baseline risk assessment, part 2, ecological risk assessment · part ii ecological risk assessment...
TRANSCRIPT
-
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
Q>
-
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
-
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
-
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
-
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:
1-1
-
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).
1-2
-
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
1-3
-
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
-
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
2-1
-
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.
2-2
-
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
-
• 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.
3-2
-
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).
3-3
-
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.
3-4
-
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.
3-5
-
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).
3-6
-
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.
3-7
-
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
-
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.
3-9
-
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.
3-10
-
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.
3-11
-
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
-
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
-
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
-
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
-
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
-
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.
4-4
-
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
-
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).
4-6
-
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).
4-7
-
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
4-8
-
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
-
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).
4-10
-
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).
4-11
-
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
4-12
-
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
4-13
-
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.
4-14
-
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