DRC-2024-004669

6D r1
~~NERGYFUELS
February 26, 2024
Sent VIA E-MAIL AND EXPRESS DELIVERY
Mr. Doug Hansen
Director
Division of Waste Management and Radiation Control
Utah Department of Environmental Quality
195 North 1950 West
Salt Lake City, UT 84114-4880
Energy Fuels Resources (USA) Inc.
225 Union Blvd. Suite 600
Lakewood, CO, US, 80228
303 974 2140
www.energyfuels .com
Re: Transmittal of White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual Performance
Monitoring Report
Dear Mr. Hansen:
In accordance with the Stipulation and Consent Agreement ("SCA" dated February 23, 2017) between the
Division of Waste Management and Radiation Control ("DWMRC") and Energy Fuels Resource (USA) Inc.
("EFRI"), EFRI constructed a cover performance monitoring test section ("Primary Test Section") on Cell 2 in
2016, completed Phase 1 cover placement on Cell 2 in 2017, constructed a supplement vegetation monitoring
test section ("Supplemental Test Section") in 2017, and initiated performance monitoring. This letter transmits
the 2023 annual performance monitoring report for the reclamation cover and includes monitoring results for
both test sections.
For your convenience, two hard copies of the report and two CDs, each containing a word searchable electronic
copy of the files, will be mailed to DWMRC.
If you should have any questions regarding this transmittal please contact me at 303-389-4134.
Yours very truly,
ENERGY FUELS RESOURCES (USA) INC.
Kathy W einel
Director, Regulatory Compliance
CC: Jordan App
David Frydenlund
Garrin Palmer
Logan Shumway
Scott Bakken
DRC-2024-004669

WHITE MESA URANIUM MILL CELL 2
RECLAMATION COVER 2023 ANNUAL
PERFORMANCE MONITORING REPORT

February 21, 2024
Prepared for:
Energy Fuels Resources (USA) Inc.
Prepared by:
Stantec Consulting Services Inc.
Project Number:
182924510 (formerly 233001001)
() Stantec
White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual Performance Monitoring Report
Project Number: 182924510 (formerly 233001001)
Rev Description Author Date Quality
Check
Date Independent
Review
Date
0 Draft for client
review
B. Van

01/31/2024 S. Regis
M. Davis
02/07/2024
02/09/2024
C. Strachan 02/21/2024
1 Final for client M. Davis 02/21/2024

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White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual Performance Monitoring Report
Project Number: 182924510 (formerly 233001001)
The conclusions in the Report titled White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual
Performance Monitoring Report are Stantec’s professional opinion, as of the time of the Report, and
concerning the scope described in the Report. The opinions in the document are based on conditions and
information existing at the time the scope of work was conducted and do not take into account any
subsequent changes. The Report relates solely to the specific project for which Stantec was retained and
the stated purpose for which the Report was prepared. The Report is not to be used or relied on for any
variation or extension of the project, or for any other project or purpose, and any unauthorized use or
reliance is at the recipient’s own risk.
Stantec has assumed all information received from Energy Fuels Resources (USA) Inc. (the “Client”) and
third parties in the preparation of the Report to be correct. While Stantec has exercised a customary level
of judgment or due diligence in the use of such information, Stantec assumes no responsibility for the
consequences of any error or omission contained therein.
This Report is intended solely for use by the Client in accordance with Stantec’s contract with the Client.
While the Report may be provided by the Client to applicable authorities having jurisdiction and to other
third parties in connection with the project, Stantec disclaims any legal duty based upon warranty,
reliance or any other theory to any third party, and will not be liable to such third party for any damages or
losses of any kind that may result.
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White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual Performance Monitoring Report
Project Number: 182924510 (formerly 233001001) i
Table of Contents

1 INTRODUCTION .......................................................................................................... 1
1.1 Background .................................................................................................................. 1
1.2 Monitoring Requirements ............................................................................................. 1
1.3 Report Organization ..................................................................................................... 2
2 COVER AND TEST SECTION DESIGNS .................................................................... 3
3 PRIMARY TEST SECTION HYDROLOGIC MONITORING ......................................... 5
4 PRIMARY AND SUPPLEMENTAL TEST SECTIONS VEGETATION INSPECTION ... 6
5 CELL 2 SETTLEMENT AND WATER LEVEL MONITORING ...................................... 8
5.1 Settlement Monuments ................................................................................................. 8
5.2 Piezometers .................................................................................................................. 9
6 CONCLUSIONS ......................................................................................................... 11
7 REFERENCES ........................................................................................................... 12
LIST OF TABLES
Table 1. Primary Test Section Water Balance for 2016 to 2023................................................................... 5
Table 2. Cell 2 Top Surface Settlement Measured Between April 2016 and December 2023 ..................... 9
Table 3. Piezometer Water Level Elevations During and After Phase 1 Cover Placement ....................... 10

LIST OF FIGURES
Figure 1 Regional Location Map
Figure 2 Site Location Map
Figure 3 Cover Profile within Lysimeter
Figure 4 Settlement Monument and Piezometer Locations

LIST OF APPENDICES
Appendix A 2023 Field Hydrology of the Cell 2 Primary Test Section at the White Mesa Mill
Appendix B 2023 Revegetation Evaluation Cell 2 Primary and Supplemental Test Sections
Appendix C Cell 2 Settlement Monitoring Data
Appendix D Cell 2 Standpipe Piezometer Water Levels
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White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual Performance Monitoring Report
1 Introduction
Project Number: 182924510 (formerly 233001001) 1
1 Introduction
This report documents the 2023 monitoring and inspection results for the reclamation cover and Primary
and Supplemental Test Sections on the Cell 2 tailings management cell at the Energy Fuels Resources
(USA) Inc. (EFRI) White Mesa Uranium Mill site (Mill site). Reclamation cover performance monitoring for
Cell 2 was initiated in 2016. Calibration monitoring was conducted from 2018 through 2019. Official cover
performance monitoring and required reporting began January 1, 2020. Stantec prepared this report at
the request of EFRI for submittal to the Utah Department of Environmental Quality, Division of Waste
Management and Radiation Control (DWMRC).
The Mill site is located in San Juan County in southeastern Utah, approximately 6 miles south of
Blanding, Utah. Figure 1 shows a regional location map and Figure 2 shows the site layout. EFRI site
facilities are within an approximately 686-acre restricted area and consist of a uranium processing mill
and lined tailings management/evaporation ponds.
1.1 Background
EFRI and the DWMRC executed a Stipulation and Consent Agreement (SCA) on February 23, 2017
(DWMRC, 2017) defining the commitments and timeframes for completing placement of reclamation
cover on Cell 2 and performance assessment of the cover system, in accordance with the Reclamation
Plan (EFRI, 2016). The Reclamation Plan was updated on February 8, 2018 to Revision 5.1B (EFRI,
2018), but the guidelines, monitoring, and reporting requirements for the test sections did not change.
Cell 2 Phase 1 cover placement commenced in April 2016, was completed in April 2017, and is
documented in Stantec (2017b). EFRI constructed a cover performance monitoring section on Cell 2
(Primary Test Section) in fall 2016 and a supplemental vegetation monitoring section (Supplemental Test
Section) in fall 2017 (Stantec, 2017a; 2018a). The Primary Test Section was constructed to assess the
overall performance of the entire reclamation cover system profile. The Supplemental Test Section was
constructed as a supplemental vegetation monitoring section to the Primary Test Section. The
Supplemental Test Section does not include evaluation of the entire cover profile but was constructed to
demonstrate that vegetation can be established and that erosional influences will not be detrimental to
long-term vegetation establishment.
In 2021, EFRI constructed a Supplemental Test Section No. 2 adjacent to the Supplemental Test Section
to provide additional data for the Cell 2 cover test section performance monitoring and to evaluate the
revegetation plan to promote vegetation success. The as-built report for this test section was provided in
Stantec (2022).
1.2 Monitoring Requirements
Per the SCA, the Primary Test Section is required to be monitored for percolation and both the Primary
Test Section and Supplemental Test Section are required to be monitored for vegetation performance.
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White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual Performance Monitoring Report
1 Introduction
Project Number: 182924510 (formerly 233001001) 2
Performance criteria are outlined in the SCA and summarized in this section. EFRI started calibration
monitoring of the test sections on January 1, 2018 and official performance monitoring on January 1,
2020. EFRI also monitored the test sections for informational purposes after constructing the test sections
and prior to starting calibration monitoring. Official monitoring ends on December 31, 2024 and the cover
performance success will be evaluated at that time. EFRI has provided quarterly data quality reports to
DWMRC since 2017 and monitoring results are summarized in annual performance monitoring reports
(Stantec, 2018b, 2019, 2020, 2021, and 2022). This report is the annual monitoring report for 2023.
Percolation monitoring procedures are outlined in the Reclamation Plan (EFRI, 2018). The percolation
rate from the base of the lysimeter in the Primary Test Section will be used as the percolation
performance parameter for the cover system. The cover design will be considered to have performed
adequately if the average annual percolation rate is 2.3 mm/yr or less over the official performance
monitoring time period.
Vegetation sampling and monitoring procedures for the test sections follow recommendations outlined in
the Reclamation Plan (EFRI, 2018). The vegetation component of the cover will be considered successful
if: (1) a minimum vegetation cover of 40 percent is achieved, and (2) acceptable vegetation diversity per
EFRI (2018) (perennial grasses, forbs and shrubs) is met for the Supplemental and Primary Test Sections
by the end of the five-year performance monitoring period. Although not required by the SCA, EFRI is
conducting vegetation sampling and monitoring of the Supplemental Test Section No. 2 (constructed in
the spring of 2021) to provide additional data for the Cell 2 cover test section performance monitoring.
EFRI is using the same vegetation sampling and monitoring procedures as the other test sections, and
the survey results are included in this report for information purposes.
As part of Cell 2 reclamation, EFRI is also conducting settlement monitoring of the Phase 1 cover surface
and monitoring water levels in the Cell 2 using procedures outlined in the Reclamation Plan (EFRI, 2018).
Monitoring results for settlement and water levels and interpretation of these results are included in this
report. Settlement and dewatering data will be evaluated after completing the cover performance
monitoring. The evaluation will determine if sufficient settlement has occurred to facilitate Phase 2 cover
placement and minimize maintenance of the final cover surface. Per the SCA, decreasing trends in
settlement followed by a maximum of 0.1 feet (30 mm) of cumulative settlement over 12 months (for at
least 90 percent of the settlement monuments), will be considered acceptable to proceed with placement
of the Phase 2 Cell 2 cover.
1.3 Report Organization
This report provides an overview of the cover and test section designs (Section 2.0), Primary Test Section
hydrologic monitoring (Section 3.0), Primary and Supplemental Test Sections vegetation survey results
(Section 4.0), Cell 2 settlement and water level monitoring (Section 5.0), and conclusions (Section 6.0).
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White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual Performance Monitoring Report
2 Cover and Test Section Designs
Project Number: 182924510 (formerly 233001001) 3
2 Cover and Test Section Designs
The Reclamation Plan (EFRI, 2018) provides detailed design information for the cover and test sections.
The cover and test section designs are summarized below.
The cover system is a monolithic water balance cover, designed to minimize percolation, meet the radon
emanation standard, and minimize short- and long-term maintenance. The design reclamation cover
thicknesses for the tailings management cells range from 9.5 to 10.5 feet. The minimum design cover
thickness of 9.5 feet was used for the lysimeter area of the Primary Test Section to evaluate the lower
bound reclamation cover thickness for the tailings management cells. The remaining area within the test
section was constructed to the full-depth Cell 2 cover profile (10.5 feet). The cover profile within the
lysimeter is shown on Figure 3. The reclamation cover contains the following layers, listed in order from
top to bottom:
Layer 4 – 0.5 feet thick Erosion Protection Layer (topsoil-gravel admixture)
Layer 3 – 3.5 feet thick Growth Medium Layer (loam to sandy clay)
Layer 2 – 3.0 to 4.0 feet thick Compacted Cover (highly compacted loam to sandy clay)
Layer 1 – 2.5 feet thick (minimum) Interim Fill Layer (loam to sandy clay)
The Primary Test Section is in the southeast corner of Cell 2, as shown in Figure 2. The test section was
constructed as a design-build project during reclamation cover construction using procedures adopted
from the test section installation instructions developed by the United States Environmental Protection
Agency (EPA) Alternative Cover Assessment Program (ACAP) (Benson et al., 1999, 2001). Test section
construction information is provided in Stantec (2017a). The test section is approximately 100 feet by 100
feet, with a 32-feet by 64-feet lysimeter centered within the test section. The longer side of the lysimeter is
oriented parallel to the cover slope. The lysimeter collects percolation from the base of the cover, surface
runoff, and interflow from the textural interface between the interim fill (Layer 1) and compacted cover
(Layer 2). Sensors monitor hydrologic state variables (temperature and water content) within the cover.
Percolation rate, lateral drainage, runoff, internal state conditions, and meteorological data are recorded
continuously using a data logger near the southern edge of the test section.
The Supplemental Test Section was constructed in a location representative of cover conditions on the
tailings management system cells (see Figure 2) and construction information is provided in Stantec
(2018a). The Supplemental Test Section is 100 feet by 100 feet in size to match the dimensions of the
Primary Test Section. The slope of the test section is greater than 1 percent (the maximum reclamation
cover slope). The cover design includes addition of gravel to the topsoil for slopes greater than 0.5
percent. However, gravel was not added to the topsoil for the test section to evaluate the short-term
impact of erosion on the vegetative cover without gravel addition. Successful Supplemental Test Section
performance will then translate to the cover both with and without the addition of gravel for erosion
protection. Mulch was placed to provide erosion protection for the seeds during germination and early
seedling growth.
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White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual Performance Monitoring Report
2 Cover and Test Section Designs
Project Number: 182924510 (formerly 233001001) 4
The Supplemental Test Section No. 2 (see Figure 2) was constructed similar to and adjacent to the
Supplemental Test Section as outlined in the as-built report provided in Stantec (2022). The revegetation
plan used for the test section was based on the plan provided in EFRI (2018) with modifications to
address the squirreltail dominance occurring on the Primary Test Section and the poor seeding
establishment on the Supplemental Test Section.
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White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual Performance Monitoring Report
3 Primary Test Section Hydrologic Monitoring
Project Number: 182924510 (formerly 233001001) 5
3 Primary Test Section Hydrologic Monitoring
Data collected from the Primary Test Section from September 9, 2016 to December 31, 2023 (last
automated data download of 2023) are described in the annual Primary Test Section Report in Appendix
A. Data in this report represent the first seven full calendar years (2017 through 2023) of monitoring.
Table 1 summarizes the water balance results.
Table 1. Primary Test Section Water Balance for 2016 to 2023
Calendar
Year
Water Balance Quantities (mm)
Precipitation Runoff Lateral
Flow ET Change
Storage Percolationc
2016a 60 0.0 0.0 35 17 0.0
2017b 223 0.0 0.0 325 39 0.6
2018 163 0.0 0.0 125 38 0.9
2019 308 0.3 0.0 325 3 1.0
2020 128 0.0 0.0 171 -63 0.9
2021 223 0.0 0.0 242 -20 0.6
2022 180 0.0 0.0 169 25 0.3
2023 242 0.0 0.0 260 -27 0.4
Notes: a. Partial year, monitoring began on September 9, 2016.
b. Damage from vault flooding precluded measuring flows 7 February 2017 – 25 March 2017 c. All water balance quantities rounded to nearest mm number except percolation, which is rounded to 0.1 mm.
The hydrology of the test section during 2023 was consistent with expectations for a water balance cover
in a semi-arid environment with lower-than-average annual precipitation. Precipitation in 2023 (242 mm)
was lower than the long-term average for the nearby Blanding, Utah station (355 mm, located at 37° 62'
N, 109° 47' W with elevation 1829 m) operated by the National Weather Service, but was modestly higher
than the average annual precipitation recorded during monitoring the test section (210 mm from 2017 to
2023). Winter and early spring of 2023 were considerably wetter than average. Summer and fall in 2023
were drier than winter and spring, and drier than average. Soil water storage gradually diminished
throughout the year, except for a short pulse of higher soil water storage that occurred in response to the
wet winter and early spring. The gradual decrease in storage continues a trend that began in 2019, as
water contents continue to gradually diminish at greater depths in the cover. At the end of the 2023, soil
water storage reached a minimum for the entire monitoring period. Nearly all precipitation that reached
the test section was returned to the atmosphere as evapotranspiration. A trace of runoff (0.09 mm) was
transmitted, and no lateral flow occurred. Annual percolation was 0.4 mm, the second lowest measured
for a full year during the monitoring period. Thermally driven flow has been the most significant
mechanism contributing to percolation to date.
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White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual Performance Monitoring Report
4 Primary and Supplemental Test Sections Vegetation Inspection
Project Number: 182924510 (formerly 233001001) 6
4 Primary and Supplemental Test Sections Vegetation
Inspection
Cedar Creek Associates, Inc. visited the Mill site on May 31, 2023 and September 6, 2023, to inspect the
status of plant development on the Primary and Supplemental Test Sections. Inspection results are
summarized below, and Appendix B presents a full report with photos.
Precipitation conditions in the months prior to the spring revegetation evaluations were favorable for plant
growth (140% of average), particularly due to extreme precipitation in March. Regionally, 2023 can be
considered a lower than average precipitation year. Vegetation observed during the spring evaluation
exhibited above average plant vigor and growth in response to the favorable precipitation conditions. The
spring months of March, April, and May are particularly important to plant growth and these months
received 78.49 mm (294% of average), 2.54 mm (11% of average), and 12.45 mm (69% of average) of
precipitation, respectively. Precipitation prior to the fall revegetation evaluation was below average (53%
of average). July, August, and September had 11.94 mm (41% of average), 14.48 mm (41% of average),
and 24.64 mm (76% of average) of precipitation, respectively. Vegetation observed during the fall
evaluation exhibited average plant vigor and growth in response to favorable spring precipitation
conditions and unfavorable fall precipitation conditions.
The revegetation performance criteria applicable to the Primary Test Section and Supplemental Test
Section are summarized in Appendix B. As described in the SCA, success is not evaluated until the end
of the official monitoring time period. Therefore, the performance evaluation presented Appendix B is for
discussion purposes. The spring evaluations were selected for the performance evaluation because the
test sections are dominated by cool season species, which should be evaluated in the spring.
In Year 4 (2023) of the performance period, both the Primary and Supplemental Test Sections are not
passing several of the success criteria. The results of the performance evaluation are summarized in
Appendix B.
For the Primary Test Section, vegetation performance criteria pertaining to diversity and woody plant
density are not being met. This is primarily due to placement of topsoil on the Primary Test Section with a
large source of squirreltail seed. This presence of squirreltail seed in the topsoil was unknown at the time
of construction and its dominance is impacting the vegetation diversity by preventing establishment of
other species. Below-average precipitation and available water through the end of 2020, into the spring of
2021, and spring of 2022 did not facilitate improved vegetation growth and vigor in the Primary Test
Section. Precipitation was well above average in Spring of 2023 contributing to increased plant cover
significantly higher than the criterion of 40%, but diversity and woody plant density vegetation
performance criteria are still not being met.
For the Supplemental Test Section, no seed species met the minimum cover criterion of 4%. Perennial
cover across the test section was low with annual and biennial cover averaging approximately a third. No
noxious weeds were observed. While the Supplemental Test Section does not currently meet the woody
plant success criteria, vegetation coverage has been generally increasing with each growing season.
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White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual Performance Monitoring Report
4 Primary and Supplemental Test Sections Vegetation Inspection
Project Number: 182924510 (formerly 233001001) 7
For the Supplemental Test Section No. 2, seed species did not meet the minimum cover criterion. Like
the Supplemental Test Section No. 1, noxious weeds were not observed and perennial cover across the
test section was low. Annual and biennial cover averaged a little over a quarter. The diversity of species
observed is encouraging for eventual performance in favorable conditions.
Further revegetation development is expected to occur throughout the performance period and future
monitoring efforts to track the trajectory of revegetation development will occur each spring, for the
remainder of the performance period. In addition, EFRI will monitor the Supplemental Test Section No. 2
to provide additional data for Cell 2 cover test section performance monitoring.
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White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual Performance Monitoring Report
5 Cell 2 Settlement and Water Level Monitoring
Project Number: 182924510 (formerly 233001001) 8
5 Cell 2 Settlement and Water Level Monitoring
Cell 2 includes settlement monuments and piezometers (Figure 4 shows locations). Settlement
monuments were installed between 1989 and 2010. Existing settlement monuments were extended
upward during Phase 1 cover construction. Standpipe piezometers were installed in June 2016 across
Cell 2 during Phase 1 cover construction to monitor water levels within the tailings. After official
performance monitoring is complete for the Primary and Secondary Test Sections, the settlement and
dewatering data will be evaluated to determine if sufficient settlement has occurred to facilitate Phase 2
cover placement.
The following sections discuss cover settlement monitoring and monitoring of water levels in the tailings
during and after Phase 1 cover construction.
5.1 Settlement Monuments
Appendix C contains graphs showing settlement monument measurements from initial installation through
December 2023. Table 2 lists the settlement measured since the start of Phase 1 cover construction
(April 2016) through December 2023. Settlement totals during this period range from 0 to 0.6 feet.
Settlement of the cover surface due to the Phase 1 cover loading is occurring as expected, with a
relatively quick response to the additional loading, as occurred when the initial interim fill was placed on
the tailings. The total settlement from Phase 1 cover placement is believed to be nearly complete since
settlement is showing a decreasing trend and annual settlement has been less than 0.1 ft in recent years
(2019 through 2022). In 2023, annual settlement was slightly higher than recent years, with
measurements ranging from 0 to 0.13 feet for the monuments. The higher settlement values are believed
to be attributed to the control point elevations being remeasured in August 2023 for the first time in
several years resulting in a shift in the readings from July to August 2023 of up to 0.1 feet on th e west
side of the cell and 0.04 feet on the east side of the cell. Excluding this shift, the annual settlement for
2023 would range from 0.08 feet of settlement to 0.01 feet of upward movement, which is similar to
annual results since 2019.
Prior to initiating Phase 2 cover placement, additional fill will be added to settled areas, and the top
surface of the compacted cover layer will be recompacted.

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White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual Performance Monitoring Report
5 Cell 2 Settlement and Water Level Monitoring
Project Number: 182924510 (formerly 233001001) 9
Table 2. Cell 2 Top Surface Settlement Measured Between April 2016 and December 2023
Settlement
Monument
April 2016 to
December 2023
Settlement (ft)
2023
Settlement
(ft)
Settlement
Monument
April 2016 to
December 2023
Settlement (ft)
2023
Settlement
(ft)
2W1 0.23 0.07 2W6-N 0.20 0.01
2W2 0.37 0.11 2W6-C 0.36 0.05
2W3 0.37 0.12 2W6-S 0.45 0.02
2W3-S 0.39 0.12 2W7-N 0.04 0.04
2W4-N 0.29 0.10 2W7-C 0.20 0.04
2W4-C 0.35 0.12 2W7-S 0.40 0.01
2W4-S 0.57 0.13 2E1-N 0.29 0.04
2W5-N 0.26 0.11 2E1 0.40 0.04
2W5-C 0.34 0.12 2E1-1S 0.45 0.04
2W5-S 0.46 0.12 2E1-2S 0.59 0.02
5.2 Piezometers
Standpipe piezometers were installed across Cell 2 prior to the first phase of cover placement to monitor
changes in the zone of saturation in the tailings due to dewatering from the sump prior to and after final
cover placement. These piezometers were completed within the tailings to provide information on the rate
and extent of tailings dewatering. The piezometers were primarily adjacent to the settlement monuments
to minimize damage to the piezometers during cover construction, while providing sufficient locations to
evaluate tailings saturation.
Appendix D presents figures showing piezometer water levels since installation (June 2016) through
December 4, 2023. Figure D.1 shows the water levels for all the piezometers. For comparison, Figures
D.2, D.3, and D.4 show the water levels in the piezometers on the west side of Cell 2 (excluding locations
near the sump), near the sump, and on the east side of Cell 2 (excluding locations near the sump),
respectively. Figures D.2 through D.4 show piezometer water levels are lower near the sump, indicating
migration of tailings porewater towards the sump.
The figures show that piezometer water levels increased during the Phase 1 cover placement (late 2016
to early 2017), and then generally decreased until the wet winter/spring of 2019. The increase in water
levels was expected during Phase 1 cover placement and is due to the excess pore water pressure from
consolidation associated with the loading from the additional cover. In 2019 water levels for piezometers
increased or were generally level for the majority of the year. These conditions are likely due to the
significantly wet 2019 winter/spring. For the piezometers with increasing water levels in 2019, water level
readings returned to a decreasing trend at the end of 2019. In 2020, water levels for piezometers were
generally level for the majority of the year. Four piezometers, C2-P01, C2-P02, C2-P03, C2-P04, showed
an increase in water levels from May to September 2020, then decreased at the end of 2020. While the
majority of other piezometers appear to be generally stable in 2023, the fluctuations in water level
appeared to continue for these four piezometers through 2023, with another notable increase from April to
I
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White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual Performance Monitoring Report
5 Cell 2 Settlement and Water Level Monitoring
Project Number: 182924510 (formerly 233001001) 10
October 2023 before decreasing through December. However, overall water levels have decreased since
Phase 1 cover placement by approximately 1 to 4 feet (net), which is summarized in Table 3.
Water balance results from monitoring the cover show the Primary Test Section is performing well with
annual percolation of 1 mm or less, even during the very wet 2019 winter/spring which allowed less than
0.1 percent of precipitation to percolate through the cover. These results indicate that after the Phase 2
cover is placed across Cell 2, the cover is expected to effectively minimize infiltrating precipitation from
percolating into tailings, even from above-average precipitation periods.
Table 3. Piezometer Water Level Elevations During and After Phase 1 Cover Placement
Piezometer
Location
on Cell
Maximum
Measured Water
Level Elevation
during Phase 1
Cover Placement
(ft)
Measured
Water Level
Elevation on
12/4/23
(ft)
Change in Water
Level Elevation
since Phase 1
Cover Placement
(ft)*
C2-P01 West 5612.55 5611.39 -1.16
C2-P02 West 5613.30 5611.60 -1.70
C2-P03 West 5612.31 5610.35 -1.96
C2-P04 West 5613.97 5611.84 -2.13
C2-P05 West 5608.39 5605.54 -2.85
C2-P06 West 5609.21 5606.41 -2.80
C2-P07 West 5610.08 5606.97 -3.11
C2-P08 West 5605.25 5602.60 -2.65
C2-P09 Near Sump 5602.94 5600.65 -2.29
C2-P10 Near Sump 5601.54 5599.50 -2.04
C2-P11 Near Sump 5602.38 5598.65 -3.73
C2-P12 Near Sump 5599.45 5594.14 -5.31
C2-P14 Near Sump 5603.99 5601.54 -2.45
C2-P15 Near Sump 5604.01 5601.45 -2.56
C2-P16 Near Sump 5604.37 5601.87 -2.50
C2-P13 East 5605.72 5603.25 -2.47
C2-P17 East 5607.49 5605.37 -2.12
C2-P18 East 5607.82 5604.00 -3.82
C2-P19 East 5609.09 5606.44 -2.62
C2-P20 East 5610.63 5608.28 -2.35
C2-P21 East 5612.40 5608.74 -3.66
C2-P22 East 5613.39 5609.23 -4.16
C2-P23 East 5614.24 5610.01 -4.23
*Negative number indicates a decrease in water level.
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White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual Performance Monitoring Report
6 Conclusions
Project Number: 182924510 (formerly 233001001) 11
6 Conclusions
The hydrologic performance of the Primary Test Section during 2023 was consistent with expectations for
a water balance cover in a semi-arid environment. Nearly all precipitation at the test section returned to
the atmosphere via evapotranspiration. Runoff and lateral flow were essentially nil, and percolation was
0.4 mm (less than 0.2% of annual 2023 precipitation). The annual percolation rate is similar to percolation
rates reported in the literature for water balance covers in similar climates. The test section is functioning
as expected and is consistent with the expectations for water balance covers in semi-arid climates.
Vegetation observed during the 2023 spring evaluation exhibited above average plant vigor and growth in
response to the favorable spring precipitation conditions. Vegetation observed during the fall evaluation
exhibited average plant vigor and growth in response to favorable spring precipitation conditions and
unfavorable fall precipitation conditions. The results of the performance evaluation indicate that the
Primary and Supplemental Test Sections are not trending to pass several success criteria. Per the SCA,
success is not evaluated until the end of the official monitoring period. Further revegetation development
is expected to occur throughout the performance period and future monitoring efforts to track the
trajectory of revegetation development will occur annually for the remainder of the performance period. In
addition, EFRI will monitor the Supplemental Test Section No. 2 to provide additional data for Cell 2 cover
test section performance monitoring and to evaluate modifications to the revegetation plan to promote
vegetation success.
Total Cell 2 cover surface settlement ranged from 0 to 0.6 feet. This represents total settlement from the
start of Phase 1 cover construction (April 2016) through December 2023. Settlement trends are similar to
settlement monitoring after the initial interim fill was placed, with a quick response to the additional
loading. The majority of total settlement due to Phase 1 cover placement is estimated to have occurred
since settlement is showing a decreasing trend and annual settlement has been less than 0.1 feet in
recent years (2019 – 2022). In 2023 less than 0.13 feet of cumulative settlement with no observed
upward movement was measured. The 2023 results show a slight increase in annual settlement from
recent years which is attributed to the control point elevations being remeasured in 2023 for the first time
in several years resulting in a shift in the measurements of up to 0.1 feet. Adjusting for this shift, the 2023
annual settlement would be less than 0.08 feet and similar to recent years.
Piezometer water levels (representing the zone of saturation in the tailings) increased during the Phase 1
cover placement (late 2016 to early 2017) and then generally decreased until the wet winter/spring of
2019. In 2020 and 2021, water levels for piezometers were generally static for the majority of the year.
However, a few locations showed increasing and then decreasing water levels, which appeared again in
2023. Overall, water levels have decreased since Phase 1 cover placement by approximately 1 to 4 feet.
Based on performance of the Cell 2 Primary Test Section, placement of the Phase 2 cover on Cell 2
would minimize precipitation infiltrating the cover and percolating into the tailings, even from above-
average precipitation periods.
IJ
White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual Performance Monitoring Report
7 References
Project Number: 182924510 (formerly 233001001) 12
7 References
Benson, C., T. Abichou, X. Wang, G. Gee, and W. Albright, 1999. Test Section Installation Instructions –
Alternative Cover Assessment Program, Geotechnics Report 99-3, Geological Engineering,
University of Wisconsin-Madison.
Benson, C., Abichou, T., Albright, W., Gee, G., and Roesler, A. 2001. Field Evaluation of Alternative
Earthen Final Covers, International J. Phytoremediation, 3(1), 1-21.
Energy Fuels Resources (USA) Inc. (EFRI), 2016. Reclamation Plan, White Mesa Mill, Blanding Utah,
Revision 5.1, December 5.
Energy Fuels Resources (USA) Inc. (EFRI), 2018. Reclamation Plan, White Mesa Mill, Blanding Utah,
Revision 5.1, February 8.
Stantec Consulting Services Inc. (Stantec), 2017a. White Mesa Uranium Mill, Cell 2 Cover Performance
Test Section As-Built Report, June 30.
Stantec Consulting Services Inc. (Stantec), 2017b. White Mesa Uranium Mill, Cell 2 Phase 1 Cover As-
Built Report, July 18.
Stantec Consulting Services Inc. (Stantec), 2018a. White Mesa Uranium Mill, Cell 2 Supplemental Test
Section As-Built Report, February 26.
Stantec Consulting Services Inc. (Stantec), 2018b. White Mesa Uranium Mill, Cell 2 Reclamation Cover
2017 Annual Performance Monitoring Report, May 2.
Stantec Consulting Services Inc. (Stantec), 2019. White Mesa Uranium Mill, Cell 2 Reclamation Cover
2018 Annual Performance Monitoring Report, April 5.
Stantec Consulting Services Inc. (Stantec), 2020. White Mesa Uranium Mill, Cell 2 Reclamation Cover
2019 Annual Performance Monitoring Report, February 14.
Stantec Consulting Services Inc. (Stantec), 2021. White Mesa Uranium Mill, Cell 2 Reclamation Cover
2020 Annual Performance Monitoring Report, February 22.
Stantec Consulting Services Inc. (Stantec), 2022. White Mesa Uranium Mill, Cell 2 Reclamation Cover
2021 Annual Performance Monitoring Report, February 24.
Stantec Consulting Services Inc. (Stantec), 2023. White Mesa Uranium Mill, Cell 2 Reclamation Cover
2022 Annual Performance Monitoring Report, February 24.
Utah Department of Environmental Quality Division of Waste Management and Radiation Control
(DWMRC). 2017. Executed Stipulation and Consent Agreement. White Mesa Uranium Mill.
Radioactive Materials License Number UT 1900479. February 23.

IJ
White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual Performance Monitoring Report
Project Number: 182924510 (formerly 233001001)
FIGURES
IJ
REGIONAL LOCATION MAP FIGURE 1
1009740 LOC MAP
WHITE MESA MILL TAILINGS RECLAMATION
FEB 2024ENERGY FUELS
I
!:I ;
f
I
I
i
I
!
i
I
i
.:J
REFERENCE :
ADAPTED FROM FIGURE 1-1 IN DENISON MINES (USA)
CORPORATION, 2009. RECLAMATION PLAN WHITE MESA MILL
BLANDING, UTAH . VERSION 4.0. NOVEMBER . '
PROJECT
~ ..., " -!.
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DATE
._ __________ ...J ____________________ ...JL _______________________ J':•LE:.:NA:M:E:._ __ ======J
SUPPLEMENTAL TEST SECTIONS LOCATION
MILL SITE BOUNDARY
CELL 1
CELL 2
CELL 3
CELL 4A
CELL 4B
DESIGNED
APPROVED
FIGURE
CHECKED
ENERGY FUELS
WHITE MESA MILL TAILINGS RECLAMATION
BLANDING, UTAH
SITE LOCATION MAP 2
233001001
FEB 2024
K REED
B VAN
M DAVIS
PRIMARY TEST SECTION
QRAWINQ RfffBfNCEOO·
1. ML C00IIDINM'ES REFER 10 UTNt STATE PLANE 90UTH.
IWJU. US SURVEY FEET.
2.IWGEIIY'SOURCE:l!IING.2011
() Stantec
9.5'
0.5'
3.5'
3.0'
2.5'
EROSION PROTECTION LAYER
LAYER 3 - GROWTH MEDIUM
LAYER 1 - INTERIM FILL
LAYER 2 - COMPACTED COVER
TAILINGS
VEGETATION
COVER PROFILE WITHIN LYSIMETER FIGURE 3
1009740 WM ET COVR
FEB 2024
WHITE MESA MILL TAILINGS RECLAMATION
ENERGY FUELS
PROJECT
ITI'i[E""TITL£ _____ _J () Stantec
DATE
FILE NAME
RESTRICTED AREA BOUNDARY
CELL2-P01
CELL2-P10
CELL2-P11
CELL2-P16
LEGEND:
CELL 2
CELL 3
MILL SITE
CELL 1
COVER PERFORMANCE TEST SECTION
EXISTING GROUND SURFACE CONTOURS (IN FEET)
(SEE DRAWING REFERENCE 2)
LIMIT OF TOPOGRAPHIC SURVEY
DESIGNED
APPROVED
FIGURE
CHECKED
ENERGY FUELS
WHITE MESA MILL TAILINGS RECLAMATION
BLANDING, UTAH
CELL 2 SETTLEMENT MONUMENT AND PIEZOMETER LOCATIONS 4
233001001
FEB 2024
K REED
B VAN
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CELL2-P07 0 6 2W4-S 0
0 : CELL2-P15
1. EXISTING TOPOGRAPHY BASED UPON FILE PROVIDED FROl.l ENERGY FUELS ON JULY 20, 2015.
PER ENERGY FUELS, GROUND SURFACE CONTOURS ARE FROt.l 2012 AERIAL SURVEY CONDUCTED BY
JONES &: DaMILLE ENGINEERING INC., EXCEPT FOR CELLS 2 AND 3. CELL 2 TOPOGRAPHY FROM
ENERGY FUELS SURVEY CONDUCTED OCTOBER 2013. CELL 3 TOPOGRAPHY FROM ENERGY FUELS
SURVEY CONDUCTED ON JULY 8, 201 +.
2. EXISTING TOPOGRAPHY BASED ON FILES PROVIDED FROM ENERGY FUELS IN MAY 2017. CONTOURS
ARE FROM DRONE SURVEY CONDUCTED BY JONES & DEMILLE ENGINEERING ON JUNE 9, 2017.
• G~
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CELL2-P2
() Stantec
7 EXISTING GROUND SURFACE
ELEVATION, FEET (SEE REFERENCE 1)
EXISTING ROAD
EXISTING WATER
EXISTING TRAIL
--x--EXISTING FENCE
□ EXISTING STRUCTURE
6 EXISTING SETTLEMENT MONITORING POINT
0 CELL 2 PIEZOMETER LOCATIONS
,,,~
APPROXIMATE SUMP AND DRAIN I \
'-/ ACCESS LOCATION
j I
,-_
White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual Performance Monitoring Report
Project Number: 182924510 (formerly 233001001)
APPENDICES
IJ
White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual Performance Monitoring Report
Project Number: 182924510 (formerly 233001001)
Appendix A 2023 Field Hydrology of the Cell 2 Primary Test
Section at the White Mesa Mill
IJ

FIELD HYDROLOGY OF THE CELL 2 PRIMARY TEST
SECTION AT THE WHITE MESA MILL

ANNUAL REPORT FOR CALENDAR YEAR 2023

WHITE MESA MILL – TAILINGS MANAGEMENT CELL 2

ENERGY FUELS RESOURCES (USA) INC.
SAN JUAN COUNTY, UTAH

Craig H. Benson, PhD, PE, NAE

30 January 2024

i

EXECUTIVE SUMMARY

This report describes monitoring data collected from the Primary Test Section at the White Mesa
Mill in San Juan County, Utah, which is being used to evaluate the water balance cover for Cell 2
of the tailings management area at the mill. The data were collected during the period 29
September 2016 to 31 December 2023. The data set includes the seven full calendar years (2017
- 2023) of monitoring for the test section. This report emphasizes data collected in 2023.

The water balance of the test section is summarized as follows:
Calendar
Year
Water Balance Quantities (mm) c
Precipitation Runoff Lateral
Flow
Evapo-
transpiration D Storage Percolation
2016a 60 0 0 35 17 0.0
2017b 223 0 0 325 39 0.6
2018 163 0 0 125 38 0.9
2019 308 0 0 325 3 1.0
2020 128 0 0 171 -63 0.9
2021 223 0 0 242 -20 0.6
2022 180 0 0 169 25 0.3
2023 242 0 0 260 -27 0.4
Notes: a2016 is partial year; bdamage from vault flooding precluded measuring flows 7 Feb. 2017 – 25 March 2017;
call water balance quantities rounded to nearest mm number except percolation, which is rounded to 0.1 mm.

The hydrology of the test section during 2023 was consistent with expectations for a water balance
cover in a semi-arid environment with lower-than-average annual precipitation. Precipitation in
2023 (242 mm) was lower than the long-term average for the nearby Blanding, Utah station (355
mm, located at 37° 62' N, 109° 47' W with elevation 1829 m) operated by the National Weather
Service, but was modestly higher than the average annual precipitation recorded during
monitoring the test section (210 mm from 2017 to 2023). Winter and early spring of 2023 were
considerably wetter than average. Summer and fall in 2023 were drier than winter and spring, and
drier than average. Soil water storage gradually diminished throughout the year, except for a short
pulse of higher soil water storage that occurred in response to the wet winter and early spring.
The gradual decrease in storage continues a trend that began in 2019, as water contents continue
to gradually diminish at greater depths in the cover. At the end of the 2023, soil water storage
reached a minimum for the entire monitoring period. Nearly all precipitation that reached the test
section was returned to the atmosphere as evapotranspiration. A trace of runoff (0.09 mm) was
transmitted, and no lateral flow occurred. Annual percolation was 0.4 mm, the second lowest
measured for a full year during the monitoring period. Thermally driven flow has been the most
significant mechanism contributing to percolation to date.

ii

TABLE OF CONTENTS

EXECUTIVE SUMMARY i

LIST OF TABLES AND FIGURES iii

1. INTRODUCTION 1

2. METEOROLOGICAL DATA 4

3. TEST SECTION DATA 7

4. SUMMARY AND CONCLUSIONS 16

5. REFERENCES 18

iii

LIST OF TABLES AND FIGURES

Table 1. Water balance quantities for the final cover test section at White Mesa from 09/29/16 to
12/31/2023.

Fig. 1. Schematic of cover profile evaluated at White Mesa.

Fig. 2. Cross-section of test section showing layering (orange = interim layer, yellow =
compacted layer, green = growth medium layer), lysimeter, pipe runs, and vault used
to monitor flows.

Fig. 3. Comparison of on-site meteorological data to historical data from the Blanding station
operated by NWS: cumulative precipitation (a) and air temperature (b).

Fig. 4. Cumulative precipitation and potential evapotranspiration (PET) on-site during 2023.
PET was computed using the FAO method described in Allen et al. (1998) with on-site
meteorological data.

Fig. 5. Water balance graph for test section through 2023.

Fig. 6. Relationship between annual precipitation (Pa), annual potential evapotranspiration
(PETa), and annual evapotranspiration (ETa) for test section at White Mesa (solid
squares) and from ACAP and other international studies (solid blue circles) as reported
by Apiwantragoon et al. (2014).

Fig. 7. Water content in the cover profile at each of depth of monitoring during the monitoring
record. Symbols shown only on 0.5% of data for clarity (green = growth medium,
orange/brown = compacted layer, blue = interim layer).

Fig. 8. Soil water storage and cumulative percolation over time for the test section. Vertical
dashed lines correspond to annual onset and cessation of percolation.

Fig. 9. Daily average air temperature and daily average soil temperature at various depths in
the test section (green = growth medium, orange = compacted layer, yellow = interim
layer).

Fig. 10. Thermal gradient in test section, thermal flow computed from thermal gradient using
method in Globus and Gee (1995), and percolation recorded with the monitoring
system.

Fig. 11. Annual percolation for the test section at White Mesa in context of data from other sites
in ACAP and other international studies as reported by Apiwantragoon et al. (2014).

1
1. INTRODUCTION

The Primary Test Section was constructed at the White Mesa Mill in San Juan County,
Utah in Summer 2016 to evaluate the field-scale hydrology of the final cover placed over the Cell
2 tailings management cell. The profile of the final cover design is shown in Fig. 1 and a cross-
section of the test section is shown in Fig. 2. The cover is an earthen design employing water
balance principles that is comprised of four layers (bottom to top): well-graded interim layer (760
mm, 2.5 ft), fine-textured compacted layer (915 mm, 3.0 ft), growth medium layer (1070 mm, 3.5
ft), and gravel-amended topsoil layer (150 mm, 0.5 ft) (Fig. 1). Construction documentation for
the test section is described in Stantec (2017).
The test section includes a drainage lysimeter and associated instruments (Fig. 2) based
on the lysimeter design developed for the Alternative Cover Assessment Program (ACAP) as
described in Benson et al. (1999, 2001). The instruments are used to monitor fluxes from the
cover profile (runoff, lateral flow, percolation), state variables (soil water content and temperature
at discrete monitoring points), and meteorological conditions. A datalogger collects data from the
sensors at intervals ranging from hourly to as short as 30 seconds depending on the hydrological
condition. A cellular modem transmits data stored on the datalogger to a computer off site on a
daily basis. Data collection began on 29 September 2016 and continues uninterrupted.
The sensors and data acquisition system used to monitor the test section are maintained
and recalibrated annually. A data quality evaluation is conducted monthly for measurements from
all sensors, and a data quality report (DQR) is issued quarterly. Instrumentation calibration and
maintenance is conducted annually, most recently on 2 August 2023.
This report describes data collected since inception of the test section, with particular
emphasis on data collected in 2023. Section 2 compares meteorological data collected on-site to
historical data from a nearby monitoring station operated by the National Weather Service (NWS).
Section 3 describes hydrological data from the test section. Section 4 provides a summary and
conclusions.

2

Fig. 1. Schematic of cover profile evaluated at White Mesa.

0
0
0
0
0.5 ft Erosion Layer
3.5 ft Growth Medium
3.0 ft Compacted Cover
2.5 ft Interim Layer
0 = WCR or thermocouple

3

Fig. 2. Cross-section of test section showing layering (orange = interim layer, yellow = compacted layer, green = growth medium
layer), lysimeter, pipe runs, and vault used to monitor flows.
5640 5640
I-5630 w 5630 I-w w
11. ,~ = w
11.
z
0 5620 i== ~ w
~ 11 I ~
~
~~
"" I I ~-
l......l _i______ --,__ _______ ---
z
5620 0
i== ~ w
....I 5610 w 5610 ....I w
~
5600
0+00 1+00 2+00 2+20
DISTANCE, FEET

4
2. METEOROLOGICAL DATA

Detailed comparisons are made quarterly between the on-site meteorological data and
meteorological data compiled by the National Weather Service at the Blanding, Utah station ( 37°
62' N, 109° 47' W, elevation 1829.1 m). Comparisons to NWS data in the quarterly DQRs indicate
general agreement between the measurements on site and those made by NWS.
Fig. 3 compares average daily precipitation (Fig. 3a) and average daily air temperature
(Fig. 3b) measured on-site with long-term historical averages reported by NWS at the Blanding
station. On-site precipitation in 2023 was lower than the long-term average annual precipitation
at the Blanding station (242 vs. 355 mm, Fig. 3a), but was modestly higher than the average
annual precipitation during the monitoring period (210 mm). Annual precipitation has been below
average recorded at the Blanding station throughout the entire monitoring period. Winter and early
spring were wetter than average, whereas summer and fall were drier than average. Average air
temperature at the test section generally fell within the long-term high and low temperatures
recorded at the Blanding station (Fig. 3b).
The long-term average precipitation record does not exhibit the short-term variability
inherent in the actual precipitation record. Smoothing associated with long-term temporal
averaging makes the long-term precipitation record smoother and more gradually varying
compared to actual records. When a daily precipitation record is averaged over long periods, the
number of days with non-zero precipitation diminishes (in the limit, the number of non-zero
precipitation days is zero). The number of days with large precipitation events diminishes as well.
For this reason, long-term precipitation records are not recommended for use in simulating the
hydrology of covers (Albright et al. 2010), but they are useful for comparative analysis.
Fig. 4 shows cumulative precipitation and potential evapotranspiration (PET) computed
with the FAO method (Allen et al. 1998) for 2023. PET far exceeds precipitation from mid-spring
to the end of the year, indicating an excess of energy for evaporation and transpiration relative to
the amount of water to manage.

5

Fig. 3. Comparison of on-site meteorological data to historical data from the Blanding station
operated by NWS: cumulative precipitation (a) and air temperature (b).
0
50
100
150
200
250
300
350
400
1/1/23
3/1/23
5/1/23
7/1/23
9/1/23
11/1/23
1/1/24
Blanding Historical Average
On-Site 2023
Cumulative Precipitation (mm)
(a)
-10
0
10
20
30
40
1/1/23
3/1/23
5/1/23
7/1/23
9/1/23
11/1/23
1/1/24
Blanding Historical Max
Blanding Historical Min
On-Site Daily Avg. 2023
Air Temperature (oC)
(b)

6

Fig. 4. Cumulative precipitation and potential evapotranspiration (PET) on-site during 2023. PET
computed using the FAO method described in Allen et al. (1998) with on-site
meteorological data.
0
200
400
600
800
1000
1200
1400
1/1/23
3/1/23
5/1/23
7/1/23
9/1/23
11/1/23
1/1/24
Cumulative On-Site Precipitation and
Potential Evapotranspiration (mm)
PET
Precipitation

7
3. TEST SECTION DATA

Table 1 summarizes the annual water balance for the test section. Fig. 5 shows the water
balance graph for the test section.

Table 1. Water balance quantities for the final cover test section at White Mesa from 09/29/16 to
12/31/2023.
Calendar
Year
Water Balance Quantities (mm)
Precipitation Runoff Lateral
Flow ET D Storage Percolationc
2016a 60 0 0 35 17 0.0
2017b 223 0 0 325 39 0.6
2018 163 0 0 125 38 0.9
2019 308 0 0 325 3 1.0
2020 128 0 0 171 -63 0.9
2021 223 0 0 242 -20 0.6
2022 180 0 0 169 25 0.3
2023 242 0 0 260 -27 0.4
Notes: a2016 is partial year; bdamage from vault flooding precluded measuring flows 7 Feb. 2017 – 25 March 2017;
call water balance quantities rounded to nearest mm number except percolation, which is rounded to 0.1 mm.

Fig. 5 shows cumulative quantities for each water balance flux (precipitation, evapotranspiration,
runoff, lateral flow, and percolation) as a function of time. Percolation is the flux from the base of
the cover that is captured by the geocomposite drain in the base of the lysimeter and would
normally flow into the tailings. Lateral flow is the flux of liquid occurring laterally at the interface
between the growth medium and the compacted layer and is captured by a collection point at the
downslope edge of the lysimeter. Fig. 5 also shows soil water storage (total water stored in the
cover per unit surface area) as function of time. Soil water storage is computed by integrating the
water content measurements over the volume of the test section at a given point in time.
Each water balance quantity is measured directly except for evapotranspiration (ET),
which is computed as the non-negative residual of the daily water balance:
ET = P – R – L – Pr – DS (1)

8

Fig. 5. Water balance graph for test section through 2023.
0
500
1000
1500
2000
0
1
2
3
4
5
9/20/16 12/7/17 2/24/19 5/13/20 7/31/21 10/18/22 1/5/24
Soil Water
Storage
ET
Surface Runoff
Percolation
Lateral Flow
Soil Water Storage, Cumulative Precipitation,
and Cumulative Evapotranspiration (mm)
Cumulative Runoff, Lateral Flow, and Percolation (mm)
Precipitation
White Mesa, UT

9

where P = daily precipitation, R = daily runoff, L = daily lateral flow, Pr = daily percolation, and DS
= daily change in soil water storage. ET computed with Eq. 1 includes actual ET and any errors
in the water balance. For 2023, 260 mm of ET was computed using Eq. 1, which exceeds annual
precipitation modestly. Cumulative annual ET computed with Eq. 1 is in agreement with the
generalized relationship between annual ET, PET, and precipitation for water balance covers and
natural watersheds, as shown in Fig. 6. Annual PET in Fig. 6 was computed with the on-site
meteorological data using the FAO method described in Allen et al. (1998).
The overall seasonal water balance trends shown in Fig. 5 are consistent with
expectations for a water balance cover in a semi-arid climate with below average precipitation.
During 2023, soil water storage continued to diminish gradually throughout the year, a trend that
began in 2019. By the end of the year, the soil water storage was at a new minimum, and lower
than the soil water storage immediately after construction. Water contents have been gradually
diminishing deeper in the profile (2134 mm bgs and deeper, Fig. 7), but remain relatively steady
at mid-depth (1524 and 1829 mm bgs). Nearly all water cycling occurs in the upper meter of the
profile.
Percolation in 2023 began on 12 July 2023 and ceased on 19 November 2023, consistent
with the beginning and end of percolation in all years except 2018, which had a very wet fall that
caused percolation to persist longer than normal (Fig. 8). In general, percolation begins between
mid-June and mid-July, and ends between mid-October and mid-November (Fall 2018 is an
exception). For each year in the record, initiation of percolation is unrelated to the magnitude of
soil water storage, and occurs when soil water storage is near a minimum. This indicates that
mechanisms other than hydraulic gradients contribute to percolation from the cover.

10

Fig. 6. Relationship between annual precipitation (Pa), annual potential evapotranspiration
(PETa), and annual evapotranspiration (ETa) for test section at White Mesa (solid
squares) and from ACAP and other international studies (solid blue circles) reported by
Apiwantragoon et al. (2014).

0.00
0.20
0.40
0.60
0.80
1.00
0 5 10 15 20
Annual Evapotranspiration to
Annual Potential Evapotranspiration (ETa/PETa)
Annual Potential Evapotranspiration/Annual Precipitation (PETa/Pa)
On-Site 2017
On-Site 2018
On-Site 2019
On-Site 2020
On-Site 2021
On-Site 2022
On-Site 2023
•
•
•
ET a [ Pa ]0.913
PET a = O.B 4 PET a
■
□
□
□
□
□
□
•

11

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0.0
0.1
0.2
0.3
0.4
0.5 9/1/16
9/1/17
9/1/18
9/1/19
9/1/20
9/1/21
9/1/22
9/1/23
White Mesa
457 mm
686 mm
914 mm
1524 mm
1829 mm
2134 mm
2743 mm
Volumetric Water Content (-)
Growth Medium
Compacted Layer
Interim Layer
t
H t
t f t

12

Fig. 8. Soil water storage and cumulative percolation over time for the test section. Vertical
dashed lines correspond to annual onset and cessation of percolation.
300
400
500
600
700
800
0.0
1.0
2.0
3.0
4.0
5.0
6.0
9/1/16 11/21/17 2/10/19 5/2/20 7/22/21 10/11/22 1/1/24
Soil
Water
Storage
Perco-
lation
Soil Water Storage (mm)
Cumulative Percolation (mm)
14 Jul 17
13 Nov 17
22 Jun 18
01 Mar 19
23 Jul 19
28 Oct 19
14 Jul 20
07 Nov 20
03 Jul 21
17 Nov 21
01 Jul 22
05 Nov 22
12 Jul 23
19 Nov 23

13
Thermal gradients have a significant influence on percolation from the cover profile. Air
and soil temperature records for the test section are shown in Fig. 9. The temporal variation is
consistent each year, with the thermal regime changing orientation seasonally. The highest soil
temperatures occur near the surface of the cover in early summer, and at the base of the cover
in early winter. Temperatures are relatively uniform with depth in early spring and early fall.
Consequently, the thermal gradient (hot to cold) is downward from late spring to late fall, and
upward during the other portion of the year, as illustrated in Fig. 10.
The thermal gradient in Fig. 10 was computed using the soil temperatures measured at
686 mm bgs and 2743 mm bgs. Temperatures recorded by the thermocouple second from the
surface (686 mm bgs) were used to compute the thermal gradient, rather than temperatures from
the uppermost thermocouple (457 mm bgs), to avoid variability in soil temperature associated
with short-term fluctuations in air temperature. Positive thermal gradients correspond to
downward heat flow and negative thermal gradients correspond to upward heat flow. The gradient
varies systematically with the seasons each year, with a maximum of approximately +4 oC/m in
early July to a minimum of approximately -4 oC/m in early January.
Thermal fluxes were computed using the method in Globus and Gee (1995) and the
thermal gradient in Fig. 10 using:

(2)

where qT is the thermal flux, KT is the thermal water conductivity (set at 2x10-11 m2/s-oC, Globus
and Gee 1995), and DT/Dz is the thermal gradient. The cumulative downward thermal flux
computed using this approach, which is captured in the drainage layer at the base of the lysimeter,
is shown in Fig. 10. The timing and magnitude of the computed thermal flux resembles the
percolation rate, suggesting that thermally driven flows are significant contributors to percolation.

qT =K T
ΔT
Δ z--

14

Fig. 9. Daily average air temperature and daily average soil temperature at various depths in
the test section (green = growth medium, orange = compacted layer, yellow = interim
layer).

0
5
10
15
20
25
30
35
40
-40
-30
-20
-10
0
10
20
30
40
9/1/16
9/1/17
9/1/18
9/1/19
9/1/20
9/1/21
9/1/22
9/1/23
457 mm
686 mm
914 mm
1524 mm
1829 mm
2134 mm
2743 mm
Air On-Site
Soil Temperature (oC)
Daily Average Air Temperature (oC)
•
■
•
----z:'.r-
~
---tr-

15

Fig. 10. Thermal gradient in test section, cumulative downward thermal flow computed from
thermal gradient using method in Globus and Gee (1995), and percolation recorded
with the monitoring system.
0.0
1.0
2.0
3.0
4.0
5.0
6.0
-10
-5
0
5
10
9/1/16 9/1/17 9/1/18 9/1/19 9/1/20 9/1/21 9/1/22 9/1/23
Cumulative Percolation or Thermal Flux (mm)
Thermal Gradient (oC/m)
Thermal
Gradient
Measured
Percolation
Computed
Thermal Flux
,",
'' ' ..
' \
' ' ' ' ' ' ' ' ' ' .,__
' ' ' ' '
' ,r. :l: :~
f 1r 11 •
: t l
' '
,,
"' .,
' '
" ' ~
' /w' ,,
'' \,'
' ' , ,
i ' ...i. ,--
' ' ' ' ' ' ' ' ' ' ' ' \ ' ' " . l}i\ \ ,,,
' ,,
' ' I' ' ' '
,,
' ' ,, ' ~ I I t~ ' ' ' ',,
\'.'
,,, V\f'1i
1

16
Fig. 11 shows annual percolation from the test section for each year in the record along
with data compiled from USEPA’s ACAP and other data sources, as reported by Apiwantragoon
et al. (2014). The annual percolation data fall with the other data reported by Apiwantragoon et
al. (2014) throughout the monitoring period. This agreement indicates consistency with other
water balance covers in similar climates.
4. SUMMARY AND CONCLUSIONS

This report describes hydrological and meteorological data collected from the Cell 2 test
section at the White Mesa Mill near Blanding, Utah. Data are reported for the period 29 September
2016 to 31 December 2023, with the discussion emphasizing data collected in 2023. The
monitoring system for the test section has been collecting the required data, except for a short
period in 2017 (7 February 2017 through 25 March 2017) when the flow monitoring systems were
not functioning due to damage by flooding of the instrument vault. The following observations and
conclusions are made based on the data collected:

• The test section is functioning as expected, and the hydrology of the cover profile is consistent
with the expectations for water balance covers in semi-arid climates.
• Precipitation at the test section in 2023 (242 mm) is lower than the long-term average recorded
at the Blanding, Utah station (355 mm) operated by the NWS. Precipitation in winter and early
spring were wetter than average, whereas late spring, summer, and fall were drier than
average.
• The test section hydrology is consistent with expectations for water balance covers in semi-
arid and arid locations in the western US. Nearly all precipitation at the test section was
returned to the atmosphere via evapotranspiration. A trace of runoff was recorded, and
percolation was 0.4 mm. No lateral flow occurred. The annual percolation rate is similar to
percolation rates reported in the literature for water balance covers in similar climates.

17

Fig. 11. Annual percolation for the test section at White Mesa in context of data from other sites
in ACAP and other international studies as reported by Apiwantragoon et al. (2014).

0.1
1
10
100
Annual Percolation (mm)

0-250 > 750500-750250-500
Annual Precipitation (mm)
ACAP Data - Solid Symbols
Other Data - Open Symbols
White Mesa - Large Solid Squares
2017
2018
2019
2020
2021
2022
2023■
□
•
•
• •
□
□
0
!':,.
□
!':,.!':,.
□
♦
♦
••

18
• Thermally driven flow has been the primary mechanism contributing to percolation. Each year
percolation begins when soil water storage is near its lowest, and the thermal gradient is
downward. Percolation ceases when the thermal gradient transitions to upward. Thermal fluxes
computed using soil temperature data collected from thermocouples in the test section yielded
a cumulative thermal flux comparable in timing and magnitude to the measured percolation
rate.
5. REFERENCES

Albright, W., Benson, C., and Waugh, W. (2010), Water Balance Covers for Waste Containment:
Principles and Practice, ASCE Press, Reston, VA, 158 p.

Allen, R., Pereira, L., Raes, D., and Smith, M. (1998), Crop Evapotranspiration-Guidelines for
Computing Crop Water Requirements.” FAO Irrigation and Drainage Paper 56, Food and
Agricultural Organization of the United Nations, Rome.

Apiwantragoon, P., Benson, C., and Albright, W. (2014), Field Hydrology of Water Balance Covers
for Waste Containment, J. Geotech. and Geoenvironmental Eng., 04014101-1-20.

Benson, C., Abichou, T., Albright, W., Gee, G., and Roesler, A. (2001), Field Evaluation of
Alternative Earthen Final Covers, International J. Phytoremediation, 3(1), 1-21.

Benson, C., Abichou, T., Wang, X., Gee, G., and Albright, W. (1999), Test Section Installation
Instructions – Alternative Cover Assessment Program, Environmental Geotechnics Report 99-
3, Dept. of Civil & Environmental Engineering, University of Wisconsin-Madison.

Cedar Creek (2020), White Mesa Mill Site, 2019 Revegetation Evaluation Cell 2 Primary and
Supplemental Test Sections, report prepared for Energy Fuels Resources Inc by Cedar Creek
Associates, Inc., Fort Collins, CO.

Globus, A. and Gee, G. (1995), Method to Estimate Water Diffusivity and Hydraulic Conductivity
of Moderately Dry Soil, Soil Sci. Soc. Am. J., 59, 684-689.

Stantec Consulting Services Inc. (Stantec), 2017, White Mesa Uranium Mill, Cell 2 Cover
Performance Test Section As-Built Report, June 30.

White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual Performance Monitoring Report
Project Number: 182924510 (formerly 233001001)
Appendix B 2023 Revegetation Evaluation Cell 2 Primary
and Supplemental Test Sections
IJ

White Mesa Mill Site

2023 REVEGETATION EVALUATION CELL 2 PRIMARY AND SUPPLEMENTAL TEST
SECTIONS

FEBRUARY 2024

PREPARED BY:

i

Table of Contents

1.0 INTRODUCTION .......................................................................................................................... 1
1.1 General ................................................................................................................................... 1
1.2 Background ............................................................................................................................. 1
1.3 Precipitation ............................................................................................................................ 2
2.0 REVEGETATION PERFORMANCE CRITERIA ................................................................................... 4
3.0 REVEGETATION MONITORING RESULTS ...................................................................................... 6
3.1 Primary Test Section ................................................................................................................ 8
3.2 Supplemental Test Section ..................................................................................................... 15
3.3 Supplemental Test Section No. 2 ............................................................................................ 18
3.4 Native Reference Area ............................................................................................................ 20
4.0 PERFORMANCE EVALUATION ..................................................................................................... 21
5.0 REFERENCES ............................................................................................................................ 23

List of Charts and Tables

Table 1. 2023 Site and Long-term Average Monthly Precipitation ........................................................... 3
Chart 1. Monthly Precipitation, White Mesa Mill Site, Blanding UT .......................................................... 6
Table 2. Summary of Species Observed on Each Test Section ................................................................ 6
Table 3. Summary of Average Cover .................................................................................................... 7
Chart 2. Average Ground Cover by Lifeform .......................................................................................... 8
Table 4. Primary Test Section Woody Plant Density ............................................................................... 9
Chart 3. Primary Test Section Perennial & Annual Cover Trend (Spring Survey) .................................... 13
Table 5. Supplemental Test Section Woody Plant Density .................................................................... 14
Chart 4. Supplemental Test Section Perennial & Annual Cover Trend (Spring Survey) ............................ 16
Table 6. Success Criteria Comparison ................................................................................................. 21

1

White Mesa Mill Site

2023 Revegetation Evaluation Cell 2 Primary and
Supplemental Test Sections

1.0 INTRODUCTION
1.1 General
Cedar Creek Associates, Inc. (Cedar Creek) was contracted to evaluate revegetation performance on
the Primary and Supplemental Test Sections for the Cell 2 tailings management cell at the Energy Fuels
Resources (USA) Inc. (EFRI) White Mesa Uranium Mill Site (Mill Site). Cedar Creek conducted spring and
fall onsite evaluations of revegetation on the test sections at the Mill Site. These evaluations occurred on
May 31, 2023, and September 6, 2023, respectively.
This report summarizes findings from the spring and fall revegetation evaluations. A full analysis of
results from the spring evaluation was also completed to evaluate progress towards meeting the
revegetation success standards for the metrics of vegetation cover, species diversity, and woody plant
density. The spring evaluations were selected for success comparisons because the test sections are
dominated by cool season species, which are best evaluated in the spring. Fall evaluations will continue
being conducted for the purpose of closely monitoring effects of precipitation on revegetation.
1.2 Background
The Primary Test Section was constructed in 2016 within the Cell 2 cover, with subsequent seeding
occurring in the fall of 2016. The test section is approximately 100 feet by 100 feet, with a 32-feet by 64-
feet lysimeter centered within the test section. The test section was constructed with the full-depth Cell 2
cover profile.
The Supplemental Test Section was constructed and seeded in fall of 2017. The Supplemental Test
Section was constructed as a supplemental vegetation monitoring section to the Primary Test Section and
is not being used to evaluate the entire cover profile. The test section is 100 feet by 100 feet in size to

2

match the dimensions of the Primary Test Section and is located to the north of the tailings management
cells.
EFRI constructed the test sections in accordance with the Stipulation and Consent Agreement (SCA)
between EFRI and the Utah Department of Environmental Quality (UDEQ), Division of Waste Management
and Radiation Control (DWMRC) executed on February 23, 2017. The SCA defines commitments and
timeframes for completing placement of reclamation cover on Cell 2 and performance assessment of the
cover system, in accordance with the approved Reclamation Plan.
In 2021, EFRI constructed a Supplemental Test Section No. 2 adjacent to and similar to the
Supplemental Test Section. This test section was constructed to provide additional data for the Cell 2 cover
test section performance monitoring and to evaluate the revegetation plan to promote vegetation success.
1.3 Precipitation
Table 1 and Chart 1 display precipitation on site for January 2018 to present compared with the long-
term normal precipitation for the nearby town of Blanding, Utah. Regionally, 2023 can be considered a
lower than average precipitation year. Precipitation conditions in the months prior to the spring revegetation
evaluations were favorable for plant growth (140% of average), particularly due to extreme precipitation
in March. Vegetation observed during the spring evaluation exhibited above average plant vigor and growth
in response to the favorable precipitation conditions. The spring months of March, April, and May are
particularly important to plant growth and these months received 78.49 mm (294% of normal), 2.54 mm
(11% of normal), and 12.45 mm (69% of normal) of precipitation, respectively. Precipitation prior to the
fall revegetation evaluation was below average (53% of average). July, August, and September had 11.94
mm (41% of normal), 14.48 mm (41% of normal), and 24.64 mm (76% of normal) of precipitation,
respectively. Vegetation observed during the fall evaluation exhibited average plant vigor and growth in
response to favorable spring precipitation conditions and unfavorable fall precipitation conditions.

3

Table 1 White Mesa -Precipitation -2023
Site and Long-term Average Monthly Precipitation
2018 2019 2020 2021 2022 2023 Blanding
Site Perce nt of Site Percent of Site Percent of Site Percent of Site Percent of Site Percent of Long Term
Precipitation Normal Precipitation Normal Precipitation Normal Precipitation Normal Precipitation Normal Precipitation Normal Average
(mm) (%) (mm) (%) (mm) (%) (mm) (%) (mm) (%) (mm) (%) (mm)
January 8,2 23% 46 ,7 132% 17.1 48 % 20 ,6 58% 0,2 1% 70,61 200 % 35.3
February 4 ,2 14% 65,6 214 % 5.4 18% 17.4 57% 7,9 26 % 20.32 66 % 30,7
March 8,3 31 % 62.2 233 % 23,7 89 % 16,6 62 % 19,9 75% 78.49 294 % 26,7
April 3,0 14% 12 .2 55 % 1.1 5% 0,0 0% 0,7 3% 2.54 11 % 22 .1
May 6.6 37% 36.7 203 % 1.8 10 % 3.2 18% a.a 0% 12.45 69 % 18.0
June 11 .7 102 % 2.3 20 % 15,8 138 % 11.2 98% 5,8 51 % 3.30 29 % 11.4
July 6.4 22% 4,7 16 % 24,9 85 % 35.4 121 % 21.4 73% 11 .94 41 % 29,2
Augu st 10,0 29% 8,7 25 % 0,5 1% 47 .2 135 % 25.1 72 % 14.48 41 % 35 .1
September 1.5 5% 0.0 0% 22.0 68 % 28 .1 87% 31.8 98 % 24 .64 76 % 32 .5
October 81.7 222 % 5.2 14 % 0,7 2% 23,8 65 % 17,6 48 % 3.8 1 10 % 36.8
November 5,6 21 % 21.1 79 % 3.4 13 % 0,3 1% 19,9 75 % 2.54 10 % 26 .7
December 10.4 31 % 42.5 126% 13 .9 41 % 19 .7 58% 29 .5 87 % 33.8
ANNUAL 157.6 47% 307.9 91% 130.3 39% 223,4 66% 179.8 53% 245,1 72% 338.3
Mar-May 17.9 a.. 111.1 166% 26.6 ... 19.8 ... 20.60 U'III 93.5 -66.8
July-Sept 17.9 ~ 13.4 ~ 47.4 .... 110.7 1140/o 78.27 ... 51.1 96.8
Chart 1 -Monthly Precipitation, White Mesa Mill Site, Blanding, UT -2023
=2019
75
60
-l ong Term Average
30
15
Ja n Fe b M ar Apr M ay Jun J ul Aug Se p Oct Nov Dec

4

2.0 REVEGETATION PERFORMANCE CRITERIA
Official performance monitoring of the Primary Test Section commenced on January 1, 2020, after
two calendar years of calibration monitoring were completed. As defined in the SCA, performance
monitoring will be conducted for five years (the "Performance Period"). Revegetation efforts will be
considered successful when the following performance criteria per the SCA are met for both the Primary
Test Section and Supplemental Test Sections at the end of the Performance Period.
Criterion 1: Species Composition
1. Total vegetative cover shall be composed of at least:
a. Five (5) perennial grass species, four (4) of which must be native species;
b. One (1) perennial forb species; and
c. Two (2) shrub species.
All species applied towards this success standard must be a listed component of the reclamation seed
mix, which can be found in Table D.1. of the Updated Tailings Cover Design Report (MWH 2015).
Seeded species recorded during monitoring are indicated on tables below.
Criterion 2: Vegetative Cover Criteria
1. Average cover must be at least 40%;
2. Individual grass and forb species applied towards the minimum 40% average cover criterion
must have a relative cover of no less than 4% and no greater than 40%;
3. Reclaimed areas shall be free of state and county listed noxious weeds; and
4. Vegetative cover must be self-regenerating and permanent. Self-regeneration must be
demonstrated by evidence of reproduction (i.e. seed production).
All species applied to the minimum average cover success standard must be a listed component of
the reclamation seed mix (MWH 2015). Species not on the list may be applied towards the vegetative
cover criterion if it can be demonstrated that the species is native and is a desirable component of
the revegetation community.
Criterion 3: Shrub Density Criteria
1. A minimum woody plant density of 500 woody plants per acre must be achieved; and
2. Shrubs must be healthy and have survived at least two complete growing seasons before being
evaluated against success criterion.

5

Per the SCA, if the vegetation criteria are not met, or more time is needed to satisfy the criteria,
DWMRC may set new vegetation acceptance criteria based on lysimeter findings (i.e. percolation
performance), revised ground water modeling, or consideration of change in annual precipitation and rate
of vegetation growth on the test sections.
During the 2022 spring vegetation survey, Cedar Creek added a Native Reference Area that is surveyed
annually along with the test sections to collect information on how the test sections are performing in
comparison to native vegetation communities. Native reference areas or analog sites are commonly used
as a suitable comparison for revegetation success. Each year, the reference area is sampled, and the
resulting data is used to establish a benchmark, then success criteria are set as a percentage of benchmark
performance (typically between 70-90% of the reference area). In general, this approach is preferable to
technical standards for revegetation performance criteria because the reference area benchmark accounts
for local climatic conditions, where vegetation cover increases in surplus precipitation years and diminishes
in droughty years. Essentially, using a reference area approach allows for the success criteria to adjust to
site climate conditions.

6

3.0 REVEGETATION MONITORING RESULTS
The results of 2023 vegetation monitoring at the Primary Test Section and Supplemental Test Section
are described for each seasonal survey in the sections below. Table 2 provides a summary of all species
observed in the test sections, including both those captured by cover sampling metrics and those noted as
incidental observations. Table 3 provides a summary of average cover by species as determined by the
2023 monitoring surveys. Chart 2 presents a summary of average cover by lifeform at each test section as
determined by the 2023 monitoring surveys. Comparison between the Primary and Supplemental Test
Section are made as they are both in their seventh growing season. Results of the Supplemental Test
Section No. 2 and the Native Reference area are described separately below.
Table 2 White Mesa -Vegeta t ion Cove r -2023
Summary of Species Observed on Each Test Section
Primary Test
Area-> Section
Gra sses Sp rin g Fall
N p Achnatherum hymenoides I ndian Ricegrass
N p Bouteloua gracilis Blue Grama
I A Bromus tectorum Chea t qrass X X
N p *Elymus e/ymoides Squ irrel t ai l X X
N p Elymus lanceolatus Thickspike Whea t grass
N p Elymustrachy cau/us Slendery./heatgrass
N p Ht/aria j amesii James' Galleta
N p *Pascopyrum smithii Western Whe atgrass X
N p Pseudoroegneria spicata spicata Bluebunch Whea t grass
N p Sporobolus airoides Al kal i Sacaton
I p Thinopyrum intermedium Intermed iate Whea t grass
N A Vu/pia octof/ora Si x Weeks Fescue
Fo rbs
N p Achillea millefolium Common Yarrow
N p Artemisia /udoviciana Wh ite Sagebrush X
N p Ca !ochortus nuttal/ii Seqo Lil y
N p Dal easp. Prairie Clover
N A Descurainia pinnata Western Tansy must ard X
I A Erodium dcutarium Redstem St ork's Bill X
N B Grindelia squarrosa Curl y cup Gum w eed
I A Kochia scoparia Summer Cypress X X
I B Lactuca serrio/a Pr ic kly Lettuce X
N A Lappu/a redowskii West ern St ickseed X
N p Unum lewisii Le wis Fl a x
N p Machaeranthera canescens HoaryJansy aster
N p Plantago patagonica Woolly Plan t ain
I A Sa /sofa tragus Russian Thistle X X
I A Sisvmbrium altissimum Tall Tumb lemust ard X X
N p Sphaeralcea cocdnea Sca r let Globemallow
N p Sphaeralcea orossularifolia Gooseberrvleaf Globemallow
Shrubs, Sub-shru bs, Cacti & Trees
N p *Atrip/ex canescens Fo urwing Saltbush X X
N p Gutierrezia sarothrae Broom Sna kew eed
N p Lvdum oallidum Pale Desert-thorn
Perennial Soecies Encountered 4
Annua l Soecies Encountered 8
Seeded Species Encoun t ered 3
Tot a l Soe cies En cou nte red 1 2
* Indica t es a seeded species, Squi relltai l was not seeded on Supplemental Test Section 2
N = Native, I = Int roduced , P = Perenn ial , B = Bi ennial , A = Annua l
Supplemental
Test Section
Spring Fall
X
X X
X
X
X X
X
X
X
X X
X
X
X
X X
X
X X
X X
X
X X
Species Observed
11
7
1
18
Sup pl emental
Test Section 2
Spring Fall
X X
X
X
X X
X
X X
X X
X X
X
X
X
X X
X
X
X X
X X
X
X
X
X X
14
6
3
20

7

Table 3 White Mesa - Vegetation Cover - 2023
Summary of Average Cover
Percent Ground Cover Based on Point-Intercept Sampling
Area ——>
Grasses Spring Fall Spring Fall Spring Fall
N P *Bouteloua gracilis Blue Grama ----0.3 0.1
I A Bromus tectorum Cheatgrass 1.3 0.1 5.4 3.2 0.5 -
N P *Elymus elymoides Squirreltail 43.7 31.1 ----
N P *Elymus lanceolatus Thickspike Wheatgrass ----0.1 8.7
N P *Elymus trachycaulus Slender Wheatgrass -----3.0
N P *Hilaria jamesii James' Galleta ----1.5 1.9
N P *Pascopyrum smithii Western Wheatgrass --0.7 -4.5 0.6
N P *Pseudoroegneria spicata Bluebunch Wheatgrass ----1.5 1.5
N P Sporobolus airoides Alkali Sacaton -----0.8
I P *Thinopyrum intermedium Intermediate Wheatgrass ----0.8 -
N A Vulpia octoflora Six Weeks Fescue --0.1 ---
Forbs
N P *Achillea millefolium Common Yarrow --0.1 0.1 --
N P *Artemisia ludoviciana White Sagebrush --0.2 ---
N P Dalea sp.Prairie Clover -----0.1
N A Descurainia pinnata Western Tansymustard ---0.7 --
I A Erodium cicutarium Redstem Stork's Bill 3.4 -25.5 7.1 17.7 1.5
N B Grindelia squarrosa Curlycup Gumweed --0.1 ---
I A Kochia scoparia Summer Cypress 0.7 1.1 ----
I B Lactuca serriola Prickly Lettuce 0.2 -----
N P Linum lewisii Lewis Flax -----0.1
N P Machaeranthera canescens Hoary Tansyaster ---0.1 -0.1
I A Salsola tragus Russian Thistle 2.8 9.6 0.3 8.5 4.9 26.9
I A Sisymbrium altissimum Tall Tumblemustard 17.1 0.6 4.3 -4.3 0.1
N P Sphaeralcea coccinea Scarlet Globemallow --0.6 0.5 0.3 -
Shrubs, Sub-shrubs, Cacti & Trees
N P *Atriplex canescens Fourwing Saltbush 5.1 9.1 ---0.2
N P Gutierrezia sarothrae Broom Snakeweed --0.5 -0.1 0.7
N P Lycium pallidum Pale Desert-thorn --0.3 0.5 --
Total Plant Cover 74.3 51.7 37.9 20.5 36.5 46.2
Rock 0.7 6.5 0.0 2.4 0.1 0.0
Litter (including plant senscence in fall)13.1 30.5 30.3 49.2 15.1 13.4
Bare ground 11.9 11.4 31.8 27.9 48.3 40.4
Total Perennial Cover 48.8 40.3 2.3 1.1 9.1 17.7
Summary by Lifeform:
Perennial Grasses 43.7 31.1 0.7 0.0 8.7 16.6
Annual Grasses 1.3 0.1 5.5 3.2 0.5 0.0
Perennial Forbs 0.0 0.0 0.9 0.6 0.3 0.2
Annual & Biennial Forbs 24.3 11.3 30.1 16.3 26.9 28.5
Noxious / Aggressive Weeds ------
Shrubs, Sub-shrubs, Cacti & Trees 5.1 9.1 0.8 0.5 0.1 0.9
Sample Adequacy Calculations:
Mean =74.3 51.7 37.9 20.5 36.5 46.2
Variance =99.0 214.8 40.4 54.6 108.6 62.0
n =15 15 15 15 15 15
nmin =3.2 14.6 5.1 23.4 14.7 5.3
* Indicates a seeded species on the Primary Test Section and Supplemental Test Section 1
N = Native, I = Introduced, P = Perennial, B = Biennial, A = Annual
Primary Test Section Supplemental Test
Section 2
Mean
Supplemental Test
Section 1
I

8

3.1 Primary Test Section

Spring 2023 Findings
The Primary Test Section was evaluated with 15 transects during the spring survey of the seventh
growing season. Table 2 displays all species observed in the Primary Test Section in 2023 including species
recorded by cover sampling metrics and incidental observations. Raw data from the spring 2023 cover
evaluation are presented in Appendix B. There was a total of 12 species observed, 2 of which were included
in the seed mix used on the plot. Total ground cover in the Primary Test Section consisted of 74.3% live
vegetation, 0.7% rock, 13.1% litter, and bare ground exposure of 11.9%. Perennial cover across the test
section averaged 48.8%, with annual and biennial cover averaging 25.5%. No noxious weeds were
observed. Below average precipitation and available water through the growing seasons of previous years
did not facilitate vegetation establishment or vigor in the Primary Test Section vegetation. However,
precipitation was well above average in Spring of 2023 contributing to increased plant cover. The only
overly dominant taxa (contributing greater than 40% relative cover) was squirreltail (Elymus elymoides)
averaging 43.7% cover. Tall tumblemustard (Sisymbrium altissimum), averaging 17.1% cover, and
100%
90%
80%
70%
... a, 60% > 0 u
"CJ
C 50% ::, e
1:1 .... 40% C a,
~ a, 30% Cl.
20%
10%
0%
Chart 2
White Mesa -Revegetation Monitoring
Average Ground Cover by Lifeform -2023
Spring Fall
Primary Test Section
□ Bare ground
■Rock
■ Litter (including p lant
senscence in fall)
■ Noxious / Aggressive
Weeds
□ Annual & Biennial
Forbs
□ Shrubs, Sub-shrubs,
Cacti & T rees
□ Perennial Forbs
■ Perennial Grasses
Spring Fall
Supplemental Test Section 1
Spring Fall
Supplemental Test Section 2

9

fourwing saltbush (Atriplex canescens), averaging 5.1% cover, were the only other Primary Test Section
species with greater than 4% cover in spring 2023.
The Primary Test Section had 22 fourwing saltbush plants present across the entire seeded area
(lysimeter and surrounding area), which equates to 96 woody plants per acre shown in Table 4 below. This
does not currently meet the success criteria of 500 woody plants per acre but has been generally increasing
with each growing season.

The following photos show the site conditions on the Primary Test Section during the spring 2022
evaluation compared with the spring 2023 evaluation.
Primary Test Section – Spring Survey –
June 7, 2022

Primary Test Section – Spring Survey –
May 31, 2023

Area ——>
Lifeform Scientific Name Common Name
Shrub Atriplex canescens Fourwing Saltbush 22
Woody Plants Per Acre 96
Primary Test Section
(0.23 acres)
Table 4 White Mesa - Woody Plant Density - 2023
Summary of Woody Plant Density - Spring Survey

10

Fall 2023 Findings
The Primary Test Section was also evaluated with 15 transects during the fall survey of the seventh
growing season. Table 2 displays all species observed in the Primary Test Section in 2023. Raw data from
the fall 2023 cover evaluation are presented in Appendix B. There was a total of 6 species observed, 2 of
which were included in the seed mix. Ground cover in the Primary Test Section consisted of 51.7% live
vegetation, 6.5% rock, 30.5% litter (including plant senescence in fall), and bare ground exposure of
11.4%. Perennial cover across the test section averaged 40.3%, with annual and biennial cover averaging
11.4%. No noxious weeds were observed. Dominant taxa were squirreltail averaging 31.1% cover, Russian
thistle (Salsola tragus) averaging 9.6% cover, and fourwing saltbush averaging 9.1% cover. These three
species were the only species that met the minimum relative cover criterion of 4%, but squirreltail
contributed to greater than 40% relative cover at 60.3%.
The following photos show the site conditions on the Primary Test Section during the fall 2022
evaluation compared with the fall 2023 evaluation.
Primary Test Section – Fall Survey –
September 12, 2022

Primary Test Section – Fall Survey –
September 6, 2023

14

Revegetation Performance Trend
Chart 3 displays the perennial and annual cover on the Primary Test Section during the spring survey
of the calibration period and year 1 through 4 of the performance period. The chart shows that perennial
cover steadily increased through 2020. Annual species cover was particularly elevated in 2019 due to
favorable precipitation conditions. After two spring growing seasons with below average precipitation in
2021 and 2022, perennial species cover was diminished in those years. However, favorable spring
precipitation in 2023 has caused a recovery of perennial cover for the year, which surpasses the SCA criteria
of 40% perennial cover.

100
80
Ii ~ 60 u
"Cl
§ e
~ I 40
~
20
0
Chart 3
White Mesa -Revegetation Monitoring
Primary Test Section Perennial / Annual Cover Trend (Spring Survey)
Yearl
{2018)
Year2
{2019)
Calibration, Period
Yearl
(2020)
Year2
{2021)
Year3
{2022)
Performanoe Period
Year 4
{2023)
□An nua l Sp eci es Cover
■ Perenn ial Spe ci es Co ve r
SCA Perfromance
Criteria = 40%
Year5
{2024)
2023
Native Ref
Area

15

3.2 Supplemental Test Section

Spring 2023 Findings
The Supplemental Test Section was evaluated with 15 transects during the spring survey of the
seventh growing season. Table 2 displays all species observed in the Supplemental Test Section in 2023.
Raw data from the spring 2023 cover evaluation are presented in Appendix B. There was a total of 16
species observed, 12 of which were captured by cover sampling metrics and 3 of which were included in
the seed mix. Ground cover in the Supplemental Test Section consisted of 37.9% live vegetation, 0% rock,
30.3% litter, and bare ground exposure of 31.8%. Perennial cover across the test section averaged 2.3%,
with annual and biennial cover averaging 35.6%. No noxious weeds were observed. The dominant taxa
were annual redstem stork’s bill (Erodium cicutarium), cheatgrass (Bromus tectorum), and Russian thistle,
with 25.5%, 5.4%, and 4.3% average cover, respectively. Redstem Stork’s Bill contributed greater than
40% relative cover at 67.1%. No seeded species met the minimum cover criterion of 4%.
The Supplemental Test Section had 41 snakeweed (Gutierrezia sarothrae) and 31 Pale Desert-Thorn
(Lycium pallidum) plants present across the entire seeded area, which equates to 314 woody plants per
acre shown in Table 5 below. This does not currently meet the success criteria of 500 woody plants per
acre but has been generally increasing with each growing season.

Table 5 White Mesa - Woody Plant Density - 2023
Summary of Woody Plant Density - Spring Survey
Area ——>
Lifeform Scientific Name Common Name
Subshrub Gutierrezia sarothrae Snakeweed 41
Shrub Lycium pallidum Pale Desert-Thorn 31
Woody Plants Per Acre 314
Supplemental Test
Section (0.23 acres)

16

The following photos show the site conditions on the Supplemental Test Section during the spring
2022 evaluation and spring 2023 evaluation.

Supplemental Test Section – Spring
Survey – June 7, 2022

Supplemental Test Section – Spring
Survey – May 31, 2023

Fall 2023 Findings
The Supplemental Test Section was evaluated with 15 transects during the fall survey of the seventh
growing season. Table 2 displays all species observed in the Supplemental Test Section in 2023. Raw data
from the fall 2023 cover evaluation are presented in Appendix B. There was a total of 9 species observed
in the Supplemental Test Section in the fall, 8 of which were captured by cover sampling metrics and 1 of
which was included in the seed mix. Ground cover in the Supplemental Test Section consisted of 20.5%
live vegetation, 2.4% rock, 49.2% litter, and bare ground exposure of 27.9%. Perennial cover across the
test section averaged 1.1%, with annual and biennial cover averaging 19.4%. No noxious weeds were
observed. The dominant taxon was Russian thistle, with 8.5% average cover, redstem stork’s bill with
7.1%, and cheatgrass with 3.2%. All other species had less than 1% average cover. No seeded species
met the minimum cover criterion of 4%, and Russian thistle contributed more than 40% relative cover at
41.6% relative cover.
The following photos show the site conditions on the Supplemental Test Section during the fall 2022
evaluation and fall 2023 evaluation.

N NE I E SE
330 0 30 60 90 120 15
•I• I• I• l •I• I• I• I• I• I• I• I• I• I• I• I• I• I• I

17

Supplemental Test Section – Fall Survey
– September 12, 2022

Supplemental Test Section – Fall Survey
– September 6, 2023

Revegetation Performance Trend
Chart 4 displays the perennial and annual cover of the revegetation on the Supplemental Test Section
during the spring survey of the calibration period and year 1 through 4 of the performance period. The
chart shows that perennial species cover has remained diminished, and cover of annual species dominates.
Annual cover was decreasing significantly each year until favorable precipitation in 2022 and 2023 caused
an increase in annual cover for these years.

100
80
...
~ 60
"0
C ::,
E
Ill
~ 40 .,
~ ., ...
20
0
Chart4
White Mesa -Revegetation Monitoring
Supplemental Test Section Perennial / Annual Cover Trend (Spring Survey)
Year 1
(2018)
70.5
Year 2
(2019)
Calibration Period
43.9
Year 1
(2020)
Year 2
(2021)
18.4
Year 3
(2022)
Performance Period
□ Annual Spec ies Cover
■ Perennial Spec ies Cover
35.6
Year4
(2023)
SCA Perfromance
Criteria = 400/o
Years
(2024)
2023
Native Ref
Area

18

3.3 Supplemental Test Section No. 2

Spring 2023 Findings
The Supplemental Test Section No. 2 was evaluated with 15 transects during the spring survey of the
third growing season. Raw data from the spring 2023 cover evaluation are presented in Appendix B. There
was a total of 14 species observed, 12 of which were captured by cover sampling metrics. Total ground
cover in the Supplemental Test Section No. 2 consisted of 36.5% live vegetation, 0.1% rock, 15.1% litter,
and bare ground exposure of 48.3%. Perennial cover across the Supplemental Test Section No. 2 averaged
9.1%, with annual and biennial cover averaging 27.4%. No noxious weeds were observed. The dominant
taxa were annual redstem stork’s bill, Russian thistle, and western wheatgrass (Pascopyrum smithii), with
17.7%, 4.9%, and 4.5% average cover, respectively. Redstem stork’s bill contributed to over 40% relative
cover at 48.5%. No seeded species met the minimum cover criterion of 4%. The diversity of species
observed is encouraging for eventual performance in favorable conditions.
The following photos show the site conditions on the Supplemental Test Section No. 2 during the spring
2022 evaluation and spring 2023 evaluation.

Supplemental Test Section No. 2 –
Spring Survey – June 7, 2022

Supplemental Test Section No. 2 –
Spring Survey – May 31, 2023

SE s I SW w
?0 15() 180 2 10 240 270 300
I • I• I • I • I• I • I • I• I • I • I • I • I • I • I • I• I • I • l •
0 215°SW (T) @37°33'4"N, 10 9°29'46"W ±19ft • 5691ft

19

Fall 2023 Findings
The Supplemental Test Section No. 2 was evaluated with 15 transects during the fall survey of the
third growing season. Raw data from the spring 2023 cover evaluation are presented in Appendix B. There
was a total of 15 species observed, all of which were captured by cover sampling metrics. Total ground
cover in the Supplemental Test Section No. 2 consisted of 46.2% live vegetation, 0% rock, 13.4% litter,
and bare ground exposure of 40.4%. Perennial cover across the Supplemental Test Section No. 2 averaged
17.7%, with annual and biennial cover averaging 28.5%. No noxious weeds were observed. The dominant
taxa were Russian thistle averaging 26.9% cover and thickspike wheatgrass (Elymus lanceolatus) averaging
8.7% cover. Russian thistle contributed greater than 40% relative cover at 58.2%. No seeded species met
the minimum cover criterion of 4%. The diversity of species observed is encouraging for eventual
performance in favorable conditions.
The following photos show the site conditions during the fall 2022 evaluation and fall 2023 evaluation.

Supplemental Test Section No. 2 – Fall
Survey – September 12, 2022

Supplemental Test Section No. 2 – Fall
Survey – September 6, 2023

20

3.4 Native Reference Area
Spring 2023 Findings
The Native Reference Area was evaluated with 10 transects during the spring survey. Raw data from
the spring 2023 cover evaluation are presented in Appendix B. There was a total of 13 species observed,
12 of which were captured by cover sampling metrics. Total ground cover in the Native Reference Area
consisted of 36.8% live vegetation, 0.1% rock, 27.2% litter, and bare ground exposure of 35.9%. Perennial
cover across the Native Reference Area averaged 24.7%, with annual and biennial cover averaging 12.1%.
No noxious weeds were observed. The reference area was only sampled in spring of 2023 to capture the
effects of growing season precipitation on the native vegetation.
The following photos show the site conditions during the spring 2022 evaluation and spring 2023 evaluation.
Native Reference Area – Spring Survey
– June 7, 2022

Native Reference Area – Spring Survey
– May 31, 2023

E ~ ~, ~ W
oo rn ~ • m m m
V NW N NE E
0 300 330 0 30 60 90
I• I • I• I• I• I • I • I • I• l •I• I• I • I• I • I • I• t •I• I • I• I• I • I • I• I• I• I· I• I• I • I • I• I • 1 •I • I• I •
0182°S (T) @37°32 '35"N, 109°29'51"W ±55ft • 5656ft 0 5°N (M) @37°32'33"N, 109°29'56"W ±14111 • 5666ft

21

4.0 PERFORMANCE EVALUATION
The revegetation performance criteria applicable to the Primary Test Section and Supplemental Test
Section are fully described in Section 2.0. As described in the SCA, success is not evaluated until the end
of the Performance Period. Therefore, this performance evaluation is only presented for discussion
purposes. The spring evaluations were selected for the performance evaluation because the test sections
are dominated by cool season species, which should be evaluated in the spring. Fall evaluations will
continue to be conducted based on the implication that precipitation events have a strong effect on the
establishment of revegetation. These effects are best monitored during the two seasons in which most of
the areas annual precipitation falls, which are spring and the fall monsoonal season. The results of the
performance evaluation are summarized in Table 6 below. In Year 4 (2023) of the performance period,
both the Primary and Supplemental Test Sections are not passing several of the success criteria. However,
further revegetation development is expected to occur throughout the performance period and future
monitoring efforts to track the trajectory of revegetation development will occur annually, in the spring and
fall, for the remainder of the performance period. The results from the native area sampling provide some
context to the revegetation performance. The poor precipitation conditions have also diminished perennial
communities in undisturbed areas, enough that even native ground could not pass several of the success
criteria.
At this point of the evaluation period, it is unlikely that the Primary and Supplemental sections will
meet performance criteria by the end of the final year of the Performance Period (year 5), primarily due to
the limited grass diversity on the Primary Test Section and the general poor performance of the
Supplemental Test Section. It is too early to determine how well Supplemental Test Section No. 2 will
progress, although it is exhibiting increased grass diversity. The Supplemental Test Section No. 2, which
EFRI constructed with a modified revegetation plan as noted above, is performing as expected through the
unfavorable (dry) precipitation year of 2022 and more favorable conditions in 2023. The diversity of species
observed at the Supplemental Test Section No. 2 is encouraging and indicates the potential for better
vegetation establishment and performance in favorable (wet) precipitation conditions for this test section.

22

Table 6 White Mesa -Success Evaluation -2023
Performance Comparison Spring survey
Primary Test Supplemental Supplemental
Section Test Section Test Section 2
1. Species Composition
a. 5 or gr ea t er per enn ial gr as s spec ies 1 1
4 or gr ea t er grass spec ies ar e nat iv e 1 1
b. At least 1 perenn ial fo rb 0 3
c. At least 2 shr ub spec ies 1 2
2. Vegeta tive cover
a. 4 0% or gr ea t er t ota l vege t at ive cov er* 74 .3% 37 .9%
b. Comprised of spec ie.s w ith r elat iv e co v er betwee n 4% and 40 %* 2 1
c. Fr ee of St at e and Co un ty li ste d noxi ous w ee ds None None
d. Se lf ge ner atin g and perm anent+ Observed Observed
3. Sh r ub Density
a. Minim um 500 ste m s per ac r e 96 314
b. Hea lth y, surived mi nim um 2 gro w ing seaso ns Observed Observed
"Spe o es hsted in Tabl e D.1 must be us ed to ach iev e the co ver perfo rman ce criteri a (M WH 201.5).
I ndividu al speci es not li sted in T able D. 1 may be acceptable if the sp eci es is nab v e or ada pted to the area and is a desirable compo nent
of th e red aimed proj ect site .
•self-fegenerabon sh all be demonstrated by evidence ofreproducbon, such as t il ers or see d producbon .
6
5
1
1
36 .5%
3
None
Observed
Not Sa mp led Yet
Not Samp led Yet

23

5.0 REFERENCES

MWH America’s, Inc. 2015. Updated Tailings Design Cover Report. Prepared for Energy Fuels Resources
(USA) Inc.

Appendix A

Vegetation Sampling Methodology

VEGETATION SAMPLING METHODOLOGY
Determination of Ground Cover
Ground cover at each sampling site was determined utilizing the point-intercept methodology as
illustrated on Figure 1, with the exception of the procedure for determining sample site location. Due to
the size of the test sections, sample points were instead determined in the field to preclude overlapping
transects. Cedar Creek utilizes state-of-the-art instrumentation that it has pioneered to facilitate much more
rapid and accurate collection of data. Implementation of the technique for the sampling effort occurred as
follows: First, a transect of 10 meters length was extended from the starting point of each sample site
toward the direction of the next site to be sampled. Then, at each one-meter interval along the transect, a
“laser point bar” was situated vertically above the ground surface, and a set of 10 readings were recorded
as to hits on vegetation (noted by species), plant, litter, rock (>2mm), or bare ground. Hits were determined
at each meter interval by activating a battery of 10 specialized lasers situated along the bar at 10-centimeter
intervals and recording the variable intercepted by each of the narrow (0.02”) focused beams (see Figure
1). In this manner, a total of 100 intercepts per transect were recorded resulting in 1 percent cover per
intercept. This methodology and instrumentation facilitate the collection of the most unbiased, repeatable,
precise, and cost-effective ground cover data possible. Furthermore, the point-intercept procedure has
been widely accepted in the scientific community as the protocol of choice for vegetation monitoring and
is used extensively within the mining industry in connection with bond release determinations.
Cedar Creek has noted that abundance of available water throughout the growing season can facilitate
above average vegetation growth and vigor. This can create an abnormally tall canopy of senesced
vegetation, that may obscure new growth in the following year, producing results that significantly
underestimate the true extent of live vegetative ground cover. In an effort to capture a more accurate
quantification of new growth, hits that would have been recorded on perennial live vegetative cover if not
for overlying litter can be recorded separately from both a species hit and litter in years where overlying
litter is extensive. These hits would be treated as live vegetative hits during data analysis and are counted
towards the cover success criteria.

Figure 1: Sampling Procedure

Ground Cover Transect
(Set-up points at 1-meter intervals)
\\lit,,,
~
Sample Site
(Starting Point)
' $ '$ $ / \\1/1✓,
\lit.,-\\lit t ~,.
,'W .,,~ \IUt.,,,-
\\111// .,, .,, .,, 9
.,,"' 8 .,,
"'1
\\llf# t laser I Point-Intercept Bar
{Intercepts at 10 cm intervals -
note path of" beams" for" hits"
on ground cover)
Note: 10 set-up points per
transect with 10 intercepts
per set-up point results in
100 intercepts per transect
Laser Bar
Laser
Focused Beam (0.02'' spot)
(Special ?. for Daylight Visibility) ~~--------(
Hit recorded as to item/species
~

Determination of Woody Plant Density
Woody plant density was evaluated during the spring evaluation of the Primary and Supplemental
Test Sections. Determination of woody plant density was completed using total enumeration to facilitate a
more accurate comparison of shrub survival between sampling years. Cedar Creek traversed the Test
Sections in a systematic manner while counting all shrubs encountered by species. These totals were used
to quantify woody plants per acre by species. Due to the relative stability in shrub populations lacking
significant disturbance, woody plant density only requires a single sampling each year and was conducted
during the spring 2023 evaluations.
Sample Adequacy Determination
Ground cover sampling was conducted to a minimum number of 15 samples. The procedure is such
that sampling continues until an adequate sample, nmin, has been collected in accordance with the Cochran
formula (below) for determining sample adequacy, whereby the population is estimated to be within 10%
of the true mean (µ) with 90% confidence. These limits facilitate a very strong estimate of the target
population.
When the inequality (nmin ≤ n) is true, sampling is adequate and nmin is determined as follows:
nmin = (t 2s 2) / (0.1 )2

where: n = the number of actual samples collected (initial size = 15)
t = the value from the one-tailed t distribution for 90% confidence with n-1
degrees of freedom;
s 2 = the variance of the estimate as calculated from the initial samples;
= the mean of the estimate as calculated from the initial samples.
As indicated above, this formula provides an estimate of the sample mean to within 10% of the true
population mean (µ) with 90% confidence. Calculations of the mean and variance are based on “total plant
cover” or total live vegetative cover.

x
x
- I

Appendix B

Raw Data

T a ble 18 White Mesa - V ea et atio n Co v e r -2023
Primary T est Secti on -Spring Surve y
Percen t Ground Cover Based on Point -I nt ercept Samphng
Tra nsect No.-> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Average Rela t ive
Cover Cover Freq.
Gra sses
I A Br omus tectorum Che atgrass 1 1 2 2 1 4 6 2 1.3 1.7 53
N p E/ymus e/ymoides Sou irre lt ail 32 42 37 42 32 63 28 65 73 64 35 50 33 38 21 4 3.7 58.7 100
Forbs
I A Er odium ci cutarium Redstem Stork's Bill 5 7 2 6 3 3 4 4 2 5 7 1 2 3.4 4 .6 87
I A Kochia s coparia Summer cypress 1 1 1 4 3 1 0.7 1.0 4 0
I B Lactua, serriola Prickly Lettuce 1 2 0.2 0.3 13
I A Sa/so/a tragus Ru ssian Th istle 3 5 2 2 8 6 5 1 4 6 2.8 3.8 67
I A Sisvmbrium altissimum Tall Tumblemustard 33 14 3 12 22 24 17 10 15 8 22 21 15 22 19 17.1 23.0 100
Shrubs, Sub-shrubs, cacti & Trees
N p A trip/ex a,n escen s Fou rwinQ Saltbu ,sh 10 8 8 15 8 6 22 5.1 6.9 4 7
Mean
Tot al Plan t Cove r 75 64 59 62 70 90 67 79 90 88 8 1 79 70 69 72 7 4 .3
Rock 1 0 0 0 0 0 5 0 0 0 1 0 3 0 0 0.7
Litte r 19 25 18 18 23 5 15 9 8 5 3 4 1 31 12 13.1
Bare qround 5 11 23 20 7 5 13 12 2 7 15 17 26 0 16 11.9
Perennial Plan t Cover 32 4 2 4 7 , 4 2 4 0 63 36 65 73 64 50 , 50 41 44 4 3 4 8.8
Sample Adequacy Calcula tions: Plant Cover Mean = 7 4.33 t= 1.35 n = 15
Variance = 98.95 Omin = 3.24
N = Native, I = Introduced, P = Perenni al, B = Bienni al, A = Annu al

T a ble 2 B White Mesa • V ea et atio n Co v e r -2023
Prim ary T est Secti on -Fa ll Survey
Percen t Ground Cover Based on Point -I nt ercept Samphng
Tra nsect No.-> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Averag e Rela t ive
Cove r Cove r Fr eq.
Gra sses
I A Bromus tectorum Che atgrass 2 0.1 0.3 7
N p E/ymu s e/ymoides Sou irreltail 34 43 46 42 31 19 27 35 21 22 17 30 25 29 46 3 1.1 60.3 100
For bs
I A Kochia scoparia Summer cypress 4 1 4 1 3 3 1.1 2.1 4 0
I A Sa/so/a tragus Ru ssian Thistle 1 3 7 1 17 5 2 2 20 13 30 30 13 9.6 18.6 87
I A Sisvmbrium altissimum Tall Tumblemustard 2 3 3 1 0.6 1.2 27
Sh rubs, Sub-sh rubs, cacti & Tr ees
N p Atriolex canescens Fou rwina Sa ltbu sh 19 15 10 40 4 34 15 9.1 17.7 4 7
Mean
Tot al Plan t Cov e r 58 4 6 54 4 3 67 26 29 48 64 28 72 63 56 59 62 5 1.7
Rock 2 6 0 0 0 22 9 34 7 10 1 1 1 3 1 6.5
Litte r 29 36 38 43 32 37 55 8 26 45 9 21 24 20 34 30.5
Ba re Qround 11 12 8 14 1 1:; 7 10 3 17 18 1:; 19 18 3 11.4
Per ennial Plan t Cov e rr 53 , 43 , 46 , 42 , 46 19 , 27 45 6 1 • 26 r 5 1 45 , 25 , 29 , 46 4 0.3
Sample Adequacy Ca lculations: Plan t Cover Mean = 51.67 t= 1.35 n = 15
Var iance = 214.81 nm;n = 14.56
N = Native, I = Introduce d, P = Perennia l, 8 = Biennia l, A = Annua l

T a bl e 3 B White Mesa -V ea et atio n Cove r -2023
Supplem ental T est Secti on 1 -Spring Survey
Percen t Ground Cover Based on Point -I nt ercept Samphng
Transect No.-> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Average Rela t ive
Gra sses Cover Cov er Freq.
I A Bromus tectorum Cheatgr ass 2 1 4 2 5 10 9 24 16 3 5 5.4 14.2 73
N p Pascopyrum smithii Western Wheatgr ass 1 1 6 2 0.7 1.8 27
N A Vuloia octoflora Six Wee ks Fescue 1 1 0.1 0.4 13
Forbs
N p Achi/lea millefolium Co mmon Yarrow 1 0.1 0.2 7
N p Artemisia ludovi ciana White Sage brush 2 1 0.2 0.5 13
I A Erodium cicutarium Redstem Stor k's Bill 23 32 33 41 36 17 26 31 30 11 14 9 21 33 25 25.5 67.1 100
N B Grindelia squarrosa Curly cup Gumw ee d 1 0.1 0.2 7
I A Sa/so/a tragus Ru ssian Thistle 2 2 0.3 0.7 13
I A Sisymbrium altissimum T all Tumblemustard 20 9 1 1 1 1 9 3 1 6 6 2 1 3 4 .3 11.2 93
N p Soh aer al cea cocdnea Scar let Globem all ow 2 2 2 3 0.6 1.6 27
Shrubs, Sub-shrubs, cacti & Trees
N p Gutierrezia sarothrae Broo m Snakew ee d 2 5 0.5 1.2 13
N p Lydum oallidum Pale Desert-th orn 2 1 2 0.3 0.9 20
Mean
Tot al Plan t Cover 4 7 4 2 39 4 6 4 0 27 3 1 4 0 38 25 36 4 5 39 37 37 37.9
Rock 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.0
Litter 23 24 30 41 31 32 29 12 20 53 39 51 25 19 25 30.3
Bare qround 30 34 31 13 29 41 40 48 42 22 25 4 36 44 38 3 1.8
Perennial Plan t Cov err 2 1 , 4 , 2 , 1 5 , 2 0 ·o ·3 r 6 ·6 , 0 , 0 , 3 2.3
Sample Adequacy Calcula tions: Plan t Cover Mean = 37.93 t= 1.35 n = 15
Variance = 4 0.35 Omin = 5.07
N = Nativ e, I = Introduce d, P = Pe r ennial, B = Biennial, A = Annual

T a bl e 4B White Mesa -V eget atio n Cove r -2023
Supplem ental T est Secti on 1 -Fa ll Survey
Percen t Ground Cover Based on Poin t -I n t ercept Samphng
Tra nsect No.-> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 A verage Rela t ive
Cover Cover Freq.
Gra sses
I A Bromus tectorum Chea tar ass 10 4 7 5 6 2 3 2 3 2 2 2 3.2 15.6 80
Forbs
N p Achi/lea millefolium Co mmon Yarrow 1 0.1 0.3 7
N A Descurainia pinnata Western T ansymustard 2 2 1 2 1 1 1 0.7 3.2 4 7
I A Erodium dcutarium Redstem St or k's Bill 12 7 14 19 16 3 6 3 5 5 7 2 3 2 2 7.1 34.4 100
N p Machaeranthera a,n escen s Hoary T ansyaster 1 0.1 0.3 7
I A Sa/so/a tragus Ru ssian Thistle 7 14 10 14 12 13 10 9 5 13 10 3 4 4 8.5 41.6 93
N p Sohaeralcea coccjnea Scar let Globem allow 1 5 1 0.5 2.3 20
Shrubs, Sub-shrubs, cacti & Trees
N p Gutierrezia sarothrae Br oo m Snakew ee d 1 6 0.5 2.3 13
Mean
Tot al Plan t Cov er 30 25 3 1 19 30 20 27 17 18 12 25 2 1 10 8 15 20.5
Rock 1 3 3 4 7 7 0 2 2 0 0 0 1 2 4 2.4
Litter 30 34 38 59 50 45 55 52 50 58 46 48 59 6 1 53 4 9.2
Bare around 39 38 28 is. 13 28 18 29 30 30 29 3 1 30 29 28 27.9
Perennial Plan t Cover r 1 • 0 • 0 0 • o r o • 0 • 0 ·o ·o r o ·1 .. 1 .. 1 ,, 6 1.1
Sample Adequacy Calculations: Plant Cov er Mean = 20.53 t= 1.35 n = 15
Variance = 54.55 nm;n = 23.41
N = Nativ e, I = Intr od uced , P = Pe r enn ial, B = Bienn ial, A = A nnual

T a bl e SB White Mesa - V eget atio n Co ve r -2023
Supplem ental T est Section 2 -Spring Survey
Percen t Ground Cover Based on Point -I nt ercept Samphng
Tra nsect No.-> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 A v erage Rela t ive
Cover Cov er Freq.
Gra sses
N p Bouteloua grad/is Blue Gram a 1 1 1 1 0.3 0.7 27
I A Bromus tectorum Che atgrass 3 2 1 1 1 0.5 1.5 33
N p Elymus l anceol atus Thickspike Wheatgrass 1 1 0.1 0.4 13
N p Hilaria Jamesii Ja mes' Gall eta 1 1 4 2 1 1 2 1 3 1 4 1 1.5 4.0 80
N p Pascopyrum smithii Western Wheatgrass 4 7 8 6 5 5 2 8 4 5 2 3 6 2 4.5 12.2 93
N p Pseudoroegneria spiecta spiecta Bluebunch Wheatgrass 1 1 3 4 1 1 5 2 1 4 1.5 4.2 67
I p Thinoo vrum intermedium Intermediate Wheatar ass 1 4 3 2 1 1 0.8 2.2 40
Forbs
1 A Erodtum Clcurartum Redstem Stork's BIii 20 17 15 26 13 13 13 26 15 20 18 9 12 34 15 17.7 48.5 100
I A Sa/so/a tragus Russian T histle 1 8 8 3 2 2 4 1 10 7 8 2 12 5 4.9 13.3 93
I A Sisymbrium altissimum Tall T umblemustar d 2 4 7 8 4 4 2 6 1 1 10 6 2 4 4 4.3 11.9 100
N p Sohaer alcea coccinea Scar let Globemallow 1 3 0.3 0.7 13
Shrubs, Sub-shrubs, cact i & Trees
N p Gutierrezia sarothrae Broom Sn akew ee d 1 1 0.1 0.4 13
Mean
Tot a l Plan t Cover 30 38 4 6 5 1 27 28 2 1 4 9 3 1 41 42 29 29 56 3 0 36.5
Rock 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0.1
Litter 20 10 17 12 25 31 20 10 15 10 9 13 12 8 14 15.1
Bare around 50 52 37 37 48 41 59 41 54 49 49 58 59 36 55 48.3
Perennial Plan t Coverr 7 • 9 • 13 • 12 10 r 8 3 '13 '14 9 r 1 • 6 '13 6 6 9.1
Sample Adequacy Calculati ons: Plan t Cover Mean = 36.53 t = 1.35 n = 15
Variance = 108.55 nm;n = 14.71
N = Nativ e, I = I ntroduce d, P = Perenn ial, B = Bienn ial, A = Annual

Table 6B White Mesa -Veaetation Cover -2023
Supplemental Test Section 2 -Fall Survey
Percen t Ground Cover Based on Point -I nt ercept Samphng
Transect No.-> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Average Rela t ive
Cover Cover Freq.
Grasses
N p Bouteloua gr ad/is Blue Gr am a 1 1 0.1 0.3 13
N p Elymus l anceol atus Thickspike Whea tgr ass 17 5 3 7 14 4 6 12 9 15 5 8 7 12 6 8.7 18.8 100
N p Elymus trachycau/us Slend er Whea tgr ass 2 3 13 5 2 1 3 1 2 7 2 4 3.0 6.5 80
N p Hilari a Jamesii Jam es' Gall et a b 7 1 1 1 3 1 7 1 1.9 4.0 60
N p Pascopyrum smithii Western Whea tgr ass 4 3 2 0.6 1.3 20
N p Pseudoroegneri a spi cata spi cata Bluebun ch Whea tgr ass 4 3 1 6 6 2 1 1.5 3.3 47
N p Soorobolus oiroides A lkali Sacaton l 1 1 1 5 2 1 0.8 1.7 47
Forbs
N p Dalea sp. Pr air ie Clov er 1 0.1 0.1 7
I A Erodium cicutarium Redste m Stork's Bill 3 7 5 3 5 1.5 3.3 33
N p Linum l ewisii Lew is Fla~ 1 0.1 0.1 7
N p Machaeranthera canescens Hoa ry T ansyaster 1 0.1 0.1 7
I A Sa/so/a tragus Ru ssian Thistle 3 1 20 29 22 34 23 52 24 41 33 28 11 18 13 24 26.9 58.2 100
I A Sisvmbrium altissimum T all Tumblemustard 1 1 0.1 0.3 13
Shrubs, Sub-shrubs, cact i & Trees
N p Atriplex canescens Fo urwing Saltbu sh 3 0.2 0.4 7
N p Gutierrezia sarothrae Br oo m Snakew ee d l 2 4 3 0.7 1.4 27
Mean
Tot a l Plan t Cover 4 8 39 4 6 4 7 55 37 66 47 5 3 50 46 4 2 37 4 3 37 4 6.2
Rock 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 .0
Litter 19 12 9 20 10 14 10 9 11 9 17 14 19 15 13 13.4
Bar~ u ruu m.1 33 49 4 5 33 3 5 4 9 2 4 44 36 41 37 44 44 4 2 so 40.4
Perennial Plan t Coverr 17 • 19 • 17 • 2 5 • 2 1 r 11 • 14 • 22 • 12 • 17 r 11 • 2 5 • 16 • 2 5 • 13 17.7
Sample Adequa cy Calculations: Plant Cover Mean = 46.20 t= 1.35 n = 15
Variance = 62.0 3 Omin = 5 .26
N = Nativ e, I = Introduced, P = Pe r enn ial, B = Bienn ial, A = Annu al

Table 78 White Mesa -Vegetation Cove r -2023
Native -Spring Survey
Percen t Ground Cover Based on Point -I nt ercept Samphng
Transect No.-> 1 2 3 4 5 6 7 8 9 10 Average Rela t ive Freq.
Grasses Cover Cover
N A Vu/pia octoflor a Six Wee ks Fescue 1 2 1 1 3 0 .8 2.2 50
Forbs
N A Cordyl an thus r am osus Bushy Bird 's Bea k 3 1 0 .4 1.1 20
N A Descur ainiil pinnata Weste rn T ansymu sta rd 4 0 .4 1.1 10
I A Descur ainiil sophia Flixwee d 1 0 .1 0 .3 10
I A Erodium dcutarium Redste m Stork's Bill ni 12 3 6 7 4 7 15 12 4 8.1 22.0 100
N p Lupinus prunophilus Robinso n's Lup ine 1 0 .1 0 .3 10
N p Machaeranthera a,n escen s Hoa ry T ansyaste r 1 0 .1 0 .3 10
I A Sa/so/a tragus Ru ssian Th istle .2 1 5 2 1 1 1 1.3 3.5 7 0
I A Sisymbrium a/tissjmum T all Tumb lemu sta rd .2 2 4 1 1 1.0 2.7 50
N p Sph aer al cea cocdnea Scarlet Globemall ow 1 1 0 .2 0 .5 2 0
Shru bs, Su b-shrubs, cacti & Trees
N p Artemisja tri dentata Big Sage bru sh H 1 4 5 16 15 18 6 12 15 10.6 2 8 .8 100
N p Gutierrezia Silrothrae Br oo m Snakew ee d 5 17 21 15 11 24 7 8 10 19 13.7 50.4 100
Mean
Tot a l Plan t Cover 3 4 33 34 29 41 50 3 5 32 37 4 3 36.8
Rock ,o 0 0 0 0 1 0 0 0 0 0 .1
Litter 3 5 43 24 29 26 18 33 17 24 23 27.2
Ba re a round 3 1 24 42 42 33 31 32 5 1 39 34 3 5.9
Perennial Plan t Coverr 19 • 18 • 26 • 2 0 28 r 40 • 26 • 14 • 22 • 34 2 4.7
Sample Adequa cy Calculations: Plan t Cover Mean = 36.80 t= 1.38 n = 10
Variance = 3 8.62 Omi n = 5.4 6
N = Native, I = Introdu ced, P = Pe renni al, B = Bienni al, A = Annu al
White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual Performance Monitoring Report
Project Number: 182924510 (formerly 233001001)
Appendix C Cell 2 Settlement Monitoring Data
IJ
5612
5614
5616
5618
5620
5622
5624
5626
5628
5630
5632
Dec-88 Dec-91 Dec-94 Dec-97 Dec-00 Dec-03 Dec-06 Dec-09 Dec-12 Dec-15 Dec-18 Dec-21 Dec-24
El
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,

f
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t

m
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Figure C.1
White Mesa Mill
Cell 2W 1 Settlement Plate Measurements
(1)
(1)
Note:  (1) Settlement plate extended during Phase 1 cover construction.  
I
'"'•
--
'I -
i
5612
5614
5616
5618
5620
5622
5624
5626
5628
5630
5632
Dec-88 Dec-91 Dec-94 Dec-97 Dec-00 Dec-03 Dec-06 Dec-09 Dec-12 Dec-15 Dec-18 Dec-21 Dec-24
El
e
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a
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i
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n
,

f
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t

m
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Figure C.2
White Mesa Mill
Cell 2W2 Settlement Plate Measurements
(1)
Note:  (1) Settlement plate extended during Phase 1 cover construction.  
I
,. ,.. --• I -
iii
II
5612
5614
5616
5618
5620
5622
5624
5626
5628
5630
5632
Dec-88 Dec-91 Dec-94 Dec-97 Dec-00 Dec-03 Dec-06 Dec-09 Dec-12 Dec-15 Dec-18 Dec-21 Dec-24
El
e
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a
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i
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n
,

f
e
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t

m
s
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Figure C.3
White Mesa Mill
Cell 2W3 Settlement Plate Measurements
(1)
(1)
Note:  (1) Settlement plate extended during Phase 1 cover construction.  
I
·--
..
II ,. ,_
-T .,_ -l • J~
5612
5614
5616
5618
5620
5622
5624
5626
5628
5630
5632
Dec-88 Dec-91 Dec-94 Dec-97 Dec-00 Dec-03 Dec-06 Dec-09 Dec-12 Dec-15 Dec-18 Dec-21 Dec-24
El
e
v
a
t
i
o
n
,

f
e
e
t

m
s
l
Figure C.4
White Mesa Mill
Cell 2W4 Settlement Plate Measurements
(1)
(1)
Note:  (1) Settlement plate extended during Phase 1 cover construction.  
I
I I
... ----l -----T'
5612
5614
5616
5618
5620
5622
5624
5626
5628
5630
5632
Dec-88 Dec-91 Dec-94 Dec-97 Dec-00 Dec-03 Dec-06 Dec-09 Dec-12 Dec-15 Dec-18 Dec-21 Dec-24
El
e
v
a
t
i
o
n
,

f
e
e
t

m
s
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Figure C.5
White Mesa Mill
Cell 2E1 Settlement Plate Measurements
(1)
(1)
Note:  (1) Settlement plate extended during Phase 1 cover construction.  
I
•"' I
-J --'
5612
5614
5616
5618
5620
5622
5624
5626
5628
5630
5632
Dec-88 Dec-91 Dec-94 Dec-97 Dec-00 Dec-03 Dec-06 Dec-09 Dec-12 Dec-15 Dec-18 Dec-21 Dec-24
El
e
v
a
t
i
o
n
,

f
e
e
t

m
s
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Figure C.6
White Mesa Mill
Cell 2E1-N Settlement Plate Measurements
(1)
Note:  (1) Settlement plate extended during Phase 1 cover construction.  
I
--• '
5612
5614
5616
5618
5620
5622
5624
5626
5628
5630
5632
Dec-88 Dec-91 Dec-94 Dec-97 Dec-00 Dec-03 Dec-06 Dec-09 Dec-12 Dec-15 Dec-18 Dec-21 Dec-24
El
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a
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i
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n
,

f
e
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t

m
s
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Figure C.7
White Mesa Mill
Cell 2E1-1S Settlement Plate Measurements
(1)
(1)
Note:  (1) Settlement plate extended during Phase 1 cover construction.  
I
~
I •
-
' Iii -
5612
5614
5616
5618
5620
5622
5624
5626
5628
5630
5632
Dec-88 Dec-91 Dec-94 Dec-97 Dec-00 Dec-03 Dec-06 Dec-09 Dec-12 Dec-15 Dec-18 Dec-21 Dec-24
El
e
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a
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i
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n
,

f
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t

m
s
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Figure C.8
White Mesa Mill
Cell 2E1-2S Settlement Plate Measurements
(1)
(1)
(1)
Note:  (1) Settlement plate extended during Phase 1 cover construction.  
I
I ..._
II
II
I ,.
I'
,_
5612
5614
5616
5618
5620
5622
5624
5626
5628
5630
5632
Dec-88 Dec-91 Dec-94 Dec-97 Dec-00 Dec-03 Dec-06 Dec-09 Dec-12 Dec-15 Dec-18 Dec-21 Dec-24
El
e
v
a
t
i
o
n
,

f
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t

m
s
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Figure C.9
White Mesa Mill
Cell 2W7-C Settlement Plate Measurements
Note:  (1) Settlement plate had three feet of rod extended October 2014
month because interim cover was added in this area of Cell 2 
(1)
I
--
-..
'
5612
5614
5616
5618
5620
5622
5624
5626
5628
5630
5632
Dec-88 Dec-91 Dec-94 Dec-97 Dec-00 Dec-03 Dec-06 Dec-09 Dec-12 Dec-15 Dec-18 Dec-21 Dec-24
El
e
v
a
t
i
o
n
,

f
e
e
t

m
s
l
Figure C.10
White Mesa Mill
Cell 2W5-N Settlement Plate Measurements
(1)
(1)
Note:  (1) Settlement plate extended during Phase 1 cover construction.  
I
I I
-... • ii .lL. -
5612
5614
5616
5618
5620
5622
5624
5626
5628
5630
5632
Dec-88 Dec-91 Dec-94 Dec-97 Dec-00 Dec-03 Dec-06 Dec-09 Dec-12 Dec-15 Dec-18 Dec-21 Dec-24
El
e
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a
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i
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n
,

f
e
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t

m
s
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Figure C.11
White Mesa Mill
Cell 2W3-S Settlement Plate Measurements
(1)
(1)
Note:  (1) Settlement plate extended during Phase 1 cover construction.  
I
, ...
I I
-
IL.
.l
-----•
5612
5614
5616
5618
5620
5622
5624
5626
5628
5630
5632
Dec-88 Dec-91 Dec-94 Dec-97 Dec-00 Dec-03 Dec-06 Dec-09 Dec-12 Dec-15 Dec-18 Dec-21 Dec-24
El
e
v
a
t
i
o
n
,

f
e
e
t

m
s
l
Figure C.12
White Mesa Mill
Cell 2W5-S Settlement Plate Measurements
(1)
(1)
Note:  (1) Settlement plate extended during Phase 1 cover construction.  
I
I ll..
I I
1i
-
--T
5612
5614
5616
5618
5620
5622
5624
5626
5628
5630
5632
Dec-88 Dec-91 Dec-94 Dec-97 Dec-00 Dec-03 Dec-06 Dec-09 Dec-12 Dec-15 Dec-18 Dec-21 Dec-24
El
e
v
a
t
i
o
n
,

f
e
e
t

m
s
l
Figure C.13
White Mesa Mill
Cell 2W7-N Settlement Plate Measurements
(2)
Notes:  (1) Settlement plate had three feet of rod extended in October 2014 
because interim cover was added in this area of Cell 2 
(2)Settlement plate extended  during phase 1 cover construction
(1)
I
••
I
;p ~
5612
5614
5616
5618
5620
5622
5624
5626
5628
5630
5632
Dec-88 Dec-91 Dec-94 Dec-97 Dec-00 Dec-03 Dec-06 Dec-09 Dec-12 Dec-15 Dec-18 Dec-21 Dec-24
El
e
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a
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i
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n
,

f
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m
s
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Figure C.14
White Mesa Mill
Cell 2W7-S Settlement Plate Measurements
(1)
(1)
Note:  (1) Settlement plate extended during Phase 1 cover construction.  
I
--
Ill
• -
■-
5612
5614
5616
5618
5620
5622
5624
5626
5628
5630
5632
Dec-88 Dec-91 Dec-94 Dec-97 Dec-00 Dec-03 Dec-06 Dec-09 Dec-12 Dec-15 Dec-18 Dec-21 Dec-24
El
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a
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i
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n
,

f
e
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m
s
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Figure C.15
White Mesa Mill
Cell 2W6-N Settlement Plate Measurements
(1)
(1)
Note:  (1) Settlement plate extended during Phase 1 cover construction.  
I
-
I -
~
5612
5614
5616
5618
5620
5622
5624
5626
5628
5630
5632
Dec-88 Dec-91 Dec-94 Dec-97 Dec-00 Dec-03 Dec-06 Dec-09 Dec-12 Dec-15 Dec-18 Dec-21 Dec-24
El
e
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a
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i
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n
,

f
e
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m
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Figure C.16
White Mesa Mill
Cell 2W6-C Settlement Plate Measurements
(1)
(1)
Note:  (1) Settlement plate extended during Phase 1 cover construction.  
I
-
I •
I
----
■
5612
5614
5616
5618
5620
5622
5624
5626
5628
5630
5632
Dec-88 Dec-91 Dec-94 Dec-97 Dec-00 Dec-03 Dec-06 Dec-09 Dec-12 Dec-15 Dec-18 Dec-21 Dec-24
El
e
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a
t
i
o
n
,

f
e
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t

m
s
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Figure C.17
White Mesa Mill
Cell 2W6-S Settlement Plate
(1)
Note:  (1) Settlement plate extended during Phase 1 cover construction.  
I
'r ii
-
----
5612
5614
5616
5618
5620
5622
5624
5626
5628
5630
5632
Dec-88 Dec-91 Dec-94 Dec-97 Dec-00 Dec-03 Dec-06 Dec-09 Dec-12 Dec-15 Dec-18 Dec-21 Dec-24
El
e
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a
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i
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n
,

f
e
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m
s
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Figure C.18
White Mesa Mill
Cell 2W5-C Settlement Plate
(1)
(1)
Note:  (1) Settlement plate extended during Phase 1 cover construction.  
I
-
I •
--
i
5612
5614
5616
5618
5620
5622
5624
5626
5628
5630
5632
Dec-88 Dec-91 Dec-94 Dec-97 Dec-00 Dec-03 Dec-06 Dec-09 Dec-12 Dec-15 Dec-18 Dec-21 Dec-24
El
e
v
a
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i
o
n
,

f
e
e
t

m
s
l
Figure C.19
White Mesa Mill
Cell 2W4-N Settlement Plate
(1)
(1)
Note:  (1) Settlement plate extended during Phase 1 cover construction.  
I
I I
-
i 1
5612
5614
5616
5618
5620
5622
5624
5626
5628
5630
5632
Dec-88 Dec-91 Dec-94 Dec-97 Dec-00 Dec-03 Dec-06 Dec-09 Dec-12 Dec-15 Dec-18 Dec-21 Dec-24
El
e
v
a
t
i
o
n
,

f
e
e
t

m
s
l
Figure C.20
White Mesa Mill
Cell 2W4-S Settlement Plate Measurements
(1)
(1)
Note:  (1) Settlement plate extended during Phase 1 cover construction.  
I
...
I •
-,.
II
White Mesa Uranium Mill Cell 2 Reclamation Cover 2023 Annual Performance Monitoring Report
Project Number: 182924510 (formerly 233001001)
Appendix D Cell 2 Standpipe Piezometer Water Levels
IJ
 5,590
 5,595
 5,600
 5,605
 5,610
 5,615
Jun‐16 Dec‐16 Jun‐17 Dec‐17 Jun‐18 Dec‐18 Jun‐19 Dec‐19 Jun‐20 Dec‐20 Jun‐21 Dec‐21 Jun‐22 Dec‐22 Jun‐23 Dec‐23
Wa
t
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 Le
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 El
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 (f
t
)
Date
Figure D.1 ‐ Cell 2 Standpipe Piezometers
Water  Level Elevations
C2‐P01 C2‐P02 C2‐P03 C2‐P04 C2‐P05 C2‐P06 C2‐P07 C2‐P08
C2‐P09 C2‐P10 C2‐P11 C2‐P12 C2‐P13 C2‐P14 C2‐P15 C2‐P16
C2‐P17 C2‐P18 C2‐P19 C2‐P20 C2‐P21 C2‐P22 C2‐P23
Notes:
1. Pieozometer C2‐P01 reading for Mar 20, 2019 was erroneous due to 
an issue with the water level meter.
2. Piezometer C2‐P10 was hit by a vehicle on September 1, 2022.  Soil 
fell in the casing and the water level increased by about 2 feet.  
(1)
(2)
--+---
 5,590
 5,595
 5,600
 5,605
 5,610
 5,615
Jun‐16 Dec‐16 Jun‐17 Dec‐17 Jun‐18 Dec‐18 Jun‐19 Dec‐19 Jun‐20 Dec‐20 Jun‐21 Dec‐21 Jun‐22 Dec‐22 Jun‐23 Dec‐23
Wa
t
e
r
 Le
v
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 El
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v
a
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i
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n
 (f
t
)
Date
Figure D.2 ‐ Cell 2 Standpipe Piezometers Water  
Level Elevations
West  Side of Cell (excluding locations near sump)
C2‐P01 C2‐P02 C2‐P03 C2‐P04
C2‐P05 C2‐P06 C2‐P07 C2‐P08
(1)
Note: 
1.Pieozometer C2‐P01 reading for March 20,
2019 was erroneous due to an issue with the
water level meter
---+-_._
 5,590
 5,595
 5,600
 5,605
 5,610
 5,615
Jun‐16 Dec‐16 Jun‐17 Dec‐17 Jun‐18 Dec‐18 Jun‐19 Dec‐19 Jun‐20 Dec‐20 Jun‐21 Dec‐21 Jun‐22 Dec‐22 Jun‐23 Dec‐23
Wa
t
e
r
 Le
v
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 El
e
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a
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i
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n
 (f
t
)
Date
Figure D.3 ‐ Cell 2 Standpipe Piezometers
Water  Level Elevations
Locations Near Sump
C2‐P09 C2‐P10 C2‐P11 C2‐P12
C2‐P14 C2‐P15 C2‐P16
Note:
1.Piezometer C2‐P10 was hit by a vehicle on September 1, 
2022.  Soil fell in the casing and the water level increased 
by about 2 feet.  
(1)
--+-
 5,590
 5,595
 5,600
 5,605
 5,610
 5,615
Jun‐16 Dec‐16 Jun‐17 Dec‐17 Jun‐18 Dec‐18 Jun‐19 Dec‐19 Jun‐20 Dec‐20 Jun‐21 Dec‐21 Jun‐22 Dec‐22 Jun‐23 Dec‐23
Wa
t
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r
 Le
v
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 El
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a
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i
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 (f
t
)
Date
Figure D.4 ‐ Cell 2 Standpipe Piezometers Water  
Level Elevations
East Side of Cell (excluding locations near sump)
C2‐P13 C2‐P17 C2‐P18 C2‐P19
C2‐P20 C2‐P21 C2‐P22 C2‐P23