THIRD FIVE-YEAR REVIEW REPORT FOR
HOCOMONCO POND SUPERFUND SITE
WESTBORO, MASSACHUSETTS
WORCESTER COUNTY
Prepared by:
U.S. Environmental Protection Agency
Region One
BOSTON, MASSACHUSETTS
¦ V& tj2S
ies T. Owens, III, Division Director Date
Office of Site Remediation and Restoration
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TABLE OF CONTENTS
Table of Contents
I. INTRODUCTION 1
II. PROGRESS SINCE THE LAST REVIEW 1
III. FIVE-YEAR REVIEW PROCESS 9
IV. TECHNICAL ASSESSMENT 14
V. ISSUES/RECOMMENDATIONS and FOLLOW-UP ACTIONS 21
VI. PROTECTIVENESS STATEMENT 21
VII. NEXT REVIEW 22
APPENDIX A 1
EXISTING SITE INFORMATION 1
A. SITE CHRONOLOGY 1
B. BACKGROUND 3
APPENDIX B - FIGURES, TABLES AND PHOTOS
APPENDIX C - SITE INTERVIEWS
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LIST OF ACRONYMS
ADAFs
Age-Dependent Adjustment Factors
ARARs
Applicable or Relevant and Appropriate Requirements
BTEX
Benzene, toluene, ethylbenzene and xylene
CERCLA
Comprehensive Environmental Response, Compensation, and Liability Act
CFR
Code of Federal Regulations
CIC
Community Involvement Coordinator
CSFs
Cancer Slope Factors
DNAPL
Dense Non-Aqueous Phase Liquid
EPA
United States Environmental Protection Agency
ESD
Explanation of Significant Differences
FYR
Five-Year Review
GEREs
Grants of Environmental Restrictions and Easements (aka: ICs)
ICs
Institutional Controls
IGCLs
Interim Groundwater Cleanup Levels (aka: RAOs)
LTMP
Long-Term Monitoring Program
MA
Massachusetts
MassDEP
Massachusetts Department of Environmental Protection
MCLs
Maximum Contaminant Levels
ug/1
microgram per liter
mg/1
milligram per liter
NAULs
Notices of Activity and Use Limitations (aka: ICs)
NCP
National Contingency Plan
NPL
National Priorities List
O&M
Operation and Maintenance
PAHs
Poly-Aromatic Hydrocarbons
PRP
Potentially Responsible Party
RAOs
Remedial Action Objectives
RCRA
Resource Conservation and Recovery Act
RfD
Reference Dose
RI
Remedial Investigation
ROD
Record of Decision
RPM
Remedial Project Manager
SDD
Supplemental Decision Document
SIM
Selective Ion Monitoring
TI
Technical Impracticability
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EXECUTIVE SUMMARY
This is the third Five-Year Review (FYR) for the Hocomonco Pond Superfund (Site) located in
the Town of Westboro, Worcester County, Massachusetts. The purpose of this FYR is to review
information to determine if the remedy is and will continue to be protective of human health and
the environment. The triggering action for this Policy FYR was the signing of the previous FYR
on September 30, 2009.
The approximately 23-acre Site is located in the Town of Westboro, Massachusetts. The Site is
bordered to the northwest by Hocomonco Pond, a 27-acre shallow freshwater pond, to the east
by Otis Street and to the south by the Smith Valve Parkway. See Figure B-l for Site location
map.
The remedial investigation (RI) identified four primary areas of contamination on the Site: (1)
the former Kettle Pond area; (2) Hocomonco Pond and its discharge stream; (3) the former
lagoon area; and (4) the Otis Street embankment. These areas are shown in Figure B-2. In
addition, the RI identified three small isolated areas; contaminated soil near MW-1; tank bases
adjacent to the former lagoon; and sediments in the southwest drainage channel. The
predominant contaminants found in all the areas were creosote compounds, primarily polycyclic
aromatic hydrocarbons (PAHs), such as acenaphthene, naphthalene, acenaphthylene, fluorene,
phenanthrene, dibenzofuran, and 2-methylnaphthalene.
The September 30, 1985 Record of Decision (ROD) specified a multi-component remedy to
address each of the areas of contamination at the Site. The remedies selected involved
excavation and dredging of contaminated soil, waste, and sediments from the Kettle Pond area,
Hocomonco Pond and its discharge stream, Otis Street, and the three isolated areas, followed by
disposal into the former lagoon or a double-lined landfill constructed on the site. The former
lagoon area would be capped. The remedy also included dewatering Kettle Pond and lowering
the groundwater level prior to and during excavation, relocating the storm drain pipe that was
laid along the eastern side of the former lagoon, and sealing the open-jointed storm drainage pipe
along the east side of Otis Street.
Pre-design investigations in the Kettle Pond area identified a number of issues, including
extensive Dense Non-Aqueous Phase Liquid (DNAPL) contamination at depth. EPA issued an
Explanation of Significant Differences (ESD) in 1992 that required active pumping to remove
recoverable DNAPL and modified the requirement for dewatering as part of the remedy for the
Kettle Pond area to implementation of bioremediation or other in-situ technologies to treat the
deeper soils.
Following issuance of the ESD, EPA established cleanup levels for groundwater, sediments, and
soil and established the limits of excavation in a 1992 Supplemental Decision Document (SDD).
All excavation and dredging activities were completed by 1996 and certification reports
documenting completion of the remedial activities were submitted and approved by EPA.
DNAPL recovery operations, required by the 1992 ESD, began in 1995. The in-situ
bioremediation system also required by the 1992 ESD was constructed and began operation, but
was not successful due to significant iron fouling. Other treatment alternatives were evaluated;
the evaluation concluded that other treatment alternatives would have limited effectiveness due
to the residual and free phase DNAPL present in the Kettle Pond area.
Hocomonco Pond 3rd Five Year Review
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A technical impracticability (TI) investigation was completed in 1997 which identified two TI
zones where groundwater restoration was deemed not practicable due to the presence of DNAPL.
See Figure B-3. A second ESD was issued by EPA in 1999 that waived compliance with the
interim groundwater cleanup levels (IGCLs) within the two TI zones and required continued
DNAPL recovery and implementation of a long-term monitoring program (LTMP) to ensure that
groundwater concentrations above IGCLs would be contained within the TI zone boundaries.
The 1999 ESD stated that, "DNAPL recovery is ongoing and shall continue until such time that
it can be demonstrated that it is no longer technically practicable."
In 2003, active pumping of DNAPL was suspended to assess the efficacy of passive recovery
methods. These methods demonstrated that active pumping is not required to achieve
meaningful DNAPL recovery. Extensive groundwater monitoring concludes that the DNAPL is
not migrating, and no potential receptors have been identified. However, in 2002, concentrations
of two PAHs, naphthalene and benzene, began to intermittently exceed groundwater cleanup
levels in sentinel monitoring well MLC-2. Then in 2007, concentrations of benzene also began
intermittently exceeding its cleanup level in sentinel well MLC-3. Both of these wells are
located down gradient and just outside of the TI zone associated with the former lagoon area. No
increasing trend was evident in either well. In 2012, two new well pairs: MLC-5S/D and MLC-
6S/D, were installed approximately 100 feet down gradient of MLC-2 and MLC-3. See Figure
A-4. Groundwater samples collected from the new well pairs have shown trace concentrations
of only a few PAHs. A third ESD was issued by EPA in September 2013 that expanded the TI
boundary associated with the former lagoon area by about 100 feet and modified the remedy for
DNAPL recovery from active to passive collection methods.
Hocomonco Pond 3rd Five Year Review
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Five-Year Review Summary Form
SITE IDENTIFICATION
Site Name:
Hocomonco Pond
EPA ID:
MAD980732341
Region: 1
State: MA
City/County: Westboro/Worcester
Five-Year Review Summary Form (continued)
Iss
u es/ Reco m in en d a tio n
s
Issues and Recommendations Identified in the Five-Year Review:
OU(s): Entire
Issue Category: Institutional Controls
Site
Issue: #1. Deed restrictions are not in place.
Recommendation: Finalize NAULs consistent with recent MassDEP
regulations approved in May 2014.
Affect Current
Protectiveness
Affect Future
Protectiveness
Party Responsible
Oversight
Party
Milestone
Date
No
Yes 1
PRP/EPA/MassDEP
EPA/MassDEP
9/30/2015
Hocomonco Pond 3rd Five Year Review
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OU(s): Entire
Site
Issue Category: Operations and Maintenance
Issue: #2. Updated O&M plan consistent with current activities is required.
Recommendation: Finalize an updated O&M plan.
Affect Current
Protectiveness
Affect Future
Protectiveness
Party Responsible
Oversight
Party
Milestone
Date
No
Yes
PRP
EPA/MassDEP
12/31/2014
OU(s): Entire
Site
Issue Category: Remedy Performance
Issue: #3. Bulk sediment concentrations intermittently exceed ecological cleanup
goals.
Recommendation: Continue annual monitoring. If sample results continue to
exceed cleanup levels, and an increasing trend in concentrations becomes
apparent, perform additional toxicity testing.
Affect Current
Protectiveness
Affect Future
Protectiveness
Party Responsible
Oversight
Party
Milestone
Date
No
Yes
PRP
EPA/MassDEP
9/30/2019
Sitewiile Protectiveness Statement
Protectiveness Determination: Addendum Due Date (if applicable):
Short-term Protective not applicable
Protectiveness Statement:
The remedy currently protects human health and the environment because physical access to
the Site is restricted and there are no potable wells. However, in order for the remedy to be
protective in the long-term, the following actions need to be taken: deed restrictions need to be
finalized and recorded, an updated O&M plan must be finalized, and active monitoring of
sediments and groundwater must continue to ensure long-term protectiveness.
Hocomonco Pond 3rd Five Year Review
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I. INTRODUCTION
The purpose of a Five-Year Review (FYR) is to evaluate the implementation and performance of a
remedy in order to determine if the remedy will continue to be protective of human health and the
environment. The methods, findings, and conclusions of reviews are documented in five-year review
reports. In addition, FYR reports identify issues found during the review, if any, and document
recommendations to address them.
The U.S. Environmental Protection Agency (EPA) prepares FYRs pursuant to the Comprehensive
Environmental Response, Compensation, and Liability Act (CERCLA) Section 121 and the National
Contingency Plan (NCP). CERCLA 121 states:
"If the President selects a remedial action that results in any hazardous substances, pollutants,
or contaminants remaining at the site, the President shall review such remedial action no less
often than each five years after the initiation of such remedial action to assure that human health
and the environment are being protected by the remedial action being implemented. In addition,
if upon such review it is the judgment of the President that action is appropriate at such site in
accordance with section [104] or [106], the President shall take or require such action. The
President shall report to the Congress a list offacilities for which such review is required, the
results of all such reviews, and any actions taken as a result of such reviews. "
EPA interpreted this requirement further in the NCP; 40 Code of Federal Regulations (CFR) Section
300.430(f)(4)(ii), which states:
"If a remedial action is selected that results in hazardous substances, pollutants, or
contaminants remaining at the site above levels that allow for unlimited use and unrestricted
exposure, the lead agency shall review such actions no less often than every five years after the
initiation of the selected remedial action."
EPA conducted a FYR on the remedy implemented at the Hocomonco Pond Superfund Site in the Town
of Westboro, Worcester County, MA. EPA is the lead agency for developing and overseeing remedy
implementation by the Potentially Responsible Parties (PRPs) for the Site. The Massachusetts
Department of Environmental Protection (MassDEP), as the support agency representing the
Commonwealth of Massachusetts, has reviewed all supporting documentation and provided input to
EPA during the FYR process.
This is the third FYR for the Hocomonco Pond Superfund Site. The triggering action for this policy
review is the completion of the second FYR on September 30, 2009. This FYR is required due to the
fact that hazardous substances, pollutants, or contaminants remain at the Site above levels that allow for
unlimited use and unrestricted exposure. There are no operable units, therefore the entire Site is
addressed in this FYR.
II. PROGRESS SINCE THE LAST REVIEW
In addition to routine maintenance and monitoring activities, several important steps have been
Hocomonco Pond 3rd Five Year Review
Page 1
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completed since the last five year review. In October 2012, the PRPs submitted, "Revised DNAPL
Recovery Enhancement and TI Zone Delineation Sampling Work Plan." Field work was completed in
late 2012 to early 2013 and included an extended evaluation of groundwater quality in the area down
gradient of the former lagoon, and inspection and cleaning of existing DNAPL recovery wells. In
addition, two groundwater monitoring wells and one additional DNAPL recovery well were installed.
This work was documented in a March 2013 report, "DNAPL Recovery Enhancement and TI Zone
Delineation Report." The conclusions gained from this additional field work resulted in EPA issuing a
3rd Explanation of Significant Differences (ESD) for the Hocomonco Pond Site in December 2013. The
ESD changed the procedure for DNAPL recovery from active pumping through a large scale
groundwater extraction system to passive collection of DNAPL from each well head using submersible
pumps, and slightly expanded the TI zone down gradient of the former lagoon area. The 2013 ESD also
allows the PRPs to decommission and remove the former groundwater treatment system and associated
above ground piping which opens the door to reuse of the property. The Town of Westboro, as the
property owner, is actively evaluating reuse options. The Massachusetts Department of Environmental
Services (MassDEP) also issued new regulations in May 2014 which will allow pending institutional
controls to be finalized on the property.
Table 1 below documents the protectiveness statement from the previous 2009 five-year review report.
Table 2 below summarizes the issues and recommendations for follow-up actions identified in the
previous 2009 five-year review report, and provides the updated Current Status and Completion Date. A
text discussion of each issue follows.
Table 1: Protectiveness Determinations/Sta
tements from the 2009 FYR
ou#
Protectiveness
Determination
Protectiveness Statement
Sitewide
Short-term Protective
The remedy currently protects human health and the environment
because physical access to the Site is restricted and there are no
potable wells. However, in order for the remedy to be protective in the
long-term, the following actions need to be taken; deed restrictions
need to be finalized and recorded, and the studies and evaluations
referenced in Section 9.0 will be completed to ensure long-term
protectiveness.
Table 2: Status of Recommendations from the 2009 FYR
OU#
Issue
Recommendations
/
Follow-up Actions
Party
Responsible
Oversight
Party
Original
Milestone
Date
Current
Status
Completion
Date (if
applicable)
Site-
Wide
#1. Deed
restrictions are
not in place
Finalize draft
documents and
record deed
restrictions
PRP
EPA
12/31/2004
Ongoing
12/31/2014
Site-
Wide
#2.
Groundwater
cleanup levels
exceeded at
wells MLC-2
and MLC-3,
outside the
former lagoon
TI Zone
Increase frequency
of sampling MLC-2
and MLC-3 from
annual; evaluate the
extent of cleanup
level exceedances
and need for
additional actions
to achieve
compliance
PRP
EPA/State
9/30/2010
Completed
11/30/2012
Hocomonco Pond 3rd Five Year Review
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ou#
Issue
Recommendations
/
Follow-up Actions
Party
Responsible
Oversight
Party
Original
Milestone
Date
Current
Status
Completion
Date (if
applicable)
Site-
Wide
#3. Analytical
reporting limit
for cPAHs is
too high
Use SIM analytical
method for PAHs
to achieve lower
reporting limits
PRP
EPA/State
9/30/2009
Completed
9/07/2011
Site-
Wide
#4. Arsenic
and chromium
data are not
available for
comparison to
IGCLs
Conduct periodic
groundwater
sampling for
arsenic and
chromium at site
monitoring wells
PRP
EPA/State
9/30/2009
Completed
4/28/2011
Site-
Wide
#5. Dissolved-
phase plume
not contained
Perform additional
studies to
determine plume
extent, discharge
location, and
presence of a
significant
exposure pathway
PRP
EPA/State
9/30/2010
Completed
9/30/2013
Site-
Wide
#6. DNAPL
plume may not
be contained
Perform additional
studies to
determine plume
extent, and evaluate
opportunities for
optimization of
DNAPL recover
PRP
EPA/State
9/30/2010
Completed
9/30/2013
Site-
Wide
#7. An
accurate, up-
to-date site
monitoring and
operations plan
does not exist
Prepare an updated
site monitoring and
operations plan
PRP
EPA/State
9/30/2010
Ongoing
9/1/2014
Issue/Recommendation #1 (Deed restrictions not in place)
• Implementation of Institutional Controls (ICs) in Massachusetts, namely the recording of Grants
of Environmental Restrictions and Easements (GEREs), has been a continued challenge for the
program. The need to complete ICs has often been identified as an issue potentially impacting
future protectiveness as part of Five Year Reviews at this and other Massachusetts sites. In an
effort to address this issue and improve the process of completing ICs at Massachusetts NPL
sites, the Massachusetts Department of Environmental Protection (MassDEP) has amended its
cleanup regulations, the Massachusetts Contingency Plan (310 CMR 40.0000), to allow the same
land use controls used at non-NPL sites in Massachusetts to now be used at NPL sites. The
amendments became effective on June 20, 2014. EPA and MassDEP are currently working on
revising the existing Notices of Activity and Use Limitations (NAULs) form for use at NPL
sites. The use of NAULs at Massachusetts NPL sites will streamline the process and result in the
implementation of ICs more quickly and efficiently, and address these Five Year review
recommendations within a reasonable time frame.
Hocomonco Pond 3rd Five Year Review
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• EPA and MassDEP have entered into discussions specific to finalizing ICs for Hocomonco Pond.
Previous draft GERE language provides a baseline for moving forward. The Town of Westboro
is the property owner and has expressed a willingness to cooperate. Consequently, ICs are
anticipated to be in place by the end of 2014.
Issue/Recommendation #2 (Groundwater cleanup levels exceeded outside TI Zone boundary')
• Interim groundwater cleanup levels were established based on federal and state drinking water
standards, referred to as Maximum Contaminant Levels (MCLs). Risk-based concentrations
were used to calculate cleanup levels for PAHs that do not have drinking water standards.
Cleanup levels for groundwater were established as "interim" concentrations in recognition of
the fact that they may need to be modified during the cleanup. Cleanup levels are waived within
the established TI zone compliance boundary.
• MLC-2 and MLC-3 are sentinel wells located down gradient and just outside the TI Zone
boundary established for the former lagoon area. In 2000, concentrations of benzene and
naphthalene in monitoring well MLC-2 climbed above their respective interim groundwater
cleanup levels. In 2006, the concentrations of benzene and naphthalene also climbed above the
interim groundwater cleanup levels in MLC-3. Through 2011, concentrations in both wells
continued to fluctuate above and below the interim cleanup levels, but were more often above.
Please see Table B-l for a summary of results from MLC-2, and Table B-2 for a summary of the
results from MLC-3. There were no monitoring wells located down gradient of MLC-2 and
MLC-3.
• Between November 5,2012 and January 3, 2013, the PRPs completed a TI Zone assessment in
the area down gradient of the former lagoon and monitoring wells MLC-2 and MLC-3. A
vertical profile boring was completed to assess groundwater quality. The groundwater table was
encountered and sampled at 35 feet below ground surface. Subsequent samples were collected
every 20 feet of depth to the top of bedrock at 130 feet below ground surface. The samples were
analyzed for benzene, toluene, ethylbenzene and xylene (BTEX) and total PAHs, including
benzene and naphthalene. The interim groundwater cleanup levels were not exceeded in any
sample.
• The PRP installed two nested well pairs in the area of the vertical profile boring; MLC-5S/D and
MLC-6S/D. These new wells were first sampled in January, and then again in November 2013.
Detected benzene concentrations ranged from 0.66 to 0.82 ppb; well below the IGCL of 5.0 ppb.
Detected naphthalene concentrations ranged from 0.34 to 2.0 ppb; well below the IGCL of 1,500
ppb. These results are summarized in Table B-3. MLC-5S/D and MLC-6S/D will continue to be
monitored annually moving forward and replace MLC-2 and MLC-3 and sentinel compliance
wells for the former lagoon TI boundary.
Hocomonco Pond 3rd Five Year Review
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• On September 30, 2013, EPA issued a 3rd Explanation of Significant Differences (ESD) for the
Hocomonco Site. Through this ESD, the TI Zone compliance boundary for the down gradient
portion of the former lagoon area was extended approximately 100 feet, and MLC-5S/D and
MLC-6S/D serve as the new sentinel wells to ensure compliance with the IGCLs.
Issue/Recommendation #3 (Analytical reporting limits for PAHs too high)
• The analytical method for PAHs in groundwater had a detection limit of 0.51 ppb for
benzo(a)pyrene which was above the IGCL. Beginning with groundwater samples collected on
September 7, 2011, the SIM method 8270C has been used to analyze PAHs. The method
detection limit for benzo(a)pyrene is now 0.11 ppb, which is lower than the IGCL of 0.2 ppb.
Issue/Recommendation #4 (Arsenic and Chromium data are not available)
• The 1985 ROD set IGCLs for arsenic at 50 ug/1 and chromium at 100 ug/1. The previous Five-
Year Review report recommended that arsenic and chromium data be collected. In response, the
PRPs conducted a thorough review of the Site file and presented their findings in a memorandum
dated April 28, 2011. Arsenic and chromium were sampled on several occasions between 1985
and 1997, including regional background/reference areas known as Jordan Pond and Assabet
River Dam, which are located outside the impacted study area. Elevated concentrations of
arsenic and chromium above IGCLs were identified in both background/reference areas. In the
most recent sampling event (1997), 33 wells across the study area were sampled for both total
and dissolved arsenic and chromium. All dissolved (filtered) results were below IGCLs. Total
arsenic exceeded the IGCL in 3 of the 33 wells; BRW-2, M-l IS and M-12S. Total chromium
also exceeded the IGCL in 3 of the 33 wells; LF-1, MLC-1, and TRC-9S. Monitoring wells LF-
1, MLC-1 and TRC-9S are located upgradient of the former lagoon and Site operations.
Monitoring well M-12S is located cross-gradient to the former Kettle Pond area, and monitoring
wells BRW-2 and M-l IS are located down gradient of the former Kettle Pond. These results are
not consistent with the primary creosote/PAH release. Arsenic and chromium are well
documented in soil throughout the New England area as the result of natural occurring releases
and depositional activities.1 A review of the Site specific data conclude that the pattern of
arsenic and chromium concentrations in Site groundwater do not follow the same distribution as
the known PAH releases. This suggests that the detected concentrations of arsenic and
chromium are attributable to background or depositional sources. No further monitoring for
arsenic or chromium is required at this time.
Issue/Recommendation #5 (Dissolved phase plume not contained)
• To clarify, the 1999 ESD did not require mechanical pumping for hydraulic containment as was
implied in the last Five-Year Review Report. The 1999 ESD did require continued monitoring to
1 Technical Update, "Background Levels of Polvcvclic Aromatic Hydrocarbons and Metals in Soil." MassDEP, 05/23/2002.
The regional background concentration for arsenic in soil was determined to be 20 mg/kg. The maximum detected
concentration was 99 mg/kg. The regional background concentration for total chromium in soil was determined to be 30
mg/kg. The maximum detected concentration was 530 mg/kg.
Hocomonco Pond 3rd Five Year Review
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ensure that concentrations above IGCLs are not exceeded outside the TI Zone boundaries (and
hence contained) as well as to establish that contaminant levels generally do not increase in
concentration or extent. As discussed in Issue/Recommendation #2, beginning in 2000,
concentrations of benzene and naphthalene in monitoring well MLC-2 climbed above their
respective IGCLs. In 2006, the concentrations of benzene and naphthalene also climbed above
IGCLs in MLC-3. Both wells were located down gradient and outside the TI zone for the former
lagoon area.
• As recommended in the last Five-Year Review Report, in April 2011, the PRPs submitted a work
plan for expanded testing of existing monitoring wells around the former lagoon area. The
purpose of this testing was to gain more data from MLC-2 and MLC-3, and determine if
additional exceedances of the TI zone boundary for the former lagoon area existed. Nine wells
were inspected and analyzed for BTEX and PAHs. Benzo(a)pyrene was detected in one sample
event from monitoring wells TRC-8D and TRC-9D above the IGCL. These wells are located
cross-gradient to the former lagoon area and subsequent samples have demonstrated compliance
with all IGCLs. The results continued to demonstrate intermittent exceedances of IGCLs in wells
MLC-2 and MLC-3.
• In October 2012, the PRPs submitted a TI Zone delineation sampling work plan which included
a vertical profile study of groundwater quality immediately down gradient of MLC-2 and MLC-
3. In November 2012, a vertical profile was advanced to the top of bedrock (135 feet below
ground surface). The groundwater table was encountered at 35 feet below ground surface. As
the boring was advanced, discrete groundwater samples were collected at 20 foot depth intervals
to the top of bedrock (6 samples collected). Samples were transferred to an off-site laboratory
for analysis of benzene, toluene, ethylbenzene and xylenes (BTEX) by EPA method 8060B and
poly-aromatic hydrocarbons by EPA method 8070C. Results showed only trace detections of
benzene and naphthalene, and two nested well pairs were installed; MLC-5S/D and MLC-6S/D.
These well pairs are approximately 100 feet down gradient of MLC-2 and MLC-3. The most
recent sampling of the new well pairs in November 2013 demonstrate continued compliance with
the IGCLs.
• In September 2013, EPA issued a 3rd ESD for the Site which extended the down gradient
compliance boundary of the TI zone around the former lagoon area by approximately 100 feet
and requires continued monitoring of the new sentinel monitoring wells MLC-5S/D and MLC-
6S/D. There are no known receptors located down gradient of the sentinel wells. Hocomonco
Pond is located approximately 100 feet down gradient of the new sentinel wells and is a natural
hydraulic barrier to further groundwater migration. See Figure B-5 for locations of the previous
and current TI zone boundaries, and monitoring wells. There is an active sediment monitoring
program established in the pond.
• The vertical profile data and subsequent installation and sampling of new monitoring well
clusters MLC-5S/D and MLC-6S/D, in conjunction with ongoing monitoring of other sentinel
Hocomonco Pond 3rd Five Year Review
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wells verifies no exceedances of IGCLs outside the current TI zone boundaries. Consistent with
the September 2013 ESD, concentrations exceeding IGCLs are hydraulically contained within
the current TI zone boundaries.
Issue/Recommendation #6 (DNAPL plume may not be contained')
• The 1999 ESD required that DNAPL recovery continue until such time as it can be demonstrated
that it is no longer technically practicable. At that time DNAPL removal was accomplished
through operation of a large scale groundwater extraction and treatment system. While the 1999
ESD established a TI waiver ending efforts to achieve IGCLs within the TI zone boundaries,
active pumping continued to remove DNAPL. This method resulted in a large volume of
groundwater being extracted and treated as a consequence of DNAPL capture. The PRPs
requested that EPA consider direct recovery of DNAPL from individual wells using submersible
pumps (the so called passive method). In order to assess the effectiveness of passive recovery
methods, EPA allowed the PRPs to switch from active pumping to passive recovery of DNAPL
in 2003. DNAPL is removed from individual wells on a weekly basis without the need to extract
and treat large volumes of groundwater. A total of 13 wells are currently inspected weekly.
DNAPL is removed when volumes of sufficient thickness are detected. A majority of the
DNAPL has consistently been recovered from three wells; DRW-1, DRW-2 and A-4, and more
recently from newly installed well DRW-4. Passive recovery rates have ranged from 30 to 120
gallons per month, with an average of about 60 gallons per month. While this rate is lower than
the 250 to 500 gallons per month that was previously recovered using active pumping, 60 gallons
per month represents a substantial and meaningful volume of mass removal. However, EPA
believed that opportunities for enhanced passive recovery existed through optimization and
additional passive recovery wells.
• As recommended in the last Five-Year Review Report, in October 2012, the PRPs submitted a
DNAPL recovery enhancement work plan which included the inspection and cleaning of existing
DNAPL recovery wells and the installation of a new passive recovery well. Inspections and
cleaning of well screens was accomplished and in November of 2012, and a new passive
recovery well, DRW-4 was installed. DNAPL recovery from DRW-4 was initiated in January
2013. An average of 15 gallons per month of DNAPL is removed from DRW-4. This additional
well is expected to increase average monthly recovery rates to 75 gallons per month, however the
most productive wells continue to be DRW-2 (-25 gals/month), A-4 (~12 gals/month) and
DRW-1 (-10 gals/month). In total, approximately 65,000 gallons of DNAPL have been
removed from the Site. The extended inspections and continued passive recovery efforts
demonstrate that the DNAPL and associated areas of impacted groundwater contamination
appear to be stable and no nearby receptors exist. Figure B-4 shows the DNAPL recovery wells
including DRW-4. Table B-4 summarizes the most recent recovered volumes.
Issue/Recommendation #7 (Up to date O&M plan does not exist)
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• In September 2013, EPA issued an ESD which changed the recovery method for DNAPL from
active to passive, and extended the TI zone boundary in the area down gradient of the former
lagoon. In support of this decision, a new DNAPL recovery well, DRW-4 was installed and two
new sentinel groundwater monitoring well clusters, MLC-5S/D and MLC-6S/D were installed.
These wells have been incorporated into the Site monitoring program and the PRPs are in the
process of updating the operations and maintenance plan for the Site to reflect these changes.
The updated plan is expected to be finalized by the end of this year.
Remedy Implementation Activities
In response to issues raised in the last Five-Year Review Report, the PRPs submitted a work plan in
October 2012 which required additional field work. EPA issued a 3rd ESD for the Site in December
2013, which required the remedial activities summarized in Table 6. The 3rd ESD also re-affirmed the
need for pending ICs which are listed in Table 7. Current O&M activities are summarized in Table 8.
This activities are discussed in more detail in Appendix A.
Table 3: Summary of Completed Remedial Activities Since 2009
Media
Nature of the Action
Remedy Change
Groundwater
Two new well clusters were
installed, MLC-5S/D and MLC-
6S/D.
The IT zone compliance boundary
down gradient of the former lagoon
area was extended by about 100 feet.
MLC-5S/D and MLC-6S/D are new
sentinel wells.
DNAPL
Existing recovery wells were
inspected and cleaned. A new
recovery well, BRD-4, was
installed.
Active recovery of DNAPL has been
changed to passive recovery methods.
The groundwater treatment plant will
be dismantled.
'able 4: Summary of Penc
ing ICs
Media
ICs
Needed
ICs Called
for in the
Decision
Documents
Impacted
Parcel(s)
IC
Objective
Title of IC
Instrument
Implemented
and Date (or
planned)
Groundwater
Yes
Yes
Entire
property
Prevent ingestion
of contaminated
groundwater.
Prevent
migration of the
DNAPL and
dissolved
plumes.
Massachusetts
activity and use
limitation to be
recorded on
deed. Planned
September
2014.
Lagoon/Landfill
caps
Yes
Yes
~1 acre
former
lagoon cap.
~2 acre
landfill cap.
Protect the cap
by preventing
any potentially
intrusive
activity.
Massachusetts
activity and use
limitation to be
recorded on
deed. Planned
September
2014.
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System Operation/Operation and Maintenance Activities
Table 5: Summary of O&M Activities Since 2009
Media
Activity
Lagoon/Landfill
Caps
1. Semi-annual mowing of grass.
2. Semi-annual inspection of side slopes.
3. Semi-annual inspection and removal (as needed) of tree seedlings and
other potentially damaging invasive vegetation.
Groundwater
1. Annual gauging for DNAPL.
2. Annual measurement of water table elevations
3. Annual sampling for BTEX, PAHs and typical field parameters from 12
area wells.
DNAPL
1. Weekly gauging of DNAPL from wells DRW-1, DRW-2, DRW-3, DRW-
4, A-2, A-4, A-6, A-10, BMW-4, BMW-6, BRW-5, M-l ID and M-12S.
2. Weekly removal of DNAPL from wells with a measurable thickness of 1
foot or 4 feet depending on well design.
3. Quarterly removal of DNAPL from all wells with a minimum of 0.3 feet
of accumulation.
III. FIVE-YEAR REVIEW PROCESS
Administrative Components
The PRP representative, Mike Bollinger of Beazer East, Inc., was notified of the initiation of the third
five-year review on 10/22/2013. The Hocomonco Pond Superfund Site Five-Year Review was led by
Jim DiLorenzo of the U.S. EPA, Remedial Project Manager for the Site and Pamela Harting-Barrat, the
Community Involvement Coordinator (CIC). Jay Naparstek of the Massachusetts Department of
Environmental Protection (MassDEP), assisted in the review as the representative for the support
agency.
The review, which began on 4/17/2014, consisted of the following components:
• Community Involvement;
• Document Review;
• Data Review;
• Site Inspection; and
• Five-Year Review Report Development and Review.
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Community Notification and Involvement
Activities to involve the community in the five-year review process were initiated with a meeting in
December 2013 between the RPM and CIC for the Site. A press release announcing 27 upcoming five-
year reviews in Region 1, including the Hocomonco Pond Site, was issued by EPA on 2/13/2014 and
provided links to each of the 27 sites where readers could find Site-specific details. On 7/31/2014, EPA
hosted a Site tour for local officials and community members interested in reuse options for the Site.
That same evening, EPA, MassDEP and the PRP representative made a brief presentation on the Site
and answered questions at a meeting hosted by local officials. The results of the review and a copy of
this report will be made available at the Site information repository located at Westboro Public Library,
on West Main Street in Westboro, MA 01581 and EPA's regional web site.
Document Review
This five-year review consisted of a review of relevant documents including O&M records and
monitoring data. Applicable sediment and groundwater cleanup standards as listed in the 1992 SDD
were reviewed along with the 1985 ROD, and 1992,1999 and 2013 ESDs.
Data Review
The O&M plan includes passive recovery of DNAPL, and routine monitoring of groundwater and
sediments for BTEX and PAHs. Volume data associated with the DNAPL recovery is presented below,
followed by analytical data from monitoring of groundwater and sediment.
DNAPL Data
The DNAPL is creosote containing various volatile and semi-volatile chemicals (primarily BTEX and
PAHs). Recovery of DNAPL began in 1995, and therefore a significant dataset exists. This section
focuses on data collected since the last five year review in 2009. DNAPL thickness is gauged on a
weekly from 13 wells with a known history of DNAPL collection. DNAPL is removed on a weekly
basis from any well with an accumulation of 4 or more feet from wells with sumps, or 1 foot or more
from wells without sumps. DNAPL which has accumulated to a thickness of 0.3 or more feet is
removed from each well at least once per quarter.
DNAPL is removed from each well via a permanently installed or portable submersible pump. Extracted
DNAPL is transferred to 55 gallon drums for off-site treatment and disposal. 13 wells are routinely
inspected for accumulation and possibly removal of DNAPL, but a majority of the DNAPL is removed
from 4 wells; DRW-1, DRW-2, DRW-4 and A-4. DRW-4 was installed in 2012 as part of the passive
recovery enhancement effort. Figure B-4 identifies the DNAPL well locations. Table B-4 provides a
summary of the most recent recovery volumes. Since 2009, passive recovery rates have average 60
gallons per month and have remained steady. Approximately 65,000 total gallons of DNAPL have been
removed to date, with about 3,500 gallons removed since the last five year review. The total remaining
volume is unknown.
Groundwater Data
Annual and expanded testing of area monitoring wells for BTEX and PAHs has been performed since
the last five year review was completed in 2009. In addition, a vertical profile borehole was completed
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and two new monitoring well clusters (MLC-5S/D and MLC-6S/D) were installed. Annual monitoring
of groundwater is performed to ensure that concentrations exceeding IGCLs are not detected outside the
TI zone boundaries. Vertical profiling and expanded groundwater testing were performed at select wells
to assess compliance with the TI zone boundary for the former lagoon area.
9 groundwater sampling events have occurred since the last five year review. A summary of the results
from each event follows. Figure B-4 identifies groundwater monitoring well locations. Tables B-l, B-2
and B-3 provide a summary of analytical results for the wells of interest during this five year review.
Table A-3 summarizes the IGCls. Generally speaking, no discernable trends exist and groundwater
conditions appear stable. No IGCLs have been exceeded outside the TI zone since the TI zone boundary
was expanded in December 2013.
November 2009
Annual testing. 10 wells were sampled for BTEX and PAHs. IGCLs were exceeded for benzene in
MLC-2 (5.2 ug/1) and MLC-3 (50.6 ug/1).
November 2010
Annual testing. 8 wells were sampled for BTEX and PAHs. IGCLs were exceeded for benzene in MLC-
2 (13.4 ug/1) and MLC-3 (7.0 ug/1); and naphthalene in MLC-2 (6,720 ug/1)
September 2011
Annual testing. 12 wells were sampled for BTEX and PAHs. IGCLs were not exceeded.
December 2011
Expanded testing. MLC-2 and MLC-3 were sampled for BTEX and PAHs. IGCLs were exceeded for
benzene and naphthalene in MLC-2 (10.4 ug/1 and 2,140 ug/1 respectively); and benzo(a)pyrene in TRC-
8D (0.21 ug/1) and TRC-9D (0.31 ug/1).
March 2012
Expanded testing. MLC-2, MLC-3, TRC-8S/D and TRC 9S/D were sampled for BTEX and PAHs. The
IGCL was exceeded for naphthalene in MLC-2 (1,590 ug/1).
May 2012
Expanded testing. MLC-2, MLC-3, TRC-8S/D and TRC 9S/D were sampled for BTEX and PAHs.
IGCLs were exceeded for benzene in MLC-2 and MLC-3 (7.6 ug/1 and 9.9 ug/1 respectively).
August 2012
Expanded testing. MLC-2 and MLC-3 were sampled for BTEX and PAHs. IGCLs were exceeded for
benzene in MLC-2 and MLC-3 (7.6 ug/1 and 39.4 ug/1 respectively); and naphthalene in MLC-2 (2,280
ug/1).
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January 2013
Expanded testing. Newly installed wells MLC-5S/D and MLC-6S/D were sampled for BTEX and
PAHs. IGCLs were not exceeded.
November 2013
Annual testing. 14 wells were sampled for BTEX and PAHs. MLC-2 and MLC-3 were not sampled and
have been replaced by MLC-5S/D and MLC-6S/D. IGCLs were not exceeded.
Sediment Data
Sediments were dredged and removed from the southeast quadrant of Hocomonco Pond in 1995, and
replaced with clean off-site material. Subsequent samples of the "clean" sediment collected along the
southeast shore line of Hocomonco Pond showed increasing concentrations of PAHs. These results
suggested that groundwater from the Kettle Pond area containing dissolved PAHs, primarily
naphthalene, was discharging through remediated "clean" sediment along the eastern shore line. A
sediment sampling plan was developed in 1998 which included annual and semi-annual sampling
events. Since the last five year review in 2009, annual sediment sampling has continued. Samples were
previously collected from four near shore stations. In 2009, the PRPs agreed to add two additional
stations to assess sediment conditions near the mid-pond limits of excavation. Samples are analyzed for
total PAHs and phenanthrene. Total organic carbon content and physical parameters are also measured.
The sediments consist predominately of sand and gravel.
Five sediment sampling events have occurred since the last five year review. A summary of results from
each event follows. Figure B-6 identifies the six sediment sample locations. Table B-5 provides a
summary of analytical results. Generally speaking, no statistical trends exist.
2009
Total PAH concentrations ranged from non-detect at station SED 3-4 to 26.44 mg/kg at station SED 1 A.
Phenanthrene concentrations ranged from non-detect at stations SED 1, SED 2A and SED 3-4 to 4.10
mg/kg at SED 1 A.
2010
Total PAH concentrations ranged from 0.04 mg/kg at station SED DSHP to 59.00 mg/kg at station SED
1A. Phenanthrene concentrations ranged from non-detect at station SED DSHP to 3.70 mg/kg at SED
2A.
2011
Total PAH concentrations ranged from 0.18 mg/kg at station SED DSHP to 107.00 mg/kg at station
SED 1. Phenanthrene concentrations ranged from non-detect at station SED DSHP to 17.00 mg/kg at
SED 1.
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2012
Total PAH concentrations ranged from 0.10 mg/kg at station SED 3-4 to 49.00 mg/kg at station SED 1.
Phenanthrene concentrations ranged from 0.0053 mg/kg at station SED 3-4 to 9.70 mg/kg at SED 1.
2013
Total PAH concentrations ranged from 11 mg/kg at station SED 2 to 161.00 mg/kg at station SED 1.
Phenanthrene concentrations ranged from 0.775 at station SED 2 to 25.00 mg/kg at SED 1.
While total PAHs and phenanthrene bulk concentrations appear to demonstrate increasing trends,
particularly in the most recent sampling event, consistent with the work plan, statistical analysis of the
results was performed using both the Mann-Kendall and Regression Analysis methods. Mann-Kendall
concludes no discernible trend exists for total PAHs and carbon-normalized phenanthrene, however an
increasing trend appears for bulk phenanthrene. Regressional Analysis shows a downward trend in
carbon-normalized total PAHs concentrations and no disceraable trend for phenanthrene.
These results may be indicative of the highly variable nature of total organic carbon content within the
sediments. While each station has a physical marker and a gps coordinate, it is not possible to extract a
sample from the exact physical location during each event. However, these results may also be
indicative of near shore discharge of the dissolve-phase plume which is no longer being hydraulically
influenced by upgradient groundwater/DNAPL extraction which was discontinued in 2003.
Site Inspection
An inspection of the Site was conducted on 7/31/2014. In attendance were Jim DiLorenzo, U.S. EPA;
Jay Naparstek, MassDEP, and the PRP representative Mike Bollinger, Beazer East, Inc. The purpose of
this inspection was to assess the protectiveness of the remedy.
Upon arrival, the gate entrance was observed to be secure and locked. No evidence of trespassing was
observed anywhere on the property. The former groundwater treatment building was locked and secure.
The former lagoon and landfill caps were observed to have been mowed and trees, shrubs and other
potentially damaging seedlings had been removed. No erosion was observed. Monitoring and DNAPL
recovery wells which were observed during the inspection were locked and secure.
No issues were identified.
At approximately 4:00pm, the town manager, local officials and about 30 interested members of the
community arrived for a tour of the property. The pending five-year review was discussed along with
potential reuse options being considered by the town including a solar panel array, walking and biking
trails and a fire department training facility.
The Site gate was secured and locked upon completion of the tour. Photos are attached in Appendix B.
Interviews
During the FYR process, the EPA RPM interviewed interested parties, including the Manager for the
Town of Westboro (who is also the current landowner), the PRP representative and a MassDEP official
Hocomonco Pond 3rd Five Year Review
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who are all involved in Site activities or aware of the Site. The purpose of the interviews was to
document any perceived problems or successes with the remedy that has been implemented to date.
Interviews were conducted on 7/31/2014. Interviews are summarized below and complete interviews are
attached.
Name
REP
DATE
ISSUES AND KEY POINTS
Jay Naparstek
MassDEP
7/31/2014
No issues. Remedy functioning as intended.
Mike Bollinger
PRP
7/31/2014
No issues. Remedy functioning as intended.
Jim Malloy
Town
7/31/2014
No issues or impacts to community.
IV. TECHNICAL ASSESSMENT
Question A: Is the remedy functioning as intended by the decision documents?
Yes. In December 2013, EPA issued a third ESP for the Site which extended the TI zone boundary and
formally changed the method of DNAPL extraction from active to passive. Dissolved phase
groundwater concentrations remain stable and below interim groundwater cleanup levels outside the
current TI zone boundaries. Passive DNAPL recovery rates remain stable. Recent sediment data
indicates an increase in bulk PAHs. but when statistically adjusted for normalized total organic carbon,
no discernable trend exists.
Remedial Action Performance. The on-Site landfill and former lagoon area caps remain in good
condition and are functioning as designed. They are covered by mature grasses and no erosion has been
noted. Seedlings have been actively removed as needed to prevent root permeation. The monitoring
program established to ensure plume containment within the identified TI zone boundaries is ongoing,
as is DNAPL recovery.
Annual groundwater monitoring around the landfill (fully encapsulated) has shown few detections of
PAHs. Monitoring around the former lagoon area (capped only, no liner) has detected naphthalene at
three of the four sentinel wells. Benzene and naphthalene concentrations in wells MLC-2 and MLC-3,
located just down gradient of the former lagoon TI zone boundary, had intermittently exceeded their
respective interim groundwater cleanup levels. In 2012, a vertical profile study of groundwater quality
was performed about 100 feet down gradient of MLC-2 and MLC-3. This study concluded only trace
detections of PAHs, and two new clustered sentinel wells were installed; MLC-5S/D and MLC-6S/D. In
December 2013, EPA issued an ESD which extended the down gradient boundary of the former lagoon
TI zone by approximately 100 feet. MLC-5S/D and MLC-6S/D are now routinely monitored in place of
MLC-2 and MLC-3 as part of the program to ensure compliance with IGCLs outside the TI zone. In
December 2011, benzo(a)pyrene was detected slightly above the interim groundwater cleanup standard
in sentinel wells TRC-8D and TRC-9D, which are located along the east boundary of the TI zone for the
former lagoon area. These wells are cross-gradient to groundwater flow. This one time exceedance has
not been repeated in any other sample event and these results are considered to be anomalous.
In December 2013, EPA issued an ESD which formally modified the method for recovery of DNAPL
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from active high-rate extraction of mixed groundwater/DNAPL to passive well-head collection of only
DNAPL using submersible pumps. Recovered DNAPL is transferred to 55 gallon drums for off-Site
treatment and disposal. Through July 2014, approximately 65,000 gallons of DNAPL have been
recovered. DNAPL is gauged weekly in approximately 13 wells and continues to be detected, and
recovered in the same group of wells where it has historically been found. Recovery rates since 2009
have remained generally stable at about 60 gallons per month. In 2012, all wells with a history of
DNAPL were inspected and, to the extent possible, cleaned. An additional recovery well, DRW-4, was
installed and has slightly increased monthly recovery rates over the past year. A majority of DNAPL is
removed from four wells; DRW-1, DRW-2, DRW-4 and A-4. No consistent trend of increasing, or
decreasing DNAPL thickness has been observed.
Total PAH and phenanthrene concentrations in sediments have varied over the last 5-year monitoring
period (2009-2013), and are generally consistent with post-remediation sediment data dating back to
1998 (See Table B-5). However, total PAH concentrations have exceeded the ecological cleanup level of
35.00 mg/kg at different stations over the past four sampling rounds. The highest detected total PAH
concentration to date, 161 mg/kg, was detected at SED 2 in May 2013. The previous highest
concentration was 143.9 mg/kg also at SED 2 in May 2002. The human health sediment cleanup level
was established in the 1992 SDD based on total carcinogenic PAHs (cPAHs). At that time, all PAHs
were considered to be equal in toxicity to the most toxic, which is benzo(a)pyrene. Since the
development of these levels, EPA has approved a relative potency method for evaluating risks to cPAHs
whereby each individual cPAH is evaluated using the toxicity value for benzo(a)pyrene in combination
with a comparative relative potency factor. Application of the currently approved method demonstrates
that measured cPAH concentrations are well below a human health level of concern. However, access
to the pond for intrusive recreational activities remains limited and where access is available, signs are
posted indicating no swimming or fishing allowed. Statistical review of the data using Mann-Kendall
and Regression Analysis shows no discernable trend when adjusted for normalized organic carbon. It is
unclear if recent sediment results are indicative of increased discharge of groundwater containing
dissolve-phase contamination or variability in total organic carbon content; or both. In response to
higher total PAHs observed at SED 2 in 2002, toxicological testing (H.azteca) was performed to survey
the health of local benthic community. A few of the replicate tests shows a slight reduction in survival
but no overt toxicity was observed.
System Operations/O&M. Annual Site costs have been higher than the ROD estimate for O&M
activities. The ROD estimated the following costs for the O&M activities associated with the selected
remedies:
•Former lagoon area - $21,000 annually for water quality monitoring and cap maintenance;
•On-Site landfill - $20,000 annually for water quality monitoring; and
•Otis Street storm drain - $5,000 annually for discharge monitoring.
Site costs from the period of 2009 to 2013 had ranged from $70,000 to $216,000 and currently average
$102,000. The modifications to the remedy specified in the 2013 ESD are not anticipated to have any
significant impact on O&M costs moving forward. Some capital costs were expended in 2012 and 2013
to complete the expanded groundwater testing, install 3 new wells, and inspect and clean existing
DNAPL recovery wells. Additional capital expenditures are anticipated to decommission the former
groundwater treatment building and related infrastructure, but collectively these costs are anticipated to
be minor as compared to reoccurring maintenance and monitoring costs.
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Opportunities for Optimization. Field work for optimization of passive DNAPL recovery methods
was completed in 2012, including:
• Installation of a new recovery well (DRW-4) designed to increase recovery of DNAPL.
• Inspection of existing DNAPL recovery wells using a borehole televiewer device.
• Cleaning of well casings and screens to the extent possible.
No further opportunities for optimization have been identified.
Early Indicators of Potential Issues. No significant problems with the remedies in place or the on-
going O&M activities were identified during this five-year review. Data collected to date indicate that
groundwater concentrations are generally stable. DNAPL recovery rates remain steady.
Recent sediment data may indicate an uptick in exceedance of ecological cleanup levels. No discernable
data trend exists and results may be indicative of variable total organic carbon content. It is
recommended that annual testing continue at all six stations to further assess sediment conditions.
Implementation of Institutional Controls. The ROD, and 1999 and 2013 ESDs all require that
institutional controls in the form of deed restrictions be put in place to protect the caps in the former
lagoon and landfill areas, prevent development along the embankment of Otis Street, and prohibit
extraction of groundwater for purposes other than the remedial action unless certain conditions are met.
These restrictions are prepared in draft form but have not yet been finalized and recorded due to
regulatory hurdles. However, in May of 2014, MassDEP finalized new regulations which are expected
to clear the way to place these restrictions by the end of 2014. The Town of Westboro, as the property
owner, is actively pursuing reuse options for the property and is prepared to cooperate with the
placement of institutional controls. There are no known potable wells located within the impacted, or
immediate downgradient, portions of the Site aquifer. The six-foot high chain link fencing around the
perimeter of the property remains in good condition and adequately restricts access. Consequently, all
known routes of exposure are currently under control.
Question B: Are the exposure assumptions, toxicity data, cleanup levels, and remedial action
objectives (RAOs) used at the time of the remedy section still valid?
Yes. Exposure assumptions and available toxicity information used at the time of remedy selection are
still valid. Subsequent changes in toxicity values and risk assessment methods have occurred since
remedy selection; however, these changes do not impact the protectiveness of the remedy.
Changes in Standards and TBCs. Since the 1985 ROD was a pre-SARA decision, no detailed listing
or analysis of applicable or relevant and appropriate requirements was included. The 2004 Five-Year
Review report provided an ARARs evaluation. As was done for the 2009 Five-Year Review, this Five-
Year Review focuses on any ARAR changes since the last 2009 Five-Year Review. For the purposes of
this review and compliance with current requirements, tables of action-, location-, and chemical-specific
ARARs are included in Appendix E of this report.
The action-specific ARARs applicable to the landfill and former lagoon area covering post-closure care
have not changed. The federal RCRA regulations in 40 CFR Part 264 (§264.310) and the companion
state regulations in 310 CMR 30.633 remain applicable to long-term post-closure care and groundwater
monitoring. Since the interim cleanup levels were established for groundwater, the interim cleanup
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levels for ethylbenzene, toluene, xylenes (total), and chromium (total) now represent the final MCLs for
each compound, rather than the final MCLGs which were in place when the SDD was completed in
1992. Consistent with the NCP, non-zero MCLGs are an appropriate reference for cleanup goals. In
most - but not all- cases, the MCL and MCLG are equal. The reference to MCLGs should be retained
where the MCLG is not zero.
The 2004 Five-Year Review report suggested that MCP Method 1 GW-1 standards are applicable for the
Hocomonco Pond Site. However, as determined in the 2009 Five-Year Review report, Site-specific
risk-based cleanup goals established in the SDD, along with the Massachusetts MCLs, provide the
protectiveness necessary at the Site. MCP Method 1 GW-1 standards would be appropriate for use in
lieu of a detailed risk evaluation, which was performed in the SDD. Therefore, the MCP Method 1 GW-
1 standards are not considered as chemical-specific ARARs. However, the standards are useful for
evaluation/comparison purposes with respect to analytes where IGCLs were not developed in the SDD.
Further discussion of analytes without IGCLs is presented later in this section.
Changes in Exposure Pathways. The zoning of the area around the Site has remained as general
industrial. In the previous five-year reviews, it was noted that the Town of Westboro was considering a
change to the zoning ordinance and addition of a village townhouse overlay district, but has not pursued
this path. The 2013 ESD allows for decommissioning of the former treatment building and related
infrastructure which have been physical barriers to reuse. Consequently, the town is actively pursuing
reuse options for the Site which currently include passive recreation such as walking trails, a solar panel
array and/or a fire training facility. All these options may be implemented consistent with the remedy
and current zoning.
Human health exposure pathways evaluated in 1992 included fish ingestion and surface water exposure.
These pathways did not show risk/hazards above the EPA risk range or a hazard index of 1 at that time.
As the remedy removed the source material, current results are not expected to have increased, even
with revisions to dermal calculation methods which have occurred since the 1992 evaluation. However,
if recontamination of sediment occurs at concentrations greater than pre-remedial actions, a re-
evaluation may be necessary. Pre-remedial sediment concentrations of total PAHs were as high as
1,108.38 mg/kg; and cPAHs were as estimated to be as high as 144.82 mg/kg.
The excavation and dredging actions, and subsequent disposal of the contaminated materials in the on-
Site double-lined landfill or within the former lagoon area cap originally eliminated the direct contact,
ingestion, and inhalation exposure pathways that were evaluated for human health risks in the SDD.
Once the required deed restrictions are in place, any future exposure to materials beneath the caps will
be prevented, as will potential exposure via ingestion of groundwater. Sediment sample results from
2013 contained some of the highest post-remediation concentrations measured to date and have been
above the ecological risk-based cleanup goals, but remain well below pre-remedial concentrations, and
the data are not inconsistent with historical post-remediation sediment results dating back to 2008.
There is no increasing trend in concentrations. It is not clear if the recent higher results are due to the
heterogeneous nature of sediments or may be indicative of groundwater recharge. Regardless, the
collective sediment data indicate that total PAH concentrations remain well below pre-remedial levels
and there does not appear to be evidence of current significant risk to human receptors.
One pathway of potential concern that was not evaluated in the previous risk assessments was the future
vapor intrusion pathway. This pathway may be of concern at sites where soil and shallow groundwater
contaminated with VOCs exists in close proximity to occupied buildings. Except for the groundwater
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treatment plant building, there are no buildings located above the groundwater plume that could contain
concentrations of VOCs above vapor intrusion groundwater screening values. The treatment building is
only occasionally occupied for short periods of time. However, should shallow groundwater VOC
contamination continue to exist coincident with future Site development involving regular use of the
treatment building or the construction of new buildings that will be occupied consistently (e.g., office
space), the vapor intrusion pathway should be further evaluated to determine if there is potential risk to
on-Site workers.
Exposure pathways for ecological receptors included potential exposure in shallow sediments of
Hocomonco Pond and the former Kettle Pond area. Future exposures in the Kettle Pond area were
eliminated based on the remedy involving excavation of contaminated soil/waste and on-Site disposal
into the double-lined landfill. Removal of the shallow sediment from the southeastern portion of
Hocomonco Pond and its discharge stream was completed to remove potential exposure to aquatic
organisms. However, a DNAPL source remains at depth and monitoring of sediments suggests that
groundwater discharge of dissolved contaminants may be contributing to exceedances of ecological
cleanup levels set by EPA for shallow sediments in the pond, further indicating that an exposure
pathway to aquatic organisms may still be present. Although an exposure pathway may still be present,
sediment toxicity testing performed in 2003 on pond sediments which had only slightly lower total PAH
concentrations as was measured in 2013 concluded that no unacceptable impacts to aquatic organisms
existed.
Changes in Toxicity and Other Contaminant Characteristics. In the development of the soil and
sediment cleanup levels in the 1992 SDD, all PAHs were considered to be equal in toxicity to the most
toxic, benzo(a)pyrene. Since the development of these levels, EPA has approved a relative potency
method for evaluating risks to carcinogenic PAHs whereby each individual cPAH is evaluated using the
toxicity value for benzo(a)pyrene in combination with a comparative relative potency factor. Among
the other cPAHs, only dibenzo(a,h)anthracene is considered equal in toxicity to benzo(a)pyrene. All
other cPAHs are considered less toxic. Since the cleanup levels were developed using the
benzo(a)pyrene toxicity factor for all cPAHs without the relative potency factors, the levels are more
protective than they would be if they were re-calculated today.
Risk-based interim groundwater cleanup levels were calculated for noncarcinogenic PAHs. Toxicity
values used in the calculation of interim groundwater cleanup levels (RfDs and CSFs) remain unchanged
with the exception of the RfD for naphthalene, which has decreased by 50 percent (historical - 4x10-2
mg/kg-day; current - 2x10-2 mg/kg-day). For this reason, if the interim groundwater cleanup level for
naphthalene was recalculated today, it would decrease to 750 ng/L from the existing cleanup level of
1,500 ng/L. Note also that current methods would utilize the naphthalene RfD as a surrogate for other
non-carcinogenic PAHs which do not have RfDs (e.g., acenaphthylene, benzo(g,h,i)perylene, and
phenanthrene). The cleanup levels for these analytes would then be the same as naphthalene. Based on
a review of the available groundwater monitoring data, application of the revised RfD would not impact
the current determination of protectiveness with respect to groundwater because there are no current
exposure pathways to groundwater.
2-Methylnaphthalene is a non-carcinogenic PAH which has historically not been reported as part of the
analytical methods used at the Site. Recent reporting has shown detections of this analyte. Using a
current RfD of 4x10-3 mg/kg-day, the cleanup goal for 2-methylnaphthalene would be one-tenth of the
historical naphthalene cleanup level (150 ng/L). The detected results are all below this concentration.
Hocomonco Pond 3rd Five Year Review
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Changes in Risk Assessment Methods. Soil and sediment cleanup levels for human health were
developed for total cPAHs assuming adult and child recreational exposures to soil and sediment through
ingestion and dermal contact. Contact was assumed to occur 24 days per year during summer months at
most locations within the Site. For the area of the discharge stream, contact was assumed to occur 12
days per year. The selected cleanup levels correspond to cancer risk levels of 10"6. The assumptions
used in developing these cleanup goals remain reasonable.
Sediment cleanup levels for protection of aquatic life were developed for total PAHs and phenanthrene.
Three different methods were used to develop the ecological cleanup levels, with the average of the
three methods selected as the final level. Since the ecological cleanup level for total PAHs is greater
than the human health level for total PAHs, the cleanup level used for shallow sediments (0 to 2 feet)
was the more stringent human health-based cleanup level. The sediment cleanup level for phenanthrene
of 4 mg/kg was established by EPA (1992) based on Site-specific sediment organic carbon
concentrations using three methods. The cleanup levels established by EPA, adjusted for Site-specific
organic carbon concentrations in the SDD, are reasonably-based and adequately protective levels.
Interim groundwater cleanup levels for human health were developed based on the assumption that
groundwater could be used as a drinking water source. The selected cleanup levels correspond to cancer
risk levels of 10"6 and Hazard Quotients of 1.0, consistent with current EPA guidelines. Exposure
assumptions were consistent with the assumptions that are still accepted today for drinking water
scenarios. Subsequent to when groundwater cleanup levels were established in the SDD, dermal
absorption and inhalation of volatile contaminants were incorporated into the development of risk-based
groundwater cleanup levels, rather than ingestion alone. The impact of this change is minor for most of
the PAHs which required development of risk-based cleanup goals, because they are not volatile and are
not adsorbed significantly. Naphthalene, however, is volatile and would include consideration of the
inhalation pathway during potable water use (e.g., showering/bathing) if cleanup goals were currently
developed. As there are no current exposure pathways to the groundwater, the protectiveness of the
remedy is not currently impacted by this change.
Subsequent to the SDD, a new method to evaluate compounds with mutagenic modes of action, such as
the carcinogenic PAHs, is now recommended by EPA. The current methodology calls for the use of
age-specific adjustment factors to account for an increased sensitivity during early life. This
supplemental early-life calculation was not performed as part of the SDD evaluation since the EPA
carcinogen risk assessment guidance was published subsequent to the completion of the Site-specific
risk evaluation. Based on the data available for this five-year review, the early-life calculation would
not be expected to change risk conclusions at the Site with respect to what would require remediation.
Risk calculated for the media/exposure areas which were not remediated were all below the EPA cancer
risk range of 10"6 to 10"4. The early-life calculation utilizes age-dependent adjustment factors (ADAFs)
which would, at most, increase the risk 10-fold (for a child 0-2 years old) and would generally increase
the risk due to cPAHs at the Site by a factor of 3 (the ADAF for ages 2 to 16 is 3 and the Site child
evaluated was ages 6 to 18). Either of these increases results in risks remaining within or below the
EPA cancer risk range of 10"6 to 10"4.
Expected Progress Towards Meeting RAOs. The portions of the remedy involving excavation and
dredging of contaminated soils and sediments, and placement in the on-Site double-lined landfill or the
capped former lagoon area, have met the RAOs described in the ROD for the areas of contamination.
The RAO for groundwater was changed by the 1999 ESD and TI waiver from groundwater restoration
to plume containment within the identified TI zones as modified by the 2013 ESD. The on-going long-
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term groundwater monitoring program was developed to demonstrate that RAOs are not exceeded
outside the TI zone boundaries. Exceedances had regularly been detected in monitoring wells MLC-2
and MLC-3, which are located just down gradient of the former lagoon area and just outside the related
TI zone boundary. A study was performed to assess groundwater quality further down gradient from
these wells. A clean boundary was determined and two new monitoring well pairs were installed, MLC-
5S/D and MLC 6S/D. In December 2013, EPA issued a third ESD for the Site which established a new
TI zone compliance boundary for the former lagoon area. Groundwater data collected from MLC-5S/D
and MLC-6S/D, and all other monitoring wells tested demonstrate compliance with the groundwater
RAOs.
Long-term monitoring of sediments in Hocomonco Pond indicates some exceedances of both total PAH
and phenanthrene ecological cleanup levels. Data collected since 2010 seem to indicate an overall
increase in the frequency of the exceedances, however statistical evaluation of the data sets indicate no
discernable trend for total organic carbon normalized results. In other words, variability in the bulk
sediment results appears to be due to the heterogenetic nature of the sediments. Biological testing of the
benthic community in 2003 indicated no significant toxicity associated with levels similar to and only
slightly lower than currently measured. The existing LTMP (currently being updated) states that if the
concentration of PAHs exceed the cleanup levels set in the SDD by EPA, and monitoring indicates
increasing trends in sediment PAH levels, additional biological monitoring may be recommended.
Further biological testing is not recommended at this time since results do not indicate increasing trends.
Question C: Has any other information come to light that could call into question the protectiveness of
the remedy?
No. There is no new information identified through this review which would call into question the
protectiveness of the remedy for known potential human health and ecological receptors.
No other information has been identified during completion of this five-year review that could affect the
protectiveness of the remedy. There have been no reports of flooding in the low-lying portions of the
Site. No new ecological risks have been identified. Additional benthic invertebrate community
monitoring will be performed if warranted based on the decision tree process outlined in the LTMP.
Technical Assessment Summary
The landfill and former lagoon area caps are in good condition and are functioning as designed. The
monitoring established to ensure plume containment within the identified TI zones is ongoing, as is
DNAPL recovery. With the establishment of a new TI zone compliance boundary around the former
lagoon area, and based on the available data, there are no exceedances of IGCLs outside the TI zone
boundaries. DNAPL recovery has been optimized through inspection and cleaning of existing wells,
and the installation of a new recovery well. DNAPL recovery rates have remained constant. While there
is no current evidence of negative impacts to human or ecological receptors, recent sediment data
suggests that dissolved-phased contaminants in groundwater may be discharging to Hocomonco Pond.
Continued monitoring of sediments is recommended. The required deed restrictions are not yet in place;
however, there is no evidence of trespassing at the Site and recent changes to regulations at the state
level should allow restrictions to be finalized this year.
There have been no changes to ARARs or other applicable standards identified in the SDD and design
documents.. There have been no land use changes or changes to exposure pathways. EPA has approved
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a relative potency method for evaluating risks to cPAHs whereby each individual cPAH is evaluated
using the toxicity value for benzo(a)pyrene in combination with a comparative relative potency factor.
All individual cPAHs are considered less toxic or equal in toxicity to benzo(a)pyrene. Since the cleanup
levels were developed using the benzo(a)pyrene toxicity factor for all cPAHs without the relative
potency factors, the levels are more protective than they would be if they were re-calculated today.
However, use of ADAFs for early-life calculations associated with mutagenic compounds would lower
the sediment cleanup goal approximately 3-fold.
The RfD for naphthalene has decreased by 50 percent. If the groundwater cleanup level for naphthalene
was recalculated today, it would decrease to 750 |j.g/L from the current cleanup level of 1,500 jj.g/L.
Furthermore, inclusion of the dermal adsorption and inhalation pathways could decrease the
groundwater cleanup level for naphthalene to below 10 jj.g/L.
V. ISSUES/RECOMMENDATIONS AND FOLLOW-UP ACTIONS
Table 6: Issues and Recommendations/Follow-up Actions
Issue
Recommendations/
Follow-up Actions
Party
Responsible
Oversight
Agency
Milestone
Date
Affects Protectiveness?
(Yes/No)
Current
Future
#1. Deed
restrictions are not
in place.
Finalize NAULs
consistent with recent
MassDEP regulations
approved in May 2014.
PRP, EPA,
MassDEP
EPA
MassDEP
9/30/2015
No
Yes
#2. Updated O&M
plan consistent with
current activities is
required.
Finalize an updated
O&M plan.
PRP
EPA
MassDEP
12/31/2014
No
Yes
#3. Bulk sediment
concentrations
intermittently
exceed ecological
cleanup goals.
Continue annual
monitoring. If sample
results continue to
exceed cleanup levels,
and an increasing trend
in concentrations
becomes apparent,
perform additional
toxicity testing.
PRP
EPA
MassDEP
9/30/2019
No
Yes
VI. PROTECTIVENESS STATEMENT
Sitewiile Protectiveness Statement
Protectiveness Determination: Addendum Due Date (if applicable):
Short-term Protective not applicable
Protectiveness Statement:
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The remedy currently protects human health and the environment because physical access to
the Site is restricted and there are no potable wells. However, in order for the remedy to be
protective in the long-term, the following actions need to be taken: deed restrictions need to be
finalized and recorded, an updated O&M plan must be finalized, and active monitoring of
sediments and groundwater must continue to ensure long-term protectiveness.
VII. NEXT REVIEW
The next five-year review report for the Hocomonco Pond Superfund Site is required five years from the
completion date of this review (September 30, 2019).
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APPENDIX A
EXISTING SITE INFORMATION
A. SITE CHRONOLOGY
Table A-l
Hocomonco Pond
Site Chronology
Event
Date
Montan Treating Company and American Lumber & Treating Company
conducted wood-treating operations on the Site.
1928-1946
Facility was converted to an asphalt mixing plant and later into a cement
plant.
Late 1940's
Beazer East, Inc. (formerly Beazer Materials and Services, Inc.; formerly
Koppers Company, Inc.) purchased the stock of the wood treating
operating company.
1950's
Smith Valve Company purchased the property of the former operations
(also operates a manufacturing plant on a separate parcel on the
southwest side of Hocomonco Pond).
April 2, 1976
An open-jointed storm drain was installed crossing the Site from Smith
Valve Parkway to Hocomonco Pond.
1976
MA Division of Fisheries & Wildlife investigated two fish kills at Hocomonco
Pond, attributed to creosote contamination.
November 1979 & April
1982
Studies and investigations were conducted to evaluate the source and
extent of creosote contamination and evaluate methods to remove or
contain the contamination (attributed to creosote and water leaking into the
storm drain laid adjacent to the former lagoon and discharging to
Hocomonco Pond).
1979-1982
Site proposed for listing on the National Priority List (NPL) due to the threat
creosote contamination posed to the Otis Street municipal well and
Hocomonco Pond.
Dec. 30, 1982
Excavation during reconstruction of Otis Street resulted in disturbance of
contamination in the Kettle Pond area and redistribution of contaminated
soil in the road embankment adjacent to the Kettle Pond area.
July 1983
Site was placed on the NPL.
Sept. 8, 1983
Information repositories were established at the Westboro Town Hall and
Public Library.
January 1984
Remedial investigation / feasibility study (RI/FS) was issued.
September 1985
ROD was signed.
Sept. 30, 1985
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Consent Decree entered into between EPA, the Commonwealth of
Massachusetts, and the PRPs. Consent Decree entered by the U.S.
District Court for the District of Massachusetts.
Jan. 10, 1988
Pre-design investigations conducted by the PRP.
1988-1992
Relocation of the storm drain (initially installed in 1976) was completed.
January 1990
First Explanation of Significant Differences (ESD), changing the remedy for
the Kettle Pond area, was issued by the EPA.
July 22, 1992
Supplemental Decision Document entitled "Cleanup Levels for Sediments,
Soils and Groundwater and Limits of Excavation of Sediments and Soils"
was issued by the EPA.
Sept. 28, 1992
Remedial design completed.
1993
Groundwater treatment plant constructed.
1993-1994
Excavation of the Kettle Pond area completed; construction of the on-Site
double-lined landfill for contaminated soil and sediments completed.
1994
Completed dredging of contaminated sediment from Hocomonco Pond and
Brook and sealing and lining of Otis Street storm drain. DNAPL recovery
begun.
1995
Soils from the former tank farm area and former storm drain excavated;
covers on landfill and former lagoon completed.
1996
EPA issued a letter to the PRP indicating that remediating groundwater to
drinking water quality may not be achievable at the entire Site.
May 20, 1997
Technical Impracticability (Tl) Work Plan submitted.
June 30, 1997
Field work was conducted to investigate the practicability of groundwater
remediation.
Sept. - Nov. 1997
"Report Demonstrating the Technical Impracticability of Restoring
Groundwater at the Hocomonco Pond Site" submitted by the PRP.
April 1998
EPA and MassDEP conducted a pre-final Site inspection and determined
construction activities were completed.
Sept. 10, 1999
Second ESD and associated Tl waiver implemented.
Sept. 21, 1999
"Preliminary Close-Out Report" issued by EPA.
Sept. 22, 1999
"Interim Remedial Action Report" issued by EPA.
Sept. 28, 2000
"Revised Long-Term Monitoring Plan" (LTMP) submitted by the PRP.
September 2001
Baseline biological monitoring conducted, per the LTMP.
May 2002
"Long Term Monitoring Report" submitted by the PRP.
June 2002
Change to passive DNAPL recovery and groundwater treatment plant
shutdown
May 2003
EPA agreed to allow passive DNAPL recovery to continue.
July 21, 2003
"Long Term Monitoring Report" submitted by the PRP.
July 30, 2004
First Five-Year Review completed.
Sept. 22, 2004
"Reuse Assessment for the Hocomonco Pond Superfund Site" issued by
EPA
September 2004
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"Final Long-Term Monitoring Report" submitted by the PRP
November 2005
Second Five-Year Review completed
September 2009
Groundwater sampling plan issued to evaluate Tl boundary
April 2011
Results of groundwater sampling to evaluate Tl boundary
December 2011
Sediment sampling report
September 2012
Work Plan to evaluate the Tl zone and evaluate/enhance DNAPL recovery
October 2012
Third ESD issued to extend the Tl zone boundary and modify the DNAPL
recovery method
September 2013
Third Five-Year Review Completed
September 2014
B. BACKGROUND
This section contains information pertaining to the Site's physical characteristics, current and prior land
use at the property, as well as waste identification and characterization information. This information
has been obtained through a review of historical information, previous investigations, zoning and flood
maps, and a Site visit.
Physical Characteristics
The approximately 23-acre Site is located in Worcester County, in the Town of Westboro,
Massachusetts (Figure B-l). The site is bordered to the northwest by Hocomonco Pond, a 27 acre
shallow freshwater pond, to the east by Otis Street, and to the south by the Smith Valve Parkway. The
Site lies approximately 3,500 feet south of Massachusetts Route 9.
The Site is located in an industrial zone and surrounding lots are used for light industrial and
commercial applications. A regional commuter train station is located across the street. There are no
private residences in immediate proximity to the Site. There are approximately 40 residential homes
within a Vi mile radius, most of which are located along Fisher Street, to the south.
There are no estimated habitats of rare wetland wildlife or priority habitats for state-listed rare species
within one mile of the Site.
Hydrology
The Site is comprised of unconsolidated sediments, characterized as glacial drift deposits and tills,
overlying consolidated bedrock (Fluor Daniel GTI, 1998). The glacial drift deposits vary in thickness,
with the greatest thickness west of the Kettle Pond. Glacial drift deposits are absent in the southeast
portion of the Site. Till is found in most of the Site, but is absent in western and southeastern areas. A
sand and gravel layer exists within the till in areas where DNAPL is routinely found. The regional
bedrock consists of Precambrian to Ordovician metamorphic rock, primarily schists, gneisses, and
granites, which dips westward while striking northeast (EPA, 1985). A dominant geological feature of
the Site is a bedrock valley that extends from the northeast to the southwest, with the eastern wall
Appendix A - Hocomonco Pond 3rd Five Year Review
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sloping towards the west from the area near Kettle Pond (Fluor Daniel GTI, 1998). Based on geologic
investigations conducted during the 1997 TI study, the "differential weathering and erosion of the
bedrock surface" indicates that the bedrock valley appears to have been formed by a fault line (Fluor
Daniel GTI, 1998).
The Site is generally well-drained due to its topography and the relatively permeable soils, which overlie
the sandy stratified drift deposits. Most of the Site contains coarse-grained, poorly-sorted glacial drift
deposits, which are comprised primarily of sand, silt, and gravel. These materials are underlain by dense
clay and gravel till. Some locations, such as Kettle Pond and the surrounding area, contain permeable
materials, increasing the potential for downward vertical migration of contaminants. Other areas, such
as the area surrounding the former lagoon, are underlain by weathered bedrock/saprolite which prevents
downward migration of contaminants (EPA, 1992a; Fluor Daniel GTI, 1998).
Groundwater flows northward towards Hocomonco Pond and discharges into the pond. In the extreme
north of the Site, data suggest that groundwater may be flowing northward following a general drainage
pattern from Hocomonco Pond to more low-lying swamps northeast of Otis Street (BBL, 2002a). The
hydrogeologic conditions present at the Site indicate that Hocomonco Pond provides a constant head
boundary, thus preventing any Site contaminants from migrating toward the Otis Street municipal well,
northwest of the pond, or toward the Smith Valve process well located west of the pond (EPA, 1985).
Site contaminants were not found in either of these wells during the remedial investigation or during
subsequent routine testing of the Otis Street well. There are no known potable wells within the impacted
or immediate down gradient groundwater aquifer.
The Federal Emergency Management Agency flood insurance rate map for the area shows that
Hocomonco Pond, its wetlands at both the inlet and discharge from the pond, and the wetlands east of
Otis Street, lie within the 100-year floodplain (FIRM, 2002). The Kettle Pond wetland, located between
Kettle Pond and Hocomonco Pond, is a 0.1-acre wooded swampy area that is occasionally inundated
during major storm events. Hocomonco Pond discharges from its northeast end and flows under Otis
Street into wetlands and the Assabet River (see Figure 3-1). The Assabet River wetland is a 70-acre
wooded wetland located northeast of Hocomonco Pond (EPA, 1985). An unnamed 8-acre wetland,
located northwest of Hocomonco Pond, is primarily wooded and is also contiguous to an inlet stream to
the pond (see Figure 3-1)
Land and Resource Use
The current Town of Westboro zoning map shows the Site and properties to the northwest of
Hocomonco Pond as town-owned land. The Westboro Master Plan identifies the properties to the
northwest as municipal protected and municipal unprotected open space (Daylor, 2003). The areas
surrounding the Site and the town-owned parcels northwest of the pond are zoned IB (General Industry).
This zoning category allows for light industrial, office, and warehouse use (Daylor, 2003). Currently,
and in the past, the surrounding lots were used for light industrial, commercial, and/or residential
purposes. Although there are no private residences that directly border the Site, there are approximately
40 residential homes within a Vz mile radius, most of which are located along Fisher Street, to the south.
Access to the Site property is restricted on three sides by a perimeter fence. While not completely
enclosed, the forth side of the Site property directly abuts Hocomonco Pond, which itself is almost
entirely restricted by a perimeter fence. Consequently, no evidence of trespassing has ever existed on
the Site property.
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The Site lies within a Zone II aquifer, which is a direct recharge area of a public water supply
(Westboro, 2001). The Otis Street municipal well is located approximately 2,000 feet northwest and
upgradient of Hocomonco Pond. The well is operated at a pumping rate that limits the radius of
influence from intersecting Hocomonco Pond (EPA, 1985). Routine testing of the Otis Street well by
the town has never detected any Site contaminants (McNulty, 2004). According to town officials, a
second municipal well planned for the Otis Street location was not installed due to concerns of the
impact of two wells pumping in this area (McNulty, 2004). There are no water supply wells within the
impacted portion of the aquifer.
There are no estimated habitats of rare wetland wildlife or priority habitats for state-listed rare species
within one mile of the Site. There are a number of potential vernal pools located in the Assabet River
wetlands east of the Site and Otis Street (Daylor, 2003).
EPA's September 2004 Draft Preliminary Reuse Assessment for Hocomonco Pond and the Westboro
Master Plan include maps that show the major land uses, resources, and zoning discussed above.
Appendix D, "Summary of 2003 Open Space and Recreation Plan," of the Westboro Master Plan
includes a plan to transfer the Hocomonco Pond Site to the care and custody of the Conservation
Commission when the cleanup is completed and the Site is released to the town by EPA (Daylor, 2003).
Town officials have indicated plans for passive recreational use of the Site and noted during the Site
inspection that a walking trail proposed for along the Smith Valve Parkway, south of the Site, was
constructed in 2004.
History of Contamination
Wood treating operations were conducted on-Site between 1928 and 1946. These activities consisted of
saturating wood products with creosote to preserve them (EPA, 1985). Waste produced during these
operations was discharged into the 1.7 acre unlined (former) lagoon, located south of Hocomonco Pond.
When the lagoon was filled with waste creosote, sludge, and water, its contents were pumped into two
depressed areas, approximately 1 acre in size, referred to as the Kettle Pond area. The Kettle Pond area
was located east of the operations and near the west side of Otis Street (EPA, 1985). Public information
indicates that creosote was not used or stored on the Site after March 26, 1946 (EPA, 1985).
After 1946, the facility was converted to an asphalt mixing plant. Aggregate and asphalt wastes
associated with this operation were discarded on the Site. The facility was later converted into a cement
plant where dry cement was sold in bulk (EPA, 1985).
An open-jointed storm drainage system was installed in 1976 per order of the Westboro Conservation
Commission to collect runoff from Smith Valve Parkway and contain a small watercourse that crossed
the Site. Unknowingly, the storm drain was constructed adjacent to the east side of the former lagoon.
Rainwater passing through the drainage system transported contaminants from the former lagoon into
Hocomonco Pond and a portion of its discharge stream. Between 1979 and the mid-1980s an oil boom
was placed in Hocomonco Pond at the drain channel discharge during heavy rains. The boom was used
to collect creosote that discharged to the pond (EPA, 1985). The Massachusetts Division of Fish and
Wildlife investigated two fish kills, in 1979 and 1982. The fish kills were attributed to creosote leaching
from the former lagoon into the storm drain and discharging into and contaminating the pond.
Road reconstruction on Otis Street in 1983 adjacent to Kettle Pond unearthed contaminated soil, which
was then redistributed along the roadway embankments (EPA, 1985). Given the historical operations in
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the area, EPA collected water, soil, and sludge samples along the Otis Street construction area for risk
assessment purposes. Contaminants detected in the sludge samples were consistent with creosote and its
by-products.
Initial Response
In the early 1980s Hocomonco Pond was closed for recreational uses, and signs were posted prohibiting
fishing, boating, and swimming (EPA, 1985). Access to the Site was restricted by placement of large
boulders across the access road. Based on the extent of creosote contamination detected in the
Hocomonco Pond area and the potential threat of contamination to the Otis Street municipal well, EPA
evaluated the Site and proposed it for inclusion on the National Priority List (NPL) in 1982. The Site
was officially placed on the NPL on September 8, 1983 (EPA, 1992). A remedial investigation (RI) was
initiated in 1984.
Basis for Taking Action
The RI identified four primary areas of contamination on the Site: (1) the Kettle Pond area; (2)
Hocomonco Pond and its discharge stream; (3) the former lagoon area; and (4) Otis Street. In addition,
the RI identified three small isolated areas: contaminated soil near MW-1; tank bases adjacent to the
former lagoon; and sediments in the southwest drainage channel. The predominant contaminants found
in all of these areas of contamination were creosote compounds, primarily polycyclic aromatic
hydrocarbons (PAHs) such as acenaphthene, naphthalene, acenaphthylene, fluorene, phenanthrene,
dibenzofuran, and 2-methylnaphthalene (EPA, 1985). The extent of the contamination identified in each
of these areas is shown on Figure 3-2. A brief description of each of the areas of contamination
identified in the RI is provided below, followed by a summary of the endangerment assessment that was
performed to address public health and environmental concerns at the Site.
(1) Kettle Pond Area
Creosote contamination was detected in soils at concentrations up to 483 mg/kg at a depth of 0 to 2 feet;
and a concentration of up to 55 mg/kg was detected at a depth of 20 feet below ground surface (bgs).
The contamination extended below the water table, which was located at approximately 8 feet bgs, and
was visible in soil borings to a depth of 17 feet bgs (EPA, 1992a). The RI estimated the volume of
contaminated soil to be approximately 24,000 cubic yards with an aerial extent of approximately one
acre (EPA, 1992a). Contamination extended to the western bank of Otis Street and north to Hocomonco
Pond (EPA, 1985). Downgradient of Kettle Pond, groundwater was contaminated with creosote
compounds and phenolic compounds at parts per million concentrations. Iron and manganese were
detected at concentrations which exceeded secondary drinking water standards (EPA, 1985). Surface
soil adjacent to Hocomonco Pond also contained creosote compounds (EPA, 1992a).
(2) Hocomonco Pond
The RI determined that creosote-contaminated leachate migrated from the former lagoon into the open-
jointed storm drain adjacent to the former lagoon, and discharged into Hocomonco Pond (EPA, 1992a).
The creosote compounds contaminated the sediments in the discharge stream and along the shoreline of
the pond. Most of the metals detected exceeded background levels in both pond and stream sediments.
Migration via the storm drain was noted as the primary source of contamination in Hocomonco Pond
and the discharge stream. Contaminated surface water was found in the pond only within the oil boom
Appendix A - Hocomonco Pond 3rd Five Year Review
Page A-6
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area at the storm drain discharge. Contamination was not found in surface water beyond the oil boom or
in the discharge stream exiting the pond near Otis Street (EPA, 1985).
(3) Former Lagoon Area
Creosote contamination was detected in the soil near the surface and at depths ranging from 5 to 20 feet
bgs. Creosote product was observed in the upper 15 feet of the soil, above the groundwater table (EPA,
1985). The RI estimated the volume of contaminated soil in the former lagoon area to be approximately
18,000 cubic yards with an estimated aerial extent of approximately 1.7 acres (EPA, 1992a).
Groundwater contamination was not found in wells located downgradient of the former lagoon.
Observations made during test pit and soil boring operations suggested that downward migration of
contaminants was apparently impeded by impervious layers of sludge and fines in the bottom of the
lagoon. The RI concluded that hydrogeologic conditions in the area would prevent migration of
contaminants deep into the aquifer and that seepage from the lagoon into the groundwater would likely
flow laterally and discharge into Hocomonco Pond (EPA, 1985).
(4) Otis Street
Creosote contamination was not detected in soils or groundwater along the eastern embankment of Otis
Street; metals above background levels were found in both soil and groundwater. Manganese was the
only compound detected in the groundwater east of Otis Street that exceeded secondary drinking water
standards (EPA, 1985). Stream sediments containing creosote contamination were detected 300 feet
downstream of Otis Street (see Section 3.5.2).
(5) Isolated Areas
The RI reported that limited creosote contamination was found in the three isolated areas. Shallow soils
near MW-1 contained creosote contamination ranging from 2.5 to 9 mg/kg (EPA, 1985). Creosote
contaminants were detected in sediments in the southwest drainage channel at concentrations ranging
from 6 to 39 mg/kg (EPA, 1985) (see Figure 3-2). Oily creosote compounds were found in the bottom
of the tank bases (Golden, 2004).
C. REMEDIAL ACTIONS
Remedy Selection
Four decision documents have been issued for the Hocomonco Pond Site as follows:
1. Record of Decision (ROD) September 30, 1985
2. Explanation of Significant Differences, July 22, 1992
3. Explanation of Significant Differences, September 21,1999
4. Explanation of Significant Differences, September 30, 2013
The September 30, 1985 ROD specified a multi-component remedy to address each of the areas of
contamination at the Site. Based on the conclusions of the RI, remedial action objectives (RAOs) were
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identified that would mitigate or eliminate impacts to human health and the environment due to
exposure to Site contaminants. The individual RAOs described in the ROD for each area of
contamination are summarized in the table below.
TABLE A-2
SUMMARY OF RAOs
Remedial Action Objectives
(per ROD)
Areas of Contamination
Former
Lagoon
Kettle
Pond
Hocomonco Pond &
Discharge Stream
Otis
Street
Isolated
Areas
Eliminate inhalation, direct contact and/or ingestion
exposure pathways
X
X
X
X
X
Eliminate the contaminant migration potential to
downstream areas and to surface waters
X
X
X
X
Ensure no future groundwater contamination
X
Eliminate impacts on wetlands
X
X
X
X
Eliminate groundwater contamination in this area and east
of Otis Street
X
Eliminate future potential impacts to wetlands and fisheries
(e.g. the ingestion exposure pathway)
X
Enhance future recreational usage of Hocomonco Pond
X
Source: EPA, 1985
Since remedial alternatives for each area were evaluated separately, the ROD selected separate remedial
actions that addressed the specific issues identified for each area. The remedial alternatives selected by
the EPA needed to ensure that "the best practical measures were used and the most cost effective
alternatives that are technologically feasible and reliable were chosen to effectively mitigate potential
harm and provide adequate protection for public health, welfare, and the environment" (EPA, 1985).
Therefore as part of the ROD, the EPA issued a separate Statement of Findings for each of the four
primary areas to ensure compliance with EPA policy, Executive Orders 11988 (Floodplains
Management) and 11990 (Protection of Wetlands), and consistency with Massachusetts state law and
local standards. The Statements of Findings were required since some of the proposed remedial actions
were in or might potentially affect a 100-year floodplain and/or a wetland. The remedies selected for
each area of contamination are briefly described below.
Kettle Pond Area. The remedy selected for the Kettle Pond area involved excavation of contaminated
soil/waste and on-Site disposal into a double-lined landfill. The remedy also included dewatering Kettle
Pond to lower the groundwater level prior to and during excavation. A groundwater pumping and
treatment system would be installed to lower the groundwater level and also to extract and treat
contaminated groundwater (EPA, 1985). This alternative was selected since it would remove the
soil/waste source of contamination to groundwater. This would be achieved by excavating all visible
contamination and approximately 2 to 3 feet of additional soil below the visible contamination and
consolidating it into an on-Site double-lined landfill (EPA, 1985).
Hocomonco Pond and Discharge Stream. The remedy selected for Hocomonco Pond and its discharge
stream involved mechanical dredging of contaminated sediments with on-Site disposal either into the
former lagoon area prior to construction of the cap and/or at an approved landfill facility. This
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alternative was selected since it would remove the contamination and essentially restore Hocomonco
Pond to a condition suitable for recreational purposes (EPA, 1985).
Former Lagoon Area. The remedy selected for the former lagoon area involved Site grading,
construction of a cap, removal/disposal of the storm drain pipe that had been installed along the eastern
side of the former lagoon, and installation of a new storm drain pipe outside of the former lagoon limits.
This alternative was selected since all soil contamination was located above the water table; therefore
containment of the waste material under the cap would prevent migration to Hocomonco Pond and
groundwater (EPA, 1985). A deed restriction was also required for the area of the cap to prevent future
development (EPA, 1985).
Otis Street. The remedy selected for Otis Street involved sealing the open-jointed storm drainage pipe
along the east side of the street. This alternative was selected since it would prevent the migration of
contamination from the drainage pipe into Hocomonco Pond, the discharge stream, and adjacent
wetlands. A deed restriction would be required for the road embankment area (EPA, 1985).
Isolated Areas. The remedy selected involved removal of the tank bases, contaminated soil near MW-1,
and contaminated sediment from the southwest storm drain channel, and consolidation of the materials
either on-Site into the former lagoon area prior to construction of the cap and/or at an approved landfill
facility. This option was selected to eliminate the potential exposure risk to humans and animals from
contaminants in these isolated areas (EPA, 1985).
On January 10, 1988, a Consent Decree was entered into between the EPA, the Commonwealth of
Massachusetts, and the following parties: Beazer East, Inc. (Beazer), Chicago Bridge & Iron Co., Smith
Valve Corp., Massachusetts Department of Public Works (DPW), and the Town of Westboro (EPA,
1992a). The Consent Decree set forth activities that Beazer would be required to carry out in order to
implement the remedies specified in the ROD. The other PRPs agreed to make settlement payments to
Beazer (EPA, 1992a). These activities, specified in the Remedial Design/Action Plan (RD/RA Plan),
attached as Appendix I to the Consent Decree, included pre-design, remedial design, remedial action,
and long term operation and maintenance (O&M) for the remedies selected in the ROD.
As part of the selected remedy for the former lagoon area, the storm drain along the east side of the
lagoon area was relocated between November 1989 and January 1990. The contaminated portions of the
former storm drain were then excavated as part of the activities described in Section 4.3.1.
Additional Investigations
Along with the remedial alternatives selected for each area of contamination, the ROD listed future
actions to support the design process and on-going monitoring. These actions included:
• Soil sampling and analysis during the design process to determine the extent of excavation
required at the Kettle Pond area, the former tank farm, the southwest storm drain area, and the
MW-1 area;
• A sediment investigation during the design process to determine the extent of dredging that
would be required to remediate Hocomonco Pond;
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• Water treatability studies for the Kettle Pond area, as necessary, to adequately design a water
treatment system for dewatering the area prior to excavation;
• Monitoring of the former lagoon area cap and double-lined landfill to ensure their effectiveness;
• Establishing final groundwater cleanup levels after soil and groundwater remedial actions were
completed in the Kettle Pond area; and
• Installing fencing during design and prior to the start of construction activities to prevent direct
exposure of the public to contaminants and to the construction activities on the Site.
Pre-Design Investigations
The PRP conducted pre-design investigations in the early 1990s, including sediment, soil, groundwater,
and fish tissue sampling, to further refine the extent of contamination in the different areas of the site.
During the remedial design, the results of these sampling activities were used to supplement the previous
investigations of the site to define the extent of excavation and dredging activities that would be required
in each area.
Sediment sampling was conducted at Hocomonco Pond, the discharge stream, and a marshy area and
abandoned stream associated with Hocomonco Pond. Soil sampling was conducted at the former wood
treating building located to the north of the former lagoon, at the former tank farm area, in the southwest
storm drain, around MW-1, Kettle Pond, and the area between Kettle and Hocomonco Ponds.
Groundwater sampling was conducted across the site to confirm the location of the bedrock valley and
determine the migration path for the creosote contamination. Five fish tissue samples were collected
from Hocomonco Pond (EPA, 1992a).
1992 Explanation of Significant Differences
The PRP also conducted additional investigations at Kettle Pond as part of the pre-design activities
specified in the Consent Decree. These investigations resulted in new information which questioned the
effectiveness and implementability of the remedy specified in the ROD for the Kettle Pond area.
During pre-design investigations in the Kettle Pond area, boulders were encountered in the glacial drift
during drilling activities. The investigation also determined that the aquifer in the Kettle Pond area was
more transmissive than estimated in the RI. The sheet piling would need to be installed to a depth of 60
to 80 feet to control groundwater inflow from the deep permeable aquifer. The PRP determined that the
boulders and overhead utility wires would impede the installation of sheet piles, as required in the ROD
to support the excavation sidewalls and prevent water from entering the excavation, since the sheeting
could bend and separate and therefore compromise the hydraulic and structural integrity of the remedy
(EPA, 1992a).
The investigations also determined that the vertical extent of visible contamination extended to a depth
of approximately 45 feet bgs into the saturated soils, rather than 20 feet bgs as reported in the RI. The
investigations concluded that lowering the groundwater level in the Kettle Pond to facilitate "dry"
excavation, as specified in the ROD, could cause subsidence of Otis Street, a heavily traveled road
(EPA, 1992a).
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A deep overburden and shallow bedrock investigation was conducted to investigate the December 1988
discovery of creosote product in deeper soils west of Kettle Pond. During this investigation, creosote
was observed as a dense non-aqueous phase liquid (DNAPL) at a depth of approximately 140 feet bgs
west of Kettle Pond (EPA, 1992a; EPA, 1992b). The DNAPL was found above dense clay soil and/or
weathered bedrock, which appeared to have acted as a barrier to further downward migration (EPA,
1992a).
In response to this new information, on July 22, 1992, the EPA issued the first Explanation of
Significant Differences (ESD) for the Site which modified the remedy originally selected for the Kettle
Pond area. The remedies selected for the other areas of the Site were not modified, as they were not
impacted by the new information. To ensure that the Kettle Pond remedy remained protective of human
health, welfare, and the environment, the 1992 ESD set forth the following changes:
• The ROD requirement for sheet piling and the dry excavation of sediments and soils was
replaced with a requirement for wet excavation of shallow contaminated material to a maximum
depth of 5 feet;
• The ROD requirement for excavating, dewatering, and landfilling the deeper contaminated soil
was replaced with a requirement for in-situ bioremediation and soil flushing; and
• Since DNAPL in the deep overburden can be a continuous source of dissolved contaminants, the
ESD required product recovery prior to and/or during in-situ bioremediation and either on- or
off-site treatment or product reuse offsite.
The EPA concluded that "these changes do not fundamentally alter the remedy selected in the ROD"
(EPA, 1992a).
Cleanup Levels and Limits of Excavation
The Consent Decree and RD/RA Plan included a requirement that EPA would establish the horizontal
and vertical limits of excavation in the Kettle Pond area, Hocomonco Pond, and its discharge stream in a
supplemental decision document. On September 28, 1992, EPA issued a final supplemental decision
document (SDD) entitled "Cleanup Levels for Sediments, Soils and Groundwater and Limits of
Excavation of Sediments and Soil." The document established the vertical and horizontal extent of
excavation for the site and also established cleanup levels for soils, sediments, and groundwater across
the site (EPA, 1992a). Based on the pre-design investigation results, and other studies, EPA identified
contaminants of concern (COCs) for the site. The COCs identified included benzene, toluene,
ethylbenzene, and xylenes (BTEX), noncarcinogenic and carcinogenic PAHs, arsenic, and chromium
(EPA, 1992a).
The groundwater cleanup levels established by EPA in the SDD are the Maximum Concentration Limits
(MCLs) and non-zero MCL goals (MCLGs) for the COCs. However, since MCLs had not been
established for non-carcinogenic PAHs and some carcinogenic PAHs (cPAHs), risk-based criteria were
used to establish interim groundwater cleanup levels. The interim cleanup levels and the criteria upon
which they were based, are shown in Table A-3.
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TABLE A-3
INTERIM GROUNDWATER CLEANUP LEVELS
Constituent
Interim Cleanup Level
(Hg/1)
Reference (criteria)
PAH - carcinogenic
Benzo(a)anthracene
None
-
Benzo(a)pyrene
0.2
final MCL
Benzo(b)fluoranthene
None
-
Benzo(k)fluoranthene
None
-
Chrysene
None
-
Dibenzo(a,h)anthracene
None
-
Indeno( 1,2,3 -cd)pyrene
None
-
PAH - noncarcinogenic
Acenaphthene
2,200
risk-based
Acenaphthylene
None
-
Anthracene
11,000
risk-based
Benzo(g,h,i)perylene
None
-
Fluoranthene
1,500
risk-based
Fluorene
1,500
risk-based
Naphthalene
1,500
risk-based
Phenanthrene
None
-
Pyrene
1,100
risk-based
VOCs
Benzene
5
final MCL
Ethylbenzene
700
final MCLG
Toluene
1,000
final MCLG
Xylenes (total)
10,000
final MCLG
Inorganics
Arsenic
50
final MCL
Chromium (total)
100
final MCLG
None = no interim cleanup level established
Source: EPA, 1992b
The SDD stated that these interim levels, which were applied to groundwater within the saturated zone
beneath the entire site, could be reassessed during implementation of the remedy and at the completion
of the remedial action to ensure its protectiveness. The SDD allowed for periodic assessments and a
possible re-evaluation of performance standards associated with the groundwater treatment remedy. The
SDD required a risk assessment to evaluate the potential risk of consumption of site groundwater once
the groundwater ARARs were achieved (EPA, 1992b). Note that the arsenic MCL has been lowered to
10 ug/1 in the time since the SDD was published.
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Based on the soil and sediment data collected during the pre-design investigations, EPA established
cleanup standards for Hocomonco Pond, the discharge stream, Kettle Pond area, and the isolated areas.
Cleanup levels were established based on risks to human health from potential exposure via dermal
contact and ingestion as well as risks to aquatic life. No cleanup levels were established for surface
water or fish since the risks calculated were less than 10"6 (EPA, 1992b). The volumes of sediment and
soil in each area that exceeded the respective cleanup standard, and thus required excavation, were then
estimated by EPA. The soil and sediment cleanup standards and estimated volumes are summarized
below for each area.
Kettle Pond Area. A human health based cleanup level of 4 mg/kg cPAHs was established for surface
soils (less than 2 feet) in the Kettle Pond area. To meet this standard, EPA determined that removal of
the top 4 feet of soil, totaling approximately 4,200 cubic yards, was required (EPA, 1992b). Excavating
this volume of soil would result in the removal of a considerable volume of contaminated material
before the in-situ bioremediation activities were implemented.
Hocomonco Pond. A human health based cleanup level of 4 mg/kg cPAHs was established for shallow
sediments in Hocomonco Pond. In the shallow sediment of the eastern portion of the pond, a cleanup
level of 35 mg/kg total PAHs and 4 mg/kg phenanthrene was established for protection of aquatic life
(EPA, 1992b). EPA determined that dredging pond sediments along approximately 4,000 feet of
shoreline at depths ranging from 0.5 to 1.5 feet bgs was required to meet the cleanup standard. The total
volume of sediments required to be removed was approximately 1,840 cubic yards (EPA, 1992b).
Discharge Stream. A human health based cleanup level of 7 mg/kg cPAHs was established for the
contaminated sediment in the upper portion of the stream, from Otis Street east approximately 440 feet.
A cleanup level of 35 mg/kg total PAHs and 4 mg/kg for phenanthrene, in shallow sediments for the
entire stream and adjacent soils, was established for the protection of aquatic life (EPA, 1992b). EPA
determined that excavation of approximately 500 cubic yards of sediments in the upper portion of the
discharge stream was required. Excavation of approximately 50 cubic yards of contaminated sediment
in the lower portion of the discharge stream was also required (EPA, 1992b).
Isolated Areas. The human health based cleanup level for soils in the former tank farm area, southwest
storm drain, and around MW-1 was 4 mg/kg cPAHs (EPA, 1992b). Since the tank base and the soil
adjacent to the tank base were contaminated, EPA determined that excavation of approximately 940
cubic yards of soil to a depth of 2 feet bgs was required. Approximately 730 cubic yards was required to
be excavated near MW-1 (EPA, 1992b).
1999 Explanation of Significant Differences
During 1997, the PRP conducted investigations to establish site-wide groundwater quality conditions
and determine whether it would be practical to restore groundwater at the site to drinking water
standards. The investigations involved drilling one soil boring downgradient of Kettle Pond, installing
24 pore water sample points in Hocomonco Pond, conducting a site-wide groundwater level and
DNAPL measurement event, and performing a groundwater and pore water sampling and analysis round
at 55 locations on-site (Fluor Daniel GTI, 1998). Groundwater and pore water samples were collected
and analyzed for PAHs, BTEX, and filtered and unfiltered (total) arsenic and chromium.
While the interim cleanup levels established in the SDD were exceeded in some locations for total, or
unfiltered, arsenic and chromium samples, the filtered results showed chromium and arsenic
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concentrations below the cleanup levels, with the exception of one arsenic exceedance. The exceedance
of the cleanup level for total arsenic was attributed to reducing conditions found in the Kettle Pond area.
Benzene and naphthalene were the most frequently detected contaminants exceeding the interim
groundwater cleanup levels (Fluor Daniel GTI, 1998). Since benzene and naphthalene had historically
exceeded the cleanup levels, the technical impracticability (TI) evaluation focused on these compounds
as the primary constituents of concern. The results and conclusions of this investigation were presented
in a "Report Demonstrating the Technical Impracticability of Restoring Groundwater at the Hocomonco
Pond Site," dated April 1998.
During this time frame, sediment data from samples collected along the southeast side of Hocomonco
Pond showed increasing concentrations of PAHs. These results suggested that groundwater from the
Kettle Pond area containing dissolved PAHs, primarily naphthalene, was discharging through
remediated sediments into the southern portion of the pond. A sediment sampling plan was developed
in 1998 using guidance provided by EPA and was used to collect a round of sediment samples from
three locations in December 1998 (BBL, 2001).
The TI report concluded that there were two primary DNAPL entry locations on the site, the Kettle Pond
area and the former lagoon area. Soil samples collected from borings in the Kettle Pond area confirmed
that DNAPL was present in both shallow and deep soil samples; test pits in the former lagoon area
encountered DNAPL in the unsaturated soils (Fluor Daniel GTI, 1998). The investigations determined
that remedial actions at these two areas were able to mitigate the presence and/or migration of DNAPL,
even though DNAPL might be present at other locations on the Site.
The TI investigations determined that the till layer located beneath the glacial drift aquifer not only acted
as a barrier to vertical migration of DNAPL, but also enhanced the horizontal migration of DNAPL
(Fluor Daniel GTI, 1998). The lateral extent of DNAPL contamination at the former lagoon area was
estimated to be approximately 125 feet from north to south and approximately 100 feet from west to
east. The lateral extent of DNAPL contamination at the Kettle Pond area was estimated to be 375 feet
from northeast to southwest and approximately 250 feet from southeast to northwest (Fluor Daniel GTI,
1998). The residual and free phase DNAPL had migrated downward through the glacial drift deposits in
areas across the site. In the area west of Kettle Pond, DNAPL was found to a maximum depth of 170
feet bgs (Fluor Daniel GTI, 1998). At the former lagoon area, DNAPL was found in the unsaturated
zone, extending to the water table surface, as the downward migration of DNAPL was limited.
Due to the lack of DNAPL at depth around the former lagoon area, DNAPL recovery efforts were
focused to the area west of Kettle Pond. By September 1999, approximately 31,000 gallons of creosote
DNAPL had been recovered. Given the extent of DNAPL contamination present at the site, the TI
report concluded that: "The presence of residual phase DNAPL represents a long-term source for
impacts to groundwater since this phase of DNAPL is difficult to remove. Locating all free phase
DNAPL sources and the inability to remediate residual phase DNAPL makes groundwater restoration
technically impracticable" (Fluor Daniel GTI, 1998).
The report also stated that there was no significant risk to human health or the environment posed by the
presence of free phase or residual phase DNAPL at the site, and suggested implementing institutional
controls to mitigate potential future risk. Based on these conclusions, the EPA "Guidance for
Evaluating the Technical Impracticability of Groundwater Restoration," and other relevant documents,
the PRP requested a waiver of interim groundwater cleanup levels for the areas within the defined TI
zone. The horizontal extent of the TI zone is shown in Figure 4-2. The vertical extent of the TI zone
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was defined as follows: Kettle Pond area (286 feet to 202 feet above mean sea level), area west of Kettle
Pond (279 feet to 155 feet above mean sea level), and the former lagoon area (306 feet to 282 feet above
mean sea level) (Fluor Daniel GTI, 1998).
Based on the PRP's TI Report, EPA determined that "remediating groundwater to drinking water quality
may not be achievable in certain areas of the Hocomonco Pond Site" (EPA, 1999). The 1992 SDD
allowed for the re-evaluation of the interim cleanup levels during implementation of the selected
remedy. The interim groundwater cleanup levels established in the SDD assumed that groundwater
restoration was an achievable goal. On September 21, 1999, EPA issued a second ESD that waived the
groundwater ARARs and interim cleanup levels in the two TI zones identified in the PRP's TI report.
The 1999 ESD also required that DNAPL recovery continue until it is determined to be "no longer
technically practicable."
EPA and MassDEP concluded that this modified remedy was adequately protective of human health and
the environment because institutional controls, long-term monitoring, and continuing DNAPL recovery
activities were required as part of the TI waiver (EPA, 1999). The 1999 ESD allowed the in-situ
bioremediation system to be discontinued, but required DNAPL recovery to "continue until the EPA and
MADEP give a written approval stating otherwise" (EPA, 1999). The 1999 ESD also required
groundwater monitoring and surface water and sediment sampling to ensure that the groundwater is
hydraulically contained and contaminant levels do not increase in concentration or extent. Should levels
increase, the ESD stated that additional site work or engineering controls may be required. Finally, the
1999 ESD required that a deed restriction be placed on the Hocomonco Pond property to prohibit
groundwater extraction, as discussed in Section 4.3.9 below. The PRP prepared a long term monitoring
plan (LTMP), as required by EPA in the 1999 ESD.
2013 Explanation of Significant Differences
This ESD was issued to require the continued removal of DNAPL by passive recovery methods. The
1992 ESD had required that DNAPL be "removed through pumping prior to or during bioremediation."
The 1999 ESD stated that "DNAPL recovery shall continue until such time that it can be demonstrated
that it is no longer technically practicable." While the 1999 ESD established a TI waiver ending active
pumping efforts to achieve cleanup levels, the above statement implied that active pumping to remove
DNAPL was required to continue. Passive recovery efforts performed since 2003 have demonstrated
that active pumping is not required to achieve meaningful DNAPL recovery. Extensive groundwater
monitoring concludes that the DNAPL is not migrating, and no potential down gradient receptors have
been identified.
The ESD also establishes a new TI zone boundary in the area just down gradient of the former lagoon.
Since 2002, concentrations of naphthalene and benzene have frequently exceeded groundwater cleanup
levels in monitoring well MLC-2. Since 2007, concentrations of benzene have also frequently exceeded
its cleanup level in MLC-3. Both of these wells are located down gradient and just outside of the
existing TI zone associated with the former lagoon area. The shore of Hocomonco Pond is about 200
feet down gradient from the former lagoon area. Previous studies have indicated that the pond provides
a natural hydraulic barrier. In 2012, the PRP completed a vertical profile boring and two new well pairs:
MLC-5S/D and MLC-6S/D, approximately 100 feet down gradient of MLC-2 and MLC-3.
Groundwater samples collected from the profile boring in November 2012 and from the new well pairs
in January 2013 show no exceedances of cleanup levels. Where detected, concentrations of naphthalene
and benzene were near the laboratory detection limits. The northwest boundary of the TI zone around
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the former lagoon area will be extended by approximately 100 feet and remain south of the new sentinel
monitoring wells MLC-5S/D and MLC-6S/D. This represents a minor expansion of the established TI
zone. MLC-5S/D and MLC-6S/D shall become the new sentinel wells and will be incorporated into the
monitoring program to ensure compliance with the expanded TI boundary. The use of monitoring wells
to ensure compliance with the TI boundary is consistent with the 1999 ESD. There are no known
receptors located down gradient of these new sentinel wells. Hocomonco Pond is located approximately
100 feet down gradient of these new sentinel wells and is a natural hydraulic barrier to further
groundwater migration. There is an active surface water and sediment monitoring program established
in the pond. Detected concentrations of PAHs in sediment and surface water have remained low and
stable.
Remedy Implementation
The groundwater treatment plant was constructed between November 1993 and July 1994 to treat water
containing dissolved and suspended oil, and/or solids pumped from several recovery wells located on-
Site, as well as the water collected in the drying beds during dewatering of excavations and saturated
sediments. The plant was designed to operate at a total flow of about 150 gallons per minute (gpm);
approximately 135 gpm would be from groundwater, and 15 gpm from solids and DNAPL. The main
unit processes in the treatment plant include pH adjustment, polymer addition, dissolved air flotation,
multimedia filtration, and carbon adsorption. Treated effluent was discharged to Hocomonco Pond.
Startup of the plant began on August 9, 1994.
The primary objectives of the groundwater pump and treat system were to remove DNAPL from a series
of recovery wells and treat the associated contaminated groundwater; and to recover and treat
contaminated groundwater from Kettle Pond, add nutrients to enhance bioremediation, and then reinject
the treated water through a series of reinjection wells.
The in-situ bioremediation portion of the treatment system began operation on March 4, 1996.
Operation of the system was suspended on March 18,1996 due to problems with dissolved, naturally-
occurring iron in the groundwater. The 1992 ESD stated that if the combination of DNAPL recovery
and in-situ bioremediation could not remediate the creosote contamination, then other technologies, such
as in-situ soil flushing, will be implemented. Two other treatment alternatives, air sparging and natural
attenuation, were evaluated. The evaluation concluded that the effectiveness of both technologies was
limited due to the presence of residual and free phase DNAPL. Based on experience with other sites
contaminated with creosote at DNAPL concentrations, EPA then recommended that a technical
impracticability demonstration be completed for certain areas of the Site.
Following shutdown of the bioremediation system in 1996, the DNAPL recovery wells continued to
operate at a rate of 5 to 10 gpm. The DNAPL was collected in a storage tank located behind the water
treatment plant for off-Site disposal; associated groundwater continued to be processed through the
treatment plant and discharged to Hocomonco Pond. Overall DNAPL recovery rates averaged 500
gallons per month (range from 150 to 1,500 gallons per month).
In 1997, the PRP conducted investigations to establish Site-wide groundwater quality conditions and
determine whether it would be practical to restore groundwater at the Site to the interim groundwater
cleanup standards. The investigations involved performing groundwater and pore water sampling and
analysis at 55 locations on-Site. Groundwater and pore water samples were analyzed for PAHs, BTEX,
and filtered and unfiltered (total) arsenic and chromium.
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Benzene and naphthalene were the most frequently detected contaminants exceeding the interim
groundwater cleanup levels. Since benzene and naphthalene had historically exceeded the cleanup
levels, the technical impracticability ("TI") evaluation focused on these compounds as the primary
constituents of concern. The results and conclusions of this investigation were presented in a "Report
Demonstrating the Technical Impracticability of Restoring Groundwater at the Hocomonco Pond Site,"
dated April 1998.
The TI report concluded that there were two primary DNAPL entry locations on the Site, the Kettle
Pond area and the former lagoon area. Soil samples collected from borings in the Kettle Pond area
confirmed that DNAPL was present in both shallow and deep soil samples; test pits in the former lagoon
area encountered DNAPL in the unsaturated soils only.
Due to the lack of DNAPL at depth around the former lagoon area, recovery efforts were focused to the
area west of Kettle Pond. By September 1999, approximately 31,000 gallons of DNAPL had been
recovered. Given the extent of DNAPL contamination present at the Site, the TI report concluded that:
"The presence of residual phase DNAPL represents a long-term source for impacts to groundwater since
this phase of DNAPL is difficult to remove. Locating all free phase DNAPL sources and the inability to
remediate residual phase DNAPL makes groundwater restoration technically impracticable."
The report also stated that there was no significant risk to human health or the environment posed by the
presence of free phase or residual phase DNAPL at the Site, and suggested implementing institutional
controls to mitigate potential future risk. Based on these conclusions, the EPA "Guidance for
Evaluating the Technical Impracticability of Groundwater Restoration," and other relevant documents,
the PRP requested a waiver of interim groundwater cleanup levels for the areas within the defined TI
zone. The horizontal extent of the TI zone is shown in Figure 2. The vertical extent of the TI zone is
approximately 80 to 120 feet below ground surface in the Kettle Pond area and 30 feet below ground
surface in the former lagoon area.
On September 21,1999, EPA issued the second ESD which waived the groundwater ARARs and
interim cleanup levels in the two TI zones identified in the PRP's TI report. The ESD required a
groundwater monitoring program be established to ensure compliance with interim groundwater cleanup
levels outside the TI zones. The 1999 ESD also required that DNAPL recovery continue until it is
determined to be "no longer technically practicable."
In May 2003, the PRP began operating the DNAPL recovery system in passive mode. This process
involves using submersible pumps already installed in wells DRW-1, DRW-2, DRW-3, BRW-4 and
BRW-5 to evacuate accumulated DNAPL on a weekly basis. In wells A-2, A-4, A-10 and BMW-6,
submersible pumps are not present and DNAPL is removed by bailers. The DNAPL product is then
transferred to drums for off-Site disposal. Monthly recovery rates have averaged approximately 60
gallons per month (range from 30 to 100 gallons per month). About 65,000 gallons of total DNAPL
have been recovered from combined efforts to date. The passive recovery method is independent of the
groundwater extraction and treatment system, therefore operation of the treatment system was
discontinued.
The PRPs have drafted deed restrictions as required by the ROD and 1999 ESD. The proposed
restrictions prohibit any future development on the landfill and former lagoon area caps, and prohibit the
extraction of the groundwater for purposes other than the remedial action unless the extracted
Appendix A - Hocomonco Pond 3rd Five Year Review
Page A-17
-------
groundwater meets or is treated to appropriate water use or disposal standards. EPA and MADEP are
working to finalize the institutional controls and record them on the property deed.
Between November 5, 2012 and January 3, 2013, the PRPs completed several activities with a goal to
enhance the passive DNAPL recovery effort. Enhancement activities included:
• Cleaning and video inspection of 6 existing recovery wells: DRW-1, DRW-2, DRW-3, A-4, A-
10 and BRW-5. The goal of this effort was to clean the well screens and remove excess sludge
from the well sumps to enhance product recovery, and then inspect the condition of the well
screens.
• Video inspection of 5 additional area monitoring wells: C-3, MW-11S, MW-1 ID, MW-12S and
MW-12D. The goal of this effort was to ensure the well screens were not blocked since these
wells are located in suspected areas of DNAPL.
• Installation and operation of a new passive recovery well: DRW-4. The goal of this effort was
to place a new well in a suspected area of DNAPL between 2 existing higher production
recovery wells to increase recovery rates. So far this well has produced an average recovery rate
of about 15 gallons of DNAPL per month.
The PRP continues to maintain the treatment system and associated building pending a final agency
decision on DNAPL recovery, which is being addressed per this ESD.
In 2000, concentrations of benzene and naphthalene in monitoring well MLC-2 climbed above their
respective interim groundwater cleanup levels. In 2006, the concentrations of benzene and naphthalene
also climbed above the interim groundwater cleanup levels in MLC-3. MLC-2 and 3 are sentinel wells
located down gradient and just outside the TI zone established in the former lagoon area (see Figure 4).
Through 2011, concentrations in both wells continued to fluctuate above and below the interim cleanup
levels, but were more often above (see Tables 1 and 2). There were no additional monitoring wells
down gradient of MLC-2 and 3.
Between November 5, 2012 and January 3, 2013, the PRPs completed a TI zone assessment in the area
down gradient of the former lagoon and monitoring wells MLC-2 and 3. A vertical profile boring was
completed to assess groundwater quality in the area. The groundwater table was encountered and
sampled at 35 feet below ground surface. Subsequent samples were collected every 20 feet of depth to
the top of bedrock at 130 feet below ground surface. The samples were analyzed for benzene and PAHs.
The interim groundwater cleanup levels were not exceeded in any samples.
The PRP installed two nested well pairs in the area of the boring: MLC-5S/D and MLC-6S/D. The new
wells were sampled on January 3, 2013. Detected benzene concentrations ranged from 0.66 to 0.82 ppb;
well below the cleanup level of 5.0 ppb. Detected naphthalene concentrations ranged from 0.34 to 2.0
ppb; well below the cleanup level of 1,500 ppb.
System Operation/Operation and Maintenance
The ROD specified the following O&M activities for the former lagoon area: long-term groundwater
monitoring, cap maintenance, and mowing to maintain the cover and prevent tree growth (EPA, 1985).
Appendix A - Hocomonco Pond 3rd Five Year Review
Page A-18
-------
In addition, institutional controls in the form of deed restrictions were required. Monitoring wells were
installed around the perimeter of the former lagoon. Following baseline monitoring, annual
groundwater monitoring was initiated in 1995.
The ROD specified the following O&M activities for the on-site RCRA double-lined landfill:
groundwater monitoring, facility inspection and maintenance, and leachate collection and treatment. In
addition, land use restrictions were required. The landfill and former lagoon area are visually inspected
on a periodic basis and the four monitoring wells around each area are sampled annually.
The remedy for the Otis Street area specified periodic surface water monitoring at the Hocomonco Pond
discharge stream as the only O&M requirement. This monitoring requirement has been fulfilled. No
surface water monitoring was performed during the current five-year review period. The ROD also
required a deed restriction for the Otis Street embankment.
The remedies for the isolated areas, Hocomonco Pond and discharge stream, and the Kettle Pond area all
involved placement of dredged or excavated materials in either the former lagoon area or in the on-site
landfill designed to meet RCRA technical standards. Therefore there are no separate O&M activities
specified in the ROD for these areas beyond those described above.
Consistent with the terms of the 1999 ESD and the TI waiver, the PRP developed a long term
monitoring plan (LTMP) for groundwater, DNAPL, and sediment to confirm that levels do not increase
in concentration or extent. The first phase of the long term monitoring program included performance
of baseline biological monitoring in May 2002. The objective of this monitoring was to characterize the
conditions prior to commencement of routine long-term monitoring and collect baseline data to be used
to confirm that the TI waiver remains a protective remedy. The baseline monitoring included analysis of
sediment samples for PAHs, total organic carbon (TOC), grain size, and percent solids, sediment
bioassay testing, and a benthic invertebrate community survey. The benthic survey included locations
within the TI zone as well as reference locations elsewhere in Hocomonco Pond.
The LTMP required semi-annual sampling events for a period of 5 years. The 5 years of data would
then be used to identify any notable trends according to the criteria in the LTMP (e.g., increasing,
decreasing, or no trend). This evaluation, following the decision tree outlined in the LTMP, would be
the basis for decisions regarding continued monitoring at the Site, or other actions.
The LTMP was implemented in late 2000, with the first semi-annual event conducted in November.
The elements of the LTMP include: water level measurements in 63 wells (semi-annually); groundwater
sampling of 6 wells (semi-annually) and 2 wells (annually); measurement of DNAPL thickness
(annually); and sediment sampling at 4 locations (semi-annually). Groundwater samples were analyzed
for PAHs and BTEX. Sediment samples were analyzed for PAHs, TOC, percent solids, and grain size.
Analysis for arsenic and chromium was not included as part of the LTMP based on the results and
conclusions of the 1997 investigation which supported the TI waiver and 1999 ESD.
In addition, the 1999 ESD also required collection of sediment samples. Each sample was a composite
collected from the upper 6 inches of sediment. All sediment samples were analyzed for PAHs, TOC,
Appendix A - Hocomonco Pond 3rd Five Year Review
Page A-19
-------
and grain size. A Sediment Sampling Plan, initially developed in 1998, was included as Appendix A of
the LTMP. This Plan states that the sediment sample results will be compared to the cleanup criteria
established in the SDD. If the sediment monitoring data indicate that cleanup levels are exceeded, the
Plan states that the agencies and PRP will "discuss and agree upon appropriate additional investigative
activities."
While these general O&M activities continue, an updated LTMP is necessary to describe the specific
monitoring activities consistent with the 2013 ESD. The specific O&M activities which are currently
being performed are summarized in Section 2, Table 5 of this report. Annual O&M costs currently
average $102,000.
Appendix A - Hocomonco Pond 3rd Five Year Review
Page A-20
-------
APPENDIX B
ADDITIONAL FIGURES, TABLES
AND PHOTOS
-------
FIGURE B-l: SITE LOCATION MAP
-------
FIGURE B-2: FOUR PRIMARY AREAS OF CONTAMINATION
-------
FIGURE B-3: TI ZONES ESTABLISHED IN 1999 ESD
-------
FIGURE B-4: Hocomonco Fond Site Monitoring Weils and DNAPL Recover}' Wells (shown in yellow highlight)
LEGEND:
wmo mjPOCM, hcmtciwio wu
m»-i n owka scoovotr *11
»» »« BQ.KOi MJCCflOM
o HOMO*. VCOViXv vcu
*-»»# yon fSKfcC ntu.
H.C-4 4^ w MX LAGOON CJIP <* JMru
ttHtOftKQ mi
»*-¦«»•£» »1A>«DC»CD VOL
NOTES:
t i»H nouRf based on a Mums rfflu rum
frVtQ. CTI, ri£ MMOt Mt«2$tl DATD
3/19/M ML LOCATOR A« tftDOBttAK
2 HfLL LOCATIONS (£*CP»T fCK AftAOONGD *1^4)
BAVD CM A*e k*«toamo
HAW IWO 1AELLS W1ACH WCU DOAlHOLE
HOCOMONCO POND SITE
WESTVOMOUOH. MMSACMJSCTTt
SITE PLAN
(9 ARCADIS
-------
FIGURE B-5: Expanded TI Zone Compliance Boundary for the Former Lagoon
l£G£mk
H© flCHirtfCAL MOMTwfKMC HCLL
w • owl wcowrr «ll
* # »olo«l>l pcc«*onr LL
o* lmoon CA*
ALL U3CAHCKS A*f APMIOWKATt
? «ELL LOCATION'S (EXCEPT FOR ASAHDONES ffflLS)
ftASEP OH su»>er PCYVftkO #T "OjQiMMC *
ULLH - Q*. OCS** OTOuf NC-*. PR04PEP CM
IM THt MASS COOHCIMaTE SYSTDl **© M
J WCH THAT MLC-M/U AND *CTtfD HUC-9SA) RAVI
TWO 1ELLS IfcSTAUXS * EACH «BLL KfEHOLE
*.AflHLA5T>fcG
HOCOMOMCO rOXD «fTE
PROPOSED FORMER LAGOON TI ZONE
»ARCAD1S
-------
2
o
e
7S
rr
33
x
«
CL
i*
»
s
s
a
r
©
n
K
O
s
-------
TABLE B-l: MLC-2 Concentrations 2000 to 2011 (Exceedances in yellow highlight)
Cotrt pounds ivilyte
Un*»
HLC-2
Wano I i»woi [ iwjuoi 1 looww J iorao«H [ isiM2 | 100003 ! t«M4 I i«i*o« ] uttvor I iwiikob I imiio* I n/uio I *7iii 1 m»n
voci
9EH2ENE
Uftl
se
21
IB 2
MA
NA
12 3
??6
132
113
44
r*
52 t
134
11
104
'OLOENE
uftt
SOL)
40'
JS4
NA
NA
21.5
353
33.4
364
W3
777
21 S
507
15
21 1
ETHYIBENZENE
uijrt.
io u
\U
133
HA
NA
11.0
143
12
143
73
10
II
ISA
12
122
iCLENE [TOTAL*
U&.
64
686
66 4
NA
NA
51.1
549
512
5® 7
?B3
374
386
026
36
568
CVOOt
JUETHVLNAPHTMAiSNE
M
HA
HA
NA
NA
NA
NA
ha
394
730
14.1
24.0
21.5
34
23 0
ACENAFHTH6NE
Ufl*.
200 U
16 7
19
51 U
51 U
NA
79
12.7
1#J
17 5
23.8
IS 5
59.7
77
1 1
^CtftAPfMVLfM
uq/L
200 U
S 3 LI
2§J
51 U
51 U
NA
13 J
18 J
S10
1QJ
1.9 J
o
C
«0
0 43
Q11U
ANTHRACENE
U&L
28J
S3 U
52U
51 U
51 U
NA
56 D
SO U
MU
S 3U
5.3 U
soy
30.8
0.11 u
0 053 U
BEr«OlA)AmHRAC£?»E
ugrt
200U
5.3 U
92U
51 U
51 U
NA
s« u
SO u
5.1 U
53U
53U
soy
540
QOSSU
ony
3£NZQ(A)PYHefciE
v&L
2R51#
5.3 U
S2U
SI U
51 U
NA
S6 U
S.0 u
5 1 U
53U
5 3lu
sou
11 U
011 u
0 032
a£NZC
81 U
51 U
NA
56 U
s.o u
51 U
S3U
5311
soy
11 a
0 <1 U
0,11 u
C'fflVSEKE
ugft.
2 CO U
5.3 U
S2U
51 U
51 U
NA
56 U
5 0 0
S1U
53U
53U
50 U
I1U
df ii
0 11 u
D0£n;cka,kiantmraCsNS
«*.
JSGU
SJU
S?y
51 U
51 U
NA
se u
5.0 U
&1U
53U
53U
SOU
ii y
eiiu
o.n y
FLUdlt*OTM0l6
U9d
200 U
S4U
52U
&1 0
51 U
NA
56 li
SO u
5 1 U
53U
5 3U
soy
n a
6.11U
344
FiUOftEME
ugA-
JC0U
90
116
51 U
51 U
MA
31 J
H
86
•S3
13.3
114
69.5
101
0 11 o
iSOENOd 2 3-CD)PYflW
Uflft
200 U
t n |«
5 2 li
51 U
si y
HA
*6 U
5.0 U
5.1 U
53U
530
sot
11 lj
0.11U
25 8
NAPHTHALENE
utf.
20OC
4140
4190
5350
4110
NA
<650
<240 0
2230
»«0
2110
701 D
6720
423
2140
PHfiNANlWRtNE
38.7
40.1
51 U
51 U
NA
114
155
68
13 3
s.e
126
304
26
H.l '
PYHENE
utfL
J0OU
S3 U
6.2 U
51 U
51 0
NA
56 U
5 .0 U
5.1 U
S3LI
53U
SOU
n y
0.11 u
0.11 U
MOT6S;
'¦^¦1 . Hfcrayimi par (tar
J Tt* eompaufa «tu eoMvely 4tcMta no*ew* tr» oj jocuied mntraii mw is an *»t>r»iaiw OMWarftatan art)
U • Th» compound was fa tout n* dateaed Tr# «tocaitad numeric^ vatut h (ha practical quanCiaton limit
C - Tne awseauW ooncarvat-ar> ms deiwnioed ttm w»W <»u>cri
-------
TABLE B-2: MLC-3 Concentrations 2004 to 2011 (Exceedances in yellow highlight)
Units
mic-s
MLC-4
WHK4 | 11/1406 | Iti'tMJ | 1 tiTI/0* | 11/17/M ] 11/2/10 I *7/11 1 MOW!
1Q/28AM | 11/1410* i 11/1JI07 | 11/11 tot | 1TH7/08 I 11/3/10 | iff Hi
12/2X11
voo» _ ,J
BENZENE
ugl i _
NA
671
84 3
s«i
"»«
Te
44
1A
NA
asou
0 50 U
a soy
osoy
0 50 U
oseu
osou
TOLUENE
NA
555
399
ti 2
417
17
1 OU
NA
10 J
toy
ton
iooy
t OC LJ
1.0 u
I0U
ETt1YU3£NZEk£
^,'t
NA
252
21#
11.2
ID 2
13
W
1.DU
NA
10 u
toy
toil
1.00U
1.00 u
10U
10U
XYtKNt (TOTALS
i«l
NA
63,3
51.8
2i 8
4*1
t '
U
1 DU
NA
TO J
ioy
1.0 J
100 Ll
i,oqu
toy
ioy
[3VOC,
2-METWYl*iAPHlX4LEN£
"»'L
NA
122
31.7
49 t
45 2
•I
V*
OSS
NA
55 LI
53U
5 4 U
54 U
0 22 U
19
0 10 u
AtfENftPHTHfNE
uotl
314
37 8
208
2*5
178
TO •
33
O'OU
24 J
SS
S.3U-
5 4 U
54 U
0.110
OSS
0 10 u
ACENAPHTNYL6NE
m>i
16 J
5 3U
2*4
2.4 J
23
0 83
czs
OTOU
au Li
56U
S3U
5411
64U
0110
039
010U
AflTHFWCENE
Mttt
HI U
53 U
SOU
S3 U
5 3D
a t j
0 11 u
oowu
50 U
SSU
83U
54 U
5 4 U
0.11 0
fl.iiy
0860U
BEI^OM ANTHRACENE
SO U
53U
sou
S3 U
5 3U
OOSi J
0,054 U
OlOU
SO U
55 o
S.3U
S4U
54U
00&4U
0 054 Lr
a io j
BcwewpweNE
m&
50 U
S3U
sou
S3 U
S3U
0 1 u
011U
0076
SO U
ssu
S3U
54U
54 U
aiiu
4-11 U
0 0E5
etfciZOlB^LLiOTWjrHtNE
SO u
53 U
sou
53 U
530
oasiy
aos*u
awo
SO U
ssy
5 3U
54y
54 U
0.O54U
Q 054 U
0 10 U
BEtJ20ia,nj/PtayL£NE
UflU
so u
530
sou
isy
S3U
0,3
0»1U
OTOU
so u
ssu
5 3 U
54 y
S4U
0 52
0 IT U
0 10 u
e*;^Ol*jFLOURAlM?t IEWE
l^ll
5.0 U
ssu
sou
5.3 U
5 3U
0.1 u
0.11 u
a wo
5.0 U
5 5U
5.3 U
;*u
54 U
anil
4.11 U
o toy
CHfrvSENE
wfl'L
5 0 U
ssu
soy
53 U
530
01U
0 11 u
0 TO u
50 U
ssu
53 U
54U
54 U
0 11U
01TU
O.OU
GiOEMZOt* HjANTHRACFNC
ug-L
5.6 U
5 3 0
5.0 U
5,3 U
5 3y
0.1 u
on u
010 0
50 U
SSU
S.3 U
54 y
s«u
0.110
H1U
0.WU
FLUORANTHSNE
«B'V
5.0 U
5-3 U
5.0 V
&3U
5 3U
0 1 'J
Q11U
0.10 0
SO y
ssu
5.3 U
5*l>
s*y
on y
SITU
oioy
FLUQRENE
"Brt.
3 3 J
53U
UJ
5.3 U
1.1
068
0.18
0.10 0
soy
55 y
8,3 U
54 U
6.4 U
ftTTO
015
Q 10 U
INCE ".CM t .ifi. CDJPV*EN£
WL _
8,0 V
5 3 U
£.90
1.3 U
S3 J
aiu
011 u
0*1
50 J
ssu
5,3 U
54U
64 U
011U
miu
020 U
NAPHTHALENE
691B
ICW
601
m*
820
2S2 0
543
123
79 t
1 to
103
54
17
011U
331
0»U
FtiENANTHRENE
uat
5-0 U
5 3 l>
sou
S J U
S3U.
oo?"
OOS4U
0.090 u
SOU
ssu
say
S4U
S4U
0.O54 U
D 054 U
0050U
fSYRCNE
•VL
5.0 U
5.3 U
sou
5,3 U
5.3 U
0 1 J
0 11U
0,10 o
SO u
SSU
5,3 y
5,4 y
54 U
011U
»ny
o.ou
MOTES:
J-71* compound how»*»r, |tn »io
-------
TABLE B-3: MLC-5S/D and MLC-6S/D Concentrations 2013 (No Exceedances)
Well ID:
Sample Date:
Interim
Groundwater
Cleanup Levels
MLC-5S
1/3/2013
MLC-5S
11/11/2013
MLC-5D
1/3/2013
MLC-5D
11/11/2013
MLC-6S
1/3/2013
MLC-6S
11/12/2013
MLC4D
1/3/2013
MLC-6D
11/12/2013
VOCs:
Benzene
5
0.50 U
0.50 U
0.50 U
0.50 U
0.50 U
0.50 U
0.50 U
0.50 U
Tohiene
1,000
1.0 U
1.0 U
1.0 U
10U
1.0 U
10U
1.0 U
1.0 U
Ethylbenzene
700
1.0 u
10U
1.0 U
1.0 U
10U
10U
1.0 U
1.0U
Xylene (Total)
10,000
1.0 u
10U
1.0 u
10U
1.0 u
10U
1.0 U
1.0 U
SVOCs:
Acenaphthene
2,200
0.11 u
0.10 U
0.11 u
0.10U
0.11U
010U
0.11U
0.10 U
Acenaphtbyiene
•
0.11 u
0.10 u
0.11 u
010U
O il u
0.10 u
0.11 U
OIOU
Anthracene
11,000
0.046 J
010U
0.11 u
0.10 U
0.11 u
010U
0.11 U
OIOU
Benzo(a)anthracene
-
0.054 U
0029 J
0.056 U
0.023 J
0.053 U
0.051 U
0.054 U
0 051 U
Benzo(a)p\Tene
0.2
0.11 U
0.10 u
0.11 U
0.10 U
0.11 U
0.10 u
0.11 U
0.10 U
Bmzo(b)fhioranlhene
-
0.054 U
0.051 U
0.056 U
0.050 U
0.053 U
0.051 U
0.054 U
0.051 U
Ben2o(giu)peryleie
-
0.11 U
0 10 u
0.11 U
0.10 U
O il u
0.10 u
0.11 U
0.10U
Benzo(k) fhioraiithene
-
0.11 u
0.10 u
0.11 U
0.10U
011U
0.10 u
0.11 U
OIOU
Chrysene
-
0.11 u
010U
0.11 u
0.10U
011U
010U
0.11 u
OIOU
Dibenzo{a.h) anthracene
-
011U
010U
0.11 u
0.10 u
011U
OiOU
0.11 u
OIOU
Fboranthene
1,500
0.049 J
027
0.11 u
0.35
0.11 u
0.18
0.11 u
022
Fhiorene
1,500
0.11 U
0.10 U
0.11 u
010U
0 065 J
OIOU
0.11 u
OIOU
Indeno{ 1.2,3 -cd)p\Tene
-
0.11 U
0.10 u
0.11 u
0.10 U
0.11U
OIOU
0.11 u
OIOU
2-Metfaytnaphthalene
-
0.22 U
0.20 U
0.22 U
0.20 U
0.21 U
0,20 U
0.22 U
0 20 U
Naphthalene
1,500
0.058 J
0.10 U
0.10 J
0.054 J
2.0
OIOU
0.11 U
OIOU
Phenanthieue
-
0.17
032
0062
0 53
0.073
012
0.032 J
021
Pyrene
1,100
0.11 U
0.17
0.11 U
0.22
011U
012
0.11 U
013
-------
TABLE B-4: Recent DNAPL Recovery Volumes
1
AM 2. 2914
Asia 7.2014
Apr917.2914
*011212014 1
Month
WBBO
VMS
Casino
WWO
OHM*. Romans
TTtt96hoUn
Depth to
BUhmi
0*p9ita
WKsr
ONAPL
TMcknooc
ONAPL
Removed*
OOP&tD
wster
ONAPL
TlflJUIOM.
CMAPL
RgBOWfl
Depth to
wafer
ONAPL
Tnckmcs
ONAPL
RlMIOWd
Oepthto
voter
ONAPL
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2.61
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241
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| lahiBwwmi
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1 Total nemwdl
1850
saso
Hay 1.2014
Mv?.2014™
Hay 98.2914
Kay 21, SOU
Kay 3% 2014
Morfh
MBO
w*o
Casino
Votme
onapl Removal
ThracftoM"
Depth to
OtpOto
Wrfar
DNAPL
TMokneK
DNAPL
OtpOtD
VMSar
ONAPL
DNAPL
Rrmn^
Depth to
water
ONAPL
TOoknocc
DNAPL
ftomovotf
Dapthto
Wrier
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IMdnKC
ONAPL
nemowd
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wafer
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00
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coat)
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1.69
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39.19
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39.29
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31.11
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3140
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Total Ranowd
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6043
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I 1
l jix»*,2aw i
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I Juno 19,2014 1
I JW0ZL2D14 |
I Jum sa 2014 1
Mom
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Depth to
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TMofeness
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| Total Removed!
am
| Ttotal Removedl
21m
6050
Notes:
(1)» Rom remmd quarter? torn ai vdi a moored ONAPL manes crater man OJ feet.
C)*C*W4itiaiedtnWeecteraDtt. OWPLmaaresgpneoaiJagav2^.2011.
O) • Tte ini&iw of ONM fenoM otsean e» te gn^ Ban ffe vauitt preM cn t« cx^ vetine v mdne^ 19 enntsnera or «8fer and cfntfproduQ duno femevs.
MU • Not Measured. Wd AC has an arcs ustcn e* wto est. wren a probe cr ape is treated, fi Becomes Axfc aw 6 net easly lefoond. As a rtsuX Ws wei has Been punped otf petodeafr CscproimateV eanttjo
«8)oUoeicfSnoattfteffierOKAR.tManessfnextfeneflBkaBe)eret8aMrKnBpui9>iAiedr)Bie«dLtie«seflBn0aaterorai4. l74oaJons ee CHAR, was removed Bora w»efAr2.
'•McagnedaoamuaoedOWft.deiiMUi^e^aredxedBmoafliJUMeMCgcnieasapneEg. Meaaigmots off WWL are rtergtfEd By oahtgottPlcDWR. noted By Pie eiteffrce grate, and 07 i&uroteervagac or OWf^sartno en ttclrtetece grate tape.
The iWnjuaarotncBcerrtdOWfLWdmes can fteBtttetcdcoflpenaBrrttfpfcstonog me aw mease/Ed djapttnataudafe and Wdttftav.trettsjaimeaaremeflJraysormesDeaawrtWdaetD
okafl smestno on tne tape of the racrtxe me atce nvhfl tttno trttei ore* wn.
-------
TABLE B-5: Summary of Sediment Results
SEDDSHP
SED-1 (T1-DS)
|
E
i
S£D-J-*(T3-OSr
at)
(T2>
(REF2 T3-T4)
SED-1 A
SED-2A
SWOay Dec-98
NA
19.5
4.3
17
—
-
Oct-OO
7.0
e.e
4J
7.1
-
—
u*oi
28
T7.4
63
42
-
NnMtl
75
17.3
55
72
—
-
Ma^E
184
319
ee
7.1
-
-
Oc$-Q2
0.7
105
iai
4.7
—
—
m^b
11
148
12.1
119
-
-
Oct-ffJ
35
11.9
7.4
3.7
_
—
May-04
133
14.9
86
7 o
-
-
Oct-04
ia7
W.4
5.0
45
-
-
M*OB
12.55
16.8
84
55
—
-
JuMJB
228
4.8
63
5.7
—
-
Auq-OS
225
-
-
-
-
*
Jun-ID
22
2.7
82
100
18-2
15
M^-1t
8.7
12.1
57
9.8
15J
M
May-12
125
8.8
102
8.1
11.7
83
Jun-13
—
257
7.3
-
12.8
0.8
Total PAW (mafcgj OeoOS
NA
105
32.6
1 18J
-
—
Oct-OO
00 U
BOS
132
00 U
—
—
May-01
0,14
80,0
156
0.07
-
—
Nov-01
QO U
215
14.8
0.18
—
—
May®
oie
143.8
22.95
0204
-
-
Oet-02
00 u
51 0
80
0.0 U
—
—
Moy-03
O0U
Etl
36.6
aou
—
—
0(3-03
aou
60.1
18.1
OD4
*
-
May0«
089 J
51 6 J
325 J
0.07 J
—
-
OctM
ami
67.5
34.7
0.0 u
—
—
MayOS
057 J
782 J
342 J
0.04 J
—
—
JuMB
2125 J
98
13.8
00 u
-
—
Aub-OC
QjOU
-
-
-
-
—
¦tafv-10
004
13.95
14-575
00795
58.7
414
May-11
018
1072
30-0
1.30
54 2
51.0
May-12
0.04
48.0
28.8
Q.K)
10.7
271
Jun-13
-
tei i
10.5
-
77
37
PtWL.Jtt.giif |mgftg| Dec-OS
NA
ffl
4.30 U
0-20 J
—
-
Oct-OO
0.42 U
390
0.43 J
042 U
-
-
MayOt
0 40 U
3.90
100
041 U
—
—
Nov-01
042 U
1.70
102
043 U
—
«
0.82 U
930
225
053 U
-
-
OcMB
0.41 U
700
oee
042 U
-
—
Mj»-£I3
0,43 U
4,15
230
0 42 U
w
—
Oct-03
0.38 U
fl-OO
1-2D
0 40U
—
—
May04
0.13 J
7.30
266
0.40 U
—
—
(MM
006 J
8 3D
22
0.4 U
—
—
May-05
ai2j
420
230
042 U
—
—
Jut-OB
0i57 J
1.4 U
1.4
0.42 U
-
—
Auj-06
0.38 U
-
-
-
-
—
Jun-tO
0.015 U
2.3
Q 86
Q 0048 J
1.07
17
May-It
0042 U
17
28
o.tt
8J2
5_ft5
May-12
Q06J
97
268
0D063 J
38
33
Jurvt3
-
25
0775
-
6.3
40
Notes:
' Asstrns novMKcti are equ^ to zero for Total PAH
" 5ED-3i«$ joJu^U*en»qoiiisoftb«i!iB«f!T3anflT4
U Net delected; vak* for ptwrianSvene is repcrtng bnvt
J EsSfruted artarnvxncn
NA Not arable
-------
Photos Taken on July 31, 2014
-------
RCRA Landfill Cap
Wooded Area Overlooking Pond
-------
APPENDIX C
INTERVIEWS
-------
INTERVIEW RECORD
Site Name: Hocomonco Pond Superfund Site (Westboro,
MA)
EPA ID No.: MAD980732341
Subject: 3rd Five Year Review
Time:
Date:
7/31/2014
Type: ~ Telephone ¦ Visit ~ Other
Location of Visit: Hocomonco Pond site
~ Incoming ~ Outgoing
Contact Made By:
Name:
Jim DiLorenzo
Title:
Remedial Project
Manager
Organization:
EPA Region 1
Individual Contacted:
Name: Jay Naparstek
Title: Deputy
Director,
Bureau of
Waste
Cleanup
Organization: Mass. Dept. of
Environmental Protection
Telephone No: 617-292-5697
Fax No:
E-Mail Address:
jay.naparstek@state.ma.us
Street Address:
One Winter Street
Boston, MA
l.A. What is your overall impression of the project? (general sentiment)
Since the previous five-year review, the project is operating as expected and there are no
major issues or problems.
2.A. What effects have site operations had on the surrounding community?
None, other than the property not being available for reuse.
-------
3.A. Are you aware of any community concerns regarding the site or its operation and
administration? If so, please give details.
None, other than the pending redevelopment of the property.
4.A. Are you aware of any events, incidents, or activities at the site such as vandalism,
trespassing, or emergency responses from local authorities? If so, please give details.
None.
5.A. Do you feel well informed about the site's activities and progress?
I do.
6.A. Do you have any comments, suggestions, or recommendations regarding the site's
management or operation?
None.
-------
INTERVIEW RECORD
Site Name: Hocomonco Pond Superfund Site (Westboro,
MA)
EPA ID No.: MAD980732341
Subject: 3rd Five Year Review
Time:
Date:
7/31/2014
Type: ~ Telephone ¦ Visit ~ Other
Location of Visit: Hocomonco Pond site
~ Incoming ~ Outgoing
Contact Made By:
Name:
Jim DiLorenzo
Title:
Remedial Project
Manager
Organization:
EPA Region 1
Individual Contacted:
Name: Mike Bollinger
Title: Project
Manager
Organization: Beazer East,
Inc.
Telephone No: 412-208-8864
Fax No:
E-Mail Address:
Mike.Bollinger@hanson.biz
Street Address:
Manor Oak One, Suite 200
1910 Cochran Road
Pittsburgh, PA 15220
l.A. What is your overall impression of the project? (general sentiment)
The project is going well. The passive recovery is working well, and good progress is
being made.
2.A. What effects have site operations had on the surrounding community?
Site operations appear to have little to no effect on the surrounding community, other
than the lack of the property to be available for reuse. However, the 3rd ESD will reduce
the site's "footprint" and make reuse viable.
-------
3.A. Are you aware of any community concerns regarding the site or its operation and
administration? If so, please give details.
None, beyond how to best reuse the property.
4.A. Are you aware of any events, incidents, or activities at the site such as vandalism,
trespassing, or emergency responses from local authorities? If so, please give details.
None observed.
5.A. Do you feel well informed about the site's activities and progress?
Yes.
6.A. Do you have any comments, suggestions, or recommendations regarding the site's
management or operation?
None.
-------
INTERVIEW RECORD
Site Name: Hocomonco Pond Superfund Site (Westboro,
MA)
EPA ID No.: MAD980732341
Subject: 3rd Five Year Review
Time:
Date:
7/31/2014
Type: ~ Telephone ¦ Visit ~ Other
Location of Visit: Hocomonco Pond site
~ Incoming ~ Outgoing
Contact Made By:
Name:
Jim DiLorenzo
Title:
Remedial Project
Manager
Organization:
EPA Region 1
Individual Contacted:
Name:
James Malloy
Title:
Town
Manager
Organization:
Town of Westboro
Telephone No: (508) 366-3030
Fax No: (508)366-3099
E-Mail Address:
_j malloy @town. W estboro.ma.us
Street Address:
34 W. Main Street, Westboro, MA 01581
I.A. What is your overall impression of the project? (general sentiment)
That it has been managed responsibly by Beazer as the responsible party and that EPA
and DEP have done a good job overseeing the remediation over a long period of time.
2.A. What effects have site operations had on the surrounding community?
The immediately surrounding area is industrial, so it has had little impact. Residents of
the community know that it exists as a Superfund site, overall site operations appears to
have had little impact on the greater community.
-------
3.A.
Are you aware of any community concerns regarding the site or its operation and
administration? If so, please give details.
No.
4.A. Are you aware of any events, incidents, or activities at the site such as vandalism,
trespassing, or emergency responses from local authorities? If so, please give details.
No.
5.A. Do you feel well informed about the site's activities and progress?
Yes, I receive regular reports from Beazer (cc'd from notices sent to EPA) and EPA has
always been very responsive to any questions we have.
6.A. Do you have any comments, suggestions, or recommendations regarding the site's
management or operation?
No.
------- |