'FINAL BASELINE RISK ASSESSMENT WORK PLAN, REMEDIAL ...

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Final v^^ *ccj-^ • ™>;-wa Baseline Risk Assessment Work Plan

Remedial Investigation/Feasibility Study Barber Orchard Site

Haywood County, North Carolina

10086099

Prepared under EPA Contract No. 68-W-99-043

USEPA Work Assignment 034-RICO-A4T9 Remedial Investigation and Feasibility Study

Barber Orchard Site

Prepared by Black and Veatch Special Projects Corporation

1145 Sanctuary Parkway, Suite 475 Alpharetta, Georgia 30004

May 16, 2001

r, v,iT*tt&<eline rtS^Assessment Work Plan Section: TOC i EPA CofljyjaqjiNo. 68-W-99043 Revision No. 0 "

'•""•' '^ork''Assignment No. 034-RJCO-A479 Revision Date: May 16. 2001 Barber dfthard Site Page i of iv

TABLE OF CONTENTS

List of Tables ii List of Figures ii List of Acronyms ii

1.0 INTRODUCTION 1-1 1.1 Site Description 1-1

1. 1.2 Operational History 1-2 1.3 Previous Investigations 1-3 1.4 Baseline Risk Assessment Protocol 1-3 1.5 Organization of the Baseline Risk Assessment 1-5

2.0 BASELINE HUMAN HEALTH RISK ASSESSMENT 2-1 2.1 Data Evaluation 2-1

2.1.1 Evaluating Data Quality 2-1 2.1.2 Identification of COPC 2-2f 2.1.3 Data Summary 2-4

2.2 Exposure Assessment 2-5 2.2.1 Conceptual Site Exposure Model 2-5 2.2.2 Quantification of Exposure-Point Concentrations 2-24 2.2.3 Quantification of Chemical Intake 2-38

2.3 Toxicity Evaluation 2-45 2.3.1 Cancer Evaluation 2-45 2.3.2 Evaluation of Noncancer Effects 2-48 2.3.3 Dermal Toxicity Values 2-49 2.3.4 Target Organ Toxicity 2-49 2.3.5 Sources of Toxicity Information 2-50

2.4 Risk Characterization 2-52 2.4.1 Cancer Risk 2-53 2.4.2 Noncancer Hazards of Chemicals 2-54 2.4.3 Risk Characterization Results 2-56

2.5 Remedial Goal Option Development 2-56 2.5.1 Selection of Chemicals of Concern 2-56 2.5.2 Remedial Goal Options Estimation Methodology 2-57

2.6 Uncertainty Analysis 2-58 2.6.1 Types of Uncertainty 2-58 2.6.2 Sources of Uncertainty 2-58J

2.7 Human Health Risk Conclusions 2-65

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3.0 ECOLOGICAL RISK ASSESSMENT 3-1 3.1 Ecological Site Description 3-2 3.2 Screening-Level Effects Evaluation 3-2

3.2.1 Identification of COPC 3-3 3.2.2 Refinement of PCOPC 3-3 3.2.3 Screening-Level Effects Uncertainty 3-5

3.3 Ecological Risk Conclusions 3-6

4.0 OVERALL CONCLUSIONS 4-1

5.0 REFERENCES 5-1

LIST OF TABLES

2-1 Receptor/Exposure Scenarios 2-9 2-2 Variables Used to Estimate Potential Chemical Intakes and Contact Rates for

Receptors 2-15

LIST OF FIGURES

2-1 Conceptual Site Exposure Model 2-6

LIST OF ACRONYMS

ABS absorption fraction

AF adherence factor

AT averaging time

BCF bioconcentration factor

BERA baseline ecological risk assessment

BHHRA baseline human health risk assessment

BRA baseline risk assessment

BRAWP baseline risk assessment work plan

BSAF biota-to-sediment accumulation factors

BW body weight

Baseline Risk Assessment Work Plan EPA Contract No. 68-W-99043 Work Assignment No. 034-R1CO-A479 Barber Orchard Site

coc COPC

cm2

CSEM

CT op

DA

DCA

DOE

ED

EF

EFH

EPA

EPC

ER

ERA

ET

FI

g/day

g/m3

GAF

HI

HQ

HSDB

ILCR

IRIS

IT

kg

L/day

Hg/L Hg/m3

MCL

MDC

chemical(s) of concern

chemical(s) of potential concern

square centimeter

conceptual site exposure model

central tendency

degrees Fahrenheit

dose absorbed

dichloroethane

U.S. Department of Energy

exposure duration

exposure frequency

Exposure Factors Handbook

U.S. Environmental Protection Agency

exposure point concentration

emergency response

ecological risk assessment

exposure time

fractional term

grams per day

grams per cubic meter

gastrointestinal absorption factor

hazard index

hazard quotient

Hazardous Substances Data Bank

incremental lifetime cancer risk

Integrated Risk Information System

IT Corporation

kilogram

liters per day

micrograms per liter

micrograms per cubic meter

maximum contaminant level

maximum detected concentration

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Revision Date: May 16, 2001 Page ivof iv

m3/hr cubic meters per hour

mg/day milligrams per day

mg/kg milligrams per kilogram

mg/kg-day milligrams per kilogram per day

mg/L milligrams per liter

mL/hr milliliters per hour

msl mean sea level

NCDC National Climatic Data Center

PAH polynuclear aromatic hydrocarbon

PCB polychlorinated biphenyl

PCOPC preliminary contaminant of potential concern

PEF particulate emission factor

PRG preliminary remedial goal

QC quality control

RBSC risk-based screening concentration

RfC reference concentration

RfD reference dosage

RGO remedial goal option

RI remedial investigation

RME reasonable maximum exposure

SA surface area

SF slope factor

SLERA screening-level ecological risk assessment

SSV ecological soil screening value

SV screening value

UCL upper confidence limit

URF unit risk factor

VOC volatile organic compound

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Section 1 Revision No.O

Revision Date: May 16, 2001 Page 1 of 6

1.0 INTRODUCTION

The purpose of this baseline risk assessment work plan (BRA WP) is to describe the protocol for

evaluating risk to human health and ecological receptors resulting from exposure to chemicals in

environmental media associated with the former Barber Orchard site (site), Haywood County, North

Carolina. The primary objective of the baseline risk assessment (BRA) is to provide risk-based

information to be used as input for site management decisions.

The BRAWP is intended to serve as the template for the BRA, which will include all the equations

and variable values necessary for quality control (QC) and replication of computations used to

calculate risks associated with exposure to chemicals in site environmental media. Human health

risk methods and results will be presented in the baseline human health risk assessment (BHHRA)

and ecological risk methods and results will be presented in the ecological risk assessment (ERA).

1.1 Site Description The site comprises approximately 500 acres on a mountainside in Haywood County, North Carolina,

approximately 3 miles west of Waynesville. It was historically used as an apple orchard from the

early 1900s until 1988. The site is currently being developed for residential use, with numerous

residences already on site. Existing property plots range in area from less than an acre to greater than

20 acres. The Barber Orchard soil has been identified as contaminated with arsenic, lead, and

pesticides.

The site extends from near the base of the mountain (approximately 3,000 feet above mean sea level

[msl]) southward up the slope to more than 4,000 feet msl. Undeveloped on-site areas include apple

trees remaining from the orchard operation, as well as secondary growth. Seven small on-site and

near-site drainages flow down (northward) the mountain to Richland Creek at the base of the site.

These drainages are each less than 2 feet wide and only a few inches deep. Of these seven, the

drainages located farthest west and farthest east are actually off site, but may be affected by flow

from the Barber Orchard site. One drainage originates from a spring that is the source for a series

of small on-site ponds. An overflow pipe in each of the ponds flows back into a drainage that flows

into the next pond in the series. None of these ponds appeared to be more than approximately

60 feet in diameter. Groundwater flow follows the topography of the land northward.

Baseline Risk Assessment Work Plan Sectioi EPA Contract No. 68-W-99043 Revision No? Work Assignment No. 020-R1CO-A479 Revision Date: May 16, 2001 Barber Orchard Site Page 2 of 6

South of the site is a wooded area bisected by the Blue Ridge Parkway. Areas east and west of the

site are generally wooded and may be described as rural residential, which includes some clusters

of houses. The northern part of the site is in a mountain valley through which Richland Creek flows

west-to-east; Richland Creek also receives drainage from the mountain ridges and associated valleys

north of the site. Another orchard (Cable Orchard) is currently operating on adjacent property east

of the site, near the base of the hill. Also, the Haywood County Head Start childcare/leaming center

is located just northeast of the site.

The climate in the region is temperate with daily mean temperatures ranging 37 degrees Fahrenheit

(°F) from for the coldest month (January) to 71°F for the warmest month (July) (National Climatic

Data Center [NCDC], 1990). Low temperatures of 32°F or less are encountered 102 days per year

on average. The average precipitation in the region is approximately 48 inches per year and is

typically rather evenly distributed throughout the year, with precipitation recorded (i.e., 0.01 inch

or greater) an average of 124 days per year. The average annual snowfall in the region is 17 inchesi

This weather information is from the NCDC weather station in Ashville, North Carolina (NCD

1990).

•

•

1.2 Operational History The site was an apple orchard operation from the early 1900s to the late 1980s. Reportedly, an

underground system of pressurized pipes was used to deliver water and pesticide mixtures to the

trees. Mixing of pesticides occurred at one or more mixing stations, pesticides were delivered via

the underground system to standpipes, and then employees would spray the pesticide mixture with

a flexible hose connected to the standpipes and onto the trees. The location of the one known mixing

station was identified as a contaminated area during an emergency response (ER) and was

remediated (see Section 1.3). This mixing area consisted of two 500-gallon concrete tanks; allegedly

spills had occurred in this area. The pipes were routinely flushed to prevent clogging, and any

pesticides present in the pipes were left to run onto the ground. Reportedly, pipes would sometimes

freeze and rupture in the winter, causing them to leak. Information obtained from the former orchard

operators and the North Carolina Department of Agriculture Extension Agent indicate that the

following pesticides were used at the site: Captan, DDT, lead arsenate, Lorsban/Dursban, lindane,

and Maneb.

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1.3 Previous Investigations An ER was completed at the site in August 2000. Composite soil samples collected from residential

plots and other areas of the site showed surface soils with arsenic concentrations warranting

remediation. Reportedly, the top 1 foot of soil containing arsenic concentrations greater that 40

milligrams per kilogram (mg/kg) was removed and replaced with clean soil and seeded, generally

only on property plots where residents were currently living. Additionally, soil was removed and

replaced in an area of the site along a drainage, which was identified as a location where pesticides

had formerly been mixed. In addition to arsenic, the following are potentially chemicals of concern:

lead;p,p'-dichlorodiphenyltrichloroethane; p,p'-dichlorodiphenyldichloroethane; dieldrin, a-hexa-

chlorocyclohexane; P-hexachlorocyclohexane; endrin, and endrin ketone. Pesticides were detected

in on-site residential wells, as well as in soil.

1.4 Baseline Risk Assessment Protocol The BRA as described in this BRAWP is based on U.S. Environmental Protection Agency (EPA)

guidance including, but not limited to, the following:

• EPA, 1989a, Risk Assessment Guidance for Superfund, Volume I, Human Health Evaluation

Manual (Part A), Interim Final, Office of Emergency and Remedial Response, Washington,

DC, EPA/540/1-89/002.

• EPA, 1991 a, Risk Assessment Guidance for Superfund Volume I: Human Health Evaluation

Manual Supplemental Guidance, Standard Default Exposure Factors, Interim Final, Office

of Solid Waste and Emergency Response, OSWER Directive: 9285.6-03.

• EPA, 1992a, Supplemental Guidance to RA GS: Calculating the Concentration Term, Office

of Solid Waste and Emergency Response, Washington, DC, Publication 9285.7-081.

• EPA, 1992b, Dermal Exposure Assessment: Principles and Applications, Interim Report,

Office of Research and Development, Washington, DC, EPA/600/8-91/01 IB, including

Supplemental Guidance dated August 18, 1992.

Baseline Risk Assessment Work Plan Sectioi EPA Contract No. 68-W-99043 Revision N Work Assignment No. 020-RJCO-A479 Revision Date: May 16. 2001 Barber Orchard Site Page 4 of 6

•

EPA, 1992c, "Guidance on Risk Characterization for Risk Managers and Risk Assessors,"

Memorandum from F. Henry Habicht II, Deputy Administrator, to Assistant Administrators,

Regional Administrators, February 26, 1992.

EPA, 1995a, Supplemental Guidance to RAGS: Region 4 Bulletins Human Health Risk

Assessment, Waste Management Division, Atlanta, Georgia, November.

EPA, 1995b, Supplemental Guidance to RAGS: Region 4 Bulletins Ecological Risk

Assessment, Waste Management Division, Atlanta, Georgia, November, and amendments

made to this document by EPA Region 4 on August 11,1999.

EPA, 1997a, Exposure Factors Handbook, Office of Research and Development,

EPA/600/P-95/002, August.

EPA, 1997b, Ecological Risk Assessment Guidance for Superfund: Process for Designing/}

and Conducting Ecological Risk Assessments, Interim Final, Emergency Response Team,

Edison, New Jersey, EPA540-R-97-006, June.

EPA, 1998, Risk Assessment Guidance for Superfund: Volume I, Human Health Evaluation

Manual (Part D, Standardized Planning, Reporting, and Review of Superfund Risk

Assessments), Interim, Office of Emergency and Remedial Response, Washington, D.C.,

January, 9285.7-01D.

EPA, 2000a, Region 9 Preliminary Remediation Goals (PRGs) 2000, Annual Update, San

Francisco, California, November.

EPA, 2000b, Integrated Risk Information System (IRIS), On-line, National Center for

Environmental Assessment, Cincinnati, Ohio.

EPA, 2000c, "Amended Guidance on Ecological Risk Assessment at Military Bases: Process

Considerations, Timing of Activities, and Inclusion of Stakeholders", memorandum from T

Simon to J. Johnston and E. Bozeman, Office of Technical Services, June 23.

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1.5 Organization of the Baseline Risk Assessment As mentioned, the BRA is composed of the BHHRA (human health risks) and the ERA (ecological

risks). The BHHRA will present the human health assessment methods used, results generated, and

the interpretation of these results. The BHHRA will be organized as follows:

• Introduction: Provides a brief description of the site and site issues. It also describes the

protocol and organization of the BHHRA.

• Data Evaluation: Identifies data sources, evaluates data quality, and identifies chemicals

of potential concern (COPC)

• Exposure Assessment: Identifies receptors and pathways, describes exposure point

concentrations (EPC), and presents methods for calculating chemical intake rates.

• Toxicity Assessment: Identifies the toxicity values that are used in the risk assessment

and describes development of dermal toxicity values.

• Risk Characterization: Describes quantitative methods for evaluating cancer risks and

noncancer hazards, and presents quantitative results.

• Remedial Goal Option Development: Describes the selection process for chemicals

of concern (COC) and the estimation methodology for deriving cancer-based and noncancer-

based, receptor-specific remedial goal options (RGO) for the COCs.

• Uncertainty Analysis: Identifies uncertainties in all phases of the BHHRA and discusses

their individual effects on the risk assessment results and interpretation.

• Summary/Conclusions: Provides a brief summary of the entire risk assessment,

including quantitative results, uncertainties, and pertinent site information. Summary and

discussion are focused on those results and issues that are most likely to directly affect site

management decisions.

1 NOTU

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The ERA will present the methods used, results generated, and the interpretation of these results.

The ERA will be organized as follows:

• Site Description: Provides a description of the site with respect to ecological concerns

such as site use, acreage, vegetation, wildlife, habitats, and the likelihood of threatened and

endangered species being present.

• Screening-Level Effects Evaluation: Identifies the sources of data and screening

benchmarks used, describes the methodology for determining chemicals of potential

ecological concern (COPC), identifies the COPC, and describes uncertainties associated with

the screening-level effects evaluation.

Problem Formulation: Compares detected concentrations of COPC to those encountered

in background samples, spatially analyzes the di

areas with respect to exposure/risks to wildlife.

in background samples, spatially analyzes the distribution of COPC, and evaluates impacltf^

• Conclusions: Briefly summarizes the results of the ERA and provides recommendations.

Discussion is focused on those results and issues that are most likely to directly affect site

management decisions.

An overall risk assessment summary will overview the results of the BHHRA and ERA. This

summary will focus on presenting the "bottom-line" conclusions and issues that are most applicable

to site management decision-making.

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2.0 BASELINE HUMAN HEALTH RISK ASSESSMENT

2.1 Data Evaluation Data used for the BHHRA will consist of the analytical results of soil, groundwater, surface water,

and sediment samples to be collected during the RI (IT, 2000a), as well as composite soil samples

collected during the ER. It is anticipated that a large majority of surface soil samples collected

during the RI will be composite samples, with grab surface soil samples collected for verification

of the composite sample analytical results and for extent-of-contamination purposes (IT, 2000a).

Subsurface soil samples will be collected as grab samples only (IT, 2000a). Groundwater samples

will be collected from monitoring wells screened in the residuum and bedrock aquifers separately.

Residential wells will also be sampled to supplement the investigation of the bedrock aquifer.

A list of chemicals present in site samples from each medium will be compiled as a first step of the

data. evaluation. From this list, COPC are selected to be carried forward into the exposure

assessment (Section 2.2). The processes of evaluating the data quality (Section 2.1.1) and identifying

COPC (Section 2.1.2) are described in the following subsections.

2.1.1 Evaluating Data Quality

The analytical data may have qualifiers from the analytical laboratory QC or from the data validation

process that reflect the level of confidence in the data. Some of the more common qualifiers and

their meanings are (EPA, 1989a):

• U - Chemical was analyzed for but not detected; the associated value is the reporting limit.

• J - Value is estimated.

• R - QC indicates that the data are unusable (chemical may or may not be present).

"J" qualified data are used in the BHHRA; "R" qualified data are not. The handling of "U" qualified

data (nondetects) in the BHHRA is described in Section 2.2.2.1. The use of data with other less

common qualifiers is evaluated on a case-by-case basis. Generally, data for which the identity of the

chemical is unclear are not used in the BHHRA. If confidence is high that the chemical is present,

but the actual concentration is somewhat in question, the data generally are used in the BHHRA.

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2.1.2 Identification of COPC COPC identification is a screening process designed to focus the BHHRA on the chemicals that may

contribute significantly to overall risk. Only those analytes detected in at least one sample may be

identified as COPCs. In this screen, chemical concentrations in environmental media are compared

with conservative chemical- and medium-specific risk-based screening concentrations (RBSC)

derived from standard exposure scenarios (Section 2.1.2.1), and on-site chemical concentrations are

compared with site background concentrations (Section 2.1.2.2).

2.1.2.1 Risk-Based Screening. The maximum detected concentration (MDC) is compared with

the appropriate RBSC. If the MDC of a chemical is less than or equal to its RBSC, the chemical in

this medium is not considered further in the BHHRA because it is very unlikely that chemical

concentrations at or below the RBSCs would contribute significantly to risk or hazard. If the MDC

exceeds the RBSC, the chemical is considered to be a COPC. The units of MDCs and RBSCs are

the same for each chemical in a given medium; e.g., for water both variables have units of

micrograms per liter (flg/L) in water.

RBSCs are derived from Region 9 preliminary remediation goals (PRG) assuming conservative,

standard exposure assumptions (EPA, 2000a). PRGs for noncancer effects are calculated using a

hazard quotient (HQ) of 1.0 and for carcinogenic effects are calculated using an incremental lifetime

cancer risk (ILCR) of 1E-6. Groundwater RBSCs are based on the household "tap water" PRG

values, and soil RBSCs are based on residential soil PRG values. For cancer effects, the PRG values

are used directly as RBSCs. Groundwater and surface soil RBSC values for noncancer effects are

derived by multiplying the respective tap water and residential soil PRG values by a factor of 0.1.

This results in RBSC values associated with an HQ of 0.1, which is selected to provide additional

protection for simultaneous exposure to multiple chemicals (EPA, 1995a).

Carcinogenic chemicals exert both carcinogenic and noncancer effects. The Region 9 PRGs listed

for these chemicals reflect the lower of the two values (cancer-based or noncancer-based) for those

chemicals for which chronic reference doses (RfD) are available (with a few exceptions that list both

noncancer-based and cancer-based values). The noncancer-based PRG values are based on an HQ

value of 1.0 and the RBSCs are based on a more health-protective value of 0.1. Therefore,

noncancer-based concentrations will be recalculated (assuming an HQ of 0.1) for COPC screening

in this BHHRA, for chemicals exerting both cancer and noncancer effects. The more conservative

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(health-protective) of the two values (the cancer-based PRG or the noncancer-based value calculated

using an HQ of 0.1) will be selected as the RBSC for the BHHRA; these are referred to as

"integrated values" in the Region DC PRG spreadsheets.

It is noted that PRGs are not specifically available for surface water or sediment. Surface water will

be screened using National Recommended Water Quality Criteria for consumption of water and

organisms (EPA, 2000d), as well as North Carolina Surface Water Standards. Sediment

concentrations will be screened against the surface soil RBSCs based on PRG values for residential

soil as described above.

Chemicals for which all samples yield nondetects will be qualitatively evaluated. This qualitative

evaluation will include:

An evaluation of detection limits to determine whether or not they conform to Contract Laboratory Program (CLP) values.

• A comparison of one-half the quantitation limit to the appropriate RBSC.

This evaluation of nondected compounds will be discussed in the uncertainties section if any (at one-

half the quantitation limit) exceed the RBSC. Emphasis will be given to such compounds that might

be expected in environmental media based on site history.

Essential nutrients such as calcium, magnesium, potassium, and sodium may be eliminated as

COPC, provided that their presence in a particular medium is judged to be unlikely to cause adverse

effects on human health (EPA, 1995a).

2.1.2.2 Background. Chemical concentrations in site samples are compared to background

concentrations as an indication of whether a chemical is present from site-related activity or as

background. An inorganic chemical may be eliminated from identification as a COPC if its

concentration in a site medium is consistent with background concentrations (EPA, 1995a).

Although this elimination from COPC status is generally used only for inorganic chemicals,

sometimes widespread anthropogenic chemicals, such as polynuclear aromatic hydrocarbons (PAH)

and pesticides, may also be present at a site due to sources unrelated to site activities (EPA, 1989a).

For the Barber Orchard site, concentrations of inorganics in site media will be compared to off-site

SJoH Baseline Risk Assessment Work Plan Seel EPA Contract No. 68-W-99043 Revision No" Work Assignment No. 020-R1CO-A479 Revision Date: May 16, 2001 Barber Orchard Site Page 4 of 60

background concentrations as part of the COPC screening process, but it is assumed that any

pesticides detected on site would have resulted from former site operations.

In accordance with Region 4 guidance for background screening (EPA, 1995a), MDCs of inorganics

in each medium that exceed the RBSC (Section 2.1.2.1) will be compared with a background

screening concentration of two times the mean concentration of the background data set for that

medium. Inorganics with concentrations less than this background screening concentration will be

eliminated from further consideration. If the MDC exceeds this value, the chemical is retained as

a COPC.

Background soil samples will be collected from various near-site locations believed to be unaffected

by the Barber Orchard operation, and background groundwater data samples will be collected from

upgradient monitoring wells (IT, 2000a). Background soil and sediment samples for the drainages

will be collected from upstream locations in each of the two site drainages whose origins extend

site. Background soil and sediment for Richland Creek will be collected from an upstream locati<J

Summary statistics for these background samples will be provided in the BHHRA, and the analytical

data for these background samples will be appended.

•

The detection at concentrations above levels in blanks, following the protocol described in the

quality assurance project plan (IT, 2000b), is presumptive evidence of site-related activity for most

organic chemicals, but there are exceptions. For example, upstream contributions of specific

organics may be responsible for the detection of these compounds in site sediment or surface water.

However, organics will not be eliminated as COPC based on background concentrations during the

screening process. Instead, such compounds that qualify as COPC (as a result of risk-based

screening) will be carried through the risk assessment process. Professional judgment will be used

to determine if any detected organics should be eliminated from further consideration after the risk

characterization (Section 2.4) based on background contributions.

2.1.3 Data Summary g^ The data evaluation will be presented for each medium in table format. These tables will incluBF

the following information:

Figure 2-1

Preliminary Human Health Conceptual Site Exposure Model Barber Orchard Site, Haywood County, North Carolina

Source

... |

Spraying and

Leaks

Source Medium

». Surface - Soil

Primary Secondary Secondary Tertiary Tertiary Release Medium Release Medium Release

1

•

1 •

Subsurface Soil

1

4-

-*

• — p

Uptake by Plants

Dust Emissions

Infiltration, Leaching

Dust Emissions Volatilization

• Leaching J

• Vegetation Grazing by Cattle Cattle

-fe>

k .

w • • w

-p*

>

w

few

• Groundwater

W

hw W Discharge -r\

1 Erosion,

Kunon

H

b Surface Water

_ h .

| •

•

i I

V S ec lime ;ni

Bio-uptake

Volatilization

• Partitioning

• 4 T

k* W

-fc,

Exposure Medium

Snil

Beef

Milk

Vegetables

Air

Soil

Air

Potable Water

Air

Surface Water

Fish

Air

Sediment

Expo Ro

- •

—fc

- •

- *

Incidenta

Derma

Inge Inge

Inge

Inha

Incidenta

Derma

Inha

Inge

Derma

Inha

Incidenta

Dermal

Inge

Inha

Incidenta Derma

* = Complete exposure route quantified in the risk assessment. 'Beef, milk, and pond exposure are included here, but are quantified separately in the BH 1 = Sportsman is evaluated for fishing activities in Richland Creek only. 2 = Contact with this medium, although plausible, is not part of this receptor's normal or expected activities; therefore contact would be sporadic and is not quantifie 3 = There is no plausible pathway for exposure to this medium. 4 = Subsurface soil exposure is not quantitatively evaluated, although this pathway is complete. KN\Black a 5 = Exposure is considered minimal compared to other pathways for this medium. 6 = Although theoretically complete, large dilution factor of ambient air is assumed to render exposure-point concentrations toxicologicalty insignificant.

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Chemical name

Frequency of detection

Range of detected concentrations

Range of detection limits

Arithmetic mean of site concentrations

Data distribution

Upper confidence limit (UCL) on the arithmetic mean

Appropriate RBSC

Background screening criterion

Selection as COPC.

2.2 Exposure Assessment Exposure is the contact of a receptor with a chemical or physical agent. An exposure assessment

estimates the type and magnitude of potential exposure of a receptor to COPC found at or migrating

from a site (EPA, 1989a). An exposure assessment includes the following steps:

Characterize the physical setting.

Identify the contaminant sources, release mechanisms, and migration pathways.

Identify the potentially exposed receptors.

Identify the potential exposure pathways.

Estimate exposure concentrations.

Estimate chemical intakes or contact rates.

2.2.1 Conceptual Site Exposure Model The conceptual site exposure model (CSEM) provides the basis for identifying and evaluating the

potential risks to human health. The CSEM (Figure 2-1) includes the receptors appropriate for all

plausible land-use scenarios and potential exposure pathways. It graphically presents all possible

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Section 2 Revision No. 1

Revision Date: May 16, 2001 Page 7 of60

pathways by which a potential receptor may be exposed, including all source media, release and

transport pathways, and exposure routes, facilitates consistent and comprehensive evaluation of risk

to human health, and helps to prevent potential pathways from being overlooked. The elements of

a CSEM include:

• Source (i.e., initially contaminated environmental) media

• Contaminant release mechanisms

Contaminant transport pathways

• Intermediate or transport media

• Exposure media

Receptors

Routes of exposure.

The receptors and pathways in Figure 2-1 reflect plausible scenarios developed from information

regarding site background and history, topography, climate, and demographics. Asterisks

identifyexposure pathways that are complete and addressed in the BHHRA. Justification for

exclusion of other pathways is provided in the figure footnotes.

2.2.1.1 Physical Setting. This section is based on the more-detailed account of the site

description, history, and summary of previous investigations provided in Section 1.0. Briefly, the

site is being developed for residential use. The surrounding area is mostly rural residential with

some commercial use. The Cable Orchard currently operates just northeast of the site. Current

residents on the site in the general vicinity use groundwater from private wells.

The terrain is characterized as sloping. Seven perennial drainages on and near the site flow down

the mountainside northward. Groundwater flow direction is assumed to follow that of the

topography (generally northward); bedrock fractures may also influence flow.

2.2.1.2 Contaminant Sources, Release Mechanisms, and Migration Pathways.

Contaminant sources, release mechanisms, and migration pathways are presented in Figure 2-1.

Although contaminants (e.g., arsenic, lead, pesticides) may be present throughout the site due to

standard orchard spraying operations, highly contaminated areas may be associated with occasional

breaks in the lines, mixing areas, and possibly other nonstandard activities



2.2.1.3 Receptors and Exposure Pathway Descriptions. Receptors were selected to represent

the upper bound on exposure from all plausibly exposed groups of people at the Barber Orchard site.

These are the on-site resident, on-site commercial worker, on-site construction worker, adolescent

visitor, and (for Richland Creek) sportsman. Small-scale beef and dairy production, as well as pond

exposure, may be associated with a limited number of residents and are evaluated separately from

the on-site resident. The pathways by which these receptors may be exposed are summarized in

Figure 2-1 and Table 2-1. It is noted that a Head Start childcare/learning facility is located near the

northeast portion of the Barber Orchard site, and presumably uses a private groundwater well.

Groundwater will be sampled from this well and compared to maximum contaminant levels (MCL),

State of North Carolina drinking water criteria, and/or tap water PRGs in the RI (IT, 2000a).

The BHHRA is based on a reasonable maximum exposure (RME) assumption. The intent of the

RME assumption is to estimate the highest exposure level that could reasonably be expected to

occur, but not necessarily the worst possible case (EPA, 1989a, 1991 a). It is interpreted as reflects*

the 90 to 95th percentile on exposure. As a result, these estimates are not intended to represeUP

broadly defined population (EPA, 1989a). In keeping with EPA (1991 a) guidance, variables chosen

for a baseline RME scenario for contact rate, exposure frequency (EF) and exposure duration (ED)

are generally upper-bounds. Other variables [e.g., body weight (BW)] are generally central or

average values. The exposure variable values to be used for each receptor in the BHHRA

contaminant intake models are compiled in Table 2-2.

The averaging time (AT) for noncancer evaluation is computed as the product of ED (in years) times

365 days per year, to estimate an average daily dose over the entire exposure period (EPA, 1989a).

For cancer evaluation, AT is computed as the product of 70 years, the assumed human lifetime, times

365 days per year, to estimate an average daily dose prorated over a lifetime, regardless of the

frequency or duration of exposure. This methodology assumes that the risk from short-term

exposure to a high dose of a given carcinogen is equivalent to long-term exposure to a

correspondingly lower dose, provided that the total lifetime doses are equivalent. This approach is

•

Seed Revision 1

Revision Date: May 16, 2001 Page 8 of60

Table 2-1 Selection of Exposure Pathways

Barber Orchard Site, Haywood County, North Carolina

Scenario

Timeframe

' Current

Medium

Groundwater

Groundwater

Exposure

Medium

Groundwater

Air

Animal Tissue

Groundwater

Air

Animal Tissue

Exposure

Point

Residuum aquifer-tap water

Residuum aquifer-vapors at showerhead

Beef/Milk from cattle fed residuum groundwater

Bedrock aquifer-tap water

Bedrock aquifer-vapors at showerhead

Beet/Mi* from cattle fed bedrock groundwater

Receptor

Population

Resident

Construction Worker

Commercial Worker

visitor

Resident

Beef/M 9k Production

Resident

Construction Worker

Commercial Worker

Visitor

Resident

Beef/Mak Production

Receptor

Age

Adult

Child

Adult

Adult

Adolescent

Adult

Chid

Adult

Ch9d

Adult

Chad

Adult

Adult

Adolescent

Adult

Chad

Adult

Chad

Exposure

Route

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Inhalation

Inhalation

Ingestion

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Inhalation

Inhatation

Ingestion

Ingestion

On-Site/ Type of

Off-Site Analysis

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

Quant

Quant

Quant

Quant

Quant

Quant

Quant

Quant

None

None

Quant

None

Quant

Quant

Quant

Quant

Quant

Quant

Quant

Quant

Quant

Quant

None

None

Quant

None

Quant

Quant

Rationale for Selection or Exclusion

of Exposure Pathway

Residents currently Rve on the Barber Orchard site and use groundwater

Residents currently Eve on the Battier Orchard site and use groundwater


Residents currently Sve on the Barber Orchard site and use groundwater

Groundwater is currently used on site

Groundwater is currently used on sHe

Groundwater b currently used on site


No groundwater seeps Identified; site drainages are evaluated as surface water

No groundwater seeps Identified: site drainages are evaluated as surface water

Residents currenSy Dve on the Barber Orchard site and use groundwater

Child is assumed not to shower

Groundwater may be available to cattle/goats currently on site




Residents currently Rve on fhe Barber Orchard site and use groundwater


Groundwater Is currently used on site

Groundwater Is currently used on site

Groundwater is currently used on she


No groundwater seeps Identified: site drainages are evaluated as surface water



Child Is assumed not to shower


Groundwater may be available to caMe/goats currently on site

CM

CD

ro



Scenario

Timeframe

Current

(Cont.)

Medium

Surface Soil

Subsurface Soil

Exposure

_Medtum

Soil

Air

SoU

Exposure

Point

Contact with soil

Receptor

Population

Suspended particulates from soil

Volatile emissions from surface soH

Contact with soil


Volatile emissions from subsurface so9

Resident

Construction Worker

Commercial Worker

Resident

Construction Worker

Commercial Worker

Visitor

Construction Worker

Commercial Worker

Visitor

Construction worker

Resident

Commercial Worker

Visitor

Construction worker

Construction worker

Receptor

Adult

Chfld

Exposure

Route

On-Site/

Off-Site

Adolescent

Adult

ChHd

Adolescent

Adult

Child

Adult

Adult

Adolescent

Adult

Adutl

Child

Adolescent

Adult

Adult

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Derma)

Ingestion

Inhalation

Inhalation

Inhalation

Inhalation

Inhalation

Inhalation

Inhalation

Inhalation

Inhalation

Inhalation

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Inhalation

Inhalation

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

Type of

Analysis

None

None

None

None

Quant

Quant

Quant

Quant

Quant

Quant

None

None

Quant

Quant

Quant

None

None

None

None

None

Quant

Quant

None

None

None

None

None

None

None

None

Quant

Quant


of Exposure Pathway

Emergency response remediated surface soil at current residential property

Emergency response remediated surface soS at current residential property

Emergency response remediated surface so9 at current residential property

Emergency response remediated surface sod at current residential property

Construction of houses and small businesses has occurred


A few commercial operations are on the site


Nearby resident cMdren/adotescents may play on the site

Nearby resident children/adolescents may play on the site

Emergency response remediated surface soB al current residential property

Emergency response remediated surface soB at current residential property



Nearby resident chBdren/adolescents may play on the site

Volatilization from surface sou is assumed to have already occurred

Volatilization from surface sofl Is assumed to have already occurred

Volatilization from surface soH is assumed to have already occurred

Volatilization from surface sofl is assumed to have already occurred

Volatilization from surface soil Is assumed to have already occurred



Contact precluded by surface sofl

Contact precluded by surface soil





Contact precluded by surface soD



Construction of houses and smat businesses has occurred

CD

O



Scenario

Timeframe

Current

(Cont.)

Medium

Surface Water

Exposure

Medium

Sediment

Air

Animal Tissue

Sediment

Animal Tissue

Exposure

.Point

Drainages

Ponds

Richland Creek

Volatilization from drainage water

Volatilization from pond water

Volatilization from Richland Creek

Ingestion of fish from ponds

Ingestion of fish from Richland Creek

Contact with sediment-drainages

Contact with sediment-ponds

Contact with sediment-Richland Creek

Ingestion of fish from pond water


Receptor

Population

Resident

Sportsman

Visitor

Resident

Sportsman

Resident

Sportsman

Resident

Visitor

Sportsman

Resident

Sportsman

Receptor

Age

Adolescent

Adult

Adolescent

Adolescent

Adult

Adolescent

Adult

Adult

Exposure

Route

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Inhalation

Inhalation

Inhalation

Ingestion

Ingestion

Combined

Combined

Combined

Ingestion

Ingestion

On-Site/

Off-Site

On-site

On-site

On-site

On-site

Off-site

Off-site

On-site

On-site

Off-sHe

On-site

Off-sHe

On-site

On-site

On-site

On-site

Off-site

Type of

Analysis

Quant


of Exposure Pathway

Quant

Quant

Quant

Quant

Quant

None

None

None

None

Quant

Qual

Qual

Qual

None

Quant

Nearby resident chBdren/adolescerrls may play on the site

Nearby resident chtktren/adolescerrls may play on the site

Resident may occasionally swim In pond

Resident may occasionally swim In pond

Dermal contact while wading in creek

Incidental ingestion while wading

Large air dilution would result In toxicotoglcaJfy insignificant exposure

Large afr dilution would result In toxkxloglcaty insignificant exposure

Large air dilution would resut In toriorioglcatty insignificant exposure

Small ponds have Insufficient carrying capacity for sustained fishing

Ingestion associated with recreational fishing

Sediment Is covered with water and adheres mWmaTry to skin

Sediment is covered with water and adheres minimally to skin

Sediment is covered with water and adheres mhiimaSy to skin

Small ponds have Insufficient carrying capacity for sustained fishing

Ingestion associated wilh recreational fishing

CD



Exposure

Medium

Groundwater

Air

Animal Tissue

Groundwater

Air

Animal Tissue

Exposure

Point

Residuum aquifer-tap water

Residuum aquifer-vapors at showerhead

Beef/Milk from cattle fed residuum groundwater

Bedrock aquifer-tap water

Bedrock aquifer-vapors at showerhead

BeeftMilk from cattle ted bedrock groundwater

Receptor

Population

Resident

Construction Worker

Commercial Worker

Visitor

Resident

Beef/Milk Production

Resident

Construction Worker

Commercial Worker

Visitor

Resident

Beef/Milk Production

Receptor

,-..£§L.-~ Adult

Chid

Adult

Aduft

Adolescent

Adult

Child

Adult

Child

Adult

CNId

Adult

Adult

Adolescent

Adult

Chid

Adult

Chid

Exposure

Route

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Inhalation

Inhalation

Ingestion

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Inhalation

Inhalation

Ingestion

Ingestion

On-Site/

Off-Sile

On-sile

On-site

On-site

On-site

On-sile

On-site

On-site

On-site

On-site

On-site

On-site

On-sile

On-sile

On-sile

On-sile

On-sile

On-sile

On-sile

On-sile

On-sile

On-sile

On-sile

On-sile

On-sile

On-sile

On-sile

On-sile

On-site

Type of

Analysis

Quant

Quant

Quant

Quant

Quant

Quant

Quant

Quant

None

None

Quant

None

Quant

Quant

Quant

Quant

Quant

Quant

Quant

QuanI

Quant

QuanI

None

None

QuanI

None

QuanI

Quant


of Exposure Pathway

Groundwater may continue to be used








No groundwater seeps identified: site drainages are evaluated as surface water



Child Is assumed not to shower

Groundwater may be used for ivestock

Groundwater may be used for livestock









No groundwater seeps identified; site drainages are befog evaluated as surface water

No groundwater seeps identified; site drainages are befng evaluated as surface water


Child is assumed not to shower



O

O en



Scenario Medium Exposure Exposure

Timeframe Medium Point

Future

(Cont.)

Surface Soil

Subsurface Soil

Soil

Air

Soil

Air

Contact with soil


Volatile emissions from surface soil

Contact with soil

Suspended particulates from sol

Volatile emissions from subsurface soil

Receptor

Population

Resident

Construction Worker

Commercial Worker

Visitor

Resident

Construction Worker

Commercial Worker

Visitor

Resident

Construction Worker

Commercial Worker

Visitor

Construction worker

Resident

Commercial Worker

Visitor

Construction worker

Construction worker

Receptor

Age

Adult

Child

Adult

Adult

Adolescent

Adult

Child

Adult

Adult

Adolescent

Adult

Child

Adult

Adult

Adolescent

Adult

Adult

Child

Adult

Adolescent

Adult

Adutt

Exposure

Route

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Inhalation

Inhalation

Inhalation

Inhalation

Inhalation

Inhalation

Inhalation

Inhalation

Inhalation

Inhalation

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Inhalation

Inhalation

On-Site/ Type of Rationale for Selection or Exclusion

Off-Site Analysis of Exposure Pathway

On-site

On-site

On-site

On-site

II

On-site

On-sHe

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-site

On-sHe

On-site

On-site

On-sHe

On-site

On-site

On-site

On-site

On-sile

On-site

On-sHe

On-sHe

On-sHe

On-sHe

On-sHe

Quart!

Quant

Quant

Quant

OuanI

Quant

Quant

Quant

Quant

Quant

Quant

Quant

Quant

Quant

Quant

None

None

None

None

None

OuanI

Quant

Qual

Qual

Oual

Qual

Oual

Oual

Oual

Oual

OuanI

Quant

Future residential use assumed for study area


Future residential use assivned for study area


Construction of houses and smafl businesses may continue

Construction of houses and small businesses may continue

On-sHe commercial operations may continue

On-sHe commercial operations may continue






On-site commercial operations may continue

Nearby resident chUdren/aoolescents may play on the site

Volatilization from surface soil is assumed to have already occurred



Volatilization from surface son is assumed to have already occurred

Volatilization from surface son is assumed to have already occurred



Exposure not quantifiable










O i

-F=»

CD ON



Scenario Medium Exposure

Timeframe Medium

Future

(Cont.)

Surface Water

Sediment

Water

Air

Animal Tissue

Sediment

Animal Tissue

Exposure

Point

Drainages

Ponds

Richland Creek

Volatilization from drainage water

Volatilization from ponds

Volatilization from Richland Creek water

Ingestion of fish from pond water



Contact with sediment—ponds


Ingestion of fish from ponds


Receptor

Population

Visitor

Resident

Sportsman

Visitor

Resident

Sportsman

Resident

Sportsman

Resident

Visitor

Sportsman

Resident

Sportsman

Receptor

___Age

Adolescent

Adolescent

Adult

Adolescent

Adolescent

Adutt

Adolescent

Adult

Adolescent

Adolescent

Adult

Adolescent

Adult

Exposure

Route

Dermal

Ingestion

Dermal

Ingestion

Dermal

Ingestion

Inhalation

Inhalation

Inhalation

Ingestion

Ingestion

Combined

Combined

Combined

Ingestion

Ingestion

On-Slte/ Type of

Off-Site Analysis

On-site

On-site

On-site

On-site

Off-sKe

Off-site

On-sile

On-site

on-site On-site

Off-site

On-site

On-site

Off-site

On-site

Off-she

Quant

Quant

Quant

Quant

Quant

Quant

None

None

None

None

Quant

Qua)

Qua)

Qual

None

Quant


of Exposure Pathway

Nearby resident chOdreiVadolescents may play in drainages

Nearby resident cMdrenfadotesoants may play in drainages

Resident may occasionally swim in pond

Resident may occasionally swim in pond

Dermal contact while wading (fishing) In creek

Incidental Ingestion while wading (fishing)

Large air dilution would result In toxicoiogtcaBy Insignificant exposure

Large air dilution wouk) result in WxfcotogicaDy Insignificant exposure

Large air dilution would resull in toxfcotogtcatly insignificant exposure

Small ponds have insufficient carrying capacity for sustained fishing





Smart ponds have Insufficient carrying capacity for sustained fishing


-Pa.

CD

CD

. V

Baseline Risk Assessment Work Plan EPA Contract No. 68-W-99-043 Work Assignment No. 034-RICO-A479 Barber Orchard Site

Table 2-2 Variables Used to Estimate Potential Chemical Intakes

and Contact Rates for Receptors Barber Orchard Site, Haywood County, North Carolina

Section: 2 Revision No. 0

Revision Date: May 18,2001 Page 15 of 61

Pathway Variable

Commercial Worker

Construction Worker Sportsman Adolescent Visitor

II On-Site Resident

General Parameters Used in All Intake Models

Exposure duration (ED) (years)

Body weight (BW) (kg)

Averaging time (AT> Noncancer (days)d

AT-Cancer (days)

25"

70a

9125ad

25550d

1b

70a

365b d

25550d

30b

70a

10950bd

25550d

10c

45e

3650cd

25550d

30° 6-child 24-adult 70-adulr9

15-childa

8760-adultd

2190-childd

25550d

Inhalation of VOCs and Resuspended Dust from Soil

Inhalation rate (IRa) (m3/hour) Exposure time (ET) (hours/day) Exposure frequency (EF) (days/year)

1.3e

8a

250"

1.9"

8a

250b

NA

NA

NA

1.5"

6b

104b

0.83-adulf 0.35-child°

24

350"

Incidental Ingestion of Soil Soil ingestion rate (IRM) (mq/day) EF (days/year)

50s

250a

100ab

250"

NA

NA

100a

104b

100-adulr3

200-childa

350a

Dermal Contact with Soil Fl.„ (unitless) Body surface area exposed to soil (SA„,) (cm2) Adherence factor (AF) (ma/cm2)

1b

3400be

0.071

1b

3400""

0.2'

NA NA

NA

1b

4900be

0.2'

1b

5700-adult b-e

2800-child be

0.07-adult' 0.2-child'

Osl

-p*.

CD CO

Kn\black and veach\risk work plan\TAB2-2.WPD/S/l8/0l(9:44 am)






Pathway Variable

Dermal absorption fraction (ABS) (unitless) EF (days/year)

Commercial Worker

CSV

250"

Construction Worker

CSV

250b

Sportsman

NA

NA

Adolescent Visitor

CSV

104b

II On-Site Resident \

CSV

350" Ingestion of Homegrown Produce Ingestion rate of produce (IR„) (kg/day) EF (days/year) Ingestion of Home-Produced Ingestion rate of beef (IRb) (kg/day) EF (days/year) Ingestion of Home-Producec Ingestion rate of milk (IRP) (kg/day) EF (days/year)

NA

NA

NA

NA

NA

NA

NA

NA

0.08"

350" Beef

NA

NA

NA

NA

NA

NA

NA

NA

0.075-adulP 0.04-childb

350" Milk

NA

NA

NA

NA

NA

NA

NA

NA

0.3"

350" Ingestion of Groundwater Groundwater ingestion rate (IrV) (L/dav) EF (days/year) Fraction of groundwater from source (FI„J (unitless) Dermal Contact with Ground Body surface area exposed to groundwater (SA^) (cm2) Partition coefficient (PC) (cm/hour)

1"

250" 1b

2"

250b

1b

NA

NA NA

NA

NA NA

2-adulP 1-child9

350" 1"

water NA

NA

NA

NA

NA

NA

NA

NA

18,000 -adult"6

7,000 - child"'

CSV

.{is.

CD i

CD

Kn\black and veachVrisk work plan\TAB2-2.WPD/5/l8/0l(9:44 am)





Revision Date: May 18, 2001 Pagel7of61

Pathway Variable

ET (hour/event)

EF (days/year)

Commercial Worker

NA

NA

Construction Worker

NA

NA

Sportsman

NA

NA

Adolescent Visitor

NA

NA

I On-Site Resident

0.25 - adult0

0.33 - child8

3506

Ingestion of Surface Water IR_ (L/hr) EF (days/year) ET(hours/day)

NA NA NA

NA NA NA

0.01" 39" 4a

0.01a

104" 1a

0.05" 26" 1

Dermal Contact with Surface Water SA^cm 2 )

PC (cm/hour) ET (hour/event) EF (days/year)

NA

NA NA NA

NA

NA NA NA

3600"e

CSV

4" 39"

3800"9

CSV

1" 104"

18,000-adult6

7.000-child8

CSV

1" 26"

Inqestion of Fish Ingestion rate of fish (IRr) (kq/day) EF (days/year)

NA

NA

NA

NA

0.0548

350"

NA

NA

NA

NA

M = Not applicable CSV = Chemical-specific value "U.S. Environmental Protection Agency (EPA), 1991, Risk Assessment Guidance for Superfund Volume I: Human Health Evaluation Manual Supplemental Guidance, Standard Default Exposure Factors, Interim Final, Office of Solid Waste and Emergency Response, OSWER Directive: 9285.6-03.

"Assumed; see text. CU.S. Environmental Protection Agency (EPA), 1995, Supplemental Guidance to RAGS: Region 4 Bulletins, Human Health Risk Assessment, Atlanta, GA, November.

"U.S. Environmental Protection Agency (EPA), 1989, Risk Assessment Guidance for Superfund, Volume I, Human Health Evaluation Manual (Part A), Interim Final, Office of Emergency and Remedial Response, Washington, DC, EPA/540/1-89/002. "U.S. Environmental Protection Agency (EPA), 1997, Exposure Factors Handbook, Final, National Center for Environmental Assessment, Washington, DC, EPA/600/P-95/002Fa, August.

'U.S. Environmental Protection Agency (EPA), 2000, Region 9 Preliminary Remedaiton Goals (PRGs), 2000, Region 9, San Francisco, CA, November.

KnVhlack and ve ,:h\risk work plan\TAB2-2.WPD/5/l8fl)l(<>:44 am)

3 4 0111

Baseline Risk Assessment Work Plan Section 2 EPA Contract No. 68-W-99043 Revision No. 1 Work Assignment No. 020-RICO-A479 Revision Date: May 16, 2001 Barber Orchard Site Page 18 of 60

consistent with current EPA (1986) policy of carcinogen evaluation, although it introduces

considerable uncertainty into the cancer evaluation component of the BHHRA.

A fractional term (FI) may be introduced into the chemical intake equations to account for scenarios

in which exposure to a potentially contaminated medium associated with the site is less than total

daily exposure to that medium. An FI value of 1 will be used in all receptor exposure scenarios in

the BHHRA.

2.2.1.3.1 Future On-Site Resident. The on-site resident scenario is created to evaluate the upper-

bound for exposure under the future land-use scenario. The on-site resident will be evaluated for

exposure to chemicals in soil and groundwater. It is assumed that a residential well will be installed

and used for tap water. Relevant pathways for residential exposure include groundwater ingestion,

dermal contact with groundwater, inhalation of volatile organic compounds (VOC) (for the adult)

emitted during showering, soil ingestion, dermal contact with soil, inhalation of fugitive dust

originating from soil, and ingestion of homegrown produce grown on impacted soil. The on-site

resident scenario is evaluated using both an adult and child. Cancer risk is estimated as the sum of

the risks calculated for the adult and the child. The child is used for the noncancer evaluation. This

approach captures the greater conservatism of the larger soil and drinking water ingestion rate for

the child, when normalized for BW.

It is assumed that the ED for a young child is 6 years (ages 1 through 6 years), and for an adult is 24

years (ages 7 through 30 years) (EPA, 1991a). Therefore, a resident's total ED is 30 years (EPA,

1991a). The adult resident is assumed to weigh 70 kilograms (kg) and the young child is assumed

to have an average BW of 15 kg throughout the 6-year ED (EPA, 1995a).' Both the adult and the

young child are assumed to spend 350 days per year at home (EF=350).

The adult is assumed to ingest 2 liters per day (L/day) of groundwater, the young child 1 L/day. The

entire body surface area (SA) of the adult (18,000 square centimeters [cm2] [EPA, 1997a]) would

be available for dermal exposure to contaminants in groundwater during daily showering. The adult

resident is assumed to spend 15 minutes per day showering (ET= 15 minutes/day) (EPA, 1997a). The

child is assumed to dermally exposed to contaminants in groundwater while taking a daily bath,

which is assumed to last for 20 minutes (ET=20 minutes/day). The entire SA of the young child

Baseline Risk Assessment Work Plan EPA Contract No. 68-W-99043 Work Assignment No. 020-RICO-A479 Barber Orchard Site

Section Revision No. 1

Revision Date: May 16. 2001 Page 19 of60

#

(7,000 cm2) (EPA, 1997a) would be available for dermal contact with contaminants in groundwater

during bathing.

The inhalation of groundwater is also evaluated for both the adult and child residents. Region 4

guidance (EPA, 1995a) assumes that the dose of VOCs received during showering is equivalent to

that resulting from daily water ingestion. Some empirical data involving dose measurements of

human subjects as a result of showering suggest that dose levels received while showering resulted

from approximately equal contributions of the inhalation and dermal absorption pathways (EPA,

1991 b). Region 4 guidance also states that these showering exposure assumptions should be applied

to adults and adolescents. Because noncancer COPC are evaluated for the resident using only the

child receptor, these showering assumptions will also be applied to the child resident as well (i.e.,

the daily dose that a child receives from inhalation and dermal contact with VOCs in groundwater

is equivalent to that received drinking 1 L/day). It is assumed that 50 percent of this dose is received

via inhalation and 50 percent via dermal absorption.

The child is assumed to ingest 200 mg of soil per day, and the adult 100 mg per day (EPA, 1991a).

The inhalation rate (IRJ is assumed to be 0.83 mVhour for the adult (EPA, 1991a) and 0.35 mVhour

for the young child (EPA, 1997a). The unpaved area of the site is currently covered with vegetation

and is assumed to be vegetated in the future; it is assumed that this vegetative cover reduces fugitive

dust emissions by 80 percent.

The median skin SA of an adult, males and females combined, is approximately 18,000 cm2; that of

a child (ages 1 through 6) is approximately 7,000 cm2. It is noted that median SA values averaged

across both sexes are used because the BW values selected as defaults (EPA, 1991a) are median

values across both sexes, and BW and SA are interdependent. Clothing provides protection against

dermal contact with soil, restricting potential contact largely to the face, neck, hands,forearms, and

lower legs; therefore, the available surface area for dermal contact is estimated to be 5,700 cm2 for

the adult (aproximately 32 percent of total body surface) and 2,800 cm2 for the young child

(approximately 40 percent of total body surface) (EPA, 1997a). Soil adherence factors (AF) of 0.07

mg/cm2 for the adult resident and 0.2 mg/cm2 are used for the child resident (EPA, 2000a).

The on-site resident is also assumed to maintain a vegetable garden and ingest the produce. A'

homegrown vegetable ingestion rate of 80 gram per day (g/day) (EPA, 1991a) is assumed for both

3 4 0112

Baseline Risk Assessment Work Plan Section 2 EPA Contract No. 68-W-99043 Revision No. 1 Work Assignment No. 020-RICO-A479 Revision Date: May 16,2001 Barber Orchard Site Page 20 of 60

the adult and child resident as a daily average throughout the 350 days assumed to be spent at home

per year.

2.2.1.3.2 Small-Scale Beef and Milk Production/Consumption. During an October 2000 site walk,

a few cattle were observed on one plot and a small herd of goats on another. Therefore, potential

exposure of an individual who has ingested meat and milk from livestock that have grazed on the

site and have been given site groundwater (or surface water) to drink will also be evaluated.

Both an adult and child are evaluated for this exposure pathway. BW, ED, and EF values are the

same as those described in Section 2.2.1.3.1 for the resident. A home-produced beef (used also as

a surrogate for goat meat) ingestion rate of 75 g/day and a home-produced milk ingestion rate of 300

g/day, described by EPA (1991a) as "reasonable worst-case" consumption rates, are used for the

adult receptor. This same milk ingestion rate is used for the young child receptor, but a home-

produced beef ingestion rate of 40 g/day is used for the young child to reflect the lower net intake.

It is noted that this beef ingestion rate for the young child is 2.7 times the rate used for the adult on

a body weight basis (i.e., 40 g per day for a 15 kg-child versus 75 kg per day for a 70-kg adult).

2.2.1.3.3 Pond Exposure. Ponds are associated with a few specific plots at the site, and it is

plausible that these could be used occasionally for swimming in the summer. It is assumed that a

resident receptor may occasionally swim in a pond. An EF of 26 events per year is assumed (twice

per week during the three summer months) in the BHHRA; each event is assumed to last 1 hour

(ET=1) (EPA, 1997a). It is noted that an adolescent would probably be the most likely age group

to swim in the pond. However, because a resident with a pond on his property is the most likely

receptor, it is assumed that both the adult and young child are exposed to pond water for ease of

comparison/addition to risks associated with the resident exposure pathways (Section 2.2.1.3.1). It

is assumed that both the child and adult ingests 50 milliliters per hour (mL/hr) of pond water (EPA,

1995a). The total body surface is assumed to be exposed to water during swimming, for SA values

of 18,000 cm2 for the adult and 7,000 cm2 for the young child (Section 2.2.1.3.1). The ED and BW

values are the same as those used for the on-site resident (Section 2.2.1.3.1). The ingestion offish

pathway was not evaluated for this receptor because the ponds are assumed to be of insufficient

carrying capacity to contribute appreciably to the diet of a human receptor (EPA, 2000e).

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•

2.2.1.3.4 On-Site Commercial Worker. Currently, a few commercial business are on the site near

the base of the hill, and it is possible that commercial use of the site may continue in the future.

Therefore, an on-site commercial worker is selected as a plausible receptor for the site. The

commercial worker is likely to be restricted to largely indoor activities (e.g., office work, tasks

associated with sales, occasional housekeeping), but may also engage in some outdoor activities

(e.g., loading/unloading). The on-site commercial worker is assumed to be a 70-kg adult who works

8 hours per day, approximately 5 days per week, year-round on site for a total of 250 days per year

(EPA, 1991a). The ED is assumed to be 25 years (EPA, 1991a).

An on-site commercial worker is assumed to ingest 1 liter per day (L/day) of water from site

groundwater while at work (EPA, 1991 a). Minimal dermal and inhalation exposure to contaminants

in water may occur during activities such as hand washing. However, it is assumed that the level of

exposure via inhalation and dermal contact would be inappreciable in comparison with the ingestion -

of 1 L/day of groundwater. Therefore, the dermal and inhalation pathways are not quantified for this^

receptor.

The inhalation rate (IRJ for the commercial worker is assumed to be 1.3 cubic meters per hour

(m3/hr). This represents a respiratory rate averaged over an 8-hour day where 4 hours are spent in

moderate activities (1.6 m3/hr) and 4 hours in light activities (1.0 m3/hr); the inhalation rates shown

in parentheses are those recommended in the Exposure Factors Handbook (EFH) (EPA, 1997a) for

these two activity levels during short-term exposure. These assumptions are likely very conservative

because studies cited in the EFH indicate that more than 80 percent of the workday for the average

outdoor worker is spent performing light activities, and most of the remainder is spent at moderate

activities. It is expected that activities and the associated inhalation rates of commercial workers

would be even lighter than those of the outdoor worker, perhaps consisting largely of sedentary

activities (inhalation rate of 0.5 m3/hr) (EPA, 1997a). An incidental soil ingestion rate of 50

milligrams per day (mg/day) is assumed (EPA, 1991a). The site is mostly covered with vegetation,

which is assumed to reduce fugitive dust emissions by 80 percent. The ED is assumed to be 25 years

(EPA, 1991a).

The median SA for an adult, males and females combined, is approximately 18,000 cm2. Clothing

provides protection against dermal contact with soil, restricting potential contact largely to the facel

neck, hands, and forearms (approximately 19 percent of the total body surface) (EPA, 1997a);

3 4 0113


therefore, the available surface area for dermal contact is estimated to be 3,400 cm2. An AF value

of 0.07 mg/cm2, the value for an adult resident (EPA, 2000a), will be used for the commercial

worker.

2.2.1.3.5 Construction Worker. The on-site construction worker represents an individual who would

be exposed over the short-term during excavation and construction projects. This receptor is

assumed to be a 70-kg adult who works 8 hours per day 250 days per year at the site for 1 year

(EF=250 days/year).

An on-site construction worker is assumed to ingest 2 liters per day (L/day) of water from site

groundwater while at work, the default value for agricultural workers (EPA, 1991a). Minimal

dermal and inhalation exposure to contaminants in water may occur during activities such as hand

washing, concrete work, and cleaning of equipment. However, it is assumed that the level of

exposure via inhalation and dermal contact would be inappreciable in comparison with the ingestion

of 2 L/day of groundwater. Therefore, the dermal and inhalation pathways are not quantified for this

receptor.

The inhalation rate (IRJ for the construction worker is assumed to be 1.9 m3/hr. This represents a

respiratory rate averaged over an 8-hour day where 4 hours are spent in heavy activities (2.5 m3/hr),

2 hours in moderate activities (1.5 m3/hr), and 2 hours in light activities (1.1 mVhr); the inhalation

^ates shown in parentheses are those recommended in the EFH (EPA, 1997a) for these three activity

;evels. These assumptions are likely very conservative because studies cited in the EFH indicate that

more than 80 percent of the workday for the average outdoor worker is spent performing light

activities, and most of the remainder is spent at moderate activities. An incidental soil ingestion rate

of 100 mg/day is assumed; this is the recommended value selected to represent the upper 95th

percentile of daily exposure for an agricultural worker (EPA, 1991a). This value is likely to be

reasonably conservative for a construction worker because most soil ingestion is assumed to result

from hand-to-mouth activity (EPA, 1997a), and soil adherence factors listed in the EFH for

agricultural workers tend to be higher than those for construction workers.

The median SA of an adult, males and females combined, is approximately 18,000 cm2. Clothing

provides protection against dermal contact with soil. Although different types of clothing might be

wom at different times of the year, it is assumed that clothing would generally restrict potential


contact largely to the face, neck, hands, and forearms (approximately 19 percent of the total body

surface) (EPA, 1997a); therefore, the available SA for dermal contact is estimated to be 3,400 cm2.

An AF value of 0.2 mg/cm2 (EPA, 2000a) will be used for the construction worker.

2.2.1.3.6 Adolescent Visitor. The adolescent visitor is likely to be an older child (who may live on

site or near site) who more broadly traverses the site while playing, but at a lower EF than under on-

site resident exposure assumptions. This receptor is assumed to be exposed to contaminants in

surface soil (via incidental ingestion, dermal contact, and inhalation) and surface water (via

incidental ingestion and dermal contact). The adolescent visitor is assumed to be a developing

child, ages 7 through 16 years, with an average BW of 45 kg throughout this 10-year exposure period

(ED=10 years). This receptor is assumed to play outdoors for extended periods at the site

approximately 6 hours per day, 2 days per week, for an EF of 104 days per year. It is assumed that

5 hours per exposure day are spent in contact with soil, and 1 hour per day is spent in contact with

surface water in the drainages. A

Incidental ingestion of surface water would be extremely limited because each of the site drainages

is only a few inches deep. A default incidental water ingestion rate for wading of 10 mL/hr (EPA,

1995a) is assumed. The adolescent visitor may also be exposed to contaminants in surface water via

dermal contact while playing in the water. It is assumed that the feet, lower legs, and hands may be

in contact with the water. As these body parts represent approximately 27 percent of the total body

SA, an SA value of 3,800 cm2 is selected for dermal exposure to surface water. Although this

receptor may also contact sediment underlying the surface water, it is assumed that very little of this

sediment would adhere to the body because it would largely be washed off by the water.

The inhalation rate (IRJ for the adolescent is assumed to be 1.5 m3/hr, the inhalation of children

ages 10 through 17 years at moderate activity levels (EPA, 1997a). An incidental soil ingestion rate

of 100 mg/day is assumed (EPA, 1991a).

The median SA of an adolescent, males and females combined, is approximately 14,000 cm2, based

on the body surface area of a 12-year-old child (EPA, 1997a). Clothing provides protection against

dermal contact with soil. Although different clothing would be worn at different times of the year^

it is assumed that clothing would, on average, restrict potential contact largely to the face, neckj

hands, forearms, and lower legs (approximately 35 percent of the total body surface) (EPA, 1997a);

Section . Revision No. 1


3 4 0114


therefore, the available surface area for dermal contact with soil is estimated to be 4,900 cm2. An

AF value of 0.2 mg/cm2 (EPA, 2000a) will be used for the adolescent visitor.

2.2.1.3.7 Sportsman. The sportsman is assumed to be a 70-kg adult who frequents Richland Creek

for sportfishing approximately 1 day per week during the nonwinter months (EF=39 days/year), over

an ED of 30 years. This receptor is assumed to be directly exposed to contaminants in surface water

via incidental ingestion and dermal contact. He is also assumed to be indirectly exposed to

contaminants in surface water and sediment via the ingestion of fish which have bioaccumulated

these compounds in their muscle tissue (i.e., fillet). The sportsman is also assumed to catch and

ingest fish from the Richland Creek. A default average fish ingestion rate of 54 grams per day, 350

days per year, is selected (EPA, 1991a; 1995a).

The median SA of an adult, males and females combined, is approximately 18,000 cm2. It is

assumed that a sportsman may wade into the water and expose his feet and lower legs. These body

parts represent about 20 percent of the total body surface area. Therefore, an SA of 3,600 cm2 is

selected for the sportsman's dermal contact with surface water. It is assumed that the sportsman will

incidentally ingest surface water at the rate of 10 mL/hr (EPA, 1995a).

2.2.2 Quantification of Exposure-Point Concentrations The EPC is an estimate of the concentration of a COPC in a given medium, to which a receptor may

be exposed over the duration of the exposure. EPCs may be based on media concentrations that

have been directly measured, or they may be derived from models. For the Barber Orchard site, soil,

groundwater, sediment, and surface water are media for which chemical concentrations will be

directly measured; separate EPCs will be derived for residuum and bedrock groundwater.

Concentrations in beef, milk, and fish fillets will be modeled based on the EPCs from the respective

measured media concentrations of soil, groundwater, sediment, and/or surface water. The following

subsections describe the approached used to derive EPCs for the various media.

2.2.2.1 Soil. Ideally, the mean concentration would be used as the site-wide EPC for each COPC

in soil. However, because of uncertainties as to the value of the true mean concentration, the 95th

percent upper confidence limit of the mean concentration (UCL) of the analytical results of the site

samples is used to capture some of these uncertainties. Generally, the UCL or MDC, whichever is

smaller, is selected as the EPC, and is understood to represent a conservative estimate of average

Baseline Risk Assessment Work Plan Section . EPA Contract No. 68-W-99043 Revision No. I Work Assignment No. 020-R1CO-A479 Revision Date: May 16, 2001 Barber Orchard Site Page 25 of 60

concentration for use in the exposure assessment (EPA, 1989a). If the data set consists of fewer than

five data points, the MDC is selected as the EPC. It is noted that for subsurface soil, only the

samples with the highest concentrations will be considered to calculate an EPC (EPA, 2000e).

The nature of the statistical distribution (e.g., normal, lognormal) is determined for data sets having

five or more samples with the Shapiro-Wilks test (EPA, 1992d). Statistical analysis is performed

only on those chemicals selected as COPC. Either a normal or lognormal UCL is calculated,

whichever provides the better fit in the Shapiro-Wilks test. Data sets that, according to the Shapiro-

Wilks results, cannot be described as either normal or lognormal will be referred to in the BHHRA

as "nonparametric." It is noted that in accordance with EPA guidance, all data found to be non-

normally distributed will be treated as lognormally distributed data (EPA, 1992a), including

nonparametric data sets.

The UCL is calculated for a normal distribution as follows (EPA, 1992a):

OCX = J + *,_„.„_ .(WS) Eq.2.1

where:

UCL = upper 95th confidence limit on the arithmetic mean concentration (calculated)

x = sample arithmetic mean

t, = critical value for Student's r-test

a = 0.05 (95 percent confidence limit for a one-tailed test)

n = number of samples in the data set

s = sample standard deviation.

The UCL may be calculated for a lognormal distribution as follows (EPA, 1992a):

t/CL = e | / + (0.5 • s*) + H, - _ i 0 9 5 ( H - 1 ) ° 5

Eq. 2.2

3 4 0115



Revision Date: May 16. 2001 Page 26 of 60

where:

UCL = upper 95th confidence limit on the arithmetic mean concentration (calculated)

7 = £y/n = sample arithmetic mean of the log-transformed data, y = In x

sy = sample standard deviation of the log-transformed data

n = number of samples in the data set

HQ 9J = value for computing the one-sided upper 95 percent confidence limit on a

lognormal mean from standard statistical tables (Land, 1975).

Recently, this method for estimating the UCL on the mean of a lognormal distribution has been the

subject of criticism (EPA, 1997c; Hardin and Gilbert, 1993). Therefore, if appropriate, an additional

statistical method such as those described in the EPA document titled, The Lognormal Distribution

in Environmental Applications (EPA, 1997c), may be applied to certain COPC data sets. The

methods include bootstrapping, jackknifing, and the Chebychev methods for determining the UCL

on the mean. The decision to use an additional statistical method would be made after initial risk

characterization results indicated that unacceptable risks may be present. Results based on both the

method shown above and that based on the alternative statistical method would be presented in the

risk characterization (Section 2.4) and discussed in the uncertainties analysis (Section 2.6). This

discussion of possible alternative methods to estimate the UCL also applies to nonparametric data

sets.

The results of both reported detections and nondetects are used to calculate the sample mean and

standard deviation used in the previous equations. The analytical results of unqualified and

estimated ("J" qualified; see Section 2.1.1) are used directly as data points for these calculations.

One-half the reporting limit is assumed for samples in which the COPC is not detected ("U" or "UJ"

qualified; see Section 2.1.1).

2.2.2.2 Groundwater Plumes. The EPC for a COPC that is spatially oriented as part of a

groundwater plume is the mean contaminant concentration collected from wells located in the most

contaminated part of the plume (EPA, 1995a). Each COPC data set is evaluated individually to

identify the data to be averaged to estimate the EPC. If multiple significant plumes are identified,


Section Revision No.


•

then professional judgment will be used to determine if more than one location should be evaluated

as exposure points.

2.2.2.3 Sitewide Groundwater. For those groundwater COPC that have not been identified as

occurring in distinct plumes, generally the UCL or MDC, whichever is smaller, is selected as the

EPC. If the data set consists of fewer than five data points, the MDC is selected as the EPC. The

discussion of soil EPCs in Section 2.2.2.1 also applies to groundwater COPC that are not identified

as occurring in distinct plumes.

2.2.2.4 Surface Water and Sediment. Surface water and sediment samples in the drainages and

Richland Creek are collected chiefly to evaluate potential contaminant transport and the upstream-to-

downstream trend of COPC concentrations. The samples collected from the drainages, in particular,

are not collected to derive an overall concentration for a given area. Also, only a few surface water

samples will be collected per drainage (and from Richland Creek). Therefore, the MDC of e a c h ^ ^

COPC in each drainage or Richland Creek will be the EPC. It is noted that two off-site, upstream^P

samples from the drainages and the upstream sample from Richland Creek will be regarded as

background samples for these respective water bodies, so concentrations associated with these will

not be included for consideration as the MDC. Neither will downstream concentrations in Richland

Creek be included as MDCs if evidence indicates that these concentrations are not associated with

the Barber Orchard site. The drainages associated with the site are perennial, so the sediment in

these is continuously covered with water. Therefore, it is assumed that direct human exposure to

contaminants in sediment is minimal (EPA, 1995a).

An evaluation of surface water and/or sediment analytical results may indicate that grouping of data

across drainages is appropriate for calculating the EPC. If this is the case, the method used to derive

EPC values for soil (Section 2.2.2.1) may be used. Justification for grouping would be provided in

the BHHRA.

2.2.2.5 Air Concentrations for COPC in Soil

COPC Concentrations from Dust. Two phenomena give rise to dust in the air to which a receptor

might be exposed: receptor activity on the site and wind erosion. The evaluation of inhalation^B

exposure to particulate (dust) emissions from soils for the maintenance worker and construction

3 4 0116


worker is based on activities that raise dust. Therefore, the most appropriate approach to estimating

chemical concentrations in ambient air is the use of an activity-based, dust-loading equation (U.S.

Department of Energy [DOE], 1989):

Ca = mcj(CF) £q. 2.3

where:

Ca = contaminant concentration in air (mg/m3, calculated)

D = dust loading factor (grams [g] of soil/m3 of air)

CM = contaminant concentration in soil (mg/kg)

CF = conversion factor (1E-3 kg/g).

Plausible values for D include 2E-4 grams per cubic meter (g/m3) for agricultural activity (DOE,

1989), 6E-4 g/m3 for construction work (DOE, 1983), and 1E-4 g/m3 for other activity (National

Council on Radiation Protection and Measurements, 1984). The value for D of 1 E-4 g/m3 for other

activity is used for the groundskeeper. It is assumed that construction activities requiring intimate

contact with soil, for which D = 6E-4 g/m3 is appropriate, may last for one-half of a construction

period. The remaining one-half of the time is more realistically characterized by D = 1 E-4 g/m3;

therefore, a time-weighted average dust loading factor for construction work of 3.5E-4 is estimated

for the construction worker.

The sportsman and adolescent visitor are more likely to be exposed to dust that arises from wind

erosion rather than from dust-raising activities on the site. EPA (1996) derived a model for

estimating a dust particulate emission factor (PEF) based on an "unlimited reservoir" model and the

assumption that the source area is square:

PEF = QIC- 2*22 F 2 4

0.036 * (l-J/) x {UJUxf * F(x) CA{- •

Baseline Risk Assessment Work Plan Section^ EPA Contract No. 68-W-99043 Revision No. f Work Assignment No. 020-RICO-A479 Revision Date: May J 6, 2001 Barber Orchard Site Page 29 of 60

where:

PEF = particulate emission factor (m3/kg, calculated) Q/C = inverse of the mean concentration at center of square source (39.54g/m2-second

per kg/m\ site-specific value from Table 3 in EPA, 1996) (Zone 6, Atlanta, Georgia, 30-acre site)

3600 = seconds/hour V = fraction of surface covered with vegetation (0.8, unitless, assumed) Um = mean annual wind speed Ut = equivalent threshold value of wind speed at 7 m (default, 11.32 m/s) F(x) = function dependent on Um/U, (default 0.194).

The concentration of COPC in air is calculated as follows:

Ca = —!2- Eq. 2.5 " PEF ^

where:

Ca = contaminant concentration in air (mg/m\ calculated) Cj,, = contaminant concentration in soil (mg/kg) PEF = particulate emission factor (m3/kg).

VOC Concentrations from Soil. The construction worker may be exposed to VOCs released from subsurface soil by volatilization. EPCs of VOCs in ambient air due to volatilization are estimated with a chemical-specific soil volatilization factor calculated from the following equations and defaults provided by EPA (1996):

VFt = QIC * CF [3.14 x £> x 7] 1/2

2 * Pi * DA Eq.2.6

3 4 ' 0117


and

where:

_ ( e r x D, * H< + e r • DJ*>

pb * Kd + e„ + efl x H'

VFS = chemical-from-soil volatilization factor (m3/kg, chemical-specific, calculated)

Q/C = inverse of the mean concentration at center of square source (39.54g/m2-second

per kg/m3, site-specific value from Table 3 in EPA, 1996) (Zone 6, Atlanta,

Georgia, 30-acre site)

CF = conversion factor (lE-4m2/cm2)

DA = apparent diffusivity (cm2/second, calculated)

T • = exposure interval (seconds, estimated as ED x 3.15E7 seconds/year)

ED = exposure duration (years, receptor-specific)

pb = dry soil bulk density (1.5 g/cm3, default, or site-specific)

0a = air-filled soil porosity (0.28 unitless, default, or site-specific estimated as n-0w)

n = total soil porosity (0.43 unitless, default, or site-specific estimated as 1 -[Pt/ps])

ps = true soil or particle density (2.65 g/cm3, default, or site-specific)

6W = water-filled soil porosity (0.15 L ^ / L ^ , , default, or site-specific)

Dj = diffusivity in air (cm2/second, chemical specific)

H' = dimensionless Henry's law constant (chemical-specific, may be estimated as H

x41

H = Henry's law constant (atmosphere-m3/mole, chemical-specific)

Dw = diffusivity in water (cm2/second, chemical-specific)

Kd = soil-water partition coefficient (cm3/g, chemical-specific, may be estimated as

Koc X foc)

K.O.. = soil organic carbon-water partition coefficient (cm3/g, chemical-specific)

f̂ = organic carbon content of soil (6E-3 g/g, default, or site-specific).

The concentration of COPC in air is calculated by substituting VFS for PEF in Equation 2.5.

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•

2.2.2.6 Home-Grown Produce. The EPCs of contaminants in homegrown produce may be

derived from the analytical results of produce samples using the approach described in Section

2.2.2.1 for soil. If produce samples are not available, EPCs for COPC in produce will be calculated

using the following equation:

Cp = C„ x Bp E q. 2.8

where:

Cp = COPC concentration in produce (mg/kg, calculated)

C^ = EPC for COPC in soil (mg/kg)

Bp = bioconcentration factor of COPC in produce (calculated in Eq. 2.9)

The Bv value for organics is calculated using the following equation (Travis and Arms, 1988):

log Bp = 1.588 - 0.578 log Km £q. 2.9

where:

Bp = bioconcentration factor of COPC in produce (vegetation)

Kow = octanol-water partition coefficient

Bp values of inorganics will be taken from Baes, et al. (1984).

2.2.2.7 Home-Produced Beef. The chemical concentration in beef from cattle that graze pastures

with contaminated soil will be estimated using Equation 2.10, based on EPA (1994):

Cb - [(^(Cp • (0,)(C,) + (QJ{Cw)] Bp x Fgr Eq. 2.10.

3 4 0118


where:

Cb = contaminant concentration in beef (mg/kg)

Qp = home-grown feedstuff ingestion rate (11 kg-dry/day)

Cp = contaminant concentration in feed items (associated with site), calculated

using Equation 2.12 (mg/kg-dry)

Qs = soil ingestion rate (0.4 kg/day)

Cs = COPC EPC in site soil (mg/kg)

Qw = water ingestion rate (48 L/day or kg/day), from National

Research Council (1996)

Cw = contaminant concentration in water (mg/L)

Bb = biotransfer factor for beef (days/kg)

F = Fraction of grazing area associated with contaminated sources

(unitless).

It is assumed that cattle consume 11 kg of feed items (dry weight) per day, and 0.4 kg of soil per day

(EPA, 1994). It is also assumed that grazing provides one-half of the dry matter intake by cattle.

This ration is supplemented with grain, hay, and/or silage (grown on other areas) during the winter

and dry periods in the summer when pasture growth is slow. Because grazing provides one-half

(0.5) of feed requirements, the fraction of ingested materials (dry weight) originating from the site

is assumed to be 50 percent. It is noted that the values associated with intake from water were added

to the original equation taken from EPA (1994) to include contaminants in water that might be fed

the cattle. Values for Bb for metals will be taken from Baes, et al. (1984); Bb for pesticides,

polychlorinated biphenyls (PCB), and polychlorinated dibenzodioxins/furans will be taken from

Travis and Arms (1988) or calculated from the equation provided therein:



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•

log*, = -7.6 + logK^ Eq.2.11

where:

Bb = biotransfer factor for beef (days/kg)

K^ = octanol-water partition coefficient.

Biotransfer factors for beef, Bb, are not estimated for VOCs, because these chemicals are fairly labile

compounds that do not persist in transfer forage or inside the cow for a significant length of time,

even if VOCs are present at high concentrations in the soil. Following the example provided by EPA

(1994), these compounds are not included in the soil-to-beef pathway.

Concentration values for feed items (Cp) used in Equation 2.10 will be estimated using Equatiol

2.12.

CP = < C W Eq.2.12

where:

Cp = concentration of contaminant in plant (forage) dry matter (DM) (mg/kg)

Cs = COPC EPC in soil (mg/kg)

Bp = soil-to-forage biotransfer factor (mg of chemical per kg of dry plant/mg of

chemical per kg of dry soil).

Values for Bp for metals will be taken from Baes, et al. (1984); Bp for organic compounds will be

taken from Travis and Arms (1988) or calculated from the equation provided therein:

log*, = 1.588 - 0.578 log K„ £q.2.1

•

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where:

log Bp = soil-to-forage biotransfer factor (mg of chemical per kg of dry plant/mg of

chemical per kg of dry soil)

Kow = octanol-water partition coefficient.

Bp is not estimated for VOCs, because these chemicals are expected to volatilize rapidly from soil

and be readily transpired and/or metabolized by plants. Hence, VOCs are regarded as likely to be

relatively unimportant in food-chain pathways.

2.2.2.8 Home-Produced Milk. The chemical concentration in milk from cattle that graze pastures

on contaminated soil will be estimated using Equation 2.14, based on EPA (1994).

Cm - [(QflCJ • (Q$C,) • (QW)(CW)] Bm * F^ Eq. 2.14

where:

= contaminant concentration in milk (mg/L)

= home-grown feedstuff ingestion rate (11 kg-dry/day)

Cp = contaminant concentration in feed items (associated with site), calculated

using Equation 2.12 (mg/kg-dry)

Qs = soil ingestion rate (0.4 kg/day)

Cs = COPC EPC in site soil (mg/kg)

Qw = water ingestion rate (48 L/day or kg/day), from National Research Council

(1996)

Cw = contaminant concentration in water (mg/L)

Bm = biotransfer factor for milk (days/kg)

FIp = Fraction of grazing area associated with contaminated sources (unitless).

It is assumed that cattle consume 11 kg of feed items (dry weight) per day, and 0.4 kg of soil per day

(EPA, 1994). It is also assumed that grazing provides one-half of the dry matter intake by cattle.

This ration is supplemented with grain, hay, and/or silage (grown on other areas) during the winter

=-p


Section Revision No. 1


•

and dry periods in the summer when pasture growth is slow. Because grazing provides one-half (0.5) of feed requirements, the fraction of ingested materials (dry weight) originating from the site is assumed to be 50 percent. It is noted that the values associated with intake from water were added to the original equation taken from EPA (1994) to include contaminants in water that might be fed the cattle. Values for Bm for metals will be taken from Baes, et al. (1984); Bm for pesticides, PCBs, and polychlorinated dibenzodioxins/furans will be taken from Travis and Arms (1988) or calculated from the equation provided therein:

log Bm = -8.1 • log Km Eq.2.15

where:

Bm biotransfer factor for milk (days/kg) octanol-water partition coefficient.

Biotransfer factors for milk, Bm, are not estimated for VOCs, because these chemicals are fairly labile compounds that are expected to volatilize rapidly from soil and be readily transpired and/or metabolized by plants. Hence, VOCs are regarded as likely to be relatively unimportant in food chain pathways.

2.2.2.9 Game Fish. The EPC for game fish caught from Richland Creek will be estimated based on surface water concentration and sediment concentration.

Surface Water-Based Fish Concentrations. The following equation will be used for estimating the exposure point concentration in ingested fish based on surface water concentration:

C * BCF Eq.2.16

where:

contaminant concentration in fish (mg/kg, calculated)

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Csw = COPC EPC in surface water (mg/L)

BCF = bioconcentration factor for fish fillets (L/kg); lipid-normalized for organics.

Bioconcentration factor (BCF) values for metals will be taken from the Hazardous Substances Data

Bank (HSDB) (National Library of Medicine, 2000) or other sources if necessary; lipid normalized

BCF values for SVOCs, pesticides, and PCBs will be taken from literature sources such as HSDB

or calculated from Equation 2.17, which is based on Bintein, et al. (1993). VOCs typically do not

bioaccumulate; therefore, no BCFs are estimated for these compounds. BCF values used will be

provided and documented in the toxicological profiles appended to the BHHRA.

BCF = 1£[0.91 log tfw - 1.975 log[(6.8£-07)(*w + 1)] - 0.786J * L„d £q. 2.17

where:

BCF = lipid-normalized bioconcentration factor for fish fillets (L/kg, calculated)

Kow = octanol-water partition coefficient (unitless)

Lf/b = fraction of whole body fat found in the fillet (site- and/or species-specific

value; default - 0.5, see below).

The Bintein, et al. (1993) equation estimates the BCF in the whole fish. However, most

contaminants that bioaccumulate tend to partition to the lipid portion of the organism. Because only

the fillets are generally eaten by humans and a significant percentage of the whole body lipid is

contained in tissue of the fish other than the fillets, the Lm value in Equation 2.17 is used to

normalize the BCF to the lipid content of the fillet only. The practice of lipid normalization is found

in EPA's Water Quality Criteria for the Great Lakes System (EPA, 1995c). Site-specific and/or

species-specific data may be used to estimate the Lf/b value. A default Lf/b of 0.5 will be used in the

BHHRA based on ranges of lipid content in fish fillets (0.7 to 7.9 percent) (Woodbridge, 1999;

Hawaii Department of Business, Economic Development, and Tourism, 1999) and whole fish (1.4

to 16.1 percent) (U.S. Geological Survey, 1995) for numerous fish species.

Sediment-Based Fish Concentrations. Concentrations of COPC in fish are also estimated

based on the concentrations of these compounds in sediments. Only chemicals that are likely to

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persist in sediment and to bioaccumulate in fish are considered. These include mercury, PCBs,

dioxins, and organochlorine pesticides. The following equation is used:

Cf'C^xD, Eq. 2.18

•

where:

Cf = concentration of COPC in fish fillet (mg/kg, calculated)

Qxi = EPC of COPC in sediment (mg/kg)

Df = ratio of the concentration of COPC in fish fillet to the

concentration found in sediment.

Values for Df are not readily available, but are estimated using biota-to-sediment accumulator

factors (BSAF). A BSAF is the ratio of the concentration of contaminant in fish lipid to the

concentration in sediment organic carbon. BSAFs are available for PCBs and a limited number of

pesticides (EPA, 1995c); BSAF values used will be taken from EPA (1995c) and documented in the

toxicological profiles appended to the BHHRA. Df values are estimated from BSAF values using

the following equation:

Df = (BSAF x FJIF^ Eq.2.19

where:

Df = ratio of the concentration of a COPC in fish fillets to the concentration in

sediment ([(mg-COPC/kg-fish)/(mg-COPC/kg-sediment)], calculated)

BSAF = ratio of the COPC concentration in fish lipid to the concentration in

sediment organic carbon ([mg-COPC/kg-fish]/[mg-COPC/kg-sediment],

chemical-specific)

FL = fish fillet lipid content (0.037, value for bass) (U.S. Department o

Agriculture, 2000)

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F^ ~ fraction of sediment organic carbon content (site-specific or default of

0.04) (EPA, 1994).

No BSAF is available for mercury. However, a Df can be estimated from studies where both the

mercury concentrations in sediment and in edible fish were measured. The most appropriate study

is probably a study of several lakes in northeastern Minnesota (EPA, 1995d). In this study, the

average sediment concentration of mercury was 0.160 mg/kg, and that in fish fillets (Northern Pike)

was 0.450 mg/kg. The resulting Df may be estimated as:

(0.450 mg/kg)/(0.160 mg/kg) = 2.8 (mg mercury/kg-fish)/(mg mercury/kg-sediment).

2.2.3 Quantification of Chemical Intake

2.2.3.1 Ingestion of Groundwater. This section describes the model used to quantify doses or intake

rates of the COPC in groundwater via ingestion, as described in EPA (1989a) guidance. The

ingested dose of COPC in groundwater used as tap water is estimated from the following equation:

(CJKFIJXIRVEFXED) j - g* g* g» p Q 2 2 0 *" " (BW)(AT) H' '

where:

1 .̂ = ingested dose of COPC in groundwater (mg/kg-day, calculated)

C^ = concentration of COPC in groundwater (mg/L)

FI^ = fraction of exposure attributed to site (unitless)

IR^ = ingestion rate for groundwater (L/day)

EF = exposure frequency (days/year)

ED = exposure duration (years)

BW = body weight (kg)

AT = averaging time (days).

As mentioned in Section 2.2.1.3.1, exposure to VOCs in groundwater via inhalation and dermal

absorption is approximated using ingestion assumptions.

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2.2.3.2 Inhalation of COPC in Air. The following equation is used to estimate the inhaled dose

of COPC in air. Air concentrations used in Equation 2.21 may be modeled based on dust originating

from soil and/or VOC concentrations volatilized from soil. Additionally, air concentrations may be

modeled for volatilization of VOCs from groundwater during household use of groundwater:

. (CaXFIa)(IRg)(EF)(ED)(ET) J„ - CXI. 2.21

where:

Ia = inhaled dose of COPC (mg/kg-day, calculated)

Ca = concentration of COPC in air (mg/m3)

FIa = fraction of exposure attributed to site media (unitless)

IRa = inhalation rate (m3/hour)



ET = exposure time (hours)



2.2.3.3 Incidental Ingestion of COPC in Soil. The incidentally ingested dose of COPC in soil

is estimated from the equation:

, (Ct0)(FIJ(IRJ(EF)(ED)(CF4)

where:

1^ = ingested dose of COPC soil (mg/kg-day, calculated)

CJO = concentration of COPC in soil (mg/kg)

FIJO = fraction of exposure attributed to site soil (unitless)

IRso = ingestion rate of soil (mg/day)


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CF = conversion factor (1E-6 kg/mg)



2.2.3.4 Dermal Contact with COPC in Soil or Water. Unlike the methodologies for estimating

inhaled or ingested dose of COPC, which quantify the intake rate presented to the barrier membrane

(the pulmonary or gastrointestinal mucosa, respectively), dermal exposure is estimated as the dose

that crosses the skin and is systemically absorbed. For this reason, dermal toxicity values are also

based on absorbed dose. The absorbed dose of COPC is estimated from the equation (EPA, 1992b):

DAD - M(SA)(EF){ED)

where:

DAD = average dermally absorbed dose of COPC (mg/kg-day, calculated)

DA = dose absorbed per unit body surface area per day (mg/cm2-day)

SA = surface area of the skin exposed (cm2), (SAM for soil, SA^ for groundwater,

SASW for surface water)





The calculation of the dose absorbed (DA) is different for dermal uptake from soil than for water.

Dermal uptake of constituents from soil assumes that absorption is a function of the fraction of a

dermally applied dose that is absorbed. It is calculated from the equation (EPA, 1992b):

DA = (CJ(FIJ(CF)(AF)(ABS) £q. 2.24


Section j Revision No.

Revision Date. May 16. 2001 Page 41 of60

where:

DA =

FIso

CF

AF

ABS

dose absorbed per unit body surface area per day (mg/cm2-day,

calculated)

concentration of COPC in soil (mg/kg)

fraction of exposure attributed to site soil (unitless)

conversion factor (1E-6 kg/mg)

soil-to-skin adherence factor (mg/cm2-day)

absorption fraction (unitless, chemical-specific).

The EPA dermal guidance (EPA, 1992b) lists absorption factor (ABS) values for a few chemicals;

these will be the first preference for ABS values used in the BHHRA. ABS values for other

chemicals will be derived using empirical data from the open literature. Where suitable studies

cannot be found, the Region 9 default ABS values (EPA, 1995a) will be used: 0.01 for organics an

0.001 for inorganics. •

Quantification of dermal uptake of COPC from water depends on the PC value, which describes the

rate of movement of a constituent from water across the dermal barrier to the systemic circulation

(EPA, 1992b). The dermal uptake of chemicals from water (i.e., DAD) is calculated the same as for

dermal uptake of chemicals from soil. DA for dermal uptake from water is calculated using the

following equation:

DA = (Q(PQ(ET)(CF) Eq. 2.25

where:

DA = dose absorbed per unit body surface area per day (mg/cm2-day,

calculated)

C = COPC concentration in surface water (Csw) or groundwater (C^).

PC = permeability coefficient (cm/hour)

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ET = time of exposure (hours/day)

CF = conversion factor (1E-3 L/cm3).

PC has been determined for very few inorganic compounds. For those inorganic compounds for

which empirical data are not available, a default value of 1E-3 cm per hour will be used (EPA

1992b).

PC for organic chemicals varies by several orders of magnitude. PC for organic chemicals is highly

dependent on lipophilicity, expressed as a function of the octanol/water partition coefficient.

When possible, values for PC are taken from EPA (1992b). If PC values are not available, they will

be calculated from the formula (EPA, 1992b):

Log{PC) = -2.72 + 0.71 (log KJ - 0.006\(MW) £q. 2.26

where:

PC = permeability coefficient (cm/hour, calculated)

log Kow = log of the octanol/water partition coefficient (unitless)

MW = molecular weight.

The ET for the adult is based on a showering time of 15 minutes (ET=0.25 hr), and the ET value for

a child is based on a bathing time of 20 minutes (ET=0.33 hr) (EPA, 1997a).

2.2.3.5 Ingestion of COPC in Homegrown Produce. The ingested dose of COPC in

homegrown produce is estimated from the following equation:

,(EF)(ED) \BW)(AT) ', - K^'WS^ Eq. 2.27

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•

where:

Ip = ingested dose of COPC in produce (mg/kg-day, calculated)

Cp = concentration of COPC in produce (mg/kg)

IRp = ingestion rate of produce (kg/day)





2.2.3.6 Ingestion of COPC in Beef. The ingested dose of COPC in beef is estimated from the

following equation:

where:

Ib = ingested dose of COPC in beef (mg/kg-day, calculated)

Cb = concentration of COPC in beef (mg/kg)

IRt = ingestion rate of beef (kg/day)





2.2.3.7 Ingestion of COPC in Milk. The ingested dose of COPC in milk is estimated from the

following equation:

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[{cm)(EFKm Eq 2 2 9 " m\BW){AT) nq. z.zy

where:

I m = ingested dose of COPC in milk (mg/kg-day, calculated)

Cm = concentration of COPC in milk (mg/kg)

Irm = ingestion rate of milk (kg/day)



B W = body weight (kg)


2.2.3.8 Ingestion of COPC in Fish. The ingested dose of COPC in game fish for the sportsman

is estimated from the following equation:

'/= <9<'W]g5^t Eq.2.30

where:

If = ingested dose of COPC in and fish (mg/kg-day, calculated)

Cf = concentration of COPC in fish (mg/kg)

IRf = ingestion rate of fish (kg/day)

FIf = fraction of daily intake offish from areas of Richland Creek contaminated by

the site (unitless)






Sectioi Revision No'


m 2.3 Toxicity Evaluation Toxicity is defined as the ability of a chemical to induce adverse effects in biological systems. The purpose of the toxicity assessment is two-fold:

• Identify the cancer and noncancer effects that may arise from exposure of humans to the COPC (hazard assessment).

• Provide an estimate of the quantitative relationship between the magnitude and duration of exposure and the probability or severity of adverse effects (dose-response assessment).

The latter is accomplished by the derivation of cancer and noncancer toxicity values, as described in the following sections.

2.3.1 Cancer Evaluation

Few chemicals are known to exhibit cancer effects in humans, but numerous chemicals are suspectel to be human carcinogens. The evaluation of the potential carcinogenicity of a chemical includes both a qualitative and a quantitative aspect (EPA, 1986). The qualitative aspect is a weight-of-evidence evaluation of the likelihood that a chemical might induce cancer in humans. The EPA recognizes six weight-of-evidence group classifications for carcinogenicity:

0

Group A - Human Carcinogen: human data are sufficient to identify the chemical as a

human carcinogen.

Group Bl - Probable Human Carcinogen: human data indicate that a causal association is credible, but alternative explanations cannot be dismissed.

Group B2 - Probable Human Carcinogen: human data are insufficient to support a causal association, but testing data in animals support a causal association.

Group C - Possible Human Carcinogen: human data are inadequate or lacking, but animal data suggest a causal association, although the studies have deficiencies that limi interpretation. •

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• Group D - Not Classifiable as to Human Carcinogenicity: human and animal data are

lacking or inadequate.

• Group E - Evidence of Noncarcinogenicity to Humans: human data are negative or lacking,

and adequate animal data indicate no association with cancer.

The toxicity value for carcinogenicity, called a cancer slope factor (SF), is an estimate of potency.

Potency estimates are developed only for chemicals in Groups A, B1, B2 and C, and only if the data

are sufficient. The potency estimates are statistically derived from the dose-response curve, using

the best human or animal study or studies of the chemical. Although human data are often

considered to be more reliable than animal data because there is no need to extrapolate the results

obtained in one species to another, most human studies have one or more of the following

limitations:

• The duration of exposure is usually considerably less than lifetime.

• The concentration or dose of chemical to which the humans were exposed can be

approximated only crudely, usually from historical data.

• Concurrent exposure to other chemicals frequently confounds interpretation.

• Data regarding other factors (e.g., tobacco, alcohol, illicit or medicinal drug use, nutritional

factors and dietary habits, heredity) are usually insufficient to eliminate confounding or

quantify its effect on the results.

• Most epidemiologic studies are occupational investigations of workers, which may not

accurately reflect the range of sensitivities of the general population.

• Most epidemiologic studies lack the statistical power (i.e., sample size) to detect a low, but

chemical-related increased incidence of tumors.

Most potency estimates are derived from animal data, which present different limitations:

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Sectio; Revision No.


•

It is necessary to extrapolate from results in animals to predict results in humans; this is

usually done by estimating an equivalent human dose from the animal dose.

The range of sensitivities arising from genotypic and phenotypic diversity in the human

population is not reflected in the animal models ordinarily used in cancer studies.

Usually very high doses of chemical are used, which may alter normal biology, creating a

physiologically artificial state and introducing substantial uncertainty regarding the

extrapolation to the low-dose range expected with environmental exposure.

Individual studies vary in quality (e.g., duration of exposure, group size, scope of evaluation,

adequacy of control groups, appropriateness of dose range, absence of concurrent disease,

sufficient long-term survival to detect tumors with long induction or latency periods).

The SF is usually expressed as "extra risk" per unit dose; that is, the additional risk abovi

background in a population corrected for background incidence. It is calculated by the equation:

•

SF = (pM - /WO - pm) Eq.2.31

where:

SF = cancer slope factor (per mg/kg-day)

p(d) = the probability of developing the types of cancer associated with the chemical

at a dose of 1 mg/kg-day

p(0) = the background probability of developing the types of cancer associated with the

chemical at a dose of 0 mg/kg-day.

The SF is expressed as risk per mg/kg per day (mg/kg-day). To be appropriately conservative, the

SF is usually the 95 percent upper bound on the slope of the dose-response curve extrapolated from

high (experimental) doses to the low-dose range expected in environmental exposure scenarios^-

EPA (1986) assumes that there are no thresholds for carcinogenic expression; therefore, a n j ( P

exposure represents some quantifiable risk.

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Section 2 Revision No. I


The oral SF is usually derived directly from the experimental dose data, because oral dose is usually

expressed as mg/kg-day. When the test chemical was administered in the diet or drinking water, oral

dose first must be estimated from data for the concentration of the test chemical in the food or water,

food or water intake data, and BW data so that dose rates may be expressed as mg/kg-day.

The EPA Integrated Risk Information System (IRIS) (EPA, 2000b) expresses inhalation cancer

potency as a unit risk factor (URF) based on concentration, or risk per microgram of chemical per

m3 of ambient air. Because cancer risk characterization requires a potency expressed as risk per

mg/kg-day, the URF must be converted to the mathematical equivalent of an inhalation cancer SF,

or risk per unit dose. Since the inhalation unit risk is based on continuous lifetime exposure of an

adult human (assumed to inhale 20 m3 of air per day and to weigh 70 kg) the mathematical

conversion consists of multiplying the unit risk (per microgram per m3 [^ig/m3]'1) by 70 kg and by

1,000 H-g/mg, and dividing the result by 20 m3 per day.

2.3.2 Evaluation of Noncancer Effects Many chemicals, whether or not associated with carcinogenicity, are associated with noncarcinogenic

effects. The evaluation of noncancer effects (EPA, 1989b) involves:

• Qualitative identification of the adverse effect(s) associated with the chemical; these may

differ depending on the duration (e.g., acute or chronic) or route (e.g., oral or inhalation) of

exposure

• Identification of the critical effect for each duration of exposure (i.e., the first adverse effect

that occurs as dose is increased)

• Estimation of the threshold dose for the critical effect for each duration of exposure

Development of an uncertainty factor; i.e., quantification of the uncertainty associated with

interspecies extrapolation, intraspecies variation in sensitivity, severity of the critical effect,

slope of the dose-response curve, and deficiencies in the database, in regard to developing

an RfD for human exposure

• Identification of the target organ for the critical effect for each route of exposure.

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These information points are used to derive an exposure route- and duration-specific toxicity value

called an RfD, expressed as mg/kg-day, which is considered to be the dose for humans, with

uncertainty of an order of magnitude or greater, at which adverse effects are not expected to occur.

Mathematically, it is estimated as the ratio of the threshold dose (usually a no-observed-adverse-

effect level in study animals) to the uncertainty factor.

IRIS (EPA, 2000b) and the Health Effects Assessment Summary Tables (EPA, 1997d) express the

inhalation noncancer reference value as a reference concentration (RfC) in units of mg/m3. Because

noncancer risk characterization requires a reference value expressed as mg/kg-day, the RfC must be

converted to an inhalation RfD. Since the inhalation RfC is based on continuous exposure of an

adult human (assumed to inhale 20 m3 of air/day and to weigh 70 kg), the mathematical conversion

consists of multiplying the RfC (mg/m3) by 20 m3/day and dividing the result by 70 kg.

2.3.3 Dermal Toxicity Values Dermal RfDs and SFs are derived from the corresponding oral values, provided there is no evidence

to suggest that dermal exposure induces exposure route-specific effects that are not appropriately

modeled by oral exposure data. In the derivation of a dermal RfD, the oral RfD is multiplied by the

gastrointestinal absorption factor (GAF), expressed as a decimal fraction. The resulting dermal RfD,

therefore, is based on absorbed dose. The RfD based on absorbed dose is the appropriate value with

which to compare a dermal dose, because dermal doses are expressed as absorbed rather than

exposure doses. The dermal SF is derived by dividing the oral SF by the GAF. The oral SF is

divided, rather than multiplied, by the GAF because SFs are expressed as reciprocal doses.

2.3.4 Target Organ Toxicity As a matter of science policy, EPA (1989a) assumes dose- and effect-additivity for noncarcinogenic

effects. This assumption provides the justification for adding the HQs or hazard indices (HI) in the

risk characterization for noncancer effects resulting from exposure to multiple chemicals, pathways,

or media. However, EPA (1989a) acknowledges that adding all HQ or HI values may overestimate

hazard, because the assumption of additivity is probably appropriate only for those chemicals that

exert their toxicity by the same mechanism. HI and HQ values are described in Section 2.4.2 and

are introduced here, because the application of hazard additivity hinges upon the followin^^

discussion.

3 4 01


Mechanism of toxicity data sufficient for predicting additivity with a high level of confidence are

available for very few chemicals. In the absence of such data, EPA (1989a) assumes that chemicals

that act on the same target organ may do so by the same mechanism of toxicity, unless the data

clearly indicate otherwise. That is, the target organ serves as a surrogate for mechanism of toxicity.

When the sum of HI values for all media for a receptor exceeds 1 due to the contributions of several

chemicals, it is appropriate to segregate the chemicals by route of exposure and mechanism of

toxicity (i.e., target organ) and estimate separate HI values for each target organ.

As a practical matter, since human environmental exposures are likely to involve near- or sub

threshold doses, the target organs chosen for a given chemical are the ones associated with the

critical effects. 'Target organs are also selected on the basis of duration of exposure (i.e., the target

organs for chronic or subchronic exposure to low or moderate doses are selected rather than the

target organs for acute exposure to high doses) and route of exposure. Because dermal RfD values

are derived from oral RfD values, the target organs for oral exposure are adopted as the target organs

for dermal exposure. For some chemicals, no target organ is identified. This occurs when no

adverse effects are observed or when adverse effects such as reduced longevity or growth rate are

not accompanied by recognized organ- or system-specific functional or morphologic alteration.

2.3.5 Sources of Toxicity Information Toxicity values are chosen for the BHHRA using the following hierarchy:

• EPA's on-line IRIS database (EPA, 2000b) containing toxicity values that have undergone

the most rigorous Agency review

• Other EPA documents, memoranda, former Environmental Criteria and Assessment Office,

National Center for Environmental Assessment derivations for the Superfund Technical

Support Center, and the latest version of the annual Health Effects Assessment Summary

Tables, including all supplements (EPA, 1997d).

All toxicity values, regardless of their source, are evaluated for appropriateness for use in the

BHHRA.


When toxicity values are not located, the primary literature may be surveyed to determine whether

sufficient data exist that would permit derivation of a toxicity value. The use of surrogate chemicals

is also considered, if the chemical structure, adverse effects and toxic potency of the surrogate and

chemical of interest are judged to be sufficiently similar. EPA toxicologists will be consulted should

it become necessary to develop toxicity values for any chemical.

GAFs, used to derive dermal RfDs and SFs from the corresponding oral toxicity values, are obtained

from the following sources:

Oral absorption efficiency data compiled by the National Center for Environmental

Assessment for the Superfund Health Risk Technical Support Center of the EPA

Federal agency reviews of the empirical data, such as Agency for Toxic Substances and

Disease Registry toxicological profiles and various EPA criteria documents _

Other published reviews of the empirical data

The primary literature.

GAFs obtained from reviews are compared to empirical (especially more recent) data, when possible,

and are evaluated for suitability for use for deriving dermal toxicity values from oral toxicity values.

The suitability of the GAF increases when the following similarities are present in the oral

toxicokinetic study from which the GAF is derived and in the key toxicity study from which the oral

toxicity value is derived:

• The same strain, sex, age, and species of test animal was used.

• The same chemical form (e.g., the same salt or complex of an inorganic element or organic

compound) was used.

Section i Revision No.'

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• The same mode of administration (e.g., diet, drinking water or gavage vehicle) was used.

• Similar dose rates were used.

The most defensible GAF for each chemical is used to develop dermal toxicity values (EPA, 1995a).

When quantitative data are insufficient to estimate a chemical-specific GAF, Region 4 default values

are used. These are 0.8 for VOCs, 0.5 for semivolatile organics, and 0.2 for inorganics.

Tables that list the cancer and noncancer toxicity values, as well as other pertinent information, will

be provided in the BHHRA. Summarized toxicity profiles for the COPC will be appended.

2.4 Risk Characterization Risk characterization is the process of applying numerical methods and professional judgment to

determine the potential for adverse human health effects to result from the presence of site-specific

contaminants. This is done by combining the intake rates estimated during the exposure assessment,

with the appropriate toxicity information identified during the toxicity assessment. Noncancer

hazards and cancer risks are characterized separately.

Quantitative expressions are calculated during risk characterization that describe the probability of

developing cancer (incremental lifetime cancer risks), or the nonprobabilistic comparison of

estimated dose with a reference dose for noncancer effects (hazard quotients and hazard indices).

Quantitative estimates are developed for individual chemicals, exposure pathways, exposure media,

and source media for each receptor. These quantitative risk characterization expressions, in

combination with qualitative information, are used to guide risk management decisions. Risk

characterization as described in this section is applied only to COPC.

Generally, the risk characterization follows the methodology prescribed by EPA (1989a), as modified

by more recent information and guidance. EPA methods are appropriately designed to be health-

protective, and tend to overestimate rather than underestimate risk. The risk results, however, may

be overly conservative, because risk characterization involves multiplication of the conservative

assumptions built into the estimation of source-term and exposure-point concentrations, the exposure

(intake) estimates, and the toxicity dose-response assessments.

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2.4.1 Cancer Risk The risk from exposure to potential chemical carcinogens is estimated as the probability of an individual developing cancer over a lifetime, and is the ILCR. In the low-dose range, which would be expected for most environmental exposures, cancer risk is estimated from the following linear equation (EPA, 1989a):

ILCR = (I)(SF) Eq. 2.32

where:

ILCR = incremental lifetime cancer risk, a unitless expression of the probability of developing cancer, adjusted for background incidence, calculated

I = intake of chemical, averaged over 70 years (mg/kg-day) SF = cancer slope factor (per mg/kg-day).

The use of Equation 2.32 assumes that chemical carcinogenesis does not exhibit a threshold, and that the dose-response relationship is linear in the low dose range. Because this equation could generate theoretical cancer risks greater than 1 for high dose levels, it is considered to be inaccurate at cancer risks greater than 1E-2. In these cases, cancer risk is estimated by the one-hit model:

ILCR = i-eK0tsF)] Eq. 2.33

where:

ILCR = incremental lifetime cancer risk, a unitless expression of the probability of developing cancer, adjusted for background incidence, calculated

.e(ixsF) = m e exponential of the negative of the risk calculated using Equation 2.32.

As a matter of policy, EPA (1986) considers the carcinogenic potency of simultaneous exposure low doses of carcinogenic chemicals to be additive, regardless of the chemical's mechanisms o 9

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toxicity or sites (organs of the body) of action. Cancer risk arising from simultaneous exposure by

a given pathway to multiple chemicals is estimated from the following equation:

Riskp = ILCR(clam 0 • ILCR(clum 2) + ... ILCR{elam 0 £q. 2.34

where:

Riskp = total pathway risk of cancer incidence, calculated

ILCR(chenij) = individual chemical cancer risk.

Cancer risk for a given receptor across pathways and across media is summed in the same manner.

Lifetime cancer risks in the range of 1E-6 to 1E-4 are generally regarded as acceptable (EPA, 1990);

risks less than this range are regarded as negligible.

2.4.2 Noncancer Hazards of Chemicals The hazards associated with noncancer effects of chemicals are evaluated by comparing an exposure

level or intake with an RfD. The HQ, defined as the ratio of intake to RfD, is estimated as (EPA,

1989a):

HQ = 11 RfD Eq. 2.35

where:

HQ = hazard quotient (unitless, calculated)

I = intake of chemical averaged over subchronic or chronic exposure period (mg/kg-

day)

RfD = reference dose (mg/kg-day).


Sectioi Revision No!


m As shown above, both "I" and the RfD are in units of mg/kg-day. The RfD has been developed to represent a dose rate unlikely to result in any adverse noncancer health effects, even to the most susceptible members of the population. Therefore, if "I" is equal to or less than the RfD (i.e., HQ<1), adverse noncancer health effects are unlikely. HQ values exceeding 1 do not indicate that noncancer hazard is likely to occur, but rather that the occurrence of an adverse noncancer health effect cannot be termed "unlikely." The HQ does not define a particular risk level, nor can it be used to infer information regarding a dose-response curve. An HQ of 0.01 does not imply a 1 in 100 chance of an adverse effect, but simply indicates that the estimated intake is 100 times lower than the RfD. This approach is different from the probabilistic approach described in Section 2.4.1 to evaluate cancer risks.

In the case of simultaneous exposure of a receptor to several chemicals, an HI is calculated as the sumoftheHQsby:

HI = /, / RfDx * I2 I R/D2 + ... /, / RfD, Eq. 2.3 •

where:

HI = hazard index (unitless, calculated) I; = intake for the i* toxicant RfDj = reference dose for the i* toxicant.

If an HI for a given pathway exceeds 1, individual HI values may be calculated for each target organ associated with COPC in that pathway, as discussed in Section 2.3.4. These are calculated as described in Equation 2.37:

HI. K - IW,., * h - 1W, - 2 + -h - /W>, -, Eq. 2.37

where:

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m^-sum = summed hazard index (unitless, calculated) of all COPC associated with

target organ x

Ix.; = intake for the i* toxicant associated with a target organ x

R/D^j = reference dose for the i* toxicant affecting target organ x.

2.4.3 Risk Characterization Results Risk characterization results will be presented in tables and discussed in text. Results are presented

separately for cancer and adverse noncancer effects using the methods described in Sections 2.4.1

and 2.4.2, and discussed for each receptor and environmental medium. Detailed spreadsheet

calculations will be appended to the BHHRA.

2.5 Remedial Goal Option Development EPA Region 4 requires development of risk-based RGOs as part of the BHHRA (EPA, 1995a).

RGOs are site-specific risk-based concentrations that are back-calculated from the BHHRA exposure

and toxicity input assumptions at specified target risk or hazard levels. Therefore, risk-based RGOs

are source medium-, receptor-, and chemical-specific.

2.5.1 Selection of Chemicals of Concern The first step in RGO development is selection of COC. Either of the following two conditions

results in designation of a COPC as a COC:

• The concentration of the COPC exceeds its medium-specific applicable or relevant and

appropriate requirements.

• The COPC contributes significantly to unacceptable cancer risk (total site-related ILCR

greater than 1 x 10"4) or hazard (total site-related HI greater than 1).

Significant contribution to cancer risk is defined as contributing an ILCR across all exposure

pathways for a given source medium exceeding 1 x 10"6; significant contribution to hazard is defined

as contributing an HI across all exposure pathways for a given source medium exceeding 0.1. The

COC, therefore, may be selected because of their cancer risk (cancer COC) or noncancer hazard

(noncancer COC). The RGO estimation process for all the receptors, source media and exposure

pathways is described in the following section.


Section < Revision No.


2.5.2 Remedial Goal Options Estimation Methodology Cancer and noncancer RGOs are calculated for each medium in which COC are identified. Medium-

specific RGOs are calculated for each receptor across all applicable exposure pathways. RGOs for

cancer for a receptor and medium are calculated by the following equation (EPA, 1995a):

£PC' TR RGO^ = — Eq. 2.38

where:

RGO ,̂,. = remedial goal option for a given COC, receptor and source medium,

calculated (mg/kg or p.g/L)

EPC,^ = exposure point concentration of the COC in the given medium (mg/kg or^

HfcVL) TR = target risk level (1 x W6,1 x 10"5, 1 x 104)

ILCR,^ = total incremental lifetime cancer risk for the COC, for a given receptor

added across all exposure pathways for a given source medium.

RGOs for noncancer COC are estimated as follows:

EPC THI RGOeae = ^£

HI Eq. 2.39

where:

RGO„

EPCC

THI

HI...

= remedial goal option for a given COC, receptor and source medium,

calculated (mg/kg or Hg/L)

= source-term concentration of the COC in the given medium (mg/kg or \igfL)

= target hazard index (0.1, 1,3)

= total hazard index for the COC, for the receptor across all pathways fo{

given source medium.

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The range of RGOs for each COC, for a given receptor and medium are based on target risk values

of lCT6,10-5, lO-4 and target HI values of 0.1,1, and 3 (EPA, 1995a). RGOs for groundwater are in

units of micrograms per liter, and those for soil are in mg/kg.

2.6 Uncertainty Analysis The primary objective of the BHHRA is to characterize and quantify potential human health risks.

However, these risks are estimated using incomplete and imperfect information that introduces

uncertainties at various stages of the risk assessment process. Uncertainties associated with earlier

stages of the risk assessment become magnified when they are concatenated with other uncertainties

in the latter stages.

The chief goal of the uncertainty analysis is to evaluate uncertainties and present them in context of

their potential impact on the interpretation of the BHHRA results and the types of environmental

management decisions that may be based on these results. Although the BHHRA will include

generic uncertainties that are common to human health risk assessment protocols (e.g., additivity of

health effects in the risk characterization), the uncertainty analysis will focus on those uncertainties

that are peculiar to the Barber Orchard site and assumptions made in the BHHRA.

2.6.1 Types of Uncertainty Uncertainties in risk assessment are categorized into two general types: (l) variability inherent in

the (true) heterogeneity of the data set, measurement precision, and measurement accuracy; and

(2) uncertainty that arises from data gaps.

Estimates of the degree of variability tend to decrease as the sample size increases. This is because

larger data sets are less impacted by individual samples/measurements and typically allow for greater

accuracy. Uncertainty that arises from data gaps is addressed by applying models and assumptions.

Models are applied because they represent a level of understanding to address certain exposure

parameters that are impractical or impossible to measure (e.g., COPC concentrations in shower room

air). Assumptions represent an educated estimate to address information that is not available (e.g.,

drinking water ingestion rates, additivity of carcinogenic effects).

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2.6.2 Sources of Uncertainty A discussion will be provided to describe an overview of general sources of uncertainty and focus

on those most likely to affect the interpretation of the BHHRA results. These sources may include,

but are not limited to, the following:

Representativeness of samples

Sampling methods

Background concentrations

Laboratory procedures

Land-use assumptions

Routes of exposure

Estimation of EPCs

Exposure assessment values

Toxicity values

Form or isomer of chemical

Interactions of multiple contaminants.

The Barber Orchard site BHHRA will identify and describe the unique set of uncertainties associated

with the site. Special attention will be given to those uncertainties that are thought to have the most

significant impact on interpretation of risk estimates and remediation decisions.

EPA (1992c) guidance urges risk assessors to address or provide descriptions of individual risk to

include the "high end" portions and "central tendency (CT)" of the risk distribution. One way of

fulfilling this request, if either cancer or noncancer risk exceed generally acceptable limits (cancer

risk greater than 1E-4 or target organ-specific HI greater than 1), is to re-compute the ILCRs or His

using CT values for as many intake model variables as possible. In contrast to the RME evaluation,

which uses upper-end values for intake or contact rates, EF and ED, the CT evaluation chooses

average or mid-range values for these variables (EPA, 1991a). The intent is to present a quantified

risk/hazard estimate more typical for the receptor of interest.

The CT exposure evaluation, however, falls short of its stated intent for several reasons. First, t h e ^ ^

same EPC is usually used for the CT evaluation as is used for the RME evaluation. EPA (1993J^^

considers that the UCL or MDC selected as a conservative estimate of average for the RME is

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appropriate for the CT estimates. Second, there is little information available as to what constitutes

a reliable CT estimate for most exposure variables, with the possible exception of a simple on-site

resident scenario. For these reasons, RME values are still used. In addition, no CT toxicity values

are available, so the uncertainty about the toxicity assessment is not included. A CT evaluation,

therefore, usually provides little real perspective compared with the RME, particularly for exposure

scenarios for which no reliable estimation of most exposure variable values can be made. Also,

management decisions are generally based on RME rather than CT evaluations. Therefore, a CT

exposure evaluation will not be performed.

2.7 Human Health Risk Conclusions The BHHRA will include a brief conclusions section that will summarize the results of the risk

characterization, with a sufficient level of elucidation addressing the effects that uncertainties may

have on these results. The goal is to present the BHHRA in a context that is most appropriate for

the support of environmental decision-making.

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3.0 ECOLOGICAL RISK ASSESSMENT

The potential for adverse ecological effects associated with the Barber Orchard site will be evaluated

through the performance of a screening-level ecological risk assessment (SLERA). The ERA will

be conducted using the procedures described in the following EPA documents: Ecological Risk

Assessment Guidance for Superfund Process for Designing and Conducting Ecological Risk

Assessment (EPA, 1997b); Region 4 Supplemental Guidance to RAGS: Region 4 Bulletins (EPA,

1995b); August 1999 revisions to the Region 4 RAGS guidance (EPA, 1999); and the memorandum

"Amended Guidance on Ecological Risk Assessment at Military Bases: Process Considerations,

Timing of Activities, and Inclusion of Stakeholders" (EPA, 2000c), as modified based on discussions

with EPA Region 4. The results of the SLERA will be used to determine one of the following:

• There is adequate information to conclude that ecological risks are negligible and therefore,

there is no need for remedial activities on the basis of ecological risk.

• The information is not adequate to fully evaluate potential ecological risks and more are data

needed before a decision concerning the need for remedial activities can be made. At this

point, the next step in the ecological risk assessment process would be to continue on to

Steps 3 through 8.

• Ecological risks determined in Steps 1 through 3a can be managed by implementation of a

specified control mechanism (a remedy) and continuation of the ecological risk assessment

process would not provide any additional value.

The SLERA typically includes a site description, screening-level effects evaluation, and screening-

level problem formulation. The site description and screening-level effects evaluation correspond

to Steps 1 and 2 of the eight-step ecological risk assessment process for Superfund (EPA, 1997b).

The site description provides an ecological overview of the site. The screening-level effects

evaluation identifies the COPC. Data sources for the screening-level effects evaluation will be the

same as for the BHHRA (Section 2.1), unless appropriate exceptions are identified; these exceptions

would be clearly noted in the SLERA. The screening-level effects evaluation also includes the initial

phases of the problem formulation, corresponding to Step 3a of the eight-step process. Following


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SectiO] Revision N

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•

Step 3a, communication between all key stakeholders is provided through the Scientific Management

Decision Point (SMDP), where the appropriate next steps are discussed and agreed upon.

The goal of this screening-level problem formulation is to develop an ecologically based conceptual

model for the site. This model addresses the environmental setting, the constituents known or

suspected of being present based on historical use, and the presence or absence of contaminant fate

and transport mechanisms, as well as the presence or absence of viable exposure pathways and

receptors. In addition, the screening-level problem formulation categorizes the general mode of

toxicity and identifies whether a chemical tends to bioaccumulate.

a n d ^

3.1 Ecological Site Description The ecological site description provided in the SLERA will consist of a brief description of site/area

use, acreage, topography, drainage, and biota. Maps and figures to illustrate the relative locations

of key site features will be provided. This section will use information provided in Section 1.1

supplemental information gathered during the remedial investigation (RI) to focus on ecolog:

concerns. Special emphasis will be given to vegetation, habitat types, soil types, stressed areas,

wildlife observed or reported, and the likelihood of the presence of threatened and endangered

species. Photos of the site and adjacent areas will be included in the SLERA and referenced to

provide additional description. Wetland areas will be identified; however, this task will not include

a jurisdictional determination of the wetland boundary.

This section will also present a summary of the analytical data generated during the previous site

investigations and sampling events that will be usable for risk assessment purposes. These sample

results will be tabulated and provided in the SLERA.

Using information gathered to describe the ecological setting and contaminants at the site, this

section will describe the potentially complete exposure pathways that connect potential ecological

receptors to contaminated media. This will also be presented as an illustrated figure in the SLERA.

3.2 Screening-Level Effects Evaluation The goal of the screening-level effects evaluation is to assess the likelihood that a chemical stressq

may be present at a level that adversely affects viable populations, communities and/or ecosyste; s o i ^

nfP

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within and around the Barber Orchard site. Region 4 screening values (SV), which are not receptor-specific, are used as ecological benchmarks (EPA, 2000c). These values were developed to provide a conservative means to screen constituents present in soil, sediment, and surface water, and are to be considered protective.

3.2.1 Identification of COPC Preliminary contaminants of potential concern (PCOPC) are identified by comparing the maximum detected concentrations (MDC) of chemicals in an environmental medium to the Region 4 SV. This is done by dividing the medium-specific MDC of each constituent by its corresponding SV to arrive at a screening-level HQ (HQ^^J as follows:

mtmen -MDCISV Eq. 3.1

The HQ value provides the risk assessors with a quantitative screening estimate of the potential hazard associated with each chemical. HQ values less than 1 indicate that the chemical MDC was less than the conservative benchmark screening value and, therefore, is unlikely to pose a hazard to any ecological receptors. HQ values equal to or greater than 1 do not necessarily indicate the presence of an ecological hazard; however, HQ values equal to or greater than 1 indicate that the chemical could potentially pose an unacceptable hazard and need further evaluation. Constituents with HQ values greater than or equal to 1 are, therefore, classified as PCOPC. Also, if a Region 4 SV is not available, the constituent is automatically retained as a PCOPC.

3.2.2 Refinement of PCOPC The portion of the ERA problem formulation step to be included in the SLERA will be the Refinement of PCOPC, typically referred to as Step 3A (EPA 2000c). The refinement process should typically narrow the list of PCOPC to those that are actually a concern at the site and are identified as COPC. This is a logical stepping off point for discussion and meetings to determine the real need to continue with the ecological risk assessment. The refinement process will segregate the PCOPC into two groups:

• PCOPCs that primarily affect ecological receptors through direct exposure

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• PCOPCs that primarily affect ecological receptors through food-chain exposure (biotransfer).

PCOPCs that lacked Region 4 SVs will be compared to alternative screening values such as the EPA

Region 5 RCRA Environmental Data Quality Levels (EDQLs) or other ecological toxicity-based

screening values. PCOPCs that cannot be screened using these alternative screening values will be

evaluated individually in the process described below to determine if they are COPC.

For each media in which PCOPCs exceed EPA Region 4 SVs, alternative ecotoxicity screening

values, or lack ecological screening values, PCOPC in each of the two groups (direct and food-chain)

will be refined based on the following considerations:

• Essential nutrients (typically calcium, magnesium, potassium, and sodium) may be

eliminated as COPC due to a general lack of toxicity, essentiality, and other factotrs that will

be described in appropriate detail in the SLERA.

• Comparison of inorganic PCOPC to background levels for specific media may allow the

elimination of several inorganics as COPC. A study of geochemistry of soils will be

conducted on background samples in the vicinity of the Barber Orchard site to determine

"background benchmark conditions." Based on these data sets, inorganic constituents with

MDC within 2 times the mean background concentration may not represent risks related to

site activities or practices. Inorganic constituents that do not exceed their respective mean

background concentrations will not be carried through as COPC.

• Refinement of direct exposure PCOPC based on comparing MDC to specific ecotoxicity

studies that are appropriate to characterize direct exposure (e.g. plant toxicity studies,

earthworm toxicity studies, soil-microbial toxicity studies). This will result in a list of COPC

for direct exposure.

• Refinement of food chain exposure PCOPC. This will require the development of a

simplified terrestrial and/or aquatic food chain model (FCM) that converts the MDC of only

bioaccumulative PCOPC to an exposure dose using an allometric equations provided in

EPA's Wildlife Exposure Factors Handbook(1993). Species selected to represent food chai1

exposure pathways will be selected to maximize exposure and will include species with

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maximal normalized food ingestion rates. Key pathways to be evaluated will include

vermivore, herbivore, and carnivore pathways. All exposure assumptions will be based on

information in EPA's Wildlife Exposure Factors Handbook(\ 993). Estimates for biotransfer

and body burden in to intermediate receptors (e.g. plants, earthworms, small animals, aquatic

invertebrates) will be based on mean biotransfer data available from specific studies in the

open literature. All biotransfer factors will consider wet weight to dry weight conversions

if appropriate.

All contaminants that still present an ecological risk after the above evaluation will be identified as

COPC in a table of the SLERA. In addition, full toxicological profiles of all COPC will be included

in the SLERA.

3.2.3 Screening-Level Effects Uncertainty By design, SLERAs have a high degree of uncertainty. The assumptions employed in a SLERA

result in the "margin of error" being on the conservative or protective side of the risk scale. It is

therefore safe to assume that constituent levels resulting in HQscreen values less than 1 do not pose

a significant risk to ecological receptors. However, constituents present at levels resulting in HQ^^,,

values of 1 or greater are not necessarily responsible for stress to ecological receptors at the site. The

presence of receptors and the likelihood of exposure are two additional factors that need to be

considered before ecological stress can be evaluated. These additional evaluations are required to

reduce the uncertainty in the SLERA process.

Ideally, the sampling protocol should adequately characterize contaminant concentration gradients

and the areal extent of contamination. The use of the MDC as representative of the level of

contamination at a site overestimates the threat posed to widely dispersed wildlife. To reduce this

uncertainty, an evaluation of the number and location of samples exceeding screening levels will be

performed and presented in table format and depicted on a site figure.

The uncertainties inherent in the SLERA will be presented and evaluated to identify potential

analytical data gaps, data quality issues, the adequacy of the sample quantitation limits, and exposure

assumptions. These uncertainties are essential in determining if further evaluations are necessary

and the scope and extent of additional evaluations. Key uncertainties that will be addresses will

include:

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• Habitat characterization (limitations of field assessment and sample representativeness);

• Geographic distribution of samples to determine widespread contamination versus hot spots;

• Data quality limitations such as blank contamination, rejected data, estimated chemical

concentrations, duplicate errors, and sample quantitation limits (SQLs) that may affect the

usability of the analytical data for ecological risk assessment purposes;

• The effect of using MDCs versus another more realistic statistical representation of the data;

and

• The effect of considering realistic bioavailability characteristics of identified COPC. This

may be particularly relevant to metals.

3.3 Ecological Risk Conclusions This section will identify and discuss the types of ecological receptors likely to use the Barber

Orchard site. Interpretation of the environmental setting and potentially complete exposure pathways

will be presented. Potential receptors will be identified by their diets and/or habitat requirement;^^

and how these relate to the impacted site media and specific COPC. The focus will be on groups o r ^

receptors and not on individual species. Issues such as protective cover and use as a feeding area will

be discussed, as will ecotoxicological characteristics of the COPC. Responsibility for the decision

as to the subsequent courses of action for the assessment of ecological risks belongs to the EPA

(EPA, 1997b). The SLERA provides input for this decision. This conclusions section is intended

to succinctly highlight the pertinent results of the SLERA, utilizing professional judgment as well

as site-specific expertise that the risk assessor and key stakeholders have gained during performance

of the SLERA.

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4.0 OVERALL CONCLUSIONS This section will briefly synthesize the conclusions of both the BHHRA (Section 2.7) and SLERA (Section 3.3), to efficiently highlight the key information to be used for site management decisions. For example, if the conclusions of the SLERA were to indicate that no adverse ecological effects are associated with exposure to surface soil, but that substantial data gaps still existed as to the potential human health effects associated with surface soil exposure, the human health data gaps would be identified in this section and it would be stated that further ecological evaluation of surface soil is not recommended.

t 01


5.0 REFERENCES

Baes, C.F., R.D. Sharp, A.L. Sjoreen, and R.W. Shor, 1984, A Review and Analysis of Parameters for Assessing Transport of Environmentally Released Radionuclides through Agriculture, Oak Ridge National Laboratory, Oak Ridge, Tennessee, ORNL-5786.

Bintein, S., J. Devillers, and W. Karcher, 1993, "Nonlinear Dependence of Fish Bioconcentration on H-Octanol/Water Partition Coefficient", SAR and QSAR in Environmental Research, Volume 1, pp. 29-39.

Hardin, J.W., and R.O. Gilbert, 1993, Statistical Tests for Detecting Soil Contamination Greater than Background, Pacific Northwest Laboratory, Richland, Washington, PNL-8989/UC-630, December.

Hawaii Department of Business, Economic Development and Tourism, 1999, Hawaii Seafood Buyers' Guide, Honolulu. Hawaii, obtained on-line at planet-hawaii.com/hsbg.

IT Corporation, 2000a, Remedial Investigation Work Plan, Barber Orchard Site, Draft, Haywood County, North Carolina, December.

IT Corporation, 2000b, Quality Assurance Project Plan, Barber Orchard Site, Draft, Haywood County, North Carolina, December.

Land, C. E., 1975, "Tables of Confidence Limits for Linear Functions of the Normal Mean and Variance," in Selected Tables in Mathematical Statistics, Vol. Ill, American Mathematical Society, Providence, Rhode Island.

National Climatic Data Center (NCDC), 1990, Comparative Climatic Data for the United States through 1989, Ashville, North Carolina.

National Council on Radiation Protection and Measurements, 1984, Radiological Assessment: Predicting the Transport, Bioaccumulation, and Uptake by Man of Radionuclides Released to the Environment, NCRP Report No. 76.

National Library of Medicine, 2000, Hazardous Substances Data Bank (HSDB), on-line.

National Research Council, 1996, Nutrient Requirements of Beef Cattle, 7th Revised Edition, Subcommittee on Beef Cattle Nutrition, National Academy Press, Washington, D.C.

http://planet-hawaii.com/hsbg

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Travis, C.C., and A.D. Arms, 1988, "Bioconcentration in Beef, Milk, and Vegetation," Environmental Science and Technology, Volume 22, pp. 271-274.

U.S. Department of Agriculture (USDA), 2000, USDA NutrientDatabase for StandardReference, On-line, Agricultural Research Service, Beltsville Human Nutrition Research Center, Beltsville, Maryland.

U.S. Department of Energy (DOE), 1989, A Manual for Implementing Residual Radioactive Material Guidelines, Argonne National Laboratory, Argonne, Illinois, ANL/ES-160, DOE/CH/8901.

U.S. Department of Energy (DOE), 1983, Pathway Analysis and Radiation Dose Estimates for Radioactive Residues at Formerly Utilized MED/AEC Sites, U.S. Dept. of Energy, Oak Ridge Operations Office, Oak Ridge, Tennessee, DOE ORO-832.

U.S. Environmental Protection Agency (EPA), 2000a, Region 9 Preliminary Remediation Goals (PRGs) 2000, Annual Update, San Francisco, California, November 1.

U.S. Environmental Protection Agency (EPA), 2000b, Integrated Risk Information System (IRIS), On-line, National" Center for Environmental Assessment, Cincinnati, Ohio.

U.S. Environmental Protection Agency (EPA), 2000c, "Amended Guidance on Ecological Risk Assessment at Military Bases: Process Considerations, Timing of Activities, and Inclusion of Stakeholders," memorandum from T. Simon to J. Johnston and E. Bozeman, Office of Technical Services, June 23.

U.S. Environmental Protection Agency (EPA), 2000d, National Recommended Water Quality Criteria for Priority Toxic Pollutants, On-line, Office of Water.

U.S. Environmental Protection Agency (EPA), 2000e, teleconference between EPA (J. Bomholm and G. Adams), Black & Veatch (E.Hicks), and IT Corporation (R. Kurth, T. Tingle, and T. Siard), December 12.

U.S. Environmental Protection Agency (EPA), 1999, Region 4 Ecological Bulletins, revision, Office of Technical Services, Atlanta, Georgia, August 11.

U.S. Environmental Protection Agency (EPA), 1998, Risk Assessment Guidance for Superfund: Volume I, Human Health Evaluation Manual (Part D, Standardized Planning, Reporting, and Review of Superfund Risk Assessments), Interim, Office of Emergency and Remedial Response, Washington, D.C., January, 9285.7-01D.

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U.S. Environmental Protection Agency (EPA), 1997a, Exposure Factors Handbook, Final, National Center for Environmental Assessment, Washington, DC, EPA/600/P-95/002Fa, August.

U. S. Environmental Protection Agency (EPA), 1997b, Ecological Risk Assessment Guidance for Superfund: Process for Designing and Conducting Ecological Risk Assessments - Interim Final, U. S. Environmental Response Team, Edison, New Jersey, (EPA 540-R-97-006).

U.S. Environmental Protection Agency (EPA), 1997c, The Lognormal Distribution in Environmental Applications, Technology Support Center Issue Paper, EPA/600/R-97/006.

U.S. Environmental Protection Agency (EPA), 1997d, Health Effects Assessment Summary Tables, FY 1997 Update, Office of Solid Waste and Emergency Response, 9200.6-303 (97-1), EPA-540-R-97-036, NTIS No. PB97-921199.

U.S. Environmental Protection Agency (EPA), 1996, Soil Screening Guidance: Technical Background Document, Office of Solid Waste and Emergency Response, EPA/540/R-95/128, NTIS No. PB96-963502.

U.S. Environmental Protection Agency (EPA), 1995a, Supplemental Guidance to RAGS: Region 4 Bulletins Human Health Risk Assessment, Waste Management Division, Atlanta, Georgia, November.

U.S. Environmental Protection Agency (EPA), 1995b; Supplemental Guidance to RAGS: Region 4 Bulletins Ecological Risk Assessment, Waste Management Division, Atlanta, Georgia, November.

U.S. Environmental Protection Agency (EPA), 1995c, Great Lakes Water Quality Initiative Technical Support Document for the Procedure to Determine Bioaccumulation Factors, Office of Water, EPA-820-8-95-005, March.

U.S. Environmental Protection Agency (EPA), 1995d, telephone communication between P. Goetchius, IT Corporation, and John Nichols, EPA Research Laboratory, Duluth, Minnesota, March 29.

U.S. Environmental Protection Agency (EPA), 1994, Implementation Guidance for Conducting Indirect Exposure Analysis at RCRA Combustion Units, Office of Solid Waste and Emergency Response, Washington, DC, April 22.

U.S. Environmental Protection Agency (EPA), 1993, Superfund's Standard Default Exposure Factors for the Central Tendency and Reasonable Maximum Exposure, Preliminary Review, Draft, May 5.

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U.S. Environmental Protection Agency (EPA), 1992a, Supplemental Guidance to RAGS: Calculating the Concentration Term, Office of Solid Waste and Emergency Response, Washington, DC, Publication 9285.7-081.

U.S. Environmental Protection Agency (EPA), 1992b, Dermal Exposure Assessment: Principles and Applications, Interim Report, Office of Research and Development, Washington, DC, EPA/600/8-91/01 IB, including supplemental guidance dated August 18.

U.S. Environmental Protection Agency (EPA), 1992c, "Guidance on Risk Characterization for Risk Managers and Risk Assessors," Memorandum from F. Henry Habicht II, Deputy Administrator, to Assistant Administrators, Regional Administrators, February 26.

U.S. Environmental Protection Agency (EPA), 1992d, Statistical Training Course for Groundwater Monitoring Data Analysis, Office of Solid Waste, EPA/530/R-93/003.

U.S. Environmental Protection Agency (EPA), 1991a, Risk Assessment Guidance for Superfund Volume I: Human Health Evaluation Manual Supplemental Guidance, Standard Default Exposure Factors, Interim Final, Office of Solid Waste and Emergency Response, OSWER Directive: 9285.6-03.

U.S. Environmental Protection Agency (EPA), 1991 b, Guidance on Estimating Exposure to VOCs During Showering, memorandum from D. E. Patton (Risk Assessment Forum) to F. H. Habicht (Risk Assessment Council), Office of Research and Development, July 10.

U.S. Environmental Protection Agency (EPA), 1990, "National Oil and Hazardous Substances Pollution Contingency Plan," Federal Register 55(46): 8666-8865.

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

U.S. Environmental Protection Agency (EPA), 1989b, General Quantitative Risk Assessment Guidance for Noncancer Health Effects, Prepared by the Office of Health and Environmental Assessment, Cincinnati, Ohio, for the Risk Assessment Forum, ECAO-CIN-538.

U.S. Environmental Protection Agency (EPA), 1986, "Guidelines for Carcinogen Risk Assessment," Federal Register, 51(185): 33992-34003.

U.S. Geological Survey, 1995, Occurrence of Selected Organochlorine Compounds in Fish Tissue from Eastern Iowa Streams, 1995, National Ambient Water Quality Criteria Program, Iowa City, Iowa.

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Woodbridge, 1999, Nutritional Guide for Seafood, Orlando, Florida, Information (based on USDA and other sources) obtained on-line at www.woodbridgechips.com/seafoodnut.html.

http://www.woodbridgechips.com/seafoodnut.html

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