PB97-964515
EPA/541/R-97/137
January 1998
EPA Superfund
Record of Decision:
Tucson International Airport Area (Vols 1 & 2)
Tucson, AZ
9/30/1997
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RECORD OF DECISION
TUCSON INTERNATIONAL AIRPORT AREA
SUPERFUND SITE
TUCSON, ARIZONA
AIRPORT PROPERTY -
SOILS AND SHALLOW GROUNDWATER ZONE
BURR-BROWN PROPERTY - SOILS
FORMER WEST-CAP PROPERTY - SOILS
Volume 1
September 1997
vvEPA
United States Environmental Protection Agency
Region 9 - San Francisco, California
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Declaration
Site Name and Location
This Record of Decision (ROD) addresses the contamination at the Tucson International
Airport Property (hereafter referred to as the "Airport Property")/ Burr-Brown Corporation
property (Burr-Brown Property) and the former West-Cap Arizona Company property
(former West-Cap Property) located within the Tucson International Airport Area
Superfund Site in Tucson, Arizona (TIAA Site). These three properties are referred to
herein as the ROD Site.
Statement of Basis and Purpose
This ROD presents the selected remedial action for the Airport, Burr-Brown and former
West-Cap properties (ROD Site) located within the TIAA Site chosen in accordance with the
Comprehensive Environmental Response, Compensation and Liability Act of 1980,42
U.S.C. §§ 9601 et seq., as amended by the Superfund Amendments and Reauthorization Act
of 1986 (SARA) (collectively referred to herein as CERCLA) and, to the extent practicable,
the National Oil and Hazardous Substances Pollution Contingency Plan, 40 CFR Part 300
(NCP). This decision is based on the Administrative Record for this site.
The State of Arizona, acting through the Arizona Department of Environmental Quality,
concurs with the selected remedy.
Assessment of the Site
Actual or threatened releases of hazardous substances from the ROD Site, if not addressed by
implementing the response action selected in this ROD, may present an imminent and
substantial endangerment to public health, welfare, or the environment.
Description of the Remedy
This ROD addresses soils and shallow groundwater contaminated with volatile organic
compounds (VOCs), soils and sludges contaminated with polychlorinated biphenyls (PCBs),
and closure of the Tucson Airport Authority Landfill (TAA Landfill). The specific areas and
media covered by this ROD include contaminated soil and shallow groundwater at the
Airport Property and contaminated soils at Burr-Brown Property and at the former West-
Cap Property. These facilities are part of the TIAA Site.
Several groundwater and soil remediation projects have already been implemented and are
currently operating in other portions of the TIAA Site (pursuant to prior RODs). The United
States Environmental Protection Agency (EPA) will propose measures to address the
remaining groundwater contamination in other portions of the TIAA Site, not covered by
this ROD or previous RODs, at a later date.
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Airport Property
VOC-Contaminated Soils
Soil Vapor Extraction (SVE) is the selected remedy to remediate soil at subsites in Area 1 (in
the vicinity of the Three Hangars Area), where contaminant levels in soil exceed levels that
will potentially cause groundwater to exceed the groundwater cleanup standards set forth
in this ROD (i.e., Safe Drinking Water Act [SDWA] maximum contaminant levels [MCLs]).
The SVE system will continue to operate until contaminants are reduced to concentrations
that will not result in impacts to groundwater above such cleanup standards.
The extracted vapors will be treated to remove or destroy VOCs. Treatment will be
accomplished using one or a combination of the following options: thermal oxidation,
catalytic oxidation, resin adsorption, and vapor phase carbon adsorption. At several
locations outside Area 1 (away from the Three Hangars Area), soil investigations have not
been completed. At these locations or "subsites", EPA will use the Plug-in Approach
(described below) to determine which subsites need to be added to the SVE remedy and
which do not require a cleanup action.
Plug-in Approach
The Plug-in Approach allows multiple, similar, but separate subsites (areas within the
larger site) to make use of the same remedy at different times. Under this approach, EPA
selects a standard remedy that applies to a given set of conditions and defines a process and
set of criteria for determining where those conditions exist. In this case, EPA's presumptive
remedy is SVE. The subsites are characterized at some time after the date of this ROD, then
EPA makes subsite-specific determinations whether or not the subsites should "plug-in" to
an SVE remedy.
PCB-Contaminated Soils and Sludges
All pipeline sludges and soils contaminated with PCBs above 0.76 mg/kg (the State soil
cleanup standard for non-residential properties) will be excavated using standard
excavation equipment such as backhoes and front-end loaders. Excavated soil will be
hauled to a permanent off-site landfill for disposal. Soils containing metals may be treated
by solidification either on-site or at the off-site landfill.
TAA Landfill
This solid waste landfill will be closed in accordance with State of Arizona RCRA Subtitle D
requirements. Closure activities include: grading the landfill so that it has a smooth but
sloped surface, placing and compacting a two-foot thick (minimum) cap and seeding the
cap with drought-resistant vegetation to minimize erosion. A closure and post-closure
monitoring program will be required in accordance with landfill closure regulations.
Shallow Groundwater Zone
The selected remedy for VOC-contaminated groundwater from the shallow groundwater
zone will inhibit contaminant migration into the Regional Aquifer. Outside of the TI Zone
(discussed below), groundwater will be extracted and treated to attain drinking water
standards (MCLs) in situ and will hydraulically inhibit any contaminant migration. In
accordance with EPA's Guidance for Evaluating the Technical Impracticability of Ground-Water
Restoration, dated September 1993, EPA has determined that it is technically impracticable
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to restore the shallow groundwater zone to cleanup levels (MCLs) within a defined two-
acre zone located within the shallow groundwater zone referred to as the Technical
Impracticability [TI] Zone. Because the groundwater cleanup standards are based upon
applicable or relevant and appropriate requirements (ARARs), this ROD includes an
ARARs waiver for in situ cleanup standards within the defined TI Zone. To ensure,
however, that the remedy remains protective of human health and the environment, the
remedy in the TI Zone will employ hydraulic containment to prevent migration of
contamination outside of the TI Zone. Extraction will continue indefinitely in the TI Zone,
unless alternative remediation technologies or processes can be developed during remedy
implementation.
All extracted groundwater will be conveyed to either a new treatment facility to be
constructed on Airport Property or to United States Air Force (USAF) Plant No. 44, for
treatment prior to disposal. Treatment options include: air stripping (at either a new plant
located on the Airport Property or at the existing plant at USAF Plant 44), carbon
adsorption (either alone or in combination with air stripping), and ultraviolet destruction
and ozonation (in combination with air stripping or carbon adsorption). EPA will approve
the final configuration of the treatment process during remedial design. Any treatment
residuals that contain unacceptable levels of VOCs would be treated further or disposed of
off-site.
A groundwater monitoring program will be implemented to ensure that hydraulic
containment is achieved and that performance standards are being met. Institutional
controls will be established as appropriate to prevent exposure to contaminated
groundwater.
Burr-Brown Property
VOC-Contaminated Soil
EPA has determined that the low levels of VOCs in soils at the Burr-Brown Property do not
pose a risk to human health or groundwater quality, and, therefore, no soil cleanup action is
needed. Burr-Brown Corporation will continue to operate its groundwater treatment
system pursuant to the Groundwater ROD, dated 1988.
Former West-Cap Property
VOC-Contaminated Soils
The soil investigation is continuing at the former West-Cap Property. Upon completion of
the investigation, EPA will use the above-described Plug-in approach to determine whether
soils at subsites on the Former West-Cap Property require response action and are suitable
for "Plug-in" to the SVE remedy.
Statutory Determinations
The selected remedy is protective of human health and the environment, complies with
federal and state requirements that are legally applicable or relevant and appropriate to the
remedial action, and is cost-effective. This remedy utilizes permanent solutions and
alternative treatment technologies to the maximum extent practicable. Components of the
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selected remedy satisfy the statutory preference for remedies that employ treatment that
reduces toxicity, mobility, or volume as a principal element. As EPA has determined that it
is technically impracticable to treat a defined 2-acre area within the shallow groundwater
zone to the in-situ groundwater cleanup standards set forth in this ROD, EPA has waived
certain ARARs within the TI Zone.
Therefore, consistent with EPA TI guidance (cited above), the remedy uses a groundwater
pump-and-treat system to contain the TI Zone and prevent migration out of the TI Zone.
Because this remedy will result in hazardous substances remaining onsite above health-
based levels, a review will be conducted at least once every 5 years after commencement of
remedial action to ensure that the remedy continues to provide adequate protection of
human health and the environment.
Keith A. Takata Date
Director of Superfund Division
U.S. Environmental Protection Agency, Region IX
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Contents
Section
Part I Decision Summary
1.0 Site Location and Description 1
1.1 Location and Topography '. 1
1.2 Climate '.. 1
1.3 Land Use 2
1.3.1 Airport Property
1.3.2 Burr-Brown Corporation Property
1.3.3 Former West-Cap Property
1.4 Surface Water 3
1.5 Geology and Hydrogeology 4
1.5.1 Geology
1.5.2 Airport Property Hydrogeologic Characteristics
1.5.3 Burr-Brown Property
1.5.4 Former West-Cap Property
2.0 ROD Site History 6
2.1 Overview of ROD Site Activities 6
2.2 Remedial Investigation Activities at the Airport Property 7
2.2.1 Three Hangars Investigation
2.2.2 Field Reconnaissance Investigation
2.2.3 Canale Sampling Program
2.2.4 Preliminary Site Characterization Study
2.2.5 Remedial Investigation (RI)
2.2.6 Preliminary Feasibility Evaluation
2.2.7 Vadose Zone Treatability Study
2.2.8 Site-Specific Zone Disposition at the Airport Property
2.3 Remedial Investigation Activities at the Burr-Brown Corporation Property 10
2.4 Remedial Investigation Activities at the Former West-Cap Property 11
2.5 Prior Remedial Actions 11
3.0 Enforcement Activities 11
3.1 Administrative Orders 13
4.0 Scope and Role of this Document with the TIAA Site Strategy 13
5.0 Highlights of Community Participation 14
6.0 Summary of Site Characteristics 15
6.1 Zone C: Hughes Credit Union Dump 16
6.2 Zone D: South Ramp and Drains 16
6.3 Zone D: Fire Drill Area D-3 and C-294 Bum Pit 16
6.4 Zone D: TAA Landfill 17
6.5 Zone E: Buildings 14/15 and Buildings 16/17 18
6.6 Zone E: Building 18 18
TIAA SITE RECORD OF DECISION PAGEI-I
CONTENTS SAC/I 10331/004.000
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Contents
6.7 Zone E: Structures 21 and 30 18
6.8 Zone E: Building 25 and Adjacent Soils (and southern portion of Building 24). 19
6.9 Zone E: Former Building 32 20
6.10 Zone E: Soils Beneath West Lease USTs 20
6.11 Zone E: Sludges in the Canale System and Soils Adjacent to Canale 20
6.12 Zone E: Drainages and Ponding Areas 21
6.13 Zone E: Building D-158 and the North and East Sides of Hangar 1 22
6.14 Zone E: Hangar 1 Drains 23
6.15 Zone E: South Portion of Hangar 2 23
6.16 Zone E: West End of Runway 3 24
6.17 Zone E: Shallow Groundwater Zone 25
" 6.17.1 Summary of Shallow Groundwater Zone Investigations
6.18 Zone F: East Side of Hamilton Aviation Buildings D-252, D-267, and D-275... 27
6.19 Zone F: North End of Samsonite Building D-167 28
6.20 Burr-Brown Corporation Property 29
6.21 Former West-Cap Property 29
7.0 Summary of Site Risks 30
7.1 Identification of Chemicals of Potential Concern 30
7.2 Exposure Assessment 30
7.2.1 Potentially Exposed Populations
7.2.2 Chemical Exposure Pathways
7.2.3 Exposure Quantification
7.3 Toxicity Assessment 33
7.4 Risk Characterization Summary 34
7.4.1 Summary of Estimated Risk - Current Conditions
7.4.2 Summary of Estimated Risk - Future Conditions
7.4.3 Baseline Human Health Risk Assessment Conclusion
7.4.4 Ecological Risk Summary
8.0 Description of Remedial Alternatives 36
8.1 VOC-Contaminated Soils Outside Area 1 (Plug-in Sites) 37
8.1.1 Alternative Al - No Action
8.1.2 Alternative A2 - Institutional Controls and Monitoring
8.1.3 Alternative A3 - Soil Vapor Extraction (SVE)
8.2 VOC-Contaminated Soils Inside Area 1 39
8.3 VOC-Contaminated Soils Inside The TI Zone 39
8.4 PCB-Contaminated Soils and Sludges 40
8.4.1 Alternative Dl - No Further Action
8.4.2 Alternative D2 - Institutional Controls and Monitoring
8.4.3 Alternative D3 - Excavation and Off-Site Landfilling
8.4.4 Alternative D4 - Excavation and On-Site Landfilling
8.4.5 Alternative D5 - Excavation, Treatment and On-Site Landfilling
8.4.6 Alternative D6 - Excavation, Treatment and Off-Site Landfilling
8.5 TAA Landfill Closure 41
8.5.1 Alternative El - No Action
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Contents
8.5.2 Alternative E2 - Institutional Controls and Monitoring
8.5.3 Alternative E3 - Landfill Closure
8.6 Shallow Groundwater (Outside the TI Zone) 42
8.6.1 Alternative Fl - No Action
8.6.2 Alternative F2 - Institutional Controls and Monitoring
8.6.3 Alternative F3 - Bioaugmentation
8.6.4 Alternative F4 - Air Sparging
8.6.5 Alternative F5 - Extraction, Ex-situ Treatment, Bioaugmentation and
' Discharge
8.7 Shallow Groundwater Zone Inside the TI Zone 45
9.0 Summary of Comparative Analysis of Alternatives 45
9.1 Overall Protection of Human Health and the Environment 47
9.1.1 VOC-Contaminated Soils Outside Area 1 (Plug-In Subsites)
9.1.2 VOC-Contaminated Soils Inside Area 1
9.1.3 VOC-Contaminated Soils Inside the TI Zone
9.1.4 PCB-Contaminated Soils and Sludges
9.1.5 TAA Landfill Closure
9.1.6 Shallow Groundwater (Outside the TI Zone)
9.1.7 Shallow Groundwater Inside the TI Zone
9.2 Compliance with ARARs 49
9.2.1 VOC-Contaminated Soils Outside Area 1 (Plug-In Subsites)
9.2.2 VOC-Contaminated Soils Inside Area 1
9.2.3 VOC-Contaminated Soils Inside the TI Zone
9.2.4 PCB-Contaminated Soils and Sludges
9.2.5 TAA Landfill Closure
9.2.6 Shallow Groundwater (Outside the TI Zone)
9.2.7 Shallow Groundwater Inside the TI Zone
9.3 Long-Term Effectiveness and Permanence 50
9.3.1 VOC-Contaminated Soils Outside Area 1 (Plug-In Subsites)
9.3.2 VOC-Contaminated Soils Inside Area 1
9.3.3 VOC-Contaminated Soils Inside the TI Zone
9.3.4 PCB-Contaminated Soils and Sludges
9.3.5 TAA Landfill Closure
9.3.6 Shallow Groundwater (Outside the TI Zone)
9.3.7 Shallow Groundwater Inside the TI Zone
9.4 Reduction of Toxiciry, Mobility and Volume Through Treatment 51
9.4.1 VOC-Contaminated Soils Outside Area 1 (Plug-In Subsites)
9.4.2 VOC-Contaminated Soils Inside Area 1
9.4.3 VOC-Contaminated Soils Inside the TI Zone
9.4.4 PCB-Contaminated Soils and Sludges
9.4.5 TAA Landfill Closure
9.4.6 Shallow Groundwater (Outside the TI Zone)
9.4.7 Shallow Groundwater Inside the TI Zone
TIM SITE RECORD OF DECISION PAGE 1-111
CONTENTS
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Contents
9.5 Short-Term Effectiveness 53
95.1 VOC-Contaminated Soils Outside Area 1 (Plug-In Subsites)
9.5.2 VOC-Contaminated Soils Inside Area 1
95.3 VOC-Contaminated Soils Inside the TI Zone
9.5.4 PCB-Contaminated Soils and Sludges
9.5.5 TAA Landfill Closure
9.5.6 Shallow Groundwater (Outside the TI Zone)
9.5.7 Shallow Groundwater Inside the TI Zone
9.6 Implementability '. 54
9.6.1 VOC-Contaminated Soils Outside Area 1 (Plug-In Subsites)
9.6.2 VOC-Contaminated Soils Inside Area 1
9.6.3 VOC-Contaminated Soils Inside the TI Zone
9.6.4 PCB-Contaminated Soils and Sludges
9.6.5 TAA Landfill Closure
9.6.6 Shallow Groundwater (Outside the TI Zone)
9.6.7 Shallow Groundwater Inside the TI Zone
9.7 Cost 55
9.8 State Acceptance 55
9.9 Community Acceptance 55
10.0 Selected Remedy 55
10.1 VOC-Contaminated Soils 58
10.1.1 VOC-Contaminated Soils outside Area 1 (Remedy Plug-In Subsites)
10.1.2 VOC-Contaminated Soils Inside Area 1 (Remedy-Required Subsites)
10.1.3 VOC-Contaminated Soils In the TI Zone
10.1.4 VOC-Contaminated Soil at Burr-Brown Corporation (No Further
Action)
10.1.5 Former West-Cap Property Soils (Plug-In Subsite)
10.1.6 SVE Off-Gas Treatment
10.1.7 SVE Enhancements
10.2 PCB-Contaminated Soils and Sludges 67
10.2.1 Performance Standards for PCB-Contaminated Soil Cleanup
10.3 TAA Landfill Closure 68
10.3.1 Performance Standards for TAA Landfill Closure
10.4 VOC Contamination Within the Shallow Groundwater Zone 68
10.4.1 VOC-Contaminated Shallow Groundwater Outside the TI Zone
10.4.2 VOC-Contaminated Shallow Groundwater in the TI Zone
10.4.3 Groundwater Treatment
10.4.4 Treated Water Discharge
10.5 Cost of the Selected Remedy 72
11.0 Applicable or Relevant and Appropriate Requirements (ARARs) 73
11.1 VOC-Contaminated Soil Remedy ARARs 74
11.1.1 VOC-Contaminated Soil Remedy - Chemical-Specific ARARs
11.1.2 VOC-Contaminated Soil Remedy - Location-Specific ARARs
11.1.3 VOC-Contaminated Soil Remedy - Action-Specific ARARs
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Contents
11.2 PCB-Contaminated Soils and Sludges Remedy ARARs 76
11.2.1 PCB-Contaminated Soils and Sludges - Chemical-Specific ARARs
11.2.2 PCB-Contaminated Soils and Sludges - Location-Specific ARARs
11.2.3 PCB-Contaminated Soils and Sludges - Action-Specific ARARs
11.3 TAA Landfill Closure Remedy ARARs 77
11.3.1 TAA Landfill Closure - Chemical-Specific ARARs
11.3.2 TAA Landfill Closure - Location-Specific ARARs
11.3.3 TAA Landfill Closure - Action-Specific ARARs
11.4 VOC-Contaminated Shallow Groundwater Remedy ARARs 78
11.4.1 VOC-Contaminated Shallow Groundwater - Chemical-Specific
ARARs
11.4.2 VOC-Contaminated Shallow Groundwater - Location-Specific ARARs
11.4.3 VOC-Contaminated Shallow Groundwater - Action-Specific ARARs
11.5 Other Legal Requirements 79
11.6 ARAR Waiver - Technical Impracticability 80
11.6.1 Spatial Identification of the TI Waiver Area
11.6.2 Hydrogeologic Factors
11.6.2 Contaminant-Related Factors
12.0 Documentation of Significant Changes 83
13.0 Statutory Determinations 83
13.1 Protection of Human Health and the Environment 83
13.2 Compliance with ARARs 84
13.3 Cost-Effectiveness 84
13.4 Utilization of Permanent Solutions and Alternative Treatment Technologies to
the Maximum Extent Practicable 85
13.5 Preference for Treatment as a Principal Element 85
13.6 Five Year Reviews 85
14.0 References 86
TlAA SITE RECORD OF DECISION PAGE i-v
CONTENTS
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Contents
Tables
Table 1 Site Summary Following the Remedial Investigation
Table 2 Chemicals of Potential Concern for Soil, Soil Gas, and Groundwater
Table 3 Estimated Site-Related Cancer Risk and Non-Cancer hazard Index - Current
Conditions
Table 4 Estimated Site-Related Cancer Risk and Non-Cancer hazard Index - Future
Conditions
Table 5 Comparison of Costs
Table 6 Selected Performance Standards, Cleanup Standards, and Discharge
Standards for Groundwater
Table 7 TCLP Regulatory Standards
Table 8 Selected Remedy Cost Estimate Summary
Table 9a Chemical-specific ARARs for VOC-Contaminated Soil
Table 9b Location-specific ARARs for VOC-Contaminated Soil
Table 9c Action-specific ARARs for VOC-Contaminated Soil
Table lOa Chemical-specific ARARs for PCB-Contaminated Soils and Sludges
Table lOb Location-specific ARARs for PCB-Contaminated Soils and Sludges
Table lOc Action-specific ARARs for PCB-Contaminated Soils and Sludges
Table lla Location-specific ARARs for TAA Landfill Closure
Table 1 Ib Action-specific ARARs for TAA Landfill Closure
Table 12a Chemical-specific ARARs for VOC-Contaminated Shallow Groundwater
Table 12b Location-specific ARARs for VOC-Contaminated Shallow Groundwater
Table 12c Action-specific ARARs for VOC-Contaminated Shallow Groundwater
Table 13 Groundwater Cleanup ARARs to be Waived in the TI Zone
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CONTENTS
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Contents
Figures
Figure 1 Tucson International Airport Area Superfund Site
Figure 2 Location of the Three Properties Addressed by this ROD
Figure 3 Airport Property Investigation Zones
Figure 4 Burr-Brown Corporation Property
Figure 5 Former West-Cap Property
Figure 6 Geologic Cross Section of the Zone E Three Hangars Area
Figure 7 Conceptual Model for Zone E
Figure 8 VOC-Contaminated Soils Subsites
Figure 9 PCB-Contaminated Soils and Sludges Subsites and the TAA Landfill
Figure 10 Water Elevation Contours - Shallow Groundwater Zone - May 1996
Figure 11 TI Zones and VOC Contamination in the Shallow Groundwater Zone
Figure 12 Approximate Limit of the TAA Landfill Cap
TIAA SITE RECORD OF DECISION PAGE i-vn
CONTENTS SAC/I 10331/004.000
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Contents
List of Acronyms and Abbreviations
AAC Arizona Administrative Code
AANG Arizona Air National Guard
ADEQ Arizona Department of Environmental Quality
ADHS Arizona Department of Health Services
ARAR Applicable or Relevant and Appropriate Requirement
ARS Arizona Revised Statutes
BACT Best Available Control Technology
BGS Below Ground Surface
CAA Clean Air Act
CERCLA Comprehensive Environmental Response Compensation and Liability Act
CFR Code of Federal Regulations
COPC Chemicals of Potential Concern
CRA Conestoga-Rovers and Associates
DBS&A Daniel B. Stephens & Associates
DCA Dichloroethane
DCE Dichloroethene
DCP Dichloropropane
DNAPL Dense Non-Aqueous Phase Liquid
EDR Existing Data Report
EPA United States Environmental Protection Agency
ESGSL Exponential Soil Gas Screening Level
FAA Federal Aviation Administration
FR Field Reconnaissance
FS Feasibility Study
GMP Groundwater Management Plans
HBGL Health-Based Guidance Levels
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TIAA SITE RECORD OF DECISION
CONTENTS
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Contents
List of Acronyms and Abbreviations
LDR Land Disposal Restrictions
MCL Maximum Contaminant Level
MCLG Maximum Contaminant Level Goal
MEK Methyl Ethyl Ketone
MPSG/GW Multi-port Soil Gas/Groundwater
NAAQS National Ambient Air Quality Standards
NAPL Non-Aqueous Phase Liquid
NCP National Oil and Hazardous Substances Pollution Contingency Plan
NFA No Further Action
NPL National Priorities List
OSWER Office of Solid Waste and Emergency Response
PCB Polychlorinated Biphenyl
PCE Tetrachloroethene
POTW Publicly-owned Treatment Works
PRG Preliminary Remediation Goal
PRP Potentially Responsible Party
PSCS Preliminary Site Characterization Study
PSD Prevention of Significant Deterioration
RACT Reasonably Available Control Technology
RAO Remedial Action Objective
RCRA Resource Conservation and Recovery Act
RI Remedial Investigation
RI/FS Remedial Investigation/Feasibility Study
RME Reasonable Maximum Exposure
ROD Record of Decision
SARA Superfund Amendments and Reauthorization Act
SDWA Safe Drinking Water Act
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Contents
List of Acronyms and Abbreviations
SGSL Soil Gas Screening Level
SGZ Shallow Groundwater Zone
SVE Soil Vapor Extraction
SVOC Semivolatile Organic Compound
TAA Tucson Airport Authority
TARP Tucson Airport Remediation Project
TBC To Be Considered
TCA Trichloroethane
TCE Trichloroethylene
TCLP Toxicity Characteristic Leaching Procedure
TI Technical Impracticability
TIA Tucson International Airport
TIAA Tucson International Airport Area
TSCA Toxic Substances Control Act
UAO Unilateral Administrative Order
UCAB Unified Community Advisory Board
USAF United States Air Force
UST Underground Storage Tank
VEMUR Voluntary Environmental Mitigation Use Restriction
VOC Volatile Organic Compound
XRF X-ray Fluorescence
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Contents
VOLUME 2
Section Page
Part II Responsiveness Summary
Responses to Written Comments 1
Responses to Comments from the Arizona Department of Environmental Quality... 1
Responses to Comments from FRx Company 3
Responses to Comments from Community Resident 3
Responses to Comments from Hughes Missile Systems Company 4
Responses to Comments from the City of Tucson Department of Transportation 8
Responses to Comments from the Unified Community Advisory Board 8
Appendix A-Transcript of Proceedings, July 22,1997 Public Meeting
Appendix BTranscript of Proceedings, July 23,1997 Public Meeting
Tables
Table 1 Arizona Department of Environmental Quality Applicable or Relevant and
Appropriate Requirements (ARARs) Comments
TIAA SITE RECORD OF DECISION PAGE i-xi
CONTENTS VOLUME 1 SAC/I 10031 AXM.DOC
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Parti
Decision Summary
1.0 Site Location and Description
This Record of Decision (ROD) covers three separate properties within the Tucson
International Airport Area (TIAA) Superfund Site. The overall TIAA Site is depicted in
Figure 1. The three properties included in this ROD are shown in Figure 2 and include the
Airport Property, the Burr-Brown Corporation property (Burr-Brown Property) and the
former West-Cap Arizona Company property (former West-Cap Property). These three
properties are collectively referred to as the "ROD Site."
The Airport Property includes all portions of the TIAA Site that are or were owned by,
leased to, or otherwise operated or controlled by the Tucson Airport Authority or its
predecessors, any areas onto or into which contaminants from such property may have
come to be located, and any other areas necessary for the response action, but specifically
excluding the area operated by the Arizona Air National Guard (AANG).
The other two properties included in the ROD Site are located adjacent to the northeast
portion of the Airport Property (Figure 2). The Burr-Brown Property is located at 6730
South Tucson Boulevard and the former West-Cap Property is located at 2207 East Elvira
Road.
1.1 Location and Topography
The ROD Site covers approximately 5.0 square miles and is located on the south side of the
City of Tucson, Arizona and is bounded, approximately, by Highway 89 (to the west),
Hughes Access Road (to the east and south) and Los Reales Road and Valencia Road (to the
north). Figure 2 illustrates the location of the ROD Site.
The ROD Site consists of industrial properties, however, residential and commercial
properties are located in the immediate vicinity of the site.
1.2 Climate
The climate of Tucson, Arizona is semi-arid with an average of between 10 and 11 inches of
rainfall annually. Annual evaporation is about four times greater than the average annual
precipitation. High temperatures in the summer average about 100 degrees Fahrenheit.
Winter high temperatures average in the upper 60s. The average annual wind speed in the
Tucson area is about 8 miles/hour.
TIAA SITE RECORD OF DECISION PAGE 1-1
PART I-DECISION SUMMARY SAC/I 10331/003.000
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1.3 Land Use
1.3.1 Airport Property
The airport property consists of the active airport and other industrial uses. These land uses
are expected to remain the same in the future.
The first industrial operations at the Airport Property began in 1940 in the area known as
the "Three Hangars Complex" on the west side of the Airport Property. From 1942 to I960,
the Three Hangars Complex was used by large-scale military contractors for aircraft
maintenance, repair, and modification. More recently, other aircraft-related firms have
occupied the property. Trichloroethylene (TCE) and other solvents, fuels, metal-plating
chemicals, hydraulic fluids, and Polychlorinated Biphenyl (PCB)-containing transformers
were used in these industrial operations.
As part of the remedial investigation/feasibility study (RI/FS), the Airport Property portion
of the ROD Site was divided into six zones based on geographical location, historical
activities, and natural or manmade boundaries. These zones are shown in Figure 3. A brief
description of each zone is as follows:
Zone A- Zone A is the general aviation and terminal area of the site. It includes the Hangar
10 area, Hudgin Air Service site, the general aviation area, the Tucson Airport Authority
(TAA) maintenance facility, the Tucson International Airport terminal complex in the
northeast portion of the Site and the Airport Wash north of the perimeter road. Activities in
the Hangar 10 structure, located in the northeastern portion of the Airport Property,
included a motor home manufacturing facility; aircraft storage, maintenance, overhaul,
repair, sale and rental; pilot training; and hangar space leasing.
ZoneB- Zone B is located on the southeast portion of the Airport Property. It includes the
air cargo apron, the former fire training facility, and the future general aviation area.
Zone C- Zone C is the industrial development area and is located in the southwest section
of the Airport Property. Several historical dumps occupy this area, as do several United
States Air Force (USAF) Plant No. 44 buildings where aircraft-related activities occurred.
ZoneD- Zone D is the South Ramp industrial area, located on the west side of the Airport
Property. The south ramp area is located between Aero Park Boulevard and Runway 3,
immediately east of the Learjet, Inc. Facility. This area was initially used as a B-47 aircraft
storage location and a work area for a B-47 modification program.
The TAA Landfill occupies a portion of Zone D.
Zone E- Zone E includes the Three Hangars area and the South Apron and was at one time
expanded to include those areas where PCBs have been detected in shallow soil samples to
the west of the Nogales Highway. The Three Hangars area was used for aircraft
modification operations between 1942 and 1960. After 1960, it was used by a number of
tenants performing a variety of industrial activities including general aircraft and vehicle
maintenance, synthetic rubber and plastics manufacturing and charter services.
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Several other building structures are located in Zone E that contain small businesses
involved in such things as aircraft maintenance, overhaul and repair, sandblasting, and
degreasing of aircraft parts prior to plating.
The South Apron area was the location of several activities involving chemical use, storage,
and disposal, including cleaning, decocooning, maintenance modification and painting of
aircraft.
Zone F- Zone F is located in the northwest corner of the Airport Property and includes the
North Apron and the former Sunnyside Property, which is currently owned by TAA.
Buildings in this zone have been occupied by various tenants, most of which were involved
in aircraft maintenance support industries or electronics.
1.3.2 Burr-Brown Property
The Burr-Brown Corporation, located at 6730 South Tucson Boulevard (Figure 4), has been
in the area since 1965. Burr-Brown is a major manufacturer of microelectric components.
The company's manufacturing processes routinely used hazardous substances, including
TCE, other solvents, acid and heavy metals including chromium. These industrial land uses
are expected to continue in the future.
1.3.3 Former West-Cap Property
West-Cap, located at 2207 East Elvira Road, was a manufacturer of small film capacitors and
magnetics. The former West-Cap facility extends west from Tucson Boulevard to Plumer
Avenue and south from Aragon Road to Elvira Road (Figure 5). West-Cap operations
primarily involved Buildings A, B, and C (see Figure 5). West-Cap carried out operations
from about 1963 to 1989, when they went out of business. Current activities at this property
include storage and warehousing in Building A and manufacturing of finely-machined
components in Building B. Buildings C, D, and E are leased to various tenants. These
industrial land uses are expected to continue in the future.
1.4 Surf ace Water
Natural surface waters at the Airport, Burr-Brown and former West-Cap Properties are
intermittent and occur primarily as runoff from storm events. The Airport Wash (Figure 3)
is the dominant surface water feature at the Tucson International Airport, and is located in
the northeastern part of the airport. The Airport Wash originates at the north end of
Runway 12 and flows southeast toward the Future General Aviation Area (Zone B). The
other surface water feature is the Diversion Channel (Figure 3), which flows from Aero Park
Road to the Hughes Access Road in Zone C. Runoff from the west side of the Airport
Property flows across the Southern Pacific Railroad spur and the Nogales Highway at three
locations south of Valencia Road. These flows continue west within arroyos.
Surface water flow at the Burr-Brown and Former West-Cap Properties appear to be
dominated by sheet flow to paved streets.
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1.5 Geology and Hydrogeology
1.5.1 Geology
The upper 200 feet of sedimentary material within the TIAA Site show a general coarsening
trend from east to west. East of Nogales Highway, predominantly fine-grained material is
interbedded with layers and lenses of sand and gravel. The sand and gravel appear to
occur in east-west trending paleochannels that represent former tributaries of the
prehistoric Santa Cruz River. West of Nogales Highway, sedimentary material becomes
more coarse-grained and contains relatively thinner interbeds of fine-grained material. The
east-west trending paleochannels coarsen to the west and merge with a major northwest-
southeast trending paleochannel that represents prehistoric Santa Cruz River deposits.
1.5.2 Airport Property Hydrogeologic Characteristics
1.5.2.1 Regional Aquifer System Hydrostratigraphy
In the vicinity of the TIAA Superfund Site, the regional aquifer system is quite complex
because of the lateral and vertical lithologic (fades) changes, and possibly faults. Generally,
on a large scale, subsurface sediments coarsen from east to west across the TIAA Site. A
relatively large-scale feature, the regional aquitard divides the Regional Aquifer into upper
and lower zones. This aquitard pinches out in the northwestern portion of the TIAA Site,
where the regional aquifer system is undivided.
In the southern portion of the TIAA Site (i.e., the area encompassing USAF Plant No. 44),
where an upper zone within the Regional Aquifer has been delineated based on soil
borings, the Nogales Highway has provided an approximate geographic feature many
investigators have referenced as a line (or vertical plane) dividing the area of the upper
zone of the Regional Aquifer with predominately coarse-grained aquifer material to the
west from the area with predominately fine-grained aquifer material to the east.
Because of its fine-grained nature, the upper zone of the Regional Aquifer east of the
Nogales Highway can be further subdivided where relatively thin coarse-grained channel
deposits are interbedded with relatively thick silt and day overbank deposits. In much of
the area east of Nogales Highway and south of Valenda Road, two such channel deposits
can be identified. However, the lateral continuity of each of these two subunits is difficult
to estimate.
1.5.2.2 Regional Aquifer System Hydrologic Characteristics
Historically, water levels in the Regional Aquifer in the vicinity of the Three Hangars area
dedined steadily starting in the early 1940's as private water companies and then Tucson
Water developed productive parts of the Regional Aquifer located generally east of Nogales
Highway. However, water levels began rising in about 1981 when TCE contamination was
first discovered and many of these production wells were shut down. In 1987, water levels
started falling again when the remedial extraction wells assodated with USAF Plant No. 44
began pumping to address TCE contamination south of Los Reales Road.
Currently, water levels in the Regional Aquifer in the vicinity of Zone E appear to be at or
near steady state. Due to the lateral fades changes, the upper zone of the Regional Aquifer
varies from confined to semi-confined and confined east to west across the TIAA Site.
Areas where predominantly fine-grained material exist in the east vary from semi-confined
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to confined, and areas where predominately coarse-grained material exist in the west are
typically unconfined.
In the future, water-level trends will probably depend on groundwater withdrawals from
the productive zones of the Regional Aquifer. As the south part of Plume A in the vicinity
of Los Reales Road is remediated and extraction wells are shut down or con verted, to
reinjection wells, groundwater levels in the vicinity of the Airport Property's Zone C, D and
E may rise again as they did between 1981 and 1987.
This Regional Aquifer system and the Shallow Groundwater Zone (described below) are
considered potential drinking water sources by the State of Arizona.
1.5.2.3 Shallow Groundwater Zone
A hydrostratigraphic unit called the Shallow Groundwater Zone exists above more
permeable, coarse-grained layers of the regional aquifer system in some areas east of the
Nogales Highway, including Zone E. A cross-section that illustrates the local stratigraphy
is shown in Figure 6. Figure 7 depicts the conceptual model for the Shallow Groundwater
Zone in Zone E. The Shallow Groundwater Zone consists predominately of saturated, fine-
grained (clay and silt) sediment interbedded with thin, generally discontinuous lenses of
coarser-grained material (i.e., sand). The eastern margin of the Shallow Groundwater Zone
is undefined, but may extend several miles to the east. Continuously saturated conditions
exist between the water table of the Shallow Groundwater Zone and the deeper, more
permeable layers of regional aquifer system. Thus, true hydraulic isolation between the
Shallow Groundwater Zone and lower parts of the aquifer does not exist.
In areas near where pumping from coarse-grained layers within the Regional Aquifer is
occurring, and/or local recharge to the Shallow Groundwater Zone is occurring, relatively
steep downward vertical hydraulic gradients exist between the Shallow Groundwater Zone
and coarse-grained layers within the Regional Aquifer (e.g. at USAF Plant No. 44 and
Airport Property Zone E). In other areas, where such pumping is not occurring, the water
table of the Shallow Groundwater Zone and the potentiometric surface of the Regional
Aquifer appear to coincide (e.g. AANG facility prior to implementation of the AANG
groundwater remedy).
Historically, before significant regional groundwater withdrawals dewatered the Regional
Aquifer, the fine-grained clay and silt layer (known as Unit 4 at the Airport Property Zone
E) was an aquitard sandwiched between sand and gravel layers within the regional aquifer
system. As water levels in the Regional Aquifer dropped, steep downward vertical
gradients developed due to the existence of interbedded coarse- and fine-grained layers. As
a result, the water table in the Three Hangars Area eventually declined into the Unit #4
Clay, with water levels in deeper coarser-grained layers settling at deeper levels. Recent
water-level data collected between 1991 and 1997 in the vicinity of the Three Hangars
indicates steady-state conditions exist in the Shallow Groundwater Zone, which is
consistent with the constant-head conditions (i.e., lack of significant groundwater
withdrawals) to the east and relatively steady pumping since 1987 from USAF Plant No. 44
extraction wells completed in coarser-grained fades of the Regional Aquifer just to the
south. In the near future, in the absence of municipal supply wells, water levels in both the
coarse-grained layers of the Regional Aquifer and the Shallow Groundwater Zone could
rise and coincide when pumping from the Air Force Plant No. 44 extraction wells in the
vicinity of Los Reales Road ceases or reinjection is initiated.
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1.5.3 Burr-Brown Property
The geology in the vicinity of the Burr-Brown Property is alluvial valley-fill sediments.
Below the water table there is a thick clay sequence. To the north of the Burr-Brown
Property, the day extends to over 150 feet below ground surface (bgs). On the property, the
clay extends to only 130 feet bgs and a sand and gravel unit is present between 130 and 140
feet bgs. This sand and gravel unit is underlain by another day unit.
The presence of the sand and gravel unit on the Burr-Brown Property, but not to the north
impacts groundwater flow conditions. Based on aquifer testing performed in 1991, a
hydrogeologic boundary was observed that corresponded to the extent of the sand and
gravel unit. Groundwater flows to the north-northwest in the Burr-Brown vicinity.
Contaminant transport appears to be limited in the downgradient direction/ likely because
of the presence of the thick clay to the north.
1.5.4 Former West-Cap Property
Very limited subsurface data are available at the former West-Cap Property. However, it is
expected that conditions are similar to those described above for the Airport Property. Data
collection assodated with investigations at the Burr-Brown Property indicates that sediment
grain size decreases from west to east in the vicinity of the former West-Cap Property. The
coarser sediments to the west provide potential pathways for groundwater flow and
contaminant migration. Finer-grained sediments may be more prevalent beneath the
former West-Cap Property. Groundwater flow is generally towards the north to northwest.
2.0 ROD Site History
2.1 Overview of ROD Site Activities
Various aviation, aerospace and electronic industrial facilities have occupied the Airport
Property at the TIAA Site since 1942.
Waste-related activities began in the area following the opening of the Consolidated
Aircraft refitting facility in 1942. Since then, approximately 20 other facilities have begun
operations in the Tucson International Airport vicinity, including aircraft and electronics
manufacturers. Waste-related activities at the Airport Property indude surface discharge of
waste liquids containing organic compounds into soil, disposal ponds and unlined landfills.
Burning of wastes as part of fire training exerdses was another release mechanism for waste
solvents and fuels. Flammable wastes were ignited in unlined fire pit areas, followed by
application of water to extinguish the blaze. These waste disposal practices resulted in
infiltration of contaminants into the underlying soils.
In May 1981, organic chemicals commonly used as solvents by electronic and aerospace
industries were found in groundwater in several City of Tucson drinking water wells in
southwest Tucson. Starting in 1981, the City of Tucson closed the contaminated wells to
ensure that water served to the public would meet drinking water standards.
Further investigations revealed a large groundwater plume containing TCE and other
volatile organic compounds (VOCs) and chromium migrating in a northerly to
northwesterly direction. The area of the plume was approximately 4 miles long and 3,000
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feet wide. This plume is called the main plume. Two smaller areas of groundwater
contamination were found to the east of the main plume. One is centered at the Burr-Brown
Property and the other is associated with the former West-Cap Property and the AANG
Base. The TIAA Site was added to the National Priorities List (NPL) in 1982.
An RI was initiated by EPA in 1983 to determine the extent of contamination and identify
contaminant sources. Based on the RI activities, sources of contamination for the main
plume include USAF Plant No. 44 and the Airport Property. Possible sources for the two
smaller areas of contamination include the Burr-Brown Property, the former West-Cap
Property, and the AANG.
In 1987, the USAF and Hughes Aircraft Company constructed an extraction wellfield and
air stripping treatment facility at USAF Plant No. 44. Subsequently, three additional
groundwater extraction and treatment systems have been installed: Burr-Brown
Corporation Facility, the AANG facility, and the Tucson Airport Remediation Project
(TARP).
2.2 Remedial Investigation Activities at the Airport Property
This section summarizes prior investigative activities at the ROD Site. Sections 2.2.1
through 2.2.8 describe activities at the Airport Property. Section 2.2.9 describes Burr-Brown
and Section 2.2.10 covers activities at the former West-Cap Property.
2.2.1 Three Hangars Investigation
As part of the RI/FS Scoping Phase for the Airport Property, an investigation was
conducted of the Three Hangars Area between September and November 1992. The intent
of this investigation was to evaluate sources of contamination in the immediate vicinity of
the Three Hangars Area. Nine monitoring wells and 12 soil borings were installed. Soil,
soil gas, and groundwater samples were collected for chemical analysis, and physical
testing was performed on soil samples. This investigation resulted in the initial delineation
of the localized stratigraphy and the early development of the Airport Property conceptual
model. The results of the Three Hangars Investigation are presented in the Existing Data
Report (EDR) (Daniel B. Stephens & Associates[DBS&A], 1993).
2.2.2 Field Reconnaissance Investigation
The Field Reconnaissance (FR) investigation was performed in 1993 in Zones A through F.
During this investigation, 26 subsites were investigated by soil gas sampling, monitoring
well sampling, and an Electromagnetic Offset Logging geophysical survey. The FR
Investigation Results (DBS&A, 1995) presents the results of this investigation.
2.2.3 Canale Sampling Program
The Canale sampling program was performed in 1994 to evaluate the series of below-grade
drain lines and inlets located in Zone E, known collectively as the "Canale system". Sludge
samples collected from within the drains contained heavy metals, including chromium,
copper, lead, and zinc at concentrations above regulatory limits for soils, as well as organic
compounds, including Aroclor 1254 (or PCB 1254), acetone, toluene, and methylene
chloride in concentrations above screening levels. Soil samples collected beneath the drain
structure did not contain appreciable contaminant concentrations. During the sampling
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program the Canale drain inlets were cleaned and the inlets and outlets backfilled with
concrete. Results of Sludge and Soil Analyses Canale Sampling Program (DBS&A, 1995)
presents the results of this investigation.
2.2.4 Preliminary Site Characterization Study
The Preliminary Site Characterization Study (PSCS) investigation was performed in 1995. A
total of 22 subsites were investigated by installing and sampling soil gas/groundwater
monitoring wells in the Shallow Groundwater Zone and Regional Aquifer, collecting
passive soil gas samples, and collecting surface and subsurface soil samples
2.2.5 Remedial Investigation (Rl)
Between April 1995 and April 1996, DBS&A completed the RI of the Shallow Groundwater
Zone and vadose zone at the Airport Property. Field activities included active and passive
shallow soil gas surveys, shallow soil and sludge sampling, drilling and installing
groundwater monitor wells, multi-port soil gas/groundwater (MPSG/GW) monitor wells,
and neutron probe access tubes. Groundwater sampling, vertical soil gas profiling, aquifer
testing, and screening of groundwater for DNAPL were also performed during this
investigation.
A total of 36 subsites were investigated during the RI. Table 1 presents the status of all
subsites that were addressed in the RI Work Plan (DBS&A, 1995). If, during the
investigation, the contaminant concentrations were below RI screening levels, that subsite
was proposed for NFA. Other subsites where contaminant concentrations exceeded
screening levels were characterized as a subsite exceeding screening criteria. Thirteen
subsites were proposed for NFA and 24 subsites were determined to be subsites "exceeding
screening criteria". Screening criteria used for the entire ROD Site is explained and
documented in Section 4 of the RI Report (DBS&A, 1996).
2.2.6 Preliminary Feasibility Evaluation
In April 1995, Conestoga-Rovers and Associates (CRA) prepared a Preliminary Feasibility
Evaluation (CRA, 1995) to identify the remedial technologies that may be applicable to the
ROD Site, to evaluate these technologies for potential use on an area-by-area basis, and to
determine which technologies could be candidates for evaluation in a treatability study.
The results of this evaluation were used to assess data generated during the RI.
2.2.7 Vadose Zone Treatability Study
In March and April 1996, CRA conducted a vadose zone treatability study south of the
Three Hangars Area in Zone E. The treatability study was conducted using a dual-phase
soil vapor extraction (SVE) system. The goals were to determine if SVE would significantly
remove contaminants in the vadose zone, to determine whether sufficient air flow and
water extraction could be achieved in selected portions of the vadose zone and Shallow
Groundwater Zone, and to evaluate whether sufficient contaminant volume could be
removed to produce an adequate cleanup rate in a full scale system. Several treatment
technologies were tested (e.g., ultra-violet oxidation for water and biological oxidation for
vapor) to evaluate the efficacy of using these technologies in a full scale system.
The conclusions of the Treatability Study Evaluation Report (CRA, 1996) can be
summarized as follows:
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Despite low vapor flow rates, acceptable vacuum distributions and radii of influence of
greater than 100 feet, were observed in lithologic Units 2 and 3;
Some vacuum propagation was observed in lithologic Units 2 and 3 during extraction
from lithologic Unit 4;
Lithologic Unit 2 is less contaminated than Units 3 or 4 and, therefore, may require a
shorter remediation time frame;
For a full-scale design, efficient vapor removal would be most readily achieved by
clusters of vapor extraction wells screened and sealed in the three distinct lithologic
units;
Because Unit 4 is saturated, it would require dewatering and high vacuum mechanical
equipment if any SVE were to be accomplished;
The predominant VOC is TCE, which has a high enough vapor pressure to be readily
removed by soil venting technology; and
The ROD Site is a candidate for bioremediation using indigenous bacteria for the soil
and bioaugmentation for the water.
2.2.8 Subsite-Specif ic Zone Disposition at the Airport Property
As a result of the Three Hangars Investigation, Field Reconnaissance Investigation, Canale
Sampling Program, the PSCS, and the RI, 46 subsites at the Airport Property were
investigated and have been classified into two categories:
Areas recommended for No Further Action (NFA)
Areas exceeding screening criteria.
Each of these groupings is summarized in Table 1.
Of the 46 subsites investigated through the completion of the RI, the following 23 subsites
were proposed for No Further Action (NFA) status:
Zone A: Fire Drill Training Area A-l;
Zone A: Hangar 10;
Zone A: Maintenance Yard Wash;
Zone A: Airport Wash North of Perimeter Road;
Zone B: Fire Training Facility;
Zone C: Hughes Aircraft Company Building 802;
Zone C: Hughes Aircraft Company Building 803;
Zone C: Hughes Aircraft Company Building 840;
Zone C: East Dump Area 1;
Zone C: East Dump Area 2;
Zone C: West Dump Area;
Zone C: Diversion channel;
Zone D: South Ramp Drainages and Ponding areas;
Zone D: Former USAF Disposal Areas;
Zone D: Fire Drill Training Area D-4;
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Zone E: Building 13 (Including Geophysical Anomaly);
Zone E: Building 24;
Zone E: Former Structure 27;
Zone E: West Lease USTs;
Zone E: Concrete structure area;
ZoneE: South apron geophysical anomalies;
Zone E: Recent Addition to the South Apron; and
ZoneF: West Side Drainage.
The following 22 subsites had concentrations exceeding the RI Screening Criteria:
Zone C: Hughes Credit Union Dump;
Zone D: South Ramp and Drains;
Zone D: Fire Drill Area D-3;
Zone D: C-294 Burn Pit;
Zone D: TAA Landfill;
Zone E: Buildings 14/15;
Zone E: Buildings 16/17;
Zone E: Building 18;
Zone E: Structures 21 and 30;
Zone E: Building 25 and adjacent soils to the north (southern portion of Building 24);
Zone E: Former Building 32;
Zone E: Soils beneath West Lease USTs;
Zone E: Sludges in the Canale System;
Zone E: Soil adjacent to Canale System;
ZoneE: Drainages and Ponding Areas;
Zone E: North and East Sides of Hangar 1;
Zone E: Hangar 1;
Zone E: South Portion of Hangar 2;
Zone E: West end of Runway 3;
Zone E: Shallow Groundwater Zone;
Zone F: East Side of Hamilton Buildings D-252, D-267, and D-275; and
Zone F: North Portion of Samsonite Building D-167.
The remaining subsite, Zone A Groundwater, is currently under investigation by EPA in
connection with the former West Cap Property remedial investigation.
2.3 Remedial Investigation Activities at the Burr-Brown Corporation Property
Groundwater monitoring wells were initially installed in 1984 at the Burr-Brown Property.
Groundwater has been monitored on a routine basis since that time. A small groundwater
plume originates beneath the facility and extends to the northwest. A groundwater
extraction and treatment facility is operating at this facility to address the groundwater
contamination.
In 1987, a shallow soil gas survey was conducted across the entire property. Additional soil
gas sampling was completed at two deeper borings (about 100 feet deep) in 1996.
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2.4 Remedial Investigation Activities at the Former West-Cap Property
A Phase I Site Assessment of the facility was conducted in 1991. Surface staining was
observed in several areas. In 1992, limited soil-vapor and soil sampling was performed.
A monitoring well located downgradient of the former West-Cap facility and upgradient of
the Burr-Brown facility was installed in 1984 as part of the investigations at the Burr-Brown
facility. Tetrachloroethene (PCE) and TCE concentrations in this well have shown a gradual
increase since being below detectable levels in October 1992. The sample collected in June
1994 had PCE at 12 ug/L and 20 ug/L TCE. In February 1997, the PCE concentration has
increased to 20 ug/L.
A soil gas survey was conducted in 1996. Thirty-four different locations were sampled,
with multiple depths being sampled at several of the locations. Additional subsurface
sampling activities are planned in 1997.
2.5 Prior Remedial Actions
The cleanup of TCE and other contaminants began in 1987 when the USAF installed a
groundwater treatment system at USAF Plant No. 44 (a.k.a., Hughes Missile Systems).
Since then, groundwater extraction and treatment systems have been installed and continue
to operate at Burr-Brown Corporation, the Arizona Air National Guard, and the Tucson
Airport Remediation Project (TARP). To date, these four groundwater systems have
cleaned up more than 40 billion gallons of water. Soil cleanup efforts are currently in
progress at USAF Plant No. 44 and the AANG Base. This ROD includes actions to address
the remaining soil contamination at the TIAA Site (particularly at the former West-Cap
Property). EPA will propose measures to address the remaining groundwater
contamination at a later date.
There have been two removal actions at the Airport Property. In 1991, liquid contaminants
and sludge were removed from an underground sump. In 1997, PCB-contaminated soil
was removed from a small portion of the Airport Property and from nearby residential
properties.
3.0 Enforcement Activities
In 1982, EPA listed the TIAA Superfund Site on the National Priorities List (NPL) following
the discovery of TCE in groundwater. The NPL listing described the TIAA Site as a broad
overall study area to investigate and define areas with soil and/or groundwater
contamination. To date, the sources of soil and/or groundwater contamination that have
been identified are:
Tucson International Airport property, including adjoining properties under the control
of the TAA
USAF Plant No. 44 property, also known as the Hughes Missile Systems plant
AANG Base property
Burr-Brown Corporation property
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Former West-Cap property
In 1988, EPA issued a ROD that established cleanup requirements for the regional
groundwater aquifer (1988 ROD). The 1988 ROD identified contamination in the regional
aquifer north of Los Reales Road as Area A of the main plume. The 1988 ROD also
identified as Area B two smaller plumes located respectively near (1) the AANG Base
Property and (2) the Burr Brown Property and the former West-Cap Property. The USAF
had issued a ROD in 1986 for groundwater cleanup at USAF Plant No. 44 that addressed the
regional aquifer contamination south of Los Reales Road (1986 ROD). The 1988 ROD
cleanup requirements do not apply to the portion of the regional aquifer contamination
addressed in the 1986 ROD.
Because the operators have varied throughout the TIAA Site, EPA has identified different
potentially responsible parties (PRPs) at each facility.
With respect to cleanup of the regional aquifer contamination north of Los Reales Road,
EPA issued special notices of potential responsibility to Hughes Aircraft Company, the
USAF, the City of Tucson, TAA, McDonnell Douglas, and General Dynamics. With the
exception of General Dynamics, these PRPs entered into a Consent Decree to undertake the
groundwater cleanup remedy for regional aquifer contamination north of Los Reales Road
pursuant to the 1988 ROD ("Groundwater Consent Decree"). The Groundwater Consent
Decree was entered with the District Court on June 4,1991. With the exception of General
Dynamics, the PRPs have been undertaking work in compliance with the Groundwater
Consent Decree, and, in accordance therewith, began operating a groundwater treatment
plant in September 1994.
With respect to the Area B plumes , EPA identified Burr-Brown Corporation and West-Cap
Arizona Incorporated as PRPs for the area of contamination located near the Burr-Brown
and former West-Cap Properties, and identified the AANG as potentially responsible for
the plume located near the AANG facility.
EPA and Burr-Brown Corporation executed a consent decree, entered with the federal
district court on March 16,1990, that requires Burr-Brown to remediate the plume
underlying its facility (1990 Consent Decree). Burr-Brown has been undertaking work in
compliance with the 1990 Consent Decree and, in accordance therewith, began operating a
groundwater treatment plant at its facility in 1992. EPA is currently investigating potential
groundwater contamination associated with the former West-Cap Property.
EPA, the State of Arizona and the Air National Guard Bureau entered into a Federal Facility
Agreement in 1994. The AANG has completed construction and, in 1997, commenced
operation of a groundwater treatment system to address the Area B contaminated plume
located near the AANG Base. An SVE system began operation at the AANG Base in April
1997.
As noted above, since 1987 the USAF has been successfully operating a groundwater
treatment system at USAF Plant No. 44 to address the portion of the regional aquifer
contamination south of Los Reales Road identified in the 1986 ROD. Soil cleanup systems
have been operating at Plant No. 44 for over one year. Soil cleanup consists of excavation
and removal of metal contaminated soils and operation of SVE systems for VOC-
contaminated soils. In early 1997, the USAF began operations of a dual-phase extraction
and bioremediation system to cleanup the Shallow Groundwater Zone at Plant No. 44. The
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remedial action at USAF Plant No. 44 has been subject to a joint federal-State Resource
Conservation and Recovery Act (RCRA) corrective action permit. As of the date of this
ROD, EPA, the State and the USAF have been engaged in negotiations to transfer oversight
of remedial actions at USAF Plant No. 44 to a Federal Facility Agreement.
3.1 Administrative Orders
EPA has issued several Administrative Orders to implement activities at the TIAA Site.
In January 1991, EPA issued a Unilateral Administrative Order, Docket No. 91-05 (1991
UAO), that directed the City of Tucson and the TAA to perform a removal action for liquid
waste stored in an underground concrete container. The 1991 UAO parties conducted the
removal in compliance therewith.
In August 1992, EPA issued a Unilateral Administrative Order, Docket No. 92-09 (1992
UAO) to the City of Tucson, TAA, McDonnell Douglas, and General Dynamics directing
them to conduct a remedial investigation and feasibility study at the Airport Property of
soils and the vadose zone, including the Shallow Groundwater Zone. EPA also requested
that the USAF participate in this RI/FS. With the exception of General Dynamics and
McDonnell Douglas, the Airport PRPs complied with the UAO and completed the RI and
the FS in October 1996 and June 1997, respectively.
In October 1996, EPA issued a Unilateral Administrative Order, Docket No. 96-14 (1996
UAO) to the same PRPs noticed in the 1992 UAO for the removal of PCB-contaminated soils
in the El Vado Road drainage, which includes certain areas of the Airport Property and
residential properties along El Vado Road. With the exception of General Dynamics, the
noticed PRPs conducted the removal in compliance with the 1996 UAO.
4.0 Scope and Role of this Document with the TIAA Site
Strategy
Cleanup activities at the TIAA Site have been addressed by dividing work among PRPs,
largely based on facility or property area and further subdividing work within such areas
according to media including the following:
Regional aquifer groundwater contamination in the southern portion of the main plume
(i.e., south of Los Reales Road in the vicinity of USAF Plant No. 44). The USAF issued a
ROD in 1986 to address such contamination. In addition, the USAF is addressing
Shallow Groundwater Zone contamination at Plant No. 44.
Regional aquifer groundwater contamination in Area A of the main plume (i.e., north of
Los Reales Road) and Area B. This contamination was addressed by EPA in the 1988
ROD.
Contaminated soil on the Airport Property, Burr-Brown Property, and the former
West-Cap Property. The soil contamination is addressed in this ROD.
Contaminated soil at USAF Plant No. 44. As noted above in Section 3, cleanup at USAF
Plant No. 44 has been subject to a joint federal-State RCRA corrective action permit.
TIAA SITE RECORD OF DECISION PAGE 1-13
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Negotiations are underway for a federal facility agreement that will cover ongoing
actions.
Contaminated soil at the AANG Base. Soil contamination at this facility is being
addressed through a federal facility agreement. The AANG issued its ROD for
contaminated soils at the AANG Base in November 1996.
Contamination in the Shallow Groundwater Zone at the Airport Property. Shallow
groundwater contamination is addressed in this ROD.
Regional aquifer groundwater contamination at and downgradient of the former West-
Cap Property. In the future, EPA will address its strategy for groundwater cleanup at
the former West-Cap Property and areas downgradient in a separate decision
document
-F
5.0 Highlights of Community Participation
The Proposed Plan for this remedy, in the form of a summary fact sheet, was distributed to
the 2,300 parties on EPA's mailing list for the TIAA Site. The Proposed Plan, together with
the Feasibility Study Report (CRA, 1997) and the Remedial Investigation Report (DBS&A,
1996), were also made available in the TIAA Site vicinity at the TCE Superfund Library
located at the El Pueblo Neighborhood Center on the south side of Tucson.
In addition, microfilm of the entire Administrative Record File, containing these three
documents and other documents considered or relied upon in developing the Proposed
Plan, are available at the TCE Superfund Library and at EPA's Regional Office in San
Francisco.
The Tucson Airport Authority held a public meeting to discuss progress towards this
remedy on April 23,1997 at El Pueblo Neighborhood Center.
Notice of EPA's public meetings, availability of the Proposed Plan, and the announcement
of a 30-day public comment period were published in the following newspapers:
Tucson Weekly July 17th, 1997
Arizona Daily Star July 21st, 1997
Tucson Citizen July 21st, 1997
El Monitor July 17th, 1997
Daily Territorial July 21st, 1997
EPA held public meetings on July 22 and 23,1997, at a church on El Vado Road and at the
El Pueblo Center to discuss its cleanup plan. At these meetings, EPA representatives made
a brief presentation of the Proposed Plan, answered questions, and solicited comments from
members of the public. A transcript of the public meeting, including oral comments and
responses, is included as Appendix A of this ROD (contained in Volume 2).
EPA extended the public comment period in response to a request from a member of the
public. A public notice mailed to the entire EPA mailing list extended the original 30-day
public comment period to 60 days. The entire public comment period ran from July 21 to
September 19,1997. EPA received several sets of written comments during the public
PAGE 1-14 TIAA SITE RECORD OF DECISION
SAC/I 10831/003.00C . PART I - DECISION SUMMARY
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comment period. These comments are addressed in the Responsiveness Summary,
included as Part II of this ROD (contained in Volume 2).
Also, EPA has been the government co-chair of the Unified Community Advisory Board
(UCAB) since its formation in 1995. A variety of public notices and public service
announcements were issued to advertise for positions on the UCAB. The UCAB meets
monthly to discuss site-related issues.
In addition to the Proposed Plan fact sheet for this remedy, EPA has periodically issued fact
sheets over the last 10 years describing investigation and cleanup activities at the TIAA Site.
The USAF and AANG have independently conducted extensive community participation
events and meetings.
This decision document presents the selected remedial action for the ROD Site (comprised
of the Airport Property, Burr-Brown Property, and former West-Cap Property) portion of
the TIAA Site, in Tucson, Arizona, which has been chosen in accordance with CERCLA, as
amended, and, to the extent practicable, the National Contingency Plan. The decision for
this ROD Site is based on the Administrative Record.
6.0 Summary of Site Characteristics
This section summarizes the nature and extent of contamination at the Airport Property,
Burr-Brown Property and former West-Cap Property. The Airport Property summaries
only discuss areas or subsites where contaminant levels have exceeded RI screening criteria.
These include the following areas (shown in Figures 8 and 9):
Zone C: Hughes Credit Union Dump;
Zone D: South Ramp and Drains;
Zone D: Fire Drill Area D-3;
Zone D: C-294 Burn Pit;
ZoneD: TAA Landfill;
Zone E: Buildings 14/15;
Zone E: Buildings 16/17;
Zone E: Building 18;
' Zone E: Structures 21 and 30;
Zone E: Building 25 and adjacent soils to the north (southern portion of Building 24);
Zone E: Former Building 32;
Zone E: Soils beneath West Lease USTs;
Zone E: Sludges in the Canale System;
Zone E: Soil adjacent to Canale System;
Zone E: Drainages and Ponding Areas;
Zone E: North and East Sides of Hangar 1;
Zone E: Hangar 1;
Zone E: South Portion of Hangar 2;
Zone E: West end of Runway 3;
Zone E: Shallow Groundwater Zone;
Zone F: East Side of Hamilton Buildings D-252, D-267, and D-275; and
Zone F: North Portion of Samsonite Building D-167.
TIAA SITE RECORD OF DECISION PAGE 1-15
PART I - DECISION SUMMARY
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6.1 ZoneC: Hughes Credit Union Dump
The Credit Union dump area is located beneath the current Hughes Credit Union building
in the southwest corner of the Airport Property. Previous investigations have cited the
possibility that unauthorized dumping of hazardous materials may have occurred in the
undeveloped area prior to construction of the building. Aerial photographs dating from
1953 to 1960 revealed an area of disturbed soil with an access road located beneath the
present location of the building PBS&A, 1996).
Soil gas analytical results showed concentrations of TCE above its soil gas screening level
(SGSL) in three samples collected south of the existing building and outside the perimeter
of the former area of disturbed soil. The TCE concentrations ranged from 2 ug/L to
4 ug/L. No other VOCs were detected above their associated SGSLs.
Follow-up RI field work at the Credit Union area showed concentrations of TCE above its
SGSL in two samples located in the parking lot south of the existing building. The TCE
concentrations in these two samples ranged from 2.05 ug/L to 3 ug/L. No other VOCs
were detected above their associated SGSLs.
6.2 Zone D: South Ramp and Drains
The south ramp area is located in the center of Zone D in the southwest section of the
Airport Property and is situated between Runway 3 and Aero Park Boulevard immediately
west of the Lockheed facility. The south ramp area encompasses the Learjet, Inc. facility
(formerly Gates Learjet) and portions of old Runway 35. The south ramp and old
Runway 35 were constructed in 1952 as a pre-flight apron by Grand Central Aircraft, a
contractor occupying the Three Hangars. The ramp was initially used for B-47 aircraft
storage and as a work area for a B-47 modification program. The south ramp has a history
of aircraft-related activities involving storage and use of chemicals and known releases of
jet fuel.
The most recent investigation of the south ramp area occurred during the FR Program
between October and November 1993. During this investigation soil gas samples were
collected at 47 locations within the south ramp area. The analytical results of the soil gas
survey indicated that two samples collected in the center of the south ramp along the storm
drain and off the southwest edge of the apron contained benzene in the range of 0.3 ug/L to
0.4 ug/L, exceeding the SGSL of 0.26 ug/L. Two other samples collected adjacent to
Building C-276 and along the storm drain in the center of the south ramp contained PCE
concentrations ranging from 0.8 ug/L to 2.0 ug/L, exceeding the SGSL of 0.4 ug/L for PCE.
Contaminants detected in regional groundwater near the south ramp include TCE, methyl
ethyl ketone (MEK), and 1,1-dichloroethene (1,1-DCE).
6.3 Zone D: Fire Drill Area D-3 and C-294 Burn Pit
The C-294 burn pit is located in Zone D, south of the Learjet facilities and north of Aero
Park Boulevard. The subsite, which was used in connection with Fire Drill Area D-3,
consisted of several fire-fighting training areas, located in an approximately 5-acre area
cleared of brush, that was used from the mid-to-late 1960s until 1973, when the new fire
drill facility was built east of Runway 29. The areas were cleared, bermed, and filled with
water then fuel was poured on top and the area set on fire. Aviation gas, waste aviation
PAGE 1-16 TIAA SITE RECORD OF DECISION
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fuel QP-4), diesel, and waste liquids possibly containing solvents from airport tenants
and/or the AANG were used for fire drills.
Aerial photograph analysis and a soil gas survey were conducted at the former fire drill
area D-3 and the C-294 bum pit as part of the FR investigation (DBS&A, 1995). The soil gas
analytical results showed that various SGSLs were exceeded in four of the 64 samples. The
SGSL for 1,2-dichloroethane (1,2-DCA) was exceeded in two samples; the SGSL for benzene
was exceeded in one sample; and the SGSLs for PCE and TCE were exceeded in one sample.
The results of a subsequent shallow soil gas survey showed 1,1-DCE, 1,1-DCA, and TCE in
one sample at 6.5 ug/L, 3.0 ug/L, and 4.3 ug/L, respectively. These levels exceed their
respective SGSLs.
Deeper soil gas data were obtained from two multi-depth soil gas monitoring wells. The
analytical results from these wells indicate that the highest concentration of VOCs in soil
gas is present near the middle of the vadose zone at approximately 42.5 feet bgs. This
sample contains the greatest number of contaminants at the highest concentrations,
including 1,1,1-trichloroethane (1,1,1-TCA) (1,744 ug/L), 1,1-DCA (252 ug/L), 1,1-DCE
(414 ug/L), benzene (1,026 ug/L), methylene chloride (97 ug/L), PCE (126 ug/L), toluene
(3340 pg/L), TCE (571 pg/L), and vinyl chloride (1.4 ug/L). The number of contaminants
and the concentrations drop off dramatically in the next deeper (59 feet bgs) and shallower
(15 feet bgs) ports, and no VOCs were detected at concentrations exceeding the
depth-specific exponential soil gas screening levels (ESGSLs) in the deepest soil gas sample
collected at 88 feet bgs. Groundwater samples from a single monitoring well collected as
part of the C-294 bum pit RI did not contain any VOCs, SVOCs, or pesticides/PCBs.
6.4 Zone D: TAA Landfill
The TAA landfill was originally developed as a material/gravel pit to support construction
of the TIA and Highway 89 during the World War D period. The landfill existed in October
1948, and was estimated to cover three to five acres in a roughly circular shape, 300 to
500 feet in diameter, with an estimated depth of approximately 20 feet bgs. Aerial
photographs show that the landfill was active in 1953, with drums and debris present in the
landfill. Aerial photographs also indicate that the eastern half of the landfill was covered
by 1979, and the entire landfill appears to have been rilled and covered by 1985 (DBS&A,
1995).
The landfill was used by various tenants and the general public as a dumping spot for
domestic garbage and debris and possibly for industrial type wastes. Dumping at the TAA
landfill reportedly stopped in the mid-1960s when TAA contracted with Arizona Transport
to haul garbage. The landfill continued to receive only construction material waste until it
was closed in 1976.
The results of the RI confirm that there are isolated areas within the TAA Landfill with soil
gas VOC concentrations above their associated SGSLs. The soil gas samples collected from
a multi-depth well exceeded the associated ESGSLs for TCE at two depths. The TCE
concentrations ranged from 13 ug/L at a depth of 42.5 feet bgs, to 86 ug/L at a depth of
68 feet bgs. The associated depth-specific ESGSLs for TCE at these depths are 8.5 ug/L and
26 ug/L, respectively. No other VOCs were detected.
TIAA SITE RECORD OF DECISION PAGE l-i 7
PART I - DECISION SUMMARY
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During follow-up investigation field work at the TAA Landfill a shallow soil gas survey
was conducted to collect screening level data at those locations identified during the PSCS.
In addition, groundwater samples were collected at four existing monitoring wells.
During this investigation, TCE was detected above its SGSL, at a concentration of 2.27 pg/L,
in one sample collected in the southeast quadrant of the landfill in the area that exhibited
elevated TCE during the PSCS survey. No other VOCs were detected in soil gas.
TCE was identified in groundwater at concentrations of 0.48 pg/L and 0.50 pg/L in
duplicate samples from one well.
Although there are isolated areas within and below the landfill that exhibit elevated VOC
concentrations in soil gas, the results of the RI groundwater investigation at the landfill do
not indicate that there has been a significant release to groundwater from this subsite to
date.
6.5 ZoneE: Buildings 14/15 and Buildings 16/17
Buildings 14/15 and 16/17 are all located south of the Three Hangars areas in Zone E. The
buildings were built in the 1940s and have been occupied over the years by tenants
involved in aircraft maintenance, overhaul, and repair.
In September through November 1992, soil and soil gas samples were collected in the
vicinity of Buildings 14/15 and 16/17. Elevated concentrations of chloroform and TCE
were detected. Chloroform was detected at concentrations ranging from 5.7 pg/L to
45 pg/L. TCE was detected at concentrations ranging from 23 pg/L to 46,000 pg/L. The
highest concentrations were detected in the deeper sampling ports.
Analyses of soil gas samples collected in December 1993 during the FR investigation
exhibited similar concentrations to those samples collected and analyzed in 1992 (described
above). The analytical results of the soil, soil gas, and water samples collected during the RI
also exhibited similar concentrations to those samples discussed above.
6.6 ZoneE: Building 18
Building 18 is located southeast of the Three Hangars area in Zone E. The building was
built in the 1940s. In conjunction with the RI, two separate phases of shallow soil gas
surveys were performed in April and May 1995. Analytical data from the samples collected
during these sampling events indicate that concentrations of 1,1-DCE and TCE were
detected above their SGSLs. 1,1-DCE was detected in concentrations ranging between
1.4 pg/L and 5.6 pg/L.
The areal distribution of TCE shows that a relatively small area of shallow TCE soil gas
contamination exists at the northwest corner of Building 18. The areal distribution of
1,1-DCE shows that the 1,1-DCE soil gas contamination is more widespread than the TCE
distribution with the highest concentration of 1,1-DCE in soil gas (57 pg/L) located below
the center of Building 18.
6.7 Zone E: Structures 21 and 30
Former Structure 21 was located in the extreme northwestern corner of Zone E and
Structure 30 is located in the western portion of Zone E. Structures 21 and 30 were built in
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the early 1940s and operated as substations for transformer pads. Structure 21 was removed
around 1984. Structure 30 remains active. PCBs were considered potential contaminants at
both locations because of the historical use of the structures. There are no known or
reported releases of transformer fluid at either location.
The results of the shallow soil sampling at Structures 21 and 30 indicate that the PCB
Arodor 1260 is present at concentrations in excess of the associated non-residential Arizona
Department of Environmental Quality (ADEQ) Health-Based Guidance Levels (HBGLs) of
0.76 mg/kg in all eight samples, with concentrations ranging between 0.78 mg/kg and
73 mg/kg. No pesticides or other PCBs were detected.
6.8 Zone E: Building 25 and Adjacent Soils (and southern portion of Building 24)
Buildings 24 and 25 are located on the West Lease area in the westernmost portion of
Zone E. Building 24 was built in the early 1940s and was occupied by various tenants
involved in aircraft maintenance and repair operations. Building 25 was built in the early
1940s and occupied by similar tenants as Building 24. The building served as a warehouse
for flammable materials in 1951, and housed an engine test stand.
The Building 24 FR soil gas survey detected both PCE and TCE above their associated
SGSLs in several samples. PCE was detected in six samples located along the southern half
of the building at concentrations ranging from 0.4 ug/L to 30 ug/L. TCE was detected in
two samples at the southern end of the building at concentrations ranging from 2 ug/L to
60 ug/L. The highest concentrations of both PCE and TCE were found in a sample
collected at the southern end of Building 24.
The FR investigation at Building 25 included a soil gas survey conducted around the
building perimeter. This soil gas survey detected both PCE and TCE above their associated
SGSLs. PCE was detected in all four samples at concentrations ranging from 16 ug/L to
53 ug/L. TCE was detected in two of the four samples at concentrations ranging from
4 ug/L to 120 ug/L. The highest concentrations of both PCE and TCE were found in a
sample located at the northern end of Building 25.
The shallow soil gas survey conducted during the RI showed that chloromethane, TCE, and
PCE were detected above their associated SGSLs. No other VOCs were detected above their
associated SGSLs. The shallow soil gas results, which show that the area of VOC soil gas
contamination is centered in the area between Buildings 24 and 25, are consistent with
previous investigation results at the subsite.
No cyanide or SVOCs were detected above EPA Region DC Preliminary Remediation Goals
(PRGs) in soil samples from one soil boring. X-ray fluorescence (XRF) field screening of
these soil samples detected arsenic in one sample at a concentration of 75 mg/kg, which is
above the EPA Region IX PRG of 3.3 mg/kg. No other metals screened by the XRF were
detected above applicable EPA Region IX PRGs.
The analytical results of soil gas samples collected from a multi-depth monitoring well
showed TCE and PCE above their associated depth-specific ESGSLs. TCE was detected in
four of the five soil gas ports in concentrations ranging between 142 ug/L and 505 ug/L.
PCE was also detected in four of the five soil gas ports in concentrations ranging between
42 ug/L and 129 ug/L. The highest concentrations of TCE and PCE were detected in the
port located at 26 feet bgs.
TIAA SITE RECORD OF DECISION PAGE 1-19
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6.9 ZoneE: Former Building 32
Former Building 32 is located in Zone E in the West Lease area southwest of Building D-170.
Building 32 was built in the early 1940s and was used as an armament building. An
automobile maintenance shop, where small amounts of fuel, solvents, and degreasers were
used occupied the southern half of Building 32 and a small storage area to the south of
Building 32 was used to temporarily store equipment and drums.
During the FR program, one soil gas sample collected below the foundation of former
Building 32 contained PCE at 6.0 ug/L, which is above the SGSL (0.43 ug/L). PCE was not
detected in soil gas samples collected north and south of that sample.
6.10 ZoneE: Soils Beneath West Lease USTs
Two USTs were encountered in October 1992, during the vadose zone investigation south of
Three Hangars. Each UST has a capacity of approximately 50,000-gallons. These two West
Lease USTs at the northern edge of the former Structure 27 are part of a former
underground fuel storage facility. During facility operations large quantities of automobile,
aviation, and possibly jet fuel were stored and distributed from this facility. Fuel was
off-loaded from railroad tanker cars at the southernmost of two railroad spurs entering the
west side of Zone E (DBS&A, 1996).
In October, 1992, TAA closed the USTs. The tank contents and soil from beneath the tanks
were sampled and analyzed. The results of TAA's limited analyses indicate that neither the
tank contents nor the soil beneath the tanks contained detectable concentrations of VOCs or
SVOCs. The tanks were backfilled with clean material°and closed in place.
A multi-port soil gas/groundwater (MPSG/GW) monitoring well was installed in the
Shallow Groundwater Zone north of the USTs in October 1992 (DBS&A, 1993). Soil gas
samples from this well indicated the presence of TCE, benzene, and toluene throughout the
vertical extent of the vadose zone. Analysis of a groundwater sample collected from this
well in November 1992 detected concentrations of TCE (990 ug/L), benzene (1,100 ug/L),
1,2-DCA (30 ug/L), chloroform (160 ug/L), 1,2-DCP (50 ug/L), and methylene chloride
(110 ug/L). Soil gas samples confirmed the consistent vertical profile of TCE, benzene, and
toluene detected.
During the RJ field work, a shallow soil gas survey was conducted along the perimeter of
former Structure 27 and the closed USTs. The analytical results show that no VOCs were
detected above SGSLs in this area.
Based on existing data from the subsite, soil contaminated with VOCs, including fuel-
related VOCs are present in the vadose zone in the vicinity of the West Lease USTs. TCE,
benzene, and other VOCs are present in the Shallow Groundwater Zone directly
downgradient of the USTs.
6.11 Zone E: Sludges in the Canale System and Soils Adjacent to Canale
The Canale system is a network of below-grade drain pipes and inlet structures (now
closed) located within the south apron area of Zone E. As designed, the Canale system
carried runoff from the south apron westward toward Park Avenue. Liquids from some
portions of the south apron, including rinse water from decocooning operations, would
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pool on the apron and run into the Canale drain system. Wastes from degreasing tanks and
plating shop tanks, and wash water from the cleanup area in the engine tear down shop
(Buildings 14/15 and 16/17) may also have entered the Canale through connecting drains.
Three previous investigations of the Canale system and adjacent soils have been conducted.
The first, in September and October 1988, resulted in detection of various VOCs above
SGSLs in soil gas samples, including TCE and carbon tetrachloride at concentrations
ranging from 4 ug/L to 75 ug/L and 0.4 ug/L to 2 ug/L, respectively. PCE and 1,2-DCE
were detected at concentrations of 5 ug/L and 29 ug/L, respectively, and benzene was
detected at a concentration of 5 ug/L.
An investigation of the Canale system in February 1991 resulted in the detection of notable
concentrations of a wide variety of VOCs, SVOCs, PCBs, and metals, as well as numerous
tentatively identified compounds, primarily petroleum hydrocarbons, within the Canale
pipe. One soil sample collected during this investigation contained dichlorobenzene
concentrations of up to 15,000 ug/L and notable concentrations of other SVOCs.
More recent investigations of the Canale system and adjacent soils indicated notable
concentrations of various VOCs, SVOCs, PCBs, and metals in Canale sludge. The sludge
samples were found to contain priority pollutant metals, including 256 milligrams per
kilogram (mg/kg) to 2,320 mg/kg chromium; 276 mg/kg to 10,400 mg/kg lead; and
9,949 mg/kg to 3,660 mg/kg zinc. The PCB Aroclor 1254 was detected in all sludge
samples at concentrations between 0.22 mg/kg and 30 mg/kg, as well as in two soil
samples at concentrations of 13 mg/kg and 14 mg/kg.
Soil gas analyses indicated elevated concentrations of VOCs, including chloroform at
0.5 ug/L to 3.7 ug/L, TCE at 20 ug/L to 130 ug/L, and detectable concentrations of
methylene chloride and tis-l,2-DCE. The highest concentrations of chloroform and TCE
occurred at 50 feet bgs. Soil gas concentrations detected in one multiport well included TCE
at 3 ug/L to 96 ug/L, benzene at 53 ug/L to 320 ug/L, and toluene at 9 ug/L to 790 ug/L.
Total xylenes, 1,2-DCE, and chloroform were also detected at elevated concentrations.
6.12 ZoneE: Drainages and Ponding Areas
The Zone E drainages and ponding areas are located to the southwest and west of the Three
Hangars. Surface runoff in Zone E originates from the north and south sides of the Three
Hangars and from the south apron, and generally moves in a westerly direction until it
flows off-site along the railroad tracks.
During the RI field investigation, a total of 45 surface soil samples were collected in the
Zone E drainages and ponding areas and analyzed for metals by XRF. No metals were
detected above background levels.
Eight additional soil samples were collected at: (1) the area south and west of Building 25
near the Canale drain and the south apron outfall; (2) the area northeast of Building 24 near
the north Three Hangars storm drain outfall; and (3) the area west of Highway 89 where the
south apron drainage exits Zone E.
Analytical results for these samples indicated that the SVOCs benzo(a)pyrene,
benzo(b)fluoranthene, and benzo(k)fluoranthene were present in several of the samples
above applicable screening levels. All are common constituents of petroleum products,
TIAA SITE RECORD OF DECISION PAGE 1-21
PART I - DECISION SUMMARY
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including tar and asphalt. The PCB Aroclor 1260 was detected in all samples ranging from
0.62 mg/kg to 140 mg/kg, exceeding both the HBGL and the PRG for PCBs.
During the follow-up investigation of the drainages and ponding areas additional soil
samples were collected from the areas that exhibited elevated concentrations of the PCB
Aroclor 1260. Several of these soil samples also contained concentrations above applicable
screening levels. In March 1996, soil samples were collected from soil on private residential
properties on El Vado Road west of Nogales Highway and two ponding areas located east
of the Southern Pacific Railroad. Analytical results of the shallow soil sampling indicate
that the PCB Aroclor 1260 is present at concentrations above the non-residential HBGL of
0.76 mg/kg in most of the soil samples collected. The PCB Aroclor 1254 was detected only
in samples collected from south and west of Building 25.
Pursuant to EPA Order 96-14, in early 1997, a removal action to cleanup the PCB-
contaminated soil was performed. All residential areas contaminated with PCBs were
remediated along with areas on the Airport Property and near the Southern Pacific Railroad
tracks (Figure 9). However, there is another Zone E drainage area near Corona and South
Park Avenue that has PCB contamination in excess of the 0.76 mg/kg standard (see Figure
9).
6.13 Zone E: Building D-158 and the North and East Sides of Hangar 1
Building D-158 and Hangar 1 are located within Zone E. The Three Hangars were
constructed in the 1940s and are three separate structures with adjoining walls and roofs.
The Three Hangars historically were occupied by a variety of tenants and used in aircraft
modification operations. Between 1942 and I960, the eastern portion of Hangar 1 contained
the TAA offices, airline offices, a restaurant, and the passenger terminal. Subsequently, the
hangar facility was subdivided and made available to a number of tenants performing a
variety of industrial activities.
Building D-158, a small building located to the north of Hangar 1, was built in 1950 and was
used as a kitchen and a storage facility.
During November 1989, one soil boring was installed near the east end of the north wall of
the Three Hangars to a depth of 85 feet. Soil samples were collected every 10 feet and
analyzed for VOCs and hexavalent chromium. Samples from the 50 and 60 foot depths of
this boring contained low concentrations of TCA and PCE. An additional boring was
installed in June 1990, near the northeast corner of Hangar 1 to a depth of 40 feet and
screened over the interval from 20 to 40 feet to perform borehole permeameter tests. Soil
samples were collected every 10 feet and analyzed for VOCs and hexavalent and total
chromium. No significant contaminant concentrations were detected.
One MPSG/GW well was installed within the Shallow Groundwater Zone at the northeast
corner of Hangar 1 as part of the FR investigation. Soil gas samples were collected from five
separate soil gas ports located at depths of 4 feet to 83 feet bgs and analyzed for VOCs. TCE
and PCE were detected above the ESGSLs below 60 feet in two soil gas samples. 1,1-DCE
was detected above its ESGSL in one sample.
During a soil gas survey of Building D-158 in November 1993, samples were collected at
four locations around the perimeter of the building. One sample from northwest of
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Building D-158 exceeded the SGSLs for TCE, PCE, and 1,1-DCE in concentrations of 3 pg/L,
0.5 pg/L, and 6 pg/L, respectively.
Analytical data from the subsequent RI shallow soil gas survey indicate that TCE exceeded
its SGSL in five soil gas samples. The areal distribution of TCE and 1,1-DCE in shallow soil
gas around Building D-158 and the north and east sides of Hangar 1 indicates elevated soil
gas concentrations in an area near the northeast corner of Hangar 1 that coincides with the
. outfall from the hangar floor drain system to the storm drain. In addition to the TCE
contamination in the northeast comer of Hangar 1, a single point of elevated TCE (3.9 pg/L)
occurred inside Hangar 1, approximately 350 feet south from the northeast corner of the
building.
Soil gas sample results collected from a MPSG/GW well show that none of the soil gas
samples from the five ports sampled contained VOCs at concentrations exceeding their
depth-specific ESGSLs.
6.14 Zone E: Hangar 1 Drains
Hangar 1 is the easternmost building of the Three Hangars located in the west central
portion of Zone E. A 1993 preliminary site survey of the Three Hangars was conducted that
identified a system of interior floor drains in the north half of the Hangar 1 connected to a
storm drain running east to west along the north side of the Three Hangars.
Where material was available, sediment/sludge and water samples were collected from
drains located within the Three Hangars during the site survey. Four water samples and
one sediment/sludge sample were collected from drains located within Hangar 1.
The analyses of the drain samples detected elevated concentrations of several SVOCs in one
sediment/sludge sample from the drain. This sample also contained 1,100 mg/kg of the
PCB Aroclor 1254.
The RI field work at Hangar 1 drains consisted of sampling sludge in the storm sewer line
to determine the horizontal distribution of PCB-contaminated materials.
The analytical results from sludge samples of the east-west running storm drain located on
the north side of the Three Hangars indicate that the PCB Aroclor 1254 is present in the
sediment at concentrations exceeding 100 mg/kg as far west as Hangar 3.
Since the completion of the RI Report (DBS&A, 1996), PCB contamination in Hangar 1
drains was remediated by the Respondents under a voluntary removal action approved by
EPA. The voluntary removal action remediated drains both inside and outside of Hangar 1.
However, there are still drains and drain inlets inside Hangar 1 that need to be investigated.
6.15 ZoneE: South Portion of Hangar 2
Hangar 2 is the central building of the Three Hangars, located along the west-central part of
the Airport Property in Zone E. The Three Hangars were built in the 1940s. Beginning in
1966, the Three Hangars, which had formerly operated primarily as a single manufacturing
complex, were subdivided and made available to a number of tenants performing a variety
of industrial activities.
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Two borings were installed in November 1989, in and near the southern end of Hangar 2 to
investigate areas of elevated VOC concentrations in soil gas. Soil samples were collected
every 10 feet and analyzed for VOCs and hexavalent chromium. Toluene and TCE were
detected at varying depths.
During a limited investigation of the Three Hangars Area in September through November
1992, one permanent MPSG monitor well was installed to a depth of approximately
87 feet bgs at a 15 degree angle underneath the building at the southern end of Hangar 2.
During drilling, soil matrix samples were collected at approximately 10-foot intervals.
The soil matrix analyses detected no concentrations above the 1992 ADEQ HBGLs or the
EPA Region DC PRGs. However, the analytical results from the soil gas analyses show that
the SGSL for TCE was exceeded in all seven soil gas samples. TCE was detected at
concentrations ranging from 150 pg/L near the surface to 10,000 pg/L at approximately
87 feet bgs.
The well was re-sampled in December 1993 during the FR investigation. TCE was again
detected in soil gas samples from all seven soil gas ports at concentrations ranging between
25 pg/L and 2,200 pg/L. Various other VOCs, including PCE, benzene, methylene chloride,
chloroform, chloromethane, and carbon tetrachloride, were also detected above their
associated SGSLs, but in fewer ports and at concentrations generally lower than those found
for TCE.
Existing data from boreholes and from depth-specific soil gas profiles indicate that the
contamination increases with depth and is greatest immediately above the water table.
Results of surface sampling of materials from drains and sumps in the vicinity of Hangar 2
do not indicate the presence of contamination. It appears that the VOC contamination in
this area may be associated with other nearby sources, including Buildings 16/17.
6.16 Zone E: West End of Runway 3
The west end of Runway 3 is located in Zone E at the south end of the south apron area.
During USAF tenancy in the Three Hangars from 1968 to 1969, JP-4 aviation fuel was
reportedly released from aircraft along die north-northwest side of the end of Runway 3
onto the native soil at the edge of the south apron. It is also possible that TCE, oil, and
hydraulic fluid were disposed of in this area (DBS&A, 1995).
Soil gas samples were collected in September 1986, along a utility trench under construction
at the southwest end of Runway 3. Chloroform concentrations up to 0.06 pg/L and TCE
concentrations up to 0.03 pg/L were detected in these samples.
In October and November 1987, soil gas samples were collected at 39 locations along both
sides of the southwest portion of Runway 3. Twenty-nine of the sample locations were
located north of Runway 3 and, therefore, lie within Zone E. Selected soil gas samples from
these locations were found to contain trace concentrations of chlorinated VOCs. In
addition, several samples collected along the edge of the south apron near the southwest
end of Runway 3 contained benzene concentrations of up to 8 pg/L.
The most recent investigation at the west end of Runway 3 was a soil gas survey conducted
in October 1993 as part of the FR investigation. Soil gas samples were collected at 17
locations at the west end of Runway 3 with an interval spacing of approximately 100 feet.
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The analytical results indicate that carbon tetrachloride was detected above its SGSL of
0.3 ug/L at six sample locations at concentrations ranging from 0.4 ug/L to 0.8 ug/L. No
other compounds were detected above SGSLs.
6.17 ZoneE: Shallow Groundwater Zone
The Shallow Groundwater Zone is present in Zone E in the vicinity of the Three Hangars.
The extent of the Shallow Groundwater Zone is not well defined, but it has been observed
near Valencia road to the north and USAF Plant No. 44 to the south. Saturated material was
initially encountered at approximately 90 feet bgs during the installation of monitoring
wells in Zone E. Additional data collected during the RI were used to construct Shallow
Groundwater Zone water elevation contours depicted on Figure 10, which indicates a
shallow gradient to the west/northwest.
The shallow stratigraphy beneath Zone E consists of four distinct lithostratigraphic units
within the vadose zone (see Figures 6 and 7). Unit 1 consists of approximately 10 to 15 feet
of unconsolidated silt or gravely sand immediately below the surface. Unit 2 consists of a
consolidated layer of calichitied silry fine sand that is approximately 35 to 40 feet thick.
Unit 3 consists of a layer of well-to-poorly graded silry and gravely sand that varies in
thickness between 20 and 40 feet. This permeable unit is continuous across the Airport
Property and contains a discontinuous clay lens beneath the western and southern portions
of Zone E. This day is absent to the east and north. Unit 4 consists of a layer of silt or silty
clay with a thickness which varies between 55 and 75 feet. Additionally, a gravel subunit
approximately 5 feet to 15 feet thick exists at an approximate depth of 115 feet bgs within
"Unit 4.
6.17.1 Summary of Shallow Groundwater Zone Investigations
Several soil and groundwater investigations had been conducted in the vicinity of the Three
Hangars prior to the RI field work. As part of the scoping phase of the RI/FS, an
investigation of the vadose zone south of the Three Hangars was performed between
September and November 1992. The following observations and conclusions were made:
Both the Shallow Groundwater Zone and the Upper Regional Aquifer were found to be
contaminated with VOCs;
The VOCs most frequently detected were either chlorinated hydrocarbons or fuel
hydrocarbons, with TCE being the most prevalent compound by far;
TCE was detected at concentrations up to 130,000 ug/L in Shallow Groundwater Zone
MPSG/GW well S-5 (completed in the top of Unit 4 day in the vicinity of
Buildings 16/17);
Soil gas samples from the deep vadose zone collected during the Three Hangars
investigation were found to be sensitive indicators of subsurface VOC contaminants;
Only one of the 48 soil samples collected was completely devoid of VOCs; and
TCE was the predominant chlorinated VOC detected in the soil gas samples, followed
by chloroform.
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Field Reconnaissance Investigation. The FR investigation was completed in Zone E in the
fall of 1993 (DBS&A, 1995). All existing and new monitor wells were sampled during the
FR investigation.
Various VOCs and metals were detected in the groundwater samples collected from the two
Regional Aquifer wells. The analytical results indicate that drinking water MCLs of various
compounds were exceeded in water samples collected from all Zone E Shallow
. Groundwater Zone monitor wells, except in monitor wells S-6 and S-8.
In general, soil gas concentrations of TCE and other VOCs within the MPSG and
MPSG/GW wells were found to be greatest at depth and to decline toward the surface,
indicating that the majority of VOC contaminants reside immediately above the Shallow
Groundwater Zone.
Remedial Investigation. The primary field program for the RI was performed during the
spring and summer of 1995. The results of this investigation are located in the PSCS
(DBS&A, 1995). However, multiple additional investigations have been conducted to
delineate the extent of contamination west of the airport. These investigation resulted in
the installation of additional monitoring wells, both in the Shallow Groundwater Zone and
in the Regional Aquifer.
Additional investigation activities within Zone E were focused on delineating the extent of
groundwater contamination in the southern and western portions of the area and on
evaluating whether any on-site sources of contamination had been overlooked during
previous investigations. Activities performed include collecting shallow soil samples from
Buildings 16/17 and 18, performing a shallow soil gas survey at 67 locations within Zone E,
installing two MPSG/GW wells and four monitoring wells completed in the Shallow
Groundwater Zone, and collecting soil samples for chemical testing from two soil borings.
A soil gas survey consisting of six soil gas samples was conducted in and around the former
Building 32. Groundwater monitor wells were installed west of Highway 89 during a
limited field investigation performed during the fourth quarter of 1995. Additional Shallow
Groundwater Zone and vadose zone RI around Zone E was conducted between April and
July 1996. The initial investigation involved the installation of six MPSG/GW wells within
the Shallow Groundwater Zone, four Shallow Groundwater Zone monitor wells, and one
perched groundwater monitor well.
In the vicinity of Three Hangars, lithologic Unit 4 consists of approximately 20 feet of low-
permeability clay, underlain by 4 to 6 feet of sand and gravel (Unit 4 gravel), which is in
turn underlain by more than 30 feet of clay. The base of the gravel subunit was
encountered at a depth of approximately 130 feet bgs. Analytical results for groundwater
from Unit 4 gravel subunit monitoring wells are summarized as follows:
Gravel subunit well S-16B exceeded the drinking water MCLs of the VOCs 1,2-DCP
(5 ug/L MCL), 1,2-DCA (5 ug/L MCL), chloroform (100 ug/L MCL), and TCE (5 ug/1
MCL), in concentrations of 73 ug/L, 5.1 ug/L, 130 ug/L, and 900 ug/L, respectively.
The drinking water MCL for nitrate (10 mg/L) was exceeded with a concentration of
26 mg/L.
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Gravel subunit well S-29 exceeded the drinking water MCLs for the VOCs benzene
(5 pg/L MCL) methylene chloride (5 pg/L MCL) and TCE (5 pg/L MCL), with
concentrations of 530 pg/L, 10 pg/L, and 210 pg/L, respectively.
Grab sample S-27-GW exceeded the drinking water MCLs for the VOCs carbon
tetrachloride (5 pg/L MCL) and TCE (5 pg/L MCL) with concentrations of 19 pg/L and
430 pg/L, respectively.
Because investigations in the Three Hangars Area of Zone E identified the Shallow
Groundwater Zone as one of the main areas of concern, a vadose zone treatabiliry study
using dual-phase SVE and treatment was conducted in the Three Hangars Area. This study
is summarized in Section 2 (of this ROD) and in the Vadose Zone Treatability Study
Evaluation Report (CRA, 1996).
A constant discharge pumping test was performed in April 1996, in the Shallow
Groundwater Zone Unit 4 gravel subunit to evaluate the hydraulic characteristics of the
sand and gravel strata. Water level response was monitored in the Shallow Groundwater
Zone gravel subunit and the overlying clay unit. The test was conducted for a period of
71 hours.
Analyses of pump test discharge water detected TCE in all three of the collected samples.
TCE was detected at concentrations of 16,000 pg/L, 13,000 pg/L, and 13,000 pg/L for the
1-hour, 12-hour, and 71-hour samples, respectively.
RI Results Summary. In completing the RI in Zone E, 41 monitoring wells and
approximately 350 shallow soil gas sample locations were used to determine the extent of
contamination in the vadose zone and Shallow Groundwater Zone. The RI Report indicates
that all sources of contamination have been identified (DBS&A, October 1996). Deep soil
gas results helped to delineate the majority of the contaminant mass in the vadose zone.
Shallow Groundwater Zone monitor wells have delineated the extent of contamination on
the Airport Property. The western margin of the Shallow Groundwater Zone has not been
fully defined. A gravel subunit within Unit 4 was identified that may be a pathway for
contaminant transport.
6.18 Zone F: East Side of Hamilton Aviation Buildings D-252, D-267, and D-275
Hamilton Aviation Buildings D-252, D-267, and D-275 are located north of the Three
Hangars on the north apron in Zone F. These buildings were built beginning in 1973, and
have historically been occupied by Hamilton Aviation. Activities undertaken at these
buildings include aircraft maintenance and repair, overhaul of electronic and hydraulic
systems, and aircraft stripping and painting. Between 1950 and 1954, the north apron area
around the current location of the Hamilton Aviation buildings was used primarily for
pre-flight operations and testing, including fueling of B-47 aircraft.
As part of an airport-wide site investigation in 1988, soil gas sampling was conducted near
Hamilton Aviation. Thirteen soil gas samples were collected along a north-south traverse
through the north apron area between Hamilton Aviation Buildings D-260 and D-267. No
VOCs were detected above their associated SGSLs in this soil gas survey.
The most recent investigation of the Hamilton Aviation area was conducted during the FR
investigation between October and December 1993. The FR program soil gas survey in this
TIM SITE RECORD OF DECISION PAGE 1-27
PART I DECISION SUMMARY SAC/I 10331/003.000
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area involved the collection of soil gas samples at 29 locations around the perimeter of
Hamilton Aviation Buildings D-252, D-267, and D-275.
At Building D-252, PCE was detected above its SGSL (0.4 pg/L) at two isolated locations
along the east side of the building. The PCE concentrations ranged from 0.7 ug/L at the
northeast end of the building (adjacent to the current Hamilton Aviation hazardous
materials storage area) to 6 ug/L at the southeast end of the building (within the former
hazardous materials storage area). No other samples collected around the perimeter of
Building D-252 contained VOC concentrations above SGSLs.
Both PCE and benzene were detected around the perimeter of Building D-267 at
concentrations above their respective SGSLs of 0.4 ug/L and 0.26 ug/L. PCE was detected
in four samples located along the northern and eastern sides of the building at
concentrations ranging from 05 ug/L to 0.8 pg/L. Benzene was detected in a single sample
at a concentration of 0.3 pg/L. No other samples collected around the perimeter of Building
D-267 contained VOC concentrations above SGSLs.
Both PCE and benzene were detected around the northern and western sides of Building
D-275 at concentrations greater than their SGSLs. PCE was detected in eight samples at
concentrations ranging from 0.9 pg/L to 9 pg/L, with the highest concentrations centered
around the paint stripping area located at the northwestern end of Building D-275. Benzene
was detected above its SGSL at only one sample point, located at the northeastern corner of
the building. No other samples collected around the perimeter of Building D-275 contained
VOC concentrations above SGSLs.
Based on the soil gas surveys around Hamilton Aviation Buildings D-252, D-267, and
D-275, it appears that four separate areas of VOC-contaminated soil exist at the subsite.
These areas are the southeast comer of Building D-252 within the former hazardous
materials storage area, the northeast comer of Building D-252 adjacent to the current
hazardous materials storage area, the area between Buildings D-267 and D-275, and the area
north of Building D-275 within the Hamilton Aviation paint stripping area.
6.19 Zone F: North End of Samsonite Building 0-167
Samsonite Building D-167 is located between Highway 89 and Park Avenue, west of the
north apron in Zone F. No known hazardous releases have occurred in this area. However,
because of its proximity to known contamination in the Three Hangars Area and a history
of aircraft-related activities since the early 1970s, the area including and surrounding the
Samsonite Building is viewed as a potential source of soil contamination.
As part of an airport-wide site investigation in 1988, soil-gas sampling was conducted near
the Samsonite Building. Nine soil gas samples were collected along a north-south line
between Park Avenue and the Samsonite Building. Elevated concentrations of 1,1-DCE
(34 to 820 pg/L) were reported in samples from two locations at the north end of the
building.
The most recent investigation of the Samsonite Building was conducted during the PR
investigation. The FR program soil gas survey was conducted around the perimeter of the
Samsonite Building in November 1993. Soil gas samples were collected at 38 locations
around the perimeter of the building with a spacing of approximately 100 feet.
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The analytical results of the soil gas survey showed that four samples contained 1,1-DCE
ranging from 4 ug/L to 17 ug/L, exceeding the SGSL of 3.8 ug/L. These samples were
located north of the building, adjacent to and immediately south of one of the locations that
contained elevated 1,1-DCE soil gas concentrations during the airport-wide site
investigation. Samples collected immediately north and east of the earlier elevated soil gas
sample did not contain VOCs above SGSLs. Thus, the northern and eastern boundaries of
soil contamination in this area have been defined, while the southern and western
boundaries have not. No other soil gas samples collected in the Samsonite Building area
contained VOC concentrations above SGSLs.
1,1-DCE has been identified in the shallow vadose zone immediately north of Samsonite
Building D-167. Follow-up samples suggest that the subsurface contamination at this
location may be limited in areal extent, but the lateral extent of contamination on the south
and west side of the initial detection has not been defined.
6.20 Burr-Brown Corporation Property
In 1987, a shallow soil gas survey was conducted across the entire Burr-Brown facility.
Detected TCE concentrations ranged from 0.04 to 15.74 ug/L. The highest concentrations
were detected in two hot spots adjacent to Buildings 1 and 3 (Figure 4). In 1996, deeper soil
borings were installed in these two areas to determine if there was a continuing source of
TCE to groundwater in the vadose zone. The 1996 data indicated that only one of 20
samples from the two borings had TCE concentrations in excess of the ESGSL. Vadose zone
transport modeling indicated that the vadose zone concentrations of TCE are not
sufficiently elevated to result in groundwater impacts above the MCL.
February and May 1997 analytical results from groundwater sampling showed
concentrations of TCE above the. MCL in two and three monitoring wells, respectively, on
and downgradient of the Burr-Brown Property. The highest concentration was 18 ug/L
detected in a well located in the vicinity of the soil gas hot spots described above. In
addition, in a monitoring well located upgradient of the Burr-Brown Property source areas,
TCE levels were 20 and 14 ug/L in February and May 1997, respectively. This monitoring
well is located between the former West-Cap Property and the Burr-Brown Property.
6.21 Former West-Cap Property
Soil gas samples were collected from 34 locations at the former West-Cap Property in
February 1996 (Figure 5). Multiple depths were sampled at several of the locations. TCE,
PCE and 1,1-DCE were all detected above SGSLs.
Concentrations of TCE and PCE were found above SGSLs in the vicinity of Building A. The
highest concentration of TCE (45 ug/L) was found inside Building A, near the center drain.
TCE concentrations east of Building A generally decrease with depth. The highest PCE
concentration (5.6 ug/L) was also found inside Building A, near the northern drain.
1,1-DCE and 1,1,1-TCA were detected in the vicinity of Buildings B and C. The SGSL was
exceeded for 1,1-DCE, but not for 1,1,1-TCA. The highest concentrations of 1,1-DCE (22
ug/L in two samples) were detected in deeper samples (15 and 30 feet bgs). 1,1-DCE
concentrations increased between the 6 and 15-foot depths at several locations. The highest
concentration of 1,1,1-TCA (4.3 ug/L) was also detected in a deeper sample (15-foot depth).
TIAA SITE RECORD OF DECISION PAGE 1-29
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A monitoring well located downgradient of the former West-Cap facility and upgradient of
the Burr-Brown facility was installed in 1984 as part of investigative activities at the Burr-
Brown facility. PCE and TCE concentrations in this well have shown a gradual increase
since October 1992. The sample collected in June 1994 had PCE at 12 ug/L.
7.0 Summary of Site Risks
The Arizona Department of Health Services (ADHS) completed the Baseline Human Health
Risk Assessment, Tucson International Airport Superfund Site, December 1,1996 (ADHS, 1996)
(hereafter referred to as the ADHS Risk Assessment) to evaluate whether there are
unacceptable human health risks from potential exposure to chemicals associated with the
Airport Property, Burr-Brown Property, or the former West-Cap Property. This section
summarizes the key components and findings of the ADHS Risk Assessment.
The primary objective of the ADHS Risk Assessment was to provide an evaluation of
human health risks that may result from exposure to identified contaminants. The
chemicals of potential concern (COPCs), exposure and toxicity assessment, and current and
potential future risks are reported in the following sections for soils, soil gas, and shallow
groundwater at Zones A through F of the Airport Property, Burr-Brown Property, and the
former West-Cap Property. More detailed information on the criteria used for estimating
risks can be found in the ADHS Risk Assessment document (ADHS, 1996).
7.1 Identification of Chemicals of Potential Concern
ADHS identified COPCs from qualified data generated during the Airport Property RI and
FR investigations, Burr-Brown Property investigations, and initial investigations at the
former West-Cap Property investigations. The ADHS Risk Assessment used available data
to evaluate human health risks that may result from contamination assumed to represent
current conditions. Table 2 lists the selected COPCs used in the ADHS Risk Assessment.
7.2 Exposure Assessment
This section briefly summarizes the potentially exposed populations, the exposure
pathways evaluated, and the exposure quantification from the ADHS Risk Assessment.
7.2.1 Potentially Exposed Populations
Potential receptors include present and potential future human populations working on or
living in the vicinity of the three properties that comprise the ROD Site. Currently, die ROD
Site is primarily used for airport and other commercial purposes. Therefore, potential
receptors include workers at the airport or in related commercial facilities. Directly west of
Zones E and F (west of Highway 89) there is a small residential population with both adults
and children that are potential receptors. There are no current receptors for the
contaminated shallow groundwater, because there are no operating water supply wells in
the Shallow Groundwater Zone.
Potential future receptors include future workers and residents in the TIAA vicinity,
including the Burr-Brown and former West-Cap Properties. The ADHS Risk Assessment
evaluated potential risk to future area residents that could be exposed to contaminated
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shallow groundwater using data from off-site monitoring wells downgradient of the known
shallow contamination.
7.2.2 Chemical Exposure Pathways
An exposure pathway describes how a receptor could be exposed to contaminants present
at a site or emitted from a site. A complete exposure pathway requires the following
elements: a source, a mechanism for release and migration, an exposure medium, a point of
potential human contact with contaminated medium, and a route of exposure (ingestion,
inhalation, dermal contact). A complete discussion of the current and future potential
exposure points and routes is presented in the ADHS Risk Assessment document (ADHS,
1996).
The current exposure pathways retained in the ADHS Risk Assessment include:
Occupational exposures to inhalation of contaminated soil gas
Potential dermal contact with or ingestion of contaminated soil or inhalation of fugitive
dust by workers
Potential dermal contact with or ingestion of contaminated soil or inhalation of fugitive
dust by residents
The retained future exposure pathways include:
Residential use (ingestion, dermal contact, and inhalation) of contaminated shallow
groundwater;
Occupational exposures to inhalation of contaminated soil gas;
Potential dermal contact with or ingestion of contaminated soil or inhalation of fugitive
dust by workers; and,
Potential dermal contact with or ingestion of contaminated soil or inhalation of fugitive
dust by residents.
7.2.3 Exposure Quantification
Exposure, defined as contact with a chemical or physical agent, was calculated as chronic
daily intake for each retained exposure pathway described in Section 7.2.2. Exposure under
a residential scenario is estimated using six factors: chemical concentration at the point of
exposure, contact rate, exposure frequency, exposure duration, body weight, and averaging
time, as described by the following general equation:
Residential Intake -
Concentration x Contact Rate x Exposure Frequency x Exposure Duration
Body Weight x Averaging Tune
Exposure under a occupational scenario is estimated using the six factors as in a residential
scenario along with exposure time (hours of exposure/workday) and a conversion factor
(workday/8 hours), as described by the following general equation:
Occupational Intake =
Concentration x Contact pate x Exposure Frequency x Exposure Time x Exposure Duration x Conversion Factor
Body Weight x Averaging Time
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Exposure, or intake, is expressed as milligrams of chemical per kilogram of body weight per
day (mg/kg-day) to normalize for time and body weight. The following presents the
parameters and methods used in estimating exposure for each of the selected exposure
pathways.
7.2.3.1 Soil Gas
Inhalation. ADHS evaluated soil gas exposures using modeled outdoor and indoor
concentrations as presented in the ADHS Risk Assessment. The Karimi model was used for
estimating flux rate from the soil. Daily intake values for each occupational exposure
setting were calculated using the equations presented above. Exposure variable values are
presented in the ADHS Risk Assessment document (ADHS, 1996).
7.2.3.2 Soils/Sediments
Ingestion. Exposure through ingestion of contaminants in soil/sediments depends on the
concentration in soil, the amount ingested, and the frequency and duration of exposure.
ADHS evaluated average and reasonable maximum exposures for both occupational and
residential exposure settings. The exposure variables are presented in the ADHS Risk
Assessment document.
Inhalation. ADHS calculated exposure via inhalation of dust and vapors from
contaminated surface soil using soil concentrations, the soil volatilization factor, the
particulate emission factor describing the amount of soil entrained in the air as dust,
inhalation rate, and the frequency and duration of exposure. The particulate emission
factor expresses the relationship of chemical concentrations adsorbed to soil and
concentrations of airborne respirable dust particles and is estimated using EPA default
values (EPA, 1991). The parameters used to estimate intake from inhaling both
contaminated dust from soil and volatile compounds from soil are provided in the ADHS
Risk Assessment document.
Dermal Contact. Dermal absorption of contaminants in soil /sediments is a function of the
concentration in soil, the surface area of exposed skin, the ability of the contaminant to
penetrate through the skin, and frequency and duration of exposure.
The parameters used by ADHS to estimate the absorbed dose for reasonable maximum and
average exposure to contaminants in soil through dermal contact are provided in the ADHS
Risk Assessment document. Exposures for both occupational and residential settings were
calculated for reasonable maximum and average exposure.
7.2.3.3 Groundwater
Residents could potentially be exposed in the future to contaminants in shallow
groundwater through ingestion, inhalation of volatile organic compounds, or dermal
contact with groundwater (if used for water supply).
Ingestion. The specific values used to calculate the intake associated with the ingestion of
contaminants in groundwater are provided in the ADHS Risk Assessment document.
Inhalation. Residents could be exposed to volatile chemicals transferred from tap water to
the air from showers, baths, toilets, dishwashers, washing machines, and during cooking.
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The exposure variable values used to evaluate inhalation of chemicals volatilized from
groundwater are provided in the ADHS Risk Assessment document.
Dermal Contact. Dermal absorption is typically an insignificant route of exposure in the
residential groundwater use setting. However, ADHS estimated dermal absorption for
chemical contaminants to ensure that any potential risks from this exposure pathway were
considered. The magnitude of potential exposure by this pathway is related to the
concentration in water, surface area of exposed skin, the dermal penetrability of the
contaminant, and frequency and duration of exposure. The exposure variable values used
to estimate exposure to groundwater through dermal contact are provided in the ADHS
Risk Assessment document.
7.3 Toxicity Assessment
Chemical contaminants may be divided into two groups according to their effects on
human health: carcinogenic or noncarcinogenic/systemic effects. Exposure to some of the
chemicals detected at the ROD Site could potentially result in both types of effects.
Noncarcinogenic or systemic effects include a variety of lexicological end points and may
include effects on specific organs or systems, such as the kidney, liver, lungs, etc.
Carcinogenic effects result in, or are suspected to result in, the development of cancer.
EPA has developed a carcinogen classification system using weight-of-evidence to classify
the likelihood that a chemical is a human carcinogen. Definitions for the weight-of-
evidence classifications are presented below.
EPA Weight-of-Evidence
Classification System for Carcinogenicity
Group
A
Bl or B2
C
D
E
Description
Human carcinogen, based on evidence from epidemiological studies.
Probable human carcinogen.
Bl indicates that limited human data are available.
B2 indicates sufficient evidence in animals and inadequate or no evidence in humans.
Possible human carcinogen, based on limited evidence in animals.
Not classifiable as to human carcinogenicity.
Evidence of noncarcinogeniciry for humans.
Source: EPA, 1989a.
EPA's Carcinogenic Assessment Group has developed cancer slope factors for estimating
excess lifetime cancer risks associated with exposure to potentially carcinogenic chemicals of
potential concern. Cancer slope factors, which are expressed in units of (mg/kg-day)"', are
multiplied by the estimated intake of a potential carcinogen, in mg/kg-day, to provide an
upper-bound estimate of the excess lifetime cancer risk associated with exposure at that intake
level. The term "upper bound" reflects the conservative estimate of the risks calculated from
the cancer slope factors. Use of this approach makes underestimation of the actual cancer risk
highly unlikely. Cancer slope factors are derived from the results of human epidemiological
studies or chronic animal bioassays to which animal-to-human extrapolation and uncertainty
TIAA SITE RECORD OF DECISION PAGE 1-33
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factors have been applied (for example, to account for the use of animal data to predict effects
on humans).
EPA has developed reference doses to indicate the potential for adverse health effects from
exposure to chemicals of potential concern exhibiting noncarcinogenic effects. Reference
doses, which are expressed in units of mg/kg-day, are estimated threshold levels for daily
exposure above which exposure is considered unsafe for humans, including sensitive
individuals. Estimated intakes of chemicals of potential concern from environmental media
(e.g., the amount of a chemical ingested from contaminated drinking water) can be compared
to the reference doses. Reference doses are derived from the results of human epidemiological
studies or animal studies to which uncertainty factors have been applied (for example, to
account for the use of animal data to predict effects on humans). These uncertainty factors
help ensure that the reference doses will not underestimate the potential for adverse
noncarcinogenic effects to occur.
Toxirity values (for both carcinogenic and noncarcinogenic effects) for the COPCs at the
ROD Site are provided in the ADHS Risk Assessment document.
7.4 Risk Characterization Summary
Information presented in the exposure assessment and the toxicity assessment is integrated
in this section to characterize risk to human health from COPCs at the ROD Site.
For carcinogens, risks are estimated as the incremental probability of an individual
developing cancer over a lifetime as a result of exposure .to the carcinogen. These risks are
probabilities that are generally expressed in scientific notation (e.g., 1x10"* or 1E-6). An
excess lifetime cancer of 1x10"* indicates that as a reasonable maximum estimate, an
individual has a one in one million chance of developing cancer as result of site-related
exposure to a carcinogen over a 70-year lifetime under specific exposure conditions at the
ROD Site. Similarly, an excess lifetime cancer risk of 1 x 10"* refers to a reasonable
maximum estimate of a one in ten thousand chance of developing cancer as a result of the
exposure.
EPA uses the general 10~* to 10"* risk range as a "target range" within which EPA strives to
manage risks as part of a Superfund cleanup. Although EPA's risk managers may deem as
acceptable waste management strategies that achieve reductions in site risks anywhere
within the risk range, EPA has expressed a preference for cleanups achieving the more
protective end of the range (for example, 10*).
The potential for non-carcinogenic health effects is evaluated by comparing an exposure
level over a specified time period (for example, a lifetime) with a reference doses derived
for a similar exposure period. The ratio of exposure to toxicity is called a hazard quotient.
If the estimated intake (exposure) is greater than the reference doses, the hazard quotient
will be greater than one. A hazard quotient greater than one indicates the potential for an
adverse nonorcinogenic health effect from exposure to the chemical.
A hazard index is generated by adding the hazard quotients for all chemicals of potential
concern within a medium or across all media to which a given population may reasonably
be exposed. A hazard index exceeding one indicates the potential for an adverse non-
carcinogenic health effect from exposure to the medium or media. The hazard index
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provides a useful reference point for gauging the potential significance of multiple
contaminant exposures within a single medium or across media.
To evaluate human health risks from exposure to contaminants in various media at the
Airport Property, Burr-Brown Property and the former West-Cap Property, noncancer
hazard indexes and cancer risks were estimated for soil, soil gas, and groundwater.
7.4.1 Summary of Estimated Risk Current Conditions
Table 3 summarizes the quantitative risk results for current exposure to contaminants at
each subsite. Detailed worksheets for each subsite are included in Appendices I and II of
the ADHS Risk Assessment document (ADHS, 1996).
Hazard indices for all subsites were less than 1, indicating that non-cancer health effects
from the contamination are unlikely. Contamination present at some of the subsites did
result in an estimated lifetime cancer risk exceeding one-in-one million (1x10"*). Estimated
risks associated with contaminated soil/sediments at the following subsites exceeded IxlO*:
Zone E: Former Structure 21 - Reasonable Maximum Exposure (RME) to the PCB
Aroclor 1260 in soil resulted in an estimated excess lifetime cancer risk of 2x10"*
Zone E: Building 25 - RME to PCBs in soil resulted in a risk of IxlO"6
Zone E: Drainages and Ponding Areas (South Drainage Outfall/Ponding Areas) - RME
to PCBs in soil resulted in a risk of 1x10*
Zone E: Drainages and Ponding Areas (Off-Site Sediment Site 1) - Central tendency (CT)
exposure to PCBs in soil resulted in a risk of IxlO"6, RME to PCBs in soil was 2x10s
Zone E: Drainages and Ponding Areas (Off-Site Sediment Site 2) - RME to PCBs in soil
resulted in a risk of IxlO'5
7.4.2 Summary of Estimated Risk - Future Conditions
Table 4 summarizes the potential future human health risk from exposure to contaminants
in each exposure area. The potential future use of all subsites was assumed to be
occupational, except for sediment in the off-site areas and shallow groundwater which
assume a residential scenario. The estimated future risks for exposure to contaminated
groundwater assume that untreated shallow groundwater is being used for residential
purposes. Detailed worksheets for each subsite are included in Appendices I and n of the
ADHS Risk Assessment document (ADHS, 1996).
Contamination present at some of the subsites did result in an estimated lifetime cancer risk
exceeding one-in-one million (1x10*). Only the shallow groundwater had an estimated
hazard index of greater than 1. At all other subsites, non-cancer health effects from
contamination are unlikely. The following subsites exceeded IxlO"6 or a hazard index of 1:
Zone E: Former Structure 21 - Central tendency exposure to PCBs in soil resulted in a
risk of 2x10"*, RME to PCBs in soil resulted in a risk of 6x10^
Zone E: Former Structure 30 - RME to PCBs in soil resulted in a risk of 4xlO'5
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Zone E: Drainages and Ponding Areas (North Drainage Outfall/Ponding Areas) - RME
to PCBs in soil resulted in a risk of 2x10s
Zone E: Drainages and Ponding Areas (South Drainage Outfall/Ponding Areas) - CT
exposure to PCBs in soil resulted in a risk of 1x10"*, risk from RME to PCBs in soil was
3x10"
Zone E: Drainages and Ponding Areas (Off-Site Sediment Zone 1) - CT exposure to
PCBs in soil resulted in a risk of IxlO"6, RME to PCBs in soil resulted in a risk of 2x10s
Zone E: Drainages and Ponding Areas (Off-Site Sediment Zone 2) - risks from RME to
PCBs in soil was IxlO"5
Zone E: Drainages and Ponding Areas (Off-Site Sediment Vacant Lot) - RME to PCBs in
soil resulted in a risk of 1x10*
Zone E: Shallow Groundwater - CT residential exposure to VOCs in groundwater
resulted in a risk of 3xlO"s for the four wells evaluated. RME to VOCs in groundwater
from the four wells resulted in a risk 2x10"*. The hazard index for the combined wells
slightly exceeded 1.
7.4.3 Baseline Human Health Risk Assessment Conclusion
EPA has determined that the potential risks associated with exposure to contaminated soil
and groundwater summarized in Tables 3 and 4 are unacceptable. In addition, for the
subsites in the vicinity of the Three Hangars area, EPA determined that concentrations of
VOCs in subsurface soils represent an unacceptable threat to groundwater. Actual or
threatened releases of hazardous substances from the ROD Site, if not addressed by
implementing the response action selected in this ROD, may present an imminent and
substantial endangerment to public health, welfare, or the environment.
7.4.4 Ecological Risk Summary
EPA conducted an assessment of potential ecological receptors and exposure pathways at
the ROD Site. Surface soil samples were collected and assessed for potential ecological risk.
EPA concluded that the remedy selected in this ROD (described in Section 10) will address
the ecological risk presented by soil contaminants.
8.0 Description of Remedial Alternatives
For purposes of evaluation, remedial alternatives are separated into the following groups :
VOC-Contaminated Soils Outside Area 1 (Plug-in subsites);
VOC-Contaminated Soils Inside Area 1;
VOC-Contaminated Soils Inside the TI Zone;
PCB-Contaminated Soils and Sludges;
TAA Landfill Closure;
Shallow Groundwater; and
Shallow Groundwater Inside the TI Zone.
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Area 1 includes the Three Hangars Area and most other portions of Zone E (Area 1 is
shown in Figure 11). The RI/FS identified an area within Area 1 where data generated
during the RI indicated that attainment of potential groundwater cleanup ARARs would be
impracticable from an engineering perspective. That area (termed the Technical
Impracticability [TI] Zone) has been proposed for a technical impracticability waiver of
ARARs, as described in Section 11.1. The inability to meet groundwater cleanup ARARs
stems from the presence of dense non-aqueous phase liquids (DNAPLs) and the complexity
of the hydrogeology in the TI Zone. Extensive evidence from sites across the country has
shown that in-situ groundwater remediation of areas with DNAPLs is difficult to achieve.
Appendix B of the FS contains a detailed discussion of the TI Zone and the need for an
ARAR waiver for this area. Section 11.6 of this ROD describes the ARAR waiver. The
approximate extent of DNAPLs, and thus the TI Zone, is shown in Figure 11.
8.1 VOC-Contaminated Soils Outside Area 1 (Plug-in Subsites)
Remedial alternatives developed in this section address specific areas or subsites (located
outside of Area 1) of the ROD Site with VOC-contaminated soils. These subsites have not
been fully characterized. After the subsites have been characterized, the Plug-in Criteria
(described in Section 10) will be evaluated to determine whether or not the subsites would
"plug-in" to the presumed remedial alternative (SVE).
The remedial objectives for subsurface soils outside Area 1 are to reduce contaminant
concentrations so that subsurface contamination will not cause water quality impacts above
MCLs in the first saturated groundwater unit underlying that area. The demonstration that
contaminant levels have been sufficiently reduced will be made using vapor transport
modeling and mixing zone calculations.
The 11 plug-in subsites requiring additional investigation include (Figure 8):
Zone C: Hughes Credit Union Dump;
ZoneD: C-294 Burn Pit;
ZoneD: Fire Drill Training Area D-3;
ZoneD: TAA Landfill;
Zone D: South Ramp and Drains;
ZoneE: West End of Runway 3;
ZoneE: Former Building 32;
ZoneF: Hamilton Buildings D-252, D-267 and D-275;
Zone F: North End of Samsonite Building D-167; and
Former West-Cap Property (2 locations).
If a subsite is selected for plug-in to an SVE remedy, subsite-specific conditions may need to
be evaluated to determine if any one or a combination of enhancement technologies are
necessary to be implemented with the SVE. Retained SVE enhancement options include:
Capping/paving to prevent short circuiting;
Bioventing to enhance the naturally occurring biodegradation process (natural
attenuation/intrinsic remediation);
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Pneumatic fracturing to increase permeability, thereby allowing VOCs to volatilize
more readily; and
Multi-phase extraction to extract soil gas, the first saturated zone groundwater, and/or
NAPL and to lower the water table to allow volatilization of VOCs at lower depths.
The need for off-gas treatment and selection of the most appropriate treatment technology
will be made during remedial design. If off-gas treatment is deemed necessary, the
following technology options have been retained:
Catalytic oxidation;
Thermal oxidation;
Vapor-phase carbon; and
Vapor-phase resin adsorption.
8.1.1 Alternative A1 - No Action
Under Alternative Al, no additional actions at the plug-in subsites would be taken. This
alternative would rely solely on natural attenuation and intrinsic remediation to degrade
contaminants. For the plug-in subsites, the no action alternative is only viable after
characterization is complete.
8.1.2 Alternative A2 Institutional Controls and Monitoring
This alternative would employ institutional controls and monitoring in conjunction with
intrinsic remediation and natural attenuation as the remedy for plug-in subsites.
Institutional controls would limit exposure to the contaminated soils and monitoring would
track changes in contaminant conditions over time and detect possible groundwater
impacts. Institutional controls and monitoring are common components to nearly all of the
alternatives. Although this alternative was included in the FS, pursuant to EPA's
Presumptive Remedy Guidance for VOCs in soil, only the No-Action and SVE alternatives
need further analysis.
8.1.3 Alternative A3 - Soil Vapor Extraction (SVE)
Alternative A3 would employ SVE as a method of treating VOC-contaminated subsurface
soils at the plug-in subsites. Vapor extraction wells would be installed and screened in
subsurface soils in areas and at depths determined to require remediation based on
additional investigations and modeling. VOCs would be extracted from subsurface soils
through the wells by generating a vacuum with blowers. Off-gas from the system could be
treated by one of the retained off-gas treatment options. As noted above, a number of
technologies could also be implemented for possible application with SVE to enhance its
effectiveness.
This alternative would employ the common components of intrinsic remediation and
institutional controls (such as deed restrictions or other appropriate means) and monitoring.
The final scope of subsurface soil remediation would be developed during the remedial
design phase through vapor transport modeling and mixing zone calculations, as
prescribed by the "Plug-in" Process.
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8.2 VOC-Contaminated Soils Inside Area 1
These remedial alternatives address soils contaminated with VOCs inside Area 1, but
outside of the TI Zone. The alternatives are the same as Alternatives Al through A3
described above in Section 8.1. The remedial objective for the contaminated soil alternatives
in this area is:
To achieve, by vapor extraction, lateral and vertical soil vapor containment within
Area 1 until contaminant concentrations are reduced such that soil contamination will
not result in water quality impacts to the Shallow Groundwater Zone above MCLs.
During implementation of this remedy, monitoring will be conducted to further evaluate
the practicability of restoration of both the Shallow Groundwater Zone (outside the TI
Zone) and the associated VOC-contaminated soils.
The specific areas found to have VOC-contaminated soils above SGSLs inside Area 1
include (Figure 8):
Zone E: Three Hangars Area (a portion of Buildings 14/15, Building 18, Building 25,
and Building D-158, Hangar 1, North and East Sides of Hangar 1, and Southern Portion
of Hangar 2; and
ZoneE: Soils Beneath West Lease USTs and former Building 32.
As noted above, the three alternatives evaluated for this area (labeled Alternative Bl
through Alternative 63) are the same as Alternatives Al through A3, described in Section
8.1. The possible SVE enhancements and treatment technologies are also the same as those
described in Section 8.1.
8.3 VOC-Contaminated Soils Inside The TI Zone
These remedial alternatives address the VOC-contaminated soil present in the TI Zone.
The remedial objective for the contaminated soil inside the TI Zone is:
To achieve lateral and vertical soil vapor containment until contaminant concentrations
have been reduced so that ceasing operation of the TI Zone remedy will not cause a
water quality impact in excess of MCLs to the Shallow Groundwater Zone outside the
TI Zone or to the Regional Aquifer.
The extent of the TI Zone is described above and shown in Figure 11. The TI Zone is located
just south of the Three Hangars and covers portions of Buildings 14/15 and
Buildings 16/17.
To meet the remedial objectives for soil associated with the TI Zone, VOC-contaminated soil
vapors must be contained. The three remedial alternatives evaluated for this area (labeled
Alternative Cl through Alternative C3) are the same as Alternatives Al through A3,
described above in Section 8.1.
SVE enhancements potentially applicable to the TI Zone soil remedy include:
Bioventing to enhance the naturally-occurring biodegradation process (Natural
Attenuation/Intrinsic Remediation); and
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PART I DECISION SUMMARY
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Multi-Phase Extraction to extract soil gas, shallow groundwater and/or NAPL, and to
lower the water table to allow volatilization of VOCs at lower depths.
Capping/Paving were eliminated from consideration as SVE enhancements because the
area is already paved with 12 inches of concrete. Pneumatic fracturing was eliminated from
consideration as an SVE enhancement because it may allow DNAPLs to migrate deeper into
the Shallow Groundwater Zone.
The SVE treatment options are the same as described above in Section 8.1.
8.4 PCB-Contaminated Soils and Sludges
Remedial alternatives developed in this section address soils and sludges contaminated
with PCBs. The remedial objective for these alternatives is to remediate all soils and
sludges contaminated with PCBs at levels that exceed cleanup standards (0.76 mg/kg).
The PCB-coritaminated soils and sludges were once found both on- and off-Airport
Property, as illustrated in Figure 9, including:
Zone E: Drainages and Ponding Areas;
ZoneE: Structures 21 and 30;
ZoneE: Hangar 1;
ZoneE: Sludges in the Canale System; and
ZoneE: Soil Adjacent to the Canale System.
PCB-contaminated soils and sludges were recently removed from all residential areas and
portions of the Zone E Drainage and Ponding Areas in response to an Unilateral Order
issued by EPA (see Figure 9).
8.4.1 Alternative 01 No Further Action
Under this alternative, no additional actions would be taken to address PCB-contaminated
soils and sludges.
8.4.2 Alternative D2 - Institutional Controls and Monitoring
Institutional controls (such as fences and signs) and monitoring would be employed to
address potential exposure to PCB contamination that exceeds cleanup levels (0.76 mg/kg).
Access to contaminated areas would be restricted with fencing. Monitoring would be used
to determine if PCB contamination in surface soils is migrating downward beyond the
current extent of contamination.
8.4.3 Alternative 03 - Excavation and Off-Site Landfilling
As part of this alternative, soils and sludges contaminated with PCBs in excess of cleanup
levels (0.76 mg/kg) would be excavated and removed. In most of the PCB-contaminated
areas, the contamination is limited to surface soil. Other PCB contamination is associated
with sludges and materials in drain lines.
Soil and sludges would be removed with conventional excavation equipment, loaded onto
trucks and/or rail cars, and transported off-site to an approved disposal facility. Soils and
sludges with PCB concentrations of 50 mg/kg or greater would require disposal at a Toxic
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Substances Control Act (TSCA)-approved landfill. Soils and sludges that contain PCBs
above the cleanup level, but less than 50 mg/kg would be disposed at any landfill that is
authorized pursuant to CERCLA's off-site rule. Excavated areas would be backfilled with
clean soils and graded to ensure proper drainage.
The PCB-contaminated sludges in the Canale System will likely also contain elevated
metals. These sludges may require stabilization prior to disposal if the metals exceed TCLP
criteria..
8.4.4 Alternative D4 - Excavation and On-Site Landfilling
This alternative differs from Alternative D3 in that excavated soils with PCB concentrations
below 50 mg/kg would be landfilled on site. This would require construction of an
appropriate cell at the TAA Landfill and construction of an Arizona-compliant RCRA
Subtitle D cap over the cell. EPA has approved the State of Arizona RCRA Subtitle D
program and has determined that it complies with 40 CFR Part 258.
Soils with PCB concentrations of 50 mg/kg or higher would either require disposal at a
TSCA-approved landfill or construction of the equivalent to a TSCA-approved cell at
TAA Landfill. TSCA requirements would typically include a cap with performance that is
consistent with a system constructed of 3 feet of clay and vegetative cover or a synthetic cap
liner with vegetative cover. These requirements for a cell liner could potentially be waived
because the water table is greater than 50 feet bgs and the arid environment virtually
eliminates the potential for infiltration through a properly graded soil cover.
As with Alternative D3, any Canale sludges that contain metals above TCLP criteria would
require stabilization prior to landfilling. Institutional controls and monitoring at the TAA
Landfill would also be a component of this alternative.
8.4.5 Alternative D5 - Excavation, Treatment and On-Site Landfilling
This alternative is the same as Alternative D4, except that the PCB-contaminated materials
that exceed 50 mg/kg would be treated to meet RCRA land disposal restrictions and would
be disposed on-site with RCRA-compliant disposal. Thus, neither a TSCA-approved cell at
TAA Landfill or off-site disposal at a TSCA-approved landfill would be required. Potential
treatment technologies include solvent extraction/washing, dechlorination or stabilization.
8.4.6 Alternative 06 - Excavation, Treatment and Off-Site Landfilling
This alternative combines the excavation and off-site landfilling described for Alternative
D3 with the treatment of more highly-contaminated materials described in Alternative D5.
All materials would be disposed off-site. For off-site disposal, a TSCA-approved facility
would not be required because all materials would be treated to below 50 mg/kg prior to
disposal. The treatment could occur on-site or at the disposal facility.
8.5 TAA Landfill Closure
Remedial alternatives developed in this section address the closure of TAA Landfill.
Materials within TAA Landfill were found to contain VOCs at a few locations. The TAA
Landfill is one of the VOC-contaminated soils "Plug-in" subsites discussed above in Section
8.1. The alternatives in this section only address landfill closure. The remedial objective for
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TAA Landfill closure is to close the landfill in accordance with State RCRA Subtitle D
landfill closure requirements.
8.5.1 Alternative E1 No Action
Under this alternative, no actions would be conducted for landfill closure.
8.5.2 Alternative E2 - Institutional Controls and Monitoring
This alternative would employ institutional controls and monitoring as the remedy for
landfill closure. Institutional controls would limit access to the landfill and appropriate
monitoring would detect any landfill impacts on groundwater. Intrinsic remediation would
act to reduce contaminant concentrations.
8.5.3 Alternative E3 - Landfill Closure
Under this alternative, the TAA Landfill would be dosed in accordance with the
substantive State of Arizona RCRA Subtitle D requirements. Because the landfill is within
the TIAA Site boundary and is being dosed pursuant to a CERCLA action, a permit is not
required to dose the landfill. A dosure and post-dosure monitoring plan, in accordance
with ARARs, would be required.
Existing fill materials would be used to achieve the required minimum and maximum
grades of 2 percent and 20 percent, respectively. A minimum 2-foot thick dean soil layer
would then be placed and compacted over the fill materials. The cap would be compacted
and provided with drought resistant vegetative cover. Intrinsic remediation and
institutional controls and monitoring are components of this alternative.
8.6 Shallow Groundwater (Outside the Tl Zone)
The alternatives in this section address VOC contamination in the shallow groundwater
outside of the TI Zone. The limits of the VOC plume in the Shallow Groundwater Zone are
shown on Figure 11.
Remedial objectives for shallow groundwater (outside the TI Zone) are:
To prevent migration of contaminants from the Shallow Groundwater Zone, using
hydraulic containment, at levels that would result in exceedances of drinking water
standards (MCLs, see Table 6) in the Regional Aquifer or in other portions of the
Shallow Groundwater Zone; and
To restore the in-situ Shallow Groundwater Zone quality outside the TI Zone to MCLs.
Information gathered during the RI/FS suggests that contamination outside the TI Zone
may prove to be persistent due to site-specific factors. Monitoring of the Shallow
Groundwater Zone and the Regional Aquifer will be conducted during implementation of
the remedy to further evaluate the practicability of restoring the Shallow Groundwater
Zone (outside the TI Zone) to MCLs. Expansion of the TI Zone would require modification
of this ROD by EPA.
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8.6.1 Alternative F1 - No Action
Under this alternative, VOC-contaminated shallow groundwater would continue to migrate
with its natural flow. The contaminated shallow groundwater would be subject to lateral
and vertical transport into the Regional Aquifer or other, currently uncontaminated
portions of the Shallow Groundwater Zone. Only natural attenuation would be acting to
reduce contaminant concentrations under the No-Action Alternative. No groundwater
monitoring would be performed to track the migration of contaminants.
8.6.2 Alternative F2 - Institutional Controls and Monitoring
Institutional controls would be implemented to restrict use of shallow groundwater. This
would limit the potential for exposure to the contaminated groundwater. Groundwater
monitoring would be used to monitor contaminant migration and the progress of natural
attenuation in reducing contaminant concentrations. As in Alternative Fl, contaminated
groundwater would continue to migrate both laterally and vertically.
8.6.3 Alternative F3 - Bioaugmentation
Bioaugmentation is a process where nutrients, amendments, and/or bacteria are added to
the in-situ groundwater to enhance the natural biological activity that is already occurring.
A variety of methods can be used to introduce these materials to groundwater, including
injection wells or diffusion through existing monitoring wells. Natural attenuation,
institutional controls and monitoring would also be incorporated as components of this
alternative. Again, contaminated groundwater would continue to migrate both laterally
and vertically.
Currently, USAF Plant No. 44 is in the process of implementing an in-situ aerobic
bioaugmentation system. USAF Plant No. 44 is located south of the ROD Site and has
groundwater contaminated with TCE and other chlorinated hydrocarbons. The plan is to
inject treated groundwater, supplemented with nutrients, an oxygen source and a co-
metabolic inducer to enhance bioremediation. Bench-scale testing (Hargis & Associates,
Inc., 1996) indicates that this treatment method can achieve a 50 percent reduction of TCE
within an expected time period of 5 years at the USAF Plant No. 44 site. Because the USAF
Plant No. 44 site is similar in nature and in proximity to the Airport Property, this
alternative shows promise in accelerating remediation of the shallow groundwater.
8.6.4 Alternative F4 - Air Sparging
This alternative would provide in-situ treatment of the shallow groundwater without the
need for extraction. The shallow groundwater would be treated as it passes through a
"curtain" of sparge (air injection) wells. Air would be injected into the Shallow
Groundwater Zone from sparge wells connected to blowers. This alternative would aid in
volatilizing VOCs within the Shallow Groundwater Zone and also provide oxygen for
enhancement of aerobic biological activity. This process would need to be employed in
conjunction with SVE, which extracts the VOCs volatilized during the sparging process.
Natural attenuation, institutional controls and monitoring are incorporated as components
of this alternative. Bioaugmentation could also be considered as an enhancement
component.
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Typically, the radius of influence with air sparging is dependent upon the depth of the well
beneath the water table (radius increases with increasing depth). In portions of the Shallow
Groundwater Zone, the well depth that can be safely achieved without breaching the clay
that separates the Shallow Groundwater Zone from the Regional Aquifer is shallow (i.e.,
10 feet). Thus, the radius of influence of each sparge well will be small and a large number
of wells would be required.
8.6.5 Alternative F5 Extraction, Ex-situ Treatment, Bioaugmentation and Discharge
This alternative would require extraction of shallow groundwater from wells installed in
strategic locations. The wells would be placed in inhibit lateral and vertical contaminant
migration and to facilitate groundwater cleanup. The extracted water would be pumped to
a central treatment facility and treated by one or more of the following treatment options:
Air Stripping with off-gas treatment;
Carbon Adsorption (alone or in combination with air stripping or UV oxidation);
Piped to and treated at the USAF Plant No. 44 air stripping treatment plant (which was
approved pursuant to the 1986 ROD); and
UV Oxidation (in combination with air stripping or carbon adsorption).
Selection of the most appropriate treatment method for extracted groundwater would be
selected during remedial design. Treatment process selection would be contingent on the
ultimate quantity of extracted groundwater and the estimated treatment plant influent
concentrations. Bioaugmentation may also be considered as a treatment enhancement
component.
If air stripping were employed for the groundwater treatment, off-gas from the stripping
process could be treated via one of the following off-gas treatment options:
Catalytic Oxidation;
Thermal Oxidation;
Vapor Phase Carbon; and
Vapor Phase Resin Adsorption.
The treated groundwater would be discharged via one of the available discharge options,
including:
Injection Wells;
Reinjection Trenches;
Sanitary Sewer;
Industrial Reuse; and
Discharge to USAF Plant No. 44 (for injection in the Plant No. 44 injection wells).
Natural attenuation, institutional controls and monitoring are included as components of
this alternative. Electro-osmosis may also be considered as an extraction enhancement
component.
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8.7 Shallow Groundwater Zone Inside the Tl Zone
This section presents alternatives for contaminated groundwater inside the TI Zone. The
lateral extent of the 2-acre TI Zone is shown in Figure 11. The bottom of the TI Zone is an
elevation of 5 feet below the base of the Unit 4 gravel subunit, where Unit 4 exists, and an
elevation of 2370 feet above mean sea level, where the gravel subunit does not exist
(Figures 6 and 7). The bottom of the TI Zone has been selected based upon the assumption
from soil quality data obtained during the RI that the vertical limit of the area impacted
above MCLs is at approximately 4 feet below the bottom of the gravel subunit. The bottom
of the TI Zone also reflects the desire of EPA and the State of Arizona to provide a "buffer"
between the TI Zone and the Regional Aquifer where vertical hydraulic gradients could be
reversed by pumping, if necessary.
The alternatives for shallow groundwater inside the TI Zone are the same as Alternatives Fl
through F5 described above in Section 8.6. The remedial objective for the Shallow
Groundwater Zone inside the TI Zone is as follows:
To provide lateral and vertical hydraulic containment of contaminated shallow
groundwater until the following condition is met:
- Contaminant concentrations inside the TI Zone have been reduced such that ceasing
operation of the TI Zone remedy will not cause water quality impacts (MCL
exceedances) in the Shallow Groundwater Zone outside the TI Zone or to the
Regional Aquifer.
Achievement of this objective would be demonstrated by groundwater modeling and
monitoring of the Regional Aquifer and the Shallow Groundwater Zone.
As noted above, the five alternatives evaluated for the Shallow Groundwater Zone inside
the TI Zone (labeled Alternative Gl through Alternative G5) are the same as Alternatives Fl
through F5, described above in Section 8.6.
9.0 Summary of Comparative Analysis of Alternatives
The remedial alternatives described in Section 8 are compared to EPA's Superfund
evaluation criteria (described below) in this section. The comparative analysis provides the
basis for determining which alternatives present the best balance of EPA's nine Superfund
evaluation criteria provided in 40 Code of Federal Regulations (CFR) Part 300.430. The first
two cleanup evaluation criteria are considered threshold criteria that the selected remedial
action must meet. The five primary balancing criteria are balanced to achieve the best overall
solution. The two modifying criteria, State and community acceptance, are also considered in
remedy selection.
Threshold Criteria
1. Overall Protection of Human Health and the Environment addresses
whether an alternative provides adequate protection from unacceptable risks
posed by the site.
2. Compliance with Applicable or Relevant and Appropriate Requirements
(ARARs) addresses whether an alternative attains specific federal and state
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environmental requirements and state facility siring requirements or
provides grounds for a waiver of these requirements.
Primary Balancing Criteria
3. Long-term Effectiveness and Permanence refers to the degree to which an
alternative provides reliable protection of human health and the
environment over time.
4. Reduction of Toxicity, Mobility, or Volume Through Treatment refers to
the degree to which an alternative uses treatment to reduce the health
hazards of contaminants, the movement of contaminants, or the quantity of
contaminants at the site.
5. Short-term Effectiveness addresses the degree to which human health and
the environment will be adversely impacted during construction and
implementation of an alternative.
6. Implementability refers to the technical and administrative feasibility of an
alternative. This includes technical difficulties and uncertainties and the
availability of materials and services. It also includes coordination of federal,
state, and local government efforts.
7. Cost evaluates the estimated capital, operation and maintenance, and
indirect costs of each alternative in comparison to other equally protective
alternatives.
Modifying Criteria
8. State Acceptance indicates whether the state agrees with, opposes, or has
concerns about the preferred alternative.
9. Community Acceptance includes determining which components of the
alternatives interested persons in the community support, have reservations
about, or oppose.
The strengths and weaknesses of the alternatives were weighed to identify the alternative
providing the best balance with respect to the nine evaluation criteria.
Several of the alternatives described in Section 8 were screened out during preliminary
screening in the FS. Pursuant to the NCP, three screening criteria were used: effectiveness,
implementability and cost. These alternatives were not carried through the detailed
comparison of alternatives in the FS and, thus, are not discussed in this section. Section 5 of
the FS Report (CRA, 1997) provides additional detail on this preliminary screening. The
alternatives screened out include:
VOC-Contaminated Soils Inside the TI Zone
- Alternative C2: Institutional Controls and Monitoring
PCB-Contaminated Soils and Sludges
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- Alternative D2: Institutional Controls and Monitoring
- Alternative D3: Excavation and Off-Site Landfilling
- Alternative D4: Excavation and On-Site Landfilling
Shallow Groundwater
- Alternative F4: Air Sparging
Shallow Groundwater Inside the TI Zone
- Alternative G2: Institutional Controls and Monitoring
- Alternative G3: Bioaugmentation
- Alternative G4: Air Sparging
9.1 Overall Protection of Human Health and the Environment
The NCP requires that all alternatives be assessed to determine whether they can adequately
protect human health and the environment, in both the short term and long term, from
unacceptable risks. These risks can be mitigated by eliminating, reducing, or controlling
exposure to hazardous substances, pollutants, or contaminants. Overall protection of human
health and the environment draws on the assessments of other evaluation criteria, especially
long-term effectiveness and permanence, short-term effectiveness, and compliance with
ARARs. Reduction of toxicity, mobility, and volume is another important criteria for this
overall evaluation.
9.1.1 VOC-Contaminated Soils Outside Area 1 (Plug-In Subsites)
Although the ADHS Risk Assessment concluded that none of the plug-in subsites pose
unacceptable human health risks from direct exposure to surface soils, the Plug-in approach
described in Section 10.1 will identify those Plug-in subsites that pose an unacceptable
threat to groundwater. Alternative Al (No Action) and Alternative A2 (Institutional
Controls and Monitoring) are not protective of groundwater. Per the Presumptive Remedy
Guidance for SVE, Alternative A2 was screened out. Alternative A3 is the only alternative
that would be protective for subsites selected for further action pursuant to the Plug-in
Approach.
9.1.2 VOC-Contaminated Soils Inside Area 1
Alternative Bl (No Action) would not be protective of human health or the environment.
These two alternatives incorporate only intrinsic remediation to treat contaminated soils.
Migration of VOCs to the Shallow Groundwater Zone and adjacent soils would continue.
Alternative B2 would provide more protection than Alternative Bl in that monitoring
would be used to track contaminant concentrations.
Alternative B3 (SVE) would provide protection to the groundwater resource (and thus
human health and the environment) by reducing the quantity of VOCs in subsurface soils.
The extraction of soil vapors and subsequent treatment of off-gases would help prevent
migration of contaminants into the Shallow Groundwater Zone and adjacent soils and
would achieve RAOs.
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9.1.3 VOC-Contaminated Soils Inside the 71 Zone
Alternative Cl (No Action) would not be protective of human health or the environment,
although intrinsic remediation alone would be used to reduce the highly-contaminated soil
in the TI Zone. Migration of VOCs to the Shallow Groundwater Zone and adjacent soils
would continue without monitoring.
Alternative C3 (SVE) would provide protection to groundwater (and thus human health
and the environment) by reducing the quantity of VOCs in subsurface soils. The extraction
of soil vapors and subsequent treatment of off-gases would help prevent migration of
contaminants into the Shallow Groundwater Zone and adjacent soils and would achieve
RAOs.
9.1.4 PCB-Contaminated Soils and Sludges
Alternatives D5 (Excavation, Treatment, and On-Site Landfilling), and D6 (Excavation,
Treatment, and Off-Site Landfilling) both provide adequate protection of human health and
the environment by eliminating the possibility of human exposure to contamination or
further contaminant migration. Alternatives D5 and D6 further reduce long-term risks
through treatment prior to disposal of more highly contaminated materials. However,
Alternative D6 is more protective than Alternative D5 because off-site landfilling provides
more permanent protection from potential exposure than on-site landfilling. Alternative Dl
(No Further Action) would not be protective of human health and the environment.
9.1.5 TAA Landfill Closure
Alternative E3 (Landfill Closure) would provide better protection of human health and the
environment than Alternatives El (No Action) and E2 (Institutional Controls and
Monitoring) by eliminating potential exposure by installing a landfill cap. Alternative E3
would also reduce infiltration and potential downward migration of contaminants to
groundwater, whereas Alternatives El and E2 would not. Alternatives E2 and E3 would be
more protective than Alternative El because groundwater would be monitored to detect
impacts.
9.1.6 Shallow Groundwater (Outside the TI Zone)
Alternatives Fl (No Action) and F2 (Institutional Controls and Monitoring) would not be
protective of human health and the environment because shallow groundwater would
continue to migrate and impact the Regional Aquifer. Alternative F2 (Institutional Controls
and Monitoring) would be slightly more protective than Alternative Fl (No Action) because
shallow groundwater use would be restricted. Alternative F3 (Bioaugmentation) provides
protection of human health and the environment through treatment of contaminated
shallow groundwater. However, contaminant migration would continue. Pilot testing
would be required to evaluate potential effectiveness of this alternative and the need for
potential enhancement options. Alternative F5 (Extraction, Treatment, and Discharge)
would be protective of human health and the environment and meet RAOs by providing
containment to inhibit further contaminant migration (into the regional aquifer or currently
clean portions the Shallow Groundwater Zone) and mass removal to begin shallow
groundwater restoration to drinking water quality wherever practicable.
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9.1.7 Shallow Groundwater Inside the Tl Zone
Alternative Gl (No Action) provides no further protection of human health and the
environment and would not meet the RAO. Alternative G5 (Extraction, Treatment, and
Discharge) meets the RAO and provides protection of human health and the environment
through the groundwater extraction and treatment. Extraction wells would be used to
hydraulically separate the TI Zone from the rest of the groundwater system. Thus,
preventing any further migration to the Regional Aquifer.
9.2 Compliance with ARARs
This section presents a comparison of alternatives with respect to compliance with
chemical-specific, location-specific, and action-specific ARARs.
9.2.1 VOC-Contaminated Soils Outside Area 1 (Plug-In Subsites)
Alternative Al (No Action) would not comply with ARARs at subsites where additional
investigations and modeling show that the contaminated soils represent a potential future
threat to groundwater. Alternative A3 (SVE) would comply with all ARARs.
9.2.2 VOC-Contaminated Soils Inside Area 1
Alternatives Bl (No Action) would not comply with chemical-specific ARARs. Alternative
B3 would be designed to comply with ARARs.
9.2.3 VOC-Contaminated Soils Inside the Tl Zone
Soil cleanup ARARs would not be waived under Alternative Cl (No Action), therefore
Alternative Cl would not comply with ARARs. Alternative C3 would be designed to
comply with all ARARs that are not waived because of the TI of cleaning up the TI Zone
soil.
9.2.4 PCB-Contaminated Soils and Sludges
Alternative Dl (No Further Action) would not comply with ARARs. Each of the other
alternatives would comply with ARARs.
9.2.5 TAA Landfill Closure
Only Alternative E3 (Landfill Closure) would comply with ARARs.
9.2.6 Shallow Groundwater (Outside the Tl Zone)
All of the alternatives may have difficulty achieving groundwater cleanup ARARs because
of hydrogeologic conditions (extensive fine-grained materials) in the Shallow Groundwater
Zone. The NCP requires that groundwater cleanup be completed in a reasonable time
frame.
Alternative Fl (No Action) would not comply with ARARs because chemical-specific
ARARs (MCLs) would not be met. There is a slight possibility that Alternatives F2
(Institutional Controls and Monitoring) and F3 (Bioaugmentation) could potentially comply
with groundwater cleanup ARARs. Alternative F2 would rely on natural attenuation to
restore groundwater quality. Natural attenuation is not likely to cleanup groundwater in a
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reasonable time and meet ARARs, even if TI Zone containment is also provided.
Alternative F3 would rely on bioaugmentation and natural attenuation for groundwater
cleanup. Although better than Alternative F2, these processes alone are still not likely to
meet groundwater cleanup ARARs in a reasonable time frame, even if containment of the TI
Zone is provided. Based on information collected to date, Alternative F5 (Extraction,
Treatment, and Discharge) would be designed and expected to comply with ARARs
through groundwater containment and remediation. However, cleanup of the Shallow
Groundwater Zone to drinking water quality may still be difficult to achieve.
9.2.7 Shallow Groundwater Inside the TI Zone
As discussed in Section 11.1, because of site-specific hydrogeologic and contaminant
conditions (including the presence of DNAPLs) EPA has determined that it is technically
impracticable from an engineering perspective to cleanup the TI Zone to drinking water
standards. Therefore, in-situ groundwater-deanup ARARs would be waived for
Alternative G5 (Extraction, Treatment, and Discharge) based on the technical
impracticability of cleanup up the TI Zone. Alternative G5 would comply with all other
ARARs. Groundwater cleanup ARARs would not be waived under Alternative Gl, and
therefore it would not comply with ARARs.
9.3 Long-Term Effectiveness and Permanence
Long-term effectiveness is evaluated through two criteria: the magnitude of residual risk
remaining after the remedy is implemented and the adequacy and reliability of engineering
and institutional controls.
9.3.1 VOC-Contaminated Soils Outside Area 1 (Plug-In Subsftes)
If additional investigations and modeling indicate that there is no potential future threat to
groundwater, then mere would be no residual risk for any of the alternatives and no
controls would be needed (i.e., Alternative Al [No Action] would be appropriate). If the
results indicate that the VOCs do represent a threat to groundwater, Alternative A3 would
provide the greatest reduction in residual risk through SVE. Alternative Al (No Action)
would not reduce residual risk and would not provide a means of monitoring the soil
contamination or any groundwater impacts.
9.3.2 VOC-Contaminated Soils Inside Area 1
Alternative Bl (No Action) provides little long-term effectiveness or permanence because
natural attenuation would do little to prevent future releases to the Shallow Groundwater
Zone and adjacent soils. Alternative B3 (SVE) is a presumptive remedy and is a well
documented means of efficiently and permanently removing VOCs from contaminated soil.
This reduces the potential for future impacts from contaminant migration.
9.3.3 VOC-Contaminated Soils Inside the TI Zone
Alternative Cl (No Action) would provide little long-term effectiveness or permanence
because natural attenuation provides minimal effectiveness in preventing future releases to
the Shallow Groundwater Zone and adjacent soils. As stated above, Alternative C3 (SVE) is
a presumptive remedy and is a well documented means of removing VGCs from
contaminated soil and reducing the potential for future impacts.
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9.3.4 PCB-Contaminated Soils and Sludges
Alternative Dl (No Further Action) would result in unacceptable residual risks and there
would be no engineering or institutional controls to limit potential exposure. Alternatives
D5 and D6 both permanently eliminate residual risk by removing and treating (if necessary)
the contaminated materials and providing for disposal in an appropriate facility. However,
off-site disposal (Alternative D6) is more reliable and permanent.
9.3.5 TAA Landfill Closure
Alternative E3 (Landfill Closure) would ensure proper drainage and limit infiltration,
effectively reducing the risk of contaminant migration to groundwater. Alternative E2
(Institutional Controls and Monitoring) would provide limited effectiveness in limiting
potential future exposure through fencing and groundwater monitoring to detect impacts.
9.3.6 Shallow Groundwater (Outside the Tl Zone)
Alternative Fl (No Action) would be least effective in reducing long-term residual risk
because it would not include any institutional controls to restrict potential use and no
remedial actions would be taken to prevent additional contaminant migration. Alternative
F2 (Institutional Controls and Monitoring) would provide limited long-term effectiveness
through restrictions on shallow groundwater use. The magnitude of residual risk would be
reduced somewhat through treatment of contaminated groundwater under Alternatives F3
(Bioaugmentation). However, there would not be any action taken to control further
contaminant migration. Alternative F5 (Extraction, Treatment, and Discharge) would best
meet the long-term effectiveness criterion because extraction and treatment would
substantially reduce residual risk (particularly if TI Zone containment is also provided).
Further, containment would limit the area of potential exposure and reduce long-term risks
to the Regional Aquifer.
9.3.7 Shallow Groundwater Inside the Tl Zone
Alternative Gl (No Action) would not be effective in reducing residual risk or mitigating
the long-term impacts to groundwater outside the TI Zone. Alternative G5 (Extraction,
Treatment, and Discharge) would be effective in reducing residual risk to groundwater
outside the TI Zone (including the Regional Aquifer) through containment and limiting
potential future exposure by removing and treating contaminants.
9.4 Reduction of Toxicity, Mobility or Volume Through Treatment
This evaluation criterion addresses the statutory preference for selecting remedial actions that
permanently and significantly reduce toxitiry, mobility, or volume of contaminants through
treatment. This criterion is evaluated through treatment processes used and materials treated;
the amount of hazardous materials destroyed or treated; expected reductions in the toxiciry,
mobility, and volume; irreversibility of the treatment; and the type and quantity of treatment
residuals.
9.4.1 VOC-Contaminated Soils Outside Area 1 (Plug-In Subsites)
Only Alternative A3 (SVE) would actively reduce toxiciry, mobility and volume of
contaminants through SVE and possible off-gas treatment. The SVE systems would be
operated until the contaminants no longer represent a threat to groundwater, thus the
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toxicity, mobility and volume of contaminants would be reduced substantially. If
additional investigations and modeling indicate that VOCs at the plug-in subsites do not
represent a threat to groundwater, then there is no reason to reduce the toxicity, mobility or
volume of contaminants.
9.4.2 VOOContaminated Soils Inside Area 1
Only Alternative B3 (SVE) would actively reduce toxicity, mobility and volume of
contaminants through SVE and off-gas treatment. As described above, the SVE systems
would be operated until the contaminants no longer represent a threat, thus the toxicity,
mobility and volume would be substantially reduced.
9.4.3 VOC-Contaminated Soils Inside the Tl Zone
As with the other VOC-contaminated soils, only the SVE alternative (Alternative C3) would
actively reduce the toxicity, mobility, or volume of soil contaminants. This alternative
would provide significant reductions in toxicity, mobility, and volume of soil contamination
inside the TI Zone, however contaminants will likely remain in the TI Zone soil indefinitely.
9.4.4 PCB-Contaminated Soils and Sludges
Alternatives D5 (Excavation, Treatment, and On-Site Landfilling) and D6 (Excavation,
Treatment, and Off-Site Landfilling) would provide permanent reduction in the toxicity and
mobility of contaminants through excavation, treatment (as necessary) and appropriate
disposal. Alternative Dl (No Further Action) would provide no reductions.
9.4.5 TAA Landfill Closure
None of the alternatives would reduce toxicity or volume of contaminants. However, only
Alternative E3 (Landfill Closure) would significantly reduce the mobility of contaminants
by reducing infiltration.
9.4.6 Shallow Groundwater (Outside the TI Zone)
Alternatives Fl (No Action) and F2 (Institutional Controls and Monitoring) would not
provide any reductions in the toxicity, mobility or volume of contaminants beyond what is
already occurring through natural attenuation. Alternative F3 (Bioaugmentation) would
provide reduction of toxicity and volume through in-situ aerobic treatment Alternative F5
(Extraction, Treatment, and Discharge) would provide significant reduction of the toxicity
and volume of contaminants through groundwater extraction and treatment. If
bioaugmentation was found to be effective, it could be used to provide additional
reductions under Alternative F5. Only Alternative F5 would limit the mobility of VOCs in
groundwater through containment.
9.4.7 Shallow Groundwater Inside the TI Zone
Alternative Gl (No Action) would not reduce the toxicity, mobility, or volume of
contaminants. Alternative G5 (Extraction, Treatment, and Discharge) would provide
significant reduction in the mobility, toxicity, and volume of contaminants through
containment, removal and treatment of highly contaminated groundwater. Because the TI
Zone can not be completely remediated, a considerable volume of contaminants may
remain in the TI Zone shallow groundwater.
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9.5 Short-Term Effectiveness
Several factors are addressed in evaluating short-term effectiveness of the remedial
alternatives, including potential short-term risk to the community during implementation,
threats to workers during remedial actions, and potential adverse environmental impacts
from construction and implementation. The No Action alternatives are not evaluated under
the Short-Term Effectiveness criterion because none of these evaluation factors are applicable.
9.5.1 VOC-Contaminated Soils Outside Area 1 (Plug-In Subsites)
Although construction activities could potentially occur over a broad area, short-term
impacts associated with Alternative A3 (SVE) would be minimized through proper health
and safety and monitoring procedures.
9.5.2 VOC-Contaminated Soils Inside Area 1
Short-term impacts to human health and the environment in Alternative B3 (SVE) would
result from construction activities and air emissions from the treatment of extracted soil gas.
Impacts associated with construction would be minimized by employing proper dust
control and health and safety procedures during construction. Air emissions would be
monitored during implementation.
9.5.3 VOC-Contaminated Soils Inside the Tl Zone
Short-term impacts to human health and the environment in Alternative C3 (SVE) would
result from construction activities and air emissions from the treatment of extracted soil gas.
Impacts associated with construction would be minimized by employing proper dust
control and health and safety procedures during construction. Air emissions would be
monitored during implementation.
9.5.4 PCB-Contaminated Soils and Sludges
Short-term impacts associated with Alternatives D5 and D6 would be minimized by
appropriate dust control measures and transportation procedures, decontamination
procedures, providing containment at potential treatment facilities, use of PPE and by
following proper health and safety procedures.
9.5.5 TAA Landfill Closure
Short-term impacts associated with Alternative E2 (Institutional Controls and Monitoring)
would be minimal. Short-term impacts associated with Alternative E3 (Landfill Closure)
would be minimized with proper dust control and health and safety procedures.
9.5.6 Shallow Groundwater (Outside the Tl Zone)
Minimal short-term impacts would be associated with Alternative F2 (Institutional
Controls and Monitoring) sampling activities and installation of additional monitoring
wells. Short-term impacts of Alternative F2 from monitoring would be minimized by using
appropriate health and safety procedures. Short-term impacts under Alternatives F3
(Bioaugmentation) and F5 (Extraction, Treatment, and Discharge) would be minimized with
proper health and safety and decontamination procedures. Greater short-term impacts are
associated with Alternative F5 than with Alternative F3 because Alternative F5 requires
ex-situ treatment operations.
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9.5.7 Shallow Groundwater Inside the Tl Zone
Short-term impacts under Alternative G5 (Extraction, Treatment, and Discharge) would be
minimized with proper health and safety procedures and monitoring.
9.6 Implementability
This evaluation criterion addresses the technical feasibility, the availability of services and
materials, and the administrative feasibility of each of the alternatives. The technical
feasibility includes the ability to construct and operate the technology and the relative ease of
undertaking the remedial action and the ability to monitor its effectiveness. The availability of
services and materials addresses the availability of the necessary equipment, technologies,
services, and other resources to construct the remedial action. The administrative feasibility
considers the activities needed to coordinate and obtain approvals from other agencies. No
Action alternatives are not evaluated under this criterion because nothing would be
implemented.
9.6.1 VOC-Contaminated Soils Outside Area 1 (Plug-In subsites)
Alternative A3 (SVE) would be readily implemented with conventional construction
equipment, methods, and materials. However, implementation will be complicated by the
possibility that SVE systems may be required in widespread areas.
9.6.2 VOC-Contaminated Soils Inside Area 1
Alternative B3 (SVE) would be readily implemented with conventional construction
equipment, methods, and materials.
9.6.3 VOC-Contaminated Soils Inside the Tl Zone
Alternative C3 (SVE) would be readily implemented with conventional construction
equipment, methods, and materials.
9.6.4 PCB-Contaminated Soils and Sludges
Alternatives D5 (Excavation, Treatment, and On-Site Landfilling) and D6 (Excavation,
Treatment, and Off-Site Landfilling) would require construction of treatment facilities with
associated containment provisions and would be readily implemented with conventional
equipment.
9.6.5 TAA Landfill Closure
A monitoring program for Alternative E2 (Institutional Controls and Monitoring) would be
readily implemented and additional monitoring wells installed with conventional well
drilling equipment. Alternative E3 (Landfill Closure) would be readily implemented with
conventional equipment.
9.6.6 Shallow Groundwater (Outside the Tl Zone)
Alternative F2 (Institutional Controls and Monitoring) would be readily implemented
alternative. Alternative F3 (Bioaugmentation) would likely require construction of injection
wells and piping as well as a program for monitoring and adding the appropriate
amendments. Alternative F5 (Extraction, Treatment, and Discharge) would be the most
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complex alternative to implement technically and administratively because it would require
significant coordination with local agencies and residents to install the extraction wells and
pipelines in the residential neighborhood west of Nogales Highway.
9.6.7 Shallow Groundwater Inside the Tl Zone
Alternative G5 (Extraction, Treatment, and Discharge) would be readily implementable
with conventional construction equipment and materials.
9.7 Cost
A summary of estimated costs for each alternative is presented in Table 5 (the various No-
Action alternatives are not shown because they do not have direct costs). The table is broken
down into capital, operation and maintenance, and net present worth cost estimates. An
overview of the cost analysis performed, as well as a detailed cost breakdown for each
alternative, is presented in the Feasibility Study Report (CRA, 1997).
9.8 State Acceptance
In a letter dated September 19,1997, the State of Arizona (Arizona Department of
Environmental Quality) concurred with EPA's selected remedies for the three properties
(the ROD Site) at the TIAA Site addressed in this ROD.
9.9 Community Acceptance
EPA received written comments from one individual and several organizations or agencies
on the Proposed Plan for this remedy at the TIAA Site. In addition, EPA received limited
oral comments and questions at the two public meetings held in July 1997 to discuss EPA's
plans. EPA responded directly to the oral questions and comments at the public meetings.
The entire transcript for each public meeting is included in the Responsiveness Summary in
Part n of this ROD (Volume 2). All of the written comments, along with EPA's responses to
these comments, are also presented in the Responsiveness Summary in Part n of this ROD.
EPA has determined that the preferred alternatives presented in the Proposed Plan
represent the most appropriate remedy for the ROD Site. The public comments received
were generally directed at specific components or technologies of the selected remedy and
did not suggest a change to the overall remedy selected by EPA. As noted above, responses
to the limited commentors that did have questions on the selected remedy are provided in
the attached Responsiveness Summary.
10.0 Selected Remedy
After considering CERCLA's statutory requirements, the detailed comparison of the
alternatives using the nine criteria, and public comments, EPA, in consultation with the
State of Arizona, has determined that the most appropriate remedy for the ROD Site
includes:
VOC-Contaminated Soils at the Burr-Brown Property
Alternative Al: No Action
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VOC-Contaminated Soils Outside Area 1 (Plug-in subsites)
Alternative Al: No Further Action
Alternative A3: SVE (potentially with treatment and enhancement)
VOC-Contaminated Soils Inside Area 1
Alternative B3: SVE (with treatment and, potentially, enhancement)
VOC-Contaminated Soils Inside the TI Zone
Alternative C3: SVE (with treatment and, potentially, enhancement)
PCB-Contaminated Soils and Sludges
Alternative D6: Excavation, Treatment and Off-Site Landfilling
TAA Landfill
Alternative E3: Landfill Closure
Shallow Groundwater (Outside the TI Zone)
Alternative F5: Extraction, Treatment, and Discharge (potentially with enhancement)
Shallow Groundwater Inside the TI Zone
Alternative G5: Extraction, Treatment, and Discharge (potentially with enhancement)
These alternatives meet the two NCP threshold evaluating criteria, overall protection of
human health and the environment and compliance with ARARs (outside of the TI Zone),
and provide the best balance of the remaining Superfund evaluation criteria. The major
components of the selected remedy for this action include:
VOC-Contaminated Soils
Installation of SVE systems at subsites where VOC concentrations in soil have and could
continue to cause groundwater to exceed chemical performance standards (provided in
Table 6). These areas include the TI Zone and selected other areas, as shown in Figure 8,
in the vicinity of the Three Hangars complex.
In other areas, soil vapor investigations have not been completed in sufficient detail to
determine whether or not the contamination could potentially cause groundwater to
exceed performance standards. At these subsites (termed plug-in subsites), additional
investigations and modeling will be performed to determine if the subsite will be
required to "plug-in" to the remedy and install an SVE system.
Conveyance of the extracted soil vapors to a new soil vapor treatment system to be
installed in the Three Hangars area. If SVE systems are installed at the plug-in subsites,
additional treatment systems may be installed.
On-site treatment of soil vapors using one of four vapor treatment technologies:
catalytic oxidation, thermal oxidation, vapor-phase carbon and vapor-phase resin
adsorption.
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PCB-Contaminated Soils and Sludges
Excavation of soils and sludges with PCS concentrations exceeding the cleanup
standards (0.76 mg/kg). The excavated areas will be backfilled and graded.
Soil and sludges with PCB concentrations above 50 mg/kg may be treated off-site prior
to disposal. Soils with elevated metals concentrations may also require treatment (via
stabilization) prior to off-site disposal.
Transport and disposal of contaminated soils and sludges to a RCRA Subtitle D facility
approved under CERCLA's off-site rule.
Implementation of institutional controls (deed restrictions) to ensure that the
appropriate portions of the Airport Property remain zoned for industrial (non-
residential) use.
TAA Landfill Closure
Landfill closure in accordance with State of Arizona RCRA Subtitle D requirements.
This includes, grading the landfill to provide a smooth, sloped surface; placing and
compacting a 2-foot-thick (minimum) clean soil cap over the graded fill materials; and
seeding the cap with drought-resistance vegetation.
Institutional controls (access restrictions) and closure and post-closure monitoring in the
landfill vicinity.
VOC-Contaminated Shallow Groundwater
Installation of groundwater extraction wells to inhibit migration of shallow
groundwater contamination into the Regional Aquifer. Containment will be provided
in the TI Zone, at the property boundary and at the downgradient extent of shallow
groundwater contamination (beyond the property boundary). Groundwater extraction
is also be intended to restore the groundwater to drinking water quality (see Table 6)
outside of the TI Zone. EPA has determined that it is not technically practicable to
restore the shallow groundwater in the TI Zone to drinking water quality standards.
Extracted groundwater will be conveyed to a groundwater treatment facility, likely
located in the Three Hangars area. The groundwater will be treated using either air
stripping with off-gas treatment, carbon adsorption, ultraviolet oxidation (for polishing
only) or piped to the existing USAF Plant No. 44 air stripping treatment plant for
treatment.
If air stripping is used, the off-gas will be treated using one of the treatment
technologies listed above for SVE (catalytic oxidation, thermal oxidation, vapor-phase
carbon and vapor-phase resin adsorption).
Discharge of the treated groundwater using one of the following discharge options:
injection wells, injection trenches, sanitary sewer, industrial reuse or discharge to the
USAF Plant No. 44 injection well system. Injection is the preferred discharge option.
Sanitary sewer and industrial reuse are secondary options.
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Institutional controls, such as deed restrictions or other appropriate measures, to restrict
use of the Shallow Groundwater Zone to limit potential exposure.
EPA will review the selected remedy no less often than every 5 years after the initiation of
the remedial action to ensure that human health and the environment are being protected
by the implemented remedy. As part of the review, EPA will evaluate whether the
performance standards specified in this ROD remain protective of human health and the
environment. EPA will continue 'reviews until no hazardous substances, pollutants, or
contaminants remain at the ROD Site above levels of concern for human health and the
environment.
The following sections describe the remedial action objectives and performance standards
for the various components of the selected remedy.
10.1 VOC-Contaminated Soils
The remedial action objective for the VOC-contaminated soils remedy is to reduce VOC
concentrations in soil such that the further contaminant migration will not cause
groundwater in the first saturated unit (either the Shallow Groundwater Zone or the
Regional Aquifer) to exceed chemical performance standards. The specific components and
technologies necessary to achieve this objective and comply with the performance
standards described below will be selected during remedial design.
10.1.1 VOC-Contaminated Soils Outside Area 1 (Remedy Plug-In Subsites)
At selected subsites outside of Area 1, investigations have not yet been completed to the
point where it can be determined whether or not the VOC concentrations in soil represent a
threat to groundwater quality. The Plug-in approach, described below, will be used to
determine which subsites need to implement an SVE remedy and which do not require a
cleanup action. The 11 Plug-in Subsites are (Figure 8):
ZoneC: Hughes Credit Union Dump;
ZoneD: C-294BumPit
Zone D: Fire Drill Training Area D-3;
ZoneD: TAA Landfill;
Zone D: South Ramp and Drains;
Zone E: West End of Runway 3
ZoneE: Former Building 32;
ZoneF: Hamilton Buildings D-252, D-267 and D-275;
Zone F: North End of Samsonite Building D-167; and
Former West-Cap Property (2 locations).
Only subsites that are determined, based on the Plug-in Criteria described below, to likely
pose a threat to future groundwater quality would be remediated with SVE. Following the
additional field investigations at the plug-in subsites, each subsite will be evaluated and
vapor transport modeling performed, as necessary, to determine the potential threat to
groundwater quality. Subsites that are concluded to pose no present or future threats to
groundwater quality would be given "No Further Action" status. The ADHS Risk
Assessment (ADHS, 1996) showed that the VOC-contaminated soils at the Plug-in subsites
do not pose an unacceptable risk to human health or the environment for the non-
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groundwater pathways (inhalation of soil vapors, ingestion of or dermal contact with soils,
and inhalation of dust).
SVE is the selected remedy for the Plug-in subsites that do represent a threat to
groundwater quality. The need for and type of off-gas treatment facilities and
enhancements (both described below) will be determined during remedial design.
Groundwater monitoring will be used to detect impacts in excess of cleanup standards.
10.1.1.1 Plug-In Process and Criteria
Traditionally, EPA investigates, evaluates, and proposes a separate cleanup remedy for
each source of contamination. However, there are a number of source areas (subsites) that
have the same type of VOC contamination found in the same soil types. For subsites that
are substantially similar, the repetition of the investigation/evaluation/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 subsite. Rather, it selects a remedial
action (in this case SVE) to apply to any subsite 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 subsites. Plug-in subsites
will be characterized concurrently or at different times. If the conditions at a subsite match
pre-defined conditions, the subsite 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 subsite. The Plug-in process contains a
"blueprint" directing decisions as to its own application.
The following sections describe the plug-in process components and terminology.
10.1.1.1.1 Existing Subsite Profile
The SVE remedy used in the Plug-in Approach must be able to address the vast majority of
Plug-in subsites for the approach to be efficient. To achieve this, the subsite profile for the
individual subsites must be very similar. The subsite 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 subsite profiles for the Plug-
in subsites, as defined in the RI and FS Reports, are sufficiently similar to implement the Plug-
in Approach.
10.1.1.1.2 Presumed Remedy
The Presumed Remedy is the action that will be taken at all subsites that meet the Remedy Profile
and the Plug-in Criteria (defined below). The Presumed Remedy is selected to meet all
ARARs. EPA 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 in Section 10.1.1.2.
Presumptive Remedy Approach. EPA 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
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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 EPA'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 desorption and incineration)
were frequently selected to address VOC contamination in soils at CERCLA sites. Based on its
evaluation, EPA 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, EPA 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 Airport Property RI/FS, various site-specific factors (including subsurface
conditions and contaminant type) were reviewed to evaluate the applicability of SVE to
remediation of ROD Site soils. The results of this evaluation indicate that the types of
contaminants present, distribution of contaminants and physical parameters of the soil are
well-suited to remediation using SVE. In accordance with the EPA 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.
10.1.1.1.3 Remedy Profile
The range of conditions appropriate for the Presumed Remedy is called the Remedy Profile.
After the Focused RI is completed at a subsite, 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
subsite 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, EPA has initially determined that 11 subsites at
the Airport and West-Cap properties meet the plug-in remedy profile for SVE.
10.1.1.1.4 Plug-In Criteria
Even if conditions at a particular Plug-in subsite 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 EPA to determine whether an action is necessary. Those subsites not exceeding
the Plug-in Criteria do not need a soil VOCs remedy and EPA will not plug in such subsites to
the remedy.
Because the ADHS Risk Assessment (ADHS, 19%) already determined that the VOC
contamination in soil does not represent a significant human health risk for non-groundwater
pathways, only potential groundwater impacts are considered in the Plug-in Criteria.
Potential groundwater impacts are defined by VOC concentrations in soils that could result in
groundwater concentrations in excess of cleanup standards.
This SVE remedy will be applied whenever certain conditions exist. There are two
conditions that a subsite must meet before being plugged in. First, the subsite must exhibit
conditions consistent with the Remedy Profile (EPA has already determined that all of the
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Plug-in subsites meet this criteria), and second, the subsite must exhibit contamination
exceeding the Plug-in Criteria. The determination of whether to plug a subsite 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. There will be one Plug-in Decision Point for each
subsite that proceeds through the Plug-in Process. Note that the Plug-in Decision Point
may occur at different times for different subsites.
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 a single subsite's soils is referred to as the incremental concentration.
For the ROD Site, the Plug-in Criteria are limits on the incremental concentrations of VOCs
from a subsite.
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 no subsite could 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 subsite 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 the cleanup standards (federal MCLs, if available, or state of Arizona
HBGLs). Table 6 presents the cleanup standards that will be used as the basis for Plug-in
Criteria and for remediation of groundwater. 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 a subsite that would reach the groundwater over time.
10.1.1.1.5 Soil Cleanup Standards
VOCs in the vadose zone at a subsite 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 subsite. Evaluating the threat of a subsite must
depend, therefore, on making an estimate of the incremental VOCs that will enter the
groundwater over time because of any one subsite. The process described in this section
will be used to estimate the maximum effect that the VOC mass distribution at a subsite
could potentially have on groundwater in the future. This estimated effect will then be
compared with the Plug-in Criteria (groundwater cleanup standards, as defined in Table 6).
The steps involved in evaluating soil cleanup standards include focused RI data collection,
VOC mass estimates, VLEACH vadose zone transport modeling (or another vadose zone
model acceptable to EPA) and estimating incremental groundwater concentrations.
Focused RI Data Collection. Data will be obtained from Focused RIs for each Plug-in
subsite. Examples of the type of information to be obtained during the Focused RI at each
subsite shall include:
Subsurface lithology from soil borings;
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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 subsite;
Groundwater quality information obtained by sampling monitoring wells at and in the
vicinity of the subsite; and
Any additional information or activities deemed necessary by EPA pursuant to
regulation, statute, or EPA 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 collected during the Focused RI. The measured
soil gas concentrations shall be converted to total contaminant mass estimates.
VLEACH Vadose Zone Transport Model (Note: VLEACH may not be the only acceptable
vadose zone model for the Plug-in Subsites). The maximum future incremental
groundwater concentrations resulting from the VOCs in soils at any one subsite will be
estimated using a computer model, subject to EPA approval. The model to be used shall be
the EPA computer model VLEACH, or an equivalent model approved by EPA for the ROD
Site. VLEACH is a one-dimensional, computer-based finite difference model. The mass
distribution of VOCs with depth in soils is input to VLEACH. 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 VLEACH
analysis is required for each VOC identified in the vadose zone.
In cases where it can be demonstrated that the outcome of VLEACH is mathematically
certain without running the model, EPA 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 a
corresponding VLEACH estimate, as VLEACH 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 VLEACH may not be necessary. EPA will have sole discretion to
make such determinations.
Estimating Incremental Groundwater Concentration. For groundwater, a simple mixing
zone model shall be used to convert the maximum mass fluxes of VOCs over time predicted
by VLEACH into concentration levels. The simple mixing zone approach calculates
groundwater concentrations on the basis of an assumed mixing depth in the groundwater
zone beneath the subsite and an estimated flow of clean groundwater originating from
upgradient sources. The depth of the mixing zone shall be based on subsite-specific
conditions, but shall not exceed 30 feet.
Note that clean water flow-though 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.
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10.1.1.1.6 Cleanup Design and Execution
Locations determined to be appropriate for plug-in to the SVE remedy can proceed directly
with cleanup design and execution. EPA will notify the public each time a Plug-in decision
is made. This step will be implemented after the ROD is finalized.
10.1.1.2 Performance Standards for VOC-Contaminated Soil Cleanup at Plug-In Subsites
The SVE system at any subsite that plugs in to the SVE remedy will operate continuously
until the VOC concentrations in soil have been reduced such that the Plug-in Criteria are no
longer exceeded. Evaluation of whether Plug-in Criteria are still exceeded as cleanup nears
completion shall be accomplished by the same process and methods used to determine that
the Plug-in Criteria were exceeded originally; through sampling of soil vapor and use of the
VLEACH and mixing zone models, or EPA-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. SVE
enhancements, described in Section 10.1.7, may be necessary to optimize system
performance.
A monitoring program will be required of each 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;
Reporting procedure to notify EPA 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 EPA.
If VOC levels rebound to above cleanup standards after an SVE system has been shut down,
SVE operation shall be resumed.
10.1.2 VOC-Contaminated Soils Inside Area 1 (Remedy-Required Subsites)
SVE shall be implemented at eight subsites inside Area 1 where contaminant levels
represent a threat to groundwater quality. These subsites are (Figure 8):
Zone E: Buildings 14/15;
Zone E: Buildings 16/17;
Zone E: Building 18;
Zone E: Building 25 and adjacent soils to the north (southern portion of Building 24);
Zone E: Soils beneath West Lease USTs;
Zone E: North and East Sides of Hangar 1;
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Zone E: Hangar 1;
Zone E: South Portion of Hangar 2;
The overall remedial action objective for VOC-contaminated soils listed above in Section
10.1 (reduction of VOC concentrations such that they no longer represent a threat to
groundwater) could potentially be difficult to achieve in portions of Area 1. However, the
SVE system(s) in this area will be operated to achieve lateral and vertical vapor containment
within Area 1 until:
VOC concentrations are reduced such that soil contamination will not result in water
quality impacts to the Shallow Groundwater Zone above cleanup standards (Table 6).
During implementation of this remedy, monitoring will be conducted to further evaluate
the practicability of restoration for both the Shallow Groundwater Zone (outside the TI
Zone) and the associated VOC-contaminated soils.
This remedy includes construction of SVE well clusters to create vapor containment and at
other specific subsites where soil vapors are impacting the Shallow Groundwater Zone.
Off-gas treatment will be installed to remove VOCs from the air discharge. The most
appropriate method of off-gas treatment, potential enhancements, and the SVE facility
layout will be determined during remedial design. Groundwater and soil vapor monitoring
will be used to ensure that vapor containment and removal is effective.
10.1.2.1 Performance Standards for VOC-Contaminated Soil Cleanup Inside Area 1
The SVE system at the subsites inside Area 1 will operate continuously until the VOC
concentrations in soil have been reduced such that the cleanup standards are no longer
exceeded. The cleanup standards for VOC-contaminated soil inside Area 1 are determined
the same as the Plug-in Criteria described in Section 10.1.1.1, using soil vapor sampling data
and VLEACH and mixing zone models, or EPA-approved alternative models. Evaluation
of whether cleanup standards are still being exceeded as cleanup nears completion shall be
accomplished by the same process and methods used to determine the cleanup standards
originally; through sampling of soil vapor and use of the VLEACH and mixing zone
models, or EPA-approved alternative models. Further, the SVE system(s) inside Area 1
shall prevent migration of soil vapors outside of Area 1 and to the Shallow Groundwater
Zone.
The remaining performance standards are the same as described in Section 10.1.1.2
10.1.3 VOC-Contaminated Soils In the TI Zone
An SVE system will be installed in the TI Zone. The overall remedial action objective for
VOC-contaminated soils listed above in Section 10.1 (reduction of VOC concentrations such
that they no longer represent a threat to groundwater) is not likely achievable in most of the
TI Zone. Thus, the specific objective of the SVE system in the TI Zone is to achieve and
maintain lateral and vertical vapor containment until contaminant concentrations have
been reduced such that ceasing operation of the system will not cause a water quality
impact to the Shallow Groundwater Zone outside the TI Zone or to the Regional Aquifer in
excess of cleanup standards (Table 6).
One or more SVE well clusters will be installed for source control in the TI Zone. Off-gas
treatment facilities will be installed to treat VOCs in the off-gas. The most appropriate
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method of off-gas treatment, potential enhancement strategies, and the SVE facility layout
will be determined during remedial design. Groundwater and soil vapor monitoring will
be used to ensure that the vapor containment is effective.
10.1.3.1 Performance Standards for VOC-Contaminated Soil Cleanup in the Tl Zone
The SVE system in the TI Zone shall prevent migration of soil vapors outside of the TI Zone
and to the Shallow Groundwater Zone. The remaining performance standards are the same
as described in Section 10.1.1.2
10.1.4 VOC-Contaminated Soil at Burr-Brown Corporation (No Further Action)
Based on the ADHS Risk Assessment results and evaluation and modeling of the threat to
groundwater, EPA has determined that the low levels of VOCs in soils at the Burr-Brown
property do not pose a risk to human health or groundwater quality. Therefore, no
remedial actions are needed for soil at Burr-Brown and the No Further Action alternative is
selected. Burr-Brown Corporation will continue to operate its groundwater treatment
system as required in previous decision documents.
10.1.5 Former West-Cap Property Soils (Plug-In Subsite)
The soil investigation has not been completed at the former West-Cap Property. However,
based on initial investigations, two areas (known as Building A and Building B [see Figures
5 and 8]) at this property have been identified for further evaluation. These two locations,
or subsites, are included in the list of "Plug-In" subsites provided above in Section 10.1.1.
These two locations will be evaluated following the process and criteria described in Section
10.1.1. As described above, a decision will be made when the investigation is complete to
select either SVE or No Action for these subsites.
10.1.6 SVE Off-Gas Treatment
Off-gas treatment technology selection for any given SVE system shall be made during
remedial design of that system. Available options for SVE off-gas treatment include:
No Treatment (Plug-in subsites only);
Catalytic Oxidation;
Thermal Oxidation;
Vapor-Phase Carbon; and
Vapor-Phase Resin Adsorption.
The need for treatment of the soil gas off-gas at any Plug-in subsites that implement SVE
will be determined during remedial design using dispersion modeling and evaluation of
the emissions with respect to air emission ARARs.
During the Remedial Design process, after additional data are available on anticipated
influent rates and concentrations, EPA will determine which of the off-gas treatment
option(s) listed above best attains the SVE performance standards described in Section
10.1.6.1. Prior to construction, EPA will take appropriate action to inform the public of the
actual technologies selected for inclusion in ROD Site SVE remedy.
10.1.6.1 SVE Off-Gas Treatment Performance Standards
The SVE off-gas treatment system must comply with all of the ARARs for air emissions
described in Section 11.1.2.
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EPA 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 impose 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
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 ground water treatment system
installed for the Shallow Groundwater Zone portion of this remedy. 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 EPA.
10.1.7 SVE Enhancements
SVE enhancements are specific technological supplements that allow SVE to remove
contaminants more efficiently or cost-effectively. Enhancements are not separate remedies,
but design options for the SVE remedy. Enhancements will not likely be necessary at most
of the SVE subsites. Four potential SVE enhancement options are available as part of the
VOC-contaminated soils remedy. If an enhancement is to be used at a particular subsite, it
shall be determined as part of the remedial design of the SVE system for that particular
subsite.
Potential enhancement options for this remedy include:
Capping/Paving to increase lateral influence of SVE wells and to prevent excessive air
leakage from the atmosphere (short circuiting)
Bioventing to enhance the naturally-occurring biodegradation process
Pneumatic Fracturing of the subsurface with high pressure are to increase permeability,
allowing VOCs to volatilize more readily
Multi-Phase Extraction to extract soil gas, groundwater and/or NAPL, and to lower the
water table to allow volatilization of VOCs at lower depths.
The most likely scenario for use of an SVE enhancement is when the enhancement would
lessen the cost of overall remediation. Shorter cleanup times would be expected when an
enhancement can increase the rate of VOC withdrawal.
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10.2 PCB-Contaminated Soils and Sludges
The remedial action objective for PCB-contaminated soils and sludges is to remove and
properly dispose of all soils and sludges contaminated with PCBs in excess of cleanup
standards. PCB-contaminated soils and sludges are found in the following areas (Figure 9):
Zone E: Drainages and Ponding Areas;
Zone E: Structures 21 and 30;
Zone E: Hangar 1;
ZoneE: Sludges in the Canale System; and
Zone E: Soil Adjacent to the Canale System.
All pipelines, sludges, and soils contaminated with PCBs above cleanup standards (0.76
mg/kg) will be excavated using standard excavation equipment such as backhoes and
front-end loaders. The excavated soil will be placed in containers for off-site landfill
disposal at an approved facility. Soil containing PCBs greater than 50 mg/kg may be
treated off-site prior to disposal. Soils with PCBs greater than 50 mg/kg will be sent to an
approved TSCA Landfill. Soils containing less than 50 mg/kg PCBs will be sent to a RCRA
Subtitle D facility approved under CERCLA's off-site program.
Some of the sludges in the Canale system contain metals in excess of RCRA toxicity
characteristic leaching procedure [TCLP] criteria and may be treated (via stabilization) prior
to off-site landfilling. The determination of whether to treat on-site and selection of
appropriate disposal facilities will be made during remedial design. Verification sampling
will be performed to ensure that all soils in excess of cleanup standards have been removed.
Excavated areas will require backfilling with dean soils and either revegetation or repaving.
The disposal facility will be selected, subject to EPA approval, during remedial design.
The cleanup standards for PCB-contaminated soils are based on an industrial land-use
scenario. To ensure that the cleanup standards are protective of human health, institutional
controls, possibly in the form of Arizona-specific deed restrictions that prohibit residential
use (termed Voluntary Environmental Mitigation Use Restriction [VEMUR]) or other
appropriate measures, will be necessary for the Airport Property.
PCB-contaminated materials have already been removed from the drain outside Hangar 1
and from the majority of the subsite "Zone E: Ponding and Drainage areas," located both
on and off the Airport Property.
Additional data collection will be required during remedial design, as part of a remedial
design investigation, to further evaluate the soils adjacent to the Canale System. The soils
will be sampled and analyzed for the constituents detected at elevated levels in Canale
System sludge. This investigation will characterize the extent of PCB contamination
requiring remediation. In addition, if any metals are detected above Arizona soil
remediation standards (HBGLs), those soils will need to be remediated along with the PCB-
contaminated soil.
10.2.1 Performance Standards for PCB-Contaminated Soil Cleanup
The chemical performance standard for cleanup of PCB contamination is 0.76 mg/kg. This
standard is the Arizona soil remediation level for non-residential areas (Arizona
Administrative Code [AAC] R18-7-201). All PCB-contaminated soil and sludges that
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exceed this cleanup level shall be excavated. In addition, if metals are detected above
Arizona soil remediation standards (AAC R18-7-201) during the additional Canale System
investigation, these soils shall also be excavated. Verification sampling shall be performed
in appropriate locations to confirm cleanup.
Excavated materials will be sampled and analyzed to identify those materials with PCB
concentrations in excess of 50 mg/kg or metals concentrations exceeding TCLP criteria.
Materials with PCBs exceeding 50 mg/kg may (depending on the disposal facility) require
treatment to below 50 mg/kg prior to disposal. Any materials with metals concentrations
exceeding RCRA TCLP criteria (Table 7) will be treated to below TCLP criteria by
stabilization prior to disposal.
10.3 TAA Landfill Closure
The remedial action objective for closure of TAA Landfill is to formally close and cap the
landfill in accordance with Arizona RCRA Subtitle D requirements. By capping, the
landfill, hazards posed by surface debris would be mitigated and infiltration would be
minimized.
Landfill closure shall consist of regrading the landfill, placing and compacting clean soil to
form the cap, and revegetation with drought-resistant plants. The approximate limit of the
landfill cap is illustrated in Figure 12. A post-closure monitoring plan will be implemented.
10.3.1 Performance Standards for TAA Landfill Closure
TAA Landfill closure shall meet the requirements for landfill closure (see Section 11 for
specific regulatory references). A soil cap that complies with Arizona landfill closure
requirements must meet, at a minimum, the following requirements:
c
A 2-foot compacted fill layer constructed from available cover soil material.
The compacted fill layer will be sufficient to provide a reduction of infiltration or
precipitation so that contaminants do not migrate to groundwater at concentrations that
exceed groundwater cleanup standards.
Cap slopes between 2 percent and 20 percent to accommodate effective drainage.
A vegetated cover that is similar to existing vegetation, drought tolerant, and requires
no ongoing irrigation.
10.4 VOC Contamination Within the Shallow Groundwater Zone
The remedial action objectives for VOC contamination in the Shallow Groundwater Zone
(shown in Figure 11) is to prevent migration of the VOCs into the Regional Aquifer (or into
currently clean portions of the Shallow Groundwater Zone) at levels that result in
exceedances of cleanup standards (Table 6) and to restore the Shallow Groundwater Zone
to drinking water quality wherever practicable. EPA has determined that it is not
technically practical to restore the Shallow Groundwater Zone to drinking water quality
within the 2-acre TI Zone (shown in Figure 11).
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10.4.1 VOC-Contaminated Shallow Groundwater Outside the Tl Zone
The remedial action objectives for shallow groundwater outside the TI Zone are as
described above in Section 10.4. The shallow groundwater remedy outside the TI Zone will
be operated until groundwater cleanup standards are met (Table 6).
Groundwater extraction wells will be constructed in both the on-property and off-property
areas of the Shallow Groundwater Zone. Extracted groundwater will be conveyed to a
treatment system for removal of the VGCs, then discharged. There are a number of
treatment and disposal options for the shallow groundwater. These are described below in
Sections 10.4.3 and 10.4.4, respectively. The groundwater treatment and discharge options
to be implemented, along with the actual layout of the remedy components will be
determined during remedial design. Groundwater monitoring will be used to ensure that
contaminant containment and removal is effective.
Potential enhancement options for this remedy include:
Electro-osmosis - as a potential shallow groundwater extraction enhancement; and
Bioaugmentation - as a potential in-situ treatment enhancement for extraction and
treatment of shallow groundwater.
Information gathered during the RI/FS suggests that contamination outside the TI Zone
may prove to be persistent due to site-specific factors. Monitoring of the Shallow
Groundwater Zone and the Regional Aquifer will be conducted during implementation of
the remedy to further evaluate the practicability of restoring the Shallow Groundwater
Zone (outside the TI Zone) to MCLs. Expansion of the TI Zone would require modification
of this ROD by EPA.
Because of the possible difficulties in achieving cleanup of the Shallow Groundwater Zone
and the potential negative impacts associated with construction of extraction wells and
conveyance pipelines through the residential neighborhood west of the airport property, a
phased approach to implementation of the remedy will likely be used.
10.4.1.1 Performance Standards
Shallow Groundwater Zone containment will be required to inhibit lateral and vertical
migration of areas where VOC concentrations exceed chemical performance (or cleanup)
standards. The groundwater cleanup standards are presented in Table 6. The standards
have been set based on MCLs promulgated pursuant to the Safe Drinking Water Act
(SDWA). If an MCL is not currently available for a specific contaminant of concern, State of
Arizona Health-Based Guidance Levels (HBGLs) have been used for cleanup standards.
Demonstration of hydraulic control, or potentially other measures acceptable to EPA, must
be used to show that the Shallow Groundwater Zone containment system is complying
with the remedial action objective.
10.4.1.2 Shallow Groundwater Containment Contingency Measures
If the shallow groundwater containment system is not demonstrated to be effective,
appropriate measures shall be taken to bring the system into compliance. Examples of such
measures may include, but are not limited to, any of the following, subject to approval by
EPA: more closely spaced extraction wells to facilitate containment, higher extraction rates
to increase hydraulic control and expedite restoration, extraction or remediation
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enhancements. EPA may also determine that more extensive groundwater monitoring is
required to ensure that VOC concentrations in the Regional Aquifer or in currently clean
shallow groundwater areas are not increasing.
10.4.2 VOC-Contaminated Shallow Groundwater in the TI Zone
The portion of the Shallow Groundwater Zone remedial action objectives (described above
in Section 10.4) that address preventing migration of VOCs into the Regional Aquifer at
levels that result in exceedances of cleanup standards (Table 6) are appropriate for the TI
Zone shallow groundwater. This containment will effectively control the major source of
contaminants in the Shallow Groundwater Zone, preventing further migration of
contaminants into the Shallow Groundwater Zone beyond the 71 Zone and protecting
Regional Aquifer groundwater quality. As is noted elsewhere in this ROD and described in
detail in Section 11.2, EPA has determined that restoration of the shallow groundwater in
the TI Zone to drinking water quality is technically impracticable.
The shallow groundwater remedy in the TI Zone will provide lateral and vertical hydraulic
containment of contaminated shallow groundwater until the contaminant concentrations
inside the TI Zone have been reduced such that ceasing operation of the TI Zone remedy
will not cause a water quality impact to the Shallow Groundwater Zone or the Regional
Aquifer in excess of cleanup standards. This will be demonstrated by groundwater
modeling and monitoring of the Regional Aquifer and the Shallow Groundwater Zone.
One or more groundwater extraction wells will be constructed for source control around the
perimeter of TI Zone. Extracted groundwater will be conveyed to a treatment system for
removal of the VOCs, then discharged. The treatment and disposal options for shallow
groundwater are described below in Sections 10.4.3 and 10.4.4, respectively. The
groundwater treatment and discharge options to be implemented, along with the actual
layout of the remedy components will be determined during remedial design.
Groundwater monitoring will be used to ensure that the TI Zone containment is effective.
Potential enhancement options for this remedy include:
Electro-osmosis as a potential extraction enhancement of shallow groundwater.
10.4.2.1 Performance Standards
The groundwater containment system in the TI Zone will be required to inhibit lateral and
vertical migration of all groundwater in the TI Zone. Because it is not expected that in-situ
restoration is achievable in the TI Zone, groundwater extraction for containment will likely
be necessary for the foreseeable future.
Periodically (every five years at a minimum), remedial technologies shall be reviewed to
determine if new technologies have been developed that can enhance remediation of
DNAPLs from fine-grained formations. If promising new technologies are developed, EPA
may require that evaluation and pilot studies of these technologies are conducted.
However, prior to implementation of an enhanced TI Zone restoration action, EPA would
require a modification to this ROD.
Demonstration of hydraulic control must be used to show that the TI Zone groundwater
containment system is complying with the remedial action objective.
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10.4.2.2 Tl Zone Contingency Measures
The potential contingency measures for the TI Zone are the same as those described above,
in Section 10.4.2.1, for the Shallow Groundwater Zone outside of the TI Zone.
10.4.3 Groundwater Treatment
The groundwater treatment technology, or technologies, to be used will be selected during
remedial design. Potential groundwater treatment options available for this remedy
include:
Air Stripping with off-gas treatment;
Carbon Adsorption (alone or in combination with air stripping or UV Oxidation);
UV Oxidation (in combination with air stripping or UV Oxidation).
Air stripping may be implemented by either constructing a treatment facility on the Airport
Property or by employing the treatment facility at USAF Plant No. 44, provided that the
USAF Plant No. 44 ROD is modified to be consistent with this ROD, including ARARs.
If air stripping is selected, the potential off-gas treatment options are the same as those
discussed in Section 10.1.6 for SVE off-gas.
During the Remedial Design process, after additional data are available on anticipated
influent rates and concentrations, EPA will determine which of the groundwater treatment
option(s) listed above best attains the performance standards described in Section 10.4.3.1.
Prior to construction, EPA will take appropriate action to inform the public of the actual
technologies selected for inclusion in the ROD Site Shallow Groundwater Zone remedy.
10.4.3.1 Performance Standards
The performance standards for effluent from the groundwater treatment plant(s) are listed
in Table 6 and are the same as the groundwater cleanup standards (MCLs or Arizona
HBGLs). These treatment plant discharge performance standards are appropriate for any of
the discharge options considered for the treated groundwater. The treatment plant(s) shall
be capable of meeting the effluent discharge standards on a continuous basis.
10.4.4 Treated Water Discharge
The groundwater discharge option will be selected during remedial design. Discharge
options for this remedy, which are described in detail in the FS Report, include:
Injection Wells;
Reinjection Trenches;
Sanitary Sewer;
Industrial Reuse; and
Discharge to USAF Plant No. 44 (for injection in their existing injection system).
EPA's preferred discharge option is injection. Three of the five discharge options
incorporate injection. The other two discharge options, sanitary sewer and industrial reuse,
will only be considered if injection can not be implemented. Sanitary sewer is the least
preferred discharge option.
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10.4.4.1 Performance Standards
Discharge performance standards for injection of treated groundwater, the preferred
discharge option, are shown in Table 6. For the other discharge options, specific discharge
performance standards can not be developed until the option has been selected and the
appropriate regulatory agencies have been contacted to discuss their requirements.
However, it is expected that the treatment plant effluent standards described above and
shown in Table 6 (MCLs or Arizona HBGLs) will be sufficient for any of the discharge
options.
10.5 Cost of the Selected Remedy
VOC-Contaminated Soils Outside Area 1. The estimated cost range for this portion of the
remedy is $1,252,000 to $5,267,000 with capital cost estimates ranging from $687,000 to
$3,097,000, and operation and maintenance cost estimates ranging from $565,000 to
$2,170,000"over a 10-year period. All of the cost estimates assume a 5 percent discount rate.
VOC-Contaminated Soils Inside Area 1. The estimated cost range for this portion of the
remedy is $1,164,000 to $2,723,000. Capital cost estimates range from $446,000 to $1,256,000,
and operation and maintenance cost estimates range from $718,000 to $1,467,000 over a
10-year period.
VOC-Contaminated Soils in the TI Zone. The total range of estimated costs for the SVE
remedy in the TI Zone is $922,000 to $3,758,000. The estimated capital costs range from
$389,000 to $1,022,000, and estimated operation and maintenance cost range from $533,000
to $2,736,000 over a 10- to 30-year period.
PCB-Contaminated Soils and Sludges. The estimated cost range for the PCB-contaminated
materials is $1,174,000 to $1,582,000. No operation and maintenance costs are associated
with this alternative.
TAA Landfill. The estimated cost range for TAA Landfill closure is $806,000 to $1,076,000,
with capital cost estimates ranging from $422,000 to $569,000, and operation and
maintenance cost estimates ranging from $384,000 to $507,000 over a 10-year period.
VOC-Contaminated Shallow Groundwater Outside the TI Zone. The cost estimate range for
this portion of the shallow groundwater remedy is $1,616,000 to $8,958,000. Capital cost
estimates range from $690,000 to $2,671,000 without bioaugmentation to $958,000 to
$3,742,000 with bioaugmentation. Operation and maintenance cost estimates range from
$926,000 to $4,673,000 without bioaugmentation to $1,185,000 to $5,216,000 with
bioaugmentation over a 10- to 30-year period.
VOC-Contaminated Shallow Groundwater in the TI Zone. The estimated cost range for this
alternative is from $698,000 to $2,204,000, with capital cost estimates ranging from $129,000
to $528,000, and operation and maintenance cost estimates ranging from $569,000 to
$1,676,000 over a 30-year period.
Table 8 presents a breakdown of the total potential range in costs.
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11.0 Applicable or Relevant and Appropriate Requirements
(ARARs)
Section 121(d) of CERCLA, 42 U.S.C. § 9621(d), requires remedial actions on CERCLA sites
to attain a degree of cleanup or standard of control that at a minimum attains or otherwise
complies with (or justifies the waiver of) applicable, or relevant and appropriate, federal, or
more stringent state, environmental or facility siting requirements (ARARs). Federal
ARARs may include requirements promulgated under any federal environmental law.
State ARARs may only include promulgated, enforceable environmental or facility-siting
laws of general application that are more stringent or broader in scope than federal ARARs
and that are identified by the State in a timely manner.
Applicable requirements are those cleanup standards, standards of control, criteria, or other
substantive environmental protection requirements, criteria, or limitations promulgated
under federal or state law that directly apply to and specifically address a hazardous
substance, pollutant, contaminant, remedial action, location or other circumstance at a
CERCLA site.
Relevant and appropriate requirements are those cleanup standards, standards of control,
criteria, or other substantive environmental protection requirements, criteria, or limitations
promulgated under federal or state law that, while not directly "applicable" to a hazardous
substance, pollutant, contaminant, remedial action, location or other condition, at a
CERCLA site, address problems or situations sufficiently similar to those encountered at the
site that their use is well suited to the particular site. A requirement that is not directly
applicable must be both relevant and appropriate, based on site-specific factors, to be an
ARAR. The criteria for determining relevance and appropriateness are listed in the NCP, 40
CFR § 300.400(g)(2).
While non-promulgated federal or state standards, criteria, advisories or guidance are not
ARARs, if no ARAR addresses a particular situation or if an ARAR is insufficient to protect
human health and the environment then such standards, criteria, advisories or guidance
(termed "To-be-Considered Material" or "TBCs") may be selected as enforceable
requirements in order to provide a remedy which is protective of human health and the
environment.
ARARs only include substantive, and not administrative requirements, and pertain only to
on-site matters. Any off-site activities must comply with all applicable federal, state, and
local laws, including both substantive and administrative requirements.
ARARs are identified on a site-specific basis from information about the chemicals at the
site, the actions that may take place at the site, and the features of the site location. There
are three general categories of ARARs:
Chemical-specific ARARs are usually either health- or risk-based numerical values or
methodologies that, when applied to site-specific conditions, result in the establishment
of numerical values. They are used to determine acceptable concentrations of specific
hazardous substances, pollutants, and contaminants in the environment. If a chemical
is subject to more than one numerical value or methodology, the most stringent is
generally selected.
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Location-specific ARARs are restrictions placed on the concentration of hazardous
substances, pollutants or contaminants or the conduct of activities solely because they
are in specific locations, such as wetlands or floodplains.
Action-specific ARARs are technology- or activity-based requirements or limitations on
actions taken with respect to hazardous substances, pollutants or contaminants. These
requirements are triggered by the particular remedial activities selected to accomplish
the remedy. Action-specific ARARs indicate how a selected remedy must be conducted.
Analysis and identification of chemical-specific, action-specific/ and location-specific
ARARs for the selected remedies for the ROD Site followed EPA guidance, including the
CERCLA Compliance with Other Laws Manual (Interim Final), EPA Office of Solid Waste
and Emergency Response (OSWER) Directive 9234.1-01, August 1988 (EPA, 1988k), and the
CERCLA Compliance with Other Laws Manual: Part II, Clean Air Act and Other
Environmental Statues and State Requirements (Interim Final), OSWER Directive 9234.1-02,
August 1989 (EPA, 1989f).
Tables 9a to 9c through 12a to 12c present the federal and state chemical-specific, location-
specific, and action-specific ARARs identified for each component of this remedy.
11.1 VOC-Contaminated Soil Remedy ARARs
The ARARs for the VOC-Contaminated Soil remedy are presented in Table 9a (chemical-
specific ARARs), Table 9b (location-specific ARARs), and Table 9c (action-specific ARARs).
Each of these categories is summarized in the following subsections.
11.1.1 VOC-Contaminated Soil Remedy - Chemical-Specific ARARs
The chemical-specific ARARs for VOC-contaminated soils will be identical at all subsites
addressed by the SVE remedy selected in this ROD, regardless of whether the subsites are
remedy-required subsites ROD or will be identified using the Plug-in Process.
The State has promulgated regulations (R18-7-206) that employ a narrative standard to
establish leaching criteria sufficient to prevent a release to groundwater in excess of the
MCL. This regulation states that "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
Rl8-11-406 at a program-specific point of compliance." A contaminant transport modeling
process will be used to monitor compliance with this narrative standard.
Pursuant to the policy stated in the memorandum dated January 24,1989 from Sylvia
Lowrance, Director of EPA Office of Solid Waste, to Jeff Zelickson, Director of EPA Region
IX Toxics and Waste Management Division, groundwater from CERCLA actions may be
treated as non-RCRA hazardous waste if the waste contains chemicals in concentrations
below health-based levels selected by EPA Region IX as set forth in Table 6. The SVE
systems may employ one or more off-gas treatment processes that remove water vapor
from the soil vapor. Such treatment-derived water may be subject to certain action-specific
ARARs if the wastewater contains contaminants in concentrations above the health-based
levels set forth in Table 6. In such case, the ARARs will be relevant and appropriate.
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Although not an ARAR, classification of waste will affect whether certain action-specific
ARARs are applicable or relevant and appropriate. As the wastes at the site are generally
characteristic wastes, most RCRA requirements will be relevant and appropriate.
11.1.2 VOC-Contaminated Soils Remedy - Location-Specific ARARs
Because some of the soils subsites are located on Airport Property, certain regulations
promulgated by the Federal Aviation Administration (FAA) may be ARARs with respect to
such subsites. Operation of the SVE system must comply with restrictions on emissions that
may cause a navigational hazard near airports (AC 150/5300-13). In addition, construction
of the SVE system may trigger FAA regulations imposing marking and lighting
requirements for construction equipment or permanent structures near airports.
Construction must also comply with State ARARs (41 A.R.S. 841-847,865) establishing
procedures for protecting artifacts. SVE sites near the Three Hangars may be also subject to
National Historic Preservation Act (NHPA) (Section 106,16 U.S.C. §§470 et seq.)
requirements because the Three Hangars have been proposed for inclusion on the National
Register of Historic Places. The National Register of Historic Places is a listing of districts,
sites, buildings, architecture, archeology engineering and culture.
11.1.3 VOC-Contaminated Soils - Action-Specific ARARs
Soil vapor extraction units and off-gas treatment units are subject to the substantive
requirements of 40 CFR Part 264, Subpart X (Miscellaneous Units), and R18-8-264. The
requirements in Subpart X address, in part, location, design, construction, operation and
maintenance, monitoring, and closure and postclosure care.
Tanks used to store or treat hazardous waste in the SVE system must comply with the
requirements of 40 CFR Part 264, Subpart J and R18-8-264.190 et seq. pertaining to design
and installation, containment and detection of releases, operations, inspections, responses to
leaks or spills and closure and post-closure. In addition, containers storing treatment
system waste (including treatment derived wastewater from the SVE air/water separator in
concentrations above the health-based thresholds and granular activated carbon [GAC])
must comply with substantive provisions of 40 CFR Part 264, Subpart I and R18-18-264.170
et seq.
Storage of hazardous waste must comply with 40 CFR Part 268, Subpart E (§268.50), and
Arizona Administrative Code §§R18-8-268 et seq.. which pertains to on-site storage of
hazardous wastes restricted from land disposal. In part, Subpart E limits on-site storage of
such wastes to 90 days, unless such storage is solely for the purpose of accumulating
sufficient quantities to allow for proper recovery, treatment and disposal in which case it
may be stored in excess of one-year.
Storage of hazardous waste (including treatment derived wastewater and spent GAC)
exceeding 90 days will trigger RCRA substantive storage requirements at 40 CFR Part 264,
and Arizona Administrative Code §§R18-8-264.170 to 254.178.
Air emissions from the SVE system are subject to ARARs that have been promulgated
pursuant to both the Clean Air Act (CAA ), 42 U.S.C. §§7401 et seq.. and RCRA. In
addition, an on-site air stripper installed as part of the Shallow Groundwater Zone remedy,
excavation and transport of materials in the PCB-contaminated soils and sludges remedy,
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and implementation of the TAA Landfill closure remedy may also trigger such regulations
as ARARs.
The CAA regulates air emissions by controlling stationary and mobile sources through
combined, federal, state and local programs. Pursuant to the CAA, EPA promulgated
National Ambient Air Quality Standards (NAAQS) and New Source Performance
Standards each of which may apply to a source depending on the pollutant involved.
NAAQS are implemented through State Implementation Plans. Upon EPA approval, the
State Implementation Plan requirements become potential federal ARARs.
In general, only "major sources", considering all source of emissions at the site, are subject to
NAAQS requirements. Pima County has been designated as an attainment area. In
attainment areas, activities at the ROD Site will only be considered a major source if all of
the activities are expected to emit 250 tons or more per year of a regulated pollutant. If,
however/catalytic or thermal oxidation is employed, the threshold is 100 tons. If applicable,
the source must use Best Available Control Technology (BACT).
EPA has promulgated primary and secondary standards in the NAAQS, 40 CFR Part 50, for
six criteria pollutants, including particulate matter equal to or less than 10 microns in
particle size (PM10), and ozone which results from the photo-chemical oxidation of VOCs.
As EPA has approved the State's State Implementation Plan, the Pima County Air Pollution
Control Regulations set forth in Table 9c are federal ARARs for the SVE system, including
off-gas treatment. (These ARARs also would be applicable to vapor recovery on any air
strippers used in the Shallow Groundwater Zone remedy and soil excavation conducted as
part of the PCB-Contaminated Soils and Sludges and TAA Landfill Closure remedies.) In
part, the Pima County Air Pollution Control Regulations require a proposal of reasonably
available control technology in the event that any stationary source emits a total of 2.4
pounds per day of VOCs.
RCRA also contains requirements for air emissions from RCRA regulated units. Therefore,
operation of the SVE system (including both the treatment units and the off-gas treatment
units) must comply with design, performance and operation and maintenance substantive
requirements of 40 CFR Part 264, Subparts AA and BB.
The SVE system may employ catalytic oxidation or thermal oxidation to treat off-gas.
Processes that employ an enclosed device that uses controlled flame combustion must
comply with the requirements of 40 CFR Part 264, Subpart O. Thermal treatment of
hazardous waste in equipment that does not employ an enclosed, controlled flame
combustion device must comply with 40 CFR Part 265, Subpart P.
In the event that the VOC-contaminated soils remedy employs the multi-phase extraction
enhancement, the ARARs will be the same as the ARARs pertaining to the Shallow
Groundwater Zone remedy.
11.2 PCB-Contaminated Soils and Sludges Remedy ARARs
The ARARs for the PCB-Contaminated Soils and Sludges remedy are presented in Table lOa
(chemical-specific ARARs), Table lOb (location-specific ARARs), and Table lOc (action-
specific ARARs). Each of these categories is summarized in the following subsections.
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11.2.1 PCB-Contaminated Soils and Sludges - Chemical-Specific ARARs
The State of Arizona has adopted HBGLs for Contaminants in Drinking Water and Soil,
AAC that, in part, prescribe concentration levels in surface soils considered safe for
residential and industrial use. The HBGLs are chemical-specific ARARs with respect to the
PCS remedy. The cleanup standard for PCS contamination is 0.76 mg/kg in industrial
areas (and 0.18 mg/kg in residential areas). Under the selected remedy, soils above the
HBGL(s) will be excavated and disposed of off-site. In addition, the HBGLs will be the
ARAR with respect to any other hazardous substances identified in the PCB-contaminated
soils and sludges during excavation.
11.2.2 PCB-Contaminated Soils and Sludges - Location-Specific ARARs
The PCBs contamination remedy is subject to the same State artifact ARARs as described in
Section 11.1.2 above. The FAA ARARs pertaining to construction at airports also are
relevant and appropriate.
11.2.3 PCB-Contaminated Soils and Sludges - Action-Specific ARARs
PCB contaminant concentrations determine which off-site disposal facilities may receive
PCB-contaminated soils and sludges. PCB contamination in soils and sludges in
concentrations greater than 50 mg/kg must be sent to a permitted facility pursuant to the
TSCA, 15 U.S.C. 2601 et seq.. and the regulations promulgated thereunder, 40 CFR Parts
702-775. Materials with PCB concentrations below 50 mg/kg may be sent to a solid waste
facility determined by EPA to be in compliance with EPA's off-site rule. Any other
hazardous substances identified as being above the HBGLs will be excavated and disposed
of off-site at a RCRA Subtitle C hazardous waste landfill. The TSCA regulations are both
chemical- and action-specific ARARs.
The storage requirements for PCBs set forth in 40 CFR 761.65 are applicable to the remedy.
PCBs of 50 mg/kg or greater must be disposed of within one year after being placed in
storage. In addition, the remedy must comply with structural and container requirements
for on-site storage of PCBs. PCB storage facilities must provide adequate roof, walls and
ceiling, contain no drains, drain valves, expansion joints, sewer lines or other openings and
be constructed to minimize penetrations of PCBs.
If PCBs are determined to be mixed with RCRA wastes, such contaminated media are
subject to the RCRA land ban restrictions (40 CFR Part 268).
Although not a regulation, EPA's PCB Spill Cleanup Policy published April 2,1987,40 CFR
761.120 - 761.139 is a performance standard that constitutes an enforceable standard in the
event of a spill during remediation activities.
11.3 TAA Landfill Closure Remedy ARARs
The ARARs for the TAA Landfill Closure remedy are presented in Table lla (location-
specific ARARs) and Table lib (action-specific ARARs). Each of these categories is
summarized in the following subsections.
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11.3.1 TAA Landfill Closure - Chemical-Specific ARARs
Chemical-specific ARARs do not exist for solid waste in municipal solid waste landfills. In
the event that groundwater monitoring in connection with the landfill closure indicates that
groundwater remediation is necessary, and such groundwater remediation has not been
addressed by this ROD or the 1988 ROD, chemical-specific ARARs may be developed at
that time.
11.3.2 TAA Landfill Closure - Location-Specific ARARs
Pursuant to 40 CFR 258.10 and the corresponding State regulations, if the TAA Landfill is
within 10,000 feet of a runway used by turbojet aircraft or 5,000 feet of a runway used by
piston-type aircraft, the design must avert a bird-hazard to aircraft.
The FAA requirements discussed in Section 11.1.2 above regarding construction at an
airport also would be applicable ARARs for the TAA Landfill. The location of the landfill
does not trigger ARARs pertaining to flood plains or wetlands.
11.3.3 TAA Landfill Closure - Action-Specific ARARs
The requirements of 40 CFR Part 258, as enforced by State RCRA Subtitle D regulations are
ARARs for closure of the solid waste landfill.
11.4 VOC-Contaminated Shallow Groundwater Remedy ARARs
The ARARs for the VOC-Contaminated Shallow Groundwater remedy are presented in
Table 12a (chemical-specific ARARs), Table 12b (location-specific ARARs), and Table 12c
(action-specific ARARs). Each of these categories is summarized in the following
subsections.
11.4.1 VOC-Contaminated Shallow Groundwater - Chemical-Specific ARARs
ARARs for groundwater that is an actual or potential drinking water source include federal,
and more stringent state, maximum contaminant levels (MCLs) and non-zero maximum
contaminant level goals (MCLGs) promulgated under the federal SDWA or State law. The
MCLs or MCLGs are relevant and appropriate to CERCLA groundwater cleanups unless
more stringent requirements apply.
The MCL for the most prevalent contaminant in the Shallow Groundwater Zone, TCE, is 5
ug/L. The MCLs, if available, for other contaminants of concern in the Shallow
Groundwater Zone are set forth in Table 6. If an MCL is not currently available for a
specific contaminant of concern, health-based criteria promulgated by the State of Arizona
for contaminants in drinking water (AAC R18-7-201 et seq.) have been used for the cleanup
and performance standards.
The MCLs or Arizona HBGLs in Table 6 are the ARARs that establish the in-situ cleanup
standards for the Shallow Groundwater Zone, except for the TI Zone (discussed in Section
11.6 below). Although this ROD waives the chemical performance standards as in-situ
standards in the TI Zone, groundwater extracted from the TI Zone as part of the
containment remedy will still be treated to the standards presented in Table 6 (MCLs or
HBGLs) and will be subject to all other ARARs that apply to the Shallow Groundwater
Zone.
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11.4.2 VOC-Contaminated Shallow Groundwater - Location-Specific ARARs
Activities near the Three Hangars area will comply with the NHPA in the manner
discussed in Section 11.1.2 above.
The State law pertaining to the protection of archeological artifacts discussed in Section
11.1.2 above is also an ARAR for the shallow ground water remedy.
11.4.3 VOC-Contaminated Shallow Groundwater - Action-Specific ARARs
Portions of the Arizona Revised Statutes for cleanup of hazardous substances related to
contaminated groundwater, Arizona Revised Statute 49-280 gt seq., and implementing
regulations, Arizona Administrative Code §R18-7-109 et seq., are ARARs for the shallow
groundwater remedy. The implementing regulations incorporate by reference state law
provisions that (1) establish that all definable aquifers are drinking water aquifers unless
they qualify for an aquifer exemption and (2) establish water quality standards for these
aquifers. Finally the State statute and regulations requires that, to the extent practicable,
remedial actions provide for the control or cleanup of hazardous substances so as to allow
the maximum beneficial use of the waters of the State.
The Groundwater Management Plans set forth in 45 A.R.S 454.01 are ARARs with respect to
the shallow groundwater remedy. The Groundwater Management Plan affects the in-siru
cleanup standard, extraction of groundwater and potential end-uses for treated
groundwater.
The state aquifer classification system, identifying all aquifers as drinking water aquifers
unless specifically exempt is more stringent than the federal aquifer classification scheme.
The aquifer classification system affects the in-situ cleanup standard, extraction of
groundwater and potential end-uses for treated water.
The CAA and RCRA emissions ARARs discussed in Section 11.1.3 above are also applicable
to any air strippers employed in the shallow groundwater remedy.
Air strippers or any other on-site groundwater treatment system components are subject to
RCRA ARARs pertaining to miscellaneous units (40 CFR Part 264, Subpart X), tanks (40
CFR Part 264, Subpart J), containers (40 CFR Part 264, Subpart I), and storage of hazardous
wastes (40 CFR Part 268, Subpart E) discussed in Section 11.1.3 above. Finally, use of
catalytic or thermal oxidation will be subject to the same ARARs discussed in Section 11.1.3
above (40 CFR Part 264, Subpart O)
If extracted water is sent to USAF Plant No. 44 for treatment, EPA will review the action-
specific ARARs set forth in the USAF Plant No. 44 1986 ROD to determine whether it is
protective and in compliance with current ARARs set forth in this ROD. If not, EPA will
condition use of such treatment and end-use component upon modification of the USAF
Plant No. 44 ROD to conform the ARARs to this ROD.
11.5 Other Legal Requirements
All activities involving off-site transportation of wastes will fully comply with 40 CFR Parts
262 and 263,49 CFR and U.S. Department of Transportation Hazardous Material
Transportation Rules. These regulations are fully applicable and are not ARARs because
they occur off-site and do not set environmental standards for the remedy.
TIAA SITE RECORD OF DECISION PAGE I-79
PART I - DECISION SUMMARY SAC/I IOUI/DOS.OOC
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In addition, the remedy will comply with all requirements for worker protection, training
and monitoring pursuant to the Occupational Safety and Health Act, 29, U.S.C. §651 et-seq..
and the regulations promulgated thereunder, 29 CFR §1910.120. These requirement are
fully applicable and are not ARARs because they do not set environmental standards for
the remedy.
Discharge of treated water to the sanitary sewer system is considered an indirect discharge
to a POTW which must comply with the requirements of 40 CFR 403.5 and any local POTW
regulations. Discharge to the sanitary sewer system is considered off-site and must comply
with all applicable regulations.
11.6 ARAR Waiver - Technical Impracticability
In certain circumstances, ARARs can be waived. The six general ARARs waivers stated in
Section 121(d) of CERCLA are paraphrased below:
1. The remedial action is an interim measure and is part of a final remedy that will attain
the waived ARAR upon completion.
2. Compliance with ARARs will result in greater risk to human health and the
environment than other options that do not comply with ARARs.
3. Compliance with ARARs is technically impracticable from an engineering perspective.
4. The remedial action will not meet ARARs, but will attain an equivalent standard of
performance through use of another method or approach.
5. The state has not consistently applied a state ARAR or demonstrated the intent to apply
the ARAR to similar remedial action sites.
6. Superfund money spent at a site will not provide a balance between the need to protect
human health and the environment and the availability of Superfund money for
response actions at other facilities.
This section focuses on the need for a waiver because it is technically impracticable from an
engineering perspective to meet in-situ groundwater ARARs in the designated TI Zone.
Technical Impracticability (TI) waivers generally apply only for ARARs that are used to
establish cleanup performance standards, such as chemical-specific MCLs.
This section summarizes the technical conditions that provide justification for the issuance
of a Technical Impracticability (TI) Waiver for a portion of Zone E at the Airport Property of
the ROD Site. A separate TI Waiver Support Document was submitted as Appendix B of
the FS Report (CRA, 1997). Pursuant to EPA's Guidance for Evaluating the Technical
Impracticability of Ground-Water Restoration (OSWER Directive 9234.2), dated September 1993
(TI Guidance), the following components should be incorporated into the TI Waiver
Support Document:
1. Specific ARARs or media cleanup standards for which TI determinations are sought.
2. Spatial area over which the TI decision will apply.
PAGE 1-80 TIAA SITE RECORD OF DECISION
SAC/110831/003.00C PART I DECISION SUMMARY
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3. Conceptual model that describes site geology, hydrology, groundwater contamination
sources, transport, and fate.
4. An evaluation of the restoration potential of the site, including data and analyses that
support any assertion that attainment of ARARs or media cleanup standards is
technically impracticable from an engineering perspective. At a minimum, this
generally should include:
a) A demonstration that contamination sources have been identified and have
been, or will be, removed and contained to the extent practicable;
b) An analysis of the performance on any ongoing or completed remedial actions;
c) Predictive analyses of the timeframes to attain required cleanup levels using
available technologies; and
d) A demonstration that no other remedial technologies (conventional or
innovative) could reliably, logically, or feasibly attain the cleanup levels at the
site within a reasonable timeframe.
5. Estimates of the cost of the existing or proposed remedy options, including construction,
operation, and maintenance costs
6. Any additional information or analyses that EPA deems necessary for the TI evaluation.
The TI Waiver Support Document incorporates all of these components that are pertinent to
the TI evaluation at the Airport Property. EPA has determined that the TI Waiver Support
Document fully and adequately identifies and evaluates existing on-site conditions that
support issuance of a TI Waiver, pursuant to the TI Guidance. EPA has further determined
that the TI Waiver Support Document fully and adequately identifies and evaluates an
alternative remedial strategy that involves source control measures in accordance with the
TI Guidance. The following sections summarize the key components of the TI Zone
conceptual model that support the TI Waiver.
11.6.1 Spatial Identification of the TI Waiver Area
The TI Waiver Area (or TI Zone) is defined as the area where Shallow Groundwater Zone
restoration is technically impractical due to contaminant-related factors (i.e., the existence of
DNAPL and substantial soil gas concentrations) and hydrogeologic factors (i.e., the
existence of low permeability clay and heterogeneous conditions). The approximate extent
of DNAPLs, and thus the TI Zone, is shown in Figure 11. The TI Zone covers
approximately two acres that basically incorporates the area beneath the south end of the
Three Hangars, extending immediately south of the in Three Hangars in the vicinity of
Buildings 14/15 and 16/17.
The proposed bottom of the TI Zone is an elevation of 5 feet below the base of the Unit 4
gravel subunit where it exists at an elevation of 2,370 feet above mean sea level
(approximately 180 feet below ground surface) where the gravel subunit does not exist. The
bottom of the TI Zone has been selected based upon the assumption from soil quality data
obtained during the RI that the vertical limit of the area impacted above MCLs is at
approximately 4 feet below the bottom of the gravel subunit. The bottom of the TI Zone
also reflects the desire of EPA and the State of Arizona to provide a "buffer" between the TI
TIM SITE RECORD OF DECISION PAGE 1-81
PART I - DECISION SUMMARY SAC/I 10331/003.000
-------
Zone and the Regional Aquifer where vertical hydraulic gradients could be reversed by
pumping, if necessary.
11.6.2 Hydrogeologic Factors
The RI showed that VOCs are present in the low permeability clays (i.e., saturated vertical
hydraulic conductivities from 10"4 to 10"* cm/s); in addition, there are significant
heterogeneous conditions within the vadose and shallow groundwater zones. These
hydrogeologic conditions are a substantial impediment to restoration of both soil and
shallow groundwater because these materials do not readily allow for the movement or
transfer of liquids or gas which is necessary for contaminant mass removal or destruction.
11.6.3 Contaminant-Related Factors
Previous investigations in Zone E of the TIAA Site have indicated the likely presence of
DNAPLs in-soil and groundwater. The presence of DNAPLs poses a long-term source of
contaminants to soil and groundwater. The presence of DNAPL will not allow for
restoration of the shallow groundwater system to cleanup standards (Table 6).
The remedial investigation showed that the Zone E Shallow Groundwater Zone near
Buildings 14/15,16/17, and 25 has been impacted with VOCs. These VOCs include TCE,
PCE, 1,2-dichloropropane, chloroform, methylene chloride and benzene. Of these VOCs,
TCE is present at the highest concentrations. The TCE concentration in the southern portion
of the Three Hangars Area (Buildings 16/17) is almost 10 percent of pure phase solubility
for TCE (1,100 mg/L). Although an investigation designed to locate DNAPL was
conducted, the specific source of DNAPL has not been located. However, the presence of
dissolved TCE at concentrations that exceed one percent of the pure phase solubility and
soil gas concentrations greater than 100 ppm (or 562 pg/L of TCE) provides strong indirect
evidence to suspect that DNAPL is present (Cohen and Mercer, 1993). Based upon
analytical data for groundwater samples collected during the Shallow Groundwater Zone
pumping test (CRA, 1996), there is indirect evidence of DNAPL at depths greater than
110 feet bgs within the gravel subunit.
At well location S-12 (Building 25), a TCE concentration of 1,702 ug/L was detected in a soil
gas sample. The TCE concentration at S-12 is comparable to other soil gas samples collected
from wells near a likely DNAPL source area (e.g., Buildings 16/17).
DNAPL remedial technologies currently available are limited and none are able to recover
all trapped DNAPL (USEPA, 1992). Therefore, complete restoration within the suspected
DNAPL zone will not be feasible with current technologies. Any trapped DNAPL will
provide a continuing long-term source of groundwater and soil vapor contamination for the
foreseeable future. Complete restoration of the TI Zone is unlikely, because remedial
technologies can only reduce the DNAPL mass, not eliminate it. Hence, it is appropriate to
waive the ARARs presented in Table 13 as they relate to vadose zone shallow groundwater
remediation within the TI Zone. As noted above, additional technical details on the TI
Waiver are provided in Appendix B of the FS Report (CRA, 1997)
PAGE 1-82 TIAA SITE RECORD OF DECISION
SAC/110831/003.00C PART I - DECISION SUMMARY
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12.0 Documentation of Significant Changes
EPA issued the Proposed Plan for this remedy at the TIAA Superfund Site for public
comment in July 1997. The Proposed Plan identified a combination of remedial
alternatives as the preferred remedy for the four contaminants and media (VOC-
contaminated soils; PCB-contaminated soils and sludges; VOC-contaminated shallow
groundwater, including the TI Zone; and TAA landfill closure) addressed in this Record
of Decision. EPA reviewed all written and verbal comments submitted during the public
comment period. After reviewing these comments, EPA has determined that no
significant changes to the remedy, as originally identified in the Proposed Plan, are
necessary.
There has been one minor change to the data presented in the Proposed Plan. Recent
field investigations have identified two additional, localized areas of Shallow
Groundwater Zone contamination. These two new areas are located near the western
boundary of the Airport Property north and south of Shallow Groundwater Zone plume
presented in the Proposed Plan. The extent of Shallow Groundwater Zone contamination
has been modified to illustrate these two new areas (see Figure 11).
13.0 Statutory Determinations
Section 121 of CERCLA establishes statutory requirements that selected remedies must
attain and statutory preferences that EPA must consider in the remedy selection process.
The selected remedial action for a site must be protective of human health and the
environment and comply with applicable or relevant and appropriate environmental
standards established under federal and state environmental requirements and state facility
siting requirements (unless a statutory waiver is justified). Section 121 requires that a
remedy, be cost-effective and utilize permanent solutions and alternative treatment
technologies or resource recovery technologies to the maximum extent practicable. Finally,
the statute includes a preference for remedies that employ treatment that permanently and
significantly reduces the volume, toxicity, or mobility of hazardous wastes as their principal
element. The following sections discuss how the selected remedy at the TIAA Site meets
these statutory requirements.
13.1 Protection of Human Health and the Environment
The selected remedy protects human health and the environment by eliminating, reducing,
or controlling site-related risk through removal and treatment of VC»C contaminants from
soil; excavation, treatment and disposal of PCB-contaminated soils and sludges in an
approved off-site landfill; proper closure of TAA Landfill in accordance with ARARs;
containment, restoration and treatment of VOC-contaminated shallow groundwater; and
implementation of institutional controls to significantly reduce the potential for future
exposure to site-related contaminants and contaminated groundwater. The selected remedy
further protects human health and the environment by providing for groundwater
monitoring that will track movement of the groundwater contamination and detect any
potential adverse impacts to the Regional Aquifer (which is the primary drinking water
aquifer). This will allow for ongoing evaluation of groundwater quality and
implementation of contingency measures, if necessary (e.g., if SVE and shallow
TIAA SITE RECORD OF DECISION PAGE I-83
PART I - DECISION SUMMARY SAC/IIOMIAXWJKX
-------
groundwater containment are not working as anticipated). There is no current use of, or
exposure to, shallow groundwater in the Airport Property vicinity.
Removal of the PCB-contaminated materials (such as those present at Structure 21)
addresses the most significant current threat to human health identified in the ADHS Risk
Assessment (ADHS, 1996).
Closure of the TAA Landfill in accordance with State of Arizona RCRA Subtitle D
requirements, including security and institutional controls, will provide protection of
human health and the environment from landfill contents.
There are no short-term threats associated with implementation of the selected remedy that
cannot be readily mitigated. Further, no adverse cross-media impacts are expected from the
remedy.
13.2 Compliance with ARARs
The selected remedy (outside of the TI Zone) will comply with all federal and state
applicable or relevant and appropriate chemical-, action-, and location-specific
requirements (ARARs). Federal and state ARARs pertinent to the selected remedy are
discussed in Section 11. The specific ARARs for the selected remedy are presented in Table
10.
EPA is invoking a waiver of groundwater cleanup ARARs in the 2-acre TI Zone based on
the determination that restoration of the Shallow Groundwater Zone is technically
impracticable. This waiver is necessary and justified because of contaminant and
hydrogeologic conditions that inhibit restoration. Liquid TCE (a DNAPL) is believed to be
present in the TI Zone. This alone severely limits the possibility for groundwater
restoration. The presence of a DNAPL, combined with the very low permeability clay
horizons present in the TI Zone area, makes groundwater restoration technically
impracticable given current technologies. Although restoration is not practicable, shallow
groundwater in the TI Zone will be contained to prevent additional impacts outside of the
TI Zone.
As discussed in the description of the selected remedy (Section 10.4), there is a possibility
that, because of the low-permeability formation and complex groundwater flow conditions in
the Shallow Groundwater Zone, it may also take an excessive amount of time to restore
shallow groundwater to cleanup standards outside of the TI Zone.
13.3 Cost-Effectiveness
EPA has determined that the selected remedy is cost-effective because it will significantly
increase protectiveness at a reasonable cost in comparison to the other alternatives. The
estimated range in total net present worth of the selected remedy is from $7.6 to $25.6
million. The selected alternatives represent the only remedy that is fully protective of
human health and the environment and that meets ARARs (outside of the TI Zone). In
general, the less expensive alternatives were either much less protective or could not meet
ARARs.
PAGE I-84 TIAA SITE RECORD OF DECISION
SAC/110831/003.DOC PART I DECISION SUMMARY
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13.4 Utilization of Permanent Solutions and Alternative Treatment Technologies
to the Maximum Extent Practicable
EPA has determined that the selected remedy represents the maximum extent to which
permanent solutions and treatment technologies can be utilized in a cost-effective manner.
EPA has determined that the selected remedy provides the best balance of long-term
effectiveness and permanence; reduction in toxitity, mobility, or volume through treatment;
short-term effectiveness; implementability; and costs. The State of Arizona has concurred
with the selected remedy and the community has expressed very few concerns with
remedy.
The selected remedy will significantly reduce the mobility and volume of VOCs in the soil
and shallow groundwater, permanently eliminating this long-term principal threat to the
regional drinking water aquifer. The selected remedy also provides a permanent solution
for PCB-contaminated materials. These materials will be excavated, treated (as necessary)
and hauled off-site for disposal, permanently eliminating the possibility of exposure.
The TI Zone has a containment-based remedy that does not necessarily represent a
permanent solution. However, based on currently available technologies, containment is
the only option for addressing the DNAPL principal threat wastes in the types of
subsurface conditions present in the TI Zone. This containment action wiU remove and
treat these DNAPL principal threat wastes to the maximum extent practicable. If new
technologies are developed during implementation of the remedy, they will be evaluated to
determine if a more permanent solution is practicable. The combination of Shallow
Groundwater Zone containment and restoration outside of the TI Zone, groundwater
monitoring, and institutional controls prevents exposure and offers a permanent solution to
the Shallow Groundwater Zone contamination away from the TI Zone.
13.5 Preference for Treatment as a Principal Element
By treating the VOC contaminants collected in the SVE and shallow groundwater extraction
systems (both inside and outside of the TI Zone), the selected remedy addresses one of the
principal threats posed by the site through the use of treatment technologies. In addition,
any of the excavated PCB-contaminated materials that contain high concentrations of PCBs
(above 50 mg/kg) or metals (above TCLP criteria) will be treated prior to disposal.
Therefore, the selected remedy satisfies the statutory preference for remedies that employ
treatment as a principal element.
13.6 Five Year Reviews
Because this remedy will result in hazardous substances remaining onsite above health-
based levels, a review will be conducted at least once every 5 years after commencement of
remedial action to ensure that the remedy continues to provide adequate protection of
human health and the environment.
TIAA SITE RECORD OF DECISION PAGE I-85
PART I - DECISION SUMMARY sAc/no83i/oo3.ooc
-------
14.0 References
Arizona Department of Health Services. 1996: Baseline Human Health Risk Assessment.
Tucson International Airport Superfund Site. Prepared by the Office of Environmental
Health. December 1.
Conestoga-Rovers & Associates. 1995. Preliminary Feasibility Evaluation, Tucson
International Airport Superfund Site. April.
Conestoga-Rovers & Associates. 1996. Vadose Zone Treatability Study Evaluation Report,
Tucson International Airport. October 11.
Conestoga-Rovers & Associates. 1997. Final Feasibility Study, Tucson International
Airport. June.
Daniel B. Stephens & Associates, Inc. 1993. Final Existing Data Report, Tucson
International Airport. Februarys.
Daniel B. Stephens & Associates, Inc. 1995. Results of Sludge and Soil Analyses, Canale
Sampling Program, Tucson International Airport. January 25.
Daniel B. Stephens & Associates, Inc. 1995. Field Reconnaissance Investigation Results,
Tucson International Airport. January 27.
Daniel B. Stephens & Associates. 1995. Remedial Investigation/Feasibility Study Work
Plan, Tucson International Airport. March 8.
Daniel B. Stephens & Associates, Inc. 1996. Final Remedial Investigation Report: Tucson
International Airport. October 31.
Hargis & Associates, Inc. 1996. Draft Shallow Groundwater Zone Removal Action
Engineering Evaluation/Cost Analysis for Air Force Plant 44. April 4.
United States Environmental Protection Agency. 1989. Risk Assessment Guidance for
Superfund, Human Health Evaluation Manual, Part A. Interim Final. OSWER, Directive
9285.701a. September.
United States Environmental Protection Agency. 1994. Feasibility Study Analysis for
CERCLA Sites with Volatile Organic Compounds in Soils. August.
United States Environmental Protection Agency. 1993. Presumptive Remedies: Site
Characterization and Technology Selection for CERCLA Sites with Volatile Organic
Compounds in Soils. OSWER Directive 9355.0-48FS. September.
PAGE 1-86 TIAA SITE RECORD OF DECISION
SAC/110831/D03.00C PART I - DECISION SUMMARY
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United States Environmental Protection Agency. 1993. Interim Final, Guidance for
Evaluating the Technical Impracticability of Ground-Water Restoration. OSWER Directive
9234.2-25. September.
TlAA SITE RECORD OF DECISION PAGE 1-87
PART I - DECISION SUMMARY
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TABLES
-------
TABLE 1
Site Summary Following the Remedial Investigation
TIAA Site Record of Decision
Subsite
Contaminants of
Concern
Screening Criteria
Soil
Gas
>SGSL
Soil
>HBGL
Soil
>PRG
No
Further
Action
Sites Exceeding
Screening
Criteria
ZONE A
Hangar 10
Airport Wash North of
Perimeter Road
Zone A Groundwater
Lead
VOCs
VOCs
X
X
X
ZONEC
Credit Union Dump
Diversion Channel
VOCs
VOCs
X
X
X
ZONED
South Ramp and Drains
South Ramp Drainages
and Ponding Areas
Former USAF Disposal
Areas
Fire Drill Area D-3
C-294 Bum Pit
TAA Landfill
VOCs
Metals, SVOCs,
VOCs, PCBs
VOCs
VOCs
VOCs
VOCs
SVOCs, Metals
X
X
X
X
-------
TABLE 1
Site Summary Following the Remedial Investigation
TIAA Site Record of Decision
Subsite
Contaminants of
Concern
Screening Criteria
Soil
Gas
>SGSL
Soil
>HBGL
Soil
>PRG
No
Further
Action
Sites Exceeding
Screening
Criteria
Buildings 16/17
Building 18
Structures 21 and 30
Building 24
Building 25 and
Adjacent Soils to the
North (D-157)
Building 25 (D-157)
Former Structure 27
Former Building 32
West lease USTs
Soils Beneath West Lease
USTs
Sludges in Canale
System
Concrete Structure Area
Soil Adjacent to Canale
Drainages and Ponding
Areas
(including sediments)
North and East Sides of
Hangar 1
ZONE
SVOCs, PCBs, Metals,
Cyanide
VOCs
VOCs
SVOCs, Metals,
Cyanide
PCBs
VOCs
VOCs, PCBs
SVOCS, Cyanide,
Metals
VOCs
VOCs
VOCs
VOCs
VOCs, SVOCs, PCBs,
Metals
VOs, SVOCs, PCBs,
Metals, Cyanide
VOCs, SVOCs,
Metals, Cyanide
PCBs
SVOCs, PCBs
Metals, VOCs
VOCs
E (contir
X
X
X
X
X
X
tued)
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
SAC/110831/001.xls
2 Of 3
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TABLE 1
Site Summary Following the Remedial Investigation
TIAA Site Record of Decision
Subsite
Hangar 1 Drains
Contaminants of
Concern
VOCs, PCBs
Screening Criteria
Soil
Gas
>SGSL
X
Soil
>HBGL
Soil
>PRG
No
Further
Action
Sites Exceeding
Screening
Criteria
X
ZONE E (continued)
Southern Portion of
Hangar 2
South Apron
Geophysical Anomalies
Recent Addition to
South Apron
West End of Runway 3
Zone E Groundwater
Zone
VOCs
VOCs
VOCs
VOCs
VOCs, Metals,
Nitrate
SVOCs, Cyanide
X
X
X
X
X
X
X
X
ZONEF
East Side of Hamilton
Building D-252, D-267, D
275
North End of Samsonite
Building D-167
West Side Drainage
VOCs
VOCs
VOCs, SVOCs,
Metals
PCBs
X
X
X
X
X
X
X
X
SGSL - Soil Gas Screening Levels
HBGL - Health-Based Guidance Levels
PRG - EPA Region IX Preliminary Remediation Goals
NFA - No Further Action
VOCs - Volatile Organic Compounds
SVOCs - Semi-Volatile Organic Compounds
PCBs - Pol/chlorinated biphenyls
Source:
Final RI Report, Daniel B. Stephens & Associates, Inc., October 1996.
- USTs - Underground Storage Tanks
- USAF - United States Air Force
- TAA - Tucson Airport Authority
SAC/110831/OOl.xls
3 of 3
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Table 2
Chemicals of Potential Concern for Soil, Soil Gas, and Groundwater
TIAA Site Record of Decision
Subsite
Soil
Chemical of Potential Concern
Soil Gas Groundwater
Zone A
NA
JHangarJO_ None.
Airport Wash North of Perimeter Road" 'None"
_None
None"
ZoneB
NA
NA
NA
ZoneC
NA
Diversion Channel
None.
None
TCE
"None"
ZoneO
NA
South Ramp and Drains
South Ramp Drainages and Ponding Areas
Former USAF Disposal Areas
Rre Drill Training Area D-3/C-294 Bum Pit
TAA Landfill
None
None
NA
NA
Qualitative results,
no COCs identified
Benzene
PCE
None
None
Benzene
1.2-DCA
1.1 -DCE
PCE
TCE
None
ZoneE
Building 13 (Indudlng geophysical I anomaly)
........ Buildings 14/15
Buildings 16/17
None
None
Chloroform
1.1-DCA
1.2-DCA
TCE
None
"Building 18~No o5cs"selected"
Former Structures 21 and 30
Chloroform
1,1-DCE
Methyfene Chloride
PCE
1.1,1-TCA
1,1,2-TCA
TCE
___Tg(uene_
Chloroform
Chtoromethane
1.1-DCA
1.1-OCE
PCE
1.1.1-TCA
1.1,2-TCA
TCE
Toluene
Xylene,
None
Budding 25 (and adjacent soils to the North)
Benzene
Chloroform
Chtoromethane
1,1-DCE
Dichtofomethane
Ethylbenzene
Fraon13
PCE
1.1.1-TCA
TCE
1,2,4-Trimethylberuene
Toluene
Xylene
SAC/110831/009.DOC
10F2
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Table 2
Chemicals of Potential Concern for Soil, Soil Gas, and Groundwater
TIAA Site Record of Decision
Subsite _ Spij
Former Structure 27/West Lease USTs None
Chemical of Potential Concern
SoM Gas Groundwater
'"None-
Sols Adjacent to the Canale System
NA
'Arocto'r"i26o'(PCB)'
Chromium
Lead
Drainages and Ponding Areas
Off-Site Sediment Contamination
North and East Sides of Hangar 1
Antimony
Cadmium
Lead
Aroclor 1254 (PCB)
Arodor 1260JPCB)
............. NA
PCE
"NA"
None
None
NA
Benzene
Chloroform
Chkxomethane
1.1-DCA
1.1-DCE
Dichloromethane
Ethytbenzene
Freon113
PCE
1.1.1-TCA
TCE
1.2,4-Trimethyl benzene
Xytene
BjJlding_r>-J58_
HangaM
None
None
Southern [.Portion |.pfJHangaf ;2
NA
_TCE.
~None"
NA
Carbon tetrachloride
Shalow Groundwater Zone
Arsenic
Lead
Nitrate
Benzene
Carbon tetrachloride
Chloroform
1,2-DCA
Dichloromethane
1,2-Dichloropropane
Di(2-ethylhexyl)phthalate
PCE
TCE
ZoneF
East Side of Hamilton Buildings D-252, D-267, None
D275
Westsdeprainage fone
NA
Benzene
PCE
TCE
None
Burr-Brown Facility
None
1.1-DCE
PCE
TCE
Vinyl Chloride
NA
Former West-Cap Property
None
1,1-DCE
PCE
TCE
NA
NA - not applicable, no analyses conducted.
SAC/110831 A509.00C
20F2
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Table 3
Estimated Site-Related Cancer Risk and Non-Cancer Hazard Index - Current Conditions
TIAA Site Record of Decision
Estimated Lifetime Hazard Index
Cancer Risk
Subsite
CT
RME CT RME
Zone A
Hangar 10
Airport Wash North of Perimeter Road
'
ZoneC
Hughes Credit Union Dump
Diversion Channel
6x10"
N/A
4x10" <1 <1
N/A N/A N/A
ZoneO
South Ramp and Drains
5x10-" <1
South Ramp Drainages and Ponding Areas
Fire Drill training Area 6-3
TAA Landfill
Zone E
Building 13 (Including geophysical anomaly)
Buildings 14/1 5
Building 18
Former Structure 21
Former Structure 30
Building 24
Building 25 (and adjacent soils to the North)
Former Structure 27
N/A
N/A
3x10"
.....~
N/A N/A N/A
6x10" <1
5x10" <1
N/A N/A N/A
4x10" <1
2x10* <1
2x10' <1
2x10* <1 <1
1x10* <1
West Lease USTs
Former Building 32
Soil Adjacent to Canale
Drainages and Ponding Areas
North Drainage Outfall/Ponding Areas
South Drainage Outfall/Ponding Areas
Off-Airport Property Sediment Site 1 m
Off-Airport Property Sediment - Site 2 m
Off-Airport Property Sediment - Vacant Lot w
North and East Sides of Hangar 1
Building D-158
1x10*
7x1 07
.?xj5::...
5x10" <1
9x10* <1
1x10* <1
2x10* <1 <1
1x10* <1 <1
6x10' <1
1x10* <1 <1
2x10" <1
Hangar 1
Southern Portion of Hangar 2
South Apron Geophysical Anomalies
West End of Runway 3
5x10"
4x10* <1 <1
__ _
2x10" <1
ZoneF
East Side of Hamilton Buildings D-252, D-267, D275
North Portion of Samsonrte Building D-167
West Side Drainage
Burr-Brown Facility
Former West Cap Property
1x10"
N/A
2x10*
7x10*
1x10" <1 <1
1x10" <1
N/A 'N/A "N/A
1x10* <1 <1
3x10' <1 <1
RME = Reasonable Maximum Exposure.
Indicates that no COPCs were detected.
CT = Central Tendency Exposure.
N/A Risk estimate not available due to Insufficient data.
'" Current exposure pathways:
Occupational exposures to inhalation of contaminated soil gas.
Potential dermal contact with or ingestion of contaminated soil or inhalation of fugitive dust by workers and by residents.
These areas have already been remediated.
SAC/110831/D10.00C
-------
Table 4
Estimated Site-Related Cancer Risk and Non-Cancer Hazard Index - Future Conditions
TIAA Site Record of Decision
Estimated Lifetime
Cancer Risk
Hazard Index
Subsite
CT
RME
CT
RME
Zone A _
Hangar 8 _
Airport Wash North of tfie Perimeter Road
JZoneC .
Hughes Credit Union Dump 6x10'" 4x10''^
-------
Table 5
Comparison of Costs (in thousands)(1)
TIAA Site Record of Decision
Alternative
Alternative A3 - Soil Vapor Extraction
(SVE)
Alternative B3 - Soil Vapor Extraction
(SVE)
Alternative C3 - Soil Vapor Extraction
(SVE)
Alternative D5 - Excavation,
Treatment and On-Site Landfilling
Alternative D6 - Excavation,
Treatment and Off-Site Landfilling
Alternative E2 - Institutional Controls
and Monitoring
Alternative E3 Arizona-Compliant
Closure
Alternative F2 - Institutional Controls
and Monitoring
Alternative F3 - Bioaugmentation
Alternative F5 - Extraction, Ex-situ
Treatment, Bioaugmentation and
Dischargejw/o bioaugmentation)
Alternative F5 - Extraction, Ex-situ
Treatment, Bioaugmentation and
Discharge (w/bioaugmentation)
Alternative G5 - Extraction, Ex-situ
Treatment, Bioaugmentation and
Discharge
Capital Cost
$ 3.100
$ 1,260
$ 1,020
$ 1,430
$ 1,580
$ 70
$ 570
$ 230
$ 1.070
$ 2,300
$ 3,740
$ 530
Annual O&M
$ 280
$ 190
$ 180
$
$
$ 10
$ 30
$ 70
$ 140
$ 300
$ 380
$ 110
Capital
Cost
$ 3,100
$ 1,020
$ 1.430
$ 1,580
$ 70
$ 570
$ 230
$ 1,070
$ 2,300
$ 3,740
$ 530
Assumed
O&M
Timeframe
10yrs
10yrs
10to30yrs
NA
NA
30yrs
30yrs
30yrs
10yrs
10to30yrs
lOyrs
30yrs
Present
Worth
O&M
$ 2,170
$ 1.470
$1.370 to 2.740
$
$
$ 200
$ 510
$ 1,000
$ 1,100
$2,350 to 4,670
$ 2,940
$ 1,680
Total
Net Present
Worth
$ 5,270
$ 2.720
$2,400 to 3,800
$ 1.430
$ 1,580
$ 270
$ 1.080
$ 1.230
$ 2.170"
$5.020 to 7.340
$ 6.680
$ 2.210
(1)
Assuming a discount rate of 5%.
SAC/lloi Lxb
-------
Table 6
Selected Performance Standards, Cleanup Standards, and Discharge Standards for Groundwater
TIAA Site Record of Decision
Contaminant of Concern'**
1,1-Dichloroethane
1,1-Oichloroethene
1 , 1 ,1 -Trichloroethane
1,2-Dtchloroethane
1 ,2-Dichloroethene (cis)
1,2-Dichloroethene (trans)
1 ,2-Dichloropropane
Acetone
Arsenic
Benzene
Bis(2-ethylhexyl)phthalate
Carbon tetrachloride
Chlorobenzene
Chloroform
Chloromethane
Chromium
Dichlorodifluoromethane
(Freon 12)
Ethylbenzene
Lead
Methyl ethyl ketone
Methylene chloride
Nitrate (as Nitrogen)
Tetrachloroethene
Toluene
Trichloroethene
Trichlorofluoroethane
Federal MCL
(ng/L)
5
7
200
5
70
100
5
50
5
6
5
100
100
100
700
15
5M
10,000
5
1.000
5
ADEQ HBGLs
(ug/L)
70
6.3
200
0.38
70
140
0.5
700
0.02
1.2
0.27
140
5.7
2.7
100
1,400
700
5
350
10,000
0.70
1,400
3.2
210,000
Selected Performance
Standard & Cleanup
Standard (\iglL)
5
7
200
5
70
100
5
700
50
5
6
5
100
100
2.7
100
1,400"
700
15
350
5
10,000
5
1,000
5
210,000
(Freon 113)
Trichlorofluoromethane
(Freon 12)
2,100
2.100
SAC/110831/012.DOC
-------
Table 6
Selected Performance Standards, Cleanup Standards, and Discharge Standards for Groundwater
TIAA Site Record of Decision
Contaminant of Concern'"
Trihalomethanes w
Xylenes
Vinyl chloride
Federal MCL
-------
Table 7
TCLP Regulatory Standards
TIAA Site Record of Decision
Constituent U.S. EPA TCLP (mg/L)
Antimony NA
Arsenic 5.0
Barium 100
Cadmium 1.0
Chromium 5.0
Lead 5.0
Mercury 0.2
Selenium 1.0
Silver 5.0
Zinc NA
Notes:
TCLP = Toxicity Characteristic Leaching Procedure standards, 40 CFR Part 261.
mg/L = milligrams/liter.
NA = not applicable.
SAC/110831/D13.0CC
-------
Table 8
Selected Remedy Cost Estimate Summary
(In thousands)
TIAA Site Record of Decision
Remedy Component
VOC-Contaminated Soils Outside Area 1
VOC-Contaminated Soils Inside Area 1
VOC-Contaminated Soils in the Tl Zone
PCB-Contaminated Soils and Sludges
TAA Landfill
VOC-Contaminated Groundwater Outside the Tl Zone
VOC-Contaminated Groundwater Inside the Tl Zone
Total Estimated Cost
Capital Cost
Range
$ 687
$ 446
$ 389
$ 1,170
$ 422
$ 690
$ 129
$ 3,930
$ 3,100
$ 1,260
$ 1,020
$ 1,580
$ 569
$ 3,740
$ 528
$ 11,800
O&M Cost
Range
$ 565
$ 718
$ 533
$
$ 384
$ 926
$ 569
$ 3,700
$ 2,170
$ 1.470
$ 2,740
$
$ 507
$ 5,220
$ 1,680
$ 13,800
Total Net Present
Worth Range
$ 1,250 $ 5.270
$ 1,160 $ 2.720
$ 922 $ 3,760
$ 1,170 $ 1,580
$ 806 $ 1,080
$ 1,620 $ 8,960
$ 698 $ 2,200
$ 7,630 $ 25,600
SAC/1H
03-xlsr
-------
Table 9a
Chemical-Specific ARARs for VOC-Contamlnated Soil
TIAA Site Record of Decision
Source Standard, Applicable or Relevant Description of Standard, Manner In Which ARAR Applies to
Requirement, Criteria, and Appropriate Requirement, Criteria, or Alternative
or Limitation Limitation
Arizona Interim Soil AAC R16-7-201 et seq. Applicable (narrative Narrative standard that states that Results in numerical standards for treating
Remediation Standards standard) and Relevant soil concentrations may not cause or sub-surface soils. Cleanup will meet
and Appropriate (surface threaten contamination of narrative and numerical HBGLs.
soil standards) groundwater In exceedance of
Arizona Water Quality Standards;
also sets soil contamination
standards called HBGLs.
SAC/110831/OU.DOC lOF 4
-------
Table 9b
Location-Specific ARARs for VOC-Contamlnated Soil
TIAA Site Record of Decision
Source
Standard,
Requirement, Criteria,
or Limitation
Applicable or Relevant
and Appropriate
Description of Standard,
Requirement, Criteria, or
Limitation
Manner In Which ARAR Applies to
Alternative
Federal Aviation
Administration Rules
Federal Aviation
Administration Rules
Endangered Species
Act,6U.S.C.§1531
AC 150/5300-13
AC/70/7460-1 F
Applicable
Applicable
50 CFR 200 and 402 Applicable
National Historic
Preservation Act,
Section 106.16 U.S.C.
§§470 fil seq.
36 CFR Parts 65 and
800
Relevant and Appropriate
until designated
Restricts emissions that may cause
a navigational hazard near airports.
Establishes marking and lighting
requirements for construction
equipment or permanent structures
near airports.
Establishes procedures for
determining presence of
endangered species and protecting
their habitats.
Preserves historic properties by
requiring that action be planned to
minimize harm to National Historic
Landmarks.
Applicable to emissions from operation of
SVE systems, thermal desorption,
excavation and construction.
Applicable to construction equipment and
the SVE system.
No endangered species have been
identified at the SVE sites and plug-in
sites. If any native plants or species are
identified as endangered or threatened,
construction or other remedial activities
will be mitigated to avoid affecting such
species or its habitat.
The Three Hangars have been proposed
for designation on the Register of Historic
Places. Any SVE activities near the Three
Hangars would be managed to minimize
harm to the buildings.
Archaeological
Discoveries, Historic
Preservation
41 ARS §§ 841-847,
865
Applicable
Preserves archaeological artifacts
and remains.
If any archaeological artifacts, human
remains, or funerary objects are
discovered during construction,
excavation or similar activities, such
activity must cease temporarily to allow for
investigation and preservation of such
artifacts, remains, or objects in
accordance with the procedures set forth
in this ARAR.
SAC/i t
IU.DOC.
>OF4
-------
Table 9c
Action-Specific ARARs for VOC-Contamlnated Soil
TIAA Site Record of Decision
Source
Standard,
Requirement, Criteria,
or Limitation
Applicable or Relevant
and Appropriate
Description of Standard,
Requirement, Criteria, or Limitation
Manner in Which ARAR Applies to
Alternative
Clean Water Act §402,
33 U.S.C. §1342; 40
CFR Part 122
Federal RCRA, Subtitle
C. 42 U.S.C. §6921 si
Sfiju (RCRA Subtitle C);
Arizona Revised
Statutes (ARS) §49-921
et seq.
RCRA Subtitle C; ARS
§49-921 et seq.
SWPCB Order No. 92-
08-DWQ, NPDES
General Permit No.
CAS000002 (Waste
Discharge requirements
for Discharges of Storm
Water Associated with
Construction Activity)
40 CFR Part 261 and
R18-8-261
Applicable to construction
activities affecting more
than 5 acres; relevant
and appropriate to such
activities affecting less
than 5 acres
Applicable
40 CFR Part 264,
Subpart X and R18-8-
264
Relevant and Appropriate
Establishes criteria for identifying
hazardous waste subject to Subtitle C
treatment, storage and disposal
requirements.
Establishes narrative criteria for
regulating miscellaneous treatment
units.
RCRA Subtitle C; ARS 40 CFR Part 264, Relevant and Appropriate Regulates emissions from process
§49-921 el seq. Subpart AA and BB and vents associated with solvent
R18-8-264 extraction.
Clean Air Act, 42 U.S.C. 40 CFR Part 61
§§7401-7671 q
Applicable
Controls air emissions of VOCs and
gaseous contaminants.
RCRA Subtitle C; ARS
§49-921 et seq.
40 CFR Part 264,
Subpart I and R18-8-
264.170s! Sag.
Relevant and Appropriate Establishes requirements for
containers holding RCRA hazardous
waste for treatment, storage or
disposal including condition,
management, and inspection of
containers, container compatibility with
The substantive portions of the general
permit are action-specific ARARs for
construction of the SVE system.
Requires determination as to whether
treatment residuals (e.g. spent carbon
from the SVE system) or drilling wastes
are classified as hazardous waste.
Location, design, construction, operation,
maintenance and closure of the SVE
system, including any on-site disposal,
must comply with the substantive portions
of the narrative criteria.
Emissions from the SVE treatment
system must comply with these Subparts.
Requires reduction of VOC emissions
from product accumulator vessels. Also,
requires leak detection and repair
programs.
Containers storing treatment system
waste (Including RCRA wastewater from
the SVE air/water separator and GAC
carbon) must comply with substantive
provisions.
SAC/110831/014.00C
30M
-------
Table 9e
Action-Specific ARARs for VOC-Contamlnated Soil
TIAA Site Record of Decision
Source
Standard,
Requirement, Criteria,
or Limitation
Applicable or Relevant
and Appropriate
Description of Standard,
Requirement, Criteria, or Limitation
Manner In Which ARAR Applies to
Alternative
RCRA Subtitle C; ARS
§49-921 et seq,
RCRA Subtitle C; ARS
§49-921 et seq.
RCRA Subtitle C; ARS
§49-921 et seq.
Clean Air Act. 42 U.S.C.
§§7401 fit fifig.
40 CFR Part 264.
Subpart J and R18-8-
264.190 fit Sfifl.
Relevant and Appropriate
40 CFR Part 264,
Subpart O and R18-8-
264
40 CFR Part 268,
Subpart E and R18-8-
268 et seq.
Pima County Bureau of
Air Pollution Control
Rules and Regulations,
Title 17 Pima County
Air Quality Code,
17.16.430,
Subparagraph F
Applicable or Relevant
and Appropriate,
depending on the waste
analysis
Applicable or Relevant
and Appropriate
Applicable
wastes, and design and operation of
container storage areas.
Establishes requirements for tank
systems used to store or treat
hazardous waste; design and
installation, containment and detection
of releases; operating requirements;
inspections; responses to teaks or
spills; and closure and post-closure.
Establishes waste analysis
requirements, performance standards,
operating requirements, monitoring and
inspection requirements and closure
requirements.
Storage of land-banned waste must
comply with these requirements.
Storage of more than one year requires
demonstration that such storage is
solely for the purpose of accumulation
to allow for proper recovery, treatment
and disposal.
Requires reasonably available control
equipment from a stationary source
that emits VOCs.
Tanks used for treatment or storage must
comply with substantive provisions.
An ARAR if the SVE system employs
catalytic oxidation or thermal oxidation to
treat off-gas.
SAC/1 114.00C,
4 Of 4
-------
Table 10a
Chemical-Specific ARARs for PCB-Contatnlnated Soils and Sludges
T1AA Site Record of Decision
Source
Standard,
Requirement, Criteria,
or Limitation
Applicable or Relevant
and Appropriate
Description of Standard,
Requirement, Criteria, or Limitation
Manner In Which ARAR Applies to
Alternative
Arizona Interim Soil
Remediation Standards
AAC R18-7-201 et seq. Applicable
Establishes numerical standards for
residential and non-residential use
based on exposure risks.
Toxic Substances
Control Act, 15 U.S.C.
2601 et seq.
40 CFR Parts 702-775 Applicable
Disposal of PCB waste in excess of 50
mg/kg must comply with TSCA
requirements
PCB contaminated soils and sludges
with concentrations above 0.18 mg/kg
in residential areas and above 0.76
mg/kg in non-residential areas will
excavated for off-site disposal.
Any other hazardous substances that
may be Identified also will be subject to
the HBGL ARARs.
PCB concentrations must be
established to determine whether the
soils must be sent to an approved
TSCA facility. This is both a chemical-
specific and an action-specific ARAR.
SAC/110831/005.00C
10F3
-------
Table lOb
Location-Specific ARARs for PCB-Contamlnated Soils and Sludges
TIAA Site Record of Decision
Source
Standard,
Requirement, Criteria,
or Limitation
Applicable or Relevant
and Appropriate
Description of Standard,
Requirement, Criteria, or Limitation
Manner In Which ARAR Applies to
Alternative
Federal Aviation
Administration Rules
National Historic
Preservation Act,
Section 106,16 U.S.C.
§§470 £1 sag.
Archaeological
Discoveries, Historic
Preservation
AC/70/7460-1 F
36 CFR Parts 65 and
600
41 ARS§§841-847,
865
Applicable
Relevant and
Appropriate, until
designated
Applicable
Establishes marking and lighting
requirements for construction
equipment or permanent structures near
airports.
Preserves historic properties, by
requiring that action be planned to
minimize harm to National Historic
Landmarks.
Preserves archaeological artifacts and
remains.
Applies to construction equipment.
The Three Hangars have been
proposed for designation on the
Register of Historic Places. Any SVE
activities near the Three Hangars would
be managed to minimize harm to the
buildings.
If any archaeological artifacts, human
remains, or funerary objects are
discovered during construction,
excavation or similar activities, such
activity must cease temporarily to allow
for investigation and preservation of
such artifacts, remains, or objects in
accordance with the procedures set
forth in this ARAR.
SAC/1 UN
..DOC
-------
Table 10c
Action-Specific ARARs for PCB-Contamlnated Soils and Sludges
TIAA Site Record of Decision
Source Standard,
Requirement, Criteria,
or Limitation
Applicable or Relevant
and Appropriate
Description of Standard, Requirement, Criteria,
or Limitation
Manner in Which ARAR
Applies to Alternative
Clean Water Act
§402. 33 U.S.C.
§1342, 40 CFR Part
122
SWPCB Order No. 92-
08-DWQ, NPDES
General Permit No.
CAS000002 (Waste
Discharge requirements
lor Discharges of Storm
Water Associated with
Construction Activity
RCRA Subtitle C; 40 CFR Part 261 and
ARS §49-921 filSfiJL R18-8-261
RCRA Subtitle C; 40 CFR Part 264.
ARS §49-921 etseq. Subpart I and R18-8-
264.170 fil sfifl.
RCRA Subtitle C; 40 CFR Part 264.
ARS §49-921 fiLSfiJU Subpart X and R18-8-
264
RCRA Subtitle C; 40 CFR Part 264,
ARS §49-921 fiLsfiO. Subpart J and R18-8-
264.190 fii Sfig.
Applicable to construction
activities affecting more
than 5 acres; relevant and
appropriate to such
activities affecting less
than 5 acres
Applicable
Relevant and Appropriate
Relevant and Appropriate
Relevant and Appropriate
RCRA Subtitle C; 40 CFR Part 264, Relevant and Appropriate
ARS §49-921 et seq. Subpart CC and R18-8-
264 fii Sfig.
Section 402(p) of the Clean Water Act establishes
a framework for regulating industrial stormwater
discharges under the NPDES program.
Discharges of stormwater associated with
construction activity from soil disturbance of more
than five acres must be regulated as industrial
activity.
Establishes criteria for identifying hazardous waste
subject to Subtitle C treatment, storage and
disposal requirements. Applicable for determining
whether excavated soils are to be classified as
hazardous waste.
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.
Establishes narrative criteria for regulating
miscellaneous treatment units.
Establishes requirements for tank systems used to
store or treat hazardous waste; design and
installation, containment and detection of releases;
operating requirements; inspections; responses to
leaks or spills; and closure and post-closure.
Establishes air emission standards for tanks and
containers.
The substantive portions of the
general permit are action-
specific ARARs for any
construction activities.
Action-specific ARAR for all site
activities that involve excavation
of hazardous media (e.g. soils
and sludges) or other handling of
hazardous waste.
Relevant and appropriate to
containers storing treatment
system waste such as soils and
sludges or treated waste.
Relevant and appropriate if
remedy employs on-site
treatment.
Relevant and appropriate if
remedy employs on-site
treatment.
Relevant and appropriate if
remedy employs on-site
treatment.
SAC/110831 AXJ5.DOC
30f3
-------
Table 11 a
Location-Specific ARARs for TAA Landfill Closure
TIAA Site Record of Decision
Source
Standard,
Requirement, Criteria,
or Limitation
Applicable or Relevant
and Appropriate
Description of Standard,
Requirement, Criteria, or Limitation
Manner In Which ARAR Applies to
Alternative
RCRA Subtitle 0
Federal Aviation
Administration Rules
Archaeological
Discoveries, Historic
Preservation
40CFR§258.10
AC/70/7460-1 F
41 ARS §§ 841-847,
865
Relevant and Appropriate
Applicable
Applicable
Establishes safety requirements for
landfills near airports.
Establishes marking and lighting
requirements for construction
equipment or permanent structures near
airports.
Preserves archaeological artifacts and
remains.
Construction equipment must comply.
If any archaeological artifacts, human
remains, or funerary objects are
discovered during construction,
excavation or similar activities, such
activity must cease temporarily to allow
for investigation! and preservation of
such artifacts, remains, or objects in
accordance with the procedures set
forth in this ARAR.
for*
-------
Table 11 b
Action-Specific ARARs for TAA Landfill Closure
TIAA Site Record of Decision
Source
Standard,
Requirement, Criteria,
or Limitation
Applicable or Relevant
and Appropriate
Description of Standard,
Requirement, Criteria, or Limitation
Manner In Which ARAR Applies to
Alternative
RCRA Subtitle D
RCRA Subtitle D
40 CFR Part 258 as
implemented by ARS
Title 49, Chapter 4
40 CFR Part 257
Applicable or Relevant
and Appropriate
Applicable
Establishes minimum operating criteria
for landfills that receive waste after
1996 and procedures for closure of
open dumps.
Establishes criteria for determining
whether a solid waste disposal facility
poses a threat to human health and the
environment.
SAC/110831/006.00C
20F2
-------
Table 12a
Chemical-Specific ARARs for VOC-Contamlnated Shallow Groundwater
TIAA Site Record of Decision
Source
Standard,
Requirement, Criteria,
or Limitation
Applicable or Relevant
and Appropriate
Description of Standard,
Requirement, Criteria, or Limitation
Manner In Which ARAR Applies to
Alternative
Federal Safe Drinking
Water Act. 42 U.S.C.
Sec. 300f et seq.
40 CFR Part 141
(Subparts B. C, G),
Federal Primary
Drinking Water
Standards-MCLs
Relevant and Appropriate
Arizona Clean Water
Act
Arizona Aquifer Water
Quality Standards, R18-
11-405, R18-11-406
Applicable
MCLs were established as health-based
drinking water standards to protect
public health from contamination that
may be found in drinking water from
public water systems. Although not
directly applicable to groundwater
remediation activities, the NCP, 40 CFR
§300.430(e)(2). provides that remedial
actions generally must attain MCLs and
non-zero MCLGs where groundwater is
a source or potential source of drinking
water.
Sets chemical-specific narrative and
groundwater standards.
Forms one of the bases for the
development of chemical-specific
Shallow Groundwater Zone cleanup
levels. The Shallow Groundwater Zone
cleanup levels are based on the federal
MCLs. as set forth in Table 6.
Narrative standard prohibits discharges
to groundwater that would cause a
pollutant to be present in an aquifer
classified for drinking water. The
numeric standards are not more
stringent than the federal or the state
MCLs and do not set in situ standards
but are ARARs with respect to any
discharges.
SAC/1 Id
7.DOC*
-------
Table 12b
Location-Specific ARARa for VOC-Contamlnated Shallow Groundwater
TIAA Site Record of Decision
Source
Standard,
Requirement, Criteria,
or Limitation
Applicable or Relevant
and Appropriate
Description of Standard,
Requirement, Criteria, or Limitation
Manner in Which ARAR Applies to
Alternative
Federal Aviation
Administration Rules
Federal Aviation
Administration Rules
Federal Aviation
Administration Rules
National Historic
Preservation Act.
Section 106. 16U.S.C.
§§470glsefl.
Archaeological
Discoveries. Historic
Preservation
AC 150/5300-13
AC150/5370-2C
AC/70/7460-1 F
36 CFR Parts 65 and
800
Applicable
Applicable
Applicable
Relevant and Appropriate
until designated
Restricts structure heights near airports Applies to construction of air strippers.
41 A.R.S. §§ 841-847,
865
Applicable
Restricts emissions that may cause a
navigational hazard near airports
Establishes marking and lighting
requirements for construction
equipment or permanent structures near
airports.
Preserves historic properties, by
requiring that action be planned to
minimize harm to National Historic
Landmarks.
Preserves archaeological artifacts and
remains.
Applicable to emissions from operation
of air strippers, thermal desorption,
excavation and construction or any
other types of emissions.
Applies to air stripper construction
equipment and air strippers.
The Three Hangars have been
proposed for designation on the
Register of Historic Places. Any SVE
activities near the Three Hangers would
be managed to minimize harm to the
buildings.
If any archaeological artifacts, human
remains, or funerary objects are
discovered during construction,
excavation or similar activities, such
activity must cease temporarily to allow
for investigation and preservation of
such artifacts, remains, or objects in
accordance with the procedures set
forth in this ARAR.
SAC/110831/007.DOC
20F5
-------
Table 12c
Action-Specific ARARs for VOC-Contamlnated Shallow Groundwater
TIAA Site Record of Decision
Source Standard, Requirement,
Criteria, or Limitation
Applicable or Relevant
and Appropriate
Description of Standard, Requirement,
Criteria, or Limitation
Manner in Which ARAR Applies
to Alternative
Arizona Remedial
Action Requirements
Arizona
Groundwater
Management Act,
ARS Title 45
Clean Water Act
§402. 33 U.S.C.
§1342; 40 CFR Part
122
RCRA Subtitle C;
ARS §49-921 et seo.
RCRA Subtitle C;
ARS §49-921
ARS 49-280
ARS 45-454.01
SWPCB Order No. 92-
08-DWQ, NPDES
General Permit No.
CAS000002 (Waste
Discharge requirements
for Discharges of Storm
Water Associated with
Construction Activity
40 CFR Part 261 and
R18-8-261
40 CFR Part 264,
Subpart X and R18-8-
264
Applicable
Applicable
Applicable to construction
activities affecting more
than 5 acres; relevant and
appropriate to such
activities affecting less
than 5 acres
Applicable
Relevant and Appropriate
Treatment of groundwater must be conducted in
a way to provide for the maximum beneficial use
of the waters of the state.
The regulation exempts new well construction,
withdrawal, treatment and injection wells at
CERCLA sites from obtaining Arizona
Department of Water Resources approval to
extract groundwater, subject to compliance with
certain substantive provisions.
Section 402(p) of the Clean Water Act
establishes a framework for regulating industrial
stormwater discharges under the NPDES
program. Discharges of stormwater associated
with construction activity from soil disturbance of
more than five acres must be regulated as
industrial activity.
Establishes criteria for identifying hazardous
waste subject to RCRA Subtitle C treatment,
storage and disposal requirements. Applicable
for determining whether excavated soils,
treatment residuals (e.g. spent carbon from
groundwater treatment or air stripper off-gas
systems), or drilling wastes are to be classified as
hazardous waste.
Establishes narrative criteria for regulating
miscellaneous treatment units (such as air
strippers).
The substantive portions of the
general permit are action-specific
ARARs for the construction
activities associated with any
construction of the groundwater
system.
Action-specific ARAR for all site
activities that involve excavation
of hazardous media (e.g. soils and
sludges) or other handling of
hazardous waste.
Location, design, construction,
operation, maintenance and
closure of air strippers, including
any on-site disposal, must comply
with the substantive portions of
the narrative criteria
SAC/1 f
r>7.DOCr
-------
Table 12c
Action-Specific ARARs for VOC-Contaminated Shallow Groundwater
TIAA Site Record of Decision
Source Standard, Requirement,
Criteria, or Limitation
Applicable or Relevant
and Appropriate
Description of Standard, Requirement,
Criteria, or Limitation
Manner in Which ARAR Applies
to Alternative
RCRA Subtitle C;
ARS §49-921 at sag.
Clean Air Act 42
U.S.C. §§7401-
7671q
RCRA Subtitle C;
ARS §49-921 et seq.
RCRA Subtitle C;
ARS §49-921 el seo.
RCRA Subtitle C;
ARS §49-921 etaeo.
RCRA Subtitle C;
ARS §49-921
Federal Clean Air
Act, 42 U.S.C.
§§7401.elSfifl.
40 CFR Part 264,
Subpari AA and BB and
R18-8-264
40 CFR Part 61
40 CFR Part 264,
Subpart I and R18-8-
264.170 ai sag.
40 CFR Part 264,
Subpart J and R18-8-
264.190 el Sfifl
40 CFR Part 264.
Subpart 0 and R18-8-
264
40 CFR Part 268 and
R18-8-268
Pima County Bureau of
Air Pollution Control
Rules and Regulations,
Relevant and Appropriate
Applicable
Relevant and Appropriate
Relevant and Appropriate
Applicable or Relevant
and Appropriate,
depending on the waste
analysis
Relevant and Appropriate
Applicable
Regulates emissions from process vents
associated with air strippers.
Controls air emissions of VOCs and gaseous
contaminants.
Establishes requirements for containers holding
RCRA hazardous waste for treatment, storage or
disposal Including condition, management, and
inspection ol containers, container compatibility
with wastes and design and operation of
container storage areas
Establishes requirements for tank systems used
to store or treat hazardous waste, including
design and installation, containment and
detection of releases, operating requirements,
inspections, responses to leaks or spills and
closure and post-closure.
Establishes waste analysis requirements,
performance standards, operating requirements,
monitoring and inspection requirements and
closure requirements.
Storage of land-banned waste must comply with
these requirements. Storage of more than one
year requires demonstration that such storage is
solely for the purpose of accumulation to allow for
proper recovery, treatment and disposal.
Requires reasonably available control equipment
from a stationary source that emits VOCs.
Emissions from air strippers must
comply with this Subpart.
Requires reduction of VOC
emissions from product
accumulator vessels. Also
requires leak detection and repair
programs.
Containers storing treatment
system waste (e.g. GAC carbons
or other RCRA waste) must
comply with substantive
provisions.
Tanks used for treatment or
storage must comply with
substantive provisions.
Applies to the air stripper off-gas
system if it employs catalytic
oxidation or thermal oxidation.
SAC/110831/007.DOC
40f5
-------
Table 12c
Action-Specific ARARs for VOC-Contamlnated Shallow Groundwater
TIAA Site Record of Decision
Source Standard, Requirement,
Criteria, or Limitation
Applicable or Relevant
and Appropriate
Description of Standard, Requirement,
Criteria, or Limitation
Manner In Which ARAR Applies
to Alternative
Safe Drinking Water
Act. 42 U.S.C. §300f
filSfifl.
Title 17 Pima County Air
Quality Code, 17.16.430,
Subparagraph F
40 CFR 144.24,146
Applicable
OSWER Directive
9355.0-28 Emissions
From Air Strippers
EPA Office of Solid
Waste, RCRA
Groundwater Monitoring:
Draft Technical
Guidance, Nov., 1992
(EPA/530-R93-001)
Performance Standard
Performance Standard
Establishes criteria for determining exempt
aquifers, including current and future use, yield
and water quality.
Limits discharges of VOCs from air strippers to 15
Ibs/day per site.
Sets forth requirements for the development and
implementation of a ground-water monitoring
program.
Applies to design, construction,
operation and maintenance of
injection wells, if selected to return
treated groundwater to the
aquifer.
Applies to the development of a
comprehensive groundwater
monitoring program for the site.
SAC/1
.ooc
1*5
-------
Table 13
Groundwater Cleanup ARARs to be Waived in the Tl Zone
TIAA Site Record of Decision
Law or Regulation
Reference
Comments
FEDERAL
Safe Drinking Water Act
National MCLGs
STATE OF ARIZONA
40 CFR 141,143, Subpart F
Pub. L99-339, 100 Stat. 642
(1986)
Arizona Numeric Aquifer Water R18-11*406
Quality Standards
Interim Soil Remediation Standards R18-7-203, 204, and 205
Regulates drinking water supplies
using MCLs
Rules establishing groundwater
quality standards
Guidelines for soil-gas and
groundwater cleanup levels
Notes:
MCL = Maximum Contaminant Level
MCLG = Maximum Contaminant Level Goal.
NA = not applicable.
SAC/110831/008.00C
-------
FIGURES
-------
_ West Cap
Tucson I
San Xavier
Indian
Reservation
Approximate Scale
(In miles)
_____ Suggested Superfund Site Boundaries
for purposes of real estate disclosure
Approximate areas of
groundwater concentrations
'// of 5 ppb TCE or greater*
Indicates identified area ol contamination prior to the start of cleanup; ongoing cleanup programs have markedly
reduced the area of contamination.
Figure 1
Tucson International Airport Area Superfund Site
TIAA Site Record of Decision
110831.06.05 Figure 1 09-04-97ato
-------
BURR-
*f|| BROWN
PROPERTY
FORMER
WEST-CAP
PROPERTY
THREE
HANGARS
COMP
Los Reales Rd
TUCSON
INTERNATIONAL
AIRPORT
Aero Park Blvd.
LEGEND
AIR FORCE PLWfT 44
Figure 2
Three Properties Addressed By This ROD
TIAA Site Record of Decision
110631.06.05 Figure 8-VOC Contaminated Soil 09-2S-97ato
-------
FUTURE GENERAL
AVIATION AREA
Explanation
[-] Airport Boundary
IB^SJ Wash
BRI/FS Study Area
and Zone Boundaries
Figure 3
Airport Property Investigation Zones
TIAA Site Record of Decision
»10831.06.05 Figures 09-O4-97ato
-------
©
AW-1
©
AW-2
MEDINA RD.
(.
BB-1
©
Be
A
fib*
N
BUILDING 2
i
o
(
B£
h
IFETERl*
]
J-2
©
n
u
D
I r
rj
u
n-
\
s*
~
-1
-^
\
cat
BUILDING 1
-S^ESSSfJWs
RTYARD
BUILDING 2
ID
?
j-4.
w
MR STRIPPER
ARE*
BUILDING 4
ARAQON HO.
©
BB-3
ap ig
SCALE
EXPLANATION
I SO*. KMM09 B-l WO B-I.
«r OCON (iwi) (UOCUXIM «momiut>
soma aoRMB B-J MO 8-4 (IMS)
BB-3
0
Source:
i/V
Figure 4
Burr-Brown Corporation Property
TIAA Site RecorctfiLPecision
110631.06.05
f '
-------
1
I
K
1 (*
UJ1
>l
DC'
UJl
2-
31
|
1
1
1
1
1
1
i
1
1
1
1
i
t:
,.
WASH
4
p.*''. .
_c 1
f
Q.t
BUXS A
lotf"
*...
^
! V^
i
i
i r
BLDG A . ..VACANT
»*V. \~
k~° ..- * MfbinJl
**>, i I ...
«* .-* o-U. ~\*
j BLOGB
4?'* 1 *
.1
*..
ELVIRA
LEGEND
^
i
1
1
ARAGON ROAD !
v. *. \
1
II
1
N
i
w
SCALE: APPROX r-100'
1 X 4i l'°
-ip
4 4"
* "* '
...
jll
4-"""
BUX5C
i
J L '
i
BLDG £
1 j
A'
BLDG O
0,
5!
i?,'
03 1
z1
O]
O'
1- '
'
1
1
1
1
1
1
)
i
1
V '
-- 0 CHAIN LINK FENCE
BLDG 8 . ..WESTERN AIR PRODUCTS
BLDG C . ..AIRCRAFT PAR
BLDG D . ..AIRPORT BUS/A
J/Ss'pLAZA* B8~3 * EXISTING GROUNDWATER MONITOR WELL
BLDG E . ..SANTA FE LASER G-7* SOIL GAS SAMPLE LOCATION
ffil . ..FLOOR DRAIN
o . ..TRANSFORMER
P-i4" PCB5 SAMPLf
LOCATION
M-4+ METALS SAMPLE LOCATION FigUFS 5
Former West-Cap Property
T1AA Site Record of Decision
110631.06.05 Figures 09-04-«7ito
-------
* tttt
-
Ifeptr Rsgfensl Ao«tr 5-
Vsrlfei E^.
rjj
GUIS
El. I
Wei land pock
Well screen
woitr level upper
fhdlow .jfoundtralei
CfO-undvolcf levef
rcqioool oquiltM
CA - ColklM
CW - W.I yoata yavel. 9iov»l/tond
mi* lure*. Wit or no lints
CP - Pootly o/adtd o/owlt. qrov«l/*ond
mtvtufts. Kttl or no lirMS
CM - SUtr grov»ri.
aroval/iand/fill tnivtijres
SW - Wrt voOtd londl.
ondt, bllto or no fn«s
«>OM«y
SP ' Pooily aradod sondl. o/avgHy
sands, lillle or no fines
SU - Silly sands, sand/sill mi.luei
SC - Claycir sands. »ond/clor miiluxs
UH - inarqonic sills, micacoous or
dialomoccou* <*< sand or sily soils
ML - InofoanK: sills and very Imo sonds.
rock Ikxir. siD or ctoy«» '» londi, o>
cloy*y HI m»> skaM pbslicily
CL - Inoraaruc ((an. griMly.
sandy. t*>
CH - Inoroanic clays ol r»oh ptoslicily
Figure 6
Geologic Cross Section of the Zone E Three Hangars Area
T1AA Site Record of Decision
110631.08.06
5 09-0*97lto
-------
CO960U9 Hun
into building
Release points
Infiltration and
recharge
Caseous-phase
diffusion/ad vection
Vodose zone
kJ transport
Aqueous-phase
diffusron/odvectton
Explanation
Silly orovels. grovel-
sand-silt mintures
ll ' I1 PA CaBche: CoC03-cement«d
I I I I »ond, grove}, silt and day
Not to
Ground-water
diffusion/advection
SM Silly and gravelly sands
Inorgonic cloys of low to
medium plosticity. gravelly
cloys, sandy cloys, silly cloys.
lean days
graded gravel-sand
mixtures. flUe or no fines
ShoBow water-bearing, zone potentiometric tvrfoce
Upper regional aquifer polenliometric surface
Figure 7
Conceptual Model for Zone E
TIAA Site Record of Decision
U083t.OB.05 Figure? 0*09-9?ito
-------
ARIZONA AIR
NATIONAL
GUARD
./I THREE
* HANGARS
Los Reales Rd
TUCSON
INTERNATIONAL
AIRPORT
LEGEND
VOC Soil Remedy
Required Subsites
VOC Soils
Plug-In Subsites
Airport Property
Boundary
AIR FORCE PLANT 44
KEY
a = Zone E: North and East Sides of Hangar 1
b Zone E: Hangar 1
c > Zone E: Building 18
d o Zone E: Buildings 16/17
e = Zone E: South Portion of Hangar 2
I -Zone E: Buildings 14/15
g Zone E: Building 25 and adjacent soils to »» north
(southern portion of Building 24)
h = Zone E: Soils beneath West Lease USTs
1 = Zone F: North Portion of Samsonite Building
D-167
2 - Zone F: East Side ol Hamilton Buildings D-252,
D-267, and D-275
3 = Zone E: Former Building 32
4 = Zone E: West End of Runway 3
5 = Zone D: South Ramp and Drains
6 = Zone D: TAA Landfill
7 = Zone D: Fire Drill Area D-3
6 = Zone D: C-294 Burn Pit
9 = Zone C: Hughes Credit Union Dump
10 = Former West-Cap Property: Building A
11 = Former West-Cap Property: Building B
Figure 8
VOC-Contaminated Soil Subsites
TIAA Site Record of Decision
110631.06.05 Figure 8-VOC Contaminated Soil 09-25-97ato
-------
Valencia Rd
ARIZONA AIR
NATIONAL
GUARD
FORMER
WEST-CAP
PROPERTY
THREE
HANGARS
COMPLEX
TUCSON
INTERNATIONAL
AIRPORT
Aero Park Blvd.
LEGEND
TAA Landfill Closure
PCB-Contaminated
Soils
AIR FORCE PLANT 44
PCB-Contaminated
Sludges
PCB Soils &
Sludges Already
Cleaned Up
Airport Property
Boundary
KEY
V = Zone E: Hangar 1
W = Zone E: Soil adjacent to and Sludges in ttie Canate System
X = Zone E: Structure 30
Y = Zone E: Drainages and Ponding Areas
Z = Zone E: Structure 21
Figure 9
PCB-Contaminated Soil and
Sludges Subsites and the TAA Landfill
TIAA Site Record of Decision
110831.O6.OS Figure 9-PCB Contaminated Soil 09-25-97ato
-------
S-2
QQ t ii nn ii
SF-16WR-74
Explanations
Shallow groundwater
zone monitor well
Upper regional aquifer
monitor well
Groundwater elevation contour (fmsl)
Figure 10
Water Elevation Contours Shallow Groundwater Zone - May 1996
TIAA Site Record of Decision
1tOB31.Oa.OS R^M.0 0»O4-97lb
-------
Valencia Rd
BURR-
BROWN
PROPERTY
ARIZONA AIR
NATIONAL
GUARD
APPROXIMATE
LIMITS OF VOC
PLUME
(BASHED WHERE
UNCERTAIN)
FORMER
WEST-CAP
PROPERTY
APPROXIMATE
WESTERN
EXTENT OF
SHALLOW
GROUNDWATER
ZONE
nc Poaloc Rrl
APPROXIMATE
LIMITS OF VOC
PLUME
(DASHED WHERE
UNCERTAIN)
TUCSON
INTERNATIONAL
AIRPORT
Aero Park Bhvd
LEGEND
; * -. Approximate Limits
'££ of VOC Plume
AIR FORCE PLANT 44
Approximate Limits
of Area 1
-» Airport Property
Boundary
Figure 11
Tl Zone and VOC Contamination
in the Shallow Groundwater Zone
TIAA Site Record of Decision
110831.06.OS Figure 11-Tl Zones 09-25-97ato
-------
UMIT OF
ARIZONA
COMPLIANT CAPtJ
S
o>
if
10-SC5
200 ft
I Soil gas sample number
I Hydro Geo Chem result (u g/L)
* Laboratory confirmation result (ug/L)
PETREX sampler location and number
(DBS&A. 1995x)
Shallow soil gas sample
location and depth
Multi-port soil gas/ground-water
monitor well number and location
NCD - No compounds detected above
soil gas screening level
SOURCE: DANIEL. 8. STEPHENS A ASSOCIATES
Figure 121
Approximate Limit of theTAA Landfill Cap
TIAA Site Record of Decision
110631.06.05 Figure 12 09-O4-97ato
-------
SFUND RECORDS CTR
0229-01527
RECORD OF DECISION
TUCSON INTERNATIONAL AIRPORT AREA
SUPERFUND SITE
TUCSON, ARIZONA
AIRPORT PROPERTY -
SOILS AND SHALLOW GROUNDWATER ZONE
BURR-BROWN PROPERTY - SOILS
FORMER WEST-CAP PROPERTY - SOILS
Volume 2
September 1997
vxEPA
United States Environmental Protection Agency
Region 9 - San Francisco, California
-------
Contents
VOLUME 2
Section Page
Part II Responsiveness Summary
Responses to Written Comments 1
Responses to Comments from the Arizona Department of Environmental Quality... 1
Responses to Comments from FRx Company 3
Responses to Comments from Community Resident 3
Responses to Comments from Hughes Missile Systems Company 4
Responses to Comments from the City of Tucson Department of Transportation 8
Responses to Comments from the Unified Community Advisory Board 8
Appendix ATranscript of Proceedings, July 22,1997 Public Meeting
Appendix BTranscript of Proceedings, July 23,1997 Public Meeting
Tables
Table 1 Arizona Department of Environmental Quality Applicable or Relevant and
Appropriate Requirements (ARARs) Comments
TIAA SITE RECORD OF DECISION PAGEII-I
CONTENTS VOLUME 2
-------
Contents
List of Acronyms and Abbreviations
ADEQ Arizona Department of Environmental Quality
ARAR Applicable or Relevant and Appropriate Requirement
ARS Arizona Revised Statutes
CERCLA Comprehensive Environmental Response Compensation and Liability Act
DNAPL Dense Non-Aqueous Phase Liquid
EPA United States Environmental Protection Agency
GWTP Groundwater Treatment Plant
HBGL Health-Based Guidance Level
NPDES National Pollutant Discharge Elimination System
NPL National Priorities List
RI Remedial Investigation
RI/FS Remedial Investigation/Feasibility Study
ROD Record of Decision
SGZ Shallow Groundwater Zone
SVE Soil Vapor Extraction
TAA Tucson Airport Authority
TARP Tucson Airport Remediation Project
TBC To Be Considered
TCE Trichloroethylene
TI Technical Impracticability
TIAA Tucson International Airport Area
UC AB Unified Community Advisory Board
USAF United States Air Force
VOC Volatile Organic Compound
PAGE ll-n
SACA11083IVOI5
TIAA SITE RECORD OF DECISION
CONTENTS-VOLUME 2
-------
Part II
Responsiveness Summary
This section presents the United States Environmental Protection Agency's (EPA's)
responses to the written and oral comments received at the public meeting and during the
public comment period. Comments were received from six parties. This part of the Record
of Decision (ROD) is divided into responses for each of the individuals or entities that
provided written comments. Comments are expressed in italics; EPA's responses in plain
text.
All of the oral questions and comments were responded to directly at the public meetings.
These comments or questions and the associated responses are included in the transcripts to
the two public meetings, attached as Appendixes A (Faith Assembly of God Church Public
Meeting) and B (El Pueblo Center Public Meeting) to this Responsiveness Summary.
Responses to Written Comments
This section provides responses to written comments that EPA received during the public
comment period. Comments were received from the Arizona Department of
Environmental Quality (ADEQ); FRx Company; community resident; Hughes Missile
Systems Company; City of Tucson Department of Transportation; and the Unified
Community Advisory Board (UCAB) for the Tucson International Airport Area Superfund
Site.
Responses to Comments from Arizona Department of Environmental Quality
(ADEQ)
ADEQ Comment No. 1. The ROD discusses many "enhancement technologies" that will
presumably be considered and evaluated in some way during the remedial design phase. ADEQ
believes the final ROD should discuss the actual methods that will be used to conduct the evaluations
and how final decisions will be made regarding enhancement feasibility during remedial design. For
example, will pilot testing be performed?
EPA's Response. This ROD sets the framework and performance standards for
implementation of the remedy. EPA agrees that the details regarding evaluation of the
enhancement technologies and the subsequent decision process need to be addressed.
These issues will be addressed during negotiations and planning for the remedial
design/remedial action phase of this remedy.
ADEQ Comment No. 2. ADEQ believes the final ROD should specify that for the offsite shallow
groundwater remedy, the importance of the unit four gravel layer to transport contamination to the
offsite shallow groundwater zone and the regional aquifer will be evaluated. ADEQ understands
that recent groundwater quality data from offsite monitor well S-21b may indicate the gravel layer is
an important conduit for the transport ofVOCs. As currently written in section 10.4 of the draft
TlAA SITE RECORD OF DECISION PAGE 11-1
PART II RESPONSIVENESS SUMMARY SACM ios3i\oi6
-------
ROD, the necessity of an offsite shallow groundwater pilot study is acknowledged, but there is no
emphasis upon the gravel layer.
EPA's Response. Although the description of the Shallow Groundwater Zone remedy does
not specifically highlight the Unit 4 gravel layer, EPA agrees that this layer may warrant
special attention. As noted above in the response to Comment No. 1, this ROD does not
provide specific details on the work to be performed during remedy implementation or the
individual components of the remedy (such as screened intervals of Shallow Groundwater
Zone extraction wells). These details will be finalized during the remedial design process.
ADEQ's concerns regarding the Unit 4 gravel layer will be addressed during remedial
design negotiations and planning.
ADEQ Comment No. 3. EPA, ADEQ, and the participants in the remedial design/remedial action
negotiations will need to specifically discuss and agree during the remedial design phase the data to
be collected and the criteria to be used in order to determine whether it is technically feasible to
remediate the shallow groundwater.
EPA's Response. EPA agrees with this comment. The remedial design /remedial action
negotiations are the appropriate forum to conduct discussions and reach agreement on
these important topics.
ADEQ Comment No. 4. Page 76,5th full paragraph. The statement that Pima County is an
attainment area is not accurate. According to Joe Gibbs, Environmental Program Specialist in
ADEQ's Air Quality Planning Section, Pima County is a non-attainment area for carbon monoxide
but that status will be changed when EPA approves Pima County's latest air quality attainment
plan for carbon monoxide, which is to be filed in September 1997.
EPA's Response. Comment noted. The actions associated with this remedy will not
discharge carbon monoxide, therefore the referenced text in Volume I of this ROD was not
modified.
ADEQ Comment No. 5. Table Wa incorrectly lists the applicable or relevant and appropriate
requirements (ARARs)for soils as Health Based Guidance Levels (HBGLs). The ARAR should be
corrected to reference Arizona Administrative Code - Interim Soil Remediation Standards R18-7-201
et Seq. The interim rules list HBGLs for ingestion of soil as part of me cleanup standard. HBGLs for
ingestion of water are to used as a to be considered (TBC) when appropriate for water only.
EPA's Response. The wording in the ARARs text and tables in Volume 1 of this ROD has
been modified as appropriate in response to this comment.
ADEQ Comment No. 6. Section 11.3.1. ADEQ believes chemical specific ARARs exist for the
TAA Landfill. The Interim Soil Remediation Standards are ARARs for all soil wherever they are
found.
EPA's Response. The section referenced in the comment, Section 11.3.1, addresses landfill
closure only. There are no chemical-specific ARARs associated with closure of the landfill.
Potential subsurface soil contamination at the landfill will be addressed through the Plug-in
process (Section 11.1.1), which does have chemical-specific ARARs for soil remediation.
ADEQ Comment No. 7. Attached is a table to correct and add information to the ARARs tables
that were presented in the draft ROD.
PAGE 11-2 TIAA SITE RECORD OF DECISION
SACM io83i\oi6 PART II - RESPONSIVENESS SUMMARY
-------
EPA's Response. The table referenced in the comment is included at the end of these
written responses as Table 1. The ARARs presented on the table have been incorporated
into Tables 9 through 12 in Volume 1 of this ROD, as appropriate.
Responses to Comments from FRx Company
FRx Company Comment No. 1. We have reviewed the July 1997 announcement of the proposed
plan, and, in general, concur with the EPA's recommended preferred alternatives. In particular, we
agree that enhanced technologies may be required for effective application ofSVE in VOC-
contaminated soils on the airport property and remaining "plug-in" sites. However, the list of
enhancements eligible for consideration should include all competent technologies. In particular,
hydraulic fracturing, which is a slightly different process than the listed pneumatic fracturing, will
probably prove to be suitably effective.
Hydraulic fracturing as an enhancement to soil remediation processes was developed under the
auspices of the US EPA laboratory in Cincinnati. Hydraulic fracturing results in sand-filled
fractures that reliably will maintain flow capacity during the life of the project. A full description of
the process, as well as a comparable description of pneumatic fracturing, can be found in Handbook
of Alternative Methods for Delivery and Recovery. US EPA EPA/625/R-94A)03, September 1994.
The US EPA SITE program evaluated the use of hydraulic fractures in conjunction with SVE and
summarized its findings in "Hydraulic Fracturing Technology - Applications Analysis and
Technology Evaluation Report," US EPA Office of Research and Development, Cincinnati, OH,
EPA/540/R-93/505, September 1993. Hydraulic fractures are being used as an enhancement to a
dual phase extraction system at the Linemaster Superfund site in Connecticut. The EPA RPMfor
Linemaster is Elise Jakabhazy of Region I in Boston.
We strongly urge you to include hydraulic fracturing along with all viable fracturing methods as
enhancement technologies to SVE alternatives for VOC contaminated soil at TIAA. We as providers
of fracturing services will be following developments at the site.
EPA's Response. Based on subsurface and contaminant conditions, the enhancement
technologies listed in the Proposed Plan and, subsequently, in this ROD are considered the
most appropriate for the selected Soil Vapor Extraction (SVE) remedy at the ROD Site of the
Tucson International Airport Area (TIAA) Superfund Site. If the parties implementing the
remedy determine that a different technology may provide better results at a particular
subsite or subsites, they are free to make this recommendation to EPA. EPA will evaluate
such recommendations on a subsite-specific basis and modify this ROD as appropriate.
Responses to Comments from Community Resident
Comment No. 1. It is my personal opinion that the presentation that I attended on July 23 at El
Pueblo N.C. was quite comprehensive and appeared to touch all areas of great concern to this
Neighborhood. (Since most of us live right over the major T.C.E. Plume.) It is unfortunate for me
that due to another commitment, I could not stay for your entire presentation. We do feel that
attention to the T.C.E. and other VOCs in the shallow groundwater zone must be directed with
greater vigor. We might have redundancy at a later point in time and it may come back to haunt us
once again.
It is my personal opinion that EPA has provided oversight of an immense value to our community.
Please do not relax these efforts. (P.S. I was right about contamination under West-Cap.).
PAGE 11-3 TIAA Srre RECORD OF DECISION
SACM io83i\oi6 PART II - RESPONSIVENESS SUMMARY
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It is my intent to review over an over EPA's Proposed Plan issued in July 97 and if I have more
questions, I will hopefully direct them to you before the ROD becomes official.
EPA's Response. EPA appreciates the support. EPA intends to continue to closely oversee
all activities related to the ongoing cleanup of the TIAA Site and to ensure that the concerns
of the local community are appropriately addressed. EPA believes that the selected
remedial action for the Shallow Groundwater Zone will provide long-term protection of
human health and the environment.
Responses to Comments from Hughes Missile Systems Company
Hughes Comment No. 1. The most significant concern relates to the potential use of the AFP44
Groundwater Treatment Plant (GWTP) as one of the four options being considered for treatment
and disposal of the contaminated groundwater extracted from the Shallow Groundwater Zone (SGZ)
at the vicinity of the Three Hangars complex located on Tucson Airport Authority (TAA) property.
With the Technical Impracticability (TI) Zone in the midst of the SGZ, it appears that the EPA's
preferred remedy, Alternative D5 (Extraction, Treatment, Bioaugmentation, and Discharge), is in
practical terms a "forever pump and treat" system to provide the EPA-required hydraulic
containment to prevent contaminants from migrating both vertically and laterally out of the Tl
Zone.
Such a remedial approach could literally be required to operate for decades, hundreds of years, or
even longer. As EPA is well aware, it is AFP44's goal to complete the restoration program cleanup
activities at AFP44 within the next 5 to 7 years. That completion includes decommissioning of the
GWTP and other remedial systems at AFP44, and petitioning for final delisting and removal of the
AFP44 site from the National Priorities List (NPL) and the TIAA Superfund Site. For EPA to
consider the AFP44 GWTP as a viable option in the context of requiring it to operate significantly
longer to satisfy the remedy required at the TAA property SGZ/TI Zone is neither reasonable,
practical, nor economical.
The AFP44 GWTP is not the optimal design to effectively handle the potentially low flow rates, and
excessively high contaminant concentration levels expected at the TAA SGZ-Three Hangar complex,
especially for the indeterminate life span of a hydraulic containment scenario due to the suspected
presence ofDNAPL's. Additionally, the increased flow and high contaminant loading from the TAA
site would impose higher operation and maintenance costs which should not be borne by AFP44.
Furthermore, it does not appear that EPA has considered potential exposure and liability problems
associated with laying pipelines and running "extremely high concentrations" of the TAA's
contaminated water across AFP44 property. Also, EPA has not approached the Air Force as owner of
AFP44, nor Hughes as the operator with long-term lease hold interest in AFP44, about permission
or concerns if EPA were to carry out such activities affecting AFP44for such a long time into the
future as contemplated in the Proposed Plan.
EPA's Response. EPA believes that use of the existing treatment plant at United States Air
Force (USAF) Plant No. 44 is a feasible option for the remedy selected in this ROD. The
considerations listed in the comment are factors that will be considered during remedial
design. In particular, the implementability (including conveyance considerations) and cost
of each treatment option will be thoroughly evaluated prior to selection of the actual
treatment technology and location to be implemented. In addition, additional evaluations
completed during remedial design will help determine if the total volume and blended
quality of the water extracted from the Shallow Groundwater Zone (from both inside of and
PAGE n-4 TIAA SITE RECORD OF DECISION
SACM io83i\oi6 PART II - RESPONSIVENESS SUMMARY
-------
outside of the TI Zone) would be compatible with treatment at the USAF Plant No. 44
treatment facility. EPA does not anticipate that the blended influent concentrations will be
"excessively high" as is noted in the comment.
Further, the costs of treating the groundwater extracted from the Shallow Groundwater
Zone will be borne by the parties to the consent decree to be negotiated for this remedy and
not by the owners or operators of the USAF Plant No. 44 system. During the initial stages
of remedial design, discussions will be held with the USAF regarding the feasibility Of
using the Plant No. 44 treatment system for this remedy.
Hughes Comment No. 2. In the Proposed Plan, EPA identifies other treatment options which
could be constructed on-site at the Three Hangers. Such treatment systems could be appropriately
designed and sized to handle the lower flow rates containing more contaminant constituents with
significantly higher concentration levels expected at the TIAA SGZ. Life cycle cleanup costs should
be significantly lower, and performance effectiveness should be improved under this alternate
scenario. More importantly, from a long-term cleanup strategy perspective, such a system could have
more built-in flexibility for adding technologies that enhance system effectiveness. This on-site
system could be left in place and operated "forever" without adversely impacting other areas at the
Superfund site. It could also be more readily adaptable to the implementation of new technologies
that may result from the EPA's legal requirement to perform 5 year reviews wherever a selected
remedy leaves contaminants in place that have the potential for adverse impacts to human health or
the environment. Furthermore, and as addressed in the next comment, such a system would allow for
the inclusion of additional upper regional aquifer extraction wells in the vicinity of the Three
Hangars which should contribute to the more effective cleanup of the area.
EPA's Response. As noted in the response to Comment No. 1, during remedial design the
parties implementing this remedy will thoroughly evaluate the various treatment options
available for the extracted groundwater Long-term costs, implementability and flexibility
are all considerations that will be evaluated prior to selecting the treatment option to be
implemented.
Hughes Comment No. 3. Another viable option for EPA to consider and not mentioned in the
Proposed Plan, is utilization of the Tucson Airport Remediation Project (TARP) plant which appears
will be running for at least 20 to 30 or more years. An added benefit provided by tie-in to the TARP
is the opportunity for installation of additional regional aquifer wells in the immediate vicinity of the
Three Hangars which appear to be a primary source of historical releases to the regional aquifer,
beginning as early as the 1940's time frame and beyond, when regional aquifer water levels were
much higher than they are now. Removing contaminants closer to the source area is a more effective
strategy than the current TARP strategy which is based on an estimated 8 to 10 year migration time
frame for molecules of contaminants in the vicinity of Three Hanger area to actually reach the
southern-most set of wells in the TARP remediation wellfield. The added potential ability to
optimally place new upper regional aquifer wells in the vicinity of the Three Hangars should result
in a significant positive improvement to the length of time and effectiveness of cleanup required to
remediate the contamination from the Three Hangars complex. The wellfield pipeline could be
extended from the TARP southern wellfield along Airport Wash and then south along the east side of
the Nogales Highway past vacant land and the TIAA site to the Three Hangar area, thereby
obviating the issues of the pipeline route that EPA previously experienced on the TARP project.
PAGE 11-5 TIAA SITE RECORD OF DECISION
SACAI io83i\oi6 PART II - RESPONSIVENESS SUMMARY
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EPA's Response. This comment provides recommendations for modifying the Regional
Aquifer remedy to place additional extraction wells closer to the Three Hangars area.
Cleanup of this portion of the Regional Aquifer has already been addressed in a prior ROD
(the 1988 ROD). Potential modifications to that remedy are reviewed as part of EPA's five-
year review process. This ROD does not address or incorporate remediation of the Regional
Aquifer. Thus, it is not the appropriate place to discuss specific components-of the Regional
Aquifer remedy.
Use of the Tucson. Airport Remediation Project (TARP) treatment plant was not considered
feasible for this remedy because of the excessive costs and implementation difficulties
associated with conveying the extracted groundwater to the TARP plant.
Hughes Comment No. 4. The Proposed Plan states that "(t)he SGZ is not now a source of
drinking water, however, it is connected to the regional aquifer. ...EPA has concluded that it is
technically impracticable to restore a 2-acre portion of the SGZ near the Three Hangars Complex to
drinking water quality. This conclusion is based on the extremely high concentrations ofTCE
present and on hydrogeologic constraints in the area. This area is called the Technical
Impracticability (Tl) Zone. Within the Tl Zone, EPA would require hydraulic containment to
prevent contaminants from migrating both laterally and vertically out of the Tl Zone" The Proposed
Plan identifies the preferred remedy for the SGZ area as Alternative D5 (Extraction, Ex-Situ
Treatment, Bioaugmentation, and Discharge) with Electro-osmosis identified as an enhancement
technology. In addition "EPA has determined that it is not technically practical to restore the SGZ to
drinking water quality within the 2-acre Tl zone."
The following comments pertain to the above preferred remedy selected:
a. The Proposed Plan does not state that EPA is legally required to perform reviews every five
years to determine if a remedy, which leaves contaminants in place (i.e. the SGZ Tl Zone), is
still protective of human health and the environment.
b. Regarding the application of hydraulic containment for contaminants in the SGZ Tl Zone,
there should also be a requirement to contain or remove vapors. As desaturation gradually
occurs over time, the concern for potential uncontrolled vapor migration from DNAPL's
increases and the preferred remedy should have a component which addresses this potential.
c. It is not clear under what conditions enhancement technologies such as electro-osmosis or
bioaugmentation would be included in the remedy. In addition, it is unclear, as to why
potential enhancements such as Dual-Phase Extraction or Hi-Vac have been omitted from
the list of potential enhancements, in light of the high probability that as the SGZ is
desaturated, the potential effectiveness of such technologies will likely increase. In addition,
they are in harmony with the presumptive remedies already identified in the Proposed Plan.
EPA's Response to Comment 4a. The purpose of the Proposed Plan was to set forth EPA's
rationale for its preferred remedy. Comprehensive Environmental Response Compensation
and Liability Act (CERCLA) statutory requirements, including the five-year review, are
described in this ROD. Please see Section 13.6 in Volume 1 of this ROD for a description of
the five-year review requirement.
EPA's Response to Comment 4b. The selected remedy does address containment of vapors
in the Tl Zone. The VOC-Contaminated Soils in the Tl Zone portion of the remedy requires
PAGE 11-6 TIAA SITE RECORD OF DECISION
SACM io83i\oi6 PART II RESPONSIVENESS SUMMARY
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that an SVE system be installed to prevent migration of vapors from the TI Zone into
surrounding areas.
EPA's Response to Comment 4c. This ROD sets the framework and performance standards
for implementation of the remedy. The specific conditions that will warrant initiation of an
enhancement technology will be addressed during negotiations and planning for the
remedial design/remedial action phase of this remedy.
The two potential enhancements listed in the comment, Dual-Phase Extraction and Hi-Vac,
are included as potential enhancements for this remedy. They are both covered under the
"Multi-Phase Extraction" enhancement technology listed for the SVE remedies.
Hughes Comment No. 5. In general, it is not clear what general conditions or key decision factors
trigger the application of a Plug-in remedy at any given site, or the selection of any of the
enhancement remedies at the Preferred remedy sites on TAA property. The Proposed Plan specifies a
preferred remedy for each site area where investigation and analysis conducted to date clearly
warrant immediate action. Additionally, EPA has developed an innovative approach to the remedy
selection process by specifying Plug-in remedies for many areas of the TAA property that still
require further investigation and analysis. The approach to identify potential enhancements to the
basic preferred remedies is commendable in that it will allow for the expeditious implementation of
remedial improvements without the potential delays of a cumbersome administrative process.
However, the Proposed Plan does not include a decision matrix, nor specify the conditions or criteria
whereby Plug-in remedies or enhancements to Preferred remedies would require implementation.
The specific concern is that without such a roadmap to guide the decision-making process, it might be
possible that no additional, or minimal actions are taken, as opposed to appropriate actions necessary
for adequate protection of human health and the environment.
EPA's Response. As noted in the response to Comment No. 4C, the specific details
regarding implementation of enhancement technologies will be addressed during
negotiations and planning for the remedial design phase of this remedy. As for the Plug-in
process, this ROD (in Section 10.1 of Volume 1) contains much more detail on
implementation of the Plug-in approach than did the Proposed Plan, which provided only a
general summary of the process.
EPA will make the final decisions on whether or not a subsite "plugs in" to the SVE remedy
and whether implementation of enhancement technologies is warranted. Providing
appropriate protection of human health and the environment in a cost-effective manner will
continue to be EPA's primary consideration in making these decisions and implementing
this remedy.
Hughes Comment No. 6. The final concern is that sufficient characterization data be collected at
each VOC Plug-in site on TAA property to adequately evaluate each site with respect to the
magnitude of the potential sources, and the groundwater impacts. This data collection should be
completed prior to the initiation of remediation at any of the 10 VOC plug-in sites. In addition to
soil contaminant data collection, the investigation should include installation of one or more
groundwater monitor wells at each site, located in the shallow groundwater zone at each site, or
within the regional aquifer if shallow groundwater is not present.
As EPA conducts further investigation or monitoring for each of the 10 VOC Soils Plug-in sites,
each of the 8 VOC Soils Cleanup, and the VOC-contaminated SGZ/TI Zone where Preferred
PAGE 11-7 TIM SITE RECORD OF DECISION
SACM io83i\oi6 PART II - RESPONSIVENESS SUMMARY
-------
remedies and potential enhancements will be implemented, the sampling and investigation data
should be made available to the public for review in a timely manner to determine the adequacy of
investigation and review the appropriateness of further remedial action decisions.
EPA's Response. At each subsite, EPA will review subsite-specific characterization data to
ensure that sufficient data have been collected to make an appropriate decision regarding
"plugging in" an SVE remedy. The site characterization activities required at each Plug-in
subsite will be determined on a subsite-specific basis during the remedial design phase.
Remediation will not be started at any subsite until sufficient data have been collected to
complete the Plug-in process, including transport modeling, and make the final Plug-in
decision.
As EPA makes decisions regarding the need for SVE remedies at the Plug-in subsites, EPA
will inform the public of the decisions and the basis for those decisions. Further, prior to
construction, EPA will take appropriate action to inform the public of the actual
technologies (e.g., SVE and groundwater treatment technologies) selected for inclusion in
the remedy.
Responses to Comments from the City of Tucson, Department of Transportation
City of Tucson Comment No. 1. In addition to proposed cleanup alternatives for soil
contamination in the adjacent neighborhood, existing and future drainage considerations need to be
addressed to ensure the cessation of any potential contamination in surface runoff from the airport.
We offer the following recommendations to further the goal of eliminating future sources of possible
contamination to adjacent neighborhoods:
1. The Tucson International Airport work together with EPA, Union Pacific Railroad, Arizona
Department of Transportation and the City of Tucson to utilize retention/detention to eliminate
runoff exiting the Airport property along Nogales Highway.
2. Stormwater quality monitoring for constituents, previously and presently utilized at the Airport
be added as a condition of the Tucson International Airport NPDES Stormwater Discharge
Permit.
EPA's Response. EPA has been actively working with the City and the Tucson Airport
Authority, outside of the federal Superfund program, to solve concerns regarding the El
Vado drainage. However, EPA will consider periodic sampling for chemicals of concern in
surface water runoff in the Medina, El Vado, and San Xavier drainages as part of our
monitoring requirements under this ROD.
Regarding the second recommendation, the Proposed Plan and this ROD do not cover the
Tucson International Airport's National Pollutant Discharge Elimination System (NPDES)
Stormwater Discharge Permit. This NPDES permit is overseen by EPA outside of the
federal Superfund program.
Responses to Comments from the Unified Community Advisory Board (UCAB)
UCAB Comment No. 1. The major question concerning the shallow water aquifer is the
permanency of the contamination. Will the TCE remain in the aquifer indefinitely or will it slowly
seep into the aquifer below it? How often will the monitoring wells be tested? As it is now the
PAGE H-8 TlAA SITE RECORD OF DECISION
SACM io83i\oi6 PART II - RESPONSIVENESS SUMMARY
-------
monitoring wells are only being tested once in six months. This is totally unacceptable. It is our
opinion that these wells should be tested at least every month, if not more often
EPA's Response. The overall groundwater monitoring program associated with this
remedy, including the groundwater monitoring frequency, will be developed during
remedial design. EPA will select a monitoring frequency that is frequent enough to detect
any significant contaminant migration. Based on the relatively slow rate of groundwater
flow and associated contaminant migration (the contaminants migrate along with the
flowing groundwater) in the Shallow Groundwater Zone, it is likely that the monitoring
frequency will be quarterly (once every three months) for some wells and remain
semiannual (once in six months) for other wells. More frequent monitoring is not needed to
be able to detect future contaminant migration.
UCAB Comment No. 2 The area surrounding the TI Zone is to continue to be treated by the
pump-and-treat method until it is safe for drinking. Do we have any idea how long this will take?
Will there be enough monitoring wells to make sure that the contaminated area does not enlarge? We
know that monitoring wells will be placed downgradient, but will this be enough to make sure that
the area does not enlarge?....
EPA's Response. The cleanup time for the Shallow Groundwater Zone outside of the TI
Zone has not yet been estimated. However, given the subsurface conditions, it could take a
considerable time to complete the cleanup (many decades). Additional information that can
be used to better estimate likely cleanup times will be generated during the first few years
of operation of the remedy.
One of the goals for the Shallow Groundwater Zone remedy is to prevent migration of
contamination beyond the current extent of contamination and into the Regional Aquifer.
To monitor for compliance with this objective, EPA will require that sufficient number of
monitoring wells be installed to detect contaminant migration.
UCAB Comment No. 3. ...~As we understand this proposal, the TI Zone will remain indefinitely.
What assurance do the people living in the TCE contaminated area have that the US Government
will be financially responsible to monitor the contaminated zone and take care of any needed
treatment a hundred years from now? We understand that a formal review of any new processes that
may be used to reduce the TCE contamination in the TI Zone will be made every five years. In
addition, a review of the TI Zone will be formally addressed every five years.
EPA's Response. Following issuance of this ROD, EPA will enter into negotiations with
responsible parties to implement the remedy. These negotiations will result in a legally-
binding consent decree or order. This ROD, along with the legal agreement, provide a legal
foundation to ensure that the requirements of the remedy are carried out for as long as
necessary to remediate the contamination.
As part of the Superfund process, each site where contaminants remain is reviewed, at a
minimum, once every five years to ensure that the remedy continues to be protective of
human health and the environment and is operating as intended. For the remedy described
in this ROD, the five-year review process will also include a review of remedial
technologies to determine if any new technologies have been developed that could facilitate
remediation of the TI Zone.
PAGE 11-9 TIAA SITE RECORD OF DECISION
SACAI io83i\oi6 PART II - RESPONSIVENESS SUMMARY
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Table 1
Arizona Department of Environmental Quality Applicable or Relevant and Appropriate Requirements (ARARs) Comments
TIAA Site Record of Decision
Arizona Administrative Code
Archaeological Discoveries;
Historic Preservation
RCRA Subtitle C
Arizona Revised Statutes §49-921
et seq.
Subtitle C
Arizona Administrative Code
INTERIM SOIL REMEDIATION
STANDARDS
Table lOb use as above
Table lla
Arizona Administrative Code
INTERIM SOIL REMEDIATION
STANDARDS
AZ Remedial action
requirements
Title 45
R18-7-206
Arizona Revised
Statutes §41-841 thru
§41-847 and A.R.S.
§41-865
R18-8-261
Subpart X
R18-8-264
R18-7-201etseq.
R18-7-201etseq.
citation should be
ARS 49-280
ARS 45-454.01
REQUIREMENT: The laws
governing archaeological
discovery and preservation
shall be followed if artifacts
or human remains are
discovered.
Applicable
Artifacts, human remains and funerary objects have been
found in areas near the Site. If such items are discovered
during remedial activity at the site, such activity shall cease
in accordance with state law. Further, the permission,
investigative and other requirements of state law must be
met..
If waste contained in carbon from off-gas, cannot be stored
on site.
These chemical specific ARARs must apply to the landfill as
anywhere else that has soil that is contaminated.
31V0017
-------
^-K»K'smi^mfm«rimim^v-f^'
ix A
^Transcript of Proceedings
Public Meeting
.': : .-;/«, . -=;,-/. » ° . ..'. - '
Tu Superfund Site
:Proposed Plan --.. -.- "-
Faith Assembly of God Church
Tucson, Arizona
? ^ ^July22,1997
>£;&
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SAC/110831/COVERDOC
-------
ENVIRONMENTAL PROTECTION AGENCY
PUBLIC MEETING
Location: El Pueblo Center
101 West Irvington Road
Tucson, Arizona
July 23, 1997
Arizona Court Reporting
177 North Church, Suite 1111
Tucson, Arizona 85701
(520) 623-3375
BY: RONALD L. LUNSFORD, R.P.R.
-------
2
1 THE FOLLOWING is a verbatim record of the
2 Environmental Protection Agency public meeting held on
3 July 23, 1997, 6:30 p.m. at the El Pueblo Neighborhood
4 Center, 101 West Irvington Road, Tucson, Arizona.
5
6
7 MS. HERRERA: Good evening everybody. My
8 name is Angeles 'Herrera. I work for the Environmental
9 Protection Agency in San Francisco. I am the Community
10 Involvement Coordinator for this project. I want to
11 thank you all for attending this meeting tonight.
12 We are here tonight to present the EPA
13 proposed plan for addressing the contamination at the
14 airport property and two nearby properties which are
15 part of the Superfund Site. Even though there is other
16 properties which are also part of the Superfund Site,
17 tonight we are going to concentrate on the airport
18 property and two nearby properties which Craig will
19 explain later on.
20 I hope you all had a chance to pick up a copy
21 of our proposed plan of action in case you did not
22 receive one in the mail. We also have some sign-in
23 sheets that we're asking you to please sign for the
24 record and also for future mailings. We also have a
25 comment form for those of you who would rather provide
ARIZONA COURT REPORTING
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3
1 your comments in writing instead of verbal tonight.
2 You can give them to me at the end of the meeting or
3 you can send it to us before August 20th which is the
4 end of the public comment period.
5 You notice that we have a court reporter with
6 us tonight. He's here to record the whole entire
7 meeting, and then he's going to create a transcript of
8 the meeting which will become a part of the
9 administrative record for the site. He needs to hear
10 your name. If you're going to make a presentation, you
11 need to speak loud, and we're asking you to please
12 state your name and affiliation for the record.
13 We also have a video camera. The reason
14 we're videotaping the meeting is number one for those
15 people who want to be here and are not here tonight,
16 they could see the video tape at any time. They're
17 just going to have to the TCE Library to check the
18 videotape. And also for training purposes to in our
19 office we provide training for staff. We like to show
20 them how the public meetings go.
21 Is there anyone here I'm just going to ask
22 if anybody needs translation.
23 (Translation. Spanish talk.)
24 Now I'm going to introduce the rest of the
25 team which is a really small team. Most of you know
ARIZONA COURT REPORTING
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4
1 Craig Cooper. He is with EPA. He is the Remedial
2 Project Manager for the site. And we have also with us
3 our state partner, Craig Kafura.
4 Now I want to take a minute to run through
5 tonight's agenda. The times are actually changing
6 because we're starting a little early. Following the
7 introduction Craig is going to present to us EPA's
8 proposed plan. He's going to do that in three
9 different ways. He's going to talk about the Superfund
10 Process. Then he's going to give us a little site
11 background, and then he's going to go into the actual
12 proposed plan.
13 If anybody has any clarifying questions
14 during his presentation, just please raise your hand
15 and ask your question, and he will be glad to clarify
16 whatever you're presenting.
17 After the presentation we're going to have a
18 formal public comment period. At this time we're going
19 to be taking comments you make on the proposed plan.
20 We are not going to be addressing your comments
21 tonight. What we're going to do is we're going to take
22 them down, and then we're going to respond to them in
23 writing in a summary, in a responsiveness summary,
24 which becomes a part of the Record of Decision, and the
25 record will document what the cleanup is going to be
ARIZONA COURT REPORTING
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5
1 for the area that we're talking about tonight.
2 Are there any questions about the way we' re
3 going to run this meeting? If there aren't any, I
4 would like to turn it over to Craig. Thanks.
5 MR. COOPER: Again, my name is Craig Cooper,
6 and I work for EPA, and I'm the Superfund Project
7 Manager for the Superfund Site here on the south side.
8 I want to thank 'everyone for showing up tonight. I
9 have a lot of information to provide. I hope we can
10 keep it informal. Anytime during my presentation if
11 you want to ask any questions, please raise your hand
12 and I can answer clarifying questions, and then as
13 Angeles said, after my presentation there will be a
14 formal public comment period which everything will be
15 taken down.
16 Okay. First of all let me talk a little
17 about briefly about what EPA's role is and what is
18 Superfund. People hear this term Superfund. What does
19 that mean and what does it mean to you on the south
20 side. Well, the Superfund law was passed in 1980, and
21 it is a federal law. Congress and Washington passed
22 this law and said: EPA, you need to go out and find
23 all of the toxic waste dump sites that are posing a
24 significant risk to human health.
25 And so in the early '80's that's what we went
ARIZONA COURT REPORTING
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6
1 out and found. We only found 1,200 of them nationwide,
2 okay, and put them on a list. And the one here on the
3 south side, as you know, the TCE was discovered in the
4 aquifer and in drinking water wells here in the south
5 side in 1981, and EPA put this Superfund Site here on
6 the south side on the list in 1982, '83, it was final
7 on the list.
8 So EPA considers this one of our most
9 important Superfund Sites. And the Superfund Process
10 is about going out, finding contamination, identifying
11 what type of contaminations we have, is it TCE or is it
12 something else, studying what type of cleanup
13 technology will clean up that contamination, and then
14 making a recommendation to the public about the cleanup
15 strategy, then making a final decision about how to
16 proceed, and then going out and doing the cleanup.
17 So at other portions of this site, for
18 example, at Hughes and at the Air National Guard, it's
19 a very large Superfund Site. We actually have six
20 project areas where TCE has been poured on the ground
21 and caused contamination.
22 For example, at Hughes, which is also known
23 as Air Force Plant 44, they've actually already made it
24 through much of the Superfund Process. They've
25 identified the contamination. They've checked in with
ARIZONA COURT REPORTING
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7
1 the public about the cleanup strategy, and they're
2 actually in the cleanup process.
3 Well, for these three properties we're going
4 to talk about tonight, which are the airport property,
5 the Burr-Brown Corporation property, and the former
6 West-Cap property, and I'll explain exactly where those
7 properties are and their history in a minute.
8 We have just finished the last four years
9 we've been studying contamination at those properties,
10 and in the last year we've been studying what type of
11 cleanup technology should we use to clean the property,
1 2 and we put that information in a document called our
13 Proposed Plan.
14 , Let me go and get it real fast. So this is
15 it right here. There's more copies in the back. This
16 is our proposed plan.
17 So basically it's EPA's way to disclose to
18 the public what we've been doing over the last four
19 years, what did we find, and how do we plan what
20 parts of it poses significant public health risk, and
21 how do we plan on cleaning it up. That's what this
22 proposed plan is about.
23 I'm going to go over the contents of this
24 proposed plan in detail tonight, and so basically the
25 purpose of this meeting is to provide the public an
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1 opportunity to give me comments. Before the EPA makes
2 a final decision on how to proceed, this is the
3 public's opportunity to provide input to say: oh, you
4 know, EPA, this part of your cleanup strategy, I don't
5 like this, you know. This is your opportunity to tell
6 me how maybe I should modify or change our strategy
7 before we go out and spend a whole bunch more money to
8 do the cleanup. Okay. So that's the Superfund
9 Process.
10 And like I said the public comment period for
11 this particular proposed plan ends August 20th. So you
12 have until August 20th to either if you don't want
13 to provide comments tonight, you can write me a letter,
14 and all that information where to write is provided
15 here.
16 After August 20th I'm going to be going over
17 everyone's comments and making a decision how should I
18 change my proposed plan to address people's comments.
19 And then by October 1st, I'm going to make a final
20 decision on how the cleanup at the airport and at Burr-
21 Brown and at West-Cap should proceed. And that will be
22 documented in a document called the Record of Decision.
23 That should be ready by October 1st.
24 So that's still just paper. Then after that
25 EPA goes out, and as part of the Superfund Process,
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1 we're allowed under this law to go out and identify
2 those parties that were responsible for the pollution,
3 responsible for putting the TCE in the soil, and then
4 EPA requests that those parties actually spend the
5 money to build and to design and construct the cleanup
6 operations.
7 So that will be happening in like 1998, and
8 by 1999 we should be actually out in the field doing
9 this cleanup that I'm going to talk about tonight.
10 Okay. So it's a bit a lengthy process, but we try to
11 be very thorough through this process, and so what I'm
12 talking about tonight will actually be happening in the
13 field in '98, '99 and beyond.
14 Any questions on that?
15 MR. ANDRATE: What companies are you
16 targeting on contamination?
17 MR. COOPER: For the okay. For the
18 airport property, EPA so far has identified the
19 following parties: The United States Air Force, Tucson
20 Airport Authority, The City of Tucson, McDonald Douglas
21 Corporation, and General Dynamics Corporation.
22 Those five so far, and we're in the process
23 of thinking through and maybe adding some more to the
24 list. So I can it's very likely that we will be
25 asking those five parties to help pay for the cleanup,
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1 and we might add some more because by October or
2 November we'll make a decision on whether we're going
3 to add a few more to that list.
4 MR. ANDRATE: It was like in early teens when
5 my cousin got out of the army, and he said that Grand
6 Central, they converted all the military planes for
7 civilian use, and he said they used some white solvent
8 that would run off the runway in the water.
9 MR. COOPER: Right.
10 MS. HERRERA: Can you please just state your
11 name for the record?
12 MR. ANDRATE: Arsenio Andrate, like Arsenic
13 Hall.
14 MR. COOPER: Okay. Thank you. Yes, Grand
15 Central EPA is aware of the activities that Grand
16 Central had as TCE disposal. Unfortunately, that
17 company is bankrupt debunked. So there's no Grand
18 Central. EPA would love to ask Grand Central to come
19 help pay for this cleanup, but they are no longer in
20 existence anymore, and there's no subsequent company
21 that we can even ask.
22 For example, the other well, I'll explain
23 that. The other companies, you know, McDonald Douglas
24 and General Dynamics, their predecessors occupied the
25 hangars before. So there's no Grand Central anymore to
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1 ask pay for the cleanup.
2 Okay. So that's a little bit of site
3 background. I think I explained a little bit already
4 EPA put this we tested TCE in the groundwater in
5 '81. Actually but there was indications of groundwater
6 contamination well before 1981, actually back in the
7 '50's, but it was formally TCE was formally detected
8 in 1981.
9 And this Superfund Site is six project areas.
10 I don't know if you can see this map, but again Hughes
11 Aircraft is down here. The airport property is here.
12 Then we have this former West-Cap facility, and the
13 former West-Cap facility, they went into operation
14 around 1963, and they made capacitors and other
15 electronic devices, and they it is alleged that they
16 used TCE in their operations. Burr-Brown Corporation,
17 which is located right off South Tucson Boulevard
18 there, they went into operation in 1965, and they're an
19 electronics company also making computer chips and
20 wafers, and it is alleged that they used TCE.
21 The Air National Guard base makes the fifth
22 project area, and then we have this groundwater project
23 over here that we call Tucson Airport Remediation
24 Project or TARP.
25 So all of this red patched area shows
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1 groundwater contamination in the deep regional aquifer.
2 All of this area is actively being cleaned up right
3 now. All right. So that's a real good news item.
4 The Burr-Brown groundwater contamination is
5 under active remediation right now as is the Air
6 National Guard Base has a groundwater system for
7 groundwater contamination directly underneath the Air
8 National Guard B"ase. So we have a lot of ground. We
9 have four groundwater cleanup systems already in place.
10 As far as soil contamination, we have the
11 soil cleanup is already in progress at Hughes. It's
12 already in progress at the Air National Guard Base, and
13 so this proposed plan is about getting the soil cleanup
14 going at the airport, West-Cap, and Burr-Brown.
15 Okay. So that is a little bit of the update
16 of the status of this Superfund Site.
17 So the cleanup we're not there all the way
18 obviously, but we've made a lot of progress as far as
19 cleaning up this Superfund Site. I want to assure
20 people that even though we still have TCE in our
21 drinking water aquifer, none of this TCE is being
22 supplied in the drinking water supply at unsafe levels.
23 That has not been happening since 1981. We have all
24 types of monitoring wells around the TCE area so we can
25 track it's movement to make sure it does not get into
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1 public drinking water supplies.
2 On top of that, EPA, along with Pima County,
3 has been monitoring private wells. That means
4 sometimes some families have their own drinking water
5 well, and we've been monitoring private wells to make
6 sure nobody has been drinking TCE also.
7 So even though the cleanup will take, you
8 know, perhaps 20, 30 years before we can get all this
9 TCE out of the deep groundwater, EPA along the way is
10 taking steps to make sure that no one is being exposed
11 to TCE anymore.
12 But basically so the real purpose of this
13 cleanup is to protect our environment for future
14 generations, our children and children's children, so
15 they don't have to inherit all this contamination
16 that's put in the soil and groundwater. So it's
17 basically this cleanup is about protection for the
18 future. All right.
19 A MEMBER OF THE AUDIENCE: Craig, what is the
20 range, potential range of cost for remediation for this
21 site?
22 MR. COOPER: For the cleanup of the airport?
23 A MEMBER OF THE AUDIENCE: The cleanup for
24 their site.
25 MR. COOPER: The EPA has a cost range for
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1 this proposed plan somewhere between 10 and 20 million
2 dollars. We put it in a range, and when I get into
3 the, you know, explain why there is some cleanup where
4 we're not too sure if we're going to implement it or
5 not. So that's why there's a range. So at least a 10-
6 million-dollar effort is going to be required here.
7 Okay. I think we can turn on the slides and
8 turn off a couple lights.
9 Okay. Now, what I'm going to do is basically
10 summarize the contents of this document here, the
11 proposed plan. All right. Again, just as a reminder,
12 the comment period ends August 20th.
13 Okay. First slide, please. This is a
14 photograph of the Tucson Airport back in the 1950's,
15 and why I put this photograph in is because the focus
16 of our discussion tonight is going to really center on
17 the complex here, shown in here. We call that the
18 Three Hangars Complex. All right. So I'm going to be
19 using that term throughout the meeting, Three Hangars
20 Complex.
21 Well, that's what I mean. I mean this large
22 industrial center located on the west side of the
23 airport. I'm sure you've all seen it when you drive
24 south on Nogales Highway heading toward Hughes or
25 Desert Diamond Casino you'll see it sitting there.
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1 This Three Hangars Complex is very important.
2 This is where Grand Central conducted its operations,
3 and actually before Grand Central, starting in 1942,
4 there was a company occupying here called Consolidated
5 Aircraft. They occupied the hangars from '42 to '48.
6 Grand Central then took over after then and carried out
7 operations from '48 to '56 or so, and then Douglas
8 Aircraft came in after that until 1960.
9 So all the way from 1942 until 1960, there
10 were military contractors inside these hangars and
11 buildings outside these hangars that conducted
12 basically aircraft modification where they would take
13 engine parts of airplane parts that were very dirty and
14 greasy and they would take them inside the hangars or
15 inside buildings near the hangars and spray TCE on them
16 or dip them in tanks of TCE or other solvents to take
17 the grease off. TCE is used as an was used a lot as
18 an industrial degreaser.
19 So it's EPA's belief that due to those
20 military contractor's activities during that time that
21 TCE and other contamination was spilled or released to
22 the ground surface at that time, and then the TCE
23 trickles through the soil and started the contamination
24 in our groundwater.
25 Okay. Next slide, please. There's just
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1 another old photograph. The Three Hangars actually
2 this side of the Three Hangars Complex was Tucson's
3 original airport also. I think starting in 1948 it was
4 used as passenger terminal, so there was maybe a
5 passenger terminal here and then the miliary
6 contractors were using operations around this in these
7 buildings.
8 Next slide. Here's an old photograph of
9 inside the Three Hangars Complex. You can see some
10 workers here carrying out operations and dealing with
11 various engine parts and metal parts, and it's possible
12 that a worker from in here would then take if a part
13 was too dirty, would take it over to somebody that
14 would be working in the degreaser area to have that
15 metal part cleaned, and then take it back and then put
16 it back on the airplane. So I think these slides are
17 very interesting and very informative of the operations
18 that were going on back then that used this
19 contaminant, TCE, that everybody, you know, cares about
20 today.
21 Next slide. So as I talk about this proposed
22 plan, I'm going to break up my talk in four parts.
23 Okay. There's four parts to this proposed plan. There
24 is the first I'm going to talk about is soil
25 contaminated with TCE and other VOCs. A VOC stands for
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1 volatile organic compound. It's a term for another
2 chemical that is very similar to TCE. TCE stands for
3 trichloroethylene. So I'm going to use TCE basically
4 throughout my presentation because I know that most of
5 you are familiar with that term, TCE. But in some
6 situations we have other contaminants similar to TCE
7 found in the soil near the Three Hangars Complex, but
8 by and large, TCE is our primary contaminant, so I'm
9 just going to continue to use that.
10 So EPA's what we're recommending to the
11 public on how to clean up TCE out of the soil is we're
12 recommending a technology called soil vapor extraction
13 and with air pollution controls associated with the
14 soil vapor extraction.
15 So I'm going to show you next slide,
16 please. This is not a good map, but I don't know if
17 people saw this chart, this map here. This shows the
18 locations of where we found TCE in the soil and where
19 we plan where we are recommending to build soil
20 vapor extraction units. So wherever you see a red dot,
21 that's where we found high enough levels of TCE to
22 require a cleanup. So definitely around the Three
23 Hangars Complex, we're going to be we're
24 recommending to build a soil vapor extraction system.
25 Where you see green triangles here on this
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1 other end of the airport, a couple here north of the
2 Three Hangars, and then two places over at the former
3 West-Cap facility, we found some TCE in the soil, but
4 we've only so far just looked at the top part of the
5 soil. But we basically have eliminated all of the
6 other contaminant sites.
7 So at these areas EPA is recommending that we
8 look in the deep part of the soil and make a decision
9 on whether there's enough TCE to warrant a cleanup. So
10 we call those our plug-in sites.
11 So to summarize, definitely around the Three
12 Hangars Complex we're recommending soil vapor
13 extraction and the other places it's a maybe situation
14 at this point, but if we do forward with a cleanup, it
15 will be soil vapor extraction there. So that's the
16 location. And notice that Burr-Brown Corporation,
17 there isn't a red dot and there isn't a green triangle.
18 That means that the investigations at Burr-Brown in the
19 soil found such low levels of TCE that there is no soil
20 cleanup being recommended by EPA. We call that no
21 further action is necessary for the soils at Burr-
22 Brown.
23 Burr-Brown does have the groundwater system
24 in place, and that will continue to operate until the
25 groundwater is cleaned, but basically all the TCE in
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1 the soil at Burr-Brown has already filtered down and
2 gotten into the groundwater. There isn't enough TCE in
3 soil to worry about there at Burr-Brown. It's not
4 causing any health risks. So those are the locations.
5 Any questions about the locations where we' re
6 recommending turn on the slide machine, please.
7 Next slide. Okay. This is how soil vapor
8 extraction technology works. What we do is we it
9 works because of the way TCE likes to act as a
10 chemical. When TCE is spilled on the ground, let's say
11 if this was the Three Hangars Complex, TCE was spilled
12 on the ground, and it will either evaporate immediately
13 and go up in the air or it will trickle down and get
14 below and trickle down deep into the soil, and this
15 is where we have this soil, but even underground, it
16 will evaporate and it will be mostly in a gas plume
17 underground. And then some of the TCE will actually
18 make it down into the groundwater. And I'll talk about
19 TCE in the groundwater later.
20 So as far as TCE in the soil, most of it we
21 have found is this most of it is like a TCE gas
22 underground. So we take advantage of that in our
23 cleanup. So what we do is we drill a well and put down
24 here in the middle of wherever TCE gas is, and put a
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1 vacuum blower so we can basically try to suck out or
2 extract out the TCE gas, and it goes right up this well
3 and into a pipeline and into a treatment unit where we
4 take the TCE out. All right.
5 So this technology has been found to be
6 extremely effective. We are using this technology at
7 Hughes right now with tremendous results. We're using
8 it at the National Guard Base, and I've got some
9 pictures of that.
10 As far as the treatment unit, EPA is
11 recommending, based on the types of concentrations that
12 we find in the TCE gas that we extract, we're
13 recommending four different types of treatment units.
14 We're recommending either what we call carbon
15 filters where the TCE gas is passed through a carbon
16 filter and the air comes out clean and the TCE is
17 trapped on carbon or we're recommending resin
18 adsorption where we have resin beads. It's the same
19 type strategy basically. The TCE sticks on resin
20 beads. And in both of those type technologies, the TCE
21 will have to be taken off the carbon and taken off the
22 resin and then the TCE is taken away to a landfill.
23 All right.
24 The other two types of treatment technologies
25 are what we call thermal oxidation or catalytic
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1 oxidation. That's completely different type
2 technology. In those technologies the TCE gas is
3 burned right here will be right there at the Three
4 Hangars Complex. So there won't be any TCE to take
5 away to a landfill. It's taken care of right there.
6 So all four of those treatment technologies
7 for TCE gas are part of EPA's proposed plan. So if
8 there is any one of those types of technologies that
9 doesn't sound right to you, and they're explained in
10 more detail in the proposed plan, and they're explained
11 in more detail in a document called the Feasibility
12 Study. If you want to get more details about what I'm
13 talking about tonight, you can always go to the TCE
14 Library which is right here at Old Pueblo Center, and
15 information about the TCE Library is on the back page
16 of our proposed.
17 So I'm not going to just so I can keep
18 things moving along, I'm not going to be able to
19 provide a lot of detail about each technology, but ask
20 clarifying questions anytime.
21 Okay. Next slide, please. This is an
22 example of a soil vapor extraction system that is
23 actually at Hughes. It shows at the end of each of
24 these white pipes, like down here, see how this one
25 goes right down into the soil. So that's one of
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1 this is an extraction well, so it sucks TCE gas out of
2 the soil, and then the TCE gas follows these pipelines
3 and goes to a next slide. The pipelines feed right
4 into a treatment plant.
5 Next slide. And this is what one of the
6 treatment plants at Hughes looks like. This is a
7 carbon filtration system. All right. So the TCE gas
8 goes in this very large container. I mean if I was to
9 stand here, it would probably come about this high. So
10 they're about ten feet high. The TCE gas goes in here,
11 and there's it's like charcoal filters, and the TCE
12 sticks to the charcoal filters, and the gas will come
13 out here, and then just to be safe we send the TCE gas
14 through yet another carbon filter, and so by the time
15 it goes through the second one, all the TCE is stuck on
16 the carbon, and then at the back part of the second
17 one, we have the air the gas that comes out doesn't
18 have any significant amounts of TCE anymore. So it's
19 all stuck onto the carbon.
20 Okay. So that's just to give you an idea of
21 what we are intending to build at the Three Hangars
22 Complex for sure and perhaps at other places. This is
23 one of the TCE gas treatment technologies that we might
24 build. All right.
25 One last thing I want to say about soil vapor
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1 extraction is that sometimes you get into a situation
2 where the TCE gas doesn't come out at a rate that you
3 want it to come out at, and there's new technologies
4 that have come along call enhancement technologies, and
5 because EPA wants to use as much of the new
6 technologies as possible, we're including four
7 enhancement technologies as options down the road
8 should we want to use them if we're having trouble
9 getting the TCE gas out, and those enhancement
10 technologies are described in more detail here, but
11 they include things as simple as just capping the
12 ground or putting a paved area over the ground.
13 It includes what's called pneumatic
14 fracturing. That means injecting air into the soil to
15 try to shake up the soil a little bit to free up more
16 TCE gas.
17 It includes bioventing which means you set up
18 your system to encourage naturally occurring bacteria
19 in the soil to eat TCE in the soil.
20 And it includes dual phase extraction which
21 means we're trying to lower the water table so we can
22 expose more of the TCE to dry up basically so it can
23 become a gas form so we can suck it out.
24 So that's the first recommendation that EPA
25 is making as part of this proposed plan is soil vapor
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1 extraction technology for TCE in soil.
2 Next slide. Our second proposal is a clean
3 up of soil with polychlorinated biphenyls. That's what
4 we have another chemical here, PCBs, polychlorinated
5 biphenyls. I'll explain those briefly. That is a
6 chemical that is very different than TCE. It was used
7 historically we believe in the Three Hangars Complex.
8 It was used in hydraulic fluid and in electrical
9 transformers. PCB was used because PCS chemicals like
10 to absorb heat. So, for example, in hydraulic fluid
11 you would use you add PCB fluids in there to absorb
12 heat so other parts of your engine can stay cool.
13 One thing about PCBs also is that when PCBs
14 are spilled to the ground as they have at the airport
15 property, they don't evaporate and they don't trickle
16 down deep into the soil. They are strongly attracted
17 to soil particles. So they will basically stay in the
18 top two or three or four feet of soil in just common
19 situations unless you're just pouring water on top of
20 it. But normal rainfall won't push PCB, at least
21 normal rainfall here in Arizona, doesn't cause this
22 chemical to go deep into the soil. So it stays right
23 at the top part of the soil.
24 So EPA's recommendation to cleanup PCB
25 contaminated soil is to basically just to dig it up,
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1 put it on a truck, and haul it away to an approved
2 landfill. All right.
3 Next slide. Not a good picture. This is
4 another I'm going to show you where we have PCB
5 contaminated soil. See the green triangles are areas
6 that we've already cleaned up. We did an expedited
7 cleanup of PCB contaminated areas. One a little bit in
8 the airport property and all along El Vado Road in this
9 residential area. We removed 10 thousands tons of soil
10 contaminated with PCB, but we have a little bit left.
11 As you can see we've got a couple spots here and one
12 more spot down here left to do, and also that's where
13 PCB is on the soil.
14 Also I forget to mention at the Three Hangars
15 Complex itself, remember the photographs I showed you,
16 there's some underground pipelines there that were used
17 for waste management, and inside those pipes, it's full
18 of contaminated sludge. Okay. And we are proposing to
19 include the cleanup of those pipelines as part of when
20 we dig up the contaminated soil, we'll also dig up
21 those pipelines with all the sludge inside and take
22 that away to the landfill also. Okay.
23 Lights. This is how we cleanup PCB
24 contaminated soil. We get a big truck loader and start
25 scooping it up. This is actual slide this is a
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1 slide that was taken earlier this year when we were
2 cleaning up the area of the airport that I showed you.
3 It's a little bit out of focus. I don't know if we can
4 fix that. There, that's better. Thank you.
5 Next slide. That's a little bit out of focus
6 also. So we scoop up some soil basically, and we dump
7 it into these large bins or we dump it in directly into
8 a truck that has a large bin on it.
9 Next slide. This is a pretty good slide. So
10 it just shows contaminated soil being dumped into a
11 truck, and then after the bin is full of soil, we cover
12 the bin with tarps to make sure that the dust won't fly
13 off, and then the trucks drive directly to the
14 landfill.
15 Next slide. Here we show soil being dumped
16 into the bin, and you can see we have workers here that
17 will spray the soil with water just to make sure that
18 the dust is kept down so when we're dumping all this
19 soil into the truck, we don't get this big, you know,
20 whoosh of contaminated soil or dust flying off. So we
21 spray down the soil to keep it moist so to keep the
22 dust under control.
23 Okay. That one is a pretty straight forward
24 cleanup, not too complicated for the PCBs. We're going
25 to dig it up and take it to a landfill.
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1 Next slide. Speaking of landfills, we
2 discovered a landfill at the airport. I will show you
3 where it is in a minute. EPA's recommended strategy to
4 address the landfill basically is to formally close the
5 landfill even though the landfill hasn't been receiving
6 any waste for some time now. But we're going to
7 basically there's some state regulations on how to
8 close the landfill, and we're going to follow those
9 guidelines by covering the landfill with two feet of
10 clean compacted soil, and we're going to but we're
11 going to continue to monitor the soil and ground water
12 around the landfill to make sure that we haven't missed
13 anything.
14 Next slide. That's a shot of where the
15 landfill what it looks like.
16 The next slide after that. That's the
17 surface area of the landfill. It's about five acres
18 big. I'll show you real quickly where it's located.
19 It's where this black square is right here. So it's
20 right off Nogales Highway in Arrow Park. Desert
21 Diamond Casino is basically located right here. So
22 it's kind of just right across the street from the
23 casino. All right.
24 Going into our investigations of this
25 landfill, EPA thought that the military contractors
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1 that were at the Three Hangars, we thought based on
2 what some of the former workers were telling us, we
3 thought that some of the disposal of TCE drums and
4 liquid happened at this landfill. So we expected to
5 find a whole bunch of TCE at this landfill. And so we
6 EPA asked the responsible parties to spend a lot of
7 money to investigate this landfill, and we used all
8 different types 'of investigation strategies, and as it
9 turned out, we really didn't find much TCE at all.
10 We're going to continue to monitor it, but
11 we've decided at this point let's at least close,
12 formally close the landfill. The trash here on top,
13 the stuff that can be removed, will be taken away and
14 taken to an approved landfill, but there's big pieces
15 of concrete and huge like construction debris that we
16 can't pick up. So what we'll do is bring clean soil
17 over the top of that, smooth everything out, grate it
18 off. We'll recede the area so aesthetically it looks
19 good, and we'll grate it for erosion control and things
20 like that. And that's basically what we're proposing
21 on that.
22 Next Slide. The fourth and final EPA
23 proposal concerns the shallow groundwater zone, which
24 is a limited area of groundwater near the Three Hangars
25 Complex, and I'll explain what the shallow groundwater
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1 zone is in a minute, but it is a groundwater zone.
2 What we're recommending at this time is to
3 pump out the contaminated groundwater, remove the TCE
4 and other VOCs from the water, and then put the clean
5 water to an appropriate use. So I'm going to talk
6 about each component of that here in a minute, but
7 briefly I want to explain what a shallow groundwater
8 zone is.
9 Next slide. I think it's the map anyway.
10 Yes. Okay. One last time for the maps. Let me show
11 you where the shallow groundwater zone is. The
12 contaminated portions of the groundwater zone are shown
13 in yellow, okay. So it's fairly limited. Now, this
14 regional aquifer that I was talking about before, that
15 sits below. So the shallow groundwater zone starts at
16 85 feet below ground surface, and this regional aquifer
17 that I've talked about that produces a lot of water, is
18 our drinking water supply, starts at 140 feet below
19 ground surface.
20 So in some places we have groundwater that
21 sits up above the regional aquifer, and that happens
22 sometimes based on the water tables back in the 1950's
23 used to be 50 feet below ground surface, but then as
24 Tucson grew, we started to drink more and more
25 groundwater. We were over tapping our groundwater, and
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1 the water table was started to drop. And in most areas
2 it's 140 to 150 feet. But in some places where the
3 water table was dropping and if it was passing through
4 clay, water got stuck in the clay layers 85, 90 feet,
5 100 feet. So that's what created some of our shallow
6 groundwater zones. The water table started to drop
7 during the '50's and '60's down to 140 feet, but in
8 some area the water gets stuck, and we call that a
9 shallow groundwater zone. Okay.
10 And as you can see what happened, TCE was
11 dumped at the Three Hangars Complex. It contaminated
12 the soil, and then it went down and it contaminated
13 this area of the shallow groundwater zone. All right.
14 I'll explain that some more.
1 5 This is the way the Three Hangars Complex
16 looks today. This is the south side of the Three
17 Hangars Complex and you can see they have these little,
18 small tin sheds just to the south side also. It's
19 basically inside these sheds is where a lot of the TCE
20 disposal occurred, and so what happened was it's
21 EPA's belief that some TCE was disposed directly to the
22 ground surface especially at this shed here and this
23 one here, and liquid TCE went down deep and got stuck
24 in that clay layer that I talked about.
25 And if you want I can pass this around. This
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1 gives you an example of the type of clay that I'm
2 talking about where we have the shallow groundwater
3 zone, and you can kind of squish it around a little
4 bit, but just imagine this clay here at around 90 feet
5 below ground surface is completely wet and has a lot of
6 TCE. You can pass that around. You can swish it
7 around. That's uncontaminated soil there. So but it's
8 in a plastic sack just for your protection. So that's
9 the type of material that this shallow groundwater zone
10 is located in.
11 So the shallow groundwater zone doesn't
12 produce much water because it's in clay. Groundwater,
13 if it's down in sand or gravel, you can pump up a whole
14 bunch of water, but if you find groundwater in clay,
15 you .'re not going to be able to pump out much water.
16 All right. And that's going to be a real problem when
17 we try for the cleanup. If we can't pump water, that
18 means we can't pump out much TCE. So that's going to
19 be a real problem. And, in fact, what EPA is
20 suggesting at this time is that for the shallow
21 groundwater zone just in this area that you can see in
22 this photograph, we're saying that the TCE
23 concentrations are so high and they're stuck in this
24 clay layer that we don't have a technology today that
25 can completely restore and remove all the TCE from that
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1 area. All right.
2 So that's kind of a bad news item. But that
3 doesn't mean that we're going to give up on that area.
4 It just means that we don't think that the shallow
5 groundwater zone so if you went 85 feet below this
6 area right here that you see the photograph, you'll
7 find high concentrations of TCB. We're saying we can't
8 restore this area to drinking water quality, but what
9 we will do is put them what the remedy will do act
10 to basically try to hold that TCE in place so it's not
11 moving around on us anymore so it's not spreading into
12 our drinking water aquifer. We call that containment,
13 and I'll explain how we do containment in a minute.
14 So that is the first part I want to say, but
15 for the rest of the shallow groundwater zone, for the
16 rest of the yellow area so the red zone that I've
17 said here, that's where we have a very high
18 concentration stuck in place. The rest of this yellow
19 area we are going to try to restore and get enough TCE
20 out so it's back to drinking water quality.
21 Again, the whole purpose of cleaning up the
22 soil, the TCE out of the soil and the TCE out of the
23 shallow groundwater zone is to stop it from leaching
24 down into our regional aquifer because that's our
25 drinking water supply for future generations. Okay.
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1 So to the extent that we can get as much TCE out, that
2 is to the benefit of future generations' drinking water
3 supply. Okay.
4 Other aspects of our shallow groundwater zone
5 remedy include, like I said, it's a groundwater what
6 we're going to do is put wells to pump out contaminated
7 groundwater.
8 Next slide, please. This is a schematic of
9 how we pump out groundwater. It's a very simple
10 process. It follows the same principle as we pump out
11 TCE gas, we can do the same thing we can pump out
12 groundwater, is that we put a well down this is our
13 shallow groundwater zone where there's high
14 concentration TCE, and we put a pump on this well. We
15 just basically pump the water out, and so the water
16 from surrounding areas around the well are drawn toward
17 the well, and it's drawn upward, it's drawn in from the
18 side in all directions.
19 So as long as we're pumping on this well,
20 water in this area has no choice but to go in the
21 direction of this well, and that's true for this well.
22 As long as we're pumping on this well, water will just
23 be naturally drawn towards those wells, and we call
24 that containment.
25 So by drawing water toward extraction wells,
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1 we're containing we're not allowing the TCE to go
2 down this way anymore or to go off this way. The TCE
3 will be forced to our 'extraction well. So it will be
4 contained. It will be kept in place. Okay.
5 Because we are pumping out of the shallow
6 groundwater zone, which is not easy because it's full
7 of clay, it's not easy to pump, we're recommending two
8 enhancement technologies to try to increase our ability
9 to get more water and more TCE out of this zone. And
10 the first enhancement is called electro-osmosis, which
11 is to apply an electrical current from one groundwater
12 extraction well to the next to try to draw water.
13 Water can be drawn by electrical current. To try to
14 the draw the water to the extraction well so we can
15 pull the water, and where the water flows, TCE will
16 flow, and so we can get more water out of this unit.
17 That is an experimental technology. I don't
18 it's left as a design option for us to use in the
19 future.
20 The other enhancement technology is that we
21 might do a pilot study to see how well we can try to do
22 what's called bioremediation, which is you add some non
23 toxic chemicals to the groundwater to stimulate
24 bacterial growth in the groundwater. There's bacteria
25 that naturally occurs on all groundwater and naturally
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1 occurs in all soil. So some of that bacteria is very
2 good and will actually start eating TCE for its food,
3 and that's a proven cleanup technology, especially for
4 gasoline spills. There's a lot of bacteria out there
5 that likes to eat gasoline. Unfortunately, there's
6 fewer bacteria out there that like to eat TCE. Usually
7 bacteria don't like to eat TCE, but we can try to
8 create an environment so we can kind of pump up the
9 bacteria so they will be happier to eat the TCE, and
10 that is another design option that we might try called
11 bioremediation.
12 But we are definitely going to be pumping
13 wells because we have to do this containment. So we'll
14 be pumping out TCE water. The TCE water will go into a
15 pipeline and to a treatment plant.
16 First of all I want to explain that means
17 we're going to be putting extraction wells here in this
18 red zone. We'll putting them all along the airport
19 property line, and we will be putting extraction wells
20 in the residential area, and we'll be putting pipeline
21 in this residential area and piping the water, the
22 contaminated water back to a treatment plant probably
23 located near the Three Hangars.
24 So if you happen to live on El Vado, Corona,
25 or Teton Road near Nogales Highway, somewhere down the
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1 road there's some likelihood that we'll be putting
2 wells and pipelines in your neighborhood.
3 Okay. Next slide. This is an example of a
4 groundwater treatment unit. So like I said, we pull up
5 the TCE water, put it in a pipeline, and send the water
6 to a treatment plant. This is a treatment plant that
7 is in operation at the Air National Guard Base. The
8 technology used in this treatment plant is called air
9 stripping technology, and that's one of three
10 groundwater treatment technologies that EPA is
11 recommending as part of our proposed plan.
12 In air stripping technology, you know, the
13 TCE water comes in the top, air is blown up the bottom,
14 and the TCE goes from the water into the air, and then
15 you have to do air pollution controls to make sure the
16 TCE comes out of the air. So then clean water comes
17 out of the bottom of this treatment plant. Okay.
18 Let me talk about what we're going to do with
19 the clean water that comes out of the treatment plant.
20 EPA is recommending a lot of flexibility in this and
21 not requiring one option. The options that we are
22 offering are on-site industrial use so the clean water
23 comes out of the groundwater treatment plant and if the
24 airport has some use at the air you know, some
25 industry or some use for the clean water, they can use
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1 it for that option.
2 They can reinject the clean water back into
3 the groundwater. They can let's see. And that
4 reinjection could either occur at the airport property
5 or we might use reinjection wells that are owned by the
6 Air Force or Hughes. Since they have some extra
7 reinjection wells, they might let us use those.
8 What else? I want to make sure I'm not
9 skipping any. Oh, or we might just dump the clean
10 water into the sanitary sewer. That you have to get
11 permission from Pima County Wastewater on that.
12 But what I was trying to do was allow as much
13 flexibility in the treated water as possible.
14 A MEMBER OF THE AUDIENCE: With regard to the
15 amount of water generated, do you have a figure like
16 gallons per day or acre feet per year at this point?
17 MR. COOPER: I could give you a rough
18 estimate at this point. Because the shallow
19 groundwater zone doesn't produce very much water, we're
20 not talking about very much, perhaps in the
21 neighborhood of 50 to 100 gallons per minute. So not
22 very much water. For example, the TARP plant is 6,000
23 gallons per minute.
24 A MEMBER OF THE AUDIENCE: Right.
25 MR. COOPER: So we're talking a pretty small
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1 flow rate here.
2 A MEMBER OF THE AUDIENCE: Right.
3 MR. COOPER: If there's another induce that I
4 didn't name as an option that you want me to add, you
5 know, I'd be willing to consider that as a comment.
6 Drinking water is not an option for the induce of this
7 treatment plant. Okay.
8 A MEMBER OF THE AUDIENCE: Before you go on,
9 that raises another question. When you came to the
10 Mayor and Council to discuss this technology, you
11 assured me that the water that came through here would
12 be as clean as the water that was coming out of the
13 other treatment facilities. And if that is below the
14 limits for TCE and clean as far as drinking water
15 standards, isn't this going to be at least that clean?
16 MR. COOPER: Yes. The
17 A MEMBER OF THE AUDIENCE: They why
18 MR. COOPER: The treated water coming from
19 the treatment plant we'll build at the Three Hangars
20 will most likely have drinking water standards by parts
21 per billion.
22 A MEMBER OF THE AUDIENCE: Right.
23 MR. COOPER: As it's treated water standard
24 for cleanup. Why not allow drinking water for that?
25 A MEMBER OF THE AUDIENCE: I'm not asking
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1 that. I just want to make sure that the reason you
2 haven't included drinking water is that you backed away
3 from treating it drinking water standards. I just want
4 to make sure that it's treated to that standard.
5 MR. COOPER: Yes.
6 A MEMBER OF THE AUDIENCE: What's done with
7 it is another issue.
8 MR. COOPER: Right. It's going to be treated
9 mostly likely be treated to drinking water MCL,
10 which is 5 parts per billion on TCE.
11 There are reasons why we didn't include a
12 drinking end-use, but I won't go into that unless
13 you're interested.
14 Okay. As far as the treatment plant itself/ I
15 talked about one technology that we have as a design
16 option. That's the air stripping technology, and
17 that's a very common technology. It's extremely
18 effective. Air stripping technology, like I said, is
19 being use at the Air National Guard Base. It's being
20 used at Hughes, and it's being used at the City's TARP
21 drinking water plant, too. It's a very effective,
22 reliable treatment technology to take TCE out of water.
23 But we wanted to include some flexibility in
24 our treatment plant design also, so we've included the
25 options to use in addition to or in addition to air
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1 stripping technology, we might use carbon/ liquid based
2 carbon to take TCE out or we might use a new technology
3 called ultraviolet oxidation, which is basically a
4 technology where the TCE water is pumped out of the
5 ground, sent to a treatment plant, and in the treatment
6 plant, we have these large light bulbs basically where
7 the TCE water will pass in front of the light bulbs and
8 the light bulbs shine ultraviolet light on them that
9 causes the TCE molecules to break apart. Okay.
10 We actually tried out that technology during
11 a treatability study a year and a half ago or whenever
12 we did that, and it worked to some degree. It didn't
13 take it all the way down MCLs, so likely if we use the
14 UV oxidation technology, we'd probably have to do a
15 little bit of what we call polishing technology at the
16 end. But it's a fairly common technology, and we like
17 it because it breaks the TCE apart. Then you don't
18 have to cart the TCE away to someplace else.
19 Okay. I believe I went over it all. Next
20 slide, please. I think I just have some more slides.
21 That gives you an idea of the treatment plant at the
22 Air National Guard is not all that big. Next slide.
23 I'm six feet tall, so. There's another shot of it.
24 So to summarize, that means I'm just about
25 done. To cleanup where EPA is recommending soil vapor
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1 extraction to take TCE out of the soil, we're going to
2 treat the TCE gas at a treatment unit, and we're going
3 to take the TCE out of soil so the groundwater doesn't
4 become recontaminated based on the groundwater cleanup
5 standards.
6 We're going to dig up PCB contaminated soils
7 and sludges and transport them to an off site approved
8 landfill.
9 We're going to cover up the airport landfill
10 with two feet of clean soil compacted down, revegetate,
11 and continuing monitoring.
i
i
12 And lastly, we're going to pump TCE and other
13 VOCs out of the shallow groundwater zone. We're going
14 to use extraction wells to contain groundwater
15 contamination. We're going to pipe contaminated water
16 to a treatment plant to remove the VOCs. We're going
17 to restore shallow groundwater zone to drinking water
18 quality wherever technically practicable, and as I said
19 before, there's one zone next to the Three Hangars
20 right here where we're saying it can't make it to
21 drinking water. We can't restore that area, but we are
22 definitely going to try to prevent the VOCs from the
23 shallow groundwater zone from spreading into the
24 regional aquifer.
25 That's the end of my presentation. So we can
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1 take clarify questions or we can go directly into the
2 formal public comment period.
3 MS. HERRERA: Are there anymore questions.
4 SHIRLEY: On that where the at the Air
5 National Guard where the vapor goes into the
6 atmosphere, is there an odor or anything to that?
7 MR. COOPER: For the Air National Guard's
8 groundwater system?
9 SHIRLEY: Uh-huh.
10 MR. COOPER: Where they have TCE water that
11 goes to the treatment plant and then it goes it a gas?
12 SHIRLEY: Right.
13 MR. COOPER: Well, the TCE is now in a gas.
14 It goes through carbon filters to take the TCE out of
15 the gas. So the gas that is actually put into the
16 atmosphere has no or very little TCE, and there should
17 be there's no odor. I stood next to the treatment
18 plant several times. To be able to smell TCE, it needs
19 to be in a fairly high concentration before your nose
20 can pick it up, and you can't smell the TCE at all.
21 Next question.
22 A MEMBER OF THE AUDIENCE: When you're
23 drilling the test well, you're sampling the soil every
24 so often, right?
25 MR. COOPER: That's correct, yes.
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1 A MEMBER OF THE AUDIENCE: How far does it go
2 down, like contamination around the south side area?
3 MR. COOPER: The deepest contamination we
4 have is in groundwater in our regional aquifer, and the
5 bottom of our regional aquifer that we have been
6 testing is around 240 feet. If someone wants to help
7 me out on that. How about the bottom of the well,
8 you're asking th'e bottom most
9 A MEMBER OF THE AUDIENCE: How far it's going
10 down.
11 MR. COOPER: How far we detected TCE, so that
12 would be the bottom of the lower divided aquifer.
13 A MEMBER OF THE AUDIENCE: Well, the aquifer
14 goes down at least a thousand feet.
15 MR. COOPER: So how far does how do we
16 detect the TCE?
17 A MEMBER OF THE AUDIENCE: The wells are
18 screened down to 500 feet.
19 MR. COOPER: 500 feet is where we're
20 extracting TCE water from, but it might be deeper than
21 that, but it hasn't been tested down deeper than 500
22 feet, but in my opinion, if there is TCE lower than 500
23 feet, it's in very low concentration.
24 A MEMBER OF THE AUDIENCE: What's the
25 heaviest of concentration of TCE right now?
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1 MR. COOPER: As far as just where you can
2 find high
3 A MEMBER OF THE AUDIENCE: In Tucson, like
4 the south side.
5 MR. COOPER: Well, that Three Hangars
6 Complex, that's one area of high concentration, but
7 that's in a shallow groundwater zone. Other high
8 concentrations can be found at Hughes. So those are
9 basically our two high concentration areas for
10 groundwater is Hughes, where they actually have high
11 concentrations in the regional aquifer, and then at the
12 Three Hangars Complex where you can find high
13 concentrations in the shallow groundwater zone.
14 A MEMBER OF THE AUDIENCE: We seen a map
15 where it covers all the south side all the way passed
16 12th.
17 MR. COOPER: Oh, yes. The TCE and I don't
18 know if you can make out this map. It goes the
19 groundwater contamination goes all the way up South
20 12th Avenue and stops between Irvington and Ajo. But
21 once, you know, so down in this area, the TCE
22 concentrations in the regional aquifer are around 1,000
23 to 500 parts per billion, and then you go up here and
24 they're around 100, and then you go up here and they're
25 50, and then up in here they're 10 and 5 parts per
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1 billion. So depending on where you are, you find
2 different concentrations of TCE.
3 Question here.
4 A MEMBER OF THE AUDIENCE: You said you have
5 an extraction pump pulling out the water, but how long
6 is it going to take for where, you know, it's filtering
7 to the ground? How long does that take about, you
8 know, to come through again.
9 MR. COOPER: To take the TCE out?
10 A MEMBER OF THE AUDIENCE: It's going to take
11 years because it's already been cut off several years
12 ago, but it's still dripping down into the water,
13 right?
14 MR. COOPER: Right, right. You're talking
15 about soil
16 A MEMBER OF THE AUDIENCE: In the future, you
17 know.
18 MR. COOPER: Right. That's why EPA's remedy
19 when I said we're going to use soil vapor extraction
20 technology, we are using that technology to suck out
21 the TCE out of the soil before it gets to the
22 groundwater. Okay. And we're doing that everywhere
23 where the TCE concentrations in the soil are high
24 enough to cause an adverse impact to groundwater. So
25 that's part of what EPA is proposing is to go after
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1 these areas of TCE in the soil to get the TCE out/ you
2 know, before even more gets into the groundwater.
3 Enough has gotten into the groundwater as it is
4 already. So we're trying to get the stuff that's left
5 in the soil. We're trying to pull it out of the soil
6 before it gets to the groundwater. And we think that
7 actually the soil cleanups for TCE can happen a lot
8 quicker than a groundwater cleanup, and that's another
9 reason to pull the TCE out of the soil before letting
10 it get into groundwater.
11 Our soil cleanups we estimate those will
12 take maybe, depending on the concentrations, between
13 one to five years to take TCE out of the soil, but as
14 you maybe know, EPA estimates for the larger
15 groundwater cleanups, that's, you know, 20, 30, 40
16 years to take TCE out of the groundwater. So you can
17 see why there's an economic incentive to take TCE out
18 of the soil instead of waiting for it to get into the
19 groundwater.
20 That was a long answer for that question. I
21 apologize for that.
22 More questions? Uh-huh.
23 A MEMBER OF THE AUDIENCE: You said you were
24 going to put it in a landfill. How about rain water
25 and stuff going through the contaminated soil? It will
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1 form TCE back into the soil, won't it?
2 MR. COOPER: Okay. You're talking about
3 A MEMBER OF THE AUDIENCE: Where you're
4 dumping it out
5 MR. COOPER: The contaminated soil?
6 A MEMBER OF THE AUDIENCE: Yes.
7 MR. COOPER: That's only for that chemical
8 called PCBs. Th'e TCE we're using a different
9 technology for cleanup. PCB soil we're going to
10 you're right, we're going to dig it up and take it to a
11 landfill. It won't be a landfill here in Tucson. It
12 will be an approved landfill that is built in a safe
13 way that all these high tech liners that stop the
14 contamination from leaching down. We've got all these,
15 you know, clay and then plastic liners and synthetic
16 liners under our new approved landfills that doesn't
17 allow groundwater contamination to happen anymore.
18 And EPA can only take wastes from a Superfund
19 Site to these new more modern landfills. I can't take
20 wastes from a Superfund Site to an old landfill that
21 might be leaking. That's against the law. I can only
22 take stuff from a Superfund Site to a new landfill
23 that's very protected.
24 A MEMBER OF THE AUDIENCE: Thank you.
25 MR. COOPER: More questions or comments about
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1 what we're proposing in this.
2 MS. HERRERA: Okay. We'll open the formal
3 comment period. Any comments?
4 MR. COOPER: Just comments where I won't
5 answer.
6 MS. HERRERA: Things you want us to consider
7 before we make our decision.
8 Okay. Well, if we don't have any more
9 questions or comments, I want to close the meeting.
10 Once again, thank you for coming. We're still going to
11 be taking comments until August 20th, so if you go home
12 and you think of anything, a great idea, suggestion, or
13 something you want to see changed from what you read in
14 the proposed plan, please send your comments to us.
15 It's your opportunity to comment on our position.
16 Thanks.
17 MR. COOPER: Thank you very much.
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CERTIFICATE
STATE OF ARIZONA )
)
COUNTY OF PIMA )
ss.
BE IT KNOWN that I transcribed the
foregoing matter-pursuant to agreement; that I was then
and there a Notary Public in and for the County of Pima,
State of Arizona; and transcribed my stenographic notes
of the Environmental Protection Agency's Public Meeting
at the El Pueblo Center on July 23, 1997, and that the
testimony of the participants was reduced to writing
under my direction, all done to the best of my skill and
ability.
I DO FURTHER CERTIFY that I am not a
relative or attorney of either party, or otherwise
interested in the events of this action.
Notary Public
My Commission Expires:
January 1, 2000
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Appendix 6
Transcript of Proceedings
Public Meeting
Tucson International Airport Superfund Site
Proposed Plan
El Pueblo Center
Tucson, Arizona
July 23,1997
SAC/110831/COVERDOC
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ENVIRONMENTAL PROTECTION AGENCY
PUBLIC MEETING
Location: Faith Assembly of God Church
Tucson, Arizona
July 22, 1997
Arizona Court Reporting
177 North Church, Suite 1111
Tucson, Arizona 85701
(520) 623-3375
BY: RONALD L. LUNSFORD, R.P.R,
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2
1 THE FOLLOWING is a verbatim record of the
2 EPA Public Meeting held on July 22, 1997, starting at
3 6:45 p.m. at the Faith Assembly of God Church, 335 East
4 El Vado Road, Tucson, Arizona.
5
6 MS. HERRERA: Good evening. My name is
7 Angeles Herrera, and I work with the Environmental
8 Protection Agency in San Francisco. I want to thank
9 you all for coming to the meeting. We are here tonight
10 I wish there were more of you. We would have less
11 empty chairs. We are here tonight propose EPA to
12 present to you EPA's proposal for addressing the
13 contamination at the airport property and two other
14 nearby properties which are part of the whole Tucson
15 Airport Area Superfund Site. So even though there is
16 other properties that are part the site, tonight we're
17 going to concentrate on the airport property and two
18 near site properties.
19 I hope you all had a chance to pick up a copy
20 of our fact sheet. If you did not receive one in the
21 mail, we also have some sign-in sheets that we are
22 asking you to please sign so you can receive future
23 mailings. We also have an agenda there even though the
24 times are going to be a little different now since we
25 are starting early, and for those of you who prefer to
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1 provide a comment in writing, we also have a comment
2 form which you can give it to me during this meeting or
3 tomorrow's meeting or you can send it to our office.
4 You notice we have a court reporter. This is
5 an official public meeting. He will be recording the
6 entire meeting, and then he will prepare a transcript
7 which will be become an official part of the
8 administrative record for the site. We're asking you
9 to please speak loud, state your name and affiliation
10 for the record. We would prefer if you spell your last
11 name for us.
12 We also have a video camera. The video
13 camera is actually just for EPA internal use. What we
14 use the tapes for are usually for training and also for
15 the presenters to go back and see ourself and try to
16 improve ourself, but if anybody here wants to say
17 something and does not want to be recorded, please just
18 let me know, and we will turn off the machine during
19 your presentation.
20 Now, I want to introduce the rest of the team
21 which is really small. Most of you probably know Craig
22 Cooper. He's the Remedial Project Manager for EPA, and
23 also our state partner which is Richard Olm, right?
24 MR. OLM: Yes.
25 MS. HERRERA: The agenda tonight, following
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1 the introduction, Craig is going to have a couple of
2 presentations. He'll have a generic superfund process
3 presentation where he's going to explain, okay, what
4 comes next after this meeting. Then he will give us a
5 short site background, and then we will have EPA's
6 proposed plan.
7 If anybody has any clarifying questions
8 during the presentation, if Craig says anything that
9 you don't that's not very clear, just please raise
10 your hand, and he will address your question during the
11 presentations.
12 Then after the presentations we will start a
13 formal commentary. We will not be addressing your
14 comments tonight. What we are going to do is we are
15 going to take them down, and we're going to respond to
16 them in writing in a responsative summary which is a
17 document that also becomes part of the administrative
18 record for the site, and it's also going to be part of
19 the Record of Decision, and what the Record of Decision
20 is is a document that documents what the cleanup is
21 going to be for these three properties.
22 Are there any questions about the way we are
23 going to run this meeting? If there aren't any, I'll
24 just turn it over to Craig. Thank you.
25 MR. COOPER: Okay. Good evening, everybody.
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1 My name is Craig Cooper, and I work for EPA. I think
2 most everybody knows me. Thank you all for showing up
3 tonight, even though it's disappointing that more
4 community people didn't come, but I'm happy with the
5 attendance we have here, and I'm going to give you a
6 little bit of information about what's happening at
7 this Superfund Site.
8 For those of you who haven't heard of the
9 Superfund law or the Superfund Process, I'm going to
10 explain that very briefly, talk a little bit about the
11 site itself, and then get right into what EPA the
12 meat of this meeting is to talk about EPA's proposal.
13 So the Superfund law was passed back in 1980
14 by Congress. It's a federal law, and it basically
15 mandates EPA to track down areas where hazardous
16 substances have been released to the environment and
17 they pose a significant risk to human health or the
18 environment.
19 EPA decided to put this Superfund Site, the
20 airport, Tucson International Airport Area Superfund
21 Site, on the list in 1983. And we broke up this
22 Superfund Site into six project areas. Most of you are
23 probably more familiar with Hughes Missile Systems,
24 with Air National Guard. Those are two project areas
25 as part of this Superfund Site.
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1 Other project areas include the airport
2 property itself, Burr-Brown Corporation, and a piece of
3 property called West-Cap. That's what we're going to
4 talk about tonight, those three properties. But it's a
5 very large Superfund Site.
6 The way EPA runs the Superfund Process is
7 that first we have to conduct an investigation and to
8 track down what "type of contamination do we have here,
9 what concentrations, and where is it. So we started
10 that process in the early 80's, and our first priority
11 was groundwater contamination in the deep ground water.
12 We call that our regional aquifer. That's the drinking
13 water supply here on the south side and for all of
14 Tucson actually. So because the groundwater
15 contamination posed the primary threat to public
16 health, we started our investigations on that.
17 The cleanup the investigation and the
18 cleanup process for the regional aquifer has already
19 gone through, and we already have our cleanup program
20 in place for the regional aquifer. So a lot of work
21 has already occurred at this Superfund Site, and as far
22 as the regional aquifer, that cleanup is already in
23 place.
24 Then in the early '90's we started to take a
25 look a soil contamination because that's important for
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1 two reasons. Number one, a lot of TCE soil
2 contamination will reach down and get into our regional
3 aquifer, and also there might be soil contamination at
4 the surface that might pose a threat to public health.
5 So at Hughes, for example, and Air National
6 Guard, they've already gone through the Superfund
7 Process of identifying soil contamination and putting
8 together a cleanup plan for those properties. Those
9 are already in place also.
10 So basically this proposed plan, what EPA is
11 going to propose to you tonight, is the last of our
12 proposals for the cleanup of soil contamination at the
13 Super fund Site, and which I think is a very big step.
14 So what is the proposed plan. The proposed
15 plan is a document. This is our proposed plan here.
16 It's just a it's 12 pages long, and it summarizes 4
17 years of investigation that EPA and other parties have
18 been conducting to investigate contamination at the
19 airport, at Burr-Brown, and the West-Cap property, and
20 we summarized all the investigations, the results of
21 these investigations in this document, and then also we
22 summarized our strategy for how we think it's best to
23 clean up the contamination. That's all contained in
24 here.
25 And so this is basically our way to disclose
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1 to the public what we found and how we plan on
2 proceeding, and it gives the public the opportunity for
3 input at this point in time before we go any further
4 into the process. So I recommend that everybody get a
5 copy of this before they leave the room, take a look at
6 it. It's a 30-day public comment period that started
7 yesterday, so that means on August 20th is the end of
8 the comment period.
9 Again, as Angeles said, you can provide
10 comments tonight or you can put them in writing and
11 mail them, and the addresses and all the information on
12 where to send your comments are provided right here on
13 the front page.
14 Speaking of more information, like I said,
15 there is a lot of information as far as paper
16 documentation of all of the work that we've been doing
17 over the last four years, and that information can be
18 found in two locations. One, very easy to find is
19 right at the Old Pueblo Neighborhood Center at 6th and
20 Irvington street. EPA has set up what we call the TCE
21 Superfund Library, and all the documents that are
22 referenced in this proposed plan that I might even talk
23 about tonight, all those documents are at the TCE
24 library. So after reading this and if you feel like
25 this doesn't give enough information, if this was too
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1 much of a summary, all the detailed information are in
2 much bigger, thicker documents that are at the TCE
3 library, and we have our librarian there to help you go
4 through those documents.
5 So that is the Superfund Process. Just to
6 summarize on how we're going to proceed, after this
7 proposed plan, like I said, the comment period ends
8 August 20th. EPA is going to write another document
9 called the Record of Decision, and we hope to get that
10 done by September 30th, and so during from August 20th
11 to September 30th, we're going to be looking over all
12 of the public's comments to see how we should modify or
13 change EPA proposals in the proposed plan. And so the
14 Record of Decision will be EPA's final decision on how
15 we should proceed. That will come out by September
16 30th. Then after that is when EPA will, for the
17 airport property, for example, we will send notice
18 letters to parties that we feel that were responsible
19 for the pollution and invite them to participate in the
20 cleanup. For the West Cap property there, there isn't
21 viable responsible parties, so EPA will implement that
22 cleanup there.
23 So that process would the enforcement
24 process would happen in '98, so hopefully by the end of
25 '98 we'll be entering the design phase for this
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1 cleanup, and then by 1999, the year 2000 we'll be out
2 in the field actually starting the cleanup operations.
3 So it is a long process. We have conducted
4 it, in my opinion, very thoroughly, and so I think
5 that's all I want to say about the Superfund Process.
6 A little bit about site background, like I
7 said, back in 1983 EPA put this site on the list, but
8 it was actually I don't know if we can turn on the
9 slide machine just briefly. Again, this is just
10 reference to our comment period on the proposed plan.
11 Next slide. This is a slide of the airport
12 back in the 1940's and *50's. I don't know the exact
13 year. Do you know the exact year, Paula, when this
14 slide was taken?
15 PAULA: '54.
16 MR. COOPER: '54. Okay. So as you can see,
17 back in the this is during the '50's, and I'm sure -
18 - it looks very similar. Maybe the airplanes looked a
19 little older during the '40's, but this was basically
20 what the developed part of the Tucson Airport looked
21 like, and what has happened as you can see these, what
22 we call the Three Hangars Complex was there, and that's
23 the facility that is just located right down El Vado
24 Street. You can see it as you step out on the street.
25 And there were several starting in 1942 all the way
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1 to I960, there was various military contractors that
2 occupied these hangar buildings. But they were
3 carrying out contracts on behalf of the Air Force
4 basically to modify aircraft which include machine and
5 engine parts, degreasing operations, taking the
6 coatings off airplanes and things like that.
7 The first tenant was a company called
8 Consolidated Aircraft that was followed by Grand
9 Central Aircraft Company, and then followed by Douglas.
10 Those companies did use TCE and other VOC
11 type contaminants, and but they weren't the only
12 parties that were or this wasn't the only operation
13 going on here on the south side that was using TCE.
14 Just to the south of the airport during the
15 '50's, Hughes Aircraft started operations. That was on
16 Air Force property, and they started their operations
17 there, and they had large-scale industrial operations
18 using TCE and other contamination also.
19 So it's EPA's belief that it was during the
20 440's and during the '50's that based on activities at
21 that airport and at Hughes there was TCE released to
22 the environment at that time that contaminated soil and
23 groundwater.
24 It wasn't until 1981 that the TCE turned up
25 in the south side's drinking water supply and the
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1 contaminated wells were immediately shut down. So, and
2 then shortly then I said in '83 is when EPA decided to
3 place this site on the Superfund list.
4 Yes, Tom?
5 MR. STUBBELFIELD: I think you misstated it.
6 1981 was the first time they tested for it.
7 MR. COOPER: Right.
8 MR. STUBBELFIELD: It was in the water before
9 1981 .
10 MR. COOPER: Oh, absolutely.
11 MR. STUBBELFIELD: And they didn't know about
12 it.
13 MR. COOPER: Right.
14 MR. STUBBELFIELD: So 1981 was the first time
15 that they knew it was in the water. So then you tell
16 me in that picture which way is north?
17 A MEMBER OF THE AUDIENCE: It's looking
18 south.
19 MR. COOPER: We're looking south.
20 MR. STUBBELFIELD: Looking south?
21 MR. COOPER: So Hughes was eventually built
22 back here?
23 A MEMBER OF THE AUDIENCE: Yes.
24 MR. STUBBELFIELD: Where is the in that
25 picture where is the airport transport terminal?
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1 A MEMBER OF THE AUDIENCE: 9 o'clock.
2 A MEMBER OF THE AUDIENCE: Right there.
3 MR. COOPER: This was the original Tucson
4 Airport starting in 1948.
5 MR. STUBBELFIELD: Yes, but you go down a
6 little bit. I came dropped it down, those buildings
7 right in there were the buildings that you went through
8 to get on the airplane.
9 MR. COOPER: Oh, really?
10 MR. STUBBELFIELD: Yes.
11 MR. COOPER: Okay.
12 MR. STUBBELFIELD: Because I went in there
13 many times.
14 MR. COOPER: All right. There you go.
15 Also I forgot to mention so there was also
16 some other operations, for example, that we're talking
17 about tonight. The Burr-Brown Corporation began their
18 operations. They are just located off the map. I'll
19 to get to that location. They started in 1965, and
20 they started producing electronic components, and they
21 used TCE in their operations.
22 And then a company called West-Cap Arizona
23 began in 1983, and they were located near the airport
24 also. I said 1963, excuse me, not 1983. And they
25 manufactured electrical capacitors and other equipment
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1 and EPA believes they used TCE in their operations
2 also.
3 So I talked about former operations here, a
4 little bit of the history, that the groundwater
5 contamination was actually formally detected in 1981,
6 and the contaminated wells were shut down, and I think
7 that's any questions on the site background. I'm
8 just kind of breezing through this so we can get
9 straight to the purpose of tonight's meeting and to
10 talk about EPA's proposed plan for the airport
11 property, Burr-Brown, and West-Cap.
12 PAUL FISHER: I have one question.
13 Approximately how long were the TCE contaminants in the
14 groundwater prior to being detected to the best of the
15 EPA's estimates?
16 MR. COOPER: Okay. EPA, we don't we have
17 no estimate of that. Other parties have tried to
18 figure out exactly when the TCE hit the groundwater.
19 There was some it is documented that a well near
20 Hughes was detected that had excess chromium
21 contamination, and that was detected, I couldn't tell
22 you off the top of my head, in the 450's sometime.
23 There was also some private wells just west
24 of the airport, just west actually right here.
25 That's where we are right now. Pretty much in the
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1 military area and their wells became contaminated.
2 Those wells were never detected. You know, back in the
3 *50's there wasn't a laboratory method to detect for
4 TCE, and but they were grossly contaminated. The well
5 owners documented that the well owner said that
6 their the water had a very poignant, you know,
7 chemical smell. And so those private wells were shut
8 down, and that happened in the mid '50's also.
9 So in the mid '50's there was some, at least
10 some indirect evidence that the groundwater was
11 contaminated, you know, with some type of organic
12 compounds, probably TCE.
13 Okay. Any other questions about site
14 backgrounds?
15 All right. I'm going to move this is
16 another old photograph from the '50's of the Hangars
17 Complex.
18 Next slide. Here's a photograph inside the
19 hangar, and you can see that there were workers here
20 working on various engine parts and so on. It's a very
21 the Hangars Complex has a very interesting history.
22 A lot of the military contractors, for example, Grand
23 Central, they had their own internal newsletters, and
24 EPA was able to track down and the internal newsletters
25 that described various operations that were going on
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1 here and show provided photographs such as this.
2 Okay. Next slide. Okay. EPA's proposed
3 plan is broken up into four parts. Okay. I'm going to
4 talk about each part one at a time.
5 The first part is for areas of soil
6 contamination that we found with TCE and other VOCs.
7 VOC stands for volatile organic compound, and it's
8 basically a chemical that's very similar to TCE. We
9 can call, you know, for example, perchloroethylene or
10 methylene chloride or chemicals like that. But usually
11 I'm going to start, you know, I'm going to use TCE
12 quite often in my presentation because people are
13 familiar with that, but when I say TCE I may not I
14 might mean other VOCs might involved also. But these -
15 - TCE and VOCs behave in a similar fashion. So we
16 group those areas of contaminates altogether in one
17 area for one remedy.
18 And EPA's preferred remedy or what we're
19 recommending to clean up the soil contaminated with TCE
20 is a technology called soil vapor extraction with air
21 pollution controls.
22 Okay. The next slide is not going to be well
23 seen. I don't if people I want to give you an idea
24 of where we found I don't know if you want to come
25 on up. This map shows out of all the investigations
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1 that we conducted at the airport and Burr-Brown
2 Corporation is here and West-Cap is here, we have found
3 TCE and VOC contaminated areas very much so around the
4 Three Hangars Complex, and where you see red dots is
5 where we found higher concentrations of TCE where EPA
6 is recommending that soil vapor extraction is
7 implemented around in the Three Hangars area for sure.
8 Where you see these green triangles is where
9 we have found TCE chemicals at lower concentrations.
10 We haven't finished our investigations yet, but if our
11 investigations show that the TCE down in these areas,
12 and also there's two locations at the West-Cap
13 property, if our investigations show that the TCE at
14 those areas are also of a significant threat to human
15 health, EPA is going to implement soil vapor extraction
16 there also.
17 So we're definitely recommending soil vapor
18 extraction in the Three Hangars area, and perhaps soil
19 vapor extraction will be implemented at these other
20 areas. Okay. So that's the locations we're talking
21 about.
22 Now, I'm going to give you a little bit of
23 information about soil vapor extraction.
24 Next slide. Okay. Soil vapor extraction
25 technology works on the principle that TCE and other
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1 chemicals like TCE, they like to evaporate. They like
2 to be in the gas phase. So when TCE is spilled on the
3 ground, often times what will happen is that some of it
4 will immediately evaporate and just go straight into
5 the atmosphere. The rest will sink down and go below
6 the first couple feet and go down into the deeper part
7 of the soil where it will stay, but even when it's
8 underground, it likes to evaporate underground. So
9 most of the TCE that you will find in the soil zone
10 will be in vapors. We call them VOC vapors or TCE
11 vapors. So it's like a big underground gas area of TCE
12 underground.
13 So what we do is put a we drill a well and
14 sink it down here. We don't go all the way down to the
15 groundwater zone, but we will before the groundwater so
16 we're still in the dry soil area, and we'll put a well
17 here and screen it, and then we'll put a vacuum blower
18 so we can basically vacuum out or suck out, extract out
19 the TCE gas from the soil zone and take it to a
20 treatment unit.
21 Okay. So this is the technology that we are
22 recommending that will be built at Three Hangars. The
23 treatment unit at this time, EPA is recommending that
24 four design options are left in the proposed plan. The
25 treatment unit will either carbon, a carbon filter
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1 system where the TCE comes in here and sticks onto
2 carbon particles or we'll use what's called resin
3 adsorption where the TCE gas will come here and stick
4 onto resin beads.
5 In both of those technologies when the carbon
6 or the resin beads become full of TCE, then that
7 treatment unit or the cartridges inside will have to be
8 taken away and disposed of at a landfill. So that's
9 one type of treatment.
10 The other types of treatment that we might
11 use down the road as a design option are what's called
12 thermal oxidation or catalytic oxidation. That's
13 different. When the TCE vapors come into a thermal
14 oxidation unit, they're basically burned right there on
15 site, and we'll have an air pollution control mechanism
16 on the top of the thermal oxidation unit, so there's no
17 more TCE left anymore, so there's nothing to be taken
18 to a landfill. And the same basically is true with
19 catalytic oxidation. Those are both, you know,
20 destructive type burning type treatment technologies.
21 We're keeping all four in our proposed plan.
22 We haven't decided which type of TCE vapor treatment
23 technology we're going to use at this time. It depends
24 on what type of mass flow rate and other designs
25 options.
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1 So if one of those vapor treatment
2 technologies, you know, doesn't sound right to you, you
3 know, send me a comment on: I don't want, you know, to
4 use thermal oxidation or I don't want to use carbon or
5 something like that. Otherwise all four will be left
6 in the Record of Decision, and then we'll make a final
7 decision when we're in the design phase and we know
8 exactly how to design our soil vapor extraction unit.
9 So, okay, I'm going to take questions only if
10 they're clarifying type questions.
11 MR. STUBBELFIELD: I want to ask you a
12 question because I think you made a mistake.
13 MR. COOPER: Okay.
14 MR. STUBBELFIELD: I don't think our resin
15 vapors take away and burn it. I think you keep and
16 remove the TCE and then reuse them.
17 MR. COOPER: Right. Okay. With the resin
18 beads, the TCE sticks on there. Then when the resin
19 beads become saturated with TCE, you turn off you
20 can basic well, you heat up the beads and then you
21 chill, and so the TCE becomes back into gas form, then
22 you chill that gas and it becomes a liquid TCE. Then
23 the liquid TCE goes into a drum, but you still have to
24 do something with the TCE. Then that drum full of
25 liquid TCE is taken away to a landfill.
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1 MR. STUBBELFIELD: But the beads can be
2 reused?
3 MR. COOPER: The beads are yes. The beads
4 are reused. You're right.
5 MR. STUBBELFIELD: And in the case of those
6 plans you have two sets. You have one set of beads
7 being used, one set that's being set aside.
8 MR. COOPER: Correct.
9 MR. STUBBELFIELD: And as soon as one set
10 fails, you take that one out and use the one that's set
11 aside.
12 MR. COOPER: Right.
13 MR. STUBBELFIELD: Okay.
14 MR. COOPER: I just wanted to get across the
15 point that with the carbon and the resin beads, the TCE
16 is just kept here and then eventually it has to go to a
17 landfill. With the thermal oxidation the catalytic
18 oxidation, that's a different that's totally
19 different. We're burning the TCE right there on the
20 spot.
21 Okay. Next slide. This is kind of a layout
22 of how soil vapor extraction system might look. Where
23 we have these white pipes go into the ground, but down
24 are this pipe goes underground and into the soil
25 zone where that's where we have our vapor extraction
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1 wells, and so we basically will be sucking the TCE gas
2 out, and then it will go into a pipeline, and there
3 will be a whole bunch of wells like this. They're go
4 through a network of pipelines that will lead to a
5 treatment unit.
6 Next slide, please. As you can see here, the
7 pipelines going in to the front end of a treatment
8 unit.
9 Next slide. And this is kind of the back
10 part. Can everyone see this okay? It's the back part
11 of the treatment unit. It's about I don't know, ten
12 feet tall. This is actually a carbon treatment unit
13 where so the gas, the TCE gas comes in the back part
14 of this carbon treatment unit, so the TCE starts to
15 stick on the carbon, and then the gas will come out
16 here again. And just to be extra safe, we send it
17 through yet a second carbon treatment unit so the
18 little bit of remaining TCE will stick onto the second
19 set and then out the back of this second carbon
20 treatment will the air will come out without any
21 TCE, and then all the TCE gets trapped in here. So
22 this is just an example of carbon vapor treatment. I
23 don't have any pictures of the other ones.
24 Okay. One last thing I wanted to say about
25 EPA proposal for the TCE soil is that we might
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1 incorporate some, what we call enhancements to the SVE
2 process to enhance the extraction of the TCE vapors or
3 the TCE gas from underground/ and those enhancements
4 include capping the ground. That means just usually
5 just putting a pave the area. The Three Hangars
6 area is already paved, but there might be other areas
7 that we might want to pave the ground. That helps us
8 suck out the vapors better.
9 We might do something called pneumatic
10 fracturing, which is injecting air and basically kind
11 of shaking up the geology a little bit so we can free
12 up of the gas so the gas will flow more freely in the
13 soil zone.
14 We might do what's call dual-phase
15 extraction, which is extract ground water to lower the
16 water table a little bit, and I'll explain that in a
17 minute, but when you lower the water table then that
18 frees up a little bit more soil that we can extract
19 soil gas from.
20 We might do what's called bio venting, which
21 is designing your soil vapor extraction system to
22 augment naturally occurring bacteria in the soil zone
23 to which will eat TCE and other contaminants.
24 So those are more design options that we
25 might do as we implement SVE remedies at the site.
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1 Okay. Our next our second proposal as
2 part of this proposed plan is to clean up soil
3 contaminated with PCBs, and in this we've included some
4 what we call pipeline sludge, and I'll explain that in
5 a minute.
6 First of all we have another acronym here.
7 This stands for polychlorinated biphenyls. It's a
8 chemical that was used historically again. It's very
9 different than TCE. First of all it was used as a
10 fluid in electrical transformers and hydraulic fluids,
11 and it was basically used as a like as an insulator
12 type fluid because PCBs can absorb a lot of heat, and
13 so you if you want like your electrical equipment to
14 stay cool or your engine motor to stay cool, you can
15 put PCBs in the electrical equipment or in the
16 hydraulic fluid of your motors so that will absorb a
17 lot of the heat so your other engine parts can stay
18 cool.
19 All right. Unlike, you know, how I said when
20 you dump TCE on the ground, the TCE will either
21 evaporate or sink down deeper, PCBs act very
22 differently. When you dump them on the ground, they
23 don't evaporate or they don't it's very difficult
24 for them to evaporate, and they won't sink down very
25 deep either. They are attracted to soil particles. So
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1 they'll stick to the soil right at the ground surface
2 or maybe they'll sink down a couple feet, but as long
3 as someone is not pouring water on top of the soil
4 pushing them down deeper, just average rain water will
5 only push the PCBs a couple feet in the soil. So it's
6 a very difficult I mean very different situation
7 than TCE, and actually it makes it easier to clean up
8 because the PCBs' are right there right near the ground
9 surface.
10 Next slide. This is our visual aid that
11 doesn't work. This is the location do you want to
12 turn off the slide projector. This shows the locations
13 of where we plan on cleaning up PCB contaminated soils.
14 First of all I want to tell you that where
15 the green triangles are, that's where EPA asked several
16 private parties to conduct a removal action, and we've
17 already cleaned up the PCB soil contamination a little
18 bit on the airport property and all along El Vado Road.
19 So basically all the way from Nogales Highway behind
20 the homes along El Vado Road behind this church all the
21 way to Geronimo. So this area has already been
22 completed.
23 We have three other places where there's PCBs
24 above our cleanup standards that we feel need to be
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1 cleaned up right along here. And then here, the Three
2 Hangars Complex, what happened is that underneath the
3 paved areas there is some underground pipeline that the
4 military contractors used for waste disposal, and those
5 pipelines are not being used anymore. We've tracked
6 that, but inside each of those pipes there's a sludge.
7 It's a very dry/ caky sludge right now that is
8 contaminated with PCBs and some metals and some VOCs
9 also. So we're going to so that's part of this
10 overall cleanup for the PCB contaminated soils, too.
11 And so these pipelines are basically in this area here
12 underneath the Three Hangars Complex and just outside
13 on the south side of the Three Hangars Complex.
14 Okay. Next slide. This was EPA's
15 recommended remedy again was to dig up the PCB
16 contaminated soils and to dig up the pipeline sludge
17 that's inside those pipes. This is an example of
18 digging up the contaminated soil when we were doing
19 just earlier this year when we were digging up the PCB
20 contaminated soil at the airport. Basically use a
21 front loader and scoop it up. First we delineate. We
22 already know the areas that need to be cleaned up
23 already, and that's kind of shown there on the map. So
24 we bring in these front loaders and basically scoop up
25 the soil.
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1 Next slide. That's not really maybe the
2 next slide's better. So this shows the front loader
3 dumping the contaminated soil with PCBs into a bin.
4 They will either go into these large bins, which are
5 then put onto trucks, or sometimes they're loaded right
6 onto a big truck that has the container right on it.
7 Okay. And then basically these trucks or
8 bins are covered with tarps to make sure the soil, you
9 know, dust can't fly away, and the trucks will drive to
10 an approved landfill for disposal.
11 Next slide. This is a slide showing the
12 contaminated soil being placed into a bin, and when the
13 soil is placed, we spray a little bit of water just to
14 make sure that we don't have any dust flying around and
15 getting into the environment when we're loading up our
16 trucks.
17 So that's basically our proposal for the PCB
18 contaminated soils and the pipelines, that we're going
19 to dig them up and take them to a landfill outside of
20 Tucson.
21 Next remedy is the airport landfill also
22 known at the TAA landfill, Tucson Airport Authority
23 landfill. EPA preferred remedy is to close this
24 landfill by covering it with two feet of clean,
25 compacted soil, and we're going to continue some soil
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1 and groundwater monitoring.
2 The landfill is located turn off the
3 just very quickly. The landfill is located right here,
4 right off Arrow Park Drive. Gates Leerjet is located
5 right over in here. Desert Diamond Casino is over
6 here. So basically like right across the street from
7 Desert Diamond Casino is the TAA landfill. It's not
8 very large. I have a couple slides of it.
9 There is some surface debris on top of the
10 landfill that will be some of it will be removed,
11 but there's also some large chunks of concrete such as
12 that that we're not going to be able to remove.
13 Next slide. So this is the way it looks like
14 right now. I don't know off the top of my head, you
15 know, the area of this landfill. Steve?
16 STEVEN QUIGLEY: Five acres.
17 MR. COOPER: Five acres? About five acres.
18 EPA thought that the military contractors from the
19 Three Hangars were taking some of their TCE and driving
20 it down to the this landfill and disposing of it at the
21 landfill. So EPA required extensive investigations of
22 the landfill by putting in groundwater monitoring wells
23 and soil gas wells. As it turned out, nothing much
24 turned up. We found some very low levels of TCE down
25 deeper, but we really didn't find much contamination
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1 there other than this surface debris.
2 So what we'll basically do is have a slide of
3 a finished landfill that what can be removed will be
4 removed, and then we'll be bringing we'll kind of
5 we'll bring in clean soil and kind of smooth out this
6 area and grate and basically follow State of Arizona
7 guidelines for landfill closure.
8 Nobody has been bringing anything to this
9 landfill for quite a while. I forget the date. '70's,
10 early '80's. But this will be basically our proposal,
11 too, put final closure to the landfill by putting this
12 soil cap over the top of it.
13 Okay. Next slide. Our fourth and final
14 proposal as part of this proposed plan concerns what we
15 call the shallow groundwater zone, and it is
16 contaminated with TCE and other VOCs. Our preferred
17 remedy: we're recommending that we pump out
18 contaminated ground water, we remove the VOCs from the
19 water, and then we put the water to an appropriate use,
20 and there are several components of this remedy I'm
21 going to explain.
22 First of all the location of the shallow
23 groundwater zones that is contaminated. First of all
24 you can see it's basically this yellow area here. It
25 basically starts this shows the shallow groundwater
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1 zone that is contaminated. It starts at the Three
2 Hangars Complex and it has migrated a little bit to the
3 west basically cutting off right about where Geronimo
4 Avenue is. So it's not that big of an area, and to
5 give you an idea of how this works I think we're
6 okay on that as far as location. I might refer to this
7 again.
8 You know how I said during the '80's we did
9 our investigations of the regional aquifer, and we've
10 already got our cleanup operations in place for the
11 regional aquifer. When we started to look into the
12 soil contamination here at the airport, we noticed that
13 in a certain localized area right on the west side of
14 the airport we found that the water table was unusually
15 higher than the water table in other parts of the site.
16 At other parts of the site if you start to drill down,
17 you won't hit the water table until maybe 120 feet or
18 130 feet below ground surface.
19 That's the beginning of what we call the
20 regional aquifer. But at other places we just we
21 noticed that the water table is elevated, and so we
22 gave it a different name, and I'll explain why because
23 ,it has different characteristics than our regional
24 aquifer.
25 So we call it a shallow groundwater zone. So
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1 we basically have a dry soil zone, and then we'll have
2 a shallow groundwater zone/ and then below that is the
3 regional aquifer. So the regional aquifer again is our
4 drinking water supply. The shallow groundwater zone, I
5 have some visual aids. I don't know if anyone saw
6 those, that the type of soil that you encounter in the
7 shallow ground water zone is a clay, a very low
8 permeable clay, and it doesn't produce much water. No
9 one can drink water from the shallow ground water zone
10 because you basically probably couldn't pump enough
11 water out to serve, you know, more than a home or two.
12 It's the EPA's position that contamination in
13 the shallow groundwater zone can leach down into the
14 regional aquifer. So that's why it's important to
15 address contamination in the shallow groundwater zone
16 even though even in the future probably people won't
17 screen a well to drink from that shallow zone, it can
18 pose an ongoing threat to our regional aquifer.
19 Next slide, please. Again, there's the
20 location of how we defined the contaminated area of the
21 shallow groundwater zone.
22 Next slide. First thing I want to tell you,
23 this is the Three Hangars area, the south side of the
24 Three Hangars area as they look today. This slide was
25 just taken a couple days ago. And what we found is
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1 that, again, remember the old slide with the military
2 contractors. This is the same complex where there was
3 chemical use in this area, and we believe that because
4 the way the TCE was disposed of, especially in these
5 buildings that sit just on the south side, especially
6 this blue building here and this building here, we
7 believe that TCE was disposed of at these buildings in
8 very high concentrations, and they were disposed of
9 basically right near or at these buildings.
10 And so the TCE went down, and what we're
11 finding is that there's a lot of TCE in this shallow
12 groundwater zone. And we've done a lot of studies on
13 during our over the last five years on what are the
14 concentrations of TCE in this shallow groundwater zone
15 in this area, and then we did some studies on can we
16 pump it out.
17 So what we found as far as concentrations, we
18 found that in this area that as you basically this
19 area that you see in this picture in this area here,
20 the concentrations are very high and they remain
21 around, you know, fifty thousand parts per billion of
22 TCE, and which is a very high concentration. It's
23 indirect evidence that we probably have liquid TCE or
24 what we call dense nonagueous phase liquid or pure TCE
25 sitting down in the shallow groundwater zone.
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1 And the other problem when we did a
2 treatability study to see if we could pump out the TCE
3 from the shallow groundwater zone, we found that that
4 clay layer was very difficult to pump out. So what EPA
5 is recommending is that because we have high
6 concentration TCE that is stuck in the this shallow
7 groundwater zone clay layer, that in that area that
8 we're showing, this red zone just on the south side of
9 the Three Hangars, that we're saying that we're still
10 going to go in there and pump and try to address the
11 contamination, but it's EPA's proposal at this point is
12 that just in this zone right here that we will not be
13 able to restore the shallow groundwater zone back to
14 drinking water quality. We won't be able to take the
15 fifty thousand parts per billion area down to five
16 parts per billion. That's the safe drinking water
17 criteria or drinking water.
18 So we call this the TI or technically
19 impractical zone for groundwater restoration. So I
20 think that's a very important point I want to make is
21 that so in this zone right here, we're saying that the
22 shallow groundwater zone will probably always have some
23 high levels of TCE. We are going to pump some out, but
24 we don't think that it will go down to drinking water
25 quality. But we do believe we'll be able to contain
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1 the TCE and the high concentrations of TCE we'll be
2 able to contain it, and I'll explain how we're going to
3 contain it, and we'll be able to keep it in this red
4 area, and we'll be able to keep it from continuing to
5 spread outside this area and to keep it from spreading
6 downward.
7 Now, the rest of the shallow groundwater zone
8 in the yellow area, EPA is also going to put in wells
9 there, and we're going to try to restore this area back
10 to drinking water quality.
11 Next slide. All right. This shows it
12 says groundwater treatment system. It's only basically
13 half of a system. This shows the extraction process
14 for groundwater pump and treat system. So what we do,
15 just like with the soil vapor extraction wells, but
16 this time we put our wells down deeper. We drill a
17 well down and screen it in a groundwater zone. It's
18 basically a soil it's soil down here that's
19 saturated with water, and so we'll put one here. This
20 is what we call we'll put some in our hot area or our
21 TI zone, and when you pump on these wells, the water
22 and the TCE along with it is drawn toward the
23 extraction wells, and so that's the water will come
24 from all different directions, from the side, so it's
25 three dimensional even upward from the bottom we'll
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1 have some influence.
2 So that's what I mean by saying we will
3 contain the contamination, in this in the TI we can
4 pump a sufficient number of wells to contain the TCE to
5 keep it going to keep the water and the TCE heading
6 towards these wells and to stop the TCE from leaching
7 downward. Okay.
8 At other portions of the shallow groundwater
9 zone, we're going to put in more wells to actually try
10 to extract groundwater contamination, and there will be
11 containment, but we'll also be trying to remove enough
12 TCE to restore the groundwater zone.
13 Okay. Also on this slide I talked about how
14 difficult this shallow groundwater zone, because it's
15 full of clay, how difficult it is to extract water out.
16 One enhancement that EPA is including in its proposal
17 is a technology called electro-osmosis, and that is a
18 technology where you apply an electrical current so
19 that the water is polar, and so you I think it's the
20 whatever, positive or negative, your groundwater
21 extraction well becomes set up so that water will be
22 attracted to the extraction well.
23 So we'll be pumping it, so that's more of a
24 hydraulic attraction, and then we might introduce this
25 technology called electro-osmosis where you set up an
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1 electrical system through here where the water will be
2 attracted to the groundwater well. That's the hardest
3 thing about cleaning up the shallow groundwater zone is
4 trying to get water to move through it so we can flush
5 out the TCE.
6 Another enhancement that we might try is
7 called bioremediation, and that is something that also
8 happens underground in the shallow groundwater zone
9 where we add certain amendments to the groundwater to
10 basically feed naturally occurring bacteria that exist
11 in the shallow groundwater zone, and we try to create
12 an environment so this naturally occurring bacteria
13 will eat the TCE.
14 So those are two enhancements that we' re
15 going to try to that we may try in the shallow
16 groundwater zone to expedite the cleanup.
17 Okay. So again, when we pump on these wells,
18 the TCE water comes out and it will go to a treatment
19 unit which this is a treatment unit at the Air National
20 Guard Base. Basically this treatment unit uses air
21 stripping technology which is one of I think three
22 treatment technologies that EPA is proposing here.
23 What happens is the TCE water comes in the
24 top and air is blown up through the bottom, and so the
25 TCE basically you got raked out of the water so you
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1 have clean water coming out of the bottom of the
2 treatment unit and the air coining out the top has TCE
3 in it, and so the air coming out the top has to go
4 through like a carbon system to take the TCE back out
5 of the air. So this is called air stripping
6 technology. It's one of the water treatment
7 technologies that EPA is proposing to treat the water.
8 We're also proposing to use carbon filters or
9 a technology called UV oxidation, and UV oxidation
10 basically ultraviolet light is shined on the TCE water,
11 and that causes the TCE molecule to break apart right
12 there in the water phase.
13 So those are the treatment technologies that
14 we might build right there. So right near the Three
15 Hangars Complex will be, you know so we'll be
16 putting groundwater extraction wells in the shallow
17 groundwater zone, piping that water to a centralized
18 treatment plant somewhere near the Three Hangars
19 Complex, and that treatment plant will use either air
20 stripping technology, carbon technology, or ultraviolet
21 light.
22 Another idea that we might use is extract the
23 water and put it in a pipeline and send it down to the
24 Hughes treatment plant and have the treatment done down
25 at that Hughes Missile Systems.
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1 So any one of those four treatment
2 technologies might be implemented.
3 If air stripping is used, then where we put
4 the TCE in a gaseous phase, then we'll have these air
5 pollution control technologies in place also.
6 Okay. Next slide. That's me to try to to
7 give you an idea how big I think the this is
8 the, just to give you a size, I'm six foot, so the air
9 stripping here is only six feet tall.
10 I expect that the size of the treatment unit
11 that we'll be building at the Three Hangars Complex
12 will be, you know, along, you know, about this no
13 bigger than this. There's another slide that kind of
14 gives you because of the water flow rate is not
15 going to be that much, we don't need a very large
16 treatment unit. So it's going to look something I
17 mean if you want to get an idea of the scale, it's
18 going to be something along this size. I believe a
19 slide I think that's it.
20 So just to summarize, I know I've bored
21 everyone to death but I have to do this for the record.
22 We're going to use EPA is proposing soil vapor
23 extraction for TCE in soil, TCE and VOCs in soil.
24 We're going to treat the VOC vapors at a treatment
25 unit, and we're going to remove the VOCs from the soil,
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1 keep taking the TCE out so the groundwater will not
2 become recontaminated.
3 Next slide. We're gong to dig up and
4 transport PCB contaminated soils and sludges to an off
5 site approved landfill. We're proposing to cover the
6 airport landfill with two feet of clean soil and
7 continue monitoring, and proposing to pump out TCE and
8 other VOCs from the shallow groundwater zone. We're
9 going to use groundwater extraction wells to extract
10 and contain groundwater contamination, pipe that
11 contaminated water to a treatment plant to remove the
12 VOCs, restore the shallow groundwater zone to drinking
13 water quality wherever technically practical and
14 prevent the VOCs in the shallow groundwater zone from
15 spreading down into the regional drinking water
16 aquifer.
17 Thank you for listening.
18 MS. HERRERA: Are there any questions.
19 MR. COOPER: Now, we go to the formal
20 question and answer period. Question period.
21 MS. HERRERA: Yes, are there any questions
22 about the last part of his presentation?
23 MR. COOPER: Yes.
24 MR. STUBBELFIELD: I have several as you
25 would expect.
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1 MR. COOPER: Okay.
2 MR. STUBBELFIELD: The shallow groundwater
3 zone, how well have you identified it?
4 MR. COOPER: How well have we identified it?
5 MR. STUBBELFIELD: Identified the shallow
6 groundwater in relationship to the aquifer below it.
7 MR. COOPER: You mean as far as how thick it
8 is?
9 MR. STUBBELFIELD: No. You had us shown out
10 there an area. I infer from what you show there that
11 this is a sort of a basin.
12 MR. COOPER: Right. A basin.
13 MR. STUBBELFIELD: A basin, a sort of a
14 basin. What's keeping them from moving along the
15 basin, along the gradient?
16 MR. COOPER: Well, the shallow groundwater
17 zone has its own gradient, too. Not only does the
18 water go downward, it moves westwardly.
19 MR. STUBBELFIELD: I understand that, but
20 does it reach a point that it drops off into the lower
21 it drops off of the shallow groundwater zone?
22 MR. COOPER: Yes. We've identified at least
23 a western extent here. We put some wells over here,
24 and when we drill down, we don't hit this shallow
25 ground water zone. We go all the way down
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1 MR. STUBBELFIELD: Okay. What happens to the
2 shallow groundwater when it goes down the gradient?
3 MR. COOPER: It's leaching into the regional
4 aquifer.
5 MR. STUBBELFIELD: Okay. So it has the
6 contaminated TCE?
7 MR. COOPER: Yes, it is.
8 MR. STUBBELFIELD: And it's contaminating the
9 aquifer?
10 MR. COOPER: That's EPA's position, yes.
11 MR. STUBBELFIELD: Okay. Now, then that
12 gradient's going to the northwest?
13 MR. COOPER: Right. That's uh-huh. Well,
14 the shallow groundwater basically due west, yes, like
15 this direction here.
16 MR. STUBBELFIELD: So it's going due west or
17 northwest, one of the other.
18 MR. COOPER: Right. Close enough.
19 MR. STUBBELFIELD: And how deep is that
20 shallow groundwater zone?
21 MR. COOPER: The top of it is about 85 feet.
22 MR. STUBBELFIELD: Okay. How deep is the
23 zone there that you have the red in?
24 MR. COOPER: How the
25 A MEMBER OF THE AUDIENCE: Excuse me. He may
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1 want to identify himself.
2 MR. COOPER: This is Tom Stubbelfield
3 talking.
4 MR. STUBBELFIELD: How deep is this aquifer
5 right there?
6 MR. COOPER: This zone?
7 MR. STUBBELFIELD: No, the red.
8 MR. CO'OPER: Where the red is?
9 MR. STUBBELFIELD: The red is primarily clay
10 or is it 100 percent clay?
11 MR. COOPER: It's primarily clay. It's just
12 at the top of the water table is about 85 feet.
13 MR. STUBBELFIELD: But doesn't that stand
14 higher than that?
15 MR. COOPER: The clay, yes. We have clay
16 above the top of the clay is I think 70 feet below
17 ground surface, 75 feet, so we have some clay that's
18 it's head is sticking up out of the water.
19 MR. STUBBELFIELD: Have you used tensiometers
20 to see how dense how much moisture it has in it?
21 MR. COOPER: Yes. I know we've yes, we
22 have. It's not, you know, what happens if you start
23 drilling down deeper and deeper, the soil gets just
24 damper and damper. It's kind of a tricky business to
25 decide where it actually where we hit groundwater
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1 because it just gets damper and damper.
2 MR. STUBBELFIELD: But at the top side,
3 there's not much what is it 100 percent saturated,
4 50 percent saturated? What's the saturation?
5 MR. COOPER: Well, that's what at 85 feet
6 that's where we're saying below that that's where it's
7 100 percent saturated.
8 MR. STUBBELFIELD: Okay. How about 70 feet?
9 MR. COOPER: Then it's less than 100 percent
10 saturated.
11 MR. STUBBELFIELD: But you still have TCE.
12 MR. COOPER: Oh, yes.
13 MR. STUBBELFIELD: Let's say at 70 feet.
14 MR. COOPER: At 70 feet, absolutely. Yes, we
15 do.
16 MR. STUBBELFIELD: And so is there any
17 indication that TCE moves more freely at that ground
18 level or does it move about the same?
19 MR. COOPER: Well, you mean well, there
20 we're not calling it ground water. We're calling that
21 part of the soil zone. So most of the transport would
22 be in gas in that area. So TCE moves a lot easier in
23 gas phase
24 MR. STUBBELFIELD: Since you have quite a bit
25 of liquid moisture there, how can you say it's gas?
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1 MR. COOPER: Oh, right. Well, it's the
2 capillary fringe. So some of it is wet, so some if it
3 is TCE dissolved in water, and some if it we have pore
4 spaces where it's dry and it's in the gaseous form. So
5 it's kind of a mixed bag in that area.
6 MR. STUBBELFIELD: Okay. Now, then, here I'm
7 sitting out here to defend this community, keep you all
8 from going out here with a half solution. How am I
9 going to be sure you're not going to let water drop
10 down and eventually get into the lower aquifer?
11 MR. COOPER: From the shallow groundwater
12 zone, especially in this area here.
13 MR. STUBBELFIELD: Especially in that area
14 there.
15 MR. COOPER: Right. Well, we hope through
16 our groundwater extraction wells, if we place them in
17 the right place, we're going to be creating a gradient
18 so the TCE in the water won't have any choice but to
19 head either up or over toward the wells, and we'll be
20 able to prove that through looking at water levels from
21 the regional aquifer and the water levels
22 MR. STUBBELFIELD: I get the impression that
23 you don't have very much movement of water in that
24 shallow groundwater aquifer.
25 MR. COOPER: Right. It's very sludgy.
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1 MR. STUBBELFIELD: And how are you going to
2 be able to discern if there's any water moving?
3 MR. COOPER: Well, if water comes gets
4 pumped out, we are moving water.
5 MR. STUBBELFIELD: Okay. I understand that,
6 but my concern is here is that you're not going to be
7 able to move water. It's going to set there like a
8 sponge, so it will be soaked up, full of TCE, stay
9 there for 100 years, and this community here is going
10 to have to be faced with the fact that sometime that
11 could break loose and contaminate the water table.
12 MR. COOPER: Well, we don't think that's
13 going to happen. In the middle of the shallow
14 groundwater zone there is what we call a gravel unit
15 that is much more porous than the clay, and we're
16 banking a lot on that that we're going to be able to
17 pump out of that gravel unit to get this gradient going
18 toward the extraction wells in the clay layers. It's
19 going to be a challenge, I agree, but we believe we can
20 contain the contamination in the shallow groundwater
21 zone.
22 MR. STUBBELFIELD: You're telling me now that
23 you anticipate being able to move that TCE out through
24 a pump and treat the wells. Now, be careful what
25 you're saying because other times I read in the this
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1 feasibility study, it says it isn't feasible to move
2 it.
3 MR. COOPER: It's not feasible to move enough
4 to restore the area to drinking water quality. So we
5 think that we can move enough water to get the gradient
6 going in the right direction to stop the leaching down
7 to the regional aquifer. That's all that we're
8 proposing basically in this area here. And to provide
9 assurances, we've got wells down at the regional
10 aquifer.
11 MR. STUBBELFIELD: Yes.
12 MR. COOPER: Okay. And we're going to
13 continue monitoring them, and so we'll know if this
14 community concern about this big break through coming
15 down, we will know if, you know we don't think it's
16 going to happen, but we will continue to monitor the
17 regional aquifer in this area to see if indeed stuff is
18 continuing to leach down from the shallow groundwater.
19 MR. STUBBELFIELD: How often will you test
20 the water in those rotten wells to make sure it's not
21 being contaminated with TCE from that shallow
22 groundwater?
23 MR. COOPER: How often? Right now we're
24 monitoring them every six months. Down the road, I
25 don't know what our final monitoring plan will be, but
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1 it will be some periodic
2 MR. STUBBELFIELD: What are you estimating
3 it's going to be? Are you going to have a we're
4 going to write a report about what we think about your
5 plan, and maybe in our report/ we want every week.
6 MR. COOPER: Okay. Well, I'm not comfortable
7 committing myself to a frequency
8 MR. STUBBELFIELD: Well, I'm just saying this
9 is one of the things that we may ask that you change
10 that thing to have it every week.
11 MR. COOPER: Right. You can certainly make
12 that as a comment on how frequent we should be
13 monitoring the regional
14 MR. STUBBELFIELD: Are you going to have
15 wells all around that area?
16 MR. COOPER: I can show you a map of the
17 wells that are located
18 MR. STUBBELFIELD: Well, as you're standing -
19
20 MR. COOPER: Yes, we've got wells
21 MR. STUBBELFIELD: No, no. I mean right
22 adjacent to that area.
23 MR. COOPER: Well, we didn't punch one right
24 yes, I think our closest regional well, D1, is right
25 here. We got some here.
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1 MR. STUBBELFIELD: I mean I like that. We
2 have to surround that whole area.
3 MR. COOPER: Well/ again, we've got one right
4 here. This is exactly
5 MR. STUBBELFIELD: And you're assuming it is
6 going down gradient, it's okay. I mean there's nothing
7 other than down gradient. It's not going to go down.
8 MR. COOPER: You're thinking it might go this
9 way?
10 MR. STUBBELFIELD: It could go anywhere.
11 We're sitting here with contamination that's highly
12 significant, and we don't want it to move at all.
13 Okay.
14 MS. HERRERA: I think that you should make
15 that an official comment, and what we're going to do
16 with the comments is
17 MR. STUBBELFIELD: Don't worry, I will.
18 MS. HERRERA: We will be required to look
19 into that option and to respond to it and consider it
20 while we're making our final decision.
21 MR. COOPER: Okay. Thanks, Tom. Yes?
22 MR. QUIGLEY: Craig, my name's Steve Quigley.
23 I just would like to point out two things. The first
24 is that EPA's belief of the ability to contain and pump
25 the groundwater within that zone is based on a 72-hour
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1 pumping test that was done in that area. So there is
2 some scientific basis for EPA's belief, not just
3 conjecture.
4 The second thing is that the frequency of
5 monitoring needs to be designed based upon the ability
6 of the clay to transmit the water, and the clay does
7 not transmit the water very quickly at all. So we will
8 reverse the flow from the clay to the regional aquifer
9 so the water flows up from the regional aquifer from
10 the clay and monitoring should be sufficient to make
11 sure that we measure the water levels and then
12 periodically measure the water quality.
13 Mr. Stubbelfield suggested weekly or made
14 a comment about weekly monitoring. I think you have to
15 look at how quickly the water actually moves on to the
16 side of frequency of testing.
17 MR. COOPER: Anymore questions?
18 MR. STUBBELFIELD: Excuse me. Will he verify
19 the water flows up through the aquifer?
20 MR. QUIGLEY: Presently the water level in
21 the clay is above the water level in the regional
22 aquifer. You have said you're concerned about the
23 vertical
24 MR. STUBBELFIELD: I agree with that.
25 MR. QUIGLEY: So what we are planning to do
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1 with this system is to pump in the shallow groundwater
2 zone so that the water level in the shallow groundwater
3 zone is below the water level pressure exerted by the
4 water in the regional aquifer. So the water will then
5 move up through the clay into the shallow groundwater
6 zone and be captured from the regional aquifer in those
7 extraction wells. That is the concept behind
8 containing getting the vertical contained as well as
9 the horizontal contained.
10 A MEMBER OF THE AUDIENCE: I'm still a little
11 dense on that particular thing because I'11 tell you
12 later on about it.
13 MR. COOPER: Okay. I didn't want to cut you
14 off. You're welcome to ask more questions. We're in
15 the formal question and answer period of our evening
16 tonight, so this is your opportunity. Raise your hand.
17 There's not that many of us here.
18 MR. CONRAD: I'm Steve Conrad. I have a
19 question for either Craig or Steve or whichever can
20 answer it. So what you're creating is an artificial
21 gradient that's opposite of the natural gradient.
22 MR. COOPER: Right.
23 MR. CONRAD: Have you ever done any studies
24 on how long you're going to have to do this? Is this
25 going to be a permanent solution or is it going to be a
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1 ten-year protection? How long do you project that this
2 pumping is going to occur?
3 MR. COOPER: We're in the TI zone because
4 we're not predicting to make it to a restoration to
5 drinking water quality. That is an in perpetuity, a
6 forever remedy that we will have to be pumping wells in
7 here at some rate to keep that gradient, that
8 artificial gradient going.
9 Now, what we hope we'll have in this Record
10 of Decision we will have what we call a reopener for
11 new technologies that maybe sometime down the road
12 there will be a new technology somebody will think of
13 that will help us figure out how to remove this TCE out
14 of the clay shallow groundwater zone. But until that
15 time, we're going to have to pump the wells, and we're
16 saying that it's going to be a until, you know,
17 forever. Forever pumping.
18 Here, where we are trying for restoration, I
19 don't think we've calculated a restoration time. I'm
20 not going to say the standard 20 or 30 years because I
21 think it's going to be a lot more. We say 20 to 30
22 years for restoration of the regional aquifer, but
23 that's where we're dealing with sandier soil where we
24 think we can get more flushing going on. Restoration
25 time for this area here, I do we have a prediction.
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1 I would guess, you know, maybe 50 years at best.
2 MR. STUBBELFIELD: Is this real clay?
3 MR. COOPER: Yes. The shallow groundwater
4 zone, the geology, that clay in the shallow groundwater
5 zone, it's the same in this whole area. What we
6 decided here is that we have the liquid TCE stuck in
7 clay. That's the area that we decided that was not
8 practical to try' to restore. Here it's still clay.
9 It's not going to be easy to try to restore, and I've
10 tried to explain to you a little a few of the
11 technologies that we're going to try to, you know, our
12 best to try to restore this area, but even trying to
13 restore the shallow groundwater is not going to be
14 something easy.
15 Okay. More questions, please.
16 MR. FISHER: My name is Paul Fisher. Now,
17 you're talking about the different methods of cleaning
18 it up. Of those methods thermal oxidation, how is that
19 cost effective as opposed to, you know, transporting it
20 to the dumping zone or a landfill? I mean does it cost
21 more or less in the long run, short run?
22 MR. COOPER: Right. The thermal oxidation is
23 a vapor treatment technology, one of four that we might
24 use for our for soil vapor extraction units. We'll
25 make a decision on which type of vapor treatment
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1 technology based on the cost effectiveness coming in on
2 the mass flow rate that we're dealing with.
3 So generally if you have a lower mass flow
4 rate, then carbon is your more cost-effective vapor
5 treatment technology. As you mass flow rate increases,
6 so if you start really pulling high concentration TCE
7 vapors, then carbon starts to become too expensive
8 because you have' to take this stuff to the landfill all
9 the time, and other technologies, such as the resin
10 adsorption or the thermal oxidation become more cost
11 effective.
12 So that's kind of a design question that
13 we'll be answering down the road based on the mass flow
14 rate that we get. So I don't know if that answered
15 your question exactly.
16 MR. FISHER: In essence it did.
17 MR. COOPER: Okay.
18 MS. HERRERA: Anymore questions?
19 MR. STUBBELFIELD: I want him to explain to
20 me how he' s going to reverse that water flow up through
21 that aquifer.
22 MR. COOPER: Okay. Can we do if it's all
23 right with you, can we do that after we close?
24 MR. STUBBELFIELD: I don't care when you guys
25 do it. I want to know how you're going to do it.
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1 MS. HERRERA: Okay. Let's open the formal
2 commentary. Are there any comments on what we're
3 doing?
4 MR. COOPER: Now, this is your time to
5 comment, and I'm not going to give an answer.
^6 MS. HERRERA: Any comments you make we will
7 be required to address them and to consider them while
8 we're making a final decision.
9 MR. STUBBELFIELD: I have a comment. Six
10 months is not often enough. At least once a month and
11 better once week.
12 MR. COOPER: For testing the regional
13 aquifer?
14 MR. STUBBELFIELD: Yes.
15 MR. COOPER: Uh-huh.
16 MR. STUBBELFIELD: For testing the wells.
17 MS. HERRERA: Any other comments?
18 MR. COOPER: Any other comments?
19 MS. HERRERA: Well, if there aren't any, we
20 should close the meeting. Once again, thank you for
21 coming, and I want to remind you that this is the
22 beginning of the public comment period. You can send
23 your comments in writing. You can come to tomorrow's
24 meeting and provide them verbally, and closing of the
25 commentary will be August 20th. Thank you.
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CERTIFICATE
STATE OF ARIZONA )
)
COUNTY OF PIMA )
SS.
BE IT KNOWN that I transcribed the
foregoing matter- pursuant to agreement; that I was then
and there a Notary Public in and for the County of Pima,
State of Arizona; and transcribed my stenographic notes
of the Environmental Protection Agency's Public Meeting
at the Faith Assembly of God Church on July 22, 1997,
and that the testimony of the participants was reduced
to writing under my direction, all done to the best of
my skill and ability.
I DO FURTHER CERTIFY that I am not a
relative or attorney of either party, or otherwise
interested in the events of this action.
Notary Public
My Commission Expires:
January 1, 2000
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