flR3Ql*305 › work › 03 › 100465.pdf · TABLE OF CONTENTS Section Title .__ Page 1 INTRODUCTION 1-1 2 HUMAN HEALTH RISK ASSESSMENT 2-1 2.1 Site Background 2-1 2.2 Site Characterization

WORK PLAN FOR

BASELINE RISK ASSESSMENT

STANDARD CHLORINE OF DELAWARE, INC

DELAWARE CITY, DELAWARE

PREPARED BY:

ROY F. WESTON, INC.

ONE WESTON WAY

WEST CHESTER, PENNSYLVANIA 19380

DESIGNERS/CONSULTANTS

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TABLE OF CONTENTS

Section Title .__ Page

1 INTRODUCTION 1-1

2 HUMAN HEALTH RISK ASSESSMENT 2-1

2.1 Site Background 2-12.2 Site Characterization 2-12.3 Contaminant Characterization 2-12.4 Exposure Assessment 2-3

2.4.1 Identification of Potential ExposureReceptors/Pathways 2-32.4.1.1 Analysis of the Probable Fate

and Transport of Site Contaminants 2-32.4,1.2 Identification of Human Populations

in the Area, Sensitive Subpopulations,and Typical Activities That MayInfluence Exposure 2-4

2.4.13 Identification of Potential ExposurePathways Under Current and FutureLand Uses 2-5

2.4.1.4 Development of Exposure Scenariosfrom the Identified Exposure Routesand Selection of Plausible ExposureScenarios 2-7

2.4.2 Exposure Point Concentrations 2-82.4.3 Estimation of Exposure Dosages 2-10.

2.5 Toxicity Assessment 2-112.6 Risk Characterization 2-14

2.6.1 Carcinogenic Risk 2-142,6.2 Noncarcinogenic Risk 2-152,6.3 Uncertainty Analysis 2-16

3 ECOLOGICAL RISK ASSESSMENT 3-1

3.1 Purpose and Approach 3-13.2 Contaminants of Concern 3-23.3 Exposure Assessment . 3-2

3,3.1 Pathways/Habitat Evaluation 3-43.3.1.1 Delineation/Wetland Functional Assessment 3-5

3.3.2 Pathways/Target Species Selection 3-83.3.3 Estimation of Exposure Point Concentration 3-93.3.4 Exposure Estimation 3-11

TABLE OF CONTENTS(Continued)

Section 3Mfi

3.4 Toxicity Assessment 3-123.5 Risk Characterization 3-14

REFERENCES R-l

ATTACHMENT A ALGORITHMS AND EXPOSURE ASSUMPTIONS FORESTIMATING EXPOSURE DOSES

u

LIST OF TABLES

Table No. . __ Title Page

1-1 U.S. EPA Guidance for Risk Assessment 1-3

2-1 ._.___. Summary of Exposure Scenarios Pertinent to 2-9SCD Human Health Risk Assessment

2-2 Available Human Health Toxicity Information 2-13for Substances of Potential Concern - SCDFacility

3-2 Wildlife Known to Commonly Occur in the 3-10Vicinity of the Standard Chlorine FacilityDelaware City, Delaware

3-3 Safety Factors Used to Derive Critical 3-13Toxicity Values

LIST OF FIGURES

Figure No. Title Page

2-1 Identification and Characterization of Human 2-6Exposure Pathways

3-1 A Conceptual Diagram of Transport Pathways of 3-6Contaminants from Standard Chlorine FacilityThroughout the Terrestrial Ecosystem

3-2 A Conceptual Diagram of Transport Pathways of 3-7Contaminants from Standard Chlorine FacilityThroughout the Aquatic Ecosystem of Red LionCreek

in

SECTION 1

INTRODUCTION

The Standard Chlorine of Delaware, Inc. (SCD), Delaware City, Delaware facility is thesubject of a Remedial Investigation/Feasibility Study (RI/FS) being conducted by under aConsent Order between the Delaware Department of Natural Resources and EnvironmentalControl (DNREC) and SCD, dated 14 November 1988. Under the ComprehensiveResponse Compensation and Liability Act, CERCLA, a baseline risk assessment isconducted to document and justify the extent to which actual or threatened releases ofhazardous substances may pose an imminent and substantial endangennent to public health,welfare, and the environment. This work plan serves as a guideline for the baseline riskassessment of the SCD site. The purpose of this work plan is to present the concepts andissues by which the baseline risk assessment will be prepared. It serves to initiate theconsideration and discussion of issues related to the baseline risk assessment by appropriateagencies and concerned parties by: 1) describing the existing information available for usein the assessment, 2) presenting the methods that will be used in conducting the assessment,and 3) presentation of the exposure assessment information to be used in the riskassessment

The baseline risk assessment is an integral component of the RI/FS under CERCLA, notonly in defining the risk to human health and the environment, but also in focusingsubsequent data collection efforts if necessary. Consequently, the baseline risk assessmentprocess can be thought of as an iterative and interactive process with the remedialinvestigation of the site. The risk assessment, then, should not be considered final until theremedial investigations at the SCD site have been completed and have been incorporatedinto the remedial investigation document.

Stringent study requirements will be considered in planning and executing the riskassessment. These requirements may be summarized as follows:

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The risk assessment of the SCD site will be an objective assessment usingmethodology consistent with EPA's Risk Assessment Guidance for Superfund(EPA, 1989a and 1989b), as well as other guidance applicable to CERCLAsites on the National Priority List.

Interaction with the Delaware Department of Natural Resources andEnvironmental Control (DNREC) and EPA Region III will be required,particularly when defining current and future exposure scenarios and whencoordinating access to other types of information such as ecological studiesperformed in the study area.

Several objectives will be accomplished under the baseline risk assessment for the SCD site.These objectives include:

Characterization of the potential human health risks (based on minimum,average, and reasonable maximum exposure) associated with the pastreleases of chlorinated benzenes in 1981 and 1986.

Characterization of the ecological risks and impacts associated with the SCDsite.

In accordance with the National Contingency Plan (NCP), the risk assessment outlinedherein will evaluate the potential human health and environmental impacts associated withthe site under the no-action alternative; i.e., in the absence of remedial (corrective) action.The no-action alternative will be defined for both present and future uses of contaminatedmedia (e.g., ground water) to the extent those uses differ. This assessment will help focusthe selection of site remedies, if necessary, for reducing the contaminant concentrations inthe environmental media associated with the greatest potential risks to human health andthe environment.

The human health risk assessment and the ecological assessment will be performed inaccordance with U.S. EPA guidelines. A list of some of the U.S. EPA guidance documentsthat will be used is presented in Table 1-1.

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Table 1-1

U.S. EPA Guidance for Risk Assessment

Risk Assessment Guidance for Superfund - Volume I, Human HealthEvaluation Manual Part A (1989).

Risk Assessment Guidance for Superfund - Volume II, EnvironmentalEvaluation Manual (1989).

Superfund Exposure Assessment Handbook (1988).

Exposure Factors Handbook (1989).

CERCLA Compliance with Other Laws Manual (1988).

Guidance for Conducting Remedial Investigations and Feasibility StudiesUnder CERCLA (1988).

Ecological Assessment of Hazardous Waste Sites: A Field and LaboratoryReference (1989).

Data Quality Objectives for Remedial Response Activities: DevelopmentProcess (1987).

Data Quality Objectives for Remedial Response Activities: Volume 2 -Example Scenario (1987).

National Oil and Hazardous Substances Pollution Contingency Plan; FinalRule, 40 CFR Part 300 (1990).

Biological Criteria • National Program Guidance for Surface Waters (1990).

Region El EPA Supplement for Data Evaluation/Reduction and ConductingRisk Assessments.

The sections that follow provide descriptions of the technical components of the baselinerisk assessment with a discussion of the objectives for each component and the technicalapproach by which each objective will be met.

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SECTION 2

HUMAN HEALTH RISK ASSESSMENT

2.1 SITE BACKGROUND

Because of the large amount of information available for the SCD site, a background sectionwill be presented at the beginning of the risk assessment to help acquaint the reviewer withthe site. This section will provide a general site description, including maps of the site, aswell as a discussion of both the site history, and the site contamination related to the twopast releases of chlorinated benzenes in 1981 and 1986.

2.2 SITE CHARACTERIZATION

The physical characteristics of the site will be discussed, including climate, geology, soils,ground-water hydrology, and the presence and location of area wetlands (including Red LionCreek). This detailed description of the site will help to characterize the exposure setting.Information will be taken from observations made during the remedial investigation fieldsampling effort. '

2.3 CONTAMINANT CHARACTERIZATIONA baseline risk assessment will be conducted and will be based on the RI results of samplingfor benzene and selected chlorinated benzenes (14 substances total). As noted in DNRECscomment letter of November 20, 1990, the types of contaminants present at the site arelimited to benzene and chlorinated derivatives of benzene. With this in mind, only thesubstances named below are considered to be site-related and relevant to a risk analysis:

BenzeneChlorobenzene1,2-Dichiorobenzene1,3-Dichlorobenzene

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1,4-Dichlorobenzene1,2,3-Trichlorobenzene1,2,4-Trichlorobenzene1,3,5-Trichlorobenzene1,2,3,4-Tetrachlorobenzene1,2,4,5-TetrachlorobenzenePentachlorobenzeneHexachlorobenzeneNitrobenzeneMetachloronitrobenzene

Data summary tables will be developed for each medium sampled (e.g., sediments, surfacewater, ground water, soil). Each data summary table will indicate the frequency of detection(number of samples), observed range of concentration, and the mean and upper 95thpercentile value for each contaminant detected in each medium.

The arithmetic mean and upper 95 percent confidence interval of that mean will be usedin the summary of potential contaminant data unless a preliminary evaluation of the dataindicates that the contaminant concentrations are not normally distributed in the sampledmedia. If log-normally distributed, the geometric mean will be used. In determining whichsamples to use in the calculation of the mean value, the spatial and temporal distributionof chemicals will be considered to avoid biasing the mean.

Note that in the calculation of the arithmetic mean, concentrations presented as "ND" ornondetects will be incorporated at one-half the detection limit.

For a more thorough discussion of data treatment, the reader is referred to Section 5, "DataEvaluation" of the EPA's Risk Assessment Guidance for Superfund. Volume 1 (EPA,1989a).

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2.4 EXPOSURE ASSESSMENT

The objectives of the exposure assessment are to characterize potentially exposedpopulations at the SCD site, to identify actual or potential exposure pathways, and todetermine the extent of exposure.

2.4.1 Identification of Potential Exposure Receptors/Pathways

In this step of the assessment, activity patterns of potentially exposed populations at theSCD site will be defined, and combined with chemical release and transport mediainformation to identify potential exposure pathways.

An exposure pathway is comprised of the following four elements:

1. A source and mechanism of chemical release to the environment.

2. The likely environmental fate of the chemicals (e.g., persistence, partitioning,transport, and intermediate transfer).

3. A point of potential contact of humans or biota with the affected medium(the exposure point).

4. An exposure route (e.g., ingestion, inhalation, dermal contact) at theexposure point.

The identification of potential exposure pathways at the SCD site will include the activitiesdescribed in the subsections that follow.

2.4.1.1 Analysis of the Probable Fate and Transport of Site Contaminants

To determine the environmental fate and transport of the contaminants of concern at thesite, and, to obtain an estimation of the persistence of the substances in the wetland area,the physical/chemical and environmental fate properties of the contaminants will be

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reviewed. Some of these properties include: volatility, photolysis, hydrolysis, oxidation-reduction, biodegradation, accumulation, persistence, and migration potential. Thisinformation can assist in predicting potential current and future exposures. It can help indetermining those media that are currently receiving site-related contaminants, or mayreceive site-related contaminants in the future. Sources that may be consulted in obtainingthis information include computer databases (e.g., AQUIRE, CHEMFATE), as well as theopen literature.

The collection of data in various media accounts for fate and transport. It does not,however, account entirely for persistence. As a result, it may be necessary to useappropriate models to predict the longevity of the substances in the wetlands.

2.4.1.2 Identification of Human Populations in the Area, Sensitive Subpopulations. andTypical Activities that May Influence Exposure

The human populations that will be evaluated for potential exposure are the residents usingthe Red Lion Creek for recreational purposes (Le., fishing and hunting) and the workers atthe currently operational SCD facility. Occasional visitors to the SCD site are to beevaluated for "occasional visits" such as haulers who might visit the site on a regularschedule. Typical types of activities that may influence exposure to the residents andworkers/site visitors include working outdoors on the site, wading in ditches while huntingand consuming fish caught in the Red Lion Creek. Workers also may be exposed at sometime in the future through use of the groundwater under the site for drinking purposes.

Certain individuals, particularly children, may be more sensitive to contamination exposurethan the general population. Thus, children will be evaluated separately from adults in theoff-site exposure assessment.

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2.4.1.3 Identification of Potential Exposure Pathways/Routes Under Current and Future

Land Uses

Based on site visits and available site data, potential exposure pathways have been identifiedfor the SCD site. The general framework for the selection of key pathways is broadlyillustrated in Figure 2-1. The following exposure routes (listed by media pathway) havebeen chosen for evaluation in the risk assessment based on a review of local water and landuses.

Soil Pathway (includes soil and sediments)

Direct ingestion (soil, sediments).Dermal absorption (soil, sediments).

Surface-Water Pathway

Dermal absorption (Red Lion Creek and tributaries).Fish ingestion (Red Lion Creek).

Ground-Water Pathway

Direct ingestion (worker only).

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IDENTIFY POTENTIAL HUMAN EXPOSUREEXPOSURE PATHWAYS

COMPARE POTENTIAL PATHWAYS WITHLOCAL LAND AND WATER USE

DETERMINE IF PATHWAY IS COMPLETE(Le., REPRESENTS A POTENTIAL EXPOSURE)

IF PATHWAY IS w PATHWA v T«COMPLETE, DETERMINE " *A *H w AY te

EXPOSURE POINTCONCENTRATIONS OFSITE CONTAMINANTS

IMCOMPLETE, REJECTPATHWAY FROM FURTHER

CONSIDERATION

COMPARE CONTAMINANT CONCENTRATIONSWITH BACKGROUND CONCENTRATIONS

IDENTIFY POLLUTANTS AND PATHWAYSFOR FURTHER ANALYSIS

FIGURE 24 IDENTIFICATION AND CHARACTERIZATIONOF HUMAN EXPOSURE PATHWAYS

NCALQU11-H/DU

Air Pathway

Inhalation of dust (soil).

Inhalation of vapors (soil, sediments).

Additional exposure routes that were considered but will not be evaluated, includeassumption that a residence could be placed in the off-site area comprising the spillpathways. The area contains extensive wetlands and heavy industrial use that likelyprecludes residential development in the off-site area of concern.

2.4.1.4 Development of Exposure Scenarios from the Identified Exposure Routes andSelection of Plausible Exposure Scenarios

Numerous exposure scenarios are possible in the vicinity of the SCD study area. Exposureroutes and potential receptors are similar for several of the contaminated media, while othermedia may only impact a subgroup of the population through specific exposure routes. Asa result, the total estimate of potential exposure to any individual is dependent on the ageof the receptor as well as the potential exposure routes and media to which the receptormight be exposed.

For the purposes of this risk assessment, two age groups will be evaluated. These agegroups were selected to be inclusive of as many exposure scenarios as possible, keeping inmind the mobility patterns and activity levels of the receptors as they relate to potentialexposure at the site.

Child (1 to 5 years)

Adult (6 to 70 years)

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Children were chosen for evaluation based on their tendency to ingest soil, as well as theirsmall body size and increased sensitivity to contaminant exposure. The exposure to childrenwill be limited to time spent while fishing Red Lion Creek. Exposure to an adult is arelevant consideration in all other exposure situations assumed to occur for site workers, sitevisitors and hunters/fishermen.

Certain exposures that would not be expected to result in adverse effects over the short termmay result in potential problems after long-term (chronic) exposures.

To simplify the process of the exposure assessment, two hypothetical exposure scenarioswere considered to evaluate the range of exposure conditions that may exist for the receptorgroups at the site. The two exposure scenarios include:

Scenario 1 - Reasonable maximum scenario

Scenario 2 - Average scenario

These scenarios differ in the number of exposure pathways that are evaluated, and aresummarized in Table 2-1.

2.4.2 Exposure Point Concentrations

After the potential contaminant migration pathways and potential target receptors have beendefined, points of likely exposure will be identified. The concentrations at these contactpoints are critical in determining exposure intake and, consequently, risk to the receptor.

Where available, the data from the previous and ongoing site investigations will be used toestimate exposure point concentrations.

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Table 2-1 - Summary of Exposure Scenarios Pertinent to SCDHealth Risk Assessment

Medium

Site soils

Groundwater

Surface water,soils andsediments

Type of ExposureInhalation ofdust/vapors, In-gestion of soil,Dermal contactwith soilIngestion ofwater under thesiteInhalation ofdust, vapors,ingestion ofsoils, fish,dermal contactwith water,dermal contactwith soils,sediments .

Land UseScenario

Current,future

Future

Current ,future

ReceptorWorker,occasionalvisitor

Worker,occasionalvisitorResident,child andadulthunter\fisherman

Exposure point concentrations may be determined directly from analytical measurementsor may be predicted by modeling (i.e., vapors emanating from soil/sediments). Whereavailable, analytical measurements will 'be used in preference to modeling to avoid theuncertainty inherent in the modeling.

Arithmetic or geometric means and upper 95 percent confidence limits of the data at theexposure point locations, will be used throughout the risk assessment. In cases wheremaximum concentrations are exceeded by the upper 95 percent confidence limit, themaximum concentrations will be used.

2.4.3 Estimation of Exposure Dosages

Exposure doses will be estimated from contaminant concentrations at the point of contactby applying factors that account for contact frequency, contact duration, absorptioncharacteristics, average body weight, and other route-specific factors such as breathing rate(inhalation), absorption percent of contaminant from a soil matrix (dermal contact), etc.These factors will be incorporated into exposure algorithms that convert the environmentalconcentrations into exposure dosages. Intakes will be reported in milligrams of contaminanttaken in by the organism (Le., ingested, inhaled, absorbed, etc.) per kilogram body weightper day (mg/kg-day).

For each individual, both weekly and yearly average daily intakes will be estimated. Theweekly average intake will be estimated for a typical week during the warmer months of theyear (April through September), and will be used to estimate potential subchronic effects.It is during the warmer months of the year that the potential for exposure to contaminantsat the site is highest. Factors contributing to an increase in exposure during the warmermonths include an increase in the amount of time spent outside; exposure to surface waters;and an increase in skin surface area exposed (e.g., short sleeves versus long sleeves). Theyearly average intakes will be used to estimate potential chronic effects. The algorithms,

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or mathematical models, to be used in the exposure assessment, along with the principalexposure assumptions, are provided in Attachment A.

2.5 TQXICITV ASSESSMENT

Toxicity values (i.e., numerical values derived from dose-response information for individualcompounds) will be used in conjunction with the intake determinations to characterize risk.Toxicity values will be taken or derived from the following sources, in order of preference:

1. EPA's Integrated Risk Information System (IRIS) - The principal toxicologydatabase, which provides updated information from EPA of cancer slopefactors, inference doses, and other standards and criteria for numerouschemicals.

2. EPA's Health Effects Assessment Summary Tables (EPA, 1990c) - A tabularsummary of toxicity information contained in IRIS.

3. EPA Region ni toxicologist in cooperation with WESTON and the EPAEnvironmental Criteria and Assessment Office.

4. Health Assessment Documents,

5- Ambient Water Quality Criteria (AWQC) Documents.

6. Health Advisory Background Information.

7. Agency for Toxic Substances and Disease Registry Toxicity Profiles.

8. International Agency for Research on Cancer.

Toxicity values will be summarized in the human health risk assessment This summary willinclude a brief description of the studies upon which selected toxicity values were based, theuncertainty factors used to calculate noncarcinogenic reference doses (RfDs) and referenceconcentrations (RfCs), and the EPA weight-of-evidence classification for carcinogens.

For those substances without EPA toxicity values (Table 2-2), a literature search, includingcomputer databases, will be conducted. Toxicity values will then (if possible) be derivedfrom this information in order that potential risks can be evaluated for all potentialcontaminants of concern at the site. EPA will be consulted regarding the appropriatenessof the data and the methodologies to be used in deriving toxicity values. Uncertaintiesregarding the toxicity assessment will be discussed in the text of the report.

Five different types of toxicity values will be used:

Reference concentrations for subchronic inhalation exposure.

Reference concentrations for chronic inhalation exposure.

Reference doses for subchronic inhalation, oral, and dermal exposure.

Reference doses for chronic inhalation, oral, and dermal exposure.

Carcinogenic slope factor (for carcinogenic substances only).

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Table 2-2 Available Human Health Toxicity informationI'or Substances of Potential Concern - SCD Facility

SubstanceBenzene

Chlorobenzeneo-Dichlorobenzenem-Dichlorobenzenep-Dichlorobenzene

1 2 3 —J-, £, f J

Trichlorobenzene1,2,4-

Trichlorobenzene1,3,5-

Trichlorobenzene1,2,3,4-

Tetrachlorobenzene1,2,4,5-

TetrachlorobenzenePentachloroben-

zeneHexachlorobenzene

NitrobenzeneMetachloronitro-

benzene

RfD* (mg/kg/day)Inhalation Oral—

5E-03

4E-02—

7E-01

—

3E-03

—

—

—

—

—

2E-03

—

— — c

2E-02

9E-02—

—

—

2E-02

—

—

3E-04

8E-04

8E-04

5E-04—

CSFb (mg/kg/day) -1Inhalation oral2.9E-02(A)d—

—

—

"(B2)d

—

—

—

—

—

—

1.6E+00(B2)d—

—

2.9E-02(A)d

-—~_

—

2.4E-02(B2)d—

—

—

—

—

—

1.6E+00(B2)d—

—

Source: HEAST (Fourth Quarter, FY 1990).*The RfD (reference dote) is. an estimate (with uncertainty spanning perhaps an order of magnitude) of the daily exposure to the human population(including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a portion of the lifetime, in the case of a subchronicRfD, or during the lifetime in the case of a chronic RfD.

" c CSF (cancer slope factor) is an estimate of the potential of a substance to cause carcinogenic effect. The CSFs arc estimated through use of mathe-matical expression models for characterizing uppcrbound risks to humans. The true risk to humans, while not identifiable, is not likely to exceed theuppcrbound estimate and in fact may be lower.

c- - No data available in HEAST.

Carcinogenic Classification A and B2 is defined as:A-Suffidcnt evidence from cpidemiologic studies to support a causal relation between exposure and cancer.B2-Sufficient evidence of cardnogenicity In animals inadequate evidence of carcinogenicity in humans.

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2.6 RISK CHARACTERIZATION

Risk characterization involves the integration of exposure doses and toxicity information toquantitatively estimate the risk of adverse health effects. Quantitative risk estimates of thereasonable maximum, average, and minimum exposures will be calculated for the sitecontaminants based on available information. To assess the potential adverse health effectsassociated with the site, the level of human exposure to the selected substances must bedetermined. Intakes of potentially exposed populations will be calculated separately for allreasonable routes of exposure. Then for each population-at-risk, the potential risk for eachsubstance will be calculated by taking into account the intakes from all exposure routes.Because short-term (subchronic) exposures may result in different effects than long-term(chronic) exposures to lower doses, two intake levels will be used in evaluating risks for eachroute of exposure, i.e., a subchronic daily intake (SDI) and a chronic daily intake (GDI).

2.6.1 Carcinogenic Risk

For the potential carcinogens that are present at the site, the carcinogenic slope factor (qj)will be used to estimate cancer risks at low dose levels. Risk will be directly related tointake at low levels of exposure. Expressed as an equation, the model for a particularexposure route is:

Excess lifetime cancer risk = Estimated dose x carcinogenic slope factor= GDI x q^

This equation is valid only for risk below 10"2 (1 in 100) because of the assumption of low-dose linearity. For sites where this model estimates carcinogenic risks of 10"2 or higher, analternative model will be used to estimate cancer risks as shown in the following equation:

Risk = 1 - exp(-CDI x q^)Where: exp = The exponential

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It will also be assumed that cancer risks from various exposure routes are additive, unlessinformation is available that suggests antagonism or synergism. Since there are nomathematical models that adequately describe antagonism or synergism, these issues will bediscussed in narrative fashion.

2.6.2 Noncarclnogenlc Risk

To assess noncarcinogenic risk, estimated daily doses will be compared with reference doses,for each substance. The potential hazard for individual substances will be presented as ahazard quotient (HQ). A hazard quotient for a particular substance through a givenexposure route is the ratio of the estimated daily intake and the applicable RfD, as shownin the following equation:

HQ - EDI/RfDWhere:

HQ - Hazard quotientEDI s Estimated daily intake (mg/kg-day)RfD - Reference dose (mg/kg-day)

To account for the additivity of risk due to exposure to all substances through numerousexposure routes, a hazard index (HI), which is the sum of all the hazard quotients, will becalculated. Ratios greater than one, or unity, indicate the potential for adverse effects tooccur. Ratios less than one indicate that adverse effects are unlikely. This procedureassumes that the risks due to exposure to multiple chemicals are additive, an assumptionthat is probably valid for compounds that have the same target organ or cause the sameeffect. If the hazard index results in a value greater than one, the compounds in the mixturewill be separated by critical effect (e.g., neurotoxicity, hepatotoxicity, etc.) and separatehazard indices derived for each effect. As previously mentioned, where information isavailable about the antagonism or synergism of chemical mixtures, it will be discussed innarrative.

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2.6.3 Uncertainty Analysis

There is uncertainty associated with any risk assessment. The exposure modeling canproduce very divergent results unless both standardized assumptions are used and thepossible variation in others are clearly understood. Similarly, toxicological assumptions suchas extrapolating from chronic animal studies to the human condition also introduceuncertainty to the risk assessment process. Uncertainty in a risk assessment may arise frommany sources including (EPA, 1986a):

Environmental chemistry sampling and analysis.

Misidentification or failure to be all-inclusive in hazard identification.

Choice of models and input parameters in exposure assessment and fate andtransport modeling.

Choice of models or evaluation of toxicological data in dose-responsequantification.

Assumptions concerning exposure scenarios and population distributions.

The variation of any factor used in the calculation of the exposure concentration will havean impact on the total carcinogenic and noncarcinogenic risk. The uncertainty analysis willqualitatively discuss non-site and site-specific factors that may produce uncertainty in the riskassessment. These factors may include key modeling assumptions, exposure factors,assumptions inherent in the development of toxicological end points, and spatio-temporalvariance in sampling. In addition, the uncertainty analysis will involve a quantitativesensitivity analysis, in which certain key assumptions are varied to determine the impact onthe risk estimates. Since it would be extremely cumbersome to attempt to vary all of thenumerous assumptions used in the assessment, the approach taken is to evaluate only thoseassumptions likely to have a significant impact on the risk estimates.

SECTION 3ECOLOGICAL RISK ASSESSMENT

3.1 PURPOSE AND APPROACH

The purpose of this ecological risk assessment is to characterize potential environmentalrisks and impacts associated with contamination at the Standard Chlorine site. Thisevaluation will focus on identifying potential adverse effects of contamination on the floraand fauna in the area. In general, the technical approach parallels the approach used in ahuman health risk assessment.

Because of the nature of previously identified contamination at Standard Chlorine, thecurrent ecological risk assessment is restricted to the area from the tide gate at the mouthof Red Lion Creek upstream to the site proper. The results of a proposed contaminanttransport evaluation will dictate if the investigation needs to include any additional areas.

The major sources of site-specific information to date have been collected by WESTON andStandard Chlorine as part of the 1981 and 1986 contaminant spill investigations (WESTON1982, WESTON 1988). Additional information by which to assess the current risks to fish,wildlife and plants will be requested from the Delaware Division of Fish and Wildlife, andthe U.S. Fish and Wildlife Service. The information provided by these sources will helpidentify data gaps that need to be addressed in the ecological evaluation and riskassessment.

The technical guidance for the performance of this ecological risk assessment comesprimarily from the following sources:

Ecological Risk Assessment (EPA, 1986).Ecological Assessment of Hazardous Waste Sites: A Field and LaboratoryReference (EPA, 1989).

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Risk Assessment Guidance for Superfund - Volume II, EnvironmentalEvaluation Manual (EPA, 1989).User's Manual for Ecological Risk Assessment (Oak Ridge NationalLaboratory, 1986). " " Ûnified Federal Methodology for Wetland Delineation (1989).Guidance on Use of Habitat Evaluation Procedures and Suitability IndexModels for CERCLA Application (USFWS, 1987).

The subsections that follow describe the approach proposed to evaluate potentialenvironmental impacts associated with contaminants found on the Standard Chlorine siteand in the surrounding area. It focuses on environmental receptors that may be affecteddirectly or indirectly by contamination associated with particular areas of concern, and thelikelihood and extent of those effects.

3.2 CONTAMINANTS OF CONCERN

The contaminants of concern for this assessment will be limited to benzene and chlorinatedderivatives of benzene. Table 3-1 provides a list of the contaminants that will be evaluatedin the ecological risk assessment.

3.3 EXPOSURE ASSESSMENT

The objectives of the exposure assessment are to:

Identify significant pathways/routes of exposure.Identify habitat types that may receive contaminants.Identify the plants, fish, and/or wildlife that may be potentially exposed to thecontaminants of concern.

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Table 3-1Contaminants of Concern for the

Ecological Assessment

BenzeneChlorobenzene1,2-Dichlorobenzene1,3-Dichlorobenzene1,4-Dichlorobenzene1,2,3-Trichlorobenzene1,2,4-Trichlorobenzene1,3,5-Trichlorobenzene1,2,3,4-Tetrachlorobenzene1,2,4,5-TetrachlorobenzenePentachlorobenzeneHexachlorobenzeneNitrobenzeneMetachloronitrobenzene

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Select indicator or target species.Predict exposure concentrations or body burdens of contaminants whenevertissue concentrations are unavailable.

In general, an ecological exposure assessment evaluates the potential magnitude andfrequency of contact with the contaminants through all appropriate exposure pathways forthe selected species. The first step of the. exposure assessment is to identify both thepathways of concern specific to the individual areas of concern and the habitats potentiallyaffected by those areas of concern.

3.3.1 Pathways/Habitat Evaluation

An assessment will be performed to determine pathways and receptors most important tothe assessment of environmental impacts. Similar to the human health assessment, factorsthat will be evaluated in the pathway and target species selection process will include:

Location of contaminant sources.Local topography.Local land use.Surrounding terrestrial habitat.

• Surrounding aquatic/wetland habitat.Availability of media-specific and location-specific contaminant data.Prediction of contaminant migration.Persistence and mobility of migrating contaminants.

Current information regarding the ecology of the site and surrounding area has beenobtained primarily from the ecological investigation performed as part of the response and

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cleanup efforts for the 5 January 1986 spill (WESTON, 1988). Conceptual diagrams of thepotential contaminant migration pathways have been developed for both the terrestrial andaquatic ecosystem (see Figures 3-1 and 3-2). Species presented in these diagrams are knownto inhabit the area and may be considered potential receptors in the risk assessment, Afinal determination of appropriate indicator or target species that will be utilized asreceptors will be made following the approach outlined in Section 3.3.2.

As previously stated, the ecological assessment of the Standard Chlorine site will focus onRed Lion Creek and its adjacent wetlands. At the time of the 1986 accidental release, RedLion Creek, which is a tributary of the Delaware River, was a brackish water tidal streamthat provided nursery and maintenance habitat for a number of estuarine species. Morerecently, stream flow was altered by the rehabilitation of a tide gate at the mouth of RedLion Creek. Consequently, the stream and its wetlands have become fresh water habitatwith little, if any, influence from the adjacent estuary.

3.3.1.1 Delineation/Wetland Functional Assessment

Due to the presence of extensive wetlands that are either in the vicinity of the StandardChlorine site or that are potentially affected by contaminant migration from the site, thereis a need to address wetland regulatory and management issues as part of the RemedialInvestigation/Feasibility Study. Consequently, there is a need to identify and delineate thewetlands associated with the site and characterize the functioning of these wetlands andother aquatic systems at both site-specific and landscape scales. Currently, a wetlanddelineation of the unnamed tributary to which contaminants were initially released has beenconducted. Additional wetland mapping will be conducted from the site proper to Route9.

As proposed in the initial RI/FS Workpian (WESTON, 1989), the wetland associated withthe unnamed tributary adjacent to the Standard Chlorine site has been identified anddelineated according to the Unified Federal Methodology (Federal Interagency Committee

3-5

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3-7

for Wetland Delineation, 1989). The horizontal limits of the existing wetlands have beenidentified and provided on a topographic plan of the site.

In addition to the wetland delineation, a functional assessment of wetlands potentiallyaffected by contamination from Standard Chlorine will be conducted. The functional statusof the adjacent wetlands will be modeled using either the standard Wetland EvaluationTechnique (WET) approach (WET-Version 2.0; Adamus et al. 1987; Adamus et al. 1988)or the Habitat Evaluation Procedure (HEP) and Suitability Index (HSI) Models forCERCLA Application (USFWS, 1987). The WET technique was developed to evaluatethe functions of a variety of wetland types throughout the U.S. Generally, WET results arefocused on site-specific evaluation of wetland functions. Briefly, WET can be used toevaluate the adjacent wetlands in terms of its potential to perform wetland functions relatedto 1) food web support and maintenance of habitat, 2) water quality, and 3) hydrology.HEP may be used to evaluate loss of habitat or reduction of habitat value provided that adistinction can be made between the impact of contamination in the marsh and changes inthe hydrologic regime resulting from the tide gate repair. In either case, potential impactswill be assessed with respect to direct effects on species, as well as, impacts which maydisrupt the overall functions of these systems. This information will be used in theecological risk assessment and will provide useful information in formulating an approachfor the remedial alternatives in the feasibility study.

3.3.2 Pathways/Target Species Selection

As with the human health evaluation, ecological exposure scenarios will be developed, thatwill include scenarios based primarily on current use of the site to the extent thatsurrounding land and water use may change and thus affect habitat, potential future use willbe considered. An identification of the plant, fish, and wildlife species that may bepotentially exposed to contaminants will be determined for each of the habitat types. From

3-8

this list of potential ecological receptors, indicator or target species will be chosen thatinclude:

Species that are threatened, endangered, or of special concern (including bothFederal and Delaware State lists);

* Species that are valuable for recreational purposes;Species that are important to the well-being of either or both of the abovegroups;Species that are critical to the structure and function of the particularecosystem which they inhabit;Species that are sensitive indicators of ecological change.

To help identify potential target species, data collected during the ecological evaluation, aswell as information provided by contacts with state and Federal trustees (e.g., NaturalHeritage database) and private agencies like the Delaware Ornithological Society and theDelaware Nature Society will be reviewed. Table 3-2 provides a partial list of speciesexpected to occur in the area.

In conjunction with the wetland functional assessment, flora identified in the wetlands willbe surveyed for signs of contaminant related stress. However, due to the reduced waterlevel fluctuations resulting from the repair of the tide gate and high levels of disturbanceassociated with previous wetland dredging, contaminant related effects on the vegetativecommunities may be difficult to assess. Therefore, literature on the phytotoxic potential forcontaminants of concern will be reviewed to determine if observed or unperceived toxiceffects may be expected.

3.33 Estimation of Exposure Point Concentration

After the potential contaminant migration pathways and affected habitats have been definedand potential target receptors identified, points of likely exposure will be described. The

3-9

Table 3-2Wildlife Known to Commonly Occur in the Vicinity of the

Standard Chlorine Facility, Delaware City, Delaware

Predatory Birds Passerine Birds Waterfowl/Wading Birds

Red-tailed Hawk Fish Crow Cattle EgretOsprey Mocking Bird Snowy EgretAmerican Kestrel Bluejay Great Blue HeronKingfisher Short-billed Marsh Wren Black-crowned Night Heron

Red-winged Blackbird Yellow-crowned Night HeronCardinal Wood DuckDowny Woodpecker Mallard DuckTree Swallow Canada Goose

Mammals Amphibians/Reptiles

White-tailed Deer Painted TurtleMeadow Vole Snapping TurtleMuskrat Northern Water SnakeMink Red-spotted NewtRaccoon Red-backed SalamanderOpossum Spring PeeperEastern Cottontail Bull Frog

3-10

concentration at these contact points (i.e., exposure point concentrations) are critical indetermining exposure intake and subsequent risk to the receptors.

Data collected only as part of the current RI/FS investigation will be used to estimateexposure point concentrations. The arithmetic or geometric mean and the upper 95thpercent confidence limit of the mean environmental concentrations for each targetcompound will serve as the basis for estimating receptor intake doses.

3,3.5 Exposure Estimation

Where the toxicity data for wildlife are presented in terms of body burden exposure, doses(in mg pollutant/kg body weight/day) will be estimated from contaminant concentrationsat the point of contact, using appropriate exposure algorithms. The type of information thatwill be incorporated into these algorithms includes contact frequency, contact duration,absorption characteristics, body weights, and ingestion rates. Body burden concentrationswill not be calculated for those species for which organ specific tissue concentration datahave been obtained and for which comparable toxicity data are available.

Where toxicity data are expressed in terms of a medium concentration (e.g., Ambient WaterQuality Criteria, fish toxicity data, terrestrial invertebrate data, phytotoxicity data, sedimentbiological effects data), the determination of a dose will not be necessary. In these cases,a comparison of predicted media concentrations with media-specific toxicity data will bemade.

3-11

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3.4 TOXICITY ASSESSMENT

The toxicities of the contaminants of concern will be assessed for aquatic life, terrestrialwildlife, and vegetation, where relevant. Scientific literature and regulatory guidelines willbe reviewed for media-specific and/or species-specific toxicity data. To the extent dataallow, a range of toxicological responses or endpoints will be evaluated. In addition tomortality, other endpoints for evaluation will include developmental abnormality, behavioralchange, changes in reproductive success and other physiological effects such as alterationof growth and respiration. These data will be used to determine critical toxicity values(CTVs) for the contaminants of concern, which will be compared with media contaminantconcentrations or estimated daily intakes. In the absence of toxicological data for indicatorspecies, CTVs may be derived using data from related species, applying safety factors thatreflect interspecies extrapolation, acute to chronic extrapolations, and added protection forendangered or threatened species.

Toxicity values from the literature will be derived using the most closely related species,where possible. Toxicity values selected for the assessment are the lowest exposure dosesreported to be toxic or the highest doses associated with no adverse effect. Data for chronicor subchronic toxicity are used wherever available.

Toxicity data for wildlife are not nearly as complete as those found for aquatic species.Consequently, extrapolation of toxicity data from other animal studies is often necessary.Because of the uncertainty associated with these extrapolations, safety factors are appliedto toxicological end points to derive CTVs. The approach taken for this study to deriveCTVs is provided in Table 3-3.

For those compounds for which only acute lethality values are available, toxicity values forthis assessment are derived by dividing the acute toxicity value by the appropriate safetyfactor. In evaluating the potential effects of pesticides on terrestrial species, EPA analyzed

3-12

Table 3-3Safety Factors Used to Derive Critical Toxicity Values

Available Toxicity Divide byEnd Points Target End Points (Safety Factors)

Acute lethality (i.e., Acute NOEL 5LD50)

Acute NOEL Chronic NOEL 10

Chronic LOEL Chronic NOEL 5

Different phylogentic Same phylogenetic 10class class

Within phylogenetic Target species toxicity 5class sensitivity(i.e., differentspecies but sameclass)

As an example, in developing a critical toxicity value for anosprey when the only datum available is an LD50 for a rate, thefollowing steps would be taken:

Rat LD50 for compound X = 500 mg/kg

(500 mg/kg^ = 100 mg/kg1. Acute lethality -*• Acute NOEL 5

(100 mg/kg) -=_-. 10 mg/kg2. Acute NOEL •* Chronic NOEL 10

3. Different phylogentic class •* Same phylogenetic class

1Q fmg/kg^ = l mg/kg10

4. Within phylogenetic class sensitivity ->a Target species CTV

fl mg/kg) 0.2 mg/kg5

3-13 e

a subset of available dose-response data and suggested that if the estimate dose is less thanone-fifth the medium lethal dose for nonendangered species, no acute hazard can bepresumed (Urban and Cook, 1986). This rule is adopted for this assessment and for CTVsfor wildlife, which are derived by dividing LOEL values by 5. Additional safety factors havebeen applied to account for differences between toxicity test species and receptor speciesselected for the site.

Sources of toxicity data for the ecological assessment include:

Ambient water quality criteria.ACQUIRE database.GEOECOLOGY database.PHYTOTOX database.ENVIROFATE database.Hazardous Substances database.

As requested by DNREC, solid phase sediment toxicity tests will be performed at the fivelocations along Red Lion Creek where surface water and sediment sampling will beconducted during the Supplemental RI activities. These tests will provide direct informationon the toxic effects, if any, of the complex mixture of compounds that have accumulated inthe sediment of Red Lion Creek. Length of tests to be performed and aquatic test speciesto be used in these assessments will be determined through discussions with DNREC.Results of the sediment toxicity testing will be incorporated directly into the toxicityassessment and risk characterization sections of the report.

3.5 RISK CHARACTERIZATION

A risk characterization integrates the exposure and toxicity assessments to estimate thepotential hazard or risk to the environmental receptors. The media concentrations or

3-14

estimated daily intakes will be compared with critical toxicity values by using a hazardquotient (HQ ), which can be expressed as:

Where:CXM s Concentration of contaminant X in medium M.CTVxM * Critical toxicity value for the same contaminant in the same medium.

When media-specific criteria are not available, hazard quotients will be calculated asfollows:

= EDI XR/CTVXR

Where:EDIXR » Estimated daily intake of contaminant X through exposure route R.CTVxR «= Critical toxicity value of the same contaminant through the same

exposure route.

A cumulative hazard index is then calculated by adding the hazard quotients across allcontaminants and all exposure routes.

If a cumulative hazard index is greater than one, the receptors or species of concern maybe potentially at risk to adverse effects from site-related contamination. If the hazard indexis less than or equal to one, then adverse effects are not expected to occur.

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REFERENCES

Adamus, P.R., Clairain, E.J., Smith, R.D., and R.E. Young. 1987. Wetland EvaluationTechnique (WET); Volume II: Methodology Operational Draft Technical Report Y-87.U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS >

Adamus, P.R., Clairain, E.J., Morrow, M.E., Rozas, UP. and R.D. Smith. 1988 (Draft).Wetland Evaluation Technical (WET) - Volume 1: literature review and evaluationrationale. Working Draft Technical Report EL-88. U.S. Army Engineer WaterwaysExperiment Station, Vicksburg, MS.

DNREC (Delaware Department of Natural Resources and Environmental Control) 1990.Review and Comment on Standard Chlorine's Soil, Sediment, and Surface Water LaboratoryAnalytical Results and Proposed Action Items (submitted to Robert J. Touhey, StandardChlorine of Delaware, 20 November 1990).

EPA (U.S. Environmental Protection Agency). 1979. Water-Related Environmental Fateof 129 Priority Pollutants. Volume I. EPA-440-14-79-029a.

EPA (U.S. Environmental Protection Agency). 1986. The Endangerment AssessmentHandbook. Office of Waste Programs Enforcement. TR-693-24B.

EPA (U.S. Environmental Protection Agency) 1986. Ecological Risk Assessment. Officeof Pesticide Programs, Washington, D.C EPA-540/9-85-001.

EPA (U.S.Environmental Protection Agency). 1988. Laboratory Data ValidationFunctional Guidelines for Evaluating Inorganics Analysis Office of Emergency andRemedial Response.

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EPA (U.S. Environmental Protection Agency). 1988. Superfund Exposure AssessmentManual. Office of Remedial Response. EPA/540/1-88/001.

EPA (U.S. Environmental Protection Agency). 1989. Risk Assessment for Superfund, Vol.I, Human Health Evaluation Manual. Office of Emergency & Remedial Response.EPA/540/1-89/002,

EPA (U.S. Environmental Protection Agency). 1989. Risk Assessment Guidance forSuperfund, Volume II. Environmental Evaluation Manual. Office of Emergency andRemedial Response. EPA/540/1-89/001.

EPA (U.S. Environmental Protection Agency). 1989. Assessing Human Health Risks fromChemically Contaminated Fish and Shellfish: A Guidance Manual. Office of Marine andEstuarine Protection. EPA-503/8-89-002.

EPA (U.S. Environmental Protection Agency). 1989. Ecological Assessment of HazardousWaste Sites: A Field and Laboratory Reference. Environmental Research Laboratory.Corvallis, Oregon. EPA/700/3-89/013.

EPA (U.S. Environmental Protection Agency). 1989. Exposure Factors Handbook. Officeof Health & Environmental Assessment. EPA/600/8-89/043.

EPA (U.S. Environmental Protection Agency). 1990.. Health Effect Assessment SummaryTables. Fourth Quarter FY-1990. NTIS No. P890-921100.

Federal Interagency Committee for Wetland Delineation. 1989. Federal manual foridentifying and delineating jurisdictional wetlands. U.S. Army Corps of Engineers, U.S.Environmental Protection Agency, U.S. Fish and Wildlife Service, and U.S.D.A. SoilConservation Service. Washington, D.C. Cooperative technical publication.

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TABLE A-2

EXPOSURE ASSUMPTIONS USED FOR THEFISH INGESTION ROUTE

ReceptorAdultHunter/

Exposure Parameter Worker Visitor Child Fisher

Total Fish Ingestion NAa NA 142b 284Rate (g/meal)

Fraction Ingested NA NA 0.5 0.5from Red Lion Creek

Exposure Frequency NA NA 30 30(meals/yr)

Exposure Duration (yr) NA NA 5 25

Body Weight (kg) NA NA 16 70

Averaging Time (yr) NA NA 70 70(carcinogens only)

a Not applicable, as worker/visitor exposure not assumed for this pathway.

b The child is conservatively assumed to ingest half the amount of fishingested by an adult.

SCD-DE5/ATTACH-A.RPT A~4

A.1.2 Fish Ingestion

Equation:Intake (mg/kg) = CF x IR x FI x'EF x ED

BW x AT

Where:CF = Contaminant Concentration in Fish (mg/kg)IR = Ingestion Rate (kg/meal)FI = Fraction Ingested from Contaminated Source (unitless)EF = Exposure Frequency (meals/year)ED = Exposure Duration (years)BW = Body Weight (kg)AT = Averaging Time (period over which exposure is averaged ~ days)

The exposure assumptions for the fish ingestion pathway are summarized inTable A-2.

A.2 DERMAL ROUTES OF EXPOSURE

The following equations are used to calculate weekly and yearly average dosesfor the dermal absorption route of exposure.

A.2.1 Dermal Absorption From Soil/Sediment

Equation:Absorbed Dose (mg/kg-day) = CS x CF x SA x AF x ABS x EF x ED

BW x AT

Where:CS = Chemical Concentration in Soil (mg/kg)CF = Conversion Factor (10"6 kg/mg)SA = Skin Surface Area Available for Contact (cm2/event)AF = Soil to Skin Adherence Factor (mg/cm2)ABS - Absorption Factor (unitless) . . . . . .EF = Exposure Frequency (event/year)ED = Exposure Duration (years)BW = Body Weight (kg)AT = Averaging Time (period over which exposure is averaged—days)

The exposure assumptions for the dermal absorption from soils contact pathwayare summarized in Table A-3.

SCD-DE5/ATTACH-A.RPT A"3

TABLE A-l

EXPOSURE ASSUMPTIONS USED FOR THESOIL INGESTION ROUTE



Total Soil Ingestion 100 100 200 100Rate (mg/day)

Fraction Ingested 0.5 0.5 0.5 0.5from Soil*

Exposure Frequency15Event/week 5 1 1 1Week/year 48 48 30 30 (fisher)

15 (hunter)

Total Years Exposed 25b 25b 5 _ 25

Body Weight (kg) 70 70 16 "~ 70

Averaging Time (yr) 70 70 70 70(carcinogens only)

* The fraction ingested from soil is conservatively assumed to equal half of totaldaily ingestion

b The frequency and duration of exposure is assumed in lieu of written guidance.

SCD-DES/ATTACH-A.RPT A-2

TABLE A-3

EXPOSURE ASSUMPTIONS USED FORDERMAL ADSORPTION FROM SOIL

Receptor •AdultHunter/


Exposed Surface 3,120 3,120 3,910s 8,620"Area (cm2)Hands and Arms

Soil Adherence 1.45 1.45 1.45 L45Factor (mg/cm2)

Absorption Factor11 50% vola- 50% vola- 50% vola- 50% vola-tiles tiles tiles tiles5% semi- 5% semi- 5% semi- 5% semi-volatiles volatiles volatiles volatiles

Exposure Frequency0days/week 5 -1 1 1weeks/year 48 48 30 30 (fisher)

15 (hunter)

Exposure Duration (yr) 25C 25C 5 25

Body Weight (kg) 70 70 16 70


a Includes legs for child and adult hunter/fisher.

b The rate of absorption of volatiles and semivolatiles were not available so draftvalues of 50% for volatiles and 5% for semivolatiles were used.

c The frequency and duration of exposure is assumed in lieu of written guidance.

SCD-DE5/ATTACH-A.RPT A-5

TABLE A-2

EXPOSURE ASSUMPTIONS USED FOR THEFISH INGESTION ROUTE



Total Fish Ingestion NAa NA 142b 284Rate (g/meal)

Fraction Ingested NA NA 0.5 0.5from Red Lion Creek

Exposure Frequency NA NA 30 30(meals/yr)


Body Weight (kg) NA NA 16 70


* Not applicable, as worker/visitor exposure not assumed for this pathway.

b The child is conservatively assumed to ingest half the amount of fishingested by an adult.

SCD-DEtfATTACH-A-RPT A-4

flR3Qt»350

A.2.2 Dermal Absorption From Surface Water

Equation:Absorbed Dose (mg/kg-day) = CW x SA x PC x ET x EF x ED x CF

BW x AT

Where:CW = Chemical Concentration in Water (nig/liter)SA = Skin Surface Area Available for Contact (cm2)PC = Chemical-specific Dermal Permeability Constant (cm/hr)ET = Exposure Time (hours/day)EF = Exposure Frequency (day/year)ED = Exposure Duration (years)CF = Volumetric Conversion Factor for Water (1 liter/1000 cm2)BW = Body Weight (kg)AT = Averaging Time (period over which exposure is averaged—days)

The exposure assumptions for the dermal contact with surface water scenario areincluded in Table A-4.

A.3 INHALATION ROUTE OF EXPOSURE

The algorithm below may be used to calculate doses received by a receptorthrough inhalation of dust or vapors.

Equation:Intake (mg/kg-day) = CA x IR x ET x EF x ED

BW x AT

Where:CA = Contaminant Concentration in Air (mg/m3)IR = Inhalation Rate (m3/hour)ET = Exposure Time (hours/day)EF = Exposure Frequency (day/year)ED = Exposure Duration (years)BW = Body Weight (kg)AT = Averaging Time (period over which exposure is averaged—days).

The exposure assumptions for the inhalation pathway are summarized in TableA-5.


TABLE A-4

EXPOSURE ASSUMPTIONS USED FORDERMAL CONTACT WITH SURFACE WATER



Exposed Surface Area (cm2) NAa NA 3,910 8,620Hands, arms, legs

Dermal Penetration6 NA NA 8.4E-04 8.4E-04Factor (cm/hr)

Exposure Time0 NA NA 4 4(hours/event)

Exposure Frequency0Events/wk N A N A 1 1weeks/year NA NA 30 30(fisher)

15(hunter)


Body Weight (Kg) NA NA 16 70


* Not applicable, as workers and visitors are not expected to be exposed bythis pathway.

b The default dermal penetration value for water is used in lieu of actualabsorption data for the substances.

c The time, frequency and duration of exposure is assumed in lieu of writtenguidance.

SCD-DE#ATTACH-A.RPT A~7

TABLE A-S

EXPOSURE ASSUMPTIONS USED FORINHALATION OF DUST/VAPORS



Air Inhalation Rate 30 30 26a 30(mVday)

Fraction of Air Inhaled 0.5 0.25 0.5 0.5

Dust Concentration in 30 30 30 30Air (ug/m3)b

Exposure Frequency2days/week 5 1 1 1weeks/year 48 48 30 30 (fisher)

15 (hunter)

Exposure Duration 25C 25C 5 25

Body Weight (kg) 70 70 16 70


a The 26 m3 inhalation value for a child represents a 6-year old's waking periodof 16 hours at an average inhalation rate of 2 m3/hr for 8 hours of lightactivity. Air is inspired at a rate of 0.4 m3/hr for the 8 hours that the childis asleep. This estimate was obtained from the EPA's Exposure FactorsHandbook.

b Assumed to be 30 ug/m3 in lieu of site data.

c The frequency and duration of exposure is assumed in lieu of written guidance.


A.4 INGESTION OF GROUNDWATER

The algorithm below is used to calculate doses received by a future worker orvisitor to SCD who are assumed to drink the groundwater.

Equation:Intake (mg/kg-day) = CW x IR x EF x ED

BW x ATWhere:

CW = Chemical Concentration in Water (mg/liter)IR = Ingestion Rate (liters/day)EF = Exposure Frequency (days/year)ED = Exposure Duration (years)BW = Body Weight (kg)AT = Averaging Time (period over which exposure is averaged-days)

The exposure assumptions for the groundwater ingestion pathway are summarizedin Table A-6.


TABLE A-6

EXPOSURE ASSUMPTIONS USED FORINGESTION OF GROUNDWATER



Water Ingestion Rate 2 2 NAa NA(L/day)

Fraction Ingested while 0.5 0.25 NA NAat siteb

Exposure Frequency0days/week 5 1 NA NAweeks/year 48 48 NA NA

Exposure Duration (yr) 25° 25° NA NA

Body Weight (kg) 70 70 NA NA

Averaging Time (yr) 70 70 NA NA(carcinogens only)

a Not applicable as exposure of a child or adult resident is not expected via thispathway.

b It was assumed that a worker drinks half and the visitor drinks one-fourth ofthe total daily water intake.

0 Exposure frequency and duration is assumed in lieu of written guidance.

SCD-DE5/ATTACH-A.RPT A- 10