DRC-2017-006427 - 0901a06880747ebe

State of Utah
GARY R HERBERT
Governor
SPENCERJ COX
Lieutenant Governor
Department of
Environmental Quality
Alan Matheson
Executive Director
DIVISION OF WASTE MANAGEMENT
AND RADIATION CONTROL
Scott T Anderson
Director
myzon-oo^J
MEMORANDUM
TO:
THROUGH:
FROM:
DATE:
Project File L-2016-93
Heather Mickelson, PE
Phil Goble, Uranium Mill Section Manager
Russell J. Topham, PE
August 22, 2017
SUBJECT: Reclamation Plan 5.1, Cover Primary Test Section
Observations from Site Visits of June 28, July 19 and August 10, 2017
Review of 4th Quarter, 2016 and 1st Quarter, 2017 Data Quality Reports
Review of As-Built Report
Authority
Radioactive Materials License #UT1900479, Proposed UDRC Amendment 8 (Renewal), Condition 9.13:
“The Licensee shall perform all decommissioning and reclamation activities in conformance to
Reclamation Plan 5.1.”
10 CFR Part 40 Appendix A, Criterion 6A(1):
“For impoundments containing uranium byproduct materials, the final radon barrier must be completed
as expeditiously as practicable considering technological feasibility after the pile or impoundment ceases
operation in accordance with a written, [Directorj-approved reclamation plan. (The term as
expeditiously as practicable considering technological feasibility as specifically defined in the
Introduction of this appendix includes factors beyond the control of the licensee.).”
Stipulation and Consent Agreement dated February 23, 2017, Agreement 1:
“The Director will approve Reclamation Plan 5.1 (the ‘Approved Reclamation Plan’) upon completion
of a public notice and comment period, and in conjunction with and conditional upon the execution and
delivery of this Agreement by EFR and the Director. This Agreement sets out the commitments and
DRC-20 195 North 1950 West • Salt Lake City, UT
Mailing Address- P O Box 144880 • Salt Lake City, UT 84114-4880
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time frames for completing placement of reclamation cover on Cell 2 and performance assessment of the
cover system, in accordance with the Approved Reclamation Plan.”
Reclamation Plan Revision 5.1, p. 1-1:
“This plan presents [Energy Fuels’] plans and estimated costs for the reclamation of cells for the tailings
management system, and for decommissioning of the Mill and Mill site. This plan is an update to the
White Mesa Mill Reclamation Plan Revision 3.2b approved by the Utah Department of Environmental
Quality[,] Division of Radiation Control on January 26, 2011.”
Updated Tailings Cover Design Report (Appendix A to Reclamation Plan Revision 5.1), Appendix L,
Section L. 4, Cover Performance Assessment:
“EFRI constructed a performance monitoring test section (Primary Test Section) within the Cell 2 cover
concurrently with the 2016 Phase 1 cover placement. The test section was constructed as a design-build
project using the guidelines provided in this appendix. The test section will be monitored to assess
performance of the cover system for the tailings cells. The test section location is shown in the Drawings
(Attachment L.l [not included in this report]). Discussion on the test section design and plan is provided
in Section L.4.1 [not addressed in this report], and discussion on the test section monitoring program is
provided in Section L.4.2.”
Requirements
1. Stipulation and Consent Agreement dated February 23, 2017, Agreement 1:
“Instrumentation for monitoring Cell 2 after Phase 1 cover placement is described in Sections L.4.2
and L.4.4 of Appendix L [to Updated Tailings Cover Design Report (which appears as Appendix A
to Reclamation Plan Revision 5.1)], and will include the existing settlement monuments and newly
installed piezometers.
2. Stipulation and Consent Agreement dated February 23, 2017, Agreement 2. (a):
“EFR constructed a performance test section within the Cell 2 cover (the ‘Primary Test Section’)
concurrently with the Phase 1 cover placement. The Primary Test Section was constructed as a
design-build project in accordance with Section L.4 of Appendix L and the Instructions set out in
Attachment L.2 of Appendix L [to Updated Tailings Cover Design Report].” [Attachment L.2 is
included as an attachment to this report rather than reproducing it in full herein.]
“The Primary Test Section, including the weather station, will be completed as of the date of this
Agreement.”
“The properties of the soil used to construct the Primary Test Section will be tested in accordance
with Section L.4.2 of Appendix L [to Updated Tailings Cover Design Report] to determine whether
the soil properties are characteristic of base case, upper, or lower bound conditions.”
“An as-built report for the Primary Test Section construction, as well as the test results for the soil
properties, will be provided to the Division within 90 days after completion of construction of the
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August 22, 2017
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Reclamation Plan 5.1, Cover Primary Test Section
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Primary Test Section and receipt of the laboratory test results, or such later date as may be approved
by the Director.”
3. Stipulation and Consent Agreement dated February 23, 20J 7, Agreement 3. (a):
“EFR will assess the performance of the cover system design by monitoring the Primary Test
Section in accordance with the provisions of Section L.4.2 of Appendix L [to Updated Tailings
Cover Design Report].”
“EFR will monitor the Primary Test Section in two stages: (i) calibration monitoring and (ii)
performance monitoring, in accordance with the provisions of Section L.4.2 of Appendix L [to
Updated Tailings Cover Design Report]....”
4. Stipulation and Consent Agreement dated February 23, 2017, Agreement 3. (a), i):
“Calibration monitoring will be conducted for two full calendar years (the "Calibration Period") after
construction is complete to confirm monitoring systems are functioning properly, vegetative cover
has had time to establish itself and the cover has equilibrated prior to entering the performance
monitoring period. The first calendar year of calibration monitoring will begin on January 1 after
construction of the Test Section has been completed.”
5. Stipulation and Consent Agreement dated February 23, 2017, Agreement 3. (b):
“Vegetation properties will be measured on the Primary Test Section, in accordance with Section
L.4.2 of Appendix L [to Updated Tailings Cover Design Report], Vegetation properties will be
measured on the Supplemental Test Section, in accordance with Section L.4.3 of Appendix L. Such
monitoring on the Primary Test Section and Supplemental Test Section will commence one year
after seeding and continue for a minimum of five years after calibration monitoring is complete. The
Supplemental Test Section will not include evaluation of the entire cover profile but will
demonstrate that vegetation can be established and that erosional influences will not be detrimental
to long-term establishment according to the acceptance criteria set out in Section L.4.3 of Appendix
L.” [Review of the Supplemental Test Section is not a part of this review.]
6. Stipulation and Consent Agreement dated February 23, 2017, Agreement 3. (c):
“EFRI will monitor on-site meteorological conditions during the seven-year test period, in
accordance with Section L.4.2 of Appendix L [to Updated Tailings Cover Design Report].”
7. Stipulation and Consent Agreement dated February 23, 2017, Agreement 3. (d):
“Soil properties of the Primary Test Section will be tested during Primary Test Section construction,
in accordance with Section L.4.2 of Appendix L [to Updated Tailings Cover Design Report].”
8. Stipulation and Consent Agreement dated February 23, 2017, Agreement 3. (e):
“EFR will submit for Director approval sampling plans for the monitoring contemplated by Items
D.3(a)-(d) above [Requirements 4 through 7 of this Report], within 90 days after the date of this
Agreement.”
Reclamation Plan 5.1, Cover Primary Test Section
August 22, 2017
Page 4
9. Stipulation and Consent Agreement dated February 23, 2017, Agreement 4. (b):
“The vegetation component of the Primary Test Section and Supplemental Test Section will be
evaluated for applicable acceptance criteria as presented in Section L.4.2 and L.4.3 of Appendix L
[to Updated Tailings Cover Design Report], respectively. The cover design will be considered to be
successful if a minimum vegetation live cover of 40 percent and acceptable vegetation diversity
(relative cover) per Appendix D [attached to this report] of the Updated Tailings Cover Design
Report (perennial grasses and forbs) is met for both the Primary Test Section and Supplemental Test
Section by the end of the Performance Period. The revegetation acceptance goal of 40 percent live
cover assumes average annual precipitation during the Performance Period (based on long-term on­
site averages). If precipitation during the Performance Period is dryer than average conditions or if
the performance criteria set out in Item 4(b) above are met notwithstanding that the vegetation
performance criteria are not met, or if it appears that more time is needed to satisfy the vegetation
performance criteria, the Director may set a new acceptance goal based on such factors, including
EFR discussion of the lysimeter findings, findings of revised ground water modeling, consideration
of the magnitude of change in annual precipitation and the rate of growth of vegetation over time.”
10. Stipulation and Consent Agreement dated February 23, 2017, Agreement 5:
“After Phase 1 cover construction is complete, settlement monuments and piezometers will be
monitored in accordance with Section L.4.4 of Appendix L [to Updated Tailings Cover Design
Report].”
11. Reclamation Plan Revision 5.1, Attachment A, Section 9.2.2:
“Species selection for the seed mixture was based on native vegetation found in the area as well as
soil and climatic conditions of the Mill site. Changes to the seed mixture will be as approved by the
Owner. The seed mixture in Table 9.1 shall be used on all seeded areas.” Table 9.1, Species and
seeding rates proposed for Mill site, which appears on Page 5 of this report, is reproduced from p.
A-72 of Attachment A to Reclamation Plan 5.1.
12. Reclamation Plan Revision 5.1, Attachment A, Section 9.8.3:
“Weed management will be conducted on the Mill site by identifying the presence of any noxious
weeds during annual vegetation surveys and developing a weed control plan that is specific to the
species that are present (Table 9.2). Noxious weed control is species-dependent and both method and
timing will vary from species to species.” Table 9.2, Noxious weed species appears on p. A-76 of
Attachment A to Reclamation Plan 5.1, and is not reproduced in this report.
“Control methods may include chemical or mechanical approaches. The optimum method or
methods for weed management vary depending on a number of site-specific variables such as
associated vegetation, weed type, stage of growth, and severity of the weed infestation.”
13. Reclamation Plan Revision 5.1, Attachment A, Section 9.8.4:
“If revegetated areas are not making satisfactory progress in meeting revegetation goals outlined
above, then remedial actions will be implemented as needed. These actions may include
Reclamation Plan 5.1, Cover Primary Test Section
August 22, 2017
Page 5
fertilization/soil amendments, reseeding, weed control, and/or erosion control depending upon the
cause of the problem that may exist and the best remediation approach to ensure plant community
success.”
14. Reclamation Plan Revision 5.1, Attachment A, Section 9.8.4, Criterion 1, Species Composition:
“The vegetative cover (the percentage of ground surface covered by live plants) shall be composed
of a minimum of five perennial grass species (at least four listed as native), one perennial forb
species, and two shrub species listed in Table 9.1.”
Table 9.1. Species aud seeding rates proposed for Mill site.
Scientific Name C ommon Name Varietal
Name
Native/
Introduced
Seeding
Rate (lbs
PLS acre)
Seeding
Rate (#
seeds ft;)
Grasses
Pascopvnm smithii Western wheaterass Amba Native 3.0 7.9
Pseudoroegneria
spicata
Bluebunch wheaterass Goldar Native 3.0 9.6
Elymus trachycaulus Slender wheaterass San Luis Native 2.0 6.2
Elymus lanceolatns Streambank wheaterass Sodar Native 2.0 7.3
Elymus elymoides Sqmrreltail bottlebrush Toe Jam Native 2.0 8.8
Thinopyrum
imennedium
Pubescent wheaterass Luna Introduced1 1.0 1.8
Achnathentm
hymenoides
Indian ncegrass Paloma Native 4.0 14.7
Poa seamda Sandbere blueerass Canbar Native 0.5 11.4
Festuca ovina Sheep fescue Covar Introduced1 1.0 11.5
Bouteloua gracilis Blue grama Hachita Native 1.0 16.5
Hilaiia jamesii Galleta Viva Native 2.0 7.3
Forbs
Achillea millefolium,
variety occidemalis
Common yarrow
VNS*
Native 0.5 32
Artemisia ludoviciana White sage VNS Native 0.5 45
Shrubs
Atriplex canescens Founvmg saltbush Wytana Native 3.0 3.4
Ericameria nauseosa Rubber rabbitbrush VNS Native 0.5 4.6
Total 26.5 188
Seeding rate is for broadcast seed and presented as pounds of pure live seed per acre (lbs PLS acre).
Tntroduced refers to species that have been introduced from another geographic region, npically outside of North
America Also referred to as exotic species
*VNS=Variety Not Specified and seed source will be from sites that are climatically similar to White Mesa.
15. Reclamation Plan Revision 5.1, Attachment A, Section 9.8.4, Criterion 2, Vegetative Cover:
a. Attain a minimum vegetative cover percentage of 40 percent.
b. Individual grass and forb species listed in Table 9.1 that are used to achieve the cover criteria
shall have a minimum relative cover (the cover of a plant species expressed as a percentage of
total vegetative cover) of 4 percent and a maximum relative cover of 40 percent.
c. Individual species not listed in Table 9.1 may be accepted as part of the cover criteria if it is
demonstrated that the species is native or adapted to the area and is a desirable component of the
reclaimed project site.
d. Species not listed in Table 9.1, including annual weeds or other undesirable species such as those
listed in Table 9.2, shall not count toward the minimum vegetative cover requirement. Every
attempt shall be made to minimize establishment of all noxious weeds.
e. Reclaimed areas shall be free of state- and county-listed noxious weeds (Table 9.2).
f. The vegetative cover shall be self-regenerating and permanent. Self-regeneration shall be
demonstrated by evidence of reproduction, such as tillers and seed production.
16. Reclamation Plan Revision 5.1, Attachment A, Section 9.8.4, Criterion 3, Shrub Density:
a. A minimum shrub density of 500 stems per acre.
b. Shrubs shall be healthy and have survived at least two complete growing seasons before being
evaluated against success criteria.
17. Updated Tailings Cover Design Report (Appendix A to Reclamation Plan Revision 5.1), Appendix L,
Section L.4.2, Primary Test Section Monitoring - Monitoring System and Instrumentation:
“The monitoring system includes instruments to measure all components of the water balance for the
cover system, including percolation from the base of the cover, runoff, interflow (internal lateral
flow), and on-site meteorological conditions. The system will also measure state variables (water
content and temperature) at discrete locations within the cover. A complementary surveillance
program will be performed according to the criteria presented in Appendix D to monitor the
vegetative community, edaphic properties of the cover soils, and pedogenic evolution of the cover
profile, as suggested in NUREG/CR-7028. Comparisons will be made between the monitoring data
and predictions and assumptions made during cover design.
“Precision tipping buckets and pressure transducers mounted in drainage basins will be used to
provide redundant measurements of percolation, interflow, and surface runoff. The drainage basins
are equipped with flouts to provide consistent repeatable basin flushing. Water content
reflectometers (WCR) employing time domain reflectometry will be used to measure water content
of the cover soils in the lysimeter. A Type-T thermocouple mounted on the head of each WCR will
be used to monitor soil temperature. The co-located WCRs and thermocouples were installed at the
quarter points along the centerline of the test section as shown in the Drawings (Attachment L. 1).
Each nest consists of eight WCRs and thermocouples, as shown in the Drawings. All WCRs will be
calibrated for the soils in the lysimeter and will include temperature compensation following the
methods in Benson and Wang (2006).
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“A meteorological station located immediately outside of the lysimeter area will be used to monitor
climatic variables. Installing a dedicated meteorological station reduces the effort and
inconsistencies that can be associated with integrating data from a site-wide weather station.
Collecting meteorological data adjacent to the lysimeter will also ensure that conditions at the
lysimeter are represented accurately. The meteorological station includes a shielded Geonor
weighing precipitation gauge that monitors frozen and unfrozen precipitation, a Visalia shielded
temperature and humidity probe to monitor air temperature and relative humidity, a Druck
barometric pressure sensor, a Visalia pyranometer to measure net solar radiation, and a RM Young
wind sentry to measure wind speed and direction. All sensors were calibrated after installation and
will be calibrated annually.
“All measurement devices are connected to a single datalogger that can be accessed remotely. The
datalogger is programed to collect data from all sensors on hourly intervals. Downloads from the
datalogger will occur daily using an automated algorithm. The datalogger algorithm will monitor
flows and meteorological variables continuously, and will reduce the sampling interval to as short as
15 s if needed to ensure data with adequate frequency to capture flows reliably. In most cases, data
will be aggregated into daily quantities for reporting.
“Vegetation sampling and monitoring procedures will follow recommendations outlined in
Appendix D. Live plant cover, shrub density, and overall plant community health and sustainability
are included in the monitoring.”
18. Updated Tailings Cover Design Report (Appendix A to Reclamation Plan Revision 5.1), Appendix L,
Section L.4.2, Primary Test Section Monitoring - Monitoring Time Period and Frequency:
“EFRI will monitor the test section in two stages: (i) calibration monitoring and (ii) performance
monitoring. Calibration monitoring will be conducted for two full calendar years after construction is
complete to confirm that the monitoring systems are functioning properly and the cover has
equilibrated prior to entering the performance monitoring period. The first calendar year of
calibration monitoring will begin on January 1 after construction of the test section has been
completed. Official performance monitoring of the cover test section will commence on January 1
after the two calendar years of calibration monitoring are complete. Performance monitoring will be
conducted for five years.
“The monitoring frequency will vary depending on the parameters measured. All hydrological
sensors will be interrogated hourly, and aggregated into daily quantities for water balance analysis.
Vegetation properties will be measured annually. Soil properties will be tested during test section
construction. In-service soil properties will be determined during the last year of the monitoring
period via sampling and testing in the buffer area of the test section outside the lysimeter.”
19. Updated Tailings Cover Design Report (Appendix A to Reclamation Plan Revision 5.1), Appendix L,
Section L.4.2, Primary Test Section Monitoring - Performance Criteria:
“Percolation rate from the base of the lysimeter will be used as the performance parameter for the
cover system. Data from secondary variables (i.e. meteorological conditions, water balance
quantities, soil water content, soil temperature, in-service soil and vegetation properties, etc.) related
to the primary performance parameter will be used for interpretative purposes, as recommended in
NUREG/CR-7028 (Benson et al., 2011). Although performance criteria are not suggested in
NUREG/CR-7028 for these parameters and are not stipulated herein, monitoring of these parameters
is recommended so that the percolation data can be interpreted mechanistically.
“Performance of the test section will be assessed using the average annual percolation rate measured
during the performance monitoring period. The objective of this assessment is to determine if the
hydrological modeling approach presented in the Infiltration and Contaminant Transport Modeling
(ICTM) report (MWH, 2010) and in updates to the modeling presented in EFRI (2015) provides a
realistic prediction (or conservative over-prediction) of percolation. The cover design will be
considered to have performed adequately, without the need for any additional modeling, if the
average annual percolation rate is 2.3 mm/yr or less. This is the average annual percolation rate
estimated from the ICTM for Base Case soil conditions and average climate conditions.
“Meteorological data recorded during the monitoring period will be compared to the meteorological
data used as input in the hydrological modeling, which is based on a 100-yr record.
“Particle size data collected from the test section will be used to determine whether the soil
properties are characteristic of Base Case, Upper Bound, or Lower Bound conditions. This
evaluation will be specific to the test section, which will be constructed with a small volume of soil
relative to the full-scale cover. Because the full-scale cover will be constructed from large volumes
of soil, the spatial average across the full-scale cover is most likely to resemble the Base Case. Thus,
the percolation rate from the test section may or may not represent the percolation rate for full-scale
conditions depending on whether the soils for the test section are representative of Base Case, Upper
Bound, or Lower Bound conditions.
“For each layer in the test section, the average and standard deviation of the gravel content, sand
content, and fines content will be computed from the data collected during construction, with the
size fractions defined using ASTM D422. These statistics will be used to identify a particle size band
for each soil layer in the test section. These particle size bands for the test section will be compared
to the particle size distributions associated with the Base Case, Upper Bound, and Lower Bound
soils used in the hydrological modeling. Particle size distributions used in the modeling will be
identified that overlap, or are most closely aligned with the as-built particle size bands for the test
section.
“Percolation rates measured from the test section that are equal to or less than the percolation rate of
2.3 mm/yr and within the precision of measurement, will confirm that the hydrological modeling
approach provides a realistic prediction (or conservative over-prediction) of percolation, and
confirms that if the average cover over the entire cell uses base case soils, as expected, the
percolation rates will be as predicted.
“The performance evaluation will be based on data collected during the performance monitoring
period. However, data collected during the calibration period will be compared with the data from
the performance monitoring period. If these two periods are not different statistically and no
temporal trend in percolation rate is found, then the average percolation rate over the entire seven-
year monitoring period will also be compared to the appropriate percolation rate in the Table L.3.
“The vegetation component of the Primary Test Section will be evaluated for applicable acceptance
criteria as presented in Appendix D. Vegetation monitoring will commence one year after seeding
and continue for a minimum of five years after calibration monitoring of the cover test section is
Reclamation Plan 5.1, Cover Primary Test Section
August 22, 2017
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Reclamation Plan 5.1, Cover Primary Test Section
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complete. The vegetation component will be considered successful if a minimum vegetation cover of
40 percent and acceptable vegetation diversity per Appendix D (peremiial grasses, forbs and shrubs)
is met for the Primary Test Section by the end of the Performance Period. The revegetation
acceptance goal of 40 percent cover assumes average annual precipitation during the Performance
Period (based on long-term on-site averages) and an accelerated rate of plant growth in this semi-
arid environment that can take as long as 10 years to achieve. If precipitation during the Performance
Period is “Dry” or if it appears that more time is needed to satisfy the vegetation performance
criteria a new acceptance goal would need to be established.”
20. Updated Tailings Cover Design Report (Appendix A to Reclamation Plan Revision 5.1), Appendix L,
Section L 4.4, Additional Monitoring:
“EFRI currently monitors settlement monuments on Cell 2. Monitoring of these monuments will
continue and the results reported after Phase 1 Cell 2 cover construction is complete. Existing
settlement monuments will be extended upward during cover construction (see Figure L.l for
existing settlement monument locations). Standpipe piezometers were installed across Cell 2 during
Phase 1 Cell 2 cover construction to monitor water levels within the tailings (see Figure F.l for
piezometer locations). After Phase 1 cover construction is complete, it is recommended that
settlement monuments and piezometers be monitored weekly for the first month, biweekly for the
second month, and monthly thereafter.” [Figures F.l and F.2 not reproduced in this report.]
Observations
Russell J. Topham, P.E. of the Utah Division of Waste Management and Radiation Control (the
Division), performed review of two documents: (1) White Mesa Uranium Mill Cell 2 Cover
Performance Test Section As-Built Report, and, (2) Fourth Quarter 2016 and First Quarter 2017 Data
Quality Reports for the White Mesa Cell 2 Cover Test Section Monitoring. Mr. Topham also performed
site observations at the White Mesa Mill with Phil Goble, Uranium Mill Section Manager on June 28,
2017 and with Heather Mickelson, P.E., also of the Division on July 19 and August 10, 2017. The
following observations reflect the cited reviews and site visits.
White Mesa Uranium Mill Cell 2 Cover Performance Test Section As-Built Report
The Division received the As-Built Report on July 11, 2017.
The As-Built Report discussed the construction protocols, methods, and standards applied. Of particular
interest, the test section construction was overseen by Dr. Craig Benson, the primary author of
NUREG/CR-7028, and a key consultant to the Ficensee during design of the cover test study design.
The Updated Cover Design Report, which appears as Appendix A to Reclamation Plan 5.1, along with
NUREG/CR-7028 provided the guidance for the construction of the test section.
The As-Built Report provided sufficient data to evaluate the construction of the Test Section. Topics
covered include a narrative summary of the construction, laboratory and field test analysis results for the
materials used and post-placement density, instrument calibration, and a summary initial monitoring
data. Details of vault repair and corrective action related to flooding of the instrumentation vault
encountered following construction appear in a section of the As-Built Report. 53 figures and six tables
supplement the text. Appendices include as-built drawings, construction documentation (quality
assurance testing and instrument calibration data), laboratory test reports, and a memorandum detailing
the vault repair and corrective action made necessary by vault flooding.
White Mesa Uranium Mill Fourth Quarter 2016 and First Quarter 2017 Data Quality Reports
The Division received the referenced Data Quality Reports on July 11, 2017.
These reports were provided for information only. Review performed herein is intended to provide a
template for future reviews, and to assess whether future reports following the same format and with the
same breadth of content will meet expectations. The Licensee is not required to submit its first report of
this type until 2018.
The quarterly Data Quality Reports provide documentation of sensor data and data quality analytics for
the instrumentation installed in the Test Section. Interpretation of the data will appear in an annual
report. The Data Quality Reports provide an introduction to explain how the Test Section works and
where instruments are installed, and a discussion of water balance data (which includes results of all
measurements reported). The Data Quality Reports include 28 figures to illustrate schematically the
construction of the Test Section and to show graphically the data and its interrelationships. The Data
Quality Reports end the narrative with a discussion of concerns identified and action items to take to
resolve those concerns. Sufficient detail is presented to assess the likely success of future such reports
in fulfilling the reports’ intent.
June 28, July 19 and August 10, 2017 Site Visits
On June 28, 2017 inspectors Russ Topham and Phil Goble, both from the Division, observed the
progress of the vegetative cover on the Primary Test Section. The sparse density of vegetation observed,
exclusive of weeds, caused concern. On July 19, 2017, inspectors Russ Topham and Heather Mickelson
availed themselves Ed Redente’s presence onsite to assess the sparse cover vegetation. Dr. Redente is a
specialists hired by Energy Fuels to assist in plant selection and plant community establishment for the
cover system and the Primary Test Section.
Reclamation Plan 5.1, Cover Primary Test Section
August 22, 2017
Page 10
Photo 1 shows a
portion of the Primary
Test Section cover
with thatch from the
hydroseeding
operation apparent.
The green vegetation
is an annual weed.
Little additional
vegetation was
observed in several
such patches. In this
photo, no forbs or
shrubs are observed,
and the present grasses
are all dormant.Photo 1: Sparsely vegetated portion of Primary Test Section. Photo taken June 28, 2017.
Reclamation Plan 5.1, Cover Primary Test Section
August 22, 2017
Page 11
Photo 2 shows a
condition encountered
in several locations in
the berm defining the
perimeter of the
lysimeter beneath the
surface of the Primary
Test Section. Bare
soil with no vegetation
and no remaining
thatch is apparent.
Note along the bottom
and in the upper right
portion of the photo
the grasses present.
Note also the lush
weed growth.
. JOl v • - r-mmbT. - '. HUmbibi nil ■■ ■ IIin iPhoto 2: A portion of the Primary Test Section runoff retention berm in profile view. Photo taken
June 28, 2017.
The grasses apparent in Photo 2 are primarily Squirreltail, which Dr. Redente believed was present
largely as the result of presence of seed in the soil stockpile. This opinion was driven by the quantity
and irregularity of Squirreltail observed. Squirreltail is one of the species included in the seed mix, but
was not expected in the quantity observed.
Photo 3 shows
approximately the
average condition of
the Primary Test Cell
cover. Although
difficult to see in this
view, Fourwing
Saltbrush is present
along with several
seeded grasses. The
inspectors were
concerned about the
lack of green, vibrant
grasses. Dr. Redente
observed that the
grasses would “green
up” with precipitation Photo 3: Average condition of surface of Primary Test Section. Photo taken June 28, 2017.
During the June 28, 2017 visit, the inspectors did not have the benefit of a specialist to help interpret
what was observed. As a result, both the inspectors and the mill staff were of the impression that the
seeding operation had resulted in introduction of very few of the intended plant species, and that those
that did germinate may have died or been consumed by animals. Photos 1 through 3 were forwarded to
the project management team, which led to Dr. Redente’s visit.
Reclamation Plan 5.1, Cover Primary Test Section
August 22, 2017
Page 12
Photo 4 shows a close-
up view of dormant
seeded grasses. Taken
during the second
visit, July 19, 2017,
this photo was
intended to provide an
alternative view of the
grasses observed.
Inspectors discounted
these dormant grasses
during the June 28,
2017 inspection.
Learning that the
grasses were dormant,
not dead, warranted
the additional photo.Photo 4: Close-up photo of dormant grasses. Photo taken July 19, 2019.
Photo 5 shows a
specimen of Fourwing
Saltbrush. Inspectors
did not note this forb
during the June 28,
2017 inspection,
making this photo an
important addition to
the file.
Dr. Redente indicated
that, under average
climatic conditions, he
would have expected
approximately 20
percent vegetative
cover from seeded
species by this time.
Review of the data from the weather station installed adjacent to the Primary Test Section revealed that,
following a wet winter and spring, the weather had abruptly turned hotter and dryer than normal in June.
Dr. Redente estimated the seeded plant density at 7 to 9 percent, less than the 10 to 12 percent he felt
should prevail under the weather conditions experienced. Thus, the inspectors’ observation that the
vegetation appeared sparse was valid, even though the inspectors had discounted some of the vegetation
present.
Photo 5: Specimen of Fourwing Saltbrush. Photo taken July 19, 2017.
Annual weeds were observed in significant quantities. Dr. Redente recommended mowing the weeds
and removing the clippings before seeds could mature and provide a fresh crop to compete with the
seeded annual species for water and nutrients.
v

,
.
On August 10, 2017, Mr. Topham and Ms. Mickelson returned to the mill and observed conditions
following the weed removal effort. Without the weeds overwhelming the scene visually, the seeded
species were more readily apparent. No additional density was observed, but the absence of large
numbers of weeds made the cover look more promising. Without the seeds from the weeds maturing
during the approaching autumn season and germinating during the spring rains, the seeded species
should have more success establishing themselves and thriving.
Analysis
This section follows the same sequence and numbering convention used in the Requirements section
above.
1. The Stipulation and Consent Agreement dated February 23, 2017, Agreement 1 refers to Sections
L.4.2 and L.4.4 of Appendix L [to Updated Tailings Cover Design Report (which appears as
Appendix A to Reclamation Plan Revision 5.1)]. See Items 17 and 20 below for a discussion of this
requirement.
2. The Stipulation and Consent Agreement dated February 23, 2017, Agreement 2.(a), first paragraph
reproduces the essence of the introductory paragraph to Section L.4 of Appendix L to Updated
Tailings Cover Design Report. The pertinent language in this paragraph directed the reader to
Sections L.4.1 through L.4.3 of Appendix L and Attachment L.2 of Appendix L to Updated Tailings
Cover Design Report for requirements.
Section L.4.1 presents a design basis, and has no enforcement parameters. The design parameters
were reviewed as part of the review of the Reclamation Plan, primarily to ensure that the parameters
were translated to the design. That review is independent of the effort chronicled in this report.
See Items 17 through 19 below for a discussion of compliance with the construction requirements
presented in Section L.4.2 of Appendix L to Updated Tailings Cover Design Report.
Section L.4.3 governs the Supplemental Test Section which has not been constructed as of the date
of this report. Therefore, discussion of the Supplemental Test Section is deferred to a later date.
Attachment L.2 provides the primary construction specifications for the Primary Test Section. The
As'Built Report addresses the quality control measures taken and results achieved during
construction of the Primary Test Section. The As-Built Report contains photographs, drawings, raw
data, charts and graphs, and analysis to demonstrate the construction results achieved. The data
presented indicate that the subgrade was properly prepared, formwork was properly installed, all of
the instrumentation and hydraulic conveyances were installed to specification, and that all required
components were present. Materials were within specification and installed to appropriate standards,
as required in Attachment L.2. Initial calibration of instruments was also documented.
The Licensee was required to complete the construction of the Primary Test Section by the date the
Stipulation and Consent Agreement was signed. The Primary Test Section became operational on
October 1, 2016, well before the signatory date on the Agreement, which was February 23, 2017.
Section L.4.2 specified material properties and compaction standards for the soils to be used in the
cover system for all tailings cells. The Primary Test Section design used the same soils in the same
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August 22, 2017
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configuration and required identical compactive effort to be applied as the broader cover system
would receive.
The Stipulation and Consent Agreement required the Licensee to provide the Division with the As-
Built Report within 90 days of completion of the physical work and receipt of final laboratory
analyses. The final laboratory data arrived at the Licensee’s offices in May of 2017, and the As-
Built Report was submitted to the Division on July 11, 2017. The narrative in the As-Built Report
did not specify on what date the last data arrived at the Licensee’s offices, but, assuming the data
arrived on May 1, the Licensee had until July 29 to submit the report.
3. The Stipulation and Consent Agreement dated February 23, 2017, Agreement 3.(a) refers the reader
to Section L.4.2 of Appendix L to Updated Tailings Cover Design Report for standards governing
the monitoring done at the Primary Test Section. The pertinent part of Section L.4.2 is titles
Monitoring Time Period and Frequency.
The Primary Test Section is currently undergoing a period of calibration monitoring, as identified in
Section L.4.2, which carries no requirement for submittal of data. However, the Licensee has
submitted Data Quality Reports for the 4th Quarter of 2016 and the 1st Quarter of 2017 for the
Division’s convenience.
Section L.4.2 requires, following the two-year calibration period that hydrological sensors “be
interrogated hourly, and aggregated into daily quantities for water balance analysis.” The submitted
quarterly data demonstrates that the Licensee is performing that frequency of data gathering and
aggregation, and that the organization and presentation of the data and resulting analysis is effective.
The soil properties were to be tested during the construction of the Primary Test Section. This work
was done, and the data reported in the As-Built Report. No instances of material properties falling
outside the specified limits were found in the data presented in the As-Built Report.
4. The Stipulation and Consent Agreement dated February 23, 2017, Agreement 3.(a).i) requires two
full years of calibration monitoring, commencing the January 1 immediately following construction
of the Primary Test Section. Under this requirement, with the Primary Test Section completed and
becoming operational on October 1, 2016, the calibration period ends on December 31, 2018.
Calibration is ongoing, as evidenced by the Licensee submitting Data Quality Reports for the 4th
Quarter of 2016 and the 1st Quarter of 2017.
5. The Stipulation and Consent Agreement dated February 23, 2017, Agreement 3.(b)requires
evaluating the vegetative cover in accordance with Section L.4.2 and L.4.3 of Appendix L to
Updated Tailings Cover Design Report. Section L.4.2 governs the Primary Test Section, and does
not become effective until the last year of the test period. Section L.4.3 governs the Supplemental
Test Section which has not been constructed, and will not be constructed until this autumn. In any
event, the provisions of Section L.4.3 do not become effective until the last year of the test period.
6. The Stipulation and Consent Agreement dated February 23, 2017, Agreement 3.(c) requires
monitoring meteorological conditions at on-site facilities for the entire test period. The specific
requirements are set forth in Section L.4.2 of Appendix L to Updated Tailings Cover Design Report.
During the site visits on June 28 and July 19, 2017, the weather station was observed. The
parameters being monitored at the meteorological station include temperature, solar radiation.
Reclamation Plan 5.1, Cover Primary Test Section
August 22, 2017
Page 14
precipitation, wind direction and speed, and relative humidity. These parameters satisfy the needs
for data to complete water balance calculations and to interpret measurements made in the lysimeter.
7. Stipulation and Consent Agreement dated February 23, 2017, Agreement 3.(d) requires the Licensee
to evaluate soil properties of the Primary Test Section during Primary Test Section construction, in
accordance with Section L.4.2 of Appendix L to Updated Tailings Cover Design Report. The As-
Built Report provides data demonstrating both that the required testing was completed, and that the
soils used in the construction met the specified standards.
8. The Stipulation and Consent Agreement dated February 23, 2017, Agreement 3.(e) requires the
Licensee to submit sampling plans for the work being completed through the Primary and
Supplemental Test Sections. This requirement should have been removed from the Agreement
inasmuch as the required sampling plans were made a part of Reclamation Plan 5.1 and were
submitted therewith. Both the Agreement and the Reclamation Plan were being revised and
reviewed at the same time. The removal of the requirement to submit the sampling plans was
overlooked during this parallel review and revision effort.
9. The Stipulation and Consent Agreement dated February 23, 2017, Agreement 4.(b) requires that
vegetative cover on both the Primary and Supplemental Test Sections achieve 40 percent density and
meet diversity benchmarks. Achieving these requirements is to be verified at the end of Year 7 of
the test period.
During the June 28, 2017 site visit, inspectors observed sufficiently sparse conditions to raise
concern about the vegetative cover. After the inspectors communicated these concerns to the
Licensee, the Licensee arranged for its botanical consultant, D. Ed Redente, to visit the site, make an
assessment of the condition of the vegetation, and recommend corrective actions that may be
necessary. Dr. Redente observed that, under normal weather conditions, he would have expected
approximately 20 percent coverage and better diversity than was observed. However, given the
rapid warming and dryer than usual late spring and summer, he would have scaled back expectations
to 10 to 12 percent density. He estimated the achieved density at 7 to 9 percent.
Dr. Redente voiced concern over annual weed growth and how that growth could discourage
competition of the perennial species included in the seed mix. He recommended mowing or pulling
the annual weeds and removing the clippings or weeds from the site to eliminate maturing of the
seeds produced by the annuals. Mr. Topham and Ms. Mickelson noted during the August 10, 2017
site visit that the weeds had been removed from the Primary Test Section.
Inasmuch as the requirement to assess the density and diversity of the cover vegetation does not take
effect until the seventh year of the test period, no action is required from the observations reported
here.
10. The Stipulation and Consent Agreement dated February 23, 2017, Agreement 5 requires the
Licensee to monitor settlement monuments and piezometers in accordance with Section L.4.4 of
Appendix L to Updated Tailings Cover Design Report commencing upon completion of the Phase 1
cover construction. Phase 1 cover construction is discussed in a separate evaluation, and only
pertains to this project in the context of effects settlement might have on the integrity of the
construction of the Primary Test Section.
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Reclamation Plan 5.1, Cover Primary Test Section
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Barring rapid settlement, evaluation of this element can be deferred until review of the Annual
Technical Evaluation Report each year. Rapid settlement will leave obvious surface clues, including
significant ponding of water, cracking of the cover surface, and like manifestations. None of these
conditions were noted during the visits on June 28, July 19 or August 10, 2017.
11. Reclamation Plan Revision 5.1, Attachment A, Section 9.2.2 governs the seed mix for use in the
cover system generally and the Test Sections in particular. The Primary Test Section As-Built
Report contains verification of implementation of this seed mix in the construction of the Primary
Test Section. This requirement duplicates Item 14 in the Requirements list above, and in Item 14
below.
12. Reclamation Plan Revision 5.1, Attachment A, Section 9.8.3 governs weed management for the
cover system, and allows both chemical and mechanical means. The recommendation received to
mow or pull the weeds satisfies this limitation. While the weeds being managed are not on the list of
noxious weeds included in the Reclamation Plan, the control of weeds is not proscribed by the
Reclamation Plan or any other governing document.
13. Reclamation Plan Revision 5.1, Attachment A, Section 9.8.4 allows remedial actions in the event
revegetated areas, including the tailings cell cover system, do not make satisfactory progress in
meeting revegetation goals. Allowable options include “fertilization/soil amendments, reseeding,
weed control, and/or erosion control depending upon the cause of the problem that may exist and the
best remediation approach to ensure plant community success.”
During the June 28, 2017 site visit, inspectors noted less than expected growth, and voiced concern
to the Licensee. Subsequently, as noted above, Dr. Ed Redente met with inspectors on-site on July
19, 2017 to assess the progress to date. From among the available remedies, Dr. Redente
recommended weed control to reduce competition between the weeds present and the
intended/seeded plant species. Mill crews removed the weeds prior to the inspectors’ visit on
August 10, 2017.
14. Reclamation Plan Revision 5.1, Attachment A, Section 9.8.4, Criterion 1, Species Composition
specifies the plant species to include in revegetation efforts, including the tailings cell cover system.
The Primary Test Section As-Built Report contains verification of implementation of this seed mix
in the construction of the Primary Test Section. This requirement duplicates Item 11 in the
Requirements list, and in Item 11 above.
Although all seeded species were not observed during the July 19, 2017 site visit, Dr. Redente stated
that some species may need an additional year to germinate and mature.
15. Reclamation Plan Revision 5.1, Attachment A, Section 9.8.4, Criterion 2, addressing the vegetative
cover, contains several requirements.
a. The plants are intended to attain a minimum vegetative cover percentage of 40 percent.
Dr. Redente estimated the cover density extant at the time of the July 19 site visit at 7 to 9
percent. This is well behind the 20 percent that Dr. Redente estimated should be present
under average, or normal conditions. With the summer coming on hotter, dryer and
quicker than usual, the slower plant development was not unexpected, but the cover had
not developed to the plant density of 10 to 12 percent expected under these conditions at
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August 22, 2017
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this early time. Dr. Redente felt that the cover should develop the required plant density
by the end of the seven year test period, so no remedial seeding was recommended at this
time.
b. The plant diversity was specified to include individual grass and forb species listed in
Table 9.1 at a minimum relative cover (the cover of a plant species expressed as a
percentage of total vegetative cover) of 4 percent and a maximum relative cover of 40
percent. Not all species were observed during the site visit, but Dr. Redente felt that
additional time would likely yield better results. The measurement for compliance with
this target will take place after the seven-year test period has concluded.
c. The reclamation plan allows that individual species not listed in Table 9.1 may be
accepted as part of the cover criteria if it is demonstrated that the species is native or
adapted to the area and is a desirable component of the reclaimed project site. This
criterion was not evaluated at the time of the site visit, and will be deferred until the
conclusion of the test.
d. Species not listed in Table 9.1, including annual weeds or other undesirable species such
as those listed in Table 9.2, shall not count toward the minimum vegetative cover
requirement. Every attempt shall be made to minimize establishment of all noxious
weeds. To this end, Dr. Redente recommended cutting and trmoving, or pulling weed
species, inasmuch as the weed density was sufficient to raise concerns about the desired
plant species’ ability to compete. Furthermore, the weeds had matured nearly to the point
of reseeding, and removal of the seeds was desirable.
e. The reclamation plan prohibits the presence of state- and county-listed noxious weeds
(Table 9.2). None of these were identified during the site visits.
f. The vegetative cover shall be self-regenerating and permanent. Self-regeneration shall be
demonstrated by evidence of reproduction, such as tillers and seed production. The site
visits occurred too early in the growth cycle of the seeded species to evaluate this
requirement except in the case of Squirreltail. Squirreltail was present and was dropping
its seed at the time of the visits.
16. Reclamation Plan Revision 5.1, Attachment A, Section 9.8.4, Criterion 3 governs shrub density. The
cover must produce a minimum shrub density of 500 stems per acre. The evaluation would take
place after at least two complete growing seasons. No shrubs were noted during the June 28, July 19
or August 10, 2017 site visits. After only one partial growing season, the time to evaluate this
criterion has not yet come.
17. Updated Tailings Cover Design Report (Appendix A to Reclamation Plan Revision 5.1), Appendix
L, Section L.4.2, Primary Test Section Monitoring - Monitoring System and Instrumentation,
contains several specifications for equipping the Primary Test Section.
a. The monitoring system must include instruments to measure all components of the water
balance for the cover system, including percolation from the base of the cover, runoff,
interflow (internal lateral flow), and on-site meteorological conditions. The system must
be equipped to measure state variables (water content and temperature) at discrete
Reclamation Plan 5.1, Cover Primary Test Section
August 22, 2017
Page 18
locations within the cover. The As-Built Report certifies to the installation of tis
equipment, and the Data Quality Reports demonstrate their effectiveness and sufficiency.
A complementary surveillance program will be performed according to the criteria
presented in Appendix D to monitor the vegetative community, edaphic properties of the
cover soils, and pedogenic evolution of the cover profile, as suggested in NUREG/CR-
7028. Comparisons will be made between the monitoring data and predictions and
assumptions made during cover design. The time to perform the analyses in this
paragraph has not yet come.
b. The specifications require use of precision tipping buckets and pressure transducers in
drainage basins to provide redundant measurements of percolation, interflow, and surface
runoff. The design calls for water content reflectometers (WCR) employing time domain
reflectometry to measure water content of the cover soils in the lysimeter. A Type-T
thermocouple mounted on the head of each WCR will monitor soil temperature. The As-
Built Report details the inclusion of this equipment, and the Data Quality Reports verify
its efficacy.
c. The licensee was required to provide a meteorological station located in a convenient
location to collect data simultaneously with the Primary Test Section equipment. The
Licensee installed the meteorological station immediately outside of the lysimeter area.
As required, the meteorological station includes a shielded Geonor weighing precipitation
gauge that monitors frozen and unfrozen precipitation, a Visalia shielded temperature and
humidity probe to monitor air temperature and relative humidity, a Druck barometric
pressure sensor, a Visalia pyranometer to measure net solar radiation, and a RM Young
wind sentry to measure wind speed and direction. All sensors were calibrated after
installation, in September of 2016. The Annual calibration is required, and is due in
September of 2017.
d. The Licensee was required to provide remote access to the data being collected. This was
done by routing all measurement devices to a single datalogger, and providing telephony
for remote access. The datalogger is programed to collect data from all sensors on hourly
intervals. Downloads from the datalogger occur daily using an automated algorithm. The
datalogger algorithm monitors flows and meteorological variables continuously. If
needed, the datalogger can be programmed to poll sensors as frequently as every 15
seconds to ensure data with adequate frequency to capture flows reliably. Currently, data
is aggregated into daily quantities for reporting. The As-Built Report details this
installation, and the Data Quality Reports demonstrate that the system is functioning.
e. Appendix D spells out the vegetation sampling and monitoring regimen. Live plant cover,
shrub density, and overall plant community health and sustainability are included in the
monitoring. The time to commence vegetation analysis has not yet arrived.
18. The Updated Tailings Cover Design Report (Appendix A to Reclamation Plan Revision 5.1),
Appendix L, Section L.4.2 defines the monitoring time period and frequency of monitoring for the
Primary Test Section. The requirements include two years of calibration monitoring, which is
currently in progress, and five years performance monitoring. All hydrological sensors will be
interrogated hourly, and aggregated into daily quantities for water balance analysis. Vegetation
properties will be measured annually. The Licensee evaluated soil properties during test section
construction. As required, the Licensee will evaluate in-service soil properties during the last year of
the monitoring period via sampling and testing in the buffer area of the test section outside the
lysimeter. The As-Built Report and the Data Quality Reports demonstrate the Licensee’s
compliance with these requirements.
19. The Updated Tailings Cover Design Report (Appendix A to Reclamation Plan Revision 5.1),
Appendix L, Section L.4.2 establishes performance criteria benchmarks to achieve during the
monitoring period. These requirements become effective once the calibration monitoring period
lapses and the performance monitoring period begins on January 1, 2019. Therefore, no further
discussion of the monitoring benchmarks is presented here, with the exception of the physical
properties of the soils used in construction of the Primary Test Section.
Soil properties for the cover system must consist of gradations and percolation values within an
envelope of set values. The Updated Tailings Cover Design Report identifies an Upper Bound and a
Lowe bound condition, along with an expected Base Case, or overall average condition. Because the
Primary Test Section contains a small volume of soil relative to the full cover, the Test Section
design calls for determining where the soils used in its construction fall on this spectrum of gradation
and percolation possibilities. The Test Section As-Built Report identifies the soils used in the
Primary Test Section as marginally coarser and more permeable than the base case expected
properties, but not significantly deviating from the expected averages. Therefore, the performance
of the Primary Test Section should provide results representative of the average soil within the
stockpiles and that already placed in the Primary Radon Barrier.
20. The Updated Tailings Cover Design Report (Appendix A to Reclamation Plan Revision 5.1),
Appendix L, Section L.4.4, contains requirements for additional monitoring. These requirements
govern the settlement monitoring program and the piezometric monitoring program. These
requirements took effect upon completion of Phase 1 of the Cell 2 cover construction, which
encompasses the Primary Radon Barrier, and which was completed during the first quarter of 2017.
The data being generated by this monitoring effort will appear in the Annual Technical Evaluation
Report, and so, will not receive treatment here.
The Licensee detailed in Cell 2 Cover Performance Test Section As-Built Report vault repair and
corrective action activities associated with flooding of the Primary Test Section instrumentation
monitoring vault in nearly February, 2017. The flood resulted from a rainstorm that produced 1-3/4
inches of rain in one day. No specific requirements appear in the License, the cover design documents,
or elsewhere to specify reporting or corrective actions for an event such as the February flooding. The
corrective actions included regrading of the ground surface to redirect runoff away from the vault,
replacement and calibration of damaged pressure transducers, and installation of a warning light visible
from the mill to signal flooding should it occur again. This made the system operational once again, and
gives the staff time to respond should the vault again begin to fill with water.
Conclusions and Recommendations
The Licensee appears fully compliant with applicable reporting requirements. The As-built Report for
the Primary test Section arrived in a timely manner and contained sufficient detail to satisfy the data
reporting requirements.
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The Licensee submitted quarterly Data Quality Reports for Division use even though the first required
submittal will cover the First Quarter, 2018. These reports provided data to help staff understand the
Primary Test Section performance to date, and demonstrated the content and format the Licensee intends
to use in required submittals. The format and content satisfy the requirements of Reclamation Plan
Revision 5.1 and the Stipulation and Consent Agreement.
The Primary Test Section construction follows requirements of Reclamation Plan Revision 5.1 and the
Stipulation and Consent Agreement.
The vegetative cover has not met expectations for plant diversity and density at this early date, but time
remains before the diversity and density requirements take effect. The Licensee is following the
approved design, and is availing itself of the advice of its consultant regarding corrective actions to
encourage success of the cover system.
The Licensee is aware of the operation of the test section and has intervened when necessary to maintain
its operability.
The Division should close out the review of the As-Built Report.
Attachments: Attachment L.2 to Updated Tailings Cover Design Report dated August 2016
Appendix D to Updated Tailings Cover Design Report dated August 2016
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ATTACHMENT L.2
COVER TEST SECTION INSTALLATION INSTRUCTIONS
Updated Tailings Cover Design Report
1.0 INTRODUCTION
This document describes the installation procedures for the test section to be constructed to
assess the performance of the White Mesa reclamation cover for the tailings cells. These
procedures and the design of the cover performance monitoring section are adopted from the
installation instructions for the test sections used in the Alternative Cover Assessment Program
(ACAP) (Benson et al., 1999). The procedures incorporate the performance monitoring
recommendations provided in NUREG/CR-7028 (Benson et al., 2011) and site-specific
recommendations provided by Dr. Craig H. Benson.
The test section is to be located in the southeast corner of Cell 2, as shown in the Drawings
(Attachment L.1). The test section will be 100 ft x 100 ft, with a 32 ft x 64 ft lysimeter centered
within the test section. The longer side of the lysimeter will be oriented parallel to the cover
slope. Design dimensions for the lysimeter and test section are shown in the Drawings. The
lysimeter will collect 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 datalogger located near the southern edge of the test section.
The following sections describe each of the major steps required to install the test section.
2.0 SUBGRADE PREPARATION AND FORMWORK INSTALLATION
The subgrade for the lysimeter should consist of well-compacted interim cover at least 6 inches
thick with no particle protruding from the surface more than 0.5 inches. Ridges, depressions,
equipment tracks, or other variations in the subgrade surface should not exceed 0.5 inches. If
such variations exist, they should be smoothed and subsequently compacted by hand to the
satisfaction of the Resident Engineer (RE). The surface grade of the subgrade must be set so
that all water in the lysimeter drains to the sump.
The entire surface should be proof-rolled with a smooth drum compactor to the satisfaction of
the RE. Soft or otherwise inferior materials should be over-excavated and replaced with hew
materials. The final surface of the subgrade must be approved by the RE before placement of
overlying cover soils or geosynthetics.
Formwork will be used to retain the lysimeter side walls during construction (see Drawings).
The formwork will be constructed in two stages, both 4 ft in height, from 0.50-in plywood (4 ft x 8
ft panels) stiffened with 2x4 lumber around the perimeter. The second stage of formwork will be
installed when the cover is within 12 in of the top of the first stage of the lysimeter construction.
A 2x4 stiffener will be installed vertically at the center of each panel. The 2x4 stiffeners will be
attached to the formwork for each stage using 2-inch deck screws on 6-inch centers. The
formwork will be anchored to the subgrade using at least two formwork stakes extending at least
1.5 ft through 0.6-in holes drilled in the bottom 2x4 stiffeners at the quarter points. Braces
comprised of 2x4 lumber will be placed on 8-ft centers and anchored with formwork stakes for
each stage. Formwork panels will be joined together at each end with 3-inch deck screws that
fasten adjacent 2x4 stiffeners. The upper and lower panels will be bolted together as shown in
the Drawings.
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Sixteen formwork panels are required for each side wall and eight formwork panels are required
for each end wall to create a lysimeter 64 ft long and 32 feet wide. The 4 ft x 8 ft panels will be
used to create 8 ft of the 9.5-ft-high side walls and end walls. The upper 1.5 ft of the lysimeter
will be constructed without formwork. The lower end wall and both side walls will be installed at
the start of construction and before soil placement begins. The upper end wall will be installed
after the soil and geosynthetic layers have been placed in the lysimeter. All walls are to be
installed vertically (end walls are not perpendicular to the slope).
3.0 LYSIMETER SUMP
3.1 Sump Drainage Pipe
The sump at the base of the lysimeter (see Drawings) will be drained by 2-inch Schedule 40
polyvinyl chloride (PVC) pipe. The pipe will be installed in a narrow trench in the subgrade and
extend from the lowest point in the sump to the collection basin. The pipe will be bedded in
clean dense sand at least 3-inches thick beneath the pipe and 6-inches thick above the pipe.
The sand is to be compacted with a vibratory plate compactor before placing the pipe and after
the pipe trench is backfilled. The pipe slope must be maintained at least 1 percent away from
the sump. All PVC pipe joints are to be solvent welded following instructions provided by the
pipe manufacturer. The upper surface of the pipe riser will be temporarily sealed with duct tape
or other material to prevent entry of soil or other materials during construction.
3.2 Sump
The sump boot is to be installed on a section of 2-inch Schedule 40 PVC pipe as illustrated
by the detail in Figure 1 and shown in the Drawings. Liberally smear silicone caulk (GE Silicon
II or equivalent) between the boot and the pipe, and then clamp the boot to the pipe using
stainless steel hose clamps. Fill the groove on the surface between the riser pipe and boot with
caulk. Remove any excess caulk from the surface of the boot and allow the caulk to cure for
at least 120 minutes.
A flexible rubber coupling will be used to join the 2-inch Schedule 40 PVC pipe in the trench to
the 2-inch Schedule 40 PVC riser that will emanate from the subgrade (see Drawings and
Figure 1). This coupling will provide flexibility within the boot as the lysimeter is constructed.
Adjust the elevation of the riser pipe so that the geomembrane rests flush against the
subgrade, and tighten the stainless steel clamps on the pipe coupler with wrenches. A
gap of approximately 0.75 inches will exist between the pipe ends within the coupler to
ensure sufficient flexibility in the sump coupling.
Backfill any open area surrounding the riser pipe with subgrade soil and form a firm surface for
the geomembrane. Place a small section of geosynthetic clay liner (GCL) on the subgrade and
over the pipe before installing the sump and add a thin fillet of granular bentonite (CETCO CG-
50 or equivalent) around the perimeter of the pipe. Check the surface grade of the subgrade to
ensure all water will flow into the sump. A completed sump installation is shown in Figure 2.
4.0 DEPLOY GEOMEMBRANE
Linear low density polyethylene (LLDPE) geomembrane textured on both sides will be used to
line the lysimeter. The geomembrane will be at least 1.5 mm (60 mil) thick. High-density
polyethylene (HOPE), polypropylene, or PVC geomembrane will not be used. The
geomembrane used for the base of the lysimeter will also be used for the end walls and the side
walls. To ensure sufficient geomembrane for the end walls, cut the geomembrane at least 12 ft
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(or more, as needed) longer than needed to cover the length of the base of the lysimeter (Figure
3) for the first stage construction. For the second stage of construction, the upper section of
geomembrane will be welded to the lower geomembrane as shown in the Drawings.
Weld geomembranes panels in accordance with the manufacturer’s recommendations using
a dual-track hot-wedge or extrusion welding technique. Check the welds for leaks using
air pressure per ASTM D 5820 (ASTM, 2011b) or a vacuum box. Inspect the entire area of
the geomembrane for defects. Repair any leaks or defects in accordance with the
manufacturer’s recommendations and to the satisfaction of the RE. The RE, along with
the geosynthetic installer, can adjust these procedures as needed.
After the geomembrane has been placed, locate the sump and carefully cut a hole (<6 in) in
the geomembrane so the sump is visible. Extrusion-weld the boot to the geomembrane
(Figure 4) and check the weld using a vacuum box per ASTM D 5641 (ASTM, 2011a) or a
spark test per ASTM D 6365 (ASTM, 2011c). Identify and repair any leaks identified until
the criteria in ASTM D 5641 (ASTM, 2011a) are met and to the satisfaction of the RE.
Cover the pipe opening in the sump with a non-woven geotextile to prevent entry of debris.
Extend the geomembrane up and over the edge of the formwork extending around the
periphery of the lysimeter. Secure the geomembrane to the upper edge of the formwork using
deck screws installed 6 inches on center. Use a small block of 2x4 lumber or similar material to
provide stress distribution between the screw head and the geomembrane. The geomembrane
will be held in place temporarily at the top of the formwork for both stages shown in the
Drawings. Weld the panels of the geomembrane near the corners of the formwork as shown in
Figure 5 and the Drawings.
5.0 DEPLOY GEOCOMPOSITE DRAIN
Geocomposite drainage layer (GDL) will be used for collecting percolation from the cover soils
and directing the percolation to the sump. The geocomposite drainage layer should have non-
woven polypropylene or polyethylene geotextiles on both sides that are heat-bonded to a
polyethylene geonet in the interior. The geotextiles should have a mass per unit area of at
least 16 oz/yd2.
A rubsheet consisting of 4 mil smooth polyethylene will be used to facilitate installation of the
geocomposite drain. Unroll the rubsheet adjacent to the side wall on one side of the lysimeter.
Lightly anchor the rubsheet with soil, sand bags, or other materials along the periphery. Move a
roll of GDL to the top of the lysimeter by hand or using a loader equipped with a gantry bar or
similar equipment, and unroll the GDL onto the rubsheet. Adjust the position of the GDL to
conform to the base of the lysimeter, and then retrieve the rubsheet. Deploy another panel of
GDL along the side wall using the same technique and then complete the installation with a
panel deployed along the centerline of the lysimeter. Join the panels following the
manufacturer’s recommendations and heat bond the flaps along the edge to prevent debris
from entering the GDL. Figure 6 shows an example of a fully deployed GDL.
Installation of the geomembrane and GDL must be completed within one day. By the end of
this day, the sump area should surcharged with a load of soil (approximately 1 cy) placed
directly on top of the GDL in the sump area. This surcharge ensures that the sump remains
in firm contact with subgrade while other construction activities are taking place. This
surcharge must be placed before the end of the work day, as cooling of the
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geomembrane overnight can impose stresses in the sump area sufficient to catastrophically
damage the sump.
6.0 PLACEMENT OF INTERIM COVER SOIL AND ROOT BARRIER
6.1 Interim Cover Soil
The interim cover soil (Layer 1) will be the first soil layer placed on top of the GDL. The interim
cover soil should be deployed as a working platform so that the construction equipment does
not contact the geosynthetics or displace the geosynthetics. The interim cover soil will be
2.5 ft thick and placed using methods expected for full-scale construction (except low pressure
equipment should be used). Extreme caution must be used when placing the interim
cover so that large particles do not damage the lysimeter geosynthetics. Any particles
larger than 3 inches should be removed from the lower layer of interim cover prior to
construction traffic on the interim cover.
Compact soil on. both sides of the side wall geomembrane with a motorized hand tamper
(jumping jack) to ensure a tight interface between the soil and geomembrane. Compact
the remaining interim cover soil using low ground pressure equipment to the conditions
stipulated per the Technical Specifications. After compaction, place a fillet of granular
bentonite (1 Ib/ft of CETCO CG-50 or equivalent) around the periphery of the interior of the
lysimeter to promote sealing between the side wall geomembrane and interim cover soil.
Soil placement will occur through the upper end of the lysimeter and will extend at least
10 ft upslope from the upper end wall when the first stage of the lysimeter is constructed.
Before placing the soil, 0.75-inch plywood panels should be placed over the geomembrane
extending upward from the end of the lysimeter (Figure 7). This section of geomembrane
will be folded up to create the upper end wall after the soil and geosynthetic layers have
been placed in the lysimeter. The plywood panels will protect the geomembrane for the end
wall from damage due to construction traffic.
6.2 Root Barrier Layer
Place the root barrier layer (Reemay Biobarrier or equivalent) directly on top of the interim
cover following the manufacturer’s instructions. Ensure that the polyethylene nodules are
oriented upward and that contact does not exist between the root barrier and the GDL or
bottom geomembrane in the lysimeter.
7.0 PLACEMENT OF FINAL COVER SOILS AND COVER GEOSYNTHETICS
Place the final cover soils following methods described in the Technical Specifications
(Attachment A to Reclamation Plan, Revision 5.1) both inside and outside the lysimeter in
the areas shown in the Drawings. The thickness of each lift should be verified using
surveys of the bottom and top of each lift and should meet the criteria in the Technical
Specifications.
Place cover soils around the inside and outside edges of the lysimeter directly adjacent to the
side wall geomembrane. Compact soil on both sides of the side wall with a motorized
hand tamper (jumping jack) to ensure a tight interface between the soil and
geomembrane. After compaction, place a fillet of granular bentonite (1 Ib/ft of CETCO CG-
50 or equivalent) around the periphery of the interior of the lysimeter to promote sealing
between the side wall geomembrane and cover soil.
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Grade the upper surface of the uppermost layer of cover soil so surface water will flow to
the surface runoff sump located at along the centerline of the test section and above the
percolation sump (see Section 9).
8.0 INTERFLOW COLLECTION
Interflow is to be collected at the contact between the interim fill (Layer 1) and compacted
cover (Layer 2). Liquid is to be collected along the lower end wall of the lysimeter using a
sump and routed to a collection basin. Schematics of the sump to be used are shown in the
Drawings. The interflow sump is to be located at the centerline of the lower end wall.
Sump is to be placed with a 2 percent increase in slope within 2 ft of the end wall to promote
flow to the slump. The cross-slope along the end wall should be at 1 percent towards the
sump.
A 2-ft long capture strip of GDL will extend across the breadth of the lower end wall and
will be buried 2. inches below the surface of the interim cover layer adjacent to the end wall
as shown in the Drawings. The depth of embedment of the GDL in the interim cover will
taper to zero at the upslope end of the GDL capture strip. A 6-inch tall strip of GDL will
also to be placed in direct contact with the end wall extending from the GDL buried in the
interim cover and into the compacted cover layer. The GDL strip placed in direct contact
with the end wall will capture flow at the interface of the layers at the end wall. The buried
GDL strip and the GDL strip in contact with the end wall can also be installed as one
contiguous material along with a sharp bend at the end wall.
Drainage will occur through a 2-inch Schedule 40 PVC pipe using a boot as shown in the
Drawings. Field fitting of the sump details may be required and is acceptable. Any field fit
must be approved by the RE.
9.0 SURFACE RUNOFF COLLECTION
9.1 Diversion Berms
Construct berms for surface runoff collection having the geometry shown in Drawings along
the periphery of the lysimeter. Compact the berm with a hand tamper and/or with
construction equipment until the soil is firm. Slope the interior swale along the bottom
berm towards the center of the lysimeter to ensure surface water flows to the collection point
near the centerline of the test section.
9.2 Collection Point
Surface runoff will be collected in an 18-inch strip drain located along the centerline of the test
section and adjacent to the bottom diversion berm as shown in the Drawings. A 2-inch
Schedule 40 PVC pipe will be used direct flow from the strip drain to the collection basins.
Adapters may be needed between the strip drain and the PVC pipe, as indicated in the
manufacturer’s instructions. Bed the PVC pipe in sand and use a plug of bentonite to ensure
that surface runoff cannot seep into the pipe trench.
Grade the interior berm to ensure water drains into the strip drain. Cover the entry grate of
the strip drain with a strip of non-woven geotextile sourced from the roll of GDL. Anchor the
GDL strip with spikes or rip rap cobbles.
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10.0 FLOW COLLECTION AND METERING SYSTEM
10.1 Collection Basin Vault
Collection basins for surface runoff, interflow, and percolation are to be installed in a
concrete vault located downslope of the lysimeter as shown in the Drawings. The location
should be field fit to ensure that all drainage pipes emanating from the lysimeter maintain a
slope of at least 1 percent. The slope on the percolation pipe should control the location and
elevation of the base of the vault. Install vault following the manufacturer’s instructions.
Ensure vault is covered with at least 1.5 ft of soil at the shallowest location (up to 3 ft is
acceptable at the shallowest location).
10.2 Collection Basins and Piping
Install three collection basins each with a flout (Orenco Model PBF-C) to collect and meter
flow from the surface runoff, interflow, and percolation pipes. Install the basins following
the manufacturer’s instructions. In each basin, install a pressure transducer (Campbell
Scientific CS450-L60), float switch (Orenco FS-48), and tipping bucket (Flydrological Services
America TB1L or TB1L/70) as described in Benson et al. (1999, 2001).
Route piping for runoff, interflow, and percolation through knock-outs near the surface of
vault and field fit piping to reach each collection basin. After installation, seal each pipe
and knock-out with polyurethane foam.
Route effluent pipes from the basins through knockouts at the base of the vault. Bury the
drainage pipes in vertical French drains at least 2 ft x 2 ft in surface area and 4 ft deep that
are backfilled with coarse rock. Cover the surface of the coarse rock with a section of
GDL after installation of the piping to prevent ingress of fines from overlying materials.
Seal the pipe and knock-out with polyurethane foam. Install a floor drain with a trap that
flows to a French drain beneath the vault. Seal the annulus in the floor drain with
polyurethane foam.
Calibrate each basin by measuring the volume of water required to initiate discharge by the
flout. Mark the elevation at which discharge begins. Repeat this procedure two more times
to check the calibration. If the calibration or flush elevation deviates significantly, find the
source of the problem, correct it, and re-calibrate the dosing siphon. Calibrate the tipping
bucket and the pressure transducer following the manufacturer’s instructions and Benson et al.
(1999).
11.0 SOIL AND METEOROLOGICAL SENSORS
11.1 Soil State Variables
Water content reflectometers (WCRs, Campbell Scientific CS616) and thermocouples
(TCs, Omega Type T) are to be installed in two nests located at the quarter points along the
centerline of the test section as shown in the Drawings. A WCR and TC are to be placed at
each of the depths shown and should be installed immediately after the lift corresponding
to the sensor elevation has been placed. Press the WCR horizontally (or at the angle of the
slope) into the cover soil by hand following the manufacturer’s instructions. Tape the end of
the TC to the head of the WCR using duct tape. Route the sensor cables in 1-inch PVC
conduit along the surface of the most recent lift to a vertical riser for all sensor cables
(Figure 8).
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11.2 Weather Station
Install the weather station tripod and grounding rod for the weather station following the
manufacturer's instructions adjacent to the test section. Bolt the data acquisition cabinets to
the tripod and install the pyranometer, temperature and humidity sensor, and wind sentry on
the tripod following the manufacturer's recommendations. Wire all sensors, including those
installed in the test section, following the manufacturer’s instructions. Install the
precipitation gage (Geonor T-200B) following the manufacturer’s instructions. Install cabling
in conduit between the weather station, precipitation gage, and sensors. Seal all open ends
of conduit with polyurethane foam.
12.0 VEGETATION
Prepare and seed the surface of the test section following the procedure adopted for
reclamation at White Mesa and outlined in Appendix D of the Updated Tailings Cover Design
Report. Employ the same procedures that will be used for the remainder of the cover. If
the surface layer is disturbed during seeding, use care to avoid damaging any of the
sensors or cables near the surface.
13.0 REFERENCES
ASTM International, 2011a. ASTM D5641-94, Standard Practice for Geomembrane Seam
Evaluation by Vacuum Chamber.
ASTM International, 2011b. ASTM D5820-95, Standard Practice for Pressurized Air channel
Evaluation of Dual Seamed Geomembranes.
ASTM International, 2011c. ASTM D6365-99, Standard Practice for the Nondestructive Testing
of Geomembrane Seams using the Spark Test.
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, Geotechnics Report 99-3,
Geological Engineering, University of Wisconsin-Madison.
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FIGURES
MWH Cell 2 Reclamation Cover
Design, Implementation, and Performance Assessment Plan
Figure 1. Rubber coupling used to ensure flexibility of boot for sump
(Photo courtesy of Dr. Craig H. Benson)
I
MWH Cell 2 Reclamation Cover
Design, Implementation, and Performance Assessment Plan
Figure 2. Sump installed on subgrade with duct tape sealing pipe opening and panel of
GCL directly beneath sump.
(Photo courtesy of Dr. Craig H. Benson)
MWH Cell 2 Reclamation Cover
Design, Implementation, and Performance Assessment Plan
Figure 3. Geomembrane extending over downslope end wall (upper) and deployed out the
upslope end of lysimeter for upper end wall (lower).
(Photos courtesy of Dr. Craig H. Benson)
MWH Cell 2 Reclamation Cover
Design, Implementation, and Performance Assessment Plan
Figure 4. Welding geomembrane on base of lysimeter to percolation sump (upper left),
completed weld and visible pipe for percolation (upper right), and non-woven
geotextile secured over sump to prevent entry of debris into pipe (bottom).
(Photos courtesy of Dr. Craig H. Benson)
MWH Cell 2 Reclamation Cover
Design, Implementation, and Performance Assessment Plan
Figures. Example of folding of geomembrane sheet for corner welds.
(Photo courtesy of Dr. Craig H. Benson)
M MWH Cell 2 Reclamation Cover
Design, Implementation, and Performance Assessment Plan
Figure 6. GDI being deployed on geomembrane (upper) and GDL fully deployed with
heat- bonded overlap (lower).
(Photos courtesy of Dr. Craig H. Benson)
MWH,Cell 2 Reclamation Cover
Design, Implementation, and Performance Assessment Plan
Figure 7. Plywood deployed over geomembrane at upper end of test section to prevent
damage from equipment traffic.
(Photo courtesy of Dr. Craig H. Benson)
MWH Cell 2 Reclamation Cover
Design, Implementation, and Performance Assessment Plan
Figure 8. PVC conduit for sensor cables from specific elevation (upper) and vertical riser
for all cables (lower).
(Photos courtesy of Dr. Craig H. Benson)
Updated Tailings Cover Design Report
APPENDIX D
VEGETATION AND BIOTINTRUSION EVALUATION
MWH
Updated Tailings Cover Design Report
D.1 INTRODUCTION
This appendix provides an evaluation of vegetation that would be used as an integral part of an
evapotranspiration (ET) cover proposed for reclamation of tailings cells at the White Mesa Mill
(Mill) site. A critical component of an ET cover is the plant community that will be established on
the cover and will function over the long term to provide protection from wind and water erosion
and assist in removing water through the process of transpiration. In this appendix, issues related
to the short-term establishment and long-term sustainability of vegetation proposed as part of the
ET cover are addressed. These issues include: plant species selection, ecological characteristics
of species (i.e., longevity, sustainability, compatibility, competition, rooting depth and root
distribution), characteristics of the established plant community (i.e., percent plant cover and leaf
area index [LAI]), and soil requirements for sustained plant growth. Information is also presented
on weed control, vegetation performance goals and criteria, and post-closure vegetation
monitoring. In addition, biointrusion from both plants and animals is addressed using information
from an on-site survey conducted in June 2012 and literature applicable to site conditions. Finally
there is discussion on climate change projections for the performance period and possible
changes that may occur with plant community composition over time.
D.2 PROPOSED SPECIES FOR ET COVER RECLAMATION
The following 15 species (11 grasses, 2 forbs, and 2 shrubs) are proposed for the ET cover
system at the Mill site. These species were selected for their adaptability to site conditions,
compatibility, and long-term sustainability. Species were also selected based on the assumption
that institutional controls will exclude grazing by domestic livestock. The proposed species are:
• . Western wheatgrass, variety Arriba (Pascopyrum smithii)
• Bluebunch wheatgrass, variety Goldar (Pseudoroegneria spicata)
• Slender wheatgrass, variety San Luis (Elymus trachycaulus)
• Streambank wheatgrass, variety Sodar (Elymus lanceolatus ssp. psammophilus)
• Pubescent wheatgrass, variety Luna (Thinopyrum intermedium ssp. barbulatum)
• Indian ricegrass, variety Paloma (Achnatherum hymenoides)
• Sandberg bluegrass, variety Canbar (Poa secunda)
• Sheep fescue, variety Covar (Festuca ovina)
• Squirreltail, variety Toe Jam Creek (Elymus elymoides)
• Blue grama, variety Hachita (Bouteloua gracilis)
• Galleta, variety Viva (Hilaria jamesii)
• Common yarrow, no variety (Achillea millefolium)
• White sage, variety Summit (Artemisia ludoviciana)
• Fourwing saltbush, variety Wytana (Atriplex canescens)
• Rubber rabbitbrush, no variety (Ericameria nauseosus).
These species are described in more detail later in this appendix.
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D.3 PROPOSED SEEDING RATES
Given a mixture of the species listed above, Table D.1 presents broadcast seeding rates for each
species. Seeding rates were developed based on the objective of establishing a permanent cover
of grasses, forbs, and shrubs in a mixture that would promote compatibility among species and
minimize competitive exclusion or loss of species over time. The proposed seeding rate is based
on number of seeds/ft2 and then converted to pounds of pure live seed per acre (lbs PLS/acre),
with further discussion presented below.
The number of seeds placed in a unit area of soil is called the seeding rate. The total seeding
rate is the sum of the individual species seeding rates. Seeding rates are normally expressed as
the number of seeds per square foot or pounds per acre. Many different seeding rates for the
same species can be found in the literature. The primary reason for these differences is that
some rates are for monocultures and other rates are for diverse mixtures. In addition, seeding
rates vary depending on the method of seeding and site conditions related to edpaphic factors,
topography and climate.
Seeding rates are developed on the basis of number of seeds per unit area (e.g. number of seeds
per square foot). Once this number is determined, then it can be converted to weight per unit
area (e.g. pounds per acre). Since each species produces seed that weighs a different amount,
the development of seeding rates based purely on weight per unit area will produce erroneous
rates that will tend to over emphasize small seeded species and under-emphasize large seeded
species. For example, blue grama has approximately 700,000 seeds per pound, while Indian
ricegrass has approximately 175,000 seeds per pound. If seeding rates were calculated simply
on the basis of weight per unit area, without recognizing the fact that a pound of blue grama seed
has four times the number of seeds per pound as Indian ricegrass, it would be very easy to over
plant blue grama and under plant Indian ricegrass.
Table D.1. Species and Seeding Rates Proposed for ET Cover at the Mill Site
MWH.
Updated Tailings Cover Design Report
Scientific Name Common Name Varietal
Name
Native/
Introduced
Seeding
Rate (lbs
PLS/acre)*
Seeding
Rate (#
seeds/ft2)
Grasses
Pascopyrum smithii Western wheatgrass Arriba Native 3.0 7.9
Pseudoroegneria
spicata
Bluebunch wheatgrass Goldar Native 3.0 9.6
Elymus trachycaulus Slender wheatgrass San Luis Native 2.0 6.2
Elymus lanceolatus Streambank wheatgrass Sodar Native 2.0 7.3
Elymus elymoides Squirreltail Toe Jam Native 2.0 8.8
Thinopyrum
intermedium
Pubescent wheatgrass Luna Introduced^1.0 1.8
Achnatherum
hymenoides
Indian ricegrass Paloma Native 4.0 14.7
Poa secunda Sandberg bluegrass Canbar Native 0.5 11.4
Festuca ovina Sheep fescue Covar Introduced*1.0 11.5
Bouteloua gracilis Blue grama Hachita Native 1.0 16.5
Hilaria jamesii Galleta Viva Native 2.0 7.3
Forbs
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Scientific Name Common Name Varietal
Name
Native/
Introduced
Seeding
Rate (lbs
PLS/acre)t
Seeding
Rate (#
seeds/ft2)
Achillea millefolium,
variety occidentalis
Common yarrow VNS*Native 0.5 32
Artemisia ludoviciana White sage VNS Native 0.5 45
Shrubs
Atriplex canescens Fourwing saltbush Wytana Native 3.0 3.4
Ericameria nauseosus Rubber rabbitbrush VNS Native 0.5 4.6
Total 26.5 188
■^Seeding rate is for broadcast seed and presented as pounds of pure live seed per acre (lbs PLS/acre).
^Introduced refers to species that have been 'introduced' from another geographic region, typically
outside of North America. Also referred to as ‘exotic’ species. *VNS=Variety Not Specified but seed
source would be designated from sites similar to the Mill site.
Seeding rate may be calculated from an expected field emergence for each species and the
desired number of plants per unit area. For purposes of calculation, field emergence for small
seeded grasses and forbs is assumed to be around 50 percent if germination is greater than 80
percent. Field emergence is assumed to be around 30 percent if germination is between 60 and
80 percent. The Natural Resource Conservation Service recommends a seeding rate of 20 to 30
pure live seeds per square foot as a minimum number of seeds when drill seeding single species
in areas with an annual precipitation between 6 and 18 inches. Twenty pure live seeds per square
foot, with an expected field emergence of 50 percent should produce an adequate number of
plants on the seeded area to control erosion and suppress annual invasion. This seeding rate is
primarily for favorable growing conditions, soils that are not extreme in texture, gentle slopes,
north or east facing aspect, good moisture, adequate soil nutrients and single species vs. multiple
species in a mixture. When conditions are less favorable when the seed is broadcast, or when
multiple species are in a mixture the seeding rates are increased.
A Quality Assurance/Quality Control Plan for application rates and procedures for confirming that
specified application rates are achieved is as follows. The first step begins with a seed order.
Seed would be purchased as pounds of pure live seed. Each State has a seed certifying agency
and certification programs may be adopted by seed growers. Certification of a container of seed
assures the customer that the seed is correctly identified and genetically pure. The State agency
responsible for seed certification sets minimum standards for mechanical purity and germination
for each species of seed. When certified, a container of seed must be labeled as to origin,
germination percentage, date of the germination test, percentage of pure seed (by weight), other
crop and weed seeds, and inert material. The certification is the consumer’s best guarantee that
the seed being purchased meets minimum standards and the quality specified.
Once the seed is obtained, seed labels would be checked to determine the percent PLS and the
date that the seed was tested for percent purity and percent germination. If the test date is greater
than 6 months old, the seed would be tested again before being accepted. Seed will be applied
using a broadcasting method. This procedure would use a centrifugal type broadcaster (or similar
implement)), also called an end-gate seeder. These broadcasters operate with an electric motor
and are usually mounted on the back of a small tractor and generally have an effective spreading
width of about 20 feet or more. Prior to seeding, a known area will be covered with a tarp and
seed will be distributed using the broadcaster and simulating conditions that would exist under
actual seeding conditions. Seed will then be collected and weighed to determine actual seeding
rate in terms of pounds per acre. This process will be repeated until the specified seeding rate is
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mmu.
obtained. During the seeding process, the seeding rate will be verified at least once by comparing
pounds of seed applied to the size of the area seeded. In addition, seed will be applied in two
separate passes. One-half of the seed will be spread in one direction and the other half of seed
will be spread in a perpendicular direction. This will ensure that seed distribution across the site
is highly uniform and also provide the opportunity to adjust the seeding rate if the specified rate
is not being achieved.
D.4 ECOLOGICAL CHARACTERISTICS OF PROPOSED SPECIES AND ESTABLISHED
PLANT COMMUNITY
D.4.1 Ecological Characteristics of Plant Species of Tailings Cover System
Important ecological characteristics for each species proposed for reclamation are provided in the
paragraphs that follow. Species information was obtained from a number of references that are
cited below. The proposed species are adapted to the elevation (5,600 feet), precipitation (13
inches per year on average), and soil textural ranges (loam to sandy clay) that are well within the
environmental conditions of the Mill site. Table D.2 presents a summary of the ecological
characteristics discussed in the following paragraphs.
Western wheatgrass, variety Arriba {Pascopyrum smithii) - Western wheatgrass is a native,
rhizomatous, long-lived perennial cool season grass. It grows well in a 10- to 14-inch mean
annual precipitation zone and is adapted to a wide range of soil textural classes at elevation
ranges up to 9,000 feet. Western wheatgrass has been an important species for restoring mining
related disturbances, for erosion control and for critical area stabilization in semi-arid regions
because of its ease of establishment and ability to grow successfully in pure or mixed stands of
both warm and cool season species. Western wheatgrass is fire tolerant and regenerates readily
following burning. The variety of Arriba is known for rapidly establishing seedlings and high seed
production. The combination of its ability to spread vegetatively and reproduce by seed ensures
long-term sustainability of this species.
Bluebunch wheatgrass, variety Goldar (Pseudoroegneria spicata) - Bluebunch wheatgrass
is a native, cool season perennial bunch grass. Bluebunch wheatgrass grows on soils that vary
in texture, depth and parent material. It is one of the most important and productive grasses found
in sagebrush communities in the intermountain west. Bluebunch wheatgrass is fire tolerant and
regenerates vegetatively following burning. This species is well adapted to a 12- to 14-inch mean
annual precipitation range and is considered to be highly drought resistant. Bluebunch
wheatgrass performs well in mixtures with other species and grows at elevations up to 10,000
feet.
Slender wheatgrass, variety San Luis {Elymus trachycaulus) - Slender wheatgrass is a
native, cool season, perennial bunch grass that occasional produces rhizomes. It is a short-lived
species (5 to 10 years) but it reseeds and spreads well by natural seeding, exceeding most other
wheatgrasses in this characteristic. Slender wheatgrass can serve as an important pioneer
species; its seedlings are vigorous and capable of establishing on harsh sites. In addition, it is
able to establish and compete with weedy species. Slender wheatgrass is commonly seeded in
mixtures with other grasses and forbs to restore disturbances and rehabilitate native communities.
It is adapted to a wide variety of sites and is moderately drought tolerant. It performs best at sites
with an annual precipitation of 15 inches or more, but can grow on sites with precipitation levels
as low as 13 inches.
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Updated Tailings Cover Design Report
Table D.2. Summary of Ecological Characteristics of Plant Species Proposed for the ET Cover at the Mill Site
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Western wheatgrass Native Perennial Vegetative 4 3 4 10-14 <9,000 S.C.L 109d 4 4 4
Bluebunch
wheatgrass Native Perennial Seed 4 4 4 12-14 <10,000 S,C,L 122®4 4 4
Slender wheatgrass Native Perennial Seed 4 4 2 13-18 <10,000 S.C.L 109d 2 2 2
Streambank
wheatgrass Native Perennial Vegetative 4 4 4 11-18 <10,000 S.C.L 165f 4 4 3
Pubescent
wheatgrass Introduced Perennial Vegetative 4 2 4 12-18 <10,000 S.C.L 185d 4 4 3
Indian ricegrass Native Perennial Seed 3 4 4 6-16 <10,000 S.L 849 2 4 2
Sandberg bluegrass Native Perennial Seed 4 4 4 12-18 <12,000 S.C.L 45h 2 3 4
Sheep fescue Introduced Perennial Seed 4 2 4 10-14 <11,000 S.C. L 56®3 4 2
Sguirreltail Native Perennial Seed 3 4 3 8-15 <11,000 S.C.L 30®''2 4 3
Blue grama Native Perennial Vegetative 2 4 4 10-16 <10,000 S.L 1199 4 4 4
Galleta Native Perennial Vegetative 3 4 4 6-18 <8,000 S.C.L 30*4 4 4
Common yarrow Native Perennial Vegetative 4 3 4 13-18 <11,000 S.C.L 105h 4 3 2
White sage Native Perennial Vegetative 4 4 4 12-18 >5,000 S.C.L 20®'3 3 2
Fourwing saltbush Native Perennial Seed 4 4 4 8-14 <8,000 S.L 600)4 4 1
Rubber rabbitbrush Native Perennial Seed 4 4 4 7-18 29,000 S.C.L 150k 4 4 1
aKey to Ratings—4 = Excellent, 3 = Good, 2 = Fair, 1 = Poor
bSoil Texture Codes—S = Sand, C = Clay, L = Loam
cDepth represents minimum depth; no information in the literature on average or maximum depth could be found.
dWyattetal., 1980.
eWeaver and Clements, 1938.
fCoupland and Johnson, 1965.
sFoxxand Tierney, 1987.
hSpence, 1937.
'USDA, 2012.
iGibbens and Lenz 2001
KMonsen et al., 2004.
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Streambank wheatgrass, variety Sodar (Elymus lanceolatus ssp. psammophilus) -
Streambank wheatgrass is considered to be part of the thickspike wheatgrass (Elymus
lanceolatus ssp. lanceolatus) taxa. Variety Sodar is a native, perennial sod grass that is highly
rhizomatous and adapted to the western intermountain area. It is highly drought tolerant and
performs well in mean annual precipitation ranges between 11 and 18 inches. It grows on a wide
range of soil textures, from sandy to clayey. Streambank wheatgrass is commonly used in mine
land reclamation and is best known for its ability to control erosion and compete with annual
weeds. Its highly rhizomatous nature ensures long-term sustainability of this species.
Pubescent wheatgrass, variety Luna (Thinopyrum intermedium ssp. barbulatum) -
Pubescent wheatgrass is a long-lived sod forming perennial introduced from Eurasia. It is highly
drought tolerant and grows where the mean annual precipitation is 12 inches or more. It is
adapted to a wide range of soil textures, from sand to clay. Pubescent wheatgrass is a highly
persistent species, should be seeded at low densities to avoid competition with native species.
Indian ricegrass, variety Paloma (Achnatherum hymenoides) - Indian ricegrass is a native,
cool season, perennial bunchgrass with a highly fibrous root system. Indian ricegrass is one of
the most common grasses on semi-arid lands in the west and is one of the most drought tolerant
species used in mine land reclamation. It generally occurs on sandy soils, but is found on soils
ranging from sandy to heavy clays. It grows from 2,000 to 10,000 feet in areas where the mean
annual precipitation is 6 to 16 inches. Indian ricegrass is slow to establish, but highly persistent
once it becomes established.
Sandberg bluegrass, variety Canbar (Poa secunda) - Sandberg bluegrass is a native, cool
season perennial bunchgrass that is adapted to all soil textures and is highly resistant to fire
damage. Sandberg bluegrass is one of the more common early-season bunchgrasses in the
Intermountain area. It grows at elevations from 1,000 to 12,000 feet and can be successfully
established in areas with a mean annual precipitation of 12 inches or more. Established plants
are not overly competitive, and therefore highly compatible with other native species.
Sheep fescue, variety Covar (Festuca ovina) - Sheep fescue is a short, mat-forming introduced
perennial that grows well on infertile soils in areas with a mean annual precipitation of 10 to 14
inches. It is long-lived and highly drought tolerant. Sheep fescue is a cool season species that
greens up early in the spring. The proposed variety, Covar, was introduced from Turkey and is
commonly used in mine land reclamation for long-term stabilization and erosion control. This
variety was selected because plants are persistent, winter hardy, and drought tolerant.
Squirreltail, variety Toe Jam Creek (Elymus elymoides) - Squirreltail is a short-lived perennial
that is selected for its ability to establish quickly and to effectively compete with undesirable annual
grasses. It grows along an elevation range from 2,000 to 11,000 feet and on all soil textures in
mean annual precipitations zones of 8 to 15 inches. Squirreltail is fairly tolerant of fire because
of its small size.
Blue grama, variety Hachita (Bouteloua gracilis) - Blue grama is a low-growing perennial
warm season bunchgrass. Blue grama produces an efficient, widely spreading root system that
is mostly concentrated near the soil surface. Blue grama is adapted to a variety of soil types, but
does best on well-drained soils and once established, is highly drought tolerant. This species is
commonly found with cool-season species and is highly compatible with other native perennials.
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Galleta, variety Viva (Hilaria jamesii) - Galleta is a strongly rhizomatous perennial warm season
grass with a dense, fibrous root system. Galleta grows on sits receiving 6 to 18 inches of annual
precipitation with soils ranging from coarse to fine. Plants have a low requirement for soil fertility
and are drought and fire tolerant.
Common yarrow (Achillea millefolium, var. occidentalis) - Yarrow is a common native forb
species that is rhizomatous and found growing from valley bottoms to timberline. It is commonly
used in mine land reclamation, establishes easily from seed and is highly persistent. It grows on
a variety of soil textures and found in a mean annual precipitation range between 13 and 18
inches. If seed is not available for Achillea millefolium var. occidentalis, then the introduced
Achillea millefolium would be used, which has the same growth characteristics as the native form.
White sage, variety Summit (Artemisia ludoviciana) - White sage is considered to be a
pioneer rhizomatous forb species that establishes quickly on disturbed sites and is highly
compatible with perennial grasses. It does best on well-drained soils, but can be found growing
on a wide range of soil textures. It is adapted to sites above 5,000 feet in elevation and to sites
with a mean annual precipitation above 12 inches.
Fourwing saltbush, variety Wytana (Atriplex canescens) - Fourwing saltbush can be
deciduous or evergreen, depending on climate. Its much-branched stems are stout and mature
plants range from 1 to 8 feet in height, depending on ecotype, the soil, and climate. Fourwing
saltbush is one of the most widely distributed and important native shrubs on rangelands in the
western United States. Fourwing saltbush is highly palatable browse and is utilized primarily in
the winter at which time it is high in carotene and digestible protein. Fourwing saltbush provides
excellent season long browse for deer. It is a good browse plant for antelope and elk in fall and
winter. It is also a food source and excellent cover for upland birds. Fourwing saltbush has
excellent drought tolerance. Fourwing saltbush is adapted to most soils but is best suited to loamy
to sandy to gravely soils. It is not especially tolerant of fire, but may re-sprout to some degree if
fire intensity is not too severe. Fourwing saltbush occurs most commonly in salt-desert scrub
communities in the desert areas of western North America in areas that receive 8 to 14 inches of
annual precipitation. It can be found from sea level in Texas to over 8,000 feet in Wyoming.
Rubber rabbitbrush (Ericameria nauseosus) - Rubber rabbitbrush is a native, perennial,
warm-season shrub that grows to 1 to 8 feet tall. Rubber rabbitbrush is an important browse
species for wildlife during the winter months. Rubber rabbitbrush occurs as a dominant to minor
component in many plant communities, ranging from arid rangelands to montane openings. It
thrives in poor conditions, and can tolerate coarse, alkaline soils. Dense stands are often found
on degraded rangelands, along roadsides, and in abandoned agricultural fields. The species is
useful in soil stabilization and restoration of disturbed sites. The root system establishes quickly
and plants produce large quantities of leaf litter. Rubber rabbitbrush is adapted to cold, dry
environments receiving 7 to 18 inches of annual precipitation at elevations ranging from 450 to
8,000 feet. Depending on the ecotype, rubber rabbitbrush can be found on loamy, sandy, gravelly
or heavy clay soils that are slightly acidic, slight to strongly basic, or saline.
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D.4.2 Longevity and Sustainability
All of the species proposed for reclamation of the tailings cells are long-lived, except for slender
wheatgrass (Elymus trachycaulus) and squirreltail (Elymus elymoides). Slender wheatgrass is a
perennial bunchgrass that is short-lived (5 to 10 years) but has the ability to reseed and spread
vegetatively with rhizomes. Squirreltail is also a short-lived perennial but has the ability to
establish quickly and is highly effective in competing with undesirable annual grasses. Both of
these species are included in the proposed seed mixture because of their ability to provide quick
cover for erosion protection and to effectively compete with annual and biennial species that
cannot be relied upon to provide consistent and sustainable plant cover. The use of these species
will facilitate the establishment of the remaining long-lived perennials that have been documented
to be highly adapted to the elevation, climate, and soil conditions found at the Mill site (Monsen
et al., 2004; Alderson and Sharp, 1994; Wasser, 1982; Thornburg, 1982).
The perennial grasses, forbs, and shrubs in the proposed seed mixture include species that
develop individual plants that are long lived (30 years or more) and are able to reproduce either
by seed or vegetative plant parts like rhizomes and tillers. The use of these species in reclamation
of the tailings cells will ensure a permanent or sustainable plant cover because of the highly
adapted nature of these species to site conditions, their tolerance to environmental stresses such
as drought, fire, and herbivory, and their ability to effectively reproduce over time.
The use of a mixture of species for the ET cover also contributes to longevity and sustainability.
The establishment of a diverse community has many advantages over a monoculture for
sustained plant growth. The use of a variety of species ensures that diverse microsites that may
exist over a seeded site are properly matched with species that are adapted to those specific
environmental conditions. In addition, a mixture of species reverses the loss of plant diversity
and enhances natural recovery processes following impacts from insects, disease organisms,
and adverse or changes in climatic conditions. Finally, mixtures provide improved ground cover
and surface stability, along with reducing weed invasion by fully utilizing plant resources such as
water, nutrients, sunlight and space. Weeds in this context are typically annual or biennial plants
considered to be undesirable, especially growing where they are not wanted.
D.4.3 Compatibility
Reclamation research and its application have been ongoing in the U.S. since the early 1900s.
First with the reseeding of millions of acres following the dust bowl of the 1930s. Then,
improvements of large tracts of arid and semi-arid rangelands between the 1960s and 1980s
following more than a half a century of rangeland exploitation through overgrazing. In 1985 the
U.S. Department of Agriculture Conservation Reserve Program was implemented which resulted
in the conversion of more than 40 million acres of marginal farm land to permanent grasslands
through an extensive seeding program. Finally, there have been tens of thousands of acres of
mined lands reclaimed across the U.S. with the implementation of federal and state rules and
regulations governing mine land reclamation. Over this time period, there have been thousands
of reclamation publications in the form of books, scientific journal articles, symposium
proceedings, and government publications. Many publications have reported on the performance
of individual species and mixtures of species under semi-arid conditions similar to southeastern
Utah (e.g., Plummer et al., 1968; Monsen et al., 2004). All of this work has led to a knowledge
base about species compatibility. Species that are seeded together in mixtures must be
compatible as young, developing plants or certain individuals will succeed and others will fail. The
species proposed for the ET cover at the Mill site are all compatible with each other and seeding
rates will be used to prevent overseeding species that may be aggressive [e.g., pubescent
wheatgrass (Thinopyrum intermedium)] and could potentially dominate the site (Monsen et al.,
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2004). These species are commonly seeded together and many studies have shown excellent
interspecies compatibility (e.g., DePuit et al., 1978; DePuit, 1982; Redente et al., 1984; Sydnor
and Redente, 2000; Newman and Redente, 2001). Finally, to increase compatibility and to reduce
competition among seeded species, sites would be broadcast seeded as opposed to drill seeded.
According to Monsen et al. (2004), drill seeding causes species in a mixture to be placed in
potentially competitive situations, while broadcasted seeds are not placed in as close contact with
each other as with drilling and therefore are less likely to be negatively impacted from competition.
D.4.4 Competition
There are two ways to view competition. In the context of establishing an ET cover on the tailings
cells, the use of seeded species to compete with weeds is a desirable attribute. However,
competition among seeded species with the potential loss of any of these species is undesirable.
Therefore, as stated earlier, the proposed seed mixtures is comprised of species that can coexist
and also fully utilize plant resources to minimize weed species establishment and excluding
seeded species. The establishment of weeds, especially invasives (i.e., non-native species
whose introduction causes economic and environmental harm) is unacceptable because of the
potential loss of seeded perennial species and the subsequent reduction in species diversity,
plant cover, and overall sustainability. Once established, the proposed seed mixture will produce
a grass-forb-shrub community of highly adapted and productive species that will effectively
compete with undesirable species.
D.4.5 Plant Cover
Monitoring of an alternative cover at the Monticello, Utah, Uranium Mill Tailings Disposal Site
showed that the plant cover performed well over a seven year period. Plant cover ranged from
5.5 percent during the first growing season to nearly 46 percent in the seventh growing season
(Waugh et al., 2008). Using results from the 2007 vegetation monitoring report (DOE, 2008) the
following contributions to relative cover were reported showing that 6 of the 16 species seeded
provided 70 percent or more of the cover when cover differences between reclamation zones is
averaged: big sagebrush—5 percent to 10 percent; rubber rabbitbrush—5.3 percent to 17
percent; western wheatgrass—38.6 percent; cicer milkvetch—11 percent; thickspike
wheatgrass—7.2 percent; and globemallow—0.1 to 0.2 percent.
Approximately 40 percent of the species proposed for the Mill site were seeded at Monticello and
of the six best-performing species, three of these species are in the White Mesa mixture (i.e.
Pascopyrum smithii, Elymus lanceolatus, and Ericameria nauseosus ). Highly competitive
species used at Monticello that are not proposed for White Mesa include three introduced species
(i.e. smooth brome, crested wheatgrass, and alfalfa) that were not considered acceptable for the
Mill site. Based on these results and the similarity in environmental conditions between Monticello
and White Mesa, a plant cover estimate of 40 percent was determined to be a reasonable estimate
for a long-term average, while a percent plant cover of 30 percent was assigned as a reduced
performance scenario. The percent vegetative cover at White Mesa is expected to be slightly
less than what would be found at Monticello because the average annual precipitation at White
Mesa is approximately 13 inches compared to 15 inches at Monticello and the average annual
maximum/minimum air temperatures are 64/37°F for White Mesa and 59/33°F for Monticello. The
slightly greater precipitation and lower temperatures at Monticello are due to its slightly higher
elevation of 7,000 feet compared to 5,600 feet at White Mesa.
A map of current vegetation at the Mill site does not exist. The most recent mapping of vegetation
at the Mill site was conducted by Dames and Moore in 1977 (Dames and Moore 1978) as part of
the Environmental Report for the White Mesa Uranium Project. In 1977, the major mapping units
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for the project site were: big sagebrush (232 acres), controlled big sagebrush (567 acres), and
reseeded grassland (369 acres). In June 2012 the area surrounding the Mill site was surveyed
for plant community composition and cover in response to Interrogatory 11/1: Vegetation and
Biointrusion Evaluation and Revegetation Plan of DRC (2012). There are two principal plant
community types in the vicinity of the Mill site. These plant communities are Big Sagebrush
shrubland and Juniper woodland. The Dames and Moore Environmental Report (1978) classified
the Juniper woodland as a Pinyon-Juniper community type, but the primary tree species is Utah
juniper (Juniperus osteosperma) and the presence of pinyon pine (Pinus edulis) is so infrequent
that the community may be more appropriately classified as a Juniper woodland. In addition to
these two principal plant community types, there are a number of disturbed areas that are in
different stages of successional development and reflect past disturbances such as sagebrush
removal (chaining and plowing) and seeding and intense grazing as evidenced by a complete'
lack of any understory species in some areas. The vegetation survey conducted in 2012 provides
information of species that exist on the Mill site and their relative importance in terms of plant
cover. All areas surveyed in 2012 show that big sagebrush (Artemisia tridentata) is the dominant
species and subdominants are either broom snakeweed (Gutierrezia sarothroae) or galleta
(Hilaria jamesii). If the area were re-mapped, most of the site would map as Big Sagebrush
association. It appears that areas that were reseeded to crested wheatgrass and areas where
controlled measures were applied to remove big sagebrush have returned to big sagebrush
following seeding and/or control measures implemented sometime prior to 1978.
The Big Sagebrush shrubland is dominated by big sagebrush (Artemisia tridentata) with
interspersed shrubs of broom snakeweed (Gutierrezia sarothroae) pale desert-thorn (Lycium
pallidum var. pallidum), and rubber rabbitbrush (Ericameria nauseosa). The understory is mostly
grasses with an infrequent occurrence of forbs. The grasses include galleta (Hilaria jamesii),
squirreltail (Elymus elymoides), Indian ricegrass (Achnatherum hymenoides), and cheatgrass
(Bromus tectorum). Forb species include scarlet globemallow (Sphaeralcea coccinea), lesser
rushy milkvetch (Astragalus convallarius), and Russian thistle (Salsola kali).
The Juniper woodland occurs on shallow soils along the canyon rim to the east and west of the
site. It is highly unlikely that this community type would expand its range into the deep, very fine
sandy loam soil that, occurs on the Mill site, which is the primary soil type supporting the Big
Sagebrush shrubland. The vegetation sampling that was conducted in 2012 focused on the Big
Sagebrush community and did not include the Juniper woodland because of the unlikely
probability that this community type would ever establish on the Mill site or tailings cell cover
system. A reconnaissance level survey was conducted in the Juniper community to observe both
plant and animal species that occupy these areas.
D.4.6 2012 Plant Survey
The big sagebrush community type within the White Mesa Control Area to the north, south, and
west of the restricted area of the mill and tailings facilities was surveyed using randomly placed
transects and estimating cover by species using a point intercept sampling method (see Figure
D.1). Along each 100 m long transect, live plant cover by species was determined by lowering a
pin at 1 meter intervals and recording the plant species or ground cover (litter and bareground)
that intersected the point. A total of 10 transects were sampled in each of the areas to the north,
south and west of the mill and tailings cells. Table D.3 presents a summary of the vegetation
survey conducted in the areas surrounding the mill and tailings cells. Tables D.4 through D.33
present plant cover data by transect for each of the three areas sampled in 2012.
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Table D.3. Average Plant and Ground Cover from June 2012 Sampling in Areas
Surrounding the Mill Site
Site and Plant Species % Cover
North of Mill
o Big sagebrush (Artemisia tridentata)19.1
o Broom snakeweed (Gutierrezia sarothroae)3.9
o Rubber rabbitbrush (Ericameria nauseosa).0.2
o Palm desert-thorn (Lycium pallidum var. pallidum)0.1
o Galleta (Hilaria jaamesii)3.6
o Squirreltail (Elymus elymoides)0.1
o Indian ricegrass (Achnatherum hymenoides)0.1
o Cheatgrass (Bromus tectorum)9.5
o Scarlet globemallow (Sphaeralcea coccinea)0.1
o Lesser rushy milkvetch (Astragalus convallarius)0.1
o Russian thistle (Salsola kali)0.6
Total Live Cover 37.4
Total Litter Cover 9.7
Total Bareground 53.1
South of Mill
o Big sagebrush (Artemisia tridentata)18.3
o Broom snakeweed (Gutierrezia sarothroae)3.0
o Galleta (Hilaria jaamesii)8.5
o Squirreltail (Elymus elymoides)0.3
o Indian ricegrass (Achnatherum hymenoides)0.1
o Cheatgrass (Bromus tectorum)6.7
o Scarlet globemallow (Sphaeralcea coccinea)0.1
o Russian thistle (Salsola kali)1.4
Total Live Cover 38.4
Total Litter Cover 13.4
Total Bareground 48.2
West of Mill
o Big sagebrush (Artemisia tridentata)20.5
o Broom snakeweed (Gutierrezia sarothroae)4.4
o Pale desert-thorn (Lycium pallidum var. pallidum)0.1
o Galleta (Hilaria jaamesii)6.6
o Squirreltail (Elymus elymoides)0.1
o Indian ricegrass (Achnatherum hymenoides)0.1
o Cheatgrass (Bromus tectorum)5.3
o Scarlet globemallow (Sphaeralcea coccinea)0.1
o Russian thistle (Salsola kali)0.8
Total Live Cover 37.9
Total Litter Cover 16.1
Total Bareground 46.0
Results from the 2012 sampling of the Big Sagebrush community surrounding the Mill site showed
a mean live plant cover of 37.8 percent after averaging live plant cover estimated in areas north,
south and west of the Mill site (Table D.3). This plant cover included an average of 23.1 percent
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cover for shrubs, 13.7 percent cover for grasses, and 1.0 percent cover for forbs. In addition, the
average percent litter was 13.1 percent and bareground averaged 49.1 percent. These cover
estimates are somewhat greater than the cover values reported in Dames and Moore
Environmental Report (1978). In the Environmental Report, the average live plant cover in the
Big Sagebrush community was 33.3 percent. This cover included an average of 19.4 percent for
shrubs and 13.8 percent for grasses. Litter was estimated at 16.9 percent and bareground was
49.9 percent. Annual precipitation in 1977 was 23.6 cm compared to a long-term average of 29.7
cm (Dames and Moore 1978). In addition, monthly precipitation during the period May-September
1978 totaled 3.8 cm compared to a long-term average of 12.5 cm for the same period.
Considering the fact that the areas sampled are currently grazed, it is highly likely that a cover of
40 percent can be achieved and maintained on the tailings cell cover system for conditions that
exclude grazing by livestock. The formation of desert pavement and potential impact on plant
cover has been raised as an issue for discussion. Desert pavements are armored surfaces
composed of angular or rounded rock fragments, usually 2 to 3 cm thick, set on or in a matrix of
finer material (Cooke and Warren, 1973). These surfaces form on arid soils through deflation of
fine material by wind or water erosion due to a lack of protection by surface vegetation (Cooke
and Warren, 1973). Desert pavements are not common in semi-arid regions and do not occur
where either wind or water erosion are controlled by plant cover (Hendricks, 1991), as would be
the case for the White Mesa cover system. In addition, there is no evidence of desert pavement
formation either on the Mill site or areas surrounding the site (which was confirmed during the
2012 plant survey). Even with the use of a topsoil layer amended with gravel, there is no
supporting evidence to indicate a potential for desert pavement formation or an associated
decrease in plant cover over the long term.
Table D.4. Plant cover data collected in 2012 north of the Mill site on Transect #1
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Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)20
Broom snakeweed (Gutierrezia sarothroae)7
Galleta (Hilaria jaamesii)6
Cheatgrass (Bromus tectorum)13
Russian thistle (Salsoia kali)1
Litter 8
Bareground 45
Total Live Cover 47
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Table D.5. Plant cover data collected in 2012 north of the Mill Site on Transect #2
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)28
Broom snakeweed (Gutierrezia sarothroae)9
Rubber rabbitbrush (Ericameria nauseosa).1
Galleta (Hilaria jaamesii)2
Cheatgrass (Bromus tectorum)8
Scarlet globemallow (Sphaeralcea coccinea)1
Russian thistle (Salsola kali)1
Litter 11
Bareground 39
Total Live Cover 50
Table D.6. Plant cover data collected in 2012 north of the Mill site on Transect #3
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)13
Rubber rabbitbrush (Ericameria nauseosa).1
Galleta (Hilaria jaamesii)6
Cheatgrass (Bromus tectorum)9
Litter 7
Bareground 63
Total Live Cover 30
Table D.7. Plant cover data collected in 2012 north of the Mill site on Transect #4
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)27
Galleta (Hilana jaamesii)3
Cheatgrass (Bromus tectorum)13
Russian thistle (Salsola kali)2
Litter 8
Bareground 47
Total Live Cover 45
Table D.8. Plant cover data collected in 2012 north of the Mill site on Transect #5
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)31
Broom snakeweed (Gutierrezia sarothroae)8
Indian ricegrass (Achnatherum hymenoides)1
Lesser rushy milkvetch (Astragalus convallarius)1
Russian thistle (Salsola kali)1
Litter 9
Bareground 49
Total Live Cover 42
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Table D.9. Plant cover data collected in 2012 north of the Mill site on Transect #6
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)6
Broom snakeweed (Gutierrezia sarothroae)6
Squirreltail (Elymus elymoides)1
Cheatgrass (Bromus tectorum)9
Russian thistle (Salsola kali)1
Litter 6
Bareground 71
Total Live Cover 23
Table D.10. Plant cover data collected in 2012 north of the Mill site on Transect #7
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)8
Broom snakeweed (Gutierrezia sarothroae)6
Galleta (Hilaria jaamesii)4
Cheatgrass (Bromus tectorum)7
Litter 12
Bareground 63
Total Live Cover 25
Table D.11. Plant cover data collected in 2012 north of the Mill site on Transect #8
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)29
Galleta (Hilaria jaamesii)11
Cheatgrass (Bromus tectorum)14
Litter 14
Bareground 32
Total Live Cover 54
Table D.12. Plant cover data collected in 2012 north of the Mill site on Transect #9
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)4
Broom snakeweed (Gutierrezia sarothroae)2
Indian ricegrass (Achnatherum hymenoides)1
Galleta (Hilaria jaamesii)4
Cheatgrass (Bromus tectorum)6
Litter 9
Bareground 74
Total Live Cover 17
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Table D.13. Plant cover data collected in 2012 north of the Mill site on Transect #10
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)24
Palm desert-thorn (Lycium pallidum var. pallidum)1
Cheatgrass (Bromus tectorum)16
Litter 13
Bareground 46
Total Live Cover 41
Table D.14. Plant cover data collected in 2012 south of the Mill site on Transect #1
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)12
Broom snakeweed (Gutierrezia sarothroae)4
Galleta (Hilaria jaamesii)7
Cheatgrass (Bromus tectorum)12
Russian thistle (Salsola kali)3
Litter 14
Bareground 48
Total Live Cover 38
Table D.15. Plant cover data collected in 2012 south of the Mill site on Transect #2
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)15
Broom snakeweed (Gutierrezia sarothroae)
Galleta (Hilaria jaamesii)17
Cheatgrass (Bromus tectorum)7
Russian thistle (Salsola kali)2
Litter 19
Bareground 40
Total Live Cover 41
Table D.16. Plant cover data collected in 2012 south of the Mill site on Transect #3
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)14
Rubber rabbitbrush (Ericameria nauseosa).7
Galleta (Hilaria jaamesii)8
Scarlet globemallow (Sphaeralcea coccinea)1
Cheatgrass (Bromus tectorum)6
Russian thistle (Salsola kali)2
Litter 16
Bareground 46
Total Live Cover 38
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Table D.17. Plant cover data collected in 2012 south of the Mill site on Transect #4
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)28
Galleta (Hilaria jaamesii)4
Indian ricegrass (Achnatherum hymenoides)1
Cheatgrass (Bromus tectorum)1
Russian thistle (Salsola kali)1
Litter 17
Bareground 48
Total Live Cover 35
Table D.18. Plant cover data collected in 2012 south of the Mill site on Transect #5
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)6
Galleta (Hilaria jaamesii)6
Squirreltail (Elymus elymoides)3
Cheatgrass (Bromus tectorum)11
Litter 14
Bareground 60
Total Live Cover 26
Table D.19. Plant cover data collected in 2012 south of the Mill site on Transect #6
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)26
Broom snakeweed (Gutierrezia sarothroae)8
Galleta (Hilaria jaamesii)8
Cheatgrass (Bromus tectorum)5
Litter 8
Bareground 45
Total Live Cover 47
Table D.20. Plant cover data collected in 2012 south of the Mill site on Transect #7
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)23
Cheatgrass (Bromus tectorum)6
Russian thistle (Salsola kali)3
Litter 12
Bareground 56
Total Live Cover 32
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Table D.21. Plant cover data collected in 2012 south of the Mill site on Transect #8
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)13
Galleta (Hilaria jaamesii)13
Cheatgrass (Bromus tectorum)11
Russian thistle (Salsola kali)3
Litter 16
Bareground 44
Total Live Cover 40
Table D.22. Plant cover data collected in 2012 south of the Mill site on Transect #9
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)18
Broom snakeweed (Gutierrezia sarothroae)8
Galleta (Hilaria jaamesii)9
Cheatgrass (Bromus tectorum)2
Litter 14
Bareground 49
Total Live Cover 37
Table D.23. Plant cover data collected in 2012 south of the Mill site on Transect #10
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)29
Broom snakeweed (Gutierrezia sarothroae)2
Galleta (Hilaria jaamesii)13
Cheatgrass (Bromus tectorum)6
Litter 4
Bareground 46
Total Live Cover 50
Table D.24. Plant cover data collected in 2012 west of the Mill site on Transect #1
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)26
Broom snakeweed (Gutierrezia sarothroae)6
Galleta (Hilaria jaamesii)4
Cheatgrass (Bromus tectorum)7
Litter 13
Bareground 44
Total Live Cover 43
I
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Table D.25. Plant cover data collected in 2012 west of the Mill site on Transect #2
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)26
Galleta (Hilaria jaamesii)9
Cheatgrass (Bromus tectorum)1
Litter 18
Bareground 46
Total Live Cover 36
Table D.26. Plant cover data collected in 2012 west of the Mill site on Transect #3
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)9
Cheatgrass (Bromus tectorum)11
Litter 23
Bareground 57
Total Live Cover 20
Table D.27 Plant cover data collected in 2012 west of the Mill site on Transect #4
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)33
Broom snakeweed (Gutierrezia sarothroae)13
Galleta (Hilaria jaamesii)7
Scarlet globemallow (Sphaeralcea coccinea)1
Cheatgrass (Bromus tectorum)4
Russian thistle (Salsola kali)4
Litter 9
Bareground 39
Total Live Cover 62
Table D.28. Plant cover data collected in 2012 west of the Mill site on Transect #5
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)29
Galleta (Hilaria jaamesii)6
Squirreltail (Elymus elymoides)1
Cheatgrass (Bromus tectorum)5
Russian thistle (Salsola kali)2
Litter 14
Bareground 43
Total Live Cover 43
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Table D.29. Plant cover data collected in 2012 west of the Mill site on Transect #6
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)12
Broom snakeweed (Gutierrezia sarothroae)9
Indian ricegrass (Achnatherum hymenoides)1
Cheatgrass (Bromus tectorum)7
Russian thistle (Salsola kali)2
Litter 17
Ba reground 52
Total Live Cover 31
Table D.30. Plant cover data collected in 2012 west of the Mill site on Transect #7
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)14
Broom snakeweed (Gutierrezia sarothroae)4
Galleta (Hilaria jaamesii)14
Palm desert-thorn (Lycium pallidum var. pallidum)1
Cheatgrass (Bromus tectorum)6
Litter 14
Bareground 37
Total Live Cover 39
Table D.31. Plant cover data collected in 2012 west of the Mill site on Transect #8
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)22
Broom snakeweed (Gutierrezia sarothroae)7
Cheatgrass (Bromus tectorum)6
Litter 20
Bareground 45
Total Live Cover 35
Table D.32. Plant cover data collected in 2012 west of the Mill site on Transect #9
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)14
Broom snakeweed (Gutierrezia sarothroae)2
Galleta (Hilaria jaamesii)11
Cheatgrass (Bromus tectorum)3
Litter 19
Bareground 51
Total Live Cover 30
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Table D.33. Plant cover data collected in 2012 west of the Mill site on Transect #10
Species and Other Cover Categories Percent Cover
Big sagebrush (Artemisia tridentata)19
Broom snakeweed (Gutierrezia sarothroae)3
Galleta (Hilaria jaamesii)15
Cheatgrass (Bromus tectorum)3
Litter 14
Bareground 46
Total Live Cover 40
D.4.7 Leaf Area Index
Monthly leaf area index (LAI) values were estimated for the proposed ET cover at the Mill site.
Three primary publications were used to estimate monthly LAI for the ET cover, including:
Groeneveld (1997), Scurlock et al. (2001), and Fang et al. (2008). Table D.34 presents a
compilation of LAI values based on North American data sets that were focused on semi-arid
herbaceous plant communities. Scurlock et al. (2001) presented mean LAI values for 15
biomes/land cover classes that included desert, grassland, and shrubland. Leaf Area Index data
was a compilation of data from the literature and represented various data collection methods.
Mean LAI values reported were 1.3 (S.D. 0.85) for desert, 2.6 (S.D. 3.0) for grassland, and 2.1
(S.D. 1.6) for shrubland. Fang et al. (2008) presented LAI data for various biomes using MODIS
(Moderate Resolution Imaging Spectroradiometer). These authors reported monthly LAIs for
grasslands and shrublands with peak values for shrubland reported at 1.5 and 1.0 for grasslands.
Finally, Groeneveld (1997) conducted field measurements of LAI in Owens Valley, CA in 1983.
He reported LAI values for individual grass and shrub species and reported the following values
in November for big sagebrush and in July for the remaining species: big sagebrush LAI’s ranged
from 0.65 to 1.8; fourwing saltbush (Atriplex canescens) LAI’s ranged from 1.2 to 4.7; shadscale
saltbush {Atriplex confertifolia) LAI’s ranged from 1.6 to 2.6; greasewood (Sarcobatus
vermiculatus) LAI’s ranged from 1.0 to 3.3; alkali sacaton (Sporobolus airoides) LAI's ranged from
0.38 to 4.0; and saltgrass (Distichlis spicata) LAI’s ranged from 0.67 to 3.9. All of the data
presented in these three papers was used to estimate an average monthly LAI for the revegetated
cover system assuming a well-established plant community. A maximum LAI of 2.6 was selected
for peak biomass in the month of September which matches the mean grassland LAI reported by
Scurlock al. (2001) and well below values reported by Groeneveld (1997). Leaf Area Index values
for the remaining months was then extrapolated from the peak month using monthly values
presented by Fang et al. (2008). It is important to note that the proposed species for the ET cover
include both cool- and warm-season species. This combination of species will maximize the
length of the growing season and transpiration from early spring to late fall. Cool-season species
are more productive and use more water during the cooler times of the growing season, while
warm-season species are more productive and use more water during the warmest period of the
year.
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Table D.34. Leaf Area Index for the ET Cover at Mill Site
Month
Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec
0 0 0.3 0.7 0.6 0.6 1.8 2.4 2.6 0.8 0.1 0
0.4.8 Project Root Biomass for Infiltration Modeling
We have chosen to use root biomass data from a seeded site in Cheyenne, Wyoming that was
seeded in the 1950s with root biomass data collected about 35 years after seeding (Redente et
al. 1989). Data were collected as g/m2 and will not be converted (Table D.35). Infiltration model
uses a normalized root density function, so root measurement units are irrelevant. The climatic
conditions between Blanding, Utah and Cheyenne, Wyoming are similar with Blanding receiving
34 cm of precipitation and Cheyenne receiving 36 cm. Potential evapotranspiration (PET) at
Blanding is 122 cm and 115 cm in Cheyenne. Finally, the precipitation to PET ratio is 0.28 for
Blanding and 0.31 for Cheyenne. Table D.35 presents both anticipated root biomass and reduced
biomass that is calculated based on a 75 percent reduction in biomass that has been reported in
long-term drought studies (Weaver and Albertson 1936).
Table D.35. Projected root biomass data for anticipated and reduced performance for
use in infiltration modelling
Depth (cm)Root Biomass (g/m2)
Anticipated Performance
Root Biomass (g/m2)
Reduced Performance*
0-5 160 64
5-10 140 49
10-20 76 23
20-60 125 32
60-100*52 2
teased on an increasing percent reduction from 60% to 80% with depth, as extended drought or reduced
precipitation with potential climate change would result in less deep infiltration and therefore greater
negative effect on deeper roots compared to shallower roots. ^Maximum rooting depth under the reduced
performance scenario would be 68 cm.
D.5 BIOINTRUSION
D.5.1 Plant Intrusion
Table D.36 presents percent of root mass by depth for grass and shrub species that exist or may
occur on the Mill site during the performance period. It is extremely important to recognize that
the rooting depths for the shrubs do not reflect the rooting depths that are expected in the cover
system but represent rooting depths reported in the literature with an effort to identify the
maximum rooting depths reported. Detailed rooting depth studies are rare and the majority of
studies do not report root mass by depth. The shrub values reported in Table D.36 represent
extrapolations from the literature using the maximum rooting depths reported and following the
general findings in the literature that the majority of root growth typically is in the upper 30 cm for
grasses and the upper 60 cm for shrubs growing in semiarid regions. The final note of importance
that relates to the cover system is that root growth is strongly influenced by the soil which the root
is growing and therefore root data from the literature must be carefully scrutinized as it is applied
to specific site conditions (Munshower 1995). The shrub root data shown in Table D.36 should
therefore not be interpreted to represent the expected rooting depths in the cover system since
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rooting depth will be controlled by the highly compacted radon attenuation layer within the cover
system.
Soil texture appears to be the most important soil property determining the growth-limiting bulk
density of a soil because of the effect of texture on soil pore size and mechanical resistance. A
soil with a large amount of fine particles (silt and clay) will have smaller pore diameters and a
higher penetration resistance at a lower bulk density than a soil with a large amount of coarse
particles (sand size). Zisa et al. (1980) reported a silt loam soil had 19 percent macropore space
and a measured penetration resistance of 2.5 bars at a bulk density of 1.4 g/cm3. A coarser sandy
loam soil had 28.9 percent macropore space and a penetration resistance of 1.2 bars at the same
bulk density.
Roots grow in soil through large soil pores and by moving soil particles aside when the roots
penetrate pores that are smaller than the root tips. When a soil is compacted to a growth-limiting
level, most soil pore diameters are substantially smaller than the diameters of growing roots. In
this situation, root growth is essentially halted because the roots cannot exert enough pressure
to overcome the mechanical resistance and move soil particles. Other pertinent studies that relate
root growth and bulk density include articles by Siegel Issem et al. 2005, Mimore and Woollard
1969, and Heilman 1981.
Most, if not all, of the root growth studies cited above that relate root growth to soil compaction
and soil bulk density are field studies in native soils that have been in place for centuries or longer.
These soils have therefore gone through countless wetting and drying cycles and freeze-thaw
cycles and still maintain certain bulk densities that impede root growth.
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Table D.36. Percent of root mass by depth for grasses and shrub species that exist or
may occur at the Mill s te during t he performance period of 200 years.
Species 0-30 cm 30-60 cm 60-90 cm 90-120 cm 120-150 cm
Western wheatgrass3 65 14 12 9 0
Blue grama3 94 4 1 1 0
Species 0-20
cm
20-40
cm
40-60
cm
60-80
cm
80-
100
cm
100-
200
cm
200-
300
cm
300-
400
cm
400-
500
cm
500-
600
cm
Big
sagebrush3 35 19 17 10 7 8 4 __f --
Fourwing
saltbush6 18 22 15 14 10 8 6 4 2 1
Shadscalec 15 20 18 14 12 8 6 4 2 1
Blackbrushd 35 50 15 -- ------
Mormon
tea6 20 35 17 13 10 4 1 -- -
aTabler 1964; bGibbens and Lenz 2001; cKearney et al 1960; dWest 1983; Manning et al. 1990;
e Gibbens and Lenz 2001;fbeyond maximum rooting depth reported in the literature
It is important to note that shrub rooting depths reported in the literature do not reflect expected
rooting depths in the cover system because of the presence of a highly compacted radon
attenuation layer.
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D.5.2 Animal Intrusion
The Dames and Moore Environmental Report (1978) included animal surveys for sites
surrounding the Mill site. The Environmental Report recorded the presence or possible presence
of a number of burrowing species in the Big Sagebrush community, including burrowing owl (Bubo
virginianus), pocket mouse (Perognathus sp.), kangaroo mouse (Microdipodops sp.), vole
(Microtus sp.), desert cottontail (Sylvilagus audubonii), coyote (Canis latrans), red fox (Vulpes
vulpes), striped skunk (Mephitis mephitis), badger (Taxidea taxus), longtail weasel (Mustela
frenata), and Gunnison prairie dog (Cynomys gunnisoni). Additional burrowing animals reported
to occur in the Juniper community included pinyon mouse (Peromyscus truei) and deer mouse
(Peromyscus maniculatus). The northern pocket gopher (Thomomys talpoides) was not observed
in either community type and no mention of the species is made in the 1978 report.
D.5.3 2012 Burrowing Animal Survey
In June 2012 the area surrounding the Mill site was surveyed for burrowing animals in response
to Interrogatory 11/1. A total of 100 km of transects were walked in Big Sagebrush and Juniper
communities surrounding the Mill Site to determine either the presence of burrowing animals or
future colonization based on existing habitat characteristics (see Figure D.2).
Transects were arranged in a systematic manner (at each location in Figure D.2) with a 50 m
spacing between transects and transect lengths running between 100 and 400 m, depending
upon physiographic features on the landscape. The primary focus of the survey was on three
species that would potentially represent the deepest potential for burrows on the tailings cells
during the performance period. These species included the badger, Gunnison prairie dog, and
northern pocket gopher. Observations were made along each transect for animal sightings,
animal presence in the form of tracks, scat or active burrows, burrow densities, and habitat
characteristics.
During the animal survey one badger sighting was made and multiple active prairie dog colonies
were observed to the north of the mill complex. There appears to be suitable habitat for the
northern pocket gopher in the sagebrush communities surrounding the Mill site, but there is no
indication that a population of northern pocket gophers occurs in the vicinity of the Mill site. There
were no evidence of pocket gophers during surveys associated with the Environmental Report
(Dames and Moore, 1978) and no evidence of pocket gophers 34 years later.
An attempt was made to estimate burrow densities for badgers but it was not always possible to
confirm a badger burrow. No badger feeding areas (i.e. dug-out prey burrows) were observed
along transects that were traversed. The reported burrow density for badgers may or may not be
low, depending upon how active badgers are in the area. One of the seminal studies on badger
ecology was conducted by Messick and Flornocker (1981) in southwestern Idaho. The authors
reported badger densities of 159/50 km2. This converts to approximately three per 100 hectares.
Our survey reported the highest burrow densities at one per 80 to 100 hectares. If each burrow
represented more than one individual badger, the densities potentially would be greater.
Regardless, the reported burrow densities from the 2012 survey are believed to be a realistic
estimate of badger presence at the Mill site.
Within the prairie dog colonies that were located in the area of the Mill site, the greatest burrow
density was estimated at 148 burrows per hectare. Over the entire Mill site the prairie dog burrow
density ranges from 0 to 148 burrows per hectare. Lupis et al. (2007) reported densities of active
burrows in southeastern Utah in the range of 41 to 131/hectare or an average of 75 active burrows
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per hectare. The burrow densities reported from out 2012 survey are well within the range of a
much larger study conducted by Lupis et al. (2007).
Lupis et al. (2007) provide a list of species in grasslands and shrublands in Utah considered
primary and secondary habitat for the Gunnison’s prairie dog as follows:
“Perennial and annual Grasslands; or herbaceous dry meadows, including mostly forbs
and grasses occurring at 640-2,740 m (2,200-9,000 ft) elevation. Principal perennial grass
species include: bluebunch wheatgrass, sandburg bluegrass (Poa secunda), crested
wheatgrass (Agropyron cristatum), basin wildrye (Elymus cinereus), galleta (Pleuraphis
jamesii), needlegrass (Achnatherum hymenoides), sand dropseed (Sporobolus
cryptandrus), blue grama (Bouteloua gracilis), Thurbers needlegrass (Achnatherum
thurberianum), western wheatgrass (Pascopyum smithii), squirreltail (Sitanion hystrix),
timothy (Phleum spp.), poa (Poa spp.), spike (Trisetum spicatum), Indian ricegrass
(Oryzopsis hymenoides), and some sedges (Cyperaceae spp.). Principle annual grass
species is cheatgrass (Bromus tectorum). Principal forb species include: yarrow (Achillea
millefolium), dandelion (Taraxacum officinale), Richardson's geranium (Geranium
richardsonii), penstemon (Penstemon spp.), mulesears (Wyethia amplexicaulis), golden
aster (Chrysopsis villosa), arrowleaf balsamroot (Balsamorhiza sagittata), hawkbit
(Agoseris pumila), larkspur (Delphinium spp.), and scarlet gilia (Gilia pulchella). Primary
associated shrub species include: sagebrush (Artemesia spp.), shadscale (Atriplex
confertifolia), greasewood (Sarcobatus spp.), creosote (Larrea tridentate), rabbit brush
(Crysothamnus spp.), cinquefoil (Potentilla simplex), snowberry (Symphoricarpos albus),
and elderberry (Sambucus spp.). Primary associated tree species is juniper (Juniperus
spp.).”
“Shrublands at 670-3,150 m (2,200-10,300 ft) elevation principally dominated by
greasewood (Sarcobatus vermiculatus), shadscale, graymolly (Kochia vestita), mat-
atriplex (Atriplex corrugata), Castle Valley clover (Atriplex cuneata), winterfat, budsage
(Artemisia spinescens), four-wing saltbush (Atriplex canescens), halogeton (Halogeton
glomeratus), Mormon tea (Ephedra spp.), horsebrush (Tetradymia canescens),
snakeweed and rabbitbrush; or low elevation perennial grassland co-dominate with
shrubland. Principal grassland species include: galleta, Indian ricegrass, three-awn grass
(Aristida glauca) and sand dropseed. Primary associated forb species include: desert
trumpet (Eriogonum inflatum). Primary associated shrub species include: sagebrush, and
black brush (Coleogyne ramosissima); other associated species include seepweed
(Suaeda torreyana).”
Based on the report by Lupis et al. (2007) we agree that the habitat that will be created at the Mill
site following revegetation will include species consistent with prairie dog occupation.
Table D.37 presents an updated assessment of maximum burrow depths for animal species that
may occur on the Mill site. Based on a review of literature for burrow depths, the species that
have the potential for the deepest burrows are badger (228 cm), northern pocket gopher (150
cm), and Gunnison prairie dog (427 cm). As discussed above, both the badger and Gunnison
prairie dog were observed during the 2012 animal survey, while there is no evidence that the
northern pocket gopher occurs in the vicinity of the Mill site from both the 1978 and 2012 surveys.
The proposed cover system is a monolithic evapotranspiration (ET) cover that consists of the
following layers from top to bottom: 15 cm of a topsoil-gravel erosion protection layer over 107
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cm of a water storage, biointrusion and radon attenuation layer over 75 cm of a highly compacted
radon attenuation layer over 75 cm of a grading and radon attenuation layer. The proposed cover
system does not contain a biobarrier (e.g. cobble layer) to minimize potential intrusion by
burrowing animals. The proposed cover system is designed to minimize burrowing animal
intrusion through the use of thick layers of soil cover in combination with a highly compacted layer
placed at a depth that is below the expected burrowing depths among species that may inhabit
the site. The thickness of the cover (total of 272 cm), the use of a highly compacted radon
attenuation layer located at a depth between 122 and 197 cm, and a final 75 cm layer below the
compacted zone will all contribute to minimizing any biointrusion through the cover. Considering
the animal species that may inhabit the tailings cells and the thickness and physical nature of the
cover, it is not anticipated that burrowing will extend below 122 cm or into the very top portion of
the highly compacted zone. Burrowing into the highly compacted radon attenuation layer that
begins at a depth of 122 cm will be restricted because of the high density of this material (95
percent Standard Proctor).
Table D.37. Range of maximum burrow depths for wildlife that inhabit or may inhabit the
Mill site during the required performance period of at least 200 years
Species Maximum Depth (cm)Source
Pocket mouse 52 to 62
35-153
Kenagy 1973; Scheriber 1978
Pinyon mouse 34 Reynolds and Wakkinen 1987
Deer mouse 13-50 Reynolds and Laundre 1988; Kritzman 1974
Kangaroo rat 24-61
20-69
Reynolds and Wakkinen 1987; Anderson
and Allred 1964
Vole 15-55 Reynolds and Wakkinen 1987
Desert cottontail Abandoned burrows and
surface nest
Wilson and Reeder 2005;
Chapman and Willner 1978
Long-tailed weasel Abandoned burrows and
surface nest
Feldhammer et al. 2003
Striped Skunk 90 Jackson 1961
Badger 150 to 228 Lindsey 1976; Anderson and Johns 1977
Gunnison prairie dog 30 to 427
69 to 185
68 to 82
Verdolin et al. 2008; Sheets et al 1971;
Whitehead 1927
Red fox 100 to 130 Feldhammer et al. 2003; Saunders 1988
Coyote Most common behavior is to
use burrows of other animals
like the badger
http://carnivora.eom/topic/932884/1/
Burrowing owl Abandoned burrows Haug et al. 1993
Northern Pocket 10 to 30 Winsor and Whicker 1980; Gettinger 1975;
Gopher 150 Felthauser and Mclnroy 1983
D.6 SOIL REQUIREMENTS FOR SUSTAINABLE PLANT GROWTH
There are two key components to establishing an ET cover with a sustainable plant community.
The first is to select long-lived species that are adapted to the environmental conditions of the
site. The second is to provide a cover soil that will function as an effective plant growth medium
over the long term by supplying plants with adequate amounts of water, nutrients and rooting
volume.
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There are a number of soil characteristics that are particularly important to achieve long-term
sustainability in semi-arid environments and include the following: pH, electrical conductivity
(EC), sodium levels, percent organic matter, texture, bulk density, cation exchange capacity,
macronutrient concentrations, available water holding capacity, and soil microorganisms. Table
D.38 presents levels for most of these soil properties that are considered necessary for long-term
sustained plant growth. In addition, the table includes soil property levels from soil samples of
potential cover soil collected from stock piles at the Mill site in May 2009.
The soil properties of the potential cover soil that are acceptable for sustaining long-term plant
growth include: pH, EC, sodium adsorption ratio (SAR), percent clay content, and extractable
phosphorus. Those soil properties that appear to be deficient and would need improvement
include: percent organic matter, total nitrogen, and extractable potassium.
Cation exchange capacity was not measured in the potential cover soil, but it is believed that the
cover soil will have an acceptable level for sustained plant growth based on the percent clay
content and a recommendation that an organic matter amendment be added to the soil during the
reclamation process. Bulk density of the emplaced cover material will be specified in the cover
design and will be controlled during the construction process to be within the sustainability range
shown in Table D.38.
Table D-38. Soil Properties and Their Range of Values Important for Sustainable Plant
Growth, Along with Analytical Results of Soil Available for ET Cover Construction at the
Mill Site
Soil Property Level for
Sustainability Reference Levels for
On-Site Soil
pH (units)6.6 to 8.4 Munshower (1994) 7.7 to 8.1
EC (mmhos/cm)<4.0 Munshower(1994)<1.5
Sodium adsorption ratio <12 Munshower (1994) <0.5
Organic matter (%)1.0 to 3.0 Smith et al. (1987)0 to 0.4
Texture (%)> 50% silt and clay Brady (1974)> 50% silt and clay
Bulk density (g/cm3)1.2 to 1.8 Brady (1974)1.59 to1.99t
Water holding capacity
(cm H20/cm soil)
0.08 to 0.16 Brady (1974)0.084-0.14t
Cation exchange capacity
(meq/100g)
5 to 30 Munshower (1994)Not measured
Total nitrogen (%)0.05 to 0.5 Harding (1954)0.02 to 0.05
Extractable phosphorus
(mg/kg)
6 to 11 Ludwick and Rogers
(1976)
10 to 57
Extractable potassium
(mg/kg)
60 to 120 Ludwick and Rogers
(1976)
11 to 36
^Calculated values
In order for the potential cover soil to function as a normal soil and provide long-term sustainable
support for the vegetation component of the ET cover, it will be amended to improve organic
matter content, nitrogen and potassium levels. An organic matter amendment will also improve
available water holding capacity and cation exchange capacity. The proposed organic
amendment is composted biosolids. Composted biosolids have been successfully used in mined
land reclamation over the past 40 years. This amendment would also provide a source of soil
microorganisms that will function to cycle nutrients over time and ensure sustainable plant growth.
Composted biosolids would be applied at a rate of 10 tons/acre and incorporated into the upper
six inches of the water storage layer of the cover system. Composted biosolids are also a source
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of nitrogen, phosphorous and potassium and will serve to improve organic matter content and soil
fertility. The following discussion provides the rationale for selecting composted biosolids as the
amendment of choice for the cover soil.
Type of Amendment, Application Rates, and Costs - There are three possible soil amendments
that would be a source of organic matter and nutrients for sustained plant growth. These
amendments include composted biosolids, a combination of manure and hay, or a commercial
organic fertilizer such as Biosol®. Biosol® is a highly effective organic amendment but would be
cost prohibitive if the objective is to achieve 1 percent organic matter content in the soil. It would
require the addition of at least 10 tons/acre to meet this organic matter target and the cost would
be approximately $12,300/acre, which includes a product cost of $12,000/acre, transportation
cost of $100/acre, and an application cost of $200/acre. Composted biosolids would be equally
effective as Biosol®, but much less expensive. Composting of biosolids is a proven method for
pathogen reduction and results in a product that is easy to handle, store, and use. The end product
is usually a Class A, humus-like material without detectable levels of pathogens that can be
applied as a soil amendment. Composted biosolids provide large quantities of organic matter and
nutrients (such as nitrogen and phosphorus) to the soil, improves soil texture, and elevates soil
exchange capacity. If composted biosolids were obtained from Farmington, NM (which appears
at this time to be the closest source), the cost for a 10 ton/acre application rate would be
$1,530/acre, which includes $260/acre for product cost, $1,070/acre for transportation, and
$200/acre for application. The use of manure and hay would be the least effective amendment
because both products have the potential of adding unwanted weed seed to the cover vegetation
and manure is relatively high in nitrogen and if not properly off set with hay, there is a potential of
having excessive nitrogen introduced into the cover system that would also lead to a proliferation
of unwanted weeds.
Method of Application - Composted biosolids are produced by mixing biosolids (treated sewage
sludge) and wood waste material. Composted biosolids are easy to apply and would be broadcast
over the soil surface using a commercial manure spreader and the amendment would then be
incorporated with a chisel plow or disc plow.
Limitations of Soil Amendments - Composted biosolids have few limitations as a soil amendment.
Composted biosolids are often low in readily available nitrogen, but have high organic nitrogen
levels that can be slowly released for plant use over time. The ERA has established rules for the
land application of biosolids that address concerns about possible pathogen transmittal, nitrate
pollution, and trace metal contamination (ERA, 1993 and 1995). In order to be land applied, a
particular biosolid must have undergone a pathogen reduction process, must contain less than a
specified amount of bacterial pathogens, and must meet limits for heavy metal concentration.
Considerable research has been conducted over the past 40 years on the interactions between
biosolids, soil properties, plant growth and environmental quality. Amendment of disturbed soils
with composted biosolids has been shown to increase soil organic matter, cation exchange
capacity, soil nutrient levels, microbial biomass and activity, water holding capacity, and
aggregate stability, and also to reduce soil bulk density and metal availability for plant uptake.
The potential for successful reclamation with composted biosolids is tremendous and most of the
highly beneficial properties of composted biosolids as a soil amendment come from its high
organic matter content (Sopper, 1993). The use of composted biosolids is extremely important
where topsoil is inadequate in amount or quality (Sopper, 1993; Munshower, 1994).
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The application of composted biosolids on disturbed land generally has had a very beneficial
effect on the establishment and growth of grasses and forbs (Sopper, 1993; Haering et al., 2000).
It facilitates rapid establishment and vigorous growth of herbaceous plants. Sites treated with
composted biosolids generally have a greater percent cover, greater aboveground production,
and better developed root systems compared to non-amended sites or sites treated with just
inorganic fertilizers (Sopper, 1993; Haering et al., 2000). The use of composted biosolids also
aids in the establishment and growth of shrubs. Annual height and diameter growth is improved
with composted biosolids and overall woody plant survival is increased if competition from
herbaceous plants is not an issue (Sopper, 1993; Haering et al., 2000).
Field studies at the Climax Molybdenum Mine near Leadville, Colorado conducted by Carlson et
al. (2006) examined the effect of composted biosolids on tailings reclamation over a seven-year
period. The findings of this study were that composted biosolids are an effective means of
establishing soil microbe and vegetation communities on tailings. The authors concluded that:
over seven years and in extreme growing conditions, biosolid amendments reduced soil toxicity
[by immobilizing heavy metals], neutralized acidity, and introduced constituents [e.g. nutrients and
soil microbes] necessary to sustain vegetation communities on tailings capped with overburden
material.
In a very long-term study conducted by Paschke et al. (2005) the effect of biosolids amendments
were assessed on disturbances in a sagebrush community in northwestern Colorado. The
authors reported that 24 years after biosolids were applied on fertile and infertile soil material that:
“... biosolids amendments have long-lasting effects on soil fertility and plant community
composition...”
The greatest limitation for the use of composted biosolids at the Mill site will be availability of the
product. Availability varies over time depending upon supply and demand. Since the Mill site is
in a remote location, sources of composted biosolids in the quantities needed for tailing cell
reclamation are limited and advanced planning will be required to secure the quantities needed
when the cover system is being constructed.
D.7 WEED MANAGEMENT
Weed management would be conducted on the Mill site by identifying the presence of any noxious
weeds during annual vegetation surveys and developing a weed control plan that is specific to
the species that are present (Table D.39). Noxious weed control is species dependent and both
method and timing will vary from species to species.
Each survey will identify noxious weed populations and locate these populations on a map using
a set of symbols to identify species, size of the infestation, and density of the population. The
effectiveness of control methods will also be documented in each annual survey. In addition,
immediately adjacent off-site properties will be visually surveyed to a distance of 100 feet.
Inspections will be conducted by personnel familiar with the identification of noxious weeds in the
area and based on Utah’s Noxious Weed List.
The selected control methods will be based on the type, size, and location of the mapped noxious
weeds. The treated area(s) will be monitored and re-inspected annually for new weed
introductions and to evaluate the success of the control methods. Prevention is the highest priority
weed management practice on non-infested lands; therefore protecting weed-free plant
communities is the most economical and efficient land management practice. Prevention is best
accomplished by ensuring that new weed species seed or vegetative reproductive plant parts of
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weeds are not introduced into new areas, and by early detection of any new weed species before
they begin to spread.
Control methods may include chemical or mechanical approaches. The optimum method or
methods for weed management will vary depending on a number of site-specific variables such
as associated vegetation, weed type, stage of growth, and severity of the weed infestation.
Table D.39. Noxious Weed Species
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Scientific Name Common Name
Utah State—Listed Noxious Weeds
Acroptilon repens Russian knapweed
Cardaria spp.Whitetop (all species)
Carduus nutans Musk thistle
Centaurea diffusa Diffuse knapweed
Centaurea solstitialis Yellow star thistle
Centaurea stoebe ssp. micranthos Spotted knapweed
Centaurea virgate ssp. Squarrosa Squarrose knapweed
Cirsium arvense Canada thistle
Convolvulus spp.Bindweed (all species)
Cynodon dactylon Bermuda grass
Elymus repens Quackgrass
Euphorbia esula Leafy spurge
Isatis tinctoria Dyer’s woad
Lepidium latifolium Broadleaf pepperweed
Lythrum salicaria Purple loosestrife
Onopordum acanthium Scotch thistle
Sorghum almum Perennial sorghum (all species)
Taeniatherum caput-medusae Medusahead
San Juan County—Listed Noxious Weeds
Aegilops cylindrical Jointed goatgrass
Alhagi maurorum Camelthorn
Asclepias subverticillata Western whorled milkweed
Solanum elaeegnifolium Silverleaf nightshade
Solanum rostratum Buffalobur
Chemical Control
Chemical control consists mostly of selective and non-selective herbicides. Considerations for
chemical controls include: herbicide selection, timing of application, target weed, desirable plant
species being grown or that will be planted, number of applications per year and number of years
a particular species will need to be treated for desired control. Also important are the health and
safety factors involved, and the need to consider undesirable impacts. The use of herbicides will
be in compliance with all Federal and State laws on proper use, storage, and disposal. The
chemical application will be done by a licensed contractor in accordance with all applicable laws
and regulations and all label instructions will be strictly followed. Applications of herbicides would
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not be permitted when the instructions on the herbicide label indicate conditions that are not
optimal.
Mechanical Control
Mechanical control is the physical removal of weeds from the soil and includes tilling, mowing,
and pulling undesirable plant species. Tillage is most effective prior to seeding and establishment
of desirable vegetation. The tillage method of weed control can be effective in eliminating noxious
perennial weeds when repeated at short intervals (every 1-2 weeks) throughout the growing
season. Tillage has the drawback of indiscriminately impacting all vegetation interspersed with
weeds in established areas and can eliminate competitive, desirable vegetation leaving behind a
prime seedbed for weeds to reinvade. Mowing can be an effective method for controlling the
spread of an infestation and preventing the formation and dispersal of seeds. Mowing is most
effective on weeds which spread solely or primarily by seed. In order to achieve this, it must be
repeated at least twice during the growing season prior to, or shortly after bloom. Also, even the
most intense mowing treatment will not kill hardy perennial weeds. Additional considerations will
be made when selecting control treatments when specific situations arise regarding type, size,
and location of weed infestations. Examples of this are perennial versus biennial, broadleaf versus
grasses, noxious weeds interspersed with desirable vegetation, large monoculture patches, or
small patches requiring spot treatment.
Treatment windows schedules, based on the control methods chosen and the noxious weeds
present, will be established for each treatment area. The best time to treat perennial noxious
weeds is in the spring or fall during their active growth phase. Different species will have different
optimum treatment times even with the same type of control. Perennial weeds usually grow
vegetatively in the spring, flower and seed in late spring and .early summer, enter dormancy during
the summer and actively grow again in the fall. The treatment windows selected will depend on
the species present and control methods selected.
The final preparatory step is to determine the priority for areas to be treated. Prioritization ensures
that the most important areas are dealt with at the most effective times. Important areas of concern
include areas that may transport weed seeds. These areas include ditches, roadsides, and land
equipment storage sites. Large monoculture patches are of concern wherever they occur and
would always be high priority. Also, small patches of weeds would be treated to prevent expansion
of weed populations.
Once the treatment plan is implemented, detailed records will be kept, and success or failure of
treatment will be recorded so as to eliminate unsuccessful treatments.
D.8 REVEGETATION ACCEPTANCE GOALS/CRITERIA AND MONITORING
The following Reveqetation Acceptance Goals/Criteria have been adapted from the Monticello
Site and would be used at the Mill site to determine reclamation success.
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Criterion 1 Species Composition
a. The vegetative cover (the percentage of ground surface covered by live plants) shall be
composed of a minimum of five perennial grass species (at least four listed as native),
one perennial forb and two shrub species listed in Table D.1.
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Criterion 2 Vegetative Cover
a. Attain a minimum vegetative cover percentages of 40 percent.
b. Individual grass and forb species listed in Table D.1 that are used to achieve the cover
criteria shall have a minimum relative cover (the cover of a plant species expressed as a
percentage of total vegetative cover) of 4 percent and a maximum relative cover of 40
percent.
c. Individual species not listed in Table D.1 may be accepted as part of the cover criteria if
it is demonstrated that the species is native or adapted to the area and is a desirable
component of the reclaimed project site.
d. Species not listed in Table D.1, including annual weeds or other undesirable species
shall not count toward the minimum vegetative cover requirement. Every attempt should
be made to minimize establishment of all non-noxious weeds.
e. Reclaimed areas shall be free of state- and county-listed noxious weeds (Table D.40).
f. The vegetative cover shall be self-regenerating and permanent. Self-regeneration shall
be demonstrated by evidence of reproduction, such as tillers and seed production.
Criterion 3 Shrub Density
a. A minimum shrub density of 500 stems per acre
b. Shrubs shall be healthy and have survived at least two complete growing seasons
before being evaluated against success criteria
Monitoring
Plant cover would be measured annually on the tailing cells for a minimum of ten years or until
the revegetation goals stated above are achieved. Cover would be measured by the point
method, using a vegetation sighting scope mounted on an adjustable tripod with a level (or similar
instrument). Cover would be measured for each species encountered, as well as litter, rock, and
bareground. Cover measurements would be made along a minimum of ten randomly placed
transects on each tailing cell that are 100 feet long. A total of 100 points would be sited at one-
foot intervals along each transect to collect cover data in the categories of live vegetation, litter,
rock, and bareground. Sample adequacy would be determined for each tailing cell using the
following formula that identifies the minimum number of samples that are necessary to estimate
the population mean at a 90 percent level of confidence. Total live vegetation cover would be
used to calculate sample adequacy.
n = t2s2
(,10x)2
Where: n = minimum number of samples required to meet sample
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adequacy requirements
s2 = variance
t2 = 1.64 for 90% confidence
x = sample mean
Shrub density would be measured in belt transects placed on either side of the cover transects.
All shrubs would be counted within a three-foot wide strip or belt transect along each side of the
transect used for point cover measurements, resulting in a belt transect that is six-feet wide and
100 feet long.
In addition to the above cover sampling, annual observations would be made of overall plant
community health and sustainability. Overall health would be based on plant vigor, presence of
annual weeds, and signs of plant deficiencies or toxicities. Plant community sustainability would
be based on observations of reproduction, including both vegetative reproduction, such as
tillering, and seed production.
If revegetated areas are not making satisfactory progress in meeting revegetation goals outlined
above, then remedial actions will be implemented as needed. These actions may include
fertilization/soil amendments, reseeding, weed control, and/or erosion control depending upon the
cause of the problem that may exist and the best remediation approach to ensure plant community
success. Potential revegetation problems that are most likely to occur based on typical
revegetation projects in the semiarid west and on experiences at the Monticello Site fall into two
categories. The first is poor initial plant establishment following revegetation practices and the
second is poor plant growth during post-revegetation management.. Poor initial plant
establishment can be caused by a number of factors including unfavorable soil conditions related
to texture or soil chemistry, improper seedbed preparation, improper seeding techniques,
improper species selection, poor seed quality, planting in the wrong season, seed predation, and
inadequate precipitation. If revegetation at the Mill site results in unacceptable initial plant
establishment, the cause of this response will be investigated, the identified cause will be
corrected, and the necessary revegetation practices will be applied until successful plant
establishment has occurred. The most likely cause of poor initial plant establishment at the Mill
site would be low precipitation and additional seedings would be required in a subsequent year(s)
until precipitation improves and an adequate stand of vegetation is achieved. Additional mulching
to control erosion and improve soil moisture conditions for seed germination and initial seedling
growth would be part of the remedial process. Poor plant growth during post-revegetation
management has been an issue at the Monticello Site as it relates to shrub establishment. The
primary species that has been an issue is big sagebrush and the cause of the problem has been
seedling damage associated with vole herbivory.
D.9 SUSTAINABILITY OF THE COVER DESIGN
D.9.1 CLIMATE CHANGE
Climate, more than any other factor, controls the broadscale distributions of plant species and
vegetation. At finer scales, other factors such as local environmental conditions including soil
nutrient status, pH, water-holding capacity and the physical elements of aspect or slope influence
the potential presence or absence of a species. However, intra- and inter-specific interactions,
such as competition for resources (light, water, nutrients), ultimately determine whether an
individual plant is actually found at any particular location (Sykes 2009). Rapid climate change
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associated with increasing greenhouse gas emissions (IPCC 2007) influences current and future
vegetation patterns. Other human-influenced factors are, however, also involved. Sala et al.
(1997) identified five different drivers of change that can be expected to affect global biodiversity
over the next 100 years. Globally, land use change was considered the most important driver of
change, followed by climate change, airborne nitrogen deposition, biotic interactions (invasive
species) and direct C02 fertilizing or water use efficiency effects.
Predicted changes in climate that may occur in the southwestern U.S. include increased
atmospheric concentrations of C02, increased surface temperatures, changes in the amount,
seasonality, and distribution of precipitation, more frequent climatic extremes, and a greater
variability in climate patterns. Recent temperature increases have made the current drought in
the region more severe than the natural droughts of the last several centuries. This drought has
caused substantial die-off of pinyon pine trees in approximately 4,600 square miles of pinyon-
juniper woodland in the Four Corners region (Breshears et al. 2005). Williams et al. (2010)
examined correlations between climate and the radial growth of trees across North America. They
show that conifer trees in the southwest are particularly sensitive to temperature and aridity
relative to other regions. They used climate-tree growth relations calculated for the past 100
years, combined with Intergovernmental Panel on Climate Change (IPCC) climate model
estimates for the 21st century to predict the likely fate of important southwest tree species such
as pinyon pine. They concluded that woodlands and forests will experience substantially reduced
growth rates and increase mortality at many southwest sites as the century progresses.
The specific physiological effects of increasing GHG emissions (particularly C02) on vegetation
include increased net photosynthesis, reduced photorespiration, changes in dark respiration, and
reduced stomatal conductance which decreases transpiration and increases water use efficiency
(Patterson and Flint 1990). Ambient temperature affects plants directly and indirectly at each
stage of their life cycle (Morison and Lawlor 1999). Water (i.e. soil moisture) is usually the abiotic
factor most limiting to vegetation, especially in arid and semi-arid regions. Carbon dioxide,
temperature, and soil moisture effects on plant physiology are exhibited at the whole-plant level
in terms of growth and resource acquisition. In addition to the individual effects of increasing
temperatures, C02 is the additional interactive effect on photosynthetic productivity and
ecosystem-level process (Long and Hutchin 1991).
Plants are finely tuned to the seasonality of their environment, and shifts in the timing of plant
activity (i.e. phenology) provide some of the most compelling evidence that species and
ecosystems are being influenced by global environmental change (Cleland et al. 2007). Changes
in the phenology of plants have been noted in recent decades in regions around the world (Bradley
et al. 1999; Fitter and Fitter 2002; Walther et al. 2002; Parmesan and Yohe 2003). Phenology of
plant species is important both at the individual and population levels. Specific timing is crucial to
optimal seed set for individuals and populations; and variation among species in their phenology
is an important mechanism for maintaining species coexistence in diverse plant communities by
reducing competition for pollinators and other resources. Global climate change could
significantly alter plant phenology because temperature influences the timing of development,
both alone and through interactions with other cues, such as photoperiod.
Shifts in the relative competitive ability of plants that experience changes in C02, surface
temperatures, or soil moisture may result in changes to their spatial distribution (Long and Flutchin
1991; Neilson and Marks 1994). Increases in temperature may enhance the competitive ability
of C4 plants (such as grasses) relative to C3 plants (shrubs and trees) (Owensby et al. 1999),
especially where soil moisture (Neilson 1993) or temperature (Esser 1992) is limiting.
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There are numerous uncertainties and complexities associated with the use of all regional climate
models with regard to their ability to reliably forecast longer-term future climate conditions in the
North American South West (NASW) and at the Mill site. Therefore, attempts to extend the results
from climate model predictions forecasting climate conditions through the end of the 21st century
to timeframes of 200 to 1,000 years will likely result in further compounding of these uncertainties
and result in unreliable predictions. We identified this concern in earlier discussions presented
on the topic of climate change.
We have reviewed references cited in the Division’s Rd 1 Interrogatories for White Mesa Revised
ICTM Report on estimating the range of future climates (CNRWA 2005; NRC 2003; NRC 1997).
The Center for Nuclear Waste Regulatory Analyses (CNRWA 2005) conducted an analysis of
factors contributing to uncertainty in estimating future climates at Yucca Mountain. Their report
concludes the following:
“In summary, research performed within the last five years suggests that the timing of
climate changes over the next 100,000 years may be difficult to infer from the patterns of
climate change over the last 500,000 years due to the unusually low eccentricity of Earth’s
orbit and, possibly, the influence of anthropogenic greenhouses gases. After 100,000
years, the Earth’s orbital climate forcing will be stronger, and the influence of greenhouse
gases may have diminished so that the Pleistocene climate history may offer a better
analog in terms of timing of climate changes. In terms of the characteristics of future
climates (i.e., mean annual precipitation and temperature, seasonal weather patterns, and
storm intensities), the characteristics inferred from paleoclimate reconstructions and
present day analog records may represent the range of climate conditions that will occur
in the future, even if the timing of these climates cannot be reliably estimated. The greatest
uncertainty in future climate conditions relates to anthropogenic effects that may result in
climates in southern Nevada that do not have analogs with present or Pleistocene
climates, such as prolonged El Nino conditions. The nature, likelihood, and duration of
such nonrepresentative climate conditions cannot be reliably assessed based on current
research. Over longer time periods, the range of conditions inferred from the Pleistocene
paleoclimate record reasonably bounds future climate during the period of geologic
stability.”
We agree with NRC’s preferred approach of using paleoclimate data to estimate the likely range
of future conditions. In fact, in our previous discussion of climate change in Attachment G (EFRI,
2012), we discussed the paleoclimate approach presented by Waugh and Petersen (1994) for
the Monticello site.
Waugh and Petersen (1994) summarize future climate change as follows:
“Global mean temperature may increase by 1.8 to 5.2°C in the next century, in response
to an industrial age buildup of carbon dioxide (CO2), methane, and other gases (Houghton
et al. 1992). Model projections of the magnitude of warming vary, depending on whether
factors such as C02 fertilization, feedback from stratospheric ozone depletion, and the
radiative effects of sulfate aerosols are taken into account. Model projections of
precipitation responses to greenhouse warming also are inconsistent (Houghton et al.
1990; Crowley and North 1991; Washington and Meehl 1984; Wilson and Mitchell 1987;
Schlesinger and Mitchell 1987). Some regions may be effectively wetter and others drier,
depending on the balance of the greater potential evaporation and the greater water­
holding capacity of a warmer atmosphere. Greenhouse warming may eventually be
overwhelmed as the earth plunges into another ice age. Models of cyclic astronomical
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forcing of climate agree that, without anthropogenic disturbances, a long-term cooling
trend that started about 6,000 years ago will continue, climaxing with a major glaciation in
about 60,000 years (Imbrie and Imbrie 1980; Berger et al. 1991). In contrast, aperiodicity
in the timing of past ice ages is evident in oxygen isotope records (Winograd et al. 1992).
Other paleorecords suggest that certain feedback mechanisms have caused rapid and
unpredictable transitions into ice ages (Berger and Labeyrie 1987; Phillips et al. 1990).”
Waugh and Petersen (1994) concluded from their investigation that despite uncertainty about
drivers of future climate change, climate extremes in the next 1,000 years likely will not exceed
those associated with the last glacial and interglacial periods. Therefore, paleo-records of full
glacial and Altithermal climates in the Four Corners region provide reasonable ranges of possible
future climate and should be incorporated in assessments of the long-term performance of tailings
disposal facilities. For Monticello, Utah, full glacial and Altithermal climate reconstructions provide
working levels of 2 to 10° C mean annual temperature and 38 to 80 cm mean annual precipitation.
If we assume that a similar range of temperature and precipitation could also occur at the Mill site,
then during the next glacial phase anticipated to occur approximately 60,000 years into the future
the climate would be a colder and wetter compared to current conditions, and if conditions post­
glaciation result in a warm period the climate would be warmer and wetter than current conditions.
Table D.41 presents a list of possible climate scenarios for the Mill site, their likelihood of
occurrence and the resulting plant community type that would develop during the required
performance period. From the review of climate change literature applicable to the southwest
U.S. and an analysis of the impact of various climate change scenarios, it is our conclusion that
the most likely plant community type that will be maintained throughout the 200- to 1,000-year
performance period is a community dominated initially by cool season grasses, with a long-term
transition to dominance by warm season grasses and shrubs as atmospheric CO2 and
temperature continues to increase and precipitation ether increases or decreases.
D.7.2 Plant Community Succession and Potential for Species Colonization
Plant succession is the ecological process of directional vegetation change over time, usually
beginning with relatively-short lived herbaceous plants and culminating in plant communities
dominated by long-lived, generally woody species. Succession occurs on all sites. The rate of
succession can be relatively rapid, especially in regions of higher rainfall, or it can be very slow,
as in some desert and arctic regions, but this process of vegetation change is constantly taking
place.
Two common aspects of succession are 1) an increase in vegetation structure and 2) an increase
in the relative amounts of woody plants. Both of these aspects have profound implications to the
function of cover systems. Vegetation structure refers to the shape of the vegetation, e.g., height,
coverage, and stratification. Structure increases as succession proceeds, both above- and
belowground. Aboveground, the height of the vegetation increases (e.g., grasses may be
replaced by shrubs), coverage of the soil surface increases, and layering (strata) of vegetation
occurs, with different species occupying different vertical layers. Similar processes occur
belowground. Root systems become deeper as shallow-rooted species are replaced by deeper-
rooted species, root biomass increases in lower soil depths as the number and types of species
increase, and the density of the root system increases in the various layers.
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Table D.40. Possible Climate Scenarios for the Mill Site, Likelihood of Occurrence and
Projected Change in Plant Species Composition Compared to the Initial Grass/forb
Community Established on the Soil Cover
Possible Climate
Scenarios
Likelihood of
Occurence9
Projected Plant Community Type in 1,000 Years with Seeded Grass/Forb as the initial Community
Warmer and Dryer
than Present1
Highly Likely Grass/forb community with an increase in warm season
species.
Warmer and Wetter
than Present2
Highly Likely Will depend on distribution of additional precipitation. If
more precipitation in winter months, then the plant
community would experience an increase in woody
plants; if more precipitation in the summer months, then
the plant community would continue as a grass/forb
type.
Warmer than Present
with Similar Total
Precipitation3
Unlikely Grass/forb community with an increase in warm season
species.
Cooler and Wetter
than Present4
Highly Unlikely Shift to more woody plants because of more snow in
winter months.
Cooler and Dryer than
Present5
Highly Unlikely Shift to more woody plants because of more snow in
winter months.
Cooler than Present
with Similar
Precipitation6
Highly Unlikely Shift to more woody plants because of more snow in
winter months.
Dryer than Present
with Similar
Temperature7
Unlikely Grass/forb community with an increase in warm season
species because of less overall moisture and increase
in atmospheric CO2.
Wetter than Present
with Similar
Temperature8
Unlikely Shift to more woody plants because of more winter
precipitation.
1Results in less total precipitation but shift to less snow and more rain in winter months.
2Results in more total precipitation with shift to less snow and more rain in winter months or more rain in
summer months.
3Results in no change in total precipitation but shift to less snow and more rain in winter months.
4Results in more total precipitation with shift to more snow in winter months.
5Results in less total precipitation but shift to more snow in winter months
6Results in no change in total precipitation but shift to more snow in winter months.
7Results in less total precipitation.
8Results in more total precipitation.
9Likelihood of occurrence based on majority of climate model estimates analyzed by Cayan et al. 2010 and
Seager and Vecchi 2010, with a focus on the southwest U.S.
As the vegetation shifts from dominance by herbaceous plants (e.g., grasses), which have
relatively shallow root systems but with very dense root mass in the upper profile, to dominance
by woody species (e.g., shrubs), which have deeper roots systems with proportionately more
roots in deeper layers, the hydrological dynamics of the system change. Early successional plant
communities tend to extract most of the water they transpire from the upper soil profile. Late
successional communities have greater ability to extract water from depth. This can be both a
positive and a negative in the functional efficiency of covers. Because of successional changes
in the vegetation, the plant-soil-water characteristics of a cover are likely to become very different
over time. Conditions 200 years or more after construction are not likely to be similar to those
soon after construction was completed. In some ways, conditions will be more favorable, e.g.,
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evapotranspiration will likely be higher thus reducing the amount of deep infiltration and stability
of the vegetation may be greater. In other ways, conditions will be less favorable, e.g., deeper
root systems increase the concern for biointrusion. Because succession is a process that is near-
universal ecologically, these changes have been accounted for in the cover design.
As stated earlier, the proposed cover system is a monolithic ET cover that consists of the following
layers from top to bottom: 15 cm of a topsoil-gravel erosion protection layer over 107 cm of a
water storage, biointrusion and radon attenuation layer over up to 110 to 136 cm of a highly
compacted radon attenuation layer over 76 cm of a grading and radon attenuation layer. The
proposed cover system does not contain a biobarrier (e.g. cobble layer) to minimize potential
intrusion by plant roots during the required performance period. The proposed cover system is
designed to minimize plant root intrusion through the use of thick layers of soil cover in
combination with a highly compacted layer placed deep within the cover. The climax community
for the Mill site is believed to be Big Sagebrush based on the current community type at the site
and the relatively deep fine loamy soils that are present. If climate trends towards a warmer and
dryer climate for the White Mesa area over the next 200 to 1,000 years, it is unlikely that
sagebrush will remain on site and a community dominated by warm season species and more
arid shrub species (e.g. shadscale saltbush, blackbrush and Mormon tea) may occur.
As discussed above, the process of succession and the effect of climate change will bring about
changes in species composition in the tailings cover system. Our best forecast for the percentage
of potential species colonization would be for a small percent of non-seeded species establishing
during the first 50 years. The seeded community will be highly sustainable and big sagebrush
would be the primary invader into the cover system. It is estimated that the established community
will consist of 60 to 70 percent seeded species and 30 to 40 percent non-seeded species at end
of the first 100 years. These non-seeded species will include big sagebrush and broom
snakeweed, and a few grass and forb species common in the area. During the next 100 years
the plant community will begin to transition to warm season species and big sagebrush will begin
to diminish. By the end of the second 100 years it is estimated that the plant community will
consist of 30 to 40 percent seeded and 60 to 70 percent non-seeded species and many of the
non-seeded species will be warm season grasses and more arid shrub species. This trend will
most likely continue through the remainder of the performance period with only 10 to 20 percent
of the original seeded species still present and these would include blue grama and galleta. The
remainder of the community would consist of more warm season grasses and shrubs that will
have migrated north and higher in elevation with the warming climate.
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L:
\
D
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s
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g
n
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D
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a
f
t
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g
\
a
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t
3
-
A
-
H
\
D
E
N
I
S
0
N
MiN
E
S
\
O
I
3
-
S
h
e
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\
2
0
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5-0
3
-
2
6
CO
V
R
DS
N
RE
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\
1
0
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9
7
4
0
TR
A
N
S