PB98-964408
EPA 541-R98-107
November 1998
EPA Superfund
Record of Decision:
Hill Air Force Base OU 1
Ogden, UT
9/29/1998
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Record of Decision
Operable Unit 1
Hill Air Force Base, Utah
IRP Sites LF01, LF03, WP02, FT09, OT14, FT81, and WP80
Prepared By:
Environmental Management Directorate
Hill Air Force Base, Utah
SEPTEMBER 1998
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RECORD OF DECISION
FOR OPERABLE UNIT 1
HILL AIR FORCE BASE, UTAH
This is a primary document for Operable Unit 1 at Hill Air Force Base. This document will
be available in the Administrative Record, which will be maintained at the following
locations:
Davis County Library
Central Branch
155 North Wasatch Drive
Layton, Utah 84041
Phone: (801) 547-0729
Hours: Monday through Thursday 10:00 a.m. - 9:00 p.m.
Friday and Saturday 10:00 a.m. - 6:00 p.m.
Environmental Management Directorate
OO-ALC/EMR
7274 Wardleigh Road
Building 5-NE 2nd Floor
Hill AFB, Utah 84056-5137
Hours: Monday through Friday 7:30 a.m. - 4:30 p.m.
Contact: Mr. Kevin Bourne
Phone: (801) 775-6892
Final Submittal Date: 17 September 1998
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Table of Contents
Declaration for the Record of Decision ix
1.0 Site Name, Location, And Description 1-1
2.0 Site History And Enforcement Activities 2-1
2.1 History of Site Activities 2-1
2.2 Enforcement Activities 2-1
2.3 Investigation History 2-2
2.4 Highlights of Community Participation 2-2
2.5 Scope and Role of Operable Unit 1 Within Site Strategy 2-3
3.0 Summary Of Site Characteristics 3-1
3.1 Topography and Hydrogeology 3-1
3.2 Nature and Extent of Contamination 3-2
3.2.1 Soil Contamination 3-2
3.2.2 Groundwater Contamination 3-2
3.2.3 Surface Water, Springs, and Sediment Contamination 3-3
3.3 Contaminant Fate and Transport 3-4
3.3.1 Fate 3-4
3.3.2 Transport 3-5
3.3.3 Exposure Potential 3-6
4.0 Summary Of Site Risks 4-1
4.1 Human Health Risks 4-1
4.1.1 Contaminants of Potential Concern 4-1
4.1.2 Exposure Assessment 4-1
4.1.3 Toxicity Assessment 4-3
4.1.4 Summary of Risk Characterization 4-4
4.2 Ecological Risk Characterization 4-6
4.3 Uncertainty Analysis 4-6
4.4 Overview of Site Risks 4-7
5.0 Description Of Alternatives 5-1
5.1 Source Area Alternatives 5-1
5.1.1 Source Area Alternative 1—No Further Action 5-1
5.1.2 Source Area Alternative 2-Existing System Upgrade 5-2
5.1.3 Source Area Alternative 3-Groundwater Dewatering 5-4
5.1.4 Source Area Alternative 4-Source Containment 5-7
5.1.5 Source Area Alternative 5-Source Containment and Cap
Upgrade 5-9
5.1.6 Source Area Alternative 6-Source Treatment and Cap
Upgrade 5-10
5.1.7 Source Area Alternative 7-Excavation, Treatment, and Offsite
Disposal 5-13
5.2 Non-Source Area Alternatives 5-14
5.2.1 Non-Source Area Alternative 1—No Further Action 5-14
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RECORD OF DECISION FOR OPERABLE UNIT 1
5.2.2 Non-Source Area Alternative 2-Monitored Natural
Attenuation 5-16
5.2.3 Non-Source Area Alternative 3-Existing Seep Collection
Upgrade 5-18
5.2.4 Non-Source Area Alternative 4-Plume Cut-off at Bottom
of Bluff 5-19
5.2.5 Non-Source Area Alternative 5-Hydraulic Containment at
Leading Plume Edges 5-21
5.2.6 Non-Source Area Alternative 6-Groundwater Collection
Throughout Plume 5-23
5.3 Elements Common to Both Source Area and Non-Source Area
Alternatives 5-26
6.0 Summary Of The Comparative Analysis Of Alternatives 6-1
6.1 Introduction 6-1
6.2 Threshold Criteria 6-2
6.2.1 Overall Protection of Human Health and the Environment 6-2
6.2.2 Compliance with ARARs 6-4
6.3 Primary Balancing Criteria 6-5
6.3.1 Long-Term Effectiveness and Permanence 6-5
6.3.2 Reduction of Toxicity, Mobility, or Volume Through Treatment 6-6
6.3.3 Short-Term Effectiveness 6-8
6.3.4 Implementability 6-9
6.3.5 Cost 6-10
6.4 Modifying Criteria 6-12
6.4.1 State Acceptance 6-12
6.4.2 Community Acceptance 6-12
7.0 The Selected Remedy 7-1
7.1 Description of the Selected Remedy 7-1
7.1.1 Remediation Goals and Performance Standards 7-4
7.1.2 Restoration Time Frame 7-8
7.1.3 Costs 7-8
7.2 Statutory Determinations 7-8
7.2.1 Protection of Human Health and the Environment 7-9
7.2.2 Compliance with Applicable or Relevant and Appropriate
Requirements 7-10
7.2.3 Cost-Effectiveness 7-11
7.2.4 Utilization of Permanent Solutions and Alternative Treatment
Technologies 7-12
7.2.5 Preference for Treatment as a Principal Element 7-13
7.3 Documentation of Significant Changes 7-13
8.0 References ; 8-1
9.0 Responsiveness Summary 9-1
9.1 Introduction 9-1
9.2 Overview 9-1
9.3 Background on Community Involvement 9-2
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9.4 Summary of Public Comments 9-2
9.4.1 Comments on the Proposed Plan 9-2
9.4.2 Comments Made During the Public Meeting 9-4
APPENDIX A: Identification of ARARs
APPENDIX B: List of Attendees at the Hill Air Force Base Operable Unit 1 Open House
APPENDIX C: Proposed Plan Comments and Hill Air Force Base Responses to Comments
List of Tables
Table 3-1 Range of Analytical Results for Selected Compounds in Soil Sample from
CDP's 1 & 2
Table 3-2 Range of Analytical Results for Selected Compounds in Soil Samples from
Landfill 3
Table 3-3 Range of Analytical Results for Selected Compounds in Soil Samples from
Landfill 4
Table 3-4 Range of Analytical Results for Selected Compounds in Soil Samples from
Fire Training Area 1
Table 3-5 Range of Analytical Results for Selected Compounds in Soil Samples from
Fire Training Area 2
Table 3-6 Range of Analytical Results for Selected Compounds in Soil Samples from
the Waste Phenol/Oil Pit
Table 3-7 Range of Analytical Results for Selected Compounds in Soil Samples from
the Waste Oil Storage Tanks
Table 3-8 Summary of Analytical Results for LNAPL Samples Downgradient of the
CDPs
Table 3-9 Summary of Analytical Results for LNAPL Samples from Fire Training Area
1
Table 3-10 Summary of Analytical Results for Groundwater Samples from On-Base
Areas
Table 3-11 Summary of Analytical Results for Groundwater Samples from the Weber
River Valley
Table 3-12 Summary of Surface Water Data for Select Compounds
Table 3-13 Summary of Metals Detected in Sediment Samples from Seeps/Springs at
OU1
Table 4-1 Summary of Cancer Risks and Hazard Indices
Table 5-1 Assumed Quality of Extracted Groundwater
Table 5-2 Source Area Alternative 7 Excavation Volumes and Disposal Methods
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Table 5-3 Northern Containment System Groundwater Contamination Concentrations
Table 5-4 Western Containment System Groundwater Contamination Concentrations
Table 5-5 Non-Source Area Alternative NSA6 Expected Maximum Contamination
Levels (Off-Base)
Table 5-6 Non-Source Area Alternative NSA6 Expected Maximum Contamination
Levels (On-Base)
Table 6-1 Source Area Alternatives Summary Cost Table
Table 6-2 Non-Source Area Alternatives Summary Cost Table
Table 7-1 Performance Standards for Soil Protective of Groundwater
Table 7-2 Performance Standards for Principal Contaminants of Concern in
Groundwater and Surface Water at Operable Unit 1
Table 7-3 Summary of Costs for the Selected Remedy at HAFB Operable Unit 1
List of Figures
Figure 1-1 Site Location
Figure 1-2 Site Topography of OUlFigure 3-1 Generalized Geologic Cross-Section
Figure 3-1 Generalized Geologic Cross-Section
Figure 3-2 Areas Exceeding Soil PRGs and/or Containing Free- and Residual-Phase
LNAPL
Figure 3-3 Areas Exceeding PRGs for Groundwater and Surface Water
Figure 3-4 Conceptual Model for Fate and Transport of Contaminants Associated with
the Major OU1 Source Areas
Figure 3-5 Conceptual Model for Fate and Transport of Contaminants Associated with
the Minor OU1 Source Areas
Figure 5-1 Source Area Alternative 2 Site Plan
Figure 5-2 Source Area Alternative 3 Site Plan
Figure 5-3 Source Area Alternative 4 Site Plan
Figure 5-4 Source Area Alternative 5 Site Plan
Figure 5-5 Source Area Alternative 6 Site Plan
Figure 5-6 Source Area Alternative 7 Site Plan
Figure 5-7 Non-Source Area Alternative 2 Site Plan
Figure 5-8 Non-Source Area Alternative 3 Site Plan
Figure 5-9 Non-Source Area Alternative 4 Site Plan
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Figure 5-10 Non-Source Area Alternative 5 Site Plan
Figure 5-11 Non-Source Area Alternative 6 Site Plan
Figure 5-12 Proposed CAMU Boundaries
Figure 7-1 Preferred Alternative
Figure 7-2 Areas Exceeding PRGs for Soil
Figure 7-3 Areas Exceeding PRGs for Groundwater
Figure 7-4 Areas Exceeding PRGs for Surface Water and Locations of Springs with
Concentrations of Arsenic in Sediment Above Background Concentrations
Figure 7-5 Areas Exceeding PRGs and/or Containing Free- and Residual-Phase LNAPL
Figure 7-6 Landfill Boundaries
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RECORD Of DECISION FOR OPERABLE UNIT 1
List of Acronyms
ARAR Applicable or Relevant and Appropriate Requirement
AST? Air Stripper Treatment Plant
BACT Best Available Control Technology
bgs Below the Ground Surface
CAMU Corrective Action Management Unit
CDP Chemical Disposal Pit
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act
COPC Contaminant of Potential Concern
CPF Cancer Potency Factor
CWSID Central Weber Sewer Improvement District
cy Cubic Yards
DCE Cis 1,2-Dichloroethene
DOQ Data Quality Objective
EPA U.S. Environmental Protection Agency
FS Feasibility Study
FTA Fire Training Area
gpm Gallons Per Minute
HAFB Hill Air Force Base
HI Hazard Index
HQ Hazard Quotient
IWTP Industrial Wastewater Treatment Plant
LDR Land Disposal Regulation
LNAPL Light Non-Aqueous Phase Liquids
MCL Maximum Contaminant Level
Hg/1 Micrograms Per Liter (parts per billion)
ug/g Micrograms Per Gram (parts per billion)
mg/kg Milligrams Per Kilogram (parts per million)
mg/1 Milligrams Per Liter (parts per million)
NCP National Oil and Hazardous Substances Pollution Contingency Plan
NPL National Priorities List
NSA Non-Source Area
pg/1 Picograms Per Liter
PAH Polynucleararomatic Hydrocarbon
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RECORD OF DECISION FOR OPERABLE UNIT 1
PA/SI Preliminary Assessment/Site Investigation
PCB Polychlorinated Biphenyl
POTW Publicly Owned Treatment Works
PRG Preliminary Remediation Goal
PSVP Performance Standard Verification Plan
O&M Operation and Maintenance
OU Operable Unit
OU1 Operable Unit 1
RAB Restoration Advisory Board
RCRA Resource, Conservation and Recovery Act
RfC Reference Concentration
RfD Reference Dose
RI Remedial Investigation
RME Reasonable Maximum Exposure
ROD Record of Decision
SA Source Area
SARA Superfund Amendments and Reauthorization Act
scfm Standard Cubic Feet per Minute
SF Slope Factor
SVE Soil Vapor Extraction
SWLC South Weber Landfill Coalition
TAG Technical Assistance Grant
TCE Trichloroethene
TMV Toxicity, Mobility, or Volume
TPH Total Petroleum Hydrocarbons
UDAQ Utah Division of Air Quality
UDEQ Utah Department of Environmental Quality
VGAC Vapor-Phase Granular Activated Carbon
VOC Volatile Organic Compound
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Declaration for the Record of Decision
Site Name and Location
Operable Unit 1
Hill Air Force Base
Davis and Weber Counties, Utah
Statement of Basis and Purpose
This decision document presents the selected remedy for Operable Unit 1 (OU1) at Hill Air
Force Base (HAFB), Utah. The remedy was selected in accordance with the Comprehensive
Environmental Response, Compensation, and Liability Act (CERCLA) of 1980, as amended
by the Superfund Amendments and Reauthorization Act (SARA) of 1986, and the National
Oil and Hazardous Substances Pollution Contingency Plan (NCP). This decision is based on
the Administrative Record for this site.
The State of Utah and U.S. Environmental Protection Agency (EPA) concur with the
selected remedy.
Assessment of the Site
Actual or threatened releases of hazardous substances from the site, if not addressed by
implementing the response action selected in this Record of Decision, may present an
imminent and substantial endangerment to public health, welfare, or the environment.
Description of the Selected Remedy
The selected remedy for OU1 is part of a Basewide effort to clean up contaminated soil,
surface water, and groundwater. At HAFB, there are nine OUs, all of which are in different
stages of investigation or cleanup. OU1 is located along the eastern Base property and is
comprised of the following individual on-Base areas of potential concern: Landfills 3 and 4,
Fire Training Areas 1 and 2, Chemical Disposal Pits 1 and 2, the Waste Phenol/Oil Pit, the
Waste Oil Storage Tank Site, and the contaminated groundwater emanating from the
individual on-Base areas of potential concern. Specific off-Base areas have been impacted bv
on-Base groundwater migrating off-Base.
The selected remedy addresses on-Base (Source Area) waste disposal areas and associated
contaminated environmental media including air, soil, and groundwater. The area
containing contaminated groundwater emanating from the Source Areas is identified as the
Non-Source Area.
The selected remedy includes the following components:
Source Area
• Dewatering of the Source Area with extraction trenches.
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RECORD OF DECISION FOR OPERABLE UNIT 1
• Light non-aqueous phase liquid (LNAPL) recovery from the extraction trenches
followed by proper disposal of the LNAPL.
• Groundwater treatment at the Operable Unit 2 Air Stripper Treatment Plant (ASTP) or
the HAFB Industrial Wastewater Treatment Plant (IWTP).
• Repair as well as operation and maintenance of the landfill caps and passive gas vent
system.
Non-Source Area
• Upgrade the spring collection system and treatment of the collected surface water at the
Operable Unit 2 ASTP, a new remote treatment plant, or the IWTP.
• Excavate arsenic-contaminated spring sediments. The sediments will be properly
disposed of offsite at an appropriate disposal facility.
• Monitored natural attenuation of contaminants in the groundwater of the Non-Source
Area. This component of the selected remedy depends on intercepting contamination in
the Source Area. Other remedies will be implemented if concentrations are not
attenuating in a reasonable time frame.
Both Source and Non-Source Areas
• Environmental monitoring.
• Institutional and engineering controls designed to prevent potential unacceptable risks
to human health and the environment.
• Designation of a Corrective Action Management Unit (CAMU) to facilitate remedial
actions. The CAMU will be designated as the contiguous area of contamination.
The selected remedy for OU1 addresses the principal threats posed by the site by
minimizing or preventing direct contact with contaminated soils and landfill contents,
preventing ingestion of and direct contact with contaminated groundwater, surface water,
and sediments as well as preventing further offsite transport of contaminants.
Statutory Determinations
The selected remedy is protective of human health and the environment, complies with
federal and State of Utah requirements that are legally applicable or relevant and
appropriate to the remedial action, and is cost effective. The remedy addresses potentially
unacceptable risks to human health and the environment at both the onsite Source Area and
the offsite Non-Source Area.
This remedy utilizes permanent solutions and alternative treatment technologies to the
maximum extent practicable for the on-Base area and satisfies the statutory preference for
remedies employing treatments that reduce toxicity, mobility, or volume as a principal
element. The toxicity and volume of contaminants in the Non-Source Area is expected to be
reduced by natural processes rather than through treatment as a principal remedial
element. The onsite Source Area treatment activities will reduce the total mass of
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RECORD OF DECISION FOR OPERABLE UNIT 1
contaminants in the groundwater at OU1, which in turn will help the offsite natural
remedial processes address Non-Source Area contamination. Since this remedy will result
in hazardous substances remaining onsite above health-based levels, a review will be
conducted within 5 years after commencement of remedial actions to ensure that the
remedy continues to protect human health and the environment.
Once the remedy is complete, Applicable or Relevant and Appropriate Requirements
(ARAR) will be met or a waiver will be justified. An ARAR waiver may be invoked,
accompanied by an Explanation of Significant Differences, if it is determined on the basis of
criteria stated in this Record of Decision (ROD) that MCLs or other chemical-specific
ARARs cannot be achieved within all portions of the area of attainment in the Source Area,
or where it is anticipated that it may be technically impracticable to reach such levels
targeted in the ROD.
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RECORD OF DECISION FOR OPERABLE UNIT 1
UNITED STATES
ENVIRONMENTAL PROTECTION AGENCY
Max H. Dodson, DATE
Assistant Regional Administrator
Office of Ecosystems Protection and Remediation
EPA Region VIII
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RECORD OF DECISION FOR OPERABLE UNIT 1
STATE OF UTAH
DEPARTMENT OF ENVIRONMENTAL QUALITY
Dianne R. Nielson,
Executive Director
DATE
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RECORD OF DECISION FOR OPERABLE UNIT 1
AIR FORCE MATERIEL COMMAND
WRIGHT-PATTERSON AIR FORCE BASE, OHIO
Stewart E. Cranston DATE
Lieutenant General, USAF
Vice Commander
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Decision Summary
1.0 Site Name, Location, and Description
1.0.0.1. Hill Air Force Base (HAFB) is located in northern Utah, approximately 25 miles
north of Salt Lake City and about 5 miles south of Ogden. HAFB occupies approximately
6,700 acres in Davis and Weber counties. The Base is bounded on the west by Interstate 15,
on the south by State Route 193, and on the northeast by the Weber River Valley
(Figure 1-1). The Base is located on a prominent terrace known as the Weber Delta.
1.0.0.2. Operable Unit 1 (OU1), one of nine OUs at HAFB, is located within Davis County,
near the eastern Base property boundary. As shown in Figure 1-2, OU1 includes the former
waste disposal areas: Landfills 3 and 4, Fire Training Areas (FTA) 1 and 2, Chemical
Disposal Pits (CDP) 1 and 2, the Waste Phenol/Oil Pit, and the Waste Oil Storage Tank Site.
1.0.0.3. The Source Area portion of OU1 includes Landfills 3 and 4, CDPs 1 and 2, FTAs 1
and 2, the Waste Phenol/Oil Pit, the Waste Oil Storage Tank Site, and the light non-aqueous
phase liquid (LNAPL) plume emanating from CDPs 1 and 2. The Non-Source Areas consist
of an on-Base groundwater plume west of the LNAPL plume, and the off-Base groundwater
contamination in the Weber River Valley. The off-Base portion of the Non-Source Area is
located on the steep, terraced, northeasterly-facing escarpment that forms the south wall of
the Weber River Valley and in the valley. There is over 250 feet of relief between the Source
Area and the off-Base Non-Source Area. The land surface in the on-Base portion of OU1 is
generally level with a slight northeasterly grade.
1.0.0.4. The Davis-Weber Canal is located off-Base (Figure 1-2) and is situated about
two-thirds of the way down the escarpment. It is a privately-owned irrigation canal that
supplies water for irrigation diverted from the Weber River from mid-April to mid-October.
The canal is concrete-lined in the area of OU1. Groundwater level measurements of
monitoring wells adjacent to the canal have shown the shallow groundwater level to be
about 90 feet below the ground surface (bgs), or about 85 feet below the canal bottom.
1.0.0.5. Land use on-Base at OU1 is military/industrial and immediately off-Base is mixed
agricultural and residential use. There are no hospitals, retirement or nursing homes,
schools, nurseries, or daycare centers currently located within OU1. The nearest daycare or
school is approximately 0.3 miles east of the contamination associated with OU1.
1.0.0.6. At present, the groundwater plume associated with the on-Base Source Area
disposal sites has migrated approximately 2,200 feet north/northeast of the Base property
boundary. The off-Base portion of the groundwater plume underlies a few residences in the
City of South Weber. Historically, there have been seven off-Base surface water springs
located within the downgradient areal extent of the groundwater plume that have been
observed with significant levels of contamination (above MCLs). Based on recent sampling
results, four of these springs continue to exceed MCLs. Other springs have been observed in
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BOX ELDER CO
WEBER CO
0 1 2 3 «
Scale in Miles
HILL AIR FORCE BASE
OPERABLE UNIT 1
SITE LOCATION
FIGURE 1-1
Source: Revised Interim Draft Final Feasibility Study Report
For Operable Unit 1. Montnnmon/ w/-«— ««~-
. Montgomery Watson 1995
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Weber River Valley
South Weber City
I andlill 4
Landfill 3
Operable Unit 1
HILL AIR FORCE BASE
PROPERTY BOUNDARY
Wole: Soil excavated from the Waste Phenol/Oil Pit was placed under the clay cap ol Landfill 3
Precise location ol disposal within Landlill 3 is unknown.
Source: Revised Interim Draft Final Feasibility
Report for OU1,(MW, 1995)
HILL AIR FORCE BASE
OPERABLE UNIT 1
SITETOPOGRAPHY OF OU 1
FIGURE 1-2
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RECORD OF DECISION FOR OPERABLE UNIT 1
the off-Base areas. Very low levels of groundwater contamination (below MCLs) or no
groundwater contamination has been observed in these other springs.
1.0.0.7. Shallow groundwater is not currently used as a source of drinking water in the area.
Municipal water for the City of South Weber is supplied by the Weber Basin Water
Conservancy District. The district provides water from wells that tap deep aquifers that are
unaffected by contaminants associated with OU1. South Weber No. 2 is the only
groundwater well located within the aerial extent of the OU1 off-Base groundwater plume.
The well is located approximately 1,500 feet from the OU1 Source Areas. This well has been
used sporadically over the years during peak demand periods. Oil was recently observed
floating on the surface of the water in the well, and the well is currently not in use due to
the dissolved contamination in the well water from the oil. Recent investigations have
shown HAFB is not the source of the oil or associated contamination in the well water. The
investigation is described in the Draft Monitoring Well Installation and Impact Assessment of
South Weber No. 2 Report (CH2M HILL, 1998b).
1.0.0.8. Land within OU1 is not located within the 100-year floodplain. There are no
jurisdicrional wetlands, as regulated by the U.S. Army Corps of Engineers, within OU1.
Apart from deeper groundwater for drinking water, there are no uses or known occurrences
of commercially valuable natural resources within the OU1 area.
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2.0 Site History and Enforcement Activities
2.1 History of Site Activities
2.1.0.1. The Base has housed numerous industrial facilities related to management and
maintenance of aircraft and missiles since the 1940s. These industrial operations have
included the use of numerous chemicals, metals, degreasing solvents, and hydrocarbon fuel
products. Historically, waste products were disposed of in onsite pits and landfills.
Additionally, fire training areas were established onsite, so facility personnel could practice
extinguishing and managing hydrocarbon fuel fires. The types of waste materials disposed
of at Source Areas, or use of the area, and the time periods the OU1 Source Areas were in
use are listed below:
• Chemical Disposal Pits 1 and 2: an industrial liquid waste disposal site in operation from
1952 through 1973.
• Landfill 3: An industrial (dump and burn) liquid and solid waste disposal site in
operation from 1940 through 1967.
• Landfill 4: A sanitary refuse landfill in operation from 1967 through 1973.
• Fire Training Area 1: A fire training practice area used by HAFB from the mid-1950s
through 1973 to extinguish simulated aircraft fires.
• Fire Training Area 2: A fire training practice area used by HAFB from 1973 until 1995 to
extinguish simulated aircraft fires.
• Waste Phenol/Oil Pit: A brick-lined pit used periodically to dispose and burn waste oil and
phenol from 1954 through 1965.
• Waste Oil Storage Tank Site: Site of four 20,000 to 25,000-gallon aboveground storage tanks
used to store fuel oil, jet fuel, and hydraulic oil. The tanks were removed in 1985.
2.2 Enforcement Activities
2.2.0.1. In 1987, the U.S. Environmental Protection Agency (EPA) placed HAFB on the
National Priorities List (NPL) under the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA). On April 10,1991, HAFB entered into a
Federal Facilities Agreement with the Utah Department of Environmental Quality (UDEQ)
and the EPA to establish a procedural framework and schedule for developing,
implementing, and monitoring appropriate response actions at the site in accordance with
existing regulations.
2.2.0.2. Prior to being placed on the NPL list, a Cease and Desist Order for leachate
discharge below Landfill 4 was issued by the Utah Water Pollution Control Board
(currently the State of Utah Division of Water Quality) on July 23,1984. The leachate was
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RECORD OF DECISION FOR OPERABLE UNIT 1
observed at Springs Ul-303 and Ul-304. HAFB implemented the interim remedial measures
to prevent exposure to contamination associated with the OU1 site and to limit the mobility
of contaminants at OU1. These actions were implemented prior to the Superfund
Amendments and Reauthorization Act (SARA) in November 1986. Some of the actions were
taken without EPA and UDEQ oversight. HAFB implemented the following remedial
measures:
• Installation of low-permeability caps over Source Areas in 1985 and 1986, designed to
reduce infiltration of precipitation.
• Installation of a subsurface physical barrier in 1985 (soil/bentonite slurry cut-off wall)
located upgradient of the Source Areas, designed to reduce groundwater recharge to the
Source Areas.
• Collection and treatment of contaminated surface water in 1985 from off-Base springs
located downgradient of the Source Areas.
• Extraction and treatment of contaminated groundwater in the on-Base Source Area
in 1985.
• Implementation of groundwater and surface water monitoring program in 1990.
2.3 Investigation History
2.3.0.1. HAFB began investigative activities in the 1980s, in the northern portion of the Base,
to determine the source of suspected contamination in this area. Supplemental investigative
activities were performed under a Preliminary Assessment/Site Investigation (PA/SI), and
the findings suggested locations within HAFB were the source of the contamination found
in the off-Base groundwater and surface water. Following the PA /SI, Remedial
Investigation (RI) activities were conducted to further characterize the extent of
contamination in the soil, as well as groundwater and springs. These RI activities were also
conducted to evaluate potential downgradient receptors, water-bearing zone properties,
and transport pathways. The RI was conducted in two phases. The Phase I RI investigation
was completed in 1992. The Phase II RI investigation was completed to fill data gaps in the
Phase I RI investigation. The work for both phases is documented in the Comprehensive
Remedial Investigation Report for Operable Unit 1 (MW, 1995).
2.3.0.2. The Comprehensive Remedial Investigation Report for Operable Unit 1, also included a
baseline risk assessment that evaluated the potential human health and environmental
effects caused by chemicals at the site. The Feasibility Study (FS)for Operable Unit I
(CH2M HILL, 1998) identifies and evaluates alternative remedial actions.
2.4 Highlights of Community Participation
2.4.0.1. The public participation requirements of CERCLA Sections 113(k)(2)(B)(i-iv) and
117 were met for the remedy selection process. HAFB has an Environmental Restoration
Community Relations Plan (HAFB, December 1997), which describes HAFB environmental
programs and community involvement. Specific to OU1, meetings were held with the
public to discuss the findings of the RI/FS, alternative and proposed remedial strategies,
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RECORD OF DECISION FOR OPERABLE UNIT 1
and the selected remedy. In particular, HAFB meets with the South Weber City Council as
necessary to update the council on specific issues and the status of remedial efforts at OU1.
Updates on OU1 activities are made to the Restoration Advisory Board (RAB) on a
quarterly basis. In addition, a public meeting was held on April 28,1993, to explain and
discuss risk assessment and risk management issues for the communities located north of
the Base that are affected by OU1, OU2, and OU4. Section 9.3 further describes community
participation.
2.4.0.2. The EPA awarded a Technical Assistance Grant (TAG) to the South Weber Landfill
Coalition (SWLC) in September 1992. The TAG funds citizen groups to obtain independent
technical assistance, information, and explanation from qualified professionals. SWLC
focused its review activities on OU1, has reviewed all RI/FS documents in the
Administrative Record, and provided comments and identified issues to HAFB through the
study process. SWLC comments to the Proposed Plan for OUT. (CH2M HILL, 1998a) and FS,
with responses, may be found in Appendix C. The SWLC is also represented on the RAB.
2.4.0.3. The Proposed Plan was released to the public on January 15,1998, for public
comment. The Proposed Plan was also mailed to federal, State, and local agencies,
Administrative Record repositories, and interested parries on the HAFB mailing list. The
Proposed Plan was hand-delivered to residents in the South Weber Area. All documents
related to the RI/FS, as they were finalized, were placed in the Administrative Record
located at the Directorate of Environmental Management at HAFB and at the Central
Branch of the Davis County Library in Layton, Utah.
2.4.0.4. The notice of availability of the Proposed Plan was published in the Salt Lake Tribune,
Ogden Standard Examiner, Hilltop Times, and Deseret News. A public comment period was
originally scheduled to be held from January 15 to February 14,1998. The SWLC requested
a 1-month extension to March 16,1998.
2.4.0.5. An open house format public meeting was held on February 5,1998, at the
South Weber Elementary School. Affected South Weber residents and all other interested
parties on the HAFB mailing list were notified about the open house. The purpose of the
open house was to answer questions and accept comments about the remedial alternatives
presented in the Proposed Plan, including the preferred remedial alternative for the site, and
other topics relevant to OU1 in an informal setting.
2.5 Scope and Role of Operable Unit 1 within Site Strategy
2.5.0.1. Response actions at HAFB are structured into nine Operable Units (OU); most of
them, including OU1, are geographically defined and address all contaminated media
within each unit. Remedial actions are addressed separately for each OU, and each of the
OUs are at different stages of investigation or remediation.
2.5.0.2. The selected remedy for OU1 incorporates or builds on prior response actions
described in Section 2.2, which will continue as part of this remedy. Extraction and
treatment of groundwater in the Source Areas will reduce concentrations of contaminants,
and hydraulic controls will prevent further transport of contaminants to Non-Source Areas.
Subsurface soil contamination will be addressed by repair and maintenance of the existing
Source Area cap, the maintenance of the landfill passive gas vent system, as well as
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RECORD OF DECISION FOR OPERABLE UNIT 1
institutional controls. Collection and treatment of contaminated surface water from springs,
in concert with institutional controls and/or selective excavation and offsite disposal of
surficial soils at selected off-Base springs, will address exposure risks associated with each
area of potential concern. Monitored natural attenuation of contaminated groundwater,
collection and treatment of groundwater, and selective excavation of sediments from
contaminated springs will reduce concentrations of contamination in Non-Source Areas.
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3.0 Summary of Site Characteristics
3.1 Topography and Hydrogeology
3.1.0.1. OU1 is located adjacent to the eastern property boundary of HAFB. The topography
is relatively flat in the on-Base portion of OU1, dropping steeply to the northeast in the
off-Base portions of OU1 toward the City of South Weber. The topography flattens in the
vicinity of the City of South Weber.
3.1.0.2. The uppermost water-bearing zone beneath OU1 is typically encountered within the
exposed Provo Formation at an approximate depth of 25 to 30 feet bgs, immediately above
the contact between the Provo Formation and the underlying Upper Clay Unit of the Alpine
Formation. Figure 3-1 presents a generalized geologic cross-section of a portion of OU1,
highlighting subsurface geologic characteristics, including the depths and thicknesses of the
Provo and Alpine Formations. At OU1, the Provo Formation is typically comprised of fine-
to coarse-grained sand with interbedded gravel. The Provo Formation ranges in thickness
from 0 to 60 feet and averages approximately 30 feet in thickness. The Alpine Formation is
comprised typically of fine-grained materials, such as silty clay with fine-grained sand
interbeds and fine-grained sand layers. Six water-bearing zones have been observed in the
Alpine Formation. The Alpine Formation overlies the groundwater aquifer and is
approximately 500 feet thick at OU1.
3.1.0.3. Most of the shallow groundwater beneath OU1 flows laterally along the interface of
the two formations, with a relatively insignificant portion migrating vertically into thin
sand layers within the Alpine Formation. Shallow groundwater flow within the Provo
Formation is mainly to the east and west along groundwater channels eroded into the
Alpine Formation. Groundwater flow in the Alpine Formation is to the north.
3.1.0.4. Shallow groundwater beneath OU1 discharges primarily to weathered residual soils
and terrace deposits, as well as sand stringers within the Alpine Formation. There are
numerous springs located along the escarpment, where shallow groundwater discharges to
the ground surface. The regional migration of shallow groundwater located off-Base and
immediately north of OU1 is generally north toward the Weber River.
3.1.0.5. Based on the State of Utah Groundwater Quality Classifications, shallow
groundwater in the Provo and Alpine formations would likely be Class II Drinking Water
Quality Groundwater. The classification is based on ambient total dissolved solids (TDS)
concentrations ranging between 500 and 3,000 milligrams per liter (mg/L). In reality, the
low yield of the relatively impermeable Alpine Formation may be more appropriately
described as an "aquitard."
3.1.0.6. The OU1 site overlies a deep confined groundwater aquifer. The top of the deep
confined groundwater aquifer is located approximately 650 feet below the OU1 Source
Areas and 400 feet below the off-Base portion of OU1. The Alpine Formation at OU1 acts as
a significant barrier to vertical migration of shallow groundwater from the Provo and
Upper Alpine Formations to the much deeper, deep confined groundwater aquifer.
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RECORD OF DECISION FOR OPERABLE UNIT 1
3.1.0.7. Municipal groundwater supplies in the area are obtained from the deep confined
groundwater aquifer systems. Natural regional flow directions for these aquifers, in the
general vicinity of the Base, are generally toward the west. The aquifers are Class HA
aquifers under EPA's groundwater quality classification system. Under the UDEQ, Division
of Water Quality's groundwater classification system, the aquifers are classified as
Class lA-Pristine Groundwater aquifers or Class II-Drinking Water Quality aquifers. The
classifications were established in Section 5.4.5.7 of the Comprehensive Remedial Investigation
Report for Operable Unit I (MW, 1995).
3.2 Nature and Extent of Contamination
3.2.0.1. Environmental samples were taken from soil, sediment, groundwater, surface water,
and air at the site during the RI. The chemical contaminants detected in these media are
primarily chlorinated volatile organic compounds (VOC), with cis 1,1-Dichloroethene
(DCE) being the most prevalent. Trichloroethene (TCE) has also been found at OU1. Some
sediments associated with a few offsite springs contain arsenic concentrations in excess of
background concentrations. Additionally, shallow onsite groundwater associated with
some onsite Source Areas contains LNAPLs, comprised typically of residual degreasing
solvent and hydrocarbon fuel constituents. LNAPLs typically float on top of the water table.
3.2.1 Soil Contamination
3.2.1.1. Residual chemical constituents detected in on-Base subsurface soil (soil at depths
greater than 2 feet) include VOCs, polynuclear aromatic hydrocarbons (PAH), petroleum
hydrocarbons, dioxins, furans, pesticides, and PCBs. Residual chemical constituents
detected in on-Base surface soil include VOCs, PAHs, petroleum hydrocarbons, dioxins,
furans, pesticides, and polychlorinated biphenyls (PCB). Tables 3-1 through 3-7 highlight
contaminant constituents and corresponding ranges of concentrations detected in soils at
the principal Source Areas of OU1. The most highly contaminated soils at OU1 occur within
FTA 1 and CDPs 1 and 2.
3.2.1.2. To date, the only off-Base subsurface soils found to have been impacted by OU1
contaminants are those soils located at or below the water table within areas of the
contaminated OU1 groundwater plume. In light of the site-specific hydrogeologic
conditions at OU1, it is anticipated that off-Base subsurface soils will not pose any
unacceptable risk to human health or the environment for the foreseeable future.
3.2.1.3. Off-Base surface soils have not been impacted by chemical constituents associated
with OU1. Off-Base surface soils do not pose any unacceptable risks to human health or the
environment.
3.2.2 Groundwater Contamination
3.2.2.1. Figure 3-2 presents the areal extent of free- and residual-phase LNAPL and areas
exceeding soil Preliminary Remediation Goals (PRGs) at the Source Area. PRGs are the
maximum contaminant constituent concentrations that represent levels of contamination
which, if left in place in the environment without any treatment, are not expected to pose
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RECORD OF DECISION FOR OPERABLE UNIT 1
any unacceptable risk to human health or the environment. An LNAPL layer on the shallow
groundwater table extends northwest from FTA 1 and the chemical disposal pit areas. The
LNAPL is composed primarily of jet fuel, based on modified EPA Method 8015 analysis
using fuel standards for identification and quantification. However, other contaminants
that have been detected in OU1 soils have also solubilized in the jet fuel. The highest
concentrations of VOCs (base, neutral, and acid extractable compounds; dioxins; and
furans) occur in the LNAPL associated with CDPs 1 and 2 and FTA 1. In addition, PCBs
exist in LNAPL associated with the CDPs. A summary of the compounds detected in the
LNAPL samples is presented in Tables 3-8 and 3-9.
3.2.2.2. Historically, the areal extent of the LNAPL has covered as much as 9 acres of OU1.
However, as shown in Figure 3-2, the lateral extent of the LNAPL has diminished
considerably during recent years. It now appears the free-phase LNAPL is limited to the
area immediately surrounding FTA 1 and an area extending primarily westward from
CDPs 1 and 2. The free-phase LNAPL is heterogeneous in composition and discontinuous
across the area. The apparent thickness of the LNAPL in OU1 monitoring wells has ranged
from a few hundredths of a foot to nearly a foot in the LNAPL plume eminating from the
CDPs. The estimated actual LNAPL thickness has ranged from 0.04 feet at the CDPs to
0.53 feet at FTA 1. The LNAPL occurs at a depth range of approximately 25 feet to 35 feet
bgs. The nature and extent of LNAPL is described in detail in the Comprehensive Remedial
Investigation Report for Operable Unit 1.
3.2.2.3. Figure 3-3 presents the extent of the on- and off-Base groundwater plumes
comprised of dissolved chemical constituents that exceed PRGs. Individual contaminant
constituents include but are not limited to DCE, TCE, and arsenic. DCE is a reliable
indicator constituent in groundwater at HAFB because DCE is the most mobile and
widespread compound in the groundwater. DCE has been used to identify the extent of
off-Base groundwater contamination. Table 3-10 summarizes the range of concentrations of
contaminants detected in on-Base groundwater since 1992. The on-Base groundwater
plumes are confined to the shallow Provo and Alpine Formation water-bearing zones. The
off-Base plume is confined to surficial terrace deposits and the Alpine Formation
water-bearing zones. There are no known users of the groundwater from these
water-bearing zones for domestic purposes.
3.2.2.4. As may be seen in Figure 3-3, a comparison of the off-Base groundwater plume
extent in 1994 versus 1996 reveals that DCE concentrations in the plume appear to be
declining, apparently due to the remedial measures previously enacted at the site, in concert
with natural attenuation. Investigative efforts to date have not identified any LNAPLs
within the off-Base groundwater plume. Table 3-11 summarizes the range of concentrations
of contaminants detected in off-Base groundwater since monitoring began in 1992. The
primary contaminants detected in the shallow off-Base groundwater are DCE and TCE.
Contaminant concentrations decrease with depth in the shallow water-bearing zones. The
nature and extent of groundwater contamination at OU1 are described in detail in the
Comprehensive Remedial Investigation Report for Operable Unit I.
3.2.3 Surface Water, Springs, and Sediment Contamination
3.2.3.1. The Davis-Weber Canal is located approximately 225 to 300 feet north of the HAFB
property boundary. Groundwater has been determined to be at least 90 feet below the
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RECORD OF DECISION FOR OPERABLE UNIT 1
Davis-Weber Canal; therefore, there is little potential for groundwater to contaminate the
water in the canal. Hydrogeologic data suggest that water from the canal leaks to the
subsurface.
3.2.3.2. There are numerous offsite springs/seeps located along the escarpment that adjoins
the northern Base property boundary at OU1 and the Weber River Valley farther to the
north. Some of these springs are hydraulically connected with the on-Base plume of shallow
groundwater that contains residual concentrations of chemical constituents, and are
therefore contaminated. Studies have shown that surface water and sediments associated
with some springs have been impacted to varying degrees by contaminant constituents,
such as DCE and arsenic, associated with OU1. Due to the incongruous nature of hydraulic
interconnection, not all of the springs that are located within the areal extent of the off-Base
plume of groundwater contamination actually contain contaminated surface water.
Table 3-12 summarizes the range of concentrations of contaminants detected in off-Base
surface water. In general, contaminants detected in surface water are a subset of and occur
at lower concentrations than the contaminants found in the upper portion of the shallow
on-Base water-bearing zone. The number of contaminants and contaminant concentrations
decrease with distance from the OU1 Source Area; i.e., fewer contaminants and lower
concentrations of contaminants occur in surface water in the Weber River Valley as
compared to hillside surface water.
3.2.3.3. Table 3-13 summarizes the range of concentrations of contaminants detected in
sediments collected at off-Base seeps and springs. All reported concentrations for
chromium, lead, cadmium, copper, and zinc are within the range of expected background
concentrations for OU1. As shown in Table 3-13, arsenic was detected in sediment from all
five sites. Arsenic most likely is precipitated (i.e., adsorbed to iron oxide surfaces) out of the
spring and seep water into the sediment in response to changes in the redox potential of the
water. Reducing conditions in the shallow groundwater at OU1 and their influence on the
distribution of redox-sensitive contaminants such as arsenic are discussed in greater detail
in the Comprehensive Remedial Investigation Report for Operable Unit 1.
3.3 Contaminant Fate and Transport
3.3.0.1. Populations and environmental receptors that could be affected, if exposed, include
HAFB personnel and any construction contractors, off-Base residents, future on-Base
residents, plants, and animals in the vicinity. The OU1 conceptual model provided as
Figures 3-4 and 3-5 are graphical illustrations of the fate and transport of contaminants in
the OU1 environment.
3.3.1 Fate
3.3.1.1. The persistence of chemical constituents in the subsurface is strongly influenced by
the physical and chemical characteristic properties of the respective chemicals (for example,
vapor pressure, vapor density, Henry's Law Constant, water solubility, organic
carbon/water partition coefficient-K^, etc.), as well as the physical and chemical properties
of the media in which the chemicals are located (soil, air, water, etc.). VOCs and most total
petroleum hydrocarbon (TPH) constituents are likely to partition to air, followed by
groundwater and soil. In surface water, chlorinated VOCs tend to readily volatilize to the
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RECORD OF DECISION FOR OPERABLE UNIT 1
air because of the large area for water-air contact. It is expected that any dissolved VOC
constituents in groundwater that discharges at the ground surface in the form of springs or
seeps at OU1 will volatilize and dissipate into the atmosphere readily.
3.3.1.2. In general, dioxins, furans, TPHs, PCBs, and pesticides do not partition into the
gaseous or aqueous phases as readily as VOCs; thus, these constituents tend to absorb to
soil materials more readily than VOCs and are therefore less mobile than VOCs.
3.3.2 Transport
3.3.2.1. The conceptual model represented by Figures 3-4 and 3-5 shows the principal
contaminants associated with each disposal site, and how these contaminants have
migrated through the soil/unsaturated zone to the LNAPL (if present) and to groundwater
both on-Base and off-Base. The model also represents transfer of contaminants from the
liquid phase to the gaseous phase in soil gas and the atmosphere. Each pathway by which
contaminants may migrate is represented by an arrow that indicates the relative importance
of that pathway to the overall distribution and migration of contaminants at OU1.
3.3.2.2. The analysis of the fate and transport of the contaminants observed at OU1 suggests
that an important factor controlling the movement and persistence of both inorganic and
organic groundwater contaminants migrating from the Source Areas is the
oxidation-reduction conditions that exist at the site. Degradation of hydrocarbons has
created reducing conditions that have led to the mobilization of metals, including iron,
manganese, and arsenic.
3.3.2.3. The predominant pathway for the majority of the contamination at OU1 was from
the waste materials in the Source Areas to the unsaturated zone, and into the shallow
on-Base groundwater. From the shallow on-Base groundwater, groundwater containing a
limited number of contaminants (primarily 1,2-DCE) migrated toward and along the
northern escarpment where it discharged either to springs and seeps or to the shallow
groundwater off-Base. Only the more mobile compounds, such as DCE, have migrated to
the off-Base groundwater. In addition, the LNAPL layer is a major secondary source of
chemical constituents to both soil and groundwater on-Base.
3.3.2.4. Typically, the highest concentrations of groundwater contaminants coincide with
the occurrence of LNAPL. The distribution and migration of LNAPL and contaminated
groundwater across the on-Base portion of OU1 is controlled largely by the sand and gravel
channels of the Provo Formation eroded into the underlying Alpine Formation clay surface.
Once groundwater reaches the northern escarpment, migration appears to be controlled by
vertical fractures, high-permeability landslide debris, and sand channels.
3.3.2.5. Off-Base contaminant migration generally is horizontal and is controlled by the
hydraulic gradient in the shallow water-bearing zone. Groundwater advection has resulted
in the transport of contaminants into off-Base groundwater, which in turn discharges, to
varying degrees, to off-Base springs and/or shallow terrace and alluvial deposits within the
Weber River Valley. Some shallow groundwater within the Weber River Valley discharges
to the Weber River. The OU1 off-Base groundwater plume does not discharge to the Weber
River based on analytical results from monitoring wells between the leading edge of the
plume and the Weber River. The off-Base groundwater plume is currently approximately
2,000 feet south of the Weber River. As groundwater discharges from the Alpine Formation
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RECORD OF DECISION FOR OPERABLE UNIT 1
at OU1 to the alluvial deposits, the groundwater within the Alpine Formation is diluted by
the existing groundwater. The water-bearing layers in the valley are comprised of deposits
that typically have higher storativity, permeability, and transmissivity characteristics than
those associated with the Alpine Formation at OLJ1. Thus, there is a reduction in dissolved
contaminant concentrations as groundwater from the Alpine Formation discharges to the
alluvial deposits, due to intrinsic processes including dilution, dispersion, and diffusion.
3.3.3 Exposure Potential
3.3.3.1. Current on-Base land use at OU1 is highly restricted. Shallow groundwater in the
area is not used as a domestic water source, edible plants are not cultivated, and the area is
not subject to cattle grazing. Because of the on-Base institutional controls and the existing
low permeability caps, there is little potential for exposure to contaminated soil onsite.
Therefore, current exposures to site-related contamination within the OU1 on-Base Source
Area are not anticipated.
3.3.3.2. Current land use in off-Base areas is mostly residential with some agricultural use.
Off-Base residents rely on municipal water for their domestic supply. Shallow groundwater
is not used as a source of drinking water in the area. Surface water from some of the springs
in the area is seasonally present. These levels are generally near the MCLs for
contamination in the area. With the exception of arsenic contaminated soils adjacent to
Springs Ul-301, Ul-303, Ul-304, Ul-305, and Ul-318, there are no contaminated soils
located off-Base that pose an unacceptable risk to human health and the environment. The
most likely current exposure to contaminants would be via inhalation of VOCs migrating
upward from the shallow water-bearing zone.
3.3.3.3. Effects of exposures to nearby ecosystems are expected to be minimal. Details
regarding the population and environmental receptors that could be affected are discussed
in Section 4, which summarizes the findings of the human health and environmental
assessments.
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TABLE 3-1
Range of Analytical Results for Selected Compounds in Soil Samples from CDPs 1 and 2
Analyte (Units)
General Compound
Type
Range of Concentrations
Detected
N
Volatile Organic Compounds (ug/kg)
1,1,1 -Trichloroethane
1,2,4-Trichlorobenzene
1,2,4-Trimethylbenzene
1,2-Dichlorobenzene
1.3,5-Trimethylbenzene
(Mesitylene)
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Fuel Hydrocarbon
Chlorinated Hydrocarbon
Fuel Hydrocarbon
1,3-Dichlorobenzene
1,4-Dichlorobenzene
Chlorobenzene
Ethylbenzene
Naphthalene
Tetrachloroethene (PCE)
Toluene
Total 1,2-Dichloroethene
Trichloroethene (TCE)
Xylenes Total
cis-1,2-Dichloroethene
BNAEs
-------
TABLE 3-1
Range of Analytical Results for Selected Compounds in Soil Samples from CDPs 1 and 2
Analyte (Units)
Dioxin/Furans (pg/g)
Tetrachlorinated Dibenzofurans,
(Total)
Pentachlorinated Dibenzofurans,
(Total)
Hexachlorinated Dibenzofurans,
(Total)
Heptachlorinated Dibenzofurans,
(Total)
Hexachlorinated Dibenzo-p-
Dioxins, (Total)
Heptachlorinated Dibenzo-p-
Dioxins, (Total)
Octachlorodibenzo-p-Dioxin
Metals (ug/g)
Arsenic
General Compound
Type
Furan
Furan
Furan
Furan
Dioxin
Dioxin
Dioxin
Metal
Range of Concentrations
Detected
1.5 to 190
57 to 190
26 to 210
13 to 370
14 to 150
29 to 840
45 to 3,500
0.8 to 6.6
N
5/5
3/5
4/5
5/5
4/5
5/5
5/5
56/56
Selected compounds only; the Comprehensive Rl contains summary tables of all compounds detected in soil.
J = indicates an estimated concentration.
N = frequency of detection (number of detections/number of analyses).
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TABLE 3-2
Range of Analytical Results for Selected Compounds in Soil Samples from Landfill 3
Analyte (Units)
Volatile Organic Compounds
1 ,2,4-Trichlorobenzene
1 ,2-Dichloro benzene
1 ,3-Dichlorobenzene
1 ,4-Dichlorobenzene
Chlorobenzene
Naphthalene
Total 1 ,2-Dichloroethene
Xylenes, Total
BNZEs (ug/kg)
Pentachlorophenol
Fluoranthene
Pyrene
General Compound
Type
(ug/g or mg/kg)
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Fuel Hydrocarbon
Chlorinated Hydrocarbon
Fuel Hydrocarbon
T
Chlorinated Hydrocarbon
Fuel Hydrocarbon
Fuel Hydrocarbon
Range of Concentrations
Detected
0.13 J to 0.4 J
0.1 J to 0.37 J
0.1 J
0.08 J to 4.2
3.9
0.041 J
0.028
0.0007 J to 0.43
2000
24 J to 180 J
36Jto 180 J
N
2/12
3/12
1/12
2/12
1/12
1/12
1/12
2/12
1/12
3/12
3/12
Total Petroleum Hydrocarbons (mg/kg)
Jet Fuel #4
Pesticides and PCBs (ug/g or mg/kg)
Aldrin
PCB-1260 (Arochlor 1260)
Dioxins/Furans (pg/g)
Tetrachlorinated Dibenzofurans, (Total)
Pentachlorinated Dibenzofurans, (Total)
Hexachlorinated Dibenzofurans, (Total)
Heptachlorinated Dibenzofurans, (Total)
Heptachlorinated Dibenzo-p-Dioxins,
(Total)
Octachlorodibenzo-p-Dioxin
Metals (pg/g or mg/kg)
Arsenic
Fuel Hydrocarbon
Pesticide
PCB
Furan
Furan
Furan
Furan
Dioxin
Dioxin
Metal
30
0.003
0.07
5 to 14
5.6 to 9.7
6.7 to 12
6.7 to 17
19 to 50
63 to 160
0.9 to 9.8
1/12
1/8
1/8
3/5
3/5
3/5
3/5
3/5
3/5
10/10
Selected compounds only; the Comprehensive Rl contains summary tables of all compounds detected in soil.
J = indicates an estimated concentration.
N = frequency of detection (number of detections/number of analyses).
\\SNOW8IRD\PROJ\136064W_1,3\FINAUREPORT\TABL£SUA8LE 3-2 DOC
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TABLE 3-3
Range of Analytical Results for Selected Compounds in Soil Samples from Landfill 4
Analyte (Units)
General Compound
Type
Range of Concentrations
Detected
N
Volatile Organic Compounds (ug/g or mg/kg)
1,1-Dichloroethane
1,2-Dichlorobenzene
Benzene
Tetrachloroethene (PCE)
Total 1,2-Dichloroethene
Trichloroethene (TCE)
Vinyl Chloride
BNAEs (ug/g or mg/kg)
2-Methylnaphthalene
Phenanthrene
Chrysene
Benzo(a)Pyrene
Total Petroleum Hydrocarbons
Pesticides/PCBs
Dioxins/Furans
Metals (ug/g or mg/kg)
Arsenic
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Fuel Hydrocarbon
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Fuel Hydrocarbon
Fuel Hydrocarbon
Fuel Hydrocarbon
Fuel Hydrocarbon
Metal
0.0045 J
0.06 J
0.0025 J
0.055
0.003to 1.6
0.0049 J to 0.190
0.0045 J
0.11 J
0.06 J
0.4 J
0.41 J
None Detected
None Detected
None Detected
0.67 to 5.1
1/6
1/6
1/6
1/6
2/6
2/5
1/6
1/6
1/6
1/6
1/6
0/6
0/3
0/1
7/7
Selected compounds only; the Comprehensive Rl contains summary tables of all compounds detected in soil.
J = indicates an estimated concentration.
N = frequency of detection (number of detections/number of analyses).
PA136064\4_1_3\FINAUREPORT\TA8LES\TABLE3-3.DOC
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TABLE 3-4
Range of Analytical Results for Selected Compounds in Soil Samples from Fire Training Area 1
Analyte (Units)
General Compound
Type
Range of Concentrations
Detected
N
Volatile Organic Compounds (ug/kg)
1,1,1 -Trichloroethane
1,2,4-Trichlorobenzene
1,2-Dichlorobenzene
1,3-Dichlorobenzene
1,4-Dichlorobenzene
Chlorobenzene
Ethylbenzene
Naphthalene
Tetrachloroethene (PCE)
Total 1,2-Dichloroethene
Trichloroethene (TCE)
Xylenes, Total
BNAEs (ug/kg)
2-Methylnaphthalene
Fluorene
Phenanthrene
Pyrene
4-Aminobiphenyl
Total Petroleum Hydrocarbons (mg/kg)
Jet Fuel #4
Pesticides and PCBs (mg/kg)
p.p'-DDD
PCB-1260 (Arochlor 1260)
Dioxin/Furans (pg/g)
Tetrachlorinated Dibenzofurans, (Total)
Pentachlorinated Dibenzofurans, (Total)
Heptachlorianted Dibenzofurans, (Total)
continued from previous page:
Tetrachlorinated Dibenzo-p-Dioxins,
(Total)
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Fuel Hydrocarbon
Fuel Hydrocarbon
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Fuel Hydrocarbon
Fuel Hydrocarbon
Fuel Hydrocarbon
Fuel Hydrocarbon
Fuel Hydrocarbon
Amine
Fuel Hydrocarbon
Pesticide
PCB
Furan
Furan
Furan
Dioxin
1.4
41,000
15,000
520 J
2,600 J
17
59 to 3,500
340 to 9,900
11
2.2
2.2 J
1.9 to 37,000
4,200 to 7,700
360 to 930
450 to 1400
100 J to 290 J
210J to 1000
270 to 3,200
0.0042
0.072 to 5
17 to 1,600
21 to 1.100
11 to 850
11 to 250
1/13
1/13
1/13
1/13
1/13
1/13
6/13
5/12
1/13
1/13
1/13
8/13
3/13
2/13
2/13
2/13
2/13
7/13
1/5
2/5
5/5
5/5
5/5
4/5
ttSNCW8IRtAPROJ\136064V«_1..3\FINAL\REPORTVr ABLEST ABLE 3-4 DOC
-------
TABLE 3-4
Range of Analytical Results for Selected Compounds in Soil Samples from Fire Training Area 1
Analyte (Units)
Pentachlorinated Dibenzo-p-Dioxins,
(Total)
Hexachlorinated Dibenzo-p-Dioxins,
(Total)
Heptachlorinated Dibenzo-p-Dioxins,
(Total)
Octachlorodibenzo-p-Dioxin
Metals (ug/g)
Arsenic
General Compound
Type
Dioxin
Dioxin
Dioxin
Dioxin
Metal
Range of Concentrations
Detected
1 1 to 390
34 to 1,800
21 to 5,700
83 to 15.000
0.7 to 4.6
N
4/5
4/5
5/5
5/5
13/13
Selected compounds only; the Comprehensive Rl contains summary tables of all compounds detected in soil.
J = indicated an estimated concentration.
N = frequency of detection (number of detections/number of analyses).
ttSNOW8IRD\PROJ\136064VO_3\FINAL\REPORTYrABI.ES\TABLE W.DOC
-------
TABLE 3-5
Range of Analytical Results for Selected Compounds in Soil Samples from Fire Training Area 2
Analyte (Units)
General Compound
Type
Range of Concentrations
Detected
N
Volatile Organic Compounds (ug/kg)
1,1.1-Trichloroethane
1 ,2-Dichlorobenzene
Benzene
Ethylbenzene
Naphthalene
Total 1 ,2-Dichloroethene
Trichloroethene (TCE)
Xylenes, Total
BNAEs (ug/kg)
2-Methylnaphthalene
Pentachloropehnol
Phenanthrene
Fluoranthene
Pyrene
Total Petroleum Hydrocarbons
Jet Fuel #4
Petroleum Hydrocarbons
Gasoline Components
Metals (ug/g or mg/kg)
Arsenic
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Fuel Hydrocarbon
Fuel Hydrocarbon
Fuel Hydrocarbon
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Fuel Hydrocarbon
Fuel Hydrocarbon
Phenol
Fuel Hydrocarbon
Fuel Hydrocarbon
Fuel Hydrocarbon
(ug/g or mg/kg)
Fuel Hydrocarbon
Fuel Hydrocarbon
Fuel Hydrocarbon
Metal
3.9 J
43 J to 50
4.5 to 29
1,100 to 1,900
880 J to 5, 100
9.4 to 32
17 to 43
88 to 12,000
50 J to 19, 000
120 J
49 J to 1 ,400 J
20 J to 910 J
20 J to 690 J
340 to 7,900
17 to 47, 000
1.2 to 6, 900
1.6 to 10
1/18
2/18
2/18
3/18
3/18
3/18
2/18
4/18
5/18
1/18
4/18
3/18
5/18
4/44
28/30
25/39 •
9/9
Selected compounds only; the Comprehensive Rl contains summary tables of all compounds detected in soil.
J = indicates an estimated concentration.
N = frequency/detection (number/detections/number/analyses).
\\SNOWBIRCAPROJ\136064\4_1 _3\FINAUREPORr\TABlES\TABLE 3-S.DOC
-------
TABLED
Range of Analytical Results for Selected Compounds in Soil Samples from the Waste Phenol/Oil Pit
Analyte (Units)
Volatile Organic Compounds (ug/kg)
1 ,2,4-Trichlorobenzene
1 ,2-Dichlorobenzene
1 ,3-Dichlorobenzene
1 ,4-Dichlorobenzene
Total 1,2-Dichloroethene
Trichloroethene (TCE)
BNAEs (ug/kg)
2,4-Dimethylphenol
Pentachlorophenol
Pyrene
General Compound
Type
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Phenol
Phenol
Fuel Hydrocarbon
Range of Concentrations
Detected
3320 J to 4,400
220 J to 540
18J
36 J to 120 J
92
560 to 1,400
180 J
240 J
52 J
N
2/3
2/3
1/3
2/3
1/3
2/3
1/3
1/3
1/3
Total Petroleum Hydrocarbons (mg/kg)
Jet Fuel #4
Pesticides and PCBs (ug/kg)
p,p'-DDT
PCB-1260 (Arochlor 1260)
Dioxin/Furans (pg/g)
Tetrachlorianted Dibenzofurans,
(Total)
Pentachlorinated Dibenzofurans,
(Total)
Hexachlorinated Dibenzofurans,
(Total)
Heptachlorinated Dibenzofurans,
(Total)
Tetrachlorinated Dibenzo-p-
Dioxins, (Total)
Pentachlorinated Dibenzo-p-
Dioxins, (Total
Hexachlorinated Dibenzo-p-
Dioxins, (Total)
Heptachlorinated Dibenzo-p-
Dioxins, (Total)
Octachlorodibenzo-p-Dioxin
Fuel Hydrocarbon
Pesticide
PCB
Furan
Furan
Furan
Furan
Dioxin
Dioxin
Dioxin
Dioxin
Dioxin
70
7.1
80
26
14
9.2
8.7
4.7
6.8
20
29
50
1/3
1/3
1/3
1/2
1/2
1/2
1/2
1/2
1/2
1/2
1/2
1/2
P:\136064V4_1_3\FINAL\REPORT\TABLES\TABLE M.OOC
-------
TABLE 3-6
Range of Analytical Results for Selected Compounds in Soil Samples from the Waste Phenol/Oil Pit
General Compound Range of Concentrations
Analyte (Units) Type Detected N
Metals (pg/g)
Arsenic Metal 2.6 to 3.4 3/3
Selected compounds only; the Comprehensive Rl contains summary tables of all compounds detected in soil.
J = indicates an estimated concentration.
N = frequency of Detection (number of detections/number of analyses).
P:\1360WV4J_3\flNAUREPOFmTABU5S\TABLE W.OOC
-------
TABLE 3-7
Range of Analytical Results for Selected Compounds in Soil Samples from the Waste Oil Storage Tanks
Analyte (Units)
General Compound
Type
Range of Concentrations
Detected
N
Volatile Organic Compounds (ug/kg)
Benzene
Chlorobenzene
Naphthalene
Toluene
Total 1,2-Dichloroethene
Trichloroethene (TCE)
Xylenes. Total
BNAEs (ug/kg)
2-Methylnaphthalene
Fuel Hydrocarbon
Chlorinated Hydrocarbon
Fuel Hydrocarbon
Fuel Hydrocarbon
Chlorinated Hydrocarbon
Chlorinated Hydrocarbon
Fuel Hydrocarbon
Fuel Hydrocarbon
Total Petroleum Hydrocarbons (ug/g or mg/kg)
Jet Fuel #4 Fuel Hydrocarbon
Pesticides and PCBs (ug/g or mg/kg)
Aldrin Pesticide
p,p'-DDD Pesticide
PCS-1260 (Arochlor 1260) PCB
Dioxin/Furans (pg/g)
Metals (ug/g or mg/kg)
Arsenic Metal
220
2,800
910
1.6 to 1200
6.8 to 13
8 to 13
5,800
1,800
1,500
0.0047
0.017
0.025 to 1.9
Not Analyzed
0.8 to 5.3
1/10
1/10
1/7
5/10
3/10
2/10
1/10
1/7
1/7
1/2
1/2
2/5
7/8
Selected compounds only; the Comprehensive Rl contains summary tables of all compounds detected in soil.
N = frequency of detection (number of detections/number of analyses).
\\ShKWBIRCAPROJ\13e064V4J_3\FINAL\REPORTYr ABLE S\TABLE3-7.DOC
-------
TABLE 3-8
Summary of Analytical Results for LNAPL Samples Downgradient of the CDPs
Analytes Sample ID
VOCs (ug/kg)
Total 1 ,2-dichloroethene
1 ,1 ,1-Trichloroethane
1 ,2-Dichlorobenzene
Tetrachloroethene
Toluene
Chloro benzene
Ethylbenzene
Total Xylene
BNZEs (ug/kg)
Naphthalene
2-Methylnaphthalene
Pesticides/PCBs (pg/ml)
Aldrin
Endosulfan Surfate
Heptachlor
Heptachlor Epoxide
PCB-1260
Dioxin/Furans (pg/ml)
TCDFs (Total)
PeCDFs (Total)
HxCDFs (Total)
HpCDFs (Total)
OCDF
TCDDs (Total)
PeCDDs (Total)
HxCDDs (Total)
HpCDDs (Total)
OCDD
Results
M-27-LF
< 52,500
< 27,500
< 400,000
< 35,000
< 35,000
2.300,000
< 27,500
< 23.500
430,000
< 400,000
<0.05
3.5
0.12
0.41
230
3.800
44.000
50,000
32,000
11,000
8,300
14,000
23,000
49.000
63,000
W-4-LF
87,000
92,000
2,700,000
38,000
770,000
< 13,000
210,000
1,400,000
640,000
810,000
0.41
5.3
0.13
0.45
190
320
350
370
290
220
16
57
86
320
630
P:\136064V4_1_3\FINAUREPORTUA8IESUABIE3-8.DOC
-------
TABLE 3-8
Summary of Analytical Results for LNAPL Samples Downgradient of the CDPs
Results
Analytes Sample ID M-27-LF W-4-LF
TPH (mg/ml)
JP4 120 72
Selected compounds only; the Comprehensive Rl contains summary tables of all compounds detected in
LNAPL.
< = Not detected at or above the specified detection limit.
J = Value is an estimated concentration below the practical quantitation limit.
P:\t36064WJ _3\FINAUREPORTVrABLES\TABLE M.DOC
-------
TABLE 3-9
Summary of Analytical Results for LNAPL Samples from Fire Training Area 1
Analytes
VOCs (pg/kg)
Ethylbenzene
Total Xylene
BNAEs (ug/kg)
Naphthalene
2-Methylnaphthalene
Pesticides (Mg/ml)
Alpha-BHC
Delta-BHC
Lindane
Dieldrin
Endosulfan Sulfate
Dioxins and Furans (pg/ml)
TCDFs (Total)
HxCDFs (Total)
HpCDFs (Total)
OCDF
TCDDs (Total)
PeCDDs (Total)
HxCDDs (Total)
OCDD
TPH (mg/ml)
JP4
Sample Location U 1 -1 -1
210,000
540,000
1 ,400,000
520,000 J
0.65
<0.05
<0.05
0.08
<0.25
8,300
1,600
480
<220
220
340
1,200
1 1 ,000
240
Results
U1-101
(Blind Duplicate Sample)
200,000
< 23,250
1 ,500,000
540,000
0.51
0.11
0.39
0.08
0.37
3,700
1,300
690
210
430
800
2.100
12,000
250
Selected compounds only; the Comprehensive Rl contains summary tables of all compounds detected in
LNAPL.
< = not detected at or above the specified detection limit.
J = value is an estimated concentration below the practical quantitation limit.
P:\136064M_l_3\flNAL\REPORT\TABLES\TABLE 3-9.DOC
-------
TABLE 3-10
Summary of Analytical Results for Groundwater Samples from OrrBase Areas
Concentration Range
Analyte (Units)
Shallow Groundwater
VOCs (pg/l)
Trichloroethene (TCE)
cis-1,2-Dichloroethene
1,2-Dichloroethene (total)
1,1-Dichloroethane
1,1,1-Trichloroethane
Vinyl Chloride
Toluene
Xylene
Benzene
1,2-Dichlorobenezene
1,4-Dichlorobenezene
Base/Neutral and Acid Extractable Compounds (BNAEs; pg/l)
2,6-Dinitrotoluene
2-Methylnaphthalene
Furans/Dioxins (pg/l)
Octachlorodibenzofuran
PCBs (M9/0
PCB-1260
Metals (ug/l)
Arsenic
Lead
Chromium (hexavalent)
Chromium (Total)
ND-2,300
ND-8,600
ND-42,000
ND-480
ND-3,000
ND-2,400
ND-2,400
ND-1,100
ND-310
ND-36,900
ND-3,300
ND-8.6
ND-140
ND-120
ND-150
ND-34,800
ND-1,630
ND-72
ND-3,190
Selected compounds only; the Comprehensive Rl contains summary tables for all compounds detected in
groundwater.
ND = not detected.
NA = not analyzed.
J = estimated concentration.
ug/l = micrograms per liter.
mg/l = milligrams per liter.
pg/l = picograms per liter.
PA136064\4J_3\FINAl\REPORTYr ABIES\TABLE3-10.DOC
-------
TABLE 3-11
Summary of Analytical Results for Groundwater Samples from the Weber River Valley
Concentration Range
Analyte (Units)
VOCs (ug/l)
Trichloroethene (TCE)
cis-1 ,2-Dichloroethene
1,2-Dichloroethene (Total)
1,1-Dichloroethane
1,1 ,1-Trichloroethane
Toluene
Xylene
Base/Neutral and Acid Extractable Compounds
(BNAEs; ug/l)
Total Petroleum Hydrocarbons (mg/l)
Furans (pg/l)
Dioxins (pg/l)
PCBs (Mg/l)
Metals (pg/l)
Arsenic (filtered)
Chromium (filtered)
Shallow
Groundwater
ND-28
ND-970
ND- 1,500
ND-28
ND-14J
1.6J
0.53J
ND
ND
NA
NA
NA
ND-30
ND-300
Groundwater from the Deeper
Part of the Aquifer
ND
ND
ND
ND
ND
ND
ND
NA
NA
NA
NA
NA
ND
30
Selected compounds only; the Comprehensive Rl contains summary tables for all compounds detected in
groundwater.
ND = not detected.
NA = not analyzed.
J = estimated concentration.
pg/l = micrograms per liter.
mg/l = milligrams per liter.
pg/l = picograms per liter.
P:\136064WJJJ\FINAUREPORTYrABlESU ABLE3-11.DOC
-------
TABLE 3-12
Summary of Surface Water Data for Select Compounds
Analytes (Units)
Metals-Unfiltered (pg/l)
Chromium, Hexavalent
Metals-Filtered (pg/l)
Arsenic
VOCs (M9/I)
Dichlorodifluoromethane
Vinyl Chloride
Chloroethane
cis=1 ,2-Dichloroethene
1,1-Dichloroethane
Total 1 ,2-Dichloroethene
1 ,2-Oichloroethane
1,1,1-Trichloroethane (TCA)
Trichloroethene (TCE)
Benzene
Toluene
Chlorobenzene
Ethylbenzene
m,p-Xylene
Hillside
Downgradient of
the Eastern Portion
ofOU1 (Seeps U1-
301,U1-302,U1-311
U1-312, andU1-319)
--
•
6-26.3
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
OU 1 Boundary
Northeast of
LF4(SeepsU1-
303, U1 -304,
and U1 -31 8)
-
31.4-1160
1.1-11
0.72J-50
1.7-5.3
1.1-3.3
2.2-8.1
0.95J-3.4T
0.82T-1.5
ND
0.19T-1.1
0.26J-7.3
0.21T-34
0.14T-2.2
0.28T-34
0.79T-26
Downgradient of
the Central
Portion of OU1
(Seep U1 -305)
ND
2.3-3.9
ND
ND
ND
0.54T-1.1
2.1-9.9
1.6T-1.6J
0.53T-0.64T
ND
1.3-4.5T
ND
ND
ND
ND
ND
Hillside Downgradient
of the Western Portion
ofOU1 (Seeps U1 -306,
U1-307, and U1 -308)
--
2.3-5.6
ND
ND
ND
450-490
0.28J-6.7
29-530
ND
ND
0.20J-0.67J
ND
ND
ND
ND
ND
Weber River Valley
Downgradient of
the Western
Portion of OU1
ND
ND
ND
ND
ND
85-140
1.4J-2.5
1 .4-240
ND
0.33J-3.3
1.6T-4.7
U
ND
ND
ND
ND
-------
TABLE 3-12
Summary of Surface Water Data for Select Compounds
Analytes (Units)
o-Xylene (1,2-Dimethylbenzene)
Xylenes, Total
Isopropylbenzene (Cumene)
n-Propylbenzene
1 ,3,5-Trimethylbenzene (Mesitylene)
1 ,2.4-Trimethylbenzene
sec-Butylbenzene
p-Cymene (p-lsopropyltoluene)
1 ,3-Dichlorobenzene
1 ,4-Dichlorobenzene
1 ,2-Dichlorobenzene
Naphthalene
Tetrachloroethene (PCE)
Hillside
Downgradient of OU 1 Boundary
the Eastern Portion Northeast of
of OU1 (Seeps U1 - LF 4 (Seeps U1 -
301.U1-302, U1-311 303, U1-304,
U1 -31 2, and U1 -31 9) and U1 -318)
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
0.80T-17
0.34J-2.8T
0.22J-0.92J
0.16J-0.58J
0.12T-1.1
0.32T-5.1
0.15T-0.29J
0.1 2J
0.13T-0.27J
0.41J-14
0.22T-1.4
0.98-1.4
ND
Downgradient of
the Central
Portion of OU1
(Seep U1 -305)
ND
ND
ND
ND
ND
0.13T
ND
ND
ND
ND
ND
ND
ND
Hillside Downgradient
of the Western Portion
ofOU1 (Seeps U1 -306,
U1-307, andU1-308)
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
4.1J
Weber River Valley
Downgradient of
the Western
Portion of OU1
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
6.2
- = not analyzed.
ND = not detectedn
J = estimated concentration.
T = detected above detection limit, but below standard reporting limit.
\\SNOWBIRD\PROJ\U60M\4JJWNAL\REPORTUABLES\TABLE 3-12.DOC
-------
TABLE 3-13
Summary of Metals Detected in Sediment Samples from Seeps/Springs at OU1
Sampling Location ID
Metal mg/kg Soil Background* U1-301 U1-303 U1-304 U1-305 U1-318
Arsenic 1.2-11 49 310 370 204 573
'Background range for arsenic in soil at OU1.
PA136064\4_1_3\FINAL\ftEPORT\TABL£S\TABLE 3-13.DOC
-------
Etovollon m fail
* Golf Course
Chemical Disposal Pits
, Weathered Zone
x Suillclal Landslides
x
Elevation in Peel
Alplne f ormafton
lowerCtby Urift
. ': . ': ': . ': . ': . ': . •'• . •'• . '• .. •' .. ' .. •' . •' , ''• .. ': .. ': .. ': , ': , ': .. ': .. •'• .. '; .. ': .. '•' .. ': .. ': . '• Alpine Formation ':
" - - '• '• ' '• ' ' ' ' ' ' ' ' ' ' ' - ' - ' ' ' "
Sand/Clay Unit .: .: ,: .: ' .:
Of MlflMCM II KVI»M
Legend
Main Groundwatei
Flow Paths
Minor Gfouncrwafef
Flow Paths
Geologic Contact
(aaproximatety Located)
Contaminated
Gioundwatet now Path
Horizontal Scale: \' - 500'
Vertical Scale: \' *•• lOff
FIGURE 3-1
HILL AFB OU1
GENERALIZED GEOLOGIC
CROSS-SECTION
-------
o:VNIIin>\ou!VRODUap\FlourMWIgur«3-]
•$>.;•-.v
%
Fire Training
Area 2
... . / Pond 10
£3 \ Waste s
Phenol/Oil Pit
LEGEND
Area Exceeding Soil PRGs
Maximum Extent of LNAPL
(all years of data considered)
Area Containing Free-Phase LNAPL
(based on April-June 1996 data)
• Existing Dewatering Well
—=•«= Existing Groundwater Extraction Trench
C ) Landfill 3 and Landfill 4
f Seeps and Springs
Waste Oil
Storage Tanks
(Removed)
V
Hill Air Force Base
Operable Unit 1
AREAS EXCEEDING SOIL PRGs
AND/OR CONTAINING FREE-
AMD RESIDUAL-PHASE LNAPL
FIGURE 3-2
-------
c:\MIHtbTBTT\ro Hm«p\>l9ur»«vllquf«3-3.
Ui-108 < PRGs (96 and
PROS (96). > PRGs (94)
1-112 < PRGs ('96); > PRGs ('94)
~
Non-Source Area Exceeding
PRGs Based on 1994 Data Only
U1-098 < PRGS ('96); > PRGs C94)
PRGs f 96 and '94
,'v
1-108>PRGsf%and'94)
rwn-Source Areas Exceeding
PRQs Based on 1996 Data
Existing S««p
Cottodton Snt
Source Areas
Exceeding PRGs
Existing Spring
allery
Existing Oewalenng WeH
Spring/Seep
Existing Groundwater E xlracllon Trench
and Spring Collection Gallery
Groundwater Monitoring Well
Proposed Boundary ol CAMU
Spring/Seep with Arsenlc-Conl-nnlnaled Sediment
Source Area Exceeding PRGs In Groundwater
f/ Hill Air Force Base
/ Operable Unit 1
AREAS EXCEEDING PRGs
FOR GROUNDWATER
AND SURFACE WATER
FIGURE 3-3
Non-Source Area Exceeding PRGs
lor Groundwaier (based on iPPfi data)
Non-Source Area Exceeding PRGs lor
Groundwalsr (based on 1994 data)
Area Exceeding PRGs In Surface Water
Preliminary Remediation Goal
-------
AnaeroDic oeoraaanon ol
ctiiormaieo hvOrocarSons
oroouces DCE, VCL
Vapor phase
Liquid phase (maior)
~~ Ijquid phase (minor)
j Burning (pyrolysis) of liguld waste
DCE Dictiloroetnene
TCE Tnchloroethene
VCL Vrnyfchloride
M,0 Water
LNAPL (residua! and tree-phase) CO: Cartxr doioe
Comamifiems solubilnet!
r ground water
Burning o' cnlonnatec
solvents sntf penucf^iorooneno!
proauces dloxinsHurans
Con;a~ir.a-ts sjr
rc »a;e*
HILL AIR FORCE BASE
OPERABLE UNIT 1
CONCEPTUAL MODEL FOR FATE AND
TRANSPORT OF CONTAMINANTS
ASSOCIATED WITH THE
MAJOR OU 1 SOURCE AREAS
FIGURE 3-4
Source1 R»»Md W»nm Dr»R Final FMsifatlity Study Ftepon
t 1. Montoom*ry VWU»m 1995
-------
Was Oil Storage
fait 5 '.(. (on" of map)
Mine ~.-.::e
Burning ol fur s ?
CO} and H,0
Aert-uic oegraoation of
tuei ryarocaroons produces
CO,. H;0. and alcoXois
Solid inaustriai and i
domestic wastes
«nae;ooic oeg-aoo'.c- o:
cnionnaiefl nyorocartwns
produces OCE. VCL
DCE Oicfiloroernene
Vapor pnsse
Liquid pnase (major)
Loud pnase (mnor)
Bummg (pyroiysis) ry bquid waste
A
LNAPL (residua
TCE Tncnloroethene
COj Carbon dioiide
Contaminants soiubilizec
r ground water
Sourc. FWviMd Inunm Dr«1 Ftn/ hMtiMiry SluoV S«poi
For Op«ru>l> Unt 1. UontKtmy VMrK . 1B95
HILL AfR FORCE BASE
OPERABLE UNIT 1
CONCEPTUAL MODEL FOR FATE AND
TRANSPORT OF CONTAMINANTS
ASSOCIATED WITH THE
MINOR OU 1 SOURCE AREAS
FIGURE V5
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4.0 Summary of Site Risks
4.0.0.1. A Comprehensive Baseline Risk Assessment was prepared for OU1 as part of the
Comprehensive Remedial Investigation Report for Operable Unit 1 (MW, 1995) to evaluate
potential health and environmental effects caused by actual or potential releases of and
exposure to OUl-related chemicals under current and hypothetical future conditions. The
risk assessment identifies the contaminants of potential concern (COPC), current and future
exposure pathways for humans, environmental receptors, and the probability of adverse
effects resulting from exposure. The four basic components of the risk assessment are
summarized in this section: identification of chemicals of potential concern, exposure
assessment, toxicity assessment, and risk characterization. Detailed descriptions of the risk
assessment are available in Appendix A of the Comprehensive Remedial Investigation Report
for Operable Unit 1.
4.1 Human Health Risks
4.1.1 Contaminants of Potential Concern
4.1.1.1. COPCs are defined by the EPA as "chemicals that are potentially site-related and
whose data are of sufficient quality for use in the quantitative risk assessment" (EPA, 1988).
All data of acceptable quality from the RI were used to identify COPCs. Detailed descrip-
tions of the screening and identification process and criteria are described in the
Comprehensive Baseline Risk Assessment. Criteria used to select COPCs followed EPA
guidance. In addition, chemicals were screened against conservative risk-based concen-
trations using calculated PRGs for a residential exposure scenario.
4.1.1.2. Although there are numerous contaminants present at OU1, only a few compounds
account for most of the potential human health and ecological risks. Chemicals dominating
the potential human health risks include DCE, vinyl chloride, arsenic, and in some
instances, TCE.
4.1.2 Exposure Assessment
4.1.2.1. Exposure assessment is the determination or estimation of the magnitude,
frequency, duration, and route of human and environmental exposures to COPCs present at
or migrating from a site. Human exposure to COPCs from OU1 was evaluated by
performing the following tasks: (1) characterizing the potentially exposed population,
(2) developing exposure scenarios, (3) identifying exposure pathways, and (4) quantifying
exposures for each scenario.
4.1.2.2. Current Off-Base Residential Exposure Scenario. The current land use in the off-Base
areas immediately north of OU1 consists of mostly residential homes and some areas used
for livestock grazing.
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Pathways for both child and adult receptors include the following:
• Inhalation of volatile compounds from basement seepage. (Note: Significant quantities
of VOCs have not been observed in air samples of basement air obtained in residences
overlying the OU1 off-Base plume).
• Ingestion of locally grown fruits and vegetables irrigated with contaminated
groundwater.
• Ingestion of locally produced beef products from animals fed contaminated water or
contaminated feed.
4.1.2.3. The Comprehensive Baseline Risk Assessment used standard equations and
assumptions available in EPA guidance to quantify chemical intake. This report documents
all the equations and assumptions used.
4.1.2.4. Future Off-Base Residential Exposure Scenario. According to State of Utah population
demographics for Davis County for the years 1990 through 2020, the resident population is
projected to increase at an annual rate of 2.14 percent (State of Utah Governor's Office of
Planning and Budget-Demographic and Economic Analysis Section, 1997).
4.1.2.5. The most likely future changes in land use in the area include increases in
residential housing and decreasing agricultural activities. New residents will most likely be
connected to the municipal water supply but could use shallow wells and drains for lawn
and garden irrigation. New residents may elect to install shallow groundwater wells even
though higher quality water is readily available from other sources; i.e., municipal sources
and deeper aquifers.
Pathways for both child and adult receptors include the following:
• Inhalation of volatile compounds from basement seepage.
• Inhalation of volatile compounds while showering.
• Dermal contact with contaminated water while showering.
• Ingestion of contaminated drinking water.
• Ingestion of locally grown fruits and vegetables irrigated with contaminated
groundwater.
• Ingestion of locally produced beef products from animals fed contaminated water or
contaminated feed.
• Dermal contact and/or ingestion of sediments associated with off-Base springs.
4.1.2.6. Future On-Base Residential Exposure Scenario. Residential development is not likely in
the on-Base areas of OU1. However, to provide a conservative assessment of the potential
risks associated with OU1, health risks based on a future on-Base residential development
were evaluated. The future potential exposure pathways associated with unrestricted,
on-Base residential land use include the following:
• Inhalation of contaminated fugitive dust from the site.
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• Inhalation of volatile compounds while showering.
• Dermal contact with contaminated water while showering.
• Dermal contact with and incidental ingestion of contaminated soils.
• Ingestion of contaminated drinking water.
• Ingestion of locally grown fruits and vegetables irrigated with contaminated
groundwater.
• Ingestion of locally produced beef products from animals fed contaminated water or
contaminated feed.
4.1.2.7. On-Base Worker Scenario. If development occurs at OU1, on-Base construction workers
could be exposed to site-related chemicals. Exposure pathways affecting workers engaged
in construction activities include the following:
• Inhalation of contaminated fugitive dust from the site.
• Inhalation of volatile compounds close to the source.
• Dermal contact with and incidental ingestion of contaminated soils.
4.1.3 Toxicity Assessment
4.1.3.1. Contaminants may have carcinogenic (cancer-causing) effects or noncarcinogenic/
systemic effects. Exposure to some of the chemicals detected at OU1 could potentially result
in both types of effects. For carcinogens, it is assumed any amount of exposure to a
carcinogenic chemical poses a potential for generating a carcinogenic response in the
exposed organism.
4.1.3.2. Noncarcinogenic or systemic effects include a variety of toxicological end points and
may include effects on specific organs or systems, such as the kidney, liver, lungs, and
others. Threshold levels generally exist for noncarcinogenic effects; i.e., a dose exceeding a
certain level must be reached before health effects are observed. No adverse effects are
assumed for doses below the threshold.
4.1.3.3. Cancer potency factors (CPF), or slope factors (SF), are used to provide conservative
estimates of excess lifetime cancer risks associated with exposure to potentially carcinogenic
chemicals. SFs, which are expressed in units of milligrams per kilogram per day
[(mg/kg-day)'] are multiplied by the estimated intake of a potential carcinogen, in
mg/kg-day, to provide an upper bound estimate of the excess lifetime cancer risk
associated with exposure at the intake level. The term "upper bound" reflects the
conservative estimate of the risks calculated from the SF. Use of this approach makes
underestimation of the actual cancer risk unlikely. SFs are derived from the results of
human epidemiological studies or chronic animal bioassays to which animal-to-human
extrapolation and uncertainty factors have been applied; e.g., to account for the use of
animal data to predict effects on humans.
4.1.3.4. Reference doses (RfD) are used to indicate the potential for adverse health effects
from exposure to chemicals causing noncarcinogenic effects. RfDs, which are expressed in
units of mg/kg-day, are estimated threshold levels for daily exposure below which
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exposure is considered safe for humans, including sensitive individuals. Estimated intakes
of COPCs from environmental media (e.g., the amount of a COPC ingested from
contaminated drinking water) can be compared with the RfD. RfDs are derived from
human epidemiological studies or animal studies to which uncertainty factors have been
applied. SFs and RfDs are specific to the route of exposure; for example, oral SFs are used to
evaluate risk through ingestion of a carcinogenic COPC.
4.1.4 Summary of Risk Characterization
4.1.4.1. Carcinogenic and noncarcinogenic risks were calculated for each of the exposure
pathways for the COPCs and compared with acceptable levels of risk. For each potentially
carcinogenic COPC, the probability that an individual will develop cancer over a lifetime
was estimated from projected intake levels and the cancer SF or the inhalation unit risk.
Risks are probabilities generally expressed in exponential form. An individual excess
lifetime cancer risk of 1 x 10"6 indicates that an individual has a 1-in-l million additional
chance of developing cancer as a result of site-related exposure to a carcinogen over a
70-year lifetime under specific exposure conditions at OU1.
4.1.4.2. To address the range of exposures that may occur now and in the future, both
average and reasonable maximum exposures (RME) were considered. Inclusion of both
average and RME values allows risks to be estimated for the upper bound exposure
situation and the more typical or average exposure. The resulting risk estimates then
present a range of possible risks based on the range of possible exposure conditions.
4.1.4.3. The EPA Superfund site remediation goal set forth in the National Oil and
Hazardous Substances Pollution Contingency Plan (NCP) allows a cancer risk of 10"1 (1 in
10,000) to 10"6 (1 in 1 million). This range is designed to be protective of human health. The
cancer risk of 10*, based on reasonable maximum exposure, is the required point of
departure for addressing risks. A cancer risk of 1 in 1 million is considered a "de minimis
level," or a level of negligible risk, for risk management decisions.
4.1.4.4. To characterize the potential systemic effects of chemicals, comparisons were made
between projected intakes of COPCs over specified rime and toxicity values, primarily oral
as well as dermal RfDs and inhalation reference concentrations. A hazard quotient (HQ),
which is the ratio between exposure to a chemical and that chemical's toxicity value, was
calculated for each COPC and exposure pathway. Chemical-specific HQs were then
summed for each COPC and each pathway of exposure to calculate the total hazard index
(HI) for each exposure scenario.
4.1.4.5. The HI is not a statistical probability of a systemic effect occurring. If the exposure
level exceeds the appropriate toxicity value (i.e., the HQ is greater than 1), there may be
cause for concern. The Superfund site remediation goal for noncarcinogens is a total HI of
less than 1.
4.1.4.6. Table 4-1 summarizes the cancer risk and hazard index estimates for each potential
exposure scenario. Excess cancer risks and hazard indices for current and potential future
pathways are summarized. Exposure pathways that may be complete at OU1 under current
conditions include inhalation of volatilized DCE (soil gas) in basements of houses that are
situated over the DCE-contaminated groundwater, and exposure to chromium in springs
used for watering livestock. Neither of these pathways poses a significant risk. (Note:
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RECORD OF DECISION FOR OPERABLE UNIT 1
significant quantities of VOCs have not been observed in air samples of basement air
obtained in residences overlying the OU1 off-Base plume).
4.1.4.7. Neither of the two potentially complete current exposure pathways identified poses
an unacceptable risk to human health or the environment. Air sampling within five homes
situated over DCE-contaminated groundwater in the Weber River Valley has shown that
excess cancer risks and risks of chronic health effects associated with current exposure to
soil gas in basements are both well below the target 1 x 10* excess cancer risk level and
hazard index of 1. The sampled homes are located off-Base over areas where concentrations
of 1,2-DCE are the highest, and one home has a basement that is partially below the water
table (the home has a sump to remove groundwater that enters the basement). Therefore,
the calculated exposure based on the results of this air sampling represents a worst case
scenario for this exposure pathway off-Base. The risks were well below acceptable levels.
4.1.4.8. Chromium was detected in one round of surface water sampling at OU1, and has
not been detected during subsequent rounds of quarterly monitoring. This suggests that the
initial chromium detections may be the result of false positives associated with matrix
interference during analysis, and are not representative of the environment. If it is assumed
chromium was present in the detected concentrations, the calculated hazard indices due to
exposure to the chromium are well below the benchmark of 1. Consequently, there are no
current significant risks to human health from exposure to chromium in surface water or to
organic compounds in basement air at OU1.
4.1.4.9. Future potential exposure pathways that could become significant involve on- and
off-Base domestic use of groundwater from the shallow unconfined water-bearing zone,
exposure of construction workers and future residents to on-Base soil contaminants, and
exposure to contaminated soil gas if it migrates into the basements of houses. When
possible, quantitative exposure estimates resulting from these pathways were made. The
scenarios were analyzed qualitatively when a large degree of uncertainty existed. When
evaluating potential exposure, the existing response actions at OU1 were not assumed to be
in place.
4.1.4.10. In the future, if the shallow groundwater beneath OU1 is used for drinking and for
showering, the resulting cancer risks and non-cancer health threats both would be greater
than permitted by the NCP. Although the health risks (1 x 10s) associated with future
exposure to contaminants present in the shallow groundwater of the Weber River Valley
fall within the NCP range of 10"6 to KT1, the hazard index is estimated to be between 1 and
10. For future exposure to shallow on-Base groundwater beneath the Source Areas, the
excess cancer risks are estimated to be greater than 103 and hazard indices range from 20
to 90.
4.1.4.11. Based on a qualitative evaluation, risks from exposure to soil gas in basements of
future on-Base residences may become significant in the future. Health risks associated with
the exposure of construction workers to on-Base contaminated soil are expected to be of
borderline significance (1 x 10"*) at most. Future excess cancer risks were estimated to be no
greater than 1 x 10*6 for any of the Source Areas, although these estimates did not include
risks from compounds that do not have published toxicity values. If these compounds were
included, it may be reasonable to assume a potential cancer risk between 1 x 10"6 and 1 x 10"*
at the CDPs and the Waste Phenol/Oil Pit. All hazard indices for soil are estimated to be
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RECORD OF DECISION FOR OPERABLE UNIT 1
less than 1. The estimated cancer risk (1 x 10"6) and the hazard index (0.01) from ingestion of
soil (contaminated with pesticides and PCBs) by future residents is not significant.
4.2 Ecological Risk Characterization
4.2.0.1. Calculated doses of the main contaminant of environmental concern (arsenic) to
alfalfa (or similar crops) and cattle were lower than doses reported to have no effect on
these receptors. While other types of vegetation and domestic animals are found in the area,
cattle and alfalfa were considered representative species for risk calculations that would
provide a reasonable indication of potential hazards to agriculture. The results of this
investigation indicate that non-domestic plants and animals are not expected to be
adversely affected by the contaminants from OU1. As discussed in the Comprehensive
Baseline Risk Assessment, neither critical habitats nor threatened or endangered species are
present. Pond No. 10 contains the area of the former Waste Phenol/Oil Pit. This pond holds
surface water runoff from nearby areas of the Base. Contaminants detected at the Waste
Phenol/Oil Pit occur in subsurface soil, and are not expected to significantly impact the
quality of water in Pond No. 10. Animals that drink from the escarpment springs/seeps
could be exposed to arsenic contaminated sediments, but exposure would be of short
duration and is not expected to produce adverse effects.
4.3 Uncertainty Analysis
4.3.0.1. Uncertainty is inherent to the risk assessment process. Uncertainty associated with
these risk estimates include uncertainties associated with the exposure estimates and
uncertainties in the toxicity evaluation. Uncertainties associated with the risk
characterization include data, indicator chemical selection, exposure, and toxicity
assumptions. The primary additional uncertainty is whether the future exposure pathways
(especially those involving residential exposure on-Base) will actually become complete in
the future. If not, the actual cancer risks and hazard indices are zero. Other uncertainties
include extrapolations from high to low dose, extrapolations from animals to human, model
uncertainties, representativeness of samples, and intraspecies variation. Because of the
arguments presented in this section, it can be stated that for those exposure scenarios which
have been quantitatively evaluated and for which the most toxic and prevalent compounds
at OU1 have reference doses and slope factors, the risk assessment is expected to be
conservative, and the actual risks are expected to be less than those calculated. Certain
exposure scenarios were not evaluated quantitatively due to a lack of information.
4.3.0.2. Risks from petroleum mixtures, including jet fuel, diesel, and gasoline, were not
addressed quantitatively in the risk assessment because the potential for risk was clear from
a qualitative assessment. These mixtures would be associated with human health risks by
all routes including oral, inhalation, and dermal exposures. However, the odor, taste, and
appearance of any groundwater mixed with LNAPL would be objectionable, and actual
direct contact with this medium is not anticipated under any future scenario. For all
evaluations, the risk assessment is expected to be conservative, and the actual risks are
probably less than those calculated in the Comprehensive Baseline Risk Assessment.
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4.4 Overview of Site Risks
4.4.0.1. Actual or threatened releases of hazardous substances from this site, if not
addressed by implementing the response action selected in this ROD, may present an
imminent and substantial endangerment to public health, welfare, or the environment.
4.4.0.2. Remedial action at OU1 is warranted on the basis of potential future risks to human
health and the environment (i.e., to prevent a significant risk to residents). Also, remedial
action is generally warranted when MCLs are exceeded in groundwater. Potential domestic
groundwater use accounts for the majority of the risk by ingesrion, inhalation, and dermal
pathways.
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TABLE 4-1
Summary of Cancer Risks and Hazard Indices
Scenario
CURRENT
Seeps and Springs
Chromium in Irrigation Water
Indoor Air Inhalation
Indoor Air Data
Soil Gas Data
FUTURE
Residential Use of Water from the Shallow Aquifer
On-Base
Chemical Disposal Pits
Landfills
Agricultural Use of Water from the Shallow Aquifer
On-Base
Chemical Disposal Pits
Landfills
Residential Use of Water from the Shallow Aquifer
Off-Base
Soil • Construction Worker
Chemical Disposal Pits
Landfill 3
Landfill 4
Fire Training Area 1
Fire Training Area 2
Hazard
Ingestlon Inhalation
0.0007 NA
NA 0.02(a)
NA 2'"
55 10
10 0.3
6 NA
5 NA
7 0.03
0.02 0.2
0.003 4
0.0005
0.01 0.0007
0.0001 0.03
Index
Dermal Total
NA 0.0007
NA 0.02""
NA 2'"
0.05 65
0.01 10
NA 6
NA 5
0.007 7
NA 0.2
NA 4
NA 0.0005
NA 0.01
NA 0.03
Cancer Risk
Ingest) on
NA
NA
NA
1 x 10'2
4 x 10'3
1 x 10'3
1 x 10'3
7 x 10"S
8x10"'
7 x 10'°
2 x 10-7
9 x 10"'
1 x 10"8
Inhalation
NA
NA
NA
5 x 10'3
4 x 10'3
NA
NA
1 x 10'5
4 x 1Q'5
3 x 10-"
1 x ID'8
2 x 10'7
3 x 10'7
Dermal
NA
NA
NA
1 x 10'5
1x10*
NA
NA
7 x 10-"
NA
NA
NA
NA
NA
Total
NA
NA
NA
2 x 10'2
6 x 10'3
1 x 10'3
1 x 10'5
8 x 10'5
4x10-*
7 x 10"*
1 x 10-*
1 x 10"*
3 x 10'7
PA1
360^|^3\FINAL\REPORTUABLES\TABLE 4-1.DOC
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TABLE 4-1
Summary of Cancer Risks and Hazard Indices
Hazard Index
Scenario
Waste Phenol Oil Pit
Waste Oil Tank Site
Surface Soil
Northern Perimeter of OU1 with Pesticides/PCBs
Northern Perimeter of OU1 without Pesticides/PCBs
Soil Gas
Chemical Disposal Pits
Ingestion Inhalation
0.004 0.000004
0.000003
0.002 NA
0.0007 NA
NA 0.0001
Dermal Total
NA 0.004
NA 0.000003
NA 0.002
NA 0.0007
NA 0.0001
Cancer Risk
Ingestion Inhalation Dermal
r
5x 10'" 6 x 10'8 NA
1 x 10'' 3 x 10'12 NA
3 x 10"* NA NA
2 x 10"* NA NA
NA 1 x 10-5 NA
Total
7x 1Q-*
1«10*
3x10-*
2x10"*
1 x 10'5
Total cancer risk and hazard index may not appear to equal the sum of the route-specific values due to rounding.
'"Most conservative result of three scenarios analyzed.
NA = Not applicable.
- = no data available.
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5.0 Description of Alternatives
5.0.0.1. The following subsections provide a detailed description of each of the developed
alternatives. The descriptions are separated into Source Area (SA) alternative descriptions
and Non-Source Area (NSA) alternative descriptions. Elements common to the SA and NSA
alternative descriptions are summarized at the end of this section. The specific details of the
remedial components are intended only to serve as representative examples to allow
order-of-magnirude cost estimates. Other viable process options to achieve the same
objectives may be evaluated during remedial design activities for OU1. The monitoring
programs developed for the alternatives represent preliminary monitoring designs that
were developed in the FS for the purpose of defining an initial scope and estimating costs.
The final design of the monitoring program, including the number and exact locations of
monitoring wells, will be defined during remedial design.
5.1 Source Area Alternatives
5.1.1 Source Area Alternative 1 (SA1) — No Further Action
5.1.1.1. Major remedial components of SA1 are described below. A description of the
component is presented in the following paragraphs. Included in SA1 are the following
components:
• Continued operation of the existing groundwater collection systems.
• Treatment of extracted groundwater at the HAFB OU2 ASTP or the IWTP.
• Maintenance of the existing landfill cap and passive gas vent system.
• Environmental monitoring, including the continued monitoring of the effectiveness of
the existing upgradient soil/bentonite cut-off wall.
• Institutional controls as described in Section 5.3.0.16.
5.1.1.2. Existing Groundwater Collection System. The existing groundwater collection system is
comprised of a series of dewatering wells and a single infiltration collection gallery in the
OU1 Source Area. SA1 includes the continued operation of these systems for containment of
contaminated groundwater.
5.1.1.3. Groundwater Treatment. Currently, groundwater from the existing collection system is
treated at the HAFB IWTP. The OU1 discharge will be redirected from the HAFB IWTP to
the new ASTP at OU2 as part of all alternatives, including SA1. These modifications were
recommended and initiated prior to the development of the FS in the Three-Mile Pipeline
Design Options Report (Radian, 1995).
5.1.1.4. Landfill Cap and Passive Gas Vent System. A low-permeability soil/bentonite cap was
constructed over Source Areas between 1983 and 1986. SA1 includes operation and
maintenance of this cap. This will include walk-over surveys of the surface soils for
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identification of defects such as desiccation cracks, animal burrows, tire ruts, localized low
areas resulting from settlement of the waste, erosional features, and any other features
indicating the hydraulic integrity of the cap has been compromised. In addition, inspection
of the landfill gas vents will be conducted. Landfill gas vents will be repaired in accordance
with the original vent design.
5.1.1.5. Environmental Monitoring. The objective of the SA1 environmental monitoring program
is to assess the degree of protection provided by the existing environmental control systems
and to determine whether performance standards and remedial goals are being met.
Further, the monitoring program for SA1 establishes a baseline monitoring scenario to
which monitoring programs for other Source Area alternatives will be compared.
5.1.1.6. Groundwater monitoring for SA1 is designed to monitor changes in hydrogeologic
conditions, contaminant concentrations, as well as lateral and vertical extent of
contamination. Five well pairs (two existing, three new) will be used to address uncertainty
associated with the effectiveness of the upgradient soil/bentonite cut-off wall. Monitoring
of water levels and contaminant concentrations in the vicinity of the soil/bentonite cut-off
wall will help identify the effectiveness of the cut-off wall. Additional Source Area
monitoring will be accomplished by collecting groundwater samples from six existing
Provo Formation (shallow) wells and four existing Alpine Formation (deep) wells. These
20 wells will be monitored monthly for LNAPL thickness and water table elevation for the
first year of remediation system operation and quarterly for the remaining years of
operation. Analytical samples will be collected semiannually for the first 3 years of
remediation system operation and annually for the remaining years of operation. It is
assumed groundwater monitoring will continue for at least the 30-year period used in
estimating present worth costs. Samples from all 20 wells will be analyzed for VOCs and
arsenic. Groundwater samples from four shallow monitoring wells located downgradient to
Landfills 3 and 4 will also be analyzed for chlorinated insecticides, chlorophenoxy
herbicides, and explosives. The continuous decline of groundwater elevations and
subsequent gradual reduction of the LNAPL plume extent in the Source Area, due to the
continuous operation of the existing extraction system, may limit the usefulness of a
number of existing monitoring wells. It is anticipated for cost estimating purposes that as
many as 20 existing monitoring wells would be abandoned as part of SA1.
5.1.1.7. Surface water sampling for SA1 will include the collection of one surface water
sample from Pond No. 10 near the former WPOP location following each major storm
event. The pond water samples will be analyzed for VOCs and arsenic.
5.1.2. Source Area Alternative 2 (SA2) — Existing System Upgrade
5.1.2.1. Major remedial components of SA2 are shown in Figure 5-1 and further described
below. A description of the component is presented in the following paragraphs. Included
in SA2 are the following components:
• Upgrade of the existing groundwater collection system along primary groundwater
flow paths.
• Groundwater treatment at the OU2 ASTP or the IWTP.
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• Repair, operation, and maintenance of the existing landfill cap and passive gas vent
system.
• Environmental monitoring, including the continued monitoring of the effectiveness of
the existing upgradient soil/bentonite cut-off wall.
• Institutional controls as described in Section 5.3.0.16.
5.1.2.2. The following paragraphs provide greater detail concerning each of these
components.
5.1.2.3. Groundwater Collection System Upgrades. The objective of the upgraded groundwater
collection system for SA2 is to prevent further offsite migration of contaminated
groundwater in the Provo Formation. Flow in the saturated Provo Formation is primarily to
the east and west; flow in the weathered Alpine Formation is primarily toward the north,
with some additional flow east and west. Under SA2, the existing groundwater collection
system will continue to be operated. Additionally, two gravel-filled trenches will be
constructed within the Base boundary across the east and west flow channels in the Provo
Formation to control the flow and migration of contaminants from the OU1 Source Area.
The western trench, as shown in Figure 5-1, is designed to extend southwest beyond the
existing soil/bentonite cut-off wall to capture contaminated groundwater attributable to
residual LNAPL in this area. The existing and new extraction sumps will include an
automated level detection system relative to downgradient piezometers to assure that
effective capture is achieved.
5.1.2.4. The vertical extent of the collection trenches was established on the basis of the flow
regimes in the Provo and Alpine Formations. It is possible that slope stability may limit the
depth of the eastern trench. For this reason, the eastern trench is intended to capture only
Provo Formation flow, while the western trench would be designed to capture flow in the
Provo Formation and in the upper 15 feet of the Alpine Formation. Total extraction rates are
estimated to be approximately 50 gallons per minute (gpm) for the eastern trench and
45 gpm for the western trench. It is assumed for the purpose of cost estimating that the
collection and treatment system will be operated for the 30-year present worth period. It is
possible that more time may be needed to fulfill remedial action objectives. However, it is
also possible that groundwater in the Provo Formation will be remediated to MCLs in a
shorter time period. Estimates of the time necessary for groundwater to be remediated are
highly uncertain for the OU1 Source Area and depend on the accuracy of many
assumptions. Based on contaminant flushing calculations, groundwater VOC
concentrations in the Provo Formation could decline to MCL concentrations in about 10
years, assuming no further contaminant loading to the groundwater from either the
unsaturated zone soil or the LNAPL residual. In reality, contamination loading will
continue at reduced levels as the water table drops below the elevation of the LNAPL
residual. In the Alpine Formation, the low hydraulic conductivity reduces the amount of
flushing achievable. Contaminant reductions in the Alpine Formation will largely depend
on the amount of degradation rather than the flushing of the water-bearing zone.
5.1.2.5. Groundwater Treatment. As discussed previously, groundwater collected from the
extraction system may be redirected to the OU2 ASTP for treatment and discharged to the
Central Weber Sewer Improvement District plant (CWSID). The groundwater may also be
treated at the IWTP.
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5.1.2.6. Landfill Cap Repair and O&M. The existing landfill cap was recently inspected and
found to have numerous depressions over Landfill 4 where water could pond and increase
infiltration through the landfill cap. These depressions are likely a result of landfill
settlement caused by decomposition of wastes and the weight of the landfill cap. SA2
includes filling these depressions and revegetating the area to promote runoff and prevent
ponding of water. SA2 also includes the same O&M provisions for the existing landfill cap
discussed for SA1.
5.1.2.7. Environmental Monitoring. The following monitoring wells will be added to the
groundwater monitoring program specified for SA1 to assess the effectiveness of the east
and west groundwater collection systems and to verify offsite contaminant migration is
mitigated:
• Monitoring of two existing shallow monitoring wells and installation/monitoring of
one new shallow monitoring well.
• Monitoring of three existing deep monitoring wells and installation of one new deep
monitoring well.
5.1.2.8. Each of these monitoring wells will be included in the monitoring program for water
level measurement, LNAPL thickness measurement, as well as VOC and arsenic analysis.
Continuous decrease of groundwater elevations and subsequent gradual reduction of the
LNAPL plume extent in the Source Area, due to the additional groundwater extraction
along the primary flow paths and continuous operation of the existing extraction system in
the Source Area, may limit the usefulness of a number of existing monitoring wells.
Although the number of monitoring wells to be abandoned for the alternative will be
established during the remedial design, it is anticipated for cost estimating purposes that as
many as 30 existing monitoring wells would be abandoned as part of SA2. In addition, eight
new monitoring wells will be installed (including the six new monitoring wells proposed
for SA1). Monitoring of water levels and contaminant concentrations in the vicinity of the
existing upgradient soil/ben tonite cut-off wall will help identify the effectiveness of the
cut-off wall.
5.1.2.9. No surface water sampling is included for SA2 or subsequent Source Area
alternatives; this is because the pump inlet at Pond No. 10 will be lowered so the pond can
be completely drained. Stormwater currently managed in Pond No. 10 will be diverted to
Pond No. 9 located approximately 2 miles west of Pond No. 10.
5.1.3 Source Area Alternative 3 (SA3) — Groundwater Dewatering
5.1.3.1. Major remedial components of SA3 are shown in Figure 5-2 and further described
below. The following paragraphs describe the conceptual design of SA3, including the
following specific components:
• Dewatering of the Source Area by a series of groundwater extraction trenches.
• LNAPL recovery from the extraction trenches followed by proper disposal of
the LNAPL.
• Groundwater treatment at the OU2 ASTP or the IWTP.
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• Repair and continued O&M of the landfill cap and passive gas vent system.
• Environmental monitoring, including the continued monitoring of the effectiveness of
the existing upgradient soil/ben tonite cut-off wall.
• Institutional controls as described in Section 5.3.0.16.
5.1.3.2. The following paragraphs provide greater detail concerning each of these
components.
5.1.3.3. Dewatering of the Source Area. As shown in Figure 5-2, six separate trenches will be
used to dewater the Source Area. These trenches are labeled Trenches A through F in
Figure 5-2. The length and alignment of the dewatering trenches were based on the
following factors:
• Current and historic extent of the LNAPL plume.
• Preferential groundwater flow paths.
• Groundwater "troughs" in the Provo Formation.
• Saturated thickness of the Provo Formation.
• Dissolved phase plume extent of total DCE exceeding 1,000 pg/L.
• Location of the individual Source Areas.
5.1.3.4. Conceptual design details were developed for cost estimating purposes. Trenches A,
B, and C are assumed to be 30 feet deep and will only dewater the Provo Formation.
Trenches D and E will dewater the Provo and Alpine Formations will be constructed to a
total depth of approximately 45 feet such that these trenches will extend approximately 10
to 15 feet into the Alpine Formation. The objective of these trenches is primarily to expedite
dewatering and ensure groundwater containment within the Base boundary. Trenches A, B,
and C are also designed to enhance the recovery of the LNAPL plume and minimize
vertical smearing of free-phase LNAPL. The total assumed design trench length is
approximately 3,700 feet. The actual location and number of trenches will be determined
during the remedial design.
5.1.3.5. As shown in Figure 5-2, the alignment of Trench B is such that construction through
the contents of Landfill 3 will be required. It is assumed that continuous trenching
construction will be applied. This technology has been successfully employed at HAFB
Operable Unit 4, Landfill 1. It is expected oversized debris present in the landfill may jam
the trench's equipment and cause minor construction delays. Large obstructions that cannot
be removed by continuous trenching will be excavated with a backhoe. The use of
continuous trenching technology will reduce the amount of potentially contaminated trench
spoils over conventional trackhoe excavation. It is expected that trench spoils generated
during construction of Trench B will include some contaminated soils or wastes. These will
be consolidated within the landfill. A cap of the same design as the existing cap will be
placed over the spoils.
5.1.3.6. In addition to the dewatering trench system, the existing groundwater extraction
trench and wells will continue to be operated as described for SA1; however, once
dewatering of the Source Area is achieved, the production rate of this system is expected to
decline substantially.
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5.1.3.7. LNAPL Recovery. Dewatering Trenches A and C are located in the LNAPL area, and it
is expected that free-phase LNAPL will flow to these trenches. Skimmer pumps may be
installed in each of the sumps of these trenches to recover LNAPL. The recovered LNAPL
will be properly disposed of. In addition, an oil/water separator will be installed prior to
discharge to the ASTP or IWTP to remove any additional LNAPL.
5.1.3.8. Groundwater Treatment. As part of SA3, fluids produced during dewatering of the
Source Area will be treated at the OU2 ASTP or the IWTP. It is assumed the dewatering
system will initially operate at 300 gpm, as calculated in the FS. Once the site is dewatered,
steady state operations will resume at approximately 30 to 130 gpm. The hydraulic capacity
of the OU2 ASTP or the IWTP is sufficient to handle the maximum pumping rate of
300 gpm from OU1.
5.1.3.9. Based on 1994-1996 groundwater analytical data, Table 5-1 presents groundwater
quality parameters that are assumed for extracted groundwater:
TABLE 5-1
Assumed Quality of Extracted Groundwater'
Constituent Concentration (\ig/L)
TCE 100
1,1,1 TCA 50
PCE 100 .
cis-1,2DCE 2,000
trans-1,2DCE 50
Vinyl Chloride 300
5.1.3.10. As a result of the potential for entrainment of small droplets of LNAPL in the water
to be treated at the OU2 ASTP or IWTP, the groundwater would be analyzed for the full list
of contaminants found in the LNAPL as part of the design of this remedy. This includes
dioxins/furans, PCBs, and semi-volatile compounds in addition to the VOCs.
5.1.3.11. To investigate the feasibility of treatment of the OU1 dewatering fluids to discharge
standards, the Shallow Tray Modeler™ (NEEP, 1996) was run for this scenario. The model
shows that with the addition of 300 gpm to the existing OU2 flow of 100 gpm, two air
strippers will be required to achieve the discharge requirements. Treated effluent will be
discharged to the CWSID.
5.1.3.12. In addition to the treatment plant capacity analysis, the air emissions were
estimated and compared to Utah Department of Air Quality (UDAQ) criteria. The resultant
air emissions will not require treatment according to established criteria.
5.1.3.13. Landfill Cap Repair and O&M. Provisions for the repair and O&M of the existing landfill
caps under SA3 are the same as those presented for SA2.
5.1.3.14. Environmental Monitoring. The following wells will be added to the groundwater
monitoring program specified for SA1 to assess the effectiveness of the dewatering system:
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• Monitoring of four existing shallow wells and installation/monitoring of five new
shallow monitoring wells.
• Monitoring of six existing deep wells and installation/monitoring of one new deep
monitoring well.
5.1.3.15. Each of these monitoring wells will be included in the monitoring program for
water level measurement, LNAPL thickness measurement, and VOC and arsenic analysis.
Rapid decline of groundwater elevations and subsequent gradual reduction of LNAPL
plume extent in the Source Area, due to the groundwater dewatering effort and continuous
operation of the existing extraction system in the Source Area, may limit the usefulness of a
number of existing monitoring wells. Although the number of monitoring wells to be
abandoned for the alternative will be established during the remedial design, it is
anticipated for cost estimating purposes that as many as 40 existing monitoring wells would
be abandoned as part of SA3. In addition, 12 new wells will be installed (including the six
new monitoring wells proposed for SA1). Monitoring of water levels and contaminant
concentrations in the vicinity of the existing upgradient soil/bentonite cut-off wall will help
identify the effectiveness of the cut-off wall.
5.1.4 Source Area Alternative 4 (SA4) — Source Containment
5.1.4.1. Major remedial components of SA4 are shown in Figure 5-3 and further described
below. The following paragraphs describe the conceptual design of SA4, including the
following specific components:
• Downgradient soil/bentonite cut-off wall.
• Dewatering of the Source Area by a series of groundwater collection trenches.
• LNAPL recovery from the extraction trenches using skimmer pumps.
• Groundwater treatment at the OU2 ASTP or the IWTP.
• Continued O&M of the landfill cap and passive gas vent system.
• Environmental monitoring, including the continued monitoring of the effectiveness of
the existing upgradient soil/bentonite cut-off wall.
• Institutional controls as described in Section 5.3.0.16.
5.1.4.2. The following paragraphs provide greater detail concerning each of these
components.
5.1.4.3. Downgradient Soil/Bentonite Cut-Off Wall. A downgradient hydraulic barrier would be
installed as part of SA4 to provide an added degree of assurance that the migration of
contaminated groundwater is mitigated. The hydraulic barrier system would be comprised
of a soil/bentonite cut-off wall approximately 30 to 45 feet deep such that the wall would
extend approximately 15 feet into the Alpine Formation. The depth of the wall is intended
to intercept groundwater flow through sand stringers in the Alpine Formation that may not
be effectively contained by the dewatering trenches.
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5.1.4.4. The alignment of the downgradient cut-off wall is shown in Figure 5-3. This
alignment was developed to achieve the following criteria:
• Intercept the primary east and west groundwater flow paths.
• Avoid the OU1 slope area based on constructability and slope stability concerns.
• Avoid the containment and treatment of "clean" precipitation from Pond No. 10 by
aligning the wall along the upgradient edge of Pond No. 10.
• Minimize groundwater contact with OU1 contaminants by aligning the wall in close
proximity to contaminant sources.
5.1.4.5. Because operation of the dewatering trench system is expected to eliminate off-Base
groundwater flow, a separate extraction system is not included in the design of the
downgradient cut-off wall. It is anticipated construction of the wall would be phased such
that dewatering of the Source Area would be completed prior to wall construction. This
would allow the exact depth and alignment of the wall to be refined to address long-term
operations under dewatering conditions.
5.1.4.6. Dewatering of the Source Area. As with SA3, dewatering of the Source Area will be
accomplished by a series of dewatering trenches installed in the areas of the greatest
saturated thickness of the Provo Formation. The existing groundwater extraction trench and
wells will continue to be operated as discussed for SA1; however, once dewatering of the
Source Area is achieved, the production rate of this system is expected to decline
substantially.
5.1.4.7. LNAPL Recovery. Provisions for the recovery of LNAPL for SA4 are the same as those
presented for SA3.
5.1.4.8. Groundwater Treatment. As with previous alternatives, groundwater collected by the
dewatering system for SA4 would be treated at the OU2 ASTP or the IWTP and discharged
to the local POTW. The quantity and quality of extracted groundwater is expected to be the
same as that discussed for SA3.
5.1.4.9. Landfill Cap Repair and O&M. Provisions for repair and O&M of the existing landfill cap
under SA4 are the same as those presented for SA2.
5.1.4.10. Environmental Monitoring. The groundwater monitoring program for SA4 is the same
as that presented for SA3, with the following additions:
• Installation of 10 new shallow piezometers along the downgradient cut-off wall.
• Installation of 10 new deep piezometers along the downgradient cut-off wall.
5.1.4.11. These piezometers would be situated as well pairs along the downgradient cut-off
wall to monitor hydraulic gradients created by the wall. Water level monitoring would be
conducted at these piezometers on a monthly basis for the first year of operation and
quarterly thereafter. Additionally, monitoring of water levels and contaminant
concentrations in the vicinity of the existing upgradient soil/bentonite cut-off wall will help
identify the effectiveness of the upgradient cut-off wall.
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5.1.5 Source Area Alternative 5 (SA5) — Source Containment and Cap Upgrade
5.1.5.1. Major remedial components of SA5 are shown in Figure 5-4 and further described
below. A description of the component is presented in the following paragraphs. Included
in SA5 are the following components:
• Upgrade the existing landfill cap.
• Downgradient soil/bentonite cut-off wall.
• Dewatering of the Source Area by a series of groundwater collection trenches.
• LNAPL recovery from the extraction trenches using skimmer pumps.
• Groundwater treatment at the OU2 ASTP or the IWTP.
• Continued O&M of the landfill cap and passive gas vent system.
• Environmental monitoring, including the continued monitoring of the effectiveness of
the existing upgradient soil/bentonite cut-off wall.
• Institutional controls as described in Section 5.3.0.16.
5.1.5.2. The following paragraphs provide greater detail concerning each of these
components.
5.1.5.3. Upgrade of Existing Landfill Cap. SA5 includes upgrading the existing cap with an
engineered cap. Preliminary assessments from the Hydrologic Evaluation of Landfill
Performance Model analysis indicate a potential reduction in percolation rates of
approximately one order of magnitude may be achieved with an improved cap. This
corresponds to approximately 70,000 cubic feet (500,000 gallons) per year of reduced
leachate generation.
5.1.5.4. The extent of the cap upgrade, as shown in Figure 5-4, was selected to reduce
infiltration to the entire OU1 Source Area. The design of the improved cap would consist of
a protective vegetation layer over a hydraulic barrier layer of either compacted clay or a
geosynthetic clay liner. From the surface down, the cap components would be as follows:
• A 6-inch-thick layer of topsoil, planted with grasses suitable for the climate and selected
to eliminate the need for irrigation.
• An 18-inch-thick layer of subsoil to provide mechanical protection of the underlying
hydraulic barrier layer.
• A hydraulic barrier layer, consisting of one of the following (the selection would be
made during remedial design):
- A 1- to 2-foot thick layer of compacted low-permeability clay. The permeability
should be less than 1 x 10"6 cm/sec, and preferably would be less than 1 x 107 cm/sec
if sufficient soil of this permeability can be obtained locally.
- A commercially manufactured geosynthetic clay layer. These materials consist of a
synthetic material (either a geotextile or a geomembrane ) coated with, or otherwise
holding, a uniform thickness of bentonite clay.
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• Grading fill, as necessary, to properly slope the surface (at least 2 percent) to promote
surface water runoff.
5.1.5.5. No drainage layer would be provided since the evapotranspiration of the site is
relatively high. As a result, the primary function of the hydraulic barrier layer would be to
retard any infiltration that does occur, and keep it in the root zone where it is available for
plant uptake and evapotranspiration. Also, no active gas venting system has been provided
since the landfill has been inactive for several years and the potential for gas generation is
low. It is anticipated nothing more complex than a limited number of passive vents would
be required. Evaluation of the need for additional venting as well as use of the existing
passive gas venting system with minor modifications would be considered during the
remedial design.
5.1.5.6. It is assumed the cap upgrade would be constructed over the existing cap without
excavation to minimize risk of exposure to the landfilled wastes during construction. The
slope of the cap would also be improved to provide greater surface runoff. The drainage
swale constructed in the landfill cap within Landfill 4 would be filled, resulting in a
continuous slope. An O&M routine similar to that described in Alternatives SA2
through SA4 would be employed to ensure long-term effectiveness of the upgraded cap.
5.1.5.7. It is assumed that the existing detention pond, Pond 10, has sufficient capacity to
collect surface runoff from the upgraded cap. An assessment would be conducted during
the remedial design to determine whether an upgrade of Pond 10 is required.
5.1.5.8. Downgradient Soil/Bentonite Cut-Off Wall. The conceptual design of the downgradient
cut-off wall for SA5 is the same as that presented in SA4.
5.1.5.9. Dewatering of the Source Area. As with SA3 and SA4, dewatering of the Source Area
would be accomplished by a series of dewatering trenches installed in the areas of the
greatest saturated thickness of the Provo Formation. The existing groundwater extraction
trench and wells would continue to be operated as discussed for SA1; however, once
dewatering of the Source Area was achieved, the production rate of this system would be
expected to decline substantially.
5.1.5.10. LNAPL Recovery. Provisions for the recovery of LNAPL for SA5 are the same as those
presented for SA3 and SA4.
5.1.5.11. Groundwater Treatment. As with previous alternatives, groundwater collected by the
dewatering system for SA5 will be treated at the OU2 ASTP or the IWTP and discharged to
the local POTW. The quality of extracted groundwater would be expected to be the same as
that discussed for SA3 and SA4; however, the quantity of extracted groundwater would be
reduced by the landfill cap upgrade.
5.1.5.12. Environmental Monitoring. The groundwater monitoring program for SA5 is the same
as that presented for SA4.
5.1.6 Source Area Alternative 6 (SA6) — Source Treatment and Cap Upgrade
5.1.6.1. Major remedial components of SA6 are shown in Figure 5-5 and further described
below. The following paragraphs describe the conceptual design of SA6, including the
following specific components:
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• Soil vapor extraction (SVE) for in situ treatment of contamination.
• Upgrade of the existing landfill cap over Landfills 3 and 4.
• Downgradient soil/bentonite cut-off wall.
• Dewatering of the Source Area by a series of groundwater collection trenches.
• LNAPL recovery from the extraction trenches using skimmer pumps.
• Groundwater treatment at the OU2 ASTP or the IWTP.
• Continued O&M of the landfill caps and passive gas vent system.
• Environmental monitoring, including the continued monitoring of the effectiveness of
the existing upgradient soil/bentonite cut-off wall.
• Institutional controls as described in Section 5.3.0.16.
5.1.6.2. The following paragraphs provide greater detail concerning each of these
components.
5.1.6.3. Soil Vapor Extraction. SVE of the Source Area would be conducted primarily through a
perforated pipeline installed above the dewatering pipeline in Trenches A, B, C, and D
(see Figure 5-5). The dewatering pipeline would dewater the zone to be remediated and
expose the residual LNAPL. The SVE system would extract the vapors present in the
unsaturated zone. The zone of influence of the dewatering/SVE pipeline is expected to be
approximately 85 feet on either side. This value is derived from data in the Final Soil Vapor
Extraction Bioventing Treatability Study Evaluation Report on Operable Unit 1 (MW, 1996). The
SVE pipeline would be installed along the entire length of Trenches A, C, and D, and along
a 200-foot section of Trench B near FTA 1. The zone of influence of this dewatering/SVE
pipeline completely encompasses CDP 1 and CDP 2 and partially covers the FTA 1 and the
LNAPL area. The total length of SVE pipeline is approximately 2,000 feet, and it would
recover approximately 1,900 standard cubic feet per minute (scfm) of vapors at 12.5 inches
of water vacuum.
5.1.6.4. To remediate the portion of the LNAPL area adjacent to FTA 1 not captured by the
dewatering/SVE pipeline, an additional SVE well would be installed and would operate at
approximately 160 scfm. To remediate the portion of the LNAPL zone north of the existing
upgradient soil/bentonite cut-off wall not covered by the dewatering/SVE pipeline, four
additional SVE wells and a 1,100 foot horizontal pipeline would be installed. The four wells
would cover the LNAPL area to the north and east of the CDPs. The horizontal pipeline
would be spaced from 50 to 85 feet to the north of the existing cut-off wall to remediate the
zone between the dewatering/SVE pipeline and the existing cut-off wall. It is estimated a
total of 1,800 scfm would be extracted from these wells and pipeline.
5.1.6.5. As shown in Figure 5-5, a portion of the historic LNAPL area is located on the south
side of the existing upgradient soil/bentonite cut-off wall. To remediate this area, a separate
dual-horizontal dewatering/SVE pipeline would be installed. The dewatering pipeline
would be operated if necessary to expose the smear zone to SVE. Currently, there is no
free-phase LNAPL in this area; therefore, no LNAPL extraction system or extra care to
avoid increasing the smear zone thickness would be required. The dual dewatering/SVE
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pipeline in this area would be approximately 600 feet long and would require
approximately 600 scfrn. Since the soils are described as silty sand in this area, the zone of
influence would be expected to be less than 85 feet. It was assumed that this dual pipeline
would be located approximately 65 feet south of the existing soil/bentonite cut-off wall.
Figure 5-5 shows the expected zone of influence of this system but not the specific location
of the drainline system.
5.1.6.6. Off-gas treatment of the emissions from the SVE system would be required.
Emissions from all SVE pipelines and wells would be manifolded to one central off-gas
treatment system. Two technologies were investigated during development of the FS:
vapor-phase granular activated carbon (VGAC) and catalytic oxidation. Other technologies
such as ultraviolet and thermal oxidation are considered to be immature, treatability-stage
processes and were not included in this review. The costs for off-gas treatment using VGAC
were determined to be excessive; therefore, catalytic oxidation was chosen.
5.1.6.7. Upgrade of Existing Landfill Cap. As shown in Figure 5-5, SA6 includes upgrading the
existing landfill cap over Landfills 3 and 4; the areal extent of the landfill cap upgrade is
smaller than that presented for SA5; the upgrade for SA6 is intended to limit infiltration to
contamination within Landfills 3 and 4, while the SVE system discussed above would treat
and remove contamination in the other areas of OU1.
5.1.6.8. Downgradient Soil/Bentonite Cut-Off Wall. The conceptual design of the downgradient
cut-off wall for SA6 is the same as that presented in SA4 and SA5.
5.1.6.9. Dewatering of the Source Area. As with SA3, SA4, and SA5, dewatering of the Source
Area would be accomplished by a series of dewatering trenches installed in the areas of the
greatest saturated thickness of the Provo Formation. The existing groundwater extraction
trench and wells would continue to be operated as discussed for SA1; however, once
dewatering of the Source Area is achieved, the production rate of this system would be
expected to decline substantially.
5.1.6.10. LNAPL Recovery. Provisions for the recovery of free-phase LNAPL in the extraction
trench sumps are the same for SA6 as those presented for SA3, SA4, and SA5.
5.1.6.11. Groundwater Treatment. As with previous alternatives, groundwater collected by the
dewatering system for SA6 would be treated at the OU2 ASTP or the IWTP and discharged
to the local POTW.
5.1.6.12. Environmental Monitoring. The groundwater monitoring program for SA6 is the same
as that presented for SA4 and SA5.
5.1.6.13. In addition to those components identified for previous Source Area alternatives,
the monitoring program for SA6 includes soil vapor monitoring to gauge the effectiveness
of the SVE system. For cost estimating purposes, it is assumed the 10 shallow Source Area
groundwater monitoring wells would be monitored monthly for oxygen, carbon dioxide,
and total VOCs. Extracted vapor samples would be collected from four separate locations in
the SVE system manifold. These samples would be collected monthly and analyzed for
VOC content. Soil samples would be collected from 10 boring locations annually for a
3-year operating period, at which time it is assumed the system would be taken offline
permanently. The soil samples would be analyzed for VOCs to gauge the effectiveness of
the SVE system in remediating contaminated soil.
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5.1.7 Source Area Alternative 7 (SA7) — Excavation, Treatment, and Offsite
Disposal
5.1.7.1. Major remedial components of SA7 are shown in Figure 5-6 and further described
below. The following paragraphs describe the conceptual design of SA7, including the
following specific components:
• Excavation, offsite incineration, and landfilling of the CDPs, FTA 1, and the LNAPL
area.
• Excavation and offsite landfilling of the contents of Landfills 3 and 4.
• Dewatering of the Source Area by a series of groundwater collection trenches.
• Groundwater treatment at the OU2 ASTP or the IWTP.
• Environmental monitoring, including the continued monitoring of the effectiveness of
the existing upgradient soil/bentonite cut-off wall.
• Institutional controls as described in Section 5.3.0.16.
5.1.7.2. The following paragraphs provide greater detail concerning each of these
components.
5.1.7.3. Excavation Evaluation. The objective of excavation is to remove all soil and landfill
debris contaminated at concentrations greater than PRGs, containing listed hazardous
waste, or characteristic hazardous waste. Soil below the water table would not be
excavated; rather, it would be remediated through groundwater collection and treatment.
An evaluation of excavation and disposal of onsite contaminant sources was conducted
during preparation of the Revised Interim Draft Final Feasibility Study Report (MW, 1995a).
During preparation of the current FS for OU1, this evaluation was refined based on analysis
of historic air photos and knowledge of typical landfill operating procedures to develop
approximate excavation volumes, disposal options, and costs. Additionally, excavation of
the historic LNAPL extent is included in this analysis.
5.1.7.4. Table 5-2 summarizes the proposed excavation areas, estimated excavation volumes,
and assumed disposal methods for areas of concern within OU1.
TABLE 5-2
Source Area Alternative SA7 Excavation Volumes and Disposal Methods
Area Excavation Volume (cubic yards)1 Disposal
FTA 1 42,000 Incinerate, Landfill Offsite
GDP 1 and 2 4,000 Incinerate, Landfill Offsite
LNAPL (clean overburden) 390,000 Stockpile, Backfill
LNAPL (contaminated) 65,000 Incinerate
Landfills 120,000 Sort, Landfill Offsite
Landfill 4 585,000 Sort, Landfill Offsite
'These volumes do not include soil expansion factors used for cost estimating (see FS Appendix B).
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5.1.7.5. The excavation volumes presented in Table 5-2 are for the purpose of estimating
remedial costs. Actual volumes to be excavated would be determined through a sampling
and analysis program conducted prior to remedial design or during the remedial action.
5.1.7.6. It is anticipated that excavation of these areas would require approximately 2 years.
Other components of SA7, such as groundwater collection and treatment, will be initiated
following completion of excavation activities.
5.1.7.7. Soil Disposal Issues. The most significant action-specific Applicable or Relevant and
Appropriate Requirement (ARAR) affecting implementation of Alternative SA7 is the
determination of whether the contaminated soils are considered to be hazardous waste. In
summary, excavated soil at the CDPs, FTA 1, and the LNAPL area would be managed as
listed hazardous waste (F001) and possibly also as characteristic waste. Incineration of half
the soil from the CDPs and FTA 1 is assumed to be necessary to meet the land disposal
restrictions (LDR) for these waste codes. All the soil from the LNAPL area would be
incinerated because of higher concentrations of solvents, pesticides, and dioxin/furans
found in these soils. Because of the high cost of incineration of soils, increases in the volume
of soil requiring incineration would greatly increase the cost of this alternative.
5.1.7.8. The majority of soils and wastes from Landfills 3 and 4 are not expected to be
characteristic wastes and are not expected to contain listed wastes. However, it is possible
that some isolated areas of wastes within the landfills would be sufficiently contaminated to
either be characteristic or be considered to contain listed wastes. In this event, the wastes
would be managed as hazardous, and the appropriate LDRs would be met or a treatability
variance would be sought. It is assumed 1,000 cubic yards of materials from Landfills 3 and
4 would be incinerated to meet LDRs.
5.1.7.9. Dewatering of the Source Area. As with previous alternatives, dewatering of the Source
Area would be accomplished by a series of dewatering trenches installed in the areas of the
greatest saturated thickness of the Provo Formation. These trenches would be installed
following completion of excavation activities.
5.1.7.10. Groundwater Treatment. As with previous alternatives, groundwater collected by the
dewatering system for SA7 would be treated at the OU2 ASTP or the IWTP and discharged
to the local POTW.
5.1.7.11. Environmental Monitoring. The groundwater monitoring program for SA7 is the same
as that presented for SA3. However, it is anticipated that the four existing shallow
monitoring wells and six existing deep monitoring wells identified in SA1 (subsequently
used in SA3) would be destroyed during excavation activities and replaced.
5.2 Non-Source Area Alternatives
5.2.1 Non-Source Area Alternative 1 (NSA1) — No Further Action
5.2.1.1. The following paragraphs describe the conceptual design of NSA1, including the
following specific components:
• Continued operation of the existing spring collection systems at Springs Ul-303, Ul-304,
and Ul-307.
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• Water extracted from the springs to be treated at the OU2 ASTP, the IWTP, or
discharged to the surface after treatment at the remote treatment facility.
• Environmental monitoring.
• Institutional controls as described in Section 5.3.0.16.
5.2.1.2. Existing Spring Collection System. As previously discussed, spring collection systems
were installed as early response actions at Springs Ul-303, Ul-304, and Ul-307. NSA1
would include the continued operation of these systems until remediation goals are
attained.
5.2.1.3. Water Treatment. As discussed previously for the Source Area alternatives, water
produced from the existing seep/spring collection systems would be treated at the IWTP or
the OU2 ASTP upon completion of modifications recommended in the 3-Mile Pipeline
Design Options Report. For cost estimating purposes, it is assumed treatment would occur in
the IWTP for the first year of operation and then switch to the OU2 ASTP for the remaining
years of operation.
5.2.1.4. Restoration Time. For comparative analysis of the Non-Source Area alternatives,
restoration time was estimated for the offsite contamination in groundwater under
representative site conditions. Assuming the Source Area is not remediated further, releases
would continue. Although recent offsite groundwater contaminant data show a decline, it is
expected PRGs would not be met for decades because of continuing releases.
5.2.1.5. Environmental Monitoring. The objective of the NSA1 environmental monitoring
program is to collect sufficient information to track the lateral and vertical extent and
chemical nature of the dissolved contaminant plumes in the offsite shallow (5 to 15 feet bgs)
and deep (40 to 45 feet bgs) water-bearing zones. The program would allow assessment of
continued releases from the Source Area. The monitoring program for NSA1 establishes a
baseline monitoring scenario onto which monitoring programs for the remaining
Non-Source Area alternatives would build.
5.2.1.6. Surface water would be sampled quarterly from all 20 springs for the first 3 years of
the monitoring program and semiannually for the remaining years of operation. The spring
samples would be analyzed for VOCs. Spring flow rate would also be approximated during
the monitoring events.
5.2.1.7. The groundwater monitoring network for NSA1 would include the following wells:
• Monitoring of seven existing shallow wells and installation/monitoring of 10 new
shallow monitoring wells.
• Monitoring of five existing deep wells and installation/monitoring of one new deep
monitoring well located on the west flank of the existing Non-Source Area plume to
monitor lateral and vertical contaminant migration.
5.2.1.8. Samples from the 13 existing monitoring wells would be analyzed for VOCs. Water
levels in all 23 wells listed above will be monitored. For the purposes of cost estimating, it is
assumed 10 existing Non-Source Area monitoring wells would be abandoned.
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5.2.1.9. The Weber Basin Water Conservancy District's potable water well, South Weber
No. 2, is the only groundwater supply well located within the areal extent of the OU1
off-Base groundwater plume. The well has been used sporadically over the years during
peak demand periods. Oil was recently observed floating on the surface of the water in the
well, and the well is currently not in use due to the dissolved contamination in the
groundwater from the oil. Recent investigations have shown HAFB is not the source of the
oil or associated groundwater contamination in the drinking water aquifer. The
investigation is described in the Draft Monitoring Well Installation and Impact Assessment of
South Weber No. 2 (CH2M HILL, 1998b). The well will be monitored to provide assurance
the water supply source is not being adversely affected by contaminants of concern from
OU1.
5.2.2 Non-Source Area Alternative 2 (NSA2) — Monitored Natural Attenuation
5.2.2.1. Major remedial components of NSA2 are shown in Figure 5-7 and further described
below. The following paragraphs describe the conceptual design of NSA2, including the
following specific components:
• Monitored natural attenuation.
• Operation of the existing spring collection systems.
• Treatment of collected water at the OU2 ASTP or the IWTP.
• Environmental monitoring.
• Control further contaminant migration from the Source Area through Source Area
Alternatives SA3, SA4, SA5, SA6, or SA7.
• Institutional controls as described in Section 5.3.0.16.
5.2.2.2. The environmental monitoring described below would be used to assess the degree
of natural attenuation and allow estimates of the time necessary to reach remedial goals. If
monitoring data indicate further spreading of the plume above remedial goals, active
restoration using one of the remaining alternatives (NSA3 through NSA6) would be
implemented.
5.2.2.3. Monitored Natural Attenuation Assessment. Monitored natural attenuation is the process
by which contaminant concentrations are reduced by various naturally occurring in situ
mechanisms. The natural processes may include:
• Biodegradation
• Dilution
• Adsorption
5.2.2.4. Based on the Comprehensive Remedial Investigation Report for Operable Unit 1 and
investigations relating to monitored natural attenuation, Draft Work Plan for a Demonstration
of Remediation by Natural Attenuation (Parsons, 1996), the following observations of the
processes as related to the site can be made:
• Dilution produces the net effect of decreasing concentrations but does not represent a
reduction in mass. Dilution occurs through processes such as advecrion, diffusion, and
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hydrodynamic dispersion. In most cases, dilution by diffusion only is small.
Advection-dispersion effects may be especially significant in areas of large
concentration gradients or low groundwater flow velocities. Because of the
heterogeneous nature of the water-bearing zone sediments, hydrodynamic dispersion is
considered significant.
• Biodegradation of "parent" compounds, such as tetrachloroethene (PCE) or TCE,
appears to be occurring within the Source Area. The primary contaminant of the offsite
plume is DCE. The degree of biodegradation in the offsite plume is not known, but it is
not likely the offsite DCE plume in the alluvium undergoes significant biodegradation
(Parsons, 1996). Vinyl chloride, a more toxic contaminant than DCE, is a degradation
product of DCE and has not been detected in the Weber River Valley plume. It is
doubtful that vinyl chloride will be detectable in the future because DCE is expected to
decline as the Source Area is entirely cutoff. Because biodegradation rates are not
known, biodegradation was not included in estimates of the time to achieve remedial
goals. Therefore, the time estimates for monitored natural attenuation may be
conservative.
• Retardation caused by the sorption of contaminants on water-bearing zone materials
will delay the migration of contaminants but will not reduce the mass in the system. The
fraction of organic carbon content representative of the site is estimated to be
0.005 percent based on total organic content (TOC) measurements. The organic carbon
fraction is utilized to estimate the retardation coefficient for the hydrogeologic unit.
5.2.2.5. Dilution (advection and dispersion) and adsorption are considered to be the most
significant processes affecting contaminants in groundwater in the Non-Source Area of
OU1.
5.2.2.6. A groundwater flow and transport analysis was conducted to assess the relative
impacts of the natural attenuation processes identified above. For model application, it was
assumed upgradient groundwater flow and contaminant migration is completely
contained. The remaining mass within the offsite plume is expected to naturally attenuate
and migrate north within the area of the current plume. Simulations were performed to
observe the effect of key parameters on the contaminant attenuation. The simulation results
indicated that the estimated restoration time (i.e., time required for the natural processes to
reduce contaminant concentration below MCLs) varies from 5 years to more than 50 years
depending on the parameter values used.
5.2.2.7. Using the site-specific organic carbon coefficient and best estimates of the critical
parameters affecting transport, the time to attain MCLs is estimated to be 12 years. If the
organic carbon fraction in the subsurface formations exceeds 5 percent, restoration of the
water-bearing zones through natural processes within a reasonable time frame is unlikely.
The Davis-Weber Canal leakage rate may also have a significant impact on the plume
migration and attenuation. Modeling indicates that restoration time may increase without
leakage through the canal bottom.
5.2.2.8. Existing Seep/Spring Collection System. Provisions for the operation of the existing
collection systems at Springs Ul-303, Ul-304, and Ul-307 are the same as those described
for NSA1.
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5.2.2.9. Water Treatment. Provisions for the treatment of water from the existing collection
systems are the same as those presented for NSA1.
5.2.2.10. Environmental Monitoring. The spring monitoring program for NSA2 includes all
components of the NSA1 program, and the analytical program would be expanded to
include monitoring for the following monitored natural attenuation indicator parameters:
• Dissolved Oxygen
• pH, Temperature, and Specific Conductance
• Oxidation/Reduction Potential
• Alkalinity
• Nitrate- and Nitrite-Nitrogen
• Sulfate- and Sulfide-Sulfur
• Total Iron, Ferrous Iron, and Ferric Iron
• Manganese
• Carbon Dioxide
• Chloride
5.2.2.11. The groundwater monitoring program for NSA2 includes all components of NSA1,
with the following modifications:
• Two existing and six new shallow monitoring wells within the Non-Source Area plume
would be added to the monitoring program.
• The analytical program for the 13 wells presented in NSA1, plus the 8 additional wells
described above, would be expanded to include monitoring for the monitored natural
attenuation parameters for surface water listed above.
• The number of Non-Source Area wells requiring abandonment would be reduced from
10 to 8.
5.2.2.12. The alternative includes development of a groundwater flow and solute transport
model to allow prediction of contaminant transport. The model would be updated annually
based on these monitoring results to reflect actual conditions.
5.2.3 Non-Source Area Alternative 3 (NSA3) — Existing Seep Collection Upgrade
5.2.3.1. Major remedial components of NSA3 are shown in Figure 5-8 and further described
below. The following paragraphs describe the conceptual design of NSA3, including the
following specific components:
• Upgraded seep collection and treatment.
• Excavation and offsite disposal of arsenic-contaminated sediment at Springs Ul-301,
Ul-303, Ul-304 Ul-305, and Ul-318.
• Monitored natural attenuation.
• Environmental monitoring.
• Control further contamination migration from the Source Area through Source Area
Alternatives SA3, SA4, SA5, SA6, or SA7.
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• Institutional controls as described in Section 5.3.0.16.
5.2.3.2. Upgraded Seep Collection and Treatment. NSA3 includes modification of the existing
off-Base spring collection system to include collection and treatment of springs with
contaminant concentrations exceeding MCLs as well as upgrading the existing systems at
Ul-303 and Ul-304. The following paragraphs provide a summary of the existing systems,
and an overview of the required additional collection and treatment systems.
5.2.3.3. In 1985, a collection gallery with pumping stations at Springs Ul-303 and Ul-304
was installed, and an additional pumping station was installed at Spring Ul-307 in 1995.
These collection systems currently pump the surface water to the OU2 ASTP for treatment.
The flow could be directed to the OU2 ASTP or the IWTP for any future design. Figure 5-8
shows the planned modifications to the spring collection system. The spring collection
system at Ul-303 and Ul-304 requires upgrade or replacement to effectively collect all
surface water from the area. The extent of the modifications required will be evaluated
during the remedial design and will probably consist of an extension of the existing
extraction trench at Springs Ul-303 and Ul-304 to Spring Ul-318. Discharge from
Springs Ul-305 and Ul-306 would be piped to the OU2 ASTP, the IWTP, or discharged to
the surface after treatment at a remote treatment facility. A remote treatment system may be
installed at Spring Ul-309. Groundwater from Ul-309 would be discharged to the local
POTW or surface after treatment. A Best Available Control Technology (BACT) analysis
would be conducted on the remote treatment system to ensure compliance with air quality
standards.
5.2.3.4. Excavation of Arsenic-Contaminated Sediment. As part of NSA3, arsenic-contaminated
sediment at seeps Ul-301, Ul-303, Ul-304, Ul-305, and Ul-318 would be excavated and
disposed of appropriately. The volume of arsenic contaminated sediment is estimated to
vary from 20 to 100 cubic yards and, for the purpose of cost estimating, it is assumed that it
would be excavated to a depth of 1 to 3 feet. It is anticipated the arsenic contamination is
limited to the upper foot because the arsenic is being accumulated as a result of the change
to an aerobic environment as the groundwater discharges to the surface. The actual depth of
excavation will be based on sediment sampling during excavation.
5.2.3.5. Natural Attenuation Monitoring. NSA3 includes the monitoring of natural attenuation
parameters discussed for NSA2. Estimated restoration time for NSA3 is the same as that
presented for NSA2 (12 years).
5.2.3.6. Environmental Monitoring. The spring monitoring program for NSA3 is the same as the
program for NSA2 except the discharge from the springs would be included as an O&M
issue rather than as a long-term monitoring issue. The groundwater monitoring program
for NSA3 is the same as the program for NSA2.
5.2.4 Non-Source Area Alternative 4 (NSA4) — Plume Cut-Off at Bottom of Bluff
5.2.4.1. Major remedial components of NSA4 are shown in Figure 5-9 and further described
below. The following paragraphs describe the conceptual design of NSA4, including the
following specific components:
• Plume cut-off at the bottom of the OU1 bluff.
• Upgraded seep collection and treatment.
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• Excavation of arsenic-contaminated sediment at seeps Ul-301, Ul-303, Ul-304, Ul-305,
and Ul-318.
• Monitored natural attenuation.
• Control further contaminant migration from the Source Area through Source Area
Alternatives SA3, SA4, SA5, SA6, or SA7.
• Environmental monitoring.
• Institutional controls as described in Section 5.3.0.16.
5.2.4.2. Two technologies were considered in the development of this alternative to achieve
plume cut-off: (1) an "aeration curtain" for in situ treatment of the ground water, and
(2) collection of groundwater in a gravel-filled trench and treatment at the OU2 ASTP, the
IWTP, or at a remote treatment plant. A comparison was conducted between these
technologies based on effectiveness, implementability, and cost. This comparison indicated
that while both technologies were comparable in effectiveness and implementability, the
net present value of in situ aeration was lower than that of a pump and treat system by
approximately $300,000. Therefore, this technology was selected for analysis.
5.2.4.3. Air Sparge System. The evaluation presented in the FS assumes an aeration curtain
would be implemented for in situ treatment of the plume. The physical system to be
installed can be retrofitted for use as a groundwater collection system, if necessary. The FS
analysis discusses the location, depth, and facilities to be constructed for the in situ aeration
system.
5.2.4.4. The cut-off system would consist of a gravel-filled trench approximately 1,600 feet
long with a perforated pipeline at the bottom of the trench. Air would be injected into the
air sparge pipeline using positive displacement blowers. The air would permeate the gravel
pack and produce a "curtain" of diffused air bubbles through which the contaminated
groundwater plume must pass. The air and water contact would volatilize the VOCs in the
groundwater, and pass from the groundwater into the vapor phase. The VOCs would be
emitted to the atmosphere through the ground surface. Preliminary analysis has indicated
that average emissions from the aeration curtain will be below UDAQ "de minimis"
health-based levels; therefore, it is assumed emissions control would not be necessary for
this application. However, a BACT analysis would be conducted prior to implementation of
this alternative, in an effort to ensure compliance with air quality standards.
5.2.4.5. The air sparge trench would be keyed into the clay formation that lies approximately
40 feet bgs. The saturated thickness of this area is approximately 30 feet, which is the
practical limit of air sparging.
5.2.4.6. Calculations were performed during development of the FS to determine the
required air flow rate for treatment of the groundwater. A mass balance was performed on
the aeration curtain. The aeration curtain pipeline would be divided into eight 200-foot
segments. Each segment would require approximately 750 scfm.
5.2.4.7. An aeration curtain performance evaluation was conducted at HAFB Operable
Unit 5 prior to construction of the aeration curtain. The results of this evaluation, conducted
primarily on TCE, were checked against the mass balance. An exact correlation between the
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model and the test was not feasible. Generally, the model predicted greater air requirements
than were actually needed to achieve removal of TCE to MCLs.
5.2.4.8. Upgraded Spring Collection and Treatment. Provisions for the collection and treatment of
springs for NSA4 are the same as these for NSA3.
5.2.4.9. Excavation of Arsenic-Contaminated Sediment. As with NSA3, NSA4 includes excavation
and offsite disposal of arsenic-contaminated sediment from Springs Ul-301, Ul-303, Ul-304,
Ul-305, and Ul-318.
5.2.4.10. Monitored Natural Attenuation. Monitored natural attenuation modeling was carried out
for NSA4 to simulate the impact of a groundwater control system located along the toe of
the bluff. For comparative purposes, the cut-off system was considered to be 100 percent
efficient so that no further contaminant loading to the Non-Source Area plume was
occurring. The Method of Characteristics model was applied to evaluate natural attenuation
for the plume downgradient of the air sparge curtain.
5.2.4.11. The estimated restoration time for this alternative varies from 5 years to greater
than 50 years depending on the parameter value used. Using the site-specific organic
carbon coefficient and best estimates for the remaining critical assumptions, the estimated
restoration time to achieve remedial goals is 11 years for the plume downgradient of the
cutoff system. The plume upgradient of the wall would remediate more rapidly because of
the cut-off of the Source Area and the greater hydraulic gradient on the bluff. The
Davis-Weber Channel recharge was found not to have significant effect on the plume
migration and attenuation for this alternative. Retardation due to the adsorption of
contaminants to soil particles will play a major role in estimating a reasonable restoration
time for the natural attenuating processes. Given the assumed site boundary conditions, the
estimated restoration time does not show significant sensitivity to variation of dispersivity.
5.2.4.12. Environmental Monitoring. The spring monitoring program for NSA4 is the same as
that presented for NSA2. The groundwater monitoring program for NSA4 is the same as the
program for NSA2, with the following exceptions:
• Nine shallow sparge system monitoring wells, situated downgradient to the air sparge
curtain in the dissolved Non-Source Area plume, would be added to the monitoring
program for VOCs and monitored natural attenuation parameters. The wells will be
used to monitor the effectiveness of the air sparge system in reducing contaminant
concentrations.
• Two existing and one new deep monitoring wells, situated immediately upgradient to
the air sparge curtain, would be added to the analytical program presented in NSA2.
• The number of Non-Source Area wells requiring abandonment would be reduced from
eight to six.
5.2.5 Non-Source Area Alternative 5 (NSA5) — Hydraulic Containment at Leading
Plume Edges
5.2.5.1. Major remedial components of NSA5 are shown in Figure 5-10 and further described
below. The following paragraphs describe the conceptual design of NSA5, including the
following specific components:
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• Hydraulic containment at leading plume edge.
• Upgraded seep collection and treatment.
• Excavation of arsenic contaminant sediment at seeps Ul-301, Ul-303, Ul-304, Ul-305,
and Ul-318.
• Monitored natural attenuation.
• Control further contaminant migration from the Source Area through Source Area
Alternatives SA3, SA4, SA5, SA6, or SA7.
• Environmental monitoring.
• Institutional controls as described in Section 5.3.0.16.
5.2.5.2. Hydraulic Containment and Groundwater. Two separate groundwater collection systems
would be constructed to achieve containment of the Non-Source Area plume, as shown in
Figure 5-10. The northern groundwater collection system would be located off-Base at the
leading edge of the northwestern section of the Weber River Valley plume. The western
groundwater collection system would be located on-Base at the leading edge of the on-Base
plume. It is estimated each of the containment systems would require approximately
10 extraction wells to a depth of approximately 45 feet. Each system would yield
approximately 60 gpm.
5.2.5.3. The northern containment system is expected to produce 60 gpm. Table 5-3 presents
the maximum expected groundwater quality concentrations based on 1994-1996
groundwater monitoring data.
TABLE 5-3
Northern Containment System Groundwater Contamination Concentrations
Constituent Concentration (ng/L)
cis-1,2DCE 1,000
trans-1,2DCE 5
PCE 5
Trichloroethane 5
TCE 10
Vinyl Chloride 5
5.2.5.4. This groundwater would be treated with a low profile tray air stripper in the of
Non-Source Area OU1. Low profile tray air strippers are being used successfully at HAFB
to treat water to MCLs. Water would be treated to MCLs and discharged to the sanitary
sewer system on South Weber Drive for conveyance to the CWSID. A BACT analysis would
be conducted on the low profile tray air stripper to ensure compliance with air quality
standards.
5.2.5.5. The western containment system is also expected to produce 60 gpm. Table 5-4
presents the maximum anticipated contaminant concentrations expected from this region
based on the 1994-1996 groundwater monitoring data.
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TABLE 5-4
Western Containment System Groundwater Contamination Concentrations
Constituent Concentration (ng/L)
cis-1.2DCE 500
trans-1,2DCE 5
PCE 5
Trichloroethane 5
TCE 5
Vinyl Chloride 5
5.2.5.6. Based on previous investigations of the capacity of the OU2 treatment plant to
accept OU1 groundwater, the OU2 ASTP would be able to accept this water without
modifications. This Non-Source Area alternative is compatible with all Source Area
alternatives with respect to treatment capacity at the OU2 ASTP. The OU2 ASTP would be
able to handle the additional load from NSA5 combined with any of the Source Area
alternatives described previously.
5.2.5.7. Upgraded Seep Collection and Treatment. Provisions for the collection and treatment of
springs for NSA5 are the same as those for NSA3 and NSA4.
5.2.5.8. Excavation of Arsenic-Contaminated Sediment. As with NSA3 and NSA4, NSA5 includes
excavation and offsite disposal of arsenic-contaminated sediment from Springs Ul-301,
Ul-303, Ul-304, Ul-305, and Ul-318.
5.2.5.9. Monitored Natural Attenuation. Contaminants in the Non-Source Area plume are
expected to naturally attenuate as discussed for NSA3. Using the site-specific organic
carbon coefficient and best estimates of other criteria parameters, the estimated time to
achieve remedial goals under NSA5 is 12 years.
5.2.5.10. Environmental Monitoring. The spring monitoring program for NSA5 is the same as
that presented for NSA1. The groundwater monitoring program for NSA5 is the same as
that presented for NSA1, with the following exceptions:
• One existing and seven new shallow monitoring wells would be added to the
monitoring program. The wells would be used to monitor system hydraulics and be
included in the analytical program for VOC and monitored natural attenuation.
• The number of Non-Source Area wells requiring abandonment would be reduced from
10 to 9.
5.2.6 Non-Source Area Alternative 6 (NSA6) — Groundwater Collection
throughout Plume
5.2.6.1. Major remedial components of NSA6 are shown in Figure 5-11 and further described
below. The following paragraphs describe the conceptual design of NSA6, including the
following specific components:
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• Groundwater collection throughout Non-Source Area plume.
• Groundwater treatment at an offsite ASTP or the IWTP.
• Upgraded spring collection and treatment.
• Excavation of arsenic-contaminated sediment at seeps Ul-301, Ul-303, Ul-304, Ul-305,
and Ul-318.
• Control further contaminant migration from the Source Area.
• Environmental monitoring.
• Institutional controls.
5.2.6.2. Groundwater Collection. NSA6 involves groundwater remediation using collection and
treatment of the Non-Source Area plume area. To accomplish this, a total of approximately
35 extraction wells would be installed. These wells would be screened to extract from both
the recent terrace deposits and the Alpine Formation.
5.2.6.3. Conceptual groundwater analysis for the entire Non-Source Area DCE plume
indicates that the restoration time would be dependent on the extent of contamination
within the clay unit. The range of restoration time estimated varies from 4 to 39 years. Using
best estimates of the critical assumptions, the restoration time to meet remedial goals is
estimated to be 5 years for the water-bearing zone associated with the recent terrace
deposits, assuming minimal effect from the underlying clay.
5.2.6.4. Groundwater Treatment. Groundwater collected from the Weber River Valley will be
treated at an offsite ASTP. An offsite facility would be as effective as the OU2 ASTP;
however, treatment at the OU2 ASTP would present an implementation problem in that the
OU2 ASTP would require an upgrade of treatment capacity. Present value cost estimates
show it is more economical to construct a remote low-profile shallow tray ASTP than to
pipe and pump the groundwater up to OU2. The valley well network is expected to
produce approximately 115 gpm. Table 5-5 presents the expected maximum concentrations
based on 1994-1996 groundwater data.
TABLE 5-5
Non-Source Area Alternative NSA6 Expected Maximum Contamination Levels (Off-Base)
Constituent Concentration (ng/L)
cis-1,2DCE 1,500
trans-1,2DCE 20
PCE 20
Trichloroethane 20
TCE 20
Vinyl Chloride 20
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5.2.6.5. Following treatment, groundwater would be discharged to the South Weber City
sanitary sewer system for treatment at the CWSID. It is assumed the water would be treated
to MCLs.
5.2.6.6. The air emissions from this system were evaluated and results showed that the
emissions would be below the UDAQ criteria for emissions treatment. Therefore, air
emissions would not require offgas treatment.
5.2.6.7. The on-Base well network is expected to produce approximately 60 gpm. Table 5-6
presents the maximum anticipated contaminant concentrations expected from the on-Base
portion of the Non-Source Area plume based on 1994-1996 groundwater monitoring data:
TABLE 5-6
Non-Source Area Alternative NSA6 Expected Minimum Contamination Levels (On-Base)
Constituent Concentration (ng/L)
cis-1,2DCE 500
trans-1,2DCE 5
PCE 5
Trichloroethane 5
TCE 5
Vinyl Chloride 5
5.2.6.8. Based on previous investigations of the ability of the OU2 ASTP to accept OU1
groundwater, the OU2 ASTP would be able to accept this water without modifications.
5.2.6.9. This Non-Source Area alternative is compatible with all Source Area alternatives
with respect to treatment capacity at the OU2 ASTP. The OU2 ASTP would be able to
handle the additional load from NSA6 combined with any of the Source Area alternatives
described previously.
5.2.6.10. Upgraded Seep Collection and Treatment. Provisions for the collection and treatment of
springs for NSA6 are the same as those for previous alternatives.
5.2.6.11. Excavation of Arsenic-Contaminated Sediment. As with previous alternatives, NSA6
includes excavation and offsite disposal of arsenic-contaminated sediment from
Springs Ul-301, Ul-303, Ul-304, Ul-305, and Ul-318.
5.2.6.12. Environmental Monitoring. The spring monitoring program for NSA6 is the same as
that presented for NSA1. The groundwater monitoring program for NSA6 is the same as
that presented for NSA1, with the following exceptions:
• Two existing anoTthree new shallow wells would be added.
• Three existing and 22 new deep wells would be added.
• The number of Non-Source Area wells requiring abandonment would be reduced from
10 to 5.
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RECORD OF DECISION FOR OPERABLE UNIT )
5.3 Elements Common to Both Source Area and Non-Source
Area Alternatives
5.3.0.1. Several specific remedial components are common to more than one of the Source
Area alternatives; these components are as follows:
• Pond No. 10 modifications.
• Localized groundwater extraction at the northern Base boundary.
• Waste Oil/Phenol Pit containment.
• Upgradient soil/bentonite cut-off wall.
• Groundwater treatment at OU2 ASTP or the IWTP.
• Landfill gas monitoring.
• Slope stability monitoring.
• Institutional and engineering controls.
• Operations, maintenance, and replacement of remedial components.
• Designation of Corrective Action Management Unit (CAMU).
5.3.0.2. The following paragraphs provide greater detail concerning each of these common
elements.
5.3.0.3. Pond No. 10 Modifications. As part of Source Area Alternative SA2 and all subsequent
alternatives, the pump inlet at Pond No. 10 will be lowered so the pond can be completely
drained after storm events to reduce potential infiltration, and thus reduce the gradient and
flow of contamination in the underlying Alpine Formation. Stormwater from Pond No. 10
will be diverted to Pond No. 9, located approximately 2 miles west of Pond No. 10. An
analysis of stormwater infiltration in Pond 10 is currently being performed. The results of
this investigation are documented in the Draft Operable Unit 1 Groundwater Pre-Design Report
(CH2M HILL, 1998c). The U.S. Army Corps of Engineers would also be contacted to
determine whether they have jurisdiction over the pond/wetland area. If so, the substantive
requirements for obtaining a permit for the pond modifications would be performed and
wetland mitigation would be undertaken, if necessary.
5.3.0.4. Groundwater Extraction at Northern Base Boundary. As part of Source Area
Alternative SA2, and all subsequent alternatives, the area of groundwater contamination
downgradient of the Waste Phenol/Oil Pit will be contained. Based on existing data, it is
estimated that a single extraction well will be required to achieve containment of
contaminants in this area. The total depth of this well is estimated to be 40 feet and
approximately 1.5 gpm will be extracted. The extracted groundwater will be treated at the
OU2 ASTP or IWTP and discharged to the local POTW.
5.3.0.5. Waste Phenol/Oil Pit Containment. As part of Source Area Alternative SA2 and all
subsequent alternatives, a containment system specific to contaminant releases to
groundwater from the Waste Phenol/Oil Pit will be constructed. The system will consist of
an extraction trench downgradient of the Waste Phenol/Oil Pit to collect contaminated
groundwater. The extraction system is expected to collect approximately 0.5 gpm, which
will be treated at the OU2 ASTP or the IWTP.
5.3.0.6. Upgradient Soil/Bentonite Cut-Off Wall. As previously discussed, an upgradient
soil/bentonite cut-off wall was installed as an early response action in 1985 to divert
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RECORD OF DECISION FOR OPERABLE UNIT 1
upgradient groundwater around the OU1 Source Area. Uncertainty associated with the
cut-off wall effectiveness make it difficult to develop proposed remedial actions for
upgradient hydraulic containment. This uncertainty stems from an investigation that
indicated the actual depth of the wall is less than the design depth in several locations
(Dames and Moore, 1985). These conclusions were reached by examining water level data,
which does not indicate a consistent head differential across the wall. Two options were
evaluated to address this uncertainty, as follows:
• Option 1: Utilize the existing wall without modification and collect leakage with the
downgradient systems proposed for each alternative.
• Option 2: Test and upgrade or replace the wall to increase the effectiveness of upgradient
flow diversion.
5.3.0.7. Evaluation of these options was based on effectiveness, implementability, and cost.
While each of the options will effectively mitigate offsite transport of contaminants,
Option 2 is more difficult to implement because of required investigations and construction.
By comparing the costs associated with these options, it was determined that the costs of
further evaluation and enhancement of the wall will exceed the costs of treating water that
may pass through or beneath the upgradient wall in the OU2 ASTP. A conservative
estimate of cut-off wall effectiveness under current conditions is 50 percent; i.e., 50 percent
of upgradient water is diverted by the wall. The 30-year net present value of Option 1
(treating 50 percent of upgradient flow) is estimated at $184,000; the 30-year net present
value of Option 2 (testing and upgrading the wall to 80 percent effectiveness) is estimated at
$384,000.
5.3.0.8. Based on these evaluations, it is evident that a substantial expenditure to test and
enhance the existing wall is not cost effective. This is primarily due to the relatively low cost
of treating upgradient groundwater that is not diverted by the wall in the OU2 ASTP. A
substantial expenditure to test and upgrade the wall is likely to result only in an
incremental reduction in groundwater treatment cost. Therefore, it is assumed for all Source
Area alternatives that the existing wall will not be modified. For the purpose of estimating
groundwater collection system flow rates and sizing groundwater treatment systems, it was
conservatively estimated that the wall does not effect the groundwater flow system.
5.3.0.9. Groundwater Treatment. As part of all Source Area alternatives, groundwater collected
in the OU1 Source Area may be redirected from the HAFB IWTP to the OU2 ASTP. The
Three-Mile Pipeline Design Option Report recommends discontinuing discharge to the IWTP
and redirecting flow from OU1 to ASTP located at the OU2 Source Removal System Facility.
This option was determined to comply with ARARs, to be flexible at incorporating future
flows, and to have a low implementation cost. The OU2 ASTP was completed in 1997. The
following paragraphs describe the existing treatment facilities and the modifications
required to implement this alternative.
5.3.0.10. As previously discussed, groundwater is currently collected from the OU1 Source
Area by a series of dewatering wells and a single extraction trench. The system also
includes pumping stations that collect water from hillside springs (see Non-Source Area
Alternative NSA3). Water collected by this system is pumped to a pump transfer building at
OU1, which pumps the water via the 3-mile pipeline to the HAFB IWTP where it is treated
and disposed.
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RECORD OF DECISION FOR OPERABLE UNIT 1
5.3.0.11. The following modifications will be implemented to discharge ground water from
OU1 to the OU2 ASTP:
• Install oil/water separation pretreatment at OU1.
• Discontinue use of the three-mile pipeline until HAFB determines a future use.
• Modify the pumps, piping, and controls in the OU1 Pump Transfer Building to pump
water in the reverse direction to the OU2 ASTP.
5.3.0.12. Landfill Gas Monitoring. As part of Source Area Alternative SA2 and all subsequent
alternatives except Source Area Alternative SA7, biannual sampling will be conducted to
monitor constituents in landfill gas. Sampling will be conducted from selected landfill gas
vents. A BACT analysis will be performed to ensure compliance with air quality standards.
5.3.0.13. Slope Stability Monitoring. The stability of the terrace north of OU1 may be
compromised by fluctuations in the static groundwater table induced by groundwater
extraction systems. Therefore, four existing inclinometers will be monitored annually for
the remediation period to provide early warning of potential failure of the slope. This
monitoring is included for all Source Area alternatives.
5.3.0.14. Institutional and Engineering Controls. Institutional and engineering controls for
properties not fee-owned by the Air Force will include: (1) water rights and well drilling
restrictions and advisories to prevent exposure to contaminated groundwater, and
(2) fencing with warning signs to restrict access to exposure areas, construction areas, and
treatment facilities. Leases or easements may be needed to enact some of the institutional
controls.
5.3.0.15. The Utah Department of Natural Resources, Division of Water Rights has
developed a groundwater management plan for the Weber Delta sub-area of the East Shore
area, which includes HAFB. Areas of groundwater contamination surrounding HAFB are
identified as restricted. No new wells will be permitted in the restricted areas nor will
change applications that propose to transfer water into these areas be granted. When the
contamination is successfully cleaned up and no longer poses a threat to groundwater
aquifers, the State Engineer will consider allowing the construction of wells in these areas.
5.3.0.16. Institutional controls for Air Force fee-owned property will include:
1. Issuing a continuing order that remains in effect as long as the property is owned by the
Air Force. These controls restrict access to or disturbance of contaminated soil, restrict
construction activities, and restrict installing water supply wells in zones of
contaminated groundwater.
2. Filing a notice to the deed detailing the restrictions of the continuing order.
3. A deed restriction or restrictive easement to the deed in the event of property transfer.
5.3.0.17. In the case of the sale or transfer of property within OU1 by the U.S. to any other
person or entity, the Air Force will place a deed restriction or restrictive easement in the
deed that will restrict access and prohibit disturbance of contaminated soils or the remedial
action without approval of the U.S. These deed restrictions or restrictive easements will be
in effect until removed upon agreement of the State of Utah, the EPA, and the U.S. Air Force
or their successors in interest. The Air Force will also include in the deed a deed restriction
PM36064V4_1_aFINAL\REPORT\FOUlROD.DOC 5-28
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RECORD OF DECISION FOR OPERABLE UNIT 1
or restrictive easement required by Section 120(h)(3) of CERCLA, which includes (1) a
warranty that the U.S. will conduct any remedial action found to be necessary after the date
of the transfer; and (2) a right of access on behalf of the EPA and the Air Force or their
successors in interest to the property to participate in any response or corrective action that
might be required after the date of transfer. The right of access referenced in the preceding
sentence shall include the State of Utah for purposes of conducting or participating in any
response or corrective action that might be required after the date of transfer.
5.3.0.18. In the event the land use is changed or structures are removed, the Air Force will
re-evaluate the protectiveness of the remedy selected for OU1, and will take any
appropriate remedial action.
5.3.0.19. Operations, Maintenance, and Replacement of Remedial Components. It is anticipated that
routine O&M of remedial components will be conducted, and periodic replacement of
specific components will be required.
5.3.0.20. Designation of Corrective Action Management Unit. A CAMU will be designated under all
Source Area and Non-Source Area alternatives, other than the no further action alternatives
(SA1 and NSA1), to include the contiguous area of contamination. The aerial extent of the
CAMU is shown on Figure 5-12. Movement of soils or landfill materials to appropriate
locations within the boundaries of the CAMU will comply with Resource, Conservation and
Recovery Act (RCRA) land disposal restrictions. It is anticipated this will be applied to
cuttings from groundwater extraction and monitoring wells, trench spoils for groundwater
collection systems, and excess soils from slurry wall construction. In all cases, the soils
would be consolidated on the landfills, covered with a landfill cap comparable to that used
by the alternative, and meet landfill closure ARARs.
P:\136064\4J_3\FINA1.\REPOHT\FOU1ROD.DOC 5-29
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Davis
ic - Weber Canal
/I"- -'
Waste
Phenol/Oil Pit
hemical
Disposal Prt 1
X
'Chemical
Disposal Pit 2
LEGEND
• Existing Dewatering Well
Proposed Groundwater
Collection Trench
—^ Existing Extraction Trenches 4 Proposed Extraction Well
Note: Location and number of extraction trenches to be determined during the remedial design.
Existing'
Soil/Bentonite
Wall
D
FIGURE 5-1 Source Area Alternative 2 Site Plan
-------
o:\Ji ilia) tAou1Vodmap\iiQucas\ 0
Disposal Pit 2- n
Fire Training
Area 1
LEGEND
• Existing Dewatering Well "^ Proposed DewateringTrench
-= Existing Extraction Trenches * Proposed Extraction Well
Note: Location and number of extraction trenches to be determined during the remedial design.
Existing ;
. Soil/Bentonite
y - Wall
FIGURE 5-2 Source Area Alternative 3 Site Plan
-------
Cnemicai
Disposal Pit 1
•v
LEGEND
* Existing Dewatering Well * Proposed DewateringTrench
«•=» Existing Extraction Trenches —••- Proposed Downgradient
* Proposed Extraction Well Soil/Bentonite Cutoff Wall
Note: Locations and number of extraction trenches to be determined during the remedial design.
Existing
Soil/Bentonite
Wall i
FIGURE 5-3 Source Area Alternative 4 Site Plan
-------
o:\hHlafb\ou1\fodmapMigurq9\ligufqS-4.wof
LEGEND
• Existing Dewatering Well C0 Proposed Landfill Cap Upgrade
=• Existing Extraction Trenches T™- Proposed Downgradient
+ Proposed Extraction Well Soil/Bentonite Cutoff Wall
Proposed DewateringTrench
Note: Location and number of extraction trenches to be determined during the remedial design.
Existing x
.Soil/Bentonite
; Wall
0
FIGURE 5-4 Source Area Alternative 5 Site Plan
-------
ic . Weber Canal
Fire Training
Area 2
Chemical
Disposal Pit 1
\
Fire Training
Area 1 f]
Disposal Pil 2
LEGEND
Existing Dewatering Well
=» Existing Extraction Trenches
Proposed Extraction Well
Proposed DewateringTrench
— Proposed SVE Trench
Proposed Landfill Cap Upgrade
Proposed SVE System Coverage
— • Proposed Combined Dewatering
and SVE Trench
Existing \
Soil/Bentonite
Wall
— Proposed Downgradient
Soil/Bentonite Cutoff Wall
• Proposed SVE Well
LNAPL (all years)
Note: Location and number of extraction trenches to be determined during the remedial design
FIGURE 5-5 Source Area Alternative 6 Site Plan
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o:\hillglb\ou1VfOdm3pMiaui9sliguiaS-6.wof
Davis-Weber Canal
LEGEND
• Existing Dewatering Well
-=» Existing Extraction Trenches
* Proposed Extraction Well
Proposed DewateringTrench
© Proposed Areas to be Excavated
and Landfilled
O Proposed Areas to be Excavated
and Incinerated
Note: Location and number of extraction trenches to be determined during the remedial design.
Existing"
.. Soil/Bentonite
- Wall Q
FIGURE 5-6 Source Area Alternative 7 Site Plan
-------
LEGEND
Existing Dewatering Well
— -Existing Extraction Trenches
Area Exceeding PRGs in Groundwater
Non-Source Area Natural
Attenuation of Groundwater
O Proposed Natural Attenuation
Monitoring Wells
Seep Collection System
FIGURE 5-7 Non-Source Area Alternative 2 Site Plan
-------
o:\hiltafb\ou1\RODMap\Figure9\FigureS-8.wor
LEGEND
Existing Dewatering Well
Existing Extraction Trenches
Area Exceeding PRGs in Groundwater
Remote Ground water
Treatment Plant and
Discharge to POTW
Ul -300 Seep Collect ton
and Piping to Remote
Treatment Plant
O Proposed Natural Attenuation
Monitoring Wells
Seep Collection System
f Seep Excavation Area
Existing S«p U1 307
Collection Sysletn |
FIGURE 5-8 Non-Source Area Alternative 3 Site Plan
-------
o.\nnmtu'uu i
'-• '"s
LEGEND
Existing Dewatering Well
— - Existing Extraction Trenches
Area Exceeding PRGs in Groundwater
O Proposed Natural Attenuation
Monitoring Wells
O Seep Collection System
* Proposed Shallow Plume Cutoff
System Monitoring Well
• Proposed Deep Plume Cutoff
System Monitoring Well
— Proposed Spring Collection Gallery
-- - Proposed Plume Cutoff System
700
FM)
1lnd<:700lN(
FIGURE 5-9 Non-Source Area Alternative 4 Site Plan
-------
o:\hillatbVou1VfOdmap\ligyma\li9me10.wof
3
3
•••3
N
N
A
700,
:
.
P
Oo
Q 0
LEGEND
• Existing Dewatering Well
—=» Existing Extraction Trenches
& Area Exceeding PRGs in Groundwater
O Proposed Natural Attenuation
Monitoring Wells
3 Proposed Groundwater Extraction
System Performance Monitoring Well
O Seep Collection System
O Proposed Groundwater Extraction Well
— Proposed Spring Collection Gallery
; Davis-W«b«Canal_
Fir* Training ' •
At.a2
•••"q,"
OitpOMIPItZ'V
• Training
Existing
Soit/Bentonite
Walk
: Landfill 4 •
FIGURE 5-10 Non-Source Area Alternative 5 Site Plan
-------
LEGEND
Existing Dewatering Well
— - Existing Extraction Trenches
Area Exceeding PRGs in Groundwater
Seep Collection System
Q Proposed Groundwater Extraction Well
— Proposed Spring Collection Gallery
FIGURE 5-11 Non-Source Area Alternative 6 Site Plan
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LEGEND
E"V>ri'j|i»«-; photo
N
A
coo
1200
I rich . 6OO b
1 (TOO
Hill Air Force Base
Operable Unit 1
PROPOSED CAMU BOUNDARIES
FIGURE S-l?
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6.0 Summary of the Comparative Analysis of
the Alternatives
6.1 Introduction
6.1.0.1. The comparative analysis evaluates relative performance of the alternatives within
the nine evaluation criteria established in the NCP listed below. The first two evaluation
criteria are threshold criteria that must be met by the selected remedial action. The five
balancing criteria are balanced to achieve the best overall solution. The final two modifying
criteria considered in the remedy selection are State acceptance and community acceptance.
6.1.0.2. Threshold criteria include overall protection of human health and the environment
as well as compliance with ARARs. These threshold criteria must be met by an alternative
before it can be evaluated under the five balancing criteria.
1. Overall Protection of Human Health and the Environment addresses whether a remedy
provides adequate protection and describes how risks posed through each pathway are
eliminated, reduced, or controlled.
2. Compliance with ARARs addresses whether a remedy will meet all substantive federal
and State environmental laws and/or provide grounds for a waiver.
6.1.0.3. The five balancing criteria form the basis of the comparative analysis because they
allow tradeoffs among the alternatives requiring different degrees of performance.
3. Long-Term Effectiveness and Permanence refers to the ability of a remedy to provide
reliable protection of human health and the environment over time.
4. Reduction of Toxicity, Mobility, or Volume through Treatment refers to the preference
for a remedy that reduces health hazards of contaminants, the movement of
contaminants, or the quantity of contaminants at OU1 through treatment at the site.
5. Short-Term Effectiveness addresses the period of time needed until protection is
achieved, and any adverse effects to human health and the environment that may be
caused during the construction and implementation of the remedy.
6. Implementability refers to the technical and administrative feasibility of an alternative
or a remedy, and the availability of goods and services needed to implement the
alternative.
7. Cost evaluates the estimated capital, operation, and maintenance costs of each
alternative.
6.1.0.4. The modifying criteria are generally addressed in response to comments from the
State and the public, after issuance of the Proposed Plan.
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RECORD OF DECISION FOfl OPERABLE UNIT 1
8. State Acceptance indicates whether the State agrees with, opposes, or has no comment
on the preferred alternative.
9. Community Acceptance indicates whether the community agrees with, opposes, or has
no comment on the preferred alternative.
6.2 Threshold Criteria
6.2.1 Overall Protection of Human Health and the Environment
6.2.1.1. The NCP requires all alternatives be assessed to determine whether they can
adequately protect human health and the environment, in both the short- and long-term,
from unacceptable risks posed by hazardous substances, pollutants, or contaminants
present at the site by eliminating, reducing, or controlling exposures to such substances,
pollutants, or contaminants. Overall protection of human health and the environment
draws on the assessments of other evaluation criteria, especially long-term effectiveness and
permanence, short-term effectiveness, and compliance with ARARs.
6.2.1.2. Source Area Alternatives. All alternatives with the exception of SA1 are protective of
public health and the environment. SA6 achieves protection because it uses protective
measures included in SA2 through SA5, as well as in situ treatment to remove the VOCs
posing the greatest risk for offsite migration in groundwater and direct contact risks for
construction workers, while also minimizing potential impacts related to construction.
6.2.1.3. SA7 achieves protection through the removal of the sources. Once the sources are
removed, there would be no need for on-Base institutional controls designed to address
unacceptable risks associated with landfill contents and soils. However, institutional
controls associated with potential groundwater risk scenarios would still be required.
Although much of the waste and soil would be treated by incineration, the majority would
be disposed untreated at an offsite landfill. There would be potential risks to on- and
off-Base human health and the environment during the excavation and offsite transport of
contaminated source materials. The potential risks would be associated with the excavation
of an estimated 765,000 cubic yards of contaminated soil and landfill wastes, and the offsite
transport that would require an estimated 38,000 truck round trips from the site to the
offsite landfill and incinerator. Even though there are potential risks to human health and
the environment during implementation of source removal activities, the short-term risks
can be managed adequately so protectiveness is maintained.
6.2.1.4. SA4 and SA5 achieve protectiveness through the use of the central dewatering
trenches and slurry wall groundwater containment system to prevent further offsite
contaminant migration. The slurry wall is protective because it provides reliability that
further releases offsite through the Alpine Formation are prevented. This is because it
prevents the offsite discharge of contaminants in narrow (about 0.5 inch) sand stringers
located near the Source Area perimeter that may connect to permeable zones on the hillside.
Groundwater flow in these stringers may not be captured by the central dewatering trench
because of the large permeability difference between the sand stringers and clay of the
Alpine Formation. The landfill cap upgrade of SA5 is also protective because it reduces
infiltration and may reduce leaching of contaminants to groundwater.
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RECORD OF DECISION FOR OPERABl£ UNIT 1
6.2.1.5. The central dewatering trench of SA3 is protective of public health and the
environment because it provides a high degree of assurance that offsite migration of
groundwater contaminants in the Provo and Alpine Formations is prevented. This is
because the trench is completed to a depth of 10 to 15 feet into the Alpine Formation, thus
allowing capture of contaminants nearer the most significant sources (CDPs and the
LNAPL area) and contaminants in the upper depths of the Alpine Formation. Because the
trench dewaters the Provo Formation, and the Alpine Formation does not supply sufficient
water for potable use, future risks from ingestion of groundwater within the Source Areas
are eliminated. SA2 includes groundwater collection trenches to capture groundwater
migrating offsite. It also relies on groundwater monitoring to verify that further releases to
offsite groundwater are not occurring. However, because the potential for offsite migration
in the Alpine Formation at concentrations exceeding PRGs is limited, SA2 combined with
groundwater monitoring and potential upgrades to the collection system, as necessary, is
also considered protective.
6.2.1.6. SA1 is not considered protective of public health and the environment because it
allows continued releases of contaminants to groundwater and their migration offsite.
However, the early response actions previously implemented have decreased infiltration
and recharge into the OU1 Source Areas, and removed large amounts of contaminated
groundwater from the Source Area. They are most likely responsible for the recently
observed decline in offsite groundwater contaminant concentrations. Although the early
response actions are not considered sufficiently protective, they have provided a substantial
increase to the protection of public health and the environment.
6.2.1.7. Non-Source Area Alternatives. For the purpose of establishing a true "no further action"
alternative, the no further action alternative for the Source Area (SA1) is combined with the
no further action alternative of the Non-Source Area (NSA1). All alternatives except NSA1
are considered protective of public health and the environment. NSA2 through NSA6 are
considered protective because institutional controls are expected to continue preventing
potable use of the springs and groundwater, while remedial actions reduce contaminant
concentrations to levels protective of human health and the environment. The time during
which reliance on institutional controls is necessary ranges from 5 years for NSA6 to
12 years for NSA2 and NSA5. While there is substantial uncertainty associated with
remediation time estimates, and actual remediation times may be longer, groundwater
monitoring data from the north plume shows declines in many of the wells over the last
few years, several of which are now below remedial goals.
6.2.1.8. NSA2 through NSA6 are also considered protective because there is little potential
for use of the groundwater during the relatively short times to achieve remedial goals. This
is because the groundwater plume is either on-Base, where access is controlled, or in the
Weber River Valley, where residences are connected to the city water supply. The greatest
potential for use would be for occasional use of spring water, particularly Spring Ul-309
that has a substantial flow rate (30 gpm). NSA2 through NSA6 prevent access through
institutional and/or engineering controls such as acquisition of easements and fencing of
springs. NSA1 is not considered protective because it does not prevent use.
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RECORD OF DECISION FOR OPERABLE UNIT 1
6.2.2 Compliance with ARARs
6.2.2.1. Applicable requirements are those cleanup standards, standards for control, and
other substantive requirements, criteria, or limitations promulgated under federal or State
law that specifically address a hazardous substance, pollutant, contaminant, remedial
action, or location at a CERCLA site. Relevant and appropriate requirements are similar
requirements, that while not applicable, clearly address problems or situations sufficiently
similar to those encountered at a CERCLA site such that their use is well suited to the
particular site. Compliance with ARARs for the Source and Non-Source Area alternatives
are discussed in the following subsections.
6.2.2.2. Each alternative is assessed to determine whether it would attain applicable or
relevant and appropriate requirements under federal environmental laws and State
environmental or facility siring laws, or provide grounds for invoking an ARARs waiver.
ARARs for all alternatives at OU1 are presented in Appendix A. Compliance with some key
ARARs is discussed in the description of alternatives and will not be repeated here.
6.2.2.3. Source Area Alternatives. Except for SA1, all Source Area alternatives are expected to
meet MCLs in groundwater in a reasonable time frame. However, there are some
uncertainties. A waiver to meet MCLs in groundwater may be needed for parts of the
Source Area in the future because it is technically impracticable to achieve these levels. The
overall uncertainty focuses on contaminated groundwater in thin sand layers in the
otherwise clayey Alpine Formation. It may be impracticable to locate and collect
groundwater from all of the sand layers. This would be the case regardless of whether the
wastes are contained, treated in place, or removed. Also, upgrading the existing system in
SA2 may not intercept some contaminated groundwater from the lowermost parts of the
Provo Formation, and MCLs may not be achieved in a reasonable time frame.
6.2.2.4. All alternatives involving treatment of groundwater and soils would be designed to
meet the action-specific ARARs. This includes meeting discharge pre-treatment limits, air
emission requirements for air stripper or SVE system offgas, and RCRA land disposal
restrictions for characteristic or listed waste. Some of the alternatives include the
designation of a CAMU. Treatability variances for CERCLA soil and debris may be sought
under SA7 for soils or wastes where the "contained in" policy applies, and the contaminant
concentrations are relatively low.
6.2.2.5. Non-Source Area Alternatives. All alternatives except NSA1 would comply with
ARARs. NSA1 would not meet ARARs because continued releases from the Source Area
would occur. With continued releases from the Source Area, it is unlikely groundwater
would meet MCLs in a reasonable time frame, as required by the NCP. The remaining
alternatives will meet ARARs because the remedial goals are expected to be achieved in a
reasonable time, possibly within 12 years for NSA2, Monitored Natural Attenuation.
Groundwater monitoring is important for all alternatives to document declines in
groundwater contaminant concentrations. In the event that declining trends are not
observed for any of the alternatives, additional actions to meet ARARs would be
considered.
6.2.2.6. Action-specific ARARs would be met for all alternatives. Surface water and
groundwater treatment included in NSA3 through NSA6 would be designed to meet
discharge standards, and air emissions from the air stripper would meet air quality
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RECORD OF DECISION FOR OPERABLE UNIT 1
standards. The air emissions from the NSA4 air sparge system are not expected to require
treatment to comply with ARARs.
6.2.2.7. All alternatives involving construction or monitoring activity would be designed to
meet the federal location-specific ARARs regarding impacts to threatened or endangered
species or their habitat, including development in a floodplain. Adverse impacts to surface
water or groundwater quality are not anticipated, and groundwater quality will be
improved over the long term, for all alternatives except SA1 and NSA1. No significant
impacts on ecosystems are expected as a result of construction. Although endangered
species may frequent the HAFB area, the OU1 Source Area does not provide critical or
important habitats for any wildlife species, and no threatened or endangered species are
known to inhabit the OU1 Source Area. Construction in the Non-Source Area under NSA3
through NSA6 will primarily impact agricultural or residential land uses.
6.3 Primary Balancing Criteria
6.3.1 Long-Term Effectiveness and Permanence
6.3.1.1. The alternatives were assessed for the long-term effectiveness and permanence they
afford, along with the degree of certainty that the alternative would prove successful.
Factors considered include the following:
• The magnitude of residual risk from untreated waste or treatment residuals remaining
at the conclusion of the remedial activities.
• The adequacy and reliability .of controls such as containment systems and institutional
controls that are necessary to manage untreated waste and treatment residuals.
6.3.1.2. Source Area Alternatives. SA7 is the most effective and permanent because it removes
and disposes offsite the soil and landfill contents posing potential risk. SA7 does not require
reliance on institutional controls to prevent exposure to the soil or landfill contents.
However, it does require institutional controls to prevent exposure to contaminated
groundwater, and it requires the least long-term management.
6.3.1.3. SA6 is the next most effective and permanent because it removes and treats the
mobile contaminants, which pose the greatest risk to human health and the environment.
SVE coupled with dewatering results in the least amount of risk from residuals of SA1
through SA6. The cap upgrade of SA6 adds some improvement in long-term effectiveness
and permanence but only reduces infiltration by an estimated 1 gpm. The landfill cap
upgrade of SA6 appears to offer only a marginal decrease in the potential for contaminant
leaching to groundwater. It is estimated the landfill cap will decrease infiltration by only
about 0.4 inches per year, equivalent to 0.6 gpm over the entire Landfills 3 and 4 cap area.
This small amount of infiltration may be adsorbed into the waste mass, and much of it may
not reach the groundwater. If it does reach the groundwater, the infiltration would
eventually be collected in the dewatering trench.
6.3.1.4. SA2 through SA5 are the next most effective and permanent alternatives when
compared to SA6 and SA7. They have similar effectiveness although there are incremental
increases in the adequacy of the prevention of offsite migration as a result of the increasing
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number of remedial actions incorporated into each sequential alternative; e.g., SA4 adds
supplemental remedial measures to those proposed in SA3, SA5 adds to SA4, etc.
6.3.1.5. SA1 is the least effective although the presence of the existing landfill cap and
existing institutional controls at HAFB reduces the likelihood that exposure through
construction within the landfill would occur. Continued releases to offsite groundwater
would continue although the declining concentrations in offsite groundwater suggest that
the response actions taken to date are reducing the releases.
6.3.1.6. Non-Source Area Alternatives. All alternatives except NSA1 are expected to be effective
in preventing future risks from exposure to groundwater or surface water through reliance
on institutional controls during the period until groundwater meets the remedial goals. The
magnitude of residual risks (i.e., the risks remaining following completion of the
remediation) are similar for NSA2 through NSA6 because each alternative continues in
operation until remedial goals are met. Residual risks related to exposure to arsenic in
sediment, though currently below target levels, would be eliminated entirely under NSA3
through NSA6.
6.3.1.7. Cleanup of DCE to its remedial goal of 70 micrograms per liter (ug/L), can be
achieved based on groundwater monitoring data for the Weber River Valley plume. The
cleanup of groundwater to remedial goals or to non-detection is often difficult because of
the slow desorption of contaminants from the water-bearing zone soil and heterogeneities
in the water-bearing zone. In particular, the Weber River Valley plume may not cleanup to
non-detectable concentrations as a result of the presence of contamination in the clay below
the alluvial water-bearing zone. This clay contamination may act as a low concentration
continuous source to the alluvium, resulting in a decline in groundwater concentrations to
an asymptote above detectable levels. The difficulty with achieving low ug/L
concentrations in the water-bearing zones also applies to NSA1 through NSA5.
6.3.1.8. NSA6 is the most reliable alternative because it actively removes contaminants from
the groundwater. NSA5 is considered the next most effective alternative because it controls
the potential spread of the western and valley plumes with active groundwater collection.
The control of the valley plume, however, may not be necessary because the plume appears
to be discharging at the springs along the northern perimeter of the plume. The western
plume is expected to diminish in concentration once further releases from the Source Area
cease. Both plumes are currently stable or contracting based on historical analytical data.
NSA3 and NSA4 are slightly more effective than NSA2 because they prevent use of the
springs by collecting and treating the water before it surfaces. Again the difference is not
great between alternatives because the concentrations at the springs may drop below levels
of concern within 12 years, and the institutional controls used in NSA2 are expected to be
effective and reliable over this time frame.
6.3.2 Reduction of Toxicity, Mobility, or Volume through Treatment
6.3.2.1. The degree to which alternatives employ treatment to reduce toxicity, mobility, or
volume (TMV) at the site is assessed and considers the following factors:
• The treatment processes the alternatives employ and materials they would treat.
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• The amount of hazardous substances, pollutants, or contaminants that would be
destroyed or treated.
• The degree of expected reduction in toxicity, mobility, or volume of the waste from
treatment and the specification of which reduction(s) would be occurring.
• The degree to which the treatment would be irreversible.
• The type and quantity of residuals that would remain following treatment, considering
the persistence, toxicity, mobility, and propensity to bioaccumulate such hazardous
substances and their constituents.
• The degree to which treatment would reduce the inherent hazards posed by principal
threats at the site.
6.3.2.2. Source Area Alternatives. SA7 results in the greatest reduction of TMV in the
contaminated soil, LNAPL, and landfill contents. However, this alternative is similar to SA2
through SA6 for treatment of groundwater. An estimated 42,000 cubic yards of
contaminated soil from the CDPs, FTA 1, and the LNAPL area would be incinerated under
SA7. The majority of the landfill contents would be disposed offsite without treatment.
6.3.2.3. SA6 offers the next best reduction in TMV for the soil and LNAPL media, with the
SVE system removing more than 90 percent of the VOCs. VOCs are the mobile
contaminants posing greatest risk for offsite transport, and the contaminants posing the
greatest risk for construction worker direct contact exposure. SA6 would result in additional
reduction in the concentration of petroleum hydrocarbons as a result of the stimulation of
aerobic biological degradation. Because the alternative includes evaluation of the ongoing
in situ treatment pilot studies, even more reduction in TMV may be obtained if an in situ
treatment process such as soil washing proves effective and is implemented. Free-phase
LNAPL would also be removed and treated with incineration.
6.3.2.4. SA3, SA4, and SA5 are similar in their reduction of TMV. SA3, SA4, and SA5 include
collection and incineration of the remaining free-phase LNAPL, representing about
10 percent of the remaining residual LNAPL. Alternatives SA3, SA4, and SA5 also include
the dewatering trench, but this results in the additional collection of only an estimated
5 gpm of lower concentration contaminants from the Alpine Formation. These alternatives,
however, initially dewater the Provo Formation and remove and treat the associated
contaminants dissolved in groundwater. As a result, they are considered better in reduction
of TMV relative to SA1 and SA2.
6.3.2.5. SA1 would continue collecting and treating an estimated 30 to 50 gpm of
groundwater from the existing groundwater collection system. The reduction in TMV is
estimated to be about half of that achieved in SA2.
6.3.2.6. Non-Source Area Alternatives. The reduction in TMV through treatment is greatest for
the alternatives that actively collect and treat the springs and groundwater. NSA5 and
NSA6 result in the greatest amount of TMV reduction because they collect all the
contaminated surface water and groundwater and treat with air stripping. These
alternatives are expected to remove about 300 pounds of the estimated 410 pounds of VOCs
from the groundwater in the western and Weber River Valley plumes prior to obtaining
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remedial goals. The air stripping treatment is expected to remove 90 percent or more of the
VOCs from the water prior to discharge to the CWSID.
6.3.2.7. NSA4 has nearly the same reduction in TMV as NSA5 and NSA6 because it collects
the springs where the majority of the groundwater is believed to discharge as well as
treating groundwater at the base of the bluff where contaminants are more concentrated.
NSA3 collects and treats groundwater at the springs. These alternatives are expected to
remove about 290 pounds of the estimated 390 pounds of VOCs from the groundwater in
the Weber River Valley plume prior to obtaining remedial goals. NSA1 and NSA2 also
result in large reductions in TMV through natural processes such as dispersion,
biodegradation, and, once discharged to seeps and springs, volatilization and
photoxidation. The most significant processes are expected to be dispersion, volatilization,
and photoxidation.
6.3.3 Short-Term Effectiveness
6.3.3.1. Factors that were considered include the following four features as components of
short-term effectiveness:
1. Short-term risks to the community during implementation.
2. Potential impacts to worker during implementation.
3. Potential environmental impacts during implementation.
4. Time until protection is achieved.
6.3.3.2. Source Area Alternatives. Short-term risks to workers, the community, or environment
are related to impacts from the construction and implementation of the remedial
alternatives. SA1 and SA2 do not have any significant impacts. SA1 has no impacts because
there is no construction. SA2 has no significant impacts because the construction of the
collection trenches is largely outside the area of soil contamination.
6.3.3.3. SA3 and SA4 include excavation through contaminated soil and landfill wastes to
install the central dewatering trench, so adherence to a health and safety plan is important
to prevent exposure of workers to contaminants. Impacts on the community and
environment are not expected, but air emission monitoring, dust suppression, and
implementation of an erosion control plan are necessary.
6.3.3.4. SA5 and SA6 include hauling large quantities of soil for upgrading of the cap.
Impacts on workers are expected to be limited to normal construction-related accidents.
Risks related to exposure to contaminants are not expected because excavation of
contaminated soil or wastes is not necessary for the cap upgrade. The new cap will be
constructed over the existing cap. Impacts on the community will be related to nuisance
noise, dust, and the potential for accidents related to truck traffic.
6.3.3.5. SA7 is the worst alternative relative to short-term impacts. It poses significant
short-term risks to workers, the community, and environment due to VOC emissions and
fugitive dust from soil and landfill contents excavation; potential for injuries from
construction- or transportation-related accidents; increased truck traffic in the surrounding
community (an estimated 38,000 truck round trips); and transportation of a very large
volume of potentially contaminated material (765,000 cubic yards) from the Base to an
off-Base disposal location. The risks to the community and environment from the dust,
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increased truck traffic, and potential spills of contaminated material could be reduced, but
not eliminated, through dust abatement procedures, careful traffic routing and traffic
control during peak hours, and emergency spill mitigation procedures.
6.3.3.6. Non-Source Area Alternatives. None of the alternatives poses a significant risk to
workers, the community, or the environment as a result of construction or operation
activities. The construction activities associated with the installation of the proposed
1,600-foot long air sparge curtain, which is recommended as part of NSA4, would pose the
greatest potential risk to human health and the environment. The installation of the
35 groundwater extraction wells recommended as part of NSA6, followed by the
installation of the 10 extraction wells recommended as part of NSA5, pose the next greatest
potential risks to human health and the environment, respectively. Construction or
initiation activities associated with Alternatives NSA3, NSA2, and NSA1 pose the least
potential risk and are listed herein in order of decreasing potential risk. Air emissions from
the air stripper or air sparge curtain wall will be treated if necessary to prevent risk. The
time until remedial goals are achieved is the least for NSA6 (as few as 5 years), followed by
NSA4 (as few as 11 years), and NSA2, NSA3, and NSA5 (as few as 12 years). NSA1 may not
achieve remedial goals for decades because continued releases from the Source Area would
occur (no further action is assumed for the Source Area). Estimates of the time to meet
remedial goals are best estimates and were made using many simplifying assumptions.
6.3.3.7 Time Until Protection is Achieved. The time to complete construction of the active Source
Area alternatives is estimated at 1 year for SA2; 2 years for SA3 through SA6; and more than
2 years for SA7. The time frames to reach Source Area alternative remedial goals are
effectively equivalent to these times to complete construction. The time to complete
construction of the active Non-Source Area alternatives are estimated at less than 1 year for
NSA2 and NSA3; 1 year for NSA4 and NSA5; and 2 years for NSA6. The time frames to
reach Non-Source Area alternative remedial goals are 12 years for NSA2, NSA3, and NSA5;
11 years for NSA4; and 5 years for NSA6.
6.3.4 Implementability
6.3.4.1. The ease or difficulty of implementing the alternatives was assessed by considering
the following factors:
• Technical feasibility, including technical difficulties and unknowns associated with the
construction and operation of a technology, the reliability of the technology, ease of
undertaking additional remedial actions, and the ability to monitor the effectiveness of
the remedy.
• Administrative feasibility, including activities needed to coordinate with other offices
and agencies, as well as the ability and time required to obtain any necessary approvals
and permits from other agencies.
• The availability of services and materials, including the availability of adequate offsite
treatment, storage capacity, and disposal capacity and services; the availability of
necessary equipment and specialists as well as provisions to provide any additional
resources; the availability of services and materials; and the availability of prospective
technologies.
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6.3.4.2. Source Area Alternatives. No significant technical or administrative implementability
problems are expected for SA1 through SA6. There are only small differences in
implementability between these alternatives. The differences relate to the technical
difficulty of constructing the dewatering trench within the landfill at a depth of about
40 feet (SA3 through SA6), and the slurry wall construction near the bluff (SA4
through SA6). These difficulties can be surmounted with good engineering design and
construction quality control.
6.3.4.3. SA7 may not be implementable in a reasonable time frame because of the lack of
sufficient incinerator capacity to treat landfill wastes and contaminated soil. About
42,000 cubic yards of soil is anticipated to require incineration. This may require at least
2 years given the existing capacity of incinerators within reasonable transport distances.
Also SA7 would be the most difficult to implement because of the uncertainties associated
with excavating in landfills.
6.3.4.4 Non-Source Area Alternatives. The most significant potential implementability problem
is obtaining easements on the properties overlying the offsite groundwater plume so that
access can be controlled. This implementability concern is greater for NSA4 through NSA6
due to the required construction and operation and maintenance of remediation systems.
NSA4 also has a potential for fouling of the air sparge system; however, this is expected to
be controlled through routine maintenance.
6.3.5 Cost
6.3.5.1. The types of costs evaluated include the following:
• Capital costs, including both direct and indirect costs.
• Annual operation and maintenance cost.
• Net present value of capital and operation and maintenance (a 30-year period is used to
calculate the present worth costs).
6.3.5.2. Source Area Alternatives. A summary of the estimated costs for each of the Source Area
alternatives is presented in Table 6-1, which breaks down the estimated capital, operations
and maintenance, and present net worth cost.
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RECORD OF DECISION FOR OPERABLE UNIT 1
TABLE 6-1
Source Area Alternatives Summary Cost Table
Alternative
SA1
SA2
SA3
SA4
SA5
SA6
SA7
Description
No Further Action
Existing System Upgrade
Groundwater Dewatering
Source Containment
Source Containment and Cap Upgrade
Source Treatment and Cap Upgrade
Excavation, Treatment, and Offsite Disposal
Capital Costs
$114,800
$1,151,100
$2,241,600
$3,767,400
$19,677,400
$20,663,400
$299,475,000
Annual O&M
Costs
$158,107
$215,768
$240,254
$244,632
$270,262
$291,963
$205,939
Total Project Costs
Present Worth
$2,545,300
$4,468,000
$5,934,900
$7,528,000
$23,837,600
$25,151,600
$302,640,800
6.3.5.3. As would be expected, SA1 has the lowest capital and operations maintenance costs.
SA2 is the next least expensive and adds approximately $1.9 million to present net worth
over SA1 for upgrades to the existing containment systems. SA3 is the next most expensive
and adds approximately $1.5 million for the dewatering systems within the Source Area.
SA4 adds to SA3 the downgradient cut-off wall at an additional cost of $1.6 million. SA5
adds to SA4 approximately $16.3 million for the upgrade of the existing cap over the OU1
Source Area. SA6 adds an SVE system to SA5 and adds an additional $1.3 million. SA7 is
the most expensive and is significantly higher than any of the other alternatives because of
the costs associated with the excavation, treatment, and disposal of the contaminated soils
and landfill contents.
6.3.5.4. Non-Source Area Alternatives. A summary of the estimated costs for each of the
Non-Source Area alternatives is presented in Table 6-2. A 30-year period is used to calculate
present worth costs rather than the best estimate time frames for the NSA alternatives
because of the overall range in the time frame estimate. Table 6-2 breaks down the
estimated capital, operations and maintenance, and present net worth cost.
TABLE 6-2
Non-Source Area Alternatives Summary Cost Table
Alternative
NSA1
NSA2
NSA3
NSA4
NSA5
Description
No Further Action
Monitored Natural Attenuation
Existing Seep Collection Upgrade
Plume Cut-Ofl at Bottom of Bluff
Hydraulic Containment at Leading Plume
Capital Costs
$439,000
$455,200
$717,500
$1,531,400
$1,289,300
Annual O&M
Costs
$60,420
$122,212
$176,266
$271,742
$174,799
Total Project Costs
Present Worth
$1,367,800
$1,538,400
$2.279,800
$3,788,600
$2,838,600
Edges
NSA6 Groundwater Collection throughout Plume
$2.258,300
$235,963
$3,279,900
6.3.5.5. As would be expected, NSA1 has the lowest capital and operations and maintenance
costs. NSA2 adds the monitored natural attenuation and costs an additional $0.2 million in
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RECORD OF DECISION FOR OPERABLE UNIT 1
present net worth over NSA1. NSA3 adds a spring collection upgrade to NSA2 and costs an
additional $0.7 million. NSA5 is the next most expensive and adds $0.6 million to NSA3 for
hydraulic containment and treatment at the leading plume edges. NSA4 and NSA6 are
similar in costs and are the most expensive of the alternatives.
6.4 Modifying Criteria
6.4.1 State Acceptance
6.4.1.1. The State of Utah agrees with the selected remedy. No change to the selected
remedy is necessary.
6.4.2 Community Acceptance
6.4.2.1. An Availability Session to answer questions concerning the Proposed Plan was held
on February 5,1998. The names of members of the public present at the Availability Session
are presented in Appendix B. Numerous comments were received regarding the Proposed
Plan. The comments and HAFB's response to comments are included as Appendix C. The
main themes noted in the public comments included the possibility of groundwater
contamination in South Weber No. 2, how institutional controls will be enacted, the
presence of buried drums in Landfills 3 and 4, and how the performance of remediation
systems will be evaluated.
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7.0 The Selected Remedy
7.1 Description of the Selected Remedy
7.1.0.1. The selected remedy at HAFB OU1 is the combination of Source Area Alternative
SA3 and Non-Source Area Alternative NSA3. The selected remedy is graphically illustrated
in Figure 7-1.
7.1.0.2. Elements of the remedy common to both the Source Area and Non-Source Area
include the following:
• Groundwater from the Source Area and spring collection systems at Springs Ul-303,
Ul-304, Ul-307, and Ul-318 will be pumped to the OU2 ASTP or the IWTP for treatment
and discharged to a local POTW. Groundwater from Springs Ul-305, Ul-306,
and Ul-309 may be piped to the OU2 ASTP or the IWTP for treatment and discharge to
a POTW or treated at a remote treatment facility and discharged at the spring. Only
those springs with contamination levels above MCLs and that continue to flow after the
Source Area groundwater extraction trenches are operational will be treated.
• Long-term monitoring for contaminants and treatment system performance will be
conducted. A performance and compliance sampling program will be implemented
during the remedial action to monitor performance and compliance with remediation
goals. This program will include the locations of performance monitoring points,
monitoring frequency, analytical parameters, sampling and analytical methods, and
statistical methods for evaluating data.
• Designation of a Corrective Action Management Unit (CAMU) to facilitate remedial
actions. The CAMU will be designated as the contiguous area of contamination.
Movement of soils or landfill materials to appropriate locations within the boundaries of
the CAMU complies with RCRA land disposal restrictions. It is anticipated that this will
be applied to cuttings from groundwater extraction and monitoring wells, and trench
spoils from groundwater collection systems.
• Institutional controls will be established to prevent completion of potential exposure
pathways or to protect facilities installed as part of the remedy. The institutional
controls are described in Section 5. Institutional controls have already been applied to
the future use of groundwater.
• Because the selected remedy will result in hazardous substances remaining onsite above
health-based levels, a review will be conducted within 5 years after commencement of
the remedial action to ensure the remedy continues to provide adequate protection of
human health and the environment.
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7.1.0.3. Elements specific to Source Area Alternative SA3 include:
• Installation of a series of dewatering trenches through the areas of greatest saturated
thickness in the shallow water-bearing zone. Extraction wells may be used in some
locations. This will prevent migration of contaminated groundwater and LNAPL from
the Source Area through the Provo Formation. Some of the dewatering trenches will be
completed in the Alpine Formation to reduce the potential for migration offsite in the
Alpine Formation. The actual location and number of trenches will be determined
during the remedial design.
• LNAPL recovery from the extraction trenches followed by proper disposal of the
LNAPL.
• The existing cap and vent system over the Source Areas will be maintained to minimize
infiltration and migration of contaminants.
• The landfill cap previously placed over Landfill 4 will be improved to prevent ponding
of water.
• The pump inlet at Pond No. 10 will be lowered so that stormwater in the pond may be
diverted to Pond No. 9 located approximately 2 miles west of Pond No. 10.
7.1.0.4. Changes in groundwater levels and spring flow may occur due to the continued
operation of the groundwater collection system, landfill cap repairs, or installation of the
dewatering trenches. Additions, reductions, or relocations of groundwater level control
points, or specific groundwater or spring extraction points may be needed.
7.1.0.5. The goals of this Source Area remedial action are to prevent migration of
contaminated groundwater and LNAPL from the Source Area, and to restore Source Area
groundwater to MCLs. The ability to prevent migration will be evaluated in a performance
monitoring system including measurements of water levels to determine adequate capture
of groundwater and through monitoring well sampling to track declines in contaminant
concentrations over time. If the selected remedy cannot meet remediation goals, additional
measures identified below will be considered.
7.1.0.6. The selected Source Area remedy will include groundwater extraction for an
estimated period of 50 or more years, during which time the system's performance will be
carefully monitored on a regular basis and adjusted as warranted by the performance data
collected during operation. Modifications may include any or all of the following:
• Discontinuing extraction and treatment where cleanup goals have been attained;
however, monitoring will continue for 2 to 5 years to ensure cleanup goals have been
attained.
• Alternating extraction rates to eliminate stagnation points, or to allow water-bearing
layer equilibration and encourage adsorbed contaminants to partition into groundwater,
as long as containment is not compromised.
• Installing additional extraction points to facilitate or accelerate control of the
contaminant plume.
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7.1.0.7. If it is determined, on the basis of the preceding criteria and the system performance
data, that restoration of certain portions of the water-bearing zones cannot be achieved, all
of the following measures involving long-term management may occur, for an indefinite
period of time, as a modification of the existing system:
• Engineering controls such as physical barriers or long-term gradient control provided
by low-level pumping will be maintained as containment measures.
• Chemical-specific ARARs will be waived for the restoration goals of those portions of
the water-bearing zones based on the technical impracticability of achieving further
contaminant reduction—a decision which would be made in the future based on all
relevant information and any new remedial technologies available at the time.
• Institutional controls will be provided and maintained to restrict access to those
portions of the aquifer that remain above remediation levels.
• Monitoring of specified wells will continue.
• Remedial technologies for groundwater restoration will be periodically re-evaluated.
7.1.0.8. The decision to invoke any or all of these measures may be made during a periodic
review of the remedial action, which will occur at least every 5 years in accordance with
CERCLA Section 121(c).
7.1.0.9. Elements specific to Non-Source Area Alternative NSA3 include:
• The existing seep collection systems will be upgraded and new collection systems
installed as necessary to prevent discharge of seeps and springs at concentrations
exceeding MCLs. If the seeps and springs cease to flow due to groundwater extraction
systems in the Source Areas, new collection systems will not be installed. Expansion and
upgrade of the existing system will occur after the source control system has been
implemented and the effects on the seeps and springs have become evident.
• Arsenic contaminated sediment having concentrations exceeding background levels, as
defined in the Baseline Risk Assessment portion of the RI, will be excavated at seeps
Ul-301, Ul-303, Ul-304, Ul-305, and Ul-318. The sediments will be properly disposed
of offsite at an appropriate disposal facility. This sediment will be excavated once source
control measures and spring collection system upgrades have been made that prevent
further discharges to the surface at these locations, or, due to Source Area controls, the
spring and seep areas cease to flow.
• Reliance on monitored natural attenuation for groundwater restoration.
7.1.0.10. The goal of this remedial action for the Non-Source Area is to minimize the
potential for human exposure to contaminated groundwater and surface water and restore
the groundwater and surface water to MCLs, since groundwater and water from the springs
are potential drinking water sources. However, there is no current domestic use of the
shallow groundwater in the vicinity of the OU1 Non-Source Area plumes.
7.1.0.11. The selected remedy for the Non-Source Area will include sediment removal,
monitored natural attenuation, and spring collection and treatment for an estimated period
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of 12 years, during which the systems performance will be carefully monitored on a regular
basis and adjusted as warranted by the performance data collected during operation.
Modifications may include any or all of the following:
• Discontinuing groundwater collection at individual springs where cleanup goals have
been attained; however, monitoring will continue for 2 to 5 years to ensure cleanup
goals have been attained.
• Installing additional springs collection points if new springs occur that exceed MCLs.
7.1.0.12. It may become apparent, during implementation or operation of the Non-Source
Area alternative, that contaminant levels have ceased to decline and are remaining constant
at levels higher than the remediation goal over some portion of the contaminated plume. In
such a case, the remedy will be re-evaluated.
7.1.1 Remediation Goals and Performance Standards
7.1.1.1. In an effort to protect human health and the environment, remedial action objectives
and remediation goals were established to address potential future unacceptable risk
scenarios. As noted in the Feasibility Study (FS) and the Proposed Plan, remedial action
objectives and remediation goals were established for each medium that might pose such
unacceptable risks, including soil and landfill contents, air, groundwater, and surface water.
Preliminary remediation goals were developed to establish media-specific concentrations of
contaminants of concern that will pose no unacceptable risks to human health or the
environment. Preliminary remediation goals associated with each medium of concern at
OU1 are discussed below and presented in more detail in the FS. The considerations used in
setting remedial action goals for OU1 soil, groundwater, surface water, LNAPL, and landfill
contents and gas are:
• PRGs representing concentration levels corresponding to an excess cancer risk between
1 x 1CT1 and 1 x 1CT6, a chronic health risk defined by a hazard quotient of 1, and/or a
significant ecological risk. PRGs will be presented in this Record of Decision at the
1 x 1CT6 level because it is the PRG serving as "the point of departure" as required by the
NCP.
• Chemical-specific ARARs (including MCLs and non-zero maximum contaminant level
goals for potential sources of drinking water).
• Background concentrations of specific constituents in soils.
• Factors related to technical limitations, uncertainties, and other pertinent information.
7.1.1.2. Soil Remedial Action Objectives. The remedial action objectives for soils are to prevent
human exposure through contact, ingestion, or inhalation to contaminated soil that presents
an unacceptable risk and to prevent migration of contaminants that cause an unacceptable
risk in groundwater.
7.1.1.3. Soil Performance Standards. The performance standards shown in Table 7-1 were used
for defining the soil areas requiring remediation. These performance standards are intended
to prevent contamination in soil from migrating to groundwater at concentrations that
would result in exceedance of groundwater performance standards. A chemical equilibrium
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RECORD OF DECISION FOR OPERABLE UNIT 1
mass-balance model was used to establish these performance standards. Areas exceeding
these standards are shown in Figure 7-2 and shall be covered with a low-permability soil
cap to prevent exposure and minimize the infiltration of surface water through the
contaminated soils to the groundwater. The existing landfill cap currently covers these
areas and shall be maintained under the selected remedy. Monitoring and maintenance of
the landfill cap will comply with the performance standards (ARARs) identified in
Appendix A. Details of the operation and maintenance measures for the landfill cap will be
defined in the Performance Standard Verification Plan (PSVP).
7.1.1.4. Groundwater Remedial Action Objectives. The remedial action objectives for
groundwater are to prevent human exposure through contact, ingestion, or inhalation to
contaminated groundwater and restore groundwater to beneficial use. Institutional and
engineering controls will prevent use of the water and contain contaminants in the Source
Area. Contaminated groundwater from the Source Area will be treated as part of the
dewatering process. Monitored natural attenuation is expected to meet these goals in the
Non-Source Area.
7.1.1.5. Groundwater Performance Standards. Chemical-specific ARARs (e.g., MCLs) exist for
some of the contaminants of concern at OU1. For those constituents, the performance
standards are based on compliance with ARARs. For contaminants that do not have
chemical-specific ARARs, performance standards are based on a maximum excess cancer
risk for ingestion, inhalation, and dermal contact with shallow groundwater or surface
water within the range of 1 x ICT* to 1 x 10"6 with a target risk level of 1 x 1CT6. Finally, for
chemicals without chemical-specific ARARs that can produce chronic health effects, the
performance standard is set at a concentration that will lead to a hazard index of 1. The area
exceeding performance standards is defined by the area over which concentrations of one
or more contaminants in the shallow groundwater exceed the performance standards for
groundwater. Table 7-2 presents the list of performance standards for the principal
contaminants of concern in groundwater and surface water at OU1. As discussed in Section
6.2.2.3 of this ROD, a waiver to meet MCLs in the groundwater may be needed for parts of
the Source Area in the future because it is technically impracticable to reach those levels.
7.1.1.6. At OU1, DCE is the most widespread groundwater contaminant exceeding
performance standards. As a result, DCE largely defines the area exceeding performance
standards shown in Figure 7-3. Other groundwater contaminants found sporadically in the
Non-Source Area plume include TCE, 1,1-dichloroethane, and 1,1,1-trichloroethane. The
area exceeding performance standards for groundwater encompasses approximately
170 acres.
7.1.1.7. Thus, the performance standard for the groundwater component of the selected
remedy is for contaminant concentrations in groundwater to be reduced to below the
performance standards (Table 7-2). Groundwater monitoring and evaluation shall be
performed to determine if groundwater restoration is progressing at an appropriate rate.
The specifics of the monitoring and evaluation program will be determined during the
remedial design.
7.1.1.8. Surface Water Remedial Action Objective. The remedial action objective for surface water
is to prevent human exposure through contact, ingestion, or inhalation to contaminated
seep or spring water by the collection and treatment of the contaminated water.
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RECORD OF DECISION FOR OPERABLE UNIT 1
7.1.1.9. Surface Water Performance Standards. Springs that have exceeded the performance
standards include Ul-303, Ul-304, Ul-305, Ul-306, Ul-307, Ul-309, and Ul-318. Many of
the springs are intermittent and have flow rates of less than 1 gpm, which vary seasonally
in response to climatic changes, depending on whether the area is in a drought or wet cycle.
Surface water from all seeps and springs exceeding performance standards in Table 7-2 will
be collected, treated, and discharged, and shall comply with all performance standards
(ARARs) identified in Appendix A. ,
7.1.1.10. Sediment Remedial Action Objective. The potential for exposure to sediments at the
springs was considered minimal. Because arsenic is found above background values
(11 mg/kg) at off-Base Springs Ul-301, Ul-303, Ul-304, Ul-305, and Ul-318, HAFB is
including the sediment at these springs in the areas for remediation. The remedial action
objective for these sediments is to prevent human exposure through contact, ingestion, or
inhalation to sediments that exceed 11 mg/kg of arsenic.
7.1.1.11. Sediment Performance Standards. The performance standard of 11 mg/kg for arsenic is
consistent with background concentrations measured in the area. Arsenic concentrations
below background levels naturally pose low-level risks in the 1 x 10"* to 1 x 10* risk range
for the residential scenario. Because the naturally occurring concentrations are widespread
throughout the area, there is no benefit to public health in attempting to attain a lower
concentration. Figure 7-4 shows those areas exceeding performance standards for surface
water, and locations of springs with concentrations of arsenic in sediment above
background concentrations. Sediments exceeding the performance standards of 11 mg/kg
will be excavated and disposed of according to performance standards (ARARs) identified
in Appendix A.
7.1.1.12. Source Area Remedial Action Objectives. The Source Area of OU1 includes Landfills 3
and 4, CDPs 1 and 2, FTAs 1 and 2, the Waste Phenol/Oil Pit, the Waste Oil Storage Tank
Site, and the light non-aqueous phase liquid (LNAPL) plume emanating from CDPs 1
and 2. The remedial action objectives for the Source Area are to prevent contaminants in
excess of MCLs from migrating away from the Source Area so that the Non-Source Area can
be effectively remediated and to restore Source Area groundwater to MCLs.
7.1.1.13. Source Area Performance Standards. Containment of the Source Area will be required
in areas where contaminants migrate from the Source Area at levels exceeding the
performance standards. Containment will be accomplished through the use of a series of
dewatering trenches and/or extraction wells through the areas of greatest saturated
thickness in the shallow water-bearing zone. The containment trenches and/or extraction
wells will be constructed and operated in accordance with the performance standards
(ARARs) identified in Appendix A. The monitoring points to be used to determine
compliance shall be identified during the remedial design. Hydraulic controls or other
measures acceptable to the EPA and UDEQ will be used to demonstrate that containment
measures are complying with the remedial action objective. The containment measures will
continue until releases are no longer occurring that impair water quality and/or represent a
potential threat to human health and the environment.
7.1.1.14. LNAPL Plume Remedial Action Objectives. The remedial action objectives for the LNAPL
plume is to remove the LNAPL that can be practicably removed and to prevent
contaminant migration from the Source Area to groundwater at levels that impair water
quality and/or represent a potential threat to human health and the environment. The
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RECORD OF DECISION FOR OPERABLE UNIT 1
LNAPL plume area requiring remediation is defined as the area where free-phase LNAPL,
including observations of sheens, has been detected in groundwater monitoring wells. Also
included is the area where observations were made while drilling soil borings that
residual-phase LNAPL was observed in the smear zone near the groundwater. The LNAPL
plume occurs over a 7-acre area. Recent 1996 monitoring data reveals that the area of
free-phase LNAPL is considerably smaller than the historical maximum extent of LNAPL,
as shown in Figure 7-5.
7.1.1.15. LNAPL Plume Performance Standards. LNAPL removal will need to be operated until it
is no longer practicable to remove. LNAPL removal and disposal will comply with the
performance standards (ARARs) identified in Appendix A. Details of the operation and
maintenance and monitoring points used to determine compliance will be identified during
the remedial design.
7.1.1.16. Landfill Remedial Action Objectives. The remedial action objectives for the landfill
contents and landfill gas are to: prevent human exposure to the contents and the gas;
minimize infiltration, thus reducing additional groundwater contamination; and prevent
landfill gas concentrations form reaching dangerous (i.e., explosive) levels.
7.1.1.17. Landfill Performance Standards. The landfill contents and landfill gas areas that need to
be addressed by the selected remedy are the boundaries of the landfills as shown in
Figure 7-6 and cover approximately 25 acres. Landfill contents are defined as landfill debris
and unsaturated contaminated soil from the base of the existing landfill caps (which cover
Landfills 3 and 4) to maximum depth of the contaminated soil or the groundwater table,
whichever is less. Because the areal extent of landfill gas is currently unknown, landfill
gases are assumed to be present throughout the landfill contents. Landfill gas is defined as
gas generated from wastes present in the landfill contents. A BACT analysis will be
performed to ensure compliance with air quality standards.
7.1.1.18. Monitoring and maintenance of the existing cap and vent system will be performed
in accordance with the performance standards (ARARs) identified in Appendix A. In
addition, the cap over Landfill 4 will be improved to prevent ponding of water. Compliance
monitoring of the cap and vent system will be identified in the remedial design.
7.1.1.19. Achievement of Remedial Action Objectives. As detailed in the FS and the Proposed Plan,
the selected remedy is designed to address each of the remedial objectives, remediation
goals, and PRGs as well as ensure that these objectives and goals are met. To this end, the
selected remedy will prevent migration of contaminants in soils, landfill contents, and air
from the Source Area by maintaining the landfill cap and gas vent system. The selected
remedy will prevent migration of contaminated groundwater and LNAPL from the Source
Area by dewatering the Provo Formation and reducing the potential for migration into the
Alpine Formation. The selected remedy will also prevent unacceptable exposure scenarios
with regard to Source Area soils, landfill contents, air, and groundwater by providing
institutional and engineering controls. The selected remedy will also provide additional
control over potential exposure to contaminants at seeps of potential concern by providing
institutional and engineering controls, upgrade to the existing surface water collection
system, and removal of sediments. The selected remedy will restore groundwater through
mass removal and natural attenuation in the Source Area and through natural attenuation
in the Non-Source Areas. The selected remedy also provides environmental monitoring and
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RECORD OF DECISION FOR OPERABLE UNIT 1
monitored natural attenuation to help ensure that remediation objectives and goals are met
in the Non-Source Area.
7.1.1.20. Compliance and Performance Monitoring. As part of the CERCLA process, there are
monitoring requirements to ensure that the selected remedy for OU1 is in compliance with
regulatory requisites, is achieving appropriate protection of human health and the
environment, and is continuing to pursue attainment of remediation goals. Media and
remediation system monitoring programs have been implemented in the past and will be
implemented in the future at OU1 in an effort to determine if, and to what degree, remedial
measures implemented to date and individual components of the selected remedy are
helping to achieve these objectives. A PSVP will be prepared during remedial design and
prior to implementation of the selected remedy. The PSVP report will more fully describe
the data quality objectives (DQO) and proposed monitoring programs that will monitor the
progress toward achieving the remediation goals, and ultimate achievement or resolution of
the goals.
7.1.2 Restoration Time Frame
7.1.2.1. The restoration time for groundwater is estimated to be greater than 50 years in the
Source Area and 12 years in the Non-Source Area. Complex hydrogeology precludes
accurate modeling with the information available. Installation of the dewatering and
performance monitoring systems will provide more hydrogeological and empirical
information by which better estimates may be made.
7.1.3 Costs
7.1.3.1. The estimated capital costs for remediating OU1 using the selected remedy (Source
Area Alternative SA3 and Non-Source Area Alternative NSA3) is presented in Table 7-3.
The total capital costs for the selected remedy is estimated at $2,959,100. The selected
remedy includes the following capital costs items: extraction trenches for dewatering in the
Source Area; LNAPL recovery systems for these trenches; repair of the landfill cap and
passive gas vent system; monitoring well installations; upgraded seep collection systems for
the Non-Source Area; and groundwater treatment at the OU2 ASTP and discharge to the
CWSID.
7.1.3.2. Operation and maintenance costs have been calculated for a 30-year period and do
not reflect costs that may be incurred if the remediation period lasts longer than 30 years.
Annual operation and maintenance for the selected remedy is estimated to be $416,520.
7.1.3.3. The total 30-year present worth cost of the selected remedy, using an interest rate of
5 percent, was estimated at $8,214,700. The present worth cost is estimated with a
+50/-30 percent accuracy for the 30-year period.
7.2 Statutory Determinations
7.2.0.1. The selected remedy for HAFB OU1 meets the statutory requirements of Section 121
of CERCLA as amended by SARA. These statutory requirements include protectiveness of
human health and the environment, compliance with ARARs, cost effectiveness, utilization
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RECORD OF DECISION FOR OPERABLE UNIT 1
of permanent solutions and alternative treatment technologies to the maximum extent
practicable, and preference for treatment as a principal element. The manner in which the
selected remedy for OU1 meets each of the requirements is presented in the following
discussion.
7.2.1 Protection of Human Health and the Environment
7.2.1.1. The selected remedy for OU1 protects human health and the environment through
the following treatments with institutional and engineering controls:
• Institutional and engineering controls in the Source Area would limit direct exposure to
contaminated soils that pose a future health risk.
• Future health risks resulting from exposure to contaminants migrating outside the
Source Area in groundwater are unlikely since essentially all of the contaminant mass
currently migrating offsite would be prevented from migrating by the dewatering
trenches. Groundwater would no longer be available for use from the Provo Formation,
and institutional controls would limit direct exposure to contaminated groundwater.
• Future health risks resulting from exposure to contaminants leaching from LNAPL
migrating outside the Source Area in groundwater are unlikely since essentially all of
the contaminant mass leaving the site would be prevented from migrating by the
dewatering trenches. Groundwater in the LNAPL area would no longer be used because
the Provo Formation is dewatered, and institutional controls would limit direct
exposure to LNAPL.
• Regarding landfill contents and gas, the existing landfill cap should continue to
minimize infiltration and leaching of contaminants to groundwater, if properly
maintained. Future health risks to construction workers are unlikely since institutional
controls require use of proper health and safety equipment for excavation in landfills.
Health or safety risks are unlikely from landfill gas because the existing gas vent system
is maintained and monitored.
• Institutional controls in place during the period until monitored natural attenuation
reduces the groundwater contaminants to MCLs should prevent potable use of the
groundwater in the Non-Source Area. The time until MCLs are met may be as few as
12 years. The presence of an existing water supply minimizes potential for potable use
of the Non-Source Area groundwater.
• Surface water from all springs exceeding MCLs will be collected and treated to MCLs.
• Institutional controls including well advisories, water rights, well drilling restrictions,
easements, and leases as necessary for monitoring and installation of equipment will be
enacted.
• G*ngoing monitoring of groundwater and water flowing from springs will provide the
basis of determining the effectiveness of the remedial action.
7.2.1.2. The selected remedy will not pose any unacceptable short-term risks. Institutional
and engineering controls and proper health and safety procedures will be implemented
during construction and monitoring to minimize short-term risks to site workers and
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RECORD OF DECISION FOR OPERABLE UNIT 1
off-Base residents. The selected remedy will minimize cross-media impacts. For example,
contamination of groundwater will be reduced by dewatering the Source Area, thus
reducing impacts on springs fed by shallow groundwater.
7.2.1.3. Because this remedy will result in hazardous substances remaining onsite above
health-based levels, a review will be conducted within 5 years after commencement of
remedial action to ensure the remedy continues to provide adequate protection of human
health and the environment.
7.2.2 Compliance with Applicable or Relevant and Appropriate Requirements
7.2.2.1. Section 121(d)(l) of CERCLA, as amended by SARA, requires that the remedial
actions for OU1 must attain a degree of cleanup that assures protection of human health
and the environment. In addition, remedial actions that leave any hazardous substances,
pollutants, or contaminants onsite must, upon completion, meet a level or standard that at
least attains ARARs under the circumstances of the release. ARARs will be adhered to
during implementation of the selected remedy. All ARARs will be met upon completion of
the selected remedy or a waiver will be justified. Federal and State ARARs for the selected
remedy are presented in Appendix A.
7.2.2.2. Chemical-Specific ARARs. The selected remedy will comply with chemical-specific
ARARs related to groundwater, springs, air quality, and discharge limits from water
treatment.
7.2.2.3. MCLs based on the Safe Drinking Water Act (Utah Primary Drinking Water
Regulations) are relevant and appropriate as cleanup standards for contaminated
groundwater and springs at OU1. The Utah Groundwater Quality Protection Rule provides
identical standards for the chemicals of concern. Also, the Utah Groundwater Quality
Protection Rule is met because the existing landfill cap minimizes infiltration through the
landfill contents.
7.2.2.4. A waiver of MCLs as restoration goals is not being considered at this time. It may be
established in the future that it is technically impracticable to remediate portions of the
Source Area groundwater to MCLs within a reasonable time frame. In this case, a waiver
will be considered.
7.2.2.5. Location-Specific ARARs. Few location-specific ARARs were identified for this site.
The location standards for hazardous wastes management units are applicable (40 CFR Part
264.18; UAC R315-8-2.9), but no remediation units will be located on a fault or in a 100-year
floodplain.
7.2.2.6. Action-Specific ARARs. The selected remedy will comply with all action-specific
ARARs, as identified in Appendix A. Federal and State action-specific ARARs include those
for air and water discharges as described under chemical-specific ARARs. Additional
action-specific ARARs include the Solid Waste Disposal Act; RCRA requirements for
treatment, storage, and disposal of wastes generated from construction; and State ARARs
which are more stringent or for which there are no federal counterparts.
7.2.2.7. A CAMU will be designated as the contiguous area of contamination. Movement of
soils or landfill materials to appropriate locations within the boundaries of the CAMU will
comply with RCRA land disposal restrictions. It is anticipated that this will be applied to
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RECORD OF DECISION FOR OPERABLE UNIT 1
cuttings from groundwater extraction and monitoring wells as well as trench spoils for
groundwater collection systems.
7.2.3 Cost Effectiveness
7.2.3.1. The selected remedy is cost effective in addressing the principal risks posed by the
LNAPL, soils, groundwater, landfill contents and gas, and springs within a reasonable
period of time. Section 300.430(f)(ii)(D) of the NCP requires evaluating cost effectiveness by
comparing all of the alternatives that meet the threshold criteria against three additional
balancing criteria that describe the alternatives overall effectiveness: long-term effectiveness
and permanence; reduction of toxicity, mobility, or volume through treatment; and
short-term effectiveness. A remedy is cost effective if its costs are proportionate to its overall
effectiveness.
7.2.3.2. The selected remedy for the Source Area (SA3) provides the best overall
effectiveness of all alternatives considered proportional to its cost. Except for the most
expensive removal SA Alternatives (SA6 and SAT), SA2 through SA5 are the next most
effective and permanent alternatives. They have similar effectiveness although there are
small increases in reliability and permanence in the prevention of offsite migration as a
result of the central dewatering trench (SA3, SA4, and SA5), the slurry wall (SA4 and SA5),
and the landfill cap upgrade (SA5). The increase in reliability is considered only slight
because contamination in these stringers is much less concentrated than in the Provo
Formation, and the groundwater flow is only a small fraction of the flow in the Provo
Formation. The landfill cap upgrade included in SA5 provides only a marginal increase in
reliability relative to SA4, which is not proportionate to the 200% higher cost for SA5. SA3,
SA4, and SA5 are similar in their reduction of TMV. SA3, SA4, and SA5 include the
dewatering trench, but this results in the additional collection of only an estimated 5 gpm of
lower concentration contaminants from the Alpine Formation. These alternatives, however,
initially dewater the Provo Formation and remove and treat the associated contaminants
dissolved in the groundwater. As a result they are considered better in reduction of TMV
relative to SA1 and SA2. Only the 30 percent higher cost of SA3 is proportionate to the
increased reduction of TMV over SA2. SA1 and SA2 have no significant short-term risks,
and SA5, SA6, and SA7 have significant risks due to excavation and hauling of large
quantities of soil and/or landfill contents. The marginal increases in protecriveness
provided by these alternatives (under 20 percent) is not proportionate to the significantly
higher costs (200—4,000 percent). SA3 and SA4 include excavation through contaminated
soil and landfill wastes to install the central dewatering trench, so adherence to a health and
safety plan is important to prevent exposure of workers to contaminants. Impacts on the
community and environment are not expected; however, air emission monitoring, dust
suppression, and implementation of an erosion control plan are necessary.
7.2.3.3. The selected remedy for the Non-Source Area (NSA3) provides the best overall
effectiveness of all alternatives considered proportionate to its cost. All alternatives except
NSA1 are expected to be effective in preventing future risks from exposure to groundwater
or surface water through reliance on institutional controls during the period until
groundwater meets the remedial goals. The magnitude of residual risks, (i.e., the risks
remaining following completion of the remediation) are similar for NSA2 through NSA6
because each alternative continues operation until remedial goals are met. Residual risks
related to exposure to arsenic in sediment, though currently below target levels, would be
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RECORD OF DECISION FOR OPERABLE UNIT 1
eliminated entirely under NSA3 through NSA6. The reduction in TMV through treatment is
greatest for the alternatives that actively collect and treat the springs and groundwater.
NSA3 (compared to NSA2) provides greater long-term effectiveness and reduction in TMV,
at a level proportionate to its 50 percent higher cost, in that more springs will be addressed
as well as the removal of arsenic contaminated sediments. NSA5 and NSA6 result in the
greatest amount of TMV reduction because they collect all the contaminated surface water
and groundwater and treat with air stripping. NSA4 has nearly the same reduction in TMV.
However, NSA4 is the most expensive (33 percent higher than NSA5). None of the
alternatives pose significant risks to workers, the community, or the environment as a result
of construction or operation activities, although the increased TMV reduction and risks due
to construction of NSA4 through NSA6 are not balanced by the proportionately higher costs
as compared to NSA3 (26 to 66 percent). The time until remedial goals are achieved is the
least for NSA6 (as few as 5 years), followed by NSA4 (as few as 11 years), and NSA2, NSA3,
and NSA5 (as few as 12 years). In summary, the differences between alternatives in their
overall protecriveness are not considered great because they all rely on the same
institutional controls to prevent exposure, and the time period for which the controls are
necessary is not significantly different. Each alternative provides some added degree of
protection and reliability in achieving ARARs. However, the alternatives do not vary
significantly in the degree to which they best balance the five balancing criteria.
7.2.4 Utilization of Permanent Solutions and Alternative Treatment Technologies
7.2.4.1. The selected remedy meets the statutory requirement to utilize permanent solutions
and treatment technologies to the maximum extent practicable. The selected remedy
provides the best balance of tradeoffs among all of the alternatives with respect to the five
balancing criteria which include:
• Long-Term Effectiveness
• Reduction of Toxicity, Mobility, or Volume Reduction through Treatment
• Short-Term Effectiveness
• Implementabiliry
• Cost
7.2.4.2. Several aspects of the selected remedy use permanent solutions, which are
statutorily preferred in the interests of public health and environmental protection.
Operation of the existing Source Area groundwater collection system will result in greater
removal of dissolved constituents in the Provo and Upper Alpine Formations. The new
dewatering trenches will also result in contaminant mass removal, including the improved
opportunity for free-phase LNAPL removal as the water table is lowered. This mass
removal in the Source Area will have a secondary benefit of permanently controlling and
reducing containment mass loading to the Non-Source Area springs. Further, the remedy
provides for removal of arsenic contaminated sediment and disposal under the existing
landfill cap or offsite at an appropriate disposal facility from these springs where
concentrations represent unacceptable risks to the public health or the environment.
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RECORD OF DECISION FOR OPERABLE UNIT 1
7.2.4.3. The criteria most critical in the selection decision for the Source Area were long- and
short-term effectiveness, implementability, and cost. All alternatives that met the threshold
criteria would reduce toxicity, mobility, and volume. Potential risks to the community and
site worker concerns of short-term effectiveness are significantly less for SA3 than SA5
through SA7. SA4 provides a similar balance of the five criteria to SA3, since its greater cost
is balanced by its slightly better long-term effectiveness. SA5 through SA7 do not provide a
good balance of the five criteria, since their costs are much greater than SA3 and SA4.
7.2.4.4. The criteria most critical in the selection decision for the Non-Source Area were
long-term effectiveness and cost. NSA3 provides a similar balance of the five criteria as does
NSA2, even though it is slightly more costly. NSA4 through NSA6 provide slightly greater
degrees of protectiveness and are greater in cost than NSA3, but are slightly poorer in their
balance of the five criteria than NSA3.
7.2.5 Preference for Treatment as a Principal Element
7.2.5.1. The selected remedy for OU1 utilizes permanent solutions and treatment
technologies to the maximum extent practicable. The use of dewatering trenches to control
and extract contaminated shallow groundwater in the Source Area satisfies the statutory
preference for actions that permanently and significantly reduce the volume, toxicity, and
mobility of hazardous substances. The upgrade of seep collection systems to control,
extract, and treat contaminated shallow groundwater in the Non-Source Area satisfies the
statutory preference for actions that permanently and significantly reduce the volume,
toxicity, and mobility of hazardous substances. This preference is not satisfied with respect
to the reliance on monitored natural attenuation in the Non-Source Area; however, these
natural treatment processes are expected to permanently reduce the concentrations of
contaminants.
7.3 Documentation of Significant Changes
7.3.0.1. The Proposed Plan was released for public comment on January 15, 1998. A public
meeting on the Proposed Plan was held on February 5,1998. The Proposed Plan identified
Source Area Alternative SA3 and Non-Source Area Alternative NSA3 as the preferred
combination of alternatives. This remedy included extraction trenches for dewatering in the
Source Area, LNAPL recovery systems for these trenches, repair and O&M of the landfill
cap and passive gas vent system, monitoring well installations, performance and monitored
natural attenuation, institutional controls, excavation of arsenic-contaminated seep
sediments, upgraded seep collection systems for the Non-Source Area, groundwater
treatment at the OU2 ASTP or the IWTP, and discharge to the local POTW. The public was
informed of the timeframe of 50 or more years to restore the groundwater to cleanup
standards. All written and verbal comments received during the public comment period
were reviewed and responded to. The responses to public comments are found in
Appendix C. No changes to the proposed remedial alternative were made based on public
comment.
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TABLE 7-1
Performance Standards for Soil Protective of Groundwater
Parameters Used to Calculate PRGs for Soil
Constituent of Concern
Trichloroethene
1,1,1 -Trichloroethane
Tetrachloroethene
1,1-Dichloroethene
1,1-Dichloroethane
1 ,2-Dichloroethane
Toluene
Benzene
Ethylbenzene
Chlorobenzene
1 ,2-Dichloroethene (cis)
Vinyl Chloride
Xylenes (total)
Benzo(a)pyrene
1 ,2-Dichlorobenzene
1 ,4-Dichlorobenzene
2,4-Dimethylphenol
4-Methylphenol
Naphthalene
Pentachlorophenol
1,2,4 Trichlorobenzene
2,3,7,8-TCDD
PCB1260
Preliminary
Remediation Goal
(mg/kg)
0.17
10
0.52
0.03
13
0.10
43
0.12
11
2.4
1.1
0.03
1,000
21
60
5.8
8
3.7
22.5
0.26
17
0.004
10.1
PRG for
Groundwater"'
(M9/0
5
200
5
7
630
5
1,000
5
700
100
70
2
10,000
0.2
600
75
300
750
60
1
70
0.00003
0.5
Koc
(ml/g)
120
180
360
14
70
70
150
83
55
83
55
50
280
370,000
350
270
96
17
1,300
900
860
481,000
70.000
rv,
(ml/g)
1.63
2.45
4.90
0.19
0.952
0.952
2.04
1.13
0.748
1.13
0.748
0.68
3.81
5.030
4.76
3.67
1.31
0.231
17.7
12.2
11.7
6,540
952
|a)Maximum contaminant level (MCL) or health-risk-based concentration. The MCL is the cleanup goal where an
MCL has been promulgated. Health-risk-based concentrations are italicized and indicate the concentration at which
the hazard index equals 1. All carcinogens have MCLs; the MCL concentration corresponds to a cancer risk
between 10"1 and 10"6.
KOC = organic carbon partitioning coefficient.
KO = soil to water partitioning coefficient (= foe *
\\SNCW8IRD\PROJ\136064UJ_3\FINAl\REPORnTABLES\TABLE7-1.DOC
-------
TABLE 7-2
Performance Standards for Principal Contaminants of Concern in Groundwater and Surface Water at Operable Unit 1
Parameters Considered in Setting PRGs for Ground and Surface Water
Compound
Arsenic
Barium
Fluoride
Benzene
Chlorobenzene
1,1-Dichloroethene (cis)
Total- 1 ,2-Dichloroethene
1 ,2-Dichlorobenzene
1 ,4-Dichlorobenzene
1,1-Dichloroethane
2,4-Dimethylphenol
4-Methylphenol
Naphthalene
Tetrachloroethene
1 ,2,4-Trichlorobenzene
1,1,1 -Trichloroethane
Trichloroethene
Toluene
Preliminary
Remediation
. Goal (ug/l)
50
1,000
2,400
5
100
7
70
600
75
790
600
1,500
1,200
5
70
200
5
1,000
Federal
MCL(ug/l)
50
2,000
2,400
5
100
7
70(a)
600
75
--
--
--
5
70
200
5
1,000
Utah MCL
(ug/l)
50
2,000
2,400
5
100
7
70""
600
75
--
--
--
--
5
70
200
5
1,000
MCLG(8>
(M9/D
--
2,000
4,000
--
100
7
70(a)
600
75
--
--
--
--
--
70
200
--
1,000
Concentration at Concentration at
which Excess Cancer which Excess Cancer
Risk Equals 1 0* (ug/l) Risk Equals 1 0"4 (ug/l)
0.04 4
-
--
0.6 60
..
0.02 2
--
..
3 290
..
..
..
--
1
-------
TABLE 7-2
Performance Standards for Principal Contaminants of Concern in Groundwater and Surface Water at Operable Unit 1
Parameters Considered in Setting PRGs for Ground and Surface Water
Compound
Vinyl Chloride
Xylenes (Total)
Preliminary
Remediation
Goal (ug/l)
2
10,000
Federal
MCL(ug/1)
2
10,000
Utah MCL
(M9/I)
2
10,000
MCLG(a)
(M9/0
10,000
Concentration at
which Excess Cancer
Risk Equals KT6 (ug/l)
0.02
Concentration at
which Excess Cancer
Risk Equals 10"* (ug/l)
2
Concentration at
awhich Hazard
Quotient Equals 1 (ug/l)
980
(a) Only non-zero MCLGs are listed.
(b) Slope factors have been withdrawal for this compound; concentrations based on slope factors estimates from the Environmental Criteria and Assessment Office of
USEPA-
- = value not available or applicable.
-------
TABLE 7-3
Summary of Costs for the Selected Remedy at HAFB Operable Unit 1
Annual Operation Total Present
Alternative Capital Cost and Maintenance Worth Cost
Source Area Alternative 3 $2,241,600 $240,254 $5,934,900
Non-Source Area Alternative 3 $717,500 $176,266 $2,279,800
Total Cost $2,959,100 $416,520 $8,214,700
P:\136064W_1_3\flNAUREPORTV OU1ROO.DOC
-------
LEGEND
. Existing Dewatermg Wai
• Spnng/Seep
=m Existing Groundwaler Extraction Trancn
and Spmg Coteclion Galery
._j Proposed Dewalemg Trench Included
In Souce Area Alemalwe 3
» Proposed Groundwater Extraction Wei
^ Included In Source Area Aftematrve 3
Area that has Exceeded PRGs in Groundwatar
. Non-Soutce Area Natural Anenuatkn
': ; ol Groundwatar
J Springs/Seeps included in Non-Source
Area Alternative 3 Monitoring Plan
• Shallow Groundwaler Monitoring Wets included in
Non-Some Are* Alternative 3 Monrformg Plan
$ Deep Groundwater Monitoring We* included n
Non-Source Area Alemaliv* 3 Montfonng PtM
O Shallow Groundwaler Monitoring Wets Situated Inside
the Contaminant Plume Area included in the
Non-Source Area Alternative 3 Monlonng Plan lor
Monitoring ol Natural Attenuation
Q S«ap Collection System
i Proposed Arsenic Contannnaied Soil Removal
Seeps/Springs
-~ .,' Groundwaler Flow Direction
1J LocMon ana m*no«r ^f tttKW scndwi la
WAS jiMud «i color
->«wn tTCTt *99S jtvial photo
N
600
120)
FM!
IncA • MO IMI
1 TOO
Hill Air Fofco Bas*
Operable Unit 1
PREFERRED ALTERNATIVE
Source Ar«a Att*maUv« 3:
GBOUNDWA T£R DEWA TERING
AND
Non-Sourc* Area Att*rnattv« 3:
NATURAL ATTENUATION AND EXISTING
SEEP COLLECTION UPGRADE
FIGURE 7-1
-------
llndl;300«Ml
Fire Training
Area 2
hemical
Disposal Pit 1
X
LEGEND
Area of Soil Exceeding PRGs or
Risk Criteria
* Existing Dewatering Well
•=» Existing Groundwater Extraction Trench
Note: Original figure was created in color.
Source: Base map drawn from 1995 aerial photo.
Waste
Phenol/Oil Pit
0 Existing
Soil/Bentonite
Chemical
Disposal Pit 2
Waste Oil
Storage Tanks
(Removed)
Hill Air Force Base
Operable Unit 1
AREAS EXCEEDING
PRGs FOR SOIL
Figure 7-2
-------
Ul -099 < PRGs ('96 and '94)
• U1 -309 < PRGs ('96). > PHGs ('94)
LEGEND
Existing Dewatering Wen
Spring/Seep
> Existing Groundwaler Exlraclion Trench
and Spring CoBeclion Gallery
Groundwater Monrlonng Well
I. Source Area Exceeding PRGs in Groundwaler
/ - Non-Source Area Exceeding PRGs
^ _ For Groundwaler (based on 1996 data)
Non-Source Area Exceeding PRGs tor
Groundwater (based on 1994 data)
Proposed Boundary o» CAMU
Notes:
(1) Data trorn 1994 and 1996 was used to establish
areas exceeding PRGs lor groundwatar.
(2) Original figure was created in color.
Source: Bua map drawn 1mm 1995 Mnal pholo.
N
A
soo
=z=
FM|
icji.eooi
1 7200
1200
Hill Air Fore* BOM
Op«nbtoUntt1
AREAS EXCEEDING PRGs
FOR GROUNDWATER
FIGURE 7-3
-------
LEGEND
• Existing Ocwalchng Wei
f Spring/Seep
__ Existing Groundwator Extraction Trench and Spnng
Ccteetkm Gallery
Area Exceeding PRGe r\ Surface Walej
> Seep/Spnng with Araemc-Cortaminaled Sediment
* ShjryWal
Now: Ongn>l figuft ww cr«ai»d in cotar.
Sourct: Bax map Aawn Inxn 190S xnal photo.
MO
ii^
FM<
1201
Hill Air Force Bas*
Opwable Unit 1
AREAS EXCEEDING PRGs FOR SURFACE
WATER, AND LOCATIONS OF SPRINGS
WITH CONCENTRATIONS OF ARSENIC
IN SEDIMENT ABOVE BACKGROUND
CONCENTRATIONS
FIGURE 7-4
-------
o:\hillattAou1\rodmap\f igures\iigure7-5.wor
Fire Training
Area 2
Waste
Phenol/Oil Pit
Landfill 3
Disposal Pit 1
B 0 Existing
Soil/Bentonite
Disposal Pit 2
Fire Training
Area 1
LEGEND
Area Exceeding Soil PRGs and
Containing Free- and Residual-Phase
LNAPL (all years of data considered)
Area Containing Free-Phase LNAPL
(based on April-June 1996 data)
• Existing Dewatering Well
«=» Existing Groundwater Extraction Trench
Note: Original figure was created in color.
Source: Base map drawn from 1995 aerial photo.
Waste Oil ,;
Storage Tanks
(Removed)
Hill Air Force Base
Operable Unit 1
AREAS EXCEEDING SOIL PRGs
AND/OR CONTAINING FREE-
AMD RESIDUAL-PHASE LNAPL
Figure 7-5
-------
o \niHaib\out\fodmjp\ln3Ufea\hqure7-6.wof
Fire Training
Area 2
Chemical - ; ,: ..
Disposal Pit 1 \. ;, >(J
X
Chemical,.
Disposal Pit 2
LEGEND
Existing Dewatering Well
Existing Groundwater Extraction Trench
and Seep Collection Galleries
Landfill Areas
Note: Original figure was created in color.
Source: Base map drawn from 1995 aerial photo.
Waste Oil ;
Storage Tanks - —.
(Removed)
O
Hill Air Force Base
Property Boundary^
Hill Air Force Base
Operable Unit 1
LANDFILL BOUNDARIES
FIGURE 7-6
-------
8.0 References
CH2M HILL, 1998. Final feasibility Study for Operable Unit 2, Hill Air Force Base, Utah,
January 1998.
CH2M HILL, 1998a. Final Proposed Plan for Operable Unit 1, Hill Air Force Base, Utah,
January 1998.
CH2M HILL, 1998b. Draft Monitoring Well Installation and Impact Assessment of South Weber
No. 2 Report, Hill Air Force Base, Utah, June 1998.
CH2M HILL, 1998c. Draft Groundwater Pre-Design Report for Operable Unit 1, Hill Air Force
Base, Utah, May 1998.
Dames & Moore, Inc. 1985. Additional Geotechnical Services, Cutoff Wall Investigation, North of
HAFB Golf Course, Hill Air Force Base, Utah.
Hill Air Force Base, 1997. Final Environmental Restoration Community Relations Plan, Hill Air
Force Base, Utah, December 1997.
Montgomery Watson (MW), 1995. Final Comprehensive Remedial Investigation Report for
Operable Unit I, Hill Air Force Base, Utah, December 1995.
MW, 1995a. Revised Interim Draft Final Feasibility Study Report for Operable Unit 1, Hill Air
Force Base, Utah, November 1995.
MW, 1996. Final Soil Vapor Extraction Bioventing Treatability Study Evaluation Report for
Operable Unit I, Hill Air Force Base, Utah, January 1996.
Northeast Environmental Products (NEEP), 1996. Shallow Tray Modeler Air Stripping
Calculation Softivare, Northeast Environmental Products.
Parsons Engineering Science, 1996. Draft Work Plan For a Demonstration of Remediation by
Natural Attenuation for Groundwater at Operable Unit I, Hill Air Force Base, Utah,
November 1996.
Radian Corporation, 1995. Three-Mile Pipeline Design Options Report, Hill Air Force Base,
Utah.
State of Utah Governor's Office of Planning and Budget-Demographic and Economic
Analysis Section, 1997. 2997 Baseline Population Projections.
U.S. Environmental Protection Agency (EPA), 1988. Guidance for Conduction Remedial
Investigations and Feasibility Studies under CERCLA, Interim Final, October 1988.
P\136064\4J_3\FINAL\REPORT\FOU1ROD.DOC 8-1
-------
9.0 Responsiveness Summary
9.1 Introduction
9.1.0.1. This section presents the HAFB response to public comments to the Proposed Plan.
These responses are known as the Responsiveness Summary. The Responsiveness Summary
is a requirement of the CERCLA process. CERCLA is the regulatory framework HAFB OU1
is governed by. The EPA and UDEQ regulate OU1. The EPA and UDEQ have reviewed and
concur with the responses to public comments.
9.1.0.2. The responsiveness summary consists of an introduction, an overview of HAFB
community involvement, and a summary of the main issues identified by the public. The
actual public comments and responses to the HAFB response to public are included as
Appendix C-l. Copies of the actual public comments as received by HAFB and responses to
South Weber Landfill Coalition comments to the Draft Final and Revised Draft Feasibility
Study are included as Appendices C-2 and C-3, respectively.
9.2 Overview
9.2.0.1. This Responsiveness Summary provides information about the views of the
community with regard to the proposed remedial action for HAFB OU1, documents how
public comments have been considered during the decision-making process, and provides
responses to concerns.
The public was informed of the selected remedial action in the following ways:
• All items contained within the Administrative Record have been on file in the Davis
County Library and at the Environmental Management Directorate at HAFB since the
final version of each document was issued. The documents include the Final
Comprehensive Remedial Investigation Report, Feasibility Study, and the Proposed Plan.
• The notices of availability for the documents in the Administrative Record were
published in the Salt Lake Tribune, Ogden Standard Examiner, Hilltop Times, and Deseret
News.
• A public comment period for the Proposed Plan was held from January 15,1998, through
March 16,1998.
• A notice about the public meeting was published in the Salt Lake Tribune, Ogden Standard
Examiner, Hilltop Times, and Deseret News.
• A public meeting in open house format was held on February 5, 1998, at South Weber
Elementary School in South Weber, Utah.
• Written comments by the public were encouraged.
P:\1360M\4J_3\FINAL\REPORT\FOU1ROaDOC
-------
9.3 Background on Community Involvement
9.3.0.1. The public participation requirements of CERCLA Sections 113(k)(2)(B)(i-v) and 117
were met. Hill Air Force Base has a Community Relations Plan, based on community
interviews, that was drafted in April 1997 (HAFB, 1997). The ongoing community relations
activities include:
• A Restoration Advisory Board (RAB) that meets at least quarterly and includes
community representatives from adjacent counties and towns.
• A mailing list for interested parties in the community.
• A bi-monthly newsletter called EnviroNews.
• Visits to nearby schools to discuss environmental issues.
• Community involvement in a noise abatement program.
• Periodic briefings to local City Councils.
• Semiannual town council meetings.
• Opportunities for public comment on remedial activities.
• Support for the community for obtaining technical assistance grants.
• Administrative record and information repository.
9.4 Summary of Public Comments
9.4.1 Comments on the Proposed Plan
9.4.1,1. The following section summarizes the main comments made by the public
concerning the Proposed Plan. The HAFB response to the general comment follows the
general comment.
9.4.1.2. Groundwater Contamination Associated with South Weber Number 2. Numerous comments
were received concerning the contamination found in South Weber No. 2, a domestic
groundwater well operated by the Weber Basin Water Conservancy District. The public is
concerned the contamination is from HAFB, and they are concerned about the action HAFB
is taking to remedy the problem.
9.4.1.3. Response to Comment. Hill Air Force Base has responded to this problem by installing
a series of monitoring wells adjacent to South Weber No. 2 to evaluate the geology and
contamination levels in the various water-bearing zones adjacent to South Weber No. 2. The
results of the installation of monitoring wells adjacent to South Weber No. 2 are presented
in the Monitoring Well Installation and Impact Assessment of South Weber No. 2 Report
(CH2M HILL, 1998b). The report is available to the public in the Administrative Record or
by requesting the report from HAFB. A summary of the investigation effort was presented
to the public at the RAB Meeting on June 18,1998, at HAFB.
P:\136064\4_1.WINAL\REPORT\FOU1ROO.DOC 9.3
-------
9.4.1.4. The purpose of the Monitoring Well Installation and Impact Assessment of South Weber
No. 2 Report investigation was to acquire groundwater samples from the water-bearing
zones to evaluate the source of the contamination, assess the lithology of the soil materials
adjacent to South Weber No. 2, and estimate the potential for OU1 contamination to migrate
to the depths of the production zones of South Weber No. 2. The results of this report
indicate that the drinking water aquifer has not been contaminated by HAFB.
Contamination, at concentrations similar to levels in adjacent monitoring wells, was
observed in the shallow water-bearing layers well above the drinking water aquifer. The
soils between the surface and drinking water aquifer were mainly fine-grained. Due to the
fine-grained layers, the area surrounding South Weber No. 2 was not found to be a recharge
area. Drinking water aquifer recharge areas are located at the base of the Wasatch
Mountains, approximately 2 miles to the east.
9.4.1.5. Institutional Controls. The definition of institutional controls and how the institutional
controls would be enforced was an area of public concern.
9.4.1.6. Response to Comment. The institutional controls or land use restrictions for off-Base
areas the Air Force has proposed include limiting the use of the property to the current land
use and limiting access to the shallow groundwater below the affected property. The land
use restrictions would be imposed by a deed restriction with the property owner. The
property owner would be paid for the deed restriction. The restriction would be recorded
on the property deed with the county. The land use restrictions are currently being
reviewed by Air Force Headquarters for final approval and should be implemented in
January 1999. After the shallow groundwater contamination has attenuated to levels safe
enough to drink, the deed restriction will be removed from the deed. The State Engineer is
currently restricting the use of the shallow groundwater. The State Engineer will not issue a
permit for a drinking water well drawing water from the shallow water-bearing zone. In
addition, a majority of the contaminated off-Base area is already under a deed restriction
imposed by the State of Utah. The deed restriction was implemented to limit development
in areas surrounding HAFB with aircraft noise levels above 70 decibels.
9.4.1.7. The on-Base portions of OU1 HAFB are limited from further development by a
continuing order from the Base General. If HAFB were closed and transferred to private
ownership, a deed restriction would be included in the deed for the property that would
limit use of the area. Deed restrictions have been used extensively for contaminated areas of
military bases that have been closed and transferred to private ownership. In addition, if the
remediation systems are still active once the Base is closed, the Air Force would probably be
required to continue operating the remediation systems.
9.4.1.8. Buried Drums in Landfills 3 and 4. Comments were received concerning the presence of
drums containing hazardous materials in the landfills that may rust out and leak causing
further groundwater contamination.
9.4.1.9. Response to Comment. An investigation of the Operable Unit 1 landfills has recently
been performed. The landfill areas were investigated to evaluate the nature and extent of
landfill debris and to determine whether drums were buried in the landfill area. This report
is available to the public. This study included a magnetic anomaly study to determine the
location of large concentrations of metals that would be the most likely location of buried
drums. These areas were identified and mapped. Trenches were excavated in these areas to
evaluate the type of debris that caused the anomalies. The anomalies were found to be
P:\136064V4J_3\FINAUREPORT\FOU1ROO.DOC 9.3
-------
related to the presence of large concentrations of metal waste materials rather than buried
drums.
9.4.1.10. Remediation System Performance Reviews. Numerous comments were received
concerning ways the performance of the remediation systems would be evaluated and how
the data would be reported.
9.4.1.11. Response to Comment. The monitoring will consist of ground water, surface water,
and possibly air monitoring. Groundwater levels will also be measured on a routine basis to
verify capture of groundwater. The monitoring schedule has not been defined at this time.
As part of the remedial design, a monitoring schedule will be developed. A report will be
prepared after each monitoring event, and it will include the results of monitoring events as
well as an assessment of the progress of the remediation effort. This report will be available
for public inspection, and it is anticipated a summary will be sent to the affected property
owners. The performance of the remediation systems will be evaluated on a Base-wide basis
every 5 years. The most current evaluation is scheduled for 1998. The next evaluation is
scheduled for 2003. The evaluation could be performed sooner if the dewatering trenches
are not performing as designed and are allowing contaminated groundwater to migrate
off-Base. The design and construction of another alternative, such as a slurry wall, could be
implemented to limit the migration of off-Base groundwater contamination.
9.4.2 Comments Made during the Public Meeting
9.4.2.1. An open house public meeting for OU1 was held from 4:30 p.m. until 8:00 p.m. on
Thursday, February 5,1998, at the South Weber Elementary School in South Weber, Utah.
Representatives from HAFB, EPA Region VIII, and UDEQ were available to explain and
answer questions about the results of the investigations, health issues, and the proposed
remedy for OU1. A list of all participants in the meeting are included in Appendix B. Public
comments and written responses to public comments are presented in Appendix C.
P:\136064V4_1_3\FINAUHEPORT\FOU1ROD.OOC 9.4
-------
Appendix A
Identification of ARARs
-------
Appendix A Tables
Table A-l Summary of Federal Chemical-Specific ARARs
Table A-2 Summary of Federal Location-Specific ARARs
Table A-3 Summary of Federal Action-Specitic ARARs
Table A-4 Summary of State Chemical-Speciric ARARs
Table A-5 Summary of State Action-Specitic ARARs
Table A-6 Summary of Preferred Alternative-Specific ARARs (see the Final Feasibility
Study for Operable Unit I (CH2M HILL, 1998) for a complete summary of key ARARs for
each of the evaluated alternatives)
-------
TABLE A-1
Identification of Federal Chemical-Specific ARARs
Standard, Requirement,
Criteria, or Limitation
Citation
Description
Applicable/
Relevant and
Appropriate
Comment
Solid Waste Disposal Act 42 USC Sec. 6901-6987
Identification and Listing of 40 CFR Part 261
Hazardous Waste
Safe Drinking Water Act
42 USC Sec. 300g
National Primary Drinking 40 CFR Part 141
Water Standards
National Secondary 40 CFR Part 143
Drinking Water Standards
Clean Water Act
Water Quality Criteria
National Pretreatment
Standards
33 USC Sec. 1251-1376
40 CFR Part 131
40 CFR Part 403
Toxic Substances Control 15 USC Sec. 2601 -2629
Act
PCB Requirements
40 CFR Part 761
Defines those solid wastes that are Yes/-
subject to regulation as hazardous
wastes under 40 CFR Parts 262-265
and Parts 270, 271, 124.
Establishes health-based standards for No/Yes
public water systems (maximum
contaminant levels).
Establishes welfare-based standards No/No
for public water systems (secondary
maximum contaminant levels).
Sets criteria for developing water Yes/-
quality standards based on toxicity to
aquatic organisms and human health.
Sets standards to control pollutants Yes/-
that pass through or interfere with
treatment processes in publicly owned
treatment works or that may
contaminate sewage sludge.
Establishes storage and disposal Yes/-
requirements for PCBs.
Determines potential waste
classifications and applicability of land
disposal restrictions under 40 CFR
268.
Meet MCLs in ground water and
surface water; e.g., TCE = 5 ug/L, vinyl
chloride = 2 ug/L.
The SMCLs are guidance only and are
not enforceable. As a result, they are
TBCs and will be considered for
inorganics such as iron.
Applicable to discharges to surface
water otherwise relevant and
appropriate because shallow aquifer is
a potential drinking water source.
Potential chemical and action-specific
ARAR for discharge to POTW.
PCBs present in soil and ground water
atOU1.
P:\136064\4 1 3\F1NAL\REPORT\APPENDIXA\RODARAH1.DOC
-------
TABLE A-1 (CONTINUED)
Identification of Federal Chemical-Specific ARARs
Standard, Requirement,
Criteria, or Limitation
Citation
Description
Applicable/
Relevant and
Appropriate
Comment
Clean Air Act
National Primary and
Secondary Ambient Air
Quality Standards
National Emission
Standards for Hazardous
Air Pollutants
42 USC Sec. 7401-7642
40 CFR Part 50 Establishes standards for ambient air Yes/-
quality to protect public health and
welfare (including standards for
paniculate matter and lead).
40 CFR Part 61 Subpart A Sets emission standards for Yes/-
designated hazardous pollutants.
Relevant and appropriate to activities
that might result in air emissions during
remedial actions at OU1.
Regulates new installations that will or
might reasonably be expected to
become a source or indirect source of
air pollution.
P:\1J
kt_3\FINAWREPORT\APPENOiJ< A\ROOARAR1.DOC
-------
TABLE A-2
Identification of Federal Location-Specific ARARs
Standard, Requirement,
Criteria, or Limitation
Citation
Description
Applicable/
Relevant and
Appropriate
Comment
Policy on Floodplains and
Wetlands Assessments for
CERCLA Actions
Endangered Species Act
Executive Order on
Floodplain Management
EPA Guidance
Aug. 6, 1985
16 DSC Sec. 1531-1543
40 CFR 6-302(h)
50 CFR Part 200
50 CFR Part 402
Exec. Order #11,988
40 CFR Sec. 6.302(B)
and Appendix A
Discusses situations that require No/No
preparation of a floodplains or
wetlands assessment and the factors
that should be considered in preparing
an assessment for response actions
taken under CERCLA.
Requires that federal agencies ensure Yes/-
that any action authorized, funded, or
carried by the agency is not likely to
jeopardize the continued existence of
any threatened or endangered species
or destroy or adversely modify critical
habitat.
Requires federal agencies to evaluate Yes/-
the potential effects of actions they
may take in a floodplain to avoid, to the
maximum extent possible, the adverse
impacts associated with direct and
indirect development of a floodplain.
TBC because it is guidance. Will be
considered because there are
floodplains designated in the vicinity of
OU1 that may be affected by remedial
actions.
Endangered species may frequent the
Hill AFB area; e.g., Peregrine falcons,
Bald Eagles.
Applicable to remedial actions that
affect or impinge on the Weber River
floodplain.
P:\136064V4.1 _3\F1NAL\REPORTWPENDIX A\RODARAR2.DOC
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TABLE A-3
Identification of Federal Action-Specific ARARs
Standard, Requirement,
Criteria, or Limitation
Clean Water Act Section 404
Citation
33 CFR 320-330
Description
Authorizes the Army Corps of
Applicable/
Relevant and
Appropriate
Yes/-
Comment
Applicable to draining and regn
Jding of
National Emission Standards
for Hazardous Air Pollutants
(NESHAP)
40 CFR 61
Engineers (COE) to issue permits for
the discharge of dredged or fill
materials to wetlands.
Designates substances as hazardous
air pollutants and establishes emission
standards.
Yes/Yes
Pond 10. The Army COE may
determine that the pond is a wetland
requiring mitigation. If so, wetlands
mitigation would be included in the
remedial action.
Relevant and appropriate to benzene,
chloroform, trichloroethene, and
toluene emissions from ground water
or surface water treatment facilities or
soil/landfill vents.
National Pollution
Discharge Elimination
Requirements
Solid Waste Disposal Act
Criteria for Classification of
Solid Waste Disposal
Facilities and Practices
Identification and Listing of
Hazardous Waste
40 CFR Part 122
42 USC Sec. 6901-6987
40 CFR Part 257
40 CFR Part 261
Establishes requirements for permits to Yes/-
authorize the point source discharge of
pollutants into waters of the United
States. Also, regulates discharges of
stormwater.
Establishes criteria for use in Yes/--
determining which solid waste disposal
facilities and practices pose a
reasonable probability of adverse
effects on health or the environment.
Defines those solid wastes that are Yes/-
subject to regulation as hazardous
wastes.
Discharge of treated surface water into
waters of the United States and
stormwater discharges may be
associated with the remedial strategy.
Applicable to remedial alternatives
involving onsite landfilling of
contaminated soils.
Determines potential waste
classification and applicability of land
disposal restrictions and other solid
and hazardous waste rules.
\\SNOW||^ROJ\136064\4J _3\FINAL\REPORT\APPENDIXA\RODARAR3.DOC
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TABLE A-3 (CONTINUED)
Identification of Federal Action-Specific ARARs
Standard, Requirement,
Criteria, or Limitation
Citation
Description
Applicable/
Relevant and
Appropriate
Comment
Standards Applicable to
Generators of Hazardous
Waste
40 CFR Part 262
Standards for Owners and 40 CFR Part 264
Operators of Hazardous
Waste Treatment, Storage,
and Disposal Facilities
General Facility
Standards
Preparedness and
Prevention
Contingency Plan and
Emergency Procedures
Subpart B
264.18
Subpart C
Subpart D
Establishes standards for generators
of hazardous waste.
Yes/-
Establishes minimum national
standards that define the acceptable
management of hazardous waste for
owners and operators of facilities that
treat, store, or dispose of hazardous
waste.
Location standards.
Specifies requirements for
communications, alarm systems, and
coordination with local authorities
Requires development of a
contingency plan and designation of an
emergency coordinator.
Yes/Yes
Yes/«
Yes/--
Yes/~
Applicable to remedial alternatives
involving excavation and generation of
hazardous waste onsite. Cuttings from
monitoring well installation and
collection system trench spoils will be
managed as hazardous waste and
disposed in the Source Area under the
CAMU Rule. LNAPL or excavated
materials that will be disposed offsite,
such as for Alternative 7, will be
characterized and hazardous wastes
managed accordingly.
See discussion of specific subparts.
Applicable to alternatives involving
treatment, storage, or disposal of
hazardous waste at onsite facilities.
Applicable to onsite waste
management of generated hazardous
waste.
Applicable to onsite waste
management of generated hazardous
waste.
\\SNOWBIRD\PROJ\136064V4_1_3\FINAL\REPORT\APPENplXA\ROOARAR3.DOC
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TABLE A-3 (CONTINUED)
Identification of Federal Action-Specific ARARs
Standard, Requirement,
Criteria, or Limitation
Citation
Description
Applicable/
Relevant and
Appropriate
Comment
Manifest System, Record Subpart E
Keeping, and Reporting
264.71
264.73
Use of manifest system.
Operating record.
Releases from Solid
Waste Management
Units
Subpart F
264.91
Required programs.
264.92
Ground water protection standard.
264.93
Hazardous constituents.
Yes/-- Applicable to onsite waste
management of generated hazardous
waste.
Yes/-- Applicable to onsite waste
management of generated hazardous
waste.
Yes/-- Applicable to onsite waste
management of generated hazardous
waste.
Yes/Yes Requirements for detection of release
from SWMUs are applicable for units
treating generated hazardous waste
and may be relevant and appropriate
to the Source Areas where hazardous
waste was disposed.
Yes/Yes Applicable to alternatives involving
treatment of generated hazardous
waste and may be relevant and
appropriate to the Source Areas where
hazardous waste was disposed.
Yes/Yes Applicable to alternatives involving
treatment of generated hazardous
waste and may be relevant and
appropriate to the Source Areas where
hazardous waste was disposed.
Yes/Yes Applicable to alternatives involving
treatment of generated hazardous
waste and may be relevant and
appropriate to the Source Areas where
hazardous waste was disposed.
\\SNOVfliiBiPROJ\136064V4_1.3\FINAUREPORT\APPENDIX A\ROOARAR3.DOC
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TABLE A-3 (CONTINUED)
Identification of Federal Action-Specific ARARs
Standard, Requirement,
Criteria, or Limitation
Citation
Description
Applicable/
Relevant and
Appropriate
Comment
Releases from Solid
Waste Management
Units (continued)
264.94
Concentration limits.
264.95
Point of compliance.
264.96
Compliance period.
264.97
264.98
General ground water monitoring
requirements.
Detection monitoring program.
264.99
Compliance monitoring program.
Yes/Yes Applicable to alternatives involving
treatment of generated hazardous
waste and may be relevant and
appropriate to the Source Areas where
hazardous waste was disposed.
Yes/Yes Applicable to alternatives involving
treatment of generated hazardous
waste and may be relevant and
appropriate to the Source Areas where
hazardous waste was disposed.
Yes/Yes Applicable to alternatives involving
treatment of generated hazardous
waste and may be relevant and
appropriate to the Source Areas where
hazardous waste was disposed.
Yes/Yes Applicable to alternatives involving
treatment of generated hazardous
waste and may be relevant and
appropriate to the Source Areas where
hazardous waste was disposed.
Yes/Yes Applicable to alternatives involving
treatment of generated hazardous
waste and may be relevant and
appropriate to the Source Areas where
hazardous waste was disposed.
Yes/Yes Applicable to alternatives involving
treatment of generated hazardous
waste and may be relevant and
appropriate to the Source Areas where
hazardous waste was disposed.
\\SNOW8IRD\PROJ\136064WJJ\FINAL\REPORT\APPENDIXA\RODARAR3.DOC
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TABLE A-3 (CONTINUED)
Identification of Federal Action-Specific ARARs
Standard, Requirement,
Criteria, or Limitation Citation
• Releases from Solid 264.100
Description
Corrective action program.
Applicable/
Relevant and
Appropriate
Yes/Yes
Comment
Applicable to alternatives involving
Waste Management
Units (continued)
264.101
Corrective action for solid waste
management units.
Closure and Post-
Closure
Subpart G
264.111
Closure performance standard.
264.112
Closure plan; amendment of plan.
264.113
Closure; time allowed for closure.
treatment of generated hazardous
waste and may be relevant and
appropriate to the Source Areas where
hazardous waste was disposed.
Yes/Yes Applicable to alternatives involving
treatment of generated hazardous
waste and may be relevant and
appropriate to the Source Areas where
hazardous waste was disposed.
Yes/Yes Applicable to alternatives involving
treatment of generated hazardous
waste and may be relevant and
appropriate to the Source Areas where
hazardous waste was disposed.
Yes/Yes Applicable to alternatives involving
treatment of generated hazardous
waste and may be relevant and
appropriate to the Source Areas where
hazardous waste was disposed.
Yes/Yes Applicable to alternatives involving
treatment of generated hazardous
waste and may be relevant and
appropriate to the Source Areas where
hazardous waste was disposed.
Yes/Yes Applicable to alternatives involving
treatment of generated hazardous
waste and may be relevant and
appropriate to the Source Areas where
hazardous waste was disposed.
\\SNOVaHftPROJ\1360WWJJ\FINALtiEPORTWPENDIX WODARAR3 DOC
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TABLE A-3 (CONTINUED)
Identification of Federal Action-Specific ARARs
Standard, Requirement,
Criteria, or Limitation
Citation
Description
Applicable/
Relevant and
Appropriate
Comment
Closure and Post-
Closure (continued)
264.114
264.115
Disposal or decontamination of
equipment, structures, and soils.
Certification of closure.
264.116
Survey plat.
264.117
Post-closure care and use of property.
264.118
Post-closure plan; amendment of plan.
264.119
Post-closure notices.
Yes/Yes Applicable to alternatives involving
treatment of generated hazardous
waste and may be relevant and
appropriate to the Source Areas where
hazardous waste was disposed.
Yes/- Applicable to alternatives involving
treatment of generated hazardous
waste and may be relevant and
appropriate to the Source Areas where
hazardous waste was disposed.
Yes/Yes Applicable to alternatives involving
treatment of generated hazardous
waste and may be relevant and
appropriate to the Source Areas where
hazardous waste was disposed.
Yes/Yes Applicable to alternatives involving
treatment of generated hazardous
waste and may be relevant and
appropriate to the Source Areas where
hazardous waste was disposed.
Yes/Yes Applicable to alternatives involving
treatment of generated hazardous
waste and may be relevant and
appropriate to the Source Areas where
hazardous waste was disposed.
Yes/Yes Applicable to alternatives involving
treatment of generated hazardous
waste and may be relevant and
appropriate to the Source Areas where
hazardous waste was disposed.
\\SNOWBIRD\PROJM 36064\4_1_3\FINAL\REPORT\APPENDIX A\RODARAR3.DOC
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TABLE A-3 (CONTINUED)
Identification of Federal Action-Specific ARARs
Standard, Requirement,
Criteria, or Limitation
Citation
Description
Applicable/
Relevant and
Appropriate
Comment
Closure and Post-
Closure (continued)
264.120
Use and Management of Subpart I
Containers
Tanks
Waste Piles
Subpart J
Subpart L
Certification of completion of post-
closure care.
Requirements for storage of hazardous
waste in containers.
Requirements for storage of hazardous
waste in tanks.
264.251
264.254
264.256
Design and operating requirements.
Monitoring and inspection.
Special requirements for ignitable or
reactive waste.
Yes/-- Applicable to alternatives involving
treatment of generated hazardous
waste and may be relevant and
appropriate to the Source Areas where
hazardous waste was disposed.
Yes/-- Applicable to alternatives involving
treatment or storage of generated
hazardous waste.
Yes/-- Applicable to alternatives involving
treatment or storage of generated
hazardous waste.
Yes/- Applicable to alternatives involving
treatment or storage of generated
hazardous waste outside the CAMU.
Generally, relevant and appropriate to
alternatives involving treatment or
storage of generated hazardous waste
inside the CAMU.
Yes/-- Treatment in piles is not included in
final remedial alternatives. Relevant
and appropriate for onsite treatment or
storage in piles.
--/Yes Treatment in piles is not included in
final remedial alternatives. Relevant
and appropriate for onsite treatment or
storage in piles.
--/Yes Treatment in piles is not included in
final remedial alternatives. Relevant
and appropriate for onsite treatment or
storage in piles.
\\SNOymtt\PROjm60WWJ_3\FlNAL\REPORTWPENDIXA\RODARAR3.DOC
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TABLE A-3 (CONTINUED)
Identification of Federal Action-Specific ARARs
Standard, Requirement,
Criteria, or Limitation
Citation
Description
Applicable/
Relevant and
Appropriate
Comment
264.257
Waste Piles (continued) 264.258
Landfills
Subpart N
Special requirements for incompatible --/Yes
wastes.
Closure and post-closure care. -/Yes
Treatment in piles is not included in
final remedial alternatives. Relevant
and appropriate for onsite treatment or
storage in piles.
Treatment in piles is not included in
final remedial alternatives. Relevant
and appropriate for onsite treatment or
storage in piles.
264.301
Design and operating requirements.
-/Yes Relevant and appropriate to capping of
CDPs, FTA 1, and Landfills 3 and 4.
264.303
264.309
264.310
264.312
264.315
Monitoring and inspection.
Surveying and recordkeeping.
Closure and post-closure care.
Special requirements for ignitable or
reactive waste.
Special requirements for containers.
-/Yes Relevant and appropriate to capping of
CDPs, FTA 1, and Landfills 3 and 4.
-/Yes Relevant and appropriate to capping of
CDPs, FTA 1, and Landfills 3 and 4.
-/Yes Relevant and appropriate to capping of
CDPs, FTA 1. and Landfills 3 and 4.
-/Yes Relevant and appropriate to capping of
CDPs, FTA 1, and Landfills 3 and 4.
-/Yes May be relevant and appropriate to
containers found during excavation
within landfills.
MSNOWBIRD\PROJt1360WWJ_3\FINAl\REPORT\APPENDIXA\RODARAR3DOC
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TABLE A-3 (CONTINUED)
Identification of Federal Action-Specific ARARs
Standard, Requirement,
Criteria, or Limitation
Citation
Description
Applicable/
Relevant and
Appropriate
Comment
Incinerators Subpart O
264.341
264.342
Incinerators (continued) 264.343
264.344
264.345
264.347
264.351
Corrective Action for Subpart S
Solid Waste
Management Units
Miscellaneous Units
Subpart X
Waste analysis.
Principal organic hazardous
constituents (POHC).
Performance standards.
Hazardous waste incinerator permits.
Operating requirements.
Monitoring and inspections.
Closure.
Establishes the corrective action
program for cleaning up solid waste
management units. This part of the
regulation also includes the definition
of a Corrective Action Management
Unit (CAMU) to facilitate waste
management associated with cleanup
activities. Hazardous waste moved
within a CAMU is not subject to LDRs.
Establishes design/operation
requirements for miscellaneous
hazardous waste management units.
Yes/-
Onsite incineration is not included in
final remedial alternatives.
Onsite incineration is not included in
final remedial alternatives.
Onsite incineration is not included in
final remedial alternatives.
Onsite incineration is not included in
final remedial alternatives.
Onsite incineration is not included in
final remedial alternatives.
Onsite incineration is not included in
final remedial alternatives.
Onsite incineration is not included in
final remedial alternatives.
Onsite incineration is not included in
final remedial alternatives.
Applicable to onsite soil treatment
units. The CAMU would be designated
as the contiguous area of
contamination Soils and wastes
excavated as part of a remedial action
from within the CAMU would be
consolidated under the landfill cap.
No onsite ex-situ treatment units
included in the remedial alternatives.
P:\1360^(^3\FINAI\REPORT\APPENDIX AiRODARAR3.DOC
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TABLE A-3 (CONTINUED)
Identification of Federal Action-Specific ARARs
Standard, Requirement,
Criteria, or Limitation
Citation
Description
Applicable/
Relevant and
Appropriate
Comment
264.601
Environmental performance standards.
Miscellaneous Units
(continued)
264.602
264.603
Monitoring, analysis, inspection,
response, reporting, and corrective
action.
Post-closure care.
Land Disposal Restrictions 40 CFR Part 268
Identifies hazardous wastes that are
restricted from land disposal.
--/-- No onsite ex-situ treatment units
included in the remedial alternatives.
Would be applicable to onsite facilities
treating RCRA characteristic
hazardous waste or soil containing
RCRA listed hazardous waste.
--/-- No onsite ex-situ treatment units
included in the remedial alternatives.
Would be applicable to onsite facilities
treating RCRA characteristic
hazardous waste or soil containing
RCRA listed hazardous waste.
--/-- No onsite ex-situ treatment units
included in the remedial alternatives.
Would be applicable to onsite facilities
treating RCRA characteristic
hazardous waste or soil containing
RCRA listed hazardous waste.
Yes/-- Applicable to storage, treatment, and
placement of generated RCRA
hazardous waste or soils containing
RCRA-listed wastes. Compliance with
the LDRs will be met by managing
excavated soils from wells, trenches,
or other subsurface installations as
hazardous waste, which will be
consolidated under the landfill cap in
the Source Area under the CAMU
Rule. Federal counterpart of UAC
R315-13.
\\SNOWBIRD\PROJ\136064W_1_3\FINAL\REPORT1APPENOIXA\RODARAR3.DOC
10
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TABLE A-3 (CONTINUED)
Identification of Federal Action-Specific ARARs
Standard, Requirement,
Criteria, or Limitation Citation
Description
Applicable/
Relevant and
Appropriate
Comment
Safe Drinking Water Act
Underground Injection
Control Regulations
Clean Water Act
National Pretreatment
Toxic Substances Control
Act
PCB Requirements
40 CFR Parts 144-147
33 USC Sec. 1251-1376
40 CFR Part 403
15 USC Sec. 2601-2629
40 CFR Part 761
Provides for protection of underground
sources of drinking water.
Sets standards to control pollutants Yes/-
that pass through or interfere with
treatment processes in publicly owned
treatment works or that may
contaminate sewage sludge.
Establishes storage and disposal Yes/-
requirements for PCBs.
Regulates injection of treated ground
water and surface water. No
underground injection is included in the
final remedial alternatives.
Discharge to POTW is an alternative.
PCBs identified at OU1.
\\SNOV2JUJPROJ\t360MV4.i.3\HNAL\REPORT\APPENDIXA\RODARAR3.DOC
11
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TABLE A-4
Identification of State Chemical-Specific ARARs
Standard, Requirement,
Criteria, or Limitation Citation
Description
Applicable/
Relevant and
Appropriate
Comment
Utah Public Drinking Water UAC R309-103-2
Regulations
Utah Public Drinking Water
Regulations - Secondary
Standards
Utah Ground Water Quality
Protection Regulations
UAC R309-103-3
UACR317-6
Division of Solid and
Hazardous Waste,
Department of Environmental
Quality
UAC R315-8-6
Establishes maximum contaminant
levels for inorganic and organic
chemicals.
Establishes welfare-based standards
for public water systems (secondary
maximum contaminant levels).
Establishes ground water quality
standards for the different ground
water aquifer classes.
Ground water protection standards for
owners and operators of hazardous
waste TSDFs.
No/Yes Requirements are relevant and
appropriate to OU1. Some MCLs
established for contaminants not
federally regulated; e.g., total dissolved
solids.
No/Yes May be relevant and appropriate for
inorganics such as iron.
--/-- The Utah Ground Water Quality
Protection Rule establishes numerical
cleanup levels and other performance
standards for contaminated ground
water. Although no determination has
been made concerning whether this
rule is an applicable or relevant and
appropriate standard at OU1, the
standards required by the Ground
Water Quality Protection Rule will be
met by complying with drinking water
MCLs.
Yes/Yes Establishes ground water protection
standards for hazardous waste TSDFs.
Standards include ground water
monitoring requirements and maximum
concentrations of hazardous
constituents allowable before
corrective action must be
implemented.
P:\136064\4_1_3\FINAL\REPORT\APPENDIXA\RODARAR4.DOC
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TABLE A-4 (CONTINUED)
Identification of State Chemical-Specific ARARs
Standard, Requirement,
Criteria, or Limitation
Cleanup and Risk-Based
Citation
UACR315-101
Description
Establishes risk-based closure and
Applicable/
Relevant and
Appropriate
Yes/~
Comment
This rule is applicable for remedial
Closure Standards
UACR315-2
Corrective Action Cleanup
Standards Policy - UST and
CERCLA Sites
UAC R311-211
Division of Water Quality,
Department of Environmental
Quality
UACR317-2
corrective action requirements.
Requires removal or control of the
source.
Criteria for the identification and listing
of hazardous waste.
Lists general criteria to be considered
in establishing cleanup standards
including compliance with MCLs in
Safe Drinking Water Act and Clean Air
Act.
Standards for quality for waters of the
state.
activities, including site management,
corrective action, and closure. The rule
references MCLs defined in UAC
R315-8-6.
Yes/-- Definition of hazardous waste mirrors
federal definition. If wastes generated
during the remediation phase are
determined to contain hazardous
constituents, they will be subject to
these requirements.
-/Yes This requirement is not applicable
because federal CERCLA sites are
remediated under CERCLA and the
NCR. It is however relevant and
appropriate. Requires action to be
taken to be protective. Requires
source removal or control of source
and prevention of further degradation.
The State of Utah maintains that UAC
R311-211 is "applicable."
Yes/-- Applicable to discharges to surface
water. These rules are specific to Utah
surface waters, though they are
derived in part by using federal criteria.
May be relevant and appropriate
where ground water is a potential
water supply if other standards are not
available. See particularly the anti-
degradation policy in UAC R317-2-3.
i 3\FW4l\REPORTWPF 4 .\ROOARAR4.DOC
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TABLE A-4 (CONTINUED)
Identification of State Chemical-Specific ARARs
Standard, Requirement,
Criteria, or Limitation
Citation
Description
Applicable/
Relevant and
Appropriate
Comment
Utah Air Conservation
Regulations
UACR307-1-3
UACR307-1-3.1.8
(A) and (B)
UACR307-1-4
UACR307-10
UAC R307-12
UACR307-14
Air quality standards for control of
installations.
Pollution control for emissions.
Emission standards.
Emission standards.
Fugitive emissions and fugitive dust.
Ozone non-attainment areas and
Davis and Salt Lake Counties.
Yes/-- Regulates new installations that will or
might reasonably be expected to
become a source or indirect source of
air pollution.
Yes/-- Requires that pollution control for
emissions meet BACT, including those
for soil venting and other projects.
Yes/-- Sets emission standards for visible
emissions, construction, and
demolition activities.
Yes/-- National Emission Standards for
Hazardous Air Pollutants (NESHAP)
are incorporated by reference (see
40 CFR 61 Subpart A).
Yes/-- Requires use of mitigative measures
such as dust suppressants and foams
if necessary.
Yes/-- Requires handling of liquid VOCs,
such as those from the LNAPL
collection system, using reasonably
• available control technology.
P:\136064\4 1 3\F1NAL\REPORT\APPENDIXA\RODARAR4.DOC
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TABLE A-5
Identification of State Action-Specific ARARs
Standard, Requirement,
Criteria, or Limitation
State Engineer, Department
Citation
UAC R655-4
Description
Standards for drilling and
Applicable/
Relevant and
Appropriate
--/Yes
Comment
Includes such requirements as
of Natural Resources
abandonment of wells.
Division of Solid and Hazardous Waste, Department of Environmental Quality
General Requirements -
Identification and Listing of
Hazardous Waste
Hazardous Waste Manifest
Requirements
UACR315-2
UACR315-4
Defines those solid wastes that are
subject to regulation as hazardous
wastes.
Establishes standards for manifesting
hazardous waste.
Hazardous Waste
Generator Requirements
UAC R315-5
Establishes standards for generators
of hazardous waste.
performance standards for casing
joints, requirements for abandoning a
well, etc. The State of Utah maintains
that UAC R655-4 is "applicable."
Yes/-- Determines potential waste
classification and applicability of land
disposal restrictions and other solid
and hazardous waste rules. State
counterpart of 40 CFR 261.
Yes/-- Applicable to remedial alternatives
involving landfilling of hazardous soil
and debris. Not applicable to landfilling
of non-hazardous materials.
Manifesting is required for offsite
disposal of any hazardous wastes.
Yes/-- Applicable to remedial alternatives
involving generation of hazardous soil
and debris. Cuttings from monitoring
well installation and collection system
trench spoils will be managed as
hazardous waste and disposed in the
Source Area under the CAMU Rule.
LNAPL or excavated materials that will
be disposed offsite, such as for
Alternative 7, will be characterized and
hazardous wastes managed
accordingly. State counterpart of
40 CFR 262.
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TABLE A-5 (CONTINUED)
Identification of State Action-Specific ARARs
Standard, Requirement,
Criteria, or Limitation
Citation
Description
Applicable/
Relevant and
Appropriate
Comment
Hazardous Waste
Transporter Requirements
UACR315-6
Standards for Owners and UACR315-8
Operators of Hazardous
Waste Treatment, Storage,
and Disposal Facilities
General Facility
Standards
Location Standards
Preparedness and
Prevention
UAC R315-8-2
UACR315-8-2.9
UACR315-8-3
Contingency Plan and UACR315-8-4
Emergency Procedures
Manifest System,
Recordkeeping, and
Reporting
UACR315-8-5
Establishes standards for transporters
of hazardous waste.
Establishes minimum standards that
define the acceptable management of
hazardous waste for owners and
operators of TSDFs.
Describes security, inspection, and
personnel training.
Describes facility siting requirements.
Describes communications, alarm
systems, and coordination with local
authorities.
Requires development of a
contingency plan and designation of an
emergency coordinator.
Requires manifesting, recordkeeping,
and regular reporting.
Yes/- Applicable to remedial alternatives
involving landfilling of hazardous soil
and debris. Not applicable to landfilling
of non-hazardous materials.
Transporter standards are
' requirements for offsite disposal of
hazardous wastes.
See discussion for specific subparts
below.
Yes/-- Applicable to alternatives involving
onsite treatment or disposal at onsite
landfills. State counterpart of
40 CFR 264 Subpart B.
Yes/- Applicable to alternatives involving
treatment, storage, or disposal of
hazardous waste at onsite facilities.
Yes/-- Applicable to alternatives involving
disposal at onsite landfills. State
counterpart of 40 CFR 264 Subpart C.
Yes/-- Applicable to alternatives involving
onsite treatment or disposal at onsite
landfills. State counterpart of
40 CFR 264 Subpart D.
Yes/-- Applicable to alternatives involving
onsite treatment or disposal at onsite
landfills. State counterpart of
40 CFR 264 Subpart E.
\\SNOWBIRD\PROJ\136064\4_1_3\FINAL\REPORT\APPENDIXA\RODARAR5.DOC
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TABLE A-5 (CONTINUED)
Identification of State Action-Specific ARARs
Standard, Requirement,
Criteria, or Limitation
Citation
Description
Applicable/
Relevant and
Appropriate
Comment
Ground Water Protection UAC R315-8-6
Closure and Post-
Closure
UAC R315-8-7
Use and Management of UAC R315-8-9
Containers
Tanks
Waste Piles
UAC R315-8-10
UAC R315-8-12
Describes ground water monitoring
requirements for TSDFs.
Establishes closure and post-closure
performance standards and plan
requirements for TSDFs.
Requires specific procedures for the
temporary storage of hazardous
wastes in containers.
Requires specific procedures for the
use of tanks for the treatment or
temporary storage of hazardous
wastes in tanks.
Establishes design, operation, and
management requirements for
storage/treatment of hazardous
materials in waste piles.
Yes/Yes Applicable to alternatives involving
treatment onsite. Some requirements
may be relevant and appropriate for
alternatives in which contaminants will
remain in place. State counterpart of
40 CFR 264 Subpart F.
Yes/Yes Applicable to alternatives involving
treatment onsite. Some requirements
may be relevant and appropriate for
alternatives in which contaminants will
remain in place. State counterpart of
40 CFR 264 Subpart G.
Yes/- Applicable to alternatives involving
onsite treatment or onsite storage or
treatment of hazardous waste. State
counterpart of 40 CFR 264 Subpart I.
Yes/-- Applicable to alternatives involving
onsite treatment or onsite storage or
treatment of hazardous waste. State
counterpart of 40 CFR 264 Subpart I.
Yes/-- Applicable to alternatives involving
onsite treatment or storage in piles
outside the CAMU. Generally relevant
and appropriate to alternatives
involving onsite treatment of
hazardous waste inside the CAMU.
The requirements for storage of
hazardous waste in waste piles would
be met for excavated soils containing
listed hazardous waste or
characteristic hazardous waste. State
counterpart of 40 CFR 264 Subpart L.
\\SNOV^|fl§£ROJ\136064W_1_3\FINAL\REPORT\APPENDIX A\RODARAR5.DOC
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TABLE A-5 (CONTINUED)
Identification of State Action-Specific ARARs
Standard, Requirement,
Criteria, or Limitation
• Landfills
Citation
UACR315-8-14
Description
Establishes design, operation, and
Applicable/
Relevant and
Appropriate
-/Yes
Comment
Relevant and appropriate to capi
ping of
Incinerators
UACR315-8-15
Miscellaneous Units UAC R315-6-16
Corrective Action for
Solid Waste
Management Units
UAC R315-8-21
Utah Emergency Control UACR315-9
Land Disposal Restrictions UAC R315-13
management requirements for landfills.
Establishes design, operation, and
management requirements for
incinerators.
Establishes design/operation
requirements for miscellaneous
hazardous waste management units.
Establishes requirements for
designation of a CAMU and defines
management practices.
Yes/-
Outlines the immediate action,
cleanup, and reporting requirements
for spills involving hazardous waste.
Identifies hazardous wastes that are
restricted from land disposal.
Yes/-
Yes/Yes
the CDPs, FTA1, and Landfills 3 and 4.
State counterpart of 40 CFR 264
Subpart N.
Applicable to onsite incinerators. No
onsite incineration is planned. State
counterpart of 40 CFR 264 Subpart O.
No onsite ex-situ treatment units
included in the remedial alternatives.
The CAMU would be designated to as
the contiguous area of contamination.
Soils and wastes excavated as part of
a remedial action from within the
CAMU would be consolidated under
the landfill cap. State counterpart of 40
CFR 264 Subpart S.
The ARAR would be met by complying
with emergency control procedures
where waste materials are generated.
Applicable to storage, treatment, and
placement of generated RCRA
hazardous waste or soils containing
RCRA-listed wastes. Compliance with
the LDRs will be met by managing
excavated soils from wells, trenches,
or other subsurface installations as
hazardous waste, which will be
consolidated under the landfill cap in
the Source Area under the CAMU
Rule. State counterpart of 40 CFR 268.
P:\l 36064\4J_3\FINAL\REPORTWPPENDIX A\RODARAR5.DOC
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TABLE A-5 (CONTINUED)
Identification of State Action-Specific ARARs
Standard, Requirement,
Criteria, or Limitation
Citation
Description
Applicable/
Relevant and
Appropriate
Comment
Cleanup and Risk-Based UAC R315-101
Closure Standards
Subtitle 0 Class I and II
Landfill Closure
Requirements
Subtitle 0 Industrial Solid
Waste Landfill Closure
Requirements
UAC R315-303-4
UAC R315-308
Division of Water Quality, UAC R317-3
Department of Environmental
Quality
UAC R317-6
Establishes risk-based closure and
corrective action requirements.
Specifies closure requirements for
commercial solid waste landfills.
Requires 18 inches of 1 x 10'5 cm/sec
permeability or less.
Regulates abandoned or closed
industrial solid waste landfills and
specifies cover requirements including
2 feet of cover soil.
Sewers and wastewater treatment
works.
Ground water quality protection.
Yes/-
--/Yes
--/Yes
No/Yes
UACR317-7
Underground injection control.
This rule is applicable for remedial
activities, including site management,
corrective action, and closure.
Relevant and appropriate to closure of
Landfills 3 and 4.
Relevant and appropriate to closure of
Landfills 3 and 4.
Construction and performance
requirements for remedial works will be
relevant and appropriate.
The Utah Ground Water Quality
Protection Rule establishes numerical
cleanup levels and other performance
standards for contaminated ground
water. Although no determination has
been made concerning whether this
rule is an applicable or relevant and
appropriate standard at OU1, the
remedy will meet the action-specific
requirements of the rule.
Underground injection is not included
in remedial alternatives for OU1.
I 3\FINAUREPORT\APPENDIXA\RODARAR5.DOC
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TABLE A-5 (CONTINUED)
Identification of State Action-Specific ARARs
Standard, Requirement,
Criteria, or Limitation
Citation
UACR317-8
Description
Establishes general requirements,
Applicable/
Relevant and
Appropriate
Yes/-
Comment
If selected alternative involves a point
Division of Air Quality, UAC R307-1 -2
Department of Environmental
Quality
UACR307-1-3
UACR307-1-4
Fugitive Emissions and
Fugitive Dust
UACR307-10
UACR307-12
UACR307-14
definitions, permitting procedures, and
criteria/standards for technology-based
treatment for point source discharges
of wastewater. Also establishes
pretreatment standards for discharge
to a POTW
Utah air conservation rules - general
requirements.
Utah air conservation rules - control of
installations
Utah air conservation rules - emissions
standards.
Emission standards.
Requires implementation of measures
to control emissions of dust.
Requirements for ozone non-
attainment areas and Davis and Salt
Lake Counties.
source discharge of wastewater,
UPDES requirements would be
applicable. Pretreatment standards
would be applicable if selected
alternative involved discharge to a
POTW.
Yes/-- Prohibits emission of air contaminants
in sufficient quantities to cause air
pollution.
Yes/-- Requires a degree of pollution control
for emissions (including fugitive
emissions and fugitive dust) to be at
least BACT.
Yes/-- These rules establish opacity limits for
visible emissions. They require
application of reasonably available
control technology (RACT) to control
VOC emissions in ozone non-
attainment areas.
Yes/-- National Emission Standards for
Hazardous Air Pollutants (NESHAP)
are incorporated by reference (see
40CFR61 SubpartA).
Yes/-- Applicable for Source Area alternatives
involving excavation of soil over an
area larger than 0.25 acres.
Yes/-- Requires use of reasonably available
control technology (RACT) for handling
of liquid VOCs. This may be applicable
for handling of recovered LNAPL.
\\SNOWBIRD\PROJ\136064VdJ_3\FINAL\REPORT\APPENDIX A\RODARAR5.DOC
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TABLE A-5 (CONTINUED)
Identification of State Action-Specific ARARs
Standard, Requirement,
Criteria, or Limitation
Citation
UACR31 1-21 1-5
Description
Corrective action clean-up standards
Applicable/
Relevant and
Appropriate
--/Yes
Comment
This requirement is not api
plicable
policy - UST and CERCLA sites. Lists
general criteria to be considered in
establishing cleanup standards
including compliance with MCLs in
Safe Drinking Water Act and Clean Air
Act. Requires action to be taken to be
protective.
because federal CERCLA sites are
remediated under CERCLA and the
NCR. It is, however, relevant and
appropriate. Requires action to be
taken to be protective. Requires
source removal or control of source
and prevention of further degradation.
The State of Utah maintains that UAC
R311-211 is "applicable."
_3\FINAt\REPORTWPENDIX A\RODARAR5.DOC
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TABLE A-6
Summary of the Preferred Alternative-Specific ARARs
Key ARARs with Which the Alternative Must Comply ARAR
Would Alternative Comply with Key ARAR?
33 CFR Part 320-330 (Discharge of Dredged or Fill
Material to Wetlands)
40 CFR Part 61 Subpart A (NESHAP Standards)
40 CFR Part 122 National Pollution Discharge
Elimination Requirements
40 CFR Part 141 (National Primary Drinking Water
Standards)
40 CFR Part 261 (Identification and Listing of
Hazardous Waste)
40 CFR Part 262 (Standards Applicable to Generators
of Hazardous Waste)
40 CFR 264 Subpart B 264.18 (Characteristics for
Location of Hazardous Waste Management Units)
40 CFR 264 Subpart C (RCRA - Preparedness and
Prevention)
40 CFR 264 Subpart D (Contingency Plans and
Emergency Procedures)
Ap Yes. Army Corps of Engineers may determine that draining and regrading Pond 10
requires mitigation of impacts to wetlands. If so, wetlands mitigation would be included in
the alternative.
Ap Yes. The ARAR would be met with use of vapor control systems for the OU2 ASTP or the
low profile air stripper at a remote treatment facility. Applicable to benzene, chloroform,
trichloroethene, and toluene emissions from groundwater or surface water treatment
facilities or soil/landfill vents.
Ap Yes. If selected alternative involves a point source discharge of wastewater, UPDES
requirements would be applicable.
R Yes. Groundwater contaminant migration to offsite groundwater and the seeps and
springs, which could be used as a source of drinking water in the future, would be
controlled with a groundwater collection system. Restoration of groundwater to MCLs
within a reasonable time frame is expected in the Source Area. However, there are some
uncertainties. A waiver to meet MCLs in groundwater may be needed for parts of the
Source Area in the future if it is technically impracticable to achieve these levels. Non-
Source Area groundwater and seep and spring contamination is expected to decline to
below MCLs in a reasonable time frame.
Ap Yes. All hazardous waste potentially excavated from sediment, trench spoils, and well
cuttings would be classified according to this ARAR.
Ap Yes. The ARAR would be met by complying with standards for generators of hazardous
waste. Cuttings from monitoring well installation and collection system trench spoils will be
managed as hazardous waste and disposed in the Source Area under the CAMU Rule.
LNAPL or excavated materials that will be disposed offsite will be characterized and
hazardous wastes managed accordingly.
Ap Yes. LNAPL in the oil/water separator unit, and the air stripper in the Weber River Valley
(WRV), would be sited in accordance with this ARAR.
Ap Yes. Requirements are applicable to onsite treatment, storage and disposal units, and
would be met for generated hazardous waste.
Ap Yes. Requirements are applicable to onsite treatment, storage, and disposal units, and
would be met for generated hazardous waste.
ttSNOWBlRD\PROJ\136064\4J_3\FINAl\REPORr\APPENDIXA\ROOARAR6.DOC
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TABLE A-6 (CONTINUED)
Summary of the Preferred Alternative-Specific ARARs
Key ARARs with Which the Alternative Must Comply ARAR
Would Alternative Comply with Key ARAR?
40 CFR 264 Subpart E (Manifest System,
Recordkeeping, and Reporting)
40 CFR 264 Subpart F (Releases from Solid Waste
Management Units)
40 CFR 264 Subpart G (Closure and Post-Closure)
40 CFR 264 Subpart I (Use and Management of
Containers)
40 CFR 264 Subpart J (Use and Management of Tanks)
40 CFR 264 Subpart L (Waste Piles)
40 CFR 264 Subpart N (Closure and Post-Closure for
Landfills)
40 CFR 264 Subpart S (CAMU Designation and
Management)
40 CFR Part 268 (Land Disposal Restrictions)
40 CFR Part 403 (National Pretreatment Standards)
Ap Yes. Requirements are applicable to onsite treatment, storage, and disposal units, and
would be met for generated hazardous waste.
R Yes. The ARAR would be met with groundwater monitoring.
R Yes. Complies with relevant and appropriate portions of hybrid landfill closure regulations
(containment, existing cap, and landfill gas monitoring).
Ap Yes. The requirements for containers holding hazardous waste would be met for the
LNAPL collection system.
Ap Yes. The requirements for tanks holding hazardous waste would be met for the LNAPL
collection system.
Ap Yes. The requirements for storage of hazardous waste in waste piles outside the CAMU
would be met for excavated soils containing listed hazardous waste or characteristic
hazardous waste. The relevant and appropriate requirements for storage of hazardous
waste in waste piles within the CAMU would be met for excavated soils containing listed
hazardous waste or characteristic hazardous waste.
R Yes. The existing Phases 1 and 2 caps with upgrades to promote runoff and prevent
ponding of water meet the Subpart N requirements (see Appendix K of the FS for a
complete discussion).
Ap Yes. CAMU management practices would be followed. The CAMU will be designated as
the contiguous area of contamination.
Ap Yes. Offsite disposal of excavated soil from trenches and from the installation of the seep
and spring collection system is not currently anticipated; however, if needed, the soils
would be treated to LDR requirements or a treatability variance would be sought. Offsite
disposal of excavated sediment would comply with LDRs. The soils that contain listed
hazardous waste or that are a characteristic hazardous waste (an estimated 5,914 cys) are
planned to be disposed on the landfills within the CAMU and capped. As a result,
compliance with the LDRs will be met by managing excavated soils from wells, trenches, or
other subsurface installations as hazardous waste, which will be consolidated under the
landfill cap in the Source Area under the CAMU Rule.
Ap Yes. All discharges to POTW would be within the standards established by this ARAR.
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TABLE A-6 (CONTINUED)
Summary of the Preferred Alternative-Specific ARARs
Key ARARs with Which the Alternative Must Comply ARAR
Would Alternative Comply with Key ARAR?
40 CFR Part 761 (PCB Requirements)
UAC R307-1-2 (Division of Air Quality, Department of
Environmental Quality)
UAC R307-1-3 (Air Quality Standards for Control of
Installations)
UAC R307-1-4 (Emission Standards)
UAC R307-10 (National Emission Standards for
Hazardous Air Pollutants)
UAC R307-12 (Fugitive Emissions and Fugitive Dust)
UAC R307-14 (Non-Attainment Area Requirements for
Ozone)
UAC R309-103 (Utah Public Drinking Water
Regulations)
UAC R311-211 (Specified State of Utah Corrective
Action Cleanup Standards for UST and CERCLA Sites)
UAC R315-2 (Criteria for the Identification and Listing of
Hazardous Waste)
UAC R315-5 (State of Utah Standards for Generators of
Hazardous Waste)
Ap Yes. Any PCB contaminated soil would be managed in accordance with the ARAR.
Ap Yes. Provisions would be made during remedial action to minimize discharge of air
pollutants.
Ap Yes. BACT would be used for control of vapor emissions.
Ap Yes. Air emissions would be controlled to comply with emissions standards.
Ap Yes. The ARAR would be met with use of vapor control systems for the OU2 ASTP or the
low profile air stripper at a remote treatment facility. Applicable to benzene, chloroform,
trichloroethene, and toluene emissions from groundwater or surface water treatment
facilities or soil/landfill vents.
Ap Yes. The ARAR would be met with use of mitigative measures such as dust suppresants
and foams, and during construction of the air stripper in the WRV, if necessary.
Ap Yes. The ARAR requires handling of liquid VOCs such as those from the LNAPL collection
system and the air stripper in the WRV, using reasonably available control technology.
R Yes. Groundwater contaminant migration to offsite groundwater and the seeps and
springs, which could be used as a source of drinking water in the future, would be
controlled with a groundwater collection system. Restoration of groundwater to MCLs
within a reasonable time frame is expected in the Source Area. However, there are some
uncertainties. A waiver to meet MCLs in groundwater may be needed for parts of the
Source Area in the future if it is technically impracticable to achieve these levels. Non-
Source Area groundwater and seep and spring contamination is expected to decline to
below MCLs in a reasonable time frame.
R Yes. The sources would be controlled by the existing cap, and offsite groundwater would
be monitored. Seeps and springs exceeding MCLs would be collected and treated. The
State of Utah maintains that UAC R311-211 is "applicable."
Ap Yes. Hazardous waste generated during the remedial action would be defined according to
the ARAR.
Ap Yes. The ARAR would be met by complying with standards for generators of hazardous
waste. Cuttings from monitoring well installation, trench spoils, and recovered LNAPL may
contain listed hazardous waste.
\\SNOWBIRD\PROJ\136064\4 t_3\FINAl\REPORT\APPENDIX A\RODARAR6.DOC
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TABLE A-6 (CONTINUED)
Summary of the Preferred Alternative-Specific ARARs
Key ARARs with Which the Alternative Must Comply ARAR
Would Alternative Comply with Key ARAR?
UAC R315-8-2 (RCRA-General Facility Standards) Ap
UAC R315-8-2.9 (Characteristics for Location of Ap
Hazardous Waste Units)
UAC R315-8-3 (RCRA - Preparedness and Prevention) Ap
UAC R315-8-4 (Contingency Plans and Emergency Ap
Procedures)
UAC R315-8-5 (Manifest System, Recordkeeping, and Ap
Reporting)
UAC R315-8-6 (Groundwater Protection Standards for R
Owners and Operators of Hazardous Waste TSDFs)
UAC R315-8-7 (State of Utah Closure and Post- R
Closure)
UAC R315-8-9 (State of Utah Use and Management of Ap
Containers)
UAC R315-8-10 (State of Utah Use and Management of Ap
Tanks)
UAC R315-8-12 (Standards for Treatment of Waste in Ap
Piles)
UAC R315-8-14 (Design, Management, and Operation R
Requirements for Landfills)
UAC R315-8-21 (CAMU Designation and Management) Ap
Yes. Requirements are applicable to onsite treatment, storage, and disposal units, and
would be met for generated hazardous waste.
Yes. LNAPL in the oil/water separator unit and the air stripper in the WRV would be sited in
accordance with this ARAR.
Yes. Requirements are applicable to onsite treatment, storage, and disposal units, and
would be met for generated hazardous waste.
Yes. Requirements are applicable to onsite treatment, storage, and disposal units, and
would be met for generated hazardous waste.
Yes. Requirements are applicable to onsite treatment, storage, and disposal units, and
would be met for generated hazardous waste.
Yes. The alternative would meet groundwater monitoring requirements of the ARAR.
Yes. Complies with relevant and appropriate portions of hybrid landfill closure regulations
(containment, existing cap, and landfill gas monitoring).
Yes. The requirements for containers holding hazardous waste would be met for the
LNAPL collection system.
Yes. The requirements for tanks holding hazardous waste would be met for the LNAPL
collection system.
Yes. The requirements for storage of hazardous waste in waste piles outside the CAMU
would be met for excavated soils containing listed hazardous waste or characteristic
hazardous waste. The relevant and appropriate requirements for storage of hazardous
waste in waste piles within the CAMU would be met for excavated soils containing listed
hazardous waste or characteristic hazardous waste.
Yes. The ARAR would be met with institutional controls, existing cap, and landfill gas
monitoring (see Appendix K of the FS for a complete discussion).
Yes. CAMU management practices would be followed. The CAMU will be designated as
the contiguous area of contamination.
PAI
3\FINAl\REPORT\APPENDIX A\RODARAR&.DOC
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TABLE A-6 (CONTINUED)
Summary of the Preferred Alternative-Specific ARARs
Key ARARs with Which the Alternative Must Comply ARAR
Would Alternative Comply with Key ARAR?
UAC R315-9 (State of Utah Emergency Control
Requirements)
UAC R315-13 (Land Disposal Restrictions)
UAC R315-101 (State of Utah Cleanup and Risk-Based
Closure Standards)
UAC R315-303-4 (State of Utah Subtitle D Class I and II
Landfill Closure Requirements)
UAC R315-304 (State of Utah Subtitle D Industrial Solid
Waste Landfill Closure Requirements)
UAC R317-2 (Standards for Quality for Waters of the
State)
UAC R317-3 (Sewers and Wastewater Treatment
Works)
UAC R317-6 (Utah Groundwater Quality Protection
Regulations)
Ap Yes. The ARAR would be met by complying with emergency control procedures where
waste materials are generated.
Ap Yes. Offsite disposal of excavated soil from trenches and from the installation of the seep
and spring collection system is not currently anticipated. However, if needed, the soils
would be treated to LDR requirements or a treatability variance would be sought. Offsite
disposal of excavated sediment would comply with LDRs. The soils that contain listed
hazardous waste or that are a characteristic hazardous waste (an estimated 5.914 cys) are
planned to be disposed on the landfills within the CAMU and capped. As a result,
compliance with the LDRs will be met by managing excavated soils from wells, trenches, or
other subsurface installations as hazardous waste, which will be consolidated under the
landfill cap in the Source Area under the CAMU Rule.
Ap Yes. Meet this ARAR with environmental monitoring, source control (with the existing cap),
and post-closure requirements. Long-term management plans and institutional controls
would also ensure compliance with risk-based closure standards.
R Yes. Upgraded landfill cover meets closure requirements (see Appendix K of the FS).
R Yes. Upgraded landfill cover meets closure requirements (see Appendix K of the FS).
A Yes. If wastes are discharged to surface water, the discharge would comply with
appropriate standards.
R Yes. Discharge of groundwater to OU2 ASTP with subsequent discharge to POTW would
comply with appropriate standards.
Yes. Groundwater would be contained and treated to appropriate standards. The Utah
Groundwater Quality Protection Rule establishes numerical cleanup levels and other
performance standards for contaminated groundwater. Although no determination has
been made concerning whether this rule is an applicable or relevant and appropriate
standard at OU1, the chemical-specific standards required by the Groundwater Quality
Protection Rule will be met by complying with drinking water MCLs. The remedy will also
comply with the action-specific requirements of the rule.
\\SNOW8IRD\PROJ\1360WWJ_3\FINAL\REPORT\APPENDIX A\RODARAR6.DOC
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TABLE A-6 (CONTINUED)
Summary of the Preferred Alternative-Specific ARARs
Key ARARs with Which the Alternative Must Comply ARAR Would Alternative Comply with Key ARAR?
UAC R317-8 (Utah Pollution Discharge Elimination Ap Yes. If selected alternative involves a point source discharge of wastewater, UPDES
System Pretreatment Requirements) requirements would be applicable. Pretreatment standards would be applicable if selected
alternative involved discharge to a POTW.
UAC R655-4 (Standards for Drilling and Abandonment R Yes. Design of extraction wells, monitoring wells, and well abandonment would be in
of Wells) accordance with the ARAR.
>_ i_J\FINAUREgORT\APPENDIX A\RODARAR6.DOC
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Appendix B
List of Attendees at the Hill Air Force Base
Operable Unit 1 Open House
-------
List of Attendees at the HAFB Operable Unit 1 Open House
South Weber Elementary School, South Weber, Utah
4:30 PM - 8:00 PM, February 5,1998
Chris & JoAnn Carter
Liesel & Joe Woodard
Deb Drain
Mark Plested
John Carter
Brent Poll
Robert L. Flinders
Fern Heninger
Scott Paxman
Mark Holt
David Friz
E.G. Gardner
Mark Perkins
Dan Shupe
Donna Poll
Louise Cash
Wayman Cash
Joel Workman
Jim O'Neill
P:\136064VM_3\FINAUflEPORT\APPENDICES A-8\RODAPOBC.DOC B-1
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Appendix C
Proposed Plan Comments and Hill Air Force Base
Responses to Comments
-------
Appendix C-l
Proposed Plan Comments and
the Hill Air Force Base Response to Comments
-------
OPERABIE UNIT 1 RECORD OF DECISION APPENDIX C
C.1.0 Public Comments and Responses
C.1.0.0.1. The following section presents written public comments received for the Proposed
Plan and HAFB's response to these comments. Each section lists an individual commentor.
The comment has been duplicated here exactly as the comment was written.
C.1.1 Comments by Anonymous #1
C.1.1.0.1. Comment #1. My understanding is that barrows have been buried. As thay rust out,
thay will start to leak which may be years. Maybe thay should be hauled away.
C.1.1.0.2. Response to Comment #1. An investigation of the Operable Unit 1 landfills was
recently performed. The landfill areas were investigated to evaluate the nature and extent of
landfill debris and to determine whether drums were buried in the landfill area. The Landfill
3 and 4 Investigation Summary Report (CH2M HILL, 1998d) documents the landfill
investigation. This study included a magnetic anomaly study to determine the location of
large concentrations of metals that would be the most likely location of buried drums. These
areas were identified and mapped. Trenches were excavated in these areas to evaluate the
type of debris that caused the anomalies. The anomalies were found to be related to the
presence of large concentrations of metal waste materials rather than buried drums. The
metal debris observed consisted mainly of vehicle parts, wire, and metal construction
materials. A majority of the metal debris could not be identified.
C.1.1.0.3. Comment #2. Something unforseen could still happen.
C.1.1.0.4. Response to Comment #2. The on- and off-Base areas have been studied and
monitored over the last 7 to 10 years, with extensive study having taken place in the
last 5 years. Although this study period is limited with respect to the remediation time
frame, groundwater contamination conditions in the on- and off-base areas have been static
or have decreased during the study period. Based on the fact that groundwater
contamination conditions in the on- and off-base areas have been static or have decreased,
HAFB is confident that risk to the public (from existing chemical contamination) is minimal.
Any transportation of contaminants off-Base is relatively slow through groundwater, but
on-going monitoring will continue. The monitoring should detect any significant changes,
which may prompt additional or immediate protective actions. The site will be formally
reviewed no less than every 5 years to assure the remedy is still protective of human health
and the environment. The USEPA and the UDEQ will be involved in the monitoring and
oversight of the site.
C.1.1.0.5. Comment #3. What is the proposed restriction of the land use by the landowner?
C.1.1.0.6. Response to Comment #3. The institutional controls or land use restrictions the Air
Force has proposed include limiting the use of the property to the current land use and
limiting access to the shallow groundwater below the affected property. The land use
restrictions would be imposed by a deed restriction with the property owner. The property
owner would be paid for the deed restriction. The restriction would be recorded on the
property deed with the county. After the shallow groundwater contamination has
attenuated to levels below Maximum Contamination Levels (MCLs) the deed restriction
will be removed from the deed. MCLs are the maximum concentration level of
contamination that can be present in a drinking water supply. The State Engineer is
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OPERABLE UNIT 1 RECORD OF DECISION APPENDIX C
currently restricting the use of the shallow groundwater. The State Engineer will not issue a
permit for a drinking water well drawing water from the shallow water-bearing zone. In
addition, a majority of the contaminated off-Base area is already under a deed restriction
imposed by the State of Utah. The deed restriction was implemented to limit development
in areas surrounding HAFB with aircraft noise levels above 70 decibels.
C.1.2 Comments by Mr. Mark Perkins
C.1.2.0.1. Comment #1. My name is Mark Perkins, 2278 Deer Run Drive. I'm the community
representative on the RAB, R-A-B, Restoration Advisory Board. My comments are
essentially concerning the source area. And I think that I would sure like to see the
Air Force be a little bit more aggressive in their treatment of the source area. I don't think it
matters too much what they do on the non-source area until they get aggressive on the
source area because that will continue to be polluted until the source area is cleaned up and
no more pollution is flowing from it off and on into the South Weber. So Alternative 3 is the
proposed alternative, I would think at least Alternative 4 which is building the slurry wall
would be prudent and perhaps even further than that. That's it.
C.1.2.0.2. Response to Comment #1. The contamination from the source area is travelling
off-Base through the groundwater. The Feasibility Study evaluated Source Area Alternative 4
and found the alternative provided little additional containment of contaminated
groundwater because a majority of the contaminated groundwater that flows off-Base will
be collected and extracted by the dewatering trenches as proposed in Source Area
Alternative 3. Based on modeling performed for the Feasibility Study, the dewatering
trenches should extract a majority of the contaminated groundwater prior to leaving the
on-Base source areas. This will make the need for a slurry wall unnecessary. Therefore,
Source Area Alternative 3 was chosen as the preferred alternative over Source Area
Alternative 4. Source Area Alternative 4 would not provide a significantly higher level of
protection over Source Area Alternative 3. The performance of the remediation systems will
be evaluated on a base-wide basis every 5 years by HAFB, EPA and UDEQ. The most
current evaluation is scheduled for 1998. The next evaluation is scheduled for 2003. The
evaluation could be performed sooner if the dewatering trenches are not performing as
designed and are allowing contaminated groundwater to migrate off-Base. The design and
construction of another alternative, such as a slurry wall, could be implemented to limit the
migration of off-Base groundwater contamination.
C.1.3 Comments by Mr. George Schrader
C.1.3.0.1. Comment #1. In general I do not consider the preferred alternative for OU1 to be
adequate. The dewatering and capping of the landfills does not satisfy the long term goals
that I feel should be achieved. As the Sierra Club representative on the HAFB Restoration
Advisory Board, I must consider the long term restoration of the area for habitation. The
length of time necessary to reach these goals as indicated in the report may be as long as
50 years. The recent information I have had on base closures indicates that disposal of the
land in closed bases has been carried out with great haste in order to save mitigation of
hazards over a long time and at great expense. This results in relying on "Institutional
Controls" which seem to have nebulous long term effectiveness.
C.1.3.0.2. Response to Comment #1. The on-base portions of OU1 HAFB are limited from
further development by a continuing order by the Base General. If the base were
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OPERABLE UNIT 1 RECORD OF DECISION APPENDIX C
transferred, a deed restriction would be included in the deed for the property that would
limit use of the area. A majority of the areas that would be restricted from use are landfills
or other areas that can not normally be built on. Deed restrictions have been used
extensively in the contaminated areas of military bases that have been closed and
transferred to private ownership. In addition, if the remediation systems are still active once
the base is closed, the Air Force would probably be required to continue operating the
remediation systems. Source Area Alternative 7, which relies on institutional controls the
least, was considered and found to present too many construction-related risks. Also,
Source Area Alternative 7 costs too much relative to the risk reduction achieved.
C.1.3.0.3. Comment #2.1 am sure no one of us likes to consider the closing of Hill, but when
considering the length of time it will take to restore OU1 to usable condition under
alternative 3 this may well outlast the base. In the short term this looks good considering
the expense required and reducing the current hazards to humans. The problem is that even
if the base is still here for the next 50 years the cost of maintaining the caps on the landfills
and constant dewatering the could well exceed the cost of removal. I really recommend
Alternative 7 because it permanently removes the problem.
C.1.3.0.4. Response to Comment #2. It is unknown whether the remediation time frame will
outlast the active life of HAFB. If the Base is closed prior to remediating the source areas,
institutional controls would be enacted to limit future use of the area. The closure of the
Base would initiate a re-evaluation of the present remedies and the EPA would have a
statutory concurrence role in the transfer of the CERCLA NFL sites. Response to
Mr. George Schrader Comment # 1 further describes the Institutional Controls that would
be enacted. The Feasibility Study describes the capital costs as well as operation and
maintenance costs for each of the alternatives. The capital costs as well as operations and
maintenance costs for Source Area Alternative 3, over a 30-year period, are projected to be
approximately $5,900,000. The capital costs as well as operations and maintenance costs for
Source Area Alternative 7, over a 30-year period, are projected to be approximately
$302,000,000. Source Area Alternative 7 is projected to be over 51 times as expensive as
Source Area Alternative 3. The costs are projected over a 30 year period to enable the costs
to be compared. In addition to a much higher cost for Source Area Alternative 7, this
alternative has a much greater potential to expose a large percentage of the public to
potentially hazardous materials by transporting the materials through surrounding
neighborhoods.
C.1.3.0.5. Comment #3. As for the recommended non source (off base) alternative, No. 3 I do
think that it is adequate because the fact that natural attenuation in the area is already
apparent and this are could be considered safe within a reasonable time. This is contingent
on preventing further contamination from the source area. Of course the plume will have to
be monitored for a long time to assure that the required result is achieved.
C.1.3.0.6. Response to Comment #3. Long-term monitoring is part of Non-Source Alternative 3.
C.1.4 Comments by Dr. John Carter, Technical Advisor to the South Weber
Landfill Coalition
C.1.4.0.1. Comment #1,1* Page, 1* Paragraph. I have previously commented on the Draft and
Revised Draft Feasibility Studies. See our letters dated January 27 and July 10,1997.1
reiterate and incorporate those comments as applicable to the Final Proposed Plan and will
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not go into detail on each Alternative. During February, I attended the public meeting at the
South Weber Elementary School. At that rime, I was informed that results of additional
studies of the landfills and Weber River Valley were forthcoming. I look forward to seeing
those studies and their implications to the residents of South Weber. However, this places
us and yourselves in an awkward position of attempting to select or approve remedial
alternatives while studies are ongoing. As I have mentioned on numerous occasions, this
argues strongly for the implementation of the proposed interim measures that were
outlined in the Engineering Evaluation/Cost Analysis for Operable Unit 1 (EE/CA 1995)
while the full and final characterization of OU1 and its potential impacts on the residents of
South Weber and the ground water are determined. I do not believe this can be brought to a
conclusion based on the Final Proposed Plan and Final Feasibility Study while more
information is being gathered that could impact the relevance of those decisions. Therefore,
it seems the wise course to follow while this additional information is collected and
evaluated and other data gaps are addressed, is to implement these proposed interim
measures and a real-time monitoring program to provide reassurance to South Weber that
their interests are of concern and that they will be protected from the contamination that is
present now and is continuing to migrate into South Weber while the investigative process
and remedial evaluation continues.
C.1.4.0.2. Response to Comment #1. Hill Air Force Base acknowledges the South Weber Landfill
Coalition comments to the Feasibility Study and reiterates its responses to the comments. The
comments are found in Appendix C-3 of this appendix. Four additional studies have
recently been completed at Operable Unit 1 to provide data for designing and monitoring
the remedial alternatives. These studies include an investigation of the Landfill 3 and 4
areas, a natural attenuation treatability study, a groundwater remediation system
pre-design investigation, and the installation of a series of monitoring wells adjacent to
South Weber No. 2. The installation of monitoring wells adjacent to South Weber No. 2 is a
separate investigation and will be further addressed as a separate project in the future. The
investigation results documented in these reports do not change the conclusions
documented in the Feasibility Study or Proposed Plan. The results of these investigations were
also presented to the RAB, and a report documenting the investigation was produced as
soon as possible after the investigation was completed. The reports are available to the
public in the administrative record or by requesting the report(s) from HAFB. Copies of
each of these reports have been sent to the South Weber Landfill Coalition. A discussion of
the EE/CA interim remedial action is presented in response to John Carter Comment #4,
Section C.l.4.0.9. through C.l.4.0.11.
C.1.4.0.3. Comment #2,1* Page, 2nd Paragraph. I have enclosed a report reviewing the geology
and groundwater data for the Weber River Valley. This report was prepared to provide an
overview for the South Weber Landfill Coalition to assist them in evaluating proposed
plans and programs. Another stimulus for this detailed look at the data was provided by
the contamination found in South Weber Well #2, which showed a relationship between the
contamination on-Base and the contaminants found in the well. The possibility that
contaminants from OU1 have entered this deep well and that it appears to lack a protective
confining layer raised the level of concern about the possibility that the deeper Sunset and
Delta aquifers may be receiving contaminants from HAFB. This issue has never been fully
resolved.
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C.1.4.0.4. Response to Comment #2. Comments in the report reviewing the geology and
groundwater data for the Weber River Valley are responded to in Section C.1.5. The results
of the installation of monitoring wells adjacent to South Weber No. 2 are presented in the
South Weber No. 2 Monitoring Well Installation Report. This report is available to the public in
the administrative record or by requesting the report from HAFB. A summary of the
investigation effort was presented to the public at the RAB Meeting on June 18,1998, at
HAFB.
C.1.4.0.5. Comment #3,2nd Page, 1st Paragraph. The summary page at the beginning of the report
provides a synopsis of the results of that review. The major conclusions are that the
Weber River Valley at South Weber where contamination presently exists is a recharge zone
for the deeper aquifers, that these aquifers lack a protective confining layer and that
contamination from OU1 is likely migrating down into these aquifers. It also concludes that
while some contaminants may be declining in some wells, new contaminants are appearing
in the Valley in recent data and the concentrations of some are increasing. Some of these are
more toxic than those previously documented. In fact, six new compounds have appeared
in the 1995-1996 time period. The area of the contamination plume itself appears to remain
unchanged, reaching to South Weber Drive. Based on this analysis, the Final Proposed Plan
does not provide adequate protection for the residents of South Weber or the deeper
aquifers. Therefore, the use of extraction trenches in Source Areas and natural attenuation
in Source and Non-Source areas must be rejected as a final solution. More specific
comments and recommendations follow.
C.1.4.0.6. Response to Comment #3. The results of the installation of monitoring wells adjacent
to South Weber No. 2 are presented in the South Weber No. 2 Monitoring Well Installation
Report. The report is available to the public in the administrative record or by requesting the
report from HAFB. Based on our interpretation of the drillers log from the South Weber No.
2, confining layers appear to exist between the surface and the drinking water aquifer. The
area does not appear to be a recharge area. The recent drilling of a monitoring well adjacent
to South Weber No. 2, to a depth of 453 feet below the ground surface, showed numerous
confining layers between the surface and the drinking water aquifer. Due to the confining
layers, the area surrounding South Weber No. 2 was not found to be a recharge area.
Drinking water aquifer recharge areas are located at the base of the Wasatch Mountains,
approximately 2-miles to the east. Please see the Response to Comments in
Sections C.1.5.4.8. through C.1.5.4.10. for an evaluation of the compounds identified by the
South Weber Landfill Coalition. Considering all the information, HAFB has determined the
selected remedy to be the proper final solution.
C.1.4.0.7. Comment #4,2nd Page, 2nd and 3rd Paragraphs. Source Area Preferred Alternative—Dewatering
by Extraction Trenches. This method was previously judged unsuitable for OU1 by HAFB in
the EE/CA. To quote from page 3 of that document, "A physical barrier is preferred over a
hydraulic barrier because it is a more positive means of containment and it is not as reliant on the
operation of electromechanical equipment (i.e. extraction pumps). If a pump in a gradient control
well were to fail, there would be adequate time to detect and respond to the problem before any
contamination escaped the containment system. This may not be the case with failure of a pump in
an extraction trench. Given that there is a steep slope immediately downgradient of the proposed
trench location, ground water that migrates through while the pumps are inoperative could not be
recovered. .. .The two alternatives using hydraulic barriers also represented a risk that the resulting
drawdown in the water table might allow the LNAPL to migrate into the clay, potentially making
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future remediation efforts more difficult." Further, from page 4-10 of the EE/CA, it is stated
that "Pump failure or poor pump performance could result in contaminants migrating beyond the
trench system. This is a distinct disadvantage of a hydraulic barrier compared to a physical barrier.
Given the estimated life of the removal action (30 years), it is likely that the pumps will fail at some
point and they will need to be replaced. For this reason, frequent performance monitoring is critical."
C.1.4.0.8. Comment #4 (cont). Modeling results presented in the EE/CA indicated that only 30
to 40 particles released would be captured. While the design of the system presented in the
EE/CA is different than that in the Final Proposed Plan (1998), it appears that capture
efficiency and reliability poses a significant risk that the Preferred Alternative will not
eliminate contaminant flow into the Weber River Valley and South Weber Non Source Area.
It is also of benefit to mention that the physical barrier proposed in the EE/CA was a slurry
wall which is the physical containment method already used to limit groundwater flow into
OU1 from the South. However, as it stated in the EE/CA, "Since the existing slurry wall at the
site is not performing as a effective barrier to ground water flow, there is some concern about the
ability to construct a slurry wall that will meet the performance objectives. The reason for its limited
effectiveness is believed to be related to poor construction quality control, such that the wall was not
properly keyed into the clay." What was not mentioned in the EE/CA was the possibility of
discontinuities in the silty clay layer that might allow continued migration of groundwater
into OU1 through or beneath the slurry wall. Alternative 4 of the Proposed Plan, proposed a
downgradient cutoff (slurry) wall to "...increase the reliability of preventing off-site migration
by providing a physical barrier to groundwater movement." This alternative was not accepted as
part of the Preferred Alternative and South Weber is left without the physical containment
that was considered necessary in the EE/CA.
C.1.4.0.9. Response to Comment #4. Source Area Alternative 4 consists of a dewatering system
and slurry wall similar to the design of the EE/CA. The location of dewatering systems
varied from the EE/CA. Because the Source Area Alternative 3 Dewatering Trenches are
much more distant from the bluff area, compared to the EE/CA design, failure of a pump
would not result in the loss of capture of contaminated groundwater. The groundwater
modeling performed as part of the Feasibility Study evaluated Source Area Alternative 4,
and found that the alternative provided little additional containment of contaminated
groundwater because a majority of the contaminated groundwater that flows off-Base will
be collected and extracted by the dewatering trenches (as proposed in Source Area
Alternative 3). Therefore, the slurry wall would be unnecessary because the groundwater
would be mostly removed by the dewatering trenches and there would be limited
groundwater for the slurry wall to contain. Recent investigation also identified the location
of the groundwater channels considered to be the main flow path for groundwater and
groundwater contamination. The location of the trenches is based on the location of the
groundwater channels.
C.1.4.0.10. Response to Comment #4 (cont.). A slurry wall was proposed as an EE/CA interim
remedial action for Operable Unit 1 in 1995. The design of the slurry wall was evaluated by
a third party reviewer who found that the slurry wall would provide limited protection to
the off-Base migration of groundwater contamination. During the public comment period,
the public also identified problems with the effectiveness of the slurry wall. Based on third
party evaluation and comments made by the public, the Air Force decided not to construct
the slurry wall. The Feasibility Study also evaluated the installation of a slurry wall (Source
Area Alternative 4) and found the slurry wall would not provide a significant level of
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additional protection when compared to dewatering trenches without a slurry wall (Source
Area Alternative 3). The slurry wall would be unnecessary because the groundwater would
be mostly removed by the dewatering trenches, and there would be limited water for the
slurry wall to contain. Therefore, Source Area Alternative 3 was chosen as the preferred
alternative over Source Area Alternative 4. In addition, the effectiveness of the upgradient
slurry wall constructed in the mid-1980's has been shown to be limited at best.
C.1.4.0.11. Response to Comment #4 (cont.). The performance of the remediation systems will be
evaluated on a base-wide basis every 5 years. The most current evaluation is scheduled for
1998. The next evaluation is scheduled for 2003. The evaluation could be performed sooner
if the dewatering trenches are not performing as designed and are allowing contaminated
groundwater to migrate off-Base. The design and construction of another alternative, such
as a slurry wall, could be implemented to limit the migration of off-Base groundwater
contamination. The dewatering system will be remotely monitored with alarms. If the
system shuts down, personnel will be immediately dispatched to resolve the problem. In
addition, the flow of groundwater is relatively slow. Once the pumps are turned back on,
the water on the downgradient side of the trench would be drawn back into the trench.
C.1.4.0.12. Comment #5,3rd Page, 1st full Paragraph. Repair and O&M of Landfill Caps and Passive Gas
Vent System. Monitoring data for landfill gases presented in the Final Comprehensive
Remedial Investigation (RI1995) indicated that numerous volatile organic compounds were
present within the landfills including TCE (340 ppb), DCE (52,000 ppb) and Vinyl Chloride
(30,000 ppb), among others. These are present in the landfill gas and are vented to the
atmosphere. Lack of monitoring within the landfills has precluded a definitive analysis of
the source(s) of these compounds. It is not known whether LNAPL or DNAPL is present, or
whether drummed or containerized wastes are present that cannot be remediated by the
Preferred Alternative in the Final Proposed Plan. A consequence of the Preferred
Alternative is that the landfills will be dewatered to varying degrees depending upon the
design and operation of the proposed extraction system and the integrity of the landfill cap.
Much of the disposal activity in the landfills resulted in disposed material being present in
the upper region of the landfills above the water table. Lowering the water table will leave
more of the landfill contents above the saturated zone. The lowered or absent infiltration
rate obtained by repair of the landfill cap will preclude water movement through this upper
zone where the disposed material resides. The result of this is that, depending upon the
state of the contaminants in the landfills, they may persist long beyond any proposed time
estimate for remediation and reappear once OU1 is deemed closed and monitoring ceases
or during failures of the extraction system.
C.1.4.0.13. Response to Comment #5. During original sampling of the landfill gas system, the
samples were obtained by inserting a tube inside the landfill vent. The samples were
collected in a SUMMA canister connected to the end of the tube. Based on this question,
HAFB recently scanned the air from the vents with an Organic Vapor Meter (OVM). A
reading was taken 3 to 6 feet inside the vent and at the vent outlet. The depth of 3 to 6 feet
was the depth at which the original samples were obtained. The OVM did not detect any
reading of Volatile Organic Compounds (VOCs) at the vent outlet. OVM readings as high as
1 part per million were observed in some of the landfill vents in Landfill 4. VOCs were not
detected inside the other vents. The minor amount of gas that these vents produce is
considered insignificant and quickly dilutes to non-detection upon venting to the
atmosphere. The amount of Volatile Organic Compounds emitted by the landfills appears
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to be well below the amount required to be treated by the State of Utah under current law.
A Best Control Technology (BACT) analysis for landfill gas will be performed to assess the
need for controls prior to implementation of the selected remedy.
C.1.4.0.14. Response to Comment #5 (cont.). The Landfill 3 and 4 Summary Investigation (CH2M
HILL, 1998d) provided information concerning the types of materials and debris contained
within the landfills. Ninety-five exploration points were excavated within Landfills 3 and
4 to evaluate the nature and extent of landfill debris. DNAPL was not found in the landfill
areas. LNAPL has been observed in Landfill 3, but is associated with Fire Training Area 1.
The extent and nature of the LNAPL from Fire Training Area 1 has been well documented
in the Remedial Investigation. Additional study was also performed to evaluate the presence
of drums that may have been buried in the landfills. This investigation did not detect
containerized hazardous waste. The results of this investigation are presented in the Landfill
3 and 4 Summary Investigation (CH2M HILL, 1998d).
C.1.4.0.15. Response to Comment #5 (cont.). The shallow groundwater under the landfills will be
collected and treated with the goal of removing and treating the majority of the shallow
groundwater. Groundwater is the transport mechanism moving contamination off-Base.
The dewatering trenches will mitigate the flow of groundwater off-Base. The improvements
to the landfill caps will also inhibit surface water infiltration to the shallow groundwater
table. These remedial efforts should lower or eliminate the shallow groundwater table,
thereby removing the main contamination transport mechanism. If the contamination does
not have a mechanism for transport, it will not migrate to off-Base areas and will not be a
threat to the public. HAFB does not believe using surface water to flush the contamination
through the landfill debris to the shallow groundwater table is in the best interest of the
public. The intent of the dewatering system is to limit contaminated groundwater from
flowing off-Base.
C.1.4.0.16. Comment #6,3rd Page, 2nd Paragraph. Environmental Monitoring. No monitoring program
description is provided. The type (groundwater, surface water, air, soil, soil gas, other),
location and frequency of monitoring as well as the contaminant list being analyzed is
critically important to the impacted populations. Depending upon these factors, the
populace could be exposed to contaminants for long periods of time corresponding to the
interval between samples or monitoring events. Reliance upon mechanical pumping
systems demands daily checks for performance, standby equipment to bring on-line when
problems occur and contingency planning for any foreseeable problem. This has not been
presented in the proposed plan. The people of South Weber cannot feel comfortable with
monitoring and reporting as it has been conducted in the past and may be conducted as
part of any interim or final solution. The design and implementation of any monitoring
program must allow for detection of known and unknown contaminants both in air, water
and soils. The monitoring network must be designed to provide early warning and be
comprehensive enough to address the monitoring gaps I have repeatedly pointed out. The
monitoring schedule and reporting must be timely and disseminated in such a way that
residents will be provided current results. There must be a response mechanism that will
activate a contingency plan to ensure protection.
C.1.4.0.17. Response to Comment #6. Hill Air Force Base agrees the remedial monitoring plan is
very important, especially with respect to the natural attenuation alternative. Proposed
plans and feasibility studies generally do not provide detailed monitoring plans. The
monitoring plans are only defined in general terms in the Feasibility Study and Proposed Plan.
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The monitoring will consist of groundwater, surface water, and possibly air monitoring.
Groundwater levels will also be measured. The monitoring schedule has not been defined
at this time. As part of the remedial design, a monitoring schedule will be developed.
Twenty-two additional monitoring wells were recently installed in an off-Base area for
natural attenuation monitoring, bringing the total number of monitoring wells in the off-
Base area to 43. These new monitoring wells include a deep well screened in the drinking
water aquifer adjacent to South Weber No. 2.
C.1.4.0.18. Response to Comment #6 (cont.). A continuous monitoring system, with alarms in the
event of failure, will be designed into the on-Base dewatering system. Contingency and
emergency plans will be included as part of operation and maintenance manuals for the
remediation system. Numerous other dewatering systems are currently operating at HAFB,
at the various operable units, with remote alarms that notify base personnel in the event of
system malfunction. This system has worked well to date. A more sophisticated system,
that will allow remote monitoring and operation of most Base remediation systems, is
currently being designed.
C.1.4.0.19. Response to Comment #6 (cont.). Hill Air Force Base does not agree that there are still
data gaps and has performed numerous investigations and studies to evaluate the nature
and extent of contamination at Operable Unit 1. The number and type of investigations and
studies have met the EPA and UDEQ requirements for similar sites.
C.1.4.0.20. Response to Comment #6 (cont.). The details of reporting monitoring results have not
yet been defined. The details will be prepared as part of the remediation system design. A
report will be prepared after each monitoring event, and it will include the results of
monitoring events as well as an assessment of the progress of the remediation effort. The
report will be available for public inspection and possibly a condensed version will be sent
to the affected property owners.
C.1.4.0.21. Comment #7,4th Page, 1" Paragraph. Institutional Controls. The scope (area, type and
duration) of "institutional controls" is not described. Property owners should be informed
about the limitations on their use of their property in order to make informed judgements
about the Proposed Plan and Preferred Alternative. The description for Non Source Area
Alternative 6 states: "...the use of institutional controls to prevent changes in land use or use of the
groundwater." This type of control could have long-term impacts to individual property
owners as well as to the Town of South Weber if enforced. How are institutional controls to
be implemented and enforced? Decades down the road, how do we obtain assurance that
innocent and unaware citizens might not inadvertently expose themselves to the
contaminants through their activities?
C.1.4.0.22. Response to Comment #7. The land use restrictions the Air Force has proposed for
off-Base areas include limiting use of the property to current land use and limiting access to
shallow groundwater below the affected property. The land use restrictions would be
imposed by a deed restriction with the property owner. The property owner would be paid
for the deed restriction. The restriction would be recorded on the property deed with the
county. After the shallow groundwater contamination has attenuated to levels safe enough
to drink, the deed restriction would be discontinued and removed from the deed. Use of the
shallow groundwater is restricted by the State Engineer. The State Engineer will not issue a
permit for a drinking water well drawing water from the shallow water-bearing zone. In
addition, a majority of the contaminated off-Base area is already under a deed restriction
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imposed by the State of Utah. The deed restriction was implemented to limit development
in areas surrounding HAFB with aircraft noise levels above 70 decibels.
C.1.4.0.23. Comment #8,4* Page, 2nd Paragraph. Upgraded Seep Collection and Treatment. Under the
Preferred Alternative in the Proposed Plan, it is expected that groundwater transport of
contaminants from the OU1 Source Areas will be stopped by the extraction trench system.
In that case, why is a separate collection and treatment system necessary for seeps? The
proposed plan states in the description of Non-Source Area Alternative 3, that "Restoration
time is estimated at 5 to 50 years, with a best estimate of 12 years." This implies that these
seeps are expected to flow for long periods of time. If so, what is the source of contaminated
water that allows this when all contaminated water flowing from the Source Areas is to be
captured under the Preferred Alternative? An additional point here relates to the statement
in the Preferred Alternative "Alternative 3 provides an additional protection by collecting
additional seeps/springs that are contaminated above remedial goals...". An inspection of Figure
13 for this Alternative shows these seep collection systems lie within and beyond the Area
Exceeding PRGs in groundwater. According to the logic regarding PRGs presented in the
Proposed Plan, it seems strange that seep collection system is proposed in an area that
doesn't exceed PRGs unless there is a recognition that not all risks are accounted for, that
concentrations could increase or that more active measures need to be taken.
C.1.4.0.24. Response to Comment #8. Good point. The springs are one of the few risk pathways
that are relatively easily completed by drinking or coming in contact with the spring water.
The source area dewatering system will be constructed in two phases. The dewatering
trenches will be constructed first. After the dewatering trenches begin to extract
groundwater, the springs will be monitored to determine whether the dewatering trenches
extract enough groundwater to cause the springs to cease to flow. With the exception of
Ul-309, located near South Weber Drive, the dewatering system is expected to dry up the
seeps and springs in question. If the springs do not cease to flow and still contain
contamination, a spring treatment system will be designed and constructed. The springs to
be treated are those springs containing contamination with a significant year-round flow
and having historic contamination levels that exceed the Maximum Contaminant Level
(MCLs) for the compound. Most of the groundwater emanating from the springs with
contamination above MCLs is already being treated.
C.1.4.0.25. Comment #9,5th Page, 1" Paragraph. Excavation of Arsenic-Contaminated Sediments. It is
noted from Figure 13 for the Preferred Alternative that four seeps located to the north and
east of LF3 and LF4 contain arsenic-contaminated sediments that are to be excavated. What
is the source or the arsenic? Since seeps arise from groundwater sources, and there is a lack
of soil or groundwater data in this Non-Source Area, what assurance exists that this is not
an indication of much more widespread soil and groundwater contamination that is being
overlooked? The results of soil gas investigations in the Non-Source Area to the north and
east of the landfills that showed significant soil gas concentrations of Benzene, DCE and
Toluene have been repeatedly pointed out to HAFB, yet the absence of data collection in
this area continues to be relied upon as proof of no contamination or threat to human
health. This area needs to be addressed more fully in any final solution.
C.1.4.0.26. Response to Comment #9. Arsenic in the soil adjacent to the springs in question has
been deposited by groundwater from the landfill areas. The groundwater is in a reducing
condition under the landfills. Due to the reducing condition under the landfills, naturally
occurring arsenic and iron dissolve into the groundwater. The arsenic and iron precipitate
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upon contact with the atmosphere as the spring discharges. The final version of the
Feasibility Study contains a technical memorandum that identifies the extent of the arsenic
contaminated soils. The technical memorandum is part of Appendix L of the Feasibility
Study. Numerous soil samples were obtained during the field investigation and were tested
for arsenic. The extent of arsenic soil contamination in the areas around the springs was
determined using these soil samples. Many of the samples contained arsenic levels within
background levels. The soils contaminated by arsenic are located immediately adjacent to
the springs.
C.1.4.0.27. Response to Comment #9 (cont.). A soil gas investigation, to evaluate the extent of soil
and groundwater contamination, was performed during the Phase I Remedial Investigation
for Operable Unit 1 in 1990. Benzene and toluene were detected in the soil gas
contamination in an area well east of the existing off-Base Operable Unit 1 DCE
groundwater plume. DCE was not noted in this area. The areas that showed soil gas
contamination were further investigated by drilling soil borings and installing monitoring
wells. Groundwater or soil contamination was not observed in this area east of the existing
plume. Investigations since the soil gas investigation have been focused in areas of
groundwater contamination, although the monitoring wells installed in the area east of the
existing plume continue to be monitored.
C.1.4.0.28. Comment #10,5th Page, 2nd Paragraph. Natural Attenuation Monitoring. In addition to the
extraction trenches natural attenuation has been proposed for remediation of groundwater
contamination. It is also proposed as the Preferred Alternative for Non-Source Areas (the
Weber River Valley), where contamination has been documented in the groundwater.
According to the description for Non-Source Alternative 3, "Restoration time is estimated at
5 to 50 years, with a best estimate of 12 years." In the Glossary of the Proposed Plan, Natural
Attenuation is " The process whereby contaminant concentrations are reduced through natural
physical, chemical and biological processes." In the Final Feasibility Study Report for Operable
Unit 1 (January 1998), natural attenuation processes are listed as biodegradation, dilution
and adsorption. Processes that are not listed include evaporation up through the soil to the
ambient environment (air), horizontal movement of contaminants in groundwater at depths
below the shallow monitoring wells currently in place and downward movement into the
deeper Delta and Sunset Aquifers which serve as a water source for thousands of people.
The attached report "Review of Off-Base (South Weber) Groundwater Data" provides
sufficient documentation that what is presumed to be natural attenuation may also include
downward migration into deeper zones that are not monitored. The recent appearance of
new, previously undetected compounds in Valley monitoring wells, some of which are
more toxic than those previously found shows that reliance on this process is a risky
strategy.
C.1.4.0.29. Response to Comment #10. The air in the basements of six residences overlying the
off-Base groundwater plume has been monitored, and vapors from groundwater
contamination have not been observed. Hill Air Force Base does not believe the
contamination mass is vaporizing and escaping to the atmosphere. The vapors may be
degrading into inert compounds by natural attenuation. Air in basements will continue to
be monitored in the future.
C.1.4.0.30. Response to Comment #10 (cont.). Deeper monitoring wells installed in water-bearing
zones below the shallowest groundwater water-bearing zone have been constructed in the
past. The Feasibility Study identified and grouped the monitoring wells screened in the same
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OPERABLE UNIT I RECORD OF DECISION APPENDIX C
water-bearing zone. Significant differences in contamination levels and groundwater
elevations were noted in the water-bearing zones. Additional monitoring wells were
recently installed in the deeper water-bearing zones in the off-Base area for future
monitoring. The results of the installation of monitoring wells adjacent to South Weber No.
2 are presented in the South Weber No. 2 Monitoring Well Installation Report (CH2M HILL,
1998b). The report is available to the public in the administrative record or by requesting the
report from HAFB.
C.1.4.0.31. Comment #11,5th Page, 3rd Paragraph. Interim Measures and Removal of Source Material.
These facts should urge HAFB to proceed with protective interim measures to stop
migration of contaminants both off-Base and within South Weber. These measures include
extraction trenches and physical barriers in the Source Areas of OU1, plume cutoff at the
bottom of the bluff and groundwater extraction and treatment in the plume in South Weber.
C.1.4.0.32. Comment #11 (cont.) Implementation of these interim measures would provide time
for HAFB to complete characterization of the site in sufficient detail to answer the
unresolved questions that persist. To conclude that removal is not an acceptable alternative
is premature. Since the EE/CA has admitted that physical containment is more certain of
success than mechanical systems, a more careful consideration of the removal option and its
costs and benefits should be made. This study should consider that there are numerous
Operable Units on Base and that a secure landfill constructed on-site could have very
positive benefits in terms of the effectiveness of cleanup actions and, with cost spread over
several Operable Units would be more cost-effective. In addition, to arrive at a cost estimate
and reject the removal alternative at OU1 without a refined volume estimate based on the
latest landfill studies, consideration of the much less expensive transport cost of on-Base
disposal, reduced monitoring and treatment costs and other benefits that may accrue by
combing this alternative with other Operable Units seems not to serve the long-term
interests of HAFB or the surrounding communities and their environment. The installation
of the previously proposed interim measures would provide the time necessary for the
more careful consideration of this alternative.
C.1.4.0.33. Response to Comment #11. The other alternatives in the Source Area and Non-Source
Area were evaluated as part of the Feasibility Study and were found not to provide a
significant level of additional protectiveness over the preferred alternatives.
Characterization of the Operable Unit 1 area has been ongoing for approximately 20 years.
Hill Air Force Base believes the area has been studied adequately, no unresolved issues that
affect the remediation plans for the area exist, and a final remedial action needs to be
implemented. Hill Air Force Base has met all substantive USEPA and UDEQ requirements
for a CERCLA site. After construction and start up of the preferred alternative, the
performance of the remediation system will be monitored. The performance of the
remediation systems will be evaluated on a base-wide basis every 5 years. The most current
evaluation is scheduled for 1998.'The next evaluation is scheduled for 2003. The evaluation
could be performed sooner if the dewatering trenches are not performing as designed and
are allowing contaminated groundwater to migrate off-Base. The design and construction of
another alternative, such as a slurry wall, could be implemented to limit the migration of
off-Base groundwater contamination. The implementation of an interim remedial action
could not be performed any faster than the remedial action proposed, as both actions have
to follow the same guidelines.
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___ OPERABLE UNIT 1 RECORD OF DECISION APPENDIX C
C.I.4.0.34. Response to Comment #11 (cpnt.). The removal alternative (Source Area
Alternative 7) was not chosen as the preferred alternative due to the cost and the fact that
the major risks are associated with the groundwater. Recent landfill investigations
confirmed the assumptions (for the most part) made in the Feasibility Study. The
construction of a base-wide landfill is interesting, although a majority of the contamination
found at HAFB is groundwater related. In addition, a majority of the landfill debris would
come from OU1 which would negate the advantage of spreading the costs between the
OUs. The permitting and operation of such a landfill would be very difficult, if not
impossible, at HAFB.
C.1.5 Comments by Environmental & Engineering Solutions, Inc. - Review of
Off-Base (South Weber) Groundwater Data
C.1.5.1. Report Summary
C.1.5.1.1. Comment #1. A review of existing data and literature describing the geology and
groundwater contamination in the Weber River Valley in South Weber was undertaken in
order to evaluate remedial alternatives proposed in the Final Proposed Plan for Operable
Unit 1 (January, 1998). The review showed that confining layers of impermeable materials
(clays, bedrock) needed to isolate the deeper Sunset and Delta aquifers from contamination
are lacking. Further, the literature indicates this area is a recharge zone for the deeper
aquifers that provide groundwater to South Weber and communities further west.
Hydrogeologic data from investigations at OU1 also show that a strong downward gradient
exists in the Valley. This further reinforces that the area is a recharge zone. Because HAFB
has indicated that the plume of groundwater contamination is shrinking in the Valley and
that concentration trends are downward, an analysis of groundwater monitoring data for
the 21 Valley wells was also undertaken. This study indicates that while some contaminants
in some wells may be declining, other contaminants have appeared in 1995-1996 that were
not detected in prior years. Two of these, benzene and vinyl chloride are known human
carcinogens. In addition, some compounds appear to be increasing in concentration. The
most recent data we have seen indicates that nearly all wells have had contamination
detected in the most recent years, therefore to conclude that the plume is shrinking may be
in error. Finally, in evaluating trends of contaminant concentration, plots were generated
for the most recent and complete data. These show that trends for many compounds appear
to be weak or lacking and that many of them cycle over a range on a yearly basis. Our
conclusion is that relying on natural attenuation and on-Base groundwater extraction lacks
certainty, is not protective of the deeper aquifers and does not provide assurance to South
Weber that more toxic contaminants are not and will not migrate into South Weber now or
in the future. In fact the recent discovery of contamination in South Weber Well #2, which is
1200' deep and contained numerous contaminants found in OU1, an issue that has not been
resolved, further raises concerns about contamination in the deeper aquifers.
C.1.5.2. Review of Off-Base (South Weber) Groundwater Data
C.1.5.2.1. Comment #1 (cont.). In order to evaluate the Final Proposed Plan for Operable Unit 1,
a thorough understanding of the status of the groundwater monitoring system and data
gathered since 1990 is needed. This report is intended to provide an analysis of the geology
and trends in groundwater contamination in the Weber River Valley and South Weber
based on HAFB data. The focus of this work is contamination by Volatile Organic
Compounds (VOCs).
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OPERABLE UNIT 1 RECORD OF DECISION APPENDIX C
C.1.5.2.2. Response to Comment #1. Report introduction; the comments responded to in
subsequent sections.
C.1.5.3. Monitoring Wells and Valley Geology
C.1.5.3.1. Comment #2. During recent efforts to understand the contamination occurring in
Weber Basin Water Conservancy District/South Weber Well #2, a review of well logs for
South Weber Well #2 and HAFB monitoring wells in the Valley indicated that there is no
confining layer that will protect deeper aquifers from contamination. The well log provided
by the Weber Basin Water Conservancy District for Well #2 (attached) showed a lack of
confining layers over its total depth of 1200'. A review of Figure 5-20 (attached) from the
Final Comprehensive Remedial Investigation Report for the Operable Unit 1 (1995) shows
that the best understanding of Valley geology is that it consists of mostly permeable
formations dominated by sand. Some thin layers of clay and silty clay are shown, but are
discontinuous. A summary of HAFB well logs taken from the Final RI, Appendix I is
provided in Table 1. This table provide dates of well installation, depth and descriptions of
layers of low permeability formations through which the wells were installed. As can be
seen, the majority of the wells do not pass through confining layers. Some wells pass
through silty clay layers. Figure 4-3 from the final RI is attached showing locations and
dates of well installation. A review of historical geological publications including Feth et al1
indicates that the area of the Weber River Valley near the Wasatch Mountain Front is
composed of permeable materials and is a recharge area for the deeper aquifers, including
the Sunset and Delta. The Final RI (page 5-19) states that there is a strong downward
gradient in the shallow aquifer in the off-Base area in the Weber River Valley. This fits with
the interpretation that there are no confining layers in the Weber River Valley and that the
area is a recharge zone for the deeper aquifers that serve South Weber and areas to the
West. Feth et al also point out that the geology is heterogeneous in nature, but that these
permeable gravel layers extend westward to Clearfield. In addition, artesian aquifers exist
to the west, which indicates that a confining layer develops at some point between the
mountains and the Salt Lake. Bolke and Waddell2 state that "The ground-water reservoir in
the East Shore area consists of unconsolidated and semiconsolidated deposits, which range
in grain size from clay to boulders. At the base of the Wasatch Range the deposits consist
chiefly of course-grained delta, alluvial fan, and slope-wash deposits; they grade westward
into fine-grained but well-sorted lacustrine deposits. The principal aquifers consists of
gravel or gravel and sand in the east half of the area and of sand in the west half." Feth et al
also indicate that the Alpine Formation consists of about 135' of fine-grained sediments
which are like those documented in the higher elevation on-Base portion of OU1. The
Weber River has cut through these deposits to form the Weber River valley, exposing the
coarser, more permeable substrate beneath the Alpine Formation (See attached Figure 5-20).
TABLE 1. SUMMARY OF VALLEY MONITORING WELL GEOLOGY
Well
U 1-090
Installed
8/90
Depth
122
Screen
si/sa
Confining Layer
Numerous thin silt/clay layers
1 Feth, J.H., D.A. Barker, L.G. Moore, R.J. Brown, and C.E. Veirs. 1966. Lake Bonneville: Geology and Hydrology of the
Weber Delta District, Including Ogden, Utah. Geological Survey Professional Paper 518. U.S. Geological Survey.
2 Bolke, E.L. and K.M. Waddell. 1972. Ground-Water Conditions in the East Shore Area, Box Elder, Davis and Weber
Counties, Utah. State ot Utah Department of Natural Resources Technical Publication No. 35.
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OPERABLE UNIT 1 RECORD OF DECISION APPENDIX C
U 1-094
U 1-095
U 1-096
U 1-097
U 1-098
U 1-099
U1-105
U1-108
U1-109
U1-110
U1-111
U1-112
U1-113
U1-155
U1-151
U1-154
U-156
U-152
U1-153
9/90
9/90
9/90
9/90
9/90
9/90
12/92
12/92
12/92
12/92
1/93
12/92
12/92
7/95
7/95
7/95
5/95
7/95
7/95
65
45
47
20
17.5
21
35
25
25
23
17
15
50
87
124
33
124
115
128
si/sa
si/sa
si/sa
si/sa
sa/gr
Sa/gr/si/cl
si/sa
sa/gr
sa/gr
sa/gr
sa/gr
sa/gr
si/sa
si/sa
sa/gr
sa/gr
si/cl
si/sa
Si/cl
None
None
None
None
None
Clay w/sand stringers
None
None-except thin clay layer at 20'
None-except thin clay layer at 24"
None-except thin clay layer at 20'
None
None
Intermediate layers of silty clay, bottom flowing sand
Silty clay 40-42', 45', 55-77', rest sand
Silty clay 6-19', 40-42', rest sand/gravel
None
Clay and silt 18-30', remainder sand/some silt
Silty clay 40-43', 92-93', 94' rest sand/silty sand
Silty clay to 54', 65', 82', 106-108', 112' rest sand
C.1.5.3.2. Response to Comment #2. Twenty-three additional monitoring wells were recently
installed in the off-Base Weber Valley area to better understand the levels of contamination
in the valley. Five of these wells were installed adjacent to South Weber No. 2. These five
monitoring wells provide a lithologic profile of the geology adjacent to South Weber No. 2
to the depths of the drinking water production zone. Many of the shallower water-bearing
zones can be correlated throughout the valley. The deepest well was drilled to a depth of
455 feet below the ground surface (bgs). The deep well penetrated through the Alpine
Formation to the drinking water aquifer. The top of the drinking water aquifer was
penetrated at a depth of 404 feet bgs. The Alpine Formation consisted mainly of layers of
unsaturated silty clays, silts, and silty sand. The lithology above the drinking water aquifer
consists of thin, saturated, medium-grained sand layers interbedded with the finer-grained
materials. The ratio of the finer-grained, unsaturated materials to the coarser grained
saturated materials is approximately 80 to 90 percent finer-grained materials. The only
exception was a 70 foot thick layer of coarse-grained sand and gravel located 263 to 334 feet
bgs. Another layer of mainly unsaturated, silty sand was observed between this gravel layer
and the drinking water aquifer. The most significant silty clay layer was observed from 200
to 263 feet bgs. Monitoring wells were screened in the following intervals: 46-66 feet bgs, 99-
109 feet bgs, 122-132 feet bgs, 175-195 feet bgs, and 433-453 feet bgs. The saturated layers
tended to be confined. With the exception of the shallowest water-bearing zone, the
groundwater levels all rose above the screened interval. This data actually correlates
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OPERABLE UNIT 1 RECORD OF DECISION APPENDIX C
reasonably wells with the drillers log from South Weber No. 2. The "shale" described in the
drillers logs are clay layers.
C.1.5.3.3. Response to Comment #2 (cont.). The lithology was described using a continuous core.
The core is stored in core boxes for future analysis if necessary. The only areas where a
continuous core was not taken were in the coarse-grained sand and gravel zones where core
could not be recovered. A wash sample was taken in these zones. The lithology in South
Weber No. 2 was described using strictly wash samples. This difference in logging methods
is the probable reason for differences in the description of lithology.
C.1.5.3.4. Response to Comment #2 (cont.). Hill Air Force Base does not consider this area to be a
recharge zone to the drinking water aquifer due to the numerous confining layers found
and the fact that most of the shallow water-bearing zones are confined. The groundwater
recharge areas are located further east toward the mouth of the Weber River. A downward
gradient can be calculated in the area, but this does not necessarily mean the area is a
recharge zone. The drinking water aquifer does consist of sand and gravel as stated by
Bolke and Waddell, but this zone is not encountered until approximately 400 feet bgs.
Additional investigation in this area has shown that the lithology is not as sandy as is
shown in Remedial Investigation (Figure 5-20) and numerous confining layers exist in the
area.
C.1.5.3.5. Response to Comment #2 (cont.). The Final Feasibility Study provides an interpretation
of the geology that is slightly different than the Remedial Investigation. This new
interpretation is based on additional exploration points and is considered a refinement of
the interpretation in the Remedial Investigation. The Draft Groundwater Pre-Design
Investigation (CH2M HILL, 1998c) and Monitoring Well Installation and Impact Assessment of
South Weber No. 2 Report (CH2M HILL, 1998b) also provided data to further refine geologic
conditions.
C.1.5.4. Chemical Contamination Trends
C.1.5.4.1. Comment #3. In the Final Proposed Plan Operable Unit 1, HAFB states that in Non-
Source Areas, i.e. the Weber River Valley/South Weber downslope of the Bambrough
Canal, Total 1,2-Dichloroethene (DCE) concentrations appear to be declining and that the
area of the DCE plume has declined from 36 to 20 acres. These observations are used to
establish natural attenuation as a preferred mode of dealing with contamination in the
Valley. Natural attenuation is defined in the Final Proposed Plan as "The process whereby
contaminant concentrations are reduced through natural physical, chemical and biological
processes." The Final Feasibility Study Report (January 1998) defines natural attenuation to
mean biodegradation, dilution and adsorption. In any case, relying on natural attenuation
precludes any active means of remediation of the Valley contamination plume. Because
such weight has been placed on the apparent dynamics of DCE in the Valley as justification
for eliminating active remediation measures, EES has also studied the groundwater
monitoring data provided by HAFB which includes data for DCE and other volatile organic
compounds (VOCs) from 1990 to 1996. In particular, we have focused on interpreting the
occurrence of VOCs in 21 monitoring wells in the Weber River Valley that were installed to
monitor contaminant migration off-Base from OU1.
C.1.5.4.2. Comment #3 (cont.). These monitoring wells were installed during three time periods.
In 1990, 7 wells were installed to depths varying from 17.5' to 122' with screened intervals
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OPERABLE UNIT t RECORD OF DECISION APPENDIX C
reflecting this overall depth. Three of these wells are less than 20' in depth, while two
penetrate to 42', 1 to 64' and 1 to 119'. In 1992-1993, 7 additional wells were installed. Six of
these were shallow, ranging in depth from 5' to 35'. A single well was installed to a depth of
50'. In 1995, 7 more wells were installed. One well was shallow, going to a depth of 33',
while the remainder ranged in depth from 77' to 128'. The differences in ages and depths of
the wells introduce comparative problems into data interpretation. This is due to different
forces operating at the different depths and having only short-term results for the more
recent wells. The following discussion looks at the volatile organic compounds found in
these Valley wells as represented in the HAFB database.
C.1.5.4.3. Comment #3 (cont). Table 2 provides a comparison of the VOCs found in the shallow
and deep wells. Of the 18 compounds found, 10 have been found in the deep wells and 18
in the shallow wells. This shows that contamination from OU1 does occur in the deeper
part of the off-Base aquifer. This could be occurring due to (1) these wells being installed
through the silty/clay layer and picking up contamination that is moving down through
this layer beneath OU1 of (2) due to the downward hydraulic gradient that is carrying
contaminants down into the deeper aquifers from the shallow off-Base zone of
contamination. This question has not been addressed to date.
C.I.5.4.4. Comment #3 (cont). Table 3 shows the pattern of contamination by VOCs as a
function of location north across the Valley from the Davis-Weber Canal to South Weber
Drive. At the wells located nearer OU1 (Davis Weber Canal), 10 VOCs were detected. At the
Bambrough Canal well locations further north, 16 VOCs have been detected and at mid-
Valley and South Weber Drive locations still further north, 13 compounds have been
detected. The detection of fewer compounds nearer OU1 (the source) at first appears to be
illogical. However, this may be due to the fact that these are also the deep wells which may
be subject to potential differences in migration pathways from OU1 (i.e. through the silty
clay layer rather than along the landslide interface on the hillslope). The lower number of
compounds detected in locations further north (mid-Valley and South Weber Drive) as
compared to locations at the Bambrough Canal could be indicative of less pollution
reaching the locations further from OU1 or, it could be that sufficient time has not elapsed
for all the migrating compounds to reach these more distant locations. For example,
ethylbenzene and vinyl chloride have been found in the wells adjacent to the Bambrough
Canal, but not at mid-Valley wells or those nearer South Weber Drive. There are anomalies
in the data as well, whereby some compounds such as acetone and xylene have appeared in
wells further from the Source Areas, but not in those at the closer locations. Some, such as
benzene and 1,2-Dichloroethane appear to have been missed in the mid-Valley locations
while being present in wells at the Bambrough Canal and at South Weber Drive.
TABLE 2. SUMMARY OF VALLEY MONITORING WELL GEOLOGY
Volatile Organic Compounds
1,1,1 -Trichloroethane
1,1-Dichloroethane
1,2-Dichloroethane
1,1-Dichloroethene
Acetone
Deep
1
3
2
Shallow
7
8
2
1
4
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OPERABLE UNIT 1 RECORD OF DECISION APPENDIX C
Benzene
Bromodichloromethane
Chloroform
Dibromochloromethane
Ethylbenzene
Methylene Chloride
Tetrachloroethylene
Toluene
Total 1 ,2-Dichlorothene
Trichloroethylene
Trichlorofluoromethane
Vinyl Chloride
Xylenes
Totals
1
3
5
4
4
2
1
10
2
5
7
2
1
12
3
9
10
9
6
1
1
18
C.1.5.4.5. Comment #3 (cont.). A chronology of occurrence of the different VOCs found in these
Valley wells is shown in Table 4. This is quite interesting in that it documents that an
increasing number of compounds have been detected in more recent years. For example in
1990 only three compounds were detected while in 1996,13 compounds were detected. In
fact, in the 1995-1996 monitoring period, six compounds were detected that had not
previously been found, including benzene and vinyl chloride, both known human
carcinogens.
C.1.5.4.6. Comment #3 (cont.). The HAFB database was used to generate plots of each VOC
compound and its concentration over time in the Valley wells. Only VOCs with three or
more data points and those found in 1996 (the most recent data) were included. Tables
showing the maximum annual VOC concentrations for each well and the plots are included
in the Appendix. The following discussion does not address each well and each
contaminant, but focuses on general patterns using specific examples. A review of the plots
shows that in most cases, the contaminant concentrations are cycling over a range more or
less on an annual basis. While many of these appear to indicate a downward trend over
time, it must be recognized that in some cases they are cycling over a narrow range. For
example, the plots for Well Ul-090 show Total DCE to be higher in 1996 than in 1990. If the
single data point for 1990 were removed, however, one could not argue that it has increased
over time. Trichloroethylene in the same well appears to decline over time, but is it
declining or merely cycling over a very narrow range of concentrations (2.6 - 3.8 ug/1)? It
could be that these concentrations reflect variations in annual groundwater flows/levels in
response to precipitation patterns rather than reflecting contaminant containment by on-
Base caps and extraction wells. Another example from well Ul-097 indicates that Total DCE
has declined from 130 ug/1 to values at or near zero in recent years (note: the graph did not
include the 1990 Total DCE concentration of 130 ug/1). However, in the same well,
chloroform first appeared in 1995 and has increased since that time. In well Ul-099,
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OPERABLE UNIT 1 RECORD OF DECISION APPENDIX C
1,1-Dichloroethane and Total DCE have both increased over time, with highest values
found in 1996 (our most recent data).
C.1.5.4.7. Comment #3 (cont.). These, as well as most of the monitoring results are following a
cyclic pattern which can have low values for a time and then suddenly increase or the
converse can be true. While HAFB has indicated that the concentrations are trending down,
upon close scrutiny it is not so obvious this is a true statement. In many cases, the
elimination of a single data point can change the entire apparent trend in a plot. Many
compounds have only appeared recently and most of the deep wells have only been
installed and sampled since 1995. These two factors make any statement about the lessening
of contamination premature, especially based on a single compound, Total 1,2-
Dichloroethene.
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OPERABLE UNIT 1 RECORD OF DECISION APPENDIX C
TABLE 3. OCCURRENCE OF VOCS ACROSS THE WEBER RIVER VALLEY SOUTH TO NORTH
Volatile Organic Compounds
1,1,1 -Trichloroethane
1,1-Dichloroethane
1,2-Dichloroethane
1,1-Dichloroethane
Acetone
Benzene
Bromodichloromethane
Chloroform
Dibromochloromethane
Ethylbenzene
Methylene Chloride
Tetrachloroethylene
Toluene
Total 1,2-Dichlorothene
Trichloroethylene
Trichlorofluoromethane
Vinyl Chloride
Xylenes
Totals
DW Canal
X
X
X
X
X
X
X
X
X
X
10
B Canal
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
16
Mid Valley
X
X
X
X
X
X
X
X
X
X
X
X
X
13
SW Drive
X
X
X
X
X
X
X
X
X
X
X
X
X
13
C.1.5.4.8. Response to Comment #3. As part of the data analysis performed for the Feasibility
Study, all monitoring wells, piezometers, or other exploration points where a groundwater
sample was obtained were divided into groups based on the depth of water-bearing zone
the sample was obtained from. The data used in this analysis were obtained from numerous
previous investigations performed at OU1. This data showed numerous confined water-
bearing zones exist below the shallow unconfined water-bearing zone. Contamination
levels in the various water-bearing zones also show substantial differences. Additional
work was performed as part of the groundwater pre-design investigation to further define
the various water-bearing zones. In the off-Base areas, the shallow groundwater is
contaminated. The shallow water-bearing zone is located at an elevation of approximately
4,475 to 4,465 feet above mean sea level (MSL). The highest levels of off-Base contamination
are found in this water-bearing zone. A second layer water bearing zone was identified at
an elevation of approximately 4,445 to 4,430 feet above mean sea level (MSL). This
water-bearing zone is also contaminated, although the contamination levels are lower than
the shallow water-bearing zone. A third water-bearing zone has also been identified at an
elevation of approximately 4,420 to 4,400 feet above MSL This water-bearing zone does not
appear to be contaminated. Other non-contaminated water-bearing zones are also found
below the third water-bearing zone. The elevation of these water-bearing zones correlate
with the elevations of the water-bearing zones observed in the monitoring wells adjacent to
South Weber No. 2. Another explanation for the higher concentrations of contamination
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closer to the OU1 source areas may be related to the natural attenuation of the
contamination. These contamination levels in these zones are consistent with contamination
levels identified in the Feasibility Study.
C.1.5.4.9. Response to Comment #3 (cont.). The greater number of contaminants observed in
later periods may be related more to the additional number of monitoring wells and slight
differences in analytical methods. A majority of the later samples were analyzed using EPA
Method SW846-8260. This method generally reports a larger number of compounds than
reported with the previously used methods, such as EPA Method E625 and SW846-8240. In
addition, some of the compounds presented in Table 2, such as Bromodichloromethane,
Dibromochloromethane, Methylene Chloride, and Trichlorofluoromethane are considered
lab surrogates and not considered site contamination. The data validation summary reports
from the various groundwater sampling rounds at OU1 can be referenced for the surrogates
used by the analytical laboratory.
C.1.5.4.10. Response to Comment #3 (cont.). As shown in the graphs provided by the SWLC, the
contamination trends are generally downward. Some contamination graphs do show an
upward trend. Considering the source areas have not been cut-off to date and
contamination can flow from on-Base source areas to the Weber River Valley, a general
downward contamination level trend provides further evidence that natural attenuation is
occurring. Further reduction in contamination levels may not occur until the source of
contamination is cut-off. Hill Air Force Base expects to observe a downward contamination
level trend after the source of contamination is cut-off. Many of the contamination levels in
the attached graphs are near detection limits and are estimated values. The use of
contamination levels below detection limits for trend analysis may not have the accuracy
necessary for this type of analysis. The Baseline Concentration Report (MW, 1998) also
contains an analysis of contamination trends.
C.1.6 Comments by Brent Poll, South Weber Landfill Coalition
C.1.6.0.1. Comment #1. HAFB's proposed plan, reached after $30.5 million and several decades
spent studying OU1, coincides exactly with the Base's initial projections made long before
these expenditures were made; i.e., any pollution leaving HAFB was restricted to the
shallow ground water so any risks associated with it were likewise restricted to those
relatively foolish few who chose to drink or shower with it. The exactness of these before
and after stances could show inordinate insightfulness if both were factually accurate.
However, we in the SWLC strongly disagree with Hill's conclusions and have conveyed the
specific reasons for our disagreements to the appropriate officials throughout the course of
Hill's efforts.
C.1.6.0.2. Response to Comment #1. Based on numerous studies performed at Operable Unit 1,
the risks associated with the groundwater contamination have been identified. The risk
assessment evaluated a number of potential exposure pathways for the off-Base area; but
the only pathways that were found to represent a significant risk are related to the domestic
use of contaminated groundwater. The conclusion that the only risk is to those who shower
and drink the shallow contaminated groundwater is valid. The studies are factually
accurate and have been reviewed by the USEPA and UDEQ.
C.1.6.0.3. Comment #2. Weber Basin's deep-water well #2, located only a few hundred yards
from OU1, was recently found to be contaminated with dozens of the same pollutants
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common to OU1. This well taps an aquifer which provides culinary water for about 250,000
people in Weber and Davis Counties. Hill is the primary suspect in a very short list of
potential polluters of this well (with Weber Basin itself as the other). The SWLC believes
this new development negates reliance on Hill's Final Proposed Plan and potentially
invalidates most of the processes Hill used in formulating it. Other factors reflecting
dubiously on HAFB's very suspect Final Proposed Plan include:
C.1.6.0.4. Comment #2 (cont.). 1. Congress enacted a special exemption in environmental law
which allows Department of Defense (DoD) installations to serve as Lead Agencies in
cleaning up their own pollution. This leadership is a conflict-of-interest comparable to
placing the fox in charge of the henhouse. Private and even other Federal polluters are not
afforded this luxury. One should expect Congress to hold DoD to a higher-than-normal
standard due to its historical misrepresentations relating to the Downwinders affected by
1950s nuclear testing, the thousands of sheep deaths near Dugway, involuntary testing of
radiation on soldiers, Desert Storm biological-weapon releases, etc. Also, at our local level,
HAFB for more than a decade denied that the pollution flowing into South Weber
originated on Base. After later admitting it was the source, Hill continued denying this
pollution was harmful even after learning from health laboratories at Brooks AFB that our
polluted springs were "unfit" for human or animal consumption.
C.1.6.0.5. Comment #2 (cont.). From the above well documented DoD improprieties, one can
conclude that Congress' legislative exception showed a callous disregard for citizens living
adjacent to polluted DoD installations.
C.1.6.0.6. Response to Comment #2. Please refer to response to Comment #1. In addition,
private and other federal polluters are responsible for their own pollution and are required
to clean the pollution up. If the private polluters are not able to clean the pollution up,
regulatory agencies will step in and remediate the pollution using remediation funds set up
for this purpose. The Air Force is the lead government agency responsible for
environmental clean up at HAFB and funds the environmental clean up efforts. The clean
up process for all polluters is regulated by the EPA and the UDEQ. Again, the studies
performed at Operable Unit 1 were reviewed and approved by the USEPA and UDEQ.
With respect to the contamination found in South Weber No. 2, HAFB responded quickly
with an investigation to determine the source of the problem.
C.1.6.0.7. Response to Comment #2 (cont.). The purpose of the Monitoring Well Installation and
Impact Assessment of South Weber No. 2 investigation was to acquire groundwater samples
from the water-bearing zones to evaluate the source of the contamination, assess the
lithology of the soil materials adjacent to South Weber No. 2, and estimate the potential for
OU1 contamination to migrate to the depths of the production zones of South Weber No. 2.
The results of this report indicate the drinking water aquifer has not been contaminated by
HAFB. Contamination, at concentrations similar to levels in adjacent monitoring wells, was
observed in the shallow water-bearing layers. The soils between the surface and drinking
water aquifer were mainly fine-grained. Due to the fine-grained layers, the area
surrounding South Weber No. 2 was not found to be a recharge area. Drinking water
aquifer recharge areas are located at the base of the Wasatch Mountains, approximately
2-miles to the east.
C.1.6.0.8. Comment #3. 2. HAFB could have risen above its conflicted situation and still
delivered analytical studies. Such studies would be predicated on facts and applied logic
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which could withstand scrutiny and serve as a solid premise for future decisions. But Hill
failed to provide this objectivity. Facts tended to contradict initial projections, so they were
replaced by the Base's more abstract assumptions and theories. For example:
C.1.6.0.9. Comment #3 (cent.), a. HAFB, in the early 1980s, theorized there was a convenient
impermeable clay layer underneath the entire mass of OU1 which allowed the Base to
envelop (through addition of surrounding impermeable sides) its pollution on Base. After
failure of its first attempt to envelop the source by 1990, the Base admitted there were holes
in the impermeable clay later, but continued to maintain it was so low in permeability that
it would take "more than a 1000 years" for any possible leakage to reach deep water
aquifers. Hill's theory of low permeability remains an essential component in its Final
Proposed Plan.
C.1.6.0.10. Comment #3 (cont.) However, there is no factual justification for this premise, and
the deep-water well below OU1 is already being polluted with ingredients closely aligned
to those at the OU1 source. Furthermore, studies by Weber Basin (Weston Engineering) at
the well site showed nothing to seriously retard downward migration of the pollution from
the Base. The absence of viable retardation suggests millions of gallons of shallow
groundwater flushed through Hill's OU1 over the last half century, carrying with it massive
amounts of pollution, are still sinking towards the drinking water supply for much of the
Wasatch Front. Unfortunately, Hill's $30.5 million study provides no help in measuring this
deep-water risk as the Base's low permeability theory inaccurately set study parameters at
surface or relatively near-surface levels.
C.1.6.0.11. Response to Comment #3. Again, the studies performed at Operable Unit 1 were
reviewed and approved by the USEPA and UDEQ. Based on numerous exploration points
that have been drilled to investigate OU1, clay layers exist throughout the on-and off-Base
areas. The Remedial Investigation, Feasibility Study, and numerous other investigation reports
describe the nature and extent of the clay layers. The recent installation of a series of
monitoring wells adjacent to South Weber No. 2 and the groundwater pre-design report
further described the nature and extent of the clay layers. The results of these reports show
that the clay layers are continuous across the site, and numerous clay layers exist between
the shallow groundwater contamination and the deeper drinking water aquifers. These
reports provide "factual justification" for the presence of the clay layer. In addition, HAFB
is not aware of a "hole in the clay layer". The presence of the clay layers limits the
downward migration of contaminated groundwater. Due to the presence of the clay layers,
the conjecture that "millions of gallons" of contaminated shallow groundwater are flushing
to the drinking water aquifer is inaccurate.
C.1.6.0.12. Comment #4. b. Facts collected by HAFB show absolutely no controls over the types
or amounts of materials dumped at OU1 throughout the 40 year active life of the site.
Witnesses interviewed (to help characterize contents) exclusively by Base personnel
mentioned an extremely wide range of chemicals, "hundreds of drums," a "sea of drums,"
tanks of various description, etc. For many years, the location was restricted for radiation
danger. Questions remain whether the munitions from Ogden Arsenal were included with
other disposals from that installation; and if biological and chemical-warfare components
found their way into the dump during the years HAFB had Air-Force-wide responsibility
for those weapon systems.
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C.1.6.0.13. Comment #4 (cont.). Rather than accept into its studies the many factual
uncertainties about the contents of OU1 or excavate it to find out (due to proclaimed risks to
the searchers), HAFB chose to inject more theories and assumptions to downsize the risks
OU1 could represent. It deemed the site equivalent to any standard municipal landfill,
stated "small" amounts of munitions (including radioactive, biological and chemical
materials) "may" be present, discounted the hundreds of drums as "alleged" drums, and
even suggested the Base fire department burned the contents of those drums for training
without analyzation of their respective contents. Hill further dismissed the potential threat
of its pollution by claiming once burned or flushed to the surface on the bluff below the
Base, that the pollution risks were greatly dissipated; hence of no further real concern for
remediation.
C.1.6.0.14. Comment #4 (cont.) Hill also elected not to fully assess the effects of the massive off-
base migration of pollution (down the steep and unstable northern bluff) during the 50
years the Base was either denying accountability or conducting studies relating to this final
proposal. Instead, HAFB again theorized that the tremendous amount of polluted water
flowing into the Weber and Davis canal was made harmless by dilution. The remainder
(also massive in quantity) was deemed restricted just to shallow ground water or dissipated
through contact with the open air. In fact, so much has migrated off-base over the past 50
years, it raises yet another unanswered question; i.e., Has most of the OU1 pollution already
left the Base and now exists somewhere beyond the self-limited range of Hill's proposed
$25 million corrective action (closing the barn doors after the horses have already escaped)?
C.1.6.0.15. Response to Comment #4. Hill Air Force Base recently completed the Landfills 3 and
4 Summary Investigation. The investigation focused on evaluating the nature and extent of
landfill debris and groundwater contamination. As part of this investigation, a search for
the drums identified above was conducted. The investigation for the drums consisted of a
geophysical survey and excavation of the landfill debris. Drums containing any kind of
liquid were not observed in the landfill debris. Groundwater samples from areas
throughout the landfills were obtained and sampled for munitions, chemical warfare
degradation products, and radionuclides. The results of this investigation did not provide
information that would change the preferred alternative. The contents of the landfill were
found to contain less contamination than previously thought.
C.1.6.0.16. Response to Comment #4 (cont.). The amount of off-Base migration of contamination
was estimated in the Feasibility Study. Approximately 390 pounds of chlorinated volatile
organic compounds were found to have migrated off-Base.
C.1.6.0.17. Comment #5. c. Hill theorized that the "only exposure scenarios which might result
in unacceptable risks to humans include possible human interaction with on-base soils or
groundwater, and future use of shallow groundwater in the Weber River Valley for
drinking or showering." This is an almost negligible window of risk. One should logically
reason such limited risk, if accurate, does not warrant the $25 million corrective action
proposed by the Base.
C.1.6.0.18. Comment #5 (cont.) However, again the Base has no factual basis for inferring that it
has a finite grasp of the full range of risks its pollution may represent when every other
reliable authority freely admits that science has only scratched the surface in this relatively
new field of study. Another view was expressed by President Clinton, in a recent State of
Union Address, where he voiced concern that no child should live within four miles of a
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toxic site. Demographics show people (children especially) are at risk for skin disorders,
immune system deficiencies, birth defects and a host of other maladies when they live near
toxic sites.
C.1.6.0.19. Comment #5 (cont.) South Weber Elementary is about 400 yards from OU1. Wind
has blown the supposedly "dissipated" dust from polluted areas below OU1 all over this
school and the surrounding neighborhood. Likewise, the smoke from open burns of gases,
chemicals and other materials at OU1 and the fire training area has floated throughout
South Weber for generations. Nevertheless, HAFB ignores these as viable pathways from
the source to our children through ingesrion, inhalation or absorption. Therefore, to trust
HAFB's assessment of risk is to disbelieve the concerns voiced by the President and the vast
majority of the professionals in the field who insist finite risk measurements for pollution
are simply beyond present scientific capabilities. Moreover, recent developments show a
multiplier effect wherein chemicals in combination are many times more hazardous than
the sum of their individual parts. This is particularly troublesome at OU1 where the
possible combinations are almost infinite in view of the multitude of chemicals found there.
C.1.6.0.20. Comment #5 (cont.) For HAFB to claim it alone has somehow transcended modern
science to grasp the "only" risks at its complex OU1 site is without factual foundation and
must not be taken seriously. In fact, none of Hill's repeated self-serving assumptions upon
assumptions can be validated through its own data base.
C.1.6.0.21. Response to Comment #5. The only exposure scenarios which might result in
unacceptable risks to humans include possible human interaction with on-base soils or
groundwater, and future use of shallow groundwater in the Weber River Valley for
drinking or showering. The Comprehensive Environmental Resource, Compensation and
Liability Act and National Contingency Plan regulations require that groundwater be
restored to beneficial use. Restoration of groundwater is a substantial portion of the cost to
remediate contamination at OU1. The projected capital costs and 30-year operation and
maintenance costs and for the source area and non-source areas preferred alternatives are
approximately $5,900,000 and $2,300,000, respectively. This equals a total cost of
approximately $8,200,000.
C.1.6.0.22. Response to Comment #5 (cont.). We agree, there is some uncertainty with the
assessment of risk to humans from pollution just as there are uncertainties in all areas of
science. Again, the studies performed at Operable Unit 1 were in accordance with the
current state of practice and in accordance with guidance from EPA and UDEQ, including
the risk assessment. The studies were also reviewed and approved by the EPA and UDEQ.
In addition, due to uncertainties associated with risk assessment, the risk-based levels
calculated in this type of study tend to be very conservative. With respect the President's
comments, it is believed the comment was in reference to active hazardous waste disposal
sites currently receiving wastes for disposal, rather than sites such as OU1.
C.1.6.0.23. Response to Comment #5 (cont.). The pathway for dust has been evaluated in the risk
assessment and was found to be an inconsequential pathway. The on-base burning of
chemicals and refuse stopped in 1967. South Weber Elementary School was built in 1976
well after the burning of chemicals had stopped. The use of jet fuel for fire training exercises
stopped in 1994. The comment: "the vast majority of the professionals in the field who insist
finite risk measurements for pollution are simply beyond present scientific capabilities" is
unreferenced and is not believed to be representative of risk assessment professionals. As
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stated in the paragraph above, there are uncertainties associated with risk assessment, but
risks can be calculated. Risk assessments are conservative by using large factors of safety for
public health (such as assuming higher water or soil intake) in the calculations. Chemicals
can have a multiplier effect wherein chemicals in combination are many times more
hazardous than the sum of their individual parts. However, chemicals can also have a
neutralizing effect on each other. Very few chemicals are found in the off-Base areas, and
the risks are relatively easily defined. In addition, there is not a current exposure pathway
for on-Base chemicals.
C.1.6.0.24. Response to Comment #5 (cont). Hill Air Force Base is unclear about what is meant
by: "the way we have transcended modem science". Again, the studies performed at
Operable Unit 1 were in accordance with current practice and EPA and UDEQ
requirements including the risk assessment. The studies were also reviewed and approved
by the EPA and UDEQ.
C.1.6.0.25. Comment #6.3. Utah State's Environmental Health Office has been helpful in some
ways to further the studies of pollution on Base. However, this office is well aware of the
current deep-water pollution at SW Well #2, but has not withdrawn its support of HAFB's
plan which only addresses shallow-groundwater issues. State officials reasoned that the
remedial process is on-going, so any deep-water problems could be corrected after Hill's
proposed plan is approved.
C.1.6.0.26. Comment #6 (cont.) We disagree. After almost 20 years of concentrated efforts, a
$30.5 million dollar study, and about $25 million more to implement Hill's proposed plan; it
would be highly implausible that the relatively cursory oversight which follows could
possibly be sufficient to reverse the direction of the huge but incorrect processes which
proceeded it.
C.1.6.0.27. Response to Comment #6. We disagree the process is incorrect. Again, the studies
performed at Operable Unit 1 were reviewed and approved by the USEPA and UDEQ who
agreed with the findings. We assume the reference to Utah State's Environmental Health
Office is the UDEQ. The UDEQ is highly concerned about the contamination in South
Weber No. 2 and is currently reviewing the South Weber No. 2 Monitoring Well Installation
Report (CH2M HILL, 1998b). The UDEQ supports HAFBs's efforts to investigate the cause
of the contamination.
C.1.6.0.28. Response to Comment #6 (cont.). Oversight will be required after the remediation
system is constructed. This oversight will consist of a formal review by the regulatory
agencies and would be performed on a base-wide basis every 5 years. The most current
evaluation is scheduled for 1998. The next evaluation is scheduled for 2003. The evaluation
could be performed sooner if the dewatering trenches are not performing as designed and
are allowing contaminated groundwater to migrate off-Base. The design and construction of
another alternative, such as a slurry wall, could be implemented to limit the migration of
off-Base groundwater contamination. The public will also be informed of the monitoring
results through a report prepared after each monitoring event. The report will include the
results of monitoring events as well as an assessment of the progress of the remediation
effort. The report will be available for public inspection and possibly a condensed version
will be sent to the affected property owners.
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C.1.6.0.29. Comment #7.4. Since South Weber Councilman Reid Stark's death in 1994, neither
the Council nor its Restoration Agency Board (RAB) representatives have regularly
attended RAB meetings or otherwise seriously studied developments concerning OU1. The
SWLC feels Hill has taken advantage of this to spin doctor data and conclusions in its favor
and against the interests of the city's citizens.
C.1.6.0.30. Response to Comment #7. Hill Air Force Base sponsors the RAB to keep members of
public and local governmental agencies informed of remediation efforts of HAFB. Hill Air
Force Base also meets with local city governments, including the city of South Weber, to
keep the cities apprised of remediation efforts. Meetings with local governments occur on
an as needed basis or every 6 to 12 months per the HAFB Community Relations Plan.
Participation in the RAB is voluntary and HAFB cannot force participation.
C.1.6.0.31. Comment #8. 5. The SWLC also has become more apathetic than issues warrant.
Our only excuse is that pursuit has been difficult and maintaining enthusiasm impossible
when the remedial processes have moved so slowly, and HAFB has remained so firmly
entrenched in its self-serving predispositions. However, we should have done more to
hopefully preclude this project from reaching this stage while still in such a sorry state.
C.1.6.0.32. Response to Comment #8. Hill Air Force Base strongly disagrees that HAFB is
"entrenched in its self-serving predispositions" and "in such a sorry state". Again, the
studies performed at Operable Unit 1 were reviewed and approved by the USEPA and
UDEQ who agreed with the findings. Decisions were based on these studies, not a
predisposition to what the data should be. The data was not modified to reach a conclusion.
C.1.6.0.33. Comment #9. In conclusion, Hill's final proposed plan must not be approved. Since
HAFB certainly cannot be excluded as a cause of the deep-water pollution in Weber Basin's
Well #2, the substance of Hill's plan fails to address the major risks everyone now knows
actually exist. Moreover, the SWLC now believes the Base has proven itself incapable of
objective leadership over the effort to remediate OU1. If Congress must realign its
environmental laws according, then such be instigated soon as too much time has already
been wasted trying to minimize Hill's culpability rather than genuinely remediating the
risks its pollution may pose to the general public.
C.1.6.0.34. Response to Comment #9. Hill Air Force Base has taken steps to investigate the
contamination found in South Weber No. 2 and has met the investigation requirements of
the EPA and UDEQ. The results of this investigation are documented in the Monitoring We//
Installation and Impact Assessment of South Weber No 2 (CH2M HILL, 1998b). The results of
this report indicate that HAFB has not contaminated the drinking water aquifer. We
strongly disagree that we are incapable. The selected remedy is strongly believed to be
protective of human health and the environment as well as be effective in the long-term.
Again, the studies performed at Operable Unit 1 were in accordance with the current state
of practice and in accordance with guidance from EPA and UDEQ, including the risk
assessment. The studies were also reviewed and approved by the EPA and UDEQ. The EPA
and UDEQ provide oversight of the clean up effort in accordance with a Federal Facility
Agreement under CERCLA Section 120.
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C.1.7 Comments by Anonymous #2
C.1.7.0.1. The following comments were received well after the end of the public comment
period. Hill Air Force Base is not legally obligated to respond to the comments, but has
chosen to do so.
C.1.7.0.2. Comment #1. Have people there to tell the truth when asked something not beat
around what we ask.
C.1.7.0.3. Response to Comment #1. Hill Air Force Base is telling the truth and has thoroughly
investigated the site. The studies performed at Operable Unit 1 were in accordance with
EPA and UDEQ requirements, including the risk assessment. The studies were also
reviewed and approved by the EPA and UDEQ. The reports can be found in the
administrative record at the Davis County Library or at HAFB. RAB meetings are a way for
members of the public to receive more information on the status of clean up of Base projects
or to become involved in the process of remediating Base contamination.
C.1.7.0.4. Comment #2. When I was told that Hill AFB was just not going to dump anymore
and let this run its course and check the ground water every so often I became angry. It
needs to be removed before it reaches the river and before it affects other generations of
people. Our animals drink the water we drink the water. We need it cleaned up NOW! Not
6 months or four years. NOW! We bought our home not even knowing we were in this area
3 years ago. Where's our value in our home now! Looks are deceiving its beautiful here in
So. Weber and the deer can't even roam free instead of transferring them last year to
another area they were killed. Fix your fences so they can't get over there or transfer the
deer. Please don't kill them or us. Please clean up the contamination. Please, please, please
for our health, and future generations.
C.1.7.0.5. Response to Comment #2. Groundwater is the mechanism that brings contamination
from the on-Base source areas to the South Weber area. The remediation effort at HAFB will
capture the contaminated groundwater prior to leaving the base. This will allow the off-
Base contamination to attenuate naturally. Cleaning up groundwater is a very difficult
process that takes a considerable length of time. Technologies other than natural
attenuation, such as pumping and treating the groundwater, will only slightly shorten the
remediation period and substantially increase the cost of remediation. Providing the public
does not drink or shower with the contaminated off-base groundwater, there is no risk to
the public. The residents of South Weber only drink water that is from the deep,
uncontaminated drinking water aquifer. The drinking water is regularly tested for harmful
contaminants. Drinking water wells found to be contaminated are shut down, and the
public is not allowed to drink from these wells. Numerous groundwater monitoring wells
are located between the contaminated groundwater and the Weber River. Based on testing
of these monitoring wells, the groundwater contamination has not migrated to the Weber
River. The contamination plume is presently located approximately 2500 feet from the
Weber River. Based on groundwater monitoring over the past 8 years, the plume appears to
be shrinking and is now further away and from the river than in the past. The
Environmental Management Directorate at HAFB does not have any information
concerning the deer.
C.1.7.0.6. Comment #3. If it were a spill at a gas station the Federal government makes them
remove the contamination Immediately I don't feel enough is being done Especially to
property owners who are within the area.
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C.1.7.0.7. Response to Comment #3. The investigations and clean up at Operable Unit 1 have
been performed in accordance with the Comprehensive Environmental Resource,
Compensation and Liability Act process.
C.1.7.0.8. Comment #4.1 think they talk about cleaning up but they are going to let it go until
its in the river.
C.1.7.0.9. Response to Comment #4. Numerous groundwater monitoring wells are located
between the contaminated groundwater and the Weber River. Based on the testing of these
monitoring wells, the groundwater contamination has not migrated to the Weber River.
C.1.7.0.10. Comment #5. They just want us to let it go because it might go away. We are
drinking well water from this area. We are not lab animals that 10 year from now you can
say oh we made a mistake you have cancer and other illnesses but we'll pay you. Money
does improve property and health now. Remove the contamination.
C.1.7.0.11. Response to Comment #5. Providing the public does not drink or shower with the
contaminated off-base groundwater, there is no risk to the public. The residents of South
Weber only drink water from the deep, uncontaminated drinking water aquifer. The
drinking water is regularly tested for harmful contaminants. Drinking water wells that are
found to be contaminated are shut down, and the public is not allowed to drink from these
wells.
C.1.8 Comments by Ms. Fern Heninger
C.1.8.0.1. Comment #1. Disbelieve premise relating to supposed clay bottom. Also question
how much still at source vs. already migrated off-base.
C.1.8.0.2. Response to Comment #1. Based on approximately 925 exploration points drilled or
sampled to investigate OU1, clay layers exist throughout the on-and off-Base areas. The
Remedial Investigation, Feasibility Study, and numerous other investigation reports describe
the nature and extent of the clay layers. The recent installation of a series of monitoring
wells adjacent to South Weber No. 2 and the groundwater pre-design report further
described the nature and extent of the clay layers. The results of these reports have shown
the clay layers are continuous across the site, and numerous clay layers exist between the
shallow groundwater contamination and the deeper drinking water aquifers. These reports
provide "factual justification" for the presence of the clay layer.
C.1.8.0.3. Response to Comment #1 (cont.). There are still substantial amounts of contamination
in the on-Base areas as evidenced by the on-Base LNAPL area and the contamination levels
in the chemical disposal pit areas.
C.1.8.0.4. Comment #2. Hill AFB understates risks and understates equally need for cleanup.
C.1.8.0.5. Response to Comment #2. Based on numerous studies performed at Operable Unit 1,
the risks associated with the groundwater contamination have been identified using
scientifically valid methods. The studies are factually accurate and have been reviewed and
approved by the USEPA and UDEQ. Based on the risks defined in these studies, the method
to remediate OU1 was chosen.
C.1.8.0.6. Comment #3. Too much left to nature and chance. Too little attention to full range of
risks public around OU1 may face.
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C.1.8.0.7. Response to Comment #3. Again, based on numerous studies performed at Operable
Unit 1, the risks associated with the groundwater contamination have been identified using
scientifically valid methods. The studies are factually accurate and have been reviewed and
approved by the USEPA and UDEQ.
C.1.8.0.8. Comment #4. Hill much too self-serving. Hence, not trustworthy.
C.1.8.0.9. Response to Comment #4. The comment is an opinion and requires no further
response.
C.1.8.0.10. Comment #5. Base must acknowledge simple fact that it does not know as much as
it claims about the (1) source, (2) the pathways to those impacted or (3) the risks those
around OU1 face.
C.1.8.0.11. Response to Comment #5. Again, based on numerous studies performed at Operable
Unit 1, the risks associated with the groundwater contamination have been identified using
scientifically valid methods. The studies are factually accurate and have been reviewed and
approved by the USEPA and UDEQ. There are uncertainties in all scientific studies, but risk
assessments are conservative as a result of using large factors of safety for public health
(such as assuming higher water or soil intake) in the calculations.
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OPERABLE UNIT 1 RECORD OF DECISION APPENDIX C
TABLE 3. OCCURRENCE OF VOCS ACROSS THE WEBER RIVER VALLEY SOUTH TO NORTH
Volatile Organic Compounds
1,1,1 -Trichloroethane
1,1-Dichloroethane
1,2-Dichloroethane
1,1-Dichloroethane
Acetone
Benzene
Bromodichloromethane
Chloroform
Dibromochloromethane
Ethylbenzene
Methylene Chloride
Tetrachloroethylene
Toluene
Total 1 ,2-Dichlorothene
Trichloroethylene
Trichlorofluoromethane
Vinyl Chloride
Xylenes
Totals
DW Canal
X
X
X
X
X
X
X
X
X
X
10
B Canal
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
16
Mid Valley
X
X
X
X
X
X
X
X
X
X
X
X
X
13
SW Drive
X
X
X
X
X
X
X
X
X
X
X
X
X
13
C.1.5.4.8. Response to Comment #3. As part of the data analysis performed for the Feasibility
Study, all monitoring wells, piezometers, or other exploration points where a groundwater
sample was obtained were divided into groups based on the depth of water-bearing zone
the sample was obtained from. The data used in this analysis were obtained from numerous
previous investigations performed at OU1. This data showed numerous confined water-
bearing zones exist below the shallow unconfined water-bearing zone. Contamination
levels in the various water-bearing zones also show substantial differences. Additional
work was performed as part of the groundwater pre-design investigation to further define
the various water-bearing zones. In the off-Base areas, the shallow groundwater is
contaminated. The highest levels of off-Base contamination are found in this water-bearing
zone. A second layer water bearing zone was identified approximately 35 to 50 feet below
the ground surface (bgs), at an elevation of approximately 4,445 to 4,430 feet above mean
sea level (MSL). This water-bearing zone is also contaminated, although the contamination
levels are lower than the shallow water-bearing zone. A third water-bearing zone has also
been identified 60 to 80 feet bgs, at an elevation of approximately 4,420 to 4,400 feet above
MSL. This water-bearing zone does not appear to be contaminated. Other non-
contaminated water-bearing zones are also found below the water-bearing zone at 60 to 80
feet bgs. The elevation of these water-bearing zones correlate with the elevations of the
water-bearing zones observed in the monitoring wells adjacent to South Weber No. 2.
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Another explanation for the higher concentrations of contamination closer to the OU1
source areas may be related to the natural attenuation of the contamination.
C.1.5.4.9. Response to Comment #3 (cont.). The greater number of contaminants observed in
later periods may be related more to the additional number of monitoring wells and slight
differences in analytical methods. A majority of the later samples were analyzed using EPA
Method SW846-8260. This method generally reports a larger number of compounds than
reported with the previously used methods, such as EPA Method E625 and SW846-8240. In
addition, some of the compounds presented in Table 2, such as Bromodichloromethane,
Dibromochloromethane, Methylene Chloride, and Trichlorofluoromethane are considered
lab surrogates and not considered site contamination. The data validation summary reports
from the various groundwater sampling rounds at OU1 can be referenced for the surrogates
used by the analytical laboratory.
C.1.5.4.10. Response to Comment #3 (cont.). As shown in the graphs provided by the SWLC, the
contamination trends are generally downward. Some contamination graphs do show an
upward trend. Considering the source areas have not been cut-off to date and
contamination can flow from on-Base source areas to the Weber River Valley, a general
downward contamination level trend provides further evidence that natural attenuation is
occurring. Further reduction in contamination levels may not occur until the source of
contamination is cut-off. Hill Air Force Base expects to observe a downward contamination
level trend after the source of contamination is cut-off. Many of the contamination levels in
the attached graphs are near detection limits and are estimated values. The use of
contamination levels below detection limits for trend analysis may not have the accuracy
necessary for this type of analysis. The Baseline Concentration Report (MW, 1998) also
contains an analysis of contamination trends.
C.1.6 Comments by Brent Poll, South Weber Landfill Coalition
C.1.6.0.1. Comment #1. HAFB's proposed plan, reached after $30.5 million and several decades
spent studying OU1, coincides exactly with the Base's initial projections made long before
these expenditures were made; i.e., any pollution leaving HAFB was restricted to the
shallow ground water so any risks associated with it were likewise restricted to those
relatively foolish few who chose to drink or shower with it. The exactness of these before
and after stances could show inordinate insightfulness if both were factually accurate.
However, we in the SWLC strongly disagree with Hill's conclusions and have conveyed the
specific reasons for our disagreements to the appropriate officials throughout the course of
Hill's efforts.
C.1.6.0.2. Response to Comment #1. Based on numerous studies performed at Operable Unit 1,
the risks associated with the groundwater contamination have been identified. The risk
assessment evaluated a number of potential exposure pathways for the off-Base area; but
the only pathways that were found to represent a significant risk are related to the domestic
use of contaminated groundwater. The conclusion that the only risk is to those who shower
and drink the shallow contaminated groundwater is valid. The studies are factually
accurate and have been reviewed by the USEPA and UDEQ.
C.1.6.0.3. Comment #2. Weber Basin's deep-water well #2, located only a few hundred yards
from OU1, was recently found to be contaminated with dozens of the same pollutants
common to OU1. This well taps an aquifer which provides culinary water for about 250,000
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OPERABLE UNIT 1 RECORD OF DECISION APPENDIX C
people in Weber and Davis Counties. Hill is the primary suspect in a very short list of
potential polluters of this well (with Weber Basin itself as the other). The SWLC believes
this new development negates reliance on Hill's Final Proposed Plan and potentially
invalidates most of the processes Hill used in formulating it. Other factors reflecting
dubiously on HAFB's very suspect Final Proposed Plan include:
C.1.6.0.4. Comment #2 (cont.). 1. Congress enacted a special exemption in environmental law
which allows Department of Defense (DoD) installations to serve as Lead Agencies in
cleaning up their own pollution. This leadership is a conflict-of-interest comparable to
placing the fox in charge of the henhouse. Private and even other Federal polluters are not
afforded this luxury. One should expect Congress to hold DoD to a higher-than-normal
standard due to its historical misrepresentations relating to the Downwinders affected by
1950s nuclear testing, the thousands of sheep deaths near Dugway, involuntary testing of
radiation on soldiers, Desert Storm biological-weapon releases, etc. Also, at our local level,
HAFB for more than a decade denied that the pollution flowing into South Weber
originated on Base. After later admitting it was the source, Hill continued denying this
pollution was harmful even after learning from health laboratories at Brooks AFB that our
polluted springs were "unfit" for human or animal consumption.
C.1.6.0.5. Comment #2 (cont.). From the above well documented DoD improprieties, one can
conclude that Congress' legislative exception showed a callous disregard for citizens living
adjacent to polluted DoD installations.
C.1.6.0.6. Response to Comment #2. Please refer to response to Comment #1. In addition,
private and other federal polluters are responsible for their own pollution and are required
to clean the pollution up. If the private polluters are not able to clean the pollution up,
regulatory agencies will step in and remediate the pollution using remediation funds set up
for this purpose. The Air Force is the lead government agency responsible for
environmental clean up at HAFB and funds the environmental clean up efforts. The clean
up process for all polluters is regulated by the EPA and the UDEQ. Again, the studies
performed at Operable Unit 1 were reviewed and approved by the USEPA and UDEQ.
With respect to the contamination found in South Weber No. 2, HAFB responded quickly
with an investigation to determine the source of the problem.
C.1.6.0.7. Response to Comment #2 (cont.). The purpose of the Monitoring Well Installation and
Impact Assessment of South Weber No. 2 investigation was to acquire groundwater samples
from the water-bearing zones to evaluate the source of the contamination, assess the
lithology of the soil materials adjacent to South Weber No. 2, and estimate the potential for
OU1 contamination to migrate to the depths of the production zones of South Weber No. 2.
The results of this report indicate the drinking water aquifer has not been contaminated by
HAFB. Contamination, at concentrations similar to levels in adjacent monitoring wells, was
observed in the shallow water-bearing layers. The soils between the surface and drinking
water aquifer were mainly fine-grained. Due to the fine-grained layers, the area
surrounding South Weber No. 2 was not found to be a recharge area. Drinking water
aquifer recharge areas are located at the base of the Wasatch Mountains, approximately
2-miles to the east.
C.1.6.0.8. Comment #3. 2. HAFB could have risen above its conflicted situation and still
delivered analytical studies. Such studies would be predicated on facts and applied logic
which could withstand scrutiny and serve as a solid premise for future decisions. But Hill
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failed to provide this objectivity. Facts tended to contradict initial projections, so they were
replaced by the Base's more abstract assumptions and theories. For example:
C.1.6.0.9. Comment #3 (cent), a. HAFB, in the early 1980s, theorized there was a convenient
impermeable clay layer underneath the entire mass of OU1 which allowed the Base to
envelop (through addition of surrounding impermeable sides) its pollution on Base. After
failure of its first attempt to envelop the source by 1990, the Base admitted there were holes
in the impermeable clay later, but continued to maintain it was so low in permeability that
it would take "more than a 1000 years" for any possible leakage to reach deep water
aquifers. Hill's theory of low permeability remains an essential component in its Final
Proposed Plan.
C.1.6.0.10. Comment #3 (cont.) However, there is no factual justification for this premise, and
the deep-water well below OU1 is already being polluted with ingredients closely aligned
to those at the OU1 source. Furthermore, studies by Weber Basin (Weston Engineering) at
the well site showed nothing to seriously retard downward migration of the pollution from
the Base. The absence of viable retardation suggests millions of gallons of shallow
groundwater flushed through Hill's OU1 over the last half century, carrying with it massive
amounts of pollution, are still sinking towards the drinking water supply for much of the
Wasatch Front. Unfortunately, Hill's $30.5 million study provides no help in measuring this
deep-water risk as the Base's low permeability theory inaccurately set study parameters at
surface or relatively near-surface levels.
C.1.6.0.11. Response to Comment #3. Again, the studies performed at Operable Unit 1 were
reviewed and approved by the USEPA and UDEQ. Based on numerous exploration points
that have been drilled to investigate OU1, clay layers exist throughout the on-and off-Base
areas. The Remedial Investigation, Feasibility Study, and numerous other investigation reports
describe the nature and extent of the clay layers. The recent installation of a series of
monitoring wells adjacent to South Weber No. 2 and the groundwater pre-design report
further described the nature and extent of the clay layers. The results of these reports show
that the clay layers are continuous across the site, and numerous clay layers exist between
the shallow groundwater contamination and the deeper drinking water aquifers. These
reports provide "factual justification" for the presence of the clay layer. In addition, HAFB
is not aware of a "hole in the clay layer". The presence of the clay layers limits the
downward migration of contaminated groundwater. Due to the presence of the clay layers,
the conjecture that "millions of gallons" of contaminated shallow groundwater are flushing
to the drinking water aquifer is inaccurate.
C.1.6.0.12. Comment #4. b. Facts collected by HAFB show absolutely no controls over the types
or amounts of materials dumped at OU1 throughout the 40 year active life of the site.
Witnesses interviewed (to help characterize contents) exclusively by Base personnel
mentioned an extremely wide range of chemicals, "hundreds of drums," a "sea of drums,"
tanks of various description, etc. For many years, the location was restricted for radiation
danger. Questions remain whether the munitions from Ogden Arsenal were included with
other disposals from that installation; and if biological and chemical-warfare components
found their way into the dump during the years HAFB had Air-Force-wide responsibility
for those weapon systems.
C.1.6.0.13. Comment #4 (cont.). Rather than accept into its studies the many factual
uncertainties about the contents of OU1 or excavate it to find out (due to proclaimed risks to
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the searchers), HAFB chose to inject more theories and assumptions to downsize the risks
OU1 could represent. It deemed the site equivalent to any standard municipal landfill,
stated "small" amounts of munitions (including radioactive, biological and chemical
materials) "may" be present, discounted the hundreds of drums as "alleged" drums, and
even suggested the Base fire department burned the contents of those drums for training
without analyzation of their respective contents. Hill further dismissed the potential threat
of its pollution by claiming once burned or flushed to the surface on the bluff below the
Base, that the pollution risks were greatly dissipated; hence of no further real concern for
remediation.
C.1.6.0.14. Comment #4 (cont.) Hill also elected not to fully assess the effects of the massive off-
base migration of pollution (down the steep and unstable northern bluff) during the 50
years the Base was either denying accountability or conducting studies relating to this final
proposal. Instead, HAFB again theorized that the tremendous amount of polluted water
flowing into the Weber and Davis canal was made harmless by dilution. The remainder
(also massive in quantity) was deemed restricted just to shallow ground water or dissipated
through contact with the open air. In fact, so much has migrated off-base over the past 50
years, it raises yet another unanswered question; i.e., Has most of the OU1 pollution already
left the Base and now exists somewhere beyond the self-limited range of Hill's proposed
$25 million corrective action (closing the barn doors after the horses have already escaped)?
C.1.6.0.15. Response to Comment #4. Hill Air Force Base recently completed the Landfills 3 and
4 Summary Investigation. The investigation focused on evaluating the nature and extent of
landfill debris and groundwater contamination. As part of this investigation, a search for
the drums identified above was conducted. The investigation for the drums consisted of a
geophysical survey and excavation of the landfill debris. Drums containing any kind of
liquid were not observed in the landfill debris. Groundwater samples from areas
throughout the landfills were obtained and sampled for munitions, chemical warfare
degradation products, and radionuclides. The results of this investigation did not provide
information that would change the preferred alternative. The contents of the landfill were
found to contain less contamination than previously thought.
C.1.6.0.16. Response to Comment #4 (cont.). The amount of off-Base migration of contamination
was estimated in the Feasibility Study. Approximately 390 pounds of chlorinated volatile
organic compounds were found to have migrated off-Base.
C.1.6.0.17. Comment #5. c. Hill theorized that the "only exposure scenarios which might result
in unacceptable risks to humans include possible human interaction with on-base soils or
groundwater, and future use of shallow groundwater in the Weber River Valley for
drinking or showering." This is an almost negligible window of risk. One should logically
reason such limited risk, if accurate, does not warrant the $25 million corrective action
proposed by the Base.
C.1.6.0.18. Comment #5 (cont.) However, again the Base has no factual basis for inferring that it
has a finite grasp of the full range of risks its pollution may represent when every other
reliable authority freely admits that science has only scratched the surface in this relatively
new field of study. Another view was expressed by President Clinton, in a recent State of
Union Address, where he voiced concern that no child should live within four miles of a
toxic site. Demographics show people (children especially) are at risk for skin disorders,
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OPERABLE UNIT 1 RECORD OF DECISION APPENDIX C
immune system deficiencies, birth defects and a host of other maladies when they live near
toxic sites.
C.1.6.0.19. Comment #5 (cont.) South Weber Elementary is about 400 yards from OU1. Wind
has blown the supposedly "dissipated" dust from polluted areas below OU1 all over this
school and the surrounding neighborhood. Likewise, the smoke from open burns of gases,
chemicals and other materials at OU1 and the fire training area has floated throughout
South Weber for generations. Nevertheless, HAFB ignores these as viable pathways from
the source to our children through ingestion, inhalation or absorption. Therefore, to trust
HAFB's assessment of risk is to disbelieve the concerns voiced by the President and the vast
majority of the professionals in the field who insist finite risk measurements for pollution
are simply beyond present scientific capabilities. Moreover, recent developments show a
multiplier effect wherein chemicals in combination are many times more hazardous than
the sum of their individual parts. This is particularly troublesome at OU1 where the
possible combinations are almost infinite in view of the multitude of chemicals found there.
C.1.6.0.20. Comment #5 (cont.) For HAFB to claim it alone has somehow transcended modem
science to grasp the "only" risks at its complex OU1 site is without factual foundation and
must not be taken seriously. In fact, none of Hill's repeated self-serving assumptions upon
assumptions can be validated through its own data base.
C.1.6.0.21. Response to Comment #5. The only exposure scenarios which might result in
unacceptable risks to humans include possible human interaction with on-base soils or
groundwater, and future use of shallow groundwater in the Weber River Valley for
drinking or showering. The Comprehensive Environmental Resource, Compensation and
Liability Act and National Contingency Plan regulations require that groundwater be
restored to beneficial use. Restoration of groundwater is a substantial portion of the cost to
remediate contamination at OU1. The projected capital costs and 30-year operation and
maintenance costs and for the source area and non-source areas preferred alternatives are
approximately $5,900,000 and $2,300,000, respectively. This equals a total cost of
approximately $8,200,000.
C.1.6.0.22. Response to Comment #5 (cont.). We agree, there is some uncertainty with the
assessment of risk to humans from pollution just as there are uncertainties in all areas of
science. Again, the studies performed at Operable Unit 1 were in accordance with the
current state of practice and in accordance wi.th guidance from EPA and UDEQ, including
the risk assessment. The studies were also reviewed and approved by the EPA and UDEQ.
In addition, due to uncertainties associated with risk assessment, the risk-based levels
calculated in this type of study tend to be very conservative. With respect the President's
comments, it is believed the comment was in reference to active hazardous waste disposal
sites currently receiving wastes for disposal, rather than sites such as OU1.
C.1.6.0.23. Response to Comment #5 (cont.). The pathway for dust has been evaluated in the risk
assessment and was found to be an inconsequential pathway. The on-base burning of
chemicals and refuse stopped in 1967. South Weber Elementary School was built in 1976
well after the burning of chemicals had stopped. The use of jet fuel for fire training exercises
stopped in 1994. The comment: "the vast majority of the professionals in the field who insist
finite risk measurements for pollution are simply beyond present scientific capabilities" is
unreferenced and is not believed to be representative of risk assessment professionals. As
stated in the paragraph above, there are uncertainties associated with risk assessment, but
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OPERABLE UNIT 1 RECORD OF DECISION APPENDIX C
risks can be calculated. Risk assessments are conservative by using large factors of safety for
public health (such as assuming higher water or soil intake) in the calculations. Chemicals
can have a multiplier effect wherein chemicals in combination are many times more
hazardous than the sum of their individual parts. However, chemicals can also have a
neutralizing effect on each other. Very few chemicals are found in the off-Base areas, and
the risks are relatively easily defined. In addition, there is not a current exposure pathway
for on-Base chemicals.
C.1.6.0.24. Response to Comment #5 (cont). Hill Air Force Base is unclear about what is meant
by: "the way we have transcended modern science". Again, the studies performed at
Operable Unit 1 were in accordance with current practice and EPA and UDEQ
requirements including the risk assessment. The studies were also reviewed and approved
by the EPA and UDEQ.
C.1.6.0.25. Comment #6. 3. Utah State's Environmental Health Office has been helpful in some
ways to further the studies of pollution on Base. However, this office is well aware of the
current deep-water pollution at SW Well #2, but has not withdrawn its support of HAFB's
plan which only addresses shallow-groundwater issues. State officials reasoned that the
remedial process is on-going, so any deep-water problems could be corrected after Hill's
proposed plan is approved.
C.1.6.0.26. Comment #6 (cont.) We disagree. After almost 20 years of concentrated efforts, a
$30.5 million dollar study, and about $25 million more to implement Hill's proposed plan; it
would be highly implausible that the relatively cursory oversight which follows could
possibly be sufficient to reverse the direction of the huge but incorrect processes which
proceeded it.
C.1.6.0.27. Response to Comment #6. We disagree the process is incorrect. Again, the studies
performed at Operable Unit 1 were reviewed and approved by the USEPA and UDEQ who
agreed with the findings. We assume the reference to Utah State's Environmental Health
Office is the UDEQ. The UDEQ is highly concerned about the contamination in South
Weber No. 2 and is currently reviewing the South Weber No. 2 Monitoring Well Installation
Report (CH2M HILL, 1998b). The UDEQ supports HAFBs's efforts to investigate the cause
of the contamination.
C.1.6.0.28. Response to Comment #6 (cont.). Oversight will be required after the remediation
system is constructed. This oversight will consist of a formal review by the regulatory
agencies and would be performed on a base-wide basis every 5 years. The most current
evaluation is scheduled for 1998. The next evaluation is scheduled for 2003. The evaluation
could be performed sooner if the dewatering trenches are not performing as designed and
are allowing contaminated groundwater to migrate off-Base. The design and construction of
another alternative, such as a slurry wall, could be implemented to limit the migration of
off-Base groundwater contamination. The public will also be informed of the monitoring
results through a report prepared after each monitoring event. The report will include the
results of monitoring events as well as an assessment of the progress of the remediation
effort. The report will be available for public inspection and possibly a condensed version
will be sent to the affected property owners.
C.1.6.0.29. Comment #7.4. Since South Weber Councilman Reid Stark's death in 1994, neither
the Council nor its Restoration Agency Board (RAB) representatives have regularly
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attended RAB meetings or otherwise seriously studied developments concerning OU1. The
SWLC feels Hill has taken advantage of this to spin doctor data and conclusions in its favor
and against the interests of the city's citizens.
C.1.6.0.30. Response to Comment #7. Hill Air Force Base sponsors the RAB to keep members of
public and local governmental agencies informed of remediation efforts of HAFB. Hill Air
Force Base also meets with local city governments, including the city of South Weber, to
keep the cities apprised of remediation efforts. Meetings with local governments occur on
an as needed basis or every 6 to 12 months per the HAFB Community Relations Plan.
Participation in the RAB is voluntary and HAFB cannot force participation.
C.1.6.0.31. Comment #8. 5. The SWLC also has become more apathetic than issues warrant.
Our only excuse is that pursuit has been difficult and maintaining enthusiasm impossible
when the remedial processes have moved so slowly, and HAFB has remained so firmly
entrenched in its self-serving predispositions. However, we should have done more to
hopefully preclude this project from reaching this stage while still in such a sorry state.
C.1.6.0.32. Response to Comment #8. Hill Air Force Base strongly disagrees that HAFB is
"entrenched in its self-serving predispositions" and "in such a sorry state". Again, the
studies performed at Operable Unit 1 were reviewed and approved by the USEPA and
UDEQ who agreed with the findings. Decisions were based on these studies, not a
predisposition to what the data should be. The data was not modified to reach a conclusion.
C.1.6.0.33. Comment #9. In conclusion, Hill's final proposed plan must not be approved. Since
HAFB certainly cannot be excluded as a cause of the deep-water pollution in Weber Basin's
Well #2, the substance of Hill's plan fails to address the major risks everyone now knows
actually exist. Moreover, the SWLC now believes the Base has proven itself incapable of
objective leadership over the effort to remediate OU1. If Congress must realign its
environmental laws according, then such be instigated soon as too much time has already
been wasted trying to minimize Hill's culpability rather than genuinely remediating the
risks its pollution may pose to the general public.
C.1.6.0.34. Response to Comment #9. Hill Air Force Base has taken steps to investigate the
contamination found in South Weber No. 2 and has met the investigation requirements of
the EPA and UDEQ. The results of this investigation are documented in the Monitoring Well
Installation and Impact Assessment of South Weber No 2 (CH2M HILL, 1998b). The results of
this report indicate that HAFB has not contaminated the drinking water aquifer. We
strongly disagree that we are incapable. The selected remedy is strongly believed to be
protective of human health and the environment as well as be effective in the long-term.
Again, the studies performed at Operable Unit 1 were in accordance with the current state
of practice and in accordance with guidance from EPA and UDEQ, including the risk
assessment. The studies were also reviewed and approved by the EPA and UDEQ. The EPA
and UDEQ provide oversight of the clean up efforts by an executive order signed by the
President of the United States.
C.1.7 Comments by Anonymous #2
C.1.7.0.1. The following comments were received well after the end of the public comment
period. Hill Air Force Base is not legally obligated to respond to the comments, but has
chosen to do so.
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C.1.7.0.2. Comment #1. Have people there to tell the truth when asked something not beat
around what we ask.
C.1.7.0.3. Response to Comment #1. Hill Air Force Base is telling the truth and has thoroughly
investigated the site. The studies performed at Operable Unit 1 were in accordance with
EPA and UDEQ requirements, including the risk assessment. The studies were also
reviewed and approved by the EPA and UDEQ. The reports can be found in the
administrative record at the Davis County Library or at HAFB. RAB meetings are a way for
members of the public who would like more information on the status of clean up of Base
projects or want to become involved in the process of remediating Base contamination.
C.1.7.0.4. Comment #2. When I was told that Hill AFB was just not going to dump anymore
and let this run its course and check the ground water every so often I became angry. It
needs to be removed before it reaches the river and before it affects other generations of
people. Our animals drink the water we drink the water. We need it cleaned up NOW! Not
6 months or four years. NOW! We bought our home not even knowing we were in this area
3 years ago. Where's our value in our home now! Looks are deceiving its beautiful here in
So. Weber and the deer can't even roam free instead of transferring them last year to
another area they were killed. Fix your fences so they can't get over there or transfer the
deer. Please don't kill them or us. Please clean up the contamination. Please, please, please
for our health, and future generations.
C.1.7.0.5. Response to Comment #2. Groundwater is the mechanism that brings contamination
from the on-Base source areas to the South Weber area. The remediation effort at HAFB will
capture the contaminated groundwater prior to leaving the base. This will allow the off-
Base contamination to attenuate naturally. Cleaning up groundwater is a very difficult
process that takes a considerable length of time. Technologies other than natural
attenuation, such as pumping and treating the groundwater, will only slightly shorten the
remediation period and substantially increase the cost of remediation. Providing the public
does not drink or shower with the contaminated off-base groundwater, there is no risk to
the public. The residents of South Weber only drink water that is from the deep,
uncontaminated drinking water aquifer. The drinking water is regularly tested for harmful
contaminants. Drinking water wells found to be contaminated are shut down, and the
public is not allowed to drink from these wells. Numerous groundwater monitoring wells
are located between the contaminated groundwater and the Weber River. Based on testing
of these monitoring wells, the groundwater contamination has not migrated to the Weber
River. The contamination plume is presently located approximately 2500 feet from the
Weber River. Based on groundwater monitoring over the past 8 years, the plume appears to
be shrinking and is now further away and from the river than in the past. The
Environmental Management Directorate at HAFB does not have any information
concerning the deer.
C.1.7.0.6. Comment #3. If it were a spill at a gas station the Federal government makes them
remove the contamination Immediately I don't feel enough is being done Especially to
property owners who are within the area.
C.1.7.0.7. Response to Comment #3. The investigations and clean up at Operable Unit 1 have
been performed in accordance with the Comprehensive Environmental Resource,
Compensation and Liability Act process.
P:\136064\4.1.3flNAL\flEPOR1\APPENDICES A-B\ROOAPDBC.DOC C-39
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OPERABLE UNIT 1 RECORD OF DECISION APPENDIX C
C.I.7.0.8. Comment #4.1 think they talk about cleaning up but they are going to let it go until
its in the river.
C.1.7.0.9. Response to Comment #4. Numerous groundwater monitoring wells are located
between the contaminated groundwater and the Weber River. Based on the testing of these
monitoring wells, the groundwater contamination has not migrated to the Weber River.
C.1.7.0.10. Comment #5. They just want us to let it go because it might go away. We are
drinking well water from this area. We are not lab animals that 10 year from now you can
say oh we made a mistake you have cancer and other illnesses but we'll pay you. Money
does improve property and health now. Remove the contamination.
C.1.7.0.11. Response to Comment #5. Providing the public does not drink or shower with the
contaminated off-base groundwater, there is no risk to the public. The residents of South
Weber only drink water from the deep, uncontaminated drinking water aquifer. The
drinking water is regularly tested for harmful contaminants. Drinking water wells that are
found to be contaminated are shut down, and the public is not allowed to drink from these
wells.
C.1.8 Comments by Ms. Fern Heninger
C.1.8.0.1. Comment #1. Disbelieve premise relating to supposed clay bottom. Also question
how much still at source vs. already migrated off-base.
C.1.8.0.2. Response to Comment #1. Based on approximately 925 exploration points drilled or
sampled to investigate OU1, clay layers exist throughout the on-and off-Base areas. The
Remedial Investigation, Feasibility Study, and numerous other investigation reports describe
the nature and extent of the clay layers. The recent installation of a series of monitoring
wells adjacent to South Weber No. 2 and the groundwater pre-design report further
described the nature and extent of the clay layers. The results of these reports have shown
the clay layers are continuous across the site, and numerous clay layers exist between the
shallow groundwater contamination and the deeper drinking water aquifers. These reports
provide "factual justification" for the presence of the clay layer.
C.1.8.0.3. Response to Comment #1 (cont.). There are still substantial amounts of contamination
in the on-Base areas as evidenced by the on-Base LNAPL area and the contamination levels
in the chemical disposal pit areas.
C.1.8.0.4. Comment #2. Hill AFB understates risks and understates equally need for cleanup.
C.1.8.0.5. Response to Comment #2. Based on numerous studies performed at Operable Unit 1,
the risks associated with the groundwater contamination have been identified using
scientifically valid methods. The studies are factually accurate and have been reviewed and
approved by the USEPA and UDEQ. Based on the risks defined in these studies, the method
to remediate OU1 was chosen.
C.1.8.0.6. Comment #3. Too much left to nature and chance. Too little attention to full range of
risks public around OU1 may face.
C.1.8.0.7. Response to Comment #3. Again, based on numerous studies performed at Operable
Unit 1, the risks associated with the groundwater contamination have been identified using
P:\136064\4JJJ\FINAUREPORT\APPENDICES A-B\RODAPDBC.DOC C-40
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OPERABLE UNIT 1 RECORD OF DECISION APPENDIX C
scientifically valid methods. The studies are factually accurate and have been reviewed and
approved by the USEPA and UDEQ.
C.I.8.0.8. Comment #4. Hill much too self-serving. Hence, not trustworthy.
C.1.8.0.9. Response to Comment #4. The comment is an opinion and requires no further
response.
C.1.8.0.10. Comment #5. Base must acknowledge simple fact that it does not know as much as
it claims about the (1) source, (2) the pathways to those impacted or (3) the risks those
around OU1 face.
C.1.8.0.11. Response to Comment #5. Again, based on numerous studies performed at Operable
Unit 1, the risks associated with the groundwater contamination have been identified using
scientifically valid methods. The studies are factually accurate and have been reviewed and
approved by the USEPA and UDEQ. There are uncertainties in all scientific studies, but risk
assessments are conservative as a result of using large factors of safety for public health
(such as assuming higher water or soil intake) in the calculations.
P:\136064\4_1_3\FINAL\REPORT\APPENDICES A-B\RODAPDBC.DOC C-41
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Appendix C-2
Copies of Public Comments to the Proposed Plan
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What do you think?
Proposed Remedial Action-page 1 of 2 . Februarys, 1998
Background
A Remedial Action has been proposed by Hill Air Force Base to clean-up groundwater contamination at Operable
Unit 1. The Air Force, Environmental Protection Agency, and Utah Department of Environmental Quality have agreed
that extraction of on-Base contaminated groundwater is desirable. Therefore, Hill AFB has proposed a Remedial
Action, which is outlined in the Proposed Plan for Operable Unit 1 .
According to the Proposed Plan, Hill AFB proposes to construct a series of on-Base groundwater extraction trenches
to remove contaminated groundwater in the Operable Unit 1 Source Areas. The extraction trenches will limit
contaminated groundwater from flowing to off-Base areas or to other areas of the Base. With groundwater flow from
the contamination source areas substantially reduced, the existing groundwater contamination found in off-Base
areas and in on-Base areas, away from the Source Areas, will be allowed to naturally attenuate (degrade). The
extracted groundwater will be treated at the existing Operable Unit 2 treatment facility and discharged into the local
sewer system for further treatment.
A complete description of the Remedial Action is available in the Proposed Plan and Feasibility Study.
Please be sure to fill out these two sheets before you leave tonight. You may leave them in the white box at the
Comment Station. If you wish to fill them out later, you may mail them to the following address:
Mr. Charles Freeman
Environmental Public Affairs Coordinator
00-ALC/EM
7274 Wardleigh Road
Hill AFB, Utah 84056-51 37
Be sure comments are postmarked no later than March 16, 1998.
If you would rather express your comments or concerns verbally, a recorder is present to transcribe what you have to
say.
Printed name (optional): _ A ^>o/J y^o as * / _
Questions (Please mark the appropriate response.)
Source Area
Overall, does Hill's proposal to clean-up the Operable Unit 1 Source Areas meet your expectations and
address your concerns?
Qves QNO IZlNot Sure
If you answered "No" or "Not Sure", please explain: -1^^/
.JLS~- AM
Are you satisfied with the approach being proposed to clean-up the Source Areas?
1 2 (3) 4 5
Very Satisfied Not Satisfied
If you chose 4 or 5, please explain why.
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What do you think?
Proposed Remedial Action-Page 2 of 2 Februarys, 1998
Are you satisfied with the method of treating the extracted groundwater, i.e. using existing facilities at
Operable Unit 2?
1 (2/ 3 4 5
Very Satisfied Not Satisfied
Non-Source Area
Overall, does Hill's proposal to clean-up the Operable Unit 1 Non-Source Areas meet your expectations and
address your concerns?
QYes QNO GttNot Sure
If you answered "No" or "Not Sure", please explain: .^am- T7///?/fe UI\J FcR S
Are you satisfied with the approach being proposed to clean-up the Non-Source Areas?
1 2 (J) 4 5
Very Satisfied Not Satisfied
If you chose 4 or 5, please explain why.
Is there anything else about the proposed Non-Source Area Remedial Action that concerns you?
W/-//VT I 5 Ttt£ PfiofoSfO RFSTRIC.TICM o F
AlVOa.SJ^ BY iT/fg LAMDCW/l/£/? ,
Add'rtional thoughts
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ORIGINAL
PLAN 1 FOR PROPOSED OPERABLE UNIT ONE PLAN
MEETING MINUTES
Held at: South Weber Elementary School
1285 Lester Avenue
South Weber, UT
February 5, 1998
4:30-8:00 p.m.
Reported by:
Tracy A. Covington, RPR
Associated Professional Reporters
(801) 322-3441
A s s o c i A i i-: u P K o I i: s s i o N A i. R i i> <> K r i K s , i..
I \\rsl »r,,.i.l>v.iv
Vill Likrl'iix Uul) «•» III I (80 I ) ».'- J44 I I .lOKOI I <-'.'- 144 »
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February 5th, 1998 7:30 p.m
2
3
4
5
6
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
PROCEEDI N G S
MR. PERKINS: My name is Mark Perkins,
2278 Deer Run Drive. I'm the community
representative on the RAB, R-A-B, Restoration
Advisory Board. My comments are essentially
concerning the source area. And I think that I
would sure like to see the Air Force be a little bit
more aggressive in their treatment of the source
area. I don't think it matters too much what they
do on the non-source area until they get aggressive
on the source area because that will continue to be
polluted until the source area is cleaned up and no
more pollution is flowing from it off and on into
the South Weber.
So Alternative 3 is the proposed
alternative, I would think that at least Alternative
4 which is building the slurry wall would be prudent
and perhaps even further than that. That's it.
(The matter concluded at 8:00 p.m.)
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CERTIFIC ATE
STATE OF UTAH
COUNTY OF DAVIS
I, Tracy A. Covington, Certified Shorthand
Reporter, Registered Professional Reporter, and
Notary Public within and for the County of Davis,
State of Utah do hereby certify:
That the foregoing proceedings were taken
by before me at the time and place set forth herein
and was taken down by me in stenotype and thereafter
transcribed into typewriting under my direction and
supervision;
That the foregoing pages contain a true
and correct transcription of my said stenotype notes
so taken.
In Witness Whereof, I have subscribed my
name this 6th day of February, 1998.
TRACY A. <£*5VINGTON
CERTIFIED SHORTHAND RE
RTER
My Commission Expires:
January 16, 2000
i-
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George F. Schrader
5473 South 850 East
Ogden, Utah 85505-7001
February 13, 1998
Kevin Bourne
OO-ALC/EMR
7274 Wardleigh Rd.
HiUAFB, UT 84056-5137
Subject: Proposed plan For OU1, Comments
In general I do not consider the preferred alternative for OU1 to be adequate. The dewatering
and capping of the landfills does not satisfy the long term goals that I feel should be achieved. As
the Sierra Gub representative on the HAFB Restoration Advisory Board I must consider the long
term restoration of the area for habitation. The length of time necessary to reach these goals as
indicated in the report may be as long as 50 years. The recent information I have had on base
closures indicates that disposal of the land in closed bases has been carried out with great haste in
order save mitigation of hazards over a long time and at great expense. This results in relying on
"Institutional Controls" which seem to have nebulous long term effectiveness.
I am sure no one of likes to consider the closing of Hill, but when considering the length
of time it will take to restore OU1 to usable condition under alternative 3 this may well outlast
the base. In the short term this looks good considering the expense required and reducing the
current hazards to humans. The problem is that even if the base is still here for the next 50 years
the cost of maintaining the caps on the landfills and constant dewatering the could well exceed the
cost of removal I really recommend Alternative 7 because it permanently removes the problem.
As for the recommended non source (off base) alternative, No. 3 I do think that ft is
adequate because the fact that natural attenuation in the area is already apparent and this are
could be considered safe within a reasonable time. This is contingent on preventing further
contamination from the source area. Of course the plume will have to be monitored for a long
time to assure that the required result is achieved.
George F. Schrader
Sierra Club Representative
Hill Air Force Base Restoration Advisory Board
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=; k N V I K O N M f N r A I 4 I V <. I M I R I S C, M > I U 1 I O N S I N (
March 13, 1998
Mr. Kevin Bourne, P E
OO-ALC/EMR
7274 Wardleigh Road, Building 5
Hill Air Force Base, Utah 84056-5127
Re: Final Proposed Plan Operable Unit 1 dated January, 1998
Dear Kevin:
I have previously commented on the Draft and Revised Draft Feasibility Studies See
our letters dated January 27 and July 10, 1997 I reiterate and incorporate those comments
as applicable to the Final Proposed Plan and will not go into detail on each Alternative
During February, I attended the public meeting at the South Weber Elementary School At
that time, 1 was informed that results of additional studies of the landfills and Weber River
Valley were forthcoming I look forward to seeing those studies and their implications to the
residents of South Weber However, this places us and yourselves in an awkward position
of attempting to select or approve remedial alternatives while studies are ongoing As I have
mentioned on numerous occasions, this argues strongly for the implementation of the
proposed interim measures that were outlined in the Engineering Evaluation/Cost Analysis
for Operable Unit 1 (EE/CA 1995) while the full and final characterization of OU1 and its
potential impacts on the residents of South Weber and the ground water are determined I do
not believe this can be brought to a conclusion based on the Final Proposed Plan and Final
Feasibility Study while more information is being gathered that could impact the relevance of
those decisions Therefore, it seems the wise course to follow while this additional
information is collected and evaluated and other data gaps are addressed, is to implement
these proposed interim measures and a real-time monitoring program to provide reassurance
to South Weber that their interests are of concern and that they will be protected from the
contamination that is present now and is continuing to migrate into South Weber while the
investigative process and remedial evaluation continues
I have enclosed a report reviewing the geology and groundwater data for the Weber
River Valley Thus report was prepared to provide an overview for the South Weber Landfill
Coalition to assist them in evaluating proposed plans and programs Another stimulus for this
detailed look at the data was provided by the contamination found in South Weber Well #2,
which showed a relationship between the contamination on-Base and the contaminants found
in the well. The possibility that contaminants from OUI have entered this deep well and that
it appears to lack a protective confining layer raised the level of concern about the possibility
that the deeper Sunset and Delta aquifers may be receiving contaminants from HAFB This
issue has never been fully resolved.
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The summary page at the beginning of the report provides a synopsis of the results of
that review The major conclusions are that the Weber River Valley at South Weber where
contamination presently exists is a recharge zone for the deeper aquifers, that these aquifers
lack a protective confining layer and that contamination from OU1 is likely migrating down
into these aquifers It also concludes that while some contaminants may be declining in some
wells, new contaminants are appearing in the Valley in recent data and the concentrations of
some are increasing. Some of these are more toxic than those previously documented. In
fact, six new compounds have appeared in the 1995-1996 time period The area of the
contamination plume itself appears to remain unchanged, reaching to South Weber Drive
Based on this analysis, the Final Proposed Plan does not provide adequate protection for the
residents of South Weber or the deeper aquifers. Therefore, the use of extraction trenches
in Source Areas and natural attenuation in Source and Non-Source areas must be rejected as
a final solution More specific comments and recommendations follow.
Source Area Preferred Alternative - Dewatering by Extraction Trenches
This method was previously judged unsuitable for OU1 by HAFB in the EE/CA To
quote from page 3 of that document, "A physical barrier is preferred over a hydraulic
barrier because it is a more positive means of containment and it is not as reliant on the
operation of electromechanical equipment (i.e. extraction pumps). If a pump in a gradient
control well were to fail, there would be adequate time to detect and respond to the problem
before any contamination escaped the containment system. This may not be the case with
failure of a pump in an extraction trench. Given that there is a steep slope immediately
downgradienl of the proposed trench location, ground water that migrates through while the
pumps are inoperative could not be recovered. ... The two alternatives using hydraulic
barriers also represented a risk that the resulting drawdown in the water table might allow
the LNAPL to migrate into the clay, potentially making future remediation efforts more
difficult. " Further, from page 4-10 of the EE/CA, it is stated that "Pump failure or poor
pump performance could result in contaminants migrating beyond the trench system. This
is a distinct disadvantage of a hydraulic barrier compared to a physical barrier. Given the
estimated life of the removal action (30 years), it is likely that the pumps will fail at some
point and they will need to be replaced. For this reason, frequent performance monitoring
is critical. "
Modeling results presented in the EE/CA indicated that only 30 of 40 particles
released would be captured. While the design of the system presented in the EE/CA is
different than that in the Final Proposed Plan (1998), it appears that capture efficiency and
reliability poses a significant risk that the Preferred Alternative will not eliminate contaminant
flow into the Weber River Valley and South Weber Non Source Area. It is also of benefit to
mention that the physical barrier proposed in the EE/CA was a slurry wall which is the
physical containment method already used to limit ground water flow into OU1 from the
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South However, as is stated in the EE/CA, "Since the existing slurry wall at the site is not
performing as an effective barrier to ground water flow, there is some concern about the
ability to construct a slurry wall that will meet the performance objectives. The reason for
its limited effectiveness is believed to be related to poor construction quality control, such
that the wall was not properly keyed into the clay. " What was not mentioned in the EE/CA
was the possibility of discontinuities in the silty clay layer that might allow continued
migration of groundwater into OU1 through or beneath the slurry wall. Alternative 4 of the
Proposed Plan, proposed a downgradient cutoff (slurry) wall to "... increase the reliability
of preventing off-site migration by providing a physical barrier to groundwater movement. "
This alternative was not accepted as part of the Preferred Alternative and South Weber is left
without the physical containment that was considered necessary in the EE/CA
Repair and O&M of Landfill Caps and Passive Gas Vent System
Monitoring data for landfill gases presented in the Final Comprehensive Remedial
Investigation (RI 1995) indicated that numerous volatile organic compounds were present
within the landfills including TCE (340 ppb), DCE (52,000 ppb) and Vinyl Chloride (30,000
ppb), among others These are present in the landfill gas and are vented to the atmosphere
Lack of monitoring within the landfills has precluded a definitive analysis of the source(s) of
these compounds. It is not known whether LNAPL or DNAPL is present, or whether
drummed or containerized wastes are present that cannot be remediated by the Preferred
Alternative in the Final Proposed Plan. A consequence of the Preferred Alternative is that
the landfills will be dewatered to varying degrees depending upon the design and operation
of the proposed extraction system and the integrity of the landfill cap Much of the disposal
activity in the landfills resulted in disposed material being present in the upper region of the
landfills above the water table. Lowering the water table will leave more of the landfill
contents above the saturated zone. The lowered or absent infiltration rate obtained by repair
of the landfill cap will preclude water movement through this upper zone where the disposed
material resides The result of this is that, depending upon the state of the contaminants in
the landfills, they may persist long beyond any proposed time estimate for remediation and
reappear once OU1 is deemed closed and monitoring ceases or during failures of the
extraction system.
Environmental Monitoring
No monitoring program description is provided. The type ( groundwater, surface
water, air, soil, soil gas, other), location and frequency of monitoring as well as the
contaminant list being analyzed is critically important to the impacted populations
Depending upon these factors, the populace could be exposed to contaminants for long
periods of time corresponding to the interval between samples or monitoring events
Reliance upon mechanical pumping systems demands daily checks of performance, standby
-------
equipment to bring on-line when problems occur and contingency planning for any
foreseeable problem This has not been presented in the proposed plan The people of South
Weber cannot feel comfortable with monitoring and reporting as it has been conducted in the
past and may be conducted as part of any interim or final solution. The design and
implementation of any monitoring program must allow for detection of known and unknown
contaminants both in air, water and soils The monitoring network must be designed to
provide early warning and be comprehensive enough to address the monitoring gaps I have
repeatedly pointed out The monitoring schedule and reporting must be timely and
disseminated in such a way that residents will be provided current results There must be a
response mechanism that will activate a contingency plan to ensure protection
Institutional Controls
The scope (area, type and duration) of "institutional controls" is not described
Property owners should be informed about the limitations on their use of their property in
order to make informed judgements about the Proposed Plan and Preferred Alternative The
description for Non Source Area Alternative 6 states, "... the use of institutional controls to
prevent changes in land use or use of the groundwater. " This type of control could have
long-term impacts to individual property owners as well as to the Town of South Weber if
enforced. How are institutional controls to be implemented and enforced9 Decades down
the road, how do we obtain assurance that innocent and unaware citizens might not
inadvertently expose themselves to the contaminants through their activities9
Upgraded Seep Collection and Treatment
Under the Preferred Alternative in the Proposed Plan, it is expected that groundwater
transport of contaminants from the OU1 Source Areas will be stopped by the extraction
trench system. In that case, why is a separate collection and treatment system necessary for
seeps? The proposed plan states in the description of Non-Source Area Alternative 3, that
"Restoration time is estimated at 5 to 50 years, with a best estimate of 12 years " This implies
that these seeps are expected to flow for long periods of time. If so, what is the source of
contaminated water that allows this when all contaminated water flowing from the Source
Areas is to be captured under the Preferred Alternative? An additional point here relates to
the statement in the Preferred Alternative "Alternative 3 provides an additional protection
by collecting additional seeps/springs that are contaminated above remedial goals...". An
inspection of Figure 13 for this Alternative shows these seep collection systems lie within and
beyond the Area Exceeding PRGs in groundwater. According to the logic regarding PRGs
presented in the Proposed Plan, it seems strange that a seep collection system is proposed
in an area that doesn't exceed PRGs unless there is a recognition that not all risks are
accounted for, that concentrations could increase or that more active measures need to be
taken
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Excavation of Arsenic-Contaminated Sediments
It is noted from Figure 13 for the Preferred Alternative that four seeps located to the
north and east of LF3 and LF4 contain arsenic-contaminated sediments that are to be
excavated. What is the source of the arsenic? Since seeps arise from groundwater sources,
and there is a lack of soil or groundwater data in this Non-Source Area, what assurance
exists that this is not an indication of much more widespread soil and groundwater
contamination that is being overlooked? The results of soil gas investigations in the Non-
Source Area to the north and east of the landfills that showed significant soil gas
concentrations of Benzene, DCE and Toluene have been repeatedly pointed out to HAFB,
yet the absence of data collection in this area continues to be relied upon as proof of no
contamination or threat to human health This area needs to be addressed more fully in any
final solution
Natural Attenuation Monitoring
In addition to the extraction trenches natural attenuation has been proposed for
remediation of groundwater contamination. It is also proposed as the Preferred Alternative
for Non-Source Areas (the Weber River Valley), where contamination has been documented
in the groundwater. According to the description for Non-Source Alternative 3, "Restoration
time is estimated at 5 to 50 years, with a best estimate of J2 years. " In the Glossary of the
Proposed Plan, Natural Attenuation is "The process whereby contaminant concentrations
are reduced through natural physical, chemical and biological processes. " In the Final
Feasibility Study Report for Operable Unit 1 (January 1998), natural attenuation processes
are listed as biodegradation, dilution and adsorption. Processes that are not listed include
evaporation up through the soil to the ambient environment (air), horizontal movement of
contaminants in groundwater at depths below the shallow monitoring wells currently in place
and downward movement into the deeper Delta and Sunset Aquifers which serve as a water
source for thousands of people The attached report "Review of Off-Base (South Weber)
Groundwater Data" provides sufficient documentation that what is presumed to be natural
attenuation may also include downward migration into deeper zones that are not monitored
The recent appearance of new, previously undetected compounds in Valley monitoring wells,
some of which are more toxic than those previously found shows that reliance on this process
is a risky strategy
Interim Measures and Removal of Source Material
These facts should urge HAFB to proceed with protective interim measures to stop
migration of contaminants both off-Base and within South Weber. These measures include
extraction trenches and physical barriers in the Source Areas of OUl, plume cutoff at the
bottom of the bluff and groundwater extraction and treatment in the plume in South Weber
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Implementation of these interim measures would provide time for HAFB to complete
characterization of the site in sufficient detail to answer the unresolved questions that persist
To conclude that removal is not an acceptable alternative is premature. Since the EE/CA has
admitted that physical containment is more certain of success than mechanical systems, a
more careful consideration of the removal option and its costs and benefits should be made.
This study should consider that there are numerous Operable Units on Base and that a secure
landfill constructed on-site could have very positive benefits in terms of the effectiveness of
cleanup actions and, with cost spread over several Operable Units would be more cost-
effective. In addition, to arrive at a cost estimate and reject the removal alternative at OU1
without a refined volume estimate based on the latest landfill studies, consideration of the
much less expensive transport cost of on-Base disposal, reduced monitoring and treatment
costs and other benefits that may accrue by combining this alternative with other Operable
Units seems not to serve the long-term interests of HAFB or the surrounding communities
and their environment The installation of the previously proposed interim measures would
provide the time necessary for the more careful consideration of this alternative
Yours Truly,
^/0u^. UxCCT~
John Carter
cc Brent Poll (SWLC)
Duane Mortensen (UDEQ)
Rob Stites (EPA)
Scott Paxman, Weber Basin Water Conservancy District
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=^ ENVIRONMENTAL t ENGINEERING SOLUTIONS. INC
Summary
Review of Off-Base (South Weber) Groundwater Data
A review of existing data and literature describing the geology and
groundwater contamination in the Weber River Valley in South Weber was
undertaken in order to evaluate remedial alternatives proposed in the Final
Proposed Plan for Operable Unit 1 (January, 1998). The review showed that
confining layers of impermeable materials (clays, bedrock) needed to isolate
the deeper Sunset and Delta aquifers from contamination are lacking
Further, the literature indicates this area is a recharge zone for the deeper
aquifers that provide groundwater to South Weber and communities further
west. Hydrogeologic data from investigations at OU1 also show that a strong
downward gradient exists in the Valley. This further reinforces that the area
is a recharge zone. Because HAFB has indicated that the plume of
groundwater contamination is shrinking in the Valley and that concentration
trends are downward, an analysis of groundwater monitoring data for the 21
Valley wells was also undertaken. This study indicates that while some
contaminants in some wells may be declining, other contaminants have
appeared in 1995-1996 that were not detected in prior years. Two of these,
benzene and vinyl chloride are known human carcinogens In addition, some
compounds appear to be increasing in concentration. The most recent data
we have seen indicates that nearly all wells have had contamination detected
in the most recent years, therefore to conclude that the plume is shrinking may
be in error. Finally, in evaluating trends of contaminant concentration, plots
were generated for the most recent and complete data. These show that
trends for many compounds appear to be weak or lacking and that many of
them cycle over a range on a yearly basis. Our conclusion is that relying on
natural attenuation and on-Base groundwater extraction lacks certainty, is not
protective of the deeper aquifers and does not provide assurance to South
Weber that more toxic contaminants are not and will not migrate into South
Weber now or in the future. In fact the recent discovery of contamination in
South Weber Well #2, which is 1200' deep and contained numerous
contaminants found in OLJ1, an issue that has not been resolved, further raises
concerns about contamination in the deeper aquifers.
March 11. 1998
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Review of Off-Base (South Weber) Groundwater Data
In order to evaluate the Final Proposed Plan for Operable Unit 1, a thorough understanding
of the status of the groundwater monitoring system and data gathered since 1990 is needed. This
report is intended to provide an analysis of the geology and trends in groundwater contamination in
the Weber River Valley and South Weber based on HAFB data. The focus of this work is
contamination by Volatile Organic Compounds (VOCs)
Monitoring Wells and Valley Geology
During recent efforts to understand the contamination occurring in Weber Basin Water
Conservancy District/South Weber Well #2, a review of well logs for South Weber Well #2 and
HAFB monitoring wells in the Valley indicated that there is no confining layer that will protect deeper
aquifers from contamination. The well log provided by the Weber Basin Water Conservancy District
for Well #2 (attached) showed a lack of confining layers over its total depth of 1200'. A review of
Figure 5-20 (attached) from the Final Comprehensive Remedial Investigation Report for Operable
Unit 1 (1995) shows that the best understanding of Valley geology is that it consists of mostly
permeable formations dominated by sand. Some thin layers of clay and silty clay are shown, but are
discontinuous. A summary of HAFB well logs taken from the Final RJ, Appendix I is provided in
Table 1. This table provide dates of well installation, depth and descriptions of layers of low
permeability formations through which the wells were installed As can be seen, the majority of the
wells do not pass through confining layers. Some wells pass through silty clay layers. Figure 4-3
from the Final RI is attached showing locations and dates of well installation
A review of historical geologic publications including Feth et al1 indicates that the area of the
Weber River Valley near the Wasatch Mountain Front is composed of permeable materials and is a
recharge area for the deeper aquifers, including the Sunset and Delta. The Final RI (page 5-19)
states that there is a strong downward gradient in the shallow aquifer in the off-Base area in the
Weber River Valley. This fits with the interpretation that there are no confining layers in the Weber
River Valley and that the area is a recharge zone for the deeper aquifers that serve South Weber and
areas to the West. Feth et al also point out that the geology is heterogeneous in nature, but that these
permeable gravel layers extend westward to Clearfield. In addition, artesian aquifers exist to the
west, which indicates that a confining layer develops at some point between the mountains and the
Salt Lake. Bolke and Waddell2 state that "The ground-water reservoir in the East Shore area consists
of unconsolidated and semiconsolidated deposits, which range in grain size from clay to boulders
At the base of the Wasatch Range the deposits consist chiefly of coarse-grained delta, alluvial fan,
Feth, J.H., D.A. Barker, L.G. Moore, R.J. Brown and C.E. Veirs. 1966. Lake Bonneville: Geology and
Hydrology of the Weber Delta District, Including Ogden, Utah. Geological Survey Professional Paper 518 U S
Geological Survey.
2Bolke. E.L. and K.M. Waddell. 1972. Ground-Water Conditions in the East Shore Area, Box Elder,
Davis and Weber Counties, Utah. Slate of Utah Department of Natural Resources Technical Publication No. 35
March 11. 1998 2
-------
0 -
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200-
300-
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HILL AIR FORCE BASE
OPERABLE UNIT 1
GENERAL/ZED
g5. CROSS SECTION H-H
FIGURE i-20
-------
HILL AIR FORCE BASE
OPERABLE UNIT 1
SPRING 1995 OFF-BASE AND
REPLACEMENT MONITORING WELL
LOCATION AND SOIL BORING MAP
FIGURE 4-3
-------
and slope-wash deposits; they grade westward into fine-grained but well-sorted lacustrine deposits.
The principal aquifers consists of gravel or gravel and sand in the east half of the area and of sand in
the west half." Feth et al also indicate that the Alpine Formation consists of about 135' of fine-
grained sediments which are like those documented in the higher elevation on-Base portion of OU1.
The Weber River has cut through these deposits to form the Weber River valley, exposing the
coarser, more permeable substrate beneath the Alpine Formation (See attached Figure 5-20).
Table 1. Summary of Valley Monitoring Well Geology
.Well
U 1-090
U 1-094
U1-095
U1-096
U1-097
U1-098
U1-099
U1-105
U1-108
U1-109
U1-110
U1-111
U1-112
U1-113
U1-155
U1-138
U1-151
U1-154
U1-156
U1-152
U1-153
Installed
8/90
9/90
9/90
9/90
9/90
9/90
9/90
12/92
12/92
12/92
12/92
1/93
12/92
12/92
7/95
7/95
7/95
7/95
5/95
7/95
7/95
Depth
122
65
45
47
20
17.5
21
35
25
25
23
17
15
50
87
135
124
33
124
115
128
Screen
si/sa
si/sa
si/sa
si/sa
si/sa
sa/gr
sa/gr/si/cl
si/sa
sa/gr
sa/gr
sa/gr
sa/qr
sa/gr
si/sa
si/sa
si/sa
sa/gr
sa/gr
si/cl
si/sa
si/cl
Confining Layer
Numerous thin silt/clay layers
^Jone
^Jone
^one
^one
slone
Clay w/sand stringers
'Jone
xlone-except thin clay layer at 20'
^Jone-except thin clay layer at 24'
^Jone-except thin clay layer at 20'
^Jone
None
ntermediate layers of silty clay, bottom flowing sand
Silty clay 40-42',45',55-771, rest sand
Silty Clay 6-28', 117-126', rest sand
Silty clay 6-19', 40-42', rest sand/gravel
None
Clay and silt 18-30', remainder sand/some silt
Silty clay 40-43', 92-93', 94' rest sand/silly sand
Silty clay to 54'. 65',82',106-1081,1121 rest sand
Chemical Contamination Trends
In the Final Proposed Plan Operable Unit 1, HAFB states that in Non-Source Areas, i.e the
Weber River Valley/South Weber downslope of the Bambrough Canal, Total 1,2-Dichloroethene
(DCE) concentrations appear to be declining and that the area of the DCE plume has declined from
36 to 20 acres. These observations are used to establish natural attenuation as a preferred mode of
dealing with contamination in the Valley. Natural attenuation is defined in the Final Proposed Plan
as "The process whereby contaminant concentrations are reduced through natural physical, chemical
and biological processes." The Final Feasibility Study Report (January 1998) defines natural
March 11. 1998
-------
attenuation to mean biodegradation, dilution and adsorption In any case, relying on natural
attenuation precludes any active means of remediation of the Valley contamination plume Because
such weight has been placed on the apparent dynamics of DCE in the Valley as justification for
eliminating active remediation measures, EES has also studied the groundwater monitoring data
provided by HAFB which includes data for DCE and other volatile organic compounds (VOCs) from
1990 to 1996. In particular, we have focused on interpreting the occurrence of VOCs in 21
monitoring wells in the Weber River Valley that were installed to monitor contaminant migration off-
Base from OU1
These monitoring wells were installed during three time periods. In 1990, 7 wells were
installed to depths varying from 17.5' to 122' with screened intervals reflecting this overall depth.
Three of these wells are less than 20' in depth, while two penetrate to 42', 1 to 64' and 1 to 119'. In
1992-1993, 7 additional wells were installed. Six of these were shallow, ranging in depth from 5' to
35' A single well was installed to a depth of 50' In 1995, 7 more wells were installed One well was
shallow, going to a depth of 33', while the remainder ranged in depth from 77' to 128' The
differences in ages and depths of the wells introduce comparative problems into data interpretation
This is due to different forces operating at the different depths and having only short-term results for
the more recent wells. The following discussion looks at the volatile organic compounds found in
these Valley wells as represented in the HAPB database.
Table 2 provides a comparison of the VOCs found in the shallow and deep wells. Of the 18
compounds found, 10 have been found in the deep wells and 18 in the shallow wells This shows that
contamination from OU1 does occur in the deeper part of the off-Base aquifer This could be
occurring due to (1) these wells being installed through the silty/clay layer and picking up
contamination that is moving down through this layer beneath OU1 or (2) due to the downward
hydraulic gradient that is carrying contaminants down into the deeper aquifers from the shallow off-
Base zone of contamination. This question has not been addressed to date
Table 3 shows the pattern of contamination by VOCs as a function of location north across
the Valley from the Davis-Weber Canal to South Weber Drive At the wells located nearer OU1
(Davis Weber Canal), 10 VOCs were detected At the Bambrough Canal well locations further
north, 16 VOCs have been detected and at mid-Valley and South Weber Drive locations still further
north, 13 compounds have been detected The detection of fewer compounds nearer OU1 (the
source) at first appears to be illogical However, this may be due to the fact that these are also the
deep wells which may be subject to potential differences in migration pathways from OUl(i.e.
through the silty clay layer rather than along the landslide interface on the hillslope) The lower
number of compounds detected in locations further north (mid-Valley and South Weber Drive) as
compared to locations at the Bambrough Canal could be indicative of less pollution reaching the
locations further from OUl or, it could be that sufficient time has not elapsed for all the migrating
compounds to reach these more distant locations. For example, ethylbenzene and vinyl chloride have
been found in the wells adjacent to the Bambrough Canal, but not at mid-Valley wells or those nearer
South Weber Drive. There are anomalies in the data as well, whereby some compounds such as
acetone and xylene have appeared in wells further from the Source Areas, but not in those at the
closer locations. Some, such as benzene and 1,2-Dichloroethane appear to have been missed in the
March 11. 1998 4
-------
mid-Valley locations while being present in wells at the Bambrough Canal and at South Weber Drive.
Table 2. Comparison of Compounds Found in Deep vs Shallow Wells
Volatile Organic Compounds
1,1,1 -Trichloroethane
1,1-Dichloroethane
1,2-Dichloroethane
1,1-Dichloroethene
Acetone
Benzene
Bromodichloromethane
Chloroform
Dibromochloromethane
Ethylbenzene
Methylene Chloride
Tetrachloroethylene
Toluene
Total 1 ,2-Dichlorothene
Trichloroethylene
Trichlorofluoromethane
Vinyl Chloride
Xylenes
Totals
Deep
1
3
2
1
3
5
4
4
2
1
10
Shallow
7
8
2
1
4
2
5
7
2
1
12
3
9
10
9
6
1
1
18
A chronology of occurrence of the different VOCs found in these Valley wells is shown in
Table 4. This is quite interesting in that it documents that an increasing number of compounds have
been detected in more recent years. For example in 1990 only three compounds were detected while
in 1996, 13 compounds were detected In fact, in the 1995-1996 monitoring period, six compounds
were detected that had not previously been found, including benzene and vinyl chloride, both known
human carcinogens
The HAFB database was used to generate plots of each VOC compound and its concentration
over time in the Valley wells Only VOCs with three or more data points and those found in 1996
(the most recent data) were included Tables showing the maximum annual VOC concentrations for
each well and the plots are included in the Appendix. The following discussion does not address
each well and each contaminant, but focuses on general patterns using specific examples. A review
of the plots shows that in most cases, the contaminant concentrations are cycling over a range more
or less on an annual basis. While many of these appear to indicate a downward trend over time, it
must be recognized that in some cases they are cycling over a narrow range For example, the plots
for Well Ul-090 show Total DCE to be higher in 1996 than in 1990 If the single data point for 1990
were removed, however, one could not argue that it has increased over time. Trichloroethylene in
the same well appears to decline over time, but is it declining or merely cycling over a very narrow
range of concentrations (2.6 - 3.8 ug/1)? It could be that these concentrations reflect variations in
annual groundwater flows/levels in response to precipitation patterns rather than reflecting
contaminant containment by on-Base caps and extraction wells. Another example from well U1-097
March 11, 1998
-------
indicates that Total DCE has declined from 130 ug/1 to values at or near zero in recent years (note:
the graph did not include the 1990 Total DCE concentration of 130 ug/1) However, in the same well,
chloroform first appeared in 1995 and has increased since that time In well U1-099, 1,1-
Dichloroethane and Total DCE have both increased over time, with highest values found in 1996
(our most recent data)
These, as well as most of the monitoring results are following a cyclic pattern which can have
low values for a time and then suddenly increase or the converse can be true. While HAFB has
indicated that concentrations are trending down, upon close scrutiny it is not so obvious this is a true
statement. In many cases, the elimination of a single data point can change the entire apparent trend
in a plot. Many compounds have only appeared recently and most of the deep wells have only been
installed and sampled since 1995. These two factors make any statement about the lessening of
contamination premature, especially based on a single compound, Total 1,2-Dichloroethene.
Table 3. Occurrence of VOCs across the Weber River Valley South to North
Volatile Organic Compounds
1,1.1 -Trichloroethane
1,1-Dichloroethane
1 ,2-Dichloroethane
1 , 1 -Dichloroethene
Acetone
Benzene
3romodichloromethane
Chloroform
Dibromochloromethane
Elhylbenzene
Methylene Chloride
Tetrachloroethylene
Toluene
Total 1 ,2-Dichlorothene
Trichloroethylene
rrichlorofluoromethane
Vinyl Chloride
Xylenes
Totals
OW Canal
X
X
X
X
X
X
X
X
X
X
3
10
B Canal
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
16
Mid Valley
X
X
X
X
X
X
X
X
X
X
X
X
X
13
SW Drive
X
X
X
X
X
X
X
X
X
X
X
X
X
13
March 11. 1998
-------
Table 4. Chronology of Volatile Organic Compounds in Valley Wells
Volatile Organic Compounds
1,1,1 -Trichloroethane
1,1-Dichloroethane
1 ,2-Dichloroethane
1,1-Dichloroethene
Acetone
Benzene
Bromodichloromethane
Chloroform
Dibromochloromethane
Ethylbenzene
Methylene Chloride
Tetrachloroethylene
Toluene
Total 1 ,2-Dichlorothene
frichloroethylene
rrichlorofluoromethane
Vinyl Chloride
Xylenes
Totals
1990
X
X
X
3
1991
0
1992
X
X
X
X
X
X
6
1993
X
X
X
X
X
X
X
X
X
X
X
11
1994
X
X
X
X
X
X
X
X
X
9
1995
X
X
X
X
X
X
X
X
X
X
10
1996
X
X
X
X
X
X
X
X
X
X
X
X
X
13
March 11, 1998
-------
APPENDIX
Tables and Plots of VOCs
in
Valley Wells at South Weber
-------
Wells in S. Weber Valley along Davis-Weber Canal from East to West
Well No | Date In.
U1-153
U1-152
U1-152
U 1-090
U 1-090
U 1-090
U 1-090
U 1-090
U1-090
U1-151
U1-151
U1-151
U1-151
U1-151
U1-138
U1-138
U1-138
U1-138
U1-138
7/95
7/95
7/95
8/90
8/90
8/90
8/90
8/90
8/90
7/95
7/95
7/95
7/95
7/95
7/95
7/95
7/95
7/95
7/95
Depthj ft
128
115
115
122
122
122
122
122
122
124
124
124
124
124
135
135
135
135
135
Contaminant
Toluene
Toluene
Tetrachloroethylene
Toluene
Trichloroethylene
Total 1,2-Dichloroethene
Trichlorofluoromethane
Tetrachloroethylene
Methylene chloride
1 ^1J -Trichloroethane
Trichloroethylene
1,1-Dichloroethane
Total 1 ,2-Dichloroethene
1,1-Dichloroethene
1.1-Dichloroethene
Vinyl chloride
1 , 1 -Dichloroethane
Trichloroethylene
Total 1,2-Dichloroethene
1990
3.4
1991
1992
1.6
3.2
8.6
1993
3.8
11
5.1
1994| 1995
3.5
10
0.11
5.1
3.2
7.9
0.51
28
7.5
572.1
6
6.5
8.5
900
I is3B
O.lff
1.3
0.17
2.9
6.9
1.6
3.5
24
9.1
501 6
2.2
4.9
10
730
Wells in S. Weber Valley along Bambrough Canal from East to West
Well No
U 1-094
U 1-094
U1-094
U1-108
U1-108
U1-108
U1-108
U1-108
U1-108
U1-108
U1-108
U1-108
U1-154
U1-154
U1-154
U1-154
U1-154
U1-154
U1-105
U1-105
U1-105
U1-105
U1-105
U1-105
U1-105
U1-105
U1-105
U1-105
U1-105
U1-105
J1-105
U1-105
U1-155
J1-155
U1-155
J1-155
U1-155
Date In.
9/90
9/90
9/90
12/92
12/92
12/92
12/92
12/92
12/92
12/92
12/92
12/92
7/95
7/95
7/95
7/95
7/95
7/95
12/92
12/92
12/92
12/92
12/92
12/92
12/92
12/92
12/92
12/92
12/92
12/92
12/92
12/92
7/95
7/95
7/95
7/95
7/95
Depth, ft
65
65
65
25
25
25
25
25
25
25
25
25
33
33
33
33
33
33
35
35
35
35
35
35
35
35
35
35
35
35
35
35
87
87
87
87
87
Contaminant
Methylene chloride
Toluene
Trichlorofluoromethane
1,1,1 -Trichloroethane
Bromodichloromethane
Dibromochloromethane
Total 1,2-Dichloroethene
1,1-Dichloroethane
Chloroform
Chloroform
Methylene chloride
Trichlorethylene
Total 1 ,2-Dichloroethene
1,1-Dichloroethane
Chloroform
Tetrachloroethylene
1,1,1 -Trichloroethane
Trichloroethylene
Toluene
Total 1,2-Dichloroethene
Methylene chloride
Ethylbenzene
Benzene
1,2-Dichloroethane
Chloroform
Vinyl chloride
1,1-Dichloroethane
1 1,2-Trichloroethane
1 , 1 -Dichloroethene
Trichlorofluoromethane
1 1,1 -Trichloroethane
Trichlorethylene
Tetrachloroethylene
Toluene
Total 1J2-Oichloroethene
1,1-Oichloroethane
Trichloroethylene
1990
1991
1992
081
1993| 1994
14
3.6
0 41
1500
28
8.3
2.3
17
28
970
34
94
59
8.3
0.31
870
16
1.2
15
930
18
10
5.9
1995
057
9.2
910
18
0.23
1.3
16
18
630
13
2.1
6.3
11
950
13
9.9
2.6
5.6
0.22
72
0.57
1996
0 16
3
I
M
34V
65|
0.071
2.2
11
480
8.1
2.5
1 9
4.4
12
3.9
952
016
33
5.9
1.5
1
12
12
02
0.6
0.89
5.7 :
1.1J
0.131
3m
0.3^!
0.27 1
-------
Wells Mid-Valley between Bambrough Canal and South Weber Drive from East to West
Well No
U 1-095
U 1-095
U 1-095
U1-095
U1-109
U1-109
U1-109
U 1-096
U 1-096
U 1-096
U 1-096
U 1-096
U1-097
U 1-097
J1-097
U 1-097
U 1-097
U 1-097
U 1-097
U1-097
U 1-097
U1-097
U1-097
U 1-098
U 1-098
U 1-098
U 1-098
U 1-098
U 1-098
U 1-098
U 1-098
U 1-098
Date In.
9/90
9/90
9/90
9/90
12/92
12/92
12/92
9/90
9/90
9/90
9/90
9/90
9/90
9/90
9/90
9/90
9/90
9/90
9/90
9/90
9/90
9/90
9/90
9/90
9/90
9/90
9/90
9/90
9/90
9/90
9/90
9/90
Depth, ft
45
45
45
45
25
25
25
47
47
47
47
47
20
20
20
20
20
20
20
20
20
20
20
17.5
17.5
17.5
17.5
17.5
17.5
17.5
17.5
175
Contaminant
Trichlorofluoromethane
Acetone
Methylene chloride
Toluene
Bromodichloromethane
Dibromochloromethane
Chloroform
Total 1,2-Dichloroethene
Methylene chloride
Acetone
Trichlorofluoromethane
Toluene
Acetone
Toluene
Trichlorofluoromethane
Xylenes
Tetrachloroethylene
Bromodichloromethane
Total 1,2-Dichloroethene
Chloroform
Methylene chloride
Trichloroethylene
1 , 1 -Dichloroethane
Toluene
1,1,1 -Trichloroethane
Chloroform
Total 1,2-Dichloroethene
Methylene chloride
Trichlorofluoromethane
1,1 -Dichloroethane
Trichloroethylene
Tetrachloroethylene
1990
130
6.2
1.7
1991
1992
23
0.8
27
26
0.91
98
2.4
1993
4
3.6
041
83
3.6
0.15
0.53
0.97
4.5
1.3
0.71
170
3.8
3
5.5
1994
0.31
1.9
5.1
2.7
0.12
1.6
0.86
230
3
3.7
6.6
1995
0.48
0.23
0.56
0.083
0.1
0.54
0.25
1
0.76
1.3
0.95
180
2.2
0.56
3
4.8
1996
0.086
0071
0.13
0.082
0.14
0.32
1.7
9.1
0.15
0.31
0.85
47
0.64
2.1
1.1
-------
Wells Mid-Valley adjacent to South Weber Drive from East to West
Well No
U1-110
U1-110
U1-110
U1-110
U1-110
U1-111
U1-111
U1-111
U1-111
U1-112
U1-112
U1-112
U1-112
U1-112
U1-112
U1-112
U1-112
U1-112
U1-112
U1-113
U1-113
U1-113
U1-113
U1-113
U1-113
U 1-099
U 1-099
U 1-099
J 1-099
U 1-099
U 1-099
Date In.
12/92
12/92
12/92
12/92
12/92
1/93
1/93
1/93
1/93
12/92
12/92
12/92
12/92
12/92
12/92
12/92
12/92
12/92
12/92
12/92
12/92
12/92
12/92
12/92
12/92
9/90
9/90
9/90
9/90
9/90
9/90
Depth, ft
23
23
23
23
23
17
17
17
17
15
15
15
15
15
15
15
15
15
15
50
50
50
50
50
50
21
21
21
21
21
21
Contaminant
1,1.1 -Trichloroethane
Chloroform
Total 1.2-Dichloroethene
Methylene chloride
Bromodichloromethane
Toluene
Methylene chloride
Chloroform
Bromodichloromethane
Toluene
Trichlorethylene
Chloroform
Total 1,2-Dichloroethene
1 , 1 -Oichloroethane
1,1, 1 -Trichloroethane
Acetone
1,2-Dichloroethane
Methylene chloride
Tetrachloroethylene
Trichlorofluoromethane
1,1 -Oichloroethane
Trichloroethylene
Toluene
Methylene chloride
Total 1,2-Dichloroethene
Methylene chloride
1,1 -Oichloroethane
Toluene
Trichloroethylene
Total 1,2-Oichloroethene
3enzene
1990
1.6
1991
1992
3.7
1993
051
0.85
4
4.1
0.3
S
0 44
4 1
0 14
170
2.8
034
4 4
4.9
021
2.5
018
0.67
18
063
7 7
1994
0.15
047
036
32
033
93
1.9
059
0.12
0.33
063
3.1
14
2.6
0.29
0.12
34
1995
1.3
22
0 56
1 7
0 35
50
0.98
0.49
0.24
058
11
96
1996
032
0059
0 11
i.' '
0 093
1 i
026
^ '
0096
1 6
0 16
0 44
0082
7 4
0 48
0 21
0 '7
J2
J '
-------
Well U1-090
Total 1,2-Dichloroethene
10/25/90 05/25/93 11/12/93 05/11/94 03/09/95 09/21/95 06/05/96
10/20/92 09/13/93 02/16/94 09/09/94 06/23/95 03/18/96
Date
Well U1-090
Trichloroethylene
3.8
3.6
X
O)
3
£3'4
_Q>
5*3.2
0)
o
2.8
$
s
sz
X
\
\
2.6
10/20/92 09/13/93 02/16/94 09/09/94 06/23/95 03/18/96
05/25/93 11/12/93 05/11/94 03/09/95 09/21/95 06/05/96
Date
-------
10
^)
fi -
E
fi
o
O 4 -
!E
O
2 .
0 -
Well U1 -097
Chloroform
•
S
/^
//
//
r
•
x^
/
/
/
/
m
09/19/95 03/06/96 06/13/96
Date
_
0)5
O
I4
CO
o
2. 3
£1
O
Q
RJ
Well U1-097
Total 1,2-Dichloroethene
\
09/14/93 02/04/94 09/07/94 03/06/95 09/19/95 06/13/96
11/11/93 06/15/94 12/09/94 06/20/95 03/06/96
Date
-------
Well U1-098
1 ,1 -Dichloroethane
0)
S2-5
o 2
£
y 1.5
Q
I
^-. 1
0.£
^
^
06/14/93 11/12/93 05/10/94 12/02/94 06/21/95 06/14/96
09/15/93 02/03/94 09/07/94 03/06/95 09/19/95
Date
Well U1-098
Total 1,2-Dichloroethene
250
1*200
c
o
"Jit 150 -
O
O
u
o
(
fO
o
I-
0 -
I
/
\
\
/•
^
i
/
/
«.
\
\
\
\
\
\
• • "•
•
/
i/
)
i
i
\
\
\
\
\
i
S*
^
i
10/20/92 09/15/93 02/03/94 09/07/94 03/06/95 09/19/95 06/14/96
06/14/93 11/12/93 05/10/94 12/02/94 06/21/95 03/22/96
Date
-------
WellU1-09B
1,1,1-Trlchloroe thane
1.4
*
3
.-1.2
«
5 1
• '
e
501
C O.I
£
£o.e
v-
*-
0.2
i
/
/
/
f
/
/
/
\
\
\
\
\
\
\
;
\
\
\
\
— - — •
7
/
/
/
/
/
/
i
\
\
\
\
\
\
\
\
1
,
1
09/15/11 02/03/94 09/07/94 03/08/95 06/14/96
1 1/1 2/93 05/10/94 1 2/02/94 08/2 1/93
Date
Well U1-098
Trichloroethylene
1
V S
c
I4.
V
e
o
2: i
£
K
1
1
1
/
/
f
•
/
/
\
. ...
\
\
\
\
\
\
^
•*«
/
If
r
/
/
\
\
\
\
\
\
\
i
i
^
i
L
1
09/15/9) 02/03/94 09/07/94 03/06/95 09/19/95 06/14/96
11/12/9) OS/10/94 12/02/94 06/21/95 03/22/96
Date
1 •
0 9
— °''
Ol
3
gO.7-
O
S06 •
O
SL
U0.5-
0.4
0.3 •
WellU1-098
Chloroform
•
•
/
/
+
/
/
/
•
\
^N
r
V
V
\
\
\
V
j
/
/
/
/
/ •
/
/
/
/
/
V
X
—
06/14/93 11/12/93 05/10/94 12/02/94 06/21/95
09/15/93 02/03/94 09/07/94 01/06/95 06/14/96
Dale
-------
Well U1-099
1,1-Dichloroethane
0.5
0.45
o
TO 0.4
0)
o
o
S0.35
o
Q
0.3
0.25
02/17/94
05/12/94
Date
07/01/96
Well U1-099
Total 1,2-Dichloroethene
50
40
o> 30
O
Q 20
CM
lio
10/20/92 09/15/93 02717/94 09/09/94 03/10/95 10/02/95 07/01/96
06/08/93 11/15/93 05/12/94 12/09/94 06/22/95 03/22/96
Date
-------
Well U1-105
1,1-Dichloroethane
1
£ .
1.1-Dlchloroeth
•* *fc m *
I
\
\
f
/
/
I
X
t
/
/
1
\
s
^-.
/
/
/
\
\
\
\
\
\
\
\
1
1
1
1
1
06/14/91 11(15/11 05/11/94 03/09/95 09/19/95 06/11/91
09/15/91 02/16/94 09/09/94 06/21/95 03/20/96 07/16/96
Data
Well U1-105
Total 1,2-Dlchloroethene
^
? Knn
tT
c
«
0
£
3
u
5 <0°
ri
0
1-
0
1
/
/
I
\
\
\
a
/
/
/
u^l
,^
s
\
\
\
;i
/
/
i
\
\
\
\
i
•
11/19/33 ' 09/15/93 02/16/94 09/09/94 06/21/95 03/20/96 07/16/96
06/14/43 11/15/93 05/11/94 03/09/95 09/19/95 06/18/96
Dale
Well U1-105
Trlchloroethylene
\
\
A
V
3.5
09115/93 02716/94 09/09194 06/21(95 07/16/96
11/15/93 05/11/94 03/09/95 09/19/95
Date
WellU1-105
Methylene Chloride
\
X
e Chlor
-* K*
» O
Met
-»
O
A
\
\
_\L
06/14/93
09/15/93
11/15/93 02/16/94
Dale
06/21/95
07/16196
-------
Well U1-108
1,1-Dichloroethane
02/01/93 09/15/93 02/07/94 09/09/94 03/09/95 10/03/95 06/14/96
06/14/93 11/12/93 06/15/94 12/02/94 06/22/95 03/19/96
Date
Well U1-108
Total 1,2-Dichloroethene
1
3
OT
c
0}
Q
1600
1400
1200
1000
2. 800
u
Q
I
CN
600
- 400
*•*
o
*- 200
7
z
02/01/93 09/15/93 02707/94 09/09/94 03/09/95 10/03/95 06/14/96
06/14/93 11/12793 06/15/94 12/02/94 06/22795 03/19/96
Date
-------
WellU1-108
1,1.1 -Trie hloroethane
1
•> '"
c
S t
• •
o
o
£
K
\
\
\
\
\
\
\
\
\
\
i
i
/
/
/
1
p
\
\
\
\
\
\
/
S
^ — ••
j
/
/
/
/
/
i
i
\
\
\
\
t
•
/
/
/
/
/
•
\
\
\
\
\
\
\
/
/
02/01/13 11112/13 OS/15/94 12/02/94 06/22/95 06/14/98
09119/91 02/07/94 09109(94 03/09/9! 10/03/95
Date
WelilM-108
Trichloroethylene
s
3 jo
S
">.
C 1«
Trichloroel
* O I
A
1
Y
\
\
\
\
\
02/01(83
V
\
\
/
/
\
\
\
^
/
/
J
1
1
^>^
f
\
\
\
\
I
/
/
/
/
1
\
\
\
\
\
/
/
09/15/93 02/07(94 09/09/94 03/09/95 10/03/95
Data
^
f
•
OS/14/96
2'5 1
2
Chloroform, ug/
o -*
o «J» -• w»
1
WellU1-108
Chloroform
i
/
/
/
/
/
<
,
\
\
V
\
\
\
\
_\
/
/
/
/
V
«
r__J_,
/
/
/
/
1
09(15(93 11(12/93 02/07(94 09/09(94 10(03/95 06/14/96
Date
-------
Chloroform
O)
3
o
05/12/94
06/22/95
09/19/95
Date
03/04/96
06/05/96
Well U1-109
Chloroform
10
. 6
E
£
"o
u.
JO 4
JZ
O
\
2 -
A
I
0 -
01/27/93
02/01/93
06/18/93
Date
06/22/95
07/01/96
-------
WellU1-112
1,1-Dichloroethane
•a
3
C
«
I"
| '
0
1
\
\
\
\
I
I
\
\
\
\
1
/
/
/
f
/
/
\
*— -p
1
\
\
\
\
\
r-—
?=-
\
\
\
^
1
01/19/1) 09/14/9] 02/01)94 09/01/94 03/10/95 07/06/96
05/26/9] 11/11/91 OS/10/94 12/02/94 06/21/95
Dale
5
O)
s
&
C 3 .
>*
01
S2
ja *
2
o
f-
0 •
WellU1-112
Trichloroethylene
i
1
\
\
•
V
\
\
/
/
/
/
t
• — <
\
\
\
J
t. '
—
1 — •
»••• — 1
<,
\
V
. J
1
\
V
—
1
31/29/91 09/14/93 02/01/94 09/06/94 01/10/95 10/02/95 07/06/96
05/26/91 11/11/93 05/10/94 12V02/94 06/21/95 01/16/99
Date
WellU1-112
Total 1,2-Dlchloroethene
c;
Ot
a
c
a
§
y
0
•
01/2
\
\
\
\
9/91
\
^
/
09/14/91
/
/
1 -«
1
\
\
\
X
1
^
^
1
02/01/94 09/06/94 01/10/95 10/02/95 07/06/96
05/76/93 11/11/93 OS/10/94 12/02J94 06/21/93 03/18/96
Dale
WellU1-112
Chloroform
0 15
0.3 •
C
O
= 0.25.
§
O
0
2*~ 02-
C
(J
0.15
0.1
i
-^j
*^
1
/
/
/
/
/
/
/
i
r^- — ^"
\
\
\
\
•
09/14/9] 11/11/91 02/01/94 05/10/94 10/02/95 07/06/96
Date
-------
WellU1-113
1,1-Dlchloroethane
o
C
«•
5
0
E
9
1
X
X
1
/
/
/
I
l^
^,
^
\
\
\
\
X
X
X
X
V
\
\
1
11/11/91 05/10/94 12/02/94 06/21/95
02/01/94 09/01/94 03/06/95 07/01/96
Date
Well U1-113
Total 1,2-Dichloroethene
1 ,2-Dichloroe thane
3 M * t
a
o
t-
8
y
/
/
/
1
{
\
\
\
\
\
\
\
\
1
/
/
•— — .
/
/
1
1
i
\
\
\
y
\
\
L
X
i-
^
\
X
01/25/tl 09/14/91 01/03/94 09/01/94 01/06/95 10/02/95 07/01/96
05/26/91 11/11/91 05/10/94 12/02/94 06/21/95 03/04/96
Dale
Well U1-113
Trichloroethylene
0.6
3
«-055
c
-fi
•C OS
2
5
|
K
0 35
•
•
1
1
1
1
1
I
I
\
-~_7
*=—*—*=
•=~^--
\
\
\
\
\
\
1
/
/
/
/
/
1
\
\
\
^
\
\
\
r- '
I
11/11/93 05/10/94 12/02/94 06/21/95 07/01/96
02/03/94 09/08/94 03/06/95 10/02/95
Date
-------
1000
900
-------
580
_ 560
"5)
3
« 540
u>
£
£ 520 -
k_
o
-C
O en ft .
Q
CM_
T— 4gQ _
15
«-*
o
460 -
440 -
WellU1-151
Total 1,2-Dichloroethene
^
i
/
/
/
/
/
/
/
/
/
/
/
i
•
\
\
\
\
\
\
\
07/24/95 09/21/95 03/19/96 06/12/96
Date
Well U1-151
Trichloroethylene
oa .
B)
3
I »
.C
O)
o
^- 74 .
.2
^:
u
)M
1-
09
\
\
\^
07/24/95 09/21/95 03/19/96 06/12/96
Date
-------
WellU1-154
1,1-Dlchloroethane
3
C
n 10 •
e
O
I .
c I
.a
0
4
\
\
\
\
.\
X
\
\
. M
^^
^^
^
•
07/25/95 10/04(95 06(14/96
Dale
Well U1 -154
1,1,1-Trlchloroethane
7
o>
a
?"«
ra
01
P , .
1.1,1-Trichloi
s* W fc. (
•
V
X
\
X
X
X
X
\
^>
^^
^s^
*^
1
07/25/95 1 0/04/95 06/1 4/96
Date
Well U1-154
Total 1,2-Dichloroethene
a700'
3
tt
-------
Well U1-155
1,1-D|ch!oroethane
1
,,•0.4 •
C
it
S 01
O 0.3
a
c
u
15 0.1
f-
0.1
0
1
k
\
\
\
\
-^
^^
I
07/21/95 10/09/9] 06/19/9*
Data
Well U1-15S
Total 1,2-Dlchloroethene
«>
c «o
«j
t>
0
•f- ift •
0 ««
Q
CN
3
h-
0
I
I
\
\
\
>
• •
07/J1/95 10/09/95 03/19/96 OS/U/96
Date
0.3
0.25
_ 0.2
Ol
3
C 0.15 •
01
3
O
H 0.1-
0.05 -
0
1
Well U1 -155
Toluene
^*
^^
^^
r^
\
^-^
\^
"\.
°7'21'95 10/09/95 06/18/96
Dale
-------
South Weber Landfill Coalition
rustees ^X" "S. Technical Advisor:
Lynn^011 --""^ -xC^IJB—«^ —_\. Dr. John Carter
Fern Heninger
Brent Poll
~~ -„'.^
"28"Jan 1998
Kevin Bourne
00-ALC/EMR
7274 Wardleigh Road
Hill AFB, Utah 84056-5137
Re: Final Proposed Plan
OU1
Dear Kevin,
This is the first of two responses from the South Weber Landfill
Coalition (SWLC) regarding the subject plan; and a request for a
30-day extension to your 14 Feb 98 deadline allowing our Technical
Advisor (Dr. John Carter) sufficient time to fully compare it with
your 14 Jan 98 release of the final OU1 Feasibility Study.
HAFB's proposed plan, reached after $30.5 million and several
decades spent studying OU1 , coincides exactly with the Base's
initial projections made long before these expenditures were made;
i.e., any pollution leaving HAFB was restricted to the shallow
ground water so any risks associated with it were likewise
restricted to those relatively foolish few who chose to drink or
shower with it. The exactness of these before and after stances
could show inordinate insightfulness if both were factually
accurate. However, we in the SWLC strongly disagree with Hill's
conclusions and have conveyed the specific reasons for our
disagreements to the appropriate officials throughout the course
of Hill's efforts.
Weber Basin's deep-water well #2, located only a few hundred yards
from OU1, was recently found to be contaminated with dozens of the
same pollutants common to OU1 . This well taps an aquifer which
provides culinary water for about 250,000 people in Weber and Davis
Counties. Hill is the primary suspect in a very short list of
potential polluters of this well (with Weber Basin itself as the
other). The SWLC believes this new development negates reliance
on Hill's Final Proposed Plan and potentially invalidates most of
the processes Hill used in formulating it. Other factors
reflecting dubiously on HAFB's very suspect final proposal include:
(1) Congress enacted a special exception in environmental law
which allows Department of Defense (DoD) installations to serve
as Lead Agencies in cleaning up their own pollution. This
leadership is a conflict-of-interest comparable to placing the
fox in charge of the henhouse. Private and even other Federal
polluters are not afforded this luxury. One should expect
1
SWLC • 1375 E. 7605 S. • So. Weber, Utah 84405
-------
Congress to hold DoD to a higher-than-normal standard due to
its historical misrepresentations relating to the Downwinders
affected by 1950s nuclear testing, the thousands of sheep
deaths near Dugway, involuntary testing of radiation on
soldiers, Desert Storm biol ogical-weapon releases, etc. Also,
at our local level, HAFB for more than a decade denied that the
pollution flowing into South Weber originated on Base. After-
later admitting it was the source, Hill continued denying this
pollution was harmful even after learning from health
laboratories at Brooks AFB that our polluted springs were
"unfit" for human or animal consumption.
From the above well documented DoD improprieties, one can
conclude that Congress' legislative exception showed a callous
disregard for citizens living adjacent to polluted DoD
installations.
(2) HAFB could have risen above its conflicted situation and
still delivered analytical studies. Such studies would be
predicated on facts and applied logic which could withstand
scrutiny and serve as a solid premise for future decisions.
But Hill failed to provide this objectivity. Facts tended to
contradict initial projections, so they were replaced by the
Base's more abstract assumptions and theories. For example:
(a) HAFB, in the early 1980s, theorized there was a
convenient impermeable clay layer underneath the entire mass
of OU1 which allowed the Base to envelop (through addition
of surrounding impermeable sides) its pollution on Base.
After failure of its first attempt to envelop the source by
1990, the Base admitted there were holes in the impermeable
clay layer, but continued to maintain it was so low in
permeability that it would take "more than a 1000 years" for
any possible leakage to reach deep water aquifers. Hill's
theory of low permeability remains an essential component
in its final proposed plan.
However, there is no factual justification for this premise,
and the deep-water well below OU1 is already being polluted
with ingredients closely aligned to those at the OU1 source.
Furthermore, studies by Weber Basin (Weston Engineering) at
the well site showed nothing to seriously retard downward
migration of the pollution from the Base. The absence of
viable retardation suggests millions of gallons of shallow
ground water flushed through Hill's OU1 over the last half
century, carrying with it massive amounts of pollution, are
still sinking towards the drinking water supply for much of
the Wasatch Front. Unfortunately, Hill's $30.5 million
study provides no help in measuring this deep-water risk as
the Base's low-permeability theory inaccurately set study
parameters at surface or relatively near-surface levels.
-------
(b) Facts collected by HAFB show absolutely no controls over
the types or amounts of materials dumped at OU1 throughout
the 40 year active life of the site. Witnesses interviewed
(to help characterize contents) exclusively by Base
personnel mentioned an extremely wide range of chemicals.
"hundreds of drums," a "sea of drums." tanks of various
description, etc. For many years, the location was
restricted for radiation danger. Questions remain whether
the munitions from Ogden Arsenal were included with other
disposals from that installation; and if biological and
chemical-warfare components found their way into the dump
during the years HAFB had Air-Force-wide responsibility for
those weapon systems.
Rather than accept into its studies the many factual
uncertainties about the contents of OU1 or excavate it to
find out (due to proclaimed risks to the searchers), HAFB
chose to inject more theories and assumptions to downsize
the risks OU1 could represent. It deemed the site
equivalent to any standard municipal landfill, stated
"small" amounts of munitions (including radioactive,
biological and chemical materials) "may" be present.
discounted the hundreds of drums as "alleged" drums, and
even suggested the Base fire department burned the contents
of those drums for training without analyzation of their
respective contents. Hill further dismissed the potential
threat of its pollution by claiming once burned or flushed
to the surface on the bluff below the Base, that the
pollution risks were greatly dissipated; hence of no further
real concern for remediation.
Hill also elected not to fully assess the effects of the
massive off-base migration of pollution (down the steep and
unstable northern bluff) during the 50 years the Base was
either denying accountability or conducting studies relating
to this final proposal. Instead, HAFB again theorized that
the tremendous amount of polluted water flowing into the
Weber and Davis canal was made harmless by delution. The
remainder (also massive in quantity) was deemed restricted
just to shallow ground water or dissipated through contact
with the open air. In fact, so much has migrated off-base
over the past 50 years, it raises yet another unanswered
question; i.e., Has most of the OU1 pollution already left
the Base and now exists somewhere beyond the self-limited
range of Hill's proposed $25 million corrective action
(closing the barn doors after the horses have already
escaped)?
(c) Hill theorized that the "only exposure scenarios which
might result in unacceptable risks to humans include
possible human interaction with on-base soils or ground-
-------
water, and future use of shallow groundwater in the Weber
River Valley for drinking or showering." This is an almost
negligible window of risk. One should logically reason such
limited risk, if accurate, does not warrant the $25 million
corrective action proposed by the Base.
However, again the Base has no factual basis for inferring
that it has a finite grasp of the full range of risks its
pollution may represent when every other reliable authority
freely admits that science has only scratched the surface
in this relatively new field of study. Another view was
expressed by President Clinton, in a recent State of Union
Address, where he voiced concern that no child should live
within four miles of a toxic site. Demographics show people
(children especially) are at risk for skin disorders, immune
system deficiencies, birth defects and a host of other
maladies when they live near toxic sites.
South Weber Elementary is about 400 yards from OU1. Wind
has blown the supposedly "dissipated" dust from polluted
areas below OU1 all over this school and the surrounding
neighborhood. Likewise, the smoke from open burns of gases,
chemicals and other materials at OU1 and the fire training
area has floated throughout South Weber for generations.
Nevertheless, HAFB ignores these as viable pathways from the
source to our children through ingestion, inhalation or
absorption. Therefore, to trust HAFB's assessment of risk
is to disbelieve the concerns voiced by the President and
the vast majority of the professionals in the field who
insist finite risk measurements for pollution are simply
beyond present scientific capabilities. Moreover, recent
developments show a multiplier effect wherein chemicals in
combination are many times more hazardous than the sum of
their individual parts. This is particularly troublesome
at OU1 where the possible combinations are almost infinite
in view of the multitude of chemicals found there.
For HAFB to claim it alone has somehow transcended modern
science to grasp the "only" risks at its complex OU1 site
is without factual foundation and must not be taken
seriously. In fact, none of Hill's repeated self-serving
assumptions upon assumptions can be validated through its
own data base.
3. Utah State's Environmental Health Office has been helpful
in some ways , to further the studies of pollution on Base.
However, this office is well aware of current deep-water
pollution at SW Well *2, but has not withdrawn its support of
HAFB's plan which only addresses shallow-groundwater issues.
State officials reasoned that the remedial process is on-going,
so any deep-water problems could be corrected after Hill's
-------
proposed plan is approved.
We disagree. After almost 20 years of concentrated efforts.
a $30.5 million dollar study, and about $25 million more tc
implement Hill's proposed plan; it would be highly implausible
that the relatively cursory oversight which follows could
oossibly be sufficient to reverse the direction of the hugf-
but incorrect processes which proceeded it.
4. Since South Weber Councilman Reid Stark's death in 1994,
neither the Council nor its Restoration Advisory Board (RAB)
representatives have regularly attended RAB meetings or
otherwise seriously studied developments concerning OU1. The
SWLC feels Hill has taken advantage of this to soin doctor data
and conclusions in its favor and against the interests of the
city's ci ti zens.
5. The SWLC also has become more apathetic than issues
warrant. Our only excuse is that pursuit has been difficult
and maintaining enthusiasm impossible when the remedial
processes have moved so slowly, and HAFB has remained so firmly
entrenched in its self-serving predispositions. However, we
should have done more to hopefully preclude this project from
reaching this stage while still in such a sorry state.
In conclusion, Hill's final proposed plan must not be approved.
Since HAFB certainly cannot be excluded as a cause of the deep-
water pollution in Weber Basin's Well #2, the substance of Hill's
plan fails to address the major risks everyone now knows actually
exist. Moreover, the SWLC now believes the Base has proven itself
incapable of objective leadership over the effort to remediate OU1.
If Congress must realign its environmental laws according, then
such be instigated soon as too much time has already been wasted
trying to minimize Hill's culpability rather than genuinely
remediating the risks its pollution may pose to the general public.
Please call if you have questions.
Brent Pol 1
Executive Director
cc: Senator Bennett
Senator Hatch
Congressman Hansen
Weber Basin Water
South Weber City
Utah State Environmental Health
Davis County Environmental Health
-------
What do you think?
Hill Air Force Base Operable Unit 1 Open House February 5,1998
Thank you for attending tonight's Open House. Its purpose is to present the proposed Remedial Action at "Operable
Unit 1 * at Hill Air Force Base and to hear your comments about the proposal. We have designed this meeting to be
informal, which allows you to move about the room freely, visiting any or all of the stations at your convenience.
As you may have noticed, we have set up several poster stations. Each station presents information on a different
topic. Experts are present at each station to discuss your concerns or answer your questions. We encourage you to
visit all the stations and carefully review the posters. Copies of selected posters are also available as handouts, if you
wish to review the information at a later time.
Please be sure to fill out these two sheets before you leave tonight You may leave them in the white box at the
Comment Station. If you wish to fill them out later, you may mail them to the following address:
Mr. Charles Freeman
Environmental Public Affairs Coordinator
00-ALC/EM
7274 Wardleigh Road
Hill AFB, Utah 84056-5137
Be sure comments are postmarked no later than March 16,1998.
If you would rather express your comments or concerns verbally, a recorder is present to transcribe what you have to
say.
Printed nar.ie (optional): AAiorOymcn*£
How did you learn of tonight's Open House?
[^Newspaper ads Qplyer QProposed Plan
'ord of Mouth Qother
Did you like the way the Open House was organized: Qves
Do you have any suggestions to improve future meetings? If so, please explain.
1 1 -\-\\je -jViiHv u3^i\ ASfe W*-^- o-*^ -ft--
Are there any other groups, companies, or individuals you feel should be sent information about the cleanup
effort at Hill Air Force Base? (Please provide names and addresses, if possible.)
, .
C\x^A-o>v Name: Qur.r^o/^ O>
Name: s.e x^-o>v Name: ^ > - °
Address: _ Address:
City, Sate, Zip: _ City, Sate, Zip:
(Continued on back of this page)
-------
Additional thoughts?
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-------
What do you think?
Proposed Remedial Action-page 1 of 2 Februarys, 1998
Background
A Remedial Action has been proposed by Hill Air Force Base to clean-up groundwater contamination at Operable
Unit 1 . The Air Force, Environmental Protection Agency, and Utah Department of Environmental Quality have agreed
that extraction of on-Base contaminated groundwater is desirable. Therefore, Hill AFB has proposed a Remedial
Action, which is outlined in the Proposed Plan for Operable Unit 1 .
According to the Proposed Plan, Hill AFB proposes to construct a series of on-Base groundwater extraction trenches
to remove contaminated groundwater in the Operable Unit 1 Source Areas. The extraction trenches will limit
contaminated groundwater from flowing to off -Base areas or to other areas of the Base. With groundwater flow from
the contamination source areas substantially reduced, the existing groundwater contamination found in off-Base
areas and in on-Base areas, away from the Source Areas, will be allowed to naturally attenuate (degrade). The
extracted groundwater will be treated at the existing Operable Unit 2 treatment facility and discharged into the local
sewer system for further treatment.
A complete description of the Remedial Action is available in the Proposed Plan and Feasibility Study.
Please be sure to (ill out these two sheets before you leave tonight. You may leave them in the white box at the
Comment Station. If you wish to fill them out later, you may mail them to the following address:
Mr. Churles Freeman
Environmental Public Affairs Coordinator
00-ALC/EM
7274 Wardleigh Road
Hill AFB, Utah 84056-51 37
Be sure comments are postmarked no later than March 16, 1998.
If you would rather express your comments or concerns verbally, a recorder is present to transcribe what you have to
say.
Printed name (optional): _
Questions (Please mark the appropriate response.)
Source Area
Overall, does Hill's proposal to clean-up the Operable Unit 1 Source Areas meet your expectations and
address your concerns?
Qves }2No QNotSure
If you answered "No' or "Not Sure", please explain: l£ TA'hK
Are you satisfied with the approach being proposed to clean-up the Source Areas?
1234
Very Satisfied _ / Not Satisfied
'i~
If you chose 4 or 5, please explain why. -r" '~ yjere p Sf>,£ ^ **•
5 4?i -r~'(c> *\
<-/
-------
What do you think?
Proposed Remedial Action-Page 2 of 2 Februarys, 1998
Are you satisfied with the method of treating the extracted groundwater, i.e. using existing facilities at
Operable Unit 2?
1234
Very Satisfied Not Satisfied
Non-Source Area
Overall, does Hill's proposal to clean-up the Operable Unit 1 Non-Source Areas meet your expectations and
address your concerns?
QYes \2rno QNotSure
If you answered "No" or "Not Sure", please explain: -~e ne&s -f-r^^ jJoi^J $ u.
#/£- /?o T~ £# b ft •/> /'
C- & h -4a "i - ^ A / ' o ^
Is there anything else about the proposed Non-Source Area Remedial Action that concerns you?
Additional thoughts
5A
-------
What do you think?
Proposed Remedial Action-page 1 of 2 February 5.1998
Background
A Remedial Action has been proposed by Hill Air Force Base to clean-up groundwater contamination at Operable
Unit 1. The Air Force, Environmental Protection Agency, and Utah Department of Environmental Quality have agreed
that extraction of on-Base contaminated groundwater is desirable. Therefore, Hill AFB has proposed a Remedial
Action, which is outlined in the Proposed Plan for Operable Unit 1.
According to the Proposed Plan, Hill AFB proposes to construct a series of on-Base groundwater extraction trenches
to remove contaminated groundwater in the Operable Unit 1 Source Areas. The extraction trenches will limit
contaminated groundwater from flowing to off-Base areas or to other areas of the Base. With groundwater flow from
the contamination source areas substantially reduced, the existing groundwater contamination found in off-Base
areas and in on-Base areas, away from the Source Areas, will be allowed to naturally attenuate (degrade). The
extracted groundwater will be treated at the existing Operable Unit 2 treatment facility and discharged into the local
sewer system for further treatment.
A complete description of the Remedial Action is available in the Proposed Plan and Feasibility Study.
Please be sure to fill out these two sheets before you leave tonight. You may leave them in the white box at the
Comment Station. If you wish to fill them out later, you may mail them to the following address:
Mr. Charles Freeman
Environmental Public Affairs Coordinator
OO-ALC/EM
7274 Wardieigh Road
Hill AFB, Utah 84056-5137
Be sure comments are postmarked no later than March 16,1998.
If you would rather express your comments or concerns verbally, a recorder is present to transcribe what you have to
say.
Printed name (optional): ^ e/vn \rV2-y\\
Questions (Please mark the appropriate response.)
Source Area
Overall, does Hill's proposal to clean-up the Operable Unit 1 Source Areas meet your expectations and
address your concerns?
Sure
If you answered "No" or "Not Sure", please explain:
O
N/
Are you satisfied with the approach being proposed to clean-up the Source Areas?
1234
Very Satisfied \Not Satisfies
If you chose 4 or 5, please explain why.
-------
What do you think?
Proposed Remedial Action-Page 2 of 2 Februarys, 1998
Are you satisfied with the method of treating the extracted groundwater, i.e. using existing facilities at
Operable Unit 2?
1 2
Very Satisfied
Non-Source Area
Overall, does Hill's proposal to clean-up the Operable Unit 1 Non-Source Areas meet your expectations and
address your concerns?
QYes / QlNp/ QNotSure
If you answered "No" or "Not Sure", please explain:
\\ \\ A r(k \ L _L • \ )- i L
Ux U t\yv> U-^-\cWy--<:tcxx1hir,g else about the proposed Nun-Source Area Remedial Action that concerns you?
T
Additional thoughts
\/M^\-e^
Q)
a^hVjcOu,^ AO
-------
What do you think?
Proposed Remedial Action-page 1 of 2 February 5,1998
Background
A Remedial Action has been proposed by Hill Air Force Base to clean-up groundwater contamination at Operable
Unit 1. The Air Force, Environmental Protection Agency, and Utah Department of Environmental Quality have agreed
that extraction of on-Base contaminated groundwater is desirable. Therefore, Hill AFB has proposed a Remedial
Action, which is outlined in the Proposed Plan for Operable Unit 1.
According to the Proposed Plan, Hill AFB proposes to construct a series of on-Base groundwater extraction trenches
to remove contaminated groundwater in the Operable Unit 1 Source Areas. The extraction trenches will limit
contaminated groundwater from flowing to off-Base areas or to other areas of the Base. With groundwater flow from
the contamination source areas substantially reduced, the existing groundwater contamination found in off-Base
areas and in on-Base areas, away from the Source Areas, will be allowed to naturally attenuate (degrade). The
extracted groundwater will be treated at the existing Operable Unit 2 treatment facility and discharged into the local
sewer system for further treatment.
A complete description of the Remedial Action is available in the Proposed Plan and Feasibility Study.
Please be sure to fill out these two sheets before you leave tonight. You may leave them in the white box at the
Comment Station. If you wish to fill them out later, you may mail them to the following address:
Mr. Charles Freeman
Environmental Public Affairs Coordinator
OO-ALC/EM
7274 Wardleigh Road
Hill AFB, Utah 84056-5137
Be sure comments are postmarked no later than March 16,1998.
If you would rather express your comments or concerns verbally, a recorder is present to transcribe what you have to
say.
Printed name (optional): _
Qll6StlOnS (Please mark the appropriate response.)
Source Area
Overall, does Hill's proposal to clean-up the Operable Unit 1 Source Areas meet your expectations and
address your concerns?
Qves GNO QNO! Sure
If you answered "No" or "Not Sure", please explain:
Are you satisfied with the approach being proposed to clean-up the Source Areas?
1 ^ 345
Very Satisfied "" Not Satisfied
If you chose 4 or 5, please explain why.
-------
What do you think?
Proposed Remedial Action-Page 2 of 2 _ Februarys, 1998
Are you satisfied with the method of treating the extracted groundwater, i.e. using existing facilities at
Operable Unit 2?
1 23 4 5
Very Satisfied Not Satisfied
Non-Source Area
Overall, does Hill's proposal to clean-up the Operable Unit 1 Non-Source Areas meet your expectations and
address your concerns?
QNotSure
If you answered "No" or "Not Sure", please explain:
Are you satisfied with the approach being proposed to clean-up the Non-Source Areas?
12345
Very Satisfied Not Satisfied
If you chose 4 or 5, please explain why.
Is there anything else about the proposed Non-Source Area Remedial Action that concerns you?
Additional thoughts
5A
-------
What do you think?
Hill Air Force Base Operable Unit 1 Open House February 5,1998
Thank you for attending tonight's Open House. Its purpose is to present the proposed Remedial Action at "Operable
Unit 1" at Hill Air Force Base and to hear your comments about the proposal. We have designed this meeting to be
informal, which allows you to move about the room freely, visiting any or all of the stations at your convenience.
As you may have noticed, we have set up several poster stations. Each station presents information on a different
topic. Experts are present at each station to discuss your concerns or answer your questions. We encourage you to
visit all the stations and carefully review the posters. Copies of selected posters are also available as handouts, if you
wish to review the information at a later time.
Please be sure to fill out these two sheets before you leave tonight. You may leave them in the white box at the
Comment Station. If you wish to fill them out later, you may mail them to the following address:
Mr. Charles Freeman
Environmental Public Affairs Coordinator
00-ALC/EM .
7274 Wardleigh Road
Hill AFB, Utah 84056-5137
Be sure comments are postmarked no later than March 16,1998.
If you would rather express your comments or concerns verbally, a recorder is present to transcribe what you have to
say.
Printed name (optional):, A
How did you learn of tonight's Open House?
{^Newspaper ads GiFlyer QProposed Plan
'ord of Mouth Qdher
Did you like the way the Open House was organized: Yes
Do you have any suggestions to improve future meetings? If so, please explain.
Are there any other groups, companies, or individuals you feel should be sent information about the cleanup
effort at Hill Air Force Base? (Please provide names and addresses, H possible.)
Name: Name:
Address: Address:
City, Sate, Zip: City, Sate, Zip:
(Continued on back of this page)
-------
Additional thoughts?
/ /
s i -J ///-. c' //. 6 ^' i / y/^y,f - />' fS
-------
Appendix C-3
South Weber Landfill Coalition Comments to the
Draft and Draft Final Feasibility Study
-------
Response to South Weber Landfill Coalition Comments on
Revised Draft Final Feasibility Study Report for Operable Unit 1,
Hill Air Force Base, Utah
(IRP Sites LF01, LF03, WP02, FT09, OT14, FT81, and WP80)
November 1996
This section presents responses to comments on the Revised Draft Feasibility Study (FS) for
Operable Unit 1 (OU1) by the South Weber Landfill Coalition (SWLC). Comments by the
SWLC are included as presented in the comment letter by Dr. John G. Carter, dated
January 27, 1997. Responses to comments follow the comments.
South Weber Landfill Coalition Comments (Dr. John G. Carter):
During the past several years as Technical Advisor to the South Weber Landfill
Coalition, I have made numerous comments concerning hydrogeology investigations and
characterizations, proposed interim remedial actions and risk assessments. These will not
be repeated here, but many of the uncertainties still remain. I have focused my comments
on the Executive Summary, Introduction and Development of RAOs and Screening of
Technologies presented in Sections 1 and 2 of the Revised Draft Feasibility Study.
Comments (in italics) are referenced to page numbers in the FS.
The "Draft Field Manual for Site Activities at Operable Unit I...", dated October,
1996 proposed additional investigations in the landfill areas to: (1) estimate the volume of
waste in the landfills, (2) assess contaminants in soils, leachate and groundwater below the
landfill debris, (3) determine the vertical and horizontal gradients below the landfills,
(4) evaluate the physical properties and continuity of the clay materials below the landfills,
(5) evaluate the Landfill 3 magnetic anomaly area, (6) compare OU1 leachate and
groundwater with other military and municipal landfills across the country and
(7) reevaluate the cost assumptions associated with the feasibility study alternative for
landfill removal.
The SWLC appreciates these planned studies which have the potential to further clarify the
picture at OU1. The same reasons that prompted these additional studies make it impossible to fully
evaluate the FS until the result of those studies are available. Other factors such as the many
assumptions made in the FS coupled with the great degree of uncertainty expressed by HAFB about
the ultimate effectiveness of remedial measures also make it impossible to fully evaluate the FS at this
time. However, the comments in this document are provided to clarify the concerns of the SWLC
and, hopefully suggest some alternatives that can provide greater peace of mind to the citizens of
South Weber. As Technical Advisor to the SWLC, I believe that it is imperative to implement
several interim remedial actions immediately because the investigation and report at OUl has
extended for decades and shows no signs of being ended soon. The interim remedial measures that
should be implemented in my view include (1) the containment alternatives proposed in the EE/CA
(October 1995) to contain groundwater migrating off-site from the Source Areas, (2) plume cut-off
at the bottom of the bluff (Alternative 4 for Non Source Areas), (3) hydraulic containment at leading
plume edges (Alternative 5 for Non Source Areas) and (4) groundwater collection throughout the
plume (Alternative 6 for Non Source Areas.). These measures could begin the process of risk
\\SLCI\rRO|l\136064\4_i_l\FINAL\MISC\RTSWLFCADOC
-------
reduction and restoration to the Non Source Areas while remedial investigations and
design/development/implementation phases are taking place on Base, a process that will undoubtedly
take years to complete. The cost of these measures is small, provides some assurance to South Weber
that progress is being made and probably cost a fraction of what has been spent on investigation and
reporting at OUT. to date.
Response to Comment. The OU1 area has been thoroughly investigated. Hill Air Force Base
(HAFB) feels that adequate investigation has been performed to develop a Feasibility Study
(FS). The Environmental Protection Agency (EPA), and State of Utah, Department of
Environmental Quality (UDEQ) have approved the investigations and agree that enough
data is available to develop an FS. Three additional investigations are currently planned for
OU1 to evaluate specific areas in the near future. If the results of these investigations
indicate that conditions are significantly different than identified in the FS, this data will be
incorporated into future versions of the FS, the Proposed Plan, and the Record of Decision.
The field data from these investigations will be available prior to the final date of the
documents.
Response to Comment (COnt.): The author's comments suggest a need to implement interim
remedial actions immediately. This is contrary to the views of the SWLC expressed by
Brent Poll in a letter dated November 14,1995, which opposed an interim remedial action
prior to the final remedy. Resources have been realigned to follow the conventional
CERCLA process of the FS, Proposed Plan, and ROD to achieve the remedial objectives.
PES-4 It is stated that the majority of groundwater flow leaves OU1 toward the west, with
some flow moving east, mostly emanating from springs and seeps and little migrating
downhill through the landslide debris formation. The Final Comprehensive RI, Figures 6-3 and
6-4 shows soil gas plumes along the hillside to both the north and east. The RI on page 5-23 states in
paragraph 5.6.3.2 "General ground-water flow paths at OUT. are to the north off the bench." Also,
for it to emanate from springs and seeps, it has to arrive at the spring or seep in some manner.
Statements like this are of great concern because they seem to be unrelated to the mass of data
presented in the past, leading one to wonder what else has been missed.
Response to Comment. It appears the referenced statements are collectively presented
somewhat out of context. The FS also supports (Figures 1-4 and 1-5) the generalized
northward flow suggested in 5.6.3.2 of the RI. The FS also identifies eastward flow, as
stated by the author, which is consistent with the seep and spring flow reported in the RI.
PES-5 It is stated that remedial action objectives include preventing human exposure that
presents an unacceptable risk, with risk being defined as HI>1 or excess cancer risk greater
than 1 X 10 "4 to 1 X 10 '". This is of great concern because the term "unacceptable" is a relative
term and in this case turns on what is believed to be the current state of knowledge of chemical
effects on humans. However, since knowledge of chemical effects on humans as well as ecosystems
continues to grow, standards can change and become more strict over time. Synergistic effects and
effects on sensitive individuals may be different than the "average" statistic or standard. It is also
stated that an objective is to prevent migration of contaminants in excess of MCL's or the
other cited risk levels beyond the Source Area perimeter. Again, this implies that continued,
long-term migration of chemicals will be allowed subject to current-day "risk standards." This does
not satisfy the concern of SWLC that the residents of South Weber will not continue to be at risk
\\SLC1\rROJl\136064\4_l_l\FINAL\MlSC\RTSWLFCA.DOC
-------
indefinitely. Other statements are made such as to "minimize the potential for human
exposure to contaminated shallow groundwater" and "enable long-term attainment of ...
remedial action objectives". SWLC is not comfortable with vague, undefined terms or qualifiers
such as this. Without firm commitments as to effectiveness and guarantees of success within a
reasonable time frame, SWLC doubts the viability of the Feasibility Study and the studies upon
which it is based. Ultimately, long-term could mean hoivever long it takes for natural attenuation to
eliminate the contamination. That could take decades or longer.
Response to Comment. The concerns of the SWLC regarding the current state of knowledge of
chemical effects on humans, the risk assessment process, and the uncertainties of how this
science could change in the future, were addressed in a special presentation by Gerry
Hervningsen/EPA, at the August 14, 1996, Restoration Advisory Board (RAB) meeting. In
addition, the Base remediations systems will be reviewed every 5 years or when necessary.
If the systems are not performing as expected or risk standards change in the future and
make the remediation systems ineffective, other remediation systems will be considered.
The general statements that the author qualifies as "vague, undefined terms or qualifiers"
were presented in the Executive Summary as general descriptions of remedial objectives.
The FS provides additional detail regarding the remedial objectives later in the document
(Section 5.0 Detailed Analysis of Alternatives).
PES-6 It is stated that "All alternatives, with the exception of Alternative 1, are protective of
public health and the environment, and should be able to meet... ARARs." With the use of
terms such as "minimize", "long-term" and now, "should" throughout the description of remedial
action objectives and alternatives, SWLC is left with a feeling of unease that the Air Force is
unwilling to stand behind the work that has been done and has little confidence in the proposed
measures. SWLC needs to see a definite set of commitments.
Response to Comment. The Draft Final Version of FS will maximize use of more definitive
language where appropriate.
PES-6 Alternative 1 - No Further Action: It is stated that "The interim actions currently in place
have reduced the extent of off-site migration. The magnitude of the current off-site
migration is, however, not known. It is likely that some migration of contaminants offsite
currently exists..." SWLC finds this set of statements scary in their degree of non-commitment. If
the site has been studied for this many years without being able to document or model the degree of
migration, how on earth can the effectiveness of proposed remedies be evaluated. To use the term
"likely", when it is known that groundwater migrates off-site and that the groundwater is
contaminated, places doubt on the efficacy of everything that follows. This is why SWLC insists that
the most aggressive measures be taken and that cost is a secondary consideration.
Response to Comment. The area has been studied extensively and some modeling has been
performed. However, as with all modeling efforts, it is very difficult to model actual
subsurface conditions and there is some uncertainty associated with the modeling efforts.
Hill Air Force Base is certain that groundwater is the main transport mechanism off-Base.
This is the reason that many of the Source Area Remedial Alternatives focus on extracting
groundwater to mitigate contamination transport off-Base. Past investigations have focused
on evaluating the groundwater flow paths and mechanisms rather than calculating the
amount of contamination flowing off-Base. By identifying the location of groundwater flow
\\SLC1 \PROI1 \I360W\4_1_I\FINAL\M1SC\RTSWLFCA.UOC
-------
paths, remediation systems that will extract the maximum amount of groundwater can be
designed. Modeling the quantity of contamination flowing off-Base has not been a high
priority of past investigations. In accordance with CERCLA guidance, cost is given
consideration in the choice of remediation systems. Section 5 of the FS provides an analysis
of the alternatives.
PES-6 Alternative 2 - Existing System Upgrade: "...would not prevent migration through the
upper Alpine Formation." This is of concern because the upper Alpine Formation is the silty clay
layer that SWLC is supposed to rely upon to protect their environment from downward migration
from the LFs and other Source Areas. Now we are told that these measures would not prevent
migration through this silty-clay layer. This heightens the level of concern of the SWLC about this
silty-clay layer and the reliance placed upon it by HAFB.
Response to Comment. The reason the existing system does not prevent migration though the
upper Alpine Formation is that the existing system does not extend into the upper
Alpine Formation. Therefore, the system does not extract groundwater from the upper
Alpine Formation. As stated in Source Area Alternatives 3, the proposed dewatering
trenches will be extended into and extract groundwater from the upper Alpine Formation.
In addition, contaminated groundwater has been found in the upper Alpine Formation, but
has only been observed in limited concentrations in the lower Alpine Formation. Therefore,
the Alpine Formation clays appear to be limiting the vertical migration of contamination.
Geology, hydrogeology and contamination levels are further described in Section 1.
PES-9 Alternatives 3 and 4 - Groundwater Dewatering and Source Containment: Both alternatives
indicate the lack of knowledge of the extent of migration through the upper Alpine Formation, but it
is indicated to be insignificant or small. The point here is that the lack of characterization of this unit
is compromising the ability of HAFB and others to have confidence in the selected alternatives. It
should also be noted that groundivater dewatering and source containment will leave in-place
contaminated soils and other contents that may be sources when exposed to groundwater.
Theoretically, this means these alternatives would have to be operated and maintained forever which
throws the economic comparisons based on 30 years out the window.
Response to Comment. Contamination levels in the upper Alpine Formation have been
investigated. Hill Air Force Base is confident that the available information is adequate and
appropriate to meet the standards required in the CERCLA process. Regarding the impact
of uncertainties on timeframes and therefore cost, these same uncertainties impact all
alternatives, resulting in a balanced comparison.
PES-9 Alternative 5 - Source Containment and Cap Upgrade: It is stated that the amount of water
infiltrating through the cap is small and that the water infiltrating through the cap "should"
be captured by the dewatering system. In the RI, page 5-18, paragraph 5.6.1.3 it is stated
"Recharge to the shallow aquifer on Base is through infiltration of precipitation with some unknown
contribution from the golf course to the south ofOUl." With the data collected to date, it is difficult
to understand why modeling and water balance calculations have not been presented in order to
better quantify the relative contributions of each source of recharge. It is only in the context of data
that an accurate evaluation of the feasibility of these options can be made. The use of the term
"should" fortifies the doubt that grows as one reads the Executive Summary. Based on the statement
above, one is left with the belief that if irrigation of the Coif Course were stopped, the cap that exists
\\Sl.CJ \PKOI 1 \1.T60M\4_1_I \FINAL\MISC\RTSWLFCA.DOC
-------
now would eliminate any further exposure of the contaminated media in OU1 to groundwater. Is
this a true statement?
Response to Comment. As stated in the Response to Comment PSE-6, past investigations have
focused on groundwater flow paths rather than the amount of groundwater in the
subsurface as calculated by modeling. If irrigation to the golf course were stopped,
groundwater elevations in the OU1 area would probably be lowered. Groundwater
migration would not be stopped because precipitation infiltrating to the groundwater table
would cause some migration of groundwater. The landfill caps only cover a portion of the
recharge area to OU1.
PES-10 Alternative 6: Source Treatment and Cap Upgrade: States that SVE would not increase the
reliability of preventing contaminant migration because the groundwater extraction system
and containment "should" effectively prevent migration. There will be a significant volume of
potentially contaminated media in the unsaturated horizon. SVE was shown to be an effective
technique in the experimental study at FTA1. Perhaps more consideration should be given to
dewatering and SVE for OU1.
Response to Comment. The groundwater extraction system will prevent migration of
contamination. The SVE system will remove source area contamination mass.
PES-10 Alternative 7 - Excavation, Treatment, and Offsite Disposal: "This alternative does not
provide a good balance of the ... criteria since the cost is so much higher than the other
alternatives, and short-term effectiveness and implementability of this alternative are poor.
The short-term risks to the community and workers ... is very high." Onsite disposal was
eliminated due to construction and permitting. It appears that a set of assumptions is made as to how
this alternative is implemented that provide a self-fulfilling prophesy. Since transport is expensive
and HAFB believes poses risks to the community, it is strange that given the number of
Operable Units at HAFB, that you haven't considered onsite remediation using a state of the art
landfill and/or incineration facility. During the design and permitting process, the alternatives
suggested for containment of Source Areas and interim remediation of Non-Source Areas could be
implemented to provide the short-term containment and treatment that would be needed until
facilities were built. It appears that HAFB is missing an opportunity to perform remediation that
provides greater long-term reliability and has the potential to save money relative to the "removal"
alternative (no. 7) by not taking an integrated look at all the operable units. Further, so many
assumptions and contingencies are included in cost estimates for the sake of being conservative, the
estimated cost could be overinflated, especially if some reasonable balance of excavation and onsite
disposal were included. In addition, to leave the mass of the Source Areas in place at OUT. means
that the sources will exist indefinitely (» 30 years) and therefore, to compare the alternatives on a
short-term (30 year) basis may be underestimating the cost of the other alternatives when compared
to some level of removal or in-situ characterization and treatment.
Response to Comment. The construction of a base-wide landfill or incineration facility is
interesting, although a majority of the contamination found at Hill Air Force Base is
groundwater related. In addition, a majority of the landfill debris would come from OU1.
The permitting and operation of such a landfill or incineration facility would be very
difficult, if not impossible, at Hill Air Force Base and would add substantial cost to
Source Area Alternative 7.
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Response to Comment (cont.). As a comparison, the capital costs as well as operations and
maintenance costs for Source Area Alternative 3, over a 30-year period, are projected to be
approximately $5,900,000. The capital costs as well as operations and maintenance costs for
Source Area Alternative 7, over a 30-year period, are projected to be approximately
$302,000,000. In addition to a much higher cost for Source Area Alternative 7, this
alternative has a much greater potential to expose a large percentage of the public to
potentially hazardous materials by transporting the materials through surrounding
neighborhoods.
PES-10. "The differences between alternatives in their overall protectiveness are not
considered great because they all rely on the same institutional controls to prevent
exposure and the time period for which the controls are necessary are not significantly
different. The reliance on institutional controls may be necessary for some time while remedial
actions return full use of the land and groundwater to the citizens of South Weber. However, to rely
on institutional controls rather than remediation and not consider the economic and other values lost
by the presence of contamination, the threat of exposure to contamination and the institutional
controls ivhich deny property owners the full use and value of their property creates an artificial
basis for feasibility evaluation. SWLC is concerned that this rationale, if followed, will result in
indefinite potential for exposure and loss of value. SWLC strongly disagrees that the time periods for
which controls are necessary are not significantly different. See the previous comment regarding the
indefinite retention of contamination in the Landfills and other Source Areas under the "non-
removal" alternatives.
Response to Comment. Overall protection is just one of the nine evaluation criteria. The
factors suggested in the comments (rimeframe, cost, effectiveness, permanence, and
implementability) are also part of the nine evaluation criteria, and have therefore been
considered. The comment references a section from the Executive Summary which
addresses a "Non-Source Area Alternatives Comparison", and as a result the relationship
of this comment to the previous comment regarding Source Areas is not clear.
PES-11 Alternative 1 - No Further Action: "... this alternative is not completely protective since
there is some potential for exposure ..." SWLC is concerned about past exposure, ongoing
exposure and the potential for greater exposure in the future. There is no guarantee that current
migration rates and concentrations will remain the same or decline in the absence of mitigation,
therefore intensive measures should be employed to insure the return of full use of the land to the
residents in as short-term period as possible.
Response to Comment. Statement, no response necessary.
PES-11 Alternative 2 - Natural Attenuation: "This alternative, coupled with the Source Area
alternatives that prevent (emphasis added) off-site migration, provides greater reliability of
meeting ARARs than Alternative I." The operative term here is "prevent". Since the ability of
the Source Area alternatives to prevent off-site migration is cast in doubt in the discussion of those
alternatives, there can be no estimate of time to achieve ARARs and no assurance that ARARs will
not need change in the future as more information becomes available. SWLC is concerned that
ARARs are an artificial construct and are not adequate parameters of risk. Meanwhile, exposure and
potential for exposure will continue indefinitely.
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Response to Comment. The Source Area Alternatives with groundwater extraction systems
identified in the FS should prevent groundwater from flowing to off-Base areas. This is
based on the investigation performed to date. Base remediation systems will also be
reviewed on a 5-year basis to evaluate performance. If performance is not as expected,
other remedial alternatives may be attempted. HAFB is unsure what is meant by
".. ..ARARs are an artificial construct and are not adequate parameters of risk" in the above
comment. HAFB is unaware of any current exposure to off-Base contamination.
PES-11 Alternative 3 - Existing Seep Collection Upgrade: Collection of seeps and springs constitutes a
loss to the ecosystem in that these water sources could be important to wildlife, habitat or other
environmental values. Of course, if Source Area remedial actions stopped migration of contaminated
water, these springs and seeps may be lost as a consequence of this action. Removal of arsenic-
contaminated soils, is of course appropriate. However, wet years coupled with uncertain success of
measures in the Source Areas, could result in a re-occurrence of events that happened in the early
1980''s ivhere visible contamination occurred on the slope and resulted in the "cease and desist
order" by the State of Utah. Therefore, it is important to have measures in place which provide
positive assurance of containment. The loss of these seeps and springs through dewatering and/or
collection represents a loss in value to the people of South Weber and to the ecosystem. Of course, the
current contaminated state of these seeps and springs provides for loss at a similar level.
Response to Comment. Based on existing investigation, only a few seeps will be impacted by
the remediation systems. Numerous other sources of water exist for the wildlife in the area.
Loss of the ecosystems will be off-set by limiting the exposure of wildlife to contaminated
groundwater and soils. The springs are located on private property, hence, the loss to the
people of the City of South Weber will be minimal.
PES-12 Alternative 4 - Plume Cut-Off at Bottom of Bluff: "... provides a slightly increased degree
of protectiveness (as compared to ?) ... . This is especially true if the Source Area alternative
implemented?) is not effective in stopping offsite migration." Again, doubt is introduced
about the ability of Source Area remedial actions to perform. This is, of course, understandable
because systems installed will begin to lose integrity from the first day and with no way to know how
long they must be kept in place and operating, no evaluation of their feasibility is possible for the
long term. SWLC is concerned that cost and effectiveness evaluations are biased by use of too many
assumption to arrive at comparisons. SWLC believes that a system such as this that intercepts
contaminated groundivater should have been installed as an interim remedial measure to
prevent further migration long ago.
Response to Comment. There are two recurring themes expressed in this and previous
comments regarding uncertainties in the FS process, and the need to implement an interim
measure. First, there are few if any absolute certainties or guarantees when dealing with the
subsurface and the CERCLA process both allows and provides, for that unavoidable fact.
Second, the issue of interim measures has been addressed previously, this Response to
Comment document, and in other correspondence.
PES-12 Alternative 5 - Hydraulic Containment at Leading Plume Edges: "However, minimal
migration is expected even without this alternative and, in the Weber River Valley,
concentrations beyond the seeps and springs are less than remedial goals." The same could
have been said in the past regarding areas in the valley that are now contaminated. The plume
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continues to migrate (after all it got to where it is by migration), there is no effective containment
and unless there is data that shows migration has stopped and will not continue, this is an invalid
assumption. In addition, there is no assurance that the contamination present will not change in
nature (e.g. to vinyl chloride, or increase as additional contamination leaves the Source Areas.
SWLC believes that the containment at leading plume edges should have been implemented
as an interim remedial action long before now and, in fact will be necessary to provide
some insurance against failure or ineffectiveness of the Source Area remediation. This
option should be placed into operation as an interim action immediately.
Response to Comment. The geologic controls limiting migration of the off-Base plume are
described in Section 1 of the FS. Existing data shows the vinyl chloride has been noted in
very small concentrations in the off-Base plume and only associated with higher levels of
DCE. In addition, groundwater monitoring data from the off-Base plume shows declines in
many of the wells over the last several years. Again, the issue of interim measures has been
addressed previously in this Response to Comment document and in other
correspondence.
PES-12 Alternative 6 - Groundwater Collection throughout the plume: "This alternative is the only
alternative that substantially decreases the time to achieve ARARs..." Reliance on
institutional controls denies property cnvners access to the full value of their property and extends
the length of time that residents are at risk of exposure. Implementation of this alternative would, as
stated, decrease the length of time of exposure and loss of value and would return the property to full
use much sooner. Therefore, SWLC believes that groundwater collection throughout the
plume should be implemented as an interim action immediately to reduce risk and provide
the residents of South Weber some assurance that full use of their property will be regained
in a reasonable length of time.
Response to Comment. The sentence in question actually states, "This alternative is the only
alternative that substantially decreases the rime to achieve ARARs compared to
Alternative 2". Alternative 2 does not assume source control. With source control,
Alternative 3, the time to achieve ARARs between Alternatives 3, 4, 5, and 6 are not
significantly different. Again, the issue of interim measures has been addressed previously
in this document and in other correspondence.
PES-13 "... further investigations of natural attenuation are currently underway at OU1... ."
SWLC believes that, while studies of this nature are useful, it is time to implement remedial
actions that will give the residents of South Weber some peace of mind. Therefore, SWLC
insists that the three Non-source Area alternatives (4, 5, 6) should be implemented
immediately. The cost is small, even on the order of some groundwater data collection
efforts, therefore, cost should not be a major factor in the evaluation.
Response to Comment. Again, the issue of interim measures has been addressed previously in
this document and in other correspondence.
P1-6 "... the golf course was removed from OU1 in 1991 because it is not a source of
groundwater contaminants at HAFB." While this may be the case, nevertheless, the Golf Course
irrigation is a source of groundivater recharge at OUl. As such, it provides part of the motive force
that moves contamination through OU1 and into South Weber. The management or irrigation and
infiltration at the Golf Course could be a low cost method of reducing the amount of water ultimately
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treated. There are a variety of soil moisture and climatic monitors that could be used to control
irrigation to minimize water use. Ultimately HAFB could save a great deal through better water
management and lowered water treatment costs.
Response to Comment. Good point, the opportunity to limit groundwater recharge will be
evaluated as part of the groundwater pre-design investigation.
P1-52 "... current exposure to soil gas in basements are both well below the target 1 x 10-6
excess cancer risk level and hazard index of 1 ..." Air samples at residences detected numerous
compounds, which, individually, were below OSHA PEL", however, the number of compounds was
large and one must assume they come from the contamination beneath the house even though
arguments were presented otherwise. Unfortunately, HAFB by way of having caused the plume of
contaminated groundwater to migrate to these residences, is considered the cause. Until
demonstrated otherwise, that will continue to be the case. Isn't it true that exposure to chemicals can,
in some individuals, create sensitivities resulting in adverse reactions to further exposures? This
investigation was not thorough enough in it's extent nor in it's analysis and interpretation to offer
comfort to the SWLC. It provides a basis for interim remedial measures to be implemented to correct
any exposure that may be occurring as a result of activities at HAFB.
Response to Comment. Trace levels of compounds have been detected in basement air of
tested residences. To date, the results have not indicated any detectable hazard to the
residents that could reasonably be attributed to the OU1 off-Base contamination plume.
P2-4 "... there are no currently complete exposure pathways to any media that pose levels
of risk considered unacceptable by the NCP." As has been pointed out in the past, demographic
studies have shown that mere proximity to Superfund sites poses risk. Also, the SWLC does not feel
that acceptability under the NCP constitutes acceptability by SWLC. The presence of a plume
beneath South Weber damages property values, denies use of property and may pose danger to
residents that are not accounted for in current risk assessments. HAFB must realize that the citizens
of South Weber are being asked to live with contamination beneath their houses for decades unless
active measures are taken to shorten the exposure time.
Response to Comment. Please identify the demographic studies. The remainder of the
comments is a statement and no response is required.
P2-8 In this section, the Utah Regulations regarding groundwater contamination are referenced. It
is pointed out that sources that may potentially degrade the quality of groundwater must be
remediated or controlled. HAFB only proposes to "minimize" continuing contamination of
groundwater. "Minimize" is a non-quantitative, general term that lacks dimensions. The intent of
the regulations is anti-degradation. The groundwater has been degraded beyond it's natural state. It
now needs to be returned to it's natural state irregardless ofARARs, etc. The same rationale applies
to the RAOsfor surface water, which also is subject to an anti-degradation policy in Utah.
Response to Comment. The sentence in Section 2.2.2.5 which uses the word "minimize" will
be replaced with language stating that "remedial actions must restore groundwater". True,
the groundwater has been degraded beyond its natural state. The point of the
investigations, this FS, and future remedial efforts is to restore the groundwater to its
natural state.
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P2-10 In these sections, a commitment to long-term attainment of groundwater, surface water, and
soil RAOs is expressed. Long-term is not defined. SWLC is concerned that conditions luill be
allowed to exist for decades or longer that may continue to pose a threat to South Weber and it's
residents. The psychological impact of living with these conditions has never been addressed. It is for
this reason that SWLC believes indefinite time periods or vague commitments are not acceptable.
Remediation should be positive and take place in a finite time period to provide assurance to the
residents that there will be an end to the process.
Response to Comment. Hill Air Force Base will take all input into consideration as we
evaluate the specific technologies that should be applied in the restoration efforts at OU1.
Future drafts of this document will provide as much definition in restoration timeframes
and land use impacts as practicable.
2-11 "... PRGs establish media-specific concentrations of contaminants of concern that will
pose no unacceptable risk to human health and the environment..." SWLC is glad to see that
HAFB proposes to protect the residents and environment of South Weber from any unacceptable
risk. It is also noted that backgroimd concentrations of specific constituents luill be used as remedial
goals. This is in line with Utah antidegradation policy and if used on both organic and inorganic
constituents would reassure the SWLC that their environment would be restored to conditions that
existed prior to the onset of contamination from HAFB. SWLC believes that remedial goals arc not
satisfied until the concentration of all contaminants are at naturally-occurring levels.
Response to Comment. Statement, no response required.
P2-12 "... due to the high uncertainty associated with the risk calculations for this
scenario..." SWLC is concerned that all risk calculations are attended by a high degree of
uncertainty. In addition, models used to calculate mass-balances involve assumptions that could
increase the degree of uncertainty. Added to these uncertainties are the uncertainties involved in the
estimates of time needed to accomplish remediation as well as the uncertainties in cost estimates.
These are all factors involved in the process used to eliminate alternatives. This is why SWLC wants
immediate attention to the interim remedial measures proposed with a permanent, long-term
solution.
Response to Comment. The Risk Assessment for Operable Unit 1 was performed in
accordance with EPA and UDEQ guidance and approved by both agencies. Again, the
issue of interim measures has been addressed previously in this document and in other
correspondence.
P2-14 We note that the PRGfor soils for xylene (WOO mg/kg) exceeds the Tier 1 risk-based level
(235 mg/kg) used for LUST sites in Utah. Inconsistencies such as this cause concern about the
PRCs in general and make the SWLC wonder how any numerical value can provide reassurance of
long-term safety. That is why interim remedial measures should be employed immediately to begin
eliminating the contamination within South Weber while the sources are being cleaned up.
Response to Comment. The referenced PRGs were developed with different models and
assumptions than those used by DERR to establish the leaking underground storage tank
Tier 1 RBCA program, which take into account basic assumptions about typical distances to
receptors in service station scenarios (e.g., 30' - 100')- The calculation of PRGs for
Operable Unit 1 was performed in accordance with EPA and UDEQ guidance and
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approved by both agencies. Again, the issue of interim measures has been addressed
previously in this document and in other correspondence.
P2-16 We note that the PRGfor naphthalene in groundivater is 1.2 mg/1 while the Tier I risk-based
level for Lust sites in Utah is 0.1 tng/l. Same comment as above.
Response to Comment. See response to the previous comment.
P2-21 // is stated that because of the steep terrain along the hillside north ofOUl, no alternatives to
remediate groundwater will be developed in the FS. SWLC believes this is another justification to
place interim remedial measures at the bottom of the hill to intercept contamination coming off base.
Response to Comment. The basic premise of the source area remediation systems is to capture
contamination prior to flowing into the hillside. The issue of interim measures has been
addressed previously in this document and in other correspondence.
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Response to South Weber Landfill Coalition Comments on
Revised Draft Final Feasibility Study Report for Operable Unit 1,
Hill Air Force Base, Utah
(IRP Sites LF01, LF03, WP02, FT09, OT14, FT81, and WP80)
November 1996
This section presents responses to comments on the Revised Draft Feasibility Study (FS) for
Operable Unit 1 (OU1) by the South Weber Landfill Coalition (SWLC). Comments by the
SWLC are included as presented in the comment letter by Mr. Brent Poll, dated
January 24, 1997. Responses to comments follow the comments.
South Weber Landfill Coalition Comments (Mr. Brent Poll):
This is the response of the SWLC to the revised draft Feasibility Study (FS) Report for
Operable Unit One. Our response supplements that submitted by Dr. John Carter who
serves as Technical Advisor to our coalition. We have received his input and considered it
in forming our own.
There are several historical facts which Dr. Carter mentioned, but did not give the full
weight we believe is necessary. These primarily evolve around HAFB" past failures to
accurately identify the scope of the problems at OU1, and its role in causing, defining and
potentially resolving them. In short, HAFB has a documented history of being less than
candid with those impacted by OU1. We were told by the Base about 25 years ago, after we
identified its pollution problem, that the substances leaking downhill from the site did not
originate on HAFB. Much later the Base reluctantly acknowledged that it was the source,
but insisted that the leakage was not harmful. The Base continued with this stance after
learning that its pollution made the springs below OU1 "harmful for human and animal
consumption." During the early 1980s, HAFB tried to put an end to its problem at OU1 by
literally covering it up. The Base then inaccurately reported that there was an impervious
clay layer below the entire mass at OU1, so its coverup would "envelope" the pollution and
protect everyone from all possible harm. Of course, most everyone but Hill (including State
officials) accurately projected than an impervious clay layer did not exist, and the pollution
continued to migrate off-base through hundreds of acres in South Weber. No apologies
ever came from Hill. In fact, it insists even today that it has never been negligent, and
continues to profess a greater interest in the public's welfare than in minimizing its own
culpability relating to HAFB pollution.
One would have to be very naive to place blind faith in HAFB's current conclusions
concerning its remedial plans in view of its historical record of deceptions and failures in
this regard. We have learned from experience to discount Hill's self-serving assumptions
and theories. Now we focus on input from HAFB which can be measured objectively. With
this premise, we made the following assessment of Hill's interpretation of evidence
collected for its FS:
1. Do HAFB's conclusions reflect a definitive understanding of the full range of
pollutants and the quantities of them placed in OU1?
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ANSWER: No. There was TOTALLY UNCONTROLLED but copious dumping for
about thirty years at OU1; so definitive records of what or how much of anything
was dumped therein simply do not exist. This is the only defensible conclusion that
an objective person can reach from looking at the complete record (including
personal interviews).
However, the Base twists this to conclude that since there are no records of
munitions, biological, radioactive or other more hazardous contaminants being
placed in OU1 (at least in large volumes); then they were not placed there. While
acknowledging the absence of concrete evidence to support its stance, Hill's
conclusions seemed to embrace any suggestions or theory which tends to minimize
the potential recipients off-base. Such conclusions are not objective. They are
self-serving. The SWLC insists that unless HAFB can produce "cradle to grave"
accounts (which it usually can for today's pollutants) for all potentially harmful
materials found anywhere on the Base between 1940-1976, one must conclude that
large amounts of these could well have been eventually discarded through
uncontrolled dumping in unknown quantities at OU1.
Response to Comment 1. Unfortunately, complete disposal records do not exist for the period
of 1940-1976. Numerous investigations have attempted to locate any records without
significant success. This is not an unusual situation for a disposal site in use during the
above referenced period. A landfill investigation is planned for the summer of 1997, which
may provide additional information on the type of materials disposed of at Landfills 3 and
4. The remainder of the comment is a statement and no response is required.
2. Is there an impervious clay layer below OU1, and does HAFB claim it can
stop the continued migration of pollution from the source?
ANSWER: No. This was a major concession for Hill to finally admit that no
miraculous impermeable barrier conveniently existed below OU1. Now it
acknowledges silty lenses or comparable gaps are present through which the
pollution from OU1 can escape the confines of the Base. The Base buffers this
admission with the unproven and self-serving theory that such discharges would be
relatively small and the levels of toxicity would not exceed "acceptable" standards.
The Base further discounted its off-base discharges by unduly minimizing the
means (e.g. drinking polluted ground water) whereby those near OU1 can ingest its
pollution.
Response to Comment 2. Statement, no response required.
3. Since Federal cleanup laws require that "relevant and appropriate"
standards be used to measure the toxicity of pollutants which at a minimum "assure
protection of human health and the environment;" has HAFB applied such
standards in its analysis to protect South Weber residents from the full range of
OUl's pollutants and the full range of potential maladies which can be associated
with them?
ANSWER: No. There are no "relevant and appropriate" standards to definitely
measure the entire wide range of pollutants in OU1 against the almost equally
expansive list of diseases, abnormalities, malfunctions, cancers, physical
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deformations, etc.; which such contamination "may reasonably be anticipated" to
cause. The absence of such standards is not the fault of HAFB. The study of
toxicology is in its infancy. Standards have not been developed which fully or
accurately address all the causes of any of the maladies cited above. However,
demographics show that people experienced more of these problems if they live
within three miles of a toxic site than if they lived further away. This too creates a
standard. President Clinton embraced such a standard in his State of the Union
addresses wherein he said no child should live within "four miles" of a toxic site.
Note that the President made no reference to supposedly valid "relevant and
appropriate" EPA standards in proposing his safeguard of children. Unlike HAFB,
the President apparently is aware that such all-inclusive and reliable standards,
while a very worthy long-term goal, are far from being a reality.
HAFB's FS relies heavily on its listing of a relative few EPA standards (mainly for
carcinogens) and "indicator chemicals" as if they were totally "relevant and
appropriate" and all inclusive. The SWLC believes this is the latest major falsehood
which must be dissolved, and challenges the Base to publicize its all inclusive list
showing all the contaminants in OU1 with its "relevant and appropriate" standards
measuring each contaminant against the wide range of maladies potentially
connected with it. Of course, the "multiplier" effect should also be incorporated into
such a listing to show that, when contaminants are combined, the resulting
combinations often are many times more toxic than the sum of their individual
components. Of course, one should expect these "relevant and appropriate"
standards to remain quite constant if worthy of such designation.
Hill will not produce such a complete listing because they don't have one, and
science in this field is so new that the Base can't manufacture one in the predictable
future. Moreover, Hill cannot attest with any reliability that it can even identify all
the harmful ingredients within OU1.
Response to Comment 3. ARARs have been evaluated with respect to a wide range of
alternatives, addressing both the Source and Non-Source areas to a degree of detail and
thoroughness required by the NCP. The commenter refers to both the existence and the
absence of an "all inclusive list" of OU1 contaminants. OU1 contaminants which are
known to pose potential risk to human health or the environment have been addressed in
the FS. As previously stated in this Response to Comments, the concerns of the SWLC
regarding the current state of knowledge of chemical effects on humans, the risk
assessment process, and the uncertainties of how this science could change in the future,
were addressed in a special presentation by Gerry Henningsen/EPA, at the August 14,
1996, RAB meeting.
Our review of the data accumulated for this Feasibility Study shows (as suggested above)
that (1) there are no definitive records of exactly what or how much is buried in OU1; but
tests show the presence of an extremely wide range of pollutants which have been
reasonably linked to a great assortment of diseases and abnormalities. (2) HAFB can retard
but not stop the migration of pollution from OU1. (3) Relevant and appropriate standards
have yet to be invented to effectively measure the complete range of risks that the
numerous contaminants from OU1 poses to the public. We also concluded:
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A. HAFB should have embraced the measures shown in options 4, 5, and/or 6
(non-source alternatives) many years ago to alleviate the spread of pollution from
OU1 to the valley below. The SWLC has always advocated doing this, but not at the
expense of also accepting Hill's plan to simply leave the leaking source in place.
Response to Comment A. The author's comments suggest a need to implement interim
remedial actions immediately. This is contrary to the views of the SWLC expressed by
Brent Poll in a letter dated November 14,1995, which opposed an interim remedial action
prior to the final remedy. Resources have been realigned to follow the conventional
CERCLA process of the FS, Proposed Plan, and ROD to achieve the remedial objectives. In
addition, the Base remediation systems will be reviewed every 5 years or when necessary.
If the systems are not performing as expected or risk standards change in the future and
make the remediation systems ineffective, other remediation systems will be considered.
B. Federal cleanup law states that "off-site treatment" of a source should be the "least
favored alternative remedial action." Yet, the leaking nature of the source and the
absence of acceptable means to measure the full adverse potential on the public,
makes elimination of it now the only viable corrective alternative. This conclusion is
irrefutable, we believe, and will remain so until application of genuinely complete
"relevant and appropriate" standards hopefully show otherwise; or until HAFB can
keep virtually every particle of its pollution onsite. Since the key distraction and
expense presently making destruction of the source so unattractive is its envisioned
off-site relocation, the Base should redirect its attention towards finding means to
destroy it onsite. Our advisor believes this is practical, yet it is not addressed as an
alternative in the FS.
Response to Comment B. Source removal is not the only alternative allowed under CERCLA.
Onsite destruction is technologically possible. The construction of a base-wide landfill or
incineration facility as identified by John Carter in Comment PES-10 is interesting, although
a majority of the contamination found at Hill Air Force Base is groundwater related. In
addition, a majority of the landfill debris would come from OU1. The permitting and
operation of such a landfill or incineration facility would be very difficult, if not impossible,
at Hill Air Force Base and would add substantial cost to Source Area Alternative 7.
C. In comparing our conclusions against those of the Base, we felt HAFB far too often
relied on what "should," "appears," or "may" happen. These nebulous modifiers
were then frequently linked by Hill to unproven theories. Having so many weak
and intangible components as influential parts of any study makes the
recommendations from it very suspect. HAFB's interpretations fall in this category.
Its conclusions are flawed by reliance on theories and variables which often are
refuted by facts and constants within its own data base. We believe HAFB has thus
skewed its interpretations to coincide with its long vocalized preferences (i.e.,
leaving its leaking source in place). This, of course, will leave a continuing problem
for us to address again and again as we have already for a quarter of a century. We
deserve better from the Base.
Response to Comment C. Statement, no response required.
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Therefore, SWLC recommends that the Base move quickly on the non-source alternatives 4,
5, and/or 6; but find an acceptable means to give some closure by eliminating the source as
a perpetual threat to the community.
Response to Comment. The author's comments suggest a need to implement interim remedial
actions immediately. This is contrary to the views of the SWLC expressed by Brent Poll in a
letter dated November 14, 1995, which opposed an interim remedial action prior to the final
remedy. Resources have been realigned to follow the conventional CERCLA process of the
FS, Proposed Plan, and ROD to achieve the remedial objectives.
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Draft Response to South Weber Landfill Coalition Comments on
Draft Final Feasibility Study Report for Operable Unit 1,
Hill Air Force Base, Utah
(IRP Sites LF01, LF03, WP02, FT09, OT14, FT81, and YVP80)
May 1997
This letter presents responses to comments on the Draft Final Feasibility Study (FS) for
Operable Unit 1 (OU1) by the South Weber Landfill Coalition (SWLC). Comments by the
SWLC are included as presented in the comment letter by the SWLC, dated July 10, 1997.
Responses to comments follow the comments.
South Weber Landfill Coalition Comments:
The essentials of the Draft Final Feasibility Study (DFFS) appear to be largely unchanged
from the Revised Draft Feasibility Study Report for Operable Unit 1 (November, 1996).
Therefore, my comments dated January 27, 1997, remain in effect and are hereby
incorporated by reference.
The following comments are referenced to Section and Page Number of the Draft Final
Feasibility Report for OUI (May, 1997). Quotes from the text of the DFFS are enclosed in
quotes. My comments on behalf of SWLC are italicized.
Page ES-1. It is noted that the LNAPL plume has thinned out and is now measurable in
only a few wells. Wliere has it gone?
Response to Comment: Recent monitoring data, gathered in 1996, has shown that the area
of free phase LNAPL has shrunk considerably in size. This is likely the result of the free
phase becoming bound within the soil pore space because of water table fluctuations and
the natural attenuation of contamination. The residual-phase LNAPL in the smear zone
extends both above and below the present water table. It now appears the free phase
LNAPL is limited to the area immediately surrounding FTA 1 and an area extending
primarily westward from CDPs 1 and 2. Contaminant transport paths also include transfer
of contaminants from the liquid phase to the gaseous phase. The predominant pathway for
the majority of the contamination at OUI is believed to be from waste materials in the
source areas to the shallow on-base groundwater and onto the unsaturated zone. Because
LNAPL is in direct contact with soil and groundwater, contaminants in the LNAPL will
continue to dissolve in groundwater, adsorb to soil particles, and naturally attenuate.
Page ES-1. It is stated that ". ..wastes placed in LF4 were predominantly solid wastes,
although some liquid wastes may (emphasis added) have been placed there." This statement
is indicative of efforts to attempt to de-emphasize the importance ofLF4. The Final RI (1995) on
Page 3-8 notes that a variety of liquid wastes such as acids, cyanide compounds, methyl ethyl ketone,
phenols and IWTP sludge were placed in LF4. In fact, it is also noted that in spite of efforts to stop
the dumping of liquid wastes in this landfill, the practice continued until the mid-1970's even
though banned years before. If it was a problem after the ban, how can SWLC believe that only
minimal liquid wastes were dumped there before. It is misleading to imply that LF4 poses no problem
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because on a weight basis, perhaps more solid waste than liquid waste was placed there. How do you
compare pound for pound the importance of concrete and paper against vinyl chloride or cyanide?
Response to Comment: The statement referenced from the FS does not appear to compare
the importance of liquid wastes versus solid wastes. An investigation to evaluate the
nature of the Landfills 3 and 4 is currently being performed. A report of this investigation
will be available next year. In order to clarify the last sentence of the second paragraph of
Page ES-1 of the FS, "may have also been" will be replaced with "were reportedly."
Page ES-2. "Of the flow that does move east, it appears that most emanates in seeps and
springs and little migrates downhill through the landslide debris formation. This may have
limited contaminant migration in an easterly direction off-base." The lack of monitoring wells
between OU1 and South Weber in the north and easterly directions makes it impossible to
characterize whether there is contamination present beneath the residences and school or to what
extent any plume exists in the easterly or northerly direction. Vinyl chloride and other compounds
have been detected adjacent to OUl to the north and east in monitoring wells at the Base boundary
and in soil gas monitoring along the hillside. This is an area that must be addressed in a more
complete manner.
Response to Comment: Investigation has been performed north and east of the unit. The
investigation has been documented in the Remedial Investigation (RI) (Montgomery
Watson, 1995). Of the areas off-Base, a majority of the investigation has been done in the
western areas because nearly all of the contamination has been found in the western area.
Only limited or no contamination has been found in northern and eastern areas.
Additional investigation is currently planned for off-Base areas north and west of the on-
Base portion of OUl. This investigation will be documented in an investigation report to be
completed in the spring of 1998.
Page ES-4. In the first paragraph the discussion centers on the conversion of TCE to DCE
and the volatilization of the contaminants from seeps, springs and groundwater - all
implying a lowering of exposure and toxicity. On the one hand, it appears the DF FS relies on
lowered risk due to the isolation of residents of South Weber from the DCE plume because there are
no users of the shallow groundwater, but on the other hand, the DF FS relies on evaporation and loss
through seeps and springs which are potential routes of exposure to people and wildlife. In addition,
the implication that the breakdown of TCE to DCE is a good thing doesn't take into account the
transformation to DCE to Vinyl Chloride (Final FI, Figure 12-1). Has vinyl chloride been found at
OU2 which also has a plume of TCE? Is the presence of vinyl chloride in LF4, along the hillside and
in wells in portions of South Weber to the north and west a result of transformation from TCE or are
LF4 and other locations in OUl the source of vinyl chloride that was placed there?
Response to Comment: Vinyl chloride has been detected in localized, off-base areas of
OU2, at concentrations marginally above method detection limits. A similar comment was
provided by the EPA on this issue (see EPA Comment No. 12, regarding the May 1997
Draft Final FS). As per the response to that comment, vinyl chloride has not been
consistently detected in the OUl DCE plume, likely indicating that it degrades at a rate
more rapid than DCE and does not accumulate in the groundwater. Vinyl chloride
generally degrades to ethylene and carbon dioxide and does not persist in the environment
for long periods of time.
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Page ES-4. Summary of Remedial Action Objectives.
• "Prevent ... excess cancer risk greater than 1 x 10"^ tp 1 x 1(H>". This appears to be a
rather broad range and it seems risk analysis should recognize demographic studies that indicate
mere proximity to Superfiind sites is related to increased incidence of disease as Brent Poll has
pointed out in several meetings. Further, the risk of cancer or disease to a single individual is
either 1 or 0, not a fractional number.
Response to Comment: The risk analyses presented and referenced in the FS have followed
agency guidelines and industry standards. The approaches suggested in the comment
would not increase the certainty of these analyses, even if they were accepted practice.
• "Minimize ... within a reasonable time frame". After 20 years of study and unknown
exposures to residents, HAFB is moving along through the recipe of the RI/FS process while the
plume has spread beyond all existing monitoring points. What is a reasonable time frame for
remediation given the time expended to this point while many questions still remain
unanswered? It appears that if we wait to answer all the questions before implementing any
remediation, the residents of South Weber will be subjected to continued risk for decades to come.
There is no good reason for not implementing interim actions now to stop the migration off-Base.
Response to Comment: Remedy selection is based on nine evaluation criteria required
by the EPA. While these criteria do not directly include "time expended to this point,"
community acceptance is an important criteria. The comment regarding "interim
measures" has been addressed previously in a letter from Hill Air Force Base, dated
April 11, 1997, that was written in response to comments in the SWLC review of the
Draft Phase I Croundwater Pre-Design Data Collection Work Plan by CH2M HILL. In
addition, please review the last paragraph of Mr. Brent Poll's letter to Hill Air Force
Base, dated November 14,1995.
• "Remediate LNAPL and landfill contents ... to enable long-term attainment of...
objectives". Again, the use of "long-term" does not provide any assurance of improvement
within a finite time period. The residents of South Weber deserve a more definitive schedule. As
pointed out in the previous comment, 20 years is a long time to be subjected to the stress of
knowing your home or school is sitting atop contaminated groundwater or that the air and soil
may contain compounds that can cause cancer, birth defects or other health problems. There has
been no attempt to address the psychological burden to the residents of South Weber. How does
the risk analysis take into account the stress of "long-term" cohabitation with the unknown
consequences ofOUl and the potential for increased susceptibility of individuals to health
problems because of this stress? Use of adjectives such as "long-term" does not provide closure
to the problems faced by the residents of South Weber.
Response to Comment: The words "enable long-term attainment" in this remedial
objective are meant to convey the importance of remediating source areas sufficiently so
that the remedial objectives for other media such as groundwater, surface water, and
soil can be met and maintained. It appears that this objective has been mis-interpreted
to imply that remedial objectives for other media only need to be met in the "long-
term." This meaning was not intended, and the verbage will be revised to clarify the
intent.
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It is recognized that the intent of the comment is directed at the time necessary to
remediate groundwater. This point has been made previously by the regulatory
agencies also. There are uncertainties in making remedial projections, and to suggest
otherwise is also unacceptable. The FS does contain numerous references to quantified
estimates of remedial time frames. In response to this SWLC comment, and several
received from the regulatory agencies, attempts will be made to present remedial time
frames more consistently and clearly in the FS and the Proposed Plan.
• "Prevent above ground landfills gas concentration and subsurface land gas
concentrations from reaching dangerous (i.e. explosive) levels at receptor locations
beyond the landfill perimeter." It doesn't take explosive concentrations of chemical vapors to
be dangerous. Certainly the consideration of exposure to landfill gases such as vinyl chloride
(present at 30,000 ppb in the landfill vent system) shouldn't be limited to areas beyond the
landfill perimeter because of the risk to Base personnel, or in the event of Base closure, to future
occupants of the Base.
Response to Comment: A similar comment was provided by the UDEQ on this issue
(see UDEQ Comment No. 3, regarding the May 1997 Draft Final FS). As per the
response to that comment, an analysis will be included (and referenced) as Section 1-5
in Appendix I of the Final FS.
Additional General Comment
A further objective should be added to recognize that a "cleanup" should be just that.
Source areas that are feeding the contaminants into the environment should be remediated
so that they can no longer be sources. Mere containment as a long-term goal leaves the
problem in place in perpetuity and, as is the case here, the contamination is allowed to
continue to migrate without controls indefinitely. The recognition in the DFFS that natural
attenuation can take up to 50 years (I assume this is discounting any further inputs from
Source Areas) is an indication that "long-term" can mean several lifetimes. It is also an
indication that cost evaluations showing the removal option is not cost feasible may be
flawed by not taking into account the potential length of time (» 30 years) other options
may have to be continued in operation.
Response to Comment: Life cycle costs, calculated on the basis of present worth, were
estimated using agency guidelines and industry standards, so the comparisons are not
biased. In general, the present worth of operation and maintenance or capital replacement
costs beyond year 30 are small and do not greatly affect the present worth costs.
Page ES-5. Source Area Alternatives Comparison.
It is admitted that Alternative 1 - No Further Action is not protective of human health and
the environment. Therefore, it is imperative to ask why HAFB continues to delay implementing
measures to control the contaminant migration from these source areas when such measures were
proposed two years ago? If HAFB knows these areas pose a risk, regardless of debate over the
ultimate remediation of the sources, interim measures should be installed immediately. In Section
1.0, page 1-7 the implication that the southern portion ofLF4 was a sanitary landfill seems weak
when the data for landfill gas in this portion of the landfill indicates numerous chemical vapors
including the above mentioned vinyl chloride (30,000 ppb). It is also important to point out that in
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an analysis of hazards posed by areas on Base, Engineering Science (1982) gave Landfill 4 the
highest risk.
Response to Comment: The comments regarding "interim measures" have been addressed
previously in a letter from Hill Air Force Base, dated April 11,1997, that was written in
response to comments in the SWLC review of the Draft Phase I Groundwater Pre-Design Data
Collection Work Plan by CH2M HILL. In addition, please review the last paragraph of Mr.
Brent Poll's letter to Hill Air Force Base, dated November 14, 1995. As stated in the RI
report, the existence of volatile organic compounds, such as vinyl chloride, in the landfill
gas collection system is consistent with volatilization of compounds found in the
groundwater underlying OU1. An investigation to further evaluate the nature of the
Landfills 3 and 4 is currently being performed. A report of this investigation will be
available next year.
Additional General Comment
Since investigations are still ongoing and data gaps continue to exist, I must reiterate my
concern that interim measures be implemented as soon as possible. These should, at a
minimum, consist of source containment by (1) a physical barrier and (2) groundwater
extraction and for non-source areas (South Weber) consist of (1) plume cut-off at the bottom
of the bluff, (2) hydraulic containment at leading plume edges and (3) groundwater
collection throughout the plume. Similar techniques have been proposed and are being
implemented for OU2.
While investigations and debate over the source areas may continue for some time, it
appears that further delay in implementing measures to mitigate off-site migration and
contamination is not in anyone's interest and is affecting South Weber and its residents
adversely. Therefore, I fail to understand the reluctance of HAFB to proceed with the
measures proposed in the EE/CA in October 1995.
Response to Comment: The comments regarding "interim measures" have been addressed
previously in a letter from Hill Air Force Base, dated April 11,1997, that was written in
response to comments in the SWLC review of the Draft Phase I Groundwater Pre-Design Data
Collection Work Plan by CH2M HILL. In addition, please review the last paragraph of Mr.
Brent Poll's letter to Hill Air Force Base, dated November 14, 1995.
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