PB98-964302
EPA 541-R98-172
March 1999
EPA Superfund
Record of Decision:
Cornhusker Army
Ammunition Plant OU 2
Hall County, NE
9/30/1998
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US Army Corps
of Engineers
Omaha District
Delivery Order No. DA01
Total Environmental
Program Support
Contract Number
DAAA15-91-D-0014
CORNHUSKER ARMY AMMUNITION PLANT
Record of Decision
Operable Unit Two
FINAL DOCUMENT
April 1998
THIS DOCUMENT IS INTENDED TO COMPLY WITH THE NATIONAL ENVIRONMENTAL POLICY ACT OF 1969
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TABLE OF CONTENTS
Sect/on Page
1.0 DECLARATION OF THE RECORD OF DECISION 1-1
1.1 SITE NAME AND LOCATION 1-1
1.2 STATEMENT OF BASIS AND PURPOSE 1-1
1.3 DESCRIPTION OF THE SELECTED REMEDY: NO REPONSE ACTION 1-1
1.4 DECLARATION STATEMENT 1-1
2.0 DECISION SUMMARY 2-1
2.1 SITE NAME, LOCATION. AND DESCRIPTION 2-1
2.2 HISTORY AND ENFORCEMENT ACTIVITIES 2-1
2.2.1 Site History 2-1
2.2.2 Histories of Areas of Concern Designated as OU2 2-3
2.2.3 Enforcement Activities 2-4
2.3 HIGHLIGHTS OF COMMUNITY PARTICIPATION 2-4
2.4 SUMMARY OF SITE RISKS 2-5
2.4.1 Human Health Risks 2-5
2.4.2 Ecological Risks 2-7
2.5 CLEANUP LEVELS 2-8
2.6 SUMMARY AND FINDINGS OF SITE INVESTIGATION AT OU2 2-9
2.7 CONCLUSIONS 2-10
2.8 DESCRIPTION OF THE "NO FURTHER ACTION/NO RESPONSE ACTION" 2-10
2.9 EXPLANATION OF SIGNIFICANT CHANGES 2-10
3.0 RESPONSIVENESS SUMMARY 3-1
3.1 OVERVIEW 3-1
3.2 SUMMARY OF COMMENTS RECEIVED DURING THE PUBLIC COMMENT PERIOD AND
AGENCY RESPONSES 3-1
4.0 REFERENCES 4-1
LIST OF APPENDICES
Appendix
Appendix A: Methodology for Calculating COPC Cleanup Levels
LIST OF TABLES
Table Page
Table 1: Chemicals of Potential Concern in Surface Soil (0-2 ft bgs) for Human Receptors at OU2 2-5
Table 2: Chemicals of Potential Concern in Subsurface Soil (>2 ft bgs) for Human Receptors at OU2.2-5
Table 3: Chemicals of Potential Concern in Groundwater at CHAAP 2-6
Table 4: Cleanup Levels for Soil COPCs (pg/g) at CHAAP 2-7
Table 5: Cleanup Levels for Groundwater COPCs (ng/L) at CHAAP 2-8
DAAA15-91-D-0014 i Record o1 Decision
TEPS 14-6 Operable Unit Two
April 1998 Final Document
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LIST OF ACRONYMS
ABA - Abandoned Burn Area
ABHA - Administration and Base Housing Areas
ADI - Allowable Daily Intake
AOC - area of concern
bgs - below ground surface
CERCLA - Comprehensive Environmental Response, Compensation, and Liability Act
CHAAP - Cornhusker Army Ammunition Plant
CHPPM - Center for Health Promotion and Preventative Medicine
COPC - Chemical of Potential Concern
CRS - Cornhusker Rail Services
DDD - 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane
DDE - 2,2-bis(p-chlorophenyl)-1,1-dichloroethene
DDT - 1,1,1-trichloro-2,2-bis(chlorophenyl)ethane
EA - Excessing Assessment
ERA - Ecological Risk Assessment
FFA -.Federal Facility Agreement
FS - Feasibility Study
ICF KE - ICF Kaiser Engineers
GOCO - government owned contractor operated
HHRA - Human Health Risk Assessment
MCL - Maximum Concentration Level
NCP - National Contingency Plan
NDEQ - Nebraska Department of Environmental Quality
NMAG - North Magazine Area
OU - Operable Unit
RBC - Risk-Based Concentration
RDX - cyclonite
Rl - Remedial Investigation
ROD - Record of Decision
SARA - Superfund Amendments and Reauthorization Act
SCO - Site Characterization Document
SI - Site Investigation
SMAG - South Magazine Area
STP - Sewage Treatment Plant
TIC - Tentatively Identified Compound
246-TNT - 2,4,6-trinitrotoluene
TRV - Toxiciry Reference Value
USAEC - United States Army Environmental Center
USATHAMA - United States Army Toxic and Hazardous Material Agency
USEPA - United States Environmental Protection Agency
UXO - unexploded ordnance
OAAA15-91-D-0014 » Record of Decision
TEPS 14-6 Operable Unit Two
April 1998 Final Document
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1.0 DECLARATION OF THE RECORD OF DECISION
1.1 SITE NAME AND LOCATION
Cornhusker Army Ammunition Plant Operable Unit Two (OU2), Grand Island, Nebraska.
1.2 STATEMENT OF BASIS AND PURPOSE
This Record of Decision (ROD) document presents the selected remedial action for the six areas of
concern (AOCs) located at the Cornhusker Army Ammunition Plant (CHAAP) in Grand Island, Nebraska
designated as OU2. The remedial action is chosen in accordance with the Comprehensive Environmental
Response, Compensation, and Liability Act of 1980 (CERCLA), as amended by the Superfund
Amendments and Reauthorization Act (SARA) of 1986, and with the National Oil and Hazardous-
Substances Pollution Contingency Plan (NCP). The information supporting the decisions on the selected
remedy is contained in the administrative record. Section 2.2.3 lists the documents contained in the
administrative record.
The U.S. Environmental Protection Agency (USEPA) and the Nebraska Department of Environmental
Quality (NDEQ) concur with the selected remedy.
1.3 DESCRIPTION OF THE SELECTED REMEDY: NO REPONSE ACTION
The remedial investigation of OU2 is part of a comprehensive environmental investigation and remediation
currently being performed at CHAAP under the CERCLA program. CHAAP is divided into three operable
units that include 17 sites representing potential sources of contamination.
Operable Unit Two has been designated for no further remedial action because there is no indication of
adverse effects from contact with environmental media at this operable unit. In addition, there is no
migration of hazardous contaminants from OU2 at concentrations that would harm human health based
on the results of the human health risk assessment. It should be noted that cleanup criteria were not
driven by ecological risk because the areas that comprise OU2 have poor quality habitat due to past and
present uses and/or abundance of manmade structures making extensive use by terrestrial receptors
unlikely.
1.4 DECLARATION STATEMENT
No further remedial actions are necessary to ensure protection of human health and the environment at
AOCs designated as OU2. A five-year review of the site will be necessary to ensure that that the decision
of no further action/no response action is protective of human health and the environment.
DAAA15-91-D-0014 1-1 Record of Decision
TEPS 14-6 Operable Unit Two
April 1998 Final Document
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25
Date
Toionei, 1-3
Thief of Staff
c
Dennis-Grams
Regional Administrator
U.S. Environmental Protection Agency. Regionc
i '
Date
OAAA15-91-0-0014
TEPS 14-5
April 1998
1-2
Record ol Decision
Operable Unit Two
Final Document
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2.0 DECISION SUMMARY
2.1 SITE NAME, LOCATION, AND DESCRIPTION
Cornhusker Army Ammunition Plant is located on an 11,936-acre (19 mi2) tract approximately two miles
west of Grand Island, Nebraska, in north-central Hall County.
The land around CHAAP is intensely cultivated and most of the original prairie grass and other vegetation
have been replaced by row crops such as corn and alfalfa. Most of the land between CHAAP and Grand
Island is used for farming, predominately for hay and/or pasture, dryland crops, and irrigated corn, alfalfa,
and soybeans.
A large portion of CHAAP is inactive; however, much of the land and buildings are leased to various
individuals and local concerns. Approximately 10,774 acres (17 mi2) is leased out for general agricultural
use as follows: 82% cropland; 15% wildlife habitat and protection areas; and 3% grazing. The majority of
the cropland acreage is irrigated. Eighty-eight magazines and 25 other buildings are leased out as
general storage space. The Nitrate Area and the on-post rail sidings are leased for industrial use by
Cornhusker Rail Services, Inc. (CRS), a railcar refurbisher.
Operable Unit Two represents one component of a comprehensive environmental investigation and
cleanup presently being performed at CHAAP. The CHAAP has been divided into three operable units
based on land use and the extent of remedial action required to protect human health and the
environment. Operable Unit One (OU1) is comprised of the explosives-contaminated groundwater plume.
The Administration and Base Housing Areas (ABHA), Abandoned Burning Area (ABA), Drainage Ditches,
Magazine Areas, Miscellaneous Storage Areas, and Sewage Treatment Plants (STPs) comprise Operable
Unit Two (OU2). Operable Unit Three (OU3) includes the Pistol Range, Nitrate Area. Shop Area, the
Sanitary Landfill and the Burning Grounds. Operable Unit Four (OU4) is comprised of the unsaturated
zone of Load Lines 1-5 and the Gravel and Clay Pits. A Feasibility Study (FS) has been completed for
OU3 and OU4. An interim ROD has been completed on the OU1 groundwater and saturated zone.
As indicated above, the AOCs contained in OU2 are the ABHA, ABA, Drainage Ditches. Magazine Areas,
Miscellaneous Storage Areas, and STPs (see Exhibit on page 2-2). The ABHA is located in the
southwestern corner of CHAAP and encompasses approximately one square mile. Some of the land is
developed and is currently cultivated for growing various crops. The ABA is located in the northwest
corner of the installation. It is approximately 100 feet x 150 feet in size and is currently part of a cultivated
dry-crop field. At CHAAP, there are three main drainage ditches (i.e., Railroad Drainage Channel, the
West Drainage Channel, and the East Drainage Channel). These ditches run north to south through the
length of the facility. The proposed use for these drainage ditches is to receive effluent from the OU1
focused well extraction system. Two magazine areas are located at CHAAP and are designated as the
North Magazine Area (NMAG) and the South Magazine Area (SMAG). The NMAG and SMAG are
situated north and south of the Load Lines, respectively. The Miscellaneous Storage Areas consist of two
buildings at the CHAAP facility. Pesticides and fertilizers have been stored and mixed in Building I-4 and
in Building F-3, which is located just north of the SMAG Area. Two inactive STPs referred to as the
Northwest STP and the Southeast STP are located at CHAAP. The Northwest STP is located just north of
Load Line 4 and the Southeast STP is located east of the ABHA. Both sites are currently abandoned and
covered with native vegetation but retain the man-made depressions and structures that were used while
the plants were in operation.
2.2 HISTORY AND ENFORCEMENT ACTIVITIES
2.2.1 Site History
The CHAAP was constructed and fully operational in 1942. The CHAAP was a U.S. government-owned,
contractor-operated (GOCO) facility, which produced artillery shells, mines, bombs, and rockets for World
War II, Korean conflict, and Vietnam conflicts. The plant was operated intermittently for 30 years; the
most recent operations ending in 1973.
DAAA15-91-D-0014 2-1 Record of Decision
TEPS 14-6 Operable Unit Two
April 1998 Final Document
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DAAAlS-91-O-OOK
TEPS 14-6
April 1998
2-2
Record of Decision
Operable Unit T.\:
Final Docurr.-rii
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The plant was operated from 1942 through 1945 by Quaker Oats Ordnance Corporation, a subsidiary of
the Quaker Oats Company that produced bombs, shells, boosters, and supplementary charges. The plant
was on standby status for munitions production from 1945 through 1950. During the standby period,
many of the buildings were also used for grain storage.
The plant was reactivated in 1950 to produce artillery shells and rockets to support the Korean conflict.
These operations were directed by Mason & Hanger-Silas Mason Company (Mason & Hanger) until 1957
when the plant was again placed on standby status (USATHAMA, 1980). In 1963, a total of 809 acres
from three parcels of land situated in the northeast, northwest, and southeast corners of the facility were
sold to the State of Nebraska for use as wildlife management areas.
The plant was reactivated from 1965 through 1973 for the production of bombs, projectiles, and
microgravel mini-mines used in the Vietnam conflict. Mason & Hanger was retained as the operator
during this period of operation (USATHAMA, 1980). In 1973, operations ceased, the plant was again
placed on standby and has not been reactivated to date. Thirty acres of the sandpit area were given to
the State of Nebraska in 1977 for use by the State Game Commission. Activities at CHAAP currently are
limited to maintenance operations, leasing of property for agriculture, leasing of buildings for storage and
industrial operations (i.e., CRS) and wildlife management.
2.2.2 Histories of Areas of Concern Designated as OU2
Administration and Base Housing Areas: Past site activities at the ABHA have not been well
documented. Records indicate that other than administration and housing facilities, there was a hospital,
cafeteria, and trap shooting facility. Adjacent to the administration area is a small fenced area used by the
U.S. Air Force as a satellite tracking station.
Abandoned Burn Area: Available documentation on the ABA suggests that this area was only used for a
short time and that only small-scale disposal or burning operations may have been conducted.
Unexploded ordnance (UXO) screening of the area found minimal evidence of past burning activities. The
area covering the ABA is currently leased for cultivation.
Drainage Ditches: The Railroad Drainage Channel was constructed in 1942, during initial construction of
the CHAAP facility. The West and East Drainage Channels were completed in 1973. A review of
engineering drawings indicates that the Railroad Drainage Channel was designed to receive runoff from
the Nitrate Area, Shop Area, and Load Line 1. The West Channel received runoff from Load Line 5, a
portion of Load Line 4, the Sanitary Landfill, and the eastern half of the Burning Grounds. The East
Channel received runoff from Load Lines 2 and 3, and the Magazine Areas. The proposed use for the
Drainage Ditches is to receive treated effluent from the OU1 groundwater extraction system.
Magazine Areas: The Magazine Areas served as the primary storage facilities for raw materials and
finished ordnance during the three production periods at CHAAP. Raw materials were received at SMAG
Building M-11 on rail cars and then transferred to individual magazines prior to use at the LAP facilities.
Finished ordnance was transported on rail cars from the LAP facilities to NMAG Building M-4 and then
transferred to individual magazines. After munitions production ceased in 1973, all of the magazines were
steam cleaned to remove any explosives residue. Many of the magazines are currently leased to farmers
for use as storage areas.
Miscellaneous Storage Areas: The Miscellaneous Storage Areas consist of Building I-4 and Building F-
3. Building F-3 was used to store pesticide spray containers. A drainage ditch is located approximately 20
It north and east of the building. Building I-4 is part of a group of buildings known as the Inert Storage
Area.
Sewage Treatment Plants: The Northwest STP was constructed in 1944 to serve Load Lines 4 and 5
during periods of production. Use of the Northwest STP ended in 1973 when production ceased. The
Southwest STP was constructed in 1942 as part of the original facility. It served the Administration Area,
Staff Housing Area, and Fire and Guard Headquarters from 1942 to 1974. This system was replaced in
1974 by a circular, bentonite-lined, stabilization lagoon located adjacent to the former leaching lagoon.
The new lagoon was never used.
DAAA15-91-D-0014 2-3 Record ot Decision
TEPS 14-6 Operable Unit Two
April 1998 Final Document
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2.2.3 Enforcement Activities
A Federal Facility Agreement (FFA) was signed between the U.S. Army, USEPA and the NDEQ (effective
September 4,1990) to set terms lor the RI/FS effort. The FFA provided the terms, listed documents to be
generated, and established target dates for delivery of reports. This ROD is being conducted in
accordance with the terms outlined in the FFA.
Prior to the FFA, numerous environmental studies had been conducted at CHAAP and in the surrounding
area to assess and delineate contamination. As part of the U.S. Army's Installation Restoration Program,
USATHAMA conducted an Installation Assessment of CHAAP in 1980. Following the Installation
Assessment, USATHAMA conducted a Production Records Review to determine past disposal activities
and sites, and to quantify the materials disposed of at each location.
From 1989 through 1991, USATHAMA conducted an Excessing Assessment (EA) to determine the
existence of or potential for environmental contamination and to assess human health and environmental
risks associated with excessing the installation. From 1982 through 1986, various investigations were
performed on the facility to determine the contamination present at the various AOCs. The information
gathered in these studies was summarized in a Site Characterization Document (SCO) in 1993 by
USATHAMA. Following this, a Public Health Evaluation was performed by Life Systems, Inc. to determine
the effects of the contamination on the exposed and potentially exposed human population and to
evaluate the potential public health impacts associated with the proposed remedial alternatives for the
site.
In accordance with the FFA, an Interim ROD was approved for OU1 groundwater in 1994. In 1996, a
Remedial Investigation (Rl) was completed for all of CHAAP. An addendum to the Rl was prepared for
OU2. Based on the decision that the future land use of AOCs in OU2 would be industrial, the addendum
presented evidence that that for AOCs designated as OU2 (1) do not contain contamination or (2) contain
contaminants, but at concentrations that are below calculated risk-based cleanup levels for soil and
Maximum Contaminant Levels (MCLs) for groundwater. Based on the evaluation of the OU2 Rl
Addendum, a Proposed Plan for no further action/no response action was prepared to solicit comments
from stakeholders and the public. No comments were received from stakeholders or the public on the
Proposed Plan for no further action/no response action for areas of concern designated as OU2. It should
be noted that if the land use or exposure assumptions change for the OU2 AOCs, the Army will reevaluate
the decision to take no action. Furthermore, five-year reviews will be conducted to ensure that the
decision of no further action/no response action is protective of human health and the environment.
The following documents provide details of the site investigations and assessments of cleanup action for
Operable Unit Two.
USAEC, 1996. Cornhusker Army Ammunition Plant Remedial Investigation/Feasibility Study
Operable Unit Two Remedial Investigation Addendum, Final Document. Prepared by USAEC.
USAEC, 1996. Cornhusker Army Ammunition Plant Remedial Investigation, Final Document.
Prepared by USAEC.
USATHAMA, 1986. Installation Restoration Program, Cornhusker Army Ammunition Plant,
Site Characterization Document, Report AMXTH-IR-86086. Prepared by U.S. Army Toxic
and Hazardous Materials Agency, Aberdeen Proving Ground, Maryland.
USATHAMA, 1980a. Installation Assessment of Cornhusker Army Ammunition Plant, Report
155. March 1980.
2.3 HIGHLIGHTS OF COMMUNITY PARTICIPATION
The Proposed Plan for Operable Unit Two was released to the public in March 1997 at the information
repositories listed below:
DAAA15-91-D-0014 2-4 Record of Decision
TEPS 14-6 Operable Unit Two
April 1998 Final Document
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CHAAP
102 North 60th Street
Grand Island, NE 68802
Grand Island Public Library
211 North Washington Street
Grand Island. NE 68802
(308)381-5333
The notice of availability of these documents was published on March 3, 1997 in the Grand Island
Independent. A public comment period was held from March 3, 1997 through April 2, 1997. A public
meeting was held at the community room of Grand Island City Hall on March 11, 1997 to inform the public
about the preferred remedial alternative for OU2 and to seek public comments. At this meeting,
representatives from the U.S. Army, USEPA, and NDEQ were present to answer questions about the site
and remedial alternatives under consideration. No comments were received by the Army, NDEQ. or
USEPA on the No Further Action/No Response Action Proposed Plan for OU2 at CHAAP.
2.4 SUMMARY OF SITE RISKS
2.4.1 Human Health Risks
A human health risk assessment (HHRA) was performed as part of the 1996 Rl (refer to Section 6.0 of the
1996 Rl) for CHAAP. However, a streamlined approach was used to determine site risks. In cooperation
with the Center for Health Promotion and Preventative Medicine (CHPPM), the EPA, and the NDEQ, the
decision was made to perform the HHRA for the three worst contaminated sites at CHAAP (i.e.. Pistol
Range, Load Line 1, and the Burning Grounds). The results indicate that the risks from carcinogenic
chemicals of potential concern (COPCs), associated with exposure to soils were within the target risk
range for health protectiveness at Superfund sites of 1x10'4 to 1x10'6. For noncarcinogenic COPCs,
hazard indices (His) associated with exposures to surface soil were not above one (with one exception for
hypothetical future child residents at the Burning Grounds). Hazard indices associated with exposures to
subsurface soil were all below one. For groundwater, only the explosives plume was associated with an
unacceptable risk. The explosives plume is addressed in the OU1 interim ROD.
For the other areas at CHAAP (e.g., OU2), COPCs were identified. Because the HHRA could not directly
be applied to OU2, the Army calculated risk-based cleanup levels for those site -specific COPCs based on
future land use (i.e., industrial). For groundwater, COPCs were compared to MCLs. Comparison of site
characterization data to those risk-based cleanup criteria was used to determine whether or not a remedial
alternatives analysis was required. The HHRA is discussed below in greater detail.
The first component of the HHRA was the identification of COPCs1 for each AOC. COPCs were selected
based on an evaluation of data, a comparison of site and background concentrations for inorganic
chemicals, and a concentration toxicity screening evaluation for noncarcinogenic chemicals. COPCs are
presented in Tables 1,2 and 3 for surface soil, subsurface soil, and groundwater, respectively.
1 COPCs in surface and subsurface soil were selected on an AOC-specific basis (thus COPCs were determined specifically for
OU2), whereas groundwater COPCs were selected based on facility-wide contamination. It should be noted that because
groundwater COPCs were not identified on an AOC-specific basis (they were identified on a facility-wide basis), groundwater
COPCs were not necessarily associated with OU2.
DAAA15-91-D-0014 2-5 Record of Decision
TEPS 14-6 Operable Unit Two
April 1998 Final Document
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TABLE 1: CHEMICALS OF POTENTIAL CONCERN IN SURFACE SOIL (0-2 ft bgs) FOR HUMAN RECEPTORS AT OU21 |
Abandoned Burning
Area
Cadmium
Magazine Areas
2.4,6-TNT
Silver
Sewage Treatment Plants
RDX
Benzo(a)anthracene
Benzo(a)pyrene
Benzo(b)(luoranthene
Benzo(k)fluoranthene
Chrysene
Dibenz(a,h)anthracene
lndeno(l,2,3-c,d)pyrene
Arsenic
Cadmium
Chromium
Copper
Lead
Mercury
Silver
Miscellaneous Storage
Areas
Benzo(a)pyrene
Benzo(b)fluoranthene
Benzo(k)fluoranthene
alpha-Chlordane
gamma-Chlordane
ODD
DDE
DDT
Lead
Mercury
Major Drainage
Ditches
DDT
Aluminum
Cadmium
Chromium
Copper
Iron
Lead
Mercury
Silver
Vanadium
No COPCs were selected in surface soil at the Administration and Base Housing Areas
TABLE 2: CHEMICALS OF POTENTIAL CONCERN IN SUBSURFACE SOIL (>2 ft bgs) FOR HUMAN RECEPTORS AT
OU21
Abandoned Burnino Area
Aluminum
Barium
Chromium
Copper
Iron
Manganese
Vanadium
Magazine Areas
Chromium
Sewage Treatment Plants
Aluminum
Barium
Chromium
Copper
Iron
Manganese
Silver
Vanadium
Miscellaneous Storaoe Areas
2,4-D
' - No COPCs were selected in subsurface soil at the Administration and Base Housing Areas or Major Drainage Ditches
TABLE 3: CHEMICALS OF POTENTIAL CONCERN IN
GROUNDWATER AT CHAAP
3,5-Dinitroaniline
2-Amino-4,6-dinitrotoluene
4-Amino-2,6-dinitrololuene
2,4-Dinitrotoluene
2,6-Dinitrotoluene
RDX
1,3,5-Trinitrobenzene
2,4.6-TriniUotoluene
Acrylonitrile
Benzene
Benzo(a)anthracene
Chrysene
1,2-Dichloroethane
bis(2-Ethylhexyl)phthalate
lndeno(1,2.3-c.d)pyrene
Methylene chloride
1,1,2-Trichloroethane
Trichloroethylene
1,2,3-Trichloropropane
1,1,2-Tri1luoro-1,2-dichloroethane
Antimony
Beryllium
Excess lifetime cancer risks were calculated in the Risk Characterization. These risks are probabilities
that are generally expressed in scientific notation (e.g., 1x10'6). An excess lifetime cancer risk of Ix10"5
indicates that an individual has a one in one million chance of developing cancer over a 70-year lifetime as
a result of site-related exposure to a carcinogen over a 70-year lifetime under the specific exposure
conditions assumed in the HHRA. Site risks are generally compared to the target risk range for health
protectiveness at Superfund sites of 1x10"* to 1x10 .
DAAA15-91-D-0014
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April 1998
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Record of Decision
Operable Unit Two
Final Document
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The potential for adverse noncarcinogenic effects to occur due to exposures to contaminants is expressed
as the hazard index (HI). The HI provides a useful reference point for gauging the potential for
noncarcinogenic effects to occur, and His above 1.0 indicate the potential for adverse effects, whereas
His below 1.0 indicate that noncarcinogenic adverse effects would not likely occur.
Quantitative risk calculations were performed for the three worst contaminated AOCs at CHAAP (i.e..
Load Line 1, Burning Grounds, and the Pistol Range). Excess lifetime cancer risks associated with
exposures to chemicals in surface soil at Load Line 1, the Burning Grounds, and the Pistol Range ranged
from lower than to the mid-point of the 1x10~6 to 1x10"4 target risk range for both current trespassers and
potential future agricultural residents; His associated with exposures to surface soil were not above one
(with one exception for hypothetical future child residents at the Burning Grounds). Because
concentrations at OU2 were generally lower than concentrations at these three AOCs, risks associated
with surface soil exposures at OU2 would similarly be lower than those calculated for the three AOCs
quantitatively evaluated in the HHRA.
Risks associated with exposures to subsurface soil were determined only for Load Line 1 and the Pistol
Range. Excess lifetime cancer risks associated with exposures to chemicals in subsurface soil at these
AOCs were lower than or equal to 1x10"6 for excavation workers; His associated with exposures to
subsurface soil were lower than one, indicating adverse noncarcinogenic effects would not likely occur.
Because concentrations at OU2 were generally lower than concentrations at these two AOCs, risks
associated with subsurface soil exposures at OU2 would similarly be lower than those calculated for the
AOCs quantitatively evaluated in the HHRA.
The results of the HHRA indicated that for groundwater, only the explosives plume (addressed in the OU1
interim ROD) was associated with an excess lifetime cancer risk above the 1x10~4 risk level for future
agricultural residents drinking and dermally absorbing COPCs in groundwater. Noncarcinogenic adverse
effects associated with explosives in groundwater could be possible for future agricultural residents if
groundwater ingestion and dermal exposure to explosives were to occur under the conditions assumed in
the HHRA.
With consent from the CHPPM, NDEQ, and USEPA, the Army calculated risk-based cleanup goals for
COPCs in soil based on exposure to industrial workers, since the site is likely to remain in its industrial
status in the future. Concentrations of COPCs that were selected in the HHRA for OU2 were compared to
calculated risk-based industrial cleanup levels for soil to determine whether remediation of soil would be
necessary. For groundwater, the Army compared concentrations of COPCs with Federal Maximum
Contaminant Levels (MCLs), Nebraska Groundwater Standards, or calculated risk-based industrial
drinking water cleanup levels if MCLs or State standards were not available. Soil and groundwater
cleanup levels are discussed and presented in Section 2.5.
2.4.2 Ecological Risks
An ecological risk assessment (ERA) was performed as part of the 1996 Rl. The purpose of this ERA
was to identify those chemicals present in soil, surface water, and sediment at CHAAP that had the
potential to harm ecological receptors (i.e., plants and animals). However, only surface soil chemicals
were evaluated in OU2 because surface water and sediment are not present. The receptor species
and/or groups that were selected for quantitative evaluation in OU2 include: terrestrial plants, earthworms,
deer mouse, deer, and American robin.
Results of the ERA indicate that concentrations in many of the OU2 surface soil areas were above Toxicity
Reference Values (TRVs) (i.e., guidelines that represent levels that are protective of terrestrial plants,
earthworms, deer mouse, and American robin). Therefore, there is potential for adverse effects to
individual plants and earthworms. However, risks associated with exposures to chemicals in surface soil
at OU2 should be considered an overestimation because the areas that specifically comprise OU2 are
generally considered to have poor quality habitat due to past and present uses (i.e., industrial operations)
and/or abundance of manmade structures. As a result of the poor quality habitat, extensive use of these
areas by terrestrial receptors is not expected. This is especially true for the Magazine Areas and
Miscellaneous Storage Areas.
In addition, terrestrial receptors would more likely occur in areas adjacent to sites evaluated at OU2, such
as cropland or shelterbelt areas, where the habitat quality is better, food is more plentiful, and chemical
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contamination may be minimal or nonexistent. Given the habitat limitations of the areas in OU2, the actual
risks to populations of terrestrial receptors are considered to be less than those calculated. As a result,
the concentrations of COPCs are not risk drivers. Therefore, cleanup levels for OU2 based upon
protection of ecological receptors were not calculated.
2.5
CLEANUP LEVELS
Cleanup levels for soil were calculated for the COPCs identified in the HHRA (see Section 2.4). Soil
cleanup levels were calculated to be protective of workers in an industrial use scenario (see Appendix A).
Federal MCLs, Nebraska Groundwater Standards, and calculated industrial drinking water cleanup levels
were used as cleanup goals for groundwater. Where an MCL was not available, a cleanup level from one
of the other sources was used. The basis for no further action/no response action for groundwater
associated with OU2 is that concentrations of COPCs in samples collected from 0112 AOC monitoring
wells were below Federal MCLs, Nebraska Groundwater Standards, and calculated risk-based industrial
cleanup levels. Tables 4 and 5 present the cleanup levels for COPCs detected in OU2 soil and CHAAP
groundwater, respectively.
TABLE 4: CLEANUP LEVELS FOR SOIL COPCs (ug/g) AT CHAAP
Chemical
Aluminum
Arsenic
Barium
Benzofalanthracene
Benzo(a)pyrene
Benzo(b)fluoranthene
Benzo(k)!luoranthene
Cadmium
alpha-Chlordane
gamma-Chlordane
Chromium
Chrysene
Copper
2,4-D
ODD
ODE
DDT
Dibenz(a.h)anthracene
lndeno(l,2.3-c.d)oyrene
Iron
Lead
Manganese
Mercury
Silver
RDX
2.4.6-TNT
Vanadium
USEPA Region III Residential RBCs
(»9>9)
78.000
0.43
5.500
O.B8
0.088
0.88
8.8
39
0.49
0.49
390
88
3,100
780
2.7
1.9
1.9
0.088
0.88
23.000
--
1.800
23
390
5.8
21
^ 1^ ^^^ » ^ .« II. I . 1 . !
550
Calculated Industrial Risk-Based
Levels (n9/g)*
1.000.000
3.82
143.080
78.4
7.8
7.8
784
2.044
4.4
4.4
10.220
784
75.628
..
17
17
17
7.8
7.8
613.200
1.620
49.056
613
10.220
520
191
.1 .III . ... 1 II i ^ ^ ^^ !
14.308
-- = Standard not developed lor this chemical because the USEPA Region III Residential RBC was not exceeded.
" - For carcinogens, concentrations are associated with a risk o( 1x10'D; (or noncarcinogens, concentrations are associated with a
hazard index of 1.0.
TABLE 5: CLEANUP LEVELS FOR GROUNDWATER COPCs (ng/L) AT CHAAP
Chemical
2-Amino-4,6-Dinitrotoluene
4-Amino-2,6-Dinitrotoluene
Antimony
Acrylonitrile
Benz[a]anthracene
Federal Maximum
Contaminant Levels (tig/L)
-
--
6
-
0.1
Calculated Industrial
Risk-Based Levels (ng/L)
6.1
6.1
--
0.53
--
Nebraska Groundwater
Standards (ng/L)
-
-
--
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TABLE 5: CLEANUP LEVELS FOR GROUNDWATER COPCs (M9/L) AT CHAAP
Chemical
Benzene
Beryllium
Chrysene
2.4-Dinitrotoluer.e
2,6-Oinitrotoluene
1 ,2-Dichloroeihane
Bis(2-Ethylhexyf) phthalale
HMX
Indeno (1 ,2,3-c.d)pyrene
Methylene chlonde
(dichloromethanel
Nitrobenzene
2-Nitrotoluene
3-Nitroioluene
4-Nitroioluene
RDX
1 ,3,5-Trinitrobenzene
2,4,6-Trinitrotoluene
1 , 1 .2-Trichloroethane
Trichloroethene
1 ,2.3-Trichloropropane
Tetryl
1 ,3-Dinitrobenzene
Federal Maximum
Contaminant Levels (jjg/L)
5
4
0.2
--
--
5
6
-
0.4
5
--
-
-
-
-
--
5
5
--
-
--
Calculated Industrial
Risk-Based Levels (ug/L)
-
-
--
0.42
0.42
-
5.110
--
38
51
1,022
1.022
1,022
2,6
5.1
9.5
--
»*
0.041
1,022
10
Nebraska Groundwater
Standards (pg/L)
5
--
--
--
5
-
--
--
-
--
--
--
--
-
-
-
-
5
--
--
--
-- = Standard not developed for this chemical.
2.6 SUMMARY AND FINDINGS OF SITE INVESTIGATION AT OU2
Based on the Rl results, OU2 has been determined to require no further remedial action. Provided below
is the sampling program and nature and extent of COPCs detected at each of the six AOCs designated as
OU2.
The Administration and Base Housing Areas (ABHA): The sampling program at the ABHA included
surface soil sampling for the 1991 EA. surface soil sampling for the 1993 SCO, and surface soil and
groundwater sampling for the 1996 Rl. No COPCs were selected in this area during the 1996 Rl.
The Abandoned Burning Area (ABA): The sampling program at the ABA included a geophysical survey
for the 1991 EA, and surface soil, subsurface soil, and groundwaler sampling for the 1996 Rl. No COPCs
were detected above calculated risk-based industrial cleanup levels and MCLs (for groundwater) during
the 1996 Rl field effort.
Drainage Ditches: The sampling program at the Drainage Ditches included surface soil sampling for the
1993 SCO and 1996 Rl. No further remedial action is recommended at this site because all COPCs
detected in the sampling effort for the 1996 Rl were below USEPA Region III Residential RBCs (chemical
concentrations corresponding to fixed levels of risk, (i.e., a hazard quotient of one or a lifetime cancer risk
of 1x10~6. whichever occurs at a lower concentration)] with the exception of iron. A soil sample collected
from the west drainage channel contained iron at a concentration far below the calculated risk-based
industrial cleanup level.
Magazine Areas: The sampling program at the Magazine Areas (NMAG and SMAG) included surface
soil sampling for the 1991 EA, annual surface soil sampling for the 1993 SCO, and surface soil sampling
and subsurface soil sampling (NMAG only) for the 1996 Rl. Explosives compound 246-TNT (29 ug/g) was
detected in a sample collected during the 1993 SCO effort from the Building M-4 loading area at the North
Magazine Area. The concentration slightly exceeds the USEPA Region III Residential RBC of 21 ug/g but
DAAA15-91-D-0014
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is below the calculated risk-based cleanup level of 191 ng/g. The area was resampled in 1995 and 246-
TNT was not detected. At the South Magazine Area, no COPCs were detected above the USEPA Region
III Residential RBCs. Therefore, no further remedial action is recommended at this location.
Miscellaneous Storage Areas: The sampling program at the Miscellaneous Storage Areas included
limited surface soil sampling for the 1991 EA, surface soil sampling and subsurface soil sampling for the
1993 SCO, and interior building wipe sampling and groundwater sampling for the 1996 Rl. No COPCs
exceeded calculated risk-based industrial cleanup levels in surface soil samples and no COPCs,
pesticides, or herbicides were detected in groundwater samples from downgradient wells in any of the
sampling events.
Sewage Treatment Plants (STPs): The sampling program at the STPs included: surface and
subsurface soil sampling for the 1993 SCO; and surface soil, subsurface soil, and groundwater sampling
for the 1996 Rl. Arsenic was detected in surface soil samples during the 1996 sampling effort for the Rl
above the calculated risk-based industrial cleanup level that is associated with a 1xO'6 risk (3.82 ug/g).
However, the maximum concentration of arsenic (11.7 ug/g) detected was below the upper range of
regional background (12 ug/g) and the risk-based cleanup level that is associated with a 1x10'5 risk (38.2
^g/g). Furthermore, no other COPCs exceeded the calculated risk-based industrial cleanup level. No
COPCs were detected in groundwater samples above their respective MCLs.
2.7 CONCLUSIONS
The Sewage Treatment Plants were the only areas of concern where a COPC (arsenic in soil) exceeded
the calculated risk-based industrial cleanup level that is associated with a risk of 1X10'6. It should be
noted that the concentrations of arsenic detected were below the upper range of regional background and
the risk-based cleanup level that is associated with a 1x10"5 risk (38.2 jig/g). Based on the minimal levels
of contamination present in soil and the lack of contamination in groundwater, the Army proposed No
Further Action/No Response Action as the preferred alternative for AOCs designated as OU2.
2.8 DESCRIPTION OF THE "NO FURTHER ACTION/NO RESPONSE ACTION"
The preferred alternative to protect human health, welfare, and the environment at the OU2 AOCs is not a
remedial action. No significant risks are associated with exposures to contamination at OU2. Therefore,
the no further action/no response action is adequate to protect human health and the environment and
meets the requirements for both short-term and long-term effectiveness and permanence set forth in the
NCP. The no further action/no response action does not lessen the toxicity, movement, or amounts of
contamination. However, the concentrations of contaminants found in the surface soil are not sufficiently
toxic, mobile, or concentrated to warrant a remedial action. A five-year review will be conducted to ensure
that the decision of no further action/no response action is protective of human health and the
environment.
2.9 EXPLANATION OF SIGNIFICANT CHANGES
The Proposed Plan presents the selected remedy as the preferred alternative. No significant changes
have been made.
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3.0 RESPONSIVENESS SUMMARY
The final component of the ROD is the Responsiveness Summary. The purpose of the Responsiveness
Summary is to provide a summary of the public's comments, concerns, and questions about the AOCs at
OU2 and the Army's responses to these concerns. The public comment period extended from March 3,
1997 to April 2, 1997. During the public comment period, no written comments, concerns, and questions
were received by CHAAP, USEPA, and NDEQ.
CHAAP held a public meeting on March 11, 1997 to formerly present the Proposed Plan and to answer
questions and receive comments. The transcript of this meeting is part of the administrative record for the
site. No comments were received by the Army, NDEQ, or the USEPA on the Proposed Plan for OU2 at
CHAAP.
3.1 OVERVIEW
At the time of the public comment period, the Army had endorsed a preferred alternative of no further
action/no response action at OU2. The USEPA and the NDEQ support the Army's plan.
3.2 SUMMARY OF COMMENTS RECEIVED DURING THE PUBLIC COMMENT PERIOD AND
AGENCY RESPONSES
No comments were received by the Army, NDEQ, or the USEPA on the Proposed Plan for OU2 at
CHAAP.
DAAA15-91-0-0014 3-1 Record ol Decision
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4.0 REFERENCES |
U.S. Army Environmental Center (USAEC). November, 1996. Cornhusker Army Ammunition Plant
Remedial Investigation/Feasibility Study Operable Unit Two Remedial Investigation Addendum,
Final Document.
U.S. Army Environmental Center (USAEC). November, 1996. Cornhusker Army Ammunition Plant
Remedial Investigation Report, Final Document.
U.S. Army Toxic and Hazardous Material Agency (USATHAMA), 1986. Installation Restoration Program,
Cornhusker Army Ammunition Plant, Site Characterization Document, Report AMXTH-IR-86086.
U.S. Army Toxic and Hazardous Material Agency (USATHAMA). 1980. Installation Assessment of
Cornhusker Army Ammunition Plant, Report 155. March 1980.
U.S. Environmental Protection Agency. 1991. Risk Assessment Guidance for Superfund. Volume I:
Human Health Evaluation Manual Supplemental Guidance. Standard Default Exposure Factors.
Interim Final. Washington, D.C. OSWER Directive 9285.6-03. March 25, 1991.
DAAA15-91-D-0014 4-1 Record of Decision
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APPENDIX A : METHODOLOGY FOR CALCULATING COPC CLEANUP LEVELS
Risk-based cleanup levels were calculated for COPCs selected for evaluation in the CHAAP HHRA. As
noted earlier, COPCs were selected based on a concentration-toxicity screening for non-carcinogenic
chemicals and a comparison to background concentrations for inorganic chemicals. In accordance with
USEPA Region VII and NDEQ, cleanup levels were based on exposures by industrial workers at the site.
The following sections present the equations that were used to calculate risk-based cleanup levels for
surface and subsurface soil and for groundwater. Equations for calculating risk-based cleanup levels are
presented separately for chemicals exhibiting carcinogenic and non-carcinogenic effects.
Surface and Subsurface Soil Cleanup Levels
The equation used to calculate worker cleanup levels for chemicals exhibiting carcinogenic effects is as
follows:
77? * BW* AT< * DAYS
*
IR * EF * ED * CF CSF.,
where:
Cs = chemical concentration in soil (mg/kg),
TR = target excess individual lifetime cancer risk (1x10"6),
BW = body weight (70 kg),
ATC = averaging time for carcinogenic effects (7O years),
DAYS = conversion factor (365 days/year),
IR = soil ingestion rate (50 mg/day),
EF = exposure frequency (250 days/year),
ED = exposure duration (25 years),
CF = conversion factor (kg/106 mg), and
SF0 = oral cancer slope factor ([mg/kg-day]"1).
The equation used to calculate worker cleanup levels for chemicals exhibiting non-carcinogenic effects is:
1 RW * AT * DAYS
c = JL^=£!L^Lif f±li± * RfD
IR* EF* ED* CF
where:
Cs = chemical concentration in soil (mg/kg),
THQ = target hazard quotient (1),
BW = body weight (70 kg),
ATnc = averaging time for carcinogenic effects (25 years),
DAYS = conversion factor (365 days/year),
IR = soil ingestion rate (50 mg/day),
EF = exposure frequency (250 days/year),
ED = exposure duration (25 years),
CF = conversion factor (kg/106 mg), and
RfD0 = oral reference dose (mg/kg-day).
The target risk and hazard quotient were assumed to be a level of 1x106 for carcinogens and a level of
1.0 for non-carcinogens. The toxicity criteria (i.e., cancer slope factors and non-cancer reference doses)
were obtained from IRIS or HEAST. Exposure parameters for workers that were obtained from USEPA
(USEPA, 1991) included the body weight, averaging time, soil ingestion rate, exposure frequency, and
exposure duration.
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Groundwater Cleanup Levels
If COPCs did not have an applicable MCL, risk-based groundwater cleanup levels were calculated. The
equation used to calculate worker groundwater cleanup levels for chemicals exhibiting carcinogenic
effects is as follows:
_ TR * BW * ATc * DAYS * CF ^ 1
Csw ~ IR * EF * ED ~CSR,
where:
Cgw = chemical concentration in groundwater (ng/L),
TR = target excess individual lifetime cancer risk (1 x106),
BW = body weight (70 kg).
ATC = averaging time for carcinogenic effects (70 years),
DAYS = conversion factor (365 days/year),
CF = conversion f actor (103ng/mg),
IR = groundwater ingestion rate (1 L/day).
EF = exposure frequency (250 days/year),
ED = exposure duration (25 years), and
SF0 = oral cancer slope factor ([mg/kg-day]"1).
The equation used to calculate worker groundwater cleanup levels for chemicals exhibiting non-
carcinogenic effects is:
= BW * xr« * DAYS * CF * RfD
fw IR* EF* ED
where:
Cg,, = chemical concentration in groundwater (ug/L),
THQ = target hazard quotient (1),
BW = body weight (70 kg),
ATnc = averaging time for carcinogenic effects (25 years),
DAYS = conversion factor (365 days/year),
CF = . conversion f actor (103 ng/mg),
IR = groundwater ingestion rate (1 L/day),
EF = exposure frequency (250 days/year),
ED = exposure duration (25 years), and
RfD0 = oral reference dose (mg/kg-day).
The target risk and hazard quotient were assumed to be a level of 1x10'6 for carcinogens and a level of
1.0 for non-carcinogens. The toxicity criteria (i.e., cancer slope factors and non-cancer reference doses)
were obtained from IRIS or HEAST. Exposure parameters for workers that were obtained from USEPA
(USEPA, 1991) included the body weight, averaging time, water ingestion rate, exposure frequency, and
exposure duration.
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April 1998 Final Document
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