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buried onsite in the process area lagoons. As a result of this
remedial action, the 25-acre process area has been extensively
disturbed. Drums were reported to have been crushed and buried
in former lagoons in the process area during this action. In
1984, an EPA emergency team removed 22 drums of waste chromic
acid and 30 cubic yards of sludge containing copper and chromium
from the Site. On July 22, 1987, the Site was listed on the
National Priorities List.
In 1988, EPA executed a Consent Order with the potentially
responsible parties ("PRPs") to conduct a Remedial Investigation
and Feasibility Study J/^RI/FS^) at the^ Site. The RI is a study
to determine the nature and extent of contaminants present at a
site and the problems caused by their release. The FS is
conducted to develop and evaluate options for the cleanup of a
site.
In December 1991, the EPA issued an Administrative Order for
removal response activities. The Respondents erected temporary -
soil erosion and sedimentation control structures, and conducted
removal activities with regard to drums and soil staged onsite-
during Phase II RI operations. The Respondents completed the
removal work in May 1992. The Phase II RI/FS reports were
released on July 28, 1993. Soil on the Site had been found to be
contaminated with heavy metals and organic compounds. Ground
water in the shallow zone is contaminated with trichloroethylene,
trichlorobenzene, and bis(2-ethylhexyl)phthalate. Copper,
chromium and mercury have been detected in the stream sediment.
EPA's Regional Administrator selected the Remedial Action
for contaminated soil, solid waste and miscellaneous debris on
portions of the Site in the OU1 ROD signed on December 28, 1993.
The major components of the selected remedy in the OU1 ROD are:
Offsite disposal of solid waste and debris;
k Treatment of VOC-contaminated soil by vacuum
extraction-; "
Source- containment by slurry wall;
Source- containment by capping;
» Fencing to limit access to capped areas;
» Site restoration by revegetation;
Deed restrictions; -:--- ._ -_-- -
. Long-term ground water monitoring~
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On December 1994, EPA issued an Administrative Order which
required the PRPs to implement the OU1 ROD remedy. In January
1995, a group of Respondents, the Revere Steering Committee
("RSC"), notrfied EPA of their intent to comply with the Order to
implement the remedy.
On December 11, 1995, the RSC submitted a request to EPA to
reevaluate one of the criteria being used by EPA to determine the
areal extent of the cap. Subsequent to that and in preparation
for the remedial design, the RSC requested clarification on the
intent of the OU1 ROD remedy with respect to Site Restoration.
The clarification follows: Section IX.A.6.A. (Site
Restoration) of the OU1 ROD is a description of the Site
restoration component of the remedy. Site Restoration applies to
the entire Site not just areas of the Site which require capping.
Section IX.A.6.A. did not clarify that areas of the Site that are
eroded, barren, or poorly vegetated due to historic Site
activities will be revegetated to prevent further erosion and,
hence, mitigate the future migration of soils that may adversely -
impact the quality of the onsite tributaries. EPA does not
consider this clarification a significant difference since one of
the goals of the OU1 remedy is to prevent the migration of
metals-contaminated soil from impacting the onsite tributaries'.
In early January 1996, the RSC completed pre-design field
investigations to delineate-further the areas where soils
contained organic chemicals above the remediation levels
specified in the ROD. In addition, a pilot-scale test for in-
situ vacuum extraction of the volatile organic- chemicals ("VOCs")
from the soil was conducted. The results of this work were
reported to EPA and PADEP in the Field Investigation Report,
Slurry Wall/Vacuum Extraction, Operable Unit One in June 1996
(referred to as the Pre-Design Study). Based on this work, the
RSC revised the estimates of the volume of soil ..impacted by VOCs
and trichlorobenzene ("TCB") to approximately 750cubic yards
("cy") or 1100 tons which was significantly less than the 26,350
cy (34J255 tons) used to evaluate remedial alternatives in the
1993 Feasibility Study for the site. In addition, the pilot-
scale vacuum- extraction testing indicated that the ROD-specified
remedy of in-situ vacuum extraction for VOCs in the soil was not
very effective given, the site-specific soil characteristics.
To confirm- the most recent volume estimate reported in the
Pre-Design Study, the RSC retained Advanced Geoservices to
conduct a Focused Field Investigation ("FFI") in September 1996.
The results of the FFI were submitted to EPA and PADEP in a
report on January 17, 1997. Since the completion of the RI in
1993, twenty-five (25) soil samples from former collection basins
AA and BB have been analyzed for TCB. The results of the FFI
indicate that: 1) TCB is not currently found in Site soils in
the vicinity of former collection basins AA and BB above the ROD
remediation level, and therefore, a slurry wall is not necessary;
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and, 2) that 320 cy of soil is found above the ROD specified
remediation level for VOCs in Site soils. Based on a conversion
factor of 1.6 tons/cy, this corresponds to an estimated 510 tons
of soil requiring treatment for VOCs.
III. DESCRIPTION 07 SIGNIFICANT DIFFERENCES
A. Criteria for Determining the Areal Extent of the Cap
The Revere OU1 ROD called for containment of contaminated
soils by capping. The cap performance specifications are set
forth in the Pennsylvania Residual Waste Regulations at 25 PA
Code §§ 288.234, 288.236, 288.436, and Appendix A, Table II.
These regulations, which are relevant and appropriate to capping
of contaminated soils, require in part that the cover achieve a
permeability of no less than 1 x 10"7 cm/sec. The ROD
establishes the following three criteria to determine which
portions of the process area and spray fields at the Site must
achieve this cap permeability requirement and thus provides the-
delineation of the areal extent of the cap:
1) Exposure to contaminated soils results in a Hazard Index
greater than one (1);
2) Exposure to contaminated soils results in a carcinogenic
risk greater than 1 x 10"4; or
3) The Synthetic Precipitation Leaching Procedure ("SPLP")
listed as EPA Method 1312 indicates the soils contain
leachable contaminants that will result in contaminant
levels above the method detection limits for those
contaminants using drinking water analytical methods.
The last criterion, in particular the use of method detection
limits as the acceptable ground water contaminant levels, is
being changed in this ESD. ,
At the time the OU1 ROD was issued, no chemical specific
applicable or relevant and appropriate requirements ("ARARs")
existed for cleanup of the contaminated soil at the Site. The
SPLP criterion w.as developed to address the concern that
contaminant, concentrations in soil that did not represent an
unacceptable risk from exposure (via dermal contact and
inhalation), if left untreated or uncapped, could potentially
leach contaminants into ground water at unacceptable levels.
To use the SPLP criterion to develop soil cleanup levels for
the Site', acceptable contaminant concentrations had to be
established for ground water. The Maximum Contaminant Levels
("MCLs") established under the Safe Drinking Water Act and set
forth at 40 C.F.R. § 141.61(a) provide acceptable levels for
exposure to hazardous substances in drinking water. Although
Federal MCLs are an .acceptable protection standard for ground
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water, PADEP determined, at that time, that the remedy for OU1
had to be consistent with the Department's Groundwater Protection.
Strategy ("GWPS"). According to this former policy, soils that
are contaminated with hazardous substances must be remediated so
that they do not impact ground water at levels above background
or method detection limits. In order to determine cleanup levels
for metals in soil, PADEP recommended the use of drinking water
method detection limits when conducting the SPLP test on the
contaminated soil.
Although the GWPS was not considered to be an ARAR for the
OU1 ROD, EPA did accept the GWPS as a standard to be considered
for the OU1 remedy. To-Be-Considered ("TBCs") standards are
advisories or guidance issued, but not promulgated, by Federal or
State governments that are not legally binding and do not have
the status of ARARs. EPA may use TBCs along with ARARs as part
of the site risk assessment and TBCs may be used in determining
the necessary level of cleanup protection for human health and
the environment. EPA incorporated method detection limits
("MDLs") into the SPLP criterion rather than MCLs to define the-
areal extent of Site soils that required capping. When EPA
issued the OU1 ROD, soil cleanup levels at this Site were
determined using health-based standards and the use of drinking
water MDLs when conducting the soil leach test as opposed to
using an ARAR standard.
Subsequent to EPA's issuance of the OU1 ROD, the
Pennsylvania General Assembly passed The Land Recycling and
Remediation Standards Act ("Act 2") of May 19, 1995. Act 2 sets
forth soil cleanup standards for contaminated sites in
Pennsylvania. In accordance with PA Act 2, the criteria for
protecting ground water from contaminated soil incorporated the
use of MCLs instead of MDLs when conducting the SPLF test.
Substituting MCLs for MDLs into the SPLP criterion is consistent
with Section 303 (b) (4) (ii) of Act 2. Accordingly EPA now-- ---
considers MCLs to be the appropriate ground water protection
goals to be used in, the SPLP criterion rather than the method
detection limits. The SPLP criterion in Section IX.A.4.A. on
page 35 of-the OU1 ROD is modified, therefore, to state "or when
using the Synthetic Precipitation Leaching Procedure ("SPLP")
listed as EPA Method 1312, the soils contain leachable
contaminants' that will leach to levels above the Maximum
Contaminant Levels set. forth in 40 C.F.R. § 141.61(a) for Site-
related contaminants using Drinking Water Analytical methods."
Based upon the implementation of Act 2, the PADEP concurs with
the change from method detection limits to MCLs. Pre-design
sampling' has shown that this modification to the SPLP criterion
will not significantly change the areal extent of the cap with
regard to this criterion.
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B. In-Situ. Vacuum Extraction and Slurry Wall. Components
Prior to construction of the cap, the OU1 ROD required:
1) treatment of Site soils with total VOC concentrations
above 22.8 parts per million ("ppm") using in-situ vacuum
extraction;
2) installation of a subsurface slurry wall to contained
soils contaminated with TCB above 4,437 ppm in the area of
former collection basins AA and BB.
Based on the findings of the pre-design sampling, the pilot-scale
test, and the FFI, EPA has determined that the following changes
to the OU1 ROD remedy are warranted.
1. Treatment of VOC-Contaminated Soil by Ex-situ Vacuum
Extraction
Vacuum Extraction (also known as soil vapor extraction) is
an in-situ or ex-situ remedial technology in which VOCs are
removed from soil by the application of a vacuum. The vacuum
pulls air through the soil, stripping the VOCs that are
subsequently treated with emission control equipment. In-situ
vacuum extraction involves placing extraction points or wells in
the unsaturated soil. A vacuum is applied to the wells, inducing
air flow toward the extraction wells. The flow of air through
the subsurface causes the VOCs to desorb front the soil as vapors.
The OU1 ROD requires in-situ vacuum extraction of soils with
total VOC concentrations above 22.8 ppm. As a result of the poor
performance results for the in-situ. vacuum extraction pilot-scale
test and the significant decrease in the volume of the VOC-
contaminated soil requiring treatment documented in the FFI, an
evaluation of alternative technologies for treating, the VOC-
contaminated soil was initiated. The RSC submitted the Focused
Feasibility Study ("FFS") Report to EPA and PADEP on January 17,
1997. The following technologies were evaluated: Low
Temperature Thermal. Treatment; Thermally Enhanced Ex-situ Vacuum
Extraction;, and .Excavation and Off-site Disposal. EPA encourages
the public to refer to the FFI and FFS reports to gain a better
understanding o£ the alternative technologies which were
evaluated~ These documents can be found in the Administrative
Record File for the Site as noted in Section VI below.
EPA is changing Section IX.A.2.A. on page 33 of the OU1 ROD
remedy to require ex-situ vacuum extraction as the treatment for
soils with total VOC concentrations above 22.8 ppm rather than
in-situ vacuum extraction. As detailed in the FFS, ex-situ
vacuum extraction will require excavation of soils containing
total VOCs above 22.8 ppm. The soil will be placed on the
concrete pad that remains onsite from the demolition of the
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fortner Process Building. Pipes will be strategically placed
within the soil as it is stockpiled to allow for injecting or
extracting of air. The entire pile will be covered with an
impermeable iriSmbrane which will minimize dust and VOC emissions.
Heated air will be forced through the air injection piping and
through the soil layers to cause the VOCs to vaporize. The
heated air is recovered in the extraction piping. Extracted air
is treated and then reinjected into the pile. It is expected
that the ROD remediation levels for VOCs will be met following 2
to 4 weeks of treatment.
2. Elimination of Slurry Wall Requirement
Since current Site conditions indicate that TCB is not found
in Site soils at concentrations greater than the ROD-specified
remediation level of 4,437 ppm, the slurry wall described in
Section IX.A.3. (Construction of slurry wall) on page 34 of the
OU1 ROD will notr be required. EPA does not consider this a
significant change since the levels of TCB contamination found
during the pre-design sampling and the FFI are below the cleanup
levels set forth in the OU1" ROD. ' ^
Since these changes do not fundamentally alter the nature-of
the remedy for VOC-contaminated soils as outlined in the OU1 ROD,
EPA has determined that a ROD amendment is not required. Vacuum
extraction technology will still be used to treat the organic
chemical hot spots in soil prior to installation of the cap.
However, the soils will be treated above ground rather than in
place. An added benefit of the ex-situ process is that if TCB is
found above the ROD cleanup level, the thermally enhanced ex-situ
vacuum extraction will also be effective in reducing the TCB
concentrations to below the ROD specified cleanup level.
Confirmation, sampling of the treated soil will be conducted for
VOCs and TCB concentrations and hazardous waste- metals prior to
backfilling.
V
XV. SUPPORT AGENCY REVIEW
PADEP assects that Act 2, Section 303 (b) (4) (ii) is an ARAR
for purposes of this ESD. Under the National. Contingency Plan
EPA is not obligated to revisit a ROD for ARARs unless there is a
new component or the remedy is not protective. Since neither is
the case at this Site, this ESD will not revisit the issue of
ARARs.
V. AFFIRMATION OF THE STATUTORY DETERMINATIONS
EPA has determined that the revised remedy complies with the
statutory requirements of CERCLA § 121, 42 U.S.C. § 9621.
Considering the changes that have been made to the scope of the
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selected remedy, the EPA and PADEP have determined that the
remedy remains protective of human health and the environment,
complies with Federal and State requirements that were identified
in the OU1 ROD~ as 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
" * '. ' " '' '. '*'"-.
This Explanation of Significant Difference is available in
both the Administrative Record located at the U.S. EPA Region III
Offices, 841 Chestnut Building, Philadelphia, Pennsylvania,
19107, and at the Site repository at the following location:
Nockamixon Township Building
Center Hill and Lake Warren Roads
Ferndale, Pennsylvania 18921
(610) 847-5058
Questions* or comments on EPA's action and requests to review
the Administrative Record at EPA's office can be directed to:
Ruth Scharr
Remedial Project Manager
Mailcode 3HW21
U.S. EPA, Region III
841 Chestnut Building
Philadelphia, PA 19107
(215) 566-3191
Date' Thomas C. VoltaTggfib.Director
Hazardous Waste Management: Division
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