HomeMy WebLinkAboutDRC-2021-003041 - 0901a06880e2605bFebruary 22, 2021
ENERGY FUELS
Div of Waste Management
and Radiation Control
Energy Fuels ResoM (PS5A)22
225 Union Blvd. Suite 600
Lakewood, CO, US, 80228
303 974 2140
rn 1)RC-ZoZi-oo3o41 www,energyfuels.co
Sent VIA E-MAIL AND EXPRESS DELIVERY
Mr. Ty L. Howard
Director
Division of Waste Management and Radiation Control
Utah Department of Environmental Quality
195 North 1950 West
P.O. Box 144880
Salt Lake City, UT 84114-4880
Re: Transmittal of White Mesa Uranium Min Cell 2 Reclamation Cover 2020 Annual Performance
Monitoring Report
Dear Mr. Howard:
In accordance with the Stipulation and Consent Agreement ("SCA" dated February 23, 2017) between the
Division of Waste Management and Radiation Control ("DWMRC") and Energy Fuels Resource (USA) Inc.
("EFRI"), EFRI constructed a cover performance monitoring test section ("Primary Test Section") on Cell 2 in
2016, completed Phase 1 cover placement on Cell 2 in 2017, constructed a supplement vegetation monitoring
test section ("Supplemental Test Section") in 2017, and initiated performance monitoring. This letter transmits
the 2020 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
Quality Assurance Manager
CC: David Frydenlund Terry Slade
Logan Shumway
Scott Bakken
February 22, 2021
Sent VIA E-MAIL AND EXPRESS DELIVERY
Mr. Ty L. Howard
Director
Division of Waste Management and Radiation Control
Utah Department of Environmental Quality
195 North 1950 West
P.O. Box 144880
Salt Lake City, UT 84114-4880
Energy Fuels Resources (USA) Inc.
225 Union Blvd. Suite 600
Lakewood, CO, US, 80228
303 974 2140
www.energyfuels.com
Re: Transmittal of White Mesa Uranium Mill Cell 2 Reclamation Cover 2020 Annual Performance
Monitoring Report
Dear Mr. Howard:
In accordance with the Stipulation and Consent Agreement ("SCA" dated February 23, 2017) between the
Division of Waste Management and Radiation Control ("DWMRC") and Energy Fuels Resource (USA) Inc.
("EFRI"), EFRI constructed a cover performance monitoring test section ("Primary Test Section") on Cell 2 in
2016, completed Phase 1 cover placement on Cell 2 in 2017, constructed a supplement vegetation monitoring
test section ("Supplemental Test Section") in 2017, and initiated performance monitoring. This letter transmits
the 2020 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,
)(my»~
ENERGY FUELS RESOURCES (USA) INC.
Kathy Weinel
Quality Assurance Manager
CC: David Frydenlund
Terry Slade
Logan Shumway
Scott Bakken
White Mesa Uranium Mill Cell 2 Reclamation Cover 2020 Annual Performance Monitoring Report
February 22, 2021
Prepared for: Energy Fuels Resources (USA) Inc. Prepared by: Stantec Consulting Services Inc.
Document Review and Revision Record
Rev. Description Author(s) Quality Check Independent Review
0 Draft for client review S Downey, C Benson, J. Dillon
2/15/2021 M Davis 2/16/2021 C Strachan 2/16/2021
1 Final for client M Davis 2/22/2021
WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2020 ANNUAL PERFORMANCE MONITORING REPORT
Table of Contents
1.0 INTRODUCTION .......................................................................................................... 1.1
1.1 BACKGROUND ............................................................................................................ 1.1
1.2 MONITORING REQUIREMENTS ................................................................................. 1.2
1.3 REPORT ORGANIZATION .......................................................................................... 1.3
2.0 COVER AND PRIMARY TEST SECTION DESIGN ..................................................... 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 – 2020
Table 2 Cell 2 Top Surface Settlement Measured Between April 2016 and December 2020 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 2020 FIELD HYDROLOGY OF THE CELL 2 PRIMARY TEST SECTION
AT THE WHITE MESA MILL
APPENDIX B 2020 REVEGETATION EVALUATION CELL 2 PRIMARY AND
SUPPLEMENTAL TEST SECTIONS
APPENDIX C CELL 2 SETTLEMENT MONITORING DATA
APPENDIX D CELL 2 STANDPIPE PIEZOMETER WATER LEVELS
WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2020 ANNUAL PERFORMANCE MONITORING REPORT
1.1
1.0 INTRODUCTION
This report documents the 2020 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
On November 11, 2015, the DWMRC recommended that EFRI develop a plan to begin reclamation of
Cell 2. This plan would consist of placing the proposed cover system presented in Reclamation Plan,
Revision 5.1 (EFRI, 2016) on Cell 2 in two phases and demonstrating acceptable cover performance via
a performance monitoring program. The Reclamation Plan was updated to Revision 5.1B (EFRI, 2018)
on February 8, 2018. Information and requirements for the Cell 2 reclamation cover construction and
monitoring did not change for Revision 5.1B. Thus, references to the Reclamation Plan in the remainder
of this report refer to Revision 5.1B.
EFRI and DWMRC executed a Stipulation and Consent Agreement (SCA) on February 23, 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 committed
to the following tasks by the end of 2017: (1) completion of Phase 1 cover placement on Cell 2, (2)
construction of a cover performance monitoring test section (Primary Test Section), and (3) construction
of a supplemental vegetation monitoring test section (Supplemental Test Section).
Cell 2 Phase 1 cover placement commenced in April 2016, was completed in April 2017, and is
documented in Stantec (2017b). The Primary Test Section was constructed within the Cell 2 cover in fall
2016 (concurrently with the Phase 1 cover placement). The Primary Test Section construction was
considered complete (per the DWMRC) after finalizing the laboratory testing for samples collected from
the test section during construction and submitting the as-built report (June 30, 2017). Construction of
this test section is documented in Stantec (2017a).
The Supplemental Test Section was constructed in fall 2017 as a supplemental vegetation monitoring
section to the Primary Test Section (Stantec, 2018a). The Supplemental Test Section does not evaluate
the entire cover profile but will demonstrate that vegetation can be established and that erosional
influences will not be detrimental to long-term vegetation establishment. The Supplemental Test Section
was constructed in a location representative of cover conditions on the tailings management system cells
WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2020 ANNUAL PERFORMANCE MONITORING REPORT
1.2
(see Figure 2). 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 both the cover with or without the addition of gravel for erosion
protection. Mulch was placed to provide erosion protection for the seeds during germination and early
seedling growth. The Reclamation Plan (EFRI, 2018) provides additional design information for the
Supplemental Test Section.
1.2 MONITORING REQUIREMENTS
The Primary Test Section is required to be monitored for percolation and vegetative cover performance.
Per the SCA, the Primary Test Section calibration monitoring was required to begin on January 1, 2018
(following Primary Test Section construction completion) and be conducted for two years. The calibration
monitoring and results from 2018 and 2019 are in the 2018 and 2019 Annual Performance Monitoring
Reports (Stantec, 2019 and Stantec, 2020, respectively). EFRI also collected monitoring data in 2017,
with the results documented in the 2017 Annual Performance Monitoring Report (Stantec, 2018b).
Official performance monitoring was required to commence two calendar years after calibration
monitoring begins (i.e., January 1, 2020) and continue for five years. The Supplemental Test Section will
be monitored annually for erosional stability and vegetative cover during official performance monitoring.
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 section 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, and (2) acceptable vegetation diversity per
EFRI (2018) (perennial grasses, forbs and shrubs) are met for the Supplemental and Primary Test
Sections by the end of the five-year performance monitoring period.
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.
WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2020 ANNUAL PERFORMANCE MONITORING REPORT
1.3
During the official performance monitoring period, EFRI is required to submit quarterly data quality reports
and annual performance monitoring reports to DWMRC. EFRI provided data quality reports and annual
reports during the calibration time period to DWMRC for information purposes. Report submittals
required for the official performance monitoring began in 2020. EFRI submitted the quarterly data quality
reports to DWMRC for 2020 and this report is the first annual monitoring report for the official
performance monitoring period.
1.3 REPORT ORGANIZATION
This report provides an overview of the cover and Primary Test Section design (Section 2.0), Primary
Test Section hydrologic monitoring (Section 3.0), Primary and Supplemental Test Section vegetation
survey results (Section 4.0), Cell 2 settlement and water level monitoring (Section 5.0), and conclusions
(Section 6.0).
WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2020 ANNUAL PERFORMANCE MONITORING REPORT
2.1
2.0 COVER AND PRIMARY TEST SECTION DESIGN
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). 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 Reclamation Plan (EFRI, 2018) provides detailed design information for the cover and Primary Test
Section.
WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2020 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 21, 2020 (last
automated data download of 2020) are described in the annual Primary Test Section report in Appendix
A. Data in this report represent the first four full calendar years (2017 through 2020) of monitoring. Table
1 summarizes the water balance results.
Table 1. Primary Test Section Water Balance for 2016 to 2020
Calendar Year
Water Balance Quantities (mm)
Precipitation Runoff Lateral
Flow ET Change Storage Percolation
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
Notes: a. Partial year, monitoring began on September 9, 2016. b. Damage from vault flooding precluded measuring flows 7 February 2017 – 25 March 2017
The hydrology of the test section during 2020 was consistent with expectations for a water balance cover
in a semi-arid climate. Precipitation at the test section in 2020 (128 mm) was substantially lower than the
long-term average recorded at the Blanding, Utah station (355 mm) operated by the National Weather
Service. The entire year was much drier than average. Soil water storage diminished throughout the
year, ending the year at one of the lowest points since 2016. Over the calendar year, the soil water
storage dropped, whereas in past years a modest net accumulation of soil water occurred. Grasses
present in the robust vegetation of 2019 were dormant in 2020 due to the lack of precipitation, but the
shrubs persisted. Annual runoff and annual lateral flow were essentially nil. Annual percolation was 0.9
mm, which is similar to the percolation rate recorded in 2018 and 2019 and compares well with
percolation rates reported in the literature for water balance covers in similar climates. Thermally driven
flow appears responsible for a majority of the percolation recorded to date.
WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2020 ANNUAL PERFORMANCE MONITORING REPORT
4.1
4.0 PRIMARY AND SUPPLEMENTAL TEST SECTIONS
VEGETATION INSPECTION
Cedar Creek Associates, Inc. visited the Mill site on May 27, 2020 and on September 15, 2020 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 revegetation evaluations were not favorable for plant
growth. Regionally, the spring of 2020 can be considered a dry year with below average precipitation.
Vegetation observed during the 2020 spring evaluation exhibited below average plant vigor and growth in
response to unfavorable precipitation conditions. Ground cover during the spring revegetation survey on
Primary Test Section consisted of 73.7 percent live vegetation, 0.6 percent rock, 14.7 percent litter, and
bare ground exposure of 11 percent. Perennial plant cover across the unit averaged 73.3 percent, with
annual species comprising 0.4 percent. Ground cover during the spring revegetation survey on
Supplemental Test Section consisted of 45.0 percent live vegetation, 0.1 percent rock, 41.2 percent litter,
and bare ground exposure of 13.7 percent. Perennial plant cover across the unit averaged 1.1 percent,
with annual species comprising 43.9 percent.
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 and show that in Year 1 of the
performance period, both the Primary and Supplemental Test Sections are not currently meeting 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 other species from establishing. 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.
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 is constructing a secondary supplemental
vegetation monitoring test section in 2021 to provide additional data for Cell 2 cover test section
performance monitoring and to evaluate modifications to the revegetation plan to promote vegetation
success. The modifications are aimed to address the squirreltail dominance occurring on the Primary
Test Section and poor seeding establishment on the Supplemental Test Section.
WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2020 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 2020. Table 2 lists the settlement measured since the start of Phase 1 cover
construction (April 2016) through December 2020. Settlement totals during this period range from 0 to
0.5 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 0.1 feet of annual settlement was
measured for 2020 for all the monuments (ranging from 0.04 feet settlement to 0.02 feet 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 2020
Settlement
Monument
April 2016 to December 2020 Settlement (ft)
2020 Settlement (ft)
Settlement
Monument
April 2016 to December 2020 Settlement (ft)
2020 Settlement (ft)
2W1 0.28 0.04 2W6-N 0.16 -0.02
2W2 0.33 0.00 2W6-C 0.29 0.00
2W3 0.31 0.01 2W6-S 0.44 0.01
2W3-S 0.34 0.01 2W7-N -0.04 -0.02
2W4-N 0.24 -0.01 2W7-C 0.09 -0.01
2W4-C 0.27 0.00 2W7-S 0.30 0.01
2W4-S 0.50 0.00 2E1-N 0.19 -0.01
2W5-N 0.24 -0.01 2E1 0.29 0.01
2W5-C 0.31 0.01 2E1-1S 0.33 0.02
2W5-S 0.41 0.01 2E1-2S 0.45 0.02
WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2020 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 January 4, 2021. 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 except for four piezometers located in the west side of Cell 2
(C2-P01, C2-P02, C2-P03, and C2-P04). These four piezometers showed an increase in water levels
from May to September 2020, then decreased. The increase in water levels at these four locations was
less in 2020 than 2019. Overall, water levels have decreased since Phase 1 cover placement by
approximately 1 to 4 feet (net), which is summarized in Table 3.
Water balance results from monitoring the cover show the Primary Test Section is performing well and
despite a very wet 2019 winter/spring, 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 precipitation from infiltrating into tailings and it is expected that a wet
precipitation season would have minimal impact on the water levels in the tailings.
WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2020 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 1/4/2021
(ft)
Change in Water Level Elevation since Phase 1 Cover Placement (ft)*
C2-P01 West 5612.55 5611.33 -1.22
C2-P02 West 5613.30 5611.78 -1.52
C2-P03 West 5612.31 5610.81 -1.50
C2-P04 West 5613.97 5612.05 -1.92
C2-P05 West 5608.39 5606.56 -1.83
C2-P06 West 5609.21 5607.51 -1.70
C2-P07 West 5610.08 5607.97 -2.11
C2-P08 West 5605.25 5603.58 -1.67
C2-P09 Near Sump 5602.94 5601.70 -1.24
C2-P10 Near Sump 5601.54 5599.84 -1.70
C2-P11 Near Sump 5602.38 5599.78 -2.60
C2-P12 Near Sump 5599.45 5595.81 -3.64
C2-P14 Near Sump 5603.99 5602.19 -1.80
C2-P15 Near Sump 5604.01 5602.01 -2.00
C2-P16 Near Sump 5604.37 5602.34 -2.03
C2-P13 East 5605.72 5604.15 -1.57
C2-P17 East 5607.49 5606.39 -1.10
C2-P18 East 5607.82 5605.31 -2.51
C2-P19 East 5609.09 5606.98 -2.11
C2-P20 East 5610.63 5609.29 -1.34
C2-P21 East 5612.40 5609.83 -2.57
C2-P22 East 5613.39 5610.21 -3.18
C2-P23 East 5614.24 5610.78 -3.46
*Negative number indicates a decrease in water level.
WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2020 ANNUAL PERFORMANCE MONITORING REPORT
6.1
6.0 CONCLUSIONS
Hydrology of the Primary Test Section during 2020 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 0.9 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 2020 spring evaluation exhibited below average plant vigor and growth in
response to unfavorable (dry) 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 is constructing a secondary supplemental vegetation monitoring test section in
2021 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 0.5 feet. This represents total settlement from the
start of Phase 1 cover construction (April 2016) through December 2020. 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 0.1 feet of cumulative settlement was measured
for 2020 for all the monuments.
Water levels for piezometers increased during the Phase 1 cover placement and then generally
decreased until the wet winter/spring of 2019. In 2020, water levels for piezometers were generally level
for the majority of the year except for a few locations which showed increasing and then decreasing water
levels. For the piezometers with increasing water levels in 2019 and 2020, recent readings show a return
to a decreasing trend in water levels. Overall, water levels have decreased since Phase 1 cover
placement by approximately 1 to 4 feet. Based on performance of the Cell 2 Primary Test Section,
placement of the Phase 2 cover on Cell 2 would minimize precipitation infiltrating into the tailings and wet
precipitation seasons would have minimal impact on water levels in the tailings.
WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2020 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.
WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2020 ANNUAL PERFORMANCE MONITORING REPORT
FIGURES
REGIONAL LOCATION MAP FIGURE 1
1009740 LOC MAP
WHITE MESA MILL TAILINGS RECLAMATION
FEB 2021ENERGY FUELS
REFERENCE:
ADAPTED FROM FIGURE 1-1 IN DENISON MINES (USA) ~~:~g1~AGTIOUNT,AH2009. RECLAMATION PLAN WHITE MESA MILL , · VERSION 4.0. NOVEMBER. '
PROJECT
!nKmLr-E _______ __JC) Stantec
DATE
FILE NAME
SUPPLEMENTAL TEST SECTION 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 2021
K REED
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PRIMARY TEST SECTION
DRAWING BmBtNCt(s)·
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9.5'
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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 2021
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
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FEB 2021
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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~
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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 2020 ANNUAL PERFORMANCE MONITORING REPORT
APPENDICES
WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2020 ANNUAL PERFORMANCE MONITORING REPORT
Appendix A 2020 FIELD HYDROLOGY OF THE CELL 2 PRIMARY TEST SECTION AT THE WHITE MESA
MILL
FIELD HYDROLOGY OF THE CELL 2 PRIMARY TEST
SECTION AT THE WHITE MESA MILL
ANNUAL REPORT FOR CALENDAR YEAR 2020
WHITE MESA MILL – TAILINGS MANAGEMENT CELL 2
ENERGY FUELS RESOURCES (USA) INC.
SAN JUAN COUNTY, UTAH
Craig H. Benson, PhD, PE, NAE
4 February 2021
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 21 December 2020 (last automated data download of 2020). The data set
includes the first four full calendar years (2017 - 2020) of monitoring for the test section. This
report emphasizes data collected in 2020.
The water balance of the test section is summarized as follows:
Calendar
Year
Water Balance Quantities (mm)
Precipitation Runoff Lateral
Flow ET D Storage Percolation
2016 60 0 0 35 17 0.0
2017 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
Note: 2016 is a partial year; monitoring began on 29 September 2016.
The hydrology of the test section during 2020 was consistent with expectations for a water balance
cover in a semi-arid environment. Precipitation in 2020 (128 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. The entire year was much
drier than average. Soil water storage generally diminished throughout the year, ending the year
at one of the lowest points since 2016. Grasses present in the robust vegetation of 2019 were
dormant in 2020 due to the lack of precipitation, but the shrubs persisted. Annual runoff and
annual lateral flow were essentially nil. Annual percolation was 0.9 mm, which is similar to the
percolation rate recorded in 2018 and 2019 and compares well with percolation rates reported in
the literature for water balance covers in similar climates. Thermally driven flow appears
responsible for a majority of 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
12/21/20.
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: (upper) air temperature and (lower) cumulative precipitation.
Fig. 4. Cumulative precipitation and potential evapotranspiration (PET) on-site during 2020.
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 end of 2020.
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. Vegetation on surface of test section on 31 May 2018 (a) and 14 July 2020 (b).
Photographs from Cedar Creek (2020).
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 14 July 2020.
This report describes data collected since inception of the test section, with particular
emphasis on data collected in 2020. 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.
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.
.
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 the average daily precipitation and the average daily air temperature
measured on-site with long-term historical averages reported by the NWS at the Blanding station.
Average air temperature at the test section generally falls within the long-term high and low
temperatures recorded at the Blanding station (Fig. 3a), except for three brief cold periods in
February, September, and October. The on-site precipitation in 2020 was much lower than the
long-term average annual precipitation at the Blanding station (128 vs. 355 mm). The entire year
was much drier than average.
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 2020. 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: (upper) air temperature and (lower) cumulative precipitation.
6
Fig. 4. Cumulative precipitation and potential evapotranspiration (PET) on-site during 2020. PET
computed using the FAO method described in Allen et al. (1998) with on-site
meteorological data.
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
12/21/20 (last day of automated downloads for 2020).
Calendar
Year
Water Balance Quantities (mm)
Precipitation Runoff Lateral
Flow ET D Storage Percolation
2016 60 0 0 35 17 0.0
2017* 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
*damage from vault flooding precluded measuring flows 7 February 2017 – 25 March 2017.
Fig. 5 shows cumulative quantities for each of the water balance fluxes (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 residual of the daily water balance:
ET = P – R – L – Pr – DS (1)
8
Fig. 5. Water balance graph for test section through end of 2020.
9
where P = daily precipitation, R = daily runoff, L = daily lateral flow, Pr = daily percolation, and DS
= daily change in soil water storage. ET computed with Eq. 1 includes actual ET and any errors
in the water balance. ET computed with Eq. 1 was only 171 mm in 2020, which reflects the very
dry conditions experienced throughout the year. Cumulative annual ET computed with Eq. 1 is in
agreement with the generalized relationship between annual ET, potential evapotranspiration
(PET), and precipitation for water balance covers and natural watersheds, as shown in Fig. 6.
Annual PET in Fig. 6 was computed using the on-site meteorological data with the FAO method
described in Allen et al. (1998) and shown in Fig. 4.
The overall seasonal water balance trends shown in Fig. 5 are consistent with
expectations for a water balance cover in a semi-arid climate. During 2020, soil water storage
diminished gradually during the winter and early spring months due to dry conditions, whereas
accumulation of soil moisture during this period is common during years with more typical
precipitation. Similar conditions occurred in 2018. Because the soil water was depleted, the
grasses in the vegetation remained dormant in 2020 relative to the abundant stand of vegetation
present in Spring 2019 after the wet winter of 2019 (Fig. 7). However, the shrubs persisted.
Percolation began on 14 July 2020, nine days earlier than in 2019, and on the same date
as in 2017 (Fig. 8). Percolation ceased on 07 November 2020, 10 days later than in 2019 and six
days earlier than in 2017. For each year in the record, percolation is unrelated to the soil water
storage record, and occurs when soil water storage is near a minimum, suggesting that
mechanisms other than hydraulic gradients are driving 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
in Fig. 9. 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,
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).
11
Fig. 7. Vegetation on surface of test section on 31 May 2019 (a) and 14 July 2020. Photograph
in (a) from Cedar Creek (2020).
(b) 14 July 2020
(a) 31 May 2019
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.
13
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).
14
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 thermocouple second from the surface
(686 mm bgs) were used to compute the thermal gradient, rather than temperatures from the
uppermost thermocouple (457 mm bgs), to avoid variability in soil temperature associated with
short-term fluctuations in air temperature. Positive thermal gradients correspond to downward
heat flow and negative thermal gradients correspond to upward heat flow. The gradient varies
systematically with the seasons each year, with a maximum of approximately +4 oC/m in early
July to a minimum of approximately -4 oC/m in early January.
Thermal fluxes were computed using the method in Globus and Gee (1995) and the
thermal gradient in Fig. 10 using:
(2)
where qT is the thermal flux, KT is the thermal water conductivity (set at 2x10-11 m2/s-oC, Globus
and Gee 1995), and DT/Dz is the thermal gradient. The cumulative downward thermal flux
computed using this approach, which is captured in the drainage layer at the base of the lysimeter,
is shown in Fig. 10. The timing and magnitude of the computed thermal flux resembles the
percolation rate, suggesting that a significant fraction of percolation captured by the lysimeter is
induced by the thermal gradient.
Fig. 11 shows annual percolation from the test section for 2017, 2018, 2019, and 2020
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,
and 2020 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
qT =KT
ΔT
Δz
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.
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).
17
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 21 December 2020 (date of last automated data download in 2020), with the discussion
emphasizing data collected in 2020. The monitoring system for the test section has been
collecting all of 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.
Data collection has continued uninterrupted since repairs to the vault were made in May 2017.
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 2020 (128 mm) was much lower than the long-term average
recorded at the Blanding, Utah station (355 mm) operated by the NWS. The entire year was
drier than the historical average, resulting very little soil moisture for vegetative growth and
evapotranspiration. The grasses established during the wet spring of 2019 were dormant in
2020. The shrub species persisted.
• The test section hydrology is consistent with expectations for water balance covers in semi-
arid locations in the western US. Nearly all precipitation at the test section was returned to the
atmosphere via evapotranspiration. Runoff and lateral flow were essentially nil, and percolation
was 0.9 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 appears responsible for most of the 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 2020 ANNUAL PERFORMANCE MONITORING REPORT
Appendix B 2020 REVEGETATION EVALUATION CELL 2
PRIMARY AND SUPPLEMENTAL TEST SECTIONS
White Mesa Mill Site
2020 REVEGETATION EVALUATION CELL 2 PRIMARY AND SUPPLEMENTAL TEST
SECTIONS
FEBRUARY 2021
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 ....................................................................................................................... 10
3.2 Supplemental Test Section ............................................................................................................. 14
4.0 PERFORMANCE EVALUATION ........................................................................................................ 17
5.0 REFERENCES .................................................................................................................................... 18
List of Charts and Tables
Table 1. 2020 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. Summary of Woody Plant Density ......................................................................................... 12
Chart 3. Primary Test Section Perennial & Annual Cover Trend (Spring Survey) .................................... 13
Chart 4. Supplemental Test Section Perennial & Annual Cover Trend (Spring Survey) ............................ 16
Table 4. Performance Comparison ...................................................................................................... 17
2
White Mesa Mill Site
2020 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 an onsite
evaluation of revegetation on the test sections at the Mill site on May 27, 2020 and on September 15, 2020.
This report summarizes field observations 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.
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
match the dimensions of the Primary Test Section and is located to the north of the tailings management
cells.
3
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.
1.3 Precipitation
Table 1 and Chart 1 display site precipitation for January 2018 – present. Precipitation conditions in
the months prior to revegetation evaluations were not favorable for plant growth. Regionally, the spring of
2020 can be considered a dry year with below average precipitation. Vegetation observed during the 2020
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 23.7 mm (89% of normal), 1.1 mm (5% of normal), and 1.8 mm (10% of normal) of
precipitation respectively. January and February were also significantly below average, likely contributing
to low overwinter increases in soil-water storage and plant available water in the spring. Precipitation
rebounded in June and July, within 138% and 85% of normal precipitation, respectively. Conditions in
August were dry, with only 1% of average precipitation, while September recorded 22.0 mm of precipitation
(68% of average).
4
Table 1 White Mesa - Precipitation - 2020
Site and Long-term Average Monthly Precipitation
Site
Precipitation
Percent of
Normal
Site
Precipitation
Percent of
Normal
Site
Precipitation
Percent of
Normal
(mm)(%)(mm)(%)(mm)(%)(mm)
January 8.2 23%46.7 132%17.1 48%35.3
February 4.2 14%65.6 214%5.4 18%30.7
March 8.3 31%62.2 233%23.7 89%26.7
April 3.0 14%12.2 55%1.1 5%22.1
May 6.6 37%36.7 203%1.8 10%18.0
June 11.7 102%2.3 20%15.8 138%11.4
July 6.4 22%4.7 16%24.9 85%29.2
August 10.0 29%8.7 25%0.5 1%35.1
September*1.5 5%0.0 0%22.0 68%32.5
October*81.7 222%5.2 14%--36.8
November*5.6 21%21.1 79%--26.7
December*10.4 31%42.5 126%--33.8
A NNUA L
+157.6 65%307.9 128%112.3 47%241.0
*Incompete Data for 2020
+January through September
2018 2019 2020 Long Term Average
Jan 8.2 46.7 17.1 35.3
Feb 4.2 65.6 5.4 30.7
Mar 8.3 62.2 23.7 26.7
Apr 3.0 12.2 1.1 22.1
May 6.6 36.7 1.8 18.0
Jun 11.7 2.3 15.8 11.4
Jul 6.4 4.7 24.9 29.2
Aug 10.0 8.7 0.5 35.1
Sep 1.5 0.0 22.0 32.5
Oct 81.7 5.2 36.8
Nov 5.6 21.1 26.7
Dec 10.4 42.5 33.8
2020*Blanding
Long Term
Average
2018 2019
8.2
4.2
8.3
3.0
6.6
11.7
6.4
10.0
1.5
81.7
5.6
10.4
46.7
65.6
62.2
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
0.0
20.0
40.0
60.0
80.0
100.0
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 -2020
201820192020Long Term Average
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 Section 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.
7
3.0 REVEGETATION MONITORING RESULTS
The results of 2020 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 2020
monitoring surveys. Chart 2 presents a summary of relative cover by lifeform at each test section as
determined by 2020 monitoring surveys.
Table 2 White Mesa - Vegetation Cover - 2020
Summary of Species Observed on Each Test Section
Area ——>
Grasses Spring Fall Spring Fall
I A Bromus tectorum Cheatgrass x
N P *Elymus elymoides Squirreltail x x
N P *Pascopyrum smithii Western Wheatgrass x x
N P *Poa secunda Sandberg Bluegrass x x
Forbs
N P *Artemisia ludoviciana White Sagebrush x
I A Descurainia pinnata Western Tansymustard x
I A Erodium cicutarium Redstem Stork's Bill x x
I A Kochia scoparia Summer Cypress x x
I B Lactuca serriola Prickly Lettuce x
I A Salsola tragus Russian Thistle x x x
N P Sphaeralcea coccinea Scarlet Globemallow x x
Shrubs, Sub-shrubs, Cacti & Trees
N P *Atriplex canescens Fourwing Saltbush x x
N P Gutierrezia sarothrae Broom Snakeweed x
N P Lycium andersonii Waterjacket x
3 2 2 2
* Indicates a seeded species
N = Native, I = Introduced, P = Perennial, B = Biennial, A = Annual
Seeded Species Encountered
Total Species Encountered
Primary Test
Section
Supplemental
Test Section
Species Observed
5 11
8
Table 3 White Mesa - Vegetation Cover - 2020
Summary of Average Cover
Percent Ground Cover Based on Point-Intercept Sampling
Area ——>
Grasses Spring Fall Spring Fall
I A Bromus tectorum Cheatgrass 0.3 ---
N P *Elymus elymoides Squirreltail 56.3 2.4 --
N P *Elymus elymoides+Squirreltail 15.3 ---
N P *Pascopyrum smithii Western Wheatgrass --0.1 -
N P *Poa secunda Sandberg Bluegrass --0.3 0.7
Forbs
N P *Artemisia ludoviciana White Sagebrush ---0.1
I A Descurainia pinnata Western Tansymustard --0.1 -
I A Erodium cicutarium Redstem Stork's Bill --43.6 0.2
I A Kochia scoparia Summer Cypress --0.1 24.8
I B Lactuca serriola Prickly Lettuce --0.1 -
I A Salsola tragus Russian Thistle 0.1 4.3 --
N P Sphaeralcea coccinea Scarlet Globemallow --0.7 1.2
Shrubs, Sub-shrubs, Cacti & Trees
N P *Atriplex canescens Fourwing Saltbush 1.7 3.4 --
N P Gutierrezia sarothrae Broom Snakeweed ---0.2
N P Lycium andersonii Waterjacket ---0.1
Total Plant Cover 73.7 10.1 45.0 27.3
Rock 0.6 3.1 0.1 0.1
Litter (including plant senscence in fall)14.7 71.5 41.2 58.5
Bare ground 11.0 15.4 13.7 14.1
Total Perennial Cover 73.3 5.8 1.1 2.3
Summary by Lifeform:
Perennial Grasses 71.7 2.4 0.4 0.7
Annual Grasses 0.3 ---
Perennial Forbs --0.7 1.3
Annual & Biennial Forbs 0.1 4.3 43.9 25.0
Noxious / Aggressive Weeds ----
Shrubs, Sub-shrubs, Cacti & Trees 1.7 3.4 -0.3
Sample Adequacy Calculations:
Mean =73.7 10.1 45.0 27.3
Variance =135.5 80.5 105.1 300.5
n =15 15 10 10
nmin =4.5 143.7 9.9 77.1
* Indicates a seeded species
* Measured under litter from the previous season.
N = Native, I = Introduced, P = Perennial, B = Biennial, A = Annual
Supplemental Test
Section
Mean
Primary Test Section
9
10
3.1 Primary Test Section
2020 Findings
The Primary Test Section was evaluated with 15 transects during the spring survey of the fourth
growing season. Table 2 displays all species observed in the Primary Test Section in 2020 during the spring
evaluation, including incidental observations and species recorded by cover sampling metrics. Raw data
from the spring 2020 cover evaluation are presented in Appendix B. An abnormally tall canopy of last year’s
senesced vegetation had obscured much of this year’s 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 this year’s 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 criterion.
There was a total of 5 species observed, 3 of which were included in the seed mix. Total ground cover in
the Primary Test Section consisted of 73.7% live vegetation, 0.6% rock, 14.7% litter, and bare ground
exposure of 11.0%. Perennial cover across the test section averaged 73.3%, with annual and biennial cover
averaging 0.4%. No noxious weeds were observed. The abundance of available water throughout the early
growing season in 2019 facilitated above average growth and vigor in the Primary Test Section. Dominant
taxa were squirreltail (Elymus elymoides), averaging 56.3% cover as a direct hit and 15.3% live vegetation
cover which below cover by litter, for a total average cover of 71.6%, and fourwing saltbush (Atriplex
canescens) averaging 1.7% cover. Squirreltail was the only species that had greater than 4% cover, but
also contributed less than 40% of the relative cover.
The following photos show the site conditions on the Primary Test Section during the spring 2019
evaluation compared with the spring 2020 evaluation.
11
Primary Test Section – Spring Survey – May 29, 2019
Primary Test Section – Spring Survey – May 27, 2020
The Primary Test Section was evaluated with 15 transects during the fall survey of the fourth growing
season. Table 2 displays all species observed in the Primary Test Section in 2020. Raw data from the fall
2020 cover evaluation are presented in Appendix B. There was a total of 3 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 Primary Test Section consisted of 10.1% live vegetation, 3.1% rock, 71.5% litter (including plant
senescence in fall), and bare ground exposure of 15.4%. Perennial cover across the test section averaged
5.8%, with annual and biennial cover averaging 4.3%. No noxious weeds were observed. Dominant taxa
were Russian thistle (Salsola tragus) and fourwing saltbush, averaging 4.3% and 3.4% cover, respectively.
Squirreltail was the only species to meet the minimum relative cover criterion of 4% but it also contributed
more than 40% of the relative cover.
The Primary Test Section had 33 fourwing saltbush plants present across the whole seeded area
(lysimeter and surrounding area), which equates to 144 woody plants per acre (Table 4).
The following photos show the site conditions on the Primary Test Section during the fall 2019
evaluation compared with the fall 2020 evaluation.
12
Primary Test Section – Fall Survey – September 11, 2019
Primary Test Section – Fall Survey – September 15, 2020
Table 4 White Mesa - Woody Plant Density - 2020
Summary of Woody Plant Density
Area ——>
Lifeform Scientific Name Common Name
Shrub Atriplex canescens Fourwing Saltbush 33
Woody Plants Per Acre 144
Primary Test Section
(0.23 acres)
13
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 of the performance period. The chart shows that perennial cover has
increased each year. However, perennial cover in 2019 was likely higher than shown on the chart as tall
tumble mustard often grew higher than the squirreltail and was recorded as the first hit. Annual species
cover was particularly elevated in 2019 due to favorable precipitation conditions.
14
3.2 Supplemental Test Section
Spring 2020 Evaluation
The Supplemental Test Section was evaluated with 10 transects during the spring survey of the fourth
growing season. Table 2 displays all species observed in the Supplemental Test Section in 2020. Raw data
from the spring 2020 cover evaluation are presented in Appendix B. There was a total of 7 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 45.0% live vegetation, 0.1% rock, 41.2% litter, and
bare ground exposure of 13.7%. Perennial cover across the test section averaged 1.1%, with annual and
biennial cover averaging 43.9%. No noxious weeds were observed. The dominant taxon was redstem
stork’s bill (Erodium cicutarium), with 43.6% average cover. Redstem stork’s bill is an introduced species
from Europe and Asia and is common throughout the western U.S. No seeded species met the minimum
cover criterion of 4% or contributed less than 40% relative cover.
The following photos show the site conditions on the Supplemental Test Section during the spring
2019 evaluation and spring 2020 evaluation.
Supplemental Test Section – Spring Survey – May 29, 2019
Supplemental Test Section – Spring Survey – May 27, 2020
15
Fall 2020 Evaluation
The Supplemental Test Section was evaluated with 10 transects during the fall survey of the fourth
growing season. Table 2 displays all species observed in the Supplemental Test Section in 2020. Raw data
from the fall 2020 cover evaluation are presented in Appendix B. There was a total of 8 species observed
in the Supplemental Test Section in the fall, 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 27.3%
live vegetation, 0.1% rock, 58.5% litter, and bare ground exposure of 14.1%. Perennial cover across the
test section averaged 2.3%, with annual and biennial cover averaging 25.0%. No noxious weeds were
observed. The dominant taxon was redstem stork’s bill, with 24.8% average cover. No seeded species met
the minimum cover criterion of 4% or contributed more less 40% relative cover, however scarlet
globemallow (Sphaeralcea coccinea) exhibited 4.4% relative cover. Scarlet globemallow is a perennial forb
native to Utah that is widely considered a desirable species on revegetation sites.
The following photos show the site conditions on the Supplemental Test Section during the fall 2019
evaluation and fall 2020 evaluation.
Supplemental Test Section – Fall Survey – September 11, 2019
Supplemental Test Section – Fall Survey – September 15, 2020
16
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 of the performance period. The chart shows
that cover of perennial species has remained diminished and cover of annual species dominates the
Supplemental Test Section.
17
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. The results of the
performance evaluation are summarized in Table 5. In Year 1 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, for the
remainder of the performance period.
Primary Test
Section
Supplemental
Test Section
2020 Finding 2020 Finding
1. Species Composition
a. 5 or greater perennial grass species 1 2
4 or greater grass species are native 1 2
b. At least 1 perennial forb 0 0
c. At least 2 shrub species 1 0
2. Vegetative cover
a. 40% or greater total vegetative cover*73.3%0.4%
b. Comprised of species with relative cover between 4% and 40%*None None
c. Free of State and County listed noxious weeds None None
d. Self generating and permanent+Observed Observed
3. Shrub Density
a. Minimum 500 stems per acre 144 Not Measured
b. Healthy, surived minimum 2 growing seasons Observed Not Measured
* Species listed in Table D.1 must be used to achieve the cover performance criteria (MWH 2015).
+ Self-regeneration shall be demonstrated by evidence of reproduction, such as tillers or seed production
Table 5 White Mesa - Success Evaluation - 2020
Performance Comparison
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.
18
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 last year’s senesced vegetation had obscured much of this year’s 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 this year’s 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
Determination of Woody Plant Density
Woody plant density was evaluated during the fall evaluation of the Primary Test Section only.
Determination of woody plant density was completed using total enumeration to facilitate a more accurate
comparison of shrub survival between sampling years. Sampling for woody plant density was completed in
the fall when herbaceous vegetation had started to senesce, allowing for easier location of small,
germinating shrubs. Cedar Creek traversed the Primary Test Section in a systematic manner while counting
all shrubs encountered by species. These totals were used to quantify woody plants per acre by species for
the Primary Test Section. Woody plant density only requires a single sampling each year due to the relative
stability in shrub populations lacking significant disturbance.
Sample Adequacy Determination
Ground cover sampling was conducted to a minimum of number of 10 or 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 = 10 or 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
Appendix B
Raw Data
Table 6 White Mesa - Vegetation Cover - 2020
Primary Test Section - 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
I A Bromus tectorum Cheatgrass 4 1 0.3 0.5 13
N P Elymus elymoides Squirreltail 42 60 43 48 69 64 68 53 64 49 52 58 50 72 53 56.3 76.4 100
N P Elymus elymoides*Squirreltail 21 20 34 10 8 11 16 1 18 26 8 14 4 11 28 15.3 20.8 100
I A Salsola tragus Russian Thistle 1 0.1 0.1 7
N P Atriplex canescens Fourwing Saltbush 3 13 9 1.7 2.3 20
Total Plant Cover 67 80 77 58 77 78 84 54 82 88 61 81 54 83 82
Rock 1 0 0 0 0 1 0 3 0 1 1 1 1 0 0
Litter 23 18 20 23 12 12 9 9 12 8 19 15 15 11 14 Bare ground 9 2 3 19 11 9 7 34 6 3 19 3 30 6 4
Perennial Plant Cover 63 80 77 58 77 78 84 54 82 88 60 81 54 83 81
Plant Cover Mean =t=n=15
Variance =nmin =
N = Native, I = Introduced, P = Perennial, B = Biennial, A = Annual
* Measured under litter from the previous season.
0.6
14.711.0
73.3
Sample Adequacy Calculations:135.50 4.51
73.73 1.35
73.7
Mean
Average
Cover
Relative
Cover Freq.
Forbs
Shrubs, Sub-shrubs, Cacti & Trees
Grasses
Table 7 White Mesa - Vegetation Cover - 2020
Primary Test Section - 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 Elymus elymoides Squirreltail 7 4 1 3 3 1 1 1 2 3 3 1 6 2.4 23.8 87
I A Salsola tragus Russian Thistle 3 3 1 1 5 4 1 2 7 7 7 23 4.3 42.4 80
N P Atriplex canescens Fourwing Saltbush 7 15 1 7 6 11 2 2 3.4 33.8 53
Total Plant Cover 14 7 3 1 4 4 21 6 2 4 14 16 21 3 31
Rock 1 1 2 1 5 2 2 4 2 1 5 6 8 0 6
Litter 84 85 80 77 76 74 57 69 81 87 67 68 39 84 44
Bare ground 1 7 15 21 15 20 20 21 15 8 14 10 32 13 19
Perennial Plant Cover 14 4 0 1 3 3 16 2 1 2 7 9 14 3 8
Plant Cover Mean =t=n=15
Variance =nmin =
N = Native, I = Introduced, P = Perennial, B = Biennial, A = Annual
5.8
Sample Adequacy Calculations:10.07 1.35
80.50 143.70
15.4
Average
Cover
Relative
Cover Freq.Grasses
Forbs
Shrubs, Sub-shrubs, Cacti & Trees
Mean
10.1
3.1
71.5
Table 8 White Mesa - Vegetation Cover - 2020
Supplemental Test Section - Spring Survey
Percent Ground Cover Based on Point-Intercept Sampling
Transect No.——> 1 2 3 4 5 6 7 8 9 10
N P Agropyron smithii Western Wheatgrass 1 0.1 0.2 10
N P Poa secunda Sandberg Bluegrass 1 1 1 0.3 0.7 30
I A Descurainia pinnata Western Tansymustard 1 0.1 0.2 10
I A Erodium cicutarium Redstem Stork's Bill 39 44 37 31 55 54 47 41 29 59 43.6 96.9 100
I A Kochia scoparia Summer Cypress 1 0.1 0.2 10
I B Lactuca serriola Prickly Lettuce 1 0.1 0.2 10
N P Sphaeralcea coccinea Scarlet Globemallow 1 4 2 0.7 1.6 30
None 0.0 0.0 0
Total Plant Cover 40 46 37 32 56 58 47 44 31 59
Rock 0 0 0 0 0 0 0 1 0 0
Litter 42 48 40 52 27 25 42 38 61 37
Bare ground 18 6 23 16 17 17 11 17 8 4
Perennial Plant Cover 1 2 0 1 0 4 0 2 1 0
Plant Cover Mean =t=1.38 n=10
Variance =nmin =
N = Native, I = Introduced, P = Perennial, B = Biennial, A = Annual
45.0
Average
Cover
Relative
Cover Freq.
Mean
Grasses
Forbs
Shrubs, Sub-shrubs, Cacti & Trees
0.1
41.2
13.7
1.1
Sample Adequacy Calculations:45.00
105.11 9.93
Table 9 White Mesa - Vegetation Cover - 2020
Supplemental Test Section - Fall Survey
Percent Ground Cover Based on Point-Intercept Sampling
Transect No.——> 1 2 3 4 5 6 7 8 9 10
N P Poa secunda Sandberg Bluegrass 1 1 2 1 2 0.7 2.6 50
N P Artemisia ludoviciana White Sagebrush 1 0.1 0.4 10
I A Erodium cicutarium Redstem Stork's Bill 2 0.2 0.7 10
I A Kochia scoparia Summer Cypress 62 40 7 24 38 4 13 25 17 18 24.8 90.8 100
N P Sphaeralcea coccinea Scarlet Globemallow 2 2 1 2 2 1 2 1.2 4.4 70
N P Gutierrezia sarothrae Broom Snakeweed 2 0.2 0.7 10
N P Lycium andersonii Waterjacket 1 0.1 0.4 10
Total Plant Cover 64 44 9 25 39 7 17 26 20 22
Rock 0 0 0 0 0 1 0 0 0 0
Litter 29 39 71 65 52 77 64 59 68 61
Bare ground 7 17 20 10 9 15 19 15 12 17
Perennial Plant Cover 2 4 2 1 1 3 4 1 1 4
Plant Cover Mean =t=1.38 n=10
Variance =nmin =
N = Native, I = Introduced, P = Perennial, B = Biennial, A = Annual
2.3
Sample Adequacy Calculations:27.30
300.46 77.11
14.1
Average
Cover
Relative
Cover Freq.Grasses
Forbs
Shrubs, Sub-shrubs, Cacti & Trees
Mean
27.3
0.1
58.5
WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2020 ANNUAL PERFORMANCE MONITORING REPORT
Appendix C CELL 2 SETTLEMENT MONITORING DATA
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Dec-88 Dec-91 Dec-94 Dec-97 Dec-00 Dec-03 Dec-06 Dec-09 Dec-12 Dec-15 Dec-18 Dec-21
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Figure C.2
White Mesa Mill
Cell 2W2 Settlement Plate Measurements
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
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Dec-88 Dec-91 Dec-94 Dec-97 Dec-00 Dec-03 Dec-06 Dec-09 Dec-12 Dec-15 Dec-18 Dec-21
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Figure C.3
White Mesa Mill
Cell 2W3 Settlement Plate Measurements
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
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Figure C.4
White Mesa Mill
Cell 2W4 Settlement Plate Measurements
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
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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
El
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Figure C.5
White Mesa Mill
Cell 2E1 Settlement Plate Measurements
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
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
El
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,
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m
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Figure C.6
White Mesa Mill
Cell 2E1-N Settlement Plate Measurements
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
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
El
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Figure C.7
White Mesa Mill
Cell 2E1-1S Settlement Plate Measurements
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
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
El
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Figure C.8
White Mesa Mill
Cell 2E1-2S Settlement Plate Measurements
(1)
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
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
El
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,
f
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t
m
s
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Figure C.9
White Mesa Mill
Cell 2W7-C Settlement Plate Measurements
Note: (1) Settlement plate had three feet of rod extended October 2014
month because interim cover was added in this area of Cell 2
(1)
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
El
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,
f
e
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t
m
s
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Figure C.10
White Mesa Mill
Cell 2W5-N Settlement Plate Measurements
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
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
El
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f
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t
m
s
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Figure C.11
White Mesa Mill
Cell 2W3-S Settlement Plate Measurements
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
5620
5622
5624
5626
5628
5630
5632
El
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f
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Figure C.12
White Mesa Mill
Cell 2W5-S Settlement Plate Measurements
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
El
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n
,
f
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t
m
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Figure C.13
White Mesa Mill
Cell 2W7-N Settlement Plate Measurements
(2)
Notes: (1) Settlement plate had three feet of rod extended in October 2014
because interim cover was added in this area of Cell 2
(2) Settlement plate extended during phase 1 cover construction
(1)
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
El
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f
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t
m
s
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Figure C.14
White Mesa Mill
Cell 2W7-S Settlement Plate Measurements
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
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
El
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f
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m
s
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Figure C.15
White Mesa Mill
Cell 2W6-N Settlement Plate Measurements
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
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
El
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f
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m
s
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Figure C.16
White Mesa Mill
Cell 2W6-C Settlement Plate Measurements
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
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
El
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,
f
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t
m
s
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Figure C.17
White Mesa Mill
Cell 2W6-S Settlement Plate
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
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
El
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Figure C.18
White Mesa Mill
Cell 2W5-C Settlement Plate
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
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
El
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s
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Figure C.19
White Mesa Mill
Cell 2W4-N Settlement Plate
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
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
El
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Figure C.20
White Mesa Mill
Cell 2W4-S Settlement Plate Measurements
(1)
(1)
Note: (1) Settlement plate extended during Phase 1 cover construction.
WHITE MESA URANIUM MILL CELL 2 RECLAMATION COVER 2020 ANNUAL PERFORMANCE MONITORING REPORT
Appendix D CELL 2 STANDPIPE PIEZOMETER WATER LEVELS
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
Wa
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(
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Date
Figure D.1 - Cell 2 Standpipe Piezometers
Water Level Elevations
C2-P01 C2-P02 C2-P03 C2-P04 C2-P05 C2-P06
C2-P07 C2-P08 C2-P09 C2-P10 C2-P11 C2-P12
C2-P13 C2-P14 C2-P15 C2-P16 C2-P17 C2-P18
C2-P19 C2-P20 C2-P21 C2-P22 C2-P23
Note (1): Pieozometer C2-P01 reading for Mar 20, 2019
was erroneous due to an issue with the water level meter
(1)
5,590
5,595
5,600
5,605
5,610
5,615
Jun-16 Dec-16 Jun-17 Dec-17 Jun-18 Dec-18 Jun-19 Dec-19 Jun-20 Dec-20 Jun-21
Wa
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E
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(
f
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Date
Figure D.2 - Cell 2 Standpipe Piezometers
Water Level Elevations
West Side of Cell (excluding locations near sump)
C2-P01 C2-P02 C2-P03 C2-P04
C2-P05 C2-P06 C2-P07 C2-P08
(1)
Note (1): Pieozometer C2-P01 reading for March 20, 2019
was erroneous due to an issue with the water level meter
5,590
5,595
5,600
5,605
5,610
5,615
Jun-16 Dec-16 Jun-17 Dec-17 Jun-18 Dec-18 Jun-19 Dec-19 Jun-20 Dec-20 Jun-21
Wa
t
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Date
Figure D.3 - Cell 2 Standpipe Piezometers
Water Level Elevations
Locations Near Sump
C2-P09 C2-P10 C2-P11 C2-P12
C2-P14 C2-P15 C2-P16
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
Wa
t
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Date
Figure D.4 - Cell 2 Standpipe Piezometers
Water Level Elevations
East Side of Cell (excluding locations near sump)
C2-P13 C2-P17 C2-P18 C2-P19
C2-P20 C2-P21 C2-P22 C2-P23