United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
Superfund
Record of Decision
United Nuclear, NM
EPA/ROD/R06-88/044
September 1988
PROTECTION
AGENCY
MLLAS, TEXAS
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REPORT DOCUMENTATION i- REPORT NO. 2.
PAGE EPA/ROD/R06-88/044
4. Till* »nd Subtitle
SUPERFUND RECORD OF DECISION
J United Nuclear Corporation, NM
^?irsfc Remedial Action
V Author(s)
9. Performing Organization Nam« and Address
12. Sponsoring Organization Nam* and Address
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
3. Recipient's Accession No.
5. Report Date
09/30/88
6.
8. Performing Organization Rept. No
10. Proiect/Task/Work Unit No.
11. Contract(C) or Grant(G) No.
(C)
(G)
13. Type of Report & Period Covered
800/000
14.
IS. Supplementary Notes
16. Abstract (Limit: 200 words)
The United Nuclear Corporation (UNC) site is located approximately
17 miles northeast of Gallup, New Mexico, in McKinley County. The site operated as a
State-licensed uranium mill facility from June 1977 to May 1982. It includes an ore
processing mill (about 25 acres) and an unlined tailings pond area (about 100 acres).
The surrounding area is sparsely populated, with the nearest residence located 1.5 miles
from the site. In July 1979, approximately 23 million gallons of tailings and pond
water were released to a nearby river as a result of a dam breach in the tailings pond
area. The site damage was repaired; however, attention was focused on ground water
contamination resulting from tailings seepage, consequently, UNC implemented a ground
water pumping system that withdrew ground water from the aquifers underlying the site
and sent it to an onsite borrow pit for evaporation. UNC also conducted tailings
neutralization from late 1979 to early 1982. Nevertheless, the offsite migration of
radionuclides and chemical constituents from uranium milling byproduct materials into
the ground water, as well as to surface water and air, are still principal threats at
the site. This remedial action will address onsite ground water contamination. Source
control and onsite surface reclamation will be implemented under the direction of the
Nuclear Regulatory commission and integrated with this ground water operable unit. The
(See Attached Sheet)
NM
17. Document Analysis a. Descriptors
Record of Decision
United Nuclear Corporation,
First Remedial Action
Contaminated Media: gw
Key Contaminants: metals (arsenic), radioactives (gross alpha, radium - 226/228)
b. Identifiers/Open-Ended Terms
c. COSATI Field/Group
(Availability Statement
19. Security Class (This Report)
None
20. Security Class (This Page)
None
21. No. of Pages
371
22. Price
(S«« ANSI-Z39.18)
See Instructions on Reverie
OPTIONAL FORM 272 (4-77)
(Formerly NTIS-35)
Department of Commerce
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EPA/ROD/R06-88/044
Jnited Nuclear Corporation, NM
irst Remedial Action
16. ABSTRACT (continued)
primary contaminants of concern affecting the ground water are metals including arsenic,
and radioactive substances including radium-226/228 and gross alpha.
The selected remedial action for this site includes: implementation of a ground water
monitoring program to detect any increases in he areal extent or concentration of
ground water contamination outside the tailings disposal area; ground water pump and
treatment using existing and/or new extraction wells to control and re: jve tailings
seepage and remediate contaminated ground water, with discharge to an enhanced
mister/pond evaporation system; and implementation of a performance monitoring and
evaluation program. The estimated present worth cost for this remedial action is
$17,000,000 over a 10-year period, with estimated annual O&M of $1,000,000.
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RECORD OF DECISION
UNITED NUCLEAR CORPORATION
GROUNDWATER OPERABLE UNIT
McKinley County, New Mexico
SEPTEMBER 1988
U.S. ENVIRONMENTAL PROTECTION AGENCY
REGION VI, DALLAS, TEXAS
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DECLARATION
FOR THE
RECORD OF DECISION
SITE NAME AND LOCATION
United Nuclear Corporation
McKinley County, New Mexico
Groundwater Operable Unit Remedial Action
STATEMENT OF PURPOSE
This decision document presents the remedial action for the Groundwater
Operable Unit of the United Nuclear Corporation (UNC) site selected by the
United States Environmental Protection Agency (EPA) in accordance with the
Comprehensive Environmental Response, Compensation, and Liability Act of
1980 (CERCLA), as amended by the Superfund Amendments and Reauthorization
Act of 1986 (SARA), and the National Contingency Plan (NCP).
STATEMENT OF BASIS
The decision is based upon the administrative record for the United Nuclear
Corporation Superfund Site. The attached index (Appendix E) identifies the
items which comprise the administrative record upon which the selection of
this remedial action is based.
Remedial action for the Groundwater Operable Unit is part of a comprehensive
response action for the United Nuclear Corporation Superfund Site. Remedial
activities addressing source control and onsite surface reclamation will be
implemented by United Nuclear Corporation under the direction of the U.S.
Nuclear Regulatory Commission (NRC), pursuant to the facility's NRC license,
and integrated with the Environmental Protection Agency's selected remedy for
the groundwater operable unit. Agency responsibilities for remedial action
at the United Nuclear Corporation site are delineated in a Memorandum of
Understanding (MOU) signed by the EPA and NRC in August 1988. (Appendix I)
The Nuclear Regulatory Commission and the State of New Mexico have reviewed
the proposed plan for remedial action, as identified in the remedial
investigation/feasibility study (RI/FS), and proposed Plan of Action Fact
Sheet, and support the remedy described in this Record of Decision.
(Appendices F, G)
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DESCRIPTION OF SELECTED REMEDY
The Operable Unit for the United Nuclear Corporation site addresses high
levels of radiological and nonradiological constituents that have seeped
from tailings into groundwater outside the tailings disposal site. The
hazardous substances of primary concern are arsenic, cadmium, cobalt.
nickel, radium-226/228, selenium, and gross alpha. The tailings seepage
has contaminated portions of the shallow alluvial groundwater system and
underlying Upper Gallup Sandstones.
The selected remedy for this operable unit is designed to contain, remove,
and evaporate contaminated groundwater resulting from tailings seepage
outside the tailings disposal area thus preventing further migration of
seepage into the environment. The remedy is comprised of the following six
elements.
1. Implementation of a monitoring program to detect any increases in the
area! extent, or concentration of groundwater contamination at, and
outside of, the boundary of the tailings disposal area.
Evaluation of geochemical and hydrological information indicates that a
tailings seepage mound exists in the tailings disposal area resulting in
migration of contaminated groundwater into the alluvium, as well as under-
lying Zone 1 and Zone 3 Upper Gallup sandstones. Tailings seepage has
migrated outside the tailings disposal area in each of these three aquifers,
and there is the potential for further downgradient migration. For these
reasons, a monitoring program will be established prior to the installation
of extraction wells in each aquifer.
The monitoring program will consist of a groundwater monitoring network
comprised of a series of wells to measure water levels and water quality.
The monitoring points shall be located upgradient, downgradient, and cross-
gradient of seepage plumes in order to further define the extent of contami-
nation in Zones 1 and 3 of the Upper Gallup Sandstone, and the southwest
alluvium. The extent of contamination in each aquifer, and concentration
of contaminants in each well, shall be used to identify the most effective
pumping well locations.
2. Operation of existing seepage extraction systems in the Upper Gallup
aquifers?
Because seepage from tailings has migrated into underlying Zone 1 and Zone
3 sandstones, the selected remedy includes operation of the East
pump-back wells in Zone 1 and the Northeast pump-back wells in Zone 3 until
adequate dissipation of the tailings seepage mound has been achieved.
Operation of these two pump-back systems will be integrated with active
seepage remediation that may be required by the NRC inside the tailings
disposal area, and with active seepage collection as required by EPA outside
the disposal area.
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3. Containment and removal of contaminated groundwater in Zone 3 of the
Upper Gallup Sandstone utilizing existing and additional wells.
Active remediation of Zone 3 outside the tailings disposal site will be per-
formed in areas contaminated by tailings seepage. The full extent of the
tailings seepage plume will be determined during remedial design, prior to
extraction well installation, and will be delineated on the basis of ground-
water flow directions in the aquifer in conjunction with identification of the
margin or amount by which standards are exceeded for hazardous constituents
in groundwater.
Seepage collection in Zone 3 will be designed to create a hydraulic barrier
to further migration of contamination. Final well locations will be guided
by observed saturated thicknesses in Zone 3, and the extent of the tailings
seepage plume as defined above. Data obtained during performance monitoring
of the extraction system should be used to determine the optimum rate of
pumping, and extent and duration of pumping actually required.
4. Containment and removal of contaminated groundwater in the southwest
alluvium utilizing existing and additional wells.
Active remediation in the southwest alluvium will be performed in areas
contaminated by tailings seepage. The extent of the tailings seepage plume
outside the tailings disposal area will be determined prior to extraction
well installation. Delineation of alluvial contamination will be based on
groundwater flow directions in the aquifer in conjunction with identification
of the margin or amount by which standards are exceeded for hazardous consti-
tuents in groundwater.
Seepage collection in the southwest alluvium will be designed to create a
hydraulic barrier to further migration of contamination while the source 1s
being remediated. The number of extraction wells required, and their final
locations, will be determined from the observed saturated thicknesses in
the alluvium, and the extent of the tailings seepage plume as defined above,
during the remedial design phase. Data obtained during performance monitoring
of the extraction system should be used to determine the optimum rate of
pumping, and extent and duration of pumping actually required.
5. Evaporation of groundwater removed from aquifers outside the disposal
area using evaporation ponds supplemented with mist or spray systems to
enhance tne rate of evaporation.
Tailings seepage extracted in pumping wells will be directed to an evapora-
tion disposal system consisting of lined evaporation ponds and mist or
spray evaporation systems. Inflow to the evaporation disposal system will
be from current and required extraction wells outside and/or within the
tailings disposal area. The evaporation pond system, coupled with mist and
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spray evaporation systems, will be sized and operated in order to provide
sufficient evaporative capacity for maintenance of a reasonable operational
water balance. Optimization of the evaporation disposal system should occur
during the first several months of operation.
6. Implementation of a performance monitoring and evaluation program to
determine water level and contaminant reductions in each aquifer, and
the extent and duration of pumping actually required outside the
tailings disposal area.
In order to evaluate predicted reductions in contaminant concentrations
with time in a particular aquifer, and declines in pumping rates, a
performance monitoring program shall be implemented. Performance
monitoring during active seepage remediation will allow a determination to
be made regarding the adequacy of groundwater remedial actions outside the
tailings disposal area at the United Nuclear Corporation site.
These elements comprise remedial action in the groundwater operable unit at
the United Nuclear Churchrock site. The Nuclear Regulatory Commission has
directed United Nuclear Corporation to submit a reclamation plan addressing
source control and surface reclamation measures at the site under the
Company's Source Material License. Upon approval of a final reclamation
plan, both groundwater and source control/surface reclamation remedial
actions will be integrated and coordinated to achieve comprehensive
reclamation and remediation of the site.
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DECLARATIONS
Pursuant to CERCLA, as amended by SARA, and the NCR, I have determined that
the selected remedy for the Groundwater Operable Unit at the United Nuclear
Corporation site, is consistent with achieving a permanent remedy, and will
provide adequate protection of public health and the environment. This
remedy attains all location-specific and action-specific requirements that
are applicable or relevant and appropriate (ARARs), and is cost effective.
EPA believes that the selected remedy will attain chemical -specific require-
ments within a reasonable time period. Because of the physical characteris-
tics of the aquifers at the site, performance monitoring will be required,
as indicated above herein. If performance monitoring indicates that these
ARARs are not being timely attained, then an alternate concentration limit
may be considered at the boundary of the tailings disposal area in order to
meet chemical-specific requirements.
The remedy satisfies the statutory preference for remedies that employ
treatment that reduces toxicity, mobility, or volume as a principal element
and utilizes permanent solutions and alternative treatment technologies to
the maximum extent practicable. Because this action will occur in concert
with reclamation of source areas, required by the U.S. Nuclear Regulatory
Commission, this remedy does satisfy the statutory preference for treatment
as a principle element.
Because this remedy will result in hazardous substances remaining outside
the tailings disposal area on a short-term basis above health-based levels,
reviews of the remedial action will be conducted no less often than each five
years after the initiation of the remedial action to assure that human
health and the environment are being protected by the remedial action being
implemented.
n
Robert E. Lay ton Jr.,/P.E.
Regional Administrator
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site is located approxi-
in McKinley County (Figure
o herein as the potentially
uranium mill facility within
West (Figure 2). The site
ond area which cover about
nd area is subdivided by
outh cell, Central cell, and
Pits No. 1 and No. 2) are
'. 2 is currently used for
.cted by three well systems
mtly used to remove contami-
ir Gallup Sandstone.
md includes Indian tribal
iperty. Section 36, Township
le site, is owned by UNC and
ration. The nearest resi-
sst of the site. The nearest
of the perimeter of the site.
four mile radius of the site.
naterials license by the
sm June 1977 to May 1982.
per day, used a conven-
it extraction method to
primarily came from two of
Id Churchrock. Ore was also
ine. The average ore grade
rcent U308 (EPA. 1988).
reduced an acidic waste of
flings. The tailings were
ated 3.5 million tons of
ing began in the area north
urchrock mine began operating
ischarged from this mine, and
und and added water to the
iuch of the site. Limited
mining, and prior to operation
le.
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r
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In July 1979, the dam on the south cell breached, releasing approximately
93 million gallons of tailings and pond water to the Rio Puerco (EPA,
1988). The dam was repaired shortly after its failure. Cleanup of the
resultant spill was conducted according to criteria imposed by state and
federal agencies, including EPA, at that time.
In October 1979, the New Mexico Environmental Improvement Division (NMEID)
ordered UNC to implement a discharge plan to control contaminated tailings
seepage. The tailings seepage had been deemed responsible for groundwater
contamination. In 1981, UNC implemented a groundwater pumping system that
withdrew groundwater from the site aquifers and returned it to Borrow Pit
No. 2 for evaporation (EPA, 1988).
UNC began tailings neutralization in late 1979, and continued the process
until early 1982. Neutralization included the addition of ammonia or lime
to the tailings; neutralization has also been conducted several times
during the history of the mill operation (EPA, 1988).
In May 1982, UNC announced that they were going to temporarily close the
Churchrock uranium mill because of depressed uranium market conditions.
The market did not recover and UNC subsequently decided to close the facil-
ity permanently (EPA, 1988).
The offsite migration of radionuclides and chemical constituents into the
groundwater, in addition to surface water and air emissions, prompted the
placement of the UNC site onto the National Priorities List (NPL) of Super-
fund sites in 1983.
EPA's RI field activities at the UNC site were conducted from March 1984 to
August 1987. The objectives of the RI field activities were to determine
the nature and extent of groundwater contamination in the three aquifers at
the site.
During early 1987, UNC submitted a closure plan to the NRC for reclamation
of the mill site. This plan has been under review by the NRC since then and
was formally approved in September 1988. On August 26, 1988, EPA and the
NRC signed a Memorandum of Understanding (MOU), a copy of which is attached
as Appendix I, which provides for the coordination of EPA's remedial action
with the U.S. Nuclear Regulatory Commission (NRC) required site reclamation
action. UNC's current activities at the site are limited to (1)
compliance monitoring activities, (2) an improved seepage collection system
operation, (3) dust control, (4) decontamination and sale of selected
equipment, and (5) enhanced spray evaporation of water contained in Borrow
Pit No. 2.
2.2 Response History
In 1981 EPA conducted a preliminary evaluation of the UNC site consisting
of an assessment of existing data and a site inspection. The site, then
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regulated by the State of New Mexico under "agreement state" status with
the NRC, was subsequently included on the Superfund Interim Priority List.
In late 1982 EPA conducted an additional sampling inspection. In 1983 the
site was formally placed on the National Priorities List of Superfund sites.
EPA began the RI in August of 1984 and fieldwork began in early 1985 after
site access problems were resolved. The RI, which addresses groundwater
outside the byproduct materials disposal site, was released in August 1988.
EPA also released a FS report in August 1988 along with a proposed plan of
action fact sheet for the UNC site groundwater operable unit. EPA held a 29-
day public comment period and a public meeting.
2.3 Enforcement History
During 1982 and 1983, EPA and UNC engaged in extensive negotiations with
the aim of entering an agreed upon Administrative Order on Consent for
conduct of investigative and remedial activities at the site in response to
groundwater contamination. In August of 1983, after UNC declined to commit
to an Order on Consent to promptly address groundwater concerns, EPA sent
notice letters to UNC indicating its plans to conduct its own Remedial
Investigation (RI) and Feasibility Study (FS).
In September of 1983 UNC objected to EPA's decision to conduct its own
RI/FS, stating that EPA had no authority under CERCLA with respect to the
site, and that EPA's work would interfere and be duplicative of UNC's own
efforts. EPA continued with development of its plans for a CERCLA RI/FS,
but progress was slowed as UNC denied EPA access to the site to conduct
RI/FS activities from April through September 1984.
In August 1984 UNC filed suit against EPA for declaratory and injunctive
relief in U.S. District Court for the District of New Mexico (No. 84-1163-
JB) seeking to prevent EPA conduct of the RI/FS. In September of 1984, EPA
obtained and executed an Administrative Warrant to conduct preliminary RI
activities. EPA also filed an action in the same District court seeking
injunctive relief and an Order in Aid of Access (No. 84-1409-BB). During
the months of October through December 1984, UNC and the United States
filed numerous motions, in relation to both cases no. 1163 and no. 1409.
In December of 1984 U.S. District Court dismissed case no. 1163 "without
prejudice". UNC also informed the Department of Justice of its intention
not to interfere with EPA access to the site to conduct the RI/FS, and
work on the study was able to proceed. In April of 1985, the U.S. District
Court entered an order granting EPA access to the UNC site for the purpose
of conducting the RI/FS. (UNITED STATES OF AMERICA v. UNITED NUCLEAR
CORP., 610 F. SUPP. 527 (D.N.M.,1985))
In June of 1986 the State of New Mexico returned its authority to regulate
uranium mills back to the NRC. This Regulatory change prompted the develop-
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ment of the previously mentioned MOD between Region VI of EPA and Region IV
of NRC for remedial action at the UNC site. The MOU, signed In August 1988.
establishes the roles and responsibilities of each agency 1n reclamation of
the UNC site (Appendix I). The MOU recognizes that EPA will conduct an RI/FS
and sign a ROD which addresses groundwater outside the byproduct materials
disposal site while NRC is responsible as the lead-agency in matters of
surface reclamation and source control.
The United States will seek to have the responsible party implement the UNC
groundwater operable unit remedy under terms of a consent decree lodged
with the Department of Justice. The remedy Is discussed, along with other
remedies, in the "Alternatives Evaluation" section of this ROD.
3. SITE CHARACTERISTICS
3.1 Geology and Hydrogeology
The stratigraphy at the UNC site is divided into two main components: the
surficial unconsolidated deposits (Quaternary alluvium) and the underlying
consolidated bedrock units. The Quaternary alluvium is the major surficial
unconsolidated deposit at the site. This laterally discontinuous deposit
consists of a mixture of sand, silt, clay, and to a lesser amount, gravel.
Alluvial thicknesses are greater than 120 feet with an average of 50 feet.
The main bedrock units at the site are the Upper Gallup Sandstone (vertically,
beneath the alluvium: Zones 3, 2, and 1) and the Upper D-Cross Tongue member
of the Mancos shale. All bedrock units are of Cretaceous age. Zone 3 of
the Upper Gallup Sandstone, which is up to 90 feet thick, contains a medium-
to coarse-grained sandstone. Zone 2 (10 to 20 feet thick) contains a carbo-
naceous shale and coal with thin sandstone lenses. Zone 1 (up to 90 feet
thick) is sandstone similar to Zone 3, but with a finer grain size. The
Mancos shale is a carbonaceous, fissile shale at the site.
There are three principal structural zones at the site: Pipeline Canyon
lineament. Fort Wingate lineament, and Pinedale monocline. These structural
features impact the site hydrogeology in some locations by affecting ground-
water flow directions. In some locations, the Zone 2 unit provides an
effective barrier to communication between the two bedrock aquifers. In
places, all three aquifers of concern are in hydraulic connection, indicating
they are not isolated units. The Mancos shale is considered a barrier to
further vertical migration into lower aquifers. Figure 3 presents general-
ized east-west and north-south cross-sections of the aquifer systems at the
UNC site.
The Remedial Investigation (RI) report for the UNC site concluded that mine
discharges and tailings seepage have impacted the alluvial aquifer, and
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Iff
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8
Zones 1 and 3 of the Upper Gallup Sandstone. Mine water discharges signifi-
cantly recharged these three aquifers and mixed with seepage from the tailings
ponds after milling operations began in 1977. A summary of the hydrogeologic
characteristics of these aquifers is presented in Table 1.
The alluvial aquifer has been affected by both surface water discharges
associated with the mine operations and by seepage of contaminants from the
tailings pond. The Zone 3 aquifer has been impacted by contaminants that
have leached from the northeast portion of the north tailings cell. The
Zone 1 aquifer has also been contaminated from seepage from the central
tailings cell and borrow pit No. 2. The remedial investigation report
concluded that each of these aquifers are contaminated to varying degrees
with heavy metals, other inorganics, and radionuclides through seepage from
the tailings ponds (EPA, 1988).
3.2 Nature and Source of Contamination
Background Levels of Contaminants
Prior to evaluating the contamination that has resulted from site activities,
a determination of background levels of contaminants must be made. These
background levels are used as cleanup criteria if at a higher concentration
than federal or state standards for a particular contaminant. For the UNC
site, two background conditions are distinguished: 1) premining, pretailings
background levels (i.e., prior to 1968), and 2) postmining, pretailings
background levels (i.e., between 1968 and mid-1977). The first condition
refers to the quality of the groundwater in the alluvium and Upper Gallup
Sandstone in the vicinity of the site prior to mine dewatering. The second
condition refers to the quality of groundwater in the same units after mine
water discharge, but prior to tailings disposal.
As stated in the Feasibility Study, and reiterated here, background levels
are based on postmining, pretailings conditions. They have been set by EPA
based on an assessment of available information from 1) pre-tailings ground-
water monitoring at the site, and 2) regional hydrogeochemical sampling in
the Gallup Sandstone and alluvium. These background levels are presented
in Table 2 along with additional contaminant-specific groundwater ARARs for
the UNC site. A discussion of the rational used in the selection of background
levels for iron, manganese, sulfate, nitrate and total dissolved solids
(TDS) is found in Appendices C and H.
Should additional information become available that would significantly alter
the estimation of background levels, such information would be evaluated in
terms of its impact on remedial actions in each aquifer.
Source Characterization
Uranium milling byproduct materials, which were discharged to unlined ponds
on UNC property, are the primary source of contaminants to the alluvial and
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Table 2
CONTAMINANT-SPECIFIC GROUNDWATER ARARs
Contaminant
Aluminum
Antimony
Arsenic
Barium
Beryllium
Cadmium
Chromium
Cobalt
Copper
Iron
Lead
Manganese
Mercury
Molybdenum
Nickel
Selenium
Silver
Thallium
Vanadium
Zinc
Chloride
Sulfate
Nitrate
TDS
Radium-226 and -228
Uranium-238
Thorium-230b
Gross Alpha
Concentration
mg/La
5.0
0.014
0.05
1.0
0.017
0.01
0.05
0.05
1.0
5.5
0.05
2.6
0.002
1.0
0.2
0.01
0.05
0.014
0.7
10.0
250.0
2,160.0
30.0C
3,170.0
5 pCi/L
5.0
(1,645 pCi/L)
15 pCi/L
15 pCi/L
Source
NMWQA
Health-based
MCL
MCL, NMWQA
Health-based
MCL, NMWQA
MCL, NMWQA
NMWQA
NMWQA
Background Level
MCL, NMWQA
Background Level
MCL, NMWQA
NMWQA
NMWQA
MCL
MCL, NMWQA
Health-based
Health-based
NMWQA
NMWQA
Background Level
Background Level
Background Level
MCL
NMWQA
MCL
MCL
.mg/L except as noted.
Based on 15 pCI/L gross alpha.
cPreoperational data of 30 mg/L appears reasonable for
background. Additional investigation and determination of
the natural NO.-N sources is necessary since NO--N is a
health-related standard.
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11
bedrock aquifers near the UNC site. Tailings leachate has migrated into
the south alluvium, the north alluvium adjacent to the tailings ponds, and
the Zone 1 and Zone 3 aquifers.
Although EPA did not sample tailings solids or liquids during the Remedial
Investigation, UNC and NRC provided EPA with several tailings analysis used
to characterize byproduct solids and liquids. These data are presented 1n
Table 3. From these analysis, the tailings fluids are characterized as an
acidic, high dissolved solids water with sulfate, ammonia and sodium as
principle ions. Metal analyses, particularly aluminum, manganese, and
iron, are very high (over 1,000 mg/L). Radioactivity as represented by Th-
230 is very high.
3.3 Pathways of Contaminant Migration
This section discusses the major contaminant pathways and the interrelation-
ships of these pathways as identified in the RI report. Figure 4 presents
a simplified schematic of the relationships between the contaminant sources
and migration pathways at the UNC site. There are two major sources of
recharge to the site aquifers: the stream in Pipeline Canyon and seepage
from the tailings pond. To a lesser extent, direct precipitation also
supplies recharge water to the aquifers.
During the period when mine water discharges to Pipeline Canyon occurred,
recharge from the stream to site aquifers was significant (up to 250 gallons
per minute) (EPA, 1988). Mine discharges occurred at the UNC mine and the
Kerr-McGee mine north of the UNC site. This recharge mechanism created an
artificially high water table under the site, and helped transport contami-
nants southwest along the canyon and within the alluvium and bedrock aquifers.
These waters, having the potential to leach constituents from the unsaturated
alluvium, Infiltrated into the bedrock aquifers and transported contaminants
that had seeped from the tailings ponds. Groundwater recharge from surface
water in Pipeline Canyon "has ceased (except during precipitation events)
following the termination of mine discharges by UNC in 1983 and Kerr-McGee
in 1986. Since that time, water levels in the alluvium have decreased and
are slowly returning to premining levels.
The tailings ponds are a source of contaminants to all aquifers at the
site. Seepage of tailing liquids has entered the alluvial system from the
three tailings cells to varying degrees. The mechanism responsible for
this transport is gravity flow of water through the tailings into the
alluvium. Where the alluvium is absent, tailings seepage has also entered
the bedrock aquifers in the northeastern portion of the north cell where
the Zone 3 aquifer contacts the tailings; and in the eastern portion of the
central cell where Borrow Pit No. 2 contacts the Zone 1 aquifer.
Water levels in several UNC wells in Zone 3 have shown a small decline in
response to termination of mine discharges to Pipeline Canyon outside the
-------
Table 3
PROBABLE TAILINGS LIQUID CHEMISTRY
Well
(2)
Parameter
Units
pH
TDS
Aluminum
Manganese
Ammonia
Nitrate
Th-230
Conductivity
Calcium
Magnesium
Sodium
Potassium
Bicarbonate
Chloride
Sulfate
Arsenic
Selenium
Iron
Lead
Cadmium
Zinc
Molybdenum
Ra-226
Ra-228
S.U.
mg/L
mg/L
mg/L
mg/L
mg/L
pCi/L
unhos/cm
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
pCi/L
pCi/L
Summary
1-3
38,462 - 61,932
1,167 - 2,906
100
1,450 - 5,500
75.5 - 282
1,064 - 277,733
24,813 43,581
0.024 0.208
0.001 - 0.161
<0.05 - 0.15
13
2.6
No. 633
2/26/86
1.71
46,793
2,880
100
438
1.84
17,718
240
287
526
4
0
253
28,209
0.65
0.29
4,350
0.6
0.013
10
(1)
(2)
(3)
NRC
Sample
April 1987
3.34
58,860
2,100
210
5,860
<50
13
460
1,100
890
580
41,000
<0.60
<1.2
2,700
3.34
0.24
20
<0.24
24
(3)
Range for 3 samples collected and analyzed by ONC.
One-time sampling event. Analytical data is also presented in Appendix G.
Total Radon (226 + 228}
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14
influence of the UNC pumping system. In addition, water levels in certain
wells in the bedrock aquifers are affected by the pumpback systems at the
site. However, groundwater, contaminated with tailings leachate, will
continue to migrate downgradient as long as the source (the tailings pond)
continues to leach; some decrease in concentration due to natural attenuation
and dispersion would be expected.
3.4 The Extent of Contamination from Tailings Seepage
Monitoring Well Data
Twenty-nine monitoring wells were installed at the UNC site during the RI
field activities (Well Nos. EPA-1 through EPA-28 and EPA-22A). Locations
of the monitoring wells that were sampled during the RI field work are
shown in Figure 2. Groundwater samples were collected from these wells in
March, May, and August 1985 for radiological and nonradiological constituents,
The March and May sampling rounds included five UNC wells (Nos. 504B, 610,
611, 621, and 625) and the 29 newly Installed EPA wells (Nos. EPA-1 through
EPA-28 and EPA-22A).
Tables 4 and 5.summarize the maximum and mean chemical and radionuclide
concentrations, respectively, within each aquifer at the site. These
concentrations were calculated using the May 1985 data for nonradiological
contaminants and both March and May 1985 data for radiological contaminants.
Mean concentrations were calculated by averaging contaminant values from
each well in a given aquifer. Maximum concentrations represent the highest
contaminant value measured in a given aquifer.
Data obtained during the 1985 RI field sampling were then compared to
contaminant-specific Applicable or Relevant and Appropriate Requirements
(ARARs) for the site. Contaminant-specific ARARs (Table 2) are the Safe
Drinking Water Act (SDWA) Maximum Concentration Limits (MCLs), New Mexico
Water Quality Act (NMWQA) standards, and background levels where background
is higher than federal and state standards. A more detailed discussion of
contaminant-specific ARARs 1s found in Appendix C.
Table 6 presents by aquifer these contaminants for which maximum detected
concentrations exceed contaminant-specific ARARs (Table 2). Zone 3, Zone 1,
and the southwest alluvial aquifer contain most of the compounds exceeding
standards.
Figures 5 through 7 indicate the number and location of wells where ARARs
have been exceeded for each aquifer at the site. Specific contaminants
exceeding ARARs and their associated concentrations are also listed. As
these figures indicate, contaminants exceed standards in fourteen wells
Immediately downgradient of the tailings ponds in Zone 3; in seven wells
adjacent to and immediately downgradient of tailings ponds in Zone 1; and
in nine wells downgradient of tailings ponds in the alluvium. Seven of the
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Table 6
COMPOUNDS EXCEEDING STANDARDS
North South Sec. 36
Contaminant Zone 3 Zone 1 Alluvium Alluvium Alluvium
Aluminum X X
Arsenic X X
Cadmium XX XX
Cobalt XX X
Manganese XX X
Molybdenum XXX X
Nickel XX X
Selenium XX X
Nitrate XX XX
TDS XXX XX
Ra-226-228 X
Gross Alpha XXX XX
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23
The locations of operating wells sampled by EPA 1n 1987 are shown In Figure 9.
Primary drinking water standards were not exceeded In any of the samples.
Well 15K-303 and the Gray Well were the only samples containing
radiological activity above 1 p1co curie per liter (pC1/L), with 15K-303
containing 12.0 +_ 2.7 pCi/L beta and 1.6 +. 0.1 pCI/L radium 226, and the
Gray Well containing 2.5 + 3.0 pC1/L alpha and 5.6 +. 3.6 pC1/L beta. These
activities are below the drinking water standards, and related to natural
background levels in area groundwater. The state standard for total
dissolved solids (1000 tng/L) was exceeded in samples from all four wells,
while the state standard for sulfate (600 mg/L) was exceeded in 15K-303.
The state standard for iron (1.0 mg/L) was exceeded in wells 16F-606 and 15K-
303, and that for manganese (0.2 mg/L) exceeded in well 15K-303.
The principal exposure pathways through which humans might potentially
become exposed to contaminants in the future are:
o 1ngest1on of groundwater from wells outside the tailings disposal
area 1n each of the contaminated target areas if water supply wells
are ever Installed before completion of remedial activity
o inadvertent ingestion of surficial tailings solids
EPA concluded from Its public health assessment 1n the Feasibility Study
that adverse health or environmental hazards could result if no action was
taken to prevent exposure to groundwater contaminants found at the site.
The public health assessment assumed ingestion of groundwater at contaminant
concentrations equal to those measured during the 1985 RI sampling events
(Tables 4 and 5). This assumption was conservative since dilution and
dispersion expected to occur if seepage were allowed to continue to migrate
downgradient from the site would likely further reduce the concentration of
contaminants from the concentrations assumed. The remedy selected for the
UNC groundwater operable unit is designed to contain and remove groundwater
contaminated by tailings seepage thereby preventing continued downgradient
migration of seepage and reducing significantly the amount of radiogenic
and nonradiogenic constituents released into the environment. Groundwater
remediation coupled with source control remedial action required by NRC
will allow further improvements in groundwater quality at the UNC site.
NRC-required source control measures, which address surficial contamination
from windblown tailings solids and control of groundwater evaporation
residues, are expected to eliminate significant potential risks to human
health and the environment via the direct contact, air emissions, or surface
exposure routes.
4. COMMUNITY RELATIONS
On April 6, 1987, EPA held its first community meeting on the UNC site to
discuss the status of on-going investigations at the site, and to clarify
the respective roles of EPA and NRC in coordinating site reclamation.
Navajo translation was provided and NRC was in attendance. Fact sheets
-------
-------
25
were mailed to local residents and Interested parties Indicating that a
Memorandum of Understanding (MOU) was being developed between EPA and NRC
establishing each agencies role and responsibility 1n achieving site reclama-
tion. Also, at the request of several citizens present at the meeting, EPA
committed to sampling of domestic/livestock wells within a four-mile radius
of the site. The well sampling was announced 1n September 1987 via a press
release.
On August 11, 1988, EPA announced through a press release that the Remedial
Investigation, Feasibility Study, and Administrative Record for the ground-
water operable unit would be available In repositories for public review by
August 19, 1988. In the same press release EPA announced that the public
comment period on the groundwater operable unit RI/FS would be held between
August 19 and September 16, 1988. The press release also announced that a
public meeting to discuss the proposed remedy would be held at Red Rock
State Park on August 31, 1988.
EPA prepared an English fact sheet and condensed Navajo fact sheet describ-
ing various alternatives evaluated in the FS and the proposed plan of action.
This was mailed to the site mailing 11st of over 325 area residents on
August 9, 1988. EPA also held an open house on August 4, 1988, with a repre-
sentative of NRC, to informally discuss results of EPA's RI and EPA/NRC juris-
diction. This meeting was announced through a mailing on July 19, 1988, and
a press release on July 29, 1988. Approximately 40 people attended including
three press representatives.
The public meeting was held August 31, 1988, at Red Rock State Park in
Gallup, New Mexico. Approximately 40 people attended. A representative of
the NRC was included on the panel and responded to questions on surface
reclamation as required by UNC's license. The Responsiveness Summary in
appendix H lists the public response to the alternatives proposed by EPA at
this meeting. The meeting began at 7:00 p.m., proceeded with Navajo
translation, and adjourned at 12:15 a.m.
5. ALTERNATIVES EVALUATION
5.1 Evaluation Criteria
To ensure compliance with Section 121 (a)(b) and (d) of the Superfund
Amendments and Reauthorization Act (SARA), the following nine factors are
considered in selecting a remedy for a Superfund site. These are summarized
below:
1. Consistency with Other Environmental Laws (ARARs)
In determining appropriate remedial actions at Superfund sites, EPA must
consider the requirements of other Federal and State environmental laws, 1n
-------
Primary consideration Is given to
proprlate Federal and State public
d standards. Not all Federal and
s are applicable or relevant and
action.
illty or Volume
treatment that reduces toxldty,
id. Relevant factors are:
dies employ and materials they will
s that will be destroyed or treated;
1n toxldty, mobility, or volume;
; Is Irreversible; and
>11 owing treatment, considering the
and propensity for bloaccumulatlon
their constituents.
/es must be assessed by
I risks; and
ed to the community, workers, or
Ion of an alternative Including
and the environment associated
nd redisposal or containment;
srmanence
term effectiveness and
>e of centalnty that the remedy
;d are:
s of amounts and concentrations
entatlon of a remedial action,
ty, mobility, and propensity to
stances and their constituents;
agement required, including
ntenance;
and environmental receptors to
potential threat to human health
tith excavation, transportation,
g1nee ring and institutional
es associated with land disposal of
and
of the remedy.
the alternatives must be assessed by
:ors:
J with constructing the technology;
of the technologies;
|tain necessary approvals and permits
i for offsite actions) from other
.pment and specialists; and
>n of needed treatment, storage, and
essed include the following:
"its;
and operation and maintenance costs;
tion costs.
-------
28
o Components of the alternatives that the community supports;
o features of the alternatives about which the community has
reservations; and
o elements of the alternatives which the community strongly opposes.
8. State Acceptance
EPA must assess the concerns of the State government which, for this site,
1s represented by the New Mexico Environmental Improvement Division. This
assessment Includes:
o Components of the alternatives the State supports;
o features of the alternatives about which the State has
reservations; and
o elements of the alternatives under consideration that the State
strongly opposes.
9. Overall Protection of Human Health and the Environment
Following the analysis of the remedial options against Individual
evaluation criteria, the alternatives must be assessed from the standpoint
of whether they provide adequate protection of human health and the
environment. EPA is also directed by SARA to give preference to remedial
actions that utilize treatment to remove contaminants from the environment.
Offsite transport and disposal without treatment is the least preferred
option where practicable treatment technologies are available.
5.2 Description of Alternatives
In conformance with the National Contingency Plan (NCP), EPA screened
Initial remedial possibilities to determine which might be appropriate for
groundwater contamination outside the byproduct materials disposal site.
The Feasibility Study describes the details of this evaluation. Source
control measures required by NRC under United Nuclear Corporation's Source
Materials License were given consideration during development of the ground-
water remediation alternatives. Source control measures will be performed
in sequence with any selected groundwater alternative. From the possible
remedies, four were chosen for detailed evaluation under the remedy selection
criteria outlined above. One other alternative, No Action, was also evaluated
to comply with the requirements of the NCP. All five alternatives are
summarized schematically in Figure 10.
Except for the No Action and Limited Action alternatives, all alternatives
require collection and physical/chemical evaporation of contaminated ground-
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30
water. The estimated duration and cost for each of the groundwater collection
and treatment alternatives was based on remediation to federal and state
standards, or background levels of constituents found in area wells prior
to the beginning of tailings disposal activity in June of 1977.
Costs associated with collection and treatment alternatives are summarized
for two physical/chemical treatment systems, column evaporation and
enhanced mister/pond evaporation. The enhanced mister/pond evaporation
system is the treatment process option proposed by United Nuclear
Corporation under NRC license requirements. Column evaporation is a second
process option evaluated by EPA to adequately treat contaminated
groundwater. Estimated costs for each alternative were summarized in 10-
year and 60-year time periods to allow for uncertainties in using models to
predict responses to various pumping and restoration rates (see Appendix A
for a discussion of hydrogeologic uncertainties; Appendix B for a discussion
of cost estimates).
Each groundwater remedial action alternative would require pilot studies
to determine reasonably achievable pumping rates in aquifers at the site and
necessary storage and evaporative capacity. All alternatives assume implemen-
tation of NRC-required reclamation and closure activities within the
tailings disposal area.
No Action Alternative
This alternative assumes that no monitoring would be performed outside the
byproduct materials disposal site currently defined by Section 2. Under
this alternative contaminants beyond the boundary of Section 2 would continue
to migrate downgradient in the alluvium and Upper Gallup aquifers (Zone 1
and Zone 3). Although some reduction in the concentration of contaminants
is expected to occur from natural flushing of the aquifers and downgradient
movement of contaminated groundwater, future use of impacted groundwater in
areas beyond Section 2 could occur with associated health risks. There is
no cost for this alternative.
Limited Action Alternative
This alternative consists of institutional controls in the alluvial and
Upper Gallup aquifers at the site, monitoring in all three aquifers, and
maintenance of current pumping systems 1n the Upper Gallup aquifers.
Operation of the East pump-back wells in Zone 1 and the Northeast pump-back
wells 1n Zone 3 would continue until adequate dissipation of the tailings
seepage mound has been achieved. Groundwater use and surface access restric-
tions would be Implemented as part of this alternative 1n areas impacted by
tailing seepage beyond Section 2 to protect public health and the environment.
Flushing of all three aquifers would occur as natural upgradient groundwater
flows through the target zones. A 50-percent contaminant reduction in the
alluvial aquifer from natural flushing could take 30 years at current flow
-------
31
rates. A 50-percent contaminant reduction from natural flushing of Zone 3
could take 75 years, and possibly 200 years in Zone 1. The estimated cost
of this alternative is $2 million over a 10 year period and $3 million over
a 60 year period.
Alternative 1 - Groundwater Pumping and Treatment in Upper Gallup
Zone 3 and Zone 1 Aquifers, In the Southwest Alluvium, and Two
Areas in the North Alluvium;"
The alternative consists of containment and selective extraction of contami-
nants in the Upper Gallup Zone 3 aquifer utilizing as many as 21 extraction
wells appropriately placed to establish a hydraulic capture zone for the
Zone 3 target area. This alternatives would require containment and selective
extraction of contaminants in the Upper Gallup Zone 1 aquifer utilizing as
many as 60 extraction wells necessary to establish a hydraulic capture zone
for the Zone 1 target area. This alternative would also require containment
and selective extraction of contaminants in the three alluvial target areas
(see Figure 8) utilizing as many as 23 extraction wells to establish necessary
hydraulic capture zones. All extracted water would be directed to either
an enhanced mister/pond evaporation system or column evaporator at an optimum
achievable flow rate. The evaporation system used would be sized in order
to provide sufficient evaporative capacity for maintenance of achievable
pumping rates. This alternative includes institutional controls, monitoring,
and maintenance which also compose the Limited Action Alternative. The esti-
mated cost of this alternative is $46 million with column evaporation and
$36 million with enhanced mister/pond evaporation over a 10 year period;
respective evaporation costs are $58 million and $43 million over a 60 year
period.
Alternative 2 - Groundwater Pumping and Treatment in Upper Gallup
Zone 3 Aquifer, the Southwest Alluvium, and Two Areas in the North
Alluvium; Limited Action in the Upper Gallup Zone 1 Aquifert
This alternative is identical to Alternative 1 for the Upper Gallup Zone 3
aquifer and three alluvial target areas. Containment and selective extraction
of contaminants in Zone 3 and the alluvium would require as many as 21 and
23 wells, respectively, in order to establish necessary hydraulic capture
zones for target areas in these aquifers.
This alternative differs from Alternative 1 in relation to mitigative action
in the Upper Gallup Zone 1 aquifer. Alternative 1 would require the installa-
tion and operation of an extensive extraction well network in Zone 1 whereas
this alternative calls for institutional controls, monitoring, and maintenance
of current pumping systems in Zone 1 (e.g. limited action). Alternative 2
includes the components of the Limited Action Alternative for the Zone 3
and alluvial aquifers. All extracted water for this alternative would be
directed to either an enhanced mister/pond evaporation system or column
-------
32
evaporater at an optimum achievable flow rate. The evaporation system used
would be sized in order to provide sufficient evaporative capacity for
maintenance of achievable pumping rates. The estimated cost of this alterna-
tive is $33 million with column evaporation and $20 million for enhanced
mister/pond evaporation over a 10 year period; respective evaporation costs
are $42 million and $26 million over a 60 year period.
Alternative 3 - Groundwater Pumping and Treatment In Upper Gallup
Zone 3 Aquifer and the Southwest Alluvial Aquifer; Limited Action
nplng
st All
in the Upper Gallup Zone 1 Aquifer;
This alternative consists of containment and extraction of contaminants 1n
the Upper Gallup Zone 3 aquifer utilizing at least 16 extraction wells
appropriately placed to establish a hydraulic capture zone for the Zone 3
target area. This alternative would also require containment and extraction
of contaminants in the southwest alluvial target area utilizing as many as
9 extraction wells appropriately placed to establish an effective hydraulic
capture zone. As 1n Alternative 2, this alternative calls for Institutional
controls, monitoring, and maintenance of current pumping systems in the
Upper Gallup Zone 1 aquifer (e.g. limited action). Components of the Limited
Action Alternative also apply to the Zone 3 and the southwest alluvial target
areas in this alternative. All extracted water for this alternative would
be directed to either an enhanced mister/pond evaporation system or column
evaporator at an optimum achievable flow rate. The evaporation system used
would be sized in order to provide sufficient evaporative capacity for main-
tenance of achievable pumping rates. The estimated cost of this alternative
is $29 million with column evaporation and $17 million for enhanced mister/pond
evaporation over a 10 year period; respective evaporation costs are $38
million and $20 million over a 60 year period.
5.3 Evaluation of Alternatives
EPA has assessed the degree to which each remedial alternative meets the
nine selection criteria; Table 7 summarizes this assessment. The following
values were used to compare the remedy selection criteria:
H- Alternative would greatly exceed a selection criterion compared to
other alternatives.
+ Alternative would exceed a criterion compared to other alternatives.
0 Alternative can meet the selection criterion.
- Special efforts will be necessary in the design of the remedy to
meet the selection criterion.
Great difficulty would result in achieving a selection criterion as
compared to other alternatives.
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The rationale for the ratings assigned in this table 1s as follows:
1. Compiles with ARARs (I.e. meets or exceeds applicable, or rele-
vant and appropriate Federal and State requirements). Appendix C discusses
the compliance of each remedial alternative with all applicable or relevant
and appropriate environmental laws. No Action and Limited Action are rated
as "" because groundwater restoration would occur at the natural rate of
flushing such that chemical-specific ARARs may not be achieved for hundreds
of years even after source control remedial action.
Alternatives 1, 2, and 3 are assigned "0" because removal of contaminated
groundwater would occur resulting In attainment of chemical-specific ARARs
for most contaminants. In the event that performance evaluations demonstrate
that It is technically infeasible to achieve all chemical-specific ARARs In
a reasonable time period, due to hydrogeologlc conditions or other factors,
then EPA may reconsider remedial levels for specific contaminants in question,
All groundwater extraction alternatives, including Limited Action, could be
designed to meet location and action specific requirements. Both enhanced
mister/pond evaporation and column evaporation systems can be designed to
meet location and action specific requirements as well.
2. Reduces Toxicity, Mobility, and Volume
No Action and Limited Action are rated as "-" because they do not reduce
toxicity, mobility, or volume to the extent expected from groundwater
containment and extraction systems proposed for Alternatives 1, 2, and 3.
Natural flushing action (No Action and Limited Action) of the alluvial and
Upper Gallup aquifers would occur following source control remedial action
thereby reducing groundwater contamination, however mobile contaminants
would continue to migrate downgradient.
Alternatives 1, 2, and 3 are assigned "0" for mobility and volume because
contaminated groundwater would be contained, extracted, and evaporated
concentrating contaminants into a dewatered residue.
Alternative 1 is assigned "+" for toxicity since some margin of contaminant
reduction would be achieved in Zone 1 of the Upper Gallup aquifer as compared
with Alternatives 2 and 3.
3. Short Term Effectiveness
Alternatives 1, 2, and 3 are assigned a "-" because while actively reducing
groundwater contamination levels within a given aquifer, remediation levels
may not be reached within a short time frame due to physical
characteristics of the aquifers.
-------
35
No Action 1s rated as "" since It does not offer the moderate reduction
1n contaminant concentrations, nor access and use restrictions, provided by
the other alternatives.
Limited action 1s rated as "-" since It does provide access and groundwater
use restrictions which would protect against public health risks from site
contaminants.
4. Long Term Effectiveness
Alternatives 1, 2, and 3 would actively reduce groundwater contamination
levels within each aquifer and are assigned a "0". Alternative 1 would
reduce groundwater contamination 1n Zone 1 more than Alternatives 2 and 3,
but only over an extremely long time period. Therefore Alternative 1 1s
not given a higher rating than Alternatives 2 or 3.
No action 1s assigned a "-" because the potential human health and
environmental risks associated with continued downgradient migration of
contaminants would not be adequately abated as discussed In Section 3.5.
Limited Action is assigned a "-" for the same reasons as for No Action.
5. Implementability
Alternatives 2 and 3 are equally feasible for the alluvial and Upper Gallup
Zone 3 aquifers and are assigned a "0". Alternative 1 is assigned a "-"
because the characteristics of the Upper Gallup Zone 1 aquifer limit the
Implementability and reliability of an extraction well network in signifi-
cantly decreasing contaminant levels in this aquifer.
No Action and Limited Action are assigned a "+" because they can be easily
implemented.
6. Cost
Table 8 lists the estimated costs for each remedial action alternative.
This table includes capital, operation and maintenance, and 10 and 60 year
present worth costs. These costs estimates were generated on the basis of
a number of assumptions (see Appendix B) and are used to allow relative
comparisons between remedial alternatives.
Limited Action is the least costly alternative apart from No Action. Costs
for Alternatives 1, 2, and 3 are directly dependent upon the length of time
required to effectively reduce groundwater contamination 1n a particular
aquifer, and the type of evaporation treatment system used. Alternative 3
costs less than Alternative 2, both of which cost less than Alternative. 1.
Enhanced mister/pond evaporation costs significantly less than column
evaporation.
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7. Community Acceptance
Most of those attending the public meeting demonstrated a preference for
active groundwater restoration in conjunction with source control remedial
action. Community representatives attending the meeting had no strong
preferences between Alternatives 1, 2, and 3. One local resident favored
Alternative 1 on the basis of elevated costs and therefore increasing poten-
tial employment opportunities in the area. In response to a question on
the effectiveness of Alternative 3 in addressing tailings seepage contamina-
tion, EPA explained that this remedy would be performance based.
In the absence of strong preferences between Alternatives 1, 2, and 3, and
in view of the duration of pumping that might be required, active
groundwater restoration alternatives were assigned a "0". No Action and
Limited Action were rated "--".
8. State Acceptance
The New Mexico Environmental Improvement Division (NMEID), the State
regulatory agency for CERCLA sites, was briefed on remedial alternatives on
July 27, 1988. The NMEID notified EPA by letter of Its preference for
Alternative 3 with enhanced mister/pond evaporation provided adecuate
protection of public health and the environment is achieved (See Appendix
G). Alternative 3 with enhanced mister/pond evaporation (to be sequenced
with source control remedial action) was therefore assigned a "C".
Alternatives utilizing column evaporation were assigned a "--" cue to cost
considerations; a similar rating was assigned for No Action and Limited
Action. Alternatives 1 and 2 using enhanced Mister/pond evaporation were
assigned a "-" since Alternative 3 would provide comparable protection to
public health and the environment at reduced costs.
9. Overall Protection of Human Health and the Environment
No Action is rated as M" because it does not provide adequate protection
from potential risks involved with continued downgradient migration of
contaminants.
Limited Action is assigned a "-" since groundwater use restrictions would
help prevent contact with contaminated groundwater in respective target
areas.
Protection of public health and the environment can best be provided by
containment and extraction of contaminated groundwater supplemented by
groundwater-use restrictions. For this reason, Alternatives 1, 2, and 3
are assigned a "0". This rating holds for both enhanced mister/pond
evaporation and column evaporation systems because both systems would be
operated under controlled conditions within the byproduct materials
disposal site and optimized during remedial design for adeqjate protection to
public health and the environment.
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38
6. SELECTED REMEDY
The selected remedy for the United Nuclear Corporation groundwater operable
unit corresponds to Alternative 3 utilizing enhanced mister/pond evaporation.
Figure 11 Is a schematic diagram showing components of the selective remedy.
EPA believes that this alternative best fulfills the statutory and selection
criteria as compared to other solutions. Specific design details of the
selected remedy will be developed during the remedial design process.
6.1 Description of Selected Remedy
The selected remedy for the United Nuclear groundwater operable unit consists
of six components described below. The EPA remedy incorporates source con-
trol remedial action (surface reclamation, capping, and mill decommissioning)
under Nuclear Regulatory Commission's licensing requirements as specified
in the Memorandum of Understanding between EPA and NRC (Appendix I).
1. Implementation of a monitoring program to detect any increases in the
areal extent, or concentration of groundwater contamination outside the
tailings disposal area.
To ensure that contamination does not exist beyond cleanup target areas
developed in the Feasibility Study, a groundwater monitoring program will
be Implemented during remedial design.
The monitoring program will consist of a groundwater monitoring network
comprised of a series of wells to measure water levels and water quality.
The monitoring points shall be located upgradient, downgradient, and cross-
gradient of seepage plumes in order to further define the extent of contami-
nation in Zones 1 and 3 of the Upper Gallup Sandstone, and the southwest
alluvium. Results of monitoring will be evaluated against contaminant-
specific ARARs or background to adjust target area to include any downgradient
areas impacted by tailings seepage. The extent of contamination in each
aquifer, concentration of contaminants in each well, and observed saturated
thickness shall be used to identify the most effective pumping well locations.
2. Operation of existing seepage extraction systems in the Upper Gallup
aquifers 7
Because seepage from tailings has migrated into underlying Zone 1 and Zone
3 sandstones, the selected remedy includes operation of the East pump-back
wells in Zone 1 and the Northeast pump-back wells in Zone 3 until adequate
dissipation of the tailings seepage mound has been achieved. Operation of
these two pump-back systems will be integrated with active seepage remediation
that may be required by the NRC inside the tailings disposal area, and with
active seepage collection as required by EPA outside the disposal area.
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ndwater in Zone 3 of the
d additional wells7
is disposal site will be
>age. The extent of the
I remedial design, prior to
ated on the basis of ground*
;ion with identification of
eded (including background)
> create a hydraulic barrier
>11 locations will be guided
i the extent of the tailings
luring performance monitoring
rmine the optimum rate of
jally required.
undwater in the southwest
wells.
ai
d)
11 be performed in areas
f the tailings seepage plume
rmined prior to extraction
tamination will be based on
onjunction with identification
exceeded (including background)
11 be designed to create a
mil nation while the source is
Is required, and their final
I saturated thicknesses in the
|e plume as defined above. If
»pt tailings seepage, then con-
n these wells. Data obtained
j system should be used to
>nt and duration of pumping
uifers using evaporation
ems to enhance the rate of
11 be directed to an evapora-
ration ponds and mist or
-------
41
spray evaporation systems. Inflow to the evaporation disposal system will
be from current and required extraction wells outside and/or within the
tailings disposal area. The evaporation pond system, coupled with mist and
spray evaporation systems, will be sized and operated in order to provide
sufficient evaporative capacity for maintenance of a reasonable operational
water balance. Optimization of the evaporation disposal system should
occur during the first several months of operation, and shall include pilot
testing to determine the optimum pH for water evaporation.
6. Implementation of a performance monitoring and evaluation program to
determine water level and contaminant reductions in each aquifer, and
the extent and duration of pumping actually required outside the
?l
tailings disposal area.
In order to evaluate predicted reductions in contaminant concentrations
with time in a particular aquifer, and declines in pumping rates, a
performance monitoring program shall be implemented. Monitoring well
locations shall be chosen at critical points to allow effectiveness
evaluations of hydraulic capture zones in collecting tailings seepage.
Performance monitoring during active seepage remediation will allow a determ-
ination to be made regarding the adequacy of groundwater remedial actions
outside the tailings disposal area at the United Nuclear Corporation site.
Monitoring data will also be used to aid in making any modifications in
remedial action outside the tailings disposal area, in order to meet CERCLA
requirements.
These elements comprise the selected remedy for the groundwater operable
unit at the United Nuclear Churchrock site. As previously mentioned the
Nuclear Regulatory Commission has directed United Nuclear Corporation to
submit a reclamation plan addressing source control and surface reclamation
measures at the site under the company's Source Material License. Upon
approval of a final reclamation plan, both groundwater and source control/
surface reclamation remedial actions will be integrated and coordinated to
achieve comprehensive reclamation and remediation of the site.
6.2 Cost of Selected Remedy
The estimated capital cost of the selected remedy is $12 million and the
present-worth estimate using a 10 percent discount rate is $17 million over
a 10-year period. This is approximate and made without detailed
engineering data. The actual final cost of the selected remedy will depend
on a number of factors which include:
o material and labor costs, extraction well development, competitive
market, conditions, and others direct and Indirect costs related to
the startup of remedial activity;
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42
o achievable flow pates from extraction wells, and therefore, the size
of the enhanced mister/pond evaporation system necessary to
accommodate these flows;
o changes in operation and maintenance costs related to well system
performance;
o changes in contaminant concentrations and pumping rates over time
resulting from groundwater extraction and source control activities
which may constrain the required duration of pumping; and
o changes in parameters such as cleanup criterion, should significant
additional information on background levels of constituents result
in any significant adjustments of such parameters.
6.3 Statutory Determinations
Section 121 of SARA requires the selected remedy to be protective of human
health and the environment, be cost effective, use permanent solutions and
alternative treatment or resource recovery technologies to the maximum extent
possible, be consistent with other environmental laws, and have a preference
for treatment which significantly reduces the toxicity, volume, or mobility
of the hazardous substances as a principle element. EPA believes that the
selected remedy best fulfills the statutory and selection criteria as compared
to the other solutions evaluated herein.
1. Protective of Human Health and Environment
The selected remedy, by containing and removing tailings seepage, will sub-
stantially reduce groundwater contamination in aquifers outside the byproduct
materials disposal site. Contaminant concentration in impacted aquifers
will be reduced to ARARs to the maximum extent practicable. The selected
remedy, in conjunction with NRC-directed source control remedial action
should effectively mitigate and minimize potential threats to human health
and the environment. Implementation of the selected remedy will not cause
unacceptable short-term risks or crossmedia impacts.
2. Cost Effective
The selected remedy offers the lowest cost of all the treatment alternatives.
Compared to other treatments alternatives, it is equally effective in remov-
ing contaminants in the alluvial and Upper Gallup Zone 3 aquifers, and is
equally implementable. As previously mentioned, the characteristics of the
Upper Gallup Zone 1 aquifer limit the Implementability and reliability of
an extraction well network (e.g. Alternative 1) 1n significantly decreasing
contaminant levels in this aquifer.
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43
3. Utilization of Permanent Solutions and Alternative Treatment
Technologies to the Maximum Extent Practicable'
The selected remedy satisfies the statutory preference for treatment as a
principle element In reducing the volume, toxicity, and mobility of contami-
nants for the groundwater operable unit. The selected remedy uses an
enhanced mister/pond evaporation system to remove all contaminants from
groundwater. The solid residue generated will be contained within the
tailings disposal area and capped along with the tailings piles as part of
the NRC-directed source control remedial action.
The selected remedy utilizes permanent solutions to the maximum extent
practicable. The principle element of the remedy 1s containment and
removal of groundwater contaminated by tailings seepage. This will be
accomplished by creating hydraulic barriers or capture zones designed to
ensure that the remedy Is effective. Future mass loading from the tailings
will be minimized under NRC requirements.
4. Consistent with Other Environmental Laws
The selected remedy should result 1n attainment of legally applicable and
relevant or appropriate requirements or ARARs. Appendix C lists all the
ARARs which were initially Identified for this operable unit in the
Feasibility Study. The specific ARARs for the selected remedy are
described below:
National Primary Drinking Water Standards:
Groundwater will attain final Maximum Contaminant Levels (MCLs), where these
levels are above background, to the maximum extent practicable. Table 2
listed the MCLs for contaminants found in seepage plumes outside the tailings
disposal area.
New Mexico Water Quality Act (NMWQA) Standards:
Groundwater will attain NMWQA standards, where these levels are above
background, to the maximum extent practicable. Table 2 listed the NMWQA
standards for contaminants found in seepage plumes outside the tailings
disposal area.
RCRA Standards Applicable to Background:
Groundwater will attain background levels if above MCLs or NMWQA standards
to the maximum extent practicable. Table 2 listed background levels for
several contaminants found in seepage plumes outside the tailings disposal area.
Health and Environmental Protection Standards for Uranium and Thorium
Mill Tailings (40 CFR Part 192) as adopted by 10 CFR 40. Appendix A
Groundwater concentration limits set herein are equivalent to MCLs and will
be attained to the maximum extent practicable where above background.
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44
Maximum Contaminant Level Goals (MCLGs):
This Is not an ARAR, but Is another factor to be considered. Groundwater
will attain the MCLGs for these contaminants to the maximum extent practi-
cable where the MCLs or NMWQA standards have yet to be promulgated (If
above background levels).
Health-Based Criteria;
This 1s not an ARAR but 1s another factor to consider for Inorganics
detected at the site without federal MCLs or NMUQA Standards. Groundwater
should attain health-based standards to the maximum extent practicable
where above background levels.
Executive Order on Flood Plains;
Solid residue resulting from groundwater treatment will be appropriately
capped with tailings to prevent washout.
*
National Archaeological and Historical Preservation Act;
Remedial actions at the site will not disturb archaeological sites on
Indian lands.
Other alternatives were not selected for the following reasons:
No Action;
This alternative does not address potential threats to human health and the
environment.
Limited Action;
The long-term effectiveness of this alternative 1s not reliable 1n reducing
potential threats to human health and the environment. Contaminated
groundwater would continue to migrate downgradient without significant
reductions 1n the toxicity, mobility, or volume offered by Alternatives 1,
2, or 3.
Alternative 1;
This alternative 1s protective of human health and the environment, but 1s
high 1n cost and does not offer a significant reduction of contamination 1n
the Upper Gallup Zone 1 aquifer as compared to Alternatives 2 or 3 over a
reasonable time period. Furthermore, the two northern alluvial target
areas will be mitigated by other actions expected to take place under
Alternative 3. More specifically, the northernmost alluvial target area
(see Figure 8) was determined to be related to a separate source during the
Remedial Investigation. During the Feasibility Study EPA learned that this
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45
area was utilized by Quivira Mining Company for temporary storage of proto-ore
and drill cuttings, drying of pond sediments from mine water treatment opera-
tions, and equipment washing, and would be mitigated under a separate reclama-
tion plan. This proposed plan titled "Abandonment and Reclamation Plan:
Churchrock I, IE and II mines, Navajo Nation Lease 14-20-20603-9988" is date
January 1987 and is currently under review by the Bureau of Land Management
(BLM), Bureau of Indian Affairs (BIA), and Navajo Nation Division of Resources
(NNDR). The second northern alluvial target area is located adjacent to the
north cell (Figure 8). This target area overlaps portions of the Upper Gallup
Zone 3 aquifer and is expected to be mitigated in part by the Zone 3 hydraulic
capture zone, and in part by downgradient containment and extraction wells
which would be located in the southwest alluvium in Alternative 3.
Alternative 2;
This alternative is protective of human health and the environment, is more
feasible than Alternative 1, but costs more than the selected remedy.
Furthermore, the two northern alluvial target areas (Figure 8) will be
mitigated by other actions expected to occur under Alternative 3. These
activities include reclamation by Quivira Mining Company of the northernmost
alluvial target area, and partial hydraulic capture of the second alluvial
target area by other seepage collections systems in Alternative 3 as
discussed above.
Column Evaporation;
This physical/chemical treatment system provides adequate treatment of
contaminated groundwater and would be protective of public health and the
environment. However, enhanced mister/pond evaporation will provide adequate
treatment of contaminated groundwater at a significantly reduced cost. On
this basis, and because no discharge 1s required, enhanced mister/pond evapo-
ration is preferred over column evaporation pending successful demonstration
during remedial design.
6.4 Future Actions
EPA has developed the following schedule for implementation of the remedy:
Action Date
Begin negotiations for responsible party
design and implementation of remedy October 1988
Review monitoring data and status of NRC- October -
directed reclamation activity December 1988
Complete negotiations for remedial design
and remedial action; consent decree February 1989
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46
Conduct remedial design as appropriate in February 1989
conjunction with NRC-directed reclamation July 1989
activity
Begin remedial actions as appropriate in
conjunction with NRC-directed reclamation July -
activity October 1989
Begin annual review of effectiveness of
remedial actions October 1989
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1
REFERENCES
I
U.S. Environmental Protection Agency, August 1988. Remedial Investigation
United Nuclear Corporation Churchrock Site, Volumes I and II.
1
U.S. Environmental Protection Agency, August 1988. United Nuclear Corporation
Churchrock Site Operable Unit Feasibility Study Gallup, New Mexico"!
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Appendix A
HYOROGEOLOGIC IMPACT OF SELECTED REMEDY
-------
Appendix A
HYDROLOGIC IMPACT OF SELECTED REMEDY
This section briefly discusses hydro!ogic Impacts of the selected remedy as
predicted by groundwater modeling In the Feasibility Study. Also
discussed are uncertainties associated with model predictions of aquifer
restoration rates and contingencies to be considered depending on the
effectiveness of remedial actions as determined from regular performance evaluations.
UNCERTAINTIES IN SIMULATED REMEDIAL ALTERNATIVES
The Intent of modeling In the Feasibility Study was to compare the
relative effectiveness of groundwater containment and extraction
alternatives 1n reducing contaminant concentrations over time in target
areas. Modeling was not intended to quantitatively predict restoration
rates. Uncertainties In model Input parameters, and simplifying
assumptions associated with the selection of model grids and boundary
conditions, for example, limit quantitative predictions of groundwater
restoration rates.
A number of assumptions made 1n simulations are mentioned in the
Feasibility Study and summarized here. Starting model concentrations used
In simulated remedial alternatives were based on 1985 Remedial
Investigation data. Simulations were run assuming that the contaminant
source, the tailings pile, was totally removed. Remediation times were
bracketed for retarded and nonretarted contaminants. In addition, the
simulated remedial alternatives were only conducted within areas of known
contamination. Because such assumptions result in a degree of modeling
uncertainty, the actual time required to reach a particular cleanup level
will be verified during a performance monitoring period.
CONTINGENCIES FOR SELECTED REMEDY
The goal of the selected remedy is to restore groundwater outside the
tailings disposal area to concentrations dictated by Federal and State
standards, or background, to the maximum extent practicable and to the
extent necessary to adequently protect public health and the environment. A
program of regular performance evaluations, required as part of the selected
remedy, will provide a measure of how well this remedial alternative meets
modelling and design expectations. The performance evaluation program may
indicate that the response objectives have been met and the remedy Is complete.
However, operational results may demonstrate that 1t is technically Impractical
-------
to achieve all cleanup levels in a reasonable time period, and a waiver to
meeting certain contaminant-specific applicable or relevant and appropriate
requirements (ARARs) may require re-evaluation as a result. Operational
results may also demonstrate significant declines In pumping rates with time
due to Insufficient natural recharge of aquifers. The probability of signi-
ficant reductions 1n the saturated thickness of aquifers at the site must be
considered during performance evaluations since much of the water underlying
the tailings disposal area 1s the result of mine water and tailings discharge,
both of which no longer occur. In the event that saturated thicknesses cease
to support pumping, remedial activity would be discontinued or adjusted to
appropriate levels.
-------
Appendix B
COST ESTIMATES
-------
Appendix B
COST ESTIMATES
Cost estimates presented In the Feasibility Study and 1n Section 5.3 of the
Record of Decision for remedial action alternatives encompass all currently
Identified direct and Indirect capital and postconstruction operation and
maintenance (0 & H) costs. The estimates were made without detailed engi-
neering data, and are normally expected to be accurate within plus 50 percent
to minus 30 percent. The actual final cost of each remedy will depend on
the material and labor costs, site conditions, productivity, competitive
market conditions, final project scope, final project schedule, the firm
selected for final project design, and other variables. Any significant
changes 1n parameters such as the contaminant concentrations, extraction
well location and flow rate, facility siting, cleanup criterion, or contin-
gencies for an alternative may also affect the estimated costs beyond the
above accuracy range.
The actual cost of the selected remedy will depend on the factors listed
above and on at least two other related factors. The first factor concerns
the size of the enhanced mister/pond evaporation system necessary to dispose
of extracted groundwater. The evaporation system for the selected remedy
was sized for 229 gpm in the Feasibility Study. The final size of the
evaporation disposal system will ultimately depend on the volume of water
removed from extraction well systems outside and/or within the tailings
disposal area during remediation. These questions will be answered during
remedial design. The second factor directly affecting costs is related to
the actual duration of pumping and evaporation required to complete remedial
activity. This time period will be determined from performance evaluations
as discussed in Appendix A.
-------
Appendix C
OR RELEVANT AND APPROPRIATE REQUIREMENTS
s amended In 1986 by SARA requires that the
n requirements adopted under Federal and State
qulrements are called "ARARs" or "applicable
equlrements".
United Nuclear Corporation Groundwater Operable
RELEVANT se laws, and Identified those which could be
INTS sstes at the site, the types of remedial actions
ration. This appendix lists all the laws
dentified as potential ARARs for this site,
ilp to the selected remedy.
> Identified for the site relate to protection
iking water supplies. The major Federal and
ive been identified as contaminant-specific
Inking Water Act (SDWA) and the New Mexico
Jdards. Where natural background water quality
an acceptable background value becomes the
ilar contaminant.
tnt Levels
is (MCLs) have been established as enforceable
water systems. An MCL is required to be set
i respective maximum contaminant level goal
:ion the best available technology and the
ng the contaminant from the water supply.
jliance with ARARs states that MCLs are applic-
sr will be provided directly to 25 or more
15 or more service connections. Furthermore,
:her cases where groundwater may be used as a
e generally relevant and appropriate. For
at the UNC site, MCLs have been set for arsenic,
id, mercury, selenium, silver, nitrate, combined
ilpha. SDWA MCLs are presented in Table 1
-------
Table 1
CONTAMINANT-SPECIFIC GROUNDWATER ARARs
Contaminant
Aluminum
Antimony
Arsenic
Barium
Beryllium
Cadmium
Chromium
Cobalt
Copper
Iron
Lead
Manganese
Mercury
Molybdenum
Nickel
Selenium
Silver
Thallium
Vanadium
Zinc
Chloride
Sulfate
Nitrate
TDS
Radium-226 and -228
Uranium-238
Thorium-230
Gross Alpha
Concentration
mg/La
5.0
0.014
0.05
1.0
0.017
0.01
0.05
0.05
1.0
5.5
0.05
2.6
0.002
1.0
0.2
0.01
0.05
0.014
0.7
10.0
250.0
2,160.0
30.0C
3,170.0
5 pCi/L
5.0
(1,645 pCi/L)
15 pCi/L
15 pCi/L
Source
NMWQA
Health-based
MCL
MCL, NMWQA
Health-based
MCL, NMWQA
MCL, NMWQA
NMWQA
NMWQA
Background Level
MCL, NMWQA
Background Level
MCL, NMWQA
NMWQA
NMWQA
MCL
MCL, NMWQA
Health-based
Health-based
NMWQA
NMWQA
Background Level
Background Level
Background Level
MCL
NMWQA
MCL
MCL
fmg/L except as noted.
Based on 15 pCI/L gross alpha.
cPreoperational data of 30 mg/L appears reasonable for
background. Additional investigation and determination of
the natural NOg-N sources is necessary since NO--N is a
health-related standard.
-------
NHWQA Standards
The NMWQA has 47 numerical groundwater standards that apply statewide to
groundwater having a total dissolved solids (70S) concentration of 10,000
mg/1 or less. These standards are set forth in Section 3-101 of the NMWQA
regulations entitled. "Regulations for Discharges Onto or Below the Surface
of the Ground." These standards are grouped into three categories: human
health, other standards for domestic water supply, and irrlgational use.
The purpose of these standards is to protect present and potential use of
groundwater. These standards were originally adopted to permit the dis-
charges of effluent or leachate onto or below the surface of the ground.
These standards are also the criteria that have been applied statewide as
the reclamation criteria in groundwater cleanups. Therefore, these stan-
dards apply to both the cleanup of the three aquifers and to any discharges
of the treated groundwater. NMWQA standards which apply to the site are
presented in Table 1.
Section 1-101.UU of the NMWQA states that if more than one water contaminant
affecting human health is present, the acceptable levels for listed toxic
contaminants will not exceed an additive excess lifetime cancer risk of 1
in 100,000. Because none of these listed toxic contaminants have been detected
at the site, this portion of the NMWQA does not apply to the cleanup criteria.
Health and Environmental Protection Standards for Uranium and Thorium Mill
Tailings (40 CFR Part 192) as adopted by 10 CFR 40, Appendix A
40 CFR Part 192 Subpart D, "Standards for Management of Uranium Byproduct
Material Pursuant to Section 84 of the Atomic Energy Act of 1954, as Amended,"
sets groundwater limits for combined Ra-226 and Ra-228 and for gross alpha
(excluding radon and uranium). These concentration limits are equivalent to
SDWA MCLs and are presented In Table 1. These standards have been adopted
in the Uranium Mill Tailings Regulations promulgated by the NRC at 10 CFR 40,
Appendix A, 52 Fed. Reg. 43553.
Background
40 CFR Part 264 sets forth standards for owners and operators of hazardous
waste treatment, storage, and disposal facilities. Many of these standards
relating to groundwater contamination were adopted by reference in the
Uranium Mill Tailings Regulations in 40 CFR 192. Part 264.94 addresses
concentration limits to be used for groundwater protection at these facili-
ties. Concentration limits can be based on: background levels, SDWA MCLs,
or Alternate Concentration Limits (ACLs). As previously discussed, back-
ground levels for a variety of contaminants have been established for the
UNC site based on available information. These levels are presented in
Table 1 for iron, manganese, sulfate, nitrate, and total dissolved solids, and
were set by EPA and the State of New Mexico. Levels were originally determined
from regional sampling data in for the alluvial and Gallup aquifers.
-------
Background values from limited pre-milling monitoring data originally
submitted by UNC to the State of New Mexico were evaluated in the
context of regional background water quality for the alluvial and Upper
Gallup Sandstone aquifers during the Feasibility Study. Experimental
studies undertaken by UNC to simulate possible changes in water quality
resulting from mine water flow through the alluvium were seriously considered
in setting cleanup criteria. To date, however, limited data are available
which can be quantaitatively applied to the determination of background
concentrations in groundwater apart from regional sampling upgradient and
downgradient of the site, thus precluding significant changes in the esti-
mation of background levels of contaminants. Table 2 summarizes differences
in proposed cleanup criteria based on comparisons of UNC and EPA background
judgements at this time. As the Table indicates, EPA has proposed more
stringent cleanup criteria for arsenic, cadmium, mercury, selenium, sulfate,
nitrate-N, total dissolved solids, Ra-226/228, and Th-230. Given the geo-
chemical complexities associated with determining the potential contribution
of mine water recharge to background conditions at the site, EPA will continue
to evaluate the background level question. Should additional information
become available that would significantly alter the estimation of background
levels, including data that may be submitted to the NRC under their licensing
requirements, such information would be evaluated in terms of its impact on
remedial actions in each aquifer.
Health-Based Criteria
Some inorganics detected at the site do not have federal MCLs or State of
New Mexico standards. For these compounds, reference doses (RFDs), if
developed, have been used to estimate groundwater concentrations that would
result in no observable adverse health effects. These concentrations are
estimated from the RfD assuming a 70-kg individual who consumes 2 liters of
water per day. The resulting concentrations for antimony, beryllium,
thallium, and vanadium are presented in Table 1.
Federal Ambient Water Quality Criteria
Ambient Water Quality Criteria (AWQC) developed under the CWA define the
concentrations of pollutants in water that will ensure water quality adequate
to support a specified use. AWQC are nonenforceable criteria and are based
solely on the relationship between concentrations of pollutants and their
effects on the environment and human health. These criteria do not reflect
considerations of economic or technological feasibility. AWQA are used as
the basis for state water quality standards. The water quality criteria
were published by EPA in 1986 and updates have been announced in the Federal
Register. These concentration limits are covered by other applicable stan-
dards in Table 1.
Federal Health Advisories
Federal health advisories are the EPA Office of Drinking Water's current
assessment of concentrations of contaminants in drinking water at which
-------
Table 2
COMPARISON OF EPA AND UNC-PROPOSED STANDARDS
EPAJ
Constituent Contaminant-specific ARAR
UNC1*2
Proposed Background
UNC Maximum1*3
Pre-operational Data
A1
Sb.
As*
Ba
Be*
Cd*
Cr
Co
Cu
Fe
Pb
Mn*
Hg*
Mo
Nr
Se*
Ag
Tl
V
Zn
ci *
so/*
N03;N
TDS*
Ra-226 and -228
U-238 .
Th-230
Gross alpha
5.0
0.014
0.05
1.0
0.017
0.01
0.05
0.05
1.0
5.5
0.05
2.6
0.002
1.0
0.2
0.01
0.05
0.014
0.7
10.0
250.0
2160.0
30.0
3170.0
5pC1/l
5.0
!5pC1/l
15pCi/l
5.0
-
0.1
1.0
_
0.12
0.05
0.05
1.0
5.5
0.05
2.5
0.004
1.0
0.2
0.08
0.05
-
-
10.0
85
2800.0
290.0
5000.0
33pC1/l
_
240pC1/l
86
.
0.02
0.99
_
0.12
0.02
0.01
0.44
5.6
0.03
2.6
0.004
.
0.04
0.08
-
-
_
0.49
86
1731
174
4337
20pCi/l
_
36pCi/l
"
1 Values in mg/1 unless noted otherwise
2 Proposed background levels from "Geochemical Background Investigation" prepared by
Billings & Associates, Inc. for United Nuclear Corporation in August 1986
3 Concentration levels reported as maximum value observed during 4 sampling rounds of
seven GW-wells. Dates: 2/77, 3/77, 4/77, and 7/77. From "Geochemical Background
Investigation" prepared by Billings & Associates, Inc. for United Nuclear Corporation
August 1986.
Indicates a difference between values in columns 1 and 2
- Background not proposed
-------
adverse health effects would not be anticipated to occur. While not an
ARAR, health advisories are a factor to be considered for those contami-
nants where the MCLs have yet to be promulgated.
Maximum Contaminant Level Goals (HCLGs)
MCLGs are nonenforceable drinking water quality "goal's -set *t level's Trf no
known or anticipated adverse health effects, with an adequate margin of
safety. While not an ARAR, MCGLs are a factor to be considered -for those
contaminants where the MCLs have yet to fee promulgated.
LOCATION-SPECIFIC ARARS
Physical characteristics of the site may Influence the type and location of
remedial responses considered for this site, the Trte is trtttrln"the"106- .
year flood plain of Pipeline Canyon. Superfund remedial actions must meet
the substantive requirements of the federal fioodplain Management E*Pri*ti4P»
Order 11988. These requirements specify assessment of flood hazards for
any remedial measure that occurs in the flood plain, further, the develop-
ment of remedial actions will consider the presence of archaeological *sttes
on adjacent Indian land, in accordance with the National Archaeological and
Historic Preservation Act.
ACTION-SPECIFIC ARARS
Action-specific ARARs are associated with the Implementation of remedial
measures. These ARARs are identified below.
Federal Action-Specific ARARs
Actions that involve treatment or storage trf mutantInaled gruundwdler "are
to take place within the tailings disposal area currently defined i>y the
boundaries of Section 2. These actions are governed by MRC requirements.
State Action-Specific ARARs
The primary action-specific ARARs affecting remedial actions at the UNC site
are the New Mexico Water Quality Regulations 3-1D3.A, B. and C. These
regulations set quantitative discharge stanttortSs for 47 Lunlaiiilnanls.
These standards are ARARs for both discharge to Pipeline Canyon and relnjec-
tion to the groundwater. However, the groundwater extraction and enhanced
mister/pond evaporation actions that accompany the selected remedy do not
involve discharge or reinjection. The enhanced mister/pond evaporation
system will be designed and operated within the tailing disposal as cur-
rently defined by the boundaries of Section 2. For these reasons, there
are no State action-specific ARARs anticipated
-------
Appendix D
TOXIC SUBSTANCES AND DISEASE REGISTRY
(ATS08)/C£NT£R FOR DISEASE CONTROL (CDC)
EVALUATION
-------
Public Health Service
Agency for Toxic Substances
and Disease Registry
Atlanta GA 30333
INDEX
=k NL? Site
ment being prepared by
for your review. The
to:
iation of the site,
g removal activities,
f^^fttamination in various
of the extent of
-> we 1 1 s ,
jod chain contamination, and
site.
i version, these reflect the
SRC reclamation activities
to contaminants from the
ith the site.
rge /iT
George /i ettigr
igrew
-------
Appendix F
U.S. NUCLEAR REGULATORY COMMISSION CORRESPONDENCE
-------
UNITED STATES
NUCLEAR REGULATORY COMMISSION
>.CEIVED
REGION IV '- KEGION Vj
URANIUM RECOVERY FIELD OFFICE
HAZARDOUS WASTE MGMT. OIV.
IECOVERY FIELD OFFICE RPCFPlI Ou ,«
BOX 2B325 OW StP 33 PM \%
DENVER. COLORADO c
SEP27 WB
URFO:GRK
Docket No. 40-8907
USEPA, Region VI
ATTN: Allyn M. Davis, Director
Hazardous Waste Management
Division, (6H)
1445 Ross Avenue, Suite 1200
Dallas, Texas 75202
Dear Mr. Davis:
Our office is in receipt of your draft Record of Decision (ROD) for the United
Nuclear Corporation Groundwater Operable Unit, submitted by cover letter dated
September 16, 1988. My staff has reviewed this document and it is our
conclusion that your proposed recommendation of active tailings seepage
collection in both the Upper Gallup aquifer (Zone 3 and limited action in
Zone 1) and the Southwest alluvial aquifer is compatible with a ground-water
restoration program we expect to achieve by implementation of the requirements
of 10 CFR Part 40, Appendix A. Similarly, we agree with your conclusion that
directing the recovered seepage waters to an evaporation system consisting of
water storage and a mister system utilizes a proven and economical technology.
As I am sure you are aware, my staff required that United Nuclear Corporation
collect appropriate data to establish ground-water protection standards.
Considering this situation, I have had my staff review your recommended
ground-water cleanup criteria for application outside of the byproduct disposal
area as shown in Table 2 of the ROD document. We believe that your recommended
cleanup criteria are generally within a range that is defensible, based upon
historical data. However, we propose that you raise the value for nitrate
concentrations in the southwest alluvium to a level of 30 mg/1 to be applied
outside the disposal area. We feel that historical records from several
ground-water monitoring wells as well as independent studies by United Nuclear
Corporation support the 30 mg/1 nitrate value. We understand that this value
is in excess of the 10 mg/1 concentration you have proposed; however, for the
reasons cited above, we feel that United Nuclear Corporation can reasonably
argue for this value as representing a pre-milling background.
-------
2 SEP 27 (968
We are pleased to have the opportunity to comment on the draft ROD.
Sincerely,
R. Dale Smith, Director
Uranium Recovery Field Office
Region IV
-------
Appendix G
STATE OF NEW MEXICO CORRESPONDENCE
-------
.11.
Post Offic* Box 968 oxinn CMOUKHXM
Sane* Ft, N«w Maxieo 87304-0868 ' Oovarno*
CMU 1» JOOT
~.--w«* KCHXIL
HEALTH AMD ENVIRONMENT Dip*tsr
MMKMNT
September 29, 1988
Allyn M. Davlj, Director
Hazardous Waste Management Division
USEPA
1445 Ross Avenue
Dallas, Texas 75202-2733
*
RE: Proposed Remedy for UNC
Dear Mr. Davis:
EID has reviewed the draft ROD for the United Nuclear Corporation
Sroundwater Operable Unit. EID concurs with remedial alternative 13 as
proposed by EPA.
Our staffs have consulted closely over the last two weeks In order to
reach agreement on outstanding Issues such as ARARs. New Mexico Water
?ua11ty Control Commission Regulations are applicable cleanup criteria.
hese standards specify numerical limits which apply unless background
concentrations exceed the numerical standards. In which case background
concentrations become the standards. As a result of our discussions,
ARARs for a limited number of constituents have been set based on reasonable
and rational estimates of pre-operatlonal, background conditions. These
estimates were derived from thorough consideration of regional and local
data, as well as site-specific data, where available.
EID finds Table 2 of the FS to be an acceptable representation of ARARs
for the site. Our conversations have specifically addressed the cleanup
criterion for nitrate nitrogen (N03-N). Because nitrate poses a human
health threat, EID prefers more conclusive documentation of background
conditions before accepting a higher value. Should EPA proceed to assign
a value greater than 10mg/l NOi-N before such documentation 1s available,
EID concurrence 1s provided with the understanding that: 1) additional
research will be conducted to determine true background conditions, and
2) the ARAR will subsequently be adjusted as appropriate, downward 1f
necessary.
BOUAU CPPOHTUNTTY tM^UOVBR
-------
QO i^'MA III I t- V---'
Allyn M. Davis
USEPA
September 29, 1988
Page -2-
EID acknowledges reasonable doubt that 10 mg/1 Is appropriate. Therefore.
regardless of the specific cleanup criterion selected for N03-N at this
time, additional Investigation Into naturally occur!ng N at the site should
be performed. We also note that the specific value assigned as the NOa-N
ARAR does not significantly affect the cleanup target area. Therefore,
additional research Into background conditions will not delay design and
Implementation of the remedy. Planning of the Investigation should be
a cooperative effort between all parties. This will maximize acceptance
of the results by all parties.
Sincerely,
Richard Mft/elfelt
Director
RM:SC:to
-------
Appendix H
RESPONSIVENESS SUMMARY
-------
RESPONSIVENESS SUMMARY
INTRODUCTION
This Responsiveness Summary has been prepared to provide
written responses to comments submitted regarding the
proposed plan of action at the United Nuclear Corporation
(UNC) Superfund site. The summary is divided into two
sections:
Section I: Background of Community Involvement and
Concerns. This section provides a brief history of
community interest and concerns raised during the
remedial planning activities at the UNC site.
Section II: Summary of Major Comments Received. The
comments (both oral and written) are summarized and
EPA's responses are provided.
SECTION I
BACKGROUND OF COMMUNITY INVOLVEMENT
Uranium mines and mills in New Mexico have received
considerable attention from local and national media during
the past years. Citizens are generally concerned for their
health and safety in areas where radioactive elements are
involved, even in low concentrations.
Since the UNC site is located in a very sparsely populated
area of the state, there are no population centers or
housing developments near the site. The nearest residents
are a Navajo allottee and his wife.
As early as 1979, the Centers for Disease Control convened
public meetings after the tailings spill to assess citizen
concern and conduct health tests on humans and livestock.
After the site was included on the National Priorities List,
EPA representatives interviewed local officials and area
residents to determine issues and concerns. At that time,
the major concern was possible contamination of nearby
private wells.
In April 1987, EPA held a public meeting to discuss the
status of the on-going investigations at the site and to
clarify the roles and responsibilities of EPA and the
Nuclear Regulatory Commission. A Navajo translator was
provided and the meeting was well-attended. Several
citizens were concerned about area wells and EPA sampled the
domestic/livestock wells within a 4-mile radius of the site.
-------
On July 18, 1988, EPA announced an open house at the Red
Rock State Park. The purpose of the open house was to
summarize the results of the remedial investigation and
reiterate the responsibilities of EPA and NRC. The open
house was held August 4, 1988 and about 40 residents
attended.
SECTION II
SUMMARY OF MAJOR COMMENTS RECEIVED
In accordance with Section 117 of CERCLA, the press release
and proposed plan fact sheet announcing the public comment
period and public meeting were released on August 11, 1988.
The comment period began on August 19, and ended
September 16, 1988. A public meeting was held with area
residents and local officials on August 31, 1988 at the Red
Rock State Park. The purpose of this meeting was to explain
the results of the remedial investigation and to outline the
various alternatives presented in the feasibility study, and
seek comments on the alternatives and EPA's proposed plan.
About 40 people from the area attended the meeting and eight
people made oral statements or asked questions. The entire
meeting was translated in Navajo and a written summary of
the fact.sheet, as well as a cassette recording, were
available in Navajo. No written comments or questions were
received from citizens. Overall, the residents and local
officials do not appear to oppose the proposed plan. During
the public comment period, EPA also received written
comments on the Public Comment Draft Operable Unit
Feasibility Study (OUFS) from the New Mexico Environmental
Improvement Division, the Navajo Environmental Protection
Administration, and United Nuclear Corporation (UNC).
RESIDENT/CITIZEN COMMENTS
(From Public Meeting)
Comment 1; Will there be employment opportunities for
residents during remedial action?
Response: EPA hopes that UNC will agree to perform the
remedial action. If so, hiring will be up to the company
itself. EPA is not familiar with any additional mining
planned for the area.
Comment 2; Are residents in the area safe?
Response; EPA sampled wells within a 4-mile radius of the
site in 1987. Results of analyses indicated that
groundwater in these wells met all primary drinking water
standards. Based on sampling of operating wells, .
groundwater is safe to drink although it contains elevated
levels of salts and metals that affect its taste such as
iron, manganese, sulfate, and total dissolved solids.
-------
UNC completed a preliminary survey of windblown tailings
which indicated that the extent of windblown tailings is not
very great. NRC will require UNC to complete a
comprehensive survey to determine the full extent of
windblown tailings during site reclamation. Tailings beyond
the site boundaries which are at concentrations that exceed
NRC standards will be removed and returned to the mill site
for disposal.
Comment 3; One commenter stated he drank underground water
when he worked in the mines. Was this safe?
Response; Water found in the mine which could have been
consumed was from the Westwater Formation and generally
considered to be potable water. Without an actual analysis
of the particular volume of water consumed, however, EPA
cannot quantitatively respond to this question.
Comment 4; Mine water caused erosion in Section 10 south of
the site. Can EPA address this?
Response: All mine dewatering has stopped in the area so
that erosion will occur under natural conditions (i.e.,
runoff). NRC will require UNC to address surface water
runoff concerns related to flooding in the area during
surface reclamation activities. Erosion control will
consist of channel improvements designed to control runoff
and prevent erosion of the tailings pile.
Comment 5; Since UNC has fenced around its property, access
to property formerly possible by crossing UNC property is no
longer possible. Can EPA build a bridge across Pipeline
Arroyo to aid in access to privately owned property, or have
UNC allow passage across the fenced area?
Response; The land owner needs to approach UNC regarding
permission to cross over fenced UNC property to gain access
to neighboring land. Providing access across Pipeline
Arroyo is not something EPA would contemplate under its
Superfund activities, since EPA's efforts by law are
directed at protecting human health and the environment.
Comment 6; Can the site be used by residents after capping?
Response; The tailings disposal area will be continually
controlled by the Department of Energy after remedial action
at the site is complete. Access to the tailings disposal
area will be restricted. The exact area to be deeded to the
Department of Energy has not been determined.
Comment 7; Can EPA wells in the southwest alluvium be used
for domestic or livestock purposes?
-------
Response; EPA installed these wells during its remedial
investigation to monitor the possible movement of
contaminants. Water quality in these wells is such that EPA
will not permit consumption of water from these wells at
this time.
Comment 8; EPA does not know the full extent of groundwater
contamination.
Response! The extent of contamination is constrained by
migration rates and flow directions outside the tailings
disposal area. EPA will require implementation of a
monitoring program to detect any increases in the areal
extent or concentration of groundwater contamination outside
the tailings disposal area.
Comment 9; Residents should be aware that tailings seepage
in Zone 1 of the Gallup Sandstone will make that aquifer in
the target areas unusable for generations.
Response: EPA studies indicate that the physical
characteristics of Zone 1 are such that sufficient
quantities of water coulS not be pumped from the sandstone
to support volumes required for domestic or livestock
purposes. Therefore, Zone 1 would not be a good candidate
for locating a domestic or livestock well even if there were
no impacts from tailings seepage.
Comment 10; Will evaporation of contaminated groundwater
cause air pollution?
Response; Contaminated groundwater does not contain
volatile organic compounds which are typically of primary
concern in physical/chemical evaporation. EPA and NRC will
require monitoring to assure that residual salts from
evaporation are controlled and contained within the tailings
disposal area. For instance, the evaporation disposal
system would not be operated on extremely windy days.
Comment 11; Background levels in the feasibility study were
too high.
Response; Background is a complex issue at the UNC site,
and was evaluated in detail by EPA, NMEID, and NRC. EPA
believes that background levels were set in a reasonable
manner. Additional information will be evaluated during
remedial design should it become available.
Comment 12; Residents living in communities close to the
UNC site are in need of assistance due to poor economic
conditions.
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Response; EPA is aware of community needs such as
employment, electricity, and running water. Since operating
groundwater wells have not been impacted by tailings
seepage, EPA does not contemplate using Superfund monies to
supply alternate water. However, EPA has and will assure
remedial action at the UNC site occurs in a timely and
protective manner.
Comment 13; How long will the tailings pile be stable?
Response: Federal requirements are that the tailings will
be stabilized for a period of at least 200 to 1,000 years.
Comment 14; When can improvements (drilling of wells by
residents in Section 10) south of the site begin?
Response; If wells are being planned for this area, EPA
recommends they be screened in deeper formations. Any well
installed in the alluvium directly south of the site in
Section 10 would require water quality testing before
consumption of the water. Deeper well installation could
start any time and would avoid the potential of groundwater
contamination immediately downgradient of the site,
providing proper well completion techniques are followed
that prevent alluvial water from mixing with lower
formations.
Comment 15; Alternative 3 does not go far enough.
Response; EPA is proposing action in the alluvium and Upper
Gallup aquifers to address groundwater contamination.
Contaminated areas will be remediated to federal and state
standards or background to the maximum extent practicable.
The selected remedy addresses health concerns by containing
downgradient migration of contaminants in target areas.
This includes seepage in the area where the tailings dam
broke in 1979.
NEW MEXICO ENVIRONMENTAL IMPROVEMENT DIVISION COMMENTS
Comment 1; The Superfund FS addresses offsite
contamination, principally groundwater remediation and
windblown tailings.
Response; The FS addresses contaminated groundwater outside
the byproduct materials disposal area, currently defined by
the boundaries of Section 2. Removal of windblown tailings
outside the tailings disposal area will occur under MRC
requirements.
Comment 2; Attempts should be made to drill additional
monitoring wells offsite in order to better define the areal
extent of contamination.
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Response: The selected remedy requires implementation of a
supplemental groundwater monitoring program to detect any
increases in the areal extent or concentration of
groundwater contamination outside the tailings disposal
area. An additional background well in Zone 3 could be
installed during the remediation phase if warranted.
Comment 3; Extracted groundwater should be lime treated
before spray misting on the tailings or disposal in
evaporation ponds.
Response; The evaporation disposal system should be
optimized during the first few months of operation. This
includes addressing the optimum pH for evaporation. EPA
will weigh the positive and negative aspects of water pH on
evaporation disposal system performance.
Comment 4; The selected remedy should foresee the need for
additional lined pond area if pumping rates have been
underestimated or design values for spray misting are not
realized.
Response; The selected remedy requires evaporation ponds to
be sized and operated in order to provide sufficient
evaporative capacity for maintenance of a reasonable
operational water balance. The number of hours of spray
misting per day, as well as the number of months during
which active spray misting takes place, can be adjusted to
optimize operation of the system.
Comment 5; Column evaporation is not a cost-effective
alternative.
Response; EPA prefers enhanced water/pond evaporation over
column evaporation as being more cost-effective and
efficient.
Comment 6; If more detailed modeling were to be conducted,
with injection wells closer to the extraction wells,
reinjection could speed up the cleanup.
Response; EPA's selected remedy calls for groundwater
extraction and mister/pond evaporation. While reinjection
was screened out in the FS, performance evaluations during
remediation may indicate specific situations where
reinjection might be considered. Therefore, EPA's selected
remedy does not preclude NRC from considering reinjection if
warranted.
Comment 7; A justification of mister system efficiency
(15%) and annual evaporation (34 inches/year) was not given
in the FS.
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Response; EPA reviewed performance data from a number of
operating mister/pond evaporation systems at mill tailings
sites, as well as design specifications of UNO's proposed
system. These reviews indicated a 15% evaporation
efficiency to be reasonable. In addition, annual
evaporation data was reviewed for the Gallup area by UNC
consultants and the EPA suggesting a net evaporation rate of
approximately 34 inches/year.
NAVAJO ENVIRONMENTAL PROTECTION ADMINISTRATION
Comment 1; Does the mill complex itself represent a
significant source of contamination?
Response; EPA focused its RI/FS on groundwater
contamination outside the tailings disposal area and,
therefore, did not address the mill itself. However, NRC
will require decommissioning of the mill complex and removal
of contaminated sediments or soils associated with the mill.
Comment 2; PH is not a reliable indicator of plume extent.
Response; PH is an indicator of acid tailings seepage. EPA
recognizes that not all contaminants are pH dependent and
does not.base its definition of tailings seepage solely on
pH.
Comment 3; Flow volumes in Pipeline Arroyo need to be
calculated.
Response; Flow volumes have been calculated by UNC for
Pipeline Arroyo. NRC is currently reviewing these
calculations.
Comment 4; What are the plans for reclamation of
Kerr-McGee's protoore pile, evaporation ponds, and equipment
storage area in Section 36? How is this related to UNC
reclamation activities?
Response; Kerr-McGee (Quivira) Mining Company has submitted
a Reclamation Plan to the Bureau of Land Management, Bureau
of Indian Affairs, and Navajo Nation. EPA expects
reclamation in Section 36 to occur when field activities are
approved by the above agencies.
Comment 5; How are molybdenum levels explained in
downgradient wells?
Response; There is no current definitive answer to the
distribution of molybdenum downgradient of the site. The RI
postulated another source could be responsible for the
observed contaminant distribution; however, current data
cannot refute or prove a second source of molybdenum.
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Comment 6; How are radium levels explained in well No. 625?
Response; Radium present in well No. 625 is attributed to
the leachate from the tailings pond. This well is located
downgradient of the pond and would intercept groundwater
leaving the disposal cells. The radium concentration of
7 pCi/L is slightly above the ARAR criterion of 5 pCi/L.
Comment 71 A leachate analysis of tailings solids needs to
be performed.
Response; To date, a leachate analyses of the tailings
solids has not been performed. However, UNC contractors
performed a leachate analysis of tailings impacted alluvium
directly beneath the base of the south cell, and discussed
it in their report entitled, "The Evolution of Groundwater
Chemistry," dated July, 1988.
Comment 8; The extent of contamination is not fully known.
Response; The extent of contamination is constrained by
migration rates and flow directions outside the tailings
disposal area. EPA will require implementation of a
monitoring program to detect any increases in the areal
extent or concentration of groundwater contamination outside
the tailings disposal area.
Comment 9; Does EPA understand structural controls on
groundwater flow?
Response; EPA recognizes some fault control in groundwater
flow in Zone 3 of the Upper Gallup Sandstone. The surficial
cover of the alluvium makes delineation of faults and
fractures more difficult. Remedial design will address
target areas of groundwater contamination. These areas may
or may not be influenced by structural controls.
Comment 10; EPA should use proposed water quality standards
for aquifers beneath inactive tailings piles.
Response; UNC-Churchrock is classified as an active mill
tailings facility. Applicable regulations will apply at UNC
to assure source control measures are implemented within the
tailings disposal area.
Comment 11; The public health assessment needs to evaluate
impacts on biota and other environmental receptors.
Response; EPA's public health assessment and FS focused on
groundwater contamination and did not attempt to address
potential contamination of biota. However, a preliminary
survey of windblown tailings at the UNC site has been
performed under NRC licensing requirements. Results
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indicate that windblown tailings are primarily concentrated
in Section 36 and do not exist north of the reservation
boundary. A comprehensive survey of windblown tailings
contamination will be completed during site reclamation
under NRC licensing requirements, and will include areas in
Section 1.
Comment 12; What is meant by long-term sampling of
groundwater in target areas?
Response: A performance monitoring program will be
implemented as part of the selected remedy. Monitoring will
continue until remedial action is complete. Limited
groundwater monitoring is expected to continue at the site
under long-term care by the Department of Energy.
Comment 13; Did consideration of an alternate water supply
influence cleanup levels or restoration rates?
Response; No. Alternate water supplies have no influence
on cleanup levels or restoration rates.
PRP COMMENTS
The Potential Responsible Party (PRP), which is UNC,
submitted two volumes of comments and several file boxes of
data and information. The documents submitted by UNC for
inclusion to the administrative record for the Churchrock
site included 217 documents. Many of the letters, reports,
graphs, maps, and data had already been in EPA's files and
have been reviewed. A summary of the major subjects
included in these documents are;
o Comments on the draft remedial investigation
o Correspondence regarding the MOU
o UNC's proposed reclamation plan
o Correspondence regarding the feasibility study
o Correspondence regarding radioactive material
licenses
o Reports on tailings pond construction
o Correspondence on the 93-million-gallon tailings
pond breach
o Correspondence between NMEID and EPA regarding
discharge plans, seepage collection system, and
groundwater monitoring
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o Graphs of water level change from 1980 through
1988 .
o Permit applications for mine water discharge
The FRF comments consist of legal and technical comments.
These are addressed separately in the following sections.
PRP Legal Comments
At the outset of this response, it should be noted that the
United States Environmental Protection Agency (EPA) contends
that many of the comments provided by United Nuclear
Corporation (UNC) concern issues that are not properly
raised in this forum. Some of these comments concern legal
and regulatory issues not unique to this case and some
concern issues arguably already decided by the courts, or
barred from further contention by rules of law.
Accordingly, EPA hereby reserves any and all legal,
equitable, administrative, and enforcement rights that it
may have, including without limitation, the right to assert
any claim, cause of action, argument, or defense and the
right to undertake environmental response action.
Response to General Comments
Initially in its comments, UNC asserts a reservation of the
right to raise all objections to the remedial action
decision after selection of the site remedy by EPA under the
Comprehensive Environmental Response, Compensation and
Liability Act (CERCLA). Insofar as the public comment
process under the National Contingency Plan (NCP) and
CERCLA, as amended, is concerned, it is the contention of
EPA that such comments must be made during the public
comment period or will be deemed as having been waived by
the commenter. Acceptance of any late comments by EPA is
purely discretionary. While UNC may seek to raise
objections in a subsequent proceeding if it wishes, EPA is
not obliged to consider them for purposes of selection of
the proposed remedial action for the UNC Churchrock Site.
Further, EPA does not agree with UNC's contention that there
is no limit to the nature and scope of the challenge that
UNC may subsequently bring against EPA's CERCLA remedial
decision. The law is clear that any judicial review of EPA
action on a record of decision (ROD) shall be upon the
administrative record established by the President (or his
delegee) and that the standard of judicial review of the
decision is whether such decision was arbitrary and
capricious or otherwise not in accordance with law.
42 U.S.C. S 9613(j). EPA notes that UNC has in fact made
substantial and extensive comments on the proposed action,
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including a voluminous annex of documents proposed for
inclusion in the EPA Administrative Record for the UNC
Churchrock, New Mexico, CERCLA Groundwater operable unit
remedial action (UNC Ad. Rec.). Many of these documents
were already contained in the UNC Ad. Rec.
EPA disagrees with UNC's contention that the CERCLA remedial
investigation and feasibility study (RI/FS) and remedy
selection process are not a "true administrative process."
EPA believes that this is not a proper forum for such an
argument to be raised/ but nevertheless will state that the
plain language of the statue, as well as relevant case law
(See UNC Ad. Rec. Doc. Nos. 433-435), including the law of
this case, demonstrate otherwise. In response to UNC's
suggestion that EPA lacks the sole discretion to cleanup the
.site, EPA will state that it cannot agree, because its
authority to select a CERCLA remedy for this site is clear,
unambiguous, and unfettered. No less than four court
decisions have been rendered in connection with this
particular uranium mill tailings site, and such sites in .
general that clarify EPA's CERCLA authority in this area.
EPA does, however, recognize the regulatory authority of the
Nuclear Regulatory Commission (NRC) over the UNC site
pursuant to the Atomic Energy Act and the Uranium Mill
Tailings Radiation Control Act (UMTRCA), and the need,
therefore, to coordinate the conduct of remediation and
reclamation with respect to the site, between the two
federal agencies.
In response to UNC's argument that determination of
consistency with the NCP is & judicial function, EPA
reasserts that determination of CERCLA remedial action at
the site is vested by law in the President (and his
delegee), and this includes any necessary supporting
determinations such as consistency with the NCP. EPA
rejects UNC's arguments that the CERCLA statute is
unconstitutional for failure to satisfy due process
requirements and that EPA has invented the public comment
period. Instead, EPA notes for the record that it has
proceeded according to its regulations and law in providing
for public comment in this case. Further, EPA disputes
UNC's contention that "operable units", such as is involved
here, are improper, noting that the NCP clearly provides for
them. 40 C.F.R. 300.68(c).
Eagle-Picher Industries, et al. v. United States
Environmental Protection Agency, et al., 822 F.2d 132 (D.C.
Circ., 1987) ("Eagle-Picher III"); American Mining
Congress, et al., v. Lee M. Thomas, et al., 722 F.2d 640
(10th Cir., 1985)("AMC") Eagle-Picher Industries, et al., v.
United States Environmental Protection Agency, et al., 759
F.2d 934 (D.C. Circ., 1985)("Eagle-Picher II"); United
States v. United Nuclear Corp., 610 F.Supp 527 (D.NM.,
1985) .
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Instead of ignoring remedial activities to be performed by
UNC under the NRC license, as UNC argues in its comments,
EPA has signed a Memorandum of Understanding (MOU) with the
NRC to coordinate the activity of the two agencies. EPA has
been in regular and substantial contact with the NRC for
more than 2 years on the issue of remediation of this site.
In contrast to the baseless argument made by UNC that it has
had no meaningful opportunity to comment, it would be hard
to imagine a site with more opportunity to provide for
comment than this one. As the record establishes, EPA has
had numerous meetings with UNC to discuss investigations and
remediation of the site, including UNC's NRC license
directed activity, as well as the EPA RI/FS.
UNC was furnished with advance copies of the RI/FS for
review and comment. UNC has also been furnished with a copy
of the EPA-NRC MOU. UNC is presumably familiar with the
site reclamation plan, which is included with other UMTRCA
related site remediation documents that were included in the
administrative record, since it authored the document for
NRC approval. The public comment period, promulgated in
accordance with the NCP, began on August 19, 1988 and closed
on September 16, 1988, with a 5-hour public meeting
conducted in Gallup, New Mexico, on August 31, 1988. An
extensive and voluminous administrative record was made
available in Gallup, New Mexico, and an informative,
detailed public information sheet in English received wide
circulation in the community. A summary of this information
sheet was distributed in Navajo, as well. EPA also
conducted a public open house on August 4, 1988, and a
public information meeting in April 1987, both in Gallup,
New Mexico. UNC and NRC representatives attended all three
meetings.
UNC's description of background information is generally
self-serving, inaccurate, and incomplete. For example,
perhaps because it flies in the face of its argument that
releases into the environment from the facility are
"federally permitted releases," UNC conveniently omitted its
93-million-gallon tailings spill in 1979. See Eagle-Picher
III at 150. See also UNC Ad. Rec. Docs. Nos. 3 and 8. EPA
categorically rejects the notion that releases of hazardous
substances and pollutants and contaminants from UNC's
disposal facilities into the soil, air, surface, and
groundwater of the environment constitute "federally
permitted releases." within the meaning of CERCLA.
Similarly, UNC's description of the New Mexico "agreement
state" Atomic Energy Act, Uranium Mill tailings regulatory
program under which it had operated since its inception is
misleading. UNC's description of the program as
"comprehensive environmental protection requirements" with
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"extensive groundwater protection requirements" is at odds
with the discussion set forth by the director of the
program, in her 1986 letters concerning the return of
jurisdiction to NRC. See UNC Ad. Rec. Doc. Nos. 472 and
474. Similarly, in citing the facility groundwater
protection standards of 40 C.F.R. Part 192 (now incorporated
into 10 C.F.R. 40, App. A) for their effectiveness, along
with its alleged cooperative working relationship with NRC,
UNC fails to note its unsuccessful litigation attempt to
have those same regulations overturned. See AMC. UNC also
fails to point out in its background argument, that EPA has
determined these same requirements as applicable or relevant
and appropriate requirements (ARAR's) pursuant to section
121(d) of CERCLA, among other requirements, to be imposed in
EPA's CERCLA groundwater cleanup action that UNC so
vehemently opposes in its comments.
This willingness to adopt any side of an argument,
regardless of its facts, is characteristic of the tactics
employed by UNC throughout the general comments. Another
example of this "fast and loose" approach to the facts used
by UNC in its background statement is its description of the
EPA RI/FS process. UNC conveniently leaves out months of
delaying and stalling tactics that it employed, designed to
prevent EPA access to the site. These access delays
followed*long, protracted and unsuccessful negotiations
between EPA and UNC to have UNC carry out such
investigations and remediate the site. These UNC tactics
culminated in a lawsuit by UNC against EPA designed to
prevent access, filed by UNC in August 1984 (see UNC Ad.
Rec. Doc. 378) , and the filing of a counter lawsuit and the
execution of an administrative warrant by EPA in September
1984. See UNC Ad. Rec. Doc. Nos. 394 and 395. UNC finally
agreed that it would not interfere with EPA access to the
site in a December 1984 letter to the Department of Justice
(UNC Ad. Rec. Doc. No. 411), and UNC lost the case in April
1985 when the District Court granted an order in Aid of
Access, Doc. Nos. 433-435.
EPA does not agree with UNC characterizations of its
investigatory work and believes that those studies, as well
as the other documents in the administrative record, will
speak for themselves. EPA's focus is, and has been, the
remediation of offsite contamination emanating from UNC's
tailings disposal facility, which threatens health and the
environment. It is an area of concern, which UNC has never
adequately investigated, and thus cannot be deemed
duplicative. Further, UNC's complaint that it was not
permitted to conduct the RI/FS misses the mark. For even
though EPA offered UNC opportunities to do such studies,
these were rejected during months of negotiations in
1982-83. UNC's belated offers to conduct such studies came
too late in the day, long after EPA had commenced its effort
to conduct them itself.
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UNC's continued argument for sole NRC authority over cleanup
and remediation is interesting, since it is not supported by
the NRC. Indeed, the NRC through the MOU and otherwise,
supports EPA CERCLA remediation efforts, as does the State
of New Mexico.
Specific Comments
1. UNC alleges "EPA failed to provide an adequate comment
period."
Response; The public comment period employed in this action
more than adequately meets the muster of 40 C.F.R. 300.67(d)
and 42.U.S.C.S9617. The comment period commenced on
August 19, 1988 and closed on September 16, 1988, using the
"postmark rule." As the previous discussion herein and the
administrative record demonstrates, this case represents a
model of agency efforts in community relations. In the
specific case of UNC, agency efforts have been substantial
at getting this potentially responsible party (PRP)
involved, as noted earlier herein. UNC's complaint is
groundless.
2. UNC argues "EPA failed to develop the Administrative
Record by withholding information from public review."
Response: EPA submitted an administrative record consisting
of more than 550 documents comprising thousands of pages to
its public repository in Gallup, New Mexico. In compiling
this record, EPA complied with its policy procedure for
preparation of interim administrative records, as well as
the statutory provisions set forth at 42 U.S.C.
§9613(k)(2)(C). These procedures provide that the agency
may incorporate by reference certain types of documents that
it would not be practical to place in the local repository.
Such documents would include items, such as raw data pages,
large and cumbersome maps or charts, and publicly available
guidance documents. EPA intends to supplement the record
with copies of the Record of Decision, the Summary of
Remedial Alternatives (including attachments such as the
Community Relations Responsiveness Summary), and documents
recommended by UNC. No attempt has been made by the agency
to withhold documents from public review, as asserted by
UNC, and EPA certainly has not engaged in the selective
inclusion argued by UNC.
EPA believes that its treatment of UNC as a PRP has been
more than fair, as discussed previously herein and
documented in the administrative record. UNC's failure to
timely avail itself of early opportunities to participate in
site investigation and remediation efforts effectively
foreclosed this discretionary opportunity. EPA believes
that it has acted consistent with the overall public
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interest and in accordance with the requirements of CERCLA.
Section 122 of CERCLA, contrary to UNC's untimely
assertions, does not require the agency to abandon existing
studies and plans, and renegotiate them to begin anew, nor
does it require at this time or previously a formal
determination that good faith negotiations with UNC are not
possible.
3. UNC comments that "EPA failed to provide for public
review and comment regarding the MOU entered into with
the NRC in violation of United Nuclear's due process
rights."
Response; The MOU entered into between EPA and NRC is an
inter-agency agreement between regional offices of the two
agencies, which provides a mechanism for coordination of the
two different regulatory efforts. It is designed to
accomplish exactly the kind of efficiency and coordination
of effort that UNC complains is lacking in EPA's efforts,
elsewhere in its comments. Such an agreement is not itself
subject to public comment, although the NRC reportedly
intends to publish it in the federal register and EPA made
it available to the public at its meeting in Gallup and is
including it as an attached to the Summary of Remedial
Alternatives. It is thus being included in the
administrative record.
The MOU, as is clear on its face, did not purport to make
any authoritative determinations with respect to the site,
including the legally applicable or relevant and appropriate
CERCLA requirements (ARAR's) that UNC alleges. Instead, it
is clear that each agency is responsible for implementing
its own requirements. The fact that the document speaks to
ARAR's is merely an acknowledgement that ARAR's have been
identified for the site, as required by the NCP.
4. UNC contends that "EPA's RI, OUFS, and RI/FS process as
applied at the Churchrock site fail to satisfy CERCLA's
and the NCP's requirement that the remedial action is
cost effective. UNC argues that EPA cannot undertake
response action for naturally occurring substances at
the site."
Response; EPA is well aware of the provisions of CERCLA
cited by UNC for its proposition, but believes that UNC's
argument is misplaced. This is because EPA does not agree
that the hazardous substances and pollutants and
contaminants which have been released into the environment
from UNC's tailings pits and spills constitute naturally
occurring substances in their unaltered form, or altered
solely through natural processes. EPA believes that the
investigative information it has gathered on the UNC site,
along with the other information and data which comprise the
administrative record more than substantiate its position.
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5. UNC asserts that "EPA's RI/FS process is not cost
effective because it duplicates the work that has been
or will be performed pursuant to NRC requirements.
"
Response : EPA is very keenly aware of the work that has
been performed pursuant to NRC requirements, along with
future plans for NRC-required investigative and remedial
efforts. EPA does not agree that its efforts are
duplicative or that this is a proper measure of cost
effectiveness. This is because EPA and NRC have taken great
care to coordinate their respective efforts, despite UNC
contentions otherwise. EPA investigative efforts have been
primarily aimed at existing and threatened contaminant
migration from the site. Based on these extensive studies,
EPA cannot agree that the NRC-required reclamation efforts
onsite will alone sufficiently remedy these threatened and
actual releases. This is confirmed by EPA's analysis of the
"no-action" alternative. UNC correctly notes, as EPA has,
that the NRC 10 CFR Part 40, Appendix A requirements
constitute ARAR's for the site. On the extent of the
contaminated groundwater migration problem, it is the
requirements of 40 CFR L92, as incorporated into the NRC
regulations, that are ARAR's along with other requirements
identified in the record. UNC's cost effectiveness
contentions are, therefore, without merit, with or without
UNC agreement on the characterization of onsite NRC directed
reclamation efforts.
6. UNC opines that "EPA can satisfy the requirement that
actions be cost effective only by recognizing that NRC
regulations are the ARAR's for the Churchrock site and
by selecting the no-action alternative."
Response; EPA has properly determined the role of the NRC
regulations as ARAR's in its action, as properly noted
previously and in the record. EPA's close examination of
the entire record, including the UNC reclamation plan has
led it to a different conclusion than the no-action
recommendation advocated by UNC. EPA notes that the
no-action alternative had virtually no support in the
community, as evidenced by the comments received at the
public meeting of August 31, 1988, and subsequently, other
than by UNC. Significantly, both the NRC and State of New
Mexico disagree with UNC on this issue, as does the Navajo
Tribal Council. EPA simply cannot agree that the no-action
or limited action alternatives provide for adequate
protection of public health and the environment, as required
by CERCLA and the NCP. Such protection is a fundamental
threshold test of cost-effectiveness. EPA believes that the
proposed alternative is technically sound and reliable, and
that it provides substantially greater environmental and
public health benefits than either the "no action" or
"limited action" alternatives.
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7. UNC argues that "the RI and OUFS fail to comply with
CERCLA and applicable EPA guidance and are inconsistent
with the NCP." UNC comments that "EPA failed to
identify correctly the applicable or relevant and
appropriate federal requirements."
Response; EPA has scrupulously followed CERCLA, the NCP,
and the interim ARAR guidance in the identification of
ARAR's for the site. These are set forth in the OUFS FS and
in Appendix C to the ROD/Summary of Removal Alternatives,
and they are discussed elsewhere herein. UNC has correctly
observed that EPA set forth the regulations of 40 CFR 192,
Subparts D and E, in the FS, and EPA is most certainly aware
as evidenced by the MOU that those requirements have been
adopted by the NRC, as mandated by the Congress, in its
regulations at 10 CFR 40, Appendix A. EPA intends to apply
them in its CERCLA groundwater remedial action at the site,
along with other ARAR's. UNC's comments miss the mark.
8. UNC contends that "EPA failed to consider adequately
the factors established for determining the appropriate
remedial action."
Response; As demonstrated by the Administrative Record for
this action, EPA has complied with the "scoping" provisions
of Section 300.68(e)(2) during the RI, which requires
assessment "as appropriate" of several factors, including
the "population... at risk" provision cited by UNC. EPA's
efforts include performance of an adequate public health
assessment. Further, unlike UNC, EPA believes that it has
performed a sufficient inquiry into the designated or
potential use of the affected groundwater media. Indeed,
protection of public health and the environment from the
threat of contaminated groundwater emanating from the UNC
site is the chief thrust of EPA's proposed action. EPA has
certainly, in contrast to UNC's assertion, adequately
examined the details of proposed NRC required actions on the
site.
9. UNC comments that "EPA failed to consider adequately
the no-action and limited action alternatives in the
OUFS."
Response; EPA has, in fact, considered a proper range of
alternatives for remedial action as aptly demonstrated by
the Administrative Record, including a detailed analysis of
those alternatives passing initial screening. EPA disputes
and disagrees with UNC's opinions concerning the potential
for contaminant migration in groundwater. EPA has also
considered the issue of restricted access under the
long-term federal or state care provisions, contrary to the
contentions of UNC. As indicated previously herein, EPA
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does not consider "no action" and "limited action" to be
adequately protective of public health and the environment.
10. UNC comments that "EPA has discouraged private party
involvement in the RI/FS."
Response; The record demonstrates that this comment is
simply untrue. UNC foreclosed the opportunity for
involvement in the RI/FS by its own action, or inaction.
EPA and UNC engaged in long and protracted negotiations
during 1982 and 1983 over the issue of UNC performance of
RI/FS and remedial design/remedial action, in accordance
with the existing EPA policy. Draft orders were developed,
but negotiations ultimately failed. EPA then proceeded with
its remedial investigation, incurring contractual
obligations and developing plans for its conduct. The law
has never required EPA to engage in RI/FS settlements.
Indeed, they are discretionary agreements. In the
circumstances here, EPA was more than justified in rejecting
UNC's offers as being too late in the game and too
disruptive of ongoing response investigation activity.
11. UNC states that "EPA's failure to remove the Churchrock
site from the National Priorities List when NRC resumed
jurisdiction violates EPA policy."
Response; As UNC obliquely infers, the UNC facility was
properly placed on the National Priorities List. See
Eagle-Picher II and III. EPA policy provides that sites
will not be removed from the NPL until EPA certifies
completion of cleanup and petitions for removal from the
list, or a final determination by EPA that no action is
required.
For the foregoing reasons, EPA rejects UNC's conclusions and
arguments as set forth in its legal ("general") comments.
PRP Technical Comments
The PRP submitted technical comments on each chapter of the
OUFS, including the Executive Summary and Appendices.
For purposes of the Responsiveness Summary, EPA grouped the
comments into the following response categories:
1. ARAR's and Background Levels of Chemical Constituents
2. Limitations of Data Base Used in the OUFS
3. Geohydrological Characteristics of the Site
4. Groundwater Modeling
18
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5. Relationship Between Selected Remedy and NRC
Requirements at the Site
6. Public Health Assessment
7. Duplication of PRP and EPA Efforts
8. Evaluation of Other Remedial Alternatives
9. Compliance with Appropriate EPA Guidance
10. Groundwater Treatment Technologies
11. Relationship Between EPA and UNC Actions
12. Costs
13. Non-Action
Individual comments were grouped into one or more response
categories. Each comment was given a code matching the
comment number used by the PRP; for example, the PRP's
second comment on Chapter 1 of the OUFS was given the
comment code "1-2". The following indicate the comments
addressed within each response category:
Response Category 1
ARAR's and Background Levels of Chemical Constituents
ES-2, ES-5, 1-2, 2-1, 2-3, 2-5, 2-6, 2-13, 2-16, 3-1, 3-2,
3-4, 3-5, 3-6, 3-8, 3-9, 5-3, D-General, D-5.
Response Category 2
Limitations of Data Base Used in the OUFS
ES-3, ES-4, 2-3, 2-8, 2-9, 2-10, 2-11, 2-12, 2-14, 3-6, 3-7,
3-8, 8-12, D-General, D-6, D-8, D-ll.
Response Category 3
Geohydrological Characteristics of the Site
ES-2, 1-1, 1-2, 1-3, 2-1, 2-2, 2-4, 2-5, 2-6, 2-13, 2-14,
2-15, 5-1, 8-7, D-General, D-8, D-ll.
Response Category 4
Groundwater Modeling
ES-7, 2-2, 2-4, 2-5, 2-7, 5-5, 6-2, 6-3, 7-1, 7-2, 8-7, 8-8,
8-10, 8-11, D-General, D-l, D-2, D-3, D-4, D-5, D-6, D-7,
D-8, D-9, D-10, D-ll, D-Alluvium Critique, D-Zone 3
Critique, H-6.
Response Category 5
Relationship Between Selected Remedy and NRC Requirements at
the Site
ES-1, 1-4, 1-6, 5-2, 5-9, 5-10, 6-1, 8-6, H-3, H-5.
19
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Response Category 6
Public Health Assessment
4-1, 4-2, 4-3, 4-4, 4-5, 4-6, 4-7, 4-8, 4-9, 4-10, 4-11,
4-12, 8-11.
Response Category 7
Alleged Duplication of PRP and EPA Efforts
ES-1, 1-4.
Response Category 8
Evaluation of Other Remedial Alternatives
ES-6, 5-4, 5-7, 6-5, C-l, H-l, H-2, H-7.
Response Category 9
Compliance with Appropriate EPA Guidance
3-3, 5-6, 5-8, 8-1, 8-2, 8-3, 8-4, 8-9.
Response Category 10
Groundwater Treatment Technologies
5-9, 6-1, 8-13.
Response Category 11
Relationship Between EPA and PRP Actions
1-7.
Response Category 12
Cost
7-1, 7-2.
Response Category 13
Non-Action
1-5, 6-4, 8-5, H-4.
DFW37/011 20
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RESPONSE CATEGORY 1
ARAR'S AND BACKGROUND LEVELS
This response category addresses ES-2, ES-5, 1-2, 2-1, 2-3,
2-5, 2-6, 2-13, 2-16, 3-1, 3-2, 3-4, 3-5, 3-6, 3-8, 3-9,
5-3, D-General, D-5. These comments all relate to
determining ARAR's and background levels.
Comment
The PRP states that EPA's choice of background levels in the
OUFS invalidates the OUFS, creates non-existent target areas
for cleanup, and ignores site-specific conditions. This
summary includes all comments included in this response
category.
Response
EPA does not intend for the PRP to pump and evaporate
groundwater located in background areas outside of the
tailings disposal area. Only areas which are impacted by
tailings seepage, which are to be further defined and
adjusted during remedial design, will be pumped.
Furthermore, EPA believes that background at the Churchrock
site must be determined in view of pre-mining conditions and
infiltration of mine discharge water into the alluvium and
sandstone formations. Site-specific conditions have been
extensively considered during EPA's review of possible
ARAR's for the Churchrock site. Preoperational data have
been evaluated in the context of regional data for the
alluvium and Gallup Sandstone since EPA perceives that some
water existed at the site prior to mining, and because EPA
considers groundwater at the site as Class IIB.
EPA was faced with a difficult and complex task of
determining a set of contaminant-specific ARAR's for the
Churchrock site. The proposed list of ARAR's was specified
in Table 3-1 of the Feasibility Study (FS).
The difficulty arises because of the limited quantity of
site-specific pre-milling groundwater data for the alluvium,
and Zones 1 and 3 of the Upper Gallup Sandstone. EPA's
approach is to consider any effects mine dewatering
discharges may have had on post-mining groundwater
conditions.
The only pre-milling site-specific ground water that is
available to EPA is the data collected from well Nos. GW-1
through GW-6, GWD-1, and GWD-2. These wells were sampled on
2-4-77, 3-8-77, and 4-15-77. Milling operations began in
June 1977; therefore, any subsequent sampling events for the
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wells listed above cannot be conclusively considered as
pre-milling groundwater data.
The PRP is well aware that the groundwater data collected
from these eight "pre-milling" wells is controversial. EPA
participated in seven meetings with UNC, NMEID, and NRC, at
which this topic was discussed at length. Pre-milling
groundwater data submitted by UNC gives the following
chemical concentrations as examples:
o Nitrate as N values range from a low of §0.1 mg/L
in well Nos. GW-1 and GW-2, to a high of 95.9 mg/L
in well GWD-1.
o Sulfate values range from a low of 470 mg/L in
well No. GW-1 to a high of 1,731 mg/L in well
No. GWD-1.
o Total dissolved solids range from a low of
904 mg/L in well No. GW-1 to a high of 4,076 in
well No. GW-4.
*
This groundwater data is controversial for the following
reasons:
o The nitrate, sulfate, total dissolved solids, and
other constituent concentrations have a larger
variance than one would expect from a
site-specific continuous alluvial formation. -Well
Nos. GW-1, GW-2, and GW-3 have the most consistent
pre-milling data of the eight wells. Nitrate
levels in well No. GW-4 are the most inconsistent
and change from 44 to 68 to 17 mg/L as N in the
first three sampling events.
o Wells currently exist in the alluvium and the two
sandstone zones that do not display such large
nitrate values. The groundwater in these wells
must either be pre-mining groundwater or mine
discharge water that has infiltrated into the
system.
o Some of the nitrate values reported in the
pre-milling wells are typical of groundwater that
has been contaminated by man-made sources and not
groundwater that represents natural pre-milling
background conditions.
o The PRP has not tagged a specific source of
nitrogen to explain the large nitrate value
reported in the pre-milling wells. Such nitrate
concentrations are not seen in background
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groundwater at other sites; therefore, there roust
be a site-specific source of pre-milling nitrogen.
The PRP has funded two studies in an attempt to quell the
pre-milling site-specific background controversy. The first
study was entitled "Geochemical Background Investigation UNC
Mining and Milling Churchrock Mill" and was prepared by
Billings & Associates, Inc. in August 1986. The second
study was entitled "Evolution of Groundwater Chemistry" and
was prepared by Canonie Environmental in July 1988. Both
studies propose that pre-milling surface water, flowing in
Pipeline Arroyo, dissolved alluvial salts and concentrated
them along groundwater flow paths, creating pre-milling
groundwater background conditions with chemical values that
exceed those proposed by EPA.
EPA and its consultants have looked at the Billings and
Canonie studies extensively in an effort to determine
pre-milling site-specific background conditions. Billings
presents groundwater data from the same pre-milling wells
that EPA has considered. Groundwater data from regional
wells are discussed by Billings; however, little data is
presented.
Billings tried to substantiate his theory that nitrate,
sulfate,'and total dissolved solids concentrations increase
along groundwater flow paths as evidenced by data collected
from well Nos. 639, 640, 641, 642, 643, 644, and 645. In
addition to the groundwater chemical data collected from
these wells, Billings performed a laboratory leaching study
on borehole samples and succeeded in leaching nitrogen.
Unfortunately, the borehole sample and groundwater data in
the 639-645 wells collected during the Billings study may
not be representative of site-specific background data due
to previous mine-related activity in the immediate area.
The Kerr-McGee Corporation has indicated that the Quivira
Mining Company (QMC) conducted activities in this area prior
to the Billings borehole sampling and flow analyses studies.
It is EPA's position that these activities could have
influenced the 639-645 wells. More specifically, QMC's
activities have included:
1. Surface storage of various equipment and material, plus
equipment washing.
2. Construction of three evaporation ponds subsequently
used for disposal of sediments extracted from mine
settling ponds at the Kerr-McGee CRI mine site. QMC
added chemicals including Calgon cation flocculants and
barium chloride for the treatment of the mine water
prior to discharge.
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3. Transport and storage of some 23,000 tons of protoore.
Maps provided by Kerr-McGee, especially in the same area
used for equipment storage, exhibit high gamma ray activity.
These data from Kerr-McGee cast doubt on background studies
in this area by the PRP. Therefore, EPA cannot base its
ARAR decisions on data and a study that is in question
because of possible outside effects.
The Canonie (1988) study has also been reviewed by EPA, and
EPA's consultants review comments are contained in the
administrative record (Jacobs Engineering Group, 1988) . In
summary, Canonie collected a very limited amount of data
indicating that soluble nitrogen may be present in the
alluvium which is unaffected by tailings pile seepage. EPA
has considered these study results, but is unable to
quantitatively apply them toward setting site-specific
pre-milling background standards for the site. Canonie also
presented technically inadequate discussions of pre-raining
groundwater levels and the possibility of ammonia conversion
to nitrate at the site.
The failure of the two studies mentioned above to resolve
the site-specific ARAR controversy has left EPA with the
following two choices:
1. Rely on the existing pre-milling groundwater data to
determine site-specific ARAR's even though the data
appears to be controversial and inconsistent; or
2. a. Determine ARAR's relying initially on existing
regional groundwater data and/or existing state
and federal standards. If chemical parameters
from regional groundwater data exceed the state
and federal standard ARAR's, then these background
parameters are the ARAR's. If regional background
is below the state and federal standards, then the
regulatory standards are the ARAR's;
b. Evaluate existing pre-milling groundwater data in
the context of ARAR's in 2a and adjust background,
if reasonable.
EPA does not believe it is appropriate to determine
site-specific ARAR's at UNC Churchrock site based on
existing inconsistent and questionable site-specific data.
Therefore, EPA has chosen the second approach after giving
due consideration to all the information and data submitted
by the PRP.
In light of the above discussion, EPA has compiled
concentration in its contaminant-specific ARAR's table
according to the following procedure.
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1. EPA reviewed regional groundwater quality data for the
Upper Gallup Sandstone and Alluvium beginning with the
results of EPA's September 1987 Field Investigation
Team (FIT) sampling of domestic/livestock wells within
a 4-mile radius of the UNC site. Results indicate that
operational wells within this radius met all federal
primary (health-related) drinking water standards, but
contained levels of iron, manganese, sulfate, and total
dissolved solids (TDS) above federal secondary
(aesthetics-related) or state standards. Nitrate as
nitrogen (N-NO.) was below 2 mg/L in all four wells.
2. EPA next chose to look at the range of background
values for each chemical constituent using data
gathered by the FIT team in September 1987. The
maximum observed concentrations of iron, manganese,
sulfate, and TDS were in Well No. 15K-303 located
approximately 1.5 miles north of the site in the Upper
Gallup Sandstone. The maximum values for this data
are:
Iron 1.75 mg/L
Manganese 0.48 mg/L
Sulfate 1,770.00 mg/L
TDS 2,593.00 mg/L
3. EPA subsequently reviewed historical data compiled by
Southwest Research and Information Center (Shuey and
Robinson, 1984) for Well No. 15K-303 since this well
was known to have high background from recent FIT
sampling. The maximum observed concentrations for
sulfate from nine sampling events between May 1955 and
July 1982 was 2,160 mg/L with a mean and standard
deviation of 1,597 +/- 472.3 mg/L. The maximum
observed concentrations for TDS from eight sampling
events between May 1955 and July 1982 was 3,170 mg/L
with a mean and standard deviation of 2,469.8 +/-
636.3 mg/L. The maximum observed value for N-NO3 from
these sampling events was 0.6 mg/L.
4. EPA subsequently compared background values of
2,160 mg/L sulfate and 3,170 mg/L TDS to regional
background data from 115 Gallup Sandstone wells at
distances of over 20 miles from the Churchrock site and
found these concentrations to be maximum values.
5. EPA compared the sulfate value of 2,160 mg/L to
pre-operational data collected in February, March, and
April 1977 from GW-wells at the Churchrock site. The
value of 2,160 mg/L was above the maximum value of
1,731 mg/L sulfate observed in GW-wells before the
onset of tailings disposal in June 1977.
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6. EPA compared the TDS value of 3,170 mg/L to
pre-operational data collected in February, March, and
April 1977 from GW-wells at the Churchrock site. The
value of 3,170 mg/L was above all values observed in
GW-1, -2, -3, -5, -6, and -D2 wells, and lower than
only two observations in the remaining wells, one in
GW-4 (4,076 mg/L) and the other in GW-Dl (3,769 mg/L).
In view of this distribution of GW-well data in the
context of regional data, EPA concluded it was
reasonable to retain the value of 3,170 mg/L.
7. EPA compared the original FIT team background value for
iron of 1.57 mg/L to the broader set of iron data
described in (3) above and noted generally low iron
concentrations in the Gallup Sandstone. However, on
the basis of elevated iron levels in the 15K-303 well,
adoption of Billings pre-operational value of 5.5 mg/L
is reasonable.
8. EPA compared the original FIT team background value for
manganese of 0.48 mg/L to regional manganese data. To
be consistent with the approach taken for iron in (7)
above, EPA has subsequently adopted Billings
pre-operational value of 2.6 mg/L observed in GW-1 in
February on 1977. Adoption of this value is reasonable
in light of two additional pre-milling observations of
1.75 mg/L and 2.3 mg/L in well GW-2, which is just
north of GW-1. Both these wells exhibit fairly
consistent patterns for sulfate and TDS making reliance
on them for manganese reasonable.
9. EPA compared the regulatory standard for arsenic of
0.05 mg/L to pre-operational data discussed in the
Billings report. The highest pre-operational
concentrations of arsenic observed were below
0.02 mg/L, therefore EPA retained the regulatory
standard of 0.05 mg/L.
10, EPA compared the regulatory standard for cadmium of
0.01 mg/L to pre-operational data which exhibit a range
from less than 0.001 mg/L to a maximum of 0.1 mg/L.
With a median pre-operational cadmium concentration of
0.003 mg/L, no regional cadmium data other than 1987
FIT data available as a context better evaluate
pre-operational data, and the historical range in
concentrations in these wells; EPA concluded that it
was reasonable to retain the regulatory standard of
0.01 mg/L.
11. EPA compared the regulatory standard for selenium of
0.01 mg/L to preoperational data which exhibit a range
from less than 0.001 mg/L to a maximum of 0.0'67 mg/L.
The regulatory standard of 0.01 mg/L was above all
values observed in GW-1, -2, -3, -5, -6, -Dl, and -D2
wells, and lower than only two observations in GW-4,
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0.067 mg/L and 0.04 mg/L. In view of this distribution
of GW-well data, combined with 1987 FIT data which
indicate selenium in the alluvium and Upper Gallup
Sandstone to be below 0.01 mg/L, EPA concluded that it
was reasonable to retain the regulatory standard of
0.01 mg/L.
12. In the absence of regional 1987 FIT data for Th-230,
EPA compared the regulatory standard for Th-230 of
15 pCi/L to pre-operational data which exhibit a range
from less than 0.6 pCi/L to a maximum of 36.3 pCi/L.
The regulatory standard of 15 pCi/L was above all
values observed in GW-1, -4, -5, -6. Dl, and -D2
wells, and lower than only two observations in
remaining wells, one in GW-2 (36.3 pCi/L) and the other
in GW-3 (19.4 pCi/L). In view of this distribution of
GW-well data, EPA concluded that the regulatory
standard for Th-230 of 15 pCi/L was representative of
background if not above background.
13. Consistent with the approach used above in evaluating
existing data for background, EPA reviewed regional and
pre-operational data for N03-N. The regional data
included 1987 FIT sampling aata from wells within a
four-mile radius of the site; regional data compiled by
Southwest Research and Information Center (Shuey and
Robinson, 1984); and U.S. Geological Survey water
quality data for the alluvium and Gallup Sandstone in
the New Mexico portion of the San Juan Basin (WATSTORE
database). As mentioned, NO--N concentrations were
below 2 mg/L based on 1987 FIT sampling. NO--N
concentrations were all below 2 mg/L based on regional
data compiled by Shuey and Robinson (1984) for the
Gallup Sandstone. NO^-N data was obtained from U.S.
Geological Survey water quality data for the alluvium
in the New Mexico portion of the San Juan Basin.
NO--N concentrations ranged from below 0.02 mg/L to a
maximum value of 47 mg/L from 224 observations. Six of
the 224 NO,-N values were above 10 mg/L and the
remainder Below. N03-N concentrations from U.S.
Geological Survey water quality data for the Gallup
Sandstone range from below 0.01 mg/L to a maximum value
of 27 mg/L for 110 observations. All required NO^-N
concentrations were below 10 mg/L except for the one
maximum observed value.
EPA also reviewed pre-operational data for NO,-N which
ranged from below 0.01 mg/L to a maximum of 95.9 mg/L.
The median concentration for NO^-N from preoperational
data is 17 mg/L. Data for N03-R are difficult to
interpret, however, as GW-1 and GW-2 reveal consis-
tently low concentrations prior to milling. GW-1
evidences a distinct rise in NO--N concentrations in
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late 1979, possibly in response to the tailings spill
of July 1979.
GW-2, however, does not respond in this manner, even
though it is located directly north of GW-1. NO--N
concentrations in GW-3 climb steadily to a maximum
preoperational value of 33.4 mg/L, while data in GW-4
and GW-Dl is sporadic with one-time values of 67.8 mg/L
and 95.9 mg/L NO«-N, respectively. Premilling
concentrations of NO--N in GW-D2 are consistently low
until mid-1978, while concentrations in GW-5 and GW-6
vary between 14.3 mg/L and 34.5 mg/L.
Trends in the above preoperational data for N03-N do
not lend themselves to simple interpretation. While
several wells indicate preoperational NO^-N concen-
trations to be consistently below 10 mg/L, other wells
indicate abrupt changes in N03-N concentrations during
the same time period. One well (GW-1) shows a distinct
increase in concentration in NO.-N after the tailings
spill. On the basis of preoperational data, a
reasonable argument, could be made for a background
concentration of 30 mg/L; an equally reasonable
argument could be made for a background concentration
below 10 mg/L, depending on which wells are used.
Regional background for NO-j-N, however, is consistently
well below 10 mg/L, except for anomalies indicated
previously. Moreover, February 1988 well data
collected by Malapai Resources, Inc. (Navajo Nation,
1988) in the vicinity of the Quivira Churchrock Mine
indicate NO,-N values to be less than 1 mg/L for the
Gallup Sandstone (Navajo Nation, 8/6/88) .
While the regulatory standard of 10 mg/L was used in
the PS, EPA recognizes that background for NO--N may
exceed 10 mg/L and appears to do so inconsistently.
EPA also recognizes that ammonia and nitrate resided in
the tailings fluids and contributed to nitrate
contaminations in alluvial and bedrock groundwater.
The selected remedy will address higher NO--N levels.
Based on evaluation of all data to date, EPA recognizes
a background for NO.,-N of 30 mg/L. If found to be
above this level during remediation of the site, then
such level will become the cleanup criteria to the
extent practicable. However, EPA sees no reason to
increase this value, and will look closely at
additional data that may call this level into question.
14. EPA compared the regulatory standard for Hg of
0.002 mg/L to preoperational data. The regulatory
standard was above all values observed in GW wells,
except for one observation of 0.004 mg/L Hg in GW-4.
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Based on this distribution of preoperational data, EPA
concluded that it was reasonable to retain the
regulatory standard of 0.002 mg/L.
15. EPA compared the regulatory standard for Ra-226 and
Ra-228 of 5 pCi/L to 1987 FIT data and preoperational
data. Preoperational concentrations of Ra-226 were
consistently below the regulatory standard in all GW
wells except for one observation of 8.7 pCi/L in GW-01.
Preoperational concentrations of Ra-228 were below the
regulatory standard in GW-1, -2, -3, -5, and -6, with
two exceptions: one observation of 6 pCi/L in GW-4,
and a second of 11 pCi/L in GW-D2. In view of this
distribution of GW well data, and because 1987 FIT data
are all below 2 pCi/L for Ra-226 and Ra-228, EPA
concluded that it was reasonable to retain the
regulatory standard of 5 pCi/L for each radioisotope.
16. EPA compared the regulatory standard for Cl of 250 mg/L
to preoperational data, the maximum observation being
85 mg/L. Consistent with EPA's approach of using a
regulatory standard as an ARAR if higher than
background, EPA retained the 250 mg/L standard.
17. Health-based standards for Sb, Be, Tl, and V are to be
considered only if elevated levels are present, which
does not appear to be the case.
18. Where background is below a federal or state standard,
then the federal and state standards becomes the
cleanup criteria. This appears to be the approach for
setting background that Billings used for Al, Ba, Cr,
Co, Cu, Pb, Mo, Ni, Ag, and Zn, and is consistent with
the approach used by EPA to determine contaminant-
specific ARAR's for these constituents. However, EPA
recognizes 10 mg/L NO--N is a health-related standard
and will require extensive monitoring of nitrate levels
in water.
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RESPONSE CATEGORY 2
LIMITATIONS OF DATA BASE USED IN THE OUFS
The following comments are addressed under this response
category: ES-3, ES-4, 2-3, 2-8, 2-9, 2-10, 2-11, 2-12,
2-14, 3-6, 3-7, 3-8, 8-12, D-General, D-6, D-8, and D-ll.
Since all these comments were of a similar nature, a single
response will be given.
Comment
The PRP stated that EPA disregarded available data which
would provide a comprehensive picture of the evaluation of
groundwater at the site, and was arbitrary and capricious in
only using its 1985 sampling data in the OUFS.
Response
EPA is very aware of the large historical database generated
by UNC, UNC consultants, and NMEID since mining and milling
operations began. This data was reviewed by EPA and its
consultants during the RI in order to characterize and
interpret site conditions. Review of this data did assist
EPA in understanding site-specific conditions, but also led
to several scientifically valid differences in
interpretation of the site and site development, many of
which were.discussed in the RI, during technical meetings
held between EPA, UNC, NMEID, and NRC during the RI/FS
period, and reiterated in other response categories to the
PRP comments. EPA has reviewed pertinent documents
describing site characteristics including the Reclamation
Plan (Canonic, 1987A, B), Geohydrologic Report (Canonie,
1987), the Geotechnical Background Investigation (Billings
and Associates, Inc., 1986), and the Evolution of
Groundwater Chemistry Report (Canonie, 1988). Discussion of
findings in these reports appears under other response
categories, particularly Response Category 3.
NMEID and UNC data were relied on to help interpret site
conditions in the RI. The RI concludes, as does UNC, that
water levels have declined in the alluvium and Upper Gallup
Sandstone, and are slowly returning to premining conditions.
EPA requested the most recent water level measures from UNC
in April 1988 for review, as well as quarterly monitoring
reports for 1986-1988. These data were used qualitatively
to indicate variations in groundwater chemistry subsequent
to termination of mine water discharge in 1986. As an
example of this, EPA compared water quality data taken by
the PRP in October 1987 with May 1985 EPA RI data (Table 2.5
OUFS). The maximum detected values and mean concentrations
were presented for samples taken in a specific aquifer. As
stated on page 2-15 of the OUFS, the comparison suggested
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that inclusion of the PRP data obtained since the completion
of the RI field, activities would not significantly change
the development and evaluation of alternatives. Several PRP
1987 mean and maximum values were higher than corresponding
EPA 1985 means and maximum values. The reverse is also
true. Further, the maximum values from both data sets are
often found in the same well. The main point is that PRP
water quality data obtained during and since the completion
of the RI field activities would not significantly change
the target areas. The critical issue, as the PRP maintains,
is the background concentration for a number of chemical
constituents (as mentioned in Appendix C).
The PRP presented arguments that EPA was arbitrary and
capricious in the manner of rejecting data during a
three-way split among EPA, NMEID, and PRP. This case in
point involves questionable inorganic sulfate data from the
EPA lab. Because EPA data was questionable and verified by
NMEID and PRP, the NMEID/PRP data was acceptable and used.
The PRP further argues that questionable Th-230 data was
used by EPA. During the split, neither the PRP nor NMEID
provided radiological analyses; therefore, EPA data was
used. The use and effect of the Thorium-230 data on the
risk assessment is further explained in Response Category 6.
The PRP has commented that EPA has not assessed all data
when EPA states that the tailings pond is a primary source
of contaminants. The PRP references the study of Canonie
1988a which concludes that alluvium in the tailings pond
neutralizes tailings fluids. EPA does not arrive at the
same conclusion which was derived from one or two boreholes
in a 100-acre tailings pond. EPA's position is that this
study has not definitively determined that the tailings pond
is not a primary source. The letter from Jacobs Engineering
Group (1988) to EPA details EPA's position on this area of
concern. In fact, the PRP's consultants, Canonie (1987a)
and Billings (1986) have also concluded that the tailings
seepage has impacted all aquifers.
The PRP has objected to the use of Table ES-1 which depicts
contamination levels, but cannot be attributed to the
source. These tables are to be used in conjunction with
Exceedance Maps provided in the OUFS. These maps, which
depict areas downgradient of the tailings ponds, represent
the areas which are addressed in the table. Target areas
are a function of background levels since 1985 EPA RI data
and 1987 PRP monitoring data are comparable. Response
Category 3 also addresses this issue.
Future well sampling results during remedial design should
be used to further define and adjust target areas as
specified in the FS in conjunction with background
determinations.
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RESPONSE CATEGORY 3
GEOHYDROLOGICAL CHARACTERISTICS OF THE SITE
This response category addresses ES-2, 1-1, 1-2, 1-3, 2-1,
2-2, 2-4, 2-5, 2-6, 2-13, 2-14, 2-15, 5-1, 8-7, D-General,
D-8, D-ll. These comments all relate to PRP's concerns
about the geohydrological characteristics and conditions at
the site. The following issues were noted by the PRP and
are addressed in this Response Category:
o pre-milling conditions
o recharge interrelationship of aquifers
o site migration pathways
o post milling conditions
PREMINING CONDITIONS
EPA's perception of premining conditions is that groundwater
existed at the site in the alluvium and bedrock aquifers.
These aquifers were unsaturated (water was not present
throughout the entire thickness). To date, the PRP has
provided little conclusive evidence for the alluvial and
bedrock aquifers as being dry prior to mining. Their
evidence'has been established by connecting water levels in
the mine shaft and the Indian well and projecting them
through the site. These projections have been made through
hydrogeologic units that do not contain water and act as
aquitards. The PRP also reports that premilling
geotechnical holes also were reportedly dry at the time of
drilling.
EPA's interpretation of the presence of groundwater during
pre-mining conditions is based on the following:
o Presence of Artesian Water in Well No. 15K-303.
This well is completed in the Gallup Sandstone and
is downgradient of the tailings disposal site.
Water in the well cannot be attributed to mine
dewatering or tailings seepage because it was
noted years before mining activity in the area.
The most likely source of water is recharge at the
outcrop from precipitation and surface water
infiltration. The outcrop of this formation is
known to be present in Section 2 (UNC tailings
disposal area) as noted by the PRP's in their
geologic map of the site. Therefore it is
difficult to conclude that recharge and water is
not available in these site aquifers.
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NECR Mine Shaft Contained Water. Geologic logs of
the NECR mine shaft, supplied by the PRP's, note
that water was found above the Zone 3/Zone 2
Gallup contact. Water reportedly entered the mine
shaft at a rate of 30 gpm. This contact is also
present in the tailings area which is less than a
mile away. If water is present at the mine shaft,
it is very plausible it was present in the same
geologic conditions less than a mile away.
Further review of Figure 1-2 in the July .26, 1988
Canonie transmittal to EPA provides a
cross-section through the alluvium in Pipeline
Canyon. This cross-section clearly shows that the
Zone 3/2 contact outcrops below the stream in
Pipeline Canyon and may be the source of water to
the mine shaft.
Premilling Drill Logs Indicate Water. The PRP has
indicated no water is present in premilling
geotechnical holes in the tailings area. The PRP
has provided drill logs of these boreholes to EPA.
Close review of these logs indicates a different
interpretation. For example, borehole 76SHB-2W is
reportedly "dry" according to Canonie, 1987A.
Review of the log indicates perched water at a
depth of less than 30 feet. Also, PRP data state
that borehole HL-5 did not yield water in a
24-hour period. Review of this drill log
indicates damp conditions over the entire extent
of the borehole. The method of drilling this
borehole (air rotary) is not conducive for finding
low yielding water supplies, especially within a
24-hour period. In fact, the PRP's consultant
(Sargent, Hauskins, and Beckwith), in a report
submitted to the PRP on May 17, 1976, indicates
that there may be a delay of much longer than 24
hours in this area before water is found in a test
well.
Review of Topographic Maps. Another piece of data
which supports the premise of premining aquifers
comes from the review of premining topographic
maps. The USGS 7.5 minute quadrangle maps of the
area that are dated 1963 were reviewed. EPA has
found the presence of numerous dams and stockponds
in Pipeline Canyon. A 5-acre pond was present in
1963 directly underneath a portion of the current
south cell disposal area. It is against sound
scientific judgment to suggest that this and other
ponds in Pipeline Canyon would not supply water
for infiltration to the aquifers.
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RECHARGE INTERRELATIONSHIPS OF AQUIFERS
The PRP refutes the existence of premining aquifers. The
PRP also states that recharge to the alluvium and the Zone 1
and 3 sandstones from precipitation and the Pipeline Canyon
stream did not exist before mining and has ended following
the cessation of mine discharge. Furthermore, all
water-bearing formations will dry up naturally. Pumping,
according to the PRP, will speed up this process.
EPA's understanding and interpretation of the hydrogeologic
conditions were summarized in Figure 2-3 and Table 2-1 of
the OUFS. The PRP apparently misunderstands EPA's
interpretation of the recharge conditions, therefore they
are resummarized here.
EPA agrees with the PRP that significant volumes of water
infiltrated the alluvium and bedrock aquifers during mine
dewatering. EPA also agrees that this source has been
removed. Figure 2-3 is in agreement as it indicates the
mine water ceased in 1986. Also, it is not EPA's contention
that precipitation and surface water are continually
supplying recharge to the alluvium as implied by the PRP.
EPA in fact states in the RI and OUFS that the Pipeline
Canyon has been an ephemeral stream since 1986. This is a
stream that flows only in direct response to precipitation.
EPA's position is that recharge cannot occur when the stream
is dry Or not flowing.
EPA also has assumed a very low infiltration areal rate for
the alluvium (0.6 inches/year). This rate was utilized in
the groundwater model. This infiltration rate is
appropriate for semi-arid areas.
Review of Canonie 1987a water balance calculations support
the existence of other sources of recharge. For example,
Canonie estimates recharge into the alluvium of only 250 gpm
during mine dewatering. In contrast, outflow southwest
through the alluvium is estimated at 360 gpm by Canonie. If
this is true, water levels would never have risen in the
canyon as high as they did. If there was a net outflow,
then another source of recharge is needed to equalize the
water balance.
SITE MIGRATION PATHWAYS
The existing site migration pathways are depicted by the
potentiometric contour maps provided in the remedial
investigation report and the Canonie 1987a report. In the
alluvium, groundwater is shown to flow from the mound in the
tailings pile radially outward. Most of this alluvial flow
is currently towards Pipeline Canyon where it enters the
main alluvial channel and flows southwest out of Section 2.
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As stated previously, the alluvium can recharge the Zone 1
and 3 aquifers. Flow direction in these aquifers also
follow the piezometric contours. In Zone 1, flow occurs to
the northeast away from the north tailings disposal cell.
Flow also occurs eastward in Zone 1 from Borrow Pit No. 2.
This is well illustrated in the D-D1 cross-section in the
Canonie 1987a report.
Zone 3 flow is towards the northeast. Recharge from this
aquifer comes from the alluvium and the tailings cell. The
PRP has acknowledged that this aquifer is contaminated in
Sections 2 and 36 (PRP response to OUFS, page 154).
POST-MILLING CONDITIONS
It is the PRP's contention that pumping one pore volume of
site groundwater will completely dewater the current aquifer
at the site. The basis for the PRP's analysis is that there
will be no recharge to the hydrogeologic system in the area.
EPA's position is that a combination of recharge to the
aquifers by natural mechanisms and dewatering of the
tailings ponds will continue to recharge the aquifer
systems. EPA does agree that water levels will continue to
decrease.if no action occurs; however, the site will not dry
up because of recharge from surface water, precipitation,
and tailings dewatering. The alluvium will eventually
return to premining conditions and receive intermittent
recharge and still maintain an overall southwestern flow
direction. The Upper Gallup sandstone also will eventually
return to previous conditions which are partially saturated
with intermittent or continual recharge from the alluvium.
The answers to how long the pile will dewater, how much
water can be pumped from the site, and how long pumping will
last cannot be precisely estimated by the PRP or EPA. To
compare alternatives, EPA utilized groundwater models as
predictive and comparative tools. As will be explained in
Response Category 4, the models provide comparative numbers.
Actual field values may be different and pumping rates and
times will require adjustment; however, relative remedial
alternative comparison would not be greatly affected.
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RESPONSE CATEGORY 4
GROUNDWATER MODELING
The following comments were grouped into Response
Category 4, and relate to groundwater modeling: ES-7, 2-2,
2-4, 2-5, 2-7, 5-5, 6-2, 6-3, 7-1, 7-2, 8-7, 8-8, 8-10,
8-11, D-General, D-l, D-2, D-3, D-4, D-5, D-6, D-7, D-8,
D-9, D-10, D-ll, D-Alluvial Critique, D-Zone 3 Critique, and
H-6.
Comment
The primary concerns expressed in the PRP response to the
OUFS groundwater model can be summarized into the following
categories:
o Incorrect input into the groundwater model
o Inability to verify the model
o Inability to calibrate the model
o Incorrect selection of remedial alternatives based
on model inaccuracies
Response
The response to the above concerns are summarized in the
following sections. However, a brief overview of why
groundwater modeling was chosen over the PRP's method of
determining pumping schemes is necessary. The PRP
calculated pumping volumes by determining "their" area of
contamination (delineated by the pH 7.0 contour),
multiplying that area by a thickness, and assigning a
porosity. The resultant volume was the PRP's contamination
volume. No inflow from any other source was included in
their volume calculation. Tailings seepage and recharge
from precipitation and alluvium was omitted. Additionally,
water outside the "PRP-determined" contamination is also not
considered. This procedure underestimates pumping and clean
up volumes.
EPA recognizes the uncertainties in estimating contamination
volumes and the complex hydrogeology of the area. For this
reason, EPA chose to develop a model to analyze and compare
remedial alternatives. This model can be changed and rerun
if future information necessitates changes. Regardless of
the exactness of the model; the time, pumping rates, and
costs should be relative for each alternative. EPA would be
pleased if the estimated cost and cleanup time developed
from the model simulation were higher than actually
experienced during site remediation.
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INCORRECT INPUT INTO THE GROUNDWATER MODEL
The PRP has commented on the flow model description for the
PLASM alluvial aquifer model. EPA acknowledges that the
Richard's equation presented is for unconfined groundwater
conditions. The model was run for unconfined conditions;
however, the text referred to an artesian aquifer. The text
entry is a mistake and the model was properly assigned as
unconfined. Therefore, the model was not erroneously run.
The PRP has commented that boundary conditions in the
alluvial model are overestimated. EPA acknowledges that
water levels are declining in the alluvium. It is also
EPA's position that water will continually recharge the
site. However, the exact volume was unknown. A
conservative, documentable approach to calculate flow from
upgradient sources was utilized. This was done by measuring
upgradient watershed areas and assigning an infiltration
rate (0.6 inches/year) that is characteristic for the area.
From this method, a flux was determined. This flux may be
higher than what will occur in the future; however, it is
considered conservative.
The PRP further comments that steady state conditions do not
exist at. the site. EPA agrees that water levels are
changing and that steady state conditions do not exist;
however, the baseline or premining site conditions are not
well known. EPA decided that assigning a steady state
condition was more useful than simulating an unknown
baseline condition.
The use of nitrate to define plume size and to calibrate the
model was also critiqued by the PRP. Their contention is
that the model cannot be calibrated to nitrate because
significant background nitrate is present and solublized
easily. This additional "background source," according to
the PRP, would cause errors in modeling. At present, EPA's
contention is that significant levels of nitrate from
background sources do not exist. EPA's position on
background is detailed in Response Category 1.
In the solute transport modeling, model times were
multiplied by a factor of 2 for non-retarded chemical
species and 5 for retarded species. The PRP questioned
these values. Non-retarded species times were taken from a
comprehensive modeling study by the Carter Mining Company.
Reference is made to the report entitled "Predicted
Post-Mining Groundwater Quality at the Caballo Mine, Permit
433-TI, February 26, 1985." As for retarded contaminants,
model times could vary significantly. A value of 5 was
determined as most appropriate for the species modeled.
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The last model critique regarding model input is the
modeling of Zone 1 and Zone 3 aquifers. These aquifers were
modeled as confined systems. The PRP points out that the
aquifers are confined in some locations of the site and
unconfined in others. EPA agrees with the PRP. Zones 1 and
3 sandstones are confined and totally saturated near the
tailings pond. Downgradient away from the ponds, the
sandstones become unconfined. Zone 3 exhibits confined
conditions for a greater distance than Zone 1. EPA believes
that modeling the aquifer as confined was more appropriate
than unconfined because confined conditions are present near
the source and in the areas with the highest contaminant
concentrations. The one minor disadvantage of the constant
confined conditions would be a conservative overestimate of
the number of pumping wells and rates in the unconfined
areas.
Review of the selected remedies for the site indicates no
major impact as the result of assuming confined conditions.
For example, Zone 3 pumping rates for the various
alternatives are similar to the current pumping rates
predicted by the PRP. Also, the selected remedy for the
Zone 1 sandstone did not include groundwater pumping because
it is deemed as not cost effective. The PRP has also agreed
with EPA's model developed conclusion on this aquifer.
In summary, EPA acknowledges that some of the assumptions
made in the development and use of the model might not be
entirely correct; however, the model was used only as a tool
for comparing alternatives. It is also important to
note that the model results mimic current field pumping
rates at the site and that the remedial selection for the
Zone 1 developed by comparison of alternatives through
modeling was acceptable to the PRP.
INABILITY TO VERIFY MODEL
The PRP has commented that all input data is not presented
in the OUFS in order that the public or the PRP can verify
and run the model. It is not common that the entire input
data base is entered into an RI, FS, or OUFS report.
However, EPA will enter the data dump into the
administrative record.
INABILITY TO CALIBRATE THE MODEL
The alluvial transport model could not be calibrated
precisely for three reasons.
1. The limits of the plume are not well defined. This
means that'the downgradient extent of the southwest
alluvial plume is not known because of the lack of
wells southwest of the PRP's property. EPA does not
imply that no plume exists.
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2. Limited data within the internal plume structure. The
majority of the site wells in the southwest alluvium
are located near the PRP's property boundary. However,
distribution of wells between the property boundary and
the tailings pond are irregular. Additional data
points in this area would have improved model
calibration.
3. The Roberts method was not able to be used to define
retardation and dispersion. The main reason for this
is anomalies in the southwestern alluvium. The source
of the anomalies are in question. The PRP believes
that they are a result of the Mancos.Shale.
Information provided to EPA indicates that definitive
proof has not been provided.
EPA used a conservative approach to solute transport
modeling because of the inability to precisely calibrate the
model. EPA input observed chemical data into the model and
assumed no additional input source. This assumption implies
no additional leaching of nitrate from the tailings pile
occurs during the future, a position held by the PRP.
INCORRECT SELECTION OF REMEDIAL ALTERNATIVES
BASED ON MODEL INACCURACIES
The purpose of groundwater modeling was to compare remedial
alternatives. A part of this comparison is cost. EPA's
opinion is that assumptions had to be made in the model.
Not all assumptions may be precise; however, the model
provides a tool to make comparisons of alternatives.
On a relative basis, the model will still perform the
comparison even if the data or assumptions are not precise.
For instance, the relative cost comparison of pumping at
each alternative would be the same if the system operated
for 20 or 30 years. Therefore, EPA believes that the use of
modeling is valid.
The results of much of the modeling effort confirms what the
PRP already prefers. The PRP-proposed pumping rate in
Zone 3 is expected to be about 60-80 gpm. This rate
approaches the pumping rate of the majority of pumping
alternatives for the Zone 3 aquifer. As for inaccurate
alternative selection, the selected alternative by the EPA
for Zone 1 and 3 through modeling is comparable to
Amendment 1 pumping rates of the PRP. EPA acknowledges that
pumping rates may not be as high as those used in modeling;
however, actual performance will indicate this.
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SUMMARY
Groundwater modeling has limitations on many sites. EPA's
purpose for using groundwater modeling was to provide
documentable comparison of alternatives. EPA believes that
the modeling effort succeeded in that purpose. EPA also
believes that the modeling effort was in large part
conservative in the development of cleanup time and costs.
The Record ofjtecision (ROD) for this site will require
performance standards for cleanup. Groundwater at the site
will be remediated to reach predetermined contaminant
levels to the maximum extent practicable. Achieving these
levels sooner than predicted by the model would be favored
by EPA.
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RESPONSE CATEGORY 5
RELATIONSHIP BETWEEN SELECTED REMEDY AND
NRC REQUIREMENTS AT THE SITE
AND
RESPONSE CATEGORY 7
ALLEGED DUPLICATION OF UNC AND EPA EFFORTS
The following comments were of a similar nature and are
addressed under a single response category: ES-1, ES-6,
1-4, 1-6, 5-2, 5-9, 5-10, 6-1, 8-6, H-3, H-5.
Comment
EPA field work has been duplicative of UNC's investigations
and resulting OUFS alternatives conflict with potential work
required by the NRC.
Response
EPA believes that its.field work has not been duplicative.
EPA has been responsible for and is the only party that
installed wells on Navajo Tribal Lands and Reservation.
These wells were critical in determining offsite migration.
The PRP has used these wells in their analysis of the site.
As stated in Chapter 1 of the FS, and consistent with the
Memorandum of Understanding (MOU) between EPA and NRC, EPA's
final design of the selected remedy will be implemented in
conjunction or sequence with NRC requirements at the site.
Any potential conflicts that may develop will be dealt with
in accordance with dispute resolutions procedures in the
MOU. As per the MOU, NRC will require the PRP to plan for
and implement a site reclamation plan meeting the
requirements of 10 CFR Part 40, Appendix A, as amended in 52
CFR 43533 through 43568, "Uranium Mill Tailings Regulations;
Groundwater Protection and Other Issues," which conforms
with EPA 40 CFR 192, Subpart p. In conjunction with the NRC
effort, EPA will develop and implement a remedial action
plan to address groundwater contamination outside the
byproduct materials disposal site in accordance with CERCLA
and the NCP.
Rather than being in conflict, EPA believes that NRC license
requirements are consistent with EPA's selected remedy in
the Upper Gallup aquifers. Rather than being duplicative,
Amendment 1 of UNC's Reclamation Plan is consistent with
requirements of both agencies. EPA understands.that NRC
approval of Amendment 1 is an effective start to work in all
Upper Gallup aquifers, but in no way precludes modification
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.es at the site and EPA's goal of protecting human
i potential future risks.
.ted that the data used in the risk assessment was
.ed and the procedures used to calculate the
. mean values were not discussed. In addition,
.ted that the highest contaminant values were
es with the PRP. The data presented in Tables
of the OUFS were used in the PHA and the methods
culate these data were fully explained in Chapter
FS. These data were repeated in Chapter 4 as
and 4-2. EPA based the risk assessment on both
ximum concentration values. The values are
n the above referenced tables.
i 2-3 and
e
is stated on
:alculated
i a given
.ghest value
.ated in
i in the
.necessary
. were
>ns to
.ion of
alue
der of
ted that the OUFS did not consider whether the
hemicals chosen were related to the site or how
hemical concentrations are related to background
e PRP also pointed out that frequency of
information was not presented in the PHA.
urce characterization data as presented in
f the RI and Table 5-1 of the RI were used to
indicator chemical list. The SPHEM indicates
ere are questions concerning background levels of
inants, these concerns should be reported but the
ould not be excluded from the evaluation (SPHEM,
The concerns relating to determination of
are addressed in the OUFS and are further
n this responsiveness summary. The OUFS referred
to Appendix D of the RI for frequency of
information for site contaminants.
agnitude
s no reason
e sample
y Control
Further, it
rs of
in the PHA.
he current
- the
ells.
ed where the high and mean values used in the
ment were obtained and how the mean values were
The PRP also asked what aquifer Well No. 625 is
Finally, the commenter stated that only by
characterizing" the site contamination would EPA
conduct an accurate exposure assessment.
h F-10 in
hazard
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alternative. The tables were developed by applying the
percent reduction in contaminant concentrations (shown in
Figures 8-4 through 8-6) to the hazard index and
carcinogenic risk numbers for the No Action Alternative.
These tables demonstrate the reduction in public health risk
for each alternative. Table 8-4 is a summary of Tables F-l
through F-10.
Comment 4-12
The PRP questioned the adequacy of using EPA RI data that
was collected in May 1985.
Response
The May 1985 data represent the roost complete RI data set
and were therefore used in the PHA and throughout the OUFS.
EPA recognized the fact that other sampling data existed
(particularly from NMEID and the PRP). Although the PRP
data had not been subjected to EPA QA/QC procedures, EPA
considered these data. A comparison between EPA May 1985 RI
data and PRP data is presented in Table 2-5 of the OUFS.
The conclusion reached from this comparison was that
inclusion of the PRP data would.not significantly change the
development and evaluation of the alternatives in the OUFS.
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RESPONSE CATEGORY 8
EVALUATION OF OTHER REMEDIAL ALTERNATIVES
Comments ES-6, 5-4, 5-7, 6-5, C-l, H-l, H-2, and H-7 relate
to the alternatives selected for evaluation in the OUFS and
the way the alternatives were selected. The comments and
associated responses are given below.
Comment ES-6, 5-4
The PRP suggested that remedial options recommended by EPA
in its guidance documents were never considered in the OUFS.
These options include more detailed institutional controls,
alternate water supplies for potential water users, inclu-
sion of remedial activities proposed by the PRP to NRC, and
other innovative technologies.
Response
EPA believes that the OUFS considered all relevant options
noted in the guidance documents. EPA notes that each of the
options mentioned by the PRP was considered in the OUFS.
Access and use restriction and alternate water supply tech-
nologies were considered when developing the Institutional
Control response action. Some alternate water supply op-
tions were not selected as representative because the
options would not meet the remedial objectives or were not
applicable to the site. The Institutional Control response
action that was retained was used to form a Limited Action
alternative and was also combined with other response ac-
tions to form the groundwater remedial alternatives.
Remedial activities proposed by the PRP are considered
throughout the OUFS. These are noted in the Key Assumptions
section of Chapter 1 and in other portions of the OUFS.
Innovative technologies were also considered in the screen-
ing portion of the OUFS. They were all some form of
physical/chemical treatment and offered no apparent benefit
over the option selected as representative.
As noted in the OUFS, process options not considered repre-
sentative of the technologies may be reinvestigated during
remedial design for the selected remedial alternative. All
process options for the selected remedial alternative,
including those options not selected as representative,
can be evaluated more closely during design.
Comment 5-7
The PRP suggested the OUFS should consider not only whether
use restrictions or other institutional controls are
effective in meeting remedial action goals, but whether the
controls protect human health and the environment and are
more cost-effective than other response actions.
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Response
The OUFS considered a number of factors during the screening
and evaluation process. A number of issues in addition to
ability to meet remedial action goals were considered when
screening use restrictions or other institutional controls.
For example, it was noted in Figure 5-4 that institutional
controls may be protective of human health. EPA believes it
is important to note that a limited action alternative,
consisting of institutional controls and use restrictions
was subsequently formed and developed for detailed analysis.
During detailed analysis, many issues were considered for
the limited action alternative, including .those described by
the commenter.
Comment 6-5
The PRP suggested that the description of the PRP
alternative in Chapter 6 is incorrect and should be
clarified.
Response
EPA believes that the description in the OUFS was correct at
the time the OUFS was released, but agrees that the proposed
system has been modified by the PRP since then.
Comment C-l
The PRP stated that drilling a new well or deepening an
existing one would be a more cost effective solution than
those proposed in the OUFS.
Response
The process option screening portion of the OUFS noted that
alternative water supply process options would either not
meet the remedial objectives or would not be applicable at
the site. An alternative water supply by itself would not
meet the remedial objectives of containing contaminant
migration or restoring groundwater quality.
Comment H-l
The PRP stated that expansion of the existing spray
evaporation system deserves more than a qualitative
evaluation in an appendix of the OUFS.
Response
EPA notes that the evaluation provided was not purely
qualitative. The OUFS evaluation of the expansion of the
existing spray system contained in Appendix H includes
qualitative and quantitative assessments of such an option.
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A cost analysis of the option, including capital, operation,
and present worth costs is provided in Appendix H.
Comment H-2
The PRP noted that the spray evaporation system described as
proposed in the OUFS had been started up. In addition, the
PRP described a PRP reclamation plan that included both
source control and offsite groundwater remediation. The
PRP suggested that this plan had not been acknowledged in
the OUFS.
Response
A component of the proposed system described in the OUFS has
been started up. EPA notes that performance data on the
system was not available at the time of the preparation of
the OUFS. The requirement for preparation of a reclamation
plan was noted in the OUFS as well as assumptions about PRP
plans for source control. PRP proposals for offsite remedi-
ation were not noted since it is EPA's responsibility, as
part of the MOU, to address offsite groundwater contami-
nation. EPA, however, was keenly aware of the proposed
active seepage collection in the Upper Gallup aquifers in
Amendment 1 to the PRP's license and coordinated closely
with the KRC on its approval.
Comment H-7
The PRP suggested that all treatment options described in
the OUFS require the same manner of disposal of dried inor-
ganic material. The commenter believes the OUFS unfairly
singles out leaching of contaminants from a spray/evapora-
tion treatment option.
Response
EPA agrees that there would be some potential for leaching
for both methods of treatment, but disagrees that the column
evaporation and spray/evaporation system would have the same
method of disposal. Smaller quantities of material would
likely be transported to the tailings pile from a column
evaporation system at any given time as compared to a spray
evaporation pond, unless the spray/evaporation system is
operated under optimum conditions to minimize and control
migration of residual solids in the tailings disposal area.
The potential for migration of inorganic material was
discussed in the effectiveness evaluation for remedial
alternatives.
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RESPONSE CATEGORY 9
COMPLIANCE WITH APPROPRIATE EPA GUIDANCE
The following comments are addressed in this category: 3-3,
5-6, 5-8, 8-1 through 8-4, and 8-9. These comments are
directed primarily to the compliance of the OUFS with
appropriate EPA Guidance.
Comment 3-3
The PRP questioned the use of Federal Safe Drinking Water
Act (SDWA) Maximum Contaminant Levels (MCLs), State
standards, and 10 CFR Part 40, Appendix A, as ARARs.
Response
As stated on Page 3-4 of the OUFS, MCLs are considered
relevant and appropriate in cases where groundwater may be
used in the future as a drinking water source. The state of
New Mexico standards apply to all groundwaters having a
total dissolved solids concentration of 10,000 mg/L or less.
As stated in the MOU between NRC and EPA, 10 CFR Part 40
Appendix A will be the applicable requirements within the
disposal site. However, the MOU also states that EPA will
develop its own site action requirements for groundwater
contamination outside the disposal site. These requirements
include MCLs and state standards referenced above.
Comment 5-6
The PRP questioned the cost criteria used in the development
and evaluation of alternatives and whether the evaluation
conformed to EPA guidance.
Response
The development and evaluation of remedial alternatives in
the OUFS was performed in accordance with EPA guidance. The
guidance on feasibility studies referenced by the PRP is a
pre-SARA, 1985 document. For the UNC OUFS, OSWER Directive
9335.3-01 "Guidance for Conducting Remedial Investigations
and Feasibility Studies Under CERCLA" (Draft March 1988) was
used. This guidance reflects the requirements of SARA. The
cost evaluation referred to by the PRP is not the
intermediate stage of evaluation; the intermediate level of
cost evaluation is performed in Chapter 7 of the OUFS.
Comment 5-8
The PRF questioned whether the column evaporation treatment
method met the requirements of implementability,
effectiveness, and cost. In addition, the PRP suggested
that spray evaporation of the groundwater would be a more
appropriate treatment technology.
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Response
The column evaporation treatment method was evaluated
against iroplementability, effectiveness/ and cost criteria
as defined in EPA's Guidance for Conducting Remedial
Investigations and Feasibility Studies Under CERCLA. As
stated in the OUFS, this process is relatively well
developed and implementable and produces a low volume of
treatment residue. A primary advantage of this process is
that it can be operated on a continuous basis. EPA
evaluated the spray evaporation system as part of Appendix H
of the OUFS. Like the column evaporation process, this
system has several unique advantages and disadvantages. As
indicated in the ROD, EPA has chosen the spray evaporation
system to treat contaminated groundwater.
Comment 8-1
The PRP questioned whether a Reliability Analyses was
included in the analysis of alternatives as required by EPA
guidance.
Response
The guidance that the PRP references is pre-SARA, 1985
guidance'. The UNC OUFS was developed in accordance with EPA
Guidance for Conducting Remedial Investigations and
Feasibility Studies Under CERCLA (Draft, March 1988). This
document reflects the mandates of SARA and the various OSWER
directives that have been issued since the publication of
the 1985 guidance. Reliability criteria are an integral
component of the implementability and effectiveness
evaluation presented in Tables 8-2 and 8-3 of the OUFS.
Comment 8-2
The PRP questioned whether the classification of the
groundwater at the site was considered in the OUFS. The
PRP suggests that the groundwater should be considered
Class 3.
Response
EPA did consider the classification of the groundwater in
developing and evaluating remedial alternatives. EPA's
OSWER Directive 92831-2 "Guidance on Remedial Actions for
Contaminated Groundwater at Superfund Sites" (Draft,
April 1988) incorporates the classifications in EPA's
Groundwater Protection Strategy. Class IIB groundwater is
groundwater that is potentially available for drinking
water. Class III groundwater is groundwater with higher
than 10,000 mg/L TDS or contaminated beyond levels that
allow remediation using methods reasonably employed in
public water treatment systems. EPA considers the
groundwater at the UNC site to be Class IIB.
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Comment 8-3
The PRP stated that a cash flow over the life of the
remedial action was not included as per EPA's 1985 Guidance.
Response
EPA developed and evaluated the remedial action alternatives
in accordance with EPA's Guidance for Conducting Remedial
Investigations and Feasibility Studies Under CERCLA (Draft/
March 1988) . As specified in this guidance, costs for
remedial alternatives were based on capital as well as
annual operation and maintenance costs. The present worth
analysis also presents short-term (0-10 years) and long-term
(11-60 years) present worth costs.
Comment 8-4
The PRP stated that the cost sensitivity analysis was not
performed in accordance with EPA's 1985 guidance.
Response
EPA conducted a sensitivity analysis for the detailed cost
comparison in accordance with EPA's Guidance for Conducting
Remedial Investigations and Feasibility Studies Under CERCLA
(Draft, March 1988). The cost sensitivity was performed for
the factors that could significantly change the overall
costs with only a small change in their values.
Comment 8-9
The PRP stated that the effectiveness evaluation for each
alternative does not address the potential replacement of
component parts, as required by 1985 EPA guidance.
Response
Reliability of controls was included as an assessment factor
in the effectiveness evaluation of each alternative, as
specified in EPA's Guidance for Conducting Remedial
Investigations and Feasibility Studies Under CERCLA (Draft,
March 1988). Specifically, reliability of controls
addressed the availability of replacement equipment during
the life of the remedial action.
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RESPONSE CATEGORY 10
GROUNDWATER TREATMENT TECHNOLOGIES
Comments 5-9, 6-1, and 8-13 relate to the technologies used
for groundwater treatment.
Comment 5-9
The PRP expressed concern that the technical discussion of
the operation of the pond evaporation system is not correct.
Specifically, the PRP is concerned that area requirements
for ponds may be overestimated because of modeling results,
that the same mechanism for wind blowing of material could
occur for other treatment/disposal alternatives, and that
the construction requirements which may be necessary would
not be needed since the ponds could be constructed in the
tailings area.
Response
EPA believes that the discussion in the OUFS is correct.
Issues regarding groundwater modeling are discussed
elsewhere in the responsiveness summary as is a discussion
of the potential for wind-blown migration of inorganic
material. The statement regarding the pond construction is
correct since more rigid requirements may be required if all
the necessary ponds cannot be constructed in the tailings
disposal area. Additional issues were also included in the
evaluation of process options that also factored into the
selection of the representative process option. These
issues were not acknowledged by the PRP.
Two additional points should be noted. First, the purpose
of the OUFS process option screening is to select a process
option that is representative of the technology. Process
options not considered representative would be reconsidered
during design of the selected remedial alternative. Because
spray evaporation was not the selected process option does
not mean it would not be reconsidered during remedial design
for physical/chemical treatment. Secondly, despite the
results of screening, a detailed analysis of the
spray/evaporation process option for physical/chemical
treatment is included in the OUFS. This analysis is
included since the PRP is presently operating such a system.
Comment 6-1
The PRP suggested that the OUFS does not include a logical
assessment of all implementable and feasible alternatives in
the OUFS. Specifically, the PRP believes that evaporation
ponds are not considered seriously in the OUFS.
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Response
EPA believes the OUFS includes a logical process for
development of final remedial alternatives, as is required
for the OUFS. Representative process options were selected
during the selection process; not all process options for a
technology can be considered in detail for the OUFS.
Despite this/ the OUFS does include a detailed analysis of
the use of evaporation ponds for physical/chemical treatment
in Appendix H. Moreover, EPA has chosen the spray
evaporation system in the ROD to treat contaminated
groundwater.
Comment 8-13
The PRP asked about the availability of the Technical
Memorandum on the spray evaporation system.
Response
Appendix H of the OUFS is the Technical Memorandum.
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RESPONSE CATEGORY 11
RELATIONSHIP BETWEEN UNC AND EPA ACTIONS
Only one comment, 1-7, fell into this category which
concerns the use of Section 2 by EPA for remediation
equipment and structures.
Comment
The PRP indicates that no agreement has been reached with
EPA regarding the placement of equipment on Section 2.
Response
For the OUFS, EPA has assumed that an agreement can be
reached whereby portions of Section 2 can be used to imple-
ment remedial actions outside the tailings disposal area, if
necessary. This assumption is a reasonable one since ample
legal enforcement authority is available in CERCLA to permit
EPA to gain access to the site in the event no agreement is
reached.
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RESPONSE CATEGORY 12
COSTS
Comments 7-1 and 7-2 relate to the cost of the remedial
alternatives. The comments are of a similar nature and are
grouped together as a single response.
Comments 7-1 and 7-2
The PRP suggested that the remedial alternatives and cost
analysis summarized in Chapter 7 is faulty because model
results are faulty.
Response
The EPA has responded to issues regarding the groundwater
model elsewhere in the responsiveness summary. The EPA
accepts that there is some uncertainty in any groundwater
model and believes the cost analysis in the OUFS provides a
satisfactory basis for comparison of the remedial
alternatives.
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RESPONSE CATEGORY 13
NON-ACTION
Comments 1-5, 6-4, 8-5, and H-4 required no action or no
response. These comments were PRP statements of agreement
with EPA's position or conclusion; therefore, a response is
not necessary.
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REFERENCES
Billings and Associates. Gechemical Background
Investigation. Prepared for United Nuclear Corporation.
1986. 105 pgs.
Canonie Environmental Services Corporation. Reclamation
Engineering Services - Geohydrologic Report. Prepared for
United Nuclear Corporation. 1987a.
Canonie Environmental Services Corporation. Reclamation
Plan, License No. SUA-1475. Prepared for United Nuclear
Corporation. 1987b.
Canonie Environmental Services Corporation. Evolution of
Groundwater Chemistry. Prepared for United Nuclear
Corporation. 1988a.
Canonie Environmental Services Corporation. Amendment 1,
Reclamation Plan License No. SUA-1475. Prepared for United
Nuclear Corporation. 1988b.
Carter Mining Company. Post-Mining Groundwater Quality at
the Caballo Mine, Permit 433 T.I., February 26, 1985.
Jacobs Engineering Group. Comments on the Canonie Report,
Evolution of Groundwater Chemistry. August 12, 1988.
Kerr-McGee Corporation. Letter to William Rowe, USEPA,
concerning the Quivera Mining Company's activities in
Section 36. Dated July 26, 1988.
Navajo Nation. Letter to USEPA transmitting monitoring well
data for the Quivira Churchrock Mine. June 6, 1988
Sargent, Hauskins, and Beckwith. Geotechnical Investigation
Report, Tailings Dam and Pond Church Rock Uranium Mill.
United Nuclear Corporation. 1976.
Shuey and Robinson. Characterization of Groundwater Quality
Near a Uranium Mill Tailings Facility and Comparison to
Background Levels and New Mexico Standards, presented at
Conference on Water Quality and Water Pollution in New
Mexico, April 11 and 12, 1984.
United Nuclear Corporation. Comments to United Nuclear
Corporation Church Rock Site Operable Unit Feasibility
Study, Gallup, New Mexico, August 1988. September 16, 1988.
1988.
U.S. Environmental Protection Agency. Guidance for
Conducting Remedial Investigations and Feasibility Studies
Under CERCLA. Draft, March 1988.
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U.S. Environmental Protection Agency Field Investigation
Team. Results of Well Sampling in the Vicinity of UNC,
Churchrock Site, McKinley County, New Mexico. Unpublished
Report prepared for the U.S. EPA, December 1987.
U.S. Environmental Protection Agency. Superfund Public
Health Evaluation Manual. October, 1986.
U.S. Geological Survey, WATSTORE data base for the alluvium
and Gallup Sandstone in the New Mexico portion of the San
.Juan Basin, 1988.
U.S. Geological Survey. Hard Ground Flats Quadrangle, New
Mexico - McKinley Co., 7.5 Minute Series (Topographic).
1963.
U.S. Geological Survey. Oak Spring Quadrangle, New Mexico
McKinley Co., 7.5 Minute Services (Topographic). 1963.
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I1
Appendix I
MEMORANDUM OF UNDERSTANDING
BETWEEN REGION VI OF THE
U.S. ENVIRONMENTAL PROTECTION AGENCY
AND
REGION IV OF THE
U.S. NUCLEAR REGULATORY COMMISSION
FOR REMEDIAL ACTION AT THE
UNC-CHURCHROCK URANIUM MILL
IN McKINLEY COUNTY, NEW MEXICO
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Memorandum of Understanding
Between Region VI of
The U.S. Environmental Protection Agency and Region IV of
The U.S. Nuclear Regulatory Commission
for Remedial Action at the UNC-Churchrock Uranium Hill
In McKinley County, New Mexico
I. PURPOSE
This document establishes the roles, responsibilities, and relationship
between Region VI of the U.S. Environmental Protection Agency ("EPA") and
Region IV of the U.S. Nuclear Regulatory Commission ("NRC"), hereinafter col-
*
lectlvely referred to as the "Parties," regarding remedial action at the UNC-
Churchrock uranium mill in McKinley County, New Mexico. The Parties have over-
lapping authority in connection with this site, and this Memorandum of Under-
standing ("MOU") will help assure that remedial actions occur in a timely and
effective manner.
II. BASIS FOR AGREEMENT
NRC will assume the role of lead regulatory agency for the byproduct
material disposal area reclamation and closure activities and EPA will monitor
all such activities and provide review and comments directly to NRC. The objec-
tive of EPA's review and comment will be to assure that activities to be conducted
under NRC's regulatory authority allow attainment of applicable or relevant and
appropriate requirements under the Comprehensive Environmental Response Compensation
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2
and Liability Act of 1980, as amended ("CERCLA"), 42 U.S.C. §9601 et seq outside
of the byproduct material disposal site. NRC will require the Licensee to
implement an approved disposal site reclamation plan which meets the requirements
of 10 CFR Part 40, Appendix A, as amended at 52 Fed. Reg 433553 through 43568,
"Uranium Mill Tailings Regulations; Groundwater Protection and other Issues,"
which conforms with the EPA 40 CFR 192, Subpart D. EPA development and Implemen-
tation of Its own site action requirements for groundwater contamination outside
of the disposal area will be conducted in accordance with CERCLA and the National
Oil and Hazardous Substances Contingency Plan ("NCP") 40 CFR Section 300 including
any revisions thereto. The EPA and NRC agree that the groundwater protection
requirements of 10 CFR Part 40, Appendix A are the Federal environmental and
public health requirements applicable or relevant and appropriate to the disposal
site. The EPA and NRC believe that conformance with 10 CFR Part 40, Appendix A
(with the possible exception of nitrate), will generally assure conformance
with CERCLA requirements. However, each Party will be responsible for assuring
compliance with it's specific regulatory requirements as discussed in this
section. The parties believe that the U.S. Department of Energy or another
responsible State or Federal authority will assume responsibility for long-term
care of the byproduct material disposal site, following remediation of the
site.
III. BACKGROUND
The State of New Mexico was responsible as an "Agreement State" for licensing
and regulating uranium mills within the State until June 1, 1986, at which time
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3
the NRC resumed this authority at the request of the Governor of New Mexico.
Prior to this change, EPA had placed the UNC-Churchrock site on the National
Priority List ("NPL") of sites for response action under CERCLA. EPA's policy
is to list only those uranium mills meeting criteria for placement on the NPL
which are located in Agreement States, that is States which have entered Into
agreements with the NRC pursuant to Section 274 of the Atomic Energy Act of
1954, as amended, to regulate certain nuclear activities in a manner compatible
with the NRC's program. Mills in states where NRC has direct licensing authority
have not been placed on the list. Although New Mexico is no longer an Agreement
State insofar as uranium recovery operations are concerned and the NRC has
reassumed primary jurisdiction, the site was properly placed on the NPL and the
physical conditions resulting in that placement are still present. Therefore,
EPA has no intention of recommending delisting the site from the NPL until all
authorized EPA and NRC controlled remedial activities, addressing releases or
threats thereof, at this facility are completed.
IV. AGREEMENT
In order to achieve satisfactory cleanup of the UNC site, the NRC and the
EPA agree to do the following:
1. The Parties shall cooperate with each other in the oversight
of reclamation and remedial activity at the UNC site.
2. Upon submittal by UNC of a proposed site reclamation plan
("the plan"), NRC and EPA will begin concurrent reviews of the
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4
proposed plan. EPA will review the plan and will provide comments
to the NRC. NRC will review and, If necessary, require revisions to
the plan to assure conformance to 10 CFR Part 40, Appendix A, as
amended, prior to approving the plan via license amendments. If EPA
cannot conclude that the plan approved by NRC meets CERCLA requirements,
then EPA may Initiate separate actions as may be necessary to ensure
conformance with CERCLA requirements outside of the disposal area
site. NRC will not approve any specific components of the groundwater
protection and recovery aspects of UNC's proposed reclamation plan
until EPA has determined, 1n a Record of Decision or by review of
the UNC plan and statement to NRC, that 1t Is consistent with CERCLA
requirements and/or remedial actions required under CERCLA. NRC
does not Intend to approve any specific aspects of UNC's groundwater
protection and recovery actions contained In UNC's proposed reclamation
plan until such time as any Inconsistencies have been resolved. If
remedial action is determined in a Record of Decision to be necessary,
EPA intends to either enter Into a Consent Decree with UNC under
which UNC will conduct, with EPA oversight, remedial actions equal
to or exceeding those outlined in an EPA Record of Decision, to take
appropriate enforcement action, or perform remedial action itself
pursuant to Section 104 of CERCLA, reserving all rights to seek cost
recovery under Section 107 of CERCLA. Such actions may be conducted
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5
as part of the NRC's approval of the UNC plan or separately;
but in any event EPA Intends to coordinate its actions first
with the NRC.
3. If either Party determines that remedial actions are deficient or
unsatisfactory, then that Party shall provide notice to the other
Party of the deficiency. The NRC shall assume the lead role for
notification to UNC, except for such notification as EPA might
statutorily be required to provide in certain events. The notifi-
cation shall specify a time period in which regulatory compliance is
expected to be achieved. Should compliance not be achieved in this
time period, EPA will assume the lead for taking or seeking any
enforcement action necessary for off-site groundwater and NRC will
assume the lead for any other enforcement actions necessary within
its area of regulatory responsibility. Both Parties reserve all
rights under this MOU to take whatever actions are determined to be
necessary, including the conduct of remedial actions on and off-site
in order to fulfill their regulatory requirements. In any event no
action will be taken by either party without prior consultation with
the other Party.
4. Both Parties shall appoint a facility coordinator who shall be respon-
sible for oversight of the implementation of the MOU and the activities
required herein. The facility coordinators shall be appointed by
each Party within seven (7) days of the effective date of this MOU.
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6
The Parties each have the right to appoint a new facility coordinator
at any time. Such change shall be accomplished by notifying the
Party, in writing, at least five (5) days prior to the appointment
of the name, telephone number, and mailing address of said facility
coordinator.
5. The Parties will meet periodically at the request of either Party
and at least semiannually Insofar as it is necessary to accomplish
the objectives of the MOU. The facility coordinators should communi-
cate with each other on a routine basis by telephone.
6. The Parties will provide technical advice and any necessary regulatory
consultation to one another upon request.
7. The Parties will generally provide each other with copies of all
official correspondence and documents related to remedial actions at
the site. The Parties will also normally provide copies of other
information upon request. In the event that one of the parties does
not wish to furnish certain specific information, documents, or
correspondence to the other, then said material shall be identified
to the other party along with the reasons for withholding it.
8. Whenever notice or information is required to be forwarded by one
party to another under the terms of this MOU, it shall be given by
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I
.1 7
and directed to the individuals at the addresses specified below:
EPA: Allyn M. Davis, Director
Hazardous Waste Management Division
Region VI, U.S. EPA
1445 Ross Ave.
Dallas, Texas 75202
NRC: Dale Smith, Director
Uranium Recovery Field Office
U.S. Nuclear Regulatory Commission
P.O. Box 25325
Denver, Colorado 80225
9. Routine communications may be exchanged verbally, in person, or by
telephone between the Parties to facilitate the orderly conduct of
work contemplated by this MOU.
10. Enforcement documentation provided under this MOU will be kept as
exempt material by EPA and NRC, to the extent legally possible,
according to the policies and procedures under 40 CFR Part 2
and 10 CFR Part 2.790, respectively.
V. AGENCY RESPONSIBILITIES
A. NRC responsibilities
1. The NRC will require the owners/operators of the UNC Churchrock mill
(UNC) to implement an approved on-site reclamation plan that meets
all relevant NRC requirements, including 10 CFR Part 40, Appendix A,
as amended. If any such plan is not complied with by UNC, NRC will
take whatever actions it deems appropriate to ensure compliance.
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8
2. The NRC will direct UNC to provide both parties with copies of major
work product submlttals as they become available. Such work products
will Include, but not be limited to, an adequate overall reclamation
plan, and any other plans and specifications for assessment, remediation,
and monitoring, including all analytical data.
3. The NRC agrees to provide progress reports on UNC remediation on a
quarterly basis.
4. The NRC will assist in the development of Information to support
EPA's deletion of the site from the NPL upon completion of the .
remedial action.
5. The NRC shall notify EPA of all pending visits to the Churchrock
property which relate to the site closure plan and shall afford EPA
and its consultants opportunity to accompany NRC personnel on such
visits.
B. EPA RESPONSIBILITIES
1. EPA will provide formalized review, consultation and comment throughout
the entire project.
2. EPA will review and provide comments on the site reclamation plan,
and other associated deliverables, within timefnames as agreed to
between NRC and EPA. In the event that EPA determines that the
Implementation of the site reclamation plan has not resulted In, or
may not result in, cleanup conditions that meet applicable or
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9
relevant and appropriate requirements under CERCLA, then EPA may
take whatever action it deems appropriate.
3. EPA intends to pursue and complete a Remedial Investigation and
Feasibility Study, public comment and agency response process, and
Record of Decision (ROD) directed at off-site groundwater contamination,
with the intention of completing this process by to October 1, 1988.
EPA intends to implement, or require UNC or other potentially responsible
parties to implement, any EPA selected remedial actions set forth in
a ROD. Any remedial actions conducted by UNC or other potentially
responsible parties to implement an EPA selected remedy will be done
under EPA oversight and in accordance with the terms of any Consent
Decree entered into with EPA. EPA intends that any such Consent
Decree would cover actions outside the byproduct material disposal
site needed to implement the ROD remedy.
VI. DISPUTE RESOLUTION
In the event of dispute between EPA and the NRC concerning site activities,
the persons designated by each Agency as primary or, in their absence, alternate
contact points will attempt to promptly resolve such disputes. If disputes
cannot.be resolved at this level, the problem will be referred to the supervisors
of these persons for further consultation. The supervisory referral and resolution
process will continue, if necessary to resolve the dispute, to the level of the
Regional Administrators of the NRC and EPA.
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10
Both Parties shall continue to maintain their respective rights or responslbllltes
under the MOU during the dispute resolution process.
VII. EXECUTION AND MODIFICATION
This agreement shall take effect upon execution by EPA and the NRC. It
shall remain In effect for the duration of the program addressed herein unless
terminated by mutual agreement by the two Agencies; or, the HOU may be terminated
unilaterally 1f any of the conditions set forth below are present.
1. The planning or conduct of groundwater cleanup actions fall to meet
standards set forth 1n the Basis for Agreement (Section II) of this
HOU.
2. The site 1s deleted from the NPL.
3. The site is turned over to the Department of Energy or other responsible
State or Federal authority for long term care.
4. Regulatory, Statutory, or other events occur which make this MOU
unnecessary, Illegal, or otherwise Inappropriate.
VIII. MODIFICATION
The Parties may modify this MOU from time to time in order to simplify
and/or define the procedures contained herein. Each Party shall keep the other
informed of any relevant proposed modifications to Its basic statutory or regulatory
authority, forms, procedures, or priorities. This MOU shall be revised, as
necessary, by the adoption of such modifications. The MOU should be reviewed
on an annual basis by both the Director-URFO, Region IV, NRC, and the Director-
Hazardous Waste Management Division, Region VI, EPA or their designated represen-
tatives.
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X
11
U. RESERVATION OF RIGHTS
p The Parties reserve any and all rights or authority that they may have,
including but not limited to legal, equitable, or administrative rights. This
f specifically includes EPA's and NRC's authority to conduct, direct, oversee,
i
and/or require environmental response in connection with the site, as well as
the authority to enter the site and require the production of information,
within each of their own areas of responsibility.
Executed and agreed to:
Robert D. Martin
Regional Administrator
U.S. Nuclear Regulatory Commission,
Region IV, Arlington, Texas
Robert E. Layton Jr/, P.E.^
Regional Administrator
U.S. Environmental Protection Agency
Region VI, Dallas, Texas
PROTECTION
AGENCY
DALLAS, TEXAJ
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