Superfund Proposed Plan U.S. Environmental Protection
Agency, Region II
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Shenandoah Road Groundwater Contamination
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Superfund Site
Town of East Fishkill, Dutchess County, New York
August 2012
A MARK YOUR CALENDAR ~
August 29, 2012 - September 28, 2012:
Public comment period for the RI/FS Reports and
this Proposed Plan.
Wednesday, September 12, 2012
From 7:00 to 9:00 PM
Public meeting at East Fishkill Fire District
Administration Building, 2502 Route 52,
Hopewell Junction, NY
EPA ANNOUNCES PROPOSED PLAN
The Administrative Record file contains the
documents upon which EPA based its selection of the
preferred remedy and is available at the following
locations:
East Fishkill Community Library
348 Route 376
Hopewell Junction, NY 12533
(845) 221-9943
Hours: Mon-Thurs: 10:00 AM - 8:00 PM
Fri: 10:00 AM - 6:00 PM
Sat: 10:00 AM - 5:00 PM
EPA Region II - Superfund Records Center
290 Broadway, 18th Floor
New York, NY 10007-1866
(212) 637-4308
Hours: Mon-Fri: 9:00 AM - 5:00 PM
This Proposed Plan describes the remedial
alternatives considered for the contaminated
groundwater at the Shenandoah Road Groundwater
Contamination Superfund site (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 groundwater contamination at the Site
and the associated human health and ecological risks
that are summarized in this Proposed Plan are
described in greater detail in the August 2012
Remedial Investigation Report (Rl) and the August
2012 Human Health Risk Assessment Report
(BHHRA), respectively. The remedial alternatives that
are summarized in this Proposed Plan are described
in greater detail in the August 2012 Feasibility Study
Report (FS). 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
groundwater remedial alternatives evaluated.
The remedy described in this Proposed Plan is the
preferred remedy for the Site which includes
monitored natural attenuation (MNA) for the
groundwater plume and extraction and treatment of
the source contamination.
Changes to the preferred remedy or a change from
the preferred remedy to another remedy may be made
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if public comments and/or additional data indicate that
such a change would result in a more appropriate
remedial action. The final decision regarding the
selected remedy will be made in a Record of Decision
(ROD) after EPA has taken into consideration all
public comments.
EPA is soliciting public comment on all the alternatives
considered in the Proposed Plan and in the FS report,
since EPA may select a remedy other than the
preferred remedy, based on overall public input.
COMMUNITY ROLE IN SELECTION PROCESS
EPA relies 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 Rl and FS reports and this Proposed Plan have
been made available to the public for a 30-day public
comment period which begins on August 29, 2012.
A public meeting will be held during the public
comment period at the East Fishkill Fire District
Administration Building on Wednesday, September
12, 2012 at 7:00 P.M. to present the findings and
conclusions of the RI/FS reports, to elaborate further
on the reasons for recommending the preferred
remedy and to receive public comments.
Comments received at the public meeting, as well as
written comments, will be documented in the
Responsiveness Summary section of the ROD, the
document which formalizes the selection of the
remedy.
Written comments on the Proposed Plan should be
addressed to:
Damian Duda
Remedial Project Manager
U.S. Environmental Protection Agency
290 Broadway, 20th Floor
New York, New York 10007-1866
Telephone: (212)637-4269
Fax: (212) 637-3966
Email: duda.damian@epa.gov
SCOPE AND ROLE OF ACTION
This Proposed Plan presents a long-term remedial
action which focuses on the cleanup of the Site
groundwater. The long-term remedial action includes
the cleanup actions performed under EPA removal
authorities: 1) the removal of contaminated soil 2) the
installation of a permanent public water supply (PWS)
for the community and 3) the ongoing operation of a
source extraction and treatment system.
The primary objectives of this action are to remediate
the groundwater at the Site which could potentially
come in contact with human and ecological receptors.
The groundwater treatment alternatives summarized
herein are fully described in the FS. EPA encourages
the public to review the FS for additional details about
the Site and EPA's preferred remedy.
SITE BACKGROUND
Site Description
The Site is located within the Town of East Fishkill
(East Fishkill), Dutchess County, New York in an area
known as Shenandoah, approximately one mile
southwest of the intersection of Interstate 84 and the
Taconic State Parkway and one-and-one-half miles
southeast of the Hudson Valley Research Park, as
shown on Figure 1. The Site is in a rural area
consisting of residential subdivisions intermingled with
extensive farmland and patches of woodlands. The
topography is dominated by a northeast/southwest
trending valley and ridge complex.
Residential well sampling conducted at the Site by the
New York State Department of Health (NYSDOH) in
April and May of 2000 indicated that 24 residential
wells were contaminated with tetrachloroethene or
PCE, a volatile organic compound (VOC) and the
primary contaminant (or chemical) of potential concern
(COPC), above the federal and state maximum
contaminant level (MCL) of 5 micrograms per liter
(jjg/L). One well was also found to be contaminated
with the VOC trichloroethene or TCE above the MCL
of 5 |jg/L. Additional residential well sampling
indicated that a total of 60 wells in the area were
contaminated with PCE above MCLs.
As further discussed below, the majority of the
impacted homes within the Shenandoah Town Water
District (STWD) have been connected to the municipal
water supply (East Fishkill PWS System) and use
septic systems for sanitary wastewater disposal.
Site History
Between 1965 and 1975, Jack Manne, Inc. rented
property and a building at 7 East Hook Cross Road in
East Fishkill (the Facility) and operated a business to
clean and repair computer chip racks supplied to it
under a contract with International Business Machines
(IBM). Available information indicates that during
these operations, solvents, including PCE, and
metals, including lead, were disposed of in a septic
tank and an in-ground pit located at the Facility.
Additionally, nitric and sulfuric acid wastes were
reportedly disposed of in another pit at the Facility.
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In Fall 2000, EPA and NYSDEC determined that the
probable source of the PCE contamination in the
nearby residential wells was linked to historical
operations at the Facility.
In 2001, EPA notified IBM and Jack Manne of their
status as potentially responsible parties (PRPs).
Site Geoloav/Hvdroaeoloav
The northern portion of the Site is underlain by
unconsolidated Pleistoicene glacial deposits that
overlie complexly folded and faulted, and highly
fractured and weathered dolostone, a
calcium/magnesium carbonate, of the Lower
Paleozoic Wappinger Group and the Poughquag
quartzite (valleys). The southern portion of the Site
occupies the east flank of Shenandoah Mountain
which is underlain by up-thrown fault blocks of the
Precambrian gneissic basement rock (ridges). The
heterogeneous glacial overburden deposits range
from zero to 100 feet thick and include glacial till, ice-
contact deposits and glacio-lacustrine deposits. The
surficial geology is dominated by glacial sediments
except where a few small dolostone and quartzite
outcrops occur at the surface.
The glacial overburden and bedrock aquifers
represent two distinct aquifer systems in the East
Fishkill area. Underlying the Facility is a shallow
saturated bedrock zone in the gneiss bedrock that
contains remnants of pure-phase PCE liquid (also
known as a dense non-aqueous phase liquid or
DNAPL) which constitute a continuing source of
contamination for the plume. Groundwater flows in
gneiss bedrock from the Facility to the north, east and
south. To the north groundwater flows from the gneiss
into the quartzite and dolostone and then into the
overlying glacial deposits. This transition occurs along
Shenandoah Road between its intersections with
Griffin Lane and Jackson Road. Groundwater then
flows northward within both the bedrock and the
glacial ice-contact deposits in the direction of the
wetland north of Townsend Road (NYSDEC HJ-54).
This northern wetland is the discharge zone for most
of the groundwater originating at the Facility.
A small portion of the groundwater which originates at
the Facility flows to the east and may discharge to an
unnamed stream and its associated wetland
(NYSDEC HJ-59) that lie east of Shenandoah Road
between Shenandoah Mountain and Hosner
Mountain.
Based on the pattern of PCE detections and the
magnitude of those detections, the groundwater flow
direction, away from the Facility to the east, moves in
the direction of Burbank Road and Shenandoah Road.
The highest concentrations found in residential wells
occur in wells on Burbank Road directly east of the
Facility on the other side of the ridge. This suggests
that groundwater transport through the vertical joint
system in this ridge has also been significant.
Detection of PCE in residential wells south of the
former Facility suggests groundwater flow to the south
along an apparent structural discontinuity (shear
zone), most likely discharging into the unnamed
stream between the two mountains.
Overall, the hydrogeology is quite complex in the area
of the Site. However, in spite of the discharge of
groundwater originating at the Facility into streams to
the north and east, groundwater and surface water
samples show that no dissolved PCE or its
degradation products ofTCE or cis-1,2-dichloroethene
(cis-1,2 DCE) reach any of the streams draining the
Site. This occurs because various attenuation
mechanisms in the bedrock aquifers remove, dilute or
disperse the PCE as it is flowing toward these
streams.
Site Characterization and Response
In June 2000, following the discovery of contamination
in the residential wells, EPA initiated an emergency
response action at the Site and began delivery of
bottled water to the affected residences. Of the then
60 known contaminated residential wells, 20 had
contamination exceeding the removal action level
(RAL) for PCE (70 |jg/L). Under the Superfund
Program, if any contaminant concentration exceeds its
RAL, EPA is authorized to take immediate, short-term
action to address that contamination. As a result,
point-of-entry treatment (POET) systems were
installed by EPA in homes where wells were
contaminated at or above MCLs to ensure a safe
supply of water. POET systems include a cartridge
particulate filter, two granular-activated carbon (GAC)
tanks and an ultraviolet light. These actions were
taken to protect the health of the public until a more
permanent solution could be implemented.
In November and early December 2000, EPA began
removal activities at the Facility with the excavation of
a septic tank and the removal of its contents to an off-
site treatment and disposal facility. EPA also
excavated contaminated soil associated with the
septic tank and temporarily stockpiled it at the Site.
Based on field screening results and post-excavation
soil sampling results collected by EPA, it was evident
that high levels of PCE still remained in the soil
beneath the Facility. As a result, it was necessary for
EPA to demolish a building at the Facility prior to
excavation of the underlying contaminated soil.
During the excavation of the soil, which extended to
the water table, two additional PCE-disposal areas
were discovered.
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In May 2001, an Administrative Order on Consent for
a Removal Action (RA-AOC) was executed between
IBM and EPA. Under the RA-AOC, IBM assumed
responsibility for the remaining soil removal at the
Facility. Also, under the RA-AOC, a separate provision
was included to allow for additional response work
that the two parties could agree should be performed.
In August 2001, under the RA-AOC and EPA
oversight, IBM removed approximately 4,800 tons of
stock-piled PCE-contaminated soils associated with
the former septic tank and the two PCE-disposal
areas and transported them for off-site treatment
and/or disposal. Prior to backfilling, at the request of
EPA, IBM installed groundwater collection pipes at
various locations at the base of the excavation for
future groundwater monitoring.
At the same time, EPA discovered a buried acid pit
behind the Facility. Field sampling of the soil
surrounding the acid pit revealed high concentrations
of PCE. In January 2002, IBM, under the RA-AOC
and EPA oversight, excavated and transported for off-
site treatment or disposal an additional 2,000 tons of
contaminated soil.
Also, in August 2001, IBM proposed to evaluate and
to construct an alternate water supply under the
provisions of the RA-AOC. In December 2001, EPA
approved IBM's final work plan to evaluate six
different water supply alternatives. Subsequently, in
November 2003, the EPA-approved Alternate Water
Supply Evaluation Report was issued. EPA held a
public meeting on November 20, 2003, identifying its
preferred response action. On August 23, 2004, EPA
issued its decision to use the Town of Fishkill
municipal water supply as the permanent drinking
water source for affected Shenandoah area residents.
Subsequently, IBM implemented EPA's decision and
constructed the PWS system within East Fishkill's
newly-formed Shenandoah Town Water District
(STWD). The PWS system work included the
installation of transmission and distributions lines, a
water storage tank and all house connections. The
PWS system was completed and deemed fully
operational in March 2009. The STWD community is
now being serviced by a permanent PWS system.
Except for eight homeowners within the STWD who
elected to keep their uncontaminated residential wells,
all residential wells located on Shenandoah Road, Old
Shenandoah Road, Seymour Lane, Burbank Road,
Jackson Road, Townsend Road, Old Townsend Road,
Jaycox Lane, Stone Ridge Lane and East Hook Cross
Road have been disconnected from the home
plumbing systems which are no longer in use.
During the course of the Rl work, IBM determined that
residual PCE-related DNAPL is present in the
groundwater and within the fractured bedrock
underlying the Facility. As a result of this finding of
DNAPL, EPA determined that conducting a non-time
critical-removal action to control the DNAPL source
would be beneficial. Subsequently, pursuant to the
RA-AOC and with EPA oversight, IBM prepared a
Non-Time-Critical Source Removal Action (NTCSRA)
work plan to address the DNAPL source. Results of a
long-term aquifer test, conducted during April-May
2011 as part of the RI/FS, were used to determine the
configuration of the NTCSRA. The final NTCSRA
Report was approved in August 2011.
In December 2011, EPA issued a Decision Document
identifying the selection of the NTCSRA to control the
DNAPL source contamination at the Facility. This
action was taken, because both the level of PCE
dissolved in groundwater in shallow bedrock
underlying the Facility and the prevalence of stable
and increasing concentration trends in many long-term
monitoring wells within the plume indicated the
presence of DNAPL underlying the Facility.
The NTCSRA operation consists of four groundwater
extraction wells and two granulated activated-carbon
(GAC) adsorption vessels in series to treat the
contaminated groundwater. The treated groundwater
would then be discharged to the designated storm
water conveyance under a NYSDEC permit. A
configuration of four extraction wells at the Facility
provides the most robust response in the surrounding
bedrock aquifer. Groundwater extraction from all four
wells at the Facility is expected to achieve the overall
objectives of reducing the DNAPL source in the
fractured bedrock and of controlling groundwater
chemical flux from the source area to the groundwater
plume. DNAPL concentrations at the source were
found to be as high as 16,000 |jg/L of PCE. The
NTCSRA capture zone is approximately 16 acres
surrounding the Facility.
The principal goal of the NTCSRA is to reduce and to
contain VOC concentrations in the source area at the
Facility to levels that reduce the mass flux from the
source significantly to levels that will permit cleanup
standards to be met.
Since the NTCSRA will remain an active part of the
preferred remedy, it will now be referred as "source
extraction and treatment" in all future discussion
herein.
RESULTS OF THE REMEDIAL INVESTIGATION
During the 2001 removal action, IBM completed an
Initial Groundwater Investigation report, pursuant to
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the RA-AOC, to show preliminary groundwater
contamination information. Subsequently, in 2002,
EPA and IBM entered into a second Administrative
Order on Consent to perform the Remedial
Investigation and Feasibility Study (RI/FS-AOC).
IBM's RI/FS Work Plan was approved in late 2005. A
conceptual site model was developed for the Site (see
Figure 2).
The Rl sampling was conducted from 2006-2012. The
Rl report also includes the pre-RI sampling efforts that
were conducted from 2002 until 2006. During the Rl,
all affected media were investigated, including surface
and subsurface soils, groundwater, surface water,
sediments and soil gas.
Groundwater Plume
Discrete sampling of groundwater occurred at each of
the monitoring well locations shown on Figure 3.
There are 11 monitoring wells that were fitted with
FLUTe® systems with a total of 41 separate sampling
intervals defined for these wells. The FLUTe® system
is a multi-level monitoring well system where a flexible
liner is installed down the well and allows for
groundwater to be sampled at select intervals along
the liner at specific depths. The use of a FLUTe® well
alleviates the installation of multiple wells at a single
location. The FLUTe® system was used at a number
of monitoring well locations in order to alleviate the
need for multiple wells to be drilled. There are an
additional 35 regular monitoring wells in place. In
addition, there are 27 residential wells which have
been converted into monitoring wells. Three distinct
rounds of groundwater samples were collected from
the monitoring well locations. Also, during the third
round of sampling, a number of residential wells which
were converted to monitoring wells were sampled.
Some of these wells will be part of the long-term
groundwater monitoring program.
During December 2007, the initial round of sampling
began for the full target compound list (TCL) (VOCs)
and target analyte list (metals) parameters.
Subsequently, wells were sampled for the COPCs as
well as other water quality parameters. The highest
concentration of PCE was detected at SRMW-18RA at
6,000 |jg/l, which is the shallowest monitoring interval
on the Facility. The next highest concentration of PCE
detected was 490 |jg/L at BRB005D (a converted
residential well along the west side of Burbank Road).
TCE was also detected at 50 |jg/L at BRB005D.
Historically, prior to the installation of the PWS, the
highest PCE (2100 jjg/L) and TCE (52 jjg/L)
concentrations in residential wells were observed at
this location.
Maximum concentrations of TCE in several other
residential wells along the west side of Burbank Road
were also measured at concentrations ranging from
29 |jg/L to 42 |jg/L. Other than these locations,
maximum TCE detections were also present at
SHN487 (39 jjg/L) and SEY001 (21 jjg/L).
In March 2012, the highest concentration of TCE
detected in the bedrock aquifer was 7.6 |jg/L at
SRMW-12RA. At SRMW-2R and SRMW-2RA, no
PCE was detected, and TCE was the principal COPC
and was found at 9.0 |jg/L and 4.3 |jg/L, respectively.
TCE was not detected above 1 |jg/L in any well
completed in the glacial sediments.
Since March 2009 when the PWS system was
installed and residential well use ceased, the highest
concentrations of PCE in groundwater beyond the
Facility were observed along the west side of Burbank
Road. Specifically, a PCE concentration at 190 |jg/L
was observed in the gneiss bedrock in SEY006 which
was shown to be downgradient from BRB005.
Wthin the bedrock aquifer to the east of the Facility,
the highest concentration of PCE found was 14 |jg/L
at SEY005S. Neither PCE nor any of its degradation
products was detected above the 5 |jg/L groundwater
standard in any other bedrock well east of the
easternmost fault line.
In October 2011, within the bedrock aquifer to the
north, the highest concentration of PCE observed,
since the use of residential wells for water supply
ceased was 39 |jg/L at SRMW-12RA. This is the most
downgradient bedrock monitoring location in this
portion of the flow system. By contrast, the maximum
concentration of PCE in residential wells on either side
of Shenandoah Road between its intersections with
East Hook Cross Road and Jackson Road ranged
from 160 |jg/L to 440 |jg/L. This location is where the
crossover of groundwater flow from the bedrock to the
glacial ice-contact deposits occurs
The highest concentrations of PCE outside the gneiss
bedrock since use of residential wells ceased occur in
three wells that monitor groundwater quality in these
glacial ice-contact deposits, SRMW-12S: 49-57 |jg/L,
SRMW-12SA: 48-74 |jg/L and SRMW-14S: 44-53
|jg/L. The concentrations of PCE in the overlying
glacial ice-contact deposits (45-49 jjg/L) are greater
than the concentrations in the underlying glacial till
(3.0 jjg/L) and in the underlying shallow bedrock (20-
21 |jg/L).
Other VOCs detected at the Site include cis-1,2 DCE,
1,1 DCE and vinyl chloride (VC). With a maximum
concentration of cis-1,2 DCE at 42 |jg/L at SRMW-
17R, cis-1,2 DCE was also detected above 5.0 |jg/L
in samples from various depth intervals at only three
wells, SRMW-15R, SRMW-16R and SRMW-17R. VC
was detected only at trace levels in one well, SRMW-
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15R. 1,1 DCE was detected at trace levels in only
three wells, SRMW-15R, SRMW-16R and SRMW-
17R.
Groundwater (Facility)
In June 2009 and March and June 2012, samples
were collected from three of the four collection
systems constructed during the backfilling of the
excavation conducted at the Facility. In the former
Acid Pit area, there were three separate collection
pipe installed: northern, central and southern. In the
former Large Pit area, there were three connected
collection pipes installed: northern, central and
southern. The water that collects in these systems is
shallow groundwater that accumulates within the
backfill that was placed in the pit following excavation
of the contaminated soil. The Acid Pit-Southern
Collection Pipe and the Large Pit-Northern Collection
Pipe were either dry or inaccessible during all
sampling events and could not be sampled. All
collection pipes in the Large Pit system were dry
during the June 2012 sampling event and could not be
sampled.
CPOCs that were detected in the groundwater of the
various collection pipes1 are as follows:
In the Acid Pit-Central Pipe: in June 2009, 660 and
630 |jg/l PCE and 5.3J and 4.8J |jg/L TCE in split
samples; in March 2012, 150 |jg/L PCE and 0.72J
jjg/L TCE; and, in June 2012, 200 |jg/L PCE and 1,2J
jjg/L TCE.
In the Acid Pit-Northern Pipe: in June 2009, 480 |jg/L
PCE and 5.2J |jg/L TCE; in March 2012, 160 |jg/L
PCE and 1.9J |jg/L TCE; and, in June 2012, 350 |jg/L
PCE and 4.8J |jg/L TCE.
In the Large Pit-Southern Pipe: in June 2009, 130
|jg/L PCE and non-detect TCE; in March 2012, 87
jjg/L PCE and 0.49J |jg/L TCE.
In the Large Pit-Central Pipe: IN June 2009, 120 |jg/L
PCE and non-detect TCE; in March 2012, 94 |jg/L
PCE and 0.5J |jg/L TCE.
Surface Water
Sampling was conducted in two New York State
(NYS)-regulated wetlands (NYSDEC HJ-54 (north)
and NYSDEC HJ-59 (southeast)) within the Site
constituents (see Figure 3). The only Site-related
COPC detected (PCE) was detected in the northern
1 The letter "J" indicates estimated values.
wetlands. The southeastern wetlands showed non-
detect in surface water and sediments.
There were three groundwater seeps identified in the
northern wetlands. The PCE that was detected in
these seeps was at maximum concentrations ranging
from 12 |jg/L to 60 |jg/L. This data were obtained
where the lowest field-measured temperature was
recorded (SRSP-3). Since groundwater temperatures
are much lower than surface water, this indicated that
this sample was collected from groundwater as it
seeped out of the ground and before there was any
mixing with surface water or other groundwater
seepage. TCE and cis-1,2 DCE were not detected in
any of the seep samples. These concentrations at
SRSP-3 are very similar to the recent groundwater
sampling results at well SRMW-12S, located just
south of this seep on the edge of Townsend Road.
Groundwater discharging from these seeps collects in
a constructed pond (SRSW-13). At the southeast inlet,
the maximum concentration of PCE is 21 |jg/L
showing warmer surface water temperatures. The
southwest inlet of the pond (SRSW-12) exhibits only a
trace of PCE at 0.42J |jg/L and similar water
temperatures to the southeast inlet.
Water that accumulates in this pond discharges at the
north end of the pond through a breach in the berm at
sampling location SRMW-14. The observed maximum
PCE concentration at this outlet is 9.7 |jg/L, which is
roughly 45% of the concentration of PCE of the
groundwater entering the pond at SRSW-13.
Beyond the pond, surface water samples were
collected from eleven locations within the wetland
south of Stream No. 3 (SRSW-15 to 25) and three
locations in that stream (SRSW-7 to 9), which drains
Wetland HJ-54. No site-related COPCs were detected
in any samples collected directly from Stream No. 3.
Between this stream and the constructed pond, only
one site-related COPC was detected above 1 |jg/L
and at only one of the 11 sampling locations. SRSW-
18 showed a maximum PCE concentration of 2 |jg/L.
TCE and cis-1,2 DCE were not detected at any of the
groundwater seep locations. All other surface water
locations, including Streams 1 and 2, showed non-
detect for the COPCs.
Sediments
Site-related CPOCs were detected in several of the
sediment locations that were identified and added
following analysis of groundwater transport pathways
within NYSDEC Wetland HJ-54 just north of
Townsend Road. These locations include SRSD-11,
just north of the storm water culvert beneath
Townsend Road, the two inlets to the constructed
pond (SRSD-12 and SRSD-13), the outlet from the
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constructed pond (SRSD-14) and one location
northeast of the constructed pond (SRSD-22).
Concentrations of site-related VOCs (corrected for
moisture) in the sediment ranged from ND to 3.7 J
jjg/kg for PCE, ND to 1.3 J |jg/kg for TCE, and cis-1,2
DCE was not detected at any sediment sampling
location.
Site-related CPOCs were not detected at any other
sediment sampling location, including locations
SRSW-7 to SRSW-9 located within Stream Number 3,
located north of the constructed pond.
Soils
Once the soil excavation and removal at the Facility
was completed by EPA and IBM, EPA confirmed that
NYS soil cleanup objectives (SCOs) were achieved for
the ingestion of soils and protection of groundwater
pathway.
In 2012, in order to ensure that no surficial soil
contamination was present at the Facility, additional
soil samples were taken in the 0-6 inch range to
ensure that no residual contamination was present.
Samples were analyzed for full TCL VOCs. COPCs
were not detected. No detections were found above
NYS Part 375 SCOs.
Soil Gas
In 2003, in order to evaluate soil gas conditions within
the Site soils, IBM collected and analyzed foundation
level soil gas samples at forty-eight (48) locations
along public right-of-ways within the boundaries of the
Site. Concentrations of CPOCs in these soil gas
samples ranged from non-detect (with a detection limit
of 10 jjg/m3) to 8200 |jg/m3 for PCE, non-detect to 99
|jg/m3 for TCE and non-detect to 39 |jg/m3 for cis-1,2
DCE.
Subsequently, EPA assessed the soil gas data and
performed a vapor intrusion investigation on a building
-by-building basis throughout the Site area. Since
then, EPA has performed annual vapor intrusion
sampling at a limited number of affected properties
and has installed four residential subslab mitigation
systems as a preventative measure. There are no
unaddressed public health issues related to vapor
intrusion at the Site.
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. A baseline human health risk assessment
(BHHRA) was performed to evaluate current and
future cancer risks and noncancer health hazards
based on the results of the Rl.
A screening-level ecological risk assessment (SLERA)
was also conducted to assess the risk posed to
ecological receptors due to site-related contamination.
Human Health Risk Assessment
As part of the RI/FS, a BHHRA was conducted to
estimate the risks and hazards associated with the
current and future effects of contaminants on human
health and the environment. A BHHRA 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 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 COPCs,
Exposure Assessment, Toxicity Assessment, and Risk
Characterization (see text box "What is Risk and How
is it Calculated").
The BHHRA began with selecting COPCs in the
various media (i.e., groundwater, surface water, and
sediment) that could potentially cause adverse health
effects in exposed populations. The current and
future land use scenarios included the following
exposure pathways and populations:
• Residents (child/adult): future ingestion,
dermal contact and inhalation of groundwater.
• Recreator (adult): current ingestion and
dermal contact of surface water and sediment.
• Trespassers (adolescent): current ingestion
and dermal contact of surface water and
sediment.
• Utility Worker (adult): future inhalation of
vapors from groundwater in a trench.
In this assessment, exposure point concentrations
were estimated using either the maximum detected
concentration of a contaminant or the 95% upper-
confidence limit (UCL) 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 BHHRA.
7
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Groundwater
Risks and hazards were evaluated for future exposure
to groundwater. The populations of interest included
adult and child residents exposed to groundwater and
future utility workers exposed to groundwater vapors
in a trench. The cancer risks for all of the receptor
populations evaluated were within or below the
acceptable EPA risk range of 1.0E-06 to 1.0E-04 with
the exception of the combined child/adult resident,
which was at the acceptable cancer risk range of
1.0E-04. The hazard indexes for all of the residential
receptor populations evaluated were above the EPA
acceptable value of 1. The hazard index for the utility
worker was below the EPA acceptable value of 1.
The primary site-related contaminants of concern
(COCs) identified for groundwater were cis-1,2-
dichloroethene, tetrachloroethene and trichloroethene
(Table 1).
Table 1. Summary of hazards and risks associated
with groundwater.
Risks and hazards were evaluated for the potential
current exposure to surface water. The population of
interest included adult recreators and adolescent
trespassers which would have the same exposure
assumptions as an adolescent recreator. The cancer
risks for both receptors were below or within the EPA
acceptable ranges. The non-cancer hazards for both
receptors were below the EPA acceptable value of 1.
There were no site-related COCs identified in the
surface water (Table 2).
Table 2. Summary of hazards and risks associated
with surface water.
Risks and hazards were evaluated for the potential
current exposure to sediment. The population of
interest included adult recreators and adolescent
trespassers. There were no site-related contaminants
that exceed the conservative screening values;
therefore, risks and hazards were not calculated for
these receptors. There were no site-related COCs
identified in the sediment (Table 3).
Table 3. Summary of hazards and risks associated
with sediment.
Receptor
Hazard
Index
Cancer Risk
Current recreator - adult
na
na
Current trespasser -
adolescent
na
na
There were no site-related COCs identified in the
sediment.
Based on the results of the human health risk
assessment, a remedial action is necessary to protect
public health, welfare and the environment from actual
or threatened releases of hazardous substances.
Receptor
Hazard
Index
Cancer
Risk
Future resident - adult
19
7.6E-05
Future resident - child
17
2.5E-05
Future resident - child/adult
36
1.0E-04
Future utility worker - adult
0.5
7.0E-08
The site-related COCs identified in the groundwater were
cis-1,2 DEC, PCE and TCE. Bolded values exceed risk
criteria.
Surface Water
Receptor
Hazard
Index
Cancer Risk
Current recreator - adult
0.006
2.7E-08
Trespasser - adolescent
0.008
8.2E-09
There were no site-related COCs identified in the surface
water.
Sediment
8
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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.
Ecological Risk Assessment
A SLERA was conducted to evaluate the potential for
ecological risks from the presence contaminants in
surface water and sediment. The SLERA focused on
evaluating the potential for impacts to sensitive
ecological receptors to site-related constituents of
concern through exposure to surface water and
sediment in the wetlands that receive groundwater
discharge. 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 all
exposure scenarios can be found in the SLERA.
Surface Water: There is a potential for adverse effects
to ecological receptors (invertebrates, reptiles,
amphibians, birds, and mammals) from exposure to
contaminated surface water due to groundwater
discharge. The hazard indices for the site-related
compounds were below an HI of 1 for both lower
effect levels (LEL) and chronic values which indicates
limited potential for adverse ecological effects (Table
4). Although the hazard indices were less than the
acceptable value of 1, additional monitoring of the
surface water is recommended to ensure that
concentrations remain at acceptable values.
Table 4. Summary of ecological hazard indices
associated with surface water.
Compound
Hazard Index
LEL
Chronic
Tetrachloroethene
0.11
0.54
Trichloroethene
0.0008
0.017
There were no site-related COCs identified in the
sediment, although the pathway is complete.
Sediment: There is a potential for adverse effects to
ecological receptors (invertebrates, reptiles,
amphibians, birds, and mammals) from exposure to
contaminated sediment due to groundwater discharge.
The hazard indices for the site-related compounds
were below an HI of 1 for both LEL and chronic values
which indicates limited potential for adverse ecological
effects (Table 5). Although the hazard indices were
less than the acceptable value of 1, additional
monitoring of the sediment is recommended to ensure
that concentrations remain below acceptable values.
Table 5. Summary of ecological hazard indices
associated with sediment.
Compound
Hazard Index
LEL
Chronic
Tetrachloroethene
0.008
0.001
Trichloroethene
0.006
0.00025
There were no site-related COCs identified in the
sediment, although the pathway is complete.
9
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Based on the results of the ecological risk
assessment, which indicated a completed pathway for
surface water and sediments due to groundwater
discharge with limited potential for any adverse
effects, an active remedial action is not necessary to
protect the environment from actual or threatened
releases of hazardous substances. As noted above,
additional surface water/sediment monitoring in the
HJ-54 area would be performed as part of the
preferred remedy to ensure that concentrations
remain at acceptable values.
Remedial Action Objectives
Remedial Action Objectives (RAOs) are based on
available information and standards, such as
applicable relevant and appropriate requirements
(ARARs) and risk-based levels established in the
SLERA and the BHHRA. The specific RAOs identified
for the Site are listed below:
• To restore groundwater to the NYS
Groundwater Quality Class GA Standards (6
NYCRR Part 703) of 5 pg/L for PCE, TCE and
cis-1,2 DCE.
• To reduce and to control the residual DNAPL
source in fractured gneiss bedrock beneath
the Facility and to prevent migration to the
groundwater.
• To reduce VOC concentrations in the source
area until the aquifer is attenuating sufficiently
to achieve MCLs.
• To prevent ingestion/direct contact of
residential human receptors with groundwater
having a concentration of PCE, TCE or cis-1,2
DCE or their degradation products which
exceed NYSDOH Drinking Water Standards
(10 NYCRR, Part 5, Subpart 5-1) of 5 |jg/L for
principal organic contaminants.
SUMMARY OF REMEDIAL ALTERNATIVES
CERCLA §121 (b)(1), 42 U.S.C. §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 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).
Common Elements
All of the alternatives include certain common
components. All alternatives: Alternative #1 - No
Further Action. Alternative #2 - Monitored Natural
Attenuation (MNA) for Groundwater Plume and
Source Extraction and Treatment and Alternative #3 -
Extraction and Treatment of Bedrock Aquifer. MNA in
Glacial Aquifer and Source Extraction and Treatment
include the continuation of the source extraction and
treatment system which consists of four groundwater
extraction wells and two GAC adsorption vessels
piped in series to treat the contaminated groundwater.
The treated groundwater is discharged to the
designated storm water conveyance under a NYSDEC
permit.
Alternatives #2 and #3 also include 1) the long-term
monitoring of the groundwater and of the surface
water and sediments in the affected areas of HJ-54
and 2) institutional controls, including existing
governmental controls consisting of local laws that
limit exposure to contaminated groundwater by
restricting the drilling of private residential wells and
their use as a domestic supply within established
public water districts, as well as proprietary
institutional controls in the form of environmental
easements and/or covenants placed on the Facility
property to ensure that no construction or other
invasive activities are conducted on the property
which would interfere with existing remedial
components, including the source extraction and
treatment system.
Also, because these alternatives will require more
than five years to achieve health-based levels, the
remedy will be reviewed at least once every five
years. Also, provisions will be made for periodic
reviews of the institutional and engineering controls. If
justified by these reviews, additional remedial actions
may be implemented at the Site.
The source extraction and treatment system that is
already in place and operating was designed to
control the groundwater chemical flux from the source
area at the Facility, namely VOCs, and to diminish the
DNAPL source in bedrock to levels that no longer
require such control. Since the soil contaminated with
levels of PCE typical of a DNAPL source was
removed, the remaining DNAPL zone in the bedrock
beneath the Facility constitutes the only remaining
primary source of continued contamination to the
10
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groundwater. This system is expected to operate for
approximately 15 years.
Current data from the operation of the source
extraction and treatment system show that PCE
concentrations in SRMW-18RA are being reduced.
The reduction in PCE concentrations in this well
indicates that pumping this well is drawing
groundwater with lower PCE concentrations than
existed prior to pumping. This is a positive sign that
the hydraulic influence of this well extends to areas of
the Facility with cleaner groundwater and drawing
cleaner groundwater through the DNAPL source zone
would enhance 1) dissolution of DNAPL in fractures
and 2) back diffusion of dissolved PCE from the rock
matrix. The operating data indicates that mass is
being removed from the source area at a rate of
approximately 50 pounds per year.
All alternatives include ongoing groundwater
monitoring to ensure the continued effectiveness of
the source extraction and treatment system. The four
extraction wells are sampled monthly for operation
and maintenance (O&M) purposes and for compliance
with discharge permitting requirements. Alternatives
#2 and #3 include the expanded monitoring of the
groundwater plume to determine the 'effectiveness of
MNA, as well as surface water/sediment sampling.
The construction time for each alternative reflects only
the time required to construct or to implement the
remedy and does not include the time required to
design the remedy, to negotiate the performance of
the remedy with any PRPs or to procure contracts for
design and construction.
The various costs for the remedial alternatives are
discussed below. All O&M costs are addressed as
operation, maintenance and monitoring (OM&M)
costs.
Detailed descriptions of the remedial alternatives for
addressing the Site contamination can be found in the
FS report. The three remedial alternatives are as
follows:
Alternative #1: No Further Action
The NCP requires that a "No Action" alternative be
developed as a baseline for comparing other remedial
alternatives. Alternative #1 satisfies the EPA
requirement in that no actions beyond that of the
existing source extraction and treatment system would
be taken to address Site risks.
Since the ongoing source extraction and treatment
system is included within all the remedial alternatives,
its implementation is designed to control groundwater
chemical flux from the source area and to reduce the
DNAPL source in bedrock to levels that no longer
require such control. It is estimated that the system
will operate over the next 15 years.
Groundwater monitoring is also included as part of the
system's operation to determine the effectiveness of
this action.
Alternative #2: Monitored Natural Attenuation
(MNA) for Groundwater Plume and Source
Extraction and Treatment
Capital Cost
N/A
Present Worth
$3,985,721
Representative Annual OM&M
$205,837
Construction Time
N/A
Alternative #2 relies on MNA to address the
groundwater contamination. Natural attenuation is the
process by which groundwater contaminant
concentrations are reduced by various naturally
occurring physical, chemical and biological processes.
These processes include biodegradation, dispersion,
dilution, sorption, volatilization and chemical or
biological stabilization, transformation or destruction of
contaminants. The processes occur naturally (in-situ)
and act to decrease the mass or concentration of
contaminants in the subsurface. At this Site, the
principal mechanisms for these reductions have been
dilution and dispersion of dissolved mass after most of
the source contamination was removed. Adsorption on
organic carbon in aquifer solids also accounts for
some of the attenuation observed. These attenuation
mechanisms are responsible for the observed patterns
in the reduction of PCE levels within the groundwater
plume chemistry.
Trends in groundwater concentrations over time in
former residential wells have indicated declining
concentrations of PCE since the original soil removal
action in 2002.
Based on projections of the groundwater monitoring
data and modeling, reductions in the concentrations of
PCE to acceptable levels in the glacial groundwater
would take place over a longer period of time than in
the bedrock groundwater.
Alternative #2 includes 1) the continued operation of
the existing source extraction and treatment system
and 2) the groundwater and surface water/sediment
monitoring program to measure the effectiveness of
Capital Cost
N/A
Present Worth (PW) (15 years)
$1,897,296
Representative Annual OM&M
$143,787
Construction Time
N/A
11
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the MNA remedy for both the bedrock and glacial
aquifers, as well as institutional controls. MNA would
rely on dispersion, dilution, degradation and sorption
within the groundwater plume.
Sixty monitoring wells/intervals are proposed in the
monitoring plan. For the first five years, it is expected
that 27 wells/intervals would be sampled quarterly, 18
sampled semiannually and 15 annually.
Similarly, five groundwater seep and surface
water/sediment sampling locations would be sampled
quarterly, semiannually and annually to provide a
sufficient number of results to permit more accurate
projections and modeling of cleanup times, i.e.,
reduction in VOCs in the groundwater plume.
For years six to 15, it is anticipated that the sampling
frequency for monitoring wells initially sampled
quarterly would be reduced to semiannual, and those
sampled semiannually would be reduced to annual.
The initial annual wells would all still be sampled on
that frequency to provide a full snapshot of
concentrations throughout the plume each year.
At the end of the 15th year, it is anticipated that the
source extraction system would be shut down, based
on the supporting groundwater data, and post-
termination sampling would be performed. Therefore,
for years 16-18, it is assumed that the frequency of
sampling would be returned to quarterly for those
wells identified for years one through five. Sampling
frequencies for years six to 15 at all other wells would
continue. For years 19 to 30, all that remains to be
monitored would be the glacial aquifer and the
groundwater seeps and surface water. Frequency of
that monitoring is assumed to be semiannual.
Alternative #3: Extraction and Treatment of
Bedrock Aquifer, MNA in Glacial Aquifer and
Source Extraction and Treatment
Alternative #3 includes 1) the continued operation of
the source extraction and treatment system, 2) the
associated groundwater and surface water/sediment
monitoring program, 3) bedrock groundwater
extraction from four (4) vertical wells installed at a
depth of approximately 300 feet with treatment to
remove suspended solids by filtration and to remove
VOCs by adsorption on aqueous phase granular
activated carbon (GAC) and 4) institutional controls,
as described above. Discharge of treated groundwater
from the bedrock system would be to surface water.
The extraction wells and associated piping would be
connected to a new groundwater treatment facility.
The groundwater treatment facility would include
instrumentation to monitor, control and record flow
rates and water levels in the extraction wells, as well
as GAC vessels to treat the extracted bedrock
groundwater.
This alternative would require acquisition of an
easement on private property in order to locate and
construct the treatment facility. Following design,
approvals, bidding and permitting, the construction
period is expected to be 10 to 12 months.
Since this remedial alternative is anticipated to reduce
the time required for plume restoration in the bedrock
from 15 years to 10 years, post-termination monitoring
for this component of the remedy would occur in years
11 to 13. This would be in addition to the post-
termination monitoring for the source extraction and
treatment system which would occur in years 16 to 30.
COMPARATIVE ANALYSIS OF ALTERNATIVES
During the detailed evaluation of remedial alternatives,
each alternative is assessed against nine evaluation
criteria: overall protection of human health and the
environment, compliance with ARARs, long-term
effectiveness and permanence, reduction of toxicity,
mobility or volume through treatment, short-term
effectiveness, implementability, cost and state and
community acceptance.
• 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 ARARs addresses whether or not
a remedy would meet all of the applicable or relevant
and appropriate requirements of other federal and
state environmental statutes, regulations and other
requirements or provide grounds for invoking a waiver.
• Long-term effectiveness and permanence refers 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 through
treatment is the anticipated performance of the
treatment technologies, with respect to these
parameters, 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
Capital Cost
$3,823,160
Present Worth
$9,789,848
Representative Annual OM&M
$395,466
Construction Time
10-12 months
12
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may be posed during the construction and
implementation period until cleanup goals are
achieved.
• Implementabilitv 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 costs, operation
and maintenance costs and net present worth costs.
• State acceptance indicates if, based on its review
of the RI/FS and Proposed Plan, the State concurs
with the preferred remedy.
• 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.
Overall Protection of Human Health and the
Environment
Alternative #2 and Alternative #3 would be protective
of overall human health and the environment.
Alternative #1 would not be as protective, since it does
not include active monitoring throughout the
groundwater plume outside the Facility. Alternative #3
would achieve ARARs in the bedrock aquifer five
years sooner than Alternative #2 and thus is
somewhat more protective than Alternative #2.
Compliance with ARARs
Location-specific ARARs would be achieved for all
alternatives. Action-specific and chemical-specific
ARARs would also be achieved for groundwater by
Alternative #2 and Alternative #3. Since the period of
time necessary to attain ARARs in the glacial aquifer
groundwater is determined by the anticipated future
effects of secondary sourcing, i.e., from mass diffused
into the matrix of the rock or adsorbed onto aquifer
solids, the time to attain groundwater standards in this
aquifer cannot be accelerated by any technology that
could be applied to this aquifer in this setting.
Therefore, the only alternative that more quickly
achieves chemical-specific ARARs is Alternative #3,
because it accelerates the attainment of groundwater
standards in the bedrock aquifer from 15 years to 10
years.
Long-Term Effectiveness and Permanence
Alternative #1 does not provide for establishment of
an environmental easement on the Facility. The two
other alternatives are rated as high and achieve this
criterion. Alternative #2 and Alternative #3 rely on a
more robust and reliable set of institutional controls to
prevent potential future exposure to groundwater for
drinking water purposes and restrict interference with
remedial components at the Facility than does
Alternative #1. The operations identified in Alternative
#3 would have long-term impacts to the northern
wetlands, since the discharge would be into the
wetlands.
Reduction of Toxicity. Mobility or Volume Through
Treatment
As discussed above, all of the alternatives include the
source extraction and treatment system as a
component of the remedial action. This system would
produce the greatest amount of mass removal from
the environment of any activity included in all of the
alternatives. The alternatives are mostly equivalent in
terms of the reduction of toxicity and volume of the
source and the reduction of contaminant migration into
the groundwater. Alternative #3 would further reduce
the mobility of the PCE in the bedrock aquifer.
Alternative #3 does the most to reduce mobility. The
other two alternatives, which include only source
extraction and treatment as an active remedial
measure, do not achieve this additional reduction.
Short-term Effectiveness
Since Alternative #1 does not rely on new construction
or activities in public areas other than the current
source extraction and treatment, there are no short-
term impacts. Alternative #2 adds additional
groundwater and surface water/sediment sampling but
no added short-term impacts. As a result of the
magnitude of construction to be performed under
Alternative #3, there would be short-term impacts to
workers and the community, as well as the surface
water in the wetlands. Safety techniques would be
used to minimize exposure risks and reduce the short-
term impacts.
Implementabilitv
All of the alternatives are implementable. Alternative
#1 and Alternative #2 are the easiest to implement,
since no further construction is required. Alternatives
#2 and #3 would require the acquisition of an
easement at the Facility to restrict activities which
would interfere with existing remedial components,
including the source extraction and treatment system.
Alternative #3 involves myriad technical and
administrative issues associated with performing
construction work in public rights-of-way and on
private property. As described above, this alternative
would also require property access and the potential
for property purchase and additional easements in
order to construct the treatment facility.
Cost
The following table identifies the various cost
estimates for the three alternatives.
13
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Alternatives
Capital
Cost
Representative
Annual OM&M
Costs
Total Present
Worth Cost
1
$0
$143,787
$1,897,296
2
$0
$205,837
$3,985,721
3
$3,823,160
$395,466
$9,789,848
As shown above, the alternatives rank from most
costly to least costly as follows: Alternative #3,
Alternative #2 and Alternative #1. Alternative #1 has
the lowest present worth at $1,897,296. Alternative #3
has the highest present worth at $9,789,848.
PROPOSED REMEDY
Based on an evaluation of the three remedial
alternatives, EPA and NYSDEC recommend
Alternative #2: Monitored Natural Attenuation (MNA)
for Groundwater Plume and Source Extraction and
Treatment.
This preference is based on the proven reliability,
effectiveness and efficiency of the ongoing source
extraction and treatment system and MNA.
The preferred remedy can be implemented in an
expeditious manner and has all the necessary
discharge permits and access agreements in place to
continue the source extraction and treatment system.
The preferred remedy would have no impact on the
community.
Other than Alternative #1, the preferred remedy
represents the lowest capital costs, O&M costs and
present worth cost.
EPA believes that the assessment of the three
alternatives has produced a preferred remedy that
would provide the best balance of trade-offs in
assessing the evaluating criteria. EPA and NYSDEC
believe that the preferred remedy would be protective
of human health and the environment, comply with
ARARs, be cost effective and utilize permanent
solutions, treatment technologies to the maximum
extent practicable and satisfy the preference for
treatment as a primary element.
Because this alternative will require more than five
years to achieve health-based levels, the remedy will
be reviewed at least once every five years. . Also,
provisions will be made for periodic reviews of the
institutional and engineering controls. If justified by
these reviews, additional remedial actions may be
implemented at the Site.
Basis for the Remedy Preference
Alternative #2 would rely on the natural attenuation
processes of dispersion, dilution, degradation and
sorption in the groundwater plume to reduce COC
concentrations to below MCLs. Historical Site data
from former residential wells show that concentrations
of COCs in the groundwater plume have declined to
the degree that unacceptable impacts to the
environment can be prevented through these
mechanisms.
Alternative #2 is capable of achieving the Site's
remediation objectives within a timeframe that is
reasonable. EPA expects that Alternative #2 would
achieve MCLs in the groundwater in the glacial aquifer
in approximately 30 years.
The soil removal action demonstrated that
groundwater can be effectively remediated by
Alternative #2 following source remediation and
control. Overall, the majority of the groundwater data
to date shows that the boundary of the groundwater
plume appears to be stable or reducing.
Public water has replaced residential wells as the
source of drinking water. The PWS is drawn from
resources outside the limits of the Site so there would
be no further demand for the groundwater resources
within the STWD. The eight homeowners within the
STWD who still use their private wells would continue
to have the opportunity to connect to the PWS at any
time, now or in the future.
Although the estimated time required to achieve
groundwater standards in the bedrock aquifer in
Alternative #3 is estimated to be 5 years less than
Alternative #2 (10 years vs. 15 years), there are
substantial capital costs, higher O&M costs and
increased short-term impacts to the community
associated with this alternative. In addition, for the
glacial aquifer, more aggressive action would only
intercept contaminant flux to surface water and would
not hasten the attainment of groundwater standards in
this aquifer any faster than Alternative #2. The MNA
timeframe for achieving groundwater standards in the
glacial aquifer for both alternatives is expected to be
30 years.
Alternative #2 is not expected to increase the risk of
generating higher concentrations of more toxic or
mobile transformation products beyond that which
already occurs. As the PCE concentrations are
reduced so are the transformation product
concentrations.
Under Alternative #2, there are both town and county
institutional controls in place to protect against the
installation of drinking water wells within the STWD
14
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and to restrict groundwater use. The DNAPL source
material underlying the Facility is the only Site location
at which COC concentrations above groundwater
standards are expected to persist in the long-term. In
addition, the O&M of the four existing vapor mitigation
systems would continue as would the vapor intrusion
monitoring program. Although not expected, additional
mitigation systems would be installed if monitoring
results demonstrate they are warranted.
Alternative #2 includes the establishment of
environmental easements and/or covenants placed on
the Facility property to ensure that no construction or
other invasive activities are conducted on the property
which would interfere with existing remedial
components, including the source extraction and
treatment system.
The continued operation of the source extraction and
treatment system and the existing and proposed
institutional controls of the preferred remedy enhance
the effectiveness of the MNA remedy.
Alternative #2 is the preferred remedy that includes a
fully operating source control action, MNA in the lower
concentration portions of the groundwater plume and
institutional controls in the form of town and county
laws and easements to prevent invasive activities on
the Facility property.
In combination, these actions would achieve
groundwater restoration in a reasonable timeframe
while utilizing active engineering controls and natural
attenuation processes to protect human health and
the environment.
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- :
i, - zZA'h.;¦ f."
H
;i3f A'< 1
^ / ^v;- \'/7*"L Si'- ./¦¦¦» • ii..
. . ¦ --
Hiils' iw,
------ - Extent of Individual Site CO PCs Detected Above 5 pg/L in Groundwater Figure 1
Study Area Setting
Shenandoah Road Groundwater Contamination Superfund Site
Qi"alo
2000" 4000'
= GROUNDWATER SCIENCES CORPORATION
21003-007-09 / 08-10-12
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<<\*DNAPL
SOURCE ZONE ,
t lN BEDROCK*
Fractured
Carbonate Rock
and Quartzite
Upwelling
Artesian
Flow
DETAIL #3
7 East Hook Cross Road Facility
- EPA-Approved Clean Backfill
Deposits High Organic Carbon
Glacial Till High Organic Carbon
Groundwater Flow
Dissolved PCE
Adsorption and
Intragranular Diffusion
1 / si v y v / V / s / \ S.4 X
x /x > /x \ J /x /x A i
Residual Soil- y Uncontaminated\ i
¦ ^ >£ . — #¦ ^Residual Soil -* V i
' Shallow Groundwater Si "V,m ,N * \;K
K*(frequently dty)', <£*>t y A /!/* %
\ v ^ h vH Vv ^ X v ,\v ^ v ^
v* . . aN / v>^v >> . / 'xN. /X.*r .
5 Dwelling
Dwelling
Previous
POET System
Previous E
POET System <3
(0
Wetlands
Volatilization from Groundwater to Soil Vapor
: -1 i ~ 1
>77
Low Organic Carbon
Low Organic Carbon
Glacial Ice Contact
f High Organic Carbon
X -IX. 4V .XI X -1 X . J\ /X A X I XX ^X1 ^ ^1X1
Dissolved Plum
w*A JS > > VA 51*™ > VX > > > VX i > > > 'X v ,-A\
.y - y - /x /N >\mN /N /x / Fractured /N v >> /x o\
> X X . TQVTQ si^f1 ^ ^ Nsi ¦ 1 JVi > >N 71 XrS\
y< X y y -y: i Gneiss y y y y y
y y y xnW/jI y y y y y y y y y
./ ./ ./ ./ V>» /|J| / / K/1'/ / / ./
-------
SRMW-14RV - Bedrock Monitoring Well Location
SRMW-14S A - Soil Monitoring Well Location
VA - Decommissioned Monitoring Well Location
~A - Currently Inaccessible
SRSW-5 ~ - Surface Water Sampling Location (approx.)
SRSD-5 + - Sediment Sampling Location (approx)
SRSP-1 • - Spring Sampling Location
NTCSRA - Non-Time Critical Source Removal Action
SHN591 • - Residential Well Used for
Hydrogeologic Characterization
SHN603© - Residential Well Retained and
Converted for Long-Term Monitoring
- Inferred Direction of Groundwater Flow
(March 2012)
- Extent of Individual Site COPCs Detected
Above 5 pg/L in Groundwater
Figure 3
Site Map
dShenandoah Road Groundwater Contamination Superfund Site
= GROUNDWATER SCIENCES CORPORATION
21003-092-A7/ 00-10-12
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