vacant, as all former buildings have been demolished.

UPI began operations as a research, design, development, testing, assembly, and manufacturing plant for ordnance components and related electromechanical devices in 1963. Site operations ceased in 1994. During late 2008 and 2009, Crane Co. undertook a


decontamination and demolition project at the Site to completely remove all of the Site buildings and structures remaining from former UPI operations. Structures on the property included 24 fixed buildings and approximately eight bunkers. Some of the bunkers were used to store chemicals and products. Programs conducted by UPI ranged from small-scale electromechanical research to the assembly and manufacture of specialized devices. UPI used approximately 180 different chemicals and/or chemical mixtures during its years of operation. Many of the chemicals, including TCE, were disposed of at the Site.

Site Characterization and Remediation

Numerous investigations have been conducted to investigate and address soil and groundwater impacts at the Site since 1984. Known waste management locations (Locations) and potential source areas have been the focus of most investigations.

The 1989 Record of Decision required that a soil vapor extraction (SVE) system be designed, installed and operated at the former UPI facility. The initial SVE system operated intermittently from 1994 to 1998. A redesigned SVE system became fully operational in May 2004 and operation was ongoing in 2012 as of the preparation of this HHRA.

A groundwater extraction and treatment system has been operating on Site since 1994 when a phased groundwater remediation program began. Groundwater treatment has expanded to include four off-site remediation systems. TCE and perchlorate are the primary chemicals addressed by the groundwater treatment systems.

Data Evaluation

Data evaluation is the process of analyzing site characteristics and analytical data to identify chemicals of potential concern (COPCs) to be evaluated in the HHRA. Crane Co. has performed several phases of soil, soil vapor, and groundwater sampling at the Site to assess potential impacts to the surface and subsurface media. Because of the multiple phases of sampling and the ongoing groundwater treatment and SVE performed within the source areas, not all historical analytical results are appropriately representative of baseline conditions for use in this HHRA. Therefore, a Draft Data Evaluation for Source Areas, Soil, and Facility Structures Human Health Risk Assessment was prepared to present the data recommended for use in this HHRA (AMEC, 2012a). Further discussion with EPA, which included a response to EPA comments dated March 29, 2012 (AMEC, 2012b), clarified the groundwater, soil vapor, and soil data to be used. The final data identified for use in the HHRA is presented herein.


For data collected recently, data usability for this HHRA was evaluated in general accordance with the procedures outlined in the EPA publication Guidance for Data Usability in Risk Assessment – Parts A and B (USEPA, 1992a and b). For earlier data, AMEC relied on the data validation results presented by previous consultants.

Not all chemicals detected at a site warrant a quantitative evaluation. In many cases, chemicals are detected at such low concentrations as to pose a negligible risk and may be eliminated from further consideration. Selection criteria used to identify COPCs for the purpose of this HHRA were the following:

Elements that are considered essential dietary nutrients were not considered as COPCs (e.g., calcium, iron, magnesium, phosphorous, potassium, and sodium).

Inorganic chemicals detected at concentrations consistent with background levels as predicted by a statistical comparison were not considered COPCs. Aluminum, arsenic, barium, beryllium, chromium (total), cobalt, copper, lead, nickel, and zinc are considered consistent with background levels based on results from the Wilcoxon-Mann-Whitney (WMW), Gehan, and quantile tests and, therefore, eliminated as COPCs. Boron, hexavalent chromium, iron, manganese, mercury, silver, and vanadium, were retained as COPCs based on limited detections in the data available.

An organic chemical detected in all samples at concentrations less than one-tenth the respective screening level was excluded as a COPC if there was sufficient toxicological data to evaluate health risks (e.g., a published regulatory value). EPA’s Regional Screening Levels (RSLs) were used as the primary screening criteria. For soil vapor, the indoor air RSL was adjusted using a generic attenuation factor in addition to the one-tenth factor for screening purposes..

Chemicals considered as Class A carcinogens (known to cause cancer in humans) were not excluded based on a comparison to screening levels.

Using these criteria, COPCs in groundwater, soil, and soil vapor were identified for the PGA-North Site.

Exposure Assessment

Exposure assessment is the process of describing, measuring or estimating the intensity, frequency, and duration of potential human exposure to COPCs in environmental media (e.g., soil, water, and air) at a site. Conditions at the Site were used to develop a Site Conceptual Model (SCM). Based on the SCM, the following exposure scenarios were evaluated:


Indoor Commercial/Industrial Workers – A future indoor commercial/industrial worker could be exposed indirectly to vapors emanating from soil vapor and groundwater via inhalation of indoor air. For the purpose of this assessment, indoor workers are assumed to spend 100% of their time indoors.

Outdoor Commercial/Industrial Workers – A future outdoor commercial/industrial worker could be exposed directly to soil via incidental ingestion, dermal contact, and inhalation of airborne particulates, and indirectly via inhalation of ambient air. For the purpose of this assessment, outdoor workers are assumed to spend 100% of their time outdoors.

Construction Workers – During redevelopment, a future construction worker could potentially be exposed directly to soil via incidental ingestion, dermal contact, and inhalation of airborne particulates and indirectly via inhalation of ambient air. Typical excavations associated with utilities for above-grade structures go to a depth of 10 feet. Thus, we have assumed that there is no potential direct contact with groundwater for this receptor. A construction worker is also considered to conservatively address a trench utility worker.

Off-site Residents – A future off-site residential receptor could be potentially exposed to the source area groundwater via ingestion and dermal contact (i.e., showering) and indirectly via inhalation of VOCs in indoor air during showering if groundwater were used as a domestic water supply.

Trespasser – A current/future trespasser could be exposed directly to soil via incidental ingestion, dermal contact, and inhalation of airborne particulates, and indirectly via inhalation of ambient air.

For the purpose of evaluating potential human health risk, the 58-acre site was broken down into smaller areas (Exposure Areas). The Exposure Areas were developed based on the distribution of data across the Site, historical activities/source areas, and the typical size of potential commercial/industrial parcels in the area. The five Exposure Areas (A through E) range in size from 7 to 18 acres. All receptors were evaluated at all Exposure Areas for soil and soil vapor. Only one Exposure Area for groundwater was evaluated.

A single estimate of an exposure point concentration is required for risk assessment calculations as currently required by EPA guidance (USEPA, 1989b, 2002a). This single value must be representative of the average concentration to which a person would be exposed over the duration of the exposure. Exposure point concentrations were calculated using EPA’s ProUCL software, Version 4.1.01 (USEPA, 2011a). Upper confidence limits were used to represent the reasonable maximum exposure (RME), and averages were used to represent


the central tendency exposure (CTE). For groundwater, only one Exposure Area was evaluated, so only one exposure point concentration for an RME and for a CTE was developed. Exposure point concentrations for soil were calculated for each of the five Exposure Areas and for each exposure scenario (RME and CTE), for a total of 10 exposure point concentrations. Soil vapor data was evaluated on a sample-by-sample basis rather than by aggregating data into an exposure point concentration. Modeling was used to estimate indoor air (based on soil vapor data) and ambient air (based on soil data) concentrations.

Exposure parameters are quantitative estimates of the frequency, duration, and magnitude of exposure to various media. The exposure parameters were selected from EPA guidance (USEPA, 2002b; 2004c; 2008b; 2009b; 2011b), as appropriate, or are based on site-specific factors when applicable.

Toxicity Assessment

The EPA has completed toxicity assessments for all of the COPCs identified in this HHRA. The associated toxicity criteria were selected according to the following hierarchy:

1. EPA Integrated Risk Information System (IRIS) online database (USEPA, 2012a).

2. Other EPA toxicity criteria, as recommended or provided for specific chemicals in EPA Regional Screening Levels for Chemical Contaminants at Superfund Sites (USEPA, 2012b).

3. Other sources include Minimal Risk Levels (MRLs) from the Agency for Toxic Substances Disease Registry (ATSDR, 2012); Provisional Peer-Reviewed Toxicity Values (PPRTVs); and California Environmental Protection Agency’s (CalEPA) Office

of Environmental Health Hazard Assessment (OEHHA).

Oral toxicity criteria based on an administered dose were adjusted to account for the difference between the administered dose in the critical study (which formed the basis of the toxicity criterion) and the absorption efficiency of the chemical in question so the oral toxicity criteria are adjusted to be appropriately applied to dermal exposures.

Risk Characterization

Risk characterization represents the final step in the risk assessment process. In this step, the results of the exposure and toxicity assessments are integrated into quantitative or qualitative estimates of potential health risks. Potential noncarcinogenic health effects and carcinogenic health risks are characterized separately. A summary of the results is presented below; more detail is provided in the HHRA text.


Source area groundwater is being actively remediated and the baseline evaluation of this hypothetical worst-case exposure scenario suggests on-Site groundwater is not currently suitable for use as tap water (groundwater via ingestion [drinking water] and dermal contact [i.e., showering], and indirectly via inhalation of VOCs in indoor air during showering if groundwater were used as a domestic water supply). All drinking water supply wells in the area are protected from the contaminated groundwater plume by currently operating remedial treatment and plume control systems.

Potential exposure to volatile chemicals that migrate from the subsurface to indoor air was evaluated in two ways: data collected prior to May 2004 to represent conditions before the current SVE system was operational and data collected from 2007 to 2011 to reflect conditions after SVE was initiated.

o Predicted exposure to volatile chemicals in indoor air of future buildings using data collected from 2007 to 2011 are within or below the acceptable risk range for future indoor commercial/industrial workers in Exposure Areas A through E. This indicates that the SVE system has been successful at reducing potential health risks (predicted risk and hazard indexes in source areas).

o Based on predicted health risks for conditions prior to remediation (data collected prior to May 2004), potential carcinogenic risk would be greater than the acceptable risk range and/or hazard indexes would exceed 1 for Exposure Areas B, C, and D. The primary chemical contributing to the exceedance is TCE. These results would only be applicable if the SVE treatment system is turned off and VOC concentrations rebound to pre-2004 levels.

Predicted exposure to soil is below the de minimis risk level or within the acceptable risk range for potential trespassers, future construction workers, and future outdoor commercial/industrial workers in all five Exposure Areas. With the exception of Exposure Area C, the hazard index for all Exposure Areas and receptors exposed to soil was less than the de minimis level. The hazard index for Exposure Area C for the RME construction worker was 2, but the target organ-specific hazard index is at the acceptable level of 1 for the RME, indicating that adverse health effects would not be observed at the highest expected exposure conditions. Additionally, the hazard index was 0.6 for the CTE for potential exposure to soil by construction workers. The primary chemical contributing to the hazard index is manganese in soil.

As in any risk assessment, the estimates of risk have many associated uncertainties. The procedures used in the HHRA result in conditional estimates of risk that incorporate assumptions concerning chemical toxicity, human exposure, and unavoidable uncertainties. To be protective of human health, the types of assumptions used in the HHRA were generally


conservative. Consequently, it is important that the magnitude of uncertainties and biases are considered when interpreting the health risk results. It is possible that currently unrecognized subsurface issues may be present at the site. However, the health risk assessment has been prepared in a manner consistent with that generally used in agency guidance at the time it was prepared. It is likely that risk assessment methods and data identifying and quantifying the toxicity of chemicals will improve with time. Should use, conditions, or toxicity criteria change, the information and conclusions in this HHRA may no longer apply.

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DRAFT SOURCE AREAS, SOIL, AND FACILITY STRUCTURES HUMAN HEALTH RISK ASSESSMENT

Phoenix-Goodyear Airport-North Superfund Site Goodyear, Arizona

1.0 INTRODUCTION

This Draft Source Areas, Soil, and Facility Structures Human Health Risk Assessment (HHRA) has been prepared by AMEC Environment & Infrastructure, Inc. (AMEC) on behalf of Crane Co., for the Phoenix Goodyear Airport-North Superfund Site (the “PGA-North Site”), in Goodyear, Arizona (Figure 1). This HHRA was prepared in support of the Unilateral Administrative Order (United States Environmental Protection Agency [EPA], 2003) and the Notice of Lodging of Partial Consent Decree under the Comprehensive Environmental Response, Compensation and Liability Act (“Consent Decree”; USEPA, 2006).

1.1 OBJECTIVES The purpose of this baseline HHRA is to provide an analysis of the potential for adverse health effects as a result of potential exposure to chemicals in soil, groundwater, and soil vapor at the PGA-North Site. As a baseline HHRA, it presents an assessment of potential adverse human health effects assuming no further remedial action of the PGA-North Site were to take place.

1.2 APPROACH This HHRA follows standard and customary practice as specified in EPA guidelines for the performance of risk assessments as specified in the following documents:

Risk Assessment Guidance for Superfund, Volume I: Human Health Evaluation Manual (Part A). (USEPA, 1989b).

Risk Assessment Guidance for Superfund. Volume I: Human Health Evaluation Manual (Part D: Standardized Planning, Reporting, and Review of Superfund Risk Assessments). (USEPA, 2001).

Risk Assessment Guidance for Superfund (RAGS): Volume 1 – Human Health Evaluation Manual (Part E, Supplemental Guidance for Dermal Risk Assessment). (USEPA, 2004c).

Risk Assessment Guidance for Superfund, Volume I: Human Health Evaluation Manual (Part F, Supplemental Guidance for Inhalation Risk Assessment). (USEPA, 2009b).

These documents were supplemented by additional EPA guidance as necessary.


Although the technical approaches to risk assessment employed in this HHRA are based on the latest scientific information, there remain numerous uncertainties in the extent to which environmental exposures affect human health. This lack of knowledge means that assumptions must be made based on information presented in the scientific literature or on professional judgment. Although some assumptions have significant scientific basis, many do not. In all cases, the assumptions made are conservative. As a result, it is generally agreed that risk estimates such as those presented herein tend to overestimate the true risks associated with a site.

1.3 REPORT ORGANIZATION This report is organized in a manner consistent with the referenced guidance documents. The remaining sections of the report are as follows:

Section 2.0 Site Characterization summarizes background information for the Site, including location and description, geology and hydrogeology, land and water use, and previous investigations.

Section 3.0 Data Evaluation presents an evaluation of the data used in the HHRA and the selection of the chemicals of potential concern (COPCs) that are evaluated in the HHRA.

Section 4.0 Exposure Assessment presents the analysis of the mechanisms by which human receptors may be exposed to chemicals at this site.

Section 5.0 Toxicity Assessment presents the quantitative criteria developed by EPA to evaluate potential adverse health effects of chemicals.

Section 6.0 Risk Characterization presents the results of the quantitative analysis of potential carcinogenic and non-carcinogenic risks to human health.

Section 7.0 Uncertainty Assessment presents a summary of the major sources of uncertainty in the analysis and their impact on the conclusions.

Section 8.0 Evaluation of Potential Leaching from Soil to Groundwater presents a summary of the potential threat to groundwater quality from concentrations of COPCs remaining in soil.

Section 9.0 Conclusions presents the conclusions of the HHRA.

Section 10.0 References presents the sources of information cited in the text.


2.0 SITE CHARACTERIZATION

This section describes the current site conditions, the site history, the data collected to characterize environmental conditions at the site, ongoing remediation activities, and geology/hydrogeology.

2.1 SITE DESCRIPTION AND HISTORY The PGA-North Site is located in Goodyear, Maricopa County, Arizona, approximately 17 miles west of downtown Phoenix. The PGA-North Site includes the former Unidynamics Phoenix Inc. (UPI) facility (the “Site”), which is located on approximately 58 acres and was the focus of the Source Areas, Soil and Facility Structures (SASFS) investigation (AMEC, 2011a and 2011b). With the exception of equipment related to remediation activities, the Site is currently vacant, as all former buildings have been demolished. The physical boundaries of the Site are Van Buren Street to the north, Litchfield Road to the east, a vacant field to the south, and the abandoned Union Pacific Railroad right of way (tracks have been removed) to the west. Land use in the area surrounding the Site is varied. Agricultural land is found to the west, vacant land zoned industrial lies to the south, residential and commercial properties lie to the east, and commercial properties are located north of the Site.

2.2 OPERATIONAL HISTORY UPI began operations as a research, design, development, testing, assembly, and manufacturing plant for ordnance components and related electromechanical devices in 1963. The present owner, Crane Co., purchased UPI and the property in 1985. In 1993, Crane Co. sold the UPI business (excluding buildings and land) to Pacific Scientific Energy Dynamics, which managed operations at the Site until 1994, when operations ceased.

The property consisted of 24 fixed buildings and approximately eight bunkers. Some of the bunkers were used to store chemicals and products. Each building was designed for a specific operation (e.g., powder processing, ordnance assembly, chemical storage, and packaging). Programs conducted by UPI ranged from small-scale electromechanical research to the assembly and manufacture of specialized devices. UPI used approximately 180 different chemicals and/or chemical mixtures during its years of operation. Many of the chemicals, including TCE, were disposed of at the Site. During late 2008 and 2009, Crane Co. undertook a decontamination and demolition project at the Site. The project objectives were to completely remove all of the buildings and structures remaining from former UPI operations. The end goal of this project was to provide easy access for ongoing site characterization activities as well to respond to requests from the City of Goodyear (COG) and local residents to remove the vacant buildings.


2.3 PREVIOUS INVESTIGATIONS In 1981, the Arizona Department of Health Services identified industrial solvent impacts to drinking water wells in the PGA-North Site area, specifically trichloroethene (TCE). The EPA added the PGA-North Site to the National Priorities List in September 1983. Investigation, evaluation, and remediation have been ongoing since that time.

Numerous investigations and remedial activities have been conducted to investigate and address soil and groundwater impacts at the Site since 1984. The known waste management locations (Locations) and potential source areas (PSAs) that have been the focus of most investigations are presented on Figure 2. A brief summary of these previous investigations is presented in the following paragraphs.

In 1984, Western Technologies (1984) drilled 10 soil borings in the main drywells source area (MDWSA). TCE was detected at concentrations as high as 5,585 milligrams per kilogram (mg/kg) in soil at a depth of 40 feet below ground surface (bgs) (ARCADIS, 2008b).

In 1985, Dames & Moore conducted a soil vapor survey at the facility (Dames & Moore, 1985). Shallow soil vapor samples were collected from depths of 4 feet below ground surface (bgs) at 40 locations on the Site to estimate the extent of impacted groundwater and to assist in selecting locations for shallow groundwater monitoring wells (ARCADIS, 2008b).

In 1988, additional soil sampling conducted by Dames & Moore (1988) provided further evidence that the MDWSA was the primary source of TCE in soil and groundwater. TCE was detected at a maximum concentration of 860 mg/kg in a soil sample collected at 41.5 feet bgs, near the MDWSA (ARCADIS, 2008b).

The Remedial Investigation/Feasibility Study (RI/FS) sampling was performed by CH2M Hill under contract with the EPA during early 1988 (USEPA, 1989a). Soil analysis focused on volatile organic compounds (VOCs), using EPA Test Method 8010. Some samples were also collected for total metals analysis. The RI/FS sampling was performed in two separate phases. Three soil borings were completed during Phase I and twenty-seven soil borings were completed during Phase II (Geomatrix, 2003a).

In 2002 and 2003, CH2M Hill conducted a Phase I and II Source Area Groundwater Investigation (CH2M Hill, 2004a) on behalf of the EPA to further investigate the cause of the impacts in nearby wells and to identify the source of impacts in Subunit C. The


investigations included the drilling and sampling of 15 exploratory boreholes and the investigation of soil vapor impacts.

In August 2003, CH2M Hill, under contract with the EPA, implemented a sampling program to assess residual concentrations of VOCs in the soil vapor near the former MDWSA (CH2M Hill, 2004b). As part of that study, soil vapor samples were collected from six soil vapor monitoring (SVM) wells, located near the soil vapor extraction (SVE) wells, which had been installed as part of the SVE system, and analyzed for VOCs.

In September 2003, Geomatrix Consultants, Inc. (Geomatrix), conducted an air sampling event at the commercial buildings located at 140, 190, and 250 North Litchfield Road north of the Site. A total of 20 air samples were collected from in and around the three buildings (Geomatrix, 2003b). The concentrations of TCE and tetrachloroethene (PCE) in indoor air during this sampling event were below risk-based criteria.

Between April 2 and 28, 2004, an SVE system pilot test was conducted using the existing SVE and SVM wells (ARCADIS G&M, Inc., 2005a). The pilot test sampling event included the collection and laboratory analysis of samples from each monitoring point in the SVM well nests (SVM-01 through SVM-15).

At the request of EPA to evaluate seasonal variability, winter air sampling was performed in February 2005 at the commercial buildings located at 140, 190, and 250 North Litchfield Road north of the Site (ARCADIS G&M, Inc., 2005b) to supplement the September 2003 sampling. ARCADIS G&M collected four to five indoor air samples in each of the buildings, as well as multiple outdoor air samples (ambient, perimeter, and air intake rooftop locations). Details of the investigation are provided in the Air Sampling Report (ARCADIS G&M, Inc., 2005b).

Between November 2004 and August 2005, ARCADIS G&M conducted a source area investigation at the MDWSA. The investigation included excavation of four drywells, drilling and sampling of 13 soil borings, collection of soil vapor samples, and installation of vapor and in-situ reactive zone injection wells. Soil, groundwater, and soil vapor samples were collected during Phases I and II (ARCADIS, 2007a).

In 2007, ARCADIS conducted a Limited Phase 1 environmental s ite assessment (ESA) and Phase 2 investigation (collectively, environmental due diligence) at Parcels B and C at the Site (ARCADIS, , 2007b). The Phase 1 ESA for Parcels B and C (referred to as Exposure Areas A and E in this HHRA) did not identify any Recognized Environmental Conditions; however, Phase 2 investigation work was executed on both parcels to provide a more comprehensive baseline of conditions at the Site. A total of


11 soil borings were drilled and sampled using direct push drilling methods that resulted in the collection of 22 soil samples and 10 soil vapor samples at Parcel B and a total of 10 soil borings at Parcel C that resulted in the collection of 26 soil samples and 7 soil vapor samples.

During the summer of 2007, ARCADIS conducted the Phase I SASFS investigation. The investigation included excavating and removing potential source structures such as drywells, sedimentation tanks, ponds, and vaults. During excavation and removal of these structures, soil samples were collected to determine if any contaminants of concern (COCs) might have impacted the surrounding soils and groundwater. The results of the SASFS Phase I Investigation are provided in the Final Source Areas, Soils and Facility Structures Investigation Work Plan, Phase II (ARCADIS, 2008a).

In 2009 and 2010, AMEC Geomatrix, Inc. (now AMEC) conducted the SASFS Phase II Investigation (AMEC, 2011b) based on the Work Plan submitted by ARCADIS. The SASFS Phase II Investigation (modified by specific addenda) was implemented to further characterize and delineate areas where COC exceedances occurred during the SASFS Phase I Investigation and to address any remaining data gaps identified. Additional samples were collected from nine of the previously identified Locations, 13 of the identified PSAs, and additional features identified during the SASFS Phase II Investigation. The SASFS Phase II Investigation also incorporated an evaluation of former facility structures and an inspection of sub-grade features identified during facility demolition activities conducted by Matrix New World Engineering, Inc.

While conducting the SASFS Phase I Investigation, ARCADIS also summarized historical soil vapor evaluations, identified data gaps, and planned for the additional characterization of soil vapor in a Final Phase I Soil Gas Investigation Workplan (ARCADIS, 2008b).

At the end of 2009, AMEC Geomatrix conducted the Phase I Soil Gas Investigation to address data gaps identified in the ARCADIS work plan (AMEC, 2011a). Six soil borings were completed and soil and soil vapor samples were collected at 10-foot intervals at sampling locations AB-1 through AB-6 (Figure 4). Depth-discrete groundwater samples were also collected at each boring at approximate 10-foot intervals to approximately 120 feet bgs. Analytical results for depth-discrete groundwater samples collected are not summarized herein, but can be found in the original report (AMEC, 2011a).


2.4 ON-SITE REMEDIATION SYSTEMS Based on the results of early (1985) soil vapor investigations, the 1989 Record of Decision (ROD) required that a SVE system be designed, installed and operated at the former UPI facility.

In 1991, four SVE wells (SVE-01, SVE-02, SVE-03, and SVE-04) and companion monitoring wells were installed to depths of approximately 80 feet bgs. Two additional SVE wells (SVE-05 and SVE-06) and companion well nests (SVM-05 and SVM-06) were installed in 1995. The SVE system used thermal oxidation and operated intermittently from 1994 until 1998, when it was shut down for evaluation of the effectiveness of the SVE system and to respond to public concern about incomplete destruction of VOCs.

In 2003, CH2M Hill, on behalf of the EPA, constructed nine additional SVM wells (SVM-07 through SVM-15).

In April 2004, a redesigned SVE system using granular activated carbon to treat extracted soil vapor prior to discharge was pilot tested and became fully operational in May 2004.

In November 2004, ARCADIS G&M installed three SVE wells (SVE-07, SVE-08, and SVE-09) which were added to the existing SVE system described above. The new SVE wells were specifically designed to draw vapors from the lower portion of vadose zone near the groundwater surface, and were screened from a depth of approximately 72 to 86 feet bgs (Matrix New World, 2011). During 2011, Matrix New World performed a number of SVE optimization tests consistent with an EPA-approved Work Plan (Matrix New World, 2011), added a SVM well (SVM-16) in proximity to groundwater monitor well, MW-07, and converted monitor well MW-07 into a temporary SVE well.

A groundwater extraction and treatment system has been operating at the Site since 1994, when a phased groundwater remediation program began.

Phase I and II activities primarily addressed on-site and proximal areas of the PGA-North Site groundwater TCE plume. Phase I and II activities included the installation of extraction well EA-01 in 1994 at the identified source area and the installation of extraction well EA-02 in 1996 approximately one-half mile north of the Site. Monitor well MW-05 was converted to extraction well EB-01 in 1994 to capture impacted groundwater from Subunit B. Groundwater from these three wells was treated by the on-site main treatment system (MTS), located in the southwest corner of the facility.


In 1994, injection wells IA-01 through IA-05 were installed as part of the MTS for injection of treated groundwater into Subunit A. These injection wells operated until December 2002, when perchlorate was identified as a COC at the Site and injection ceased.

Phase III activities expanded groundwater remediation efforts to include source containment measures. Extraction wells EA-03 and EA-04 were installed in 1997 and 1998, respectively, on the northern limits of the Site to create a hydraulic barrier (referred to as “the Van Buren Barrier” for its proximity to East Van Buren Street) to mitigate further migration of COCs from the Site. Extraction well EA-04 operated for only a short period in 1998 due to a casing failure. In March 2002, Subunit C monitor well MW-20 was converted to an extraction well, to address the occurrences of increasing concentrations of TCE in Subunit C, and its discharge was directed to the MTS for treatment.

Once injection operations stopped, all extracted groundwater from the MTS was treated for TCE and then conveyed to the City of Goodyear Waste Water Treatment Plant for perchlorate treatment. On April 29, 2005, injection of treated groundwater at the MTS injection wells resumed after installation of the ion exchange perchlorate treatment system. In 2006, the treatment capacity of the MTS was increased by installing Subunit C extraction well EC-01 and Subunit A injection well IA-06, which were fully operational by 2007. In October 2008, Subunit A piezometer PZ-01 was converted to an extraction well as part of the MTS Stage 1 Expansion effort to increase the removal of COCs from groundwater in accordance with the Final Main Treatment System Stage 1 Expansion Construction Complete and Operations Summary Report (Matrix New World, 2009a). In May 2010, Subunit C monitor well MW-29 was converted to an extraction well as part of the MTS Stage 2 Expansion effort to increase the treatment capacity of the MTS in accordance with the Final Main Treatment System Stage 2 Expansion Construction Complete and Operations Summary Report (Matrix New World, 2009b). In addition to monitor well MW-29 being converted into an extraction well, a low profile air stripper (Phase 4) was also added to the MTS to increase the treatment capacity.

Currently, the MTS treats TCE and perchlorate from groundwater pumped from eight wells; four Subunit A groundwater extraction wells (EA-01, EA-02, EA-03, and PZ-01), one Subunit B extraction well (EB-01), and three Subunit C extraction wells (EC-01, MW-20, and MW-29).

2.5 GENERAL GEOLOGY/HYDROGEOLOGY The PGA-North Site is located in the West Salt River Valley (WSRV) basin, which is part of the Basin and Range physiographic province. The Basin and Range province is characterized by


deep alluvial basins separated by generally north to northwest trending mountain ranges. Locally, the WSRV alluvial deposits are subdivided into three hydrogeologic units. These three units are designated the Upper Alluvial Unit (UAU), the Middle Alluvial Unit (MAU), and the Lower Alluvial Unit (LAU). The UAU is further subdivided into three subunits, which are designated Subunit A, Subunit B, and Subunit C (Geomatrix, 2002).

2.5.1 Upper Alluvial Unit This section summarizes the composition of Subunits A, B, and C of the UAU. Based on the objectives of the SASFS Investigations, Phase II was limited to Subunit A.

2.5.1.1 Subunit A Subunit A is generally composed of interbedded sands, silty sands, and clayey sands that can locally contain sequences of gravel and cobbles suggesting high energy deposits from the ancestral Agua Fria River. Subunit A typically extends from ground surface to approximately 150 to 160 feet bgs in the vicinity of the Site and generally deepens to the north, to depths of approximately 190 to 200 feet bgs. Approximately one-third to one-half of the lower portion of Subunit A is saturated and is considered an unconfined aquifer.

2.5.1.2 Subunit B Subunit B is primarily composed of interbedded silts and clays with lenses of fine to coarse sand suggesting distal facies of an alluvial fan sequence. It is generally 50 to 70 feet thick near the Site extending from about 160 to 230 feet bgs and is fully saturated. Field data collected from the groundwater investigations suggest that it deepens and thins (20 to 40 feet thick) north of I-10 and it may not be laterally continuous near the Agua Fria River channel. However, where Subunit B is present, the finer-grained deposits appear to impede the vertical movement of groundwater from Subunit A into Subunit C.

2.5.1.3 Subunit C Subunit C is composed of interbedded mixtures of silty sands, sandy silts, and gravelly sands suggesting mid-fan facies of an alluvial fan sequence with braided channels. On average Subunit C is approximately 130 feet thick and extends from about 230 to 350 feet bgs. Subunit C is fully saturated and is considered to be a leaky to confined aquifer.

2.5.2 Middle Alluvial Unit The UAU grades into the MAU at approximately 350 to 360 feet bgs. The MAU primarily consists of clay, silt, mudstone, and gypsiferous mudstone with interbedded sand and gravel deposits. In the central portions of the Salt River Valley Basin, the MAU may be up to 1,600 feet thick (Corell and Corkhill, 1994).


2.5.3 Lower Alluvial Unit The LAU is the deepest alluvial unit within the Salt River Basin and overlies or is in fault contact with the underlying bedrock. Regionally, the LAU is composed of conglomerate and gravel near the basin margins, grading to mudstone and some evaporites in the central areas of the basin. No wells within the PGA-North Site are completed within the LAU. Hydraulic conductivity of the LAU is variable ranging from 5 to 60 feet per day (Corell and Corkhill, 1994).

3.0 DATA EVALUATION AND SELECTION OF CHEMICALS OF POTENTIAL CONCERN

Data evaluation is the process of analyzing site characteristics and analytical data to identify COPCs to be evaluated in the HHRA. This section of the HHRA identifies data of sufficient quality for use in the risk assessment, summarizes the chemical characterization of each environmental medium at the site, and provides a summary of all COPCs identified at the site by medium.

3.1 DATA QUALITY The first step in this process is to identify and evaluate all of the available data to determine if they are of sufficient quality for inclusion in the risk assessment. Analytical data available from ARCADIS G&M (ARCADIS G&M, 2005a); ARCADIS (ARCADIS, 2007b, 2008a); CH2M Hill (USEPA, 1989a; CH2M Hill, 2004b); and AMEC (2011a, 2011b) were considered in this evaluation.

Data usability for this HHRA was evaluated in general accordance with the procedures outlined in the EPA publication Guidance for Data Useability in Risk Assessment – Parts A and B (USEPA, 1992a, 1992b). Usability of the data for risk assessment was based on the following criteria:

documentation;

data sources;

analytical methods;

data review;

data quality indicators (precise, accurate, complete, representative, and comparable).

Completeness and compliance checks of data quality were performed on all ARCADIS and AMEC results according to a Tier I data validation, which includes 100% data quality review,


and consistent with the Final Quality Assurance Project Plan Addendum Main Drywells Source Area Investigation (Source Area QAPP; ARCADIS G&M, 2004). A portion (10%) of the samples underwent Tier III data validation which includes a full data validation of results. Data validation procedures were performed based on the principles of the EPA National Functional Guidelines (USEPA, 2004a, 2008a) and are designed to ensure completeness and adequacy of the data set. Data validation appendices were provided in their respective reports (ARCADIS G&M, 2005a; ARCADIS, 2007b, 2008a) and AMEC (2011a, 2011b). The analytical results reported by CH2M Hill (USEPA, 1989a; CH2M Hill, 2004b) were collected before the Source Area QAPP (ARCADIS G&M, 2004) and Sitewide QAPP (Geomatrix, 2003c) were prepared; therefore, their data quality is discussed separately.

The specific level of independent data validation was not described in the report of soil vapor data collected by CH2M Hill (2004b). However, field and laboratory quality control criteria that describe precision and accuracy were collected and reported, including blind field duplicate samples, laboratory split samples, laboratory method blanks, and laboratory control samples. The analytical results reported by CH2M Hill in the RI/FS (USEPA, 1989a) were generally not reported in sufficient detail to evaluate data quality. As presented in response to EPA comments dated March 29, 2012 (AMEC, 2012b), the analytical method used for arsenic has been replaced and the analytical reports provided do not contain laboratory quality control criteria (e.g. laboratory control samples and method blanks).

For some analytical results, quality control criteria were not met and EPA data qualifiers were appended to the data records to indicate limitations and/or bias in the data. The definitions for the data qualifiers or data validation flags used during validation are provided in the data tables and are consistent with those defined in EPA guidelines (USEPA, 2004a, 2008a). AMEC obtained these qualifiers from the PGA-North Site database that was created by ARCADIS G&M in 2004 and is now maintained by Matrix New World. AMEC confirmed the qualifiers in the data validation appendices of the original reports when available. Soil vapor data collected by CH2M Hill (2004b) and associated qualifiers were not obtained from the database, but from the original report. The specific level of data validation was not described in the CH2M Hill report, but the laboratory data reported did include qualifiers and laboratory control samples. The soil analytical results reported in the 1989 RI/FS prepared by CH2M Hill on behalf of EPA did not include sufficient information to verify data quality. Therefore, only limited results from the RI/FS were included in the HHRA. Specifically, six soil samples (three locations at two surface soil depths) were collected by Dames & Moore in the PSA-J area and analyzed for pesticides in 1988 (USEPA, 1989). ARCADIS (2008a) conducted supplemental pesticide sampling in this area during the Phase I sampling. Because the 1988 results detected pesticides not detected in the ARCADIS investigation (chlordane) and provided


results from a depth (1.5 feet bgs) not sampled by ARCADIS (0.5 feet bgs), the 1988 results were conservatively included in the HHRA.

Reported analytical data, including data qualifiers applied by the analytical laboratories and during independent quality assurance and quality control review, are reproduced in Tables 1 through 7 and Appendices A and B. The data review demonstrates that the analytical results presented herein are of sufficient quality to support the completion of the HHRA.

3.2 DATA USED IN RISK ASSESSMENT Crane Co. has performed several phases of soil, soil vapor, and groundwater sampling at the Site to assess potential impacts to the surface and subsurface media. Because of the multiple phases of sampling and the ongoing groundwater treatment and soil vapor extraction performed within the source area, not all historical analytical results are appropriately representative of baseline conditions for use in this HHRA. Therefore, a Draft Data Evaluation for Source Areas, Soil, and Facility Structures Human Health Risk Assessment (Draft Data Evaluation Report) was prepared to present the data recommended for use in the HHRA (AMEC, 2012a). Further discussion with EPA, which included a response to EPA comments dated March 29, 2012 (AMEC, 2012b), clarified the data to be used for groundwater, soil vapor, and soil. The final data identified for use in the HHRA is presented in following subsections.

3.2.1 Groundwater As presented on Figure 3, a general response action area has been identified in the on-Site area with the highest concentration of TCE in groundwater within Subunit A. This area is the focus of proposed groundwater remediation and will be used to represent the current worst-case source area impacts to groundwater in the SASFS. The most recent two years of analytical results from the monitor wells and two extraction wells within this area will be used to characterize potential groundwater exposure for the SASFS HHRA. At a minimum, samples were collected quarterly from these locations. A subsequent baseline risk assessment will be conducted to assess groundwater in off-Site areas. The analytical results and statistical summary of source area groundwater results used are presented in Table 1.

Groundwater samples were analyzed for VOCs using EPA Method 8260B and perchlorate using EPA Test Method 314.0. Currently, 20 compounds are listed as target COCs in groundwater for the PGA-North Site as specified in the Record of Decision (ROD) and subsequent Explanation of Significant Difference. The full list of COCs designated in the ROD (ROD COCs) in groundwater is also presented in Tables 1 and 2 of the Groundwater Investigation Quality Assurance Project Plan (QAPP) dated December 29, 2005 (ARCADIS G&M, 2005c).


• 1,1-dichloroethene • ethylbenzene

• 1,1,2,2-tetrachloroethane • methylene chloride

• 1,2-dichloropropane • TCE

• cis-1,2-dichloroethene • trichlorofluoromethane

• trans-1,2-dichloroethene • toluene

• 2-butanone • m,p-xylenes

• acetone • o-xylene

• benzene • PCE

• carbon tetrachloride • vinyl chloride

• chloroform • perchlorate

3.2.2 Soil Vapor As described in Section 2.1.3, the SVE system is currently active and has been operating since May 2004. In addition to continuous monitoring of the SVE system wells, other phases of soil vapor investigation have occurred throughout the site while remediation has been ongoing. Phase I and II soil vapor samples collected in 2007 by ARCADIS and in 2009 and 2010 by AMEC were collected to comprehensively characterize current soil vapor conditions across the Site. It should be noted, however, that soil vapor extraction occurs only in the central and northeast portions of the Site. Parcels without historical operations and at some distance from the SVE system are not expected to be affected by the ongoing extraction.

In addition to the data representing current conditions described above, EPA requested that pre-remediation conditions also be evaluated in the HHRA based on soil vapor data collected between 1999 and 2004. Pre-remediation conditions were represented by soil vapor results from the two following sources: 1) CH2M Hill, 2003 Subsurface Soil Vapor Investigation (2004b) and 2) baseline soil vapor results collected from the soil vapor monitoring well network in April 2004 before the SVE system was restarted (ARCADIS G&M, Inc., 2005a). It should be noted that because these data are characterized by high reporting limits, several VOCs were not detected in the pre-remediation database, but have been detected in the data collected since 2004. Therefore, although the pre-remediation soil vapor data collected has been considered in the HHRA, the data collected since 2007 are considered more representative of current Site conditions. Further, the pre-remediation soil vapor results principally characterize the former source areas, but do not represent the Site as a whole. Table 2 presents the analytical results for the soil vapor data used in the HHRA. For the purposes of evaluating exposure in the HHRA, analytical results of soil vapor samples are divided into Exposure Areas A through E, which are further discussed in Section 4.1.4. Soil vapor sample locations and exposure area boundaries are presented on Figure 4.


Historical soil vapor data not used in the HHRA include data collected in 1985 (Dames & Moore, 1985) to direct previous field investigations and remediation and data collected in 2005 in the MDWSA by ARCADIS G&M while expanding the SVE system. These two soil vapor data sets are presented in the Draft Data Evaluation Report (AMEC, 2012a), but are not considered in the HHRA because the Dames & Moore investigation occurred prior to 1999 and does not represent pre-remediation conditions (as defined as data collected between 1999 and 2004), and the 2005 MDWSA investigation is not likely to be representative of current conditions. While optimizing the SVE system in 2011, soil vapor samples were collected from monitor well MW-07, which was temporarily converted to a SVE well. These results are also presented in the Draft Data Evaluation Report (AMEC, 2012a), but are excluded from the HHRA because the location is adequately characterized by the associated well SVM-16 that has a more complete monitoring record.

In summary, the 2007 and 2009/2010 Phase I and II soil vapor investigation results (ARCADIS, 2007b; AMEC, 2011a, 2011b) and the monitoring results from the SVM wells are used to characterize soil vapor conditions while the SVE system is operational (ongoing operation) and to characterize additional areas of the Site. Pre-remediation conditions were represented by soil vapor results from the 2003 Subsurface Soil Vapor Investigation (CH2M Hill, 2004b) and the 2004 baseline soil vapor results collected from the soil vapor monitoring well network (ARCADIS G&M, Inc., 2005a). These data are presented in Appendix A.

3.2.3 Soil The project database, which contains data collected since 2004, was used as the primary source of data relevant to baseline Site conditions. Based on the Draft Data Evaluation Report (AMEC, 2012a) and response to EPA comments on the Draft Data Evaluation Report (AMEC, 2012b), soil data considered suitable for evaluation in the HHRA are presented in Tables 3 through 7 and soil data for all depths are presented in Appendix B.

Historical VOC data collected prior to 2006, including the ARCADIS G&M 2004 and 2005 soil samples collected during the MDWSA investigation and SVE expansion (ARCADIS, 2007a), were not included in the HHRA. These data have been superseded by samples collected in the Phase I and II soil investigations. For nonvolatile compounds, all applicable soil data available in the project database was considered in the HHRA regardless of age; only off-Site data and investigation-derived waste were excluded. In addition, limited historical data for nonvolatile compounds that were collected prior to development of the database were also included in the HHRA.


Chemicals detected in soil include VOCs, metals, organochlorine insecticides, explosives, bis-2-ethylhexyl phthalate (BEHP), nitrate (as nitrogen), and perchlorate. Radionuclides (uranium, Cobalt 60 activity, and gross alpha/beta/gamma activities) were analyzed in the Phase II SASFS (AMEC, 2011b). All 22 soil samples had detectable activities of uranium, 6 had gross alpha activity, and 9 had gross beta activity above the laboratory reporting limit. However, results were generally consistent with alpha and beta activities noted in the background samples as concluded in the SASFS report (AMEC, 2011b). Based on this conclusion, radionuclides are not evaluated in this HHRA. A more specific discussion of radionuclide results is presented in Appendix C.

3.2.4 Duplicate Samples One additional step was performed with regard to data review. Duplicate sample results for soil and groundwater were compared with the primary sample results to select a single value to represent a specific sample in the HHRA. The higher of the detected concentrations or the lower of the reporting limits if a chemical was not detected in either sample was used to represent the chemical concentration for that sample in the HHRA. The value that will not be used in the HHRA is shaded in the appendices and tables. This selection was not performed for soil vapor samples because they were evaluated on a sample-specific basis and not combined into representative exposure concentrations like soil and groundwater.

3.3 CHEMICAL CHARACTERIZATION This section briefly summarizes the nature and extent of chemicals detected in each medium at the site for purposes of providing context to the HHRA. Summary tables of the chemicals detected in each medium include chemical name, total number of samples analyzed, total number of detections, frequency of detection, range of detection limits, and range of concentrations detected.

3.3.1 Groundwater Table 8 presents the statistical summary of the groundwater data used in the HHRA. Ten VOCs (benzene, carbon tetrachloride, chloroform, 1-1-dichloroethene, cis-1,2-dichloroethene, 1,2-dichloropropane, PCE, toluene, TCE, and m,p-xylenes) and perchlorate have been detected in source area groundwater over the last two years. As presented in Table 8, while TCE and perchlorate were detected in 100% of the source area groundwater measurements used, the other chemicals were detected with a frequency between 1% and 66%. Specifically, 1,2-dichloropropane, toluene, and m,p-xylenes were only detected once in 81 samples collected from seven wells.


3.3.2 Soil Vapor Table 9 presents the statistical summary of the soil vapor data used in the HHRA. Twenty-eight VOCs were detected in pre-remediation soil vapor collected in 2003 and 2004 before the SVE system was restarted. As presented in Table 9, while TCE was detected in 95% of the soil vapor samples collected, the other chemicals were detected with a frequency between 0.7% and 25%. Specifically, 18 chemicals were detected in less than 5% of samples. Thirty-five VOCs were detected in ongoing remediation soil vapor collected from 2007 through 2011 while the SVE system was operational. As presented in Table 9, while TCE was detected in 91% of the soil vapor samples collected, the other chemicals were detected with a frequency between 0.4 and 98%. Propene (99%), hexane (82%), acetone (59%), toluene (52%), and methyl-n-butyl ketone (52%) were detected in more than 50% of the samples. Eleven chemicals were detected in less than 5% of samples.

3.3.3 Soil Table 10 presents a summary of the soil data collected from the Site. Chemicals detected in soil include VOCs, metals, pesticides, explosives, BEHP, nitrate, and perchlorate. TCE was detected in only three of 181 samples collected in shallow soil less than 10 feet bgs (2% frequency of detection). Other VOCs were also detected infrequently, with detections ranging from 1% to 13% of samples. Perchlorate was detected in 73% of samples (80 out of 109 samples) at concentrations ranging from 0.008 to 53 mg/kg. Only soil data collected between 0 and 10 feet bgs are considered in the HHRA.

Soil samples from depths deeper than 10 feet bgs are not relevant for the purpose of direct human exposure because soil deeper than 10 feet is not typically accessed. For the purpose of evaluating exposure, analytical results of soil samples are divided into two depth intervals: (1) surface soil from 0 to 2 feet bgs; and (2) subsurface soil from 2 to approximately 10 feet bgs. The analytical results are further divided into Exposure Areas A through E, which are discussed in Section 4.1.4. Soil sample locations and exposure area boundaries are presented on Figures 5a and 5b.

3.4 SELECTION OF CHEMICALS OF POTENTIAL CONCERN Not all chemicals detected at a site warrant a quantitative evaluation. In many cases, chemicals are detected at such low concentrations as to pose a negligible risk and may be eliminated from further consideration. Selection criteria used to identify COPCs for the purpose of this HHRA were the following:

Elements that are considered essential dietary nutrients were not considered COPCs (e.g., calcium, iron, magnesium, phosphorous, potassium, and sodium).


Inorganic chemicals detected at concentrations consistent with local background levels as predicted by a statistical comparison as described below were not considered COPCs.

An organic chemical detected in all samples at concentrations less than one-tenth the respective screening level was excluded as a COPC if there was sufficient toxicological data to evaluate health risks (e.g., a published regulatory value).

Chemicals considered as Class A carcinogens (known to cause cancer in humans) were not excluded based on a comparison to screening levels.

The following sections summarize the selection of COPCs for each medium.

3.4.1 Groundwater Maximum concentrations of chemicals detected in groundwater (perchlorate and VOCs) were compared to one-tenth of the EPA regional screening levels (RSLs) for tap water. All chemicals detected above one-tenth of the RSL are considered COPCs and are presented in Table 8. Chemicals detected in at least one sample and any of the twenty ROD COCs that were not detected are presented in Table 8.

3.4.2 Soil Vapor Maximum concentrations of all chemicals detected in soil vapor were compared to values 100-fold higher than the RSLs for residential air. Specifically, the RSL was multiplied by a site-specific attenuation factor of 1000 (USEPA, 2002c) and divided by 10 for screening purposes. All chemicals detected above the adjusted RSL are considered COPCs and presented in Table 9.

3.4.3 Soil With the exception of naturally occurring metals consistent with background, maximum concentrations of all chemicals detected in soil were compared to one-tenth of the EPA RSLs for residential soil. All chemicals detected above one-tenth of the RSL are considered COPCs and are presented in Table 10. Benzene was detected below its screening level, but was included as a COPC because it is identified as a Class A human carcinogen. Several chemicals were excluded as COPCs because they are essential nutrients (calcium, magnesium, potassium, and sodium) and silicon was excluded because of insufficient toxicity criteria available.

3.4.3.1 Comparison to Background Because metals occur naturally in soils, metal results from the Site were compared to the metal results from local background sampling to determine if on-Site levels are consistent with


natural levels or potentially indicative of site-related contamination. A report prepared for the Arizona Department of Environmental Quality (ADEQ) which compiled background metals data for Arizona soils (Earth Technology, 1991) was used to obtain local background metals data. Samples in the report that were labeled as being in Maricopa County were included in the background data set. These results included a data set collected near the Goodyear Airport and have been previously referenced in the Phase II Work Plan (ARCADIS, 2008a). A total of 28 samples in the top 10 feet of the subsurface were used and are presented in Appendix D-1.

The background evaluation was only performed on metals that have a detection frequency greater than 50% in Site samples and detected in at least four background samples. Although cobalt was only detected in three background samples, cobalt was included as an exception because it was detected in all three background samples at concentrations (10 to 15 mg/kg) greater than the maximum detected concentration at the Site (9.6 mg/kg). Therefore, the background testing was performed on aluminum, arsenic, barium, beryllium, chromium (total), cobalt, copper, lead, nickel, and zinc. Nine metals, boron, cadmium, hexavalent chromium, iron, manganese, mercury, selenium, silver, and vanadium, were considered as COPCs because these chemicals were detected at a frequency of less than 50% (Table 10) or had insufficient background data available.

As described below, a tiered, statistical testing approach was employed in the comparison of on-site metal concentrations to background concentrations. In the first tier of testing, the Wilcoxon-Mann-Whitney (WMW) test or the Gehan test was used to determine whether or not measurements from the site data sets tended to be larger (or smaller) than those from the corresponding background data set (Appendix D-2). Both tests are nonparametric (i.e., not sensitive to the underlying distribution of data) and can be used with censored data (i.e., non-detect values). Test selection was dependent on the frequency of detection of each of the populations being compared and the number of detection limits within each data set. In the second tier of testing, the quantile test was employed as it is more powerful than the WMW test or Gehan test for detecting cases of high value measurements present in the upper quantile (right-hand tail) of a distribution (USEPA, 2010). When applied together, these tests are better at revealing true differences between two population distributions. One-sided statistical tests were used in all cases, employing a Type I error rate of 0.05 (5%).

The tiered, statistical testing of metals against background described below was conducted as recommended by EPA (2010b).

1st Tier - The WMW test was performed for metals with consistent detection limits and a frequency of detection of at least 60% in the site data set. The Gehan test was


performed for metals with multiple detection limits or less than 60% frequency of detection. Both tests were applied with the following null hypothesis (H0):

H0: the median concentration for the site is less than or equal to the median concentration in the background population

2nd Tier - When either the WMW test or Gehan test did not reject the H0 (when it was concluded that the median concentrations were not significantly different), the quantile test was performed to confirm the results.

All statistical tests were conducted using EPA’s ProUCL Version 4.1.01 product (USEPA, 2011a). The results of the two-population statistical testing are presented as ProUCL output in Appendix D (parts D-3 and D-4, which are summarized in part D-2).

Using the prescribed two-tiered approach, the on-Site soil results for nine metals (aluminum, arsenic, barium, chromium (total), cobalt, copper, lead, nickel, and zinc) are considered consistent with background levels based on results from the WMW test and quantile test. Concentrations of beryllium were considered consistent with background levels based on results from the Gehan test and quantile test. In addition, Quantile-Quantile (Q-Q) plots (i.e., cumulative probability plots) containing both data sets were graphed using ProUCL and are presented in Appendix D-5. Q-Q plots and can be visually evaluated to identify potential outliers or the presence of a mixture of samples (e.g., data from different populations) in a data set (USEPA, 2009b). Although the Site population is similar to the background population, nonparametric tests, such as WMW, are not sensitive to the magnitude of concentration at one end of the distribution. The Q-Q plot for lead displays a Site concentration of 2,200 mg/kg that is significantly higher than the rest of the Site data set. This value was measured in Exposure Area C in sample B10-02A. An adjacent sample (B10-02) collected at the same depth did not detect lead at 0.5 mg/kg and next highest concentration in the area was detected at 10-fold lower concentration at 210 mg/kg. This result for lead is an isolated result that is not characteristic of Exposure Area C or the Site. Therefore, this result did not change the conclusion that lead concentrations were consistent with background.

4.0 EXPOSURE ASSESSMENT

Exposure assessment is the process of describing, measuring or estimating the intensity, frequency, and duration of potential human exposure to COPCs in environmental media (e.g., soil, water and air) at a site. This section of the HHRA discusses the mechanisms by which people (receptors) might come in contact with COPCs at the Site. The exposure assessment follows the recommendations for conducting an exposure assessment provided in the EPA’s

“Risk Assessment Guidance for Superfund” (USEPA, 1989b), and the more recent guidance in


EPA's “Guidelines for Exposure Assessment” (USEPA, 1992c), and associated guidance. In accordance with EPA (1989b), an exposure assessment consists of three basic steps:

Characterization of the exposure setting (physical environment and potential receptors).

Identification of exposure pathways (potential sources, points of release, and exposure routes).

Quantification of pathway-specific exposures (exposure point concentrations and intake [dose] assumptions).

The purpose of the first step is to characterize the salient features of the site that might influence current or future human exposure to COPCs and to identify potential receptors. Potential pathways of human exposure are identified in the second step by characterizing the sources of COPCs released to the environment, points of release, and potential exposure routes. In the third step, the qualitative information from the first two steps is integrated with estimates of exposure concentrations and intake assumptions to quantitatively estimate exposure (dose).

Exposure assessment is conducted within the context of a site conceptual model (SCM). As described in EPA’s Guidance for Conducting Remedial Investigations and Feasibility Studies under CERCLA (USEPA, 1988), the purpose of the SCM is to describe w

draft source areas, soil, and facility · table of contents (continued)...

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