HomeMy WebLinkAboutDRC-2023-001936 - 0901a0688119eaee/ii,;�
�'f;NERGYFUELS
February 24, 2023
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
[nerg) Fuels Resources (USA) Inc. 225 Union Blvd. Suite 600 Lakenood, CO, US, 80228
303 974 2140
www.energyfuels.com
Re: Transmittal of White Mesa Uranium Mill Cell 2 Reclamation Cover 2022 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 l 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 2022 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 Weinel Director, Regulatory Compliance
CC: Jordan App Dav id F rydenl und Garrin Palmer Logan Shumway Scott Bakken John Uhrie
DRC-2023-001936
Div of Waste Management
and Radiation Control
MAR 02 2023
?1!);~
C:'T:NERGYFUELS
February 24, 2023
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 .energy fuels .corn
Re: Transmittal of White Mesa Uranium Mill Cell 2 Reclamation Cover 2022 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 201 7, constructed a supplement vegetation monitoring
test section ("Supplemental Test Section") in 2017, and initiated performance monitoring. This letter transmits
the 2022 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 Weinel
Director, Regulatory Compliance
CC: Jordan App
David Frydenlund
Garrin Palmer
Logan Shumway
Scott Bakken
John Uhrie
White Mesa Uranium Mill Cell 2 Reclamation Cover 2022 Annual Performance Monitoring Report
February 24, 2023
Prepared for: Energy Fuels Resources (USA) Inc. Prepared by: Stantec Consulting Services Inc.
~ Stantec
Document Review and Revision Record
Rev. Description Author(s) Quality Check Independent Review
0 Draft for client review C. Romano, S. Regis
1.26.2023 M. Davis 2.17.2023 C. Strachan 02.22.2023
1 Final for client M. Davis 2.24.2023
WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2022 ANNUAL PERFORMANCE MONITORING REPORT
Table of Contents
1.0 INTRODUCTION .......................................................................................................... 1.1
1.1 BACKGROUND ............................................................................................................ 1.1
1.2 MONITORING REQUIREMENTS ................................................................................. 1.1
1.3 REPORT ORGANIZATION .......................................................................................... 1.2
2.0 COVER AND TEST SECTION DESIGNS .................................................................... 2.1
3.0 PRIMARY TEST SECTION HYDROLOGIC MONITORING ......................................... 3.1
4.0 PRIMARY AND SUPPLEMENTAL TEST SECTIONS VEGETATION
INSPECTION ............................................................................................................... 4.1
5.0 CELL 2 SETTLEMENT AND WATER LEVEL MONITORING...................................... 5.1
5.1 SETTLEMENT MONUMENTS...................................................................................... 5.1
5.2 PIEZOMETERS ............................................................................................................ 5.2
6.0 CONCLUSIONS ........................................................................................................... 6.1
7.0 REFERENCES ............................................................................................................. 7.1
LIST OF TABLES
Table 1 Primary Test Section Water Balance for 2016 – 2022
Table 2 Cell 2 Top Surface Settlement Measured Between April 2016 and December 2022 Table 3 Piezometer Water Level Elevations During and After Phase 1 Cover Placement
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 2022 Field Hydrology Of The Cell 2 Primary Test Section At The White Mesa Mill Appendix B 2022 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 2022 ANNUAL PERFORMANCE MONITORING REPORT
1.1
1.0 INTRODUCTION
This report documents the 2022 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 and the Supplemental Test Section are required to be monitored for vegetation performance and the Primary Test Section is required to be monitored for percolation.
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WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2022 ANNUAL PERFORMANCE MONITORING REPORT
1.2
Performance criteria are outlined in the SCA (DWMRC, 2017) 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 2022.
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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2.1
2.0 COVER AND TEST SECTION DESIGNS
The Reclamation Plan (EFRI, 2018) provides detailed design information for the cover and test sections
and the designs are summarized below.
The cover system is a monolithic water balance cover, designed to minimize percolation, meet the radon
emanation standard, and minimize maintenance over the short- and long-term. 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
as-built 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 2022 ANNUAL PERFORMANCE MONITORING REPORT
2.2
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 squirrel tail 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 2022 ANNUAL PERFORMANCE MONITORING REPORT
3.1
3.0 PRIMARY TEST SECTION HYDROLOGIC MONITORING
Data collected from the Primary Test Section from September 9, 2016 to December 31, 2022 (last
automated data download of 2022) are described in the annual Primary Test Section Report in Appendix
A. Data in this report represent the first six full calendar years (2017 through 2022) of monitoring. Table 1
summarizes the water balance results.
Table 1. Primary Test Section Water Balance for 2016 to 2022
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
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 2022 was consistent with expectations for a water balance cover
in a semi-arid environment with lower-than-average annual precipitation. Precipitation in 2022 (180 mm)
was substantially 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 only modestly lower than the average annual precipitation recorded during monitoring the test
section (204 mm from 2017 to 2022). Winter and spring in 2022 were considerably drier than average.
Summer and fall in 2022 were wetter than winter and spring, but drier than average. Soil water storage
gradually diminished throughout the year, continuing a trend that began in 2019, as water contents
continued to gradually diminish at all depths except at the near surface. At the end of 2022, soil water
storage was at the lowest point since construction. Nearly all precipitation that reached the test section
was returned to the atmosphere as evapotranspiration. A trace of runoff (0.1 mm) and lateral flow (0.01
mm) were transmitted. Annual percolation was 0.3 mm, the lowest measured for a full year during the
monitoring period. Thermally driven flow has been the most significant mechanism contributing to the
percolation recorded to date.
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WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2022 ANNUAL PERFORMANCE MONITORING REPORT
4.1
4.0 PRIMARY AND SUPPLEMENTAL TEST SECTIONS
VEGETATION INSPECTION
Cedar Creek Associates, Inc. visited the Mill site on June 7, 2022 and September 12, 2022, 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 not favorable for
plant growth (31% of average). Regionally, 2022 can be considered a dry year with well below average
precipitation. Vegetation observed during the spring evaluation exhibited below average plant vigor and
growth in response to unfavorable precipitation conditions. The spring months of March, April, and May
are particularly important to plant growth and these months received 19.9 mm (75% of normal), 0.7 mm
(3% of normal), and 0 mm (0% of normal) of precipitation, respectively. Precipitation prior to the fall
revegetation evaluation was also below average (81% of average) but not as drastically as the spring
evaluation. July, August, and September were all below average with 21.4 mm (73% of normal), 25.1 mm
(72% of normal), and 31.8 mm (98% of normal) of precipitation, respectively. Vegetation observed during
the fall evaluation also exhibited below average plant vigor and growth in response to unfavorable
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.
The results of the performance evaluation are summarized in Appendix B. In Year 3 (2022) of the
performance period, both the Primary and Supplemental Test Sections are not passing several of the
success criteria.
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.
For the Supplemental Test Section, the seeding never established due to poor precipitation conditions
following seeding. Local native species are slowly volunteering on the test section. Perennial species
cover has remained diminished, and cover of annual species dominates. Annual cover was decreasing
significantly each year until favorable precipitation in 2022 caused an increase in annual cover for the
year.
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WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2022 ANNUAL PERFORMANCE MONITORING REPORT
4.2
For the Supplemental Test Section No. 2, seedling emergence was not identified during the spring survey
likely due to very low precipitation during the months of April and May following the seeding and prior to
the survey (June 2021). However, the fall survey conducted in September 2022 identified moderate
densities of emerging seedlings dominated by perennial grasses. The diversity of species observed at the
Supplemental Test Section No. 2 is encouraging and indicates the potential for better performance in
favorable (wet) precipitation conditions for this test section.
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, 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 2022 ANNUAL PERFORMANCE MONITORING REPORT
5.1
5.0 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 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 installation (June 2016)
through December 2022. Table 2 lists the settlement measured since the start of Phase 1 cover
construction (April 2016) through December 2022. 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 majority of total settlement due to Phase 1 cover placement is estimated to have
occurred. Settlement is showing a decreasing trend and less than 0.05 feet of annual settlement was
measured for 2022 for all the monuments (ranging from 0.04 feet settlement to 0.03 feet upward
movement). Negative values indicate upward movement.
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.
Table 2. Cell 2 Top Surface Settlement Measured Between April 2016 and December 2022
Settlement
Monument
April 2016 to December 2022 Settlement (ft)
2022 Settlement (ft)
Settlement
Monument
April 2016 to December 2022 Settlement (ft)
2022 Settlement (ft)
2W1 0.16 0.01 2W6-N 0.19 0.00
2W2 0.26 -0.02 2W6-C 0.31 0.00
2W3 0.25 -0.02 2W6-S 0.43 0.00
2W3-S 0.27 -0.03 2W7-N 0.00 0.03
2W4-N 0.19 -0.01 2W7-C 0.16 0.02
2W4-C 0.23 -0.02 2W7-S 0.39 0.04
2W4-S 0.44 -0.02 2E1-N 0.25 0.02
2W5-N 0.15 -0.01 2E1 0.36 0.03
2W5-C 0.22 -0.02 2E1-1S 0.41 0.03
2W5-S 0.34 -0.02 2E1-2S 0.57 0.04
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WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2022 ANNUAL PERFORMANCE MONITORING REPORT
5.2
5.2 PIEZOMETERS
Standpipe piezometers were installed across Cell 2 prior to the first phase of final cover placement to
monitor changes in water levels 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 dewatering of the tailings. 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 water levels.
Appendix D presents figures showing water levels in the piezometers since installation (June 2016)
through December 1, 2022. 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 water levels are lower near the sump, indicating
migration of water 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. These
fluctuations in water level appeared to continue for these four piezometers throughout 2021 but appear to
be trending more level than prior years. Overall, water levels have decreased since Phase 1 cover
placement by approximately 1 to 5 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
migrating into tailings. A wet precipitation season would have minimal impact on the water levels in the
tailings.
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WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2022 ANNUAL PERFORMANCE MONITORING REPORT
5.3
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 12/2/2022
(ft)
Change in Water Level Elevation since Phase 1 Cover Placement (ft)*
C2-P01 West 5612.55 5610.89 -1.66
C2-P02 West 5613.30 5610.98 -2.32
C2-P03 West 5612.31 5609.78 -2.53
C2-P04 West 5613.97 5611.08 -2.89
C2-P05 West 5608.39 5605.50 -2.89
C2-P06 West 5609.21 5606.37 -2.84
C2-P07 West 5610.08 5606.92 -3.16
C2-P08 West 5605.25 5602.77 -2.48
C2-P09 Near Sump 5602.94 5600.99 -1.95
C2-P10 Near Sump 5601.54 5599.96 -1.58
C2-P11 Near Sump 5602.38 5599.02 -3.36
C2-P12 Near Sump 5599.45 5594.59 -4.86
C2-P14 Near Sump 5603.99 5603.49 -0.5
C2-P15 Near Sump 5604.01 5601.68 -2.33
C2-P16 Near Sump 5604.37 5601.54 -2.83
C2-P13 East 5605.72 5601.92 -3.80
C2-P17 East 5607.49 5605.78 -1.71
C2-P18 East 5607.82 5604.41 -3.41
C2-P19 East 5609.09 5606.34 -2.75
C2-P20 East 5610.63 5608.73 -1.90
C2-P21 East 5612.40 5609.16 -3.24
C2-P22 East 5613.39 5609.47 -3.92
C2-P23 East 5614.24 5609.77 -4.47
*Negative number indicates a decrease in water level.
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WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2022 ANNUAL PERFORMANCE MONITORING REPORT
6.1
6.0 CONCLUSIONS
Hydrology of the Primary Test Section during 2022 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 0.3 mm. 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 2022 spring evaluation exhibited below average plant vigor and growth in
response to unfavorable (below-average) 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 2022. 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.
Settlement is showing a decreasing trend and less than 0.05 feet of cumulative settlement with some
minimal upward movement for 2022.
Water levels for piezometers 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, but now appear to be trending toward more static
conditions. There was a slight rise in piezometer reading elevations for early 2022 but have generally
stabilized throughout the year. Overall, water levels have decreased since Phase 1 cover placement by
approximately 1 to 5 feet. Based on performance of the Cell 2 Primary Test Section, placement of the
Phase 2 cover on Cell 2 would minimize precipitation infiltrating into the tailings and wet precipitation
seasons would have minimal impact on water levels in the tailings.
IJ
WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2022 ANNUAL PERFORMANCE MONITORING REPORT
7.1
7.0 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.
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 2022 ANNUAL PERFORMANCE MONITORING REPORT
FIGURES
REGIONAL LOCATION MAP FIGURE 1
1009740 LOC MAP
WHITE MESA MILL TAILINGS RECLAMATION
FEB 2023ENERGY FUELS
I
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f
I
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ADAPTED FROM FIGURE 1-1 IN DENISON MINES (USA)
CORPORATION, 2009 RECLAMATION PLAN WHITE M BLANDING, UTAH. VERSION 4.0. NOVEMBER ESA MILL,
. -./ ':/ ;~-:7 .... ~ ~-
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limimLEr--_______ _J() Stantec
DATE
I
i .:i ____ ..1....--___ ____l... _____ ~====1 FILE NAME
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 2023
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
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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 2023
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 2023
K REED
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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~
C!':LL2-P18 06 2W7-C "'
() 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 2022 ANNUAL PERFORMANCE MONITORING REPORT
APPENDICES
IJ
WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2022 ANNUAL PERFORMANCE MONITORING REPORT
Appendix A 2022 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 2022
WHITE MESA MILL – TAILINGS MANAGEMENT CELL 2 ENERGY FUELS RESOURCES (USA) INC. SAN JUAN COUNTY, UTAH
Craig H. Benson, PhD, PE, NAE
10 February 2023
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 2022. The data set includes the six full calendar years (2017 -
2022) of monitoring for the test section. This report emphasizes data collected in 2022.
The water balance of the test section is summarized as follows:
Calendar
Year
Water Balance Quantities (mm) c
Precipitation Runoff Lateral
Flow
Evapo-transpiration ∆ Storage Percolation
2016 a 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
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 2022 was consistent with expectations for a water balance
cover in a semi-arid environment with lower-than-average annual precipitation. Precipitation in
2022 (180 mm) was substantially 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 only modestly lower than the average annual precipitation recorded
during monitoring the test section (204 mm from 2017 to 2022). Winter and spring in 2022 were
considerably drier than average. Summer and fall in 2022 were wetter than winter and spring, but
drier than average. Soil water storage gradually diminished throughout the year, continuing a
trend that began in 2019, as water contents continued to gradually diminish at all depths except
at the near surface. At the end of the 2022, soil water storage was at the lowest point since
construction. Nearly all precipitation that reached the test section was returned to the atmosphere
as evapotranspiration. A trace of runoff (0.1 mm) and lateral flow (0.01 mm) were transmitted.
Annual percolation was 0.3 mm, the lowest measured for a full year during the monitoring period.
Thermally driven flow has been the most significant mechanism contributing to the percolation
recorded 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 17
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 12/31/22.
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 2022.
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 31 December 2022. 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 13 July 2022.
This report describes data collected since inception of the test section, with particular
emphasis on data collected in 2022. 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.
0.5 ft Erosion Layer
3.5 ft Growth Medium
3.0 ft Compacted Cover
0 2.5 ft Interim Layer
= 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-w w u.
5630-r-5630 I-w w u.
'Z ---'Z 0 5620-5620 0 i= ' ~ ~ .L..l '-w cfj
..J 5610-"r-5610 -' w w ..__
I I I 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 2022 was considerably lower than the long-term average annual
precipitation at the Blanding station (180 vs. 355 mm, Fig. 3a). Precipitation was lower only in
2018 (163 mm) and 2020 (128 mm) (Table 1). Annual precipitation has been below average
recorded at the Blanding station throughout the entire monitoring period. All seasons were drier
than average, with winter and spring particularly dry. Average air temperature at the test section
generally falls 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 2022. PET far exceeds precipitation throughout much
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).
400
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--On-Site 2022
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--Blanding Historical Max
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--On-Site Daily Avg. 2022
N ~ ...... --(W)
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Cumulative On-Site Precipitation and
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...... ...... ...... ......
N ~ m ~ o N ~ m 0 0 0 0 0 0 0 0 1/1 /220 0 0 0 0 0 0 0 0
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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
12/31/22.
Calendar Year
Water Balance Quantities (mm)
Precipitation Runoff Lateral
Flow ET ∆ 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
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 – ∆S (1)
8
Fig. 5. Water balance graph for test section through 31 December 2022.
1500 5
White Mesa, UT 0 C
3
C C o-m ;.:;E 4 -~E <" a.-(D
·-C :;o () 0 ~ ;.:; ET C a.. l! 1000 ::::J 0 G) --_=11 > a. --UJ 3 r -c (U (U m
::::J~ -Soil Water Precipitation (D E o ...
::::J a.
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0 0
9/20/16 10/7/17 10/24/18 11/10/19 11/26/20 12/13/21 12/31/22
9
where P = daily precipitation, R = daily runoff, L = daily lateral flow, Pr = daily percolation, and ∆S
= daily change in soil water storage. ET computed with Eq. 1 includes actual ET and any errors
in the water balance. For 2022, 169 mm of ET was computed using Eq. 1, which is slightly lower
than annual precipitation. 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 2022, soil water storage continued to diminish gradually throughout the year, a trend that
began in 2019. Water contents have been gradually diminishing at all depths except at the near
surface (Fig. 7), with nearly all water cycling occurring in the upper 500 mm of the profile except
in much wetter years. Under more typical conditions, soil water storage would accumulate
significantly in fall and winter, and diminish in spring and summer, with water contents rising and
falling at greater depths.
Percolation began on 1 July 2022 and ceased on 5 November 2022, 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. 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,
occurring when soil water storage is near a minimum. This indicates that mechanisms other than
hydraulic gradients contribute to percolation from the cover.
Thermal gradients likely have a significant influence on percolation from the cover profile,
as thermally driven flows can comprise a substantial portion of deep drainage in semi-arid and
arid environments (Milly 1996). The air and soil temperature records for the test section are shown
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).
.......
1-w a..
al
-al
1-0.80 oW --cc o.Q .:::...,
(U ~ ._ __
·a a-o.so
u, C
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-(U (U __
::::,-c C C (I)
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•
■ On-Site 2017
D On-Site 2018
D On-Site 2019
D On-Site 2020
D On-Site 2021
D On-Site 2022
•
0. 00 ...__...._____.____, _ _.__......____.__.,__...._____.____, _ _.__......____.__.,__...._____.____, _ _.__......___,
0 5 10 15 20
Annual Potential Evapotranspiration/Annual Precipitation (PET /P ) a a
11
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).
Growth Medium
--------45 7 m m
--------------6 8 6 m m
---+---914 mm
Compacted Layer Interim Layer
-----.-1 5 2 4 m m ~ 2 7 4 3 m m
~ 1 8 2 9 m m
----k-2134 mm
0.5 .------r-""T"""""T---r--.------r---r-T---r--.------r---r-T---r-T"""""T"""T""""T---r-T"""""T""""T"""""">C"""T"""T"""""T""""T"""""">C"""T""""T"""""T"---r--.------r-"T"""""T"---.-----,
White Mesa
2 0.4 -C Cl) -C 0
U 0.3 L.. Cl)
~
0 ·;:: 02 G) -
E ::::,
~ 0.1
0.0 ~~~~~~~~~~~~~~~~~~~~
9/1/16 9/1/17 9/1/18 9/1/19 9/1/20 9/1/21 9/1/22
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.
800 6.0 I I I I I
I t--00 I I I I I t--O> O> O> I 0 I N ..... ..... 0 ..... ..... N ..... N ..... > ..... ..... N N N N N
0 C .... -> > ::i ::i (13 ::i 0 > :j """) z ~ 0 ::i 0 ::i 0 0 """) """) """) z """) z """) z ,;:t-('I') N ..... ('I') 00 ,;:t-('I') ..... 5.0 ..... ..... N 0 N N ..... t--0 t--0 LO 700 0 ..... 0
(') -C
E I 3
E 4.0 £ -D>
(I) -C) 600 <" m (D
L. "1J 0 -I 3.0 (D <f) Soil a L. Water 0 (I) D> -m 500 Storag~ -$'. o·
J I 2.0~ 0
<f) 3 3 -I 400 Percolatio~ 1.0 I I
I
300L=:t=~....L...L....L..----1.1.----l..----l:..,__LL...-.1....-...&...-..u..........!L..---'-.....I..L___J,L-L......1....L......J::I 0. 0
9/1/16 9/21/17 10/12/18 11/1/19 11/21/20 12/11/21 1/1/23
13
in Fig. 9. The temporal variation is consistent each year. The thermal regime changes orientation
with the seasons, with the highest soil temperatures 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 ∆T/∆z 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.
Fig. 11 shows annual percolation from the test section for each year in the record along
with data compiled from USEPA’s Alternative Cover Assessment Program (ACAP) and other data
sources, as reported by Apiwantragoon et al. (2014). Percolation data for 2017, 2018, 2020, and
QT =K AT T -Az
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).
• 457 mm -6-1524mm ---z:'.l--2 7 43 mm
■ 686 mm -----v-18 29 mm Air On-Site • 914 mm ----h--21 34 mm
40 40
35 30
,--... 0 0 30 20 Ill
0 '< .........
Q) )>
I.... 25 10 < J CD +-' -, cu Ill
I.... (C
Q) 20 CD c.. 0 ?. E -,
~ 15 ~ -10 3
0 "'C CD (f) 10 -,
-20 Ill ..... C -,
CD
5 -30
0 -40
U) ...... CX) O> 0 ...-N ...-...-...-T""" ~ ~ ~ - - --T""" ...-T""" T""" ...-...-...-- - --- - -O> O> O> O> O> O> O>
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.
_ 6.0 ,._.,.._......,....,.......,....._..._...~,._-................. _..._.._...,._.,.._......,.. ................... 10
E
E -X :::, 5.0
u..
(0
E m 4.0
.c I-
"-0
C 3.0 0
1u
0 ~ 2.0
n..
(I) > +i m 1.0
:::,
E :::,
Thermal
Gradient
Measured
Percolation
Computed
Thermal Flux
5 --i :::,-
<D
3
D>
G> o m a. <D.
:::,
r+ -0
{) --5 ~
0 0.0 l:::::l:::11:::::1::::~.1....L...1....1....&....1....l....L....1...1....i....&....l....&....&...1....a....ii....L..L...L...1...1....L...L.1....1...1....1....a....L..1....J -10
9/1/16 9/1/17 9/1/18 9/1/19 9/1/20 9/1/21 9/1/22
16
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).
■ On-Site 2017 D On-Site 2019 C On-Site 2021
D On-Site 2018 D On-Site 2020 C On-Site 2022
-100 E E -C: 0 :;::::;
(U
0 ~
(I) a..
"'ffi :::,
C: C:
<(
10
1
•
•
■□□co ·~ • • 0 0.1 -----
0-250
6.
6.
/',.
£:,,L,
6. /',. /',. □ 6. 6.
/',.
/',.
/',. /',. 6.
♦
■ •♦ ■
■ ••
■
■
■
••
ACAP Data -Solid Symbols
Other Data -Open Symbols
White Mesa -Large Solid Squares
·---■ □
250-500 500-750 >750
Annual Precipitation (mm)
17
2022 fall in the middle of the data reported by Apiwantragoon et al. (2014) for the bin
corresponding to annual precipitation between 0 to 250 mm/yr. For 2019, the percolation falls at
the lower end of the data reported by Apiwantragoon et al. (2014) for annual precipitation between
250 and 500 mm/yr. 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 2022, with the discussion emphasizing data collected in 2022. 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 flooding damage. 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 2022 (180 mm) was considerably lower than the long-term
average recorded at the Blanding, Utah station (355 mm) operated by the NWS. Precipitation
in winter and spring were much lower than average. Summer and fall were wetter, but still
below average for the latter half of the year.
• 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 and lateral flow were
recorded, and percolation was 0.3 mm. The annual percolation rate is similar to percolation
rates reported in the literature for water balance covers in similar climates.
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.
Milly, P. (1996), Effects of Thermal Vapor Diffusion on Seasonal Dynamics of Water in the Unsaturated Zone, Water Resources Research, 32(3), 509-518.
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 2022 ANNUAL PERFORMANCE MONITORING REPORT
Appendix B 2022 REVEGETATION EVALUATION CELL 2
PRIMARY AND SUPPLEMENTAL TEST SECTIONS
IJ
White Mesa Mill Site
2022 REVEGETATION EVALUATION CELL 2 PRIMARY AND SUPPLEMENTAL TEST
SECTIONS
FEBRUARY 2023
PREPARED BY:
i
Table of Contents
1.0 INTRODUCTION ................................................................................................................................... 2
1.1 General .............................................................................................................................................. 2
1.2 Background ....................................................................................................................................... 2
1.3 Precipitation ....................................................................................................................................... 3
2.0 REVEGETATION PERFORMANCE CRITERIA ................................................................................... 5
3.0 REVEGETATION MONITORING RESULTS ........................................................................................ 7
3.1 Primary Test Section ......................................................................................................................... 9
3.2 Supplemental Test Section ............................................................................................................... 2
3.2 Supplemental Test Section No. 2 ...................................................................................................... 5
4.0 PERFORMANCE EVALUATION .......................................................................................................... 8
5.0 REFERENCES .................................................................................................................................... 10
List of Charts and Tables
Table 1. 2022 Site and Long-term Average Monthly Precipitation ......................................................... 4
Chart 1. Monthly Precipitation, White Mesa Mill Site, Blanding UT ......................................................... 4
Table 2. Summary of Species Observed on Each Test Section .............................................................. 7
Table 3. Summary of Average Cover .................................................................................................. 8
Chart 2. Average Ground Cover by Lifeform ....................................................................................... 9
Table 4. Primary Test Section Woody Plant Density ........................................................................... 10
Chart 3. Primary Test Section Perennial & Annual Cover Trend (Spring Survey) ................................... 12
Table 5. Supplemental Test Section Woody Plant Density………………………………………………………….………13
Chart 4. Supplemental Test Section Perennial & Annual Cover Trend (Spring Survey) .......................... 15
Table 6. Supplemental Test Section No. 2 Emergent Density .............................................................. 17
Chart 5. Supplemental Test Section No. 2 Emergent Density .............................................................. 17
Table 7. Success Criteria Comparison ............................................................................................... 20
2
White Mesa Mill Site
2022 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
June 7, 2022, and September 12, 2022, 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
3
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, 2022 can be considered a dry
year with well below average precipitation. Precipitation conditions in the months prior to the spring
revegetation evaluations were not favorable for plant growth (31% of average). Vegetation observed during
the spring evaluation exhibited below average plant vigor and growth in response to unfavorable
precipitation conditions. The spring months of March, April, and May are particularly important to plant
growth and these months received 19.9 mm (75% of normal), 0.7 mm (3% of normal), and 0 mm (0% of
normal) of precipitation, respectively. Precipitation prior to the fall revegetation evaluation was also below
average (81% of average) but not as drastically as the spring evaluation. July, August, and September
were all below average with 21.4 mm (73% of normal), 25.1 mm (72% of normal), and 31.8 mm (98% of
normal) of precipitation, respectively. Vegetation observed during the fall evaluation also exhibited below
average plant vigor and growth in response to unfavorable precipitation conditions.
4
Table 1 White Mesa - Precipitation - 2022
Site and Long-term Average Monthly Precipitation
Site Precipitation Percent of Normal Site Precipitation Percent of Normal Site Precipitation Percent of Normal Site Precipitation Percent of Normal Site Precipitation Percent of Normal
(mm)(%)(mm)(%)(mm)(%)(mm)(%)(mm)(%)(mm)
January 8.2 23% 46.7 132% 17.1 48% 20.6 58%0.2 1%35.3
February 4.2 14% 65.6 214% 5.4 18% 17.4 57%7.9 26%30.7
March 8.3 31% 62.2 233% 23.7 89% 16.6 62% 19.9 75%26.7
April 3.0 14% 12.2 55%1.1 5%0.0 0%0.7 3%22.1
May 6.6 37% 36.7 203% 1.8 10%3.2 18%0.0 0%18.0
June 11.7 102% 2.3 20% 15.8 138% 11.2 98%5.8 51%11.4
July 6.4 22%4.7 16% 24.9 85% 35.4 121% 21.4 73%29.2
August 10.0 29%8.7 25%0.5 1%47.2 135% 25.1 72%35.1
September 1.5 5%0.0 0%22.0 68% 28.1 87% 31.8 98%32.5
October 81.7 222% 5.2 14%0.7 2%23.8 65% 17.6 48%36.8
November 5.6 21% 21.1 79%3.4 13%0.3 1%19.9 75%26.7
December 10.4 31% 42.5 126% 13.9 41% 19.7 58% 29.5 87%33.8
A NNUA L 157.6 47% 307.9 91% 130.3 39% 223.4 66% 179.8 53% 338.3
Mar-May 17.9 27% 111.1 166% 26.6 40% 19.8 30% 20.6 31% 66.8
July-Oct 17.9 18% 13.4 14% 47.4 49% 110.7 114% 78.3 81% 96.8
2018 2019 2020 2021 2022 Long Term Average
Jan 8.2 46.7 17.1 20.6 0.2 35.3
Feb 4.2 65.6 5.4 17.4 7.9 30.7
Mar 8.3 62.2 23.7 16.6 19.9 26.7
Apr 3.0 12.2 1.1 0.0 0.7 22.1
May 6.6 36.7 1.8 3.2 0.0 18.0
Jun 11.7 2.3 15.8 11.2 5.8 11.4
Jul 6.4 4.7 24.9 35.4 21.4 29.2
Aug 10.0 8.7 0.5 47.2 25.1 35.1
Sep 1.5 0.0 22.0 28.1 31.8 32.5
Oct 81.7 5.2 0.7 23.8 17.6 36.8
Nov 5.6 21.1 3.4 0.3 19.9 26.7
Dec 10.4 42.5 13.9 19.7 29.5 33.8
2020 Blanding Long Term Average
2018 2019 2021 2022
8.2
4.2
8.3
3.0
6.6
11.7
6.4
10.0
1.5
5.6
10.4
46.7
12.2
36.7
2.3
4.7
8.7
0.0
5.2
21.1
42.5
17.1
5.4
23.7
1.1 1.8
15.8
24.9
0.5
22.0
0.7
3.4
13.9
20.6
17.4 16.6
0.0
3.2
11.2
35.4
47.2
28.1
23.8
0.3
19.7
0.2
7.9
19.9
0.7 0.0
5.8
21.4
25.1
31.8
17.6
19.9
29.5
0
15
30
45
60
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Mi
l
l
i
m
e
t
e
r
s
Chart 1 -Monthly Precipitation, White Mesa Mill Site, Blanding, UT -2022
20182019202020212022Long Term Average
65.6 62.2 81.7-= ---
5
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.
6
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 will now
be 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.
7
3.0 REVEGETATION MONITORING RESULTS
The results of 2022 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
2022 monitoring surveys. Chart 2 presents a summary of relative cover by lifeform at each test section as
determined by the 2022 monitoring surveys. Comparison between the Primary and Supplemental Test
Section are made as they are both in their third growing season. Results of the Supplemental Test Section
No. 2 and the Native Reference area are described separately below.
Table 2 White Mesa -Vegetation Cover -2022
Summary of Species Observed on Each Test Section
Primary Test Supplemental
Area-> Section Test Section
Grasses Spring Fall Spring Fall
I A Bromus tectorum Cheatgrass X X X
N p * Elymus elymoides Squirreltail X X
N p Elymus lanceo/atus Thickspike Wheatgrass X
N p * PascoJJvrum smithii Western Wheatqrass X X X
N p * Poa secunda Sandberg Bluegrass X
N A Vu/JJia octof/ora Six Weeks Fescue X
Forbs
N A Descurainia oinnata Western Tansvmustard X
I A Descurainia sophia Fixweed X
I A Erodium cicutarium Redstem Stork's Bill X
I A Kochia scof)aria Summer Cvp~E:!~~ X X
I A Portulaca o/eracea Little Hogweed X
I A Sa/so/a tragus Russian Thistle X X X X
I A Sisymbrium a/tissimum Tall Tumblemustard X X
N p SJJhaera/cea coccinea Scarlet Globemallow X X
N p Sohaera/cea orossu/arifo/ia Gooseberrvleaf Globemallow X
Shrubs, Sub-shrubs, Cacti & Trees
N p * Atrip/ex canescens Fourwing Saltbush X X
N p Gutierrezia sarothrae Broom Snakeweed X X
N p Lycium andersonii Waterjacket X
N p Lvcium oal/idum Pale Desert-thorn X
Species Observed
Seeded Speci es Encountered 3 2 2 1
Total Species Encountered 7 16
* Indicates a seeded species
N = Native, I = Introduced, P = Perennial, B = Biennial, A = Annual
8
Table 3 White Mesa -Vegetation Cover -2022
Summary of Average Cover
Percent Ground Cover Based on Point-Intercept Sampling
Primary Test Section SU,IJJ)lemental Test
Area --> Section
Grasses Spring Fall SJ)ring Fall
I A Bromus tectorum Cheatgrass 0.2 0.1 0.6 -
N p * Elymus elymoides Sq u i rrelta i I 8.0 0.3 --
N p * Pascopyrum smithii Western Wheatgrass 0.1 -0.1 0.1
N p * Poa secunda Sandberg Bluegrass -·-0.1 -
N A Vulpia octollora Six Weeks Fescue --0.1 -
Forbs
N A Descurainia pinnata Western Tansymu.stard --0.2 -
I A Erodium cicutarium Redstem Stork's Bill --7.3 -
I A Kochia scoparia Summer Cypress 2.4 ---
I A POrtulac.a oleracea Little Hogw eed ---0.2
I A Salsola tragus Russian Thistle 6.7 3.1 9.4 27.7
I A Sisvmbrium altissimum Tall Tumblemu.stard --0.7 -
N p Sphaeralcea cocdnea Scarlet Globemallow --0.1 -
Shrubs, Sub-shrubs, Cacti & Trees
N p * Atriplex c.anescens Fourwing Saltbush 5.1 9.3 --
N p Gutierrezia sarothrae Broom Snakew eed --0.5 0.9
N p LycJum pal!idum Pale Desert-thorn --0.2 -
Mean
Total Plant Cover 22 .. 5 12.8 19.3 28.9
Rock 6.9 6.1 0.6 0.2
litter (including JJlant senscence in fall) 44.8 46.3 30.1 19.4
Bareqround 25.9 34.8 50.0 51.5
Total Perennial Cover 1.3.1 9.5 1.0 1 .. 0
Summary by Lifefonn:
Perennial Grasses 8.1 0 . .3 0.1 0.1
Annual Grasses 0.2 0.1 0.7 0.0
Perennial Forbs 0.0 0.0 0.1 0.0
Annual & Biennial Forbs 9.1 3.1 17.7 27.9
Noxious / Aggressive Weeds ----
Shrubs, Sub-shrubs, Cacti & Trees 5.1 9..3 0.7 0.9
Sample Adeouacv Calculations:
Mean= 22.5 12.8 19.3 28.9
Variance= 24.1 75.0 44.4 71.8
n= 15 15 15 15
n:min = 6.4 82.8 21 .. 5 15 .. 5
* Indicates a seede•d species
N = Native, I = Introduced, P = Perennial, B = Biennial, A = Annual
9
3.1 Primary Test Section
Spring 2022 Findings
The Primary Test Section was evaluated with 15 transects during the spring survey of the sixth growing
season. Table 2 displays all species observed in the Primary Test Section in 2022 including species recorded
by cover sampling metrics and incidental observations. Raw data from the spring 2022 cover evaluation
are presented in Appendix B. There was a total of 6 species observed, 3 of which were included in the seed
mix used on the plot. Total ground cover in the Primary Test Section consisted of 22.5% live vegetation,
6.9% rock, 44.8% litter, and bare ground exposure of 29.5%. Perennial cover across the test section
averaged 13.1%, with annual and biennial cover averaging 9.3%. No noxious weeds were observed. Below
average precipitation and available water through the end of 2020 and into the spring of 2021 and spring
of 2022 did not facilitate improved vegetation growth and vigor in the Primary Test Section vegetation.
Dominant taxa were squirreltail (Elymus elymoides) averaging 8.0% cover and Russian Thistle (Salsola
tragus) averaging 6.7% cover, with fourwing saltbush (Atriplex canescens) averaging 5.1% cover. These
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Spring Fall Spring Fall
Primary Test Section Supplemental Test Section
Pe
r
c
e
n
t
G
r
o
u
n
d
C
o
v
e
r
Chart 2White Mesa -Revegetation Monitoring
Average Ground Cover by Lifeform -2022
Bare ground
Rock
Litter (including plant
senscence in fall)
Noxious / AggressiveWeeds
Annual & Biennial
Forbs
Annual Grasses
Shrubs, Sub-shrubs,Cacti & Trees
Perennial Forbs
Perennial Grasses
□
■
C
■
C
C
□
C
■
10
were the only Primary Test Section species with greater than 4% cover in spring 2022, and none of the
species were overly dominant (contributing greater than 40% relative cover).
The Primary Test Section had 28 fourwing saltbush plants present across the entire seeded area
(lysimeter and surrounding area), which equates to 122 woody plants per acre shown in Table 4 below.
This does not currently meet the success criteria of 400 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 2021
evaluation compared with the spring 2022 evaluation.
Primary Test Section – Spring Survey –
June 8, 2021
Primary Test Section – Spring Survey –
June 7, 2022
Table 4 White Mesa - Woody Plant Density - 2022
Summary of Woody Plant Density
Area ——>
Lifeform Scientific Name Common Name
Shrub Atriplex canescens Fourwing Saltbush 28
Woody Plants Per Acre 122
Primary Test Section
(0.23 acres)
11
Fall 2022 Findings
The Primary Test Section was also evaluated with 15 transects during the fall survey of the sixth
growing season. Table 2 displays all species observed in the Primary Test Section in 2022. Raw data from
the fall 2022 cover evaluation are presented in Appendix B. There was a total of 5 species observed, 4 of
which were captured by cover sampling metrics, of which 2 were included in the seed mix. Ground cover
in the Primary Test Section consisted of 12.8% live vegetation, 6.1% rock, 46.3% litter (including plant
senescence in fall), and bare ground exposure of 34.8%. Perennial cover across the test section averaged
9.5%, with annual and biennial cover averaging 3.3%. No noxious weeds were observed. Dominant taxa
were fourwing saltbush averaging 9.3% cover and annual Russian thistle averaging 3.1% cover. These two
species were the only species that met the minimum relative cover criterion of 4% but fourwing saltbush
contributed to greater than 40% relative cover at 72.4%.
The following photos show the site conditions on the Primary Test Section during the fall 2021
evaluation compared with the fall 2022 evaluation.
Primary Test Section – Fall Survey –September 22, 2021
Primary Test Section – Fall Survey – September 12, 2022
1
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 3 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 has continued to decrease.
100
80
.. .,
""60 8
"II-"' j e (:,
~40
~ ., a.
20
0
Chart 3
White Mesa -Revegetation Monitoring
Primary Test Section Perennial/ Annual Cover Trend (Spring Survey}
Year1
{2018)
Year2
{2019)
Calibration Period
Year 1
{2020)
Year 2
{2021)
Year3
(2022)
Performance Period
Dt.lnnual Species Cover
l!I PerennTal Species Cover
Year4
(2023)
SCA Perftomance
Criteria =-400/o
Years
(2024)
2022
Native Ref
Area
2
3.2 Supplemental Test Section
Spring 2022 Findings
The Supplemental Test Section was evaluated with 15 transects during the spring survey of the fifth
growing season. Table 2 displays all species observed in the Supplemental Test Section in 2022. Raw data
from the spring 2022 cover evaluation are presented in Appendix B. There was a total of 11 species
observed, all of which were captured by cover sampling metrics and 2 of which were included in the seed
mix. Ground cover in the Supplemental Test Section consisted of 19.3% live vegetation, 0.6% rock, 30.1%
litter, and bare ground exposure of 50.0%. Perennial cover across the test section averaged 1.0%, with
annual and biennial cover averaging 18.3%. No noxious weeds were observed. The dominant taxa were
annual Russian thistle and Redstem Stork’s Bill (Erodium cicutarium), with 9.4% and 7.3% average cover,
respectively. Russian thistle contributed greater than 40% relative cover. No seeded species met the
minimum cover criterion of 4%.
The Supplemental Test Section had 59 snakeweed (Gutierrezia sarothrae) and 22 waterjacket (Lycium
andersonii) plants present across the entire seeded area, which equates to 353 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 Supplemental Test Section during the spring
2021 evaluation and spring 2022 evaluation.
Table 5 White Mesa - Woody Plant Density - 2022
Summary of Woody Plant Density
Area ——>
Lifeform Scientific Name Common Name
Subshrub Gutierrezia sarothrae Snakeweed 59
Shrub Lycium andersonii Waterjacket 22
Woody Plants Per Acre 353
Supplemental Test Section
(0.23 acres)
3
Supplemental Test Section – Spring
Survey – June 8, 2021
Supplemental Test Section – Spring
Survey – June 7, 2022
Fall 2022 Findings
The Supplemental Test Section was evaluated with 15 transects during the fall survey of the fifth
growing season. Table 2 displays all species observed in the Supplemental Test Section in 2022. Raw data
from the fall 2022 cover evaluation are presented in Appendix B. There was a total of 10 species observed
in the Supplemental Test Section in the fall, only 4 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 28.9%
live vegetation, 0.2% rock, 19.4% litter, and bare ground exposure of 51.5%. Perennial cover across the
test section averaged 1.0%, with annual and biennial cover averaging 27.9%. No noxious weeds were
observed. The dominant taxon was Russian thistle, with 27.7% average cover. 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 95.9% relative cover.
The following photos show the site conditions on the Supplemental Test Section during the fall 2021
evaluation and fall 2022 evaluation.
N NE I E SE 330 0 30 60 90 120 15
•I• I• l •I • I• I• I• I • I • I • I • I • I • I • I • I• t • l • I
4
Supplemental Test Section – Fall Survey
– September 21, 2021
Supplemental Test Section – Fall Survey
– September 12, 2022
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 3 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 caused an increase
in annual cover for the year.
Chart 4
White Mesa -Revegetation Monitoring
Supplemental Test Section Perennial / Annual Cover Trend (Spring Survey)
100
□Annual Species Cover
c Pe~onial Spec.ies Cover
80
SCA Perf1·0man.ce
Criteria = 400/o
"'70.!. ~ -
43.9
20 -3.20
0
:u
I I 18.39 9.9 .iT__ --•-& . -·-Year1 Year2 Year1 Year 2 Year 3 Year4 Year s 2022
{2018) (2019} {2020} {2021) (2022} (2023) (2024}
Calibration Period Performance Period Native Ref
Area
5
3.2 Supplemental Test Section No. 2
Spring 2022 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 2022 cover evaluation are presented in Appendix B. There
was a total of 17 species observed, all of which were captured by cover sampling metrics and 2 of which
were included in the seed mix. Total ground cover in the Supplemental Test Section No. 2 consisted of
17.7% live vegetation, 1.1% rock, 16.8% litter, and bare ground exposure of 64.4%. Perennial cover across
the Supplemental Test Section No. 2 averaged 5.5%, with annual and biennial cover averaging 12.2%. No
noxious weeds were observed. The dominant taxa were annual Redstem Stork’s Bill and Russian thistle,
with 6.3% and 5.3% average cover, respectively. No species had over 40% relative cover. No seeded
species met the minimum cover criterion of 4%. The diversity of species observed is encouraging for
eventual performance in favorable conditions. A photo showing the site conditions during the spring
evaluation in 2022 is presented below.
Fall 2022 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 2022 cover evaluation are presented in Appendix B. There
was a total of 8 species observed, all of which were captured by cover sampling metrics and 1 of which
were included in the seed mix. Total ground cover in the Supplemental Test Section No. 2 consisted of
Supplemental Test Section No. 2
SE s I SW w
W 150 180 210 240 270 300
I • I • I • I • I • I • I • I • I • I • I • I • I • I • I • I • I • I • I •
0 215°SW (T) @ 37°33'4"N, 109°29'46"W ±19ft & 5691ft
6
19.2% live vegetation, 0.1% rock, 14.9% litter, and bare ground exposure of 65.8%. Perennial cover across
the Supplemental Test Section No. 2 averaged 2.3%, with annual and biennial cover averaging 16.9%. No
noxious weeds were observed. The dominant taxa were Russian thistle averaging 16.8% cover and James’
Galleta (Pleuraphis jamesii) averaging 1.2% cover. Russian thistle contributed greater than 40% relative
cover at 87.5%. No seeded species met the minimum cover criterion of 4%. The diversity of species
observed is encouraging for eventual performance in favorable conditions. A photo showing the site
conditions during the fall evaluation in 2022 is presented below.
3.3 Native Reference Area
Spring 2022 Findings
The Native Reference Area was evaluated with 15 transects during the spring survey. Raw data from
the spring 2022 cover evaluation are presented in Appendix B. There was a total of 4 species observed, all
of which were captured by cover sampling metrics. Total ground cover in the Native Reference Area
consisted of 19.7% live vegetation, 0.3% rock, 27.9% litter, and bare ground exposure of 52.1%. Perennial
cover across the Native Reference Area averaged 19.5%, with annual and biennial cover averaging 0.2%.
No noxious weeds were observed. A photo showing the site conditions during the spring evaluation in 2022
is presented below.
Supplemental Test Section No. 2
7
Spring Survey Conditions (June 7th 2022)
Fall 2022 Findings
The Native Reference Area was evaluated with 15 transects during the fall survey. Raw data from the
fall 2022 cover evaluation are presented in Appendix B. There was a total of 3 species observed, all of
which were captured by cover sampling metrics. Total ground cover in the Native Reference Area consisted
of 25.3% live vegetation, 0.1% rock, 17.9% litter, and bare ground exposure of 56.7%. Perennial cover
across the Native Reference Area averaged 19.9%, with annual and biennial cover averaging 5.4%. No
noxious weeds were observed.
E SE Sf SW W
90 120 150 18 210 240 270
l•l•l•l•l•l•l•l•l•l•l•l•l•l•l•l•l•l•I•
0182°S (T) @ 37°32'35"N, 109°29'51"W ±55ft & 5656ft
8
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 7. In Year 3 (2022) 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 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. The Supplemental Test Section No. 2, which EFRI constructed with a modified revegetation plan
as noted above, is also performing as expected in an unfavorable (dry) precipitation year. However, the
diversity of species observed at the Supplemental Test Section No. 2 is encouraging and indicates the
potential for better performance in favorable (wet) precipitation conditions for this test section.
9
Primary Test
Section
Supplemental
Test Section
Supplemental Test Section #2
1. Species Composition
a. 5 or greater perennial grass species 2 2 10
4 or greater grass species are native 2 2 9
b. At least 1 perennial forb 0 1 2
c. At least 2 shrub species 1 2 1
2. Vegetative cover
a. 40% or greater total vegetative cover*13.1%1.0%5.5%
b. Comprised of species with relative cover between 4% and 40%*1 2 3
c. Free of State and County listed noxious weeds None None None
d. Self generating and permanent+Observed Observed Observed
3. Shrub Density
a. Minimum 500 stems per acre 144 536 Not Sampled Yet
b. Healthy, surived minimum 2 growing seasons Observed Observed Not Sampled Yet
* Species listed in Table D.1 must be used to achieve the cover performance criteria (MWH 2015).
Individual species not listed in Table D.1 may be acceptable if the species is native or adapted to the area and is a desirable component
of the reclaimed project site.
+ Self-regeneration shall be demonstrated by evidence of reproduction, such as tillers or seed production.
Table 6 White Mesa - Success Evaluation - 2022
Performance Comparison
10
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.
As noted in the 2019 monitoring report, the abundance of available water throughout the early
growing season facilitated above average growth and vigor in both test sections. An abnormally tall
canopy of 2019 senesced vegetation had obscured much of the 2020 new growth, producing results
that significantly underestimate the true extent of live vegetative ground cover. In an effort to capture a
more accurate quantification of 2020 new growth, hits that would have been recorded on perennial
live vegetative cover if not for overlying litter were recorded separately from both a species hit and litter.
These hits were treated as live vegetative hits during data analysis and were counted towards the cover
success criteria.
Figure 1: Sampling Procedure
Ground Cover Transect
(Set-up points at 1-meter intervals)
Sample Site
(Starting Point)
\
~ ~ 1/1
ij
.,..
.,..r --~
Re vegetated Unit
laser/ Point-Intercept Bar
(Intercepts at 1 O cm intervals -
note path of'' beams'' for" hits"
on ground cover)
Note: 10 set~up points per
transect with 1 o fnte(cepts
per set-up point results in
100 intercepts per transect
Laser Bar
1 Laser
Focused Beam (0.02' spot) j
(Special J.. for Daylight Visiblllty) \ / ~---1-.;
Hit recorded as ~em/species / I
~---I I
I
I
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 2022 evaluations.
Sample Adequacy Determination
Ground cover sampling was conducted to a minimum of 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
Table 7 White Mesa -Veaetation Cover -2022
Primary Test Section -Spring Survey
Percent Ground Cover Based on Point-InterceDt Samnllnn
Transect No.-> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Average Relative
Grasses Cover Cover Freq.
I A Bromus tectorum Cheatgrass 1 2 0.2 0.9 13 . ~ N p Elymus elymoides Squirreltail 6 11 9 18 6 6 9 9 4 8 13 3 5 8 5 8.0 35.6 100
N p Pascoovrum smithii Western Wheatarass 1 0.1 0.3 7
rorbs
I A Kochia scoparia Summer cypress 1 5 6 3 5 4 4 1 1 1 3 1 1 2.4 10.7 87
I A Sa/so/a traous Russian Thistle 3 3 2 5 5 7 14 11 7 11 6 8 8 11 6.7 30.0 93
Shrubs, Sub-shrubs, cacti & Trees
N p Atria/ex canescens Fourwina Saltbush 13 14 3 14 10 14 8 5.1 22.6 47
Mean
Total Plant Cover 20 19 18 24 30 15 23 24 30 16 24 20 30 19 25 22.5
Rock 1 6 4 2 1 11 8 14 9 7 7 9 10 6 8 6.9
Litter 62 44 59 46 45 24 32 35 34 54 46 45 39 56 51 44.8
Bare around 17 31 19 28 24 50 37 27 27 23 23 26 21 19 16 25.9
Perennial Plant Cover 19 11 9 18 20 6 12 9 18 8 13 14 19 8 13 13.1
Sample Adequacy calculations: Plant Cover Mean = 22.47 t= 1.35 n= 15
Variance = 24.12 Omin = 8.65
N = Native, I = Introduced, P = Perennial, 8 = Biennial, A = Annual
Table 8 White Mesa - Vegetation Cover -2022
Primary Test Section - Fall Survey
Percent Ground Cover Based on Point-Intercept Samolin<l
TransectNo.-> I 1 2 3 4 5 I 6 7 8 9 10 11 12 13 14 15 Average Relative
Grasses Cover Cover Freq.
I A Bromus tectorum Cheatgrass 2 0.1 1.0 7
N p EIYmus e!Ymotdes SQUlrreltall 2 ! ! 0.3 2.1 20
Forbs
I A Sa/so/a traous Russian Thistle 4 2 4 4 2 3 2 5 3 11 2 5 3.1 24.5 80
Shrubs, Sub-shrubs, cacti & Trees
N p Atrip/ex ecnescens Fourwino Saltbush 8 8 8 17 18 17 22 3 33 5 9.3 72.4 67
Mean
Total Plant Cover 14 10 13 5 19 20 3 2 5 20 22 11 5 33 10 12.8
Rock 9 1 5 5 7 6 7 8 6 3 8 4 6 5 11 6.1
Litter 49 65 43 57 41 53 62 60 47 47 14 47 45 44 21 46.3
Bare <1round 28 24 39 33 33 21 28 30 42 30 56 38 44 18 58 34.8
Perennial Plant Cover 10 8 9 1 17 18 0 0 0 17 22 0 3 33 5 9.5
Sample Adequacy calculations: Plant Cover Mean = 12.80 t= 1.35 n= 15
Variance = 75.03 nm;n = 82.85
N = Native, I = Introduced, P = Perennial, B = Biennial, A = Annual
Table 9 White Mesa -Vegetation Cover -2022
Supplemental Test Section -Spring Survey
Petcent Ground Cover Based on Point-Int ercept Sampi ng
Transect No.-> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Average Relative
Cover Cover Freq. Grasses
I A Bromus tedorum Cheatgrass 4 2 2 1 0.6 3.1 27
N p Pascopyrum smithii Western Wheatgrass 1 0.1 0.3 7
N p Poasecunda Sandbero Blueorass 1 0.1 0.3 7
N A Vu/pia odoflora Six Weeks Fescue 1 0.07 0.3 7
Forbs
N A Descurainia pinnata Western Tansymustard 1 1 1 0.2 1.0 20
I A Erodium dcutarium Redstem Stork's Bill 6 4 3 3 6 7 5 15 20 4 2 14 13 8 7.3 37.9 93
I A Sa/so/a traous Russian Thistle 17 12 19 6 5 17 17 7 6 7 3 10 8 7 9.4 48.6 93
I A Sisymbrium altissimum Tall Tumblemustard 1 1 2 7 0.7 3.8 27
N p SPhaeralcea cocdnea Scarlet Globemallow 1 1 0.1 0.7 13
Shrubs, Sub-shrubs, cacti & Trees
N p Gutierrezia sarothrae Broom Snakew eed 2 6 0.5 2.8 13
N p Lydum pa/lidum Pale Oc::;crt-thorn 2 1 0.2 1.0 13
Mean
Total Plant Cover 20 19 26 10 8 27 26 18 21 27 7 15 23 22 21 19.3
Rock 2 0 2 0 0 0 0 0 0 0 2 1 1 0 1 0.6
Litter 25 41 37 35 52 20 18 20 15 24 50 50 24 20 20 30.1
Bare qround 53 40 35 55 40 53 56 62 64 49 41 34 52 58 58 50.0
Perennial Plant Cover 2 0 2 0 o r o • o • 3 0 0 0 2 • 0 0 6 1.0
Sample Adequacy Calculations: Plant Cover Mean = 19.33 t= 1.35 n= 15
Variance = 44.38 nm;n = 21.48
N = Native, I = Introduced, P = Perennial, B = Biennial, A = Annual
Table 10 White Mesa -Veaetation Cover -2022
Supplemental Test Section -Fall Survey
Percent Ground Cover Based on Point-Intercept Samphng
Transect No.-> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Average I Relative I
Cover Cover Freq.
Grasses
N p Pascopyrum smithii Western Wheatorass 1 1 0.1 I 0.5 I 13
Forbs
I A Portu/aa, o/eracea Little Hogweed 1 1 1 0.2 I 0.7 I 20
I A Sa/so/a traous Russian Thistle 26 15 25 32 22 16 20 43 34 22 45 27 23 37 29 27.7 95.9 100
Shrubs, Sub-shrubs, cacti & Trees
N p Gutierrezia Sarothrae Broom Snakeweed 3 5 5 0.9 I 3.0 I 20
Mean
Total Plant Cover 27 15 26 32 22 19 25 44 35 28 45 27 23 37 29 28.9
Rock 0 1 0 0 0 1 0 0 0 0 0 0 1 0 0 0.2
Litter 38 44 22 18 22 13 19 19 17 15 10 21 7 10 16 19.4
Bare Qround 35 40 52 50 56 67 56 37 48 57 45 52 69 53 55 51.5
Perennial Plant Cover 1 0 0 0 0 3 5 0 1 5 0 0 0 0 0 1.0
Sample Adequacy Calculations: Plant Cover Mean = 28.93 t= 1.35 n= 15
Variance = 71.78 nm;n = 15.51
N = Native, I = Introduced, P = Perennial, B = Biennial, A = Annual
Table 11 White Mesa - Vegetation Cover - 2022
Supplemental Test Section No. 2 - Spring Survey
Percent Ground Cover Based on Point-Intercept Sampling
Transect No.——> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
N P Achnatherum hymenoides Indian Ricegrass 1 1 0.1 0.8 13
N P Elymus elymoides Squirreltail 1 1 0.1 0.8 13
N P Elymus lanceolatus ssp psammophilus Streambank Wheatgrass 1 0.1 0.4 7
N P Elymus trachycaulus ssp trachycaulus Slender Wheatgrass 1 0.1 0.4 7
N P Pascopyrum smithii Western Wheatgrass 2 1 1 1 1 0.4 2.3 33
N P Pleuraphis jamesii James' Galleta 1 1 3 2 1 2 2 0.8 4.5 47
N P Poa secunda Sandberg Bluegrass 1 1 2 1 2 0.5 2.6 33
N P Pseudoroegneria spicata Bluebunch Wheatgrass 3 2 3 2 3 1 1 1 1 1 1.2 6.8 67
N P Sporobolus cryptandrus Sand Dropseed 1 1 0.1 0.8 13
I P Thinopyrum intermedium Intermediate Wheatgrass 1 2 4 1 3 1 3 1 1 2 2 1 3 2 1.8 10.2 93
I A Erodium cicutarium Redstem Stork's Bill 9 2 6 6 5 5 9 4 11 2 5 6 13 11 6.3 35.3 93
N A Lappula redowskii Flatspine Stickseed 1 0.1 0.4 7
I A Salsola tragus Russian Thistle 7 4 5 3 2 13 8 9 4 7 3 2 1 5 6 5.3 29.7 100
I A Sisymbrium altissimum Tall Tumblemustard 1 2 2 5 0.7 3.8 27
N P Sphaeralcea coccinea Scarlet Globemallow 1 0.1 0.4 7
N P Sphaeralcea grossulariifolia Gooseberryleaf Globemallow 1 1 0.1 0.8 13
N P Gutierrezia sarothrae Broom Snakeweed 1 0.1 0.4 7
Total Plant Cover 20 11 15 14 15 24 24 21 22 11 16 13 13 24 23
Rock 2 0 1 1 4 1 0 0 3 0 3 0 0 1 0 Litter 15 10 29 37 28 4 3 2 1 6 31 34 37 7 8
Bare ground 63 79 55 48 53 71 73 77 74 83 50 53 50 68 69
Perennial Plant Cover 3 5 4 5 7 6 5 8 5 2 8 5 7 6 6
Plant Cover Mean =t=1.35 n=15
Variance =nmin =
N = Native, I = Introduced, P = Perennial, B = Biennial, A = Annual
64.4
Average
Cover
Relative
Cover Freq.Grasses
Forbs
Shrubs, Sub-shrubs, Cacti & Trees
Mean
17.7
1.116.8
5.5
Sample Adequacy Calculations:17.73
24.78 14.26
,
Table 12 White Mesa - Vegetation Cover - 2022
Supplemental Test Section No. 2 - Fall Survey
Percent Ground Cover Based on Point-Intercept Sampling
Transect No.——> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
N P Achnatherum hymenoides Indian Ricegrass 1 0.1 0.3 7
N P Bouteloua gracilis Blue grama 1 1 1 1 2 2 1 2 1 0.8 4.2 60
N P Pascopyrum smithii Western Wheatgrass 1 1 0.1 0.7 13
N P Pleuraphis jamesii James' Galleta 3 5 1 2 3 3 1 1.2 6.3 47
N P Sporobolus cryptandrus Sand Dropseed 1 0.1 0.3 7
I P Thinopyrum intermedium Intermediate Wheatgrass 1 0.1 0.3 7
I A Salsola tragus Russian Thistle 20 28 24 13 18 20 15 5 16 13 11 23 7 17 22 16.8 87.5 100
I A Sisymbrium altissimum Tall Tumblemustard 1 0.1 0.3 7
None 0.0 0.0 0
Total Plant Cover 25 29 25 20 20 21 15 5 18 15 17 24 12 19 23
Rock 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 Litter 8 5 6 13 8 11 19 32 17 22 20 24 17 14 8
Bare ground 67 66 69 67 72 67 66 63 65 63 63 52 71 67 69
Perennial Plant Cover 5 0 1 7 2 1 0 0 2 2 5 1 5 2 1
Plant Cover Mean =t=1.35 n=15
Variance =nmin =
N = Native, I = Introduced, P = Perennial, B = Biennial, A = Annual
65.8
Average
Cover
Relative
Cover Freq.Grasses
Forbs
Shrubs, Sub-shrubs, Cacti & Trees
Mean
19.2
0.114.9
2.3
Sample Adequacy Calculations:19.20
35.74 17.54
.
Table 13 White Mesa - Vegetation Cover - 2022
Native Reference Area - Spring Survey
Percent Ground Cover Based on Point-Intercept Sampling
Transect No.——> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
None 0.0 0.0 0
I A Salsola tragus Russian Thistle 3 0.2 1.0 7
N P Artemisia tridentata Big Sagebrush 2 3 7 5 4 18 1 5 3.0 15.2 53
N P Gutierrezia sarothrae Broom Snakeweed 8 12 8 9 27 18 16 19 13 22 20 25 11 19 19 16.4 83.1 100N P Opuntia polyacantha Plains Pricklypear 2 0.1 0.7 7
Total Plant Cover 10 15 8 16 32 20 16 19 13 25 24 25 29 20 24 Rock 0 0 0 1 0 0 0 0 0 0 0 0 0 2 1
Litter 31 41 10 37 37 17 35 35 33 28 18 28 23 21 25 Bare ground 59 44 82 46 31 63 49 46 54 47 58 47 48 57 50
Perennial Plant Cover 10 15 8 16 32 20 16 19 13 22 24 25 29 20 24
Plant Cover Mean =t=1.35 n=15
Variance =nmin =
N = Native, I = Introduced, P = Perennial, B = Biennial, A = Annual
52.1
Average
Cover
Relative
Cover Freq.Grasses
Forbs
Shrubs, Sub-shrubs, Cacti & Trees
Mean
19.70.3
27.9
19.5
Sample Adequacy Calculations:19.73
46.92 21.80
I I
I I
I I
I I
Table 14 White Mesa -Vegetation Cover -2022
Native Reference Area -Fall Survey
Percent Ground Cover Based on Point-Intercept Sampling
Transect No.-> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Average I Relative I
Cover Cover Freq.
Grasses
None 0.0 I 0.0 I 0
Forbs
I A Portulaca o/eracea Little Hogweed 1 2 1 3 3 1 3 3 1.1 I 4.5 I 53
I A Sa/so/a traous Russian Thistle 17 8 2 3 5 18 2 2 7 4.3 16.8 60
Shrubs, Sub-shrubs, cacti & Trees
N p Artemisia tridentata Big Sagebrush 7 12 4 4 1 25 11 10 9 5.5 I 21.8 I 60
N p Gutierrezia sarothrae Broom Snakeweed 15 2 8 11 16 9 22 7 10 9 16 21 23 24 23 14.4 56.8 100
Mean
Total Plant Cover 16 28 16 24 21 16 31 29 37 20 26 21 33 29 33 25.3
Rock 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0.1
Litter 14 26 23 21 30 36 20 22 21 9 8 1 16 14 8 17.9
Bare qround 70 46 61 54 49 48 49 49 42 71 66 78 51 57 59 56.7
Perennial Plant Cover 15 9 8 23 16 13 26 8 35 20 26 21 32 24 23 19.9
Sample Adequacy Calculations: Plant Cover Mean = 25.33 t= 1.35 n= 15
Variance = 46.38 nm;n = 13.07
N = Native, I = Introduced, P = Perennial, B = Biennial, A = Annual
WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2022 ANNUAL PERFORMANCE MONITORING REPORT
Appendix C CELL 2 SETTLEMENT MONITORING DATA
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 Jan‐23
Wa
t
e
r
Le
v
e
l
El
e
v
a
t
i
o
n
(f
t
)
Date
Figure C.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
Note:
(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)
-.......
-+---e----+-
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 Jan‐23
Wa
t
e
r
Le
v
e
l
El
e
v
a
t
i
o
n
(f
t
)
Date
Figure C.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 Jan‐23
Wa
t
e
r
Le
v
e
l
El
e
v
a
t
i
o
n
(f
t
)
Date
Figure C.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
(2)
Note:
(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
........ --+-
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 Jan‐23
Wa
t
e
r
Le
v
e
l
El
e
v
a
t
i
o
n
(f
t
)
Date
Figure C.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
.......
WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2022 ANNUAL PERFORMANCE MONITORING REPORT
Appendix D CELL 2 STANDPIPE PIEZOMETER WATER LEVELS
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
e
v
a
t
i
o
n
,
f
e
e
t
m
s
l
Figure D.1White Mesa MillCell 2W1 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
v
a
t
i
o
n
,
f
e
e
t
m
s
l
Figure D.2White Mesa MillCell 2W2 Settlement Plate Measurements
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
I
-Mi---• I --
i
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
v
a
t
i
o
n
,
f
e
e
t
m
s
l
Figure D.3White Mesa MillCell 2W3 Settlement Plate Measurements
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
I
·---
II
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 D.4White Mesa MillCell 2W4 Settlement Plate Measurements
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
I
I I
] .._ ---1 -----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 D.5White Mesa MillCell 2E1 Settlement Plate Measurements
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
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
l
Figure D.6White Mesa MillCell 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
e
v
a
t
i
o
n
,
f
e
e
t
m
s
l
Figure D.7White Mesa MillCell 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
v
a
t
i
o
n
,
f
e
e
t
m
s
l
Figure D.8White Mesa MillCell 2E1-2S Settlement Plate Measurements
(1)
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
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
e
e
t
m
s
l
Figure D.9White Mesa MillCell 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 D.10White Mesa MillCell 2W5-N Settlement Plate Measurements
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
I
..
... • --,,
.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
v
a
t
i
o
n
,
f
e
e
t
m
s
l
Figure D.11White Mesa MillCell 2W3-S Settlement Plate Measurements
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
I
·--
II
-
11...
~ .........
-■
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 D.12White Mesa MillCell 2W5-S Settlement Plate Measurements
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
I
. .._
11
i
--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 D.13White Mesa MillCell 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
,.
~ ~
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 D.14White Mesa MillCell 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
e
v
a
t
i
o
n
,
f
e
e
t
m
s
l
Figure D.15White Mesa MillCell 2W6-N 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
v
a
t
i
o
n
,
f
e
e
t
m
s
l
Figure D.16White Mesa MillCell 2W6-C Settlement Plate Measurements
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
I
-
I •
I
L.. -
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 D.17White Mesa MillCell 2W6-S Settlement Plate
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
I
1•
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
v
a
t
i
o
n
,
f
e
e
t
m
s
l
Figure D.18White Mesa MillCell 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
t
i
o
n
,
f
e
e
t
m
s
l
Figure D.19White Mesa MillCell 2W4-N Settlement Plate
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
I
II
-
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 D.20White Mesa MillCell 2W4-S Settlement Plate Measurements
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
I
. .._
I I
-,
,.