Superfund Record of Decision Nebraska Ordnance Plant Former OU 2 Mead NE


                                   EPA/ROD/R07-97/143
                                   1997
EPA Superfund
     Record of Decision:
     NEBRASKA ORDNANCE PLANT (FORMER)
     EPA ID: NE6211890011
     OU02
     MEAD, NE
     04/07/1997

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October 1, 1996
WCC Project 92KW030M

Commander
U.S. Army Engineer District, Kansas City
ATTN: CEMRK-EP-EC (Ms. Rosemary Gilbertson)
700 Federal Building
601 East 12th Street
Kansas City, Missouri 64106-2896

Re: Transmittal of Final Record of Decision for Signature Pages Completion
For Operable Unit No. 2 (Groundwater)
Former Nebraska Ordnance Plant, Mead, Nebraska
Contract No. DACA41-92-C-0023

Dear Ms. Gilbertson:

We are hereby transmitting seven copies of the subject document. We understand that after the signature
pages have been completed, we will distribute copies of the signed document according to the attached
distribution list.

On September 30, 1996, we transmitted to you 13 pages of this document which showed revisions from the
draft final document in redline/strikeout format. We also copied the transmittal to Mr. Craig Bernstein
of the U.S. Environmental Protection Agency and Mr. Troy Bredenkamp of the Nebraska Department of
Environmental Quality. Electronic facsimile was used to make the transmittals.

Please contact us should you have any guestions.

Very truly yours,

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DISTRIBUTION LIST (After Signature)
OF THE FINAL RECORD OF DECISION
OPERABLE UNIT NO. 2
FORMER NEBRASKA ORDNANCE PLANT
MEAD, NEBRASKA
Organization
U.S. Army Corps of Engineers
Kansas City District
ATTN: CEMRK-EP-EC (Rosemary Gilbertson)

U.S. Army Corps of Engineers
Kansas City District
ATTN: CEMRK-MD-H (Steve Iverson)
Copies
7
Letter of Transmittal
Only
U.S. Army Corps of Engineers
HTRW Center of Expertise
ATTN: HTRW Document Distribution (Ric Hines)

Nebraska Department of Environmental Quality
ATTN: Mr. Troy Bredenkamp

University of Nebraska Lincoln
Agricultural Research and Development Center
ATTN: Mr. Daniel J. Duncan

U.S. Environmental Protection Agency Region VII
Waste Management Division
ATTN: Mr. Craig Bernstein

Natural Resources District
ATTN: Mr. Larry Angle

Nebraska Department of Health
ATTN: Mr. Scott Petersen

Lincoln Water System
ATTN: Mr. Jerry Obrist

University of Nebraska Hazardous Materials Safety Officer
ATTN: Mr. Del Weed
Nebraska National Guard
ATTN: Dave Wunibald
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TABIiE OF CONTENTS

Section Page

1.0 DECLARATION 1-1

2.0 DECISION SUMMARY 2-1
2.1 SITE NAME, LOCATION, AND DESCRIPTION 2-1
2.2 SITE HISTORY AND PREVIOUS INVESTIGATIONS 2-2
2.2.1 Site History 2-2
2.2.2 Previous Investigations 2-4
2.2.3 Summary of OU2 RI Results 2-6
2.3 COMMUNITY PARTICIPATION 2-7
2.4 SCOPE AND ROLE OF OPERABLE UNIT 2 REMEDIAL ACTION
WITHIN THE SITE STRATEGY 2-8
2.5 SUMMARY OF SITE CHARACTERISTICS 2-10
2.6 REMOVAL ACTIONS 2-11
2.7 SUMMARY OF SITE RISKS 2-11
2.7.1 Potential Human Health Risks 2-12
2.7.2 Ecological Risk Assessment 2-14
2.8 SUMMARY OF ALTERNATIVES 2-15
2.8.1 Alternative 1 - No Action 2-19
2.8.2 Alternative 2 - Hydraulic Containment 2-20
2.8.3 Alternative 3 - Focused Extraction 2-20
2.8.4 Alternative 4 - Focused Extraction and Soil Excavation 2-21
2.8.5 Alternative 5 - Focused Extraction with Air Sparging 2-21
2.8.6 Alternative 6 - Focused Extraction with Air Sparging and
Soil Excavation 2-22
2.8.7 Alternative 7 - Groundwater Extraction 2-23
2.8.8 Alternative 8 - Groundwater Extraction and Soil Excavation 2-23
2.9 TREATABILITY STUDIES 2-24
2.10 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES 2-24
2.10.1 Introduction 2-24
2.10.2 Comparison of Alternatives 2-25
2.10.3 Summary 2-31
2.11 THE SELECTED REMEDIAL ACTION 2-32
2.12 STATUTORY DETERMINATIONS 2-33
2.12.1 Protection of Human Health and the Environment 2-33
2.12.2 Compliance with ARARs 2-33
2.12.3 Cost Effectiveness 2-40
2.12.4 Utilization of Permanent Solutions and Innovative Treatment
Technologies to the Maximum Extent Practicable 2-40
2.12.5 Preference for Treatment Which Reduces Toxicity, Mobility,
or Volume 2-41
2.13 DOCUMENTATION OF SIGNIFICANT CHANGES 2-41

3.0 RESPONSIVENESS SUMMARY 3-1
3.1 OVERVIEW 3-1
3.2 BACKGROUND ON COMMUNITY INVOLVEMENT 3-1
3.3 SUMMARY OF PUBLIC COMMENTS AND AGENCY RESPONSES 3-2
3.3.1 Remedial Alternative Preferences 3-3
3.3.2 Impact on Groundwater Supply 3-9
3.3.3 Reuse of Treated Water 3-10
3.3.4 Nitrates Contamination 3-11
3.3.5 Current Ecological Impacts 3-12
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LIST OF FIGURES After Page

FIGURE 1 GENERAL SITE LOCATION MAP 2-1
FIGURE 2 SITE MAP 2-1
FIGURE 3 AREA OF GROUNDWATER WITH
CONCENTRATIONS EXCEEDING FINAL TARGET
GROUNDWATER CLEANUP GOALS 2-9
FIGURE 4 SOIL EXCAVATION AREAS - FORMER NOP LOAD LINE 1 2-10
FIGURE 5 SOIL EXCAVATION AREAS - FORMER NOP LOAD LINE 2 2-10
FIGURE 6 SOIL EXCAVATION AREAS - FORMER NOP LOAD LINE 3 2-10
FIGURE 7 TYPICAL SOIL EXCAVATION SECTIONS 2-10
LIST OF TABLES

TABLE 1 RANGE OF COG CONCENTRATIONS DETECTED
IN MONITORING WELL SAMPLES 2-6
TABLE 2 FINAL TARGET GROUNDWATER CLEANUP GOALS 2-15
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LIST OF ACRONYMS
AFBMD
AOP
ARARs
ARDC
AT SDR
CAMUs
CERCLA
CERCLIS

COCs
DNT
DoD
DWEL
DRE
FS
GAG
HA
HI
IAG
MCL
Ig/L
NCP
NDEQ
NOP
NPDES
NPL
NRD
O&M
OU
PCB
RAOs
RCRA
RDX
RI
RME
ROD
SARA
SMCLs
SVE
SVOCs
TBCs
TCE
TNB
TNT
TRC
TUs
USAGE
USATHAMA
US EPA
UXO
VOCs
Air Force Ballistic Missile Division
advanced oxidation processes
applicable or relevant and appropriate requirements
Agricultural Research and Development Center
Agency of Toxic Substances and Disease Registry
corrective action management units
Comprehensive Environmental Response, Compensation, and Liability Act
Comprehensive Environmental Response, Compensation, and Liability
Information System
chemicals of concern
2,4 or 2,6-dinitrotoluene
Department of Defense
Drinking Water Equivalent Level
destruction and removal efficiency
Feasibility Study
granular activated carbon
Health Advisory
Hazard Indices
Interagency Agreement
Maximum Contaminant Level
micrograms per liter
National Oil and Hazardous Substances Pollution Contingency Plan
Nebraska Department of Environmental Quality
Nebraska Ordnance Plant
National Pollutant Discharge Elimination System
National Priorities List
Natural Resources District
operation and maintenance
Operable Unit
Polychlorinated Biphenyl
remedial action objectives
Resource Conservation and Recovery Act
hexahydro-1,3,5-trinitro-l, 3,5-triazine
Remedial Investigation
Reasonable Maximum Exposure
Record of Decision
Superfund Amendments and Reauthorization Act
Secondary Drinking Water Standards
soil vapor extraction
semi-volatile organic compounds
To Be Considered standards
trichloroethene
1,3,5-trinitrobenzene
2,4,6-trinitrotoluene
Technical Review Committee
temporary units
U.S. Army Corps of Engineers
U.S. Army Toxic and Hazardous Materials Agency
U.S. Environmental Protection Agency
Unexploded ordnance
volatile organic compounds
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1. 0 DECLARATION

Site Name and Location

Former Nebraska Ordnance Plant
Mead, Nebraska

Operable Unit 2: Contaminated groundwater, explosives-contaminated soil which could act as a source of
explosives contamination of groundwater and which does not meet the Operable Unit 1 (OU1) excavation
criteria, and soil contaminated with volatile organic compounds (VOCs). Comprehensive Environmental
Response, Compensation, and Liability Information System (CERCLIS) Identification Number: NE6211890011

Statement of Basis and Purpose

This decision document presents the selected remedial action for OU2 at the former Nebraska Ordnance
Plant (NOP) site near Mead, Nebraska, which was chosen in accordance with the Comprehensive Environmental
Response, Compensation, and Liability Act (CERCLA), as amended by the Superfund Amendments and
Reauthorization Act (SARA) and, to the extent practicable, the National Oil and Hazardous Substances
Pollution Contingency Plan (NCP). This decision is based on the administrative record file for this site
and has been made by the U.S. Environmental Protection Agency (USEPA) and the U.S. Army Corps of
Engineers (USAGE), in consultation with the Nebraska Department of Environmental Quality (NDEQ).

Assessment of the Site

Actual or threatened releases of contaminants from this site, if not addressed by implementing the
remedial action selected in this Record of Decision (ROD), may present a current or potential threat to
public health, welfare, or the environment.

Description of the Selected Remedial Action

The former NOP site was used as an ordnance loading, assembly, and packing facility. Operations at the
NOP resulted in contamination of soil and groundwater with explosive compounds. Subseguent to NOP
operations, a missile facility was constructed and parts were cleaned on the site. These activities
resulted in contamination of groundwater with trichloroethene (TCE). The site has been divided into
three operable units. Operable Unit 1 encompasses the upper 4 feet of soil contaminated with explosive
compounds. OU2 includes contaminated groundwater, explosives-contaminated soil not remediated during OU1
which could act as a source of explosives contamination of groundwater, and soil contaminated with
volatile organic compounds. A former on-site landfill and areas of waste not previously identified are
included in OU3.

The remedial action for OU2 addresses one of the principal threats at the site, contaminated groundwater,
by containing, extracting, and treating the contaminated groundwater on-site. The major components of
the selected remedy include:

• Hydraulically contain contaminated groundwater exceeding the Final Target Groundwater Cleanup
Goals.

• Focused extraction of groundwater in areas with relatively high concentrations of TCE and
explosives.

• Treat all extracted groundwater using granular activated carbon (GAG) adsorption, advanced
oxidation processes (AOP), and air stripping. GAG adsorption and AOP may be applied
individually or in combination, while air stripping must be applied in combination with one
of the other technologies to effectively treat explosives.

• Dispose of the treated groundwater by beneficially reusing it or through surface discharge.

• Provide a potable water supply to local groundwater users whose water supply contains
hexahydro-1,3,5-trinitro-l,3,5-triazine (RDX) exceeding the Lifetime Health Advisory (HA)
and/or TCE exceeding the Maximum Contaminant Level (MCL).

• Monitor the groundwater elevations and water guality.

• Excavate and treat explosives-contaminated soil which could act as a source of explosives
contamination of groundwater and which does not meet the Operable Unit 1 (OU1) excavation
criteria.
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The OU1 soil remediation will remove all of the identified explosives contaminated soils that pose an
unacceptable risk with respect to dermal contact or ingestion. The maximum depth of the OU1 remediation
will be 4 feet. Low concentrations of explosives will remain in soil outside and beneath the OU1
remediation areas. These soils which do not meet the OU1 excavation criteria could potentially act as a
source of continuing explosives contamination of groundwater and are referred to subseguently as
"leaching soils", and are addressed by the OU2 remedy.

Statutory Determinations

The selected remedial action is protective of human health and the environment, complies with Federal and
State laws and regulations that are applicable or relevant and appropriate to the remedial action, and is
cost-effective. This remedial action utilizes permanent solutions and alternative treatment technologies
to the maximum extent practicable, and satisfies the statutory preference for a remedial action that
employs treatment that reduces toxicity, mobility, or volume as a principal element. A five-year review
as specified in CERCIA Section 121(c) will be reguired for this remedy because hazardous substances will
remain on-site in groundwater above health-based remediation goals at the end of five years. No review
would be reguired for the soil remediation.
LEAD AND SUPPORT AGENCY ACCEPTANCE
OF THE RECORD OF DECISION
FORMER NEBRASKA ORDNANCE PLANT SITE
OPERABLE UNIT 2

Signature sheet for the following Record of Decision for Operable Unit 2; contaminated groundwater,
explosives-contaminated soil which could act as a source of explosives contamination of groundwater and
which does not meet the OU1 excavation criteria, and soil contaminated with VOCS, final action at the
Former Nebraska Ordnance Plant site by the U.S. Army Corps of Engineers and the U.S. Environmental
Protection Agency.

LEAD AND SUPPORT AGENCY ACCEPTANCE
OF THE RECORD OF DECISION
FORMER NEBRASKA ORDNANCE PLANT SITE
OPERABLE UNIT 2

Signature sheet for the following Record of Decision for Operable Unit 2; contaminated groundwater,
explosives-contaminated soil which could act as a source of explosives contamination of groundwater and
which does not meet the OU1 excavation criteria, and soil contaminated with VOCs, final action at the
Former Nebraska Ordnance Plant site by the U.S. Army Corps of Engineers and the U.S. Environmental
Protection Agency.

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2.0 DECISION SUMMARY

2.1 SITE NAME, LOCATION, AND DESCRIPTION

The former NOP site occupies approximately 17,250 acres located one-half mile south of the town of Mead,
Saunders County, Nebraska as shown on Figure 1. During World War II and the Korean Conflict, bombs,
shells, and rockets were assembled at the site. The site includes four load lines, where bombs, shells,
and rockets were assembled; the Burning/Proving Grounds, where fuses were tested and materials were
destroyed by burning; a Bomb Booster Assembly Area, where boosters that amplify the effect of the
detonators and assure the complete detonation of the main explosive were assembled; Administrative Area,
which included offices, residences, and a laundry; an Air Force Ballistic Missile Division (AFBMD)
Technical Area, where historical information suggests that parts were cleaned; and an Atlas Missile Area.
The locations of these features are shown on Figure 2. According to reports, wastewater from both the
load line plant operations and the laundry was discharged into a series of sumps, ditches, and
underground pipes. Historical information also suggests that TCE was released at the AFBMD Technical
Area and the Atlas Missile Area.

The former NOP site is located in the Todd Valley, an abandoned alluvial valley of the ancestral Platte
River. The thickness of unconsolidated material above bedrock in the Todd Valley at the site ranges from
approximately 81 feet to 157 feet. The unconsolidated material consists of topsoil, loess, sand, and
gravel. The uppermost bedrock unit is the Omadi Shale in the northwest and the Omadi Sandstone in the
southeast portions of the site.

Three aguifers are present at the site: the Omadi Sandstone aguifer, the Todd Valley aguifer, and the
Platte River alluvial aguifer. Three aguitards are present: the Pennsylvanian shales, the Omadi Shale,
and the Platte River aguitards. Where the Omadi Shale is absent, the Todd Valley aguifers and the Platte
River alluvial aguifer are in hydraulic communication with the Omadi Sandstone and behave as single
aguifers without hydraulic barriers.

The water-bearing portions of the unconsolidated material in the Todd Valley are divided into two units,
an upper fine sand unit and a lower sand and gravel unit. During the OU2 Remedial Investigation (RI),
the sand and gravel unit was found to range from 17.5 to 72 feet thick and the fine sand unit was found
to range from 12 to 77 feet thick. The upper fine sand unit is overlain by 4 to 23 feet of the Peoria
Loess.

The unconsolidated material in the Platte River Valley, which ranges from 39 to 49 feet thick. Overbank
silts and clays ranging from 10 to 17 feet thick overlie the Platte River alluvial sands and gravels.

The water table surface of the Todd Valley slopes toward the south-southeast with depths to groundwater
table in the Todd Valley ranging from 6.6 feet to 58.0 feet. A local zone of groundwater discharge is
located along the western side of the Platte River floodplain in the southeastern portion of the site.
East of Johnson Creek, the water table surface of the Platte River alluvial aguifer slopes to the south,
paralleling the Platte River Valley with depths to groundwater table in the Platte Valley ranging from
0.0 to 10.2 feet.

The site is nearly flat, with a few gentle slopes. Surface water drainage in the eastern portion of the
site is generally to the southeast, toward Johnson Creek and the Natural Resources District (NRD)
Reservoir. In the western portion of the site, surface water drains to the southwest, toward Silver
Creek.

According to the draft National Wetlands Inventory Map for the Mead Quadrangle, a number of wetland types
occur in the vicinity of the site, however, these areas will not be influenced by the activities
addressed in OU2.

Most of the site is owned by the University of Nebraska, which operates an agricultural experiment
station called the Agricultural Research and Development Center (ARDC) on the premises. Crop, hog,
dairy, and cattle research take place on site. Other portions are owned by the Nebraska National Guard,
United States Air Force, and Army Reserves. Some private pasture and crop production also take place on
site, and some private light industry exists near the northern end of the site. Adjacent land use is
primarily agricultural, except for the Village of Mead which is located north of the site.
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2.2 SITE HISTORY AND PREVIOUS INVESTIGATIONS

2.2.1 Site History

The former NOP was a load, assemble, and pack facility which produced bombs, boosters, and shells. The
NOP included four bomb load lines, a Bomb Booster Assembly plant, an ammonium nitrate plant, two
explosives burning areas, a proving range, a landfill, a wastewater treatment plant, analytical
laboratories, and storage and administration facilities. Most of the raw materials used to manufacture
the weapons were produced at other locations and shipped to the NOP facility for assembly. However,
ammonium nitrate was produced at the Ammonium Nitrate Plant during the first months of operation.
Finished munitions, bulk explosives, and related ordnance materials and components were stored and
demilitarized at the site.

Routine plant operations included washout of explosive materials prior to bomb loading and assembly, and
bomb washing following assembly. Wash water was discharged to sumps and in open ditches.

The production facilities were active during both World War II and the Korean Conflict. The Nebraska
Defense Corporation operated the NOP for the Army from 1942 until 1945 and produced munitions which were
loaded with trinitrotoluene (TNT), amatol (TNT and ammonium nitrate), tritonal (TNT and aluminum), and
Composition B (RDX and TNT). Tetryl boosters were assembled for bombs in the Bomb Booster Assembly Area.
In 1945, ordnance production operations were terminated, and the facilities and operations were placed on
inactive status.

During the interim period (1945 through 1949) , the NOP was decontaminated and used primarily for storage
and disposal of bulk explosives and munitions, and production of ammonium nitrate for use as fertilizer.
Decontamination consisted of flushing and sweeping buildings that were not being used for storage. After
decontamination operations were completed, explosives residues in the sumps, settling basins, pipelines
leading to the drainage ditches, and an unspecified quantity of contaminated soil and sludge from the
drainage ditches were removed and reportedly taken to the Burning/Proving Grounds. In some instances,
portions of the tile pipe composing the drainage system from the sump to the open ditches were removed
and disposed.

In 1950, the plant was temporarily reactivated and produced an assortment of weapons for use in the
Korean Conflict. The NOP was placed on standby status in 1956 and declared excess to Army needs in 1959.

After the NOP was declared excess in 1959, it was transferred to the General Services Administration for
disposition. Approximately 1,000 acres were retained by the Army for National Guard and Army Reserve
training, 12 acres were retained by the Amy for use as a Nike Missile maintenance area, 2,000 acres were
transferred to the U.S. Air Force to build the Offutt Air Force Base Atlas Missile Site, and 40 acres
were transferred to the Department of Commerce. From 1959 to 1960, the Offutt Air Force Base Missile
Site S-l launch area (Atlas Missile Area) was built on 1,185 acres north of Load Line 4. TCE was used
during construction to degrease and clean pipelines used to carry liquid oxygen fuel for missiles.
Historical information suggests that TCE was released as ground spills and/or discharged into surface
drainage features during the construction activities. The exact locations, quantities, and dates of TCE
disposal are not known. The missile facilities were abandoned in 1964, and the Atlas Missile Area and
the Nike Area were transferred to the Nebraska National Guard. The U.S. Air Force also occupied 34 acres
of the northern portion of Load Line 1 for use as the AFBMD Technical Area. The purpose of the
AFBMD Technical Area is unclear, but historical site information suggests that parts were cleaned with
TCE in a laboratory, and the spent TCE was discharged into the sewer. The potential TCE soil
contamination is not located in the area contaminated with explosives. In 1962, approximately 9,600
acres of the former NOP site were purchased by the University of Nebraska for use as an agricultural
research farm which is now the ARDC, and an additional 600 acres were obtained in 1964. The remaining
5,250 acres were eventually purchased by private individuals and corporations.

Since NOP closure, the property has been used primarily for agricultural production and research. In
addition to these land uses, several commercial operations were conducted on former NOP property. Apollo
Fireworks operated for a period of approximately 20 years until 1989 in the Bomb Booster Assembly Area.
At the former administration buildings, various commercial enterprises were in operation including
insulation board manufacturing and expanded styrene foam packing material processing. Property was
leased for these and other purposes by private individuals.

Several environmental investigations (discussed below) resulted in the listing of the former NOP site on
the National Priorities List (NPL) under Section 105 of CERCLA on August 30, 1990. In September 1991,
USAGE, USEPA, and NDEQ entered into an Interagency Agreement (IAG)under Section 120 of CERCLA to
investigate and control environmental contamination at the former NOP site.
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2.2.2 Previous investigations

Soil

Previous investigations include an archives search for the U.S. Army Toxic and Hazardous Materials Agency
(USATHAMA, now called Army Environmental Center) in 1983; Polychlorinated Biphenyl (PCB) investigations
by the University of Nebraska in 1984 and 1985, USEPA in 1988, and USAGE in 1993; a soil, sediment,
surface water, and groundwater investigation by USAGE in 1989; a shallow soil gas investigation in 1990;
a soil investigation by the USAGE in 1991; an unexploded ordnance (UXO) survey and soil investigation by
USAGE Lin 1991; a preliminary health assessment by the Agency of Toxic Substances and Disease Registry
(ATSDR) in 1991; and a Supplemental Soil RI for OU1 by USAGE in 1991.

The 1983 archives search was conducted to assess the potential for contamination at the NOP site from
Army operations. Findings of the Archive Search Report were based primarily on the U.S. Army Ordnance
Ammunition Command's 1959 Survey of Explosives Contamination. Areas recognized in the Archives Search
Report as having the greatest potential for explosives-contamination were the four load lines, the Bomb
Booster Assembly Area, and the Burning/Proving Grounds.

In 1989, USAGE conducted a confirmation study to determine if past Army activities at the NOP site
resulted in environmental contamination. A geophysical survey was conducted to screen boring locations
and locate buried materials. The study concluded that explosive residues are present in soil around
three of the load lines.

In 1991, USAGE identified and assessed potential sources of explosives contamination and UXO. USAGE
performed a records review and site inspection which included excavation of two test pits and collection
of 18 soil samples. Locations potentially reguiring remedial action were identified as those where solid
pieces of TNT were visibly present or where TNT was found in soil at concentrations greater than 2
percent by weight. The areas identified based on these criteria were at three of the load lines and
parts of the Burning/Proving Grounds.

ATSDR completed its Preliminary Health Assessment in 1991. ATSDR concluded that potential human exposure
to hazardous substances at the former NOP may result in adverse health effects. It was concluded that
the public could be exposed to the explosive compounds RDX and TNT via skin contact or soil ingestion.

In 1991 and 1992, USAGE conducted an OU1 RI to evaluate the extent (area and depth) of
explosives-contaminated soil at the former NOP site. Most sampling was based on historical washwater
disposal practices during the ordnance production process. Explosives compounds were detected in soil in
all four load lines, the Bomb Booster Assembly Area, and the Burning/Proving Grounds. No significant
explosives contamination was identified in the Administration Area. No live ordnance was found on-site.

OU1 RI results indicate that explosives contamination in soil is mostly limited to soils in and under
drainage ditches and sumps in the load lines and the Bomb Booster Area. It is believed that this
contamination originated from the discharge of water used to wash away explosives dust and residue which
resulted from the ordnance load, assemble, and pack process. In the Burning/Proving Grounds, testing and
burning activities probably contributed to soil contamination. The majority of the explosives
contamination was detected in shallow soil. At some locations, however, explosives compounds were
detected at depths of approximately 30 feet below the surface. Explosives contaminant concentrations in
the ditches generally decreased downstream from collection sumps. TNT, RDX, and 1,3,5-trinitrobenzene
(TNB) were the explosives contaminants most often detected. The OU1 results are presented in the
Supplemental RI Report for OU 1.

Based on the PCB investigations, PCB-contaminated soil was identified in locations associated with former
transformer pads and subseguently removed by the University in 1985 and USAGE in 1994 and 1995. Removal
of remaining PCB-contamination is ongoing. Unexploded ordnance has not been found on-site, but some
internal components of ordnance (booster adapters, fuses, propellants, and bulk TNT) were found and
disposed. Investigation of unexploded ordnance is ongoing at the site. Documents related to the site
are available for review in the information repository at the Ashland Public Library.

Groundwater

Groundwater sampling was initiated by USAGE during the 1989 Confirmation Sampling when samples were
collected from monitoring wells and water supply wells. RDX, TNT, and TCE were identified in the
groundwater samples. Some of the TCE concentrations exceeded the MCL of 5 micrograms per liter (Ig/L).
As a result of the Confirmation Study, carbon filtration systems were installed at two residences
southeast of the former NOP, a carbon filtration system was installed at the ARDC Agronomy Building, and
two ARDC water supply wells were removed from service. Subseguently, the water supply well sampling was
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continued on a periodic basis. Additional residences were identified where the TCE concentrations
exceeded the MCL or the RDX concentrations exceeded the HA of 2 Ig/L. Currently, water is being treated
and/or bottled water is being supplied at four private residences which are all southeast of the former
NOP. In addition, water is being treated with GAG adsorption at 26 ARDC locations.

In late 1989 and early 1990, a soil gas survey was conducted by USAGE to evaluate areas of soil that may
be contributing TCE contamination to groundwater. TCE and other VOCs were detected in some samples;
however, source areas were not definitively identified.

USAGE installed and sampled additional monitoring wells prior to the OU2 RI.

2.2.3 Summary of OU2 RI Results

USAGE conducted an OU2 RI in 1992 to evaluate the nature and extent of potential chemicals of concern
(COCs) in the groundwater at the former NOP site attributable to past Department of Defense (DoD)
activities. The secondary objective was to evaluate the potential nature and extent of VOC contamination
in soils at three areas (Administration Area, Atlas Missile Area, and the AFBMD Technical Area) to assess
whether or not these contaminated areas are possible continuing sources of VOCs in the groundwater.
Groundwater samples were also collected from 136 monitoring wells and were analyzed for VOCs, explosives
compounds, and general water guality parameters. Selected monitoring wells were also analyzed for
semi-volatile organic compounds (SVOCs) and metals. Soil and soil gas samples were collected and
analyzed for VOCs. Field data were also collected to characterize the geology at the former NOP site,
and to estimate the direction and rate of groundwater flow. Groundwater samples were collected from
every monitoring well on a guarterly basis beginning during the OU2 RI (August 1992) and continuing for
one year. Subseguent sampling has been performed periodically at selected monitoring wells, and the
monitoring program is ongoing.

The OU2 RI identified four groundwater contamination plumes with separate source location identified for
each plume. Two of the plumes consist of explosives contaminated groundwater (primarily RDX) and two of
the plumes consist of primarily TCE-contaminated groundwater. The plumes overlap in two arm where both
TCE and RDX are in the groundwater in the same location. Both the TCE plume with its source at the Atlas
Missile Area and the explosives plume with its source at Load Lines 2, 3 and 4 extend past the eastern
boundary of the former NOP.

Higher groundwater contamination was found in the upper fine sand units than in the sand and gravel units
below. Generally, lower contamination was found in the deepest of the three aguifers which is the Omadi
Sandstone aguifer. Table 1 lists the ranges of the COCs detected in groundwater.

The OU2 RI data indicated that the Administration Area was not a continuing source of groundwater
contamination. However, data did not conclusively indicate whether the Atlas Missile Area or the AFBMD
Technical Area are, or are not, continuing sources of TCE to groundwater. The data do indicate TCE
groundwater contamination did originate in those areas.

Subseguent to the OU2 RI, a Groundwater Containment Removal Action was developed to stop the spread of
the TCE plumes. The implementation of that removal action awaits acguisition of necessary easements for
property access. If the containment of the TCE plumes is not accomplished by this removal action, it
will be conducted as a part of the remedial action instead. Section 2.6 contains more details regarding
the Groundwater Containment Removal Action.
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Table 1
Range of COC Concentrations Detected in Monitoring Well Samples
Contaminant of Concern

Methylene chloride
1,2-dichloropropane
TCE
TNB
TNT
RDX
2,4-DNT
Range of Detected Concentrations on MWs
Maximum (Ig/L) Minimum (Ig/L)
610
27
4800
4
39
534
1.9
0.5 JB
0.7J
0.6J
0.1
0.10
0.08
0.13
Notes:
1) J = Below Quantitation Limit (estimated)
2) B = Compound also detected in laboratory blank
3) TCE = Trichloroethene
4) TNB = 1,3,5-trinitrobenzene
5) TNT = 2,4, 6-trinitrotoluene
6) RDX = Hexahydro-1,3,5-trinitro-l,3,5-triazine
7) 2,4-DNT = 2,4-dinitrotoluene
2.3 COMMUNITY PARTICIPATION

Community participation activities provide the public with an opportunity to express their views on the
preferred remedial action. USEPA, NDEQ, and USAGE consider public input from the community participation
activities in selecting the remedial alternative to be used for the site.

Community participation was provided in accordance with CERCLA, as amended by SARA. Community
participation highlights include the availability of several key documents in the administrative record,
public comment periods, and public sessions.

A Community Relations Plan for the former NOP site was prepared by USAGE, and approved by USEPA and NDEQ
in May 1992. This document lists contacts and interested parties throughout government and the local
community. It also establishes communication pathways to ensure timely dissemination of pertinent
information.
A Technical Review Committee (TRC) was established to insure that the cleanup of the former NOP site
would be carried out in the best interests of the communities involved. The TRC periodically meets and
reviews and comments on all official plans and documents and advises the appropriate agencies before
decisions are made regarding activities at the site.

Public meetings were held at the ARDC in July 1989 and in June 1990 to discuss the progress of the
ongoing studies at the site and to give the community a chance to voice their concerns and offer
comments. A public meeting and availability session in June 1994 and a public availability session in
February 1995 were held primarily to address OUl-related concerns; however, personnel familiar with OU2
activities also addressed OU2-related concerns. Both meetings were held at the ARDC.

USAGE and USEPA released the OU2 Proposed Plan on October 13, 1995 and made it available for public
review and comment. The information repository for the site has been established at the Ashland Public
Library, 207 North 15th Street, Ashland, Nebraska. The information repository contains the
administrative record including the RI report, Baseline Risk Assessment, Feasibility Study (FS) Report,
Proposed Plan, and other documents relevant to the former NOP site. This information was made available
to the public to facilitate public input concerning the investigation, remediation evaluation process,
and preferred alternative identification.

Legal notice of the Proposed Plan and the Public Meeting was included in the Wahoo Newspaper and the
Ashland Gazette on October 19, 1995. Legal notice advertisements also appeared in the Lincoln Star,
Lincoln Journal, and the Omaha World-Herald on October 16, 1995. A press release announcing the release
of the Proposed Plan and the Public Meeting date were provided to the Wahoo Newspaper, the Ashland
Gazette, the Lincoln Journal, and the Omaha World-Herald. A press release was also provided to National
Public Radio and KOLN-TV in Lincoln and WOWT-TV and KETV in Omaha. A public comment period on the
Proposed Plan was held from October 30, 1995, to November 29, 1995. The Proposed Plan was presented at a
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Public Meeting held on November 8, 1995, at the University of Nebraska-Lincoln ARDC Research and
Education Building at the site. At this meeting, representatives of USAGE, USEPA, and NDEQ answered
guestions from the public about the former NOP site and the OU2 remedial alternatives under
consideration.

All comments received by the USEPA and the USAGE during the public comment period, including those
expressed at the public meeting, are addressed in the Responsiveness Summary which is included with this
document.

This ROD presents the selected remedial action for OU2 at the former NOP site near Mead, Nebraska, chosen
in accordance with CERCLA, as amended by SARA, and to the extent practicable, the NCP. The decision for
this site is based on the administrative record.

2.4 SCOPE AND ROIiE OF OPERABLE UNIT 2 REMEDIAL ACTION WITHIN THE SITE STRATEGY

Early site characterization activities identified some sources of contamination that could be addressed
before full characterization activities were complete for other sources. USAGE, in consultation with
NDEQ and USEPA, organized the response actions into three OUs. These are as follows:

• Operable Unit 1: The upper 4 feet of soil contaminated with explosives compounds.

• Operable Unit 2: Contaminated groundwater, explosives-contaminated soil which could act as a
source of explosives contamination of groundwater and which does not meet the OU1 excavation
criteria, and soil contaminated with VOCs.

• Operable Unit 3: An on-site landfill and other disposal areas not identified at the signing
of the IAG.

Investigations and remediation feasibility evaluations have been or are conducted in accordance with the
OU designations. A record of decision selecting soil excavation and incineration as the remedy for OU1
was signed November 1995. The OUS RI is currently ongoing.

The objectives of the OU2 remediation are to:

• Minimize the potential for ingestion of contaminated groundwater, or reduce concentrations to
acceptable health-based levels.

• Minimize the potential for dermal exposure to contaminated groundwater, or reduce
concentrations to acceptable health-based levels.

• Minimize the potential for inhalation of chemicals released during the use of contaminated
groundwater, or reduce concentrations to acceptable health-based levels.

Data collected during the OU2 RI indicated that the soils at the Administration Area are not continuing
sources of TCE to groundwater. Other RI data did not conclusively indicate that the soils at the Atlas
Missile Area and the AFBMD Technical Area are, or are not, continuing sources of TCE to groundwater. The
data included soil gas data which indicated the presence of TCE; however, the TCE concentrations measured
by a laboratory in the soil samples did not correspond to the soil gas concentrations measured in the
field. Pilot-scale soil vapor extraction (SVE) studies to address the TCE-containing soil gas at the
Atlas Missile Area and the AFBMD Tech Area were also performed. While the pilot study concluded there is
a recoverable mass of TCE at these areas, the guantities of TCE present do not merit implementation of
full scale SVE remediation. Therefore, remedial actions to address VOCs in soil vapor are not proposed.
However, in the event TCE in soil vapor should contribute additional contamination to groundwater, that
contamination would be addressed by the focused extraction system.

The selected alternative includes the following processes to meet the objective identified above:

• Hydraulically contain contaminated groundwater.

• Focused extraction of groundwater in areas with relatively high concentrations of TCE and
explosives.

• Provide a potable water supply to local groundwater users whose water supply contains RDX
exceeding the HA and/or TCE exceeding the MCL

• Monitor the groundwater elevations and water guality.

• Excavate and treat leaching soils using the same methods as, and concurrently with, OU1
remedial activities.

This alternative will protect both human health and the environment. Groundwater containment,
extraction, and treatment is expected to prevent the spread of COCs to new areas; soil excavation and
treatment is expected to remove a potential source of explosives contamination of groundwater; and
potable water supply is expected to prevent human consumption of water which contains unacceptable COG
concentrations. In addition, groundwater containment, extraction, and treatment will eventually restore
the aguifer so that groundwater can be used in a beneficial manner directly without treatment.

2.5 SUMMARY OF SITE CHARACTERISTICS

Results of the OU2 RI indicate that there are two groundwater contamination plumes which consist
primarily of TCE-contaminated groundwater, and two plumes which consist primarily of RDX and other
explosives compounds. These four groundwater plumes are shown on Figure 3. Higher groundwater
contamination was found in the upper fine sand units than in the underlying sand and gravel units and
lower contamination was found in the bedrock aguifer. The concentration range of the COCs are given in
Table 1. Six of the seven COCs are classified as possible or probable human carcinogens, and all seven
may cause noncancer health effects. Potential risk from ingestion, dermal exposure, or inhalation of
these compounds is discussed in more detail in Section 2.7, Summary of Site Risks.

The fate and transport of the COCs were analyzed as a part of the OU2 RI to identify off-site areas
potentially affected by contamination and to estimate contaminant concentrations in those areas. The fate
and transport analysis was a multiple step procedure which consisted of screening the potential routes of
contamination, identifying the persistence of the contaminants in terms of their physicochemical
properties, and guantitatively simulating contaminant migration for the predominant transport mechanisms
identified during the screening process. The concentrations which were estimated using the analytical
model were compared to concentrations measured in the monitoring wells. The validity of representing
both the off-site areas potentially affected by contamination and the off-site contaminant concentrations
derived from the OU2 RI nature and extent characterizations were confirmed by the comparison.

The estimated volume of groundwater with COG concentrations exceeding the Final Target Groundwater
Cleanup Goals is approximately 23 billion gallons, or 69,000 acre-feet, underlying approximately 6,000
acres as shown on Figure 3. The Final Target Groundwater Cleanup Goals are described further in Section
2.8.

The OU1 soil remediation will remove all of the explosives contaminated soils that pose an unacceptable
risk with respect to dermal contact or ingestion. The maximum depth of the OU1 remediation will be 4
feet. Low concentrations of explosives will remain in soil outside and beneath the OU1 remediation
areas. These unremediated soils could potentially act as a source of continuing explosives to
groundwater and are referred to as "leaching soils". The OU2 FS Report details the criteria which were
used to determine the locations of the leaching soils shown on Figures 4 through 7. The criteria which
define theses leaching soils were developed using a combination of the HYDRUS Model, a modified version
of the Summers Model, and the Batch Flushing Model. The HYDRUS Model was used to predict the movement of
explosives through the unsaturated zone, and the modified Summers Model was used to predict the resulting
groundwater concentration after the leachate reached the saturated zone. The concentration of
groundwater contamination resulting from the leaching soils was plotted against time, and the time that
the groundwater concentration fell below the clean up goals was noted. The Batch Flushing Model was used
to estimate the restoration time frame for groundwater contamination assuming that leaching soils did not
contribute any contamination to the saturated zone. The restoration time frame estimate was compared to
leaching time determined during the unsaturated zone analysis.

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The leaching soils volume is estimated to be 2,600 cubic yards. The OU2 FS Report details the procedures
which were used to estimate the remediation areas and volumes.

2.6 REMOVAL ACTIONS

Five removal actions have been conducted to address potential risk from COG contamination in existing
drinking water on the former NOP site. Four of those removal actions consisted of installing
point-of-entry or point-of-use granular activated carbon adsorption treatment systems in private
residences or University of Nebraska ARDC facilities. The fifth action consisted of supplying bottled
water to a private residence.

A Groundwater Containment Removal Action has been developed for the site to allow an early start for the
TCE containment, which otherwise will take place under this ROD. The specific objectives for this
removal action are:

• Hydraulic containment of groundwater contamination to minimize expansion of the two TCE
contamination plumes prior to the initiation of the remedy. The Groundwater Containment
Removal Action is being conducted to stop the downgradient movement of the TCE plumes

• Protection of unimpacted downgradient groundwater users.

• Treatment and discharge of extracted groundwater to meet applicable standards.

• Periodic monitoring of the effectiveness of the containment system.

Because all of the proposed alternatives for the OU2 remedy at the site, except for the no action
alternative, include the element of hydraulic containment, the Groundwater Containment Removal Action
will be consistent with the final remedy. TCE containment work, if not carried out as a removal action,
will take place during the remedial action described in this ROD.

2.7 SUMMARY OF SITE RISKS

CERCLA reguires protection of human health and the environment from risks due to current and potential
future exposure to releases of hazardous substances at or from a site. As part of the OU2 RI/FS, a
Baseline Risk Assessment was prepared to evaluate potential human health risks associated with exposure
to contaminated groundwater and subsurface soils in the absence of any remedial action. Potential risks
were estimated based on a number of assumptions, including the populations that could be exposed to site
contaminants and the likely magnitude of any such exposures.

It was concluded that actual or threatened releases of contaminants from this site, if not addressed by
implementing the remedial action selected in this Record of Decision, may present a current or potential
threat to public health, welfare, or the environment.

2.7.1 Potential Human Health Risks

A detailed Baseline Risk Assessment was performed to characterize risks to both current and hypothetical
future populations. The key components of the risk assessment included a chemical analysis section that
identified the site-related chemicals, an exposure assessment that identified potentially exposed
populations and intake assumptions, a toxicity assessment that identified chemical specific toxicity
values, a risk characterization that guantified potential risks, and an uncertainty section that
identified the primary sources of uncertainty associated with the risk assessment and the likely impacts
of these uncertainties on the results.

Identification of Site-Related Chemicals

An evaluation of site groundwater data identified several VOCs, SVOCs, explosives, and one metal that
appeared to be contaminants related to the former NOP site. In addition, several site-related VOCs were
identified in subsurface soil at the former Atlas Missile Area and Load Line 1. These chemicals were
evaluated guantitatively in the risk assessment.

Exposure Assessment

An evaluation of local populations and land use was used to identify exposure scenarios for guantitative
evaluation in the risk assessment. Potential risks were estimated for both current and future use
scenarios. Site workers, and child and adult residents were evaluated for potential exposure to
groundwater from the two most-contaminated monitoring wells found on-site (MW-5B and MW-40B), while
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construction workers were evaluated for potential exposure to subsurface soils during excavation
activities and subsequent showering in water from the two most-contaminated wells. These populations are
believed to have the greatest potential for exposure at the site. For site workers and residents,
potential groundwater risks were evaluated quantitatively for three exposure pathways (ingestion,
inhalation, and direct dermal contact). For construction workers risks were evaluated for ingestion,
inhalation and direct dermal contact with subsurface soil, as well as for inhalation and direct dermal
contact with groundwater while showering. Upperbound exposure concentrations and parameters were
selected to estimate risks associated with Reasonable Maximum Exposure (RME), while mid-range values were
used to calculate risks and hazards under anticipated average exposure conditions. USEPA has defined the
RME as the highest exposure that can reasonably be expected to occur at a site.

Toxicitv Assessment

Two types of risk estimates were prepared as part of the Baseline Risk Assessment, potential excess
cancer risks (i.e., risks above the normal expected cancer rate) and non-cancer Hazard Indices (HI). The
cancer risks represent estimates of the probability that an individual might develop cancer as a result
of exposure over a lifetime to a chemical. For example, a 3 in 10,000 (also expressed as 3 x 10-4) risk
estimate means that not more than an additional 3 out of 10,000 people exposed would be expected to
develop cancer. Non-cancer health hazards are addressed by comparing average (chronic) daily intakes to
reference doses. A reference dose is the amount of a chemical that a person can take in over a long term
without suffering adverse health effects.

Risk Characterization

When the calculated cancer risk from lifetime exposure to site-related chemicals is estimated to be more
than one additional (excess) cancer case in 10,000 (1 x 10-4), some kind of remedial action is generally
required under CERCLA. When the cancer risk is between one additional cancer case in 10,000 and one in
1,000,000 (1x10-6) people, action may be necessary depending on such site-specific factors as location,
environmental impact, and non-cancer health effects. If the risk is less than one additional cancer case
in 1,000,000 people, action is generally not required unless there are also environmental risks or
non-cancer health effects. For non-cancer effects, an HI value of 1 is considered an upper "threshold"
for possible adverse health effects. The following tables summarize the cancer risks and the non-cancer
hazards associated with OU2 groundwater and subsurface soil at the Site.

Summary of Cancer Risks
Adult
Resident
Child
Resident
On-Site
Worker
Construction
Worker in
Load Line 1
Construction
Worker in Atlas
Missile Area
Monitoring
Well MW-5B
3 x 10-4 7 x 10-5 4 x 10-5
3 x 10-E
3 x 10-E
Monitoring
Well MW-40B
2 x 10-3 6 x 10-4 2 x 10-4
4 x 10-6
4 x 10-6
Summary of Non-Cancer His
Acceptable HI range is less than 1
Adult
Resident
Child
Resident
On-Site
Worker
Construction
Worker in
Load Line
Construction Worker
in Atlas Missile Area
Monitoring 3 7 1 0.02
Well MW-5B
Monitoring 3 13 0.9 1
Well MW-40B
0.02
1
The Baseline Risk Assessment identifies several chemicals as the principal sources of health risks. At
well MW-5B, approximately 90 percent of the total cancer risk is due to RDX. Other explosives compounds
(TNT and 2,4 or 2,6-dinitrotoluene (DNT)) which were also found in MW-5B, contribute an additional 9
percent to cancer risk. Virtually all of the cancer risk due to chemicals detected at well MW-40B is
attributable to TCE. Similar to the case of carcinogens, non-cancer hazards for MW-5B were driven by
explosives and non-cancer hazards for N4W-40B were driven by VOCs.
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As discussed above, the two monitoring wells with the highest measured concentrations of TCE and RDX in
groundwater were used to develop the tables presented above. Cancer risks and His calculated in an
identical manner for RDX and TCE concentrations measured in other monitoring wells would be lower than
these tabulated values.

Uncertainties

The procedures and inputs used to estimate risks are subject to a wide variety of uncertainties. The
main sources of uncertainty identified in the OU2 risk assessment include the following:

• Environmental chemical sampling and analysis
• Estimation of exposure point concentrations
• Exposure parameter estimation
• Toxicological data

Because of these uncertainties, conservative (health-protective) assumptions have been made at each step
of the risk assessment process to prevent an underestimation of site risks.

2.7.2 Ecological Risk Assessment

In the absence of a remedy, the only known potential for exposure or risk from OU2 contaminated
groundwater or subsurface soil to ecological species or habitats is via irrigation. The potential for
irrigation water to affect ecological species and habitats was not addressed as part of OU2, and will be
evaluated in the OU3 risk assessment as part of an ongoing plant bio-uptake study.

An ecological risk assessment was performed as a part of OU1. Potential risks to the environment from
contaminated soil at the site are limited to areas where high levels of contaminants have been detected.
Plants and small animals exposed to high contaminant levels may experience inhibited growth or other
adverse effects. Due to the localized distribution of contaminated areas, however, exposure to
contaminants is not likely to cause measurable effects on plant or animal populations. Likewise, based on
OU1 studies, concentrations of contaminants in on-site surface water are not likely to cause adverse
effects to exposed organisms.

There may be a potential for endangered and threatened species, critical habitats, and wetlands to exist
at the former NOP. The potential for endangered and threatened species, critical habitats, and wetlands
to be impacted during construction and system operation will be evaluated during the Remedial Design
process. The negative impacts, if any, will be mitigated or avoided. The appropriate regulatory
agencies have been and will be involved in identifying endangered and threatened species, critical
habitats, and wetlands.

2.8 SUMMARY OF ALTERNATIVES

Remedial Action Objectives

Remedial action objectives (RAOs) were developed to address the contaminated groundwater and
explosives-contaminated soil which could act as a source of explosives contamination of groundwater while
considering the long-term goals of protecting human health and the environment and meeting applicable or
relevant and appropriate reguirements (ARARs) of Federal and State laws and regulations. The overall OU2
RAOs are:

• Minimize the potential for ingestion of contaminated groundwater, or reduce concentrations to
acceptable health-based levels

• Minimize the potential for dermal exposure to contaminated groundwater, or reduce
concentrations to acceptable health-based levels

• Minimize the potential for inhalation of chemicals released during the use of contaminated
groundwater, or reduce concentrations to acceptable health-based levels

The remedial action for explosives-contaminated leaching soils is to remediate those soils to the degree
that the groundwater remediation potentially benefits by saving time and money, and/or increasing
protectiveness.

Table 2 presents the Final Target Groundwater Cleanup Goals selected by USAGE, USEPA, and NDEQ for OU2.
This selection was based on balancing protection of human health and the environment with conservation of
public funds consistent with the need to meet regulatory reguirements including MCLs. The following
-------
rationale was used to develop the Final Target Groundwater Cleanup Goals:

• For those chemicals with MCLs established, the MCL is the cleanup goal

• For those chemicals that do not have MCLs, but have carcinogenic effects, non-carcinogenic
effects, or HAs, the cleanup goal is the lowest of any of the following: the value from the
carcinogenic risk of 1x10-5; the value calculated from the (non-carcinogenic) HI of 1.0; or
the HAs

The plumes shown on Figure 3 delineate the area of attainment.
TABIiE 2
FINAL TARGET GROUNDWATER CIiEANUP GOALS
CHEMICAL OF CONCERN

Methylene chloride
1,2-dichloropropane
TCE
TNB
TNT
2,4-DNT
RDX
CONCENTRATION (Ig/L)

5
5
5
0.778
2
1.24
2
Alternative Descriptions

Eleven preliminary remedial action alternatives were developed during the FS to address the RAOs. Three
of the alternatives were eliminated because they were determined to be ineffective. The remaining eight
alternatives were evaluated in detail in the FS Report. The following sections summarize these eight
alternatives, and the FS Report provides greater detail.

Certain elements were common to specific groups of the eight alternatives. To simplify the descriptions
of the individual alternatives, the common elements are discussed once below instead of repeating the
discussions within individual alternatives' descriptions.

Groundwater monitoring is common to all eight alternatives. Additional elements which are
common to Alternatives 2 through 8 are:

• Potable water supply (point-of-entry treatment)
• Hydraulic containment
• Groundwater treatment
• Treated groundwater disposal

Groundwater Monitoring

The purpose of groundwater monitoring is to evaluate the changes in the distribution of the COCs and to
monitor the quality of groundwater used for human consumption. Groundwater monitoring will consist of
measurement of water levels, and sampling for VOCs, explosives compounds, and general water quality
parameters. The exact location, number of wells, and monitoring frequency will be selected during
remedial design.

Potable Water Supply

Groundwater treatment at the point-of-entry is included as a part of Alternatives 2 through 8.
Point-of-entry treatment will provide potable water to those households with water supply wells which
contain RDX exceeding the HA and/or TCE exceeding the MCL.

Hydraulic Containment

Hydraulic containment is a component of Alternatives 2 through 8. The goal of the hydraulic containment
is to prevent groundwater outside the area of attainment from becoming contaminated in excess of the
Final Target Groundwater Cleanup Goals in the future. Hydraulic containment consists of the installation
and operation of a series of extraction wells to hydraulically control the movement of groundwater.
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These wells will be located in the vicinity of the downgradient boundary of the area of attainment
defined by the Final Target Groundwater Cleanup Goals. This is similar to the hydraulic containment
component of the planned Groundwater Containment Removal Action described in Section 2.6. The difference
is that the removal action hydraulic containment specifically addresses TCE contamination while the
hydraulic containment component of Alternatives 2 through 8 addresses both TCE and RDX-contaminated
groundwater.

Therefore, there are more extraction wells and a higher total extraction flowrate associated with the
hydraulic containment component of Alternatives 2 through 8 because the area of TCE and RDX-contaminated
groundwater is larger than the area of groundwater contaminated with just TCE. A total flowrate of 2,100
gallons per minute was estimated for the hydraulic containment component of Alternatives 2 through 8 so
that costs could be estimated in the OU2 FS Report. The containment system wells will be completed so
that groundwater is extracted from the Todd Valley aquifer and the Platte Valley alluvial aguifer. The
containment system wells will not be completed in the underlying Omadi Sandstone aguifer because COG
concentrations measured in that aguifer near the downgradient boundaries of the area of attainment are
significantly below the Final Target Groundwater Cleanup Goal Concentrations. The final well locations
and flowrates will be developed during the remedial design. If COG concentrations measured in Omadi
monitoring wells located near the downgradient edges of the area of attainment egual or exceed the
respective cleanup goal concentrations, additional remedial actions may be taken to contain groundwater
in the upper portion of the Omadi Sandstone aguifer. The actions might include, but would not be limited
to:
• Increasing the flowrate in existing extraction wells to induce upward vertical flow from the
Omadi Sandstone aguifer to the extraction wells completed in the Todd Valley aguifer and/or
Platte River alluvial aguifer.

• Installing and operating extraction wells which are designed to selectively extract water
from the Omadi Sandstone aguifer along the downgradient edge of the respective areas of
attainment.

• Installing and sampling additional monitoring wells completed in the Omadi Sandstone aguifer
in conjunction with one or both of the above actions.

In addition to groundwater extraction as a part of hydraulic containment, some of the alternatives
include different levels of additional groundwater extraction. The purpose of the additional extraction
is to more rapidly remove contamination and shorten remediation time when compared to hydraulic
containment pumping alone. The first level of additional groundwater extraction is called focused
extraction and includes extraction of groundwater from areas with relatively high TCE and/or RDX
concentrations. The second level of additional groundwater extraction is simply called groundwater
extraction and includes extraction of groundwater throughout the area of attainment.

During the remedial design, mathematical models will be used to predict the aguifer drawdown at nearby
domestic and irrigation wells. Seasonal aguifer stresses caused by irrigation and regional aguifer
stresses resulting from a hypothetical drought season will be included in the analyses. The remedial
design will specify how the drawdown predictions will be used as a part of an aguifer drawdown management
program to help maintain the capacity of local wells to produce water at current levels. The remedial
design and the groundwater monitoring program will specify the collection of water level and water
guality data after the start up of the remedial extraction system. The data will be used to evaluate
aguifer drawdown, and the remedial design will specify potential system operation modifications which may
be enacted to effectively manage that drawdown while meeting the objectives of the remedial extraction.
It may not be feasible to maintain the capacity of all local wells to produce water at current levels
while maintaining the effectiveness of the hydraulic containment system. In the event remediation
pumping has a negative effect on groundwater availability, the negative impacts will be evaluated and
addressed by the Army. The details of determining impacts on groundwater availability and responses to
the impacts will be better defined during the Remedial Design process.

Groundwater Treatment

Extracted groundwater will be pumped to a central location and treated using one of, or a combination of,
the following potential treatment process options:

• GAG adsorption
AOP
• Air stripping combined with either GAG adsorption or AOP

GAG, AOP, and air stripping will be compared before final selection of the treatment process. This
selection will be made in the design analysis of the remedial design after completion of the on-going
treatability studies. The selection will be based on the following factors:
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• Nature and disposition of any degradation products created during treatment
• Total present worth cost
• Schedule to implement technology
• Reliability

Extracted groundwater will be treated to meet disposal dependent standards which may vary for different
disposal options. The remedial design will include monitoring provisions to ensure that the
disposal-dependent treatment standards are achieved. The use of one or a combination of the three
potential treatment process options satisfies the statutory preference for remedies that employ treatment
that reduce toxicity, mobility, or volume as a principal element.

Treated Groundwater Disposal

Subseguent to treatment, the water will be beneficially reused and/or discharged to a nearby stream. The
selection of the treated groundwater disposal option, either surface water discharge or beneficial reuse,
will be made during the remedial design analysis and will be based on the following:

• Cost/benefit analysis
• Technical feasibility
• Public acceptance

The types of beneficial reuse which may be considered include reinjection into the aguifer, agricultural
use (irrigation, livestock watering, processing, or other use), and water supply (including supply to a
potential rural water district, the ARDC, a nearby community or municipality, or some combination of
these potential water users). A Saunders County Rural Water Project Committee has been formed to
evaluate the beneficial reuse options related primarily to water supply. As a part of the committee's
evaluation activities, a study is being conducted to determine the economic feasibility of constructing
and operating a number of different water distribution systems. The study has been funded by a
combination of local funding and matching federal funds. The study was initiated when matching funds
were received from local communities, and it is estimated that the study can be completed approximately
January 1997. If the study is completed in time to incorporate into the Remedial Design (approximately
January 1997) , the results of the study will be considered when choosing between surface water discharge
and beneficial reuse during the future remedial design analysis. If not, the Army will either gather the
necessary information directly, or choose not to pursue beneficial reuse.

In the OU2 FS Report, some details such as well locations and alternatives were developed for cost
estimating purposes so that the various alternatives could be compared to each other. For the purposes
of cost estimating, GAG adsorption was assumed to the be the selected process option for groundwater
treatment during the cost analysis, and surface discharge was assumed to be the selected treated
groundwater disposal option. As discussed above, these details will be addressed during the remedial
design analysis.

The estimated time reguired to reduce the COG concentrations to the Final Target Groundwater Cleanup Goal
was calculated in the same manner for each plume for Alternatives 2 through 8. The restoration time
frame estimates used for the comparative cost estimates for these alternatives are assumed to be the
longest of the estimates for the individual plumes. For example, the following plume restoration time
frame estimates were developed for Alternative 4:

• Load Line 1 TCE plume: 31 years.
• Load Lines 2, 3, and 4 explosives plume: 77 years.
Atlas Missile Area TCE plume: 130 years.

A restoration time was not estimated for the Load Line 1 explosives plume because analysis shows that it
would always be less than the restoration time estimated for the co-located TCE plume. Based on these
estimates, the part of the remedial system which extracts groundwater from the Load Line 1 plume could be
turned off approximately 100 years earlier than the Atlas Missile Area extraction system. Conceptual
extraction well locations and flow rates were used to develop the restoration time frame estimates as a
basis for the FS cost estimate. The actual extraction well locations and flow rates will be determined
during remedial design. The restoration time frame assumption may potentially result in overestimation
of the cost of the alternative because the extraction wells associated with the plumes that reguire
shorter periods of time to clean up will not operate for the entire time periods presented in the
descriptions of Alternatives 2 through 8.
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2.8.1 Alternative 1 - No Action

This alternative was included in the FS Report as a NCP requirement to provide a baseline against which
other alternatives are compared. The no-action alternative, by definition, involves no remedial action.
No reduction in risks associated with potential groundwater exposure to the COCs is achieved, nor is
migration of contaminants controlled. Groundwater monitoring is included to allow for ongoing evaluation
of contaminant migration in the absence of remedial action. The following costs were estimated for
Alternative 1:

• Estimated capital cost: $0
• Estimated annual operation and maintenance (O&M) cost: $2 million
• Sum of estimated capital and O&M present worth cost: $11 million

The present worth was calculated for all alternatives assuming a 6 percent discount rate over an 80 year
period. The cost estimates are conceptual with an estimated +50 percent to -30 percent level of
accuracy.

2.8.2 Alternative 2 - Hydraulic Containment

Alternative 2 includes the following previously discussed components:

• Hydraulic containment
• Groundwater treatment
• Disposal of treated groundwater
• Potable water supply
• Groundwater monitoring

An estimated total extraction flowrate of 2,100 gallons per minute and restoration time frame estimate of
970 years were used to develop the following cost estimate:

• Estimated capital cost: $8 million
• Estimated annual O&M cost: $3 million
• Sum of estimated capital and O&M present worth cost: $35 million

2.8.3 Alternative 3 - Focused Extraction

Alternative 3 includes all of the elements of Alternative 2 plus additional groundwater extraction wells
which focus on areas with relatively high TCE and/or RDX concentrations. The focused extraction area
will be defined during the remedial design analysis. Alternative 3 includes the following components:

• Focused extraction
• Hydraulic containment
• Groundwater treatment
• Disposal of treated groundwater
• Potable water supply
• Groundwater monitoring

It is estimated that Alternative 3 would take approximately 130 years to reduce the existing groundwater
COG concentrations to the Final Target Groundwater Cleanup Goals. However, it is estimated that the
leaching soils will continue contributing contamination to the groundwater for an unknown time period
greater than 130 years. Therefore, the estimated restoration time frame for Alternative 3 is an unknown
time period which is greater than 130 years. An estimated total extraction flowrate of 3,300 gallons per
minute was used to develop the following cost estimate:

• Estimated capital cost: $13 million
• Estimated annual O&M cost: $4 million
• Sum of estimated capital and O&M present worth cost: $57 million

2.8.4 Alternative 4 - Focused Extraction and Soil Excavation

Alternative 4 includes the elements of Alternative 3 with the addition of the excavation and incineration
of leaching soils. The OU1 remedial design would address both the soils that meet the OU1 excavation
criteria and the OU2 leaching soils. Subsequent to the completion of the OU1 remedial design, the OU1
and OU2 soils would be excavated and incinerated together. A cost and time savings will be realized by
remediating; the OU1 and OU2 soils at the same time. It is estimated that approximately 5,500 cubic
yards of soil meet the OU1 excavation criteria, and that the volume of OU2 leaching soils is
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approximately 2,600 cubic yards. Therefore, the total volume of soil to be excavated and incinerated is
estimated as 8,100 cubic yards. The OU2 leaching soils are shown on Figures 4 through 7.

Alternative 4 includes the following components:

• Soil excavation and incineration
• Focused extraction
• Hydraulic containment
• Groundwater treatment
• Disposal of treated groundwater
• Potable water supply
• Groundwater monitoring

An estimated total extraction flowrate of 3,300 gallons per minute and restoration time frame estimate of
130 years were used to develop the following cost estimate:

• Estimated capital cost: $17 million
• Estimated annual O&M cost: $4 million
• Sum of estimated capital and O&M present worth cost: $61 million

2.8.5 Alternative 5 - Focused Extraction with Air Sparging

Alternative 5 includes the elements of Alternative 2 with the addition of focused groundwater extraction
wells and air sparging. The air sparging system will be located in the Atlas Missile Area TCE plume
where there are relatively high groundwater concentrations of TCE without the presence of explosives.
Air sparging is an emerging technology which removes VOCs such as TCE from the groundwater without
extracting the groundwater. This is accomplished by drilling wells in the aquifer to inject air into the
contaminated groundwater. The air moves up through the groundwater, and some of the TCE transfers from
the groundwater to the migrating air. The organic vapors which exit the saturated zone are collected
below the ground surface by a SVE system and treated if necessary. This technology is not effective at
removing explosives and is only proposed for areas of TCE-contaminated groundwater. Therefore, the
focused extraction wells would be installed in areas where RDX concentrations or TCE and RDX
concentrations are relatively high. Alternative 5 includes the following components:

• Air sparging
• Focused extraction
• Hydraulic containment
• Groundwater treatment
• Disposal of treated groundwater
• Potable water supply
• Groundwater monitoring

It is estimated that Alternative 5 would take approximately 110 years to reduce the existing groundwater
COG concentrations to the Final Target Groundwater Cleanup Goals. However, it is estimated that the
leaching soils will continue contributing contamination to the groundwater for an unknown time period
greater than 110 years. Therefore, the estimated restoration time frame for Alternative 5 is an unknown
time period which is greater than 110 years. An estimated total extraction flowrate of 2,770 gallons per
minute was used to develop the following cost estimate:

• Estimated capital cost: $32 million
• Estimated annual O&M cost: $4 million
• Sum of estimated capital and O&M present worth cost: $76 million

2.8.6 Alternative 6 - Focused Extraction with Air Sparging and Soil Excavation

Alternative 6 includes the elements of Alternative 5 with the addition of the excavation and incineration
of leaching soils which was described for Alternative 4.
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Alternative 6 includes the following components:

• Soil excavation and incineration
• Air sparging
• Focused extraction
• Hydraulic containment
• Groundwater treatment
• Disposal of treated groundwater
• Potable water supply
• Groundwater monitoring

An estimated total extraction flowrate of 2,770 gallons per minute and restoration time frame estimate of
110 years were used to develop the following cost estimate:

• Estimated capital cost: $36 million
• Estimated annual O&M cost: $4 million
• Sum of estimated capital and O&M present worth cost: $81 million

2.8.7 Alternative 7 - Groundwater Extraction

Alternative 7 includes all of the elements of Alternative 2 plus additional groundwater extraction wells
to extract contaminated groundwater throughout the contaminated areas. Alternative 7 includes the
following components:

• Groundwater extraction
• Hydraulic containment
• Groundwater treatment
• Disposal of treated groundwater
• Potable water supply
• Groundwater monitoring

It is estimated that Alternative 7 would take approximately 90 years to reduce the existing groundwater
COG concentrations to the Final Target Groundwater Cleanup Goals. However, it is estimated that the
leaching soils will continue contributing contamination to the groundwater for an unknown time period
greater than 90 years. Therefore, the estimated restoration time frame for Alternative 7 is an unknown
time period which is greater than 90 years. An estimated total extraction flowrate of 4,200 gallons per
minute was used to develop the following cost estimate:

• Estimated capital cost: $15 million
• Estimated annual O&M cost: $4 million
• Sum of estimated capital and O&M present worth cost: $62 million

2.8.8 Alternative 8 - Groundwater Extraction and Soil Excavation

Alternative 8 includes the elements of Alternative 7 with the addition of the excavation and incineration
of leaching soils which was described for Alternative 4.

Alternative 8 includes the following components:

• Soil excavation and incineration
• Groundwater extraction
• Hydraulic containment
• Groundwater treatment
• Disposal of treated groundwater
• Potable water supply
• Groundwater monitoring

An estimated total extraction flowrate of 4,200 gallons per minute and restoration time frame estimate of
90 years were used to develop the following cost estimate:

• Estimated capital cost: $19 million
• Estimated annual O&M cost: $4 million
• Sum of estimated capital and O&M present worth cost: $66 million
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2 . 9 TREATABILITY STUDIES

On-going treatability studies are being performed to provide performance data needed to evaluate the
potential feasibility of technologies for treating the COCs. The bench-scale treatability studies focus
on RDX and TCE which are two major site contaminants. The primary objectives of the studies are to:

• Develop Freundlich adsorption isotherm constants for TCE and RDX in former NOP site
groundwater using GAG

• Assess the efficiency of selected AOP technologies to treat former NOP site groundwater

The results of the GAG isotherm tests will be used to refine the literature-based GAG usage rate used to
estimate costs in the FS. The AOP test results will be used to evaluate whether oxidation technologies
are effective in removing contaminants detected in former NOP site groundwater. If the AOP or the GAG
processes are successful, the results may be used to design on-site pilot studies. Details of the
treatability studies are presented in the Groundwater Treatability Study Work Plan.

2.10 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES

2.10.1 Introduction

USEPA has established nine criteria that balance health, technical, and cost considerations to determine
the most appropriate remedial action alternative. These criteria are used to select a remedial action
that is protective of human health and the environment, attains ARARs, is cost effective, and utilizes
permanent solutions and treatment technologies to the maximum extent practicable. The remedial action
alternatives developed in the FS have been evaluated and compared using the nine criteria set forth under
NCP 300.430(e) (9) (iii) . These nine criteria are summarized as follows:

1. OVERALL PROTECTION OF PUBLIC HEALTH AND THE ENVIRONMENT addresses whether a remedial action provides
protection of human health and the environment and describes how risks which are posed through each
exposure pathway are eliminated, reduced, or controlled through treatment, engineering controls, or
institutional controls.

2. COMPLIANCE WITH APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS (ARARs) addresses whether a
remedial action will meet all applicable or relevant and appropriate reguirements of Federal and
State laws and regulations and/or provides grounds for invoking a waiver.

3. LONG-TERM EFFECTIVENESS AND PERMANENCE refers to the ability of a remedial action to maintain
reliable protection of human health and the environment over time, after RAOs have been met.

4. REDUCTION OF CONTAMINANT TOXICITY, MOBILITY, OR VOLUME THROUGH TREATMENT addresses the anticipated,
performance of the treatment technologies that a remedial action employs.

5. SHORT-TERM EFFECTIVENESS addresses the period of time needed to achieve protection from adverse
impacts on human health and the environment that may be posed during the construction and
implementation period, until RAOs are achieved.

6. IMPLEMENTABILITY is the technical and administrative feasibility of a remedial action, including the
availability of materials and services needed to implement a particular option.

7. COST includes estimated initial capital, O&M costs, and present worth costs.

8. STATE ACCEPTANCE indicates whether the state agency concurs with, opposes, or has no comment on the
preferred remedial action alternative at the present time.

9. COMMUNITY ACCEPTANCE is based on comments received from the public during the public comment period.
These comments are assessed in the Responsiveness Summary included with this ROD.

2.10.2 Comparison of Alternatives

Alternatives were compared in the FS with respect to the nine evaluation criteria. This comparison is
discussed below. For the purpose of this discussion, the evaluation criteria have been divided into
three groups (threshold, balancing, and modifying criteria) based on the function of each criterion
during remedial action evaluation and selection.
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A. Threshold Criteria

Threshold criteria are statutory requirements that must be satisfied by a remedial action alternative in
order for it to be eligible for further detailed evaluation in the FS and subsequent selection. These
two criteria are discussed below.

Overall Protection of Human Health and the Environment

Alternative 1 (no action) would not have satisfied the requirement for overall protection of human health
and the environment. Estimated risks remaining with the no action alternative would have been the same
as those identified in the Baseline Risk Assessment. Because Alternative 1 does not meet the threshold
criteria, it is not evaluated under the remaining criteria.

Alternatives 4, 6, and 8 provide the highest degree of overall protection of human health and the
environment because the alternatives address contaminants in both groundwater and soil.

Alternatives 2 through 8 use point-of-entry systems and groundwater extraction to protect potential
future groundwater users.

Alternatives 2 through 8 provide environmental protection by containing contaminated groundwater and
minimizing its potential for migration past the area of attainment. These alternatives also reduce
contaminant concentrations; by groundwater treatment. The potential for contaminated soils to be a
continuing source of groundwater contamination will be reduced by soil excavation and treatment in
Alternatives 4, 6, and 8 thereby providing additional protection of human health and the environment.

Compliance with ARARs

Alternatives 2 though 8 would comply with ARARs although Alternative 2 would require a very long time to
do so.

B. Balancing Criteria

Five balancing criteria are used to identify major trade-offs between the remedial action alternatives
which satisfy the two threshold criteria. These tradeoffs are ultimately used to identify the preferred
alternative and to select the final remedy.

Long-Term Effectiveness and Permanence

Alternatives 2 through 8 control long-term risk by point-of-entry groundwater treatment systems for
impacted residences, and downgradient groundwater users are protected by hydraulic containment.
Long-term risk is further reduced in Alternatives 3 and 8 by groundwater extraction wells (in addition to
the containment system). Soil treatment associated with Alternatives 4, 6, and 8 reduces the potential
for long-term risk associated with the transfer of contaminants from the soil to the groundwater. The sum
of the excess cancer risks calculated using each Final Target Groundwater Cleanup Goal concentration is
2x10-5. This aggregate risk is estimated to be the maximum value of the residual risk associated with
groundwater at the completion of remediation.

The point-of-entry treatment systems associated with Alternatives 2 through 8 are reliable and adequate
to treat the COCs. Hydraulic containment and other extraction systems which are a part of Alternatives 2
through 8 are reliable. Air sparging (Alternatives 5 and 6) is an emerging technology, and reliability
and adequacy must also be monitored. Long-term engineering controls are not necessary for the soil
treatment included as a part of Alternatives 4, 6, and 8.

Alternatives 2 through 8 will require periodic evaluations or reviews to ensure that the remedial action
objectives are being met and human health and the environment are being protected. The effectiveness of
the remedy will be periodically evaluated on a frequent basis beginning shortly after implementation.
After the initial implementation period, the frequency of review will be reduced, however, reviews will
continue to be conducted no less than once every five years until the remedial action objectives are
achieved.

Reduction of Toxicitv, Mobility, or Volume through Treatment

Alternatives 2 through 8 will eventually clean up all groundwater contamination, although the rate at
which the groundwater is cleaned up will vary between alternatives. For example, it is estimated that
Alternative 2 would take a very long time, almost 1,000 years, to clean up the groundwater while
Alternative 4 is estimated to take 130 Years. Explosives contamination in approximately 2,600 cubic
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yards of soil will be destroyed as a part of Alternatives 4, 6, and 8.

Alternatives 2 through 8 will reduce toxicity and volume of contaminated groundwater. The rate at which
the volume of contaminated water is removed is proportional to the total extraction flowrate. The
following list ranks the alternatives in terms of decreasing total extraction flow rate. The flow rates
were used to estimate costs in the FS Report.

• Alternatives 7 and 8 (4,200 gallons per minute or gpm)
Alternatives 3 and 4 (3,300 gpm)
• Alternatives 5 and 6 (2,770 gpm)
Alternative 2 (2,100 gpm)

For Alternatives 2 through 8, the groundwater contaminants remain mobile but the mobility (potential for
migration) is managed through containment. The incineration of explosives-contaminated soils, which is
an element of Alternatives 4, 6, and 8; reduces toxicity, mobility, and volume of the explosive
contaminants in the soils through treatment and reduces the potential threat of groundwater
contamination.

The treatment technologies being considered for soil and/or groundwater as a part of Alternatives 2
through 8 destroy the contaminants and are therefore irreversible. Residual materials resulting from the
treatment of groundwater as a part of Alternatives 2 through 8 may include spent carbon from both
groundwater and/or off-gas treatment. Residual materials from soil incineration (Alternatives 4, 6, and
8) may include scrubber water and/or ash. The guantities of all residual materials for Alternatives 2
through 8 are manageable and do not pose residual risk when properly managed.

Alternatives 2 through 8 satisfy the statutory preference for treatment.

Short-Term Effectiveness

In terms of adverse environmental impacts, aguifer drawdown associated with the extraction of groundwater
during Alternatives 2 through 8 may reduce the amount of groundwater available for aguifer users. The
potential for groundwater drawdown to adversely impact groundwater users is related to the extraction
flowrates. Therefore, the highest potential for adverse environmental impacts is associated with
Alternatives 7 and 8, and the lowest potential is associated with Alternative 2.

Risks to the community are not increased by the implementation of the groundwater remedies which are
included as elements of Alternative 2 through 8. For Alternatives 4, 6, and 8, there is potential for
exposure due to explosives-contaminated dust during soil excavation, transportation, stockpiling and
incineration. The potential for fugitive dust emissions during excavation, transportation, and
stockpiling can be managed using standard construction dust control practices such as the application of
water, other dust suppressants, and the use of tarps.

OU1 and OU2 soils will be treated at the same time using the same incinerator. The incinerator will be
operated at a 99.99 percent destruction and removal efficiency (DRE). The DRE is a measurement of the
effectiveness of the combustion process in an incinerator. The 99.99 percent DRE reguirement applied to
the principal contaminants, explosives compounds, will prevent unacceptable exposure to the principal
contaminants. Metals (which naturally occur in soil) associated with airborne particulates will be
managed by the incinerator air pollution control system. All adverse health risks associated with the
incineration process are manageable.

There are relatively low risks to construction workers beyond the general construction safety issues
during the implementation of the groundwater remedies which are included as elements of
Alternative 2 through 8. For Alternatives 4, 6, and 8, there is potential for ingestion or inhalation of
airborne material during excavation and transportation of contaminated soil. Such emissions can be
controlled as discussed above.

There are relatively small adverse environmental impacts associated with the implementation of the
groundwater remedies associated with Alternatives 2 through 8. Operation of groundwater remediation
systems will lower the water table to varying degrees at different locations. The potential aguifer
drawdown at existing water supply wells (primarily domestic, irrigation, and stock wells) which may
result from groundwater extraction could not be guantified during the FS because the extraction well
locations and pumping rates will be selected during the remedial design. The remedial design will
minimize groundwater drawdown at existing water supply wells while balancing effectiveness and technical
feasibility. The excavation and treatment of contaminated soils as a part of Alternatives 4, 6, and 8
will have a beneficial environmental impact because the potential for continuing contribution to
groundwater contamination will be reduced.
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The point-of-entry treatment system associated with Alternatives 2 through 8 will be immediately
available. Alternatives 2 through 8 are listed below in order of increasing restoration time frame
estimates:

Alternative 8 (90 years)
• Alternative 6 (110 years)
• Alternative 4 (130 years)
• Alternative 3 (greater than 130 years), Alternative 5 (greater than 110 years), and
Alternative 7 (greater than 90 years)
• Alternative 2 (970 years)

Alternatives 3, 5, and 7 are listed in the same bullet because it is expected that the release of
explosives from leaching soils to the groundwater will last approximately the same period of time for
these alternatives which do not include leaching soils clean up. This time is not known, but it is
expected to be a finite time greater than 130 years.

Please remember that the time frame estimates listed above are the longest individual plume restoration
time frame calculated for each alternative. The restoration time frame estimates are shorter for the
other plumes.

Implementability

Carbon adsorption, air stripping, and advanced oxidation treatment technologies are being considered for
the treatment of extracted groundwater as a part of Alternatives 2 through 8. Advanced oxidation is an
emerging treatment technology. The air sparging element of Alternatives 5 and 6 is also an emerging
technology. Incineration of explosives-contaminated soil (Alternatives 4, 6, and 8) is a proven and
effective treatment process.

Alternatives 2 through 8 possess the same degree of implementability with the exception of Alternatives 5
and 6 which rely on air sparging, an emerging technology. The emerging technology status means that the
alternatives may be more difficult to implement.

The groundwater treatment system elements of Alternatives 2 through 8 can be constructed and operated
using common practices. As discussed earlier, advanced oxidation treatment processes are emerging
technologies. The air sparging element of Alternatives 5 and 6 may reguire specialized drilling
procedures. The incineration of soils which is included as a part of Alternatives 4, 6, and 8 is a
highly technical process but is commonly used and has demonstrated effectiveness.

Additional point-of-entry treatment systems and additional extraction wells can easily be added to
Alternatives 2 through 8. The groundwater treatment system for those alternatives can be designed to
allow for varying volumes and concentrations of groundwater. Additional capacity can be added with
relative ease to the air sparging system which is an element of Alternatives 5 and 6. There is no need
for expansion of the soil treatment system included as a part of Alternatives 4, 6, and 8.

Groundwater monitoring and the proposed treatment system would provide notice of potential failure of the
groundwater extraction systems which are a part of Alternatives 2 through 8, and the air sparging system
component of Alternatives 5 and 6. The soil treatment system of Alternatives 4, 6, and 8 will reguire
emissions monitoring during implementation.

There is no anticipated difficulty in obtaining approvals and coordination with USEPA and NDEQ for the
groundwater treatment elements of Alternatives 2 through 8. Alternatives 4, 6, and 8 include soil
incineration which will include a test of the treatment process called a trial burn prior to
implementation of the OU1 remedy.

All services are available for the groundwater treatment elements of Alternatives 2 through 8, although
the air sparging element of Alternatives 5 and 6 is an emerging technology. All services are available
for the soil treatment element of Alternatives 4, 6, and 8.

All materials, eguipment, and specialists are available for Alternatives 2 through 8, although the air
sparging element of Alternatives 5 and 6 is an emerging technology.

All technologies are available for Alternatives 2 through 8, although the air sparging element of
Alternatives 5 and 6 is an emerging technology.
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Cost

The alternatives are listed below in order of increasing estimated capital costs:

Alternative 2 ($8 million)
Alternative 3 ($13 million)
Alternative 7 ($15 million)
Alternative 4 ($17 million)
Alternative 8 ($19 million)
Alternative 5 ($32 million)
• Alternative 6 ($36 million)

The annual operation and maintenance costs are estimated to be approximately $3 million for Alternative
2. The annual operation and maintenance costs for Alternatives 3 through 8 are estimated to be
approximately $4 million.

The alternatives are listed in order of increasing sum of capital cost and present worth costs of the
operation and maintenance costs:

Alternative 2 ($35 million)
Alternative 3 ($57 million)
• Alternative 4 ($61 million)
Alternative 7 ($62 million)
Alternative 8 ($66 million)
• Alternative 5 ($76 million)
Alternative 6 ($81 million)

C. Modifying Criteria

The two modifying criteria were evaluated following comment on the proposed plan and are addressed as the
final decision is made and the ROD is prepared. The results of the modifying criteria are summarized
below.

State Acceptance

This assessment evaluates technical and administrative issues and concerns NDEQ may have regarding each
of the alternatives. NDEQ has been actively involved in the entire RI/FS process leading to the
development of this ROD, including being party to the IAG, participating in all TRC, IAG Project
Managers, and public meetings, oversight of field work, and review and comment on all draft project
documents.

Community Acceptance

Public comments on the selected remedial action were presented at the public meeting on November 8, 1995.
Eight written comments were received during the comment period which extended from October 30, 1995 to
November 29, 1995

In general, the public had differing opinions regarding Alternative 4 as the preferred alternative. Four
written comments supported Alternative 4, and three written comments neither supported nor opposed the
use of Alternative 4. One written comment opposed any pump and treat alternative. A summary of public
comments and USEPA/USACE responses are provided in the Responsiveness Summary, Section 3.0 of this
document.

2.10.3 Summary

Based on the nine evaluation criteria, Alternative 1 would not have provided protection from the
potential site risks and would not have complied with the ARARs. Therefore, it does not meet the
threshold criteria for selection of a remedial action alternative for this site.

If it had been selected, Alternative 2 would have controlled long-term risk using point-of-entry
groundwater treatment systems at impacted residences, and downgradient groundwater users would have been
protected by the element of hydraulic containment. However, it is estimated that Alternative 2 would
take a very long time, almost 1,000 years, to clean up all of the groundwater.

If Alternative 3 had been selected, it would have controlled long-term risk in a manner similar to
Alternative 2, plus Alternative 3 would have provided additional protection through the element of
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focused extraction. The focused extraction would have extracted groundwater from areas with relatively
high concentrations of TCE and/or RDX. Alternative 3 would have potentially reached the Final Target
Groundwater Cleanup Goals at an earlier date relative to Alternative 2. However, Alternative 3 does not
reduce the potential for transfer of explosives from the soil to the groundwater.

Alternative 4 will be protective of human health and the environment and will attain the ARARs using
proven technologies. Leaching soils excavation and treatment will remove a potential source of
groundwater contamination. Focused extraction will shorten the restoration time while causing less
adverse impact on groundwater availability when compared to Alternatives 7 and 8.

If Alternative 5 had been selected, it would have controlled long-term risk in a manner similar to
Alternative 3 except that Alternative 5 would have included air sparging, an emerging technology.

If Alternative 6 had been selected, it would have controlled long-term risk in a manner similar to
Alternative 4 except that Alternative 6 would have included air sparging, an emerging technology, at a
higher capital and annual O&M cost.

If Alternative 7 had been selected, it would have controlled long-term risk in a manner similar to
Alternative 2 plus Alternative 7 would have provided additional protection through the element of
groundwater extraction. The groundwater extraction would have extracted groundwater throughout the area
of contamination. Alternative 7 would have potentially reached the Final Target Groundwater Cleanup
Goals in the shortest time period with the exception of Alternative 8. However, Alternatives 7 and 8
would have extracted groundwater at the highest rate thereby creating the greatest potential for water
availability conflicts with other groundwater users.

If Alternative 8 had been selected, it would have provided all of the Alternative 7 controls. In
addition, Alternative 8 would have reduced the potential for transfer of explosives from the soil to the
groundwater.

2.11 THE SELECTED REMEDIAL ACTION

Alternative 4 was selected because it will be protective of human health and the environment, will comply
with ARARs, will utilize permanent solutions to the maximum extent practicable, will significantly reduce
the toxicity, mobility, and volume of contaminants through treatment, and is implementable. This
alternative satisfies the RAOs for this remedial action discussed in Section 2.8.

Alternative 4 provides the best balance of tradeoffs among the alternatives, with respect to the
evaluation criteria, especially the five balancing criteria. Alternative 4 was distinguished from the
other alternatives by the inclusion of both leaching soils excavation and treatment, and focused
extraction of groundwater. The soils excavation and treatment will remove a potential source of
groundwater contamination. The focused extraction will shorten the restoration time with the least
adverse impact on groundwater availability.

The major components of the selected remedial action for OU2 include:

• Hydraulically contain contaminated groundwater exceeding the Final Target Groundwater Cleanup
Goals.

• Focused extraction of groundwater in areas with relatively high concentrations of TCE and
explosives.

• Treat all extracted groundwater using GAG adsorption, AOP, and air stripping, any of which
may be applied individually or in combination.

• Dispose of the treated groundwater by beneficially reusing it or through surface discharge.

• Provide a potable water supply to local groundwater users whose water supply contains RDX
exceeding the HA and/or TCE exceeding the MCL

• Monitor the groundwater elevations and water guality.

• Excavate and treat explosives-contaminated soil which could act as a source of explosives
contamination of groundwater and which does not meet the Operable Unit 1 (OU1) excavation
criteria.
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Alternative 4 will reduce the groundwater contaminants within the area of attainment shown on Figure 3 to
concentrations at, or below, the Final Target Groundwater Cleanup Goals listed in Table 2. The residual
risk will be less than or egual to the aggregate risk of 2x10-5.

2.12 STATUTORY DETERMINATIONS

CERCIA Section 121(d) reguires that the selected remedy comply with all federal and state environmental
laws that are applicable or relevant and appropriate to the hazardous substances, pollutants, or
contaminants at the site or to the activities to be performed at the site. Therefore, to be selected as
the remedy, an alternative must meet all ARARs or a waiver must be obtained. A discussion of how each
ARAR applies to the selected OU2 remedial actions is provided in the following paragraphs.

2.12.1 Protection of Human Health and the Environment

The selected remedial action will protect human health and the environment through provision of a potable
water supply, hydraulic containment and focused extraction of contaminated groundwater, and subseguent
treatment and disposal of the extracted groundwater. This will eliminate the groundwater pathways
through which contaminants pose risks. In addition, the potential for transfer of explosives from the
soil to the groundwater will be reduced by excavation and incineration of selected soils.

2.12.2 Compliance with ARARs

The selected remedy will be designed to comply with all Federal and State ARARs. A list of ARARs
pertinent to the site can be found in Table 3. The ARARs that will be achieved by the selected remedy
are:

FEDERAL

Clean Air Act of 1963, as amended (42 U.S.C. °°7401-7642)

40 CFR Parts 50 and 61

This regulation is pertinent to excavation, materials handling activities, and emissions from an air
stripper (if included for treatment of VOC-contaminated groundwater) which may result in fugitive air
emissions. Control measures, including water or other dust suppressants, truck tarpaulins, covers for
soil stockpiles, and temporary structures for the treatment process train will be used to minimize the
potential for air emissions. Thermal treatment emissions are also of concern. The air pollution control
system for the incinerator will be designed to meet appropriate Clean Air Act reguirements.

Clean Water Act of 1977, as amended (33 U.S.C. °°1251-1376)

40 CFR Part 122, 125

The National Pollutant Discharge Elimination System (NPDES) was established to control discharge of
pollutants from any point source into waters of the United States. A permit will not be reguired since
the site is being remediated as part of the Superfund program; however, the substantive reguirements of
the regulation must be met. This regulation applies to the discharge of treated groundwater to surface
water on or near the site; decontamination fluids discharged to the ground, surface water, or treated
on-site prior to discharge to the ground or surface water; and process water. Process water may be
recycled to guench the ash, sprayed on-site for dust control, discharged to the ground or a nearby
surface water body, or treated off-site.

Discharge limits for the COCs will be established during remedial design and will be consistent with the
reguirements of the NPDES program. If established surface water discharge limits are not met, provisions
for alternate effluent limits can be found in this part.

40 CFR Part 122.2b

Stormwater runoff must be monitored and controlled on construction sites greater than five acres. This
part will apply during the implementation of the remedy in areas of soil excavation, stockpiling, and
preparation for incineration.

40 CFR Part 131

States must establish ambient water guality criteria for the protection of surface water based on use
classifications and the criteria stated under Section 304(a) of the Clean Water Act. These criteria are
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applicable and will be used to establish discharge limits for treated groundwater, decontamination
fluids, or process water.

40 CFR Part 136.1-5 and Appendices 1-C

Analytical methods specified in this part will be used to analyze samples pursuant to NPDES reguirements.
Applicable reporting procedures and formats will be used.

Safe Drinking Water Act of 1986, as amended (40 U.S.C. °300)

40 CER Part 141

Primary Drinking Water Standards are established by this part. MCLs are health-based standards for
public water supplies. The discharge of treated groundwater, decontamination fluids, or process water
will not directly impact drinking water; however, the potential for residual contaminants percolating to
groundwater exists. The NCP reguires consideration of MCLs, where they exist, as relevant and
appropriate to groundwater cleanup standards when the aguifer is a current or potential source of
drinking water. MCLs for COCs, where established, are relevant and appropriate for establishing
discharge limits to be met during implementation of the remedy.

40 CFR Part 143

Secondary Drinking Water Standards (SMCLs) are criteria applied to ensure the aesthetic guality of
drinking water (color, taste, and odor). These standards will be considered during the evaluation of
disposal options for treated water.

Resource Conservation and Recovery Act (RCRA) of 1976, as amended (42 U.S.C. °°6901-6987)

40 CFR Part 261

The criteria set forth in this part will be used to determine if soils, treatment residuals, or other
solid wastes excavated, created through treatment, or otherwise generated during the implementation of
the remedy are hazardous or non-hazardous. The goal is to incinerate excavated soil until it is no
longer hazardous.

The soils (ash) remaining after incineration will be tested and compared to the criteria for determining
if a solid waste is hazardous so that the appropriate final disposition can be made. If the ash is
hazardous due to the presence of metals, then off-site disposal and/or treatment at an approved hazardous
waste management facility will be included in the remedy. If the ash is not hazardous, the waste will be
disposed off-site.

Scrubber blowdown or vapor phase granular activated carbon may be generated as part of the control of air
emissions from the incinerator. Spent GAG, if used to treat groundwater, will be generated. These
treatment residuals will be assessed and managed in accordance with 40 CFR Part 261.

40 CFR Part 262.11

The methods for determining whether a solid waste is hazardous are set forth in this part. All
generators of solid wastes are reguired to determine if a waste is hazardous. Wastes determined to be
hazardous will be managed in accordance with the rules applicable to hazardous wastes.

40 CFR Part 262.34

The accumulation of hazardous waste on-site is addressed by this part. In the event any of the soils,
treatment residuals, or other solid waste excavated, created through treatment, or otherwise generated
during the implementation of the remedy are hazardous, these regulations will be applied.

40 CFR Part 263

Any solid waste generated on-site, determined to be a hazardous waste per Part 261, and to be removed
from the site for disposal must be transported in accordance with the reguirements of this part. The
reguirements provide standards for transporters of hazardous waste. Transporters used during the remedy
must comply with this part.

40 CFR Part 264
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This part establishes minimum national standards defining the acceptable management of hazardous waste
for owners and operators of facilities which treat, store, or dispose of hazardous waste. The
regulations of this part pertaining to incineration of soil and management of treatment residuals
determined to be hazardous are applicable or relevant and appropriate. RCRA reguirements are applicable
to any treatment residuals which are TCLP toxic and will be removed from the site. RCRA reguirements are
applicable for any treatment residuals which are TCLP toxic.

The technical reguirements for incinerators (Subpart 0) are relevant and appropriate to the incineration
of soil included in the remedy.

Subpart S of part 264 addresses corrective action at solid waste management units. Reguirements for
corrective action management units (CAMUs) and temporary units (TUs) for management of remediation wastes
are specified. This part will govern the excavation and stockpiling of soil for incineration.

40 CFR Part 264.30-56

Preparedness, prevention, and contingency planning for hazardous waste facilities is discussed in this
part. In the event any of the soils, treatment residuals, or other solid waste excavated, created
through treatment, or otherwise generated during the implementation of the remedy are hazardous, these
regulations will be applied.

Hazardous Materials Transportation Act (Chapter 81, Article 15)

42 CFR Part 107

Hazardous materials removed from the site for disposal or treatment will need to be transported in
accordance with the regulations of this part.

49 CFR Part 171

This part contains packaging, marking, and other reguirements related to the transportation of hazardous
materials. In the event any of the soils, treatment residuals, or other solid waste excavated, created
through treatment, or otherwise generated during the implementation of the remedy determined to be
hazardous are removed from the site, these regulations will be applied.

49 CFR Part 172

Tables of hazardous materials and shipping reguirements for same are provided in this part. In the event
any of the soils, treatment residuals, or other solid waste excavated, created through treatment, or
otherwise generated during the implementation of the remedy determined to be hazardous are removed from
the site, these regulations will be applied.

STATE

Nebraska Environmental Protection Act (Revised Statutes of Nebraska, Chapter 81)

This chapter establishes the state's policy on environmental control.

Nebraska Air Pollution Control Rules and Regulations (Title 129)

Chapter 2.5, 17

The definition of a "major source" of air pollution is established in Chapter 2. Chapters 5 and 17
define the appropriate permit reguirements for operation, construction, or modification of a source of
air emissions. The incinerator will be evaluated in accordance with Chapter 2 to verify that it is not a
major source; however, the substantive reguirements for a permit, contained in Chapters 5 and 17, must be
met.

Chapter 4

This chapter specifies primary and secondary ambient air guality standards for particulate matter, sulfur
dioxide, nitrogen dioxide, carbon monoxide, ozone, and lead. Standards established in this chapter will
be considered during the design of the incinerator.

Chapter 16
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This chapter sets forth the best engineering practices for incinerator stack height design. The
recommended procedures for stack height design will be followed during the design of the incinerator.

Chapter 19

40 CFR 52.21, Prevention of Significant Deterioration of Air Quality, is adopted. This chapter would
prevent the operation of an incinerator without appropriate measures to control potentially detrimental
air emissions. The incinerator included in the remedy will have the appropriate pollution controls to
prevent significant deterioration of air guality.

Chapter 20

This chapter prohibits visible dust beyond the limits of the property line where handling,
transportation, or construction is taking place. Dust control measures will be applied during soil
excavation, stockpiling, and feeding into the incinerator to prevent visible emissions beyond the former
NOP site boundaries.

Chapter 22

Emission limits for new incinerators are specified along with the outline and content reguired for
emission control reports. The emission limits for new incinerators will be considered during design of
the incinerator.

Chapter 39

This chapter limits visible emissions from diesel-powered construction eguipment or vehicles. Eguipment
used on-site for excavation, stockpiling, or transportation will comply with these limits.

Rules and Regulations Pertaining to the Management of Wastes (Title 126, NDEQ)

This statute reguires permits or licenses for various state management activities and establishes policy
for releases of oil or hazardous substances.

Water Quality Standards for Surface Waters of the State (Title 117)

Water guality standards for surface waters of the state. Similar to ambient water guality, these
criteria are applicable and will be used to establish discharge limits for treated groundwater,
decontamination fluids, or process water.

Groundwater Quality Standards and Use Classification (Title 118, NDEQ)

This statute specifies standards and use classifications for groundwater used as drinking water and is
used by the State of Nebraska to establish priorities for groundwater remedial actions. The selection
and design of the remedy is based on the use of groundwater at the former NOP as a drinking water source.

National Pollutant Discharge Elimination System (NPDES) (Title 119, NDEQ)

This statute establishes the reguirements for permitting a point source discharge to waters of the state.
As is the case for the federal NPDES program, no permit is reguired because of the site's Superfund
status. However, the substantive reguirements of a permit must be met. Discharge limits will be
established during remedial design and compliance with these values will be demonstrated in accordance
with NPDES reguirements.

Nebraska General NPDES Rules for New and Existing Sources (Title 121, NDEQ)

The effluent standards set forth in this statute will be used in developing discharge limits for the
groundwater treatment system, decontamination fluids, or process water.

Rules and Regulations Governing Hazardous Waste Management in Nebraska (Title 128, NDEQ)

The procedures specified in this statute will be used to notify the appropriate state authorities of the
activities at the site, including the construction of the incinerator.

Regulations Governing Licensure of Water Well and Pump Installation Contractors and Certification of
Water Well Drilling and Pump Installation, and Water Well Monitoring Supervisors (Nebraska Administrative
Code, Title 178, Nebraska Department of Health, Chapter 12)
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Contractors installing extraction wells, pumps, and/or monitoring wells at the site will be licensed in
accordance with Title 178 of the Nebraska Administrative Code.

Regulations Governing Water Well Construction, Pump Installation, and Water Well Abandonment Standards
(Nebraska Administrative Code, Title 178, Nebraska Department of Health, Chapter 12)

Extraction wells and pumps will be installed and registered in accordance with the reguirements of Title
178 of the Nebraska Administrative Code. Any future abandonment of wells (including existing monitoring
wells not included in the long-term monitoring network) will comply with these regulations.

Nebraska Drinking Water Standards (Nebraska Administrative Code, Title 179, Department of Health)

State MCLs are established by this regulation. The discharge of treated groundwater, decontamination
fluids, or process water will not directly impact drinking water; however, the potential for residual
contaminants percolating to groundwater exists. State MCLs for COCs, where established will be
considered when establishing discharge limits for treated water.

TO BE CONSIDERED STANDARDS (TBCs)

Lifetime Health Advisories (HAs)

Lifetime Health Advisories are drinking water criteria designed to protect human health and include a
margin of safety. The numerical standards are TBCs and do not have the status of potential ARARs. The
lifetime HA for both TNT and RDX is 2 Ig/1. These criteria will be considered when establishing effluent
discharge criteria for treated groundwater.

Drinking Water Eguivalent Levels (DWELs)

Drinking Water Eguivalent Levels (DWELs) are health-based drinking water criteria designed to protect
against adverse non-cancer effects. The DWEL for methylene chloride is 2000 Ig/L and for TCE is 300
Ig/L. For TNT, the DWEL is 20 Ig/L. The DWEL for both 2,4-DNT and RDX is 100 Ig/L. These criteria are
TBCs for the site and will be considered when establishing effluent discharge criteria for treated
groundwater.

2.12.3 Cost Effectiveness

The selected remedial action is cost-effective because it provides overall effectiveness proportional to
its costs. The estimated costs of the selected remedy are the lowest for any alternative which controls
long-term risk to groundwater consumers and reduces the potential for transfer of explosives from the
soil to the groundwater. The selected remedy will be effective in the long-term due to the significant
and permanent reduction of the toxicity, mobility, and volume of contaminated groundwater.

2.12.4 Utilization of Permanent Solutions and Innovative Treatment Technologies to the Maximum Extent
Practicable

SARA specifies a preference for use of permanent solutions and innovative treatment technologies or
resource recovery technologies to the maximum extent practicable. The selected remedial action utilizes
a permanent solution but not an innovative treatment technology. Of those alternatives that comply with
the threshold criteria, USAGE, USEPA, and NDEQ have determined that the selected alternative provides the
best balance in terms of long-tern effectiveness and permanence, reduction of toxicity, mobility, and
volume through treatment, short-term effectiveness, and cost.

2.12.5 Preference for Treatment Which Reduces Toxicity, Mobility, or Volume

By hydraulically containing and extracting groundwater containing COCs greater than the Final Target
Groundwater Cleanup Goals, the selected remedial action addresses one of the principal threats posed by
the former NOP site. The selected remedy also satisfies the statutory preference for remedial actions
that employ treatment to significantly reduce toxicity, mobility, or volume of contaminants in
groundwater and soil.

2.13 DOCUMENTATION OF SIGNIFICANT CHANGES

The selected remedy has not been significantly changed from the preferred remedy presented in the OU2
Proposed Plan.
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3.0 RESPONSIVENESS SUMMARY

In October 1995, USEPA and USAGE released the Proposed Plan for the former NOP site, OU2, i.e.,
contaminated groundwater, explosives-contaminated soil not remediated during OU1 which could act as a
source of explosives contamination of groundwater, and soil contaminated with VOCs. The public comment
period for the Proposed Plan lasted from October 30, 1995 to November 29, 1995. The USEPA and the USAGE
sponsored a public meeting on November 8, 1995, during which the preferred alternative was presented and
explained to the public, and guestions and comments were taken for the record.

This Responsiveness Summary serves two purposes. First, it summarizes the comments of the public.
Second, it provides responses to the comments on the Proposed Plan that were made at the public meeting
and that were submitted in writing during the public comment periods.

3.1 OVERVIEW

The preferred alternative for OU2 at the former NOP site that was proposed by the USEPA and the USAGE in
the Proposed Plan, and presented during related public sessions, was focused extraction of groundwater
and soil excavation.

Verbal public comments on the preferred alternative were documented at the public meeting on November 8,
1995. Eight comment letters were received during the public comment period.

In general, the public had differing opinions regarding Alternative 4 as the preferred remedial action
alternative. Four written comments supported Alternative 4. Three written comments neither supported
nor opposed the use of Alternative 4. One written comment opposed any pump and treat alternative which
would include Alternatives 2 through 8.

3.2 BACKGROUND ON COMMUNITY INVOLVEMENT

Prior to the public meeting in November 1995, efforts were undertaken to inform the public of steps
toward remedial action at the site, and to involve the public in the decision-making process. Community
relations activities increased in 1994 with the culmination of the investigation activities for OU1 and
the decision-making regarding cleanup of soil at the site. Some of the major activities aimed at
involving the community and obtaining their feedback have been:

1. A community survey of residents and local officials via on-site interviews, as well as telephone
interviews, was conducted in January 1992.

2. A Community Relations Plan dated May 28, 1992 outlines the approach to be taken toward community
relations and public participation.

3. Periodic fact sheets were mailed to the public in May 1992, June 1994, August 1994, and February 1995
to provide updates and additional information as necessary.

4. Public meetings were held in May 1989, June 1990, June 1994, and November 1995 to report on project
progress and to solicit comments. Notices of these meetings were published in the Ashland, Wahoo,
Lincoln and Omaha newspapers.

5. Two availability sessions were held at the site in June 1994 and February 1995 to discuss progress,
answer guestions and discuss concerns. The primary purpose of these sessions was to address
OUl-related concerns; however, personnel familiar with OU2 activities addressed OU2-related concerns.

6. A public session was held in June 1995 to solicit comments on the OU2 Groundwater Containment Removal
Action.

7. Technical Review Committee meetings are held periodically with representation by the USEPA, NDEQ,
USAGE, Lincoln Water System, Natural Resources District, Nebraska Department of Health, the
University of Nebraska - Lincoln and the Saunders County Board of Supervisors.

8. An information repository was established at the Ashland Public Library in Ashland, Nebraska. Site
information is also available at the USEPA office in Kansas City, Kansas and the NDEQ office in
Lincoln, Nebraska.

9. A collect telephone line to the USAGE was established so that the public can call to get guestions
answered without charge.
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3.3 SUMMARY OF PUBLIC COMMENTS AND AGENCY RESPONSES

This Responsiveness Summary includes statements made at the November 8, 1995, public meeting and comments
submitted to the USAGE during the public comment period from October 30, 1995 to November 29, 1995. It
also includes USEPA and USAGE responses to those comments and guestions.

Comments and guestions have been paraphrased or guoted in italic text. Every attempt has been made to
accurately preserve the intent of the comment and to include all issues raised. The letters in
parentheses following the comments identify the commentors according to the Commentor Key following the
Responsiveness Summary. All commentors who raised similar or related comments are identified.

The official public meeting transcript and written comments on file in the information repository at the
Ashland Public Library in Ashland, Nebraska contain the verbatim comments from all commentors. The
comments have been grouped according to common issues to avoid repetition in the responses, and the
issues have been grouped into the following categories for ease of reference:

• Remedial Alternative Preferences
• Impact on Groundwater Supply
• Reuse of Treated Water
• Nitrates Contamination
• Current Ecological Impacts

3.3.1 Remedial Alternative Preferences

ISSUE 1. The identification of Alternative 4 as the preferred alternative was supported by the Nebraska
Department of Environmental Quality and several residents living at or near the site. (A, G, I, L)

Alternative 4 will provide the best balance of trade-offs among alternatives with respect to the
evaluating criteria established by the Superfund Law. Alternative 4 consists of the following elements:
groundwater monitoring, potable water supply, hydraulic containment, focused extraction, and soil
excavation and treatment. USAGE, USEPA, and NDEQ concur that Alternative 4 will be protective of the
human health and the environment, will comply with ARARs, will be cost effective, and will use permanent
solutions and alternative treatment technologies to the maximum extent practicable. Alternative 4 will
also meet the statutory preference for the use of treatment as a principal element.

ISSUE 2. It makes sense to eliminate the source of groundwater contamination and let the aguifer cleanse
itself. I strongly agree with soil excavation and treatment and continued groundwater monitoring. (N)

Natural attenuation is a relatively slow process. For example, either the sources of TCE contamination
ceased to release TCE to the groundwater sometime in the past or the current release is relatively minor,
but the TCE plumes have continued to expand. Although natural attenuation processes have been acting on
the TCE plumes, the expansion of the plumes means that beneficial use of the natural resource is
continually being lost at an increasing rate. In addition, remediation is reguired to meet all of the
applicable and relevant State and Federal laws and regulations. Therefore, it is appropriate to take
action to remediate groundwater at the former Nebraska Ordnance Plant. However, the Superfund law
provides a formal mechanism to change the selected remedy if it proves ineffective or if another
technology is shown to be more appropriate. Currently, research is being conducted at other sites to
evaluate a particular type of natural attenuation called intrinsic bioremediation. The results of this
and other research is the type of information that may be considered during future evaluations of the
clean up progress at the former Nebraska Ordnance Plant.

The excavation and treatment of explosives-contaminated soil concurrently with OU1 remedial activities
will reduce the potential for the soils to contaminate groundwater. It is estimated that both cost and
time savings will be realized by this action.

Data from groundwater monitoring is used to evaluate changes in the distribution of groundwater
contaminants with time. Such information is important when assessing the effectiveness of the
groundwater remediation. Additionally, groundwater monitoring is used to determine when groundwater
drinking water supplies need to be treated or replaced at local residences.

ISSUE 3. Where has pump and treat groundwater remediation been attempted and where has it been
successful? Is this going to be an experimental site? The cost of the remediation is too high when the
remediation will probably not succeed. (N)

Remediation of groundwater contamination by pumping the contaminated water from the aguifer and
subseguently treating the water to reduce the contaminant concentrations are proven technologies.
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According to a study published in 1994 by the National Research Council Committee on Ground Water Cleanup
Alternatives, 73 percent of the cleanup agreements at Superfund groundwater contamination sites specified
pump and treat strategies. The same study suggests that pump and treat strategies are effective at
stopping the spread of groundwater contamination and have mixed results for reducing contaminant
concentrations to the cleanup goals in a "reasonable" time. Alternative 4 includes a pump and treat
process called hydraulic containment to stop the spread of contamination. A second pump and treat
process called focused extraction was included as an element of Alternative 4 so that groundwater is
removed from areas with relatively high TCE and/or RDX concentrations.

The following list summarizes some on-going pump and treat remediation projects implemented by Federal
agencies at Federal facilities. Typically, these remediation projects are large sites which reguire
decades to restore. Therefore, the projects may be considered successful to date, although complete
restoration has not yet been achieved.

• McClellan Air Force Base, California, Operable Unit B/C - Approximately 660 million gallons
of TCE-contaminated groundwater were extracted and successfully treated in 7 years. The
system consists of 7 extraction wells and has been operational since 1988.

• McClellan Air Force Base, California, Operable Unit D - TCE-contaminated groundwater has been
extracted using 6 wells as a part of a large-scale cleanup. The cleanup system, which also
includes treatment of the extracted water, has been operational since 1987.

• Twin Cities Army Ammunition Plant, Minnesota - Approximately 1.4 billion gallons of
TCE-contaminated groundwater were extracted and treated between the October 1991 and
September 1992. The ongoing cleanup is expected to take between 50 and 70 years.

• U.S. Department of Energy Kansas City Plant, Missouri - TCE-contaminated groundwater has been
extracted and treated since 1983. Approximately 11.2 million gallons of groundwater were
extracted during 1992.

• U.S. Department of Energy Savannah River Site, South Carolina, A/M Area - 198 million gallons
of TCE-contaminated groundwater have been extracted and treated annually by a system that has
been operational since 1983.

In Nebraska, a pump and treat system is currently being designed to remediate explosives contaminated
groundwater at the Cornhusker Army Ammunition Plant near Grand Island. It is estimated that eight wells
will extract a total of 1,650 gallons per minute from a 2,000 acre area of contamination.

The use of this remedy at the former Nebraska Ordnance Plant is not experimental. The use of proven
groundwater remediation technologies is being employed to accomplish specific objectives. Unproven,
experimental, or research and development-type processes have not been used for this remedy.

Remedial action is reguired to ensure overall protection of human health and the environment. Remedial
action will also restore a valuable resource to its beneficial use. Remediation is also reguired to meet
all of applicable and relevant State and Federal laws and regulations. The Superfund law reguires that
the clean up activities be reviewed periodically. If at the time of the review, the existing technology
is not effective or a new, more effective technology is available, changes to the remedy can be made.
Pump and treat is the only feasible containment technigue presently available for sites with such large
areas of contamination.

As discussed in the response to Issue 1, Alternative 4 provides the best balance of trade-offs among the
alternatives with the respect to the evaluation criteria which include cost. The costs estimated for
Alternative 4 are reasonable for the magnitude of the pump and treatment system which is being developed.

ISSUE 4. University of Nebraska faculty members are doing wetlands research at the Agricultural Research
and Development Center, and remediation of TCE-contaminated water using alfalfa or cattails has been
researched at the University of Kansas. The two research concepts should be combined to treat
contaminated groundwater at the former Nebraska Ordnance Plant. (M)

Constructing a wetlands and using plants to remove TCE and explosives contamination is not feasible at
the former Nebraska Ordnance Plant for the following reasons:

• The use of plants for treatment of explosives and TCE contaminated groundwater is not a
proven technology. Existing research has not proceeded past the pilot study stage and
involves the in-situ remediation of groundwater. At the former Nebraska Ordnance Plant, the
depth to groundwater is greater than the depth of the root zone, and in situ treatment is not
feasible.
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• The growing season at Mead is not year round, and it is not feasible to store the large
quantities of water for subsequent treatment that would be extracted during the off season.

ISSUE 5. Sulfur dioxide should be injected into the aquifer to form sulfurous acid which in turn will
remove TCE from the groundwater. (L)

Theoretically, TCE will hydrate in the presence of sulfurous acid. The products of the hydration will
include other chlorinated compounds. Use of sulfurous acid to treat TCE-contaminated groundwater is not
a proven technology for remediating environmental contamination. From a practical viewpoint, the
injection of acid into the aquifer in large quantities would lower the pH of the groundwater to
unacceptable levels.

ISSUE 6. A pilot study of treatment processes should be conducted before full scale design is
initiated. (C)

Bench-scale treatability studies are currently being conducted for two of the potential treatment
processes, granular activated carbon adsorption and advanced oxidation processes. The treatability study
data will be used to select the type of groundwater treatment option prior to the design of the treatment
plant. If advanced oxidation processes are selected, pilot scale studies may be required prior to full
scale design.

ISSUE 7. There is a threat to human health if individuals come in contact with the extracted water
before it reaches the treatment plant. (M)

The potential for contact with the water before it reaches the treatment plant would be in the event that
the pipeline breaks. Extraction wells would be shut down and breaks would be repaired rapidly by workers
following an appropriate set of health and safety protocols. Generally, the threat to human health
identified in the Baseline Risk Assessment at the former Nebraska Ordnance Plant is based on chronic
exposure to the contaminated water. If an individual were to be exposed to contaminated groundwater
during a pipeline break, the period of exposure would be so short that there would be negligible and
immeasurable threat to human health.

ISSUE 8. Will untreated water be discharged to surface streams? (I, M)

Untreated groundwater will not be surface discharged during the normal operation of the remediation
system. In the event that treated groundwater is surface discharged, the treated groundwater will be
monitored prior to discharge to insure that treated water whose quality does not meet the acceptable
discharge standards is not released.

ISSUE 9. The chemicals present in the groundwater are known carcinogens. (M)

The chemicals of concern in the groundwater and their corresponding USEPA weight-of-evidence carcinogenic
classification are:

• Methylene chloride - B2
• 1,2-dichloropropane - B2
Trichloroethene (TCE) - B2
• 1,3,5-trinitrobenzene (TNB) - None
2,4,6-trinitrotoluene (TNT) - C
2,4 or 2,6-dinitrotoluene (DNT) - B2
Hexahydro-l,3,5-trinitro-l,3,5-triazine(RDX) - C

The chemicals classified as B2 are probable human carcinogens based on sufficient evidence in animals and
inadequate or no evidence in humans of carcinogenicity. TNT is classified as C which means that TNT is a
possible human carcinogen based on limited carcinogenicity in animals. TNB has not been classified due
to a lack of data.

Although none of the chemicals have been classified as known human carcinogens (Class A), Class B2
chemicals present at the site are considered probable human carcinogens. The B2 classification is based
on sufficient evidence in animals and inadequate or no evidence in humans of carcinogenicity.

ISSUE 10. The City of Mead water supply should be monitored. (K)

Since the wells that supply water to Mead are located outside the area of groundwater contamination
associated with the former Nebraska Ordnance Plant, they are not a part of this project. However, Mead's
water supply is a public water supply which is regularly monitored for contaminants in accordance with
federal Safe Drinking Water Act and the Nebraska Safe Drinking Water Act. Questions concerning both the
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historic and current water quality should be addressed to the village of Mead, or to the Nebraska
Department of Health at (402) 471-2541.

ISSUE 11. Why is it taking a long time to clean up the groundwater? (J)

The Superfund process of site cleanup includes a number of procedures intended to ensure that public and
private funds are effectively used to mitigate unacceptable threats to human health and the environment.
These procedures are commonly time-consuming.

At the former NOP site, approximately 23 billion gallons of groundwater are contaminated above acceptable
levels. Much more than 23 billion gallons of groundwater will have to be removed before the aguifer is
cleaned up. It will reguire decades to remove that quantity of groundwater via numerous wells. However,
the groundwater contamination occurs in distinct bodies, called plumes. At the former NOP site, some
plumes are considerably smaller than others, and the smaller plumes will be cleaned up more quickly than
the larger plumes. For example, it is estimated that Alternative 4 will clean up the TCE plume with the
suspected source at the AFBMD Technical Area and the overlapping explosives plume in a few decades, the
explosives plume with suspected source at Load Lines 2 and 3 will take more than twice as long to clean
up, and the TCE plume with the suspected source at the Atlas Missile Area is estimated to take 130 years
to clean up.

Prior to the selection of the remedy represented by this Record of Decision, efforts were planned to stop
the spread of TCE contaminated groundwater at the former NOP site. These efforts are called the
Groundwater Containment Removal Action.

ISSUE 12. Currently, the Army is providing treatment units to the ARDC and homeowners whose wells
contain unacceptable concentrations of RDX and/or TCE. The treated water has an offensive odor and
taste. (G, J)

The Army is supplying bottled water to the private residences where the aesthetic quality of the treated
groundwater is unacceptable. The Army has either supplied water to residences or replaced the carbon in
treatment units with aesthetic problems. Similar actions will be taken in the future if problems arise.
The Army is committed to resolving potential future problems associated with treated water in a timely
manner.

If beneficial reuse is selected as the treated groundwater disposal option, a rural water district could
be used to supply water to locations whose groundwater contains unacceptable concentrations of Department
of Defense-related contamination.

ISSUE 13. Does the transfer of contamination from the groundwater to the atmosphere during treatment
pose an unacceptable threat to human health? (G)

If the selected treatment process includes the transfer of volatile organic chemicals from the
groundwater to the atmosphere, the airstream will be treated, if necessary, so that it does not pose an
unacceptable threat to human health.

ISSUE 14. What is potable water? (N)

In the context of the remedial alternatives considered for the former NOP site, potable water is drinking
water where the Department of Defense-related chemical concentrations have been reduced to or below
acceptable levels. For example, the concentration of RDX would have to be reduced to or below the
Lifetime Health Advisory.

ISSUE 15. Soil excavation and treatment should be combined with Alternative 2 to create a new
alternative. This new alternative would remove the current source of groundwater contamination and
prevent the existing contamination from expanding. After 20 or 30 years, there is some potential that a
yet to be discovered technology can then be used to clean up the contamination more effectively and less
expensively than today's technologies. (H)

Soil excavation was not combined with Alternative 2 because it was estimated that the contaminated soil
would stop being a source of contamination by the time that Alternative 2 cleaned up the existing
groundwater contamination.

As far as waiting for new technologies to be invented and proven effective, the Superfund Law requires
that the clean up activities be reviewed periodically. If at the time of the review, the existing
technology is not effective or a new, more effective technology is available, changes to the remedy can
be made.
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3.3.2 Impact on Groundwater Supply

ISSUE 16. What actions will be taken to prevent shortages of groundwater at irrigation and domestic
wells? What action will be taken if irrigation and domestic wells go dry? (E, F, G, I, J, D)

Mathematical modeling will be used to predict the aguifer drawdown at domestic and irrigation wells.
Seasonal aguifer stresses caused by irrigation and regional aguifer stresses resulting from a
hypothetical drought season will be included in the analyses. The drawdown predictions will be used to
locate extraction wells and to develop extraction well operation plans with the intent of managing
aguifer drawdown. For example, focused extraction wells will be located where there is a relatively low
potential that the remedial pumping will cause unacceptable drawdown at supply wells, and the operation
plans may indicate that focused extraction pumping will be reduced or stopped during the irrigation
season. Data will be collected after the start up of the remedial pumping system, and the operation of
the system may be modified in response to that data to effectively manage the aguifer drawdown.

It may not be feasible to mitigate negative drawdown impacts while maintaining the effectiveness of the
hydraulic containment system. In the event that remediation pumping has a negative impact on the ability
of local supply wells to produce water at current use levels, the negative impact will be evaluated and
addressed by the Army. The details of determining impacts on groundwater availability and responses to
the impacts will be better defined during
the Remedial Design process.

ISSUE 17. Potentially, future development of groundwater resources will be limited. (D)

The implementation of a pump and treat groundwater remediation system does not preclude the future
installation of water supply wells.

Locally, groundwater is produced from the Todd Valley aguifer, the Platte River alluvial aguifer, and the
Omadi Sandstone aguifer which underlies the other two aguifers. Only a fraction of the water available
in the Todd Valley aguifer and the Platte River alluvial aguifer will be extracted as a result of
remediation pumping. The water remaining in those aguifers and virtually all of the Omadi Sandstone
water will remain available for future development. The Lower Platte North Natural Resources District
has been guardedly optimistic that groundwater is available for future development. Water levels
measured by the Lower Platte North Natural Resources District in Todd Valley irrigation and monitoring
wells have shown that there has been very little decline in groundwater elevations during either dry or
wet years.

In the event that remediation pumping has a negative impact on future groundwater development, the
operation of the remediation system may be modified to some degree without hurting the effectiveness of
the hydraulic containment system.

3.3.3 Reuse of Treated Water

ISSUE 18. A beneficial reuse for the treated groundwater should be developed so that the water is not
solely discharged to a surface stream. (C, E, G, F)

The selection of the treated groundwater disposal option, either surface water discharge or beneficial
reuse, will be made during the remedial design analysis and will be based on the following criteria:

• Cost/benefit analysis
• Technical feasibility
• Public acceptance

A Saunders County Rural Water Project Committee has been formed to evaluate the beneficial reuse options
related primarily to water supply. Mr. Larry Angle of the Lower Platte North Natural Resources District
chairs the committee. Other organizations which are represented on the committee include the Army, the
University of Nebraska, the Nebraska Department of Environmental Quality, the City of Ashland, the
Lincoln Water System Saunders County Board of Supervisors, Wahoo Utilities, and the Nebraska Department
of Health. One of the committee's activities includes conducting a study to determine the economic
feasibility of constructing and operating a number of different water distribution systems. The study
area encompasses Saunders County, and supplying water to the City of Lincoln is included in some of the
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study scenarios. The study has been funded by a combination of local funding and matching federal funds.
The study was initiated when matching funds were received from local communities, and it is estimated
that the study can be completed approximately January 1997. If the study is completed in time to
incorporate into the Remedial Design (approximately January 1997), the results of the study will be
considered when choosing between surface water discharge and beneficial reuse during the future remedial
design analysis. If not, the Army will either gather the necessary information directly, or choose not
to pursue beneficial reuse.

ISSUE 19. Discharging 4 million gallons of water a day to Clear Creek during flooding will cause a
negative public reaction. (I)

The impact of discharging water on Clear Creek water levels has not been guantitatively evaluated because
the total combined flowrate from the extraction wells has not been calculated. However, a depth analysis
was performed as a part the Groundwater Containment Removal Action. That analysis showed that a
discharge of 5 cubic feet per second, which is approximately 3.2 million gallons per day, to Clear Creek
during a flood flow would increase the water depth in the channel approximately 0.24 inches. If surface
discharge is used for disposal of treated water, the remedial design will include a water depth analysis.
If the results show that the discharge of the treated water during specific flood conditions may cause
overtopping of the levees along the creek, the remedial design may specify that discharge of the treated
water to the creek cease during such flood conditions. The remedial design will also include an analysis
of the overall effectiveness of the hydraulic containment system when pumping is stopped temporarily, as
would be the case if it was temporarily not possible to dispose of the treated water.

In addition, the Army has contacted Mr. Dean Busing, President of the Clear Creek Drainage District, to
inguire about the board's reaction to discharging treated water to Clear Creek. Mr. Busing indicated that
the Drainage Board did not perceive that significant problems would develop from the potential discharge
of treated groundwater to the creek. However, public acceptance is one of the three criteria that will
be used to select the treated groundwater disposal option. The selection criteria are discussed in the
response to the preceding issue.

ISSUE 20. A rural water district should be developed. What area would the rural water district serve?
(F, I)

A rural water district is among the scenarios included in the Saunders County Rural Water Project
Committee feasibility study. Although the Natural Resources District is the agency associated with
establishment of rural water districts, USAGE anticipates that any potential future rural water district
would include provision of service to residents whose water was contaminated with TCE and/or explosives.

ISSUE 21. The treated water should be reinjected into the aguifer. (I)

Reinjection of treated groundwater is being considered as a beneficial reuse option.

3.3.4 Nitrates Contamination

ISSUE 22. Nitrate contamination is a big problem. Groundwater treatment should address nitrates in
addition to TCE and explosives. (C, G)

Nitrates contamination is a regional problem which did not result from Department of Defense-related
activities. Therefore, USAGE does not have the authority or means to expend funds for nitrates
treatment.

The State of Nebraska has the responsibility to address nitrate contamination. All of the Lower Platte
North Natural Resources District will be established as a Groundwater Management District beginning in
January 1997. Some of the activities associated with the Groundwater Management District will focus on
preventing future problems associated with high nitrate levels. Additional guestions regarding regional
nitrates contamination should be addressed to the Natural Resources District, the Nebraska Department of
Environmental Quality, or the Nebraska Department of Health.

ISSUE 23. Who has the responsibility for remediating nitrates contamination that migrates to areas which
would normally not be contaminated if Department of Defense-related groundwater remedial activities did
not change groundwater flow patterns? (D)

The hydraulic containment and focused extraction components of Alternative 4 rely on regional groundwater
flow to be effective. These components will not change the direction of the regional flow, and nitrates
contamination will continue to follow the regional flow patterns. Therefore, areas outside of the
regional groundwater flow path will not become contaminated.
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3.3.5 Current Ecological Impacts

ISSUE 24. A species count was not performed as a part of an Environmental Impact Statement. (M)

An environmental impact statement is normally performed to fulfill the requirements of the National
Environmental Policy Act (NEPA). The work performed at the former NOP site conforms with the
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) as amended by the
Superfund Amendments and Reauthorization Act, and its governing regulations, the National Contingency
Plan. The CERCLA process satisfies NEPA requirements, and an Environmental Impact Statement is not
required at the former NOP site.

An ecological risk assessment was performed for the former NOP site. The risk assessment focused
primarily on ecological exposures to contaminants in surface soils, sediment, and surface water.
Exposure of ecological receptors flora and fauna to contaminated groundwater was considered unlikely,
except through crop irrigation, and was not addressed specifically. The assessment did not identify any
unacceptable risks to ecological receptors.

SUMMARY OF COMMENTORS

Public Meeting, November 8, 1995

The following people made oral comments:

A Ed Louis (NDEQ)
B Larry Angle
C Jerry Obrist
D Dan Duncan
E Doug Irvin
F John Kirchmann
G Mrs. Jerry Proctor
H Dwight Hanson
I Harold Kolb

The following people made written comments at or outside of the public meeting:

D Dan Duncan
F John Kirchmann
I Jerry L. Proctor
J Vi Irvin
K Marilyn Benal
L Ross H. Rasmussen
M Katherine A. Saniuk
N Joe Schlueter
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