SEMS-RM DOCID # 100032393
Interim Record of Decision Amendment
Tucson International Airport Area
Superfund Site Area A
North of Los Reales Road
Tucson, Arizona
March 2023
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U.S. Environmental Protection Agency, Region 9
ID: AZD980737530
75 Hawthorne Street
San Francisco, California 94105
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Table of Contents
1.0 PART I: DECLARATION FOR THE RECORD OF DECISION AMENDMENT 1-1
1.1 Site N ame and Location 1-1
1.2 Statement of Basis and Purpose 1-1
1.3 Assessment of the Site 1-1
1.4 Description of the Revised Remedy 1-2
2.0 STATUTORY DETERMINATIONS 2-1
3.0 ROD DATA CERTIFICATION CHECKLIST 3-1
3.1 Authorizing Signature 3-1
4.0 PART II: DECISION SUMMARY 4-1
4.1 Site Name, Location, and Brief Description 4-1
4.2 Site History and Enforcement Activities 4-3
4.3 TARP Project Area 4-4
4.4 Air Force Plant 44 Project Area 4-6
4.5 Airport Property Project Area 4-7
4.6 Community Participation 4-8
4.7 Scope and Role of Response Action 4-8
4.8 Site Characteristics 4-9
4.8.1 Physical Characteristics 4-9
4.8.2 Site Hydrogeology 4-9
4.8.3 Contaminant Distribution 4-12
4.9 Current and Future Site and Resource Use 4-13
4.10 Summary of Site Risks 4-16
4.11 Remedial Action Objectives 4-18
4.12 Description of Alternatives 4-18
4.12.1 Alternative 1: No Further Action 4-19
4.12.2 Alternative 2: Monitored Natural Attenuation and Institutional Controls 4-19
4.12.3 Alternative 3: Enhanced Existing Pump-and-Treat System with UV- Peroxide Plus
Long-Term Monitoring and ICs (EPA's Preferred Alternative) 4-20
4.12.4 Alternative 4: Optimized Pump-and-Treat with UV-Peroxide and Partial Management of
Water by Reinjection to the Regional Aquifer Plus MNA and ICs 4-21
4.12.5 Alternative 5: Existing Pump-and-Treat with UV-Peroxide Plus In Situ Bioremediation
and MNA and ICs 4-22
4.12.6 Alternative 6: Existing Pump-and-Treat with UV-Peroxide Plus In Situ Chemical
Oxidation and MNA and ICs 4-22
4.13 Comparative Analysis of Alternatives 4-22
4.13.1 Threshold Criteria 4-25
4.13.2 Balancing Criteria 4-25
4.13.3 Modifying Criteria 4-29
4.14 Principal Threat Waste 4-30
4.15 Selected Remedy 4-30
4.16 Statutory Determinations 4-32
4.17 Protection of Human Health and Environment 4-32
4.18 Compliance with Applicable or Relevant and Appropriate Requirements 4-33
4.19 Chemical-Specific Applicable or Relevant and Appropriate Requirements 4-37
4.20 Location-Specific Applicable or Relevant and Appropriate Requirements 4-37
4.21 Action-Specific Applicable or Relevant and Appropriate Requirements 4-38
4.22 Cost-Effectiveness 4-38
4.23 Utilization of Permanent Solutions and Alternative Treatment Technologies 4-38
4.24 Preference for Treatment as a Principal Element 4-39
4.25 Five-Year Review Requirements 4-39
4.26 Documentation of Significant Changes 4-40
5.0 PART III: RESPONSIVENESS SUMMARY 5-1
6.0 REFERENCES 6-1
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List of Figures
Figure 4-1 TIM Superfund Site, Site Location, and Generalized Groundwater Plume Map 4-2
Figure 4-2 Summary Conceptual Site Model 4-11
Figure 4-3 1,4-Dioxane and TCE Concentration Contour Map 4-14
Figure 4-4 General Land Use Zoning Classifications, Tucson International Airport Area, Superfund
Site-Area A 4-15
Figure 4-5 Alternative 3 Site Map 4-31
List of Tables
Table 4-1 Summary of CERCLA Milestones for TIAA Superfund Site Area A North of Los Reales
Road 4-4
Table 4-2 Treatment and Cleanup Levels for Primary Contaminants of Concern 4-12
Table 4-3 Groundwater Risk Evaluation 4-17
Table 4-4 Remedy Alternatives and Estimated Cost 4-20
Table 4-5 Comparative Analysis of Alternatives (Excluding State and Community Acceptance) 4-23
Table 4-6 Chemical-Specific ARARs for 1,4-Dioxane and VOC-Contaminated Regional Groundwater 4-34
Table 4-7 Action-Specific ARARs for 1,4-Dioxane and VOC-Contaminated Regional Groundwater 4-35
List of Appendices
Appendix A Present Value of Cash Flow and Value of Cash Flow Over Time Calculation Summary Tables
TIAA SUPERFUND SITE AREA A
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Acronyms
and
Abbreviations
Hg/L
microgram per liter
ADEQ
Arizona Department of Environmental Quality
AFP44
Air Force Plant 44
AOP
advanced oxidation process
ARAR
Applicable or Relevant and Appropriate Requirement
Area A
TIAA Superfund Site Area A
bgs
below ground surface
CERCLA
Comprehensive Environmental Response, Compensation, and Liability Act
COC
contaminant of concern
CTWD
City of Tucson Water Department
EPA
U.S. Environmental Protection Agency
FBHHRA
Focused Baseline Human Health Risk Assessment
FFS
Focused Feasibility Study
GAC
granular-activated carbon
gpm
gallon per minute
GWTP
groundwater treatment plant
IC
institutional control
ISB
in situ bioremediation
ISCO
in situ chemical oxidation
KMn04
potassium permanganate
LZ
Lower Aquifer Zone
MCL
maximum contaminant level
MCLG
maximum contaminant level goal
MNA
monitored natural attenuation
NCP
National Oil and Hazardous Substances Pollution Contingency Plan
NOI
Notice of Intent
NWF
North Well Field
OU
operable unit
PCA
packed column aeration
RAO
remedial action objective
RCRA
Resource Conservation and Recovery Act
RI/FS
Remedial Investigation/Feasibility Study
ROD
Record of Decision
SARA
Superfund Amendments and Reauthorization Act
SASR
Semi-annual Status Report
SDWA
Safe Drinking Water Act
SWF
South Well Field
TARP
Tucson Airport Remediation Project
TCE
trichloroethylene
TIAA
Tucson International Airport Area
UFHHRA
Unified Focused Human Health Risk Assessment
USAF
U.S Air Force
UV
ultraviolet light
UV-AOP
ultraviolet light peroxide advanced oxidation process
UZ
Upper Aquifer Zone
VOC
volatile organic compound
WTP
water treatment plant
TIAA SUPERFUND SITE AREA A
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1.0 PART I: DECLARATION FOR THE RECORD OF DECISION
AMENDMENT
1.1 Site Name and Location
The following lists site information:
• Tucson International Airport Area Superfund Site (herein referred to as TIAA Superfund Site or
Site).
• Superfund Enterprise Management System (SEMS) Identification: AZD980737530.
• TIAA Superfund Site Area A consists of the groundwater project areas north of Los Reales Road
and both airport property (including Tucson International Airport and Three Hangars Building)
and the Tucson Airport Remediation Project (TARP).
1.2 Statement of Basis and Purpose
This interim Record of Decision (ROD) Amendment presents fundamental changes to the August 22, 1988
Record of Decision (ROD) for the Site's Area A north of Los Reales Road. The U.S. Environmental Protection
Agency (EPA) considered and approved this ROD Amendment in accordance with Section 117 of
Comprehensive Response, Compensation and Liability Act (CERCLA) and Section 300.435(c)(2)(ii) of the
National Oil and Hazardous Substances Pollution Contingency Plan (NCP), which require the amendment
of a ROD when making fundamental changes to the remedy. The ROD Amendment is based on the
information contained in the Administrative Record for this Site. The ROD Amendment will become part
of the Administrative Record file (in accordance with Section 300.825(a)(2) of the NCP).
The 1988 ROD and this ROD Amendment respond to specific volatile organic compounds (VOCs) and
1,4-dioxane, which are hazardous substances under CERCLA. Within recent years, EPA has also identified
pollutants and contaminants, which will be addressed in a future decision document.
The lead agency is EPA, and the support agency is the Arizona Department of Environmental Quality
(ADEQ). The State of Arizona concurs.
1.3 Assessment of the Site
The response action selected in this ROD Amendment is necessary to protect human health from actual
or threatened releases of hazardous substances into the environment.
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1.4 Description of the Revised Remedy
On August 22, 1988, the U.S. Environmental Protection Agency (EPA) signed a Record of Decision (ROD)
selecting the remedy for groundwater contamination north of Los Reales Road, which includes Area A
(and Area B). The 1988 ROD addressed certain VOCs: trichloroethylene (TCE), as well as
1,1-dichloroethene, trans-l,2-dichloroethene, and chloroform.
The main components of the remedy documented in the 1988 ROD, which applied to Area A, included the
following:
• Control of groundwater contamination through extraction wells.
• Treatment of contaminated groundwater using packed column aeration (PCA; air stripping).
• Treatment of generated off-gas using reasonably available control technology (in this case,
granular-activated carbon [GAC]).
• Beneficial use of treated groundwater as drinking water to the City of Tucson potable water
distribution system.
• Groundwater monitoring.
Following the implementation of the 1988 EPA ROD, the City of Tucson Water Department (CTWD)
constructed a water treatment plant (WTP) utilizing PCA to treat volatile organic compounds (VOCs)
extracted from the aquifer. The system is collectively known as the Tucson Area Remediation Project
(TARP). Following the discovery of 1,4-dioxane in the groundwater in 2002, and EPA's publishing of a
reduced Drinking Water Health Advisory for 1,4-dioxane in 2011, the City of Tucson proactively modified
the on-site WTP to include an advanced oxidation process (AOP) treatment system using ultraviolet (UV)
light and hydrogen peroxide to create the oxidants (CTWD 2014). The UV-AOP system is capable of
reducing concentrations of VOCs, primarily TCE, and the more recently discovered 1,4-dioxane to below
target treatment levels for drinking water (EGC, Inc. 2016a and 2016b). The excess hydrogen peroxide
from the UV-AOP system is quenched using GAC. The redundant operation of both the UV-AOP and the
PCA towers at the WTP continued from startup of the UV-AOP system in February 2014 through April
2020. Over this six-year operation period, treated water quality data demonstrated that the UV-AOP
system is capable of meeting all obligations under the 1990 Consent Decree and treating 1,4-dioxane in
water from the TARP remediation well fields to levels below its 0.1 micrograms per liter (ng/L) detection
limit.
In early 2017, EPA published a Proposed Plan and provided a public comment period, which proposed
fundamental changes to the remedy. In September 2021, EPA signed a Minor Changes Memorandum to
remove the specification of the end use of treated water, but made no other changes to the remedy.
TIM SUPERFUND SITE AREA A
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This Interim ROD Amendment revises the remedy for the Site's Area A as follows:
• Treatment of the groundwater for 1,4-dioxane using the ultraviolet light-hydrogen peroxide
advanced oxidation process (UV-AOP) system, which is already in place at TARP, and
elimination of the PCA system.
• Enhancement of the current remedy by installation of an additional remediation/extraction
well to further reduce contaminant mass.
• Continued monitoring of treated groundwater at TARP to ensure cleanup levels are met.
• Alternate options for beneficial use of the water other than as drinking water, including
discharge to the City of Tucson recycled water system.
• Continued long-term monitoring of the groundwater contamination.
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2.0 STATUTORY DETERMINATIONS
This interim action is protective of human health and the environment in the short term and is intended
to provide adequate protection until a final ROD is signed; complies with (or waives) those federal and
state requirements that are applicable or relevant and appropriate for this limited-scope action; and is
cost-effective. Although this interim action is not intended to address fully the statutory mandate for
permanence and treatment to the maximum practicable, this interim action does utilize treatment and
thus supports that statutory mandate. Because this action does not constitute the final remedy for Area
A of the Site, the statutory preference for remedies that employ treatment that reduces toxicity, mobility,
or volume as a principal element will be addressed by the final response action. Subsequent actions
planned to address fully the threats posed by conditions will be addressed by the final response action.
Because this remedy will result in hazardous substances remaining on-site above health-based values, a
review will be conducted to ensure that the remedy continues to provide adequate protection of human
health and the environment within five years after commencement of the remedial action.
Because this is an interim action ROD, review of this site and remedy will be ongoing.
TIM SUPERFUND SITE AREA A
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3.0 ROD DATA CERTIFICATION CHECKLIST
The following information is included in Section 4.0, "Part II: Decision Summary" of this ROD
Amendment:
• COCs and their respective concentrations. This interim action decision is only addressing
CERCLA hazardous substances, specifically VOCs and 1,4-dioxane. The term COCs used herein
refers to hazardous substances. Not addressed in this interim decision document are
substances that are "pollutants and contaminants/' such as per-and polyfluorinated
substances, which will be addressed in a future decision document.
• Baseline risk represented by the COCs.
• Cleanup levels established for COCs and the basis for these levels.
• How source materials constituting principal threats are addressed.
• Current and reasonably anticipated future land use assumptions and current and potential
future beneficial uses of groundwater used in the baseline risk assessment and ROD
Amendment.
• Potential land and groundwater use that will be available at the Site as a result of the selected
remedy.
• Estimated capital, annual operation and maintenance, total present worth costs, discount rate,
and the number of years over which the remedy cost estimates are projected.
• Key factor(s) that led to selecting the amended remedy (i.e., describe how the selected remedy
provides the best balance of trade-offs with respect to the balancing and modifying criteria,
and highlight the criteria significant to the decision).
Additional information can be found in the Administrative Record file for this Site.
3.1 Authorizing Signature
Digitally signed by MARTHA
MARTHA ACEVES ACEVES
Date: 2023.03.21 11:25:03-07'00'
Martha Guzman Date
Regional Administrator
U.S. Environmental Protection Agency, Region 9
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4.0 PART II: DECISION SUMMARY
This decision summary provides a description of TIAA Superfund Site Area A and the analyses that led to
the amendment of the selected remedy for the Site. This section includes background information about
the Site, the nature and extent of contamination found at the Site, the assessment of human health and
environmental risks posed by the contaminants at the Site, and the identification and evaluation of
remedial action alternatives for the Site.
4.1 Site Name, Location, and Brief Description
In 1981, VOCs were detected in the City of Tucson drinking water wells in the vicinity of Tucson
International Airport, which resulted in the establishment of the TIAA Superfund Site (Figure 4-1). EPA
divided the Site into two geographic areas: (1) Area A, which comprises the main groundwater
contamination plume located to the west of the Airport, and (2) Area B, which includes the West Plume B,
an Arizona Air National Guard facility, a former Texas Instruments facility, and the former West-Cap
project area, located to the north and east of the airport. This ROD Amendment is restricted to the portion
of Area A north of Los Reales Road. EPA is the lead agency for TIAA Superfund Site Area A, with the Arizona
Department of Environmental Quality (ADEQ) in the support role. The Comprehensive Environmental
Response, Compensation, and Liability Information System Identification is AZD980737530.
TIAA SUPERFUND SITE AREA A
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4.2 Site History and Enforcement Activities
From the 1940s through the mid-1970s, defense and industrial operators stored, handled, and disposed
of hazardous materials in a manner that caused releases into the environment. In the early 1950s,
residents within the present-day Site complained that water from private wells had a foul odor (EGC, Inc.
2016a). Chromium was identified as a contaminant in a municipal water supply well located near Air Force
Plant 44 (AFP44) in the late 1950s. In 1976, the State of Arizona closed one well at AFP44 because of a
high chromium concentration (EGC, Inc. 2016b). Starting in 1981, the City of Tucson and EPA collected and
analyzed water from municipal wells within the main plume of groundwater contamination (EGC, Inc.
2016b). The investigation discovered VOC contamination in excess of safe drinking water levels.
Subsequent investigations defined the main plume of groundwater contamination as containing TCE and
other chlorinated VOCs. To avoid exposure to the contamination, 11 city and several private household
wells were shut down (EGC, Inc. 2016b).
The Site was placed on the preliminary EPA National Priorities List (NPL) in July 1982 (Arizona Department
of Health Services 1985) to address VOC and chromium contamination in groundwater. It was declared a
Superfund site and placed on the final National Priorities List in September 1983 (EPA 2013).
Environmental response actions are conducted in accordance with CERCLA, as amended and as
implemented under the U.S. Air Force (USAF) Installation Restoration Program or Defense Environmental
Restoration Program. Substantive corrective action requirements under the Resource Conservation and
Recovery Act (RCRA) were integrated through the ARARs process.
In 1985, the USAF adopted a remedy to address the groundwater contamination associated with AFP44,
which is located south of Los Reales Road. Three years later, on August 22, 1988, EPA signed a ROD to
address the regional groundwater contamination in Area A (and in some Area B locations) at the TIAA
Superfund Site (EPA 1988).
The TARP groundwater plume and treatment system are the major focus of this ROD Amendment. While
not part of TIAA Superfund Site Area A, the AFP44 groundwater treatment plant (GWTP) treats and
controls groundwater south of Los Reales Road, and is discussed in the context of TIAA Superfund Site
Area A because the plant owner, the USAF, has been identified as a responsible party for the Area A
groundwater plume both north and south of Los Reales Road.
The WTP is currently operated by the CTWD to supply public water to the City of Tucson and to perform
the remedial action at this site, as documented in the 1988 EPA ROD. The WTP is used to capture and treat
contaminated groundwater at the leading edge of the groundwater plume to prevent further migration
to the north. The WTP consists of nine extraction wells (from two separate well fields) currently used to
pump approximately 5,000 gallons per minute (gpm) from the regional aquifer to the packed column
aeration system, which was designed to use PCA towers with GAC for off-gas treatment of TCE and other
VOCs (EGC, Inc. 2016a).
Table 4-1 summarizes the major CERCLA milestones for the Area A portion of the TIAA Superfund Site
work. The histories of the individual areas associated with the TIAA Superfund Site Area A follow.
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Table 4-1
Summary of CERCLA Milestones for TIAA Superfund Site Area A North of Los Reales
Road
Year
Document or Milestone
Key Points
1988
Record of Decision for the TIAA Superfund
Site
Pump-and-treat technology was selected as the remedial
action for treatment of VOCs prior to discharging treated
groundwater to the municipal water distribution system.
1994
TARP Remedial Action
TARP treatment plant begins operation.
1996
Airport Property Remedial Investigation (Rl)
Rl characterized extent of contamination in shallow
groundwater zone and vadose zone.
1997
Airport Property Remedial Action
Polychlorinated biphenyls-contaminated soil is excavated.
1997
Airport Property Feasibility Study
Feasibility Study presented remedial technologies which
might be applicable to the site.
1997
Airport Property ROD
EPA issued a ROD for the selected remedial alternative.
2002
TARP, Airport Property, and AFP44
1,4-dioxane is discovered in the groundwater.
2002
Airport Property Remedial Action
Installed five extraction wells to cut off shallow groundwater
zone from TARP plume.
2004
Airport Property Remedial Design
Finalized the shallow groundwater zone remedy and soil-
vapor extraction remedy design report and remedial action
work plan.
2006
Airport Property Remedial Action
ISCO using potassium permanganate to treat VOCs in soil
and groundwater.
2010
TARP's UV-Peroxide AOP T reatment Pilot
System
Pilot test confirmed that UV-peroxide AOP treatment is the
preferred technology for treatment of 1,4-dioxane in
groundwater.
2014
TARP's UV-Peroxide AOP Treatment;
Operation Begins by Tucson Water
TARP begins operation of UV-peroxide AOP treatment
system in addition to operation of the WTP.
Ongoing
All Project Areas
Groundwater sampling of both the groundwater plume and
effluent of the groundwater treatment systems is ongoing.
4.3 TARP Project Area
Historical industrial and defense-related activities at the airport property and at AFP44 led to the presence
of TCE and related compounds in the regional aquifer within Area A north of Los Reales Road. Because
this portion of the plume contained contaminants from multiple parties, a Consent Decree was signed in
June 1991 to establish the work responsibilities of each party and to provide funding to implement the
1988 EPA ROD for groundwater remediation north of Los Reales Road. The signing parties included the
United States (on behalf of the USAF and EPA), Raytheon Company (then Hughes Aircraft Company),
Tucson Airport Authority, City of Tucson, and the Boeing Company (then McDonnell Douglas Corporation).
In 1994, as part of the implementation of the 1988 EPA ROD, a groundwater remediation system consisting
of five extraction wells in the south well field (SWF) and four in the north well field (NWF) was constructed
to provide hydraulic capture and control, and remediation of groundwater at the TIAA Superfund Site Area
TIAA SUPERFUND SITE AREA A
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A plume north of Los Reales Road (Figure 4-1). This system, known as TARP, used PCA or air stripping with
vapor-phase GAC to remove chlorinated VOCs in the exhaust from the PCA towers (EGC, Inc. 2016a).
In 2002, 1,4-dioxane was detected in groundwater samples collected from monitoring and remediation
wells within the TIAA Superfund Site Area A plume. The concentrations of 1,4-dioxane are likely from
1,1,1-trichloroethane solutions that were used as solvent stabilizers at AFP44 and the airport property
(EGC, Inc. 2016b). The PCA towers used at the WTP were not designed to treat 1,4-dioxane. In January
2014, CTWD built the new UV-AOP system, which it currently operates. The UV-AOP system removes
1,4-dioxane and VOCs in groundwater before the water is filtered through GAC to quench residual
hydrogen peroxide. Once treated by the UV-AOP system, the treated water was passed through the PCA
towers in compliance with the 1990 Consent Decree. The City of Tucson, citing EPA's Drinking Water
Health Advisory for 1,4-dioxane, had used 0.35 ng/L as its interim treatment goal in the absence of an MCL
(CTWD 2014). The UV-AOP system reduces 1,4-dioxane and TCE concentrations to non-detect at a
detection limits of 0.10 ng/L and 0.5 ng/L, respectively, even before the water was passed through the air
stripping towers. Prior to the 2014 construction of the UV-AOP system to remove 1,4-dioxane, the CTWD
blended water from the City's Southside Well Field and from other portions of the system with the
effluent from the PCA WTP prior to delivery to the potable water distribution system at the Santa Cruz
Lane Reservoir. The City of Tucson began a program of collecting samples directly from the distribution
system and analyzing the samples for 1,4-dioxane. Results indicated that 1,4-dioxane concentration in
served water was less than 0.35 ng/L. Samples were collected on a weekly basis at the WTP input and
output locations, and at the blended point-of-entry to the potable water distribution system. With the
implementation of the UV-AOP, a blending strategy was no longer needed.
On March 30, 2017, EPA and CTWD participated in a public meeting presenting the Proposed Plan for the
remedy of 1,4-dioxane in groundwater of the Area A plume north of Los Reales Road. The Proposed Plan
recommended continuing remediation of the plume using the UV-AOP facility at the TARP WTP as
described in Alternative 3 of the Focused Feasibility Study (FFS) for 1,4-Dioxane North of Los Reales Road
(EGC, 2016c). Some public comments were focused on alternatives including in situ bioremediation (ISB;
Alternative 5 of the FFS) and in situ chemical oxidation (ISCO; Alternative 6 of the FFS) approaches because
of claims to reduce the duration of the remedy by 10 years. The in situ remediation approaches were
proposed in the FFS for the portion of the TARP plume north of Los Reales Road and south of Valencia
Road, as illustrated on Figure 4-1, which is nearest to the groundwater contamination source areas at
AFP44 and the Three Hangers site at the Tucson Airport Property. Groundwater quality data collected on
a quarterly basis each year from the plume are documented in the TARP Semi-annual Status Reports
(SASRs). Groundwater quality data collected from 2011 through 2022 demonstrate significant reductions
in contaminant concentrations in this portion of the plume between Los Reales Road and the SWF. Due to
the greatly reduced mass of contaminants in groundwater of this portion of the plume, little benefit would
be gained by in situ treatment of groundwater in this area as described in Alternatives 5 and 6 of the FFS
(EGC, 2016c).
Due to the public's desire for a faster conclusion to the remedial action for TCE and 1,4-dioxane at TARP,
the City of Tucson developed an approach that would accelerate the remedy. Years of monitoring data
documented in the SASRs for TARP reveal that although contaminant concentrations in groundwater in
the southern portion of the TARP plume have decreased significantly, the mass of contaminants in the
TIAA SUPERFUND SITE AREA A A £ INTERIM RECORD OF DECISION AMENDMENT
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Regional Undivided Aquifer has remained relatively unchanged over the 30-year operation of the TARP
remedy. As part of this remedy, EPA and the City of Tucson proposed installation of a new remediation
well south of Irvington Road and west of 12th Avenue in the portion of the plume with the highest current
levels of chemical contamination. Extraction of groundwater from the new well increases the removal of
contaminant mass and, therefore, will reduce the duration of the remedy. The design concepts and cost
estimates associated with the additional remediation well were documented in a technical memorandum
to EPA (Carollo, 2018). To accommodate the public's desire for a more aggressive remedy and the City of
Tucson's desire to have flexibility in managing water resources, the EPA completed an FFS Addendum that
included enhancements to the preferred alternative, Alternative 3 (Carollo 2021). The enhancements to
Alternative 3 included a new remediation well and infrastructure to deliver treated water from the TARP
WTP to the City's recycled water system and the Santa Cruz River (Carollo, 2021).
4.4 Air Force Plant 44 Project Area
AFP44 is a Government-owned, contractor-operated defense industrial plant used for the production of
weapons systems since its inception in 1951. Historical industrial processes conducted at AFP44, in
conjunction with the production, maintenance, and modification of weapons systems, have included
cleaning and degreasing, plating, anodizing, chemical milling, chemical etching, printed circuit board
production, heat treating, and painting. These processes generated wastewater and general industrial
wastes such as solvents, paint sludge, and thinners, many of which contained VOCs. In 1983 and 1984, the
USAF/Hughes Aircraft Company conducted studies that defined an off-site TCE groundwater
contamination plume substantially attributable to AFP44 that extended off site to the northwest from the
center of AFP44. In 1986, the USAF issued a Final AFP44 Remedial Action Plan and ROD for a groundwater
extraction, treatment, and reinjection system to address the contamination south of Los Reales Road
(USAF 1986). In April 1987, the GWTP began to extract, treat (using air stripping/sparging with GAC vapor
emissions treatment), and re-inject treated groundwater into the aquifer. An extensive series of reports
detailing the GWTP operations from startup until the present time are available in the Administrative
Record for AFP44 (EGC, Inc. 2016a).
The discovery of 1,4-dioxane in 2002 resulted from development and implementation of improved
analytical methods (AECOM 2010). The existing air stripping system at AFP44 was not a viable treatment
technology for 1,4-dioxane, as shown by sampling of the GWTP's input and output (EGC, Inc. 2016a). The
USAF took several actions to respond to 1,4-dioxane, including initiating studies of possible treatment
technologies, programming funding to upgrade the GWTP, conducting weekly sampling, and modifying
the pumping and recharge schemes used in the regional aquifer system to minimize spreading 1,4-dioxane
through the AFP44 project area. In 2004, the USAF conducted a technology evaluation (Earth Tech, Inc.
2004) that determined that an AOP system could treat both chlorinated VOCs and 1,4-dioxane for
roughly the same annual cost as the system then in place. Based on the recommendations of the
technology evaluation, the USAF programmed funds to design and install an AOP system at the GWTP for
completion in Fiscal Year 2009. EPA issued an Administrative Order, which required installation of an AOP
system capable replacing the existing treatment system, to the USAF and Raytheon Company in July 2007
under Section 1431 of the Safe Drinking Water Act (SDWA) (EPA 2007).
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The original groundwater extraction system and GWTP went off-line in November 2008 to allow
construction of the AOP system. The system upgrades, necessary repairs, and startup testing were
completed, and the system was brought on-line in September 2009. This system has been functioning
since 2009 to treat TCE and 1,4- dioxane. On September 30, 2009, EPA issued a Notice of Completion to
the USAF, which stated that the work set forth in the 2007 Administrative Order had been completed to
EPA's satisfaction. EPA, ADEQ, and the USAF signed a Federal Facilities Agreement in 2011.
In a separate action, in 2013, the USAF enacted an Optimized Exit Strategy plan to address contaminated
groundwater south of Los Reales Road at the AFP44 site. The plan included:
1. Continued operation of the groundwater extraction system using the existing extraction wells
and AOP system.
2. Institute a focused treatability study of remediating hot spots in soil and shallow groundwater
using ISB.
3. Conduct a technical and economic feasibility analysis of remediating contamination in the
shallow groundwater zone hot spots at AFP44.
In 2014 and 2015, the USAF completed 131 injection wells at three groundwater hot spot locations across
AFP44. Hydrofracturing technology was used to create fissures in tight subsurface formations by injecting
a slurry of sand and chemical reagents to allow treatment in non-permeable formations where traditional
in situ methods do not perform well. Post-injection monitoring has demonstrated significant reductions
of VOCs, 1,4-dioxane and chromium in treated hot spot locations. A ROD was issued by the USAF in
August 2020 entitled "ROD for Site OT012 AFP 44 Tucson, Arizona" which implemented ISB and ISCO
remediation at AFP44 property while maintaining operation of the groundwater remediation system to
control migration of contaminants north of Los Reales Road.
4.5 Airport Property Project Area
Airport property includes all portions of the TIAA Superfund Site that are, or were owned by, leased to, or
otherwise operated or controlled by the Tucson Airport Authority, or its predecessors. Additionally, 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 outlined in the 1998 EPA ROD are included. The airport property
housed defense and industrial-related activities from the 1950s to the 1970s. These activities included the
handling, use, and disposal of hazardous materials in a manner consistent with widely accepted industry
practices of the time. These materials included solvents used as degreasers and fuels for aircraft and
ground vehicles. Operations at this location resulted in soil and groundwater contamination, primarily in
the area of three large hangars (Figure 4-1) (EGC, Inc. 2016a). Several parties were involved in the
operation and management of this area, including the USAF, the Tucson Airport Authority, and defense
contractors. Following investigations of potential sources of contamination and affected areas, a Remedial
Investigation Report (Daniel B. Stephens & Associates, Inc. 1996) was prepared and submitted to EPA for
the airport property. EPA issued a ROD selecting remedial actions for the airport property (EPA 1998). The
final Soils Consent Decree, effective 2000 (EPA 1999), specified four separate remedies for the site: 1) a
soil-vapor extraction remedy to remove VOCs from soil, 2) a pump- and-treat system to remove VOCs
from the shallow groundwater zone, 3) a remedy for excavation and removal of soil contaminated with
TIAA SUPERFUND SITE AREA A A 7 INTERIM RECORD OF DECISION AMENDMENT
H~' MARCH 2023
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polychlorinated biphenyls and metals, and 4) a remedy for the closure of the inactive construction landfill
at the airport, including capping and long-term monitoring (EGC, Inc. 2016a).
In 2002, 1,4-dioxane was detected in the regional aquifer monitoring wells at the airport property site at
concentrations up to approximately 12 ng/L. In 2004, 2006, and 2011, groundwater sampling programs
were conducted to further delineate the presence and extent of 1,4-dioxane at the site (EGC, Inc. 2016a).
4.6 Community Participation
A Proposed Plan that detailed the proposed site remedy was issued by EPA in March 2017. In conjunction
with issuance of the Proposed Plan, EPA completed a summary fact sheet of the Proposed Plan, which was
mailed hard copy to the established TIAA mailing list of 137 people. The fact sheet was also delivered
electronically to an additional 71 people. The Proposed Plan meeting and comment extension period were
advertised in both the Arizona Daily Star (March 21 and May 1, 2017) and hard copies were placed in the
Pima County Public Library-Valencia Branch. Additionally, the fact sheet was translated into Spanish and
distributed by both hard copy and electronic copy to the TIAA mailing list. The meeting notices and
comment extension period were advertised in the Spanish publication La Estrella de Tucson on March 24
and May 5, 2017. The Public Meeting took place on March 30, 2017.
In addition, EPA actively participates in regular quarterly Unified Community Advisory Board meetings.
These meetings are advertised locally in both English and Spanish newspapers and a Spanish translator is
available at many meetings. These meetings are usually very well attended.
Sometime during 2019, the City of Tucson requested that the beneficial end use of the water, which had
been limited to drinking water use via the City's water system, to also include distribution via the City's
recycled water system and discharge to the Santa Cruz River for the purpose of aquifer recharge. After
several months of negotiation and meetings with EPA headquarters, the EPA issued a memorandum to
file dated September 21, 2021, which removed the specification of the end use of the treated water from
the ROD. In addition, a focused feasibility study was prepared and approved, and engineering design and
construction was implemented, adding approximately four years to complete the process.
4.7 Scope and Role of Response Action
The response action presented in this ROD Amendment is a modification to the Area A portion of the
selected remedy described in the 1988 EPA ROD (EPA 1988). This document is an interim ROD Amendment
that provides for containment and treatment of 1,4-dioxane, based on the original 1988 EPA ROD that
provides for containment and treatment of VOCs including TCE, 1,1-dichloroethylene, trans-1,2-
dichloroethylene, benzene, and chloroform. Afinal ROD Amendment will be prepared in the future, when
an MCL is established for 1,4-dioxane by EPA or the State of Arizona. The goals of this action are to address
the residual contamination that exists in the groundwater, prevent migration of contaminants, and treat
extracted groundwater prior to reuse. The selected modified remedy continues the operation of the
current groundwater remediation well network, but modifies the water treatment approach to rely solely
on UV-AOP instead of both UV-AOP and the packed column aeration WTP and enhances the recovery
network with installation of an additional remediation/extraction well. In addition, the modified remedy
provides for alternate options for the end-use of the treated water other than as drinking water, including
TIAA SUPERFUND SITE AREA A
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discharge to the Tucson Water recycled water system. The remedy will also continue monitoring of the
groundwater plume. This interim action will neither be inconsistent with, nor preclude, implementation
of the final remedy.
4.8 Site Characteristics
A summary of site characteristics is presented below.
4.8.1 Physical Characteristics
Based on historical data, the total length of the axis of the Area A Site as it is currently understood is over
3 miles long. It is located to the west of the Tucson International Airport and north of Los Reales Road; it
continues to the northwest towards the packed column aeration WTP. The Area A plume is over 1 mile
wide at its widest point and approximately 2,000 feet wide at its narrowest point (Figure 4-1).
4.8.2 Site Hydrogeology
The Tucson Basin is described as saturated alluvial sediments that compose a single regional aquifer
system, and all aquifers are considered to be potential drinking water aquifers in the State of Arizona. In
the vicinity of the Site, the regional aquifer system is hydrogeologically complex because of lateral and
vertical stratigraphic changes. The stratigraphy within the Area A plume is dominated by a thick clay layer
that acts as an aquitard dividing the regional aquifer into two groundwater-bearing units: the Upper
Aquifer Zone (UZ) and the Lower Aquifer Zone (LZ). Figure 4-2 provides an illustration of the stratigraphy
of the Area A plume with the divided aquifer to the south and east and the Regional Undivided Aquifer to
the north and west. The clay aquitard pinches out to the north and west within the Area A plume creating
a single groundwater-bearing unit at the northern end of the Area A plume: Regional Undivided Aquifer.
The approximate location of the demarcation between the Regional Undivided Aquifer and the UZ and LZ
of the Divided Aquifer is illustrated in Figure 4-3.
The UZ consists of sands and gravels with clayey sand and clays to a depth of approximately 200 feet below
ground surface (bgs), and ranges in thickness from approximately 60 to 100 feet (Earth Tech, Inc. 1992).
Groundwater of the UZ occurs at depths of approximately 100 to 200 feet bgs. In general, the UZ shows
a gradual coarsening of sediments from east to west. The UZ in the southern portion of the Area A plume
can also be divided into an upper and a lower unit separated by a second, discontinuous clay aquitard.
This clay aquitard varies in thickness across AFP44 and begins to pinch-out west of Nogales Highway,
trending south-north from AFP44 towards the TARP area. The second clay aquitard is not present to a
significant degree in the Area A plume north of Los Reales Road with the line of demarcation between the
UZ and the shallow groundwater units located in the southern portion of the plume near the Three
Hangers site as seen on Figure 4-3.
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The clay aquitard separating the UZ and LZ is generally thicker and finer-grained than the second aquitard
separating the upper and lower units of the UZ. The lithology of the regional undivided aquifer, which
underlies the LZ, does not vary much from east to west in comparison to the regional divided aquifer's UZ;
the majority of sediments are coarse-grained. Once the thicker clay aquitard pinches-out, groundwater
flows from the UZ and the LZ into the Regional Undivided Aquifer. The groundwater elevation of the UZ
level drops dramatically to join the groundwater elevation of the Regional Undivided Aquifer, causing
steep hydraulic head gradients in the transition zone from the divided aquifer to the Regional Undivided
Aquifer. The steepening water level or hydraulic head gradient may also be due in part to the operation
of the TARP North Well Field as illustrated on Figure 4-2.
In general, the LZ is more cemented than the UZ. Groundwater occurs in the LZ under semi-confined
conditions and at depths of approximately 300 feet bgs. The total depth of the LZ has not been well
established, but existing data suggest it reaches depths of up to 600 feet bgs (Daniel B. Stephens &
Associates 1993). The permeability of the LZ is one to two orders of magnitude less than the permeability
of the UZ because it contains more clay and is more heavily cemented than the UZ sediments (Hughes
Missile Systems Company 1995). Aquifer pumping tests have shown no interconnection between
groundwater in the UZ and LZ. The LZ is substantially less contaminated than the groundwater of the UZ
in the vicinity of the contaminant sources at AFP44 and the Three Hangers site. The LZ discharges directly
to the Regional Undivided Aquifer at the northern end of the TARP plume. A majority of contaminant mass
in groundwater of the TARP plume is located in the Regional Undivided Aquifer at the line of demarcation
with the LZ of the Divided Aquifer, as illustrated in Figure 4-3.
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Shallow QW Zone
Aquitard
Upper Zone
(Upper Uti«)
Aquitard
Aquitard
Lower Zone
Gruvul ftuteunB (GSU
North
Wall
Field.
Souih
Wall Field
Cicrwgn Creek Fan
Deposits
i J.OOOgpm
lOwftr Aquiler /Ofi«
Gatanria River
Deposit &
Uppei Aqmlnr
Zom
(UrWifterentiettd*
UndtVKlod
Regional
Aquile«
Catalina River
Deposits
Figure 4-2
'i
< o
«s!n
^ u 5
Uj O <
8o»
ass
C (J
V
Prcfua UcriMT
-------
4.8.3 Contaminant Distribution
Several remedial investigations and remedial actions have been performed since 1982 to establish the
COCs for the Site and their distribution within the Area A plume (ECG, Inc. 2016a). The COCs for the TARP
include both the first identified historic COCs, including TCE, benzene, and xylenes (identified in the 1988
EPA ROD) and newly identified COCs (principally 1,4-dioxane). Table 4-2 summarizes the COCs that have
been detected in the regional groundwater above their respective treated water and in-situ groundwater
cleanup levels within the past 2 years. The treated water and in-situ groundwater cleanup levels are a
conservative combination of SDWA maximum contaminant levels (MCLs), maximum contaminant level
goals (MCLGs), cumulative VOC risk-based concentrations, or, in the case of 1,4-dioxane, a Drinking Water
Health Advisory. There is currently no established MCL or MCLG for 1,4-dioxane. EPA has published a
Drinking Water Health Advisory range for 1,4-dioxane of 0.35 to 35 ng/L that corresponds to an excess
lifetime cancer risk range of 10 s to 10"4, respectively. The UFHHRA (EPA and Air Force Civil Engineer
Center, 2015) recommended 0.35 ng/L treatment level (10 s risk level). The two most prevalent COCs at
the Site are TCE and 1,4-dioxane. The TCE plume extends from AFP44 and the airport property to north
of Irvington Road. The TARP packed column aeration WTP was placed at the end of the plume. Figure 4-3
shows the concentrations of TCE are between 5 ng/L and 80 ng/L in the area north of Los Reales Road.
Currently, the majority of the mass of TCE in groundwater of the Area A plume resides in the Regional
Undivided Aquifer in the vicinity of the demarcation line with the LZ of the Divided Aquifer as illustrated
on Figure 4-3. The 1,4-dioxane groundwater plume extends from AFP44 to the TARP northern well field
at concentrations greater than 3 ng/L (Figure 4-3). The plume north of Los Reales Road contains
concentrations in the 3 to 8 ng/L range, but concentrations greater than 6 ng/L are not extensive or
contiguous. Based on groundwater data collected from new wells installed near the eastern and western
plume boundaries, the lateral extent of the 1,4-dioxane plume is defined in the UZ of the Divided Aquifer
and the Regional Undivided Aquifer and LZ near the demarcation line of the two aquifers, as illustrated in
Figure 4-3.
Table 4-2
Treatment and Cleanup Levels for Primary Contaminants of Concern
Chemical of Concern
Treatment and Cleanup Levels (|jg/L)1
Basis
TCE2
1.5 |jg/L (treatment level)
Indicator of cumulative VOC risk as
described in the 1988 EPA ROD and
1990 Consent Decree (CD)
5 |jg/L (cleanup level)
1990 CD (MCL based)
1,1-DCE
7 |jg/L(cleanup level)
1990 CD (MCL based)
trans-1,2-DCE
100 |jg/L(cleanup level)
1990 CD (MCL based)
1,4-dioxane3
0.35 (treatment level)4
November 2015 Final Unified
Focused Human Health Risk
Assessment
Chloroform
70 |jg/L5 (cleanup level)
1990 CD (MCL based)
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Table 4-2 (continued)
Cleanup Levels for Primary Contaminants of Concern
Notes:
1 Table is amended from the Volume I Final Focused Feasibility Study for 1,4-Dioxane North of Los Reales Road (EGC, Inc. 2016c).
2 The water distributed from the TARP plant has a lower treatment level as it is intended for direct drinking water usage (EPA 1998).
3 A groundwater cleanup level will be established when a maximum contaminant level (MCL) for 1,4-dioxane has been established by the
federal government or the State of Arizona.
4 This treatment level is supported by U.S. Environmental Protection Agency (EPA) as documented in the Final Unified Focused Human
Health Risk Assessment, Focused Remedial Investigation and Feasibility Study for 1,4-Dioxane North of Los Reales Road, Tucson
International Airport Area Superfund Site Area A (EPA, 2015).
5 In addition to the maximum contaminant level goal (MCLG), as listed, that needs to be met since the groundwater is a source of drinking
water, chloroform is also a trihalomethane. The total trihalomethanes (sum of the concentrations of four trihalomethanes as an annual
average) MCL is 80 yg/L. Both levels apply since the regional groundwater is a drinking water source, and chloroform is generated when
drinking water is disinfected.
Although chloroform is listed as a COC, chloroform is currently not present in groundwater above its
cleanup level at the TARP packed column aeration WTP. Chloroform is only present above its cleanup level
in the airport property shallow groundwater zone (Figure 4-3). A more detailed evaluation of these COCs
and an evaluation regarding other potential COCs is provided in the conceptual site model (EGC, Inc.
2016b).
4.9 Current and Future Site and Resource Use
TIAA Superfund Site Area A contains a mix of industrial, commercial, and residential land uses. The areas
north of Los Reales Road are more residential, while the areas to the south are industrial. The Site overlies
the Tucson groundwater basin, which is designated as a Sole Source Aquifer by EPA under the Safe Drinking
Water Act and is a critical water resource for residents of the City of Tucson and surrounding communities.
In addition to the municipal supply of drinking water, there are private wells found throughout the area in
and near the City of Tucson. The reasonably anticipated future land use is the same as the current use.
Figure 4-4 shows the general land use zoning classifications.
TIAA SUPERFUND SITE AREA A
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INTERIM RECORD OF DECISION AMENDMENT
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WR-163A
Tucson '
i
Airport /
Remediation
Project ¦
(TARP) i
Valencia Road
Tucson lnter£iat|pna#/^rport
Three Hangers Site
/
' ® O- Q
Irvington Road
Drexel Road
v Los Reales Road
Air Force
Plant 44
(AFP44)
I Miles
The 1,4-dioxane base map was prepared by the Arizona Department of Environmental
Quality (ADEQ). Trichloroethene (TCE) contours, aquifer demarcation lines, and the
1,4-dioxane contour in the Lower Zone of the Divided Aquifer were added by the
United States Environmental Protection Agency (EPA).
LEGEND
1,4-Dioxane > 0.35 ug/l
1,4-Dioxane > 3.5 ug/l
TCE > 5.0 ug/l
TCE > 50 ug/l
ug/l - Micrograms per liter
~ Data from 2019 to 2022 (unstarred data collected prior to 2019).
1,4-Dioxane < 0.35 ug/l
Q 1,4-Dioxane > 0.35 < 3.5 ug/l
; 1,4-Dioxane > 03.5 ug/l
- • - Demarcation line between Regional Undivided Aquifer and Divided Aquifer.
— Demarcation line between Upper Zone of Divided Aquifer and shallow groundwater units.
Figure 4-3
1,4-Dioxane and
TCE Concentration
Contour Map
Data from WR-163A used to complete 1,4-dioxane contour in Lower Zone of the
Divided Aquifer by USEPA.
-------
TARP Groundwater
Treatment Plant
Irv ngtc- RD
iWilrviriqloH
1,4-Dioxane
Historical
Plume
-—.—.—.—.—-
VV-t>texe 'HD'
b U'exel-HD
Tucson
Airport
?emediatioi
Project
(TARP)t/
•nciasRD:
Three Hangars
Airport Pro perty.,Qround water.
Treatnieni PlantV Jtk
rAFP44 SitrpT^rz"(IRP Sitc ,17)' Regio nal G roundwater, Plume
Legend
• Wells TARP North Field TIAAAREA A/AFP44, Historical
• Wells TARP South Field " ! TCE Plume (Approximate)
Approximate Groundwater Flow Direction —' >-ornm'eroial Zone
—I— Railroad Industrial Zone
I I Groundwater Treatment Mobile Home Zone
I I Three Hangars Office Zone
I I I TIAA Property Boundary (Approximate) Parlt Industrial Zone
T1AA AREAA/AFP44, Historical Parking Zone
1,4-Dioxane Plume (Approximate) Recreational Vehicle Zone
Residence Zone
REFERENCE PRGJECVCM NK3 19B3 StatePlane AltZEOa Central FIPS 0202 Feet i Ttl
FIGURE
NUMBER
4-4
General Land Use Zoning Classifications
Tuscan International Airport Area
Superfund Site - Area A
U.S. EPA Region 9
San Francisco, CA
-------
4.10 Summary of Site Risks
A Unified Focused Human Health Risk Assessment, Focused Remedial Investigation and Feasibility Study for
1,4-Dioxane North of Los Reales Road, Tucson International Airport Area Superfund Site Area A (UFHHRA)
was conducted by EPA and the USAF Civil Engineer Command Center (EPA/Air Force Civil Engineer Center
2015) to support the Focused Remedial Investigation/Feasibility Study (RI/FS) (EGC, Inc. 2016a and 2016c).
The UFHHRA combines the results of the Revised Limited Risk Assessment for 1,4- Dioxane and
Trichloroethylene in Groundwater at the Tucson International Airport Area Superfund Site (EPA 2015) and
the Focused Baseline Human Health Risk Assessment (FBHHRA; EGC, Inc. 2015). The UFHHRA found
potential risk due to 1,4-dioxane and TCE exposure exceeding the 1 in 10,000 excess lifetime cancer risk
and the non-cancer hazard index of 1.0. Table 4-3 includes the risk for each exposure point for each COC.
The FBHHRA assessed potential pathways of exposure to current and hypothetical future residents from
contaminants in groundwater by direct contact (i.e., ingestion of groundwater, dermal absorption, and
inhalation of vapors from groundwater during dishwashing, showering, etc.), and volatilization of
groundwater to indoor air. The COCs are limited to 1,4-dioxane and TCE, and exposure pathways are
limited to groundwater produced either by the CTWD commercial water supply or by private wells.
The Final Revision 1 Baseline Human Health Risk Assessment Work Plan (AECOM 2013), Focused RI/FS for
1,4-Dioxane North of Los Reales Road (EGC, Inc. 2016a, 2016b, and 2016c), and Draft Baseline Human
Health Risk Assessment for 1,4-Dioxane North of Los Reales Road (AECOM 2014a) were conducted to
support the Focused RI/FS (EGC, Inc. 2016a and 2016c). Based on discussions among the USAF, EPA, and
ADEQ (EPA 2014), the Draft Baseline Human Health Risk Assessment (AECOM 2014a) was revised and
renamed as the Draft Final FBHHRA for 1,4-Dioxane and Trichloroethylene (AECOM 2014b). EPA and USAF
concluded that an additional EPA risk assessment would provide another line of evidence regarding
potential risks to human health from groundwater contamination at the Site, and that a summary of both
risk assessments jointly written by EPA and Air Force Civil Engineer Center as a Unified FBHHRA (EPA/Air
Force Civil Engineer Center 2015) would be the appropriate document to support the Focused RI/FS.
EPA focused on a lifetime exposure of 70 years because, as stated in the Unified FBHHRA, "(i) demographic
information indicates that people in Southside Tucson, the most impacted community, move less
frequently (at Unified Community Advisory Board meetings we have heard of/from a number of lifetime
residents), and (ii) since the treated water is being served via the Tucson Water distribution system, an
individual may consume the same water even though he/she moves to a different location within the city."
(EPA/Air Force Civil Engineer Center 2015).
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Table 4-3
Groundwater Risk Evaluation
Location
EPC
(mq/l)
30-Year RME Cancer Risk
70-Year RME Cancer Risk
Non-Cancer Hazard
Quotient
Non-Cancer Hazard
Index*
1,4-Dioxane
TCE
1,4-Dioxane
TCE
Total
1,4-Dioxane
TCE
Total
1,4-Dioxane
TCE
Total
Hypothetical Future Well
13.4
27.5
2.00E-05
6.20E-05
8.20E-05
4.10E-05
1.80E-04
2.20E-04
0.02
9.8
9.8
Private Wells
CO
LO
o
O
CO
7.5E-07 - 1.1E-05
1.8E-06 - 3.3E-05
3.5E-06 - 4.4E-05
1.5E-06 - 2.2E-05
5.3E-06 - 9.8E-05
9.5E-06 - 1.2E-04
0.0008-0.01
0.3-1.9
0.3-1.9
South Well Field
6.8-8.1
8.0 - 60.3
1.0E-05 - 1.2E-05
1.8E-05 - 1.4E-04
2.8E-05 - 1.5E-04
2.1E-05 - 2.4E-05
5.3E-05 - 4.0E-04
7.4E-05 - 4.3E-04
0.01
2.9-21.5
2.9-21.5
North Well Field
0.25
3.5 -22.8
3.7E-07
8.0E-06 - 5.2E-05
8.3E-06 - 5.2E-05
7.6E-07
2.3E-05 - 1.5E-04
2.4E-05 - 1.5E-04
0.0004
1.2-8.1
1.2-8.1
Tap Water Screening
Levels
....
....
0.67 [jg/L
0.44 |jg/L
—
0.33 [jg/L
0.15 |jg/L
—
600 [jg/L
2.8 |jg/L
....
Notes:
* Since both TCE and 1,4-dioxane have the potential to produce liver and kidney non-cancer toxicities, their non-cancer hazard quotients were summed to calculate a cumulative non-cancer hazard index.
Tap water screening levels represent the levels used in this assessment.
The Hypothetical Future Well would be located near the intersection of Los Reales Road and Nogales Highway.
The South Well Field is part of the Tucson Airport Remediation Project system and, following treatment, supplies the Tucson Water public drinking water system.
The North Well Field is part of the Tucson Airport Remediation Project system and, following treatment, supplies the Tucson Water public drinking water system.
The risk data provided for the private wells, South Well Field, and North Well Field present a risk range based on the analytical data range collected from each of the well groups.
The risk data presented in this table were presented in the Revised Limited Risk Assessment for 1,4-Dioxane and Trichloroethylene in Groundwater at the Tucson International Airport Superfund Site (EPA 2015).
EPC exposure point concentration
TCE trichloroethylene
RME reasonable maximum exposure
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4.11 Remedial Action Objectives
The 1988 EPA ROD states that the groundwater remedy selected by the Air Force in 1987 for AFP44 and
EPA's 1988 groundwater remedy, together provide the strategy to restore the Sole Source Aquifer of the
Tucson Basin. The 1988 EPA ROD developed objectives for the response actions in the TIAA. These
objectives included:
• To manage migration of contaminants (i.e., containment).
• To achieve public acceptance of the remedy.
• To protect public health and the environment.
• To attain consistency with ARARs.
• To determine the most environmentally sound, technically feasible, and cost-effective
remedy, which can be implemented in a timely manner.
• To ensure consistency with AFP44 remedial actions.
For the purposes of this Interim ROD Amendment, the RAOs for groundwater are as follows:
• Prevent human ingestion, inhalation, and/or direct contact exposure to COCs in groundwater
above levels that would pose an acceptable health risk.
• Prevent migration of 1,4-dioxane in groundwater that would pose an unacceptable risk to
human receptors.
• Restore contaminated groundwater throughout the VOC plume to levels that allow for
beneficial use (i.e., drinking water).
EPA completed a Focused Feasibility Study (FFS) Addendum that evaluated alternative end uses of
treated water from TARP other than as drinking water; these included discharge to the Tucson
Water recycled water system (Carollo Engineers, Inc. 2021).
4.12 Description of Alternatives
CERCLA requires that each selected remedial alternative: a) be protective of human health and the
environment, b) be cost-effective, c) comply with all applicable or relevant and appropriate
requirements, and d) use permanent solutions and alternative treatment technologies or resource
recovery technologies to the maximum extent practicable. In addition, the statute includes a
preference for the use of treatment as a principal element of the remedy which significantly
reduces the toxicity, mobility, or volume of hazardous substances. The estimated cost for the
alternatives below is estimated as a net present value cost as defined in the Focused FS (ECG, Inc.
2016c) and the cost opinion for FFS Addendum for management of treated water (Carollo
Engineers, Inc., 2021).
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EPA evaluated six alternatives in this revised remedy:
• Alternative 1: No Further Action.
• Alternative 2: Monitored Natural Attenuation (MNA) and Institutional Controls (ICs).
• Alternative 3: Enhanced Existing Pump-and-Treat System with UV-Peroxide Plus Long-term
Monitoring and ICs (EPA's preferred alternative).
• Alternative 4: Optimized Pump-and-Treat with UV-Peroxide and Partial Management of
Water by Reinjection to the Regional Aquifer Plus MNA and ICs.
• Alternative 5: Existing Pump-and-Treat with UV-Peroxide Plus In Situ Bioremediation (ISB)
and MNA and ICs.
• Alternative 6: Existing Pump-and-Treat with UV-Peroxide Plus In Situ Chemical Oxidation
(ISCO) and MNA and ICs.
Common Elements: With the exception of the Alternative 1, "No Further Action/' and Alternative 2, "MNA,"
all of the alternatives evaluated include common elements. All alternatives include active pump and
treatment of the VOCs and 1,4-dioxane groundwater plume, as follows:
• Alternative 3: Pump-and-treat utilizing ten remediation wells and UV-peroxide AOP.
• Alternatives 4, 5, and 6: Pump and treat utilizing nine remediation wells and UV-peroxide
AOP.
Attenuation parameters outside of the in-situ treatment zones would be monitored to ensure the
effectiveness of the remedies for Alternatives 5 and 6. All active alternatives, except for Alternatives 1 and
2, are expected to attain the RAO's objectives. Finally, other than the No Further Action alternative, all
alternatives evaluated here contain long-term monitoring for TIAA Superfund Site Area A. These common
elements are consistent with the 1988 EPA ROD, which proposed that cleanup efforts manage migration
of contaminants in groundwater at TIAA Superfund Site Area A.
4.12.1 Alternative 1: No Further Action
EPA is required to consider the No Further Action alternative to provide a baseline for the purpose of
comparison to other alternatives. Under this alternative, no additional treatment would be implemented,
and monitoring would cease (EGC, Inc. 2016c). The estimated cost for this alternative is $0, and this
alternative is not anticipated to achieve RAOs within the balanced timeframe of 30 years.
4.12.2 Alternative 2: Monitored Natural Attenuation and Institutional Controls
This alternative relies on natural attenuation processes for remediation of contaminants to an appropriate
degree and within a reasonable timeframe based on site-specific objectives. MNA includes no active
remediation, but does include groundwater monitoring to document the reduction in contaminant
concentrations in groundwater over time. MNA is discussed in further detail in the common elements of
the alternatives in this section. The net present value for this alternative is $3.2 million (Table 4-4), and
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this alternative does not achieve either containment or restoration and does not meet RAOs within a
reasonable 30-year timeframe (EGC, Inc. 2016c).
Table 4-4
Remedy Alternatives and Estimated Cost
Alternative
Total Capital*
Total Operation
and Maintenance
Total Cost
Net Present Value**
(7% Discount Rate)
Alternative 2
$13,000
$7,710,000
$7,723,000
$3,205,000
Alternative 3
$38,870,000
$85,860,000
$124,730,000
$53,000,000
Alternative 4
$258,000
$88,240,000
$88,499,000
$37,887,000
Alternative 5
$6,498,000
$161,913,000
$168,411,000
$75,390,000
Alternative 6
$4,040,000
$104,327,000
$108,367,000
$49,880,000
Notes:
* Total capital construction cost for Alternative 3 is presented in the FFS Addendum (Carollo, 2021), including infrastructure to
deliver treated water to the recycled water system (RWS) and Santa Cruz River outfall. Total capital costs for Alternatives 2,4, 5,
and 6 are presented in Table 7-1 of the Volume III Final Focused Feasibility Study for 1,4-Dioxane North of Los Reales Road
(EGC, Inc. 2016c). These alternatives were developed assuming delivery of treated water to the potable water system only,
without infrastructure for delivery to RWS or outfall to the Santa Cruz River.
** Net present value is the difference between the present value of cash How and the value of the cash flow over time, taking
into account the estimated 30-year time frame for implementation of the remedy. The net present value discount rate of 1
percent is based on Circular A-94, U.S. Office of Management and Budget (October 1992), discount rate policy for Base-Case
Analysis. Net present values at the 7 percent discount rate are presented in Appendix A for Alternatives 2 through 6.
Alternative 1 (No Further Action) is not included in this analysis because there is no cost associated with this alternative, and it
does not meet the threshold criteria.
All costs are rounded to the nearest $1,000.
4.12.3 Alternative 3: Enhanced Existing Pump-and-Treat System with UV-
Peroxide Plus Long-Term Monitoring and ICs (EPA's Preferred
Alternative)
Alternative 3 involves continued pump and treatment using the existing pump-and-treat system for TIAA
Superfund Site Area A (consisting of nine extraction wells) in addition to optimizing the existing system
with installation of one additional high-capacity remediation well and expanding the existing AOP system.
The new well will be located within the area of largest contaminant mass of the plume just south of TARP
North Well Field. The new well will be designed and constructed for a pumping capacity of approximately
1,300 gpm to enhance the removal of contaminant mass from the aquifer and reducing the remedy
duration. The AOP system will be upgraded with installation of a third pair of UV-reactors, four additional
GAC contactors, an additional desander unit, an outfall to the Santa Cruz River, and reservoir/booster
station for delivery of treated water to the Tucson Water recycled water system (Carollo Engineers, Inc.
2021). The groundwater extraction system currently pumps groundwater to the TARP WTP and UV-AOP
facility in addition to the original air strippers. Since the UV-AOP has effectively demonstrated that it
meets all treatment objectives for both 1,4-dioxane and VOC contaminants, this alternative would
eliminate the packed column aeration from the TARP WTP (Arcadis 2016). The end use of treated water
from TARP will include the options to discharge the water to the Santa Cruz River and the City of Tucson
recycled water system, in addition to the current option of the drinking water distribution system. The
recycled water system includes use as turf and landscape irrigation water for golf courses, parks, and some
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residences; additional managed discharge to the Santa Cruz River channel as aquifer recharge and
hydroriparian habitat; and constructed aquifer recharge projects.
This alternative would also include long-term monitoring of the plume contamination levels. This
alternative will evaluate the currently used technologies (including current monitoring and controls) for
the enhanced TARP remediation system at TIAA Superfund Site Area A.
Although the existing pump-and-treat system will likely operate for a longer period of time, cost-
estimating is provided for a 30-year operating period. In addition to the current pump-and-treat system,
long-term monitoring will be applied over portions of the plume to monitor reduction in dissolved-phase
concentrations in groundwater, and investigate if the plume is stable or decreasing over the 30-year
timeframe. The net present value for this alternative is approximately $51 million (Table 4-4). The
duration of the remedy is assumed to be 30 years for estimation of operation costs. Alternative 3 would
likely require several decades to meet RAOs (EGC, Inc. 2016c).
4.12.4 Alternative 4: Optimized Pump-and-Treat with UV-Peroxide and Partial
Management of Water by Reinjection to the Regional Aquifer Plus MNA
and ICs
Alternative 4 is similar to Alternative 3 with optimized pump and treatment using the operations of the
existing TARP system and removal of TCE and 1,4-dioxane in groundwater using UV-AOP and air stripping.
Alternative 4 would also include partial reinjection (approximately 1,200 gpm) of the treated groundwater
back into the regional aquifer to help control plume migration. The remaining flow (approximately
3,800 gpm) would continue to be sent to the City of Tucson drinking water distribution system.
In addition to the pump and treatment, MNA would be applied to portions of the plume to monitor
reduction in dissolved-phase concentrations in groundwater, and to show that the plume is stable or
decreasing over a 30-year timeframe. The net present value for this alternative is estimated at $38 million
(Table 4-4) (EGC, Inc. 2016c). Although the pump-and-treat system will likely operate for a longer period
of time, cost-estimating is provided for a 30-year operating period. Alternative 4 would not likely meet
RAOs sooner than the 30-year timeframe (EGC, Inc. 2016c).
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4.12.5 Alternative 5: Existing Pump-and-Treat with UV-Peroxide Plus In Situ
Bioremediation and MNA and ICs
Alternative 5 is similar to Alternative 3, as it involves continued use of the pump-and-treat system with
treatment by the existing TARP plant including the UV-AOP system. However, under Alternative 5, ISB
injection wells would be installed in the UZ between Los Reales Road and Valencia Road throughout the
middle of the 1,4-dioxane groundwater plume. Active treatment would be maintained until groundwater
concentration criteria are met, which this alternative assumes will occur after 20 years. The exact method
and delivery of ISB would be determined in the subsequent remedial design documents. Alternative 5 also
includes MNA over portions of the plume to confirm treatment progress and plume stability, or to monitor
reduction. The estimated net present value for this alternative is approximately $75 million (Table 4-4),
and the estimated time to achieve RAOs is 20 years for the ISB and pump-and-treat components, and
30 years for MNA for the mass of contaminant in the UZ (EGC, Inc. 2016c). The previously described
30-year operating period is assumed for the contaminant mass in the Regional Undivided Aquifer.
4.12.6 Alternative 6: Existing Pump-and-Treat with UV-Peroxide Plus In Situ
Chemical Oxidation and MNA and ICs
Alternative 6 is similar to Alternative 3, as it involves continued use of the pump-and-treat system with
treatment by the existing TARP plant including the UV-AOP system. However, under Alternative 6, ISCO
injection wells would be installed throughout the 1,4-dioxane groundwater plume, and a chemical oxidant
injected on a semi-annual basis. Active treatment would be maintained until groundwater concentration
criteria are met, which this alternative assumes will occur after 10 years. The exact method and delivery
of ISCO would be determined in the subsequent remedial design documents. Alternative 6 also includes
MNA, which would be extended for 10 years following ISCO implementation. The estimated net present
value for this alternative is approximately $50 million (Table 4-4), and the estimated time to achieve RAOs
is 10 years for the ISCO and pump-and-treat components, and 20 years for MNA (EGC, Inc. 2016c). The
previously described 30-year operating period is assumed for the contaminant mass in the Regional
Undivided Aquifer.
4.13 Comparative Analysis of Alternatives
EPA evaluates each of the alternatives based on nine standard criteria. The first two criteria are threshold
criteria: overall protection of human health and the environment, and compliance with ARARs. The next
five criteria are balancing criteria: long-term effectiveness and permanence; reduction of toxicity,
mobility, or volume through treatment; short-term effectiveness; implementability; and cost. The final
two criteria are modifying criteria: State acceptance and community acceptance, which were evaluated
after the close of the public comment period on the proposed remedy. Table 4-5 illustrates comparative
analysis of the alternatives, not including the modifying criteria.
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Table 4-5
Comparative Analysis of Alternatives (Excluding State and Community Acceptance)
Alternative
Overall Protection of Human
Health and the Environment
Compliance with Federal and
State ARARs
Long-Term Effectiveness and
Permanence
Reduction of Toxicity, Mobility,
and/or Volume
Short-Term Effectiveness
Implementability
Cost*
No Further Action
No - Future exposure to impacted
groundwater is not prevented under
this alternative; therefore, existing
risks from impacted media will
remain. This alternative will not be
protective of human health or the
environment.
No - Chemical-specific ARARs
may be met over a long time
frame. However, without
monitoring this cannot be
confirmed. There are no location
or action-specific ARARs for this
alternative.
Low - Impacted groundwater would
remain in place. No Action has a low
degree of long-term effectiveness in
ensuring the continued protection of
human health and the environment.
Low - Only reduction of toxicity,
mobility, and volume would be
through natural attenuation.
Low - Impacted groundwater would
remain in place. No treatment is
implemented; therefore, short-term
effectiveness is not relevant to this
alternative.
High - No construction or operation
would be required; therefore, issues
regarding technology availability,
agency approvals, constructability,
and reliability are not applicable.
Remedial effectiveness cannot be
determined due to lack of any
monitoring program.
No Cost
2. Monitored Natural Attenuation
No - Institutional controls provide
protection of human health by
preventing use of groundwater. The
institutional controls would be
applied to the areas impacted by the
groundwater plume. Groundwater
monitoring would allow the
identification and control of any
future risks that would result from
constituent migration; however,
dissolved-plume may migrate
without P&T or other active remedy
(e.g., ISCO orlSB).
No - Chemical-specific ARARs
for groundwater may be met
over a long time frame. There
are no location-specific ARARs
for this alternative. Action-
specific ARARs will be met
through proper design,
planning, and implementation.
Low - Non-destructive MNA
mechanisms: dispersion, sorption and
diffusion, are known to be active in
groundwater at AFP 44 and should also
exist at TARP Area A. Studies are in
progress to further evaluate MNA
effectiveness for TCE and 1,4-dioxane
at AFP 44. No action would be
performed beyond monitoring.
Contaminants would remain in the
aquifer above MCLs for an indefinite
period (likely longer than 30 years).
Low - Only reduction of toxicity,
mobility, and volume would be
through natural attenuation.
Low - Low for TCE and 1,4-dioxane.
There is field evidence that local
microorganisms can degrade 1,4-
dioxane and TCE at AFP 44 and the
same microorganisms should exist
at Area A. Natural degradation rates
are not known but are thought to be
very slow for TCE and 1,4-dioxane.
High - Little construction and no
operation would be required;
therefore issues regarding
constructability and implementability
are not applicable. Remedial
effectiveness determined by
monitoring program.
Low Cost
3. Enhanced Existing P&T System
with UV-Peroxide plus Long-Term
Monitoring
Yes - Hydraulic containment and
reduction in contaminant detections
in the aquifer and pumping from
higher-concentration zone and
active treatment will meet RAOs,
thereby reducing risk to human
health and the environment.
Includes ICs to prevent exposure.
Yes (compliance with ARARs) -
Chemical-specific ARARs for
groundwater will be met over
time. There are no location-
specific ARARs for this
alternative. Action- specific
ARARs will be met through
proper design, planning, and
implementation.
High - Existing system P&T has been in
operation since 1994, and has
demonstrated long-term hydraulic
containment and removal of
contaminants from the groundwater, but
long-term effectiveness has been
limited by source removal through
dissolved- phase only. The addition of a
new remediation well will increase
source removal through the northern
portion of the plume.
Moderate - The existing P&T
system's mass reduction only occurs
through dissolved-phase
groundwater extraction and is back-
diffusion limited. Mobility of
1,4- dioxane impacted groundwater
is reduced through groundwater
pumping for 30 years. Toxicity and
volume of COC-impacted
groundwater would decrease in the
future as the concentrations
attenuate, albeit over long-periods of
time.
High - The existing P&T system and
installation of one additional
remediation well and associated
piping has low short-term risk to
human health and the environment.
Moderate - Treatment system in
place and in use, upgrades would
be required to treat additional
extracted water. New remediation
well and piping would be required.
New infrastructure to discharge
treated water to the recycled water
system would be required.
Moderate Cost
4. Optimized Pump-and-Treatwith
UV-Peroxide and Partial
Management of Water by
Reinjection to the Regional Aquifer
plus MNA
Yes - Hydraulic containment and
reduction in contaminant detections
in the aquifer and pumping from
higher-concentration zones and
active treatment will meet RAOs,
thereby reducing risk to human
health and the environment.
Includes ICs to prevent exposure.
Yes (compliance with ARARs) -
Chemical-specific ARARs for
groundwater will be met over
time. There are no location-
specific ARARs for this
alternative. Action- specific
ARARs will be met through
proper design, planning, and
implementation.
Moderate - P&T removal of
contaminants from the groundwater will
meet RAOs and restore the aquifer to
its beneficial use, but back-diffusion
limited source removal through
dissolved-phase only (likely longer
than 30 years).
Low/Moderate - Mass and volume
reduction only through dissolved-
phase groundwater extraction.
Concentrations would remain
because sources are back-diffusion
limited. Mobility of 1,4-dioxane
impacted groundwater is reduced
through groundwater pumping for 30
years and MNA processes for 30
years. Toxicity and volume of COC-
impacted groundwater would
decrease in the future as the
concentrations attenuate via MNA.
High- the existing treatment system
has low short-term risk to human
health and the environment. The
chemicals used for treatment
provide a potential risk to workers if
not properly handled and disposed.
Low risk to workers during
installation of new recovery wells
and piping.
Moderate - Treatment system in
place and in use, no construction or
operation would be required. New
injection wells and piping will be
required.
Moderate Cost
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Table 4-5 (continued)
Comparative Analysis of Alternatives (Excluding State and Community Acceptance)
Alternative
Overall Protection of Human
Health and the Environment
Compliance with ARARs
Long-Term Effectiveness and
Permanence
Reduction of Toxicity, Mobility,
and/or Volume
Short-Term Effectiveness
Implementability
Cost*
5. Pump-and-Treatwith UV-
Peroxide plus ISB and MNA
Yes - P&T with ISB reduction of
contaminants in aquifer will meet
RAOs, thereby reducing risk to
human health and the environment.
Includes ICs to prevent groundwater
use.
Yes (compliance with ARARs) -
Chemical-specific ARARs for
groundwater will be met over
time. There are no location-
specific ARARs for this
alternative. Action- specific
ARARs will be met through
proper design, planning, and
implementation.
Moderate - Groundwater P&T will
meet RAOs and restore the aquifer to
its beneficial use. ISB can reduce
plume longevity if conducted within a
contamination source area, but the
location of the ISB in this alternative is
in the LIZ, which is not a source area,
and no study has been conducted to
determine the efficacy of ISB at this
site. This location was proposed prior
to source treatment at AFP 44, which
has decreased the concentrations in
the proposed location. Therefore, ISB
will not address the majority of the
contaminant mass in the Regional
Divided Aquifer.
Low - Studies have shown that ISB
will remove groundwater
contaminants and reduce
contaminant mass, volume, and
toxicity when applied at contamination
source areas. The ISB location in this
alternative is not a source area. Back-
diffusion limited sources and
migration from the airport could
extend the plume longevity. The AFP
44 source treatment has reduced
contaminant migration north of Los
Reales Road, thereby limiting the
effectiveness of active treatment in
the proposed location.
Low - The chemicals used for in situ
treatment (i.e., propane) provide a
potential risk to workers if not
properly handled and disposed.
Moderate risk to workers during
installation of new injection wells
and piping which would impact a
treatment area of 253 acres and
installation of 156 injection points
within the public right-of-way.
Construction would impact a
densely-populated and long-
established residential area.
Low - New construction would be
required. New wells and piping will
be required for injection points and
co-metabolites. This construction
would require a large number of
wells in a densely populated and
long-established residential area
that is not a source area for
1,4-dioxane, resulting in disruptions
to the community without assurance
of effectiveness.
Highest Cost
6. Pump-and-Treatwith UV-
Peroxide plus ISCO and MNA
Yes - P&T with ISCO reduction of
contaminants in aquifer will meet
RAOs, thereby reducing risk to
human health and the environment.
Includes ICs to prevent groundwater
use.
Yes (compliance with ARARs)
- Chemical-specific ARARs for
groundwater will be met over
time. There are no location-
specific ARARs for this
alternative. Action- specific
ARARs will be met through
proper design, planning, and
implementation.
Moderate - Groundwater P&T will
meet RAOs and restore the aquifer to
its beneficial use. ISCO can reduce
plume longevity if conducted within a
contamination source area, but the
ISCO location in this alternative is not
a source area, and no study has been
conducted to determine the efficacy of
ISCO at this site. This location was
proposed prior to source treatment at
AFP 44, which has decreased the
concentrations in the proposed
location. Therefore, ISCO will not
address the majority of the
contaminant mass in the Regional
Divided Aquifer.
Low - Studies have shown that ISCO
will remove groundwater
contaminants and reduce
contaminant mass, volume, and
toxicity when applied at contamination
source areas. The ISCO location in
this alternative is not a source area.
Back-diffusion limited sources and
migration from the airport could
extend the plume longevity. The
AFP 44 source treatment has
reduced contaminant migration north
of Los Reales Road, thereby limiting
the effectiveness of active treatment
in the proposed location.
Low - The existing treatment system
has low short-term risk to human
health and the environment. The
chemicals used for treatment (i.e.,
Na2S208) provide a potential risk to
workers if not properly handled and
disposed. Moderate risk to workers
during installation of new injection
wells and piping which would impact
a treatment area of 253 acres and
installation of 156 injection points
within the public right-of-way.
Construction would impact a
densely-populated and long-
established residential area.
Low - New construction would be
required. New wells will be required
for in situ chem-ox. This
construction would require a large
number of wells in a densely
populated and long-established
residential area that is not a source
area for 1,4-dioxane, resulting in
disruptions to the community
without assurance of effectiveness.
Moderate Cost
Notes:
The table has been modified from Table 7-1 of the Focused Feasibility Study. Alternative 3 has been updated and Alternatives 5 and 6 were evaluated within the context of how effective the active remediation technologies (ISB and ISCO) would be once implemented across a large diffused groundwater plume rather than
within a contamination source area.
* A detailed summary of alternative costs are presented in Table 4-4.
ARAR
Applicable or Relevant and Appropriate Requirement
COC
contaminant of concern
GW
groundwater
IC
institutional control
ISB
in situ bioremediation
ISCO
in situ chemical oxidation
MCL
maximum contaminant level
MNA
monitored natural attenuation
P&T
pump-end-treat
RAO
remedial action objective
TARP
Tucson Airport Remediation Project
TCE
trichloroethylene
UV
ultraviolet light
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4.13.1 Threshold Criteria
Overall Protection of Human Health and Environment
Overall protection of human health and the environment criterion is the final and determining assessment
of an alternative's ability to satisfy the protectiveness requirement. To be deemed protective, an
alternative must meet the RAOs, reduce risks to acceptable levels, meet ARARs, and generally satisfy the
balancing criteria.
Alternative 1, "No Further Action/' and Alternative 2, "MNA," are not protective, because they do not treat
source areas and prevent plume migration. The other four alternatives provide for treatment of TCE and
1,4-dioxane and are protective of human health and environment.
Compliance with Federal and State ARARs
Section 121(d) of CERCLA and NCP § 300.430(f)(l)(ii)(B) require that remedial actions at CERCLA sites at
least attain ARARs unless such ARARs are waived under CERCLA section 121(d)(4). Compliance with ARARs
is based on an alternative's ability to the ARARs. ARARs can be chemical-specific, action-specific, or
location-specific. Chemical-specific and action-specific ARARs are presented in Tables 4-6 and 4-7,
respectively, in Section 4.18. There are no location-specific ARARs associated with the alternatives in this
interim ROD Amendment.
The No Further Action alternative does not comply with ARARs because that alternative does not include
monitoring, and there would be no way to determine when or if groundwater cleanup levels were
achieved. For Alternative 2, because the source of the TCE and 1,4-dioxane in groundwater may still be
present in the aquifer south of Los Reales Road and at the Three Hangars Building, natural attenuation of
the groundwater contaminants could take decades and would not meet ARARs in a reasonable 30-year
timeframe. Alternatives 3 and 4 both include existing groundwater pump-and-treat systems that would
achieve compliance with ARARs by hydraulically containing the plume while gradually reducing
concentrations of contamination in groundwater. Alternatives 5 and 6 assume the TARP groundwater
pump-and-treat and UV-AOP systems as well as the proposed in situ treatment of wells will also meet
ARARs based on currently available information.
4.13.2 Balancing Criteria
Long-Term Effectiveness and Permanence
This criterion connotes the level of protection afforded by an alternative after completion of the proposed
remedial actions. EPA must assess the anticipated effectiveness of the remedy in controlling potential
residual risks due to untreated materials, or treatment of residuals remaining on site after completion of
the remedial actions. This assessment includes a judgment regarding the potential for realizing long-term
improvements in environmental quality resulting from the alternative. Factors considered under the long-
term effectiveness evaluation include the following:
• The magnitude of residual risks upon completion of the remedy, such as the volume, toxicity,
mobility, and potential for bioaccumulation of COCs remaining on site.
• The expected adequacy and reliability of engineering controls performed under the
alternative, including the suitability and continued effectiveness of controls used to manage
the residual risks after the RAO has been met.
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Alternative 1 has the lowest long-term effectiveness and permanence because potential exposures to
known areas of contamination would not be controlled. For Alternative 2, an MNA assessment would
need to be made to demonstrate protectiveness, and then a contingency plan would need to be included.
Additionally, the rate of natural attenuation and plume longevity for the groundwater plume north of Los
Reales Road is unknown; therefore, it is also unknown if the rate of natural attenuation meets or exceeds
the rate of groundwater migration. Alternative 2 would require ICs to prohibit the use of aquifers as a
source of drinking water, plus monitoring to confirm the plume is not migrating over time.
Alternative 3 involves both groundwater pumping, which would continue to provide hydraulic
containment of the groundwater plume, in addition to installation of a new remediation well which
increases mass removal within the plume. Alternative 4, which also involves groundwater pumping, would
only provide hydraulic containment with limited mass removal and would require more time to meet site
closure than Alternative 3. The new remediation well in Alternative 3 was designed to remove the mass
from the most contaminated portion of the aquifer. Operation of this well, therefore, will achieve RAOs
quicker than all other alternatives. Both Alternatives 3 and 4 would be moderately to highly effective in
achieving long-term effectiveness and permanence because they would provide hydraulic containment
while minimizing exposure to contaminated groundwater for a period of 30 years.
Alternative 5 uses ISB to treat 1,4-dioxane and TCE in groundwater north of Los Reales Road. An additional
study would be required to provide evidence to support natural attenuation of 1,4-dioxane, and to
validate natural and engineered ISB. Until additional studies are conducted, it is unknown if Alternative 5
would provide long-term effectiveness and permanence with currently available treatment technologies.
The proposed location for ISB is within the UZ of Plume A, which would not impact the long-term
effectiveness of Alternative 5 to address the large mass of contaminant in the Regional Undivided Aquifer.
Actual ISB treatments have been conducted at the source location on AFP44 and have been included in the
2020 ROD prepared by the USAF.
Alternative 6 includes ISCO for plume treatment in groundwater and destruction of 1,4-dioxane and TCE.
Currently, available chemicals such as sodium persulfate have been shown to be effective in the
destruction of 1,4-dioxane and TCE and would have high long-term effectiveness and permanence
addressing contamination in the UZ of Plume A. The long-term effectiveness of ISCO treatment on
groundwater of the UZ would lower for the contaminant mass in groundwater of the Regional Undivided
Aquifer. Alternative 6 would require ICs to adequately protect workers who may come into contact with
contaminated groundwater.
Reduction in Toxicity, Mobility, or Volume through Treatment
The NCP states a preference for remedies that reduce toxicity, mobility, or volume of through treatment
(which is an active process). The degree to which alternatives employ recycling or treatment that reduces
toxicity, mobility, or volume are assessed, including how treatment is used to address the principal threats
posed by the site. Factors used in deciding if the extent to which each alternative meets this criterion
include the following, to the extent appropriate:
• The treatment or recycling processes the alternatives employ and materials they will treat.
• The amount of hazardous substances, pollutants, or contaminants that will be destroyed
treated, or recycled.
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• The degree of expected reduction in toxicity, mobility, or volume of the waste due to treatment
or recycling and the specification of which reduction(s) are occurring.
• The degree to which the treatment is irreversible.
• The type and quantity of residuals that will remain following treatment, considering the
persistence, toxicity, mobility, and propensity to bioaccumulate of such hazardous substances
and their constituents.
• The degree to which treatment reduces the inherent hazards posed by principal threats at the
site.
Alternative 1 does not meet any of the criteria and would not reduce toxicity, as there is no treatment.
Alternative 2, which also eschews active treatment, would rely on reduction in toxicity, mobility, or volume
of contaminated groundwater through natural attenuation mechanisms.
Due to the scale of the diffused groundwater plume and the multiple aquifers, Alternatives 3 and 4 are
expected to have moderate reductions in mobility and toxicity of contaminants over the 30-year period.
These alternatives will treat the COCs, is irreversible, over time will eliminate residuals, and eliminate the
hazards inherent to the site.
Alternatives 5 and 6 would reduce the volume of contaminated groundwater through treatment of
elevated concentration areas. The degree of effectiveness of source treatment and reduction in dissolved-
phase plume longevity would require further testing to quantify those processes. These alternatives have
the potential to cause residual chemicals used in the injections to persist in the aquifer or be extracted by
the remediation wells and delivered to the TARP treatment system.
Short-Term Effectiveness
This criterion addresses the potential impacts an alternative might have on human health or the
environment during the construction or implementation phase, through and up to the time the RAO is
achieved. The following factors are considered in the short-term effectiveness assessment:
• Short-term risks that might be posed to the community during implementation of an
alternative.
• Potential impacts on works during remedial action and the effectiveness and reliability of
protective measures.
• The potential impacts on the environment during construction or implementation, and the
reliability of mitigation measures for preventing or reducing these potential impacts.
• The time required to implement the proposed remedial measures and achieve the RAO.
Alternatives 1 and 2 would have the lowest relative short-term effectiveness because they do not meet
RAOs. Alternatives 3 and 4 would require less disruption to the surrounding community than Alternatives
5 and 6, and are expected to have high short-term effectiveness due to the site history of pump and
treatment and the demonstrated effectiveness of the technology.
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Alternatives 5 and 6 would have the highest short-term risk and, therefore, the lowest short-term
effectiveness to workers and the surrounding community because the remedy involves installation of
in-situ treatment wells in a densely populated residential area, which would increase the risk of exposure
to dust, noise, and increased traffic. Both Alternatives 5 and 6 would affect a treatment area of
approximately 253 acres and would include construction and installation of approximately 156 injection
points within the public right-of-way. Because of the elevated risks and longer construction duration of
Alternatives 5 and 6, their short-term effectiveness are lower than for Alternatives 3 and 4.
Implementability
The implementability criterion is a measure of the ease or difficulty of implementing the alternatives to
be assessed by considering the following types of factors, as appropriate:
• Technical feasibility, including technical difficulties and unknowns associated with the
construction and operation of a technology, the reliability of the technology, ease of
undertaking additional remedial actions, and the ability to monitor the effectiveness of the
remedy.
• Administrative feasibility, including activities needed to coordinate with other offices and
agencies and the ability and time required to obtain any necessary approvals and permits from
other agencies (for off-site actions).
• Availability of services and materials, including the availability of adequate off-site treatment,
storage capacity, and disposal capacity and services; the availability of necessary equipment
and specialists, and provisions to ensure any necessary additional resources; the availability of
services and materials; and availability of prospective technologies.
The scale of the dissolved-phase plume, complexities of the multiple aquifers, and the effect of back-
diffusion from sources of dissolved-phase contaminants make any technology difficult to implement at
the Site. Other potential complications with implementability of a remedy include proximity of the plume
to potential receptors and limited right-of-way access due to existing building, foundations or
roadways. Additionally, there could be detrimental effects on the community caused during
implementation of the remedy, including waste transportation through neighborhoods, mobilization and
demobilization of construction equipment, drilling, excavating, and road closures (ECG, Inc. 2016c).
Alternatives 1 and 2 are highly implementable. For the remaining alternatives, Alternative 3 followed by
Alternative 4 are moderately easy to implement because they involve the least amount of construction
activities and materials and supplies are readily available. Alternatives 5 and 6 are the least easy to
implement because they would require extensive construction activities and specialty equipment and
chemicals as detailed in the paragraph above.
Cost
EPA compares each alternative based on upfront capital costs (including both direct and indirect costs);
annual operation and maintenance cost; and overall net present value of capital and O&M costs, which is
a measure of the total future project cost over a 30-year timeframe.
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There is no cost for Alternative 1. Since Alternatives 1 and 2 do not meet the RAOs, the next least costly
alternative is Alternative 4. Alternative 3 and Alternative 6 have moderate costs. Alternative 5 is the most
costly of all alternatives. Table 4-4 summarizes the estimated costs of each of the remedy alternatives for
the site.
4.13.3 Modifying Criteria
State Acceptance
This criterion considers whether the State agrees with the analyses and recommendations, as described
in the Focused RI/FS and Proposed Plan.
In a letter dated March 16, 2023, from ADEQ's Remedial Projects Section to EPA, ADEQ provided its
concurrence for the Preferred Alternative stating "ADEQ supports the Proposed Plan and Draft Interim
Record of Decision Amendment for the TARP remedy."
Community Acceptance
This criterion considers whether the local community agrees with EPA's analyses and Preferred
Alternative. Comments received on the Proposed Plan are an important indicator of community
acceptance.
The community includes residents of the City of Tucson and City of South Tucson, the Unified Community
Advisory Board (UCAB), and all the various stakeholders. The UCAB has been in existence for more than
25 years and original members were South Tucson residents. There are quarterly UCAB meetings where
members, residents, and stakeholders are kept apprised of the status of the site. The UCAB is a
collaborative relationship with EPA, the City, and ADEQ. Members of the UCAB expressed support for the
Preferred Alternative, as referenced in Part III (Section 5.0) of this ROD Amendment, Responsiveness
Summary.
During the public comment period, EPA received a number of comments from the community. EPA
received oral comments from members of the public who attended the March 30, 2017 Public Meeting,
and the entire transcript of the public comments is included in the Administrative Record file for this ROD
Amendment. EPA also received written and oral comments from UCAB members, City of Tucson Water
Department, and the community, including residents, property owners, and stakeholders.
The City of Tucson Water Department operates the groundwater treatment facility and delivers the
treated water to the public water supply system. In a letter dated June 8, 2017, Tucson Water stated its
support for the Preferred Alternative. The letter stated "Alternative 3 has been in use since early 2014 and
has proven to be protective of human health and the environment."
The community, in particular the UCAB, generally supports the Preferred Alternative, and has expressed
support throughout the process during the quarterly meetings and public meetings related to the
Proposed Plan. During the public meetings some citizens expressed that the site was not being cleaned up
quick enough. Therefore, EPA added the enhancements of the additional extraction well to increase the
mass of contaminants being removed and upgrades to the AOP facility to treat the additional extracted
volume of groundwater. The City of Tucson requested that alternative end-uses of the treated water be
considered, including conveyance to the recycled water system which includes discharge to the Santa Cruz
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River. The proposal of these enhancements has been well-received by the citizens, the Mayor, the City
Council for Tucson, and the UCAB. (See Section 4.26, Documentation of Significant Change). We
acknowledge that some commenters expressed a preference for Alternative 5 and/or Alternative 6 prior
to the enhancements were added to Alternative 3.
The comments provided to EPA during the public comment period and EPA's responses to comments are
addressed in Part III (Section 5.0) of this ROD Amendment, Responsiveness Summary.
4.14 Principal Threat Waste
The NCP establishes an expectation that EPA will use treatment to address the principal threats posed by
a Site wherever practicable. The principal threat concept is applied to the characterization of source
materials at a Superfund site. Source material is material that includes or contains hazardous substances,
pollutants or contaminants that act as a reservoir for migration of contamination to ground water, surface
water or air, or acts as a source for direct exposure. Contaminated ground water generally is not
considered to be a source material. Contaminated groundwater, as addressed by the six alternatives, does
not constitute a principal threat waste at this Site.
4.15 Selected Remedy
Based on information currently available, EPA believes Alternative 3 meets the threshold criteria and
provides the best balance of trade-offs among the other alternatives with respect to the balancing and
modifying criteria. EPA expects the selected remedy to satisfy the following statutory requirements of
CERCLA §121(b): 1) be protective of human health and the environment, 2) comply with ARARs; 3) be cost-
effective, 4) utilize permanent solutions and alternative treatment technologies or resource recovery
technologies to the maximum extent practicable, and 5) satisfy the preference for treatment as a principal
element. Figure 4-5 shows a conceptual design of Alternative 3. This remedy provides for containment
and treatment of 1,4-dioxane, based on the original 1988 EPA ROD that provides for containment and
treatment of TCE.
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Valency Itoad
Air Force
Plant 44
(AFP44)
Miles
Reales
Los
Tucson
Airport
Remediation
Project
(TARP)
"rvington Road
Drexel Road
The 1,4-dioxane base map was prepared by the Arizona Department of Environmental
Quality (ADEQ). Trichloroethene (TCE) contours, aquifer demarcation lines, and the
1,4-dioxane contour in the Lower Zone of the Divided Aquifer were added by the
United States Environmental Protection Agency (EPA).
LEGEND
1,4-Dioxane > 0.35 ug/l
1,4-Dioxane > 3.5 ug/l
TCE > 5.0 ug/l
TCE > 50 ug/l
ug/l - Micrograms per liter
~ Data from 2019 to 2022 (unstarred data collected prior to 2019).
1,4-Dioxane < 0.35 ug/l
1,4-Dioxane > 0.35 < 3.5 ug/l
1,4-Dioxane > 03.5 ug/l
O North Well Field (NWF) Remediation Well
O South Well Field (SWF) Remediation Well
o New Remediation Well
Figure 4-5
Alternative 3
Site Map
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4.16 Statutory Determinations
This interim action (the Selected Remedy) should protect human health and the environment until a final
ROD is implemented, complies with ARARs, and is cost-effective. This interim action is not designed or
expected to be final. But this interim action represents the best balance of trade-offs among alternatives
with respect to pertinent criteria, given the limited scope of the action. This interim action also supports
permanent solutions and alternative treatment technologies or resource recovery technologies to the
maximum extent practicable. In addition, this interim action supports a preference for remedies that
employ treatment that permanently and significantly reduces the volume, toxicity, or mobility of
hazardous substances, pollutants, or contaminants as a principal element, and a bias against off-site
disposal of untreated wastes.
4.17 Protection of Human Health and Environment
Exposure to the public of contaminated groundwater through public water supplies or private water wells
is the potential risk. The selected remedy will be protective of human health by reducing the COCs in
groundwater through treatment to meet drinking water standards, which will be in place until remedial
action objectives are achieved. ICs will protect human health by reducing or managing the likelihood of
humans coming into contact with contaminated groundwater as outlined below. Institutional Controls will
include various Arizona well siting, permitting, and construction restrictions, and notices distributed by
the Arizona Department of Water Resources, Arizona Department of Health Services, ADEQ or EPA
concerning risks from exposure to contaminated groundwater. The remedy will not have detrimental
cross-media impacts such as air emissions or contaminated surface water discharges.
The State of Arizona can impose restrictions with respect to registration of wells and drilling within the
groundwater plume area. As provided in Arizona Revised Statues 45, Chapter 2, Article 10, drilling a well
in Arizona must meet administrative requirements that the well is drilled by a licensed contractor, the
contractor will use approved well construction methods, a Notice of Intent (NOI) will be filed with Arizona
Department of Water Resources, and its staff will review the NOI for proximity to a contaminated site and
confer with ADEQ before approving the NOI.
In addition to State of Arizona restrictions on installation or modifications of wells, Pima County monitors
and inspects all private wells within the TCE groundwater plume footprint and provide reports to the
public, ADEQ, and EPA.
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4.18 Compliance with Applicable or Relevant and Appropriate
Requirements
The following sections describe the chemical-specific and action-specific ARARs for the Selected Remedy.
There are no location-specific ARARs. Tables 4-6 and 4-7 present the chemical-specific and action-specific
ARARs, respectively. This is in compliance with NCP § 300.430(f)(5)(ii)(B) & (C). All ARARs will be met upon
completion of the selected remedy, and no ARARs are being waived.
Applicable requirements are those cleanup standards, standards of control, and other substantive
environmental protection requirements, criteria, or limitations promulgated under Federal or State law
that 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, and other
substantive environmental protection requirements, criteria, or limitations promulgated under Federal or
State law that, while not "applicable" to a hazardous substance, pollutant, contaminant, remedial action,
location, or other circumstance at a CERCLA site, address problems or situations sufficiently similar to
those encountered at the CERCLA site that their use is well-suited to the particular site.
To Be Considered Criteria: in addition to legally binding laws and regulations, many Federal and State
environmental and public health programs also develop criteria, advisories, guidance, and proposed
standards that are not legally binding, but that may provide useful information or recommended
procedures. These materials are not potential ARARs but are evaluated along with ARARs, as part of the
risk assessment conducted for each CERCLA site, to set protective cleanup level targets. Chemical- specific
TBC values such as health advisories and reference doses will be used in the absence of ARARs or where
ARARs are not sufficiently protective to develop cleanup goals. In addition, other TBC materials such as
guidance or policy documents developed to implement regulations may be considered and used as
appropriate, where necessary to ensure protectiveness.
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Table 4-6
Chemical-Specific ARARs for 1,4-Dioxane and VOC-Contaminated Regional Groundwater
Source
Standard, Requirement,
Criteria, or Limitation
ARAR/TBC Status
Description of Standard, Requirement,
Criteria or Limitation
Manner in which ARAR Applies
to Alternative
Arizona Aquifer
Boundary
Protected Use
AAC Title R18-11-501 to-506
ARS 49-224
Applicable
Classifies Arizona waters as "drinking water
protected" use and establishes the procedure to
petition for reclassifying aquifer to a "nondrinking
water protected" use classification.
Groundwater concentrations must
meet any drinking water standard.
Safe Drinking
Water Act
42 U.S.C. § 300g-1; 40
C.F.R. Part 141, Subpart G
Relevant and
Appropriate
MCLs for certain contaminants in drinking water to
protect human health.
TARP-treated water delivered to
EPTDS shall meet MCLs.
Arizona Class A
Reclaimed
Water
A.A.C§ R18-11-304
Relevant and
Appropriate
Class A reclaimed water shall meet treatment and
water quality requirements.
The RWS distributes Class A
reclaimed water and will meet the
treatment and water quality
requirements.
Arizona Aquifer
Water Quality
Standards
A.R.S.§ 49-223; A.A.C.
Title 18, Chapter 11, Article 4
Relevant and
Appropriate
Standards for drinking water use of Arizona aquifers.
On-site discharge from the RWS be
protective of the aquifer water quality
standards.
Arizona Surface
Water Quality
Standards
A.R.S.§ 49-222; A.A.C.
Title 18, Chapter 11,
Article 1
Relevant and
Appropriate
Standards for certain surface waters to protect
designated uses.
On-site discharge from the RWS
certain surface waters shall be
protective of designated uses.
Safe Drinking
Water Act
MCLGs
40 CFR Part 141 Subpart F
40 CFR§ 300.430(e)(2)
TBC
EPA identifies the level of a contaminant in drinking
water below which there is no known or expected
risk to health. MCLGs allow for a margin of safety
and are non-enforceable public health goals.
Relevant and appropriate non-zero MCLGs shall be
attained by groundwater remedial actions that are
current or potential sources of drinking water.
These goals are not enforceable
should be considered for any
constituent with a non-zero MCL For
example, chloroform has a MCLG of
70 |jg/L.
Notes:
(1) ARAR = Applicable or Relevant and Appropriate Requirement
(2) TBC = To Be Considered
(3) MCL = Maximum Contaminant Level
(4) MCLG = maximum contaminant level goal
(5) RSL = regional screening level
(6) fig/L = microgram per liter
(7) COC = contaminant of concern
(8) EPA= U.S. Environmental Protection Agency
(9) TCE = trichloroethene
(10) VOC = volatile organic compound
(11) U.S.C. = United States Code
(12) C.F.R. = Code of Federal Regulations
(13) A.R.S. = Arizona Revised Statutes
(14) A.A.C. = Arizona Administrative Code
(15) EPTDS = Entry Pointto the Distribution System
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Table 4-7
Action-Specific ARARs for 1,4-Dioxane and VOC-Contaminated Regional Groundwater
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
Stationary Air Pollution Source (Pima
County Department of Environmental
Quality and ADEQ Air Pollution Control)
Pima County Ordinance Chapter 17.12 and AAC
R18-2 Articles 3, 5, and 6
Relevant and Appropriate if remedial
alternative has a source that discharges
to air.
Requires stationary air pollution sources to obtain an air permit prior to construction
or alteration so overseeing agency can establish requirements and limitations.
Regulations have established air quality standards and requirements for reasonable
available control technology for sources that emit hazardous air pollutants.
Although CERCLA exempts facilities from obtaining permits for on-site
remedial actions, the Site will comply with the substantive requirements of
these regulations.
Mobile and Non-Point Source (Pima
County Department of Environmental
Quality and ADEQ Air Pollution Control)
Pima County Ordinance Chapter 17.16 and AAC
R18-2 Articles 6
To Be Considered during
construction/modification activities.
Requires non-stationary sources to minimize visible emissions and odor. Abatement
equipment may be required if adjoining property is impacted with pollution.
Reasonable precautions, such as wetting or covering, must be taken for dust-
producing sources (e.g., machinery or storage piles) to minimize fugitive dust.
ANSI Standards - Arizona Safe Drinking
Water Act
AAC R18-4-213
Relevant and Appropriate if products are
added to TARP water during treatment.
Each product added directly to water during treatment must conform to
ANSI/National Sanitation Foundation (NSF) Standard 60. Material or products (e.g.,
granular-activated carbon or pipes) that come into contact with water must conform
to ANSI/NSF Standard 61.
Added products (e.g., peroxide or new piping) shall have a seal of the
certifying entity that it is accredited by ANSI. If they are not certified,
regulation lists other steps that the TARP plan can take to meet the
requirement.
Blending - Arizona Safe Drinking Water
Act
AAC R18-4-217
Relevant and Appropriate if TARP water
continues to incorporate blending.
Public water system may use a blending technique to achieve MCL compliance
after it obtains ADEQ's approval for a blending plan and quarterly monitoring
program.
The TARP water has historically been blended to meet the Health Advisory
for 1,4-dioxane (no MCL for 1,4-dioxane currently exists). Currently, water is
treated by the AOP system and water is not being blended following
treatment. If the implemented alternative requires blending, the TARP plan
shall submit an amended blending plan to confirm the new blend achieves
compliance.
Construction Arizona Pollution Discharge
Elimination System Storm Water Permit
Tucson City Ordinance 26-23 and AAC R18-9-A9
To Be Considered if construction
activities disturb an acre or more of land.
The Arizona Pollution Discharge Elimination System regulations establish overall
requirements and standards for discharge of storm water to navigable waters. The
City of Tucson further defines discharges to include generated or naturally-
occurring runoff or flow into, or through, the City's municipal separate storm sewer
or water of the United States.
Although CERCLA exempts facilities from obtaining permits for on-site
remedial actions, the Site will comply with the substantive requirements of
these regulations.
Hazardous Waste Management/RCRA
Requirements
Title 40 CFR Part 262 Subparts A-D, Part 273
Subpart B and/or C, and Part 279 Subpart C
Applicable if TARP generates waste
material (e.g., hazardous waste,
universal waste, and used oil) during
remediation activities.
Substantive, but not administrative, parts of RCRA requirements must be met on a
CERCLA site.
Requires waste analysis, inspection, training, and handling and storage
requirements.
Hazardous Materials Transportation
Regulations
Title 49 CFR Part 172 Subparts C-H and Part 173
Subparts A, B, D and E
Applicable if shipping wastes to another
site.
Covers requirements for marking, labeling, and placarding of shipping containers. If
waste is identified as hazardous, recordkeeping and manifesting are required.
Requires marking and labeling investigative-derived waste and other
hazardous material shipments before shipping off site.
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Table 4-7 (continued)
Action-Specific ARARs for 1,4-Dioxane and VOC-Contaminated Regional Groundwater
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
Well Construction and Abandonment
Standards
Arizona Administrative Code, Title 12, Chapter
15, Article 8: ell construction and abandonment
regulations (these are regulations promulgated
pursuant to A.R.S. 45-594, under the Arizona
Groundwater Management Act):
R12-15-811 (Minimum Well Construction
Requirements)
R12-15-813 (Unattended Wells)
R12-15-816(G, H, I, and J) (Abandonment of
Wells)
R12-15-822. Capping of Open Wells.
Applicable
Well construction and well abandonment will comply with the substantive
requirements within the regulations Those regulations include:
R12-15-811, Minimum Wells Construction Requirements.
R12-15-813, Unattended Wells: "All wells, when unattended during well drilling,
shall be securely covered for safety purposes and to prevent the introduction of
foreign substances into the well."
R12-15-816(G, H, I, and J), Abandonment of Wells
R-12-15-822, Capping of Open Wells
Applies to construction of new wells or replacement wells; unattended
wells; abandonment of wells, and open wells.
Pipeline Conveyances of Reclaimed
Water
A.A.C. § R18-9-B702(J)
Relevant and Appropriate
Engineering standards for pipeline conveyances of reclaimed water.
Reclaimed water conveyances shall be constructed according to the
standards.
Aquifer Protection
A.R.S. § 49-243(B)
Relevant and Appropriate
A person who discharges shall obtain an Aquifer Protection Permit (APP). APPs
implement technology standards and aquifer water quality standards. Remedial
actions are exempt from the requirement to obtain this permit, under A.R.S. §49-
250 and CERCLA§121(e).
On-site discharges shall meet the substantive standards at the point of
compliance.
Arizona Pollutant Discharge Elimination
System
A.R.S. § 49-255.01; A.A.C. Title 18, Chapter 9,
Article 9
Applicable
A person who discharges to certain surface waters shall obtain an AZPDES
permit. AZPDES permits implement surface water quality standards. CERCLA
actions are exempt from obtaining a permit and other procedural requirements
AZPDES under CERCLA § 121(e) unless discharge is considered to be off-site.
An AZPDES permit will be obtained for discharges to the Santa Cruz River.
Arizona Type 3 Recycled Water
Blending
A.R.S. §49-203(A)(6), A.A.C. Title 18, Chapter 9,
Article 7 (Use of Recycled Water), Part B
(Reclaimed Water)
Applicable
Blending of reclaimed water with other water may be authorized, and blended
water quality must meet the water quality standards for reclaimed water.
Type 3 Recycled Water Blending Permit will be obtained for the
introduction of treated water from TARP WTP to the RWS.
Notes:
AAC
Arizona Administrative Code
ADEQ
Arizona Department of Environmental Quality
ANSI
American National Standards Institute
AOP
advanced oxidation process
ARAR
Applicable or Relevant and Appropriate Requirements
ARS
Arizona Revised Statute
CERCLA
Comprehensive Environmental Response, Compensation, and Liability Act of 1980
CFR
Code of Federal Regulations
EPA
U.S. Environmental Protection Agency
NSF
National Sanitation Foundation
RCRA
Resource Conservation and Recovery Act
TARP
Tucson Airport Remediation Project
TBC
To Be Considered
VOC
volatile organic compound
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Section 121 (e) of CERCLA, 42 U.S.C § 9621(e), states that no federal, state, or local permit is required for
remedial actions conducted entirely on site. Actions conducted entirely on site must meet substantive
ARARs, but not administrative requirements. Any action conducted off site is subject to the full
requirements of federal, state, and local regulations.
The most significant ARARs are discussed below.
4.19 Chemical-Specific Applicable or Relevant and Appropriate
Requirements
The major statutes and regulations that contribute to the list of potential chemical-specific ARARs are the
SDWA and the Arizona Water Quality Standards (Arizona Administrative Code Title 18, Chapter 11). If an
MCL does not exist for a specific compound, EPA will consider as standards the Region 9 screening levels
for contaminants at Superfund Sites, the EPA Integrated Risk Information System assessment, or the
SDWA MCLGs. A list of site-specific cleanup levels for primary COCs is presented in Table 4-2, using the
most appropriate standard among the MCL, MCLG, regional screening levels, or Health Advisory value.
The chemical-specific ARARs that have been evaluated are those that affect drinking water.
The cleanup levels address the quality of drinking water at the tap pursuant to the SDWA and are ARARs
for treated groundwater when the end use is for purposes of human consumption. Pursuant to 40 C.F.R.
§§ 300.430(e)(2)(i)(A)(D), cleanup levels are relevant and appropriate as in situ aquifer standards for
groundwater that is or may be used for drinking water. The State of Arizona has adopted the federal MCLs
by reference as stated in Arizona Administrative Code §§ 18-4-108 & 109. Table 4-2 presents the cleanup
levels.
Five contaminants are identified as COCs for this Site. Table 4-6 presents the chemical-specific ARARs for
VOC-contaminated regional groundwater.
4.20 Location-Specific Applicable or Relevant and Appropriate
Requirements
Location-specific ARARs differ from chemical- specific or action-specific ARARs in that they are not closely
related to the characteristics of the contaminants at the Site, or to the specific remedial alternative under
consideration. Location-specific ARARs are concerned with the area in which the Site is located. Actions
may be required to preserve or protect aspects of the environment or cultural resources of the area that
could be threatened by the existence of the Site, or by the remedial actions to be undertaken at the Site.
As stated in Section 4.13.1, here are no location-specific ARARs associated with the alternatives in this
interim ROD Amendment.
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4.21 Action-Specific Applicable or Relevant and Appropriate
Requirements
Table 4-8 lists the action-specific ARARs for this Site. These ARARs include well construction and
abandonment requirements, discharge requirements, blending of drinking water if necessary, and air
discharge requirements. RCRA is a federal statute passed in 1976 to meet three goals: 1) to protect human
health and the environment, 2) to reduce waste and to conserve energy and natural resources, and 3) to
eliminate the generation of hazardous waste as expeditiously as possible. The Hazardous and Solid Waste
Amendments of 1984 significantly expanded the scope of RCRA by adding new corrective action
requirements, land disposal restrictions, and technical requirements. Substantive RCRA requirements are
applicable to response actions at CERCLA sites if contaminants are characterized as hazardous waste.
Untreated groundwater containing VOCs at the Site is not a listed waste. The groundwater is not a
characteristic waste because the contaminants in the groundwater are below the levels established for
the characteristic of toxicity. Consequently, the RCRA requirements triggered by the hazardous nature of
waste are not applicable, and not relevant and appropriate with respect to the groundwater.
4.22 Cost-Effectiveness
A cost-effective remedy is defined as one in which "costs are proportional to its overall effectiveness"
(Title 40 Code of Federal Regulations § 300.430(f)(l)(ii)(D)). Assessing cost-effectiveness involves
comparing costs to overall effectiveness, which is determined by evaluating the following three of the five
balancing criteria: 1) longer term effectiveness and permanence, 2) reduction in toxicity, mobility, or
volume through treatment, and 3) short-term effectiveness.
The selected remedy is cost-effective and has a high level of long-term effectiveness and permanence
because much of the infrastructure for the remedy is already in place and can be expanded relatively
easily to increase the volume of extracted and treated water, and provides for alternative end uses of the
treated water including discharge to the Santa Cruz River.
4.23 Utilization of Permanent Solutions and Alternative Treatment
Technologies
EPA has determined that the selected remedy represents the maximum extent to which permanent
solutions and treatment technologies can be used in a practicable manner in Area A. Of the alternatives
that are protective of human health and the environment and comply with ARARs, EPA has determined
that the selected remedy provides the best balance in terms of the five criteria, the statutory preference
for treatment, and state and community acceptance. All of the groundwater treatment will take place at
the TARP. The selected remedy will treat the groundwater contaminants before they are conveyed to the
City of Tucson drinking water or recycled water distribution systems.
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4.24 Preference for Treatment as a Principal Element
EPA has determined that the selected remedy meets the statutory preference for treatment as a principal
element. The contamination is not highly toxic when compared to the EPA standard definition of principal
threat waste. However, the selected remedy does employ pump and treatment with the UV- AOP system,
which meets the preference for treatment as a principal element.
4.25 Five-Year Review Requirements
NCP § 300.430(f)(4)(ii) requires a five-year review if the remedial action selected results in hazardous
substances, pollutants, or contaminants remaining on-site above levels that allow for unlimited use and
unrestricted exposure. A previous five-year review was conducted in 2013 and focused on Operable Unit
(OU)-l (TARP area-wide groundwater), OU-2 (airport property), and OU-3 (AFP44/Raytheon) as part of
the TIAA Superfund Site. The 2013 Five-Year Review determined that the remedy for OU-1 was currently
protective of human health and the environment for historically identified COCs; however, the RAOs
written in the 1988 EPA ROD are unclear and the decision document should be revised as part of future
amendments, and the treatment goal of 1x10 s excess cancer risk should be reviewed for technical
feasibility to assure that long-term-protectiveness can be achieved. The 2018 Five-Year Review also
focused on OU-1, OU-2, and OU-3 with OU-1 divided into Area A and Area B groundwater plumes. The
2018 Five-Year Review determined that OU-1 is currently protective of human health and environment.
COCs are being contained and groundwater treatment systems are operating to treat contaminated
groundwater to below MCLs and to reduce groundwater contaminant concentrations. The Five-Year
Review notes that for the remedy to be protective in the long-term, the following actions need to be taken
to ensure protectiveness: re-evaluate the operation of the remedy, if groundwater levels continue to rise;
and investigate the extent of perfluorinated compounds in groundwater (EPA 2018). Tucson Water is
currently testing water in TIAA Area A for perfluorinated compounds and the remedy will be continuously
evaluated.
Because the Selected Remedy will result in hazardous substances remaining on-site above levels that
allow for unlimited use and unrestricted exposure, further five-year reviews will be conducted to ensure
that the remedy is, or will be, protective of human health and the environment.
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4.26 Documentation of Significant Changes
The Proposed Plan, which was issued by EPA in March 2017, identified pump and treatment using the
existing UV-AOP system combined with MNA for the Area A groundwater plume as the preferred
alternative for groundwater remediation. EPA reviewed all written and verbal comments submitted
during the public comment period. Section 5 includes a response to those comments. Changes to the
proposed alternative that occurred after and in response to the public comment period following the
March 2017 Proposed Plan are outlined below.
1. The Selected Remedy modifies the preferred remedy (Alternative 3) by removal of MNA and
inclusion of long-term monitoring during the ROD phase.
2. The Selected Remedy enhances the preferred remedy outlined in the March 2017 Proposed
Plan with installation of another remediation/extraction well within the groundwater plume
and upgrades to the AOP system. The remediation well will help to further capture and
remove COCs; thereby, increasing total mass removal.
3. This interim ROD Amendment provides for containment and treatment of contaminated
groundwater, not restoration of the aquifer for 1,4-dioxane. A final restoration ROD
Amendment will be completed in the future that will provide for aquifer restoration with
cleanup levels when an MCL is determined for 1,4-dioxane.
4. Alternative end uses for the treated water from TARP other than as drinking water will be
employed, including discharge to the Tucson Water recycled water distribution system.
5. The UFHHRA (EPA and Air Force Civil Engineer Center, 2015) recommended the 0.35 ng/L
treatment level (10 s risk level) for 1,4-dioxane in water from the Area A plume north of Los
Reales Road. A groundwater cleanup level will be established in a future decision document.
No other significant changes to the remedy, as originally identified in the Proposed Plan, were necessary
or appropriate. The public was able to reasonably anticipate any significant changes.
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5.0 PART III: RESPONSIVENESS SUMMARY
Proposed Plan for Tucson International Airport Area, Superfund Site Area A, North of Los Reales Road, Tucson, Arizona
dated March 2017
Comment No.
Comment
Response
Spoken Comments by Debra Serrano at the public meeting held on March 30,2017
1
First of all, I wanted to ask about the pipelines because I do know that certain chemicals
do stay in the pipelines, even though they have been cleaned with certain chemicals to
solutionize and clean out all the whatever contaminants there is. But no one so far that
I know of, that I've researched on, which is hardly any good research anyways because
I do it on my own, but has cleaned out the pipelines, the actual south side pipelines.
You know, who's to say that there is chemicals still in a pocket somewhere, or being
leaked out every so often in certain areas, or what. But who is coming over and checking
those pipelines to see, you know, what kind of contaminants are - remain in those lines?
The U.S. Environmental Protection Agency (EPA) has received a
number of comments expressing concern about possible residual
contamination in the treatment system and/or the public water
distribution system, including piping used to transport
contaminated water to the treatment plant. The treatment system
piping and treatment plant were constructed so that there is no
connection between the system and the Tucson public water
supply until after contaminated water has been treated to remove
contamination at the Tucson Airport Remediation Project (TARP)
treatment plant. EPA believes it is unlikely that any "pockets" or
deposits of contamination remain within the system piping that
could affect the health of area residents. In making this
observation, EPA notes that routine periodic testing of water
supplied by the TARP treatment plant to the public water supply
shows that the plant meets existing and proposed clean up levels
for groundwater contaminants and also meets drinking water
standards set under the Safe Drinking Water Act.
It is EPA's understanding that the City of Tucson Water
Department (herein referred to as Tucson Water) is planning an
investigation of this piping within the area of the Superfund Site
and EPA will assist where possible in that investigation.
If you have questions about the quality of the water at your home,
you are encouraged to contact the Tucson Water Quality &
Pressure Hotline at (520) 791-5945.
2
And then third of all, there has to be something done about the south side water
because not only my whole family and my six sisters all have pain came down one
EPA has received a number of comments from individuals who
feel their health problems, or those of family members, may be
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Comment No.
Comment
Response
after another. And currently still, my sister, bless her heart, is getting surgery today,
Sonya, and in and out of the hospital with cancer. My sister, Jenny, here, my sister,
Terry. We just lost my nephew. And this is on and on, going on ever since we moved to
the south side. We were healthy, young, blemishing young people then. And we moved
to the south side, all of us, since we were in grade school. Each of us - each one of us
in our family is with cancer or has a limb missing from cancer and stuff. And it's been
ever since we moved to the south side. You know, who's responsible, what's being done,
and who's hearing us? You know, who's backing us up on all this, you know. That's -
those are my questions, and that's - you know, I'm just trying to get - let everybody
know that. You know, let's try to stick together, and let's tell our neighbors, let's get
everybody. Even if we have to stand out here day and night, try to get as many people
as we can that have people, members of their family from the south side that are
suffering from these unknown illnesses, you know, leukemia, fibromyalgia, lupus, all
these other symptoms that are coming out that, you know, that are being due from
chemicals and all that. Let's do something about it and find out why they did research in
the first place so it won't get this far.
related to contamination at the Tucson International Airport Area
(TIAA) Superfund Site. Unfortunately, in the past there was
documented exposure to site-related contamination, primarily due
to use of contaminated groundwater as a source of drinking water
and water used for cooking, bathing, and other home uses. This
unfortunate situation prompted EPA to become involved and
declare a Superfund Site. As a result of actions taken by the
Arizona Department of Environmental Quality (ADEQ), City of
Tucson, EPA and others, EPA believes that there is no current
exposure. Pima County continues to annually monitor private
wells.
EPA sympathizes with anyone experiencing health issues and
understands the worry, stress, and difficulties that a family
experiences when a loved one develops serious health issues.
EPA is committed to protecting human health at Superfund sites,
such as TIAA.
Based in part on public comment and concern, EPA is enhancing
the selected remedy (Alternative 3) by adding an additional
remediation well, which will extract additional contaminated
groundwater and treat it at the TARP advanced oxidation process
(AOP) system. The installation of this additional well will assist
with containing the groundwater plume and removing additional
contamination from the plume.
EPA feels that this enhancement of the remedial action will help
ensure that people living in the area and/or using treated tap water
continue to be protected from site-related contamination.
For additional information concerning water quality concerns at
TIAA, please reference Comment #1.
With regard to information on health impacts in the Tucson
community, please refer to the Arizona Department of Health
Services (ADHS) or the Pima County Health Department. Public
health assessments and reports conducted by ADHS on the
groundwater contaminants at TIAA Area A can be referenced
here: http://www.azdhs.gov/preparedness/epidemiology- disease-
control/environmental- toxicology/index.php#assessments-reports.
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Comment No.
Comment
Response
Spoken Comments by Linda Shosie at the public meeting held on March 30,2017
3
So my comment today is I'm asking EPA to shut down the wells, the pipelines. Take
them somewhere else, give them to somebody else, but don't feed them to us, and don't
feed them to any person or any human beings. You do your stuff, you clean up because
it's your problem, not ours. You clean it up, you pay for it. It's your responsibility, and
that's enough. Enough is enough. Too many of our children have died. We are tired of
having to pay these funeral costs and having to bear the grieving of our family, and our
family members, and our children, and now our grandchildren, with these illnesses. And
you guys know exactly what's going on. So what my comment here today is that you
shut down the wells on the north well field, the south well field. Take your TARP, take
your AOP, and take it to your own - your own properties, but keep them out of our south
side. Get them out of our communities.
Removing the wells or associated pipelines could allow
contaminants to enter the drinking water of Tucson residents and
allow contaminated groundwater to spread farther without any
means to stop its spread. At this time, the wells and associated
pipelines are an integral part of the groundwater cleanup program
and cannot be removed.
Spoken Comments by Bill Jeffers at the public meeting held on March 30,2017
4
I just wanted to say that I'm Bill Jeffers. I'm a member of the UCAB. I just wanted to say
that plans in the back of the room, very, very good. I've toured all of them before I came
up to sit down, and very informative, very clear, very concise, outstanding. That's my
comment.
EPA appreciates the feedback on the posters presented at the
Proposed Plan meeting.
Spoken Comments by Eduardo Quintana at the public meeting held on March 30,2017
5
In the summer of 1985, if I recall correctly, there was a series of articles in the Arizona
Daily Star by a reporter. Her name was Janey Kay (phonetic), who had just discovered
that there was an abnormal incidence of cancer clusters on the south side. In just one
block of Elvira there were 25 cancers in just one block. And when we started looking
around, we saw that the pattern duplicated itself in other parts of the south side. So at
that time we began organizing. We organized Tucsonans for a Clean Environment,
known as the TCE Committee, which had held news conferences, and rallies, and what
we felt was a big, big issue, the TCE contamination that needed to be addressed. At that
time we had to struggle against all the regulatory agencies. You know, the main function
of a government is to protect the people, and the regulatory agencies are supposed to
serve that service by making sure that industry is regulated so it doesn't poison the
population. But the regulatory agencies instead fought us. They said we didn't know what
we were talking about, there was no TCE in the groundwater. If there was any TCE in
the groundwater, it was so minimal it couldn't possibly hurt anyone.
The regulatory agencies failed us. They failed in protecting the public health. They failed
in protecting the health of our children, and the generations that were to come.
EPA sympathizes with anyone experiencing health issues and
understands the worry, stress, and difficulties that a family
experiences when a loved one develops serious health issues.
The Agency is committed to protecting human health at
Superfund sites, such as TIAA.
Your concerns are best addressed by the public health agencies.
For further information on health impacts in Tucson, please refer
to Comment 2.
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Comment No.
Comment
Response
We warned at the time that unless those issues were addressed, that they could expect
- so 1985 we would be seeing the same problem duplicated. And I'm real disappointed
that here we are 30 years later, and now grandchildren are coming down with all kinds
of exotic diseases. This is not normal, in spite of the propaganda that's out in the
newspapers saying that a lot of cancers are just chance mutations. That's preposterous.
So I'd like to thank everyone for being here tonight. I'd like to thank the hardworking
engineers that work for some of these regulatory agencies. I know that you - a lot of you
have the same obstacles that we have. But, you know, there's a rumor out there that
comments that Donald Trump, the new President, is going to eliminate the EPA. And
that would be - that would be a shame. But in the case of Tucson, I don't know that we
would notice the difference. I think there's very little difference between 1985 when we
fought the regulatory agencies to admit that there was a problem to today. We're getting
the same answers. EPA does not address the health concerns of the people. Who else
is there to address? You clean up the water, remediate the aquifer, but don't address
the health of the people. That's preposterous.
Written Comments by Nicole Fyffe received on April 21,2017 via email
6
Ms. Aycock, the past weekend I read 2 articles in the Arizona Daily Star on this issue. I
had heard generally of the issue before, but had no idea that the treated water was being
delivered to households in Tucson, one of which is mine. Until now, I thought my
households water came from the recharge facilities in Avra Valley, which is a combo of
Colorado River Water and ground water. From the little I learned since this weekend, my
understanding is that as part of some type of agreement or settlement, Tucson Water is
required to put this treated water to "beneficial use", which they or someone determined
to be the Tucson water distribution system. I do not understand why it could not be
beneficially used by either reinjecting it into the ground water in that area or distributing
it to industrial users (mines, etc.) that would not be drinking it. I trust that the EPA and
Tucson Water do believe the risks are low enough to serve us this water. But, just like
with the recent discovery of 1,4-dioxane, I can imagine that that there is a likelihood that
other contaminants may be discovered in this plume years from now. Why should we
have to drink this water when there are plenty of other potential users for this water?
Why couldn't Tucson Water exchange this water for a share of CAP water being used
by one of the mines and pump this water down to the mines? I'm guessing it has to do
with infrastructure costs. Or why could Tucson Water not treat it like reclaimed water and
only deliver it to parks and landscaped areas? These did not appear to be one of the
alternatives that EPA evaluated, so I can't see what those alternatives would have cost. Were
those alternatives considered early on, but dismissed?
The EPA Record of Decision (ROD) signed in 1988 mandated that
treated water from the TIAA Superfund area be reused for
drinking water under the beneficial reuse clause. Per the 1988
ROD, the impacted aquifer had been designated a Sole Source
Aquifer under the Safe Drinking Water Act. According to the
Groundwater Management Plans for the Tucson Active
Management Area, any water withdrawn from the aquifer had to
be put to its highest beneficial use, which limited the end-use
options to direct drinking water use, or reinjection for drinking
water use at a later time. These criteria were used in the
evaluation of all alternatives in both the original Feasibility Study
conducted by Arizona Department of Water Resources (Malcolm
Pirnie 1988) and the Focused Feasibility Study (EGC 2016).
However, in the modified remedy, the end use of treated water
from TARP will include the option to discharge the water to the
Tucson Water recycled water system, in addition to the current
option of the drinking water distribution system. The recycled
water system includes use as turf and landscape irrigation water
for golf courses and parks, managed discharge to the Santa
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Comment No.
Comment
Response
Cruz River channel as aquifer recharge and hydroriparian habitat,
and constructed aquifer recharge projects.
Currently, treated groundwater is tested by the City of Tucson and
meets the requirements of the Safe Drinking Water Act and City
of Tucson target treatment levels.
Written Comments by the students at The University of Arizona undergraduate "Ecological Anthropology" course received via email on April 24,2017
7
The presentation of the proposed plan in its current format is complicated to understand
as a non-expert community member. The plan claims to "provide the public with
background information" on the state of the area's groundwater. However, the
complicated language and scientific jargon utilized in the Plan would likely be unclear to
most Tucson citizens. Discussions of specific scientific terms, the mechanics of the
water remediation system, and the potential risks and benefits of altering the current
system of water remediation was difficult for our class to understand, and is therefore
likely incomprehensible to a majority of the public it aims to address.
For example, when comparing the costs of each alternative, Presented Worth and Value
Cost are undefined, making it extremely difficult to accurately compare the options
without consulting experts. In addition, it was unclear to us what entity is paying for the
costs. This is vital information to have when forming an opinion on the matter. In
summary, terms and language throughout the report are confusing and undefined. The
heavily reliance on acronyms causes confusion and lack of clarity (despite the inclusion
of a glossary). There is no real comprehensive way for an average Tucson citizen to
understand this document.
EPA understands the concern that the Proposed Plan is difficult
to understand because of the complicated language, acronyms,
and scientific jargon. EPA follows national Superfund guidance
when preparing CERCLA documents. EPA reviews every
Proposed Plan in an effort to make it as easy to read and
understand for the general public while still being technically and
scientifically correct in its descriptions. Many residents of the area
of Tucson encompassed by the site are actively involved in
attending the regular Unified Community Advisory Board (UCAB)
meetings, and find it a good opportunity for asking questions and
gaining a better understanding of current treatment systems.
In accordance with standard EPA procedures, community
meetings are advertised locally in English and Spanish
newspapers and take place on a quarterly basis, the third
Wednesday in January, April, July, and October. If you are
interested in attending any meetings in the future and would like
to be added to the site mailing or email list, please contact the
EPA community outreach coordinator, David Yogi, at
yogi.david@epa.gov.
The responsible parties (U.S. Air Force, City of Tucson, Tucson
Airport Authority [TAA], Hughes Aircraft Company, and
McDonnell Douglas Corporation) are listed on Page 1 of the
Proposed Plan and are ultimately responsible for paying for the
cleanup.
8
Another factor compounds the inaccessibility of the document. By incorporating an
anthropological perspective, we have isolated one of the deficiencies in your plan and
implementation, which is the accommodation the EPA has made for Spanish speakers
in the community impacted. Although translation services were offered at the meeting,
EPA understands that many of the citizens who live in the area
around the Superfund Site are Spanish speakers and believes
that the Spanish-speaking community was adequately engaged
in the Proposed Plan process as described below:
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Comment No.
Comment
Response
and a pamphlet about the plan was administered in Spanish, the pamphlet is not
informational enough to allow individuals to make an informed decision about picking an
alternative. We are also concerned about the accessibility of this meeting, and whether
or not it was circulated in the impacted communities.
This is a valid concern because the demographics of the zip codes surrounding the
Superfund site indicate that a majority of the individuals in those areas are linguistically
isolated, and are not English speakers. According to the EPA's Environmental Justice
Survey Tool, for the zip codes closest to the Superfund Site (85746 and 85706), these
areas were 80% and 91% linguistically isolated respectively, and about half of the
population there did not speak English "Well" or "Very well". We are concerned that this
demographic is not being included and fully represented by the EPA.
We are also concerned that these individuals would not be able to access the materials
through other means because of their inaccessibility. According to the 2015 American
Community Survey, out of the 206,448 people listed in the Tucson population, 25,171
individuals do not have access to a computer and 24,989 do not have an internet
subscription. This means that the entire population does not have equal accessibility to
these materials, so do not have the means to actively participate in the discussion of
choosing an alternative that would work best for the community.
The point of this EPA Proposal Plan Meeting was to give some agency to the
communities adversely affected by environmental toxins (in which the health disparities
they are experiencing are the fault of the Tucson International Airport, Hughes Aircraft
Company, and the United States Air Force). By limiting the means of information sharing
to the internet (and not handing this information out directly to communities), and by not
presenting the information as completely in Spanish (or advertising for this meeting in
Spanish in affected communities) these individuals are not actually granted agency
because they are not given the means to contribute and participate in deciding the route
of implementation for the proposed plan.
EPA developed a summary fact sheet of the Proposed Plan,
which was translated into Spanish and mailed to 137 people on
the EPA mailing list developed for the Superfund Site.
Additionally, EPA emailed the fact sheets to an additional 71
people. The Proposed Plan meeting announcement and the
comment extension period were advertised in both the Arizona
Daily Star (March 21 and May 1, 2017) and translated into
Spanish for publication in La Estrella de Tucson (March 24 and
May 5, 2017) newspapers. Additionally, Spanish-speaking
translators were available to assist community members at the
public meeting. The fact sheet and copies of the Proposed Plan
in Spanish and English were also placed in the Pima County
Public Library—Valencia Branch for people who do not have their
own computer or access to internet services.
9
An additional flaw within the Proposed Plan is that it clearly biases the reader in favor of
Alternative 3 from the beginning. The very language of the Plan—the use of the positive
"preferred" rather than "selected", speaking of "community acceptance of the Preferred
Alternative" rather than a more neutral "community response to"—generates positive
associations in the reader's mind. While mere connotation may be overlooked, the
constant holding and color emphasis of "Preferred Plan" draws attention to Alternative 3
throughout the Plan. These factors, and the way that the document dedicates an
individual section to Alternative 3 on page 1 and a lengthy section to Alternative 3 on
page 11, it seems that any reader, regardless of comprehension level,
The Proposed Plan was written in accordance with the EPA
document, A Guide to Preparing Superfund Proposed Plans,
Records of Decision, and Other Remedy Selection Decision
Documents, July 1999. The use of the term "Preferred Alternative"
and the appropriate discussion of the Preferred Alternative are in
accordance with the guidance document and with legal
requirements, including in Title 40 Code of Regulations
300.430(f).
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Comment No.
Comment
Response
would come away from this Plan with Alternative 3 fixed firmly in their mind.
Given the inadequacy of this document to provide an unbiased, accessible Proposed
Plan for public readership, it was difficult for us to choose an alternative. However, after
some additional research and much debate we would like to encourage the EPA to not
accept the minimal alleviation of risk, but instead move forward with Alternative
5. Alternative 5 has been proven to be effective. A case study by Palumbo et al., entitled
"Influence of nitrogen and phosphorus on the in situ bioremediation of trichloroethylene,"
states: "In the field, the addition of TEP+N20 to the pulsed injection of CH4 resulted in
dramatic stimulation of TCE-degrading potentials observed in ground water
enrichments" (1).
Another set of researchers, Travis and Rosenberg, explain the process a little more
simply, writing "an in situ bioremediation field demonstration was performed at the U.S.
DOE's Savannah River site in 1992-1993 to remediate subsurface TCE contamination.
This demonstration involved stimulating indigenous methanotrophic bacteria with
injection of methane, air, and air-phase nutrients below the water table and vacuum
extraction in the vadose zone" (2). This case study in Aiken, South Carolina,
demonstrates that in-situ (on-site) remediation can be successful, creating optimal
conditions for microbes to break down the toxic chemical solvents we've used in the
past. We have surpassed the point of allowing these processes to break down naturally,
because without the help of microbes biogeochemical time is too slow for Tucson
citizens already ingesting contaminated water.
EPA received several comments expressing a preference for
Alternative 5 and has reviewed the case studies cited in the letter.
While active remediation strategies have shown to reduce
concentrations of trichloroethylene (TCE) and 1,4-dioxane at
localized areas of concentrated sources in subsurface
groundwater, the studies do not focus on the type of widespread
diffused TCE and 1,4-dioxane contamination generally found in
the Area A aquifer. One source area is located at Air Force Plant
44 (AFP44), and that source area is being treated separately
using technologies similar to those outlined in Alternatives 5 and
6 and is not part of the remedy outlined in the Proposed Plan. The
USAF issued a ROD in August 2020, which implemented ISCO and
ISB within hot spot source areas at AFP44. This remedy has
significantly reduced concentrations of VOCs and 1,4-dioxane in
shallow groundwater source areas.
Despite the timeframes projected by the preparer of the focused
feasibility study (ECG, Inc. 2016), information developed after the
2016 study indicate in-situ treatment of contamination in
groundwater of the Area A plume south of Valencia Road will not
address the largest existing mass of contamination in the
Regional Undivided Aquifer. The active remediation strategies
evaluated in Alternatives 5 and 6 are not as effective at treating
large dissolved groundwater plumes with relatively low
concentrations of contaminants like the one in Area A compared
to smaller source areas with relatively high concentrations. Other
data gaps and uncertainties associated with Alternatives 5 and 6
are outlined in Section 8 of the Focused Feasibility Study (EGC,
Inc., 2016). The data gaps identified for Alternatives 5 and 6 are
extensive, and it would take several more years and various
studies to resolve the issues.
Based in part on public comment and concern, EPA is enhancing
the selected remedy (Alternative 3) by adding an additional
remediation well, which will extract additional contaminated
groundwater and treat it at the TARP AOP system. The
installation of this additional well will assist with containing the
groundwater plume and removing additional contamination from
the plume.
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Comment No.
Comment
Response
In addition, for the modified remedy, the end use of treated water
from TARP will include the option to discharge the water to the
Tucson Water recycled water system, in addition to the current
option of the drinking water distribution system. The recycled
water system includes use as turf and landscape irrigation water
for golf courses and parks, managed discharge to the Santa Cruz
River channel as aquifer recharge and hydroriparian habitat, and
constructed aquifer recharge projects.
EPA is tasked with selecting a remedy that is implementable and
effective. As the data gaps and uncertainties identified in the
Focused Feasibility Study are addressed, and if a source
area within Area A is identified, EPA will re-evaluate conditions at
the site and propose additional remediation activities for removing
the contaminants in groundwater.
This ROD Amendment will be an interim decision document that
addresses containment and treatment of 1,4-dioxane, not restoration
of the aquifer. The groundwater cleanup level for 1,4-dioxane will be
evaluated by EPA and State of Arizona when an MCL is established,
and a final ROD Amendment will address insitu groundwater
addressing restoration options.
In addition, EPA must also take into account extenuating factors not
discussed in the case studies such as community impact from
construction activities; long-term impact of additional widespread
wells, pumps, equipment, and maintenance to the surrounding
community; overall treatment effectiveness; long- term impact to a
drinking water aquifer; cost; and city, state, and community
acceptance before choosing a Preferred Alternative.
In response to the final sentence of the comment, City of Tucson is
providing tap water that meets the standards of the Safe Drinking
Water Act and the existing and proposed cleanup standards for the
TIAA Superfund Site.
TIM SUPERFUND SITE AREA A
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Comment No.
Comment
Response
Written Comments by Gerardo Sanchez received on April 18,2017 via email
10
I am very concerned of this proposed plan because I have being [sic] living in the area
drinking the water. I think the alternative 5 is a good start, but plans need to be created
on actually cleaning the contaminated ground soil. Also plans need to be approved on
rerouting the wells and aftercare for future aliments for me and my offspring as a result
of this situation. I also have had my parents died of cancers that could be linked to this
situation. Please keep me advised of your status concerning the cleanup, after care
and results of your clean up alternatives with this situation.
EPA sympathizes with anyone experiencing health issues and
understands the worry, stress, and difficulties that a family
experiences when a loved one develops serious health issues.
The Agency is committed to protecting human health at Superfund
sites, such as TIAA.
Alternative 3 has been evaluated and will be enhanced with the
addition of another remediation well in the groundwater plume. The
alternative would continue to provide drinking water or water for
Santa Cruz River discharge and the City of Tucson's recycled
water system with only a relatively small immediate impact from
construction activities to install the remediation well. For additional
information on Alternative 5 and the data gaps and uncertainties
associated with this alternative as it relates to the groundwater
contamination at Area A, please refer to Comment 9.
With regard to information on health impacts in the Tucson
community, please refer to Comment 2.
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Comment No.
Comment
Response
Written Comments by Barbara A. Sanchez received on April 18,2017 via email
11
I am very concerned of this proposed plan because I have being [sic] living in the area
drinking the water. I think the alternative 5 is a good start, but plans need to be created
on actually cleaning the contaminated ground soil. Also plans need to be approved on
rerouting the wells and aftercare for future aliments for me and my offspring as a result
of this situation. I also have had my parents died of autoimmune and kidney diseases
that could be linked to this situation. I am current suffering from autoimmune diseases.
Please keep me advised of your status concerning the cleanup, after care and results of
your clean up alternatives of this situation.
EPA sympathizes with anyone experiencing health issues and
understands the worry, stress and difficulties that a family
experiences when a loved one develops serious health issues.
The Agency is committed to protecting human health at
Superfund sites, such as TIAA.
Please refer to Comments 2, 9, and 10 for additional information
on health resources and alternative selections, respectively.
Written Comments by Michael List received on April 21,2017 via email
12
I strongly oppose the closing of the TARP. The combined TARP/AOP process (while
possibly redundant) provides greater assurance to the citizens of Tucson that are served
by this treated water.
The TARP plant is not being closed. The AOP process has been
proven to be effective and efficient at treating groundwater
contaminants to levels below the existing and proposed treatment
standards. Only the aging packed column aeration process is
being taken out of service, as its purpose is addressed by the
AOP, which fully destroys contaminants.
Written Comments by Linda Shosie received on March 30,2017 via comment card at Proposed Plan public meeting
13
Re-route pipelines and shut down
Please see response to Comment 3.
Written Comments by Bill Jeffers received on March 30,2017 via comment card at Proposed Plan public meeting
14
Placards were outstanding, very clear, concise, and to the point. Very informative.
Hostess is outstanding in everyway!
EPA appreciates the feedback on the Proposed Plan public
meeting.
Written Comments by Eduardo Quintana received on March 30,2017 via comment card at Proposed Plan public meeting
15
What is being done to remediate/restore the people who have been exposed to
contamination?
The comment is best addressed by a public health agency.
Please refer to Comment 2 for additional information on public
health assessments and appropriate contact agencies.
TIAA SUPERFUND SITE AREA A
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Comment No.
Comment
Response
16
Why does the EPA charter or mandate not include the input on the health of the people
exposed to contamination?
EPA's basic mission under the CERCLA law is remediate
environmental contamination in order to protect human health and
the environment—air, water, and land. EPA, state, local and tribal
agencies work together to ensure compliance with environmental
laws passed by Congress, state legislatures and tribal
governments.
Other agencies such as the Agency for Toxic Substances and
Disease Registry (ATSDR) have responsibility for evaluating the
health of individuals who may have been exposed to
contamination. ATSDR is a federal public health agency within the
United States Department of Health and Human Services. This
agency focuses on minimizing human health risks associated with
exposure to hazardous substances. In Arizona, the ADHS can
help. Their mission is to promote, protect, and improve the health
and wellness of individuals and communities in Arizona. In Pima
County, the Pima County Health Department has a similar
mission to ensure the health, safety, and well- being of the
community.
Written Comments by Patricia Velasquez received on March 30,2017 via comment card at Proposed Plan public meeting
17
The water needs to get cleaned up. Our children are now living in the area and raising
their children. We need the routine to stop so we must clean up the water ASAP so our
grandkids don't have any drama due to the problem/contaminated water. The psycho
[cycle] must stop clean up the water is a must.
EPA is committed to cleaning up the groundwater at the TIAA
Superfund Site. Additionally, EPA is working to identify long- term
solutions and a remedy for the groundwater contamination within
Area A.
Written Comments by Eva Carrillo Dong received on March 30,2017 via comment card at Proposed Plan public meeting
18
Since my childhood, I have lost many family members and classmates to this
contamination of our water. The losses have been very difficult. Just as difficult has been
watching my family members and friends suffer in their daily lives with illnesses brought
on by this contamination. Our quality of life, longevity in our ancestors, has all been
dramatically changed. When the contamination first occurred, I expected EPA to install
a process that would as quickly as possible remove the contamination from my
community. I am extremely disappointed to see and hear how much of our community
is still under contamination. I must insist that EPA and ADEQ choose the treatment that
will clean up our water as swiftly as possible. We do not want to wait for more decades
to pass regardless of cost. Our children depend on this.
EPA sympathizes with anyone experiencing health issues and
understands the worry, stress, and difficulties that a family
experiences when a loved one develops serious health issues.
The Agency is committed to protecting human health at
Superfund sites, such as TIAA. The Superfund law requires that
alternatives be evaluated using all of the nine criteria explained in
the Proposed Plan. For additional information on the other active
treatment alternatives and a description of the enhanced
Alternative 3, please refer to Comment 9.
TIAA SUPERFUND SITE AREA A
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Comment No.
Comment
Response
Written Comments by Joseph Jaramillo received on May 11,2017 via email
19
I will be going with choice number 5.
Thank you for your comment. For additional information on the
active treatment alternatives and a description of the enhanced
Alternative 3, please refer to Comment 9.
Written Comments by Georgina L. Gomez received on May 14,2017 via email
20
My name is Georgina L. Gomez. I have lived on the southside of Tucson AZ for 55 yrs;
where a few of the wells were closed due to TCE contamination. In 19921 was diagnosed
with Lupus. In 2009 was diagnosed with two brain tumors. I had benign tumor on left
side next to brain stem removed. The tumor on right side of brain stem is being
monitored.
EPA sympathizes with anyone experiencing health issues and
understands the worry, stress, and difficulties that a family
experiences when a loved one develops serious health issues.
The Agency is committed to protecting human health at
Superfund sites, such as TIAA.
Please refer to Comment 2 for additional information on public
health assessments and appropriate contact agencies.
Written Comments by Edna San Miguel received on May 8,2017 via email
21
My name is Ms. Edna San Miguel and I am writing to you today to respectfully request
that The United States Environmental Protection Agency extend its comment period for
the Proposed Plan of the Tucson International Airport Area Superfund Site Area A, North
of Los Reales Road Tucson, Arizona.
I want to bring your attention the 30 day Public comment period of March 30, 2017, in
which a rather rapid period of time was allotted so as to submit letters of concern and
poignant questions by Tucson's concerned citizens. Am I also correct to state that this
meeting took place at the El Pueblo Neighborhood Center?
The EPA Proposed plan states that the Public comment period started March 22, 2017
and was ending on set date of April 21, 2017, but according to my calculations, this is
an inappropriate time constraint placed upon concerned Tucson citizens for a proper
response period.
Our community is being rushed through your set of time constraints and was also given
negative eight days whereas to respond on the matter.
Am I correct to state that April 24, 2017 is the cutoff date, according to the EPA Fact
sheet, and whereas community members comments and questions are to be submitted
via e-mail or through the United Stated U.S. Postal Service, and any other delivery
services as such?
EPA concurred with the request to extend the comment period.
The Proposed Plan comment period was extended from April 24,
2017 to May 21, 2017. It is correct that the Public Meeting, which
occurred on March 30,2017, took place at the El Pueblo Activities
Center.
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Comment No.
Comment
Response
At this time it is inevitable time constraints restricts proper community response time and
should be deemed as unattainable.
Respectfully please members of the United States Environmental Protection Agency,
honor my request for a time extension on the matter of the Proposed Plan for the Tucson
International Airport Area, Superfund Site Area A. It would be most appreciated and
worry less to community.
Written Comments by Yolanda Herrera received on May 16,2017 via email
22
Can you please send a PDF to all I have copied regarding the Proposed Plan/Public
Meeting/Comment? I shared the hard copy I had during a tour of the TW facilities
Lab/TARP/AOP Saturday 5/13/17. And for the record, I support the "preferred
alternative", shutting down TARP and continuing using the AOP to remove TCE/1,4-
Dioxane and continue to monitor natural attenuation of the groundwater plume so COT
can continue to provide safe drinking water. The Unified Community Advisory Committee
-UCAB- will continue to provide oversight and community outreach.
EPA has submitted a PDF copy of the Proposed Plan to all
individuals in the email as requested. EPA appreciates the
feedback from the Unified Community Advisory Committee with
regards to the selection of the preferred alternative.
Written Comments by Roberto S. Jaramillo received on May 20,2017 via email
23
I, have read the 13 page Proposed Plan EPA has given the community to take into
consideration and comment on it as well. I feel what is being recommended by EPA and
other agencies is NOT what our community needs or desires. On page 10 it states on
4.Reduction of Toxicity, Mobility, and/or Volume through Treatment: Alternatives 3 and
4 are strictly Pump-and-Treat technologies, which are expected to have MINIMAL
REDUCTION in toxicity, mobility, and volume of contaminants in our groundwater.
Alternatives 5 and 6 could POTENTIALLY REDUCE the toxicity, mobility, and volume
through source treatment by using either in situ bioremediation or in situ chemical
oxidation. I, ask EPA why would they recommend and propose that Alternatives 3 and
4 be the BEST solution to consider and has MINIMAL REDUCTION in toxicity, mobility,
and volume of contaminants in our groundwater.
I, would ask EPA to take into consideration Alternatives 5 and 6 as these could
POTENTIALLY REDUCE the toxicity, mobility, and volume of contaminants in our
groundwater. I know cost is a BIG factor and when it comes to Healthy Living it should
not be taken into consideration!
I've lived in this community for over 60 years and have seen first what the effects of
contaminated water has had on our families, friends, classmates and coworkers. It has
NOT been a VERY pleasant experience. I, HOPE EPA will do what is BEST for the
community.
The AOP pump-and-treat technology referred to in Alternative 3
does reduce the toxicity, mobility, and volume of the groundwater
contaminants in the groundwater plume. Based in part on public
comment and concern, EPA is enhancing the selected remedy
(Alternative 3) by adding an additional remediation well, which will
extract additional contaminated groundwater and treat it at the
TARP AOP system. The installation of this additional well will
assist with containing the groundwater plume and removing
additional contamination from the plume. Alternatives 5 and 6 are
more appropriate for addressing concentrated source areas. The
USAF issued a ROD in August 2020, which implemented ISCO and
ISB within hot spot source areas at AFP44. This remedy has
significantly reduced concentrations of VOCs and 1,4-dioxane in
shallow groundwater areas with high levels of contamination.
For further information on why EPA prefers enhanced Alternative
3 over Alternatives 5 and 6, please refer to Comment 9.
While cost is one component used to evaluate all the alternatives,
it is neither the only nor the most important factor when EPA
chooses a preferred alternative.
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Comment No.
Comment
Response
Written Comments by Carmen Aguayo Touhey received on May 20,2017 via email
24
This email is in response to the requested public comment regarding TARP. Looking at
the proposed remediation does not make me or anyone I have spoken to feel very
satisfied. If we have to choose then our desire would be # 5. The first 3, qualify only as
a band-aid on gangrene. I still have no idea why this as important as it is, was not
publicized in a manner that would have truly gotten the word out to the public. This should
have been on every free spot available as a public service on the radio, tv newspaper
and whatever other methods available.
EPA disagrees that responsibility has been negated; the
responsible parties are listed in the Proposed Plan and are being
held accountable for the cleanup.
With respect to outreach conducted as part of the Proposed Plan
process, please refer to Comment 8.
Additionally, information on the water pipes is included in
Comments 1 and 3.
The USAF issued a ROD in August 2020, which implemented I SCO
and ISB within hot spot source areas at AFP44. This remedy has
significantly reduced concentrations of VOCs and 1,4-dioxane in
shallow groundwater areas with high levels of contamination. For
further information on why EPA prefers enhanced Alternative 3
over Alternatives 5 and 6, please refer to Comment 9.
I also feel that the old water pipes and ground was never cleaned, and so cleaning the
water and then putting it thru the contaminated water system, that is often compromised
by broken lines and the contaminated ground that surrounds it is not healthy.
We need to stop going thru the motions of doing something, knowing full well is not good
enough.
I have spoken to many in our community that are really discouraged by the way all this
had been handled. Please protect the public not the culprits of this mess. Way too many
are dying and some are really ill and negating responsibility is just plain out wrong.
Written Comments by Eva Carriilo Dong received on May 21,2017 via email
25
Although EPA prefers number three as presented, I do not feel that this is sufficient nor
will it address our needs. I prefer number 5 with the existing Pump and Treat with UV
Peroxide Plus In Stu. Please take this alternative into consideration for the sake of our
community and all that they have gone through already.
For further information on why EPA prefers enhanced Alternative
3 over Alternatives 5 and 6, please refer to Comment 9.
Written Comments from "Tucsonans for a Clean Environment" Environmental Justice Task Force & Concerned Southside Tucson Residents received on May 21,
2017 via email
26
The proposed plan does nothing to contribute to the actual cleanup of the subsurface
regions above our aquifer, in fact Preferred Alternative #3 is simply business as usual.
We appreciate the EPA's acknowledgement of 1,4 Dioxane as a contaminant in the
Superfund site, however, TCA (of which 1,4 Dioxane is a byproduct, according to the
EPA) was known to be part of the slurry of contaminants discovered in the early 1980's
and detailed in a 1988 EPA assessment.
Enhanced Alternative 3 includes a pump-and-treat system,
installation of one new remediation well, and continues operation
of the current on-site treatment plant.
1,4-dioxane is typically found in association with 1,1,1-
trichlorethane (TCA); however, as documented in the 1988 ROD,
TCA had only been detected twice while TCE was
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Comment No.
Comment
Response
Why was cleanup of TCA and 1,4 Dioxane not included in the 1988 ROD? Why did
Tucson Water only start testing for 1,4 Dioxane in 2002? As far as we can tell the EPA
failed to protect human health and the environment from the very beginning of its
investigation and management of the TIAA site.
Because it has taken the EPA nearly 30 years to address this contaminant and offer this
proposed plan, notwithstanding the development of the treatment systems in the 1990's
and 2000's and their operation to this day, we the community do not have confidence in
the EPA's ability to effectively cleanup the contamination, be it TCE, DCE, trans-1,2-
DCE, TCA, chloroform, 1,4 Dioxane, or any of the other number of chemicals that were
illicitly dumped and ultimately contaminated our subsurface zones and aquifer.
detected 435 times. Due to the low number of detections and the
concentrations that were below the cleanup standards, TCA was
not identified as a site contaminant of concern. In addition to the
identified chemicals of concern at the site, TCA is still sampled
for, and current results can be referenced in the TARP Semi-
Annual Status Reports; these reports are present at the Pima
County Public Library—Valencia Branch.
As documented in the Focused Remedial Investigation, 1,4-
dioxane was sampled at AFP44 (an original contributing source
to the groundwater contamination found in Area A) in the 1990s,
but no detections were noted. An improved and more accurate
analysis method was developed and subsequently allowed for a
lower detection limit. Using the new analytical method, 1,4-
dioxane was discovered in monitoring wells at AFP 44, the Airport
Property, and at TARP in 2002. Eventually, in 2011, EPA reduced
its Drinking Water Health Advisory, which prompted
implementation of AOP treatment at TARP.
27
As it reads, the Proposed Plan is an all-or-nothing plan lacking specifics on each of the
alternatives it offers. For instance, the specific long-term effectiveness of Alternative #5
is not mentioned under Balancing Criteria #3 Long-term Effectiveness. Rather, it is
lumped together with Alternatives 3,4 and 6. This is perhaps disingenuous, especially
because Alternative #5's "Short-Term Effectiveness" is presented in detail as posing
short-term risks to the community and workers involved in that process. Somehow this
feels forced.
The Proposed Plan is intended to be a summary of the proposed
alternatives, which are originally presented in the Focused
Feasibility Study. Based in part on public comment and concern,
EPA will enhance Alternative 3 by installing an additional
remediation well within the groundwater plume. Additional in-
depth discussion of the alternatives and their application to the
evaluation criteria is contained in the Focused Feasibility Study
dated March 2016. This document can be found at the Pima
County Public Library—Valencia Branch.
28
Also, Alternative #3 is, "Expected to have minimal reduction in toxicity, mobility, and
volume of contaminants in groundwater." Whereas, Alternative #5, "Could potentially
reduce the toxicity, mobility, and volume" of contaminants in the groundwater and soil
through the use of in situ bioremediation.
"Expected to" and "Could Potentially" are not phrases indicating confidence in either of
the alternatives. How can the public be confident in voicing their opinions and
suggestions if the proposed plan is deficient in assertive and balanced information? Isn't
it part of the EPA's mission is that, "all parts of society - communities, individuals,
businesses, and state, local and tribal governments—have access to accurate
information sufficient to effectively participate in managing human health and
environmental risks?"
EPA recognizes your concern with how the evaluation of
remediation technologies is described. When evaluating how
processes, reactions, or methods will work in the natural
environment, the expected outcome cannot be 100 percent
guaranteed; therefore, the language in these documents must
reflect a certain level of uncertainty. The Proposed Plan was
prepared in accordance with EPA guidance documents, and the
guidance requires the use of phrases such as "Expected to" and
"Could Potentially" to qualify certain statements.
Enhanced Alternative 3 is expected to create a moderate
reduction in the toxicity, mobility, and volume of the
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Comment No.
Comment
Response
Notwithstanding the lack of confidence in the proposal language, Alternative #3 is
expected to have minimal reduction in toxicity, mobility, and volume of contaminants in
groundwater." And this is the EPA's preferred alternative?!
We the people affected by this contamination are not accepting of the EPA's complacent
approach to "managing" the contaminants. We want the contamination cleaned up!
contamination, and will continue to remove groundwater
contaminants to levels that are safe for human consumption. Over
time, concentrations of TCE and 1,4-dioxane have declined in
Area A; thus, indicating that cleanup is occurring. To monitor the
effectiveness of the preferred remedy, routine periodic monitoring
of the groundwater and tap water will continue to be performed.
For additional information on why enhanced Alternative 3 is
preferred over Alternatives 5 and 6, please refer to Comment 9.
29
This Proposed Plan is ineffective at addressing the needs of the community to make an
informed decision. It is skewed in favor of the Preferred Alternative #3 which is nothing
more than business as usual, and the "cheapest' option. And it does not address the
long-term sustainability of the regions subsurface zones and aquifer.
This Proposed Plan is deficient in informing the public about the long-term effectiveness
of any of the alternatives being considered, therefore, the plan needs to be reconsidered
in light of this deficiency, modified and resubmitted to the public for comment.
The long-term viability of Tucson's aquifer is paramount in this decision. The uncertainty
presented in this proposed plan does not bode well for the long-term sustainability of the
regional aquifer. Regardless of what other sources of water we may have access to
(CAP) or how fast the aquifer is being recharged, it is the only one we have.
The purpose of the Proposed Plan is to evaluate all alternatives
and propose the preferred alternative. Total costs for Alternative
3 are not the lowest among the alternatives, and cost is only one
component used to evaluate alternatives before EPA chooses a
preferred alternative.
As noted in Comment 9, additional detail concerning the long-
term effectiveness of the various alternatives can be referenced
in the 2016 Focused Feasibility Study.
30
We would like to see an alternative that addresses the actual cleanup of the
contamination. Perhaps a hybrid of Alternatives #3 and #5, where in situ bioremediation
is piloted on a small scale to test its effectiveness.
Anything short of actually cleaning up the contamination will be met with fierce opposition
by the community. We do not want to go another 30 years before hearing about another
contaminant and its proposed cleanup.
We are understanding of the current political climate and how it may affect the EPA's
ability to effectively do its job but this issue is over 30 years old and, from our perspective,
so far it has not been an effort that has protected human health and the environment in
the region.
Per the 1990 Consent Decree, any source areas identified will be
investigated and remediated. Until a defined source (high
concentration) area is identified, Alternative 5 or a similar pilot test
would be premature. However, EPA is open to the conductance
of pilot tests at any time in the future when a source area is
identified, and an appropriate technology could be applied. As
outlined in Comment 9, bioremediation is currently being utilized
at AFP44 which has a concentrated source.
Written Comments from the TAA and The Boeing Company received on May 20,2017 via email
31
The Airport Property (including the Tucson International Airport and Three
The 1988 ROD presented the selected groundwater remedial
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Comment No.
Comment
Response
Hangars Building) is not part of TIAA Superfund Site Area A, nor is it a "covered
matter" under the 1988 TARP Record of Decision (ROD) and 1991 TARP Consent
Decree.
EXECUTIVE SUMMARY (Page 1): The text states 'TIAA Superfund Site Area A is the
area north of Los Reales Road and consists of the Airport Property (which includes the
Tucson International Airport and Three Hangers [sic] Building) and the Tucson Airport
Remediation Project (TARP), as shown on Figure 1".
As indicated in the following excerpts from the 1988 TARP ROD and 1991 TARP
Consent Decree, TIAA Superfund Site Area A is associated with the groundwater
remedy for the regional aquifer located north of Los Reales Road:
TARP ROD Page iii, Statement of Basis and Purpose: This decision document presents
the selected groundwater remedial action for the portion of the Tucson International
Airport Area Site that lies north of Los Reales Road.
TARP ROD Page iii, Description of the Remedy: The selected groundwater remedy for
Area A includes control of groundwater contamination through segregation of the upper
and lower divided aquifers and through extraction from both the upper divided aquifer
and the regional undivided aquifer (all north of Los Reales Road).
TARP Consent Decree Page 4, Definitions: "Covered Matters" shall mean the Remedial
Action, Oversight Costs associated with the performance of the Remedial Action and all
Response Costs, including interest accrued thereon.
The Airport Property (including the Tucson International Airport and Three Hangars
Building) is addressed under a 1997 ROD and 1999 Soils Consent Decree. Furthermore,
page 13 of the 1999 Soils Consent Decree states:
"Site" shall mean the areas within the TIAA Superfund Site that were identified during
the Remedial Investigation as Zones A through F and are generally depicted in their
areal extent on the figure attached hereto as Appendix C. The Site does not include the
Regional Aquifer or any Covered Matter, as that term is defined in the TARP (Tucson
Airport Remediation Project) Consent Decree".
TAA and Boeing request that statements indicating and/or implying that the Airport
Property (including the Tucson International Airport and Three Hangars Building) is part
of TIAA Superfund Site Area A be removed from all TIAA Superfund Site documents.
action for the portion of TIAA Superfund Site that lies north of Los
Reales Road, and included Areas A and Area B of the site "not
currently addressed by the Air Force's action." Tucson
International Airport is specifically included in the TIAA per the
Site Location and Description section on Page 1. Additionally,
Figure 4 of the ROD identified potential sources of groundwater
contamination, and it includes the TAA Hangar Area, Runway
Dump, TAA Landfill, and TAA Drainage Channels. Portions of
Airport Property extend geographically over the 1,4-dioxane
plume as currently identified.
32
The Proposed Plan does not "reinforce the original remedy". Rather, the
Proposed Plan contradicts the original remedy for groundwater cleanup as
The original remedy outlined in the 1988 EPA ROD as
documented on page iii, is summarized as follows:
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Comment No.
Comment
Response
described in the 1988 TARP ROD and associated 1991 TARP Consent Decree.
EXECUTIVE SUMMARY (Page 1): The text states "Currently, the remedy for
groundwater cleanup at the TIAA Superfund Site Area A was documented in an EPA
Record of Decision (ROD) signed in 1988. The alternatives in this Proposed Plan add to
and reinforce the original remedy..."
Control groundwater contamination in the various aquifers via
segregation and extraction
Treat groundwater using packed-column aeration
Treat groundwater to an overall cancer risk level (for all
contaminants combined) of 10 6 which requires treatment of TCE
concentrations to approximately 1.5 parts per billion.
Implement reasonably available control technology for reduction
of air emissions if needed
Deliver treated groundwater to the municipal water distribution
system
The new remedy outlined in the Proposed Plan reinforces some
of the components of the original remedy in bullets 1, 3, and 5
above. Based in part on public comment and concern, EPA is
enhancing the selected remedy (Alternative 3) by adding an
additional remediation well, which will extract additional
contaminated groundwater and treat it at the TARP AOP system.
The installation of this additional well will assist with containing
the groundwater plume and removing additional contamination
from the plume. In addition, the text of the ROD Amendment does
not use the phrase "reinforces" in the description of the remedy.
32A
Dr. Hiatt's statements regarding the remediation goals fail to distinguish between
the insitu groundwater remediation goal and the goal for the effluent of the TARP
treatment system.
On March 23,2017 TAA received a copy of a letter from M. Aycock (EPA) addressed to
G. Warner (USAF) regarding "Remediation Goal for 1,4-dioxane, TIAA Superfund Site
Area A ROD Amendment, Tucson, Arizona". The purpose of the letter was "to provide
details about the process EPA uses to determine remediation goals at a Superfund site
and how this process led EPA Region 9 to set a 0.35 micrograms per liter (jug/L)
remediation goal for 1,4-dioxane in contaminated groundwater at Area A of the TIAA
site". Attached to the letter was a "remediation goal analysis" prepared by Dr. Gerald
Hiatt of EPA Region 9. Below is an excerpt from Dr. Hiatt's analysis:
The remediation goal was set to be protective at a 1x10-6 excess lifetime cancer risk.
This determination was made to be consistent with a precedent for the site established
The ROD documents that the EPA's selected target treatment
level for 1,4-dioxane is 0.35 |jg/L in drinking water served to the
public. This ROD Amendment will be an interim decision
document that addresses containment and treatment of 1,4-
dioxane, not restoration of the aquifer. EPA is not establishing an
in situ groundwater cleanup level at this time. The groundwater
cleanup level for 1,4-dioxane will be evaluated by EPA and State
of Arizona when an MCL is established, and a final ROD
Amendment will address insitu groundwater.
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Comment No.
Comment
Response
in the 1988 ROD addressing contamination north of Los Reales Road.
The above statement from Dr. Hiatt's analysis is incorrect. The treatment goal of
groundwater leaving the TARP treatment system and entering the Tucson Water potable
water distribution system was set at 1.5 micrograms per liter (|jg/l) corresponding to a
1x10-6 excess lifetime cancer risk. However, the insitu groundwater remediation goal
established in the 1988 ROD was not set to a 1x10-6 excess lifetime cancer risk. Rather,
the insitu groundwater remediation goal was set at 5 |jg/l corresponding to the MCL for
TCE. The distinction between an insitu groundwater remediation goal and a TARP
treatment system goal is clearly explained in the follow excerpt from the 1991 TARP
Consent Decree, Section V. Obligations for the Remedial Action:
Notwithstanding any approvals which may be granted by the EPA or other governmental
entities, the Settling Parties shall remain liable for attainment of each of the performance
objectives set forth in the ROD. Those objectives are as follows:
Control Contaminant Migration. To control the migration of groundwater contamination
at the Site by extracting all groundwater in Area A that contains volatile organic
compounds (VOCs) at levels above their respective MCLs. Groundwater shall be
extracted at such locations and rates as is necessary to prevent groundwater containing
VOCs at concentrations greater than MCLs within Area A from migrating beyond the
area of capture of the well field designed as part of the Remedial Action.
Aquifer Remediation. To restore the aquifer water quality in Area A by reducing chemical
contaminant concentrations in Area A to no more than the MCLs.
Treatment of Extracted Groundwater. To treat extracted groundwater with packed-
column aeration to a TCE concentration not to exceed 1.5 micrograms per liter (parts
per billion), a level that EPA believes will achieve an overall excess cancer risk level of
1X10-6 for chemical contaminants in the treated water.
The above excerpts from the 1991 TARP Consent Decree clearly differentiate between
the TCE insitu groundwater remediation goal of 5.0 |jg/l (i.e., the MCL for TCE) and the
TCE TARP treatment system goal of 1.5 |jg/l. By setting the insitu groundwater DX
remediation goal equal to the TARP treatment system goal, the Proposed Plan is
inconsistent with, and contradicts the 1988 TARP ROD.
The Final Unified Focused Human Health Risk Assessment for 1,4-Dioxane North of Los
Reales Road, Tucson International Airport Area Superfund Site Area A, Tucson Arizona
(EPA and EGC, 2015) repeats the same error as described above when it states:
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Comment No.
Comment
Response
The 1988 ROD set a risk-based remediation goal for cleanup of the groundwater north
of Los Reales Road and supplying the TARP plant which feeds the public water system
for the City of Tucson.
The 1988 ROD set a risk-based TCE treatment system goal of 1.5 |jg/l for TARP effluent
that feeds the City of Tucson public water system. However, the 1988 ROD did not set
a risk-based insitu groundwater remediation goal for TCE. Rather, the 1988 ROD
adopted the TCE MCL of 5 |jg/l for the remediation goal for insitu groundwater.
TAA and Boeing request the Agencies 1) acknowledge that setting the DX insitu
groundwater remediation goal equal to the DX TARP treatment system goal is
inconsistent with, and contradicts the 1988 ROD and 1991 TARP Consent Decree, and
2) revise the Proposed Plan and associated risk assessments to be consistent with the
1988 ROD and 1991 TARP Consent Decree.
32B
The insitu groundwater remediation goal proposed in the Proposed Plan is
inconsistent with and contradicts the 1988 TARP ROD and 1991 TARP Consent
Decree.
The Revised Limited Risk Assessment for 1,4-Dioxane and Trichloroethylene in
Groundwater at the Tucson International Airport Area Superfund Site (EPA, 2015)
indicates the excess lifetime cancer risk (ELCR) corresponds to TCE concentrations in
drinking water as follows:
TCE concentration of 50 |jg/l equates to a ELCR of 1X10-4,
TCE concentration of 5.0 |jg/l equates to a ELCR of 1X10-5,
TCE concentration of 0.5 |jg/l equates to a ELCR of 1X10-6
Therefore, the insitu groundwater remediation goal of 5.0 |jg/l established for TCE in the
1988 TARP ROD and 1991 TARP Consent Decree corresponds to a ELCR of 1X10-5.
TAA and Boeing request the Agencies 1) acknowledge that setting the DX insitu
groundwater remediation goal equal to an ELCR of 1X10-6 is inconsistent with and
contradicts the 1988 ROD and 1991 TARP Consent Decree, and 2) revise the Proposed
Plan and associated risk assessments to be consistent with the 1988 TARP ROD and
1991 TARP Consent Decree.
See response to Comment 32A.
32C
The Risk Assessments referenced in the Proposed Plan greatly overestimate the
actual risks associated with TIAA Superfund Site groundwater contaminants, and
indicate the proposed insitu groundwater remediation cleanup goals are not
The risk assessments referenced in the Proposed Plan follow
standard Superfund risk assessment guidance, are consistent
with risk assessments typical for Superfund sites nationwide,
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Comment No.
Comment
Response
realistic or achievable.
The above-referenced "remediation goal analysis" prepared by Dr. Gerald Hiatt of EPA
Region 9 states:
If no federal or state MCL is available for identification as an ARAR-based remediation
goal, the NCP defines a health protective remediation goal for carcinogens thusly: "For
known or suspected carcinogens, acceptable exposure levels are generally
concentration levels that represent an excess upper bound lifetime cancer risk to an
individual of between 10-4 and 10-6... The 10-6 risk level shall be used as the point of
departure for determining remediation goals for alternatives when ARARs are not
available ..."
The following is an expanded excerpt from the NCP:
Final remediation goals will be determined when the remedy is selected. Remediation
goals shall establish acceptable exposure levels that are protective of human health and
the environment and shall be developed by considering the following:
Applicable or relevant and appropriate requirements under federal environmental or
state environmental or facility siting laws, if available, and the following factors:
(1) For systemic toxicants, acceptable exposure levels shall represent concentration
levels to which the human population, including sensitive subgroups, may be exposed
without adverse effect during a lifetime or part of a lifetime, incorporating an adequate
margin of safety;
(2) For known or suspected carcinogens, acceptable exposure levels are
generally concentration levels that represent an excess upper bound lifetime cancer risk
to an individual of between 10-4 and 10-6 using information on the relationship between
dose and response. The 10-6 risk level shall be used as the point of departure for
determining remediation goals for alternatives when ARARs are not available or are not
sufficiently protective because of the presence of multiple contaminants at a site or
multiple pathways of exposure;
(3) Factors related to technical limitations such as detection/quantification limits for
contaminants;
(4) Factors related to uncertainty; and
(5) Other pertinent information.
The expanded excerpt clearly indicates the 10-6 is the conservative point of departure
prior to considering other factors that may move the acceptable exposure levels away
and are based on actual groundwater contaminant concentration
data collected at the site. EPA's target treatment level for 1,4-
dioxane in treated water is consistent with the National
Contingency Plan's guidance to use the 10 6 risk level as a point
of departure when no Applicable or Relevant and Appropriate
Requirement is available. Therefore, the risk assessments will not
be revised to modify the risk scenarios. See also response to
Comment 32A.
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Comment No.
Comment
Response
from 10-6 and toward 10-4 ELCR. "Other pertinent information" includes data indicating
the proposed cleanup levels are achievable. Operational data exist that show the TARP
treatment system can remove DX from extracted groundwater to concentrations that
meet the 10-6 ELCR. However, EPA has not provided data that show a 10-6 insitu
groundwater cleanup level is achievable. In fact, the Revised Limited Risk Assessment
for 1,4-Dioxane and Trichloroethylene for the Groundwater at the Tucson International
Superfund Site (EPA, 2015) calculates risks based on the assumption that the DX and
TCE groundwater concentrations remain constant indefinitely (i.e., the concentrations
never decrease). The following is an excerpt from the Revised Limited Risk Assessment
for 1,4-Dioxane and Trichloroethylene for the Groundwater at the Tucson International
Superfund Site (EPA, 2015):
This limited risk assessment does not rely on groundwater modeling to predict future
concentrations at the various points of exposure—developing a groundwater model
sufficiently robust to make such predictions at the site has proven a significant challenge.
Rather, by using groundwater concentrations from a limited period of sampling and
analysis, the risk assessment inherently assumes the EPCs (exposure point
concentrations) will remain constant over the exposure periods assessed herein.
By assuming the contaminant concentrations never decrease, the risk assessment 1)
greatly overestimates the actual risks associated with TIAA Superfund Site groundwater
contaminants, and 2) indicates the proposed insitu groundwater remediation cleanup
goals are not realistic or achievable.
TAA and Boeing request the Agencies 1) revise the TARP risk assessments and
evaluate risks based on realistic conditions and 2) select insitu groundwater cleanup
standards that are achievable.
32D
The insitu groundwater remediation goal proposed in the Proposed Plan was
derived in a manner inconsistent with the process for establishing enforceable
groundwater remediation goals.
The above-referenced "remediation goal analysis" prepared by Dr. Gerald Hiatt of EPA
Region 9 states:
Taking these 2 factors into consideration, the Region arrived at a proposed remediation
goal for 1,4-dioxane of 0.35 micrograms per liter (iJg/L). The 0.35 yg/L concentration for
1,4-dioxane is the 10-6 excess lifetime cancer risk (ELCR level specified in the
Integrated Risk Information System (IRIS) file for lifetime (70 year)
consumption of drinking water containing 1,4-dioxane. It is also the EPA Office of Water
Health Advisory value for a lifetime 10-6 ELCR (see 2012 Edition of Drinking
See responses to Comment 32C and 32A.
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Comment No.
Comment
Response
Water Standards and Health Advisories published by Office of Water, but note that the
value in the table is for a 10-4 risk and therefore must be divided by 100 for the 10-6
value).
As shown in the attached Table 5 Chemical-Specific ARARs for VOC-Contaminated
Regional Groundwater (see Attachment A), the EPA IRIS numbers, EPA Office of Water
Health Advisory Values, and EPA Region 9 Regional Screening Levels for DX are not
enforceable aquifer remediation standards. MCLs established through the Safe Drinking
Water Act (SDWA) are enforceable groundwater remediation standards. The process of
establishing MCLs includes identifying the 10-6 risk level. Other pertinent information is
then incorporated prior to establishing an enforceable cleanup standard.
TAA and Boeing request the Agencies follow established processes in accordance with
the Safe Drinking Water Act and EPA guidance/policies; move beyond the initial 10-6
point of departure; and incorporate other pertinent information prior to selecting insitu
aquifer cleanup standards for the TARP regional aquifer.
32E
Risks at the TIAA Superfund Site should not be calculated based on a 70- year
lifetime exposure.
The above-referenced "remediation goal analysis" prepared by Dr. Gerald Hiatt of EPA
Region 9 states:
The remediation goal was set to be protective for a 70 year Reasonable Maximum
Exposure (RME) residential exposure scenario. At most Superfund sites, remediation
goals for residential exposures (such as drinking water consumption) are based on
levels protective for a 26 to 30 year exposure period (this is because most people are
assumed to move away from the site within that timeframe and hence are no longer
exposed). However, at Tucson, the Region focused on a lifetime (70 year) exposure
assumption for 2 reasons: (i) demographic information indicates that people in Southside
Tucson, the most impacted community, move less frequently (at Unified Community
Advisory Board meetings we have heard of/from a number of lifetime residents) and (ii)
since the treated water is being served via the Tucson Water distribution system, an
individual may consume the same water even though he/she moves to a different
location within the city (Unified Focused Human Health Risk Assessment, EPA/Air Force
Civil Engineer Center, 2015).
The above statement is incorrect and misleading. It is an established fact that the treated
TARP effluent is not served to residents in Southside Tucson. Rather, the
treated TARP effluent is served to a well-defined area in north and northwest Tucson.
Therefore, "demographic information indicating people in the Southside Tucson move
Superfund risk assessment guidance provides the option to use
site-specific exposure assumptions, including exposure duration,
in assessing risks and setting remediation goals for contaminants
at a Superfund site. In the present case, EPA determined that 70
years is an appropriate site-specific exposure duration
assumption. Therefore, the Proposed Plan and risk assessments
will not be revised to modify the lifetime exposure scenario.
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Comment No.
Comment
Response
less frequently" is irrelevant for TIM Superfund Site Area A risk assessment purposes.
In addition, there are no demographic data indicating the people in north and northwest
Tucson do not move away from the these areas within a 26 to 30 year timeframe.
TAA and Boeing request the Agencies 1) acknowledge that calculating risks based on
a 70-year lifetime exposure in not applicable to the TIAA Superfund Site, and 2) revise
the Proposed Plan and associated risk assessments and base risks on standard 30
lifetime exposure data.
33
The March 2016 Focused Remedial Investigation/Feasibility Study for 1,4- Dioxane
North of Los Reaies Road (FRI/FS) contains errors, inconsistencies, omissions,
and scientifically unsupported interpretations and conclusions. The FRI/FS, in its
current state, is 1) unsubstantiated and thereby fundamentally flawed, and 2) unfit
to serve as the basis for the Proposed Plan, the proposed TARP ROD Amendment,
or the proposed TARP Consent Decree modifications.
EPA ANNOUNCES PROPOSED PLAN (Page 3): The text states "This Proposed Plan
summarizes the information that is presented in detail in the Focused Remedial
investigation/Feasibility Study (Ri/FS) completed by EGC, Inc. on behalf of the USAF in
2016, and other documents in the TIAA Superfund Site Administrative Record File".
Below is a timeline associated with the FRI/FS:
2008—2016: The United States Air Force (USAF) conducted investigatory actions,
culminating in the preparation of the Focused Remedial Investigation and Feasibility
Study for 1,4-Dioxane North of Los Reaies Road.
Feb. 2016: In letter from M. Aycock (EPA) addressed to G. Warner (USAF) dated
February 3, 2016, EPA states that "the Agencies (EPA and Arizona Department of
Environmental Quality [ADEQ]) concur that the AF (Air Force) has addressed all the
comments and revised the text in accordance with the agreed upon responses. Please
finalize these documents."
May 2016: TAA and the Airport Property Settling Parties (SP) are given an opportunity
to review and provide comments on the FRI/FS.
September 2,2016: TAA submits comments to EPA on the FRI/FS.
November 22, 2016: The Agencies (EPA and ADEQ) provide responses to TAA
comments on the FRI/FS. Note: Although TAA FRI/FS comments were submitted
directly to EPA on September 2, 2016, EPA's November 22, 2016 response to
comments combined TAA's comments with comments submitted to EPA separately by
the SP on September 20, 2016.
EPA does not agree with the TAA and Boeing interpretation of the
data and information in the Focused Remedial
Investigation/Feasibility Study (Focused RI/FS); therefore,
disagrees that the document is fundamentally flawed or unfit to
serve as the basis for the Proposed Plan, ROD Amendment, or
Consent Decree modifications. EPA's responses to the TAA
comments to the Focused RI/FS were grouped where a common
response applied for clarity purposes.
EPA has convened multiple joint meetings between the Air Force
and TAA with ADEQ and contractor support to develop a
consensus on the nature and extent of groundwater
contamination and the Conceptual Site Model in the vicinity of Los
Reaies Road. The Air Force is evaluating the need for additional
groundwater monitoring and/or extraction wells south of Los
Reaies Road and has made significant upgrades to the
groundwater treatment plant at AFP 44 to further enable plume
capture.
The TAA has been provided responses to the comments to the
Focused RI/FS received in September 2016.
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Comment No.
Comment
Response
December 19, 2016: A teleconference was held with the TAA, SP, EPA, ADEQ, USAF,
and respective consultants to discuss the FRI/FS and associated comments.
TAA and SP comments submitted to EPA on September 2, 2016 and September 20,
2016, respectively, identified numerous deficiencies in the FRI/FS including 1)
unsupported assumptions that the existing groundwater remediation system located at
U.S. Air Force Plant 44 (AFP-44) is sufficiently controlling DX source areas and thereby
preventing DX migration into the aquifer located north of Los Reales Road, 2) the
unsubstantiated claim that the Airport Property is a primary source of DX), 3) inadequate
characterization of DX source areas including the Inactive Drainage Channel Disposal
Pits (DP-03) and Sludge Drying Beds (WP-05) located on AFP-44 property, 4) lack of
fate and transport analysis of DX re-injected into wells (with gravel/filter packs extending
within 20 feet of land surface) adjacent to Airport Property from 1987 to 2004.
In the Agencies November 22, 2016 response to TAA comments, the Agencies agreed
with TAA that "...the Airport Property has not been identified by the Agencies as a
primary source of DX to the regional aquifer" and "...AFP-44 is a primary source of DX
in the regional aquifer" thus concurring that the Airport Property should not be referred
to as a primary DX source area.
As noted above, a teleconference was scheduled for December 19, 2016 to provide an
opportunity for TAA, SP, EPA, ADEQ, USAF, and EGC (USAF's consultant and author
of the FRI/FS) to discuss the FRI/FS. However, during the teleconference, TAA and the
SP were informed by the USAF and EPA that EGC was no longer on contract with the
USAF and were therefore unavailable to participate in the teleconference, discuss
investigative data, and explain FRI/FS claims and conclusions. Consequently, the
FRI/FS accepted as final by EPA on February 3, 2016 continues to contain significant
errors and inaccuracies including but not limited to:
Unsupported assumptions that the AFP-44 groundwater remediation system is
sufficiently controlling DX source areas and thereby preventing DX migration into the
aquifer located north of Los Reales Road.
Unsubstantiated claims that the Airport Property is a primary source of DX.
No evaluation of the fate and transport of DX re-injected into wells (with gravel/filter
packs extending within 20 feet of land surface) adjacent to Airport Property from 1987
to 2004.
Inaccurate plume maps.
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Comment No.
Comment
Response
Inadequate characterization of DX source areas including the Inactive Drainage Channel
Disposal Pits (DP-03) and Sludge Drying Beds (WP-05) located on AFP-44 property.
Errors, inconsistencies, omissions, and scientifically unsupported interpretations and
conclusions.
As noted above, TAA submitted comments on the FRI/FS to EPA on September 2,2016.
Although TAA submitted 44 comments, the Agencies November 22, 2016 response
states:
Review of the submittals indicates that the comments belong to one of two general
categories: Conceptual Site Model and Nature and Extent of Contamination issues, and
Remedy Selection issues.
Based on this gross oversimplification, the Agencies responded to multiple TAA
comments with a single response.
The following is an excerpt from the Agencies response to TAA comments 1,2,3,4, 5,
14, 19, 20, 22, 26, 30, and 39:
The Air Force has completed the Fall 2016 semi-annual sampling event and a report
with the results of that sampling will be available in December 2016. The results will
show that the Air Force has begun to control the migration of DX north of Los Reales
Road, and the Agencies viewed figures during the October 2016 Air Force quarterly
meeting that showed DX was being contained.
As described below, US Geological Survey (USGS) DX groundwater sampling results
clearly show the AFP-44 groundwater treatment system and network of extraction wells
have not, and are not, preventing DX from migrating to the aquifer located north of Los
Reales Road.
The following is an excerpt from the Agencies response to TAA comments 6,7, 8,9,11,
12, 13, 15, 16, 17, 18, 25, and 38:
The Source Area comments will be incorporated as appropriate into the ROD
Amendment and PP; the documents will be revised to indicate that AFP 44 was a primary
source of DX in the Regional Aquifer and plume containment on AFP 44 property is
addressing that source.
The Proposed Plan does not indicate that 1) AFP-44 was a primary source of DX in the
Regional Aquifer, or 2) plume containment on AFP-44 property is addressing that source.
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Comment No.
Comment
Response
In the above referenced November 22,2016 letter responding to TAAand SP comments
on the FRI/FS, the Agencies state:
The Agencies have determined that the Final FRi/FFS (sic) documents will not be
revised; rather, the TAA and SP comments will be addressed and incorporated as
appropriate in revised Record of Decision (ROD) Amendment and Proposed Plan (PP)
documents prior to those documents being submitted to the public for review.
As documented by the above excerpts, the Proposed Plan does not appropriately
address or incorporate TAA and SP comments on the FRI/FS.
The Agencies may believe they have adequately responded to and addressed TAA and
SP comments on the FRI/FS in the Agencies' November 22, 2016 letter. However, as
noted above, EGC are the subject matter experts who compiled, evaluated, and drew
conclusions based on the data provided in the FRI/FS. Because the Agencies did not
perform the investigative work or prepare the resulting FRI/FS, they cannot with authority
respond to TAA and SP comments on behalf of EGC.
TAA and Boeing hereby reassert requests that EGC be made available to respond to
TAA and SP comments, concerns, and questions. Until EGC subject matter experts
explain how they reached their conclusions and provide the data upon which the
conclusion were made, the FRI/FS should be considered unsubstantiated and thereby
fundamentally flawed. Consequently, the FRI/FS in its current state, is unfit serve as the
basis for the Proposed Plan, the proposed TARP ROD Amendment, or the proposed
TARP Consent Decree modifications.
34
The aquifer in TIAA Superfund Site Area A north of Los Reales Road is being
contaminated by DX-impacted groundwater from source areas located south of
Los Reales Road.
SITE BACKGROUND AND CHARACTERISTICS (Page 3): The text states "The
groundwater plumes associated with Area Band Air Force Plant 44 are not summarized
as part of this Proposed Plan and are being addressed in separate decision
documents".
Although the groundwater plumes associated with AFP-44 are addressed in separate
decision documents, the Proposed Plan should, in fact, address the DX entering the
TIAA Superfund Site Area A, from the aquifer south of Los Reales Road. The 2017
USGS DX groundwater sampling results clearly show DX contamination migrating from
the aquifer south of Los Reales Road into the TIAA Superfund Site Area A north of Los
Reales Road (see Attachment B). In fact, water quality data collected since 2007 from
monitor well WR-075S show movement of DX at concentrations one to two orders of
Historical site data shows that higher levels of contaminants
migrated into Area A at some time in the past; however, there is
historical information, which documents the use of TCA in other
locations within Area A. One of the breakdown products of TCA is
1,4-dioxane.
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Comment No.
Comment
Response
magnitude greater than EPA's proposed in situ aquifer cleanup level of 0.35 micrograms
per liter (|jg/l) from the aquifer south of Los Reales Road into the TIM Superfund Site
Area A north of Los Reales Road.
In the above-referenced November 22,2016 response to comments, the Agencies state
"AFP-44 plume containment is being achieved". However, water quality data clearly
show wide-spread movement of DX at concentrations well above EPA's proposed in situ
aquifer cleanup level of 0.35 |jg/l, from the aquifer south of Los Reales Road into the
TIAA Superfund Site Area A north of Los Reales Road (Attachment B). The Agencies'
claim that "AFP-44 plume containment is being achieved" is contradicted by water quality
data.
TAA and Boeing request the Agencies acknowledge and address the ongoing
contamination of the aquifer in TIAA Superfund Site Area A north of Los Reales Road
by DX-impacted groundwater and source areas located south of Los Reales Road.
35
The Proposed Plan is proposing to obligate the TARP Responsible Parties north
of Los Reales Road to remediate insitu groundwater and contain DX in the aquifer
north of Los Reales Road, while the USAF is not required to remediate insitu
groundwater or contain the DX present in the aquifer south of Los Reales Road
(i.e., the Source Area for DX found in the regional aquifer).
SITE BACKGROUND AND CHARACTERISTICS (Page 3): The text states "The
groundwater plumes associated with Area B and Air Force Plant 44 are not summarized
as part of this Proposed Plan and are being addressed in separate decision
documents".
On July 13, 2007, EPA issued an administrative order directing the USAF to install an
Advanced Oxidation Process (AOP) system to treat DX in extracted groundwater. The
administrative order's Scope of Work (SOW) established the following Groundwater
Treatment AOP Performance Standard:
Treated groundwater at the site shall be reinjected in to the regional aquifer. The
modified AOP groundwater treatment system will have removal efficiency of 90%, but
not to discharge more the 3 ppb (parts per billion or yg/l) DX into the regional aquifer.
Although the administrative order and associated SOW directed the USAF to treat DX
to a concentration no greater than 3 |jg/l, the administrative order and associated SOW
did not direct the USAF to remediate the in situ aquifer. Consequently, the USAF is not
currently obligated to prevent DX, at any concentration, from migrating from the aquifer
south of Los Reales Road into the TIAA Superfund Site Area A aquifer north of Los
Reales Road.
As noted in the response to Comment 32A, the groundwater
cleanup level for 1,4-dioxane will be evaluated by EPA and the
State of Arizona when an MCL is established.
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Comment No.
Comment
Response
TAA and Boeing request the Agencies explain why they are proposing to obligate the
TARP Responsible Parties north of Los Reales Road to remediate insitu groundwater
and contain DX in the aquifer north of Los Reales Road, when the USAF is not required
to remediate insitu groundwater or contain the DX present in the aquifer south of Los
Reales Road (i.e., the Source Area for DX found in the regional aquifer).
36
The FRI/FS and Proposed Plan do not include alternatives that adequately address
the ongoing DX contamination emanating from the aquifer south of Los Reales
Road into the TIAA Superfund Site Area A aquifer north of Los Reales Road.
SUMMARY OF REMEDIAL ALTERNATIVES (Page 6). The text states "EPA
developed remedial alternatives to achieve remediation of groundwater to the cleanup
levels identified in Table 1, as summarized below. A more detailed evaluation of the
alternatives is included in the
Focused Ri/FS."
TAA and Boeing request that the FRI/FS and Proposed Plan be revised to include an
alternative that adequately addresses the ongoing DX contamination (at concentrations
greater than EPA's proposed in situ aquifer cleanup standard of 0.35 |jg/l) emanating
from the aquifer south of Los Reales Road into the TIAA Superfund Site Area A aquifer
north of Los Reales Road.
It is correct that the Focused RI/FS and Proposed Plan do not
include alternatives that address contamination south of Los
Reales Road because that part of the site is the responsibility of
the Air Force. The cleanup south of Los Reales Road is
addressed under the Air Force decision documents. Please see
response to Comments 34 and 35 above.
The Air Force completed a Feasibility Study for the cleanup of the
regional groundwater south of Los Reales Road in 2017, and a
recent Proposed Plan was reviewed by EPA and ADEQ that
covered the evaluation of alternatives for continuing to clean up
source areas on AFP44 and to control and cleanup up the
regional groundwater plume south of Los Reales Road.
37
The Preferred Alternative identified in the Proposed Plan does not meet
Evaluation Criteria for Superfund Remedial Alternatives. EVALUATION OF
ALTERNATIVES (Page 9).
The text states "This section of the Proposed Plan profiles the relative performance of
each alternative against the nine criteria, noting how each compares to the other options
under consideration. The "Detailed Analysis of Alternatives" is presented in the 2016
Focused RI/FS".
There are no federal or state ARARs for DX. Therefore, the Proposed Plan needs to be
revised to indicate that the Threshold Criteria "Compliance with Federal and State
Applicable or Relevant and Appropriate Requirements" is not applicable for DX.
The Preferred Alternative identified in the Proposed Plan is not effective in the long- term
due to the lack of treatment and containment of DX contamination (at concentrations
greater than EPA's proposed in situ aquifer cleanup standard of 0.35 |jg/l) emanating
from the aquifer south of Los Reales Road into the TIAA Superfund Site Area A aquifer
north of Los Reales Road. In addition, as noted above, the Revised
There is no established MCL for 1,4-dioxane; however, the target
treatment level has been established by EPA for treated
groundwater. A groundwater cleanup level for 1,4-dioxane will be
established when an MCL is adopted by the State of Arizona or
EPA.
The Preferred Alternative is effective in the long-term because it
contains the plume north of Los Reales Road and is reducing
concentrations of TCE and 1,4-dioxane. Please see response to
Comment 34 regarding contamination south of Los Reales Road.
Please see response to Comment 23 regarding reduction of
toxicity, mobility, and/or volume and contamination south of Los
Reales Road.
Please see response to Comment 34 regarding calculation of
costs as it relates to contamination south of Los Reales Road.
77A4 SUPERFUND SITE AREA A
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INTERIM RECORD OF DECISION AMENDMENT
MARCH 2023
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Comment No.
Comment
Response
Limited Risk Assessment for 1,4-Dioxane and Trichloroethylene for the Groundwater at
the Tucson International Superfund Site (EPA, 2015) assumes the DX and TCE
groundwater concentrations remain constant indefinitely. This indicates the insitu aquifer
cleanup standards identified in the Proposed Plan are not achievable. Consequently, the
Preferred Alternative identified in the Proposed Plan does not meet the Balancing
Criteria "Long-Term Effectiveness."
The Preferred Alternative identified in the Proposed Plan does not reduce the toxicity,
mobility, and/or volume due to the lack of treatment and containment of DX
contamination (at concentrations greater than EPA's proposed in situ aquifer cleanup
standard of 0.35 |jg/l) emanating from the aquifer south of Los Reales Road into the
TIAA Superfund Site Area A aquifer north of Los Reales Road. In addition, as noted
above, the Revised Limited Risk Assessment for 1,4-Dioxane and Trichloroethylene for
the Groundwater at the Tucson International Superfund Site (EPA, 2015) assumes the
DXand TCE groundwater concentrations remain constant indefinitely. This indicates the
insitu aquifer cleanup standards identified in the Proposed Plan are not achievable.
Consequently, the Preferred Alternative identified in the Proposed Plan does not meet
the Balancing Criteria "Reduction of Toxicity, Mobility, and/or Volume through
Treatment."
Costs cannot be estimated for the Preferred Alternative identified in the Proposed Plan
due to the ongoing DX contamination (at concentrations greater than EPA's proposed
insitu aquifer cleanup standard of 0.35 |jg/l) emanating from the aquifer south of Los
Reales Road into the TIAA Superfund Site Area A aquifer north of Los Reales Road. In
addition, as noted above, the Revised Limited Risk Assessment for 1,4-Dioxane and
Trichloroethylene for the Groundwater at the Tucson International Superfund Site (EPA,
2015) assumes the DX and TCE groundwater concentrations remain constant
indefinitely. However, cost estimates in the Proposed Plan and FRI/FS are based on a
finite 30 year aquifer cleanup timeframe.
Cost cannot be estimated until 1) the USAF is obligated to contain DX in the aquifer
south of Los Reales Road, and 2) EPA selects an insitu aquifer cleanup standard that is
achievable. Consequently, the Preferred Alternative identified in the Proposed Plan does
not meet the Balancing Criteria "Cost."
TAA and Boeing request that the FRI/FS and Proposed Plan be revised to include a
preferred alternative that meets all nine Evaluation Criteria for Superfund Remedial
Alternatives.
Accordingly, the Focused RI/FS does not require revision to
address the alternative evaluations. The new enhanced
Alternative 3 is summarized in this responsiveness summary and
recorded in greater detail in the ROD Amendment.
TIAA SUPERFUND SITE AREA A
5-30
INTERIM RECORD OF DECISION AMENDMENT
MARCH 2023
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Comment No.
Comment
Response
Written Comments from the Sierra Club Rincon Group received on May 25,2017 via email
38
The Sierra Club Rincon Group strongly recommends that the Environmental Protection
Agency adopt Alternative 6 or Alternative 5 for cleaning 1,4-dioxane and other toxic
solvents from groundwater in the Tucson International Airport Area Superfund Site.
While these alternatives are the most expensive initially of the six the agency suggests
for this Superfund Site, they would clean up the contamination much more quickly that
the other alternatives and thus are likely to save money in the long run.
The Sierra Club Rincon Group has more than 4,000 members in Tucson and Pima,
Santa Cruz and Cochise counties. We are concerned about all aspects of our physical
environment, including the disastrous contamination of ground water on Tucson's
southside, where many thousands of people over the years have suffered or died
prematurely as a result of their exposure to this toxic pollution.
Available information about the cleanup methods proposed in the EPA's six alternatives
indicates that in situ bioremediation and in situ chemical oxidation would clean the
contamination more swiftly than the preferred alternative, Existing Pump and Treat with
UV Peroxide, which is likely to require additional decades of operation to complete the
task.
In contrast, information about alternatives 5 and 6 indicate they could accomplish the
contamination clean up in just a few years. And the literature states the EPA and other
agencies and responsible parties are employing these two cleanup methods at
numerous contamination sites, many of them Superfund sites, so they are viable and
affordable.
The folks whose health is impacted have been exposed to this contaminated water via
ingestion, bathing and the operation of evaporative coolers for many decades already.
They deserve the swiftest relief available.
We implore the EPA to select Alternative 6 or Alternative 5 when it makes a final decision
on how to proceed with cleaning this Superfund site.
EPA appreciates the input from the Sierra Club. Please refer to
Comment 9 for additional information on Alternatives 5 and 6.
77A4 SUPERFUND SITE AREA A
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INTERIM RECORD OF DECISION AMENDMENT
MARCH 2023
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Comment No.
Comment
Response
Spoken Comments by Ms. Yolanda Hererra, Community Co-Chair of the Unified Community Advisory Board (UCAB) for the TIAA Superfund Site
at the public meeting held on March 30,2017
39
Ms. Hererra, current Co-Chair and a member since 1995 of the UCAB, recommends that
the United States Environmental Protection Agency adopt Alternative 3: Enhanced
Existing Pump-and-Treat System with UV-Peroxide Plus Long-Term Monitoring and
Institutional Controls for cleaning 1,4-dioxane and other toxic solvents from groundwater
in the Tucson International Airport Area Superfund Site.
EPA appreciates the input from Ms.Hererra and her support for
Alternative 3: Enhanced Existing Pump-and-Treat System with
UV- Peroxide Plus Long-Term Monitoring and ICs (EPA's
Preferred Alternative).
77A4 SUPERFUND SITE AREA A
5-32
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MARCH 2023
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Comment No.
Comment
Response
Written Comments from the City of Tucson Water Department received on June 8,2017 via email
40
Full text of letter received from City of Tucson Water Department:
June 8, 2017
Ms. Mary T. Aycock
Remedial Project Manager
United States Environmental Protection Agency, Region IX
7 5 Hawthorne Street
San Francisco, CA 94105
Re: Proposed Plan, Tucson International Airport Area Superfund Site
Area A - North of Los Reales Road (U.S. EPA, October 2016)
Dear Ms. Aycock:
The City of Tucson provided comments to EPA on the draft Proposed Plan via email on
September 9, 2016. Accordingly, the City did not submit additional feedback during the
public comment period for the referenced document. We would, however, like to reiterate
our previously communicated support for EPA's adoption of Alternative 3 - Existing
Pump and Treat System (Status Quo) with Ultraviolet (UV)-Peroxide plus Monitored
Natural Attenuation (MNA) for remediation of volatile organic compounds (VOCs) and
1,4-dioxane in groundwater of Area A. As previously indicated in our email comments,
Alternative 3 has been in use since early 2014 and has proven to be protective of human
health and the environment.
The City agrees with EPA's assessment resulting in elimination of Alternatives 1, 2, 4,
5, and 6. We also previously expressed specific concerns regarding use of the additional
technologies included in Alternative 5 - Pump and Treat with UV-Peroxide plus in-situ
Bioremediation (ISB) and Alternative 6 - Pump and Treat with UV-Peroxide plus In-situ
Chemical Oxidation (ISCO). Both of those alternatives would include construction of
over 150 injection wells and introduction of chemical agents into the regional potable
aquifer. Tucson Water is familiar with the use of ISB and ISCO approaches to
remediating groundwater impacted by high concentrations of VOCs in perched
groundwater and shallow aquifers as a strategy to control the source of contamination
to potable groundwater resources. However, we are not aware of projects using these
approaches to remediate large, diffuse VOC plumes in aquifers serving as active
sources of potable water to the public.
There is a large degree of uncertainty in the impact to future groundwater quality in Area
A north of Los Reales Road associated with the injection of chemical agents into the
regional aquifer. Additionally, there is uncertainty on future aquifer water levels as
Tucson Water continues to reduce groundwater pumpage. Could this "Re-Wet" the
Vadose Zone and mobilize these injected chemicals? Site-specific pilot studies would
EPA appreciates the input from the City of Tucson and the
support for Alternative 3: Enhanced Existing Pump-and-Treat
System with UV- Peroxide Plus Long-Term Monitoring and ICs
(EPA's Preferred Alternative).
TIAA SUPERFUND SITE AREA A
5-33
INTERIM RECORD OF DECISION AMENDMENT
MARCH 2023
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Comment No.
Comment
Response
be required to determine the effectiveness of in-situ approaches for remediation of
relatively low levels of VOCs in groundwater and the potential for mobilization of
contaminants from soil. In addition, Alternatives 5 and 6 would have a large impact on
the local community due to private land acquisition requirements and disruptions from
the construction and operation of 150 injection wells within the affected neighborhoods.
These impacts to residents and businesses would likely include restricted access,
detours, and traffic congestion associated with extensive injection well
drilling/construction activities.
For these reasons, Tucson Water continues to support EPA's adoption of Alternative 3.
This approach is protective of public health and the environment without introducing
uncertainty in future groundwater quality impacts or causing disruptions to the affected
neighborhoods. We continue to appreciate the opportunity to participate in this process.
Sincerely,
Jeff B. Biggs
Administrator
Strategic Initiatives Division
Tucson Water Department
cc:
Albert Elias, Assistant City Manger
Timothy M. Thomure, Tucson Water Director
Mike Rankin, City Attorney
77A4 SUPERFUND SITE AREA A
5-34
INTERIM RECORD OF DECISION AMENDMENT
MARCH 2023
-------
Comment No.
Comment
Response
Written Comments from ADEQ received on March 2,2018 via email
41
Full text of letter received from ADEQ:
March 2, 2018
Ms. Angeles Herrera
Branch Chief, Federal Facilities
U.S. Environmental Protection Agency (EPA), Region 9
Mail Code SFD-8-1
75 Hawthorne Street
San Francisco, California 94105-3901
Re: Concurrence with Proposed Plan and Draft Record of Decision Amendment for the
Tucson International Airport Area (TIAA) Superfund Site Area A, North of Los Reales
Road, Tucson, Arizona
Dear Ms. Herrera:
As you are aware, the Arizona Department of Environmental Quality (ADEQ) has been
closely involved with the TIAA site for well over 20 years. We appreciate the opportunity
to partner with U.S. EPA in the important work of investigating and cleaning up this site.
Undoubtedly, the most significant event that has occurred at this site in the past 20 years
was the discovery in 2002 of 1,4-dioxane throughout the regional aquifer from U.S. Air
Force Plant 44 (AFP-44) in the south to Irvington Road in the north. Groundwater
treatment systems were already operational to pump and treat TCE contaminated
groundwater from the regional aquifer at both AFP-44 and at the Tucson Airport
Remediation Project (TARP) at the downgradient northern end of site, but with the
discovery of 1,4-dioxane these treatment systems became obsolete. Therefore, the Air
Force initially modified their pumping strategy at AFP-44 to limit the off-site migration of
1,4-dioxane. Then in 2009, the Air Force installed an advanced oxidation treatment
system that was capable of treating 1,4-dioxane so that their goal of containing
groundwater contamination south of Los Reales Road could resume.
To the north, the treatment system at TARP continued to use air stripping technology
and the City of Tucson Water Department (Tucson Water) modified the operation of the
TARP extraction wells to minimize the amount of 1,4-dioxane entering their treatment
plant which delivers treated water to the public water supply. This strategy proved to only
be a temporary solution though because the Regional Screening Level (RSL) for 1,4-
dioxane was lowered in 2011 to 0.35 |jg/L and Tucson Water could no longer serve water
from the TARP system that met the new RSL. Therefore, in 2013 and 2014
Tucson Water constructed an advanced oxidation treatment plant that could effectively
treat both TCE and 1,4-dioxane. The advanced oxidation treatment plant at TARP has
been operating effectively since 2014.
EPA appreciates the input from ADEQ and the support for
Alternative 3: Enhanced Existing Pump-and-Treat System with
UV- Peroxide Plus Long-Term Monitoring and ICs (EPA's
Preferred Alternative).
TIAA SUPERFUND SITE AREA A
5-35
INTERIM RECORD OF DECISION AMENDMENT
MARCH 2023
-------
Comment No.
Comment
Response
The Proposed Plan and Draft Record of Decision Amendment proposed by U.S. EPA
formally modifies the TARP remedy to treat TCE and 1,4-dioxane contaminated
groundwater using the advanced oxidation process that is already in place. ADEQ fully
supports this change to the TARP remedy.
If you have any questions, I can be reached at 520-770-3127 or at TL1 @azdeg.gov.
Sincerely,
Tina LePage, Manager
Remedial Project Section
cc:
ADEQ-FPU reading file
Brian Stonebrink, ADEQ Federal Programs Unit Manager (email)
Mary Aycock, Remedial Project Manager, U.S. EPA Region IX (email)
William Ellett, ADEQ Associate Hydrogeologist (email)
77A4 SUPERFUND SITE AREA A
5-36
INTERIM RECORD OF DECISION AMENDMENT
MARCH 2023
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6.0 REFERENCES
AECOM, 2010, Draft Shallow Groundwater Zone Investigation Summary, U.S. Air Force Plant 44, U.S. Air
Force, December.
AECOM, 2013, Final Revision 1 Baseline Human Health Risk Assessment Work Plan, Focused Remedial
Investigation and Feasibility Study for 1,4-Dioxane North of Los Reales Road at Air Force Plant 44, Tucson,
Arizona, February.
AECOM, 2014a, Draft Baseline Human Health Risk Assessment for 1,4-Dioxane North of Los Reales Road,
Tucson International Airport Area Superfund Site Area A, Tucson, Arizona, January.
AECOM, 2014b, Draft Final Focused Baseline Human Health Risk Assessment for 1,4-Dioxane and
Trichloroethylene, Focused Remedial Investigation and Feasibility Study for 1,4-Dioxane North of Los
Reales Road, Tucson International Airport Area Superfund Site Area A, Tucson, Arizona, August.
Arcadis, 2016, Technical Memorandum: Advanced Oxidation Process (AOP) Water Treatment System
Performance at the Tucson International Airport Area Groundwater Remediation Project (TARP),
September.
Arizona Department of Environmental Quality, 2023, Letter to EPA Region 9, "Concurrence with the
Proposed Plan and Draft Interim Record of Decision Amendment fortheTucson International Airport Area
Superfund Site Area A, North of Los Reales Road, Tucson, Arizona."
Arizona Department of Health Services, Division of Environmental Health Services, Office of Emergency
Response and Environmental Analysis, 1985, Results of the Tucson Airport Area Remedial Investigation
Phase I, Volume III, An Evaluation of the Potential Sources of Groundwater Contamination Near the Tucson
International Airport, Tucson, Arizona, November.
Carollo Engineers, Inc., 2018, Cost Opinion Model for AFP44 Feasibility Study (FS) North of Los Reales Road,
Enhanced Alternative 3, Tucson International Airport Area Groundwater Remediation Project (TARP),
October.
Carollo Engineers, Inc., 2021, Focused Feasibility Study for 1,4-Dioxane North of Los Reales Road,
Addendum: Management of Treated Water, Tucson International Airport Area Superfund Site, Area A,
Tucson Airport Remediation Project (TARP), August.
City of Tucson Water Department, 2014 (May 2014).
Daniel B. Stephens & Associates, Inc., 1993, Final Existing Data Report Tucson International Airport RI/FS
Volume I: ERD.
Daniel B. Stephens & Associates, Inc., 1996, Final Remedial Investigation Report Soils and Shallow
Groundwater Zone Tucson International Airport Superfund Site, October.
Earth Tech, Inc., 1992, Installation Restoration program (IRP) Stage 1, Remedial Investigation Report for
Air Force Plant 44, Tucson, Arizona, July.
Earth Tech Inc., 1997, Final Record of Decision, Sites 1, 2, and 3, Air Force Plant 44, Tucson, Arizona,
April.
TIAA SUPERFUND SITE AREA A C /| INTERIM RECORD OF DECISION AMENDMENT
U~ 1 MARCH 2023
-------
Earth Tech, Inc., 2004, Final Technology Evaluation for Treatment of 1,4-Dioxane in Groundwater,
December.
EGC, Inc., 2015, Final Focused Baseline Human Health Risk Assessment, Focused Remedial, Investigation
and Feasibility Study for 1,4-Dioxane North of Los Reales Road, Tucson International Airport Area
Superfund Site Area A, Tucson, Arizona, September.
EGC, Inc., 2016a, Focused Remedial Investigation and Feasibility Study, Volume I Final Focused Remedial
Investigation for 1,4-Dioxane North of Los Reales Road, Tucson International Airport Area Superfund Site
Area A, Tucson, Arizona, January.
EGC, Inc., 2016b, Focused Remedial Investigation and Feasibility Study, Volume II Draft Final Conceptual
Site Model, Tucson International Airport Area Superfund Site Area A, Tucson Arizona, January.
EGC, Inc., 2016c, Focused Remedial Investigation and Feasibility Study, Volume III Final Focused Feasibility
Study for 1,4-Dioxane North of Los Reales Road, Tucson International Airport Area Superfund Site Area A,
Tucson, Arizona, March.
Hughes Missile Systems Company, 1995, Draft Final Shallow Groundwater Zone, Remediation Feasibility
Study, United States Air Force Plant No. 44, January.
Malcolm Pirnie, Inc., 2012,1,4-Dioxane Treatment Preliminary Design Report, Tucson International Airport
Area Groundwater Remediation Project, April.
URS, 2020, Final Record of Decision, Installation Restoration Program, Site OT012, Air Force Plant 44,
Tucson Arizona. August,
U.S. Air Force, 1986, Final Air Force Plant 44 Remedial Action Plan, Responsiveness Summary, and Record
of Decision, Air Force Plant 44, Tucson, Arizona, April.
U.S. Environmental Protection Agency (EPA), 1988, EPA Superfund Record of Decision: Tucson
International Airport Area, Tucson, AZD980737530; EPA/ROD/R09-88/021, August 22.
EPA, 1998, Record of Decision, Tucson International Airport Area Superfund Site, Airport Property—Soils
and Shallow Groundwater Zone, Burr-Brown Property—Soils, Former West-Cap Property—Soils, Tucson,
Arizona, January.
EPA, 1999, Soils Consent Decree, the United States of America, Plaintiffs, Tucson Airport Authority, City of
Tucson, General Dynamics Corporation and McDonnell Douglas Corporation Defendants, March.
EPA, 2007, Administrative Order for Response Action, Tucson International Airport Authority Area Site,
Pima County, Arizona, Docket PWS-AO 2007-007, EPA Region IX, San Francisco, CA, July 13.
EPA, 2013, First Five-Year Review Report for Tucson International Airport Area Superfund Site, Pima
County, Arizona, September 30.
EPA, 2014, Letter to USAF, "Activities Related to April 17, 2014 Technical Meeting Regarding 1,4-Dioxane
Risk Assessment, Chromium Characterization and Related Groundwater Model—Tucson International
Airport Area (TIAA) Superfund Site."
TIM SUPERFUND SITE AREA A
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INTERIM RECORD OF DECISION AMENDMENT
MARCH 2023
-------
EPA, 2015, Revised Limited Risk Assessment for 1,4-Dioxane and Trichloroethylene in Groundwater at the
Tucson International Airport Superfund Site, September.
EPA, 2018, Second Five-Year Review Report for Tucson International Airport Area Superfund Site, Pima
County, Arizona, Prepared by U.S. Army Corps of Engineers, Seattle District, EPA Region 9, September 21.
EPA, 2021, Memorandum for File, "Tucson International Airport Area Superfund site, Minor Changes
Memorandum for the U.S. Environmental Protection Agency's Record of Decision for Groundwater
Remediation North of Reales Road (August 1988)," September 21.
EPA and Air Force Civil Engineer Center, 2015, Final Unified Focused Human Health Risk Assessment,
Focused Remedial Investigation and Feasibility Study for 1,4-Dioxane North of Los Reales Road, Tucson
International Airport Area Superfund Site Area A, November.
TIAA SUPERFUND SITE AREA A
6-3
INTERIM RECORD OF DECISION AMENDMENT
MARCH 2023
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APPENDIX A
Present Value of Cash Flow and Value of Cash Flow Over Time Calculation Summary Tables
Contents
Attachment A-l
Attachment A-2
Attachment A-3
Attachment A-4
Attachment A-5
Alternative 2 - Monitored Natural Attenuation and Institutional
Controls
Alternative 3 - Enhanced Existing Pump-and-Treat with UV-Peroxide
Plus Long-Term Monitoring and ICs
Alternative 4 - Optimize Pump-and-Treat with UV-Peroxide and Partial
Management of Water by Reinjection to the Regional Aquifer Plus MNA
and ICs
Existing Pump-and-Treat with UV-Peroxide Plus In Situ Bioremediation
and MNA and ICs
Existing Pump-and-Treat with UV-Peroxide Plus In Situ Chemical
Oxidation and MNA and ICs
-------
ATTACHMENT A-1
-------
ALTERNATIVE 2
Record of Decision Amendment
TARP Plume: Area A North of Los Reales Road
Alternative Name: AFP44 FS LR North Alternative 2 - Monitored Natural Attenuation (MNA) and Institutional Controls (IC)
March 2023
Phase Type
Design
Remedial Action
Total
Phase Name
AFP44 FS LR North Alternative 2 MNA Design1
AFP44 FS LR North Alternative 2 MNA LTM2
Fiscal Year 12014 Fiscal Year 2 2015 Fiscal Year 3 2016 Fiscal Year 4 2017
$ 13,106
$
13,106 $
263,188 $
263,188 $
256,772 $
256,772 $
256,772 $
256,772 $
Fiscal Year 5 2018
256,772
256,772
Year
1.9 % Present Value Discount Rate3 1.9%
Net Present Value
13,106 $
1
0.9814
258,281
2
0.9631
247,286
3
0.9451
242,675
4
0.9275
238,150
7% Present Value Discount Rate
Net Present Value
7.0%
13,106 $
0.9346
245,970 $
0.8734
224,275 $
0.8163
209,602 $
0.7629
195,890
Notes:
1 - Fiscal Year (FY) 2014 cost based on USAF RI/FS cost for design of monitoring program presented in Alternative Cost Over Time, AFP44 FS LR North Alternative 2, Appendix B, Volume III Final Feasibility Study
for 1,4-Dioxane North of Los Reales Road (EGC, 2016).
2 - LTM Based on USAF RI/FS cost for Monitored Natural Attenuation presented in Alternative Cost Over Time, AFP44 FS LR North Alternative 2, Appendix B, Volume III Final Feasibility Study for 1,4-Dioxane.
North of Los Reales Road (EGC, 2016).
3 - Air Force Present value calculations based on assumptions in RI/FS of 30-year term at 1.9% (Appendix C OMB Circular-94 for 2014)as presented in Appendix B, Final FFS 1,4-Dioxane NLRR (EGC, 2016).
4 - Based on Circular-94, U.S. Office of discount rate of Management and Budget (OMB) 7% discount rate for base case analysis.
Page 1 of 4
-------
ALTERNATIVE 2
March 2023
Record of Decision Amendment
TARP Plume: Area A North of Los Real
Alternative Name: AFP44 FS LR North ,
Phase Type
Design
Remedial Action
Total
Fiscal Year 6 2019 Fiscal Year 7 2020
$
$
256,772 $
256,772 $
256,772 $
256,772 $
Fiscal Year 8 2021
256,772 $
256,772 $
Fiscal Year 9 2022 Fiscal Year 10 2023 Fiscal Year 11 2024 Fiscal Year 12 2025 Fiscal Year 13 2026 Fiscal Year 14 2027
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772
256,772
Year
1.9 % Present Value Discount Rate3
Net Present Value
5
0.9102
233,710
6
0.8932
229,352
7
0.8766
225,076
8
0.8602
220,879 $
9
0.8442
216,760
10
0.8284
212,719
11
0.8130
208,752
12
0.7978
204,860
13
0.7830
201,040
7% Present Value Discount Rate
Net Present Value
0.7130
183,075 $
0.6663
171,098 $
0.6227
159,905 $
0.5820
149,444 $
0.5439
139,667 $
0.5083
130,530 $
0.4751
121,991
0.4440
114,010 $
0.4150
106,551
Page 2 of 4
-------
ALTERNATIVE 2
March 2023
Record of Decision Amendment
TARP Plume: Area A North of Los Real
Alternative Name: AFP44 FS LR North ,
Phase Type
Design
Remedial Action
Total
Fiscal Year 15 2028 Fiscal Year 16 2029 Fiscal Year 17 2030 Fiscal Year 18 2031 Fiscal Year 19 2032 Fiscal Year 20 2033 Fiscal Year 21 2034 Fiscal Year 22 2035 Fiscal Year 23 2036
$
$
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772
256,772
Year
1.9 % Present Value Discount Rate3
Net Present Value
14
0.7684
197,292
15
0.7540
193,613
16
0.7400
190,003
17
0.7262
186,460 $
18
0.7126
182,984
19
0.6993
179,572
20
0.6863
176,224
21
0.6735
172,938
22
0.6609
169,713
7% Present Value Discount Rate
Net Present Value
0.3878
99,581 $
0.3624
93,066 $
0.3387
86,978 $
0.3166
81,287 $
0.2959
75,970 $
0.2765
71,000 $
0.2584
66,355 $
0.2415
62,014 $
0.2257
57,957
Page 3 of 4
-------
ALTERNATIVE 2
Record of Decision Amendment
TARP Plume: Area A North of Los Real
Alternative Name: AFP44 FS LR North ,
March 2023
Phase Type
Design
Remedial Action
Total
Fiscal Year 24 2037 Fiscal Year 25 2038 Fiscal Year 26 2039 Fiscal Year 27 2040 Fiscal Year 28 2041 Fiscal Year 29 2042 Fiscal Year 30 2043 Fiscal Year 312044
$
$
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
256,772 $
$
256,772 $
256,772 $
Total
13,106
7,709,576
7,722,682
Year
1.9 % Present Value Discount Rate3
Net Present Value
23
0.6486
166,549
24
0.6365
163,443
25
0.6247
160,396
26
0.6130
157,405 $
27
0.6016
154,470 $
28
0.5904
151,590 $
29
0.5794
148,763 $
30
0.5686
145,990 $
5,850,051
7% Present Value Discount Rate
Net Present Value
0.2109
54,165 $
0.1971
50,622 $
0.1842
47,310 $
0.1722
44,215 $
0.1609
41,322 $
0.1504
38,619 $
0.1406
36,093 $
0.1314
33,731 $
3,205,397
Page 4 of 4
-------
ATTACHMENT A-2
-------
ALTERNATIVE 3
March 2023
Record of Decision Amendment
TARP Plume: Area A North of Los Reales Road
Alternative Name: AFP44 FS LR North Alternative 3 - Enhanced Existing Pump & Treat w/UV-Peroxide, LTM, and IC
Phase Type
Phase Name
Fiscal Year 1 2014
Fiscal Year 2 2015
Fiscal Year 3 2016
Fiscal Year 4 2017
Fiscal Year 5 2018
Design
AFP44 FS LR North Enhanced Alternative 3 Design1
$
13,700
Remedial Action
AFP44 FS LR North Enhanced Alternative 3 Capital Cost2
Remedial Action
AFP44 FS LR North Enhanced Alternative 3 LTM3
$
286,000
$
286,000
$
286,000
$
286,000
$
286,000
Remedial Action
AFP44 FSA LR North Enhanced Alternative 3 Recycled Water System and Outfall4
Operations and Maintenance
AFP44 FS LR North Enhanced Alternative 3 AOP O&M 2014-20445
$
977,000
$
977,000
$
977,000
$
977,000
$
977,000
Operations and Maintenance
AFP44 FS LR North Enhanced Alternative 3 PCA O&M 2014-20446
$
405,000
$
405,000
$
405,000
$
405,000
$
405,000
Operations and Maintenance
AFP44 FS LR North Enhanced Alternative 3 TARP Well O&M 2014-20447
$
735,000
$
735,000
$
735,000
$
735,000
$
735,000
Operations and Maintenance
AFP44 FS LR North Enhanced Alternative 3 AOP Ballast and GAC Replacement8
Operations and Maintenance
g
AFP44 FS LR North Enhanced Alternative 3 Remediation Well Replacement
$
1,200,000
Operations and Maintenance
1 n
AFP44 FSA LR North Enhanced Alternative 3 Recycled Water System and outfall
Total
$
2,417,000
$
2,403,000
$
2,403,000
$
2,403,000
$
3,603,000
Year
0
1
2
3
4
1.9% Present Value Discount Rate11
1.9%
0.9814
0.9631
0.9451
0.9275
Net Present Value
$
2,417,000
$
2,358,000
$
2,314,000
$
2,271,000
$
3,342,000
7% Present Value Discount Rate12
7.0%
0.9346
0.8734
0.8163
0.7629
Net Present Value
$
2,417,000
$
2,204,000
$
2,021,000
$
1,854,000
$
2,550,000
Notes:
1 - Fiscal Year (FY) 2014 cost based on USAF RI/FS cost for design of monitoring program, FY 2019 and 2021 cost based on design, bidding, construction administration, and records for capital
construction costs of Enhanced Alternative 3 (Appendix B, FocusedFeasibility Study Amendment, Carollo, 2021).
2 - Capital cost of remediation well and pipeline construction and AOP plant upgrades as presented in Table IB (Appendix B, Focused Feasibility Study Amendment Carollo, 2021) is based on actual
contracted costs.
3 - LTM Based on USAF RI/FS cost for Monitored Natural Attenuation (Appendix B, Final FFS 1,4-Dioxane NLRR, EGC, 2016).
4 - Capital cost of recycled water system delivery booster station, pipeline, and outfall on Santa Cruz River as presented in Table B4 (Appendix B, Focused Feasibility Study Amendment Carollo, 2021).
5 - AOP O&M costs based on operations associated with three trains with three reactor pairs per train and H202 at 35 percent as presented in Table B2 (Appendix B, Focused Feasibility Study Amendment,
(Carollo, 2021).
6 - Costs for operations of PCA process as presented in Table B2 (Appendix B, Focused Feasibility Study Amendment Carollo, 2021) assumed to terminate after acceptance of amended Record of Decision
assumed in 2020.
7 - Well O&M based on 9 remediation wells from 2014 through 2018 and 10 remediation wells 2019 through 2044 as summarized in Table B2 (Appendix B, Focused Feasibility Study Amendment Carollo, 2021).
8 - Assumed Ballast replacements every 5 years at an approximate cost of $400,000 per change out and GAC replacement at approximately $600,000 per replacement based on operational data.
9 - Remediation well replacement program is assumed to proceed as planned by Tucson Water with the remaining North Well Field replacement costing approximately
$1,200,000 in 2020 and replacement of South Well Field wells at 2-year intervals and approximately $600,000 in cost.
10 - Costs for operations of recycled water system booster station as presented in Table B5 (Appendix B, Focused Feasibility Study Amendment Carollo, 2021).
11 - Air Force Present value calculations based on assumptions in RI/FS of 30-year term at 1.9% (Appendix C OMB Circular-94 for 2014)as presented in Appendix B, Final FFS 1,4-Dioxane NLRR (EGC, 2016).
12 - Based on Circular-94, U.S. Office of discount rate of Management and Budget (OMB) 7% discount rate for base case analysis.
Page 1 of 4
-------
Record of Decision Amendment
TARP Plume: Area A North of Los Reales I
Alternative Name: AFP44 FS LR North Alt
Phase Type
Design
Remedial Action
Remedial Action
Remedial Action
Operations and Maintenance
Operations and Maintenance
Operations and Maintenance
Operations and Maintenance
Operations and Maintenance
Operations and Maintenance
Total
Year
1.9% Present Value Discount Rate11
Net Present Value
7% Present Value Discount Rate12
Net Present Value
Fiscal Year 6 2019
$ 3,726,000
$ 286,000
$ 977,000
$ 405,000
$ 735,000
$ 600,000
$ 6,729,000
5
0.9102
$ 6,125,000
0.7130
$ 4,367,000
Fiscal Year 7 2020
$ 14,982,000
$ 286,000
$ 1,257,000
$ 405,000
$ 849,000
$ 17,779,000
6
0.8932
$ 15,880,000
0.6663
$ 10,582,000
Fiscal Year 8 2021
$ 3,357,000
$ 286,000
$ 1,257,000
$ 849,000
$ 400,000
$ 34,000
$ 6,183,000
7
0.8766
$ 5,420,000
0.6227
$ 3,375,000
ALTERNATIVE 3
March 2023
Fiscal Year 9 2022 Fiscal Year 10 2023 Fiscal Year 11 2024 Fiscal Year 12 2025 Fiscal Year 13 2026 Fiscal Year 14 2027
286,000 $
16,785,000
1,257,000 $
849,000 $
1,200,000
34,000 $
20,411,000 $
8
0.8602
17,558,000 $
286,000 $
1,257,000 $
849,000 $
$
$
34,000 $
2,426,000 $
9
0.8442
2,048,000 $
286,000 $
1,257,000 $
849,000 $
600,000
1,200,000
34,000 $
4,226,000 $
10
0.8284
3,501,000 $
286,000 $
1,257,000 $
849,000 $
$
$
34,000 $
2,426,000 $
11
0.8130
1,972,000 $
286,000 $
1,257,000 $
849,000 $
400,000
600,000
34,000 $
3,426,000 $
12
0.7978
2,733,000 $
286,000
1,257,000
849,000
34,000
2,426,000
13
0.7830
1,899,000
0.5820
10,219,000 $
0.5439
1,114,000 $
0.5083
1,780,000 $
0.4751
937,000 $
0.4440
1,213,000 $
0.4150
788,000
Page 2 of 4
-------
ALTERNATIVE 3
March 2023
Record of Decision Amendment
TARP Plume: Area A North of Los Reales I
Alternative Name: AFP44 FS LR North Alt
Phase Type Fiscal Year 15 2028 Fiscal Year 16 2029 Fiscal Year 17 2030 Fiscal Year 18 2031 Fiscal Year 19 2032 Fiscal Year 20 2033 Fiscal Year 21 2034 Fiscal Year 22 2035 Fiscal Year 23 2036
Design
Remedial Action
Remedial Action $ 286,000 $ 286,000 $ 286,000 $ 286,000 $ 286,000 $ 286,000 $ 286,000 $ 286,000 $ 286,000
Remedial Action
Operations and Maintenance $ 1,257,000 $ 1,257,000 $ 1,257,000 $ 1,257,000 $ 1,257,000 $ 1,257,000 $ 1,257,000 $ 1,257,000 $ 1,257,000
Operations and Maintenance
Operations and Maintenance $ 849,000 $ 849,000 $ 849,000 $ 849,000 $ 849,000 $ 849,000 $ 849,000 $ 849,000 $ 849,000
Operations and Maintenance $ 600,000 $ 400,000 $ 600,000 $ 400,000
Operations and Maintenance $ 600,000 $ 600,000
Operations and Maintenance $ 34,000 $ 34,000 $ 34,000 $ 34,000 $ 34,000 $ 34,000 $ 34,000 $ 34,000 $ 34,000
Total $ 3,026,000 $ 3,026,000 $ 3,026,000 $ 2,826,000 $ 2,426,000 $ 2,426,000 $ 3,026,000 $ 2,426,000 $ 2,826,000
Year 14 15 16 17 18 19 20 21 22
1.9% Present Value Discount Rate11 0.7684 0.7540 0.7400 0.7262 0.7126 0.6993 0.6863 0.6735 0.6609
Net Present Value $ 2,325,000 $ 2,282,000 $ 2,239,000 $ 2,052,000 $ 1,729,000 $ 1,697,000 $ 2,077,000 $ 1,634,000 $ 1,868,000
7% Present Value Discount Rate12 0.3878 0.3624 0.3387 0.3166 0.2959 0.2765 0.2584 0.2415 0.2257
Net Present Value $ 902,000 $ 827,000 $ 758,000 $ 650,000 $ 512,000 $ 469,000 $ 537,000 $ 395,000 $ 422,000
Page 3 of 4
-------
ALTERNATIVE 3
Record of Decision Amendment
TARP Plume: Area A North of Los Reales I
Alternative Name: AFP44 FS LR North Alt
March 2023
Phase Type
Design
Remedial Action
Remedial Action $
Remedial Action
Operations and Maintenance $
Operations and Maintenance
Operations and Maintenance $
Operations and Maintenance
Operations and Maintenance
Operations and Maintenance $
Total $
Year
1.9% Present Value Discount Rate
Net Present Value
Fiscal Year 24 2037 Fiscal Year 25 2038 Fiscal Year 26 2039 Fiscal Year 27 2040 Fiscal Year 28 2041 Fiscal Year 29 2042 Fiscal Year 30 2043 Fiscal Year 312044
ii
7% Present Value Discount Rate
Net Present Value
12
286,000 $
1,257,000 $
849,000 $
34,000 $
2,426,000 $
23
0.6486
1,574,000 $
0.2109
332,000 $
286,000 $
1,257,000 $
849,000 $
34,000 $
2,426,000 $
24
0.6365
1,544,000 $
0.1971
304,000 $
286,000 $
1,257,000 $
849,000 $
$
34,000 $
2,426,000 $
25
0.6247
1,515,000 $
0.1842
279,000 $
286,000 $
1,257,000 $
849,000 $
600,000 $
34,000 $
3,026,000 $
26
0.6130
1,855,000 $
0.1722
319,000 $
286,000 $
1,257,000 $
849,000 $
400,000
34,000 $
2,826,000 $
27
0.6016
1,700,000 $
0.1609
274,000 $
286,000 $
1,257,000 $
849,000 $
34,000 $
2,426,000 $
28
0.5904
1,432,000 $
0.1504
215,000 $
286,000 $
1,257,000 $
849,000 $
34,000 $
2,426,000 $
29
0.5794
1,406,000 $
0.1406
198,000 $
$
$
286,000 $
$
1,257,000 $
$
849,000 $
$
$
34,000 $
2,426,000 $
30
0.5686
1,379,000 $
0.1314
181,000 $
Total
7,100,000
14,980,000
8,870,000
16,790,000
37,290,000
2,840,000
25,640,000
5,000,000
5,400,000
820,000
124,730,000
100,000,000
53,000,000
Page 4 of 4
-------
ATTACHMENT A-3
-------
ALTERNATIVE 4
Record of Decision Amendment
TARP Plume: Area A North of Los Reales Road
Alternative Name: AFP44 FS LR North Alternative 4 - Optimized Pump & Treat w/UV-Peroxide, Partial Management of Water by Reinjection, MNA, and ICs
March 2023
Phase Type
Phase Name
Fiscal Year 1 2014
Fiscal Year 2 2015
Fiscal Year 3 2016
Fiscal Year 4 2017
Design
AFP44 FS LR North Alternative 4 Design1
$
258,452
Remedial Action
AFP44 FS LR North Alternative 4 MNA, LTM, &
2
Injection Well Installation
$
3,649,898
$
256,772
$
256,772
$
Operations & Maintenance
AFP44 FS LR North Alternative 4 Groundwater
Reinjection O&M3
$
18,406
$
18,406
$
18,406
$
Operations & Maintenance
AFP44 FS LR North Alternative 4 AOP O&M3
$
927,200
$
927,200
$
927,200
$
Operations & Maintenance
AFP44 FS LR North Alternative 4 TARP O&M3
$
1,494,500
$
1,494,500
$
1,494,500
$
Operations & Maintenance
AFP44 FS LR North Alternative 4 O&M 20303
Operations & Maintenance
AFP44 FS LR North Alternative 4 O&M 20353
Total
$
258,452
$
6,090,004
$
2,696,878
$
2,696,878
$
Year
0
1
2
3
Present Value Discount Rate4
1.9%
0.9814
0.9631
0.9451
Net Present Value
$
258,452
$
5,976,451
$
2,597,245
$
2,548,818
$
Present Value Discount Rate5
7.0%
0.9346
0.8734
0.8163
Net Present Value
$
258,452
$
5,691,593
$
2,355,558
$
2,201,456
$
Fiscal Year 5 2018
256,772
18,406
927,200
1,494,500
2,696,878
4
0.9275
2,501,293
0.7629
2,057,435
Notes:
1 - Fiscal Year (FY) 2014 cost based on USAF RI/FS cost for design of monitoring program presented in Alternative Cost Over Time, AFP44 FS LR North Alternative 2, Appendix B, Volume III Final Feasibility Study
for 1,4-Dioxane North of Los Reales Road (EGC, 2016).
2 - Remedial Action costs based on USAF RI/FS information presented in Alternative Cost Over Time, AFP44 FS LR North Alternative 3, Appendix B, Volume III Final Feasibility Study for 1,4-Dioxane.
North of Los Reales Road (EGC, 2016).
3 - Operations and maintenance costs based on USAF RI/FS information presented in Alternative Cost Over Time, AFP44 FS LR North Alternative 3, Appendix B, Volume III Final Feasibility Study for 1,4-Dioxane.
North of Los Reales Road (EGC, 2016).
4 - Air Force Present value calculations based on assumptions in RI/FS of 30-year term at 1.9% (Appendix C OMB Circular-94 for 2014)as presented in Appendix B, Final FFS 1,4-Dioxane NLRR (EGC, 2016).
5 - Based on Circular-94, U.S. Office of discount rate of Management and Budget (OMB) 7% discount rate for base case analysis.
Page 1 of 4
-------
Record of Decision Amendment
TARP Plume: Area A North of Los
Alternative Name: AFP44 FS LR Ni
Phase Type
Design
Remedial Action
Operations & Maintenance
Operations & Maintenance
Operations & Maintenance
Operations & Maintenance
Operations & Maintenance
Total
Year
Present Value Discount Rate4
Net Present Value
Present Value Discount Rate5
Net Present Value
Fiscal Year 6 2019
$ 256,772
$ 18,406
$ 927,200
$ 1,494,500
Fiscal Year 7 2020
$ 256,772
$ 18,406
$ 927,200
$ 1,494,500
Fiscal Year 8 2021
$ 256,772
$ 18,406
$ 927,200
$ 1,494,500
$ 2,696,878
5
0.9102
$ 2,454,655
0.7130
$ 1,922,837
$ 2,696,878
6
0.8932
$ 2,408,886
0.6663
$ 1,797,044
$ 2,696,878
7
0.8766
$ 2,363,970
0.6227
$ 1,679,480
ALTERNATIVE 4
March 2023
Fiscal Year 9 2022 Fiscal Year 10 2023 Fiscal Year 11 2024 Fiscal Year 12 2025 Fiscal Year 13 2026 Fiscal Year 14 2027
256,772 $
18,406 $
927,200 $
1,494,500 $
256,772 $
18,406 $
927,200 $
1,494,500 $
256,772
18,406
927,200
1,494,500
256,772 $
18,406
927,200
1,494,500
$
$
$
256,772
18,406
927,200
1,494,500
256,772
18,406
927,200
1,494,500
2,696,878 $
8
0.8602
2,319,892 $
2,696,878 $
9
0.8442
2,276,636 $
2,696,878 $
10
0.8284
2,234,187 $
2,696,878 $
11
0.8130
2,192,529 $
2,696,878 $
12
0.7978
2,151,647 $
2,696,878
13
0.7830
2,111,528
0.5820
1,569,608 $
0.5439
1,466,923 $
0.5083
1,370,956 $
0.4751
1,281,267 $
0.4440
1,197,446 $
0.4150
1,119,108
Page 2 of 4
-------
Record of Decision Amendment
TARP Plume: Area A North of Los
Alternative Name: AFP44 FS LR Ni
ALTERNATIVE 4
March 2023
Phase Type
Design
Remedial Action
Operations & Maintenance
Operations & Maintenance
Operations & Maintenance
Operations & Maintenance
Operations & Maintenance
Fiscal Year 15 2028 Fiscal Year 16 2029 Fiscal Year 17 2030 Fiscal Year 18 2031 Fiscal Year 19 2032 Fiscal Year 20 2033 Fiscal Year 21 2034 Fiscal Year 22 2035 Fiscal Year 23 2036
256,772 $
18,406 $
927,200 $
1,494,500 $
256,772 $
18,406 $
927,200 $
1,494,500 $
$
256,772 $
18,406 $
927,200 $
1,494,500 $
411,000
256,772 $
18,406 $
927,200 $
1,494,500 $
256,772 $
18,406 $
927,200 $
1,494,500 $
256,772 $
18,406 $
927,200 $
1,494,500 $
256,772 $
18,406 $
927,200 $
1,494,500 $
$
256,772 $
18,406 $
927,200 $
1,494,500 $
3,530,000
256,772
18,406
927,200
1,494,500
Total
Year
Present Value Discount Rate4
Net Present Value
2,696,878 $
14
0.7684
2,072,157 $
2,696,878 $
15
0.7540
2,033,520 $
3,107,878 $
16
0.7400
2,299,731 $
2,696,878 $
17
0.7262
1,958,394 $
2.696.878 $
18
0.7126
1.921.879 $
2,696,878 $
19
0.6993
1,886,044 $
2,696,878 $
20
0.6863
1,850,877 $
6,226,878 $
21
0.6735
4,193,846 $
2,696,878
22
0.6609
1,782,499
Present Value Discount Rate
Net Present Value
0.3878
1,045,896 $
0.3624
977,473 $
0.3387
1,052,746 $
0.3166
853,763 $
0.2959
797,909 $
0.2765
745,709 $
0.2584
696,925 $
0.2415
1,503,873 $
0.2257
608,721
Page 3 of 4
-------
Record of Decision Amendment
TARP Plume: Area A North of Los
Alternative Name: AFP44 FS LR Ni
ALTERNATIVE 4
March 2023
Phase Type
Design
Remedial Action
Operations & Maintenance
Operations & Maintenance
Operations & Maintenance
Operations & Maintenance
Operations & Maintenance
Total
Year
Present Value Discount Rate4
Net Present Value
Fiscal Year 24 2037
$ 256,772 $
$ 18,406 $
$ 927,200 $
$ 1,494,500 $
2,696,878
23
0.6486
1,749,263
Fiscal Year 25 2038
256,772 $
18,406 $
927,200 $
1,494,500 $
2,696,878
24
0.6365
1,716,647
Fiscal Year 26 2039
256,772 $
18,406 $
927,200 $
1,494,500 $
2,696,878
25
0.6247
1,684,638
Fiscal Year 27 2040
256,772 $
18,406 $
927,200 $
1,494,500 $
Fiscal Year 28 2041
256,772 $
18,406 $
927,200 $
1,494,500 $
2,696,878 $
26
0.6130
1,653,227 $
2,696,878
27
0.6016
1,622,401
Fiscal Year 29 2042
256,772 $
18,406 $
927,200 $
1,494,500 $
Fiscal Year 30 2043 Fiscal Year 31 2044
2,696,878
28
0.5904
1,592,151
256,772 $
18,406 $
927,200 $
1,494,500 $
2,696,878
29
0.5794
1,562,464
$
256,772 $
18,406 $
927,200 $
1,494,500 $
$
$
2,696,878 $
30
0.5686
1,533,331 $
Total
258,452
11,096,286
552,180
27,816,000
44,835,000
411,000
3,530,000
88,498,918
67,509,258
Present Value Discount Rate
Net Present Value
0.2109
568,898 $
0.1971
531,680 $
0.1842
496,898 $
0.1722
464,390 $
0.1609
434,010 $
0.1504
405,616 $
0.1406
379,081 $
0.1314
354,281
37,887,029
Page 4 of 4
-------
ATTACHMENT A-4
-------
ALTERNATIVE 5
Record of Decision Amendment
TARP Plume: Area A North of Los Reales Road
Alternative Name: AFP44 FS LR North Alternative 5 - Existing Pump & Treat w/UV-Peroxide, In-situ Bioremediation, MNA, and ICs
March 2023
Phase Type
Phase Name
Fiscal Year 1 2014
Fiscal Year 2 2015
Fiscal Year 3 2016
Fiscal Year 4 2017
Design
AFP44 FS LR North Alternative 5 Design1 $
550,104
Remedial Action
AFP44 FS LR North Alternative 5 MNA2
$
265,609
$
256,772
$
256,772
$
Remedial Action
AFP44 FS LR North Alternative 5 ISB System Install2
$
5,948,144
Operations & Maintenance
AFP44 FS LR North Alternative 5 AOP O&M3
$
927,200
$
927,200
$
927,200
$
Operations & Maintenance
AFP44 FS LR North Alternative 5 TARP O&M3
$
1,494,500
$
1,494,500
$
1,494,500
$
Operations & Maintenance
AFP44 FS LR North Alternative 5 O&M ISB System3
$
3,791,030
$
Operations & Maintenance
AFP44 FS LR North Alternative 5 O&M 20303
Operations & Maintenance
AFP44 FS LR North Alternative 5 O&M 20353
Site Closeout
AFP44 FS LR North Alternative 5 Well Abandonment3
Total
$
550,104
$
2,687,309
$
8,626,616
$
6,469,502
$
Year
0
1
2
3
Present Value Discount Rate4
1.9%
0.9814
0.9631
0.9451
Net Present Value
$
550,104
$
2,637,202
$
8,307,916
$
6,114,322
$
Present Value Discount Rate5
7.0%
0.9346
0.8734
0.8163
Net Present Value
$
550,104
$
2,511,504
$
7,534,821
$
5,281,041
$
Fiscal Year 5 2018
256,772
927,200
1,494,500
3,790,817
6,469,289
4
0.9275
6,000,118
0.7629
4,935,390
Notes:
1 - Fiscal Year (FY) 2014 cost based on USAF RI/FS cost for design of monitoring program presented in Alternative Cost Over Time, AFP44 FS LR North Alternative 2, Appendix B, Volume III Final Feasibility Study
for 1,4-Dioxane North of Los Reales Road (EGC, 2016).
2 - Remedial Action costs based on USAF RI/FS information presented in Alternative Cost Over Time, AFP44 FS LR North Alternative 3, Appendix B, Volume III Final Feasibility Study for 1,4-Dioxane.
North of Los Reales Road (EGC, 2016).
3 - Operations and maintenance costs based on USAF RI/FS information presented in Alternative Cost Over Time, AFP44 FS LR North Alternative 3, Appendix B, Volume III Final Feasibility Study for 1,4-Dioxane.
North of Los Reales Road (EGC, 2016).
4 - Air Force Present value calculations based on assumptions in RI/FS of 30-year term at 1.9% (Appendix C OMB Circular-94 for 2014)as presented in Appendix B, Final FFS 1,4-Dioxane NLRR (EGC, 2016).
5 - Based on Circular-94, U.S. Office of discount rate of Management and Budget (OMB) 7% discount rate for base case analysis.
Page 1 of 4
-------
ALTERNATIVE 5
Record of Decision Amendment
TARP Plume: Area A North of Los R(
Alternative Name: AFP44 FS LR Nor
March 2023
Phase Type
Fiscal Year 6 2019
Fiscal Year 7 2020
Fiscal Year 8 2021
Fiscal Year 9 2022
Fiscal Year 10 2023
Fiscal Year 112024
Fiscal Year 12 2025
Fiscal Year 13 2026
Design
Remedial Action
$
256,772
$
256,772
$
256,772
$
256,772
$
256,772
$
256,772
$
256,772
$
256,772
$
Remedial Action
Operations & Maintenance
$
927,200
$
927,200
$
927,200
$
927,200
$
927,200
$
927,200
$
927,200
$
927,200
$
Operations & Maintenance
$
1,494,500
$
1,494,500
$
1,494,500
$
1,494,500
$
1,494,500
$
1,494,500
$
1,494,500
$
1,494,500
$
Operations & Maintenance
$
3,790,817
$
3,790,817
$
3,790,817
$
3,770,107
$
3,770,107
$
3,770,107
$
3,770,107
$
3,770,107
$
Operations & Maintenance
Operations & Maintenance
Site Closeout
256,772
927,200
1,494,500
3,770,107
Total
Year
Present Value Discount Rate4
Net Present Value
6,469,289 $
5
0.9102
5,888,242 $
6,469,289 $
6
0.8932
5,778,451 $
6,469,289 $
7
0.8766
5,670,708 $
6,448,579 $
8
0.8602
5,547,158 $
6,448,579 $
9
0.8442
5,443,727 $
6,448,579 $
10
0.8284
5,342,225 $
6,448,579 $
11
0.8130
5,242,615 $
6,448,579 $
12
0.7978
5,144,863 $
6,448,579
13
0.7830
5,048,933
Present Value Discount Rate
Net Present Value
0.7130
4,612,514 $
0.6663
4,310,760 $
0.6227
4,028,748 $
0.5820
3,753,132 $
0.5439
3,507,600 $
0.5083
3,278,131 $
0.4751
3,063,673 $
0.4440
2,863,246 $
0.4150
2,675,931
Page 2 of 4
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ALTERNATIVE 5
March 2023
Record of Decision Amendment
TARP Plume: Area A North of Los R(
Alternative Name: AFP44 FS LR Nor
Phase Type
Fiscal Year 15 2028
Fiscal Year 16 2029
Fiscal Year 17 2030
Fiscal Year 18 2031
Fiscal Year 19 2032
Fiscal Year 20 2033
Fiscal Year 21 2034
Fiscal Year 22 2035
Design
Remedial Action
$
256,772
$
256,772
$
256,772
$
256,772
$
256,772
$
256,772
$
256,772
$
256,772
$
Remedial Action
Operations & Maintenance
$
927,200
$
927,200
$
927,200
$
927,200
$
927,200
$
927,200
$
927,200
$
927,200
$
Operations & Maintenance
$
1,494,500
$
1,494,500
$
1,494,500
$
1,494,500
$
1,494,500
$
1,494,500
$
1,494,500
$
1,494,500
$
Operations & Maintenance
$
3,770,107
$
3,770,107
$
3,770,107
$
3,770,107
$
3,786,727
$
3,786,727
$
3,786,727
$
3,786,727
$
Operations & Maintenance
$
411,000
Operations & Maintenance
$
3,530,000
Site Closeout
256,772
927,200
1,494,500
3,786,727
Total $ 6,448,579 $ 6,448,579 $ 6,859,579 $ 6,448,579 $ 6,465,199 $ 6,465,199 $ 6,465,199 $ 9,995,199 $ 6,465,199
Year 14 15 16 17 18 19 20 21 22
Present Value Discount Rate4 0.7684 0.7540 0.7400 0.7262 0.7126 0.6993 0.6863 0.6735 0.6609
Net Present Value $ 4,954,792 $ 4,862,407 $ 5,075,870 $ 4,682,771 $ 4,607,301 $ 4,521,394 $ 4,437,090 $ 6,731,837 $ 4,273,167
Present Value Discount Rate5 0.3878 0.3624 0.3387 0.3166 0.2959 0.2765 0.2584 0.2415 0.2257
Net Present Value $ 2,500,870 $ 2,337,262 $ 2,323,577 $ 2,041,455 $ 1,912,819 $ 1,787,681 $ 1,670,730 $ 2,413,971 $ 1,459,281
Page 3 of 4
-------
ALTERNATIVE 5
Record of Decision Amendment
TARP Plume: Area A North of Los R(
Alternative Name: AFP44 FS LR Nor
March 2023
Phase Type
Design
Remedial Action
Remedial Action
Operations & Maintenance
Operations & Maintenance
Operations & Maintenance
Operations & Maintenance
Operations & Maintenance
Site Closeout
Fiscal Year 24 2037 Fiscal Year 25 2038 Fiscal Year 26 2039 Fiscal Year 27 2040 Fiscal Year 28 2041 Fiscal Year 29 2042 Fiscal Year 30 2043 Fiscal Year 312044
$
$
256,772 $
927,200 $
1,494,500 $
256,772 $
927,200 $
1,494,500 $
256,772 $
927,200 $
1,494,500 $
256,772 $
927,200 $
1,494,500 $
256,772 $
927,200 $
1,494,500 $
256,772 $
927,200 $
1,494,500 $
256,772 $
927,200 $
1,494,500 $
2,019,644
$
256,772 $
$
927,200 $
1,494,500 $
$
$
$
$
Total
550,104
7,711,997
5,948,144
27,816,000
44,835,000
75,589,003
411,000
3,530,000
2,019,644
Total
Year
Present Value Discount Rate4
Net Present Value
4,698,116
23
0.6486
3,047,316
2,678,472
24
0.6365
1,704,931
2,678,472
25
0.6247
1,673,141
2,678,472 $
26
0.6130
1,641,944 $
2,678,472
27
0.6016
1,611,329
2,678,472
28
0.5904
1,581,284
2,678,472
29
0.5794
1,551,800
2,678,472
30
0.5686
1,522,866
168,410,892
131,197,825
Present Value Discount Rate
Net Present Value
0.2109
991,053 $
0.1971
528,052 $
0.1842
493,506 $
0.1722
461,221 $
0.1609
431,047 $
0.1504
402,848 $
0.1406
376,494 $
0.1314
351,863 $
75,390,324
Page 4 of 4
-------
ATTACHMENT A-5
-------
ALTERNATIVE 6
Record of Decision Amendment
TARP Plume: Area A North of Los Reales Road
Alternative Name: AFP44 FS LR North Alternative 6 - Existing Pump & Treat w/UV-Peroxide, In-situ Chemical Oxidation, MNA, and ICs
March 2023
Phase Type
Phase Name
Fiscal Year 12014
Fiscal Year 2 2015
Fiscal Year 3 2016
Fiscal Year 4 2017
Design
AFP44 FS LR North Alternative 6 Design1
$ 550,104
Remedial Action
AFP44 FS LR North Alternative 6 MNA2
$
265,609
$
256,772
$
256,772
$
Remedial Action
AFP44 FS LR North Alternative 6 ISCO System Install2
$
3,489,573
Remedial Action
AFP44 FS LR North Alternative 6 ISCO 1st Yr Injection2
$
2,093,708
Operations & Maintenance
AFP44 FS LR North Alternative 6 AOP O&M3
$
927,200
$
927,200
$
927,200
$
Operations & Maintenance
AFP44 FS LR North Alternative 6 TARP O&M3
$
1,494,500
$
1,494,500
$
1,494,500
$
Operations & Maintenance
AFP44 FS LR North Alternative 6 O&M ISCO System3
$
Operations & Maintenance
AFP44 FS LR North Alternative 6 O&M 20303
Operations & Maintenance
AFP44 FS LR North Alternative 6 O&M 20353
Site Closeout
AFP44 FS LR North Alternative 5 Well Abandonment3
Fiscal Year 5 2018
256,772
927,200
1,494,500
1,795,633
Total
Year
Present Value Discount Rate4 1.9%
Net Present Value
Present Value Discount Rate5 7.0%
Net Present Value
550,104 $
0
550,104 $
550,104 $
2,687,309 $
1
0.9814
2,637,202 $
0.9346
2,511,504 $
6,168,045 $
2
0.9631
5,940,174 $
0.8734
5,387,409 $
4,772,180 $
3
0.9451
4,510,184 $
0.8163
3,895,520 $
4,474,105
4
0.9275
4,149,631
0.7629
3,413,273
Notes:
1 - Fiscal Year (FY) 2014 cost based on USAF RI/FS cost for design of monitoring program presented in Alternative Cost Over Time, AFP44 FS LR North Alternative 2, Appendix B, Volume III Final Feasibility Study
for 1,4-Dioxane North of Los Reales Road (EGC, 2016).
2 - Remedial Action costs based on USAF RI/FS information presented in Alternative Cost Over Time, AFP44 FS LR North Alternative 3, Appendix B, Volume III Final Feasibility Study for 1,4-Dioxane.
North of Los Reales Road (EGC, 2016).
3 - Operations and maintenance costs based on USAF RI/FS information presented in Alternative Cost Over Time, AFP44 FS LR North Alternative 3, Appendix B, Volume III Final Feasibility Study for 1,4-Dioxane.
North of Los Reales Road (EGC, 2016).
4 - Air Force Present value calculations based on assumptions in RI/FS of 30-year term at 1.9% (Appendix C OMB Circular-94 for 2014)as presented in Appendix B, Final FFS 1,4-Dioxane NLRR (EGC, 2016).
5 - Based on Circular-94, U.S. Office of discount rate of Management and Budget (OMB) 7% discount rate for base case analysis.
Page 1 of 4
-------
ALTERNATIVE 6
March 2023
Record of Decision Amendment
TARP Plume: Area A North of Los
Alternative Name: AFP44 FS LR N
Phase Type
Fiscal Year 6 2019
Fiscal Year 7 2020
Fiscal Year 8 2021
Fiscal Year 9 2022
Fiscal Year 10 2023
Fiscal Year 112024
Fiscal Year 12 2025
Fiscal Year 13 2026
Fiscal Year 14 2027
Design
Remedial Action
$
256,772
$
256,772
$
256,772
$
256,772
$
256,772
$
256,772
$
256,772
$
256,772
$
256,772
Remedial Action
Remedial Action
Operations & Maintenance
$
927,200
$
927,200
$
927,200
$
927,200
$
927,200
$
927,200
$
927,200
$
927,200
$
927,200
Operations & Maintenance
$
1,494,500
$
1,494,500
$
1,494,500
$
1,494,500
$
1,494,500
$
1,494,500
$
1,494,500
$
1,494,500
$
1,494,500
Operations & Maintenance
$
1,795,633
$
1,795,633
$
1,795,633
$
1,795,633
$
1,795,633
$
1,795,633
$
1,795,633
$
1,795,633
Operations & Maintenance
Operations & Maintenance
Site Closeout
$
1,768,829
Total
$
4,474,105
$
4,474,105
$
4,474,105
$
4,474,105
$
4,474,105
$
4,474,105
$
4,474,105
$
6,242,934
$
2,678,472
Year
5
6
7
8
9
10
11
12
13
Present Value Discount Rate4
0.9102
0.8932
0.8766
0.8602
0.8442
0.8284
0.8130
0.7978
0.7830
Net Present Value
$
4,072,258
$
3,996,327
$
3,921,813
$
3,848,688
$
3,776,926
$
3,706,503
$
3,637,392
$
4,980,793
$
2,097,117
Present Value Discount Rate5
0.7130
0.6663
0.6227
0.5820
0.5439
0.5083
0.4751
0.4440
0.4150
Net Present Value
$
3,189,975
$
2,981,285
$
2,786,248
$
2,603,970
$
2,433,617
$
2,274,408
$
2,125,615
$
2,771,937
$
1,111,471
Page 2 of 4
-------
ALTERNATIVE 6
March 2023
Record of Decision Amendment
TARP Plume: Area A North of Los
Alternative Name: AFP44 FS LR N
Phase Type Fiscal Year 15 2028 Fiscal Year 16 2029 Fiscal Year 17 2030 Fiscal Year 18 2031 Fiscal Year 19 2032 Fiscal Year 20 2033 Fiscal Year 212034 Fiscal Year 22 2035 Fiscal Year 23 2036
Design
Remedial Action $ 256,772 $ 256,772 $ 256,772 $ 256,772 $ 256,772 $ 256,772 $ 256,772 $ 256,772 $ 256,772
Remedial Action
Remedial Action
Operations & Maintenance $ 927,200 $ 927,200 $ 927,200 $ 927,200 $ 927,200 $ 927,200 $ 927,200 $ 927,200 $ 927,200
Operations & Maintenance $ 1,494,500 $ 1,494,500 $ 1,494,500 $ 1,494,500 $ 1,494,500 $ 1,494,500 $ 1,494,500 $ 1,494,500 $ 1,494,500
Operations & Maintenance
Operations & Maintenance $ 411,000
Operations & Maintenance $ 3,530,000
Site Closeout
Total $ 2,678,472 $ 2,678,472 $ 3,089,472 $ 2,678,472 $ 2,678,472 $ 2,678,472 $ 2,678,472 $ 6,208,472 $ 2,678,472
Year 14 15 16 17 18 19 20 21 22
Present Value Discount Rate4 0.7684 0.7540 0.7400 0.7262 0.7126 0.6993 0.6863 0.6735 0.6609
Net Present Value $ 2,058,015 $ 2,019,642 $ 2,286,111 $ 1,945,029 $ 1,908,762 $ 1,873,172 $ 1,838,245 $ 4,181,450 $ 1,770,333
Present Value Discount Rate5 0.3878 0.3624 0.3387 0.3166 0.2959 0.2765 0.2584 0.2415 0.2257
Net Present Value $ 1,038,758 $ 970,802 $ 1,046,511 $ 847,936 $ 792,463 $ 740,620 $ 692,168 $ 1,499,427 $ 604,566
Page 3 of 4
-------
ALTERNATIVE 6
Record of Decision Amendment
TARP Plume: Area A North of Los
Alternative Name: AFP44 FS LR N
March 2023
Phase Type
Design
Remedial Action
Remedial Action
Remedial Action
Operations & Maintenance
Operations & Maintenance
Operations & Maintenance
Operations & Maintenance
Operations & Maintenance
Site Closeout
Fiscal Year 24 2037 Fiscal Year 25 2038 Fiscal Year 26 2039 Fiscal Year 27 2040 Fiscal Year 28 2041 Fiscal Year 29 2042 Fiscal Year 30 2043 Fiscal Year 31 2044
$
$
256,772 $
927,200 $
1,494,500 $
256,772 $
927,200 $
1,494,500 $
256,772 $
927,200 $
1,494,500 $
256,772 $
927,200 $
1,494,500 $
256,772 $
927,200 $
1,494,500 $
256,772 $
927,200 $
1,494,500 $
256,772 $
927,200 $
1,494,500 $
$
256,772 $
$
$
927,200 $
1,494,500 $
$
$
$
$
Total
550,104
7,711,997
3,489,573
2,093,708
27,816,000
44,835,000
16,160,697
411,000
3,530,000
1,768,829
Total
Year
Present Value Discount Rate4
Net Present Value
2,678,472 $
23
0.6486
1,737,324 $
2,678,472 $
24
0.6365
1,704,931 $
2,678,472 $
25
0.6247
1,673,141 $
2,678,472 $
26
0.6130
1,641,944 $
2,678,472 $
27
0.6016
1,611,329 $
2,678,472 $
28
0.5904
1,581,284 $
2,678,472 $
29
0.5794
1,551,800 $
2,678,472 $
30
0.5686
1,522,866 $
108,366,908
84,730,490
Present Value Discount Rate
Net Present Value
0.2109
565,015 $
0.1971
528,052 $
0.1842
493,506 $
0.1722
461,221 $
0.1609
431,047 $
0.1504
402,848 $
0.1406
376,494 $
0.1314
351,863 $
49,879,633
Page 4 of 4
------- |