PB96-963105
EPA/AMD/R03-96/225
August 1996
EPA Superfund
Record of Decision Amendment:
Tyson Dump, Superfund Site
Upper Merion Township, PA
7/20/1996
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RECORD OF DECISION AMENDMENT
TYSONS SUPERFUND SITE
MONTGOMERY COUNTY, PENNSYLVANIA
DECLARATION
SITE NAME AND LOCATION
Tyson's Superfund Site
Upper Merion Township, Montgomery County, Pennsylvania
STATEMENT OF BASIS AND PURPOSE
This Record of Decision Amendment ("ROD Amendment")modifies
the selected remedy' described in the Revised Record of Decision
for the Tyson's Superfund Site ("Site") issued by the U.S.
Environmental Protection Agency ("EPA") on March 31, 1988 ("1988
Revised ROD"). In the 1988 Revised ROD, EPA selected a soil
vapor extracton ("SVE") remedy for lagoon area soils. The SVE
system has removed approximately 200,000 pounds of volatile
organic compounds ("VOCs") from the lagoon area soils. However,
SVE performance has been limited by various factors which have
contributed to declining VOC removal rates. Although several
enhancements and modifications have been employed to improve
performance, the SVE system will not achieve the cleanup
standards specified in the 1988 Revised ROD. This decision
document presents the selected remedial action for the lagoon
area soils at the Tyson's Site. The selected remedial action was
chosen in accordance with the Comprehensive Environmental
Response, Compensation, and Liability Act of 1980 as amended,
("CERCLA") and, to the extent practicable, the National Oil and
Hazardous Substances Pollution Contingency Plan ("N.CP").
This decision is based on the Administrative Record for the
Site.
The Commonwealth of Pennsylvania concurs with the selected
remedy for the Tyson's Superfund Site described in this ROD
Amendment.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from
this Site, if not addressed by implementing the response action
selected in this ROD Amendment, may present an imminent and
substantial endangerment to public health, welfare, or the
environment.
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DESCRIPTION OF THE SELECTED REMEDY
This response action addresses contaminated lagoon area
soils at the Tyson's Site. The 1988 Revised ROD addressed the
lagoon area soils by using an innovative technology, namely soil
vacuum extraction. That remedy did not.achieve the cleanup .
standards specified in the 1988 Revised ROD.
At the Tysons Site, the lagoon area soils present a
principal threat to human health through the direct contact and
inhalation pathways. EPA therefore plans to mitigate these
potential threats by placing a wet soil cover over the lagoon
area soils.
The selected remedy includes the following major components:
* Installation of a contingent vent layer consisting of a
high permeability layer for grading of the site and
control of lateral migration of vapors.
* Installation of a low permeability barrier layer covering
the vent layer which will maintain nearly saturated
conditions to control and virtually eliminate upward
migration of vapors. This barrier would become nearly
saturated through natural precipitation and suface
irrigation.
* Installation of a vegetated cover layer.
* Installation of a surface irrigation system.
* Continued operation of the existing french drain, seep
sump pumps, and groundwater well pumps.
* Installation of vent pipes as necessary.
STATUTORY DETERMINATIONS
The selected remedy is protective of human health and the
environment, complies with Federal and State requirements that
are legally applicable or relevant and appropriate, and is cost
effective. This remedy utilizes permanent solutions and
alternative treatment (or resource recovery) technology to the
extent practicable, and satisfies the statutory preference for
remedies that employ treatment that reduces toxicity, mobility,
or.volume as a principal element.
Thomas C. VoltaggM* Director Date
Hazardous Waste ^-Mariafcfement Division
U.S. EPA, Region III
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DECISION SUMMARY
TYSON'S SUPERFUND SITE
INTRODUCTION
Tyson's Dump Site is an abandoned septic waste amd chemical
waste disposal site located in Upper Merion Township, Montgomery
County, Pennsylvania. Several unlined lagoons were used to
dispose of septic and chemical wastes during the period of
operation. The U.S. Environmental Protection Agency ("EPA"),
following consultation with the Pennsylvania Department of
Environmental Protection ("PADEP"), is issuing this Record of
Decision Amendment ("ROD Amendment") to address contaminated soil
at the site. The selected remedy described in this ROD Amendment
was chosen in accordance with the Comprehensive Environmental
Response, Compensation, and'Liability Act of 1980, as amended by
the Superfund Amendments and Reauthorization Act of 1986, U.S.C.
§§ 9601 et al. ("CERCLA"), and the National Oil and Hazardous
Substances Pollution Contingency Plan ("NCP").-
In 1984 EPA issued a Record of Decision (ROD) for the
excavation and off-site disposal of contaminated soils at the
Tyson's Site. Before the 1984 ROD was implemented, a Revised ROD
was issued on March 31, 1988 ("1988 Revised ROD"). This ROD
Amendment modifies the selected remedy described in the 1988
Revised ROD. In the 1988 Revised ROD, EPA selected a soil vapor
extraction ("SVE") remedy for lagoon area soils. The 1988
Revised ROD also specified the installation of a groundwater
recovery and treatment system to prevent site-related compounds
in the groundwater from entering the Schuylkill River. The
Responsible Parties ("RPs") signed a Consent Decree ("CD") with
EPA on June 20, 1988 to implement the 1988 Revised ROD. An SVE
system was designed and constructed during the Spring and Summer
of 1988 and full scale operation of this system began in
November, 1988. Since then, the SVE system has removed
approximately 200,000 pounds of volatile organic compounds
("VOCs") from the lagoon area soils. However, SVE performance
has been limited by low contaminant volatility, soil
heterogeneity, soil moisture and low soil temperature which have
contributed to declining VOC removal rates. Although several
enhancements and modifications have been employed to improve
performance, the SVE system has reached a low asymptotic limit of
mass removal and will not achieve the cleanup standards specified
in the 1988 ROD in a timely or cost-effective manner. In
accordance with the CD, a Focussed Feasibility Study ("FFS") was
conducted to identify an alternative remedial action for the
lagoon area soils. This ROD Amendment addresses lagoon area soil
contamination not fully remediated by the 1988 Revised ROD. This
ROD Amendment does not modify the 1988 ROD with respect to the
groundwater recovery and treatment system.
In accordance with Section 117 of CERCLA, 42 U.S.C. § 117,
the FFS, Proposed Plan, and background documentation for the
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Tyson Site were made available to the public on February 20, 1996
in the local information and administrative record repository at
the Upper Merion Township Municipal Building, Upper Merion
Township, Pennsylvania. In accordance with Section 300.825 (a)
(2) of the NCP, this ROD Amendment will become part of the
Administrative Record File. The Administrative Record File is
available for review at the following locations:
Upper Merion Township Building U.S. EPA Region III
175 West Valley Forge Road 841 Chestnut Bldg.
King of Prussia, Pennsylvania 19406 .Philadelphia, PA 19107
For a detailed description of the Site background and Site
characteristics, refer to the 1988 ROD, the July 14,.1995 FFS,
and the Proposed Plan dated January 31, 1996 for this ROD
Amendment.
REASONS FOR ISSUING .THE ROD AMENDMENT
As described above, the remedy selected in the 1988 Revised
ROD was soil vacumm extraction for the lagoon area soils and
groundwater recovery and treatment to prevent the discharge of
contaminated groundwater from entering the Schuylkill River. The
clean-up levels identified in the 1988 Revised ROD for the lagoon
area soils were 50 parts per billion (ppb) for 4 indicator
compounds, namely 1,2,3-trichloropropane, benzene,
trichloroethene and tetrachloroethene. Between 1988 and the
present, the SVE system was installed, modified and enhanced and
resulted in the removal of nearly 200,000 pounds of VOCs. The
current levels of these compounds in the lagoon area soils range
from 10 .parts per million (ppm) in the upper 2 feet to 10,000 ppm
in the deeper soils. Beginning.in 1993 the ability of the SVE
system to efficiently remove the remaining contaminants has
decreased significantly. As a result the SVE system is incapable
of achieving the clean-up levels set forth in the 1988 Revised
ROD in a timely and cost effective manner. Therefore, EPA
determined that an alternative remedial action for the lagoon
area soils would be necessary to address the VOC contamination
remaining in these soils.
As required by Section VIII. C. 2. of the 1988 CD, the
Settling Defendants were to propose an alternate remedial action
to EPA if it were determined by EPA that excavation of greater
than ten percent of the volumetric area of soils in the Lagoon
Area was necessary to achieve the clean-up levels. In 1993, EPA
and the RPs determined that the SVE technology would not be able
to achieve the clean-up levels. As a result, EPA directed the
RPs to conduct a Focused Feasibility Study to identify an
alternate remedial action with respect to contaminated soils in
the Lagoon Area. The FFS identified and evaluated alternatives
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for remedial action to prevent, mitigate, contain, or otherwise
remedy the release of hazardous substances from the Lagoon Area
Soils.
DESCRIPTION OF THE NEW ALTERNATIVES
CERCLA and the NCP require that the alternative chosen to
clean up a hazardous waste site meet several criteria. The
alternative must protect human health and the environment, meet
the requirements of environmental laws and regulations, and be
cost-effective. Permanent solutions to contamination problems
should be developed wherever possible. The solutions should
reduce the volume, toxicity, or mobility of the contaminants.
Emphasis is also placed on treating the waters at the site,
whenever this is possible, and on applying innovative
technologies to clean up the contaminants.
In accordance with Section 300.430 of the NCP, a list of
remedial response actions and representative technologies were
screened to meet the remedial action objectives at the Tysons
Site. The FFS studied a variety of technologies to determine if
they could address the lagoon area soil contamination at the
Tysons Site. The technologies determined to be most applicable
to the contaminants and contaminated soils were developed into
remedial alternatives. In addition, EPA has evaluated the'No
Action Alternative (Alternative 1) as required by the .NCP. The
alternatives are presented and discussed below. All costs and
implementation time frames provided for the alternatives below
are estimates.
Original Alternative - Soil Vacuum Extraction
The vacuum extraction process is an in-situ treatment
process used to clean soils that contain volatile compounds. The
process utilizes extraction wells to induce a vacuum on
subsurface soils that are above the water table. 'Subsurface
vacuum spreads laterally, causing in-situ volatilization of
compounds adsorbed to the soils. Volatilized compounds and
subsurface air migrate rapidly to extraction points and are then
passed through and collected on activated carbon.
Total Estimated Costs: $ 10.2 million
(From 3/31/88 ROD)
Total SVE Costs to date $ 43.4 million
(From 3/31/88 ROD)
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No Action Alternative
The Superfund program is required to evaluate the "No
Action" Alternative. Under this alternative, no additional
remedial action, beyond the SVE activities initiated under the
1988 ROD for OU-1, would be taken to reduce the amount of VOCs in
the lagoon area soils. The SVE system would be completely
shutdown and dismantled. This alternative would be selected only
if the Site posed little or no risk to public health or the
environment from hazardous substances left on-site.
Alternative 1; Soil Cover
This alternative consists of covering the lagoon area.soils
with an 18-inch to 24-inch-thick vegetated soil cover. The soil
cover (from the top to bottom} would include a 6-inch vegetated
topsoil layer and a 12 to 18-inch cover layer of imported general
fill soil. Previous characterization activities for the lagoon
area soils indicate that the total area to be covered is
approximately 2.5 acres. Surface water control measures for the
cover would include a sloped surface leading to perimeter
drainage swales and sediment basins as necessary. An irrigation
system would be included as necessary to maintain the vegetative
cover. Institutional controls would include upgrading and
extending as necessary the perimeter security fence to further
restrict unauthorized site access. Deed restrictions and
easement agreements will provide for long-term control of the
Site, as required, to minimize potential future risks and to
provide for the maintenance and implementation of required
remedial activities.
Short-term risks associated with this alternative are less
than IxlO"6, as only minor disturbance and covering of
contaminated soils are required, and because the time required
for implementation is .relatively short. Although the soil cover
does not completely control VOC emissions, it does prevent
potential direct contact and ingestion exposure risks and erosion
of contaminated soil. As a result, the estimated total
carcinogenic risk associated with this alternative is less than
8xlO"5 for all receptors.
Capital Costs: $ 812,000 to 1,073,000
Annual O&M Cost: $ 42,000
Preseint Worth: $1,528,000 to 1,788,000
Estimated Time To Implement: 18 Months
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Alternative 2; Capping
This alternative consists of covering the lagoon area soils
with a cap that includes a 2-foot-thick clay layer and a
vegetative soil layer to restrict VOC emissions. The cap (from
the top to bottom) would include a 6-inch vegetated topsoil
layer, a 12 to 18-inch compacted cover soil layer and a 24-inch
compacted clay layer. Previous characterization activities
indicate that the area to be covered is approximately 2.5 acres.
To maximize the reduction of VOC emissions, the clay layer would
be compacted to a relatively high density and high moisture
content so as to minir.ize the total air porosity. An irrigation
system would be included as necessary to maintain the vegetative
cover and high moisture content within the clay layer. Surface
water control measures for the cap would include a sloped surface
leading to perimeter drainage swales and sediment basins as
necessary. Institutional controls would include upgrading and
extending, as necessary, the perimeter security fence to further
restrict unauthorized site access. Deed restrictions and
easement agreements will provide for long-term control'of the
Site, as required, to minimize potential future risks and to
provide for the maintenance of required remedial activities.
Short-term risks associated with this alternative are less
than IxlO"6, as only minor regrading and covering of contaminated
soils are required and because the required implementation time
is relatively short. This alternative will prevent direct
contact and ingestion exposure risk from the contaminated lagoon
area soils and will effectively reduce VOC vapor emissions,
•thereby reducing the inhalation exposure risk. As a result, the
total estimated carcinogenic risk for this alternative is IxlO"5,
which is within EPA's target risk range. If it is determined
that the residual risks associated with this alternative are not
acceptable, the clay cap can be constructed with a granular
venting layer beneath the clay layer to provide for the active
venting of VOC's beneath the cap. The estimated carcinogenic
risk for this alternative (with venting) is 6xlO"7 for all
receptors.
Capital Costs: $1,218,000 to 1,614,000
Annual O&M Costs: . $ 48,000
Present Worth: $2,350,000 to 2,746,000
Estimated Time To Implement: 20 Months
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Alternative 3; Wet Soil Cover
This alternative consists of a low permeability barrier
layer which will maintain nearly saturated conditions as a result
of natural precipitation and surface irrigation. The wet soil
cover (from top to bottom) would include a vegetated cover layer,
a low permeability barrier layer and a contingent vent layer.
Water introduced to the vegetated cover layer through
precipitation and irrigation is expected to nearly saturate the
low permeability layer to create a wet soil layer. Water would
percolate through the wet soil layer into the lower layers of the
lagoon area soils to control and virtually eliminate upward
migration of VOC vapors. The contingent vent layer consists of a
high permeability layer for grading of the site and control of
lateral migration of vapors, if necessary. Additional water .may
be added, as needed, which will combine with the natural
groundwater beneath the lagoon area. The shallow groundwater
flows to the existing french drain along the northern edge of the
lagoon area and deeper groundwater flows to the existing
groundwater recovery and treatment system. The operation of the
french drain, seep sump pumps and groundwater well pumps would
continue to operate as part of this remedy.
Institutional controls would include upgrading and
extending, as necessary, the perimeter security fence to further
restrict unauthorized site access. Deed restrictions and
easement agreements will provide for long-term control of the
Site, as required, to minimize potential future risks and to
provide for the maintenance and implementation of required
remedial activities'.
Short term risks associated with this alternative are less
than IxlO"6, as only minor disturbance of the surface soil is
expected for site grading and wet soil construction and because
the implementation time is short. This alternative will prevent
direct contact and ingestion exposure risks from the contaminated
lagoon area soils and will effectively eliminate VOC vapor
emissions, thereby eliminating inhalation exposure risks. As a
result, the total carcinogenic risk estimated for this
alternative is less than 4xlO"7 for all receptors.
Capital Costs: $1,098,000 to 1,505,000
Annual O&M Costs: $ 60,000
Present Worth: $2,090,000 to 2,497,000
Estimated Time To Implement: 20 Months
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Alternative 4; Low Temperature Thermal Desorption (LTTD)
This alternative includes excavation of the lagoon area
soils, on-site treatment of excavated soil by low temperature
thermal desorption (LTTD), backfilling the excavated area with
treated soil and installation of a soil cover. A pilot test of
the LTTD process would be conducted to provide the necessary
evaluation and design data. Excavation and treatment includes
those soils with total average VOC concentrations in excess of
1,000 mg/kg (about 13,070 cubic yards or 19,600 wet tons). An
LTTD unit using indirect heating of the lagoon area soils would
be used for evaluation of this alternative. However, there are a
number of available commercial LTTD processes, and the selection
of the most appropriate equipment would be made during remedial
design.
Site disturbance associated with soil excavation and feed
preparation is a source of fugitive dust and increased VOC
emissions. The short-term carcinogenic risks associated with this
alternative is less than 4xlO"5. This alternative would prevent
direct exposures and will result in reduced VOC emissions.
Immediately after treatment and backfilling, the overall
reduction of soil VOC concentrations would be more than 99% for
the treated soils. However, the clean backfilled soil would be
recontaminated by diffusion of VOC vapors from the inaccessable
DNAPL sources remaining in the bedrock upward through the
backfilled soils, resulting in VOC emissions to the atmosphere.
Although the levels of this recontaminatipn would, over time, be
much lower than the current concentrations, the effects of this
recontamination will partially offset the VOC mass removal
achieved by soil treatment. The total carcinogenic risks
estimated for this alternative are less than 7xlO"5 for all
receptors.
Capital Costs: $7,135,000 to 9,293,000
Annual O&M Costs: $ 42,000
Present Worth: $7,851,000 to 10,008,000
Estimated Time To Implement: 38 Months
Alternative 5; Off-Site Incineration/Disposal
This alternative includes excavation of lagoon area soils,
transportation of excavated soil by rail to an off-site facility,
off-site incineration/disposal, backfilling the excavation area
with imported soil, and installation of a soil cover. Soils with
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average total VOC concentrations in excess of 1,000 mg/kg (about
13,070 cubic yards or 19,600 wet tons) would be excavated for
off-site incineration/disposal. The actual facility to be used
for incineration/disposal would be selected during the design and
bidding phase of the project. Because the site is located
adjacent to Conrail's Abrams switchyard, shipping of excavated
soils via rail using available Conrail facilities is feasible.
On-site activities required for implementation of this
alternative are estimated to take 8 to 10 months. Emissions from
soil processing and loading operations would be captured under an
enclosure. Soil excavation would include appropriate measures to
control vapor emissions from the open excavation. The short-term
carcinogenic risk associated with this alternative is less than
4xlO"5. After implementation of this alternative, the backfilled
soil would not contain any hazardous organic chemicals, thereby
reducing VOC emissions and eliminating direct contact and
ingestion risks from the areas of excavation and backfilling.
However, the clean backfilled soil would be recontaminated via
vapor-phase migration which partially offsets the risk reduction
gained by soil removal and treatment. The total carcinogenic
risk associated with this alternative is less than 6xlO"5.
Capitol Costs: $21,084,000 to 25,919,000
Annual OficM Costs: $ 42,000
Present Worth: $21,799,000 to 26,634,000
Estimated Time To Implement: 31 Months
EVALUATION OF ALTERNATIVES
In evaluating remedial alternatives for Superfund Sites, EPA
considers nine specific criteria .(see Table 1). These nine
criteria are categorized into the following three groups:
Threshold Criteria
Overall protection of human health.and the environment
Compliance with applicable or relevant and appropriate
requirements (ARARs)
Primary Balancing Criteria
Reduction of toxicity,. mobility, or volume through
treatment
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TABLE 1
DESCRIPTION OF EVALUATION CRITERIA
Overall protection of human health and the environment -
Addresses whether a remedy provides adequate protection and
describes how risks posed through each pathway are eliminated,
reduced, or controlled through treatment, engineering controls,
or institutional controls.
Compliance with applicable or relevant and appropriate
requirements (ARARs) - Addresses whether a remedy will meet all
of the ARARs of other Federal and State environmental laws and/or
justifies a waiver.
Long-term effectiveness and permanence - Addresses expected
residual risk and the ability of a remedy to maintain reliable
protection of human health and the environment over time, once
cleanup goals have been met.
Reduction of toxicitv. mobility, or volume through treatment -
Addresses the anticipated performance of the treatment
technologies a remedy may employ.
. Short-term effectiveness - Addresses the period of time needed to
achieve protection and any adverse impacts on human health and
the environment that may be posed during the construction and
implementation period, until cleanup goals are achieved.
Implementability - Addresses the technical and administrative
feasibility of a remedy, including the availability of materials
and services needed to implement a particular option.
Cost - Includes estimated capital and operation and maintenance
costs, as well as present worth costs.
State/Support Agency Acceptance - Indicates the support agency's
comments. Where the State or Federal agency is the lead for the
ROD, EPA's acceptance of the selected remedy is addressed under
this criterion.
Community Acceptance - Summarizes the public's general response
to the alternatives described in the Proposed Plan and Remedial
Investigation/Feasibility Study Report. The specific responses
to public comments are addressed in the Responsiveness Summary
section of the Record of Decision.
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Short-term effectiveness
Long-term effectiveness and permanence
Implementability
Cost •
Modifying Criteria
Community acceptance
State acceptance
These evaluation criteria relate directly to requirements of
Section 121 of CERCLA, 42 U.S.C. § 9621, for determining the
overall feasibility and acceptability of a remedy. Threshold
criteria must be satisfied in order for a remedy to be eligible
for selection. Primary balancing criteria are used to weigh
major trade-offs between remedies. The modifying criteria are
formally taken into account after public comment is received on
the Proposed Plan.
The following paragraphs summarize how the new alternatives,
including the selected alternative for the Tysons Site, compare
*•.-> each other with respect to the nine criteria.
Overall Protection of Human Health and the Environment
Each of the remedial alternatives generally meet the
established remedial action objectives, and achieve carcinogenic
risks within or below EPA's target risk range (i.e., lxlO~A to
IxlO"6. By effectively controlling VOC emissions and direct
contact exposures, the Capping and Wet Soil Cover alternatives
achieve the greatest overall protection to human health .and the
environment. .
Compliance with Applicable or Relavent and Appropriate
Requirements (ARARs)
CERCLA requires that remedial actions meet ARARs of other
federal and state environmental laws, or that there be grounds
for invoking a waiver. A "legally applicable" requirement is one
which would legally apply to the response action if that action
were not taken pursuant to Sections 104, 106, or 122 of CERCLA.
A "relevant and appropriate" requirement is one that, while not
"applicable", is designed to apply to problems sufficiently
similar that their application is appropriate.
The alternative remedies considered herein are not
inconsistent with the remedial actions taken pursuant to the RODs
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dated March 31, 1988, September 30, 1988 and.September 28, 1990,
to the extent that the previous RODs provided for the
installation and operation of a groundwater extraction and
treatment system. The selected remedy is designed to work in
conjunction with the above referenced groundwater extraction
system. Accordingly, all the remedial alternatives discussed in
this ROD Amendment, including the selected alternative, will
comply with all ARARs including the ARARs identified and
discussed in the aforementioned RODs. The potential Federal and
State ARARs for this ROD Amendment are presented in table 2.
There are no additional chemical-specific or location-
specific ARAR's of concern identified. Also, all alternatives
include the appropriate measures to ensure that all action-
specific ARAR's are satisfied. Thus, all remedial alternatives
considered in this ROD Amendment will comply with all ARAR's.
Long Term Effectiveness and Permanence
Each of the alternatives discussed above will be effective
for as long as the remedial components are maintained. The Soil
Cover alternative requires minimal maintenance and allows for
natural attenuation of contaminants from the lagoon area soils,
but is less effective at controlling long-term VOC emissions than
other alternatives. The Capping alternative is expected to
provide a high degree of overall long-term effectiveness due to
the ability of the clay barrier to restrict VOC emissions, and
the minimal maintenance requirements. The.Wet Soil Cover
alternative provides for effective long-term VOC emission control
and enhanced natural attenuation of contaminants, although
operation and maintenance requirements are greater than for the
Soil Cover or Capping alternatives. The LTTD and Off-Site
Incineration/Disposal alternatives will result in permanent
destruction of the VOC mass from the unsaturated lagoon area
soils, but risk reduction will be partially offset by
recontamination.
Reduction of Toxicity, Mobility or Volume
Operation of the SVE system over the past six years has
removed approximately 200,000 pounds of VOCs from the lagoon area
soils. The Soil Cover and Capping alternatives provide little
additional reduction in toxicity or volume. Reduction in
mobility is achieved by reducing VOC emissions and erosion of
contaminated soils. The Capping alternative reduces surface
water infiltration and subsequent contaminant leaching, and is
more effective at restricting VOC emissions than the Soil Cover
alternative. The Wet Soil Cover alternative effectively controls
VOC vapor emissions, and reduces toxicity and volume through
enhanced natural attenuation. By eliminating VOC emissions, the
Wet Soil Cover also prevents contamination of the cover soils.
The LTTD and Off-Site Incineration/Disposal alternatives provide
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Table 2 - Potential Action-Specific ARARS
Federal Action Specific ARARs
Citation
* 40 CFR §264.14
* 40 CFR §264.97
and §264.98
* 40 CFR §§264.111-
.112, 264.114,
. 264.117-118
* 40 CFR §264.302
and
40 CFR §264.310
40 CFR §258.60
Oswer Directive
9335.4-01
Requirement
Security requirements will
be followed through completion
of the construction of the cap
Groundwater monitoring
requirements
Hazardous waste landfill
regulations concerning
closure and post-closure
activities
Cap construction and operation
Cap design requirements
Long-term monitoring
requirements
This is not an ARAR but a TBC
(to be considered) that will be
met by this remedy and which
directs action toward containment
remedial actions
Status
Relevant &
Appropriate
Relevant &
Appropriate
Relevant &
Appropriate
Relevant &
Appropriate
Relevant &
Appropriate
* State requirements, as authorized pursuant to RCRA, are ARARs
These United States counterparts are cited for convenience.
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Table 2 - Potential Action-Specific ARARs (Cont'd)
Pennsylvania Action-Specific ARARs
Citation
Pennsylvania Air
Pollution Regulations
25 Pa. Code §§123.1,
123.2
25 Pa. Code, §102.4
Requirement
Regulates fugitive air
emissions for remedial
actions
The substantive requirements
for control of soil erosion/
sedimentation resulting from
earth moving activities
25 Pa. Code §75.264
(d), (n), (o), (s)
Status
Applicable
Applicable
Substantive requirements as
set forth in Pa. Bull.,
Vol. 12, No.36 Saturday
September 4, 1982
as those provisions are amended
in Pa. Bull. Vol. 15, No. 37,
Saturday, September 14, 1985,
and Pa. Bull. Vol. 15, No. 22,
Saturday, June 1, 1985
for security, operations,
and post-closure
Applicable
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immediate reduction of toxicity and volume through treatment,
although VOC vapor migration will result in contamination of the
backfilled soils. Additionally, the VOC mass reduction for the
LTTD and Off-Site Incineration/Disposal alternatives is only a
small percentage of the total VOC mass at the Site.
Short-term Effectiveness
The Soil Cover, Capping and Wet Soil Cover alternatives
provide the highest level of short-term effectiveness because
they can be constructed in a relatively short period of time, the
short term risks are minimal, and the benefits will be realized
immediately. The short term effectiveness of the LTTD and Off-
Site Incineration/Disposal alternatives is less than that of the
other alternatives because of the significant soil disturbances,
VOC emissions generated and associated risks, the. significant.
health and safety requirements, and the longer implementation
schedules associated with the LTTD and the Off-Site
Incineration/Disposal alternative.
Imp lamentability
The Soil Cover, Capping and Wet Soil Cover alternatives
involve the use of available construction materials, equipment
and approaches, and can be easily and quickly implemented. The
LTTD and Off-Site Incineration/Disposa? alternatives are
moderately difficult to implement because significant volume of
material must be excavated, associated engineering and health and
safety controls are required, specialized equipment, materials
and approvals are needed and the proximity of a residential .
neighborhood. In addition, Off-Site Incineration/Disposal will
require coordination with rail shipping concerns. A pilot study
is required for LTTD prior to design activities to verify process
effectiveness.
Cost
The present worth cost for the Preferred Alternative is
$2,090,000 to $2,497,000, which is considerably less than the
cost for LTTD ($7,851,000 to $10,008,000) and Off-Site
Incineration/Disposal ($21,799,000 to 26,634,000).
State Acceptance
The Commonwealth of Pennsylvania has verbally concurred with
the selected remedy described in this ROD Amendment.
Community Acceptance
A public meeting on the Proposed Plan was held on February
20, 1996 in Upper Merion Township, Pennsylvania. Citizens who
attended the meeting did not voice any significant concerns about
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the preferred alternative. Community acceptance is more fully
assessed in the attached Responsiveness Summary, which provides a
thorough review of the public comments received on the FFS and
Proposed Plan, and EPA's responses to the comments received.
SELECTED REMEDY
After carefully considering the requirements of CERCLA, the
findings of the FFS, the detailed analysis of the alternatives,
public comments, and other documents contained in the
Administrative Record, EPA has selected Alternative 3, Wet Soil
Cover, as the remedy for amending the 1988 Revised ROD with
respect to the Lagoon Area Soils at the Tysons Site.
DESCRIPTION OF THE SELECTED REMEDY
The major components of the selected remedy include a low
permeability capping system, an irrigation system to supplement
natural water infiltration, as necessary, and a venting layer for
contingent use. The primary mechanism for control of VOC
migration is maintaining near saturated conditions within or
above the barrier layer. The intermittent downward infiltration
of water will provide an additional factor of safety for control
of VOC migration. The physical properties of the low
permeability barrier layer and the infiltration water application
rate and schedule will be defined during the Remedial Design.
As part of the Remedial Action implementation, data will be
collected to evaluate the performance of the capping system. The
contingent vent layer underneath the barrier layer provides a
multiple factor of safety for VOC control. Monitoring plans and
decision points for operation of the vent layer will be
established in the Remedial Design.
STATUTORY DETERMINATIONS
Section 121 of CERCLA, 42 U.S.C. § 9621, requires that the
selected remedy accomplish all of the following: be protective
of human health and the environment; comply with ARARs; be cost
effective; utilize permanent solutions and alternative treatment
technologies or resource recovery technologies to the maximum
extent practicable; and address whether the preference for
treatment as a principal element is satisfied.
The Selected Remedy in this ROD Amendment will be protective
of human health and the environment for Site-related contaminants
over time because Site-related contaminants in the groundwater
will be permanently removed through the existing extraction and
treatment system. The selected remedy will comply with all
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chemical-, location-, and action-specific ARARs pertinent to this
action.
The Commonwealth of Pennsylvania has identified The Land
Recycling and Environmental Remediation Standards Act, the Act of
May 19, 1995, P.L. 4, No. 1995.2, 35 P.S. §§ 6018.101 et. sea.
("Act 2") as an ARAR for this remedy; EPA has determined that Act
2 does not, on the facts and circumstances of this remedy, impose
any requirements more stringent than the federal standards.
Section 121 of CERCLA, 42 U.S.C. § 9621, requires that the
selected.remedy accomplish all of the following: be protective
of human health and the environment; comply with ARARs; be cost
effective; utilize permanent solutions and alternative treatment
technologies or resource recovery technologies to the maximum
extent practicable; and address whether the preference for
treatment as a principal element is satisfied.
The selected remedy is the most cost-effective of the
alternatives and addressess the Site-related risks posed by the
contaminated lagoon area soils by eliminating.the direct contact
and inhalation exposure pathways.
EPA has determined that the selected remedy represents the
maximum extent to which permanent solutions and treatment
technologies can be utilized while providing the best balance
among the other evaluation criteria. Of tl.3 alternatives that
are protective of human health and the environment, the selected
remedy provides the best balance in terms of the eight other
evaluation criteria.
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RESPONSIVENESS SUMMARY
TYSON'S SUPERFDND SITE
UPPER MERION TOWNSHIP
MONTGOMERY COUNTY, PENNSYLVANIA
This document summarizes comments and questions raised by the
local community with respect to the U.S. Environmental Protection
Agency's ("EPA") preferred alternative for remediating the Lagoon
Area Soils at the Tyson's Superfund Site ("Site"). These
comments and questions were raised at the public meeting held on
February 20, 1996 and during the public comment period held from
January 31, 1996 to March 30, 1996. This document also
summarizes EPA's responses to the local community's questions and
comments.
The following questions were asked by one resident during the
public meeting and in a follow-up letter to EPA.
* The resident asked if the comment period could be extended for
90 days, or until May 31, 1996 and at the end of such extension
another public meeting be conducted.
EPA Response: The public comment was extended for 30 days until
March 30, 1996. Since this citizen was the only person to
request a second public meeting EPA did not feel that a second
pubic meeting was not justified.
* The resident asked who generated the risk numbers in the
Focused Feasibility Study.
EPA Response: The risk numbers in the Focused Feasibility Study
were generated by the Responsible Parties and reviewed by an EPA
toxicologist.
* The resident asked if a percolation test was performed on the
lagoons.
EPA Response; A rather extensive pumping test was performed on
the lagoons and it was determined that the lagoons had a
hydraulic conductivity of 2 to 3 gallons per minute.
* Source of Water: Where will the water come from to saturate
the cap?
EPA Response: At this time, plans are to utilize
city water or possibly treated groundwater from the existing
treatment system as a source of water to irrigate the cap. Final
details on the source of water for the cap will be determined
during the remedial design. Untreated groundwater will NOT be
used as a source of water to irrigate the cap.
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* Drought: What would happen if we experience a drought in
ensuing years such that water use restricitons limit water usage
as happened in the year 1995?
EPA Response: The concept for the wet soil cap is
based on maintaining near saturated conditions by irrigation on a
intermittent schedule. On average, we anticipate that the water
usage requirement will be less than 5 gallons per minute. This
usage rate is approximately equivalent to the flow rate from a
typical garden hose. The wet soil cap will not require a high
demand for water.
* Disassembling the SVE piping: If these pipes are disassembled,
will they be cleaned at the site: If so, what safeguards are in
place once the SVE system is removed, to ensure no atmospheric
contamination. If they are not precleaned at the site, will they
be removed and transported through residential areas?
EPA Response: Just prior to the construction of the wet soil
cap, the existing SVE system will be decommissioned. This means
that the components of the SVE system, including the piping, will
be dismantled, decontaminated, and removed from the site.
Dismantlement and decontamination procedures will be conducted on
site. The specific procedures will be defined during the
remedial design. The in-place soil vapor extraction wells will
be sealed by grouting. The decommissioning of the SVE system
will NOT present a risk of exposure.
Heterogeneous subsurface: Will the same heterogeneous soil
conditions which led to channeling of the flow of vapors to the
SVE system lead to channeling of the downward flow of water and
possible a failure of the wet soil cap system? Should we gamble
on an untried, unproved technology?
EPA Response: The wet soil cap provides for a homogeneous
compacted soil layer to be installed across the site which will
control volatile emissions through the cap. The system will
permit water to move through the subsurface and inhibit the
migration of VOCs upward.
The wet soil cover is based on conventional, well understood
scientific and engineering principles. It is very similar to a
"clay cap" except that instead of an impermeable clay layer, a
more permeable wet soil layer is used. It is simply the use of a
well-founded cap technology in a slightly different way, with the
objective being VOC emisisons control and allowing natural
attenuation of contaminants. In addition, a large safety factor
is provided by the contingency vent layer, which allows for
venting if it becomes necessary. .
* Seepage along the north wall: Previously, there has been a
problem with seepage of VOC-containing liquid through the
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embankment on the northern side of the site by the railroad
tracks. Is it possible that such seepage could occur again with
the addition of the wet soil cap? Has this been considered in
the post implementation and long-term risk assessments?
EPA Response: With respect to the spring/seep that developed
along the floodplain in May 1994, it was determined that a
malfunctioning pump and check valve in the west sump did not
allow for the sump to empty its contents into a holding tank.
Rather, it operated in a high level condition. Once discovered,
the sump pump and check valve were repaired and the seep
collection system inspection program revised to prevent a similar
.occurrence.
Since that time, no seeps have been -observed, including
periods of shutdown of the SVE dewatering wells, when the water
table was allowed to rebound to static pre-SVE levels. Further,
the potential for seep outbreaks will be evaluated during the
remedial design phase and, if necessary, modifications to the
seep collection system will be made. Since the design and
performance criteria for the wet soil cover and seep collection .
system will evaluate seeps, consideration of potential long-term
risk is not appropriate.
* Clogging by siltation: How would we know if siltration of the
various layers occurred: Are there any plans to monitor the
success or failure of the various strata?
EPA Response: Operation of the wet soil cap will include
monitoring of the system to ensure that all objectives are being
met. The compacted oils layer is likely to consist of a medium
.to fine silty clayey sand and siltation of this layer is not
anticipated to be a problem. Plans for operation of the system
include monitoring for contaminants of concern within the layers
of the cap and groundwater elevation beneath the cap.
* Design and engineering questions: Questions raised regarding
performance and operation should be ansered before proceeding,
not afterward. The concern is not only that some of the ultimate
answers might not be acceptable but that by the time it is
realized, the project would be so far along that retreat might
not be feasible and we would possibly be stuck with a
dysfunctional system.
EPA Response: The feasibility study and remedial design process
established by EPA is a systematic process to identify, select,
and design the most appropriate remedial alternative to protect
human health and the environment. The feasibility study phase
focuses on nine evaluation criteria for selection of the most
appropriate alternative, including technical feasibility and
short and long-term effectiveness of the system. This phase is
not intended to answer all detailed design questions. Detailed
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items are addressed in the remedial design phase. This phase
develops the design criteria for all elements of the project.
The EPA review and approval process during .the remedial design
phase ensures that all the objectives of the selected remedy are
addressed.
* Seep system failure: Would the additional burden placed on the
seep system by the added water make it more prone to failures of
the type that resulted in the eruption of a spring of
contaminated water across the RR tracks in the floodplain area?
EPA Response: Upgrades to the seep interceptor system will be
evaluated as part of the remedial design. Operation of the wet
soil cap will not require a high demand for water; therefore, the
addition of this capping system on the site will NOT result in a
seep collection system which is more prone to failure.
* Risk assessments: generic questions.
EPA Response: The FFS,'including an assessment of the risks
associated with the remedial alternatives, was conducted by the
responsible parties with EPA guidance and approval. In
conducting the risk assessment, various assumptions are used in
developing the chemical specific toxicity factors and in defining
the circumstances under which exposure occurs (i.e., the exposure
duration or the inhalation rate). There are ranges of values
available for most of these parameters, including statistical
information on likelihood of occurrence. In preparing for the
risk assessment, EPA. requested that a protocol be prepared
describing the approach that would be applied, and enumerating
the values that were proposed for these key toxicity and exposure
parameters. EPA's risk assessment expert and air monitoring
personnel reviewed the protocol for consistency with EPA
guidelines prior to conducting this assessment. EPA assigns
values to the toxicity and expcisure parameters, and requires the
use of values that are at the 95 percentile or high end of the
range for these parameters. Thus, the outcome of the risk
assessment is largely defined by the protocol that required EPA
approval prior to conducting the assessment, and EPA guidance
that was used in conducting the assessment, rather than the group
that implements the protocol.
A detailed description of the risk assessment methodology, and
results of the risk assessment are contained in Appendix F of the
FFS Report.
* Horizontal migration of water from the site: Water migratiang
in an easterly or westerly direction will not, in all likelihood,
end up in the seep system. Where will it go?
EPA Response: Groundwater beneath the Tyson's site is contained
by two systems. Shallow groundwater is intercepted by the seep
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collelction system. Deep groundwater is contained by the
extraction wells and treated at the site. The addition of the
wet soil cap will result in groundwater mounding beneath the cap
and a component of groundwater flow in the east and west
directions. Groundwater flow toward the east and west will be
contained by the deep groundwater collection and treatment
system.
* Adding water: In what manner will water be added to the
capping system?
EPA Response: At this time, plans include a spray irrigation
system. A final decision on the selection of the irrigation
system will be made druing the remedial design.
* Volume of water: What volume of water will be added?
EPA Response: On average, the water usage requirements will be
less than 5 gallons per minute.
The following ernestions were asked bv other residents present
during the public meeting.
* A resident asked for a description of what the continuing
operations at the site would be leading up to the
implementation of the proposed remedy (wet soil cover). The
resident also asked if there was a schedule for monitoring the
site in the future.
EPA Response; Since the volume of contaminants being removed by
the Soil Vacuum Extraction system has significantly declined,
particularly during the fall and winter 'seasons, the system has
been operating on a reduced schedule beginning May 1 and ending
on September 30th. The wet soil cover will be designed during
the SVE operating months and installed during the SVE shutdown
months. Therefore, the SVE system will remain operational right
up until the time the wet soil cover is ready to be installed.
An extensive monitoring program will be developed during the
design of the wet soil cover. The monitoring plan would be
available for review by township officials.
* Will the Responsible Parties continue to operate the
groundwater recovery and treatment system.
EPA Response: The existing groundwater and recovery and treatment
system is not affected by this ROD Amendment and will continue to
operate.
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* A resident asked how long the selected alternative will be in
place in order to reach some acceptable level of cleanup.
EPA Response: The wet soil cover, once installed, must remain in
place in order to eliminate the risk that may exist through the
direct contact, inhalation and ingestion exposure pathways.
There is ongoing research being conducted by the Responsible
Parties to develop a technology capable of destroying the
contaminants that exists in the lagoon area soils. Until such a
technology is developed, the wet soil cover will remain in place.
* A resident asked how dependent is the operation and maintenance
of the wet soil cover in keeping the risk levels low.
EPA Response: A comprehensive operation and maintenance plan will
need to be developed and implemented in order to keep the wet
soil cover functional and capable of eliminating the risks
associated with the lagoon area soils.
* A resident asked what impact the wet soil cover will have on
the roadway that is proposed to be constructed in the vicinity
of the Site.
EPA Response: At this time, with the information currently
available to EPA, the installation of the wet soil cover will not
preclude the roadway from being constructed. The operation and
maintenance plan developed for the wet soil cover will also
address any concerns associated with the construction of the
proposed roadway.
* A resident asked if the wet soil cover would need to be
actively irrigated.
EPA Response: An active irrigation system will be developed
during the design phase of the wet soil cover.
* A resident asked what the primary long term risk was associated
with and if air quality testing was being performed at the
site and how much organics were presently being released into
the air.
EPA Response: The primary long term risk associated with the Site
is from inhalation. Air quality testing has been conducted, as
required, since the SVE system began operation in 1988. The air
emissions that are being released as a result of the SVE system
are within acceptables levels as established by EPA and PADEP.
* A resident asked if air quality was monitored prior to the
start up of the SVE system in 1988.
EPA Response: Prior to 1988 there has been no air monitoring
performed at the Site.
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* A resident asked what contaminants exists in the lagoon soils
and what were the concentrations.
EPA Response: During the Remedial Investigation various organic
compounds were identified. The four primary indicator compounds
identified at the Site are 1,2,3-trichloropropane, benzene,
trichloroethene and tetrachloroethene. The concentrations of
these compounds range from 10 parts per million in the upper
soils to 10,000 parts per million in the deeper soils.
* A resident asked if bioremediation was considered during the
focused feasibility study.
EPA Response: Bioremediation was one of the technologies that was
screened in the feasibility study, but it did not pass the
screening arid was not developed into a remedial alternative.
* A resident asked what will happen to the contamination that
exists beneath the soils, in the bedrock groundwater, once the
wet soil cover is placed over the lagoon area soils.
EPA Response: Groundwater contamination that exist beneath the
lagoon area soils, in the underlying bedrock, has migrated beyond
the boundary of the lagoon area soils to the North, East and
West. The groundwater contamination plume has been defined
through an extensive groimdwater remedial investigation. The
placement of the wet soil cover will not impact the the quality
of the groundwater or the flow direction of the groundwater
plume.. The groundwater investigation is nearly complete and a
remedial -action for the contaminated groundwater will be selected
in the near future.
The following questions were asked by the Upper Merion
Township. Environmental Advisory Council in a letter to EPA
dated March 13. 1996.
* A monthly long term monitoring program of all activities at the
site be adopted. The results of this testing to be forwarded
to Upper Merion Township for review.
EPA Response: The monitoring program for the wet soil cover will
be developed as part of the Operation and Maintenance Plan. Once
the monitoring program is developed it will be submitted to the
Township for review and comment. Once the plan is approved and
implemented, the results of all testing will be forwarded to the
Township for review.
* Annual testing of all private wells in the area around the
Tyson's site to be included in the long term testing program.
EPA Response: A groundwater monitoring program of private wells
around the Site will be developed as part of the remedial action
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for the deep aquifer. This action will be implemented in the
near future. As part of this action, a groundwater monitoring
program will be developed and submitted to the Township for
review and comment.
* A public safety emergency program be in place prior to the
commencement of further remedial action. This program .to be
coordinated with Upper Merion public safety officials.
EPA Response: During the design phase of the wet soil cover,
prior to construction, a Health and Safety Plan will be developed
and submitted to the Township for review and comment. Health and
Safety aspects of the construction, operation and maintenance of
the wet soil cover will be coordinated with Township officials.
* In the future, bioremediation may be the long term solution to
the Tyson's site. With that prospect in mind, we suggest that
Gibs consider the mechanical infra-structure of the SVE system be
left in place and in such condition that it could be restarted in
the future to enhance the delivery of oxygen to a bioremediation
program. Ciba-Geigy/Sandoz should continue to provide the
township with information regarding this new technology.
EPA Response: Ciba-Geigy will continue to research a
bioremediation technology that could be implemented at the
Tyson's site in the future. Ciba-Geigy will also update EPA and
Upper Merion Township on occasions regarding any progress that is
being made in this research. Should a bioremediation technology
that could be implemented at Tyson's become available, a new
system to deliver this technology to the subsurface would need to
be developed. Leaving the infra-structure of the SVE system in
place has been considered and found not to be feasible.
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