PB98-964512
EPA541-R98-181
May 1999
EPA Superfuod
Record of Decision:
Tucson International Airport Area
OU 3 (AFP 44)
Tucson, AZ
9/28/1998
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Record of Decision
Installation Restoration Program
Sites 4, 5, and 6
FINAL
Air Force Plant 44
Tucson International Airport Area Superfund Site
Tucson, Arizona
September 1998
UNITED STATES AIR FORCE
AERONAUTICAL SYSTEMS CENTER
Acquisition Environmental Management
Wright-Patterson AFB, Ohio
AIR FORCE CENTER
FOR ENVIRONMENTAL EXCELLENCE
Environmental Restoration Division
Brooks AFB, Texas
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INSTALLATION RESTORATION PROGRAM (IRP)
RECORD OF
SOIL CLEANUP og§iTEsl, 5, AND 6
for
Air Force Plant 44
Tucson International Airport Area Superfund Site
Tucson, Arizona
Dennis Scott
Remedial Project Manager
United States Air Force
Aeronautical Systems Center
Acquisition Environmental Management
Wright-Patterson Air Force Base, Ohio
September 1998
Capt Casey Hackathorn
Restoration Team Chief
Air Force Center for Environmental Excellence (AFCEE)
Environmental Restoration Division
Brooks Air Force Base, Texas
Prepared by:
Earth Tech Inc.
Alexandria, Virginia
Final Record of Decision for Soil Cleanup of Sites < 5, and 6 - September 1998
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TABLE OF CONTENTS
Section Page No.
1.0 Declaration 1-1
1.1 Site Name and Location 1-1
1.2 Statement of Basis and Purpose 1-1
1.3 Assessment of the Sites 1-1
1.4 Description of the Selected Remedy 1-1
1.5 Statutory Determinations 1-3
2.0 Decision Summary 2-1
2.1 Air Force Plant 44 History and Background 2-2
2.2 Site Investigation and Regulatory Activities 2-2
2.3 Community Participation 2-6
2.4 Scope and Role of Response Action at AFP 44 2-7
2.5 Summary of Site Characteristics 2-8
2.5.1 Site 4 (Former Unlined Surface Impoundments) 2-8
2.5.1.1 Site 4 Soil Gas Contaminants 2-8
2.5.1.2 Site 4 Soil Contaminants 2-10
2.5.1.3 Results Associated with Lined Surface Impoundment Closure 2-10
2.5.2 Site 5 (Former Sludge Drying Beds ) 2-11
2.5.2.1 Site 5 Soil Gas Contaminant 2-11
2.5.2.2 Site 5 Soil Contaminants 2-16
2.5.3 Site 6 (Drainage Ditch and Channels) 2-16
2.5.3.1 Site 6 Soil Contaminants 2-16
2.5.4 Groundwater 2-18
2.5.4.1 Groundwater Contaminants 2-19
2.6 Summary of Site Risks 2-19
2.7 Applicable or Relevant and Appropriate Requirements 2-23
2.8 Summary of Cleanup Levels 2-26
2.8.1 Inorganic contaminants 2-26
2.8.2 Organic Contaminants 2-26
2.9 Description of Remedial Alternatives 2-30
2.10 Comparative Analysis of Alternatives 2-33
2.10.1 Site 4: Former Unlined Surface Impoundments and Site 6: Drainage
Ditch and Channels, Preferred Alternative: Offsite Stabilization and
Disposal in a RCRA Landfill 2-35
2.10.2 Site 5 - Former Sludge Drying Beds Preferred Alternative: Offsite
Stabilization and Disposal in a RCRA Landfill and SVE Presumptive
Remedy 2-35
Final Record of Decision for Soil Cleanup of Sites 4,5, and 6 • September 1998
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TABLE OF CONTENTS
Section Page No.
2.10.3 Plug-in Approach for VOC-Contaminated Soils 2-37
2.10.3.1 Plug-In Process and Criteria 2-37
2.10.3.2 Performance Standards for VOC-Contaminated Soil Cleanup
at Site 5 2-41
2.11 The Selected Remedy for Sites 4 and 6: Offsite Stabilization, Disposal in a
RCRA Landfill 2-42
2.12 The Selected Remedy for Site 5: Offsite Stabilization, Disposal in a RCRA
Landfill and SVE Presumptive Remedy 2-42
2.13 Shutdown and Decommissioning 2-44
2.14 Statutory Determination 2-45
2.14.1 Protection of Human Health and the Environment 2-45
2.14.2 Compliance with ARARs 2-45
2.14.3 Cost Effectiveness 2-46
2.14.4 Utilization of Permanent Solutions and Alternative Treatment
Technologies 2-46
2.14.5 Preference for Treatment as a Principal Element 2-46
3.0 Responsiveness Summary: Proposed Plan and Engineering Evaluation/Cost
Analysis Sites 1,2,3,4, and 5 3-1
Appendix A References
Appendix B Groundwater Contaminant Contours
Final Record of Decision for Soil Cleanup of Silts 4, S, and 6 - September 1998
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TABL&OF CONTENTS
Page No.
LIST OF FIGURES
Figure 2-1 Location of Air Force Plant 44, Tucson, Arizona 2-3
Figure 2-2 IRP Site Location Map 2-5
Figure 2-3 Site 4 Former Unlined Surface Impoundments 2-9
Figure 2-4 Site 5 Former Sludge Drying Beds 2-12
Figure 2-5 VOCs in Shallow Soil Gas - Site 5, May 1997 2-13
Figure 2-6 Shallow Soil Gas Survey Results West Site 5, March 1998 2-14
Figure 2-7 Site 5 West Soil Vapor Monitoring Well Results, March 1998 2-15
Figure 2-8 Site 6 Drainage Ditch, Channels and Hotspots 2-17
Figure 2-9 Solidification/Stabilization Process Schematic 2-36
LIST OF TABLES
Table 2-1 Total Site Human Receptor Cancer Risk 2-21
Table 2-2 Total Site Human Receptor Hazard Index 2-21
Table 2-3 Ecological Receptors Potentially at Risk at AFP 44 Due to Soil
Contamination: All Depths 2-22
Table 2-4 Contaminants of Concern and Associated ARARs and TBCs at AFP 44 IRP
Sites 4,5, and 6 2-25
Table 2-5 Location-Specific ARARs at AFP 44 2-27
Table 2-6 Action-Specific ARARs at AFP 44 2-28
Table 2-7 Applicable Drinking Water Maximum Contaminant Levels 2-30
Final Record of Decision for Soil CUanup of Sites 4,5, and 6- September 1998
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Page iii
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LIST OF ACRONYMS & SBBJ^YIATIONS
ADEQ Arizona Department of Environmental Quality
ADHS Arizona Department of Health Services
ADWR Arizona Department of Water Resources
AFP 44 Air Force Plant 44
ARAR Applicable or Relevant and Appropriate Requirement
BACT Best Available Control Technology
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act
CFR Code of Federal Regulation
DCE Dichloroethylene
DERP Defense Environmental Restoration Program
D OT Department of Transportation
DPE Dual Phase Extraction
EE/CA Engineering Evaluation/Cost Analysis
FACO Final Assembly and Checkout
FFA Federal Facility Agreement
FS Feasibility Study
GAC Granular-activated Carbon
GPL Groundwater Protection Level
GWTP Groundwater Treatment Plant
HSWA Hazardous and Solid Waste Amendment
HWMA Hazardous Waste Management Act
IRP Installation Restoration Program
ISV In-situ Vitrification
ug/L Micrograms per Liter
MCL Maximum Contaminant Level
mg/L Milligrams per Liter
mg/kg Milligrams per Kilogram
MSL Mean Sea Level
NCP . National Oil and Hazardous Substances Pollution Contingency Plan
NPDES National Pollutant Discharge Elimination System
O&M Operation and Maintenance
PCB Polychlorinated Biphenyl
PCE Tetrachloroethylene
RACT Reasonably Available Control Technology
RCRA Resource Conservation and Recovery Act
RI Remedial Investigation
RI/FS Remedial Investigation/Feasibility Study
ROD Record of Decision
SARA Superfund Amendments and Reauthorization Act
S/S Solidification/Stabilization
S VE Soil Vapor Extraction
Final Record of Decision for Soil Cleanup of Sites 4,5, and 6 - September 1998
Page iv
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LIST OF ACRONYIVIS& ABBREVIATIONS
Continued
TBC To-Be-Considered
TCA 1,1,1-Trichloroethane
TCE Trichloroethyiene
TPH Total Petroleum Hydrocarbon
UCAB Unified Community Advisory Board
USC United States Code
USEPA United States Environmental Protection Agency
VEMUR Voluntary Environmental Mitigation Use Restriction
VOC Volatile Organic Compound
Final Record of Decision for Soil Cleanup of Sites 4, 5, and 6- September 1998
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SECTION 1.0
1.1 SITE NAME AND LOCATION
Air Force Plant 44 (AFP -44) is located within the Tucson International Airport Area
Superfund Site, Tucson, Arizona, and is identified as such on the National Priorities List.
The Installation Restoration Program (IRP) sites addressed in this Record of Decision
(ROD) are:
• Site 4: Former Unlined Surface Impoundments
• Site 5: Former Sludge Drying Beds
• Site 6: Drainage Ditch and Channels
It should be noted that IRP Site 4 consists of shallow soil contaminated with metals. Deeper soil and
ground water contaminated with volatile organic compounds (VOCs) are part of IRP Site 14, the
shallow groundwater zone, and are being addressed in separate remedial actions and associated
documentation. Additionally, note that IRP Site 5 includes VOC-contaminated soil located west of
the sludge drying beds, which were discovered recently.
1.2 STATEMENT OF BASIS AND PURPOSE
This ROD presents the selected remedial action for Sites 4, 5, and 6 at AFP 44, Tucson, Arizona,
chosen in accordance with the Comprehensive Environmental Response, Compensation, and
Liability Act (CERCLA), as amended by Superfund Amendments and Reauthorization Act (SARA),
and the National Oil and Hazardous Substances Pollution Contingency Plan (NCP). This decision
is based on the administrative record for this site.
1.3 ASSESSMENT OF THE SITES
Hazardous substances present at these sites, if not addressed by implementing the response actions
selected in this ROD, may result in a release or substantial threat of a release of a hazardous
substance into the environment and associated threats to public health, welfare, or the environment.
1.4 DESCRIPTION OF THE SELECTED REMEDY
The Air Force has decided that excavation and offsite disposal in a Resource Conservation and
Recovery Act (RCRA) Class I landfill with solidification/stabilization (S/S) is the preferred remedy
for excavated metals-contaminated materials under CERCLA for these three specific sites and
sources. The decision regarding metals-contaminated soil was based on treatability studies
Final Record of Decision for Soil CUanup of Sites 4,5, and 6 • September 1998
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conducted under the Feasibility Study (FS) (Reference 1) and other documents in the administrative
record (see Appendix A for references). The preferred remedy will remediate soil to levels at or
below the State of Arizona Final Soil Remediation Standards (residential levels) promulgated in
December 1997 for each contaminant of concern. Due to the great depth to groundwater (e.g., 120-
feet), the relatively low solubility of most of the contaminants of interest (e.g., metals), and previous
research demonstrating negligible impacts to groundwater from metals at AFP 44 (Reference 2), the
minimum groundwater protection levels (GPLs) are not applicable as remediation goals for metals
in soils at Sites 4,5, and 6.
The major components of the selected remedy for metals-contaminated soils at Sites 4, 5, and 6
include:
• Characterization trenching, as required
• Excavation of contaminated soils
• S/S for soils containing metals in excess of action levels
• Disposal of soils in a RCRA Class I landfill.
Recently discovered VOC-contaminated soil identified west of IRP Site 5 will be assessed using the
U.S. Environmental Protection Agency's (USEPA's) presumptive remedy plug-in approach. The
plug-in approach, which is discussed in detail in Section 2.10, defines a process by which a limited
number of remedial alternatives are evaluated to address a specific, but relatively common set of
contaminants and site conditions. The alternatives evaluated using the plug-in approach for Site 5
soils will be limited to no further action and SVE. SVE removes contaminants from the soil by
withdrawing air at extraction wells, which induces an air flow from the surface. The withdrawn air
is laden with volatilized contaminants, which are treated aboveground. A VOC detector may be
installed to monitor for vapors in the treated air, and can automatically shut down the vapor
treatment system if vapor concentrations exceed emissions standards. Treated air is then discharged
to the atmosphere. For organic contaminants, rather than using numeric standards as remedial
objectives, a narrative standard will be applied as allowed by Arizona Department of Environmental
Quality (ADEQ) regulations (R18-7-206). The application of this narrative standard is detailed in
Section 2.8.
The Air Force is currently performing non-time critical removal actions at these sites, implementing
the selected remedies. These removal actions are being performed concurrently with the ROD
process, and allowed site cleanup to begin in February 1996 instead of waiting until the conclusion
of the ROD process.
Other sites at AFP 44 have been addressed in a separate ROD, with the following proposed
remedies: SVE at Site 1 (Ranch Site), Site 2 (Final Assembly and Checkout [FACO] Landfill), and
Site 3 (Inactive Drainage Channel Disposal Pits). A no further action ROD has been issued for four
other sites including: Site 7 (North FACO Fire Training Area), Site 8 (South FACO Fire Training
Area and Magnesium Burn Area), Site 9 (Explosive Detonation Pit), and Site 15 (Potential Trench
Site) (References 4, 5, 6, and 7). Site 14 (Shallow Groundwater Zone) will be addressed in a
separate ROD.
Final Retard of Decision for Soil Cleanup of Sites 4, S, and 6 - September 1998
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Action Plan Responsiveness Summary and Record '•,....,.,., , . ....
1.5 STATUTORY DETERMINATIONS
The selected remedies are protective of human health and the environment, comply with Federal and
State requirements that are legally applicable or relevant and appropriate to the remedial action, and
are cost-effective. Offsite disposal and S/S and SVE utilize permanent solutions to the maximum
extent practicable and satisfy the statutory preference for remedies mat employ treatment that reduces
toxicity, mobility, or volume as a principal element. Because all inorganic contaminants above
required cleanup levels will be removed from Sites 4, 5, and 6, no future review of metals
contamination related to this ROD is necessary. However, cleanup of VOCs west of Site 5 may
require a five-year review of organic contamination to ensure protection of human health and the
environment has been achieved.
Stewart E. Cranston
Lieutenant General. Air Force
Vice Commander, Headquarter* Air Force Materiel Command
Wright-Patterson Air Force Base. Ohio
Date
Daniel Opalski. Chie/^~
Federal Facilities Cleanup Branch
United States Environmental Protection Agency
San Francisco, California
Dat/ /
Russell F. Rhoades, Director
Arizona Department of Environmental Quality
Phoenix, Arizona
Date
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SECTION 2.0
DECISION
The Air Force has selected excavation and offsite disposal at a RCRA Class I landfill with S/S
for remediation of metals-contaminated soils that exceed universal treatment standards at
Sites 4, 5, and 6. In addition, VOC-contaminated soils located west of Site 5 will be
addressed utilizing the USEPA's presumptive remedy plug-in approach, which allows for no further
action or SVE as remedial alternatives. The remediation objectives addressed in this ROD are
cleanup of three sites to address potential risks to human health and the environment, which includes
eliminating potential sources of groundwater contamination. This ROD serves the following three
purposes:
• Certify that the remedy selection was carried out in accordance with the requirements
of CERCLA and the NCP.
• Outline the engineering components and remediation goals of the selected remedies.
• Provide the public with a consolidated source of information about the history,
characteristics, and risks posed by the conditions at the sites, as well as a summary
of the cleanup alternatives considered, their evaluation, and the rationale behind
selection of the remedies.
The ROD consists of three major components:
• The Declaration, which is an abstract of key information and includes signatures.
• The Decision Summary is the main component of the ROD, and provides background
information, an overview of the site characteristics, the remedial alternatives
evaluated, and a statutory determination of the selected remedy.
• The Responsiveness Summary, which addresses public comments received on the
Proposed Plan and other information in the administrative record.
This ROD addresses three sites at AFP 44:
• Site 4: Former Unlined Surface Impoundments
• Site 5: Former Sludge Drying Beds
• Site 6: Drainage Ditch and Channels.
Final Record of Decision for Soil Cleanup of Situ 4, 5, and 6 • September 1998
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The mailing address for the AFP 44 Remedial Project Manager is:
Mr. Dennis Scott
AFP 44 Remedial Project Manager
HQASC/FJvlR
1801 Tenth Street, Suite 2
Wright-Patterson AFB, Ohio 45433-7626
Telephone: 1-800-982-7248, extension 417
2.1 AIR FORCE PLANT 44 HISTORY AND BACKGROUND
AFP 44 was first constructed in 1951 for the purpose of manufacturing Falcon air-to-air missiles.
Over the years, industrial facilities have been constructed to support several other missile systems.
At present, industrial facilities occupy a total building area in excess of 2 million square feet
(Reference 9).
AFP 44 is located within the Tucson International Airport Area Superfund Site, Tucson, Arizona;
a location map is provided in Figure 2-1. AFP 44 is located on flat terrain at an approximate altitude
of 2,600 feet above mean sea level (msl). The plant is located 15 miles south of downtown Tucson
and is bounded on the east by Tucson International Airport property. The Nogales Highway (Route
89) lies west of the facility. The plant is bounded to the south by Hughes Access Road and on the
west by Southern Pacific's Tucson-Nogales railroad spur. A service spur enters the plant from the
north, and a temporary spur was installed south of the surface impoundments in support of a RCRA
closure effort. The northern boundary of AFP 44 lies along the north section line of Sections 29 and
30. Vacant land and light commercial property is located to the south. The Santa Cruz River, which
is located approximately 1.5 miles west of the plant's western boundary, flows in a north-
northwesterly direction and drains the Tucson Basin. Review of the Flood Insurance Rate Map for
Pima County, Arizona (Reference 10) shows that AFP 44 is not in the 500-year floodplain of the
Santa Cruz River.
Other neighboring areas include the San Xavier Indian Reservation (west of Route 89), Davis-
Monthan Air Force Base (approximately 3 miles northeast of the plant), Saguaro National Park (the
eastern unit is approximately 10 miles to the northeast and the western unit is approximately 15
miles to the northwest), and the Santa Rita Experimental Range (also known as the Sahuarita
Bombing and Gunnery Range). The range, located approximately 10 miles south of AFP 44, has not
been used since the 1950s.
2.2 SITE INVESTIGATION AND REGULATORY ACTIVITIES
Manufacturing activities at AFP 44 precede the November 19, 1980 effective date of the RCRA.
Past disposal practices included treatment, storage, and disposal of industrial wastewater, use of
unlined surface impoundments, as well as land disposal of general industrial wastewaters, spent
solvents, and dilute and concentrated acids and alkalines (Reference 9).
Final Record of Decision for Soil Cleanup of Sites 4, 5, and 6 - September 1998
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Page 2-3
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In early 1981, the USEPA and the Arizona Department of Health Services (ADHS) identified
contaminants "in the upper zone of the regional aquifer underlying the areas around the Tucson
International Airport in Tucson, Arizona. In response to this finding, the Air Force initiated
extensive groundwater investigations to determine if contamination existed under AFP 44, and if so,
to determine the extent of the contamination. These investigations showed contamination was
present. A groundwater reclamation system was activated in 1987 and continues to operate under
an April 1986 ROD (Reference 8).
In 1988, USEPA and ADEQ issued a joint permit to the Air Force and its contractor (Hughes Missile
Systems Company) pursuant to the RCRA of 1976, 42 USC §6901 et seq., as amended by the
Hazardous and Solid Waste Amendments of 1984 ("HSWA"), (collectively referred to as "RCRA").
The joint permit consists of (I) a State permit (Hazardous Waste Management Act "[HWMA]
Permit") issued pursuant to certain RCRA provisions authorized to be implemented by the State
through its approved HWMA, and (ii) an USEPA issued permit which addresses corrective ac" tion
regulations promulgated pursuant to HSWA, for which the State had not yet received authorization
("HSWA Permit"). When discussed together, the HWMA Permit and the HSWA Permit are
collectively referred to as the Permit.
Since 1988, the Air Force has been conducting cleanup work at AFP 44 pursuant to the Permit. The
Air Force, USEPA, and the State (the Project Management Team) have agreed to enter into a Federal
Facilities Agreement ("FFA") that will address corrective action activities being conducted under
the HSWA Permit to allow termination of the HSWA Permit The FFA will not affect the HWMA
Permit. The terms of the HSWA Permit remain in effect until the FFA is finalized and the HSWA
Permit is terminated.
A Remedial Investigation (RI) of potential soil contamination at ten historic waste management sites
was conducted in 1991, with supplemental field work in 1993 (Reference 11) and 1995 (Reference
12). A risk assessment, to identify sites for remediation, was completed in 1993 (Reference 13). A
FS (Reference 1), which evaluated potential remedial alternatives for contaminated soils, was
completed in January 1995. Cleanup of five sites to remove continuing sources of groundwater
contamination or to address potential risks to human health and the environment is specifically
addressed in the FS: Site 1 (Ranch Site), Site 2 (FACO Landfill), Site 3 (Inactive Drainage Channel
Disposal Pits), Site 4 (Former Unlined Surface Impoundments) including portions of the area which
were originally sampled during investigation of Site 6 (Drainage Ditch and Channels), and Site 5
(Former Sludge Drying Beds). A no further action ROD has been issued for four other sites
including: Site 7 (North FACO Fire Training Area), Site 8 (South FACO Fire Training Area and
Magnesium Bum Area), Site 9 (Explosive Detonation Pit), and Site 15 (Potential Trench Site)
(References 4, 5, 6, and 7). Site 14 (Shallow Groundwater Zone) remediation will be addressed in
a separate ROD. This ROD addresses Sites 4,5, and 6 soils cleanup only. Figure 2-2 presents the
locations of IRP sites addressed in this ROD.
The CERCLA response process uses the RI and FS as succeeding steps in the investigation of a site.
The goal of an RI is to gather site information to characterize the nature and extent of contamination,
and to recommend either no further action or cleanup based, in part, on the results of a risk
Final Record of Decision for Soil Cleanup of Sites 4, 5, and 6 • September 1998
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assessment to quantify potential exposure risks to the most likely receptors. The FS includes detailed
evaluations of a variety of potential technologies for each site requiring cleanup and suggests specific
cleanup actions for each site or group of sites based upon the results of the evaluations. RI and FS
activities have been completed for AFP 44. The initial RI report dated January 1992 and its addenda.
the Risk Assessment report dated August 1993, the FS report dated January 1995, the Proposed Plan
(Reference 14), and this ROD are available for public review in the Information Repository located
at:
TCE Superfund Library
El Pueblo Neighborhood Center
Building B-2
101 West Irvington
Tucson, Arizona 85714-3099
(520) 889-9194
This ROD will also be placed in the Administrative Record for AFP 44.
The Air Force is currently performing non-time critical removal actions for Sites 1 through 6, and
Site 14 implementing the preferred alternatives identified in the FS. The Air Force determined the
appropriateness of the non-time critical removal action based on the factors outlined in the NCP
Sections 300.415 (b)(2) and 300.415 (b)(4). These removal actions are being performed
concurrently with the ROD process, and are consistent with the final remedies selected in the ROD.
This allowed site cleanup to begin in February 1996 instead of waiting for the extensive ROD
process to be completed.
2.3 COMMUNITY PARTICIPATION
The Air Force has completed a RI, risk assessment, and a FS at AFP 44. A public'meeting was held
to discuss the results of the RI and the risk assessment. A second public meeting was held with a
45-day public comment period to obtain community input on the Draft Final FS which was made
available to the public in October 1994. The final version of the FS report (January 1995) included
written responses to comments received from the public and regulatory agencies (Reference 1). The
FS recommended SVE for cleanup of volatile organic contaminants at IRP Sites 1, 2, and 3; and
excavation with offsite disposal at a RCRA landfill for metal contaminants at JRP Sites 4 and 5, and
portions of Site 6. Additionally, IRP Sites 7, 8,9, and 15 have been recommended for No Further
Action (References 4,5, 6, and 7).
Engineering Evaluation/Cost Analysis (EE/CAs) (Reference 15,16,17, 18,19, and 20) describing
proposed removal actions, and a Proposed Plan (Reference 14) describing preferred final remedial
alternatives at the sites requiring remediation, were released for a 30-day public comment period.
The public comment period for the Proposed Plan was extended twice at the request of the Tucson
Community. The first extension was for 15 days and the next extension was for 30 days, for a total
review period of 75 days. A public meeting was held on July 18,1995 to discuss these documents.
A responsiveness summary was prepared following the close of the comment period. The Air Force
prepared written responses to comments received from the public, USEPA, ADEQ, and any other
Final Record of Decision for Soil Cleanup of Sites 4,5, and 6 • September 1998
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comments received. The responses are included in Section 3.0, Responsiveness Summary, of this
ROD. This Responsiveness Summary represents an evaluation of community acceptance. These
documents and the removal action work plan (Reference 21) were submitted to the USEPA and
ADEQ for review and comment. The Air Force began implementation of the removal action work
plan approximately two weeks after submittal of the final work plan.
Public input on all the cleanup alternatives considered and the preferred cleanup method was an
important contribution to the remedy selection process. To assist the public in its review, an
overview of the cleanup methods evaluated during the FS and an explanation of the reason for
selecting the recommended cleanup methods were presented in the Proposed Plan (Reference 14).
The Proposed Plan included a description of the ROD process under CERCLA and the intent to
conduct early removal actions consistent with the final ROD remedy.
It should be noted that VOC-contaminated soils west of Site 5 were not identified in the remedial
investigation/feasibility study (RI/FS) process and therefore the Proposed Plan did not address the
remedial alternatives for this recently identified media. Under the guidance of the USEPA, the Air
Force is proceeding to investigate these soils further and will utilize the USEPA's presumptive
remedy plug-in approach to select the appropriate treatment technology. Section 2.10 of this ROD
elaborates on the application of the plug-in approach under CERCLA.
The Air Force participated in monthly meetings of the Unified Community Advisory Board (UCAB),
the group which represents the City of Tucson community's interest regarding the Tucson Airport
area Superfund site. The UCAB was briefed monthly on the status of both the ROD and EE/CA
removal action processes, including a treatability study using the preferred alternative for metals-
contaminated soils. Comments were received from the UCAB on the Proposed Plan; responses to
these comments are included in Section 3.0.
Detailed explanations of the extent of contamination at each site, possible health risks to unprotected
workers at AFP 44 or to the community posed by the contaminants, and the methods considered for
cleaning up the sites are contained in the RI (Reference 11), Risk Assessment (Reference 13), and
the FS (Reference 1) reports.
PUBLIC COMMENT PERIOD: A 75-day public comment period for the Proposed Plan was held from
July 10 to September 23,1995 to accept comments from the Tucson community and other interested
parties.
2.4 SCOPE AND ROLE OF RESPONSE ACTION AT AFP 44
Soil sites at AFP 44 were categorized in the FS into three groupings:
• Soil sites for which SVE is the preferred remedial method (Sites 1,2, and 3).
• Soil sites for which excavation and offsite stabilization and disposal is the preferred
remedial method (Sites 4, 5, and Site 6).
• Soil sites which required no further action (Sites 7,8, 9, and 15).
Final Record of Decision for Soil Cleanup of Silts 4,5. and 6- Septtmbtr 1998 ~~~
«LvMT4J-IVIOI7UA-l\SrTES4-»WpW639«S39WTI WPD PSLRC 2-7
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Only Sites 4, 5, and 6 are addressed by this ROD; the remaining soil sites requiring cleanup have
been addressed in a separate ROD (Reference 22). These site groupings were established due to the
similarity of site conditions and proposed actions.
Groundwater at AFP 44 was addressed in a 1986 ROD (Reference 8), and is being remediated with
a reclamation well field and treatment plant In addition, IRP Site 14, the shallow groundwater zone,
is being remediated as part of the regional groundwater remediation program. Site 14 remediation
will be addressed in a separate ROD.
2.5 SUMMARY OF SITE CHARACTERISTICS
Brief overviews of the characteristics and contaminants associated with Sites 4, 5, and 6 are
presented in the following sections.
2.5.7 Site 4 (Former Unlined Surface Impoundments)
Site 4 occupies approximately 10 acres, and consists of three former unlined impoundments which
were used from approximately 1961 to 1977. The site is located in the vicinity of the former lined
brine evaporation ponds (see Figure 2-2). The surface impoundments, which are known as Site 4
east and west, are currently undergoing closure under RCRA (Reference 23) (see Figure 2-3).
Treated and untreated industrial wastewaters were discharged from the wastewater treatment plant
to the former unlined impoundments. The wastewaters consisted primarily of rinsewater from
plating processes, neutralized caustics, cooling tower blowdown, and some concentrated solutions
of chromium and cyanide (Reference 11). Site 4 is located directly above IRP Site 14, the shallow
groundwater zone. Remediation of VOCs associated with Site 14 will be addressed in a separate
ROD.
2.5.1.1 Site 4 Soil Gas Contaminants
Eight soil gas samples collected at Site 4 in 1987 contained trichloroethylene (TCE), 1,1-
dichloroethylene (DCE), toluene, ethylbenzene, and xylenes at concentrations less than 2.3
micrograms per liter (ug/L) (Reference 24).
A soil gas survey of Site 4 was conducted during the RJ (Reference 11) which showed the presence
of DCE, Freon 113, and TCE in concentrations on the order of 1 u.g/L; 1,1,1-trichloroethane (TCA)
was detected at an order of magnitude less. Carbon tetrachloride and tetrachloroethylene (PCE) were
present in concentrations on the order of 0.001 ug/L. VOC concentrations detected were below
action levels and therefore pose no risk to human health or the environment. Hence, VOC
remediation is not a part of the Site 4 removal action or this ROD.
Site 4 overlies Site 14 (shallow groundwater zone). During preparation of an EE/CA and a removal
action work plan in June 1996 for Site 14, concern was raised regarding the potential occurrence of
VOC contamination in the vadose zone. This concern was raised based on S VE tests conducted on
shallow groundwater zone wells. Low concentrations of VOCs were detected during these tests.
Dual-phase extraction (DPE) of groundwater and soil vapors has been initiated at Site 14 as pan of
Final Record ofDteisionfor Soil Cleanup of Sites 4,5, and 6- September 1998
VIW39VJ«]9RPTl.WPt> PaC 2-8
-------
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a broader groundwater remediation effort DPE systems operating at Site 14 are removing more than
100 pounds of VOCs per month. Additional vapor monitoring wells were installed and sampled in
Spring 1998 at Site 14. Both TCE and DCE levels in soil vapors were negligible down to
approximately 55 feet and were elevated at depths of 70 and 80 feet below grade. The wells
terminated 10's of feet above the water table, but the pattern of contamination suggests that no
shallow VOC source is present. Additional future soil vapor monitoring will be performed to clarify
the relationship between deep vadose zone contamination and groundwater contamination in the
shallow groundwater zone. The Site 14 removal action addresses VOCs in the vadose zone
associated with Site 14 which is overlain by Site 4. Remedial action goals associated with VOCs
in the vadose zone will be addressed in the Site 14 ROD.
2.5.1.2 Site 4 Soil Contaminants
Metals detected at levels above background concentrations include antimony (maximum
concentration 172 milligrams per kilogram [mg/kg]), cadmium (70.1 mg/kg), total chromium (8,535
mg/kg), copper (6,930 mg/kg), nickel (707 mg/kg), silver (45.9 mg/kg), and zinc (Reference 11).
Surface soils also appear to be contaminated with metals. Soil will be remediated to meet ADEQ
cleanup levels for target metals (e.g., chromium, cadmium, and nickel). Remediation of target
metals is anticipated to reduce concentrations of all other metals to acceptable levels. The potential
source for cadmium, chromium, copper, nickel, silver, and zinc is plating waste. Antimony, which
was not detected in background samples is a hardening alloy and bearing metal; it is possible that
antimony-containing metals were disposed at the site. Additional investigation of Site 4 in the area
of geophysical anomalies identified during the RI (Reference 11) occurred in January to February
of 1995 (Reference 12). Trenching was conducted at locations as shown in Figure 2-3. The trenches
were visually inspected and soil samples were collected from the trenches for chemical analysis.
Layers of dried green sludge were delineated. Samples were collected above, below, and in the
sludge layers. Some samples contained metals in excess of cleanup levels established by the ADEQ
for the closure of the former lined brine evaporation ponds.
2.5.1.3 Results Associated with Lined Surface Impoundment Closure
The area designated as Site 4 East is the portion of Site 4 underlying the former 3 and 4 series
surface impoundments as shown in Figure 2-3. To achieve clean closure of the 3 and 4 series
impoundments, the Air Force elected to remove Site 4 East soil exceeding ADEQ cleanup levels
established for the impoundments. A removal action for Site 4 East was conducted under IRP, in
conformance with CERCLA and in accordance with RCRA requirements in conjunction with the
closure of the 3 and 4 series surface impoundments. Soils in Site 4 East were removed concurrently
with the closure of the 3 and 4 series surface impoundments. In addition, portions of IRP Site 6 that
were co-located with Site 4 were removed as part of the Site 4 cleanup. Excavation of contaminated
soil was initiated in February 1996 and completed in June 1996. A total of 13,949 tons of soil were
excavated and disposed of offsite at a RCRA Class I landfill (Reference 23).
Final Record of Decision for Soil Cleanup of Situ 4,5, and 6- September 1998
IL:\An»44-l\lfl07(JA-l\SlTES4.|\WW)639«)«9Rrri.WPD PaC 2-10
-------
2.5.2 SiteS (Former Sludge Drying Beds)
The two sludge drying beds, located just east of Building 801 (Figure 2-4), were square in shape.
The beds were originally unlined. At an unknown time, one was lined with a plastic membrane and
the other with bentonite. These beds received treated wastewaters and precipitated metal sludge,
which contained chromium and cyanides, as well as traces of cadmium, silver, lead, and copper
compounds. The beds were constructed in the early 1960s and used until 1977, at which tune they
were excavated and covered with native soil (Reference 11). Both beds are currently covered by an
asphalt parking lot
A former oil spreading area was located southwest of Building 811 in an area approximately 200 feet
wide and 1,400 feet long. Waste oils were spread on the area as a means of dust control. Much of
the area is now covered by a structure and parking lot The area was graded during construction of
the parking lot and some soil was removed to an unknown location (Reference 1).
Pipelines conveying waste metals from the industrial wastewater treatment plant to the sludge drying
beds were located west of Site 5. Additionally, VOC-contaminated soils have been identified west
of Site 5, which may be related to Site 5 activities. These areas, while not explicitly within the
mapped boundary of Site 5, are considered part of Site 5 and are subject to the provisions of this
ROD.
2.5.2.1 Site 5 Soil Gas Contaminant
A shallow soil gas survey was conducted at Site 5 and in an area immediately west of Site 5 in May
1997 (Reference 26). This work was conducted to ensure that all potential sources of VOCs had
been identified. No VOCs were present at significant levels (>0.04 ug/L) within the limits of IRP
Site 5. However, west of Site 5 several widely spaced and isolated samples did contain elevated
concentrations of VOCs, warranting further investigation and evaluation. Figure 2-5 presents total
VOCs detected during that study. TCE levels were elevated at two points; one on the north side of
Building 810 (22 ug/L at point SG-42), and one near the southeast comer of Building 801 (31 ug/L
at point SG-40). DCE and TCA were also present at point SG-40 at concentrations of 0.1 ug/L and
13 ug/L, respectively. Near Building 814A. DCE was noted at 13 ug/L along with low levels of
TCE and TCA (5 and 2 ug/L, respectively).
Supplemental investigative activities were performed west of Site 5 in March and April 1998 and
reported in a Supplemental Investigation Report (Reference 28) in April 1998. The findings of the
study indicated that VOC contamination in the shallow vadose zone was negligible (Rgure 2-6),
possibly indicating reduction of contamination due to ongoing DPE activities conducted in the
immediate vicinity. Elevated levels of VOCs were noted in deeper soil gas samples (Figure 2-7).
Additional investigative activities are planned to determine if potential sources of solvent
contamination are present in or beneath the buildings west of Site 5.
Future discussions will be required to determine if the boundaries of Site 5 should be formally
expanded or if a new IRP site should be designated to address the VOC soil contamination in the
vicinity of Building 801.
Final Rtcord of Decision for Sell Otatup of Sites 4,5, and 6 • Stjrttmber 1998 "~
fUWP44-i\ioo7QA-i\STTES4-i\wpiM3wu9iti'n.wi>c Page 2-11
-------
• - FULL SCAN BORING LOCATIONS
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- RECLAMATION WELL
OH. SPREAD AREA (APPROX. SJZE)
SLUDGE DRYING BEDS (APPROX. SIZE]
SITES
FORMER SLUDGE DRYING BEDS
Page 2-12
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812
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FORMER SLUDGE DRYING BEDS
TOTAL VOCs IN SOIL GAS
(HARGIS. 1997)
Page 2-13
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LEGEND
/ yiinfr T.inkj ^^ Groundvvalvr Monitoring Well
Former Dcgrc.iscrs Ouil| phale £,|,,Clion Well
jr A A Soil Gas Point
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in concrete containment '<=' String and Concentrations (ug
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oil Vapoi Monitoring Well Resulls.
March 1 998
Page 2-15
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2.5.2.2 Site 5 Soil Contaminants
Metals detected in soil at Site 5 in levels above background concentrations include cadmium
(114 mg/kg), total chromium (18,144 rag/kg), copper (7,049 mg/kg) and zinc (247 mg/kg)
(Reference 11). Soil was excavated then sampled for confirmation and reexcavated as necessary
until the area of removal was confirmed to be below ADEQ soil cleanup standards for cadmium,
chromium, cyanide, lead, and nickel (Reference 27). Polychlorinated biphenyls (PCBs) were
detected in one Site 5 soil sample at 3.1 mg/kg (Reference 11). Site 5 was formerly sprayed with
waste oil for dust control; this may have been the source of PCBs. Total petroleum hydrocarbon
(TPH) concentrations ranged from 45.3 mg/kg to 1,905 mg/kg (Reference 11); however, this area
is currently covered by an asphalt parking lot. Soil removal activities at Site 5 were conducted from
March through May 1997. A total of 5,033 tons of contaminated soil was excavated from Site 5 and
transported to a RCRA Class I landfill for disposal. The remediation of metals-contaminated soils
at Site 5 is completed and final documentation has been submitted (Reference 27).
2.5.3 Site 6 (Drainage Ditch and Channels)
Site 6 is a system of open, unlined drainage channels which transported industrial wastewaters west
from Building 801, with the exception of the channel which enters AFP 44 along the northern
boundary (Figure 2-8). This channel conveys stormwater from Tucson International Airport. The
drainage channels and ditches originally led to the desert area of the western portion of AFP 44 but
were routed to unlined surface impoundments (Site 4) in the early 1960s. The channels occupy
approximately 3 acres, based on an estimated average width of 5 to 10 feet. The drainageways are
dry most of the year, flowing only during and immediately following rainstorms (Reference 11).
From approximately 1955 to 1961, these drainage ditches received various types of wastewaters
including treated chromium- and cyanide-bearing wastewaters, neutralized acid solutions, and
chromium- and cyanide-free rinsewaters. From approximately 1962 to 1977, the only untreated
liquid wastes that entered the channels were alkaline cleaning and chromium- and cyanide-free
rinsewaters, paint booth wash, accidental spillage and accidental process tank overflows, and cooling
tower blowdown and condensate from throughout the plant. All other wastes were initially treated.
Since 1977, when a new wastewater treatment plant was installed, the industrial process rinsewaters
and concentrated wastes have been transported in piping and managed in lined surface
impoundments and tanks.
2.5.3.1 Site 6 Soil Contaminants
Portions of the Site 6 drainage ditches and channels are co-located with Site 4 (see Figure 2-2).
Elevated metal concentrations (cadmium, chromium, copper, nickel, silver, and zinc) were detected
in three boreholes within and to the northeast of Site 4, suggesting that the former unlined surface
impoundments could have been a possible source of metal contamination in these areas. Soil
samples collected from Site 6 during the RI contained metals and organic compounds (Reference
11). Potential risk to ecological receptors due to the presence of cadmium, chromium, copper,
nickel, silver, and zinc were identified in the February 1993 Risk Assessment report (Reference 13).
However, a large amount of uncertainty was associated with the risk evaluations.
Final Record of Decision for Soil Cleanup of Sites 4,5, and 6 • September 2998
«L\AFP44-|\tn070A-t\SrTES4-|\Wptf)6)9VD639RFT).WPD PaC 2-16
-------
LEGEND
S(TE BOUNDARY
FENCE
RAILROAD
ROADWAY
EXISTING DRAINAGE DITCH
APPROXIMATE LOCATION OF
FILLED DRAINAGE DtTCH
(BASED ON HISTORIC AERIAL PHOTOS)
GEOPHYSICAL ANOMALY
10' DEEP BORING LOCATIONS
SOU
EXISTING AND HISTORIC
SITE 6 DRAINAGE DITCH, CHANNELS.
AND HOTSPOTS
Page 2-17
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Additional soil samples were collected to further characterize the site, and seed germination toxicity
tests were conducted to determine if there is risk to ecological receptors. The sampling results and
the seed germination test results indicated that risk to ecological receptors was over-estimated. No
further action is planned for most of Site 6 (Reference 24).
Additional investigation of Site 6 in the area of geophysical anomalies identified during the RI
(Reference 11) occurred from January through February of 1995 (Reference 12). Trenching was
conducted at locations as shown on the Site 4 location map (Figure 2-3). The trenches were visually
inspected and soil samples were collected from the trenches for chemical analysis. Layers of dried
green sludge were delineated. Samples were collected above, below, and in the sludge layers. Metal
concentrations in anomalies SI and S3 exceeded ADEQ cleanup levels for the surface impoundment
closure. A few VOCs (acetone, methylene chloride, and one detection of toluene) were detected
sporadically, generally at or near the detection limit hi soil samples from SI and S3 and are not
considered contaminants.
The cleanup of Site 6 soils is being conducted pursuant to the Site 6 Non-time Critical Removal
Action Work Plan" (Reference 21) and is due to be completed hi February 1998. Soil is being
remediated to meet ADEQ cleanup levels for target metals (e.g.; cadmium, chromium, nickel, and
lead, as well as cyanide). Remediation of target metals is anticipated to reduce concentrations of all
other metals to acceptable levels. To date, approximately 2,300 tons of metals-contaminated soil
have been excavated and transported to a RCRA Class I landfill for disposal. As discussed in
Section 2.5.1, some of the Site 6 drainage channels and ditches are co-located with Site 4 East and
Site 4 West. The Site 6 soil co-located and Site 4 soil has been remediated in association with
RCRA closure of former surface impoundments and brine beds. The remaining Site 6 soils are being
addressed under the IRP in confonnance with CERCLA.
During the execution of the approved Site 6 remedial action, additional soil metals contamination
was observed west of Site 4. This area has been designated Site 6 West and is comprised of metals
contaminated soil in channels, interchannel areas, and a sheet flow area. The area of additional soil
contamination will be better defined in 1998 and removed in 1999.
2.5.4 Groundwater
In 1981, the ADHS discovered groundwater contamination in the upper zone of the regional aquifer
in the vicinity of the Tucson International Airport. Extensive studies of the area from 1981 to 1982
revealed groundwater contamination under AFP 44. The principal contaminants of concern include
chromium, TCE, DCE, and TCA. In 1987, the Air Force activated a Groundwater Treatment Plant
(GWTP) to treat the groundwater and return it to the aquifer.
The reclamation wellfield system associated with the GWTP consists of extraction wells from which
groundwater is pumped to a treatment facility. Treated groundwater is then reinjected into the
aquifer through recharge wells. The extraction wells create a cone of depression drawing
contaminated groundwater toward the wells. The recharge wells are located on the fringe of the
contaminated areas. By pumping water into the recharge wells, a hydraulic gradient is formed which
Final Record of Decision for Soil CUanup of Sites 4,5, and 6 - September 1998
•u\Af?M-i\im? Page 2-18
-------
forces water back toward the extraction wells. This system of extraction and recharge wells has
altered the historical groundwater flow.
To date, over eleven billion gallons of water have been remediated to drinking water standards and
returned to the aquifer, significantly reducing the areal extent and concentration of contaminants, and
separating one large plume into three smaller plumes.
Remediation systems have been installed and are operating to treat contaminated groundwater in the
shallow groundwater zone (IRP Site 14), which is overlain by Sites 4 and 6. These systems utilize
biorcmediation, pump and treat, and DPE (i.e., soil vapor and groundwater) technologies.
2.5.4.1 Groundwater Contaminants
AFP 44 personnel are responsible for the collection and analysis of groundwater samples from the
reclamation wellfield on a quarterly basis. A contour map of TOE in the upper zone of the regional
aquifer from February 1998 is presented in Appendix B. Source areas for these contaminants appear
to be primarily associated with former unlined surface impoundments and the FACO landfill (IRP
Site 2).
2.6 SUMMARY OF SITE RISKS
This section describes the risks which were analyzed in the risk assessment report (Reference 13),
and describes the cleanup goals to be achieved at AFP 44. The State of Arizona promulgated Final
Soil Remediation Standards in December 1997, which apply to soil remediation activities at Sites
4,5, and 6. Soil remediation activities are being conducted to comply with these standards as well
as RCRA permitted cleanup standards.
The risk assessment report considered die RI findings to determine if exposure to soil and air
contaminants could be a risk to humans, plants, or animals. The baseline risk assessment was
performed following Headquarters USEPA, USEPA Region K, and ADEQ guidance (Reference
13). A baseline risk assessment is a scientific procedure that uses facts and assumptions to estimate
the potential for adverse effects on humans, plants, or animals from exposure to chemicals, assuming
no cleanup occurs. The risk assessment is used to determine if a site requires cleanup. For humans,
risk was estimated by determining the amount of a chemical in soil that a person may ingest, inhale,
or contact over a period of time (exposure) and comparing the exposure to a dose of the chemical
known to cause harm. The risk potential was expressed in terms of the chance of a disease
occurring. To calculate this chance, conservative (worst case) assumptions were made to protect
public health.
Because cancer can result from exposure to chemicals at levels lower than that which cause other
health problems, the greatest concern is that exposure may result in cancer. Therefore the exposure
is compared to the probability of increasing the incidence of cancer in a potentially exposed
population. A risk level of 1 in 1,000,000 means that one additional person out of one million
people exposed could develop cancer as a result of the exposure. In accordance with federal
regulations (40 Code of Federal Regulation [CFR] 300.430(e)(2)(I)(A)(2)), carcinogenic risk within
Final Ricord of Decision for Soil Cleanup of Slut 4, S. and 6 • September 1998
TO Page 2-19
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the benchmark range of 1 cancer case in 10,000 (KT1) to 1 cancer case in 1,000,000 (fO ) is
considered acceptable. In the absence of applicable or relevant and appropriate requirements
(ARARs), the W4 to 106 cancer risk level is used as a starting point for analysis of remedial
alternatives (Reference 25). None of the carcinogenic risk estimates for potential receptors exceeded
the 10"4 benchmark established in the AFP 44 Risk Assessment (Reference 13) as summarized in
Table 2-1 and as discussed in Section 2.1 of the FS Report (Reference 1).
Non-cancer causing effects are measured in terms of their hazard index, which is an index of the
potential for adverse, non-cancer health effects. A summary of hazard indices for AFP 44 is
presented in Table 2-2. The hazard index acceptable to regulatory agencies for protection of human
health is less than or equal to 1. This level was exceeded for receptors associated with Site 3.
Noncarcinogenic cleanup levels were derived based on the hazard indices. However, these levels
were too conservative, i.e., below background concentrations (Reference 1).
The ecological risk was estimated by considering the source of exposure for plants and animals; the
primary source of exposure at AFP 44 is contaminated soil. Several exposure pathways were
considered, including intake of contaminants by plants, intake of contaminants in soil by herbivores
(plant-eating animals), intake of contaminants hi plants by herbivores, and intake of contaminants
in herbivores by carnivores (meat-eating animals). Factors were used to determine the concentration
of a soil contaminant available for intake, transfer of contaminants from soil-to-plants, from plants-
to-animaJs, and other factors which affect the transfer and uptake of contaminants. These factors
were used to calculate the ecological quotient, which is an index of potential risk. Ecological
receptors identified as potentially at risk in the risk assessment are listed in Table 2-3. If an
ecological quotient is greater than or equal to one, the plant or animal may potentially be at risk as
a result of exposure to the contaminant via the defined exposure pathway.
The human health and ecological risk assessment was completed in August 1993 for AFP 44
(Reference 13). Potential risks due to exposure to soil, groundwater, and air contaminants were
estimated based on the assumption that no cleanup would occur. Comparisons were made between
analyte concentrations at each site to background concentrations, and the soil depth of concern at
which humans, plants, or other animals are exposed.
The following pathways for migration of contaminants were identified: migration of VOCs from
soil to the atmosphere; migration of dust containing paniculate-bound contaminants to the
atmosphere; migration of surface soil contaminants in surface water runoff through drainage
channels and ditches; and migration of soil contaminants to groundwater.
Humans considered included current workers, resident children, and future excavation workers.
Plants and animals were selected following a biological field survey conducted in February 1992,
an endangered species clearance study conducted in September 1992, and discussions with local,
state, and federal agencies (Reference 13).
Final Rtcord of Decision far Soil Cleanup of Sites 4,5, and 6 • September 1998
•L.AAFP*4-IVIH070A-ltfrrES<-l\WIV)63»W639WTI.WPD PaC 2-20
-------
*!<•<*• ••-M~t ^ (W^i
^r;/^a^2rf^^ir^ftBaBaa&ai
'..%. •;^;3d^.;jjhjgfr^'-"
. - .-c.,issi^s3^To]
Site
fe^.i^.5" Total CancerlRisk Range
.•Receptor
Jit Risk
Offsite Non-AFP 44 Workers Who Jog Onsite and
Work Offsite in Building 847
2xlO-5
5xlO'J
No
Resident Children
7XI04
9X104
No
1 Cancer risk benchmark is Iff4 to 10*.
Total Site Human Receptor Hazard Index™ - . - • . .- _ .- ..."
•<•'-..- •?,;•*££,: ~ Current Land Use '•''•!.•• "i •' '• .„•••,.•.. -.-..c •-.••'', -...'---
Site
4
6
Site
4
5
. > .•• - '^•wnni&ft-'j^^^"
Offsite Non-AFP 44 Workers Who Jog Onsite and work
Offsite in Building 847
Resident Children
. -Total Hazard Index Range . -^
Average ."
Case
7
2x10''
Reasonable
M^BTillT^'Tn n^Blf
9
5x10'
- • ".• '•.'"'"- FntnreLanfUse "...'..'.'... .— ' . •' . '.-.T?:
Receptor'- "•'/:-.:''"•• '*«?^vvv ^ •
Excavation Worker
Excavation Worker
Receptor
at Risk
Yes
No
*r-; • .
Total Hazard Index Range
.Average
Case
5x10'
Ixltf
Reasonable • *• •
Maximum Case^
7x10*
3x10*
-Receptor
at Risk
Yes
Yes
(t)
'Hazard index benchmark is 1.
Final Rtcant ffDtdiienfor SaO CUtaatp ofStla 4,S,md6. Stpltmber 1998
2~2 1
-------
"
All Plant Receptors0
04
10.000
Cadmium
0.6
Black-throated Sparrow (Amphijpiia
belli)
0-6
1.000
Copper
1.9
1.0
Pocket Mouse (Perognathjg spp.)
0-6
38
1.000
Chromium
36.9
Round-tailed Ground Squirrel
(Spermophilis tereticaudur)
14
1.000
Ohdmiun
Copper
9.2
2.5
Creosote Bush (Larrca iridentaia)
and Mesquite (Prosopa juliflora)
0-58
10.000
Cadmium
0.4
All Plant Receptors"
0-6
6*1
10.000
Silver
0.3
Black-ihroaied Sparrow (Amphispiza
belli)
1.000
Copper
Chronuum
Silver
0.4
0.4
0.4
Pocket Mouse (ferofnoihuj ipp.)
1.000
Chromium
6.6
Round-tailed Ground Squirrel
(Spermophilis lereiicaudus)
04
1.000
Cadmium
Copper
Chromium
0.9
0.9
1.6
(a) EQtr = Expression of total risk for each receptor at each site which is the sum of all contaminant specific EQs, as described in Section 3.3.4.2 of
Reference 13.
(b) EQf = All pathway-specific EQ values as described in Section 3.3.4.2 of Reference 13.
O Estimated EQtr value for each plant receptor at the given site.
(d) This assessment is also applicable to ofisite receptore dowogradieat to drainage.
Final Record of Decision for SoU Cleanup of Sites 4,5, and 6- September 1998
Page 2-22
-------
There are uncertainties when estimating risk of exposure to site contaminants. Risk at AFP 44 has
been deliberately overestimated for a worst-case scenario. For example, average exposures may be
overestimated by an order of magnitude. A detailed discussion of uncertainties is presented in the
risk assessment report (Reference 13).
The results of the risk assessment show that the actual or threatened releases of hazardous substances
from some sites at AFP 44, if not addressed by the preferred cleanup methods or other measures
considered in the Proposed Plan (Reference 14), may present a future threat to public health, welfare,
or the environment.
Site-by-site conclusions from the risk assessment are discussed below.
SITE 4: The following VOCs were selected for human risk characterization: carbon tetrachloride,
Freon 113, PCE, DCE, TCE, and TCA. The following metals in soil were selected for human and
ecological risk characterization: antimony, cadmium, chromium, copper, nickel, silver, and zinc.
The risk assessment identified potential risk for humans, plants, and animals (Reference 13).
SITE 5: No VOCs were selected for risk evaluation at Site 5 because the area is paved Ecological
risk at Site 5 was not assessed because the area is covered by an asphalt parking lot, and no plants
or animals are present The following organic compounds hi soil were selected for human risk
characterization: bis(2-ethylhexyl)phthalate and PCB-1260. Metals in soil selected for human risk
characterization are cadmium, chromium, copper, and zinc. The risk assessment identified a
potential risk for humans from inorganic contaminants (Reference 13). VOC-contaminated soils
west of Site 5 may pose a threat to local groundwater, based on site conditions similar to those
present at IRP Sites 1, 2, and 3.
SITE 6: VOCs considered for Site 6 risk evaluation were incorporated in the analyses of Sites 3 and
4, which Site 6 overlies. Bis(2-ethylhexyl)phthalate, methylene chloride, and total xylenes were
selected for evaluation as organic compounds in soil. The following metals in soil were selected for
human and ecological risk characterization: cadmium, chromium, copper, nickel, silver, and zinc.
No significant risk to human health was identified for Site 6. The risk assessment identified
unacceptable risk for plants or animals at Site 6 (Reference 13). However, the report also stated a
high degree of uncertainty was associated with the assessment, and recommended performing a seed
germination test to assess the potential for adverse effects on plants. The test concluded that Site 6
soils did not inhibit seed growth, and Site 6 was not adversely affecting plants or animals (Reference
24). However, subsequent investigation (Reference 12) within Site 6 revealed elevated metals
contamination in specific areas which warranted remediation. As a result of this finding, specific
areas contaminated with metals will be subject to excavation and offsite S/S.
2.7 APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS
Section 12 l(d) of the CERCLA requires that site cleanups comply with Federal ARARs or state and
local ARARs in cases where these requirements are more stringent than federal requirements. A
requirement may be either "applicable" or "relevant and appropriate." Applicable requirements are
Final Ricord of Decision for Soil dtonup ofSiUz 4.5, and 6 - Stpttmber 1998
«u\An>*t-i\ioo70A-i\srreii-i\wiv)S3«o«3»iuTi.wro Page 2-23
-------
those promulgated federal and state requirements that would be legally applicable to the response
action if that action were noyaken pursuant to Sections 104 or 106 of CERCLA. Relevant and
appropriate requirements are those promulgated federal or state requirements that, while not legally
applicable, are designed to apply to problems sufficiently similar to'those encountered at CERCLA
sites that their application is appropriate. Relevant and appropriate requirements are applied in the
same manner as applicable requirements.
In determining whether a requirement applies to AFP 44, potential ARARs were initially screened
for applicability. If determined not to be applicable, the requirement was then reviewed for both
relevance and appropriateness. Requirements that are determined to be relevant and appropriate
command the same importance as applicable requirements.
In addition to ARARs, federal, state, and local criteria, advisories, or guidances that also may apply
to the conditions found at the site were reviewed and are "to-be-considered (TBC)" materials. TBCs,
which generally address health effects, technical effects and policy, may be useful in determining
what is protective at a site or hqw to carry out certain actions or requirements. ARARs (and TBCs
necessary for protection) must be attained for remedial actions regarding hazardous substances.
Potential ARARs to be reviewed for CERCLA sites fall into three broad categories, based on the
chemical contaminants, site conditions, and the remedial alternatives being considered:
• Chemical-specific ARARs are numeric values that represent a health- or risk-based
standard or the results of methodologies used to determine acceptable concentrations
of chemicals that may be found in or discharged to the environment An example of
a chemical-specific ARAR is a maximum contaminant level or air quality standard.
• Location-specific ARARs govern activities in certain environmentally sensitive
areas. Examples are floodplains, wetlands, endangered species habitat, or historically
significant resources.
• Action-specific ARARs are technology- or activity-based requirements or
restrictions. Examples of action-specific ARARs include monitoring requirements,
effluent discharge limitations, hazardous wastes manifesting requirements, and
occupational health and safety requirements.
AFP 44 is also a RCRA Part B permitted facility and the three sites undergoing removal actions are
classified as inactive Solid Waste Management Units. The Project Management Team (Air Force,
USEPA, and ADEQ) are negotiating a FFA. Upon realization of the FFA, the State and USEPA
will terminate portions of the RCRA Part B Permit which pertain to the remediation and all
procedural requirements will be governed by the FFA. Any substantive requirements set forth in the
RCRA Permit will be included as ARARs in this ROD.
Chemical-, location-, and action-specific ARARs were reviewed and described in the FS (Reference
1) and the Proposed Plan (Reference 14). Table 2-4 presents a summary of chemical-specific
ARARs and TBCs.
Final Recant ofDtciiion far Soil Cleanup of Sites 4,5, and 6 • September 1998
~24
-------
• Table2-4 ' . ; f ':-A^;-i|o. •'•/•' .'V.'.' ; ' &
ConLamlnanLs of Concern and Associated ARARs and TBCs at AFP 44 1JRP Sites 4, 5, and 6(I);
Analyte
Mudmum Delected Concentrations
In Soils bj Site (mg/kg)
.
Slte4w; "•
TBCa
•• Proposed .
•:;:r>RC»A;:'.v
•:--CtfiredlVe--
Action U)T«1
.
Final Soil Cleanup
?- \ .:<:&..
^ .iJ"^ .'
V--.-'-!:^,
fell:
'• ''
**••.% %M®&&
RO
Cadmium
201
114
7JU
40.0
0.8
40
850
38
38
Chromium. Total
8J35
18.144
127J
20.9
400
4^00
2,100
400
Cyanide, Total
9.6
13
NA
2.000
ND
2,000
14,000
uoo
1.300
Lead
74.8
56.5
54.3
25.1
400
2,000
400
400
Nickel
707
13.5
2,000.0
15.9
2,000
34,000
uoo
1.500
Trichloroethylene
0.006
ND
0.041
60.0
ND
70r4>
1 , 1 -Dichloroethylene
ND
ND
0.045
ND
0.8'4'
1,1,1-Trichloroelhane
ND
ND
ND
ND
4.80014'
l.200<4>
I. Doyb|e Underlined text indicates exceedance or ARARs or TBCs.
2. Includes one sample location from Site 6 which overlaps Site 4.
3. Chromium (VI) is used Tor RCRA Corrective Action Level.
4. ADEQ Soil Cleanup Standards may not be sufficiently low to prevent groundwater contamination for these relatively mobile contaminants.
5. In accordance with ADEQ regulations (R18-7-206), a narrative standard will be applied to VOC contaminants of concern.
USEPA Proposed RCRA Corrective Action Level
ADEQ Soil Cleanup Standard
ND
ROD
NA
mg/kg
Proposed concentrations that trigger need for action (40 CFR 264.521 (a)(2KI-vi)).
Arizona Department of Environmental Quality, "R-18-7-201 Appendix A", ADEQ December 1997.
Not delected. There were no valid detections above the instrument detection limit.
Record of Decision
Not Analyzed or Not Applicable.
Milligrams per kilogram.
U WP«-niC070A-HSmS4-1WfP«B3f06MT^ WTO
-------
Although the concentrations of some analytes (beryllium and thallium) exceed ARARs or TBCs,
they fall within 20 percent of the background range and are considered to be naturally occurring.
These analytes are not considered to be contaminants of concern as described in detail in the Risk
Assessment (Reference 13). Table 2-5 summarizes location-specific ARARs and Table 2-6
summarizes action-specific ARARs.
2.8 SUMMARY OF CLEANUP LEVELS
The selected remedies required by the ROD shall comply with all Federal and State ARARs as listed
in Tables 2-4,2-5, and 2-6. In addition, the Air Force will comply with all laws applicable to offsite
transport, treatment, or disposal activities. Site 4 is being cleaned up to prevent exposure of potential
future workers and joggers, and to prevent potential migration of metal contaminants in soil to
groundwater. Sites 5 and 6 are being cleaned up to prevent potential migration of metal
contaminants in soil to groundwater. VOCs have been confirmed in Site 5 soils at sufficient levels
to warrant further investigation and evaluation using the USEPA's presumptive remedy plug in
process. If a VOC remedy is found to be required, a narrative standard will be applied to ensure
protection of the groundwater from migration of VOC contaminants. The goal of soil and
groundwater cleanup efforts at AFP 44 is to protect human health and the environment. Cleanup
levels for AFP 44 are listed hi Table 2-4.
2.8.1 Inorganic contaminants
The cleanup levels for metals-contaminated soils at AFP 44 are listed in Table 2-4. Remediation of
metals-contaminated soil at Sites 4,5, and 6 was initiated to achieve removal to closure standards
issued by ADEQ for RCRA impoundments on site. Subsequently, ADEQ promulgated Final
Residential Cleanup Standards (R18-7-201) in December 1997. All cleanup activities for metal-
contaminated soils will be completed to meet the December 1997 ADEQ residential soil standards.
2.8.2 Organic Contaminants
For organic contaminants, the state has promulgated regulations (R18-7-206) which set forth the
following narrative standard to prevent leaching from causing a release to groundwater in excess of
the maximum contaminant level (MCL) (or the state standard if there is no MCL):
At the conclusion of remediation, the remaining concentration for the contaminants
of concern will not cause or threaten contamination of groundwater to exceed any
Arizona Water Quality Standard pursuant to R18-11-405 and R18-11-406 at a
program-specific point of compliance.
Based on this ARAR, the narrative cleanup level at Site 5 is to reduce the level of each VOC
contaminant concentration in soils to levels that do not cause or contribute to contamination of the
regional aquifer in excess of the MCL for each such contaminant (or State Aquifer Water Quality
Standard if there is not MCL).
Final Record of Decision for Soil Cleanup of Sites 4,5, and 6 - September 1998
*UAFPu-i\im70A-i\srrES4-i\wpt0639\0639OT!.wpD Page 2-26
-------
Reqmrement
The Archaeological and Historical Preservation
Act, 16 United States Code (USC) 469a-l
Any artifacts discovered during construction
must be preserved and the Secretary of Interior
must be contacted.
Endangered Species Act, 16 USC 1531,50 CFR
402 and 50 CFR 17
Pima Pineapple Cactus, a plant species listed in
October 1993 as endangered, is present at AFP
44. Any remedial action that may affect
federally listed species or their critical habitats
requires consultation with the United States Fish
and Wildlife Service and the state conservation
agency. No Pima Pineapple Cacti are located in
or near areas to be remediated.
Final Record of Decision for Soil Cleanup o/Sitet 4,5, and 6 • September 1998
•L:\AfPia-l\l0070A-WrTES4-l\WIVXUWM39RfTI.WPD PagC 2-27
-------
., . ...... ."AKAR.-'U--^^'"-i^
RCRA Land Disposal Restrictions,
40 CFR 268.35
Pima County Code 17.12.080 (G)
Pima County Industrial Wastewater
Ordinance No. 1991-140
RCRA Part B Hazardous Waste
Management Permit AZ009005422
Poor Quality Groundwater
Withdrawal Modified Permit No. 59-
516313
National Pollutant Discharge
Elimination System (NPDES), 40
CFR 122.26(a)(14)
AAC Title 18, Chapter 8. Article 16,
Best Management Practices for
Petroleum Contaminated Soil
AAC Title 18, Chapter 7, Article 2,
Soil Remediation Standards
Hazardous Waste Operations and
Emergency Response (HAZWOPER).
19 CFR 1910.120
RCRA Subtitle C, 40 CFR Pan 264,
Subpart X
RCRA Subtitle C, 40 CFR Pan 264,
Subpart I
..f»r-aw*^iW^^i<8n«hipiro««lvCi«w .KtqUlTOIMDt • -.... • • •. •
Contaminated soil must be treated to meeta^xidty^'arScTcriStftrleach
proceduro-fTCLP) level before land disposal.-^<, - - '- ^
Reasonably available control technology (RACT) must be proposed to
reduce all actual emissions of metallic particulates to the air (no standard is
given). Metallic paniculate means antimony, beryllium, cadmium,
chromium, cobalt, lead, mercury, nickel, phosphorus, or selenium.
Water or non-hazardous liquid sludge discharged to the local Publicly
Owned Treatment Works must be in compliance with Industrial Waste
Pretreatment Program.
Stipulates corrective action and closure requirements and schedules.
Numeric standards for cleanup under Resource Conservation and Recovery
Act (RCRA) were approved by Arizona Department of Environmental
Quality (ADEQJ and are contained in Table 2-4. Present requirement* for
groundwater monitoring will soon be eliminated with acceptance of clean
closures of all RCRA permitted facilities as well as the Federal Facility
Agreement (FFA).
Permit requires modification if annual withdrawal rate will exceed 8,200-acre
feet/year. If new groundwater extraction wells are constructed o. justing
wells are modified, a permit modification must be requested from and
payment of fees made to Arizona Department of Water Resources ( ADWR)
and a Notice of Intent (NOI) to drill well must be filed.
Areas where industrial activities have taken place and significant materials
remain and are exposed to stonnwater including hazardous substances
regulated under Comprehensive Environmental, Response, Compensation,
and Liability Act (CERCLA) and sludge that have the potential to be released
with stormwater discharges require a NPDES permit.
These regulations set standards for treatment, storage, and disposal of
petroleum contaminated soils.
This December 1997 regulation supersedes previous guidance setting
standards for cleanup of contaminated soils.
Establishes health and safety requirements for workers conducting cleanup
operations involving hazardous substances.
Establishes narrative criteria for regulating miscellaneous treatment units
(such as soil vapor extraction [SVE] systems). Applicable to operation,
maintenance and closure of the SVE system, including any on-site disposal.
Establishes requirements for containers holding RCRA hazardous waste for
treatment, storage, or disposal including condition, management, and
inspection of containers, container compatibility with wastes and design and
operation of container storage areas. Containers storing treatment system
waste (including RCRA waste water from any SVE air/water separator or any
granular-activated carbon (GAC) carbons) must comply with substantive
provisions.
Final Record of Decision for Soil Cleanup ofSilu 4,5, and 6 - September 1998
Page 2-28
-------
.— — .-. •••• -T -J.-.^.^.fc...^" ' • '• .; •• / •>^.-.-I:>*!..«-P^ •.. .:.*mi!f& ?f.*i; —~
• '.". :•'.•/••• :-.'• :>• -tf'4;#>*'-\v~.:''Tallte.Z<>O '..'», ~.;'-L. ^V--V- •'.;-*.;• -^.i.^-... .•_—-.....,-
* -^ - -w^s^ -. : •
. ••• •••ij"»~'V«.-V«»!Sftv;."«-»i%iL1Kli!'!1'S
• -AKAKv •-,•> ,'rr.* A«./MyjN
40 CFR Part 264, Subpan J
40 CFR Part 268, Subpan E (§
268.50)
Clean Air Act (CAA) 42 USC £§
7401, Pima Co. Bureau of Air
Pollution Control Rules and
Regulations, Title 17 Pima Co. Air
Quality Code, 17.16.430,
Subparagraph F
Clean Air Act, 42 USC 7401-767Q.
40 CFR Pan 61
40 CFR Part 264 AA and BB
Clean Water Act (CWA) 402.
SWPCD Order No. 92-08-DWQ,
NPDES General Permit No.
CAS000002 (Waste Discharge
Requirements for Discharges of
Stormwater Associated with
Construction Activity)
'&t&fi®&;*£&$&^ ;":--
Establishes requirements for design, installation, containment and detection
of releases, operations, inspections, response to leaks or spills and closure
and post-closure for tanks used to store or treat hazardous waste in the SVE
system.
Land disposal restriction which limits on-site storage of hazardous wastes to
90 days, unless within the exception for accumulation to allow for proper
recovery treatment and disposal.
Requires reasonably available control equipment from a stationary source
that emits VOCs.
Controls air emissions of volatile organic compounds (VOCs) and gaseous
Contaminants. Requires reduction of VOC emissions from product
accumulator vessels. Also, requires leak detection and repair programs.
Establishes design, performance, and operation and maintenance
requirements for air emissions from RCRA regulated units (including SVE
treatment units and SVE off-gas treatment units).
Substantive portions of the general permit are relevant and appropriate to
construction of the SVE system.
Key:
AAC
ARAR
CFR
USC
Arizona Administrative Code
Applicable or Relevant and Appropriate Requirement
Code of Federal Regulations
United States Codes
Final Record of Decision for Soil Cleanup of Sites 4,5, and 6 • ScpUmbtr 1998
•kVOTU-|\|OOTOA-IVSrTES^I\WP«63MM}m!Tl.WI>D PigC 2-29
-------
The methodology to test compliance with the above narrative standard shall be conducted via vadose
zone and groundwater modeling as specified in the Operation and Maintenance (O&M) Manual for
SVE system at Sites 1,2, and 3. Because the predominant VOC soil contamination consists of TCE
and 1,1-DCE, this methodology may assign these two VOC contaminants to be used as indicator
chemicals. The MCLs as of March 1997 for TCE and 1,1-DCE are listed in Table 2-7. Because all
inorganic contaminants above required cleanup levels will be removed from Sites 4,5, and 6, no
future review of metals contamination is necessary. However, SVE remedial action at IRP Site 5
may necessitate a five-year review of organic contamination to ensure that protection of human
health and the environment has been achieved.
•:•*•
Trichloroethylene 0.005
1.1 -Dichloroethylene 0.007
Key: TCE = Trichloroethylene
1,1-DCE = 1,1-Dichloroethylene
mg/L = Milligrams per liter
2.9 DESCRIPTION OF REMEDIAL ALTERNATIVES
A wide range of cleanup methods that could reduce the risks posed by inorganic chemicals at each
site were evaluated during the FS (Reference 1). Some methods were eliminated during a
preliminary screening if they did not effectively address contamination at AFP 44, could not be
implemented at a site, or had excessive costs compared to another method that achieves the same
degree of protection. Those methods that successfully passed the preliminary screening were then
evaluated in detail. Brief summaries of the alternatives considered in the preliminary screening are
presented below.
ALTERNATIVE 1 — No ACTION: Every site was evaluated for the "no action" alternative to provide
a basis for comparison of existing site conditions with other proposed alternatives. Under this
alternative, no action would be taken to address soil contamination or to minimize further
contaminant releases or migration. It is appropriate for use at sites where the risk has been
determined to be acceptable.
ALTERNATIVE 2 — LIMITED ACTION: Limited action was evaluated for every site. Under die
limited action response, mechanisms to prevent access to the site and direct contact with the
contaminants are implemented. Under this alternative, access to the site is controlled and periodic
monitoring of the soil contaminant concentrations is conducted. This alternative reduces risk by
limiting exposure to contaminants.
Final Record of Decision for Soil Cleanup of Sites 4,5, and 6 • September 1998
•L-\AFPW-IM0070A-l\SrTCS4-nW1M639\0639RJTI.WPD PaC 2~30
-------
ALTERNATIVE 3—ONSITE RCRA LANDFILL: This alternative was considered for every site and
would require construction and permitting of a RCRA landfill within the boundaries of AFP 44. The
landfill would be constructed to fulfill RCRA requirements, including a multilayered base of sand,
clay, high-density polyethylene plastic, a leachate collection system, and a cap. The cap would
include a drainage layer and vegetation to prevent infiltration and erosion. A groundwater
monitoring system and provisions for inspection, maintenance, and closure of the landfill would also
be required, as well as provisions for post-closure care.
ALTERNATIVE 4 — SOIL FLUSHING: Soil flushing was considered for use at Sites 4,5, and 6. It
involves the in-situ extraction of contaminants from vadose zone soils with water, solvents,
surfactants, or chelating agents. The spent flushing solutions are recovered for further treatment.
The flushing solutions are poured through the soil; the contaminants are removed in the flushing
agents as they percolate through the soil, leaving behind remediated soil. The spent flushing solution
is collected with wells or subsurface drains and is then treated prior to disposal.
ALTERNATIVE 5—iN-Snv VITRIFICATION: In-situ vitrification (ISV) was considered for use at
Sites 4,5, and 6. ISV is an effective treatment for inorganic and organic compounds at depths less
than 40 feet below ground surface. The process works by melting soil containing silica, pyrolyzing
organic compounds, and fusing or vaporizing metallic materials. A hood is placed over the area to
collect off-gassing volatile compounds, metals, and paniculate matter. Soils are heated to
temperatures above the silica melting point (i.e., in excess of 1100°C) using an electrical current.
When the melt reaches the desired depth, the current is turned off and the vitrified block is allowed
to cool.
ALTERNATIVE 6—SOIL WASHING WITH CHEMICAL PRECIPITATION: Soil washing is a water-
based process for removing contaminants, such as metals, from excavated soils. It was considered
for use at Sites 4,5, and 6. Contaminants are removed by dissolving or suspending them in the wash
solution or by particle size separation. Most metal contaminants are non-volatile and tend to bind
to clay and silt particles. Separating these materials from coarser sand and gravel concentrates the
contaminants into a smaller volume of soil for further treatment.
The excavated soil is mixed with the wash solution to remove contaminants from the soil and
transfer them into the wash solution. The soil and wash solution are then separated, and the soil is
rinsed with clean water. Clean soil is then returned to the excavation or placed elsewhere. Soil
particles suspended in the wash water, which contain the bulk of the contamination, are held for
further treatment or disposal. Water used in the process is treated by conventional wastewater
treatment processes to enable it to be recycled for further use in the soil washing process. Four types
of residuals are generated from soil washing: contaminated solids, wastewater. wastewater treatment
sludges, and in some cases, air emissions.
ALTERNATIVE 7—ONSITE SOLIDIFICATION/STABILIZATION AND DISPOSAL: The S/S process.
sometimes referred to as immobilization, fixation, or encapsulation, uses additives to physically or
chemically immobilize non-volatile soil contaminants, such as metals. It was considered for use at
Sites 4,5, and 6. The basic S/S procedure involves pretreatment of contaminated soils to concentrate
Final Record ofDeettian for SoO Cleanup of Sites 4,5, and 6 • September 1998
•l-\AFP44-l\l0070A-l\SrTESi-I\WPM36J5M)«39IUTI.Wro PagC 2*31
-------
the contaminants into a smaller volume of soil for further treatment. A stabilizing reagent is mixed
with the soil, which is then allowed to cure. The treated soil can then be landfilled.
ALTERNATIVE 8—OFFSTTE SouoincATioN/STABiLiZA'noN AND DISPOSAL IN AN INDUSTRIAL
LANDFILL: The S/S process has been described in Alternative 7. This alternative was considered
for Sites 4,5, and 6. It would require excavation of contaminated soils, backfilling of excavations
with clean fill, and bulk transportation of soils to an industrial landfill for stabilization and disposal.
This process would not be suitable for materials classified as a RCRA hazardous waste since land
disposal of a listed waste is restricted to a RCRA Class I landfill.
ALTERNATIVE 9 — ONSITE SOUDMCAHON/STABILIZATTON AND PLACEMENT IN A RCRA
LANDFILL: This alternative is similar to Alternative 8 above and was considered for Sites 4,5 and
6. Soils with metals content above certain thresholds would be stabilized and disposed in an offsite
RCRA Class I landfill.
After completion of the RI/FS and Proposed Plan, VOC contamination was identified in the vadose
zone west of Site 5. This portion of the site was not evaluated in the above referenced documents,
so none of the remedial alternatives described above address VOC contamination in soil. Under the
guidance of the USEPA, the Air Force is conducting additional investigative activities at Site 5 to
identify potential VOC sources and to better characterize the vertical and horizontal extent of
contamination. In accordance of recent USEPA guidance, the remedy selection will be achieved
using the presumptive remedy plug-in process. This process is described in detail in Section 2.10.
The remedial alternatives for VOC-contaminated soils at Site 5 are no further action and SVE. SVE
was evaluated as a remedial alternative for similar contaminants and geologic conditions at Site 1,
2, and 3. The following three alternatives were extracted from the approved ROD for IRP Sites 1,
2 and 3.
VOC ALTERNATIVE 1—No ACTION: Every site was evaluated for the "no action" alternative to
provide a basis for comparison of existing site conditions with other proposed alternatives. Under
this alternative, no action would be taken to address soil contamination or to minimize further
contaminant releases or migration. It is appropriate for use at sites where the risk has been
determined to be acceptable.
VOC ALTERNATIVE 2—SVE WITH RESIN ADSORPTION: SVE is a technique for in-situ removal
of VOCs from contaminated soils and was considered for use at Sites 1,2, and 3, and now Site 5.
The process can be used to treat sites where excavation of contaminated soils is not practical. In an
SVE system, fresh air is introduced into the contaminated subsurface. As the air moves through the
soil, VOCs are stripped into the air. The vapor-laden air is withdrawn under vacuum from extraction
wells and brought to the ground surface for treatment. At sites where contaminants are concentrated
in the capillary fringe, dewatering the site to lower the water table and expose soils to the vacuum
may be desirable to enhance removal rates. This alternative uses the SVE system with a resin
adsorption process to treat the vapors. The system considered for use at Sites 1, 2, and 3 is the
proprietary PADRE™ system, manufactured by the Thermatrix Company. This system removes
contaminants from the vapor stream by adsorption onto a proprietary resin. The process involves
using parallel resin beds, where one bed treats the vapor stream while a second bed undergoes a
Final Record of Decision for Soil Cleanup ofSila 4, S, and 6 • Stptembtr 1998
2-32
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desoiption cycle. The desorption cycle uses a combination of temperature and pressure to remove
the VOCs from the resin. The vapors are then condensed and transferred to a storage tank. The
recovered liquid VOCs may then be redistilled for product recovery or disposed of offsite.
VOC ALTERNATIVE 3 -- SVE WITH GRANULAR-ACTIVATED CARBON ADSORPTION: This
alternative uses the SVE system discussed in VOC Alternative 1 above to remove contaminants from
soil, but with granular activated carbon to treat the vapors. Carbon adsorption systems typically
consist of a single large vessel with two smaller vessels all connected in series. Vapors enter the
larger vessel, where most of the vapors are adsorbed to the carbon. The vapor stream continues
through the next two smaller vessels, and treated air is discharged to the atmosphere. A VOC
detector installed downstream of the final vessel continuously monitors for VOCs in the treated air,
and will automatically shut down the system if concentrations exceed the Pima County standard.
The GAC is considered fully saturated when the removal efficiency of the first small vessel falls
below 85 percent for TCE or DCE. At this point, the blower is shutoff and the GAC is removed for
regeneration or disposal offsite at a permitted facility.
2.10 COMPARATIVE ANALYSIS OF ALTERNATIVES
The remedial alternatives were evaluated using USEPA's nine evaluation criteria. The cleanup
methods evaluated for API' 44 are described in Section 2.9 together with certain categories which
encompass the nine criteria analysis. A detailed presentation of the cleanup method selection and
screening process is presented in the FS report (Reference 1).
USEPA'S NINE EVALUATION CRITERIA: The remedial alternatives were evaluated using the nine
criteria set forth in the N.C.P., 40 CFR 300.430(o)(9)(iii). A detailed presentation of the cleanup
method selection and screening process is presented in the FS report. The USEPA criteria used to
evaluate cleanup methods are given in "Guidance for Conducting Remedial Investigations and
Feasibility Studies Under CERCLA" (October, 1988) and are listed below:
1. Overall Protection of Human Health and the Environment. Addresses whether a
cleanup method provides adequate protection in both the short- and long-term, and
describes how risks are eliminated, reduced, or controlled through treatment,
engineering controls, or institutional controls.
2. Compliance with ARARs. Addresses whether a cleanup method will meet all federal
and state requirements.
3. Long-Term Effectiveness and Permanence. Refers to the ability of a cleanup
method to maintain reliable protection of human health and the environment over
time and the permanence of the alternative.
4. Reduction of Toxicity, Mobility, or Volume Through Treatment. Refers to the
anticipated ability of a cleanup method to reduce the toxicity, mobility, or volume of
the hazardous substances present at the site through treatment or recycling.
Final Recant of Decision far SoO Cleanup of Sites 4, 5, and 6 • September 1998
2~33
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5. Short-Term Effectiveness. Addresses the short-term risks to workers or the
community, potential environmental impacts of the cleanup alternative, and the time
needed until protection is provided.
6. ImplementabiUty. Refers to me technical and administrative feasibility of a cleanup
method, including the availability of materials and services required by the method.
7. Cost. Evaluates the estimated capital and O&M costs of each cleanup method.
8. State Acceptance. Assessment against this criterion evaluates the technical and
administrative concerns regulatory agencies may have for each alternative.
9. Community Acceptance. This assessment evaluates the issues and concerns the
public may have for each alternative. Public comment is an important part of the
final decision. A public comment period addressing the FS was held on November 1
through December 15,1994. The Proposed Plan provided the community a second
opportunity to comment (July 10 - September 23, 1995) on the proposed cleanup
methods.
The USEPA criteria were applied to the evaluations of potential cleanup methods. The following
remedial alternatives passed the preliminary screening and were evaluated in detail: No Action,
Limited Action, Soil Washing, Solidification/Stabilization. For a detailed discussion of the
comparative analysis of alternatives, please refer to the FS Report (Reference 1).
The evaluation summary tables presented in this section list the alternatives considered to be feasible
based on data available at the time of the FS. Estimated costs and the preferred alternatives are
presented. The preferred alternatives provide the best balance of tradeoffs among the other
alternatives with respect to the evaluation criteria. The Air Force expects that the preferred
alternatives will satisfy the statutory requirements in CERCLA Section 121(b) that the selected
alternatives:
Be protective of human health and the environment
Comply with ARARs
Be cost-effective
Utilize permanent treatment alternatives
Satisfy the statutory preference for treatment.
The comparative analyses for selection of the preferred cleanup method for Sites 4, 5, and 6 are
summarized in the following sections.
Final Record of Decision for Soil Cleanup of Sites 4,5, and 6 • September 1998
•L:\AR'44.|\lfln70A-IVSITCSJ-l\WW)639«639WTl.Wro PagC 2~34
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2.10.1 Site 4: Former UnKned Surface Impoundments and Site 6: Drainage Ditch and Channels,
Preferred Alternative: Offsite Stabilization and Disposal in a RCRA Landfill
Site 6 is considered with Site 4 due to their geographic proximity, co-location of contaminated soil
areas, and the presence of similar contaminants. The preferred method for cleanup of metals-
contaminated soil is to remove the soil, transport it to an off-site RCRA-permitted facility for
stabilization as needed, and dispose of it in a RCRA-permitted landfill. A schematic diagram of the
process is shown in Figure 2-9. This alternative provides the overall best balance in terms of
satisfying the nine evaluation criteria described in Section 2.10 of this document, and will result in
the cleanup being accomplished in a timely and cost-effective manner. As noted previously, Site 4
is underlain by Site 14 the perched groundwater zone. VOCs associated with the deep vadose zone
are being remediated along with Site 14 groundwater using dual vapor extraction.
The selected method removes the contaminated soil from the site, then stabilizes it offsite to render
the contaminant immobile. The stabilized soil is then disposed in a RCRA landfill, which is
constructed and monitored to ensure no leaching contamination escapes to the environment. This
alternative effectively reduces risks, is technically easy to implement, and has been proven in
numerous other projects nationwide. More than 100 vendors offering hazardous waste solidification
services exist in the United States. Many of these vendors have wide experience and offer custom
mixtures of solidification agents for various wastes.
S/S techniques will increase waste volume, but will decrease contaminant mobility and toxicity.
Short-term effectiveness considerations include exposure of workers and the public during
excavation, transport, mixing, and curing of contaminated soils. These exposures can be minimized
through the use of engineering controls, personnel protective equipment, and standard operating
procedures.
The removal action at Site 4 was completed in June 1997. Approximately 13,589 tons of soil were
excavated and disposed of offsite at a RCRA Class I Landfill (Reference 23). The removal action
at the originally defined Site 6 is in progress with an expected completion date of December 1997.
To date, 8,674 tons of soil have been excavated and transported to a RCRA Class I Landfill for
disposal.
2.10.2 Site 5 • Former Sludge Drying Beds Preferred Alternative: Offsite Stabilization and
Disposal in a RCRA Landfill and SVE Presumptive Remedy
The preferred method for cleanup of metals-contaminated soil at Site 5 is similar to Sites 4 and 6
above, where the contaminated soil is removed, stabilized, and disposed of in a RCRA-permitted
landfill. This alternative provides the overall best balance in terms of satisfying the nine evaluation
criteria described in Section 2.10 of this document, and will result in the cleanup being accomplished
in a timely and cost-effective manner.
The removal action for metals contaminated soils at Site 5 was completed in May 1957. A total of
5,033 tons of contaminated soil was excavated from Site 5 and transported to a RCRA Class I
landfill for disposal.
Final Kiccrd ofDteition for Soil Cleanup of Sites 4,5, and 6 • Sepltmbtr 1998
ttAMT>M-manoA-i\srTCs*-i\w\0439<06»WT-i.wro Page 2-35
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SOLIDIFICATION
REAGENTS
ONSITE
OFFSITE AT
RCRA PERMITTED
FACILITY
SOURCE:
"SILICATE TECHNOLOGY CORPORATION'S
SOLIDIFICATION/STABILIZATION TECHNOLOGY
FOR ORGANIC AND INORGANIC CONTAMINANTS
IN SOIL.' EPA/540/AR-92/010. DEC., 1992.
I » i T N S? 1 i « e ii
FIGURE 2-9
SOLIDIFICATION/STABILIZATION
PROCESS SCHEMATIC
Page 2-36
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As noted previously, additional investigative activities related to shallow VOCs in soil west of Site 5
have indicated remediation will be required in the future. The contaminants of concern and
geological conditions present at Site 5 are comparable to those found at Sites 1, 2, and 3. Due to
similarities and based on the success of SVE systems operating at"Sites 1,2, and 3. The USEPA's
presumptive remedy plug-in approach (as described in the following sections) will be used to
determine if SVE will be performed as the selected remedy or if no further action is required.
2.103 Plug-in Approach for VOC-Contaminated Soils
The remedial action objective for the VOC-contaminated soils remedy is to reduce VOC
concentrations in soil such that any further contaminant migration will not cause groundwater to
exceed chemical performance standards. The specific components and technologies necessary to
achieve and comply with performance standards will be selected during remedial design. The plug-
in approach, described below, will be used to determine if the Air Force needs to implement an SVE
remedy at Site 5 or if site conditions allow the no further action alternative.
Following the additional field investigations at Site 5, the site will be evaluated and vapor transport
modeling performed, as necessary, to determine the potential threat to groundwater quality. If Site
5 soils are concluded to pose no present or future threats to groundwater quality, they would be given
"No Further Action" status. If Site 5 soils are determined, based on the Plug-in Criteria described
below, to likely pose a threat, to future groundwater quality they would be remediated with SVE. The
type of off-gas treatment equipment will be determined during remedial design. Groundwater
monitoring will be used to detect impacts in excess of cleanup standards.
2.10.3.1 Plug-In Process and Criteria
Traditionally, a responsible party investigates, evaluates and proposes a separate cleanup remedy for
each source of contamination. However, there are a number of source areas or sites that have the
same type of VOC contamination found in the same soil types. For sites that are substantially
similar, the repetition of the investigation/eyaluation/proposed remedy process can be avoided using
an innovative approach called the "plug-in" approach.
The ROD does not select a remedial action for a specific site. Rather, it selects a remedial action (in
this case SVE) to apply to any site exhibiting certain conditions. This section defines what these
conditions are and identifies a process for determining whether they exist.
The remedy is selected prior to fully characterizing the plug-in sites. If the conditions at a site match
pre-defined conditions, the site will "plug in" to the SVE remedial action and be subject to its
requirements. This section fully contains the basis and process to be used for all plug-in decisions.
Therefore, following the prescribed process in this section completes the remedy selection process
for any particular site. The plug-in process contains a "blueprint" directing decisions as to its own
application.
Final Record of Decision for Soil Cleanup of Sties 4, 5, and 6 • September '1998
2-37
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The following sections describe the plug-in process components and terminology.
EXISTING SHE PROFILE: The SVE remedy used in the plug-in approach must be able to address
the vast majority of plug-in sites for the approach to be efficient To achieve this, the site profile for
the individual sites must be very similar. The site profile is defined in terms of various physical and
contaminant parameters that might have an impact on the effectiveness of a remedial alternative.
For example, for SVE, the air permeability of the soil and the volatility of the contaminants strongly
impact its effectiveness. The existing site profile for Site 5, as defined in the RI and FS Reports, is
sufficiently similar to other sites at AFP 44 (IRP Sites 1, 2, and 3) to implement the plug-in
approach.
PRESUMED REMEDY: The Presumed Remedy is the action that will be taken at all sites that meet
the Remedy Profile and in the plug-in criteria (defined below). The Presumed Remedy is selected
to meet all ARARs. The Air Force has selected SVE as the Presumed Remedy for the cleanup of
VOC-contaminated soils in this ROD in accordance with the presumptive remedy approach
(described in the following paragraphs). Performance standards for SVE systems are described
below.
Presumptive Remedy Approach. USEPA has studied various technologies applied at CERCLA
sites with VOC-contaminated soils as part of its effort to streamline the FS process. This evaluation
consisted of an analysis of the technical literature and review of the results of the remedy selection
process from FSs and RODs. The purpose of the evaluation was to formulate general conclusions
about the application of these technologies at sites with VOC contamination in soils. The evaluation
is summarized in USEPA's report titled Feasibility Study Analysis for CERCLA. Sites with Volatile
Organic Compounds in Soils, August 1994. The evaluation concluded that certain technologies were
routinely screened out during the FS process based on lack of effectiveness, difficult implementation,
or excessive costs. The evaluation also concluded that three remedies (SVE, thermal description, and
incineration) were frequently selected to address VOC contamination in soils at CERCLA sites.
Based on its evaluation, USEPA also determined that several treatment technologies could be
eliminated from consideration during the FS process at sites where the presumptive remedy of SVE,
thermal desorption, or incineration would be appropriate. Furthermore, USEPA recommended that
its August 1994 report could be used as a reference in an FS when the technology identification and
screening steps are abbreviated or eliminated when adopting the presumptive remedy approach.
As part of the AFP 44 Rl/FS, various site-specific factors (including subsurface conditions and
contaminant type) were reviewed to evaluate the applicability of SVE to remediation of soils at IRP
Sites 1, 2, and 3, which are located near Site 5 and exhibit similar geological conditions and
contaminants of concern. The results of this evaluation indicate that the types of contaminants
present, distribution of contaminants and physical parameters of the soil at AFP 44 are well-suited
to remediation using SVE. In according with the USEPA guidance document titled Presumptive
Remedies: Site Characterization and Technology Selection for CERCLA. Sites with Volatile Organic
Compound (OSWER Directive 9355.0-48FS), only SVE was further evaluated for sites exhibiting
VOC-contaminated soils.
Final Record of Dteuton for Soil Cleanup ofSiUi 4,5, and 6 • September 1998
Page 2-38
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REMEDY PROFILE: The range of conditions appropriate for the Presumed Remedy is called the
Remedy Profile. After the RI is completed at a site, the first test of whether it can be plugged in to
the remedy is whether it exhibits conditions within the Remedy Profile. Like the existing site profile,
the Remedy Profile is defined in terms of physical and contaminant parameters that may have an
impact on the effectiveness of the Presumed Remedy.
Based on investigations completed to date, the Project Management Team (Air Force, USEPA, and
ADEQ) has initially determined that Site 5 meets the plug-in remedy profile for S VE.
PLUG-IN CRITERIA: Even if conditions at a particular plug-in site are amenable to SVE (within the
Remedy Profile), there still may not be enough VOC contamination present to make SVE necessary.
Therefore, "plug-in criteria," based on potential health threats, are necessary to serve as the standard
for determination of whether an action is necessary. Those sites not exceeding the plug-in criteria
do not need a soil VOCs remedy and the Air Force will not plug in such sites to the remedy.
Because the AFP 44 Risk Assessment (Reference 13) already determined that the VOC
contamination in soil does not represent a significant human health risk for non-groundwater
pathways, only potential groundwater impacts arc considered in the plug-in criteria. Potential
groundwater impacts are defined by VOC concentrations in soils that could result in groundwater
concentration in excess of cleanup standards.
This SVE remedy will be applied whenever certain conditions exist. There are two conditions that
a site must meet before being plugged in. First, the site must exhibit conditions consistent with the
Remedy Profile (the Project Management Team has already determined that Site 5 meets this
criteria), and second, the site must exhibit contamination exceeding the plug-in criteria. The
determination of whether to plug a site into the SVE remedy will be made at the Plug-in Decision
Point. This decision is made according to the process set in advance by this ROD.
This remedy addresses VOC-contaminated soils as future sources of groundwater contamination.
The amount that the concentration of VOCs in groundwater would increase due solely to VOCs in
Site 5 soils is referred to as the incremental concentration. The plug-in criteria are limits on the
incremental concentrations of VOCs from Site 5 soils.
The plug-in criteria are not point-specific concentration limits for the soil medium itself. Rather,
they apply to the effect of soil VOCs on the groundwater media. This effect is estimated by
evaluation and modeling, as described below. It is important to ensure that the future threat to
groundwater is reduced sufficiently so Site 5 could not by itself produce enough groundwater
contamination to make a groundwater remedy necessary in areas where it is not otherwise needed
today. The Arizona drinking water classification for aquifers, which is an ARAR, requires that
stringent source control be implemented with the objective of keeping or restoring the aquifer to
drinking water standards.
The plug-in criteria are based directly on the cleanup standards. SVE will be selected at any plug-in
site where data evaluation and modeling (described below) indicate the potential for an increase in
the concentration of VOCs in groundwater (incremental concentration ) by an amount greater than
Final Record of Decision for Soil Cleanup of Sites 4,5, and 6 • September 1998
«L:WTJ4-UIO(r?OA-l\SlTES4-hWJV)6J9«)6MRFri.WPD Pae 2-39
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the cleanup standards (federal MCLs, if available, or state of Arizona drinking water criteria). Note
that this plug-in criterion does not set a limit on the allowable total concentration of VOCs in
groundwater. Rather, it limits that part of the groundwater concentration due solely to the
incremental (extra) VOCs from soils at Site 5 that would reach the groundwater over time.
SOIL CLEANUP STANDARDS: VOCs in the vadose zone at Site 5 may pose a threat if they migrate
from soils to groundwater. The purpose of the soil remedy is to limit the amount of VOCs that can
enter the groundwater from any particular site. Evaluating the threat of a site must depend, therefore,
on making an estimate of the incremental VOCs that will enter the groundwater over time because
of migration from Site 5 soils. The process described in this section will be used to estimate the
maximum effect that the VOC mass distribution at Site 5 could potentially have on groundwater in
the future. This estimated effect will then be compared with the plug-in criteria (groundwater
cleanup standards). The steps involved in evaluation of soil cleanup standards include additional
data collection, VOC mass estimates, T2VOC vadose zone transport modeling (or another vadose
zone model acceptable to USEPA) and estimating incremental groundwater concentrations.
Additional Data Collection. Data will be obtained from investigative activities at Site 5. Examples
of the type of information to be obtained shall include:
• Subsurface lithology from soil borings;
• Vertical distribution and type of VOC contaminants in the vadose zone from soil gas
samples obtained from soil vapor monitoring;
• Sufficient numbers of soil vapor samples to provide a mass estimate of vadose zone
contamination at the site;
• Groundwater quality information obtained by sampling monitoring wells at and in
the vicinity of the site; and
• Any additional information or activities deemed necessary by USEPA pursuant to
regulation, statute, or USEPA guidance.
VOC Mass Estimates. The total contaminant mass and the horizontal and vertical distribution of
mass shall be estimated for each VOC. The sources of data that will be available to estimate the
horizontal and vertical mass distribution are shallow soil gas surveys and depth-specific soil gas
samples. The measured soil gas concentrations shall be converted to total contaminant mass
estimates.
T2 VOC Vadose Zone Transport Model (Note: T2VOCmay not be the only acceptable vadose zone
model for Site 5). The maximum future incremental groundwater concentrations resulting from the
VOCs in soils at Site 5 will be estimated using a computer model, subject to USEPA approval. The
model to be used shall be T2VOC, or an equivalent model approved by USEPA. T2VOC is a three-
dimensional, computer-based finite difference numerical model. The mass distribution of VOCs
with depth in soils is input to T2VOC. The model then simulates the movement of VOCs in the
vadose zone and predicts the mass loading (flux, or rate of leaching) of VOCs to groundwater and
ambient air over time. A separate T2VOC analysis is required for each VOC identified in the vadose
zone, however, due to its high mobility and prevalence at the site, TCE will be considered a
surrogate for other VOCs that may be present at low levels.
Final Record ofDtdtlonfor SoO Cleanup of Sites 4,5, aid 6 • September 1998
tL.\AFP*4-iMoo70A-i\srrES4-i\wpio6jWK»WTi.wpD Page 2-40
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In cases where-it can be demonstrated that the outcome of T2VOC is mathematically certain without
running the model, USEPA may approve that the conclusion be accepted without running the model.
For example, one could make'the extreme assumption that the entire VOC mass in the vadose zone
instantly arrived in groundwater. An estimate of the effect of VOCs on groundwater under such an
assumption would be much greater than corresponding T2VOC estimate, as T2VOC computes the
gradual arrival of VOCs over many years. If even under this assumption, the plug-in criteria would
not be exceeded, then actually running T2VOC may not be necessary.
Estimating Incremental Groundwater Concentration. For groundwater, T2VOC calculates the
mixing of migrating VOCs and groundwater beneath the site. This mixing zone approach calculates
groundwater concentrations on the basis of an assumed mixing depth in the groundwater zone
beneath the site and an estimated flow of clean groundwater originating from upgradient sources.
The depth of the mixing zone shall be based on site-specific conditions, but shall not exceed 30 feet
Note that clean water flow-through is assumed in the mixing cell model, even though the current
groundwater may be already contaminated. This is because the plug-in criteria address the
incremental VOCs resulting from leaching from soils only.
CLEANUP DESIGN AND EXECUTION: Locations determined to be appropriate for plug-in to the S VE
remedy can proceed directly with cleanup design and execution. The Air Force wUl notify the public
each time a plug-in decision is made. This step will be implemented after the ROD is finalized.
2.10.3.2 Performance Standards for VOC-Contaminated Soil Cleanup at Site 5
The SVE system at Site 5 will operate continuously until the VOC concentrations in soil have been
reduced such that the narrative standard as described in Section 2.8 is no longer exceeded.
Evaluation of whether a narrative standard is still exceeded as cleanup nears completion shall be
accomplished by the same process and methods used to determine that the narrative standard was
exceeded originally; through sampling of soil vapor and use of the T2VOC and mixing zone models,
or USEPA-approved alternative models.
The SVE system shall be designed to draw soil vapors from the entire lateral and vertical extent of
contamination that represents a threat to groundwater quality.
A monitoring program will be required for the SVE system. Components of the monitoring program
shall include:
• Provisions to meet all requirements in this ROD;
• Periodic sampling of soil vapor monitoring wells to estimate the mass of VOC
contamination remaining in the vadose zone;
• Sampling of off-gas, before and after treatment, to assess the quality of discharged
air;
• Minimum number of sampling events over a specified time period that must show
contamination not exceeding cleanup standards before the SVE system can be shut
down;
Final Record of Decision for Soil Cleanup of Situ 4, 5, and 6- September 1998
•L\An'44.|Moo70A-i\srres4-i\ww)6j9W6j9RJiTi.wpo Page 2-41
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• Reporting procedure to notify USEPA when cleanup requirements have been
consistently met (after any VOC rebound period); and
• Provisions for SVE decommissioning and potential continued monitoring after
cleanup requirements have been met, if determined necessary by USEPA.
If VOC levels rebound to above cleanup standards after an SVE system has been shut down, SVE
operation shall be resumed. An appropriate discussion of monitoring and shutdown procedures for
SVE systems at AFP 44 can be found in the O&M Manual for Sites 1,2, and 3 (Reference 29).
2.11 THE SELECTED REMEDY FOR SITES 4 AND 6: OFFSTTE STABILIZATION, DISPOSAL IN A
RCRA LANDFILL
Sites 4 and 6 are grouped together for discussion of remedies because Site 4 overlies Site 6 and the
removal actions will be concurrent Off-site stabilisation and disposal in an off-site RCRA landfill
removes the contaminated soil from the site, then stabilizes it offsite to immobilize the contaminants.
The stabilized soil is then disposed of in an off-site RCRA landfill, which is constructed and
monitored to ensure no leaching contamination escapes to the environment This alternative will
require a short time frame, one year or less, to implement for Site 4 and Site 6.
Soil removal actions at Site 4 were completed in June 1996. A total of 13,589 tons of soil were
excavated from Site 4 and disposed of offsite at a RCRA Class I Landfill (Reference 23). Soil
removal actions at Site 6 are scheduled to be complete in February 1997. This soil removal includes
segregating clean rip-rap from contaminated rip-rap to reduce the quantity of material disposed. To
date, approximately 8,674 tons of soil df rock have been excavated and transported to a RCRA Class
I landfill for disposal. Groundwater and deep vadose zone VOC contamination immediately below
Sites 4 and 6 is being addressed as part of the Site 14 (Shallow Groundwater Zone) remedial actions,
which will be detailed in a separate ROD. , _• •'
During Site 6 removal actions and confirmation sampling, additional metals contaminated soil was
observed west of Site 4. This area, designated as Site 6 West, consists of soil contamination in
channels, interchannel areas, and a sheet flow area. The area will be better defined through sampling
and trenching in 1998 and will be excavated in 1999.
2.12 THE SELECTED REMEDY FOR SITE 5: OFFSITE STABILIZATION, DISPOSAL IN A RCRA
LANDFILL AND SVE PRESUMPTIVE REMEDY
Off-site stabilization and disposal in a RCRA landfill removes the metals-contaminated soil from
the site, then stabilizes it offsite to render the contaminants immobile. The stabilized soil is then
disposed of in a RCRA landfill, which is constructed and monitored to ensure no leaching
contamination escapes to the environment. This alternative will require a short time frame, one year
or less, to implement for Site 5. Soil removal activities at Site 5 were completed in May 1997. A
total of 5,033 tons of contaminated soil was excavated and transported to a RCRA Class I Landfill
for disposal (Reference 27).
Final Record of Decision for Soil Cleanup of Sites 4,5, and 6- September 1998
«i_AAFP*i-i\ino70A-i\srrES4-nww)63»«w»(UTi.wpo Page 2-42
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Additional investigation west of Site 5 is in progress; the results of the investigation have shown the
presence of VOC contamination, therefore, either no further action or S VE will be considered the
presumptive remedy for the site in accordance with the USEPA's plug-in approach, as described in
Section 2.10.3. SYE removes contaminants from the soil by withdrawing air at extraction wells,
which induces an air flow from the surface. The withdrawn air is laden with volatilized
contaminants, which are treated aboveground. A VOC detector may be installed to monitor for
vapors in the treated air, and can automatically shut down the vapor treatment system if vapor
concentrations exceed emissions standards.
Off-gas treatment technology selection for an SVE system shall be made during remedial design of
that system. Available options for SVE off-gas treatment include:
• Vapor-Phase Carbon; and
• Vapor-Phase Resin Adsorption.
During the remedial design process, after additional data are available on anticipated influent rates
and concentrations, the Air Force will determine which of the off-gas treatment option(s) listed
above best attains the SVE performance standards described hi Section 2.10.3.2. Prior to
construction, the Air Force will take appropriate action to inform the public of the actual
technologies selected for inclusion hi the SVE remedy.
The SVE off-gas treatment system must comply with all of the ARARs for air emissions described
in Section 2.8.
The Project Management Team believes that the SVE off-gas treatment options for this remedy
would meet both reasonably available control technology (RACT) and best available control
technology (BACT) requirements even though emissions are expected to be well below the mass
generation rates that impost these requirements. The following additional performance standards
shall apply to SVE off-gas controls:
• Emission controls for off-gas treatment shall attain a minimum 85 percent efficiency
rate, however once influent levels are less than 100 ug/L, this standard may not be
achievable.
• Routine monitoring of the off-gas shall be performed during the remedial action to
ensure that no ARARs or performance standards are being violated
• If the emission controls should fail, the SVE system will be shut-down until the
emission controls are again effective. If necessary, additional treatment processes
shall be installed to ensure compliance with the performance standards.
Operation of the SVE off-gas treatment system will generate some liquids (primarily condensate).
If feasible, these liquids will be handled in the groundwatcr treatment system installed at the facility.
Thus, the groundwater treatment plant performance standards would also be applicable to these
liquids. If the concentrations in the SVE off-gas treatment wastewater are sufficiently elevated that
the treatment plant will not be able to handle them, the liquids shall be disposed of at an off-site
disposal facility approved by USEPA.
Final,Record of Decision for Soli CUanup of Sites 4,5, and 6- September 1998
Page 2-43
-------
2.13 SHUTDOWN AND DECOMMISSIONING
The major contaminants of concern at Sites 4, 5, and 6 are metals. Excavation procedures,
confirmation sampling, waste management, and site restoration activities will be conducted in
accordance with the Sites 4 and 5, and Site 6 Hot Spots Removal Action Work Plan (Reference 21).
Because all inorganic contaminants above required cleanup levels will be removed from Sites 4,5,
and 6, no future review of metals-contamination related to this ROD will be necessary. However,
remediation of VOC-contaminated soils found west of Site 5 may necessitate a five-year review of
organic contamination to ensure that protection of human health and the environment has been
achieved.
The organic-contaminants of concern at Site 5 are TCE and DCE. Other similar VOCs are also
present. Because these other VOCs are physically similar to TCE and DCE, they will also be
removed from soils when the TCE and DCE are removed. Measurements of TCE and DCE in the
AFP 44 on-site laboratory, as well as TO-14 analyses at an off-site laboratory will be used to monitor
the progress of SVE cleanup activities at Site 5 as described in Section 3.0 of the O&M Manual for
SVE Systems at IRP Sites 1,2 and 3 (Reference 29).
System operations may vary depending on site conditions, such as focused efforts on specific hot
spots or cycling individual wells on- and off-line to measure rebound. These variations are at the
discretion of the operator using the procedures described in the Site 1, 2 and 3 O&M Manual.
The progress of the soil remediation will be measured by a combination of methods as listed below:
• SVE/Treatment system performance monitoring.
• Routine site monitoring (including collection and analysis of depth-specific soil gas
samples).
• Periodic evaluation of the impact of soils on groundwater quality:
initial baseline computer model
annual cleanup progress evaluation.
When these measurements indicate cleanup levels for all of Site 5 or portions of it have been met,
more sampling will be conducted for confirmation. The SVE system(s) or portions of the system(s)
will be shut off and the following statistically-based activities will occur:
• Depth-specific soil gas sampling and analysis.
• Reevaluation of the impact of soils on groundwater quality.
If the results of these activities show the cleanup levels have not been met, the SVE system(s) will
be turned back on. If the results show cleanup levels have been met, monitoring of soil vapor will
continue for four quarters to verify the cleanup levels have been met If the results show the cleanup
levels have not been met, the SVE system(s) or portions of the system(s) will be turned on again.
This process will continue until me cleanup levels have been met. At the end of me cleanup process,
soil samples will be collected from the ground surface to the water table and analyzed to provide
further confirmation that the cleanup levels have been met If soil vapor data indicate contamination
Final Record of Decision for Soil Cleanup of Slut 4, S, and 6 • September 1998
•L.\AFp4J-iMuo70A-ivsrrES4-i\wpvau9«S39RPTi.wpo • Page 2-44
-------
extends beyond the areal extent of the SVE weUfields. the Air Force may consider installing
additional wells.
When the site cleanup levels have been met, the schedule for removal of SVE system or portions of
the system(s), including equipment, piping, and wells will be at the discretion of the Air Force.
Wells will be destroyed to the standard in effect at the time of destruction as established by the
Arizona Department of Water Resources (ADWR). The sites will be restored to a land use
compatible with the immediately adjacent land, or as required to accommodate production
requirements.
2.14 STATUTORY DETERMINATION
The Air Force has selected excavation of soils, coupled with offsite S/S and disposal in a RCRA
Class I landfill as the cleanup method for metals-contaminated soils at AFP 44IRP Sites 4,5, and
6, and SVE for VOC-contaminated soils west of Site 5.
This ROD incorporates by reference the comparative nine criteria analysis set forth in Table 5-3 of
the FS as the basis for its remedy selection pursuant to the NCP, 40 CFR 300.430(e)(9)(iii) and
300.430(f)(4). According to the NCP preamble, the nine evaluation criteria give effect to the
statutory mandates of Section 121 of CERCLA, and in particular, the remedial action factors of
section 121(b)(l)(A)-(G); an analysis performed pursuant to the nine criteria concludes with
selection of a remedy that meets the statutory mandates.
2.14.1 Protection of Human Health and the Environment
Soil excavation with offsite S/S and disposal in a RCRA Class I landfill will achieve adequate
protection of human health and the environment at Site 4 by preventing exposure of potential future
workers and joggers, and eliminating a source of potential ongoing contamination of groundwater.
Soil excavation with offsite S/S and disposal in a RCRA Class I landfill will achieve adequate
protection of human health and the environment at Sites 5 and 6 by eliminating a potential
continuing source of groundwater contamination. The SVE presumptive remedy for VOC-
contaminated soils at Site 5 will eliminate a potential continuing source of groundwater
contamination. There are no short-term threats associated with the selected remedies that cannot be
readily controlled. In addition, no adverse cross-media impacts are expected from the remedies.
2.14.2 Compliance with ARARs
The selected remedies will comply with all applicable or relevant and appropriate chemical-,
location-, and action-specific requirements (ARARs). These ARARs are:
• Chemical-Specific ARARs:
- See Table 2-4.
• Location-Specific ARARs:
- See Table 2-5.
Final Rteord of Decision for Soil Cleanup ofSiia 4, S, and 6- September 1998
2-45
-------
• Action-Specific ARARs:
- See Table 2-6.
In addition to the site-specific ARARs listed above, the Air Force will comply with all applicable
laws related to offsite transportation, treatment, and disposal activities related to AFP 44 waste.
2.14.3 Cost Effectiveness
The selected remedies are cost-effective because they have been determined to provide overall
effectiveness proportional to their costs.
2,14.4 Utilization of Permanent Solutions and Alternative Treatment Technologies
The Air Force has determined that the selected remedies represent the maximum extent to which
permanent solutions and treatment technologies can be utilized in a cost-effective manner. Of those
alternatives that are protective of human health and the environment and comply with ARARs, the
Air Force has determined that these selected remedies provide the best balance of tradeoffs in terms
of long-term effectiveness and permanence, reduction in.toxicity, mobility or volume achieved
through treatment, short-term effectiveness, implementability and cost; also considering the statutory
preference for treatment as a principal element and considering State of Arizona and community
preference.
The selected remedies treat the principal threats posed by the soils, achieving significant reduction
of metal and VOC concentrations. The remedies can be implemented in the short term in a cost-
effective manner.
2.14.5 Preference for Treatment as a Principal Element
Excavated soils that exceed action levels established by ADEQ will be treated by S/S to immobilize
metal contaminants. In addition, the SVE presumptive remedy for VOCs in soils at Site 5 will be
coupled with off-gas treatment such that VOC-laden vapors will be withdrawn from the soil, then
captured for offsite destruction or recycling. Therefore, the statutory preference for remedies that
employ treatment as a principal element is satisfied. '
Final Kteord of Decision for Soil Cleanup of Sues 4,5, and 6- September 1998
2~46
-------
SECTION 3.0
£&g^ -*
EVALUATION/COST ANALYSE SITES 1,2, 3,4, AND 5
Ftaa/ *«c,»rd ofDtdtitmfor Sott Cleanup ofSUei 4,5, and 6- Stptembtr 1998
«u\Amu.i\iao70A-i«rres4-nwp>o63«)«j9RpTi.wi>o Page 3-1
-------
Tliis section presents the Responsiveness Summary related to comments received on the Proposed
Plan and Engineering Evaluation/Cost Analysis for Sites 1,2,3,4, and 5 (References 14 through 20).
The comments and responses reflect questions and answers from public meetings, as well as written
questions from various community members and organizations, that were received and addressed
during 1995. This section has not been updated to reflect the current regulatory climate, recently
promulgated regulations, or site conditions that may have changed.
Final Record of Decision for Soii Cleanup of Sites 4,5, and 6 • September 1998
•L:VAFpii.iMon70A-i\srres4-i\wi>vo639«63»Rrri.vm) Page 3-2
-------
INSTALLATION RESTORATION PROGRAM (IRP)
at
Air Force Plant 44
Tucson International Airport Area Supernind Site
Tucson, Arizona
Dennis Scott
Remedial Project Manager
U.S. Air Force
Aeronautical Systems Center
Acquisition Environmental Management
Wright-Patterson Air Force Base, Ohio
November 1995
Capt. Patrice Melancon
Restoration Team Chief
Air Force Center for Environmental Excellence (AFCEE)
Environmental Restoration Division
Brooks Air Force Base, Texas
Prepared by:
EARTH TECH
Alexandria, Virginia
PropotcdPlan andE&CA Sites I, 2. 3. 4, and5 RapcviveaeuSummary. AFP 44. November 1995
-------
ACRONYMS AND ABBREVIATIONS
ADEQ Arizona Department of Environmental Quality
ADHS Arizona Department of Health Services
AFCEE Air Force Center for Environmental Excellence
AFP 44 Air Force Plant 44
ARAR Applicable or Relevant and Appropriate Requirements
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act
EE/CA Engineering Evaluation/Cost Analysis
FACO Final Assembly and Checkout
IRP Installation Restoration Program
GAC Granular Activated Carbon
DNAPL Dense Nonaqueous Phase Liquid
DOD Department of Defense
MCL Maximum Contaminant Level
mgd Million gallons per day
mg/L Milligrams per liter
mg/cm3 Milligrams per cubic meter
NAPL Nonaqueous Phase Liquid
NCP National Oil and Hazardous Substances Pollution Contingency Plan
QA/QC Quality Assurance/Quality Control
RCRA Resource Conservation and Recovery Act
ROD Record of Decision
SVE Soil Vapor Extraction
TCE Trichloroethylene
UCAB Unified Community Advisory Board
/zg/L Micrograrns per liter
USEPA U.S. Environmental Protection Agency
VOC Volatile Organic Compound
•OJM.WT
Proposed flat, onrf EE/CA Sila 1, 2.3. 4. and S Rapcasifenat Summary. AFP 44- November 1995
-------
RESPONSE TO ADEQ COMMENTS
ON PROPOSED PLAN FOR SOIL CLEANUP
(JULY 1995)
4.
5.
Page 1-1:
Comment:
Response:
Page 1-2:
Comment:
Response:
Page 1-3:
Comment:
Response:
Page 1-5:
Comment:
Response:
Page 3-12:
Comment:
Explain that the removal actions for Sites 1-5 are in advance of the Record
of Decision (ROD) and may be modified, if so required.
A statement will be added to Section 1.1 subparagraph (2) that the remedial
actions finalized in the ROD may result hi modifications to work being
conducted under the removal action.
Correct the apparent typo in the last sentence of the Public Hearing
paragraph. Also, review all documents for editorial correctness.
The last sentence will be corrected to read "A transcript of the hearing..."
Clarify the third paragraph to show that the Resource Conservation and
Recovery Act (RCRA) and Comprehensive Environmental Response,
Compensation and Liability Act (CERCLA) processes require extensive
public and government review of design documents. The time for that
process is not a delay.
The sixth sentence of the third paragraph will be changed to "Both
CERCLA and RCRA allow early implementation of cleanup actions
provided that...".
Figure 1-1 should include a remedial action event after the ROD.
The Remedy Operation and Maintenance event will be renamed to
Remedial Action Operation and Maintenance.
Will an effectiveness program be defined in the ROD? That program must
be subject to government approval and public review. The program must
include both a quantifiable determination and a mandatory restart of the soil
vapor extraction (SVE) after some period of shutdown to determine if
volatile organic compound (VOC) removals can occur. Those elements
must: be defined in the Operation and Maintenance Manual. There is also
a need for site restoration and proper shut down and removal of equipment.
When will this be defined?
mit.urr
Proposed Plait and E&CA Sita 1.2,3, 4. and 5 Rapomivcnea Summary. AFP 44. November 199S
Page 1
-------
8.
9.
Response: Shut down, equipment removal, and site restoration will be addressed in the
ROD for Sites 1, 2, and 3. Site restoration for Sites 4, 5, and Site 6
hotspots is addressed in the Work Plan. After these issues are resolved,
they will be attached as addenda to the Operation and Maintenance Manual.
Page 3-13:
Comment:
Response:
Page 5-1:
Comment:
Response:
As above, when will the site restoration be addressed? The excavated sites
must be filled and covered for sound drainage and compatible land use.
The ROD will address restoration of Sites 1,2, and 3 to a land use
compatible with Government-related activities. The restoration of Site 4,
5, and 6 Hotspots is described in the Removal Action Work Plan.
While deemed acceptable, the Purus system has not been tested at steady
state conditions using the proper resin. Arizona Department of
Environmental Quality (ADEQ) reserves all rights to re-evaluate the
effectiveness of the Purus system during final operations.
The Pursorb 200 resin used in the treatability study was the optimal resin
for Site 3, and was adequate at Site 2. The Pursorb 400 resin proposed for
use at Site 2 is better suited for the high levels of trichloroethylene (TCE)
encountered at that site, and will enhance the already-satisfactory
performance of the Purus system.
Tables 5-1 thru 5-5:
Comment: The estimated costs for the selected alternatives were revised, based upon
data reanalysis since the Feasibility Study was completed. Similar changes
should have been made to the cost of other alternatives. Why weren't these
costs revised?
Response: The costs for SVE with Resin Adsorption were revised using actual
operating cost data determined from the treatability study. These data were
specific to resin adsorption only, resulting in no change to the estimate for
SVE with catalytic oxidation. The costs for offsite stabilization were
refined due to the economy of scale gained by combining this work with
similar work being conducted under closure of the surface impoundments
at Air Force Plant 44 (AFP 44).
Page 5-3:
Comment:
Response:
Figure 5-1 does not indicate a loss of nitrogen, yet considerable nitrogen
was consumed during the Purus field tests. If this loss occurred during
cycling from desorption to adsorption, then please show the anticipated
nitrogen losses and related TCE carry off.
Figure 5-1 will be revised to indicate that nitrogen and non-condensed VOC
vapors are returned to the process inlet line where the VOCs are exposed
to the adsorbing bed. The nitrogen passes through and is released with au-
to the atmosphere.
•W7S.WT
Proposed Flan anaEE/CA Slta I, 2,3, 4, and 5 Respcrafrtnas Summary, AFP 44- November 1995
Page 2
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10.
Page 5-3:
Comment:
Response:
Figure 5-2 shows screening offsite, while Page 5-5 of the overall
Engineering Evaluation/Cost Analysis (EE/CA) states that screening and
hornogenization are pretreatment activities that occur onsite. Which
protocol is applicable, and what precautions for health and safety will be
taken?
Health and safety precautions are described in the work plan and health and
safety plan. All pretreatment activities such as screening and
homogenization will be conducted at the disposal facility, and will be
performed under the health and safety plan for that facility. The second
and third sentences of the second paragraph on page 5-5 of the overall
EE/CA will be changed to "If necessary, pretreatment of excavated
contaminated soils will be conducted offsite. Pretreatment will include
screening size reduction, and homogenization of the soil."
•OJ76.WT
PropotedPlanandEEKASite 1.2,3, 4,andS RapendvenasSummary, AFP44-November 199S Page 3
-------
RESPONSE TO USEPA COMMENTS
ON PROPOSED PLAN FOR SOIL CLEANUP
(JULY 1995)
GENERAL COMMENTS:
1. Comment: U.S. Environmental Protection Agency (USEPA) strongly recommends
adding either granular activated carbon (GAQ or a second set of resin beds
in series to the two parallel resin beds of a Purus treatment system. This
second tier of vapor treatment would significantly reduce VOC levels in the
off-gas and practically eliminate the potential of an unwanted air release.
Response: Results from treatability studies conducted at AFP 44 in 1995 indicate this
extra safeguard is not necessary (Site 2 and Site 3 Purus Demonstration
Letter Report, September 1995). Pima County air emission regulations
(Pima County Code 17.20.090 (E)) require 85 percent removal of
contaminants prior to venting the off gas to the atmosphere. Sampling
during the startup period will be performed to optimize the
adsorption/desorption process. A VOC detector permanently installed on
the effluent line will shut down the system in the event effluent VOC
concentrations that would result in an exceedance of Pima County air
emission standards are encountered. The Purus system parameters will be
set to ensure emissions are within this standard.
2. Comment: USEPA has published guidance on the preparation of Superfund decision
documents (PB91-921265). These guidance documents are available from
the National Technical Information Service. USEPA strongly recommends
using these documents as a resource in preparation of the upcoming ROD
for the AFP 44 Site.
Response: This guidance will be considered during development of the ROD.
SPECIFIC COMMENTS ON THE PROPOSED PLAN
1. Page 2-5, Paragraph 4:
Comment: Please use consistent soil gas units throughout the document; USEPA
prefers micrograms per liter.
Response: The units expressing VOC concentrations will be converted from
milligrams per cubic meter to micrograms per liter (/tg/L)..
2. Section 3 General Comment:
Comment: Please use risk terminology consistent with USEPA guidance and the
National Oil and Hazardous Substances Pollution Contingency Plan (NCP)
Proposed Plan and EE/CA Sites 1,2, 3. 4, and 5 Respanrirenea Summary, AFP 44- November 1995
Page 4
-------
Response:
regarding such terms as baseline risk assessment, reasonable maximum
exposure scenario, acceptable and unacceptable risk. USEPA again
suggests including in this section a table summarizing the results of the
baseline risk assessment for the Sites.
Some terminology will be changed as recommended. Summary tables
(similar to Tables 4-1 and 4-2 in the August 1993 Risk Assessment) will be
added to the Proposed Plan.
Page 3-1, Paragraph 4:
Comment: Pursuant to the National Oil and Hazardous Substances Pollution
Contingency Plan (NCP) (Section 300.430 (e) (2) (D (A) (2)) the ID* risk
level shall be used as the point of departure in the absence of applicable or
relevant and appropriate requirements (ARARs). Therefore any cleanup
levels not established at the 10"6 risk level must be explained and justified.
Response: The following statement is from 40 CFR 300.430(e)(2)(I)(A)(2) of the
NCP:
"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~* to 10* using information on the relationship
between dose and response. The Ifr6 risk level shall be used
as the point of departure for determining remediation goals
for alternatives when ARARs are not available or are not
sufficiently protective because of the presence of multiple
contaminants at a site or multiple pathways of exposure."
As is stated, the 10"6 risk level should be used as a point of departure for
determining remediation goals for alternatives in the absence of ARARs.
But, acceptable exposure levels can be considered within the risk range of
10"* to 10*. For the AFP 44 approved risk assessment, the regulators as
risk managers accepted and approved exposure levels which fell within the
risk range of ICr4 to 10* as acceptable. Consequently, exposure levels
which cause risk exceeding the benchmark of 10"* would require remedial
alternatives.
4.
Section 3.3:
Comment:
This section acknowledges the need to remediate soils at the Sites in order
to prevent further migration of contaminants to ground water thereby
assisting in the exceedence of maximum contaminant levels (MCLs).
USEPA again suggests adding a section discussing the development of
residual soil cleanup levels for the protection of ground-water quality. As
a starting point, this section could include the following cleanup standard
for subsurface soils:
Proposed Flan anaE&CA Sites 1.2,3,4, mad5 Rcsptmnenca Summary, AFf 44 - November 1995 Page 5
-------
"Each contaminant shall be removed from target area soils
until an Allowable Residual Contaminant Concentration
(ARCCP) is achieved. An ARCCP is any CCP that will not
cause or contribute to ground-water (first saturated unit)
contamination in excess of site ground-water cleanup
levels."
This standard would supplement (not replace) numeric soil
standards adopted for this site. All key words (such as
target area, ground-water, etc.) in the above soil cleanup
standard discussion would need to be defined.
Response: A similar comment on the Draft Final Feasibility Study was resolved by
adding the following statement, which will be added to Section 3.3:
"Subsurface soil remediation will continue until no adverse
impact to groundwater in excess of risk-based clean up
levels is achieved. Risk-based clean up levels will be
established which are protective of human health and the
environment, and consider migration of soil contaminants to
groundwater. A method to demonstrate that this has been
achieved will be established through the joint efforts of the
U.S. Air Force, USEPA Region DC, and the ADEQ."
5. Page 5-2, Table 5-1:
Comment: There is no explanation in the text of this section on how these four
evaluation criteria were developed and used, particularly in light of the fact
that USEPA uses a nine criteria evaluation. Please include some
explanatory language in the text, or use the nine criteria evaluation.
Response: These tables summarise the results of the detailed evaluations described in
the Feasibility Study. The Feasibility Study considered both the nine
USEPA evaluation criteria and the seven evaluation Air Force Center for
Environmental Excellence (AFCEE) criteria. Readers are referred to the
Feasibility Study for a detailed discussion of the comparative analysis. The
first paragraph of Section 5.0 will be expanded to reference the USEPA and
AFCEE evaluation criteria presented in Section 4.0, and an added statement
that the tables represent a synopsis of the USEPA and Air Force criteria.
«OJMWT
Proposed flan andEE/CA Sites 1,2,3,4. and S Roperaiveness Summary, AFP 44 - November 1995
Page 6
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RESPONSE TO UCAB COMMENTS
ON PROPOSED PLAN FOR SOIL CLEANUP
(JULY 1995)
1,2. Comment:
2. Comment:
Response:
3. Comment:
Response:
Final levels of (soil) cleanup standards should be lower than the Maximum
Contaminant Levels, if the technology is capable of achieving the lower
levels.
Because measurements of the groundwater cleanliness will be the
determining indicator for a successful soil cleanup, assurances must be
placed in the ROD to equate soil cleanup levels to this groundwater
measurement. These should be based on a change to residential use with
children involved.
The Arizona Health-Based Guidance Levels are the cleanup standards for
Sites 4, 5, and Site 6 Hotspots. ADEQ and Arizona Department of Health
Services (ADHS) considered the migration pathway to protect groundwater
in approving the soil cleanup standards for metals at AFP 44. No cleanup
standards exist for the deep soil. The Air Force, USEPA, and ADEQ will
work together to determine the standard for cleanup of Sites 1, 2, and 3.
Computer models or other means may be used to determine the point at
which groundwater is no longer adversely impacted by soil contamination.
Once this is determined, the standard will be formally established in the
ROD. Groundwater which does not exceed the MCLs is protective of
resident children.
Individual (air) emissions must be identified in terms of pounds per day.
Total of all emissions must be stated in pounds per day and this must be
agreeable to the citizens of Tucson. Use of Pirna County DEQ to monitor
air quality more closely (ex. unannounced inspections with a qualified
citizen). Possible grant from USEPA to fund this.
Pima County requires that air pollutant sources which emit more than 2.4
pounds of VOCs per day must be equipped with a control device to remove
at least 85% of the VOCs. The Purus resin adsorption system is capable
of removing up to 99% of the VOCs. A VOC detector will be
permanently installed which will shut down the system if VOC emissions
approach the 85% limit. The actual pounds per day emitted will depend on
the concentrations of extracted vapors and the flow rate. Adjusting the
system to a lower flow rate will reduce the number of pounds emitted, but
will result in a longer time to remediate the soils. Pima County DEQ has
the authority to make unannounced inspections.
•OS76.RTT
Proposed Plan ondEEKX Sites 1,2,3, 4. and 5 Rapc*sivtnas Summary, AFP 44-November 1995
Page?
-------
4a. Comment:
Response:
4b,15. Comment:
Comment:
Response:
4c.
4d.
5.
Comment:
Response:
Comment:
Response:
Comment:
Response:
6. Comment:
Soil vapor extraction technology requires a draw-down at the capillary
fringe which may disturb the soil vapor levels over time.
Water levels are already being drawn down by operation of the
groundwater treatment plant. This exposes contamination in the capillary
fringe to the SVE system and enhances removal of contaminants.
A longer term monitoring program is essential for the protection of the
citizens.
Is the 1 year period to verify cleanup goals adequate?
The Proposed Plan includes monitoring soil gas concentrations for a year
after completion of the cleanup. If soil vapor concentrations were to
rebound after shutting down the system, it would typically occur within a
few months. Increasing this time to a year is much more conservative and
adequately protective of human health. Monitoring requirements may be
formally established in the ROD.
A plan is desirable detailing how citizens will be informed of activities in
the future including current reports and unannounced tests.
The AFP 44 Community Relations Plan describes the methods used by the
Air Force to keep the public informed of cleanup activities. A copy is
available in the Superfund Library.
The superfund library must be funded for the life of the project and the
library address must become the official Unified Community Advisory
Board (UCAB) address.
The Superfund Library is funded by the USEPA, which is subject to
adequate firading by the U.S. Congress.
The concerns of the Neighboring Nations must be addressed. Suggest
Federal Agencies authorize funds for the Tohono O'odham Nation for an
independent consultant to help with their questions and concerns.
AFP 44 environmental managers have been meeting with the Tohono
O'odham Nation for the past several years. The most recent meeting was
held on October 17, 1995 with the San Xavicr District to make sure that
their concerns are being considered during cleanup decisions. A
representative of the Nation is a member of the UCAB for the Superfund
Site and another position on the Board has been offered to the San Xavier
District. The Tohono O'odham Nation may wish to submit a request for
a Technical Assistance Grant for consulting services to the USEPA, Region
IX. Information on how to do this is available at the TCE Superfund
Library at the El Pueblo Neighborhood Center.
The ROD should include assurances in the event the property in question
is transferred or sold.
•0576 *rr
Proposed Plan andEE/CA SUa 1,2,3. 4. and S Respostivenea Summary, AFP 44- November 1995
PageS
-------
7, 8. Comment:
Comment:
Response:
Response: On July 21, 1994, the Air Force signed a lease with Hughes Missile
Systems Company for a 10-year period with provision for two 10-year
extensions by mutual agreement of the parties. The rent proceeds from the
lease are used to fund capital maintenance of the property as payment in
kind, as provided in 10 USC 2667 (b)(4) and (b)(5). During the lease
period, all Air Force environmental restoration efforts required by RCRA
and CERCLA will be completed. At that time, the Air Force will seek to
dispose of AFP 44 in accordance with applicable statutes, which may
require notification or deed restrictions.
While the agencies and involved parties are the authorities on the
requirements regulating the transportation of hazardous waste materials
during a cleanup, it is essential that this plan be reviewed with the
community.
(Emergency response plans) must be reviewed prior to the start of work.
The plan for the transportation of the hazardous materials from AFP 44 to
a disposal site has been discussed with the public at the Public Meeting in
July of 1995 and is laid out in the EE/CAs for the individual sites.
Transport of hazardous waste is heavily regulated by the Department of
Transportation and AFP 44 will follow all of these regulations carefully.
Emergency Response Teams are under the control of local agencies and are
on call 24 hours a day in every community. They are trained to deal with
any accident that may occur. The transportation of the soils from Sites 4
and 5 has been discussed in the quarterly Progress Reports sent by AFP 44
to almost 3,000 area citizens. AFP 44 will be glad to give a more detailed
presentation on this matter to the UCAB at any time. Please see the
response to Question #1 from the Response Cards and to Question Number
#1 from the Sunnyside School District for a detailed description of the
health and safety measures that are in place.
What additional steps will be taken in the event the Soil Vapor Extraction
and removal of contaminated soils does not stop the ongoing contamination
of the groundwater? What are the plans if it becomes evident that dense
nonaqueous phase liquid (DNAPL) is a problem on AFP 44? How will this
affect the remediation plans?
Response: The treatability study demonstrated the ability of the SVE system to
effectively remove VOCs from contaminated soils. In the event
contaminant removal is not effective and an alternative remedial method is
considered, regulatory review and a public comment period would be
required. Based on existing data, there is no DNAPL in the groundwater
at AFP 44. The 1986 ROD outlines the groundwater remediation. If the
presence of DNAPL was suspected, a response action may be taken under
the 1986 ROD. Possible actions could include adjustments to the
9. Comment:
•0576.KTT
Proposed Plan and E&CA Sites 1,2.3, 1. and S Responsiveness Summary,AFP44 . November 1995 Page 9
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10. Comment:
Response:
11. Comment:
Response:
12. Comment:
Response:
13.
Comment:
Response:
14.
Comment:
Response:
groundwater reclamation system and installation of additional groundwater
extraction wells.
What means of transportation will be used to move excavated material from
site.
Excavated materials from Sites 4, 5, and Site 6 Hotspots will be hauled
primarily by railroad to Henderson, Colorado, where they will be
transferred to trucks for ultimate disposal in the Rollins Highway 36
landfill in Colorado. Some materials may be hauled from AFP 44 by
truck.
Is there an Emergency Response Plan required for accidental spills during
transport?
Once materials are loaded and removed from AFP 44, the hauler's
emergency response plan will be in effect. All transporters and disposal
facUities have extensive emergency response plans and are ready to
implement immediate action in the event of an emergency. CHEMTREC,
a company that provides information to emergency response personnel
about appropriate response actions in an emergency, has been contracted
by AFP 44 to provide accurate and timely information regarding the waste
material transported by rail.
Were the concentrations of soil and groundwater samples consistent with
depth of soil gas concentrations?
Soil gas samples collected from shallow depths and from the SVE
treatabiliry study generally indicated much higher concentrations than the
concentration of contaminants in soil samples. No direct correlation
between soil gas and groundwater concentrations can be made with the
existing data.
Is the soil cover at Site 2 adequate to prevent infiltration? Explain the
reasoning.
All but one of the proposed extraction wells at Site 2 are sufficiently deep
that vertical short-circuiting of air from the surface is unlikely. This well,
and the shallow Site 1 wells require a liner on the ground surface to prevent
vertical infiltration.
Will Pirna County DEQ be actively involved in reviewing the quality data
for emissions from the individual sites?
This remedial action must meet the substantive requirements of the Pima
County air emissions standards. Air emissions data will be maintained on
site and is subject to review by Pima County DEQ, which has the authority
to make unannounced inspections. The USEPA and ADEQ also have
authority to inspect and review data.
nomiirr
Proposed Plan and EE/CA Sites 1.2.3, 4. and S Responsiveness Summary, AFP 44-November 1995 Page 10
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15. Comment: Is the 1 year period to verify cleanup goals adequate?
Response: See comment 4b above.
16. Comment: How can we be sure that the intent of our statements from the UCAB are
understood and implemented into the ROD?
Response: All comments received are addressed in this Responsiveness Summary. If
the public feels the response to the comment is not appropriate, individuals
or me UCAB can contact the Air Force Remedial Project Manager.
17. Comment: Have the USEPA and ADEQ formally accepted the No Further Action
Reports at the AFP 44?
Response: Draft versions of the No Further Action reports for Sites 7, 8, 9, and 15
were submitted to the USEPA and ADEQ for their review. Approval of
these reports is anticipated following incorporation of their review
comments. The Site 6 No Further Action report has been put on hold
pending removal of the Site 6 hotspots.
18. Comment: Have any tests been made for radiation at AFP 44? What were the results?
If AFP 44 has never been used for storage of radioactive materials can
independent testing be performed to assure the citizens of this? What steps
can be taken to inform the community of a status for concerns now or in
the future?
Response: To date, no radioactive materials have been used as a component of a
missile at AFP 44. The explosive storage bunkers located within the Final
Assembly and Check Out area store conventional explosives only.
Some soils and groundwater in the Tucson Basin contain naturally
occurring radioactive nuclides. Radioactive nuclide tests in groundwater
were conducted as part of the normal characterization of the RCRA
groundwater monitoring wells. One perched zone well (Well No. S-10)
showed the presence of radioactive nuclides exceeding drinking water
standards one time in August 1987. However, that well was almost
completely dry and the only samples that could be obtained were murky
(muddy). This well remained dry for several years. It became wet again
in 1994 as a result of AFP 44 Groundwater Remediation efforts. Water
samples were immediately obtained and re-tested for radioactive nuclides
and results were below drinking water standards. An additional sample has
recently been taken and submitted for radioactive nuclide analyses. Results
have not been received to date.
AFP 44 currently has a license from the Arizona Radiation Regulatory
Agency which permits them to use very small quantities (microcurie to
millicurie range) of radioactive sources in areas as equipment calibration
and test positions for use in checking electronic circuitry. The calibration
equipment and test positions use Krypton and Tritium gases. The license
•OJ76 R/T
Proposed Plan and E&CASUa 1,2,3, 4, and S Responsiveness Summary, AFP 44. November 199$ Page 11
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19. Comment:
Response:
20. Comment:
Response:
21. Comment:
Response:
22. Comment:
Response:
requires AFP 44 to properly store, conduct leak tests, and perform
inventories of all radioactive sources identified on the license. Storage of
minimal quantities of radioactive sealed sources (microcurie range) are
currently being conducted onsite (Building 815 - Drum Storage Area)
because of the unavailability of approved waste disposal sites across the
country. Some of these items will be returned to the vendor for reuse.
This storage is being conducted in accordance with AFP 44's license.
The Air Force has indicated its intent to sell AFP 44. If land use changes
to residential how can the community be assured that the No Further Action
sites will be cleaned up?
These sites are being recommended for No Further Action because the risk
assessment concluded that the risk to onsite workers was well within the
standard for acceptable risk. If the property is sold, notification or deed
restrictions may be a condition of the property transfer to ensure the land
use remains as an industrial area.
Will the wells at AFP 44 ever be used to deliver water to the community?
The Air Force is not aware of any such plans. Future decisions on
municipal water wells located off the AFP 44 property will be made by the
City of Tucson or other authorities.
Who has confirmed the capacity of the out of state sites to handle the
hazardous waste from the soil cleanup? How has the capacity of the
receiving facility been determined?
The State of Colorado regulatory agencies have permitted the disposal
facility to accept the types and volumes of hazardous waste sent there.
How will the final soils clean up be tied to the ongoing water cleanup? The
ROD seems to be the important link. What agency is responsible for
ensuring that the ROD is written to reflect the community concerns?
The soils cleanup will remove the ongoing source of groundwater
contamination at Sites 1,2, and 3. Final cleanup levels and the method of
shutting down the remedial systems will be established in the ROD. The
Air Force, USEPA, and ADEQ share responsibility to ensure the
community's concerns are addressed.
GENERAL COMMENTS (attached to UCAB Comments)
23. Comment:
Response:
The remedial action objectives should be stated in the plan.
The second sentence on page ES-1 and the second sentence on page 1-1 will
be changed to "The remedial action objectives addressed in this Proposed
Plan are cleanup of five sites to address potential risks to human health and
the environment, which includes removing continuing sources of
groundwater contamination."
•0574 HPT
Proposed Plan and E&CASila 1,2.3.4, and S RaponnventB Summary, AFP 44- November 1995 Page 12
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24. Comment:
Response:
25. Comment:
Response:
26a. Comment:
Response:
26b. Comment:
Response:
Please define "resident children." More importantly, has there been any
analysis or discussion of why a future residential scenario was not used?
How would the remediation strategy change if a future residential scenario
were assumed?
Because the Pima County zoning plans indicate the Tohono O'odham land
as being residential, the risk assessment considered the health effects on
those resident children playing in the drainage ditch downstream of AFP
44. The risk assessment assumed no future changes to the AFP 44 site-
it would remain as an industrial facility. The assessment included
calculations for potential effects of contaminants on current workers and
current offsite resident children assuming no cleanup was performed, and
the potential effects on future excavation workers during site cleanup.
Other off-site residential receptors were not considered because modeling
indicated that workers on AFP 44 would receive greater exposures
(maximum impacted receptors). Should the property be sold, a deed
restriction may be included to ensure future land use is limited to industrial
facilities. (See response to UCAB Comment Number 6.)
The plan nor the EE/CAs state the soil cleanup standards for organic
compounds.
The Arizona Health-Based Guidance Levels are the cleanup standards for
Sites 4, 5, and Site 6 Hotspots. ADEQ and ADHS considered the
migration pathway to protect groundwater in approving the soil cleanup
standards for metals at AFP 44. No cleanup standards exist for the deep
soil. The Air Force, USEPA, and ADEQ will work together to determine
the standard for cleanup of Sites 1, 2, and 3. Computer models or other
means may be used to determine the point at which groundwater is no
longer adversely impacted by soil contamination. Once this is determined,
the standard will be formally established in the ROD. Groundwater which
docs not exceed the MCLs is protective of resident children.
What is the effectiveness of the (Purus) system in capturing all
contaminants found at each site?
The Purus PADRE1** system demonstrated at AFP 44 removed more than
99% of the total VOCs based on gas chromatographic analyses of vapor
influent and effluent.
What are the anticipated releases to the air (in pounds per hour) from each
installation?
Pima County requires that air pollutant sources which emit more than 2.4
pounds of VOCs per day must be equipped with a control device to remove
at least 85% of the VOCs. The Purus resin adsorption system is capable
of removing up to 99% of the VOCs. A VOC detector will be
permanently installed which will shut down the system if VOC emissions
approach the 85% limit. The actual pounds per day emitted will depend on
Proposed Plan andEESCA SUa 1.2,3,4. and 5 Repoanvenea Summary. AFP 44. November 1995 Page 13
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26c. Comment:
Response:
26d. Comment:
Response:
27. Comment:
Response:
28. Comment:
Response:
the concentrations of extracted vapors and the flow rate. Adjusting the
system to a lower flow rate will reduce the number of pounds emitted, but
will result in a longer time to remediate the soils. Pima County DEQ has
the authority to make unannounced inspections.
There is no discussion of chemicals which may break through the resin bed
when the system is first starting up (this was identified to me when I saw
the demonstration facility in May, 1995).
During initial startup of the Purus PADRE™ system, a break through test
will be performed to determine the saturation level for the resin beds. The
system's operating parameters (flow rates and cycle times) will then be
adjusted to ensure the system is effectively removing contaminants.
Furthermore, a VOC detector will be permanently installed on the effluent
line which will shut down the system hi the event of high VOC emissions.
During the demonstration at AFP 44, no emissions in excess of Pima
County air emission limits occurred.
The Purus system reportedly does not perform well in conditions in which
water vapors are present. Please discuss this fact, and identify how you
will design the system to prevent water vapor from coming into contact
with the resin beds.
Water vapors are not a concern, but water droplets within the resin beds
could lead to corrosion of the steel pressure vessel which holds the resin.
A water-vapor separator will be used to remove any water droplets from
the vapor stream. The piping between the water-vapor separator and the
resin beds will be insulated to help prevent temperature fluctuations which
could allow water to condense in the pipes. A lower temperature will be
used in the desorpdon cycle to reduce hydrochloric acid formation, and
metal test strips inside the resin beds will be used to monitor corrosion.
(Vapor-phase GAC) along with SVE/cataJytic oxidation should be
compared with the Purus PADRE1" system for cost and effectiveness in
controlling air emissions.
GAC was considered in the Feasibility Study, but was screened out due to
the extremely high carbon usage rate experienced in the 1993 treatability
study. SVE with catalytic oxidation was evaluated in the Feasibility Study,
but was not selected because it would constitute a flame source within the
Final Assembly and Checkout (FACO) explosives storage area.
...Wouldn't it be prudent to begin with a few (Purus) systems at first to
make sure they work under field conditions?
The 1995 treatability study demonstrated the effectiveness of the Purus
system by removing over 99% of the VOCs from the vapor stream at Sites
2 and 3. Installation of the remedial systems will be done in phases, such
•OS74.RIT
Proposed flan and E&CA Sites 1,2,3,4, and 5 Kapaaaveaea Summary, AFP44- November 1995 Page 14
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29.
30.
Comment:
Response:
Comment:
Response:
31. Comment:
Response:
32. Comment:
Response:
that some systems will be installed and operating before the remainder of
the systems are delivered.
What contingency would be implemented should the Purus systems fail to
operate as specified?
A contingent alternative is not included in the Proposed Plan. If an
alternative technology is required the Air Force would make this selection
in cooperation with the public and regulatory agencies.
How (do) you anticipate monitoring performance of the Purus system, and
what would trigger a shutdown of the system?
A VOC detector permanently installed on the effluent line would shut down
the system if emissions approach allowable limits established by Puna
County. Periodic sampling of the vapor stream will provide data for
evaluating the system's operations and removal efficiency. Any changes
• in the flow rates and volume of condensate produced would give the
operator an indication of fluctuations in the vapor stream or system
performance. Any other faults within the computer-controlled system
would immediately shut down the system, including the blower.
There is no analysis in the plan or in the EE/CAs of why soil stabilization
was selected as opposed to soil washing for Sites 4 and 5. Please provide
a detailed explanation.
Section 4.0 of the Overall EE/CA presents an analysis of alternatives
(including soil washing) based on USEPA and AFCEE criteria. The
remedial technology selection for Sites 4, 5, and Site 6 Hotspots was
intended to match that method selected for RCRA closure of the surface
impoundments at AFP 44, thereby resulting in an economy of scale. On
site soil washing was not selected due to capital costs and concerns over the
potential exposure to harsh chemicals used in the soil washing process.
The Air Force should develop a program to monitor the development and
migration of vinyl chloride at those sites where TCE and petroleum
products are found together.
Vinyl chloride, which is a potential break down product of TCE, was not
detected in any of the soil vapor samples collected during the Feasibility
Study. Periodic sampling of soil vapors at Sites 1, 2, and 3 will include
analysis for vinyl chloride.
•OH4.WT
Page 15
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RESPONSE TO COMMENTS FROM THE
SAN XAVIER DISTRICT OF THE
TOHONO O'ODHAM NATION
ON PROPOSED PLAN FOR SOIL CLEANUP
(JULY 1995)
Comment: If the Air Force begins remediation as stated in the Proposed Plan they will
do so lacking some degree of information (such as cleanup standards) and
some degree of oversight (from the regulatory agencies and the public)
which would normally be reflected in the ROD.
Response: SVE will be used to cleanup TCE contaminated soil. The cleanup of
metals contaminated soil will be by excavation and offsite disposal at a
RCRA licensed landfill. The proposed cleanup standards are the same as
those already approved by ADEQ for the surface impoundment closure
project. Achieving the cleanup standard for TCE is primarily a function
of how long the SVE systems operate, so an early start on cleanup will not
be adversely affected by the outcome of the standards established in the
ROD. The USEPA and ADEQ are bom actively providing project review
and oversight to the extent that work will not begin until their approval is
received. The Proposed Plan and EE/CAs were all available for public
review, a public hearing was held, and this responsiveness summary is the
result of all comments received.
Comment: The Draft Feasibility Study warranted No Further Action for Site 6, but the
Proposed Plan includes remediation for portions of Site 6. We request that
more information be provided on this decision to remediate Site 6 hotspots.
Response: Sites 4 and 6 overlap in some areas. The Site 6 hotspots which will be
cleaned up are actually portions of Site 4 and exhibit metals contamination
found elsewhere in Site 4. ADEQ agreed to no further action at Site 6
provided the hotspots were cleaned up. The No Further Action report for
Site 6 is on hold, and will be completed after the hotspots removal. The
removal will provide verification that these hotspots have been fully
investigated and remediated.
Comment: The District remains concerned with the failure of the Air Force to
properly determine if any activities at Plant 44 have contaminated soils on
District land... The San Xavier District's Land Use Plan was never
consulted when analyzing health risks.
•OJ76 RTT
Proposed Plan ami EE/CA Sites 1,2,3, 4. and 5 Resppiaivenas Summary. AFP 44. November 199S Page 16
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Response: The investigation of Site 6 included extensive soil sampling along the
drainage channels at AFP 44. These channels merged into a single wash
at the northwest corner of the facility, which then exited westward through
a culvert under the Old Nogales Highway. The wash resumes on the west
side of the highway, and crosses District land. Soil samples were taken
along the wash bottom inside the AFP 44 boundary, and across the
highway on privately owned land immediately adjoining District land. The
surface and subsurface soil samples indicated no significant contamination
was present in the wash. The risk assessment considered the Tohono
O'odham land as being a residential area as identified in the Pima County
zoning plans. A residential land use assumption would result in the most
stringent, conservative conclusions. The risk assessment calculated the
potential exposure of resident children temporarily playing in the drainage
channel located to the west of Old Nogales highway. Standard risk
assessment assumptions were made for residential children exposed through
incidental ingestion of surface water and dermal adsorption of contaminants
in surface soils. The risk assessment concluded that no significant risk was
present at Site 6. In 1994, the Tohono O'odham Nation and San Xavier
District representatives, Bureau of Indian Affairs, the USEPA, Hughes and
Air Force all agreed that USEPA would conduct sampling in the wash on
district lands. The USEPA was to prepare a sampling plan acceptable to
the San Xavier District and Tohono O'odham Nation.
•0574 WT
Propose*Plan andEEJCA Sites /. 7. J. 4, and5RapeesfrenosSummary, AFP 44- November 1995 Page 17
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RESPONSE TO SUNNYSIDE UNIFIED SCHOOL
DISTRICT No. 12 COMMENTS
ON PROPOSED PLAN FOR SOIL CLEANUP
(JULY 1995)
1. Comment: .. .All precautionary safety measures (should) be taken in moving hazardous
waste via rail to a disposal facility...
Response: The cleanup at Site 4 will be accomplished as pan of the ongoing Pond
Closure project at AFP 44. This involves excavating and shipping
approximately 63,000 tons of contaminated soils. These soils are
contaminated with metals left from the industrial wastewaters that were
once put into the holding ponds in this area. The soil will be excavated,
placed in railroad gondola cars, and shipped via Southern Pacific Railroad
to a disposal site in Colorado. Many safety measures are taken during this
process to protect both the community and the workers at AFP 44.
During excavation and loading, the soils are kept moist at all times to
prevent any dust from entering the air. Pima County DEQ does periodic
inspections, as does the Arizona DEQ. The soils are placed in the gondola
cars through a chute that has sides on it, as well as water misters, to control
dust.
The gondola cars have been reconditioned and inspected for safety and are
lined with a heavy liner that covers the soil once it is loaded. Then the
entire gondola car is covered with a heavy tarp. The cars are labeled as
hazardous waste and are tracked 24 hours a day by a computer system that
links the railroad and the disposal facility in Colorado.
The Department of Transportation heavily regulates the transport of
hazardous waste and all procedures are being carefully followed. The
waste is also registered with CHEMTREC, a national registry that has a
24-hour hotline available to give information to emergency crews in case
of a problem. Each local area through which the waste will pass has an
emergency response team on call, as does the railroad.
Every effort has been made to ensure safe transport of these soils to the
disposal facility. There is no exposure to residents from this transport.
Should an accident occur, the soils are doubly contained in wraps and tarps.
Even if the tarp or wrap should rupture in an accident, the soil is shipped
damp and would create a minimum of dust. There is no liquid or gas to
«0576.W»T
Propaied Plan and EEAZ^ Sites J, 2, S, 4. and SKespcxsiveness Summary. A Ff> 44-November 1995 Page 18
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escape. Any spilled dirt can easily be recontainerized if an accident
occurred.
On October 17, 1995, a presentation was given to the Sunny side Unified
School District by AFP 44 environmental managers on the transport of
soils. Those present were invited to tour the pond closure and loading area
at their convenience to view the safety procedures first hand.
2. Comment: The burden of cost should be shared by the responsible parties and the U.S.
Department of Defense (DOD).
Response: This project is being initially funded by the DOD. Liability of potentially
responsible parties may be established at a later date.
•OJ76WT
Page 19
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RESPONSE TO COMMENTS AT THE
18 JULY 1995 PUBLIC HEARING
ON PROPOSED PLAN FOR SOIL CLEANUP
(JULY 1995)
1. Comment:
Response:
2,5,11
Comment:
Comment:
Comment:
Response:
Comment:
Response:
Comment:
Response:
What's the average depth of those (SVE) wells?
The average drilled depth for SVE wells will be 40 feet in Site 1, 130 feet
in Site 2, and 110 feet in Site 3.
To what degree will the contaminated area be cleaned related to parts per
billion? In other words, when you have accomplished your major goal for
cleanup, how many parts per billion of TCE will remain in that area?
How do you determine (when the site is sufficiently clean) with no measure
in place as to what is safe?
I am concerned that (the cleanup level) to prevent further contamination in
the water table is not known.
There is no numerical regulatory standard for cleaning up deep soils for
volatile organic compounds. For the metals, we do have standards. The
State of Arizona has standards for surface soils, and there are federal
standards for groundwater, but none exist for the deep soils. The SVE
system will mitigate the contamination in the deep soils that is migrating
down to the groundwater. The risk assessment or perhaps other models
will be used to determine if there is a continued risk to human health and
the environment The final cleanup standard and the process to determine
when cleanup is complete must be established in the ROD and will be
protective of human health and the environment.
Will you allow some statement or provision to state that if these methods
do not remove as much of the volatiles as you think should be removed,
that you will alter the plan so as to do so.
The Air Force made a commitment that if the SVE process does not meet
our cleanup standards, then we will look at other technologies and either
supplement or replace it.
What happens if the Superfund runs out of money?
The Air Force does not use Superfund money to clean up historical
hazardous waste sites at facilities it owns. It uses the Defense
Environmental Restoration Account, which comes directly out of the DOD
budget.
•0576.OT
Proposed Flan andEE/CA. Sites 1,2.3,4, andS Responsiveness Summary, AFP 44. November 1995 Page 20
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10.
11.
Comment: How do you determine (when the site is sufficiently clean) with no measure
in place as to what is safe?
Response: See comment .2 above.
Comment: (What) modifications to the (Purus) systems (will be made to make it)
appropriate to the site being cleaned up?
Response: The types and concentrations of contaminants is slightly different at each
of the three sites. We will provide the Purus vendor with the site
conditions and contaminant levels, and they make a recommendation as to
the type resin we use.
Comment: How safe are the vapors going out into the air? How safe is the storage
and transport of the tanks of waste?
Response: The Purus system works at almost 99% efficiency, removing the vast
majority of TCE out of the vapor stream. What is discharged to the
atmosphere is not 100% pure, but it's pretty close. Drums or tanks for
collecting the waste will be stored in a secondary containment system to
capture any spilled fluids. Transport of the wastes will be conducted in
accordance with Department of Transportation regulations.
Comment: Where is the disposal facility (for the TCE wastes)?
Response: Different facilities are available, including but not limited to, California or
Utah. The shipments are bulked together, then run through an incineration
process at the offsite disposal facility which destroys the TCE and leaves
non-hazardous residuals.
Comment: Have (the regulators) signed off as to the vapors (being released) into the
air? (You have not signed off on transport of wastes.) They can't start
until you all sign off?
Response: Air emissions have to meet Pima County requirements. Work will not start
until the regulatory agencies approve the work plans, which provides
detailed information on operation and safety issues.
Comment: Will the wastes be hauled out of state? Do you have unit costs for
disposal?
Response: Yes, wastes will be disposed out of state. Soils with metals contamination
will be excavated and shipped off site, costing approximately $152 a ton if
it is shipped by rail. Recovered liquid VOCs will be disposed off-site at an
estimated cost of $400 per drum.
Comment: I am concerned that (the cleanup level) to prevent further contamination in
the water table is not known.
Response: See comment 2 above.
aadEr&SUa1.2.3. 4. aadSRape^iweaSummary. AFP44-November 1995 Page 21
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12. Comment:
Response:
13. Comment:
14.
15.
16.
Response:
Comment:
Response:
Comment:
Response:
Comment:
Response:
What is the projected cost of the cleanup?
Our estimate for the SVE at three sites is $17 million. The excavation and
disposal for Sites 4, 5, and 6 hotspots is approximately S4 million, totaling
about $20 million. Add to that the $60 million expenditures for
investigating, building, and operating the groundwater treatment plant, and
the total will be over $80 million.
Anything the Air Force does or proposes to do has to meet the approval of
the USEPA and the ADEQ; it this correct?
Yes.
Does the no further action at Site 6 refer to all of it or just parts of it?
The no further action at Site 6 refers to the drainage channels excluding the
areas referred to as Site .6 hotspots. The hotspots will be addressed as part
of the Site 4 removal action in conjunction with the ongoing surface
impoundment closure efforts. Site 6 requires no further action because the
drainage channels do not pose a risk. ADEQ agreed with the no further
action finding so long as the hotspots were cleaned up. The Site 6 No
Further Action report is on hold until completion of the hotspots cleanup.
Does Site 6 include the Three Hangars area?
The Three Hangars area is part of the airport property. It is not part of
AFP 44.
When will the public know the transportation routes for removal of soils?
This information is in the EE/CAs which were released for public review
and comment on 10 July 1995. The primary transportation mode will be
by rail car through Dalhart, Texas, then north to outside of Denver. At
that point they would be transferred to trucks, then hauled by truck to the
disposal facility about 80 miles northeast of Denver, Colorado area.
Proposed Plan and EEKA Sites 1,2.3, 4. and S Responsiveness Summary, AFP 44- November 199S Page 22
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RESPONSE TO COMMENT CARDS
i.
ON PROPOSED PLAN FOR SOIL CLEANUP
(JULY 1995)
Comment: Just how minimized is the exposure to residents when the procedure
(cleanup activities at Site 4) is happening?
Response: The cleanup at Site 4 will be accomplished as part of the ongoing Pond
Closure project at AFP 44. This involves excavating and shipping
approximately 63,000 tons of contaminated soils. These soils are
contaminated with heavy metals left from the industrial wastewaters that
were once put into the holding ponds in this area. The soil will be
excavated, placed in railroad gondola cars, and shipped via Southern
Pacific Railroad to a disposal site in Colorado. Many safety measures are
taken during this process to protect both the community and the workers at
AFP 44.
During excavation and loading, the soils are kept moist at all times to
prevent any dust from entering the air. Pima County DEQ does periodic
inspections, as does the Arizona DEQ. The soils are placed in the gondola
cars through a chute that has sides on it, as well as water misters, to control
dust.
The gondola cars have been reconditioned and inspected for safety and are
lined with a heavy liner that covers the soil once it is loaded. Then the
entire gondola car is covered with a heavy tarp. The cars are labeled as
hazardous waste and are tracked 24 hours a day by a computer system that
links the railroad and the disposal facility in Colorado.
The Department of Transportation heavily regulates the transport of
hazardous waste and all procedures are being carefully followed. The
waste is also registered with CHEMTREC, a national registry that has a
24-hour hotline available to give information to emergency crews in case
of a problem. Each local area through which the waste will pass has an
emergency response team on call, as does the railroad.
Every effort has been made to ensure safe transport of these soils to the
disposal facility. There is no exposure to residents from this transport.
Should an accident occur, the soils are doubly contained in wraps and tarps.
Even if the tarp or wrap should rupture in an accident, the soil is shipped
damp and would create a minimum of dust. There is no liquid or gas to
escape. Any spilled dirt can easily be recontainerized if an accident
occurred.
•CM76.WT
Propottd Plan and EE/Ci Sites I, 2,3, 4, and 5 Responsiveness Summary, AFP 44-November 1995 Page 23
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RESPONSE TO USEPA COMMENTS
ON ENGINEERING EVALUATION/COST ANALYSIS
SITES 1,2,3,4, AND 5 (JULY 1995)
1. General Comments:
Comment: USEPA strongly recommends adding either GAC or a second set of resin
beds in series to the two parallel resin beds of a Purus treatment system.
This second tier of vapor treatment would significantly reduce VOC levels
in the off-gas and practically eliminate the potential of an unwanted air
release.
Response: Results from treatability studies conducted at AFP 44 in 1995 indicate this
extra safeguard is not necessary (Site 2 and Site 3 Purus Demonstration
Letter Report, September 1995). Pima County ah* emission regulations
(Puna County Code 17.20.090 (E)) require 85 percent removal of
contaminants prior to venting the off gas to the atmosphere. Sampling
during the startup period will be performed to optimize the
adsorption/desorption process. A VOC detector permanently installed on
the effluent line will shut down the system in the event effluent VOC
concentrations that would result in an exceedance of Pima County air
emission standards, are encountered. The Purus system parameters will be
sent to ensure emissions are within this standard.
2. Comment: USEPA has published guidance on the preparation of Superfund decision
documents (PB91-921265). These guidance documents are available from
the National Technical Information Service. USEPA strongly recommends
using these documents as a resource in preparation of the upcoming ROD
for the AFP 44 Site.
Response: This guidance will be considered during development of the ROD.
•0176 RJT
Proposed Plan mtEEM Sties 1.2,3,4, and S Responsiveness Summary, AFP 44-November 1995 Page 24
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RESPONSE TO ADEQ COMMENTS
ON ENGINEERING EVALUATION/COST ANALYSIS
SITES 1,2,3,4, AND 5 (JULY 1995)
Overall Engineering Evaluation/Cost Analysis (EE/CA)
1. Page 2-5:
Comment: Should the heading of 2.1.3 be Geographic or Geologic to be consistent
with the text.
Response: The title will be changed to Installation Description, and the sentence
changed to read "A brief overview of the environmental setting..." This
is consistent with the corresponding section in the Remedial Investigation
Report.
2. Overall EE/CA, Page 2-7: See Comment 2 above (Page 1-2 of Proposed Plan):
Comment: Correct the apparent typo in the last sentence of the Public Hearing
paragraph. Also, review all documents for editorial correctness. Neither
Kitt Peak nor Mt. Hopkins is in Tucson. If the U.S. Air Force has
prepared these documents within an Quality Assurance/Quality Control
(QA/QC) program, then accurate information concerning local interests
must be supplied.
Response: The fifth sentence of the third paragraph on page 1-2 of the proposed plan
will be changed to "a transcript of the hearing...". The second sentence on
page 2-7 of the Overall EE/CA will be rephrased to read "...made their
home in the Tucson area." All documents are reviewed for editorial
correctness.
3. Overall EE/CA, Page 2-14:
Comment: The April/May 1995 groundwater pumpage data supplied by AFP 44
indicates a daily rate of 5.2 million gallons per day (mgd). Which amount
is correct? That same report shows that well E-06 does not exist and wells
E-23 and E-24 do exist.
Response: The pumping rate and wells in use will be updated using the latest
infonnation obtained from Hughes Missile Systems Company: "In July
1995, 165.7 million gallons of groundwater was treated over 706 hours,
resulting hi an average daily treatment rate of approximately 5.6 mgd. In
July 1995 the system consisted of 20 extraction wells in the upper aquifer
(E-01 through E-05, E-07, E-08, E-10, E-12 through E-21, E-23, and
E-24) and 4 extraction wells hi the lower aquifer (EL-01 through EL-04)."
•OS76RPT
Page 25
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SITE 2 EE/CA COMMENTS
Page 2-1:
Comment:
Response:
Page 2-3:
Comment:
Response:
Page 2-10:
Comment:
Response:
Page 3-1:
Comment:
Response:
How does the 7000 gallons per week for 11 years relate to the material in
the ground?
This information summarizes past waste disposal practices. As explained
on Page 2-1, the flammable liquids were burned. The amount of material
entering the ground is unknown.
Is 1,12-trichloro a typo? Also, please provide the data source to
substantiate TCE concentrations of 1,100,000 milligrams per cubic meter
(mg/m3).
The first name on page 2-3 will be changed to l,l,2-trichloro-l,2,2-
trifluoroethane. An influent vapor sample analyzed using Method TO-14
during the 1993 SVE treatability study at Site 2 resulted in a concentration
of 1,100,000 mg/m3 (Feasibility Study Report, Table 4-20).
Was nonaqueous phase liquid (NAPL) removed from the wells prior to
SVE? If NAPL were present, the data could be skewed. Was there a
subsequent confirmation of the absence or presence of NAPL in the SVE
wells?
An interface probe was used to check for NAPL approximately 2 months
after completing the Purus/SVE treatability study at Site 2. NAPL was not
detected.
Why is the spill mass unknown, when it was described in the previous
chapter? Also, how does the 250,222 pounds relate to die 626 drums per
year for seven years shown in Table 5-1 (Approx. 3,000,000 Ibs.)?
No spill mass is estimated in Chapter 2; it describes past disposal practices.
These practices included burning of flammable liquids. The amount of
material entering the ground is unknown. The estimated spill mass of
113,500 kg (250,222 pounds) presented on Page 3-1 is a very rough
estimate of the amount of material hi the ground. This quantity of material
would fill approximately 626 55-gallon drums. Table 5-1 shows the total
number of drums over the lifetime of the project. It is anticipated that large
amounts of VOCs will be recovered from Site 2 initially, and that the
amount of VOCs removed will decrease over time as the site is cleaned up.
For costing purposes, the number of drums in Table 5-1 will be changed
to 90 drums annually. This is an average obtained by dividing 626 (the
estimated total number of drums) by the estimated project duration (7
years).
•0574 art
Proposed Plan andEEKA Sties 1.2,3. 4. anil 5 Kespenavenai Summary. AFP 44- November 1995 Page 26
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5. Page 5-1:
Comment: Providing a number of wells (69) is inconsistent with the fourth sentence
in that same paragraph. Is the number of wells predetermined? They
should be based upon the field findings.
Response: The first sentence in Section 5.1.1 on page 5-1 will be changed to "This
SVE alternative requires installation of an estimated 69 SVE piezometer
nests."
6. Comment: Is the TCE disposal cost a typo? How does this relate to the spill mass
estimate?
Response: The disposal cost will be recalculated based on the revised number of
drums being generated as discussed in the response to ADEQ Comment 4.
Propped Pian ,nd EESCA Site 1, 2,3. 4, and S Responsive**: Summary, AFP 44. November 1995 Page 27
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APPENDIX A
"* v-'-Vt-S1:***,"?'^- >'" ••" t "'•* *-•* '• ."-•' .V*. '• >•• • * *»'***,•-/•* *ii'
'>•. . — -y Jsvjjf"iij^Vt,r..* -.". \:P':%fy'*'£'*r.-\i*\££?' '. •* " ' "•'j.'Xj'" '; 'i^1
!^M
«mi/ A«on/ of Decision for Soil CUantrp ofSiut 4, S, and 6 - September 1998
•LAAB'il-IVI007UA-l\SITES4-l\WW)6J9«6J»RPTI.Wro
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APPENDIX A
1. The Earth Technology Corporation, Feasibility Study Report, U.S. Air Force Plant 44,
Tucson, Arizona, January 1995.
2. Tischler/Kocurek, Historic Waste Management Sites Potential Effects of Soil Contamination
on Ground water, July 1994.
3. USEPA, Tucson International Airport Area Superfund Site Record of Decision (ROD),
September 1997.
4. EARTH TECH, No Further Action Report for Site 7, U.S. Air Force Plant 44, Tucson,
Arizona, September 1994.
5. EARTH TECH, No Further Action Report for Site 8, U.S. Air Force Plant 44, Tucson,
Arizona, September 1994.
6. EARTH TECH, No Further Action Report for Site 9, U.S. Air Force Plant 44, Tucson,
Arizona, September 1994.
7. EARTH TECH, No Further Action Report for Site 15, U.S. Air Force Plant 44,
Tucson, Arizona, September 1994.
8. U.S. Environmental Protection Agency, Record of Decision, Air Force Plant 44, 1986.
9. IT Corporation, Management Action Plan, Air Force Plant 44, December 1995.
10. Flood Insurance Rate Map prepared by the Federal Emergency Management Agency for
Pima County, Arizona (unincorporated areas).
11. EARTH TECH, Remedial Investigation Report, U.S. Air Force Plant 44, Tucson, Arizona,
January 1994.
12. EARTH TECH, Investigation of Geophysical Anomalies Report, U.S. Air Force Plant 44,
Tucson, Arizona, September 1995.
13. The Earth Technology Corporation, Risk Assessment Report, Air Force Plant 44, Tucson,
Arizona, August 1993.
Final Record ofDetttianfar Soil Cleanup cfSlta 4, S, and 6 - September 1998
PageA-1
-------
14. EARTH TECH, Proposed Plan for Soil Cleanup, Air Force Plant 44, Tucson, Arizona,
November 1995.
15. EARTH TECH, Engineering Evaluation/Cost Assessments (Overall), Air Force Plant 44,
Tucson, Arizona, November 1995.
16. EARTH TECH, Engineering Evaluation/Cost Assessments (Site 1), Air Force Plant 44,
Tucson, Arizona, November 1995.
17. EARTH TECH, Engineering Evaluation/Cost Assessments (Site 2), Air Force Plant 44,
Tucson, Arizona, November 1995.
18. EARTH TECH, Engineering Evaluation/Cost Assessments (Site 3), Air Force Plant 44,
Tucson, Arizona, November 1995.
19. EARTH TECH, Engineering Evaluation/Cost Assessments (Site 4), Air Force Plant 44,
Tucson, Arizona, November 1995.
20. EARTH TECH, Engineering Evaluation/Cost Assessments (Site 5), Air Force Plant 44,
Tucson, Arizona, November 1995.
21. EARTH TECH, Sites 4 and 5, and Site 6 Hotspots Non-time Critical Removal Action Work
Plan, October 1995.
22. EARTH TECH, Record of Decision, Sites 1,2, and 3, Air Force Plant 44, Tucson, Arizona,
April 1997.
23. Holmes and Narver, Documentation of Removal Action at IRP Site 4 East, US AF Plant No.
44, Tucson, Arizona, October 1996.
24. EARTH TECH, No Further Action Report for Site 6, U.S. Air Force Plant 44, Tucson,
Arizona, October 1995.
25. U.S. Environmental Protection Agency, Risk Assessment Guidance for Superfund, Volume
I, Human Health Evaluation Manual Part B Development of Risk-based Preliminary
Remediation Coals, December 1991.
26. Hargis & Associates, Inc., Draft Results of Shallow Soil Gas Survey, Installation Program
Site 5 Former Sludge Drying Beds, U.S. Air Force Plant 44, Hughes Missile Systems
Company, Tucson, Arizona, June 1997.
Final Recant ofDtdtion for Soil Cleanup of Slut 4, 5, and 6 - Stpumbtr 1998
•LAAH>*ui\ioo70A-nsrrBs«-nwpwuw)6j9RfTi.wro Page A-2
-------
27. Holmes and Narver, Removal Action Completion Report, IRP Site 5, U.S. Air Force Plant
No. 44', Tucson, Arizona, August 1997.
28. Earth Tech, Draft Supplemental Investigation Report for Activities West of IRP Site 5, Air
Force Plant 44, Tucson, Arizona, April 1998.
29. Operation and Maintenance Manual for SVE Systems at IRP Sites 1, 2, and 3, Air Force
Plant 44, Tucson, Arizona, January 1995.
Final Record of Decision for Soil CUanup of Sites 4, 5. and 6 • September 1998
PageA-3
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APPENDIX B
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U-1
TRICHCOROETHYLENE
CONCENTRATION
REGIONAL. AQUIFER
UPPER ZONE
FIRST QUARTER I99S
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