PB96-963121
EPA/AMD/R09-96/157
March 1997
EPA Superfund
Record of Decision Amendment:
Williams Air Force Base,
Operable Unit 2, Chandler, AZ
8/16/1996
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U.S. AIR FORCE
FINAL
RECORD OF DECISION AMENDMENT
DEEP SOIL, OPERABLE UNIT 2 (OU-2)
CONTRACT NUMBER F41624-94-D-8047, D0007
AIR FORCE BASE CONVERSION AGENCY
WILLIAMS AIR FORCE BASE, AZ 85206
DECEMBER 1996
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Table of Contents.
Page
List of Tables iv
List of Figures iv
List of Acronyms v
1.0 Declaration 1-1
1.1 Site Name and Location 1-1
1.2 Statement of Basis and Purpose 1-1
1.3 Assessment of the Site 1-2
1.4 Description of the Selected Remedy 1-2
1.5 Statutory Determinations 1-3
2.0 Decision Summary 2-1
2.1 Highlights of Community Participation 2-1
3.0 Scope and Role of Operable Unit 3-1
4.0 Summary of Site Characteristics 4-1
4.1 Deep Soil at Liquid Fuels Storage Area 4-1
4.2 Contaminant Fate and Transport 4-2
4.2.1 Contaminant Persistence in the Environment 4-2
4.2.2 Organics in ST-12 4-3
5.0 Summary of Potential Site Risk 5-1
5.1 Chemicals of Potential Concern 5-1
5.2 Preliminary Remediation Goals 5-2
5.3 Cleanup Goals 5-3
5.4 Remedial Action Objectives 5-4
6.0 Description of Alternatives 6-1
6.1 Alternative ST12-1: No Action 6^2
6.1.1 Source Treatment Component 6-2
6.1.2 Source Containment Component 6-2
6^1.3 Groundwater Component 6-2
6.1.4 General Components 6-2
6.1.5 Compliance with ARARs 6-3
6.2 Alternative ST12-2: Natural Attenuation 6-3
6.2.1 Source Treatment Component 6-3
KN/3066/WP3066.COW)6-
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Table of Contents (Continued).
Page
6.2.2 Source Containment Component 6-3
6.2.3 Groundwater Component 6-3
6.2.4 General Components 6-4
6.2.5 Compliance with ARARs 6-5
6.3 Alternative ST12-3: Soil Vapor Extraction 6-5
6.3.1 Source Treatment Component 6-5
6.3.2 Source Containment Component 6-6
6.3.3 Groundwater Component 6-6
6.3.4 General Components 6-6
6.3.5 Compliance with ARARs 6-7
6.4 Alternative FT02-5: Bioventing 6-8
6.4.1 Source Treatment Component 6-8
6.42 Source Containment Component 6-9
6.4.3 Groundwater Component 6-9
6.4.4 General Components 6-9
6.4.5 Compliance with ARARs 6-10
6.5 Alternative ST12-5: Synergistic Alternative, SVE, Bioventing,
and Natural Attenuation 6-10
6.5.1 Source Treatment Component 6-10
6.5.2 Source Containment Component 6-11
6.5.3 Groundwater Component 6-11
6.5.4 General Components 6-11
6.5.5 Compliance with ARARs 6-11
7.0 Comparative Analysis of Alternatives 7-1
7.1 Overall Protection of Human Health and the Environment 7-1
7.2 Compliance with ARARs 7-2
7.3 Long-Term Effectiveness and Permanence 7-2
7.4 Reduction of Toxicity, Mobility, or Volume Through Treatment 7-3
7.5 Short-Term Effectiveness 7-3
7.6 Implementability 7-3
7.7 Cost 7-4
7.8 Support Agency Acceptance 7-4
7.9 Community Acceptance 7-4
KN/3066/WP3066.CONA>«B-96(3:13poi) U D1/E1
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Table of Contents (Continued).
Page
8.0 Selected Remedy 8-1
8.1 Major Components of the Selected Remedy 8-1
8.2 Cost 8-4
9.0 Statutory Determinations 9-1
9.1 Protection of Human Health and the Environment 9-1
9.2 Compliance with ARARs 9-2
9.2.1 Chemical-Specific ARARs , 9-2
9.22 Location-Specific ARARs 9-2
9.2.3 Action-Specific ARARs 9-2
9.3 Cost Effectiveness 9-3
9.4 Utilization of Permanent Solutions and Alternative Treatment
Technologies or Resource Recovery Technologies to the Maximum
Extent Possible 9-4
9.5 Preference for Treatment as a Principal Element 9-5
10.0 Documentation of Significant Changes 10-1
11.0 Responsiveness Summary 11-1
12.0 References 12-1
Appendix A - Cost
Appendix B - Location-Specific Applicable or Relevant and Appropriate Requirements
KN/3066/WP3066.CONA)«B-96<3:13pin) ill D1/E1
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List of Tables.
Number Title Follows Page
5-1 Evaluation of Chemicals of Potential Concern 5-1
5-2 Determination of Chemicals of Concern and Cleanup Levels in
Deep Soil Liquid Fuels Storage Area (ST-12), Operable Unit 2 5-3
List of Figures.
Number Title Follows Page
1-1 Site Location Map 1-1
1-2 Site Map for the Liquid Fuels Storage Area, (ST-12) 1-1
4-1 JP-4 Concentration in 1993 Deep Soil Borings at ST-12 4-1
5-1 Groundwater Contamination Plume at ST-12, August 1995 5-2
5-2 Line of Transport from Source Area to Compliance Point 5-3
5-3 Concentration of Benzene in Groundwater at the Compliance Point
Using the Modeled PRG value of 5 mg/kg Benzene in Soil 5-3
5-4 Concentration of Toluene in Groundwater at the Compliance Point
Using the Modeled PRG value of 4000 mg/kg Toluene in Soil 5-3
5-5 Concentration of Naphthalene in Groundwater at the Compliance Point
Using the Modeled PRG value of 3000 mg/kg Naphthalene in Soil 5-3
6-1 Initial Screening - Deep Soils at ST-12 6-1
6-2 Secondary Screening - Deep Soils at ST-12 6-1
6-3 Remedial Alternative Evaluation Criteria 6-1
6-4 Soil Vapor Extraction (SVE) System Conceptual Flow Diagram
Deep Soils at Liquid Fuels Area (ST-12) 6-5
6-5 Bioventing System Conceptual Flow Diagram Deep Soils at
Liquid Fuels Area (ST-12) at OU-2 6-8
KN0066/WP3066£ONfl«B-96(3:13pm) IV
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List of Acronyms.
Arizona Department of Environmental Quality
Arizona Department of Water Resources
Air Force Base
applicable or relevant and appropriate requirements
benzene, toluene, ethyl benzene, and xylene
British thermal unit
Comprehensive Environmental Response, Compensation, and Liability Act
CFR Code of Federal Regulations
COC chemicals of concern
COPC chemicals of potential concern
EPA U.S. Environmental Protection Agency
FFA Federal Facilities Agreement
FS feasibility study
HBGL health-based guidance levels
IT IT Corporation
JP-4 jet petroleum grade 4
LFSA Liquid Fuels Storage Area
p.g/L micrograms per liter
mg/kg milligrams per kilogram
NCP National Contingency Plan
NPL National Priorities List
O&M operation and maintenance
OU Operable Unit
POTW publicly owned treatment works
PRG preliminary remediation goals
RA remedial action
RAO remedial action objectives
RCRA Resource Conservation and Recovery Act
RD remedial design
RI remedial investigation
ROD record of decision
RODA record of decision amendment
scfm standard cubic feet per minute
KN/3066/WP3066.COW6-
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List of Acronyms (Contmuedi
SHPO State Historic Preservation Officer
SVE soil vapor extraction
TOC total organic compound
TPH total petroleum hydrocarbons
UCL upper confidence limit
UST underground storage tank
USAF U.S. Air Force
VOC volatile organic compound
KW3066/WP3066.CONA)«B-96(3:13pm) VI D1/E1
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1.0 Declaration
1.1 Site Name and Location
Williams Air Force Base (AFB) is located in Maricopa County, east of the city of Chandler,
Arizona (Figure 1-1). Operable Unit (OU>2 of the Williams AFB National Priority List
(NPL) is located at the Base's Liquid Fuels Storage Area (LFSA), which is also referred to as
its site designation "ST-12" (Figure 1-2).
1J2 Statement of Basis and Purpose
This record of decision amendment (RODA) prepared by IT Corporation (FT) selects a
remedial action (RA) for site cleanup of the deep soil (from a depth of 25 feet to the top of
groundwater) at ST-12. Deep soil at ST-12 was originally included in the feasibility study
(FS) of remedial alternatives for OU-2 at Williams AFB (Figure 1). As the FS proceeded at
OU-2, it became apparent that deep soil at ST-12 required further study. Therefore, it was
agreed that deep soil at ST-12 would be removed from OU-2 and grouped with OU-3 sites.
This action allowed the FS of the remaining sites in OU-2 to proceed on schedule and
provided additional time to study the impact of potential contaminant migration to the
groundwater. Extensive testing and modeling conducted as part of the OU-3 FS showed that
contaminants in deep soil could travel to groundwater and impact the cleanup remedy selected
for groundwater in the OU-2 proposed plan. For this reason, the decision was made to
consider all the environmental media at ST-12 as a unit in subsequent studies. Deep soil at
ST-12 is, therefore, reincorporated into OU-2.
The results of the deep soil contamination investigation at ST-12 are reported in the OU-3
remedial investigation (RI) report (IT, 1994). The results of the OU-2 investigations are
reported in the OU-2 RI report (TT, 1992a). Because this is a RODA, per U.S. Environmental
Protection Agency (EPA) guidance (1989), it does not include some of the introductory
sections generally found in a record of decision (ROD). This amendment focuses on the
changes at ST-12 since the issuance of the OU-2 ROD (IT, 1992b); its primary purpose is to
recombine the ST-12 deep soil into OU-2. The selected remedy for shallow soil and ground-
water at OU-2 is presented in me OU-2 FS report (IT, 1992c) and ROD (IT, 1992b). This
amendment does not change the remedies specified in the OU-2 ROD.
KN/3066/WP3066.]A>S-22-96(ll:52«n) 1-1 D4JE1
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o
E
O
*
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LEGEND:
^== PRIMARY ROADS
SSt FACILITY NUMBER
-—x x- FENCE
A\ FENCE CATC •
BOUNDARY OF ST-12
— - — FUEL DISTRIBUTION UNES
FORMER FUEL STORAGE
TANK LOCATION
*H AREA OF PAST LEAKS
STRUCTURE
SCALE:
r
0
200
400 FEET
FIGURE 1-2
SI1E MAP FOR THE LIQUID FUELS
STORAGE AREA (ST-12)
WILLIAMS AIR FORCE BASE
CQ
INTERNATIONAL
TECHNOLOGY
CORPORATION
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1.3 Assessment of the Site
Releases of jet petroleum grade 4 (JP-4) and aviation gasoline have contaminated soils at OU-
2. Actual or threatened releases of hazardous substances from this site, if not addressed by
implementing the response actions selected in this RODA, may present an imminent and
substantial endangerment to public health and the environment. Benzene, which is present in
JP-4, is the most prevalent and mobile of the contaminants at OU-2. Where benzene or JP-4
is referred to in this RODA, all of the chemicals of potential concern (COPC) exceeding
action levels are also included by reference and will be treated by the selected remedy.
1.4 Description of the Selected Remedy
Environmental remediation at Williams AFB has been organized into five OUs. The U.S. Air
Force (USAF), in conjunction with EPA and the State of Arizona, has selected cleanup
remedies for OU-1, OU-2, and OU-3. The groundwater and shallow soil at this site are
addressed in OU-2. The deep soil at ST-12 will be addressed in this RODA and remedies for
the rest of OU-3 are presented in the OU-3 ROD. Investigations at OU-4 and removal
actions at OU-5 have been completed and reports are being prepared to document the
activities at these sites.
Data garnered from investigations of the deep soil at ST-12 indicated that concentrations of
contaminants in the soil warrant further action. The selected remedy is a synergistic
combination of soil vapor extraction (SVE), bioventing, and natural attenuation. These
remedies will be applied to various zones of deep soil contamination, either separately or
sequentially, to accomplish cleanup goals in the most cost-effective manner. The proper
application of these three technologies to the site would be determined after treatability
studies and pilot tests are conducted to determine their relative effectiveness specific to the
ST-12 deep soil. A fume incineration system will be required to destroy organic compounds
in soil gas from the SVE or bioventing systems to comply with the applicable Maricopa
County air quality requirements.
The major components of the selected remedy are:
• The SVE system will volatilize and extract organic contaminants from the
subsurface soil for subsequent destruction in the fume incinerator. The system
will operate until the concentration of benzene in the soil is reduced to cleanup
levels.
• Bioventing will induce air flow into the subsurface soil to stimulate the biodeg-
radation of organic contaminants by indigenous soil microorganisms. The
KN/3066/WP3066.1/D5-22-96(llJ2Bn) 1-2 D4/E1
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quantity of air extracted from the soil will be controlled to maximize biodegra-
dation and minimize volatilization of contaminants.
• Natural attenuation will include bench-scale biodegradation studies, contaminant
transport modeling, periodic soil monitoring, and other evaluations needed to
predict the rate of contaminant attenuation, and will confirm that these natural
biodegradation processes are proceeding at a rate consistent with meeting
remedial action objections (RAO), described in more detail in Section 5.4.
• The selected remedy will mitigate future migration of chemicals of concern
(COC) to groundwater, which presents the principal threat to human health at
this site. The remedy will remain in operation until the concentrations of COCs
are reduced to cleanup levels.
1.5 Statutory Determinations
The selected remedy is protective of human health and the environment, complies with
federal and state requirements mat are legally applicable or relevant and appropriate to the
RA, and is cost effective. This remedy uses permanent solutions and alternative treatment (or
resource recovery) technologies to the maximum extent practicable and satisfies the statutory
preference for remedies that employ treatment that reduces toxicity, mobility, or volume as a
principal element. A 5-year review will apply to this action because this remedy will take
greater than 5 years to reduce the hazardous substances remaining on site below cleanup
levels.
DV3066/WP3066.1A>5.22-96) 1-3 D4/E1
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This Record of Decision Amendment for Operable Unit Number Two at Williams Air Force
Base, Arizona may be executed and delivered in any number of counterparts, each of which
when executed and delivered shall be deemed to be an original, but such counterparts shall
together constitute one and the same document.
Alan K. Olsen, Director
U.S. Air Force, Base Conversion Agency
Date
?- 1C - 76
Julie Anderson, Director
Federal Facilities Cleanup Office
U.S. Environmental Protection Agency, Region DC
Date
Russell F. Rhoadei, Director
Arizona Department of Environmental Quality
Date
Rita Pearson, Director
Arizona Department of Water Resources
Date
KN/3066WP3066.1/07-31-%(l2:10pm)
1-4
D4/EI
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2.0 Decision Summary
2.1 Highlights of Community Participation
Ongoing Public Involvement A community relations plan for the Base was issued in
February 1991 (IT, 1991c) and updated in March 1995. This plan listed contacts and
interested parties throughout the USAF, government, and the local community. The plan also
established communication channels to ensure timely dissemination of pertinent information to
the surrounding community through mailings, public announcements in the local newspaper,
public meetings, public comment periods, public service announcements, and the establish-
ment of information repositories in local libraries.
Early in the IRP, the Base established a Technical Review Committee (TRC) to provide
review and offer comment and recommendations on the progress of the cleanup effort The
TRC included representatives from the USAF and other governmental agencies as well as
appointed representatives from the surrounding communities. Governmental agencies
represented included EPA Region IX, the ADEQ, ADWR, and the Maricopa County Depart-
ment of Health.
With the advent of Base closure, the TRC was expanded to include additional community
stakeholders and is now called the Restoration Advisory Board (RAB). Much the same as a
TRC, the RAB acts as a forum for discussion and exchange of information regarding cleanup
between the installation, governmental agencies and the community. However, because the
RAB provides for an expanded and more diverse membership representing the community, a
greater opportunity is afforded to those directly affected by the cleanup process to participate
and provide input This input will be especially valuable as decisions are made regarding
transfer and end uses of Base property.
An Administrative Record that contains the documents relating to investigation and cleanup
activities proposed for the Base has been established and is available for public inspection as
part of the information repositories at the Gilbert Public Library, Gilbert Arizona and the
Base Conversion Agency (Williams AFB), Mesa, Arizona.
Public Involvement Specific To OU-2 Amendment for Deep Soil. The recommended
remedy for the OU-2 amendment for deep soil is described in the OU-2 Amendment
Proposed Plan. Concurrently, this document was made available to the public in the
KN/3066/WP306&206-03-96<£50pm) 2-1 D1/E1
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Administrative Record. The notice of their availability was published in the Arizona
Republic/Phoenix Gazette on February 12,1996, an action which coincided with the begin-
ning of the 30-day public comment period.
The USAF has met the community relations requirements of CERCLA Sections 113 and 117
in the remedy selection process for OU-3 through the following activities. The OU-3 RI/FS
which outlined the actions for the deep soil included in this OU-2 amendment was released
for public review on June 26,1995. A public meeting was held February 21, 1996 at the
former Williams AFB in Building 1, Mesa, Arizona to discuss the proposed remedial
alternatives. A fact sheet describing the proposed plan.was distributed at the public meeting,
placed in the information repositories, and to other interested individuals upon request There
were no written comments received during the public comment period but the verbal
comments and the corresponding USAF responses are included in the Responsiveness
Summary (Chapter 11.0).
KN/306fi/WP3066;W«)W6(230pn) 2-2 D1/E1
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3.0 Scope and Role of Operable Unit
As with many Superfund sites, the environmental problems at Williams AFB are complex.
As a result, the USAF has organized the work into the following OUs.
• OU-1 addresses soil and groundwater contamination at the following ten sites:
- Landfill (LF-04)
- Fire Protection Training Area No. 1 (FT-03)
- Northwest Drainage System (SD-10)
- Radioactive Instrumentation Burial Area (RW-11)
- Pesticide Burial Area (DP-13)
- Hazardous Materials Storage Area (SS-01)
- Underground storage tanks (UST) at four area (ST-05, ST-06, ST-07, ST-08).
• OU-2 addresses soil and groundwater at the LFSA (ST-12). Deep soil at ST-12
is added to OU-2 by this amendment.
• OU-3 addresses soil and groundwater at the following two sites:
- Fire Protection Training Area No. 2 (FT-02)
- Southwest Drainage System (SD-09) (soil only).
• OU-4 addresses investigations of contamination at 11 sites.
• OU-5 addresses removal actions at eight sites.
The USAF, in conjunction with EPA and the State of Arizona, has selected cleanup remedies
for OU-1, OU-2, and OU-3. These remedies are specified in their respective RODs. The
deep soil at ST-12 will be addressed in mis RODA. Investigations at OU-4 and removal
actions at OU-S have been completed and reports are being prepared to document the
activities at these sites.
OU-1 includes soil and groundwater at ten sites. Of the ten sites within OU-1, only the soil
at the Landfill (LF-04) presented an unacceptable risk to human health and the environment.'
Surface soil at LF-04 contaminated with beryllium and the pesticide dieldrin at concentrations
above remediation goals were covered with a permeable cap over the Landfill. This remedy
limited human exposure to dieldrin and beryllium-contaminated surface soil, controlled natural
erosion processes, and included warning signs and perimeter fencing. This remedy has been
completed and soil and groundwater for OU-1 is in the operation and maintenance (O&M)
phase.
KN/3066/WP3066.3A>S-22-96
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The principal risks to human health and the environment at OU-2 result primarily from
contamination of soil and groundwater by JP-4 and its constituents (e.g., benzene, toluene),
although other organic compounds have also been detected at the site. The ROD for OU-2,
signed in December 1992, specified a remedy involving a combination of SVE with bioen-
hancement to remediate shallow soil, and groundwater extraction and treatment via air
stripping with emission abatement to remediate the contaminated groundwater. The remedial
design (RD)/RA phase for OU-2 was conducted with a pilot study/demonstration study on the
treatment of contaminated groundwater and a pilot study on the treatment of contaminated
soiL The shallow soil has been remediated via the Phase I SVE remedy. Source control for
groundwater is continuing and the treatment remedy is being reviewed.
Investigation and modeling of deep soil at ST-12 presented in OU-3 RI projected that
contaminants in soil will migrate to the groundwater, providing a continuing source of
contaminants Deep sofl at ST-12 is being incorporated into OU-2 to initiate action to abate
threats to human health and the environment, by mitigating COC migration to groundwater.
The remedy selected in mis RODA is designed to be consistent with any subsequent remedies
and planned future actions at the Base proposed in all subsequent RODs.
KN/3066/WP30«3/05-22-96
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Boring 58-86
LEGEND:
Boring SB-87
E
5
!
>5
PRIMARY ROADS
557 FACILITY NUMBER
x x FENCE
/A FENCE GATE
BOUNDARY OF ST-12
FUEL DISTRIBUTION LINE".
FORMER FUEL STORAGE
TANK LOCATION
1993 SOIL BORINGS AT
ST-12 COU-3)
STRUCTURE
CONCENTRATION OF JP-4
t
£
o
•••JI..IL.I—•••
NOTES:
1. JP-4 CONCENTRATION LESS THAN
THAN 100 MG/KG NOT SHOWN.
S 19 » IB «9 » «9 n 19 « H9H9ini»H9l99K9IT9IM
Depth (feet)
Depth I foot I
JP-4 CONCENTRATION IN l'U.5
DEEP SOIL BORINGS AT SI 17
WILLIAMS AIR FORCE BASE
INTERNATIONAL
TECHNOLOGY
CORPORA IIOH
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4.0 Summary of Site Characteristics
Chapter 4.0 provides an overview of the assessments conducted during the RI to characterize
deep soil at ST-12. Investigations on first 25 feet of soil and groundwater are summarized in
the OU-2 ROD (IT, 1992b). Investigations on deep soil at ST-12 were conducted as part of
the OU-3 efforts and details of these investigations are presented in the OU-3 RI (IT, 1994).
This summary presents the following information:
• Quantity, types, and concentrations of hazardous substances
• Estimated volume of contaminants
• Lateral and vertical extent of contamination
• Mobility of identified contaminants
• Potential surface and subsurface pathways of contaminant migration.
4.1 Deep Soil at Liquid Fuels Storage Area
Deep soil investigations at ST-12 were limited to determining the levels of organic constitu-
ents of total petroleum hydrocarbons (TPH) using a JP-4 standard, benzene, toluene, ethyl
benzene, and xylene (BTEX), and total organic compound (TOC) as specified in the approved
work plan and field sampling plan addendums for OU-3 (IT, 1993a,b). This section sum-
marizes the results of 16 soil borings installed in 1993. The nature of contamination at ST-12
is from JP-4 contamination as specified in the OU-2 RI report (FT, 1992a). The extent of
JP-4 contamination to a depth of 25 feet was identified in the OU-2 ROD (IT, 1992b) in four
areas. The deep soil investigations focused on these areas to better define the extent of
contamination at depths exceeding 25 feet. These areas, shown in Figure 1-2, are associated
with former Tank 688 (Area 1), former Tank 514 (Area 2), former Tank 538 and the former
distribution line that led from Tank 538 south along distribution lines that have been removed
between Tanks 538 and 555 (Area 3), and former location of tanks at Facility 548 (Area 4).
The OU-2 FS report (IT, 1992c) further concluded that the worst-case dispersion of contami-
nation migrating downward was at a 30-degree angle from vertical. This conclusion was
based on data presented in the OU-2 RI report (IT, 1992a).
Soil has been classified as contaminated if the JP-4 concentration exceeds 7,000 milligrams
per kilogram (mg/kg) as set forth in the Arizona Department of Environmental Quality
(ADEQ) UST soil cleanup levels (ADEQ, 1990). JP-4 results for the deep soil borings with
JP-4 concentrations exceeding 100 mg/kg are presented in Figure 4-1. The last sample from
each soil boring was taken at the approximate top of groundwater at 215 feet. Also, some
KN/3066/W?30«UA>S-22-96
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samples were taken at depths less than 25 feet to confirm or deny the presence of contamina-
tion in the first 25 feet of soil.
The deep soil investigation at ST-12 clarified many of the conclusions drawn in the OU-2 RI
report and provided new data regarding the extent of subsurface contamination. Results from
the soil borings showed that the approximate dispersion angle of 30 degrees assumed in the
OU-2 FS report (TT, 1992c) was exaggerated. Actual dispersion patterns were nearly vertical.
Also, it was found that the higher concentrations were detected with depth. Such a distribu-
tion pattern of JP-4 (TPH) in the soil was likely created by a continuous release of JP-4 at, or
near, the ground surface. Elevated contaminant concentrations were also periodically detected
in isolated fine-grained layers above the water table.
Soil samples collected during the deep soil investigation at ST-12 were not analyzed for
inorganic compounds. Previous investigations do not indicate significant concentrations of
constituents involving inorganics in deep soil at ST-12 (IT, 1992c).
4.2 Contaminant Fate and Transport
As previously noted, the focus of the investigations at the site was contamination due to JP-4;
therefore, this summary of fate and transport is restricted to behavior of organics in soil.
Detailed discussions of contaminant fate and transport were presented in the OU-3 RI report
(TT, 1994).
Contaminant Persistence in the Environment
Chemical persistence in environmental media is determined by the chemical's ability to move
through a medium, to transfer from one medium to another, and to transform or degrade.
These processes are controlled both by the chemical or element properties and the medium.
Migration to groundwater can occur via water infiltration, dispersion, and diffusion. Sorption
of chemicals onto soil particles or soil organic matter can reduce migration; similarly,
chemically or biologically mediated transformation or degradation of chemicals can reduce
migration.
The mobility of organic compounds within the soil is affected by chemical processes that are
in part due to a chemical's volatility, octanol-water partition coefficient (a measure of the
affinity of a chemical to partition from water to organic materials), water solubility, and
concentration. In general, the more water insoluble a compound is, the more likely it is to
adsorb on a sediment or organic surface. For several groups of compounds (including
KN/30«/WP30664flS-22-96(ll-J7«n) 4-2 D4/E1
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phenols, phthalates, and monocyclic aromatics such as benzene) volatilisation soiption and
biodegradation are all prominent processes. The behavior of polynuclear aromatic hydro-
carbons was found to be a function of the number of rings present. Important processes for
this class of compound are soiption and aerobic and anaerobic biodegradation. The fate of
chlorinated pesticides is determined by soiption, volatilization, and/or biotransfbrmation.
422. Organics in ST-12
A site-specific unsaturated flow and multiphase transport model was developed to determine
the potential downward migration of contaminants detected in deep soil boring soil samples at
ST-12. As part of this effort, the model was used to determine (1) if JP-4 has the potential to
move vertically or is in an immobile, residual state, (2) the rate of movement, if any, and (3)
whether the BTEX components entering the aqueous phase would impact the uppermost
water-bearing unit The modeling effort focused on the unsaturated movement characteristics
of the various phases present beneath ST-12. The information provided in this section
summarizes the modeling input and results. A more thorough presentation of the input
parameters, their derivation, model development, calibration and use, results, and discussions
are provided in Appendix D of the OU-3 RI report (IT, 1994).
The model was run for a period of 100 years to estimate the long-term impacts to ground-
water by JP-4. Modeling progressed under the assumptions that no biodegradation of the
chemical components occurs, and mat no RAs were in place. The model indicated that from
ground surface to a depth of 60 or 70 feet, little movement of the JP-4 and its chemical
components will occur. It appears to be essentially immobile. Definite movement was
indicated by the model below a depth of 70 feet However, the majority of the movement
was predicted to occur within 25 years, with little additional movement observed after this
time.
The model results indicate mat JP-4 can be expected to accumulate on the groundwater
surface, representing a source of contamination to the groundwater. The results project little
JP-4 will be added to the groundwater after approximately 25 years. Any accumulated mass
of JP-4 can be expected to contribute benzene to the groundwater system over time.
Using average groundwater flow velocities (0.021 feet per day) and an average aquifer
thickness of 25 feet, an average benzene concentration in groundwater resulting from the
movement of JP-4 through the subsurface soil is approximately 30 micrograms per liter
(|ig/L) (at boring SB-04). This average concentration occurs at a predicted time of approxi-
KN/3066/WP3066>«A)5-22-96(llJ7tm) 4-3 D4/E1
-------
mately 25 years. By the end of the simulated time period (100 years), an average benzene
concentration in groundwater is estimated to be approximately 0.4 u,g/L. The method by
which concentrations were calculated was unable to account for any additional benzene (or
other chemical constituent) dissolving into groundwater from the JP-4 present on the
groundwater surface. This phenomenon may account for an overall increase in the average
concentrations by perhaps an order of magnitude.
Groundwater modeling efforts for deep soils was further extended to establish preliminary
remediation goals (PRO) for benzene, toluene, naphthalene, and TPH. This modeling effort is
discussed in the site risk chapter, because these PRGs were developed using health-based
standards established in the OU-2 ROD (IT, 1992b).
4-4 D4/E1
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5.0 Summary of Potential Site Risk
Deep soil (25 feet and deeper) at ST-12, which was part of OU-3, was not evaluated in the
baseline human health risk assessment because there are no complete pathways by which the
occupational or residential receptors would be exposed to the deep soil. The only potentially
complete pathway is leaching of contaminants from the deep soil to the groundwater, and the
remedy for contaminated groundwater is addressed by the ROD for OU-2 (IT, 1992b).
5.1 Chemicals of Potential Concern
The OU-2 ROD (TT, 1992b) addressed the health risks associated with the top 25 feet of soil
at ST-12, and identified a number of COPC for the deep soil. There are no human health
risks associated with the COPCs in deep soil at ST-12 because no direct exposure pathways
exist from contaminated soil to potential receptors. Migration of deep soil contaminants to
groundwater is the only potential exposure pathway to human receptors. There are no
applicable or relevant and appropriate requirements (ARAR) for soil at ST-12 because no
statutory mandated levels exist for contaminants in soil. To-be-considereds such as Arizona
health-based guidance levels (HBGL) and risk-based calculated allowable concentrations are
not pertinent requirements because they are predicated on exposure pathways that do not exist
for ST-12 in this operable unit. Therefore, an approach was developed to calculate PRGs for
soil contaminants based on their potential environmental impact on groundwater when
measured at compliance points (IT, 1995).
The first step in the process of identifying COPCs for the deep soil was to consider the list of
COPCs for subsurface soil identified in the OU-2 ROD (IT, 1992b) and listed in Table 5-1,
then compare this list to the COCs selected for groundwater. A chemical was eliminated as a
COPC for deep soil if it met any of the following exclusionary criteria.
• The chemical was not identified as a COC for groundwater.
• The chemical was determined to be not characteristic of site contamination (i.e.,
laboratory error, chemical not fuel-related) in the OU-2 FS.
The rationale for eliminating individual chemicals as COPCs is also documented in Table 5-1.
The table shows that benzene, naphthalene, and toluene were determined to be COPCs for
deep soil. Each of these chemicals are constituents of JP-4.
KN/3066/WP3066.5/05-2Z-96(12.-COpin) 5-1 D3/E1
-------
Table 5-1
Evaluation of Chemicals of Potential Concern
ST-12 Deep Soil
Operable Unit 2, Williams Air Force Base
Chemicals of
Potential Concern0
Basis for Elimination
from Further Consideration
Organlcs
Acetone
Benzene
Bis(2-ethy1hexyl)phtha!ate
Chlorobenzene
1 ,2-Dichlorobenzene
1 ,3-Oichlorobenzene
1 ,4-Dichlorobenzene
Ethyl benzene
2-Hexanone
Methylene chloride
2-Methyl naphthalene
4-Methyl-2-perrtanone
Naphthalene
Phenol
Toluene
Xylenes
Not a COC for groundwater.
Retained as a COPC for soil.
Chemical is not fuel-related.
Not a COC for groundwater.
Not a COC for groundwater.
Not a COC for groundwater.
Not a COC for groundwater.
Not a COC for groundwater.
Not a COC for groundwater.
Not a COC for groundwater.
Not a COC for groundwater.
Not a COC for groundwater.
Retained as a COPC for soil.
Not a COC for groundwater.
Retained as a COPC for soil.
Not a COC for groundwater.
Inorganics
Antimony
Cadmium
Lead
Chemical is not fuel-related.
Not a COC for groundwater.
Not a COC for groundwater.
"Chemicals of potential concern (COPC) subsurface soil from OU-2 Record of Decision (IT, 1992b)
COC = Chemical of concern.
KN\3066\WP3066.5-1\05-22-96{12.-13pm)
D2\E1
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!
EXTENT OF DISSOLVED
BENZENE PLUME. AUGUST 1995
LEGEND:
Q IT/CDM MONITORING WELL
• AV MONITORING WELL
P) DENOTES DEEP MONITORING WELL
GROUNDWATER CONTAMINANT PLUME
AT ST-12, AUGUST 1995
LIQUID FUELS STORAGE AREA (ST-12)
WILLIAMS AIR FORCE BASE
INTERNATIONAL
TECHNOLOGY
CORPORATION
-------
5.2 Preliminary Remediation Goals
A computer modeling effort was conducted to establish PRGs for benzene, toluene, naph-
thalene, and TPH. The model was used to calculate the concentrations of benzene, toluene,
and naphthalene in deep soil that would, upon migration, result in maximum future ground-
water concentrations at the compliance point approximately equal to the OU-2 remediation
goals. The OU-2 ROD (IT, 1992b) established remediation goals for benzene, toluene, and
naphthalene in groundwater at 5, 1,000, and 28 u,g/L, respectively. Soil concentrations that
result in these predicted groundwater concentrations at the compliance points are proposed as
the deep soil PRGs. The model was also used to estimate the TPH concentration below
which no further bulk movement of residual JP-4 would be expected.
The following assumptions form the basis upon which PRGs were calculated for COPCs
using the vadose zone and groundwater transport models:
• The aquifer under ST-12 was assumed to be initially uncontaminated, even
though the groundwater underneath the deep soil is contaminated with JP-4, and
a significant layer of free-phase JP-4 is floating on the surface of the ground-
water. Groundwater contamination beneath ST-12 is addressed by the selected
remedy for OU-2. A groundwater pilot study/demonstration study at ST-12 is
ongoing to determine the effectiveness of the selected groundwater remedy for
OU-2.
• A groundwater compliance point was established at a distance from the major
source of contamination represented by the line between or through monitoring
wells SS01-W26, SS01-W28, and SS01-W29 (Figure 5-1). This compliance
point was established to determine the allowable extent of plume migration in
groundwater. The final compliance point for determining when all RAs have
been completed will be established during the RD/RA phase.
• A biodecay factor was neither appropriate nor used for modeling the transport of
COPCs in soil. A soil biodecay factor was evaluated as a component of some of
the remedial alternatives presented in Chapters 3.0 and 4.0 of die OU-3 FS (IT,
1995).
• A biodecay factor was appropriate and used in modeling the transport of COPCs
in groundwater. The longest half-life for any COPC identified in the literature
search was 2 years for benzene (Howard, et al., 1991). An iterative approach
was then initiated with this period as a point of departure to determine the
effects of different biodecay factors on modeling results. Based on this
approach, a biodecay half-life of 10 years was used for all COPCs. The 10-year
half-life is considered conservative. The appropriateness of the 10-year half-life
can be verified based on natural attenuation treatabflity tests for groundwater.
KN/3066/WP3066JA)5-22-96(lZ-OOpm) 5-2 D3/E1
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3 DEEP SOIL BORING LOCATION
GROUNOWATER MONITORING WELL
(ONLY SELECTED WELLS DISPLAYED)
JUUULJLJO J)
inririnnnn
!l JLJUULJUU
0 200
FIGURE 5-2
LINE OF TRANSPORT FROM
SOURCE AREA TO THE
COMPLIANCE POINT
JI.IULJ
innnnru
WILLIAMS AIR FORCE BASE
PHOENIX. ARIZONA
INTERNATIONAL
TECHNOLOGY
CORPORATION
-------
3.5
3.0
2.5
O 2.0
O)
o
U
0.5
0.0
Notes:
TPH = 2000 mg/Kg in soil
Benzene = 5 mg/Kg in soil
Biodecay half-life = 10 years
25
50
75
100
Time (years)
125
Figure 5-3
Concentration of Benzene in Groundwater at the Compliance Point
Using the Modeled PRG value of 5 mg/Kg Benzene in Soil.
150
-------
ctf
O)
i
u
600
500 -
400 ~
300 ~
200 -
100 -
Notes:
TPH = 4000 mg/Kg in soil
Toluene = 4000 mg/Kg in soil
Biodecay half-life = 10 years
50
100
150
Time (years)
Figure 5-4
Concentration of Toluene in Groundwater at the Compliance Point
Using the Modeled PRG value of 4000 mg/Kg Toluene in Soil.
-------
Table 5-2
Determination of Chemicals of Concern and Cleanup Levels In Deep Soil
Liquid Fuels Storage Area (ST-12)
Operable Unit 2, Williams Air Force Base
Chemicals of
Potential Concern
jBensebe* ;
Naphthalene
Toluene
TPH as JP-41
Base-Specific
Background Range
or Value
(mg/kg)
'; -, " NA* .„;'
NA
NA
~- , NA"' ' ' ."
Value of Range of
Detected
Concentrations
(mg/kg)
, 0,001 to 090 .
3.5 to 14
0.001 to 1500
o,4a to 3$o,doo ;
PRQa
(mg/kg)
; 5»>; '
3000
4000
. 2000* ";,
UCLb
(mg/kg)
, 31
10
91
6100
Decision Basis
Requites action to meet PftQ,
UCL concentration below PRQ.
UCL concentration below PRQ.
Requires action i to meet PRQ,
"Preliminary remediation goals based on modeling concentration of contaminants that would result in concentrations at the compliance points greater
than action levels for groundwater (OU-2 ROD).
bUCL concentrations are calculated using all available deep soil data.
"Chemical of concern for ST-12 deep soil.
dNA - Not available.
"Target cleanup level.
*rPH Is .parameter of concern for ST-12 deep soil.
KN/3066/WP306«.5'2A>5.22.96(t2:i3pm)
DO/HI
-------
25
nJ
bo
O)
u
a
o
U
20 h
15 h
10 h
5 h
Notes:
TPH = 4000 mg/Kg in soil
Naphthalene = 3000 mg/Kg in soil
Biodecay half-life = 10 years
50
100
150
Time (years)
Figure 5-5
Concentration of Naphthalene in Groundwater at the Compliance Point
Using the Modeled PRG value of 3000 mg/Kg Naphthalene in Soil.
-------
field data (e.g., groundwater elevation data). The determination of COCs and their respective
cleanup levels in deep soil at ST-12 are presented in Table 5-2.
5.4 Remedial Action Objectives
The objectives of conducting RAs in the deep soil at ST-12 are to reduce the time required
for groundwater cleanup and to remove sources of JP-4 in deep soil that may continue to
impact groundwater at ST-12, thereby minimizing the cost of remediating the entire site. The
cleanup level for deep soil remediation is 5 mg/kg for benzene. In addition, TPH will be
reduced to an initial target concentration of 2,000 mg/kg. These concentrations may be
revised based on the results of soil and groundwater treatability studies, and other field data
(e.g., groundwater elevation data), with the concurrence of the Parties to the Federal Facilities
Agreement (FFA).
KN/3066/WP3066JA»-22-96(liOOPm) 5-4 D3/E1
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6.0 Description of Alternatives
Under the Comprehensive Environmental Response, Compensation, and Liability Act
(CERCLA), a process has been established to develop, screen, and evaluate appropriate
remedial alternatives. A wide range of cleanup options were considered for RA for deep soil
at ST-12.
The initial process options considered during the preliminary screening process are presented
in Figure 6-1. The process options were evaluated, and retained or eliminated from further
consideration on the basis of technical feasibility. Figure 6-1 presents the rationale for
eliminating process options.
A second screening step was then performed to evaluate the remaining process options on the
basis of implementabflity, effectiveness, and cost. The result of mis screening process was
intended to select one representative process option for each technology type for detailed
analysis. The secondary screening was a two-step process. First, the process options retained
from preliminary screening were ranked according to the previously mentioned three criteria
to eliminate those options that were obviously inappropriate. The results of this step are
presented in Figure 6-2. After this evaluation process, the following remedial alternatives
were screened for contaminated deep soil at ST-12:
• Alternative ST12-1: No Action
• Alternative ST12-2: Natural Attenuation
Alternative ST12-3: SVE
Alternative ST12-4: Bioventing
Alternative ST12-5: Synergistic alternative, SVE, Bioventing, and Natural
Attenuation.
These alternatives were developed based on site-specific needs and evaluated using the nine
criteria developed by EPA to address CERCLA requirements. The evaluation criteria pre-
sented in Figure 6-3 are used to determine the most appropriate alternative. The following
sections present detailed descriptions of the previously noted remedial alternatives.
KN/3066/WP30664A>»2-96(12.
-------
ral Response Action Technology Type
Process Option
Comments
No Action
institutional Action [
Containment r~~
1 1 »%t T-
In Situ Treatment —
/^pro'yal/pfspd'saf'y/ ~"
^n^^fJf^a^^t/J^sj^s^
. 1 N/A
I ,
1— Natural Attenuation — —
Hpnnninn ___^_
•M^BH
P j Physical
Chemical I
1 Rlnlnntrnl __.-»._
H^X^^^P^p^X^yl
Hl^^tjdn/rfeafn>eV6^^
N/A
Deed Restrictions
Monitoring
IrnnnrmAsiKlo r^an
Soil Flushing
Soil Vapor Extraction
if y yW-t/at/n/ / J
/ S jf*'x'*»a^IIOpr ^^ ^r
1 yfnofaaKicyatanilhMtiun/
[ftly/i \jjpl ny &yOUyfLoJA \j\jr
01
Dtoventing
Land use restrictions in place due to OU-2.
See Section 2.10.3.3
Not applicable below 30 feet.
Not applicable for volatile organic contaminants.
Excavation not feasible down to 220 feet.
Excavation not feasible down to 220 feet.
- Retained
\//////\ • Eliminated
Figure 6-1. Initial Screening - Deep Soils at ST-12
-------
General Raiponi* Action Technology Type
Procei* Option
No Action
H
N/A
H
N/A
ImplanMntablllty
Easily Implemented
Effect) v*n**e
Potentially effective over an
extended duration due to natural
attenuation of contaminant*.
Economics
Leatt eoatly alternative
Institutional Action
< / X X / /I ////// \ Already Implemented at •
WM)l*Mvtol*e/"l /D*«dR«ltrlj|(one/ Xl component of the OU-2 ROD
Nttural Anemutlen
H
Monitoring
Eeilly Implemented
Limit* risk by controlling direct Inexpensive to Implement
expoaure to contaminant*. Doe* not
prevent migration or actively treat
contamlnanta.
Potentially effective over an extended |n.xp9n.|Ve to Implement
duration. Effectlveneta can be evaluated
by lab treatablllty teit*. modeling and
monitoring to confirm degradation rate*.
Implementable.
Not effective In mitigating migration Moderately expentlve
of free phaia JP-4.
In Shu Treatment
Phyttcal
Biological
Bfovantlng
Difficult to maintain hydraulic Potentially effective. May require
control. Potential contaminant Injection of environmentally
tolublllty and me** raqulrea Injection ftalgnlflcant chemical* to Improve
treatment of large volume* of water, the aolublllty of contaminant*.
Implementable. Field pilot
teitt required.
Difficult to Implement. Difficult to
transport oxldant* to deep aollt.
Oxldant* will react with aolla
Implementable. Field pilot teit*
required.
Effective for remediation of fuel
hydrocarbon* In permeable aollt.
Limited effeetlvene** with fuel
hydrocarbon*.
Expensive. Significant
groundwatar extraction and
treatment lyitem required.
Economical method to
remediate vadoie zone. Normally
requlrea air pollution control*.
Not coat effective. Large amount*
of oxidizing agent required for
highly contaminated loll*.
Effeetlvene** depend* on *lte- Economical method to remediate
apaclflc characteriitlea auch at vadote xone. Air pollution
mlcroblal population, toll moltture. control* not normally required.
pH. nutrient*, pretence of Inhibitory
toxicant*. Generally effective for
removal of JP-4.
J • Retained
' ' '
flg0-2.dm/ltd/0*-20-fl6
Figure 6-2. Secondary Screening - Deep Soils at ST-12
-------
THRESHOLD CRITERIA
OVERALL PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT
Requires the assessment of alternatives to determine how they will provide
human health and environmental protection from the risks present at a site by
eliminating, reducing, or controlling the hazardous material detected during the
Remedial Investigation.
COMPLIANCE WITH ARARs
Requires the assessment of alternatives to determine how
ARARs meet the requirements under federal environmental
laws and state environmental or facility siting laws.
PRIMARY BALANCING CRITERIA
LONG-TERM EFFECTIVENESS AND PERMANENCE
This criterion requires the evaluation of residual risks remaining at a site after
completion of the remedial action.
SHORT-TERM EFFECTIVENESS
This criterion evaluates a remedial alternative's
Impact on human health and the environment
during implementation
IMPLEMENTABILITY
REDUCTION OF TOXICITY.
MOBILITY. AND VOLUME
This criterion addresses the statutory preference for selecting
remedial actions that permanently and significantly reduce
the toxicity, mobility, or volume of hazardous substances at a
site by evaluating the extent to which this Is achieved by
each alternative.
This criterion evaluates both the technical and
administrative feasjbility of Implementing an alternative
Including the availability of key services and material
required during Its Implementation.
MODIFYING CRITERIA
STATE ACCEPTANCE
This criterion addresses the statutory requirement for substantial and meaningful
state involvement. Evaluation of this criterion Is conducted by EPA and
addressed during development of the record of decision.
COST
Under this criterion, capital
costs, annual operation and
maintenance costs and the net
present value of capital O&M
costs are assessed for each
alternative.
COMMUNITY ACCEPTANCE
This criterion assesses the community's apparent preference
for, or concerns about, the remedial alternatives. This
process is conducted by EPA and addressed during
development of the record of decision.
Figure 6-3. Remedial Alternative Evaluation Criteria
KNfl066/WP3066P.6-3/05.22-96
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6.1 Alternative ST12-1: No Action
6.1.1 Source Treatment Component
The no-action alternative is evaluated as a remedial alternative in accordance with EPA
guidance to serve as a baseline for comparison with the other alternatives. This alternative
would leave the contaminated soil in place with no additional means to prevent accidental
exposure other than those measures already in place, such as fencing. Contaminants in the
subsurface soil may naturally attenuate. However, under Alternative ST12-1, the monitoring
and modeling required to evaluate the progress of natural attenuation would not be performed.
A review/reassessment of the site conditions would be performed in accordance with Section
300.430 of the National Contingency Plan (NCP) at 5-year intervals.
6.1.2 Source Containment Component
This alternative does not incorporate a containment component that would restrict the
migration of contaminants from soil to groundwater.
6.1.3 Groundwater Component
This remedial alternative does not incorporate a groundwater extraction and treatment
component
6.1.4 General Components
No institutional controls will be utilized in the implementation of this alternative. Ground-
water at the site would be sampled annually and analyzed for specified chemicals and/or
indicator parameters.
There are no implementation requirements of concern for this alternative.
The initial risk in implementing the remedial alternative is very low because no RA would be
taken at the site that could create potential exposures.
The residual risk for this alternative is higher than for the other alternatives because no action
would be taken to prevent the migration of contaminants to groundwater. Long-term
groundwater monitoring would be required to ensure that contaminants left in place do not.
impact groundwater.
KN/306£/WP3066£/DS-22-96
-------
There are no capital costs associated with this alternative. Initial capital cost of Alternative
ST12-1 is $0. The annual O&M cost is $0.4 million. The annual O&M cost includes $0.3
million for the cost of 5-year site reviews allocated over each year, and $0.4 million per year
for operation of the OU-2 groundwater remediation system. The estimate of operating cost
for the.OU-2 groundwater remediation system was obtained from the OU-2 ROD (IT, 1992b).
Detailed O&M costs for Alternative ST12-1 are presented in Appendix A. The net present
worm of Alternative ST12-1 was $0.7 million for O&M costs associated with 5-year site
reviews, and $9.6 million for O&M costs of the OU-2 groundwater remediation system for
the estimated 30 years required to meet remediation goals. This results in a total net present
worth for Alternative ST12-1 of $10.3 million.
5.7.5 Compliance with ARARs
Because this alternative does not incorporate any active remedial measures, ARARs are not
applicable.
63 Alternative ST12-2: Natural Attenuation
6.2.1 Source Treatment Component
Under Alternative ST12-2, no direct RA would be implemented. Contaminants in the deep
soil may naturally attenuate, resulting in a reduction in the mass of contaminants. The
aerobic degradation of fuel-contaminated soil by in situ remedial measures such as bio-
remediation and bioventing has been well demonstrated and supported in the scientific lite-
rature. However, the anaerobic degradation of fuel-contaminated soil by natural processes is
not as well documented, and is dependent on a number of site-specific characteristics.
Therefore, monitoring and modeling efforts would be conducted throughout the natural
attenuation process to confirm mat benzene and TPH degradation is proceeding at rates
consistent with RAOs described in Section 5.4.
6.2.2 Source Containment Component
This alternative does not incorporate a containment component that would restrict the
migration, of contaminants from soil to groundwater.
5.2.3 Groundwater Component
This remedial alternative does not incorporate a groundwater extraction and treatment
component because groundwater was addressed in the OU-2 ROD.
KN/3066/WP3066A05-22-96(lZ-02fmi) 6-3 D7/E1
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6.2.4 General Components
Natural attenuation would be in operation under the institutional action remedy (Figure 6-1)
and can be differentiated from the no-action remedy, Alternative ST12-1, because this
alternative would utilize biodegradation studies, modeling, and other evaluations to estimate
the rate at which natural biodegradation processes would attenuate the concentration of
benzene in the environment. These estimates would be used to technically evaluate the
suitability of natural attenuation as a remedial measure in comparison to active treatment
alternatives. Sampling and analysis would also be conducted throughout the natural attenua-
tion period to confirm mat benzene and JP-4 degradation is proceeding at rates consistent
with meeting RAOs. The evaluation and implementation of the no-action alternative does not
consider these technical factors and involves only a limited monitoring effort. Natural
attenuation has been chosen as the selected remedy at CERCLA sites where active remedial
measures are considered either technically impractical, or would not significantly accelerate
remediation time frames.
Over an extended period of time, natural biodegradation processes should continue to reduce
the benzene and TPH concentrations in soil to protective levels. However, significant
migrations of JP-4 constituents to groundwater could occur from highly contaminated zones
before natural biodegradation processes reduce COCs to PRGs. Institutional controls
implemented as a component of the OU-2 selected remedy could be left in place until a
determination is made that any potential residual risks are no longer significant. The OU-2
groundwater remediation system would continue to operate until RAOs are achieved for soil
and groundwater at ST-12.
The initial capital cost of Alternative ST12-2 is $0.2 million. The annual O&M cost for this
alternative includes $0.2 million per year for sampling, analysis, and data evaluation associat-
ed with monitoring the progress of natural attenuation in soil and groundwater, and $0.4
million per year for operation of the OU-2 groundwater remediation system. This results in a
total O&M cost of $0.6 million per year. Detailed O&M costs for Alternative ST12-2 are
presented in Appendix A. The net present worth of Alternative ST12-2 includes $5.1 million
for capital and O&M costs associated with natural attenuation studies, and $9.6 million for
the operation of the OU-2 groundwater remediation system for the estimated 30 years
required to meet remediation goals. It may be noted that the modeling efforts to determine
compliance in groundwater (Appendix F, OU-3 FS) assumed that a groundwater pump and
treatment system for OU-2, working in conjunction with natural attenuation in groundwater,
would result in compliance. This model also assumed that contamination in deep soil would
KN/3066/WP3066J5A>5-22-96(lZ-02piD) 6-4 D7/E1
-------
not be remediated or attenuated naturally and would be leaching to groundwater. Thus, the
modeling effort assumed that natural attenuation, not in isolation, but in conjunction with the
groundwater treatment system, would require 30 years; therefore, the 30 years required by the
groundwater treatment system for OU-2 to be in compliance is included in the cost estimates
for the natural attenuation alternative (ST12-2). This results in a total net present worth for
Alternative ST12-2 of $14.7 million.
6.2.5 Compliance with ARARs
The ARARs appropriate for this alternative are presented in Appendix B.
The action-specific ARAR concerning air emissions during remediation is not applicable to
Alternative ST12-2 because this alternative will not generate any air emissions.
The action-specific ARAR concerning surface water control is considered an appropriate
requirement. The alternative will meet this requirement by providing storm water collection
in areas where soil cuttings are stored.
The action-specific ARAR concerning on-site container storage is an applicable requirement.
The alternative win comply with the requirements of Resource Conservation and Recovery
Act (RCRA) Section 40 Code of Federal Regulations (CFR) 264 concerning the handing,
inspection, and maintenance issues associated with the storage of soil cuttings.
The action-specific ARAR concerning concentration limits on treated water discharged to a
publicly owned treatment works (POTW) is not applicable to Alternative ST12-2 because this
alternative will not generate any water discharge.
6.3 Alternative ST12-3: Soil Vapor Extraction
6.3.1 Source Treatment Component
This alternative would volatilize contaminants from the subsurface by imposing a vacuum on
the subsurface soil through a series of vadose zone extraction wells. The contaminants in the
extracted sofl gas would subsequently be destroyed by a fume incineration system. A typical
process flow diagram for an SVE system is presented in Figure 6-4.
Based on the nature and extent of contamination determined in the remedial investigation, a
preliminary design was calculated for a SVE well network. This could consist of 33 4-inch
KN/3066AVP3066.«A>5-22-96(12.02J>m) 6-5 D7/E1
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TREATED VAPOR
TO ATMOSPHERE
•AUXIUARY FUEL
(NATURAL GAS
OR PROPANE)
CONDENSED WATER
CONTAINER
(TO TREATMENT)
FIGURE 6-4
SOIL VAPOR EXTRACTION (SVE) SYSTEM
CONCEPTUAL FLOW DIAGRAM
DEEP SOILS AT LIQUID FUELS
AREA (ST-12)
OU-2. WILLIAMS AFB
INTERNATIONAL
TECHNOLOGY
CORPORATION
-------
extraction wells screened over varying depths, and 11 4-inch-diameter passive vent wells that
will provide a conduit for air into the deep soil formations. The cost estimates in this RODA
are based on these preliminary designs. The final number of wells will be based on the
results of sofl and groundwater treatability studies, with the concurrence of the Parties to the
FFA. The numbers and costs stated herein could therefore change. The vacuum system
would consist of two vacuum exhausters rated for 18 inches of vacuum with a combined flow
capacity of approximately 2,000 standard cubic feet per minute (scfin). The fume incineration
system would be rated for a 90 percent destruction efficiency at 3,000 scfin. Fume incihera-
• tion was selected over carbon adsorption as the air pollution control technology because the
high concentrations of organics present in the extracted soil gas during the early periods of
SVE system operation would consume large quantities of activated carbon, making this option
economically infeasible. Water entrained in the extracted air would be removed by an
air/water separator on the SVE skid. The water would be collected in a 55-gallon drum or a
tote tank for subsequent transportation to and treatment by the groundwater treatment system
at ST-12. The quantity of extracted water is anticipated to be very small, based upon the
results of the SVE pilot test conducted on the shallow soil at ST-12. Details pertaining to the
conceptual design for the SVE treatment system and estimating the duration of RA are
presented in Appendix E2 of the OU-3 FS (TT, 1995).
It is estimated that the SVE system could achieve PRGs for benzene and TPH in approxi-
mately 8 years. Approximately 21,400 kg of benzene and 1,885,750 kg of TPH would have
to be extracted from the deep soil to reach PRGs.
6.3.2 Source Containment Component
The remedial alternative does not incorporate a groundwater extraction and treatment
component because groundwater was addressed in the OU-2 ROD (IT, 1992b).
6.3.3 Groundwater Component
The remedial alternative does not incorporate a groundwater extraction and treatment
component because groundwater was addressed in the OU-2 ROD (IT, 1992b).
6.3.4 General Components
Short-term risks would be minimal because air emissions would be controlled. Fume
incineration is an extremely effective air pollution control technology. A 90 percent destruc-
tion efficiency would ensure that Alternative ST12-3 would comply with ARARs concerning
volatile organic compounds (VOC) emissions from remediation operations. Risk to workers
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from exposure during well drilling and trenching operations can be controlled by proper
protective equipment. Short-term risks include potential release of contaminants in the event
the air pollution control system malfunctions. However, the incorporation of operating alarms
and interlocks into the treatment system design would mitigate this problem. There is a
potential for workers to be exposed to fugitive contaminant vapors during operation of the
system. SVE is a technically straightforward and well-proven process and should be reliable
in performing as designed.
Periodic monitoring of the extracted air prior to emission control could be used to monitor the
progress of remediation by estimating the rate of contaminant removal and the total mass of
contaminants removed. Periodic monitoring of residual contaminant levels in the soil would
be necessary to determine when the RA is complete. No long-term management, monitoring,
or periodic site reviews would be required after remedial activities are complete.
The initial capital cost of Alternative ST12-3 is $2.6 million. The annual O&M cost for this
alternative includes $0.6 million per year for operation of the SVE treatment system, and $0.4
million per year for operation of the OU-2 groundwater remediation system. This results in a
total O&M cost of $1.0 million per year. Detailed annual O&M costs are presented in
Appendix A. The net present worth of Alternative ST12-3 includes $7.1 million for capital
and O&M costs associated with construction and operation of the SVE system, and $2.8
million for the operation of the OU-2 groundwater remediation system for the estimated 8
years required to meet remediation goals. This results in a total net present worm for
Alternative ST12-3 of $9.9 million.
5.3.5 Compliance with ARARs
The ARARs appropriate for this alternative are presented in Appendix B.
The location-specific ARAR concerning the protection of significant archaeological artifacts is
a relevant and appropriate requirement. Prior to the initiation of any remedial activities at the
site, remedial plans will be reviewed with the State Historic Preservation Officer (SHPO) to
obtain his approval. If any obvious archaeological artifacts are encountered during remedial
operations, work will be stopped and die SHPO will be consulted. Through these actions,
Alternative ST12-3 would comply with the archaeological ARAR.
The action-specific ARAR concerning air emissions during remediation is an applicable
requirement This requirement will be met through the application of fume incineration to
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soil gas extracted by the SVE system. The fume incinerator would be designed, operated, and
maintained to ensure compliance with this ARAR.
The action-specific ARAR concerning the treatment of extracted soil moisture will be met by
containerizing the water in a 55-gallon drum or a tote tank for subsequent transport to and
treatment by the ST-12 groundwater treatment system. Currently, the treated groundwater at
ST-12 is discharged to the sanitary sewer and must comply with pretreatment limits in the
Base's permit with the local POTW. In the future, the treated water may be reinjected at ST-
12. At that time, the treated water would have to comply with reinjection standards.
6.4 Alternative FJ02-5: Bioventing
6.4.1 Source Treatment Component
This alternative would deliver oxygen to contaminated unsaturated deep soils by forced air
movement to stimulate aerobic metabolism of fuel hydrocarbons by indigenous soil microor-
ganisms. Depending on site characteristics, bioventing systems can be designed to supply
oxygen to the subsurface by blowing air into the soil under positive pressure, extracting air
from the soil under vacuum, or a combination of both. The preferred method is typically to
supply air to the subsurface under positive pressure. This mode of operation eliminates point
source air emissions that may require air pollution controls. A bioventing system would
supply air to the subsurface using a blower (positive pressure) or exhauster (vacuum), piping
system, and a network of air injection or extraction wells screened in the deep contaminated
soils. Air would be supplied to the soil at rates that would provide sufficient oxygen to
stimulate biodegradation while irriinimizing volatilization and release of contaminants to the
atmosphere. As a result, bioventing systems typically operate at 10 to 30 percent of the air
flow requirement for an SVE system in the same application. The bioventing system would
also include the installation of a number of narrowly screened soil gas monitoring points to
sample gas in short vertical sections of the soil. These points are used to monitor local
oxygen concentrations. A block flow diagram for a bioventing treatment system is presented
in Figure 6-5.
The preliminary design is based on air extraction (using vacuum) rather than air injection
(using positive pressure) because the contaminated soil is deep and spread over a relatively
wide area. Air injected into the formation would have to displace resident soil gas and push
it to the surface. The injected air must be supplied at a pressure sufficient to overcome the
resistance to flow presented by the torturous path the displaced sofl gas must travel from the
KN#066/WP3066.6A>5-22-96<12:02fmi) 6-8 D7/E1
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-I
a
i
TREATED VAPOR
TO ATMOSPHERE
BLOWER
(OPTIONAL)
- AUXILIARY FUEL
(NATURAL GAS
OR PROPANE)
VENT/INJECTION
WELL SYSTEM
CONDENSED WATER
CONTAINER
(TO TREATMENT)
FIGURE 6-5
MICROORGANISMS
DEGRADE CONTAMINANTS
BIOVENTING SYSTEM
CONCEPTUAL FLOW DIAGRAM
LIQUID FUELS STORAGE AREA (ST-12)
DEEP SOIL AT OU-2
WILLIAMS AFB
INTERNATIONAL
TECHNOLOGY
CORPORATION
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injection point through the upper soils to the surface. The resistance to flow increases as air
is supplied deeper into the subsurface and the air flow path to the surface becomes longer.
The resistance to flow is also affected by the soil type, as fine grain soils present more
resistance to flow. Other bioventing design configurations (e.g., air injection) are possible,
but a system designed to operate in an air injection mode would probably require more
powerful blowers and additional wells. No attempt has been made during this stage of
preliminary design to optimize the design of the treatment system, and the most effective
mode of operation will be determined after field treatability studies and pilot tests are
completed.
If site conditions are favorable for the implementation of bioventing, this alternative should
reduce the concentrations of benzene and TPH in deep soil to respective PRGs of 5 and 2,000
mg/kg. Based on the system configuration previously described, it is estimated that bioven-
ting would require 26 years to reduce contaminant concentrations in the deep soil to PRGs.
6.4.2 Source Containment Component
The alternative does not incorporate a containment component that would restrict the
migration of contaminants from soil to groundwater. A containment component is not
required because the treatment component would effectively remediate the contaminated soil.
6.4.3 Groundwater Component
The remedial alternative does not incorporate a groundwater extraction and treatment
component because groundwater contamination was addressed in the OU-2 ROD.
5.4.4 General Components
There are no major implementation concerns associated with the construction and operation of
a bioventing system. The units operate with limited operator attention. Initial monitoring of
ambient air, similar to mat for FT-02 soils (OU-3), in the vicinity of the treated soil would be
required to confirm compliance with Maricopa County air quality standards.
Short-term risks will be similar to those described in Section 6.3.4 for SVE.
No long-term management, monitoring, or periodic site reviews would be required after
remedial activities are complete. Sampling and analysis of subsurface soil would be used to
confirm that the alternative has met RAOs. It is unlikely that the alternative would not
accomplish RAOs at the site once a field treatability test has been conducted to predict its
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effectiveness. However, if bioventing proved to be ineffective after implementation, a
properly designed system could be convertible to an SVE system with some equipment
replacements or modifications. Nevertheless, the OU-2 groundwater remediation system
would remain in operation until RAOs are achieved for soil and groundwater at ST-12.
The initial capital cost of Alternative ST12-4 is $2.5 million. The annual O&M cost for this
alternative includes $0.3 million per year for operation of the bioventing treatment system,
and $0.4 million per year for operation of the OU-2 groundwater remediation system. This
results in a total O&M cost of $0.7 million per year, with details provided in Appendix A.
6.4.5 Compliance with ARARs
The ARARs appropriate for this alternative are presented in Appendix B.
6.5 Alternative ST12-5: Synergistic Alternative, SVE, Bioventing, and Natural
Attenuation
6.5.1 Source Treatment Component
Alternative ST12-5 is a synergistic combination of the technologies in Alternatives ST12-2,
-3, and -4 applied in a targeted and phased approach. This alternative is postulated to
accomplish remediation goals in the most cost-effective manner by combining the best
attributes of the previous three alternatives. SVE would be applied in areas with the highest
contamination where significant migration of contaminants to groundwater could occur if
remediation goals were not accomplished in a timely manner. Bioventing would be applied in
areas where me impact of contaminant migration to groundwater is not a significant short-
term threat, such as areas of more moderate contamination, or areas in the upper zone of the
deep soil. Soil in areas where the concentration of contaminants represent no significant
long-term migration threat to groundwater would be allowed to naturally attenuate. Alter-
natively, these individual process options could be applied in a sequential approach in some
areas. For example, SVE could be applied to heavily contaminated soil to quickly remove the
volatile components, and the system could be reconfigured for bioventing to remediate the
semivolatile components of JP-4 that are not as easy to remove with SVE. Also, soil mat
have been partially remediated by SVE or bioventing such that the threat of contaminant
migration to groundwater has been significantly reduced may be allowed to naturally
attenuate.
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This alternative should reduce the concentration of contaminants in the deep soil at the ST-12
site to levels below the PRGs.
6.5.2 Source Containment Component
The alternative does not incorporate a containment component that would restrict the
migration of contaminants from soil to groundwater. A containment component is not
required because the treatment component would effectively remediate the contaminated soil.
6.5.3 Groundwater Component
The remedial alternative does not incorporate a groundwater extraction and treatment
component because groundwater was addressed in the OU-2 ROD.
6.5.4 General Components
Periodic soil gas monitoring and in situ respiration tests would be required for the SVE/bio-
venting systems to assess the effectiveness of operation and determine set points for operating
parameters. Sampling and analysis of subsurface sofl would be used to confirm mat the
alternative has met PRGs. The OU-2 groundwater remediation system would remain in
operation until RAOs are achieved for sofl and groundwater at ST-12.
Short-term risks will be similar to those described for the SVE alternative in Section 6.3.4.
It is estimated that Alternative ST12-5 would achieve the RAOs for the site within approxi-
mately 9 years.
The initial capital cost of Alternative ST12-S is $2.8 million. The annual O&M cost for this
alternative includes $0.4 million per year for operation of the SVE/bioventing treatment
system, and $0.4 million per year for operation of the OU-2 groundwater remediation system.
This results in a total O&M cost of $0.8 million per year. Detailed annual O&M costs are
presented in Appendix A.
6.5.5 Compliance with ARARs
The ARARs appropriate for this alternative are presented in Appendix B.
Compliance with location- and action-specific ARARs is achieved in the manner presented for
Alternatives ST12-3 and ST12-4.
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7.0 Comparative Analysis of Alternatives
The final phase in the evaluation of remedial alternatives for deep soil at ST-12 involves a
comparison of various alternatives. The advantages and disadvantages of each alternative are
reviewed relative to each of the nine EPA evaluation criteria used in the previous detailed
analyses. For each criterion, the apparent best alternative is identified first, with the other
alternatives presented in order relative to this alternative.
7.1 Overall Protection of Human Health and the Environment
All of the alternatives are determined to be protective of human health for the following
reasons:
• No direct pathway exists for potential receptors to be exposed to contaminated
deep soil.
• The OU-2 groundwater remediation system intercepts and treats contaminants
migrating from deep soil into groundwater such that they will not present an
acceptable human health risk at the OU-2 compliance point.
• Institutional controls have been implemented as a component of the OU-2
selected remedy to prevent excavation in ST-12 soil greater than 10 feet below
ground surface and construction of a drinking water well in the contaminated
aquifer underneath ST-12.
• Groundwater downgradient of the contaminated deep soil is periodically moni-
tored to ensure the OU-2 groundwater remediation system is adequately pro-
tective of human health.
Alternative ST12-3 would be most protective of the environment because it would remediate
deep soil contaminants to PRGs in the shortest duration (8 years). Alternative ST12-S would
protect the environment by reducing soil contaminants to PRGs in approximately 9 years.
Alternative ST12-4 would protect the environment by reducing soil contaminants to PRGs
over an estimated 26 years. Alternative ST12-2 would be less protective of the environment
than any of the active remedial measures. Because no reliable data exists on natural
attenuation of JP-4 in soil, it is difficult to predict its effectiveness. Significant migration of
JP-4 to groundwater could occur from highly contaminated zones before natural biodegra-
dation process would reduce soil contaminants to concentrations that would be protective of
the environment. However, the long-term monitoring associated with Alternative ST12-2
would permit periodic reassessments to determine if the progress of natural attenuation is
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consistent with RAOs. In the absence of any natural biodegradation in the deep soil, it is
estimated that 30 years would be required before sufficient contaminants have migrated from
soil such that further migration would be limited in nature and consistent with RAOs. It may
be noted that the modeling efforts to determine compliance in groundwater (Appendix F, OU-
3 FS) assumed that a groundwater pump and treat system for OU-2, working in conjunction
with natural attenuation in groundwater, would result in compliance. This model also
assumed that contamination in deep soil would not be remediated or attenuated naturally and
would be leaching to groundwater. Thus, the modeling effort used natural attenuation in
conjunction with the groundwater treatment system and yielded a 30-year estimate for OU-2
to be in compliance. Alternative ST12-1 would not be protective of the environment because
no active RAs would be implemented, and no monitoring would be conducted to evaluate the
progress of natural attenuation or determine the environmental impact of contaminant
migration.
7.2 Compliance with ARARs
No chemical-specific ARARs exist for COPCs in soil. ARARs for alternatives ST12-2
through ST12-5 are presented in Appendix B. ARARs are not applicable for Alternative
ST12-1. Alternatives ST12-2 through ST12-5 would meet all applicable action- and location-
specific ARARs.
7.3 Long-Term Effectiveness and Permanence
Alternatives ST12-3 through ST12-5 present approximately equivalent measures of long-term
effectiveness and permanence by permanently reducing soil contaminants to PRGs, which
would prevent the future migration of contaminants to groundwater at levels that would not
be protective of human health at the OU-2 groundwater compliance point. Alternative ST12-
2 should eventually reduce contaminants to PRGs, but it is not clear that the majority of this
reduction would occur as a result of natural biodegradation. Migration to groundwater might
be the dominant natural attenuation process. However, the operation of the OU-2 ground-
water remediation system would mitigate the impact of deep soil contaminants on ground-
water. Alternative ST12-1 does not achieve long-term effectiveness or permanence because
the alternative does not incorporate a monitoring component that would confirm eventual
compliance with RAOs. As with Alternative ST12-2, the dominant natural attenuation
process may be migration of contaminants to groundwater.
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7.4 Reduction of Toxicity, Mobility, or Volume Through Treatment
Alternatives ST12-3 through ST12-5 would provide approximately equivalent degrees of
toxicity reduction, because all are capable of reducing contaminant levels to PRGs and of
effecting irreversible destruction of contaminants. By reducing the concentration of TPH in
soil to PRGs, Alternatives ST12-3 through ST12-5 also eliminate further migration of free-
phase JP-4. These three alternatives satisfy the statutory preference for treatment. Alter-
natives ST12-1 and ST12-2 do not actively remediate soil and, therefore, do not satisfy the
statutory preference for treatment. These alternatives may eventually reduce the level of JP-4
in soil to PRGs through natural attenuation. However, it is not clear mat a significant degree
of toxicity reduction would be involved, because migration to groundwater may be the
dominant natural attenuation process. For all alternatives, migration of contaminants to
groundwater during the remediation process would be mitigated by the operation of the OU-2
groundwater remediation system (IT, 1992b).
7.5 Short-Term Effectiveness
Alternative ST12-3 is the most effective in the short term because it would achieve RAOs in
the shortest duration and minimize the environmental impact of JP-4 migration to ground-
water. Alternative ST12-5 would be effective by meeting RAOs in approximately 9 years.
Alternative ST12-4 would also be effective during the remedial period, but because this
alternative would take longer to reach PRGs, a larger mass of JP-4 could potentially migrate
to groundwater in comparison to Alternatives ST12-3 and ST12-5. Alternatives ST12-1 and
ST12-2 would be the least effective over the short term. Even though these alternatives
present slightly less risk to the community or site workers than Alternatives ST12-3 through
ST12-5, no active effort would be made to prevent the migration of JP-4 to groundwater.
This could result in an extension of institutional actions and RAs at ST-12 implemented under
the OU-2 ROD (TT, 1992b).
A significant uncertainty is associated with the estimates of remedial duration for all of the
alternatives. In terms of relative uncertainty, the estimate for ST12-3 is probably the most
reliable, with correspondingly increasing degrees of uncertainty associated with Alternatives
ST12-5, ST12-4, and ST12-2.
7.6 Implementabllity
Alternative ST12-1 is the easiest to implement because no action is taken. Alternative ST12-
2 is also relatively easy to implement because only long-term monitoring is required.
Alternatives ST12-3 through ST12-5 are relatively equivalent in terms of implementability.
KN/3066/WP3066.7A>5-2246(12.-C3pm) 7-3
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7.7 Cosf
Table A-l, Appendix A summarizes the estimated capital, O&M, and present worth cost for
.each of the five remedial alternatives. Alternative ST12-5 has the lowest net present value of
any alternative ($9.6 million). It has the highest initial capital cost, but the overall net present
value is low due to its relatively short remedial duration. Alternative ST12-3 has the second
lowest net present value ($9.9 million). Although this alternative has the second highest
initial capital cost, its overall net present value is low because it has the shortest remedial
duration. Alternative ST12-1 has a net present value of $10.3 million. There are no initial
capital costs associated with this alternative, but it has a remedial duration estimated to be 30
years. Alternative ST12-2 has a net present value of $14.7 million. The initial capital costs
are low, but the estimated 30-year remedial duration inflates the net present value. Alter-
native ST12-4 has the highest net present value of all the remedial alternatives ($18.4
million). It has the lowest initial capital cost of the active remedial alternatives, but has an
estimated remedial duration that is more than double that of Alternative ST12-3.
The difference in net present value between the alternatives are all within the margin of error
of the cost estimates. In particular, the cost estimates are very sensitive to the estimated
period of RA. The RA duration of each alternative has been estimated using best engineering
judgement. However, additional engineering data would be required to refine the RA
duration for each alternative. The RA duration of several of the alternatives is heavily
dependent on the rate of biodegradation in soil and/or groundwater. Therefore, it is recom-
mended that an SVE, bioventing, and natural attenuation treatability study be conducted to
optimize the location and volume of soil to which each technology should be applied. The
final decision on the preferred remedy can then be based on these results.
•
7.8 Support Agency Acceptance
The various remedial alternatives will be evaluated after comments from state support
agencies and the public have been received on the OU-2 proposed plan amendment.
7.9 Community Acceptance
The various remedial alternatives will be evaluated after public comment has been received
on the OU-2 proposed plan amendment.
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8.0 Selected Remedy
The selected remedy for the deep sofl at ST-12 is Alternative ST12-5: synergistical alter-
native, SVE, bioventing, and natural attenuation. The specific components of this alternative
were presented in summary form in Section 6.5 and are fully described in this section.
Alternative ST12-5 satisfies the two threshold criteria, overall protection of human health and
the environment and compliance with ARARs, and provides the best balance of the nine
criteria presented in Figure 6-3. The selected remedy will provide the greatest level of
effectiveness that is technically and economically feasible. The criterion of protection of
human health and the environment is appropriately balanced with both effectiveness and
technical/economic feasibility.
8.1 Major Components of the Selected Remedy
Alternative ST12-5 is a synergistic combination of Alternatives ST12-2, ST12-3, and ST12-4.
This alternative endeavors to accomplish remediation goals in the most cost-effective manner
by combining the best attributes of the SVE, bioventing, and natural attenuation remedial
alternatives. SVE would be applied in areas with the highest contamination where significant
migration of contaminants to groundwater could occur if cleanup goals were not accomplished
in a timely manner. Bioventing could be applied in areas where the impact of contaminant
migration to groundwater is not a significant short-term threat, such as areas of more
moderate contamination, or areas in the upper zone of the deep soil. Soil in areas where the
concentration of contaminants represent only a limited long-term migration threat to ground-
water could be allowed to naturally attenuate. Alternatively, these individual process options
could be applied in a sequential approach in some or all areas. For example, SVE could be
applied to heavily contaminated sofl to quickly remove the volatile components, and the
system could be reconfigured for bioventing to remediate the semivolatfle components of JP-4
that are not as amenable to treatment via SVE. Also, sofl that has been partially remediated .
by SVE or bioventing such that the threat of contaminant migration to groundwater has been
significantly reduced may be allowed to naturally attenuate. The proper mix of these three
process options would be defined after the appropriate treatability studies are completed to
determine the relative effectiveness of each remedial component.
Field treatability studies are recommended to better predict the effectiveness of SVE,
bioventing, and natural attenuation with respect to site-specific conditions, and determine the
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staging points at which each technology should be implemented. After these field treatability
studies are completed, the proper staging of each of these remedial technologies can be made
at various areas of the site to maximize their effectiveness.
An SVE field treatability test is recommended to confirm the effectiveness of this remedial
technology and determine important design parameters such as soil gas permeability and the
organic composition of soil gas. These values would be used to size the vacuum exhauster
system and the fume incinerator. The soil gas flow rate and initial gas composition would
also be used to calibrate an SVE model to predict the duration of this component of the
overall RA.
A bioventing field treatability test is recommended to determine that site conditions such as
soil moisture, pH, permeability, oxygen utilization, and nutrients are adequate to support its
implementation. The results of this testing would be used in predictive models to determine
those areas where bioventing could be appropriately applied such that RAOs are cost-
effectively achieved. The results of the bioventing tests would also be used to determine its
effectiveness and predict the duration of this component of the overall RA.
A natural attenuation treatability study is recommended to estimate the rate at which natural
biodegradation processes remove COCs from soil and groundwater. The results of these tests
will be used in conjunction with predictive transport models to determine natural attenuation
effectiveness and identify those areas where it can be appropriately applied such that RAOs
are cost-effectively achieved. Because an assumed biodegradation factor in groundwater was
used in the calculation of cleanup levels for deep soil, the results of natural attenuation
studies for groundwater will also be used to confirm the protectiveness of these cleanup levels
based on the biodecay factor.
Because the deep soil at ST-12 presents no direct threat to human health via exposure to
contaminated soil, the objectives of conducting RAs are to reduce the time required to effect
groundwater cleanup and to remove sources of JP-4 that may continue to impact groundwater,
thereby minimizing the cost of remediating the entire site. The cleanup levels for deep soil
were determined through a computer modeling approach used to estimate the migration rate
of chemicals from ST-12 deep soil to groundwater. Vadose zone and groundwater transport
models were used to calculate the soil concentrations for individual compounds that would
not result in groundwater concentrations at the compliance point in excess of cleanup levels,
and the TPH concentration at which the residual deep soil contamination would no longer
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represent a viable source of contamination to groundwater. The ST-12 groundwater compli-
ance point is to be determined in the future based upon the mutual agreement of the parties to
the FFA. The selected remedy will be implemented in the deep soil until the cleanup level of
5 mg/kg benzene has been attained. In addition, the JP-4 contamination in the deep soil,
measured as TPH, will be reduced to a concentration of 2,000 mg/kg. These cleanup levels
are to be considered as target concentrations that are subject to change. Enforceable cleanup
levels will be established by the Parties to the FFA after additional post-ROD information is
collected, such as natural attenuation treatability data for soil and groundwater, performance
data for the ST-12 groundwater extraction system, SVE and bioventing pilot test data, and
other pertinent field data (e.g., groundwater elevation data).
Approximately 422,000 cubic yards of contaminated soil requires RA to achieve the RAOs
for the deep soil. It was estimated during the OU-3 FS that the successful remediation of the
deep soil will result in the volatilization and thermal destruction or biodegradation of approxi-
mately 21,400 kg of benzene and 1.9 million kg of TPH.
In the absence of site-specific treatability data for SVE and bioventing in the deep soil, a
computer model approach was used during the OU-3 FS to estimate the parameters (i.e.,
vacuum and air flow) required to develop a preliminary treatment system design and predict
the duration of RA. It was estimated that 33 air extraction/injection wells would be con-
structed at ST-12 based on the projected area and depth of soil requiring remediation. The
final number of wells will be based on die results of soil and groundwater treatability studies,
with the concurrence of the Parties to the FFA. The numbers and costs stated herein could
therefore change. A preliminary air extraction/injection well layout is presented in Figure 6-
4. The extraction wells were assumed to be 4 inches in diameter, screened over a 35-foot
interval, with a 40-foot radius of influence. The treatment system would be sized to operate
initially as an SVE system at a total air flow rate of 2,000 scfm at 15 inches of mercury
vacuum. The system would be constructed to be convertible to a bioventing system operating
at approximately 600 scfm. In estimating the remedial duration required to achieve RAOs, it
was assumed that the treatment system would operate in an SVE mode for the first 2 years of
operation, and then in a bioventing mode for approximately 7 more years. At the end of this
period, the remaining deep soil contamination would be allowed to naturally attenuate.
A fume incinerator will be required to control emissions from the SVE system. Based upon
the results of the computer model used to predict the concentration of organic compounds in
extracted soil gas, it is estimated that the fume incinerator would be sized for 3,000 scfm of
air flow, and a heat duty of 10 million British thermal unit (Btu) at 1400°F. The concentra-
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tion of VOCs in the exhaust duct from the fume incinerator wfll be monitored at start-up to
confirm that the system is in compliance with Maricopa County Air Pollution Control
Division requirements.
Operation of the fume incinerator may not be required during bioventing, depending on the
final design and operating configuration of the bioventing system. Bioventing systems that
are operated in an air injection configuration do not typically require emission controls
because the potential for volatile emissions is very low. Bioventing systems are characterized
by a low rate of air injection. Because the horizontal permeabilities of the ST-12 deep soil is
typically greater man the corresponding vertical permeabilities, and the most highly contami-
nated soil are at significant depths, the injected air will tend to move outward rather than
upward. This will promote in situ biodegradation of organic vapors as they move slowly
outward from the air injection zone. To ensure compliance with Maricopa County Air
Pollution Control Division requirements, a surface emission monitoring program will be
initiated following start-up of the bioventing phase of the RA.
Soil and soil gas monitoring will be conducted periodically during the operation of the
treatment system to evaluate the effectiveness of the RA and determine when cleanup levels
have been met. The details of the monitoring program will be determined during the RD/RA
process.
No institutional or engineering controls will be required for the deep soil after the remedy has
achieved cleanup goals.
Because field treatability tests have not yet been performed to evaluate the relative effec-
tiveness of each treatment component, some changes may be made to the design of the
selected remedy as presented here after additional information is gathered. In general, these
changes reflect modifications to the remedy resulting from the engineering design process.
The size and configuration of the treatment system components wfll be finalized during RD •
after all field treatability tests have been completed.
8.2 Cost
The initial capital cost of the selected remedy is $2.8 million. As shown in Appendix A,
Table A-9, this includes the cost of the SVE, bioventing, and natural attenuation treatability
tests; SVE and bioventing treatment system design, construction, and start-up; and the
monitoring required to document the effectiveness of natural attenuation processes.
KN/3066/WP3066-M>5-22-96(lZ-OSj>ni) 8-4 D7/E1
-------
The annual O&M cost for the selected remedy includes $0.4 million per year for operation of
the SVE/bioventing treatment system, and $0.4 million per year for operation of the OU-2
groundwater remediation system. This results in a total O&M cost of $0.8 million per year.
Detailed annual O&M costs are presented in Appendix A, Table A-10 and A-ll.
The net present worth of the selected remedy includes $6.4 million for capital and O&M
costs associated with construction and operation of the SVE/bioventing system, and $3.2
million for the operation of the OU-2 groundwater remediation system for the estimated 9
years required to meet cleanup goals. This results in a total net present worth for the selected
remedy of $9.6 million.
KN/3066/WP3066.8A>5-22-96(12.-05pin) 8-5 OT/E1
-------
9.0 Statutory Determinations
Under Section 121 of CERCLA, the selected remedy must be protective of human health and
the environment and must comply with all ARARs. The selected remedy also must be cost-
effective and utilize permanent solutions and alternative treatment technologies to the
maximum extent practicable. Remedies that employ treatment options that permanently and
significantly reduce the volume, toxicity, or mobility of hazardous wastes as a major part of
the remedy are preferable. This chapter discusses how the selected remedy meets these
requirements.
The State of Arizona and the communities surrounding Williams AFB were involved in the
determination of the selected remedy. The state was represented in the process by ADEQ and
Arizona Department of Water Resources (ADWR), both of whom are parties to the FFA.
They have been intrinsically involved in the review and approval of all documents and
decisions concerning the various stages of the remedial process, including all work plans,
RI/FS reports, proposed plans, and RODs.
The communities surrounding Williams AFB have been involved in the decision-making
process through the Technical Review Committee, the Restoration Advisory Board, and
through public meetings and comment periods on proposed remedies and removal actions.
Chapter 11.0 of this document addresses the communities' involvement in more depth.
Alternative ST12-5 (synergistic alternative, SVE, bioventing, and natural attenuation) was the
selected remedy. The selected remedy represents the best balance among alternatives with
respect to the pertinent criteria, given the scope of this action.
9.1 Protection of Human Health and the Environment
The deep soil at ST-12 presents no direct threat to human health because the soil are a
minimum of 25 feet below ground surface; therefore, there are no complete exposure
pathways to the contaminated soil. The groundwater beneath ST-12 soil is contaminated with
JP-4 constituents. A free-phase layer of JP-4 is floating on top of the groundwater. Vadose
zone transport modeling performed during the OU-3 Rl predicted that the contaminants from
JP-4 in the deep soil would continue to migrate to groundwater for many years if no action
was taken to remediate the deep soil. Although the deep soil contamination presents no direct
KN/3066/WP30665/05-22-96(lZ-09pm) 9-1 DS/E1
-------
threat to human health, the implementation of the selected remedy would minimize the future
impact of deep soil contamination on groundwater by removing organic contaminants through
in situ biodegradation and/or soil gas extraction followed by thermal destruction.
9.2 Compliance with ARARs
The selected remedy of SVE, bioventing, and natural attenuation will comply with all
chemical-, action-, and location-specific ARARs. A discussion of the pertinent ARARs
follows.
9.2.1 Chemical-Specific ARARs
No statutory limits have been promulgated by state or federal regulatory authorities for
organic contaminants in soil. Therefore, chemical-specific ARARs do not exist for soil.
9.22 Location-Specific ARARs
The ARAR concerning the protection of significant archaeological artifacts is a relevant and
appropriate requirement. Prior to the initiation of any remedial activities at the site, remedial
plans will be reviewed with the SHPO to obtain his approval. If any obvious archaeological
artifacts are encountered during remedial operations, work will be stopped and the SHPO will
be consulted. Through these actions, die selected remedy would comply with the archaeologi-
cal ARAR.
Action-Specific ARARs
The ARAR concerning air emissions during remediation is an applicable requirement. The
Maricopa County Air Pollution Control Division places a 3-pound-per-day limit on uncon-
trolled VOC emissions during remedial operations. This requirement will be met during
operation of the SVE treatment system by thermally destroying organic contaminants in
extracted soil gas via fume incineration. The fume incinerator will be designed, tested,
operated, and maintained to ensure compliance with this limit. It is anticipated that the
operation of the bioventing system will not require emission controls because soil gas is
typically not extracted from the subsurface. However, a surface emission monitoring program
will be initiated following start-up of the bioventing system to ensure compliance with the
VOC limit
The ARAR concerning surface water control is considered an appropriate requirement. The
selected remedy will meet this requirement by providing storm water collection in areas
where soil cuttings are stored.
9~2 D5/E1
-------
The ARAR concerning on-site container storage is an applicable requirement. The selected
remedy will comply with the requirements of RCRA Section 40 CFR 264 concerning the
handing, inspection, and maintenance issues associated with the storage of soil cuttings.
The ARAR concerning the treatment of extracted soil moisture will be met during operation
of the SVE system by containerizing the water in a 55-gallon drum or a tote tank for subse-
quent transport to and treatment by the ST-12 groundwater treatment system. Treated
groundwater at ST-12 has been discharged to the sanitary sewer and complied with pretreat-
ment limits in the Base's permit with the local POTW. In the future, the treated water may
be reinjected at ST-12. However, based on results of field treatability studies and natural
attenuation testing, either groundwater withdrawal may not be required or if required, treated
water could be discharged to the sanitary sewer or reinjected. At the time, a decision is
made, any treated water would comply with reinjection standards. Because bioventing
systems do not typically extract vapors from the subsurface, water collection and treatment ,
equipment would not be necessary during this mode of operation.
9.3 Cost Effectiveness
The selected remedy was evaluated for cost effectiveness against the other four potential
remedial alternatives that were subjected to a detailed analysis in the OU-3 FS report. The
selected remedy has the lowest net present value of all the alternatives when its impact on the
duration of groundwater remediation is factored into the cost analysis. Because the selected
remedy has the potential to minimize the duration of groundwater remediation, its implemen-
tation as a component of the overall RA at ST-12 should result in reducing the total cost to
clean up the site.
The methodology used to calculate the comparative costs of the various remedial alternatives
is based on a number of assumptions that may be validated with data collected during future
field treatability studies and pilot tests. Because the type of RA selected for the deep soil
will potentially affect the duration and cost of groundwater remediation at the site, the annual
O&M cost for the groundwater extraction and treatment system has been included in the net
present value of each deep soil alternative. This is based on the premise that the existing
groundwater contamination will be reduced to cleanup levels within the period required to
meet cleanup levels for COCs in the deep soil. Groundwater extraction and treatment system
effectiveness in removing the free- and dissolved-phase organic contaminants from the aquifer
within the RA period for deep soil is necessary for the premise to be valid. Because the net
present value of several of the alternatives are within a narrow range, any significant change
KH0066/WP3066.9A>S.22-96(12.-0»pm) 9-3 D5/E1
-------
in the basis used to calculate the costs could result in a different alternative being selected as
the most cost-effective remedy. As shown in Appendix A, Table A-l, there is only a 7.5
percent difference in the net present value of the selected remedy and the no-action alterna-
tive. Information to be collected during SVE, bioventing, and natural attenuation field
treatability studies and the pilot/demonstration study for the groundwater extraction and
' treatment system wfll permit a more accurate prediction of the cost of total site remediation
under various deep soil remedial alternatives.
9.4 Utilization of Permanent Solutions and Alternative Treatment Technologies
or Resource Recovery Technologies to the Maximum Extent Possible
The selected remedy (SVE, bioventing, and natural attenuation) utilizes permanent solutions
and treatment technologies to the maximum extent practicable. It is the remedial alternative
that represents the optimum balance among the alternatives with respect to the nine EPA
evaluation criteria, especially the balancing criteria of short-term effectiveness, implemen-
tability, and cost.
The selected remedy achieves the same degree of long-term effectiveness and permanence as
SVE or bioventing because all these alternatives involve treatment that will achieve cleanup
levels for the deep soil. The no-action and natural attenuation alternatives provide no
measure of short-term effectiveness because any natural reduction in contaminant concentra-
tions would occur only over a long period of time. The selected remedy and the SVE and
bioventing alternatives will also achieve essentially equivalent reductions in the toxicity,
mobility, and volume of contaminated soil because all three alternatives would achieve
cleanup levels. The no-action and natural attenuation alternatives would achieve only limited
reductions in toxicity, mobility, and volume of contaminated soil. The selected remedy and
the SVE alternative would achieve similar measures of short-term effectiveness because they
are currently projected to meet cleanup objectives within approximately 8 to 9 years.
Bioventing would be much less effective over the short term because it is predicted to require
26 years to meet cleanup levels. The no-action and natural attenuation alternatives would not
be effective in the short term. The implementability of the selected remedy is essentially
equivalent to the implementability of either the SVE or bioventing treatment alternatives
because these two treatment technologies use the same components as the selected remedy.
The selected remedy has the lowest net present value of all the alternatives, because it will
optimize the contaminant reduction with a given technology and, therefore, be the most cost
effective.
KN/3
-------
The ADEQ and ADWR were involved at each step in the remedy selection process for OU-3,
reviewing and approving the engineering evaluation/cost analysis, RI/FS, proposed plan,
proposed plan fact sheet, and the ROD. The specific actions that implement the RODA will
be included in the RD/RA documents, which will be in accordance with the FFA and will be
coordinated with ADEQ, ADWR, and EPA.
9.5 Preference for Treatment as a Principal Element
The ADEQ and ADWR were involved at each step in the remedy selection process for the
OU-2 amendment and OU-3 under which operable unit the deep soil had been investigated,
reviewing and approving the RI/FS, proposed plan, proposed plan fact sheet, and the ROD.
The public was invited to offer comment at each step in the process through public comment
periods advertised in local newspapers and at a public meeting. A fact sheet providing a
condensed version of the remedy selection process contained in the proposed plan was
distributed to the media along with a news release and to those who attended the public
meeting. In addition, the proposed plan and the proposed plan fact sheet were placed in the
information repository located at the Gilbert Public Library. The RAB was briefed on the
selected remedy for the Deep Soil in the OU-2 amendment.
KN/3066/WP3066.9A)6-0^96tt50pm) 9-5 D5/E1
-------
10.0 Documentation of Significant Changes
There have been no significant changes on the OU-2 as a result of the public meeting held on
February 21, 1996.
KW306£/WP3066.1W%<>3-96(233pm) 10-1 D4/E1
-------
11.0 Responsiveness Summary
This section documents that no public comments were received after the issuance of the
proposed plan, therefore; there were no USAF responses required. There were comments
received during the public meeting regarding the extent of the plume. The questions and
answers are shown below:
• Deletes Spidel who lives on 185th Street, right by Ray Road, where Ray Road
dead-ends, asked about the plume. Dr. Harris indicated the direction of ground-
water flow was east. Mr. Carter added that groundwater flows east but has a
component that swings north and moves toward the northern boundary of the
Base. Richard Freitas had no comment.
• Len Fuchs then asked Ms. Spidel if she felt secure living next to Williams AFB.
Delores Spidle said that she did, but that she wanted to move and wanted
somebody to buy the property.
• Richard Freitas mentioned that the record of decision will be issued after the
proposed plan.
• Dr. Harris said that the OU-2 record of decision amendment, which is the
official document that says what technology will be used for a remedial alterna-
tive, will be issued after the treatability study is complete and the Air Force has
demonstrated that the new technologies being proposed will work.
KN/3066/WP3066.UA)6-Ofr9«aO«pm) H-l w/£}
-------
12.0 References
Arizona Department of Environmental Quality (ADEQ), 1990, LUST Site Characterization
Report Checklist.
Howard, P. H., R. S. Boethling, W. F. Jarvis, W. M. Meylan, and E. M. Michalenko, 1991,
Handbook of Environmental Degradation Rates, Lewis Publishers, Inc., Chelsea, Michigan.
IT Corporation, 1995, Final Feasibility Study Report, Operable Unit 3, prepared for Air
Force Base Conversion Agency, Williams Air Force Base, Arizona, May 1995.
IT Corporation, 1994, Final Remedial Investigation Report, Operable Unit 3, prepared for
Air Force Base Conversion Agency, Williams Air Force Base, Arizona, September 1994.
IT Corporation, 1993 a, Final Work Plan Addendum, Operable Unit 3, prepared for the
USAF Air Training Command, Randolph Air Force Base, Texas, August 1993.
IT Corporation, 1993b, Field Sampling Plan Addendum, Operable Unit 3, prepared for the
USAF Air Training Command, Randolph Air Force Base, Texas, August 1993.
IT Corporation, 1992a, Final Remedial Investigation Report, Liquid Fuels Storage Area -
Operable Unit 2, Williams Air Force Base, prepared for the USAF Air Training Command,
Randolph Air Force Base, Texas, January 1992.
IT Corporation, 1992b, Final Record of Decision Report, Operable Unit 2, prepared for the
USAF Air Training Command, Randolph Air Force Base, Texas, December 1992.
IT Corporation, 1992c, Final Feasibility Study Report, Operable Unit 2, prepared for the
USAF Air Training Command, Randolph Air Force Base, Texas, April 1992.
U.S. Environmental Protection Agency (EPA), 1989, Interim Final Guidance on Preparing
Superfund Decision Documents, Office of Emergency and Remedial Response, Washington
DC, November, 9355.3-02.
KN/3066/WP3066.12A£-224«(12:12{n>) 12-1 DO/E1
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APPENDIX A
COST
KN/3066/WP3066^PBA35-22-96(12;15pni) DO/E1
-------
TABLE A-l. COST SUMMARY FOR STI
)EEP SOIL ALTERNATIVES
Williams AFB
Project-409877.010
KT - wiu3niw2 • 04/07/95
COST COMPONENT
INSTALLED CAPITAL COST (A)
REMEDIATION TIME (YEARS) (1)
ANNUAL SOIL O*M (Pint * SWOB) Year)
ANNUAL SOIL O*M (lUid Year tnd bkr)
ANNUAL OROUNDWATER O * M
O A M SUBTOTAL COST (WEAR)
NET PRESENT VALUE COST (B) (b)
SOIL OPERATINO AND MAINTENANCE
OROUNDWATER O*M
TOTAL NET PRESENT VALUE (A+B)
TABLE B.2-2
NOAC1ION
ST12-1
NO MONITORINO
SO
30
$28,000
$385,500
$413,500
$698,700
$9,620,200
$10,318.900
TABLES B.2-3,2-4
NATURAL
ATTENUATION
ST12-2
BIODEORADATION
MONITORINO
$234,900
30
$195,700
$385,500
$581,200
$4,883,700
$9,620,200
$14,738,800
TABLES B.2-5.2-6
son. VAPOR
EXTRACTION (SVE)
ST12-3
FUME INCINERATION
CPI)
$2,637,100
8
$599,200
$385,500
$984,700
$4,416,000
$2,841,100
$9,894,200
TABLES B.2-7.2-8
BIOVENTINO
FI
ST12-4
$2,456,600
26
$338,600
$385,500
$724,100
$7,458,300
$8,491,400
$18,406,300
TABLES B.2-9,10,11
SVB, BIOVENTINO.
AND NATURAL
ATTENUATION, FI
ST12-5
$2,812,100
9
$599,200
$388,700
$385,500
$774,200
$3,606,600
$3,181,200
$9,599,900
INFLATION 4%
INTEREST 5%
a. Remediation lime for ftee product layer will be the time for my remediation alternative.
b. Net Pretent Valuei for the remediation •Itematlvei are bated on 4% inflation, and 5% intereit rate.
-------
TABLE A-2. NO ACTION FOR ST-12 DEEP SOILS
Annual Operation and Maintenance Costs
Williams AFB
Project-409877.010
KT-SI-03/29/95
COST COMPONENT
1. Monitoring labor
UNIT COST ($)
50
UNIT
hour (hr)
QTY UNITS/ PERIOD
0 hrper
sampling event
ANNUAL
COST ($)
0
TOTAL OPERATING COST 0
1. Insurance, permits, taxes
2 Rehabilitation costs
3. Contingency
4. Periodic site review (a)
4% operating
25% operating
0
NA
0
28,000
TOTAL ANNUAL OPERATING COST (450%, -30%) 28,000
a. Every 5 years, including groundwater modeling, cost shown is allocation for 1 year.
NA-Not applicable.
-------
TABLE A-3. NATURAL ATTENUATION FOR ST-12 DEEP SOILS
Initial Capital Costs
jplliams AFR
lject-409877.010
KT-S2-03/29/95
COST COMPONENT
DESCRIPTION
COST<$)
DIRECT CAPITAL COSTS
1. Soil gas monitoring wells for natural
biodcgradationtest
-A3(AieasSB-5,8,10,ll)
- A34 (Anas SB-4, 6 , 7, 9A, 9B)
-All (Area SB-3)
2^ Groundwatcr monitoriiug wells for
natural biodegradation test
2 wells, 215 ft deep, 10' diameter bore
each has two 0.5" diameter vapor probe,
0.5 ft screen per probe
2 wells, 215 ft deep, 10* diameter bore,
each has ten 0.5" diameter vapor probe,
0.5 ft screen per probe
1 well, 215 ft deep, 10" diameter bore,
has three 0.5" diameter vapor probe,
0.5 ft screen per probe
(one background sample will be mrHnAfA
m campling)
TOTAL DIRECT COSTS (TDQ
174,000
174,000
INDIRECT CAPITAL COSTS
1 Fnffincw"1!' ind related tech support
2. License, Permit, and Legal Fees
3. Start-up
4. -Contingency
8%TDC
2%TDC
5%TDC
25%TDC
13920
3,480
NA
43,500
TOTAL INSTALLED COST (+50%, -30V.) 234,900
NA-Not applicable.
NI -Not included
-------
TABLE A-4. NATURAL ATTENUATION FOR ST-12 DEEP SOILS
Annual Operation and Maintenance Coati
Williams AFB
Piojec*-409877.010
KT-S2-03/2905
COST COMPONENT
1. Soil gas coUcctionfbr
btodcgyidihop ponitonug
2. Sofl gasanalyiesfbr
3. Soil Boring (a)
4. Sofl monitoring (VOC)(b)
5. Soil Bio Monitoring
(11 bores)
6. Ground water collection fa
biodegndation monitoring
7. Groundwater monitoring
8. Gfoundwater data evaluation
9. Soil gas data evaluation
TOTAL OPERATING COST
L. Insurance, pcrmity taxes
2. Rehabilitation costs
3. Periodic ate review (c)
4. Contingency
UNIT COST (S)
100
450
84,000
10.000
26,000
7,000
1,000
100
100
UNIT
ample
sample
Sampling
event
event
Sampling
event
Sampling
event
sample
far
or
QTY UNITS' PERIOD
28 samptes/6 months
28 samplea/6 months
11 borings/5 years
5 yean
1 sampling event/
5 years
1 • sampling event/
Smooths
7 samples/3 months
128 noun/year
64 hours/year
4% operating
25% operating
ANNUAL
COST (5)
5.600
25,200
16.800
2,000
5.200
28,000
28,000
12.800
6.400
130,000
5.200
NA
28,000
32,500
TOTAL ANNUAL OPERATING COST (+50%, -30%) 195,700
a. Eleven borings vrilh split spoon sampling.
b. Sofl analysis includes a total of 25 samples.
c. Every 5 year, including groundwater modeling, cost shown is allocation for lyear.
NA-Not applicable.
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TABLE A-5. SVE FOR ST-12 DEEP SOILS
Initial Capital Costs
Williams AFB
Project-409877.010
KT-S3FI- 03/29/95
COST COMPONENT
DESCRIPTION
COST(S)
DIRECT CAPITAL COSTS
1. Site Preparation
2. Extraction Wells
- A4 (Area SB-6, 7, 9A, 9B), and
-A3 (Area SB-4, 5, 8, 10, 11).
• A2(SB-3)
3. Passive vent wells
4. Demobilization of operating wells
5. Nested pieziometers
6. Piping system and foundation
(surface sealing is not included)
7. SVE Vacuum Skid-Mounted Systems
Two 1,000 scfm blowers
8. Condensate transfer system
(pump, tank and piping)
9. One Thermal Oxidation System with
catalytic module (no heat exchanger)
10. Electrical equipment
11. Shipping
3 acres
All wells are 4" diameter
16 wells at 180 ft deep, and 16 wells at
215 ft deep, each has 35 ft screen
1 well at 215 ft deep, 35 ft screen
11 wells at 215 ft deep, 4" diameter
After completion of me operation (44 wells)
extraction well nearby will be used
2,000 linear feet (4",6"and 10" diameter)
(underground construction cost is included)
Including air/water separator & instrumentation
18" Hg vacuum, 200 hp motor each
Condensate from 2 air/water separators
will be pumped to the existing system
Skid mounted system, rated for 3,000 scfm
10 million (MM) btu/hour, 1,400 ° F
Including installation, wiring, and
telemanager monitoring system
6% of items 7 and item 9 (approx)
TOTAL DIRECT COSTS (TDC)
10,000
651,000
236,000
143,000
0
183,000
218,000
14,000
191,000
52,000
24,500
1,722,500
INDIRECT CAPITAL COSTS
1. Engineering and related tech support
2. SVE Pilot Test
3. License, Permit, and Legal Fees
4- Start-up (sampling costs me included)
5. Contingency
15% TDC
Air permeability and pressure test
(well installation is not included)
2% TDC
5% TDC
25% TDC
258,400
105,000
34,500
86,100
430,600
TOTAL INSTALLED COST (+50%, -30%) 2,637,100
NA - Not applicable.
-------
TABLE A-6. SVE FOR ST-12 DEEP SOILS
Annual Operation and Maintenance Costs
WffliamsAFB
Project-409877.010
KT-S3FI-03/29/95
COST COMPONENT
1. Operating labor (a)
2. Monitoring labor
3. Maintenance
4. Materials
5. Utilities
. Electric Power
2 Vacuum skids (400 Hp),
gas fan^ and water pimps
6. Disposal
7. Purchased services:
a) Vapor samples analyses (b)
b) Water samples analyses
c) Soil Boring (b)(c)
d) Soil Monitoring (VOC) (d)
8. Data evaluation
UNIT COST (S
50
50
0.08
5.00
400
350
90,000
10,000
100
UNIT
hour (hr)
hr
Kwhr
million btu
sample
sample
samnlmp
event
eairmling
event
hr
QTY UNITS/ PERIOD
8 hours /week
8 hours /month
8,146 Kwhr/day
50.4 million btu/day
6 samplesAnonth
9 borings/2 years
1 S3mi)liii£ event/
2 years
40 hr/3 months
ANNUAL
COST(S)
20,800
4,800
10,000
NA
237,900
92,000
NA
28,800
4,200
45,000
5,000
16,000
TOTAL OPERATING COST 464,500
I. Insurance, permits, taxes
2. Rehabilitation costs
3. Periodic site review (e)
4. Contingency
4% operating
25% operating
18,600
NA
NA
116,100
TOTAL ANNUAL OPERATING COST (+50%, -30%) 599,200
a. Operator is required to check system once per week (at 8 hours/trip).
b. Start-up sampling costs are not included.
c. 9 Borings with split spoon sampling
d. Soil analysis includes a total of 25 samples.
e. Every 5 year, cost shown is allocation for 1 year.
NA-Not applicable.
-------
TABLE A-7. BIOVENTING FOR ST-12 DEEP SOILS
Initial Capital Costs
Williams AFB
Project-409877.010
KT-S4FI-03/29/95
COST COMPONENT
DESCRIPTION
COST(S)
DIRECT CAPITAL COSTS
1. Site Preparation
2. Extraction Wells
-A34 (AreaSB-6,7,9A,9B),and
-A3 (AreaSB-4,5,8,10,11)
-A2(SB-3)
3. Passive vent wells
4. Demobilization of operating wells
5. Nested pieziometers
6. Piping system pnd foundation
(surface sft*^'nc is not included)
7. Bio Vacuum Skid-Mounted Systems
One 600 scfin blower
8 Condensate transfer system
1 nuiiin tiiilic &nn Dining )
9. One Thermal Oxidation System with
catalytic module (no heat exchanger)
10. Nutrient system
11. LJcctnc&i equipment
12. Shipping
3 acres
All wells are 4" diameter
16 wells at 180 ft deep, and 16 wells at
215 ft deep, each has 35 ft screen
1 well at 215 ft deep, 35 ft screen
1 1 wells at 215 ft deep, 4" diameter
After completion of the operation (44 wells)
Extraction well nearby will be used
2,000 linear feet (4N,6"and 10" diameter)
(underground construction cost is included)
-, i •• ... « . .-
18" Hg vacuum, 125 hp motor
Condensate from 1 air/water separator
will be pumped to the existing system
Skid mounted system, rated for 1,000 scfin
3 million (MM) btu/hour, 1,400 ° F
Ammonia and nhosDhate system
Including installation, wiring, and
telemanager monitoring system
8% of items 7 and item 9 (approx)
TOTAL DIRECT COSTS (TDC)
10,000
651,000
236,000
143,000
0
183,000
93,000
14,000
103,000
NA
32,000
15,700
1,480,700
INDIRECT CAPITAL COSTS
1 Engineering and related tech support
2. SVE Pilot Test
3 . Bioassessment, bio treatability test
4 License Permit, and Legal Fees
5. Start-up (sampling costs are included)
6. Contingency
15%TDC
Air permeability and pressure test
(well installation is not included)
In situ pilot bio treatability test
2 % TDC
5%TDC
25% TDC
222 100
105,000
175,000
29,600
74,000
370,200
TOTAL INSTALLED COST (+50%, -30%) 2,456,600
NA-Not applicable.
-------
TABLE A-S. BIOVENTING FOR ST-12 DEEP SOILS
Annual Operation and Maintenance Costs
Williams AFB
Prqject-409877.010
KT-S4FI-03/29/95
COST COMPONENT
1. Operating labor (a)
2. Monitoring labor
3. Maintenance
4. Materials
5. Utilities
. Electric Power
1 Vacuum skid (125 Hp),
gas fan, and water pumps.
. Fuel for fume incineration.
6. Disposal
7. Purchased services:
a) Vapor samples analyses (b)
b) Water samples analyses
c) Soil Boring (b) (c)
d) Soil Monitoring (TCL and VOC)
(d)
e) Soil Bio Monitoring
(9 bores, IS samples)
8. Data evaluation
UNIT COST (S
50
50
0.08
5.00
400
350
90,000
10,000
8,000
100
UNIT
hour (hr)
hour (hr)
Kwhr
million btu
sample
sample
fiAfnniTn
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TABLE A-9. SVE AND BIOVENTING FOR ST-12 DEEP SOILS
Initial Capital Costs
Williams AFB
Project-409877.010
KT-S5F1-03/29/95
COST COMPONENT
DESCRIPTION
DIRECT CAPITAL COSTS
1. She Preparation
2. Extraction Wells
- A34 (Area SB-6, 7, 9A, 9B), and
• A3 (AreaSB-4,5,8, 10,11)
• A2(SB-3)
3. Passive vent wells
4. Demobilization of operating wells
5. Nested pieziometers
6 Piping system v*d foundation
(surface sealing is not included)
7 Bin Vnmnim SIcid-KfnimtMl Svsteme
Two 1,000 scfin blower
8. Condensate transfer system
(pump, tank, and piping)
9. One Thermal Oxidation System with
catalytic module (no heat exchanger)
10. Nutrient system
11. Electrical equipment
12. Shipping
3 acres
All wells are 4" dianifftffr
16 wells at 180 ft deep, and 16 wells at
215 ft deep, each has 35 ft screen
1 well at 215 ft deep, 35 ft screen
11 wells at 215 ft deep, 4" diameter
After completion of the operation (44 wells)
Extraction well nearby will be used
2 000 linear feet (4" 6 "and 10" diameter)
(underground construction cost is included)
Tnclutliiur air/water senarainr &. instrumentation
1 8" Hg vacuum, 200 hp motor each
Condensate from 2 air/water separator
will be pumped to the existing system
Skid mounted system, rated for 3,000 scfin
10 million (MM) btu/hour, 1,400 ° F
Ammonia and phosphate system
Tnglndifig installation, wiring, and
telemanager monitoring system
6% of items 7 and item 9 (approx)
TOTAL DIRECT COSTS (TDQ
COST (5)
10,000
651,000
236,000
143,000
0
183,000
218,000
14,000
191,000
NA
52,000
24,500
1,722^00
INDIRECT CAPITAL COSTS
1 . Enjrineerini* and related tech support
2. SVE Pilot Test
3. Reassessment, bio treatability test
4. License, Permit, and Legal Fees
5. Start-up (sampling costs are included)
6. Contingency
15%TDC
Air permeability and pressure test
(well installation is not included)
In situ pilot bio treatability test
2%TDC
5%TDC
25 % TDC
258,400
105,000
"
175,000
34,500
86,100
430,600
TOTAL INSTALLED COST (+50%, -30%) 2,812,100
NA-Not applicable.
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TABLE A-10. SVE AND BIOVENTING FOR ST-12 DEEP SOILS
Annnal Operation and Maintenance Costs
(First and Second Year)
Williams AEB
Project-409877.010
KT-S5FI- 03/29/95
COST COMPONENT
1. Operating labor (a)
2. Monitoring labor
3. Maintenance
4. Materials
5. Utilities
. Electric Power
2 Vacuum slads (400Hp),
gas fan, and water pumps.
. Fuel for fame .mriinerarinn
6. Disposal
7. Purchased services:
a) Vapor samples analyses (b)
b) Water samples analyses
c) Soil Boring (b)(c)
»y «*T«--- • • •• 'o \ / v™y
d) Soil Monitoring (VOQ
(d)
e) Soil Bio Monitoring
(9 bores, IS samples)
8. Data evaluation
UNIT COST (S
SO
so
0.08
5.00
400
350
90,000
10,000
8,000
100
UNIT
hour (hr)
hr
Kwhr
MMBTU
sample
sample
camnltncr
event
sampling
event
sampling
event
hr
QTY UNITS/ PERIOD
8 hours/week
O JffOff^^mQflth
8,146 Kwhr/day
50.4 million btu/day
6 samples^nonth
1 samples/month
9 borings/2 years
1 sampling event/
2 years
1 sampling event/
2 years
40 hr/3 months
ANNUAL
COST(S)
20,800
4,800
10,000
NA
237,900
92,000
NA
28,800
4,200
45,000
5,000
NA
16,000
TOTAL OPERATING COST 464,500
1. Insurance, permits, taxes
2. Rehabilitation costs (e)
3. Periodic site review
4. Contingency
4% operating
25% operating
18,600
NA
NA
116,100
TOTAL ANNUAL OPERATING COST (+50%, -40%) 599,200
a. Operator is required to check system once per week (at 8 hours/trip).
b. Start-up sampling costs are not included.
c. Nine borings with split spoon sampling.
d. Soil analysis includes a total of 25 samples.
e. Replacement of mechanical components every 10 years.
NA - Not applicable.
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TABLE A-ll. SVE AND BIOVENTING FOR ST-12 DEEP SOILS
Annual Operation and Maintenance Costs
(Third Year and Later)
Williams AFB
Project-409877.010
KT-S5FI-03/29/95
COST COMPONENT
1. Operating labor (a)
2. Monitoring labor
T Maintenance
4. Materials
5. Utilities
. Electric Power
1 Vacuum skid (200 Hp)
gas fan, <""* water pumps.
Fyel fnr -fimis incineration
6. Disposal
7. Purchased services
a) Vapor samples analyses (b)
b) Water samples analyses
c) Soil Borine(bXc)
wy •**•» v •• • •wgy^v^^w^
d) Soil Monitoring (VOQ (d)
[) Soil Bio Monitoring
(11 bores, 15 samples)
8. Data evaluation
UNIT COST (S)
50
50
0.08
5.00
400
350
90,000
10,000
8,000
100
UNIT
hour (hr)
hour (hr)
*
Kwhr
million htii
sample
sample
enmnlino
event
camnlintr
"" r G
event
cnnmlino-
event
hr
QTY UNITS/ PERIOD
8 hr/week
8 hours/month
4,521 Kwhr/day
16.8 million btu/day
6 samples/month
1 samples/month
Q hririmys/sarnplinp
event •'
1 samplinf event/
2 years
1 sampling event/
A «ri fr.H.^i w » Trr-T-
2 years
40 hr/3monms
ANNUAL
COST®
20,800
4,800
10,000
NA
132,000
30,700
NA
28,800
4,200
45,000
5,000
4,000
16,000
TOTAL OPERATING COST 301,300
1. Insurance, permits, taxes
2. Rehabilitation costs
3. Periodic site review
4. Contingency
4% operating
25% operating
12,100
NA
NA
75,300
TOTAL ANNUAL OPERATING COST (+50%, -30%) 388,700
a. Operator is required to check system once per week (at 8 hours/trip).
b. Start-up sampling costs are not included.
c. Nine borings with split spoon sampling.
d. Soil analysis includes a total of 25 samples.
|6. Replacement of mechanical components every 10 years.
NA - Not applicable.
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APPENDIX B
LOCATION-SPECIFIC APPLICABLE OR RELEVANT AND
APPROPRIATE REQUIREMENTS
KN/3066/WP30«.AW>S-2M6<12:14pm) DO/E1
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Table B-1
Location-Specific Applicable or Relevant and Appropriate Requirements
Liquid Fuels Storage Area (ST-12)
Operable Unit 2, Williams Air Force Base
Location
Within area where action
may cause Irreparable
harm, toss, or destruction
of significant artifacts
Requirements)
Action to recover and preserve
artifacts
Prerequlslta(s)
Alteration of terrain that
threatens significant scientific,
prehistoric, historic, or
archaeological data
Citation
National Archaeological
and Historical Preservation
Act (16 USC Section 469);
36 CFR Part 65
Comments
A-
RARb
ST12-3
ST12-4
ST12-5
"Criteria is applicable for alternatives fisted.
bCriterla Is relevant and appropriate for alternatives listed:
Alternative ST12-1: No Action
Alternative ST12-2: Natural Attenuation
Alternative ST12-3: Soil Vapor Extraction
Alternative ST12-4: Bloventlng
Alternative ST12-5: Soil Vapor Extraction, Bloventlng, and Natural Attenuation
KN/3066/WP3066.APBA>S-22-96(12:14pm)
DO/HI
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Table B-2
Action-Specific Applicable or Relevant and Appropriate Requirements
Liquid Fuels Storage Area (ST-12)
Operable Unit 2, Williams Air Force Base
(Page 1 of 2)
Action
Requirements)
Prerequlslte(s)
Citation
Comments
RAR"
Air Emissions
Control During
Remediation
Control of air emissions of volatile organlcs,
partlculates, and gaseous contaminants.
Emission of VOCs,
partlculates, and
gaseous air
contaminants
Marlcopa County Air
Quality Standards
(Rules 200, 210,220,
320) as dictated by
the Clean Air Act
ST12-3
ST12-4
ST12-5
Surface Water
Control
Prevent run-on and control and collect runoff from a
24-hour 25-year storm (land treatment facility).
RCRA hazardous waste
treated, stored, or
disposed after the
effective date of the
requirements.
40 CFR 264.273 (c)
ST12-2
ST12-3
ST12-4
ST12-5
Container
Storage
(On Site)
Containers of hazardous waste must be:
• Maintained In good condition
• Compatible with hazardous waste to be stored
• Closed during storage (except to add or remove
waste).
Inspect container storage areas weekly for
deterioration.
Place containers which contain free liquid on sloped,
crack-free base, and protect from contact with
accumulated liquid. Provide containment system
with a capacity of 10 percent of the volume of
containers of free liquids or the volume of the largest
container, whichever is greater.
RCRA hazardous waste
(listed or characteristic)
held for a temporary
period before treatment,
disposal, or storage
elsewhere (40 CFR
264.10) In a container
(I.e., any portable
device in which a
material Is stored,
transported, disposed
of, or handled).
40 CFR 264.171
40 CFR 264.172
40 CFR 264.173
40 CFR 264.174
40 CFR 264.175
These requirements are
applicable for any
contaminated soil,
groundwater, or treatment
system waste that might
be containerized and
stored on site prior to
treatment or final
disposal. Groundwater or
soil containing a listed
waste must be managed
as If It were a hazardous
waste so long as it
contains a constituent of
the listed waste.
ST12-2
ST12-3
ST12-4
ST12-5
KN/3066/WP30«6.APB/05-22-96(l2:Mpm)
DO/BI
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Table B-2
(Page 2 of 2)
Action
Container
Storage
(On Site)
(Continued)
Pretreatment
for Discharge
toPOTW
Requirements)
Remove spilled or leaked waste In a timely manner
to prevent overflow of the containment system.
Keep containers of Ignltable or reactive waste at
least 50 feet from the facility's property line.
Keep Incompatible materials separate. Separate
Incompatible materials stored near each other by a
dike or other barrier.
At closure, remove all hazardous waste and residues
from the containment system, and decontaminate or
remove all containers and liners.
Storage of banned wastes must be In accordance
with 40 CFR 268. When such storage occurs
beyond 1 year, the owner/operator bears the burden
of proving that such storage Is solely for the purpose
of accumulating sufficient quantities to allow for
proper recovery, treatment, and disposal.
Establish agreement with POTW with regards to
pretreatment effluent discharge limits for treated
water.
Prerequlslte(s)
Discharge of treated
water to POTW
Citation
40 CFR 264.1 75
40 CFR 264.1 76
40 CFR 264.1 77
40 CFR 264.1 78
40 CFR 268.50
40 CFR 403
Comments
Need to establish with
POTW prior to discharge.
A"
ST12-2
ST12-3
ST12-4
ST12-5
ST12-3
ST12-4
ST12-5
RARb
' Criteria Is applicable for alternatives listed.
6 Criteria Is relevant and appropriate for alternatives listed.
Alternative ST12-1: No Action
Alternative ST12-2: Natural Attenuation
Alternative ST12-3: Soil Vapor Extraction
Alternative ST12-4: Bloventlng
Alternative ST12-5: Soil Vapor Extraction, Bloventlng, and Natural Attenuation
KN/3066/WP30«6.APB/05-22-96(12:14pin)
DO/BI
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