PB94-964316
EPA/ROD/R07-94/081
April 1995
EPA Superfund
Record of Decision:
Cornhusker Army Ammunition Plant
(O.U. 1), Hall County, NE
9/29/1994
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INTERIM ACTION RECORD OF DECISION DECLARATION
SITE NAME AND LOCATION
Operable Unit 1 - Groundwater
Old Potash Highway
Cornhusker Army Ammunition Plant
Grand Island, Hall County, Nebraska 68803
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected interim remedial action for the groundwater operable unit
at the Cornhusker Army Ammunition Plant (CAAP). This action was chosen in accordance with the
Comprehensive Environmental Response, Compensation and Liability Act of 1980 (CERCLA), as
amended by the Superfund Amendments and Reauthorization Act of 1986 (SARA), and. to the extent
practicable, the National Oil and Hazardous Substances Pollution Contingency Plan (NCP). This decision
is based on the administrative record for the site and additional information supporting the selected
interim remedial action for Operable Unit 1 - Groundwater. is contained in the administrative record for
this site.
The letter from the Nebraska Department of Environmental Quality (NDEQ) regarding concurrence of
the selected remedy as an interim action for this site is attached.
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from this site, if not addressed by implementing
the response action selected in this interim action Record of Decision (ROD), may present a current or
potential threat to public health, welfare, or the environment.
DESCRIPTION OF THE SELECTED INTERIM REMEDY
Operable Unit One encompasses the explosives groundwater piume(s), both on-post and off-post.
Explosives of concern in the contaminant plume include RDX. TNT. HMX. and their decomposition
products.
The objective of this interim action is to contain the plume and prevent further migration of contaminants.
and does not encompass full restoration of the plume of contaminated groundwater. The recommended
alternatives provide an approach to containing and removing contaminant mass from the groundwater
plume. This approach will control further migration of the plume and reduce the levels of the
contamination in groundwater. The overall interim action for OU 1 addresses two areas of groundwater
contamination, the on-post source areas and the off-post or distal end. The substances detected in the
source area groundwater are primarily explosives, metals, and nitrates, however the objective of this
action is to focus on the containment of the explosives contaminant plume. The treatment for metals and
nitrates will be applied as necessary to meet the surface water discharge criteria. The groundwater at the
distal end of the plume in the off-post area contains primarily RDX at low concentrations.
The interim groundwater remedies were developed to protect public health, welfare and the environment
by controlling the migration and reducing the volume and mass of contaminants present in the
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groundwater beneath and downgradient of the facility. Operable unit interim actions will be consistent
with all planned future remedial activities. The final remedial action for groundwater will augment and
expand upon this interim remedial action to provide an effective overall groundwater remediation project.
The major components of the selected interim remedies include:
Source Area: Groundwater will be extracted from multiple extraction wells at a total estimated
extraction rate of 1000 gallons per minute (gpm). The extraction of the contaminated
groundwater will contain the source contamination and prevent further migration. The extracted
groundwater will be treated with granular activated carbon for explosives, granular media
filtration for suspended solids, chemical precipitation (as needed to meet NPDES limits), and
wetlands for nitrates (as needed to meet NPDES limits). Treated water will be routed via
pipeline through the easement of the proposed Wood River Diversion Channel to the Platte River.
The system will be designed to actively control migration of more highly contaminated
groundwater in the source area and to rapidly remove contaminant mass from the aquifer.
Contaminant mass removal will be monitored by using new or existing monitoring wells. A
schedule of sampling and analysis of the groundwater will be initiated to observe the effectiveness
and progress of the remediation system. .
Distal End: Groundwater will be extracted at a rate sufficient to prevent further migration of
the explosives plume at the distal end. Groundwater will be extracted from multiple wells at an
estimated total rate of 3000 gpm at the end of the contaminant plume and 1000 gpm at the tongue
of the 20 ppb isopleth (intermediate location). The distal end treatment system uses some of the
same technology as the Source Area, but due to differences in the groundwater quality does not
require as extensive treatment. This system will prevent further migration of the end of the
contaminant plume and the intermediate tongue. The pumped groundwater will be treated with
granular activated carbon for the explosives. The treated water will be routed via pipeline
through the easement of the proposed Wood River Diversion Channel to the Platte River.
Contaminant mass removal will be monitored by using new or existing monitoring wells. A
schedule of sampling and analysis of the groundwater will be initiated to observe the effectiveness
and progress of the remediation svstem.
DECLARATION
This interim action is protective of public health, welfare and the environment. The action complies with
action-specific and chemical-specific federal and state applicable or relevant and appropriate requirements.
are cost effective, and address public concerns. Although the interim action is not intended to fully
address the statutory mandate for permanence and treatment to the maximum extent practicable, this
interim action utilizes treatment and thus is in furtherance of that statutory mandate. This action does
not constitute a final remedy for the site, therefore the statutory preference for remedies that employ
treatment that reduces toxicity, mobility, or volume as a principal element (although partially addressed
by this remedy), will be more fully addressed by the final response action. Subsequent actions are
planned to fully address the principal threats posed by providing comprehensive remediation of Operable
Unit 1 - Groundwater.
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This interim remedy will result in hazardous substances remaining on site above the health-based levels,
therefore if the final remedy is not underway prior to the five year review, then the requirement of the
five year review is applicable to the interim action. Review of this interim remedy will be ongoing as
the Army continues to develop the final comprehensive remedial action for CAAP.
Date
Dennis Grams
Regional Administrator
US Environmental Protection Agency
Region VII
Date.
LTC Mtry G. Goodwin
Army Ammunition Plant
_. trbD. Walker
Deputy Assistant Secretary of the Army
(Environment Safely. *wi Occupational Health)
Atachnwnttr Pccisioo Sunniary
Rcsponstveneu Soniaiary - Attschracnt A
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DEC 05 '94 12=15 NEBRASKA DEQ 402*471-2909 . P.I
STATE OF NEBRASKA
DhmXfMliNT OF ENinRflNMFNSU. QUAtlTV
Suite 4iKI. Tha AMim
r/OOKTStreot
RO. Eat 98922
Phono (403 471-2186
Governor
Mr. Dennis Grama
.Regional Administrator
BPA Region VII
726 Minnesota Avenue
Kansas City/ Kansas 66101
Dear Mr. drama:
Upon consideration of the Decision Summary for Cornhusker Army Aonunition Plant
operable unit one - Grouaduater dated September 20, 1994, the Nebraska
Department of Environmental Quality (HDBQ) concurs with bhv Interim Action
Record of Decision remedy selection for the grouodwator at the Cornboeker Army
Ammunition Plant (CAAP) aita.
NOEQ believea this interim remedy will contain and remove grouodwatac
contaminated wir.h expioeivo compounds posing a threat to human health and tho
environment. This interim remedy, when implemented, will prevent the future
spread of contaminated ground water in the northwest area of Oraad Zalaad.
appreeia««a ch« njiportunity foe involvement in the'remedy saleetion
preceea and the Army and EPA'a consideration of NDEQ'a input throughout thin
investigation. MflKu conaidere the development of ehxs doetmont and tne
participation of the citizens of Grand Zaland aad aurroundirtg counties to
exemplify a high degree of producttva cooperation.
Ranaoipn wooa, P.E.
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TABLE OF CONTENTS
PAGE
1.0 SITE LOCATION AND DESCRIPTION
2.0 SITE HISTORY, OPERATIONS, PREVIOUS INVESTIGATIONS AND REMEDIAL
ACTIONS : i
2.1 SITE HISTORY 1
2.2 OPERATIONS 4
2.3 PREVIOUS INVESTIGATIONS 5
2.4 REMEDIAL ACTIONS . . 6
2.4.1 ALTERNATE WATER SUPPLY 6
2.4.2 INSTALLATION RESTORATION INCINERATION PROGRAM 7
3.0 HIGHLIGHTS OF COMMUNITY PARTICIPATION .-. .... 7
4.0 SCOPE AND ROLE OF OPERABLE UNIT - 9
5.0 SITE CHARACTERISTICS 9
5.1 GEOLOGY 9
5.2 HYDROGEOLOGY II
5.3 RDX GROUNDWATER PLUME 12
5.4 CONTAMINATION ASSESSMENT 12
6.0 SUMMARY OF SITE RISK 14
7.0 ALTERNATIVES EVALUATION 17
7.1 DESCRIPTION OF REMEDIAL ACTION ALTERNATIVES 17
7.2 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES 21
7.2.1 COMPARISON OF REMEDIAL ACTION ALTERNATIVES FOR THE SOURCE
AREA 24
7.2.2 COMPARISON OF REMEDIAL ACTION ALTERNATIVES FOR THE DISTAL
END 27
7.3 PROPOSED REMEDY 30
8.0 STATUTORY DETERMINATIONS 37
8.1 DOCUMENTATION OF SIGNIFICANT CHANGES 44
8.2 SUMMARY OF SELECTED REMEDY AFTER MODIFICATION 45
ATTACHMENT A RESPONSIVENESS SUMMARY
ATTACHMENT B GROUNDWATER CONTAINMENT STANDARDS
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LIST OF TABLES
PAGE
Table 6-1 Concentrations of Chemicals of Potential Concern for CAAP 15
Table 7.1-1 Components of Remedial Action Alternatives for Source Area 22
Table 7.1-2 Components of Remedial Action Alternatives for Distal End 23
Table 7.3-1 Summary Cost Estimate for Source Area, Alternative T-7A 35
Table 7.3-2 Summary Cost Estimate for Distal End, Alternative T-3A 36
Table 8-1A Chemical-Specific ARARs 38
Table 8-1B Chemical-Specific ARARs 39
Table 8-2 Location-Specific ARARs 40
Table 8-3 Action-Specific ARARs . . . . '. 41
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LIST OF FIGURES
PAGE
?
Figure 1-1 General Location Map
Figure 1-2 Facility Location Map 3
Figure 5-1 Geologic Cross Section of the RDX Plume Area 10
Figure 5-2 Water Table Contour/RDX Plume Map 13
Figure 7-2 Groundwater Extraction, Granular Activated Carbon (Spent Carbon Recycled).
Discharge to Surface Water) 32
Figure 7-3 Schematic Diagram of Groundwater Extraction, Chemical Precipitation.
Granular Media Filtration. Granular Activated Carbon (Spent Carbon
Recycled), Constructed Wetlands Treatment and Discharge to Surface Water . . 33
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1.0 SITE LOCATION AND DESCRIPTION
Cornhusker Army Ammunition Plant (CAAP) is located in south-central Nebraska 2 miles west of the
city of Grand Island and lies near the eastern margin of the Great Plains Physiographic Province. The
site lies approximately 7 miles north of the Platte River, within the flood plain. The terrain is nearly
level to slightly undulatory. The ground surface at CAAP and the surrounding vicinity slopes gently from
southwest to northeast with elevations ranging from 1,950 ft above sea level in the southwest to 1.850
ft in the northeast (Figure 1-1). The facility was constructed and fully operational in 1942 as a U.S.
government-owned, contractor-operated (GOCO) facility. The facility produced artillery shells, mines,
bombs, and rockets for World War II and the Korean and Vietnam Conflicts. CAAP comprises 11,936
acres consisting of five munitions production facilities (load lines), two munitions storage areas (magazine
areas), a pistol range, sanitary landfill, burning grounds, shop area, ammonium nitrate production area.
administration area, and railroad holding yard (Figure 1-2).
Activities at the site have resulted in contamination of groundwater with explosives compounds.
Groundwater is die primary drinking water source in Grand Island and the surrounding areas. The
explosives contaminant plume has migrated to the east-northeast approximately four miles beyond the
installation boundary, contaminating domestic wells in northwestern Grand Island. Between CAAP and
the Grand Island city limits, a distance of approximately two miles, the explosives contaminant plume
underlies stockyards and irrigated row crops. The sources of groundwater contamination were unlined
cesspools and leaching pits used to dispose of explosives contaminated wastewater from ordnance
production activities.
2.0 SITE HISTORY. OPERATIONS. PREVIOUS INVESTIGATIONS AND REMEDIAL ACTIONS
The following sections present a summary of the history of CAAP. describe the operations that occurred
at the site that resulted in contamination, and discusses previous investigations and remedial actions
conducted at CAAP.
2.1 SITE HISTORY
CAAP was operated from 1942 through 1945 by the Quaker Oats Ordnance Corporation, a subsidiary
of the Quaker Oats Company. CAAP was placed on standby status for munitions production from 1945
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Capital Heights
Subdivision
Grand Island
City Limits
-N-
WATKINS-JOHNSON ENVIRONMENTAL, INC.
Ground-Water Consulting. Environmental Engineering,
Remediation Services
GENERAL LOCATION MAP
Date: June 1994 Figure 1-1
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Burning
Grounds
f /Railroad
'f I Holding
'/( Yard
North
Magazine
Area
Sanitary /
Landfill
Pistol Range
Northwest
Sewage f
Treatment-
Plant
South
Magazine
Area
Nitrate
Area
Southeast
Sewage)
Treatment
Plant
LI
A
Administration
Area
WATKINS-JOHNSON ENVIRONMENTAL. INC.
Ground-Water Consulting, Environmental Engineering
Remediation Services
FACILITY LOCATION MAP
0 325 650
=5=
METERS
Figure 1 -2
Date: June 1994
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through 1950. From 1945 through 1948, the ammonium nitrate production area was used for the
production of fertilizer.
CAAP was reactivated in 1950 to produce munitions for the Korean conflict. Operations were directed
by Mason & Hanger-Silas Mason Company (Mason & Hanger) until 1957 when CAAP was again placed
on standby status. In 1963 a total of 809 acres from three parcels of land the northeast, northwest, and
southeast corners of the facility were sold to the State of Nebraska for use as wildlife management areas.
CAAP was reactivated from 1965 through 1973 to produce munitions for the Vietnam Conflict. Mason
& Hanger was retained as the operator during this period of operation. CAAP was placed on standby
status when ordnance production operations ceased in 1973. Standby status was terminated on January
30. 1989 when AMCCOM declared CAAP "Excess". The Excessing process was begun and is currently
in progress. Activities at CAAP are currently limited to maintenance operations, leasing of property for
agriculture, leasing of buildings for storage, limited manufacturing, and wildlife management.
CAAP was listed as a site on the National Priorities List (NPL) on July 22. 1987. As required under
CERCLA of 1980 and amended by the Superfund Amendments and Reauthorization Act (SARA) of 1986.
The U.S. Army initiated a Remedial Investigation/Feasibility Study (RI/FS). A Federal Facility
Agreement (FFA) was signed between the U.S. Army, USEPA, and the State of Nebraska (effective
September 4. 1990) to set terms for the RI/FS effort. The FFA provided the terms, listed documents to
he generated, and established target dates for the delivery of reports. A number of investigations and
studies to address environmental impacts of activities-at CAAP were conducted during the I980"s and are
continuing today. These are summarized in Section 2.3.
2.2 OPERATIONS
The principal explosive compounds used during munitions production at CAAP were 2.4.6-trinitrotoluene
(246TNT). cyclotrimethylenetrinitramine(RDX) and. to a lesser extent, cyclotetramethylenetetranitramine
(HMX). Other chemical materials used to support munitions production include freon. paints, grease.
oil. and solvents. Solvents reportedly used at CAAP include acetone (ACET). trichloroethylene (TRCLE)
(TCE). and 1 1 1 -trichloroethane ( 1 1 1TCE) (TCA).
Major operations conducted in Load Lines 1 through 4 included screening, melting and mixing, rod and
pellet manufacturing, and remelting and refilling. These operations generated explosives dust (246TNT
and RDX). Ventilation systems with Schneibie wet scrubbers removed explosives dust from the air.
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Process water from the Schneible units was circulated through sealing tanks and recycled through the
scrubbers. Wastewater from this process was disposed via interior-building open drains into concrete pits
equipped with filter bags called sack sumps. The bags, made of canvas-like material, were designed to
filter out solid explosives particles. The filtered wastewater flowed through open concrete channels into
circular earthen impoundments (cesspools). The walls of these impoundments were masonry lined, with
the bottom open to the sand and gravel strata. Water that did not infiltrate through the bottom of the
impoundment was routed through an overflow pipe into a leaching pit.
The limited filtering effectiveness of the sack sumps allowed explosive panicles to flow into the earthen
impoundments. The residue was periodically scraped from the bottom of the earthen impoundments and
leaching pits and ignited at the Burning Grounds. Wastewater was also generated from periodic washing
>f machinery, interior building surfaces, and carts used for transporting "the munitions during the
production process. This wash water was also discharged to the sack sumps, cesspools, and leaching pits.
2.3 PREVIOUS INVESTIGATIONS
Several investigations relating to the characterization and remediation of contamination at CAAP have
been completed. As pan of the U.S. Army's Installation Restoration Program. USATHAMA completed
an installation assessment of CAAP. A follow-on'contamination survey was completed in 1482.
Results from sampling and analysis or soils and groundwater indicated that some 01 the leaching pits aiul
. jsspoois were highly contaminated with explosives (especially 24ATNT .UKI RDX'i resulting in
contamination of the shallow aquifer. The explosives contamination was round to have migrated at least
> the installation boundary and potentially migrated off site. The Army during ll'X3 through l°Sft
performed groundwater sampling and analysis and monitored water table elevations at CAAP and in the
Mwngradiont otfpost area. The sampling network included up to 472 weils. including monitoring wells.
irrigation wells, and domestic water supply wells. Sampling and analysis conducted in 1^X4 confirmed
that RDX was migrating northeast, and had moved at least 3 mi offpost. It was confirmed that at least
ZOO domestic water supply wells in the Capital Heights residential area were contaminated with RDX.
In NS4 the Army evaluated remedial solutions to the groundwater contamination and extension of the
( "ity of Grand Island water supply system into the affected area was selected. The extension action w;is
carried out during 1984 through 1^86. In N85 the Army collected samples from eight locations at Load
Lines I. 2. 3. and 4 including leaching pits, trench drains, cesspools, and sack sumps. Detections oi
explosives, predominantly 246TNT. 135TNB. and RDX. were found in most samples.
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Sampling and analysis of groundwater for explosives contamination was conducted eleven times from
September 1986 through June 1991. In 1991 an Remedial Investigation/Feasibility Study was initiated
by the Army in accordance with the Interagency Agreement with the U.S. Environmental Protection
Agency (USEPA) and the Nebraska Department of Environmental Quality (NDEQ). The results of this
investigation relating to explosives contamination in groundwater are discussed in Section 5 of this
document.
2.4 REMEDIAL ACTIONS
Confirmation of offpost migration of explosives contaminated groundwater led to response actions to
remove the source(s) of contamination and provide water to households whose water supplies were
affected. The following sections summarize these response actions.
2.4. l ALTERNATE WATER SUPPLY
Bottled water was supplied from January 1984 through June 1986 by the Army to those households
affected by explosives contamination in groundwater. In July 1984 the Army entered into a contract with
the City of Grand Island to extend the city water system to the affected area and provide a permanent
water supply for the impacted area.
Construction of the Northwest Grand Island Water Supply Extension commenced in August 1984.
Residential water hookups were completed by December 1986. Approximately 800 residences, both in
the affected area and adjacent areas, were given the opportunity to hook up to the Northwest Grand Island
Water Supply Extension.
As a result of the continued groundwater monitoring, the Army recommended a second extension of the
Grand Island Water Supply. This action was carried out in accordance with the removal action provisions
of CERCLA/SARA. An Engineering Evaluation/Cost Analysis (EE/CA) was issued for public comment.
Following the comment period and public meeting, the decision to extend the water supply system to an
additional 65 residents was selected. This action started in the fall of 1993 and will be completed in the
fall of 1994.
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2.4.2 INSTALLATION RESTORATION INCINERATION PROGRAM
Fifty-eight impoundments (cesspools and leach pits) were identified as containing contaminated soil
resulting from munitions manufacturing at CAAP. The Installation Restoration Incineration Program
(IRIP) was an onsite CERCLA removal action, implemented to remove contamination at these sites.
Incineration of contaminated soil began in August, 1987. Excavation of contaminated soil was performed
by Mason & Hanger personnel, and incineration of contaminated soil was performed by International
Technology (IT).
Incineration, decontamination, and demobilization were completed by August 8, 1988. Ash from the
incineration was placed into trenches northeast of Load Line 2 and south of the North Magazine Area.
A 2-ft cap of topsoil was applied and the site was fertilized and seeded. Excavated impoundments were
backfilled with sand taken from a sand pit located on State Land (Nebraska State Game and Parks
Commission) along the eastern boundary of the facility. Excavations were covered with 2 ft of rich
black loam, fertilized, and seeded.
Clean-up action levels for incinerated soils were set jointly by U.S. Army and the Nebraska Department
of Environmental Quality (NDEQ). These levels were as follows: 246TNT. 5 ppm; RDX, 10 ppm;
135TNB, 15 ppm; 24DNT. 0.5 ppm: and 26DNT, 0.4 ppm. Excavation and incineration were carried
out until these action levels were met or until soil had been removed to a depth of 5 ft below the water
table. Verification sampling and analysis was accomplished using composite samples comprised of
subsamples from the bottoms and sides of the excavations. Since vertical excavation was limited by high
water table and the discharge requirement action levels were almost always achieved laterally, inclusion
of subsamples from the excavation sidewails in the composite sample tended to underestimate contaminant
content of the soils. In order to determine whether any of the 58 excavated impoundments are continuing
sources of explosives contamination in groundwater, groundwater samples were collected upgradient and
downgradient of the locations of these impoundments. Results from this sampling are forthcoming.
3.0 HIGHLIGHTS OF COMMUNITY PARTICIPATION
CERCLA Section 113(K)(2)(B)(i-v) requirements for public participation were met through the following
activities. Community relations activities for the CAAP site were initiated by the Army in 1984. Early
community relations activities included meeting with City and state officials to discuss the extension of
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the water line to homes with contaminated domestic wells. A Public Meeting was held on July 25. 1985
to explain the dewatering process and health risks of RDX. As part of the remedial action plan for
CAAP. the Army conducted thermal treatment of the explosive-contaminated soils and debris. In order
to keep the community informed of Army actions, the Army established information repositories at CAAP
and at the Grand Island Public Library.
In 1985. the Army provided funding for a waterline extension to affected residences. The Army offered
access to city water for those residents whose wells were in the approximate area of the contaminated
plume. In an ongoing effort to assure protection of human health, the Army is currently extending the
waterline to 65 additional residences. Estimated completion of this project is in the fall of 1994.
In January 1991 the Army and EPA conducted interviews with the community and in March of 1991 a
community meeting was held to announce the interagency Agreement between the Army, EPA. and the
State. A Technical Review Committee (TRC) was formed in November. 1991 with local citizens
participating in these meetings. The TRC has met periodically throughout the RI/FS process. The
Community Relations Plan for CAAP was prepared in November 1991 and approved in January 1992.
The public notice for this interim action for OU1 - Groundwater was issued on April 19. 1994. This
notice announced the availability of the Administrative Record for public review and the location of the
public repositories at CAAP and at the Grand Island Public Library, the public comment period and set
dates for the public meetings.
The Army held a public comment period from April 26. 1994 to May 26. 1994 following the release or
the Proposed Plan for this Interim Action for OU1- Groundwater. The Proposed Plan identified the
preferred alternative for the Interim Action for GUI - Groundwater. On May 4. 1994 the Army held
a public availability session, a less formal open house to allow visitors to speak one-on-one with
representatives of the Army. NDEQ. and EPA. The public meeting was conducted on May 5. 1994. to
discuss the preferred alternative and to receive citizens' comments and questions. Agency responses to
these comments received at the meetings and otherwise during the public comment period are included
in the Responsiveness Summary.
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4.0 SCOPE AND ROLE OF OPERABLE UNIT
The purpose of the Interim Action for this Operable Unit 1 -Groundwater is to contain the plume and
prevent further migration of contaminants. It is the first of two operable units planned for the site.
According to the NCP, the EPA regulation which establishes procedures for the selection of response
actions, an interim action is appropriate where a contamination problem will become worse if left
unaddressed and where the interim action will be consistent with a final remedial action. Consistent with
the principles of the NCP, this Interim Action is designed to promptly initiate an interim remedial action
response which will prevent further degradation of the aquifer, and contain the plume, thereby preventing
further migration of contaninants.
The implementation of the interim Action for OU1 is key to the stabilization of groundwater leading to
the final remedy. Remedial activities planned for OU2 will consist of actions necessary to remediate the
soils and groundwater to final clean-up goals, for explosives and any other contaminants determined to
be present as a result of past activities at CAAP.
5.0 SITE CHARACTERISTICS
The following sections describe the geology and hydrogeology of the site, the nature and extent of the
RDX groundwater plume, and the results of the contamination assessment conducted as part of the Site
Characterization Study.
5.1 GEOLOGY
The RDX plume area is underlain by Quaternary deposits of unconsolidated eolian. fluvial, and lacustrine
silt and clay and fluvial sand and gravel (Figure 5-1). These units rest on an erosional surface carved
into the Tertiary Ogallala Formation, a heterogeneous deposit of poorly lithified to unconsolidated fluvial
sand. silt, and clay. In most of the offpost explosives plume area, the Ogallala was completely removed
by erosion prior to deposition of Quaternary deposits, exposing the underlying Cretaceous Pierre Shale
and Niobrara Chalk.
The Quaternary deposits are comprised, in descending order, of the Peorian Loess and the Grand Island.
Fullerton. and Holdrege Formations. The Peorian Loess consists of silt and silty clay which covers most
of the onpost area. It ranges from 5 to 25 ft in thickness and thins to the east. The Grand Island
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A
SOUTHWEST
A'
NORTHEAST
UNDtfTERENTIATED
SURFACE SILT
AND CUT
FULLERTON
FORMATION
(BLUE CUT
AQUnARO)
(SAND &
CRAVa)
(PALEOVALLET
FU.AQUFER)
JJOLDREGE
FORUATKIN'
(SOT & CLAY)
APPROXIUATE VERTICAL SCALE: f = 75'
APPROXBUTE HORIZONTAL SCALE: T = t.l Uik
WATKINS-JOHNSON ENVIRONMENTAU INC.
Craundwoter Consulting. Environmental Engineering.
Remediation Services
GEOLOGIC CROSS SECTION
OF THE RDX PLUME AREA
CH4I002XOV1
Date: June 1994
Figure 5-1
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Formation is a laterally persistent, fluvial sand and gravel and ranges from 40 to 65 ft thick in the RDX
plume area. The Grand Island Formation is underlain by the Fullerton Formation, locally referred to as
the Blue Clay. The Fullerton consists predominantly of bluish green, silty clay of eolian, fluvial, and/or
lacustrine origin and ranges from 5 to 25 ft in thickness. East of the plume area, the Fullerton has been
locally removed by erosion which occurred prior to deposition of the Grand Island Formation. The
Fullerton Formation is underlain by the Holdrege Formation, a heterogeneous unit consisting of fluvial
sand and gravel and silt and clay of fluvial, lacustrine, and eolian origin. The Holdrege was deposited
on an erosional surface developed on the Tertiary and Cretaceous bedrock units. The Holdrege is thicker
and contains proportionately more sand and gravel where the erosional surface is most deeply incised into
the underlying bedrock. These erosional lows are paleovalleys. In the explosives plume area the
Holdrege ranges from 30 ft in thickness, over the erosional high, to greater than 220 ft in the paleovalley.
5.2 HYDROGEOLOGY
The Quaternary sand and gravel deposits are the primary source for groundwater in the Grand Island
area. In the explosives plume area. Quaternary deposits consist of three hydrostratigraphic units: the
Alluvial aquifer, the Blue Clay aquitard. and the Paleovalley Fill aquifer (Figure 5-1). The Alluvial
aquifer is comprised of the saturated sand and gravel of the Grand Island Formation. The silty clay of
the Fullerton Formation is the Blue Clay aquitard. The sand and gravel deposits of the Holdrege
Formation constitute the Paleovalley Fill aquifer. East of the explosives plume, and other areas where
the Fullerton Formation is not present, the Alluvial and Paleovalley Fill aquifers comprise one aquifer.
The Alluvial aquifer is an uncontlned aquifer and has a saturated thickness ranging from approximately
28 to 65 ft in the study area. Analysis of data obtained during a constant rate pumping test of the
Alluvial aquifer at CAAP yielded hydraulic conductivities ranging from 263 to 337 ft/day. The Blue C'lay
aquitard separates the Alluvial and Paleovalley Fill aquifers and is laterally continuous throughout CAAP
and the explosives plume area. Detailed analysis of all available lithologic logs from subsurface
penetrations in the RDX plume area and surrounding vicinity indicate that the Blue Clay aquitard is
continuous in this area. Groundwater sampling results indicate that the Blue Clay is an effective barrier
to the vertical migration of contamination in the RDX plume area. Analysis of potentiometric surface
data, aquifer testing in the plume area, and laboratory permeability testing of the Blue Clay support this
conclusion. The Paleovalley Fill aquifer consists of laterally discontinuous deposits of sand, gravel, silt.
and clay. Analysis of data obtained during slug tests of the Paleovalley Fill aquifer both on and offpost
yielded hydraulic conductivities ranging from 10 to 147 ft/day. The thickness and relative proportion of
-11-
-------
coarser sediments, and therefore transmissivity, of the Paleovailey Fill aquifer are greatest over the
paleovalley axis.
The water table slopes uniformly with an average gradient of 0.001 from southwest to northeast in the
explosives plume area (Figure 5-2). Depth to groundwater ranges from 5 to 20 ft. Since groundwater
pumpage and recharge occur over broad areas, consequent changes in groundwater flow direction and
lateral hydraulic gradients are minimal. Recharge of the Alluvial aquifer occurs by seepage of
streamflow, infiltration of precipitation and irrigation water, and lateral movement of groundwater from
areas west of CAAP. Except for water-supply and irrigation wells, there are no groundwater discharge
areas at CAAP. '
5.3 " RDX GROUNDWATER PLUME
The ROX groundwater plume is approximately six miles long and one half mile wide. The main plume
originates in the ordnance production facilities at CAAP and trends east-northeast to a point about 4 miles
beyond the eastern boundary of CAAP (Figure 5-2). Past investigations have noted that the depth to the
maximum contamination increases with distance from CAAP. This apparent downward migration of
RDX with distance from the source is not a density phenomenon, but a function of aquifer recharge at
the surface from infiltration of precipitation and irrigation water.
5.4 CONTAMINATION ASSESSMENT
During the RI process, several areas were identified in the load lines which were potentially associated
with explosives contamination of groundwater. These include wastewater impoundments: areas where
explosives were produced, handled, or stored: interior floor drain outlets: surface depressions and
drainage ditches associated with munitions productions areas: and nonexpiosive wastewater
impoundments.
During the RI process 96 groundwater monitoring wells, including 25 well clusters were sampled in the
explosives plume area. Forty-six of the wells were installed during the RI process. Well clusters were
designed to provide groundwater samples from the upper, middle, and lower portions of the Alluvial
aquifer. Four clusters located along the axis of the plume in the offpost area included a well screened
in the upper portion of the Paleovalley Fill aquifer. One onpost well (G0070), located along the plume
axis, is also screened in this aquifer. Each well was sampled two times and analyzed for a variety of
-------
-CAAP
I \ BOUNDARY
Grand Island
Cliy Limits
1900-
Water Table Elevation
(ft above mean sealevel)
-N-
0 6000 18000
= '
METERS
WATKINS-JOHNSON ENVIRONMENTAL. INC.
Groundwoler Consulting, Environmental Engineering.
Remediation Services
WATER TABLE CONTOUR/RDX
PLUME AREA MAP
CH41001\DV1
Dote; June 1994 | Figure 5-2
-------
contaminants, including explosives compounds. Evaluation of these analytical results and previous
groundwater investigations at the site yields the following conclusions.
1. The most extensive explosive compound detected in all zones of the Alluvial aquifer is
RDX. RDX has migrated at least 4.2 mi beyond the CAAP boundary. HMX has
migrated at least 2.2 mi beyond the CAAP boundary. Although 246TNT and several
of its breakdown products were detected at the installation boundary, they were not
detected in the next tier of monitoring wells approximately 1 mi downgradient.
2. The primary sources of explosives contamination in groundwater are located in Load
Lines 1 and 2.
3. Explosives have not contaminated the Paleovalley Fill aquifer. The wells screened in
this aquifer, all located along the RDX plume axis, did not yield any detections of
explosives compounds during the Remedial Investigations.
4. The depth to the maximum concentration of RDX in the plume increases with distance
from CAAP. At and near CAAP, groundwater contamination is detected only in the
upper and middle part of the Alluvial aquifer. At the far end of the plume. RDX is
detected only in the lower part of this aquifer.
6.0 SUMMARY OF SITE RISK
The chemicals detected in the groundwater are presented in Table 6-1. A statistically designed
background study will be performed to refine the final list of site-specific chemicals of concern (COCs).
Any additional COCs identified will be addressed by the final remedial action. The volume of the
affected groundwater is estimated to be approximately 7.2 billion gallons.
ROOS.TXT
09/5IW4
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Table 6-1 Concentrations of Chemicals of Potential Concern for CAAP
Groundwater Concentration (ue/D
Chemical
12DCLE
135TNB
13DNB
246TNT
24DNT
2A46DT
B2EHP
CH2CL2
HMX
NB
RDX
TCLTFE
TFDCLE
AS
AL
SB
BA
BE
CD
CL
F
FE
PB
MN
HG
Nl
NIT
SE
SO4
V
ZN
Minimum
31.000
0.839
2.310
0.898
0.106
0.203
0.920
30.000
1.590
1.230
2.060
70.000
7.000
2.100
270.000
26.000
61.700
2.190
11.800
1690.000
1070.000
116.000
6.980
21.400
1.340
29.200
14.300
2.930
7190.000
8.360
21.400
Maximum
31.000
180.000
2.310
820.000
24.000
87.000
23.000
30.000
79.200
1.230
96.400
1000.000
10.000
17.900
8050.000
60.100
1 130.000
2.190
24.300
190000.000
1310.000
14000.000
14.200
1640.000
1.340
59.500
270000.000
17.800
970000.000
57.600
107.000
Average
31.000
54.963
2.310
101.028
6.750
11.366
2.938
30.000
11.746
1.230
14.664
423.333
8.500
4.734
1948.920
37.680
348.694
2.190
19.022
32842.581
1 190.000
1545.871
11.160
246.816
1.340
45.850
14719.143
6.139
1 10503.978
17.110
38.914
No. of Detections
1
7
1
11
7
16
20
1
19
1
28
3
2
72
25
40
99
1
9
93
2
62
3
55
1
4
82
35
93
56
14
ROIH.TXT
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-15-
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The results of the site characterization indicate that the levels of RDX in groundwater at the distal end
are continuing to migrate to east-northeast at levels above the drinking water health advisory. In addition.
high levels of 246TNT, RDX, and HMX have been located on the CAAP facility. The health advisories
for these compounds are 2 ppb for 246 TNT, 2 ppb for RDX, and 400 ppb for HMX. The results of
the sampling conducted during the 1986 through 1992 time-frame, indicate that the compounds will
continue to migrate and affect additional drinking water sources. Refer to the Focused Feasibility Study
(1994) (FFS) and the Site Characterization Report (1993) for sampling data. Concentrations of explosive
compounds in groundwater samples range from 2 ppb to 95 ppb RDX, 0.8 ppb to 820 ppb 246-TNT. and
1.6 ppb to 79.2 ppb HMX. The high stability and high mobility RDX compound warrants the need to
contain and prevent further degradation of the aquifer. If left unchecked, further spread of the
contaminants in groundwater would increase human exposure to explosives and further degrade the
drinking water aquifer. Increased exposure could result from additional residential drinking water wells.
additional irrigation wells, and a City of Grand Island supply well becoming affected by the contaminant
plume.
A baseline risk assessment will be included in the site-wide RI/FS and in the subsequent final action
ROD. The risk assessment will determine the final remedial action criteria for the aquifer. The proposed
interim remedy is consistent with the expected final remedy in that this interim action contains the
contaminant plume and prevents its spread into unaffected areas.
Information on the human health effects resulting from over-exposure to explosive compounds comes
primarily from workers exposed during munitions production. At sufficient concentrations, explosive
compounds can affect the Central Nervous System (CNS) and may cause headaches, irritability, anorexia.
insomnia, seizures and in extreme cases unconsciousness. The primary contaminants which are TNT and
RDX are listed as EPA Group C. possible human carcinogens. Lifetime feeding studies in rats and mice
showed increased mortality, weight loss, anemia, liver and kidney toxicity. testicular degeneration, and
prostate inflammation.
ROK.TXT
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7.0 ALTERNATIVES EVALUATION
A total of fourteen remedial action alternatives were developed for groundwater containment at the on-
post source area (load line). A total of five remedial action alternatives were developed for the distal end.
These alternatives were developed in the FFS and summarized in the Proposed Plan, prior to public
comment. Modification of these alternatives, based on public review and comment is addressed in
Section 8.0. Except for the No Action and Limited Action alternatives, all remedial action alternatives
involve pumping and treatment of groundwater. The remedial action alternatives were developed to meet
the interim discharge requirements for groundwater remediation. The pump and treat options for
groundwater consists of the following steps:
pumping of the contaminated groundwater from the source area, and the distal end of the
plume.
groundwater containment to meet interim action standards
discharge of treated water to meet NPDES requirements
Discharge limits would be established during the NPDES permit process by NDEQ and the Army. This
process is applicable due to the necessity of discharging of treated water.
A groundwater monitoring system would be established to evaluate the extraction system's effectiveness
in containing the plume.
7.1 DESCRIPTION OF REMEDIAL ACTION ALTERNATIVES
Based on the FFS, this section presents a description of the remedial action alternatives analyzed for
OU1. The explosives contaminated groundwater extends from the load lines at the CAAP through the
Capital Height subdivision to approximately 2 miles into the Grand Island city limit in the off-post areas.
Two separate treatment facilities have been proposed for the pump and treat options. A treatment facility
is proposed to be installed near the load lines which are the sources of contamination for groundwater.
Another treatment facility would be installed to treat contaminated groundwater from the distal end of
the plume.
Response of the groundwater system was evaluated with the aid of a three-dimensional flow model
(MODFLOW) and a corresponding flowpath model (PATH3DX Model development and use is
ROO2.TXT _
04/21/94 -17-
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documented in Appendix A of the FFS (WJE, 1994). The groundwater flow model was calibrated to the
measured distribution of hydraulic heads during 1993. Water-level variations as large as 5 ft occurred
in response to seasonal variations in recharge and discharge. The difference between measured and model
estimated hydraulic head was generally less than 1 ft. Recharge and discharge was simulated using the
Nebraska soil-water program (NEB_SWP). Results of flowpath simulations corresponding to long-term
average recharge and discharge conditions were compared to the present-day plume configuration. This
comparison demonstrated that the model is a reliable means of estimating advective contaminant
migration. . The developed models were used to estimate the capture zones and cones of depression
associated with various groundwater extraction rates and well-field locations.
Source Area: The substances detected in the groundwater at the source area are primarily explosives,
other organics. metals and nitrates. Treatment for explosives are required at the CAAP. Metals and
nitrates in the groundwater may have to be treated if during the implementation phase, the levels exceed
discharge requirements. Except for the No Action and Limited Action alternatives, all alternatives
represent pump and treat option and involve extraction and treatment of the groundwater. The
components for the pump and treat options are described as follows:
Ground water Extraction:
Extraction Wells: Based on preliminary modeling, the groundwater extraction rate from the source
area is approximately 1.000 gpm. The actual extraction rate would be determined during remedial
design.
Metals Removal:
Chemical Precipitation: The extracted groundwater would be fed to a chemical precipitation unit, if
required. This technology would be employed to remove metals and other inorganics from the
groundwater. The process includes addition of a precipitating agent followed by coagulation.
flocculation. and sedimentation. The metals and other inorganics would precipitate as sludge and would
be removed from groundwater. The sludge would be tested and disposed of in accordance with RCRA
standards as applicable.
The effluent from the chemical precipitation unit would be pumped through sand filters where any floes
which were not settled in the sedimentation process would be removed. The filter media would be
periodically backwashed to remove trapped suspended panicles. Filtration would be employed following
precipitation and before carbon adsorption or Enhanced Oxidation.
KOK.TXT .
OW2I/44 - I O~
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Organics Removal:
The explosives and other organics from the groundwater would be removed using either Granular
Activated Carbon or Enhanced Oxidation.
Granular Activated Carbon: This is one of the two technologies selected for removal of explosives
and other organics. This technology can remove dissolved organics, including explosives, to levels below
1 pg/L. The groundwater leaving the granular media filters would flow through GAC columns which
would adsorb the explosives from the groundwater. The GAC columns would be designed based on
average flowrate of 1,000 gpm. Regarding disposal of spent carbon, the first protocol would be to look
at fuel amendment recycling. The spent carbon would be tested in accordance with TCLP protocols, if
TCLP is not triggered subtitle C standards would be applied for disposal of the spent carbon. Treatability
studies would be performed to determine the performance efficiency of the GAC system, carbon usage
rates, breakthrough time and other operating parameters prior to remedial design.
Enhanced Oxidation: Enhanced Oxidation would be employed to destroy organic contaminants
dissolved in water by chemical oxidation with or without the presence of ultraviolet radiation. Chemicals
such as ozone and hydrogen peroxide may be used alone or in combination to generate hydroxyl radical.
The hydroxyl radicals destroy organic contaminants by initiating a series of oxidative reactions that
eventually lead to destruction of organics including explosives. If complete oxidation is achieved.
explosives and other organic contaminants would be oxidized to simpler non-toxic forms. It" oxidation
is not complete, small chain aliphatics compounds, organonitrogen intermediates and other undesirable
by-products may form. Treated effluent from the Enhanced Oxidation will be subject to neutralization
prior entering the ion-exchange unit or constructed wetland.
Nitrates Removal
After the groundwater has been treated for metals and explosives, the nitrates in the groundwater would
be treated if required. The following treatment technologies were considered:
Ion Exchange: Following removal of explosives and other organics either using GAC or Enhanced
Oxidation, the treated effluent would enter ion exchange units or flow through constructed wetlands.
Multiple ion-exchange units consisting of 3 to 5 feet of anionic resin beds would be used to remove
nitrate from the groundwater. Once resin has been exhausted, one of the two actions may be taken.
Some vendors offer regeneration services. This service replaces the entire ion exchange unit with a new
ROW.TXT
OM2I/M -19-
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one. thereby avoiding downtime caused by regeneration cycles. Another option is to set up a number
of permanent units which would be occasionally rinsed with brine to remove nitrate. This process would
prolong the life of the resin and reduce the frequency of resin change-out. The second option has been
considered in the costing of alternatives. Brine used for regeneration of the resin beds is not expected
to be hazardous because all contaminants in the groundwater except nitrate is essentially treated prior
entering the ion-exchange units. Brine would be disposed to an appropriate facility or reclaimed. The
treated effluent from ion-exchange units would be discharged either to an infiltration basin or to surface
water.
Constructed wetlands: Wetlands (80 to 160 acres) would be designed and constructed specifically to
remove nitrate from the groundwater. The bed of the constructed wetland would be compacted in-situ
to prevent infiltration of nitrates into the groundwater. Plant uptake and microbial activities would remove
nitrates from the groundwater. The plants used most frequently in constructed wetland include cattails.
reeds, rushes, bulrushes, and sedges. The plants would be periodically harvested and disposed of at a
landfill, by composting, or burning. Cold weather slows the nitrates removal process but does not stop
it all together. To compensate for the slowing of the removal process, the cells are designed with extra
capacity for operations during the winter months. Constructed wetlands have been used to treat nitrates
in municipal wastewater treatment facilities and are becoming increasingly popular. Constructed wetlands
are a proven technology with low maintenance requirements. Infiltration of nitrates, if any. from the
constructed wetlands into the groundwater would be monitored using one upgradient and two
downgradient wells which would be sampled twice a-year.
Discharge Options The treated effluent from the treatment facility at the source area would be discharged
either to an infiltration basin or to surface water.
Surface Water Discharge
The Proposed Plan recommended that the treated groundwater would be discharged to surface water.
Infiltration Basin
The treated effluent would be applied through an infiltration area. Soil with permeabilities of 1.0 in/hr
or more are necessary for successful rapid infiltration. It is estimated that approximately 80 acres of land
would be required for infiltration.
ROM.TXT
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The combination of the above treatment components for each alternative is shown in Table 7.1-1.
Alternatives T-3 to T-6 are similar to Alternatives T-7 to T-10 except for the variation in the discharge
option.
Distal End: The groundwater at the distal end of the plume contains primarily RDX at low
concentrations. Should metals or other inorganics be detected in the influent groundwater above the
interim discharge standards, appropriate treatment units would be incorporated at the distal end treatment
system. This system uses some of the technologies as described above for the source area. Based on
preliminary modeling, the groundwater would be extracted at an approximate rate of 3,000 gpm in order
to prevent further migration of the contaminants. The actual extraction rate would be determined during
remedial design. The pumped groundwater at the distal end would be treated using either GAC or
Enhanced Oxidation System. The treated water would be discharged to surface water.
The combination of the treatment components for each of the five alternatives for the distal end are
presented in Table 7.1-2.
7.2 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
The NCR sets forth nine evaluation criteria which serve as a basis for comparing the remedial action
alternatives for final actions. Interim actions, such as proposed here, may not achieve final discharge
requirement levels for groundwater although they are effective in the short-term in preventing further
degradation of the groundwater and initiating reduction in toxicity. mobility or volume. The following
is a discussion on the comparison of the remedial action alternatives with respect to the nine evaluation
criteria.
ROD2.TXT _
OW2I/94 -2.1-
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TABLE 7.1-1 COMPONENTS OF REMEDIAL ACTION ALTERNATIVES FOR SOURCE AREA
Rcmedhil
Action
Alternatives
T-l
T-2
T_3<.>
T-4W
T-5
T-6
7.70
T-8W
T-9
T-IO
Groundwuior
Monitoring
X
X
X
X
X
X
X
X
X
X
Administrative
Control
X
Groundwater
Extraction
X
X
X
X
X
X
X
X
Chemical
Precipitation
X
X
X
X
X
X
X
X
(iramikir
Media
Filtration
X
X
, X
X
X
X
X
X
Granular
Activated
Carbon
X
X
X
X
Enhanced
Oxidation
X
X
X
X
Wetland
X
X
X
X
Ion
Exchange
X
X
X
X
Discharge
To
Infiltration
'Basin
X
X
X
X
Discharge
To
Surface
Water
X
X
X
X
Cost
($)
1,016,000
1,068,400
17,244,000'"-
17,714,000«>
I7,057,000<"-
17,528,000"'
28,129,000
27,941,000
I6,398,000fl"-
16,870,000W
\6,2\0,m«*-
16,681,000"
27,282,000
27,094,000
(a) For GAC units, both regeneration/reuse and disposal of spent carbon have been studied. Carbon regeneration/reuse considered for Alternatives: T-3A, T-4A, T-7A, and T-8A.
Carbon disposal considered for Alternatives: T-3B, T-4B, T-7B, and T-8B. (b) Cost for alternative based on regeneration/reuse of spent carbon, (c) Cost for alternative based on disposal of spent
carbon.
-------
TABLE 7.1-2 COMPONENTS OF REMEDIAL ACTION ALTERNATIVES FOR DISTAL END
Remedial
Action
Alternatives
T-l
T-2
T-3
T-4
Groundwater
Monitoring
X
X
Administrative
Control
X
Groundwater
Extraction
X
X
Granular
Activated
Carbon
X
Enhanced
Oxidation
X
Discharge ;
to
Surface
Water
X
X
Present
Worth
S $ 217,000
''; $ 270,000
$ 9,320,000(b)-10,747,000w
$38,406,000
(a) For GAC units, both regeneration/reuse and disposal of spent carbon have been studied. Carbon regeneration/reuse considered
for Alternatives: T-3 A.
(b) Cost for alternative based on regeneration/reuse of spent carbon, (c) Cost for alternative based on disposal of spent carbon.
-------
7.2.1 COMPARISON OF REMEDIAL ACTION ALTERNATIVES FOR THE SOURCE AREA
A. Threshold Criteria
I. Protection of Human Health and the Environment
Alternative T-l, No Action would not meet this criterion since no actions are taken to eliminate, reduce
or control exposure pathways. Alternative T-2, Limited Action, does provide some protection in that it
limits access to, and use of the contaminated groundwater through institutional controls. However, these
controls do not prevent further migration of COCs present in the groundwater.
The remaining alternatives would provide adequate protection of human health and the environment as
defined by the interim action objectives. The objective is to contain and prevent migration which would
result in further degradation of the aquifer. When implemented with an extraction system, the
contaminated groundwater would be contained and migration of COCs would be prevented. These
alternatives would be able to meet the interim action objectives focused to protect human health and the
environment.
2. Compliance with ARARs
Alternatives T-l and T-2 would not comply with chemical-specific ARARs. Over a long period of time.
the concentrations of explosives and other organics may decrease due to natural degradation and dilution.
In this case, eventual compliance with the ARARs may be achieved. However, the length of time before
this occurs may be extensive. Alternatives T-3 to T-6 would be designed to meet chemical specific
ARARs (Nebraska Groundwater Standards. Federal MCLs. TBCs). Alternatives T-4 to T-10 would be
designed to meet NPDES permit limits to be specified by the regulatory agencies. Alternatives T-3B.
T-4B. T-7B and T-8A would comply with RCRA requirements for pre-transportation and transportation
of hazardous wastes. A detailed analysis of the ARARs is presented in chapter 3 of the Focused
Feasibility Study and chapter 8 of this Record of Decision.
B. Primary balancing Criteria:
1. Long-Term Effectiveness and Permanence
ROMDCT 0/,
(M/2I/W -ifr-
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Alternatives T-l and T-2 would not provide long-term effectiveness and permanence. The remaining
alternatives T-3 to T-10 would provide long-term effectiveness and permanence to varying degrees.
Alternatives T-3 and T-7 incorporating GAC and constructed wetland as treatment units for removal of
organics and nitrate respectively, would offer moderate long-term effectiveness and permanence. Under
this alternative, explosives and other organics would not be permanently destroyed, but transferred from
the groundwater to GAC. Nitrate would be effectively removed in the constructed wetland system
through plant uptake and biological denitrification. These reactions are irreversible and would result in
permanent removal of nitrate from the groundwater.
Alternatives T-4 and T-8 which include GAC and ion exchange as treatment units would offer lesser long-
term effectiveness and permanence than Alternative T-3 and T-7 respectively. This is because both
organics and nitrate would not be destroyed, but transferred from the groundwater to GAC and ion-
exchange resin respectively. Both the GAC and ion exchange units combined would generate larger
quantity of spent residuals which may be regenerated, recycled or disposed.
i
Alternatives T-5 and T-9 incorporating Enhanced Oxidation and constructed wetlands would offer very
high long-term effectiveness and permanence. The reactions involving organics and nitrate are irreversible
and result in permanent transformation of the COCs: The treatment residual generated by this alternative
is minimum compared to Alternatives T-3, T-4, T-6. T-7, T-8 and T-IO.
Alternatives T-6 and T-IO are similar to Alternatives T-5 and T-9 respectively, except that ion exchange
would be used to remove nitrate instead of constructed wetlands. These alternatives would offer
moderately long-term effectiveness and permanence. Explosives and other organics would be completely
mineralized. Nitrate would be transferred to resins and eventually to brine solution through the
regeneration process.
2. Reduction of Toxicitv. Mobility and Volume Through Treatment
Alternatives T-l and T-2 do not result in any reduction of toxicity. mobility and volume of the
contaminants, because removal and treatment are not components for this alternative. With effective
extraction process as implemented in all the pump and treat options, there would be considerable
reduction of toxicity, mobility and volume of COCs present in the groundwater.
ROO2TXT
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Alternatives T-3 and T-7 would offer moderate reduction of toxicity, mobility and volume through
treatment. The concentration, mobility or the volume of the explosives and other organics would not be
reduced by GAC treatment. This constructed wetland treatment would result in reduction of toxicity,
mobility and volume of nitrate present in the treated groundwater.
Alternatives T-4 and T-8 would result in lower reduction of toxicity, mobility and volume than
Alternative T-3 and T-7, respectively . Explosives and other organics, and nitrate would not be
transformed; these contaminants would be transferred from the groundwater to either GAC or ion
exchange resin.
Alternatives T-5 and T-9 would result in very high reduction of toxicity, mobility and volume.
Explosives and other organics would be completely mineralized to carbon dioxide, nitrogen oxides and
water. Nitrate would be converted to organic nitrogen (plant assimilation) and molecular nitrogen.
Alternatives T-6 and T-10 would be less effective than Alternatives T-5 and T-9. respectively, in the
reduction of toxicity, mobility and volume. Although explosives and organics would be destroyed
through Enhanced Oxidation, nitrate will be not be destroyed or transformed. Nitrate would be
eventually transferred to brine which will be disposed.
3. Short-Term Effectiveness
This criterion is not applicable for Alternatives T-l or T-2.
Alternatives T-3 to T-10 would require approximately equal amount of time, similar construction
equipment and effort, and none would entail any additional risk beyond those inherent in construction
projects. The short-term effectiveness for Alternatives T-3 to T-10 is the same because no additional
risks are incurred in the implementation of one alternative as compared to another.
4. Impiementabilitv
All alternatives are implementable. However, some alternatives are easier to implement then others. In
some instances, requirement of administrative approval may make an alternative less implementable.
Administrative requirements can encompass property easements, permits for off site discharge, and/or
ROO2.TXT
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waivers. From the administrative standpoint. Alternative T-l is the least implementabie. since a waiver
would very likely not be granted.
5. Cost
Among the alternatives implementing surface water discharge, Alternative T-8A has the lowest cost. The
cost of Alternative T-7A exceeds that of Alternative T-8A by one percent.
Of those alternatives developed for discharge to infiltration basins (T-3 to T-6), Alternative T-3A has the
lowest present worth value. The overall costs of Alternative T-5 and T-6 are significantly higher than
Alternatives T-3 and T-4. This is primarily due to the considerably high capital Cost of Enhanced
Oxidation compared to GAC units. The cost of pump and treat options incorporating discharge to
infiltration basin range between $17,056,400 and $28,128,900; those incorporating discharge to Silver
Creek range between $16,209,800 and $27,094,200.
7.2.2 COMPARISON OF REMEDIAL ACTION ALTERNATIVES FOR THE DISTAL END
A. Threshold Criteria
I. Overall Protection of Human Health and the Environment
Alternative T-l. No Action would not meet this criterion since no actions are taken to eliminate, reduce
or control exposure pathways. Alternative T-2, Limited Action, does provide some protection in that it
limits access to, and use of the contaminated ground water through institutional controls. However.
institutional controls would be difficult to implement at the distal end of the plume which is located at
the off-post areas of CAAP.
The remaining alternatives are capable of providing adequate protection of the human health and the
environment. The explosives contaminated groundwater would be contained and prevented from further
migration. These alternatives would be able to meet the interim discharge requirements which would be
focused to protect human health and the environment.
2. Compliance with ARARs
KOB2.TXT
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Alternatives T-l and T-2 would not comply with chemical-specific ARARs.
Alternatives 3 and 4 would be designed to meet the NPDES permit limits. Both these alternatives would
comply with all Federal and State air quality standards.
Primary Balancing Criteria:
1. Long-Term Effectiveness and Permanence
Over a period of time. Alternatives T-l and T-2 may be able to meet the criterion of long-term
effectiveness and permanence due to natural or biological degradation and dilution.
Alternative T-3 incorporating GAC for removal of explosives would offer moderate long-term
effectiveness and permanence. Explosives would not be permanently destroyed, but transferred from the
groundwater to the GAC media.
Alternative T-4 incorporating Enhanced Oxidation would offer high long-term effectiveness and
permanence. The organics would be transformed into simpler non-toxic by-products.
2. Reduction of Toxicitv. Mobility and Volume through Treatment
The Alternatives T-l and T-2 would not result in any reduction of toxicity. mobility and volume of
organics. except through natural degradation or dilution over a period of time.
The GAC treatment by itself in Alternative T-3 would not reduce the toxicity. mobility and volume of
explosives. If spent carbon is utilized for fuel amendment, there would be a significant reduction in the
toxicity. mobility and volume of contaminants adsorbed by the GAC units. If spent carbon is disposed
to a permitted facility, there would no such reduction in the toxicity. mobility or volume of contaminants.
Alternative T-4 would result in very high reduction of toxicity. mobility and volume of explosives which
will be mineralized to simpler non-toxic by-products.
3. Short-Term Effectiveness
ROIH.TXT
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This criterion is not applicable for Alternatives T-l and T-2.
Alternatives T-3 and T-4 would require approximately equal period of time, similar construction
equipment and effort, and would not entail any additional risk beyond those inherent in construction
projects. The short-term risks for both these alternatives are the same because no additional risks are
incurred in implementation of one alternative as compared to another.
4. Implementabilitv
From the administrative standpoint. Alternative T-l is the least implementable. All alternatives are
technically implementable.
5. Cost
Alternative T-4 incorporating Enhanced Oxidation has the highest present worth. The cost of remedial
action alternatives ranges between $217,400 and $38,405,900.
Modifying Criteria
i. State Acceptance
The letter from the Nebraska Department of Environmental Quality (NDEQ) regarding concurrence of
the selected remedy as an interim action for this site is attached.
2. Community Acceptance
The Army held a public meeting and public comment period to allow the community to comment on the
preferred alternative as set forth in the Proposed Plan and the alternatives considered. Many community
members were opposed to the discharge of treated effluent to Moores Creek. The residents were
concerned that continuous discharge of 3.000 gpm of water would potentially flood their basement and
property, and would result in significant loss of property, crops and livestock. The residents and City
of Grand Island representatives were also concerned that extraction of groundwater at the distal end would
induce contaminant migration from intermediary locations of the plume to the distal end.
ROK.TXT
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In response, the Army has decided to extract an additional 1,000 gpm of groundwater from intermediary
location under the Capital Heights area. The total discharge of treated water will be transferred through
a pipeline constructed to and through the easement of the Wood River Diversion Channel to the Plane
River. The rationale supporting this amendment is documented in Section 8.1.
7.3 PROPOSED REMEDY
The Army has selected the following interim actions (Alternative T-7A for the source area and T-3A for
the distal end of the plume) to address groundwater contamination (OU 1):
A. Source Area
Extraction of contaminated groundwater.
Treatment of contaminated groundwater using chemical precipitation, granular media
filtration, granular activated carbon, and constructed wetlands.
Discharge of treated effluent to surface water
The flow diagram for this alternative is presented in Figure 7-2.
B. Distal End
Extraction of contaminated groundwater
Treatment of contaminated groundwater using granular activated carbon.
Discharge of treated effluent to surface water
Should nitrate and metal concentrations in the groundwater at the point of discharge exceed the discharge
limits, then contingencies for nitrate and metal treatment will be implemented.
The flow diagram for this alternative is presented in Figure 7-3.
The groundwater plume would be monitored to determine effectiveness of the Alternative T-7A (source
area) and Alternative T-3A (distal end) as selected interim action remedies.
The Army has identified these interim actions as its selected alternatives because they provide the best
balance among other alternatives with respect to the evaluation criteria based on the information available.
The Army believes that these interim actions are protective of human health and the environment.
ROO2.TXT
(N/21/94 -30-
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implementable, and effective in reducing the toxicity, mobility and voiume of contamination present in
the groundwater plume. This approach will contain and prevent further migration of the contaminant
plume. This approach has been modified based on public comment. Discussion of the modifications is
found in Section 8.1.
For treatment of explosives, the Army considers the GAC a better option than Enhanced Oxidation since
it is a proven technology, which is half the cost of Enhanced Oxidation for this site. The GAC
technology has been used by the Army since the mid 70's to treat explosive contaminated discharge water
from production facilities.
Chemical precipitation was the proposed metals treatment process, should it be needed. The Army has
proposed to carry a metals process as a contingency should the metals levels in the extracted groundwater
be determined to be above discharge levels. A statistically designed background study is being conducted
and should be finalized prior to the design of the selected remedy. The background study will be used
to determine if chemical precipitation of metals is necessary as a pan of the final action.
ROU2.TXT
M/7I/M -31-
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FILTER
BACKWASH
TO FILTER PRESS
pH ADJUSTMENT
CHEMICALS
GROUNDWATER
TREATED
WATER
DISCHARGE
TO SURFACE
WATER
; CHEMICAL CLARIFICATION
PRECIPITATION j
GRANULAR
MEDIA
FILTRATION
GRANULAR
ACTIVATED
CARBON
WETLANDS
SPENT CARBON TO
REGENERATION FOR
RECYCLE
FILTRATE
SLUDGE TO DISPOSAL
FILTER PRESS
LEGEND
SLUDGE
Ml 193064
GROUNDWATER
SPENT CARBON
WATKINS-40HNSON ENVIRONMENTAL. INC.
Ground-Water Consulting. Environmental Engineering
Remediation Services
ALTERNATIVE T-7A
SCHEMATIC DIAGRAM OF GROUNDWATER
EXTRACTION, CHEMICAL PRECIPITATION, GRANULAR
MEDIA FILTRATION, GRANULAR ACTIVATED CARBON
(SPENT CARBON RECYCLED), WETLANDS TREATMENT
AND DISCHARGE TO SURFACE WATER
Date: June 1994
Figure 7-2
-------
GROUNDWATER
CO
TREATED WATER DISCHARGE TO SURFACE WATER
GRANULAI.
ACTIVATED
CARBON
SPENT CARBON TO REGENERATION FOR RECYCLE
LEGEND
M1193069a
GROUNDWATER
SPENT CARBON
WATKWSOOtMSOM EMVMONUCWTAL, INC.
OAOUKOWATmCCTBACTTOH
QflANUtAD ACTIVATED CMtBOK
OSCMMWeiO SUKFACCWATEfl
Date: June 1984
Figure 7-3
-------
Constructed wetlands were compared to ion exchange, which removes the nitrates through the use of
synthetic resins. The ion exchange technology is effective but is prone to clogging which increases
maintenance requirements over that of constructed wetlands approach. Constructed wetlands have been
used to treat nitrates in municipal wastewater treatment facilities and are becoming increasingly popular.
The Army viewed constructed wetlands as a better option for on-post remediation.
Surface water discharge is the selected discharge option. The alternative to surface water discharge is
reinjection through infiltration basins which is a proven technology, but prone to clogging and requires
higher maintenance than surface water discharge.
The Army estimates that the interim actions for the source area and the distal end are $16.398,100 and
S9.320.000 respectively. The cost breakdown for these alternatives is presented in Tables 7.3-1 and 7.3-
2. Based upon the cost of the alternatives and the degree of protect!veness that one alternative affords
as compared to the other alternative, the Army has selected the most cost effective alternatives which
meet the evaluation criteria.
KOD:.TXT
34
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Table 7.3-1 Summary Cost Estimate (or Source Area, Alternative T-7A.
ITEM
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
A.
B.
C.
Site Preparation/Support
Extraction Wells
Chemical Precipitation
Granular Media Filtration
Sludge Disposal
Granular Activated Carbon
Wetlands Treatment
Surface Water Discharge
Piping, Connections, and Pumping
Treatment Systems Operator
Groundwater Sampling
Subtotal
Contingency 35% of total Capital Costs
Contingency . 5% of total Annual Costs
TOTAL CAPITAL COSTS
TOTAL ANNUAL COSTS
TOTAL PRESENT WORTH OF ANNUAL COSTS
CAPITAL
COST
$103,300
$31,200
$510,400
$387,000
$180,000
$929.800
$552,000
$569.900
$3,263,600
$1,142,300
$4,405,900
ANNUAL
O&M
COST
$17,600
$409,900
$115,600
$28,900
$151,100
$37.100
$26.600
$58,400
$576,200
$1,421,400
$71,100
$1,492,500
PRESENT WORTH OF
ANNUAL COSTS
30YEARS,5% 30YEARS,7%
$270,600
$6,301,200
$1,777,000
$444,300
$2,322,700
$570,300
$408,900
$897,800
$1,045,900
$14,038,700
$701,900
$14,740,600
$218,400
$5,086,400
$1,434.500
$358,600
$1,875,000
$460,300
$330,100
$724,700
$933,100
$11,421,100
$571,100
$11,992,200
TOTAL PRESENT WORTH OF CAPITAL AND ANNUAL COSTS (A + C)
$19,146,500 $16,398,100
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Table 7.3-2 Summary Cost Estimate for Distal End, Alternative T-3A.
ITEM
1.
2.
3.
4.
5.
6.
7.
8.
g.
A.
B.
C.
Site Preparation/Support
Extraction Wells
Granular Activated Carbon
Surface Water Discharge
Piping, Connections, and Pumping
Treatment Systems Operator
Groundwater Sampling
Subtotal
Contingency 35% of total Capital Costs
Contingency 5% of total Annual Costs
TOTAL CAPITAL COSTS
TOTAL ANNUAL COSTS
TOTAL PRESENT WORTH OF ANNUAL COSTS
CAPITAL
COST
$117,700
$33,800
$540,000
$283,000
$188,500
$1,163,000
$407,100
$1,570,100
ANNUAL
O&M
COST
$49.700
$496,300
$26,600
$8,300
$13,900
$594,800
$29,700
$624,500
PRESENT WORTH OF
ANNUAL COSTS
30YEARS,5% 30YEARS,7%
$764,000
$7,629,300
$408,900
$127,600
$213,700
$9,143,500
$457,200
$9.600,700
$616,700
$6,158,600
$330,100
$103,000
$172,500
$7,380,900
. $369,000
$7,749,900
TOTAL PRESENT WORTH OF CAPITAL AND ANNUAL COSTS (A -f C)
$11,170,600 $9,320,000
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8.0 STATUTORY DETERMINATIONS
The selected interim remedy will contain and prevent further migration of the contaminant plume, which
left uncontained would result in further degradation of the aquifer. This will be accomplished by
pumping and treating the groundwater.
All ARARs potentially considered for this action are listed in section 3.0 of the Focused Feasibility
Study. The requirements determined to be Applicable or Relevent and Appropriate are listed in tables
8-1 A, 8-1B. 8-2 and 8-3 which respectively are the chemical-specific, location-specific and action-specific
ARARs. The numeric standards for the containment criteria for explosives are presented in Appendix
B. In the absence of chemical-specific ARARs for explosives: health advisories and risk concentrations
are utilized for determining the containment goals.
The selected remedy consists of extraction of contaminated groundwater from three areas of the plume:
source area, intermediary and distal end. The objective is to capture the groundwater at the source area
containing relatively high concentrations of contaminants, primarily RDX and prevent migration of these
contaminants. The extraction rate will be ascertained during the preliminary implementation stages based
on the ability of the well network to capture the contaminants. Groundwater exposure is likely through
the usage of private wells in the Capital Heights area, therefore, groundwater will be extracted an ^
intermediary location before the plume enters Webb Road and Capital Avenue. In this area. RDX
concentrations range between 4.2 and 21.0 (ig/L. Continuous extraction of groundwater at an
approximate rate of 1.000 gpm is expected to result in significant decrease in both the concentrations and
volume of contaminants. The distal end contains RDX at concentrations slightly above the health
advisory of 2 ng/L. The extraction of groundwater at the distal end will prevent migration of" the plume
to a municipal supply well located approximately 1.5 miles down gradient. Extraction of groundwater
at the distal end will also prevent impact to additional downgradient residential and irrigation wells.
ROIH.TXT
04/21/M . -371'
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Table 8-1A Chemical-Specific ARARs for Groundwater Containment
Standard Requirement,
Criteria, or Limitation
Citation
Description
Applicable/
Relevant and
Appropriate
Comments
National Primary Drinking
Water Standards
40 CFR Part 141
Maximum Contaminant
Levels
Establishes maximum contaminant
levels (MCLs) which are health-
based standards for public water
systems.
No/Yes
The MCLs for organic and
inorganic contaminants are relevant
and appropriate for deriving the
NPDES discharge levels.
National Secondary
Drinking Water Standards
40 CFR Part 143
Establishes secondary maximum
contaminant levels (SMCLs) which
are non-enforceable guidelines for
public water systems to protect the
iicslhclic quality of the water.
Relevant and appropriate for
establishing discharge limits.
No/Yes
SMCLs may be relevant and
appropriate for deriving the
NPDES discharge levels.
Maximum Contaminant
Level Goals (MCLGs)
Stat. 642(1986)
Establishes drinking water quality
goals set at levels of no known or
anticipated adverse health with an
adequate margin of safety.
No/Yes
MCLGs for organics and inorganic
contaminants may be relevant and
appropriate for deriving the
NPDES discharge levels. SB,
BA,CD,BE,CD,F,HG have non-
zero MCLGS.
Groundwater Quality
Standards and Use
Classification
NDEQ, Title 118,
Chapter 5,
Appendix A
Establishes standards and use
classifications for groundwater
sources of drinking water.
Yes/-
Is applicable because groundwater
is a drinking water source.
-------
Table 8-IH Chemical-Specific ARARs for Surface Water Discharge
Standard Requirement,
Criteria, or Limitation
Citation
Description
Applicable/
Relevant and
Appropriate
Comments
Water Quality Standards
for Surface Water of the
State
NDEQ, Title 117
Chapter 4
Establishes standards for the
surface waters of the state.
Yes/-
Applicable because treated
water will be discharged to
surface water. More relevant
than Federal ambient water
quality criteria. Contains
antidegradation clause and
numeric waste quality
standards for water bodies in
the state. Does not contain
standards for explosives.
Antidegradation policy apply
to discharge to Platte River.
Discharge standards will be
established in accordance with
(IAW) NPDES permit.
-------
Table 8-2 Location-Specific ARARs
Standard Requirement.
Criteria, or Limitation
Federal
Floodplain Management
pish and Wildlife
Coordination Act 6
Farmland Protection
Policy Act
Protection of Wetlands
Citation
40 CFR 6.302(D)
Executive Order
1 1988 and 40 CFR, Part 6,
Appendix A
16 USC 66! el seq.
7 USC 420 et seq.
40 CFR Part 6.
Appendix A. Part (j)
Executive Order 11990 Part
7(c)
Description
Establishes requirements
for federal agencies to
reduce risk of flood loss,
minimize the impacts of
floods on human safely,
health and welfare, and
restore and preserve the
natural and beneficial
values of floodplains.
Establishes requirements
for actions taken to
prevent, mitigate, or
compensate for project-
related damages or losses
to fish and wildlife
resources.
Establishes requirement
for federal agencies for
acquiring, managing and
disposing of lands and
facilities; or provide
criteria that identify and
take into account the
adverse effects of actions
on the preservation of
farmland.
Establishes requirements
for federal agencies to
avoid or minimize adverse
impacts on wetlands.
Applicable/
Relevant and Appropriate
Yes/-
No/Yes
No/Yes
Yes/-
Comments
.
Applicable, the treatment
facility will be is located
within a floodplain.
Executive Order 11988 is
TBC guidance.
Relevant and appropriate
if project related activities
affect fish and wildlife
resources.
Relevant and appropriate
if treatment facility
location and project
related activities affect
farmland.
Wetlands are likely to be
present in the vicinity of
(he piping route to the
Platte River. Executive
Order 11990 Part 7(c) is
TBC guidance.
KIIII:. r\i
in :i n
-41)-
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Table 8-3 Action-Specific ARARs (page I of 3)
Standard Requirement,
Criteria, or Limitation
Citation
Description
Applicable/
Relevant and
Appropriate
Comments
Federal
(Hazardous Waste
Classification
40 CFR Part 261
Provides determination
of hazardous waste;
procedures for delisting
of wastes.
No/Yes
Relevant and appropriate if
treatment residuals such as
sludge/spent carbons are determined
to be hazardous.
Hazardous Waste
Determination
40CFR262.il
Requires hazardous
waste generator to
determine if a waste is
hazardous pursuant to
40CFR Part 261.
Yes/~
Potentially applicable to sludge
from dewatering and backwash
residue.
Hazardous Waste
Management
40 CFR Part 264
.Establishes requirement
that affects generation,
transportation,
treatment, storage and
disposal of hazardous
waste.
No/Yes
Relevant and appropriate if
treatment residuals are determined
to be hazardous.
Land Disposal
40 CFR Part 268
Establishes regulations
on land disposal
restrictions and
treatment standards for
land disposal of RCRA
hazardous waste.
Yes/No
Relevant and appropriate if
treatment residuals such as sludge
are determined to be hazardous.
IMP.' IX I
IN'.'I-'M
41-
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Table 8-3 Action-Specific ARARs (page 2 of 3)
CO
ro
CO
CD
Standard Requirement,
Criteria, or Limitation
Standards Applicable to
Transporters of
Hazardous Waste
Wetlands Protection
State
Tr&StC nf cUlfl&CVflCllt
Rules
Hazardous Waste
Management
Citation
40 CFR Part 263
dean Water Act 404,
40 CFR 230.3(1)
33CFR328(b)
«
NDEQ, Title 126, Chapter
18
NDEQ, Title 128, Chapter 3
Description
Establishes standards
which apply to
tttutspurlets of
hazardous wastes.
Establishes requirement
to avoid degradation of
wetlands due to
construction activities.
Establishes regulations
on releases of oil or
hazardous substances
into water or land.
Establishes requirement
for notification of
hazardous waste
activity.
Applicable/
Relevant and
Appropriate
No/Yes
Yes/No
Yes/No
No/Yes
Comments
Relevant and appropriate if
treatment residuals such as
sludge/spent carbon are determined
to be hazardous.
Applicable to construction activities
near the wetlands which may be
present near the Platte River.
Applicable to sludge from
dewatering, backwash, and residues
that are hazardous substances and
could be spilled or leaked to land or
water during treatment operations.
Relevant and appropriate if
treatment residuals are determined
to be hazardous.
ROD2.1XT
OMMM
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Table 8-3 Action-Specific ARARs (page 2 of 3)
Standard Requirement,
Criteria, or Limitation
hazardous Waste
Management
Air Pollution Controls
Rules & Regulations
Air Pollution Control
Rules and Regulations
i
Groundwater
Monitoring Wells
Requirements
Groundwater
Management or Control
Citation
NDEQ, Title 128, Chapter
17
NDEQ, Title 129. Chapter
32
NDEQ, Title 129, Chapter
20
Neb. Rev. Stat 46-602, 46-
1201, 46-651 to 46-655
Neb. Rev. Stat 46-656 et.
seq.
Description
Establishes requirement
that affects generation,
transportation,
treatment, storage and
disposal of hazardous
waste.
Pertains to generation
of dust and air-borne
paniculate matter.
Establishes standards on
paniculate matter
emissions.
Provides
requirements/restriction
s for groundwater
monitoring wells.
Restricts access to
groundwater from
certain surface areas.
Applicable/
Relevant and
Appropriate
No/Yes
Yes/No
No/Yes
Yes/No
Yes/No
Comments
Relevant and appropriate if
treatment residuals are determined
to be hazardous.
Dust/air borne paniculate matter
may generate during construction,
transportation or handling.
Relevant and appropriate if
treatment residuals are determined
to be hazardous.
Potentially applicable for all
groundwater wells to be used for
extraction.
Potentially applicable.
mn>:.m
43-
-------
The selected treatment processes consisting of extraction, chemical precipitation, GAC and constructed
wetlands which are capable of meeting discharge criteria and containing the contaminant plume to the
levels as prescribed in attachment B. However, the actual design and configuration of these treatment
units will be based on the required discharge limits to be specified by the regulatory agencies during the
NPDES permitting process for off site surface water discharge. The treatment process will utilize
permanent solutions and alternative treatment technologies or resource recovery technologies to the
maximum extent practicable. The treatment processes will result in reduction of toxicity, mobility and
volume of contaminants present in the groundwater extracted from the different locations of the plume.
This action will stabilize the risk and prevent further degradation of the environment, therefore protecting
human health and the environment. This selected alternative based on capital and operational costs
balanced with community acceptance and compliance with ARARs provides for an implementable and
cost effective alternative.
It is expected that the final remedy would be implemented prior to the five-year review period. If the
final remedy is not underway within five years after the commencement of this interim action, a review
would be conducted to ensure that the remedies continue to contain the plume and reduce the risk
associated with the contaminated groundwater.
8.1 DOCUMENTATION OF SIGNIFICANT CHANGES
The FFS and Proposed Plan recommended that groundwater would be extracted from the source area
(1000 gpm) and the distal end (3000 gpm). treated, and discharged to surface water in the areas of Silver
Creek and Moores Creek respectively. During the public meeting held on May 5,1994, the residents of
Merrick County were concerned that continuous discharge of 4000 gpm of water would exceed the
creeks' capacity and potentially flood their basements and property. The discharge of treated groundwater
to the creeks was found to be unacceptable by the local residents. In addition, the residents were
concerned that extraction of groundwater at the distal end would induce contaminant migration from
intermediary locations of the plume to the distal end.
In response, the Army evaluated potential flooding problems that may result due to discharge of treated
water to the creeks. It was estimated that flooding would most likely occur during winter months (culvert
icing is expected) and also during temperate months when high flow events occur. During high flows.
the additional 7000 gpm discharged from the treatment facility would make the natural problem worse.
A gross estimate based on a visual site inspection and discussions with the local community, estimated
KOD2.TXT
0*21/94
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that approximately 1900 acres of land and about 90 residences could be potentially affected by flooding
due to discharge of treated water to the Silver and Moores creeks. The loss of crops that could result
due to flooding of property is estimated to be $ 1,000.000 each year. Based on new information
obtained during the public meeting, the Army re-evaluated the surface water discharge point and
determined discharge to Silver or Moores Creek may not comply with 40 CFR Part 6, which has been
determined to be an ARAR.
In response to the concerns raised by the citizens, the Army evaluated the option of discharging the
treated water directly to the Plane River by means of pipeline. A piping system was evaluated based on
a total discharge rate of 7000 gpm including an additional 1000 gpm of groundwater extracted from the
groundwater plume before it enters the intermediary area under the Capital Heights area. This additional
1000 gpm of extracted groundwater would prevent migration of contaminants, particularly RDX from
the central portion of the plume where RDX concentration exceeds 20 jig/L. Note that additional
discharge capacity will be designed into the pipe line as a contingency for the final remedial action
selection. The pipeline traverses a total distance of 25 miles and the present worth (7% ,30 years) ranged
between $10,392,000 and $14,041,300. The surface water discharge of treated water to Platte River
will eliminate potential flooding impacts and will become cost comparative over the system life-cycle
should the metals and nitrate treatment not be needed to meet the discharge levels at the Platte River.
The treated effluent discharged to the Silver and Moores creek would have had to meet MCLs. where
applicable, due to the fact that both Silver Creek and .Moores are hydraulically connected to the aquifer.
If discharged directly to Platte River, the treated effluent would be required to meet NPDES permit
limits. It is expected that effluent limits for the NPDES at the Platte may not warrant the treatment tor
metals and nitrates. This reduced treatment requirement would offset the cost associated with piping the
treated effluent to the Platte River.
If for any unforseen reasons the Wood River Diversion Channel is not implemented, the Army will
undertake the responsibility of completing the piping route (not the diversion channel) and provide the
piping system for discharge of treated water to the Platte River. This may require additional time for
construction of the selected treatment system.
8.2 SUMMARY OF SELECTED REMEDY AFTER MODIFICATION
A. Source Area
Extraction of contaminated groundwater.
RODiTXT
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Treatment of contaminated groundwater using granular activated carbon and granular
media filtration; and chemical precipitation and constructed wetlands, if necessary.
Discharge of treated effluent to the Platte River through Wood River Diversion Channel
easement.
B. Distal End/Intermediary Area
Extraction of contaminated groundwater at the distal end and the intermediate area.
Treatment of contaminated groundwater using granular activated carbon and granular
media filtration.
Discharge of treated effluent to Platte River through Wood River Diversion Channel
easement.
RODZ.TXT
04/21/M -46-
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GROUNDWATER - OPERABLE UNIT ONE
CORNHUSKER ARMY AMMUNITION PLANT
RESPONSIVENESS SUMMARY
SUMMARY OF COMMENTS RECEIVED DURING THE PUBLIC COMMENT PERIOD AND
AGENCY RESPONSES
The public comment period on the preferred interim remedial action alternative for Groundwater -
Operable Unit One, Cornhusker Army Ammunition Plant extended from April 26 to May 26, 1994. A
public availability session took place on May 4, 1994 from 4pm to 8pm at the Grand Island City Hall.
Grand Island, Nebraska. The Public Meeting took place on May 5, 1994 from 7pm to 9pm, also at the
Grand Island City Hall. Approximately 16 people attended the public availability session with 7 people
making oral statements or asking questions. 19 people attended the Public meeting on May 5, 1994, with
7 people making oral statements or asking questions. Seven written statements were received during the
comment period. The transcript of the Public Availability Session and the Public Meeting for the
Proposed Plan is attached. During the question and answer session, the Army, EPA. and the State of
Nebraska representatives responded to questions from the audience. These responses are contained the
transcript of the proceeding, which is included in the Administrative Record for the site. A summary of
the written comments and the Army's response is provided herein.
Overview
Four of the seven written comments reflect the opinion that the groundwater should be cleaned up, but
the discharge of treated water should not be to the local drainage due to chronic flooding problems along
these drainages. One comment received voiced a concern about the lack of extraction wells in die central
portion of the plume and one comment concerned the effect infiltration basins would have on the water
table in Capitol Heights.
Comments on the Discharge Options
1. Several citizens of Merrick County commented that any water discharged to Moores
or Silver Creek would adversely impact them by causing flooding. The area where
these individuals reside along Moores Creek is prone to flooding. The citizens also
opposed the discharge because they believed that the added water to the creeks would
raise the water table sufficiently to prevent farming of adjacent land.
Army's Response: Prior to the Public Meeting and Public Availability Session the
Army's estimates of stream capacity and ability to bear the additional water did not
indicate flooding problems would occur if the treated water would be discharged into these
drainage. Due to the concern of Merrick County residents voiced during the 2 day public
information gatherings, the Army has reassessed the discharge options for the treated
groundwater. Information about the planned diversion channel for Wood River has been
collected to develop other viable discharge options which were assessed according to the
same criteria used in the Focused Feasibility Study. Through this evaluation the Army
has determined that discharge of treated water via pipeline through the easement for the
diversion channel to the Platte River is a viable alternative and the Army has changed the
discharge option for the selected remedy as documented in this ROD.
KOK.TCT
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Other Comments
1. One citizen asked what effect the infiltration basins would have on the groundwater
table in the Capital Heights area.
Army's Response: Computer modeling indicates that the areas beneath and immediately
adjacent to the basins would see a 1 to 2 foot rise in the water table, causing what is
referred to as a groundwater mound. This mounding effect would dissipate by the time
the groundwater reached the site boundary. Therefore, no impact on the water table
would occur in the Capital Heights area.
2. The City of Grand Island voiced a concern over the lack of extraction wells in the
central portion of the plume. They were concerned that pumping at the distal end
would cause groundwater with higher concentrations of RDX to migrate at an
accelerated rate, causing an increase in RDX levels in areas which currently have
detections at or around the detection limit. The City expressed that the accelerated
migration of the plume would cause a reduction in property values and would cause
problems if any dewatering had to be done for construction projects due to discharge
of more highly contaminated groundwater into ditches. They expressed a concern that
potential for growth and development would be hindered due to the complications of
providing construction dewatering due to the anticipated increases in contaminant levels
in this area of the plume.
Army's Response: The Army has reconsidered the option to control migration of the 20
ppb RDX zone in the central portion of the plume. Currently it is anticipated that 3 wells
would be utilized to contain the explosive contaminants in this area. Actual well
placement and extraction rates will be ascertained during the final design phase.
3. The NDEQ raised the issue of the applicability of the State's Title 118 to the proposed
action and requested the Army to clarify its position on Title 118.
Army's Response: The Army has since requested the State's action specific ARAR
determinations and their interpretation. The Army has since included Title 118 as an
applicable ARAR for this selected action.
KOM.TXT
M/21/94 -48-
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ATTACHMENT B
GROUNDWATER CONTAINMENT STANDARDS
COMPOUND STANDARD (ppb)
2,4,6,-trinitrotoluene 2.0 (b)
HMX 400.0 (b)
RDX . 2.0 (b)
nitrobenzene 3.5 (c)
1,3-dinitrobenzene 1.0 (b)
1,3.5-trinitrobenzene 3.5 (c)
2-amino-4,6-dinitroluene 0.4 (d)
2,4-Dinitrotoluene 0.05 (a)
Note:
a. USATHAMA. Assessment of ARARs. January 1992 (Based on Carcinogenic Slope Factor)
h. USEPA. Office of Drinking Water Lifetime Health Advisory (72-year Lifetime advisory)
c. WJE. Modified USATHAMA's Assessment of ARAR's. December 1991 (Based on Estimated RfD)
d. Based on provisional RfD of 6E-05 mg/kg-day. USEPA/ECAO 1993
ROO2.TXT
(N/21/94
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