DRC-2012-003461 - 0901a06880559dd9

State of Utah
GARY R. HERBERT
Goveraor
GREG BELL
Lieutenant Governor
Department of
- Environmental Quality
Amanda Smith
Executive Director
DTVISION OF RADIATION CONTROL
Rusty hndberg
Director
DR L-zotz- 0c34b1
Apil3,2012
David Frydenlund
Vice President Regulatory Affairs and Counsel
Denison.Mines (USA) Corp.
1050 l7tn Sffeet. Suite 950
Denver, Colorado 80265
RE: Review of Reclamation Plan 5.0 and the Infiltration Contaminate Transport Model Report;
Radioactive Material License (RML) Number UT1900479
Dear Mr. Frydenlund
As mentioned in the email dated March28,20l2, enclosed is the first Round Interrogatories
regarding Reclamation Plan 5.0 and the revised Infiltration Contaminate Transport Model (ICTM)
Report.
If you have concerns or questions regarding these documents, please feel free to contact us at 801-
536-4250.
Hul
Low Level Waste & Uranium Mills Licensing Manager
JDH jh
Cc: Jo Ann Tischler, Director, Compliance and Permitting
Enclosures
195 North 1950 West . Salt Lake City, UT
Mailing Address: P.O. Box 144850 . Salt lake City, UT 841l4-4850
Telephone (801 ) 536-4250. Fax (801 ) 5334097 . T.D.D. (80 I ) 53644 l4
w.deq.uah.gov
Printed on 100% rccycled paper
Review of Revised Infiltration and Contaminant Transport Modeling Report
March 2012
UTAH DIVISION OF RADIATION CONTROL
DENISON MINES (USA) CORP'S
REVISED INFILTRATION AND
CONTAMINANT TRANSPORT MODELING REPORT
INTERROGATORIES - ROUND 1
MARCH 2012
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TABLE OF CONTENTS
Section Pafie
ACRONYMS AND ABBREVIATIONS ii
INTERROGATORY WHITE MESA REV'D ICTM; R313-24-4; 10CFR40 APPENDIX A, CRITERION
6(1); INT 01/1: INCONSISTENCIES BETWEEN REVISED ICTM REPORT AND
RECLAMATION PLAN REV 5.0 3
INTERROGATORY WHITE MESA REV'D ICTM; R313-24-4; 10CFR40 APPENDIX A, CRITERION
6(1); INT 02/1: COMPARISON OF COVER DESIGNS, SENSITIVITY ANALYSES,
'BATHTUB' ANALYSIS, AND RADON EMANATION MODELING 6
INTERROGATORY WHITE MESA REV'D ICTM; R313-24-4; 10 CFR40 APPENDIX A,
CRITERION 6(1); INT 03/1: MOISTURE STORAGE CAPACITY OF COVER 13
INTERROGATORY WHITE MESA REV'D ICTM; R313-24-4; 10 CFR40 APPENDIX A,
CRITERION 1; INT 04/1: EVALUATION OF POTENTIAL FLOW THROUGH TAILINGS
CELL LINERS 16
INTERROGATORY WHITE MESA REV'D ICTM; R313-24-4 -05/1: CONTAMINANT
TRANSPORT MODELING 19
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ACRONYMS AND ABBREVIATIONS
ACZ ACZ Laboratories, Inc.
ANP acid neutralization potential
CFR Code of Federal Regulations
cm centimeter
DO Dissolved oxygen
DUSA Denison Mines (USA) Corporation
E East
ET Evapotranspiration
ft foot
HFO hydrous ferric oxide
HP 1 Reactive transport model (HYDRUS-1D coupled with PHREEQC)
IUC International Uranium Corporation
Kd distribution coefficient
mg/L milligram per liter
mi mile
N North
ICTM Infiltration and Contaminant Transport Model
NRC U.S. Nuclear Regulatory Commission
NUREG Label denoting a collection of documents published by the US Nuclear
Regulatory Commission
pCi picocurie; 10"12 curie
Rev. Revision
S South
s, sec second
SWCC soil water characteristic curve
UAC Utah Administrative Code
W West
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INTERROGATORY WHITE MESA REV'D ICTM; R313-24-4; 10CFR40
APPENDIX A, CRITERION 6(1); INT 01/1: INCONSISTENCIES BETWEEN
REVISED ICTM REPORT AND RECLAMATION PLAN REV 5.0
REGULATORY BASIS:
UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion
6(1): In disposing of waste byproduct material, licensees shall place an earthen cover (or
approved alternative) over tailings or wastes at the end of milling operations and shall
close the waste disposal area in accordance with a design which provides reasonable
assurance of control of radiological hazards to (i) be effective for 1,000 years, to the
extent reasonably achievable, and, in any case, for at least 200 years, and (ii) limit
releases of radon-222 from uranium byproduct materials, and radon-220 from thorium
byproduct materials, to the atmosphere so as not to exceed an average release rate of 20
picocuries per square meter per second (pCi/m2s) to the extent practicable throughout
the effective design life determined pursuant to (l)(i) of this Criterion. In computing
required tailings cover thicknesses, moisture in soils in excess of amounts found normally
in similar soils in similar circumstances may not be considered. Direct gamma exposure
from the tailings or wastes should be reduced to background levels. The effects of any
thin synthetic layer may not be taken into account in determining the calculated radon
exhalation level. If non-soil materials are proposed as cover materials, it must be
demonstrated that these materials will not crack or degrade by differential settlement,
weathering, or other mechanism, over long-term intervals.
INTERROGATORY STATEMENT:
Refer to Executive Summary, Section 2.1, Figures 2-2 and 3-1, Table 3-1, and
Appendices D through N of the ICTM Report Rev 2:
1. Revise the description of the proposed evapotranspiration (ET) cover, including
revised cover material characteristics (e.g., soil textures [percent clay content,
etc.], expected in-place saturated soil layer hydraulic conductivities, particle
size distributions, porosities and bulk densities) for each layer of the cover and
revised thicknesses, where applicable, to be consistent with the ET cover
description that will be presented in the next revision of Reclamation Plan Rev.
5.0 reflecting the responses to comments contained in the Round 1 Interrogatories
submitted on the Reclamation Plan rev. 5.0 and these Round 1 interrogatories.
Update Figures 2.2 and 3-1 to reflect the ET cover thicknesses and materials and
to be consistent with the descriptions to be provided in the updated Reclamation
Plan.
2. Update analyses in the referenced Appendices to reflect ET cover characteristics
that are consistent with the descriptions to be given in the next revision of the
Reclamation Plan Rev 5.0.
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3. Provide an updated Appendix D (Vegetation Evaluation for the
Evapotranspiration Cover) that reflects information to be presented in the next
revision of the Reclamation Plan Rev. 5.0 on vegetation occurrence and the
proposed revegetation plan and that addresses the additional considerations and
additional information described or requested in "INTERROGATORY WHITE
MESA RECPLAN REV 5.0 R313-24-4; 10CFR40 APPENDIX A; INT 11/1:
VEGETATION AND BIOINTR USION E VUALA TION AND REVEGETATION
PLAN".
4. For Appendix E (Comparison of Cover Designs Based on Infiltration Modeling),
Appendix F (Evaluation of the Effects of Storm Intensity on Infiltration through
Evapotranspiration Cover), Appendix G (Sensitivity Analysis Comparing
Infiltration Rates through the Evapotranspiration Cover Based on Vegetation,
Biointrusion, and Precipitation), and Appendix H (Radon Emanation Modeling
for the Evapotranspiration Cover):
a. Provide revised discussion of the impacts of the results of an updated frost
penetration calculation and the maximum predicted frost penetration
depth for the cover system
b. Provide revised discussion and revised infiltration analyses to:
i. Reflect the results of the updated frost penetration depth analysis
requested in ••INTERROGATORY WHITEMESA RECPLAN 5.0
R313-24-4; 10CFR40, APPENDLX A, CRITERION 6; INT 10/1:
TECHNICAL ANALYSES - FROST PENETRATION ANALYSIS"
ii. Address the additional considerations and additional information
described or requested in "INTERROGA TORY WHITE MESA
REV'D ICTMR313-24-4; 10CFR40 APPENDIX A, CRITERION
6(1); INT 02/1: COMPARISON OF CO VER DESIGNS,
SENSITIVITY ANAL YSES, 'BA THTUB' ANAL YSIS, AND RADON
EMANA TION MODELING "
5. For Appendices K through N provide updated/revised information and/or results
to reflect updated information and results provided as requested for Appendices E
through H in Items 1 through 4 of this interrogatory.
URS
BASIS FOR INTERROGATORY:
Section 3.3 and Figures 2.2 and 3-1 of the revised ICTM Report present the thickness of
the ET cover as 9.3 feet extending from the cover surface to the top of the tailings. The
Reclamation Plan, Rev. 5.0 (Section 3.2.2, Appendix G, and Figure 1-1 of Appendix G),
describes the ET cover as being 9 feet thick from the cover surface to the top of the
tailings. Revisions need to be made to the ICTM Report to be consistent with the ET
cover details to be presented in the next revision of the Reclamation Plan Rev. 5.0. Also,
the description of the materials comprising the ET tailings cover design is different in the
ICTM Report than in the Reclamation Plan Rev. 5.0. The ICTM describes the ET tailings
cover design from top to bottom as follows:
• 0.5 ft (15 cm) Erosion Protection Layer (gravel-amended topsoil mixture)
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• 3.5 ft (107 cm) Water Storage/Biointrusion/Frost Protection/Radon Attenuation
Layer (random fill soil [sandy clayey silt])
• 2.8 ft (75 cm) Radon Attenuation Layer (highly compacted loam to sandy clay
• 2.5 ft (75 cm) Radon Attenuation and Grading Layer (random fill soil [sandy
clayey silt])loam to sandy clay
However, Figure 1-1 of the Reclamation Plan Rev. 5.0 describes the water
storage/biointrusion/frost protection/radon attenuation layer as a loam to sandy clay
with the radon attenuation layer being comprised of highly compacted loam to sandy clay
The intended proposed tailings cover design needs to be made consistent for the ICTM
Report and the next revision of the Reclamation Plan Rev. 5.0.
Finally, on page E-2, it is stated that "TITAN Environmental (1996) completed a freeze-
thaw evaluation based on site-specific conditions which indicated that that the
anticipated maximum depth of frost penetration was 6.8 inches (0.6 ft)." The frost
penetration depth estimate presented by TITAN Environmental (1996) is out of date and
needs to be replaced with an updated frost penetration depth calculation.
Refer to the Basis for Interrogatory sections in "INTERROGATORY WHITEMESA
RECPLAN 5.0 R313-24-4; J0CFR40, APPENDIX A, CRITERION 6; INT 10/1:
TECHNICAL ANALYSES - FROST PENETRATION ANALYSIS", "INTERROGATORY
WHITE MESA REV'D ICTM R313-24-4; 10CFR40 APPENDIX A, CRITERION 6(1);
INT 02/1: COMPARISON OF COVER DESIGNS, SENSITIVITY ANALYSES,
•BATHTUB' ANALYSIS, AND RADON EMANATION MODELING" and
"INTERROGATORY WHITE MESA RECPLAN REV 5.0; R313-24-4; 10CFR40
APPENDIX A; INT 11/1: VEGETATION AND BIOINTRUSION EVUALATION AND
REVEGETATION PLAN" for additional information and bases for this interrogatory.
REFERENCES:
Denison Mines (USA) Corp. 2010. Revised Infiltration and Contaminant Transport
Modeling Report, White Mesa Mill Site, Blanding, Utah (Revision 2), March 2010.
Denison Mines (USA) Corp. 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah,
Radioactive Materials License No. UT1900479, Revision 5.0, September 2011.
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INTERROGATORY WHITE MESA REV'D ICTM; R313-24-4; 10CFR40
APPENDIX A, CRITERION 6(1); INT 02/1: COMPARISON OF COVER
DESIGNS, SENSITIVITY ANALYSES, 'BATHTUB' ANALYSIS, AND RADON
EMANATION MODELING
REGULATORY BASIS:
UAC R313-24-4 invokes the following, requirement from 10CFR40, Appendix A, Criterion
6(1): In disposing of waste byproduct material, licensees shall place an earthen cover (or
approved alternative) over tailings or wastes at the end of milling operations and shall
close the waste disposal area in accordance with a design which provides reasonable
assurance of control of radiological hazards to (i) be effective for 1,000 years, to the
extent reasonably achievable, and, in any case, for at least 200 years, and (ii) limit
releases of radon-222 from uranium byproduct materials, and radon-220 from thorium
byproduct materials, to the atmosphere so as not to exceed an average release rate of 20
picocuries per square meter per second (pCi/m2s) to the extent practicable throughout
the effective design life determined pursuant to (l)(i) of this Criterion. In computing
required tailings cover thicknesses, moisture in soils in excess of amounts found normally
in similar soils in similar circumstances may not be considered. Direct gamma exposure
from the tailings or wastes should be reduced to background levels. The effects of any
thin synthetic layer may not be taken into account in determining the calculated radon
exhalation level. If non-soil materials are proposed as cover materials, it must be
demonstrated that these materials will not crack or degrade by differential settlement,
weathering, or other mechanism, over long-term intervals.
INTERROGATORY STATEMENT:
1. Please refer to Sections 3-1, 4-1 and Appendix E, F, G, and H of the ICTM
Report: Please provide the following:
a. Provide additional information to justify the assumed cover soil layer properties,
including the value of porosity of 0.25 in Table H-3 for the Erosion Protection
Layer. Demonstrate that the values used in modeling appropriately reflect: (a)
the composition and characteristics of the soil and gravel components of the
admixture layer and of other layers in the cover system; and (b) the level of
compaction proposed for each cover layer (see also "INTERROGA TORY
WHITEMESA RECPLAN REV 5.0 R313-24-4; 10CFR40, APPENDIX A,
CRITERION 6(4); INT 12/1: REPORT RADON BARRIER EFFECTIVENESS).
b. Provide additional sensitivity analyses projecting potential performance of the
four different conceptual cover designs where the cover materials are assumed to
have experienced degradation under postulated worst-case long-term conditions.
Specifically, adjust parameters (including at least, bulk density and porosity, in
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accordance with recommendations in NUREG-1620, Section 5.1.3 [NRC 2003]))
of soil and/or clayey materials within the maximum projected frost-impacted zone
for the 1,000-year recurrence interval (see also "INTERROGATORY
WHITEMESA RECPLAN 5.0; UAC R313-24-8; 10CFR40, APPENDIX A,
CRITERION 6; INT 10/1: TECHNICAL ANALYSES - FROST PENETRA TION
ANALYSIS"). Consistent with recommendations provided in Benson et al. 2011,
adjust other cover soil properties (e.g., hydraulic conductivities and the a [or
alpha] parameter in the mathematical expression for the soil water characteristic
curve [SWCC]) consistently for all alternative cover systems considered (or
justify why inconsistent parameter values are appropriate) in assessing long-term
degraded conditions.
c. Define and justify a range ofpossible future climate conditions that may
reasonably be expected to occur during the performance period of the closed
tailings embankment system (up to 1,000 years), taking into account the projected
variability of climate conditions over such time periods. Provide infiltration
modeling results that incorporate such peak/higher precipitation and/or minimum
evapotranspiration conditions. Alternatively, provide detailed justification why
consideration of such changed climatic conditions in the infiltration simulations is
not justified or would be otherwise inconsistent with relevant guidance and policy
determinations and with regulatory precedent established on other projects of a
similar nature (Note: on similar projects, formal future climate analysis
techniques have been used to forecast possible future climate states occurring
during the next 1,000 years, and infiltration sensitivity analyses were performed
to assess long-term future cover system performance under these projected future
climate conditions). Incorporate worst-case meteorological conditions into the
sensitivity analyses and the "bathtub " analysis for the proposed
evapotranspiration (ET) cover system.
d. Extend the timeframe for calculations projecting the "bathtub effect" to a period
of up to 1,000 years. Adjust soil properties in the proposed ET cover components
to include initial and worst case long-term degraded cover conditions as stated in
Item I of this interrogatory. Incorporate potential worst-case forecasted future
climate conditions as stated in Item 2 of this interrogatory.
e. Provide additional justification for selecting a three-consecutive-year period for
the higher precipitation regime in the infiltration sensitivity analysis provided in
Appendix G. Discuss and evaluate the appropriateness of results and/or
recommendations from other published studies (other than the Khire et al. 2000
study cited in Appendix G) for arid and semi-arid sites and assumptions that were
made for other similar projects (e.g., Monticello, Utah tailings repository design,
where a 10-consecutive-year wetter period was used in infiltration sensitivity
analyses). Demonstrate that the duration of the wetter period used in the
sensitivity analyses ensures that dynamic equilibrium conditions will be achieved
in modeling the cover system performance.
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2. Refer to Revised ICTM Report, p. ES-6, Sections 4.1.2 and 5.1.2, and Appendix
G: Please justify assuming a tailings porosity of 57% in evaluating
infiltration/potential for "bathtubbing" ofleachate on the liner systems. Perform
and report results of sensitivity analyses that assess the dependence of result on
variations in the values of tailings porosity used in analyses.
3. Refer to Appendix E, p. E-5, Paragraph 2 of the ICTM Report: Please
clarify/provide the information referenced as being included in Attachment E-l
(not apparently provided in the report).
BASIS FOR INTERROGATORY:
Various sets of assumptions were made when estimating parameter input values for
various cover materials for use in the infiltration model simulations and in the infiltration
comparisons evaluating the hydraulic performance of the four different cover designs.
However, several simplified assumptions were included, and additional justification/
rationale needs to be provided to support the representativeness and appropriateness of
these input values. Site-specific testing data should be better developed and utilized and
real correlations developed between field parameters and laboratory results, and
between soil properties and soil compaction levels for each of the different proposed ET
soil cover layers.
Properties assumed for the various soil layers in the proposed ET cover system need to
be fully justified. For example, the porosity value of 0.25 listed in Table H-3 for the
Erosion Protection Layer has not adequately been justified and appears to be low. The
value should be determined through calculation (e.g., using the U.S. Bureau of
Reclamation Earth Manual estimation formula for total density of a soil/gravel
admixture), information in Earth Manual or elsewhere on predicted percentages of
Proctor maximum dry densities obtainable using standard compactive effort in relation
to percent of gravel present, and correcting for the percentage of maximum density
corresponding to the specified compaction level), followed by calculations of the void
ratio and porosity.
The meteorological and soil parameter values used in the sensitivity analysis should
better reflect the range ofpossible future meteorological and hydrological conditions
that may occur at the site during the long-term performance period of the closed tailings
embankment cover system. Adjusted bulk density and porosity values for the portion of
the cover potentially affected by the maximum frost penetration depth over a 1,000-year
recurrence period should be employed in the radon emanation model as per NUREG-
1620 recommendations. Equivalent or consistent adjusted soil properties should be used
in cover infiltration simulations or adequate justification provided for assuming different
material properties. The estimates of the material parameters used in the infiltration
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sensitivity analyses performed to assess long-term cover performance need to be
reasonably conservative, considering the uncertainty associated with these values.
Determination of soil properties should be based on testing of soils from the site and
more precise correlations of key soil properties (e.g., soil layer hydraulic conductivity vs.
relative soil compaction level) should be developed with supporting information
describing the test method and its precision, accuracy, and applicability provided. It
needs to be demonstrated that the parameter values selected and used in the performance
analyses are conservative. For example, the code (HYDRUS) default-defined hydraulic
conductivity values (based on particle size gradation information - Table E-l in
Appendix E to the Updated Tailings Design Report) may not always be conservative. The
infiltration model should result in a representative and a reasonably conservative (given
the uncertainty in some values) long-term infiltration estimate. Determination of
variations in hydraulic conductivity with actual relative compaction levels for on-site soil
samples, and associated permeameter tests used to determine saturated hydraulic
conductivities of son-site soils with testing of on-site soils to determine the soil water
retention curves could likely result in considerably less uncertainty in soil parameter
input values used in modeling (e.g., see McCartney and Zornberg 2006).
An adequate range of climate data providing a conservative representation of recorded
historical climate conditions in the site area (e.g., Blanding, Utah climate data for the
period 1904 through the most recent year available), and a conservative estimate of the
range of future climate conditions that might reasonably be expected to occur during the
performance period of the closed tailings embankment system are required for evaluating
the long-term performance of the embankment s cover system. The evaluation should
consider projections of long-term extreme events and potential shifts in climate states
that could reasonably expected to occur over 100's of years to up to 1,000 years, as well
as annual and decadal variability in meteorological parameters. To better capture and
assess uncertainties in long-term performance of the tailings embankment cover system
resulting from possible future changes in climate conditions, a projection (e.g., first
approximation) of possible future climate states at the White Mesa site should be
developed using a future climate forecasting approach similar to or equivalent in
approach to the future climate analysis approach used in other recent studies completed
for similar facilities in Utah, such as the Monticello tailings repository (e.g., see Waugh
et al. 1995; Sharpe 2004). Identification of the potential climate conditions should be
based on analysis of several facts and considerations, including, but not limited to: (I)
Annual total precipitation amounts that have occurred at the Blanding Meteorological
Station (e.g., 23.50 inches, and 24.42 inches, in 1906 and 1908, respectively) that are
higher than the range of annual precipitation values considered in the current Infiltration
and Contaminant Transport Model (ICTM) Report, which only considered Blanding
climate data acquired between 1932 and 1988;
(2) Subtotals of precipitation amounts that have occurred during any two, or any
three consecutive months at Blanding (e.g., 9.04 inches combined total precipitation for
January and February 1993 and 11.33 inches combined total precipitation for December
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1992 through February 1993; 7.98 inches combined total precipitation for January and
February 2005 and 10.46 inches combined total precipitation for December 2004
through February 2005; 11.95 inches combined total precipitation for December 1908
through February 1909; 5.75 inches total precipitation for April and May 2011
combined; etc..) which are higher subtotal amounts than for any of the same
consecutive sets of months that were included in the 1932-1988 data set considered in the
current ICTM Report and three-month sub-total precipitation amounts recorded at
Blanding that were higher than during the same three months as the Summer 1987
summer monsoon period selected for use in the sensitivity analysis presented in the
current ICTM Report. Also, in 1908 and 1909, the months of December alone were the
second highest, and the highest of record, for any winter season months with 6.20 and
6.84 inches, respectively. This further suggests that winter-season precipitation
conditions may be expected to be the most critical (most conservative) as a basis for
extrapolating potential abnormal future wetter weather conditions for use in assessing
the effects (sensitivity)of such possible future conditions on modeled infiltration
performance (see also items (4) and (5) below);
(3) Site-specific monitoring data, if any, from measurements made within a cover test
cell considered representative of the proposed ET cover system, that might indicate one
or more sets of consecutive months of the year when infiltration rates in the cover would
likely be the highest;
(4) Identification and justification for selecting a specific climatological data set such
as choosing precipitation data for the wettest consecutive months or sets of consecutive
months recorded at Blanding that may correspond to those months when the highest on-
site infiltration rates would be expected to occur through the ET cover system, for use in
extrapolating (forecasting) potential long-term climate conditions at the White Mesa site.
In this regard, additional information should be provided to justify not selecting the
wettest consecutive winter months observed for the precipitation period of record for
Blanding, e.g., rather than selecting the 92-day-long 1987 summer monsoon season as
was done in the sensitivity analysis in Appendix F in the current ICTM Report, as the
basis for extrapolating potentially wetter future climate conditions, since doing the
former could likely result in more moisture breakthrough than that predicted by the
current modeling;
(5) A description of the specific historical climate data set (e.g., wettest three
consecutive winter months, if selected), or other sub-annual or annual data set(s)
selected, and a description of the procedure used for extrapolating this data set or these
data sets to simulate inferred future climate conditions at the White Mesa site should be
provided;
(6) A projection (e.g., first approximation) ofpossible future climate states at the
White Mesa site should be developed based on paleoecological evidence and/or a
global/regional climate change model using a future climate forecast approach, e.g.,
involving the use of analogue present-day climate sites, similar in rigor to the future
climate analysis approach used in other recent studies completed for other similar
facilities in Utah (e.g., see Waugh et al. 1995; Sharpe 2004); and
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(7) A description of the correlation of the extrapolated climate conditions derived
based on the considerations listed in items (1) through (5) above to future climate
conditions (climate states) forecasted using the future climate analysis approach, as
described in item (6) above, should also be provided.
NUREG/CR-7028, a peer-reviewed report published for the NRC in December 2011,
reports the findings from investigations of several earthen and soil/geosynthetic cover
systems to assess changes in properties of cover materials in those cover systems 5 to 10
years following their construction. A key conclusion of the report is that findings from
these investigations demonstrate that changes in the engineering properties of cover soils
generally occur while in service and that long-term engineering properties should be
used as input to models employed for long-term performance assessments. The report
indicates that changes in hydraulic properties occurred in all cover soils evaluated due
to the formation of soil structure, regardless of climate, cover design, or service life. The
report includes recommendations for appropriate input based on the data that were
collected. This document therefore contains information important to the design of the
final cover system for the White Mesa uranium tailings management cells area.
Additional sensitivity analyses should be performed that allow for and incorporate effects
ofpotential long-term degradation of the cover materials in a manner consistent with
conclusions and recommendations given in NUREG/CR-7028, i.e., that "engineering
properties of cover soils change while in service and... that long-term engineering
properties for soils cover materials should be used as input for performance
assessments ".
Based on available information and data for other uranium mill tailings, a porosity value
of 57% may be considered more representative of the finer particle fraction of the
tailings (slimes) than the tailings materials on average (mixture of sands and clays/silt
materials) in the saturated and unsaturated portions of the tailings masses in the cells.
Although a porosity of 57% may be considered conservative for estimating radon flux
through the cover (Appendix H of the ICTM Report), such an assumption may not be
appropriate for the infiltration and bathtub analyses, for which a lower average porosity
value appears to be warranted (e.g., approximately 39% to 40%, based on data for the
Moab uranium tailings). Additional justification should be provided supporting the use
of a lower porosity value in the infiltration/bathtubbing analyses and revised analyses
and conclusions should be provided that incorporate the lower porosity value.
Material referenced as being included in Attachment E-l of Appendix E was not
provided.
REFERENCES:
Benson, CH. W.H Albright, W.H., Fratta, D.O.Jinjum, J.M., Kucukkirca, E., Lee, S.H.,
J. Scalia, J., Schlicht, P.D., and Wang, X. 2011. Engineered Covers for Waste
Containment: Changes in Engineering Properties and Implications for Long-Term
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Performance Assessmentdn 4 volumes). NUREG/CR-7028, Prepared for the U.S.
Nuclear Regulatory Commission, Washington, D.C, December 2011.
Denison Mines (USA) Corp. 2010. Revised Infiltration and Contaminant Transport
Modeling Report, White Mesa Mill Site, Blanding, Utah (Revision 2), March 2010.
Denison Mines (USA) Corp., 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah,
Radioactive Materials License No. UT1900479, Revision 5.0, September 2011.
Khire, M.V., Benson, CH., and Bosscher, P.J. 2000. Capillary Barriers: Design
Variables and Water Balance. Journal of Geotechnical and Geoenvironmental
Engineering. August 2000.
McCartney, J.S, and Zornberg, J.G. 2006. Decision Analysis for Design of
Evapotranspirative Landfill Covers", Proceedings UNSAT '06, April 2-6, Carefree, AZ,
ASCE.pp. 694-705.
NRC 2003. NUREG-1620: Standard Review Plan for the Review of a Reclamation Plan
for Mill Tailings Sites under Title II of the Uranium Mill Tailings Radiation Control Act
of1978. Washington DC, June 2003.
Sharpe, S. 2004. Future Climate States at Monticello, Utah. Desert Research Institute,
February 25, 2004.
Waugh, W.J. and Petersen, K.L. 1995. "Paleoclimatic Data Application: Long-Term
Performance of Uranium Mill Tailings Repositories, " in: W.J. Waugh (ed.J, Climate
Change in the Four Corners and Adjacent Regions: Implications for Environmental
Restoration and Land-Use Planning, CONF9409325, U.S. Department of Energy, Grand
Junction, Colorado, USA, pp. 163185 (1995). Available at:
http://www.osti.sov/enersvcitations/product.biblio.isp7osti id=167170
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INTERROGATORY WHITE MESA REV'D ICTM; R313-24-4; 10 CFR40
APPENDIX A, CRITERION 6(1); INT 03/1: MOISTURE STORAGE CAPACITY
OF COVER
REGULATORY BASIS:
UAC R313-24-4 invokes the followins requirement from 10CFR40. Appendix A, Criterion
6(1): In disposing of waste byproduct material, licensees shall place an earthen cover (or
approved alternative) over tailings or wastes at the end of milling operations and shall
close the waste disposal area in accordance with a design which provides reasonable
assurance of control of radiological hazards to (i) be effective for 1,000 years, to the
extent reasonably achievable, and, in any case, for at least 200 years, and (ii) limit
releases of radon-222 from uranium byproduct materials, and radon-220 from thorium
byproduct materials, to the atmosphere so as not to exceed an average release rate of 20
picocuries per square meter per second (pCi/m2s) to the extent practicable throughout
the effective design life determined pursuant to (l)(i) of this Criterion. In computing
required tailings cover thicknesses, moisture in soils in excess of amounts found normally
in similar soils in similar circumstances may not be considered. Direct gamma exposure
from the tailings or wastes should be reduced to background levels. The effects of any
thin synthetic layer may not be taken into account in determining the calculated radon
exhalation level. If non-soil materials are proposed as cover materials, it must be
demonstrated that these materials will not crack or degrade by differential settlement,
weathering, or other mechanism, over long-term intervals. INTERROGATORY
STATEMENT:
Refer to Appendix F of the ICTM Report: Please provide the following:
1. Redefine and further justify the critical meteorological design event (or sequence
of contiguous events). State and justify the basis for the critical event conditions
addressing the location of the meteorological weather station for determining the
wettest year on record; duration of the critical event (i.e., single-day storm or
multiple-day storm; number of consecutive days of rainfall followed by a large,
single-day rainfall event). Justify excluding recorded historical monthly/daily
precipitation data for Blanding, Utah from consideration in all infiltration
analyses conducted in the ICTM Report that indicate larger two-month-long and
three-month-long precipitation amounts than the 92-day-long 1987 summer
monsoon season used in the sensitivity analysis in Appendix F (see also
INTERROGATORY WHITE MESA REV'D ICTM; R313-24-4; 10CFR40
APPENDIX A, CRITERION 6(1); INT 02/1: COMPARISON OF COVER
DESIGNS, SENSITIVITY ANALYSES, 'BATHTUB' ANALYSIS, AND RADON
EMANATION MODELING above). Identify the month(s) of the year that would
be expected to comprise the most critical percolation period. Justify why
consideration of summer monsoon conditions (when plant cover would be more
developed and ET rates more enhanced) has been considered to be more
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conservative than assuming the most critical meteorological period as occurring
during the winter months.
2. Provide additional details regarding the assumed gradient at the soil
cover/atmosphere interface and include, as needed, an increase to an otherwise
assumed gradient of unity to address the potential for higher infiltration rates into
the cover due to matric suction gradients greater than unity (corresponding to
low suction at the soil surface and a higher suction corresponding to the initial
moisture content) - see, e.g., McCartney and Zornberg 2006. Discuss how
localized surface ponding, if it were to occur, would or would not affect the
assumptions about the gradient at the soil cover interface;
3. Revise the water balance analysis to demonstrate that the cover system will
provide sufficient moisture storage capacity to retain precipitation resulting from
a redefined, largest and most critical meteorological event/set of conditions (most
stressful hydraulic conditions)) that the cover might be exposed to during its
required performance life (1,000 years, to the extent practicable and technically
and economically feasible, and in no case less than 200 years).
4. Discuss, justify, and apply a recommended safety factor to the design of the cover
to provide additional assurance that the thickness of the cover system will be
adequate to accommodate the most stressful hydraulic conditions determined in
Items 1 and 2 above, as required, and to also address uncertainties relating to
the following (e.g., Khire et al. 2000; Hauser et al. 2001; Hauser and Gimon
2004):
a. The size of the soil water reservoir in the cover soil must be adequate to
contain the predicted extreme event/conditions (critical event or events)
and potentially uncertain, intense future storm events;
b. The potential variability of climate conditions over the required
performance evaluation period;
c. The time required to empty the soil-water reservoir; and
d. Other factors, such as the potential long-term degradation of the cover
materials due to desiccation cracking, water erosion, freeze-thaw damage,
and other environmental processes (see, e.g., Benson et al. 2011).
BASIS FOR INTERROGATORY:
Estimates of deep percolation through the cover are of particular concern for ET cover
design and evaluation. The performance of ET covers should be estimated for large and
critical climatic events expected to occur during the service life of the cover. Therefore,
a major concern for ET cover performance is the determination of the greatest storage
capacity required for the ET cover during a defined? most-critical meteorological event
or set of consecutive (contiguous) meteorological events. Critical events causing
maximum soil-water storage may result from a single-day storm, a multiple-day storm, or
other events.
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As a further check for ensuring that the proposed surface cover layer thickness is
adequate, an evaluation should be completed that uses suitable long-term simulations
performed with the most stressful conditions that the cover is likely to endure (Khire et al.
2000). The assessment should include any potentially wetter future climate conditions
that may reasonably be expected to occur during the performance period of the
embankment cover system spanning up to on the order of 1,000 years following the end of
the institutional control period, as described in INTERROGATORY WHITE MESA
REV'D ICTM; R313-24-4; 10CFR40 APPENDIX A, CRITERION 6(1); INT 02/1:
COMPARISON OF COVER DESIGNS, SENSITIVITY ANALYSES, 'BATHTUB'
ANALYSIS, AND RADON EMANATION MODELING above.
REFERENCES:
Benson, CH. W.H. Albright, W.H., Fratta, D.O.Jinjum, J.M., Kucukkirca, E., Lee, S.H.,
J. Scalia, J., Schlicht, P.D., and Wang, X. 2011. Engineered Covers for Waste
Containment: Chans.es in Engineering Properties and Implications for Long-Term
Performance Assessment (in 4 volumes). NUREG/CR-7028, Prepared for the U.S.
Nuclear Regulatory Commission, Washington, D.C., December 2011.
Denison Mines (USA) Corp., 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah,
Radioactive Materials License No. UT19004 79, Revision 5.0, September 2011.
Hauser, V.L., Weand, B.L., and Gill, M.D. 2001. Alternative Landfill Covers. July 2001.
Hauser, V.L and D.M. Gimon 2004. Evaluating Evapotranspiration (ET) Landfill Cover
Performance Using Hydrologic Models. January 2004.
Khire, M. V, Benson, CH, and Bosscher, P.J. 2000. Capillary Barriers: Design
Variables and Water Balance. Journal of Geotechnical and Geoenvironmental
Engineering. August 2000.
McCartney, J.S, and Zornberg, J.G. 2006. Decision Analysis for Design of
Evapotranspirative Landfill Covers", Proceedings UNSAT '06, April 2-6, Carefree, AZ,
ASCE, pp. 694-705.
U.S. Nuclear Regulatory Commission (NRC) 2003. Standard Review Plan (NUREG-
1620) for Staff Reviews of Reclamation Plans for Mill Tailings Sites under Title II of the
Uranium Mill Tailings Radiation Control Act", NUREG-1620, June, 2003.
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INTERROGATORY WHITE MESA REV'D ICTM; R313-24-4; 10 CFR40
APPENDIX A, CRITERION 1; INT 04/1: EVALUATION OF POTENTIAL
FLOW THROUGH TAILINGS CELL LINERS
REGULATORY BASIS:
Refer to UAC R313-24-4, which invokes the following requirement from 10CFR40,
Appendix A, Criterion I: The general goal or broad objective in siting and design
decisions is permanent isolation of tailings and associated contaminants by minimizing
disturbance and dispersion by natural forces, and to do so without ongoing maintenance.
For practical reasons, specific siting decisions and design standards must involve finite
times (e.g., the longevity design standard in Criterion 6). The following site features
which will contribute to such a goal or objective must be considered in selecting among
alternative tailings disposal sites or judging the adequacy of existing tailings sites:
• Remoteness from populated areas;
• Hydrologic and other natural conditions as they contribute to continued
immobilization and isolation of contaminants from ground-water sources; and
• Potential for minimizing erosion, disturbance, and dispersion by natural forces
over the long term.
• The site selection process must be an optimization to the maximum extent
reasonably achievable in terms of these features.
• In the selection of disposal sites, primary emphasis must be given to isolation of
tailings or wastes, a matter having long-term impacts, as opposed to
consideration only of short-term convenience or benefits, such as minimization of
transportation or land acquisition costs. While isolation of tailings will be a
function of both site and engineering design, overriding consideration must be
given to siting features given the long-term nature of the tailings hazards.
Tailings should be disposed of in a manner such that no active maintenance is required
to preserve conditions of the site.
INTERROGATORY STATEMENT:
Refer to Appendix L (Evaluation of Potential Water Flow through Tailings Cell
Liners) of the ICTM Report: Please provide the following:
1. Revise and provide justification for the estimated saturated hydraulic conductivity
of the compacted foundation [liner bedding] layers underlying the geomembrane
in Cells 2 and 3, which are both comprised of a compacted gravel-sand mixture
derived from crushing of loose sandstone, possibly with washed concrete sand
used in some areas);
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2. Provide additional justification to support the various assumed lower bound, base
case, and upper bound geomembrane defect frequencies for the liners in Cells 2,
3, 4A, and 4B. Justify the upper bound assumption of 1 small hole and 3 large
hole defects per acre for the geomembrane defect frequency in the Cells 2 and 3
liners and the assumption of 1 small-hole defect per acre as the base case
assumption for the geomembrane defect frequency for Cells 4A and 4B, or
alternatively, provide revised assumed defect frequencies to ensure that the
assumed defect frequencies are adequately conservative and reasonably represent
actual or potential in-place liner conditions; and
3. Revise the calculations of potential flow through the Cell 3 and Cell 2 liner
systems using a more suitable and appropriate methodology such as the modified
methodology developed by Giroud and others (Giroud et al. 1997a) for estimating
the rate of liquid migration through defects in a geomembrane placed on a semi-
permeable medium. Utilize and incorporate information from Giroud et al. 1997a
as appropriate to interpolate between results obtained using the Giroud equation
(as it was used in Appendix L of the current ICTM Report) and results that would
be obtained using Bernouli's equation.
BASIS FOR INTERROGATORY:
The Construction Report, Second Phase Tailings Management System (Energy Fuels
Nuclear, Inc. 1983) indicates that a gravel-sand mixture derived from crushing of loose
sandstone, with some washed concrete sand in some areas, was used to construct the
compacted bedding layer immediately underlying the geomembrane in Cell 3. That
report also indicates that a similar process and similar materials were used for
constructing the compacted bedding layer beneath the geomembrane liner in Cell 2. On
page L-7 of Appendix L, the saturated hydraulic conductivity for these compacted
bedding layers is assumed to be 2.0 x IO7cm/sec. This value is likely too low to be
representative of these in-place compacted materials. Giroud et al. 1997a developed a
modified methodology for calculating the rate of liquid migration through a defect in a
geomembrane liner underlain by a semi-permeable medium. This modified methodology
appears to be more appropriate for calculating leakage rates through the geomembrane
liners in Cells 3 and 2 and should therefore be used instead of the method used in
Appendix L for estimating flow through defects in liners in Cells 2 and 3.
Additional justification should be provided to support the various assumed geomembrane
defect frequencies for the different geomembrane liners in Cells 2 and 3 vs. Cells 4A and
4B for the lower bound, base case, and upper bound scenarios. Additional justification
should be provided to demonstrate why higher assumed base-case and/or upper bound
defect frequencies would not be considered more reasonably conservative assumptions
and more reasonably representative of actual or potential in-place liner conditions for
some or all of the cell liners for the purpose of estimating potential leakage rates through
the various liner systems. Justify why a lower bound assumption of 1 small defect per
acre for Cells 2 and 3 (the same assumption as made for the base case for Cells 4A and
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4B) is adequately conservative for the Cell 2 and Cell 3 liners given that they were
constructed 30 or more years ago when construction quality assurance practices might
have been somewhat less rigorous than those would have been used during installation of
high density polyethylene geomembranes in Cells 4A and 4B. Additionally, the merit and
applicability of assuming a geomembrane defect frequency (four defects per hectare
(10,000 m2) analogous to that discussed in Giroud et al. 1997b, which suggests an
average of approximately 1.62 defects per acre for a typical defect frequency for a
modern constructed liner, should be discussed for the Cells 4A and 4B liners,
particularly given that this defect frequency was used in previous leakage equations for
calculating leakage rates to support the design of the liner system in Cell 4B. Further,
for assessing a range ofpotential upper bound (worst -case) defect frequencies for the
Cell 2 and Cell 3 liners, consideration should be given to other published data, such as
Nosko and Touze-Folz 2000, which provide estimates of actual liner defect frequencies
(the Nosko and Touze-Folz data suggest a post-construction, pre repair average defect
frequency of approximately 5 defects per acre of liner installed - based on study of over
300 landfill liners before construction quality assurance measures were undertaken to
reduce the presence of defects but not eliminate them completely). Allowance should also
be made for additional defects to occur after liner construction is complete.
REFERENCES:
Denison Mines (USA) Corp. 2010. Revised Infiltration and Contaminant Transport
Modeling Report, White Mesa Mill Site, Blanding, Utah (Revision 2), March 2010.
Energy Fuels Nuclear, Inc. 1983. Construction Report, Second Phase Tailings
Management System. White Mesa Uranium Project. SUA-1358. Docket 40-8681.
Giroud, J.P., King, T.D., Sanglerat, T.R., Hadj-Hamou, T, and Khire, M.V. 1997a.
"Rate of Liquid Migration Through Defects in a Geomembrane Placed on a Semi-
Permeable Medium", Geosynthetics International, Vol. 4, Nos. 3-4, pp. 349-372.
Giroud, J.P., King, T.D., Sanglerat, T.R., Hadj-Hamou, T, and Khire, M. V. 1997b.
"Leachate Flow in Leakage Collection layers Due to Geomembrane Defects ",
Geosynthetics International, Vol. 4, Nos. 3-4, pp. 215-2922.
Nosko, V. and Touze-Foltz, N. 2000. Geomembrane Liner failure: Modeling of its
influence on Contaminant Transfer. Proc. 2nd European Conf. on Geosynthetics,
Bologna, Italy, 2: 557-560.
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INTERROGATORY WHITE MESA REV'D ICTM; R313-24-4 -05/1:
CONTAMINANT TRANSPORT MODELING
PRELIMINARY FINDING:
Refer to UACR313-24-4, which invokes the following requirement from 10CFR40,
Appendix A. Criterion 1: The general goal or broad objective in siting and design
decisions is permanent isolation of tailings and associated contaminants by minimizing
disturbance and dispersion by natural forces, and to do so without ongoing maintenance.
For practical reasons, specific siting decisions and design standards must involve finite
times (e.g., the longevity design standard in Criterion 6). The following site features
which will contribute to such a goal or objective must be considered in selecting among
alternative tailings disposal sites or judging the adequacy of existing tailings sites:
• Remoteness from populated areas;
• Hydrologic and other natural conditions as they contribute to continued
immobilization and isolation of contaminants from ground-water sources; and
• Potential for minimizing erosion, disturbance, and dispersion by natural forces
over the long term.
• The site selection process must be an optimization to the maximum extent
reasonably achievable in terms of these features.
• In the selection of disposal sites, primary emphasis must be given to isolation of
tailings or wastes, a matter having long-term impacts, as opposed to
consideration only of short-term convenience or benefits, such as minimization of
transportation or land acquisition costs. While isolation of tailings will be a
function of both site and engineering design, overriding consideration must be
given to siting features given the long-term nature of the tailings hazards.
Tailings should be disposed of in a manner that no active maintenance is required to
preserve conditions of the site.
INTERROGATORY STATEMENT:
/. Refer to Revised ICTM Report, Section 2.2 Site Characteristics and Section 4.3
Uncertainty and Assumptions: Provide additional information on the potential
presence and distribution of fractures and/or joints, and uncementedfhigher
permeability intervals in the unsaturated zone portions of the Dakota Sandstone
and Burro Canyon geologic units underlying the site area, including the footprint
area of and downgradient vicinity of Cells 1, 2, 3, 4A, and 4B. Describe the
possible effects of such fractures and/or joints, and uncementedfhigher
permeability intervals, on the flow and transport of potential contaminants
through the vadose zone, including potential effects on estimated contaminant
travel times to the perched groundwater zone beneath the tailing management
cells.
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2. Refer to Revised ICTM Report, Section 2.2.4: Please summarize the geochemical
characteristics of the perched groundwater and discuss in greater detail the
potential relevance of perched zone water geochemistry to the development of
specific geochemical modeling input assumptions made for the vadose zone in
Appendix M (address, for example, the effects of dissolved oxygen concentration,
redox conditions).
3. Refer to Revised ICTM Report, Section 3.4.4, Contaminants Modeled: Please
provide the rationale and justification for using aluminum, versus some other
constituent, to obtain charge balance in the HP1 (PHREEQC) simulations.
4. Refer to Appendix C, Table C-4, p. C-15 in Appendix C to the ICTM Report:
Please provide a corrected maximum ANP value for MW-24 and corrected
arithmetic and geometric means for ANP in the TW4-22 boring. Please confirm
the results used in calculating the statistics for all of the borings and revise the
summary statistics presented in Table C-4 as necessary. If the statistical results
in Table C-4 for the entire population change, please revise reactive transport
model as needed, to reflect these changes and report the results.
5. Refer to Appendix M, p. M-10, Paragraphs 2 and 3: Please provide and justify
the bulk density of the bedrock used to convert the ANP and HFO values from
rock mass to rock unit volume.
6. Refer to Appendix M, p. M-ll, Paragraph 1: Please justify the assumption that
the redox conditions in the tailing slimes drainage and the vadose zone are
controlled by the oxygen (O2/H2O) couple. Perform and report results of
sensitivity analyses that assess the dependence of result on variations in the
values of redox value.
7. Refer to Appendix M, p. M-ll, Paragraph 2: Please provide justification for
using a chloride diffusion coefficient (1.75 cm2/day) for seawater in the model.
Perform and report results of sensitivity analyses that assess the dependence of
results on variations in the values of the diffusion coefficient used in analyses.
8. Refer to Appendix M, p. M-ll, Paragraph 4: Please justify the assumption to
establish the initial soil water pressure heads within the bedrock vadose zone as
ik&t-those resulting from percolation at a rate equal to 1% of the average annual
precipitation. Compare the resulting pressure head distribution in the vadose
zone with the water content distribution that could be expected to result from
potential leakage from the tailings cells area, especially the area of Cells 2 and 3
(see also "INTERROGATORY WHITE MESA REV'D ICTM; R313-24-4; 10
CFR40 APPENDIX A, CRITERION 1; INT 04/1; EVALUATION OF POTENTIAL
FLOW THROUGH TAILINGS CELL LINERS").
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9. Refer to Appendix M, Figures M-3 and M-4: Please state and justify the value(s)
of the effective uranium retardation factor that would be consistent with the HP1
model output for the bedrock vadose zone. Please see (summarised in Appendix M
of the Revised ICTM Report, Figures M-3 and M-4,) which shows concentration
profiles for sulfate and uranium, clearly indicating that uranium is transported
more slowly than sulfate. Please quantify the rate of uranium transport relative
to species, such as sulfates, that are not retarded.
10. Refer to Appendix M, Figures M-3 and M-4, pp. M-25 and M-26: Please clarify
why the initial concentrations for sulfate or uranium are not shown at a depth of 0
feet on Figures M-3 and M-4 and/or revise the figures as necessary.
11. Refer to Appendix M, Figure M-4. Please explain why dissolved uranium
concentration at the top of the vadose zone appears to decrease from 50 years to
100 years but then to increase from 100 years to 240 years.
BASIS FOR INTERROGATORY:
The initial soil water pressure heads in the vadose zone beneath existing Cells 2 & 3 may
be higher than the initial soil water pressure heads derived from an assumption of 1% of
the average annual precipitation (1% of 13.3 in/yr or 3.4 mm/yr). Leakage from Cells 2
& 3 may have already occurred. In Appendix L the estimated leakage rate through the
liners in Cell 2 and 3 during the operational phase is calculated as 8.3 mm/yr (Base Case
scenario) with estimated lower and upper bound values of 3.5 and 18 mm/yr; these
values arm likely underpredicted as the methodology used in that calculation does not
appear to be conservative (see also "INTERROGATORY WHITE MESA REV'D ICTM;
R313-24-4; 10 CFR40 APPENDIX A, CRITERION 1; INT 04/1: EVALUATION OF
POTENTIAL FLOW THROUGH TAILINGS CELL LINERS"). Please discuss the
potential effects on vadose zone flow and transport if the initial soil water pressure heads
in the vadose zone were derived from the flux rate through the Cells 2 and 3 liners as
calculated using the alternative flux rate calculation approach (Giroud et al. 1997)
recommended in INTERROGATORY WHITE MESA REV'D ICTM; R313-24-4; 10
CFR40 APPENDIX A, CRITERION 1; INT 04/1: EVALUATION OF POTENTIAL FLOW
THROUGH TAILINGS CELL LINERS".
The presence and distribution offractures and/or joints and/or uncemented zones in the
bedrock materials beneath the tailing management cells area is not discussed in the
Revised ICTM Report, and no discussion is provided regarding the potential effects of
such fractures and/or joints and/or uncemented zones on subsurface contaminant flow
and transport. The possible presence and distribution of such fractures and/or joints in
the bedrock materials should be discussed in the Revised ICTM Report, along with an
evaluation of the potential effects of such fractures and/or joints and/or uncemented
zones on subsurface contaminant flow and transport. For example, the 1978
Environmental Report (e.g., see Dames & Moore 1978., p. 2-106) indicates the
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following: " ...jointing is common in the exposed Dakota-Burro Canyon sandstones along
the mesa's rim...more often than not, the primary joints are parallel to the cliff faces and
the secondary joints are almost perpendicular to the primary joints... two sets of joint
attitudes exist [in these sandstone units] ..to the west side of the project site...These sets
range from N10-18° E and N 60-85 E° and nearly parallel to the cliff faces ".
In addition, information provided by UMETCO (UMETCO 1993, p, 2-3) indicates that
"during an investigation of the White Mesa site, a number offracture attitudes were
measured (in the Dakota and Burro Canyon sandstone units) along the rims of Corral
and Cottonwood Canyons [in the general site area], ..(with) analysis of the data
indicating the presence of two joint sets... [and] distances between the joints in each set
varies from 5 to 20 feet, ...the primary joints strike from north-south to N 20° E with a
vector mean ofNIl°E and the secondary fractures have a strike ranging between N 40°
WtoN 60° Wwith a vector mean ofN4r W... All joint sets observed were near vertical
to vertical."
The boring log for Borehole No. 19 (see Dames & Moore 1978, Plate A-9; International
Uranium Corporation [IUC] 2000, Figure 1.5.3-1), installed near the Cell 4B footprint,
indicates horizontal fracturing may be present at one or more depth zones (e.g., 45 ft,
and 53-58ft below ground surface) within the Dakota Sandstone unit underlying and/or
adjacent to the area of proposed Cell 4B. That boring log also indicates the occurrence
of some orange iron staining and considerable limonite staining along bedding fractures
(which suggest zones of localized movement of groundwater) as well as some uncemented
zones of rock within the Dakota Sandstone materials.
An injection test conducted within the Dakota unit in Boring 19penetrating the Dakota
and Burro Canyon units yielded permeability values that differed by more two orders of
magnitude, depending on whether the tested interval spanned a zone (37.5 - 52.5ft below
ground surface) containing "considerable near horizontal fracturing and some orange
staining " (permeability of 9.12 x 10'4 cm/sec) or had no reported fracturing
(permeability 6.77 x 10'6 cm/sec).
The issue of the potential presence offractures and/or joints and/or uncemented zones in
the bedrock materials beneath and in the vicinity of the Cell 4B tailing management cells
area and the potential effects of such features on vadose zone flow and transport was
previously considered and evaluated in responses provided by Denison Mines (USA)
Corp (DUSA), with attached letters from Hydro Geo Chem, Inc., to First Round
Interrogatories submitted to DUSA by the Division on the Cell 4 B Design Report (DUSA
2010a ) and Second Round Interrogatories submitted to DUSA by the Division on the
License Amendment Request and Environmental Report for Cell 4B (DUSA 2010b;
2010c). A similar discussion/evaluation should be included in the ICTM Report to
assesses the potential significance of such features on the transport modeling
assumptions and approach.
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The maximum ANP value of27g CaCOi/kg rock listed for MW-24 (Table C-14, p. C-15
of Appendix C) does not appear to be correct based on a review of the ACZ analytical
data sheets provided in Appendix A. The correct maximum value appears to be 25 g
CaCOs/kg rock. It also appears that the arithmetic and geometric means for ANP in the
TW4-22 boring may also be incorrect. Data used to randomly check the arithmetic and
geometric means for boring TW4-22 were obtained from the ACZ analytical data sheets.
Statistical results for the entire population presented on Table C-4 are used as input to
the Reactive Transport Model described in Appendix M. If these results change, please
modify the reaction transport model as needed.
The discussion presented in Section 2.2.4 of the ICTM Report refers to a number of
hydrogeologic and background groundwater quality reports but does not summarize
information on any pertinent geochemical conditions that are relevant to the development
of input parameters for use in the transport modeling. The potential relevance of the
perched zone geochemical data, if any, to the development of geochemical modeling
input assumptions made in Appendix M should be discussed and discussion should be
provided as to whether the vadose zone input and results are consistent with existing
perched water geochemical conditions at the site.
The fixed dissolved oxygen concentration (2 mg/L) arbitrarily chosen and used to define
the (O2/H2O) redox couple may be an overestimate of the likely redox potential
conditions in the tailing slimes drainage. With modeling conditions fixed in this way, all
calculations in Eh-pH space will be confined to a line just below the upper stability limit
for water. Bass Becking et al. (I960) and Garrels and Christ (1965) showed the
inadequacy of this approach for all but a few rare surface geologic situations. Redox
equilibrium is typically not established in most waters because of the presence of living
organisms, the dependence of most redox reactions on biological catalysis, and the slow
kinetics of many oxidation and reduction reactions. The redox potential should therefore
correspond to the potential range of the predominant redox reaction under given
conditions.
The tailing slimes drainage chemistry data presented in Table K-l indicate that the
tailing slimes contain ammonia and dissolved iron which suggests that the redox
conditions in the tailing slimes drainage may be less than those defined by the chosen
fixed dissolved oxygen concentration for the oxygen redox couple. It is important to have
a reasonable redox estimate for both the tailing slimes and the vadose zone because *# the
redox potential value controls solubility and/or precipitation of some constituents/solids
such as Fe2+/HFO during reactive transport. For example, if more reducing tailing
slimes drainage percolates through the vadose zone, the assumed redox condition in the
vadose zone may be less and result in the dissolution of HFO which serves as a sorption
site for uranium and other constituents. Thus, less sorption would occur and uranium
might be transported to the underlying perched zone. Because the reactive transport
model will likely be sensitive to redox and the uncertainty in redox, the redox value
should be included as a parameter in the sensitivity analyses.
URS
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March 2012
A summary of the existing dissolved oxygen (DO) and/or oxidation-reduction potential
(ORP) data for the vadose or perched zones, as well as area groundwater seeps should
be presented so that these data can be compared to the dissolved oxygen concentration (2
mg/L) assumed for the vadose zone (pages M-10 thru M-12 in Appendix M) to determine
if the assumed vadose zone oxygen content is consistent with those found in the perched
zone. Relevant information might be found in the INTERA hydrogeology reports,
background reports, etc. cited on pages 2-12 and 2-13 of the Revised ICTM Report.
The diffusion coefficient would be expected to affect transport of solutes through
groundwater, including the amount of time required for peak solute concentrations to
arrive at a downgradient location.
Chloride diffusion coefficients reported in the literature (e.g., Barone et al 1990; Barone
et al 1992; Kincaid et al 1995; Rowe and Badv 1996; Badv and Faridfard 2005) suggest
that a smaller chloride diffusion coefficient may be more reasonable than the one
selected because the salinity of water in the vadose zone will be less than seawater.
Because the reactive transport model will likely be sensitive to the diffusion coefficient,
the diffusion coefficient should be included as a parameter in the sensitivity analyses.
The HP1 reactive transport model (HYDRUS-1D coupled with PHREEQC) does not use
the traditional concept of a distribution coefficient (Kd) from which a retardation factor
can be calculated; rather it uses a surface complexation modeling approach that is
functionally similar to the methodology developed by the U.S. Geological Survey for the
U.S. Nuclear Regulatory Commission, as presented in NUREG/CR-6820 (Davis and
Curtis 2003). According to information presented in Appendix M, in this modeling
approach, uranium adsorption is allowed to compete with other metals, which would
decrease the total amount of uranium that could adsorb. The transport model shows the
concentration front of uranium proceeding more slowly than the concentration of species,
such as sulfate, that are not retarded (see Appendix M, Figures M-3 and M-4).
Therefore, while the conceptual basis of the transport model is different from a simple Kd
and retardation factor approach, the predicted uranium transport could still be described
by an "effective " retardation factor, e.g., relative to the "effective " retardation factors
for other modeled species. An estimate should be made of effective retardation factor for
uranium, that would be consistent with the output of the reactive transport model, and the
resulting predicted "effective " attenuation behavior for uranium should be further
discussed and compared to observations or model predictions for other case studies/
similar sites, if available, and further discussion and evaluation provided in the context
of demonstrating the suitability/adequacy of the modeling approach used.
The model results depicted on Figures M-3 and M-4 do not appear to show the initial
concentrations for sulfate (62,847 mg/L) or uranium (24.3 mg/L) introduced at depth 0
feet. The initial concentrations should be shown.
URS
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March 2012
REFERENCES:
Badv, K. and M. R. Faridfard. 2005. Laboratory determination of water retention and
diffusion coefficient in unsaturated sand. Water, Air, and Soil Pollution, v. 161, no. 1-4,
pp. 25-38
Barone, F. S.; R. K. Rowe, R. M. Quigley. 1990. Laboratory determination of chloride
diffusion coefficient in an intact shale. Canadian Geotechnical Journal, v. 27, no. 2,
(April), pp. 177-184.
Barone, F. S.; R. K. Rowe, R. M. Quigley. 1992. Estimation of chloride diffusion
coefficient and tortuosity factor for muds tone. Journal of Geological Engineering, v. 118,
no. 7, (July), pp. 1031-1046.
Bass-Becking, L.G.M., I.R. Kaplan, and D. Moore. I960. Limits of the natural
environment in terms ofpH and oxidation-reduction potentials. Journal of Geology, v.
68, pp. 243 - 284.
Dames & Moore 1978. Environmental Report - White Mesa Uranium Project, San Juan
County, Utah for Energy Fuels Nuclear, Inc. January 30.
Davis, J.A., and G.P. Curtis, 2003. Application of Surface Complexation Modeling to
Describe Uranium(VI) Adsorption and Retardation at the Uranium Mill Tailings Site
at Naturita, Colorado, Report NUREG CR-6820, U. S. Nuclear Regulatory
Commission, Rockville, MD., pp. 223.
Denison Mines (USA) Corp. 2010a. Round 1 - Interrogatory Response for the Cell 4B
Design Report, White Mesa Mill Site, Blanding, Utah. January 2010.
Denison Mines (USA) Corp. 2010b, Second Round of Interrogatories from Review of
License Amendment and Environmental Report for Cell 4B. DUSA Letter with
attachment dated February 8, 2010.
Denison Mines (USA) Corp. 2010c. Second Round of Interrogatories from Review of
License Amendment and Environmental Report for Cell 4B. DUSA Letter with
attachment dated February 12, 2010.
Denison Mines (USA) Corp. 201 Od. Revised Infiltration and Contaminant Transport
Modeling Report, White Mesa Mill Site, Blanding, Utah (Revision 2), March 2010.
Garrels, R.M and C. L. Christ. 1965. Solutions, Minerals, and Equilibria. Freeman,
Cooper & Company, San Francisco, California. 450pp.
URS
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March 2012
Giroud, J.P., King, T.D., Sanglerat, T.R., Hadj-Hamou, T, and Khire, M. V. 1997. Rate
of Liquid Migration Through Defects in a Geomembrane Placed on a Semi-Permeable
Medium", Geosynthetics International, Vol. 4, Nos. 3-4, pp. 349-372.
International Uranium (USA) Corporation (IUC). 2000. Reclamation Plan - White Mesa
Mill, Blanding, Utah. Source Material Reference No. SUA-1358. Docket No. 40-8681.
Rev. 3, July.
Kincaid, C. T, J. W. Shade, G. A. Whyatt, M. G. Piepho, K. Rhoads, J. A. Voogd, J. H.
Westsik, Jr., M. D. Freshley, K. A. Blanchard, B. G. Lauzon. 1995. Performance
Assessment of Grouted Double-Shell Tank Waste Disposal at Hanford, WHC-SD-WM-
EE-004, Rev. 1, Westinghouse Hanford Company. Richland, WA.
Rowe, R. K. and K. Badv. 1996. Chloride migration through clayey silt underlain by fine
sand or silt. Journal of Geotechnical Engineering, v. 122, no. 1 (January), pp. 60-68.
UMETCO Minerals Corporation 1993. Peel Environmental Services. Groundwater
Study, White Mesa Mill. January.
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UTAH DIVISION OF RADIATION CONTROL
DENISON MINES (USA) CORP'S
WHITE MESA RECLAMATION PLAN, REV. 5.0
INTERROGATORIES - ROUND 1
MARCH 2012
i
TABLE OF CONTENTS
Section Page
ACRONYMS AND ABBREVIATIONS iii
INTERROGATORY WHITEMESA RECPLAN REV 5.0; R313-24-4; 10CFR40.31(H); INT 01/1:
RESPONSES TO RECLAMATION PLAN REV. 4.0 INTERROGATORIES 1
INTERROGATORY WHITEMESA RECPLAN REV 5.0; R313-24-4; 10CFR40, APPENDIX A,
CRITERION 4; INT 02/1: ENGINEERING DRAWINGS 3
INTERROGATORY WHITEMESA RECPLAN Rev. 5.0; R313-24-4; 10CFR40 APPENDIX A
CRITERIA 1 AND 4; INT 03/1: CONSTRUCTION QUALITY ASSURANCE/QUALITY
CONTROL PLAN, COVER CONSTRUCT ABILITY, AND FILTER AND ROCK RIP RAP
LAYER CRITERIA AND PLACEMENT 5
INTERROGATORY WHITEMESA RECPLAN Rev5.0; R313-24-4; 10CFR40, APPENDIX A,
CRITERION 4; INT 04/1: VOID SPACE CRITERIA AND DEBRIS, RUBBLE PLACEMENT
AND SOIL/BACKFILL REQUIREMENTS 8
INTERROGATORY WHITEMESA RECPLAN Rev. 5.0 R313-24-4, 10 CFR 40 APPENDIX A; INT
05/1: SEISMIC HAZARD EVALUATION 13
INTERROGATORY WHITEMESA RECPLAN REV5.0; R313-24-4; 10CFR40 APPENDIX A,
CRITERION 1; INT 06/1: SLOPE STABILITY 16
INTERROGATORY WHITEMESA RECPLAN Rev. 5.0; R313-24-4; 10 CFR 40 APPENDIX A,
CRITERION 4; INT 07/1: TECHNICAL ANALYSIS - SETTLEMENT AND POTENTIAL
FOR COVER SLOPE REVERSAL AND/OR COVER LAYER CRACKING 25
INTERROGATORY WHITEMESA RECPLAN Rev5.0 R313-24-4; 10cfr40 APPENDIX A
CRITERION 4; INT 08/1: TECHNICAL ANALYSIS -EROSION STABILITY EVALUATION
34
INTERROGATORY WHITEMESA RECPLAN Rev. 5.0; R313-24-4; 10CFR40 APPENDIX A
CRITERION 1; INT 09/1: LIQUEFACTION 39
INTERROGATORY WHITEMESA RECPLAN 5.0 R313-24-4; 10CFR40 APPENDIX A, CRITERION
6; INT 10/1: TECHNICAL ANALYSES - FROST PENETRATION ANALYSIS 43
INTERROGATORY WHITE MESA RECPLAN REV 5.0 R313-24-4; 10CFR40 APPENDIX A; INT
11/1: VEGETATION AND BIOINTRUSION EVUALATION AND REVEGETATION PLAN
46
INTERROGATORY WHITEMESA RECPLAN REV 5.0 R313-24-4; 10CFR40 APPENDIX A,
CRITERION 6(4); INT 12/1: REPORT RADON BARRIER EFFECTIVENESS 52
INTERROGATORY WHITEMESA RECPLAN REV 5.0 R313-24-4; 10CFR40, APPENDIX A,
CRITERION 6(6); DMT 13/1: CONCENTRATIONS OF RADIONUCLIDES OTHER THAN
RADIUM IN SOIL 57
INTERROGATORY WHITE MESA RECPLAN REV 5.0 R313-24-4; 10CFR40 APPENDIX A; INT
14/1: COVER TEST SECTION AND TEST PAD MONITORING PROGRAMS 59
INTERROGATORY WHITEMESA RECPLAN REV 5.0 R313-24-4; 10CFR40, APPENDIX A,
CRITERION 9; INT 15/1: FINANCIAL SURETY ARRANGEMENTS 65
INTERROGATORY WHITE MESA REC PLAN REV 5.0 R313-15-501; INT 16/1; RADIATION
PROTECTION MANUAL -. 68
INTERROGATORY WHITE MESA REC PLAN REV 5.0 R313-15-1002; INT 17/1; RELEASE
SURVEYS 69
INTERROGATORY WHITE MESA REC PLAN REV 5.0 R313-12; INT 18/1: INSPECTION AND
QUALITY ASSURANCE 70
INTERROGATORY WHITE MESA REC PLAN REV 5.0 R313-24; 10 CFR 40.42(J); INT 19/1:
REGULATORY GUIDANCE 71
PRELIMINARY DRAFT i PRELIMINARY DRAFT
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March 2012 W*WJ
INTERROGATORY WHITE MESA REC PLAN REV 5.0 R313-24,; 10 CFR 40 APPENDIX A
CRITERION 6(6); INT 20/1: SCOPING, CHARACTERIZATION, AND FINAL SURVEYS ..72
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ACRONYMS AND ABBREVIATIONS
ALARA As Low As Reasonably Achievable
BMF Berggren Model Formula
Cc Coefficient of Consolidation, cubic centimeter
CERCLA Comprehensive Environmental Response, Compensation, and Liability
Act
CFR Code of Federal Regulations
CLSM Controlled low strength material (grout)
cm centimeter
CQA Construction Quality Assurance (officer)
Cv Coefficient of Compression
DOE U.S. Department of Energy
DUSA Denison Mines (USA) Corp
D15, D5o, Das, etc. Diameter of soil particle below which 15%, 50%, 85%, etc. of the mass of
a sample is comprised of this or smaller sized particles
EPA U.S. Environmental Protection Agency
ET Evapotranspiration
F Fahrenheit
ft foot
g gram; gravitational acceleration (32.2 ft/sec
IBC International Building Code
ICTM Infiltration and Contaminant Transport Modeling
km kilometer; 1000 meters
m meter
MARS AME Multi-Agency Radiation Survey and Assessment of Materials and
Equipment Manual
MARSSIM Multi-Agency Radiation Survey and Site and Investigation Manual
MCE Maximum Credible Earthquake
mg/l milligram per liter
mi mile
mm millimeter
MUSLE Modified Universal Soil Loss Equation
NRC U.S. Nuclear Regulatory Commission
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NRCS Natural Resources Conservation Service
NUREG Label denoting a collection of documents published by the US Nuclear
Regulatory Commission
pcf pounds per cubic foot
pCi picocurie; 10"12 curie
PGA Peak ground acceleration
PMP Probable Maximum Precipitation (event)
psf pounds per square foot
QA/QC Quality assurance/quality control
RCRA Resource Conservation and Recovery Act
Rev. Revision
RG, RegGuide Regulatory Guide (NRC)
sec second, Section
SPT Standard Penetration Test
TEDE Total Effective Dose Equivalent
T.O.C. Table of Contents
UAC Utah Administrative Code
USGS United States Geologic Survey
Vs30 average shear-velocity down to 30 m
5h:lv/10v:lh five/ten horizontal units (5h/10h) to one vertical unit (1 v); represents slope
or steepness
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INTERROGATORY WHITEMESA RECPLAN REV 5.0; R313-24-4; 10CFR40.31(H);
INT 01/1: RESPONSES TO RECLAMATION PLAN REV. 4.0 INTERROGATORIES
REGULATORY BASIS:
UAC R313-24-4 invokes the following requirement from 10CFR40.31(h): An application for a
license to receive, possess, and use source material for uranium or thorium milling or byproduct
material, as defined in 10CFR40, at sites formerly associated with such milling shall contain
proposed written specifications relating to milling operations and the disposition of the
byproduct material to achieve the requirements and objectives set forth in appendix A of
10CFR40. Each application must clearly demonstrate how the requirements and objectives set
forth in appendix A of 10CFR40 have been addressed. Failure to clearly demonstrate how the
requirements and objectives in Appendix A have been addressed shall be grounds for refusing to
accept an application.
INTERROGATORY STATEMENT:
The Division has reviewed the responses to Reclamation Plan 4.0 and is not asking for
additional information at this time; however, the Division reserves the right and may submit
comments and/or additional interrogatories following completion of review of the Denison
Mines (USA) Corp (DUSA) response document dated December 28, 2011 (DUSA 2011).
BASIS FOR INTERROGATORY:
The State transmitted Interrogatory Round 1 following its review and evaluation of Reclamation
Plan Rev. 4.0 (o/a September 10, 2010). A meeting was held on October 5, 2010 with DUSA
personnel regarding Denison's plan to prepare and submit a Reclamation Plan Rev. 5.0
incorporating an evapotranspiration cover system. The State prepared and issued Interrogatory
Round IA for the purpose of giving guidance to DUSA on topics that it must address in
Reclamation Plan Rev. 5.0 for matters relating to the evapotranspiration cover system. A
complete review of DUSA's December 28, 2011 response to the Round 1 and Round IA must be
performed to ensure that all issues that are still relevant have been adequately addressed.
The Division received a letter from Denison Mines (USA) Corp (DUSA ) dated December 28,
2011 (DUSA 2011) that provided responses) to: (i) Round 1 and Round IA interrogatories that
were submitted to DUSA on Rev. 4.0 of the Reclamation Plan Rev. (DUSA 2009) in 2010
(Division 2010); and (ii) Round IA interrogatories that were submitted to DUSA in 2011
(Division 2011) regarding an alternative cover system design that was proposed by DUSA in
2010 (see DUSA letter dated October 6, 2010 [DUSA 2010]. The December 28, 2011 response
document was forwarded to URS Corporation on February 23, 2012 and is currently under
review.
REFERENCES:
Denison Mines (USA) Corp. 2009. Reclamation Plan, White Mesa Mill, Blanding, Utah,
Radioactive Materials License No. UT1900479, Revision 4.0, November 2009.
Denison Mines (USA) Corp. 2011. Responses to Supplemental Interrogatories - Round IA for
Reclamation Plan, Revision 4.0, November 2009. December 28, 2011.
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March 2012 URS
Division (Utah Division of Radiation Control) 2010. Denison Mines (USA) Corporation
Reclamation Plan, Revision 4.0, November 2009: Interrogatories - Round I. September 2010
Division (Utah Division of Radiation Control) 2011. Denison Mines (USA) Corporation
Reclamation Plan, Revision 4.0, November 2009: Supplemental Interrogatories - Round IA.
April 2011.
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INTERROGATORY WHITEMESA RECPLAN REV 5.0; R313-24-4; 10CFR40,
APPENDIX A, CRITERION 4; INT 02/1: ENGINEERING DRAWINGS
REGULATORY BASIS:
UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 4:
"The following site and design criteria must be adhered to whether tailings or wastes are
disposed of above or below grade:
... (c) Embankment and cover slopes must be relatively flat after final stabilization to minimize
erosion potential and to provide conservative factors of safety assuring long-term stability. The
broad objective should be to contour final slopes to grades which are as close as possible to
those which would be provided if tailings were disposed of below grade; this could, for example,
lead to slopes of about 10 horizontal to 1 vertical (10h:lv) or less steep. In general, slopes
should not be steeper than about 5h:lv. Where steeper slopes are proposed, reasons why a slope
less steep than 5h:lv would be impracticable should be provided, and compensating factors and
conditions which make such slopes acceptable should be identified.
(d) A full self-sustaining vegetative cover must be established or rock cover employed to reduce
wind and water erosion to negligible levels.
Where a full vegetative cover is not likely to be self-sustaining due to climatic or other
conditions, such as in semi-arid and arid regions, rock cover must be employed on slopes of the
impoundment system. The Executive Secretary will consider relaxing this requirement for
extremely gentle slopes such as those which may exist on the top of the pile.
....Furthermore, all impoundment surfaces must be contoured to avoid areas of concentrated
surface runoff or abrupt or sharp changes in slope gradient. In addition to rock cover on slopes,
areas toward which surface runoff might be directed must be well protected with substantial rock
cover (rip rap). In addition to providing for stability of the impoundment system itself, overall
stability, erosion potential, and geomorphology of surrounding terrain must be evaluated to
assure that there are not ongoing or potential processes, such as gully erosion, which would lead
to impoundment instability."
NUREG-1620, Section 2.5.3: The assessment of the disposal cell cover design and engineering
parameters will be acceptable if it meets the following criteria:
(3) Details are presented (including sketches) of the disposal cell cover termination at boundaries,
with any considerations for safely accommodating subsurface water flows.
(4) A schematic diagram displaying various disposal cell layers and thicknesses is provided. The
particle size gradation of the disposal cell bedding layer and the rock layer are established to
ensure stability against particle migration during the period of regulatory interest (NRC 1982).
INTERROGATORY STATEMENT:
Drawing REC-1: Provide design details for Discharge Channel.
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March 2012 URS
Drawing REC-3: Provide design details for Discharge Channel. Identify the limits of the
proposed Sedimentation Pond.
Establish and indicate on the appropriate drawing(s) the location of the main drainage channel.
Demonstrate that the Cell 1 embankment and appurtenant apron are designed to remain stable
under PMP conditions.
Drawing TRC-2: Correct the location shown by green dashes for the "Approximate limit of
compacted cover,"
Drawing TRC-4: State where "Filter Layer" is defined. Link Rock Apron A and Rock Apron B
to characteristics presented in the table at Detail 1/8.
Drawing TRC-5: In Sections A/3 and B/3, indicate the cover thickness to be 9 feet minimum.
State the maximum tailings elevation on the North end of each section.
Drawing TRC-6: Please explain why the Compacted Cover cannot continue through the entire
sections rather that terminating as "wedges ".
Drawing TRC-7: Please explain why the Compacted Cover cannot continue through the entire
sections rather that terminating as "wedges ". State maximum slope on transitional slopes in
Section A/3, B/3, and C/3 to be 5:1. State maximum tailings elevations in each section.
Drawing TRC-8: Revise both the Plan and the Elevation of Detail 1/8 to refer to the table
provided below rather than stating D50 = 7.4" min. State where "Filter Layer " is defined.
Show the "Riprap Filter Layer" on the side slopes of Details 3/5, Detail 4/8, and Detail 5/8 or
otherwise resolve the conflict involving "Riprap Filter Layer " that exists between Detail 1/8 and
the details cited. State where "Clay Liner " called out in Detail 4/8 is defined. Justify
terminating the "Clay Liner" shown in Detail 4/8 at the exterior extreme (of top) of the "Radon
Attenuation and Grading Layer". State the cover thickness shown in Detail 4/8 to be 9 feet
minimum. Show the correct maximum tailings elevations in Details 6/8 (presently incorrectly
stated) and 7/8 (presently not stated).
BASIS FOR INTERROGATORY:
The Licensee should resolve conflicts, clarify ambiguities, and provide missing information to
properly document the proposed designs.
Upstream of the discharge channel, it appears that drainage from precipitation events would
likely create a random main drainage channel location in Cell 1. It is not desirable for this
drainage channel to have the northern toe of the Cell 1 dike as a channel wall. Controlling the
location of drainage channeling in Cell 1 appears to be important. Without establishing the
location of the main drainage channel location, the Cell 1 embankment and appurtenant apron
would need to be designed to be stable under PMP drainage channel wall depth and velocities.
Note: Drawing TRC-4 shows topsoil and vegetation east of the riprap rock in Cell 1 and bedrock
to the west.
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REFERENCES:
NRC 1992. "Preparation of Environmental Reports for Uranium Mills, " Regulatory Guide 3.8,
October, 1992.
NRC 2003. Standard Review Plan for the Review of a Reclamation Plan for Mill Tailings Sites
under Title II of the Uranium Mill Tailings Radiation Control Act of1978. Washington DC, June
2003.
NRC 2008. "Standard Format and Content Of License Applications for Conventional Uranium
Mills, " Draft Regulatory Guide DG-3024, Ma, 2008.
INTERROGATORY WHITEMESA RECPLAN REV. 5.0; R313-24-4; 10CFR40
APPENDIX A CRITERIA 1 AND 4; INT 03/1: CONSTRUCTION QUALITY
ASSURANCE/QUALITY CONTROL PLAN, COVER CONSTRUCTABILITY, AND
FILTER AND ROCK RIP RAP LAYER CRITERIA AND PLACEMENT
REGULATORY BASIS:
UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 1: " The
general goal or broad objective in siting and design decisions is permanent isolation of tailings
and associated contaminants by minimizing disturbance and dispersion by natural forces, and to
do so without ongoing maintenance. For practical reasons, specific siting decisions and design
standards must involve finite times (e.g., the longevity design standard in Criterion 6)...
UAC R313-24-4 invokes the following requirement from 10CFR40. Appendix A. Criterion 4:
"The following site and design criteria must be adhered to whether tailings or wastes are
disposed of above or below grade:
... (c) Embankment and cover slopes must be relatively flat after final stabilization to minimize
erosion potential and to provide conservative factors of safety assuring long-term stability. The
broad objective should be to contour final slopes to grades which are as close as possible to
those which would be provided if tailings were disposed of below grade; this could, for example,
lead to slopes of about 10 horizontal to 1 vertical (10h:lv) or less steep. In general, slopes
should not be steeper than about 5h:lv. Where steeper slopes are proposed, reasons why a slope
less steep than 5h:lv would be impracticable should be provided, and compensating factors and
conditions which make such slopes acceptable should be identified.
(d) A full self-sustaining vegetative cover must be established or rock cover employed to reduce
wind and water erosion to negligible levels.
Where a full vegetative cover is not likely to be self-sustaining due to climatic or other
conditions, such as in semi-arid and arid regions, rock cover must be employed on slopes of the
impoundment system. The Executive Secretary will consider relaxing this requirement for
extremely gentle slopes such as those which may exist on the top of the pile.
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....Furthermore, all impoundment surfaces must be contoured to avoid areas of concentrated
surface runoff or abrupt or sharp changes in slope gradient. In addition to rock cover on slopes,
areas toward which surface runoff might be directed must be well protected with substantial rock
cover (rip rap). In addition to providing for stability of the impoundment system itself, overall
stability, erosion potential, and geomorphology of surrounding terrain must be evaluated to
assure that there are not ongoing or potential processes, such as gully erosion, which would lead
to impoundment instability."
INTERROGATORY STATEMENT:
Refer to Section 5 of Attachment B, Construction Quality Assurance/Quality Control Plan, to
the Reclamation Plan, Rev. 5.0: Please provide the following:
1. In Sections 5.3 and 5.4, clarify the nature and characteristics of wastes that would be
placed into the reclaimed Cell 1 footprint area within which the 1-foot-thick compacted
clay liner would first be installed. Verify whether and state consistently throughout the
CQA/CQC Plan whether any uranium mill tailings materials would be placed into the
clay-lined Cell 1 footprint area. If no tailings will be placed in the Cell 1 area, then
change the name ("Cell 1 Tailings Area ") given in the T.O.C., and Sections 1.1, 5.3,
5.4.2, and 5.6 of the CQA/CQA Plan to "Cell 1 Contaminated Soil and Demolition
Debris Disposal Area " or other name as appropriate, and revise the descriptions of
waste materials to be placed into the clay-lined Cell 1 area as needed throughout the
CQA/CQC Plan to be consistent with the proposed disposal plan.
2. In Sections 5.6.4 and 5.6.5, provide a detailed justification to support the technical
appropriateness and the constructability of the proposed topslope areas of the proposed
cover system having such extremely flat slopes (e.g. 0.1 to 0.82 %). Provide information
demonstrating that such topslope areas of the cover could be constructed with such
shallow inclinations maintained continuously over the long distances that are required
based on the currently proposed over design drawings such that no areas of runoff
concentration or areas where ponding or could occur would result. Provide information
justifying that appropriate required tolerances specified for final grades for ensuring
conformance to the proposed extremely flat slope inclinations can be maintained and
measured in the field with sufficient accuracy to ensure compliance with the specified
slope requirements.
3. In Section 5.7.1.2, described material sampling frequency and filter gradation and filter
permeability calculations (with associated acceptance criteria) that will be performed for
the granular materials used in constructing the granular filter layer beneath the riprap
layer on the sideslopes, to ensure that all applicable filter acceptance criteria will be
achieved between the granular filter layer and each topslope cover layer component.
4. In Section 5.7.1, specify the minimum required thickness of the rock riprap layer on the
sideslopes - equal to 1.5 times the DM of the rock rip diameter of 7.4 inches, or the Dwo
of the rock rip rap materials, whichever is greater, as per NUREG-1623 (NRC 2002) -
for clarity and transparency in the CQA/CQC process.
5. In Sections 5.7.2, 5.7.4, and 5.7.5 provide additional details regarding the minimum
thickness for placed riprap layer material and requirements for using specialized
equipment or rearranging of rocks by hand, as needed, in accordance with the specified
minimum required final thickness of the rock rip rap layer. Also provide additional
details and requirements regarding procedures to be used to verify proper in-place rock
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riprap layer thickness and procedures for gradation testing in a completed initial riprap
layer section, and for visual observations of the test section by field personnel. Provide
criteria and procedures for testing additional test sections where observations suggest
rock placement appears to be inadequate or where difficulties are experienced during
rock place activities.
BASIS FOR INTERROGATORY:
In Section 5.4.4 of the CQA.CQC it states that backfill materials placed around placed
demolition debris might include stockpiled soils, contaminated soils, tailings and or other
approved materials [as approved by the Construction Manager and CQA officer]; however, in
other sections of the CQA/CQAC Plan and in the Reclamation Plan it is indicated that no
tailings placement would occur in the Cell 1 area.
The ability to accurately construct the extremely flat topslope areas with a uniform slope to the
proposed specified grades and within the associated allowable tolerances, and the ability to
accurately verify that these fiat slopes have been constructed uniformly and without the
occurrence of areas offlow concentrations or areas where ponding of water could occur has not
been adequately demonstrated.
It has not been adequately demonstrated that all applicable filter layer criteria have been met for
all interfaces that would occur between the sideslope filter layer and topslope cover components.
NUREG-1623 (NRC 2002), Section 2.1.2 recommends that the minimum required thickness of a
rock riprap layer be no less than 1.5 times the Dso of the rock riprap materials, or the D/oo of
the rock rip rap materials, whichever is greater.
NUREG-1623 (NRC 2002), Appendix Fprovides specific recommendations regarding rock rip
placement procedures and procedures for conducting testing and visual observations during
rock rip rap placement that should be adhered to during construction and that should be
addressed in the CQA/CQC Plan.
REFERENCES:
NRC 2002. U.S. Nuclear Regulatory Commission, "Design of Erosion Protection for Long-Term
Stability", NUREG-1623, September 2002.
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INTERROGATORY WHITEMESA RECPLAN REV5.0; R313-24-4; 10CFR40,
APPENDIX A, CRITERION 4; INT 04/1: VOID SPACE CRITERIA AND DEBRIS,
RUBBLE PLACEMENT AND SOIL/BACKFILL REQUIREMENTS
REGULATORY BASIS:
UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 4: "The
following site and design criteria must be adhered to whether tailings or wastes are disposed of
above or below grade:
...(c) Embankment and cover slopes must be relatively flat after final stabilization to minimize
erosion potential and to provide conservative factors of safety assuring long-term stability. The
broad objective should be to contour final slopes to grades which are as close as possible to
those which would be provided if tailings were disposed of below grade; this could, for example,
lead to slopes of about 10 horizontal to 1 vertical (10h.lv) or less steep. In general, slopes
should not be steeper than about 5h:lv. Where steeper slopes are proposed, reasons why a slope
less steep than 5h:lv would be impracticable should be provided, and compensating factors and
conditions which make such slopes acceptable should be identified.
(d) A full self-sustaining vegetative cover must be established or rock cover employed to reduce
wind and water erosion to negligible levels.
Where a full vegetative cover is not likely to be self-sustaining due to climatic or other
conditions, such as in semi-arid and arid regions, rock cover must be employed on slopes of the
impoundment system. The Executive Secretary will consider relaxing this requirement for
extremely gentle slopes such as those which may exist on the top of the pile.
...Rock covering of slopes may be unnecessary where top covers are very thick (or less); bulk
cover materials have inherently favorable erosion resistance characteristics; and, there is
negligible drainage catchment area upstream of the pile and good wind protection as described
in points (a) and (b) of this criterion.
Furthermore, all impoundment surfaces must be contoured to avoid areas of concentrated
surface runoff or abrupt or sharp changes in slope gradient. In addition to rock cover on slopes,
areas toward which surface runoff might be directed must be well protected with substantial rock
cover (rip rap). In addition to providing for stability of the impoundment system itself, overall
stability, erosion potential, and geomorphology of surrounding terrain must be evaluated to
assure that there are not ongoing or potential processes, such as gully erosion, which would lead
to impoundment instability.
INTERROGATORY STATEMENT:
1. Refer to Section 6.0 of Appendix G and Section 7.0 of Attachment A (Technical
Specifications) of the Reclamation Plan, Rev. 5.0:
a. Please define and justify a maximum void space percentage that will be allowed when
disposing of demolition and decommissioning debris fragments and rubble in Cell 1.
Describe, in detail, construction practices that will enable satisfying this specified
limit.
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b. Please provide detailed procedures that will be used to control residual voids to meet
the specified maximum allowable void space percentage(s) and a description of the
specific construction quality assurance / quality control and verification procedures
to be used to demonstrate that the void space criteria will be achieved.
c. Demonstrate how the percentage of allowable void space relates to the settlement
analyses performed to evaluate the effectiveness of the procedures for placing debris
fragments and rubble, placement of backfill in/around/under debris items, and
compaction of the debris/backfill materials, for precluding the potential for slope
reversal in the Celll cover system. Please also refer to "INTERROGATORY
WHITEMESA RECPLAN REV. 5.0; R313-24-4; 10CFR40 APPENDLXA; INT 07/1:
TECHNICAL ANALYSIS - SETTLEMENT AND POTENTIAL FOR COVER SLOPE
REVERSAL AND/OR COVER LAYER CRACKING".
d. Please further define the characteristics of, and estimate the percentage of organic
materials (including, for example, wood, branches, roots, paper, and plastic),
expected to be disposed of. Provide specifications and procedures for disposing of
organic materials such that long-term biodegradation of the disposed organic
materials will not compromise the integrity and stability of the cover system.
e. Please provide detailed specifications for segmenting and placing metallic waste
materials in layers so that structural shapes or other large pieces will not lie across
or on top of each other. Please indicate that placement of metallic materials will
allow large voids to be minimized and filled with soil. Please address special
handling and disposal procedures for oversized and/or odd-shaped steel materials,
including cutting or trimming dimensions before positioning for burial, and
placement procedures to ensure that no large "slip planes " will occur within the
disposal mass. Specify maximum allowable lift thickness for such material
placement. Please also describe shredding, cutting or trimming procedures required
to ensure that such materials following shredding, cutting or trimming can be placed
within the specified allowable layer thickness.
f. Provide additional details of type of materials and placement practices, including
specific dimensions of all demolition debris expected to be disposed of in Cell 1.
Please justify that items needing to be size-reduced prior to disposal will in fact be
size reduced. Provide additional information to justify that a maximum allowable size
of dismantled or cut materials of 20 feet in the longest dimension (as proposed) and a
maximum volume of 30 cubic feet are acceptable criteria for placement of such
objects in a disposal cell.
g. Please provide a contingency plan to address the situation in which an insufficient
quantity of demolition debris and rubble and contaminated soil would be available to
fill the Cell 1 footprint area to a sufficiently high final waste grading configuration to
provide a smooth, continuous transition between the completed Cell 1 cover system
and the Cell 2 cover system, with no sudden, abrupt changes in slope between the two
cover systems. Discuss means and methods that will be used, regardless of achieved
final debris/rubble/contaminated soil placement grades, for ensuring that a smooth
cover slope transition will occur between these two cell area cover systems.
h. Clearly and consistently define procedures/specifications for backfilling of interior
void spaces inside debris objects (e.g., backfill of insides of smaller segmented pipe
sections). Rectify apparent current inconsistencies between descriptions of backfill
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materials proposed for such use as described in Attachment A (e.g., controlled low-
strength materials fCLSMJ or flowable fill) and backfill materials for this use as
described in Appendix (random fill materials). Provide rationale for selecting
preferred backfill materials (e.g., CLSM) for different types and/or sizes of internal
void space, as appropriate. For CLSM/flowable fill, etc... used, provide information
on the minimum required compressible strength of the material,
i. Describe how the compressive strength requirement for CLSM or other grout backfill,
in conjunction with the void space backfilling requirements and ultimate allowable
void space and organic waste percentages relate to the design objectives for
minimizing settlement of the backfilled Cell 1 area debris/rubble/backfill mass to
preclude the possibility for long-term cover slope reversals.
BASIS FOR INTERROGATORY:
The placement of debris materials in the reclaimed tailings embankment has the potential to
create voids or areas of insufficient compaction. The presence of excessive voids in the final
reclaimed waste disposal embankment following waste placement and construction of the final
closure cover could lead to unacceptable amounts of long-term total or differential settlement in
the reclaimed embankment. Excessive amounts of such settlement could impact the integrity of
the final closure cover system, and, if sufficient in extent, result in localized slope change(s)
and/or slope reversals) in the final slopes of the reclaimed embankment. A slope reversal would
create an opportunity for localized ponding of moisture or water which could result in increased
infiltration rates through the embankment. To address/mitigate potential concerns relating to
settlement following waste placement, procedures for placing and compacting soil and debris
wastes should incorporate several requirements, including specifying a method or methods for
filling of larger-sized void spaces (e.g., with CLSM/flowable fill or other grout, etc..) that
cannot be readily accessed by standard construction equipment for backfilling with soil or
tailings.
Appendix G to the Reclamation Plan Rev. 5.0 states "Contaminated soils will be disposed of in
last active tailings cell or Cell 1. Contaminated soils will be placed in the last active cell or Cell
1 as random fill material (material used to fill voids within mill material, achieve desired cover
system slopes, and provide a firm base for construction of the cover system) ". In contrast,
Attachment A to the Reclamation Plan Rev. 5.0 states " ...The voids on the inside of the item shall
be filled with sand or grout (controlled low-strength material, flowable fill, etc.) ". Clarification
needs to be made on which method/methods will be used for filling larger-sized void spaces.
It is recommended that if the void space resulting from placement of such large concrete
monoliths is greater than approximately 5%, then an acceptable cement grout or flowable fill
such as controlled low-strength material be placed between the monoliths, or alternativelythat
monoliths be placed far enough apart to allow proper equipment access to compact as
necessary.
Attachment A to the Reclamation Plan Rev. 5 states that "the maximum size of dismantled or cut
materials shall not exceed 20 feet in the longest dimension and a maximum volume of 30 cubic
feet for placement in the cells ". Additional justification needs to be provided to demonstrate that
these dimensions will be adequate for disposal with respect to minimizing potential for
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differential settlement occurring within the disposal cell. For other similar projects (e.g., DOE
1995; DOE 2000), based on experience gained at several uranium mill demolition debris and
rubble disposal projects, specified the following procedures for placing and compacting soil and
debris and rubble wastes into tailings repositories to address/mitigate potential concerns
relating to settlement:
• Limiting the maximum dimension of larger-sized debris items to a maximum allowable
length (e.g., 10 ft) in longest dimension;
• Limiting at least one dimension of larger-sized debris items to no more than a maximum
allowable width (e.g., 10 to 12 inches for pipes); and
• Specifying a method or methods for filling of larger-sized void spaces (e.g., with flowable
fill or grout) that cannot be readily accessed by standard construction equipment for
backfilling with soil or tailings.
To accomplish the above objectives, it was specified that larger sized items be placed as flatly as
possible rather than in a tangled mass that could result in "nesting", i.e., result in a
compressible mass that would be subject to excessive compression as additional fill is placed
and compacted. For these projects, individual loads of larger sized items were also specified to
be spread out as necessary to ensure proper filling of any open voids with contaminated soil or
tailings and so that contaminated soil or tailings backfill materials and the debris items could be
adequately compacted.
Additionally, these projects included specifications that window frames, siding, and roofing
material be placed and compacted, at a minimum, as pieces or stacks of such materials (e.g.,
bundles of siding) in an 18-inch lift, occasionally increased to 24 inches for taller bundles of
wood pieces; that placement be accomplished in a compact, dense layer with bundles placed
next to each other to the extent possible, that voids between bundles be reduced to the minimum
achievable, and that bundles that are broken be separated into stacks 12 inches or less in height;
and that contaminated soil or tailings then be spread and compacted over the layer not
exceeding 12-inches in loose lift thickness.
Similar sets of detailed specifications were developed and used on the above-described projects
for size-reduction and controlled placement of pipe sections, concrete rubble, monoliths, and
large rock fragments, and associated backfill placement, and compaction of debris/rubble and
soil mixtures.
The applicability and benefit of employing these specifications or similarly detailed
specifications, should be evaluated, and implemented for this project as warranted.
REFERENCES:
Denison Mines (USA) Corporation. 2011. Reclamation Plan, Revision5.0, White Mesa Mill,
Blanding, Utah: September 2011
Denison Mines (USA) Corporation. 2G09a. Reclamation Plan, Revision 4.0, White Mesa Mill,
Blanding, Utah, Exhibit C: November 2009
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Exhibit C: Probable Maximum Precipitation (PMP) Event Computation, White Mesa Mill - Cell
4B, Blanding, Utah ". September 10, 2009. Letter to Dane Finerfrock, dated September 11,
2009.
DOE (U.S. Department of Energy). 1989. Technical Approach Document, Revision II. UMTRA-
DOE/AL 050425.0002.
DOE 1995. Uranium Mill Tailings Remedial Action Project, Slick Rock, Colorado Subcontract
Documents. U.S. Department of Energy, Albuquerque, New Mexico. October 1, 1995.
DOE/AL/62350—21F-Rev. 1-Attachment.
DOE 2000. WSSRAP Disposal Facility Technical Specifications, Section 2300: Waste Removal,
Handling, and Placement. WP-437, Disposal Cell Construction. May 15, 2000.
EPA (U.S. Environmental Protection Agency). 1989a. Final Covers on Hazardous Waste
Landfills and Surface Impoundments, Technical Guidance Document, EPA/530-SW-89-047,
Office of Solid Waste and Emergency Response, Washington, D.C. URL:
http://webcache.googleusercontent.com/search?q=cache:VEVCaJfiyPDQJ:nepis.epa.gov/Exe/Zy
PURL.cgi%3FDockey%3D100019HC.txt+site:epa.gov+EPA+Final+Covers+Guidance&cd=4
&hl=*en&ct=clnk&gl=us.
EPA 1991. Seminar Publication, Design and Construction of RCRA/CERCLA Final Covers.
EPA/625/4-91/025.May 1991, 208 pp.
EPA 2004. (Draft) Technical Guidance for RCRA/CERCLA Final Covers. U.SEPA 540-R-04-
007, OSWER 9283.1-26. April 2004, 421 pp. URL:
nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P10074PP.txt.
Gilbert, P.A., and Murphy, W.M. 1987. Prediction/Mitigation of Subsidence Damage to
Hazardous Waste Landfill Covers.EPA/600/2-87/025, March 1987, 81 pp. NTIS PB-175386.
Nelson, J.D., Abt, S.R., Volpe, R.L, van Zyl, D., Hinkle, N.E., and Staub, W.P. 1986.
Methodologies for Evaluating Long-Term Stabilization Designs of Uranium Mill Tailings
Impoundments.Prepared for Nuclear Regulatory Commission, Washington, DC.NUREG/CR-
4620. ORNL/TM-10067.June 1986, 151 pp.
NRC 2002. U.S. Nuclear Regulatory Commission, "Design of Erosion Protection for Long-Term
Stability", NUREG-1623, September 2002.
NRC 2003. Standard Review Plan for the Review of a Reclamation Plan for Mill Tailings Sites
under Title II of the Uranium Mill Tailings Radiation Control Act of1978. Washington DC, June
2003.
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INTERROGATORY WHITEMESA RECPLAN REV. 5.0 R313-24-4,10 CFR 40
APPENDIX A; INT 05/1: SEISMIC HAZARD EVALUATION
REGULATORY BASIS:
UAC R313-24-4 invokes the following requirement from 10CFR40. Appendix A. Criterion 1: " The
general goal or broad objective in siting and design decisions is permanent isolation of tailings
and associated contaminants by minimizing disturbance and dispersion by natural forces, and to
do so without ongoing maintenance. For practical reasons, specific siting decisions and design
standards must involve finite times (e.g., the longevity design standard in Criterion 6).
Refer to R313-24-4, 10 CFR 40 Appendix A, Criterion 4 (e): The impoundment may not be
located near a capable fault that could cause a maximum credible earthquake larger than that
which the impoundment could reasonably be expected to withstand. As used in this criterion, the
term "capable fault" has the same meaning as defined in section 111(g) of Appendix A of 10 CFR
Part 100. The term "maximum credible earthquake " means that earthquake which would cause
the maximum vibratory ground motion based upon an evaluation of earthquake potential
considering the regional and local geology and seismology and specific characteristics of local
subsurface material.
UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A. Criterion 6(1): "In
disposing of waste byproduct material, licensees shall place an earthen cover (or approved
alternative) over tailings or wastes at the end of milling operations and shall close the waste
disposal area in accordance with a design which provides reasonable assurance of control of
radiological hazards to (i) be effective for 1,000 years, to the extent reasonably achievable, and,
in any case, for at least 200 years, and (ii) limit releases of radon-222from uranium byproduct
materials, and radon-220from thorium byproduct materials, to the atmosphere so as not to
exceed an average release rate of 20 picocuries per square meter per second (pCi/ms) to the
extent practicable throughout the effective design life determined pursuant to (l)(i) of this
criterion. In computing required tailings cover thicknesses, moisture in soils in excess of
amounts found normally in similar soils in similar circumstances may not be considered. Direct
gamma exposure from the tailings or wastes should be reduced to background levels. The effects
of any thin synthetic layer may not be taken into account in determining the calculated radon
exhalation level. If non-soil materials are proposed as cover materials, it must be demonstrated
that these materials will not crack or degrade by differential settlement, weathering, or other
mechanism, over long-term intervals. "
NUREG-1620 specifies that "Reasonable assurance [shall be] provided that the requirements of
10 CFR Part 40, Appendix A, Criterion 6(1), which requires that the design of the disposal
facility provide reasonable assurance of control of radiological hazards to be effective for 1,000
years, to the extent reasonably achievable, and, in any case, for at least 200 years, have been
met."
INTERROGATORY STATEMENT:
Refer to Appendix E and Attachment EA to Appendix E to Appendix D, Updated Tailings
Cover Design Report of the Reclamation Plan, Rev. 5: Please provide the following:
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1. Please further clarify the rationale for selecting the annual probability of exceedance of
hazard for the facility.
2. Adjust the cited USGS National Hazard Map PGA (peak ground acceleration) value of
0.15 g for the site Vs30 as appropriate.
3. Explain why the calculated hazard for the background earthquake PGA of 0.24 g was
estimated but ignored in the recommendations provided in Appendix E.
4. Provide information to justify the use of 15 km distance for a background earthquake Mw
6.3 event.
5. Perform and report results of a site-specific probabilistic seismic analysis in lieu of
using the USGS National Hazard Maps for developing site-specific seismic design
parameters.
BASIS FOR INTERROGATORY:
The rationale for selecting the annual probability of exceedance of hazard for the facility needs
to be clarified. Appendix E to the Appendix D of the Reclamation Plan Rev. 5 states that the
"10,000 year return period (1 in 10,000 annual probability) is adopted for evaluating the long-
term stability of the facility ". However, in the following sentences, the report states that a return
period of2,500 years (1 in 2500 annual probability) is appropriate for the operational
conditions of the facility. It needs to be clarified if or how the facility is being evaluated for the
two annual probabilities. Is so, further details would need to be provided.
It is unclear how the 0.15 g PGA is "reasonable for the White Mesa site ". Appendix E cites the
USGS National Hazard Maps and a PGA of 0.15 g for a 10,000 year return period. This value is
for a Vs30 of 760 m/sec. The report continues by stating that the Vs30 for the site is 586 m/sec.
The 0.15 g value cited in this regard needs to be adjusted for the site Vs30.
Appendix E describes background earthquakes and adopts an Mw 6.3 event at a distance of 15
km. Additional justification needs to be provided for the use of the 15 km distance.
A single ground motion prediction model should not be used in hazard analysis because the
epistemic uncertainty in ground motion prediction is being ignored. Currently, there are five
Next Generation Attenuation (NGA) ground motion models, including an update of Campbell
and Bozorgnia (2007), which should be used in the deterministic calculation for the PGAs in
Table 1, Peak Ground Accelerations for White Mesa, in Attachment E. 1 ofAppendix E.
The USGS National Hazard Maps should not be used for developing site-specific seismic design
parameters (Personal Communication between Dr. Mark Petersen, Chief, National Seismic
Hazard Mapping Project, and Ivan Wong of URS Corporation 2010) for critical and important
facilities. For such types of facilities, a site-specific probabilistic seismic hazard analysis is
recommended.
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REFERENCES:
Campbell, K. W. and Bozorgnia, Y., 2007, Campbell-Bozorgnia NGA Ground motion relations
for the geometric mean horizontal component of PGA, PGV, PGD and 5% Damped Linear
Elastic Response Spectra for Periods Ranging from 0.01 to 10 s: Earthquake Spectra 24, pp.
139-171. 2008
Denison Mines (USA) Corp., 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah,
Radioactive Materials License No. UT1900479, Revision 5.0, Appendix E, September 2011.
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INTERROGATORY WHITEMESA RECPLAN REV5.0; R313-24-4; 10CFR40
APPENDIX A, CRITERION 1; INT 06/1: SLOPE STABILITY
REGULATORY BASIS:
UAC R313-24-4 invokes the following requirement from 10CFR40 Appendix A, Criterion 1: The
general goal or broad objective in siting and design decisions is permanent isolation of tailings
and associated contaminants by minimizing disturbance and dispersion by natural forces, and to
do so without ongoing maintenance. For practical reasons, specific siting decisions and design
standards must involve finite times (e.g., the longevity design standard in Criterion 6)... .
Refer also to INTERROGATORY WHITEMESA RECPLAN Rev. 5.0 R313-24-4, 10 CFR 40
APPENDIX A; INT 05/1: SEISMIC HAZARD EVALUATION above.
Slope Stability
NUREG-1620, Section 2.2.3: The analysis of slope stability will be acceptable if it meets
the following criteria:
(1) Slope characteristics are properly evaluated.
(a) Cross sections and profiles of natural and cut slopes whose instability would directly
or indirectly affect the control of radioactive materials are presented in sufficient number
and detail to enable the reviewer to select the cross sections for detailed stability
evaluation.
(b) Slope steepness is a minimum of five horizontal units (5h) to one vertical unit (Iv) or
less. The use of slopes steeper than 5h:lv is considered an alternative to the requirements
in 10 CFR Part 40, Appendix A, Criterion 4(c). When slopes steeper than 5h:lv are
proposed, a technical justification should be offered as to why a 5h:lv or flatter slope
would be impractical and compensating factors and conditions are incorporated in the
slope design for assuring long-term stability.
(c) Locations selected for slope stability analysis are determined considering the location
of maximum slope angle, slope height, weak foundation, piezometric level(s), the extent of
rock mass fracturing (for an excavated slope in rock), and the potential for local erosion.
(2) An appropriate design static analysis is presented.
(a) The analysis includes calculations with appropriate assumptions and methods of
analysis (NRC, 1977). The effect of the assumptions and limitations of the methods used is
discussed and accounted for in the analysis. Acceptable methods for slope stability analysis
include various limit equilibrium analysis or numerical modeling methods.
(b) The uncertainties and variability in the shape of the slope, the boundaries and
parameters of the several types of soils and rocks within and beneath the slope, the material
properties of soil and rock within and beneath the slope, the forces acting on the slope, and
the pore pressures acting within and beneath the slope are considered.
(c) Appropriate failure modes during and after construction and the failure surface
corresponding to the lowest factor of safety are determined. The analysis takes into account
the failure surfaces within the slopes, including through the foundation, if any.
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(d) Adverse conditions such as high water levels from severe rain and the probable
maximum flood are evaluated.
(e) The effects of toe erosion, incision at the base of the slope, and other deleterious effects
ofsurface runoff are assessed.
(f) The resulting safety factors for slopes analyzed are comparable to the minimum
acceptable values of safety factors for slope stability analysis given in NRC Regulatory
Guide 3.11....
(3) Appropriate analyses considering the effect of seismic ground motions on slope stability
are presented.
(a) Evaluation of overall seismic stability, using pseudostatic analysis or dynamic analysis,
as appropriate (U.S. Army Corps of Engineers, 1977; NRC, 1977). Alternatively, a dynamic
analysis following Newmdrk (1965) can be carried out to establish that the permanent
deformation of the disposal cell from the design seismic event will not be detrimental to the
disposal cell. The reviewer should verify that the yield acceleration or pseudostatic
horizontal yield coefficient necessary to reduce the factor of safety against slippage of a
potential sliding mass to 1.0 in a "Newmark-type" analysis has been adequately estimated
(Seed and Bonaparte, 1992).
(b) An appropriate analytical method has been used. A number of different methods of
analysis are available (e.g., slip circle method, method of slices, and wedge analysis) with
several variants of each (Lambe and Whitman, 1979; U.S. Army Corps of Engineers, 1970b;
NRC, 1977; Bromhead, 1992). Limit-equilibrium analysis methods do not provide
information regarding the variation of strain within the slope and along the slip surface.
Consequently, there is no assurance that the peak strength values used in the analysis can
be mobilized simultaneously along the entire slip surface unless the material shows ductile
behavior (Duncan, 1992). Residual strength values should be evaluated if mobilized shear
strength at some points is less than the peak strength. The reviewer should ensure that
appropriate conservatism has been incorporated in the analysis using the limit equilibrium
methods. The limit equilibrium analysis methodologies may be replaced by other
techniques, such as finite element or finite difference methods. If any important interaction
effects cannot be included in an analysis, the reviewer must determine that such effects have
been treated in an approximate but conservative fashion. The engineering judgment of the
reviewer should be used in assessing the adequacy of the resulting safety factors (NRC,
(c) For dynamic loads, the dynamic analysis includes calculations with appropriate
assumptions and methods (NRC, 1977; Seed, 1967; Lowe, 1967; Department of the Navy,
1982a,b,c; U.S. Army Corps of Engineers, 1970a,b, 1971, 1972; Bureau of Reclamation,
1968). The effect of the assumptions and limitations of the methods used is discussed and
accounted for in the analysis.
(d) For dynamic loads, a pseudostatic analysis is acceptable in lieu of dynamic analysis if
the strength parameters used in the analysis are conservative, the materials are not subject
to significant loss of strength and development of high pore pressures under dynamic loads,
the design seismic coefficient is 0.20 or less, and the resulting minimum factor of safety
suggests an adequate margin, as provided in NRC Regulatory Guide 3.11 (NRC, 1977).
1983a,b).
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(e) For pseudostatic analysis of slopes subjected to earthquake loads, an assumption is
made that the earthquake imparts additional horizontal force acting in the direction of the
potential failure (U.S. Army Corps of Engineers, 1970b, 1977; Goodman, 1989). The
critical failure surface obtained in the static analysis is used in this analysis with the added
driving force. Minimum acceptable values for safety factors of slope stability analysis are
given in Regulatory Guide 3.11 (NRC, 1977).
(f) The assessment of the dynamic stability considers an appropriate design level seismic
event and/or strong ground motion acceleration, consistent with that identified in Chapter 1
of this review plan. Influence of local site conditions on the ground motions associated with
the design level event is evaluated. The design seismic coefficient to be used in the
pseudostatic analysis is either 67 percent of the peak ground acceleration at the foundation
level of the tailings piles for the site or O.lg, whichever is greater.
(g) If the design seismic coefficient is greater than 0.20g, then the dynamic stability
investigation (Newmark, 1965) should be augmented by other appropriate methods (i.e.,
finite element method), depending on specific site conditions.
(h) In assessing the effects of seismic loads on slope stability, the effect of dynamic stresses
of the design earthquake on soil strength parameters is accounted for. As in a static
analysis, the parameters such as geometry, soil strength, and hydrodynamic and pore
pressure forces are varied in the analysis to show that there is an adequate margin of safety.
(i) Seismically induced displacement is calculated and documented. There is no universally
accepted magnitude of seismically induced displacement for determining acceptable
performance of the disposal cell (Seed and Bonaparte, 1992; Goodman and Seed, 1966).
Surveys offive major geotechnical consulting firms by Seed and Bonaparte (1992) indicate
that the acceptable displacement is from 15 to 30 cm [6 to 12 in.] for tailings piles. The
reviewer should ensure that this criterion is also augmented by provisions for periodic
maintenance of the slope(s).
(j) Where there is potential for liquefaction, changes in pore pressure from cyclic loading
are considered in the analysis to assess the effect of pore pressure increase on the stress-
strain characteristics of the soil and the post-earthquake stability of the slopes. Liquefaction
potential is reviewed using Section 2.4 of this review plan. Evaluations of dynamic
properties and shear strengths for the tailings, underlying foundation material, radon
barrier cover, and base liner system are based on representative materials properties
obtained through appropriate field and laboratory tests (NRC, 1978, 1979).
(k) The applicant has demonstrated that impoundments will not be located near a capable
fault on which a maximum credible earthquake larger than that which the impoundment
could reasonably be expected to withstand might occur.
(4) Provision is made to establish a vegetative cover, or other erosion prevention, to include
the following considerations:
(a) The vegetative cover and its primary functions are described in detail. This
determination should be made with respect to any effect the vegetative cover may have on
reducing slope erosion and should be coordinated with the reviewer of standard review plan
Chapter 3. If strength enhancement from the vegetative cover is taken into account, the
methodology should be appropriate (Wu, 1984).
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(b) In arid and semi-arid regions, where a vegetative cover is deemed not self-sustaining, a
rock cover is employed on slopes of the mill tailings. If credit is taken for strength
enhancement from rock cover, the reviewer should confirm that appropriate methodology
has been presented. The design of a rock cover, where a self-sustaining vegetative cover is
not practical, is based on standard engineering practice. Standard review plan Chapter 3
discusses this item in detail.
(5) Any dams meet the requirements of the dam safety program if the application
demonstrates the following:
(a) The dam is correctly categorized as a low hazard potential or a high hazard potential
structure using the definition of the U.S. Federal Emergency Management Agency;(b) If the
dam is ranked as a high hazard potential, an acceptable emergency action plan consistent
with the Federal Emergency Management Agency guide (U.S. Federal Emergency
Management Agency, 1998) has been developed.
(6) The use of steeper slopes as an alternative to the requirements in 10 CFR, Part 40,
Appendix A, will be found acceptable if the following are met:
(a) An equivalent level of stabilization and containment and protection of public health,
safety, and the environment is achieved.
(b) A site-specific need for the alternate slopes is demonstrated.
INTERROGATORY STATEMENT:
1. Demonstrate slope stability for the tailings impoundment and new cover system using
shear strength parameters and other soil properties assigned to the various components
(cover, embankment/dike, tailings, and foundation) consistent with soil type, degree of
compaction, and anticipated degree of variability. Justify selection of values for soil
parameters.
2. In evaluating slope stability, address and report the effects of shallow and non-circular
failure surfaces, in addition to circular and/or deeper ones.
3. Demonstrate that assumed drainage conditions are appropriate, are at least consistent
with, or are conservative compared with drainage/seepage results, projected immediately
at closure and at the end of the impoundment design life (i.e., 1,000 years, to the extent
reasonably achievable, and, in any case, for at least 200 years).
4. Assess the slope stability of Cell 1 adjacent to Cell 2 where mill debris and contaminated
soils are to be placed and covered.
5. Explain and justify the selection of the pseudo-static coefficient used in the assessment of
seismic stability. If the selected value of the pseudo-static coefficient cannot be justified,
revise the value of the coefficient used in stability analyses and revise and report the
results of stability analyses.
BASIS FOR INTERROGATORY:
The slope stability analyses presented by the Licensee uses the same shear strength parameters
(phi=26 degrees, c=900 psf) for the reclamation cover, impoundment dikes, and the foundation
soils above the bedrock. These properties were derived from limited triaxial testing of very stiff/
very dense material recovered from apparently in-situ soil. Given that the different soil zones in
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the cover system are to be placed with varying degrees of compaction (some being quite loose)
and that the density of the dikes may vary from that of the foundation, the use of singular soil
properties throughout the analyses is inappropriate. Shear strength parameters and other soil
properties such as unit weight should be assigned to the various earthen components consistent
with soil type, degree of compaction, and anticipated degree of variability. The selection of
strength parameters should also be explained and justified. Because of the relatively loose state
proposed for some of the cover soils, the Licensee's stated approach (i.e., "circular failure
surface analyses were conducted by targeting deeper, full-slope failures as opposed to
shallower, superficial failures. ") may miss truly critical failure surfaces. Shallow surfaces as
well as non-circular ones should be considered.
The slope stability analyses performed by the Licensee assume that the tailings impoundment
cells behave fully drained, thus phreatic surfaces were not included in the analyses. The
Licensee should demonstrate that such assumptions are appropriate (i.e., are at least consistent
with, if not conservatively interpreted) based on the results of drainage/seepage analyses
representing conditions immediately at closure as well as at the end of the design storage life of
the facility. Such analyses should reflect the variations in the tailings properties and drainage
systems (slimes dewatering systems) particular to each tailings management cell (e.g.,
approximately 600-ft by 400-ft area containing slimes "burrito drain " array in each of Cell 2
and Cell 3 vs. area blanket sand layer and slimes drain piping system in Cells 4A and 4B;).
Tailings properties will vary in response to variations in historic (and future) milling processes
as well as deposition history (and future) and discharge -related distribution within each cell.
The soil shear strength parameters (particularly those of the tailings) used in the slope stability
analyses should be consistent with the drainage conditions thus demonstrated.
As described in the Basis for Interrogatory section of "INTERROGATORY WHITEMESA
RECPLAN REV. 5.0 R313.-24-4; 10CFR40 APPENDIXA, CRITERION 4; INT 07/1:
TECHNICAL ANALYSIS - SETTLEMENT AND POTENTIAL FOR COVER SLOPE REVERSAL
AND/OR COVER LA YER CRACKING ", the tailings dewatering analyses presented in
Appendix H to the Updated Tailings Cover Design Report, do not adequately represent (i.e.,
account for) potential variations in the tailings properties, nor their potential distribution within
the various tailings management cells. As requested in the interrogatory cross-referenced
above, the tailings dewatering analyses should be revisited or at least clarified and better
substantiated, and the Licensee should test actual tailings specimens from the site. The number
of specimens involved should be commensurate with anticipated variability of the tailings
conditions in the containment cells.
The slope stability analyses presented by the Licensee are based on a selected cross-section in
Cell 4A apparently intended to represent the greatest height of an otherwise uniformly designed
embankment. However, different conditions exist in Cell 1 adjacent to Cell 2 where mill debris
and contaminated soils are to be placed and covered. The slope stability of this section should
be analyzed.
To aid future review, the shading applied to the slices of the failure mass should be removed
(thus enabling the profile lines of the underlying soil type to be seen). It is also suggested that
contours for the factor of safety be added to the search grid as well as definitions of the search
radii.
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The explanation and justification for the factor applied to the PGA to establish the pseudo-static
coefficient provided by the Licensee appears to be flawed. The Licensee's report reads thusly:
"The seismic coefficient represents an inertial force due to strong ground motions during
the design earthquake, and is represented as a fraction of the PGA at the site (typically at
the base of the structure). Tetra Tech (2010) recommended using a value of 0.1 g for the
seismic coefficient in accordance with IBC (2006) recommendations to multiply the PGA
by 0.667 to determine a design acceleration value. The strategy of representing the
seismic coefficient as a fraction of the PGA has been adopted in review of uranium
tailings facility design and documented in DOE (1989). A value of0.667 typically
represents post-reclamation conditions. Based on this guidance and the
recommendations in Tetra Tech (2010), the seismic coefficient used for the pseudo-static
stability analysis was 0.1 g. "
The 2006 International Building Code (IBC) does not contain such a recommendation (it does
not discuss pseudo-static slope analysis). The code does use a factor of 2/3 to convert MCE
ground accelerations to design accelerations for structural components, but this is an issue
separate from and not related to the seismic coefficient used for slope stability. Explain why
reference is made to the IBC since that document is for the design of buildings and not earthen
tailings impoundments, or revise the discussion accordingly to more clearly state the
justification for use of the selected seismic coefficient.
Assessment of slope stability under seismic conditions is dependent upon the Licensee's seismic
hazard analysis. Any revisions to the seismic hazard analysis may necessitate revisions to this
assessment.
NUREG-1620 (NRC 2003), Section 2.2.3 specifies that: "The analysis of slope stability will be
acceptable if it meets the following criteria:
(1) Slope characteristics are properly evaluated.
(a) Cross sections and profiles of natural and cut slopes whose instability would directly or
indirectly affect the control of radioactive materials are presented in sufficient number and
detail to enable the reviewer to select the cross sections for detailed stability evaluation.
(b) Slope steepness is a minimum of five horizontal units (5h) to one vertical unit (Iv) or less.
The use of slopes steeper than 5h:lv is considered an alternative to the requirements in 10 CFR
Part 40, Appendix A, Criterion 4(c). When slopes steeper than 5h:lv are proposed, a technical
justification should be offered as to why a 5h:lv or flatter slope would be impractical and
compensating factors and conditions are incorporated in the slope design for assuring long-term
stability.
(c) Locations selected for slope stability analysis are determined considering the location of
maximum slope angle, slope height, weak foundation, piezometric level(s), the extent of rock
mass fracturing (for an excavated slope in rock), and the potential for local erosion.
(2) An appropriate design static analysis is presented.
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(a) The analysis includes calculations with appropriate assumptions and methods of analysis (NRC,
1977). The effect of the assumptions and limitations of the methods used is discussed and accounted
for in the analysis. Acceptable methods for slope stability analysis include various limit equilibrium
analysis or numerical modeling methods.
(b) The uncertainties and variability in the shape of the slope, the boundaries and parameters of the
several types of soils and rocks within and beneath the slope, the material properties of soil and
rock within and beneath the slope, the forces acting on the slope, and the pore pressures acting
within and beneath the slope are considered.
(c) Appropriate failure modes during and after construction and the failure surface corresponding
to the lowest factor of safety are determined. The analysis takes into account the failure surfaces
within the slopes, including through the foundation, if any.
(d) Adverse conditions such as high water levels from severe rain and the probable maximum flood
are evaluated.
(e) The effects of toe erosion, incision at the base of the slope, and other deleterious effects of
surface runoff are assessed.
(f) The resulting safety factors for slopes analyzed are comparable to the minimum acceptable
values ofsafety factors for slope stability analysis given in NRC Regulatory Guide 3.11....
(3) Appropriate analyses considering the effect of seismic ground motions on slope stability are
presented.
(a) Evaluation of overall seismic stability, using pseudostatic analysis or dynamic analysis, as
appropriate (U.S. Army Corps of Engineers, 1977; NRC, 1977). Alternatively, a dynamic analysis
following Newmark (1965) can be carried out to establish that the permanent deformation of the
disposal cell from the design seismic event will not be detrimental to the disposal cell. The reviewer
should verify that the yield acceleration or pseudostatic horizontal yield coefficient necessary to
reduce the factor of safety against slippage of a potential sliding mass to 1.0 in a "Newmark-type "
analysis has been adequately estimated (Seed and Bonaparte, 1992).
b) An appropriate analytical method has been used. A number of different methods of analysis are
available (e.g., slip circle method, method of slices, and wedge analysis) with several variants of
each (Lambe and Whitman, 1979; U.S. Army Corps of Engineers, 1970b; NRC, 1977; Bromhead,
1992). Limit-equilibrium analysis methods do not provide information regarding the variation of
strain within the slope and along the slip surface. Consequently, there is no assurance that the peak
strength values used in the analysis can be mobilized simultaneously along the entire slip surface
unless the material shows ductile behavior (Duncan, 1992). Residual strength values should be
evaluated if mobilized shear strength at some points is less than the peak strength. The reviewer
should ensure that appropriate conservatism has been incorporated in the analysis using the limit
equilibrium methods. The limit equilibrium analysis methodologies may be replaced by other
techniques, such as finite element or finite difference methods. If any important interaction effects
cannot be included in an analysis, the reviewer must determine that such effects have been treated
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in an approximate but conservative fashion. The engineering judgment of the reviewer should be
used in assessing the adequacy of the resulting safety factors (NRC, 1983a,b).
(c) For dynamic loads, the dynamic analysis includes calculations with appropriate assumptions
and methods (NRC, 1977; Seed, 1967; Lowe, 1967; Department of the Navy, 1982a,b,c; U.S. Army
Corps of Engineers, 1970a,b, 1971, 1972; Bureau of Reclamation, 1968). The effect of the
assumptions and limitations of the methods used is discussed and accounted for in the analysis.
(d) For dynamic loads, a pseudostatic analysis is acceptable in lieu of dynamic analysis if the
strength parameters used in the analysis are conservative, the materials are not subject to
significant loss of strength and development of high pore pressures under dynamic loads, the design
seismic coefficient is 0.20 or less, and the resulting minimum factor of safety suggests an adequate
margin, as provided in NRC Regulatory Guide 3.11 (NRC, 1977).
(e) For pseudostatic analysis of slopes subjected to earthquake loads, an assumption is made that
the earthquake imparts additional horizontal force acting in the direction of the potential failure
(U.S. Army Corps of Engineers, 1970b, 1977; Goodman, 1989). The critical failure surface
obtained in the static analysis is used in this analysis with the added driving force. Minimum
acceptable values for safety factors of slope stability analysis are given in Regulatory Guide 3.11
(NRC, 1977).
(f) The assessment of the dynamic stability considers an appropriate design level seismic event
and/or strong ground motion acceleration, consistent with that identified in Chapter 1 of this review
plan. Influence of local site conditions on the ground motions associated with the design level event
is evaluated. The design seismic coefficient to be used in the pseudostatic analysis is either 67
percent of the peak ground acceleration at the foundation level of the tailings piles for the site or
0. Ig, whichever is greater.
(g) If the design seismic coefficient is greater than 0.20g, then the dynamic stability investigation
(Newmark, 1965) should be augmented by other appropriate methods (i.e., finite element method),
depending on specific site conditions.
h) In assessing the effects of seismic loads on slope stability, the effect of dynamic stresses of the
design earthquake on soil strength parameters is accounted for. As in a static analysis, the
parameters such as geometry, soil strength, and hydrodynamic and pore pressure forces are varied
in the analysis to show that there is an adequate margin of safety.
(i) Seismically induced displacement is calculated and documented. There is no universally
accepted magnitude of seismically induced displacement for determining acceptable performance of
the disposal cell (Seed and Bonaparte, 1992; Goodman and Seed, 1966). Surveys of five major
geotechnical consulting firms by Seed and Bonaparte (1992) indicate that the acceptable
displacement is from 15 to 30 cm [6 to 12 in.] for tailings piles. The reviewer should ensure that this
criterion is also augmented by provisions for periodic maintenance of the slope(s).
REFERENCES
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March 2012 UAil
International Building Code 2006. International Code Council, Inc.
MWH Americas 2011. Appendix E - Slope Stability Analysis, contained in Appendix D,
Updated Tailings Cover Design Report, White Mesa Mill, September 2011 to the Reclamation
Plan, White Mesa Mill, Rev. 5.0, September 2011.
Tetra Tech, Inc. (Tetra Tech) 2010. "White Mesa Uranium Facility Seismic Study Update for a
Proposed Cell, " Technical Memorandum to Denison Mines, February 3.
U.S. Department of Energy (DOE) 1989. Technical Approach Document, Revision II,
UMTRADOE/AL 050425.0002, Uranium Mill Tailings Remedial Action Project, Albuquerque,
New Mexico.
NRC 1982. U.S. Nuclear Regulatory Commission, "Regulatory Guide 3.8; Preparation of
Environmental Reports for Uranium Mills ", Washington DC, Rev. 2, October 1982.
NRC 2003. Standard Review Plan (NUREG-1620) for Staff Reviews of Reclamation Plans for
Mill Tailings Sites Under Title II of The Uranium Mill Tailings Radiation Control Act",
NUREG-1620, June 2003.
NRC 2008. DG-3024, "Standard Format and Content of License Applications for Conventional
Uranium Mills, " Draft Regulatory Guide DG-3024, May, 2008.
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INTERROGATORY WHITEMESA RECPLAN REV. 5.0; R313-24-4; 10 CFR 40
APPENDIX A, CRITERION 4; INT 07/1: TECHNICAL ANALYSIS - SETTLEMENT
AND POTENTIAL FOR COVER SLOPE REVERSAL AND/OR COVER LAYER
CRACKING
REGULATORY BASIS
Refer to UAC R313-24-4 which invokes the followins requirement from 10CFR40, Appendix A,
Criterion 4: "The following site and design criteria must be adhered to whether tailings or
wastes are disposed of above or below grade:
...(c) Embankment and cover slopes must be relatively flat after final stabilization to minimize
erosion potential and to provide conservative factors of safety assuring long-term stability. The
broad objective should be to contour final slopes to grades which are as close as possible to
those which would be provided if tailings were disposed of below grade; this could, for example,
lead to slopes of about 10 horizontal to 1 vertical (10h.lv) or less steep. In general, slopes
should not be steeper than about 5h:lv. Where steeper slopes are proposed, reasons why a slope
less steep than 5h:lv would be impracticable should be provided, and compensating factors and
conditions which make such slopes acceptable should be identified.
(d) A full self-sustaining vegetative cover must be established or rock cover employed to reduce
wind and water erosion to negligible levels.
Where a full vegetative cover is not likely to be self-sustaining due to climatic or other
conditions, such as in semi-arid and arid regions, rock cover must be employed on slopes of the
impoundment system. The Executive Secretary will consider relaxing this requirement for
extremely gentle slopes such as those which may exist on the top of the pile.
...Rock covering of slopes may be unnecessary where top covers are very thick (or less); bulk
cover materials have inherently favorable erosion resistance characteristics; and, there is
negligible drainage catchment area upstream of the pile and good wind protection as described
in points (a) and (b) of this criterion.
Furthermore, all impoundment surfaces must be contoured to avoid areas of concentrated
surface runoff or abrupt or sharp changes in slope gradient.
INTERROGATORY STATEMENT
Refer to Appendix D, Updated Tailings Cover Design Report of the Reclamation Plan, Rev. 5,
and Drawings TRC-1 through TRC-8 in the Reclamation Plan, Rev. 5.0 :
1. Please revise (i.e., steepen) the slopes of the top slope portions of the final cover system
to provide an adequate factor of safety to ensure long-term stability of the covered
embankment area considering:
a. The potential for future slope reversals) and/or cracking to occur in the cover
system due to long-term total and differential settlement or subsidence which
could lead to conditions where ponding of precipitation could occur on the cover
system in the future, after the end of the active institutional control period; and
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b. The significant disparity between the presently proposed topslope inclination
ranges and published recommended ranges of slopes for final cover systems for
uranium mill tailings repositories, surface impoundments, and landfills - namely
ranging between 2% to 5% (e.g., see DOE 1989; EPA 1989; EPA 1991, and ITRC
2003 and EPA 2004).
OR, alternatively, provide additional evaluations that clearly and unequivocally
demonstrate (1) the ability to construct such gently sloped cover systems as proposed,
designed, and specified and (2) the ability of the proposed embankment closure cover
design to accommodate settlement-induced slope changes (including slope reversal)
without increasing infiltration into the stabilized tailings impoundment.
2. Provide technical justification for 1) quantitative acceptance criteria to be used as the
basis for evaluating the potential for slope reversal within the cover system in terms of
potential long-term total and differential settlement, 2) quantitative assessments of
maximum tensile strain capacity and other engineering properties such as Atterberg
limits of the materials to be used in design of the cover system, and 3) quantitative
acceptance criteria, including maximum allowable linear and angular distortion values,
including effects of bending within any select layer or layers of the cover, and (4) the
minimum acceptable factor of safety for concluding that cover layer cracking will not
occur.
3. Provide engineering analyses (including calculations and numerical modeling
simulations as applicable) documenting the range of anticipated total and differential
settlements within each of the containment cells. In doing so, use consolidation
parameters obtained from site-specific testing of the tailings materials, reflecting both
spatial and temporal variations in the tailings. Data from other sources may supplement
(but not replace) site-specific test data in the analyses.
4. Demonstrate that tailings have been deposited in such a way that variations in tailings
properties by location do not compromise the stability of the tailings as a foundation for
cover system construction. Consider effects of sand-rich tailings zones lying adjacent to
our near slime-rich tailings zones, due to deposition during slurry flow. Describe and
account for effects of any different tailings placement methods (e.g., wet slurry vs.
thickened slurry deposition) used throughout the mill's operating life. Identify and
quantify the effects on stability of variations in such tailings physical characteristics as
moisture content, consolidation coefficients, specific gravity, hydraulic conductivity (as
listed in Appendix D Updated Tailings Cover Design Report, September 2011). Perform
and provide results of numerical analyses using this information to project differential
settlement across the tailings impoundments using software such as the Fast Lagrangian
Analysis of Continuum (FLAC®) code (Itasca 2009) or other similar software, as
appropriate. Alternatively, provide information to justify why such analyses are not
warranted.
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5. Include secondary settlement (i.e., creep) and any seismically induced settlement of the
tailings in settlement analyses and consider their effects when assessing the anticipated
performance of the cover system.
6. Demonstrate that the results of settlement analyses are consistent with results of
drainage/dewatering analyses. Ensure that drainage/dewatering analyses reflect the
tailings and drainage conditions (including slime drain system) existing in each cell.
7. Perform and report results of sensitivity and uncertainty analyses to demonstrate that the
cover system will remain stable despite the effects of differential settlement. Report the
time required to reach 90% consolidation.
8. As part of the analyses identified above, please also perform a seepage analyses to
evaluate the shape of the phreatic surface within the tailings prism for each
representative area within Cells 2 and/or 3, 4A, and 4B to be analyzed for consolidation
timeframes and in differential settlement analyses. Ensure that effects of planned
dewatering procedures and the dewatering system design configuration in each specific
cell analyzed are reflected in seepage analyses.
9. Provide sensitivity analyses to assess the effect a of changes in tailings coefficients of
consolidation parameters, void ratios, and tailings hydraulic conductivity values (note: it
is acknowledged that values of all of these parameters are subject to uncertainty) on the
amount of time required to reach approximately 90% consolidation of the tailings at each
locations assessed within each cell and/or across individual tailings cells.
10. Using the information obtained from the analyses identified above, for each critical
section defined, complete differential settlement analyses and compare the analyses
results to the specified design criteria and evaluate the potential for slope reversals) to
occur in the cover system over the tailings cells over the worst-case sections analyzed.
11. Provide information on the expected range ofplasticity characteristics of the soil
materials proposed for use for constructing the highly compacted upper portion of the
radon attenuation and radon attenuation and grading layer of the proposed cover system,
and specify design criteria (including maximum allowable values of both linear and
angular distortion) to be used for evaluating the potential for cracking of this layer to
occur as a result of any differential settlement that may occur.
BASIS FOR INTERROGATORY
The proposed cover slope (minimum of 0.1% to a maximum of 1.0 %) is very flat and, based on
the information provided, has to be considered to likely be problematic from the standpoint of
potential long-term subsidence/differential settlement. 10CFR 40, Appendix A, Technical
Criterion 4(c) specifies that embankment and cover slopes must be relatively flat after final
stabilization to minimize erosion and provide conservative factors of safety assuring long-term
stability (emphasis added). Technical guidance developed for and typically utilized by the U.S.
Department of Energy on the UMTRA Project for design and construction of uranium mill
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tailings repositories included typical repository topslope inclinations of 2 to 3 percent (U.S.
DOE 1989, Section 3, Figure 3-3). Further, minimum technology guidance for final cover
systems for surface impoundments recommended by the USEPA (EPA 1989; EPA 1991) consists
of the following:
"...a top layer..., the surface of which slopes uniformly at least 3 percent but not more
than 5 percent, to facilitate runoff while minimizing erosion, ..."
Additionally, an EPA document published in 2004 (EPA) further discusses this guideline in the
following context:
"...[In the Draft Technical Guidance for RCRA/CERCLA Final Covers, EPA states that]
most landfill cover system top decks are designed to have a minimum inclination of 2% to
5%, after accounting for settlement, to promote runoff of surface water. ...However,
[EPA states that] in some cases involving the closure or remediation of existing landfills,
waste piles, or source areas, flatter slopes may already exist and that the cost to increase
the slope inclination by fill placement or waste excavation may be significant. In these
cases, slightly flatter inclinations can be considered if the future settlement potential can
be demonstrated to be small, if concerns about localized subsidence can be adequately
addressed, and if monitoring and maintenance provisions exist to repair areas of grade
reversal or subsidence... "
The proposed cover topslope inclinations (minimum of 0.1%) are much flatter than the above
recommended ranges. The cover design should include a topslope slope inclination that ensures
that an adequate factor of safety is provided to maintain long-term stability of the completed
embankment(s), considering the potential for future slope reversals) due to long-term
differential settlement or subsidence, given a reasonable estimate of the range of different
tailings characteristics and tailings consolidation conditions that may exist within the different
tailings placement cells. The final topslope inclinations must ensure that the topslope portion of
the embankment will maintain a positive slope across the entire embankment after
settlement/subsidence, thus providing lateral runoff ofprecipitation without ponding throughout
the performance period of the covered and closed embankment.
Drawings TRC-3 through TRC-8 of the Reclamation Plan Rev. 5.0 depict several areas where
slopes are nearly flat and have low-lying areas already (e.g. over portions of Cell 2) where
differential settlement, if it were to occur, could further aggravate these areas from the
standpoint offurther flattening or creating of larger areas offlat ground surface for future
ponding of incident precipitation.
Available published information and/or testing should be used to estimate the maximum amount
of strain/maximum distortion value that can be tolerated within the compacted layer over the
design life of the embankment and not crack the radon barrier. Such a limit should be based on
properties (e.g., range ofplasticity indices) of the soils proposed for constructing the compacted
portion of the radon barrier layer. Engineering analyses should be provided for various
representative disposal configurations involving disposed tailings to demonstrate that predicted
settlement/subsidence magnitudes and locations will not exceed specified acceptance criteria for
strain or distortion value.
To quantify the amount of settlement in the tailings due to the placement of the interim and final
soil covers, the Licensee has attempted to quantify the coefficients of consolidation (cv) and
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compression indices (Cc) for the tailings based on back-analysis of existing settlement
monitoring data from Cells 2 and 3. While this approach is a conceptually sound approach for
obtaining site-specific parameters, successful implementation often proves to be problematic.
For instance, high quality monitoring data is needed. Unfortunately, the monitoring data
exhibits an appreciable amount of "noise " and numerous erratic shifts, making it uncertain as to
which data points are the "real data" to which the modeled settlement response should be
matched. This approach also typically requires that the initial portion of the load-settlement
curve be well defined. Without this initial data, the total amount of settlement ultimately
expected to occur can be difficult to accurately quantify, particularly if the rate of consolidation
is rapid relative to the rate of loading (i.e., cover placement). Any settlement occurring during
construction of the cover and before monitoring begins is lost, leading to questions as to how
tightly the "bend" in the time rate of consolidation curve should be matched in the absence of a
well-defined starting point for the settlement model. It should also be noted that assessing the
goodness of the fit itself can also be problematic. For example, while the report states that the
model values of Cc and cv were varied "until the observed settlement curve correlated well with
the calculated settlement", it is the reviewer's opinion that the degree of correlation achieved
was not always "well", particularly for the first and most meaningful part of the consolidation
time history curve shown in Fig F-l, and for the entire plots shown for cells 2W1, 2W3, 3-1C, 3-
1S. It may be simply fortuitous that the back-calculated values appear to be within the ranges
suggested Keshian and Rager (cited by the Licensee), particularly recognizing that the ranges
cover one or more orders of magnitude. It should also be noted that no assessment has been
made as to whether or not the tailings' behavior in Cells 2 and 3 are applicable to the other
cells.
It is noted that the calculated/estimated amounts of settlement presented in the report appear to
be based on assumed dry and saturated unit weights of 86.3 and 117.1 pcf, respectively.
However, elsewhere in the report, (Section C.2.4 of sub-Appendix C in Appendix D), the tailings
are described as having a dry unit weight of 74.3 pcf. Consistent characterization of the tailings
throughout the report seems to be needed, or at least this variation should be accounted for
when reporting values of settlement. It is also noted that all the back analyses involved the same
initial void ratio for the tailings which is a very unlikely scenario given that the other
consolidation parameters (which are not entirely independent of void ratio) were varied.
A key deficiency of the settlement assessment presented by the Licensee lies in the following
conclusion: "Additional settlement due to the construction of the final cover is estimated to be on
the order of 5 to 6 inches. The estimated amount of additional settlement is sufficiently low such
that ponding is not expected with a cover slope of 0.5 percent. " The calculated settlements are
magnitudes of settlement without specified locations, whereas an assessment of ponding
potential (i.e., localized grade reversal of the cover) requires that the spatial variation of
settlement be known or calculated. The reported magnitudes of vertical settlement need to be
translated into reliable estimates of differential settlement in order to properly assess the
adequacy of the cover slope. In doing this, the Licensee should evaluate the various areas within
individual tailings placement cells and/or or spanning more than one of the tailings Cells 2, 3,
and 4A/B where tailings slurry deposition modes may vary, leading to different tailings
conditions within and/or between cells (e.g., tailings areas comprised of sand/slime mixture
located laterally adjacent to tailings areas containing mostly slimes, including, for example,
areas near side slope portions of tailings placement cells where more sand-rich tailings may be
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laterally juxtaposed against slime-rich tailings areas). The analysis should particularly account
for varying thicknesses of compressible tailings along the side slopes of the cells as well as the
potential for differences in stress conditions along such slopes. The locations and
characteristics for the different tailings materials (such as moisture content, horizontal and
vertical coefficients of consolidation, specific gravity, void ratios, unit weights, hydraulic
conductivity, etc.) should be clearly shown for one or more analyzed critical cross-sections.
While the above discussion focuses on the settlement of tailings, different conditions exist in Cell
1 adjacent to Cell 2 where mill debris and contaminated soils instead of tailings are to be placed
and covered. Total and differential settlement based on the particular conditions of this cell
together with their effects on both the liner and cover systems should be assessed.
To more reliably quantify total and differential settlements as well as settlement rates for the
tailings impoundments, the Licensee should test tailings specimens to determine their
consolidation properties. The number of specimens involved should be commensurate with
anticipated variability of the tailings conditions in the containment cells. The Licensee should
then consider performing coupled stress and seepage analyses of critical cross-section of Cells 2
and 3, and/or 4A/B. As a minimum, the settlement analyses should be compared with the
drainage/seepage/dewatering analyses to demonstrate that they are consistent. It appears that
such a check was not performed since the discussion of the results of the time-rate of
consolidation/settlement does not make any reference to the dewatering analyses in sub-
Appendix H, despite the fact that the back-calculated coefficients of consolidation of the former
should be proportional to the hydraulic conductivity values of the latter (the coefficient of
consolidation is a composite variable which includes hydraulic conductivity).
Unfortunately, the tailings dewatering analyses presented in sub-Appendix H do not adequately
represent (i.e., account for) potential variations in the tailings properties, nor their potential
distribution within the containment cells. In the models presented for Cells 2 and 3, isotropic
conditions are assumed (which is very unlikely) and a single hydraulic conductivity value is
assigned to all of the tailings (which might be acceptable if the effect/sensitivity of the parameter
had been assessed parametrically - but it wasn't). The hydraulic conductivity value itself
appears to be flawed, apparently being based on the geometric mean of four discrete hydraulic
conductivity values taken from technical literature (representing four generic soil types ranging
from medium sand to silty clayey) which span 5 orders of magnitude. It is inappropriate to use a
type of average, single value to represent such a vast range of hydraulic conductivity. (Although
there is seemingly contradictory information as to what was really used as the basis for the
hydraulic conductivity in the analysis. On page JfsicJ-4 of sub-Appendix H, the text states that
hydraulic conductivity values are based on testing from the Canon City Mill tailings whereas
attachment H-2 indicates that the hydraulic value is based on the aforementioned averaging of
typical values. Clarification is needed). The tailings dewatering analyses should be revisited or
at least clarified and better substantiated. To reliably quantify total and differential both
drainage and settlement characteristics of the tailings, the Licensee should test actual tailings
specimens from the site.
Drainage/seepage/dewatering analyses performed should reflect the tailings and drainage
conditions (including drainage system) associated with each particular cell. One or more cross-
sections may need to be considered. Due to uncertainty and/or inherent variability of the
tailings materials, multiple analyses bracketing the ranges of anticipated engineering properties
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should be performed. Contingencies for less-than-most-likely performance should be
incorporated into the design of the cover system. Particular consideration should be given to
variations in the magnitude of differential settlement as well as the time required to reach 90%
consolidation. In light of the particularly large range in the coefficients of consolidation already
presented by the Licensee, it can be misleading to cite or use "average " values when discussing
or planning other activities (for example, see the monitoring section of the report (sub-Appendix
I ofAppendix D) which states, "a monitoring period offour years prior to final cover system
construction is anticipated, based on the estimated time required to reach 90 percent
consolidation. " All references to settlement magnitude, rate, and duration should be provided as
ranges.
Given the erratic nature exhibited in the existing settlement monitoring data, it is recommended
that the monitoring process be reviewed and revised to assure greater accuracy. As a minimum,
the data should be reviewed as soon as it is gathered and its quality be checked by plotting it
with previous data and making certain that the data makes sense (i.e., is consistent with expected
trends; not showing significant amounts of upward displacement, for example). Questionable
data should be confirmed or replaced with new measurements. Without such quality control
measures, it may become difficult or impossible to demonstrate that 90% consolidation has been
reached and that cover materials can be placed.
It is suggested that statements such as the following from page 1-2 of sub-Appendix I of Appendix
D: "typically less than 0.1 feet (30 mm) of cumulative settlement over a 12 month period is
acceptable " be avoided because such statements might be mistakenly substituted for the real
requirement of 90% consolidation.
The Licensee's assessment of settlement only addresses primary settlement and does not consider
secondary settlement effects (i.e., creep) or seismically-induced settlement of the tailings.
Secondary settlement and seismically induced settlement of the tailings (if any) and their
subsequent effects on the cover system should be assessed. Assessment of settlement under
seismic conditions is dependent upon the Licensee's seismic hazard analysis. Any revisions to
the seismic hazard analysis may necessitate revisions to such an assessment.
NUREG-1620 (NRC 2003), Section 2.3.3, specifies that: "The analysis of tailings settlement will be
acceptable if it meets the following criteria:
(1) Computation of immediate settlement follows the procedure recommended in NAVFAC
DM-7.1 (Department of the Navy, 1982). If a different procedure is used, the basis for the
procedure is adequately explained. The procedure recommended in NAVFAC DM-7.1
(Department of the Navy, 1982) for calculation of immediate settlement is adequate if
applied incrementally to account for different stages of tailings emplacement. If this method
is used, the reviewer should verify that the computation of incremental tailings loading and
the width of the loaded area, as well as the determination of the undrained modulus and
Poisson's ratio, have been computed and documented. Settlement of tailings arises from
compression of soil layers within the disposal cell and in the underlying materials. Because
compression of sands occurs rapidly, compression of sand layers in the disposal cell and
foundations must be considered in the assessment of immediate settlement. However, the
contribution of immediate settlement to consolidation settlement cannot be ignored. Clay
layers and slime undergo instantaneous elastic compression controlled by their undrained
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stiffness as well as long-term inelastic compression controlled by the processes of
consolidation and creep (NRC, 1983a).
(2) Each of the following is appropriately considered in calculating stress increments for
assessment of consolidation settlement:
(a) Decrease in overburden pressure from excavation
(b) Increase in overburden pressure from tailings emplacement
(c) Excess pore-pressure generated within the disposal cell
(d) Changes in ground-water levels from dewatering of the tailings
(e) Any change in ground-water levels from the reclamation action
(3) Material properties and thicknesses of compressible soil layers used in stress change
and volume change calculations for assessment of consolidation settlement are
representative of in situ conditions at the site.
(4) Material properties and thicknesses of embankment zones used in stress change and
volume change calculations are consistent with as-built conditions of the disposal cell.
(5) Values of pore pressure within and beneath the disposal cell used in settlement analyses
are consistent with initial and post-construction hydrologic conditions at the site.
(6) Methods used for settlement analyses are appropriate for the disposal cell and soil
conditions at the site. Contributions to settlement by drainage of mill tailings and by
consolidation/compression of slimes and sands are considered. Both instantaneous and
time-dependent components of total and differential settlements are appropriately
considered in the analyses (NRC, 1983a,b,c). The procedure recommended in NAVFAC
DM-7.1 (Department of the Navy, 1982) for calculation of secondary compression is
adequate.
(7) The disposal cell is divided into appropriate zones, depending on the field conditions, for
assessment of differential settlement, and appropriate settlement magnitudes are calculated
and assigned to each zone.
(8) Results of settlement analyses are properly documented and are related to assessment of
overall behavior of the reclaimed pile.
(9) An adequate analysis of the potential for development of cracks in the radon/infiltration
barrier as a result of differential settlements is provided (Lee and Shen, 1969). "
REFERENCES
DOE (U.S. Department of Energy). 1989. Technical Approach Document, Revision II. UMTRA-
DOE/AL 050425.0002.
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EPA (U.S. Environmental Protection Agency). 1989. Final Covers on Hazardous Waste Landfills
and Surface Impoundments, Technical Guidance Document, EPA/530-SW-89-047, Office of
Solid Waste and Emergency Response, Washington, D. C. URL:
httpJ/webcache.googleuser content, com/search ?q =cache: VEVCaJfyPDQJ.nepis. epa.gov/Exe/Zy
PURL.cgi%3FDockey%3D100019HC.txt+site:epa.gov+EPA+Final+Covers+Guidance&cd=4
&hl=en&ct-clnk&gl=us.
EPA 1991. Seminar Publication, Design and Construction of RCRA/CERCLA Final Covers.
EPA/625/4-91/025.May 1991, 208 pp.
EPA 2004. (Draft) Technical Guidance for RCRA/CERCLA Final Covers. USEPA 540-R-04-
007, OSWER 9283.1-26. April 2004, 421 pp. URL:
nepis. epa.gov/Exe/ZyPURL. cgi?Dockey=Pl 0074PP. txt.
U.S. Nuclear Regulatory Commission 2003. "Standard Review Plan (NUREG-1620) for Staff
Reviews of Reclamation Plans for Mill Tailings Sites Under Title II of The Uranium Mill
Tailings Radiation Control Act", NUREG-1620, June, 2003.
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INTERROGATORY WHITEMESA RECPLAN REV5.0 R313-24-4; 10CFR40
APPENDIX A CRITERION 4; INT 08/1: TECHNICAL ANALYSIS -EROSION
STABILITY EVALUATION
REGULATORY BASIS:
UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A. Criterion 4:
"The following site and design criteria must be adhered to whether tailings or wastes are
disposed of above or below grade:
... (c) Embankment and cover slopes must be relatively flat after final stabilization to minimize
erosion potential and to provide conservative factors of safety assuring long-term stability. The
broad objective should be to contour final slopes to grades which are as close as possible to
those which would be provided if tailings were disposed of below grade; this could, for example,
lead to slopes of about 10 horizontal to 1 vertical (10h.lv) or less steep. In general, slopes
should not be steeper than about 5h:lv. Where steeper slopes are proposed, reasons why a slope
less steep than 5h:lv would be impracticable should be provided, and compensating factors and
conditions which make such slopes acceptable should be identified.
(d) A full self-sustaining vegetative cover must be established or rock cover employed to reduce
wind and water erosion to negligible levels.
Where a full vegetative cover is not likely to be self-sustaining due to climatic or other
conditions, such as in semi-arid and arid regions, rock cover must be employed on slopes of the
impoundment system. The Executive Secretary will consider relaxing this requirement for
extremely gentle slopes such as those which may exist on the top of the pile.
The following factors must be considered in establishing the final rock cover design to avoid
displacement of rock particles by human and animal traffic or by natural process, and to
preclude undercutting and piping:
• Shape, size, composition, and gradation of rock particles (excepting bedding material
average particles size must be at least cobble size or greater);
• Rock cover thickness and zoning of particles by size; and
Steepness of underlying slopes.
Individual rock fragments must be dense, sound, and resistant to abrasion, and must be free from
cracks, seams, and other defects that would tend to unduly increase their destruction by water
and frost actions. Weak, friable, or laminated aggregate may not be used.
Rock covering of slopes may be unnecessary where top covers are very thick (or less); bulk cover
materials have inherently favorable erosion resistance characteristics; and, there is negligible
drainage catchment area upstream of the pile and good wind protection as described in points
(a) and (b) of this criterion.
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Furthermore, all impoundment surfaces must be contoured to avoid areas of concentrated
surface runoff or abrupt or sharp changes in slope gradient. In addition to rock cover on slopes,
areas toward which surface runoff might be directed must be well protected with substantial rock
cover (rip rap). In addition to providing for stability of the impoundment system itself, overall
stability, erosion potential, and geomorphology of surrounding terrain must be evaluated to
assure that there are not ongoing or potential processes, such as gully erosion, which would lead
to impoundment instability.
INTERROGATORY STATEMENT:
Refer to Section 3.3.5 of the Reclamation Plan, Rev. 5.0 and Section 4.9 and Appendix G to
Appendix D (Updated Tailings Cover Design Report), and Drawings TRC-1 through TRC-8 to
the Reclamation Plan, Rev. 5.0: Please provide the following:
I. To further confirm the appropriateness and currency of the calculated Probable Maximum
Precipitation (PMP) value and as used, for example, in the ET cover design erosion
protection rock rip rap sizing calculations, please provide a revised PMP calculation
updating the PMP distribution that incorporates information from the following documents,
in addition to HMR 49 (Hansen et al.1984):
• "2002 Update for Probable Maximum Precipitation, Utah 72 Hour Estimates to
5,000 sq. mi". - March 2003 Jensen 2003); and
• "Probable Maximum Precipitation Estimates for Short Duration, Small Area Storms
in Utah " - October 1995 (Jensen 1995)
2. Using the revised PMP information obtained from Item 1 above, provide revised
calculations of required rock rip rap sizes for the cover sideslope areas using the updated
method developed for round-shaped rip rap as described in Abt et al. 2008. Update and
revise other erosion protection calculation presented in Appendix G, as required and
appropriate, to reflect the revised PMP determination.
3. Please provide additional calculations to estimate the magnitude and location of a potential
gully intrusion into each soil-covered portion of the proposed cover system (e.g., using the
procedure described in Thornton and Abt 2008). Demonstrate that excluding rock (gravel)
particles from the currently proposed fattest (0.1 % and 0.5%) top slope areas would
adequately protect against sheet flow under potential precipitation conditions and would
adequately control longer-term rill and/or gully initiation and development. Provide
information on required "overdesign " of the cover thickness needed to accommodate
maximum predicted gully depths and locations.
4. Provide additional detailed cross sections showing every interface that will occur between
sidelope cover layers and topslope cover layers. Demonstrate that all applicable filter
criteria will be met for each interface between each topslope cover layer component and the
proposed granular filter layer on the sideslope, including standard filter gradation criteria
as well as applicable permeability filter criteria (e.g., for filter layer underlying riprap on
sideslope areas). Consider filter criteria for preventing migration of granular materials
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into an adjacent coarser grained granular layer (e.g., Nelson et al. 1986, Equation 4.35);
for preventing piping of finer grained cohesionless soil particles into an adjacent coarser-
grained material layer (e.g., Cedegren 1989, Equation 5.3); and for preventing erosion of a
finer-grained material layer from occurring over the long term as a result of flows in an
adjacent coarser (filter zone) layer (e.g., Nelson et al. 1986, Equation 4.36). Include
consideration of different specific filter stability criteria (e.g., NRCS 1994, Tables 26-1 and
26-2) for determining the maximum allowable D15 of a granular filter layer material for
preventing erosion of any adjacent layer (e.g., sacrificial soil layer) consisting offine-
grained/finer-grained particles, as a function of soil type. Address applicable filter
permeability criteria for the filter layer in the sideslope cover system, including Table 26-3
of NRCS 1994.
5. Provide revised cover system cross sections to include a thicker riprap layer on the cover
sideslope areas (i.e., minimum thickness of 1.5 times the D$o of the rock rip size of 7.4
inches, or the Dm of the rock rip rap materials, whichever is greater) to bring the cover
design into compliance with recommendations contained in Section 2.1.2 of NUREG-1623
(NRC 2002).
6. Provide revised construction drawings for the final cover that preclude the presence of low
areas that have the potential for experiencing future concentrated flows (e.g., portion of
cover overlying Cell 2 as depicted on Section B-3 on Drawing TRC-7) and that avoid areas
having abrupt changes in slope gradient across the cells, (e.g., areas of cover having
proposed 5h:lv slopes shown on Sections B-3 and C-3 on Drawings TRC-6 and TRC-7 and
Detail 7/8 on Drawing TRC-8, etc..) to be consistent with UAC R313-24-4 10CFR40,
Appendix A, Criterion 4.
BASIS FOR INTERROGATORY:
When determining the PMP for facilities such as High Hazard and Moderate Hazard dams, the
State of Utah currently requires the use ofHMR 49, which DUSA has used in Attachment G to
the Reclamation Plan 4.0 (Denison 2009) and referenced in Appendix D to the Reclamation Plan
5.0 (Denison 2011), but also in conjunction with the use of two other reports: (1) the "2002
Update for Probable Maximum Precipitation, Utah 72 Hour Estimates to 5,000 sq. mi. - March
2003 " and (2) "Probable Maximum Precipitation Estimates for Short Duration, Small Area
Storms in Utah - October 1995. " Although these two methods were developed (by the Utah
Climate Center) for estimating PMF conditions for design of dams, these methods are
considered to be more representative of actual meteorological conditions in Utah than those
considered in HMR 49. The erosion protection calculations presented in Appendix G (Erosion
Stability Evaluation) should to be revised as needed to reflect the revised PMP determination
findings, as appropriate, to demonstrate that applicable erosion protection requirements will be
met.
The Modified Universal Soil Loss Equation (MUSLE) was used (Appendix G to Appendix D to
the Reclamation Plan) to evaluate erosion losses from the topslope areas of the cover due to
sheet flow but does not consider the potential for gully development or intrusion due to the
topographic features of the tailings area which are assumed to remain constant with time
(Nelson 1986).
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Although the Temple method (Appendix D) was appropriately used to evaluate the erosional
stability of portions of the cover comprised of "topsoil and vegetation " and "topsoil mixed with
gravel" —coveredslopes, the method assumes only minor channeling, gullying, or rilling. Due to
the relatively large and flat nature of the currently proposed topslope areas, these assumptions
may or may not reflect actual conditions that are expected to occur. It is possible that less or
more severe flow concentrations would occur and vegetation would or would not provide
significant protection. Research has demonstrated that if localized erosion and gullying occurs,
damage to unprotected soil covers may occur rapidly, probably in a time period shorter than 200
years (NUREG-1623 [NRC 2002]). It needs to be demonstrated that all slopes are designed to
meet NUREG-1623 requirements, i.e., that "Soil slopes of a reclaimed tailings impoundment
should be designed to be stable and thus inhibit the initiation, development, and growth of
gullies. " A procedure developed by Thornton and Abt (2008), which builds upon a preliminary
procedure developed by Abt et al. 1997 (as discussed in Appendix B of NUREG-1623), provides
a means of estimating the magnitude and location of a potential gully intrusion into the flat
topslope areas of the cover.
Additional descriptive information and supporting calculations need to be provided to
demonstrate that all applicable filter criteria are met for all topslope cover/ sideslope cover
layer interfaces. Acceptable filter sizing criteria for preventing migration of the selected
filter/bedding materials into the riprap and for minimizing or preventing erosion of the soil layer
below the filter/bedding layer, and for meeting filter permeability criteria are described in
NUREG/CR-4620 (Nelson et al. 1986), Cedegren 1989 and NCRS 1994.
In addition, currently, it is unclear from Drawings TRC-1 through TRC-8 of the Reclamation
Plan Rev. 5.0 as to whether filter blankets or bedding layers are or are not included in some
areas, for example, areas along toes of slopes, transition areas, diversion ditches and channels,
stilling areas, and flow impact areas, which are typically areas described in NUREG-1623 as
areas where filters are generally recommended. A demonstration of long-term layer stability is
needed to justify the omission of a filter/bedding blanket in the final cover system and in any
such areas.
Cross sections TRC-6 and TRC-7 provided in the Reclamation Plan Rev. 5.0 depict abrupt slope
changes in the tailings cover when crossing Cell 2 to Cell 1 and Cell 2 to Cell 3. The cross
sections should be revised to meet the above UAC R313-24-4, 10CFR40, Appendix A, Criterion
4 "....all impoundment surfaces must be contoured to avoid areas of concentrated surface runoff
or abrupt or sharp changes in slope gradient. "
NUREG-1623 (NRC 2002), Section 2.1.2 recommends that the minimum required thickness of a
rock riprap layer be no less than 1.5 times the D50 of the rock riprap materials, or the D100 of
the rock rip rap materials, whichever is greater.
REFERENCES:
Abt, S.R., Thornton, CI, Batka, J.H., and Johnson, TL. 1997. "Investigation of Gully
Stabilization Methods with Launching Stone: Pilot Laboratory Tests " Prepared for the U.S.
Nuclear Regulatory Commission, Washington, D.C. February 1997.
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Abt, S.R., Thornton, CL, Gallegos, H, and Ullmann, C. 2008. "Round-Shaped Riprap
Stabilization in Overtopping Flow, "Journal of Hydraulic Engineering, Vol. 134, No. 8, August
2008, pp. 1035-1041.
Bertram, G.E. 1940. An Experimental Investigation of Protective Filters. Graduate School of
Engineering, Harvard University, Cambridge, Massachusetts. Soil Mechanics Series No. 7. pp.
1-21.
Cedegren.H.R. 1989. Seepage, Drainage, and Flow Nets. 3rd Edition. John Wiley $ & Sons,
Inc., New York, NY.
Denison Mines (USA) Corporation. 2011. Reclamation Plan, Revision 5.0, White Mesa Mill,
Blanding, Utah, September 2011.
Hansen, E., Schwarz, F., and Riedel, J. 1984. Probable Maximum Precipitation Estimates,
Colorado River and Great Basin Drainages. Hydrometeorological Report No. 49. US
Department of Commerce, National Oceanic and Atmospheric Administration, Reprinted 1984.
Jensen, D. 1995. 2002 Update for Probable Maximum Precipitation, Utah 72 Hour Estimates to
5,000 sq. mi. - March 2003. Utah Climate Center.
Jensen, D. 2003. Probable Maximum Precipitation Estimates for Short Duration, Small Area
Storms in Utah - October 1995. Utah Climate Center.
Nelson, J.D., Abt, S.R., Volpe, R.L, van Zyl, D., Hinkle, N.E., and Staub, W.P. 1986.
Methodologies for Evaluating Long-Term Stabilization Designs of Uranium Mill Tailings
Impoundments. Prepared for Nuclear Regulatory Commission, Washington, DC. NUREG/CR-
4620, ORNL/TM-10067. June 1986, 151 pp.
NRC 2002. U.S. Nuclear Regulatory Commission, "Design of Erosion Protection for Long-Term
Stability ", NUREG-1623, September 2002.
NRCS (Natural Resources Conservation Service) 1994. U.S. Department of Agriculture, Part
633, National Engineering Handbook, Chapter 26: Gradation Design of Sand and Gravel
Filters. October 1994.
Thornton, C, and Abt, S. 2008. "Gully Intrusion into Reclaimed Slope: Long-Term Time-
Average calculation Procedure", Journal of Energy Engineering, Vol. 134, No. 1, March 2008,
pp. 15-23.
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INTERROGATORY WHITEMESA RECPLAN REV. 5.0; R313-24-4; 10CFR40
APPENDIX A CRITERION 1; INT 09/1: LIQUEFACTION
REGULATORY BASIS
UAC R313-24-4 invokes the following requirement from 10CFR40 Appendix A. Criterion 1: The
general goal or broad objective in siting and design decisions is permanent isolation of tailings
and associated contaminants by minimizing disturbance and dispersion by natural forces, and to
do so without ongoing maintenance. For practical reasons, specific siting decisions and design
standards must involve finite times (e.g., the longevity design standard in Criterion 6). The
following site features which will contribute to such a goal or objective must be considered in
selecting among alternative tailings disposal sites or judging the adequacy of existing tailings
sites:
• Remoteness from populated areas;
• Hydrologic and other natural conditions as they contribute to continued immobilization
and isolation of contaminants from ground-water sources; and
• Potential for minimizing erosion, disturbance, and dispersion by natural forces over the
long term.
... While isolation of tailings will be a function of both site and engineering design, overriding
consideration must be given to siting features given the long-term nature of the tailings hazards.
Tailings should be disposed of in a manner that no active maintenance is required to preserve
conditions of the site.
INTERROGATORY STATEMENT:
Refer to Section 4.8 and Appendices C and F to the Appendix D, Updated Tailings Cover
Design Report of the Reclamation Plan, Rev. 5:
1. Provide revised liquefaction analyses that rely upon actual site-specific data for the
tailings materials, rather than assumed parameters. In doing so, revise the Reclamation
Plan to correctly and defensibly characterize tailings properties consistent with these
revisions throughout the document.
2. Correct apparent errors and conduct revised analyses using parameter values that are
based on site-specific data. Correct discrepancies between calculated results and
summarized, reported results.
3. Demonstrate that conditions assumed for liquefaction analyses are consistent with or
conservative compared to results of tailings dewatering analyses. If this is not true,
revise liquefaction analyses to be consistent with or conservative compared to results of
tailings dewatering analyses, report results, and demonstrate that impoundments will
remain stable with regard to liquefaction.
BASIS FOR INTERROGATORY
NUREG-1620 (NRC 2003), Section 2.2.3, specifies the following with respect to slope stability
analyses and assessment of liquefaction potential: "...The analysis of slope stability will be
acceptable if it meets the following criteria:
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...(3) Appropriate analyses considering the effect of seismic ground motions on slope stability are
presented.
...(j) Where there is potential for liquefaction, changes in pore pressure from cyclic loading are
considered in the analysis to assess the effect of pore pressure increase on the stress-strain
characteristics of the soil and the post-earthquake stability of the slopes. Liquefaction potential is
reviewed using Section 2.4 of this review plan. Evaluations of dynamic properties and shear
strengths for the tailings, underlying foundation material, radon barrier cover, and base liner
system are based on representative materials properties obtained through appropriate field and
laboratory tests (NRC 1978, 1979)....
NUREG-1620 (NRC 2003), Section 2.4.3, specifies that: "The analysis of the liquefaction
potential will be acceptable if the following criteria are met:
(1) Applicable laboratory and/or field tests are properly conducted (NRC, 1978, 1979; U.S.
Army Corps of Engineers, 1970, 1972).
(2) Data for all relevant parameters for assessing liquefaction potential are adequately collected
and the variability has been quantified.
(3) Methods used for interpretation of test data and assessment of liquefaction potential are
consistent with current practice in the geotechnical engineering profession (Seed and Idriss,
1971, 1982; National Center for Earthquake Engineering Research, 1997). An assessment of
the potential adverse effects that complete or partial liquefaction could have on the stability
of the embankment may be based on cyclic triaxial test data obtained from undisturbed soil
samples taken from the critical zones in the site area (Seed and Harder, 1990; Shannon &
Wilson, Inc. and Agbabian-Jacobsen Associates, 1972).
(4) If procedures based on laboratory tests combined with ground response analyses are used,
laboratory test results are corrected to account for the difference between laboratory and
field conditions (NRC, 1978; Naval Facility Engineering Command, 1983).
(5) The time history of earthquake ground motions used in the analysis is consistent with the
design seismic event.
(6) If the potential for complete or partial liquefaction exists, the effects such liquefaction could
have on the stability of slopes and settlement of tailings are adequately quantified.
(7) If a potential for global liquefaction is identified, mitigation measures consistent with
current engineering practice or redesign of tailings ponds/embankments are proposed and
the proposed measures provide reasonable assurance that the liquefaction potential has been
eliminated or mitigated.
(8) If minor liquefaction potential is identified and is evaluated to have only a localized effect
that may not directly alter the stability of embankments, the effect of liquefaction is
adequately accounted for in analyses of both differential and total settlement and is shown
not to compromise the intended performance of the radon barrier. Additionally, the disposal
cell is shown to be capable of withstanding the liquefaction potential associated with the
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expected maximum ground acceleration from earthquakes. The licensee may use post-
earthquake stability methods (e.g., Ishihara and Yoshimine, 1990) based on residual
strengths and deformation analysis to examine the effects of liquefaction potential.
Furthermore, the effect ofpotential localized lateral displacement from liquefaction, if any,
is adequately analyzed with respect to slope stability and disposal cell integrity.
The liquefaction analysis presented by the Licensee is based on the procedures presented in
Youd et al. (2001). While newer methods have been introduced and are being used, this method
is still an acceptable, state-of-practice method provided that borderline finer-grained soils are
appropriately assessed (see Boulanger and Idriss, 2006; Bray and Sancio, 2006; Boulanger and
Idriss, 2011). Aside from the earthquake magnitude and ground acceleration, the most
important parameter in the analysis is the in-situ penetration resistance parameter (which in this
case is an SPT blowcount) which provides a measure of the soil's resistance to liquefaction. In
the Licensee's analysis, this SPT blowcount has been assumed to be 4 without any substantial
justification - the justification provided in the report is that the analyst considered the tailings to
be "loose " and that such a term is often correlated with a blowcount in the range of 4 to 10.
However, it seems that analyst could have alternatively assumed that the tailings were "very
loose, " leading to a blowcount in the range of 0 to 4, thus significantly affecting the outcome of
the analysis. Also, elsewhere in the report (when approximating the shear strength of the
drained tailings), the Licensee assumes that the tailings have a relative density of near zero, and
a relative density of zero and a blow count of 4 are typically inconsistent.
A similar issue with consistency appears to exist in the characterization of the tailings' unit
weight where dry and saturated unit weights of 86.3 and 117.1 pcf, respectively, are presented in
Section F.2.2 of sub-Appendix F in Appendix D of the Reclamation Plan, Rev. 5.0, whereas a dry
unit weight of 74.3 pcf is presented in Section C. 2.4 of sub-Appendix C ofAppendix D).
Consistent characterization of the tailings throughout the report seems to be needed, and more
importantly, with respect to liquefaction, a more substantiated blowcount describing the tailings
is needed. If data doesn't exist, it must be collected, not manufactured.
It is noted that the results presented in Table F.5 'Summary of Liquefaction Results' do not agree
with the calculated values shown in Attachment F.3. Further, it appears from the text that the
Licensee intended to have the cover in place for the analysis (the Licensee should clearly explain
the configuration of the impoundment and tailings reflected in the calculations); however, the
weight of the cover seems to have been omitted from the calculated total and effective vertical
stresses. Also, if the depth parameter "z " in the calculations is intended to reference from the
top of the tailings as the datum, and given the stated "depth from top of tailings to water
surface ", it appears that effective stresses have been calculated incorrectly. Calculation of the
overburden correction factor should also be checked.
Assessment of liquefaction is dependent upon the Licensee's seismic hazard analysis. Any
revisions to the seismic hazard analysis may necessitate revisions to this assessment. Also, the
applicability of the liquefaction hazard analysis is dependent upon the outcome of tailings
dewatering analyses, and the Licensee should demonstrate that the results such analyses are
appropriately interpreted (i.e., are at least consistent with, if not conservative) for the
liquefaction hazard analysis.
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REFERENCES
Boulanger, R. W. and Idriss, I.M. (2006). "Liquefaction susceptibility criteria for silts and
clays. " J. of Geotechnical and Geoenvironmental Eng., ASCE, Vol. 132, No. 11, pp. 1413-1426.
Bray, J.D. and Sancio, R.B. (2006). "Assessment of the liquefaction susceptibility offine grained
soils. "J. of Geotechnical and Geoenvironmental Eng., ASCE, Vol. 132, No. 9, pp. 1165-1177.
Boulanger, R. W. and Idriss, I.M. (2011). "Cyclic failure and liquefaction: Current issues. "
Proc. Fifth International Conf. of Earthquake Geotechnical Eng., Santiago, Chile.
MWH Americas 2011. Appendix C - Radon Emanation Modeling, and Appendix F-
Settlement and Liquefaction Analysis, contained in Appendix D, Updated Tailings Cover Design
Report, White Mesa Mill, September 2011 to the Reclamation Plan, White Mesa Mill, Rev. 5.0,
September 2011.
NRC 1982. U.S. Nuclear Regulatory Commission, "Regulatory Guide 3.8; Preparation of
Environmental Reports for Uranium Mills ", Washington DC, October 1982.
NRC 2001. U.S. Nuclear Regulatory Commission, "Environmental Review Guidance for
Licensing Actions Associated with NMSS Programs. " Washington, DC, 2001.
NRC 2003. U.S. Nuclear Regulatory Commission, "Standard Review Plan for the Review of a
Reclamation Plan for Mill Tailings Sites Under Title II of the Uranium Mill Tailings Radiation
Control Act of1978. " Washington DC, June 2003.
Youd, T. L., Idriss, I. M., Andrus, R. D., Arango, I., Castro, G., Christian, J. T, Dobry, R., Finn,
W. D. L., Harder, L. F., Jr., Hynes, M. E., Ishihara, K., Koester, J. P., Liao, S. S. C, Marcuson,
W. F., Ill, Martin, G. R., Mitchell, J. K., Moriwaki, Y., Power, M. S., Robertson, P. K., Seed, R.
B., and Stokoe, K. H, II. (2001). "Liquefaction resistance of soils: summary report from the
1996 NCEER and 1998 NCEER/NSFworkshops on evaluation of liquefaction resistance of
soils. " J. of Geotechnical and Geoenvironmental Eng., ASCE, Vol. 127, No. 10, pp. 817-833.
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INTERROGATORY WHITEMESA RECPLAN 5.0 R313-24-4; 10CFR40 APPENDIX A,
CRITERION 6; INT 10/1: TECHNICAL ANALYSES - FROST PENETRATION
ANALYSIS
REGULATORY BASIS:
Refer to R313-25-8(4). Analyses of the long-term stability of the disposal site shall be based
upon analyses of active natural processes including erosion, mass wasting, slope failure,
settlement of wastes and backfill, infiltration through covers over disposal areas and adjacent
soils, and surface drainage of the disposal site. The analyses shall provide reasonable
assurance that there will not be a need for ongoing active maintenance of the disposal site
following closure.
UAC R313-24-4 invokes the following requirement from 10CFR40. Appendix A, Criterion 6(1): "In
disposing of waste byproduct material, licensees shall place an earthen cover (or approved
alternative) over tailings or wastes at the end of milling operations and shall close the waste
disposal area in accordance with a design which provides reasonable assurance of control of
radiological hazards to (i) be effective for 1,000 years, to the extent reasonably achievable, and,
in any case, for at least 200 years, and (ii) limit releases of radon-222from uranium byproduct
materials, and radon-220from thorium byproduct materials, to the atmosphere so as not to
exceed an average release rate of 20 picocuries per square meter per second (pCi/m2s) to the
extent practicable throughout the effective design life determined pursuant to (l)(i) of this
criterion. In computing required tailings cover thicknesses, moisture in soils in excess of
amounts found normally in similar soils in similar circumstances may not be considered. Direct
gamma exposure from the tailings or wastes should be reduced to background levels. The effects
of any thin synthetic layer may not be taken into account in determining the calculated radon
exhalation level. If non-soil materials are proposed as cover materials, it must be demonstrated
that these materials will not crack or degrade by differential settlement, weathering, or other
mechanism, over long-term intervals. "
NUREG-1620 specifies that "Reasonable assurance [shall be] provided that the requirements of
10 CFR Part 40, Appendix A, Criterion 6(1), which requires that the design of the disposal
facility provide reasonable assurance of control of radiological hazards to be effective for 1,000
years, to the extent reasonably achievable, and, in any case, for at least 200 years, have been
met."
INTERROGATORY STATEMENT:
Refer to Section 4.3 of Appendix D (Updated Tailings Cover Design Report) and Appendix
B (Freeze/Thaw Modeling) to Appendix D to the Reclamation Plan Rev. 5.0:
1. Please revise freeze/thaw analyses to incorporate the following:
a. Extrapolation offrost depth to recurrence interval to a minimum period of up to
1,000 years, to the extent practicable, or, to not less than 200 years, using a Gumbel
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extreme statistics (probability functions) approach (e.g., Smith and Rager 2002;
Smith 1999; Yevjevich 1982).
b. Additional justification for selection of an N -factor (surface temperature correction
factor) of 0.6, instead of an N-factor of 0.7, based on published recommendations
(e.g., DOE 1989).
c. Additional justification that using climate data for Grand Junction, Colorado in the
Berggren Model Formula (BMF) is representative of site conditions at the White
Mesa site Address the considerably lower elevation and average warmer
temperatures of Grand Junction compared to the White Mesa site. Either (1) prepare
and report results of the BMF calculations using a default location having an
elevation and Design Freezing Index equal to or greater than those of the White Mesa
site AND mean average temperatures equal to or less than those of the White Mesa
site OR (2) justify that the Grand Junction data is applicable and representative as
input to the BMF calculations for the White Mesa site.
2. Based on the results of the revised frost penetration analysis, justify revised soil
parameter values for soils within the cover system above the projected frost penetration
depth considering the effects of repeated freezing and thawing over the recurrence
interval considered (referred to in Item La above). Use these parameter values in
performance assessment modeling, including infiltration modeling and radon attenuation
modeling, consistent with recommendation provided in Sections 2.5 and 5.1 of NUREG-
1620 (NRC 2003).
3. If applicable after addressing the instructions stated above, revise Appendix B to
Appendix D of the Reclamation Plan to ensure that all intended text is present in the
document.
BASIS FOR INTERROGATORY:
The Division acknowledges that the Modified Berggren Formula has been used to estimate the
depth offrost penetration at the site, relying upon input from a built-in long-term weather
database. However, the input parameters do not account for extreme climate conditions. • In
addition, in Appendix B, it is noted that the mean annual temperature for Blanding given by
Dames and Moore (1978) is 49.8 degrees F and the mean annual temperature for Grand
Junction, CO, is 53.1 degrees F. The Grand Junction mean annual temperature used in the
White Mesa calculations is higher, i.e. less conservative, than Blanding's mean temperature.
Grand Junction's elevation is also considerably lower than that of either Blanding or the White
Mesa site.
The use of a Gumbel extreme value statistics approach provides an accepted means for
extrapolating a worst case value from a limited set of data. This technical approach has been
successfully applied at other similar facilities (e.g., Monticello, Utah tailings repository cover -
200 year recurrence interval; Crescent Junction, Utah tailings repository cover- 1,000 year
recurrence interval [e.g., see NRC 2008]). Extending the recurrence interval for the frost depth
penetration analysis further informs predictions ofpotential future maximum frost penetration
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depths and allows insights into the potential risk reduction afforded to performance assessment
predictions made for evaluating the performance of the cover system over long term
performance periods.
U.S.D.O.E. (1989), based on recommendations by the U.S. Army Corps of Engineers Cold
Regions Research and Engineering Laboratory (CRREL), and Smith (1999) recommend that an
N-factor of 0.7 be used for landfill cover designs. Additional information should therefore be
provided to support the selection and use of an N-factor value of 0.6, rather than 0.7, in the
calculation, or alternatively, an N-factor value of 0.7 should be used in the calculation.
Section numbers in Appendix B ofAppendix D of the Reclamation Plan suggest that sections are
missing or that the section numbering is incorrect.
REFERENCES:
Denison Mines (USA) Corporation. 2011. Reclamation Plan, Revision 5.0, White Mesa Mill,
Blanding, Utah, Appendix D: September 2011.
NRC 2003. NUREG-1620: Standard Review Plan for the Review of a Reclamation Plan for Mill
Tailings Sites under Title II of the Uranium Mill Tailings Radiation Control Act of1978.
Washington DC, June 2003.
NRC 2008. "Summary of Changes to Moab Disposal Cell Calculations ". NRC ADAMS
Website: Document Accession Number ML081700262.
Smith, G.M., and Rager, R.E. 2002. "Protective Layer Design in Landfill Covers Based on Frost
Protection ". Journal of Geotechnical and Geoenvironmental Engineering, Vol. 128, No. 9,
September 1, 2002, pp. 794-799.
Smith, G.M., 1999. Soil Insulation for Barrier Layer Protection in Landfill Covers, in
Proceedings from the Solid Waste Association of North America's 4th Annual Landfill
Symposium, Denver, Colorado, June 28-30, 1999.
U.S.D.O.E. 1989. Technical Approach Document, Rev. II, UMTRA-DOE/AL 050425.0002,
Albuquerque, New Mexico.
Yevjevich, V. 1982. Probability and Statistics in Hydrology, 3rd Edition. Water Resources
Publications, Littleton, Colorado.
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INTERROGATORY WHITE MESA RECPLAN REV 5.0 R313-24-4; 10CFR40
APPENDIX A; INT 11/1: VEGETATION AND BIOINTRUSION EVUALATION AND
REVEGETATION PLAN
REGULATORY BASIS:
UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 1:-The
general goal or broad objective in siting and design decisions is permanent isolation of tailings
and associated contaminants by minimizing disturbance and dispersion by natural forces, and to
do so without ongoing maintenance. For practical reasons, specific siting decisions and design
standards must involve finite times (e.g., the longevity design standard in Criterion 6). The
following site features which will contribute to such a goal or objective must be considered in
selecting among alternative tailings disposal sites or judging the adequacy of existing tailings
sites:
• Remoteness from populated areas;
• Hydrologic and other natural conditions as they contribute to continued immobilization
and isolation of contaminants from ground-water sources; and
• Potential for minimizing erosion, disturbance, and dispersion by natural forces over the
long term.
• The site selection process must be an optimization to the maximum extent reasonably
achievable in terms of these features.
In the selection of disposal sites, primary emphasis must be given to isolation of tailings or
wastes, a matter having long-term impacts, as opposed to consideration only of short-term
convenience or benefits, such as minimization of transportation or land acquisition costs. While
isolation of tailings will be a function of both site and engineering design, overriding
consideration must be given to siting features given the long-term nature of the tailings hazards.
Tailings should be disposed of in a manner that no active maintenance is required to preserve
conditions of the site.
UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 4: The
following site and design criteria must be adhered to whether tailings or wastes are disposed of
above or below grade:
(a) Upstream rainfall catchment areas must be minimized to decrease erosion potential and the
size of the floods which could erode or wash out sections of the tailings disposal area.
(b) Topographic features should provide good wind protection.
(c) Embankment and cover slopes must be relatively flat after final stabilization to minimize
erosion potential and to provide conservative factors of safety assuring long-term stabililty. The
broad objective should be to contour final slopes to grades which are as close as possible to
those which would be providedif tailings were disposed of below grade; this could, for example,
lead to slopes of about 10 horizontal to 1 vertical (10h.lv) or less steep. In general, slopes
should not be steeper than about 5h:lv. Where steeper slopes are proposed, reasons why a slope
less steep than 5h:lv would be impracticable should be provided, and compensating factors and
conditions which make such slopes acceptable should be identified.
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(d) A full self-sustaining vegetative cover must be established or rock cover employed to reduce
wind and water erosion to negligible levels.
Where a full vegetative cover is not likely to be self-sustaining due to climatic or other
conditions, such as in semi-arid and arid regions, rock cover must be employed on slopes of the
impoundment system. The Executive Secretary will consider relaxing this requirement for
extremely gentle slopes such as those which may exist on the top of the pile....
UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A. Criterion 6(1): In
disposing of waste byproduct material, licensees shall place an earthen cover (or approved
alternative) over tailings or wastes at the end of milling operations and shall close the waste
disposal area in accordance with a design which provides reasonable assurance of control of
radiological hazards to (i) be effective for 1,000 years, to the extent reasonably achievable, and,
in any case, for at least 200 years, and (ii) limit releases of radon-222 from uranium byproduct
materials, and radon-220 from thorium byproduct materials, to the atmosphere so as not to
exceed an average release rate of 20 picocuries per square meter per second (pCi/m2s) to the
extent practicable throughout the effective design life determined pursuant to (l)(i) of this
Criterion. In computing required tailings cover thicknesses, moisture in soils in excess of
amounts found normally in similar soils in similar circumstances may not be considered. Direct
gamma exposure from the tailings or wastes should be reduced to background levels. The effects
of any thin synthetic layer may not be taken into account in determining the calculated radon
exhalation level. If non-soil materials are proposed as cover materials, it must be demonstrated
that these materials will not crack or degrade by differential settlement, weathering, or other
mechanism, over long-term intervals.
INTERROGATORY STATEMENT:
Refer to Section 1.7.1, 3.3.1.0 and Appendices D and J of the Reclamation Plan Rev. 5.0:
Please provide the following:
1. Provide additional information (e.g., in the form of a survey and additional
documentation of existing animal and vegetation species that exist at the White Mesa
site and nearby surrounding region at this time to update the older information
provided earlier.
2. Update the list of plant and animal species to include plant and animal species (e.g.
burrowing animals) that could reasonably be expected to inhabit or colonize the
White Mesa site within the required performance period of the embankment (1,000
years, and in no case less than 200 years). In revising these lists, account for the
types of vegetation and soils present in the vicinity of the White Mesa site and
proximity to the high quality northern pocket gopher and badger habitat indicated in
Utah distribution maps (Utah Division of Wildlife Resources).
3. Please report the estimated range of burrowing depths and burrow densities for
animal species found at the site and nearby surrounding region (once the updated
study requested above is complete), and for burrowing species that may reasonably
be expected to inhabit the site within the required performance period of the
embankment (1,000 years, and in no case less than 200 years). Please comment on
the root densities provided in Appendix D of the ICTM report. Indicate whether the
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correct root density units were used in Table D-3 and Figure D-1. Also verify that
the correct values were used in the HYDRUS-2D infiltration model, since an
erroneously high value of root density could overestimate plant transpiration and
underestimate infiltration.
4. Rectify the mischaracterization of two plant species as presented in the two
referenced documents (Festuca ovina and common yarrow).
5. Provide additional documentation to support conclusions made regarding the ability
of the proposed vegetation to establish at the cover percentages predicted. Also,
provide additional discussion regarding the potential sustainability of the cover
design and characteristics as proposed relative to changes that could occur due to
the effects of natural succession and climate change during the performance period
(1,000 years, and in no case less than 200 years).
6. Perform and report results of an additional infiltration sensitivity analysis to address
the effects of deep-rooted plants projected by the updated analysis described above.
In particular, account for any potentially deep-rooted species to assess the their
effects of such deep-rooted species on the characteristics of soil layers in the
embankment cover system. Please provide a forecasted percentage of potential
species invasions in the ET cover system.
BASIS FOR INTERROGATORY:
Burrowing animals have the potential to penetrate the cover system and disturb the waste
tailings of a cell. The burrowing animal could disturb the cover system resulting in "channels for
movement of water, vapors, roots, and other animals " EPA, Draft Technical Guidance for
RCRA/CERCLA Final Covers, April 2004 [EPA 2004]). The extent of damage caused by animal
burrowing depends on the animals burrowing depth ability. Mammals such as the badger and
deer mouse have been reported at the site and/or nearby the site and can burrow to depths of
150-230 cm [4.9 to 7.5 ft] (Anderson and Johns 1977, Gano and States 1982, Cline, et al. 1982
and Lindzey 1976) and 50 cm [1.6 ft], respectively (Reynolds and Laundre 1988 and Reynolds
and Wakkinen 1987, and Smith, et al. 1997). Moisture content and physical features of the soil
can affect burrowing potential (Reichman and Smith 1990). Maximum burrowing depths for
animals at or near the site should be identified and appropriate measures taken to protect the
cover system, especially the radon barrier layer, from potential long-term damage/disruption by
burrowing animals.
Although Dames and Moore (1978) did not report pocket gophers and reported badgers only
had possibly a minor presence, the type of vegetation and soils present surrounding the facility is
typical habitat and Utah distribution maps (Utah Division of Wildlife Resources) show that the
facility is within or near the edge of high quality northern pocket gopher and badger habitat.
Given the 34 years since the Dames and Moore study, these species could occur now and will
likely occur at some point during the next 200 - 1000 years. Their potential presence needs to
be acknowledged and considered in the design. Other burrowing species that are not addressed
and should be assessed include coyote and red fox.
The prairie dog species that could occur in this area is Gunnison's prairie dog. The statement
regarding maximum burrowing depths for Gunnison's prairie dog does not appear to represent
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current data, for example Verdolin, Lewis, and Slobodchikoff (2008), which show studies with
depths over one meter. The statement that prairie dogs are unlikely to colonize the tailing cells
is generally true, but does not consider all potential events that could occur over an extended
period of time, such as prolonged drought, fire, or natural succession, that could affect plant
cover.
The documents provide one reference (Waugh et al. 2008) for the ability to achieve 40%
vegetation cover for a long-term average and 30% under drought conditions. More support is
needed that this cover can be sustained long-term and under drought conditions. Regional data
and/or data on the current plant cover of the grassland vegetation at the White Mesa Mill should
be present to support these cover percentages. The ground cover measurements by Dames and
Moore 1978 (provided on page 1-125 of Reclamation Plan) are substantially less than 40%, but
were collected during a drought and were likely affected by past grazing.
The vegetation map and cover data presented in the Reclamation Plan Rev. 5.0 for the
vegetation present at the facility are 35 years old and do not represent current conditions. In
addition, some of the cells are identified as being partially reclaimed and no information is
provided on reclamation methods or success that would support the claim of being able to
achieve 40%> average cover. Current data should be provided to support the estimates of
potential cover expected to be achieved on the tailing cells. More detailed information should be
provided on deep-rooted species that currently occur in the study area and that could become
established on the tailing cells. There is little information provided on the composition of local
plant communities.
The plan does not adequately address the potential for natural succession over the 200-1000
year time frame. The use of competitive grasses may exclude sagebrush for several decades, but
may not work in perpetuity. Shrub succession in seeded grasslands is a common phenomenon,
and appears to be occurring on portions of the seeded grasslands surrounding the White Mesa
facility, based on current aerial photographs. There should be a discussion of natural
successionalprocesses that could occur. Big sagebrush is the regional climax dominant on deep
soils such as the tailing cells will provide. The eventual occurrence of some amount of big
sagebrush should be identified as a possibility and the analysis should include an evaluation of
the compatibility of big sagebrush root systems with the cover design, including depth of the soil
and compacted layers. The highly compacted zone is likely to exclude all or most roots, even for
deep rooted species. References could be added to support this. There is a lower potential for
establishment ofpinon and juniper.
According to Dames and Moore (1978), Table 2.8-2, community types identified within the site
boundary include Pinion-juniper Woodland, Big Sagebrush, and Controlled Big Sagebrush.
Different published references indicate that Big Sagebrush in the western U.S. can exhibit
deeper rooting depths (e.g., see Waugh, et al. 1994; Foxx, et al.1984; Klepper, et al. 1985,
Reynolds 1990b). The statement in D.4.3 to Appendix D to Appendix D of the Reclamation Plan
Rev. 5.0, that "... species like sagebrush, pinon pine, and Utah juniper have become dominant
components of the regional flora primarily because of decades of overgrazing that has removed
more palatable grasses and forbs and allowed less palatable woody species to establish and
expand their range... " is an oversimplification and does not recognize that these species are the
climax species over a large portion of the Intermountain area. While overgrazing has certainly
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reduced the abundance of perennial grasses and has led to shrub/tree invasion in some areas,
there is no evidence that these areas were primarily grassland prior to European settlement.
Table D-3 lists root densities that were used in the infiltration modeling. The values range from
zero to 6.2 grams per cubic centimeter. The same values are shown graphically in Figure D-1
and again in Appendix G, Figure G-l. It seems unreasonable to have such high root densities
when the soil densities are no greater than about 2 grams per cubic centimeter. Clarify whether
the units in Table D-3 (g cm-3) are correct. Alternative units might be milligrams (rather than
grams) of roots per cubic centimeter or centimeters of root length per cubic centimeter of soil.
It appears that all of the conclusions in the analysis of the effects of climate change are based on
one 23-year old study. Additional support is needed. In particular, the effects of extended
droughts should be addressed in more detail.
The documents mischaracterize the native status of two species. Festuca ovina is considered to
be introduced and not native throughout the entire lower 48 states (NRCS 2012). Common
yarrow includes both introduced and native sub-species. The seed mix should specify the yarrow
subspecies that is native to southern Utah. Several statements are made that the seed mix is
comprised of natives, while it is actually a mix of native and introduced species.
In the Reclamation Plan Rev. 5.0, no information is provided for the Tamarisk-Salix community
identified in Section 1.7.1. Based on current photography, they appear to be wetlands. It is
unclear how they will be affected by reclamation activities.
REFERENCES:
Anderson, D. C, and Johns, D.W. 1977. "Predation by Badger on Yellow-Be Hied Marmot in •
Colorado, " Southwestern Naturalist, Vol. 22, pp. 283-284.
Cline, J.F.. 1979. Biobarriers Used in Shallow-Burial Ground Stabilization. Technical Report..
Pacific Northwest Laboratory PNL-2918. March 1, 1979.
Cline, J. F., K. A. Gano, and L. E. Rogers, 1980, "Loose Rock as Biobarriers in Shallow Land
Burial, " Health Physics, Vol. 39, pp. 494-504.
Cline, J. F., F.G. Burton, D. A. Cataldo, W. E. Skiens, and K. A. Gano. 1982. Long-Term
Biobarriers to Plant and Animal Intrusion of Uranium Tailings, DOE/UMT-0209, Pacific
Northwest Laboratory, Richland, Washington.
Denison Mines (USA) Corp., 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah,
Radioactive Materials License No. UT1900479, Revision 5.0, September 2011.
EPA (U.S. Environmental Protection Agency). 2004. (Draft) Technical Guidance for
RCRA/CERCLA Final Covers. USEPA 540-R-04-007, OSWER 9283.1-26. April 2004, 421 pp.
URL: nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P10074PP.txt.
Foxx, T.S., G.D. Tierney, andJ.M. Willimas, 1984. Rooting Depths of Plants Relative to
Biological and Environmental Factors, Los Alamos Report LA-10254-MS, November 1984.
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Gano, K. A. andJ. B. States, 1982, Habitat Requirements and Burrowing Depths of Rodents in
Relation to Shallow Waste Burial Sites, PNL-4140, Pacific Northwest Laboratory, Hanford,
Washington.
Hakonson, T.E. 1986. Evaluation of Geologic Materials to Limit Biological Intrusion into Low-
Level Radioactive Waste Disposal Sites. LA-10286-MS. Los Alamos National Laboratory, Los
Alamos, New Mexico.
Lindzey, F. G. 1976. "Characteristics of the Natal Den of the Badger, " Northwest Science, Vol.
50, No. 3, pp. 178-180.
Natural Resource Conservation Service (NRCS). 2012. Plants Database,
http://plants, usda.gov/java/
Reichman, O.J., and Smith, S. C. 1990. "Burrows and Burrowing Behavior by Mammals," pp.
197-244 in HH. Genoways, ed., Current Mammology. Plenum Press, New York and London.
1990.
Reynolds, T.D.andJ. W. Laundre, 1988. "Vertical Distribution of Soil Removed by Four
Species of Burrowing Rodents in Disturbed and Undisturbed Soils, " Health Physics, Vol. 54, No.
4, pp. 445-450.
Reynolds, T. D. and W. L. Wakkinen, 1987. "Burrow Characteristics of Four Species of Rodents
in Undisturbed Soils in Southeastern Idaho, "American Midland Naturalist, Vol. 118, pp. 245-
260.
Smith, E.D., Luxmoore, R.J., and Suter, G. W. 1997. "Natural Physical and Chemical Processes
Compromise the Long-Term Performance of Compacted Soil Caps, " in Barrier Technologies for
Environmental Management - Summary of a Workshop. National Research Council, National
Academy Press, Washington, DC, pp. D-61 to D-70.
Verdolin, Jennifer, Kara Lewis, and Constantine N. Slobodchikoff. 2008. Morphology of
Burrow Systems: A Comparison of Gunnison's (Cynomy gunnisoni), White-tailed (C. leucurus),
black-tailed (C. ludovicianus), and Utah (C parvidens) Prairie Dogs. The Southwestern
Naturalist 53(2): 201-207.
Waugh, W. J, M. K. Kastens, L. R. L. Sheader, C. H. Benson, W. H. Albright, and P. S.
Mushovic. 2008. Monitoring the performance of an alternative landfill cover at the Monticello,
Utah, Uranium Mill Tailings Disposal Site. Proceedings of the Waste Management 2008
Symposium. Phoenix, AZ.
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INTERROGATORY WHITEMESA RECPLAN REV 5.0 R313-24-4; 10CFR40
APPENDIX A, CRITERION 6(4); INT 12/1: REPORT RADON BARRIER
EFFECTIVENESS
REGULATORY BASIS:
UAC R313-24-4 invokes the following requirement from 10CFR40. Appendix A, Criterion 6(4):
Within ninety days of the completion of all testing and analysis relevant to the required
verification in paragraphs (2) and (3) of 10CFR40. Appendix A, Criterion 6, the uranium mill
licensee shall report to the Executive Secretary the results detailing the actions taken to verify
that levels of release of radon-222 do not exceed 20 pCi/m2s when averaged over the entire pile
or impoundment. The licensee shall maintain records until termination of the license
documenting the source of input parameters including the results of all measurements on which
they are based, the calculations and/or analytical methods used to derive values for input
parameters, and the procedure used to determine compliance. These records shall be kept in a
form suitable for transfer to the custodial agency at the time of transfer of the site to DOE or a
State for long-term care if requested.
INTERROGATORY STATEMENT:
Refer to Reclamation Plan Rev. 5.0, Section 3 (Tailings Reclamation Plan) and Appendix D
(Updated Tailings Cover Design Report dated Sept 2011):
Please revise radon flux calculations using actual site-specific material properties data.
a. Clearly demonstrate that values of material parameters:
1) Are reasonably conservative
2) Are based on site material samples, measured values, assumptions, or other
origins
3) Are based upon appropriate analytical methods and sufficient number of
representative samples for cover soils and tailings
4) Consider the variability and uncertainties in actual site-specific data.
5) Are consistent with anticipated construction specifications
6) Are based upon representative long-term site conditions.
b. Justify values of material parameters used in the radon flux calculations
c. Demonstrate that test methods and their precision, accuracy, and applicability are
supported by suitable standards and procedures.
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d. Justify that values chosen for radon emanation and diffusion coefficients are consistent
with long-term moisture contents projected to exist within tailings and cover materials in
the impoundments.
e. Demonstrate that the quality assurance program used in obtaining parameter data is
adequate
f. Revise the design density and porosity values of cover soils to comply with the usual
compaction of 95% of Standard Proctor (D 698). Alternatively, clearly justify the basis
for the lower compactions utilized in the radon flux calculations and their expected long-
term stability.
g. Please revise the tailings density, porosity, and moisture values to reflect expected long-
term conditions in each of the disposal units. Alternatively, demonstrate the basis for the
long-term stability of the values used in the radon flux calculations.
h. Please utilize one of the two accepted methods for long-term moisture estimates (D 2325
or Rawls correlation) with representative samples. Alternatively, justify the use of an
acceptable alternative method.
i. Please resolve or justify the discrepancy between the 91.4 pcf "best correlation " between
the Rawls and in-situ moisture data (Appendix D page C-4) and the density range of 94
to 111 pcf used in the radon flux calculations. Revise and report results of radon flux
calculations, as necessary to reflect the resulting changes.
j. Please utilize a source term based on representative sampling and analysis of the sand,
slime, and mixed tailings to 12-ft depths in sufficient and representative locations of each
tailings area (e.g., Cells 2, 3, 4A, and 4B.). Alternatively, justify and use the average ore
grade method identified in Reg Guide 3.64 for the radon flux calculations.
k. Please justify the assumed value of zero for Ra-226 concentrations in cover soils by
sampling and measurement of background Ra-226 soil concentrations and comparison of
their values with corresponding representative measurements in the proposed cover soils.
Alternatively, use values of Ra-226 concentrations in radon flux calculations that are
supported by cell-specific measurements.
I. Please utilize measured radon emanation coefficients that are representative of the sand,
slime, and mixed tailings in the various tailings cell areas; emanation coefficients
averaged over measurements for each tailings cell. Alternatively, use default values
conservatively estimated from site-specific measurements.
m. Please utilize measured or calculated radon diffusion coefficients in radon flux
calculations that represent the long-term properties of the tailings and cover soil
materials.
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n. Please provide written procedures for identifying and placing contaminated soils into the
disposal cell(s) and substantiating characterization data and site history.
o. Provide a revised radon emanation model that incorporates lower values of initial bulk
density for the erosion protection layer in the model. The bulk density value selected
needs to fall within the range of bulk densities that is recommended (approximately 1.2 to
1.8 g/cm3, or about 75 to 112 pcf) in the section entitled "Soil Requirements for
Sustainable Plant Growth " and listed in Table D-5 in Appendix D to the Reclamation
Plan as the recommended range required for promoting sustainable plant growth.
BASIS FOR INTERROGATORY:
a. The material parameters used in the radon flux calculations are not shown to be
reasonably conservative, and in some cases appear to be non-conservative. For example,
the tailings density (1.19 g/cc) appears to correspond to only 71% of standard proctor
(based on Appendix D Table 3.4-1). If tailings settle to a greater density upon cover
placement, the required cover thickness is likely to increase.
b. The material parameters used in the radon flux calculations appear to ignore the
variabilities and uncertainties in parameter values. For example, some random-fill
moistures are estimated from 15-bar capillary suction values and others from the Rawls
correlation, yet no account is given for their uncertainties, equivalence, or applicability
in apparently combining them for the constant value of 7.8% moisture assumed for the
range of cover layers (~78%> to 92% of Proctor density based on Appendix D Table 3.4-1
values).
c. Supporting information was not found for the test methods, their precisions, accuracies,
and applicability for the radon flux calculations.
d. Information was not found to identify the numerical origin of most parameter values used
in the radon flux calculations, their basis in site samples, measurements, or assumptions.
e. Information was not found to link the radon emanation and diffusion coefficients used in
the radon flux calculations to estimated long-term moisture contents at the site.
f. Information was not found to demonstrate that sufficient and representative samples were
tested to adequately determine material property values. For example, the tailings
radium and emanation values appear to be based on a single sample, whose identity,
origin, or composition is not identified (sand, slime, mixture? [Attachment A.1.5]).
Approximately half of all "random fill" to be used as cover soil appears to have never
been sampled or characterized (Appendix D Table 2-1).
g. Information was not found about quality assurance applicable to the parameter data used
in the radon flux calculations.
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h. The consistency of material parameter values with anticipated construction specifications
and representation of long-term site conditions is not demonstrated. For example, the
material compactions of 71% for tailings, 82% for the first random fill layer, and 71%>
for the upper random fill layer may increase with time due to natural settlement under
the cover weight and future land usage.
i. The target compaction values for two of the cover soil layers are less than the guideline
compaction values.
j. The tailings density, porosity, and moisture value appear unsustainable for long-term
support of the overlying cover mass.
k. The deep in-situ moisture data referred to by NUREG-1620 Sec 5.1.3.1 (6) are intended
for comparison with D 2325 or Rawls values, not for averaging with them. The intent is
to assure that the measured D 2325 or Rawls values do not exceed the present field
values, (i.e., the smaller of the 15-bar or in-situ moistures should be used).
I. The chosen long-term moisture values should have a clear and traceable origin in
representative samples from the site.
m. The present Ra-226 concentration and radon emanation coefficient utilized for tailings in
the radon flux calculations is not justified by sampling and analysis data from
representative sands, slimes, and mixed tailings over the requisite depth interval and
spatial distribution in the different tailings areas nor by the ore-grade method described
in Regulatory guide 3.64.
n. The Reclamation Plan does not demonstrate that the proposed cover soil materials are
not associated with ore formations or other radium-enriched materials or that their
radioactivity is essentially the same as surrounding soils as demonstrated by an
appropriate procedure. Procedures such as those in the MARSSIM manual are
acceptable for this demonstration.
o. The single measured radon emanation coefficient of 0.19 lacks representation of sand,
slime, mixed, and cell-specific materials, and in particular, any potentially different
values derived from processing of alternate feed materials at the mill.
p. The radon diffusion coefficients used for tailings and cover soils in the radon flux
calculations lack traceability to representative, valid estimates of long-term moisture
contents, densities, and porosity values.
q. A written procedure was not found in the Reclamation Plan for identifying and placing in
the disposal cell all contaminated soils on and adjacent to the processing site ,
substantiated by radiological characterization data and site history.
r. ....In the referenced section of Appendix D to the Reclamation Plan, it is stated that bulk
densities of emplaced cover materials will be specified in the cover design and will be
controlled during cover construction to be within the sustainability range shown in Table
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D-5. The radon emanation modeling should therefore assume bulk density values for all
cover layers that are representative of the range of recommended bulk densities.
NOTE: The same comments as above also apply to Appendix D (Vegetation Evaluation for the
Evapotranspiration Cover) and Appendix H (Radon Emanation Modeling for the
Evapotranspiration Cover) of the Infiltration and Contaminant Transport Modeling (ICTM)
Report.
REFERENCES:
NRC 2000. NUREG-1575 Rev.l. Multi-Agency Radiation Survey and Site Investigation Manual
(MARSSIM), August 2000.
NRC 2003. Standard Review Plan for the Review of a Reclamation Plan for Mill Tailings Sites
under Title II of the Uranium Mill Tailings Radiation Control Act of1978. Washington DC, June
2003.
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INTERROGATORY WHITEMESA RECPLAN REV 5.0 R313-24-4; 10CFR40,
APPENDIX A, CRITERION 6(6); INT 13/1: CONCENTRATIONS OF
RADIONUCLIDES OTHER THAN RADIUM IN SOIL
REGULATORY BASIS:
UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A. Criterion 6(6): The
design requirements in this criterion for longevity and control of radon releases apply to any
portion of a licensed and/or disposal site unless such portion contains a concentration of radium
in land, averaged over areas of 100 square meters, which, as a result of byproduct material,
does not exceed the background level by more than: (i) 5 picocuries per gram (pCi/g) of radium-
226, or, in the case of thorium byproduct material, radium-228, averaged over the first 15
centimeters (cm) below the surface, and (ii) 15 pCi/g of radium-226, or, in the case of thorium
byproduct material, radium-228, averaged over 15-cm thick layers more than 15 cm below the
surface.
Byproduct material containing concentrations of radionuclides other than radium in soil, and
surface activity on remaining structures, must not result in a total effective dose equivalent
(TEDE) exceeding the dose from cleanup of radium contaminated soil to the above standard
(benchmark dose), and must be at levels which are as low as is reasonably achievable. If more
than one residual radionuclide is present in the same 100-square-meter area, the sum of the
ratios for each radionuclide of concentration present to the concentration limit will not exceed
"1" (unity). A calculation of the potential peak annual TEDE within 1000 years to the average
member of the critical group that would result from applying the radium standard (not including
radon) on the site must be submitted for approval. The use of decommissioning plans with
benchmark doses which exceed 100 mrem/yr, before application of ALARA, requires the
approval of the Executive Secretary after consideration of the recommendation of the staff of the
Executive Secretary. This requirement for dose criteria does not apply to sites that have
decommissioning plans for soil and structures approved before June 11, 1999.
Relevant NRC Guidance
Background Radiological Characteristics
RG 3.8, Section 2.10: Regional radiological data should be reported, including both
natural background radiation levels and results of measurements of concentrations of
radioactive materials occurring in important biota, in soil and rocks, in air, and in
regional surface and local ground waters. These data, whether determined during the
applicant's preoperational surveillance program or obtained from other sources, should
be referenced.
INTERROGATORY STATEMENT:
1. Please propose appropriate soil background values (for different geological areas as
needed) for Ra-226, U-nat, Th-230, and/or Th-232, as appropriate, with supporting data.
2. Please indicate whether elevated levels of uranium or thorium are expected to remain in
the soil after the Ra-226 criteria have been met, and if so, describe your use of the
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radium benchmark dose approach (Appendix H of NUREG-1620) for developing
decommissioning criteria for these radionuclides.
3. Please provide a description of the instruments and procedures that will be used for soil
background analyses, radium-gamma correlations, and verification data along with
information about the sensitivity of the procedures.
4. Please provide final verification (status survey) procedures to demonstrate compliance
with the soil and structure cleanup standards. The procedures should specify instruments,
calibrations, and testing, and the verification soil sampling density should take into
consideration detection limits of samples analyses, the extent of expected contamination,
and limits to the gamma survey. The gamma guideline value should be appropriately
chosen, and the verification soil radium-gamma correlation should be provided along
with the number of verification grids that had additional removal because of excessive
Ra-226 values. The plan should provide for adequate data collection beyond the
excavation boundary. Surface activity measurements should demonstrate acceptable
compliance with surface dose standards for any structures to remain onsite.
BASIS FOR INTERROGATORY:
1. Soil background values with supporting data were not found in the Reclamation Plan for
Ra-226, U-nat, Th-230, and/or Th-232.
2. No assessment ofpotentially elevated levels of uranium or thorium was found in the
Reclamation Plan for the post-Ra-226-reclamation site condition. This assessment should
be included with the requisite benchmark dose approach if elevated uranium or thorium
may remain.
3. The Reclamation Plan does not describe the instruments and procedures that will be used
for soil background analyses, radium-gamma correlations, and verification data, nor
information about the sensitivity of the procedures. Helpful information may be found in
the MARSSIM Manual.
4. The requisite procedures were not found for final verification surveys of the site to
demonstrate compliance with the soil and structure cleanup standards.
REFERENCES:
NRC 1982. U.S. Nuclear Regulatory Commission. 'Regulatory Guide 3.8; Preparation of
Environmental Reports for Uranium Mills ", Washington DC, October 1982.
NRC 2003. Standard Review Plan for the Review of a Reclamation Plan for Mill Tailings Sites
under Title II of the Uranium Mill Tailings Radiation Control Act of1-978. Washington DC, June
2003.
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INTERROGATORY WHITE MESA RECPLAN REV 5.0 R313-24-4; 10CFR40
APPENDIX A; INT 14/1: COVER TEST SECTION AND TEST PAD MONITORING
PROGRAMS
REGULATORY BASIS:
UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 1:-The
general goal or broad objective in siting and design decisions is permanent isolation of
tailings and associated contaminants by minimizing disturbance and dispersion by
natural forces, and to do so without ongoing maintenance. For practical reasons, specific
siting decisions and design standards must involve finite times (e.g., the longevity design
standard in Criterion 6). The following site features which will contribute to such a goal
or objective must be considered in selecting among alternative tailings disposal sites or
judging the adequacy of existing tailings sites:
• Remoteness from populated areas;
Hydrologic and other natural conditions as they contribute to continued immobilization
and isolation of contaminants from ground-water sources; and
• Potential for minimizing erosion, disturbance, and dispersion by natural forces over the
long term.
The site selection process must be an optimization to the maximum extent reasonably
achievable in terms of these features.
In the selection of disposal sites, primary emphasis must be given to isolation of tailings or
wastes, a matter having long-term impacts, as opposed to consideration only of short-term
convenience or benefits, such as minimization of transportation or land acquisition costs. While
isolation of tailings will be a function of both site and engineering design, overriding
consideration must be given to siting features given the long-term nature of the tailings hazards.
Tailings should be disposed of in a manner that no active maintenance is required to preserve
conditions of the site.
UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 6(1):
In disposing of waste byproduct material, licensees shall place an earthen cover (or approved
alternative) over tailings or wastes at the end of milling operations and shall close the waste
disposal area in accordance with a design which provides reasonable assurance of control of
radiological hazards to (i) be effective for 1,000 years, to the extent reasonably achievable, and,
in any case, for at least 200 years, and (ii) limit releases of radon-222from uranium byproduct
materials, and radon-220from thorium byproduct materials, to the atmosphere so as not to
exceed an average release rate of 20 picocuries per square meter per second (pCi/m2s) to the
extent practicable throughout the effective design life determined pursuant to (l)(i) of this
Criterion. In computing required tailings cover thicknesses, moisture in soils in excess of
amounts found normally in similar soils in similar circumstances may not be considered. Direct
gamma exposure from the tailings or wastes should be reduced to background levels. The effects
of any thin synthetic layer may not be taken into account in determining the calculated radon
exhalation level. If non-soil materials are proposed as cover materials, it must be demonstrated
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that these materials will not crack or degrade by differential settlement, weathering, or other
mechanism, over long-term intervals.
INTERROGATORY STATEMENT:
Refer to Section 8.0 of Attachment A (Technical Specifications and Attachment B
(Construction Quality Assurance/Quality Control Plan) to the Reclamation Plan and Section
5.0 of Appendix D (Updated Tailings Cover Design Report) of the Reclamation Plan Rev. 5.0
(DUSA 2011a):
1. Please provide plans and specifications for constructing and performing monitoring and
testing of a cover system section representative of the proposed ET cover system for
verifying the hydraulic performance characteristics of the cover system. Demonstrate
that the proposed test pad/plot will be sufficient in size to eliminate or minimize lateral
boundary effects. Describe objectives and criteria for construction and testing of the test
pad cover materials /layers. Include information in the CQAQC Plan regarding
procedures for sampling and testing of the cover system section specifically pertinent to
demonstrating the (short-term and long-term) performance of the ET cell cover design.
Address, as part of the testing program, testing ofparameters specifically recommended
by Benson et al. 2011; Waugh et al. 2008; the National Research Council 2007; Albright
et al. 2007; others) including, but not necessarily limited to:
a. Monitoring of in-situ soil water tension and volumetric water content as a function of
time (e.g., using heat dissipation probes and TDR [time domain refiectometryj);
b. Monitoring of in-situ flux rates as a function of time (e.g., through use of one or more pan
lysimeters as recommended by Benson et al. 2011 and Dwyer et al. 2007) on both north
and south-facing slopes as required);
c. Physical sampling and laboratory testing for index properties, including Plasticity Index
and saturated hydraulic conductivity, and other pertinent parameters including
compaction properties, organic matter and CaC03 content, and measurement of soil
edaphic properties (properties that influence vegetation establishment and growth - e.g.,
see Waugh et al. 2008);
d. Other testing if needed for determining changes in water in storage and soil water
characteristic curves (SWCCs, e.g., according to ASTM D6836 [ASTM 2008]) and
monitoring for potential changes in SWCCs through time;
e. Conducting soil vegetation surveys (as recommended by Benson et al. 2011); and
f. Monitoring of relevant climatological parameters (precipitation and evaporation rates,
temperature, barometric pressure, snow amounts, wind speed and wind direction, etc.),
including continuous monitoring over several years necessary to understand how covers
are influenced by fluctuations in climate and other environmental factors (Waugh et al.
2008) such as an extraordinarily wet year or consecutive wet years.
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2. Provide additional information and plans and specifications for constructing and testing
a cover system "test pad/test plot" prior to construction of the proposed ET cover system
over the consolidated, dewatered tailings. Demonstrate that the proposed test pad/plot
will be sufficient in size to eliminate or minimize lateral boundary effects. Describe
objectives and criteria for construction and testing of the test pad cover materials /layers
including but not limited to:
a. Acquisition of data of the types described in Item 1. above;
b. Determination of an acceptable zone (AZ) for soil textures in soils used for constructing
the final cover system (e.g., Williams et al. 2010);
c. Determination of most effective means of "bonding " individual soil cover soil layers
(e.g., Dwyer et al. 2007); and
d. Determination of appropriate lift thickness/placement and compaction equipment
combinations (e.g., Dwyer et al. 2007).
BASIS FOR INTERROGATORY:
The need for constructing and monitoring a cover test section representative of the proposed ET
cover system, with supporting basis and rationale for building and monitoring such a test cover
section, was previously addressed in a Round IA Interrogatory submitted to DUSA on Revision
4.0 of the Reclamation Plan in October 2010. DUSA's response (DUSA 2011b) to that
interrogatory indicated the following:
"Denison is not proposing a test pad for demonstrating short- and long-term performance of the
alternative tailings cell cover system. Rather, Denison has completed extensive modeling of the
cover system for demonstrating that the cover will perform effectively for a variety of climatic
and vegetative scenarios. It may be possible to extend a portion of the cover system beyond the
edge of the first tailings cell such that the hydraulic conditions within the cover system could be
evaluated through time (in a test pad like setting) without causing deleterious effects to the cover
above the tailings. This "test pad" would be further evaluated after approval of the cover
design "; and
"Denison is proposing monitoring in situ performance of the alternative tailings cell cover
system to include monitoring hydraulic conditions at nested intervals within the soil profile at
three locations within the first tailings cell that is reclaimed. The depth intervals that are
evaluated would depend on the final design specifications of the approved alternative cover
system, but would likely represent data collected from three depths. The first depth interval
would be located immediately below the soil-gravel admixture (0.6 feet), the second depth
interval would be located near the midpoint of the maximum rooting depth (1.5 feet), and the
third depth interval would be located at or slightly below the maximum rooting depth (3.8 feet)
but above the proposed upper compacted layer;
"The pertinent hydraulic properties to be monitored would include soil water tension and
volumetric water content. Soil water tension would be measured with a heat dissipation probe,
while volumetric water content would be measured with a time domain reflectometry (TDR)
probe. The use of these monitoring methods is consistent with what was used to monitor
conditions as part of the Alternative Cover Assessment Program (ACAP). Changes in water
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content through time can be used to assess changes in soil water storage through time.
Measurements of volumetric water content and soil water tension can be related to the soil water
retention and hydraulic conductivity curves to estimate a water flux rate and cover performance
through time"...; and
"Climatologicalparameters are currently being measured at the site and include precipitation,
wind speed, and wind direction. In addition, air temperature and barometric pressures are
measured monthly for environmental air station calibrations. Based on this information in
addition to supplemental climate data from the nearest weather station (Blanding, Utah station
420738), the daily amount of evapotranspiration can be computed. "
Although the response provided by DUSA to the Round IA Interrogatory includes a proposal to
monitor the performance of the cover, additional details, including plans and construction
specifications for constructing a representative cover section, and detailed sampling and testing
procedures and associated quality assurance and quality control methods need to be provided
that demonstrate that the test section and monitoring/testing program: (1) is consistent with
applicable current published guidance for such programs: (2) is fully integrated with, and
compatible with, the essential elements of the currently proposed ET Cover design; (2) that data
acquired from the monitoring/testing program will allow the short-term and longer-term
performance predictions made with regard to the proposed cover system to be validated.
Applicable recent published guidance documents include NUREG/CR-7028 (Benson et al. 2011),
a peer-reviewed report published for the NRC in December 2011, which reports the findings
from investigations of several earthen and soil/geosynthetic cover systems to assess changes in
properties of cover materials in those cover systems 5 to 10 years following their construction.
A key conclusion of the report is that findings from these investigations demonstrate that changes
in the engineering properties of cover soils generally occur while in service (and that long-term
engineering properties should be used as input to models employed for long-term performance
assessments). The report indicates that changes in hydraulic properties occurred in all cover
soils evaluated due to the formation of soil structure, regardless of climate, cover design, or
service life. The report includes the following conclusions and recommendations:
• Because cover systems change over time, they should be monitored to ensure that
they are functioning as intended. Monitoring using pan lysimeters combined with
secondary measurements collected for interpretive purposes (water content,
temperature, vegetation surveys, etc.) is recommended; and
* At a minimum, at least one pan lysimeter having a minimum dimension of 10 m
should be installed for performance monitoring. If only one lysimeter is installed,
the location should be selected to represent the most unfavorable condition at the
site.
Additional relevant guidance documents include Waugh et al. 2008, Albright et al. 2007; Benson
et al. 2007; and the National Research Council 2007, and Dwyer et al. 2007, which indicate
that characteristics of the proposed alternative cover will inevitably change in the long term in
response to climate, pedogenesis, and ecological succession.
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Monitoring the proposed alternative cover system or monitoring of a test cover section
simulating the cover system components and geometry) to assess the long-term performance of
the alternative cover is needed to verify the characteristics and infiltration performance of the
constructed cover system as well as to gain confidence in understanding long-term changes that
may occur in the physical/hydraulic properties of the alternative cover system over time
following its construction.
Additionally, a cover system test pad/test plot capable of assisting in confirming the performance
of the proposed alternative cover system should be constructed and monitored. The proposed
alternative cover design incorporates more loosely compacted soil layers. Dwyer et al. 2007, for
example, describes results of recent research and field investigations of arid climate closure
covers conducted by Los Alamos National Laboratory. As discussed in that report, lift thickness
should be maximized for placement and compaction of a soil cover. During cover placement, it is
crucial that each lift be bonded to the previous lift to cut down on the creation of interlift
passageways (cracks) for the water to travel along as it passes from an overlying lift to a lower
one. Test pads prior to cover material placement may prove beneficial in determining
appropriate lift thickness/placement and compaction equipment combinations.
A full-scale cover system test pad/test plot can provide information that can lead to additional
performance criteria for the cover design process. Quantification of soil properties, soil
placement conditions and agronomic characteristics used in the test pad could, for example,
help refine selection criteria for selection of onsite soils for use in final cover construction,
including, further definition of soils that would result in a texture within a defined Acceptable
Zone (AZ). The determination of the AZ for soil texture may be based on the field test pad
demonstration, hydraulic property testing, and percolation modeling of the successful test plot
soils.
REFERENCES:
Albright, W.H., Waugh, W.J., and Benson, CH. 2007. "Alternative Covers: Enhanced Soil Water
Storage and Evapotranspiration in the Source Zone. " Enhancements to Natural Attenuation:
Selected Case Studies, Early, TO. (ed), pp 9-17. Prepared for U.S. Dept. of Energy by
Washington Savannah River Company, WSRC-ST1-2007-00250. URL:
http://www. dri. edu/images/stories/research/programs/acap/acap-publications/10.pdf.
Benson, CH, Sawangsuriya, A., Trzebiatowski, B., and Albright, W.H. 2007. "Postconstruction
Changes in the Hydraulic Properties of Water Balance Cover Soils ", Journal of Geotechnical
and Geoenvironmental Engineering, 133:4, pp. 349-359.
Benson, CH W.H. Albright, W.H, Fratta, D.O.,Tinjum, J.M., Kucukkirca, E., Lee, S.H., J.
Scalia, J., Schlicht, P.D., and Wang, X. 2011. Engineered Covers for Waste Containment:
Changes in Engineering Properties and Implications for Long-Term Performance Assessment(in
4 volumes). NUREG/CR-7028, Prepared for the U.S. Nuclear Regulatory Commission,
Washington, D.C, December 2011.
Denison Mines (USA) Corp. 2011a. Reclamation Plan, White Mesa Mill, Blanding, Utah,
Radioactive Materials License No. UT1900479, Revision 5.0, September 2011.
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Denison Mines (USA) Corp. 2011b. Responses to Supplemental Interrogatories - Round IA for
Reclamation Plan, Revision 4.0, November 2009. December 28, 2011.
Dwyer, S.F., Rager, R.E., and Hopkins, J. 2007. Cover System Design Guidance and
Requirements Document. LA-UR-06-4715. EP2006-0667. Los Alamos National Laboratory.
April 2007. URL: http://www.lanl.gov/environment/cleanup/req_docs.shtml
National Research Council 2007. Assessment of the Performance of Engineered Waste
Containment Barriers. Board of Earth Sciences and Resources. The National Academies Press,
Washington, D.C, 2007, 134pp.
Waugh, W. J., M. K. Kastens, L. R. L. Sheader, C. H. Benson, W. H. Albright, and P. S.
Mushovic. 2008. Monitoring the performance of an alternative landfill cover at the Monticello,
Utah, Uranium Mill Tailings Disposal Site. Proceedings of the Waste Management 2008
Symposium. Phoenix, AZ.
Williams, L.O., Zornberg, J.G., Dwyer, S.F., Hoyt, D.L., andHargreaves, G.A. 2010. "Design
Rationale for Construction and Monitoring of Unsaturated Soil Covers at the Rocky Mountain
Arsenal. 6th International Congress on Environmental Geotechnics, New Delhi, India. URL:
http://www. ce. utexas. edu/prof/zornberg/pdfs/CP/Williams_Zornberg_Dwyer_Hoyt_Hargreaves
2010.pdf
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INTERROGATORY WHITEMESA RECPLAN REV 5.0 R313-24-4; 10CFR40,
APPENDIX A, CRITERION 9; INT 15/1: FINANCIAL SURETY ARRANGEMENTS
REGULATORY BASIS:
UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 9:
Financial surety arrangements must be established by each mill operator prior to the
commencement of operations to assure that sufficient funds will be available to carry out the
decontamination and decommissioning of the mill and site and for the reclamation of any
tailings or waste disposal areas. The amount of funds to be ensured by such surety arrangements
must be based on Executive Secretary-approved cost estimates in a Executive Secretary-
approved plan for (1) decontamination and decommissioning of mill buildings and the milling
site to levels which allow unrestricted use of these areas upon decommissioning, and (2) the
reclamation of tailings and/or waste areas in accordance with technical criteria delineated in
Section I of this Appendix. The licensee shall submit this plan in conjunction with an
environmental report that addresses the expected environmental impacts of the milling
operation, decommissioning and tailings reclamation, and evaluates alternatives for mitigating
these impacts. The surety must also cover the payment of the charge for long-term surveillance
and control required by Criterion 10. In establishing specific surety arrangements, the licensee's
cost estimates must take into account total costs that would be incurred if an independent
contractor were hired to perform the decommissioning and reclamation work. In order to avoid
unnecessary duplication and expense, the Executive Secretary may accept financial sureties that
have been consolidated with financial or surety arrangements established to meet requirements
of other Federal or state agencies and/or local governing bodies for such decommissioning,
decontamination, reclamation, and long-term site surveillance and control, provided such
arrangements are considered adequate to satisfy these requirements and that the portion of the
surety which covers the decommissioning and reclamation of the mill, mill tailings site and
associated areas, and the long-term funding charge is clearly identified and committed for use in
accomplishing these activities. The licensee's surety mechanism will be reviewed annually by the
Executive Secretary to assure, that sufficient funds would be available for completion of the
Reclamation Plan if the work had to be performed by an independent contractor. The amount of
surety liability should be adjusted to recognize any increases or decreases resulting from
inflation, changes in engineering plans, activities performed, and any other conditions affecting
costs. Regardless of whether reclamation is phased through the life of the operation or takes
place at the end of operations, an appropriate portion of surety liability must be retained until
final compliance with the Reclamation Plan is determined.
INTERROGATORY STATEMENT:
1. Justify the decrease in costs estimated for mill decommissioning and reclamation of Cells
1, 2, and 3 from those estimated in the White Mesa Reclamation Plan, Rev. 4.0 dated
November 2009. Explain why several estimated levels of effort (e.g., total effort for Mill
Yard Decontamination, Ore Storage Pad Decontamination, Equipment Storage Area
Cleanup and Cell 1 Construct Channel) are smaller in 2011 than those estimated in
2009. Explain and rectify apparent discrepancies between labor rates used in cost
estimates and those presented in the exhibit in Attachment C titled "Labor Costs ".
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2. Identify analytes for which soil samples identified in the cost estimate for "Cleanup of
Windblown Contamination " will be analyzed. Justify (or revise with justification) the
assumed sample analysis cost of $50.
3. Revise and report estimated reclamation costs, incorporating responses to instructions
listed above.
4. Estimate and report the costs for a third party to conduct decommissioning and
impoundment reclamation in the coming year rather than at the end of planned life.
5. Please provide and justify estimates of costs associated with complying with the current
Air Quality Approval Order (DAQE-AN1205005-06, issue date July 20, 2006) and
License Condition 11.4 and 11.5 during final reclamation, as stated in Section 1.5 of
Reclamation Plan 5.0, Attachment A, Technical Plans and Specifications.
6. Please state and justify the times projected to be necessary to dewater Cell 2 and Cell 3.
Provide and justify estimates of all costs associated with the apparently lengthy
dewatering time for Cell 2 and Cell 3.. Also see Interrogatory 7/01, item 8.
BASIS FOR INTERROGATORY:
Comparing the cost estimate contained in Attachment C to Reclamation Plan Rev. 4.0 2009 with
those contained in Attachment C to Reclamation Plan Rev. 5.0 2011 reveals differences that
should be addressed. Contrary to expectations, the costs associated with mill decommissioning
and reclamation of most of the cells and some durations and levels of effort are smaller in 2011
than they were in 2009. Some labor costs are not obviously supported by the data sources
presented in the attachment.
Once Items 1 and 2 above have been addressed, the reclamation cost estimate should be revised
and resubmitted.
Without justification for an assumption to the contrary, the Division interprets the cost estimate
as applying to decommissioning and reclamation that occur at the projected end of facility life.
If so, the Licensee should also estimate the cost to decommission the mill area and reclaim all
ponds under conditions likely to exist within the next year. The financial assurance provided
should ensure that funds sufficient to cover costs of decommissioning and reclaiming within the
next year are available to the State.
Costs associated with complying with the current Air Quality Approval Order and License
Condition 11.4 and 11.5 during final reclamation need to be included in the surety. Section 1.5
of Reclamation Plan 5.0, Attachment A, Technical Plans and Specifications, states that
reclamation will comply with State of Utah Air Quality Approval Order (DAQE^ANl205005-06,
issue date July 20, 2006).
The times required to dewater Cell 2 and 3 qppear to will be lengthy, based on current
dewatering rates. Costs associated with this lengthy dewatering time for Cell 2 and 3 need to be
included in the surety.
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REFERENCES:
Denison Mines (USA) Corp. 2009. Reclamation Plan, White Mesa Mill, Blanding, Utah,
Radioactive Materials License No. UT1900479, Revision 4.0, November 2009.
Denison Mines (USA) Corp., 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah,
Radioactive Materials License No. UT1900479, Revision 5.0, Appendix E, September 2011.
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INTERROGATORY WHITE MESA REC PLAN REV 5.0 R313-15-501; INT 16/1;
RADIATION PROTECTION MANUAL
REGULATORY BASIS:
UAC R313-15-501; Surveys and Monitoring General invokes the following requirement from
10CFR40. Appendix A, Criterion 1: "(1) Each licensee or registrant shall make, or cause to be
made, surveys that.fa) Are necessary for the licensee or registrant to comply with Rule R313-15;
and(b) Are necessary under the circumstances to evaluate.fi) The magnitude and the extent of
radiation levels; and(ii) Concentrations or quantities of radioactive material; and(iii) The potential
radiological hazards.
INTERROGATORY STATEMENT:
Refer to Appendix D, Radiation Protection Manual for Reclamation: Provide information on
how these largely operational radiation protection practices will change to support the changed
needs of decommissioning and reclamation. Describe how the Radiation Protection program
will be evaluated and revised to address the range of activities required to support
decommissioning and reclamation activities. The following are selected examples of topics (not
exhaustive) that should be evaluated and possibly revised to support decommissioning and
reclamation.
• Section 1.3 Beta Gamma Surveys: Conduct beta gamma frisk surveys where appropriate
during decommissioning and reclamation.
• Section 1.4 Urinalysis Surveys: State the frequency of conducting urinalyses during
decommissioning and reclamation.
• Sections 2.1.2, 2.3.2, 2.4.2 Frequency/locations: State how the frequency and locations
for all monitoring methods will be modified to accommodate decommissioning and
reclamation activities.
BASIS FOR INTERROGATORY:
The Radiation Protection program provides information on regarding current operations but
does not any information on how these practices will change to support reclamation. While
reclamation will occur at a future date and the specific details may not be available at this time,
it is important that the Radiation Protection Program identify the approach that will be taken to
address these needs.
REFERENCES:
Denison Mines (USA) Corp., 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah,
Radioactive Materials License No. UT1900479, Revision 5.0, Appendix E, September 2011
: Attachment D Radiation Protection Manual for Reclamation September 2011
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INTERROGATORY WHITE MESA REC PLAN REV 5.0 R313-15-1002; INT 17/1;
RELEASE SURVEYS
REGULATORY BASIS:
UAC R313-15-1002; Method for Obtaining Approval of Proposed Disposal Procedures. A licensee
or registrant or applicant for a license or registration may apply to the Executive Secretary for
approval ofproposed procedures, not otherwise authorized in these rules, to dispose of licensed or
registered material generated in the licensee's or registrant's operations. Each application shall
include.fl) A description of the waste containing licensed or registered material to be disposed of,
including the physical and chemical properties that have an impact on risk evaluation, and the
proposed manner and conditions of waste disposal; and(2) An analysis and evaluation ofpertinent
information on the nature of the environment; and(3) The nature and location of other potentially
affected facilities; and(4) Analyses and procedures to ensure that doses are maintained ALARA and
within the dose limits in Rule R313-15.
INTERROGATORY STATEMENT:
Refer to Attachment D, Section 2.6, Release Surveys: Revise to address the decontamination,
release, and disposal of equipment and buildings necessary to support decommissioning and
reclamation. Develop and present detailed release survey procedures and identify appropriate
radiation survey equipment that will be used. Develop and present additional decontamination
procedures during decommissioning and reclamation and include section on disposal of
equipment that cannot be decontaminated.
BASIS FOR INTERROGATORY:
The decommissioning plan indicates equipment and structural material may be removed,
decontaminated and surveyed for unrestricted release. But the radiation protection plan does
not include procedures, or identify instruments that would be used on conduct these release
surveys. NUREG-1575 Supplement 1 "Multi-agency Radiation Survey and Assessment of
Materials and Equipment Manual (MARSAME) " may be helpful in developing these procedures.
REFERENCES:
Denison Mines (USA) Corp., 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah,
Radioactive Materials License No. UT1900479, -Revision 5.0, Appendix E, September 2011
.•Attachment D Radiation Protection Manual for Reclamation September 2011
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INTERROGATORY WHITE MESA REC PLAN REV 5.0 R313-12; INT 18/1:
INSPECTION AND QUALITY ASSURANCE
REGULATORY BASIS:
UAC R313-12: an individual who has the knowledge and responsibility to apply appropriate
radiation protection rules and has been assigned such responsibility by the licensee or registrant.
INTERROGATORY STATEMENT:
Refer to Attachment A, Plans and Technical Specifications, Section 1.6, Inspection and
Quality Assurance: Revise the provided the "Radiation Protection Manual for Reclamation "
cited in this section, to define the responsibilities and duties of the Radiation Safety Officer.
Refer to Attachment A, Plans and Technical Specifications, Section 1.8b, Inspection and
Quality Assurance: Revise the wording to indicate that the DRC must review and approve all
design modifications to the Reclamation Plan.
BASIS FOR INTERROGATORY:
Although Attachment A points to "Radiation Protection Manual for Reclamation " in identifying
responsibilities and duties of the Radiation Safety Officer, the provided manual does not identify
these responsibilities. The Radiation Safety Officers responsibilities during reclamation need to
be identified, as they will be different than what is required during operations.
DRC must be designated to approve of any design modifications to the Reclamation Plan.
Section 1.8b of Reclamation Plan 5.0, Attachment A, Technical Plans and Specifications,
describes "Possible submittal to, and review by, DRC for approval" of design modifications.
Attachment A needs to be revised to indicate that the DRC must review and approve all design
modifications to the Reclamation Plan.
REFERENCES:
Denison Mines (USA) Corp., 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah,
Radioactive Materials License No. UTI900479, Revision 5.0, Appendix E, September 2011
.Attachment A, Plans and Technical Specifications
Denison Mines (USA) Corp., 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah,
Radioactive Materials License No. UTI900479, Revision 5.0, Appendix E, September 2011
.•Attachment D, Radiation Protection Manual for Reclamation September 201J
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INTERROGATORY WHITE MESA REC PLAN REV 5.0 R313-24; 10 CFR 40.42(J); INT
19/1: REGULATORY GUIDANCE
REGULATORY BASIS:
UAC R313-24 incorporates 10 CFR 40.42(i) by reference: As the final step in decommissioning,
the licensee shall—(1) Certify the disposition of all licensed material, including accumulated
wastes, by submitting a completed NRC Form 314 or equivalent information; and (2) Conduct a
radiation survey of the premises where the licensed activities were carried out and submit a
report of the results of this survey, unless the licensee demonstrates in some other manner that
the premises are suitable for release in accordance with the criteria for decommissioning in 10
CFR part 20, subpart E or, for uranium milling (uranium and thorium recovery) facilities,
Criterion 6(6) of Appendix A to this part.
INTERROGATORY STATEMENT:
Refer to Attachment A, Plans and Specifications, Sections 6.4 Guidance: Please revise the
decommissioning plan to reference and incorporate current guidance, namely NUREG-1757
"Consolidated Decommissioning Guidance "; NUREG-1575 "Multi-Agency Radiation Survey
and Site Investigation Manual (MARSSIM) "; and NUREG-1575 Supplement 1 "Multi-agency
Radiation Survey and Assessment of Materials and Equipment Manual (MARSAME) "
BASIS FOR INTERROGATORY:
This document references the use ofNUREG-5849: "Manual for Conducting Radiological
Surveys in Support of License Termination " as the applicable guidance document. The current
NRC guidance documents for decommissioning are NUREG-1757 "Consolidated
Decommissioning Guidance "; NUREG-1575 "Multi-Agency Radiation Survey and Site
Investigation Manual (MARSSIM) "; and NUREG-1575 Supplement 1 "Multi-agency Radiation
Survey and Assessment of Materials and Equipment Manual (MARSAME) ".
REFERENCES:
Denison Mines (USA) Corp., 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah,
Radioactive Materials License No. UTI900479, Revision 5.0, Appendix E, September 2011:
Attachment A, Plans and Technical Specifications
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INTERROGATORY WHITE MESA REC PLAN REV 5.0 R313-24,;10 CFR 40
APPENDIX A CRITERION 6(6); INT 20/1: SCOPING, CHARACTERIZATION, AND
FINAL SURVEYS
REGULATORY BASIS:
UAC R313-24 incorporates by reference 10 CFR 40 Appendix A Criterion 6(6): The design
requirements in this criterion for longevity and control of radon releases apply to any portion of
a licensed and/or disposal site unless such portion contains a concentration of radium in land,
averaged over areas of 100 square meters, which, as a result of byproduct material, does not
exceed the background level by more than: (i) 5 picocuries per gram (pCi/g) of radium-226, or,
in the case of thorium byproduct material, radium-228, averaged over the first 15 centimeters
(cm) below the surface, and (ii) 15 pCi/g of radium-226, or, in the case of thorium byproduct
material, radium-228, averaged over 15-cm thick layers more than 15 cm below the surface.
INTERROGATORY STATEMENT:
1. Refer to Attachment A, Plans and Specifications, Sections 6.6 Scoping Surveys & Figure
A-l: Provide a figure identifying the areas and survey grid sizes. Clarify how use of the
large grids and the spacing shown in Figure A-l will ensure compliance with the 100 square
meter criteria. Explain how samples will be collected from these larger grids.
2. Refer to Attachment A, Plans and Technical Specifications, Sections 6.6 Scoping Surveys:
Provide details (including information on instrument sensitivity) on the beta gamma
radiation instruments that will be used for the scoping surveys. Indicate the frequency of
calibration checks, daily operational checks, and other QA/QC requirements for the
instruments. Also indicate whether these same instruments (used during facility operations)
will be used for subsequent characterization, remediation, and final survey work.
3. Refer to Attachment A, Plans and Technical Specifications, Sections 6.6 Scoping Surveys:
Explain how areas contaminated with radium, thorium, and uranium will be identified and
surveyed to ensure they will not result in a dose that is greater than the radium standard
alone.
4. Refer to Attachment A, Plans and Technical Specifications, Sections 6.6 Scoping Surveys:
Identify what types of samples (e.g., grab or composite samples) will be collected to support
developing the gamma correlation. Explain how locations for taking these samples will be
selected. State how many correlations will be developed and how they will differ from each
other.
5. Refer to Attachment A, Plans and Technical Specifications, Sections 6.6 Scoping Surveys:
Identify the analytes including radioisotopes for which samples will be analyzed by chemical
analysis and identify the preferred analytical method.
6. Refer to Attachment A, Plans and Technical Specifications, Sections 6.6 Scoping Surveys:
Provide information on how other materials that may be left will be identified during scoping
surveys. Identify additional survey procedures for alpha beta and gamma surface surveys as
appropriate.
7. Refer to Attachment A, Plans and Technical Specifications, Sections 6.7 Characterization
and Remediation Control Surveys: Explain how many and how samples will be collected to
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ensure the correlation developed for the scoping is consistent with the characterization and
reclamation surveys. Explain how the correlation will be modified to address gamma
variations that may arise during decommissioning and reclamation?
8. Refer to A ttachment A, Plans and Technical Specifications, Sections 6.8 Final Survey,
Figure A-2 and Attachment B Construction QA/QC Plan, Section 5.4.1: Please clarify the
terminology used in the two documents. Ensure that the activities described are consistent.
Provide details on how the 10% of locations are selected for sampling. Demonstrate that
collection offour samples as shown on Figure A-2 is sufficiently representative of the entire
100-square-meter area. Explain whether samples taken from the four sample locations
identified in Figure A-2 will be analyzed separately or will be composited.
9. Refer to A ttachment A, Plans and Technical Specifications, Sections 6.8 Final Survey,
Figure A-2: Explain how the areas where final survey soil sample results exceed the criteria
will be addressed. State the basis for determining whether additional removal will be
required. A soil sample that exceeds the criteria may also indicate a problem with the
gamma correlation. Since the majority of the area will be released based on the gamma
correlation, explain how the gamma correlation will be reviewed to ensure the use of the
correlation in place of sampling is still valid.
BASIS FOR INTERROGATORY:
1. The discussion in Section 6.6 does not clearly identify the survey grid sizes that will be used
in the described areas. Figure A-l describes a serpentine gamma survey path, but this also
indicates that a total of 3 transects across the 30 meter grid will be made. With each
transect representing only a 1-meter-square area, a significant majority of the grid is not
surveyed, and compliance with the 100-square-meter standard cannot be documented. It is
unclear how the 30m x 30m grid relates to the 50m x50m grid.
2. Without more detailed information on the instrument that will be used it is impossible to
determine if the sensitivity is appropriate to verify compliance with the standard.
3. While the radium standard is appropriate for much of the site, as mentioned in the technical
specifications there are areas that are contaminated with a combination of nuclides, how will
these be identified, and what other survey procedures will be used to ensure the uranium and
thorium are addressed.
4. The general criteria for identifying appropriate sample locations should be developed to
ensure the resulting correlation is appropriate. Typically correlations are generated based
on grab samples but the discussion does not detail how the samples will be collected. Also
it appears that multiple correlations may be developed so proper communication regarding
which correlation is appropriate for each area is necessary to ensure compliance with the
soil standard.
5. Specifics on the analyses to be performed are necessary to evaluate the proposed
correlations. The analytical methods need to be identified to ensure the appropriate
analytical costs are included in the cast estimate.
6. Additional definition and description is required to provide assurance that all contaminants
will be identified and properly processed during decommissioning and reclamation.
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7. The gamma correlation that is developed for the scoping surveys may be valid, how will
variations in gamma rates associated with excavation depth and differences in material at
depth be addresses.
8. The radiological survey descriptions in the documents are not consistent. The
characterization survey described in Attachment B is different than the characterization
remediation survey described in Attachment A. Without consistent terminology and survey
descriptions it is impossible to evaluate the survey descriptions. To ensure that collecting
samples at only 10% of the remediated grids is sufficient, the criteria used as the basis for
the 10% must be provided. Typically, composite soil samples for a 100 square meter area
include between 5 and 11 aliquots to ensure the data is representative of the entire area.
9. The plan should contain a commitment to perform a radium-gamma correlation on the
verification data, to track soil samples that fail the Ra-226 criteria, and to perform
additional cleanup after a verification soil sample exceeds the Ra-226 standard. Just
cleaning the failed grid is not adequate because the failed sample could indicate that the
gamma value may not be conservative and that some of the unsampled grids may also fail to
meet the standard. For example, the plan could indicate that neighboring grids would also be
analyzed for Ra-226 or, if the number offailed grids is excessive, the gamma guideline would
be adjusted downward and areas further remediated, as necessary.
REFERENCES:
Denison Mines (USA) Corp., 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah,
Radioactive Materials License No. UTI900479, Revision 5.0, Appendix E, September 2011;
Attachment A, Plans and Technical Specifications
Denison Mines (USA) Corp., 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah,
Radioactive Materials License No. UTI900479, Revision 5.0, Appendix E, September 2011:
Attachment B, Construction Quality Assurance/Quality Control Plan
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