Superfund Proposed Plan
Hopewell Precision Area Groundwater Contamination Site
Hopewell Junction, Dutchess County, New York
JULY 2009
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PURPOSE OF THE PROPOSED PLAN
This Proposed Plan identifies the preferred remedy for
Operable Unit (OU) 1 at the Hopewell Precision site (the
Site), and provides the rationale for this preference. The U.S.
Environmental Protection Agency's (EPA's) preferred remedy
consists of the following components:
• An investigation and pilot study of aerobic cometabolic
bioremediation (ACB) to determine the rate and the
parameters for full-scale enhancement of aerobic
cometabolic degradation in the aquifer.
• Remedial design and implementation of full-scale
enhancement of the ACB remedy to achieve restoration
of the groundwater to drinking water standards within a
reasonable time period.
• Long-term monitoring to track the movement of and
changes in the contaminated groundwater plume.
• Vapor monitoring of homes determined to be "at risk" for
vapor intrusion and implementation of vapor mitigation
systems in houses that exceed protective levels, based
on changes in the plume.
The Site consists of the Hopewell Precision facility and the
hydraulically downgradient area affected by the contaminated
groundwater plume and vapors. This Proposed Plan was
developed by the EPA in consultation with the New York
State Department of Environmental Conservation (NYSDEC)
and the New York State Department of Health (NYSDOH).
The preferred remedy for OU 1 addresses contaminated
groundwater and vapors at the Site (see Figures 1 and 2).
Dilute groundwater plumes, such as the one found at the
Hopewell site, are particularly difficult to address through
active remediation because of the relatively low levels of
contamination and the size of the plume. Traditional
treatment technologies work best when applied to much
higher levels of contamination. At the Hopewell site, EPA
has determined that it is appropriate to utilize an innovative
technology - aerobic cometabolic bioremediation - to
accelerate the reduction in contaminant levels in the aquifer.
ACB involves a process whereby micro-organisms present in
the aquifer consume organic substrates and oxygen under
aerobic conditions and produce an enzyme which destroys
contaminants such as trichloroethene (TCE). Aquifer
conditions at the Site are favorable for reduction of the site
contaminants through this technology.
EPA divides Superfund sites into remedial phases or OUs to
prioritize and accelerate selection of a remedy, when
warranted. EPA has divided the Hopewell Precision site into
two OUs. OU 1, which is the focus of this Proposed Plan,
Mark Your Calendar
July 31,2009 -August 30,2009: Public Comment Period
on the Proposed Plan.
August 11, 2009 at 7:00 p.m.: The U.S. EPA will hold a
Public Meeting to explain the Proposed Plan. The meeting
will be held at the Gayhead Elementary School, 15 Entry
Road, Hopewell Junction, New York 12533. Telephone:
(845)227-1756.
For more information, the Administrative Record file
(which will include the Proposed Plan and supporting
documents), is available at the following locations:
Town of East Fishkill Community Library
348 Route 376
Hopewell Junction, NY 12533
Telephone: (845) 221-9943
Website: www.eastfishkilllibrary.org
Hours:Monday-Thursday: 10 am - 8 pm
Friday: 10 am-6 pm
Saturday: 10 am - 5 pm
and
USEPA-Region 2
Superfund Records Center
290 Broadway, 18th Floor
New York, NY 10007-1866
(212)637-4308
Hours/Monday-Friday, 9:00 a.m. - 5:00 p.m.
Written comments on this Proposed Plan should be
addressed to:
Lorenzo Thantu
Remedial Project Manager
Eastern New York Remediation Section
U.S. Environmental Protection Agency
290 Broadway, 20th Floor
New York, New York 10007-1866
Telephone: (212)637-4240
Telefax: (212)637-3966
Email address: Thantu.lorenzo@epa.qov
The EPA has a web page for the Hopewell Precision Site
atwww.epa.gov/region2/superfund/npl/hopewell.
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addresses exposures to contaminated or potentially
contaminated media such as the groundwater, soils, surface
water, sediments and vapors associated with the Hopewell
groundwater plume. OU 2 includes provision of an alternate
water supply to the area with private drinking water wells that
have been or have the potential to be affected by the
groundwater plume from the Hopewell Precision facility. The
OU 2 Record of Decision (ROD) was completed in
September 2008.
OU 1 elements summarized in this Proposed Plan are further
described in the June 2008 Remedial Investigation (Rl)
Report and the July 2009 Feasibility Study (FS) Report. 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 there.
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 of 1980, as amended (CERCLA, also
commonly known as the federal "Superfund" law), and
Sections 300.430(f) and 300.435(c) of the National Oil and
Hazardous Substances Pollution Contingency Plan (NCP).
The Proposed Plan is being provided to inform the public of
EPA's preferred remedy and to solicit public comments on
the preferred remedy and the remedial alternatives that were
evaluated.
The remedy described in this Proposed Plan is EPA's and
NYSDEC's preferred remedy forOU 1 at the Site. Changes
to the preferred remedy or a change from the preferred
remedy to another remedy 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 for OU 1 will be made after
EPA has taken into consideration all public comments. EPA
is soliciting public comment on all of the alternatives
considered in this Proposed Plan.
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 meet this goal,
the Proposed Plan, along with the supporting Remedial
Investigation and Feasibility Study Reports, has been made
available to the public for a public comment period which
begins on July 31, 2009 and concludes on August 30, 2009.
A public meeting will be held on August 11,2009 at 7:00 P.M.
during the public comment period at the Gayhead Elementary
School, 15 Entry Road, Hopewell Junction, New York, to
present the preferred remedy (or "Proposed Plan") and to
receive public comments.
Comments received at the public meeting, as well as written
comments that EPA receives during the comment period, will
be documented in the Responsiveness Summary Section of
the ROD, the document which formalizes the selection of
the remedy.
SCOPE AND ROLE OF ACTION
This Proposed Plan presents the preferred remedy for OU
1 at the Site. The objective of the preferred remedy is
restore the groundwater to drinking water standards within
a reasonable time period as well to ensure that homes over
the contaminated plume do not have unacceptable levels of
contaminants due to vapor migrations from the soil and
groundwater and to prevent the build-up of contaminated
vapors in those situations. OU 2 has been addressed in a
separate Proposed Plan and ROD.
SITE BACKGROUND
Site Description
The Hopewell Precision site is located in Hopewell
Junction, Dutchess County, New York. The Site consists
of the Hopewell Precision facility and the hydraulically
downgradient area affected by the groundwater plume and
its vapors. The Hopewell Precision facility was located at
15 Ryan Drive from 1977 to 1980. The facility moved to
the adjacent property at 19 Ryan Drive in 1980 and
continues to operate at that location. The combined size of
the two properties is 5.7 acres. The rest of the Site
consists mostly of residential neighborhoods, all of which
are currently served by private wells and septic systems.
An alternate water supply will be provided in the near
future, in accordance with the OU 2 ROD dated September
30, 2008. Almost 27,000 people live within 4 miles of the
Hopewell Precision facility. Commercial development (e.g.,
strip malls, businesses, and gas stations) in the area is
primarily along New York State Route 82, which traverses
the area in a northeast-southwest direction. An area of
farmland borders the eastern side of a section of Route 82.
Whortlekill Creek flows in a southerly direction across the
residential area and along the western border of the Site.
Several ponds are present within the area, including two
large former quarries (Redwing Lake and the gravel pit)
that are partially fed by groundwater.
Site Geology/Hydroqeology
The Site is situated in a glaciated valley underlain by the
Hudson River Formation in the northern portion of the Site
and the Stockbridge Limestone in the southern portion.
The bedrock is overlain by unconsolidated sediments
deposited by glaciers and glacial meltwater. The glacial
outwash deposits are a complex mixture of boulders,
gravel, sand, silt, and clay which form discontinuous beds
or lenses. Due to multiple glaciation events, subsurface
units are heterogeneous and highly localized. Glacial till
deposits are also present in some areas of the Site,
including a tear drop shaped mound between Creamery
Road and Clove Branch Road. Glacial tills generally have
low permeability and limited ability to transmit groundwater.
EPA Region 2 - July 2009
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The unconsolidated deposits at the Site have been grouped
into three hydrostratigraphic units: 1) sand and gravel unit
(including silty sand, silty gravel, and mixtures of sand, silt,
and gravel), 2) silt and clay (including silty clay), and 3) the till
mound between Creamery Road and Clove Branch Road.
The sand and gravel units transmit groundwater more readily
than the silt and clay units and act as preferential flow paths
for groundwater contamination. All of these units are
localized and discontinuous, and they are likely to create
multiple complex flow pathways throughout the
unconsolidated deposits.
In general, groundwater flow is towards the valley from the
upland areas on the east and west sides of the valley. In the
valley, groundwater flow is generally towards the southwest
along the valley axis. The glacial till mound located between
Creamery Road and Clove Branch Road impedes
groundwater flow within the valley. Groundwater flows
preferentially in silty sand and gravel units. The vertical
gradient in most monitoring wells is upwards, indicating
groundwater discharges into the valley and Whortlekill Creek
which runs along the axis of the valley and also flows toward
the southwest. The contaminant flow velocity at the Site was
estimated to average from 0.8 to 1.1 feet per day in the
permeable preferential flow pathways. The depth to
groundwater across the Site varies but is generally about 15
feet below the ground surface. The groundwater at the Site
is classified by NYSDEC as Class GA, indicating it is
considered a source of drinking water.
Dissolved oxygen readings were collected during
groundwater sampling to evaluate the aerobic nature of the
aquifer. The dissolved oxygen readings ranged from 3.4 to
6.4 milligrams per liter (mg/L) in the background monitoring
wells. As the groundwater flows across the facility toward the
plume core, no apparent decrease in dissolved oxygen was
observed (e.g., readings greater than 5 mg/L in plume core
wells during both sampling rounds) and the aquifer conditions
remained aerobic. Downgradient and beyond the plume core
area, dissolved oxygen readings showed more variation, but
generally remained well in the aerobic range.
Site History
Hopewell Precision manufactures sheet metal parts that are
assembled into furniture. The property at 19 Ryan Drive was
vacant land prior to 1980, and the company has been the
sole occupant of the building. Since 1981, the former facility
at 15 Ryan Drive has been used by Nicholas Brothers Moving
Company for equipment storage and office space.
Processes at Hopewell Precision include shearing, punching,
bending, welding, and painting. The painting process includes
degreasing prior to application of the wet spray paint
application. Hopewell Precision currently uses a water-based
degreaser, but the company used TCE and 1,1,1-
trichloroethane (1,1,1-TCA) in a vapor degreasing machine
until 1998.
EPA was made aware of Hopewell Precision in October 1979
through a letter from a former Hopewell Precision employee.
During an on-site inspection at the former facility (15 Ryan
Drive) in November 1979, EPA observed solvent odors
coming from an open disposal area. At the time of the
1979 inspection, Hopewell Precision was dumping one to
five gallons per day of waste solvents, paint pigments, and
sodium nitrate directly onto the ground. In August 2003, a
former employee reported that the common practice for
disposal of waste solvents at the former facility was to pour
the material on the ground outside the building. Waste
paints and thinners were dumped on a daily basis and
waste solvents from the degreasers were dumped on a
biweekly basis while he worked at Hopewell Precision in
1979 and 1980. The results of EPA's November 1979
inspection were sent to the NYSDEC, along with a
memorandum recommending that the facility be required to
drum the solvents and dispose of them in a proper manner
rather than open dumping.
NYSDEC installed three monitoring wells at the former
facility in May 1985 and sampled the wells in March 1986.
The analytical results for Monitoring Well B-3, located
between the current and former buildings, indicated the
presence of 1,1,1-TCA at 23 micrograms per liter (ug/L)
and TCE at an estimated 4 ug/L. In 1985, the Dutchess
County Department of Health sampled four private drinking
water wells near the Site, and no volatile organic
compounds (VOCs) were detected in any of the samples.
NYSDEC performed a Hazardous Waste Compliance
Inspection of Hopewell Precision in May 1987. The
inspector observed eleven 55-gallon drums of waste paint
and thinners; six 55-gallon drums of waste 1,1,1-TCA; and
one 55-gallon drum of unknown material. During another
inspection in October 2002, NYSDEC observed four full or
partially full 55-gallon drums of waste paint and solvent at
the facility.
In February 2003, as part of an effort to make final
decisions on whether to archive historic sites, EPA
sampled 75 residential wells near the Hopewell Precision
facility. Analysis of these samples revealed that five
residential wells were contaminated with TCE ranging from
1.2 ug/L to 250 ug/L. At that time, NYSDEC, on behalf of
NYSDOH, requested that EPA conduct a removal action at
the Site, including installation of carbon filter systems on
the residential wells.
From February to November 2003, EPA collected
groundwater samples from hundreds of private drinking
water wells in the vicinity of Hopewell Precision. TCE and
1,1,1-TCA were detected in numerous private well
samples, at individual concentrations up to 250 ug/L for
TCE and 11.7 ug/L for 1,1,1-TCA. EPA subsequently
installed point of entry treatment (POET) systems to
remove VOCs at 41 homes where TCE exceeded or
approached the maximum contaminant level (MCL).
NYSDEC installed POET systems at 14 homes in the
southern part of the groundwater plume, to remove 1,1,1-
TCA that exceeded its New York State drinking water
standard, but that fell below the Federal MCL.
In April 2003, EPA also collected water and sediment
samples from small, unnamed ponds located about 300
EPA Region 2 - July 2009
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feet south-southwest (downgradient) of the Hopewell
Precision facility. TCE was detected at concentrations of 4
ug/L and 3.4 ug/L in the water samples and 88 micrograms
per kilogram (ug/kg) in one of the two sediment samples.
EPA collected additional samples from two unnamed ponds
located approximately 900 and 4,500 feet southwest of
Hopewell Precision in May 2003. TCE was detected at an
estimated concentration of 3.6 ug/kg in a sediment sample
from the closer pond, but was not detected in a water sample
from the same location or in sediment and water samples
collected from the distal pond on Creamery Road.
In July 2003, EPA collected 19 soil samples at and
downgradient of the Hopewell Precision facility. TCE was
detected in two on-site soil samples and 1,1,1-TCA was
detected in one on-site sample, but neither contaminant was
detected in any off-site samples. Additional sampling was
conducted at the Hopewell Precision facility in December
2003. TCE was detected in five soil samples, at depths
ranging from 0 to 12 feet. The maximum detected
concentration was 3.7 ug/kg; TCE was not detected in
background samples from the same depth range.
In October and December 2003, EPA installed and sampled
temporary shallow monitoring wells on both properties, 15
and 19 Ryan Drive. The results indicated TCE
concentrations up to 144 ug/L in groundwater at depths
ranging from 10 to 30 feet below the ground surface.
EPA has conducted vapor intrusion indoor air testing at the
Site. Since February 2004, EPA has collected sub-slab
and/or indoor air samples from over 200 homes in the area
above the groundwater plume. EPA installed sub-slab
ventilation systems (SVSs) at 53 homes with vapors above
the action level to reduce the residents' exposure to indoor air
contaminants associated with the Site. The SVS systems are
designed to vent vapors from beneath the foundation, thereby
preventing the entry into the structure. In addition, at
selected locations, EPA conducts annual vapor sampling
during the winter heating season to monitor the migration of
vapors to structures that may be at potential risk in the area
of the groundwater plume.
The Site was listed on the National Priorities List in April
2005.
SUMMARY OF REMEDIAL INVESTIGATION SAMPLING
In December 2005, EPA initiated a remedial investigation and
feasibility study (RI/FS) as part of the long-term Site cleanup
phase. The RI/FS evaluated the nature and extent of
groundwater, soil, sediment, surface water, and vapor
contamination at the Site, and will help EPA determine the
appropriate cleanup alternatives for the identified
contamination prior to selection of a comprehensive cleanup
plan for the Site. EPA completed all Rl field activities during
the Summer of 2007 and publicly released the Rl Report in
June 2008 and the OU 1 FS Report, the subject of this
Proposed Plan, in July 2009.
The field activities performed as part of the Rl for OU 1
included two rounds of monitoring well sampling, soil
sampling at the properties occupied by Hopewell Precision,
surface water and sediment sampling in Whortlekill Creek
and two ponds, and vapor sampling. Residential well
sampling results were summarized in the Proposed Plan
for OU 2. The results of the sampling related to OU 1 are
summarized below.
Monitoring Well Results
During the Rl, two rounds of groundwater samples were
collected from 35 monitoring wells installed during the Rl
and from three monitoring wells installed by NYSDEC at
the Hopewell Precision facility. Two wells, EPA-07S and
EPA-07D, are background wells. All of the wells were
installed in the unconsolidated sediments, with shallow
wells generally screened just below the groundwater table
and deep wells screened just above the top of weathered
bedrock. The analytical results were compared to the
Federal MCLs and the New York State Drinking Water
Standards. The following summary focuses on the seven
contaminants that were determined to be related to
activities at the Hopewell Precision facility. The site-related
contaminants include TCE, 1,1,1-TCA, 1,1-dichloroethene
(1,1-DCE), cis-1,2-dichloroethene (cis-1,2-DCE),
chloromethane, methyl ethyl ketone (MEK) and
tetrachloroethene (PCE). Although the discussions below
do not include the results from the residential wells (see
Proposed Plan for OU 2), the results from these wells were
included in all mapping of the groundwater contaminant
plumes. Figure 1 indicates the locations of monitoring wells
and Figure 2 shows the mapped TCE and 1,1,1-TCE
groundwater plumes. The monitoring well results will be
discussed from north to south, based on proximity to the
Hopewell Precision facility.
Upgradient of the Hopewell Precision Facility: Monitoring
wells EPA-07S and EPA-07D were installed upgradient of
the Hopewell Precision facility to determine background
groundwater conditions. No site-related contaminants were
detected in either well during Round 1. During Round 2,
1,1,1-TCA was detected at trace levels in both upgradient
wells (0.052 J ug/L at EPA-07S and 0.065 J ug/L at EPA-
07D), below the screening criterion of 5 ug/L. The "J"
qualifier indicates the results were estimated. No othersite-
related contaminants were detected in the Round 2
samples at EPA-07S or EPA-07D.
Hopewell Precision Facility: Five wells at the Hopewell
Precision facility were sampled (EPA-05, MW-B1, MW-B3,
EPA-08S, and EPA-08I). In Round 1, TCE and 1,1,1-TCA
were detected in MW-B3 at 0.58 J ug/L and 0.11 J ug/L,
respectively, both below the screening criteria of 5 ug/L. In
Round 2,1,1,1-TCA was detected in four of the five wells at
concentrations ranging from 0.094 J ug/L at EPA-08S and
MW-B3 to 0.05 J ug/L at MW-B1. PCE was only detected
in one of the five wells, EPA-08I, in the Round 2 sample at
0.076 J ug/L, below the screening criterion of 5 ug/L. PCE
was not detected in any of the Round 1 samples. TCE was
detected in two of the five wells, MW-B3 and EPA-08S, at
0.56 ug/L and 3.1 ug/L, respectively. None of the
EPA Region 2 - July 2009
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detections of site-related contaminants in these wells
exceeded screening criteria.
Oak Ridge Road to Hamilton Road: Ten wells are located
between Oak Ridge Road and Hamilton Road (EPA-10S,
EPA-10D, EPA-12S, EPA-12D, EPA-14S, EPA-15D, EPA-
16S, EPA-16D, EPA-19S, and EPA-19D). At 6 of the 10
wells (EPA-10S, EPA-12S, EPA-15D, EPA-16S, EPA-16D,
and EPA-19S), TCE was detected above the screening
criterion of 5 |jg/L during both sampling rounds. Levels
ranged from 94 ug/L at EPA-10S to 13 ug/L at EPA-19S.
1,1,1-TCA was detected in these six wells at concentrations
below the screening criterion of 5 ug/L, ranging from 2.7 ug/L
in EPA-16D to 0.67 ug/L in EPA-15D. No PCE or
chloromethane was detected in these six wells.
Four of the 10 wells (EPA-1 OD, EPA-12D, EPA-14S, and
EPA-19D) had no site-related contaminants above the
screening criteria of 5 ug/L. EPA-10D, EPA-12D, and EPA-
19D are likely screened below the plume core and EPA-14S
is located on the western edge of the plume. TCE was
detected in all four wells at low levels, ranging from 1.9 ug/L
at EPA-10D to 0.1 J ug/L at EPA-14S. 1,1,1-TCA was
detected in two of the four wells, EPA-12D and EPA-19D, at
2.4 ug/L and 0.54 ug/L, respectively. PCE was detected in
EPA-1OD, EPA-14S, and EPA-19D at concentrations ranging
from 0.61 ug/L at EPA-1 OD to 0.099 J ug/L at EPA-14S.
Hamilton Road to the Gravel Pit: Eleven wells were located
downgradient of the plume core, between Hamilton Road and
the gravel pit (EPA-18S, EPA-18D, EPA-21S, EPA-21D,
EPA-23S, EPA-23D, EPA-24S, EPA-25S, EPA-25D, EPA-
26S, and EPA-26D). Concentrations of site-related
contaminants in these wells were below the screening criteria
of 5 ug/L. 1,1,1-TCA was detected in 8 of the 11 wells
ranging from 3.7 ug/L in EPA-23S to 0.08 J ug/L in EPA-26D.
TCE was detected in two of 11 wells, EPA-21S and EPA-
21D, at 0.29 J ug/L and 0.52 ug/L, respectively. PCE was
not detected in any of these wells during Round 1, but was
detected in four of the 11 wells (EPA-18D, EPA-21S, EPA-
21 D, and EPA-23D) during Round 2, at concentrations
ranging from 0.23 J ug/L at EPA-23D to 0.11 J ug/L at EPA-
18D. TCE was not detected in samples collected from EPA-
25S and EPA-25D during Rounds 1 and 2.
Other Site Monitoring Wells: No site-related contaminants
were detected during either round of sampling at EPA-09S,
EPA-11S, EPA-11 D, EPA-17S, EPA-20S, or EPA-22S. EPA-
09S is likely to the west of the plume and EPA-11S, EPA-
11D, EPA-17S, EPA-20S, and EPA-22S are likely to the east
of the plume. The results for Round 1 indicated that EPA-
13S, EPA-13D, EPA-17D, and EPA-22D were also outside of
the plume boundary. However, PCE was detected at
concentrations an order of magnitude below the screening
criterion of 5 ug/L in each of these wells during Round 2.
Chloromethane was detected in three monitoring wells, EPA-
19S, EPA-23D and EPA-25S, at concentrations ranging from
0.46 J ug/L at EPA-25S to 0.19 J ug/L at both EPA-23D and
EPA-19S. Levels were below the screening criterion of 5
ug/L. No 1,1-DCE, cis-1,2-DCE, or MEK was detected in
either round of monitoring well samples.
EPA Region 2 - July 2009
Summary of Groundwater Contamination: As shown in
Figure 2, the shape of the TCE plume is indicative of the
heterogeneous nature of the aquifer and the presence of
preferential flow paths. The area of highest concentration,
or the plume core, is denoted by the 50 ug/L contour. This
area extends from just south of Oak Ridge Road to just
north of Creamery Road. The shape of the plume mirrors
the potentiometric surface and shows the groundwater
turning to the west in this area as it flows preferentially
between a low conductivity till to the north and the till
mound to the south. The till mound is further defined by an
area where TCE is not detected. The plume appears to
flow around the till to both the east and west. There are
low-level detections of TCE both to the west and south of
the 5 ug/L contour and low levels of TCE discharge to the
stream, Redwing Lake and the gravel pit.
Figure 2 also shows the outline of the 1,1,1-TCA plume to
the 1 ug/L level. The 1 ug/L level was chosen because the
majority of the detections were approximately 1 ug/L;
detections above the screening criterion (5 ug/L) are rare.
The concentrations and extent of the 1,1,1-TCA plume are
significantly different than the TCE plume. 1,1,1-TCA is not
detected in the groundwater in the eastern TCE lobe. The
lower overall concentrations of 1,1,1-TCA may reflect the
history of disposal practices at the Hopewell Precision
facility. It may also be caused by 1,1,1-TCA's low vapor
pressure and greater tendency to partition to the
atmosphere or soil vapor. In addition, 1,1,1-TCA degrades
approximately three times fasterthan TCE in groundwater.
Soil Results
Several VOCs were detected in soil samples as described
below. The soil screening criteria were the most
conservative of available federal and New York State
standards.
15 Ryan Drive Sample Results: A total of 33 soil samples
were collected from the former facility location varying in
depth from 2-4 feet bgs to 13-15 feet bgs. Four site-related
contaminants were detected. TCE was detected in 10
samples from five borings, ranging in concentration from
0.29 J ug/kg to 5.9 ug/kg; only one sample exceeded the
screening criterion of 3 ug/kg. TCE was predominantly
detected in the deeper samples, at 10-12 feet and/or 13-15
feet. PCE was detected at B-21 at 13-15 feet at 2.6 J
ug/kg, and at B-24 at 13-15 feet at 1.7 J ug/kg, below the
screening criterion of 3 ug/kg. Cis-1,2-DCE was detected
in borings B-21 and B-24 in the deepest samples, with
concentrations of 0.47 J ug/kg and 0.58 J ug/kg, below the
screening criterion of 20 ug/kg. MEK (2-butanone) was
detected once, in B-16 at 10-12 feet at 11 ug/kg, below the
screening criterion of 120 ug/kg.
19 Ryan Drive Sample Results: A total of 39 soil samples
were collected from the current location of the Hopewell
Precision facility, varying in depth from 2-4 feet to 13-15
feet. One site-related contaminant was detected. TCE
was detected in four samples from two borings (B-10 and
B-11) south of the building, ranging in concentration from
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0.44 J |jg/kg to 1.4 J |jg/kg. All concentrations were below
the screening criterion of 3 |jg/kg.
Background Sample Results: Three background samples
were collected from one boring (B-25) in a
background/upgradient location (north) of 15 and 19 Ryan
Drive. Two contaminants identified as related to site
activities were detected in these samples. However, as they
are upgradient from the Site, they are from sources other
than the Site. PCE was detected in all three samples at
concentrations ranging from 2.2 J ug/kg to 3.3 J ug/kg. The
PCE detection at B-25 at 8-10 feet (3.3 J ug/kg) exceeded
the site-specific screening criterion of 3 ug/kg. Cis-1,2-DCE
was detected below the 20 ug/kg screening criterion in all
three samples, ranging from 0.52 J ug/kg to 1.2 J ug/kg.
Summary of Soil Contamination: The low concentrations and
limited distribution of site-related contaminants indicate that
no significant soil source remains at the facility. PCE and cis-
1,2-DCE were not detected in the groundwater samples at
the facility, so the concentrations in soil do not appear to
impact the local groundwater.
Surface Water Results
Surface water samples were collected at 37 locations
downgradient of the Hopewell Precision facility, and two
background samples. Analytical results for surface water
samples were compared to New York State surface water
standards. Sampling areas included: Ryan Drive wetland
area, Unnamed Pond 1, Unnamed Pond 2, a pond on Clove
Branch Road, Redwing Lake, the gravel pit and Whortlekill
Creek.
Ryan Drive Wetland Area: One sample, SW-001, was
collected from the Ryan Drive Wetland area. No site-related
contaminants were detected.
Unnamed Ponds 1 and 2 and Pond on Clove Branch Road:
Two samples, SW-002 and SW-003, were collected from
Unnamed Pond 1. No site-related contaminants were
detected in either sample.
Three samples, SW-004 through SW-006, were collected
from Unnamed Pond 2. No site-related contaminants were
detected.
One sample, SW-027, was collected from a pond on Clove
Branch Road. TCE was detected at 0.28 J ug/L, but did not
exceed the 5 ug/L screening criterion.
Redwing Lake: Ten samples, SW-007 through SW-016,
were collected from Redwing Lake. No site-related
contaminants were detected.
Gravel Pit: Ten samples, SW-017 through SW-026, were
collected from the gravel pit. Site-related contaminants
1,1,1-TCA and chloromethane were both detected at SW-
017, below the 5 ug/L screening criteria for these
compounds. 1,1,1-TCA was detected at SW-018 and
chloromethane was detected at SW-021, SW-025 and SW-
026. No site-related contaminants exceeded screening
criteria.
Whortlekill Creek: Ten samples, SW-028 through SW-037,
were collected from Whortlekill Creek. Site-related
contaminants 1,1,1-TCA and TCE were both detected at
SW-030 and SW-031. 1,1,1-TCA was detected at SW-028
and SW-029 and TCE was detected at SW-033.
Concentrations did not exceed the 5 ug/L screening
criteria.
Background: Two background samples, SW-038 and SW-
039, were collected from Whortlekill Creek upstream of the
Hopewell Precision facility in areas that should not be
impacted by activities at the facility. No site-related
contaminants were detected.
Summary of Surface Water Contamination: Potentiometric
data show that the southern portion of Whortlekill Creek is
characterized as a gaining stream. This is supported by
detections of site-related contaminants at locations
immediately north and south of Clove Branch Road,
indicating very low levels of contaminated groundwater
discharge into the water bodies. In addition, the southern
portion of the creek does not flow in a distinct channel; the
water is very slow moving, and prone to marshy areas.
However, no site-related contaminants identified in surface
water samples exceeded their screening criteria.
Sediment Sample Results
Sediment samples were collected at the same locations as
surface water samples. Analytical results were compared
to New York State sediment criteria. The sediment
sampling areas include: Ryan Drive wetland area,
Unnamed Pond 1, Unnamed Pond 2, a pond on Clove
Branch Road, Redwing Lake, the gravel pit and Whortlekill
Creek.
Ryan Drive Wetland Area: One sample, SD-001, was
collected from the Ryan Drive Wetland area. No site-
related contaminants were detected.
Unnamed Ponds 1 and 2 and Pond on Clove Branch Road:
Two samples, SD-002 and SD-003, were collected from
Unnamed Pond 1. No site-related contaminants were
detected.
Three samples, SD-004 through SD-006, were collected
from Unnamed Pond 2. No site-related contaminants were
detected.
One sample, SD-027, was collected from a pond on Clove
Branch Road. No site-related contaminants were detected.
EPA Region 2 - July 2009
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Redwing Lake: Ten samples, SD-007 through SD-016, were
collected from the Redwing Lake. MEK (2-butanone) was
detected at 7 |jg/kg at SD-014; no screening criterion is
available for MEK. No other site-related contaminants were
detected.
Gravel Pit: Ten samples, SD-017 through SD-026, were
collected from the gravel pit. No site-related contaminants
were detected.
Whortlekill Creek: Ten samples, SD-028 through SD-037,
were collected from Whortlekill Creek. No site-related
contaminants were detected.
Background: Two samples, SD-038 and SD-039, were
collected from Whortlekill Creek in areas that should not be
impacted by activities at the Hopewell Precision facility and
were designated as background samples. No site-related
contaminants were detected.
Summary of Sediment Contamination: No site-related
contaminants were detected in any sediment samples with
the exception of MEK (2-butanone) in one sample from
Redwing Lake. The sediments in the area are generally free
of site-related contaminants.
Deep Water Sample Results
Ten deep water samples were collected from Redwing Lake
and from the gravel pit. Results were compared to surface
water criteria.
Redwing Lake: TCE was detected below the 5 ug/L
screening criterion at DW-001 at 0.26 J ug/L. No other site-
related contaminants were detected.
Gravel Pit: Ten samples, DW-011 through DW-020, were
collected from the gravel pit. 1,1,1 -TCA was detected at DW-
013, DW-015, DW-016, DW-017, DW-018, DW-019, and
DW-020, ranging from 0.15 J ug/L to 0.37 J ug/L. TCE was
detected at DW-018 at 0.14 J ug/L. Concentrations of both
compounds did not exceed the 5 ug/L screening criteria.
Summary of Deep Water Contamination: Site-related
contaminants 1,1,1-TCA, and TCE were detected in deep
water samples; however, all concentrations were well below
the screening criteria. Results of the deep water samples
were similar to the surface water in that most site-related
contaminants were found in the gravel pit at very low levels.
The presence of very low levels of site-related contaminants
indicates that groundwater discharges to the two ponds that
were formerly gravel pits.
Sub-slab and Indoor Air Results
Sub-slab and indoor air investigations included two rounds of
sampling for sub-slab air and one round for indoor air. The
first round of sub-slab sampling included 64 properties in the
winter of 2006, and the second round included 135 properties
in the winter of 2007. The only round of indoor air sampling
was conducted at 44 properties in the winter of 2007. Air
analytical results were compared to the screening criteria
developed by EPA Region 2 risk assessors. The analytical
results are discussed by rounds and are described as
clusters by street names.
Round 1 Sub-Slab Air Sample Results
Seventy-three samples were collected in February and
March 2006 from various locations southwest of the
Hopewell Precision facility, primarily in the area where the
groundwater plume is dominated by 1,1,1-TCA.
Sub-Slab TCE: TCE was only detected in two samples
during Round 1. The sample from Cavelo Road exceeded
the screening criterion with a concentration of 18
micrograms per cubic meter (ug/m3). The sample from
Hamilton Road contained 1.5 ug/m3, below the site-specific
screening criterion. There were no other detections of TCE
during Round 1 sub-slab air sampling.
Sub-Slab 1,1,1-TCA: 1,1,1-TCA was detected at 31
sample locations; none exceeded the screening criteria. A
cluster of detections is located south of Clove Branch Road
and north of Cavelo Road. Concentrations within this
cluster range from 3 ug/m3 to 94 ug/ m3; all below the site-
specific screening criterion. A second cluster is located
north of West Old Farm Road, with concentrations ranging
from 8.8 ug/m3 to 270 ug/m3. There were no detections of
1,1,1-TCA east of Route 82. Blue Jay Boulevard and
Mockingbird Court had two detections at 0.89 ug/m3 and
5.5 ug/m3. Two detections were observed north of Clove
Branch Road, west of Route 82 and south of Creamery
Road, at 1.8 ug/m3 to 270 ug/m3.
Sub-Slab PCE: PCE was detected in 23 samples; none
exceeded the screening criterion. A small cluster of
detections were located east of Route 82 and north of
Clove Branch Road, with concentrations ranging from 1.2
ug/m3 to 7.1 ug/m3. One detection was found south of
Clove Branch Road, west of Route 82 with a concentration
of 3.8 ug/m3. The majority of detections were found in an
area bounded by Old Farm Road to the south, Clove
Branch Road to the north, Route 82 to the east and Purse
Lane and Mockingbird Court to the west. Concentrations of
PCE ranged from 1.2 ug/m3 to 14 ug/m3. There were two
detections of PCE north of Creamery Road and west of
Route 82, at 1.1 ug/m3 and 1.2 ug/m3.
Sub-Slab Other Site-Related Compounds: MEK (2-
butanone) was detected in 17 samples at concentrations
ranging from 2.2 to 16 ug/m3. All detections were below
the screening criterion. The detections were sporadic, with
the majority of detections on Clove Branch Road, southern
Route 82 and west of Farm Road. The highest
concentration was detected at Blue Jay Boulevard.
Chloromethane was detected in 11 samples with
concentrations ranging from 0.33 to 1.4 ug/m3. All
detections were below the screening criterion. More than
half of the detections of Chloromethane were located along
Clove Branch Road. Cis-1,2-DCE was detected in two
samples and 1,1-DCE was detected in one sample at
concentrations below screening criteria.
EPA Region 2 - July 2009
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Round 2 Sub-slab Sample Results
Sub-slab samples were collected in February and March
2007 from 135 buildings lying over the TCE/1,1,1-TCA
groundwater plume.
Sub-Slab TCE: TCE was detected in 30 samples during
Round 2; 16 exceeded the screening criterion. Detections
generally lie along a north-south line from Creamery Road to
Clove Branch Road and ranged in concentration from 1
ug/m3 to 280 ug/m3. This cluster is surrounded to the east
and west by non-detects.
Sub-Slab 1.1.1-TCA: Eighty-one samples had 1,1,1-TCA
concentrations ranging from 0.76 ug/m3 to 120 ug/m3.
Detections did not exceed the screening criterion. Detections
were scattered, from immediately bordering the Hopewell
Precision facility to areas southwest of the facility. Detections
immediately surrounding the facility ranged from 1.1 ug/m3 to
19 ug/m3. Further south of the facility, 1,1,1-TCA was
detected in a cluster north of Creamery Road, ranging from
1.9 ug/m3 to 21 ug/m3. West of Route 82, detections follow
Route 82 to Clove Branch Road, ranging from 0.76 ug/m3 to
32 ug/m3. West of Route 82, the largest cluster of detections
was found between Creamery Road and West Old Farm
Road, with the majority of detections west of Hamilton Drive.
Concentrations ranged from 0.78 ug/m3 to 120 ug/m3.
Sub-Slab PCE: PCE was detected in 54 samples during
Round 2. Three samples exceeded the site-specific
screening criterion; two were located east of Route 82 with
detections of 170 ug/m3 to 9,800 ug/m3. The third location
was west of Route 82 with a concentration of 250 ug/m3.
Detections greater than 10 ug/m3 but below the screening
criterion were observed throughout the area south of
Creamery Road and north of West Old Farm Road. A cluster
of PCE detections was found west of Route 82 and east of
Cavelo Road, ranging from 1.1 ug/m3 to 10 ug/m3. Sporadic
detections below 10 ug/m3 were observed throughout the
sample area.
Sub-Slab Other Site-Related Compounds: Cis-1,2-DCEwas
detected in four of the samples at concentrations ranging
from 1.1 to 15 ug/m3, one detection exceeded the screening
criterion. 1,1-Dichloroethene was detected in 10 samples at
concentrations ranging from 0.55J to 2 ug/m3, with all
concentrations below the screening criterion.
Round 2 Indoor Air Sample Results
Forty-three air samples were collected during Round 2 in
March 2007, at locations that exceeded the sub-slab
screening criteria during Round 2. Three samples were
generally collected at each residence, including a sub-slab
sample, an indoor sample, and an ambient (outdoor) air
sample. The following samples were collected: 14 indoor
samples, 17 sub-slab samples, and 12 ambient samples. If
buildings were closely spaced, one ambient air sample was
designated to be representative of multiple structures. The
properties sampled during Round 2 are scattered throughout
the sampling area. No VOCs were detected in the ambient
air samples so they will not be discussed further.
Sub-Slab and Indoor TCE: TCE was detected in 13 sub-
slab air samples, with 10 exceeding the sub-slab criterion.
Concentrations ranged from 0.24 ug/m3 to 150 ug/m3. TCE
was detected in seven indoor air samples. All exceeded
the indoor screening criterion. Concentrations ranged from
0.89 ug/m3 to 20 ug/m3.
Sub-Slab and Indoor 1,1,1-TCA: 1,1,1-TCA was detected
in 13 sub-slab air samples collected during Round 2; none
exceeded the screening criterion. Concentrations ranged
from 4.9 ug/m3 to 51 ug/m3. 1,1,1-TCA was detected in
four indoor air samples: none exceeded the screening
criterion. Concentrations ranged from 0.86 ug/m3 to 2.6
ug/m3.
Sub-Slab and Indoor PCE: PCE was detected in five sub-
slab air samples; none exceeded the screening criterion.
Concentrations ranged from 1.5 ug/m3 to 16 ug/m3. PCE
was detected in six indoor air samples. One sample
exceeded the site-specific screening criterion with a
concentration of 560 ug/m3. A second sample was just
below the screening criterion at 98 ug/m3. The remaining
detections of PCE ranged from 1.1 ug/m3 to 5.9 ug/m3.
Summary of Vapor Sample Results
TCE is the primary contaminant detected above its
screening criterion. 1,1,1-TCA was frequently detected,
however, all of the detections were below the screening
criterion. PCE was also frequently detected but only one
sample, collected from an automotive garage, exceeded
the screening criterion. MEK, 1,1-DCE, cis-1,2-DCE and
chloromethane were all detected in at least one sample,
but the detections were sporadic.
The distribution of vapors in the subsurface is controlled by
processes and stratigraphy similar to those controlling the
distribution of contamination in groundwater. The areas of
vapor detections generally correlate with areas of
groundwater detections. However, there does not appear
to be a direct correlation between the magnitude of
groundwater contamination and the magnitude of vapor
contamination in a given area. The large area of till south
of Creamery Road appears to impede the vapors and
groundwater contamination in that area. No homes in this
area had VOC detections in sub-slab samples.
The Round 2 sub-slab air sample results were compared to
the Round 2 indoor air sample results. Seven of the
locations sampled showed detections of the same
compounds at similar magnitudes in both Round 2 sub-slab
air samples and the indoor air samples. Four of the
locations had detections in the sub-slab during both sub-
slab and indoor air sampling, but there were no detections
in the indoor air samples. Three locations showed no
correlation between the compounds detected or the
magnitude of detection between the various samples. The
migration of sub-slab vapors to indoor air is affected by a
number of factors, including the construction and age of the
EPA Region 2 - July 2009
Page 8
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building and the presence of cracks or other migration
pathways in the substructure of the building.
RISK SUMMARY
The purpose of the risk assessment is to identify potential
cancer risks and noncancer health hazards at the Site
assuming that no further remedial action is taken. This
Proposed Plan presents the results of the Human Health Risk
Assessment and the Screening Level Ecological Risk
Assessment.
Human Health Risk Assessment
As part of the RI/FS, a baseline human health risk
assessment was conducted to estimate the current and future
cancer risks and noncancer health hazards associated with
the current and future effects of contaminants on human
health and the environment. A baseline human health risk
assessment is an analysis of the potential adverse human
health effects caused by hazardous-substance exposure in
the absence of any actions to control or mitigate these
exposures under current and future land uses.
A four-step human health risk assessment process was used
for assessing site-related cancer risks and noncancer health
hazards. The four-step process is comprised of: Hazard
Identification of Chemicals of Potential Concern (COPCs),
Exposure Assessment, Toxicity Assessment, and Risk
Characterization (see box "What is Risk and How is it
Calculated").
The baseline human health risk assessment began with
selecting COPCs in the groundwater, soil, surface water and
sediment, using Rl data, which could potentially cause
adverse health effects in exposed populations. The
populations evaluated are indicated below for each
medium. In this assessment, exposure point
concentrations were estimated using either the maximum
detected concentration of a contaminant or the 95 percent
upper confidence limit of the average concentration.
Chronic daily intakes were calculated based on the
reasonable maximum exposure (RME), which is the
highest exposure reasonably anticipated to occur at the
Site. The RME is intended to estimate a conservative
exposure scenario that is still within the range of possible
exposures. Central tendency exposure (CTE)
assumptions, which represent typical average exposures,
were also developed. A complete summary of all exposure
scenarios can be found in the baseline human health risk
assessment.
Groundwater
Risks and hazards were evaluated for current and future
adult and child residents for ingestion of untreated tap
water, dermal contact with untreated tap water, and
inhalation of vapors during showering or bathing. Risks
and hazards were evaluated for current and future facility
workers for ingestion of untreated tap water at the
Hopewell Precision facility. The total incremental lifetime
cancer risk estimates were:
• Adult: RME = 7x10'4; CTE = 4 x 10'5
• Child: RME = 1x10'3; CTE = 2 x 10'4
• Facility Worker: RME = 2x10'5; CTE = 6 x 10'6
EPA Region 2 - July 2009
Page 9
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These estimates of risk were above EPA's target range of 1 x
10"6to1 xio~4. Exposure to TCE and arsenic in groundwater
accounted for approximately 65 and 35 percent, respectively,
of the total excess cancer risk. Arsenic is considered a known
human carcinogen (Group A) by EPA. However, arsenic is
not related to any activities at the Hopewell Precision facility,
and it was only detected in one monitoring well sample.
Therefore, risks from arsenic are likely to be minimal.
Hazard indices (His) greater than 1.0 indicate the potential for
noncancer hazards. The calculated His were:
• Adult: RME HI = 4; CTE HI = 3
• Child: RME HI = 12; CTE HI =4
• Facility Worker: RME HI = 0.2; CTE HI = 0.1
The total HI for the adult and child resident, based on
individual health endpoints, is above EPA's acceptable
threshold of 1 and could possibly have adverse effects on the
liver, kidney, central nervous system, fetus, endocrine, and
skin. TCE and arsenic contribute most of the potential
noncancer hazard.
The installation of a public water supply in the area affected
by the Hopewell groundwater plume will eliminate risks to
residents from consumption of and contact with contaminated
drinking water.
Vapor Intrusion
Inhalation of vapors volatilizing from the subsurface into
indoor air is also a potentially completed exposure pathway
related to the groundwater contamination from the Hopewell
Precision site. A quantitative evaluation of risks and hazards
associated with this pathway was not completed as part of
the groundwater investigation. Instead, EPA's Response and
Prevention Branch conducted and addressed vapor intrusion
and indoor air issues on a house-by-house basis using a
multiple-line of evidence approach. A similar approach (i.e.,
evaluating subslab soil gas, indoor air concentrations, and
other site-specific factors) will be utilized to monitor and
respond to "at risk" homes (i.e., homes that lie over the
contaminated groundwater plume without mitigation systems)
as part of the proposed remedy.
Surface Water/Sediment
Risks and hazards were evaluated for current and future
recreational users for incidental ingestion of and dermal
contact with sediment and surface water. Each water body
was evaluated separately. The total incremental lifetime
cancer risk estimates and His are shown below.
Redwing Lake
• Adult: RME = 1 X10'6; RME HI = 0.3
• Child: RME = 2 xlO'6; CTE = 7 xlO'7; RME HI = 3; CTE
HI = 0.7
Gravel Pit
EPA Region 2 - July 2009
WHAT IS RISK AND HOW IS IT CALCULATED?
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 to assess site-related
human health risks for reasonable maximum exposure scenarios.
Hazard Identification: In this step, the chemicals of potential
concern (COPCs) at a 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 identified in the previous step are evaluated.
Examples of exposure pathways include incidental ingestion of
contaminated groundwater. Factors relating to the exposure
assessment include, but are not limited to, the concentrations
that people might be exposed to and the potential frequency and
duration of exposure. Using these factors, a Areasonable
maximum exposures 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 noncancer health effects, 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 noncancer health effects.
Risk Characterization: This step summarizes and combines
outputs of the exposure and toxicity assessments to provide a
quantitative assessment of site risks. 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 explained in the Exposure Assessment. Current
Superfund guidelines for acceptable exposures are an individual
lifetime excess cancer risk in the range of 10"4 to 10"6
(corresponding to a one-in-ten-thousand to a one-in-a-million
excess cancer risk) with 10"6 being the point of departure. For
noncancer health effects, a hazard index (HI) is calculated. An HI
represents the sum of the individual exposure levels compared to
their corresponding reference doses. The key concept for a non-
cancer HI is that a threshold level (measured as an HI of less
than 1) exists below which non-cancer health effects are not
expected to occur.
Adult: RME = 3
Child: RME = 5
CTE HI = 3
CTE = 3 xlO'6; RME HI = 1
; CTE = 1 xlQ'5; RME HI = 13;
Page 10
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Whortlekill Creek
Adolescent: RME cancer risk: 5 xio~6 and CTE cancer
risk: 2 xirj6; RME HI = 0.08
Unnamed Pond 1
• Adolescent: RME = 4 xiO'7; RME HI = 0.04
Unnamed Pond 2
• Adolescent: RME = 6 xiO'7; RME HI = 0.05
Pond on Clove Branch Road
• Adolescent: RME = 5 xiO'7; RME HI = 0.04
Wetland Area South of Ryan Drive
• Adolescent: RME = 1 xiO'6; RME HI = 0.09
These estimates for recreational users are within or below
EPA's target range of 1 x 10-6 to 1 x 10-4, with the exception
of the total HI for a child in Redwing Lake and the gravel pit.
For Redwing Lake and the gravel pit, the calculations for the
child RME scenario is above EPA's acceptable threshold of
1.0. The calculations suggest the potential for adverse
effects on the whole body and blood due to concentrations of
antimony. Antimony is not a site-related chemical. All other
total His are below EPA's acceptable threshold of 1.0.
Subsurface Soil
Risks and hazards were evaluated for future construction
workers for incidental ingestion of, dermal contact with, and
inhalation of particulates released from subsurface soil. The
total incremental lifetime cancer risk estimate and HI are
shown below.
• RME = 3x 1Q-7;RMEHI = 0.1
This estimate is below EPA's target range of 1 x io~6 to 1 x
10"4. The total HI based on individual health endpoints forthe
RME scenario is below EPA's acceptable threshold of 1.0.
Screening Level Ecological Risk Assessment
The SLERA evaluated the potential ecological impact of
contaminants in surface water and sediment at the Site.
Conservative assumptions were used to identify exposure
pathways and, where possible, quantify potential ecological
risks. Based on a comparison of maximum detected
concentrations of contaminants in site sediment and surface
water to conservatively-derived ecological screening levels
(ESLs), there is no potential for ecological risk from
contaminants related to the Hopewell Precision site. The
SLERA indicated the potential for ecological risk from
contaminants not related to the site. Specifically, hazard
quotients (HQs) greater than 1.0 may indicate potential risk
from exposure to the following media-specific contaminants:
Sediment
VOCs: acetone and carbon disulfide
Semi-volatile organic compounds (SVOCs): acenaphthene,
anthracene, benzo (a) anthracene, benzo (a) pyrene,
benzo (b) fluoranthene, benzo (g,h,i,) perylene, benzo (k)
fluoranthene, chrysene, dibenzo (a,h) anthracene,
dibenzofuran, fluoranthene, fluorene, indeno (1,2,3-cd)
pyrene, phenanthrene, and pyrene
Pesticides: 4,4'-DDD, 4,4'-DDE, 4,4'-DDT, alpha-BHC,
beta-BHC, alpha-chlordane, and gamma-chlordane
Inorganics: antimony, arsenic, cadmium, chromium,
copper, cyanide, iron, lead, manganese, nickel, selenium,
and silver
Surface Water
SVOCs: benzo(a)pyrene and fluoranthene
Pesticides: 4,4'-DDT, gamma-chlordane, and heptachlor
Inorganics: barium, copper, iron, manganese, and
vanadium
COPCs in the SLERA were comprised of different classes
of contaminants; none are the identified site-related
contaminants. TCE and 1,1,1-TCA were detected in some
surface water samples; however, levels detected were
orders of magnitude below their respective screening
criteria. In addition, MEK (2-butanone) was detected in one
sediment sample below its screening criterion. These site-
related compounds were not retained as COPCs due to
their low concentrations. Chloromethane was identified as
a site-related contaminant and was retained as a COPC
because no ESL was located; however, only trace levels
were detected in surface water. It is unlikely any risks exist
to ecological receptors from exposure to this compound.
The SLERA indicates no risk to ecological receptors from
site-related contaminants. COPCs such as polycyclic
aromatic hydrocarbons and pesticides are typically
associated with suburban/agricultural areas such as those
within the Hopewell area, and are unlikely to be related to
activities at the Hopewell Precision facility. In addition,
Whortlekill Creek receives surface and road runoff via
overland flow and storm water drains; other surface water
bodies are subject to overland flow, further contributing to
the loading of non site-related COPCs. Although
groundwater has been observed to discharge to several
surface water bodies in the site vicinity (e.g., Whortlekill
Creek, Redwing Lake, and the gravel pit), the contaminant
levels discharging to water bodies are expected to remain
at extremely low levels or decrease as the groundwater
plume dissipates. Therefore, no further ecological
investigations or risk assessments were warranted.
REMEDIAL ACTION OBJECTIVES
Remedial action objectives (RAOs) are media-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
EPA Region 2 - July 2009
Page 11
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requirements (ARARs), to-be-considered (TBC) guidance,
and risk-based levels established in the risk assessment.
The overall RAO is to ensure the protection of human health
and the environment. The specific RAOs identified for OU 1
at the Site are listed below.
For groundwater:
• Prevent inhalation of contaminants from groundwater.
• Restore the groundwater aquifer to drinking water
standards throughout the plume within a reasonable time
frame.
For soil vapor:
• Mitigate impacts to public health resulting from existing,
or the potential for, soil vapor intrusion into buildings at
the Site.
Remediation Goals
Remediation goals or cleanup levels for OU 1 were selected
based on federal and state promulgated ARARs known as
groundwater Federal MCLs and New York State Drinking
Water Standards, respectively. These MCLs were then used
as a benchmark in the technology screening, alternative
development and screening, and detailed evaluation of
alternatives presented in the FS Report. The cleanup levels
for groundwater are the most conservative of Federal MCLs
or New York State Drinking Water Standards and are shown
in Table 1 below.
Table 1: Remediation Goals
Site-Related Contaminants
Trichloroethene (TCE)
1 ,1 ,1-Trichloroethane (1 ,1 ,1-TCA)
1,1-Dichloroethene (1,1 -DCE)
Cis-1 ,2-Dichloroethene (cis-1 ,2-
DCE)
Chloromethane
Methyl ethyl ketone (MEK)
Tetrachloroethene (PCE)
Remediation Goals
for Groundwater
(ug/L) *
5
5
5
5
5
50
5
* Groundwater Cleanup levels for site-related contaminants
are based on the more conservative of the Federal MCLs and
the New York State Drinking Water Standards.
SUMMARY OF REMEDIAL ALTERNATIVES
CERCLA Section 121(b)(1), 42 U.S.C. Section 9621 (b)(1),
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)(1) 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
EPA Region 2 - July 2009
site. CERCLA Section 121(d), 42 U.S.C. Section 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 Section 121(d)(4),42U.S.C.
Section 9621 (d)(4).
The objective of the FS for OU 1 was to identify and
evaluate remedial action alternatives for contaminated
groundwater at the Site, and also to mitigate impacts to
human health resulting from existing, or the potential for,
soil vapor intrusion into building at a site.
Detailed descriptions of the groundwater remedial
alternatives for the Site can be found in the FS report. The
sections below present a summary of the four alternatives
that were evaluated. All alternatives were evaluated for a
duration of 30 years and used a 7 percent discount rate
because these are the standard default timeframe and
interest rate used for comparison purposes. The use of the
30-year timeframe does not imply that the remedy would
become ineffective or be removed after 30 years.
Consistent with EPA Region 2's Clean and Green policy,
EPA will evaluate the use of sustainable technologies and
practices with respect to any remedial alternative selected
for the Site.
Alternative 1 - No Action
Capital Cost: $0
Annual Cost: $0
Present-Worth Cost: $0
Duration Time: 0 years
The "No Action" alternative is considered in accordance
with NCP requirements and provides a baseline for
comparison with other alternatives. If this alternative were
implemented, the current status of the Site would remain
unchanged. No remedial actions would be implemented as
part of this alternative. Groundwater would continue to
migrate and contamination would continue to attenuate
through dilution. This alternative does not include
institutional controls or long-term groundwater monitoring.
Alternative 2 - Aerobic Cometabolic Bioremediation
Capital Cost: $6,790,000
Annual Cost: $410,000
Present-Worth Cost: $12,000,000
Duration Time: 30 years
Construction Time: 2 years
Under Alternative 2, a pre-design investigation of aerobic
cometabolic bioremediation (ACB) would be conducted
along with a pilot study, and long-term monitoring. ACB
involves a process whereby micro-organisms while
consuming organic substrates such as methane or
propane, and oxygen, produce an enzyme which
fortuitously destroys contaminants. The pilot study results
Page 12
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will be used to design and scale-up ACB in a manner that
would enhance and accelerate ACB processes.
The pre-design investigation of aerobic cometabolism would
involve collection of samples from 8 to 10 monitoring wells for
standard groundwater chemistry parameters, enzyme probe
assays, and application of molecular biological tools (i.e.,
DMA analysis to provide evidence that the blueprint for the
enzyme is present). The wells would be selected to represent
various conditions at the Site (e.g., relatively higher and lower
concentration areas, and background wells not impacted by
the plume). Results would be compiled and evaluated with
the groundwater chemistry, contaminant results, the enzyme
probe results, the DMA results, and historical data to
determine the degree to which ACB is occurring and to
estimate an overall contamination degradation rate. The
second step would involve laboratory microcosm studies,
using Site groundwater, to simulate in-situ biodegradation of
TCE in the Site aquifer. Specifically, these microcosm
studies would measure TCE degradation and enzyme activity
in Site groundwater; these results would then be used to
estimate actual intrinsic cometabolic degradation rates.
In addition to more fully documenting the occurrence of
intrinsic ACB and estimating the effective degradation rate, a
pilot study would be conducted to determine the best
methods to enhance the rate of ACB. The objective of the
pilot study would be to investigate available primary
substrates suitable for the site conditions; optimal
concentrations of the primary substrate and oxygen for the
enhancement; and proper layout and configurations of the
enhancement system.
Based on the results of the initial aerobic cometabolism
investigation and the pilot study, a full-scale system for
adding the substrate will be developed and constructed. The
full-scale ACB enhancement will be designed to address the
entire groundwater contaminant plume, including the plume
core defined by the 50 ug/L contour. Alternative 2 would
consist of up to two rows of diffuser wells, with the wells
estimated to be 5 feet apart. Approximately 160 diffuser
wells would be installed. The wells would be flush mounted
with piping connected to each well head for delivery of
additive. Final configuration, however, will be determined
during the remedial design. A staging area would be needed
for each row.
Under this alternative, long-term monitoring would include
groundwater samples collected initially annually from the
monitoring well network of 35 wells strategically located in
and around the groundwater plume. The analytical results
would be used to evaluate the migration of and changes in
the contaminant plume over time. The monitoring well
samples would be collected in the late spring or early
summer to allow adequate time to evaluate changes in the
geometry of the plume in order to plan the vapor sampling
during the winter heating season.
Vapor intrusion caused by volatilization from the groundwater
contaminant plume has been monitored and mitigated by
EPA for several years. Under the long-term monitoring
program, a periodic inspection would be conducted of the 53
existing vapor extraction systems to ensure that the
systems are working properly. In addition, EPA would
initially conduct a vapor sampling program each winter
heating season at homes within the areas of the Site
considered to have the potential to experience vapor
intrusion, based on the groundwater plume as determined
by the periodic monitoring well sampling and previously
conducted vapor sampling. Since 2003, EPA has
conducted vapor sampling at 209 homes over the
groundwater plume, with many of the homes sampled
multiple times. During the initial years of annual vapor
sampling, the vapor monitoring would focus on structures
that have never been sampled (approximately 18 homes)
and/or homes that have been sampled for vapors only once
(approximately 35 homes). This would ensure that each
home would have been sampled at least twice. After the
first few years of annual vapor monitoring, homes to be
sampled each year would be selected based primarily on
other factors including, any changes in the contaminant
plume, especially in any areas where the groundwater
contaminant levels might show the potential to increase,
and proximity to properties experiencing vapor intrusion.
Alternative 3 - Pump and Treat
Capital Cost: $7,980,000
Annual Cost: $940,000
Present-Worth Cost*: $17,470,000
Duration Time: 30 years
Construction Time: 1.5 years
* annual operation, maintenance and monitoring (O&M)
costs for treatment for years 2 to 15.
Under Alternative 3, contaminated groundwater would be
extracted from the core of the plume and treated, in order
to enhance the restoration of the aquifer and to alleviate
the occurrence of vapor intrusion. Since the contaminant
plume is large and has generally reached a steady state,
and TCE concentrations within a large portion of the plume
are relatively low, it is neither practical nor cost-effective to
extract and treat the entire plume. In the FS, the
groundwater extraction wells are designed to capture the
50 ug/L TCE contaminant plume. A pre-design
investigation would be conducted to obtain additional
lithologic and hydrogeologic data and to further delineate
the vertical characteristics of the plume and preferential
flow paths. The existing groundwater flow model would be
further developed. The final locations and configuration of
groundwater extraction wells would be determined by
additional groundwater modeling and the pre-design
investigations. Contaminated groundwater extracted from
the extraction wells would be treated with an ex-situ
treatment system such as precipitation for iron and
manganese removal, air-stripper and/or liquid phase
carbon adsorption units forTCE/VOC removal. The treated
groundwater would meet appropriate state and federal
standards so that it could be re-injected into the aquifer,
discharged to a local recharge basin, or discharged to
Whortlekill Creek.
It is important to note that there are residential wells in
operation within the 50 ug/L contaminant plume. The
EPA Region 2 - July 2009
Page 13
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impact of groundwater extraction wells on the yields of the
residential wells was not evaluated because the OU2 ROD
selected an alternate water supply for the residential area
impacted by the contaminant plume.
Underthe pump-and-treat alternative, long-term monitoring of
groundwater and vapor intrusion identical to Alternative 2
would be implemented for the groundwater and vapors.
Alternative 4 - In-Situ Chemical Oxidation
Capital Cost: $10,720,000
Annual Cost: $4,600,000*
Present-Worth Cost*: $25,530,000
Duration Time: 30 years
Construction Time: 2 years
* annual O&M costs for treatment for years 2 to 4.
Under Alternative 4, an oxidant would be injected into
selected locations of the plume core areas (i.e., greaterthan
50 ug/L) to reduce dissolved TCE concentrations and to
enhance the restoration of the aquifer. Because the oxidation
reaction can be non-selective between contaminants in
groundwater and soil constituents, in-situ chemical oxidation
(ISCO) would involve high costs. In the FS, it was assumed
that only selected areas within the 50 ug/L TCE plume would
be treated.
Alternative 4 would consist of four rows of injection wells.
Within each row, the injection wells would be approximately
30 feet apart and 10 to 18 wells would be in each row. The
wells would be flush mounted, with piping connecting each
well head to oxidant tanks during injection. A staging area
comprised of tanks, pumps and chemicals would be required
for each row. A pre-design investigation would be necessary
to better define the horizontal and vertical extents of the
treatment area. Depending on what oxidant was used, a
bench-scale treatability study would be necessary to
determine the quantity of oxidant required. Furthermore, the
groundwater geochemistry within the treatment zone would
be temporarily altered after the injection of the oxidant.
Groundwater samples would be collected prior to and post-
chemical injection to evaluate the changes in groundwater
quality and the effectiveness of ISCO treatment.
Under the ISCO alternative, long-term monitoring of
groundwater and vapor intrusion identical to Alternative 2
would be implemented for the groundwater and vapors.
EVALUATION OF ALTERNATIVES
In selecting a remedy for a site, EPA considers the factors set
forth in CERCLA '121, 42 U.S.C. '9621, by conducting a
detailed analysis of the viable remedial alternatives pursuant
to the NCP, 40 CFR ' 300.430(e)(9) and OSWER Directive
9355.3-01. The detailed analysis consists of an assessment
of the individual alternatives against each of nine evaluation
criteria and a comparative analysis focusing upon the relative
performance of each alternative against those criteria.
• Overall protection of human health and the
environment addresses whether or not a remedy
provides adequate protection and describes how risks
posed through each exposure pathway (based on a
reasonable maximum exposure scenario) are
eliminated, reduced, or controlled through treatment,
engineering controls, or institutional controls.
• Compliance with applicable or relevant and appropriate
requirements addresses whether or not a remedy
would meet all of the ARARs of federal and state
environmental statutes and regulations or provide
grounds for invoking a waiver.
• Long-Term effectiveness and permanence refer to the
ability of a remedy to maintain reliable protection of
human health and the environment over time, once
cleanup goals have been met. It also addresses the
magnitude and effectiveness of the measures that may
be required to manage the risk posed by treatment
residuals and/or untreated wastes.
• Reduction of toxicity, mobility, or volume (TMV)
through treatment is the anticipated performance of the
treatment technologies, with respect to these
parameters, that a remedy may employ.
• Short-Term effectiveness addresses the period of time
needed to achieve protection and any adverse impacts
on human health and the environment that may be
posed during the construction and implementation
period until cleanup goals are achieved.
• Implementability is the technical and administrative
feasibility of a remedy, including the availability of
materials and services needed to implement a
particular option.
• Cost includes estimated capital and annual operation
and maintenance costs, and net present-worth costs.
• State acceptance indicates whether, based on its
review of the RI/FS reports and the Proposed Plan, the
State concurs with, opposes, or has no comment on
the preferred remedy at the present time.
• Community acceptance will be assessed in the ROD,
and refers to the public's general response to the
alternatives described in the Proposed Plan and the
RI/FS reports.
A comparative analysis of the remedial alternatives forOU
1, based upon the evaluation criteria noted above, is
presented below.
Comparative Analysis of Alternatives
• Overall Protection of Human Health and the
Environment
For all four alternatives, protection of human health from
the contaminated groundwater is provided through
EPA Region 2 - July 2009
Page 14
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installation of a potable water system throughout the
impacted community under the OU 2 ROD. Alternative 1 -
No Action would not include any monitoring or remedial
measures, and as such, would not provide any additional
protection of human health orthe environment. Alternative 2
- Aerobic Cometabolic Bioremediation includes evaluation of
intrinsic cometabolic degradation of TCE and pilot testing
followed by implementation of measures to enhance ACB.
Due to presence of favorable aerobic conditions in the
aquifer, it is highly likely that cometabolic degradation of TCE
is occurring, which would provide TCE destruction and would
protect human health and the environment. Alternatives 2, 3,
and 4 would accelerate the cleanup of the plume by reducing
groundwater contaminant concentrations within the plume.
Alternatives 2, 3, and 4 would also rely on certain natural
processes to achieve the cleanup levels for areas outside of
the treatment zones. The long-term monitoring program for
groundwater and vapor would monitor the migration and fate
of the contaminants and ensure human health is protected.
Alternative 1 would not meet the RAOs. Alternatives 2, 3,
and 4 would meet the RAOs.
• Compliance with ARARs
Alternative 1 would not comply with chemical-specific ARARs
because no action would be taken. Alternatives 2, 3, and 4
would comply with chemical-specific ARARs through
treatment and certain natural processes (dilution, dispersion,
and discharge to surface waters). Alternatives 2, 3, and 4
would comply with action-specific ARARs for all associated
well-drilling activities. Alternative 3 would also comply with
action-specific ARARs by controlling emissions of hazardous
vapors and complying with effluent discharge requirements.
Alternatives 2, 3, and 4 would comply with location-specific
ARARs by minimizing any wetland impact from their
implementation (e.g, well-drilling activities).
• Long-Term Effectiveness and Permanence
Alternative 1 is not considered a permanent remedy since no
action would be taken. Alternative 2 would provide long-term
effectiveness and permanence through aerobic cometabolic
degradation of TCE and accelerated destruction of the toxic
compounds through enhancements to the process, thereby
decreasing the time for aquifer restoration. Alternatives 3
and 4 would provide long-term effectiveness and
permanence by treating contaminated groundwater within the
50 ug/L TCE plume to shorten the time required for overall
aquifer restoration. Groundwater contamination outside the
50 ug/L plume would decrease through certain natural
processes including dilution, dispersion, and discharge to
surface waters. Alternatives 2, 3 and 4 also would provide
annual vapor sampling and vapor intrusion mitigation as
necessary.
• Reduction in Toxicitv, Mobility or Volume (TMV)
Alternative 1 would not reduce TMV through treatment since
no treatment would be implemented. Alternative 2 would
reduce TMV through cometabolic degradation of TCE
through certain natural processes and measures to enhance
these processes. Alternative 3 would reduce the mobility and
volume of the contaminant plume through groundwater
extraction and reduce the toxicity of water through ex-situ
treatment using air-stripper and/or liquid phase carbon
adsorption units. Alternative 4 would reduce the toxicity of
the contaminant plume through in-situ destruction of the
contaminants. The volume and mobility of the contaminant
plume would also be reduced by the ISCO process.
• Short-Term Effectiveness
Alternative 1 would not have any short-term impact since
no action would be taken. Alternative 2 would have some
impact to the community during the pilot testing and
enhancement pre-design investigation and installation of
wells. Construction of the treatment system may require
access to private property. Alternative 3 would involve the
use of heavy equipment and the traffic on local roads would
be impacted. Alternative 4 would also have some impact
on the community since access to private properties would
be necessary.
• Implementability
Alternative 1 involves no action. Because Alternative 2
involves an innovative technology, understanding of the
cometabolic process and selection of proper equipment are
still under development. Property access may add to the
implementation challenges. Alternative 3 would be easy to
implement technically, but challenging to implement
administratively. Obtaining land for the treatment system
and piping of influent and effluent lines would be difficult in
the fully-developed residential area. Discharge of the
treated effluent would also need to be resolved. Like the
other action alternatives, land access would be needed to
implement Alternative 4; however, access to a larger
number of private properties would be required. An
experienced vendor would be necessary in order to
effectively distribute the oxidant in the subsurface via
multiple injection wells. Implementation of ISCO in
widespread and groundwater dilute plumes is typically not
a proven and cost-effective technology.
• Cost
The estimated capital, annual cost, and present-worth
costs for each alternative are presented in Table 2. All
costs are presented in U.S. dollars and were developed
using a discount rate of 7%.
Table 2: Cost Comparison for Groundwater
Alternatives
Remedial
Alternative
1
2
3
4
Capital
Cost
0
6,790,000
7,980,000
10,720,000
Annual
Cost
0
410,000
940,000
460,000
Present
Worth
0
12,000,000
17,470,000
25,530,000
Dura-
tion
NA
SOyrs
SOyrs
SOyrs
According to the capital cost, annual cost and present-
worth cost estimates, Alternative 1 has the lowest cost and
Alternative 4 has the highest cost when comparing all
alternatives.
EPA Region 2 - July 2009
Page 15
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• State Acceptance
NYSDEC concurs with the preferred remedy.
• Community Acceptance
Community acceptance of the preferred remedy will be
assessed in the ROD following review of the public
comments received on the Proposed Plan.
PREFERRED REMEDY
Based upon an evaluation of the four alternatives, EPA
recommends Alternative 2 - Aerobic Cometabolic
Bioremediation - as the preferred remedy for OU 1.
Implementation of this alternative would be expected to
provide the best overall protection of human health,
especially when combined with the OU 2 alternative water
supply remedy. Alternative 2 will include testing to determine
to what degree TCE levels are decreasing due to cometabolic
degradation and allow calculation of degradation rates. Pilot
testing will determine the types of appropriate substrate(s)
that can be added to the aquifer to accelerate the rate of
biodegradation of TCE. Based on the pilot test results, a
system for adding the substrate will be developed and
constructed. In addition, long-term monitoring of the
groundwater will track and monitor changes in the
groundwater contamination through collection of samples on
an annual or more frequent basis from the monitoring well
network around the Site. An assessment of the groundwater
plume indicates that contaminant levels are generally
decreasing and would be expected to continue to decrease
through certain natural processes within the aquifer. Limited
areas where the contaminant levels are potentially not
decreasing will be monitored closely for soil vapor and
groundwater. The annual monitoring well sample results
would 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.
A work plan detailing the testing for ACB and the pilot study
would be developed along with a long-term monitoring plan
during the design phase of the project. The results from the
long-term monitoring program would be used to evaluate the
migration and changes in the contaminant plume overtime.
The long-term monitoring program would be modified
accordingly.
Vapor intrusion caused by volatilization from the groundwater
contaminant plume has been monitored by EPA. As of July
2009, 53 homes have been outfitted with vapor mitigation
systems. These systems would be inspected periodically to
ensure 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.
Basis for the Remedy Preference
EPA is proposing Alternative 2 due to the somewhat
unique set of conditions at the Site (e.g., large, dilute
plume) which presents a particular challenge for existing
remedial tools and approaches. While the scientific
understanding of ACB processes and tools for
implementing and monitoring ACB continue to evolve, most
field work to date has focused on monitored natural
attenuation of dissolved phase plumes. Deploying ACB as
an 'active' remedy will require careful attention to substrate
effectiveness and cost-effectiveness of delivery systems for
such large volumes. The remedy will determine the rate of
aerobic degradation of TCE in the aquifer via certain
natural processes, and also determine, through a pilot
study, the extent to which natural conditions can be
enhanced to accelerate reduction of TCE to non-toxic
compounds. Long-term monitoring of the groundwater and
vapors will track and monitor the groundwater
contamination at the Site, in combination with the remedy
selected for OU 2. The Agency believes that these
combined remedies for the Site would be the most
protective of human health in the long-term.
While Alternative 3 would include installation of extraction
wells and a treatment system for the extracted
groundwater, it would be difficult to locate extraction wells
and a treatment system in the core of the plume since it is
beneath a fully-developed residential area. Construction
activities under Alternative 3, which would involve the use
of heavy equipment (e.g., drill rigs), would impact the traffic
on local roads during its construction duration of one and a
half years.
Alternative 4 would also require access to private
properties in order to install a number wells to inject the
oxidant chemical into the aquifer. Multiple injections are
likely to be necessary over time. In addition, ISCO is
typically employed to reduce high levels of groundwater
contamination in smaller geographic areas. It is not
expected to be a cost-effective technology under the
conditions at the Hopewell site, where the groundwater
contamination is relatively dilute and spread over a large
area.
Alternative 1, No Action, would rely solely on certain natural
processes to restore groundwater quality to beneficial use,
and it does not include any long-term groundwater
monitoring to assess the effectiveness of this remedy.
Therefore, EPA and NYSDEC believe that Alternative 2,
Aerobic Cometabolic Bioremediation, when combined with
the selected remedy for OU 2, would provide the best
balance of trade-offs among the alternatives with respect to
the evaluation criteria.
EPA Region 2 - July 2009
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C:\IMS\GIS\Hopewell\GIS_projects\MW_Locat:ons_2007.mxd
A Staff Guages
-$- EPA Monitoring Well
• Previous Investigation Monitoring Well
O Piezometer
^ Parcel Boundary
A
500 1,000
Figure 1
Monitoring Well and Piezometer Locations
—Feet Hopewell Precision Site
2'000 HopewellJunction, New York
COM
Topographic Contours - Feet amsl
amsl = above mean sea level
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C:\IMS\GIS\Hopewell\GIS_projects\Site_location_Rl.mxd
FS Study Area
1,1,1-Trichloroethane plume (1 ug/L)
Trichloroethene plume (5 ug/L)
Trichloroethene plume (50 ug/L)
N
]Feet
0 500 1,000 2,000
3,000
Figure 2
Contaminant Plumes
Hopewell Precision Site
Hopewell Junction, New York
COM —
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