Super fund Proposed Plan
U.S. Environmental Protection Agency, Region 2
Peninsula Boulevard Groundwater Contamination Superfund site
Nassau County, New York
July 2011
EPA ANNOUNCES PROPOSED PLAN
This Proposed Plan describes the remedial alternatives
considered for the contaminated groundwater at the
Peninsula Boulevard Groundwater Contamination
Superfund site and identifies the preferred remedy with
the rationale for this preference. This Proposed Plan was
developed by the U.S. Environmental Protection Agency
(EPA) in consultation with the New York State
Department of Environmental Conservation (NYSDEC).
EPA is issuing this Proposed Plan as part of its public
participation responsibilities under Section 117(a) of the
Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA) of 1980, as
amended, and Sections 300.430(f) and 300.435(c) of the
National Oil and Hazardous Substances Pollution
Contingency Plan (NCP). The nature and extent of the
contamination at the site and the remedial alternatives
summarized in this Proposed Plan are described in the
June 2011 Remedial Investigation (RI) Report and
Feasibility Study (FS) Report, respectively. EPA and
NYSDEC encourage the public to review these
documents to gain a more comprehensive understanding
of the site and the Superfund activities that have been
conducted.
This Proposed Plan is being provided as a supplement to
the above-noted documents to inform the public of EPA
and NYSDEC's preferred remedy and to solicit public
comments pertaining to all of the remedial alternatives
evaluated, including the preferred alternative. EPA and
NYSDEC's preferred alternative involves the extraction
and on-site treatment of contaminated groundwater. The
treated groundwater effluent would be disposed by
discharge to a waste-water treatment plant, surface water
or reinjection to groundwater.
The remedy described in this Proposed Plan is the
preferred remedy for the site. Changes to the preferred
alternative or a change from the preferred alternative to
another alternative may be made if public comments or
additional data indicate that such a change will result in
a more appropriate remedial action. The final decision
regarding the selected remedy will be made after EPA
has taken into consideration all public comments. EPA
is soliciting public comment on all of the alternatives
considered in the Proposed Plan and in the detailed
analysis section of the FS report, since EPA and NYSDEC
may select a remedy other than the preferred alternative.
MARK YOUR CALENDAR
PUBLIC COMMENT PERIOD:
July 28, 2011 -August 27, 2011
EPA will accept written comments on the Proposed Plan
during the public comment period.
PUBLIC MEETING: August 3, 2011 at 7:00 pm
EPA will hold a public meeting to explain the Proposed
Plan and all of the alternatives presented in the Feasibility
Study. Oral and written comments will also be accepted at
the meeting. The meeting will be held at the Village of
Hewlett High School, 60 Everit Avenue, Hewlett, NY.
COMMUNITY ROLE IN SELECTION PROCESS
EPA and NYSDEC rely on public input to ensure that the
concerns of the community are considered in selecting an
effective remedy for each Superfund site. To this end, the
RI and FS reports and this Proposed Plan have been made
available to the public for a public comment period which
begins on July 28, 2011 and concludes on August 27,
2011.
A public meeting will be held during the public comment
period at the Hewlett High School on August 3, 2011 at
7:00 p.m. to present the conclusions of the RI/FS, to
elaborate further on the reasons for recommending the
preferred alternative, and to receive public comments.
INFORMATION REPOSITORIES
Copies of the Proposed Plan and supporting
documentation are available at the following information
repositories:
Hewlett-Woodmere Public Library
1125 Broadway
Hewlett, New York 11557-0903
Telephone: (516)374-1967
Hours of operation:
Mon-Thurs 9 am - 9 pm
Fri 9-6, Sat 9 am - 5 pm, Sun 12:30 pm - 5 pm
USEPA-Region II
Superfund Records Center
290 Broadway, 18th Floor
New York, New York 10007-1866
(212)637-4308
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Comments received at the public meeting, as well as
written comments, will be documented in the
Responsiveness Summary Section of the Record of
Decision (ROD), the document which formalizes the
selection of the remedy.
Written comments on the Proposed Plan should be
addressed to:
Gloria M. Sosa
Remedial Project Manager
Western New York Remediation Section
U.S. Environmental Protection Agency
290 Broadway, 20th Floor
New York, New York 10007-1866
telephone: (212) 637-4283
fax: (212) 637-3966
e-mail: sosa.gloriaigiepa.gov
SCOPE AND ROLE OF ACTION
The primary objectives of this action are to remediate the
groundwater contamination, to minimize the migration
of contaminants, and to minimize any potential future
health and environmental impacts. This Proposed Plan
addresses groundwater contamination, designated
Operable Unit 1 (OU 1) at the site. EPA is currently
conducting an RI to identify and delineate the potential
source(s) of the tetrachloroethylene (PCE)
contamination, designated Operable Unit 2 (OU 2). A
final remedy to address the source contamination will be
presented in a future Proposed Plan and Record of
Decision.
SITE BACKGROUND
Site Description
The Peninsula Boulevard Groundwater Plume
Superfund Site (the Site) consists of the area within and
around a groundwater plume located in the Village of
Hewlett, Town of Hempstead, Nassau County, New
York. John F. Kennedy International Airport is located
approximately three miles to the west of the Site. A
Site location map is provided as Figure 1.
The area consists of a mix of commercial and
residential properties, with the majority of the
commercial properties being located along Mill Road,
Peninsula Boulevard, Broadway, and West Broadway.
Woodmere Middle School is located along the western
site boundary. Portions of Motts Creek, Doxey Brook
Drain, and an unnamed tributary leading to Motts Creek
are located within the Site.
The residences in the area of the Site are serviced by the
Long Island American Water Company (LIAWC). The
LIAWC operates a well field approximately 1000 feet
north of the Site. The water delivered to these residents is
a blend of water from several well fields. Since 1991,
LIAWC has been treating groundwater pumped from this
well field with an air stripper prior to distribution. Based
on a records review of water supply wells in the area,
private wells are not utilized for drinking water in the
area.
Site History
A series of investigations and removal actions from 1991
to 1999 on behalf of the owner of the former Grove
Cleaners and the NYSDEC revealed an extensive
groundwater contaminant plume extending both to the
north and south of Peninsula Boulevard, primarily
consisting of the chlorinated volatile organic compound
(CVOC) PCE.
The investigation revealed that operations at the former
Grove Cleaners, located at 1274 Peninsula Boulevard,
from 1987 to 1992 resulted in the disposal of hazardous
wastes, including the volatile organic compounds (VOCs)
PCE and trichloroethylene (TCE) to the environment. In
March 1991, the Nassau County Department of Health
(NCDH) cited Grove Cleaners for discharging hazardous
waste into on-site dry wells. PCE was detected in soil and
sludge samples collected at the Grove Cleaners site, and in
other media at and near the property. The results of the
investigation suggested the potential for additional source
areas other than the former Grove Cleaners site.
Following the implementation of interim remedial
measures, which consisted of the removal of impacted
soils related to solvent discharge to a dry well, a No
Further Action remedy was selected by NYSDEC in
March 2003 for the former Grove Cleaners site.
On March 7, 2004, EPA proposed inclusion of the Site on
the National Priorities List (NPL) and on July 22, 2004,
EPA placed the Site on the NPL.
EPA conducted an RI at the Site from 2005 through 2010.
Environmental sampling of groundwater, surface water,
soil and sediment was performed and a Data Evaluation
Report (DER) presenting the results of the environmental
sampling was prepared in October 2008. Supplemental RI
work was conducted at the Site in 2010 to address data
gaps including hydrogeological sampling and analyses,
and to develop a baseline human health risk assessment
(HHRA) and screening-level ecological risk assessment
(SLERA). A DER Addendum was issued in December
2010 presenting the results of this sampling. A RI Report
was released in June 2011.
The RI identified groundwater contaminated with PCE,
PCE breakdown products and low levels of other VOCs.
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The source of the PCE groundwater contamination has
not yet been identified.
Site Hydrogeology
The Upper Glacial Aquifer (UGA) underlies the Site.
Groundwater flow in the UGA is dominated by a
groundwater divide located approximately 2000 feet
south of Peninsula Boulevard, along a low ridge trending
southwest to northeast. North of the divide, groundwater
flow is both north and west, depending upon depth.
South of the divide, groundwater flow within the UGA
southward toward Macy Channel.
North of the Site, the UGA overlies the Jameco Aquifer.
In this area of Long Island, the Jameco Aquifer is
limited in extent, but is an important water-bearing zone
because of its high hydraulic conductivity on the order
of 200 feet per day. The LIAWC Plant #5 Well Field
adjacent to the Site utilizes the Jameco as its source
aquifer and does not utilize the UGA for water
production. Given the similar hydraulic properties of
the UGA and Jameco, there is the potential for
significant hydraulic connection between the two units.
However, data obtained as a result of the supplemental
RI activities indicate that the Gardiners Clay acts as a
confining unit in the localized area of the Site and the
LIAWC well field.
The inter-bedded nature of sediments in the UGA
suggests significant vertical and horizontal variability in
hydraulic conductivity values. The "20-foot clay" is a
discontinuous, semi-confining layer which separates the
UGA into an upper and lower zone in some areas of the
Site.
The depth to groundwater within the unconfined portion
of the UGA ranges from approximately 3 to 15 feet
below ground surface (bgs), while ranging from 6 to 17
feet bgs in the semi-confined portion of aquifer.
Saturated thickness of the unconfined UGA above the
"20-foot clay" layer ranges from 10 to 30 feet. Saturated
thickness of the deeper portion of the UGA below the
"20-foot clay", including the pressure head component
caused by the semi-confined conditions, is
approximately 55 to 65 feet.
RESULTS OF THE REMEDIAL INVESTIGATION
The results of the RI indicate that the shallow and deep
portions of the UGA have been impacted by CVOC
contamination. The shallow UGA groundwater (0 to 30
feet bgs) PCE plume is approximately 3,500 feet long,
oriented in a north-south direction. South of Peninsula
Boulevard (upgradient), the plume is approximately
1,000 feet wide and north of Peninsula Boulevard
(downgradient) the plume is approximately 400 feet wide.
(See Figures 2 & 3)
The deep UGA (40 to 75 feet bgs) groundwater plume is
approximately 1,110 feet long, oriented in a northeast-
southwest direction.
Groundwater
EPA conducted a Membrane Interface Probe (MIP)
investigation and Hydropunch® sampling at the Site in
2006 and 2007. A total of 160 groundwater samples
were collected from 61 locations. The results of this
effort assisted EPA in selecting locations for the
installation of groundwater-monitoring wells. Twenty-
six monitoring wells were installed at the Site and several
rounds of sampling were conducted in 2007, 2008, 2010,
and 2011. Analytical results for these samples were
compared to the EPA and New York State Department of
Health (NYSDOH) promulgated health-based protective
Maximum Contaminant Levels (MCLs), which are
enforceable standards for various drinking water
contaminants.
Groundwater contamination exceeding applicable
drinking water standards has been shown to exist within
the Site plume area, at highly elevated concentrations in
some areas. Chlorinated VOCs, PCE in particular, were
identified as the plume-related contaminants of concern
for the shallow and deep portions of the UGA at the Site.
Seven VOCs were detected at concentrations exceeding
applicable criteria. Specifically, PCE was detected at
levels up to 30,000 micrograms per liter (ug/1) and TCE,
at concentrations up to 10,000 ug/1.
The RI groundwater data indicate that the Site
contaminant plume in the deep portion of the UGA,
dominated by PCE, appears stable and centered in the
south-central portion of the Site.
Information obtained from LIAWC and the results of EPA
sampling at new production wells on LIAWC Plant #5
property in October 2010 indicate that the Plant #5 Well
Field has contamination similar to that found in the Site
plume and, therefore, may have been impacted by the
contamination from the Site.
An engineering control (air stripper) is maintained at the
Plant #5 Well Field by LIAWC. The treated groundwater
is tested and monitored by LIAWC in accordance with
New York State and Nassau County rules and
regulations. No MCL exceedances of chlorinated VOCs
in water distributed to the general public have been
identified during the RI.
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The results of the RI indicate that the potential for
natural attenuation of chlorinated compounds varies
across the Site. PCE daughter products were not
consistently detected in the same groundwater wells as
PCE. Given site-specific conditions, natural attenuation
of CVOCs does not appear to be a dominant process in
the subsurface.
Surface Water, Soils and Sediments
The RI included sampling of soil at depths of 0-10 feet
bgs. Surface soil (0-2 ft bgs) samples were collected at
locations along the long axis (N-S) of the plume and in
areas of elevated exposure potential. Subsurface soil
sample locations were co-located with the Membrane-
Interface Probe (MIP) and Hydropunch® groundwater
sampling locations.
Surface water and sediment samples were collected
from the Doxey Brook Drain, Motts Creek and the
unnamed waterway. There were no exceedances of
applicable criteria for plume-related compounds in
surface water or sediment samples. No VOCs were
detected in surface soil and no plume-related VOCs
exceeded screening criteria in subsurface soil.
Vapor Intrusion
EPA is investigating the soil vapor intrusion pathway at
the Site. VOC vapors released from contaminated
groundwater and/or soil have the potential to move
through the soil and seep through cracks in basements,
foundations, sewer lines and other openings.
EPA conducted vapor intrusion sampling at fifteen
residences at the Site. EPA drilled through the sub-slabs
in the basements and installed ports in order to sample
the soil vapor under these residences. Sampling devices
called Summa canisters were attached to these ports to
collect air at a slow flow rate over a twenty-four hour
period. Summa canisters were also placed outside
several residences to determine if there were any outdoor
sources that may impact indoor air. The Summa
canisters were then collected and sent to a laboratory for
analyses.
The results of the analyses indicated that one residence
had concentrations of VOCs at or above EPA Region 2
screening levels in sub slab and indoor air. EPA
installed a sub-slab depressurization system at this
residence in 2009 to mitigate the impacts of soil vapor
intrusion by reducing or eliminating vapor entry into the
building. EPA sampled indoor air in this residence in
2010 and VOCs were not detected in indoor air.
In addition to sampling residences for soil vapor intrusion,
EPA sampled the North Woodmere Middle School in
2004 using a mobile laboratory to analyze the results.
PCE was not detected in the basement, the area through
which vapors would enter the building if there were vapor
intrusion impact from the groundwater plume (there is no
slab in the basement, but a dirt floor). No PCE was
detected in the classrooms or the auditorium. PCE was
detected in trace levels in the art room and in the drains in
a bathroom (possibly from art supplies and personal
hygiene products such as hair gel). The trace levels
detected (0.15 - 0.35 parts per billion or ppb) do not pose
any health concern.
EPA will continue to investigate the soil vapor intrusion
pathway at the Site.
Source Investigation
The source of the PCE contamination was not identified
during the OU 1 RI. Groundwater-plume characteristics
(areal extent and relative concentrations) appear to
indicate a potential source area at in the area along West
Broadway. The wider width of the plume south of
Peninsula Boulevard may be the result of comingling of
contaminant plumes from additional upgradient source
areas, radial groundwater flow induced from pumping, or
the flat groundwater surface. EPA is currently conducting
an OU 2 RI in order to delineate the source(s) of the
groundwater contamination.
RISK SUMMARY
As part of the RI, EPA conducted a baseline risk
assessment to estimate the current and future effects of
contaminants on human health and the environment. A
baseline risk assessment is an analysis of the potential
adverse human health and ecological effects of releases of
hazardous substances from a site in the absence of any
actions or controls to mitigate such releases, under current
and future land, groundwater, surface water and sediment
uses. The baseline risk assessment includes a Human-
Health Risk Assessment (HHRA) and an ecological risk
assessment.
The cancer risk and non-cancer health hazard estimates in
the HHRA are based on current reasonable maximum
exposure scenarios and were developed by taking into
account various health protective estimates about the
frequency and duration of an individual's exposure to
chemicals selected as chemicals of potential concern
(COPCs), as well as the toxicity of these contaminants.
Cancer risks and non-cancer health hazard indexes (His)
are summarized below (please see the text box on page 6
for an explanation of these terms).
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The Site is currently a residential neighborhood, with
some nearby properties designated as mixed commercial.
Future land use is expected to remain the same. The
baseline risk assessment began by selecting COPCs in
the various media that would be representative of Site
risks. The media evaluated as part of the human health
risk assessment included soil (0-10 feet), groundwater,
and surface water and sediment from the Doxy Brook
Drain, Motts Creek and the unnamed waterway.
Groundwater at the Site is designated by NYSDEC as a
potable water supply. The chemicals of concern (COCs)
for the Site are cis-l,2-dichloroethylene (cis-l,2-DCE),
PCE, TCE, and vinyl chloride (VC) for groundwater
pathways.
The baseline risk assessment evaluated health effects
that could result from exposure to contaminated media
though use of groundwater for potable purposes
(including inhalation of vapors in the bathroom after
showering), direct exposure to groundwater in an
excavation trench, wading in Site waterways, direct
contact exposure to surface (0-2 feet) and subsurface soil
(2-10 feet), and inhalation of vapors from surface soils.
Based on the current zoning and anticipated future use,
the risk assessment focused on a variety of possible
receptors, including current and future recreational users,
future residents, future commercial workers and future
construction workers. However, consistent with the
anticipated future use of the Site, the receptors most
likely to be in contact with media impacted by site-
related contamination [e.g., groundwater] were primarily
considered when weighing possible remedies for the
Site.
These include the future residents, future commercial
workers and future construction workers. A complete
discussion of the exposure pathways and estimates of
risk can be found in the Human Health Risk Assessment
for the Site in the information repository.
A screening-level ecological risk assessment (SLERA)
was conducted to evaluate the potential for ecological
effects from exposure to surface soil, surface water and
sediment. Surface soil, surface water, and sediment
concentrations were compared to ecological screening
values as an indicator of the potential for adverse effects
to ecological receptors. A complete summary of the
methodology utilized can be found in the Screening
Level Ecological Risk Assessment for the Site in the
information repository.
The results of the RI indicated that sediments and soils
were not contaminated with site-related contaminants;
therefore, no risks were calculated for exposure to Site
sediments or soils. Exposure to surface waters did not
pose an unacceptable cancer risk or non-cancer hazard.
EPA is currently conducting an ongoing investigation of
vapor intrusion into structures within the area that could
be potentially affected by the groundwater contamination
plume. To date, one home has received a sub-slab
depressurization system to mitigate vapors entering the
home. If results of current or future sampling of other
homes indicate the presence of site-related vapors above
protective levels, EPA would expect to implement similar
measures.
Human Health Risk Assessment
EPA's statistical analysis of ground water sampling data
found that the average exposure concentration of cis-1,2-
DCE, PCE, TCE, and VC in the groundwater were 710
ug/1, 11,000 ug/1, 920 ug/1, and 59 ug/1, respectively. All
are in excess of EPA's Safe Drinking Water Act MCLs of
70 ug/1, 5 ug/1, 5 ug/1, and 2 ug/1, respectively; these
concentrations also exceed the NYSDOH MCLs, which
are 5 ug/1 for cis-l,2-DCE, PCE, and TCE, and 2 ug/1 for
VC. These concentrations are associated with an excess
lifetime cancer risk 2 x 10"1 for the future adult and child
resident and 2 x 10"2 for the future commercial worker.
The calculated non-carcinogenic hazard quotients (HQs)
are: future adult resident HQ=300, future child resident
HQ=600 and future commercial worker HQ=50.
These cancer risks and non-cancer health hazards indicate
that there is significant potential risk to potentially
exposed populations from direct exposure to groundwater
or and groundwater vapors. For these receptors, exposure
to groundwater results in either an excess lifetime cancer
risk that exceeds EPA's target risk range of 10"4 to 10"6 or
an HI above the acceptable level of 1, or both. The
chemicals in groundwater that contribute most
significantly to the cancer risk and non-cancer hazard are
cis-l,2-DCE, PCE, TCE, and VC.
Ecological Risk Assessment
The SLERA focused on potential exposure to plume-
related contaminants (i.e., CVOCs). The CVOCs
identified in the surface water, interstitial water and/or
sediments include cis-DCE; methylene chloride; PCE;
TCE, and VC. While other contaminants were detected in
environmental samples, these other compounds and their
concentrations may be indicative of the urbanized nature
of the area and are not considered site-specific
contaminants.
The ecologic receptors evaluated in the risk assessment
included benthic macroinvertebrates in the aquatic
environment and birds and small mammals in the
terrestrial environment. Birds that were observed using
the Site included mallard duck, American robin, red-
winged blackbird, common grackle, double-crested
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WHAT IS RISK AND HOW IS IT CALCULATED?
Human Health Risk Assessment: A Superfund baseline human
health risk assessment is an analysis of the potential adverse
health effects caused by hazardous substance releases from a
site in the absence of any actions to control or mitigate these
under current- and future-land uses. A four-step process is
utilized for assessing site-related human health risks for
reasonable maximum exposure scenarios.
Hazard Identification: In this step, the chemicals of potential
concern (COPCs) at the site in various media (i.e., soil,
groundwater, surface water, and air) are identified based on such
factors as toxicity, frequency of occurrence, and fate and
transport of the contaminants in the environment, concentrations
of the contaminants in specific media, mobility, persistence, and
bioaccumulation.
Exposure Assessment: In this step, the different exposure
pathways through which people might be exposed to the
contaminants in air, water, soil, etc. identified in the previous step
are evaluated. Examples of exposure pathways include
incidental ingestion of and dermal contact with contaminated soil
and ingestion of and dermal contact with contaminated
groundwater. Factors relating to the exposure assessment
include, but are not limited to, the concentrations in specific media
that people might be exposed to and the frequency and duration
of that exposure. Using these factors, a "reasonable maximum
exposure" scenario, which portrays the highest level of human
exposure that could reasonably be expected to occur, is
calculated.
Toxicity Assessment: In this step, the types of adverse health
effects associated with chemical exposures, and the relationship
between magnitude of exposure and severity of adverse effects
are determined. Potential health effects are chemical-specific
and may include the risk of developing cancer over a lifetime or
other non-cancer health hazards, such as changes in the normal
functions of organs within the body (e.g., changes in the
effectiveness of the immune system). Some chemicals are
capable of causing both cancer and non-cancer health hazards.
Risk Characterization: This step summarizes and combines
outputs of the exposure and toxicity assessments to provide a
quantitative assessment of site risks for all COPCs. Exposures
are evaluated based on the potential risk of developing cancer
and the potential for non-cancer health hazards. The likelihood of
an individual developing cancer is expressed as a probability. For
example, a 10"4 cancer risk means a "one-in-ten-thousand excess
cancer risk"; or one additional cancer may be seen in a population
of 10,000 people as a result of exposure to site contaminants
under the conditions identified in the Exposure Assessment.
Current Superfund regulations for exposures identify the range for
determining whether remedial action is necessary as an individual
excess lifetime cancer risk of 10"4 to 10"6, corresponding to a
one-in-ten-thousand to a one-in-a-million excess cancer risk. For
non-cancer health effects, a "hazard index" (HI) is calculated.
The key concept for a non-cancer HI is that a "threshold"
(measured as an HI of less than or equal to 1) exists below which
non-cancer health hazards are not expected to occur. The goal
of protection is 10"6 for cancer risk and an HI of 1 for a non-cancer
health hazard. Chemicals that exceed a 10"4 cancer risk or an HI
of 1 are typically those that will require remedial action at the site
and are referred to as Chemicals of Concern or COCs in the final
remedial decision or Record of Decision.
cormorant, blue jay, mourning dove, white-throated
sparrow, green-winged teal, black-capped chickadee,
tufted titmouse, northern flicker, song sparrow, Canada
goose, northern cardinal, house sparrow, house finch,
European starling, and killdeer. Mammals that were
observed included Norway rat, raccoon and gray squirrel.
Potential risks were not quantified for each observed
species, however, the risk for each category of species was
estimated using a receptor species (e.g., raccoon) or
species groups (e.g., benthic macroinvertebrates) as
surrogates to represent the various components of the
ecological community.
The ecological receptors were assumed to be exposed to
CVOCs in surface waters, interstitial waters and
sediments. However, it was assumed that the ecological
receptors would not be exposed directly to groundwater
resources. Additionally, it should be noted that VOCs
were not detected in surface soil samples. Therefore, it is
assumed that there was no contamination of these soils
from the groundwater plume by the contaminants of
concern.
The SLERA analyses included the comparison of the
maximum concentrations of the contaminants of potential
concern with the most appropriate, conservative
ecological screening values that were identified for these
compounds for each of the media of interest. The
comparison of the maximum concentrations of each
contaminant detected in the surface water, interstitial
water, sediment, and surface soil with the ecological
screening value(s) for each media medium did not reveal
any contaminants in excess of these screening values.
Additionally, none of the contaminants of interest are
known to bioconcentrate, biomagnify, or bioaccumulate.
Based on the results of the SLERA, concentrations of
contaminants detected in surface water, interstitial water,
sediment and surface soil at the Site are unlikely to pose
any unacceptable risks to aquatic or terrestrial ecological
receptors at the Site.
Summary of Human Health and Ecological Risks
The results of the human health risk assessment indicate
that the contaminated groundwater presents an
unacceptable exposure risk. The screening-level
ecological risk assessment indicated that the Site does not
pose any unacceptable risks to aquatic or terrestrial
ecological receptors.
Based upon the results of the RI and the risk assessment,
EPA has determined that actual or threatened releases of
hazardous substances from the Site, if not addressed by
the preferred remedy or one of the other active measures
considered, may present a current or potential threat to
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human health and the environment. It is the EPA's
current judgment that the Preferred Alternative
identified in the Proposed Plan is necessary to protect
public health or welfare or the environment from actual
or threatened releases of hazardous substances into the
environment.
REMEDIAL ACTION OBJECTIVES
Remedial action objectives (RAOs) are specific goals to
protect human health and the environment. These
objectives are based on available information and
standards, such as applicable or relevant and appropriate
requirements (ARARs), to-be-considered guidance, and
site-specific risk-based levels.
The following remedial action objectives for
contaminated groundwater (OU 1) will address the
human health risks and environmental concerns:
• Restore the impacted aquifer to beneficial use as
a source of drinking water by reducing
contaminant levels to the federal and State
MCLs; and,
• Reduce or eliminate the potential for migration
of contaminants towards the LIAWC.
The following remedial action objective for soil vapor
will address the human health risks and environmental
concerns:
• Address existing or potential future exposure
through inhalation of vapors migrating from
contaminated groundwater into buildings at the
Site.
SUMMARY OF REMEDIAL ALTERNATIVES
CERCLA §121(b)(l), 42 U.S.C. §9621(b)(l), mandates
that remedial actions must be protective of human
health and the environment, cost-effective, comply with
ARARS, and utilize permanent solutions and alternative
treatment technologies and resource recovery
alternatives to the maximum extent practicable. Section
121(b)(l) also establishes a preference for remedial
actions which employ, as a principal element, treatment
to permanently and significantly reduce the volume,
toxicity, or mobility of the hazardous substances,
pollutants and contaminants at a site. CERCLA §121(d),
42 U.S.C. §9621(d), further specifies that a remedial
action must attain a level or standard of control of the
hazardous substances, pollutants, and contaminants,
which at least attains ARARs under federal and state
laws, unless a waiver can be justified pursuant to
CERCLA §121(d)(4), 42 U.S.C. §9621(d)(4).
Detailed descriptions of the remedial alternatives for
addressing the contamination associated with the Site can
be found in the FS report. The FS report presents four
groundwater alternatives, including a no action alternative.
Based on the screening analyses and evaluations
performed in the initial stages of the FS, remedial
alternatives G3 and G5 were screened out of the final
alternatives which are discussed below.
The construction time for each alternative reflects only the
time required to construct or implement the remedy and
does not include the time required to design the remedy,
negotiate the performance of the remedy with any
potentially responsible parties, or procure contracts for
design and construction.
Common Elements
All of the alternatives, with the exception of the no action
alternative, include monitored natural attenuation (MNA)/
long-term monitoring to address areas of the plumes
outside of the active remediation areas, and institutional
controls for groundwater use restrictions. Monitored
natural attenuation is a variety of in-situ processes which,
under favorable conditions, act without human
intervention to reduce the mass, toxicity, mobility,
volume, or concentration of contaminants in groundwater.
Alternative 1: No Action
The National Oil and Hazardous Substance Pollution
Contingency Plan (NCP) requires that a "No Action"
alternative be developed as a baseline for comparing other
remedial alternatives. Under this alternative, there would
be no remedial actions conducted at the Site to control or
remove groundwater contaminants. This alternative does
not include monitoring or institutional controls.
Because this alternative would result in contaminants
remaining above levels that allow for unrestricted use and
unlimited exposure, CERCLA requires that the Site be
reviewed at least once every five years. If justified by the
review, additional response actions may be implemented.
Capital Cost:
Annual O&M Costs:
Present-Worth Cost:
Construction Time:
$0
$0
$0
Not Applicable
Alternative G2: Enhanced Bioremediation
Capital Cost:
Annual O&M Costs:
Present-Worth Cost:
Construction Time:
$4,344,000
$835,000
$15,830,000
9-12 months
-------
This remedial alternative consists of implementing
enhanced bioremediation in the plume area. Enhanced
bioremediation is the process of destruction of
contaminants by microorganisms in contaminated soil
and water. Microrganisms consume organic substances
for nutrients and energy. Enhanced bioremediation
involves creating the proper conditions by injecting
microorganisms or nutrients to the subsurface to
accelerate the biodegradation of the CVOC
contamination. The end products include carbon
dioxide, water and microbial cell mass. Monitoring of
biogeochemical parameters is used to monitor the
effectiveness of remediation.
Enhanced bioremediation can be implemented in
different system configurations. For the purposes of
developing a conceptual design and cost estimate for
comparison with other technologies in the FS, a transect
configuration was evaluated. This conceptual design
would require the installation of approximately 146
permanent injection wells to remediate contamination in
the shallow UGA plume and 78 permanent injection
wells to remediate contamination in the deeper UGA.
This conceptual design would require further evaluation
during the remedial design if chosen to be implemented.
Additional wells would have to be installed to monitor
the progress of the remediation. This alternative is
expected to remove the contaminant mass within eight to
16 years in the shallow UGA plume remediation area
and within 25 to 50 years in the deep UGA plume
remediation area.
Alternative G4: In-Well Air Stripping
Capital Cost:
Annual O&M Costs:
Present-Worth Cost:
Construction Time:
$7,730,000
$730,000
$16,710,000
9-12 months
This remedial alternative includes the installation of in-
well air stripping systems over the plume area. In-well
air stripping is a physical treatment technology whereby
air is injected into a vertical well that is installed and
screened at two depths in the groundwater. Pressurized
air is injected into the well below the water table,
aerating the water. The aerated water rises in the well
and flows out of the system at the upper screen, inducing
localized movement of groundwater into (and up) the
well as contaminated groundwater is drawn into the
system at the lower screen. VOCs vaporize within the
well at the top of the water table, where the air bubbles
out of water. The contaminated vapors accumulating in
the wells are collected via vapor extraction contained
within the well. Typically, extracted vapors are treated
(if necessary) above grade and discharged to the
atmosphere. Vapor treatment, if required, generally
consists of vapor-phase granular activated carbon (GAC).
The partially treated groundwater is never brought to the
surface; it is forced into the unsaturated zone, and the
process is repeated as water follows a hydraulic
circulation pattern that allows continuous cycling of
groundwater. As groundwater circulates through the
treatment system in-situ, and vapor is extracted,
contaminant concentrations are reduced.
In-well air stripping can be implemented in different
system configurations. For the purposes of developing a
conceptual design and cost estimate for comparison with
other technologies in the FS, a grid configuration was
evaluated. This conceptual design would require the
installation of approximately 80 permanent air stripping
wells to remediate contamination in the shallow UGA
plume and 30 permanent air stripping wells to remediate
contamination in the deeper UGA. This conceptual design
would require further evaluation during the remedial
design if chosen to be implemented. Additional wells
would have to be installed to monitor the progress of the
remediation. This alternative is expected to remove the
contaminant mass within five to 10 years in the shallow
UGA plume remediation area and within 10 to 20 years in
the deep UGA plume remediation area.
Alternative G6: Groundwater Pump and Treat
Capital Cost:
Annual O&M Costs:
Present-Worth Cost:
Construction Time:
$2,997,000
$1,185,000
$21,560,000
6-9 months
This remedial alternative consists of the extraction of
groundwater via pumping wells and treatment prior to
disposal. Groundwater is pumped to remove contaminant
mass from areas of the aquifer with elevated PCE
concentrations. Pumping from downgradient wells will
provide hydraulic control of the contaminated
groundwater with lower PCE concentrations. For this
conceptual design, it is estimated that nine groundwater
extraction wells would be installed in the shallow and
deep UGA. A treatment plant with the capacity of
approximately 350 (gallons per minute) gpm would be
constructed within or nearby the Site to achieve the mass
removal and hydraulic control objectives. Extracted
groundwater with VOC contamination is typically treated
with either liquid phase GAC or air stripping, or both. Air
stripper effluent air stream may be treated with vapor
phase GAC, if necessary. During the remedial design, a
determination will be made whether to discharge treated
extracted groundwater to a publically owned treatment
works (POTW), surface water or reinjection to
groundwater.
-------
In-situ chemical treatment would be utilized to enhance
the groundwater pump and treat remedy, as appropriate.
During the remedial design, a treatability study would be
performed to evaluate the use of in-situ chemical
treatment, either in-situ chemical oxidation (ISCO) or in-
situ chemical reduction (ISCR). The results of the study
would be used to design the in-situ chemical treatment
component of this alternative in a manner that
complements and improves the effectiveness of the
groundwater extraction and treatment component.
ISCO is a process that involves the injection of reactive
chemical oxidants (such as Peroxide, Fenton's Reagent,
Permanganate) into the subsurface for rapid contaminant
destruction. Oxidation of organic compounds using
ISCO is rapid and exothermic and results in the
reduction of contaminants to primarily carbon dioxide
and oxygen. ISCR uses chemical reductants such as
zero-valent iron (ZVI). The ZVI donates electrons,
acting as the reductant in a reaction that removes
chlorine atoms from chlorinated hydrocarbon
contaminants such as PCE.
In-situ chemical treatments, such as ISCO and ISCR
were evaluated in the initial stages of the FS, but were
screened out of the final alternatives as stand-alone
remedies, because of the difficulty in implementation in
a residential neighborhood, specifically obtaining access
to residential properties. However, the use of in-situ
chemical treatments targeting areas containing high
concentrations of PCE that may reside outside the radius
of influence of the pump within the inferred plume, as
appropriate, in combination with groundwater extraction
could potentially reduce the remediation time frames and
the costs of this alternative.
EVALUATION OF ALTERNATIVES
During the detailed evaluation of remedial alternatives,
each alternative is assessed against nine evaluation
criteria, namely, overall protection of human health and
the environment, compliance with applicable or relevant
and appropriate requirements, long-term effectiveness
and permanence, reduction of toxicity, mobility, or
volume through treatment, short-term effectiveness,
implementability, cost, and state and community
acceptance. Refer to the table on the next page for a
description of the evaluation criteria.
This section of the Proposed Plan profiles the relative
performance of each alternative against the nine criteria,
noting how each compares to the other options under
consideration. A detailed analysis of alternatives can be
found in the FS Report.
Overall Protection of Human Health and the
Environment
All of the alternatives except Alternative Gl (No Action)
would provide protection of human health and the
environment. Alternatives G2, G4, and G6 are active
remedies that address groundwater contamination and
would restore groundwater quality over the long term.
Alternatives G2, G4, and G6 would also rely on certain
natural processes to achieve the cleanup levels for areas
outside of the treatment zones.
Protectiveness under Alternatives G2 and G4 requires a
combination of reducing contaminant concentrations in
groundwater and limiting exposure to residual
contaminants through maintenance of existing, and
implementation of additional institutional controls, as well
as MNA.
Protectiveness under Alternative G6 is achieved through
reducing contaminant concentrations via extraction and
treatment of groundwater. Alternative G6 also protects
against the further migration of contaminated
groundwater, as the extraction functions as a hydraulic
plume containment mechanism.
The long-term monitoring program for groundwater and
vapor would monitor the migration and fate of the
contaminants and ensure that human health is protected.
Combined with MNA, long-term monitoring, and
institutional controls, Alternatives G2, G4, and G6 would
meet the RAOs. Alternative Gl would not meet the
RAOs
Because Alternative Gl (No Action) is not protective of
human health and the environment, it was eliminated from
consideration under the remaining evaluation criteria.
Compliance with Applicable or relevant and
Appropriate Requirements (ARARs)
EPA and NYSDOH have promulgated health-based
protective MCLs (40CFR Part 141, and 10NYCRR,
Chapter 1), which are enforceable standards for various
drinking water contaminants (chemical-specific ARARs).
The aquifer is classified as Class GA (6 NYCRR 701.18),
meaning that it is designated as a potable water supply.
Although the groundwater at the Site is not presently
being utilized as a potable water source, achieving MCLs
in the groundwater is an applicable or relevant and
appropriate standard, because area groundwater is a source
of drinking water. Alternatives G2 and G4 may
-------
EVALUATION CRITERIA FOR SUPERFUND
REMEDIAL ALTERNATIVES
Overall Protectiveness of Human Health and the
Environment evaluates whether and how an alternative
eliminates, reduces, or controls threats to public health and
the environment through institutional controls, engineering
controls, or treatment.
Compliance with Applicable or Relevant and Appropriate
Requirements (ARARs) evaluates whether the alternative
meets federal and state environmental statutes, regulations,
and other requirements that pertain to the site, or whether a
waiver is justified.
Long-term Effectiveness and Permanence considers the
ability of an alternative to maintain protection of human health
and the environment overtime.
Reduction of Toxicity, Mobility, or Volume (TMV) of
Contaminants through Treatment evaluates an
alternative's use of treatment to reduce the harmful effects of
principal contaminants, their ability to move in the
environment, and the amount of contamination present.
Short-term Effectiveness considers the length of time
needed to implement an alternative and the risks the
alternative poses to workers, the community, and the
environment during implementation.
Implementability considers the technical and administrative
feasibility of implementing the alternative, including factors
such as the relative availability of goods and services.
Cost includes estimated capital and annual operations and
maintenance costs, as well as present worth cost. Present
worth cost is the total cost of an alternative over time in terms
of today's dollar value. Cost estimates are expected to be
accurate within a range of +50 to -30 percent.
State/Support Agency Acceptance considers whether the
State agrees with the EPA's analyses and recommendations,
as described in the RI/FS and Proposed Plan.
Community Acceptance considers whether the local
community agrees with EPA's analyses and preferred
alternative. Comments received on the Proposed Plan are
an important indicator of community acceptance.
potentially reach ARARs in the active remediation area
of the plume sooner than Alternative G6. However,
chemical-specific ARARs will be attained through
treatment and certain natural processes (dilution and
dispersion) for groundwater in all three of these
alternatives.
Alternatives G2, G4, and G6 would comply with
location- and action- specific ARARs.
Long-Term Effectiveness and Permanence
Enhanced bioremediation under Alternative G2 is
considered a reliable method for reducing contaminant
concentrations in groundwater. In-well stripping under
Alternative G4 and pump and treat under Alternative G6
are also considered effective technologies for treatment
and/or containment of contaminated groundwater, if
designed and constructed properly.
All three alternatives rely on a combination of treatment in
the active remediation area, natural processes, including
dilution and dispersion for areas where active remediation
is not implemented, and institutional controls.
Enhanced bioremediation under Alternative G2 has been
demonstrated to be effective and reliable at numerous sites
for groundwater treatment for CVOCs in contaminated
areas. However, groundwater concentrations may
rebound if there is continued migration of CVOCs from
unknown source areas. Enhanced bioremediation
treatment may be required over the long-term to address
continued migration of contaminants from unknown
source areas into groundwater.
In-well air stripping under Alternative G4 is expected to
be effective and reliable to significantly remove CVOCs.
However, the effectiveness of this alternative is limited by
radius of influence (ROI) or "reach" into the aquifer. The
ROI will depend on pumping capacity of each well and
the hydrogeologic characteristics of the Site. The ability
to secure access to residential properties may impact the
placement of the in-well air stripping wells and ultimately
the effectiveness of the technology. In addition, the
effectiveness of in-well air stripping may be limited in
shallow aquifers, due to the lack of vertical space in the
well for "stripping." A field pilot study would be
necessary to determine pre-design parameters such as
actual ROI, optimal well spacing, flow rates, and pumping
capacity prior to full-scale implementation.
Some residual risk above levels of concern would remain
under contaminated groundwater in Alternatives G2 and
G4; these alternatives rely upon institutional controls and
MNA for protection. Residual risk under Alternative G6
would likely be reduced below levels of concern over a
longer-term remedial time frame as natural attenuation
appears to be limited and contaminant removal from
groundwater slower.
Reduction of Toxicity, Mobility, or Volume Through
Treatment
Alternatives G2, G4 and G6 reduce the toxicity and
volume of contaminants at the Site through treatment of
contaminated groundwater. Alternative G2 uses
10
-------
biological processes to degrade contaminants in
groundwater to less harmful compounds. Alternative
G4 uses physical processes to remove the contaminants
from the aquifer, and provides chemical treatment for
the collected vapor-phase contamination. Alternative
G6 removes contaminated groundwater and treats it via
a carbon treatment process. Alternative G2 does not
remove contamination from the saturated zone, while
Alternatives G4 and G6 do remove contamination.
Alternative G2 does not reduce the mobility of the
contaminants in groundwater and Alternative G4 may
change the movement of contaminants in groundwater
because the in-well air stripping treatment is expected to
create groundwater mounding. Alternative G6 would be
the most effective at reducing the mobility of the
groundwater contamination by providing hydraulic
control of the plume.
Each of the three active alternatives includes an MNA
component for the lesser contaminated portion of the
plume outside the active remediation area. MNA would
provide limited further reduction in the toxicity and
volume of contaminants in groundwater by transforming
them into less harmful substances through natural
biological, chemical and other processes.
During the enhanced bioremediation and MNA
biological degradation processes, PCE, TCE and cis-1,2-
DCE could be transformed into the more toxic vinyl
chloride under anaerobic conditions in the subsurface,
prior to aerobic degradation to the less toxic ethane.
This transformation would need to be monitored and
managed to prevent exposure via drinking contaminated
water or inhalation through the vapor intrusion pathway.
After treatment, Alternatives G4 and G6 would generate
residuals in a form of used GAC that would require
regeneration, destruction or disposal.
Short-Term Effectiveness
Alternatives G2, G4 and G6 may have short-term
impacts to remediation workers, the public, and the
environment during implementation. Remedy-related
construction (e.g., trench excavation) under Alternatives
G4 and G6 would require disruptions in traffic and street
closure permits. In addition, Alternatives G4 and G6
have aboveground treatment components and
infrastructure that may create a minor noise nuisance and
inconvenience for local residents during construction.
Exposure of workers, the surrounding community and
the local environment to contaminants during
implementation of the three alternatives is minimal. No
difficulties are foreseen with managing the required
quantity of the bioremediation injection material needed in
Alternative G2, as it is non-hazardous. Excavation
activities in Alternatives G4 and G6 could produce
contaminated vapors that present some risk to remediation
workers at the Site. Drilling activities, including the
installation of monitoring, in-well air stripping, injection,
and extraction wells for Alternatives G2, G4, and G6
could produce contaminated liquids that present some risk
to remediation workers at the Site. The potential for
remediation workers to have direct contact with
contaminants in groundwater could also occur when
groundwater remediation systems are operating under
Alternative G6. Alternative G6 could increase the risks of
exposure, ingestion and inhalation of contaminants by
workers and the community because contaminated
groundwater would be extracted to the surface for
treatment. However, measures would be implemented to
mitigate exposure risks.
All three alternatives include monitoring that would
provide the data needed for proper management of the
remedial processes and a mechanism to address any
potential impacts to the community, remediation workers,
and the environment. Risk from exposure to groundwater
during excavation would also require management via
occupational health and safety controls.
Groundwater monitoring and discharge of treated
groundwater will have minimal impact on workers
responsible for periodic sampling. The time required for
implementation of Alternative G6 is estimated at 6 - 9
months. Alternatives G2 and G4 are estimated to take
about 9-12 months to implement.
RAOs would be achieved in Alternatives G4, G2, and G6
within short, medium and longer time frames,
respectively. In-well air stripping is expected to achieve
groundwater RAOs within five to 20 years under
Alternative G4. Enhanced bioremediation is expected is
expected to achieve RAOs within eight to 50 years under
Alternative G2, and groundwater pump and treat
technology is expected to achieve groundwater RAOs in
30 or more years under Alternative G6. The time frame to
meet groundwater RAOs in the non-active remediation
area where MNA/LTM would be implemented is difficult
to predict, but is expected to exceed 30 years.
Implementability
All three technologies are well-established technologies
that have commercially available equipment and are
implementable. All three alternatives have access
challenges that would have to be addressed with property
owners. Of the three alternatives, Alternative G6
Groundwater Pump and Treat is probably the easiest
alternative to construct at the Site and would require the
11
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least amount of street closure permits and would require
less land and disruption in residential areas. Alternatives
G2 and G4 would be moderately difficult to construct in
the residential areas, requiring securing access to homes
and obtaining street closure permits. The need to
reconfigure the treatment injection and in-well air
stripping well locations in Alternatives G2 and G4 due
to access constraints map be possible, however doing so
potentially impacts the effectiveness and schedule of
these remedial alternatives.
All alternatives would require routine groundwater
quality, performance and administrative monitoring,
including five-year CERCLA reviews. Alternatives G4
and G6 require periodic operations and maintenance
(e.g., substrate injection, GAC replacement) for the life
of the treatment.
Cost
The estimated capital cost, operation, maintenance and
monitoring (O&M) and present worth cost are discussed
in detail in the FS Report. The cost estimates are based
on the best available information. Alternative Gl (No
Action) has no cost because no activities are
implemented. The present worth cost for Alternatives
G2 and G4 are $15.8 million and $16.7 million,
respectively. The highest present worth cost alternative
is Alternative G6, at $21.5 million.
The estimated capital, O&M and present-worth costs
for each of the alternatives are presented below.
Alternative
G-l
G-2
G-4
G-6
Capital
Cost
$0
$4,344,000
$7,730,000
$2,997,000
Annual O&M
Cost
$0
$835,000
$730,000
$1,185,000
Present
Worth
$0
$15,830,000
$16,710,000
$21,560,000
State/Support Agency Acceptance
NYSDEC concurs with the preferred alternative.
Community Acceptance
Community acceptance of the preferred alternative will
be evaluated after the public comment period ends and
will be described in the Record of Decision for this Site.
The Record of Decision is the document that formalizes
the selection of the remedy for a site.
PREFERRED REMEDY
Based upon an evaluation of the remedial alternatives,
EPA, in consultation with NYSDEC, recommends
Alternative G6, Groundwater Pump and Treat, as the
Preferred Alternative. Alternative G6 has the following
key components: extraction of the groundwater via
pumping and ex-situ treatment of the extracted
groundwater prior to discharge to a POTW, surface water
or reinjection to groundwater (to be determined during
design); in-situ chemical treatment of targeted high
concentration contaminant areas, as appropriate;
monitored natural attenuation for the areas where active
remediation is not performed; long-term monitoring in
conjunction with implementation of institutional controls.
In addition, EPA will continue to evaluate the potential for
vapor intrusion at the Site, and will install vapor
mitigation systems, where necessary.
The groundwater extraction well network will be designed
to effectuate removal of the contaminant mass from the
groundwater plume and establish hydrodynamic control of
the plume. Figures 4 and 5 provide the conceptual pump
& treat well locations within the shallow and deep UGA
plume areas. The exact number of extraction wells and
their placement will be determined in the remedial design.
An aquifer pump test would be conducted as part of the
pre-remedial design to collect necessary aquifer data
necessary to complete the design of the groundwater pump
and treat system.
The use of in-situ chemical treatments, targeting areas
containing high concentrations of PCE that may reside
outside the radius of influence of the pump within the
inferred plume, as appropriate, in combination with
groundwater extraction could potentially reduce the
remediation time frames and the cost of this alternative.
The implementation of in-situ chemical treatment (e.g.
ISCO, ISCR) will be designed to enhance the remediation
of the contaminated groundwater in conjunction with the
pump and treat system. The remedial design will
determine how best to execute the ISCR or ISCO with the
pump and treat system.
A treatment plant with the capacity to achieve the mass
removal and hydraulic control objectives of the remedy
will be constructed within or nearby the Site. EPA
estimates that a capacity of 350 gallons per minute may be
required. The extracted groundwater would be treated for
CVOC removal with either liquid phase GAC or air
stripping, or both. Treated groundwater effluent will be
discharged to a POTW, surface water, or reinjected to
groundwater. The method of discharge will be determined
in the remedial design. The design of the treatment facility
will take discharge requirements into account.
The pump and treat system would operate until MCLs are
attained in the shallow and deep UGA at the Site. The FS
presents calculations determining the duration of the
operation of the extraction system. These calculations to
12
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determine the remedial time frame require additional
data regarding contaminant mass flux, as well as more
detailed process design to determine the actual number
of recovery/injection wells and pore volumes of clean
water required to reach RAOs. This data will be
collected during the pre-remedial design phase. EPA
assumes the duration of this alternative is 30 years or
more.
The environmental benefits of the preferred remedy
may be enhanced by consideration, during the design,
of technologies and practices that are sustainable in
accordance with EPA Region 2's Clean and Green
Energy Policy1. This will include consideration of
green remediation technologies and practices, including
GAC regeneration.
Monitored natural attenuation is a necessary component
in those areas where active remediation is not
anticipated, such as the areas of lower contaminant
concentrations at edges of the contaminant plume.
A long-term groundwater monitoring program would be
implemented to track and monitor changes in the
groundwater contamination and ensure the remedial
action objectives are attained. The results from the long-
term monitoring program will be used to evaluate the
migration and changes in the contaminant plume over
time. The long-term monitoring program will be
modified accordingly.
The groundwater monitoring well sample results will
also be used to track changes in the contaminant plume
in order to determine homes considered "at risk" for
vapor intrusion. Selected structures/homes determined
to be "at risk" would be sampled periodically for vapor
intrusion during the winter heating season.
Vapor intrusion caused by volatilization from the
groundwater contaminant plume has been monitored by
EPA. To date, 15 homes have been sampled and one
home has been outfitted with a vapor mitigation system.
These systems would be inspected periodically to ensure
that they are operating properly. A review of
groundwater and vapor data would be relied upon to
determine which homes without vapor mitigation
systems would be tested in that year's monitoring
program. These homes would be monitored through
collection of three samples (sub-slab, basement, and first
floor) at each building. Vapor extraction systems would
be installed, if warranted. EPA will continue to
investigate the soil vapor intrusion pathway at the Site.
1 See http://epa.gov/region2/superfund/green_remediation.
Institutional controls are incorporated into this remedy
for protection of human health and the environment over
the long term. EPA anticipates using existing
government controls to prevent use of groundwater and
informational and or governmental controls to ensure that
vapor intrusion issues are identified.
While this alternative will ultimately results in reduction
of contaminant levels in groundwater to levels that would
allow for unlimited use and unrestricted exposure, it will
take longer than five years to achieve these levels. As a
result, in accordance with EPA policy, the Site is to be
reviewed at least once every five years.
Basis for the Remedy Preference
EPA is proposing Alternative G6 due to the difficulty in
implementing Alternatives G2 and G4 in the densely
populated and fully-developed residential and commercial
setting of the Site. Alternative G2, and Alternative G4 to
a somewhat lesser degree, would require securing access
to a significant number of residential properties to perform
construction activities. Under Alternatives G2 and G4,
access would be necessary to the residential properties for
an extended period of time to perform the initial
construction activities and to subsequently conduct
monitoring. Under Alternative G2, multiple injections are
likely to be necessary over time. These activities would
cause a significant disturbance to the residential
neighborhood. Reconfiguration of the injection or in-well
stripping wells due to access constraints could potentially
impact significantly the effectiveness of the technology.
Access to install extraction wells under the preferred
remedy, Alternative G6 Groundwater Pump and Treat,
though still complicated, is more manageable. Access to
property and construction of the treatment plant would be
performed in an area zoned for commercial activity.
Furthermore, the uncertainty of an unknown source
investigation that could result in a continued migration of
contamination from source areas adds to the uncertainty
that the remedial action objectives would be achieved with
Alternative G2.
Alternative G6, Groundwater Pump and Treat, uses
proven technologies that can be more readily implemented
than the other alternatives. The treatment components can
be expanded to improve treatment effectiveness or
decrease the remedial time frame, if required.
Groundwater Pump and Treat has been demonstrated as an
effective remedial approach for contaminant mass removal
over the long term. This approach would be particularly
effective as the contaminant plumes are relatively
accessible and have a specific configuration. The shallow
UGA groundwater (0 to 20 feet bgs) PCE plume is
approximately 3,500 feet long and between 400 and 100
feet wide. The deep groundwater plume is approximately
13
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1,110 feet long. Groundwater Pump and Treat would
also be the most effective of the alternatives in
establishing hydrodynamic control of the aquifer to
minimize off-site migration of contaminants and isolate
the contaminated groundwater area. The prevention of
off-site migration would prevent CVOC contamination
from flowing toward the LIAWC well field. Long-term
groundwater monitoring would ensure that remedial
action objectives are achieved at the Site.
The preferred remedy is more expensive than either
Alternatives G2 or G4. However, there is a greater
degree of uncertainty that the remedial action objectives
would be achieved by both Alternatives G2 and G4.
Based on the Site conditions, Alternative G6,
Groundwater Pump and Treat, is the most effective of
the alternatives.
The addition of in-situ chemical treatments targeting
areas containing high concentrations of PCE that may
reside outside the radius of influence of the pump within
the inferred plume, as appropriate, in combination with
groundwater extraction could potentially reduce the
remediation time frames by reducing the contaminant
mass of PCE, and, therefore, the costs of this alternative.
EPA, in conjunction with NYSDEC, believes that
Alternative G6, Groundwater Pump and Treat, would be
protective of human health and the environment,
provide the greatest long-term effectiveness, comply
with ARARs, and be cost-effective among alternatives
with respect to the evaluation criteria. The preferred
remedy also will meet the statutory preference for the
use of treatment as a principal element.
14
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SHALLOW UGA PLUME MAP
FEASIBILITY STUDY
PENINSULA BOULEVARD GROUNDWATER PLUME
TOWN OF HEMPSTEAD, VILLAGE OF HEWLETT,
NASSAU COUNTY, NEW YORK
Honnlngson, Durham &
Richardson. Architecture and
Engineering, P.O. InAssoclaHon
with HDR Engineering, he.
-------
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Honnlngson, Durham &
Richardson. Architecture and
Engineering, P.O. In Association
with HDR Engineering, he.
DEEP UGA PLUME MAP
FEASIBILITY STUDY
PENINSULA BOULEVARD GROUNDWATER PLUME
TOWN OF HEMPSTEAD, VILLAGE OF HEWLETT,
NASSAU COUNTY, NEW YORK
DATE
06-23-2011
FIGURE
-------
Honnlngson, Durham &
Richardson. Architecture and
Engineering, P.O. In Association
with HDR Engineering, he.
SHALLOW UGA PUMP & TREAT LOCATIONS
FEASIBILITY STUDY
PENINSULA BOULEVARD GROUNDWATER PLUME
TOWN OF HEMPSTEAD, VILLAGE OF HEWLETT,
NASSAU COUNTY, NEW YORK
DATE
06-23-2011
FIGURE
-------
>^b^4
Honnlngson, Durham &
Richardson. Architecture and
Engineering, P.O. In Association
with HDR Engineering, he.
DEEP UGA PUMP & TREAT LOCATIONS
FEASIBILITY STUDY
PENINSULA BOULEVARD GROUNDWATER PLUME
TOWN OF HEMPSTEAD, VILLAGE OF HEWLETT,
NASSAU COUNTY, NEW YORK
DATE
06-23-2011
FIGURE
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