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Arthir D Little Final TechnicalMemorandum

Ecological RiskAssessment at theOttati & Goss SiteKingston, NH

Submitted toU.S. EnvironmentalProtection AgencyRegion I

December 9,1997

ADL Reference 62364

Contract 68-W8-0120W.A. No. 13-1N05

Arthur D. Little, Inc.Acorn ParkCambridge, Massachusetts02140-2390

62364ARCS\058

Table of Contents

1.0 Introduction 2 1.2 Objectives 2

2.0 Site Ecological Characterization 3 2.1 Hydrogeology and Soils 3 2.2 Overview of Major Habitats 3 2.3 Comparison of Site-affected and Reference Area Wetlands 3 2.4 Potential Faunal Receptors 3

2.4.2 Wetland Fauna - Amphibians 4 2.4.2.2 Potential Occurrence of American Woodcock, Mink

and Short-tailed Shrew 4 2.5 Wetland Ecological Functions 5 2.6 Symptoms of Wetland Ecological Stress 5 2.7 Trustee Resources 5

3.0 Problem Formulation 5 3.1 Nature and Extent of Contamination 5

3.1.1 Wetland Soils 6 3.2 Contaminant Transport Pathways 9 3.3 Contaminants of Concern 9 3.4 Conceptual Model for Ecological Exposures 10 3.5 Indicator Species Selection 10

3.5.2 Indicator Communities and Species Selected 10 3.5.3 Biological Profiles of Indicator Species - Short-tailed Shrew . . 11 3.5.4 Habitat Suitability for American Woodcock, Mink, and Short-

tailed Shrew 11

4.0 Exposure Assessment 12 4.1 Exposure Pathways 12

4.1.2 Exposure Pathways for Earthworms and Benthic Invertebrates . 12 4.1.4 Exposure Pathways for the Short-tailed Shrew 12

4.2 Exposure Models 13 4.2.2 Earthworm and Benthic Invertebrate Communities of the

Wetland 13 4.2.3 American Woodcock 13 4.2.4 Mink 15 4.2.5 Short-tailed Shrew 15

4.3 Exposure Scenarios 18 4.3.2 Earthworm and Benthic Invertebrate Communities of the

Wetland 18 4.3.3 Short-tailed Shrew 19

4.4 Bioaccumulation Factors 20 4.4.1 Soil-to-Earthworm Bioaccumulation Factors 20 4.4.2 Bioaccumulation Factors for the Mink Model 20

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Table of Contents (continued)

5.0 Toxicity Assessment 21 5.1 Ecotoxicological Data Sources 21 5.2 Summary of Effects Measurement Endpoints Considered 21 5.3 Quantitative Dose-Response Data Used in Toxicity Assessment 22

5.3.2 Earthworm and Benthic Invertebrate Communities of the Wetland 22

5.3.3 American Woodcock, Mink, and Short-tailed Shrew 22

6.0 Risk Characterization and Computation of Cleanup Goals 23 6.1 Ecological Risk Characterization 23

6.1.2 Earthworm and Benthic Invertebrate Communities of the Wetland 24 6.1.2.1 Site-affected Wetland 24 6.1.2.2 Reference Wetland 25

6.1.3 American Woodcock 25 6.1.3.1 Site-affected Wetland Scenarios for the American

Woodcock 25 6.1.3.2 Reference Area Wetland Scenarios for the American

Woodcock 28 6.1.4 Mink 29

6.1.4.1 Site-affected Wetland and/or Country Pond Scenarios for Mink 29

6.1.4.2 Reference Area Wetland and Great Pond Scenarios for Mink 32

6.1.5 Short-tailed Shrew 33 6.1.5.1 100 Percent Foraging in the Site-Affected Wetland. . 33 6.1.4.2 100 Percent Foraging in the Reference Area Wetland.

34 6.2 Computation of Wetland Soil Cleanup Goals 34 6.3 Conclusions 34

6.3.1.1 Risks to the Benthic Invertebrate Community of the Wetland 34

6.3.1.2 Risks to the American Woodcock, Mink, and Short-

tailed Shrew 35

7.0 Uncertainties and Limitations in the Ecological Risk Assessment 37 7.1 Uncertainty and Limitations of the Chemical Data 38 7.2 Modelling and Site-specific Exposure Assumptions 39

7.2.2 Bioaccumulation Factors 39 7.3 Effects Measurement Endpoints 40

7.3.1 Selection of NOAELs 40 7.3.3 Bird Endpoints 41 7.3.4 Mammal Endpoints 41 7.3.5 Benthic Invertebrate Endpoints 42

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Table of Contents (continued)

8.0 Human Health Risk Assessment for Fish Ingestion 42

9.0 References 42 9.1 Primary versus Secondary References 42 9.2 New References 42 9.3 References from the Draft ERA Report 43

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Ottati & Goss Ecological Risk Assessment: Final Technical Memorandum Work Plan Amendments 8, 9, 10, and 12

Work Assignment No. 13-1N05 December 9, 1997

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This Final Technical Memorandum is intended to serve as the final report on the Ecological Risk Assessment (ERA) conducted for the Ottati & Goss/Great Lakes Container Corporation (O&G) Superfund Site in Kingston, New Hampshire. This technical memorandum has been designed to supplement and serve as a companion document to the Draft ERA Report for Ecological Risk Assessment at the Ottati & Goss Site, Kingston, NH submitted to EPA by Arthur D. Little on May 2, 1994. This work has been conducted under Work Assignment No. 13-1N05 and in accordance with Work Plan Amendment (WPA) Nos. 8, 9, 10, and 12.

The objectives of this Final ERA Technical Memorandum are to:

• Summarize the revised inputs to both the deterministic and probablistic (Monte Carlo) exposure assessment models originally presented in the Draft ERA Report (Arthur D. Little, 1994), regarding:

Body weights, foraging scenarios, and dietary profiles for each species Frogrsediment pesticide bioaccumulation factor (BAF) in the mink model Earthwormrsediment BAFs for use in the woodcock and shrew models Derivation and use of Toxicity Reference Values (TRVs) Total polychlorinated biphenyl (PCB) and Total Pesticide concentration terms developed for modeling of risks from the wetland sediments

• Summarize a reassessment of the useability of sediment and earthworm analytical data gathered between 1990 and 1993

• Present a statistical summary of all sediment PCB and pesticide data compiled from different sampling events between 1990 and 1996

• Provide a Total PCB concentration contour map based on these cumulative data for the wetland sediments

• Summarize the revised deterministic and probablistic (Monte Carlo) risk estimates for the mink (Mustela vison) and American woodcock (Scolopax minor)

• Introduce the new deterministic exposure assessment model added for the short-tailed shrew (Blarina brevicauda) and summarize the shrew's risk estimates for both the O&G and reference wetlands

• Incorporate an evaluation of the sediment contamination risks to the benthic invertebrate community inhabiting the wetland sediments, based on the Ontario Ministry of Environment (MOE) sediment criteria (Persaud et al, 1994, 1992).

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As this Draft Final Technical Memorandum is designed to complement, rather than replace the Draft ERA Report we have modified only those sections of the Draft ERA that were affected by the various scope of work (SOW) modifications and/or refinements made to the Draft ERA and have added new report sections, as needed, due to expansions of the ERA scope, such as the addition of risk calculations for the short-tailed shrew. Only the new SOW elements for the ERA are presented in detail in this report, along with discussions of the refined exposure assessment modeling approaches and other new ERA elements that have yielded revisions of our results and conclusions as originally presented in the 1994 Draft ERA Report.

To maintain consistency and continuity with and to facilitate cross-references to the 1994 Draft ERA Report, we have organized the format and contents of this Final ERA technical memorandum to mirror those of the Draft ERA Report. For each section of the Draft ERA Report, therefore, we either indicate below that no modification was needed of the original content of each report section or subsection, or we provide a supplemental discussion of the new and/or revised methods, results, and conclusions for that element of the original, Draft ERA Report. This technical memorandum, thus, should be read in concert with and as a companion document to the 1994 Draft ERA Report.

1.0 Introduction

Minimal modifications and terminology clarifications are needed to supplement those presented in the introduction of the 1994 Draft ERA Report.

Terminology. Throughout this report, the terms wetland soil and wetland sediment may be used synonymously, in a broad sense, because a combination of solid media samples were collected and analyzed from both the unflooded (soil) and flooded (sediment) niches of the wetland and associated stream channel habitats. While the Draft ERA Report was based on 5 wetland soil samples collected from hummock niches capable of supporting earthworm populations, the cumulative database used in this report to calculate ecological risks from solid media of the wetland included samples of hummock soils, hollow sediments, and stream channel sediments.

1.2 Objectives

The objectives of the Draft ERA have been modified as follows:

Additional Receptors. Two new objectives of this ERA are to calculate ecological risks from site-derived soil/sediment contaminants found in the affected wetland, to:

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• Benthic invertebrates presumed to inhabit the sediments of the wetland

• The short-tailed shrew, a carnivorous mammal with a small foraging range that can realistically be expected to be exposed to the full range of both average and maximum contaminant concentrations found throughout the wetland

Development of Cleanup Goals. It is no longer an objective of this Final ERA to present a revised set of those risk-based, wetland sediment cleanup goals originally provided in the Draft ERA Report. Rather, those cleanup goals in the Draft ERA that were based on the food chain models for the American woodcock and mink, and new cleanup goals to be based on the newly added food chain model for the short-tailed shrew, will be developed in consultation with EPA and the Superfund Ecological Assessment Team (SEAT), following the approval of this Final ERA by EPA.

The SOW and approach to be used in developing these final, risk-based wetland soil and sediment cleanup goals are presented in WPA No. 14. The deterministic and probablistic exposure models presented as part of this Final ERA will be used to calculate risk-based cleanup criteria, develop risk reduction curves for different remediation scenarios, and ultimately to define the spatial extent of soil/sediment contamination in the wetland that requires remedial action.

2.0 Site Ecological Characterization

2.1 Hydrogeology and Soils

No modification.

2.2 Overview of Major Habitats

No modification.

2.3 Comparison of Site-affected and Reference Area Wetlands

No modification.

2.4 Potential Fauna! Receptors

Supplemental field observations made since completion of the 1994 Draft ERA Report were significant only for amphibians found in the contaminated wetland. This

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new information is provided here since it reduces the uncertainty associated with the dietary exposure assessment for the mink.

2.4.2 Wetland Fauna - Amphibians As discussed in Draft ERA Report (Section 2.4.2.1 Significance of Observed versus Expected Wildlife), the apparent absence of amphibians from the wetland was noted by several biologists during site visits in 1993. While the causes for this absence of a visible amphibian community from the wetland were unclear, the apparent lack of frogs was discussed in Section 7.0 of the Draft ERA Report as a key uncertainty factor regarding food chain exposures of the mink. Since the consumption of frogs by the mink is a dietary exposure model input that significantly drove the total site pesticide risk to the mink, this had represented a significant uncertainty in the ERA.

Since completion of the Draft ERA Report, however, mature adults of unidentified amphibians were seen on several occasions. On September 25, 1996, John Glasser (USEPA, Cincinnati) saw an unidentified salamander near North Brook at Grid Point B300. On July 2, 1997, Dr. Phillip Rury of Arthur D. Little saw what appeared to be a spotted salamander (Ambystoma maculatum) in this same area near the northern fenceline at North Brook.

During 1997, adults of unidentified frog species (Rana spp.) also were observed by Athur D. Little staff in flooded hollows in several different areas of the wetland, including habitats near grid points with some of the highest Total PCB sediment concentrations (see Figure 2-1):

• At two locations on July 22, 1997 (A500 and B800) • At one location, between D700 and E700, on October 10, 1997 • At three more locations on October 15, 1997 (B400, D550, and D600)

These supplemental observations of amphibians in 1996 and 1997 indicate that the inclusion of frogs as a dietary element for the mink model is realistic for this site.

2.4.2.2 Potential Occurrence of American Woodcock, Mink and Short-tailed Shrew. No supplemental discussion is needed as to the ability of the on-site, contaminated wetland and other adjacent habitats to support mink and American woodcock.

Short-tatted Shrew. The topography, soils, hydrology, and vegetation of the site-affected wetland combine to provide suitable habitat for the short-tailed shrew, with respect to both the food and cover value of the wetland and adjacent upland areas. This shrew is a carnivorous mammal that prefers terrestrial and wetland habitats with moist soils and abundant soil invertebrates. The wetland offers suitable habitat for

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the shrew for two key reasons: food and cover. Earthworms, which were found to occur at several locations within the wetland, constitute the bulk of the shrew's normal diet. The very dense shrub and herbaceous vegetation found in the wetland also support abundant soil insects that the shrew can prey upon to complement its earthworm diet. The presence of small vertebrates such as frogs and salamanders, which shrews also may prey upon, also contributes to the abundance and diversity of this food resource. The dense, stratified, vegetation structure also provides good cover from predators of the shrew, such as raptors, while providing abundant nesting sites among the woody root systems found on the wetland hummocks.

2.5 Wetland Ecological Functions

No modification.

2.6 Symptoms of Wetland Ecological Stress

No modification.

2.7 Trustee Resources

No modification is needed for this original report section to accommodate the SOW changes. However, it is noteworthy that a migratory waterfowl species, the great blue heron (Ardea herodias), was seen landing in the concrete decontamination pad in the terrestrial portion of the O&G site, at 9:20 AM on September 25, 1996. This bird is a trust species pursuant to the Migratory Bird Treaty Act, that had been presumed to occur at the project site in the Draft ERA, but previously had not been seen on site.

3.0 Problem Formulation

No modification is required for the problem formulation elements pertaining to the aquatic biota inhabiting the surface waters of the wetland, nor to the mink and American woodcock. As discussed below, however, a revised soil/sediment contamination database and two additional ecological receptors have been integrated into the Problem Formulation and other elements of the Final ERA.

3.1 Nature and Extent of Contamination

An expanded wetland soil/sediment analytical database has been integrated into this Final ERA, as a basis for revising the characterization of the nature and extent of wetland soil/sediment contamination used in the Problem Formulation step.

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3.1.1 Wetland Soils For the Draft ERA, Arthur D. Little estimated baseline risk for the mink and woodcock using the average and maximum detected concentrations of chemicals of concern (COC) for five samples of site-affected wetland soils and one reference wetland soil sample that were collected in 1993 for the earthworm uptake study. Since the limited spatial coverage of these analytical data introduced an unacceptable level of uncertainty as to the average risks to wildlife species that forage throughout the entire wetland, such as the mink, it was decided to perform a more extensive sampling program for Total PCBs in wetland soil and sediment samples from both the previously sampled and unsampled portions of the wetland. In 1995, a 100 foot by 100 foot grid was surveyed and staked in the wetland by a professional land survey crew (Figure 2-1). Arthur D. Little then collected additional soil and sediment samples from these grid points, between December 1995 and June 1996, for analysis of Total PCBs.

For this revised ERA we integrated all existing wetland soil and sediment data for samples collected from both unflooded (e.g., hummocks) and flooded (e.g., channels, hollows) wetland locations, during the following time periods and sampling events:

• PCB and pesticide analyses of samples collected from a baseball field-shaped area adjacent to Rte. 125 between 1990 through 1992 data (the "ballfield data")

• PCB, pesticide, and metals analyses of unflooded soil samples collected in 1993 for use in the earthworm uptake study and Draft ERA (the "Draft ERA data")

• Total PCB analyses of wetland soil/sediment samples collected from hummocks, hollows, and channels on the 100 foot grid in 1995 and 1996 (the "grid data")

Statistical summaries for each of these three individual data subsets and for the single, cumulative database formed by combining these three subsets, were presented in the October 9, 1996 interim technical memorandum submitted by Arthur D. Little to the EPA. Because only the cumulative, integrated database was used to calculate risks to all ecological receptors in this Final ERA, the separate data summaries for each of the three subsets included in the interim memorandum are not included in this document. The integrated, cumulative data summary used to revise the risk calculations for this Final ERA, however, do appear in the summary of risk calculations for the benthic invertebrate community of the wetland, which appear below in Section 6.1.6

Reassessment of Sediment and Earthworm Data Useability. A review of the following sediment analytical data was completed to assess useability for the revised risk calculations using the cumulative historical dataset:

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• Cadmium and mercury data for the 1993 reference wetland sediments

• Pesticide and PCB data for sediments collected in 1991 from locations at 20 foot spacings within the "ballfield" shaped sampling area

• Earthworm pesticide data from the 1993 samples collected during the uptake/toxicity test, for which JN-qualified detections were reported, due to possible Aroclor-induced matrix interferences

Since the basis for rejecting the cadmium and mercury data for the reference wetland sediments (Sample E-6) during the original data validation for the Draft ERA cannot be refuted, the uses of these analytical data were not revised in this Final ERA. The 1991, wetland sediment pesticide and PCB data already had been validated and results for all samples not meeting the moisture requirement for these parameters already had been rejected. Thus, these 1991 "ballfield" sediment PCB and pesticide data were used in the new and revised exposure assessment models and in producing the Total PCB concentration contour map for this Final ERA (see Figure 2-1).

Reassessment of the 1993 earthworm pesticide data consisted of a review of the prior data validation packages, including inspection of sample-specific chromatograms, that was focused on a subset of those pesticides for which the worms revealed a higher concentration after the 28 day uptake study than the baseline worm sample had prior to the experimental exposure in the laboratory: beta-BHC, delta-BHC, heptachlor, aldrin, dieldrin, 4,4'-DDE, 4,4'-DDD, and alpha-chlordane. Although the results of this reassessment included changes from positive detections to non-detects (NDs) for several of the pesticide/sample pairings, the original positive detections of one or more of these pesticides were confirmed for all of the earthworm samples. Among the seven pesticides considered, positive detections were confirmed in at least one sample for all of the pesticides except beta-BHC.

Since a combination of comparative, sediment and earthworm analyses in the site-derived versus reference wetland samples had been used to select pesticide COCs in the Draft ERA Report, this earthworm data reassessment indicated that the original COC screening for pesticides in sediments need not be repeated. Rather, only beta-BHC was removed from the Draft ERA list of pesticide COCs for wetland sediments and/or earthworms prior to integrating the pesticide data for the 1991 ballfield and 1993 Draft ERA samples for use in the revised risk calculations presented herein.

A more detailed discussion of this data useability reassessment was presented in the October 1996 interim technical memorandum and is thus omitted from this report. Based on this review of the sediment and earthworm pesticide data, the 1990/1991

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and 1993 sediment pesticide data were used as a combined dataset in the revised risk calculations of this Final ERA Technical Memorandum.

Averaging of COC Concentrations for Use in Modeling. After the addition of the historical (ballfield) and new (grid) datasets to the Draft ERA dataset the average COC concentrations used in the exposure assessment models were re-calculated. Two different averaging methodologies were used to generate the exposure concentrations used for various COC/receptor combinations, as discussed in the following sections.

Deterministic Models - Two separate methodologies were used to estimate the COC concentrations used in the deterministic exposure models. For Total PCBs, the cumulative data were first contoured using an inverse distance-weighted interpolation algorithm available in the ARCView Geographic Information System (GIS) software (see Figure 2-1). Average concentrations of Total PCBs were then calculated for each of the discrete wetland sectors falling between successive pairs of contours or within detached contour "islands" in more distant parts of the wetland, by averaging location-specific Total PCB concentrations for all points falling within each sector. Care was taken to not double count any single point by including it in more than one contour-bound sector. The sector-specific, average Total PCB concentrations were then spatially-weighted, based on the relative acreage of each sector, to determine the average Total PCB concentration used in the exposure assessment models for each of the three wildlife indicator species (i.e., 1.48 mg/kg). These sector-specific acreage and associated ranges of Total PCB concentrations appear in Figure 2-1.

Because extensive, grid-based analytical data were not available for the pesticide and metal COCs, and because PCBs are the focus of the remedial action, data for these two classes of COCs were averaged arithmetically and without spatial weighting of each discrete, contoured sector of the wetland, using the methodologies outlined in the Draft ERA Report.

Arithmetic mean concentrations also were calculated, without spatial weighting, for the soil/sediment COCs for which risks to the benthic invertebrates were calculated. Because soil/sediment invertebrates do not migrate throughout the wetland, in contrast to wildlife receptors such as the mink and woodcock, it is not ecologically appropriate to calculate a spatially-weighted average COC concentration with which to evaluate exposure risks to these organisms. These arithmetic mean concentrations used to calculate benthic invertebrate risks are presented in Section 6.1.6.

Probablistic Models - For the probablistic models, concentration distributions for each COC were developed using BestFit Software and professional judgment. The

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distribution type (i.e., normal, log-normal, gaussian) of each COC was first determined using a goodness of fit analysis. The identified distribution was then modified to reduce uncertainty in the tails. For example, a dataset identified as lognormal with an average of 17 and a standard deviation of 28 might need to be adjusted to a lognormal distribution with an average of 17 and a standard deviation of 20 to enhance the site-specific accuracy of the Monte Carlo simulation. Without this modification the Monte Carlo analysis would include many scenarios with COC concentrations greater than the maximum concentration actually detected in the wetland. Since the sampling effort at the site has been extensive and it is highly unlikely that the maximum detected Total PCB concentration is exceeded significantly at some unsampled location in the wetland, a modification of the lognormal distribution used in the Monte Carlo analysis was needed to reflect the actual site conditions. The table below presents the lognormal distributions used in the Monte Carlo analysis for the soil/sediment concentrations of each COC.

Chemical of Concern Distribution* PCBs Lognorm (17.68,19)

Total Pesticides Lognorm (1.12,0.65)

Chromium Lognorm (304,85)

Lead Lognorm (825,210)

Note: LogNorm denotes a log normal distribution, wherein the first parameter inside the parenthesis is the average COC concentration and the second is the corresponding standard deviation.

3.2 Contaminant Transport Pathways

No modification.

3.3 Contaminants of Concern

No modification of the COC list for wildlife indicator species was required from that presented for the mink and American woodcock in the Draft ERA Report. These same COCs also were applied in calculating risks to the short-tailed shrew.

However, a separate list of COCs was identified for the invertebrate community presumed to inhabit the soils and sediments of the wetland. This COC list includes all of the COCs identified in the Draft ERA Report for one or more of the wildlife indicator species and pelagic biota inhabiting the surface waters of the wetland. This list includes all detected pesticides, the two metals identified as COCs for the wildlife indicator species (chromium and lead), and other metals identified as surface

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water COCs, including cadmium and mercury. These COCs are included in the risk characterization for benthic invertebrates (Section 6.1.6).

3.4 Conceptual Model for Ecological Exposures

No modification was required of the conceptual site model (CSM) for ecological exposures of either the aquatic biota inhabiting the surface waters of the wetland or the mink and American woodcock.

As discussed below, however, two additional ecological receptors and pertinent soil/sediment COC exposure pathways have been integrated into the CSM of the Problem Formulation and all other elements of this Final ERA.

3.5 Indicator Species Selection

3.5.2 Indicator Communities and Species Selected Supplemental exposure assessment elements added to the CSM for this Final ERA are two additional ecological receptors and associated exposure pathways:

• Sediment-dwelling invertebrates that are exposed chronically to COCs in wetland soils and sediments, through direct sediment contact and ingestion pathways.

• The short-tailed shrew, which is exposed to wetland sediment/soil COCs via the consumption of earthworms or other sediment/soil-dwelling invertebrates.

While the earthworm community of the wetland soils/sediments and the pelagic biota of the wetland's surface waters were included as ecological receptors in the Draft ERA, other species and populations of the invertebrate community inhabiting wetland soils and sediments were not evaluated in the Draft ERA Report. Because they are chronically exposed to COCs throughout their entire life span, invertebrates found in soils of the wetland hummocks and/or in sediments of the wetland hollows and stream channels were evaluated as a new receptor group in this Final ERA.

The short-tailed shrew was added as an ecological indicator species for several reasons. As discussed below, its small foraging range and dietary habits are such that it is a good indicator for population-level exposures to average COC concentrations found throughout the wetland, while also providing a realistic model for exposures of some individual animals to localized or isolated COC "hot spots" in the wetland. The short length of the food chain that connects the shrew to soil/sediment COCs also is very useful in allowing an assessment of such exposure risks with a minimum of uncertainty regarding the degree and efficiency of trophic transfers of COCs. The use of site-specific data collected on earthworm bioaccumulation of COCs from

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wetland soils/sediments further reduces uncertainty in the risk estimates for the shrew, as for the American woodcock, by allowing a site-specific calibration of these food chain transfers of COCs from wetland soils/sediments to the shrew. Another important reason for adding the shrew as an indicator species is its important role as a prey species that contributes to food chain risks to other wildlife species at higher trophic levels, such as the mink and various raptor species likely to occur at the site.

3.5.3 Biological Profiles of Indicator Species - Short-tailed Shrew Short-tailed shrews are small, primarily carnivorous mammals that inhabit most regions of the United States. The northern short-tailed shrew is likely to eat insects, worms, snails, and other invertebrates. Potential prey may also include mice, voles, frogs and other small vertebrates (EPA, 1993). Shrews have a high metabolic rate and may eat their body weight in food each day. Shrews, in turn are prey for owls and other raptors, as well as carnivorous mammals such as fox, mink, and weasels (EPA, 1993). The short-tailed shrew is the largest species of the genus Blarina, weighing up to 22 grams and measuring approximately 8-10 cm with a 2-3 cm tail. Because the short-tailed shrew preys on soil dwelling invertebrates and sometimes on other vertebrates, such as the white-footed mouse (Peromyscus spp.), it is likely to concentrate bioaccumulative chemicals up to ten times more than other genera of small mammals (EPA, 1993). Shrews inhabit round underground nests usually in the top 10 cm. of the soil. Home ranges vary from 0.03 hectares to 0.22 hectares , with a mean home range of 0.39 hectares.

3.5.4 Habitat Suitability for American Woodcock, Mink, and Short-tailed Shrew No modification is needed for the original discussions of habitat suitability for the American woodcock and mink, as presented in the Draft ERA Report.

Based on the original wildlife survey and wildlife habitat evaluation presented in the Draft ERA Report, the O&G wetland and adjacent upland forests provide habitats that are suitable for the short-tailed shrew. As noted above in Section 2.4.2.2, the food and cover resources of the site-affected wetland combine to provide suitable habitat for the short-tailed shrew. Earthworms and other soil insects, which were found to occur at several locations within the wetland, often constitute the bulk of the shrew's normal diet. The presence of other potential prey for the shrew, such as amphibians, also has been recently confirmed for the wetland. The dense, stratified vegetation of the wetland also provides good cover from predators of the shrew, while providing abundant nesting sites among the woody root systems found on the numerous wetland hummocks that are rarely or only intermittently flooded.

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4.0 Exposure Assessment

The exposure assessment presented in the Draft ERA Report was expanded to include chronic exposures of the benthic invertebrate community and the short-tailed shrew to COCs of wetland soils and sediments. Most of the exposure assessment modifications and refinements for the American woodcock and mink were discussed in detail in the October 1996 interim technical memorandum and/or the various WPAs leading to this Final ERA. Key modifications or refinements of these models, together with an explanation of the new, short-tailed shrew exposure model, are presented here.

Input parameters for the food chain models are summarized for all three indicator species in Table 4-1. Bioaccumulation factors (BAFs) used in the exposure assessment for each wildlife indicator species are summarized in Table 4-2.

4.1 Exposure Pathways

4.1.2 Exposure Pathways for Earthworms and Benthic Invertebrates No modification was required of the discussion of the earthworm exposure pathways originally presented for the wetland in Section 4.2.2 of the Draft ERA Report.

However, the earthworm exposures pathways described in the CSM of the Draft ERA Report for the soil/sediment COCs are applicable to all other soil/sedimentdwelling invertebrates found in the hummocks, hollows, and stream channels of the O&G wetland, such as benthic macroinvertebrates and both the larval and adult life stages of insects. Exposure pathways to all of these invertebrates include direct contact with COCs in soils, sediments, and/or interstitial pore water, as well as direct ingestion exposures to COCs in these same media.

4.1.4 Exposure Pathways for the Short-tailed Shrew As with the American woodcock, the key exposure pathway for the short-tailed shrew is the ingestion of earthworms. As for the woodcock, surface water ingestion is not considered as a significant exposure pathway for the shrew. However, the incidental ingestion of soil during feeding on earthworms and other soil invertebrates is a significant exposure pathway because the shrew may consume up to 2 percent of its body weight per day in soil (dry weight). Therefore, ingestion of earthworms and associated wetland soil are the two pathways evaluated in the exposure assessment model for the short-tailed shrew.

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4.2 Exposure Models

4.2.2 Earthworm and Benthic Invertebrate Communities of the Wetland No modification was required for the qualitative earthworm exposure assessment originally presented in Section 4.2.2 of the Draft ERA Report.

However, the exposure assessment of this Final ERA also was expanded to consider chronic exposures of all taxa of soil/sediment-dwelling invertebrates to both the arithmetic average and maximum COC concentrations detected in the soils and sediments of the wetland, using a simple hazard quotient approach.

4.2.3 American Woodcock Minor modifications were made to both the deterministic and probablistic exposure assessments performed for the American woodcock in this Final ERA. The model inputs for the woodcock are summarized in Table 4-1.

Deterministic Exposure Model - The most significant modification made to this exposure assessment was the use of revised concentration terms for Total PCBs and Total Pesticides. A spatially-weighted, average Total PCB concentration was used in this exposure assessment model when calculating risks for the O&G site wetland, whereas the revised Total Pesticide concentrations used for the woodcock exposure assessment did not include a spatially-weighted average calculation. No changes were made in the average or maximum concentrations of chromium or lead from those used in the Draft ERA Report.

Another refinement of the exposure assessment as presented in the Draft ERA Report for the O&G wetland is that the COC concentrations measured in the earthworms and applied to this woodcock model in the Draft ERA Report were not re-used. Rather, the new COC concentration terms for the wetland soils were combined with the site-specific earthworm:soil BAFs, summarized in Table 4-2, to calculate daily exposure doses of these COCs to the woodcock. This refinement was made because the earthworm tissue concentrations of the COCs were based on uptake studies of sediments from only five locations, whereas the expanded analytical database used herein for Total PCBs and Total Pesticides covers a much larger expanse of the wetland for which empirical earthworm body burden data were not collected. The methods used to revise the earthworm BAFs for use in this Final ERA are discussed below in Section 4.4.1 and these BAFs are calculated in Table 4-3.

As done originally in the Draft ERA Report, average and maximum detected COC concentrations in both the O&G and reference wetland soils were used to calculate daily COC doses received by the woodcock from incidental soil ingestion.

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Use of Earthworm Tissue Data for the Reference Wetland. Because only one soil location was sampled in the reference area wetland, average soil COC concentrations could not be calculated (see Table 4-3). However, three samples of earthworm tissues from the earthworm uptake study were analyzed for PCBs and pesticides after the 28 day exposure of the worms to three replicates of the single, bulk soil sample collected. As also done in the Draft ERA Report, average concentrations of Total PCBs and Total Pesticide were calculated for three of the earthworm tissue replicates and used in the deterministic exposure assessment for reference wetland, to calculate a daily PCB and pesticide exposure dose to the woodcock. This was done rather than using a combination of these organic COC concentrations for only one soil sample and the earthworm:soil BAFs for these COCs to reconstruct a daily dose for Total PCBs and Total Pesticides. A fourth earthworm replicate sample was analyzed for metals after completion of the COC uptake study, so that the chromium and lead risks to the woodcock were calculated on the basis of this single earthworm tissue sample.

Probablistic Exposure Model - The existing probablistic model for the American woodcock was expanded to account for the known biological variability associated with several additional dietary exposure parameters (see Table 4-1). These parameter values are as follows:

• COC Concentration Terms: Site-specific calculations • Body Weight: Triang (0.127, 0.15, 0.216 kg) • Food Ingestion Rate: Triang (0.0139, 0.0126, 0.308 kg/day) • Soil Ingestion Rate: Triang (0.00033, 0.003, 0.0073 kg/day)

The triangular distributions ("Triang") shown in parentheses represent the minimum, most likely, and maximum exposure parameter values selected for the woodcock, in consultation with SEAT, based on published data on woodcock biology and ecology.

The derivation of the soil/sediment COC concentration terms used in the woodcock exposure assessment is explained above in Section 3.1. The woodcock body weight and food/soil ingestion rates used as inputs to this model were derived from the Wildlife Exposure Factors Handbook published by EPA (1993). As was also done for the deterministic exposure models for the O&G wetland, a combination of the empirical data on the soil/sediment COC concentrations of the wetland and the site-specific, earthworm:soil BAFs for each COC was used in the Monte Carlo simulations, rather than using the earthworm tissue concentrations measured in the replicates of the earthworm samples that had been exposed to a subset of only five wetland soil samples during the 28 day uptake study.

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4.2.4 Mink Similar types of modifications were made to both the deterministic and probablistic exposure assessments performed for the mink in this Final ERA.

Deterministic Exposure Model - As for the American woodcock, a key modification made in the mink exposure assessment was the use of revised concentration terms for both Total PCBs and Total Pesticides. A spatially-weighted average Total PCB concentration was applied to this model, whereas the revised Total Pesticide concentrations used for the mink exposure assessment did not include a spatially-weighted average calculation. No changes were made in the average or maximum concentrations of chromium or lead from those used in the Draft ERA Report.

Another refinement made since the Draft ERA Report is in the calculation of the frog:sediment BAFs for pesticides that were used in the mink model for this Final ERA. The methods used to revise these BAFs for use in this Final ERA are discussed below in Section 4.4.2 and the new frog BAFs are presented in Table 4-2.

Probablistic Exposure Model - The existing probablistic model for the mink was also expanded to account for the variability in body weight and food ingestion rates that are associated with differences in the age, gender, and seasonal foraging behaviors reported in the literature for individual animals throughout the natural range of mink in North America (see Table 4-1). These parameter values are as follows:

• COC Concentration Terms: Site-specific calculations • Body Weight: Triang (0.974, 1, 1.734 kg) • Food Ingestion Rate: Triang (0.116, 0.15, 0.381 kg/day)

The triangular distributions ("Triang") shown in parentheses represent the minimum, most likely, and maximum exposure parameter values selected for the mink, in consultation with SEAT, based on published data on mink biology and ecology.

The derivation of the soil/sediment COC concentration terms used in the mink exposure assessment was explained above in Section 3.1. The mink body weight and food ingestion rates used as inputs to this model were derived from the Wildlife Exposure Factors Handbook published by EPA (1993).

4.2.5 Short-tailed Shrew The conceptual, dietary exposure model for the short-tailed shrew is identical to the model used for the woodcock in that it calculates estimated doses of contaminants, based exclusively on the ingestion of earthworms and associated soil, by assuming that ingestion of COCs in water and dermal contact with COCs in soil and water are

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less significant than ingestion of COC-contaminated food and soil. While shrews do consume water to compensate for their high evaporative water-loss rate, for this model the shrew is assumed to obtain its daily water requirement entirely from the consumption of earthworms.

The exposure model calculates daily dietary doses of each COC for the shrew, using the input parameters summarized in Table 4-1. Site-specific earthworm:soil BAFs used in the model were calculated for the O&G wetland using the average COC concentrations measured in the soils collected from the site-affected and reference area wetlands and in the earthworms exposed to these soils during the laboratory-based uptake study (see Table 4-3). For the site-affected, O&G wetland, these measured soil COC concentrations were combined with the site-specific earthworm BAFs calculated for each COC and the actual soil COC concentrations of the wetland to calculate daily COC doses, using information on the shrew's body weight and its ingestion rates for contaminated earthworms.

The average and maximum detected COC concentrations detected in both the O&G and reference wetland soils also were used to calculate daily COC doses received by the short-tailed shrew from incidental soil ingestion.

Use of Earthworm Tissue Data for the Reference Wetland. Because only one soil location was sampled in the reference area wetland, average soil COC concentrations could not be calculated (see Table 4-3). However, three earthworm tissue replicate samples from the earthworm uptake study were analyzed for PCBs and pesticides after the 28 day exposure of the worms to three replicates of the single, bulk soil sample collected (Table 4-3). Therefore, average concentrations of Total PCBs and Total Pesticide were calculated for three of the earthworm tissue replicates and used in the deterministic exposure assessment for the reference wetland, to calculate a daily PCB and pesticide exposure dose to the short-tailed shrew. This was done rather than using a combination of these organic COC concentrations for only one soil sample and the earth worm: soil BAFs for these COCs to reconstruct a daily dose for Total PCBs and Total Pesticides. A fourth earthworm replicate sample was analyzed for metals after completion of the COC uptake study, so that the chromium and lead risks to the shrew were calculated on the basis of this single earthworm tissue sample (Table 4-3).

Short-tailed Shrew Diet. The short-tailed shrew's diet reportedly consists of earthworms, slugs, snails and other insects as well as a small amount of vegetation, and occasionally small vertebrates such as amphibians (EPA, 1993). For simplicity, the model used here conservatively assumes that the shrew's diet consists exclusively of earthworms. Wildlife biologists report that the short-tailed shrew can consume its body weight, approximately 15 grams, per day in earthworms (EPA, 1993). The

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model assumes both this body weight and feeding rate in calculating the daily contaminant doses in units of milligrams of COC per kilogram of shrew body weight per day (mg/kgBW/day).

Incidental Ingestion of Soil. There is no consensus in the literature concerning the amount of soil which may be incidentally ingested by birds and mammals. Beyer et. al. (1992) examined the stomach contents of the meadow vole, a carnivorous small mammal species with foraging habits similar to the shrew, and found the amount of soil consumed on a dry weight basis to be approximately 2 percent of the dry weight of earthworms consumed. To estimate the incidental soil ingestion rate we converted the ingestion rate of earthworms in wet weight, 11.9 grams/day, to dry weight, by applying a factor of 0.2 to account for the water content in earthworms, and then multiplied by 2 percent to derive an estimated soil ingestion rate of 0.05 grams/day. The conversion factor of 0.2 is derived from the 80 percent moisture content reported for the earthworm Lumbricus terrestris (Stafford et al., 1988). This soil ingestion exposure parameter is based on the conservative assumption that all soil-bound contaminants are bioavailable.

Ingestion of Water. Ingestion of COCs in surface water was not evaluated in the exposure model for the shrew. Shrews are reported to require approximately 0.223 gram of water per gram body weight per day or 3.3 grams of water per day (EPA, 1993). Since the shrew consumes approximately 12 grams of earthworms per day and earthworms commonly consist of about 80 percent water (Stafford et al., 1988), the shrew would obtain approximately 9.6 grams of water per day. Since this daily intake of water from earthworm tissues exceeds the shrew's daily water requirement, the shrew probably ingests little or no surface water from hollows or streams in the wetland, so ingestion of surface water is an insignificant COC exposure pathway.

Mathematical Model. The formula and parameters used for the short-tailed shrew exposure assessment model are:

r. / /^ ,j ^ [(CSxIS) + (CFxIF)] x PF Dose (rngfKg/day) = ̂ '- ^— ^ BW

where: Dose = Shrew ingestion dose (mg/Kg body weight/day, wet weight)

CS = exposure concentration of compound i in soil (mg/Kg, dry weight).

CF = measured exposure concentration of compound i in earthworms exposed in the laboratory to site-affected wetland soils (mg/Kg, wet weight)

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IS = ingestion rate of soil (Kg soil/day, dry weight) = 0.00005 Kg/day

EF = ingestion rate of food (earthworms) (Kg earthworm/day, wet weight)

= 0.0119 Kg/day

PF = percentage of time spent foraging in the site-affected wetland. Since the area of the site-affected wetland is greater than the foraging area of the Shrew, 0.5 acres, this value may range from (0 to 100 percent).

BW = Shrew body weight (Kg) = 0.015 Kg

An overview of the exposure scenarios evaluated for the Short-tailed Shrew, as well as the parameters for each scenario, is presented in Table 4-1 and explained below in Section 4.3.3.

4.3 Exposure Scenarios

4.3.2 Earthworm and Benthic Invertebrate Communities of the Wetland No modification was required for the qualitative earthworm exposure assessment as originally discussed in Section 4.2.2 of the Draft ERA Report.

The same chronic exposure scenario assessed for the earthworm community in the Draft ERA Report also was evaluated for the remainder of the soil/sedimentinhabiting invertebrate biota of the wetland in this Final ERA. Although wetland hummocks are likely to be inundated less frequently than are the hollows and stream channels, the perennially moist or saturated condition of the hummock soils are assumed to support an invertebrate community, at least throughout the growing season when the soils/sediments and associated surface waters are not frozen. It is assumed that the invertebrate community of the wetland hummocks, hollows, and stream channels is chronically exposed to the arithmetic average and maximum COC concentrations detected in these soils and sediments during the spring, summer, and autumn growing seasons, as well as during any mild, warmer periods of the winter when the wetland surface is not frozen. Chronic exposures of the entire invertebrate community to the arithmetic average COC concentrations found throughout the wetland and exposures of at least some individual organisms to the maximum detected COC concentrations are considered realistic because many of these invertebrates are immobile and spend their entire lifetimes at a single location. Although exposures of winged insect species to soil/sediment COCs in the wetland

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may be more significant during their larval, soil/sediment-dwelling life stages than during their more mobile, adult stages, chronic exposures are likely to be significant even for these species.

4.3.3 Short-tailed Shrew One deterministic exposure scenario was evaluated for short-tailed shrew exposure for both the site-affected and reference wetland. Exposure parameters for this scenario are summarized in Table 4-1 and discussed below.

Exposure Assumptions and Parameters. Since the short-tailed shrew prefers to forage in moist soils and wetland habitats, including ecotonal zones between different cover types, it is likely that there are shrews that feed both in clean, local terrestrial and wetland habitats, and in contaminated areas of the site-affected wetland. However, because of the shrew's small reported foraging range of 0.5 acres it is also conceivable that a shrew subpopulation resides within the wetland that feeds exclusively in the contaminated areas of the wetland. Thus, this model conservatively assumes 100 percent feeding by the short-tailed shrew in the contaminated wetland.

Exposure Scenarios. Shrew exposures are assessed for single-zone foraging scenarios in the reference area and site-affected wetlands. Based on its foraging range and the local habitat diversity, a single shrew or an entire population could conceivably forage:

• Entirely within a single zone such as the 100-acre site-affected wetland or within one of the smaller subareas of the site-affected wetland where chemical concentrations are elevated.

• Entirely outside of this contaminated wetland area, in clean upland/wetland areas

• In various combinations of clean and contaminated upland and wetland habitats

For this ERA we have modeled the 100 percent wetland foraging scenario. Risks for additional foraging scenarios can be estimated by multiplying the appropriate hazard quotient or indices by the desired factor. For example, to estimate the total hazard index for a short-tailed shrew that forages 40 percent of the time in the site-affected wetland and the remainder of the time in clean habitat, multiply the total hazard index presented for the site-affected wetland by a factor of 0.4.

Unlike the American woodcock and mink, the smaller foraging range of the shrew (0.5 acres), increases the likelihood that at least some shrews will feed exclusively in the most contaminated areas. This worst-case, single-zone wetland exposure scenario,

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thus, presumes that at least some individual shrews forage at the most contaminated locations in the site-affected wetland. However, the worst-case exposure scenario evaluated for the maximum Total PCB concentration detected in the site-affected wetland sediments is presumed not to be realistic even for a few individuals of the resident shrew population, since the maximum Total PCB concentration (300 mg/kg) was detected in a sample from the bottom of a perennially flooded drainage ditch (SD-07) in which the shrew (or woodcock) probably cannot forage for invertebrates. However, since the soil sample with the second highest Total PCB concentration (289 mg/kg) was found in an unflooded reach of the wetland in which the shrews (and woodcock) could easily forage (SD-E1), chronic exposures of shrews (and woodcock) to one or more "hot spots" where COC concentrations approach these COC maxima might actually occur for some individuals of the local population.

4.4 Bioaccumulation Factors

4.4.1 Soil-to-Earthworm Bioaccumulation Factors For those COCs that were positively detected in worms and in at least one of the paired, pre-/post-uptake sediment samples, the BAFs are based on the mean COC concentrations in the pre-uptake, site-derived wetland soil samples. The data for the post-uptake sediment samples was used to calculate these BAFs only when analytical data for the pre-uptake samples were non-detects or had been rejected by data validators. A single earthworm BAF was developed for all pesticides (i.e., a total pesticide BAF) and for all Aroclors (i.e., a BAF for Total PCBs) and used in the shrew and woodcock models. These recalculated BAFs are presented in Table 4-3.

4.4.2 Bioaccumulation Factors for the Mink Model In the Draft ERA Report, we conservatively applied the highest of the reported sediment to frog pesticide BAFs in the mink exposure model (i.e., a BAF of 22). Because of the sensitivity of the mink model to this exposure parameter an additional literature search was conducted. Based on a reinspection of the frog BAF data presented by Niethammer et al. (1984) and Meeks el al. (1968), it was decided to average all of the frogrsediment BAFs for pesticides reported in these two studies, to develop a new frog:sediment pesticide BAF that was then used in the mink exposure model of this Final ERA. As noted above, the BAF of 22 was the maximum of 11 frog:sediment pesticide BAFs reported by Niethammer et al., whereas the lowest of Niethammer's BAFs was 0.38 and the average was 3.6 (see Table 4-3). In an earlier study cited by Niethammer et al., Meeks (1968) had reported frog:sediment pesticide BAFs ranging from 0.3 to 6.5 with an average BAF of 2.7. The sediment to frog pesticide BAF for this Final ERA technical memorandum, therefore, was adjusted to a value of 3.2, which is the arithmetic average of all of the frog:sediment pesticide BAFs reported in these two studies. The new frog:sediment pesticide BAF and all other COC-specific, prey:sediment BAFs used in the exposure models of the Draft ERA Report were retained in this Final ERA and appear in Table 4-2.

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5.0 Toxicity Assessment

The only significant modifications made to the toxicity assessment originally presented in the Draft ERA Report are the addition of sediment benchmark criteria and the consideration and/or application of additional toxicity reference values (TRVs) for the mink, American woodcock, and/or short-tailed shrew. The TRVs used in this Final ERA are discussed below and summarized in Table 5-1.

5.1 Ecotoxicological Data Sources

No modification is needed for the explanation of the ecotoxicological data resources as presented originally in the Draft ERA Report because all of the candidate TRVs from these sources were retained for consideration and/or use in the revised toxicity assessment for this Final ERA. In addition to those ecotoxicity data sources previously described in the Draft ERA, supplemental data sources were consulted for use in this revised toxicity assessment. Key new data sources consulted were:

• The lowest effects level (LEL) sediment benchmark criteria published by the Ontario Ministry of the Environment (MOE; Persaud et al., 1992, 1994)

• TRVs reported for avian and mammalian test species and/or extrapolated to the indicator wildlife species evaluated in this ERA, by Opresko et al. (1994)

5.2 Summary of Effects Measurement Endpoints Considered

No modifications are needed for the original text of Section 5.2 in the Draft ERA Report, since no changes were made in the range of effects measurement endpoints considered for the pelagic community, earthworm community, American woodcock or mink. However, a similar range of ecotoxicity benchmark criteria and/or wildlife toxicity effects measurement endpoints was considered for the benthic invertebrate community and short-tailed shrew population, after they were added as ecological receptors in this Final ERA.

Use of the MOE LELs to assess benthic invertebrate risks was prescribed by EPA and SEAT. The TRVs considered for the American woodcock, mink, and short-tailed shrew were chosen jointly by Arthur D. Little and the SEAT representatives. All of the revised and/or newly identified TRVs that were considered or used for the three wildlife indicator species in this Final ERA were compiled in the October 1996 interim technical memorandum. Several candidate TRVs were subsequently revised as requested by SEAT and used in the preliminary risk calculations presented for SEAT'S review on May 12, 1997. A complete listing of all of the candidate TRVs that were considered as effects measurement endpoints for the three indicator species appears in Table 5-2.

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5.3 Quantitative Dose-Response Data Used in Toxicity Assessment

As discussed below, the toxicity assessment from the Draft ERA Report was revised, as needed, both to incorporate a new toxicity assessment for the benthic invertebrate community and short-tailed shrew population of the wetland, and to refine the TRVs originally used for the American woodcock and mink in the Draft ERA Report. The toxicity assessment for the pelagic community of the wetland required no revisions.

5.3.2 Earthworm and Benthic Invertebrate Communities of the Wetland No modifications were needed of the toxicity assessment for the earthworm community of the wetland as presented in Section 5.3.2. of the Draft ERA Report.

The chronic toxicity assessment performed in this Final ERA for the benthic invertebrate community presumed to inhabit the hummocks, hollows, and stream channels of the wetland is based on the MOE LELs, which appear in the benthic community risk calculations of Section 6.1.2. A combination of the 1992 and 1994 LELs was used because only the 1992 benchmarks include Aroclor-specific LELs, whereas the 1994 revision of these criteria includes a single LEL for Total PCBs. Since the Aroclor composition of the Total PCBs found in the wetland sediments varies significantly from location to location, a combination of Aroclor-specific and Total PCB LELs was used in this toxicity assessment to clarify the full potential range of PCB risks to benthic organisms.

5.3.3 American Woodcock, Mink, and Short-tailed Shrew Several modifications were made in the TRVs used for the American woodcock and mink from those originally presented in Section 5.3.3 of the Draft ERA Report. All of the revised and new TRVs used in this Final ERA for the woodcock, mink, and short-tailed shrew are presented in Table 5-1.

Endpoints Considered. TRVs used in the Draft ERA Report were reviewed in consultation with SEAT and additional literature research was performed to identify and/or derive supplemental TRVs for the mink, American woodcock, and short-tailed shrew to be used in the Final ERA for selected COC/species pairings. The TRVs summarized in Table 5-2 were considered because they include a variety of acute and chronic, effects measurement endpoints for numerous test species and, in some cases, for the ecological indicator species being evaluated in this ERA (e.g., PCB TRVs for mink and heptachlor TRVs for the American woodcock).

Selection Procedure. The comprehensive TRV compilation in Table 5-2 illustrates the step-wise derivation of all TRVs considered. This TRV derivation table includes the original test species, TRV reported for that species, the toxicity effects measurement endpoint, and the extrapolation factors that we applied to derive a corresponding TRV for each of the ERA indicator species. TRVs reported for acute exposures to COCs, such as lethal concentrations for 50 percent of a test population (LC50), first were converted to a lowest observed adverse effects level (LOAEL) for

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the test species by dividing the LC50 by ten (10). Whether published or extrapolated, the test species LOAELs were then divided by a factor of five (5) to convert them to a no observed adverse effects level (NOAEL) for the same species. To extrapolate from the test species to the indicator species, the test species NOAEL was then divided by a factor of ten (10) to derive a NOAEL for the indicator species.

Endpoints Selected. Species-specific TRVs are used in this Final ERA whenever available for an ecological indicator species (see Tables 5-1 and 5-2). The lowest applicable TRV was used in both the deterministic and probablistic exposure models, unless the associated effects endpoint was a biochemical alteration ("biomarker") for which no corresponding, adverse anatomical, behavioral, or reproductive effect was observed in the test species. After reaching consensus with SEAT as to the final TRV selection for each COC/species pairing, the candidate TRVs shown in boldfaced type in Table 5-2 were used in preliminary risk calculations that were submitted to SEAT on May 12, 1997. The only modifications made to a few of these TRVs following the May 12th submittal were some minor corrections to the derivation of the lead TRV for the mink and shrew, which were derived from a NOAEL for the rat cited in Opresko et al. (1994) as having been published by Azar et al. (1973). These pre-approved TRVs were used as inputs both to the deterministic exposure assessment models and to the probablistic, Monte Carlo simulations to produce the final wetland risk calculations for the American woodcock, mink, and short-tailed shrew presented below.

6.0 Risk Characterization and Computation of Cleanup Goals

The revised risk calculations for the American woodcock and mink, as well as the new risk calculations for the benthic invertebrate community and short-tailed shrew, are presented in the following discussions of Section 6.1.

It was decided by EPA and SEAT to defer the recalculation of wetland soil/sediment cleanup goals for Total PCBs, Total Pesticides, chromium, and lead until after the exposure assessment models for each of the three indicator species are finalized in the Final ERA Technical Memorandum. The results and discussions originally presented in Section 6.2 of the Draft ERA Report have not yet been revised.

6.1 Ecological Risk Characterization

None of the ecological risk calculations were revised for the pelagic community of the wetland from those presented for the surface water COCs in Section 6.1. of the Draft ERA Report.

A summary of the average and maximum, deterministic and/or probablistic, hazard indices (His) for chronic exposures of the benthic invertebrates, American

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woodcock, mink, and short-tailed shrew to each chemical class of wetland soil/sediment COCs is presented below in Table 6-1. These average and maximum, COC class-level His are derived from the COC-specific hazard quotients(HQs) for these same receptors that are discussed in the following sections and presented in Tables 6-2 through 6-19.

6.1.2 Earthworm and Benthic Invertebrate Communities of the Wetland No modification was required for the earthworm exposure assessment originally presented in Section 6.2.1 of the Draft ERA Report.

6.1.2.1 Site-affected Wetland. The arithmetic average and maximum, chronic exposure risks to benthic invertebrates of the wetland are summarized below in Table 6-2. As noted previously, spatially-weighted average concentrations of Total PCBs were not used to estimate risks to the benthic invertebrate community because most of these organisms are immobile and therefore do not integrate exposures across sectors of the wetland with significantly different PCB concentrations. Rather, they are chronically exposed to PCBs and other soil/sediment COCs at one location during most (e.g., insect larvae) or all (e.g., benthic macroinvertebrates) of their life span.

Ecological risks to the benthic invertebrate community of the O&G wetland are high to very high for the average (HI=603) and maximum (HI=8,716) concentrations of COCs detected in the wetland (see Tables 6-1 and 6-2). PCBs and pesticides account for over 80 percent of the total average and maximum risk to benthic invertebrates, with the remainder of the risk being driven by nine different metals (Table 6-2).

When calculated using the LEL for Total PCBs, the average risk from Total Pesticides (ffl=279) exceeds that for Total PCBs (ffl=210; Table 6-2). However, the Total PCB risks actually may be more significant than the combined risks from the 16 pesticides and 9 metals for which LELs are available, due to the very low LELs for two of the Aroclors detected in the wetland. When calculated using the LEL of 0.07 mg/kg for Total PCBs (Persaud et al., 1994), the combined risks from all five Aroclors is more than five times lower than when the Aroclor-specific LELs (Persaud et al., 1992) are used to calculate both the average and maximum, Total PCB risks for the wetland sediments (see Table 6-2).

Total PCB risk may be underestimated for Aroclor mixtures at some of the wetland sample locations, when calculated using the LEL for Total PCBs, because:

• LELs for Aroclor 1016 (LEL=0.007 mg/kg) and Aroclor 1260 (LEL=0.005 mg/kg) are up to an order of magnitude lower than LELs for the other Aroclors

• The Aroclor mixtures vary significantly among these samples/locations, and

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• Aroclor 1260 was detected in more than 100 samples.

For example, the average risk for Total PCBs is an LEL-based HQ of 210 for Total PCBs, whereas use the Aroclor-specific LELs yields average Aroclor-specific risks ranging from a low of HQ=30.7 (Aroclor 1242) to a high for of HQ=844 (Aroclor 1260) and a subtotal average risk for all five Aroclors of HI= 1,134 (Table 6-2).

Based on a comparison to the reference wetland risks presented below for the same COCs and COC classes, these site-derived benthic invertebrate risks in the O&G wetland are significantly elevated above background risk levels for wooded swamps.

6.1.2.2 Reference Wetland. Site risks to benthic invertebrates in the wetland are low for a few individual COCs that occur at trace levels, such as 4,4'-DDE (HQ=3.6), Total PCBs (HQ=1), mercury (HQ=3), lead (HQ=1.8) and copper (HQ=1.1). All of these and the other trace levels of COCs combine to represent a total, aggregate site HI of 11.7 (see Table 6-2).

6.1.3 American Woodcock A comparison is presented here of the site-related versus reference area dietary risks to the American woodcock, for a range of deterministic and probablistic foraging scenarios, based on the exposure input parameters and risk calculation formula summarized in Table 6-3. These deterministic and/or probablistic risk estimates are presented in Tables 6-4 through 6-8. The probablistic, on-site risks to the woodcock, based on the Monte Carlo simulation for the O&G wetland, also are illustrated in Figure 6-1.

It should be noted that the Monte Carlo simulations for the background exposures to the reference wetland and Great Pond have not been revised from those originally presented in the Draft ERA Report, because the background risks to the woodcock were very low or non-existent for all COCs and exposure scenarios evaluated in the Draft ERA Report, using both the deterministic models and probablistic, Monte Carlo exposure assessment simulations. The various refinements of the deterministic and probablistic models presented in the Draft ERA Report that are made herein for all of the O&G site-affected wetland exposure scenarios, thus, can reliably be compared with the background risk estimates in either the Draft ERA or this Final ERA. This comparison serves to evaluate the significance of site-derived risk increments to the woodcock for the full range of single-zone and multi-zone foraging considered.

6.1.3.1 Site-affected Wetland Scenarios for the American Woodcock. All foraging scenarios in which the woodcock feeds in the site-affected wetland to some degree result in significant ecological risks from one or more site-derived COCs. These risks are summarized below for each scenario and quantified in Tables 6-4 through 6-6.

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Single-zone Foraging: 100 Percent Site-Affected Wetland. Aggregate, potential dietary exposure risks to the American woodcock from a worst-case scenario of 100 percent foraging within the site-affected wetland are high for both the average (HI= 1,265) and maximum detected (HI=4,636 ) COC concentrations (see Table 6-4). These average risks to the woodcock are driven primarily by the COC-specific risks for lead (HQ=806) and chromium (HQ=454). Although, the maximum theoretical risks from lead (HQ=2,412) and chromium (HQ=1,598) are more than three times higher than these average risks, they probably overestimate the worst-case risks from these metals to the woodcock, since none of these individual birds would selectively forage only at the locations with the maximum detected lead and chromium concentrations.

Average risks from the unweighted average concentrations of Total Pesticides are low (HI=1.8) while the moderate, maximum Total Pesticide risk (HQ= 26.4) is not realistic for the woodcock, as noted above for the other COCs, due to its 5.5 acre foraging range. A more realistic, maximum exposure scenario for at least some individual birds that might forage exclusively within the site-affected wetland would fall somewhere between these average and maximum risk estimates, with most of the woodcock risk attributed to chromium and lead.

Although PCB risks to the woodcock also are low (HQ=3) when calculated using the spatially-weighted average concentration of Total PCBs calculated for the entire wetland (1.48 mg/kg), they would be about ten times higher if calculated using the simple, unweighted arithmetic average Total PCB concentration of 14.7 mg/kg. As noted for the other COC classes, because the woodcock typically forages over an area of 5.5 acres, it would not be chronically exposed to the maximum Total PCB concentration (300 mg/kg), so that the maximum Total PCB risk (HQ=600) is not realistic even for some individual birds. However, an estimated 14.5 acres of the wetland have Total PCB concentrations that range between 1 and 300 mg/kg and Total PCB concentrations as high as 289 mg/kg do occur in unflooded niches of the wetland (e.g., SD-E1). Therefore, it is possible that the use of the spatially-weighted, average Total PCB concentration for the wetland yields an average risk quotient that is underestimated for any individual birds of the local woodcock population that may forage preferentially within these more contaminated, "hot spot" areas of the wetland.

Multi-zone Foraging: 35 Percent Site-affected Wetland. To account for the suboptimal American woodcock habitat found in the permanently flooded niches of the O&G wetland (e.g., stream channels) and the availability of more suitable, upland and wetland habitat found nearby (see Section 2.4.2.2), it was assumed that a more likely percentage of foraging by woodcock in the site-affected wetland is 35 percent.

The aggregate, potential risks to the woodcock from an exposure scenario of 35 percent foraging in the contaminated reaches of the site-affected wetland are high for

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both the average (HI=443) and maximum (HI= 1,623) COC concentrations, with most of the average risk being driven by the maximum concentrations of lead (HQ=844) and chromium (HQ=559; see Table 6-5). As noted above, however, the average Total PCB risk to at least those birds foraging in hot spots of the wetland could be slightly higher than that estimated using the spatially-weighted average Total PCB concentration for the wetland, while a more realistic, reasonable maximum risk might occur from exposure to chromium, lead, and Total Pesticides concentrations that fall somewhere between the arithmetic mean and maximum detected concentrations.

Monte Carlo Analysis: Site-affected Wetland. A Monte Carlo analysis was conducted for the risk characterization to derive a probability distribution of potential risks that accounts for both the natural variability in foraging, body weight, and food and incidental soil ingestion rates reported in the literature for the woodcock, and for the range and spatial variability of COC concentrations detected in the O&G wetland. To obtain this probability distribution of risks the percentage of woodcock foraging in the site-affected wetland was varied from 5 to 100 percent, based on a triangular distribution defined by a minimum of 5 percent, a most likely value of 35 percent, and a maximum value of 100 percent. The body weight and incidental soil ingestion rates of the woodcock were similarly defined. Triangular distributions are often used in Monte Carlo analysis when data on the site-specific foraging behavior of an indicator species, needed to document the actual distribution, are absent. Wetland soil/sediment COC concentration distributions were derived from the empirical dataset for the O&G wetland rather than using fixed, average COC concentrations, as was done for the deterministic exposure assessment models (see Section 3.1).

From the defined foraging distribution for contaminated versus clean habitats, random numbers were selected for 10,000 iterations to generate the risk distribution. The statistical results of this analysis are presented in Table 6-6 and a graph of the cumulative distribution of potential risks is presented in Figure 6-1. In this graph, each intercept point on the curve represents the probability (i.e., percentage of Monte Carlo iterations on the y-axis) that the total site risk to the woodcock will equal or exceed the HI value shown at the corresponding intercept point on the x-axis.

The potential aggregate risks (His) calculated in the Monte Carlo simulations for the woodcock ranged from a low HI of 36 to a maximum HI of 4.095, with a median HI of 705 (i.e., a 50 percent probability of a HI>705). Note that the maximum site risk estimated for a deterministic foraging scenario of 100 percent site-affected wetland (HI=4,636), is slightly higher than the maximum risk predicted by the Monte Carlo analysis. This resulted because a combination of the maximum possible, site-affected wetland foraging percentage with the maximum chemical concentrations was not generated by the Monte Carlo simulation during random number generation. As shown in the summary of class-level His for the woodcock presented in Table 6-6, the 10,000 Monte Carlo iterations (i.e., exposure scenarios)

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also indicate that there is a 90 percent probability that the average total site risk to the American woodcock will equal or exceed a HI of 259, whereas there is only a 10 percent chance that the average total site risk will equal or exceed a HI of 1,268 (see Figure 6-1).

Comparison of Deterministic versus Monte Carlo Results. The Monte Carlo exposure analysis indicates that there is about a 65 percent probability that the average, probablistic total site risk to the woodcock will equal or exceed the average, total HI (HI=443) that was estimated separately for a deterministic scenario in which these birds forage in the contaminated O&G wetland only 35 percent of the time (Figure 6-1). In contrast, the Monte Carlo analysis indicates that there is only a 10 percent probability that the total site HI for the woodcock would exceed a HI of 1,268 and thus also exceed the worst-case, deterministic scenario in which the woodcock forages entirely within the contaminated wetland (i.e., average HI=1,265; see Table 6-6). Based on these results, therefore, this worst-case scenario of 100 percent foraging by the American woodcock in the O&G wetland is probably unrealistic. This worst-case foraging scenario is unrealistic even for the average COC concentrations found throughout the wetland. Because the American woodcock is a migratory species, it would presumably be exposed to COCs in the O&G wetland only during the spring, summer, and autumn seasons when the birds would reside on-site or in adjacent, upland and wetland habitats abutting the contaminated wetland.

6.1.3.2 Reference Area Wetland Scenarios for the American Woodcock. As noted above, only the deterministic exposure assessments for the American woodcock were revised in this Final ERA, whereas the Monte Carlo simulations performed in the Draft ERA were not modified. Because several of the American woodcock TRVs were revised in this Final ERA from those used in the Draft ERA Report, the most reliable comparisons of woodcock risks in the O&G versus reference wetlands are those based on the deterministic models presented in this Final ERA.

All of the American woodcock foraging scenarios evaluated in both the deterministic exposure assessments of this Final ERA and in the Monte Carlo simulation as originally presented in the Draft ERA Report, in which these birds feed to some degree in the reference area wetland, resulted in no PCB or pesticide risks, and low to moderate risks from chromium and lead. These risks are summarized below for each of the deterministic and probablistic (Monte Carlo) exposure scenarios.

Single-zone Foraging: Reference Area Wetland. The aggregate, potential dietary exposure risks to the American woodcock from a scenario of 100 percent foraging in the reference wetland are moderate (HI=87). The soil/sediment COCs driving all of the risks for the woodcock in this reference wetland are lead (HQ=64) and chromium (HQ=23; Table 6-7). Total PCB and Total Pesticide risks to the woodcock foraging entirely within the reference wetland are far below one (see Table 6-7).

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As noted above in the exposure assessment of Section 4.2.3, average risks could be calculated in the reference wetland only for Total PCBs and Total Pesticides, while the chromium and lead risks are based on a single replicate of earthworm tissue.

Multi-zone Foraging: Reference Area Wetland. The aggregate, potential dietary exposure risks to the American woodcock from a scenario of 35 percent foraging within the reference wetland remain moderate (HI=30). The soil COCs driving risks for the woodcock in this zone again are lead (HQ=22) and chromium (HQ=8). PCB and pesticide risks are far below one (see Table 6-8).

Monte Carlo Analysis: Reference Area Wetland. None of the Monte Carlo simulations presented for the American woodcock in the Draft ERA Report were revised during the preparation of this Final ERA Technical Memorandum. The probablistic, reference habitat risk to the woodcock presented in the Draft ERA Report was low to moderate, since its His ranged from a low of 3 to a high of 61 with a mean of 29; these risks were driven entirely by chromium and lead, with no background risk from PCBs or pesticides. Since the probablistic model inputs and TRVs have been revised from those used in the 1994 Draft ERA Report, the original Monte Carlo risk estimates for the reference wetland are no longer entirely comparable to those presented above for the O&G site wetland.

6.1.4 Mink A comparison is presented here of the site-related versus reference area dietary risks to the mink, for a range of deterministic and/or probablistic foraging scenarios based on the exposure input parameters and risk calculation formula shown in Table 6-9. These risk estimates are presented in Tables 6-10 through 6-16. The probablistic, on-site risks to the mink estimated with the Monte Carlo simulation for the O&G wetland also are illustrated graphically in Figure 6-2.

It should be noted that the Monte Carlo simulations for the background exposures to the reference wetland and Great Pond have not been revised from those originally presented in the Draft ERA Report, because the background risks to the mink were very low or non-existent for all COCs and exposure scenarios evaluated in the Draft ERA Report, using both the deterministic models and probablistic, Monte Carlo exposure assessment simulations. The various refinements of the deterministic and probablistic models presented in the Draft ERA Report that are made herein for all of the O&G site-affected wetland exposure scenarios, thus, can reliably be compared with the background risk estimates in either the Draft ERA or this Final ERA, in order to infer and evaluate the significance of the site-derived increments of risks to the mink for the full range of single-zone and multi-zone foraging by the mink.

6.1.4.1 Site-affected Wetland and/or Country Pond Scenarios for Mink. All foraging scenarios evaluated for mink that feed to some degree in the site-affected wetland result in low to moderate, average ecological risks that exceed background risks by at least one order of magnitude (see Table 6-1). Average risks to the mink

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based on most deterministic and probablistic wetland foraging scenarios are greater for metals than for either PCBs or pesticides. Risks to the mink from consuming a pure fish diet from Country Pond, however, are comparable to those for a diet consisting entirely of fish from Great Pond. These risks to the mink are summarized below and presented in Tables 6-10 through 6-13, for each of the deterministic and probablistic exposure scena

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