PB98-963128
EPA541-R98-119
March 1999
EPA Superfund
Explanation of Significant Difference
for the Record of Decision:
Iron Horse Park OU 1
Boston/Marine Wastewater Lagoons
Billerica, MA
10/1/1997
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Final Explanation of Significant Differences
Boston & Maine Wastewater Lagoons
Operable Unit 1, Iron Horse Park Superfund Site
INTRODUCTION
A. Site Name and Location
Site Name: Boston & Maine Wastewater Lagoons
Iron Horse Park
Site Location: High Street, Billerica
Middlesex County, Massachusetts
B. Lead and Support Agencies
Lead Agency: United States Environmental Protection Agency
Contact: Don McElroy, RPM
(617)223-5571
Support Agency: Massachusetts Department of Environmental
Protection (MADEP)
Contact: Janet Waldron
(617)556-1156
C. Legal Authority for BSD
Section 117(c) of the Comprehensive Environmental Response,
Compensation and Liability Act (CERCLA) requires that, if any remedial
or enforcement action is taken under Section 106 of CERCLA after
adoption of a final remedial action plan, and such action differs in any
significant respects from the final plan, the EPA shall publish an
explanation of the significant differences (ESD) and the reasons such
changes were made.
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D. Public Record
In accordance with Section 117(d) of CERCLA, the Final ESD will be part
of the Administrative Record File, which is available for public review at
the two locations listed below at the given times:
EPA Region I Records Center
90 Canal Street
Boston, MA 02114
(617)573-5729
Monday-Friday: 10:00am - 1:00pm
2:00pm - 5:00pm
Billerica Public Library
25 Concord Road
Billerica, MA 01821
(508)671-0949
Monday-Thursday: 9:00am - 9:00pm
Friday-Saturday: 9:00am - 5:00pm
II. Summary of Site History, Contamination, Selected Remedy, and
Circumstances Leading to an ESD
A. Site History
The entire Iron Horse Park Superfund Site (Site) consists of
approximately 552 acres of land in North Billerica, near the Tewksbury
town line. The Site is an active industrial complex and railyard with a long
history of activities that have resulted in contamination of soils,
groundwater, and surface water. The Site includes open storage areas,
landfills, and lagoons. A more complete description of the Site can be
found in the Phase 1A Remedial Investigation Report (July, 1987).
The Site was placed on the National Priorities List in September 1984
following investigations by the Massachusetts Department of
Environmental Quality Engineering (now the Massachusetts Department
of Environmental Protection or MADEP) in the early 1980's and a Site
Investigation Report completed by the NUS Corporation for EPA in
August 1984
In August 1984, EPA, under its removal authority, covered a portion of the
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Site known as the Johns-Manville Asbestos Landfill with gravel and
topsoil to prevent asbestos in the landfill from becoming airborne.
In 1985, EPA began investigations of the Site to determine the nature and
extent of contamination. Under the first phase of the evaluation, EPA
conducted a broad study of the Site to define the potential problem areas.
This study was entitled the Phase 1A Remedial Investigation (Rl). As a
result of the Phase 1A Rl, EPA concluded that the size and complexity of
the Iron Horse Park Site necessitated using a phased approach for
subsequent, more detailed studies. Under this approach, the Site was
separated into a number of different problem areas. Where possible, the
areas studied and the decisions on how to clean them up are made as
operable units. An operable unit is defined as a discrete portion of an
entire response action that, by itself, manages migration or eliminates or
mitigates a release, threat of release, or pathway of exposure.
The Boston & Maine Wastewater Lagoons (B&M Lagoons) were grouped
together as the first operable unit for the Site. In May 1988, EPA
completed a study, referred to as the Phase 1B Rl, which focused on the
nature and extent of contamination in and around the B&M Lagoons. The
Feasibility Study (FS) of potential remedial alternatives for the cleanup of
the B&M Lagoons was issued in June 1988.
B. Contamination Problems
The B&M Lagoons are a series of lagoons (two active, one "overflow" and
one inactive) which were initially constructed and put in use around 1915.
The two active lagoons received untreated wastewater from various
facilities in Iron Horse Park from 1915 until 1992. Over this time period,
sludge was periodically dredged from the bottom of the active lagoons
and placed in piles nearby. Investigations of the B&M Lagoons identified
contamination in sludge located on the lagoon bottoms, as well as
contamination in the piles of material dredged from the lagoons. The Rl
detected poly-aromatic hydrocarbons, volatile organic compounds, metals
and other compounds in the lagoons and the associated soil piles. Of the
contaminants detected, poly-aromatic hydrocarbons (PAH) and total
petroleum hydrocarbons (TPH) require cleanup.
C. Summary of Remedy Originally Described in the Record of Decision
The September 15, 1988 Record of Decision (ROD) called for treatment
of contaminated soil and sludge from the lagoons by bioremediation,
returning the treated material to the lagoon area, covering it with clean
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soil and establishing a vegetative cover. The ROD also required
decontamination and disposal of piping and pumps associated with the
lagoons. In 1990 a settlement was reached whereby Boston and Maine
Corporation agreed to undertake the cleanup of the B&M Lagoons
Operable Unit.
D. Summary of Circumstances That Gave Rise to the Need for an ESD
A Pre-Design Evaluation Report was produced by Boston & Maine
Corporation in January 1991. This Report was significant in that it:
- delineated the limits of material to be excavated and treated;
- identified, based on the cleanup criteria, which dredged soil piles would
require excavation and remediation; and
- concluded, based on treatability studies that cleanup results could be
achieved in a given batch within approximately 40 days.
A Remedial Design produced by Boston & Maine Corporation was
approved by EPA in July of 1991. The Remedial Design called for
development of an unlined treatment cell. Contaminated soils and sludge
would be placed in the treatment cell in 6-9 inch "lifts" or layers. Once
placed, conditions within each lift in the treatment cell (oxygen, moisture
and nutrients) would be optimized to allow biological treatment by soil
microorganisms to take place.' The cleanup requirements for the B&M
Lagoons are: Total PAH -60% removal or 1part per million (ppm) and
TPH - 5,000 ppm.
Despite conclusions reached in the Pre-Design Evaluation, experience at
full scale in the treatment cell was significantly different. Progress to
achieve cleanup levels was significantly slower than predicted. The
remedy has taken an inordinate amount of time to reduce contamination
levels, and has had difficulty in achieving cleanup levels.
The first lift of contaminated material (approximately 1,200 cubic yards)
was placed in the treatment cell in October 1991. It contained moderate
levels of TPH and had no detectable levels of PAH. This lift was
considered to be complete in July 1993. A second lift containing elevated
levels of PAH and TPH was placed in the treatment cell in October 1993.
By November 1994, TPH cleanup levels had been achieved. PAH
sampling results indicated that PAH levels were approaching cleanup
levels asymptotically (i.e., getting closer and closer but never meeting)
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This second lift has never been considered to be complete.
Bioremediation has not proven to be an effective remediation method at
the B&M Lagoons. The process has had difficulty in achieving cleanup
levels and in addition, the time involved has been extensive(one year or
more per lift when 40 days was predicted). Under this extended time
scenario, if it is assumed that cleanup levels could be attained, the
remedy would still require ten years or more to complete. The ROD
estimated that utilizing bioremediation the remedy would be completed
within a five year period.
Description of Significant Differences and the Basis for these Differences
A. Significant Differences
Due to the lack of success of bioremediation, alternative remedial
alternatives evaluated during the June 1988 Feasibility Study (FS) of
B&M Lagoons were reinvestigated. In particular, the on-site stabilization
alternative utilizing concrete was reevaluated in light of changes in
stabilization technology. Since the release of the ROD, stabilization
through asphalt batching has become an economical means by which
contaminated materials can be stabilized and recycled for beneficial
reuse. Asphalt batching has become an accepted treatment technology
that can be used to produce a cleanup that is more cost effective than the
on-site stabilization option considered in the FS. This technology would
result in off-site treatment and reuse which eliminates the need to utilize a
costly on-site cap over the concrete-stabilized material as is discussed in
the FS.
A Supplemental Feasibility Study (SFS), which is in the Administrative
Record, was conducted which reevaluated the stabilization alternative
utilizing off-site asphalt batching.
The SFS analyzed this alternative in light of seven of the nine criteria
under Section 121 of CERCLA and Section 300.430(e)(9)(iii) of the
National Contingency Plan (NCR) and concluded that the alternative
satisfied these criteria: overall protection of human health and the
environment; compliance with applicable or relevant and appropriate
requirements (ARARs); long-term effectiveness and permanence,
reduction of toxicity, mobility, or volume through treatment, short-term
effectiveness; implementability; and cost. The eighth criterion, state
acceptance, is addressed in Section IV of this document. The ninth
criterion, community acceptance, is addressed in Section VI of this
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document.
The B & M Lagoons contaminated material will undergo treatment at an
off-site, state-approved, soil recycling facility which treats contaminated
soils through asphalt batching. Contaminated material will be excavated
and transported off-site to a hot mix or cold mix asphalt batching plant.
At the plant, the material will be blended with asphaltic material to
produce a stabilized mixture in which the contaminants of concern will be
permanently immobilized. This stabilized mixture is suitable for use as a
base for paving.
The asphalt batching process consists of three stages. The first stage
consists of producing material of uniform size through screening and/or
crushing and blending. Stage two involves feeding the pre-processed soil
into a mixing unit where it is blended with asphaltic emulsions. The third
stage involves stockpiling the asphalt emulsion-coated material for
"curing." Curing consists of evaporation of the water component of the
emulsion. This stabilized mixture is suitable for use as a base for paving.
B. Basis for Change
The basis for this change is the inability of bioremediation to achieve
cleanup levels in a timely manner, and possibly at all, at this Site. The
experience to date has shown that the original remedy is inordinately
difficult to implement, and may never result in the overall protection of
human health and the environment. In contrast, as analyzed in the SFS,
asphalt batching will satisfy the statutory criteria.
Asphalt batching provides numerous benefits. A bench-scale test was
performed to evaluate the effectiveness of asphalt batching on the B&M
Lagoons material. This test demonstrated that asphalt batching provides
permanent immobilization of the contaminants of concern. In contrast to
cement-based stabilization, which was considered in the original
Feasibility Study, asphalt batching would result in little or no increase in
volume of material. Asphalt batching will be easy to implement. Several
permitted batching plants are available to treat soil. Asphalt batching is a
very reliable technology that can be controlled and monitored by the
operator. Periodic samples of treated soil are collected and analyzed to
verify that contaminants have been immobilized.
Asphalt batching is consistent with the Massachusetts policy for
managing petroleum contaminated soils. The material will be asphalt
batched at a Massachusetts permitted soil recycling facility As the
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batched material is a useable product, i.e., base paving material, it will be
beneficially used. An obvious advantage of this is that the treated
material will not be left at the B&M Lagoons or placed in a landfill.
The primary community impacts of asphalt batching will be associated
with the transportation of contaminated material to the asphalt batching
facility. Iron Horse Park is approximately 3 miles from Route 495 and
Route 3. Protective measures will be implemented to minimize
transportation through residential areas, and to prevent spillage of
material during transportation. In addition, controls will be implemented
during handling of materials at the Lagoons to prevent the creation of
excess dust.
It is estimated that the asphalt batching process will be completed by the
end of 1998. Approximately 6,000 cubic yards of material will be asphalt
batched this fall (1997). Activities to be conducted in 1998 are:
- sampling to delineate the remainder of contaminated material which
must be excavated and treated;
- excavation and asphalt batching of the remaining material; and
- verification sampling to ensure that all material requiring treatment has
been excavated and that any material left at the lagoons does not contain
contamination above cleanup levels.
While a final volume of material to be asphalt batched is not known, it is
estimated that a maximum of 28,000 cubic yards may require treatment.
This volume is consistent with the volume utilized in the Feasibility Study
and is being retained for comparative purposes. Using this volume, the
estimated remedial cost is $3.3 million. This cost is very comparable to a
number of the alternatives previously considered.
IV. Supporting Agency Comments
In a letter to EPA dated August 20, 1997, MADEP expressed its agreement with
the changes documented in the draft ESD.
V. Statutory Determinations
This ESD documents the EPA's modification of the ROD to use removal of
contaminated soils to an asphalt batching facility and treatment by asphalt
batching, rather than treating through bioremediation.
EPA believes that the remedy as modified herein remains protective of human
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health and the environment, complies with all Federal and State requirements
that are applicable or relevant and appropriate to this remedial action, and is
cost-effective. In addition, the revised remedy utilizes permanent solutions and
alternative treatment technologies to the maximum extent practicable for this
Site.
VI. Public Participation Activities
Notice and information regarding these proposed changes to the ROD were
disseminated by (1) a mailing to all parties on the Community Relations Mailing
List and (2) a published notice and a brief description of the draft ESD on
September 8, 1997 in the Lowell Sun. In addition, the draft ESD was made
available as part of the Administrative Record for this matter, which is available
for public review at the locations and times stated in Section I.D. A public
comment period was conducted from September 8 through September 26, 1997.
During this time no comments were received by EPA on this matter. In addition,
a public meeting was held at 7:00 p.m. on September 16, 1997 at the Billerica
Town Hall to provide information and answer questions regarding this matter.
/
Harley F. Laing, Gnrector Date
Office of Site Remediation & Restoration
EPA-New EnglaKjdJ
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