PB98-964407
EPA 541-R98-106
November 1998
EPA Superfund
Record of Decision:
Monticello Mill Tailings (USDOE)
OU3
Monticello, UT
9/29/1998
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GJO-98-51-TAR
Record of Decision for an
Interim Remedial Action at
The Monticello Mill Tailings Site,
Operable Unit III—Surface Water and
Ground Water, Monticello, Utah
August 1998
/J wJ
m»* Performed Under DOE Contract No. DE-AC13-96GJ8733S tor the U.S. Department of Energy
Approved for public releaie; Attribution n unlimited.
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RECORD OF DECISION
FOR AN INTERIM REMEDIAL ACTION AT
THE MONTICELLO MILL TAILINGS SITE,
OPERABLE UNIT IH—SURFACE WATER AND GROUND WATER,
MONTICELLO, UTAH
This is a primary document for Operable Unit HI at Monticello, Utah. It will be available in the
Administrative Record, which is maintained at the following locations:
Monticello City Offices
17 North 1st Street East
Monticello, UT 84535
Hours: 8 a.m.-4:30 p.m.
• DOE Grand Junction Office
2597 B% Road
Grand Junction, CO 81503
Hours: 8 a.m.-4:30 p.m.
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Record of Decision for an Interim Remedial Action
at The Monticcllo Mill Tailings Site,
Operable Unit in—Surface Water and Ground Water,
Monticello, Utah
August 1998
Prepared by
U.S. Department of Energy
Albuquerque Operations Office
Grand Junction Office
Project Number MSG-035-0009-00-000
Document Number Q0011601
Work Performed Under DOE Contract Number DE-AC 13-96GJ87335
Task Order Number MAC98-03
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Document Number Q0011601 Contents
Contents
Page
Acronyms v
Glossary vii
Declaration for the Interim Remedial Action Record of Decision 1
Decision Summary for the Interim Remedial Action Record of Decision 1-1
1.0 Site Name, Location, and Description 1-3
2.0 Site History and Enforcement Activities 2-1
2.1 Site History 2-1
2.2 Investigation History '. 2-1
2.3 Enforcement Activities and Administrative History 2-2
2.4 Highlights of Community Participation 2-3
2.5 Scope and Role of Operable Unit ffl Surface Water and Ground Water Within
Site Strategy 2-3
3.0 Summary of Site Characteristics 3—1
3.1 Hydrologic Setting 3-1
3.1.1 Surface Water 3-1
3.1.2 Ground Water 3-1
3.2 Operable Unit m Source Areas 3-3
3.3 Nature and Extent of Contamination 3-3
3.3.1 Surface-Water Contamination 3-3
3.3.2 Ground-Water Contamination 3-4
3.4 Conceptual Model of Contaminant Transport 3-8
4.0 Summary of Site Risks 4-1
4.1 Human-Health Risks 4-1
4.2 Environmental Risk 4-1
4.3 Need for the Interim Remedial Action 4—2
5.0 Description and Comparison of Interim Remedial Action Alternatives 5-1
5.1 The No-Action Alternative (Alternative I) 5-1
5.2 Institutional Controls, Millsite Dewatering and Treatment, Monitoring, and
PeRT Wall Installation and Evaluation (Alternative 2) 5-1
5.3 Summary of Comparative Analysis of Alternatives 5-3
5.3.1 Threshold Criteria 5-3
5.3.2 Primary Balancing Criteria 5-9
5.3.3 Modifying Criteria 5-11
6.0 Selected Remedy 6-1
DOE/Crand Junction Office MMTS OU HI Interim ROD
August 1998 . Uj
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Contents
Document Number Q0011601
Contents (continued)
Page
7.0 Statutory Determinations 7-1
7.1 Protection of Human Health and the Environment 7-1
7.2 Compliance with Applicable or Relevant and Appropriate Requirements 7-1
7.3 Cost Effectiveness 7-1
7.4 Use of Permanent Solutions and Treatment Alternative Technologies or Resource
Recovery Technologies to the Maximum Extent Practical 7-2
7.5 Preference for Treatment as a Principal Element 7-2
7.6 Balancing Criteria 7-2
8.0 References 8-1
Appendices
Appendix A
Responsiveness Summary
A-l
Table 3.3.1-1
Table 3.3.2-1
Table 3.4-1
Table 5.3-1
Tables
Contaminants that Exceed Utah Surface-Water Standards 3-4
Contaminant Concentrations in Ground Water that Exceed Regulatory
Standards 3-7
Human Exposure Pathway Analysis Summary 3-8
Comparison of the Alternatives Against the Nine CERCLA Criteria 5-3
Table 5.3.1-1 Federal ARARs for OU m Surface Water and Ground Water 5-5
Table 5.3.1-2 State ARARs for OU m Surface Water and Ground Water 5-7
Figures
Figure 1-1. Monticello Mill Tailings Site Map 1-4
Figure 3.3.2-1. OU ffl Ground-Water Plume 3-5
Figure 3.4-1. Ecological Conceptual Site Model 3-9
MMTS OU UI Interim ROD
iv
DOE/Crand Junction Office
August 1998
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Document Number Q0011601
Acronyms
Acronyms
ARAR applicable or relevant and appropriate requirements
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act
CT central tendency
DOE U.S. Department of Energy
EPA U.S. Environmental Protection Agency
FFA Federal Facilities Agreement
ft feet
MMTS Monticello Mill Tailings Site
NCP National Contingency Plan
O&M operation and maintenance
OU operable unit
PeRT permeable reactive treatment
RCRA Resource Conservation and Recovery Act
RME reasonable maximum exposure
State State of Utah
UMTRCA Uranium Mill Tailings Radiation Control Act
UPDES Utah Pollutant Discharge Elimination Systems
yd3 cubic yards
DOE/Grand Junction Office
August 1998
MMTS OU HI Interim ROD
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Document Number Q0011601 Glossary
Glossary
Administrative Record: All documents which were considered or relied on in selecting the
response action at a Superfund site, culminating in the record of decision for remedial action or,
an action memorandum for removal actions.
Alluvial aquifer: An aquifer composed of unconsolidated materials (sand, gravel, cobbles, silt)
deposited by stream flow. Usually is the uppermost aquifer of a ground-water system and is
affected by processes at the land surface (e.g., precipitation, streamflow).
Aquifer: A geologic formation, group of formations, or part of a formation capable of yielding a
significant amount of ground water to wells or springs.
Aquitard: Geological formation that may contain ground water but is not capable of transmitting
significant quantities of it under normal hydraulic gradients. May function as a confining bed.
Applicable or Relevant and Appropriate Requirements (ARARs): Any state or federal statute
that pertains to protection of human life and the environment in addressing specific conditions or
use of a particular cleanup technology at a Superfund site.
Baseline Risk Assessment: Baseline risk assessments provide an evaluation of the potential
threat to human health and the environment in the absence of any remedial action. They provide
the basis for determining whether or not remedial action is necessary and the justification for
performing remedial actions. Baseline Risk Assessments can be performed to evaluate both
human health risks and ecological risks.
Burro Canyon Formation: A unit of rock composed of sandstone and conglomerate that is
present in the subsurface and surface at various locations in the Four Corners region of the U.S.
The Burro Canyon Formation is Cretaceous in age. Locally, the Burro Canyon Formation may be
used as a source of drinking water.
Conceptual Model: A preliminary "model" of a site developed using readily available
information. Used to identify all potential or suspected sources of contamination, types and
concentrations of contaminants detected at the site, potentially contaminated media, and potential
exposure pathways, including receptors.
Feasibility Study: A study undertaken by the lead agency to develop and evaluate options for
remedial action. The feasibility study emphasizes data analysis, implementability of alternative,
and cost analyses, as well as compliance with mandates to protect human health and the
environment and attain regulatory standards of other laws. The feasibility study is generally
performed concurrently and in an interactive fashion with the remedial investigation, using data
gathered during the remedial investigation.
OOE/Grand Junction Office MMTS OU ffl Interim ROD
August 1998 vii
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Glossary Document Number Q00116(M
Glossary (continued)
Focused Remedial Investigation: A streamlined process undertaken by the lead agency to
determine the nature and extent of the problem presented by a release. A focused remedial
investigation emphasizes use of existing data and very limited and specific additional data
collection. The remedial investigation includes gathering of specific information to determine the
necessity for remedial action and to support the evaluation of remedial alternatives.
Ground Water: Water in the ground that is wholly saturated.
Hazard Ranking System: Formal system employed by the U.S. Environmental Protection
Agency (EPA) to rank the hazards of a site on the basis of preliminary investigation and
assessment. Ranking scores determine site eligibility for the National Priorities List.
High water content: Containing a large percentage of water per volume of material.
Interim Remedial Action: A remedial action that initiates remediation of a site but may not
constitute the final remedy.
Lithic scatter: Scattering of rock material that has been altered by historic or ancient humans for
tools or weapons.
National Priorities List: EPA's list of the most serious uncontrolled or abandoned hazardous
waste sites identified for possible long-term remedial action under Superfund.
Non-time critical Removal Action: A removal action under CERCLA is a short-term
immediate action taken to address releases of hazardous substances that require expedited
response (removals generally mitigate or stabilize individual threats rather than all threats at a
CERCLA site). Non-time critical removal actions require more than 6-months planning prior to
field implementation.
Permeable Reactive Treatment (PeRT) Wall: This is a permeable wall that is placed across an
aquifer perpendicular to ground-water flow; it contains reactive media that removes or degrades
contaminants as the ground water passes through.
Potable: Suitable for drinking.
Potentiometric surface: An imaginary surface representing the level to which ground water
would rise in a well.
Radionuclides: Naturally occurring or artificially produced radioactive element or isotope.
Radioactive materials spontaneously emit ionizing radiation.
Recharge zone: An area (land surface) in which water infiltrates and reaches the zone of
saturation in one or more aquifers.
MMTS OU III Interim ROD DOE/Grand Junction Office
viii August 1998
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Document Number Q0011601 Glossary
Glossary (continued)
Receptors: Living organisms that could be exposed to chemicals and/or conditions that can
cause adverse effects on those organisms.
Regulatory standards: Concentrations of chemicals that are minimum requirements for quality
of a given medium (e.g., ground water, air) for a particular purpose (e.g., drinking water,
irrigation). If standards are met, the medium is considered safe to use (i.e., no adverse effects will
occur) for that purpose.
Removal Action: A removal action under CERCLA is a short-term immediate action taken to
address releases of hazardous substances that require expedited response (removals generally
mitigate or stabilize individual threats rather than all threats at a CERCLA site).
Responsiveness Summary: A summary of oral and/or written public comments received by the
lead agency on key cleanup-related documents and the agency's response to those comments.
Saturated thickness: The thickness of an aquifer in which all the interconnected spaces are
completely filled with water.
Secular equilibrium: The condition whereby sufficient time has elapsed such that the rates of
decay and creation are equal for each radioisotope in a radioactive decay series.
Slurry: A highly fluid mixture of water and a very fine-grained solid material.
Stakeholder: Any organization, governmental entity or individual that has a stake in or may be
impacted by a given approach to environmental regulation, pollution prevention, energy
conservation, etc.
DOE/Grand Junction Office MMTS OU III Interim ROD
August 1998 ix
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DECLARATION FOR THE
INTERIM REMEDIAL ACTION
RECORD OF DECISION
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Document Number Q0011601 . Declaration
Site Name and Location
Operable Unit HI - Surface Water and Ground Water
Monticello Mill Tailings Site
Monticello-, Utah
Statement of Basis and Purpose
This decision document presents the selected interim remedial action for Operable Unit (OU) HI
surface water and ground water at the Monticello Mill Tailings Site (MMTS) in San Juan
County, Utah. The selected interim remedial action was chosen in accordance with the
Comprehensive Environmental Response, Compensation, and Liability Act as amended by the
Superfund Amendments and Reauthorization Act of 1986 and, to the extent practicable, with the
National Oil and Hazardous Substances Pollution Contingency Plan (NCP). This decision is
based on the administrative record for this site. The State of Utah concurs with the selected
interim action.
The selected alternative for the interim remedial action for OU ID surface water and ground water
at the MMTS is Alternative 2—implementing institutional controls, continuing Millsite
dewatering and treatment of excavation water and surface runoff, continuation of ongoing
monitoring efforts, and evaluation of a permeable reactive treatment (PeRT) wall through the use
of a pilot-scale treatability study. The PeRT wall is an enhancement to the interim remedial
action. This remedial action is only an interim measure. If monitoring results indicate that the
interim remedial action is not achieving the objectives of preventing exposure to and reducing
contaminants in contaminated ground water, other alternatives will be evaluated from the OU in
feasibility study. The final remedy for the site surface water and ground water will be
documented in the final Record of Decision (ROD) for OU EL
Assessment of the Site
Current risks to human health associated with the contaminants in OU in surface water and
ground water are below levels considered by the U.S. Environmental Protection Agency to be
significant. However, this interim remedial action is warranted based on possible future risks to
human health and the environment, to limit exposure to contaminants while further information
is gathered to characterize the site, to determine the effectiveness of a PeRT wall in removing
contaminants, and to evaluate final remedial actions.
Description of the Selected Remedy
OU in is one of three OUs at the MMTS; a remedial investigation and feasibility study have been
completed for OU D3. A ROD was signed for OUs I (the Millsite) and n (Peripheral Properties
adjacent to the Millsite) which stipulated that contaminated materials from OUs I and n would be
excavated and placed in an on-site repository. Mill tailings piles and contaminated soils and
sediments associated with OUs I and n of the MMTS are the primary sources of OU in surface-
water and ground-water contamination. These contaminant sources are being excavated and
disposed of in the repository just south of the Millsite. Excavation in some areas requires
dewatering operations, involving extraction and treatment of ground water; some on-site surface
DOE/Grand Junction Office MMTS OU ID Interim ROD
August 1998 3
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Declaration Document Number Q0011601
water is also collected and treated during excavation. Thus, source control activities are
achieving some mass reduction of contaminants in the aquifer system and, in turn, the surface
water. As documented in an Action Memorandum (DOE 1998a), DOE recently initiated a
removal action (OU HI soils and sediments) to excavate contaminated soils and sediments within
the Montezuma Creek floodplain downgradient of the Millsite. Results of the risk assessment
indicate that current ground-water contaminant levels may cause unacceptable future risks.
Because Millsite conditions arc changing due to excavation activities, it is not yet possible to
select a final remedy for OU ID surface water and ground water. However, this interim remedial
action is prudent to prevent exposure to contaminated ground water and to further reduce
contaminant mass in surface water and ground water. This interim remedial action will be
ongoing until the final remedy for OU HI surface water and ground water is implemented. The
major components of this interim remedial action for OU ID surface water and ground water
include
• Using institutional controls to restrict use of contaminated ground water.
• Continuing ground-water extraction and treatment during excavation and dewatering of the
Millsite and continuing, if necessary, after Millsite excavation in areas of concentrated
contamination.
• Continuing monitoring efforts, including surface-water and ground-water sampling, to better
understand effects of Millsite remediation on water quality.
• Installing a pilot-scale treatability study (PeRT wall) downgradient (east) of the Millsite to
assess its effectiveness in reducing contaminant levels in OU HI surface water and ground
water.
Declaration
This interim remedial action is protective of human health and the environment, complies with
Federal and State applicable or relevant and appropriate requirements directly associated with
this action, and is cost-effective. Although this interim remedial action is not intended to fully
address the statutory mandate for permanence and treatment to the maximum extent practicable,
this interim remedial action utilizes some treatment and thus is in furtherance of that statutory
mandate. Because this action does not constitute the final remedy for OU HI surface water and
ground water, the statutory preference for remedies that employ treatment that reduces toxicity,
mobility, or volume as a principal element, although partially addressed in this remedy, will be
addressed by the final response action. Subsequent actions are planned to address fully the threats
posed by the conditions at this portion of OU HI. Soils and sediments associated with OU ffl are
being remediated as a separate removal action that is being conducted in accordance with an
Action Memorandum addressing that removal action (DOE 1998a). Because this is an interim
remedial action ROD, review of this site and of this remedy will be continuing as the final
remedial alternatives for OU ffl are developed.
MMTS OU III Interim ROD DOE/Crand Junction Office
4 August 1998
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Document Number Q0011601
Declaration
RECORD OF DECISION
FOR AN INTERIM REMEDIAL ACTION AT
OPERABLE UNIT HI—SURFACE WATER AND GROUND WATER
MONTICELLO MILL TAILINGS SITE, UTAH
OF UTAHxBEPARTMENT OF ENVIRONMENTAL QUALITY
/^C^L/^fC /
r Nielson, Ph.D.
Executive Director
Date
U.S. ENVIRONMENTAL PROTECTION AGENCY, REGION
Max H. Dodson
Assistant Regional Administrator
Office of Ecosystems, Protection, and Remediation
Date
F ENERGY-ALBUQUERQUE OPERATIONS OFFICE
W. John Arthur '
Assistant Manager
Office of Environment Project Management
Date
DOE/Grand Junction Office
August 1998
MMTS OU m Interim ROD
5
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DECISION SUMMARY FOR THE
INTERIM REMEDIAL ACTION
RECORD OF DECISION
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Document Number Q0011601 Decision Summary
1.0 Site Name, Location, and Description
The Monticello Mill Tailings Site (MMTS) is located in southeast Utah, in and near the city of
Monticello in San Juan County (Figure 1-1); the city of Monticello has a population of
approximately 1,900. Operable Unit (OU) in encompasses ground water and surface water at and
downgradient of the Monticello Millsite, as well as contaminated soil and sediment deposited
downstream of the Millsite in and adjacent to Montezuma Creek. The Millsite is a 110-acre tract
of land owned by the U.S. Department of Energy (DOE). Mill tailings and associated
contaminated material remain on the Millsite as a result of historical vanadium and uranium
milling operations. An estimated 200,000 cubic yards (yd3) of contaminated material has been
identified in the former mill area, and approximately 2.1 million yd3 of tailings and contaminated
soil have been identified in the tailings-impoundment area of the Millsite. The tailings were
contained in four piles within the floodplain of Montezuma Creek and are in hydraulic contact
with a shallow alluvial aquifer underlying the site. The tailings are the primary source of
contamination in ground water, surface water, soil, and sediment within OU EL Surface-water
and ground-water contamination are the subject of this interim remedial action Record of
Decision (ROD).
A detailed description of OU in is presented in the remedial investigation report for OU in
(DOE 1998b). MMTS is located in the east-central part of the Colorado Plateau physiographic
province. The Abajo Mountains, Great Sage Plain, and Blanding Basin are the three
physiographic subdivisions that dominate the landscape in the Monticello area. Approximately
5 miles west of Monticello, the Abajo Mountains, reaching elevations above 11,000 feet (ft), rise
more than 4,000 ft above the broad, nearly flat, upland surface of the Great Sage Plain. A canyon
network consisting of the upper part of Montezuma Creek and its tributaries has incised the
western part of the Great Sage Plain. Montezuma Creek canyon becomes more deeply incised as
the creek flows southward into the Blanding Basin.
The Millsite and adjoining areas within the Montezuma Creek valley are underlain by two
ground water-bearing units (aquifers). The upper unit is the alluvial aquifer consisting of
unconsolidated soil, sediment, and rock. The water table is generally 2 to 10 ft below the ground
surface. The alluvial aquifer both discharges ground water to and receives surface water from
Montezuma Creek depending on location. The alluvial aquifer and Montezuma Creek have been
contaminated by past Millsite activities. The contaminants that present the greatest risks at the
site include uranium, vanadium, lead-210, and arsenic. A lower sandstone aquifer within the
Burro Canyon Formation, is locally separated from the alluvial aquifer by sandstones and shales
of the Mancos Shale and the Dakota Sandstone Formations that restrict vertical ground-water
movement. The Burro Canyon Formation is used as a secondary source of potable water.
The upper surface of the Burro Canyon Formation is about 125 ft below the ground surface in the
west end of the Millsite and 60 ft below ground surface immediately east of the Millsite. About
4,000 ft east of the Millsite, erosion has removed the entire thickness of the relatively
impermeable beds of the Mancos Shale and Dakota Sandstone Formations and the alluvial
aquifer and Burro Canyon aquifer are in direct contact. Where the aquifers are in direct contact,
ground water flows upward from the Burro Canyon aquifer into the alluvial aquifer. The upward
movement of Burro Canyon ground water seems to have prevented contaminant movement from
the alluvial aquifer to the Burro Canyon aquifer.
DOE/Cnod Junction Office MMTS OU ID Intern) ROD
August 1998 1-3
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E
ET
!
o
i
MONTICEL .0
EXPLANATION
EXTENT OF CROUNDWATER
CONTAMNAHON
UONTEZUMA CREEK
— MlLSITt BOUNDARY
>00 0 SOO I«M IWO
rrii
R JJ E Ft :-\ E
if
F/gt/re /-/. Monticello Mill Tailinns Site Map
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Document Number QOO11601 Decision Summary
MMTS is a former uranium and vanadium ore-processing mill that was placed on the National
Priorities List (NPL) in 1989 because of potentially elevated risks associated with contaminated
materials related to past milling activities. The Millsite and nearby contaminated properties are
currently being remediated in accordance with the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA). Surrounding private lands are used for residential,
recreational, and agricultural (both farming and grazing) purposes. Ground water within the
alluvial aquifer is not currently used for any domestic, agricultural, or industrial purpose. Water
from Montezuma Creek is used for agricultural purposes.
DOE/Grand Junction Office MMTS OU ID Interim ROD
August 1998 1-5
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Document Number Q0011601 '_ Decision Summary
2.0 Site History and Enforcement Activities
2.1 Site History
The site operated from the mid-1940s until 1960 to produce materials used in the production of
steel and construction of nuclear weapons. Initially, the mill was built to produce only vanadium
for the purpose of hardening steel needed for World War n. With the scale-up of the nuclear
weapons program, the site began processing domestic uranium ore as well. Uranium and
vanadium ores that were mined from across the region were transported to the Millsite for
milling and refining. The uranium concentrate was shipped to production facilities that
manufactured nuclear weapons components; vanadium concentrate was shipped to steel-
producing facilities. Processing of the ores resulted in the generation of mill tailings, which were
disposed on the site in four tailings piles. The tailings contain elevated concentrations (compared
to background) of a variety of radioactive materials and heavy metals that pose risk to human
health and the environment.
The tailings piles were covered with soil and seeded with native grasses in the early 1960s to
prevent erosion by wind and water. However, the high water content in the tailings and
infiltration of precipitation provided a continuing source of ground-water contamination as it
seeped through the subsurface over time. Some of the piles extend into the alluvial aquifer water
table and contaminants are leached by ground water. Montezuma Creek becomes contaminated
as contaminated ground water discharges to the surface water east of the Millsite. Contamination
of the creek also occurs as it flows through contaminated soils and sediments. Prior to Millsite
excavation, seeps emanating from the tailings piles also contributed to Montezuma Creek
contamination.
2.2 Investigation History
Environmental investigations of the MMTS have been conducted at and near OU ffl since the
early 1950s. Investigations performed before 1979 focused primarily on surface-water quality in
Montezuma Creek and to a lesser degree on ground-water quality in the alluvial aquifer. Before
the mill closed in 1960, investigations focused on the effects on surface-water quality in
Montezuma Creek from milling operations, stream overflow, and seepage from tailings ponds
and piles. Those early investigations assessed effects on the surface water and ground water
largely on the basis of uranium and radium-226 concentrations in samples collected upstream and
downstream of the Millsite. As early as 1950, radium levels in Montezuma Creek were known to
be increasing as a result of releases from uranium milling. Between 1960 and 1979, surface-water
samples were occasionally collected from Montezuma Creek to assess site impacts to surface-
water quality. Ground-water sampling was also performed during this period. An environmental
assessment report (Bendix 1980) noted an increase in uranium and radium concentrations in
Montezuma Creek as a result of the facility. This 1980 report also noted an indication of ground-
water contamination downgradient (east) of the Millsite.
Environmental investigations performed between 1979 and October 1992 were more
comprehensive than earlier studies. Routine monitoring of surface water and ground water from
1979 to 1991 is documented in annual environmental monitoring reports [Bendix (1980), Korte
and Thul (1981 to 1984); Korte and Wagner (1985, 1986); Sewell and Spencer (1987); and
DOE/Grand Junction Office MMTS OU III Interim ROD
August 1998 2-1
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Decision Summary Document Number QOOl 1601
DOE (1988a, 1989, 1990a, 1991, 1992)]. More recent efforts have focused on supplementing
monitoring data with information needed to complete ground-water modeling as part of the
remedial investigation for OU ED*. Ongoing activities associated with the site include continued
monitoring .and collection of surface-water and ground-water data to be used in evaluating final
cleanup alternatives.
2.3 Enforcement Activities and Administrative History
The administrative history of OU ffl is intricately linked with the histories of OU I and OU n, the
other components of the MMTS. OU I addresses excavation of mill tailings and other
contaminated materials from the Millsite and containment of these materials in a permanent
repository; OU n addresses the remediation of peripheral properties that are contaminated by
radioactive material from the Millsite. In December 1988, DOE, the U.S. Environmental
Protection Agency (EPA), and the State of Utah (State) entered into a Federal Facilities
Agreement (FFA) (DOE 1988b) pursuant to Section 120 of CERCLA, for the MMTS. A Hazard
Ranking System score was developed that led to the inclusion of MMTS on EPA's National
Priorities List on November 16, 1989.
The Monticello Vicinity Property site was listed on the National Priorities List in 1986 and
consists of 420 contaminated vicinity properties grouped into 8 operable units. Contamination of
these properties occurred when mill tailings from the Millsite were wind blown off the Millsite
or used as fill or other similar purposes. A ROD was signed for the Monticello Vicinity Property
site in 1989. Approximately 414 of the properties have been remediated to date. Contaminated
material from the vicinity properties was placed at the Millsite for later disposal in the repository,
As stated in the FFA, DOE serves as the Federal lead agency and provides the principal staff and
resources to plan, direct, and implement response actions at the MMTS. EPA and the State share
the responsibility for oversight of the MMTS activities performed under the FFA. However, EPA
has ultimate responsibility and authority for program oversight. Oversight by the State is
performed by the Utah Department of Environmental Quality.
In 1990, the FFA parties signed a ROD (DOE 1990b) for the MMTS, which stipulated that
contaminated materials from OUs I and n would be excavated and placed in an on-site
repository; approximately 1,800,000 yd3 of tailings and contaminated soil were identified at that
time. The ROD for MMTS also stipulated that a ROD for OU ffl would be produced when
sufficient data were gathered through a focused remedial investigation/feasibility study and
specified that "the Upper and Lower Montezuma Creek peripheral properties" (which are now
referred to as Upper, Middle, and Lower Montezuma Creek) would be remediated as part of
OU HI. Remediation of OUs I and n is currently being implemented pursuant to the 1990 ROD.
OU I is scheduled for completion, as defined by concurrence on the Millsite Restoration
Remedial Action Report, by October 2001.
OU DI soil and sediment cleanup are being conducted as a non-time critical removal action that
will be completed in the summer of 1999 (DOE 1998a). The selected action involves excavation
of contamination in discrete areas to alternate cleanup levels through the application of
supplemental standards to comply with 40 Code of Federal Regulations (CFR) Part 192
requirements, and implementation of institutional controls (restrictive easements) to ensure that
MMTS OU III Interim ROD DOE/Crand Junction Office
2-2 August 1998
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Document Number QOOI1601 Decision Summary
habitable structures are not built within the OU HI contaminated soil and sediment areas. These
actions reduce risk from exposure to contaminants and remove the continued soil and sediment
source to surface-water and ground-water contamination.
2.4 Highlights of Community Participation
The public participation requirements of CERCLA Section 113(k)(2)(B)(i-v) and Section 117 are
being followed for this interim remedial action. MMTS has a Community Relations Plan that is
updated annually; the 1999 Plan is currently undergoing revision. The community relations
activities include (1) distribution of fact sheets and other written materials, (2) news releases to
the local newspaper, (3) public meetings, (4) display ads announcing the availability of key
documents and meetings, (5) public comment periods, and (6) responsiveness summaries for
Records of Decision.
Copies of all site-specific documents used in developing the interim-action decision were made
available to the public through the Administrative Record for the site. The Administrative Record
is housed at the Monticello City Offices and at the DOE-Grand Junction Office. Draft versions
of the OU in Remedial Investigation and Alternatives Analysis documents were released in
January 1998 (DOE 1998c and DOE 1998d) and the Feasibility Study and Proposed Plan in
March 1998 (DOE 1998e and DOE 1998f). These documents were placed in the reading room
and Administrative Record in March 1998, prior to the start of the public comment period.
Copies of the Proposed Plan (DOE 1998f) for an interim remedial action at OU HI were also
placed in the site Administrative Record and distributed to stakeholders in March 1998. The
notice of availability for all these documents was published in the local Monticello newspaper on
March 18, 1998. A public comment period on the interim remedial action was held from
March 27 to April 27, 1998, and a public meeting was held on April 7, 1998. At this meeting,
representatives from DOE, EPA, and the State answered questions about the site and the
preferred alternative, which has become the selected interim remedial action. A summary of the
meeting and public comments received at that meeting and during the public comment period are
presented in the Responsiveness Summary of this document (Appendix A) for inclusion in the
Administrative Record. The decision for an interim remedial action at this site is based on
information in the Administrative Record.
2.5 Scope and Role of Operable Unit III Surface Water and Ground Water
Within Site Strategy
OU HJ is one of three OUs at the MMTS. A draft remedial investigation and feasibility study
have been completed for OU in. A ROD was signed for OUs I and H which stipulated that
contaminated materials from OUs I and n would be excavated and placed in an on-site
repository. OU ffl surface-water and ground-water quality is expected to be positively affected by
remediation of OUs I and H and by excavation of OU ffl soils and sediments as specified in the
Action Memorandum (DOE 1998a). Because it is not possible to definitively predict the effects
remediation will have on OU ffl, the interim remedial action is designed to (1) prevent the use of
contaminated ground water by implementing institutional controls, (2) remove soluble
contaminants from the ground water and, in turn, surface water, by treating extracted ground
water through dewatering activities, (3) continue to monitor the changing conditions in the
alluvial aquifer and in surface water, and (4) examine the feasibility of a PeRT wall for in-situ
DOE/Crand Junction Office~~" ~" ~~MMTS OU III Interim ROD
August 1998 2-3
-------
Decision Summary Document Number QOO11601
treatment by conducting a pilot-scale treatability study. Treated water (generated by treating
water pumped during Millsite excavation or, if necessary, following Millsite excavation) will
meet Utah Pollutant Discharge Elimination Systems (UPDES) requirements. The interim
remedial action will complement OUI and OU m soil and sediment cleanup activities and will
have no negative effect on these cleanup efforts. The interim remedial action is consistent with
the long-term strategy for surface-water and ground-water cleanup and will not adversely affect
the final remedy for OU m.
MMTS OU m Interim ROD DOE/Crand Junction Office
2-* August 1998
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Document Number Q0011601 Decision Summary
3.0 Summary of Site Characteristics
3.1 Hydrologic Setting
3.1.1 Surface Water
The following discussion is summarized from the OU HI Remedial Investigation report
(DOE 1998c).
The primary surface-water body in the OU in area is Montezuma Creek, which flows west to east
throughout most of the OU IH area. Approximately 2.5 miles east of the Millsite, Montezuma
Creek is joined by a lesser tributary, Vega Creek, at which point stream flow is south through
Montezuma Canyon (Figure 1-1). Other surface-water bodies include seeps and springs,
municipal water-treatment lagoons, Loyd's lake, and various ponds used to water livestock.
Typical flow rates in Montezuma Creek in the OU ffl area are about 1 cubic foot per second.
Flow is generally perennial; however, portions of the creek are seasonally dry some years. Peak
flow of 30 cubic feet per second may occur during spring runoff. Sources to Montezuma Creek
are the in-stream base flow entering the Millsite near Highway 191, run-off from the surrounding
watershed, and any inflow or gain of shallow ground water.
The State of Utah groups surface waters of the State into classes so as to protect against
controllable pollution for the beneficial uses designated within each of those classes
(R317-2-6, U.A.C.). Four broad classes of use are recognized—domestic (1), recreational
(2), aquatic (3), and agricultural (4). Additionally, subclasses are identified within some of these
classes (e.g., 2A, 2B, etc.). Higher standards of water quality apply to lower numbered classes
and to those subclasses having letters earlier in the alphabet.
Montezuma Creek water is not used as a source of potable water; however, it is used as a water
source for livestock. Montezuma Creek is classified in the Utah Administrative Code as follows:
1C—Protected for domestic purposes with prior treatment processes as required by the Utah
Division of Drinking Water.
2B—Protected for secondary contact recreation such as boating, wading, or similar uses.
3 A—Protected for cold water species of game, fish, and other cold water aquatic life,
including the necessary aquatic organisms in their food chain.
A—Protected for agricultural uses including irrigation of crops and stock water.
3.1.2 Ground Water
The hydrologic units associated with OU IH are an upper alluvial aquifer consisting mostly of
Quaternary alluvium and colluvium, an aquitard of Mancos Shale and Dakota Sandstone, and the
underlying Burro Canyon Formation aquifer. Below the Burro Canyon aquifer is the Brushy
Basin Member of the Morrison Formation, which is relatively impermeable to ground-water
DOE/Grand Junction Office MMTS OU HI Interim ROD
August 1998 3-1
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Decision Summary Document Number QOO11601
flow. Ground-water flow in the alluviaJ aquifer is generally to the east, parallel to the axis of
Montezuma Creek. Flow rates of water moving past the eastern edge of the Millsite are
approximately 40 to 50 gallons per minute.
The saturated thickness of the alluvial aquifer ranges from approximately 2 to 25 ft but is
generally less than 15 ft. The alluvial aquifer is recharged by infiltration of precipitation, surface-
water loss from Montezuma Creek, and lateral ground-water flow from upgradient of the
Millsite. Leaking water lines, from the city of Monticello water supply system, are suspected to
recharge the aquifer in the northwest portion of the Millsite. Depths to ground water generally
range from 8 to 15 ft. However, in the northwest area of the Millsite, and in areas of eastern
Upper Montezuma Creek, ground water is present within several feet of ground surface.
As with surface water, the State of Utah also classifies ground-water resources
(R317-6, U.A.C.). The following ground-water designations have been established:
Class IA—Pristine Ground Water
Class IB—Irreplaceable Ground Water
Class 1C—Ecologically Important Ground Water
Class H—Drinking Water Quality Ground Water
Class in—Limited Use Ground Water
Class IV—Saline Ground Water
Class LA ground water has the most stringent water quality standards; Class IV has the least
stringent. The alluvial aquifer is not currently used for drinking water, irrigation, or livestock
watering; because it could be a potential source of drinking water in the future, Utah ground-
water standards classify the alluvial ground water as Class EL
The Mancos Shale and Dakota Sandstone act as aquitards between the alluvial aquifer and the
underlying Burro Canyon aquifer in the Millsite area. Ground-water flow within these aquitards
is minimal and predominately vertically downward.
The Dakota Sandstone has been eroded away and the alluvial aquifer is in direct contact with the
Burro Canyon Formation in the Montezuma Creek Valley approximately 4,000 ft east of the
Millsite. Ground water discharges from the Burro Canyon aquifer to the alluvial aquifer and
Montezuma Creek within the valley where Dakota Sandstone is absent. Discharge also occurs
from cliff outcrops along the margin of Montezuma Canyon below the Vega Creek confluence.
The primary recharge zone for the Burro Canyon aquifer is in outcrop areas on the east side of
the Abajo Mountains.
The thickness of the Burro Canyon Formation is 114 ft approximately 600 ft east of the Millsite.
The depth from ground surface to the potentiometric surface at this location is about 33 ft. The
potentiometric surface of the Burro Canyon aquifer is above ground surface in the easternmost
portion of Upper Montezuma Creek, where the farthest downgradient monitoring wells are
located.
MMTS OU HI Interim ROD DOE/Grand Junction Office
3-2 August 1998
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Document Number QOO11601 Decision Summary
The city of Monticello occasionally withdraws Burro Canyon ground water from city-owned
wells for non-potable use only. Burro Canyon ground water has also been used by private
households. Most of the wells are old and have not been used for several years; however, some
wells have been used during the last 10 years for domestic irrigation and for watering livestock.
3.2 Operable Unit III Source Areas
Based on previous investigations, including the Remedial Investigation for OUs I and n
(DOE 1990c), the primary source of ground-water contamination associated with OU ffl are the
mill tailings piles on the Millsite (OU I). To a lesser extent, contaminated soils and sediments in
the floodplain of Montezuma Creek could serve as a secondary source of ground-water
contamination, but the results from surface-water sampling indicate this is not a significant
source.
3.3 Nature and Extent of Contamination
Monitoring data indicate that ground-water contamination is restricted to the alluvial aquifer; the
contaminant plume follows Montezuma Creek and extends approximately one mile east of the
Millsite. Sediment contamination extends further down Montezuma Creek, past the confluence
with Vega Creek. Monitoring data also indicate that surface water in Montezuma Creek is
contaminated throughout the OU HI area. Removal of the major source of ground-water
contamination (the tailings piles), including associated dewatering and treatment, through
remediation of OU I is expected to have a major positive effect on the quality of OU HI ground
water and surface water. The full effect of the OU I remediation on ground-water and surface-
water quality will not be known for some time. Implementing the proposed interim remedial
action ensures protectiveness of human health and the environment until sufficient information is
available to make a final remedial action decision. Contaminated media are discussed further
below.
3.3.1 Surface-Water Contamination
Surface-water samples collected from seeps and springs on the Millsite and from Montezuma
Creek on and downstream of the Millsite contain elevated concentrations (relative to
background) of various metals, uranium decay-series radionuclides, sulfate and nitrate. The
highest concentrations were detected in samples collected from tailings pile seeps on the Millsite.
One or more samples collected from the seeps contained arsenic, copper, radium-226, selenium,
and gross alpha that exceeded Utah surface-water quality standards. Among samples collected
from Montezuma Creek on the Millsite, only selenium and gross alpha were detected in
concentrations above a Utah surface-water standard.
Downstream of the Millsite, concentrations of arsenic, copper, manganese, molybdenum,
selenium, uranium, vanadium, and gross alpha exceed background concentrations. Contaminant
concentrations generally decrease with distance from the Millsite and generally reach background
concentrations in the easternmost section of OU HI. Copper and selenium concentrations
sporadically exceeded Utah standards in samples collected at different monitoring locations
throughout the remedial investigation. Only uranium, gross alpha activity, and manganese were
detected above background levels throughout OU in. Elevated manganese concentrations in the
DOE/Grend Junction Office MMTS OU III Interim ROD
August 1998 3-3
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Decision Summary
Document Number Q0011601
surface water at distances greater than 4,000 ft from the Millsite are attributed to discharge of
Burro Canyon ground water which is naturally high in manganese. The Utah standard for gross
alpha activity was exceeded consistently throughout the remedial investigation at all downstream
sampling locations. The high gross alpha activity is attributed to uranium in surface water. With
the exception of gross alpha, all contaminants in OU ffl downgradient from the Millsite are
reduced to levels suitable for any purpose relative to Utah surface-water quality standards.
Table 3.3.1-1 compares surface-water sample results with the applicable standards for all
contaminants that were detected above a standard in one or more sample collected since
November 1992. The Millsite sample concentrations include samples collected from the tailings
pile seeps. The UCL^j values represent the 95 percent upper confidence limit of the mean
concentration computed from all samples collected from each Millsite and downstream surface-
water monitoring location, respectively, between November 1992 and April 1996.
Table 3.3.1-1 Contaminants that Exceed Utah Surface-Water Standards
Analyte
Arsenic (pg/L)'
Copper (pg/L)
Selenium (ug/L)
Radium-226 (pCI/L)'
Gross Alpha (pCl/L)
Millsite
Concentrations
ucu"
179
11.7
65
4.7
554
Downstream
Concentrations'*
ucu
3.5
3.4
4.5
0.7
145
Domestic*
Standard
(Class 1C)
50
—
10
5
15
Agricultural*
Standard
(Class 4)
100
200
50
—
15
Aquatic Wildlife*
Standard
(Class 3A)
190
39"
5.0
—
—
* pg/L = microgram per liter; pCi/L = pico curies per liter
"UCL,,, = 95 percent upper confidence limit of mean concentration computed from all samples collected from each
Millsite and downstream monitoring location.
"The aquatic wildlife standard for copper was adjusted for hardness
"Concentrations reported are for Upper Montezuma Creek (i.e., the reach from the Millsite to approximately 6,500 ft
downstream)
•State of Utah surface-water class; see discussion in Section 3.1.1.
Surface-water data obtained since November 1992 (DOE 1998c, e) indicate that concentrations
of several contaminants decreased at some locations in Montezuma Creek after flow from a
tailings pile seep was intercepted between October 1994 and April 1995. The monitoring data for
the periods prior to and after ditch construction do not indicate significant changes in
concentrations during the respective periods suggesting quasi steady-state conditions have been
achieved with respect to other sources. However, some contaminants indicate a trend of slightly
decreasing concentrations. High-flow during the spring has a variable effect on concentrations;
both a decrease and an increase in concentrations are seen.
33.2 Ground-Water Contamination
Ground-water samples from wells completed in the alluvial aquifer contained elevated
concentrations (relative to background) of various metals, uranium decay-series radionuclides,
sulfate, and nitrate. The highest concentrations were detected in samples collected from wells on
the Millsite. Arsenic, manganese, molybdenum, selenium, vanadium, uranium, and lead-210
have migrated through the alluvial aquifer off the Millsite and have contaminated the alluvial
ground water on private property east of the Millsite (Figure 3.3.2-1). Selenium, nitrate, and
MMTS OU Ul Interim ROD
DOE/Crand Junction Office
August 1998
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Doc union I Number QOOII600
Decision Summary
Municipal
Water
Treatment
Lagoons
MIDDLE
MONTEZUMA CREEK
FKNJNDARlt V "I nl'I'IK. Mllil'll. Mil'
I OWI R MONK /I IMA >'l'l I I
Mi'lNII ?IIMA i !•!
REPOSITORY , i;
LI A|i .'III. MOI fbliLNUM. SI.II'IIIUM.
kAl.l.iM 27'.'.. ANlJ MANCANLSE
UK'ANIIIM
nrnU c<>n<
.}f uultd tOVr
&nfri|tlinq ev
LOWER
MONTEZUMA CREEK
I
I
HOHTEZUH&! CREEK'
I
Figure 332-1 OUI1I Ground-Water Plume
DOE/Gund lunclioit OITia
/ulr IWI
J-S,
MMTS OU III Irucrim ROD
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Document Number O0011601
Decision Summary
radium-226/228 were detected in concentrations above Federal/State regulatory standards on the
Millsite only. Molybdenum, selenium, and uranium were detected in concentrations above
regulatory standards both on the Millsite and downgradient of the Millsite. The downgradient
extent of uranium, which has migrated the farthest in the alluvial aquifer, is approximately
5,000 ft from the eastern Millsite boundary. The volume of uranium-contaminated ground water
greater than the Uranium Mill Tailings Radiation Control Act (UMTRCA) ground-water
standard of 30 pCi/L (or 44 |jg/L) is estimated to be 97,000,000 gallons. Contaminants that were
detected in excess of various ground-water regulatory standards in one or more samples collected
during the remedial investigation are listed in Table 3.3.2-1. The UCL^j values represent the
95 percent upper confidence limit of the mean concentration computed from all samples
collected from each Millsite and dpwnstream monitoring well, respectively, between
November 1992 and April 1996.
Table 3.3.2-1 Contaminant Concentrations in Ground Water that Exceed Regulatory Standards
Analyte
Arsenic (ug/L)*
Molybdenum (ug/L)
Nitrate as N (mg/L)6
Selenium (ug/L)
Uranium (ug/L)
Radium-226 (pCi/L)b
Gross alpha (pCi/L)c
Gross Beta (pCi/L)*
Millsite
Concentration
UCLV
59
4,710
20.3
25.7
2.370
3.5
447 (2.090)"
695
Downgradient
Concentration
UCL^
11.3
86.1
1.8
13.7
837
0.5
101 (588)"
206
Federal
SDWA
Standards
50
—
10
50
—
5.0
15
4 mrem/year
Federal
UMTRCA
Standards
50
100
10
10
44'
5.0
15
—
Utah Ground-
Water
Standards,
Table 1
50
—
10
50
—
5.0
15
4 mrem/year
= 95 percent upper confidence limit of mean concentration computed from all samples collected from each
Millsite and downstream monitoring location.
"ug/L x microgram per liter pCi/L • pico Curies per liter; mrem = millirem; mg/L = milligrams per liter
CAII3 standards for gross alpha include radium-226 but exclude radon and uranium.
"Total gross alpha minus uranium activity; number in parenthesis is total gross alpha activity.
'Gross beta concentrations in pCi/L are used qualitatively as indicators of contamination. Existing data do not permit
accurate conversions of these data.
'Actual standard is 30 pCi/L Where secular equilibrium exists, this equates to 44 ug/L
Key: SDWA = Safe Drinking Water Act; UMTRCA = Uranium Mill Tailings Radiation Control Act; N = nitrogen
Contaminant concentrations in ground water generally decrease with distance from the Millsite.
Just east of the Millsite, concentration contours change direction from being predominantly east-
west (parallel to ground-water flow on the Millsite) to being northwest to southeast. The
concentration contours immediately east of the Millsite are consistent with the change in ground-
water flow direction, which generally follows the alignment of the historic natural channel of
Montezuma Creek in that area.
The ground-water data collected since November 1992 during the remedial investigation
(DOE 1998c) do not indicate significant changes in concentration over time, which suggests that
the plumes had generally reached near steady-state conditions with respect to contaminant
DOE/Grand Junction Office
August 1998
MMTS OU HI Interim ROD
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Decision Summary
Document Number Q0011601
sources on the Millsite prior to OU I remediation. At some monitoring locations the
concentrations of some contaminants are consistently lower during seasonal high-flow periods
(high water levels and greater dilution) relative to low-flow periods. At other locations, some
contaminants exhibit the opposite relationship between flow conditions and concentrations.
Burro Canyon ground water is not contaminated. The Mancos Shale and Dakota Sandstone
appear to be adequate aquitards in areas where the water level is the alluvial aquifer is greater
than that in the Burro Canyon aquifer (downward flow potential). East of the Millsite, where the
alluvial aquifer directly overlies the Burro Canyon aquifer, there is upward flow from the Burro
Canyon aquifer to the alluvial aquifer which prevents contaminant movement into the Burro
Canyon aquifer. In these eastern areas, the alluvial aquifer ground-water quality is strongly
affected by influx from the Burro Canyon aquifer.
3.4 Conceptual Model of Contaminant Transport
Table 3.4-1 summarizes the potential human-health exposure pathways for all of OU ffl.
Although the pathway of most concern for ground water is ingestion as a drinking water source,
interaction of ground water with other media (e.g., by irrigation, discharge to surface water) can
have an effect on risk posed by other pathways. A secondary pathway of exposure, ingestion of
beef or game that ingest contaminated vegetation, water, and soil was also evaluated.
Table 3.4-1 Human Exposure Pathway Analysis Summary
Exposure
Medium
Air
Soil and sediment
Surface water
Ground water
Beef/game
tissues
Potential Routes of
Exposure
Inhalation
Ingestion. inhalation, direct
radiation exposure (gamma)
Ingestion (incidental)
Ingestion (as a drinking
water source)
Ingestion
Potential Receptors
Agricultural workers, recreational
users, future residents
Agricultural workers, recreational
users, future residents
Agricultural workers, recreational
users, future residents
Future residents
Agricultural workers, recreational
users, future residents
Comments
Particulate inhalation
Incidental ingestion,
inhalation of dust
Dermal exposure is
insignificant when
compared to ingestion.
Currently not a complete
pathway; this is an
improbable, but
potentially complete
future exposure
pathway.
Beef/game are exposed
to contaminated
vegetation, surface
water, and soil.
Figure 3.4—1 depicts the ecological conceptual site model. This model considered effects of
contaminant uptakes in vegetation in contact with contaminated surface water or ground water
and subsequent ingestion of this vegetation as a major food source. The effects of ingesting
contaminated prey (e.g., swallows, flying insects) were also evaluated as well as the effects from
the use of contaminated surface water as a primary source of water for ingestion. The likelihood
of exposure from any of the potential pathways is discussed in Section 4.0.
MMTS OU m Interim ROD
DOE/Gnuid Junction Office
August 1998
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F/g
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Document Number Q0011601 Decision Summary
4.0 Summary of Site Risks
This section presents a semiquantitative description of the potential risks associated with surface
water and ground water at OU ffl.
4.1 Human-Health Risks
The Baseline Human Health Risk Assessment for OU in (DOE 1998g) indicated that the most
significant exposures could occur from the potential future ingestion of contaminated ground
water. This ground water is currently not used for domestic purposes and its lack of palatability
makes its future use unlikely, though this possibility was evaluated. If the alluvial ground water
was used as a source of drinking water, significant long-term risks would occur from both
carcinogens (contaminants that cause cancer) and noncarcinogens (contaminants that cause other
negative health effects except cancer). Risks were calculated for both a reasonable maximum
exposure (RME; above average, but within the range of possible values) and a central tendency
(CT) exposure (average or best-estimated).
For carcinogens, using the RME scenario, approximately 4 in 10,000 people could develop
cancer from drinking the alluvial ground water over a lifetime (assumed to be 70 years). This is
four times greater than the upper end of a risk range used by EPA to evaluate risks from
carcinogens. Using the CT scenario, risks of developing cancer are 9 in 100,000 people; this is
within EPA's acceptable risk range. For noncarcinogenic contaminants, the RME risk would be
10 times greater than the value defined as acceptable by EPA; CT risks for noncarcinogens
would be 5 times EPA's acceptable value. Risks calculated for the CT scenario from carcinogens
related to OU in are 10 to 14 times those associated with background contaminant
concentrations. Risks associated with noncarcinogens are 42 times background. The
contaminants that pose the greatest amount of risk include uranium, vanadium, lead-210, and
arsenic. More details on the actual numerical values associated with site contaminants and their
interpretation was presented in the Baseline Human Health Risk Assessment.
The most likely future use of the Millsite is for recreational purposes. The community has a
strong interest in expanding its existing nine-hole golf course to an eighteen hole golf course that
would encompass the Millsite. It is assumed that future residential development will occur east
of the Millsite, and these future residents are the most likely receptors. Risks from ingestion of
surface water were evaluated along with other pathways under a recreational/agricultural use
scenario. This scenario assumes Montezuma Creek could be used for hunting, hiking, and other
similar activities and that water would only be infrequently ingested in small amounts. Exposure
associated with ingestion of surface water did not produce significant risk. Risks from eating
game or beef that ingest contaminated soil, vegetation, and water were estimated by DOE to be
negligible; contaminant levels in animals were measured by EPA and found to be safe.
4.2 Environmental Risk
Vegetation and Wildlife. DOE conducted an ecological risk assessment (DOE 1998h) to
evaluate potential risks to the environment associated with exposure to contaminants of concern
within OU ffl. This assessment determined that surface-water ingestion is not a risk-driving
pathway for environmental receptors and contaminated ground water is of negligible concern
DOE/Crand Junction Office MMTS OU ID Interim ROD
August 1998 4-1
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Decision Summary Document Number Q0011601
because a direct exposure pathway does not exist between the receptors and ground water. The
only receptors that potentially could be exposed to ground water directly are plants with roots
deep enough to tap into the alluvial aquifer. Animals or aquatic organisms can be indirectly
exposed to jround water by ingesting the plants that take up contaminated ground water or by
ingesting or directly contacting certain surface waters that receive ground-water discharge.
Results of the risk assessment indicate that these potential exposures to contaminated ground
water do not pose an excess risk to environmental receptors.
Air quality. Air quality is not an issue with this site, except for any dust generated during
remediation actions. Dust suppression measures will be taken during remediation to prevent dust
generation.
Surface Water, Ground Water, and Wetlands. Surface-water and ground-water contamination
are the focus of this interim remedial action. Both surface-water and ground-water quality are
expected to improve through implementation of the interim remedial action though the action
affects ground water directly. Sediments in the Montezuma Creek floodplain and wetland areas
are also contaminated; these are being addressed through a separate removal action.
Scenic, Historic, and Cultural Resources. Scenic resources within the area include rural and
pastoral views of the plains and mountains and picturesque views of canyon walls within the
Montezuma Creek valley. Some of these views may be temporarily disturbed during
construction, but effects will not be permanent. Historic and cultural resource surveys conducted
within the OU IK area revealed one historic site on the floodplain of Montezuma Creek and
numerous prehistoric sites along the canyon walls of Upper, Middle, and Lower Montezuma
Creek. The historic site is a homestead; the prehistoric sites are rock-shelters and open lithic
scatters. The interim remedial action will not have an adverse effect on these sites.
4.3 Need for the Interim Remedial Action
The primary objectives of the interim remedial action are to prevent exposure to contaminated
ground water and to reduce contaminant levels in ground water and surface water. The interim
remedial action is needed primarily to achieve risk reduction in the near term by removing
contamination (through dewatering and treatment) that is being disturbed through remediation of
OUs I and EL This action will prevent further environmental degradation while a long-term
solution for OU IH can be evaluated. Institutional controls will prevent exposure to contaminated
ground water while the near-term interim measures are being implemented. Monitoring data will
provide information needed to develop a long-term solution as well as provide an assurance that
any unexpected contaminant releases can be detected. PeRT wall treatability studies will assist in
determining the viability of that technology as a longer term remedial alternative and may also
serve as an enhancement to the overall interim remedial action.
MMTS OU ffl Interim ROD DOE/Onuid Junction Office
4-2 August 1998
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Document Number Q0011601 Decision Summary
5.0 Description and Comparison of Interim Remedial Action
Alternatives
This section-provides a brief discussion of the alternatives being considered for interim remedial
action of OU in surface water and ground water. The Feasibility Study for OU in (DOE 1998f)
contains an evaluation for a range of remedial alternatives that are being considered for the final
remedial action at the site. The alternatives include a range of options for institutional controls
(restrictive easements, deed annotation, administrative controls through the State) and ground-
water extraction and treatment technologies (such as conventional water treatment and the PeRT
wall). However, only two actions were considered to address the interim remedial action goals of
exposure prevention and contaminant reduction.
5.1 The No-Action Alternative (Alternative 1)
Consideration of the no-action alternative is required by CERCLA. The no-action alternative for
OU ID surface water and ground water includes long-term monitoring. Monitoring is currently
being conducted on a semiannual basis; this monitoring frequency would continue. Up to
24 wells are in the monitoring program, including 3 upgradient wells. Eight surface-water
locations are sampled downstream of the Millsite, including 1 upstream location. All samples are
analyzed for metal and radiologic COCs. Refer to the OU IE Annual Monitoring Program
(DOE 1997) for more details. The present plan for monitoring will be evaluated to determine if
additional sampling locations are necessary and if the present frequency of sampling events is
adequate to assess changing Millsite conditions and to support selection of the final remedy.
5.2 Institutional Controls, Millsite Dewatering and Treatment, Monitoring,
and PeRT Wall Installation and Evaluation (Alternative 2)
Institutional controls prohibiting the use of water rights within the area of contaminated ground
water will be implemented through the State Engineer. A moratorium on drilling of water wells
into the contaminated aquifer will be put in place. Surface-water and ground-water monitoring
(as described above) will be used initially to assess the effects of Millsite cleanup activities on
the concentration of contaminants in the ground water and Montezuma Creek and be used in
subsequent ground-water modeling, if necessary. Additional wells will be installed and
monitored to support evaluation of the PeRT wall treatability study.
In conjunction with the cleanup of OU I, ground-water dewatering and treatment will continue
and also contribute to the remediation of OU BX Currently, water is being treated with a
combination of chemical and physical processes. Chemicals are added to precipitate
contaminants as particulates, which are filtered out using microfiltration and reverse osmosis.
Secondary wastes are disposed in the onsite repository. Treated water is discharged to
Montezuma Creek in accordance with UPDES requirements. Current treatment rates range from
50 to 200 gallons per minute. Following remediation of OU I, water treatment may continue, if
necessary. Ground-water and surface-water monitoring will be conducted to determine the
effectiveness of the PeRT wall and ground-water treatment in restoring the aquifer to natural
conditions. A five-year review of the data will be conducted to determine the effectiveness of the
interim remedial action.
DOE/Crand Junction Office MMTS OU HI Interim ROD
August 1998 5_l
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Decision Summary Document Number QOO11601
conditions. A five-year review of the data will be conducted to determine the effectiveness of the
interim remedial action.
In-situ treatment of ground water will be evaluated with a PeRT wall installed across the
contaminant plume. The selected location for the PeRT wall is in the area east of Pond 3 (the
collection pond for the water treatment plant located just east of the Millsite). The PeRT wall
will be oriented perpendicular to the direction of ground-water flow; contaminants are removed
as ground water flows through the wall, thereby preventing additional downgradient movement
of contamination. The exact location of a PeRT wall is not yet finalized and much of the site-
specific information needed has not been determined. Laboratory treatability studies are ongoing
and field treatability studies will be completed to determine the optimum configuration of the
PeRT wall.
The PeRT wall will be a ruhnel-and-gate system that consists of an impermeable barrier (such as
a slurry wall or sheet piles) to direct ground-water flow through a gate made of reactive material.
The size of the wall selected for OU III will be optimized for site-specific geologic and
hydrologic conditions, operation and maintenance (O&M) requirements, and economic
considerations. Before emplacement of the PeRT wall, additional treatability studies will be
conducted with various reactive materials to determine the most suitable material for site-specific
conditions.
It is anticipated that the PeRT wall will operate for a minimum of 5 years, unless preliminary
monitoring results indicate problems with the system. The wall may become part of the final
proposed remedial action if monitoring demonstrates it is performing successfully. When the
wall is removed at the end of its operation, the contaminated reactive materials will be disposed
in an appropriate disposal facility.
Preliminary treatability study results for the PeRT wall are favorable. Using site-specific waters,
materials tested have shown to be effective at removing contaminants of concern, especially
uranium. As with many processes, some uncertainty regarding performance exists in scaling up
from laboratory to full-scale implementation. Field installation of the PeRT wall is expected to
begin in the spring of 1999 and be completed by the end of the year. Monitoring is ongoing.
Additional wells will be installed in conjunction with PeRT wall construction to assess its
performance. An annual review of the data collected will be conducted to determine the
effectiveness of the PeRT wall.
This alternative complies with applicable or relevant and appropriate requirements (ARARs) to
the maximum extent practicable, given the limited nature of the interim remedial action. All data
collection activities (including new well installation, water sampling, etc.) will take place in
accordance with established protocols and procedures, including those regarding disposal of
investigation-derived waste (GJO 1997 and MACTEC 1996). Treatment and discharge of water
through dewatering activities will meet UPDES requirements. The interim remedial action will
not meet federal or state drinking- or surface-water standards, but because the goal of the interim
remedial action is simply contaminant reduction in ground water, these specific standards are not
applicable to the proposed action.
MMTS OU 111 Interim ROD DOE/Grand Junction Office
5-2 August J998
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Document Number Q0011601
Decision Summary
5.3 Summary of Comparative Analysis.of Alternatives
CERCLA requires that cleanup alternatives for a site be evaluated against nine criteria. These
criteria and a comparative analysis are provided in Table 5.3-1 and discussed in the following
sections.
Table 5.3-1 Comparison of the Alternatives Against the Nine CERCLA Criteria
Criteria
Overall Protection of Human
Health and the Environment
Compliance with applicable or
relevant and appropriate
requirements
Short-term Effectiveness
Long-term Effectiveness
Reduction of Toxicity, Mobility
and Volume through Treatment
Implementability
Cost
State Acceptance
Community Acceptance
Alternative 1
No Action
Potential future risks posed.
Allows unrestricted use of
contaminated ground water.
Complies with ARARs
applicable to interim
remedial action.
None; current conditions
would exist.
None, except by natural
attenuation.
None, except through
natural processes.
Implementable— represents
current situation.
Capital $ 39,000
Annual O&M 161,000
Not acceptable
Less acceptable
Alternative 2
PeRT Wall, Monitoring, Dewatering and
Treatment, and Institutional Controls
Assumes protectiveness through use of institutional
controls. Ground-water treatment will reduce
contaminant mass.
Complies with ARARs applicable to interim
remedial action. Will comply with construction and
operational requirements. Will at least contribute to.
or possibly meet, water-quality standards.
Effective at meeting goal of limiting use of
contaminated ground water. Expected to reduce
mass of contaminants with ground-water treatment.
Interim remedial actions are not required to provide
long-term solutions although it is believed that this
action will significantly contribute toward meeting
long-term goals. Institutional controls provide long-
term restrictions on ground-water use.
Dewatering with treatment will reduce mass of
contaminants on site and downgradient of barrier:
PeRT wall may reduce mobility of contaminants.
Implementable — uses standard construction
practices and available expertise.
Capital $2,313,000
Annual O&M 414,000
Acceptable
Acceptable
5.3.1 Threshold Criteria
Overall Protection of Human Health and the Environment
Alternative 2 is anticipated to be protective of human health and the environment by preventing
exposure to contaminated ground water through the use of institutional controls, which will
(1) lock out existing water rights, if any, and (2) place a moratorium on new water well drilling
into the contaminated alluvial aquifer. Treatment of ground water collected during excavation
dewatering activities will remove contaminants from the aquifer. Discharge of treated water to
Montezuma Creek will comply with UPDES requirements. The pilot-scale treatability study of
the PeRT wall will evaluate its effectiveness in reducing contaminant levels downgradient of the
Millsite. The PeRT wall is designed to act as a "filter" to retain contaminants at the wall and
release clean water downgradient.
DOE/Grand Junction Office
August 1998
MMTS OU ID Interim ROD
5-3
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Decision Summary Document Number QOQ11601
Alternative 1 could lead to potential future risks associated with use of contaminated ground
water. No restrictions would be placed on use of ground water. Wells could be drilled into the
alluvial aquifer and used for domestic purposes, resulting in unacceptable risks to users.
Compliance with Applicable or Relevant and Appropriate Requirements
Background
Section 121(d)(l) of CERCLA, as amended by the Superfund Amendments and Reauthorization
Act of 1986 (SARA), requires that the interim remedial action proposed for OU in must attain, to
the extent practical under the selected interim remedial action, a degree of cleanup that ensures
protection of human health and the environment. In addition, remedial actions that leave any
hazardous substances, pollutants, or contaminants on site must, upon completion, meet a level or
standard that at least attains legally applicable or relevant and appropriate standards,
requirements, limitation, or criteria that are ARARs under the circumstances of the release.
ARARs include Federal standards, requirements, criteria, and limitations and any promulgated
standards, requirements, criteria, or limitations under the State environmental or facility siting
regulations that are more stringent than Federal standards. In addition, the State ARARs include
all promulgated standards and rules associated with delegated State environmental programs and
those State regulations with no corresponding Federal regulations.
Applicable requirements are those cleanup standards, standards of control, and other substantive
environmental protection requirements, criteria, or limitations promulgated under Federal or
State law that specifically address the hazardous substances, pollutants, or contaminants,
remedial action, location, or other circumstances at the OU in site. Relevant and appropriate
requirements are cleanup standards, standards of control, and other substantive environmental
protection requirements, criteria, or limitations promulgated under Federal or State law that,
. while not applicable to the hazardous remedial action site, address problems or situations
sufficiently similar that their use is well-suited to the site.
The criteria for evaluating which requirements are applicable or relevant and appropriate differ
depending on whether the requirement is chemical-, action-, or location-specific. According to
the NCP, chemical-specific ARARs are usually health- or risk-based numerical values that
establish the acceptable amount or concentration of a chemical that may remain in, or be
discharged to, the ambient environment. Action-specific ARARs are usually technology- or
activity-based requirements or limitations on actions taken with respect to hazardous wastes, or
requirements to conduct certain actions to address particular circumstances at the site. Location-
specific ARARs generally are restrictions placed on the concentration of hazardous substances or
the planned activities solely because they are in special locations. Examples of special locations
include floodplains, wetlands, historic places, and sensitive ecosystems or habitats.
Comparative Analysis
Alternative 2 for OU ffl will meet the ARARs that are applicable or relevant and appropriate to
this interim remedial action. Federal ARARS that potentially apply to the interim remedial action
are summarized in Table 5.3.1-1; State ARARs are summarized in Table 5.3.1-2. The OU m
MMTS OU ID Interim ROD OOE/Crand Junction Office
5-« August 1998
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II
ii
TaWe 5.3. /-/ Federal ARARs for OU III Surface Water and Ground Water
o
8
o
§'
Standard, Requirement,
Criterion, or Limitation
Safe Drinking Water Act
National Primary and
Secondary Drinking Water
Standards
Clean Water Act
Water Quality Criteria
National Pollutant
Discharge Elimination
System
Dredge or Fill
Requirements
(Section 404)
Clean Air Act
National Primary and
Secondary Ambient Air
Quality Standards
Citation
42 USC 300(g)
40 CFR Part 141
40 CFR Part 143
33 USC
1251-1376
40 CFR Part 131
•Quality Criteria
for Water
40 CFR Parts
122 through 125
40 CFR Parts
230 and 231
33 CFR Part 323
40 CFR Part 404
42 USC
7401-7462
40 CFR Part 50
Description
Establishes health-based
standards for public water
systems (maximum contaminant
levels (MCLsJ).
Criteria for states to set water
quality standards on the basis of
toxicity to aquatic organisms
and human health.
Establishes standards for
discharges of pollutants Into
waterways and through the use
of underground injection wells.
Regulates the discharge of
dredged or fill material into
navigable waters and manages
wetland areas.
Establishes standards for
ambient air quality to protect
public health and welfare.
Status
Not applicable as a goal for
the interim action.
Not applicable as a goal of
the interim action.
Applicable through the
State.
Applicable as location- and
action-specific requirement.
Applicable through the
State of Utah standards as
a chemical-, location-, and
action-specific requirement.
Comment
Because the quality of the alluvial
aquifer could allow it to be used as a
drinking water aquifer, the MCLs
may apply as final cleanup
standards. However, the interim
action alone may not achieve these
standards.
Addresses Montezuma Creek
contamination. May not be
achievable through the interim action
alone.
A point source effluent discharge into
Montezuma Creek will be used.
Potential storm-water discharges into
Montezuma Creek must be
controlled.
Dredged or fill material requirements
applicable through the State of Utah
standards. EPA has jurisdiction over
wetlands at CERCLA sites in the
State but no significant effects to
wetlands are anticipated.
Seeks to protect and enhance the
quality of the nation's air resources.
f
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sr
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3
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Table 5.3.1-1 Federal ARARs for OU III Surface Water and Ground Water (continued)
O
c
c
Standard, Requirement,
Criterion, or Limitation
Citation
Description
Status
Comment
Resource Conservation and
Recovery Act (RCRA)
42 USC 6901 Regulates the generation,
40 CFR Parts treatment, storage, and disposal
260-279 of hazardous waste.
Applicable through the
State of Utah Standards as.
a chemical-, location-, and
action-specific requirement.
Hazardous waste Is not known to'
exist within OU III. However, these
regulations will apply If hazardous
waste Is generated during installation
of the PeRT wall.
Uranium Mill Tailings
Radiation Control Act
(UMTRCA)
42 USC 2022,
42 USC
7901-7942
40 CFR Part 192
Establishes health-based
ground water remediation
standards for inactive uranium
processing sites.
Not appropriate as a goal of
the Interim action.
The goals of the interim remedial
action are contaminant reduction and
prevention of exposure. These
ground-water standards may or may
not be achieved.
Floodplaln/Wetlands
Environmental Review
40 CFR Part 6,
Appendix M
Establishes agency policy and
guidance for carrying out the
provisions of Executive Orders
11988, "Floodplain
Management," and 11990,
•Protection of Wetlands."
Applicable as a location-
and action-specific
requirement.
Remediation actions could affect site
floodplains and wetlands and will
comply with requirements of the
Monticello Wetlands Master Plan.
i
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p
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Tabte 5.3.1-2 State ARARs for OU III Surface Water and Ground Water
Department/Division
Subject
Statute
Rule
Comments
I
o
Department of
Environmental Quality,
Division of Drinking Water
Safe Drinking Water Rules
Title 19. Chapter 4.
Utah Code
Annotated (U.C.A.)
R309, Utah The goals of the Interim action are contaminant
Administrative reduction In and prevention of exposure to
Code (U.A.C.) contaminated ground water. These standards
may or may not be met by the Interim action
alone.
Department of
Environmental Quality,
Division of Water Quality
Standards for Quality for
Waters of the State
Ground Water Quality
Protection
Utah Pollutant Discharge
Elimination System
Title 19, Chapters,
U.C.A.
Title 19, Chapters,
U.C.A.
Title 19, Chapter 5,
U.C.A.
R317-2, U.A.C. The goals of the Interim action are contaminant
reduction In and prevention of exposure to
contaminated ground water. These standards
may or may not be met by the interim action
alone.
R317-6, U.A.C. The goals of the interim action are contaminant
reduction in and prevention of exposure to
contaminated ground water. These standards
may or may not be met by the interim action
alone.
R317-8, U.A.C. Applicable requirement. Discharge Into
Montezuma Creek will comply with the
requirement of the permit. Potential storm-water
runoff Into Montezuma Creek will be controlled.
Department of
Environmental Quality,
Division of Air Quality
Utah Air Conservation Rules
Title 19, Chapter 2,
U.C.A.
R307-1 and This is the State-Implemented National Primary
R307-12, and Secondary Ambient Air Quality Standards
U.A.C. program. These rules are applicable through the
State of Utah standards. Mltigatlve and
restrictive measures such as dust suppressants
and reduced speeds on access roads will be
used to limit dust emissions and meet fugutive
dust requirements.
o
n
1'
YO
•Ij D
Department of
Environmental Quality,
Division of Radiation Control
Radioactive Material
Management
Title 19, Chapter 3,
U.C.A.
R313-12,
R313-15-301,
R313-19
through
R313-22, and
R313-25-18
through
R313-25-22,
U.A.C.
These provisions address the safe
management, including disposal, of radioactive
material. Installation of the PeRT wall will
comply with these applicable state
requirements.
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1 2
2
Table 5.3.1-2 State ARARs for OU III Surface Water and Ground Water (continued)
o
Department/Division
Subject
Statute
Rule
Comments
Department of
Environmental Quality,
Division of Solid and
Hazardous Waste
Hazardous Waste
Management Rules
(RCRA Subpart C)
Title 19, Chapters,
ParM.U.CA
R315, U.A.C. These rules are applicable requirements through
the State of Utah standards. Hazardous waste
may be generated during Installation or removal
of the PeRT wall. Compliance with these
requirements will be attained. Also, R315-101,
Cleanup Action and Risk-Based Closure
Standards, is of importance to the interim
remedial action because it establishes
requirements to support risk-based cleanup at
sites where remediation of hazardous
constituents to background levels will not be
achieved.
Department of Natural
Resources, Division of
Water Rights
Well-drilling standards
(standards for drilling and
abandonment of wells)
73-3-25(2)(b), R655-4. U.A.C. Includes such requirements as performance
U.C.A. standards for casing Joints and requirements for
abandoning a well. Also included are water right
Issues associated with consumptive use. This
law Is applicable to all drilling anticipated and is
an applicable requirement.
s
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53
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Document Number Q0011601 Decision Summary
Feasibility Study identified Federal and State ARARs that apply to the final remedial alternative.
Those requirements are more extensive than requirements for the interim remedial action because
of differences in goals and scope. Because the goal of the interim remedial action is to prevent
the use of contaminated ground water, reduce contaminant levels in the ground water and surface
water, and to evaluate an innovative ground-water treatment technology, restoration of the
contaminated aquifer to drinking-water standards is outside the scope of this interim remedial
action. However, the interim remedial action should have a significant positive effect toward
meeting these standards. Aquifer restoration will be addressed during selection of the final
remedy for all of OU Ed. For this reason, regulations that address restoration of contaminated
ground water are not ARARs for this interim remedial action. Those rules and regulations
include maximum contaminant levels, the Utah ground-water quality standards, and the Safe
Drinking Water Act. Mass contaminant reduction achieved by this interim remedial action will
contribute to meeting ARARs for the final remedy.
Because Alternative 1 involves no action, and because the goals of the interim remedial action
are not to meet drinking water standards, Alternative 1 complies with ARARs applicable to the
interim remedial action. However, it does not meet the objectives of the interim remedial action
to prevent exposure to and reduce contaminant mass in the alluvial aquifer.
53.2 Primary Balancing Criteria
Short-term effectiveness
Alternative 2 would include construction activities associated with the PeRT wall installation.
Mitigative measures, such as dust suppression, would be implemented to minimize short-term
impacts. Construction may generate noise and vibrations; heavy equipment use would be
required. Activities that could cause disruptions to area residents will be implemented during the
times of day that minimize negative effects. The ground-water treatment portion of this
alternative would cause short-term reductions of contaminant mass from the alluvial aquifer
while a longer-term alternative is being evaluated. Implementation of institutional controls
through the Utah State Engineer's office can be quickly accomplished and therefore will provide
short-term effectiveness in preventing exposure to contaminated ground water.
For Alternative 1, only monitoring activities would be conducted. Workers conducting these
activities would take appropriate precautions (e.g., following appropriate sample collection and
handling procedures) to prevent exposure to contaminants. Small localized disturbances to soils
and vegetation may occur with the installation and/or maintenance of monitoring wells, but
environmental resources would not be significantly affected during the short term. This
alternative would have no short-term effects on ground-water or surface-water quality.
Long-term effectiveness
Alternative 2 provides good long-term effectiveness through the use of institutional controls to
restrict use of contaminated ground water. Dewatering and treatment of contaminated ground
water will result in improved water quality in the alluvial aquifer. Though the interim remedial
action is not intended as a long-term solution, it is a first step toward meeting long-term goals.
DOE/Grand Junction Office MMTS OU ID Interim ROD
August 1998 5-9
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Decision Summary Document Number QOQ11601
Long-term effectiveness will be evaluated through monitoring and modeling and a final solution
will be selected at a later date.
Alternative 1 would result in a slow decrease in contaminant concentrations in the alluvial
aquifer over time as the system attenuates naturally. Modeling indicates this attenuation would
take greater than 100 years to return to acceptable concentrations. Additionally, this alternative
provides no controls to limit the use of or access to OU HI ground water during the time
contaminant concentrations are decreasing.
Reduction ofToxicity, Mobility, and Volume through Treatment
Dewatering and treatment of ground water through implementation of Alternative 2 results in an
irreversible reduction of contaminant mass in ground water. The treatment process will remove
contaminants from the ground water and immobilize the contaminants by placing them in the
repository constructed for OU I. Discharge of treated ground water will meet UPDES
requirements for surface water. If effective, the PeRT wall will achieve a reduction in mobility of
contaminants and a reduction in volume of the contaminant plume downgradient of the wall.
Alternative 1 does not achieve a reduction in toxicity, mobility, or volume through treatment.
Implementability
Alternative 2 is implementable. Institutional controls can be put in place and administered
through the State Engineer. Monitoring and ground-water extraction/treatment are a continuation
of ongoing activities and are therefore implementable. The PeRT wall is less proven, but
treatability studies have shown that the technology is successful in removing contaminants of
concern from site-specific ground-water samples. Use of the same technology in similar
situations has been successful. Standard construction practices and materials are used for PeRT
wall installation; a number of vendors are available to supply each of the component parts and
services.
Alternative 1 is implementable and represents the current situation.
Cost
For Alternative 1, capital costs are estimated at $39,000; O&M costs are estimated at $161,000
annually.
For Alternative 2, capital costs are estimated at $2,313,000; O&M costs are estimated at
$414,000 annually.
Breakdown of costs for Alternative 2 are as follows:
Institutional Controls
Capital Costs $ 20,000
MMTS OU m Interim ROD DOE/Grand Junction Office
5-10 August 1998
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Document Number QOO11601 Decision Summary
Monitoring
Capital Costs $ 39,000
Annual Costs $ 161,000
Geochemical Testing
Capital Costs $ 52,000
PeRTWall
Capital Costs $2,203,000
Annual Costs $ 253,000
Costs for dewatering and treatment of the Millsite are not included in the estimate for
Alternative 2, because currently, they are included as part of OUI and the need to continue those
activities after Millsite excavation is completed is not known at this time.
533 Modifying Criteria
State Acceptance
Alternative 2 is acceptable to the State.
Alternative 1 is not acceptable to the State.
Public Acceptance
Public input was not specifically sought on the acceptability of Alternative 1. As support of
Alternative 2 was made publicly, it can be assumed that Alternative 2 has more public support
than Alternative 1. Generally, the public showed little interest in the OU HI remedy selection
process, but those involved reacted favorably toward the preferred Alternative 2. For more
information see the Responsiveness Summary in this document (Appendix A).
EPA Acceptance
Because DOE was the lead agency for this interim remedial action, and because DOE is the
agency proposing the action, EPA acceptance is also addressed here (though it is not one of the
CERCLA criteria).
Alternative 2 is acceptable to EPA.
Alternative 1 is not acceptable to EPA.
DOE/Cnnd Junction Office MMTS OU 01 Interim ROD
August 1998 5-11
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Document Number Q0011601 Decision Summary
6.0 Selected Remedy
The selected interim remedial action for MMTS OU HI is Alternative 2—Institutional Controls,
Millsite Dewatering and Treatment, Monitoring, and PeRT Wall Installation and Evaluation.
Institutional controls will restrict the use of contaminated ground water while ground-water
remediation is in progress. Access to water rights will be prohibited and a moratorium will be
placed on drilling new water wells in the contaminated alluvial aquifer. These controls will be
administered through the State Engineer. Monitoring will continue on a semiannual basis and be
reviewed as data becomes available to assess the effectiveness of the interim remedial action.
Monitoring will involve sampling up to 24 monitoring wells and 8 surface-water locations and
analyzing for all metal and radionuclide COCs for OU ffl (DOE 1997). Ongoing Millsite
dewatering and treatment will continue during the remediation of OU I and if determined
necessary, will be continued after excavation of source material from the Millsite is complete.
Water is currently undergoing chemical treatment followed by microfiltration and/or reverse
osmosis. Secondary wastes generated are disposed in the on-site repository. Clean water is
discharged to Montezuma Creek in accordance with UPDES requirements. Installation of the
pilot-scale PeRT wall will determine the effectiveness of the technology in removing
contaminants from the ground water at the MMTS.
Costs associated with this alternative are as follows:
Present worth (5-year period): $4,010,400
Capital: $2,313,000
Annual O&M: $ 414,000
The PeRT wall is an innovative technology, so there are uncertainties associated with its
performance. However, treatability studies have proven promising to date, and the technology
has been used successfully at sites similar in nature to OU EL Performance of the PeRT wall will
be monitored on a regular basis, and if problems arise, steps can be taken to correct them.
Additionally, a five-year review of the monitoring data will be conducted to assess the
performance of the interim remedial action and assist in the development of the final remedial
action for OU m.
DOE/Gnnd Junction Office MMTS OU ffi Interim ROD
August 1998 6-1
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Document Number Q0011601 ___ Decision Summary
7.0 Statutory Determinations
The selected interim remedial action meets the statutory requirements of CERCLA. These
statutory requirements include protection of human health and the environment, compliance with
ARARs (within the scope of the interim remedial action), cost effectiveness, and use of
permanent solutions and alternative treatment technologies to the maximum extent practicable.
Water extracted through dewatering will be treated at the existing water treatment plant. If
effective, the PeRT wall will treat contaminated ground water. The manner in which the selected
interim remedial action for OUIH meets each of the requirements is presented in the following
discussion.
7.1 Protection of Human Health and the Environment
The interim remedial action is anticipated to be protective of human health and the environment
by limiting exposure to contaminated ground water through use of institutional controls and by .
reducing contaminant mass in surface water and ground water downgradient of the Millsite.
Implementation of the selected interim remedy is a preliminary step in achieving long-term
protection.
7.2 Compliance with Applicable or Relevant and Appropriate Requirements
The interim remedial action selected for OU HI will meet the ARARs that are applicable or
relevant and appropriate to this interim remedial action. These ARARs include the National
Pollutant Discharge Elimination System (administered through the State as the UPDES), the
State of Utah's Hazardous Waste Management rules, and the Floodplain/Wetlands
Environmental Review.
Aquifer restoration will be addressed during selection of the final remedy for all of OU EL For
this reason, regulations that address water quality standards are not ARARs for this interim
remedial action though the interim remedial action should make progress toward meeting those
standards. These standards include maximum contaminant levels, the Utah ground-water quality
standards, and the Safe Drinking Water Act. Additional information regarding ARARs for the
interim remedial action is provided in Tables 5.3.1-1 and 5.3.1-2.
7.3 Cost Effectiveness
Overall cost effectiveness can be defined as the overall effectiveness proportionate to cost, such
that an action represents a reasonable value. The selected remedy for OU ffl will prevent
exposure to contaminated ground water at a reasonable cost, thus improving protection to human
health and the environment. The selected interim remedial action has a cost that is within the
same range as alternatives considered in the feasibility study for the site. If greater treatment
efficiency, cost effectiveness, or ease of implementability can be established at a later date, other
alternatives would be considered.
DOE/Crand Junction Office MMTS OU ffl Interim ROD
August 1998 7-1
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Decision Summary Document Number Q0011601
7.4 Use of Permanent Solutions and Treatment Alternative Technologies or
Resource Recovery Technologies to the Maximum Extent Practical
Ongoing dewatering and treatment of ground water at the Millsite fulfills this requirement.
Contaminated water is treated to meet UPDES requirements before discharge to Montezuma
Creek. Ground water is permanently treated by removal of contaminants by chemical and
physical methods.
If the PeRT wall is effective, the final proposed remedial action for OU HI may employ treatment
through the use of an innovative technology. However, the reactive materials installed in
constructing the PeRT wall may require recovery and disposition at an off-site disposal facility at
some time in the future. Because this is only an interim remedial action measure, its effectiveness
will be evaluated in the final feasibility study for OU ffl. This action utilizes permanent solutions
and alternative treatment technologies to the maximum extent possible, given the limited scope
of this action.
7.5 Preference for Treatment as a Principal Element
Water recovered during Millsite dewatering is being treated before discharge. If the PeRT wall is
successful, it will treat ground water in situ. Thus, this alternative satisfies the preference for
treatment as a principal element. The final decision document for the site will further address this
preference as it relates to the final alternative selected for the site.
7.6 Balancing Criteria
The selected interim remedial action provides the best balance of tradeoffs compared with the
no-action alternative with respect to the five summary balancing criteria, which include
• Long-term effectiveness and permanence.
• Reduction of toxicity, mobility, or volume through treatment.
• Short-term effectiveness.
• Implementability.
• Cost.
The criteria most critical in the selection of this remedy were short- and long-term effectiveness
and reduction of toxicity, mobility, or volume through treatment. The no-action alternative would
have no effect on site conditions and would not prevent exposure to contaminated ground water.
The combination of institutional controls and Millsite dewatering and treatment prevents near-
term exposure to ground water and reduces contaminant mass in the aquifer, contributing to long-
term effectiveness.
MMTS OU ffl Interim ROD DOE/Grand Junction Office
7-2 August 1998
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Document Number QOOI1601 Decision Summary
The selected remedy was the preferred alternative identified in the proposed plan. No significant
changes were made to the preferred alternative. Because the public meeting and comment period
did not generate any significant comments opposed to the interim remedial action presented in
the Proposed Plan, the selected remedy is assumed to have community acceptance.
DOE/Grand Junction Office MMTS OU ID Interim ROD
August 1998 7_3
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Document Number Q0011601 Decision Summary
8.0 References
Bendix Field Engineering Corporation, 1980. 7979 Environmental Monitoring
Report—U.S. Department of Energy Facilities, Grand Junction, Colorado, and Monticello,
Utah.
Grand Junction Office, 1997. Environmental Procedures Catalog, Manual GJO 6, June.
Korte, N.E., and R. Thul, 1981.1980 Environmental Monitoring Report—U.S. Department of
Energy Facilities, Grand Junction, Colorado, and Monticello, Utah. BFEC-1981-3, Bendix Field
Engineering Corporation, prepared for the U.S. Department of Energy, Grand Junction
Operations, Grand Junction, Colorado, April.
, 1982.1981 Environmental Monitoring Report—U.S. Department of Energy Facilities,
Grand Junction, Colorado, and Monticello, Utah. BFEC-1982-4, Bendix Field Engineering
Corporation, prepared for the U.S. Department of Energy, Grand Junction Operations, Grand
Junction, Colorado, April.
, 1983.1982 Environmental Monitoring Report—U.S. Department of Energy Facilities,
Grand Junction, Colorado, and Monticello, Utah. GJO-113(83), Bendix Field Engineering
Corporation, prepared for the U.S. Department of Energy, Grand Junction Operations Office,
Grand Junction, Colorado, April.
, 1984. 7983 Environmental Monitoring Report—U.S. Department of Energy Facilities,
Grand Junction, Colorado, and Monticello, Utah. GJO-113(84), Bendix Field Engineering
Corporation, prepared for the U.S. Department of Energy, Grand Junction Projects Office, Grand
Junction, Colorado, April.
Korte N.E., and S. Wagner, 1985. Environmental Monitoring Report on Department of Energy
Facilities at Grand Junction, Colorado, and Monticello, Utah, for Calendar Year 1984. GJ-30,
Bendix Field Engineering Corporation, prepared for the U.S. Department of Energy, Grand
Junction Project Office, Grand Junction, Colorado, March.
, 1986. Environmental Monitoring Report on Department of Energy Facilities at Grand
Junction, Colorado, and Monticello, Utah, for Calendar Year 1985. GJ-45, Bendix Field
Engineering Corporation, prepared for the U.S. Department of Energy, Grand Junction Projects
Office, Grand Junction, Colorado, March.
MACTEC, 1996. Field Services Procedures Manual, MAC-3000, Rev. 07, December.
Sewell, J.M., and L. Spencer, 1987. Environmental Monitoring Report on Department of Energy
Facilities at Grand Junction, Colorado, and Monticello, Utah, for Calendar Year 1986,
UNC/GJ-HWMP-2, UNC, for the U.S. Department of Energy, Grand Junction Projects Office,
Grand Junction, Colorado, March.
DOE/Gnnd Junction Office MMTS OU 01 Inienm ROD
August 1998 8-1
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Decision Summary Document Number Q0011601
U.S. Department of Energy, 1988a. Environmental Monitoring Report on U.S. Department of
Energy's Inactive Millsite Facility, Monticello, Utah, for Calendar Year 1987,
DOE/ID/12584-24, prepared by UNC Geotech for the U.S. Department of Energy, Grand
Junction Projects Office, Grand Junction, Colorado, March.
, 19885. Federal Facility Agreement, U.S. Environmental Protection Agency Region Vffl,
State of Utah Department of Environmental Quality, U.S. Department of Energy, February 24.
Agreement Pursuant to Section 120 of the Comprehensive Environmental Response,
Compensation, and Liability Act of 1980, and amended by the Superfund Amendments and
Reauthorization Act of 1986.
, 1989. Environmental Monitoring Report on U.S. Department of Energy's Inactive
Millsite Facility, Monticello, Utah, for Calendar Year 1988, DOE/ID/125 84-40, prepared by
UNC Geotech for the U.S. Department of Energy, Grand Junction Projects Office, Grand
Junction, Colorado, May.
, 1990a. Environmental Monitoring Report on U.S. Department of Energy's Inactive
Millsite Facility, Monticello, Utah, for Calendar Year 1989, DOE/ID/12584-67, prepared by
UNC Geotech for the U.S. Department of Energy, Grand Junction Projects Office, Grand
Junction, Colorado, May.
, 1990b. Monticello Mill Tailings Site: Declaration for the Record of Decision and
Record of Decision Summary, DOE/10/12584-50, Grand Junction Projects Office, Grand
Junction Colorado, August.
, 1990c. Final Remedial Investigation/Feasibility Study—Environmental Assessment for
the Monticello, Utah, Uranium Tailings Site, Vols. I and JJ, DOE/EA/0424, prepared by UNC
Geotech for the U.S. Department of Energy, Grand Junction Projects Office, Grand Junction,
Colorado.
, 1991. Monticello Millsite Environmental Report for Calendar Year 1990,
DOE/ID/12584-87, prepared by Chem-Nuclear Geotech, Inc. for the U.S. Department of Energy,
Grand Junction Projects Office, Grand Junction, Colorado, May.
, 1992. Environmental Monitoring Report on U.S. Department of Energy's Inactive
Millsite Facility, Monticello, Utah, for Calendar Year 1991, DOE/JD/12584-103, prepared by
UNC Geotech for the U.S. Department of Energy, Grand Junction Projects Office, Grand
Junction, Colorado, May.
, 1996. Monticello Wetlands Master Plan, prepared by Rust Geotech for the
U.S. Department of Energy Grand Junction Office, Grand Junction, Colorado, March.
, 1997. Monticello Mill Tailings Site, Operable Unit HI, Annual Monitoring Program,
MAC-MSGRAP 1.3.5, prepared by MACTEC Environmental Restoration Services for the U.S.
Department of Energy Grand Junction Office, Grand Junction, Colorado, September.
MMTS OU m Interim ROD DOE/Grand Junction Office
8-2 August 1998
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Document Number Q0011601 Decision Summary
U.S. Department of Energy, 1998a. Monticello Mill Tailings Site. Operable Unit HI. Action
Memorandum, prepared by MACTEC Environmental Restoration Services for the
U.S. Department of Energy Grand Junction Office, Grand Junction, Colorado.
, 1998b. Monticello Mill Tailings Superfund Site. Monticello Vicinity Properties
Superfund Site, Monticello, Utah, Community Relations Plan Update, draft, prepared by
MACTEC Environmental Restoration Services for the U.S. Department of Energy Grand
Junction Office, Grand Junction, Colorado.
, 1998c. Monticello Mill Tailings Site, Operable Unit III, Remedial Investigation,
GJO-97-6-TAR, prepared by MACTEC Environmental Restoration Services for the
U.S. Department of Energy Grand Junction Office, Grand Junction, Colorado.
,1998d. Monticello Mill Tailings Site, Operable Unit III, Alternatives Analysis of Soil and
Sediment, GJO-97-10-TAR, prepared by MACTEC Environmental Restoration Services for the
U.S. Department of Energy Grand Junction Office, Grand Junction, Colorado.
, 1998e. Monticello Mill Tailings Site, Operable Unit III, Feasibility Study, prepared by
MACTEC Environmental Restoration Services for the U.S. Department of Energy Grand
Junction Office, Grand Junction, Colorado.
,1998f. Monticello Mill Tailings Site, Operable Unit III, Proposed Plan, prepared by
MACTEC Environmental Restoration Services for the U.S. Department of Energy Grand
Junction Office, Grand Junction, Colorado.
, 1998g. Monticello Mill Tailings Site, Operable Unit III, Baseline Human Health Risk
Assessment, prepared by MACTEC Environmental Restoration Services for the U.S. Department
of Energy Grand Junction Office, Grand Junction, Colorado.
,1998h. Monticello Mill Tailings Site, Operable Unit HI, Ecological Risk Assessment,
prepared by MACTEC Environmental Restoration Services for the U.S. Department of Energy
Grand Junction Office, Grand Junction, Colorado.
DOE/Grand Junction Office MMTS OU ffl Interim ROD
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Responsiveness Summary
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Document Number Q0011601 Appendix A
Overview
This Responsiveness Summary provides information about the views of the community with
regard to the proposed interim remedial action for Operable Unit (OU) HI ground water at the
Monticello Mill Tailings Site (MMTS), documents how public comments have been considered
during the decision-making process, and provides responses to concerns.
The public was informed of the selected remedial action in the following ways:
• All items contained within the Administrative Records have been on file at the subject
repositories since the final, OF in some cases draft final, version of each document was issued.
• A copy of the Proposed Plan for the interim remedial action was sent to interested
stakeholders and was made available in the public reading room and at the public meeting.
• A public comment period was held from March 27, 1998, to April 27, 1998.
• A full page notice of the public comment period and public meeting was published in the
local weekly newspaper before the public meeting.
• Notices of the public comment period and public meeting were prominently posted at several
of the most frequented businesses in the Monticello area.
• A public service announcement was aired by a local radio station to notify listeners about the
time and location of the public meeting.
• A public meeting was held on April 7,1998, at the Monticello High School auditorium.
• Written comments by the public were encouraged.
The public meeting was sparsely attended. The few questions and comments that were received
are summarized, along with responses, in this responsiveness summary. The selected remedy
presented in the Proposed Plan was not modified based on any comments received. The public
meeting also included a discussion of proposed cleanup of soils and sediments associated with
OU HI through a removal action. Comments received on the removal action are included in the
Action Memorandum for that removal action.
Background on Community Involvement
The public participation requirements of the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA) Section 113(k)(2)(B)(i-v) and Section 117 are being
followed for OU m. MMTS has a Community Relations Plan that has been updated annually.
The most recent revision of the plan is currently undergoing revision. The community relations
activities include (1) distribution of fact sheets and other written materials, (2) news releases to
the local newspaper, (3) public meetings, (4) display ads announcing the availability of key
documents and meetings, (5) public comment periods, and (6) responsiveness summaries for
Records of Decision.
DOE/Crand Junction Office ~~ MMTS OU ID Interim ROD
August 1998 A-3
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Appendix A . Document Number Q0011601
Copies of all site-specific documents used in developing the interim-action decision were made
available to the public through the Administrative Record for the site housed at the Monticello
City Offices. Copies of the Proposed Plan (DOE 19985) for an interim remedial action at OU ffl
were included in the site Administrative Record and distributed to stakeholders. The notices of
availability for these documents were published in the local Monticello newspaper. A public
comment period on the interim remedial action was held from March 27 to April 27, 1998, and a
public meeting was held on April 7, 1998. At this meeting, representatives from DOE, the
Environmental Protection Agency, and the State of Utah answered questions about the site and
the selected remedy. A summary of the meeting and public comments received at that meeting
and during the public comment period are presented in this appendix for inclusion in the
Administrative Record. The decision for an interim remedial action at this site is based on
information in the Administrative Record.
Summary of Public Comments and Agency Responses
I. Comments received at the Public Meeting
(1) One community member asked if the contaminated ground water could be pumped into
Montezuma Creek to dilute it instead of treating it.
DOE Response: This isn't possible because State laws don't allow it.
(2) One community member asked what process would be used to treat the ground water.
DOE Response: Ground water will be treated with a combination of chemical reaction and
filtration (both microfiltration and reverse osmosis).
(3) One community member perceived the levels of contaminants in the ground water to be so
low that the need for treatment was questioned.
DOE Response: The contamination, though measured in small amounts, would be harmful if
someone were to drink it for their main source of water for their lifetime. CERCLA requires
that both current and potential future uses be considered.
(4) One community member suggested pumping out contaminated ground water and using it as
dust control in the repository. The community member noted that when the tailings source
removal was complete, then the whole site would be cleaned up.
DOE Response: Contaminated ground water is being used as dust control in the repository,
but it is predicted that areas of ground-water contamination will remain after Millsite
cleanup.
(5) One community member asked what the ground-water flow rates were at the site.
DOE Response: The amount of water moving past the eastern boundary of the Millsite is 40
to SO gallons per minute.
MMTS OU III Interim ROD DOE/Grsnd Junction Office
A-4 August 1998
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Document Number Q0011601 Appendix A
(6) One community member asked if the creek water was dangerous to animals.
DOE Response: The ecological risk assessment concluded that there is no significant risk to
animals from drinking the water.
(7) One community member commented that the original study claimed that there would be
2 cancer deaths in 100,000 people after 70 years. The commenter noted that Monticello has
less than 2,000 people, so there should be no effect on its population.
DOE Response: This was a statement; no response was given.
n. Informal comments and other community involvement activities
(1) The week following DOE's public meeting on April 15, 1998, the Site-Specific Advisory
Board for the MMTS met. Members of the board unanimously supported the preferred
interim remedial action alternative as presented by DOE the previous week.
1H. Written comments and responses
None were received.
DOE/Grand Junction Office MMTS OU ffl Interim ROD
August 1998 A-5
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