PB96-964207
EPA/ROD/R06-96/105
August 1997
EPA Superfund
Record of Decision:
Air Force Plant #4 (General Dynamics)
Fort Worth, TX
8/26/1996
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Final
Record of Decision
Air Force Plant 4
Tarrant County, Texas
July 1996
U.S. Department of the Air Force
Headquarters Aeronautical Systems Center
Wright-Patterson Air Force Base, Ohio
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GJPO-TP-11
Final
Record of Decision
Air Force Plant 4
Tarrant County, Texas
July 1996
U.S. Department of the Air Force
Headquarters Aeronautical Systems Center
Wright-Patterson Air Force Base, Ohio
Prepared by Rust Geotech under
DOE Contract No. DE-AC04-94AL96907 for the
U.S. Department of Energy
Albuquerque Operations Office
Grand Junction Projects Office
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Record of Decision
Air Force Plant 4
Declaration
Statutory Preference for Treatment
as a Principal Element Is Met
and Five-Year Review Is Required
Site Name and Location
Air Force Plant 4
Tarrant County, Texas
Statement of Basis and Purpose
This decision document presents the selected remedial actions for Air Force Plant 4 in Tarrant
County, Texas. The selected remedial actions were chosen in accordance with the
Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA),
as amended by the Superfund Amendments and Reauthorization Act (SARA) of 1986, 42 United
States Code Section 9601 et seq. Selection of the remedial actions also considered the National
Contingency Plan, to the extent practicable, and are based on information in the Administrative
Record for Air Force Plant 4.
Assessment of the Site
Actual or threatened releases of hazardous substances from Air Force Plant 4, if not addressed by
implementing the response actions selected in this Record of Decision (ROD), may present an
imminent and substantial endangerment to public health, welfare, or the environment.
Description of Selected Remedies
This ROD addresses the final response actions planned for all areas of Plant 4, including soil,
sediment, and groundwater. No previous RODs or decision documents have been issued for
Plant 4. All of Plant 4 is considered one operable unit, but the operable unit has been divided
into different areas. The baseline risk assessment conducted as part of the remedial investigation
identified six areas on Plant 4 that have the potential for excess risk or risk that exceeds the lower
threshold level of 1.0 x 10~6 incremental lifetime cancer risk (ILCR). These six areas are
Landfill No. 4
Landfill No. 3
• Meandering Road Creek
• Paluxy Aquifer and Upper Sand Groundwater
• East Parking Lot Groundwater Plume
Building 181
Declaration FINAL iii
Air Force Plant 4 July 1996
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Three areas—Landfill No. 4, Landfill No. 3, and Meandering Road Creek—are grouped together
and considered as one area. Soil areas on Air Force Plant 4 that did not cause excess risk or
exceed the lower threshold of acceptable risk were grouped together as the No Further Action
Sites. The final response actions for the six areas and the No Further Action Sites are briefly
described in the following sections.
Landfill No. 4, Landfill No. 3, and Meandering Road Creek
Landfill No. 4, Landfill No. 3, and Meandering Road Creek are grouped together because they
have similar soil contamination problems (i.e., metals). No Action is the selected remedy for soil
at Landfill No. 4 and Landfill No. 3 and for sediments in Meandering Road Creek. The selected
remedy does not take any action to mitigate risk but monitors contaminant levels to ensure that
the risk remains within acceptable levels for both human health and the environment. This is the
final action planned. The purpose of the selected action is to ensure that risk to human health
and the environment are within acceptable limits. Monitoring is the only activity included in the
selected remedy. This monitoring will involve surface-water sampling in Meandering Road
Creek and in Lake Worth.
The primary ecological threat is from metals contamination in the soil on or near the surface at
Landfill No. 4 and Landfill No. 3 and from silver and polychlorinated biphenyls in the sediments
in Meandering Road Creek and the inlet to Lake Worth. The ecological risk assessment was
conducted in a conservative manner that likely overestimated the risk and no action was deemed
acceptable. The primary human health risk at Landfill No. 4 is from benzo[a]pyrene in the soil
that causes a human health risk of 1.6 x 10~6 ILCR. This risk is within the acceptable risk range
of 1.0 x 10'6 to 1.0 x ID"4 ILCR.
Paluxy Aquifer and Upper Sand Groundwater
No previous actions have addressed contamination in the Paluxy aquifer. The primary threat to
the Paluxy aquifer is trichloroethene (TCE) and 1,2-dichloroethene (1,2-DCE) contamination.
The selected response action for the Paluxy aquifer and Upper Sand groundwater—Groundwater
Extraction and Treatment With Near-Zero Off-Gas Emissions—addresses TCE and 1,2-DCE
contamination and is the final action planned.
The purpose of this response action is to reduce contamination levels in the Paluxy aquifer to
below regulatory levels and to prevent contamination in the Upper Sand groundwater from
causing contamination in the Paluxy aquifer to exceed regulatory levels. The source of
contamination in the Paluxy aquifer under Landfill No. 3 has been eliminated. The source of
contamination for the Upper Sand groundwater is addressed by the selected remedy for the East
Parking Lot Groundwater Plume. Cleanup levels for the Paluxy aquifer are 5.0 micrograms per
liter (Mg/L) for TCE, 70 (jg/L for cw-1,2-DCE, and 100 |ug/L for tarns-1,2-DCE. Major
components of the selected remedy include
• Extracting contaminated groundwater from the Paluxy aquifer near Landfill No. 3, from the
Paluxy aquifer near the East Parking Lot (if contamination concentrations exceed maximum
iv FINAL Declaration
July 1996 Air Force Plant 4
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contaminant levels [MCLs]), and from the Upper Sand groundwater near the East
Parking Lot. Exceedance of MCLs will be determined on a statistical basis.
• Treating the extracted groundwater with ultraviolet oxidation, or another technology with off-
gas treatment that results in near-zero emissions to the atmosphere, and discharging the
treated water to surface water or to a publicly owned treatment works (POTW).
• Monitoring the movement of contamination in the Paluxy aquifer and Upper Sand
groundwater and installing additional monitoring wells.
Upper Sand groundwater is not used for drinking water purposes but is of concern because it is
hydraulically connected to the Paluxy aquifer and is the pathway through which contamination in
the East Parking Lot Plume reaches the Paluxy aquifer.
East Parking Lot Groundwater Plume
No previous RODs or decision documents have been issued concerning the East Parking Lot
Groundwater Plume, located in the Terrace Alluvial flow system. The selected response action
for the East Parking Lot Plume—Enhanced Dense Nonaqueous Phase Liquid (DNAPL)/
Groundwater Extraction and Treatment With Air Stripping and Destruction of Contaminants—
addresses the contamination that causes excess risk in the Paluxy aquifer and is the final response
action planned.
The purpose of the response action is to reduce TCE concentrations in the East Parking Lot
Plume to levels that will not cause MCLs to be exceeded in the Paluxy aquifer. Cleanup goals
for the East Parking Lot are 400 |ug/L for TCE in the Window Area; removal of DNAPL, as
demonstated by TCE concentrations of less than 10,000 Mg/L; and MCLs for groundwater
migrating off Air Force Plant 4 or Naval Air Station Fort Worth boundaries. The Window Area
is the name given to the area under the East Parking Lot where the Terrace Alluvial flow system
is hydraulically connected to the Upper Sand groundwater. Major components of the selected
remedy include
• Removing DNAPL by enhanced dissolution into the groundwater and then extracting the
groundwater.
• Treating the extracted groundwater with air stripping before discharging the treated water to
surface water or to a POTW. Air discharged from the air stripper will be treated with an off-
gas treatment system that results in near-zero emission of contaminants to the atmosphere.
• Potentially using a barrier, physical or hydraulic, to separate the Window Area of the Terrace
Alluvial flow system from areas upgradient of the Window Area. Use of a barrier will
depend on whether separation of the Window Area is required to meet remediation goals.
Determination of whether a barrier is needed at the beginning of the remedial action will be
made during remedial design.
Declaration FINAL v
Air Force Plant 4 July 1996
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• Initiating institutional controls to restrict future use of the Terrace Alluvial ground water on
Air Force Plant 4 and on Naval Air Station Fort Worth (located adjacent to Plant 4).
• Monitoring to track contamination movement and levels in the Terrace Alluvial flow system
(includes the East Parking Lot Plume, the North Plume, and the West Plume), Meandering
Road Creek, Lake Worth, and Farmers Branch Creek. Additional monitoring wells also will
be installed.
• Initiating containment actions, if necessary, to prevent groundwater contamination above
MCLs from migrating beyond the Air Force Plant 4 or the Naval Air Station Fort Worth
boundaries.
Terrace Alluvial groundwater under Plant 4 and Naval Air Station Fort Worth is not used as a
drinking water source. TCE contamination in the East Parking Lot Plume is a concern because it
is the source of contamination in the Upper Sand groundwater and in the Paluxy aquifer under
the East Parking Lot. The Air Force has initiated a groundwater extraction and treatment system
for Terrace Alluvial groundwater in the East Parking Lot as an interim measure. This interim
measure will continue operation until a final remedy is implemented for contamination in the
East Parking Lot Plume.
Building 181
No previous RODs or decision documents have been issued concerning Building 181. The
selected response action, Soil-Vapor Extraction, addresses the contamination under Building 181
and is the final response action planned. The purpose of the response action is to prevent the
migration of TCE contamination from the vadose zone to the Terrace Alluvial groundwater that
may ultimately result in exceedance of MCLs in the Paluxy aquifer. TCE in the vadose zone
under Building 181 is of concern because it is a source of TCE contamination in the East Parking
Lot Plume. The East Parking Lot Plume, in turn, is the source of the contamination in the Paluxy
aquifer. Major components of the selected remedy include
• Using vapor-recovery wells to extract volatilized TCE.
• Removing contaminants from the extracted air before release to the atmosphere.
Contaminants will be removed with an off-gas treatment technology that results in near-zero
emission of contaminants to the atmosphere.
• Using vacuum-enhanced recovery wells to remove groundwater that is encountered during
installation of the vapor extraction wells.
• Treating the extracted groundwater with air stripping and a near-zero off-gas emission
system. Air discharged from the air stripper will be treated with an off-gas treatment system
that results in near-zero emission of contaminants to the atmosphere.
vi FINAL Declaration
July 1996 Air Force Plant 4
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• Installing soil-gas probes to monitor performance of the selected remedy. Monitoring will
continue as long as remedial activities are ongoing.
The Air Force initiated a pilot-scale soil-vapor extraction system for TCE contamination in the
vadose zone under this building. In March 1996, the system was modified to incorporate
treatment of perched groundwater. Operation of the soil-vapor extraction system will continue as
an interim measure until the final remedial action is implemented.
No Further Action Sites
No previous RODs or decision documents have been issued concerning the soil at the No Further
Action Sites. No action is necessary to ensure protection of human health and the environment.
The selected remedy does not include monitoring of soil contaminant levels. The soil areas
included in the No Further Action Sites are
• Landfill No. 1
• Landfill No. 2
• Fire Department Training Area No. 2
• Fire Department Training Area No. 3
• Fire Department Training Area No. 4
• Fire Department Training Area No. 5
• Fire Department Training Area No. 6
• Chrome Pit No. 1
• Chrome Pit No. 2
• Chrome Pit No. 3
• Die Yard Chemical Pits
• Fuel Saturation Area No. 1
• Fuel Saturation Area No. 2
• Fuel Saturation Area No. 3
• Former Fuel Storage Area
• Solvent Lines
• Nuclear Aerospace Research Facility
• Wastewater Collection Basins
• West Compass Rose
• Jet Engine Test Stand
• Underground Storage Tank No. 19
• Underground Storage Tank No. 20
• Underground Storage Tank No. 24A
• Underground Storage Tank No. 24B
• Underground Storage Tank No. 25A
Underground Storage Tank No. 30
Declaration FINAL vii
Air Force Plant 4 July 1996
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Statutory Determinations
The following sections describe how the selected remedies meet the statutory requirements of
Section 121 of CERCLA.
Landfill No. 4, Landfill No. 3, and Meandering Road Creek
The selected remedy, No Action, is protective of human health and the environment; complies
with Federal and State requirements that are legally applicable or relevant and appropriate to the
remedial action; and is cost effective. This remedy uses permanent solutions to the maximum
extent practicable for this site. However, because treatment of the principal threats was not
found to be practicable, this remedy does not satisfy the statutory preference for treatment as a
principal element of the remedy. Treatment was not necessary because the risk associated with
existing contamination at the site is within acceptable limits. However, the selected remedy will
ensure that the remediation goals are met.
Because the remedy will not result in hazardous substances remaining on site above health-based
levels, a 5-year review will not be conducted.
Paluxy Aquifer and Upper Sand Groundwater
The selected remedy, Groundwater Extraction and Treatment With Near-Zero Off-Gas
Emissions, is protective of human health and the environment; complies with Federal and State
requirements that are legally applicable or relevant and appropriate to the remedial action; and is
cost effective. This remedy uses permanent solutions to the maximum extent practicable for this
site and satisfies the statutory preference for remedies employing treatment that reduces toxicity,
mobility, or volume as a principal element.
Because the remedy will result in hazardous substances remaining on site above health-based
levels, a review will be conducted within 5 years after the start of remedial action to ensure that
the remedy continues to provide adequate protection of human health and the environment.
East Parking Lot Groundwater Plume
The selected remedy, Enhanced DNAPL/Groundwater Extraction and Treatment With Air
Stripping and Destruction of Contaminants, is protective of human health and the environment;
complies with Federal and State requirements that are legally applicable or relevant and
appropriate to the remedial action; and is cost effective. This remedy uses permanent solutions
to the maximum extent practicable for this site and satisfies the statutory preference for remedies
employing treatment that reduces toxicity, mobility, or volume as a principal element.
Because the remedy will result in hazardous substances remaining on site above health-based
levels, a review will be conducted within 5 years after the start of remedial action to ensure that
the remedy continues to provide adequate protection of human health and the environment.
viii FINAL Declaration
July 1996 Air Force Plant 4
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Building 181
The selected remedy, Soil-Vapor Extraction, is protective of human health and the environment;
complies with Federal and State requirements that are legally applicable or relevant and
appropriate to the remedial action; and is cost effective. This remedy uses permanent solutions
to the maximum extent practicable for this site and satisfies the statutory preference for remedies
employing treatment that reduces toxicity, mobility, or volume as a principal element.
The remedy is projected to remove hazardous substances remaining on site above health-based
levels within 5 years after the start of remediation. Therefore, a 5-year review to ensure that the
remedy continues to provide adequate protection of human health and the environment is not
planned. However, if remeditation goals have not been met within 5 years after the start of
remediation, a review will be conducted.
No Further Action Sites
No remedial action is necessary for the soil at the No Further Action Sites to ensure protection of
human health and the environment.
Declaration FINAL ix
Air Force Plant 4 July 1996
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x FINAL Declaration
July 1996 Air Force Plant 4
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Signature
LAWRENCE P. FARRELL, JR. Date
Lieutenant General, USAF
Vice Commander
Air Force Materiel Command
Declaration FINAL xi
Air Force Plant 4 July 1996
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xii FINAL Declaration
July 1996 Air Force Plant 4
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Signature
AU8 2 6
JanfeN. Saginj
Regional AdRiinistrafcor, Region 6
}.B. Environmental protection Agency
Date
Declaration
Air Force Plant 4
FINAL
xiii
July 1996
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xiv FINAL Declaration
July 1996 Air Force Plant 4
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Signature
Dan Peapfcn
ExecutivVPirectcjjl
Texas Naturarttesource Conservation Commission
Date
Declaration
Air Force Plant 4
FINAL
xv
July 1996
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xvi FINAL Declaration
July 1996 Air Force Plant 4
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The Decision Summary
The Decision Summary FINAL xvii
Table of Contents July 1996
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xviii FINAL The Decision Summary
July 1996 Table of Contents
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Contents
Page
Abbreviations, Acronyms, and Initialisms xxiii
1.0 Site Name, Location, and Description 1-1
2.0 Site History and Enforcement Activities 2-1
2.1 CERCLA Enforcement Activities 2-1
2.2 Interim Remedial Actions 2-3
3.0 Highlights of Community Participation 3-1
4.0 Scope and Role of Response Actions 4-1
4.1 Landfill No. 4, Landfill No. 3, and Meandering Road Creek Soils
and Sediments 4-2
4.2 Paluxy Aquifer and Upper Sand Groundwater 4-3
4.3 East Parking Lot Groundwater Plume 4-3
4.4 Building 181 4-4
4.5 No Further Action Sites 4-4
5.0 Summary of Site Characteristics 5-1
5.1 Climatic Conditions 5-1
5.2 Geology 5-1
5.3 Groundwater 5-2
5.4 Surface Water 5-4
5.5 Sources and Characteristics of Contamination 5-5
6.0 Summary of Site Risks 6-1
6.1 Human Health Risk Assessment 6-1
6.2 Ecological Risk 6-22
6.3 References 6-23
7.0 Landfill No. 3, Landfill No. 4, and Meandering Road Creek 7-1
7.1 Remediation Goals 7-1
7.2 Description of Alternatives 7-2
7.3 Comparative Analysis of Alternatives 7-5
7.4 The Selected Remedy 7-10
7.5 Statutory Determinations 7-12
8.0 Paluxy Aquifer and Upper Sand Groundwater 8-1
8.1 Remediation Goals 8-1
8.2 Documentation of Significant Changes 8-1
8.3 Description of Alternatives 8-2
The Decision Summary FINAL xix
Table of Contents July 1996
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Contents (continued)
Page
8.4 Comparative Analysis of Alternatives 8-4
8.5 The Selected Remedy 8-10
8.6 Statutory Determinations 8-14
9.0 East Parking Lot Groundwater Plume and Terrace Alluvial Flow System 9-1
9.1 Remediation Goals 9-1
9.2 Description of Alternatives 9-2
9.3 Comparative Analysis of Alternatives 9-5
9.4 The Selected Remedy 9-11
9.5 Statutory Determinations 9-15
9.6 Documentation of Significant Changes 9-17
10.0 Building 181 10-1
10.1 Remediation Goals 10-1
10.2 Description of Alternatives 10-1
10.3 Comparative Analysis of Alternatives 10-2
10.4 The Selected Remedy 10-6
10.5 Statutory Determinations 10-8
10.6 Documentation of Significant Changes 10-9
11.0 No Further Action Sites . - 11-1
11.1 Selected Remedy 11-1
11.2 Basis of No Action as the Selected Remedy 11-1
11.3 Documentation of Significant Changes 11-10
Appendix A, Responsiveness Summary A-l
Appendix B, Administrative Record Index B-l
Figures
Figure 1 -1. Air Force Plant 4 Location Map 1-2
2-1. Air Force Plant 4 Sites and Areas of Concern 2^4
5-1. Air Force Plant 4 Geology and Groundwater Areas 5-3
5-2. Contamination That May Cause Excess Ecological Risk at
Air Force Plant 4 5-6
5-3. Contamination in the Terrace Alluvial Flow System at Air Force Plant 4 . 5-9
5-4. Contamination in the Upper Sand Groundwater at Air Force Plant 4 .... 5-12
5-5. Contamination in the Paluxy Aquifer at Air Force Plant 4 5-13
6-1. Site Conceptual Exposure Model for Air Force Plant 4 6-4
7-1. Evaluation Criteria Specified in the National Contingency Plan 7-6
11-1. Air Force Plant 4 Sites and Areas of Concern . 11-2
xx FINAL The Decision Summary
July 1996 Table of Contents
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Tables
Page
Table 6-1. Chemicals of Potential Concern 6-2
6-2. Concentrations for Chemicals of Potential Concern in Groundwater 6-5
6-3. Concentrations for Chemicals of Potential Concern in Surface Water .... 6-5
6-4. Concentrations for Chemicals of Potential Concern in Soil 6-6
6-5. Concentrations for Chemicals of Potential Concern in Air 6-6
6-6. Parameters Used To Estimate Exposure in Baseline Risk Assessment ... 6-8
6-7. Results of the Exposure Assessment—Ingestion 6-9
6-8. Results of the Exposure Assessment—Inhalation 6-10
6-9. Results of the Exposure Assessment—Dermal 6-11
6-10. Summary of Toxicity Values 6-12
6-11. Summary of Potential Incremental Lifetime Cancer Risks
Associated With Plant 4: Current Land Use 6-14
6-12. Summary of Potential Incremental Lifetime Cancer Risks
Associated With Plant 4: Future Land Use 6-15
6-13. Summary of Potential Hazard Indices Associated
With Plant 4: Current Land Use 6-16
6-14. Summary of Potential Hazard Indices Associated
With Plant 4: Future Land Use 6-17
6-15. Summary of Proposed Actions 6-18
6-16. Summary of Contaminants That Exceed Ecological-Risk
Threshold Levels 6-23
7-1. Comparative Analysis of Alternatives for Landfill No. 4,
Landfill No. 3, and Meandering Road Creek 7-7
7-2. Summary of ARARs for Landfill No. 4, Landfill No. 3,
and Meandering Road Creek 7-8
8-1. Comparative Analysis of Alternatives for the Paluxy Aquifer
and Upper Sand Groundwater 8-5
8-2. Summary of ARARs for the Paluxy Aquifer and Upper
Sand Groundwater 8-6
9-1. Comparative Analysis of Alternatives for the East Parking Lot Plume . . . 9-6
9-2. Summary of ARARs for the East Parking Lot Plume 9-7
10-1. Comparative Analysis of Soil Alternatives for Building 181 10-3
The Decision Summary FINAL xxi
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xxii FINAL The Decision Summary
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Abbreviations, Acronyms, and Initialisms
ARAR applicable or relevant and appropriate requirement
BAP benzo[0]pyrene
BRA baseline risk assessment
CAS Chemical Abstracts Services
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act
CFR Code of Federal Regulations
BAP benzo[0] pyrene
GDI chronic daily intake
COE U.S. Army Corps of Engineers
COPC chemical of potential concern
CP-1 Chrome Pit No. 1
CP-2 Chrome Pit No. 2
CP-3 Chrome Pit No. 3
CT central tendency
CWA Clean Water Act
DC A 1,1 -dichloroethane
DCE 1,2-dichloroethene
DNAPL dense nonaqueous phase liquid
DOE U.S. Department of Energy
EPA U.S. Environmental Protection Agency
FDTA-2 Fire Department Training Area No. 2
FDTA-3 Fire Department Training Area No. 3
FDTA-^ Fire Department Training Area No. 4
FDTA-5 Fire Department Training Area No. 5
FDTA-6 Fire Department Training Area No. 6
FFSA Former Fuel Storage Area
FSA-1 Fuel Saturation Area No. 1
FSA-2 Fuel Saturation Area No. 2
FSA-3 Fuel Saturation Area No. 3
ft foot
gal/min gallons per minute
HARM Hazard Assessment Rating Methodology
HI Hazard Index
HQ Hazard Quotient
ILCR incremental lifetime cancer risk
in. inch
IRP Installation Restoration Program
JETS Jet Engine Test Stand
LF-1 Landfill No. 1
LF-2 Landfill No. 2
LF-3 Landfill No. 3
LNAPL light nonaqueous phase liquid
The Decision Summary
Abbreviations, Acronyms, and Initialisms
FINAL
XXlll
July 1996
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Abbreviations, Acronyms, and Initialisms (continued)
MCL maximum contaminant level
MCLG maximum contaminant level goal
|ig/L micrograms per liter
mg/kg milligrams per kilogram
mg/L milligrams per liter
NARF Nuclear Aerospace Research Facility
NCP National Contingency Plan
ND not detected
NFA No Further Action Site
NPDES National Pollutant Discharge Elimination System
NPL National Priorities List
O&M operation and maintenance
OSWER Office of Solid Waste and Emergency Response
PA/SI Preliminary Assessment/Site Inspection
PCB polychlorinated biphenyl
PCE tetrachloroethene
pCi/g picocuries per gram
POTW publicly owned treatment works
PRGs preliminary remediation goals
RAB Restoration Advisory Board
RCRA Resource Conservation and Recovery Act
RfD reference dose
RI/FS Remedial Investigation/Feasibility Study
RME reasonable maximum exposure
ROD Record of Decision
SARA Superfund Amendments and Reauthorization Act
SF slope factor
SVOC semivolatile organic compound
TAG Texas Administrative Code
TC A 1,1,2-trichloroethane
TCE trichloroethene
TNRCC Texas Natural Resource Conservation Commission
TRC Technical Review Committee
UST underground storage tank
UST-19 Underground Storage Tank No. 19
UST-20 Underground Storage Tank No. 20
UST-24A Underground Storage Tank No. 24A
UST-24B Underground Storage Tank No. 24B
UST-25A Underground Storage Tank No. 25A
UST-30 Underground Storage Tank No. 30
VOC volatile organic compound
yd3 cubic yard
XXIV
July 1996
FINAL
The Decision Summary
Abbreviations, Acronyms, and Initialisms
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1.0 Site Name, Location, and Description
Air Force Plant 4 is a government-owned, contractor-operated facility consisting of 602 acres
adjacent to the northwest boundary of the city of Fort Worth (Figure 1-1) in Tarrant County,
Texas. The plant is bounded on the north by Lake Worth, on the east by Naval Air Station Fort
Worth (formerly known as Carswell Air Force Base), and on the south and west by the city of
White Settlement. The plant has manufactured military aircraft since 1942 and is currently
operated by Lockheed Martin Corporation.
The manufacturing operations and associated processes at the plant have resulted in the
generation of waste oils, waste fuels, paint residues, used solvents, and process chemicals.
Presently, contamination from the disposal of these wastes exists in the soil beneath the site, in
the surface water, and in the groundwater.
Plant 4 and the surrounding areas to the south and east are highly urbanized and, consequently,
do not contain much natural vegetation for wildlife. Approximately 70 percent of the Plant 4
surface area is covered by buildings, concrete, or asphalt. The remaining 30 percent of the
surface area (the west and north portions of Plant 4) is primarily grass-covered soil. The area
west-northwest of Plant 4 is mainly residential with an abundance of natural vegetation. Lake
Worth provides recreational boating, fishing, and water skiing. This lake also furnishes
municipal water to the city of Fort Worth and is a recharge source to the underlying Paluxy
aquifer that supplies municipal water to the city of White Settlement.
Residential housing is immediately adjacent to Plant 4 on the south and west. Six schools are
within a 2-mile radius of Plant 4; the closest school is 0.5 mile south of the facility. The area is
accessed by two major interstate highways, 1-820 from the north and south and 1-30 from the
east and west. Plant 4 is accessed directly from 1-30 by State Highway 341. The communities of
White Settlement, Lake Worth Village, Westworth Village, River Oaks, and Sansom Park
Village lie within a 3-mile radius of Plant 4.
The topography of the land surrounding Plant 4 is generally flat, with the exception of areas
adjacent to Meandering Road Creek and Lake Worth. Elevations at the site range from 590 feet
(ft) above mean sea level along the shore of Lake Worth to approximately 670 ft above mean sea
level at the southwest corner of the site. On the basis of results from a 1982 flood insurance
study, neither a 100- nor a 500-year flood event will directly affect Plant 4.
The Decision Summary FINAL 1-1
1.0 Site Name, Location, and Description July 1996
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Lubbock
Fort Worth
Air Force
Plant 4
Naval Air Station
Fort Worth
012345
W0049000 DWG 3/7/96
Cl-l.Cdr 4/96
Figure 1-1. Air Force Plant 4 Location Map
1-2
July 1996
FINAL
The Decision Summary
1.0 Site Name, Location, and Description
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2.0 Site History and Enforcement Activities
Air Force Plant 4 became operational in 1942 and began manufacturing the B-24 bomber for
national defense during World War H The facility has since produced B-36, B-58, F-l 11, and
F-16 aircraft. In addition, Plant 4 produces spare parts, radar units, and missile components.
Waste oil, solvents, and fuels generated during the manufacturing operations were disposed of at
on-site landfills or were burned in fire-training exercises during most of the plant's operation.
Chemical process wastes were initially discharged to the sanitary sewer system and treated by the
city of Fort Worth's treatment system. Beginning in the 1970s, chemical process wastes were
treated on site at a newly constructed chemical waste-treatment system before being discharged
to the sanitary sewer system. Currently, waste oils and solvents are disposed of off site; burning
of these wastes on site has been discontinued. Chemical process wastes continue to be treated
on site.
Potential contamination at Plant 4 was first noted by a private citizen in September 1982.
General Dynamics, the contractor operating Plant 4 from 1953 to 1993, was notified and took
immediate action. The source of the observed contamination was thought to be leachate from
a landfill.
A'Technical Review Committee (TRC) for Plant 4 was established in 1983 consisting of
representatives from the U.S. Environmental Protection Agency (EPA), Region 6; the Texas
Natural Resource Conservation Commission (TNRCC); the city of Fort Worth; the city of White
Settlement; the U.S. Air Force; the U.S. Army Corps of Engineers (COE); U.S. Geological
Survey; and Lockheed Martin, current operator of Plant 4. Periodic TRC meetings have been
held since 1983 to keep the local authorities and the community informed of environmental
restoration activities at Plant 4.
The TRC was converted to a Restoration Advisory Board (RAB) in 1995. The RAB brings
together a diverse cross section of the community to act as a focal point for the exchange of
information regarding restoration activities. The Air Force Plant 4 RAB has held monthly
meetings since March 1995 and is currently meeting every other month.
2.1 CERCLA Enforcement Activities
Characterization activities have been ongoing at Plant 4 since the 1982 observance of
contamination. The following Comprehensive Environmental Response, Compensation, and
Liability Act (CERCLA) enforcement activities were initiated before the remedial investigation
was started:
• October 1982 — General Dynamics constructed French Drain No. 1 (at Landfill No. 1) to
prevent migration of contaminated groundwater toward Meandering Road Creek and to divert
the flow of surface water from the outfall.
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2.0 Site History and Enforcement Activities July 1996
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• November 1982 — Aeronautical Systems Center (formerly Aeronautical Systems Division),
through General Dynamics, retained Hargis & Montgomery, Inc., to investigate the potential
for groundwater contamination at Plant 4. Hargis & Montgomery and later Hargis +
Associates, Inc., drilled approximately 260 soil borings, of which approximately 160 were
constructed as monitoring wells.
• March 1984 — CH2M Hill, Inc., conducted a Phase I Records Search as part of the
Installation Restoration Program (IRP). CH2M Hill used the U.S. Air Force's Hazard
Assessment Rating Methodology (HARM) in August 1984 to rank 20 identified
disposal sites.
• June 1985 — COE was contracted to further delineate groundwater conditions along the
southern boundary and under the East Parking Lot area of Plant 4. COE drilled 28 soil
borings and constructed 6 monitoring wells.
• September 1985 — Radian Corporation was contracted to perform the Phase n, Stage I,
Confirmation/Quantification of the IRP. Radian Corporation drilled 26 soil borings and
constructed 14 groundwater monitoring wells. Additional work included a confirmation
sampling round of all existing monitoring wells.
• December 1985 — Intellus Corporation was contracted to conduct an IRP Phase IV Remedial
Action Plan for 10 potential disposal sites and a Phase IV-A Remedial Action Plan and a
Phase IV-B Design and Construction for Fuel Saturation Areas No. 1 and No. 3. In support
of these tasks, Intellus Corporation drilled 36 soil borings and constructed 24 groundwater
monitoring wells.
Environmental contamination identified at the facility during these site investigations resulted in
Plant 4 being placed on the National Priorities List (NPL) in August 1990. Pursuant to
CERCLA, as amended by the Superfund Amendments and Reauthorization Act (SARA) of 1986,
the Air Force, EPA Region 6, and TNRCC entered into a Federal Facility Agreement, in
November 1990, to address environmental effects of past waste-disposal practices at Plant 4.
In October 1990, Rust Geotech, formerly known as UNC Geotech, Inc., through a Memorandum
of Agreement between the U.S. Air Force and the U.S. Department of Energy (DOE), began a
Preliminary Assessment/Site Inspection (PA/SI) and a Remedial Investigation/ Feasibility Study
(RI/FS).
The PA/SI activities delineated possible contaminant source areas beneath the Assembly
Building/Pans Plant and investigated the locations of previously removed underground storage
tanks. The RI activities characterized the nature and extent of contamination at Plant 4 and
assessed the potential risk to human health and the environment associated with the
contamination. The FS developed remedial alternatives to address contamination that exceeded
risk threshold values as calculated by the baseline risk assessment (BRA). The Plant 4 RI/FS
was approved in September 1995 by EPA Region 6 and TNRCC.
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July 1996 2.0 Site History and Enforcement Activities
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The Proposed Plan was issued in November 1995. It presented outlines of the results of the
remedial investigation activities, summaries of the results of the BRA and the remedial action
alternatives identified in the FS, and discussions of the preferred alternatives for six sites and
other areas of concern at Plant 4. The public meeting on the proposed plan was held
December 14, 1995.
2.2 Interim Remedial Actions
The Air Force has implemented several interim remedial actions in an attempt to mitigate the
effects of contamination at the site until final remedies are determined. These interim remedial
actions were implemented before completion of the BRA. On the basis of results of the BRA,
some of the actions can be discontinued because the contamination at that site does not present
an excess risk to human health and the environment.
Landfill No. 3—Vacuum-Enhanced Extraction System
Landfill No. 3 (Figure 2-1) is a 3-acre site that has been covered with dirt and rubble and graded
to its present state. It has not been covered with an engineered cap. A vacuum-enhanced
extraction system has been installed at Landfill No. 3 to minimize contamination in the Terrace
Alluvial groundwater that may discharge to Meandering Road Creek. Before the baseline risk
assessment was completed, the Air Force installed a fence across Meandering Road Creek (near
Landfill No. 3) as a precautionary measure to prevent access to the creek. Operation of the
system is not required by the selected remedy for groundwater under Landfill No. 3, (i.e., the
West Plume of the Terrace Alluvial flow system). However, the Air Force plans to voluntarily
operate the system.
This system consists of 42 extraction wells spaced 20 ft apart and a trench 150 ft long with four
extraction points. The wells and the trench are located along the western edge of Landfill No. 3.
The trench was installed where the depth to the bedrock (i.e., the Walnut Formation) is shallow,
approximately 4 ft.
The vacuum-enhanced extraction system was chosen for this site because of the low permeability
of the aquifer in this area. The extraction wells are designed to extract contaminated
groundwater using a drop tube inside the well casing and also to extract volatile organic
compounds (VOCs) in the vadose zone with a vacuum applied to the well. Treatment of the
extracted groundwater will be with an air stripper or ultraviolet oxidation. If an air stripper is
used, the contaminants in the air will be treated with vapor-phase carbon adsorption or catalytic
oxidation before discharge from the unit. The vapor extracted from the wells will be treated with
an off-gas treatment system that results in near-zero emission of contaminants to the atmosphere.
French Drains No. 1 and No. 2
French Drains No. 1 and No. 2 were installed to mitigate contamination related to Landfill No. 1
(Figure 2-1). French Drain No. 1 was installed in November 1982 in response to complaints of
odors coming from Stormwater Outfall No. 5, which drains into Meandering Road Creek. The
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2.0 Site History and Enforcement Activities July 1996
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Assembly Building/Parts Plant
ai-l Plant 4 ,,
Boundary £
LJ x .**
East Parking Lot/
Flight Line
Naval Air Station Fort Worth
Legend
| Site Warrants Development of Alternatives £ No Further Action (NFA) Site [ii] Building Number
O Landfill No. 1
0 Landfill No. 2
Q Landfill No. 3
Q Landfill No. 4
A Fire Department Training
Area No. 2
Q Fire Department Training
Area No. 3
ft Fire Department Training
Area No. 4
Q Fire Department Training
Area No. 5
Q Fire Department Training
Area No. 6
(£) Chrome Pit No. 1
o:\Q\A95plnt4\FIG2-1.cdr 4\9€
Chrome Pit No. 2
0 Chrome Pit No. 3
(D Die Yard Chemical Pits
(J) Fuel Saturation Area No. 1
0 Fuel Saturation Area No. 2
(£) Fuel Saturation Area No. 3
(^ Former Fuel Storage Area
(£) Solvent Lines
(P) Nuclear Aerospace
Research Facility
(J) Wastewater Collection Basins
Q) West Compass Rose
© East Parking Lot/Flight Line
French Drains No. 1 and No. 2
Jet Engine Test Stand
Underground Storage Tank
No. 19
Underground Storage Tank
No. 20
Underground Storage Tank
No. 24A
Underground Storage Tank
No. 24B
Underground Storage Tank
No. 25A
Underground Storage Tank
No. 30
Building 181
Figure 2-1. Air Force Plant 4 Sites and Areas of Concern
2-4
July 1996
FINAL
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2.0 Site History and Enforcement Activities
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French drain system consists of 90 ft of perforated 4-inch (in.) drain pipe. The pipe is placed on
bedrock east of Stormwater Outfall No. 5. Two 6-in. perforated pipes that were found during
excavation, installed before the parking lot was paved in 1967, were connected to the French
drain system. French Drain No. 2 was installed in 1983 in the area of the former waste oil pits.
This area was excavated to bedrock, and six 24-in. drainlines were placed in the bottom of the
excavation and were connected to a collector box.
Before French Drain No. 2 was installed, French Drain No. 1 was evacuated daily. Initially, the
evacuated water was disposed of by deep-well injection at an off-site location; later, the disposal
method was incineration. After operation of French Drain No. 2 began, groundwater collected
from French Drain No. 1 was diverted to the sanitary sewer. Evacuation to the sanitary sewer
was no longer considered feasible after May 1990, and these drains remained inactive until
October 1992 when the evacuated groundwater was treated at Fuel Saturation Area No. 1
(FSA-1).
Building 181—Soil-Vapor Extraction System
A pilot-scale soil-vapor extraction system was installed at Building 181 (Figure 2-1) and began
operation in December 1993 to extract trichloroethene (TCE) contamination from the vadose
zone under the building. The presence of TCE in the vadose zone under Building 181 is the
result of spills and leaks from TCE tanks in that building. Some of the TCE contamination in the
vadose zone migrates down to the Terrace Alluvial groundwater and has the potential to work its
way to the Paluxy aquifer through the Window Area in the East Parking Lot. Accurate
information is not available on the total amount of TCE that has spilled or leaked from the
tanks, how much TCE is in the vadose zone, and how much TCE is in the Terrace Alluvial
groundwater.
A pilot-scale test was run with the objectives to remove as much TCE from the subsurface as
possible within the time period of the test, 90 days, and to develop pilot-test parameters
necessary to evaluate the applicability of a full-scale soil-vapor extraction system. The pilot-
scale soil-vapor extraction system used eight extraction wells to withdraw TCE from the soil.
The extracted vapor was treated with carbon adsorption after condensate removal.
During the 90-day test, approximately 4,400 pounds (367 gallons) of TCE was extracted from the
vadose zone, as measured by carbon vessel removal. A full-scale soil-vapor extraction system is
the selected alternative for Building 181. In March 1996, the system was modified to incorporate
treatment of groundwater from three groundwater extraction wells. Recovered groundwater is
being treated with an air stripper. The soil-vapor extraction system has been expanded to include
three vacuum-enhanced pumping wells and will continue to operate until the final remedy can be
implemented.
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East Parking Lot—Groundwater Treatment System
Air Force Plant 4 installed a groundwater extraction and treatment system for Terrace Alluvial
ground water in the Window Area of the East Parking Lot (Figure 5-3 in Section 5.0) in
January 1993 and continues to operate that system. This system includes extraction wells, a
treatment system, and piping to convey the extracted groundwater to the treatment system. The
treatment system consists of an equalization tank, an air stripper, and carbon adsorption units
used as a polishing step for the treated groundwater. Treated water is discharged to the sanitary
sewer system. TCE concentrations in samples obtained at the influent to the treatment system
have ranged from approximately 10,000 to 20,000 micrograms per liter (|ug/L).
Contamination in the East Parking Lot Plume is the source of contamination in the Paluxy
aquifer because the Terrace Alluvial flow system and the Upper Sand groundwater are
hydraulically connected through the Window Area. The BRA determined that TCE
contamination in the Paluxy aquifer will exceed human health risk threshold values if the
domestic drinking water wells are affected by this contaminant in the future. The Air Force will
continue to operate the groundwater extraction system until the final remedy for the East Parking
Lot is implemented.
Fuel Saturation Area No. 1 (FSA-1)—Groundwater Treatment System
The Air Force implemented a groundwater treatment system at FSA-1 (Figure 2-1) that has
operated intermittently since it was installed in 1992. This site was contaminated by fuels
leaking from an underground distribution system and three leaking underground storage tanks
(USTs). The system at FSA-1 is designed to extract groundwater and fuel floating on the
groundwater and then treat the extracted fuel or groundwater. It has a design capacity of
70 gallons per minute (gal/min) and consists of an oil/water separator, an air stripper, and carbon
adsorption units. Groundwater is recovered from two extraction wells. Groundwater evacuated
from French Drains No. 1 and No. 2 also was treated at FSA-1.
The Air Force has also tested a pilot-scale bioventing system at FSA-1. The bioventing system
is designed to enhance natural biodegradation of fuel-related hydrocarbons by supplying oxygen
to the subsurface. The system, which is fairly simple, includes vent wells where the oxygen is
injected into the subsurface, monitoring points, and a blower to force oxygen into the vent wells.
The BRA determined that contaminant levels in the soil and groundwater near FSA-1 do not
cause excess risk to human health or the environment because there is no exposure pathway.
Because there is no excess risk, remedial action in this area is not required.
Fuel Saturation Area No. 3 (FSA-3)—Groundwater Treatment System
The Air Force implemented a groundwater treatment system at FSA-3 (Figure 2-1) that has
operated intermittently since it was installed in 1992. This site was contaminated by fuels
leaking from an underground distribution system and one leaking UST. The system at FSA-3 is
designed to extract groundwater and fuel on the groundwater and then treat the extracted fuel or
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July 1996 2.0 Site History and Enforcement Activities
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groundwater. It has a design capacity of 20 gal/min and consists of an oil/water separator, an air
stripper, and carbon adsorption units. Groundwater is recovered from two extraction wells.
The Air Force has also tested a pilot-scale bioventing system at FS A-3 that is similar to the
system at FS A-1.
The BRA determined that contaminant levels in the soil and groundwater near FS A-3 do not
cause excess risk to human health or the environment because there is no exposure pathway.
Because there is no excess risk, remedial action in this area is not required. Therefore, the Air
Force does not plan to continue operation of the groundwater treatment system or the
bioventing system.
Naval Air Station Fort Worth Landfills No. 4 and No. 5—Groundwater Treatment System
The Air Force implemented a groundwater extraction and treatment system located immediately
downgradient of Landfills No. 4 and No. 5 on Naval Air Station Fort Worth (Figure 5-3 in
Section 5.0). Although the site is located on Naval Air Station Fort Worth, Air Force Plant 4
undertook this action because contamination from the East Parking Lot Plume has migrated onto
Naval Air Station Fort Worth. Upgradient of Landfills No. 4 and No. 5, the TCE plume is
caused entirely by contamination originating at Air Force Plant 4. TCE concentrations are higher
downgradient of the landfills than they are upgradient of the landfills. This increase in TCE
concentrations indicates that contamination in the landfills is responsible for a portion of the
downgradient TCE plume. Dissolved TCE concentrations in samples obtained from extraction
wells range from 300 to 4,000 |ug/L, averaging around 1,500 |ug/L at the influent to the treatment
system.
The dissolved TCE in the groundwater discharges to surface water, causing TCE contamination
in surface waters on Naval Air Station Fort Worth. However, the BRA determined that present
levels of TCE in surface waters on Naval Air Station Fort Worth do not cause excess human
health or ecological risk. Also, the selected alternative for the East Parking Lot Plume will
reduce TCE concentrations in the groundwater, resulting in reduced TCE concentrations in
surface waters on Naval Air Station Fort Worth.
The Air Force does not plan to continue operation of the groundwater treatment system on Naval
Air Station Fort Worth but may operate the system as a corrective measure if remediation goals
are not being met. Section 9.4, 'The Selected Remedy," discusses the conditions under which a
corrective measure may be needed.
No Further Action Sites
Contaminated soil was removed from several of the No Further Action Sites and was taken to an
off-site location. These actions were completed before Air Force Plant 4 was placed on the
National Priorities List. The selected remedy for soil at the No Further Action Sites is
No Action. The No Further Action Sites are described in Section 5.5 under "No Further
Action Sites."
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July 1996 2.0 Site History and Enforcement Activities
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3.0 Highlights of Community Participation
In March 1995, the Air Force Plant 4 Restoration Advisory Board (RAB) was set up as a forum
for exchange of information on environmental issues at Plant 4. This board is designed to
identify and to educate interested citizens on how they can become active participants in the
decision-making process during cleanup.
The RAB is composed of local citizens and a community cochairperson and meets every other
month at the White Settlement Senior Services Center. The public is invited to all meetings as
well as regulators, Plant 4 personnel, Air Force representatives, contractors, and news media
representatives. The RAB charter was accepted at the November 1995 meeting.
The RI and FS for Air Force Plant 4 were released to the public in September 1995, including
members of the RAB. The Proposed Plan was released to the public in November 1995. These
three documents were made available to the public in the Administrative Record maintained at
the White Settlement Public Library.
The public comment period for the Proposed Plan was held from November 22, 1995, through
January 22, 1996. A public meeting on the Proposed Plan was held on December 14, 1995.
Representatives from the Air Force, EPA, TNRCC, Rust Geotech, other site contractors, and
government support agencies attended this meeting and answered questions about problems at
the site and the remedial alternatives under consideration. Responses to comments received at
the public meeting and during the public meeting are included in Appendix A, "Responsiveness
Summary," of this Record of Decision (ROD).
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4.0 Scope and Role of Response Actions
This ROD addresses the final response actions planned for all areas of Plant 4. No previous
RODs or decision documents have been issued for Plant 4. All of Plant 4 is considered one
operable unit; however, the operable unit has been divided into different areas. The BRA that
was conducted as part of the RI identified six areas on Plant 4 that have the potential for excess
risk or risk that exceeds the lower threshold of the allowable risk range. The final response
actions for these six areas and other areas that did not cause excess risk are defined in this ROD.
The six areas that have the potential to cause excess risk are
• Contamination in the soil at Landfill No. 4, based on the potential for excess ecological risk
and human health risk that exceeded the lower threshold of the allowable risk range.
• Contamination in the soil at Landfill No. 3, based on the potential for excess ecological risk.
• Contamination in the sediments in Meandering Road Creek and in the inlet of Meandering
Road Creek to Lake Worth, based on the potential for excess ecological risk.
• Contamination in the Paluxy aquifer and Upper Sand groundwater, based on excess
human health risk.
• Contamination in the East Parking Lot Groundwater Plume, based on excess human
health risk.
• Contamination in soil in the vadose zone under Building 181, based on excess human
health risk.
Areas with soil contamination that did not cause excess risk, either human health or ecological
risk, are grouped together as No Further Action Sites. These sites are
• Landfill No. 1
• Landfill No. 2
Fire Department Training Area No. 2
• Fire Department Training Area No. 3
• Fire Department Training Area No. 4
* Fire Department Training Area No. 5
• Fire Department Training Area No. 6
The Decision Summary FINAL 4-1
4.0 Scope and Role of Response Actions July 1996
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• Chrome Pit No. 1
• Chrome Pit No. 2
• Chrome Pit No. 3
• Die Yard Chemical Pits
• Fuel Saturation Area No. 1
• Fuel Saturation Area No. 2
• Fuel Saturation Area No. 3
• Former Fuel Storage Area
• Solvent Lines
• Nuclear Aerospace Research Facility
• Wastewater Collection Basins
• West Compass Rose
• Jet Engine Test Stand
• Underground Storage Tank No. 19
• Underground Storage Tank No. 20
• Underground Storage Tank No. 24A
Underground Storage Tank No. 24B
• Underground Storage Tank No. 25A
• Underground Storage Tank No. 30
4.1 Landfill No. 4, Landfill No. 3, and Meandering Road Creek Soils
and Sediments
Landfill No. 4, Landfill No. 3, and Meandering Road Creek are grouped together because they
have similar contamination problems. The primary threat at Landfill No. 4 is from metals
contamination on or near the surface. Concentrations of arsenic, cadmium, and copper have the
potential to cause excess risk to terrestrial prey species (e.g., mice). Contamination in the soil at
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July 1996 4.0 Scope and Role of Response Actions
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Landfill No. 4 also caused a human health risk of 1.6 x 10"6 incremental lifetime cancer risk
(ILCR). This risk is within the acceptable risk range of 1.0 x 10"6 to 1.0 x 10^ ILCR, but exceeds
the lower limit of the risk range. The contaminant causing the human health risk is
benzo[a]pyrene (BAP).
Concentrations of copper, lead, and zinc at Landfill No. 3 also have the potential to cause excess
risk to mice. The contaminant silver, found in the sediments of Meandering Road Creek and the
inlet to Lake Worth, has the potential to cause excess risk to aquatic prey species (e.g., minnows
and aquatic organisms living in the sediments). It also was determined that Aroclor-1254 (a
polychlorinated biphenyl [PCB] compound) detected in the sediments in the inlet where
Meandering Road Creek enters Lake Worth has the potential to cause excess risk to
largemouth bass.
The selected action, No Action, for Landfill No. 4, Landfill No. 3, and Meandering Road Creek
manages the risk to acceptable levels for both human health and the environment and is the final
action planned. The goal of the selected action is to ensure risks to human health and the
environment are within acceptable limits. Remediation goals for Landfill No. 4, Landfill No. 3,
and Meandering Road Creek are presented in Section 7.0.
4.2 Paluxy Aquifer and Upper Sand Groundwater
No previous actions have addressed contamination in the Paluxy aquifer. The primary threat to the
Paluxy aquifer is TCE and 1,2-dichloroethene (1,2-DCE) contamination. Both TCE and 1,2-DCE
are at concentrations in the Paluxy aquifer above the maximum contaminant levels (MCLs). TCE
contamination in the Paluxy aquifer could cause a future human health risk that is above the upper
limit of the acceptable risk range (1.0 x 10"4 ILCR).
TCE and 1,2-DCE contamination is also present in the Upper Sand groundwater. This
groundwater is not used for drinking water purposes but is of concern because it is hydraulically
connected to the Paluxy aquifer and is the pathway through which contamination in the East
Parking Lot Plume reaches the Paluxy aquifer.
The selected response action of Groundwater Extraction and Treatment With Near-Zero Off-Gas
Emissions for the Paluxy aquifer and the Upper Sand groundwater addresses TCE and 1,2-DCE
contamination and is the final action planned. The purpose of this response action is to reduce
contamination levels in the Paluxy aquifer to below regulatory levels and to keep contamination
in the Upper Sand groundwater from causing contamination in the Paluxy aquifer above
remediation goals. Remediation goals for the Paluxy aquifer and the Upper Sand groundwater
are presented in Section 8.0.
4.3 East Parking Lot Groundwater Plume
The Air Force has initiated a groundwater extraction and treatment system in the East Parking
Lot as an interim measure for the Terrace Alluvial groundwater. This interim measure will
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4.0 Scope and Role of Response Actions July 1996
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continue operation until a final remedy is implemented for the contamination in the East Parking
Lot Plume.
Terrace Alluvial groundwater under Plant 4 and Naval Air Station Fort Worth is not used as a
drinking water source. However, TCE contamination in the East Parking Lot Plume is the source
of contamination in the Upper Sand groundwater and in the Paluxy aquifer under the East
Parking Lot.
The selected response action of Enhanced DNAPL/Groundwater Extraction and Treatment With
Air Stripping and Destruction of Contaminants for the East Parking Lot Plume addresses the
contamination that causes excess risk in the Paluxy aquifer and is the final response action
planned. The purpose of the response action is to reduce TCE concentrations in the East Parking
Lot Plume so contamination that reaches the Upper Sand groundwater will not exceed allowable
levels and, therefore, will not cause MCLs to be exceeded in the Paluxy aquifer. Remediation
goals for the East Parking Lot Plume are presented in Section 9.0.
4.4 Building 181
The Air Force has initiated a pilot-scale soil-vapor extraction system for TCE contamination in
the vadose zone under Building 181. Operation of the pilot-scale system is being continued as an
interim measure until the final remedial action is implemented.
TCE in the vadose zone under Building 181 is of concern because it is a source of TCE
contamination in the East Parking Lot Plume, which is the source of contamination in the Paluxy
aquifer. The selected response action of Soil-Vapor Extraction addresses the contamination
under Building 181 and is the final response action planned. The purpose of the response action
is to prevent TCE contamination in the vadose zone from exceeding allowable levels in the
Terrace Alluvial groundwater. Remediation goals for Building 181 are presented in
Section 10.0.
4.5 No Further Action Sites
No action is the selected remedy for soil at the No Further Action Sites. No action is necessary
because the concentrations of contaminants in the soil do not cause excess human health risk or
excess ecological risk. No monitoring of contamination levels in the soil is required for the
selected remedv.
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5.0 Summary of Site Characteristics
5.1 Climatic Conditions
The climate at Plant 4 is typified by hot summers and cool, dry winters. Mean annual
precipitation is 31.6 inches, with some precipitation occurring every month. Precipitation
.typically consists of a mixture of rain and snow during the late fall and winter months. Snowfall
amounts are generally greatest in January and February, when average snowfalls of 1 in. can be
expected. Although average snowfall amounts are typically low, snowfall amounts to 12 in.
during 1 month have been recorded.
During most of the year, the predominant wind direction is from the south. During the winter
months (i.e., December through February), the predominant wind direction is from the north.
Constant winds with an average speed of 7 knots are typical year round. The average cloud cover
in the area is 50 percent. Average relative humidity values range from 57 percent in July and
August to 70 percent in May. Average relative humidity is 63 percent; the area has a mean
annual temperature of 66 °F.
5.2 Geology
Geologic units of concern at the site include fill material, alluvium, terrace deposits, Goodland
Limestone, the Walnut Formation, and the Paluxy Formation. The following sections describe
the physical characteristics and thickness of each of these units in the vicinity of Plant 4.
Alluvial Deposits
Unconsolidated terrace and alluvial deposits are present at ground surface across much of
Plant 4. These deposits consist of interbedded clay, silt, sand, and gravel. The terrace alluvium
varies in thickness from several feet to 60 ft, reflecting the presence of hills and valleys in the
underlying bedrock surface. On the west and north sides of Plant 4, the terrace alluvial deposits
were excavated and replaced with the fill material now present in Landfill Nos. 1 through 4 and
in various waste pits.
Goodland Limestone and Walnut Formation
Limestone bedrock of the Goodland Limestone and the Walnut Formation underlies the terrace
alluvial deposits. The limestone has eroded to varying degrees, but averages approximately 25 to
35 ft thick. One area where the limestone aquitard is eroded or thin is known as the "Window
Area." The Window Area is in the vicinity of the East Parking Lot.
Paluxy Formation
The Paluxy Formation underlies the limestone deposits and averages approximately 170 to 180 ft
thick. It consists predominantly of fine-grained sandstone with several thin interbeds of shale. In
the vicinity of the East Parking Lot, the uppermost 5 to 10 ft of the Paluxy Formation is
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5.0 Summary of Site Characteristics July 1996
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characterized by layers of sandstone, shale, siltstone, and claystone. These characteristics of the
uppermost portion of the Paluxy Formation beneath the East Parking Lot, referred to as the
Upper Sand, are not found in the rest of the Plant 4 area. Figure 5-1 is a conceptual model of the
geology and groundwater areas for Plant 4.
5.3 Groundwater
As noted in the preceding section, three distinct types of subsurface material are of interest
beneath Air Force Plant 4, specifically, the terrace alluvium, the limestone aquitard (includes the
Goodland Limestone and Walnut Formation), and the Paluxy Formation. Groundwater is present
in the terrace alluvium and in the Paluxy Formation. Figure 5-1 is a schematic showing the
water-bearing zones in the terrace alluvium and in the Paluxy Formation.
Terrace Alluvial Flow System
The water-bearing or saturated portion of the terrace alluvium is referred to as the Terrace
Alluvial flow system. Most of the groundwater contamination at Plant 4 occurs in the Terrace
Alluvial flow system. Because the natural water quality of the Terrace Alluvial groundwater is
generally poor and because sustainable withdrawal rates are often small, Terrace Alluvial
groundwater is not used as a water supply in the Plant 4 area. Instead, wells are drilled into
underlying groundwater systems such as the Paluxy or Twin Mountains Formations.
Groundwater in the Terrace Alluvial flow system is separated from groundwater in the deeper
Paluxy Formation by the Goodland Limestone and the Walnut Formation. The limestone rock of
these two formations does not easily transmit water and behaves as an aquitard that serves to
restrict the downward flow of water from the terrace alluvium to the Paluxy Formation.
Natural recharge to the Terrace Alluvial flow system in the vicinity of Plant 4 occurs through
direct infiltration of precipitation and surface runoff. Extensive paved areas and buildings
restrict natural infiltration of precipitation over much of the Plant 4 site. In addition, recharge
occurs as leakage from Plant 4 pipe systems (including water-supply lines, fire-fighting pipe
systems, and cooling-water systems) and storm sewers. This recharge influences the direction
and rate of contaminant transport and contributes to the dilution of groundwater contamination.
Discharge from the Terrace Alluvial flow system occurs primarily as seeps into Meandering
Road Creek, base flow into Farmers Branch Creek (which flows into the West Fork of the Trinity
River), and as vertical leakage through the aquitard into the Paluxy Formation.
Discharge through the aquitard into the Paluxy Formation is generally confined to a localized
area under the East Parking Lot where the limestone rock of the aquitard is relatively thin. In this
area, referred to as the Window Area (Figure 5-1), groundwater drains slowly from the bottom of
the Terrace Alluvial flow system, passes vertically through the thin section of the limestone
aquitard, and enters the Upper Sand portion of the Paluxy Formation.
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July 1996 5.0 Summary of Site Characteristics
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The Decision Summary
5.0 Summary of Site Characteristics
FINAL
5-3
July 1996
-------
Paluxy Formation
The Paluxy aquifer is the continuously saturated portion of the Paluxy Formation. In the Plant 4
area, the Paluxy Formation is approximately 170 to 180 ft thick. The upper 10 to 20 ft of the
formation is generally unsaturated; the lower 150 to 160 ft of the formation is continuously
saturated and constitutes the Paluxy aquifer.
In the vicinity of the East Parking Lot, the uppermost portion of the Paluxy Formation is
composed of low-permeability rock that is recharged by groundwater seeping through the
aquitard from the overlying Terrace Alluvial flow system. This setting has produced a localized
area beneath the East Parking Lot in which the uppermost portion of the Paluxy Formation is
variably saturated. This localized, variably saturated portion of the Paluxy Formation is referred
to as the Upper Sand. Groundwater in the Upper Sand is separated from groundwater in the
Paluxy aquifer by approximately 10 ft of unsaturated Paluxy Formation sandstone and shale
(Figure 5-1).
Natural recharge to the Paluxy aquifer occurs as infiltration of precipitation falling on formation
outcrops north and west of Plant 4 and as infiltration of water from the south and east portions of
Lake Worth. Limited additional recharge occurs as infiltration of water from streams flowing
across exposed sections of the formation.
Discharges from the Paluxy aquifer include withdrawals from private and municipal wells and
base flow to streams during dry periods. Discharge also occurs as seepage into Lake Worth
along the northwest portion of the lake.
Groundwater flow in the Paluxy aquifer is generally from west to east, reflecting the effect of
large groundwater withdrawals for municipal, commercial, and private use in the vicinity of east
Fort Worth and Dallas. Near Plant 4, recharge from Lake Worth and pumping from White
Settlement wells has produced flow directions directed to the southeast.
5.4 Surface Water
The primary surface water features at Plant 4 include Meandering Road Creek, Lake Worth, and
Farmers Branch Creek. Farmers Branch Creek is on Naval Air Station Fort Worth but was
included in the Plant 4 remedial investigation.
Meandering Road Creek borders Plant 4 to the west and flows north to Lake Worth. Stream flow
in Meandering Road Creek is intermittent and is derived from rainfall runoff. Groundwater from
the Terrace Alluvial flow system also contributes to flow in Meandering Road Creek.
Farmers Branch Creek originates in White Settlement and flows easterly across the southern
portion of Naval Air Station Fort Worth and then empties into the West Fork of the Trinity River.
Farmers Branch Creek also flows intermittently and derives most of its flow from rainwater
runoff, with some contribution from groundwater in the Terrace Alluvial flow system.
5-4 FINAL The Decision Summary
July 1996 5.0 Summary of Site Characteristics
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Lake Worth borders Plant 4 to the north. An inlet from Lake Worth that connects with
Meandering Road Creek also borders the northwest portion of Plant 4. The lake was constructed
in 1914 as a municipal water supply for the city of Fort Worth
5.5 Sources and Characteristics of Contamination
Soil and Sediment
During the remedial investigation, approximately 2,500 soil and sediment samples were collected
between February 1991 and May 1992 at various sites to assess potential effects of past
operations. The following sites were identified as having contaminant concentrations that
potentially pose an excess risk to human health or the environment or exceed the lower threshold
of the acceptable risk range: (1) soil associated with Landfills No. 3 and No. 4, (2) sediment
along Meandering Road Creek and the inlet of Meandering Road Creek to Lake Worth, and
(3) soil under Building 181. The remaining sites on Plant 4 are discussed in the "No Further
Action Sites" section. Figure 2-1 shows the locations of areas investigated at Plant 4.
Landfill No. 3
Landfill No. 3, located along the western boundary of Plant 4 adjacent to Meandering Road
Creek, is a grass-covered area approximately 3 acres in size (Figure 5-2). The landfill is
presently enclosed by a chainlink fence. Miscellaneous wastes, including mixed oils and
solvents, were discarded at this site from 1942 to 1945; the landfill was inactive from 1945 to
1966. Dirt and rubble were used to fill and grade the landfill during 1966 and 1967.
Fifty-six soil samples were collected at 2-ft intervals from depths to 19.3 ft, in 16 soil borings
drilled in Landfill No. 3. The ranges of concentrations for key chemicals of potential concern
(COPCs) detected in samples from Landfill No. 3 are
• TCE (not detected [ND]-19 milligram per kilogram [mg/kg])
Cadmium (ND-96.2 mg/kg)
Copper (ND-5,590 mg/kg)
• Lead (2-10,400 mg/kg)
• Zinc (3.8-17,400 mg/kg)
The highest metal concentrations were detected in samples collected on the western edge of the
landfill and east of Meandering Road Creek. The two Landfill No. 3 samples shown on
Figure 5-2 (CS-005 and CS-007) are the only two samples with concentrations of metals high
enough to potentially cause excess ecological risk. The highest concentrations of the other
constituents were reported for samples collected in historic drainage ditches that have been filled.
The Decision Summary FINAL 5-5
5.0 Summary of Site Characteristics July 1996
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LEGEND
5MI-01M SM4PL£ LOCATION
(0-5) SAMPLE DEPTH INTERVAL (FT)
850 CONCENTRATION
CS-007
0-2) 1580 COPPER /
0-2) 10400 LEAD
0-2) 17400 ZINC /
MEANDERING ROAD CREEK
C-i) 15
C-5) 3000 COPPER
CHROME PIT No. 3
Figure 5-2. Contamination That May Cause Excess Ecological Risk at Air Force Plant 4
5-6
July 1996
FINAL
The Decision Summary
5.0 Summary of Site Characteristics
-------
Landfill No. 4
Landfill No. 4, located near the southwest boundary of the Plant 4 facility, occupies
approximately 2 acres of land between Bomber Road (sometimes referred to as Meandering
Road) and Meandering Road Creek (Figure 5-2). Landfill No. 4 is grass covered but is not
capped with an engineered cap. This landfill was used for disposal of construction rubble from
1956 to the early 1980s. Other types of wastes may have been disposed there between 1966 and
1973. These wastes are thought to have included small quantities of solvents, oils, fuels, and
thinners.
Soil borings were drilled to bedrock and samples were collected at 2-ft intervals in Landfill
No. 4. The highest concentrations of metals and semivolatile organic compounds (S VOCs) were
detected in samples collected along the western shoulder of the landfill. The three Landfill No. 4
samples shown on Figure 5-2 (GMI-OIM, GMI-04M, and GMI-05M) are the only samples near
the surface with metals concentrations high enough to potentially cause excess ecological risk.
The ranges of concentrations for key COPCs detected in all samples from Landfill No. 4 are
• TCE (ND-0.03 mg/kg)
• Benzo[0]pyrene (ND-13 mg/kg)
Arsenic (2.4-170 mg/kg)
Cadmium (ND-160 mg/kg)
Copper (ND-3,200 mg/kg)
• Zinc (4.6-12,200 mg/kg)
Meandering Road Creek and Lake Worth
Sediment samples were collected at seven locations along Meandering Road Creek. The ranges
of concentrations for key COPCs detected in samples of Meandering Road Creek sediments are
• Arsenic (3.1-6.1 mg/kg)
• Cadmium (ND-2.4 mg/kg)
Copper (13.4-17.8 mg/kg)
Lead (10-77.4 mg/kg)
Silver (ND-6.9 mg/kg)
• Zinc (17.8-87 mg/kg)
The Decision Summary FINAL 5-7
5.0 Summary of Site Characteristics July 1996
-------
Twenty-five Lake Worth sediment samples were collected offshore north of Plant 4, in a cove at
the northwest corner of Plant 4, $nd in the inlet that connects to Meandering Road Creek.
Several organic compounds, including TCE, were detected in seven sediment samples at
concentrations less than 1.0 mg/kg. SVOCs were detected at concentrations between 1.3 and
7.9 mg/kg. In addition, two PCB compounds, Aroclor-1254 and Aroclor-1260, were detected in
two sediment samples at concentrations of 0.1 and 0.11 mg/kg, respectively. The three
Meandering Road Creek and Lake Worth samples on Figure 5-2 (SW-6, LW-2, and LW-3) are
the only samples with concentrations high enough to potentially cause excess risk. The ranges of
concentrations for key metal COPCs detected in samples of Lake Worth sediments are
• Arsenic (3.5-6 mg/kg)
• Cadmium (0.4-11.4 mg/kg)
Copper (8.5-88.4 mg/kg)
Lead (8-444 mg/kg)
Silver (ND-13 mg/kg)
Zinc (21.9-303 mg/kg)
Building 181
The Assembly Building/Parts Plant is a mile-long building located in the approximate center of
Plant 4 (Figure 2-1). Building 181, the Chemical Process Facility, is part of the Assembly
Building/Parts Plant. Past spills of TCE have reportedly occurred within the Chemical Process
Facility. Trenches, sumps, floor drains, and buried pipelines are present throughout this
manufacturing facility and are possible pathways for soil contamination under this building.
The key COPC at Building 181 is TCE. The presence of this organic compound was detected
at concentrations ranging from ND to 0.22 mg/kg in samples collected from 35 soil borings
drilled to depths of approximately 59 ft near the perimeter of Building 181. However, soils
saturated with TCE were found during the installation of a soil-vapor extraction system under
Building 181. No analyses were performed on these saturated soils. TCE in the soil under
Building 181 is the main source of TCE contamination in the East Parking Lot Plume.
Groundwater
Terrace Alluvial Flow System
The three flow directions within the Terrace Alluvial flow system beneath the Assembly
Building/Parts Plant have resulted in three separate plumes with organic constituents. These
plumes are (1) the East Parking Lot Plume, (2) the West Plume, and (3) the North Plume
(Figure 5-3). Thirty-seven monitoring wells were installed in the Terrace Alluvial flow system,
ranging in depth from 12.3 to 58.8 ft.
5-8 FINAL The Decision Summary
July 1996 5.0 Summary of Site Characteristics
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r?
3 s:
s.2
t/i 3
S 1
>
r
£.
y:
VO I
ON vO
Assembly Building/
Suspected DNAPL*
Distribution * 7
North Plume
Approximate
Location of
Landfills No. 4
Dissolved TCE
Distribution
1000— H9/L Trichloroethene
100 — jtg/L Trichloroethene
Area of Contamination
Approximate Direction
of Groundwater Flow
Figure 5-3. Contamination in the Terrace Alluvial Flow System at Air Force Plant 4
-------
The largest plume of groundwater contamination is the East Parking Lot Plume. This plume
begins at the groundwater divide located south and west of the Assembly Building/Parts Plant
and Building 12. The plume also has source areas west of the Assembly Building in the vicinity
of Warehouse Building 14 and Plant Maintenance Building 88 (Figure 2-1). From the main
source area south of the Parts Plant, the plume extends in an easterly and northeasterly direction
toward the East Parking Lot and later spreads east and southeast in the direction of Naval Air
Station Fort Worth (Figure 5-3). On Naval Air Station Fort Worth, the plume has merged with
Naval Air Station Fort Worth source areas located at Naval Air Station Fort Worth Landfills
No. 4 and No. 5, Landfill No. 6 north of Farmers Branch Creek, and the North Apron.
The East Parking Lot Plume appears to have several sources of contamination. One major
potential source is the degreaser tanks T-534 and T-544 located within Building 1.81. One
documented release from tank T-534 was discovered in June 1991, but the volume of this TCE
release is not known. The size of the East Parking Lot Plume indicates other releases of organic
solvents may have occurred at this location during the past 40 years of operation.
Other potential sources of VOC contamination in the western portion of the East Parking Lot
Plume include Chrome Pits Nos. 1, 2, and 3; Die Yard Chemical Pits; FDTA-5; and the
Wastewater Collection Basins. These potential sources are located along the groundwater divide
in the south-central portion of Plant 4. Historically, high concentrations (approaching saturation)
of TCE have been reported in the south central portion of Plant 4.
The extent of the East Parking Lot Plume is defined by elevated concentrations of TCE, cis- and
rra/7s-l,2-dichloroethene, vinyl chloride, 1,1,2-trichloroethane (TCA), 1,1-dichloroethane
(DCA), 1,1-dichloroethene, methylene chloride, tetrachloroethene (PCE), benzene, toluene,
xylene, acetone, chlorobenzene, and chloroform. By far the greatest occurrence of any single
organic compound is TCE. During the RI, TCE was detected in concentrations exceeding the
detection limit in samples from 50 monitoring wells. All TCE results listed exceed the MCL
ofSpg/L.
During the RI, the highest TCE concentrations detected in samples from the East Parking Lot
Plume were from monitoring wells located along a paleochannel in the East Parking Lot,
including wells HM-094y W-149, W-158, and W-159. TCE concentrations in samples from
these monitoring wells ranged from 15,000 to 31,000 Mg/L. The magnitude of these
concentrations suggests that TCE may be migrating along the paleochannel in the form of a dense
nonaqueous phase liquid (DNAPL). Before the RI, TCE concentrations exceeding 10,000 |ig/L
were reported in samples from monitoring wells F-218, F-220, and HM-082. Samples from
monitoring well F-220 have had TCE concentrations in excess of 100,000 ng/L; monitoring well
F-220 is located within Chrome Pit No. 3.
The second largest plume of groundwater contamination in the Terrace Alluvial flow system is
the West Plume (Figure 5-3). The West Plume extends from near the Assembly Building/Parts
Plant westward toward Meandering Road Creek. Groundwater flow is toward the west. TCE
concentrations in samples from the West Plume range from ND to 490,000 |jg/L near FDTA-2.
Potential source areas for the West Plume include chlorinated organic solvent contamination
from FDTA-2, leachate contamination from Landfills No. 1 and No. 3, and leaking fuel-line
5-10 FINAL The Decision Summary
July 1996 5.0 Summary of Site Characteristics
-------
contamination from an area between Building 14 and the Parts Plant. Because of the
ground water divide, Chrome Pit No. 3, the Die Yard Chemical Pit, and Fire Department Training
Area No. 5 can also be considered potential source areas.
The North Plume underlies the north portion of the Assembly Building/Parts Plant (Figure 5-3).
Groundwater flow is to the north. TCE concentrations in samples from this plume range from
ND to 530 ng/L. In addition, JP-4 jet fuel has been identified on top of the groundwater in six
monitoring wells in the vicinity of the North Plume. The potential source of this contamination
is leaking fuel supply lines and storage tanks surrounding the Jet Engine Test Stand.
Groundwater flow in the North Plume is toward Lake Worth, but the flow is restricted by higher
elevations of bedrock. Contaminant concentrations in samples from Lake Worth have not
exceeded MCLs.
Paluxy Aquifer and Upper Sand Groundwater
Five monitoring wells were installed in the Paluxy aquifer, ranging in depth from 94 to 157 ft.
TCE has been detected in samples of the Upper Sand groundwater beneath Plant 4 in the vicinity
of the Window Area (Figure 5-4). Vertical migration of TCE from the Terrace Alluvial flow
system has likely occurred through the Window Area into the Upper Sand groundwater. TCE
concentrations in samples of the Upper Sand groundwater range from ND to 11,000 |ig/L.
TCE has been detected in Paluxy aquifer samples from an area near Landfill No. 3 and near the
East Parking Lot (Figure 5-5). TCE most likely reached the area under Landfill No. 3 by vertical
migration down a monitoring well that may not have been constructed according to design
specifications. This well has been abandoned and sealed, thus preventing further TCE
contamination. TCE concentrations in samples from the Paluxy aquifer near Landfill No. 3 range
from ND to 100 |ug/L. As shown in Figure 5-5, the lateral extent of TCE in the Paluxy aquifer is
relatively small. TCE concentrations in the Paluxy aquifer near the East Parking Lot currently
are less than MCLs.
Surface Water
To assess the potential effect of chemical constituents on surface-water features, water samples
were collected from Meandering Road Creek, Farmers Branch Creek, and Lake Worth. Forty
samples were collected during seven sampling rounds from Meandering Road Creek between
February 1990 and October 1991; nine surface water samples were collected from Lake Worth in
October 1991, and up to five locations in Farmers Branch Creek were sampled quarterly between
April 1992 and February 1995. COPCs identified in the BRA for surface water are the VOCs
cw-l,2-DCE and vinyl chloride.
Meandering Road Creek
Neither vinyl chloride nor cw-l,2-DCE was detected in 40 water samples obtained from
Meandering Road Creek. However, the presence of TCE was detected in 7 of the 40 samples at
concentrations ranging between 8 and 140 pg/L.
The Decision Summary FINAL 5-11
5.0 Summary of Site Characteristics July 1996
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5-12
July 1996
FINAL
The Decision Summary
5.0 Summary of Site Characteristics
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The Decision Summary
5.0 Summary of Site Characteristics
FINAL
5-13
July 1996
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Farmers Branch Creek
Concentrations of TCE and cw-l,2-DCE have been detected in samples from five surface-water
sampling points in Farmers Branch Creek since 1992. TCE concentrations were highest in 1992
when 880 ^ig/L was measured in a sample. Since that time, TCE concentrations have ranged
between 1 and 500 |ag/L. Concentrations of ds-l,2-DCE also were highest in 1992 when
380 (ig/L was detected in a sample; concentrations since that time have ranged between 84 and
250 ng/L.
Lake Worth
Water samples were collected from seven sampling locations in Lake Worth along the northern
border of Plant 4. The presence of only one VOC, carbon disulfide, was detected in the Lake
Worth surface-water samples collected north of Plant 4. This compound was detected in three
samples at concentrations ranging from 18 to 200 |ug/L. Concentrations of no other volatile,
semivolatile, or metal compounds were detected.
No Further Action Sites
Information on the sources and characteristics of soil contamination at the No Further Action
Sites is presented in Section 11.0, along with the justification for the selected remedy for each
site. Figure 2-1 shows the locations of the No Further Action Sites.
5-14 FINAL The Decision Summary
July 1996 , 5.0 Summary of Site Characteristics
-------
6.0 Summary of Site Risks
An evaluation of the potential risks to human health and the environment from site contaminants
was conducted as part of the BRA, which was part of the RL The methods used to develop the
human health risk assessment are based on EPA Risk Assessment Guidance for Superfund—
Human Health Evaluation Manual (EPA 1989a). The method used to develop the ecological
risk assessment are based on Framework for Ecological Risk Assessment (EPA 1992).
The objectives of the BRA were (1) to identify COPCs for human health and ecological risk, -
(2) to provide a basis for determining residual chemical levels that are adequately protective of
human health and the environment, (3) to help determine if response actions are necessary at the
site, and (4) to provide a basis for comparing potential effects on human health of various
remedial alternatives. The BRA consists of two parts: a quantitative human health risk
assessment and a semiquantitative study of the effects on significant ecological communities at
and near Plant 4 (i.e., the ecological risk assessment).
The approach for the Plant 4 risk assessment was to first conduct a sitewide risk assessment,
using sampling data from across the site, to determine which contaminants and media were
present in sufficient concentrations and quantities to pose an unacceptable risk for the site as a
whole. The sitewide assessment was used to narrow the focus of evaluations performed for
individual units (e.g., landfills, tanks); only contaminants that were unacceptable from a sitewide
standpoint were considered in evaluating individual units. The sitewide risk assessment also was
used to develop contaminant concentration levels that were deemed to be acceptable in each
medium of concern. These acceptable levels were used in developing preliminary remediation
goals (PRGs).
6.1 Human Health Risk Assessment
Chemicals of Potential Concern
The initial step in developing the human health risk assessment is to identify the site-related
COPCs. COPCs are hazardous compounds that may be present at or released from a site that
may pose health risks to humans coming in contact with them. COPCs were determined for four
different media at Plant 4: groundwater, surface water, soil and sediments, and air. Table 6-1
presents the list of COPCs (and associated Chemical Abstracts Services [CAS] Registry
Numbers) at Plant 4 and indicates the media with which they are associated. The list includes
noncarcinogenic and carcinogenic compounds.
Exposure Assessment
The objective of the exposure assessment is to identify the populations that may be most exposed
to site-related chemicals; the pathways by which exposure may occur; and the magnitude,
frequency, and duration of the exposures. The results of the exposure assessment are the
pathway-specific chemical intakes of identified COPCs.
The Decision Summary FINAL 6-1
6.0 Summary of Site Risks July 1996
-------
Table 6-1. Chemicals of Potential Concern*
CAS No.
7440-38-2
513-77-9
71-43-2
56-55-3
50-32-8
205-99-2
207-08-9
7440-43-9
7440-47-3
218-01-9
156-59-2
7440-50-8
95-50-1
106-46-7
75-34-3
75-35-4
540-59-0
105-67-9
100-41-4
206-44-0
76-13-1
74VJ-92-I
74^)-l)7-h
75-(H>-2
91-57-6
(>S-4X-"
91-20-3
7440-02-0
85-0 1-X
129-00-0
IOS-88-3
71-55-6
Chemical
Arsenic
Barium
Benzene
Benzofa] anthracene
Benzofajpyrene
Benzof b] fluoranthene
Benzo[£] fluoranthene
Cadmium
Chromium
Chrvsene
c/.v-l ,2-Dichloroethene
Copper
1 ,2-Dichlorobenzene
1 ,4-Dichlorobenzene
1 . 1 -Dichloroethane
1,1 -Dichloroethene
1 .2-Dichloroethene
2,4-Dimethylphenol
Ethvlbenzene
Fluoranthene
Freon 1 1 3
Lead
Mercurv
Methvlene Chloride
2-Mcthylnaphthalene
Mcihylphcnol
Naphthalene
Nickel
Phenanthrene
Pvrene
Toluene
IJJ-Trichloroethane
GTOtmdwater
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Surface Water
X
Sofl
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Air
X
X
X
X
X
Exposure concentrations are provided in Tables 6-2 through 6-5 for chemicals and media marked with an X.
6-2
July 1996
FINAL
The Decision Summary
6.0 Summary of Site Risks
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Table 6-1 (continued). Chemicals of Potential Concern8
CAS No.
79-01-6
95-63-6
33
75-01-4
7440-66-6
Chemical
Trichloroethene
1 ,2,4-Trimethylbenzene
1 3.5-Trimethvlbenzene
Vinyl Chloride
Zinc
Groondwattr
X
Surface Water
X
Sofl
X
X
Air
X
X
X
X
Exposure concentrations are provided in Tables 6-2 through 6-5 for chemicals and media marked with an X.
Exposed Populations and Exposure Pathways
The populations on and near the site were characterized to assess the likelihood and extent of
exposure to site contaminants. Plant 4 is adjacent to residential communities on the south and
west sides. The public has recreational access to Lake Worth, which borders the north side of the
site. Naval Air Station Fort Worth lies to the east of the site. Plant 4 has been a military facility
since 1941. It covers 602 acres, of which 70 percent is covered by asphalt, concrete, or
buildings. Because of the history of this facility and the existing military and industrial
infrastructure, it is anticipated that Plant 4 and Naval Air Station Fort Worth will continue to be
used for industrial purposes while the surrounding areas will continue to be residential.
The site conceptual exposure model presented in Figure 6-1 illustrates the pathways by which
contaminants can make their way from contaminant sources to potential receptors. The model
indicates that the major sources of contamination are surface and subsurface soils (including
landfill contents) and the groundwater in the Terrace Alluvial flow system. The complete
exposure pathways that were used in the BRA are
• Ingestion of groundwater from White Settlement production wells by future
residents (adults).
• Inhalation of and dermal contact with VOCs from groundwater by future residents (adults)
during showering in water from White Settlement production wells.
• Dermal contact with contaminated surface water (Lake Worth) by current residents (adults).
• Ingestion and dermal contact with contaminated soil by current Plant 4 personnel.
• Inhalation of contaminated air by current Plant 4 personnel.
The Decision Summary
6.0 Summary of Site Risks
FINAL
6-3
July 1996
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6-4
July 1996
FINAL
The Decision Summary
6.0 Summary of Site Risks
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Exposure Point Concentrations
Exposure point concentrations are the chemical concentrations to which a receptor is assumed to
be exposed to when contact is made with a specific environmental medium. Tables 6-2 through
6-5 provide concentrations used in the BRA for each contaminant in each medium.
Concentrations for future exposure estimates for groundwater and surface water were made using
a 30-year interval. To estimate potential risks associated with using water from White Settlement
production wells, the concentrations were calculated in an analytical groundwater contaminant
transport model. To be conservative, the highest calculated concentrations were used. Surface
water exposures were modeled for swimming only. The highest reported concentrations were
used in the model for a conservative estimate.
For soil and air, the upper 95-percent confidence limit of the arithmetic means of concentrations
measured in soil and air during characterization of the site were used as exposure concentrations.
A concentration of one-half the sample quantitation limit was used for all nondetects in the
soil samples.
Table 6-2. Concentrations for Chemicals of Potential Concern in Groundwater
CAS No,
7440-39-3
7440-47-3
75-34-3
540-59-0
108-88-3
79-01-6
Chemical
Barium
Chromium
1 . 1 -Dichloroethane
1 ,2-Dichloroethene
Toluene
Trichloroethene
Concentration
(udl)
100
6.7
14
370
7.0
980
ReceotorWell
P-12UN
WS-12
WS-12
WS-12
WS-2
WS-12
Table 6-3. Concentrations for Chemicals of Potential Concern in Surface Water
CAS No.
156-59-2
75-01-4
Chemical
r/.v- 1 ,2-Dichloroethvlene
Vinvl Chloride
Concentration
(LLti/L)
430
14
The Decision Summary
6.0 Summary of Site Risks
FINAL
6-5
July 1996
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Table 6-4. Concentrations for Chemicals of Potential Concern in Soil
CASNo.
71-43-2
56-55-3
50-32-8
205-99-2
207-08-9
206-44-0
7440-43-9
7440-47-3
218-01-9
7440-50-8
7439-92-1
91-20-3
7440-02-0
85-01-8
129-00-0
7440-66-6
Chemical - '
Benzene
Benzofalanthracene
Benzofalovrene
BenzoFblfluoranthene
Benzof&lfluoranthene
Fluoranthene
Cadmium
Chromium
Chrvsene
Conner
Lead
Naphthalene
Nickel
Phenanthrene
Pvrene
Zinc
Concentration
fmc/kfir)
0.180
1.662
1.590
1.868
1.551
2.701
3.963
206.1
1.704
2070
14.20
1.376
193.3
2.570
1.915
6174
Table 6-5. Concentrations for Chemicals of Potential Concern in Air
CAS No.
71-47-2
7440-47-3
76-13-1
7439-92-1
75-OQ-2
"^-Ol-ft
i)5-63-6
IOX-67-8
7440-66-6
Chemical
Benzene
Chromium
Freon 113
Lead
Methvlene Chloride
Trichloroethene
1 ,2,4-Tnmethvlhenzene
1 ,3,5-Trimethvlhen7.ene
Zinc
Concentration
(LLV/m*}
0.89
0.0043
1.66
0.00624
0.245
1.26
0.60
0.269
0.0253
6-6
July 1996
FINAL
The Decision Summary
6.0 Summary of Site Risks
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Chemical Intake
The magnitude of human exposures to COPCs at the site is described as the potential dose or
intakes by each receptor. The magnitude of exposure to a chemical (or intake) is a function of a
number of variables, including exposure concentration and variables that describe the exposed
population (e.g., contact rate, exposure frequency and duration, body weight). Each of the
variables can be described by a range of parameters. For purposes of this assessment, two
measures of exposure have been defined using two sets of exposure variables: a reasonable
maximum exposure (RME) and a central tendency (CT) exposure (when applicable).
The RME gives a reasonable upper-bound estimate of the potential magnitude of an individual
exposure to chemicals from the sites. The intent of the RME is to estimate a conservative, well
above average exposure case that is still within the range of possible exposures. CT provides a
more typical or average value than RME. Table 6-6 lists the exposure assumptions used in the
BRA. The majority of these assumptions are derived from EPA guidance (EPA 199la,
EPA 1989a). Tables 6-7 through 6-9 present calculated intakes for each COPC via each
relevant exposure pathway. Note that intake values are given for both carcinogenic and
noncarcinogenic effects because carcinogenic intakes are averaged over an expected lifetime for
an individual, whereas noncarcinogenic intakes are based on actual expected daily exposures
during the period of exposure.
Toxicity Assessment
The purpose of the toxicity assessment is to evaluate the toxicity of site-related COPCs and to
estimate the dose-response relationship for each of these chemicals. The evaluation of the
toxicity of the site-related chemical determined if exposure to a chemical could cause an increase
in the incidence of a particular adverse health effect (carcinogenic or noncarcinogenic) and if the
adverse health effect would likely occur in humans. The second step, dose-response relationship,
quantitatively evaluated the toxicity information and characterized the relationship between the
dose of the chemical received and the potential for incidence of adverse health effects in an
exposed population.
Noncarcinogenic responses are generally characterized by a threshold: a certain minimum intake
of a substance below which the likelihood of adverse deleterious effects is expected to be low.
Carcinogenic responses are assumed to have no threshold. This assumption means that there is
some cancer risk no matter how small the dose.
The two principal indices of toxicity are the reference dose (RfD) and slope factor (SF). These
values are derived by EPA for the most commonly occurring chemicals and the most toxic
chemical generally associated with chemical releases to the environment for which adequate,
scientific, dose-response data are available. An RfD is the intake or dose per unit of body weight
per day that is unlikely to result in noncarcinogenic (toxic) effects to human populations,
including sensitive subgroups (e.g., the very young or old).
The Decision Summary FINAL 6-7
6.0 Summary of Site Risks July 1996
-------
Table 6-6. Parameters Used To Estimate Exposure in Baseline Risk Assessment
Parameter
Value Used*
RME
CT
Rationale
Ingestion of Groundwater From White Settlement Production Wells in 30 Years
Adult/Child Water Ingestion Rate (liters per day)
Exposure Frequency (days per year)
Exposure Duration (years)
Adult/Childb Body Weight (kg)
2/1
350
30
70/16
Occupational Exposure: Adult Ingestion of Contaminated Soil
Adult Ingestion Rate (milligrams per day)
Exposure Frequency (days per year)
Exposure Duration (years)
Body Weight (kg)
50
250
25
70
1.4
9.0
9.0
EPA 1991b/EPA 1989b; Rauscher 1992 for CT
Exposure is assumed to be daily
Upper 90th percentile for time spent in one residence (EPA
1991b); Rauscher 1992 for CT
EPA 1991b
EPA 1991b
Assumes workers are exposed 5 days per week, 50 weeks
per year
Assumes 25-year work period: Rauscher 1992 for CT
EPA 1991b
Inhalation of Volatile Organic Compounds During Showering (White Settlement wells, 30 years in the future)
Adult Inhalation Rate (cubic meters per hour)
Exposure Time (hours per day)
Exposure Frequency (davs per year)
Exposure Duration (years)
Body Weight (kg)
Dermal Exposure While Showering
Skin Surface Area (square meters)
Exposure Time (hours per day)
Exposure Frequency (days per year)
Exposure Duration (years)
Body Weight (kg)
0.6
0.2
350
30
70
9.0
Upper-bound rate for daily, indoor, residential activities (EPA
1991b)
Reasonable maximum (EPA 1991b)
Reasonable maximum
Upper 90th percentile for time spent in one residence (EPA
1991b); Rauscher 1992 for CT
EPA 1991b
1.94
0.2
350
30
70
9.0
50th percentile total body surface area (EPA 1989a)
Reasonable maximum
Reasonable maximum
Upper 90th percentile for time spent in one residence (EPA
1991b): Rauscher 1992 forCT
EPA 1991b
Dermal Exposure to Contaminated Surface Water During Swimming
Skin Surface Area (square meters)
Exposure Time (hours per day)
Exposure Frequency (days per year)
Exposure Duration (years)
•iodv ueiL'ht (ki!)
1.94
0.5
60
30
70
9.0
Occupational Exposure: Adult Inhalation of Contaminated Air
Adult Inhalation Rate (cubic meters per hour)
ixpoxure Tune (hours per dav)
Exposure Frcquenc) (days per year)
•xposure Duration (years)
Bodv Weight (kL'i
2.5
8
250
25
70
9.0
50th percentile total body surface area (EPA 1989a)
Reasonable maximum
Reasonable maximum
Upper 90th percentile for time spent in one residence (EPA
1991b); Rauscher 1992 for CT
EPA 1991b
Upper-bound occupational rate (EPA 1991b)
Worst-case assumption
Assumes workers are exposed 5 days per week, 50 weeks
per year
Assumes 25-year work period; Rauscher 1992 for CT
EPA 1991b
The left side of this column contains data for RME calculations; the right side of the column is for CT calculations. CT data are only
provided when applicable.
Child exposure values are provided for comparison.
6-8
July 1996
FINAL
The Decision Summary
6.0 Summary of Site Risks
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Table 6-7. Results of the Exposure Assessment—Ingestion
Potentially Exposed
Population
Chemical
Chnmk Dafly Intake
(rag**1**1)
Carcinogenic Noncarrinogenk
Effects Effects
Ingestion of Groundwater from White Settlement Production Wells in 30 Years
Residents and
Plant 4 Workers
Barium
Chromium
U-Dichloroethane
1,2-Dichloroethene
Toluene
Trichloroethene
a
a
a
a
a
1.2x 10 2
Ingestion of Contaminated Soil
Plant 4 Workers
Benzene
Benzo[a]anthracene
Benzo[fl]pyrene
Benzofb] fluoranthene
Benzoffc] fluoranthene
Cadmium
Chromium
Copper
Fluoranthene
Naphthalene
Nickel
Phenanthrene
Pvrene
Zinc
3.1 x 10-"
2.9 x 10 7
2.8 x 107
3.3 x 107
2.7 x 10 7
a
a
a
a
u
a
a
a
a
2.7 x 10 •>
1.8x10^
3.8 x 10^
l.OxlO2
1.9x 10^
b
8.8 x 10 8
b
b
b
b
1.9x lO^1
1.0 x 10-"
l.Ox 10 >
UxlO-11
6.7 x 10 7
9.5 x 10-'
b
9.4 x 107
3.0 x 10'
Chronic daily intake (CDI) for carcinogenic effects not calculated for chemicals not considered to be potential carcinogens
or for chemicals without slope factors.
CDI for noncarcinogenic effects not calculated because RfDs are not available.
The Decision Summary
6.0 Summary of Site Risks
FINAL
6-9
July 1996
-------
Table 6-8. Results of the Exposure Assessment—Inhalation
Potentially
Exposed
Population
Chemical
Chronk Daily Intake
(mrkg^)
Carcinogenic Noncaranogenic
Effects Effects
Inhalation of Volatile Organic Compounds During Showering With Groundwater (White Settlement wells in 30 years)
Residents
1,1-Dichloroethane
1 ,2-Dichloroethene
Toluene
Trichloroethene
a
a
a
9.2 x 10 3
3.1 x lO^1
b
1.5 x 10"1
b
Inhalation of Chemicals in Air
Plant 4 Workers
Benzene
Chromium
Freon 113
Lead
Methylene Chloride
Trichloroethene
1 ,2,4-Trimethylbenzene
1 ,3,5-Trimethylbenzene
Zinc
6.2 x 10 5
3.0 x 10 7
a
a
1.7x 10s
8.8 x 105
a
a
u
1.7 x 10^
8.4 x 107
b
b
4.8 x 10'5
b
b
b
5.0 x 106
'^Chronic daily intake (CDI) for carcinogenic effects not calculated for chemicals not considered to be potential carcinogens.
GDI for noncarcmogenic effects not calculated because RfDs are not available.
6-10
July 1996
FINAL
The Decision Summary
6.0 Summary of Site Risks
-------
Table 6-9. Results of the Exposure Assessment—Dermal
Potentially
Exposed
Population
Chemical
Chronic Daily Intake
(mrkr1**1)
Carcinogenic Noncartinogenic
Effects Effects
Dermal Exposure to Chemicals of Concern During Showering With Groundwater (White Settlement wells in 30 years)
Residents
Barium
Chromium
1,1-Dichloroethane
1,2-Dichloroethene
Toluene
Trichloroethene
a
a
a
a
a
4.5 x 103
4.5 x 1(V*
7.1 x 10 7
6.3 x 10 7
1.7 x 105
3.7 x KT1
b
' Dermal Exposure to Chemicals of Concern While Swimming in Lake Water
Residents
cis- 1 ,2-Dichloroethene
Vinyl Chloride
a
1.1 x 107
8.2 x 10-*
b
Chronic daily intake (CDI) for carcinogenic effects not calculated for chemicals not considered to be potential carcinogens.
CDI for noncarcinogenic effects not calculated because RfDs are not available.
SF is used to estimate an upper-bound probability of an individual developing cancer as a result
of exposure to a potential carcinogen. Carcinogens with EPA-derived SFs are also given an EPA
weight-of-evidence classification; this classification groups potential carcinogens according to
the quality and quantity of carcinogenic potency data for a given chemical. The footnotes in
Table 6-10 present the EPA weight-of-evidence classification system. Table 6-10 also presents
available RfDs and SFs for each COPC.
Risk Characterization
In the risk characterization, the results of the toxicity assessment (SFs and RfDs) and the
exposure assessment (chemical intakes for potentially exposed populations) are integrated to
arrive at quantitative estimates of carcinogenic risks and noncarcinogenic risks. The results of
the risk characterization potentially provide a basis for any remedial action that might be needed
to protect public health and the environment.
According to the 1990 National Oil and Hazardous Substances Pollution Contingency Plan
(NCP) that provides the framework for implementation of the Superfund program, the ILCR
(excess) cancer risk should not exceed the 1.0 x 10"4 to 1.0 x 10"6 range. The Office of Solid
Waste and Emergency Response (OSWER) Directive 9355.0-30 (EPA 1991b) states "Where
cumulative carcinogenic site risk to an individual based on an RME scenario for the current and
future use is less than 1.0 x 10"4, and the noncarcinogenic hazard quotient (index) is less than one,
remedial action is generally not warranted. . . ." Noncarcinogenic health hazards are expressed in
terms of a Hazard Quotient (HQ) for a single substance or Hazard Index (HI) for multiple
substances and/or exposure pathways. The terms HQ and HI are the ratios of particular chemical
The Decision Summary
6.0 Summary of Site Risks
FINAL
6-11
July 1996
-------
Table 6-10. Summary of Toxicity Values"
Chemical of Potential Concern
Benzene
d
Benzoffllanthracene
Benzofalovrene
d
Benzol^?] fluoranthene
d
Benzof&lfluoranthene
Cadmium
Chromium
Chrvsene
cis- 1 .2-Dichloroethene
Copper
1 .2-Dichlorobenzene
1 ,4-Dichlorobenzene
1,1-Dichloroethane
1.1-Dichloroethene
1.2-Dichloroethene
2.4-Dimethvlphenol
Ethvlbenzene
Fluoranthene
Frcon 113
Lead
Methvlene chloride
2-Methvlnaphthalene
Meihvlphenol
Naphthalene
Nickel
Phenanthrene
Pvrene
Toluene
l.l.I-Tnchloroethanc
Tnchioroethene
1 .2.4-Tnnielhvlhen/ene
1 .3.5-Tnmcthvlben/ene
Vinvl chloride
Zinc
Slope Factor
fms's*ke«d)
Ingestion*
2.9xl02
5.79 xlO'1
5.79
5.79 x 10 '
5.79x10'
7.5 x 10 3
1.1 x 10:
1.9
Inhalation
2.9 x 10'2
6.1
41
1.6x 10 •'
8.4 x 10'
1.7 x 10:
Weight of
Evidence6
A
B2
B2
B2
B2
Bl
A
B2
D
D
D
C
C
C
D
D
B2
B2
C
D
A
D
D
C
B2
A
Reference Dose
fmc'^kc-d)
Ingestion*
l.Ox 10 '
l.OxlO3
5.0 x 10 3
l.Ox 10 2
3.7 x 102
9.0 x 10 2
2.4 x 102
l.Ox 10 •'
9.0 x 10 3
l.Ox 102
2.0 x 10 2
4.0 x 102
6.9 x 10^
6.0 x 10 2
5.0 x JO2
4.0x 10:
2.0 x 10 :
3.0 x 10 :
2.0 x 10'
9.0 x 10 2
2.0 x 10'
Inhaiation
l.Ox 10'
2.0 x 10'6
4.0 x 10 2
1.4 x 10'
5.0 x 10'
4.3 x lO"4
9.0 x 10'
6.0x10'
3.0 x 10 '
'A blank means that it is not applicable or that data do not exist.
Oral toxicity data were used for dermal exposure as necessary.
Group A—Human carcinogen (sufficient evidence of carcinogenicity in humans); Group B—Probable human carcinogen (Bl—limited
evidence of carcinogenicity in humans; B2—sufficient evidence of carcinogenicity in animals with inadequate or lack of evidence in humans);
Group C—Possible human carcinogen (limited evidence of carcinogenicity in animals and inadequate or lack of human data); Group D—Not
classified as to human carcinogenicity (inadequate or no evidence).
Slope factor is based on a benzo[a]pyrene toxicity equivalency factor of 0.1 (from EPA Region 6 guidance).
6-12
July 1996
FINAL
The Decision Summary
6.0 Summary of Site Risks
-------
exposures to reference doses, as discussed in the following sections. If the value of the HQ is
less than 1.0, the hazards are not considered to pose a threat to public health, including sensitive
subgroups.
Carcinogenic Risk
Carcinogenic risks are estimated as the incremental probability of an individual developing
cancer over a lifetime as a result of exposure to a potential carcinogen. The estimate of ILCR is
calculated by multiplying the chronic (lifetime) daily intake (GDI) by the cancer SF.
EPA policy must be considered to interpret the significance of the cancer risk estimates. In the
NCP (40 CFR 300.430[e][2][I][A][2]), EPA states that "For known or suspected carcinogens,
acceptable exposure levels are generally concentration levels that represent an excess upper-
bound lifetime cancer risk to an individual of between 10"4 and 10"6." The agency further
discusses in the preamble to the NCP that the 1.0 x 10~6 risk level be used as a point of departure
for establishing remediation goals for the risks from constituents at Superfund sites (Federal
Register, Vol. 55, No. 46, 8713). EPA guidance indicates that if the estimated total cancer risk
based on maximum exposure conditions is 1.0 x 10"4 or less, further action at the site is generally
not warranted unless there are adverse environmental impacts, or drinking water standards
(MCLs or maximum contaminant level goals [MCLGs]) are exceeded (40 CFR Parts 141
and 143).
Tables 6-11 and 6-12 summarize the potential ILCRs for RME associated with Plant 4 for both
the current and future land-use scenarios for the COPCs for each exposure pathway. The only
risks that are outside the acceptable risk range, as defined by EPA, are those associated with
ingestion and inhalation of TCE-contaminated water in the future land-use scenario (RME
assumptions). The total risk associated with exposure to TCE is 3.4 x 10"4. Remedial
alternatives were developed that would address RME.
Noncarcinogenic Risk
The potential for noncarcinogenic health effects, expressed as HQ and HI, is calculated in a
manner similar to the carcinogenic risks. HQ applies to individual chemicals, whereas HI applies
to the sum of potential noncarcinogenic health effects for all COPCs in a given exposure
scenario. HQ is calculated by dividing the daily intake by the reference dose.
Tables 6-13 and 6-14 present summaries of the potential hazard indices for the RMEs that are
associated with Plant 4 for both current and future land-use scenarios for the COPCs for each
exposure pathway. The only exposure scenario that exceeds the acceptable hazard index of 1.0 is
the future land-use exposure pathway involving ingestion of groundwater from White Settlement
production wells. This pathway, using RME assumptions, yields an HI of 1.1. Using CT
, assumptions, the HI is 7.7 x 10"1, which is below the threshold value. Remedial action
alternatives were developed to address the RME.
The Decision Summary FINAL 6-13
6.0 Summary of Site Risks July 1996
-------
Table 6-11. Summary of Potential Incremental Lifetime Cancer Risks
Associated With Plant 4: Current Land Use
Chemical
Estimated
Average
Daily Intake*
(imrfef1-*1)
Slope Factor
(mr'-kg-d)11
Weight of
Evidence11
Chemical-
Specific
ILCR
Total
Pathway
ILCR
Total
Exposure
ILCR
Exposure Pathway: Occupational Ingestion of Soil
Benzene
Benzo[a]anthracene
Benzo[a]pyrene
Benzofb] fluoranthene
Benzo[&]fluoranthene
3.1 x lO*8
2.9 x lO'7
2.8 xlO-7
3.3 x lO'7
2.7 x 10'7
2.9 xlO'2
0.579
5.79
0.579
0.579
A
B2
B2
B2
B2
9.0 xlO'10
1.7x lO*7
1.6x lO'6
1.9xlO'7
1.6xlO'7
Exposure Pathway: Occupational Inhalation of Contaminated Air
Benzene
Chromium
Methylene Chloride
Trichloroethene
6.2 xlO"5
3.0 x 1C'7
1.7x 10'5
8.8 x ID'5
2.9 xlO'2
4.1 x 101
1.6x 10'3
1.7x 10'2
A
A
B2
B2
1.8x10-*
1.2xlO'5
2.7 x 10'8
1.5x10-*
Exposure Pathway: Dermal Exposure During Swimming
Vinyl Chloride
1.1 x 10'7
1.9
A
2.1 x lO'7
2.1 x lO'6
1.5x 10 5
2.1 x lO'7
Current Occupational Exposure: Total Potential ILCR (weight of evidence predominantly A)
1.7x 10 -~
The parameter values used to calculate the estimated average daily intakes are provided in Table 6-6.
Group A—Human carcinogen (sufficient evidence of carcinogenicity in humans); Group B—Probable human carcinogen (Bl—limited
evidence of carcinogenicity in humans; B2—sufficient evidence of carcinogenicity in animals with inadequate or lack of evidence in humans);
Group C—Possible human carcinogen (limited evidence of carcinogenicity in animals and inadequate or lack of human data).
6-14
July 1996
FINAL
The Decision Summary
6.0 Summary of Site Risks
-------
Table 6-12. Summary of Potential Incremental Lifetime Cancer Risks
Associated With Plant 4: Future Land Use
Chemical
Estimated Average
Daily Intake*
fmff-ka*1^*1}
Slope Factor
fimr^kjrd)
Weighing
Chemical*
Specific
ILCR
Total
Pathway
ILCR
Total
£xposure
ILCR
Exposure Pathway: Ingestion of Groundwater From White Settlement Production Wells
Trichloroethene
1.2 xlO'2
1.1 xlO"2
B2
1.3X10-4
l.SxIO"1
Exposure Pathway: Inhalation of Volatile Organic Compounds During Showering With Groundwater From White Settlement
Production Wells
Trichloroethene
9.2x10°
1.7xlO'2
B2
1.6X.1CT1
1.6x 10"1
Exposure Pathway: Dermal Exposure During Showering
Trichloroethene
4.5xl03
1.1 x lO'2
B2
5.0 xlO'5
5.0 x 10-5
Future Residential Exposure: Total Potential ILCR (weight of evidence predominantly A)
3.4 x 1C"4
The parameter values used to calculate the estimated average daily intakes are provided in Table 6-6.
Group A—Human carcinogen (sufficient evidence of carcinogenicity in humans); Group B—Probable human carcinogen (Bl—limited
evidence of carcinogenicity in humans; B2—sufficient evidence of carcinogenicity in animals with inadequate or lack of evidence in humans);
Group C—Possible human carcinogen (limited evidence of carcinogenicity in animals and inadequate or lack of human data).
The Decision Summary
6.0 Summary of Site Risks
FINAL
6-15
July 1996
-------
Table 6-13. Summary of Potential Hazard Indices Associated
With Plant 4: Current Land Use
Chemical
Estimated Average
Daily Intake*
-------
Table 6-14. Summary of Potential Hazard Indices Associated
With Plant 4: Future Land Use
Chemical
Estimated Average
Daily Intake*
(mg-kgV)
Reference Dose
(mgMcg-iI)
Chemical-
Specific
HQ
Total
Pathway
m
Total
Exposure
HI
Exposure Pathway: Ingestion of Groundwater From White Settlement Production Wells
Barium
Chromium
1 , 1 -Dichloroethane
1 ,2-Dichloroethene
Toluene
2.7 xlO'3
l.SxlO"4
3.8x10^
l.OxlO-2
1.9X10-4
7.0 x 10-2
5.0 xlO'3
1.0 xlO'1
l.OxlO-2
2.0 xlO'1
3.9 xlO'2
3.6 xlO'2
3.8 xlO'3
1.0
9.5 xlO-4
1.1
Exposure Pathway: Inhalation of Volatile Organic Compounds During Showering With Groundwater From
White Settlement Production Wells
1 , 1 -Dichloroethane
Toluene
3.1 x 10-4
l.SxlO-4
l.OxlO'1
6.0x10-'
3.1 x lO'3
2.5 xlO"1
3.4 x IO'3
Exposure Pathway: Dermal Exposure to Groundwater During Showering
Barium
Chromium
1 , 1 -Dichloroethane
1,2-Dichlorocthene
Toluene
4.5 x JO'6
7.1 x 10'7
6.3 x lO'7
1.7 x 10'5
3.7 x 10-4
7.0 x 10 2
5.0 x 10°
l.Ox 10-'
l.Ox 10 2
2.0 x 10-'
6.4 x 10 5
1.4X10"1
6.3 xlO'6
1.7x lO'3
1.9x 10°
3.8 x 10°
Future Residential Exposure: Total Potential HI
1.1
'The parameter values used to calculate the Estimated Average Daily Intakes are provided on Table 6-6.
The Decision Summary
6.0 Summary of Site Risks
FINAL
6-17
July 1996
-------
Site-Specific Evaluation
Results of the human-health risk assessment were use to determine threshold values of
contaminants that equate to a 1.0 x 10"6 risk level. These values were compared to contaminant
concentrations detected at individual sites at Plant 4 to further evaluate the need for remedial
action to reduce the overall risks at Plant 4. Table 6-15 shows the results of this evaluation
arranged by medium. Groundwater and air contamination do not lend themselves to site
boundaries like soil and sediment. Therefore, rather than addressing the groundwater
contamination on a site-by-site basis, the groundwater was addressed by individual aquifer and
by areas of contamination within each aquifer.
Table 6-15. Summary of Proposed Actions
Site
Finding
Voluntary Action/
Selected Remedy
Soil and Sediments
Landfill No. 1
(SiteLFOl)
Landfill No. 2
(Site LF02)
Landfill No. 3
(Site LF03)
Landfill No. 4
(SiteLF04)
Fire Department
Training Area (FDTA)
No. 2 (Site FT05)
FDTA-3
(SiteFT()6)
FDTA-4
(SiteFTO?)
FDTA-5
(SiteFT08)
FDTA-6
(Site FT09)
Concentrations of BAP exceed the human
health-risk threshold value. However, the
BAP contamination is suspected to be from
asphalt paving fragments and not from past
waste-disposal practices.
Contaminants do not pose an excess risk to
human health or the environment.
Concentrations of copper, lead, and zinc
exceed ecological risk thresholds.
Contaminants do not pose an excess risk to
human health.
Concentrations of BAP exceed human
health-risk threshold and concentrations of
arsenic, cadmium, and copper exceed
ecological risk thresholds.
Contaminants do not pose an excess risk to
human health or the environment.
Contaminants do not pose an excess risk to
human health or the environment.
Contaminants do not pose an excess risk to
human health or the environment.
Contaminants do not pose an excess risk to
human health or the environment.
Contaminants do not pose an excess risk to
human health or the environment.
Completed voluntary action to
partially remove contaminated soil.
Selected remedy is no action.
Selected remedy is no action.
Remedial action alternatives for
ecological risk developed in
Feasibility Study.
Remedial action alternatives
developed in Feasibility Study.
Selected remedy is no action.
Selected remedy is no action.
Selected remedy is no action.
Selected remedy is no action.
Completed voluntary action to
partially remove contaminated soil.
Selected remedy is no action.
6-18
July 1996
FINAL
The Decision Summary
6.0 Summary of Site Risks
-------
Table 6-15 (continued). Summary of Proposed Actions
Site
Finding;
Voluntary Action/
Selected Remedy
Soil and Sediments (continued)
Chrome Pit No. 1
(Site DP 10)
Chrome Pit No. 2
(Site DPI 1)
Chrome Pit No. 3
(Site DP 12)
Die Yard Chemical Pits
(Site DP 13)
Fuel Saturation Area
(FSA) No. 1
(Site SS 14)
FSA-2
(Site SS 15)
FSA-3
(SiteSS16)
Former Fuel Storage
Area (Sue SS17)
Solvent Lines
(SiteSSIS)
Nuclear Aerospace
Research Facility
(SneOT19)
Wastewater Collection
Basins (Site WP20)
West Compass Rose
(SiteOT21)
East Parking Lot/Flight
Line (Site OT22)
French Drains No. 1
and No. 2
(SiteOT23)
Jet Engine Test Stand
(Site OT24)
Contaminants do not pose an excess risk to
human health or the environment.
No sampling was done at the site because the
site could not be found.
Suspected TCE DNAPL area, although
contaminants do not pose an excess risk to
human health or the environment.
Contaminants do not pose an excess risk to
human health or the environment.
Fuel contamination at site, although
contaminants do not pose an excess risk to
human health or the environment.
Contaminants do not pose an excess risk to
human health or the environment.
Fuel contamination at the site, although
contaminants do not pose an excess risk to
human health or the environment.
Contaminants do not pose an excess risk to
human health or the environment.
Contaminants do not pose an excess risk to
human health or the environment.
Contaminants do not pose an excess risk to
human health or the environment.
Contaminants do not pose an excess risk to
human health or the environment.
Contaminants do not pose an excess risk to
human health or the environment.
Soil is not considered part of this site, only
groundwater.
The French drains are part of Landfill No. 1.
Contaminants do not pose an excess risk to
human health or the environment.
Selected remedy is no action.
Selected remedy is no action.
Completed voluntary action to
remove contaminated soil. Selected
remedy is no action.
Completed voluntary action to
remove contaminated soil. Selected
remedy is no action.
Installed groundwater recovery
system and vadose-zone bioventing
system. No further response action
planned.
No response action planned.
Installed groundwater recovery
system and vadose-zone bioventing
system. Selected remedy is no action.
Selected remedy is no action.
Selected remedy is no action.
Selected remedy is no action.
Selected remedy is no action.
No response action planned.
Not applicable; soil not included as
part of this site.
Installation of French Drain No. 1
was a voluntary action at
Landfill No. 1.
Selected remedy is no action.
The Decision Summary
6.0 Summary of Site Risks
FINAL
6-19
July 1996
-------
Table 6-15 (continued). Summary of Proposed Actions
Site
Finding
Soil and Sediments (continued)
Underground Storage
Tank(UST)No. 19
(Site ST25)
UST No. 20
(Site ST26)
UST No. 24A
(Site ST27)
UST No. 24B
(Site ST28)
UST No. 25A
(Site ST29)
UST No. 30
(Site ST30)
Assembly
Building/Parts Plant
Perimeter
(Building 181)
Meandering Road
Creek (includes inlet to
Lake Worth)
Contaminants do not pose an excess risk to
human health or the environment.
Contaminants do not pose an excess risk to
human health or the environment.
Contaminants do not pose an excess risk to
human health or the environment.
Contaminants do not pose an excess risk to
human health or the environment.
Contaminants do not pose an excess risk to
human health or the environment.
Contaminants do not pose an excess risk to
human health or the environment.
Contaminants do not pose an excess risk to
human health or the environment, although
the presence of TCE in the vadose zone
causes groundwater contamination.
Concentrations of silver exceed ecological
risk thresholds. Contaminants do not pose an
excess risk to human health.
Voluntary Action/
Selected .Remedy
Completed voluntary action to
remove UST. Selected remedy is
no action.
Completed voluntary action to
remove UST. Selected remedy is
no action.
Completed voluntary action to
remove UST. Selected remedy is
no action.
Completed voluntary action to
remove UST. Selected remedy is
no action.
Completed voluntary action to
remove UST. Selected remedy is
no action.
Completed voluntary action to
remove UST. Selected remedy is
no action.
Ongoing voluntary action (soil-vapor
extraction) to remove TCE
contamination in the vtfdose zone.
Remedial action alternatives
developed in Feasibility Study.
Remedial action alternatives
developed in the Feasibility Study.
Groundwater
Paluxy Aquifer
Terrace Alluvial Flow
System — East Parking
Lot Plume
Presence of TCE and 1 ,2-DCE may cause
excess human health risk in the future in two
areas: ( 1 ) East Plume under the East Parking
Lot and (2) West Plume under Landfill
No. 3.
TCE and DCE contamination is the source of
contamination in the Paluxy aquifer.
Suspected DNAPLs at the Assembly
Building and Window Area. Upper Zone
flow system is hydraulically connected to the
Paluxy aquifer.
Remedial action alternatives
developed in Feasibility Study.
Ongoing voluntary action at the East
Parking Lot to extract and treat
contaminated groundwater in the
Window Area.
Remedial action alternatives
developed in the Feasibility Study.
6-20
July 1996
FINAL
The Decision Summary
6.0 Summary of Site Risks
-------
Table 6-15 (continued). Summary of Proposed Actions
Site
Finding
Voluntary Action/
Selected Remedy
Groundwater (continued)
Terrace Alluvial Flow
System — West Plume
Terrace Alluvial Flow
System — North Plume
Contaminants do not pose an excess risk to
human health or the environment.
Contaminants do not pose an excess risk to
human health or the environment.
Voluntary actions for groundwater
include a vacuum-enhanced pumping
system at Landfill No. 3, French
Drains No. 1 and No. 2, and
collection of leachate at
Landfill No. 1.
Voluntary action at FSA-3 removed
light nonaqueous phase liquids and
extracted and treated groundwater.
Surface Water
Meandering Road
Creek
Lake Worth
Farmers Branch Creek
Contaminants do not pose an excess risk to
human health or the environment.
Contaminants do not pose an excess risk to
human health or the environment.
Contaminants do not pose an excess risk to
human health or the environment.
No remedial action planned.
No remedial action planned.
No remedial action planned.
To estimate the RME risk from exposure to contaminated air and soil, on-site workers were
assumed to work at the site 250 days each year for a period of 25 years. The workers were
assumed to spend an equal amount of time at all the contaminated sites on Plant 4. For on-site
workers exposed to noncarcinogenic contaminants in the soil (considering soil ingestion, skin
exposure, and inhalation of particulates), the HI was 0.5. This value indicates that no adverse
effects to on-site workers from noncarcinogenic contaminants in the soil are anticipated.
Only one carcinogenic contaminant, benzo[#]pyrene, in the soil exceeds the lower limit of the
acceptable risk range (1 in 1,000,000 incremental cancer risk). The calculated risk for
benzo[fl]pyrene in Landfill No. 4, using maximum values, was 1.6 in 1,000,000 incremental
cancer risk. This risk is within the acceptable risk range, but remedial alternatives were
developed because the risk exceeds the lower limit of the range.
The risk to on-site workers exposed to contaminants in the air resulted in a cumulative
incremental cancer risk of 1.7 in 100,000 for the maximum-exposure scenario and 6.4 in
1,000,000 for the average-exposure scenario (CT). The primary contaminants in the air that cause
risk are chromium, TCE, and benzene.
Even though the incremental cancer risk for contaminants in the air is above the lower limit of
the acceptable risk range, remedial alternatives were not developed because (1) chromium and
benzene levels measured on site were comparable to levels measured off site, indicating remedial
The Decision Summary
6.0 Summary of Site Risks
FINAL
6-21
July 1996
-------
actions at Plant 4 would not reduce the risk to off-site residents, and (2) TCE levels were found
to be the result of ongoing operations at the plant and, therefore, should not be considered under
the CERCLA process but under a different regulatory authority. TCE is no longer used at Plant 4,
but the air sampling was completed before the use of TCE was discontinued.
The TCE concentrations measured in air appear to correlate directly with the wind direction and
the location of the on-site sampling location with respect to Building 181. However,
concentrations of TCE in air was most likely the result of ongoing Plant 4 operations and not a
result of contamination at CERCLA sites on Plant 4. Further, the use of TCE has been
discontinued at the plant. Therefore, no remedial action objectives were developed for TCE as
an air contaminant.
Most of the sites evaluated have either been addressed by an interim removal action or contain
contaminants at levels that do not exceed human-health threshold values. No further action is
deemed necessary at these sites. For soil and sediments, only the contaminants present at
Landfill No. 3 and Landfill No. 4 required the development of remedial action alternatives from a
human health perspective. The main human health concern is from contaminated groundwater
under the future land-use scenario. Remedial action alternatives were developed that would
address the potential future contamination of the Paluxy aquifer.
6.2 Ecological Risk
The Plant 4 site includes large paved areas and buildings, as well as grassy areas with scattered
oak trees, and lake-side and creek-side areas with various types of trees, shrubs, and vines. Most
of the site has been altered from its natural state by human activities. The Plant 4 ecological risk
assessment focused on the relatively natural areas near Meandering Road Creek, Lake Worth,
and Farmers Branch Creek.
Receptors considered for the ecological risk assessment were identified on the basis of several
criteria, including ecological or social significance, potential for exposure, and availability of
pertinent lexicological data. These receptors include largemouth bass, red-tailed hawk, red fox,
raccoon, terrestrial prey species (e.g., mice and squirrels), and aquatic prey species
(e.g., aquatic insects and minnows).
The ecological risk assessment determined if there is a potential risk to a receptor from a certain
contaminant by estimating HQs. HQ represents a comparison of projected exposure levels to
what is considered to be the acceptable limit of exposure. It is based on the ratio of the estimated
daily intake to an acceptable daily exposure. An HQ greater than 1.0 indicates there is a potential
for excess risk to a receptor.
Two types of assessments were used to quantify ecological risk at Plant 4: (1) food web modeling
and (2) direct toxicity assessments. Both types of assessments produce conservative estimations
of ecological risk.
6-22 FINAL The Decision Summary
July 1996 6.0 Summary of Site Risks
-------
The HQs calculated for receptors exposed to contamination in the surface water from
Meandering Road Creek, Lake Worth, and Farmers Branch Creek are less than a value of 1.0,
which indicates there is not a potential for excess risk from contaminants in the surface water.
The HQs calculated for some receptors exposed to soils and sediments exceed a value of 1.0,
specifically at Landfill No. 3 and Landfill No. 4. Table 6-16 summarizes the results of the
ecological risk assessment for these areas. Remedial action alternatives were developed for these
areas to mitigate the potential ecological risk. Sediments from Meandering Road Creek,
including the inlet to Lake Worth, contained silver and Aroclor-1254 (a PCB compound) in
concentrations that have the potential to cause excess ecological risk. Remedial action
alternatives were also developed to address sediments in this location.
Table 6-16. Summary of Contaminants That Exceed Ecological-Risk Threshold Levels
Contaminant
Arsenic
Cadmium
Copper
Lead
Zinc
Silver
Aroclor-1254
Exposure Pathway
Mice exposed to soil at
Landfill No. 4
Mice exposed to soil at
Landfill No. 4
Mice exposed to soil at
Landfills No. 3 and No. 4 '
Mice exposed to soil at
Landfill No. 3
Mice exposed to soil at
Landfill No. 3
Aquatic organisms exposed to
sediment in Meandering
Road Creek
Largemouth bass exposed to
sediment in Lake Worth
HQ Based on Average
Concentrations
2.8
1.2
0.63 (Landfill No. 3)
0.31 (Landfill No. 4)
0.44
1.1
1.9
1.2
HQ Based on Maximum
Values
5.8
1.2
4.9 (Landfill No. 3)
1.0 (Landfill No. 4)
2.8
8.3
7.8
1.8
6.3 References
U.S. Environmental Protection Agency (EPA), 1989a. EPA Risk Assessment Guidance for
Superfund-Human Health Evaluation Manual (Part A), EPA/540/1-89/002, Office of
Emergency and Remedial Response, December 1989.
, 1989b. Exposure as Factors Handbook, EPA/600/8-89/043.
, 199 la. Risk Assessment Guidance for Superfund, Volume 7, Human Health
Evaluation Manual (Part B), Publication 9285.7-01B.
, 1991 b. Role of the Baseline Risk Assessment in Superfund Remedy Selection
Decisions, Office of Solid Waste and Emergency Response (OSWER) Directive 9355.0-30.
The Decision Summary
6.0 Summary of Site Risks
FINAL
6-23
July 1996
-------
U.S. Environmental Protection Agency (EPA), 1992. Framework for Ecological Risk
Assessment, Risk Assessment Forum, Washington, DC.
Rauscher, Jon, 1992. Memorandum on "Central Tendency and RME Exposure Parameters."
6-24 FINAL The Decision Summary
July 1996 , 6.0 Summary of Site Risks
-------
7.0 Landfill No. 3, Landfill No. 4, and
Meandering Road Creek
This section discusses and presents the remediation goals, descriptions of alternatives, and
comparative analysis of alternatives for Landfill No. 4, Landfill No. 3, and Meandering Road
Creek. Landfill No. 4, Landfill No. 3, and Meandering Road Creek were combined to develop
alternatives because they have similar contamination problems. Lake Worth sediments in the
inlet where Meandering Road Creek enters Lake Worth also are included in this set of
alternatives.
7.1 Remediation Goals
The remediation goals for soil at Landfill No. 4 are
• Prevent human ingestion of BAP at concentrations that cause an excess DLCR.
• Prevent ecological exposure to concentrations of arsenic, cadmium, and copper from causing
harm.
The remediation goal for soil at Landfill No. 3 and the sediments in Meandering Road Creek and
Lake Worth is
• Prevent ecological exposure to concentrations of copper, lead, and zinc in Landfill No. 3 soil
and concentrations of silver and Aroclor-1254 in Meandering Road Creek sediments from
causing harm.
These remediation goals are developed to be protective of human health and the environment.
The cleanup levels established for this site are based on these remediation goals and on reducing
the HI or the HQ to 1.0 and the ILCR to 1.0 x 10'6.
The soil at Landfill No. 4 has concentrations of BAP that result in an incremental cancer risk of
1.6 x 10 (\ which is within the acceptable risk range. Although the risk to human health is within
the acceptable risk range, alternatives were evaluated to determine if any significant risk
reduction could be achieved through a reasonable degree of remediation.
Levels of arsenic, cadmium, and copper in the soil at Landfill No. 4 could cause harm to mice.
Limiting the exposure of mice to the presence of arsenic, cadmium, and copper at Landfill No. 4
to levels less than 29.1 mg/kg, 132 mg/kg, and 563 mg/kg, respectively, would reduce the
respective HQs to 1.0. Limiting the exposure of mice to copper, lead, and zinc contamination at
Landfill No. 3 to less than 563 mg/kg, 2,000 mg/kg, and 1,000 mg/kg, respectively, would reduce
the respective HQs to 1.0.
Concentrations of silver in the sediments of Meandering Road Creek could cause harm to aquatic
insects and minnows. Reducing silver concentrations in the sediments in Meandering Road
The Decision Summary FINAL 7-1
7.0 Landfill Nos. 3 and 4 and Meandering Road Creek July 1996
-------
Creek (and Lake Worth) to 1.0 mg/kg would reduce the HQ to 1.0. The presence of the chemical
Aroclor-1254 causes potential risk to largemouth bass. Reducing the levels of Aroclor-1254 to
0.1 mg/kg would reduce the HQ to 1.0.
7.2 Description of Alternatives
The alternatives developed for Landfill No. 4, Landfill No. 3, and Meandering Road Creek use
capping, solidification and disposal in a hazardous-waste landfill, and monitoring. These
alternatives are:
• Alternative 1, No Action (selected alternative)
• Alternative 2a, Capping That Addresses Human Health Risk Areas
• Alternative 2b, Capping That Addresses All Risk Areas
• Alternative 3a, Removal and Disposal That Address Human Health Risk Areas
• Alternative 3b, Removal and Disposal That Address All Risk Areas
Alternative 1, No Action (selected alternative)
Present Worth: $73,000
Implementation Time: 0 months
This alternative assumes there would be no additional activities to remediate the contaminated
soil but does include monitoring of contaminant levels in the surface water and sediments in
Meandering Road Creek and Lake Worth. Monitoring will continue as long as contamination
remains in soil at Landfill No. 4 and Landfill No. 3 and in sediments in Meandering Road Creek
or until the Air Force, EPA, and State of Texas agree that monitoring is no longer required. The
monitoring is described in more detail in Section 7.4, 'The Selected Remedy."
If monitoring indicates that the concentrations of contaminants will cause unacceptable risks to
the aquatic environment or MCLs to be exceeded in Lake Worth, appropriate remedial actions
will be taken. Remedial actions may include removal of the sediments or containment of
contaminants in the landfills that are causing the unacceptable risks or contamination levels.
Alternative 2a, Capping That Addresses Human Health Risk Areas
Present Worth: $430,000
Implementation Time: 12 months
7-2 FINAL The Decision Summary
July 1996 7.0 Landfill Nos. 3 and 4 and Meandering Road Creek
-------
Alternative 2a involves capping areas to contain BAP contamination in the soil (areas with
contamination that exceeds human health-risk threshold values) to eliminate the exposure
pathway to on-site workers. Components of this alternative include
• Place a cap over Landfill No. 4. The cap could be constructed of material such as concrete,
clay, or synthetic material.
Monitor contamination in Meandering Road Creek and Lake Worth to determine if
contaminants from Landfill No. 4 and Landfill No. 3 are leaching to the surface water.
Monitoring will continue as long as contamination remains in Landfill No. 4, Landfill No. 3,
and Meandering Road Creek sediments.
This alternative does not involve excavation of BAP-contaminated soil and does not include
areas at Landfill No. 3 and Meandering Road Creek where there is a potential for excess
ecological risk.
Alternative 2b, Capping That Addresses All Risk Areas
Present Worth: $473,000
Implementation Time: 12 months
.-
Alternative 2b involves capping areas to contain BAP contamination in the soil (areas with
contamination that exceeds human health-risk threshold values) to eliminate the exposure
pathway to on-site workers and removal of soil and sediments that have the potential to cause
excess ecological risk. Components of this alternative include
• Excavate 185 yd3 of soil contaminated with copper, lead, and zinc at Landfill No. 3 and
place the soil on Landfill No. 4.
• Remove 177 yd3 of sediments contaminated with silver and Aroclor-1254 from Meandering
Road Creek and Lake Worth and place the sediments on Landfill No. 4.
• Place a cap over Landfill No. 4 after soil from Landfill No. 3 and sediments from
Meandering Road Creek and Lake Worth have been placed on the landfill.
• Monitor contamination in Meandering Road Creek and Lake Worth to determine if
contaminants from Landfill No. 4 and Landfill No. 3 are leaching to the surface water.
Monitoring will continue as long as contamination remains in Landfill No. 4, Landfill No. 3,
and Meandering Road Creek sediments.
Alternative 3a, Removal and Disposal That Address Human Health Risk Areas
Present Worth: $19,151,000
Implementation Time: 12 months
The Decision Summary FINAL 7-3
7.0 Landfill Nos. 3 and 4 and Meandering Road Creek July 1996
-------
Alternative 3a involves removing approximately 32,000 yd3 of BAP-contaminated soil (areas
with contamination that exceeds human health-risk threshold values) and transporting the soil to
a hazardous-waste landfill. Components of this alternative include
Excavate 32,000 yd3 of BAP-contaminated soil at Landfill No. 4.
• Place the soil in suitable containers for transportation.
• Transport the soil to a hazardous-waste landfill.
• Stabilize the soil before disposal.
• Establish site safeguards such as storm-water controls.
• No monitoring is required with this alternative.
This alternative does not include soil areas at Landfill No. 3 and sediment in Meandering Road
Creek and Lake Worth where there is a potential for excess ecological risk.
Alternative 3b, Removal and Disposal That Address All Risk Areas
Present Worth: $19,244,000
Implementation Time: 12 months
Alternative 3b has all the components of Alternative 3a except that this alternative also includes
removing contaminated sediments in Meandering Road Creek and contaminated soil from
Landfill No. 3. Components of this alternative include
Excavate 32,000 yd3 of BAP-contaminated soil at Landfill No. 4.
Excavate 185 yd3 of soil contaminated with copper, lead, and zinc at Landfill No. 3 and
transport to a solid-waste landfill.
• Remove 177 yd3 of sediments contaminated with silver and Aroclor-1254 from Meandering
Road Creek and Lake Worth and transport to a solid-waste landfill.
• Place the soil from Landfill No. 4, Landfill No. 3, and Meandering Road Creek in suitable
containers for transportation.
• Transport the soil to a hazardous-waste landfill.
• Stabilize the soil before disposal.
• No monitoring is required with this alternative.
7-4 FINAL The Decision Summary
July 1996 7.0 Landfill Nos. 3 and 4 and Meandering Road Creek
-------
7.3 Comparative Analysis of Alternatives
Alternatives must be evaluated against the nine criteria specified in the NCP. Figure 7-1
presents these criteria. A comparative analysis of alternatives for Landfill No. 4, Landfill No. 3,
and Meandering Road Creek are given in the following text and are summarized in Table 7-1.
Overall Protection of Human Health and the Environment
All the alternatives, including the selected alternative, Alternative 1, No Action, are considered
protective of human health and the environment. The No Action Alternative results in a human
health risk of 1.6 x 10'6 ILCR from concentrations of BAP left in Landfill No. 4. This risk is
within the acceptable risk range for human health. The No Action Alternative was deemed
acceptable even though the BRA determined there is the potential for excess ecological risk.
Three factors were considered in determining that no action to mitigate the potential for
ecological risk was acceptable. One factor was that the conservative manner in which potential
ecological risk was determined likely overestimated the risk. Another factor was that the
calculated HQs were relatively close to an HQ of 1.0, the threshold value. The third factor was
that the risk was to prey species (i.e., mice and minnows) and not to predators such as hawks or
largemouth bass.
Alternatives 2a and 3a both reduce the potential for human exposure to below an ILCR of
1.0 x 10"6. However, these alternatives do not reduce the potential for excess ecological risk.
Only Alternatives 2b and 3b reduce both human health risk and the potential for excess
ecological risk.
The selected alternative, Alternative 1, No Action, provides protection within the acceptable
range for human health. The selected alternative does not reduce the potential ecological harm
(there is a potential for harm to mice and aquatic organisms and largemouth bass from
contaminants in sediment). However, the No Action Alternative was deemed to be acceptable by
the Air Force, the EPA, and the State of Texas.
Alternatives 2a and 3a are protective of human health but are the same as the No Action
Alternative for mitigation of ecological risk. Alternatives 2b and 3b are protective of human
health and reduce ecological risk to below threshold values.
Compliance With Applicable or Relevant and Appropriate Requirements
All the alternatives can meet the requirements for compliance with chemical-specific, action-
specific, and location-specific applicable or relevant and appropriate requirements (ARARs).
Table 7-2 summarizes the ARARs for all the alternatives.
The Decision Summary FINAL 1-5
7.0 Landfill Nos. 3 and 4 and Meandering Road Creek July 1996
-------
The following nine criteria are used to evaluate alternatives. Overall protection of human health and the
environment and compliance with applicable or relevant and appropriate requirements (ARARs) (unless a
specific ARAR is waived) are the threshold criteria that each alternative must meet to be the selected alternative.
Long-term effectiveness and permanence; implementability; short-term effectiveness; reduction of toxicity,
mobility, and volume through treatment; and cost are the balancing criteria that are used to compare and weigh
the major trade-offs among the alternatives. The remaining two criteria, State acceptance and community
acceptance, are the modifying criteria. Modifying criteria are based on input from the State of Texas or the
public and may be used to modify an alternative or select a different alternative.
Threshold Criteria
Overall protection of human health and the environment addresses if an alternative can adequately protect
human health and the environment, in both the short- and long-term, from unacceptable risks posed by hazardous
substances, pollutants, or contaminants present at the site by eliminating, reducing, or controlling exposures to
contamination. Overall protection of human health and the environment draws on the assessments of other
evaluation criteria, especially long-term effectiveness and permanence, short-term effectiveness, and compliance
with ARARs.
Compliance with ARARs assesses if the alternatives attain ARARs under Federal environmental laws and State
environmental laws or provide a basis for invoking a waiver.
Balancing Criteria
Long-term effectiveness and permanence assesses the ability of an alternative to provide long-term protection
after remediation goals have been met, along with the degree of certainty that the alternative will prove
successful.
Reduction oftoxicity, mobility, or volume through treatment evaluates the degree to which alternatives employ
recycling or treatment that reduces toxicity, mobility, or volume, including how treatment is used to address the
principal threats posed by the site.
Short-term effectiveness addresses the time it takes for an alternative to be implemented and the potential effect
on human health (including the community and workers) and the environment during implementation.
Implementability evaluates the ease or difficulty of implementing the alternatives. Implementability considers
technical feasibility (e.g., technical difficulties and unknowns associated with the construction and operation of
the technology), administrative feasibility (e.g., activities needed to coordinate with other offices and agencies),
and availability of services and materials.
Cost includes capital costs, including both direct and indirect costs, annual operation and maintenance (O&M)
costs, and net present value of capital and O&M costs. Cost is considered and compared to the benefit that will
result from implementing the alternative.
Modifying Criteria
State acceptance considers the concerns of the State on the alternatives and offers comments. The State may
agree with, oppose, or have no comment on the proposed remedy.
Community acceptance allows for a public comment period when interested persons and organizations can
comment on the proposed remedy. Evaluating community acceptance includes determining which components of
the alternatives interested persons in the community support, have reservations about, or oppose.
Figure 7-1. Evaluation Criteria Specified in the National Contingency Plan
7-6 FINAL The Decision Summary
July 1996 ' 7.0 Landfill Nos. 3 and 4 and Meandering Road Creek
-------
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and Lake Worth from
excavation and dredging and
transportation-related risk. M
short-term risk of all other
alternatives.
Rating: Fair
Small risk during construction
activities. Small risk of affecting
wetlands. Transportation-related
risks. More short-term risks than
Alternatives 1 , 2a, and 2b.
Rating: Fair
„, w> ao
S c .e c
Small risk expected during
construction activities. Moi
short-term risk to Meanderi
Road Creek and Lake Wort!
from excavation and dredgi
than Alternative 2a.
Rating: Good
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Transportation issues to be
resolved, but services are
available. Readily implementi
but most difficult of all
alternatives.
Rating: Good
Transportation issues to be
resolved, but services are
available. More difficult to
implement than Alternatives 1 ,
2a, and 2b.
Rating: Good
Easy to implement, but
slightly more difficult than
Alternatives 1 and 2a.
Rating: Good
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The Decision Summary
7.0 Landfill Nos. 3 and 4 and Meandering Road Creek
FINAL
7-7
July 1996
-------
Table 7-2. Summary of ARARs for Landfill No. 4, Landfill No. 3, and Meandering Road Creek
ARAR
Description
Compliance Aspects
Alternatives
Texas Industrial
Waste Management
Regulatipns (Texas
Administrative Code
[TAG], Title 30,
Chapter 335)
These regulations establish minimum
standards of operation for all aspects of
the management and control of
hazardous waste generated in the State
of Texas. Land disposal restrictions
would determine if excavated soil
could be placed in a Resource
Conservation and Recovery Act
landfill.
Sets requirements for storage,
treatment, and disposal of
excavated soil and dredged
sediments, if it meets the
definition of hazardous waste.
Excavated soil from Landfill
No. 4 was assumed to be
hazardous waste and would
require treatment before
disposal.
2b, 3a, 3b
Clean Water Act
(CWA) (Section 404)
The Federal Water Pollution Control
Act, commonly known as the CWA,
governs the control of pollution of the
nation's surface water. The objective
of the CWA is to restore and maintain
the chemical, physical and biological
integrity of the nation's surface water.
Section 404 of the CWA addresses
surface-water dredging and filling.
Controls storm-water
management and erosion control
during construction of a cap or
excavation of soil for
transportation. Also, controls
dredging of the sediments from
Meandering Road Creek and
Lake Worth.
2a, 2b, 3a, 3b
No ARARs (chemical-, action-, or location-specific ARARs) are applicable to soil and sediment
contamination at Landfill No. 4, Landfill No. 3, and Meandering Road Creek. Therefore,
Alternative 1, No Action, would comply with ARARs.
Alternative 2a, Capping That Addresses Human Health Risk Areas, involves the capping of soil
contamination at Landfill No. 4. Selection of Alternative 2a requires compliance with
Section 404 of the Clean Water Act, a chemical-specific ARAR. This ARAR sets requirements
for storm-water management and erosion control during construction of the cap over
Landfill No. 4.
ARARs for Alternative 2b consist of the Clean Water Act (Section 404) and Texas Industrial
Waste Management Regulations (Texas Administrative Code [TAG], Title 30, Chapter 335),
which are chemical-specific ARARs. Section 404 of the Clean Water Act sets requirements for
storm-water management and erosion control during construction of the cap on Landfill No. 4
and dredging of sediment from Meandering Road Creek and Lake Worth. The Texas Industrial
Waste Management Regulations will determine the storage, treatment, and disposal requirements
for soil and sediment excavated from Landfill No. 3 and Meandering Road Creek.
ARARs for Alternative 3a, Removal/Disposal That Addresses Human Health Risk Areas, consist
of the Clean Water Act (Section 404) and Texas Industrial Waste Management Regulations
(TAG, Title 30, Chapter 335), chemical-specific ARARs. Section 404 of fhe Clean Water Act
sets requirements for storm-water management and erosion control during excavation of soil
from Landfill No. 4. The Texas Industrial Waste Management Regulations will determine the
7-8
July 1996
FINAL The Decision Summary
7.0 Landfill Nos. 3 and 4 and Meandering Road Creek
-------
storage, treatment, and disposal requirements for the soil excavated from Landfill No. 4. Land
disposal restrictions would determine if excavated soil could be place in a Resource
Conservation and Recovery Act (RCRA) landfill. ARARs for Alternative 3b, Removal/Disposal
That Addresses All Risk Areas, are the same ARARs as for Alternative 3a.
Long-Term Effectiveness and Permanence
The selected alternative, No Action, provides long-term effectiveness because residual risk from
existing contamination will be within the acceptable range. The alternative also is permanent,
but, compared to the other alternatives, it is the least effective and provides the least permanence.
However, monitoring will be conducted to ensure that the selected alternative maintains its
required effectiveness and permanence. All the other alternatives provide long-term
effectiveness by reducing risk to levels below the threshold criteria. Long-term effectiveness is
the highest for Alternatives 3a and 3b because the contaminants in the soil are stabilized before
disposal at an off-site location. The selected remedy will ensure the remediation goals are met.
Reduction of Toxicity, Mobility, or Volume Through Treatment
The selected alternative provides no reduction in toxicity, mobility, or volume through treatment.
Alternatives 2a and 2b also provide no reduction in toxicity, volume, or mobility through
treatment. Although mobility is not reduced through treatment, the mobility of the contaminants
is reduced because the cap on Landfill No. 4 will reduce storm-water infiltration into the landfill
that could mobilize the contaminants.
Alternatives 3a and 3b are the only alternatives that use treatment (stabilization) to reduce
mobility. Treatment of the excavated soil will involve testing to determine if it is hazardous
waste. Soil that is hazardous waste will need to comply with land disposal restrictions in
40 CFR 268. No reduction in toxicity or volume of contaminants is achieved with
Alternatives 3a and 3b. Alternative 3b provides the greatest reduction in mobility because it
considers areas with potential ecological risk.
Short-Term Effectiveness
The selected alternative, No Action, is the best for short-term effectiveness because it has the
least risk to workers and the community during implementation of the alternative. It also has the
shortest project life for implementation. However, Alternatives 2a, 2b, 3a, and 3b also provide
good short-term effectiveness because risk to the community and workers will be minimal and
the alternatives will be completed within 1 year.
Alternative 3b involves the greatest short-term risk because of excavation and dredging
activities in wetland and stream areas and transportation of contaminated soil and sediments.
Alternative 2b involves the same excavation and dredging activities as Alternative 3b.
Alternative 3a involves the same transportation activities as Alternative 3b.
The Decision Summary FINAL 7-9
7.0 Landfill Nos. 3 and 4 and Meandering Road Creek July 1996
-------
Implementability
The selected alternative, No Action, is the easiest to implement, involving only monitoring
activities. The other alternatives use established technologies, are relatively easy to implement,
and should be successful from a construction standpoint. Comparatively, Alternatives 3a and 3b
are the most difficult to implement.
Cost
The No Action Alternative is the best alternative in terms of cost because it requires only
monitoring. The estimated present worth cost of the selected alternative is $73,000.
Alternatives 3a and 3b have significantly higher present worth costs of $19,151,000 and
$19,244,000, respectively. These higher costs are because the excavated soil is assumed to be
classified as hazardous waste for disposal, requiring stabilization and expensive disposal fees.
The present worth costs for Alternatives 2a and 2b are $430,000 and $473,000, respectively, and
involve capping and monitoring for Alternative 2a and capping, monitoring, and dredging for
Alternative 2b.
State Acceptance
TNRCC concurs with Alternative 1, No Action, as the selected remedy for Landfill No. 4,
Landfill No. 3, and Meandering Road Creek.
Community Acceptance
The Air Force solicited input from the community and from members of the Restoration
Advisory Board on the remediation alternatives proposed for Landfill No. 4, Landfill No. 3, and
Meandering Road Creek. The comments received from the public and Restoration Advisory
Board members indicate that the community will accept the selected remedy with monitoring of
contamination levels in Lake Worth and Meandering Road Creek.
There is some concern by members of the public about leaving the contamination in the landfills
and the resulting effect on contamination levels in Lake Worth. The city of Fort Worth, which
obtains drinking water from Lake Worth, was especially concerned about contamination leaching
from the landfills and entering Lake Worth. All comments received during the public comment
period and the Air Force responses are in Appendix A, "Responsiveness Summary."
7.4 The Selected Remedy
The Air Force, with the concurrence of the EPA and the State of Texas, has determined that
Alternative 1, No Action, meets the threshold criteria while providing the best balance of long-
term effectiveness and permanence; reduction in toxicity, mobility, and volume; short-term
7-10 FINAL The Decision Summary
July 1996 7.0 Landfill Nos. 3 and 4 and Meandering Road Creek
-------
effectiveness; implementability; and costs while being acceptable to the State and community.
As presented in Section 7.1, the remediation goals for Landfill No. 4 are
• Prevent human ingestion of BAP at concentrations that cause an excess ILCR.
• Prevent ecological exposure to concentrations of arsenic, cadmium, and copper from
causing harm.
The remediation goal for soil at Landfill No. 3 and the sediments in Meandering Road Creek is
• Prevent ecological exposure to concentrations of copper, lead, and zinc in Landfill No. 3 soil
and concentrations of silver and Aroclor-1254 in Meandering Road Creek sediments from
causing harm.
Alternative 1, No Action, meets these remediation goals because the current risk to human health
from BAP is 1.6 x 10~6 ILCR, which is within the acceptable risk range. Existing levels of
contamination show a potential for excess ecological risk; however, a risk management decision
was made that no action is acceptable because of the conservative manner in which ecological
risk was calculated, the lack of risk for predator species, and the calculated risk was not
significantly higher than threshold levels.
The selected remedy will ensure the remediation goals are met by
• Monitoring the contaminant levels in the surface water of Meandering Road Creek. Monitoring
will be conducted semiannually and samples will be analyzed for VOCs and metals. The
frequency of monitoring may be reduced if contaminant levels continue to decline and the
Air Force, EPA, and State of Texas agree to the reduced monitoring. During the remedial
design phase, the Air Force will submit to EPA and the State of Texas for their concurrence a
detailed monitoring plan defining the frequency of sampling, sampling points, and an analyte
list. The detailed monitoring plan may differ slightly from the assumptions stated here.
• Implementing corrective measures if monitoring indicates the concentration of contaminants in
Meandering Road Creek are increasing to levels that may cause excess risk or MCLs are being
exceeded in Lake Worth. A TCE concentration of approximately 5,000 ug/L is the level that
may cause excess risk in Meandering Road Creek surface water, based on ecological risk. The
primary MCLs of concern for Lake Worth are TCE with an MCL of 5 ug/L, cw-l,2-DCE with
and MCL of 70 pg/L, trans-l,2-DCE with an MCL of 100 |jg/L, and vinyl chloride with an
MCL of 2 ug/L. Corrective measures that may be taken include capping or enhancements to
the vacuum-enhanced extraction system at Landfill No. 3. Exceedance of MCLs will be
determined on a statistical basis.
• Implementing contingency measures if monitoring indicates an increase in the concentrations
of contaminants. Contingency measures will include removal or containment of the source
material that is causing the increase in surface-water contamination. One contingency measure
The Decision Summary FINAL 7-11
7.0 Landfill Nos. 3 and 4 and Meandering Road Creek July 1996
-------
the Air Force has voluntarily installed, and is operating, is the vacuum-enhanced extraction
system at Landfill No. 3, as described in Section 2.2, "Interim Remedial Actions."
The primary factors for selecting Alternative 1, No Action, was that it met the threshold criteria
(protection of human health and the environment and compliance with ARARs) and was the most
cost effective of all the alternatives. Because the remediation goals are already being met, the long-
term effectiveness and permanence for the selected remedy is good. Short-term risks are minimal
for the selected remedy, the least short-term risk of all the alternatives, because this alternative only
involves monitoring and is readily implemented. The selected remedy does not satisfy the statutory
preference for treatment as a principal element.
7.5 Statutory Determinations
The most important aspect of the selected remedial action is to be protective of human health and
the environment. Section 121 of CERCLA also requires that the selected remedial action comply
with ARARs established under Federal or State laws, unless a waiver is granted. In addition, the
selected remedy must be cost effective and use permanent solutions or resource-recovery
technologies to the maximum extent practicable. Section 121 also contains a preference for
remedial actions that use treatment as a primary element. The following text discusses how selected
remedy, Alternative 1, No Action, meets these statutory requirements.
Protection of Human Health and the Environment
The selected remedy, Alternative 1, No Action, is protective of human health and the environment
because existing contamination levels do not cause excess risk or are considered acceptable. The
most significant human health risk is caused by concentrations of BAP in the soil at Landfill No. 4.
Concentrations of BAP in the soil at Landfill No. 4 cause a human health risk of 1.0 x 10~6 ILCR,
which is within the acceptable range of 1.0 x 10"6 to 1.0 x 10"4 ILCR.
Concentrations of metals in the soil at Landfill No. 4, soil at Landfill No. 3, sediment in Meandering
Road Creek, and sediment in Lake Worth were determined to have the potential to cause excess
ecological risk. The potential excess ecological risk is primarily to prey species (e.g., mice,
minnows, and aquatic organisms) and not to predator species such as hawks or largemouth bass.
One sediment sample from Lake Worth has a concentration of Aroclor-1254, a PCB compound,
high enough to potentially cause excess risk to largemouth bass.
Three primary factors were considered in determining that no action to mitigate the potential for
ecological risk was acceptable. One factor was that the conservative manner in which potential
ecological risk was determined likely overestimated the risk. The ecological risk assessment
assumed that the prey species or a largemouth bass would live its entire life only in the area with
the contamination. Figure 5-2 shows the sample locations that had concentrations high enough
to potentially cause excess risk. The sample locations are isolated, indicating an animal or a fish
probably would not spend its entire life in the areas of contamination. The second factor was that
the calculated HQs were relatively close to an HQ of 1.0, the threshold value. The third factor
was that the risk was primarily to prey species and not to predators.
7-12 FINAL The Decision Summary
July 1996 , 7.0 Landfill Nos. 3 and 4 and Meandering Road Creek
-------
Compliance With Applicable or Relevant and Appropriate Requirements
No ARARs are applicable to soil and sediment contamination at Landfill No. 4, Landfill No. 3,
and Meandering Road Creek. Therefore, Alternative 1, No Action, would comply with ARARs
and no waiver of ARARs is required to implement this alternative.
Cost Effectiveness
The No Action Alternative is the most cost effective at managing risk to human health and the
environment to within acceptable limits. It is the least expensive alternative, only involving the
cost of monitoring.
Use of Permanent Solutions and Treatment or Resource-Recovery Technologies to the
Maximum Extent Practicable
The selected remedy, No Action, uses permanent solutions to the maximum extent practicable,
considering cost effectiveness and the existing risk to human health and the environment from
contamination remaining at sites.
Of the alternatives that are protective of human health and the environment and comply with
ARARs, the selected alternative provides the best balance of long-term effectiveness and
permanence; reduction in toxicity, mobility, and volume through treatment; short-term
effectiveness; implementability; costs; and the statutory preference for treatment, while
considering State and community acceptance.
Preference for Treatment as a Principal Element
Treatment of the contamination at Landfill No. 4, Landfill No. 3, and Meandering Road Creek is
not required because the existing risk to human health and the environment is within acceptable
limits. However, because contamination will remain on site, a review will be conducted 5 years
after the start of the remedial action. The only activity involved in the remedial action is
monitoring. Monitoring has been an ongoing activity at the site and, therefore, the remedial
action will begin immediately after the ROD becomes effective.
Documentation of Significant Changes
The Proposed Plan was released for public comment in November 1995. The Proposed Plan
identified Alternative 1, No Action, as the selected alternative. The Air Force reviewed all
written and oral comments submitted during the public comment period. Comments by members
of the Restoration Advisory Board, made before and during the public comment period, also
were reviewed. After review of these comments, no significant changes to the selected remedy,
, as originally identified in the Proposed Plan, were made.
The Decision Summary FINAL 7-13
7.0 Landfill Nos. 3 and 4 and Meandering Road Creek July 1996
-------
This Page Intentionally Left Blank
7-14 FINAL The Decision Summary
July 1996 7.0 Landfill Nos. 3 and 4 and Meandering Road Creek
-------
8.0 Paluxy Aquifer and Upper Sand Groundwater
8.1 Remediation Goals
The remediation goals for the Paluxy aquifer are to prevent future human exposure by ingestion,
inhalation during showering, and dermal exposure during showering to TCE concentrations
exceeding 5.0 |ug/L and to concentrations of 1,2-DCE isomers exceeding 70 jag/L for
cw-1,2-DCE and 100 |ug/L for trans- 1,2-DCE.
The remediation goals for TCE and 1,2-DCE concentrations in the Paluxy aquifer are based on
the MCLs set in the Safe Drinking Water Act. A TCE level of 5.0 |ig/L results in a cumulative
future risk of 1.7 x 10"6 ILCR, which is within the acceptable risk range of 1.0.x 10'6 to 1.0 x 10"4
ILCR. The risk for exposure to levels of 70 |ug/L for cis- 1,2-DCE and 100 |ig/L for
trans- 1,2-DCE results in an HQ that is less than 1.0. Current TCE levels in the Paluxy aquifer
are as high as 100 |ug/L.
The remedial action objective for groundwater in the Upper Sand is to prevent contamination in
the Upper Sand from causing TCE contaminant levels in the Paluxy aquifer to exceed 5.0 ng/L.
The Upper Sand groundwater is only found in the area of the East Parking Lot. A TCE level of
400 ^ig/L in the Upper Sand groundwater was determined adequate to prevent contaminant levels
in the Paluxy aquifer from exceeding 5.0 fig/L. The TCE level of 400 |ug/L is based on a mixing
calculation that estimates a volume and concentration of Upper Sand groundwater that would
mix with a volume of clean Paluxy aquifer groundwater. Current contamination levels in the
Upper Sand groundwater range from ND to approximately 10,000 pg/L.
8.2 Documentation of Significant Changes
The Proposed Plan was released for public comment in November 1995. A draft of the Proposed
Plan was released to members of the Restoration Advisory Board before the public comment
period. The Draft Proposed Plan identified Alternative 3a, Groundwater Extraction With Air
Stripping, as the selected alternative. Members of the Restoration Advisory Board expressed
considerable concern about the use of air stripping because contaminants would be released to
the atmosphere. Considering the concern expressed by members of the Restoration Advisory
Board, the Air Force chose Alternative 3b, Groundwater Extraction With Ultraviolet Oxidation,
as the selected alternative.
The Final Proposed Plan dated November 1995 identified Alternative 3b, Groundwater
Extraction With Ultraviolet Oxidation, as the selected alternative. Alternative 3b was presented
as the selected alternative at the public meeting on the Proposed Plan. The Air Force reviewed
all written and oral comments submitted during the public comment period.
After review of these comments, the Air Force changed the name of the selected alternative,
Alternative 3b, from "Groundwater Extraction and Treatment With Ultraviolet Oxidation" to
"Groundwater Extraction and Treatment With Near-Zero Off-Gas Emissions." The name of the
The Decision Summary FINAL 8-1
8.0 Paluxy Aquifer and Upper Sand Groundwater July 1996
-------
alternative was changed to allow, use of other technologies that would result in near-zero off-gas
emissions. The alternative is still based on using ultraviolet oxidation (a technology with near-
zero off-gas emissions) but accommodates the use of other technologies such as air stripping
with off-gas treatment if that technology is deemed more appropriate during remedial design.
The selected alternative still meets the public's concern of minimizing contaminants released to
the atmosphere.
8.3 Description of Alternatives
Three alternatives were developed to address contamination in the Paluxy aquifer and Upper
Sand groundwater in the Paluxy Formation. Alternative 3 is presented as Alternative 3a and
Alternative 3b because two different approaches to treatment of the extracted groundwater were
considered. Several treatment processes were screened in the Feasibility Study. Treatment by air
stripping with no control of off-gas emissions and ultraviolet oxidation (a technology that limits
off-gas emissions to a minimum) were identified as the best processes for contaminated Paluxy
groundwater. The alternatives make use of treatment, containment, and institutional controls.
• Alternative 1, No Action
• Alternative 2, Alternate Water Supply
• Alternative 3a, Groundwater Extraction and Treatment With Air Stripping
• Alternative 3b, Groundwater Extraction and Treatment With Near-Zero Off-Gas Emissions
(selected remedy)
Alternative 1, No Action
Present Worth: $274,000
Implementation Time: 0 years
Alternative 1, No Action, assumes that no additional activities would be conducted to remediate
TCE and 1,2-DCE contamination in the Paluxy aquifer and the Upper Sand groundwater. The
only activity in the alternative is monitoring to track the movement and contaminant levels in the
aquifer. Monitoring will continue as long as contamination exceeds remediation goals in the
Paluxy aquifer and Terrace Alluvial flow system. The implementation time of 0 years does not
include the length of time that monitoring will be required. Monitoring will continue as long as
contaminant levels exceed remediation goals in the Paluxy aquifer and Terrace Alluvial
flow system.
Alternative 2, Alternate Water Supply
Present Worth: $937,000
Implementation Time: 1 year
8-2 FINAL The Decision Summary
July 1996 8.0 Paluxy Aquifer and Upper Sand Groundwater
-------
Alternative 2 supplies a source of water for the city of White Settlement that would not be
jeopardized by TCE and 1,2-DCE contamination. New water supply wells will be drilled into the
Travis Peak/Twin Mountain aquifer, the aquifer below the Paluxy aquifer. The Travis
Peak/Twin Mountain aquifer has proven production rates and water quality and currently is being
used by the cities of Fort Worth and White Settlement.
This alternative also includes monitoring the TCE plume in the Paluxy aquifer and Upper Sand
groundwater to track its movement and concentration levels but does not include any extraction
or treatment of contaminated groundwater. Monitoring will continue as long as contamination
exceeds remediation goals for the Paluxy aquifer and Terrace Alluvial flow system. The
implementation time of 1 year does not include the length of time that monitoring will be
required.
Alternative 3a, Groundwater Extraction and Treatment With Air Stripping
Present Worth: $2,541,000
Implementation Time: 3 years for Paluxy aquifer
15 years for Upper Sand groundwater
Alternative 3a uses extraction and treatment with air stripping to remove contaminants from the
Paluxy aquifer and Upper Sand groundwater. Two areas of the Paluxy aquifer are included in
this alternative, an area under Landfill No. 3 and an area under the East Parking Lot.
Components of the alternative include
• Extraction of contaminated Paluxy aquifer groundwater from under Landfill No. 3.
• Extraction of contaminated Paluxy aquifer groundwater from beneath the Window Area of
the East Parking Lot Plume. Contamination in this area currently is below MCLs but
extraction of groundwater will be initiated if MCLs are exceeded.
• Extraction of contaminated Upper Sand groundwater to minimize contamination that moves
vertically from groundwater in the Terrace Alluvial flow system to the Paluxy aquifer.
• Treatment of the extracted groundwater with air stripping and discharge of the treated water
to surface water or a sewage treatment plant.
• Installation of additional monitoring wells in the Upper Sand groundwater and in the
Paluxy aquifer.
• Monitoring of contaminant movement and concentrations in both the Paluxy aquifer and
Upper Sand groundwater. Monitoring will continue as long as contamination exceeds
remediation goals in the Paluxy aquifer and Terrace Alluvial flow system, estimated at
15 years for the Terrace Alluvial flow system.
The Decision Summary FINAL . 8-3
8.0 Paluxy Aquifer and Upper Sand Groundwater July 1996
-------
Air stripping will be used to treat the contaminants in the extracted groundwater, primarily TCE
and 1,2-DCE. The air-stripping system for this alternative will be a modification to the system
being used for the interim action currently operating in the East Parking Lot. The air stripper will
comply with all Federal, State, and local clean air requirements, including those specific to
Tarrant tounty, Texas. Based on anticipated concentration levels in the groundwater, off-gas
treatment would not be required to meet air-quality requirements. If the air stripper does not
meet air quality requirements, catalytic oxidation or carbon adsorption will be added to help the
system meet requirements. The cost of catalytic oxidation or carbon adsorption is not included in
the cost estimate.
Remediation of contamination in the Paluxy aquifer (i.e., the plume located under Landfill No. 3)
is estimated to take 3 years. This alternative assumes one extraction well in the vicinity of
Landfill No. 3 to extract groundwater from the Paluxy aquifer. Extraction of groundwater from
the Upper Sand portion of the Paluxy Formation will continue until remediation of the East
Parking Lot Plume is completed, estimated at 15 years.
Alternative 3b, Groundwater Extraction and Treatment With Near-Zero Off-Gas
Emissions (selected remedy)
Present Worth: $3,101,000
Implementation Time: 3 years for Paluxy aquifer
15 years for Upper Sand groundwater
Alternative 3b is the selected alternative for remediation of contamination in the Paluxy aquifer
and Upper Sand groundwater. This alternative has all the components of Alternative 3a except
that extracted groundwater is treated with ultraviolet oxidation (or another technology that would
result in near-zero off-gas emissions) instead of air stripping. Other technologies may be air
stripping with an off-gas treatment system that uses vapor-phase carbon adsorption or catalytic
oxidation. Ultraviolet oxidation is the representative technology used for evaluation in this
alternative. Ultraviolet oxidation treatment is a fully developed technology that uses ultraviolet
light and oxidation to destroy contaminants in the groundwater and minimizes contaminants
released to the air. No treatability tests have been conducted using ultraviolet oxidation at
Plant 4.
Remediation of contamination in the Paluxy aquifer is estimated to take 3 years. Extraction of
groundwater from the Upper Sand portion of the Paluxy Formation will continue until
remediation of the East Parking Lot Plume is completed, estimated at 15 years for this
alternative.
8.4 Comparative Analysis of Alternatives
The selected remedy for the Paluxy aquifer and the Upper Sand groundwater is Alternative 3b,
Groundwater Extraction and Treatment With Near-Zero Off-Gas Emissions. Table 8-1 presents
a comparative analysis of the four alternatives.
8^ FINAL The Decision Summary
July 1996 . 8.0 Paluxy Aquifer and Upper Sand Groundwater
-------
25?
*1
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Table 8-1. Comparative Analysis of Alternatives for the Paluxy Aquifer and Upper Sand Groundwater
Criteria
Alternative 1,
No Action
Alternative 2,
Alternate Water Supply
Alternative 3a,
Extraction With Air-Stripping
and Treatment
Alternative 3b
Extraction and Treatment With
Near-Zero Off-Gas Emissions
(selected remedy)
Overall Protection of Human
Health and the Environment
Contaminants unmitigated;
may a licet White Settlement
production wells in time.
Rating: Not Protective
Contaminants unmitigated; safe;
alternate water supply provided
for White Settlement.
Rating: Protective
Protects human health and the
environment by removing
contaminated groundwater and
treating with air stripping.
Rating: Protective
Protects human health and the
environment by removing
contaminated groundwater and
treating with ultraviolet
oxidation,
Rating: Protective
Compliance with ARARs
Would not comply with any
ARARs.
Rating: Docs Not Comply
Complies with some but not all
ARARs.
Rating: Does Not Comply
Would comply with all ARARs.
Rating: Complies
Would comply with all ARARs.
Rating; Complies
2
3
>
Long-Term Effectiveness and
Permanence
Provides the worst long-term
effectiveness or permanence of
all alternatives.
Rating: Poor
Provides permanent, long-term,
and safe drinking water for
White Settlement but has no
effect on the contaminant
plumes.
Rating. Poor
Effective at removing TCE and
1,2-DCE from the groundwater;
permanent solution for extracted
contaminants.
Rating: Good
Effective at removing TCE and
1,2-DCE from the groundwater;
permanent solution for extracted
contaminants.
Rating: Good
Reduction of Toxicity,
Mobility, or Volume Through
Treatment
Reduction in toxicity and
volume over time through
natural attenuation. No change
to mobility. No reduction
through treatment.
Rating: Poor
Reduction in toxicity and
volume over time through
natural attenuation. No change
to mobility. No reduction
through treatment.
Rating: Poor
Reduces mobility and volume of
contaminants in the
groundwater.
Rating: Good
Reduces mobility and volume of
contaminants in the groundwater.
Reduces toxicity by destroying
contaminants with ultraviolet
oxidation. Best of all
alternatives.
Rating: Good -•
Short-Term Effectiveness
No effects on the community
or the workers Best of all
alternatives
Rating: Good
No expected effects on the
community or the workers.
Rating: Good
Safety requirements for system
installation but no expected
effects on the community or the
workers.
Rating: Good
Safety requirements for system
installation but no expected
effects on the community or the
workers*
Rating: Good
Implementability
Requires no action to
implement. Easiest to
implement of all alternatives.
Rating: Good
Services, vendor, and
equipment readily available.
Requires coordination with the
city of White Settlement.
Rating: Good
Straightforward construction
and operation. Services,
vendors, and technology are
readily available.
Rating: Good
Straightforward construction and
operation. Services, vendors,
and technology available. Most
difficult of all alternatives to
implement but still readily
implemented,
Rating: Good
oo
A,
$274,000
$937,000
$2,541,000
$3,101,000
-------
Overall Protection of Human Health and the Environment
The selected alternative, Alternative 3b, is protective of human health and the environment.
Alternatives 2 and 3a also are protective of human health and the environment. Alternative 2,
Alternate Water Supply, protects human health by providing a source of drinking water in the
Travis Peak/Twin Mountain aquifer. Alternative 3a and Alternative 3b provide protection by
removing the contamination in the Paluxy aquifer. Alternative 1, the No Action Alternative, is
not protective of human health and the environment because contamination exceeding MCLs in
the Paluxy aquifer is allowed to migrate to drinking-water wells.
Compliance With Applicable or Relevant and Appropriate Requirements
Table 8-2 summarizes the ARARs applicable to all the alternatives.
Table 8-2. Summary of ARARs for the Paluxy Aquifer and Upper Sand Groundwater
ARAR
Texas Drinking
Water Standards
(TAG, Title 31,
Part IX,
Chapter 290)
Texas Surface
Water Quality
Standards (TAG,
Title 30, Part II,
Chapter 307)
National Pollutant
Discharge
Elimination
System (NPDES)
(40CFR Part 403)
Texas
Regulation V:
Control of
Pollution from
Volatile Organic
Compounds
(TAC, Title 31,
Chapter 11 5)
Description
This State regulation establishes Texas
Drinking Water Standards. These standards
are written to comply with the requirements of
the Safe Drinking Water Act and Federal
Primary Drinking Water Regulations. The
purpose of these standards is to ensure the
safety of public water supplies.
The goal of this chapter is to maintain the
quality of surface water in the State consistent
with public health and enjoyment, protection
of the environment, and operation of existing
industries and economic development.
Quality standards for surface water are
established in this chapter.
The NPDES was designed to regulate and
reduce pollution discharges to navigable
waters of the United States.
This chapter requires the control of VOCs and
sets standards for VOC emissions and
controls.
Compliance
This ARAR set
standards for
contaminant levels in
the water supply of
White Settlement.
The effluent from the
treatment systems
would need to be in
compliance with State
surface-water quality
standards.
Discharges from the
treatment systems
would need to meet
the requirements
established in this
ARAR.
Releases of VOCs to
the air, caused by
treatment of
groundwater, would
need to comply with
these State
regulations.
Alternatives
l,2,3a,3b
3a, 3b
3a, 3b
3a,3b
8-6
July 1996
FINAL The Decision Summary
8.0 Paluxy Aquifer and Upper Sand Groundwater
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Table 8-2 (continued). Summary of ARARs for the Paluxy Aquifer and
Upper Sand Groundwater
ARAR
TAG Guidance
Document,
Exemption 68
Description
This document provides guidance for the air
emissions from various treatment systems to
be used on remediation projects.
Compliance
The chosen air
stripping and
ultraviolet oxidation
treatment systems
would comply with
the levels set in this
document.
Alternatives
3a,3b
Alternative 1, No Action, fails to ensure safe drinking water for the population of White
Settlement in the future and does not provide for remediation of contaminated groundwater. This
alternative would not comply with the following ARARs:
• Texas Drinking Water Standards (Texas Administrative Code [TAG], Title 31, Part DC,
Chapter 290)
Alternative 2, Institutional Controls, involves procuring a new water supply for White
Settlement. This procurement would ensure that the White Settlement population is not
adversely affected by the presumed contamination of its potable production wells. By providing
a safe potable water supply to the population of White Settlement, this alternative would comply
with the following ARAR:
• Texas Drinking Water Standards (TAG, Title 31, Part DC, Chapter 290)
However, the NCP requires that drinking water aquifers be remediated to MCLs or nonzero
MCLGs, as specified in the Safe Drinking Water Act. The Texas Drinking Water Standards is
the State standard that incorporates the requirements of the Safe Drinking Water Act.
Alternative 2 does not meet the requirement of remediating the Paluxy aquifer (a drinking water
aquifer) to levels set in the Texas Drinking Water Standards.
Alternative 3a involves installation of a groundwater extraction and treatment system to protect
the White Settlement drinking water supply and provide remediation for existing groundwater
contamination. The effluent water from the treatment system would be discharged to the surface
water requiring compliance with the National Pollutant Discharge Elimination System (NPDES).
The treatment system for Alternative 3a uses air stripping to remove dissolved volatile
contaminants. Air emissions from the air stripper are regulated under TAG Guidance Document,
Exemption 68. Removal of contaminants from the groundwater would result in compliance
with Federal and State contaminant-level standards. Alternative 3a would comply with the
following ARARs:
The Decision Summary
8.0 Paluxy Aquifer and Upper Sand Groundwater
FINAL
8-7
July 1996
-------
• Texas Drinking Water Standards (TAG, Title 31, Part IX, Chapter 290)
• Texas Surface Water Quality Standards (TAG, Title 30, Part H, Chapter 307)
• National Pollutant Discharge Elimination System (40 CFR Part 403)
• Texas Regulation V: Control of Pollution from Volatile Organic Compounds (TAG,
Title 31, Chapter 115)
• TAG Guidance Document Exemption 68
Alternative 3b also involves installation of a groundwater extraction and treatment system to
protect the White Settlement drinking water supply and provide remediation for existing
groundwater contamination. The effluent water from the treatment system would be discharged
to the surface water and would require compliance with NPDES and State of Texas criteria.
The treatment system for Alternative 3b uses ultraviolet oxidation to destroy dissolved volatile
contaminants. Air emissions from the air stripper are regulated under TAG Guidance Document
Exemption 68. Removal of contaminants from the groundwater would result in compliance with
Federal and State contaminant-level standards. Alternative 3b would comply with the following
ARARs:
• Texas Drinking Water Standards (TAG, Title 31, Part DC, Chapter 290)
• Texas Surface Water Quality Standards (TAG, Title 30, Part H, Chapter 307)
• National Pollutant Discharge Elimination System (40 CFR Part 403)
• Texas Regulation V: Control of Pollution from Volatile Organic Compounds (TAG,
Title 31, Chapter 115)
• TAG Guidance Document Exemption 68
Long-Term Effectiveness and Permanence
The selected alternative, Alternative 3b, provides good long-term effectiveness because
contaminants are permanently removed from the aquifer. Alternative 3a provides the same
degree of permanence as the selected alternative. Alternative 2 provides less long-term
effectiveness and permanence because contamination is left in the aquifer. The No Action
Alternative provides the least long-term effectiveness.
Reduction of Toxicity, Mobility, or Volume Through Treatment
Alternatives 1 and 2 provide no reduction in toxicity, mobility, or volume of contaminants. Only
Alternatives 3a and 3b provide a reduction in mobility and volume of contaminants through
8-8 FINAL The Decision Summary
July 1996 8.0 Paluxy Aquifer and Upper Sand Groundwater
-------
treatment. Alternative 3b provides more reduction in toxicity than the other alternatives because
contaminants are destroyed when treating the extracted groundwater. The contaminants are
transferred from the groundwater to the air with Alternative 3a, Groundwater Extraction and
Treatment With Air Stripping.
Short-Term Effectiveness
Alternatives 3a and 3b involve the most activities to complete and provide the highest
potential for short-term risk to the community and workers. The short-term risk is highest for
Alternatives 3a and 3b because of the activities (construction and operation of remediation
equipment) that are not included in the other alternatives. These alternatives also require the
longest time to complete: 3 years to remediate contamination in the Paluxy aquifer and 15 years
for groundwater remediation activities in the Upper Sand. Even though the short-term risk is
highest for Alternatives 3a and 3b, the risk is expected to be minimal.
There are no expected short-term risks to the community from activities required for
Alternative 2. Short-term risks to workers for Alternative 2 would be minimal because the only
activities are drilling new production wells. The No Action Alternative provides the least
short-term risk to the community and workers and the shortest time to implement because there
are no activities, other than monitoring, that could endanger workers or the community.
Implementabilitv
Alternative 3b is relatively easy to implement because readily available technology is used.
However, when compared with the other alternatives, it is the most difficult to implement
because it involves more activities. Alternative 3a is also relatively easy to implement because
readily available technology is used. However, Alternative 3a and Alternative 3b will be more
difficult to implement than Alternative 1 and Alternative 2. The No Action Alternative is the
easiest to implement because it involves only monitoring.
Cost
The present worth cost of Alternative 3b is $3,101,000, the highest of the alternatives.
Alternative 3b has a higher present worth cost than Alternative 3a ($2,541,000) because
ultraviolet oxidation treatment is more expensive than treatment with air stripping. Alternative 2,
Alternate Water Supply, has a present value of $937,000. The No Action Alternative is the least
expensive because it involves only monitoring. It has a present worth cost of $274,000.
State Acceptance
The Texas Natural Resource Conservation Commission concurs with selection of Alternative 3b,
Groundwater Extraction and Treatment With Near-Zero Off-Gas Emissions, as the preferred
remedy for contamination in the Paluxy aquifer and Upper Sand groundwater.
The Decision Summary FINAL 8-9
8.0 Paluxy Aquifer and Upper Sand Groundwater July 1996
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Community Acceptance
The Air Force solicited input from the community and from members of the Restoration
Advisory Board on the remediation alternatives proposed for the Paluxy aquifer and Upper Sand
groundwater. The comments received from the public and Restoration Advisory Board members
indicate that the community is supportive of the selected remedy, Alternative 3b, Groundwater
Extraction and Treatment With Near-Zero Off-Gas Emissions.
A draft of the Proposed Plan presented to members of the Restoration Advisory Board had
Alternative 3a, Groundwater Extraction and Treatment With Air Stripping, as the preferred
alternative. Members of the Restoration Advisory Board expressed concern over the use of air
stripping for treatment because contaminants would be released to the atmosphere. Tarrant
County, Texas, is a nonattainment zone for ozone, and air stripping would release VOCs to the
atmosphere. This release of VOCs could contribute to ozone formation. However, the levels of
VOCs released to the atmosphere would be within the allowable limits established by State of
Texas regulations.
On the basis of comments received from the public, the Air Force, with the concurrence of EPA
and the State of Texas, agreed to select Alternative 3b, Groundwater Extraction and Treatment
With Near-Zero Off-Gas Emissions, as the selected alternative. Alternative 3b was the preferred
alternative in the final Proposed Plan that was presented at the public meeting in December 1995.
All comments received during the public comment period and the Air Force responses are in
Appendix A, "Responsiveness Summary."
8.5 The Selected Remedy
The Air Force, with the concurrence of the EPA and the State of Texas, has determined that
Alternative 3b, Groundwater Extraction and Treatment With Near-Zero Off-Gas Emissions, is
the best remedy for achieving the remediation goals and meeting public acceptance. As
presented in Section 8.1, the remediation goals for the Paluxy aquifer and Upper Sand
groundwater are
• Prevent future human exposure by ingestion, inhalation during showering, and dermal
exposure during showering to TCE concentrations exceeding 5.0 ng/L and to concentrations
of 1,2-DCE isomers exceeding 70 |jg/L for d
-------
the risk from exposure to levels of cw-l,2-DCE at 70 \igfL and trans-l,2-DCE at 100 \igfL
results in a HQ of less than 1.0.
The allowable TCE concentration in the Upper Sand groundwater of 400 pg/L is based on a
mixing calculation. The mixing calculation used estimated horizontal flow in the Paluxy aquifer,
an allowable TCE concentration in the Paluxy aquifer of 5.0 ng/L, and estimated vertical flow
from the Terrace Alluvial flow system to the Upper Sand groundwater to determine an allowable
TCE concentration in the Window Area of the Terrace Alluvial flow system. The allowable TCE
concentration of 400 |ig/L determined for the Window Area of the Terrace Alluvial flow system
was also the allowable level assumed for the Upper Sand groundwater because all the flow in the
Upper Sand groundwater is from the Terrace Alluvial flow system. The remediation goal for the
Upper Sand groundwater may be lowered if the calculated level of 400 |ug/L is shown not to be
protective of the Paluxy aquifer.
On the basis of information obtained during the remedial investigation and the analysis of
remedial alternatives, the Air Force, the EPA, and the State of Texas believe that the selected
groundwater remedy will attain these goals. The selected alternative meets the remediation
goals by
• Extracting contaminated Paluxy aquifer groundwater from under Landfill No. 3.
• Extracting contaminated Paluxy aquifer groundwater from beneath the Window Area of the
East Parking Lot. Contamination in this area currently is below MCLs but extraction of
groundwater will be initiated if MCLs are exceeded. Exceedance of MCLs will be
determined on a statistical basis.
• Extracting contaminated Upper Sand groundwater to minimize contamination that moves
vertically from groundwater in the Terrace Alluvial flow system to the Paluxy aquifer.
• Treating the extracted groundwater with ultraviolet oxidation and discharging the treated
water to surface water or a sewage treatment plant.
• Installing additional monitoring wells in the Upper Sand groundwater and in the Paluxy
aquifer to monitor contaminant movement and concentrations in both the Paluxy aquifer and
Upper Sand groundwater. Monitoring will continue as long as contamination exceeds
remediation goals in the Paluxy aquifer and Terrace Alluvial flow system, estimated at
15 years for the Terrace Alluvial flow system.
The Decision Summary FINAL 8-11
8.0 Paluxy Aquifer and Upper Sand Groundwater July 1996
-------
A more detailed description of the selected remedy follows. It should be noted that certain
aspects of the selected remedy may change during remedial design. The costs of the selected
remedy are
Capital Cost (extraction system with air stripping) $2,091,000
Present Worth of Operation and Maintenance (O&M) Costs 451,000
Present Worth of Monitoring 559,000
Worth of Selected Remedy $3,101,000
Capital costs are assumed to occur within the first year and include installation of groundwater
extraction wells, installation of an ultraviolet oxidation treatment system, piping from the
treatment system to the discharge point, electrical connections, and installation of monitoring
wells. O&M costs would include electrical requirements, water sampling for compliance, and
equipment maintenance and replacement. Monitoring costs include obtaining samples from
monitoring wells and laboratory analysis of those samples to monitor contaminant concentrations
and movement.
Extraction of groundwater from the Paluxy aquifer under Landfill No. 3 will be performed with
one extraction well estimated to pump at 45 gallons per minute (gal/min). Groundwater will be
extracted from the Upper Sand groundwater to contain contamination that has migrated from the
Terrace Alluvial flow system. Extraction from the Upper Sand groundwater will be from eight
wells, five existing monitoring wells and three new wells. Pumping rates are expected to vary
from 1 to 19 gal/min. One ultraviolet oxidation unit will be located near Landfill No. 3 to treat
water extracted from the Paluxy in this area and another ultraviolet oxidation unit will be located
near the East Parking Lot to treat water extracted from the Upper Sand groundwater.
Monitoring will be conducted to track contaminant levels in the Paluxy aquifer and Upper Sand
groundwater, especially near the downgradient edge of the plume. The locations of monitoring
wells, number of monitoring wells, and frequency of sampling will be established to provide
early detection of contamination before it migrates off site and to monitor performance of the
remedial action. If the contamination appears to be moving off site at concentrations that exceed
MCLs (i.e., 5.0 |ug/L for TCE) in either the Paluxy aquifer or Upper Sand groundwater, the
remedial action will be modified to capture the contamination before it moves off
Federal property.
The following assumptions for monitoring are based on a preliminary plan. The final monitoring
plan, to be developed during remedial design, will be more detailed and may be slightly different.
• Contamination levels in the Paluxy aquifer near Landfill No. 3 will be monitored with
samples obtained from two wells located near the downgradient extent of the plume.
• Contamination levels in the Paluxy aquifer near the East Parking Lot will be monitored with
samples obtained from wells located near the downgradient extent of contamination in the
Upper Sand groundwater.
8-12 FINAL The Decision Summary
July 1996 8.0 Paluxy Aquifer and Upper Sand Groundwater
-------
• Contamination levels in the Upper Sand groundwater will be monitored with samples
obtained from wells near the downgradient extent of contamination and near the Window
Area. The downgradient (eastern) extent of contamination in the Upper Sand groundwater is
not well defined and new monitoring wells are anticipated in this area to better define the
contamination.
• Sampling will be conducted semiannually during remediation and then annually after
remediation is completed. Monitoring will be discontinued when contaminant levels have
been shown to remain below remediation goals. The remediation goal for the Upper Sand
(400 |iig/L) is an estimate based on a calculated TCE concentration in the Upper Sand
groundwater that is protective of groundwater in the Paluxy aquifer (i.e., will not cause TCE
concentrations in the Paluxy aquifer to exceed 5.0 |ug/L). The remediation goal for the Upper
Sand groundwater may be lowered if the calculated level of 400 jag/L is shown not to be
protective of the Paluxy aquifer.
• Sampling will be discontinued in the Paluxy aquifer near Landfill No. 3 if contamination
levels remain below remediation goals. Sampling in the Paluxy aquifer near the East Parking
Lot will be discontinued if contamination levels remain below remediation goals after
remediation of the Upper Sand groundwater is completed. Sampling of the Upper Sand
groundwater will be discontinued if contamination remains below remediation goals after
remediation of the Upper Sand groundwater and the Window Area of the East Parking Lot
are completed.
• All samples will be analyzed for VOC and metal concentrations.
Groundwater contamination may be especially persistent in the immediate vicinity of a source
(e.g., the area under Building 181 in the Terrace Alluvial flow system). The ability to achieve
cleanup goals at all points throughout the area of attainment, or plume, cannot be determined
until the extraction system is implemented and modified, as necessary, and the plume response is
monitored over time. If the selected remedy cannot meet remediation goals, at any or all of the
monitoring points during implementation, contingency measures and goals may replace the
selected remedy.
If implementation of the selected remedy clearly demonstrates, in corroboration with strong
hydrogeological and chemical evidence, that it will be technically impracticable to achieve and
maintain remediation goals, contingency measures will be implemented. At a minimum, and as a
necessary condition for invoking any contingency, the Air Force will demonstrate that
contaminant levels have ceased to substantially decline over time and are remaining relatively
constant at some statistically significant level above remediation goals in a discrete portion of the
plume, as verified by samples obtained from multiple monitoring wells.
The Decision Summary FINAL 8-13
8.0 Paluxy Aquifer and Upper Sand Groundwater July 1996
-------
If it is determined, on the basis of the preceding criteria and system performance data, that certain
portions of the aquifer cannot be restored to the remediation goals, all or some of the following
measures involving long-term management may occur for an indefinite period of time:
• Source containment involving either a physical barrier system or a hydraulic barrier system.
• Low-level pumping as a long-term control of groundwater flow and containment measure.
• Institutional controls, such as deed notifications on water-supply well construction and use.
• Waiver of chemical-specific ARARs for the cleanup of those portions of the aquifer on the
technical basis of the impracticability of achieving further contaminant reduction.
The decision to implement any or all of these measures may be made during a periodic review of
the remedial action that will occur at 1-year intervals. A ROD amendment or an Explanation of
Significant Differences will be issued to inform the public of the details of these actions when
they occur.
8.6 Statutory Determinations
The most important aspect of the selected remedial action is to be protective of human health and
the environment. Section 121 of CERCLA also requires that the selected remedial action comply
with ARARs established under Federal or State laws, unless a waiver is granted. In addition, the
selected remedy must be cost effective and use permanent solutions or resource-recovery
technologies to the maximum extent practicable. Section 121 of CERCLA also contains a
preference for remedial actions that use treatment as a primary element. The following sections
discuss how the selected remedy, Alternative 3b, Groundwater Extraction and Treatment With
Near-Zero Off-Gas Emissions, meets the statutory requirements.
Protection of Human Health and the Environment
The selected remedy protects human health and the environment by reducing concentrations of
TCE and 1,2-DCE in the Paluxy aquifer to MCLs. Of all the alternatives, the selected remedy
provides the best protection of human health and the environment and addresses the public's
concern regarding releasing contaminants to the atmosphere.
The selected remedy will eliminate the potential for excess future risk to human health by
reducing concentrations of TCE and 1,2-DCE in the Paluxy aquifer. Future human health risk
may be caused by exposure from contaminated groundwater through ingestion, inhalation during
showering, and dermal exposure during showering. The cumulative carcinogenic risk from
exposure to groundwater with TCE concentrations of 5.0 |tig/L is 1.7 x 10 "6ILCR. The HQ for
exposure to cis- 1,2-DCE concentrations of 70 |ug/L and trans- 1,2-DCE concentrations of
100 jig/L is less than 1.0.
8-14 FINAL The Decision Summary
July 1996 8.0 Paluxy Aquifer and Upper Sand Groundwater
-------
Compliance With Applicable or Relevant and Appropriate Requirements
The selected remedy will comply with all ARARs and an ARAR waiver will not be required for
implementation. The Paluxy aquifer is a drinking water aquifer and remediation to MCLs is
required. The treated groundwater will be discharged to surface waters so the requirements of
State of Texas water quality standards and NPDES must be met. ARARs governing the release
of VOCs to the atmosphere are applicable, but the selected remedy will use ultraviolet oxidation,
a technology that destroys the contaminants, or a technology that uses off-gas treatment to
minimize contaminants that are released to the atmosphere.
Cost Effectiveness
The Air Force, with the concurrence of the EPA and the State of Texas, believe the selected
remedy, Alternative 3b, Groundwater Extraction and Treatment With Near-Zero Off-Gas
Emissions, is cost effective at meeting the remediation goals and protecting human health and the
environment. The selected remedy has the highest net present worth of all the alternatives
($3,101,000) but is the only alternative that meets the remediation goals, complies with all
ARARs, and does not release contaminants to the atmosphere. Alternative 3a, Groundwater
Extraction and Treatment With Air Stripping, has a lower net present worth ($2,541,000), meets
remediation goals, and complies with ARARs but uses a treatment technology that releases
contaminants to the atmosphere. Alternative 3b was chosen as the selected remedy because it
does not release contaminants to the atmosphere and has a net present worth that is not
significantly higher than Alternative 3a.
Use of Permanent Solutions and Treatment or Resource-Recovery Technologies to the
Maximum Extent Practicable
The selected remedy uses permanent solutions and treatment technologies to the maximum
extent practicable. Of the alternatives that meet the threshold criteria, the selected remedy
provides the best balance of trade-offs in terms of the balancing criteria. The selected remedy
provides the best long-term effectiveness and permanence and the best reduction in toxicity,
mobility, and volume. Short-term risks for the selected remedy are reasonable and do not
endanger the community or workers during implementation of the remedy. The cost of the
selected remedy is the highest of all the alternatives, but it is considered cost effective because it
meets the remediation goals, complies with ARARs, and addresses the public's concern about
releasing contaminants to the atmosphere.
Preference for Treatment as a Principal Element
The selected remedy meets the statutory preference for treatment as a principal element. The
principal threat to human health is TCE and 1,2-DCE contamination in the Paluxy aquifer that
exceeds MCLs. The selected remedy addresses the principal threat by extracting and treating
contaminated groundwater until contamination levels in the Paluxy aquifer are below MCLs.
Extracted groundwater is treated with ultraviolet oxidation before being discharged to
surface waters.
The Decision Summary FINAL 8-15
8.0 Paluxy Aquifer and Upper Sand Groundwater July 1996
-------
The selected remedy also uses treatment to address contamination in the Upper Sand
groundwater that is a cause of contamination in the Paluxy aquifer under the East Parking Lot.
The same treatment technology, ultraviolet oxidation, will be used for contaminated groundwater
extracted from the Upper Sand groundwater as will be used for contaminated groundwater in the
Paluxy aquifer.
8-16 FINAL The Decision Summary
July 1996 8.0 Paluxy Aquifer and Upper Sand Groundwater
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9.0 East Parking Lot Groundwater Plume and
Terrace Alluvial Flow System
9.1 Remediation Goals
The following remediation goals for groundwater in the East Parking Lot Groundwater Plume
and Terrace Alluvial flow system are based on preventing further contamination of the Paluxy
aquifer and migration of contamination off site:
• Prevent TCE concentrations in the Window Area of the East Parking Lot Groundwater
Plume from exceeding 400 |ug/L.
• Remove DNAPL from the groundwater in the area under Building 181 and under the
southern portion of the Assembly Building/Parts Plant.
• Prevent groundwater in the East Parking Lot Plume and Terrace Alluvial flow system with
contamination above MCLs from migrating off Air Force Plant 4 or Naval Air Station
Fort Worth and prevent groundwater contamination from causing excess risk in surface
water. Exceedance of MCLs will be determined on a statistical basis.
The first remedial action objective is based on a calculated maximum concentration in the
Window Area of the East Parking Lot Plume that will not cause TCE levels in the Paluxy aquifer
to exceed 5.0 |ug/L. DNAPL may be present in the Window Area and, if present, would have to
be removed before TCE concentrations of 400 |iig/L could be met.
For purposes of compliance with the TCE concentration of 400 |ug/L, the Window Area is
defined as the area beneath the East Parking Lot where the aquitard is less than 2 ft thick (see
Figure 5-1). The Window Area is approximated by an area 500-ft in diameter centered around
monitoring well W-149. During remedial activities, other areas could be identified that meet the
definition of the Window Area (i.e., an area where the aquitard is less than 2 ft thick). If other
areas do meet the definition of the Window Area, the allowable TCE concentrations for those
areas also will be 400 |ug/L.
The second remedial action objective of removing DNAPL from the groundwater will be
demonstrated by reducing TCE concentrations to levels below 10,000 (Jg/L. The TCE level of
10,000 |iig/L is approximately 1 percent of TCE's solubility in water (1,100,000 |Jg/L). This
value was chosen on the basis of technical information suggesting that DNAPL may be present
when TCE concentrations are as low as 1 percent of its solubility in water.
Groundwater in the Terrace Alluvial flow system is not used as a drinking water source by Air
Force Plant 4 or Naval Air Station Fort Worth because of low yield and poor quality of water and
because the Paluxy aquifer is a readily available source of good quality water. However, the
potential exists that an individual off site could use this groundwater as drinking water. Because
of this potential, the third remedial action objective was established to prevent groundwater that
The Decision Summary FINAL 9-1
9.0 East Parking Lot Plume July 1996
-------
has contamination above MCLs from migrating beyond Federal property boundaries.
Exceedance of MCLs also applies to the West Fork of the Trinity River and will be the target for
determining if corrective action is needed. A TCE concentration of 5,000 |ug/L in Fanners
Branch Creek, based on ecological risk, will be another target for determining if corrective action
is needed.
9.2 Description of Alternatives
Three alternatives were developed to address contamination in the East Parking Lot Groundwater
Plume of the Terrace Alluvial flow system. Alternative 2 is presented as Alternative 2a and
Alternative 2b because two different types of treatment for the extracted groundwater were
considered. Treatment, containment, and institutional controls are used in Alternatives 2a, 2b,
and 3. Alternative 3 uses an innovative technology.
• Alternative 1, No Action
• Alternative 2a, DNAPL/Groundwater Extraction and Treatment With Air Stripping
• Alternative 2b, DNAPL/Groundwater Extraction and Treatment With Ultraviolet Oxidation
• Alternative 3, Enhanced DNAPL/Groundwater Extraction and Treatment With Air Stripping
and Destruction of Contaminants (selected remedy)
Alternative 1, No Action
Alternative 1 assumes that no additional activities would occur to impede or remediate the
DNAPL or the dissolved TCE concentration in the East Parking Lot Plume. The only activity
included in this alternative is monitoring to track the movement and the concentrations of
contaminants in the East Parking Lot Plume and Terrace Alluvial groundwater.
In addition to the East Parking Lot Plume, monitoring would include the North Plume and West
Plume in the Terrace Alluvial flow system, Meandering Road Creek, Lake Worth, and Farmers
Branch Creek. The present worth cost of Alternative 1 is $822,000.
Alternative 2a, DNAPL/Groundwater Extraction and Treatment With Air Stripping
Alternative 2a involves removal of DNAPL, remediation of dissolved TCE, and treatment of
extracted groundwater. Components of this alternative include
• Remove DNAPL by dissolution into the groundwater and then extract the groundwater.
Removal of DNAPL would be expedited by injection of clean water to help increase
dissolution of the DNAPL.
9-2 FINAL The Decision Summary
July 1996 9.0 East Parking Lot Plume
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• Treat the extracted groundwater with air stripping as the primary treatment after the
extracted groundwater passes through an oil/water separator. Treated groundwater would be
discharged to surface water or to a sewage treatment plant.
• Potential use of a barrier to separate the Window Area from high TCE concentrations in the
area of Building 181. The barrier could be a slurry wall, a system of interceptor wells, or a
horizontal well. The barrier may be installed at the beginning of the project or following
efforts to remove the DNAPL (whether or not the DNAPL is successfully removed). The
remedial design will determine if a barrier is needed at the beginning of the project.
• Initiate institutional controls to restrict future use of the Terrace Alluvial groundwater at Air
Force Plant 4 and Naval Air Station Fort Worth.
• Monitor to track plume movement and determine if the plume is likely to move off site.
Monitoring also would include the North Plume and West Plume in the Terrace Alluvial
flow system, Meandering Road Creek, Lake Worth, and Farmers Branch Creek. Monitoring
will be conducted to ensure that remediation goals are being met and to determine if
contaminated groundwater is moving off site.
• Install additional monitoring wells.
If migration of contamination in the groundwater appears to be moving off site at concentrations
above MCLs, remedial measures will be taken to stop movement of the plume. Remedial
measures could involve various containment measures, such as interceptor wells, an interceptor
trench, a combination of wells and a trench, or a slurry wall, and operation of the pump-and-treat
system at Naval Air Station Fort Worth Landfills No. 4 and No. 5.
DNAPL contamination removal would be by natural dissolution into the groundwater and
extraction from wells. A TCE concentration of 10,000 \ig/L will be used to determine if the
DNAPL has been removed to acceptable levels. When TCE concentrations drop below
10,000 |ug/L, the assumption will be that DNAPL has been removed. However, recognizing that
TCE concentrations will increase after extraction has stopped, remediation will continue until
concentrations drop below 7,500 |ug/L (75 percent of 10,000 |ug/L). If concentrations then
increase to levels above 10,000 pg/L, remediation will begin immediately and continue until the
TCE concentration drops below 7,500 jag/L again. This level would apply to the groundwater
under Building 181.
The allowable TCE concentration for the Window Area is 400 |iig/L, which is based on meeting
the MCL for TCE in the Paluxy aquifer. Although the Window Area is not directly
downgradient from Building 181, it will be affected by TCE concentrations under Building 181.
If the higher TCE concentrations under Building 181 affect the TCE concentrations in the
Window Area so that the 400-|ng/L concentration goal cannot be attained, a barrier will be used
to isolate the Window Area from higher upgradient TCE concentrations.
The Decision Summary FINAL 9-3
9.0 East Parking Lot Plume July 1996
-------
Air stripping will be used to treat the contaminants in the extracted groundwater, primarily TCE
and 1,2-DCE. The current groundwater extraction and air-stripping system in the East Parking
Lot will be expanded and used for this alternative. The air stripper will comply with all Federal,
State, and local clean air requirements, including those specific to Tarrant County, Texas. If the
air stripper does not meet air quality requirements, catalytic oxidation or carbon adsorption will
be added to help the system meet requirements.
The present worth cost of this alternative is $6,882,000. Remediation of contamination in the
East Parking Lot Plume with this alternative is estimated to take more than 100 years. This
alternative requires extraction of groundwater from the Upper Sand portion of the Paluxy
Formation to continue for the entire life (more than 100 years) of this alternative to keep
contamination from reaching the Paluxy aquifer.
Alternative 2b, DNAPL/Groundwater Extraction and Treatment With
Ultraviolet Oxidation
Alternative 2b has all the components of Alternative 2a except that treatment is by ultraviolet
oxidation rather than air stripping. Ultraviolet oxidation treatment uses ultraviolet light and
oxidation to destroy contaminants in the groundwater. Use of the current air-stripping system in
the East Parking Lot will be discontinued.
The present worth cost of this alternative is $7,334,000. Remediation of contamination in the
East Parking Lot Plume is estimated to take more than 100 years. This alternative requires that
extraction of groundwater from the Upper Sand portion of the Paluxy Formation continue for the
entire life of this alternative (more than 100 years) to keep contamination from reaching the
Paluxy aquifer.
Alternative 3, Enhanced DNAPL/Groundwater Extraction and Treatment With Air
Stripping and Destruction of Contaminants (selected remedy)
Alternative 3 is the selected alternative for the East Parking Lot Groundwater Plume. This
alternative is similar to Alternatives 2a and 2b except that removal of DNAPL would be
enhanced with the use of surfactants. Surfactants are chemicals that can be injected into the
groundwater to increase the dissolution of DNAPL and, therefore, reduce the remediation time.
The use of surfactants is considered an innovative technology.
The existing groundwater extraction and air-stripping system in the East Parking Lot will be
expanded and modified to allow surfactant recovery and reuse. Also, destruction of
contaminants in the effluent from the air stripper will be done with catalytic oxidation or vapor-
phase carbon adsorption. The present worth cost of this alternative is $10,118,000. Remediation
of contamination in the East Parking Lot Plume with this alternative is estimated to take 15 years.
This alternative requires that extraction of groundwater from the Upper Sand portion of the
Paluxy Formation continue for the entire life (15 years) of this alternative to keep contamination
from reaching the Paluxy aquifer.
9-4 FINAL The Decision Summary
July 1996 9.0 East Parking Lot Plume
-------
9.3 Comparative Analysis of Alternatives
The selected alternative for the East Parking Lot Groundwater Plume is Alternative 3, Enhanced
DNAPL/Groundwater Extraction and Treatment With Air Stripping and Destruction of
Contaminants. Table 9-1 presents a comparative analysis of the four alternatives.
Overall Protection of Human Health and the Environment
Alternative 3, Enhanced DNAPL/Groundwater Extraction and Treatment With Air Stripping and
Destruction of Contaminants, provides the best protection of human health and the environment
because it has the highest potential of removing DNAPL from the groundwater within a
reasonable time period and thereby meet the remediation goals. Alternatives 2a and 2b are
protective of human health and the environment because the traditional groundwater extraction
techniques used in these alternatives eventually will remove the DNAPL, but it will take more
than 100 years to complete. Alternative 1, No Action, is not protective of human health and the
environment because contamination from the Terrace Alluvial flow system would continue to
migrate to the Paluxy aquifer.
Overall Compliance With Applicable or Relevant and Appropriate Requirements
This section describes the ARARs that each alternative will be required to meet and if the
alternatives will be able to meet those ARARs. Table 9-2 presents a summary of the ARARs for
the East Parking Lot Groundwater Plume.
The No Action Alternative, Alternative 1, would result in a decrease in TCE concentrations
measured across the site because of natural attenuation, decomposition, and dispersion from the
plume as it migrates with the groundwater. This process is slow and would not occur in time to
prevent risk to human health and the environment. TCE would continue to diffuse through the
Window Area into the Paluxy aquifer and could affect the potable wells in White Settlement.
This alternative does not adequately provide any control or prevention of this exposure risk. This
alternative fails to ensure safe drinking water for the population of White Settlement and does
not provide environmental remediation of contaminated groundwater and would not comply with
the following ARAR:
Texas Drinking Water Standards (TAG, Title 31, Part IX, Chapter 290)
Alternative 2a uses air stripping to remove dissolved volatile contaminants and an oil/water
separator to remove emulsified DNAPL. Air emissions from the air stripper are regulated under
TAG Guidance Document Exemption 68. Removal of contaminants from the groundwater would
The Decision Summary FINAL 9-5
9.0 East Parking Lot Plume July 1996
-------
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Table 9-2. Summary of ARARs for the East Parking Lot Plume
ARAR
Texas Drinking Water
Standards (TAG,
Title 31, Part IX,
Chapter 290)
Texas Surface Water
Quality Standards (TAG,
Title 30, Part II,
Chapter 307)
National Pollutant
Discharge Elimination
System (NPDES)
(40 CFR Part 403)
Texas Regulation V:
Control of Pollution
from Volatile Organic
Compounds (TAG,
Title 3 1 . Chapter 115)
TAG Guidance
Document Exemption 68
Description
This State regulation establishes
Texas Drinking Water Standards.
These standards are written so as to
comply with the requirements of the
Safe Drinking Water Act and
Federal Primary Drinking Water
Regulations. The purpose of these
standards is to ensure the safety of
public water supplies.
The goal of this chapter is to
maintain the quality of surface
water in the State consistent with
public health and enjoyment,
protection of the environment, and
operation of existing industries and
economic development. Quality
standards for surface water are
established in this chapter.
NPDES was designed to regulate
and reduce pollution discharges to
navigable waters of the United
States.
This chapter requires the control of
VOCs and sets standards for VOC
emissions and controls.
This document provides guidance
for the air emissions from various
treatment systems to be used on
remediation projects.
Compliance
Dissolved TCE
contamination migrating to
the Paluxy Upper Sand and
then to the Paluxy aquifer
must be controlled to
comply with this
alternative.
Discharges from the
treatment systems would
need to be in compliance
with State surface water
quality standards.
Discharges from the
treatment systems would
need to meet the
requirements established in
this ARAR.
Releases of VOCs to the
air, caused by treatment of
groundwater, would need
to comply with these State
regulations.
The air-stripping treatment
system would comply with
the levels set in this
document.
Alternatives
l,2a,2b, 3
2a, 2b, 3
2a, 2b, 3
2a, 3
2a, 3b
result in compliance with Federal and State contaminant level standards. Alternative 2a would
comply with the following ARARs:
Texas Drinking Water Standards (TAC Title 31, Part IX, Chapter 290)
Texas Surface Water Quality Standards (TAC, Title 30, Part H, Chapter 307)
National Pollutant Discharge Elimination System (40 CFR Part 403)
The Decision Summary
9.0 East Parking Lot Plume
FINAL
9-7
July 1996
-------
Texas Regulation V: Control of Pollution from Volatile Organic Compounds (TAG,
Title 31, Chapter 115
• TAG Guidance Document Exemption 68
Alternative 2b also involves installing a groundwater extraction/remediation system to pump
ground water and remove dissolved TCE. The major treatment method to be used in
Alternative 2b is an ultraviolet oxidation process with an oil/water separator to remove
emulsified DNAPL. This method oxidizes the molecules of the contaminants into components
that are nontoxic and is an irreversible treatment process. It does not involve changing the state
of the contaminants as does air stripping. ARARs controlling releases of VOCs are not included
for Alternative 2b because the treatment process destroys the contaminants and does not release
them to the atmosphere. Alternative 2b would comply with the following ARARs:
Texas Drinking Water Standards (TAG, Title 31, Part IX, Chapter 290)
Texas Surface Water Quality Standards (TAG, Title 30, Part H, Chapter 307)
National Pollutant Discharge Elimination System (40 CFR Part 403)
Alternative 3 involves locating and removing the DNAPL and installing a groundwater
extraction/remediation system. By first locating the DNAPL through tracers, then targeting the
DNAPL with surfactants designed for the Terrace Alluvial flow system, the DNAPL may be
removed. After the source is removed or if it is detemined necessary before the source is
removed, a slurry wall may be installed upgradient of the Window Area. This installation would
alter the direction and amount of contaminated water flowing to the Window Area. The
construction of the slurry wall with DNAPL-resistant materials should not pose a regulatory
problem as such materials are already in use. The addition of surfactants into the groundwater
must be approved by TNRCC.
Alternative 3 uses air stripping with vapor-phase carbon adsorption or catalytic oxidation to
remove dissolved volatile contaminants and then destroy the contaminants before they are
released to the atmosphere. Air emissions from the air stripper would be directed to the vapor-
phase carbon adsorption or catalytic oxidation units. Releases from the vapor-phase carbon
adsorption or catalytic oxidation units are regulated under TAG Guidance Document
Exemption 68. Alternative 3 would comply with the following ARARs:
Texas Drinking Water Standards (TAG, Title 31, Part EX, Chapter 290)
Texas Surface Water Quality Standards (TAG, Title 30, Part H, Chapter 307)
National Pollutant Discharge Elimination System (40 CFR Part 403)
9-8 FINAL The Decision Summary
July 1996 9.0 East Parking Lot Plume
-------
• Texas Regulation V: Control of Pollution from Volatile Organic Compounds (TAG,
Title 31, Chapter 115
• TAG Guidance Document Exemption 68
Long-Term Effectiveness and Permanence
No reliable and proven techniques are available for effectively removing DNAPL from
groundwater. Alternative 3, the selected alternative, is an innovative technology that increases
the dissolution of TCE contamination into the groundwater and, therefore, has the highest
potential of removing the DNAPL. However, because Alternative 3 is an innovative technology,
there is considerable uncertainty with its performance. If it is successful, it would provide the
most-effective and permanent solution within a reasonable time period.
Alternatives 2a and 2b use groundwater pumping to extract DNAPL from groundwater. This
method is not effective because it relies on natural dissolution of TCE contamination into
groundwater to remove the concentration of TCE. Groundwater extraction is an effective
method of removing dissolved contamination but dissolution of TCE DNAPL into the
groundwater is a slow process that makes Alternatives 2a and 2b ineffective. No Action,
Alternative 1, provides the least long-term effectiveness and permanence because it relies entirely
on natural dissolution of the TCE DNAPL into the dissolved phase and then natural attenuation
of the dissolved TCE.
Reduction of Toxicity, Mobility, or Volume Through Treatment
Alternatives 2a and 2b and the selected alternative, Alternative 3, all reduce mobility and volume
through treatment by removing TCE contamination from the groundwater. Alternatives 2b and 3
provide reduction in toxicity because contaminants are destroyed in the ultraviolet oxidation,
catalytic oxidation, or carbon adsorption process. It should be noted that contaminants are only
destroyed with the carbon adsorption process when the carbon is regenerated. Contaminants are
only transferred from groundwater to air with the air-stripping treatment used in Alternative 2a.
Alternatives 2a and 2b provide a much slower reduction in toxicity, mobility, and volume than
Alternative 3 because removal of contaminants from the groundwater is dependent on natural
dissolution.
Alterative 1, No Action, provides the least reduction in toxicity, mobility, or volume through
treatment because it relies on natural attenuation.
Short-Term Effectiveness
The No Action Alternative would have the least short-term risk to workers and the community
from a remedial action but would take the longest time to reach cleanup levels. Alternatives 2a
and 2b will have minimal short-term risks to workers and the community but have long
remediation times, more than 100 years. Alternative 3 also will have minimal short-term risk to
workers and the community but will be the most intensive remedial action and, therefore, have
The Decision Summary FINAL 9-9
9.0 East Parking Lot.Plume July 1996
-------
the highest short-term risks to workers and the community during its project life of 15 years.
Because Alternatives 2a and 2b have such long project lives, they have higher overall short-term
risks to the community and workers than the selected alternative.
Alternatives 2a and 2b rely on the natural dissolution of DNAPL into the groundwater for
removal. Because TCE has a low solubility, the estimated time for the DNAPL to dissolve and
allow cleanup levels to be reached is more than 100 years. The No Action Alternative would
take longer to dissolve the DNAPL than Alternatives 2a and 2b.
Implementability
The No Action Alternative is the easiest to implement, requiring only monitoring.
Alternatives 2a and 2b are relatively easy to implement because established technologies are
used. Alternative 2b is more difficult to implement than Alternative 2a because treatment with
ultraviolet oxidation is more complex than treatment with air stripping. The selected alternative,
Alternative 3, is the most difficult to implement because it uses new technology.
Cost
The selected alternative is the most expensive with a present worth cost of $10,118,000. The No
Action Alternative is the least expensive, involving only monitoring, with a present worth cost of
$822,000. Alternatives 2a and 2b have present worth costs of $6,882,000 and $7,334,000,
respectively.
If either Alternative 2a or 2b were the selected alternative, the selected alternative for the Paluxy
aquifer and Upper Sand groundwater will be required to operate for the entire project life of more
than 100 years. This extended period of operation would result in an increase of the present
worth cost of the selected alternative for the Paluxy aquifer and Upper Sand groundwater.
State Acceptance
The Texas Natural Resource Conservation Commission concurs with the selected alternative.
Community Acceptance
The Air Force solicited input from the community and from members of the Restoration
Advisory Board on the remediation alternatives proposed for the East Parking Lot Plume. The
comments received from the public and Restoration Advisory Board members indicate that the
community is supportive of the selected remedy, Alternative 3, Enhanced DNAPL/Groundwater
Extraction and Treatment With Air Stripping and Destruction of Contaminants.
The draft Proposed Plan was presented to members of the Restoration Advisory Board. The
preferred alternative in the draft Proposed Plan was Alternative 3, but it did not include
destruction of contaminants from the air stripper. Members of the Restoration Advisory Board
expressed concern over the use of air stripping for treatment because contaminants would be
9-10 FINAL The Decision Summary
July 1996 9.0 East Parking Lot Plume
-------
released to the atmosphere. Tarrant County, Texas, is a nonattainment zone for ozone; air
stripping would release VOCs to the atmosphere and could contribute to ozone formation.
However, the levels of VOCs released to the atmosphere would be within the allowable limits
established by State of Texas regulations.
On the basis of comments received from the public, the Air Force, with the concurrence of the
EPA and the State of Texas, agreed to modify Alternative 3 to include destruction of
contaminants. Air discharged from the air stripper will pass through a catalytic oxidation unit or
vapor-phase carbon adsorption units to remove contamination before being released to the
atmosphere. Alternative 3, as modified to include destruction of contaminants, was the preferred
alternative in the final Proposed Plan that was presented at the public meeting in December 1995.
All comments received during the public comment period and the Air Force responses are in
Appendix A, "Responsiveness Summary."
9.4 The Selected Remedy
The Air Force, with the concurrence of the EPA and the State of Texas, has determined that
Alternative 3, Enhanced DNAPL/Groundwater Extraction and Treatment With Destruction of
Contaminants, is the best remedy for achieving the remediation goals. As presented in
Section 9.1, the remediation goals for the East Parking Lot Groundwater Plume are
• Prevent TCE concentrations in the Window Area of the East Parking Lot Groundwater
Plume from exceeding 400 |Jg/L.
• Remove DNAPL from the groundwater in the soil under Building 181 and under the
southern portion of the Assembly Building/Parts Plant.
• Prevent groundwater in the East Parking Lot Plume and Terrace Alluvial flow system with
contamination above MCLs from migrating off Air Force Plant 4 or Naval Air Station
Fort Worth and prevent groundwater contamination from causing excess risk in surface
water. Exceedance of MCLs will be determined on a statistical basis.
The first remedial action objective is based on a calculated concentration in the East Parking Lot
Plume that will not cause TCE levels in the Paluxy aquifer to exceed 5.0 |ug/L. DNAPL may be
present in the Window Area and, if present, would have to be removed before TCE
concentrations of 400 |ug/L could be met. For purposes of compliance with the TCE
concentration of 400 Mg/L, the Window Area is defined as the area where the aquitard is less than
2 ft thick. This area is approximately 500 ft in diameter and is centered around monitoring
well W-149. During remedial activities, other areas could be identified that meet the definition
of the Window Area. If other areas do meet the definition of the Window Area, the allowable
TCE concentrations for those areas also will be 400 |ug/L.
The second remedial action objective is to remove DNAPL from the groundwater. This remedial
action objective will be demonstrated by reducing TCE concentrations to levels below
10,000 ng/L. The TCE level of 10,000 ng/L is approximately 1 percent of TCE's solubility in
The Decision Summary FINAL 9-11
9.0 East Parking Lot Plume July 1996
-------
water (1,100,000 |ug/L). This value was chosen on the basis of technical information suggesting
that DNAPL may be present when TCE concentrations are as low as 1 percent of its solubility
in water.
Groundwater in the Terrace Alluvial flow system is not used as a drinking water source by Air
Force Plant 4 or Naval Air Station Fort Worth because of low yield and poor quality of water and
because the Paluxy aquifer is a readily available source of good quality water. Therefore, no risk
is associated with contamination in the Terrace Alluvial flow system within the boundaries of
Plant 4 and Naval Air Station Fort Worth. However, the potential exists that an individual off
site could use this groundwater as drinking water. Because of this potential, the third remedial
action objective was established to prevent groundwater that has contamination above MCLs
from leaving Federal property boundaries.
Exceedance of MCLs also applies to the West Fork of the Trinity River and will be the target for
determining if corrective action is needed. A TCE concentration of 5,000 |ag/L in Farmers
Branch Creek, based on ecological risk, will be another target for determining if corrective action
is needed.
On the basis of information obtained during the remedial investigation and the analysis of
remedial alternatives, the Air Force, the EPA, and the State of Texas believe that the selected
groundwater remedy will attain these goals. The selected remedy meets the remediation goals by
• Removing DNAPL by enhanced dissolution into the groundwater and then extracting
the groundwater.
• Treating the extracted groundwater with air stripping as the primary treatment after the
extracted groundwater passes through an oil/water separator. Treated groundwater would be
discharged to surface water or to a sewage treatment plant. Air discharged from the air
stripper will pass through a catalytic oxidation unit or vapor-phase carbon adsorption units
before being discharged to the atmosphere.
• Potential use of a barrier to separate the Window Area from high TCE concentrations in the
area of Building 181. The barrier could be a slurry wall, a system of interceptor wells, or a
horizontal well. The barrier may be installed at the beginning of the project or following
efforts to remove the DNAPL (whether or not the DNAPL is successfully removed). The
remedial design will determine if a barrier is needed at the beginning of the project.
• Initiating institutional controls to restrict future use of the Terrace Alluvial groundwater at
Air Force Plant 4 and Naval Air Station Fort Worth.
• Monitoring to track the areal extent and movement of contamination, the contaminant levels
within and around the DNAPL remediation area, and the changes in contaminant
concentrations within the plume. Monitoring also would include the North Plume and West
Plume in the Terrace Alluvial flow system, Meandering Road Creek, Lake Worth, and
9-12 FINAL The Decision Summary
July 1996 9.0 East Parking Lot Plume
-------
Farmers Branch Creek. Monitoring will be conducted to ensure that remediation goals are
being met and to determine if contaminated ground water is moving off site.
• Installing additional monitoring wells.
• If migration of contamination in the groundwater appears to be moving off site at
concentrations above MCLs, corrective actions will be taken to stop the plume. Corrective
actions could involve various containment measures, such as interceptor wells, an
interceptor trench, a combination of wells and a trench, or a slurry wall, and operation of the
pump-and-treat system at Naval Air Station Fort Worth Landfills No. 4 and No. 5.
A more detailed description of the selected remedy follows. It should be noted that certain
aspects of the selected remedy may change during remedial design. The costs of the selected
remedy are
Capital Cost $ 7,753,000
Present Worth of O&M Costs 1,166,000
Present Worth of Monitoring Costs 1,199,000
Total Present Worth of Alternative 3 $ 10,118,000
Capital costs are assumed to occur within the first year and include installation of groundwater
extraction wells, purchase of surfactants, installation of an air-stripping treatment system and a
catalytic oxidation unit to treat the air discharged from the air stripper, piping from the treatment
system to the discharge point, electrical connections, and installation of additional monitoring
wells. O&M costs include electrical requirements, water sampling for compliance, and
equipment maintenance and replacement. Monitoring costs are annual costs that include
obtaining samples from monitoring wells and laboratory analysis of those samples.
Extraction of groundwater from the East Parking Lot Plume will be from approximately
10 extraction wells operating at one time with each well estimated to pump 5 gal/min. Only a
small area of the East Parking Lot Plume will be remediated at a time to ensure better control of
the surfactant injection and extraction processes. The initial assumption is that an area being
remediated would have 10 injection and 10 extraction wells.
Monitoring will be conducted to track contaminant levels in the Terrace Alluvial flow system
(includes the East Parking Lot Plume, North Plume, and West Plume) and potentially affected
surface waters. The location of monitoring wells, number of monitoring wells, and frequency of
sampling in the North Plume and the West Plume will be established to provide early detection
of contamination before it migrates off site at levels that exceed MCLs of the contaminants.
The locations of monitoring wells, number of monitoring wells, and frequency of sampling in the
East Parking Lot Plume will be established to monitor remedial action in the Window Area
(remediation goal of 400 |ug/L), to monitor remedial action in the DNAPL area (remediation goal
of 10,000 |ug/L), and to provide early detection of contamination along the perimeter of the
plume before it migrates off site at levels that exceed the MCLs of the contaminants.
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9.0 East Parking Lot Plume July 1996
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If monitoring indicates that contamination in the East Parking Lot Plume, the North Plume, or
the West Plume may migrate off Federal property at levels that exceed MCLs, remedial actions
or additional monitoring wells will be considered. Remedial actions may include an interceptor-
well system similar to the system at Landfill No. 3. The existing system at Naval Air Station
Fort Worth Landfills No. 4 and No. 5 could also be reactivated if remediation goals are not being
met. Also, the Air Force, with the concurrence of the EPA and the State of Texas, may use other
technologies such as permeable treatment walls to mitigate contamination moving off Federal
boundaries.
The following assumptions for monitoring are based on a preliminary plan. The final monitoring
plan, to be developed during remedial design, will be more detailed and may be slightly different.
• Contamination levels in the DNAPL remediation area of the East Parking Lot Plume will be
monitored with analysis of samples from wells located near the edge of the suspected
DNAPL area and within the Window Area. Monitoring will be performed as needed during
DNAPL remediation (estimated at 15 years), semiannually at a minimum, and then annually
after the remediation is completed.
• Contamination levels along the perimeter of the East Parking Lot Plume and the boundaries
of Plant 4 and Naval Air Station Fort Worth will be monitored with analysis of samples
from wells located to allow detection of contamination before it can migrate off Federal
boundaries. Samples will be taken semiannually during remediation of the DNAPL area and
then may be taken annually if contamination levels remain relatively steady and are not
increasing.
• -Contamination levels in the West Plume will be monitored with analysis of samples from
wells near the boundary of Plant 4. Sampling will be conducted semiannually for at least
5 years and then may be performed annually if contamination levels remain relatively steady
and are not increasing.
• Contamination levels in the North Plume will be monitored with analysis of samples from
wells near the boundary of Plant 4. Sampling will be conducted semiannually for at least
5 years and then may be performed annually if contamination levels remain relatively steady
and are not increasing.
• Contamination levels in the surface waters of Lake Worth, Farmers Branch Creek, and the
West Fork of the Trinity River will be monitored with analysis of samples from several
locations. Sampling points will be located where the surface water is most likely to be
affected by contaminated groundwater discharge. Sampling will be conducted semiannually,
except for annual sampling of the West Fork of the Trinity River.
• Sampling of the North Plume, the West Plume, and the perimeter areas of the East Parking
Lot Plume will be discontinued when it can be demonstrated that the concentrations of
contaminants in the plumes will not exceed MCLs at the Federal property boundaries.
Sampling of Lake Worth will be discontinued when sampling of the North Plume is
9-14 FINAL The Decision Summary
July 1996 9.0 East Parking Lot Plume
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discontinued. Sampling of Farmers Branch Creek and the West Fork of the Trinity River
will be discontinued when sampling of the East Parking Lot Plume perimeter is
discontinued.
• Additional monitoring wells will be installed where needed.
• All samples will be analyzed for VOC and metal concentrations.
Surfactant-enhanced extraction of DNAPL is the most promising of all technologies and
approaches considered to meet the remediation goals that are applicable to the East Parking Lot
Plume. However, the use of surfactants to remove DNAPL is an innovative technology and there
is considerable uncertainty about its performance.
The contingency measures described in Section 8.5, "The Selected Remedy," for the Paluxy
aquifer and Upper Sand groundwater are also applicable to the selected remedy for the East
Parking Lot Plume.
9.5 Statutory Determinations
The most important aspect of the selected remedy is to be protective of human health and the
environment. Section 121 of CERCLA also requires that the selected remedial action comply
with ARARs established under Federal or State laws, unless a waiver is granted. In addition, the
selected remedy must be cost effective and use permanent solutions or resource-recovery
technologies to the maximum extent practicable. Section 121 also contains a preference for
remedial actions that use treatment as a primary element. The following text discusses how the
selected remedy, Alternative 3, Enhanced DNAPL/Groundwater Extraction and Treatment With
Air Stripping and Destruction of Contaminants, meets the statutory requirements.
Protection of Human Health and the Environment
The selected remedy protects human health and the environment by reducing concentrations of
TCE in the Window Area of the East Parking Lot Plume to 400 |ug/L. The selected remedy has
the best potential of restoring the groundwater in the East Parking Lot Plume to required levels.
A TCE concentration of 400 |Jg/L was determined as the maximum allowable concentration in
the Window Area that would not cause TCE concentrations in the Paluxy aquifer to exceed
5.0^g/L,theMCLforTCE.
Contamination in the East Parking Lot Plume has migrated onto Naval Air Station Fort Worth
where TCE-contaminated groundwater discharges to Farmers Branch Creek. Present levels of
TCE contamination do not cause excess human health or ecological risk in Farmers Branch
Creek. Contamination levels in Farmers Branch Creek will be monitored to ensure allowable
levels are not exceeded.
The Decision Summary FINAL 9-15
9.0 East Parking Lot Plume July 1996
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Farmers Branch Creek flows into the West Fork of the Trinity River, which is used as a drinking
water supply. Monitoring of contamination in the West Fork of the Trinity River also will be
conducted to ensure MCLs are not exceeded.
Compliance With Applicable or Relevant and Appropriate Requirements
The selected remedy will comply with all ARARs, and an ARAR waiver will not be required for
implementation. The groundwater in the East Parking Lot Plume and Terrace Alluvial flow
system is not used as drinking water on Air Force Plant 4 or Naval Air Station Fort Worth so
remediation to MCLs is required. The treated groundwater will be discharged to surface waters
so the requirements of State of Texas water quality standards and NPDES must be met. ARARs
governing the release of VOCs to the atmosphere are applicable, but the selected remedy will use
air stripping with off-gas treatment to minimize contaminants that are released to the atmosphere.
Cost Effectiveness
The Air Force, with the concurrence of the EPA and the State of Texas, believes the selected
remedy, Alternative 3, Enhanced DNAPL/Groundwater Extraction and Treatment With Air
Stripping and Destruction of Contaminants, is cost effective at meeting the remediation goals and
protecting human health and the environment, The selected remedy has the highest net present
worth of all the alternatives ($10,118,000) but is the only alternative that has the potential to
meet the remediation goals within a reasonable time period (i.e., 15 years), complies with all
ARARs, and does not release contaminants to the atmosphere.
Alternatives 2a and 2b have a lower net present worth ($6,882,000 and $7,334,000, respectively)
but cannot meet the remediation goals within a reasonable time period. Traditional groundwater
extraction techniques have been shown to be ineffective at removing DNAPL and, therefore, it
would take more than 100 years for Alternative 2a or 2b to meet remediation goals.
Use of Permanent Solutions and Treatment or Resource-Recovery Technologies to the
Maximum Extent Practicable
The selected remedy uses permanent solutions and treatment technologies to the maximum
extent practicable. Of the alternatives that meet the threshold criteria (protection of human
health and environment and compliance with ARARs), the selected remedy provides the best
balance of trade-offs in terms of the balancing criteria. The selected remedy provides the best
long-term effectiveness and permanence and the best reduction in toxicity, mobility, and volume
and is best in terms of short-term risks to workers and the community.
The cost of the selected remedy is the highest of all the alternatives, but it is considered cost
effective because it has the best chance of all the alternatives of meeting remediation goals. The
selected remedy also is the most difficult of all the alternatives to implement because it uses an
innovative technology. However, the selected remedy is still readily implemented.
9-16 FINAL The Decision Summary
July 1996 9.0 East Parking Lot Plume
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Preference for Treatment as a Principal Element
The selected remedy meets the statutory preference for treatment as a principal element. The
principal threat to human health is TCE and 1,2-DCE contamination in the Paluxy aquifer that
exceeds MCLs. The selected remedy addresses the principal threat by removing DNAPL and
reducing contamination levels in the Window Area of the East Parking Lot Plume to levels that
will not cause MCLs to be exceeded in the Paluxy aquifer. Extracted groundwater is treated with
air stripping before being discharged to surface waters. Also, air discharged from the air stripper
will be treated with an off-gas treatment system before being released to the atmosphere.
9.6 Documentation of Significant Changes
The Proposed Plan was released for public comment in November 1995. A draft of the Proposed
Plan was released to members of the Restoration Advisory Board before the public comment
period. The Draft Proposed Plan identified Alternative 3, Enhanced DNAPL/Groundwater
Extraction and Treatment With Air Stripping and Destruction of Contaminants, as the selected
alternative. There was considerable concern by members of the Restoration Advisory Board
about the use of air stripping because contaminants would be released to the atmosphere.
Considering the concern expressed by members of the Restoration Advisory Board, the Air Force
revised the selected alternative to include vapor-phase carbon adsorption or catalytic oxidation to
remove TCE from the effluent of the air stripper.
The final Proposed Plan, dated November 1995, included the revised Alternative 3, Enhanced
DNAPL/Groundwater Extraction and Treatment With Air Stripping and Destruction of
Contaminants, as the selected remedy. The revised Alternative 3 was presented as the selected
remedy at the public meeting on the Proposed Plan. The Air Force reviewed all written and oral
comments submitted during the public comment period. After review of these comments, no
significant changes to the selected remedy, as identified in the Proposed Plan dated
November 1995, were made.
The Decision Summary FINAL 9-17
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9-18 FINAL The Decision Summary
July 1996 9.0 East Parking Lot Plume
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10.0 Building 181
10.1 Remediation Goals
The remedial action objective for the soil under Building 181 is to prevent TCE concentrations in
the soil from causing unacceptable groundwater contamination in the Paluxy aquifer.
The soil cleanup level was based on a concentration of TCE in the soil that would not allow
leachate from the soil to exceed Terrace Alluvial groundwater cleanup levels. A TCE soil
contamination level of 11.5 mg/kg was established on the basis of an allowable leachate
concentration that would migrate from the soil to the Terrace Alluvial groundwater. The
allowable TCE concentration in the leachate was assumed to be 5,000 |Jg/L. A level one-half the
remedial action objective for TCE in groundwater (10,000 |ug/L) was used to add conservatism
and to ensure that peak concentrations in the groundwater would not result from TCE
contamination in soil.
10.2 Description of Alternatives
Two alternatives were developed for TCE contamination in the soil under Building 181, No
Action and Soil-Vapor Extraction. Soil-vapor extraction was the only treatment alternative
developed because EPA has designated this method as a presumptive remedy for VOC
contamination in soil, where the technology is applicable on the basis of site conditions. Pilot
tests conducted at Plant 4 to test the applicability of soil-vapor extraction show it to be effective.
• Alternative 1, No Action
• Alternative 2, Soil-Vapor Extraction (selected remedy)
Alternative 1, No Action
Present Worth: $0
Implementation Time: 0 years
Alternative 1 assumes that no activities will occur to remediate the contaminated soil.
Monitoring is not included in this alternative. TCE concentrations in the groundwater will be
monitored as part of the selected alternative for the East Parking Lot Groundwater Plume. No
costs are associated with the No Action Alternative because the only monitoring would be of the
Terrace Alluvial groundwater and costs for monitoring the Terrace Alluvial groundwater are
included in the alternatives for the East Parking Lot Plume.
Alternative 2, Soil-Vapor Extraction (selected remedy)
Present Worth: $612,000
Implementation Time: 5 years
The Decision Summary FINAL 10-1
10.0 Building 181 July 1996
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Alternative 2 is the selected alternative for this site. It will be used to remove TCE
contamination from the soil under Building 181. Alternative 2 is essentially an expansion of the
pilot-scale system currently in operation. Components of this alternative include
• Vapor-recovery wells. An initial estimate of 18 vapor-recovery wells has been determined,
but this number could change depending on the subsurface conditions encountered.
• A blower to create a vacuum in the wells and extract the TCE contamination.
• Removal of contaminants from the extracted air before release to the atmoshpere.
Contaminants may be removed with vapor-phase carbon adsorption, catalytic oxidation, or
another technology that removes the contamination in the air before it is released to the
atmosphere.
• Vacuum-enhanced recovery wells to remove groundwater within the vadose zone
(groundwater on top of clay layers in the soil above the Terrace Alluvial groundwater).
• Treatment of the extracted groundwater with air stripping and near-zero off-gas emissions.
Contaminants in the off gas may be destroyed with with vapor-phase carbon adsorption,
catalytic oxidation, or other technologies that remove the contamination in the air before it is
released to the atmosphere. The treated groundwater will be discharged to surface water or a
sewage treatment plant.
• Soil-gas probes to monitor performance. Monitoring will continue as long as remedial
action activities are ongoing.
Soil-vapor extraction works by creating a vacuum in recovery wells; the vacuum volatilizes the
TCE and causes it to be drawn into the wells. The vapor is then conveyed by piping to
vapor-phase carbon adsorption units where the TCE adheres to the carbon. The air that is free of
TCE is then vented to the atmosphere.
Vapor-phase carbon adsorption units were selected for pilot-scale testing to remove TCE.
Another method of removing the TCE contamination is to destroy the TCE with catalytic
oxidation. Both carbon adsorption and catalytic oxidation are equally effective at removing TCE
contamination and will be considered for the final design. The present worth of the alternative is
$612,000. Remediation will continue until cleanup levels of 11.5 mg/kg of TCE in the soil are
met, which is expected to take approximately 5 years.
10.3 Comparative Analysis of Alternatives
The selected alternative for Building 181 is Alternative 2, Soil-Vapor Extraction. Table 10-1
presents a comparative analysis of the two alternatives.
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July 1996 10.0 Building 181
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Table 10-1. Comparative Analysis of Soil Alternatives for Building 181
Criteria
Alternative 1,
No Action
Alternative 2,
Soil Vapor Extraction
(selected remedy)
Overall Protection of Human
Health and the Environment
Protective of human health and the
environment only for exposure to
soil in the vadose zone; not
protective of groundwater.
Rating: Not Protective
Protective of human health and the
environment for both the soil in the
vadose zone and the groundwater.
Rating: Protective
Compliance with ARARs
Complies with ARARs related to
TCE in the soil because there are no
ARARs requiring action.
Rating: Complies
Release of TCE to the atmosphere
needs to comply with ARARs.
Alternative would comply with
ARARs.
Rating: Complies
Long-Term Effectiveness and
Permanence
Allows continued mitigation of TCE
to the groundwater. No change over
baseline condition.
Rating: Poor
Residual risks are significantly
reduced because TCE is permanently
removed. Pilot tests have shown
soil-vapor extraction to be effective
at this site.
Raring: Good
Reduction of Toxicity,
Mobility, or Volume Through
Treatment
No reductions in toxicity, mobility,
or volume over baseline condition.
Rating: Poor
Reduces toxicity, mobility, and
volume through treatment. TCE
removed from the vadose zone is
destroyed by off-gas treatment or
during regeneration of the carbon
adsorption canisters.
Rating: Good
Short-Term Effectiveness
Least short-term risks to the
community, workers, or the
environment.
Ratine: Good
Small risk potential to workers in the
plant from TCE vapor but controls
for the TCE vapor are effective.
Estimated cleanup time is 5 years.
Rating: Good
Implementability
Easiest to implement. There are
no administrative or technical
difficulties.
Rating: Good
Relatively easy to implement.
Technology is available from many
sources and it uses material that is
readily available.
Rating: Good
Cost
No costa
$612,000
aNo cost is assigned to this alternative because monitoring costs are included in the alternatives for the East
Parking Lot Plume.
Overall Protection of Human Health and the Environment
The selected alternative, Alternative 2, is protective of human health and the environment
because it stops contamination from reaching the groundwater at unacceptable levels. The No
Action Alternative is not protective of human health and the environment because contamination
The Decision Summary
10.0 Building 181
FINAL
10-3
July 1996
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in the soil under Building 181 causes groundwater contamination that ultimately contaminates
the Paluxy aquifer.
Compliance With Applicable or Relevant and Appropriate Requirements
No chemical-, action-, or location-specific ARARs are applicable to the TCE contamination in
the vadose zone under Building 181. Therefore, Alternative 1, No Action, would not violate any
ARARs for the vadose zone. However, selection of this alternative would result in continued
contamination of the groundwater and subsequent contamination of the Paluxy aquifer at levels
above regulatory levels.
Alternative 2 involves using soil-vapor extraction to extract vapor-phase TCE from the vadose zone
under Building 181 and then remove TCE concentrations from the air stream before discharging the
air to the atmosphere. Alternative 2 must comply with ARARs governing the release of TCE and
other VOCs. Specific requirements are established for releases of VOCs in Tarrant County, Texas,
because it is a nonattainment area for ozone. Releases from the vapor extraction system will be
controlled to allowable levels with vapor-phase carbon adsorption or catalytic oxidation. The
following ARARs are applicable to Alternative 2:
• Texas Regulation V: Control of Pollution from Volatile Organic Compounds (TAC, Title 30,
Chapter 115) — This chapter requires the control of VOCs and sets standards for VOC
emissions and controls. Release of VOCs to the air, caused by treatment of groundwater,
requires compliance with these State regulations.
• TAC Guidance Document Exemption 68 — This document provides guidance for the air
emissions from various treatment systems to be used on remediation projects. The chosen
treatment system would comply with this document.
Long-Term Effectiveness and Permanence
The selected alternative, Alternative 2, provides the best long-term effectiveness by permanently
removing TCE contamination from the soil under Building 181. However, because of limitations of
the technology, complete removal of all TCE in the vadose zone will not be achieved. TCE will
remain in varying amounts in some areas. Alternative 1, No Action, provides minimal long-term
effectiveness through natural biodegradation of the TCE contamination in the soil.
Reduction of Toxicity, Mobility, or Volume Through Treatment
Alternative 2, Soil-Vapor Extraction, provides reduction in toxicity, mobility, and volume through
active treatment by removing contaminants from the soil and destroying the contaminants. The
toxicity and volume of the contaminants are reduced when the carbon adsorption units that extract
the TCE contamination from the air are regenerated or when the TCE is destroyed by a catalytic
oxidation unit. Alternative 1, No Action, does not provide any reduction in toxicity, mobility, or
volume through treatment.
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July 1996 10.0 Building 181
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Short-Term Effectiveness
Alternative 1, No Action, is the best for short-term effectiveness because it involves the least risk to
workers and the community during implementation of the alternative. However, the short-term
risks of the selected alternative, Alternative 2, are minimal and there will be no noticeable increase
in risk to the community and workers from the selected alternative. Also, the selected alternative
will be completed within a reasonable time period, estimated at 5 years. There is considerable
uncertainty in the time-to-cleanup estimate because no information is available on the quantity of
TCE that has been spilled and how much TCE remains in the vadose zone. The estimate of 5 years
to meet the remediation goal is based on an assumption that 61,000 pounds (5,000 gallons) of
TCE are present in the vadose zone and the soil-vapor extraction system will be able to remove
12,200 pounds (1,000 gallons) per year.
Implementability
The selected alternative will be relatively easy to implement because established technologies are
used, equipment is readily available from several vendors, and pilot-scale tests have been
performed to help work out any difficulties with operating the equipment. However,
Alternative 1, No Action, is easier to implement because it does not require any construction or
operation of equipment.
Cost
The No Action Alternative does not have any costs but would result in higher groundwater
treatment costs for the East Parking Lot Groundwater Plume. The higher groundwater treatment
costs have not been estimated. The present worth cost of the selected alternative, Alternative 2,
is estimated at $612,000. This is based on a 5-year project life and a discount rate of 5 percent
applied to O&M costs.
State Acceptance
The Texas Natural Resource Conservation Commission concurs with Alternative 2, Soil Vapor-
Extraction, as the preferred remedy for TCE contamination in the vadose zone under
Building 181.
Community Acceptance
The Air Force solicited input from the community and from members of the Restoration
Advisory Board on the remediation alternatives proposed for Building 181. The comments
received from the public and Restoration Advisory Board members indicate that the community
is supportive of the selected remedy for Building 181. All comments received during the public
comment period and the Air Force responses are in Appendix A, "Responsiveness Summary."
The Decision Summary FINAL 10-5
10.0 Building 181 July 1996
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10.4 The Selected Remedy
The Air Force, with the concurrence of the EPA and the State of Texas, has determined that
Alternative 2, Soil-Vapor Extraction, is the best remedy for achieving the remediation goal.
As presented in Section 10.1, the remediation goal for Building 181 is to prevent TCE
concentrations in the soil from causing unacceptable groundwater contamination in the
Paluxy aquifer.
An allowable TCE soil contamination level of 11.5 mg/kg was established to meet the
remediation goal. The TCE soil contamination level is not based on risk but on an allowable
leachate concentration that would migrate from the soil to the Terrace Alluvial groundwater. The
allowable TCE concentration in the leachate was assumed to be 5,000 pg/L. A level that is
one-half the remedial action objective for TCE in groundwater (one half of 10,000 |ng/L) was
used to ensure that peak concentrations in the Terrace Alluvial groundwater under Building 181
would not result from TCE contamination in soil.
On the basis of information obtained during the remedial investigation and the analysis of
remedial alternatives, the Air Force, the EPA, and the State of Texas believe that the selected
remedy for Building 181 will attain this goal. The selected remedy will meet this goal by
• Using vapor-recovery wells to extract volatilized TCE. An initial estimate of 18 vapor-
recovery wells has been determined, but this number could change depending on the
subsurface conditions encountered.
• Installing a blower to create a vacuum in the wells and extract the TCE contamination.
• Removal of contaminants from the extracted air before release to the atmosphere.
Contaminants may be removed with vapor-phase carbon adsorption, catalytic oxidation, or
other technologies that remove the contamination in the air before it is released to the
atmosphere.
• Vacuum-enhanced recovery wells to remove groundwater within the vadose zone
(groundwater on top of clay layers in the soil above the Terrace Alluvial groundwater).
• Treatment of the extracted groundwater with air stripping and near-zero off-gas emissions.
Contaminants in the off gas may be destroyed with vapor-phase carbon adsorption, catalytic
oxidation, or other technologies that remove the contamination in the air before it is released
to the atmosphere. The treated groundwater will be discharged to surface water or a sewage
treatment plant.
• Installing soil-gas probes to monitor performance. Monitoring will continue as long as
remedial action activities are ongoing.
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July 1996 10.0 Building 181
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A more detailed description of the selected remedy follows. It should be noted that certain
aspects of the selected remedy may change during remedial design. The costs of the selected
remedy are
Capital Cost $259,000
Present Worth of O&M Costs 353,000
Total Present Worth of Alternative 2 $612,000
Capital costs are assumed to occur within the first year and include installation of additional
vapor extraction wells (e.g., perched zone wells and upper zone wells), a blower, installation of
an air-stripping treatment system and carbon adsorption units to treat the air discharged from the
air stripper and from the vapor recovery wells, piping from the extraction wells to the carbon
adsorption units, and electrical connections. O&M costs include electrical requirements,
equipment maintenance and replacement, replacement of carbon adsorption canisters, and
sampling with the soil-gas probes. O&M costs include carbon adsorption canisters but other off-
gas treatment technologies may be used. The cost of the completed pilot tests is not included in
this estimate.
Extraction of volatilized TCE will be from 18 extraction wells. Eleven of the extraction wells
are assumed to be perched wells (screened at approximately 5 ft below ground surface), and 7 of
the extraction wells are assumed to be upper zone wells (screened at approximately 25 ft below
ground surface). Extraction wells that encounter groundwater will be made into dual-phase
extraction wells that allow both groundwater and air to be extracted and treated. Extracted
groundwater will be treated with air stripping. Air discharged from the air stripper will be sent
through the carbon adsorption units before being released to the atmosphere. Approximately
30 to 40 soil-gas probes will be installed to monitor the concentrations of TCE in the vadose
zone.
Soil-vapor extraction is an effective technology at removing TCE from the vadose zone.
However, because of limitations of the technology and conditions that are inherent to the
subsurface, removal of TCE to the levels specified by the remediation goal (11.5 mg/kg) from all
areas under Building 181 may not be possible. If implementation of the selected remedy
demonstrates that it is technically impracticable to meet the remediation goal for the area of
attainment (the area under Building 181), operation of the soil-vapor extraction system may be
discontinued, with concurrence of EPA and the State of Texas. For example, if TCE levels in the
extraction wells are minimal and measures such as the placement of additional extraction wells
does not increase removal rates, operation of the system may be discountinued.
No other actions are currently planned if it is deemed technically impracticable to meet
remediation goals. Measures such as containment of the groundwater under Building 181 may
be considered. The result of discontinuing operation of the soil-vapor extraction system before
remediation goals are met is not known because the remediation goal is based on assumed
subsurface conditions that may not represent actual conditions. Discontinuing operation of the
extraction system may result in a longer remediation time for the Terrace Alluvial groundwater
under Building 181 or it may have no noticable effect.
The Decision Summary FINAL 10-7
10.0 Building 181 July 1996
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An assumption for remediation of the vadose zone under Building 181 is that the Terrace
Alluvial groundwater under Building 181 will be remediated to levels below 10,000 (ig/L.
Remediation of the Terrace Alluvial groundwater under Building 181 requires removal of
DNAPL and may not be technically practicable. If it is determined that remediation of the
Terrace Alluvial groundwater under Building 181 is technically impracticable and adequate
containment measures are implemented, the operation of the soil-vapor extraction system may be
discontinued.
10.5 Statutory Determinations
The most important aspect of the selected remedy is to be protective of human health and the
environment. Section 121 of CERCLA also requires that the selected remedial action comply
with ARARs established under Federal or State laws, unless a waiver is granted. In addition, the
selected remedy must be cost effective and use permanent solutions or resource-recovery
technologies to the maximum extent practicable. Section 121 also contains a preference for
remedial actions that use treatment as a primary element. The following text discusses how the
selected remedy, Alternative 2, Soil-Vapor Extraction, meets the statutory requirements.
Protection of Human Health and the Environment
The selected remedy protects human health and the environment by reducing concentrations of
TCE in the vadose zone to concentrations that will not exceed the allowable levels for the
Terrace Alluvial groundwater under Building 181 (10,000 |ug/L). Maintaining an allowable TCE
concentration in the Terrace Alluvial groundwater is an important aspect of protecting the
groundwater in the Paluxy aquifer, which is the exposure route for human health risk.
Compliance With Applicable or Relevant and Appropriate Requirements
The selected remedy will comply with all ARARs and an ARAR waiver will not be required for
implementation. The selected remedy will comply with State ARARs governing the release of
TCE and other VOCs to the atmosphere. There also are specific ARARs for releases of VOCs in
Tarrant County, Texas, because it is a nonattainment area for ozone. Releases from the vapor
extraction system will be controlled to allowable levels with vapor-phase carbon adsorption or
catalytic oxidation. The discharge of treated groundwater will comply with NPDES and Texas
Surface Water Quality Standards.
Cost Effectiveness
The Air Force, with the concurrence of the EPA and the State of Texas, believes the selected
remedy, Alternative 2, Soil-Vapor Extraction, is cost effective at meeting the remediation goals
and protecting human health and the environment. The selected remedy has the highest net
present worth of the two alternatives ($612,000) but is the only alternative that has the potential
to meet the remediation goal. Alternative 1 has a lower net present worth ($0) but cannot meet
the remediation goal.
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July 1996 10.0 Building 181
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Use of Permanent Solutions and Treatment or Resource-Recovery Technologies to the
Maximum Extent Practicable
The selected remedy, Alternative 2, uses permanent solutions and treatment technologies to the
maximum extent practicable. It meets the threshold criteria (protection of human health and
environment and compliance with ARARs) and provides the best balance of trade-offs in terms
of the balancing criteria. The selected remedy provides the best long-term effectiveness and
permanence and the best reduction in toxicity, mobility, and volume.
The cost of the selected remedy is higher than Alternative 1, No Action, but it is considered cost
effective because it has the best chance of meeting the remediation goal. The selected remedy is
more difficult to implement than Alternative 1, No Action, because it requires an action
involving treatment, whereas Alternative 1 does not require any action. However, the selected
remedy can be readily implemented.
Preference for Treatment as a Principal Element
The selected remedy meets the statutory preference for treatment as a principal element. The
principal threat to human health is TCE contamination in the Paluxy aquifer that exceeds MCLs.
The selected remedy addresses the principal threat by removing TCE from the vadose zone under
Building 181 that would eventually result in TCE contamination levels in the Window Area
exceeding MCLs in the Paluxy aquifer. The treatment processes use carbon adsorption or
catalytic oxidation for extracted air that is contaminated with TCE and air stripping with carbon
adsorption or catalytic oxidation for extracted groundwater.
10.6 Documentation of Significant Changes
A draft of the Proposed Plan was released to members of the Restoration Advisory Board before
the public comment period. The Draft Proposed Plan identified Alternative 2, Soil-Vapor
Extraction, as the selected alternative. Members of the Restoration Advisory Board did not have
any significant comments on the preferred alternative for Building 181. The final Proposed Plan,
dated November 1995, also listed Alternative 2 as the preferred alternative.
Alternative 2 was presented as the selected remedy at the public meeting on the Proposed Plan.
The Air Force reviewed all written and verbal comments submitted during the public comment
period. After review of these comments, no significant changes to the selected remedy were
made, as identified in the Proposed Plan dated November 1995.
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10.0 Building 181 July 1996
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10-10 FINAL The Decision Summary
July 1996 . 10.0 Building 181
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11.0 No Further Action Sites
11.1 Selected Remedy
No action is the selected remedy for soil in the No Further Action Sites based on the findings of
the BRA. The selected remedy applies only to soil at the No Further Action Sites. The BRA
determined that chemical concentrations in the soil at these sites do not pose an unacceptable risk
to human health or the environment. Figure 11-1 shows the locations of the No Further Action
sites; this figure is the same as Figure 2-1 in Section 2.0 but is included here for the convenience
of the reader. Removal of soil has been completed at several of the areas. These actions were
taken as voluntary actions before Air Force Plant 4 was listed on the NPL. The BRA was
performed after those voluntary actions were completed.
The Terrace Alluvial flow system, which includes the East Parking Lot Plume, the West Plume,
and the North Plume, is the affected groundwater under these sites. Information on
contamination in the Terrace Alluvial flow system is presented in Section 5.0, "Summary of Site
Characteristics." The selected remedy for contamination in the Terrace Alluvial flow system is
addressed separately in Section 9.0, "East Parking Lot Groundwater Plume."
11.2 Basis of No Action as the Selected Remedy
The basis for the selected remedy, No Action, for soil at each of the No Further Action Sites is
presented in the following sections.
Landfills No. 1 and No. 2
Landfill No. 1—Landfill No. 1 (LF-1) is a 6-acre site that was used from 1942 to approximately
1966 for disposal of general refuse, construction rubble, solvents, thinners, paint sludges, oil,
fuels, and unspecified liquid wastes. In 1966, the landfill was closed and the area was graded and
paved for employee parking. Before grading and paving, two 6-in. perforated pipes were laid in
trenches on bedrock just east of Bomber Road to channel leachate to a storm sewer outfall.
In 1982, a French drain (No. 1), was constructed in the center of LF-1 to prevent leachate from
entering the storm sewer. The two drain pipes installed in 1966 were rerouted to the French
drain system, and a 90-ft section of 4-in. perforated drain pipe was placed on bedrock on the
western edge of the storm sewer outfall.
In 1983, the storm sewer was lined to prevent infiltration of leachate into the storm-water
collection system. Liquids and approximately 11,000 cubic yards (yd3) of contaminated soil in
the landfill were excavated and removed as part of an interim remedial action. A second French
drain (No. 2) was constructed within the excavation to intercept leachate. This excavation was
backfilled and the site was repaved.
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11.0 No Further Action Sites July 1996
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-------
During the remedial investigation, COPCs for soil, as identified in the BRA, that were detected at
LF-1 include TCE (ND to 0.11 mg/kg) and toluene (ND to 350 mg/kg). One SVOC,
benzo[#]pyrene (BAP), was detected at concentrations between 1.1 and 62 mg/kg. These
concentrations exceed the human health risk-based concentration of 1.0 mg/kg for BAP.
However, BAP was only present in soil samples collected directly below the asphalt cover.
Therefore, the presence of this compound is attributed to the overlying asphalt, not to past waste
disposal practices.
On the basis of the BRA, and because BAP appears to be derived from the overlying asphalt
cover, the soil at this site does not pose an unacceptable excess risk to human health or the
environment. Therefore, the selected remedy for Landfill No. 1 is no action.
Landflll No. 2—Landfill No. 2 (LF-2) is an 8-acre site that was used from the early 1940s to the
early 1960s for the disposal of construction rubble, plaster, lumber, and tires. No information
exists indicating that hazardous materials were disposed of in this landfill. The site is now
covered with grass.
Soil in LF-2 was sampled in 1982 and again in 1989. In 1982, three volatile organic COPCs
were detected in soil samples obtained during the installation of a monitoring well. Benzene,
toluene, and TCE were detected at low concentrations (less than 1.0 mg/kg). In 1989,
39 samples were collected from 7 borings at LF-2. Toluene contamination was detected in only
one sample at a concentration less than 1.0 mg/kg. On the basis of these analytical results and
detected metal concentrations, the soil at Landfill No. 2 does not pose an unacceptable excess
risk to human health or the environment. Therefore, the selected remedy for this area is no
action.
Fire Department Training Areas
Fire Department Training Area Nos. 2 through 6 (FDTA-2 through FDTA-6) are the sites
discussed in this section. Waste oils, fuels, and other unspecified chemicals were burned at
FDTA-2, FDTA-3, FDTA-5, and FDTA-6 during fire-training exercises. FDTA-4 received
clean fill material from a nearby foundation excavation.
FDTA-2—FDTA-2 is a 50-ft-diameter earthen ring located north of Landfill No. 1. This area
was used for semiannual fire-training exercises between 1955 and 1965. It currently is overlain
by the asphalt of the West Parking Lot. No detectable concentrations of VOCs were reported for
four samples collected from two borings drilled in 1986. Twenty-three samples were collected
from four borings in 1991. TCE and 1,2-DCE were detected at concentrations of less than
1.0 mg/kg. The sitewide BRA determined that those concentrations and the detected metal
concentrations do not pose an unacceptable excess risk to human health or the environment. On
the basis of available information, the selected remedy for this area is no action.
FDTA-3—FDTA-3, reportedly located near the western edge of Plant 4 and northeast of
Landfill No. 4, was used for fire-training exercises in the 1960s. It is now covered with grass.
The exact location of FDTA-3 could not be determined from a review of historical aerial
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11.0 No Further Action Sites July 1996
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photographs. Soil samples were not collected during the installation of one monitoring well
reportedly installed near FDTA-3; laboratory analyses of groundwater samples indicate no
elevated concentrations of VOCs or metals. On the basis of available information, the selected
remedy for this area is no action.
FDTA-4—FDTA-4 was reported to be located near the northern tip of Plant 4. However,
Plant 4 fire department personnel report that no fire-training exercises were ever conducted in
that immediate area. Personnel reported that the site received clean fill from a foundation
excavation. The exact location of FDTA-4 could not be determined from historical aerial
photographs. On the basis of available information, no soil samples were required from FDTA-4
and the selected remedy for this area is no action.
FDTA-5—FDTA-5, located at the south-central boundary of Plant 4, was a shallow pit about
35 ft wide by 45 ft long. It was used for fire training exercises in the mid-1960s. Two soil
samples were collected near the FDTA-5 area in 1986; 19 soil samples were collected from five
borings in 1991 near the approximate location of FDTA-5. No VOCs were detected in two soil
samples collected in 1986. Low concentrations (less than 2.0 mg/kg) of VOCs and SVOCs were
detected in the 1991 samples. The sitewide BRA determined that those concentrations and the
detected metal concentrations do not pose an excess risk to human health or the environment.
On the basis of available information, the selected remedy for this area is no action.
FDTA-6—FDTA-6, the primary fire department training area from the late 1960s to 1982, was
located in the northwest portion of Plant 4 adjacent to Bomber Road. FDTA-6 was a
50-square-foot gravel-lined area approximately 2 ft deep, surrounded by an earthen berm.
Interim remedial action was performed at FDTA-6 in 1983 when oil- and fuel-contaminated soil
was removed and hauled to an approved hazardous-waste landfill. Since that time, 17 soil
samples were collected in three separate investigations at FDTA-6. Detected concentrations of
VOCs and SVOCs were less than 1.0 mg/kg, with the exception of two SVOCs detected at
approximately 3.0 mg/kg. The sitewide BRA determined that those concentrations and the
detected metal concentrations do not pose an excess risk to human health or the environment.
On the basis of available information, the selected remedy for this area is no action.
Chrome Pits
This section describes site investigations at Chrome Pit No. 1, No. 2, and No. 3.
Chrome Pit No. 1—Chrome Pit No. 1 (CP-1) was an unlined earthen pit that received liquid
wastes during the early 1940s. Building 181 was constructed on the site of CP-1. The exact
location of CP-1 could not be determined from interviews or a review of historical aerial
photographs. Analytical results indicate the presence of chromium in the soils around
Building 181; however, the concentrations are below the upper background limit for the Western
United States. Given the limited usage of the pit and its present location under a building, the
selected remedy for this area is no action.
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Chrome Pit No. 2—Chrome Pit No. 2 (CP-2), an unlined earthen pit, was located near the
southwest corner of the Assembly Building/Parts Plant. CP-2 received liquid chrome wastes
during the mid-1940s. The actual location of CP-2 could not be determined from interviews or
reviews of historical aerial photographs. Given that the site could not be located, the selected
remedy for this area is no action.
Chrome Pit No. 3—Chrome Pit No. 3 (CP-3) was a large earthen pit (approximately 55 ft wide
by 165 ft long by 15 ft deep) located in the southern portion of Plant 4 west of Building 12. It
was operational from 1957 to 1973 and received chromate sludge, dilute metal solutions, and
other unidentified liquids. An interim remedial action was conducted in December 1983 and
January 1984 to excavate and remove approximately 8,900 yd3 of contaminated soil from CP-3.
The excavated soil was disposed of at an approved hazardous-waste landfill off the Air Force
Plant 4 facility. Soil was excavated to a depth of approximately 20 ft below grade.
Following excavation of the soil, confirmatory soil sampling at CP-3 detected the presence of
TCE in one sample at a concentration of 4.8 mg/kg. In 1989, soil samples were collected from
11 shallow (10-ft-deep or less) soil borings around the perimeter of CP-3. These samples were
analyzed for VOCs and total extractable chlorinated organics. The maximum concentration of
total extractable chlorinated organics in one sample was 72.5 mg/kg. On the basis of the low
concentrations of organic compounds detected following the removal of soil, the soil at CP-3
does not pose an excess risk to human health or the environment and the selected remedy for this
area is no action.
Die Yard Chemical Pits
The Die Yard Chemical Pits site is located in the southern portion of Plant 4, south of
Building 12. Three pits (approximate dimensions of 20 ft wide by 90 ft long and 10 ft deep)
were constructed in 1956 and used for the disposal of chromate sludges, metal solutions, and
other chemical wastes. In 1962, the site was graded and the entire area was paved for parking. In
1983 and 1984, the original die pits were excavated and 1,100 yd3 of contaminated soil was
removed and transported to an approved hazardous-waste landfill for disposal. Confirmatory soil
sampling conducted following soil removal reported ethylbenzene, naphthalene, toluene, and
TCE at concentrations between ND and 5.6 mg/kg. In 1991, 4 soil samples were collected from
4 soil borings drilled within the excavated pits, and 17 soil samples were collected from 6 soil
borings drilled around the former pits. Four volatile organic COPCs were detected at low
concentrations (i.e., less than 0.5 mg/kg). No SVOC contamination was detected. On the basis
of those data and detected metal concentrations, the soil in this area does not pose an excess risk
to human health or the environment and the selected remedy for this area is no action.
Fuel Saturation Areas
Fuel Saturation Areas No. 1, No. 2, and No. 3 reportedly were saturated by fuel from leaking
pipelines in the mid-1970s to early 1980s.
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11.0 No Further Action Sites July 1996
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Fuel Saturation Area No. 1—Fuel Saturation Area No. 1 (FSA-1) is located immediately west
of the Assembly Building/Parts Plant, partially beneath Building 14. Soil at this site reportedly
became saturated with JP-4 jet fuel leaking from underground piping during the 1970s and
early 1980s.
In 1987, one soil sample was collected in the area east of Building 14. No VOC contamination
was detected in that sample. In 1991, 45 soil samples were collected from 10 soil borings drilled
in the vicinity of FSA-1. Two volatile organic COPCs, ethylbenzene and benzene, were detected
in three samples, all at concentrations less than 1.0 mg/kg. Only one sample, collected from 5 to
10 ft below grade to the east of Building 14, contained semivolatile organic COPCs.
Semivolatile compounds were detected in one sample at concentrations ranging from 0.9 to
2.7 mg/kg, but no semivolatile COPCs were identified in the other soil samples.
The BRA determined that the soil contamination at FSA-1 does not cause an excess risk to
human health or the environment and the selected remedy for this area is no action. Ground water
contamination in this area is addressed in Section 5.5 of this Record of Decision.
Fuel Saturation Area No. 2—Fuel Saturation Area No. 2 (FSA-2) was originally designated as
a site requiring environmental investigation because of reports of saturated soil along an
underground pipeline in the northwest portion of Plant 4. However, no COPCs were detected in
the reported vicinity of FSA-2 in (1) a gridded soil-gas survey, (2) samples from six soil borings,
and (3) samples from two monitoring wells. On that basis, no COPCs that pose an excess risk to
human health and the environment are present at FSA-2, and the selected remedy for this area is
no action.
Fuel Saturation Area No. 3—Fuel Saturation Area No. 3 (FSA-3) is located east of Bomber
Road in the northwest portion of Plant 4. This site also was investigated because of reports of
leaking underground fuel lines in the area. In 1991, approximately 60 soil samples were
collected from 13 borings in the vicinity of FSA-3. Three volatile organic COPCs (acetone,
benzene, and ethylbenzene) were detected at concentrations below 1.0 mg/kg in soil samples.
Low levels of two semivolatile organic COPCs, naphthalene and 2-methylnaphthalene, were
detected at concentrations between 0.85 and 5.9 mg/kg.
The baseline risk assessment determined that soil contamination at FSA-3 does not cause excess
risk to human health or the environment and the selected remedy for this area is no action.
Former Fuel Storage Area
The Former Fuel Storage Area (FFSA) is the site of a former 100,000-gallon aboveground JP-4
fuel storage tank located in the southwest portion of Plant 4. The storage tank was used from the
early 1940s to 1962, when it was removed from the site and relocated. Soil beneath the tank
reportedly contained jet fuel at the time the tank was removed.
In 1982, five soil samples were collected from a test hole and a monitoring well was installed at
FFSA. Low levels of VOCs and SVOCs were reported in those samples. In 1991, soil samples
11-6 FINAL The Decision Summary
July 1996 11.0 No Further Action Sites
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were collected from four borings that were drilled around the monitoring well. No volatile or
semi volatile COPCs were identified in those samples. On the basis of these data and detected
metal concentrations, the soil at this area does not pose an excess risk to human health or the
environment and the selected remedy for this area is no action.
Solvent Lines
The Solvent Lines site was designated for No Further Action by the Plant 4 Technical Review
Committee before the start of remedial investigation; therefore, no samples were collected during
the remedial investigation.
The Solvent Lines area is located in the north-central portion of Plant 4. It was identified as an
area requiring investigation on the basis of personnel accounts of reported leaks in the early
1940s. The underground lines were used to transport xylene, 2-butanone, and kerosene from
1942 until 1944, when they were drained, capped, and abandoned in place because of the
reported leaks. In 1985, two soil samples collected during installation of a monitoring well were
analyzed for xylene and 2-butanone. The presence of neither compound was detected.
Therefore, the selected remedy for this area is no action. Also in 1985, 10 groundwater samples
were collected from 4 monitoring wells. VOC concentrations in these groundwater samples did
not exceed their respective MCLs.
Nuclear Aerospace Research Facility
The Nuclear Aerospace Research Facility (NARF) was located on approximately 120 acres at the
northern tip of Plant 4. It was the site of three atomic reactors used between 1953 and 1974 for
research and development activities. In 1974, NARF was decontaminated and dismantled.
High-level and low-level radioactive components were segregated and shipped to regulated
off-site disposal areas. A total of more than 2 million pounds of miscellaneous parts and
15 million pounds of concrete rubble were removed for off-site disposal.
During the decontamination and decommissioning activities, radiological surveys were
performed on a regular basis. Soil and vegetation samples were analyzed from the area around
NARF and core samples of structures and subsurface soil in the vicinity were collected for
analyses. The results of these analyses were not available; however, soil excavation and removal
was documented in the decommissioning records. Following decommissioning activities,
radiological surveys were performed and verified to confirm that areas and facilities were
available for unrestricted use. The final postclosure report indicates that no radiological
contamination remained at the site.
To confirm that all contaminated soil had been removed, nine soil samples were collected in
1989 adjacent to NARF and submitted for laboratory analyses for total alpha and total beta.
Alpha radiation in the soil samples ranged from 6.7 to 12.4 picocuries per gram (pCi/g). Beta
radiation ranged from 10.0 to 23.1 pCi/g. Gamma radiation was not measured directly, but
samples were analyzed for cesium-137, a fission by-product and gamma emitter. The presence
The Decision Summary FINAL 11-7
11.0 No Further Action Sites July 1996
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of cesium-137 was not detected at the instrument detection limit. The alpha and beta activities
are typical of natural background levels encountered in most undisturbed soil.
In 1991, six sediment samples were collected from Lake Worth to confirm that NARF activities
had not adversely affected lake sediments. One background sediment sample was collected
approximately 1 mile west of NARF activities, on the west side of the inlet from Lake Worth.
This sample was collected for comparison purposes from a location that likely was not affected
by NARF. Sediment samples were analyzed for the presence of cobalt-60, cesium-137,
radium-226, thorium-230, and uranium. The presence of cobalt-60 was not detected in any
samples. Cesium-137 was detected in two samples at concentrations of 0.10 and 0.53 pCi/g;
radium-226 was detected in all six samples at concentrations between 0.45 and 1.19 pCi/g (the
maximum concentrations for cesium-137 and radium-226 were from the background sample).
Thorium-230 was detected in all samples at concentrations of 0.6 to 2.0 pCi/g, and uranium was
detected in four samples at concentrations between 1.1 and 2.7 mg/kg. These concentrations are
typical of background levels encountered in most undisturbed soil. On the basis of these data,
the NARF site does not pose an unacceptable excess risk to human health or the environment and
the selected remedy for this area is no action.
Wastewater Collection Basins
The Wastewater Collection Basins, located south of Building 181, are two lined, concrete waste
basins, each with an approximate capacity of 85,000 gallons. They are designed to collect and
settle suspended solids from plant wastewater. Several known spills of TCE from vapor
degreasers in Building 181 have flowed to the basins via floor drains. Other chemical spills also
may have entered the basins via the floor drains.
In 1991, the basins were drained and the concrete walls, floors, and liners were examined. The
plastic liners were no longer present over much of the floors and walls; however, the concrete
appeared to be in good condition, with no visible cracks. Also in 1991, two soil borings were
drilled near the basins, one near the northeast corner and one to the west of the basins. One
sample from one of the borings had a reported concentration of less than 1.0 mg/kg of TCE; no
other organic COPCs were detected in these samples. On the basis of these data, this area does
not pose an excess risk to human health or the environment and the selected remedy for this area
is no action.
West Compass Rose
The West Compass Rose site was included as an environmental investigation site at Plant 4
chiefly on the basis of indirect evidence (i.e., personnel recollections of past surface spills). This
approximately 150-square-foot area is located in the northern portion of Plant 4. It was reported
that fuel spills may have occurred during aircraft refueling operations at the site.
Twenty-four shallow soil borings were drilled in the area in 1985 as part of a foundation soil
study for several buildings planned for the area. Organic vapors were detected in samples from
only 3 of the 24 borings. One sample was submitted for VOC analyses but no contaminants were
11-8 FINAL The Decision Summary
July 1996 11.0 No Further Action Sites
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detected. In 1991, an additional boring was drilled at the site and no fuel hydrocarbons were
present in soil samples from this boring. On the basis of these data, soil at the West Compass
Rose does not pose an excess risk to human health or the environment and the selected remedy
for this area is no action.
Jet Engine Test Stand
The Jet Engine Test Stand (JETS) site is located in the northern portion of Plant 4, east of
Bomber Road. It was included as an environmental site on the basis of employee reports of jet
fuel and gasoline in a sump near the site.
In 1986, five soil samples were collected from six soil borings drilled around the periphery of
JETS. Fuel hydrocarbon analysis revealed that two of the samples contained concentrations of
1,700 and 1,300 mg/kg of fuel hydrocarbons. In 1991, seven soil samples were collected from
three soil borings drilled around the periphery of JETS. Two of these soil samples contained low
concentrations (between 1.1 and 5.1 mg/kg) of semivolatile COPCs. On the basis of the
analytical data collected for JETS, this area does not pose an excess risk to human health or the
environment and the selected remedy for this area is no action.
Underground Storage Tanks No. 19 and No. 20
Underground Storage Tanks No. 19 and No. 20 (UST-19 and UST-20) were two
12,000-gallon-capacity tanks, formerly located in the south-central portion of Plant 4.
UST-19 was used for storage of 2-butanone; UST-20 stored 2-butanone, ethylbenzene, and
xylene. Both tanks and a related pumping station were removed in 1988. Following excavation
and tank removal, four soil samples were collected from the excavations. Xylene, ethylbenzene,
and 2-butanone were detected at the following concentrations: xylene at 0.14 to 46 mg/kg,
ethylbenzene at 0.051 to 22 mg/kg, and 2-butanone at 2.7 to 43 mg/kg. In 1991, 27 soil samples
were collected from 5 borings drilled at the tank excavation sites. Detected concentrations of
2-butanone, xylene, and ethylbenzene in the soil samples were less than 1.0 mg/kg. Analyses of
groundwater samples from wells in the vicinity of UST-19 and UST-20 did not detect any
contamination. These wells were sampled in September and October 1991 and in May and
June 1993. On the basis of the analytical data collected for UST-19 and UST-20, these areas do
not pose an excess risk to human health or the environment and the selected remedy is no action.
Underground Storage Tanks No. 24A and No. 24B
Underground Storage Tanks No. 24A and No. 24B (UST-24A and UST-24B) were located side
by side in the south-central portion of Plant 4. These tanks each had a capacity of 8,000 gallons
and were used to store gasoline. The two tanks were excavated and removed in 1988. Low
concentrations (less than 1.0 mg/kg) of three organic COPCs were detected in confirmatory soil
samples obtained from the excavation. In 1991, nine soil samples were collected from four soil
borings drilled at the site. No organic COPCs were detected in any of these samples. On the
basis of analytical data collected for UST-24A and UST-24B, these areas do not pose an excess
risk to human health or the environment and the selected remedy for this area is no action.
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Underground Storage Tank No. 25A
Underground Storage Tank No. 25A (UST-25A) was located adjacent to JETS in the northern
part of Plant 4. UST-25A formerly was the site of two vertical underground tanks used to store
JP-4 jet fuel. The tanks were removed in 1988. Nine confirmatory soil samples collected from
the excavation were submitted for fuel hydrocarbon analyses. One soil sample contained low
concentrations of benzene (2.2 mg/kg), ethylbenzene (3.6 mg/kg), and toluene (8.3 mg/kg).
In 1991, four soil borings were drilled at the site of the UST-25 A tank excavation. Eleven soil
samples were submitted for SVOC and VOC analyses. Ethylbenzene was detected at less than
1.0 mg/kg and 2-methylnaphthalene was detected at 3.9 mg/kg. No groundwater samples were
collected at UST-25A. Groundwater contamination in this area is discussed in Section 5.5 under
the subheading "Terrace Alluvial Flow System." On the basis of these data, soil remaining at
UST-25 A does not pose an excess risk to human health or the environment an.d the selected
remedy for this area is no action.
Underground Storage Tank No. 30
Underground Storage Tank No. 30 (UST-30), formerly located in the northern portion of Plant 4,
was a 2,000-gallon steel tank used to store JP-4 fuel. This tank was installed in 1956 and
removed in 1988. Following excavation and removal, one soil sample was collected from the
excavation. It contained benzene, ethylbenzene, and toluene concentrations between
1.0 and 3.1 mg/kg.
In 1991, eight samples were collected from four soil borings drilled at the site of the former
UST-30. No volatile organic or semivolatile organic COPCs were detected in these samples.
No groundwater samples were collected at UST-30. Groundwater contamination in this area is
discussed in Section 5.5, "Terrace Alluvial Flow System." On the basis of the analytical data
collected for UST-30, this area does not pose an excess risk to human health or the environment
and the selected remedy for this area is no action.
11.3 Documentation of Significant Changes
A draft of the Proposed Plan was released to members of the RAB before the public comment
period. The Draft Proposed Plan identified no action as the preferred alternative for soil at the
No Further Action Sites. Members of the RAB did not have any significant comments on the
preferred alternative for the No Further Action Sites. The final Proposed Plan, dated
November 1995, also identified no action as the preferred alternative.
No action was presented as the selected remedy at the public meeting on the Proposed Plan. The
Air Force reviewed all written and oral comments submitted during the public comment period.
After review of these comments, no significant changes to the selected remedy were made, as
identified in the Proposed Plan dated November 1995.
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Appendix A
Responsiveness Summary
The Decision Summary FINAL A-l
Appendix A, Responsiveness Summary July 1996
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Overview
This Responsiveness Summary was prepared to provide written responses to comments regarding
the Proposed Plan of Action that were submitted during the public meeting on December 14,
1995, and during the public comment period, November 22, 1995, to January 22, 1996. The
section "Background of Community Involvement" provides a brief history of community interest
and concerns raised during the remedial planning activities at Air Force Plant 4. The section
"Summary of Public Comments Received and Air Force Responses" contains a summary of the
comments made during the public meeting and the comments received in writing during the
public comment period.
Background of Community Involvement
Overall public interest in the remedial planning activities at the site has been light, with the
exception of local citizens who volunteered to serve on the Air Force Plant 4 Restoration
Advisory Board. The Restoration Advisory Board was established to inform interested citizens
of the remedial planning and restoration activities at Air Force Plant 4. The Restoration
Advisory Board meets monthly at the White Settlement Senior Services Center and is open to the
public. In addition to members of the public, Restoration Advisory Board meetings also were
attended by regulatory agency representatives, Plant 4 personnel, Air Force representatives,
contractors, and sometimes representatives of the news media.
The Remedial Investigation Report and the Feasibility Study Report were released to the public
in September 1995. A draft version of the Proposed Plan was presented for review to members
of the Restoration Advisory Board in October 1995. Comments received from the Restoration
Advisory Board expressed concern about the preferred alternatives for the Paluxy aquifer, the
Upper Sand groundwater, and the East Parking Lot Groundwater Plume because the preferred
alternatives for these sites would use air stripping that releases contaminants to the atmosphere.
There was also concern by Restoration Advisory Board members and the City of Fort Worth
Water Department about the preferred alternative for Landfill No. 4, Landfill No. 3, and
Meandering Road Creek. The preferred alternative for Landfill No. 4, Landfill No. 3, and
Meandering Road Creek was No Action with monitoring. Restoration Advisory Board members
and the City of Fort Worth Water Department were concerned that contamination from the
landfills could migrate to Lake Worth.
On the basis of the comments received from the Restoration Advisory Board, the Air Force, with
the concurrence of the U.S. Environmental Protection Agency (EPA) and the State of Texas,
selected a different alternative for the Paluxy aquifer and the Upper Sand groundwater and
modified the alternative for the East Parking Lot Groundwater Plume. For the Paluxy aquifer
and Upper Sand groundwater, the Air Force selected the alternative that includes destruction of
contaminants. The technology evaluated for the alternative was ultraviolet oxidation, but other
technologies that meet the criteria of near-zero off-gas emissions may be used.
The alternative for the East Parking Lot Plume was modified to include destruction of the
contaminants before release from the air stripper. The Air Force did not select a different
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alternative or modify the alternative of No Action for Landfill No. 4, Landfill No. 3, and
Meandering Road Creek but addressed the concerns of the Restoration Advisory Board members
with the explanation that this alternative includes monitoring. Monitoring will detect any
increase in contamination levels. If the contamination levels increase to levels that cause excess
risk, corrective action would be taken.
The Air Force held a public comment period regarding the remedial investigation, feasibility
study, Proposed Plan, and Administrative Record from November 22, 1995, to January 22, 1996.
The Proposed Plan presented at the public meeting included the modifications that were based on
comments from the Restoration Advisory Board members. Originally scheduled to end
December 22, 1995, the public comment period was extended to January 22, 1996, at the request
of a member of the local community. During the public comment period, a formal public
meeting was held on December 14, 1995, at the White Settlement Senior Services Center.
Most of those who attended the public meeting were supportive of the proposed actions for
Plant 4. However, one member of the public was concerned that the remedial investigation did
not adequately characterize contamination that may be in residential areas near Plant 4 and was
not satisfied that contamination from Plant 4 was being contained on Federal property and
prevented from migrating to residential areas. All the written comments received during the
public comment period were submitted by this individual.
Summary of Public Comments Received and Air Force Responses
Comments and questions made during the formal public meeting held on December 14, 1995,
along with the Air Force responses, are presented in "Comments and Questions Received During
the Public Meeting." Comments and questions received in writing during the public comment
period held from November 22, 1995, to January 22, 1995, along with the Air Force responses,
are presented in "Comments and Questions Received During the Public Comment Period."
Many of the responses use the term "excess risk." Excess risk, as used in the responses, is risk
that exceeds 1.0 x 10"4 incremental lifetime cancer risk (ILCR) for carcinogenic risk or has a
hazard quotient or hazard index greater than 1.0 for noncarcinogenic risk.
Comments and Questions Received During the Public Meeting
Comment 1:
An individual requested that the 30-day comment public period, which ended
December 22, 1995, be extended 30 days. The individual also asked what the end of the
public comment period represented.
Air Force Response: The Air Force agreed to extend the public comment period 30 days
to January 22, 1995, and explained that the end of the public comment period is when
written comments about the content of the Proposed Plan are no longer accepted.
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Comment 2:
An individual with the City of Fort Worth Water Department had a comment on the
preferred alternative for Landfill No. 4, Landfill No. 3, and Meandering Road Creek. The
individual suggested that language be added to the preferred alternative stating remedial
action conducted to reduce harm to aquatic life or to continue use of Lake Worth as a
drinking water source should be based on trigger concentrations. The trigger
concentrations should be low enough so that remedial action can be performed before
there is harm to aquatic life or use of Lake Worth for drinking water is endangered.
There was also a related question from another individual if bass from the lake are safe
to eat.
Air Force Response: The Air Force agrees with the idea of using trigger concentrations
to indicate if corrective action is needed. The Record of Decision is being written to
require that appropriate corrective measures will be taken if concentrations in Lake Worth
exceed maximum contaminant levels (MCLs).
In response to the question if the bass in Lake Worth are safe to eat, the Air Force's
response is that bass from Lake Worth are safe to eat and consumers are not at excess
risk, according to the baseline risk assessment.
Comment 3:
An individual questioned the results of the risk assessment that indicated there is not an
excess risk from heavy metals, such as mercury, radioactive materials, and other
contaminants in the soil. The individual feels that even though the sampling done to date
has not shown high levels of contamination, the contamination in the soil will eventually
leach to surface water, especially Lake Worth, causing harm to humans and the
environment. To prevent this from happening, he suggested that a subsurface concrete
wall should be built around the site as an inexpensive way to prevent contamination from
getting into the surface water. The individual stated that a concrete subsurface wall
would be preferable to a hydraulic containment system, like the one installed at Landfill
No. 3, because a subsurface wall would not require continual operation to be effective.
The individual also suggested that heavy metals present in the soil could be stabilized
with sulfur.
The individual submitted written comments about these same issues. The written
comments and the corresponding Air Force responses, along with a rough cost estimate
for a subsurface wall, are in "Comments and Questions Received During the Public
Comment Period," comments 3 and 4.
Air Force Response: Because the risk assessment did not show that contamination in the
soil poses an excess risk, the suggested subsurface wall is not needed. However, it is
possible that some contamination in the soil was not detected during the remedial
investigation and that this contamination could cause excess risk in the future. Because
of this possibility, the Air Force will monitor surface water and groundwater on Plant 4
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and at areas adjacent to Plant 4. If monitoring indicates that contamination levels are
increasing to levels that cause excess risk, corrective actions will be taken.
Because of the length of time that the contamination has been in the soil, it is likely that
contamination levels will not increase in the future but will decrease. Until
contamination levels increase to levels that cause excess risk, the Air Force, with the
concurrence of the EPA and the State of Texas, does not plan to install a subsurface wall
or initiate other remedial actions, other than those specified in the ROD.
If a subsurface wall or barrier is considered in the future, this wall could be a physical
barrier, as suggested by the individual, or a hydraulic barrier. Construction material for
such a physical barrier is usually a concrete/bentonite mixture or a bentonite/soil mixture;
effective subsurface walls have been constructed of both materials. Bentonite is more
commonly used for subsurface walls. When concrete is used, bentonite is usually added
to the concrete to make it more flexible.
Comment 4:
An individual expressed concern about radioactive materials at the Nuclear Aerospace
Research Facility (NARF). The individual stated that even though radioactive materials
were not detected in the surveys and sampling conducted during the remedial
investigation, there will eventually be a release of these materials. Because the
contamination will eventually be released, a subsurface wall should be installed around
the site.
The individual also submitted a written comment about this same issue. The written
comment and the more detailed Air Force response is in "Comments and Questions
Received During the Public Comment Period," comment 5.
Air Force Response: The Air Force removed approximately 26 tons of material from this
area. Sampling conducted for the remedial investigation did not show radiation levels to
be different than normal background levels. The records search of activities at the site
indicates that all radioactive materials were removed from the site. The Air Force
reasoning for not installing a subsurface wall is provided in comment 3.
Comment 5:
An individual expressed concern that carbon fibers had been dumped at Landfill No. 3
and that carbon fibers can be hazardous to an individual's health if inhaled or the fibers
come into contact with the skin.
Air Force Response: Carbon fibers were never dumped or stored at Landfill No. 3. This
area was fenced as a precautionary measure to keep individuals out of the area because
there is a potential for exposure to TCE contamination.
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Comment 6:
A question was asked if untreated sewage from Plant 4 was discharged to Lake Worth
during a period around 1990 to 1991, a period when employment at the plant was as high
as 30,000 employees. The question was raised because the individual said he could smell
raw sewage near some storm drains and Lake Worth had a high bacteria count at
that time.
Air Force Response: Sewage from Plant 4 has been sent to the city of Fort Worth
sewage treatment plant since the 1940s. Process water at the plant is treated in the
process water treatment facility. Raw sewage was not discharged to Lake Worth in 1990,
1991, or at any time. The smell the individual noticed could have been due to a sewer
backing up, but it was not because raw sewage was being discharged to Lake Worth.
Comment 7:
An individual expressed concern about contamination from Plant 4 migrating to the
residential areas near the plant. He wanted the Air Force to do an analysis of
contamination levels in the residential areas.
The individual also submitted a written comment about this same issue. The written
comment with a more detailed Air Force response is in "Comments and Questions
Received During the Public Comment Period," comment 1, parts la, Ib, and Id.
Air Force Response: In addition to extensive sampling conducted at Plant 4, the Air
Force installed two nested wells (three wells that are screened in the upper, middle, and
lower portions of the Paluxy aquifer) at off-site locations. One nested well was located
near the National Guard Armory and the other was located north of the National Guard
Armory along Shore View Drive. The Air Force may do additional monitoring of
groundwater directly south of Plant 4 during the remedial design phase to further define
the plume in that area.
Comment 8:
An individual stated that General Dynamics (the operator of Plant 4 at that time) supplied
fill material for an area of the football field located south of Brewer High School. Also,
other sites may have possible contamination and are not known but should be sampled.
The Air Force should sample the residential areas to ensure there is no contamination.
The individual also submitted a written comment about this same issue. The written
comment with a more detailed Air Force response is in "Comments and Questions
Received During the Public Comment Period," comment 1, part Ic.
Air Force Response: The Air Force does not plan to do any additional soil sampling in
off-site residential areas. The records search conducted for the remedial investigation
does not indicate removal or off-site disposal of material from Plant 4 during the
construction period for Brewer High School. The high school was constructed in 1953.
No other evidence is available that landfill material was transported to other locations in
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the Fort Worth area. Without any indication of where the contamination caused by
Plant 4 could be, it is futile to sample to determine if there is contamination.
The Air Force did sample existing residential wells located near Plant 4 and no
contamination was detected in any samples from these wells. Additional groundwater
sampling directly south of the site, off Plant 4 property, may be performed to better define
the extent of contamination in the Terrace Alluvial groundwater that is from a known
. source. However, the Air Force will not install monitoring wells at random locations in
residential areas unless there is a source suspected to be caused by Plant 4.
Comment 9:
An individual asked about "asphalt contamination" and benzo[0]pyrene. Another
individual stated that benzo[#]pyrene is a powerful carcinogen and is used to induce
cancer in animals for experiments. He described benzo[a]pyrene as an indicator of other
contaminants, just as trichloroethene (TCE) is an indicator of organic contamination
because TCE carries other contaminants with it as it is washed down.
Air Force Response: "Asphalt contamination" refers to the chemical benzo[a]pyrene,
which is a derivative of tar and is found in asphalt. The levels of benzo[tf]pyrene in the
landfills are within acceptable limits. The Air Force analyzed samples for hundreds of
different chemicals and did not use the analysis of benzo[#]pyrene or TCE for an
indication of other contamination or focus on either of these contaminants.
Several other contaminants that are similar to benzo[#]pyrene or TCE were detected but
the levels were not high enough to cause excess risk. Measured TCE and benzo[a]pyrene
concentrations were at levels that either cause excess risk, as is the case with TCE, or
exceed the lower threshold of the acceptable risk range but are within acceptable limits,
as is the case with benzo[fl]pyrene. The presence of TCE does not indicate that there are
more contaminants in the groundwater.
Comment 10:
An individual from the city of White Settlement commented that the city of White
Settlement has more wells than what is shown on the figures in the Proposed Plan. Also,
the Air Force should check with the city of White Settlement about possibly monitoring
wells owned by the city and drilling new wells on city property, if the Air Force has the
funding available. There may be information available about contamination levels in the
groundwater that does not require additional monitoring.
Air Force Response: The Air Force agrees that using existing wells is a cost-effective
way of obtaining information about groundwater contamination levels in the residential
areas. To date, no contamination has been detected in samples from residential wells that
could be attributed to contamination from Plant 4.
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Comments and Questions Received During the Public Comment Period
All comments received during the public comment period where from one individual who lives
near Plant 4.
Comment 1:
The commentor expressed concern that contamination from Plant 4 has been transported
by various means to the residential areas near the plant. Also, because only limited
sampling has been conducted in residential areas, a comprehensive sampling program
should be performed to determine contamination levels within the residential areas. Four
additional parts to the comment (part la, Ib, Ic, and Id) address specific contamination
concerns.
Air Force Response: A small amount of contamination could have been transported by
various means to areas adjacent to Plant 4, including residential areas. However, the
relevant issue is not if small amounts of contamination has been transported off-site, but
if the levels of contamination at an off-site location are high enough to cause excess risk
(i.e., an incremental lifetime cancer risk greater than 1 in 10,000 and a hazard quotient
greater than 1.0).
The most significant ways contamination can be transported off site at levels high enough
to cause excess risk are (1) by groundwater discharging to surface water and then
individuals being exposed to contamination in the surface water and (2) by groundwater
migrating off site and individuals using the groundwater. Transportation of
contamination by these methods is addressed in the ROD. Current contamination levels
in surface water adjacent to Plant 4 are not high enough to cause excess risk but surface
water will continue to be monitored to determine if contamination levels increase to
levels that can cause excess risk.
The ROD also requires that contamination levels in the groundwater be monitored to
determine if contamination is moving off site. The monitoring will determine if
contamination is likely to move off site before it actually reaches Federal boundaries so
that corrective action can be taken before any groundwater contamination migrates off
site at levels that will cause excess risk.
Transport of contamination to off-site locations at levels that will cause excess risk by
other methods, such a volatilization to the atmosphere or dumping of contaminated soil,
are not supported by any records or sampling data. Therefore, the Air Force, with the
concurrence of the EPA and the State of Texas, does not plan any additional sampling at
off-site locations, other than what is specified in the ROD. Concerns about specific
contaminants are addressed in parts la, Ib, Ic, and Id of this comment.
Comment la:
The commentor expressed concern that a significant amount of TCE has evaporated to
the atmosphere and that, once in the atmosphere, the TCE is carried by the wind to
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eventually be deposited off site by rain and condensation where it can collect on the
ground. Also, the commentor stated that because TCE is a "heavy" chemical, with a
boiling point higher than water, it stays low to the ground when it evaporates, even while
being carried off site by the wind. This route represents a path by which volatile
chemicals such as TCE are carried to the community. Because of the long time period
that TCE was used at Plant 4, there could be high levels of TCE in the community.
Air Force Response: The commentor is correct with the statement that TCE is likely to
have evaporated from Plant 4 and that, once in the atmosphere, TCE can be carried off
site by the wind. However, because of the nature of TCE, it will not have accumulated in
the community at levels that will cause excess risk. Other statements made by the
commentor concerning the fate and transport of TCE are incorrect.
TCE has a relatively high vapor pressure and a boiling point lower than water (86.7 °C).
Because of its high vapor pressure, TCE evaporates rapidly to the atmosphere. Once in
the atmosphere, TCE exists entirely in the vapor phase and has a half-life of
approximately 7 days before it is degraded. A half-life of 7 days means that half the TCE
that has evaporated to the atmosphere will degrade within 7 days.
TCE can be removed from the atmosphere by rainfall and dew, called wet deposition.
Once it has been removed from the atmosphere by wet deposition, it will be in surface
water. TCE in surface water will rapidly partition from the water, as evidenced by its
Henry's law constant of 2.0 x 10~2 atmosphere-cubic meters per mole at 20 °C, and
revolatilize back to the atmosphere. This principle also applies to TCE in surface water
found in streams or lakes, such as Meandering Road Creek or Lake Worth. Experimental
studies have shown that the volatilization half-life of TCE in a rapidly moving river is
approximately 3.4 hours. Other studies have calculated a volatilization half-life of TCE
in a typical pond, lake, and river of 11 days, 4 to 12 days, and 1 to 12 days, respectively.
Reevaporation of TCE from dry surfaces also will occur rapidly because of its high
vapor pressure.
TCE has evaporated from Plant 4 and has then been carried by the wind to off-site
locations. However, considering the characteristics of TCE (i.e., its high vapor pressure
and rapid partitioning from surface water to the atmosphere), significant accumulations of
TCE within the community that could cause excess risk, as determined by a risk
assessment, are unlikely. This conclusion is supported by air sampling conducted as part
of the remedial investigation while TCE was still used at Plant 4 (TCE is no longer used
at the plant) to determine if TCE evaporating from Plant 4 was being carried off site at
levels that would cause excess risk. The off-site air sampling was conducted at a location
approximately 0.75 mile west of Plant 4. Analysis of the air samples determined that the
highest levels of TCE in the air at the off-site location were approximately one-fourth the
highest levels of TCE in the air at the on-site location. The baseline risk assessment
determined that the levels of TCE in the air at the on-site location do not cause excess
risk, and, therefore, the risk to off-site receptors is not an excess risk. This sampling and
determination of risk are documented in the Remedial Investigation Report. Because
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TCE is no longer used at Plant 4, any risk to the community from TCE evaporating and
being carried off site is nonexistent.
Comment Ib:
The commentor wrote that because Plant 4 was and is a volume user of mercury, mercury
vapors have been released to the atmosphere. Once in the atmosphere, the mercury
vapors could have been carried by the wind to off-site locations where members of the
community could be exposed to mercury. The commentor also expressed concern that
mercury could migrate to groundwater and to surface water, ending up in Lake Worth.
The mercury used at Plant 4 is a form, mercury oxide, that is not detectable by sampling
methods. Also, the commentor was concerned that once the mercury was in Lake Worth,
it would be flushed downstream where it could contaminate a source of the nation's food
supply.
Air Force Response: The commentor is correct in that mercury was and is in
instruments and equipment used at Plant 4. The historical record search does not show
that mercury was disposed of at on-site locations. However, it is possible that
instruments and other equipment containing mercury were disposed of on site. If they
were disposed of on site, low amounts of mercury or mercury compounds could be in the
soil at Plant 4, even though they were not detected by sampling conducted for the
remedial investigation.
Also, if mercury were in the landfills near the surface, a portion of the mercury would
vaporize to the atmosphere and once in the atmosphere could be transported by wind.
However, any mercury vapors that were transported by the wind would be redeposited at
concentrations significantly less than the concentration of the source of the mercury on
Plant 4. Analyses of groundwater samples conducted as part of the remedial investigation
detected the presence of mercury in two samples at very low concentrations. Mercury
concentrations were detected in two samples from the Terrace Alluvial groundwater. The
levels of mercury were approximately 0.2 microgram per liter (|ug/L), which is 10 times
less than the allowable level for drinking water. However, Terrace Alluvial groundwater
is not used for drinking water. The presence of mercury was not detected in groundwater
samples from the Paluxy aquifer (which is used for drinking water), in surface water, or
in soil near the surface.
On the basis of sampling results conducted for the remedial investigation, the baseline
risk assessment determined there is no excess risk from exposure to mercury in the
groundwater, surface water, or soil. Because mercury was not detected in the surface soil
samples, the air samples collected at the on-site and off-site locations were not analyzed
for mercury.
The determination that there is no excess risk from mercury will be verified by
monitoring described in the ROD. Sampling of surface water and groundwater will be
conducted at areas on and near Plant 4. Future analyses will be able to detect mercury
compounds, such as mercury oxide, that are insoluble in water; analyses performed for
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the remedial investigation also were able to detect insoluble mercury compounds. In
addition, public water supplies are regularly sampled for mercury to ensure that drinking
water supplies do not contain excess contaminants, including mercury.
Although the scenario described by the commentor is theoretically possible, it is highly
improbable, given the results of the sampling performed for the remedial investigation,
that mercury found on site has vaporized and then been carried off site by the wind at
levels that will cause excess risk. Therefore, the Air Force, with the concurrence of the
EPA and the State of Texas, does not plan to collect samples in the residential areas
adjacent to Plant 4.
Comment Ic:
The commentor expressed concern that landfill material from Plant 4, containing
hazardous contamination and some dies used for metal shaping, has been disposed of at
various locations around Fort Worth, such as a low area south of Brewer High School.
This landfill material is another way that contamination has been transported to
residential areas.
Air Force Response: A records search in 1984 found no evidence of any removal or off-
site disposal during the construction period for Brewer High School. The high school
was constructed in 1953 (phone conversation with White Settlement Independent School
District Communications Office) and contractor removal of Plant 4 material to off-site
locations did not begin until 1966. During the period of construction for Brewer High
School, two landfills were active at the facility and the necessity for off-site disposal was
nonexistent. Records also indicate that all dies and metals used at Plant 4 during this
time were recycled.
No other evidence is available that landfill material was transported to other locations in
the Fort Worth area. Without an indication of where the contamination caused by Plant 4
could be, sampling to determine if contamination does exist at other locations is futile.
Therefore, the Air Force does not plan to conduct any additional off-site soil sampling.
Comment Id:
The commentor expressed concern that rainwater runoff from Plant 4 can transport
contamination into residential areas.
Air Force Response: Soil analyses performed during the remedial investigation have
shown that contamination in soils at the ground surface of Plant 4 is negligible and does
not cause an excess risk, except at Landfill No. 4 and Landfill No. 3 where there is a
potential for excess ecological risk (the potential risk is only to mice). Because surface
soil on Plant 4 is the only source of contamination for rainwater runoff to transport
contamination off site, the absence of soil contamination at the surface that causes excess
risk eliminates the potential for the transportation of contamination via rainwater runoff.
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Although surface contamination at Landfill No. 3 is low, it is higher than surface
contamination at other areas and is the area most likely to be a source of contamination
that could be transported off site by rainwater runoff. Other areas of Plant 4 are covered
by concrete or asphalt and would not be affected by rainwater. Rainwater runoff from
Landfill No. 3 drains into Meandering Road Creek. Contamination has been detected
in samples from Meandering Road Creek but not at levels that cause excess risk.
Monitoring of the surface water in Meandering Road Creek will be conducted to
ensure that contamination levels in Meandering Road Creek do not increase to
unacceptable levels.
Comment 2:
The commentor is a member of the Restoration Advisory Board and requested the names
and phone number of other members of the Restoration Advisory Board.
Air Force Response: The names and phone numbers of other Restoration Advisory
Board members have been sent to the commentor. The Air Force only has the phone
numbers of those that wished to provide them and, therefore, does not have the phone
numbers of all Restoration Advisory Board members. However, the commentor was sent
all the phone numbers available to the Air Force.
Comment 3:
The commentor requested consideration of installation of subsurface concrete walls
around the site or around individual "dumps" (landfills). This written comment is a
continuation of a comment made during the public meeting held December 14, 1995.
During the public meeting, the response from the Air Force was that a subsurface wall
was not needed. However, if a subsurface wall were needed, it would probably be
constructed of bentonite rather than concrete. The commentor disagrees with the use of
bentonite for a subsurface wall and stated that a concrete wall would be better because it
is less permeable than bentonite.
Air Force Response: A subsurface wall is not needed around individual landfills, such
as Landfill No. 3 or Landfill No. 4, or around the entire site because the levels of
contamination that are being discharged from the groundwater to surface water is not
causing excess risk. The main concern of the Air Force is if contamination at the landfills
is migrating to the groundwater and then to the surface water at levels that will cause
excess risk. Currently, small levels of contamination are migrating from the landfills but
not at levels that cause excess risk. Therefore, a subsurface barrier is not needed. The
determination that contamination is not causing excess risk will be verified with sampling
of the surface water near the landfills.
Further, for a subsurface wall to be useful, such a wall would have to encompass each
plume individually and entirely, or it would have to encompass the majority of the
property within the boundaries of the two Federal facilities (Air Force Plant 4 and Naval
Air Station Fort Worth). In either case, the wall would serve to stop contaminated
groundwater flow through unconsolidated alluvial deposits at the location of the wall.
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Also, the concrete wall would not prevent the slower migration occurring along bedding
planes and in weathered bedrock.
Within the perimeter of the wall, groundwater recharge would continue, as would the
flow of groundwater toward the edges of the plume where the wall is located. Because
groundwater would not be able to go through the subsurface wall, water levels would
increase until the water flowed over the top of the subsurface wall. To prevent this
overflow, discharge pumps, wells, and/or drains would be required to extract
contaminated water, which would then be treated at the surface. In short, the active
remediation involving pumps, wells, etc., that this proposal seeks to avoid would still be
required. If contamination levels do not increase, as is expected, a subsurface wall will
not be required.
The comment also suggests that concrete is preferable to bentonite because the bentonite
would become saturated and has only a limited capacity to adsorb contaminants. A
bentonite wall is not under consideration for use at Plant 4 at this time. Contrary to the
comment, bentonite walls do not become ineffective when saturated and they are not
intended to adsorb contaminants. Bentonite walls are intended to provide a low
permeability barrier to groundwater flow. To be effective, bentonite walls must be
saturated. When dry, bentonite walls shrink and crack, losing low-permeability properties
because of shrinkage and cracking. Also, the permeability (i.e., ability of water to flow
through the wall) of bentonite is about the same as that of concrete.
A subsurface wall would have to be approximately 6 miles long to encircle all the
groundwater contamination in the Terrace Alluvial flow system on Plant 4 and Naval Air
Station Fort Worth. A subsurface wall constructed of a concrete/bentonite mixture would
cost approximately $70 million over a 50-year operation period and $95 million over a
100-year operation period. A subsurface wall constructed of a bentonite/soil mixture
would cost approximately $58 million over a 50-year operation period and $83 million
over a 100-year operation period.
Comment 4:
The commentor suggested that the toxicity of heavy metals found on Plant 4 can be
minimized by adding a safe naturalizing agent to the dump sites. This process was
suggested as a low-cost way to detoxify the heavy metals before they leach from the
dump sites.
(a) The commentor stated pure metals at the dump sites could be treated by spreading
sulfur over a dump site. The sulfur would mix with the effluents and create a water-
insoluble metal sulfide salt. The metal sulfide salt would be comparatively nontoxic and
pose minimal threats to the environment.
(b) The commentor also suggested that metal salts could theoretically be converted to
less-toxic insoluble products by adding a safe liquid, such as sodium silicate, that will
precipitate largely insoluble silicates of metals elements.
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In addition, the commentor stated that if a solid silicate type of reagent is preferred,
aluminum silicate earth would be an inexpensive and effective method and that a number
of other chemicals could be used.
Air Force Response: The commentor is suggesting various methods of stabilization or
chemical fixation of the metals in the landfills, chrome pits, and dump areas. The
important point is not if the suggested methods of stabilization are effective, but if
stabilization is needed to manage risk to within acceptable levels. On the basis of results
of the baseline risk assessment, metals do not present excess risk to human health (risk
with an ILCR higher than 1.0 x 10"4 or a hazard quotient higher 1.0). There is a potential
for excess risk to mice from metals. Because the potential risk was only to mice, a risk
management decision was made that no action was acceptable. The findings of the
baseline risk assessment will be verified over the long term by monitoring the
groundwater and surface water.
The methods of stabilization suggested by the commentor may work for certain metals
under certain conditions, but generally will not be effective for treating a mixture of
metals and organics found in the landfills, chrome pits, and dump areas, with the
exception of aluminum silicate. Aluminum silicate is a primary ingredient in Portland
cement, and Portland cement is potentially the best method of stabilizing the waste
mixtures found in the landfills. However, as stated earlier, stabilization of the metals and
organics found in these waste areas was determined as not required to manage risk to
within acceptable levels.
Comment 5:
The commentor is concerned that the analysis of water samples taken as part of the
remedial investigation will not detect insoluble compounds, such as radioactive dust and
small radioactive particles in the water. These compounds are likely present at the site
but have not been detected because they are insoluble. The commentor suggested that if
radioactive elements are detected above safe levels, the area should be capped to prevent
radioactive dust from being transported by the wind. The commentor also recommended
two actions to detect the presence of radioactive elements.
(a) The commentor suggested that a Geiger-counter scan of the selected areas be
performed to verify the presence or the absence of radioactive materials.
(b) The commentor also suggested extracting soil samples with a strong oxidizing acid
as a way to detect radioactive materials that would not be detected in analysis of a
water sample.
Air Force Response: The only area where radioactive metals and compounds were used
or stored on Plant 4 is at NARF. During the remedial investigation, sediment samples
and groundwater samples were collected from the drainage near NARF and analyzed for
radioisotopes. Previous investigation activities also included the collection and analysis
of soil samples from boreholes drilled around the perimeter of NARF.
The Decision Summary FINAL A-15
Appendix A, Responsiveness Summary July 1996
-------
Results from previous soil analyses indicate gross alpha, gross beta, and radioisotopes
levels are within background ranges. Maximum uranium, radium, and thorium
concentrations were 2.7 milligrams per kilogram, 1.19 picocuries per gram (pCi/g), and
2.0 pCi/g, respectively, which are well within equilibrium levels. The maximum cesium
concentration was 0.53 pCi/g, which is within expected levels that are due to fallout from
worldwide nuclear testing. The presence of cobalt was not detected in any sample. These
concentrations are within the range of normal background levels; therefore, no action is
necessary for the NARF area. In addition to laboratory analyses, a field scan was
performed for alpha, beta, and gamma radiation on all samples collected from sediments
near the former NARF site; no radiation levels above background were detected.
In response to the commentor's suggestion to use a Geiger counter to verify the presence
or the absence of such radioactive materials, a Geiger counter is not as effective at
detecting the presence of plutonium or uranium because Geiger counters only detect
gamma radiation and are not as sensitive as gamma spectroscopy, the method used in the
remedial investigation. Plutonium and uranium emit low levels of gamma radiation but
are primarily alpha particle emitters.
In response to the commentor's suggestion to extract soil samples with a strong oxidizing
acid, such a procedure can be performed, but is unnecessary. Radioactive elements will
decay and emit alpha, beta, or gamma radiation regardless of the matrix. The methods
used in the remedial investigation are established and proven methods to detect
radioactive elements.
Comment 6:
The commentor stated that waste disposal by deep-well injection was probably used at
Plant 4. Unless records are available to prove that deep-well injection did not occur at
Plant 4, it must be assumed to have occurred and a "deep-well survey" should be
conducted to investigate this supposed problem. The commentor did not specify what
constitutes "deep-well disposal."
Air Force Response: A records search and subsequent telephone conversations with
Plant 4 personnel indicate there never has been deep-well disposal of wastes on site.
Waste disposed of by deep-well injection at off-site locations was manifested waste and
the waste was disposed of in permitted off-site wells.
If records documenting the occurrence of deep-well injection on site were available,
further investigation might be warranted. However, investigating the potential of deep-
well disposal of wastes simply because there is no evidence to prove it did not occur is an
expensive use of resources.
Analyses required by the Safe Drinking Water Act are performed on samples of all
groundwater pumped from aquifers in the area that is used as a municipal water supply.
These analyses have not shown any contamination problems in the drinking water
aquifers that could be attributed to Plant 4. Given the absence of Plant 4 records
A-16 FINAL The Decision Summary
July 1996 Appendix A, Responsiveness Summary
-------
documenting deep-well disposal on site and the lack of evidence supporting
contamination that could be caused by Plant 4, there is insufficient justification to search
for contamination caused by deep-well injection at Plant 4.
The Decision Summary FINAL A-17
Appendix A, Responsiveness Summary July 1996
-------
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A-18 FINAL The Decision Summary
July 1996 Appendix A, Responsiveness Summary
-------
Appendix B
Administrative Record Index
Prepared by
U.S. Army Corps of Engineers
Louisville District
The Decision Summary FINAL B-l
Appendix B, Administrative Record Index July 1996
-------
This Page Intentionally Left Blank
B-2 FINAL The Decision Summary
July 1996 Appendix B, Administrative Record Index
-------
Contents
Page
Introduction B-5
Administrative Record Index Guide B-6
Administrative Record Index Category List B-7
Administrative Record Index B-l 1
The Decision Summary FINAL B-3
Appendix B, Administrative Record Index July 1996
-------
This Page Intentionally Left Blank
FINAL The Decision Summary
July 1996 Appendix B, Administrative Record Index
-------
Administrative Record for U. S. Air Force Plant 4
Introduction
The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of
1980 as amended by the Superfund Amendments and Reauthorization Act (SARA) of 1986
requires establishing administrative records.
The administrative record established under § 113(k) of CERCLA serves two primary purposes.
First, the record contains those documents which form the basis for selection of a response action
under § 113(j). Judicial review of any issue on the adequacy of a response action is limited to
the record. Second, § 113(k) requires that the administrative record act as a vehicle for public
participation in selecting a response action.
This administrative record file and accompanying index have been compiled according to
provisions of the U. S. Environmental Protection Agency's Office of Solid Waste and Emergency
Response (OSWER) Directive No. 9833.3A-1, "Final Guidance on Administrative Records for
Selecting CERCLA Response Actions."
The documents included in this administrative record are a subset of information included in the
project files for this site. Documents contained in the administrative record file are identified
with unique numbers to aid in tracking and retrieval of the documents.
The index and file will be updated about once each quarter. As the updates are issued, the file
will be inventoried against the new index to ensure its completeness.
According to OSWER Directive No. 9833.3A-1, certain documents are not physically included
in this administrative record file but are included by reference. Among these documents are
chain-of-custody forms and sampling data, such as laboratory analytical results. The sampling
data are summarized in the reports included in the administrative record file. Typically, the
sampling data and related chain-of-custody forms are retained by the contractors that published
the reports and/or their subcontractors. To receive further information concerning specific
sampling data and chain-of-custody forms, please reference the document number of the report
and write to the individual identified below.
Please forward any questions, comments, or requests for additional information or copies to:
(Note: Costs for copies are borne by the requester.)
U. S. Air Force, ASC/EMR, Building 8
1801 10th Street, Suite 2
Wright-Patterson AFB, OH 45433-7626
Attention: Mr. David Lawrence
The Decision Summary FINAL B-5
Appendix B, Administrative Record Index July 1996
-------
Administrative Record Index Guide
The Administrative Record file for Air Force Plant 4 Installation Restoration Program
(IRP) has been assembled per the Administrative Record Category List. The category list
was developed based upon OSWER Directive No. 98333A-1.
The Index contains the following fields: DOCNO, CATEGORY, TITLE, AUTHOR,
PAGE, and DATE. A description of each field is presented below.
1. DOCNO: This is the unique document number assigned to each document contained
in the Administrative Record file. The first two digits identify the general category
(e.g., 01-Site Identification, 03-Remedial Investigation, etc.). The last three digits are a
sequential number assigned from the database as documents are entered into the
Administrative Record file.
2. CATEGORY: This is the specific category identification from the Administrative
Record Index Category List (e.g., 01.04-Site Investigative Reports, 03.04-Remedial
Investigation Work Plans, etc.). Documents of a specific nature can be located through
review of this field.
3. TITLE: This is the complete title as it is shown on each document. Clarifications have
been provided where appropriate.
4. AUTHOR: This is the specific organization responsible for generating the document.
Individuals are identified where known.
5. PAGE: This is the number of pages contained in each document. For documents
containing more than one thousand pages, the total page count is identified as 999.
6. DATE: This is the date of each document. If an actual date is not provided, the last
date of the month is used (e.g., a document dated September 1991 is listed as
09/30/91).
7. Notes: Documents listed in Section 11.00 are available to the public through original
sources and are included in this Administrative Record file for reference only.
Document titles preceded by an asterisk (*) will be included in the Administrative
Record file at the next scheduled update.
B-6 FINAL The Decision Summary
July 1996 Appendix B, Administrative Record Index
-------
Administrative Record
Index Category List
01.00 SITE IDENTinCATION
OL01 Background
01.02 Notification/Site Inspection Reports
01.03 Preliminary Assessment Reports
01.04 Site Investigative Reports
01.05 Miscellaneous Investigation Reports
01.06 Correspondence
01.07 Quality Assurance Program/Project Plans
01.08 Health and Safety Plans
01.09 Miscellaneous Program/Project Management Documents
02.00 REMOVAL RESPONSE
02.01 Sampling and Analysis Plans
02.02 Sampling and Analysis Data/Chain-of-Custody Forms
02.03 Engineering Evaluation/Cost Analysis (EE/CA)
02.04 EE/CA Approval Memorandum
02.05 Action Memorandum and Amendments
02.06 Correspondence
03.00 REMEDIAL INVESTIGATION (RI)
03.01 Sampling and Analysis Plans
03.02 Sampling and Analysis Data/Chain-of-Custody Forms
03.03 Manifests
03.04 Remedial Investigation Work Plans
03.05 Remedial Investigation Reports
03.06 Correspondence
04.00 FEASIBILITY STUDY (FS)
04.01 Applicable or Relevant and Appropriate Requirement (ARARs)
Determinations
04.02 Feasibility Study Reports
04.03 Proposed Plans
04.04 Correspondence
The Decision Summary FINAL B-7
Appendix B, Administrative Record Index July 1996
-------
05.00 RECORD OF DECISION (ROD)
05.01 Records of Decision
05.02 Amendments to Records of Decision
05.03 Explanations of Differences
05.04 No Further Action Documents
06.00 STATE COORDINATION
06.01 Cooperative Agreements/State Memorandums of Agreement (SMOAs)
06.02 State Certification of ARARs
07.00 ENFORCEMENT
07.01 Enforcement History
07.02 Endangerment Assessments
07.03 Administrative Orders
07.04 Consent Decrees
07.05 Affidavits
07.06 Documentation of Technical Discussions with Potentially Responsible
Parties (PRPs)
07.07 Notice Letters and Responses
07.08 Correspondence
07.09 Permit Applications
08.00 HEALTH ASSESSMENTS
08.01 Agency for Toxic Substance and Disease Registry (ATSDR)
Health Assessments
08.02 Toxicological Profiles
09.00 NATURAL RESOURCE TRUSTEES
09.01 Notices Issued
09.02 Findings of Fact
09.03 Reports
B-8 FINAL The Decision Summary
July 1996 Appendix B, Administrative Record Index
-------
10.00 PUBLIC PARTICIPATION
10.01 Comments and Responses
10.02 Community Relations Plans
10.03 Public Notice of Availability of Information
10.04 Public Meeting Transcripts
10.05 Documentation of Other Public Meetings
10.06 Fact Sheets and Press Releases
10.07 Responsiveness Summaries
11.00 TECHNICAL SOURCES AND GUIDANCE DOCUMENTS
11.01 U. S. Environmental Protection Agency (EPA) Headquarters' Guidance
11.02 EPA Regional Guidance
11.03 State Guidance
11.04 Technical Sources
11.05 Department of the Air Force Guidance
11.06 Technical Information Reports
The Decision Summary FINAL B-9
Appendix B, Administrative Record Index July 1996
-------
This Page Intentionally Left Blank
B-10 FINAL The Decision Summary
July 1996 Appendix B, Administrative Record Index
-------
AFP4
DOCUMENT SUMMARY
DOCNO CATEGORY TITLE AUTHOR
1001
1002
1003
1004
1005
1006
1008
1009
1 .04 Phase I Investigation, Drilling and Construction of Upper Hargis & Montgomery, Inc.
Zone Test Holes and Monitor Wells
1 .04 Installation Phase I Investigation of Subsurface Hargis & Montgomery, Inc.
Conditions at U.S. Air Force Plant 4, Fort Worth, Texas,
Volume I (Text)
1 .04 Installation Phase I Investigation of Subsurface Hargis & Montgomery, Inc.
Conditions at U.S. Air Force Plant 4, Fort Worth,
Texas, Volume II, (Illustrations)
1 .04 Installation Phase I Investigation of Subsurface Hargis & Montgomery, Inc.
Conditions at U.S. Air Force Plant 4, Fort Worth, Texas,
Volume HI (Appendices)
1 .04 Construction of Paluxy Monitor Well P-l , U.S. Air Force Hargis & Montgomery ,Inc.
Plant 4, Fort Worth, Texas
1.04 Specification for Waste Disposal Project - West Parking General Dynamics
Lot
1.04 Environmental, Energy, and Resource Conservation JRB Associates
Review of Air Force Plant 4
1 .04 Seismic Refraction Survey, Letter Report, General D'Appolonia Waste Management
PAGE DATE
13 01/31/83
73 02/03/83
9 03/03/83
168 03/03/83
17 03/18/83
93 06/30/83
250 09/30/83
8 12/31/83
Dynamics, Ft. Worth Division, Project No. 840002 Services
1010
1011
1012
1013
1014
1015
1016
1017
1018
1 .04 Copy of Field Engineer's Notes for Die Yard and Chrome General Dynamics
Pits Excavation Project and Analytical Lab Results
1 .04 Installation/Restoration Program Records Search for Air CH2M Hill
Force Plant 4, Texas
1 .04 Conclusion and Recommendations for Completion of Hargis & Associates, Inc.
Phase II Investigation
1 .04 Phase II Investigation of Subsurface Conditions Vol. I Hargis & Associates, Inc.
1.04 Phase II Investigation of Subsurface Conditions, Volume Hargis & Associates, Inc.
II, Appendices A-E
1 .04 Phase II Investigation of Subsurface Conditions, Volume Hargis & Associates,Inc.
Ill, Appendices F-G
1 .04 Phase II Investigation of Subsurface Conditions, Volume Hargis & Associates, Inc.
IV, Appendices H-I
1 .04 Phase II Investigation of Subsurface Conditions, Volume Hargis & Associates, Inc.
V, Appendices J-M
1.04 Draft Installation Restoration Program, Phase II, Radian Corporation
Confirmation/Qualification, Stage 1, Volume 1, Final
Draft Report for Cars well AFB
The Decision Summary FINAL
Appendix B, Administrative Record Index
77 01/31/84
394 08/31/84
35 10/25/84
155 09/30/85
300 09/30/85
238 09/30/85
264 09/30/85
167 09/30/85
_
237 09/30/85
B-ll
July 1996
-------
AFP 4
DOCUMENT SUMMARY
DOCNO
1019
1020
1021
1022
1023
1024
CATEGORY TITLE
AUTHOR
1025
1026
1027
1028
1029
1031
1032
1033
1034
1.04
1.04
1.04
1.04
1.03
1.04
1.04
1.04
1.04
1.04
1.04
1.04
1.04
1.04
Installation Restoration Program, Phase II,
Confirmation/Qualification, Stage 1, Volume 2 -
Appendix A, Draft Final Report for Carswell AFB
Installation Restoration Program, Phase II,
Confirmation/Qualification, Stage 1, Volume 3 -
Appendices B-L, Draft Final Report for Carswell AFB
Assessment of French Drain Pumpage
Results of Soil and Groundwater Assessment for the
Proposed Systems Development Laboratory and An echoic
Chamber Buildings
Proposed 1986 Hydrologic Monitoring Plan.U.S. Air
Force Plant No. 4, Ft Worth, Texas
Three-Site RAP Review Action Items, Attachment A
Design Basis and Preliminary Calculations for
Conceptual Design of Alternate 4, Onsite Contaminated
Groundwater Treatment and Discharge to AFP No. 4
Process Water Makeup System
Draft Remedial Action Plan and Conceptual Documents
for Fuel Saturation Areas No. 1 and No. 3
Interim Report for Ten-Site Field Investigation, Prepared
for Air Force Plant 4, Fort Worth, Texas
Construction Site Assessment Report for the Die Yard
Zone, Plant Services Contract No. 5161
Summary Report Window Area Investigation
Assessment Report for Landfill No.3,Prepared for U.S.
Air Force Plant No. 4, Fort Worth, Texas
Proposed 1988 Hydrologic Monitoring Plan
Installation Restoration Program, Phase II,
Confirmation/Quantification, Stage 1, Volume 2 -
Appendix A-l, Final Report for September 1985 through
September 1986
Installation Restoration Program, Phase II,
Confirmation/Quantification, Stage 1, Volume 3,
Appendix A-l (conlined). Final Report for September
1985 through September 1986
Installation Restoration Program, Phase II,
Confirmation/Quantification, Stage 1, Volume 4 -
Appendix A-l (continued), Final Report for September
1985 through September 1986
Radian Corporation
Radian Corporation
Hargis & Associates, Inc.
Hargis & Associates, Inc.
Hargis & Associates,Inc.
Inlellus Corporation
Intellus Corporation
In tell us Corporation
Intellus Corporation
Hargis & Associates, Inc.
Intellus Corporation
Hargis & Associates, Inc.
Radian Corporation
Radian Corporation
Radian Corporation
PAGE
728
362
27
60
48
53
501
461
90
69
51
121
621
DATE
09/30/85
09/30/85
12/06/85
12/16/85
01/02/86
07/16/86
07/31/86
11/30/86
01/30/87
04/21/87
08/31/87
12/02/87
12/31/87
552 12/31/87
603 12/31/87
B-12
July 1996
FINAL
The Decision Summary
Appendix B, Administrative Record Index
-------
AFP 4
DOCUMENT SUMMARY
CATEGORY
TITLE
DOCNO
1035 1.04 Installation Restoration Program, Phase II,
Confirmation/Quantification, Stage 1, Volume 5 -
Appendix A-2, Final Report for September 1985 through
September 1986
1036 1.04 Installation Restoration Program, Phase II,
Confirmation/Quantification, Stage 1, Volume 6 -
Appendix A-2 (continued), Final Report for September
1985 through September 1986
103 7 1.04 Installation Restoration Program, Phase II,
Confirmation/Quantification, Stage 1, Volume 7 -
Appendices A-3 and A-4, Final Report for September
1985 through September 1986
103 8 1.04 Installation Restoration Program, Phase II,
Confirmation/Quantification, Stage 1, Volume 8 -
Appendices B-E, Final Report for September 1985
through September 1986
1039 1.04 Installation Restoration Program, Phase II,
Confirmation/Quantification, Stage 1, Volume 9 -
Appendices F-K, Final Report for September 1985
through September 1986
1040 1.04 Installation Restoration Program, Phase II, Final Report -
Volume 10, Appendix L, Final Report for September
1985 through September 1986
1041 1.04 Installation Restoration Program, Phase II,
Confirmation/Quantification, Stage 1, Volume 1, Report
Text, Final Report for September 1985 through
September 1986
104 2 1.07 Installation Restoration Program,Phase II,
Confirmation/Quantification, Stage 2, Carswell Air Force
Base Quality Assurance Project Plan
104 3 1.04 Evaluation of Condenser Water Pipeline and Interim
RemdiaJ Measures Fuel Saturation Area No. 3
1044 1.04 Engineering Report Remedial Action for Fuel Saturation
Areas 1 and 3 and treating leachate of French Drain No.
1, Air Force Project 1-86-59, Plant Services Contract
6246
1045 1.04 Underground Storage Tank Program Evaluation,
Analysis of USTS at AFP No. 4, Ft. Worth, Texas,
Volume III, Appendix F
1046 1.04 Industrial Hygiene Assessment of Organic Solvents at
General Dynamics Plant Fort Worth, Texas
AUTHOR
PAGE DATE
Radian Corporation 526 12/31/87
Radian Corporation 492 12/31/87
Radian Corporation 394 12/31/87
Radian Corporation 155 12/31/87
Radian Corporation 353 12/31/87
Radian Corporation 622 12/31/87
Radian Corporation 491 12/31/87
Radian Corporation 174 01/31/88
Hargis & Associates, Inc. 37 07/15/88
General Dynamics 101 03/02/89
Hargis & Associates, Inc. 309 06/02/89
Clayton Environmental 37 08/28/89
Consultants, Ltd. for Hargis &
Associates, Inc.
The Decision Summary
Appendix B, Administrative Record Index
FINAL
B-13
July 1996
-------
DOCNO
1047
1048
1049
1050
1051
1052
1053
1054
1055
AFP4
DOCUMENT SUMMARY
CATEGORY TITLE AUTHOR
1 .04 Environmental Assessment, Advanced Materials Hargis & Associates, Inc.
Development Laboratory Site
1 .07 Preliminary Assessment/Site Inspection and Remedial UNC Geotech
Investigation/Feasibility Studies, Final Quality Assurance
Project Plant Air Force Plant 4, Volume III
1 .08 Preliminary Assessment/Site Inspection and Remedial UNC Geotech
Investigations/Feasibility Studies, Final Health and Safety
Plan, Air Force Plant 4, Volume IV
1 .04 Draft Decision Paper for Landfill Number 2 Site Geotech, Inc.
1 .04 Draft Decision Paper for Chrome Pit Number 1 Site Geotech, Inc.
1.04 Draft Decision Paper For Chrome Pit Number 2 Site Geotech, Inc.
1 .04 Draft Decision Paper for Fire Department Training Area Geotech, Inc.
Number 4 Site
1 .09 Preliminary Water Quality Monitoring Plan Geotech, Inc.
1 .04 Installation Restoration Program, Stage 2, Site Radian Corporation
PAGE DATE
122 10/20/89
60 08/31/90
300 08/31/90
34 09/30/90
22 09/30/90
19 09/30/90
34 09/30/90
86 10/31/90
321 11/30/90
1056
1057
1058
1059
1060
1061
1062
Characterization Report for the Flightline Area, Carswell
Air Force Base
1.09 Preliminary Assessment/Site Inspection and Remedial
Investigations/Feasibility Studies, Waste Management
Plan.Air Force Plant 4
1.05 Draft Final Groundwatcr Quality Monitoring Report,
January 1992, GJPO-WMP-68, prepared for
Headquarters Department of the Air Force, Aeronautical
Systems Division, Wright-Patterson AFB, Ohio, Volumes
1 through 5
1.04 Investigation of Ground Water Pollution at Air Force
Plant No. 4, Fort Worth, Texas
1.04 Phase II Report, Field Sampling, Analysis and Testing,
Air Force Plant 4, Window Area, Fort Worth, Texas
1.04 Installation Restoration Program, Quarterly Groundwater
Monitoring Comprehensive Sampling Round Letter
Report, Air Force Plant 4, Fort Worth Texas
1.04 Installation Restoration Program (IRP) Quarterly
Groundwater Monitoring Quarterly Letter Report; Air
Force Plant 4; Texas
1.04 Installation Restoration Program (IRP) Quarterly
Groundwaler Monitoring Data Validation Letter Report;
Air Force Plant 4; Texas
Chem-Nuclear Geotech, Inc.
Chem-Nuclear Geotech, Inc.
U.S. Army Corps of Engineers,
Kansas City District, Fort Worth
District
International Technology
Corporation
Jacobs Engineering Group Inc.
Jacobs Engineering Group, Inc.
Jacobs Engineering Group, Inc.
15 12/03/90
999 01/31/92
142
56
99
317
161
10/31/86
08/31/93
08/31/93
02/28/95
02/28/95
B-14
July 1996
FINAL
The Decision Summary
Appendix B, Administrative Record Index
-------
AFP 4
DOCUMENT SUMMARY
DOCNO CATEGORY TITLE
1063
1064
1065
1066
1067
1068
1069
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
AUTHOR
1.08
1.04
1.07
1.03
1.04
1.04
3.02
3.02
3.02
3.04
3.04
3.04
3.02
3.02
3.01
3.05
Soil Vapor Extraction Pilot Plant Site Specific Health and
Safety Plan; Air Force Plant 4, Fort Worth Texas
Results of Chemical Analyses of Liquid Samples Various
Sites; Air Force Plant 4, Fort Worth Texas
Site Health and Safety Plan, Groungwater Remediation of
Landfills 4 and 5, Carswell Air Force Base, Fort Worth,
Texas
Contractor Quality Control Plan (Addendum)
Groundwater Remediation System Installation and
Startup, Landfills 4 and 5 (Carswell); Air Force Plant 4,
Fort Worth, Texas
Soil Vapor Extraction Pilot Plant Operations and
Maintenance, Sampling, and Test Manual; Air Force
Plant 4, Fort Worth Texas
Installation Restoration Program (IRP) Data Validation
Letter Report; Air Force Plant 4, Fort Worth, Texas
Installation restoration Program (IRP) Basewide
Groundwaler Monitoring Quarterly Letter Report; Air
Force Plant 4, Fort Worth, Texas
Water Quality Data, May 1985 to May 1986
Water Quality Data, May 1986 to May 1987, Volume I,
Appendices A through C
Water Quality Data, May 1986 to May 1987, Volume II,
Appendices D through G
Final Draft Work Plan, Remedial Investigation and
Feasibility Study, Volume I (Text)
Final Draft Work Plan, Remedial Investigation and
Feasibility Study, Volume II, Appendices C through I
Final Draft Work Plan, Remedial Investigation and
Feasibility Study, Volume III (Figures)
Water Quality Data, May 1987 to January 1989, Volume
I, Appendix A
Water Quality Data, May 1987 to January 1989, Volume
II, Appendices B through G
Draft Annual Hydrologic Monitoring Plan
Summary of Interim Remedial Investigations, January
1987 to April 1989, Volume 1, Text, Tables and
Illustrations
Environmental Science and
Engineering, Inc.
U.S. Army Corps of Engineers
Southwest Division Laboratory,
Dallas, Texas
IT Corporation, Monroeville, PA
Environmental Science and
Engineering, Inc.
Jacobs Engineering Group, Inc.
Jacobs Engineering Group, Inc.
Hargis & Associates, Inc.
Hargis & Associates, Inc.
Hargis & Associates, Inc.
Hargis & Associates, Inc.
Hargis & Associates, Inc.
Hargis & Associates, Inc.
Hargis & Associates, Inc.
Hargis & Associates, Inc.
Hargis & Associates, Inc.
Hargis & Associates, Inc.
PAGE
111
326
344
181
61
DATE
09/30/93
122 01/27/93
82 04/30/93
IT Corporation, Monroeville, PA 215 01/31/94
43 09/30/93
214 08/31/95
690 08/31/95
08/15/86
08/05/87
149 08/31/87
202 01/31/89
285 01/31/89
0 01/31/89
263 04/20/89
211 04/20/89
07/19/89
07/19/89
The Decision Summary
Appendix B, Administrative Record Index
FINAL
B-15
July 1996
-------
DOCNO
3011
3012
3013
3014
3015
3016
CATEGORY
3.05
3.05
3.01
3.01
3.02
3.02
AFP 4
DOCUMENT SUMMARY
TITLE AUTHOR
Summary of Interim Remedial Investigations, January Hargis & Associates, Inc.
1987 to April 1989, Volume II, Appendices A through F
Summary of Interim Remedial Investigations, January Hargis & Associates, Inc.
1987 to April 1989, Volume III, Appendices G through L
Annual Hydrologic Monitoring Plan Hargis & Associates, Inc.
Water Sampling Manual, Preliminary Draft Hargis & Associates, Inc.
Collection and Analysis of Soil Samples Versar, Inc.
Installation Restoration Program(IRP),Quarterly Jacobs Engineering Group, Inc.
PAGE DATE
252 07/19/89
279 07/19/89
199 01/31/89
127 07/27/89
180 01/24/90
217 06/30/92
3018
3019
3020
3021
3022
3023
3024
3026
4001
4002
Groundwater Monitoring, Quarterly Letter Report, Air
Force Plant 4, Texas
3.01 Preliminary Assessment/Site Inspection and Remedial
Investigations/Feasibility Studies, Final Sampling and
Analysis Plan, Air Force Plant 4, Volume II
3.04 Preliminary Assessment/Site Inspection and Remedial
Investigation/Feasibility Studies, Final Work Plan,
AirForce Plant 4, Volume I
3.06 Coordination of Installation Restoration Program (IRP)
Efforts for Carswell AFB and AFP4 (RE: Letter
14Mar84)
3.02 Installation Restoration Program (IRP) Quarterly
Groundwater Monitoring Quarterly Letter Report, Air
Force Plant 4, Fort Worth, Texas
3.02 Installation Restoration Program (IRP) Quarterly
Groundwater Monitoring Quarterly Letter Report; Air
Force Plant 4; Fort Worth, Texas
3.05 Soil Vapor Extraction, Pilot Plant Study; Air Force Plant
No. 4, Building 181; Fort Worth Texas
3.02 Installation Restoration Program (IRP) Quarterly
Groundwater Monitoring Quarterly Letter Report; Air
Force Plant 4; Fort Worth, Texas
3.05 Groundwater Monitor Well Installation, Landfill No. 4,
U.S. Air Force Plant No. 4, Fort Worth, Texas
3.02 Installation Restoration Program (IRP) Quarterly
Groundwater Monitoring Data Validation Letter Report;
Air Force Plant 4, Fort Worth, Texas
4.02 Characterization of Tnchloroethcne Plume, Air Force
Plant 4 and Carswell Air Force Base, Fort Worth, Texas
4.02 Final Report - Summary of Remediation Projects at Air
Force Plant 4 and Carswell Air Force Base, Fort Worth,
Texas Volume I
UNC Geotech 330 08/31/90
UNCGeolech 117 08/31/90
AFSC 9 04/24/84
Jacobs Engineering Group, Inc. 254 03/31/94
Jacobs Engineering Group, Inc. 352 07/31/94
Environmental Science and 240 08/31/94
Engineering, Inc.
Jacobs Engineering Group, Inc. 265 11 /30/94
Geo-Marine, Inc. 393 11 /30/94
Jacobs Engineering Group, Inc. 132 11/30/94
Environmental Science & 68 07/31/94
Engineering Group
Environmental Science & 207 07/31 /94
Engineering, Inc.
B-16
July 1996
FINAL
The Decision Summary
Appendix B, Administrative Record Index
-------
AFP 4
DOCUMENT SUMMARY
DOCNO
4003
4004
4005
4006
5001
5002
5003
5004
5005
5006
5007
7001
11001
11002
11003
CATEGORY TITLE
AUTHOR
PAGE DATE
4.02
4.02
4.02
4.02
5.04
5.04
5.04
5.04
5.04
5.04
5.04
7.01
1.03
11.03
11.03
Final Report - Summary of Remediation Projects at Air
Force Plant 4 and Carswell Air Force Base, Fort Worth,
Texas Volume II
Final Report - Summary of Hydrologic and Chemical
Characterization Studies Volume I; Air Force Plant 4,
Fort Worth, Texas
Final Report - Summary of Hydrologic and Chemical
Characterization Studies Volume II; Air Force Plant 4,
Fort Worth, Texas
Final Report - Summary of Hydrologic and Chemical
Characterization Studies Volume III; Air Force Plant 4,
Fort Worth, Texas
Draft Final No Further Action Decision Document,
Lanfill No. 2, Site LF02
Draft Final No Further Action Decision Document,
Chrome Pit No. 1, Site DPI 1
Draft Final No Further Action Decision Document,
Chrome Pit No. 2, Site DP10
Draft Final No Further Action Decision Document, Fire
Department Training Area No. 4, Site FT07
Air Force Plant 4, Draft No Further Action Decision
Document, Nuclear Aerospace Research Facility, IRP
Site OT19
Air Force Plant 4, Draft No Further Action Decision
Document, West Compass Rose, IRP Site OT21
Air Force Plant 4, Draft No Further Action Decision
Document, Solvent Lines, IRP Site ST18
Investigation of Disposal/Cleanup Activities, Waste
Disposal Project - West Parking Lot, USAF Plant 4,
General Dynamics, Fort Worth Division, Fort Worth,
Texas
Texas State Board of Water Engineers, Ground Water
Resources of Fort Worth and Vicinity, Texas
Geology and Ground Water Resources of Tarrant
County, Texas
Bulletin 6309, Reconnaissance Investigation of the
Ground Water Resources of the Trinity River
Basin.Texas
Environmental Science &
Engineering, Inc.
Environmental Science &
Engineering, Inc.
Environmental Science &
Engineering Group, Inc.
Environmental Science &
Engineering, Inc.
Chem-Nuclear Geotech, Inc.
Chem-Nuclear Geotech, Inc.
Chem-Nuclear Geotech, Inc.
Chem-Nuclear Geotech, Inc.
Chem-Nuclear Geotech, Inc.
Chcm-Nuclear Geotech, Inc.
Chem-Nuclear Geotech, Inc.
U.S.Environmental Protection
Agency Office of Enforcement and
Compliance Monitoring
W.O. George and N. A. Rose -
Prepared in cooperation with the
U.S.G.S.
Texas Stale Board of Water
Engineers
Texas Water Commission
293 07/31/94
196 07/31/94
284 07/31/94
411 07/31/94
29 09/30/91
17 09/30/91
15 09/30/91
30 09/30/91
20 09/30/92
09/30/92
22 09/30/92
106 12/31/83
0 09/30/42
0 09/30/57
0 09/30/63
The Decision Summary
Appendix B, Administrative Record Index
FINAL
B-17
July 1996
-------
AFP 4
DOCUMENT SUMMARY
DOCNO
11004
11005
11006
11007
11008
11009
CATEGORY TITLE
AUTHOR
11.03
11.03
11.03
11.03
11.03
11.05
11010
11011
11012
11013
11014
11015
11017
11018
11019
11020
11021
11.04
11.04
11.03
11.03
11.03
11.03
11.03
11.03
11.03
11.04
11.04
Water-level and Water-Qua lily Data From Observation
Weils in Northeast Texas, Report 198
Variations in Specific Yield in the Outcrop of the Carrizo
Sand in South Texas as Estimated by Seismic Refraction
Texas Surface Water Quality Standards
Occurrence, Availability, and Chemical Quality of
Ground Water in the Cretaceous Aquifers of
North-Central Texas, Report 269, Volume 1
Occurrence, Availability, and Chemical Quality of
Ground Water in the Cretaceous Aquifers of
North-Central Texas, Report 269, Volume 2
Air Force Installation Restoration Program Management
Guidance
Water Resources Data, Texas 86, Volume 1
Water Resources Data, Texas 87, Volume 1
Ground Water Conditions in Texas 1980-1985, Report
309
Permanent Rule Change
Official Texas Administrative Code, Titlc31, Natural
Resources and Conservation
Water Resources Data, Texas 89, Volume 1
Official Texas Administrative Code, Title 31, Natural
Resources and Conservation, 1990-1991 Supplement,
Amendments effective through April 1, 1990
Index to Texas Water Well Drillers Board
FEMA, Flood Insurance Study, Tarrant County, Texas
Unincorporated Areas
Geotech, Soil & Water Sample Analytical Data
Certificate of Analysis
Texas Water Development Board
Texas Department of Water
Resources
Texas Department of Water
Resources
Texas Department of Water
Resources
Texas Department of Water
Resources
Department of the Air Force
U.S. Geological Survey
U.S. Geological Survey
Texas Water Development Board
Texas Water Commission
The State of Texas
U.S. Geological Survey
The State of Texas
PAGE
0
Federal Emergency Management
Agency
U.S. Department of Energy
ITT
0
0
0
0
0
0
0
DATE
03/28/76
04/30/79
04/30/81
04/30/82
07/31/82
07/30/85
01/31/86
01/31/87
10/31/88
12/28/88
01/31/89
01/31/89
01/31/90
0 / /
126 .08/04/87
0 05/22/90
199 05/29/90
B-18
July 1996
FINAL
The Decision Summary
Appendix B, Administrative Record Index
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