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Description of the Significant Differences and the Basis for
those Differences
The differences between the remedy selected in the 1989 ROD, as
modified by the 1994 BSD, and the actions described in this BSD
relate to the on-site treatment of the inorganic-contaminated
soil. Other portions of the remedy selected in the 1989 ROD, as
amended by the 1994 BSD, remain unchanged.
In the ROD, EPA evaluated the following three alternatives for
remediating the inorganic-contaminated soil on the site: no
action/limited action; excavation, on-site solidification/
stabilization and backfilling of the solidified mass in the
excavation; and off-site disposal. Each alternative was
evaluated with respect to a number of criteria including overall
protection of human health and the environment; long-term
effectiveness and permanence; reduction of toxicity, mobility, or
volume; and cost.
The no action/limited action alternative was eliminated from
consideration because it was not protective of human health and
the environment. Although EPA determined that the off-site
disposal alternative would provide the greatest overall
protection to human health and the environment at the site, it
was not selected primarily because its cost was estimated to be
approximately $2 million more than the on-site treatment
alternative, which EPA believed would be effective. It was
thought that the on-site solidification/stabilization alternative
would reduce the mobility of the inorganic contaminants, be
protective of human health and the environment, and be cost
effective. Based on that evaluation, on-site solidification/
stabilization was selected as the preferred alternative for the
inorganic-contaminated soil.
The ROD indicated that additional studies would need to be
performed during the Remedial Design to determine if the
solidified material could be returned to the site. The ROD
contained a provision that, if it was determined that the
material could not be returned to the site, the contaminated spil
would be disposed of off site in accordance with applicable
regulations.
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As required by the ROD, EPA conducted treatability study tests
during the Remedial Design to determine if returning the
solidified mass to the excavation would be protective of human
health and the environment. During the treatability study, EPA
tested a total of 28 different stabilization mixes. The results
of the treatability tests showed that the solidified mass would
continue to leach inorganic contaminants into the ground water at
levels above the New Jersey State Drinking Water Maximum
Contaminant Levels (MCLs). In fact, in a number of instances,
adding the stabilization mixture actually increased the leaching
of inorganic contaminants due to pH changes. Since a primary
goal of treating the inorganic-contaminated soil by the
solidification/stabilization process was to prevent the migration
of contaminants into the ground water, this situation was
considered to be unacceptable. Based on the results of the
treatability study tests performed during the Remedial Design,
EPA determined that returning the solidified mass to the
excavation would not be protective of human health and the
environment. As a result, EPA has decided that off-site disposal
of the inorganic-contaminated soil is preferable to on-site
disposal. Because no costs associated with mobilizing and
demobilizing a solidification/stabilization unit at the site will
be incurred, this change to the remedy for the inorganic-
contaminated soil will not increase the overall cost of the
remedy and may actually decrease the cost of the remedy.
During the RI, EPA collected a number of soil samples to
determine the volume of contaminated soil at the site. EPA
collected all of the RI soil samples from above the water table,
which is located a minimum of eight feet below the ground.
surface. Prior to initiating the Remedial Design, EPA collected
several samples of the soil located below the water table. The
results of the analysis of these samples showed that
approximately 6,500 cubic yards of soil below the water table
contained concentrations of chromium that were above the cleanup
goal established in the ROD. No other inorganic contaminants
were found to be present in the samples at concentrations above
their respective cleanup goals. Based on these results, EPA
initially believed that the saturated chromium-contaminated soil
would need to be excavated along with the shallower soil.
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As part of the treatability studies performed during the Remedial
Design, EPA conducted leaching tests on untreated samples of the
inorganic-contaminated soil from both above and below the water
table. The results of the leaching tests involving soil samples
collected above the water table showed that inorganic
contaminants were leaching from the soil at levels above their
respective MCLs. These results confirmed that the inorganic-
contaminated soils located above the water table represent a
continuing source of contamination to the ground water. In
contrast, test results involving chromium-contaminated soil
samples collected from below the water table showed that the soil
was not leaching chromium into the ground water above its MCL.
Therefore, EPA has determined that this soil does not represent a
source of ground water contamination. Based on the results of
the leaching tests which indicated that the chromium detected in
this soil is not adversely impacting the ground water, and the
fact that it is located 10 to 15 feet below the ground surface,
EPA has determined that excavation of this soil is not required.
In summary, based on the results of the treatability studies
performed as part of the Remedial Design at the site, EPA has
determined that the remedy selected in the ROD for the inorganic-
contaminated soil at the site, on-site solidification/
stabilization and disposal, would not be protective of human
health and the environment. Therefore, the excavated inorganic-
contaminated soil will be transported off site for disposal. EPA
has also determined that the chromium-contaminated soil located
below the water table will not require excavation because the
soil is not leaching chromium into the ground water at a level
above its MCL.
Following completion of the remedial action for the soil, EPA
will reevaluate the need for remediation of the ground water at
the site. All other portions of the remedy selected by EPA in
the 1989 ROD, as amended by the 1994 ESD, remain the same.
Support Agency Comments
The State of New Jersey supports EPA's revision to the remedy and
decision to issue this ESD.
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Affirmation of Statutory Determinations
Considering the new information that has been developed and the
changes that have been made to the selected remedy, EPA and NJDEP
believe that the remedy remains protective of human health and
the environment, complies with federal and state requirements
that were identified in the ROD and this BSD 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.
Public Participation Activities
In accordance with the NCP, a formal public comment period is not
required when issuing an ESD. However, EPA will announce the
availability of the ESD in the Delaware Valley jJews. The ESD has
been placed in the Administrative Record for the site.
Date
Regional Administrator
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