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PREPARED FOR
U.S. ENVIRONMENTAL PROTECTION AGENCY
REGION I, BOSTON, MASSACHUSETTS
EPA Contract No. 68-W9-0036EPA Work Assignment No. 21-1PB8
EPA Project Officer: Diana KingEPA Work Assignment Manager: Jane
Dolan
BARKHAMSTED-NEW HARTFORD LANDFILL SUPERFUND SITE
BASELINE RISK ASSESSMENT
PART II
ECOLOGICAL RISK ASSESSMENT
JANUARY 1996
PREPARED BY:
METCALF & EDDY, INC.WAKEFIELD, MASSACHUSETTS
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TABLE OF CONTENTS
PARTH ECOLOGICAL RISK ASSESSMENT
Page
1.0 INTRODUCTION AND SITE DESCRIPTION 1-1 1.1 Introduction 1-1
1.2 Site Description 1-2
2.0 METHODS 2-1
3.0 HAZARD IDENTIFICATION 3-1 3.1 Media of Concern 3-1 3.2
Contaminant Screening 3-3
3.2.1 Sediment 3-5 3.2.2 Surface Soil 3-8 3.2.3 Surface Water
3-10 3.2.4 Summary of Contaminants of Ecological Concern 3-12
3.3 Potential Ecological Receptors 3-12 3.3.1 Benthic
Invertebrates 3-13 3.3.2 Fish 3-13 3.3.3 Amphibians 3-13 3.3.4
Reptiles 3-14 3.3.5 Mammals 3-15 3.3.6 Birds 3-16 3.3.7 Soil
Invertebrates 3-17 3.3.8 Plants 3-17
3.4 Assessment and Measurement Techniques 3-18
4.0 EXPOSURE ASSESSMENT 4-1 4.1 Source Characterization and
Selection of
Exposure Pathways 4-1 4.1.1 Plants 4-2 4.1.2 Animals 4-2
4.2 Fate and Transport Analysis 4-5 4.2.1 Poly cyclic Aromatic
Hydrocarbons (PAHs) 4-5 4.2.2 Metals 4-7 4.2.3 Pesticides 4-11
4.2.4 Phenolics 4-12
4.3 Exposure Scenarios and Integrated Exposure Analysis 4-13
4.3.1 Benthic Invertebrates 4-13 4.3.2 Earthworm 4-13 4.3.3 Green
Frog 4-14
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4.3.4 Spotted Salamander 4-14 4.3.5 American Robin 4-15 4.3.6
Deer Mouse 4-15 4.3.7 Woodchuck 4-15 4.3.8 Mink 4-16 4.3.9 Beaver
4-16 4.3.10 Muskrat 4-16
4.4 Uncertainty Analysis 4-17
5.0 TOXICITY ASSESSMENT 5-1 5.1 Qualitative Dose-Response
Assessment 5-1
5.1.1 Benthic/Aquatic Invertebrates 5-4 5.1.2 Earthworms 5-4
5.1.3 Amphibians 5-5 5.1.4 American Robin 5-7 5.1.5 Mammals 5-9
5.2 Hazard Indices 5-12 5.3 Uncertainty Analysis 5-12
6.0 RISK CHARACTERIZATION 6-1 6.1 Selection of Risk
Characterization Methodology 6-1 6.2 Risk Assessment
Characterization 6-1
6.2.1 Benthic/Aquatic Invertebrates 6-1 6.2.2 Earthworms 6-3
6.2.3 Amphibians 6-3 6.2.4 American Robin 6-4 6.2.5 Mammals 6-4
6.3 Hazard Indices 6-7 6.4 Uncertainty Analysis 6-8 6.5
Conclusions 6-9
7.0 REFERENCES 7-1
APPENDIX A Wildlife Data APPENDIX B Protected Species
Correspondence
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LIST OF FIGURES
ECOLOGICAL RISK ASSESSMENT
1-1 Site Location Map 1-2 Site Layout, 1993 1-3 Limits of Refuse
1-4 Wetland Delineation Map 3-1 Surface Water/Leachate Seep and
Sediment Sample Locations 3-2 Soil Sample Locations and Potential
Disposal Areas 3-3 Proposed Extent of Landfill Cap
LIST OF TABLES
ECOLOGICAL RISK ASSESSMENT
3-1 Soil, Surface Water and Sediment Samples - Evaluation for
Exposure Potential 3-2 Contaminant Screening - Sediment 3-3
Contaminant Screening - Surface Soil 3-4 Contaminant Screening -
Surface Water 3-5 Contaminants of Ecological Concern 4-1 Potential
Exposure Pathways of Concern for Indicators Species 5-1 Hazard
Quotients for Aquatic Invertebrates from Exposure to
Sediment 5-2 Hazard Quotients for Deer Mouse from Ingestion of
Soil 5-3 Hazard Quotients for Woodchuck from Ingestion of Soil 5-4
Hazard Quotients for Beaver from Ingestion of Soil 5-5 Hazard
Quotients for Mink from Ingestion of Soil 5-6 Hazard Quotients for
Beaver from Ingestion of Sediment 5-7 Hazard Quotients for Mink
from Ingestion of Sediment 5-8 Hazard Quotients for Deer Mouse from
Dermal Absorption of Soil 5-9 Hazard Quotients for Woodchuck from
Dermal Absorption of Soil 5-10 Hazard Quotients for Mink from
Dermal Absorption of Soil 5-11 Hazard Quotients for Beaver from
Dermal Absorption of Sediment 5-12 Hazard Quotients for Mink from
Dermal Absorption of Sediment 5-13 Hazard Quotients for Woodchuck
from Ingestion of Plant Tissue 5-14 Hazard Quotients for Muskrat
from Ingestion of Plant Tissue 5-15 Hazard Indices for Indicator
Species
Surface Water and
6-1 Number of Macroinvertebrates Detected during the Phase IA
Site Characterization
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SECTION 1.0
INTRODUCTION AND SITE DESCRIPTION
1.1 INTRODUCTION
The Barkhamsted-New Hartford Landfill Superfund Site is located
approximately 20 miles
northwest of Hartford within the Farmington River Valley in the
towns of Barkhamsted and New
Hartford, Connecticut (Figure 1-1). The landfill occupies much
of a 98-acre parcel of land
owned by the Regional Refuse Disposal District #1 (RRDD #1) and
has been used for solid
waste disposal since 1974 (O'Brien & Gere Engineers, Inc.,
[OBG], 1993). In 1993, landfill
operations were restricted to approximately 17 acres of the
northern area of the RRDD #1
property (Figure 1-2) and refuse was being disposed on
approximately 13 acres (OBG, 1993 see
Figure 1-3). Since 1988, the landfill has been utilized only for
the disposal of bulky and non
processible wastes, such as construction and demolition debris,
(OBG, 1993), as well as serving
as a community collection facility for recyclable materials.
Leaf composting is also conducted
on the site. The site is surrounded mostly by undeveloped land,
although some residential
properties are located adjacent to the RRDD #1 property. The
Barkhamsted Town Garage
facility borders the RRDD #1 property to the northeast, as does
U.S. Route 44, and the
Farmington River is located approximately 0.5 miles east of the
site. A history of waste
handling at the site is presented in Section 1.0 of the Human
Health Risk Assessment.
Media that were investigated as part of Remedial Investigation
Phase 1A included surface water,
groundwater, leachate, surface sediment, surface soil,
subsurface soil, ambient air, and
landfill/soil gas (OBG, 1993; OBG, 1994a). The risk assessment
assumes that a presumptive
remedy consisting of a landfill cap, a leachate collection
system, and a landfill gas collection
system will be installed as described hi the Engineering
Evaluation/Cost Analysis (EE/CA)
(OBG, 1994b) and discussed hi Section 2.0 of the Human Health
Risk Assessment. The
ecological risk assessment consists of six major sections:
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1) Introduction and Site Description: provides information on
history, physical features and natural resources
2) Objectives and Methods: defines the goal of the assessment
and the guidelines under which the assessment is conducted
3) Hazard Identification: contaminants are screened to determine
which are of ecological concern; indicator species and endpoints
are selected
4) Exposure Assessment: includes characterization of contaminant
source(s), selection of exposure pathways, fate and transport
analysis, exposure scenarios and integrated exposure analysis, and
uncertainty analysis
5) Toricity Assessment: includes identification of toxic
endpoints for indicator species, quantitative dose-response
assessment, and uncertainty analysis
6) Risk Characterization: includes selection and presentation of
risk assessment characterization, uncertainty analysis, and
conclusions.
1.2 SITE DESCRIPTION
Based on a survey of the site conducted by Metcalf & Eddy
(M&E) and U.S. Environmental
Protection Agency (USEPA) biologists on 11 June 1993 and the
qualitative ecological assessment
conducted by OBG (1993), the various features of the site are
described. Except for the landfill
itself and the support areas, the site was covered by relatively
mature forest, which provides
excellent habitat for a variety of wildlife. On the southern
portion of the site, the overstory was
dominated by eastern hemlock (Tsuga canadensis). To the north,
the forest was mixed and then
primarily deciduous. The borrow area (located off the southeast
comer of the main landfill
area), where tree stumps and other vegetative debris were
disposed, was unvegetated as was the
active part of the landfill (Figure 1-2). The inactive portion
of the landfill was covered by
grasses, with small pockets of low shrubs in some locations.
Areas around buildings were
unvegetated or consisted of mowed lawn. Wetlands at the site
were small and consisted of two
sedimentation basins, a small emergent wetland area adjacent to
one of the sedimentation basins,
and areas bordering an unnamed brook (Figure 1-4).
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There were two sedimentation basins present on the site and one
unnamed pond bordered the site
to the north (Figure 1-2). Sedimentation Basin #1 was
approximately 50 by 100 feet in size.
No emergent or submergent growth was observed hi the basin
during the 11 June 1993 site visit.
A drainage swale channeled water from the storage/borrow area
and entered the southern portion
of the landfill from the east. The northern shore area of the
basin had been recently disturbed
by a bulldozer and was unvegetated at the tune of the June 1993
site visit. To the east, west,
and south, woody scrub was located on the immediate border of
the basin, with relatively
mature, mixed forest cover types beyond the scrubby growth.
Sedimentation Basin #2 was approximately 50 by 40 feet in size.
Based on the June 1993 site
visit, no emergent or submergent growth was observed in the
basin. A small emergent wetland
area dominated by cattail (Typha spp.) was located just
northeast of the basin and was connected
to the basin by a short (3 to 4 foot) swale. A drainage swale
channeled water from the
storage/borrow area entering the basin from the south. A
combination of shrub and herbaceous
growth occurred on the upland border of the basin. Forested
cover types were located to the
north and east of the basin; to the west and south were the
landfill and borrow area,
respectively.
The unnamed pond was surrounded by forested habitats. Water
depth was approximately 1 foot
at the fringes, but 2 to 3 feet deep toward the center. The
rocky substrate was covered by a
layer of detritus. Two channels connected the pond to the
unnamed brook but appeared to
channel water from the brook to the pond only during high flow
periods.
The unnamed brook was generally 2 to 4 feet wide and 1 to 8
inches deep. Wider (up to 6 feet)
and deeper (up to 12 inches) pools were observed hi some
locations during the June 1993 site
visit. Flow rates were variable (1 to 12 inches per second),
ranging from minimal (in pooled
areas) to relatively swift (in steeper, rocky areas). The
generally sandy/gravelly substrate of the
brook had little organic matter hi the sediments. Numerous
rocks, covered with moss and algae
hi some locations, were present throughout the length of the
stream channel. The brook passed
through relatively mature forested habitats, dominated by
conifers on the southern portion of the
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site and by deciduous trees on the northern portion of the site,
and the dense canopy (canopy
cover from 75 to 90 percent) effectively shaded the brook.
Downgradient of the landfill, two
outfalls (OF-1 and OF-2) entered the brook (Figure 1-2). These
outfalls were connected to
approximately 25 catch basins located along the main access
roads to the landfill and recycling
areas, in the area containing the offices and recycling
facilities, and on the Barkhamsted Town
Garage property (OBG, 1993).
1-4
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SECTION 2.0
METHODS
The ecological risk assessment was conducted based on guidance
provided in USEPA (1989a),
USEPA (1989c) and USEPA (1992). The hazard identification
process allowed the various
contaminants and media to be preliminarily screened, thereby
identify ing potential chemicals and
media of concern. Hazard identification and the selection of
sensitive receptors were conducted
under the assumption that the presumptive remedy consisting of a
cap and a leachate and landfill
gas collection system will be implemented. The presumptive
remedy will limit the area under
consideration to sites outside of the proposed cap and eliminate
exposures to some media outside
of the boundary of the cap as detailed in Section 3.1. Hazard
identification involved the
following:
• A review of Remedial Investigation Phase 1A - Round 1 and
Round 2 analytical data (OBG, 1993; OBG, 1994a) from on-site
sampling of environmental media to determine the nature and extent
of contamination.
• A review of the soil and surface water analytical data
collected on-site during the Site Investigation (Fuss &
O'Neill, 1991). These data were used for reporting site maximums
only. The more recent and comprehensive set of samples collected by
OBG (1993; 1994a) were used to generate average concentrations,
detection frequencies, and number of exceedances of screening
levels.
• An assessment of the toxicity, bioavailability, and
bioconcentration, bioaccumulation, and biomagnification potential
of the detected contaminants to determine if existing levels in
particular media are known to cause adverse effects to ecological
receptors.
• A brief assessment of the types of organisms and habitats
present on-site and in areas potentially affected by migration of
site contaminants in order to identify sensitive ecological
receptors. This was accomplished by reviewing existing data
collected by O'Brien and Gere during Phase 1A studies (OBG, 1993;
OBG, 1994a) and conducting a brief site reconnaissance survey on 11
June 1993.
Exposure assessment included identification of exposure pathways
based on the fate and transport
characteristics of chemicals of concern and the life histories
of observed or likely inhabitants of
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the site. Indicator species or species groups were selected to
represent a range of trophic levels
and life history patterns. Exposure scenarios were outlined in
detail for indicator species and
then quantified. Estimates of exposure were compared against
toxicity reference values to obtain
pathway- and species-specific hazard quotients. Hazard quotients
and hazard indices were used
to characterize and evaluate the potential risks to ecological
resources at die site. Uncertainties
associated with the ecological risk assessment were
discussed.
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SECTION 3.0
HAZARD IDENTIFICATION
Section 3.0 includes a discussion of the site media of concern,
and the presentation of the
contaminant screening process. Potential ecological receptors
are discussed and indicator species
and species groups are selected. At the end of the section,
assessment and measurement
endpoints are defined.
3.1 MEDIA OF CONCERN
Media that were investigated as part of Phase 1A investigations
included surface water,
groundwater, leachate, surface sediment, surface soil,
subsurface soil, ambient air, and
landfill/soil gas. Groundwater and subsurface soils (soils at
depths greater than two feet) were
eliminated as media of ecological concern because potential
indicator species have little direct
contact with these media. The hazard identification and exposure
assessment were written under
the assumption that a presumptive remedy consisting of a cap,
leachate collection system, and
gas collection system will be employed (OBG, 1994b). Based on
the assumption of a
presumptive remedy, the following media and analytical data were
excluded from consideration:
• Surface soil samples and shallow boring samples (less than two
feet) from within proposed cap perimeter - regraded waste will be
inaccessible under the cap
• All leachate samples - leachate is to be diverted to the
collection system so seeps are expected to dry up
• Surface water samples from storm drams and catch basins -
surface water is expected to improve after installation of the cap
and leachate collection system
• Seep sediment samples from within the proposed cap perimeter -
regraded waste will be inaccessible under the cap
• Surface water and sediment samples from the sedimentation
basins - sedimentation basins will be regraded
3-1
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• All landfill soil gas and vapor samples - impacts of the
landfill on ambient air, following capping, are not evaluated in
this assessment; it is expected that the need for remediation of
landfill gases will be determined by sampling vented gas
Based on the presumptive remedy and likely exposure pathways for
faunal and floral species
observed or expected to occur on-site, the following media are
of potential concern to ecological
resources:
• Surface sediment in the unnamed brook and unnamed pond
• Surface water in the unnamed brook and unnamed pond
• Surface soil (0-2 feet) outside the boundary of the proposed
cap
• Soil in leachate seeps outside the boundary of the proposed
cap - will be dry due to the leachate collection system and cap
Surface water, sediment, and soil samples were collected hi 1992
and 1993 (OBG, 1993; OBG,
1994a). The locations of surface water and sediment samples are
depicted in Figure 3-1. Soil
sampling locations are shown in Figure 3-2. Sample locations
were chosen to characterize media
quality and to enable the identification of current and
potentially adverse impacts of the landfill
on ecological resources inhabiting the site and surrounding
area. Sample locations are described
in the Remedial Investigation reports (OBG, 1993; OBG, 1994a).
Selection of sample locations
to be included in the risk assessment (Table 3-1) was based on
the proposed extent of the landfill
cap (Figure 3-3) and the potential effects of the proposed cap
on the quality and accessibility of
media (see above bullets regarding data and media included and
excluded from the risk
assessment). Sediment, surface water, and soil sample locations
included hi the ecological risk
assessment are identical to those used in the human health risk
assessment. Analytical data from
sample locations in which an exposure potential could not be
ruled out were included hi the
contaminant screening process. These included sample locations
at the edge of the proposed
landfill cap. Sample locations included hi the risk assessment
are identified hi Table 3-1.
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3.2 CONTAMINANT SCREENING
Screening of contaminants and selection of chemicals of
ecological concern included a number
of variables: observed maximum contaminant concentrations in the
media of concern; frequency
of detection; mobility and persistence; toxicity (based on
published effect levels); potential for
bioconcentration or bioaccumulation; background levels; and
existing regulatory guidelines,
standards, or criteria. Hereafter, guidelines, standards,
criteria, and effect levels are collectively
referred to as screening levels. Maximum sample concentrations
were compared against
screening levels to determine whether on-site contaminant
concentrations could potentially pose
a threat to the health of ecological resources.
Site background samples, collected by OBG (1993) in an adjacent
but uncontaminated area, were
not used to screen analytical data for contaminants of concern.
Site background data were not
utilized for three reasons. First, the background concentrations
of many inorganics were the
highest detected, on-site or off-site. Second, background data
were limited, particularly for
surface water. For soil, sediment, and surface water there were
2, 2, and 1 background
sample(s), respectively. Based on these factors, background data
were not considered to be
representative of the non-site related concentrations in the
areas surrounding the site. In
addition, ecological criteria, standards, guidelines, or effect
levels were available to evaluate the
majority of the potential contaminants of concern without
depending on such limited background
data.
Maximum contaminant levels hi surface sediments were compared to
USEPA Region V
guidelines for the pollution classification of Great Lakes
harbor sediments (USEPA, 1977),
sediment criteria issued by the New York State Department of
Environmental Conservation
(NYSDEC, 1994), USEPA interim sediment quality criteria (USEPA,
1988), Guidelines for the
Protection and Management of Aquatic Sediment Quality Criteria
in Ontario (Ontario Ministry
of Environment and Energy [OMEE], 1993), and low effect range
levels (ER-Ls) and median
effect range levels (ER-Ms) from the National Oceanic and
Atmospheric Administration (NOAA)
National Status and Trends Program (Long and Morgan, 1990).
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The USEPA Region V sediment values are guidelines for the
pollution classification of Great
Lakes harbor sediments (USEPA, 1977). The NYSDEC sediment
criteria are considered
guideline values, as opposed to enforceable standards or
department policy (NYSDEC, 1994).
NYSDEC sediment criteria for non-polar organic chemicals were
developed using the
equilibrium partitioning approach while sediment criteria for
metals are based on empirical data
from field and laboratory studies on the effects of metals hi
sediments on benthic organisms.
The USEPA interim sediment quality criteria for non-polar
organic chemicals were also
developed using the equilibrium partitioning approach. Where
appropriate, screening levels for
organic compounds were adjusted for total organic carbon content
as specified hi the USEPA
and NYSDEC criteria guidance documents.
Ontario Ministry of Environment and Energy sediment quality
guidelines were developed for the
protection of aquatic environments (OMEE, 1993). OMEE sediment
guidelines provide the
lowest effect level (LEL) and the severe effect level (SEL). The
lowest effect level is defined
as "a level of contamination which has no effect on the majority
of sediment-dwelling
organisms." Concentrations at the LEL indicate that a sediment
is clean to marginally polluted.
A concentration at the SEL indicates "the sediment is considered
heavily polluted and likely to
affect the health of sediment-dwelling organisms." During the
contaminant screening process,
sample concentrations were compared against OMEE LEL values.
ER-Ls and ER-Ms provided by NOAA are based primarily on marine
and estuarine sediment
concentrations although some freshwater sediments were included
hi their derivation. Long and
Morgan (1990) identified the lower 10th percentile of
concentrations hi the data as Effects
Range-Low (ER-L) and the median as Effects Range-Median (ER-M).
ER-Ls and ER-Ms may
be used as general guidelines hi evaluating potential ecological
effects from sediment
contaminants. Because a substantial proportion of the data used
to derive ER-Ls and ER-Ms was
obtained from marine systems rather freshwater systems, only
ER-Ms (the higher standards)
were used hi the screening process thus reducing the weight of
these guidelines.
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Contaminant concentrations in surface soils were compared to
guidelines, standards, and criteria,
as well as U.S. national background levels for soil and other
surficial materials [Shacklette et
al. (1971) as cited in Beyer (1990)]. Other literature sources
used to evaluate soil contamination
included U.S. Fish and Wildlife chemical hazard reports and
effect level studies.
Maximum contaminant concentrations hi surface water were
compared to chronic and acute
water quality criteria. For the protection of aquatic life,
USEPA and the Connecticut
Department of Environmental Protection (CDEP) have established
freshwater Ambient Water
Quality Criteria (AWQC) for a number of chemicals hi surface
water (USEPA, 1986; CDEP,
1992). However, federal and Connecticut AWQC have not yet been
established for a large
number of contaminants, particularly for volatile and semi
volatile compounds. Rhode Island has
established AWQC for a number of volatile and semivolatile
compounds (RIDEM, 1988), and
these criteria are used, when available, for chemicals without
existing USEPA or Connecticut
AWQC. Where appropriate, criteria for metals were adjusted for
water hardness as specified
hi AWQC guidance.
The results of the contaminant screening process are presented
by media hi the following
subsections (surface sediment, surface soil, and surface water).
Chemicals that were selected
for further consideration (chemicals of concern or COCs) are
summarized at the end of each
media discussion.
3.2.1 Sediment
Sediments constitute the organic and inorganic material that
settle hi a water body over time.
For the purposes of the ecological risk assessment, substrate is
considered sediment if it is
inundated by water on a fairly permanent basis. Sediment samples
were collected from the
unnamed pond and brook by OBG (1993; 1994a). Under the condition
of a presumptive remedy
(landfill cap, leachate collection system, and landfill gas
collection system), leachate will no
longer flow and leachate seep sediments will dry. Therefore, the
substrate within leachate seeps
was considered to be soil rather than sediment and consequently
screened hi Section 3.2.2 - Soil.
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Sediments were analyzed for volatile organic compounds, semi
volatile organic compounds,
pesticides, polychlorinated biphenyls (PCBs), and inorganics.
The analytical sediment data
collected from Phase 1A - Rounds 1 and 2 sediment are summarized
in Table 3-2. Analytical
detection limits were higher than the lowest criteria value in
one or more samples for PCBs,
pesticides, poly cyclic aromatic hydrocarbons (PAHs), antimony,
mercury, silver, and cyanide.
Therefore, there may be more exceedances of criteria than can be
delineated based on existing
data.
Four volatile organic compounds (acetone, ethylbenzene,
tetrachloroethane, and xylene) were
detected in sediments (Table 3-2). Ethylbenzene,
tetrachloroethane, and xylene were eliminated
from further consideration because they were each detected in
only 1 of 24 samples. Acetone
was also determined not to be of concern due to a low maximum
detected concentration (190
ppb) and because its toxicity to aquatic organisms is considered
to be low (USEPA, 1985).
Eighteen semivolatile organic compounds were detected in
sediment, including 14 PAHs, three
phthalates, and carbazole (Table 3-2). Twelve of the 14 PAHs had
existing criteria values.
Benzo(a)pyrene, phenanthrene, and pyrene were selected as
chemicals of concern because
concentrations exceeded screening levels at more than one
sampling location. Screening levels
were not available for acenaphthylene and benzo(b)fluoranthene.
Acenaphthylene was detected
at low concentrations (maximum = 170 ppb) and was therefore
determined to not be of concern.
By contrast, the maximum concentration of benzo(b)fluoranthene
was high (2100 ppb). Based
on high concentrations and frequency of detection (7 of 17
samples), benzo(b)fluoranthene was
selected as a chemical of concern.
No screening criteria were available for phthalates. However,
phthalates were detected relatively
infrequently (2 of 17 samples, 3 of 17 samples, and 4 of 18
samples) and concentrations were
low (maximums of 79 to 300 ppb). Carbazole was detected in over
one-third of sediment
samples (6 of 17 samples). Although screening levels were not
available, carbazole was
eliminated from further consideration based on a low maximum
concentration (78 ppb).
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Of the twelve pesticides detected in sediment, screening levels
were available for ten (Table 3
2). Concentrations of gamma-chlordane, DDE, DDT, endosulfan I,
endosulfan n, and endrin
exceeded screening levels. Endosulfan I was determined not to be
of concern because it
exceeded the screening level in only one sample. Although they
did not have screening levels,
alpha-BHC and endrin ketone were screened out of the risk
assessment based on a low frequency
of detection (2 of 23 and 1 of 23 samples, respectively). The
PCB Aroclor-1254 was detected
in only 3 of 23 sediment samples. Although concentrations
exceeded the OMEE LEL in two
samples, the maximum concentration of Aroclor 1254 was
substantially lower than the screening
levels from four other sources. Based on this, Aroclor-1254 was
eliminated from further
consideration.
Twenty-three inorganics were detected in sediments (Table 3-2).
Concentrations of barium,
chromium, copper, iron, lead, manganese, nickel, and zinc
exceeded screening levels in more
than one sample. Although a high percentage of barium is likely
to be present in insoluble, non
toxic forms (USEPA, 1985), barium was retained as a chemical of
ecological concern. Mercury
was detected in 5 of 24 samples, but concentrations exceeded
screening limits in only one
sample. Therefore, mercury was not considered to pose a
significant risk of harm at the site.
No screening levels were available for aluminum, beryllium,
calcium, cobalt, magnesium,
potassium, sodium, thallium, and vanadium. Calcium, potassium,
magnesium, and sodium were
screened out of the assessment because they are essential
nutrients and naturally occur in high
concentrations. Thallium was screened out because it was
detected in only 2 of 24 samples.
Average U.S. background concentrations in soil and other
surficial materials [Shacklette et al.
(1971) as cited hi Beyer (1990)] were used as a reference to
judge the significance of aluminum,
beryllium, cobalt, and vanadium hi sediment. These background
data were used because no
ecological criteria were available and they provided the average
and range of concentrations that
can be expected to occur naturally hi the United States.
Although the background concentrations
were based primarily on soil samples, their application to
sediment data was considered
appropriate for a conservative screening process.
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The average concentrations of aluminum, beryllium, and vanadium
were all less than the average
U.S. background concentrations. In contrast, the average
sediment concentration of cobalt (11.7
mg/kg) slightly exceeded the U.S. background average
concentration (10 mg/kg). Therefore,
cobalt was selected as a COC. Comparison of the concentrations
of aluminum, beryllium,
vanadium, and cobalt to Massachusetts Department of
Environmental Protection background soil
numbers yielded the same results and selection of cobalt as a
COC (MADEP,1995).
In summary, chemicals of concern in sediment include
benzo(a)pyrene, phenanthrene, pyrene,
benzo(b)fluoranthene, gamma-chlordane, DDE, DDT, endosulfanfl,
endrin, barium, chromium,
cobalt, copper, iron, lead, manganese, nickel, and zinc.
3.2.2 Surface SoU
For the purposes of the ecological risk assessment, soil is
defined as substrate that is directly
accessible by terrestrial or semi-aquatic receptors (i.e., not
covered by water for any significant
length of time). Soil samples, grouped under the heading of
"surface soil," included surface soil
samples, soil borings from 0 to 2 feet, and leachate seep
sediments. Leachate seep sediments
were treated as soils because leachate will no longer flow and
seep sediments will dry after the
installation of the landfill cap and leachate collection
system.
Soils samples were collected by OBG (1993; 1994a) during Phase
1A -Rounds 1 and 2. Soils
were analyzed for volatile organic compounds, semivolatile
organic compounds, pesticides,
PCBs, and inorganics (Table 3-3). Average U.S. background
concentrations for soil and other
surficial materials [Shacklette et al. (1971) as cited hi Beyer
(1990)] were used to screen
inorganics for which no ecological criteria existed.
Detected analytes hi surface soils were compared to guidelines
and standards hi Beyer (1990)
and Fitchko (1989), as well as to effect levels found hi the
literature. In the following text,
guidelines, criteria, standards and ecological effect levels are
collectively referred to as screening
3-8
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levels. In general, detection limits were lower than screening
levels. However, detection limits
for a few PAHs (particularly benzo(a)pyrene), phthalates, and
antimony exceeded criteria.
Six volatile organics were detected in surface soils (Table
3-3). Concentration of all volatiles
were below existing screening levels. Of the 23 semivolatile
compounds detected in surface soil,
ecological screening levels were available for 16.
Concentrations of four PAHs,
benzo(a)anthracene, benzo(a)pyrene, benzo(g,h,i)perylene and
indeno(l,2,3-cd)pyrene exceeded
screening levels in one to six samples. These compounds were
selected as chemicals of concern.
The concentrations of anthracene, benzo(b)fluoranthene,
benzo(k)fluoranthene, bis(2
ethylhexyl)phthalate, chrysene, 1,4-dichlorobenzene,
fluoranthene, naphthalene, phenanthrene
and pyrene were below screening levels. As a group, phthalates
were infrequently detected and
only diethylphthalate exceeded screening levels (in one sample).
Consequently, phthalates were
not considered to be of ecological concern.
Screening levels were not available for seven semivolatile
compounds: acenaphthene,
acenaphthylene, bis(2-chloroethyl)ether, carbazole,
dibenzofuran, fluorine, and
2-methylnaphthalene. Bis(2-chloroethyl)ether was screened out
because it was detected in only
1 of 22 samples. With the exception of 2-methylnaphthalene, the
remaining five compounds
were screened out of the risk assessment based on a relatively
low frequency of occurrence (4
of 22 or 5 of 22 samples) and low concentrations (maximum
concentrations ranged from 92 to
290 ppb, see Table 3-3). Detected at a maximum concentration of
2300 ppb,
2-methylnaphthalene was retained as a chemical of concern.
Ten pesticides (including two metabolites of DDT) were detected
in surface soil samples (Table
3-3). All were eliminated as ecological chemicals of concern.
Eight of ten compounds had
screening levels that were higher than the maximum observed soil
concentration. Screening
levels were not available for aldrin and methoxychlor. However,
because they were each
detected in only 2 of 21 samples, they were eliminated from
further consideration. The PCB
Aroclor-1254 was detected hi only one sample and the
concentration was an order of magnitude
below the screening level.
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Twenty inorganics were detected in surface soil samples (Table
3-3). Screening levels or
background concentrations were available for all metals.
Concentrations of arsenic, chromium,
cobalt, copper, lead, nickel, and silver exceeded ecological
criteria. With the exceptions of
arsenic and cobalt, these metals were retained as chemicals of
concern. Arsenic and cobalt were
determined not to be of concern because they exceeded respective
screening levels in only one
sample each and average concentrations of each were less than
one-fifth of the screening levels.
No screening levels were available for aluminum, calcium, iron,
magnesium, potassium, and
sodium. Calcium, magnesium, potassium and sodium were screened
out of the assessment
because they are essential nutrients and naturally occur in high
concentrations. Aluminum was
screened out because the average concentration found on-site was
lower than the average U.S.
background concentration [Shacklette et al. (1971) as cited in
Beyer (1990)]. Iron concentrations
exceeded the average U.S. background concentration (25,000
mg/kg) in 6 of 22 soil samples.
Since iron may cause ecological toxicity in terrestrial habitats
at very high levels (USEPA,
1985), iron was selected as a chemical of ecological concern in
surface soil.
In summary, chemicals of ecological concern hi soil include
benzo(a)anthracene, benzo(a)pyrene,
benzo(g,h,i)perylene, indeno(l,2,3-cd)pyrene,
2-methylnaphthalene, chromium, cobalt, copper,
lead, iron, nickel, and silver.
3.2.3 Surface Water
Relatively few organic compounds were present in surface waters
at concentrations above
detection limits and most occurred at relatively low frequencies
(Table 3-4). The detection
frequencies of inorganics were greater. There were numerous
compounds for which detection
limits were higher than chronic AWQC in one or more samples.
This is particularly a problem
for PCBs, pesticides, aluminum, mercury, and silver. Due to low
hardness values at some
sampling locations, calculated AWQC were also below detection
limits for cadmium, copper,
lead, and zinc. Thus, some potential exceedances of criteria
values may be missed based on
existing data.
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Four volatile organic compounds were detected in surface water
(Table 3-4). Methylene
chloride and toluene did not exceed screening levels. Although
no screening levels were
available for acetone and 2-butanone, 2-butanone was eliminated
from further consideration
based on frequency of detection (two of twenty-one samples).
Acetone was eliminated because
its toxicity to aquatic organism is considered to be low (USEPA,
1985).
Five semivolatile organic compounds were detected (Table 3-4).
Of those with screening levels,
only 2,4-dimethylphenol exceeded chronic AWQC. Based on
frequency of detection (1 of 24
samples), 2-methylphenol was determined to be of no further
concern. By contrast, 4
methylphenol was detected more frequently (5 of 24 samples) and
its maximum concentration
was the highest of any semivolatile. Two semivolatile organics
were selected as chemicals of
concern, 2,4-dimethylphenol and 4-methylphenol.
Methoxychlor, DDT and gamma-chlordane were detected in surface
water. Each compound was
detected hi 1 of 24 samples. Consequently, pesticides were
considered to not be of concern hi
surface water.
Of the 12 inorganics with screening levels, six exceeded chronic
AWQC while three exceeded
acute criteria (Table 3-4). The metals that were detected hi
excess of acute criteria (aluminum,
copper and zinc) were selected as contaminants of concern. Iron
and lead exceeded chronic
criteria and were also contaminants of concern. Mercury exceeded
chronic criteria as well, but
was determined not to be of concern since it was detected in
only 2 of 25 samples.
No screening levels were available for barium, calcium, cobalt,
magnesium, manganese,
potassium, sodium, and vanadium. Calcium, magnesium, potassium
and sodium were not
considered of concern because they are nutrients and naturally
occur at high concentrations.
Likewise, cobalt and vanadium were not considered to be
important contaminants due to low
frequency of detection (3 of 25 and 1 of 25 samples). Barium and
manganese, however, were
selected as chemicals of concern because they were detected hi
20 or more samples at significant
concentrations.
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In summary, the chemicals of ecological concern for surface
water at the site were
2,4-dimethylphenol, 4-methylphenol, aluminum, copper, iron,
lead, manganese, barium, and
zinc.
3.2.4 Summary of the Contaminants of Ecological Concern
Soil, sediment, and surface water were determined to be media of
concern via which ecological
resources may be exposed to contaminants. Ecological
contaminants of concern are summarized
by media in Table 3-5. All of the volatile organic compounds
detected at the site were
determined not to pose a risk of harm because individual
compounds had low toxicity potential,
were detected infrequently, and/or were present hi
concentrations that were lower than screening
levels.
3.3 POTENTIAL ECOLOGICAL RECEPTORS
Species groups most likely to receive potential exposure are
those whose activities frequently
bring them into direct contact with surface sediments, wetland
or upland surface soils, or surface
water; that directly consume plants growing on or hi these
media; or that feed upon species
possessing one or both of these characteristics. These species
groups are evaluated hi this
section to determine those potentially at risk of significant
exposure. For those species or
species groups determined to be at risk of significant exposure,
assessment and measurement
endpoints are outlined hi Section 3.4.
Selection of potential ecological receptors was based on
wildlife observations made by M&E
biologists during a site walkover on 11 June 1993 and by OBG
staff during the Remedial
Investigation (OBG, 1994a). M&E and OBG prepared tables
listing wildlife observed directly
or by sign at the site (Appendix A). Based on 1994
correspondence with the US Fish and
Wildlife Service (USFWS), no federally protected species are
known to inhabit the site (OBG,
1994a). Consequently, protected plants and animals were not
considered hi selecting potential
indicator species for this assessment. Correspondence with the
Connecticut Department of
3-12
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Environmental Protection dated January 22, 1996 confirms that
there are no known extant
populations of federal or state protected species that occur at
the site (Appendix B).
3.3.1 Benthic Invertebrates
Benthic organisms living hi the sediments of the unnamed brook
are potentially at risk because
of their direct contact with contaminants hi this medium.
Exposure could result from direct
contact with exposed outer membranes and respiratory surfaces,
the direct ingestion of sediments
during feeding activities, and the consumption of contaminated
prey or detritus, depending upon
the species' feeding habits. These organisms could also be
directly exposed to contaminants in
surface water by the same pathways. The presence of pollution
tolerant taxa in qualitative kick-
net surveys conducted in the unnamed brook (OBG, 1993) suggest
that benthic invertebrate
community structure has been affected by site contaminants.
Thus, benthic invertebrates are
considered a primary indicator species group to evaluate
ecological risk hi aquatic areas.
3.3.2 Fish
No resident fish species are known to use the unnamed brook in
the vicinity of the site and no
fish were observed hi this water body (OBG, 1993). Various fish
species are known to use the
Farmington River. However, contaminant transport from the site
is unlikely to reach the river,
due to a series of intervening wetland areas. Thus, exposure of
fish to site contaminants is
unlikely and they are not considered to be potential ecological
receptors.
3.3.3 Amphibians
As immature forms, adults, or both, salamanders, newts, toads,
and frogs are potentially at risk
of exposure because of their close association with sediments,
soils, and water. Most newts,
toads, and salamanders are terrestrial hibernators, whereas most
species of frogs hibernate under
water hi mud (DeGraaf and Rudis, 1983). Thus, exposure to
contaminants in sediments or soils
continues even during hibernation (although metabolism is
greatly slowed), because of direct
3-13
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absorption through their relatively unprotected membranous skin.
These organisms conduct
considerable metabolite exchange directly through their skin
(Schmidt-Nielsen, 1983).
Salamanders, newts, toads, and frogs consume earthworms, aquatic
insects, and small fish or
tadpoles (DeGraaf and Rudis, 1983). These prey are among the
most likely to contain elevated
levels of contaminants in their tissues. Amphibians may also
ingest contaminated soil, sediment,
and detritus during feeding activities.
Frogs (including egg masses and tadpoles) were observed in the
unnamed pond, and salamander
larvae were observed in the unnamed brook. Thus, frogs and
salamanders will be used as
indicator species groups for the risk assessment.
3.3.4 Reptiles
Turtles and, to a lesser degree, snakes are potentially at risk
of exposure based upon their life
history characteristics. Turtles are mostly aquatic and spend
considerable time on the bottom
sediments of water bodies. Many snakes are sensitive to
pollutants and have frequent contact
with water, soil, or sediment (Hall, 1980; DeGraaf and Rudis,
1983).
Turtles consume tadpoles, small fish, crustaceans, and some
carrion (DeGraaf and Rudis, 1983).
Semiaquatic snakes also consume fish, frogs, aquatic insects,
and salamanders, while more
terrestrial species may consume large numbers of soil
invertebrates, especially earthworms
(DeGraaf and Rudis, 1983). These food items are likely to
contain the highest levels of
contaminants of available food items present on the site.
Reptiles may also ingest contaminated
soil, sediment or detritus during feeding activities.
No turtles were observed on the site and habitat appears to be
marginal for most species.
Although snakes were observed on-site, lack of sufficient
information on contaminant effects for
this taxa makes it difficult to use in a risk assessment. Thus,
reptiles are not considered as
potential indicator species for use in the risk assessment.
3-14
-
3.3.5 Mammals
Several mammalian primary consumers are potentially at risk of
exposure to site contaminants.
These include, for wetland and aquatic areas, species such as
beaver (Castor canadensis) and
muskrat (Ondatra zibethicus), and for upland areas, species such
as woodchuck (Marmota
monax) and white-tailed deer (Odocoileus virginianus) and other
small rodents (e.g., mice,
moles, and voles).
Beaver spend considerable time in potentially contaminated water
and hi contact with potentially
contaminated sediments and wetland soils. Beavers carry
sediments (mud) in their forefeet for
the purpose of lodge and dam building (Novak, 1987). The floors
of the lodge are at least partly
composed of bare soils and/or sediments. Young animals would
have considerable dermal
exposure to these soils/sediments before emerging from the
lodge. Both adults and young would
be exposed to contaminants volatilizing from the soils or
sediments into the confined airspace
of the lodge. This species may directly ingest contaminated
soils or sediments hi the course of
dam or lodge construction, during grooming activities, and as
they forage. Contaminants could
be absorbed directly through the skin (dermal exposure) and from
the digestive tract after
ingestion. Exposure to contaminated water could also occur from
these routes.
Beaver exposure via contaminated plant tissues is not likely to
be significant because beavers
feed mainly on the bark of woody plants. Bark is not likely to
concentrate contaminants to
levels that actively growing tissues may concentrate (e.g.,
roots and shoots). Muskrat are more
likely to be exposed to metals through the consumption of plant
tissue than beaver since the
majority of the muskrat diet is roots and basal portions of
aquatic plants (USEPA, 1993).
Likewise, exposure via plant ingestion is likely to be greater
for woodchuck compared to beaver
because woodchuck primarily consume herbaceous vegetation
(DeGraaf and Rudis, 1983).
Upland burrowing mammals, such as woodchuck and moles, could be
at risk of exposure
through dermal contact with the soil or through the inhalation
of semivolatile compounds. Soil
3-15
-
could also be directly ingested by these species during feeding
and grooming activities. Species
such as white-tailed deer could be exposed to surface water
contaminants in dietary water.
Mammalian secondary consumers with a possible risk of exposure
include mink (Mustela visori)
and raccoon (Procyon lotor). Mink and, to a lesser degree,
raccoon, preferentially feed upon
aquatic animals (e.g., fish, frogs, and tadpoles) and small
mammals, depending upon relative
prey abundances (Linscombe et al., 1982; Kaufmann, 1982). These
prey species are among the
organisms most likely to contain significant levels of
contaminants in their tissues.
Since mink and raccoon have relatively large home ranges, the
percentage of time spent on-site
and the percentage of food obtained on-site would influence the
potential exposure. Raccoon
home ranges vary between 0.6 and 1.8 miles in diameter (400 to
1,200 acres), while mink home
ranges vary between 0.6 and 3.0 miles of river or up to 2,000
acres if the length of river is
considered the diameter of a circular home range (Linscombe et
al., 1982; Kaufmann, 1982;
DeGraaf and Rudis, 1983; Eagle and Whitman, 1987).
All of the above species are known or likely to occur on-site or
in downgradient areas. Based
on the above discussion, beaver and muskrat (primary consumers
in aquatic areas downgradient
of the site), mink (predator; aquatic/wetland areas), woodchuck
(primary consumer in upland
areas/burrows), and small rodents (primary consumer in upland
areas/burrows) are proposed as
mammalian indicator species for use in the risk assessment.
3.3.6 Birds
Avian primary consumers are not likely to have significant
exposure to site contaminants. Avian
secondary consumers at potential risk of exposure include
species such as American robins
(Turdus migratorius). American robins consume earthworms and
other upland soil biota
(DeGraaf and Rudis, 1983; Ehrlich et al., 1988). These prey
species are among the most likely
upland fauna to contain contaminants in their tissues. Upland
avian secondary consumers are
unlikely to be receive significant exposure along any other
route. Since the unnamed pond and
3-16
-
brook adjacent to the landfill lack fish, wading birds (such as
herons) are unlikely to forage in
these areas. Thus, American robins are selected as the avian
indicator species hi upland areas
while no avian species are selected for aquatic/wetland
areas.
3.3.7 Soil Invertebrates
Due to then: close association with surface soils and then-
importance hi terrestrial food chains,
soil invertebrates are evaluated as part of the risk assessment.
Since most of the available
information for this group of organisms consists of studies on
earthworms, earthworms are used
as an indicator species hi the risk assessment.
3.3.8 Plants
Terrestrial, wetland, and aquatic plants rooted hi contaminated
soils or sediments may uptake,
through their root surfaces, some of the contaminants present hi
the pore water of these media
during water and nutrient uptake. A secondary exposure route,
absorption through leaf surfaces
of gaseous contaminants or contaminants deposited on these
surfaces by ah- or water, is not
likely to be important at the site due to the lack of exposed
contaminated soils and low
deposition rates. Unrooted, floating aquatic plants, such as
duckweed (Lemna spp.), and other
emergent and submergent aquatic plants may uptake contaminants
directly from surface water.
Plants are discussed in this risk assessment as a potential
contaminant source. Plants may take
up some contaminants from soil, sediment, and/or water, and
transfer them to herbivores. This
pathway also includes the consumption of detritus, particularly
by benthic and terrestrial
invertebrates. Many invertebrate species feed on detritus and
could therefore become a source
of contaminant exposure for secondary consumers.
3-17
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3.4 ASSESSMENT AND MEASUREMENT ENDPOINTS
To evaluate whether risks to ecological resources exist at a
site, an assessment endpoint must
be selected. The assessment endpoint defines the nature of site
risk. USEPA (1992) defined
assessment endpoint as an explicit expression of the
environmental value that is to be protected.
The presence of a reproductively viable community of species was
selected as the assessment
endpoint at the Barkhamsted site. If site contaminants are
negatively affecting ecological
resources, it would be expected that the natural community would
be less diverse, of a different
composition, or less abundant than at an uncontaminated site of
similar character.
Many taxa are expected to inhabit the site. A representative
subset of organisms was selected
to represent this community of species. The subset includes
benthic invertebrates, earthworms,
green frog, spotted salamander, American robin, deer mouse,
woodchuck, muskrat, mink, and
beaver. These organisms represent a significant fraction of the
guilds, trophic levels, and
general life histories that are expected to occur at the site.
The term "reproductively viable"
was added to the assessment endpoint to indicate that, for each
species, a minimum number of
individuals must be present and reproductively viable for the
species to be continually
represented at the site.
Measurement endpoints illustrate the performance of the
assessment endpoint. USEPA (1992)
defined measurement endpoint as a measurable ecological
characteristic that is related to the
valued characteristic chosen as the assessment endpoint. Each
assessment endpoint must have
at least one measurement endpoint. The measurement endpoint at
the Barkhamsted site is the
comparison of a site-specific Hazard Quotient (HQ - calculated
by dividing the estimated
exposure by the reference dose that is known to cause an adverse
effect on a receptor) to a
reference HQ (i.e., HQ = 1 and HQ=10). Contaminant specific HQs
were calculated for each
of the species representing the Barkhamsted community. When
calculated HQs are high, site
contaminants may be harmful enough to preclude, through death or
reproductive impairment,
the presence of a reproductively viable community (the
assessment endpoint).
3-18
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In addition to calculating HQs for each contaminant, cumulative
impacts for classes of chemicals
(e.g., metals) were evaluated for each exposure pathway
attributable to an indicator species.
HQs for each chemical class were summed to obtain Hazard Indices
(HI). If the HI for a
specific pathway was high, it was presumed uiat the particular
species, and others within the
same guild, were being negatively affected (i.e., the assessment
endpoint is degraded).
3-19
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SECTION 4.0
EXPOSURE ASSESSMENT
The objective of the exposure assessment is to evaluate the
status of soil, sediment, and surface
water as potential exposure sources for ecological receptors.
Meeting this objective requires
integration of information on the fate and transport of
chemicals of concern and the life histories
of potential ecological receptors inhabiting the site.
4.1 SOURCE CHARACTERIZATION AND SELECTION OF EXPOSURE
PATHWAYS
Potential exposure to contaminant sources will be reduced with
the installation of the landfill
cap. All seeps, sediments, and soil located on the landfill will
be covered. Potential threats
from contaminants in the sedimentation basins will also be
removed because these areas will be
regraded. The installation of an infiltration barrier such as a
bentonite clay/polyethylene
composite liner will lower the level of groundwater under the
landfill, and will eliminate seepage
outside of the cap. Therefore, those seeps located outside the
cap, and not covered, will cease
to receive water and will dry up. Since contaminated groundwater
will no longer be emanating
from the landfill, surface water in discharge areas such as the
wetlands or streams may receive
less contamination. However, potential exposure to contaminants
via surface water and
sediments were evaluated to determine the current status of this
media as a potential exposure
source.
Soil, sediments and surface water remain as media of ecological
concern. In addition to all
uncovered soils, the sediments hi the seeps outside of the cap
are treated as terrestrial soils,
since they will be dry. The sediments and surface waters of
concern are located hi the unnamed
brook, hi the beaver ponds along the unnamed brook east of U.S.
Route 44, and hi the unnamed
pond located north of the unnamed brook (Figure 1-2). Since the
capping of the landfill will
presumably not affect the hydrology of these areas, substrate
that is currently considered
sediment will be evaluated as such. The text that follows is a
discussion of potential exposure
pathways of indicator plant and animals species to the media of
concern (Table 4-1).
4-1
-
4.1.1 Plants
Terrestrial, wetland, and aquatic plants rooted in contaminated
soils or sediments may uptake,
through their roots surfaces, some of the contaminants present
in the pore water of these media
during water and nutrient uptake. Free floating plants such as
duckweed may uptake
contaminants directly from the surface water. A secondary
exposure route, absorption through
leaf surfaces of gaseous contaminants or contaminants deposited
on these surfaces by air, water
or dust, is not likely to be important at the site due to the
lack of exposed contaminated soils and
low deposition rates. Plants are discussed in this assessment
only as a potential medium,
uptaking contaminants from soil, sediment, leachate, and/or
water, and transferring them to
herbivorous animals who consume their tissues or to
invertebrates that consume detritus and
become a potential exposure source for secondary consumers.
4.1.2 Animals
There are four major ways fauna might be exposed to
contaminants: (1) direct ingestion of
contaminated abiotic media, (2) the consumption of contaminated
animal or plant tissues
(includes detritus), (3) direct inhalation, and (4) absorption
through skin or gill surfaces.
Direct Ingestion of Contaminated Abiotic Media. Media of
potential concern are surface soil,
surface water and sediment. Direct ingestion of contaminated
soil or sediment could occur while
animals grub for food, feed on plant matter covered with
contaminated soil, filter feed in areas
where sediments have been resuspended in the water column, or
preen or groom themselves.
In addition, aquatic deposit feeders and earthworms directly
ingest large quantities of bulk
sediment or soil in order to obtain the energy-rich fraction;
these organisms would likely have
a significant exposure from this pathway. Surface water may also
be directly ingested by
organisms while obtaining dietary water or feeding.
Ingestion of Contaminated Tissues. It is possible that
terrestrial, wetland, and aquatic plants
rooted in contaminated soils or sediments could uptake
contaminants from these media and
4-2
-
incorporate these compounds into their tissues, thereby
presenting a possible risk to animals
(primary consumers) feeding upon those plants (e.g., woodchuck
and muskrat). Many
invertebrates may be exposed to contaminants through the
consumption of detritus. Predatory
organisms (secondary consumers) may be at risk when feeding upon
prey containing elevated
levels of contaminants in their tissues. The risk of exposure to
predators would depend upon
the concentration of contaminants in the particular tissues
consumed and the rate of food
consumption. The dose received would also depend upon the rate
of assimilation of the
contaminants (or toxic metabolites resulting from chemical
changes in the compounds) from the
digestive tract during digestion and the rate of metabolism.
Various common food species (e.g., earthworms) for upper-level
consumers in terrestrial
environments are known to bioaccumulate some inorganic and
organic compounds to levels
above those found in the environment. Although no site-specific
data on tissue concentrations
of contaminants exist for earthworms, these organisms have been
shown to bioaccumulate certain
metals, such as copper and lead, from surface soils (Roberts and
Dorough 1985; Bysshe 1988)
and pesticides such as DDT. Thus, prey organisms may pose a
potential exposure risk to
predators that consume them.
Inhalation Exposure. To some extent, semivolatile compounds tend
to volatilize from surface
soils or surface water. In vapor form, these compounds may
become bioavailable to organisms
during respiration, which becomes an important exposure route.
The lungs, with their large
surface area for gas exchange, readily absorb many chemicals and
pass them directly into the
bloodstream. Most hazards from volatile organic compounds are
associated with inhalation
exposure (USEPA, 1985); for metals and semivolatile compounds
with higher molecular weights
(e.g., benzo(a)pyrene), there is a reduced exposure risk from
inhalation because these
compounds tend to remain adhered to surface particles. However,
these particles may be inhaled
as dust, depending upon conditions at the site. Since the
landfill will be capped and on-site
vegetation keeps soil intact and reduces erosion, exposure via
the inhalation of dust is not likely
to be an important exposure pathway.
4-3
-
Exposure via inhalation exposure could be important for animals
such as muskrats, beavers, and
woodchucks that spend a considerable amount of time in a
confined space. For example,
semivolatile contaminants present in the soil could volatilize
into the confined airspace of the
woodchuck burrow, where they could reach relatively high
concentrations. This exposure risk
would be most severe for postnatal animals as they would have
continuous exposure during the
early period of their life, prior to their exit from the
burrows. The risk would also be severe
since the animals would be most susceptible to the effects of
the contaminants because of the
high rate of growth experienced at this life stage. Exposure of
the pregnant female to
contaminants in the burrow air may also have effects at the
fetal stage, resulting hi fetal death,
birth defects, or reduced birth weight.
Since volatile organic compounds are not present hi on-site
surface soils at levels considered to
be of concern to ecological systems, and the concentrations of
the few semivolatile compounds
in the areas with suitable soils (based upon soil type and soil
depth) for most burrowing animals
(e.g., woodchuck) were relatively low, inhalation is not likely
to be an important exposure
pathway. The ultimate fate of PAHs hi sediment is chemical
oxidation, biotransformation, or
biodegradation by bacteria and other benthic organisms (Eisler,
1987).
Dermal Exposure. Direct exposure to contaminated surface soils
or surface sediments is
another exposure pathway important to some species. Exposure
could result from direct dermal
contact with the soils or sediments on unprotected surfaces
[e.g., gill membranes (from
suspended sediments) or exposed skin].
Dermal exposure may be an exposure pathway for semi-aquatic
animals such as muskrat, mink,
and beaver that spend a considerable amount of time hi water.
Dermal exposure is also likely
important to burrowing mammals (such as woodchucks), amphibians
and reptiles that hibernate
hi the sediments (such as frogs and turtles), and benthic
invertebrates. These taxa all have
extensive contact with surface water, sediments and/or surface
soils during all or part of their
lives.
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4.2 FATE AND TRANSPORT ANALYSIS
This section summarizes the pertinent information concerning the
fate and transport of the
ecological chemicals of concern (Table 3-5) applied to
ecological receptors. The chemicals of
concern for the ecological risk assessment are pesticides, PAHs
and inorganic analytes in
sediment, PAHs and inorganic analytes in soil, and phenols and
inorganic analytes in surface
water.
Fate and transport in the environment depends on the properties
of both the contaminant and the
environmental medium in which it occurs. For each chemical type,
the physical and biological
pathways are identified, as are the storage and degradation
mechanisms present in the
environment.
4.2.1 PAHs
PAHs are virtually ubiquitous in the environment, originating
from anthropogenic sources as
well as forest fires, microbial synthesis, and volcanic
activity. They have been detected in
animal and plant tissues, sediments, air, surface water,
drinking water and groundwater (Eisler,
1987). Anthropogenic sources of PAHs in the environment include
combustion processes used
in the steel industry, heating and power generation, and
petroleum refining.
The primary fate of PAHs in die environment is adsorption onto
particulates, especially in media
high in organic content, which tends to reduce their
bioavailability. Higher molecular weight
PAHs are relatively immobile because of the large molecular
volumes and their low volatility
and solubility. Most PAHs can be metabolized by higher organisms
and therefore tend not to
be bioaccumulated over long time periods.
PAHs in water may volatilize, disperse into the water column,
become incorporated into bottom
sediments, concentrate in aquatic biota, or experience chemical
oxidation and biodegradation
(Eisler, 1987). The chemical properties of PAHs suggest that the
most likely fate is adsorption
4-5
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onto suspended paniculate matter, especially particulates high
in organic content. PAHs in
aquatic sediments generally degrade slowly and may persist
indefinitely due to the absence of
penetrating radiation and oxygen. The ultimate fate of PAHs in
sediments is chemical oxidation,
biotransformation or biodegradation by bacteria and other
benthic organisms (Eisler, 1987).
PAHs hi surface soils will likely be volatilized into the
atmosphere. PAHs in subsurface soils
may be assimilated by plants, degraded by soil microorganisms,
or accumulated to relatively
high levels hi the soil. High PAH concentrations in the soil can
lead to high microorganism
populations capable of degrading the compounds (Eisler,
1987)
Biodegradation and biotransformation by benthic organisms,
including microbes and
invertebrates, are the most important biological fate processes
for PAHs in sediments. Most
animals and microorganisms (shellfish and algae are notable
exceptions) can metabolize and
transform PAHs to breakdown products that may ultimately
experience complete degradation
(Eisler, 1987). PAHs of high molecular weights degrade slowly
(half-lives of up to a few years)
by microbes and readily by multicellular organisms (USEPA,
1979). Biodegradation probably
occurs more slowly hi aquatic systems (especially anaerobic
systems) than hi soil (USEPA,
1985).
Some PAHs rapidly bioaccumulate in animals because of the their
high lipid solubility (Eisler,
1987). The rate of bioaccumulation is inversely related to the
rate of PAH metabolism and is
also influenced by the concentration of PAH to which the
organism is exposed. Both rates are
dependent on the size of the specific PAH molecule; PAHs with
less than four rings are readily
metabolized and not bioaccumulated, while PAHs with more than
four rings are more slowly
metabolized and tend to bioaccumulate on a short-term basis
(USEPA, 1979; USEPA 1985;
Eisler, 1987).
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4.2.2 Metals
Assessing the mobility and persistence of metals in
environmental media is complicated and often
difficult because of the many inorganic and organic complexes
and salts they form. In addition,
metals undergo a variety of processes in soils and water, which
include hydrolysis, reduction,
oxidation, and ion exchange. These reactions are highly
dependent on factors such as pH,
salinity, ionic strength, particle-surface reactions, and the
presence of anions and natural organic
acids (humics and fulvics). Many of the metals of concern at
this site are relatively insoluble
either in metallic form or as inorganic complexes and salts yet
become soluble in the presence
of organic acids and oxidizing conditions. Cation exchange of
metals by soils and sediments is
the dominant fate mechanism in natural systems.
Aluminum is one of the most abundant elements in the earth crust
and occurs in nature primarily
as aluminum silicates and aluminum oxide. The direct toxic
potential of aluminum is low
compared to that of many other metals. Mammals and birds can
effectively limit the absorption
of aluminum and excrete any excess (Scheuhammer, 1987).
Scheuhammer (1987) as well as
USEPA (1985) have shown that the direct toxicity of aluminum to
some animal species is
relatively low.
Aluminum is not known to biomagnify hi terrestrial or aquatic
food chains (Wren et al., 1983)
in large part because it is toxic to plants. Soil-to-plant
bioconcentration factors (BCFs) are low,
ranging from 0.00065 to 0.004 (Bysshe, 1988) indicating a low
probability of significant plant
uptake from soil.
Barium readily forms insoluble carbonate and sulfate salts which
have low toxicity (USEPA,
1985). In contrast, soluble barium salts are toxic.
Bioaccumulation is not an important fate
process for barium, but it is an important trace element for
plants. Estimated soil-to-plant BCFs
are 0.015 to 0.15 (Bysshe, 1988).
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Chromium is a heavy metal that is most frequently found in a
trivalent or hexavalent oxidation
state. Chromium (VI) is readily converted to chromium (HI) in
the presence of reducing agents
(USEPA, 1985). Chromium (HI) adsorbs to soil/sediment and
organic paniculate matter and
therefore is generally less mobile than chromium (VI).
Chromium is an essential nutrient that often accumulates in
aquatic organisms at concentrations
higher than ambient water concentrations, but lower than
sediment concentrations. Chromium
accumulates in semi-aquatic and terrestrial organisms as well
(Eisler, 1986). Chromium may
also be transferred through trophic levels (USEPA, 1985).
Although the genus does not occur
at the Barkhamsted site, Giblin et al. (1980) showed that
chromium accumulates in marsh grass
(Spartina spp.). Estimated soil-to-plant BCFs range from 0.0045
to 0.0075 (Bysshe, 1988).
In biological materials, chromium is usually present in the
trivalent form (Eisler, 1986).
According to Eisler (1986), chromium (VI) is generally more
toxic to freshwater species than
chromium (III). Chronic exposure to chromium (VI) has been
demonstrated to reduce growth
rates hi freshwater algae and duckweed and to affect the
survival and growth of cladocerans
(USEPA, 1985). Some salts of chromium are carcinogenic and
chromium (VI) is a teratogen
in hamsters. The toxicity of chromium (III) to mammals is lower
than the toxicity of chromium
(VI) (Eisler, 1986).
Cobalt is an essential element that can be accumulated by plants
and animals although it is not
thought to accumulate to excessive concentrations (USEPA, 1985).
Estimated soil-to-plant BCFs
range from 0.007 to 0.02 (Bysshe, 1988). Soluble cobalt is found
in low concentrations in
aquatic ecosystems. Mobility is limited because cobalt adsorbs
to clay minerals and hydrous
oxides of iron, manganese, and aluminum in the clay fractions of
sediments and soils (USEPA,
1985). Chelation of cobalt with organic compounds also occurs.
Information regarding the
toxicity of cobalt to wildlife is limited.
Copper, an essential element, is accumulated by plants and
animals, although it is not generally
biomagnified (USEPA, 1985). Plants may take up copper from soils
and translocate it from
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roots to edible portions of the plant. Estimated soil-to-plant
BCFs range from 0.25 to 0.40
(Bysshe, 1988). Bysshe (1988) determined that concentrations of
copper hi soils will generally
kill plants before they can accumulate tissue concentrations
that are toxic to grazing animals.
Earthworms bioconcentrate copper and can be negatively affected
via a decrease hi survival,
growth and reproduction rates (Beyer, 1990; M&E, 1992).
Bioconcentration factors vary with
soil concentration (Beyer, 1990). The bioavailability of copper
hi earthworm tissues to predators
is unknown.
Iron is an essential element required by both plants and
animals. Ferrous, or bivalent (Fe++),
and ferric, or trivalent (Fe+++) iron are the primary forms of
concern hi aquatic environments.
The ferrous form can persist hi anaerobic waters. Iron can
persist hi natural organometallic,
humic compounds, or hi colloidal forms. Black or brown swamp
waters may contain iron
concentrations of several mg/1 hi the presence or absence of
dissolved oxygen, but this form of
iron has little effect on aquatic life (USEPA, 1985). The
ingestion of excessive amounts of iron
can produce toxic effects hi mammals (USEPA, 1985). Therefore,
iron is not likely to cause
toxicity hi animals unless it is present at high levels. Iron is
not known to biomagnify within
food chains (Wren et al., 1983), and estimated soil to plant
BCFs are low (0.001 to 0.004)
(Bysshe, 1988).
Lead is a non-essential element that is largely immobile hi
soils (Bysshe, 1988). There is little
translocation from plant roots to edible parts and soil-to-plant
BCFs are estimated at 0.009 to
0.045 (Bysshe, 1988). Adverse effects to terrestrial plants have
been reported (Bysshe, 1988;
Eisler, 1988). Earthworms may bioconcentrate lead (Beyer, 1990;
Roberts and Dorough, 1985)
and lead may be toxic at high concentrations, affecting both
survival and reproductive rate.
Ducks and raptors have been poisoned by ingestion of lead shot.
For example, the American
black duck (Anas rubripes) showed weight loss, emaciation, or
were killed by a single oral lead
dose of 254 mg (Eisler, 1988). However, Eisler (1988) indicated
that adverse effects due to
4-9
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other exposure or dietary routes, such as the consumption of
plant and animal tissues, are less
likely to occur. Food chain magnification of lead is negligible
(Eisler, 1988).
In most natural aquatic systems, manganese is expected to be
present predominantly in the
suspended particulates and sediments as MnO2 or Mn304 or both.
The soluble chelated
manganese in aquatic systems is likely to be less soluble than
free manganese ions. Thus,
although manganese may undergo speciation through chemical and
microbial reactions hi
systems, it may persist for a long period.
Evidence suggests that significant bioaccumulation of manganese
may not occur in organisms
at higher trophic levels (USEPA, 1985). Manganese may, however,
be bioaccumulated at lower
trophic levels, but biomagnification hi food chains is not
likely to be significant (Wren et al.,
1983). Plants may uptake manganese from soils and translocate it
to edible portions of the plant.
Soil-to-plant conversion factors range from 0.05 to 0.25
(Bysshe, 1988). Levels of manganese
in soils will generally kill plants before plants can accumulate
levels that are toxic to most
grazing animals.
Nickel is a non-essential element that is usually present in
nature within mobile and highly
soluble compounds. In organic-rich and polluted waters, sorption
of nickel to other chemicals
is less likely and incorporation into sediment becomes an
important fate process (USEPA, 1985).
Nickel is not significantly accumulated by aquatic organisms
(USEPA, 1985). Bysshe (1988)
estimated a soil-to-plant BCF of 0.06 for nickel.
Silver is a non-essential metal that exists in variety of
chemical forms in aqueous systems.
Reducing conditions of sediment, formation of insoluble silver
sulfides and metallic silver may
reduce the concentration of soluble silver in the water column
(USEPA, 1985). Although silver
is readily bioaccumulated by aquatic plants, invertebrates, and
vertebrates, there is little
magnification of silver through the food chain (USEPA, 1985).
Estimated soil-to-plant BCFs
range from 0.1 to 0.4 (Bysshe, 1988).
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Zinc is an essential element. In nature, the most common form of
zinc is the +2 valence state.
Sorption of the divalent cation by hydrous iron and manganese
oxides, clay minerals, and
organic material removes zinc from the water column. In reducing
environments, precipitation
of zinc sulfide also limits zinc mobility. Zinc is
bioaccumulated because it is an essential
nutrient (USEPA, 1985). Soil-to-plant BCFs estimated by Bysshe
(1988) range from 0.9 to
15.0.
4.2.3 Pesticides
Five pesticides (DDE, DDT, endosulfan II, endrin, and
gamma-chlordane) were identified to be
of concern hi the sediments hi the beaver ponds. Although
several pesticides were present hi
soils surrounding the landfill (Table 3-3), concentrations were
below the screening criteria and
thus were not considered to be of concern.
DDE is a breakdown product of DDT. These chlorinated
hydrocarbons were used extensively
as pesticides hi the United States. Bioaccumulation of DDT and
its breakdown products has
been documented hi a variety of species. Bioaccumulation occurs
via direct absorption by
aquatic organisms through contaminated water. The concentrations
of DDT, DDE, and ODD
biomagnify hi the food chain via transfer of residues through
sequential feeding by predators
(USEPA, 1990).
The DDT series of pesticides is acutely toxic to aquatic
invertebrates and birds, but information
on damage to aquatic plants is limited. However, DDT and DDE
have been found to reduce
the level of photosynthesis hi freshwater algae.
While there is variation, sublethal effects to mammals
attributable to DDT include teratogenic,
mutagenic, and carcinogenic damage. Birds may also be affected
by the DDT series of
pesticides through a decrease hi reproductive rate, hatchling
survivability, shell thickness, and
fecundity, as well as through an increase hi embryo death rate
(USEPA, 1993).
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The chlorinated hydrocarbon endrin is also a very persistent
insecticide. Like DDT and its
metabolites, endrin is very toxic to aquatic organisms and is
known to bioaccumulate in the food
chain, particularly in benthic organisms as a result of the
direct ingestion of contaminated
sediments (Nimmo, 1985). Endrin is acutely toxic to terrestrial
wildlife as well, and has been
utilized as both a rodenticide and avicide. The compound is not
a carcinogen, but has been
shown to be a potent teratogen and reproductive toxin (USEPA,
1985).
Chlordane was also formerly used as a pesticide in the United
States. It is very persistent in the
environment and strongly bioaccumulates in aquatic and
terrestrial organisms. Chlordane
persists in aquatic environments to a greater degree when
organic material is present hi surface
water (USEPA, 1985). Chlordane may sorb to sediment or bind to
soil particles for years after
surface application.
Chlordane is very toxic, particularly for aquatic organisms.
Although biotransformation may
be an important fate of chlordane, it is likely a slow process.
Chlordane appears not to
concentrate extensively in the higher members of the food chain
(USEPA, 1985).
Endosulfan is a pesticide that exists hi alpha (endosulfan I)
and beta (endosulfan II) forms.
Along with the other pesticides described above, it is toxic to
animals other than insects.
Endosulfan has been found to affect the nervous system of
mammals as well as organs and
immune system at low level chronic doses (M&E, 1992).
Reproduction hi animals may also be
affected by endosulfan.
4.2.4 Phenolics
Two phenolic compounds were determined to be contaminants of
concern hi surface water, 2,4
dimethylphenol and 4-methylphenol. Due to high water
solubilities, phenolics will leach from
soils into groundwater or surface water (M&E, 1994).
Volatilization from soils and water is
minimal because of low vapor pressure and low Henry's Law
Constant. Phenolics biodegrade
quickly in soil and water systems under both aerobic and
anaerobic conditions to form simple
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aliphatic alcohol and carboxylic compounds. Degradation of
2,4-dimethylphenol may occur
throughphotooxidation, metal-catalyzed oxidation, sorption,
andbiodegradation(USEPA, 1985).
In unaerated water, absorption onto organic materials may also
be a fate of 2,4-dimethylphenol.
4.3 EXPOSURE SCENARIOS AND INTEGRATED EXPOSURE ANALYSIS
Eight species and one taxa (benthic invertebrates) were selected
as indicators (Table 4-1) to
evaluate the effect of contamination at the site. In this
section, information on existing site
conditions, coupled with additional information on the life
histories of biota utilizing the study
area are integrated to determine the most probable scenarios for
contaminant exposure.
Exposure scenarios are outlined for each indicator species/taxa
group.
4.3.1 Benthic Invertebrates
Benthic invertebrates may be exposed to site contaminants via
sediment or surface water.
Chemicals of concern hi sediments included PAHs, pesticides and
metals. Metals and phenolics
were identified as of concern in surface water. The most likely
exposure scenario involves three
pathways that apply to both sediment and surface water: dermal
contact, absorption through
respiratory surfaces (e.g., gills), and ingestion of
contaminated abiotic media, detritus, or plant
and animal tissue.
4.3.2 Earthworm
The exposure scenario for earthworms (potentially several
species) entails the consumption of
metals and PAHs as they burrow through soil. Neuhauser et al.
(1985) and Thompson (1971),
among others, have documented the toxicity of organic compounds
on the survival of
earthworms. Likewise, there is a wealth of literature on the
bioaccumulation of heavy metals
in earthworms (Diercxsens et al., 1985; Gish and Christensen,
1973; Helmke et al., 1979;
Morgan and Morgan, 1988a; Morgan and Morgan, 1988b). Toxicity
and bioaccumulation data
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from the literature in combination with on-site soil
concentrations will enable a determination
of the level of risk to earthworms.
4.3.3 Green Frog
Frogs (including egg masses and tadpoles) were observed in the
unnamed pond during the June
1993 M&E site visit. The green frog (Rana clamitans
melanota) likely inhabits the site. This
species may be exposed to contaminants hi surface water and
sediment through dermal contact,
absorption through respiratory surfaces, and ingestion of
contaminated abiotic media or detritus.
The green frog may also be exposed to contaminants in soil
through dermal contact or direct
ingestion. Another exposure scenario involves the consumption of
plants (larval stage) and
invertebrates (adult stage) that contain contaminants hi their
tissues. Contaminants of concern
for the green frog include metals, pesticides, PAHs and
phenolics, since frogs are potentially
exposed through pathways that include water, soil, and
sediment.
4.3.4 Spotted Salamander
Salamander larvae were observed in the unnamed brook during the
June 1993 M&E site visit.
According to habitat preference and distribution information hi
DeGraaf and Rudis (1983), the
spotted salamander (Ambystoma maculatum) likely inhabits the
site. As for the green frog, there
are two scenarios for exposure of the spotted salamander to site
contaminants. First, the spotted
salamander may be exposed to contaminants hi soil, surface
water, and sediment through dermal
contact, absorption through respiratory surfaces, and ingestion
of contaminated abiotic media or
detritus. Hibernation within soil may be an important exposure
point for the spotted salamander.
The second exposure scenario involves the consumption of
primarily invertebrate prey that
contain contaminants hi their tissues. Contaminants of concern
for the spotted salamander
include metals, pesticides, PAHs and phenolics.
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4.3.5 American Robin
The exposure scenario for the American robin (Turdus
migratorius) involves the consumption
of earthworms that have accumulated contaminants hi body tissue
and also the incidental
consumption of soil. Contaminants of concern for American robins
include PAHs and metals,
since these were identified as contaminants of concern.
4.3.6 Deer Mouse
The deer mouse (Peromyscus maniculatus) is a common inhabitant
of open areas and is therefore
likely to inhabit the site. The deer mouse may be exposed to
contaminants through dermal
contact with soil or direct ingestion of soil. Nests are
constructed just below ground in a
burrow, under rocks, or in debris.
The deer mouse rarely drinks free water in nature (Jones and
Birney, 1988) and would not likely
contact sediments. Consumption of food items (primarily seeds
and invertebrates) that contain
tissue contaminants is a second exposure pathway. Deer mice are
unlikely to consume
significant quantities of contaminants hi vegetative forage.
Chemicals of concern for deer mice
include metals and PAHs, since these were identified as COCs in
soil.
4.3.7 Woodchuck
Woodchucks (Marmota monax) are typical inhabitants of forest
edges and open habitat. OBG
biologists observed a woodchuck burrow on-site during the Phase
1A site characterization (OBG,
1993). Woodchucks burrow hi the ground and are herbivorous. They
may be exposed to si