DRC-2013-001243 - 0901a0688034af7d

State of Utah
GARY R HERBERT
Governor
GREG BELL
Lieutenant Governor
Department of
Environmental Quality
Amanda Smith
Executrve Director
DIVISION OF RADIATION CONTROL
Rusty Lundberg
Director
February?, 2013
Harold Roberts
Executive Vice President and Chief Operating Officer fiPP O f) 4 "7 r\ f\
Energy Fuels Resources (USA) Inc. UfTO-* CU I 0 ^ UQ 1 P ii ^
225 Union Blvd., Suite 600 J. ^ -/
Lakewood, CO 80228
RE: Radioactive Material License (RML) Number UT 1900479: Review of September 10,
2012 Energy Fuels Resources (USA) Inc. Responses to Round 1 Interrogatories on Revised
Inflltration and Contaminant Transport Modeling (ICTM) Report, White Mesa Mill Site,
Blanding, Utah, report dated March 2010
Dear Mr. Roberts:
Enclosed is URS Professional Solutions' review of Energy Fuels Resources responses to the
Round I Interrogatories. The enclosed table (Table 1) and attached Technical Memorandum
(Attachment A - Rev. ICTM Report Round 1 [Rd 1] Interrogatories, Responses, and
Discussion) document the results of URS Professional Solutions' (Professional Solutions')
review, conducted on behalf of the Utah Division of Radiation Control (the Division), of
Energy Fuels Resources (USA) Inc.'s (EFR's) Responses to Round 1 (Rd 1) Interrogatories
submitted bv the on Revised ICTM Report dated March 2010 prepared by Denison Mines
(USA) Corp. (now EFR).
Table 1 presented below is intended to succinctly state additional analyses and information
required, to enable the Division to thoroughly evaluate EFR's Revised Infiltration and
Contaminant Transport Modeling report and responses to the Round 1 Interrogatories
previously submitted on that report. Salient additional information requested from EFR is
summarized in the third column of the table. The table summarizes remaining technical issues
related to the Revised ICTM Report (and associated appendices and other supporting
documents), identifies additional actions, analyses, and/or revisions that are requested from
EFR in conjunction with the review of the Revised ICTM Report in order to allow these
identified issues to be adequately evaluated and resolved.
Attachment A restates the Rd 1 interrogatories the Division transmitted to EFR on the Revised
ICTM Report, repeats EFR's responses to those interrogatories, and provides discussion
summarizing the results of the review of each response. The Rd 1 Interrogatories and EFR's
195 North 1950 West • Salt Lake City, UT
Mailing Address P O Box 144850 • Salt Lake City, UT 84114-4850
Telephone [phone] • Fax [phone] -TDD [phone]
Vf wvf deq Utah gov
Pnnted on 100% recycled paper
Page 2
Responses to those interrogatories are summarized in the same order in which the Rd 1
Interrogatories were originally submitted.
If you have any questions regarding this letter or the enclosure, please feel free to contact me
at 801-536-4263.
Sincerely,
John Hultquist, Section Manager
LLRW/Uranium Mill Licensing Section
JH:jh
Cc: Jo Aim Tischler, Director, Compliance and Permitting
TJDC Technical
Memorandum
bate: February 6, 2013 UTl 1.1102.004 OUT
To: John Hultquist, Utah Division of Radiation Control
From:
Jon Luellen, URS Professional Solutions
Robert Baird, URS Professional Solutions
Subject:
Review of September 10,2012 Energy Fuels Resources (USA) Inc. Responses to
Round 1 Interrogatories on Revised Infiltration and Contaminant Transport Modeling
Report, White Mesa Mill Site, Blanding, Utah, report dated March 2010
The enclosed table (Table 1) and attached Technical Memorandum (Attachment A - Rev. ICTM Report
Round 1 [Rd 1] Interrogatories, Responses, and Discussion) document the results of URS Professional
Solutions' (Professional Solutions') review, conducted on behalf of the Utah Division of Radiation
Control (the Division), of Energy Fuels Resources (USA) Inc.'s (EFR's) Responses to Round 1 (Rd 1)
Interrogatories submitted by the on Revised ICTM Report dated March 2010 prepared by Denison
Mines (USA) Corp. (now EFR).
Table 1 presented below is intended to succinctly state additional analyses and information required, in
Professional Solutions' opinion, to enable the Division to thoroughly evaluate EFR's Revised
Infiltration and Contaminant Transport Modeling report and responses to the Round 1 Interrogatories
previously submitted on that report. Salient additional information requested from EFR is summarized in
the third column of the table. The table summarizes remaining technical issues related to the Revised
ICTM Report (and associated appendices and other supporting documents), identifies additional actions,
analyses, and/or revisions that are requested from EFR in conjunction with the review of the Revised
ICTM Report in order to allow these identified issues to be adequately evaluated and resolved.
Attachment A restates the Rd 1 interrogatories the Division transmitted to EFR on the Revised ICTM
Report, repeats EFR's responses to those interrogatories, and provides discussion summarizing the
results ofthe review of each response. The Rd 1 Interrogatories and EFR's Responses to those
intciTOgatorics arc summiirizcd4nihc-samc-ordcHnwhtch the Rd 1 Intcrrogatories^ere-originally
submitted.
URS Corporation
756 E Winchester Street, Suite 400
Salt Lake City, UT 84107
Tel. [phone]
Fax [phone]
www urscorp com
TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
Table of Contents
1.0 Inconsistencies Between Revised ICTM Report and Revised Reclamation Plan 12
1.1 Round 1 Interrogatory White Mesa Revised ICTM Report; R313-24-4; 10CFR40 Appendix A,
Criterion 6(1); INT 01/1: Inconsistencies Between Revised ICTM Report And Reclamation Plan
Rev 5.0 12
1.2 EFR Responses to Rd 1 Interrogatory White Mesa Revised ICTM Report; R313-24-4; 10CFR40
Appendix A, Criterion 6(1); INT 01/1: Inconsistencies Between Revised ICTM Report And
Reclamation Plan Rev 5.0 13
1.3 Division's Assessment of EFR Responses to Rd 1 Interrogatory White Mesa Revised ICTM Report;
R313-24-4; 10CFR40 Appendix A, Criterion 6(1); INT 01/1 17
2.0 Comparison of Cover Designs, Sensitivity Analyses, 'Bathtub Analysis', and Radon Emanation
Modeling 21
2.1 Round 1 Interrogatory White Mesa Revised ICTM Report; R313-24-4; 10CFR40 Appendix A,
Criterion 6(1); INT 02/1: Comparison of Cover Designs, Sensitivity Analyses, 'Bathtub Analysis',
and Radon Emanation Modeling 21
2.2 EFR Responses to Rd 1 Interrogatory White Mesa Revised ICTM Report; R313-24-4; 10CFR40
Appendix A, Criterion 6(1); INT 02/1: Comparison of Cover Designs, Sensitivity Analyses, 'Bathtub '
Analysis', and Radon Emanation Modeling 23
2.3 Division's Assessment of EFR Responses to Rd 1 Interrogatory White Mesa Revised ICTM Report;
R313-24-4; 10CFR40 Appendix A, Criterion 6(1); INT 02/1 33
3.0 Moisture Storage Capacity of Cover 44
3.1 Round 1 Interrogatory White Mesa Revised ICTM Report ; R313-24-4; 10CFR40 Appendix A,
Criterion 6(1); INT 03/1: Moisture Storage Capacity of Cover 44
3.2 EFR Responses to Rd 1 Interrogatory White Mesa Revised ICTM Report; R313-24-4; 10CFR40
Appendix A, Criterion 6(1); INT 03/1: Moisture Storage Capacity of Cover 45
3.3 Division's Assessment of EFR Responses to Rd 1 Interrogatory White Mesa Revised ICTM Report;
R313-24-4; 10CFR40 Appendix A, Criterion 6(1); INT 03/1 46
3.4 Other Cover Design-Related Issues (Related to Rd Interrogatories 02/1 and 03/1) 46
4.0 Evaluation of Flow Through Tailings Cell Liners 50
4.1 Round 1 Interrogatory White Mesa Revised ICTM Report; R313-24-4; 10CFR40 Appendix A,
Criterion-6fflt I^fT 01/1: Evahiatton-of^^ow-Throa^t-TaiKngs-GelHjinefs 50
4.2 EFR Responses to Rd 1 Interrogatory White Mesa Revised ICTM Report; R313-24-4; 10CFR40
Appendix A, Criterion 6(1); INTO 01/1: Evaluation of Flow Through Tailings Cell Liners 51
4.3 Division's Assessment of EFR Responses to Rd 1 Interrogatory White Mesa Revised ICTM Report;
R313-24-4; 10CFR40 Appendix A, Criterion 6(1); INT 01/1 52
5.0 Contaminant Transport Modeling 57
5.1 Round 1 Interrogatory White Mesa Revised ICTM Report; R313-24-4; 10CFR40 Appendix A,
Criterion 6(1); TNT 01/1: Contaminant Transport Modeling 57
5.2 EFR Responses to Rd 1 Interrogatory White Mesa Revised ICTM Report; R313-24-4; 10CFR40
Appendix A, Criterion 6(1); INTO 01/1: Contaminant Transport Modeling 58
5.3 Division's Assessment of EFR Responses to Rd 1 Interrogatory White Mesa Revised ICTM Report;
R313-24-4; 10CFR40 Appendix A, Criterion 6(1); INT 01/1 72
REFERENCES 78
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TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
ATTACHMENT A
Rev. ICTM Report Rd 1 Interrogatories, Responses, and Discussion
1.0 Inconsistencies Between Revised ICTM Report and Revised Reclamation
Plan
Round 1 (Rd 1) Interrogatory INT. 01/1 items related to the currently proposed ET cover design,
EFR's Responses to those interrogatories, and the Division's findings based on review of those
Responses, are discussed in the foUow^ing section.
1.1 Round 1 Interrogatory White Mesa Revised ICTM Report; R313-24-4; 10CFR40
Appendix A, Criterion 6(1); INT 01/1: Inconsistencies Between Revised ICTM
Report And Reclamation Plan Rev 5.0
Interrogatory White Mesa Revised ICTM Report: R313-24-4: 10CFR40 Appendix A, Criterion
6(1); INT 01/1: "Inconsistencies Between Revised ICTM Report And Reclamation Plan Rev
5.0" -- Referencing the Executive Summary, Section 2.1, Figures 2-2 and 3-1, Table 3-1, and
Appendices D through N ofthe ICTM Report Rev 2, THE INTERROGATORY REQUESTED,
that EFR do the following:
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 v^ll 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;
Update analyses in the referenced Appendices to reflect ET cover characteristics that are
consistent with the descriptions to be given in the next revision ofthe Reclamation Plan
Rev 5.0;
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 BIOINTRUSION EVUALATION AND
REVEGETATION PLAN";
For Appendix E (Comparison of Cover Designs Based on Infiltration Modeling),
Appendix F (Evaluation of the Effects of Storm Intensity on Infiltration through
12
TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
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 firost penetration depth for the
cover system
b. Provide revised discussion and revised infiltration analyses to:
i. Reflect the results of the updated fi"ost penetration depth analysis requested in
"INTERROGATORY WHITEMESA RECPLAN 5.0 R313-24-4; 10CFR40,
APPENDIX A, CRITERION 6; INT 10/1: TECHNICAL ANALYSES - FROST
PENETRATION ANALYSIS"
ii. Address the additional considerations and additional information described or
requested 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"; and
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.
1.2 EFR Responses to Rd 1 Interrogatory White Mesa Revised ICTM Report; R313-24-
4; 10CFR40 Appendix A, Criterion 6(1); INT 01/1: Inconsistencies Between Revised
ICTM Report And Reclamation Plan Rev 5.0
IN ITS RESPONSE to the first two items of above interrogatory, EFR indicated the following:
• "The Revised Inflltration and Contaminant Transport Modeling (ICTM) Report was
submitted during March 2010 and was meant to introduce the conceptual design of an
evapotranspiration (ET) cover. Infiltration modeling contained within the 2010 Revised
ICTM Report indicated that the design and construction of a monolithic ET cover is the
preferred alternative for inflltration control The construction of an ET cover as
proposed in the 2010 Revised ICTM Report was in contrast to previous iterations of the
Reclamation Plan that were based on the cover design from 1996. Therefore, the
Reclamation Plan Revision 5.0 submitted during September 2011 used the initial March
2010 conceptual design of the ET cover as a starting point, but modified some of the
material descriptions and thicknesses to provide an update to the analyses based on
additional information subsequently collected after the 2010 Revised ICTM Report was
submitted. The gap in time between publication of these two reports, combined with the
collection of additional soils data between March 2010 and September 2011, explains the
13
TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
discrepancy between reports. Consequently, the material layering, thicknesses, and
physical characteristics presented in the next iteration of the ICTM Report including text,
figures, and tables will be consistent with next iteration of the Reclamation Plan.
• In addition to the response to Comment One of this interrogatory, the analyses presented
in the next iteration of the ICTM Report including information and analyses presented in
the appendices will be consistent with the next iteration of the Reclamation Plan.
Applicable appendices that would be updated include Appendices E, F, G, H, and N.
However, as discussed later in this interrogatory response document, we propose
eliminating Appendix F from the next iteration of the Report to minimize confusion. "
IN ITS RESPONSE to the third item of above interrogatory, EFR indicated that:
"The next iteration of the ICTM Report will include an updated Appendix D that reflects the
request for additional information (i.e., vegetation occurrence and proposed revegetation plan).
Revisions to Appendix D will be consistent with material presented in Attachment G included
with Denison's August 15, 2012 Responses to the Reclamation Plan, Revision 5.0 Interrogatories
(Denison 2012b). Overall, supporting text was updated to:
• Include the results of a plant and burrowing animal survey that was completed at the mill
site during June 2012.
o The results of the plant survey were used to support the range ofpercent vegetative
cover and root density/distribution for plant species that are expected to occur on the
cover during the design performance period;
o The plant survey, and the similarity in environmental conditions between Monticello
-artdrWIiite Mesa, suggests that-crplaitt-cov€r-esttn'mte-of40% is a reasonable cstimate-
for a long-term average, while a percent plant cover of 30% is a reasonable estimate
for a reduced performance scenario. The root density/distribution for plants species
expected to occur on the cover is summarized in Table 01/1/3-1; and
• Include a discussion regarding the sustainability of the cover system as it relates to
potential climate change and plant community succession and potential for species
colonization.
o From the review of climate change literature applicable to the southwest United
States and an analysis of the impact of various climate change scenarios, the most
likely plant community type that will be maintained throughout the 200 to 1,000 year
performance period is a community dominated initially by cool season grasses, with a
long-term transition to dominance by warm season grasses as atmospheric C02 and
14
TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
temperature continues to increase and precipitation decreases and shifts from winter
storage to pulse dominated; and
o While shrubs such as big sagebrush could establish through natural succession
during the short-term, it is unlikely that big sagebrush will be sustainable on site, but
it is likely to establish through natural succession before the effects of climate change
alter the environment.
Table for Response 3 (September 10, 2012):
Table 01/1/3-1. Root biomass for species expected to occur on the cover system
Depth (cm) Root Biomass Density,
Anticipated Performance
(g/cmh
Root Biomass Density,
Reduced Performance
(g/cm')
0-15 0.11 0.04
15-30 0.17 0.12
30-45 0.035 0.02
45-60 0.023 0.015
60-75 0.021 00.014*
75-90 0.019 0.0
90-107 0.011 0.0
l^QtP - * Mqrimum rnnting Hppth under the reducedpp.rfnrmnmrP sr^nnrin yvnulH HP 6^ CP? "
IN ITS RESPONSE (EFR Response 4a), to the fourth item of above interrogatory, EFR indicated
the following:
"Frost Penetration
The frost penetration analysis for the tailings cover system was revised and presented in Denison
(2012a) to address interrogatories for the Reclamation Plan, Revision 5.0 (DRC, 2012). This
analysis again will be updated after approval ofthe conceptual final cover design is obtained.
Revisions will be completed to be consistent with the revised cover design presented in the
August 15, 2012 responses to the interrogatories for the Reclamation Plan, Revision 5.0
15
TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
(Denison, 2012b). The frost penetration analysis requires revision to incorporate additional data
collected from a site investigation conducted on April 19, 2012 to further evaluate cover borrow
materials. It is anticipated that the results of the updated analyses will be similar to the analyses
presented in Denison (2012a), with a frost penetration depth on the order of 81 cm (32 in).
Pedogenic Processes
Soil cover layers and their respective hydraulic and physical material properties potentially
could be affected from wet/dry, freeze/thoM^, and other pedogenic processes as suggested by
Benson et al. (2011). However, as noted in Benson et al. (2011), potential changes to the cover
can be minimized by designing the cover system to be as close as practical to the anticipated
equilibrium state under long-term conditions; furthermore, their study also noted that long-term
changes are more prone to occur for less permeable soils compared to more permeable soils.
Because the frost penetration depth is not anticipated to exceed the depth ofthe erosion
protection and water storage layers (combined depth of 107 cm), a minor increase or decrease
in the frost penetration depth will not affect the radon barrier and grading layers that are
located beneath 107 cm. Therefore, any potential modifications to the hydraulic and physical
properties of the cover that could be influenced by freeze/thaw processes would be restricted to
the erosion protection and water storage layers.
Hydraulic test results for the soils stockpiled at White Mesa are within the range of parameter
values anticipated to occur long-term as noted by Benson et al. 2011 (See Interrogatory 02/1,
Response 1 of this Response. Based on this comparison, and the relatively permeable nature of
the soils, corrections to account for potential pedogenic processes are not warranted at this time
because the physical and hydraulic properties at the emplaced conditions are such that
postconstruction changes should be minimal. "
IN ITS RESPONSE (EFR Response 4b), EFR also stated the following:
"The cover model has been updated from those presented in the 2010 Revised ICTM Report (see
also Interrogatory 02/1, Response 1 of this [Response] document, to reflect additional
laboratory test results and revisions to the cover design as presented in Denison (2012b). In
regard to the next iteration of the ICTM Report, applicable appendices that would be updated
include Appendices E, F, G, H, andN However, we propose eliminating Appendix Ffrom the
next iteration of the Report to minimize confusion.
Revisions to the amount of percolation that may recharge the tailings affects the "bathtub effect"
calculations, and are discussed in Interrogatory 02/1, Response 1 in this Response set. These
potential effects and resultant calculations will be incorporated into the next iteration ofthe
ICTM Report.
16
, TECHNICAL MEMORANDUM
"I
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
IN ITS RESPONSE to the fifth item of above interrogatory, EFR indicated the following:
The updated frost penetration analysis will not affect the, analyses presented in Appendix K
(tailings pore water source term chemistry). For the calculations presented in Appendix L
(potential water flux rates through the liners), flux rates predicted at the end of dewatering were
assumed to equal the rate during post-closure conditions. This approach was incorporated as an
appropriate simplification based on discussions and comments previously received by the
Division (DRC, 2009) and responses provided by MWH (2009). Additionally, the upper
' boundary condition assigned in Appendix M (reactive flow and transport model through the
bedrock vadose zone) used the flux calculations presented in Appendix L. Therefore Appendices
K, L, and Mdo not require revision based on modifications to the frost penetration analysis.
Appendix N (model input/output files) will require revision once the infiltration modeling is
updated and a future iteration of the ICTM Report is submitted. "
1.3 Division's Assessment of EFR Responses to Rd 1 Interrogatory White Mesa Revised
ICTM Report; R313-24-4; 10CFR40 Appendix A, Criterion 6(1); INT 01/1
Based on review of the information provided in the above EFR Response(s), the Division
has concern that the argument provided by EFR that post-construction changes in soil
properties at the White Mesa site should be minimal is not adequately-supported, e.g., it
does not accord with published data, which show significant changes occur over time with
nearly all soils, some more than others. EFR has not adequately demonstrated that the
cover system has necessarily been designed to be close to the anticipated equilibrium state
under long-term conditions, considering the many processes that can potentially disturb
the soil over time in the currently designed cover system. These include freeze-thaw cycles,
potential soil desiccation during drier climate episodes, reduction of or loss of vegetation in
the cover, and deeper animal burrowing depths and deeper plant root penetration than
currently estimated by EFR (see Section 11.3 of the Technical Memorandum and Table
documenting the Division's review of EFR's Responses to the Rd 1 Interrogatories on the
Rev 5.0 Reclamation Plau for additional details), coupled with the exacerbation of
potential long-term biointrusion impacts due to the absence of a specifically designed
biointrusion barrier in the currently proposed cover
Additional technical information needs to be provided to support the contention that post-
construction changes in soil properties in the cover at the White Mesa site should be
minimal. At a minimum, such information should include technical data on cover soil
characteristics from other similarly-constructed soil cover systems using similar soils and
at a site having climate, soils, and vegetation and animal species and population
characteristics similar to those present at the White Mesa site. Such data should be
acquired within several years (e.g., 5-10 years) after initial cover construction. Based on the
April 2012 on-site soils testing, the geometric mean saturated hydraulic conductivity of
soils expected to be representative of cover-system soils is approximately 9.5 x IO"'* cm/s (see
data in Benson and Wang, 2012). This geometric mean saturated hydraulic conductivity
value is outside (above) the range of values given above for long-term '^terminal values"
17
TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
expected for cover-system soils (8 x 10'^ to 6 x 10"^ cm/s [Benson et al. 2011). Therefore, the
statement on Page 4 of 70 of the Response that "the hydraulic test results for the soils
stockpiled at White Mesa are within the range of parameter values anticipated to occur
long-term as noted by Benson et al. (2011)" is not technically correct. Although the
magnitude of changes in hydraulic conductivity values that might be expected to occur in
the cover using soils having the range of saturated hydraulic conductivity values
determined from the April 2012 soil stockpile tests would likely be less than for a cover
initially constructed with lower-permeability soils, data are limited and insufficient data
have been provided to demonstrate EFR's contention that that post-construction changes
in soil properties at the White Mesa site should be minimal.
Based on the above considerations, the Division requests that, for modeling purposes, EFR
more conservatively model the saturated hydraulic conductivity values of cover-system
soils increasing over time. Alternatively, EFR may propose incorporating alternative
components into cover system design or propose to revise the cover design to better deter
such expected alterations from ever occurring.
The Division also requests that EFR complete a sensitivity analysis by modifying the soil
hydraulic properties (e.g., residual and saturated soil water contents, soil water retention
function parameters alpha and n, and saturated hydraulic conductivity) in a manner
consistent with the likely increased saturated hydraulic conductivity and alpha parameter
expected in the maximum potentially impacted frost damage zone due to soil structure
development. The soil hydraulic parameter modifications should be adjusted in a manner
that either is consistent with NRC recommendations for adjusting similar properties in this
soil zone when estimating radon flux emanation (U.S. NRC 2003a, Section 5.1.3), or
consistent with Benson et al. 2011 recommendations, whichever is more conservative for
inflltration modeling. Provide information demonstrating that the speciflc adjustments
selected and used in the inflltration modeling sensitivity analysis provide the most
conservative results (i.e., highest inflltration rate) (See also discussion under Response to
Interrogatory 02/1 below).
EFR's response also addressed items in Interrogatory White Mesa RECPLAN Rev 5.0
R313-24-4; 10CFR40 Appendix A; Int. 11/1 relating to the "Vegetation and Biointrusion
Evaluation and Revegetation Plan" by referring to new information presented in Revised
Attachment G dated August 2012. Based on review of that document, the information
presented is not sufflcient to demonstrate that vegetation cover will be sustainable over the
long term and that it will be effective in promoting evapotranspiration. The Division
requests that EFR: (i) Provide information on current vegetation on previously revegetated
areas at the White Mesa Mill Site and the history of revegetation efforts and results at the
site; (ii) Provide more detail on the results of vegetation surveys conducted in June 2012;
(iii) Provide a map of current vegetation; (iv) Provide information on soil properties at
reference areas to document that "sustainable levels" are achievable; and (v) Provide
additional information on procedures to be used during soil amendment and weed
management practices to be employed. In the discussion of succession, EFR should address
18
TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
regionally common shrub species that may colonize the site from lower elevation, warmer
and drier sites.
Additional information also needs to be provided to support/defend the range of root
density values listed in Table 01/1/3-1 of EFR's Response to Interrogatory 01/1, Item 3 on
the Revised ICTM Report. The Division requests EFR provide example root density
calculations showing how the estimated root density values were derived, and that EFR re-
evaluate and further demonstrate that use of speciflc information contained in reference
sources cited by EFR as the basis for deriving estimated root densities in soil are
valid/appropriate for the semi-arid conditions at the White Mesa site. EFR should revise
the root density estimation approach and estimated range of root densities in the cover as
needed based on this re-evaluation (see discussion below). Additional comments on
Revised (August 2012) Attachment G relative to sustainability ofthe vegetation cover and
biointrusion issues are provided in Section 2.3 below and in the Technical Memorandum
and Table documenting the Division's review of EFR's Responses to the Rd 1
Interrogatories on the Rev 5.0 Reclamation Plan.
In its Response, EFR indicated (Page D-13 in Revised Attachment G appended to the
Response to the Rd 1 interrogatory) that the estimates of root density listed in Table D.7 of
Revised Attachment G were based on the information contained in the following
references: Bartos and Sims (1974), Sims and Singh (1978), Hopkins (1953), Lee and
Lauenroth (1994), Jackson et al. (1996) and Gill et al. (1999)
In the Revised ICTM Report, stated root density values (e.g., 4.3 g/cm^) were off by several
orders of magnitude and were revised downwards in EFR's Response to the Rd 1
interrogatories. However, root density calculation results still appear to be in error
considerably. No calculations are shown. The Division request that pertinent calculations
be provided. Supporting references were not provided. However, references were cited on
Page D-13 of the Revised Attachment G.
These references include Bartos and Sims (1974) and Sims and Singh (1978)» who arc also -
referenced in regard to this topic in the original Revised ICTM Report. These particular
references are not for semi-arid-zone plants but for grasses in other biomes, where root
density may be greater than is realistic to assume for plants in a semi-arid environment.
Use of t data from those references therefore may not be appropriate for describing root
density in the cover-system soils at White Mesa under semi-arid conditions. Values
obtained using those data should therefore be reconsidered when making application to
synthetic soils in a different environment in southeastern Utah. Please address this issue
and justify, if possible, the use of Bartos and Sims (1974) and Sims and Singh (1978).
Bartos and Sims (1974) reported yearly-averaged densities of shortgrass at four sites in Ft.
Collins, Colorado of up to 1309 g/m^ in the upper 80 cm of soil. Dividing 1309 g/m^ by 0.80
m yields 1636 g/m^, or 1.6 x 10"^ g/cm^ for a[n average, near-surface] root density on a per-
volume basis. This value is one to two orders of magnitude smaller than what is claimed in
19
TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
Table 1/1/3-1 ofthe Response to the Rd 1 interrogatory for anticipated performance at a
comparable depth.
Sims and Singh (1978) reported a maximum value of average root biomass for grazed
grasslands at eight areas of North American as varying from 71 to 1547 g/m^ in the upper
10 cm. Dividing 71 g/m^ by 0.10 m yields 710 g/m^, which is equal to 7.1 x lO"'* g/cm^ [for an
average, near-surface root density]. Dividing 1547 g/m^ by 0.10 m yields 15470 g/m^, which
is equal to 1.5 x 10'^ g/cm^ [for an average, near-surface root density]. Thus, average root
biomass for grazed grasslands at the eight areas of North American studied by Sims and
Singh (1978) tends to vary from 7.1 x 10"^ g/cm^ to 1.5 x 10"^ g/cm^ These values are also
one to two orders of magnitude less than what is claimed in Table 1/1/3-1 of the Response
for anticipated performance at a comparable depth. It therefore appears that the root
density values listed in Table 01/13-1 ofthis Response may be in error by one to two orders
of magnitude.
Other references cited on Page D-13of Revised Attachment G include Hopkins (1953), Lee
and Lauenroth (1994), Jackson et al. (1996) and Gill et al. (1999). Hopkins (1953) work was
done on fertile farmland in Kansas, not comparable to the semi-arid land typical of
southeastern Utah or to the synthesized soil material planned for fabrication and use for
constructing the cover system. Such differences in soil characteristics notwithstanding,
calculating root biomass for the fertile Kansas soil, based on Hopkins' (1953) numbers, an
estimate for the root biomass, for example for the 30-45 cm depth interval, is 0.002 g/cm^.
This is an order of magnitude lower than 0.035 g/cm^, the anticipated performance root
biomass for that depth interval claimed in Table D.7. (The estimated root biomass (on a
per-volume basis) for the 30-45 cm depth interval based on Hopkins (1953) data can be
made in the following way. The soil columns are described in Hopkins (1953) as being
three (3) inches thick, and 12 inches wide. The roots are cut into 6-inch segments, each
representing a 6-inch long vertical section of earth. Thus, the block of earth for a Hopkins
(1953) listed weight of soil is 3" x 12" x 6", or 216 cubic inches (3540 cm"'). However, in
this case, the relevant volume uf soil is foi a depth intei val from 30^45 cm, equal to two
and a half blocks (one from 30-36", one from 36-42", and one halfway down 42-48"). Thus,
the volume of soil over that interval = 2.5*3540 cm"' = 8850 cm^. The total weight of roots
for the 30-36" block, plus the total weight of roots for the 36-40" block, plus some fraction
of the weight from the 40-45" block are added. For convenience, it is assumed that half of
the root weight ofthe 40-45" block is in the upper part of that block. Dividing the total
weight of roots (17.94 g) for these 2.5 blocks by the volume of the blocks gives 0.002 g/cm^.
If it were instead assumed that, for example, 70 percent of the weight of the roots is in the
upper half ofthe deepest block, then a root biomass value of 0.0021 g/cm"' could be
estimated, essentially the same as when 0.5 was assumed)
20
TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
Based on the above information, the Hopkins (1953) root mass values are an order of
magnitude lower than those listed in Table D.7 of Revised Attachment G, i.e., 0.035 g/cm^.
It appears, therefore, that the values in Table D.7 are in error.
Lee and Lauenroths (1994) focused on only three species of plants and do not provide
weights needed to assess root biomass density, but they do provide an assessment of percent
root length as a function of depth. Jackson et aL (1996) offer root biomass expressed on a
per-area basis (rather than on a per-volume basis as is used in the Response) for eleven
different biomes, ranging from boreal forest to tundra. It is not apparent to the Division
which of these biomes, if any, would be comparable to that of the flnished cover system. It
is also not readily apparent how root biomass expressed on a per-area basis would be
transformed from this data to a per-volume basis. Gill et al. (1999) likewise offer root
biomass expressed on a per-area basis, and it is not readily apparent how root biomass
expressed on a per-area basis would be transformed to a per-volume basis.
In addition to showing examples of calculations for all new results, the Division requests
that EFR correct errors in Table D.7 of Revised Attachment G and on Page D-13 and Page
D-14 of Revised Attachment G and elsewhere in the Revised ICTM Report and other
supporting documents, as needed, and make appropriate corrections in the model and in
the expression of its results. Alternatively, justify the existing values, if possible. Please cite
references appropriately, and justify how information used from these references is
relevant and appropriate for conditions at the White Mesa site.
2.0 Comparison of Cover Designs, Sensitivity Analyses, 'Bathtub Analysis',
and Radon Emanation Modeling
2.1 Round 1 Interrogatory White Mesa Revised ICTM Report; R313-24-4; 10CFR40
Appendix A, Criterion 6(1); INT 02/1: Comparison of Cover Designs, Sensitivity
Analvses, ^Bathtub AnalvsisVaud Radon~Emanation Modeling
Interrogatory White Mesa Rev'd ICTM: R313-24-4: 10CFR40 Appendix A. Criterion 6(1): INT
02/1: "Comparison of Cover Designs. Sensitivity Analvses, 'Bathtub Analysis', and Radon
Emanation Modeling". Referencing Sections 3-1 and 4-1 and Appendices E, F, and G of the
Revised ICTM Report, THE INTERROGATORY REQUESTED that EFR:
1. Provide the foliowdng:
• 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,
and demonstrate that the values used in modeling appropriately reflect: (a) the
composition and characteristics ofthe 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;
21
TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
Provide additional sensitivity analyses projecting potential performance ofthe 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
accordance with recommendations in NUREG-1620, Section 5.1.3 [NRC 2003a]) of
soil and/or clayey materials within the maximum projected frost-impacted zone for
the 200- 1,000-year recurrence interval; and, 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]) consistenfly for all altemative cover systems
considered (or justify why inconsistent parameter values are appropriate) in assessing
long-term degraded conditions;
Define and justify a range of possible 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, and provide infiltration modeling results
that incorporate such peak/higher precipitation and/or minimum evapotranspiration
conditions; or, altematively, 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 fixture cover system
performance under these projected fiiture climate conditions). Therefore, please
incorporate worst-case meteorological conditions into the sensitivity analyses and the
"bathtub" analysis for the proposed evapotranspiration (ET) cover system;
Extend the timeframe for calculations projecting the "bathtub effect" to a period of up
lu 1,000 >'eais, hicluding adjusting soil piupeitics in the piupuscd ET cover
components to include initial and worst case long-term degraded cover conditions as
stated in Item 1 of this interrogatory, and incorporating potential worst-case
forecasted future climate conditions; and
• 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); and
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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TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
2. Justify the assumption of a tailings porosity of 57% in evaluating infiltration/potential for
"bathtubbing" of leachate on the liner systems; and perform and report results of
sensitivity analyses that assess the dependence of result on variations in the values of
tailings porosity used in analyses; and
3. Clarify/provide the information referenced as being included in Attachment E-1 (not
apparently provided in the report).
2.2 EFR Responses to Rd 1 Interrogatory White Mesa Revised ICTM Report; R313-24-
4; 10CFR40 Appendix A, Criterion 6(1); INT 02/1: Comparison of Cover Designs,
Sensitivity Analvses, ^Bathtub Analysis', and Radon Emanation Modeling
A discussion of EFR's Response (s) to the specific interrogatory items included in this Rd 1
interrogatory is provided below. The majority ofthe interrogatory items included in this
interrogatory relate to the issue of estimation of long-term infiltration rates through the
proposed ET, and ultimately to the long-term performance ofthe closed tailings management
cells and cover with regard to limiting infiltration rates. Because this is a primary concern for
the ICTM Report and site reclamation plan, EFR's response to these items are discussed in the
framework of applicable cover performance objectives, relevant and applicable design criteria,
and the analyses and documentation provided by EFR to demonstrate the projected (long-term)
performance of the proposed ER cover.
Minimize Infiltration/Encourase Runoff
Minimizing infiltration and encouraging/promoting runoff of incident precipitation falling on the
cover system throughout the required closed tailings cells embankment's performance period are
important design criteria for assessing the likelihood that the cover system will achieve required
long-term performance requirements. EFR's Responses to INT 02/1 on Revised ICTM Report -
"Comparison of Cover Designs. Sensitivity Analvses, 'Bathtub Analvsis \ and Radon Emanation
Modeling" are therefore discussed below in the context of desi^ criteria and performance
criteria that are important for evaluating the expected long-term effectiveness of the reclaimed
tailings cell embankment at: (i) restricting infiltration rates into the tailings, and (ii) promoting
lateral runoff ofprecipitation from the cover system, throughout the required performance
period of the reclaimed tailings area of200 to 1,000 years.
Cover Soil Laver Properties Related to Inflltration Reduction
IN ITS RESPONSE to the interrogatory item requesting further justification be providedfor the
assumed cover soil layer properties, EFR indicated that additional site-specific tests were
conducted to evaluate the hydraulic and physical properties of stockpiled materials that will be
used to construct the ET cover; therefore the cover soil layer material/hydraulic properties are
updated from values previously used to support the Revised ICTM Report. The testing of borrow
source materials (samples collected at the Mill Site in April 2012) was performed by the
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TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
Wisconsin Geotechnics Laboratory at the University of Wisconsin- Madison. The laboratory
testing program consisted of two phases:
• Phase I testing consisted of standard material characterization tests, including Atterberg
limits, specific gravity, and full gradation. The test results were reviewed, along with the
existing soils data, to refine the Phase II laboratory testing program.
• Phase II testing consisted of standard Proctor compaction, water retention characteristic
testing, and saturated hydraulic conductivity tests in the vertical direction (Ks). The
moisture retention and hydraulic conductivity tests were compacted to 85% of maximum
dry unit weight and optimum water content from the standard Proctor compaction tests.
Low relative compaction was used to simulate a structured soil representing a longer
term condition, as suggested in Benson et al. (2011).
EFR summarized the results of the laboratory testing program established to evaluate the
hydraulic and physical properties of cover materials (as summarized below). EFR reviewed the
results ofthe Phase I laboratory testing program (standard material characterization tests),
along with the existing soils data, to define the Phase II laboratory testing program (compaction,
water retention, and hydraulic conductivity tests). This information, along with the original
laboratory data summary reports, is included in Attachment B of this Response (Denison
[2012b]). EFR identified three different soil groups, based on evaluation of the index tests, and
used the results of the Phase I program to select individual samples that would bracket the range
in material properties within the three soil groups:
• Group B: These materials are more broadly (B) graded with some to no plasticity, and
represent approximately 48% by volume of the existing stockpiles. On average, these
materials contain approximately 30% gravel. This group is represented by samples W2-B1/2
and W5-B1/2 because they bracket the particle size distribution for the plastic soil samples,
and by sample W8-B1/2 to represent the non-plastic soil samples.
• Group U: These materials are more uniformly (U) graded with some plasticity, and represent
approximately 47% by volume of the existing stockpiles. On average, these materials contain
approximately 2% gravel. This group is conservatively represented by sample W9-B1/2
because it contains the highest amount of gravel for the soil samples within Group U. The
topsoil samples fall within Soil Group U and are represented by sample El-A 1/2 which has a
measured plasticity index (PI) equal to the average of the PI values for all the topsoil
samples and the gradation of the sample represented the average gradation ofthe topsoil
samples; and
• Group F: These materials are fine textured (F), plastic, and represent approximately 5% by
volume of the existing stockpiles. On average, these materials contain approximately 0.5%
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TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
gravel. This group is conservatively represented by sample E3-A1/2 because it contains the
lowest amount of fines for the clay samples.
EFR then categorized the results of the Phase II program to bracket the range in hydraulic
properties. The hydraulic characterization tests identified three hydraulic classification groups
for the cover soils as summarized in Table 02/1/1-1, the results of which were used to
parameterize the cover model:
• High hydraulic conductivity and low storage. This group would be considered as an upper
bound scenario since water flow through the cover should be higher, and storage should be
low, compared to the other soil samples. This group is represented by sample W2-B1/2.
• Intermediate hydraulic conductivity and storage. This group would be considered as a base
case (average) scenario since water flow through the cover should be intermediate compared
to the other soil samples. This group is represented by an average of the soil sample test
results (W2-B1/2, W5-B1/2, W8-A1/2, and W9- Bl/2).
• Low hydraulic conductivity and high storage. This group would be considered as a lower
bound scenario since water flow through the cover should be slower, and storage should be
high, compared to the other soil samples. This group is represented by sample W9-B1/2.
EFR indicated that the topsoil samples are represented by sample El-A 1/2.
EFR used the hydraulic classification groups to parameterize the cover model for the proposed
ET cover. The erosion protection layer was represented by sample El-A 1/2, the water storage
layer was represented by the samples identified above, and the radon barrier layer and grading
layer were represented by the samples identified above after applying a correction factor to
account for a decrease/increase in the satufuted watei content. The tuneUion factor was
calculated from the anticipated change in porosity for the different compaction efforts. In the
model, the values for alpha and n were not changed to maintain a conservative approach for
simulation of the radon barrier layer.
While increasing compaction would lower alpha by reducing the largest pore size, and lower n
by making a more uniform pore size distribution, keeping these parameter values constant will
simulate a soil that releases water more readily than a soil at higher compaction (Tinjum et al,
1997). Additionally, the Ks values for the radon layer were assumed to equal that for the water
storage layer to maintain a conservative approach.
EFR stated that the Ks of the radon barrier layer will be lower near term and perhaps long term,
and assuming a higher Ks is conservative. Parameter values for the grading layer were assumed
to equal those for the water storage layer. EFR concluded that effects on the grading layer,
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TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
which has a lower relative compaction compared to the water storage and radon barrier layers,
are not anticipated to affect the model results since this layer is located below the terminal root
zone and low permeability radon barrier layer. The three scenarios and corresponding input
values are summarized in Table 02/1/1-2 for the proposed ET cover design. The material
layering and thicknesses of the cover design are based on those determined to be in compliance
with radon emanation at the surface as evaluated by the RADON model (Denison 2012b):
• The erosion protection layer will be placed at 85% standard Proctor at optimum water
content and will include 25% gravel as add-in to the topsoil materials;
• The water storage layer will be placed at 85% standard Proctor at optimum water content
and will include variable gravel contents based on the material distribution for the soils;
• The radon barrier layer will be placed at 95% standard Proctor at optimum water content
and will include variable gravel contents based on the material distribution for the soils; and
• The grading layer will be placed at 80% standard Proctor at optimum water content and will
include variable gravel contents based on the material distribution soils.
EFR indicated that soil cover layers and their respective hydraulic and physical material
properties potentially could be affected by wet/dry, freeze/thaw, and other pedogenic processes
as suggested by Benson et al. (2011). EFR also indicated, however, as noted in Benson et al
(2011), that potential changes to the cover can be minimized by designing the cover system to be
as close as practical to the anticipated equilibrium state under long-term conditions; EFR noted
furthermore, that Benson et al's 2011 study also noted that long-term changes are more prone to
occur for less permeable soils compared to more permeable soils.
EFR cunduded that the hydraulic test results for the soils stockpiled at White Mesa ate withii
the range of parameter values anticipated to occur long-term as noted by Benson et al (2011),
indicating that the hydraulic properties used as input are likely to represent long-term
conditions. EFR noted that, for example, soil that will be used to construct the water storage
layer reported a range of values as follows:
• The hydraulic conductivity values at White Mesa range between 35 and 130 cm/day (cm/d)
while those reported by Benson et al range between 0.86 and 43 cm/d (with a recommended
value equal to 4.3 cm/d).
• The saturated volumetric water contents at White Mesa range between 0.23 and 0.40 while
those reported by Benson et al. range between 0.35 and 0.45 (with a recommended value
equal to 0.40).
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TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
• The alpha values at White Mesa range between 0.0073 and 0.022 cm'' while those reported
by Benson et al range between 0.001 and 0.033 cm'' (with a recommended value equal to
0.02 cm'').
• The n values at White Mesa range between 1.26 and 1.32 while those reported by Benson et
al 2011 range between 1.1 and 1.5 (with a recommended value equal to 1.3).
EFR, based on the above comparison, and the relatively permeable nature of the soils,
concluded that corrections to account for potential pedogenic processes are not warranted at
this time because the physical and hydraulic properties at the emplaced conditions are such that
post-construction changes should be minimal Furthermore, the soil properties for the water
storage layer are similar to data collected at the Monticello site for long-term conditions that
accounted for pedogenic processes (Ks of 13 cm/d; saturated volumetric water content of 0 41;
alpha of0.0021 cm-1; andn of 1.30) as reported in Benson et al (2008).
Table 02/1-1, Identified Hydraulic Classification Groups and Scenarios for the Soils Used to
Parameterize the Cover Model
Scenario ID Soil Type Storage (cm) Ks (cm/d) Gravel (%)
Upper Bound WB2-B1/2 B 11.2 130
(1.5x10'^ cm/s)
41
Base Case
(Average)
-B&U 18.1 62
(7.2 xlO'"^ cm/s)
15
Lower Bound W9-B1/2-U 21.7 35
(4.1 X 10"^ cm/s)
0
Note: Storage or available water content was computed at the difference between the volumetric water
content at field capacity and wilting point tensions multiplied by the thickness for the erosion protection
and water storage layers. Storage accounts for reduced capacity from the amount of gravel calculated
using the approach suggested by Bouwer and Rice (1984). The amount of gravel for the upper bound
scenario was taken as measured. The amount of gravel for the base case scenario was based on a
weighted average for the material volumes and percentage of gravel for the B, U, and F soil types. The
amount of gravel for the lower bound scenario was assumed to equal zero based on previous
geotechnical results.
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TECHNICAL MEMORANDUM
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Table 02/1-2, Parameter Values Used to Parameterize the Cover Model for the Three Hydraulic
Scenarios Modeled Using the van Genuchthen-Mualem Functions
Cover
Layer
Purpose Thickness
(cm)
Or
(-)
Gs (•) a
(1/cm)
n
(-)
Ks
(cm/d)
I
(-)
Pb
(g/cm')
9per Bound Soils
1 Erosion
Control
75 0.02 0.32 0.0080 1.35 11 0.5 1.70
2 Water
Storage
107 0 0.23 0.022 1.32 130 0.5 1.85
3 Radon
Barrier
110 0 0.16 0.022 1.32 130 0.5 2.07
4 Grading 76 0 0.26 0.022 1.32 130 0.5 1.74
Base Case Soils (Average)
1 Erosion
Control
15 0.02 0.32 0.0080 1.35 11 0.5 1.70
2 Water
Storage
107 0 0.34 0.011 1.30 62 0.5 1.67
3 Radon
Barrier
110 0 0.27 0.011 1.30 62 0.5 1.87
4 Grading 76 0 0.37 0.011 1.30 62 0.5 1.58
Lower Bound Soils
1 Erosion 15 0.02 0.32 0.0080 1.35 11 0.5 1.70
2 Water
Storage
107 0 0.40 0.0073 1.26 35 0.5 1.56
3 Radon
Barrier
110 0 0.33 0.0073 1.26 35 0.5 1.75
4 Grading 76 0 0.43 0.0073 1.26 35 0.5 1.47
Note: The saturated and residual volumetric water contents for the erosion protection and water storage
layers were corrected for the amount of gravel calculated using the approach suggested by Bouwer and
Rice (1984). The base case scenario was obtained by averaging the B and U soil samples: the
saturated/residual volumetric water contents, n, and pb were arithmetically averaged while a and Ks
were geometrically averaged.
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TECHNICAL MEMORANDUM
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Cover Design Sensitivity Analyses Using Revised Cover Soils Properties
IN TTS RESPONSE, EFR indicated the following:
• "The purpose of Appendix E (cover design sensitivity analysis) in the Revised ICTM
Report was to compare the potential performance of different conceptual cover designs
based on model results assuming as-built material properties; and
• MWH does not believe that inclusion of additional sensitivity analyses is warranted for
the four different conceptual cover designs assuming weathered material properties.
Revised ET Cover Sensitivity Analyses
For the proposed ET cover, the analysis presented above suggests that the soils will be
constructed in a manner that is close to the anticipated equilibrium state under long-term
conditions, and that correcting the material properties to account for pedogenic processes is not
warranted at this time. Rather, additional sensitivity analysis assuming various scenarios for the
soil material properties, and vegetative conditions, has been completed for the proposed ET
cover design. These updated model results are discussed below.
Soil Properties
The model-simulated water flux rate through the tailings cell cover during the anticipated 57-
year climate record (between 1932 and 1988) is shown on Figure 02/1/1-2 for the upper bound
and lower bound hydraulic scenarios. These climatic conditions are the same as those applied in
the Revised ICTM Report. The base case scenario is also plotted and compared to the departure
from the average amount of winter precipitation (November through February).
The average water flux rates predicted for the above scenarios are summarized below:
• The upper bound hydraulic scenario had an average water flux rate equal to approximately
6.0 mm/yr or about 1.9% of the average annual amount of precipitation;
• The base case scenario had an average water flux rate equal to approximately 2.8 mm/yr or
about 0.9% of the average annual amount of precipitation; and
• The lower bound hydraulic scenario had an average water flux rate equal to approximately
2.4 mm/yr or about 0.8% of the average annual amount of precipitation.
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TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
These rates are approximately 5 to 12 times higher than the value reported in the Revised ICTM
Report (Denison 2010) The higher values are attributed to the laboratory Ks results which were
on the order of 80 cm/d (9x10' cm/s) while the value used in the previous model was on the
order of 8 cm/d (9x10'^ cm/s) for the water storage layer. In actuality, the water flux rates could
be slightly lower than modeled depending on the Ks value assumed for the radon barrier layer.
In the model, the Kg value for the water storage and radon barrier layers were assumed to be
equal Because the radon barrier layer will be compacted to 95% standard Proctor compaction
the material would be expected to have a lower permeability than used in the model. EFR
indicated that additional data may be collected to evaluate the Ks values at 95% compaction.
EFR indicated that, overall, these simulated values are slightly higher than measurements
collected at the Monticello site for the last 12 years (average percolation rate of 0.63 mm/yr with
a minimum and maximum rate of 0 and 3.8 mm/yr).
Vegetation Properties
EFR performed sensitivity analyses to predict water flux rated through the tailings cell cover
during the anticipated 57-year climate record (between 1932 and 1988) for the upper bound and
lower bound vegetation scenarios assuming 30% and 40% cover (base case hydraulic scenario).
Results of those simulations are provided on Figure 02/1/1-3 of the Response.
The upper bound scenario assumed a reduced root biomass distribution as presented in Table
01/1/3-1. The lower bound vegetation scenario assumes a lower wilting point pressure head
equal to -30,000 cm, and a minimum surface pressure head equal to -150,000 cm. The water
stress response function for grass was selectedfrom the default database in HYDRUS. The
database does not distinguish between different species of grass, and transpiration is assumed to
cease at soil water pressures below the assumed wilting point of -8,000 cm. However, plants in
semiarid environments, many of which were selectedfor the ET cover, commonly maintain
transpiration at significantly lower (more negative) soil water pressures. For example, crested
wheat^ass can survive in soil water conditions where the soil water pressure ranges between -
20,000 and-40,000 cm (Chabot andMooney, 1985; Brown, 1995). Unless otherwise noted, all
simulations assume the default wilting point of -8,000 cm and a minimum surface pressure head
of- 15,000 cm.
Results ofthe sensitivity analysis simulations indicate the following average water flux rate
based on an assumed 40% vegetated cover:
• The upper bound vegetation scenario had an average water flux rate equal to approximately
4.9 mm/yr.
• The lower bound vegetation scenario had an average water flux rate equal to approximately
0.7 mm/yr.
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TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
The average model-predicted water flux rate predicted assuming 30% vegetation cover was as
follows:
• The upper bound vegetation scenario had an average water flux rate equal to approximately
5.1 mm/yr; and
• The lower bound vegetation scenario had an average water flux rate equal to approximately
0.9 mm/yr."
Possible Future Climate Conditions and Impacts on Inflltration Rates through Cover
IN ITS RESPONSE to the interrogatory item requesting further justification be provided for the
assumed range of future climate conditions at the White Mesa site, EFR reviewed selected
published studies related to past and predicted future climate simulations to further develop an
estimate of the range ofpotential future climate conditions that might exist at the White Mesa
site during the next 200 to 1,000 years.
EFR's evaluation offuture climate changes/conditions focused on discussion of results of certain
recent climate and hydrological model simulations (e.g, Seager et al 2007; Seager and Vecchi
2010; Cayan et al 2010) that suggest that continued warming and drought conditions may be
expected to occur in the southwestern U.S. through the latter half of the current (21^^) century
EFR also provided additional discussion regarding expected plant response to future climatic
conditions, including big sagebrush, one species that EFR indicates could invade a portion of the
ET cover during the early portion of its post-closure design life.
EFR included a summary of previous long-range future climate forecasts done for the Four
Corners region (e.g., Waugh and Peterson 1995) but concluded that due to the magnitude of the
uncertainties involved (including the large range of temperature and precipitation ranges
developed) that "it becomes extremely difficult and highly unreliable to make predictions on
future changes in vegetation for the White Mesa Mill site or any waste facility ", and that "the
analog approach in combination with climate models may be the most effective path forward, but
further work is needed before these tools can be applied with a reasonable degree of
confidence". EFR concluded that "based on the preceding review [the discussions provided in
Attachment G], the most consistent view of climate change in the southwest U.S. is for warmer
conditions and greater evaporative loss of water"... and the "it also appears likely that winter
precipitation may decrease and summer precipitation may increase, with an accompanied shift
in the water balance from winter storage to pulse dominated"...
Based on the paleoclimate and paleorecharge studies summarized above, and EFR's assessment
offorecasted conditions that may occur in the future as a result of climate change EFR
concluded that "the assumption of applying the maximum annual or winter precipitation value
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TECHNICAL MEMORANDUM
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for a ten year period does not appear to be justified. Rather, repetition at a lower frequency for
one ofthe wetter (and drier winter seasons is a more practical approach to determine if the ET
cover will have sufficient storage capacity to minimize percolation during a period of climatic
stress. Based on this conclusion, EFR performed the following additional infiltration model
sensitivity analyses:
• To simulate an increased precipitation scenario we used the Blanding 1993 winter
precipitation (296 mm) and PET data repeatedfor a five year period as part ofthe 57-year
simulation incorporated in the Revised ICTM Report The January and February
measurements recorded during the 1993 winter season correspond to the maximum and
second highest measured values recorded during the period of record, respectively. The
winter precipitation during 1993 corresponds to the 4th wettest year and the 97th percentile,
and is anticipated to be similar to a Holocene wet climate scenario (up to about 13,000 years
ago) based on information presented by Waugh and Peterson (1995); and
• To simulate a decreased precipitation scenario we propose using the Blanding 1977 winter
precipitation (39 mm) and PET data repeated for a five year period as part of the 57-year
simulation incorporated in the Revised ICTM Report The winter precipitation during 1977
corresponds to the 7th driest year and the sixth percentile, and is anticipated to be similar to
a short-term drought
EFR stated that this approach is functionally similar to the approach incorporated to design the
Monticello repository, and therefore is considered appropriate for this semiarid site in the same
region.
Results of these additional sensitivity analysis simulations indicated model-simulated water flidx
rntP thrmiali fhe takings Cell cover for upppr bound an^ Inwpr hpj^nd cijrrt^tp .Kr.p.nnrins is
shown on Figure 02/1/1-4 (base case hydraulic scenario, 40% cover, anticipated root biomass,
and default wilting point). The average water flux rate is summarized below:
• An upper bound climate scenario having an average water flux rate equal to approximately
6.4 mm/yr; and
• A lower bound climate scenario having an average water flux rate equal to approximately
2.6 mm/yr.
Revised Bathtubbing Analysis
IN ITS RESPONSE to the interrogatory item relating to the bathtubbing analysis, EFR provided
a revised bathtubbing analysis using a revised base case estimated tailings porosity of 47%. EFR
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TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
also conducted sensitivity analyses calculations using a range of estimated porosity values (44%
to 51%. In its revised analyses, EFR assumed a saturated tailings thickness in Cells 2 and 3, and
in Cells 4A and 4B, of 1.1 m (3.6 ft), and 0.3 m (1 ft), respectively. An average water flux rate
through the cover of 2.8 mm/yr (0.11 inches/yr) , based on the revised inflltration modeling
described above, and 50% saturation (volumetric water content of 22% to 26%) of the cover soil
materials were used in the revised bathtubbing analysis. Results ofthe revised analyses
suggested that equilibrium levels of leachate in the tailings cells would not result in the
occurrence of bathtubbing in any of the tailings cells within a 1,000-year periodfollowing
tailings cell closure. The response provide by EFR also included (in Attachment A to its May 31,
2012 Response to the Round 1 Interrogatories on the Revised ICTM Report) the information
inadvertently omitted from Attachment E-1 in the revised ICTM Report.
2.3 Division's Assessment of EFR Responses to Rd 1 Interrogatory White Mesa Revised
ICTM Report; R313-24-4; 10CFR40 Appendix A, Criterion 6(1); INT 02/1
2.3.1 Properties of Soils Proposed for Use in Cover Construction/ Inflltration Sensitivity
Analyses
The hydraulic conductivity results from the August 2012 on-site soils testing provide useful
information. However, EFR should provide additional information to allow the Division to
further assess whether the parameterization of the hydraulic conductivity soil properties
for use in the revised inflltration simulations is representative of long-term cover hydraulic
conductivities that may occur in the cover during the postclosure period. Additional
information provided should include the following:
• For the Phase II soil sample testing to determine hydraulic conductivity, provide
information on the diameter of, and the thickness of the prepared (recompacted)
soils samples tested in the laboratory testing device (flexible-wall permeameter) that
was used, and the speciflc ASTM D5084 Method testing procedure used in the
testing; and
Provide additional explanation and rationale to allow the Division to further assess
whether the tested samples and tested sample sizes, and the soil samples themselves,
may be considered as providing representative samples for estimating expected in-
place long-term constructed conditions in the cover system proposed to be
constructed using such soils. Consider the fact that the samples received by the
testing laboratory were disturbed soil samples in 20-L buckets (Attachment B
supporting EFR's Response to the Round 1 Interrogatory 02/1 on the Revised
Reclamation Plan/Benson and Wang 2012), Le., disturbed samples were used.
Disturbed soil samples were used in the laboratory testing, rather than, for example,
large (> 0.30 m- (12-inch-) diameter, > 15 cm (6 inch-) thick undisturbed block
samples of soil from an on-site compacted Test Pad constructed to simulate
conditions in the cover system from which a large block undisturbed sample of
compacted soil, if such a Test Pad were available, could have been collected for use
in the testing.
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TECHNICAL MEMORANDUM
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In supplying additional supporting information, EFR should consider relevant guidance
such as that contained in Benson et al. 1994 and Benson et al. 1997, which recommend that
small- diameter soil samples not be used in laboratory soil sample testing for hydraulic
conductivity, and that for obtaining the most representative test results, laboratory testing
should be conducted on undisturbed block soil samples of compacted soils (e.g., carved
from oversized block samples excavated from an on-site compacted soil cover Test Pad )
having a minimum diameter of 0.30 m (12 inches) and a minimum soil sample thickness of
15 cm ( 6 inches), and that ASTM D5084 [Standard Test Method for Measurement of
Hydraulic Conductivity of Saturated Porous Materials Using a Flexible Wall
Permeameter], Method C procedures should be followed. These recommendations are
intended to capture macropore characteristics of compacted clayey soil layers. Pending
receipt and conflrmation of testing results of samples performed using such procedures, the
Division will consider that the April 2012 sample hydraulic conductivity testing results as
preliminary and provisional and subject to unquantifled uncertainty.
Based on review of EFR's Responses to the speciflc issues addressed in the flrst of this
interrogatory, the Division has determined the following:
• Additional information regarding details of the laboratory soil sample testing
performed on the April 2012 soil samples needs to be provided for review to permit
the Division to be able to independently evaluate whether the soil conditions
assumed in the revised ET cover sensitivity analyses may or may not conservatively
represent (bound) degraded soil cover conditions in the proposed ET cover [see the
discussion provided in boldface text under * Cover Soil Layer Properties' above];
• EFR's flnding that "...overall, these simulated values are slightly higher than
measurements collected at the Monticello site for the last 12 years (average
percolation rate of 0.63 mm/yr with a minimum and maximum rate of 0 and 3.8
mm/yr )" is not useful for corroborating the "reasonableness" of the revised
predicted inflltration results. For instance, EFR has made no speciflc comparison
between the in-situ soil conditions present at the subsurface inflltration test sites
installed at the Monticello site and the soil conditions expected to occur within the
degraded ET cover soils at the White Mesa site; and
• In the revised ET cover inflltration analyses, EFR has not conducted and/or has not
provided model output or details regarding an inflltration sensitivity case involving
a scenario where water ponds on the proposed ET cover as a result of potential
flattening of the cover surface due to future differential settlement within one or
more areas of the tailings management cells [see the discussion provided under
^Revised Bathtubbing Analysis', in Section 3.3 under "Moisture Storage Capacity
of Cover", and in Section 3.4, Other Cover Design-Related Issues, under "Cover
Long-Term Erosion Protection Design Basis/Justiflcation and Differential
Settlement Issues Related to Inflltration Modeling Assumptions" below].
EFR has conducted additional cover sensitivity analyses to assess effects of different
assumed percentages of vegetation on the cover on predicted inflltration rates through the
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TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
cover. However, EFR has not provided or supported sufflcient details regarding the -
charaicteristics of the cover vegetation assumed in the revised inflltration sensitivity
analyses. For example, the Division has concerns regarding the estimated root biomass
(root density) values listed in Table 01/1/3-1 in EFR's September 10,2012 Response to Rd
Interrogatory 01/1 Item No.3 (see Section 1.3 above). Additionally, the ICTM report (or
the Reclamation Plan) needs to provide: (1) deflnition of clear, concise, and measurable
revegetation acceptance goals/criteria for the vegetation establishment on the tailings cell
cover system, (2) a description of how EFR will conduct periodic post-closure monitoring
and reporting to the Division of the vegetation community health, viability, success, and
sustainability, (3) a description of proposed action plans, schedules and deadlines for
remedial actions i£^when needed to effectuate plant community success, and (4) similar
follow-up monitoring of the plant community/cover system to ensure successful
performance before release of the facility's surety bond and/or transfer of title to DOE.
EFR should describe speciflc, quantitative goals for sustained shrub establishment
(including rooting depths and minimum acceptable shrub cover percentages) that consider
the need for deeper rooted plants to remove water that may accumulate lower in the cover
proflle in response to an exceptionally wet year or successive wet years. If that water is not
removed, then it would be available for subsequent downward movement into the waste. At
the same time, however, protection against biointrusion by roots of the compacted lower
portion of the cover or the waste is required (see additional discussion below under
"Potential Plant Root Penetration Depths"). The Division has concern that attempting to
balance these competing objectives effectively in a cover system that has no capillary
barrier would be very difflcult or problematic. A capillary barrier, or a thorough
justiflcation for not incorporating one, is required by the Division. In developing the
descriptions, plans, and goals for the vegetation establishment on the tailings cell cover,
EFR should consider and address lessons learned from the post-closure monitoring and
maintenance activities and corrective revegetation measures required at the Monticello,
Utah tailings repository and other similar facilities in this regard (e.g., Waugh 2008;
Sheader and Kastens undated, circa 2007; U.S. DOE 2007). EFR should assess the
potential applicability and benefits uf using vegetation health monituiing tools/metrics such
as the Cover Vegetation Index recently implemented at the Monticello Repository (U.S.
DOE 2009).
Corrective measures that may be needed to address/correct issues related to establishment
of undesirable species, e.g., colonization by certain undesired grass/weedy species that may
have more limited water stress tolerance than initially seeded grass species (e.g., Smesrud
et al. 2012), seed or sprout predation following seeding/reseeding efforts, possible low
success rates resulting from for shrub establishment efforts, etc., should be described.
Estimated costs for conducting these post-closure activities and corrective actions, and for
reporting, once approved by the Division, will need to be incorporated in the financial
surety estimate.
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TECHNICAL MEMORANDUM
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EFR also has not considered (as part of a possible upper bounding [reasonably worst-case]
set of conditions), a scenario that includes no shrub vegetation on the cover (or
alternatively, if adequately justified based on data available for ET cover revegetation
activities conducted at other similar sites, an assumed grass vegetation cover percentage
value lower than the 30% lower bound value currently assumed). Such a scenario would
be consistent with cover infiltration scenarios that have been performed in infiltration
sensitivity analyses completed for other, similar facilities (e.g., for a proposed uranium mill
tailings facility in Colorado [Kleinfelder 2009]). The Division also views this type of
conservative scenario as appropriate and consistent with information provided in Sections
4.3.1 and 4.3.3 of U.S. DOE 1989 which indicate that "desert climates usually do not
provide enough moisture to support plant reproduction except once every few years", and
"...At very arid sites, vegetation on the cover may be sparse or absent (in the case of a
sustained drought)".
Additionally, the soils proposed by EFR for use in constructing the ET cover are extremely
low in natural organic matter (OM) content, e.g., compared to soils used for constructing
the Monticello Tailings Repository cover system e.g., zero to about 0.4 % according to
Table D-5 in Appendix D of the Revised ICTM Report, compared to a recommended
minimum OM content of from approximately 1.5 to 3.0%). These factors indicate that,
given the natural climate conditions at the site (which could include possible prolonged
(e.g., decadal to multi-decadal) future drought periods likely to create conditions
unfavorable for sustaining plant growth in the cover), and without substantial and
extensive OM enhancements incorporated into the soils prior to cover construction and
possible periodic active post-closure intervention/maintenance measures such as reseeding,
possible irrigation of the cover, etc..., the on-site soils tested to date appear to be
unfavorable for use in constructing the ET cover. Use of such soils could result in a cover
that is detrimental for vegetation growth and sustainability, especially during possible
future drought periods.
The Division requests that EFR provide the additional information requested in the
discussion under 'Cover Soil Layer Properties' above and conduct the additional
infiltration sensitivity analyses discussed in Section 3.3 under 'Revised Bathtubbing
Analysis', under "Moisture Storage Capacity of Cover", and in Section 3.4, Other Cover
Design-Related Issues, under "Cover Long-Term Erosion Protection Design
Basis/Justification and Differential Settlement Issues Related to Infiltration Modeling
Assumptions" below. Based on the results of developing and providing this additional
information and completing these additional sensitivity analyses, EFR should revise their
conclusions and interpretations and proposed technical approach and/or revise the
currently proposed cover design accordingly to reflect the new information/modeling
results.
Potential Plant Root Penetration Depths
Aspects of EFR's response to this interrogatory related to cover inflltration sensitivity
analyses do not sufflciently address the Division's concerns with respect to the potential
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TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
impacts on the cover from future plant root penetration. Assumptions made by EFR
regarding the potential depth of bioinvasion by plants do not appear to be supported and
do not appear to be accurate.
Jackson et al. (1996) discussed plant root depths in grasslands, deserts and other biomes.
They reported^on studies showing that plant roots can penetrate earthen materials very
deeply, even in compact clay, hard pan or rock, and emphasized that many plants send tap
roots down to great depths if needed to reach the groundwater table. They reported such
depths to be up to 7 m for trees, 5 m for shrubs, 2.5 m for herbs, and 2 m for crops.
Goodwin (1956), according to Tabler (1964), indicated that Big Sagebrush roots apparently
can penetrate indurate layers by slow vertical extension.
Schenk and Jackson (2002) indicated that the 90% range for root-system depth for forbs
and semi-shrubs in areas of low water availability extends to 3.7 meters, with some
signiflcant percentage of other forbs and semi-shrubs penetrating to deeper depths. They
also indicated that the 90% range for root-system depth for shrubs in areas of low water
availability extends to 7.2 meters, with some signiflcant percentage of shrubs penetrating
deeper, with many tree roots tending to grow considerably deeper into soils, with the 90%
range extending down to nearly 17 meters, with a maximum depth of about 58 m. these
documented root-system depths far exceed the currently modeled one-meter root depth.
Schenk and Jackson (2002) indicate that ""...root channels and macro-pores are likely to
act as conduits for water recharge deeper than predicted by simple inflltration models."
Hakonson (2002) suggested that most plants, including common plants as well as
phreatophytes, are capable of sending down roots much more deeply than is generally
anticipated if it is necessary for plants to do so to reach and acquire water. With respect to
2-m thick cover system in New Mexico, he indicated that"most 'shallow rooted' plant
species have the capability to send roots much deeper than the couple of meters of cover
proposed." ——=——=—=—=——=—__=___=_=_=
In an extreme case in fractured terrain. Phoenix (1955) reported that in the interior of
Calamity Mesa, Colorado, miners encountered roots in fractures at depths of about 50 feet.
In contrast to the 1.8 meters assumed in the response, others have reported greater
maximum rooting depths for big sagebrush. Cook and Lewis (1963) indicated that roots of
big sagebrush were found in their study down to depths of 183 cm (6 feet). Sturges (1977)
reported root depths of big sagebrush down to 213 cm. Campbell and Harris (1977) stated
that roots of big sagebrush species have been found to extend to depths greater than 3
meters. Reynolds and Fraley (1989) reporedt big sagebrush root depths in their study down
to 2.25 meters.
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TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
Others have reported even deeper rooting depths for big sagebrush. For example. Cook
and Lewis (1963) reference work by Weaver and Clements (1938) who indicated Big
Sagebrush roots extending to depths of 5 to 11 feet.
Figure 2 of Plate XLIV of Kearney et al. (1914) is said to be a copy of a photograph of Big
Sagebrush at the edge of a stream near Nephi, Utah, where some of the stream banks had,
at the time the photo was taken, recently caved in. The photo shows a Big Sagebrush
taproot extending downward a great distance along the remaining cut bank edge. The
flgure caption states the distance is about 11 feet, while the text describes the distance as
over 15 feet. Both depths are signiflcantly large.
Tabler (1964) references work of Shantz and Zon (1924) who reported Big Sagebrush roots
extending to depths of 4 to 18 feet. Foxx and Tierney (1984; 1985) claimed documentation
in their database of reports of Big Sagebrush putting down roots to 914 centimeters (30
feet).
Please further address issues associated with plant bioinvasion of the cover system,
including additional inflltration sensitivity analysis, to account for the potential for deeper-
rooted plant penetration based on this and possibly other additional published information.
Note that Big Sagebrush has been reported to send roots down deeper than 3 meters (9.84
feet), which, according to the Revised ICTM Report, is deeper than the base of the White
Mesa cover system soil package, as currently planned in the Revised ICTM report, and as
described for some areas of the cover and depicted on Sheet TRC-7 from the Revised
Reclamation Plan (Denison Mines 2011).
2.3.2 Range of Possible Future Climate Conditions at White Mesa Site
Based on the review of the Response and the information provided in Attachment G, and
selected published information, the Division has concern that EFR has not adequately
addressed uncertainties associated with future climate conditions that may occur at the
White Mesa site during the closed tailings embankment's required service nie (^200 lo i,000
years). The Division has concern , that EFR has consequently not adequately addressed the
types and ranges of plant responses that might occur for vegetation that would be
established on the ET cover and in the surrounding terrain as a result of the potential
changes in climate conditions during that required service period. Rather, EFR has
primarily focused on the results of selected climate models/ hydrological model simulations
which have several associated uncertainties and that are limited to timeframes of on the
order of about 100 years, and has attempted to extrapolate flndings from those selected
climate model simulations to apply to, and to be representative of, conditions over a much
longer time period than for which those simulation results were intended to apply. In so
extrapolating those flndings, EFR has not provided supporting technical justiflcation,
described what assumptions are involved, or quantifled what uncertainties are involved in
attempts to project those flndings/assumed conditions over that much more extended time
period.
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TECHNICAL MEMORANDUM
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As part of the review of this Response, the Division conducted a preliminary literature
review of additional published information on climate models, and in particular, of some of
the uncertainties associated with the use of such climate models. A summary of some of the
uncertainties associated with such model, based on this review, is provided in the inset text
below.
Discussion of Some Uncertainties Associated with Current Climate Models
Climate model practitioners and investigators acknowledge that there are several
uncertainties associated with current climate models of the types that were cited in EFR's
response and described in further detail in Attachment G of the Response. For example,
MacDonald (2010) indicated that Cayan et al. 2010 considered the warming that has
occurred during the Early 21^*- Century Drought as part ofthe basis for their conclusions,
but that although the warming that has occurred during that period is consistent with the
warming that occurred during other periods of regional aridity in portions of the
southwestern U.S. in the 20*" century (e.g., 1900-9014; 1924-1936; 1953-1964, and 1988-
1991), the amount of warming and the magnitude and prolonged nature of the high
temperatures of the Early 21''*-Century Drought have no analog in the 20*'' century.
Woodhouse et aL 2010 used paleoclimatic records to show that the current warming in the
Southwest may exceed any other warming episode experienced over the past 1,200 years.
Seager and Vecchi (2010) suggest that the great North American droughts of the past 200
years were caused by very small sea surface temperature (SST) anomalies in the eastern
Paciflc Ocean. They indicate that there has been a general cooling trend in the eastern
Paciflc following 1979 and that such cooling typically is associated with drought in the
North American Southwest (NASW). MacDonald (2010) indicates that the drivers of such
SST anomalies remain poorly understood, as does the potential impact of increasing
greenhouse gasses on Paciflc SSTs. Seager and Vecchi (2010) conclude that the general
drying in recent decades and the 21st-century Drought could be a result of natural decadal
variability in Paciflc SSTs.
In millennial-scale climate model simulations, coats et al. (iOli) tound mat ihe climate
forecast model they used, although capable of simulating megadroughts through a
persistent anomalous SST forcing in the tropical Paciflc (e.g. the late 6th-century drought
in the control run and the late 13th-century drought in the forced run), indicated that other
mechanisms in the model could produce similarly extreme moisture anomalies in the
NASW. Coats et al. (2012) noted a number of other uncertainties associated with the
climate models being currently in use such as: (i) In the observational record, persistent
droughts in the NASW have been tied to cool tropical Paciflc SSTs but it is not known if
this relation holds for the entire last millennium; (ii) There is observational evidence that
warm tropical Atlantic SSTs can create a tendency towards dry conditions in the NASW
(Seager et aL 2008; Kushnir et aL 2010; Nigam et al. 2011); and (iii) Longer records of
proxy estimated tropical Paciflc SST are needed to assess the state of El Nino Southern
Oscillation (ENSO) during megadroughts and to determine how coherent previous NASW
drought and ENSO variability may have been prior to the observational record.
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TECHNICAL MEMORANDUM
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As noted in Coats et. aL 2012, Cook et al. (2009) also indicated that although IPCC [AR4]
climate models robustly predict a shift towards dry conditions in NASW, there is no
agreement on the future state of the tropical Paciflc, despite the strong connection between
ENSO and NASW hydroclimate. Hunt (2011) also analyzed global multi-year drought and
pluvial occurrences in a 10,000- year control run ofthe CSIRO AOGCM and found that
persistent hydroclimate features can result from internal climatic variability, with
stochastic atmospheric variability playing an important role.
Coats et al. 2012 indicated that model intercomparison employing multiple coupled
Atmosphere Ocean General Circulation Models (AOGCMs) is needed to determine if
stochastic atmospheric variability similarly influences NASW drought occurrences in the
most recent generation of AOGCMs.
In summary, there are numerous uncertainties and complexities associated with the use of
all regional climate models with regard to their ability to reliably forecast longer-term
future climate conditions in the NASW and at the White Mesa Site. The above discussion
appears to corroborate an earlier assessment of the uncertainties associated with future
climate modeling as developed and discussed in U.S. NRC 2003b. For this reason, attempts
to extend the results from climate model predictions forecasting climate conditions through
the end of the 21"* century to timeframes of 200 to 1,000 years will likely result in further
compounding of these uncertainties and is likely to result in highly unreliable predictions.
The above discussion is also generally consistent with previous assessments of the
uncertainties associated with future climate modeling completed for the proposed Yucca
Mountain Repository as described in NRC 1997 and by the Center for Nuclear Waste
Regulatory Analysis (CNRWA) 2005. Those assessments provide some useful guidance and
insights with respect to the forecasting potential future climate change at Yucca Mountain
and for other sites. These assessments are summarized in the following paragraphs.
NRC staff, when evaluating methods for estimating future climates at Yucca Mountain in
an Issue Resolution Status Report in 1997 (NRC 1997), concluded that careful
consideration of indicators of past climatic conditions provides adequate information to
bound the likely range of future climate conditions. The NRC staff also concluded that
although anthropogenic influences on climate (Le., emission of greenhouse gases such as
carbon dioxide and methane) could overwhelm natural climate cycles inferred from the
past 1 to 2 million years, the anthropogenic influences on climate are likely to diminish over
the next few thousand years, allowing natural cycles to be reestablished. This conclusion
was found to be consistent with the results of an expert elicitation study on future climate
(Dewispelare, et al. 1993) in which three ofthe five participating experts believed that the
principal effects of greenhouse gas emissions would dissipate in 3,000 to 5,000 years. The
other two experts believed that the effects would last much longer.
The 1997 NRC review also commented on the role of mathematical climate models in
estimating future climate. Based on the state of the art at the time, the NRC staff believed
that "...attempts to use GCMs [global circulation models] to predict climate changes over
tens of thousands of years would almost certainly remain controversial, leading to debate
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TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
over the competence of one model and data set vs. another" (NRC 1997, p. 13). The help
resolve this concern about mathematical climate models, NRC provided (1997) the
following acceptance criterion:
• The staff will not require climate modeling to estimate the range of future climates.
If DOE uses numerical climate models, determine whether such models were
calibrated with paleoclimate data before they were used for projection of future
climate, and that their use suitably simulates the historical record (NRC, 1997, p. 6).
Subsequent work by the NRC (NRC 2003b) and a 2005 independent review report
(CNRWA 2005) reexamining the NRC 1997 evaluation of methods for estimating future
climate change (at Yucca Mountain) found that, in terms of the characteristics of future
climates (i.e., mean annual precipitation and temperature, seasonal weather patterns, and
storm intensities), the characteristics inferred from paleoclimate reconstructions and
present day analog records may represent the range of climate conditions that will occur in
the future, even if the timing of these climates cannot be reliably estimated. The greatest
uncertainty in future climate conditions relates to anthropogenic effects that may result in
climates in southern Nevada that do not have analogs with present or Pleistocene climates,
such as prolonged El Nino conditions. The nature, likelihood, and duration of such
nonrepresentative climate conditions cannot be reliably assessed based on current
research. Over longer time periods, the range of conditions inferred from the Pleistocene
paleoclimate record reasonably bounds future climate during the period of geologic
stability.
A primarily concern that was identified with respect to use of mathematical climate models
was that such models could predict a prolonged period of semi-arid conditions at Yucca
Mountain (at least over the next 10,000 years) that would not lead to a reasonably
conservative estimate of net infiltration. The acceptance criterion that was established in
the Yucca Mountain Review Plan (NRC 2003b) to address this concern is (CNRWA 2005):
• "Verify that paleoclimate information is evaluated [over the past 500,000 years for
the Yucca Mountain Repository case] as tho basis for projections of future climate
change." For example, confirm that numerical climate models, if used for projection of
future climate, are calibrated based on such paleoclimate data (NRC 2003b, p, 2,2-58)
[Italics added],"
The preferred approach that was selected by the NRC for characterizing future climate
conditions in assessing the performance of the potential repository was to rely on
paleoclimate data to estimate the likely range of future climate conditions.
In addition to the above considerations, the EFR Response and the discussion in
Attachment G do not specifically adequately address the known, long-term recurrent nature
of pluvial (anomalously wet periods) climatic events. Persistent, multi-decadal drought and
multi-decadal pluvial events have been a recurrent feature of North American
hydroclimate since at least the time of the Medieval Climate Anomaly (e.g., see Cook et al.
2010; Schwinning et al. 2008). For example, the early twentieth century pluvial period
(1905-1917), briefly described in EFR's Response (p. 12 of 70) in general terms as an early
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TECHNICAL MEMORANDUM
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20*** century wetter period, was likely one of the largest pluvial events in the last thousand
years (Woodhouse et al. 2005), where the climate in almost the entire western region of the
U.S. was wetter than normal. The major wet anomaly for this pluvial period extended
along an axis from the southwest and into the northern Great Plains (Cook et al. 2010). The
time period for this pluvial event exceeds 10 years.
Peterson (1994) also evaluated paleoclimate and paleocultural information to define a Little
Climate Optimum or Medieval Warm Period (A.D. 900 to A.D. 1300) as having occurred in
the northern Colorado Plateau region of the southwestern U.S. During the height of that
period, the region was characterized by greater winter and greater summer precipitation
than today.
For the above reasons, EFR's choice to simulate an increased precipitation scenario by
repeating the Blanding 1993 winter precipitation of 296 mm and PET data for a five-year
period as part of the 57-year infiltration simulation [using climate data spanning the years
1932-1988]), as discussed above, is not clearly and transparently supported or
demonstrated.
Based on the above considerations, the Division requests that EFR:
• Reevaluate and further define an appropriate reasonably conservative upper
bounding future climate condition using a method that is consistent with that
described in the guidance outlined in NRC 1997 and NRC 2003b. Specifically, please
provide additional information demonstrating, as appropriate, that any numerical
climate models or results derived from any such models, if used as a basis for
projecting future climate conditions at the White Mesa site be clearly calibrated to
paleoclimate data; and
• Provide additional information, as appropriate, to support the contention made in
this Response that "the 1993 winter precipitation of 296 mm and PET data for a
five-year period as part of the 57-year infiltration simulation [using climate data
spanning the years 1932-1988]) is anticipated to be similar to a Holocene wet climate
scenario (up to about 13,000 years ago) based on information presented by Waugh
and Peterson (1995)".
Porosity of Tailings (Item No. 2 of Interrogatory 02/1)
The Division views the base case and range of porosity values used in the revised analyses
to be reasonable and consistent with porosity values assumed in radon emanation analyses
competed for similar facilities in Utah (e.g., NRC 2008) and is similar to the default
porosity value of 0.40 (40%) recommended for tailings for use in radon emanation
modeling in Regulatory Guide 3.64 (NRC 1989). For evaluating potential for bathtubbing,
a lower tailings total porosity value is more conservative than a higher porosity value (e.g.,
porosity estimate of 57% previously assumed).
The tailings dewatering systems in Cells 2 and 3 are known to be much less efficient at
dewatering the tailings in those cells than the tailings dewatering systems in Cells 4A and
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TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
4B are expected to be (based on calculations). The Division interprets the current low
efflciency of the tailings dewatering systems in Cells 2 and 3 as indicating that signiflcantly
longer amounts of time will be required to dewater tailings in Cells 2 and 3 compared to
the time (estimated to be on the order of 5 Vz years) needed to dewater tailings in Cells 4A
and 4B. Greater uncertainty exists regarding flnal thicknesses of the saturated portions of
the tailings in Cells 2 and 3 when flnal cover placement would take place over these cells.
Consistent with the intent of guidance contained in Sections 2.1 and 4.1 of NRC 2003a,
more conservative upper bound saturated thicknesses should be estimated and evaluated in
the bathtubbing analysis, based on extrapolation of current dewatering system rates, more
detailed tailings dewatering analyses (see below) and that reflect the degree of uncertainty
associated with the future dewatering of tailings in Cells 2 and 3.
Additionally, EFR needs to provide additional information and details regarding the
speciflc range of in-situ tailings properties and conditions used in the tailings dewatering
analysis for Cells 2 and 3, including the range and distribution of hydraulic conductivity
values (related to the range of possible distributions of sand vs. slimes tailings) assumed in
the analysis. The analysis provided by EFR does not adequately reflect the variable tailings
conditions that may exist in Cells 2 and 3, the dewatering model for Cells 2 and 3 appears
to be overly simplistic, and the input parameters for the tailings properties used in the
analysis appear to be estimated values and not based on site-speciflc testing of the tailings.
The absence of in situ testing of the tailings properties is not consistent with guidance
contained in Sections 2.1.2 through 2.1.4 of NRC 2003a. The possible maximum saturated
thicknesses of tailings in Cells 2 and 3 prior to cover placement need to be estimated in
more conservative manner (and incorporated accordingly into sensitivity analyses) to
account for uncertainties associated with the continued effectiveness of the dewatering
systems in Cells 2 and 3. A conservative range of possible in-situ residual tailings hydraulic
conductivity conditions/distributions in Cells 2 and 3 needs to be considered in the analysis.
Revised Bathtubbing Analysis
Additionally, fur assessing the putential fui bathtubbing, the Divisiun recommends that the
value of inflltration used in the bathtubbing analysis scenario be the highest average
inflltration rate obtained from the full range of model inflltration sensitivity analysis
scenarios considered. The Division recommends that the same analysis scenario include a
combination of: (i) maximum (upper bound) assumed hydraulic conductivities for the
cover soils; (ii) an assumption of no grass vegetation on the ET cover; (iii) a flattened
topslope inclination (unless the topslope inclinations in the current proposed cover design
are increased to a minimum of 2 to 3 %); and (iv) an assumption that liner conditions in
the tailings cells have the lowest defect sizes and frequencies and least permeable soil/GCL
underliner values (effectively yielding the lowest overall calculated leakage rates) that EFR
determined in its cell liner leachate leakage analyses.
Additional information needs to be provided on effects of expected higher inflltration rates
through the (rock riprap-covered) sideslope areas on bathtubbing under such assumed
reasonably worst-case conditions as described in the previous paragraph. Speciflcally,
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TECHNICAL MEMORANDUM
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£FR needs to provide additional information on inflltration rates through the sideslope
portions of the proposed cover and the potential effects (depending on geometric
relationship of sideslope areas relative to areas covered by the cell liners) of such
inflltration on bathtubbing, under the reasonably worst-case assumed conditions described
in the above paragraph.
Missing Information in Attachment E-1
EFR provided the information was inadvertently omitted from Attachment E-1 of
Appendix E of the Revised ICTM Report. The missing information was submitted as part
of EFR's Response to the Rd 1 Interrogatories on the Revised (Rev 5.) Reclamation Plan
(submitted to the Division on August 31,2012),
3.0 Moisture Storage Capacity of Cover
3.1 Round 1 Interrogatory White Mesa Revised ICTM Report; R313-24-4; 10CFR40
Appendix A, Criterion 6(1); INT 03/1; Moisture Storage Capacity of Cover
Interrogatory White Mesa Rev ICTM: R313-24-4: 10 CFR40 Appendix A. Criterion 6(1): INT
03/1: "Moisture Storage Capacity of Cover": Referencing Appendix F of the Revised ICTM
Report, THE INTERROGATORY REQUESTED that EFR:
• Redefine and further justify the critical meteorological design event (or sequence of
contiguous events) used in the bathtubbing analysis;
• State and justify the basis for the critical event conditions addressing the location ofthe
meteorological weather station for determining the wettest year on record; and the
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
fiom consideration in all infiltration analyoco conducted in the ICTM Rep(
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 ;
• Identify the month(s) of the year that would be expected to comprise the most critical
percolation period; and
• 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
conservative than assuming the most critical meteorological period as occurring during
the winter months.
THE INTERROGATORY REQUESTED, referencing Appendix F ofthe Revised ICTM Report,
that EFR also-
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TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
• Provide additional details regarding the assumed gradient at the soil cover/atmosphere
interface, including the possibility of the gradient exceeding unity due to matric suction
gradients that might be greater than unity;
• 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; and
• 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 stressfiil hydraulic
condition(s)) 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.
3.2 EFR Responses to Rd 1 Interrogatory White Mesa Revised ICTM Report; R313-24-
4; 10CFR40 Appendix A, Criterion 6(1); INT 03/1: Moisture Storage Capacity of
Cover
IN ITS RESPONSE, EFR recommended that Appendix F be eliminated from the next revision of
the ICTM Report and provided additional information intended to address these requests. EFR
indicated that this information would be incorporated (instead) into the next revision of
Appendix G to the ICTM Report.
IN ITS RESPONSE, EFR indicated that a gradient of unity was not assumed for the soil
cover/atmosphere interface, and that the upper surface boundary condition representing the air-
soil interface follows a system-dependent boundary condition. The soil surface boundary
condition within the model may change from prescribed flux to prescribed head type conditions
and vice-versa. EFR also indicated that in the model presented in the 2010 Revised ICTM
Report, a maximum surface ponding depth of five centimeters was assigned. EFR stated that
localized Surface ponding, if it were lo occur, would act lo inctease hydraulic gradients along
the air-soil interface resulting in greater amounts of water that could infiltrate into the cover
until the surface pond reservoir was depleted.
EFR also stated that the infiltration modeling was updated to account for an increased
precipitation scenario; and this scenario was selected to correspond to the most critical time
period for which percolation through the cover could occur during its required performance life.
EFR stated that such an evaluation would be presented in another appendix (e.g., Appendix G)
because it is not applicable to the original intent of Appendix F, and because Appendix F would
be deletedfrom the next revision of the ICTM Report.
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TECHNICAL MEMORANDUM
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3.3 Division's Assessment of EFR Responses to Rd 1 Interrogatory White Mesa Revised
ICTM Report; R313-24-4; 10CFR40 Appendix A, Criterion 6(1); INT 03/1
Based on review of the EFR Response to the items addressed in this Rd 1 interrogatory on
the ICTM Report and the EFR Response to the Round 1 Interrogatories on the Revised
(Rev 5.0) Reclamation Plan to inflltration rates through the proposed ET cover, the
Division flnds the information provided in the Response regarding the gradient
parameterization incorporated into the inflltration modeling to be acceptable. However,
the Division has concern that the inflltration analyses presented in the Revised ICTM
Report and described in the Response to the Round 1 Interrogatories on the Revised ICTM
Report and on the Rev 5.0 Reclamation Plan are not sufflciently conservative to bound the
uncertainty associated with possible future flattening of the cover topslope inclination (see
the discussion under Section 3.4, Other Cover Design-Related Issues, under "Cover Long-
Term Erosion Protection Design Basis/Justiflcation and Differential Settlement Issues
Related to Inflltration Modeling Assumptions" below). Additionally, similar to the
assessment for potential for bathtubbing, the Division recommends that the value of
inflltration used in the inflltration sensitivity analysis scenario for evaluating the cover soil
moisture holding capacity be the highest average inflltration obtained from the full range
of model inflltration scenarios considered, and that the same scenario include the following
additional assumptions: (i) assumed maximum (upper bound) assumed hydraulic
conductivities for the cover soils; (ii) the assumption of no grass vegetation on the ET
cover; (iii) the assumption of a flattened topslope inclination (unless the topslope
inclinations in the current proposed cover design are increased to a minimum of 2 to 3 %).
Additional information needed from EFR in order to resolve these concerns related to the
soil moisture storage capacity of the cover is provided in the table attached to this
Technical Memorandum and in the "Technical Memorandum, Revised (Rev. 5.0)
Reclamation Plan Review".
3.4 Other Cover Design-Related Issues (Related to Rd Interrogatories 02/1 and 03/1)
3.4.1 Cover Long-Term Erosion Protection Design Basis/Justiflcation and Differential
Settlement Issues Related to Inflltration Modeling Assumptions
3.4.1.1 Round 1 Interrogatory White Mesa Revised ICTM Report: R313-24-4: 10CFR40
Appendix A, Criterion 6(1): INT 03/1: Cover Long-Term Erosion Protection Design
Basis/Justification and Differential Settlement Issues Related to Infiltration Modeling
Assumptions
As described above, INTERROGATORY 02/1 on the Revised ICTM Report included an item
(Item No. 1) addressing the erosion protection layer for the proposed ET cover.
INTERROGATORY 08/1 on the Rev 5.0 Reclamation Plan - "Erosion Stability Evaluation"
REQUESTED THAT EFR address long-term erosion and filter layer criteria for the proposed ET
cover layers.
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TECHNICAL MEMORANDUM
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3.4.1.2 EFR Responses to Cover Long-Term Erosion Protection Design Basis/Justification
and Differential Settlement Issues Related to Infiltration Modeling Assumptions
IN ITS RESPONSE to the above interrogatory items, EFR included revised calculations and text
discussing the results of the revised calculations.
3.4.1.3 Division's Assessment of EFR Responses to Cover Long-Term Erosion Protection
Design Basis/Justification and Differential Settlement Issues Related to Infiltration
Modeling Assumptions
Information presented in the EFR Responses to the above interrogatory items and a
discussion of the content of the revised calculations are described in detail in the document
entitled "Technical Memorandum, Revised (Rev. 5.0) Reclamation Plan Review". However,
the erosion protection analyses methodology used by EFR to support the proposed cover
design is based on assumptions that EFR has not yet demonstrated valid assumptions for
the proposed ET cover design for the tailings management cells area. Based on the
Division's review of the information provided by EFR to date, EFR has not adequately
demonstrated to the Division's satisfaction that flattening ofthe proposed ET cover surface
would not occur (due to post-closure differential settlement). Based on this consideration,
the Diyision has concern that the inflltration analyses presented in the Revised ICTM
Report and described in the Response to the Round 1 Interrogatories on the Revised ICTM
Report and on the Rev 5.0 Reclamation Plan are not sufflciently conservative to bound the
uncertainties associated with predicting whether such cover topslope flattening might occur
following construction of the (currently proposed) cover. Additional information needed
from EFR in order to resolve concerns related to the current erosion protection technical
basis justiflcation and future cover inflltration rate - related uncertainties is provided in
the table attached to this Technical Memorandum and in the "Technical Memorandum,
Revised (Rev. 5.0) Reclamation Plan Review".
3.4.2 Suitability of/Impacts from Using Soils Tested in April 2012 for Constructing ET
Cover
3.4.2.1 Round 1 Interrogatory White Mesa Revised ICTM Report: R313-24-4: 10CFR40
Appendix A. Criterion 6(1): INT 03/1:Suitability of/Impacts fi-om Using Soils Tested
in April 2012 for Constructing ET Cover
As described above, INTERROGATORY 02/1 on the Revised ICTM Report included an item
(Item No. 1) REQUESTED THAT EFR provide additional information to justify the assumed
cover soil layer properties.
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TECHNICAL MEMORANDUM
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3.4.2.2 EFR Responses to Suitability of/Impacts from Using Soils Tested in April 2012 for
Constmcting ET Cover
IN ITS RESPONSE, as described previously, EFR provided and discussed results of additional
testing of stockpiled on-site soils proposedfor use in constructing the ET cover, completed in
April 2012.
3.4.2.3 Division's Assessment of EFR Responses to Suitability of/Impacts from Using Soils
Tested in April 2012 for Constmcting ET Cover
The results of April 2012 soil testing suggest that the on-site soils tested appear to be
suitable for establishment of vegetation cover, with the use of soil amendments as discussed
in Attachment G submitted by EFR in its Response. However, the Reclamation Plan, and
speciflcally. Attachment G, do not provide sufflcient information on the types, amounts,
sources, methods of application, estimated costs, and limitations of the potential
amendments that are discussed to demonstrate that use of the on-site soils will be suitable
and cost-effective. The Revised ICTM Report, and the Rev 5.0 Reclamation Plan and
Appendix G also do not provide sufflcient details regarding future contingency measures
that would be implemented for rectifying cover revegetation problems if they occur.
The Division requests that EFR provide additional information in the Reclamation Plan,
and speciflcally, in Attachment G to allow the Division to determine that sufflcient
information has been provided on the types, amounts, sources, methods of application,
estimated costs, and limitations of the potential soil amendments and soil amendment
practices to demonstrate that use ofthe on-site soils will be suitable and not cost-
prohibitive. EFR should provide additional details regarding the soil amendment
procedures to further substantiate/demonstrate that use ofthe on-site soils will be adequate
for facilitating sustainable performance of the cover with respect to the establishment and
sustainability/longevity of vegetation on the cover for promoting evapotranspiration
throughout the cover performance period (200 to 1,000 years). The Division also requests
that EFK provide additional details regarding contingency measures fur rectifying cuvei
and provide information demonstrating that such proposed future remedial measures, if
required, are reasonable and reflective of cover revegetation remedies that have been
required and shown to be effective for other similar facilities (e.g., Monticello tailings
repository - e.g., see U.S. DOE 2007; Waugh et al. 2008).
Alternatively, EFR should explain a plan for use of alternate soils and/or the possible need
for bentonite amendment of these higher-Ksat soils, if necessary, for constructing the cover,
in order to satisfy applicable long-term cover design (e.g., inflltration reduction) objectives,
considering results of additional inflltration sensitivity analyses using these amended soils
that include more conservative assumptions regarding the effects of potential long-term
changes in properties of these amended soils in the completed cover.
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TECHNICAL MEMORANDUM
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3.4.3 Cover Design Safety Factor
3.4.3.1 Round 1 Interrogatory White Mesa Revised ICTM Report: R313-24-4: 10CFR40
Appendix A, Criterion 6(1): INT 03/1 Cover Design Safety Factor
INTERROGATORY 03/1 also REQUESTED, referencing Appendix F ofthe Revised ICTM
Report, that EFR discuss, justify, and apply a recommended safety factor to the design of the
cover to provide additional assurance that the thickness ofthe 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).
3.4.3.2 EFR Responses to Cover Design Safety Factor
IN ITS RESPONSE, EFR indicated that the inclusion of a factor of safety (FOS) to the design of
the cover is not appropriate considering the conservative nature of the assumptions used to
evaluate the cover design and performance.
3.4.3.3 Division's Assessment of EFR Responses to Cover Design Safety Factor
Based on review of this Response, it appears to be acceptable to not include a speciflc FOS
into the cover design to speciflcally address the above-identifled uncertainties. In a
preliminary review of peer-reviewed literature, no published guidance documents
speciflcally addressing this matter were identifled by URS or by the Diyision. However,
during its review of the information provided by EFR, the Division/URS evaluated the
information to determine whether an appropriate, and adequately justifled, reasonably
conservative range of input conditions and parameter values have been assumed by EFR,
and that sufficient sensitivity analyses have been included as part of all modeling
simulations and calculations that incorporate the full range of these assumed conditions
and parameter values. All analyses and model sensitivity analyses have also been reviewed
to determine whether they have been performed in accordance with applicable NRC
guidance and other applicable and relevant criteria and accepted industry practices.
Results of that evaluation are applied to other specific interrogatory items that are
addressed in this document. Therefore no further action is required of EFR with respect to
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TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
the request that a speciflc safety factor be applied to the projected inflltration design or
performance of the cover.
3.4.4 Cover Long-Term Erosion Protection Design Basis/Justiflcation and Differential
Settlement Issues Related to Inflltration Modeling Assumptions
3.4.4.1 Round 1 Interrogatory White Mesa Revised ICTM Report : R313-24-4: 10CFR40
Appendix A. Criterion 6(1): INT 03/1 Cover Long-Term Erosion Protection Design
Basis/Justification and Differential Settlement Issues Related to Infiltration Modeling
Assumptions
4.0 Evaluation of Flow Through Tailings Cell Liners
4.1 Round 1 Interrogatory White Mesa Revised ICTM Report; R313-24-4; 10CFR40
Appendix A, Criterion 6(1); INT 01/1: Evaluation of Flow through Tailings Cell
Liners
EFR's Response to INT 04/1 on Revised ICTM Report Plan - "Evaluation of Potential Flow
through Tailings Cell Liners": THE INTERROGATORY REQUESTED that EFR do the
following:
1. Refer to Appendix L (Evaluation of Potential Flow through Tailings Cell Liners) of the
Revised ICTM Report: Please provide the follov^ng:
2. Revise and provide justification for the value of saturated hydraulic conductivity assumed
for the compacted foundation [liner bedding] layers (comprised of a compacted gravel-
sand mixture derived from cmshing of loose sandstone, possibly with washed concrete
sand used in some areas) underlying the geomembranes in Cells 2 and 3;
3. 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 pel acie fui
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 altematively, 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
4. 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 ofthe
current ICTM Report) and resuhs that would be obtained using Bemouli's equation.
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TECHNICAL MEMORANDUM
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4.2 EFR Responses to Rd 1 Interrogatory White Mesa Revised ICTM Report; R313-24-
4; 10CFR40 Appendix A, Criterion 6(1); INTO 01/1: Evaluation of Flow Through
Tailings Cell Liners
IN ITS RESPONSE, EFR provided analyses and a series of calculations to estimate flux rates
(flow rates) and calculate estimated travel times for liquids to migrate vertically from the base of
either Cell 2 or Cell 3 through the vadose zone to the perched groundwater zone underlying
these cells. Analyses were conducted for a range of possible different assumed saturated zone
values for the in-place bedding materials underlying the geomembrane liners and considered
various geomembrane defect sizes and frequency scenarios. All calculation scenarios assumed a
base-case pressure head value of 5.82 m (19.1 ft), based on the analysis provided in Appendix L
of the Revised ICTM Report (Denison 2010). For calculation purposes, the footprint area of
each of Cell 2 and Cell 3 was assumed to be 70 acres, and a vadose zone thickness of 12.8 m (42
ft) was assumed (the thinnest thickness determined for Cells 2 and 3 based on groundwater depth
information from the nearest wells and information on the bottom depths of Cells 2 and 3, as
described in the analysis provided in Appendix L ofthe Revised ICTM Report [Denison 2010).
EFR indicated that the material installed beneath the liners in Cells 2 and 3 consists of crushed
Dakota sandstone that was compacted with a smooth drum roller, but in some locations, in
which a smooth base grade was available, portions ofthe liner were placed over sections of in
situ Dakota sandstone (H. Roberts, 2012). The Second Phase Tailings Management System
Construction Report generally is consistent with this observation: Energy Fuels Nuclear Inc.
(1983) noted that a gravel-sand mixture derived from crushing of loose [Dakota] sandstone, with
some washed concrete sand in some areas, was used to construct the compacted bedding layer
immediately beneath the liner in Cell 3; and that a similar process and materials were used for
the liner bedding material in Cell 2.
Acknowledging that no estimates of the hydraulic conductivity for the in-place liner bedding
materials bcricath Cells 2 and 3 arc available for incorporation into the leakage analyses, EFR .
referred to results of saturated hydraulic conductivity tests in the vertical direction (Ks)
measured on intact core-samples of the Dakota sandstone using a flexible wall permeameter
(Appendix B) of the 2010 Revised ICTM Report for use as a starting point to assess the potential
Ks value for the liner bedding materials. EFR used intact core-sample intervals, measured in feet
below ground surface (ft bgs) from the following monitoring wells (MWs), and the corresponding
Ks measurements in meters per second (m/s) are as follows for the Dakota sandstone (Appendix
B), to derive a corresponding geometric mean Ks value of 9.0x10'^ m/s (9.0x10'^ cm/s):
MW-30 35.5-36.0ft bgs was measured at 8.1x10-6 m/s.
MW-30 44.0-44.5 ft bgs was measured at 8.2x10-8 m/s.
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TECHNICAL MEMORANDUM
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• MW-23 55.5-56.0ft bgs was measured at 1.1x10-6 m/s.
This geometric mean value is approximately eleven times higher than the minimum value and
nine times lower than the maximum value. EFR acknowledged that, in actuality, the Ks value for
these materials could be higher or lower than the test measurements listed above indicate, based
on the reported variability and because the liner underlay material consists of crushed Dakota
sandstone which may have experienced some compaction from hydraulic loading and tailings
deposition.
4.3 Division's Assessment of EFR Responses to Rd 1 Interrogatory White Mesa Revised
ICTM Report; R313-24-4; 10CFR40 Appendix A, Criterion 6(1); INT 01/1
EFR discussed various lines of evidence to support their contention that their assumption
that an appropriate Ks value for the crushed sandstone/washed gravel bedding layers
underlying Cells 2 and 3 to use in the leakage analysis similar to the Ks value used in the
December 2010 Revised ICTM Report (2 x 10'' m/sec) and that the geomembrane defect
sizes and frequencies assumed in the calculations presented in Appendix L of the Revised
ICTM Report (Denison 2010) are reasonable and do not require revision. Evidence cited by
EFR includes:
• "No signiflcant leakage indicated by the leak detection systems;
No leakage indicated by mounding of the perched aquifer water table surface;
No observations of contamination (e.g., acid leaching, dissolution of carbonates,
gypsum precipitation, staining) in the bedrock core samples were recorded during
drilling of monitoring wells installed adjacent to the cells during spring 2005 as
noted during inspection of the core by MWH (Appendix C);
Total uranium was detected at background levels in bedrock core samples collected
while drilling monitoring "^ells adjacent to the cells as noted by analyses presented m Appendix A; ===========—==.========================^
No contaminants detected in groundwater at levels above natural background
concentrations (INTERA, 2007a; 2007b; 2008). The lack of groundwater
contamination is corroborated by the following:
The apparent groundwater age beneath the tailings cells is dominated by water that
is at least approximately 55 years old as determined from measurements of tritium
and helium in groundwater within the vicinity and downgradient of the mill (Hurst
and Solomon 2008). In other words, recharge at the land surface occurred prior to
1952 (Schwartz and Zhang 2003) and takes at least 55 years to reach the perched
aquifer.
Groundwater beneath the tailings cells is not influenced by more modern water that
may have leaked from the tailings cells.
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TECHNICAL MEMORANDUM
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o No contaminants detected in groundwater as evaluated through measurements of
stable isotopes for oxygen and sulfate in groundwater within the vicinity and
downgradient of the mill (Hurst and Solomon 2008) indicative that signiflcant
leakage from the tailings cells have not occurred."
Based on review of the above Response, in the opinion of the Division, the bullet points
listed by EFR do not provide evidence that no signiflcant leakage has occurred through the
liner systems beneath Cells 2 & 3 over the past 30 years. The Division flnds that the
analyses and conclusions presented in this Response do not sufflciently bound and are not
sufflciently conservative to represent the full range of site and liner conditions that likely
exist at and beneath cells 2 and 3 to assess potential impacts associated with potential
leakage of leachate from Cells 2 and 3.
The point that "no observations of contamination (e.g., acid leaching, dissolution of
carbonates, gypsum precipitation, staining) were recorded during drilling of monitoring
wells installed between and adjacent to the cells during spring 2005" is not evidence that
"no signiflcant leakage has occurred through the liner systems beneath Cells 2 & 3 over the
past 30 years." Instead, this flnding indicates that leakage was not observed at these well
locations, but it still could exist elsewhere inside/directly below the footprint area of the
contiguous tailings cells.
Average groundwater flow velocities in the Burro Canyon Formation downgradient of the
tailings cells are indicated in the Revised ICTM Report (p. 2-12) to be on the order of 1.7 to
3.2 ft/yr. This would imply that a constituent in a hypothetical groundwater plume in the
groundwater would have only moved approximately 102 feet (e.g., 32 years x 3.2 ft/yr) in
the aquifer over the past 32 years. The distance between upgradient and downgradient
edges of Cell 3, where upgradient and downgradient wells are located, is, by comparison,
on the order of 1,000 feet. If a release source (e.g., the location of a defect in the cell liner)
were situated near the northern margin of Cell 3, and the release resulted in a plume of
capable of being detected in a downgradient monitoring well, it is unlikely that the
contamination would have been detected in any of the monitoring wells (e.g., MW-39, MW-
30, MW-31) installed along the downgradient edge of Cell 3 by the present time. Hence,
groundwater contaminant detection at the present time may be more likely only in cases
where the contaminant source is located just a short distance upgradient from one of these
monitoring wells.
Additionally, analytical results of groundwater monitoring conducted during the 1"* and/or
2"** Quarters of 2012 indicate that Groundwater Concentration Limits (GWCLs) for the
constituents listed in the following table were exceeded for the monitoring wells Hsted in the
table that are located immediately downgradient of the edge of either Cell 2 or Cell 3:
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Well No./ Cell
Downgradient of
Parameter
Exceeding GWPL
GWCL Concentration
Detected
MW-29/ Cell 2 Manganese 5624 ng/L 6140 ng/L
MW-30/ Cell 2 Nitrate + Nitrite
Uranium
Selenium
5 mg/L
8.32 mg/L
34 pg/L
15-18 mg/L
8.38 ng/L (March
2012)
35-39.1 ng/L
MW-31/Cell 2 Nitrate + Nitrite
TDS
Chloride
Sulfate
5 mg/L
1320 mg/L
143 mg/L
532 mg/L
20 -22 mg/L
1360- 1460 mg/L
151 - 160 mg/L
538-547 mg/L
MW-5/ Cell 3 Uranium 7.5 [ig/L 18.6 ng/L(Ql 2012)
MW-11/Cell 3 Manganese 131.29 ng/L 154 ng/L; 132 ng/L
MW-12/ Cell 3 Selenium 25 iig/L 27.2 ng/L (Ql 2012)
Although the magnitudes of exceedance of applicable GWCLs for the constituents reported
in the above table are typically small and/or might have only occurred once to date, these
reported exceedances reflect more recent groundwater monitoring data than referenced in
the EFR Response and indicate that EFR's argument that no contaminants have been
released from Cell 2 and/or Cell that have been detected in groundwater monitoring wells
above background concentrations is not, or may not be defensible.
Additionally, information provided by EFR in "Response 2 (May 31,2012)" to this
interrogatory indicates that substantial volumes (but at rates below specifled Action
itc trigger levels) of leachate have accumulated in the Leak Detection Systems
underlying the primary geomembrane liners in Cells 4A and 4B since the time of their
installation. Because the liners in Cells 2 and 3 were installed using older liner technologies
and materials than were used in Cells 4A and 4B, and the Cell 2 and Cell 3 liners are older
than those in Cells 4A and 4B, it would be reasonable and conservative to assume that
leakage rates through the liners in Cells 2 and 3 would be substantially higher than leakage
rates occurring through the primary liners in Cells 4A and 4B. For example, estimates of
failure time for PVC liners range from about two decades to possibly a century or more.
However, there remains much uncertainty about PVC liner longevity, and actual lifetimes
will vary depending on liner and leachate properties and other environmental
characteristics. One manufacturer, for example, claims a lifetime for their PVC liners,
when buried in the subsurface, of only up to 20 years (Enviroconsystems, 2012). Likewise,
CLI (2010), a geosynthetic solutions provider, indicates that for landflU liners,... "in buried
applications, PVC can provide a service life of over 20 years." AccuGeo (2012), another
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TECHNICAL MEMORANDUM
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liner manufacturer, indicates, "...buried PVC liners will have a life of 20 years or more"
(AccuGeo, 2012).
For further evaluating potential leakage rates from Cells 2 and 3, the Division requests that
EFR perform an uncertainty analysis relative to PVC liner longevity in its inflltration
modeling, or justify not doing so. Uncertainty analyses should involve at least one model
run for liner failure occurring after decades (e.g., 20 years), and at least one model run for
failure at about 100 years, or some alternative timeframe as justifled by EFR.
For evaluating the appropriateness of some of the evidence EFR provided in the Response
to support EFR's contention that Cells 2 and 3 are not currently experiencing signiflcant
leakage, detailed calculations were not provided (with input parameter assumptions and
information supporting those assumptions) directly calculating the vertical transport time
of constituents potentially seeping from below the base of Cell 2 and Cell 3 through the in-
situ vadose zone bedrock materials underlying the liners of these cells to the top of the
perched water zone underlying those cells, but would have been useful.
Based on the considerations described above and the available information, the Division
assumes that tailings Cells 2 and 3 have a higher probability of releasing leachate to the
groundwater system than do tailings Cells 4A and 4B. This probability is further
heightened due to the much lower tailings dewatering rate observed in these two cells
compared to Cells 4A and 4B, which has resulted in a more prolonged duration of elevated
leachate levels present in Cells 2 and 3 to the present time. The rate at which leachate head
levels in Cells 4A and 4B are predicted to be reduced is considerably higher than the
dewatering rate in Cells 2 and 3 due to the more modern and more extensive tailings
dewatering systems installed in Cells 4A and 4B.
Conclusions presented by EFR in the current Response to this interrogatory are as follows:
The Ks value assigned to the liner underlay materials using the value assumed in
Appendix L is considered to be a reasonable and appropriate assumption, and that
an attempt to decrease this value would result in potential leakage rates that do not
appear to be realistic (i.e., too conservative); and
Therefore, a higher Ks for the liner bedding materials does not seem to be justifled
to represent potential in-place liner conditions beneath Cells 2 and 3 and the
calculations presented in the 2010 Revised ICTM Report do not require adjustment.
Based on review of the Response, the Division requests that EFR:
• Revise the liner leakage calculations and resulting conclusions from those currently
presented in the Response to reflect a more conservative range of assumptions and
the results of revised analyses incorporating those more conservative assumptions,
that coincide more closely with current site information and conditions (see
additional discussion at the end of this section), and that are consistent with a
postulation that the liners in Cells 2 and 3 could allow leakage rates higher than or
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equal to measured leakage flux rates currently occurring through the primary liners
in Cells 4A and 4B;
Quantify the degree to which the revised analyses result in flux rates through the
liner systems in Cells 2 and 3 indicate higher leakage rates than leachate flux rates
currently observed through the primary liners in Cells 4A and 4B, under all
comparable assumed operational conditions and all assumed liner defect
frequencies; and
Provide a detailed travel time calculation or calculations, analogous to those
discussed on p. 38 of 70 in "Response 1 (May 31,2012)", but that instead calculate
the vertical transport time of constituents potentially seeping from directly below
the base of Cells 2 and 3 through the in- situ vadose zone bedrock materials to the
top of the perched water zone. Include information on the hydraulic conductivity
yalue(s) assumed and the effective fleld porosity value assumed for the bedrock
materials and provide a basis for the value assumed (i.e., fleld measurements).
Alternatively, if no single value of effective porosity is available or appropriate for
the site, provide a range of effective porosity values assumed and use this range of
values in the travel time calculations. Compare the value(s) of effective porosity
used to the default value of 10 percent recommended for use by NRC at Title I
UMTRCA sites in Section 4.3.1.3.2 of NRC 1993 (considered by the Division to be a
relevant conservative default value for this type of analysis).
The Second Phase Tailings Management System Construction Report (Energy Fuels
Nuclear Inc. 1983) noted that a gravel-sand mixture derived from crushing of loose
[Dakota] sandstone, with some washed concrete sand in some areas, was used to construct
the compacted bedding layer, where present, immediately beneath the liner in Cell 3; and
that a similar process and materials were used for the liner bedding material in Cell 2. In
some areas, liner was laid directly on compacted bedrock.
Table 5.5.1 of Bear (1972) differentiates between "gravel" and "clean sand or sand and
gravel", and gives a range of values for hydraulic conductivity for sand and gravel between
10"^ and 10° cm/sec. These values may approximate values of hydraulic conductivity for a
crushed sandstone. USACE (1993) refers to a value for hydraulic conductivity of 1.4 x 10'^
cm/sec and indicates that "clean, washed concrete sand is usually about this permeable".
Elsewhere, USACE (1993) refers to "clean washed concrete sand with a permeability
[hydraulic conductivity] of 10 ft/day", which equates to 3.5 x 10 "' cm/sec. "Washed
concrete sand" used in one project is reported by Dwyer (1998) as having a hydraulic
conductivity of at least 10'^ cm/sec. A falling-head permeameter test of "Nova Scotia
washed concrete sand" is reported as having indicated a hydraulic conductivity ofthe sand
in the range of 1 x IO"'* to 2 x IO""* m/s (Mooers and Waller,1997), equivalent to 1 x 10'^ to 2 x
10'^ cm/sec. All of these reported ranges of hydraulic conductivity values exceed (by a few
to several orders of magnitude) the geometric mean value of 9.0 x 10'^ m/sec (9 x 10 ^
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cm/sec) assumed for this underlay material by EFR in the revised calculations described in
the Response (August 31,2012) to this Rd 1 interrogatory.
Based on the above information, unless EFR can provide more conclusive data, the
Division requests that these higher values be used for the hydraulic conductivity of the
underlay materials, or, at a minimum, that EFR run additional sensitivity analyses that
incorporate these higher hydraulic conductivity values, to assess the impact of these higher
values on the Cells 2 and 3 leakage rate calculations.
5.0 Contaminant Transport Modeling
5.1 Round 1 Interrogatory White Mesa Revised ICTM Report; R313-24-4; 10CFR40
Appendix A, Criterion 6(1); INT 01/1: Contaminant Transport Modeling
EFR's Responses to INT WHITE MESA REV'D ICTM: R313-24-4-05/1: Contaminant
Transport Modeling: THE INTERROGATORY REQUESTED that EFR provide the information
requested in Items No. 1 through 11 as follows:
1. Refer to Revised ICTM Report, Section 2.2 Site Characteristics and Section 3.4
Uncertainty and Assumptions: "Provide additional information on the potential presence
and distribution of fractures and/or joints, and uncemented/higher 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
uncemented/higher 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."
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 HPl (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.
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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-11, Paragraph 1: Please justify the assumption that the redox
conditions in the tailing slimes drainage and the vadose zone are controlled by the oxygen
(02/H20) 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-11, Paragraph 2: Please provide justification for using a
chloride diffusion coefficient (1.75 cm7day) 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-11, Paragraph 4: Please justify the assumption to establish
the initial soil water pressure heads within the bedrock vadose zone as that 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").
9. Refer to Appendix M, Figures M-3 and M-4: Please state and justify the value(s) ofthe
effective uranium retardation factor that would be consistent with the HPl model output
for the bedrock vadose zone. Please see (summarized in Appendix M ofthe 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 uramum are not shown ai a depih of 0 feet on Figures
M-3 and M-4 and/or revise the figures as necessary.
11. 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.
5.2 EFR Responses to Rd 1 Interrogatory White Mesa Revised ICTM Report; R313-24-
4; 10CFR40 Appendix A, Criterion 6(1); INTO 01/1: Contaminant Transport
Modeling
IN ITS RESPONSE, EFR indicated the following:
"Response 1:
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The potential occurrence of increased flow and transport from the presence and distribution of
fractures and/or joints in the unsaturated zone ofthe Dakota sandstone and Burro Canyon
Formation underlying the site area is not supported by geologic and hydrogeologic observations
as summarized below:
• The lack offaulting and lack of extensive jointing combined with the largely structurally
intact and sub-horizontal dip of the geologic units should act to limit the downward
movement of water within the bedrock vadose zone. Structural control of water movement
is likely limited due to the absence of faults and the apparent low frequency ofjoints.
o The Dakota sandstone and Burro Canyon Formation are nearly flat-lying with
reported dips of less than 1 degree to the south (D'Appolonia, 1979).
o No faults have been mapped or identified within the Blanding Basin (Kirby, 2008)1or
White Mesa area (D'Appolonia, 1979).
o The Dakota sandstone and Burro Canyon Formation are relatively devoid of joints.
Where present, primary joints are nearly vertical and north striking, and commonly
several meters in length; secondary joints are oriented east-west and commonly
terminate at the intersection with primary joint surfaces (Kirby, 2008).
• Observational data collected during a 1994 drilling program of three perched
monitoring wells and four angled borings beneath Cell 3 and Cell 4A concluded that few
fractures were present in the cores or observed in video logs. And where such features
were present the fractures were closed and/or sealed with gypsum (Hydro Geo Chem Inc.
[HGC], 2010a).
u The polenliomelric surface map in the viciniiy and downgradient of the tailings celh
resembles that of a perched aquifer system in that the projected and inferred lines of
equipotential are nearly parallel to one another (Figure 2-5 of the 2010 Revised
ICTM).
• Age dating of groundwater in the vicinity and downgradient of the tailings cells indicates
that inflltration takes longer than 55 years to travel through the vadose zone except in the
vicinity of the-wildlife ponds (Hurst and Solomon, 2008). The recharge mound near the
wildlife ponds, combined with the absence of tritium in groundwater beneath the mesa,
imply that the bedrock vadose zone can generally be considered as recharge-limited
rather than permeability-limited (Hurst and Solomon, 2008), which corroborates the
assumption that recharge and flow through the bedrock vadose zone is predominately via
matrix flow rather than through fracture flow.
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TECHNICAL MEMORANDUM
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The potential occurrence of increased flow and transport from the presence ofuncemented
and/or higher permeability intervals in the unsaturated zone of the Dakota sandstone and Burro
Canyon Formation underlying the site area is not supported by geologic and hydrogeologic
observations as summarized below: >
• Sub-horizontal units of potentially more permeable lithologic units (e.g., conglomerate
and sandstone with intermittent conglomeratic features) cannot be correlated as broad
continuous lenses beneath the tailings cells (HGC, 2010b). However, these,units can be
correlated short distances between boreholes as thin discontinuous lenses of limited
thickness.
• A poor correlation between conglomeritic intervals and enhanced permeability has been
observed through interpretation of hydraulic testing (HGC, 2010a):
o Hydraulic conductivity tests in the horizontal direction for conglomeratic lenses
beneath Cell 4B (MW-16) were approximately 5.1x10-7 m/s which is within the
middle of the range of values (2.9x10-7 to 9.1x10-6 m/s) reported for the more
massive sandstone lithology (HGC, 2010a).
o Hydraulic conductivity tests in the horizontal direction for conglomeratic lenses
beneath Cell 3 (angled borings) were lower than 1x10-7 m/s for three tests and
higher than 1x10-7 m/s for one test (HGC, 2010a).
o The similar hydraulic behavior between the sandstone and conglomeritic lenses can
be explained because the conglomerate matrix is represented by sandstone and the
gravel-sized clasts within the conglomerate are generally present in low percentages
(less than 30 percent).
• The presence of unidentified high permeability discontinuous conglomeritic layers of
limited thickness within the vadose zone would likely result in more timely detection of
any seepage that may occur; because these units, if present, could act to spread any
seepage over a wider area, and make such fluids less likely to pass undetected between
monitoring wells (HGC, 2010a).
A discussion regarding the material presented above will be included in the next iteration ofthe
ICTM Report to some extent within Sections 2.2 and 4.3. "
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TECHNICAL MEMORANDUM
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"Response 2 (May 31. 2012):
A brief summary of the geochemical characteristics of the perched groundwater as it relates to
the development of input assumptions for the vadose zone will be included in the next iteration of
the ICTM Report. The following discussion is anticipated to be included in Appendix M, to
support the reactive transport model for the next iteration ofthe ICTM Report
The geochemical modeling requires input assumptions regarding (i) the chemistry of the tailings
pore water, (ii) the chemistry of the bedrock vadose zone pore water, and (ii) the mineralogy of
the bedrock vadose zone. The geochemical characteristics ofthe vadose zone pore water can be
constrained by the solid phases present within the bedrock and the pore water chemistry within
the perched aquifer. The conceptual model used to support the geochemical modeling input
assumptions for the vadose zone is explained below, while the conceptual model used to support
the geochemical modeling input assumptions for the tailings pore water seepage chemistry is
explained in the response to Comment Six (6) below.
Recharge, especially from the unlined wildlife ponds east ofthe mill site, represents the
dominant source of the perched groundwater beneath the mill (Hurst and Solomon, 2008).
Recharge from water (percolation) within shallow portions ofthe bedrock is likely to be near
atmospheric conditions with a concentration of dissolved oxygen (DO) on the order of 8
milligrams per liter (mg/L). As percolation continues to migrate through the bedrock, the
oxidation of organic compounds is likely to consume a portion ofthe dissolved and gaseous
oxygen through aerobic respiration because this process is the most energetically favorable
redox reaction anticipated to occur within the oxic vadose zone (Langmuir, 1997). Redox
reactions within the bedrock and resultant pore water chemistry will be controlled by the water
to rock and microbial reactions that occur during transport through the vadose zone. The
presence of iron hydroxides and carbonate minerals in the bedrock suggests that oxic conditions
coincident with aerobic respiration at near neutralpH are likely to dominate within the vadose
zone. Therefore, the vadose ^one pore water is anticipated to contain DO at detectable———=
concentrations that reflect oxic conditions consistent with the presence of hydrous ferric oxide
(HFO) within the bedrock.
Additionally, as the percolation continues to migrate downward through the vadose zone, the
recharge water will eventually mix with the perched groundwater and equilibrate with minerals
present within the zone of saturation. While there are naturally-occurring concentrations of
chloride, sulfate, uranium, and other trace elements in the vadose zone initially, the modeling
assumed zero concentrations as a simplification Initial solution concentrations in the vadose
zone pore water were estimated by assuming equilibrium ofcalcite with HFO (Appendix M),
consistent with minerals observed in the bedrock, such that only calcium, carbonate, and
dissolved oxygen were included as aqueous species initially present within the vadose zone pore
water.
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Dissolved Oxygen
The concentration of DO is not being measured for wells screened within the perched aquifer
because this analyte is not required by the groundwater discharge permit. However, DO was
measured at a subset of the monitoring wells as part of the evaluation completed by the
University of Utah (G. Hurst, 2012). These measurements are summarized below (see Table
05/1/2-1). The concentration of DO within groundwater appears to be related to the vadose zone
thickness such that a thinner vadose zone correlates with a higher DO concentration in
groundwater. Therefore, taking the measurement reported for the minimum vadose zone
thickness (MW-30) to be consistent with the numerical model, the concentration of DO within the
vadose zone pore water is likely greater than the 5 mg/L concentration reported for groundwater
at this monitoring location. Within the bedrock vadose zone, the partial pressure of oxygen was
fixed in the geochemical model assuming a DO concentration of 2 mg/L in pore water.
Therefore, this assumption appears to be valid for the bedrock vadose zone, based on
measurements of DO in groundwater for the minimum vadose zone thickness, at least as an
initial condition.
Redox
The study completed by the University of Utah (Hurst and Solomon, 2008) did not measure
concentrations within groundwater for any complete pair of redox species. However, in spite of
observations ofpyrite at some locations in the aquifer matrix, the presence of DO within
groundwater suggests that oxic conditions and aerobic respiration are likely to dominate redox
reactions in the vadose zone and in groundwater influenced by seepage from the wildlife ponds.
Therefore, the oxygen redox couple is anticipated to control redox reactions within the bedrock
vadose zone and in groundwater, at least as an initial condition. Whether or not this assumption
would hold true if potential tailings seepage water was transported through the vadose zone will
Be discussed in the Response to Comment Six (6) below. "
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TECHNICAL MEMORANDUM
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Table for Response 2 (May 31, 2012):
Table 05/1/2-1, Dissolved Oxygen (DO) Measurements For a Subset of Wells Screened
Within the Perched Aquifer
Well Location DO at Upper
Measurement
Point (mg/L)
DO at Upper
Measurement
Point (mg/L)
Vadose Zone
Thickness (m)
MW-5 Between Cell 3
and4B
0.02 0.01 22.9
MW-11 Between Cell 3
and 4A
0.25 0.01 19.5
MW-14 South of Cell 4A 0.14 0.04 22.9
MW-15 Between Cell 4A
and4B
1.43 0.24 19.5
MW-29 Between Cell 2
and 3
0.41 0.03 22.6
MW-30 Between Cell 2
and 3
5.24 5.12 12.8
MW-31 Between Cell 2
and 3
8.33 9.10 13.1
Notes: Data provided electronically by G. Hurst Samples were collected during July 2007. Dissolved
oxygen measurements were made at the depths at which the passive diffusion samplers (PDSs) were
deployed. The PDSs were deployed approximately 1 meter above the bottom of the screened interval
and 1 meter below the top of the Screened inter val In wells that did not have a fully saturated
screened interval (MW-5, 14, 15, 29, 30, 31), the top diffusion sampler was placed approximately 1
meter below the top of the water level Vadose zone thickness taken as difference between cell depth
and water table depth.
"Response 3 (May 31, 2012):
Aluminum was selected to obtain charge balance because it was not measured in the various
solutions representing the input chemistry, and the solutions had a negative charge imbalance
which suggested cation deficiency. This additional text will be added to Sections 3.4.4 and
Appendix M of the next iteration of the ICTM Report.
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^-'Response 4 (May 31, 2012):
The values used to compute the statistics were derived from arithmetic averaging of primary and
duplicate sample results (where applicable) after rounding to the nearest whole number for the
acid neutralization potential (ANP) data. Duplicate samples for materials submitted May 2009
were labeled as being blind (i.e., collected from MW-100 with arbitrary depth intervals). The
following sample locations corresponded to the following sample labels:
• MW-24 80.0-80.3 Duplicate labeled as MW-lOO 11.1-11.3. The primary and duplicate
samples results for ANP were equal to 25 and 28 grams of CaC03 per kilogram of rock
(g CaC03/kg rock), respectively.
• MW-24 56 0-56 2 Duplicate labeled as MW-100 16 0-16 2. The primary and duplicate
samples had the same ANP results.
• TW4-22 69.8-70.0 Duplicate labeled as MW-lOO 19.8-20.0. The primary and duplicate
samples results for ANP were equal to 10 and 29 g CaC03/kg rock, respectively.
• MW-23 103.0-103.3 Duplicate was labeled as is to be consistent with the original sample
labeling criteria for samples submitted to the laboratory during February 2007.
Therefore the summary statistics presented in Appendix C are valid and do not require
adjustment Clarifying text will be included in Appendix C for the next iteration ofthe ICTM
Report to avoid future confusion. "
"Response 5 (May 31, 2012):
The dry bulk density of the bedrock was assigned to equal 2.0 grams per cubic centimeter
(g/cm3). This value was based on the measurement reported for MW-23 (55.5-56.0ft) to be
consistent with the sample interval test results used to parameterize the bedrock hydraulic
properties (Appendix C). The value assigned to the model is approximately equal to the
arithmetic average (2.1 g/cm3) of the samples tested (Appendix B and C). Clarifying text will be
included in Appendix Mfor the next iteration of the ICTM Report to avoidfuture confusion. "
"Response 6 (May 31, 2012):
The presence of measured DO in groundwater suggests that oxic conditions and aerobic
processes are likely to dominate redox reactions in groundwater and also in the vadose zone as
discussed in the response to Comment Two in this interrogatory. Whether or not this assumption
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would hold true if potential tailings seepage water was transported through the vadose zone is
discussed below.
The conceptual model used to support the geochemical modeling input assumptions for the
tailings pore water seepage chemistry is based on the following observations and hypothesized
processes anticipated to occur in tailings pore water at depth.
Concentrations of DO in the tailings pore water at depth are not available because this analyte
is not required to be measuredfor the GWDP, license or tailings sampling plan.
Surface water or tailings pore water near the upper surface of the impoundment is likely to be
near atmospheric conditions with a concentration of DO on the order of 8 mg/L. The
concentration of DO at depth can only be estimated and bounded by the chemistry of the tailings
solutions combined with potential redox reactions that may occur at depth within the
impoundment. The tailings solutions are acidic and contain detectable concentrations of some
organic compounds and elevated concentrations of chloride, nitrogen (nitrate plus nitrite and
ammonium), sodium, and sulfate. The oxidation of minerals within the ore during acid leaching
is the likely cause of elevated concentrations of iron and other ions in the tailings solutions.
Based on the chemistry of the tailings solutions discussed above the following redox reactions
are anticipated to occur within the tailing pore water at depth to some extent
The DO within the tailings pore water at depth is likely to be consumed to some extent if
oxidation of organic compounds, ammonium, and ferrous iron occurs. If DO was completely
consumed anoxic conditions would develop. Considering the solution chemistry of the tailings
pore water, and the energetics of the reaction, nitrate reduction and ammonium oxidation would
be the next most favorable anaerobic reaction to occur once DO is consumed. Therefore,
rnnsidp.ring the P.lp.vatp.d nnncentrations of nitrogen species within the tailings pore water at
depth, and thermodynamic constraints, measurements for the nitrogen species can be used to
calculate redox (pE) conditions in the tailings pore water at depth. Redox conditions calculated
from the nitrogen species can then be used to infer redox reactions and mineral stability within
the iron system.
Using the chemistry for the tailings pore water at depth (Appendix K) but assuming a DO
concentration of zero:
• The redox value calculated by PHREEQC for the upper bound concentrations is
approximately 629 millivolts (mV). Using the nitrogen calculated pe value iron would
partition approximately 70% as ferrous iron. The saturation index for HFO is calculated
to be 0.07, implying that the solution is at equilibrium with HFO.
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• The redox value calculated by PHREEQC for the base case concentrations is
approximately 631 millivolts (mV). Using the nitrogen calculated pe value iron would
partition approximately 67% as ferrous iron. The saturation index for HFO is calculated
to be 0.15, implying that the solution is slightly supersaturated with HFO, and HFO
could precipitate barring any sort of kinetic constraints.
• The redox value calculated by PHREEQC for the lower bound concentrations is
approximately 628 millivolts (mV). Using the nitrogen calculated pe value iron would
partition approximately 72% as ferrous iron. The saturation index for HFO is calculated
to be 0 02, implying that the solution is at equilibrium with HFO.
For these redox conditions, the calculated pe of the tailings pore water at depth is approximately
10.6 and HFO is anticipated to be a stable phase within the tailings pore water at depth. These .
calculations are used to support an alternative conceptual model for conditions in which the iron
redox couple is used to constrain redox conditions within the vadose zone during reactive
transport This conceptualization differs from the scenario presented in the 2010 Revised ICTM
Report in that the concentration of DO was fixed to equal 2 mg/L in the tailings pore water.
Originally, this assumption was incorporated into the model to maintain consistency with the DO
concentration in the vadose zone as a simplification. The sensitivity ofthis assumption is
evaluated and discussed below.
Sensitivity Analysis
The initial concentration of DO within the vadose zone was assigned to equal 2 mg/L, as
supported by data presented in response two of this interrogatory. The oxygen couple was used
to determine the redox of the initial solutions (a pE of 13.6) within the vadose zone. This is
equivalent to the parameterization for the 2010 Revised ICTM Report.
The initial concentration of DO within the tailings pore water was assigned lo be infinitely small
(essentially 0 mg/L), and the iron couple was used to determine the redox ofthe seepage water (a
pE of 10.6) and during reactive transport through the vadose zone.
Furthermore, for this sensitivity analysis, concentrations of DO within the vadose zone during
reactive transport were not fixed but allowed to vary as a function ofthe geochemical reactions.
Subsequent calculations did not assume a fixed Eh, rather redox conditions were allowed to
change as a function of the geochemical reactions with redox being controlled by the iron
couple. This is generally the preferred approach rather than fixing the Eh to a specific value that
may have little to no quantitative meaning during reactive transport Additionally, the mass of
HFO initially present within the vadose zone was allowed to change based on changing redox
conditions. To maintain geochemical conditions consistent with this alternative conceptual
model, the mass of HFO available to participate in sorption was allowed to vary depending on
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the simulated redox and geochemical conditions; the conceptual model incorporated into the
2010 Revised ICTM Report limited sorption to the mass of HFO initially present in the vadose
zone. The simulatedpH, redox, aqueous concentration of uranium, and sorbed concentration of
uranium within the shallow vadose zone for these two conceptual models are plotted below (see
Figure 05/1/6-1 and 05/1/6-2) (Refer to EFR's response for these figures).
The iron redox couple scenario has a slightly higher pH immediately beneath the liners
compared to the oxygen redox couple scenario. This slightly higher pH is related to the mass of
HFO that precipitates, which is slightly higher for the iron redox couple scenario: the
precipitation of HFO consumes acidity which results in a slightly higher pH. Both scenarios
show complete dissolution of calcite at about the same depth. The iron redox couple scenario has
a lower pE immediately beneath the liners compared to the oxygen redox couple scenario. The
slightly lower pE is based on the value input at the upper boundary. The lower pE at greater
depths for the iron redox couple scenario is lower than the oxygen redox couple scenario;
because DO that is originally present within the vadose zone is oxidized and consumes electrons.
The concentration of uranium in the shallow vadose zone is significantly lower for the iron redox
couple scenario compared to the oxygen redox couple scenario. Decreased transport of uranium
is attributed to in'creased sorption onto HFO for the iron redox couple scenario because more
HFO is present within the vadose zone. The increased mass of HFO is consistent with the
conceptualization that the mass of HFO available to participate in sorption was allowed to vary
depending on the simulated redox and geochemical conditions. "
"Response 7 (May 31, 2012):
The diffusion coefficient (Dw) for the solutes modeled was assumed to equal 1.75 centimeters
squared per day (crr^/d). The value for Dw was based on measurements for chloride at infinite
dilution in water at 25°C, and do not represent measurements in seawater. The value of Dw for
some ofthe more common aqueous species are summarized below (see iabie i)5/h/-ij. Ihe
maximum value of Dw corresponds to the value for chloride while the minimum value of Dw
corresponds to the value for uranium (uranyl ion).
Diffusive transport was assumed to be species-independent as a necessary simplification because
the model is not set-up to simulate multicomponent diffusive transport Diffusive transport
through the variably saturated porous media is simulated as an effective diffusion coefficient
(De) that is calculated as a function of space and time as the product ofDw and tortuosity factor
in the liquid phase (rw). While the value for Dw is constant, the model simulated values for De
vary through space and time as a function ofthe simulated spatial variations in water content
and resultant tortuosity.
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In unsaturated porous media the value for De tends to increase as the degree of saturation
increases because of the increased connectivity of the porous media (decreased tortuosity). For
example, using the value for Dw referenced above (1.75 crrf/d), if the VWCs were equal to 8
percent and 15 percent the corresponding values for De would equal approximately 0.14 and
0.62 cm^/d, respectively. The calculated values for De are within the range of values presented in
the literature:
• Hu and Wang (2003) report values for De equal to approximately 0.13 and 0.22 cm^/d
for a sand soil at VWCs approximately equal to 8 percent and 15 percent
• Badv and Mahmoundi (2009) report values for De from 0.30 to 0.60 crrf/d for a silty
sand soil at VWCs approximately equal to 19percent and 37percent'
In part, the value for De represents an intrinsic property of the porous media such that a direct
comparison with values reported in the literature should be completed with caution because
diffusive transport will vary depending on the retention curve which influences the tortuosity
factor.
Theoretically, a higher value for De will result in increased diffusion which will tend to increase
mass spreading resulting in faster transport times for the migrating diffusive front during
transport through the vadose zone. These postulated effects are confirmed by the following plot
which illustrates the chloride concentration profile within the bedrock vadose zone using the
maximum and minimum values for Dw reported in Table 05/1/7-1.
The concentration profiles using two different values for Dw are plotted after 240 years for the
base case flow and transport scenario described in the 2010 Revised ICTM Report (see Figure
05/1/7-1).
The results presented above indicate that the higher value of Dw equal to 1.75 cm2/d based on
measurements for chloride as implemented in the 2010 Revised ICTM Report result in increased
diffusive transport (more conservative assumption) at the leading edge ofthe plume. Therefore, a
sensitivity analysis for the value assigned to the diffusion coefficient at infinite dilution in open
water (Dw) is not warranted. "
"Response 8 (May 31, 2012):
Initial Pressure Heads
The initial pressure heads within the bedrock vadose zone were assigned to represent conditions
prior to construction of the tailings cells. Initial values were based on an assumed pre-tailing-
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cell recharge rate equal to 1 percent of the average annual amount ofprecipitation between
1932 and 1988. The assumption that 1 percent ofthe annual precipitation will occur as recharge
generally is in agreement with recharge studies completed at other semiarid sites. For example,
a synopsis of recharge measurements suggests that average recharge rates in arid and semiarid
environments can vary between 0.1 to 5 percent ofthe long-term average annual amount of
precipitation (Scanlon et al. 2006). The review paper authored by Scanlon et al (2006) reported
the following recharge rates for relatively comparable environments in the southwestern United
States as compared to Blanding:
• 3 percent of precipitation for the Middle Rio Grande Basin in central New Mexico. This •
regional recharge rate (8.5 mm/yr) was estimated using a steady state, inverse
groundwater model and carbon-14 age dating. Recharge occurs primarily in the
surrounding mountain block and mountain front settings through ephemeral streams,
with little or no recharge in inter-stream basin floor settings.
• 0.4 percent ofprecipitation on the Pajarito Plateau of northern New Mexico beneath a
pinon juniper cover within the shallow subsurface soils. This localized recharge rate (0.2
mm/yr) was estimated using cumulative chloride water plots. The major source of
recharge at this location is derived from snowmelt and spring rains.
• 0.02 to 2 percent ofprecipitation for the High Plains in the Texas panhandle. Vadose
zone modeling studies found that focused higher recharge rates (11 mm/yr) occur
beneath ephemeral lakes andplayas while little to no recharge (<0.1 mm/yr) in inter-
playa settings.
• 1 to 6 percent of precipitation for the Black Mesa basin in northeastern Arizona. This
regional recharge rate (5 to 20 mm/yr) was estimated using carbon-14 age dating
combined with a coupled carbon-14 flow and transport model This recharge rate was
independently verified using chloride mass balance. The aquifer is recharged seasonally
from precipitation in the highlands principally during the winter and spring, with less
recharge at lower elevations.
Based on the measurements reported above a recharge rate assuming 1 percent of the average
annual amount ofprecipitation (approximately 3 mm/yr) is justifiedfor use in determining the
initial conditions of the bedrock vadose zone. This assumption is further supported by numerical
modeling completed by Scanlon et al. (2003) for conditions of a single deep borehole located in
the High Plains of Texas. Their model simulations suggest that water potential and chloride
profiles at depth are out of equilibrium with current climatic forcing, and reflect Pleistocene
climate conditions Current water fluxes in the shallow subsurface, which developed over
thousands of years, currently are upward. Their simulations further suggest that the drying front
was initiated during the Pleistocene/Holocene climate shift, and that chloride concentrations at
69
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depth are low, which suggests that water fluxes during the Pleistocene were quite high on the
order of 1.3 mm/yr while Holocene recharge rates are negligible at <0.1 mm/yr.
Comparison of Water Content and Pressure Head Profiles
The volumetric water content throughout the vadose zone beneath Cells 2 and 3 during the
operational, dewatering, and post-closure steady-state timeframes is plotted in Figure 4-4 ofthe
2010 Revised ICTM Report. A comparison between water contents and pressure head is plotted
below (see Figure 05/1/8-1). The synoptic timeframes plotted correspond to maximum head
conditions (13 and 23 years), the end of dewatering (33 years), and post-closure steady-state
(100 and 240 years). The change in subsurface hydraulic conditions during the assumed
maximum tailings seepage duration from 0 through 23 years is evident by the increasing VWC
and decreasing pressure head within the shallow vadose zone (less than 5 meters depth). In
response to dewatering and reduced potential seepages rates, the VWC and pressure head
conditions within the vadose zone become drier and eventually reach steady state conditions.
The nearly identical profiles after 100 and 240 years indicate that steady state flow conditions
have developed in the bedrock vadose zone. "
"Response 9 (Mav 31. 2012):
In the 2010 Revised ICTM Report sulfate is not transported as a conservative species. Sulfate is
allowed to sorb onto HFO and precipitate as gypsum. Sulfate concentrations within the bedrock
vadose zone are predominately dictated by mineral precipitation reactions, as noted in Figure
M-3. Even though the precipitation ofgypsum results in a faster transport rate compared to
uranium, sulfate nonetheless, is retarded. Therefore, the most applicable conservative species for
comparison of uranium sorption/retardation would be with chloride or fluoride.
The distribution coefficient (Kd) in units of milliliters per gram (mL/g) and the corresponding
retardation factor (Rf) in dimensionless units, as calculatedfrom the output ofthe reactive
transport model after 240 years, are summarized below for the conditions represented in Figure
M-4 (see Table 05/1/9-1). Data below 2.3 meters depth are not tabulated since the concentration
of uranium in pore water was less than 0.005 mg/L.
The calculated Kd values ranged between approximately 0.002 to 1.5 mL/g corresponding to
calculated Rf values between approximately 1 and 41. The calculated Rf values suggest that
uranium is moving at about the same rate as groundwater for acidic pH conditions and 41 times
slower than groundwater for near-neutral pH conditions.
A comparison between calculated Kd values listed above, and those presented in the literature
need to be made with some caution. This is because of the site-specific nature ofthe values
calculated using the results of the reactive transport model may not directly correlate with other
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TECHNICAL MEMORANDUM
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studies. Krupka et al (1999) summarized measured Kd values for uranium for the following pH
values:
• pH 3 a minimum Kdof < 1 mL/g.
• pH 5 a minimum Kd of 25 mL/g.
• pH 7 a minimum Kd of 63 mL/g.
Significant research has investigated Kd values at the Naturita site in Colorado for a variety of
test conditions. For example, the geometric mean Kd value for measurements in Curtis et al
(2006) is approximately 1.6 mL/g covering a range between 0.55 and 12.5 mL/g for sediments
suspended in wells at the Naturita field site at near-neutral pH For comparison, the average Kd
value for the reactive transport model at near-neutral pH is approximately 0.43 mL/g. The
minimum Kd values presented by Krupka et al (1999) are orders of magnitude higher than the
Kd values calculated using the output of the reactive transport model while the Kd values
presented by Curtis et al (2006) are approximately a factor offour higher. The model calculated
Kd values for the iron redox couple scenario (defined in the response to comment six of this
interrogatory) varies between calculated values hovering around 10 mL/g. Therefore, the
sorption and attenuation of uranium is reasonably represented by simulations using the reactive
transport model Approximately 0.5 and 18 mL/g within the upper 0.75 meters with the majority
of the calculated values hovering around 10 mL/g. Therefore, the sorption and attenuation of
uranium is reasonably represented by simulations using the reactive transport model "
Table for Response 9 (May 31, 2012):
Table 05/1/9-1. Calculated distribution coefficients and retardation factors as a function of
depth after 240 years.
Depth (m) pH (s.u.) Aqueous U
Cone. (mg/L)
Volumetric
Water
Content (-)
Kd (mL/g) Rf(-)
0-0.15 3.2 21 0.073 0.0015 1,.04
0.20-0.45 4.7 12 0.073 0.68 20
0.50-0.70 4.7 3.1 0.074 0.87 25
0.75-2.15 4.9 0.38 0.074 1.5 41
1.0-2.15 7.3 0.073 0.075 014 4.6
2.2-2.3 7.3 0.015 0.076 0.72 20
Note: Values summarized above were calculated as the arithmetic average of simulated values
within the noted depth interval for conditions represented by Figure M-4.
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"Response 10 (May 31, 2012):
The results plotted in Figures M-3 and M-4 were meant to illustrate concentration profiles after
various times, and not the source term concentration. The concentration at the upper boundary
(0 centimeters depth) is a function of the applied boundary condition (mass flux rate equal to
time variable flux multiplied by the concentration); therefore, plotting the source term
concentration would be contradictory to the boundary condition implemented at the upper
surface and likely would be a source of confusion. The initial source term concentrations are
summarized in Table M-1, which the reader can easily transfer to Figures M-3 and M-4 if
necessary.
"Response 11 (May 31. 2012):
The decrease in uranium concentration (approximately 0.7 mg/L) within the upper 15
centimeters from 50 years to 100 years is attributed to subtle differences in sorbed
concentrations. The increase in uranium concentration from 100 years to 240 years
(approximately 7 mg/L) is attributed to decreased sorption from increased surface site loading
resulting from increased total mass released into the vadose zone.
5.3 Division's Assessment of EFR Responses to Rd 1 Interrogatory White Mesa Revised
ICTM Report; R313-24-4; 10CFR40 Appendix A, Criterion 6(1); INT 01/1
Response 1
Based on a review of the EFR Response, the clariflcation regarding the primary and
duplicate sample pairs is useful and the explanation regarding duplicates in this Response
should be included in the revised ICTM report. However, the sample statistics, particularly
ANP ranges derived from the geometric mean and standard deviation appears to be in
error. The apparent error is based on a misconception concerning the use of the geometric
mean and tne geometric standard deviation in describing the spread or disti ibutiun uf the
data. EFR states on page C-7 of Appendix C that "to support the sensitivity analysis, and
determine a range of values for the amount of ANP, the geometric mean plus one geometric
standard deviation was selected for an upper bound, while the geometric mean minus one
standard deviation was selected as a lower bound. The geometric mean plus one geometric
standard deviation corresponds to approximately 68yo of the observations." These are
incorrect approaches to use with lognormally distributed data. To And the proper
bounding limits, the geometric mean must be multiplied (or divided) by the geometric
standard deviation. Naturally log-normally distributed data have an asymmetric
distribution and different values for mode, median and mean.
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TECHNICAL MEMORANDUM
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Adding the same value on either side of the mean, as EFR has done, does not properly
characterize the interval containing 68.3% ofthe data. Bleam (2011)' explains the concept:
"Log-normal distributions are asymmetric about the geometric mean. The lower limit of a
range covering 68.3% ofthe population is the geometric mean divided by the geometric
standard deviation while the upper limit is the geometric mean multiplied by the geometric
standard deviation." Thus, the approach used in the Revised ICTM Report is not
statistically correct; it does not follow standard professional practice. The natural data
need to be flrst transformed by taking their logarithms, the transformed data need to be
tested for normality, the mean and standard deviation of the transformed data need to be
calculated, and then these intermediate parameters need to be exponentiated to obtain the
geometric mean (GM) and the geometric standard deviation (GSD). The value of the lower
bound of the population interval containing the central 68.3% of the data is equal to the
geometric mean divided by the geometric standard deviation (GM/GSD) ; the upper bound
is equal to geometric mean multiplied by the geometric standard deviation (GM*GSD). A
similar issue exists for the HFO data.
An example is provided for ANP at Well MW-24. There are 9 data points. Thus, N-1 = 8.
As indicated in Table C-15, the arithmetic mean is 7. The standard deviation is 7.68. The
geometric mean (GM) is 5.17. The geometric standard deviation (GSD) is 2.06. The
geometric mean is an appropriate measure of central tendency for the data, assuming that
the ANP data are lognormally distributed. The lower bound of the interior 68.3% data-
dispersion interval is the quotient of the geometric mean divided by the geometric standard
deviation. This quotient is equal to 2.51 mg CaCOj/kg rock. The upper bound of the
interior 68.3% data-dispersion interval is the product ofthe geometric mean and the
geometric standard deviation. This product is equal to 10.7 mg CaCOj/kg rock. Thus,
again assuming log-normality, the interior 68.3% ofthe data in the actual population
should statistically fall within the range 2.51 to 10.7 mg CaCOs/kg rock. Within the sample
population, six of nine values, or 67%, fall in that estimated range, which is in excellent
agreement with the theoretical value for the population.
Thus, the results uf ICTM mudel sensitivity runs for ANP arc in error because they do not
account for a sufflciently wide distribution of data. Accordingly, please correct all incorrect
statistical calculations, and re-run the model sensitivity analysis for ANP and HFO using
the lognormal distribution and the correct distribution parameters. Alternatively, the most
conservative (i.e., the lowest) ANP or HFO values can be used in the model. A value of the
geometric mean divided by two geometric standard deviations can be used. This will give a
limit or bound above which 95.5% of the data values in the population should exist. Only
4.4% ofthe data values in the population should be less. Revise, as appropriate, the text,
tables, and figures in the revised ICTM report and Appendix C to correct any statistical
' Bleam, W.F.,2011, Environmental Soil Chemistry, Academic Press, 496 pp.
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errors that may be present for ANP and HFO. Furthermore, revisit the statistics for any
other data that have a lognormal distribution and determine the correct, as appropriate,
upper and lower bounds of the data determined using geometric means and standard
deviations.
As an aside, a minor editorial clariflcation is needed on page M-10 where it is stated that
"the amount of ANP present in the bedrock vadose zone was reported as grams of calcite
(CaCOa) per kilogram or rock." P'lease note that the original data reported in Appendix A
are not reported using these particular units, although the units reported are equivalent.
The text should be revised to reflect the actual reported units and the subsequent
conversion to equivalent units used to develop the model input parameters.
Response 2
Based on a review of the EFR Response, the approach discussed concerning the initial
geochemical conditions in vadose zone pore water where only calcium, carbonate, and DO
(2 mg/L) at concentrations representing equilibrium with calcite and HFO is reasonable
and is supported by the solid phase data available for the vadose zone bedrock and DO
data available for the underlying groundwater. An assumption that redox is controlled by
the oxygen couple and the concentrations of other constituents is zero is also reasonable
and provides for a conservative simulation of constituent transport. The discussion
provided in the Response should be included in the revised ICTM report to justify the
initial geochemical conditions assumed for the vadose zone pore water.
Response 3
Based on a review of the EFR Response, using aluminum to obtain a charge balance in the
PHREEQC modeling appears to be reasonable for cation deficient solutions. The
explanation provided in the Response should be included in the revised ICTM report for
clarity.
Response 4
The Divisiun request that EFR provide additiunal iiifurmatiun legaiding the putential
locations and distribution of fractures in the area beneath and downgradient of the tailings
management cells area based on the information discussed below.
The interpretation provided in EFR's response above is similar to that presented in
previous correspondence submitted by the Licensee in response to Round 1 Interrogatories
submitted by on the Cell 4B Environmental Report (DUSA 2009). In that Response, the
Licensee provided a letter, dated November 10, 2009, from Hydro Geo Chem which
indicated that the reported sub-horizontal, limonite-stained features interpreted in the
1978 ER (Dames & Moore 1978) as bedding plane fractures may not be actual fractures
but may represent structurally weaker zones along bedding planes that appear as partings
in core samples. According to the Hydro Geo Chem report, examination of core samples
collected during drilling of angle borings beneath tailings Cells 3 and 4A indicate that
where fractures were present in cores, they were cemented with gypsum. They indicated
that open fractures significant enough to impact groundwater movement in the perched
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TECHNICAL MEMORANDUM
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zone were not identified in that investigation. Hydro Geo Chem also concluded that no
fractures were reported in cores from MW-3A, MW-16, or MW-23, the existing wells
adjacent to or at the current location of Cell 4B. Hydro Geo Chem concluded that this
made it even less likely that potentially undetected fractures could significantly affect
subsurface fluid flow in the vicinity of proposed Cell 4B, and that, should the sub-
horizontal features reported in the 1978 ER actually represent fractures, their sub-
horizontal nature would prevent them from acting as vertical conduits from the tailing cell
to the perched groundwater.
The Licensee also previously referred to the same Hydro Geo Chem Letter Report dated
February 8, 2010 ('HGC, 2010a') that provided additional information and also
recommended the installation of new monitoring wells MW-33 and MW-34 in the area of
Cell 4B. These wells, as proposed, would be screened across the perched zone. In a meeting
with the Division on February 18, 2010, the Licensee agreed to install three new wells,
including a third monitoring well, MW-35, adjacent to the western edge of Cell 4B. New
well MW-35 was proposed to help further define subsurface conditions and potential
groundwater migration patterns downgradient of proposed Cell 4B.
The Division incorporated a new Permit condition requiring that a minimum of three
additional downgradient groundwater monitoring wells be installed near Cell 4B. The
Division requests that additional geologic data available from the wellbores for these three
wells (MW-33 through MW-35) be evaluated and interpreted with respect to the additional
information that these wells borings provide regarding the potential occurrence and
distribution of fractures and conglomeratic zones downgradient of the Cell4 B/tailings
management cells area. EFR should supplement and/or revise the interpretation provided
in the Response above to reflect the results of their evaluation of this additional wellbore
data.
Response 5
Based on a review of the EFR Response, a question arises as to why a dry bulk density of
'1
used for selecting a bulk density value of 2.0 g/cm for bedrock for use in converting ANP
and HFO values from rock mass to rock unit volume. Discuss locations of core samples
considered with respect to: (1) locations of core boreholes with respect to the different
disposal cells; and (2) the depth intervals of the core sample intervals considered with
respect to the thickness of the vadose zone at each core interval location. Further justify the
value of bulk density chosen (or different bulk density values that may be selected for use
at different locations), including need for excluding from consideration any core interval(s)
that lie within the saturated zone (e.g.. See Table C-3 in Appendix C ofthe Revised ICTM
Report). Please revise any affected calculations, re-run the model, and revise the ICTM
report, as appropriate.
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Response 6
Based on a review of the EFR Response, the approach discussed concerning the DO
concentration in the tailings pore water is reasonable and is supported by the geochemical
data available for the tailings pore water. The results suggest that the flxed DO condition is
likely more conservative as it predicts uranium to be transported to greater depths than
redox value determined using nitrogen and iron species. The decreased uranium transport
under the iron redox couple scenario is likely due to increased sorption on HFO
precipitated in the vadose zone. The discussion provided in the Response should be
included in the revised ICTM report to justify the initial DO concentrations selected.
Response 7 ^
Based on a review of the EFR Response, the chloride diffusion coefflcient selected to
represent all solutes in the model is reasonable. The sensitivity analysis provided in the
Response suggests that the selected diffusion coefflcient likely overestimates the diffusive
transport depth of most of the solutes simulated. The discussion provided in the Response
should be included in the revised ICTM report to justify the diffusion coefflcient selected.
Response 8
' Based on a review of the EFR Response, the discussion provided outlines recharge rates for
relatively comparable environments to White Mesa and suggests that regional recharge
rates can vary from 0.1 to 6 percent of average annual amount of precipitation. However,
EFR's justiflcation for assuming 1 percent of the average annual amount of precipitation is
not clear. It appears based on the studies cited in the Response that the assumed 1 percent
recharge rate used in the model is on the lower end of the recharge rates reported for
similar sites. In fact, the recharge rate chosen for the model appears to be up to 5 times less
than average annual recharge rates reported for similar sites located on the Colorado
Plateau (Healy 2010^). Additional justiflcation for selecting a recharge rate equal to 1
percent of the average annual amount of precipitation should be provided or sensitivity
analyses varying the initial average annual recharge rate within a reasonable range (e.g., 1
to d percent; snouid De pertormed to demonstrate tne sensitivity oi the model results to tne
initial volumetric water contents and pressure head distributions.
The comparison of volumetric water content and pressure head proflles provided in the
Response appears to reasonably demonstrate that the post-closure volumetric water
contents and pressure heads reach steady state in about 100 years, given the assumed initial
recharge rate of 1 percent, the assumed maximum head conditions estimated for the
operation of Cells 2 and 3 and the subsequent estimated dewatering rate used in the model.
The discussion provided in the Response, as well as any additional sensitivity analyses of
^ Healy, R. W., 2010, Estimating Groimdwater Recharge, Cambridge University Press, United Kingdom, 245 pp,
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TECHNICAL MEMORANDUM
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the assumed initial recharge rate, should be included in the revised ICTM report to justify
the initial water content and pressure head distributions selected for the flow model.
Response 9
Based on a review of the EFR Response, the explanation provided is reasonable and should
be included in the revised ICTM report for clarity. The revised ICTM report should
further indicate
Response 10
Based on a review of the EFR Response, the explanation provided is reasonable and should
be included in the revised ICTM report for clarity.
Response 11
Based on a review of the EFR Response, the explanation provided is reasonable and should
be included in the revised ICTM report for clarity. Further discussion should be provided
regarding the relative degree or percentage of loading predicted for the surface sites and its
impact on sorption of uranium as well as other constituents.
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REFERENCES
Abraham, J.D. and W.J. Waugh, 1995. Technical Task Cover Sheet, Re: Cover Drainage and
Leakage Rate Estimation Using the HELP 3.1 Code, Prepared March 10, 1995.
Abt, S.R., Thomton, CL, Gallegos, H., and Ullmann, C. 2008. "Round-Shaped Riprap
Stabilization in Overtopping Flow," Joumal of Hydraulic Engineering, Vol. 134, No. 8, August
2008, pp. 1035-1041.
AccuGeo (2012) PVC liners. Retrieved June 2012 from wvyw.accugeo.com/products/pvc.htm.
Allen, R.G., L.S. Pereira, D. Raes, and M. Smith, 1998. FAO Irrigation and Drainage Paper, No.
56, Crop Evapotranspiration (Guidelines for Computing Crop Water Requirements), FAO - Food
and Agriculture Organization of the United Nations, Rome, Italy, pp. 300.
Albright, W.H., CH. Benson, G.W. Gee, A.C Roesler, T. Abichou, P. Apiwantragoon, B.F.
Lyles, and S.A. Rock, 2004. Field Water Balance of Landfill Final Covers. Joumal of
Environmental Quality 33:2317-2332.,
Albright, W.H., Waugh, W.J., and Benson, CH. 2007. "Altemative Covers: Enhanced Soil
Water Storage and Evapotranspiration in the Source Zone." Enhancements to Natural
Attenuation: Selected Case Studies, Early, T.O. (ed), pp 9-17. Prepared for U.S. Dept. of Energy
by Washington Savannah River Company, WSRC-STI-2007-00250. URL:
http://vyvyw.dri.edu/images/stories/research/programs/acap/acap-publications/10.pdf.
Badv, L. and M. Mahmoudi, 2009. The study of moisture and contaminant migration through
soil. Paper presented at the 33rd Intemational Association of Hydraulic Engineering & Research
(lAHR) Congress: Water Engineering for a Sustainable Environment.
Barth, G. R., fllangasekare, T. H., Hill, M. C. and Rajaram, H. 2001. A New Tracer-Density
Criterion for Heterogeneous Porous Media, Water Resources. Research, v. 37, p. 21-31.
Bartos, D.L. and Sims, P.L. (1974) Root dynamics of a shortgrass ecosystem, Joumal of Range
Management, v. 27, p. 33 - 36.
Bear, J. 1972. Hydraulics of Cjroundwater. McGraw-Hill, New York.
Benson, C, Hardianto, F., and Motan, E., 1994. "Representative specimen size for hydraulic
conductivity of compacted clay," Hydraulic Conductivity and Waste Containment Transport in
Soils: ASTM STP 1142, S. Trautwein and D. Daniel, eds., ASTM , Philadelphia, Pa., p. 3-29.
Benson,C.H., Gunter, J.A., Boutwell, G.P., Trautwein, S.J., and Berzanskis, P.H. 1997."
Comparison of Four Methods to Assess Hydraulic Conductivity", Joumal of Geotechnical and
Geoenvironmental Engineering, October 1997, Vol. 123, No. 10 pp. 929-
Benson, C.H., S.H. Lee, X. Wang, W.H. Albright, and W.J. Waugh, 2008. Hydraulic Properties
and Geomorphology of the Earthen Component of the Final Cover at the Monticello Uranium
Mill Tailings Repository, Geo Engineering Report No. 08- 04.
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:
78
TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
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.
Benson, Craig, 2012. Electronic communication from Craig Benson, University of Wisconsin-
Madison, to Melanie Davis, MWH Americas, Inc., Regarding Evaluation of Gradations
Performed for Potential Cover Soils for White Mesa, May 20.
Benson, C.H., and Wang, X. 2012. Index Properties of Soils From Blanding, Utah. Geotechnics
Report No. 12-37, Wisconsin Geotechnics Laboratory. University of Wisconsin-Madison. May
20, 2012.
Bleam, W.F.,2011, Environmental Soil Chemistry, Academic Press, 496 pp
Bolen, M.M., A.C Roesler, CH. Benson, and W.H. Albright, 2001. Altemative Cover
Assessment Program: Phase II Report. Geo Engineering Report 01-10, Department of Civil and
Environmental Engineering, University of Wisconsin-Madison.
Brown, R.W. 1995. The Water Relations of Range Plants: Adaptations to Water Deficits, In:
Bediinah, D.J. and R.E. Sosebee (eds.), Wildland Plants: Physiological Ecology and /
Developmental Morphology, Society for Range Management, Denver, Colorado, pp. 291-413.
Campbell, G.S. and Harris, G.A. (1977) Water relations and water use pattems iox Artemisia
tridentate nutt. in wet and dry years. Ecology, v. 58, p. 652-659.
Cedegren.H.R. 1989. Seepage, Drainage, and Flow Nets. 3rd Edition. John Wiley $ & Sons, Inc.,
New York, NY.
Chabot, B.F. and H.A Mooney 1985. Physiological Ecology of North American Plant
Communities. Chapman and Hall. New York, NY.
CLI (2010) Design Notes, PVC Geomembranes, Colorado Lining Intemational, Parker, CO.
Retrieved June 2012 from http://www.coloradolining.com/products/pvc.htm.
QJRWA (Ccntoi4br Nuclear Waste Regulator)^ Analyoio) 2005. x\nalyoio of Factors
Contributing to Uncertainty in Estimating Future Climates at Yucca Mountain. San Antonio,
Texas. Revised November 2005.
Coats, S., Smerdon, J.E., Seager, R, Cook, B.I., and Gonzalez-Rouco, J.F. 2012. Megadroughts
in Southwestem North America in ECHO-G Millennial Simulations and their Comparison to
Proxy Drought Reconstructions. Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades,
NY.
Cook, CW. and Lewis, CE. (1963) Competition between big sagebrush and seeded grasses on
foothill ranges in Utah, Joumal of Range Management, v. 16, p. 245-250.
Cook, E. R., R. Seager, R. R. Heim, R. S. Vose, C. Herweijer, and C. A. Woodhouse, 2009:
Megadroughts in North America: Placing IPCC Projections of Hydroclimatic Change in A Long-
Term Paleoclimate Context. Joumal of Quatemary Science, 25, doi:10.1002/jqs.
79
TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
Cook, B.J., Cook, E.R., Anchukaitis , K.J., Seager, R., and Miller,R.L. 2010. Forced and
Unforced Variability of Twentieth Century North American Droughts and Pluvials. Climate
Dynamics. DOI 10.1007/s00382-010-0897-9. Springer 2010.
Curtis, G.P., J.A. Davis, and D.L. Naftz (2006) Simulation of reactive transport of uranium(VI)
in groundwater with variable chemical conditions, Water Resources Research, 42, W04404,
doi: 10.1029/2005WR003979.
Dai, D., Barmaco, F.T., Jr., and Illangasekare, T.H. 2001. Partitioning and Interfacial Tracers
for Differentiating NAPL Entrapment Configuration: Column-Scale Investigation, Environ. Sci.
Technol., v. 35, p. 4894-4899.
Dames & Moore 1978. "White Mesa Uranium Project, San Juan County, Utah" Environmental
Report prepared for Energy Fuels Nuclear, Inc., January 30, 1978.,
D'Appolonia, 1979. Engineers Report, Tailings Management System, White Mesa Uranium
Project, Blanding, Utah. Prepared for Energy Fuels Nuclear, Inc. June.
Denison Mines (USA) Corp. 2009. White Mesa Uranium Mill - [Response to] First Round of
Interrogatories from Amendment Request and Environmental Report for Cell 4B, December 23,
2009.
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.
Denison Mines (USA) Corp. 2012a. Responses to Interrogatories - Round 1 for Reclamation
Plan, Revision 5.0, March 12. May 31, 2012.
Denison Mines (USA) Corp. 2012b. Responses to Interrogatories - Round 1 for Reclamation
Plan, Revision 5.0, March 12. August 15, 2012.
-BeWtspelarc, A.PL., L.T. Horrcn, M.P. Miklas, and P^.T. Clemen. "Expert Elicitation of Future
Climate in the Yucca Mountain Vicinity." CNWRA 93-016. San Antonio, Texas: CNWRA.
1993.
Dwyer, S.F. 1998. Constmction Costs of Six Landfill Cover Designs. SAND98-1988. Sandia
National Laboratories, Albuquerque, New Mexico.
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://vy\vw.lanl.gov/environment/cleanup/req docs.shtml
Energy Fuels Nuclear, Inc. 1983. Constmction Report, Second Phase Tailings Management
System, White Mesa Uranium Project, SUA-1358, Docket 40-8681.
Enviroconsystems (2012) Polyvinyl Chloride, Materials, From
http://w^ww.enviroconsvstems.com/materials.htm
80
TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
Foxx, T.S. and G. D. Tiemey, G.D. (1984) Rooting depths of plants relative to biological and
environmental factors. Los Alamos National Laboratory report LA-10253-MS.
Foxx, T.S. and Tiemey, G.D. (1985) Rooting pattems in the pinyon-juniper woodland, in
Pinyon-Juniper Symposium, Reno, NV, USA, 12 Jan 1986, OSTI ID 6387432, 12 pp.
Gill, R., Burke, I.. Milchunas, D.. and Lauenroth, W. 1999. Relationship Between Root
Biomass and Soil Organic Matter Pools in the Shortgrass Steppe of Eastem Colorado.
Ecosystems 2: 226-236.
Goodvsdn, D.L. (1956) Autoecological studies of Artemisia tridentata nutt, Ph.D. thesis, State_,
College of Washington (L.C. Card No. Mic 57-775), 79 p. Univ. Microfilms. Arm Arbor, Mich.
(Dissertation Abstr., v. 17, p. 487).
Hakonson, T.E. (2002) Review of Sandia National Laboratories/New Mexico Evapotranspiration
Cap Closure Plans for the Mixed Waste Landfill, Prepared for Citizen Action 2/15/02.
Hansen, E., Schwarz, F., and Riedel, J. 1984. Probable Maximum Precipitation Estimates,
Colorado River and Great Basin Drainages. Hydrometeorological Report No. 49. U.S
Department of Commerce, National Oceanic and Atmospheric Administration, Reprinted 1984.
Hauser, V.L., Weand, B.L., and Gill, M.D. 2001. Altemative Landfill Covers. July 2001.
Hauser, V.L. and D.M. Gimon, 2004. Evaluating Evapotranspiration (ET) Landfill Cover
Performance Using Hydrologic Models, Report Prepared for the U.S. Air Force Center for
Environmental Excellence, January 2004.
Hopkins, H. 1953. Root Development of Grasses on Revegetated Land. Joumal of Range
Management. Vol. 6, pp, 382-392.
Hu, Q. and J.S.Y. Wang, 2003. Aqueous-phase diffusion in unsaturated geologic media: A
review. Critical Reviews in Environmental Science and Technology, 33(3):275-297.
Hunt, B. G., 2011. Global Characteristics of Pluvial and Dry Multi-Year Episodes With
Emphasis on Megadroughts. Intemational Joumal of Climatology, 31, pp. 1425-1439.
Hurst, T.G, and D.K. Solomon, 2008. Summary of Work Completed, Data Results,
Interpretations, and Recommendations for the July 2007 Sampling Event at the Denison Mines,
USA, White Mesa Uranium Mill, near Blanding, Utah. Prepared for the Utah Division of
Radiation Control. May.
Hurst, G. 2012. Email correspondence from Greg Hurst, University of Utah, to Ryan
Jakubowski, MWH Americas, Inc. April 22.
Hydro Geo Chem, Inc. (HGC), 2010a. Letter from Stewart J. Smith of Hydro Geo Chem, Inc. to
David Frydenlund, Esq. of Denison Mines. Febmary 8.
Hydro Geo Chem, Inc. (HGC), 2010b. Letter from Stewart J. Smith of Hydro Geo Chem, Inc. to
David Frydenlund, Esq. of Denison Mines. Febmary 12.
Interstate Technology & Regulatory Council (ITRC), 2003. Technical and regulatory guidance
for design, installation, and monitoring of alternative final landfill covers. Report Prepared by
81
TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
Prepared by the Interstate Technology & Regulatory Council Altemative Landfill Technologies
Team, December 2003.
Jackson, R.B., Canadell, J., Ehleringer, J.R., Mooney, H.A., Sala, O.E. and Schulze, E.D. (1996)
A global analysis of root distributions for terrestrial biomes, Oecologia, v. 108, p. 389-411.
Jacques, D., and J. Simunek, 2005. User Manual of the Multicomponent Variably-Saturated
Flow and Transport Model HPl, Description, Verification and Examples, Version 1.0,
SCK-CEN-BLG-998, Waste and Disposal, SCK-CEN, Mol, Belgium, 79 pp., 2005.
Jensen, D. 1995. Probable Maximum Precipitation Estimates for Short Duration, Small Area
Storms in Utah - March 2003. Utah Climate Center . October 1995.
Jensen, D. 2003. Final Report. 2002 Update for Probable Maximum Precipitation, Utah 72 Hour
Estimates to 5,000 mi^. Utah Climate Center.
Keamey, T.H., Briggs, L.J., Shantz, H.L., McL^e, J.W. and Piemeisel, R.L. (1914) Indicator
Significance of Vegetation in Tooele Valley, Utah, p. 365-418, Joumal of Agricultural Research,
V. 1, October, 1913-March, 1914, Department of Agriculture, Washington, D.C, 534 pp.,
retrieved October 2012 from http://naldc.nal.usda.gov/download/IND43965418/PDF .
Khire, M.V., CH. Benson, and P.J. Bosscher, 2000. Capillary Barriers: Design Variables and
Water Balance, Joumal of Geotechnical and Geoenvironmental Engineering, 126(8):965-708.
Kirby, S., 2008. Geologic and hydrologic characterization of the Dakota-Burry Canyon Aquifer
near Blanding, San Juan County, Utah, Special Study 123, Utah Geological Survey.
Kleinfelder, 2009. Tailings Cell Closure Design Report. Pinon Ridge Project, Montrose County,
Califomia. Rev. 0, Febmary 13, 2009.
Kmpka, K.M., D.I. Kaplan, G. Whelan, R.J. Seme, and S.V. Mattigod (1999) Understanding
variation in partition coefficient, Kd, values Volume II: Review of Geochemistry and Available
Kd Values for Cadmium, Cesium, Chromium, Lead, Plutonium, Radon, Strontium, Thorium,
Tritium (3H), and Uranium, U.S. Environmental Protection Agency 402-R-99-004B.
Kushnir, Y., R. Seager, M. Ting, N. Naik, and J. Nakamura, 2010. Mechanisms oj Tropical
Atlantic SST Influence on North American Hydroclimate Variability. Joumal of Climate, 23, pp.
5610-5628.
Langmuir, D., 1997. Aqueous Environmental Geochemistry, Prentice-Hall.
Lee, C.A., and Lauenroth, W.K. 1994. Spatial Distributions of Grass and Shrub Root Systems in
the Shortgrass Steppe. The American Midland Naturalist 132: 117-123.
Li, Y-H. and S. Gregory, 1974. Diffusion of Ions in Sea Water and Deep-Sea Sediments,
Geochemica et Cosmochemica Acta 38:703-714.
MacDonald. G.M. 2010. Water, Climate Change, and Sustainability in the Southwest, PNAS,
December 14, 2010, Vol. 107, No. 50, pp. 21256-21262. URL:
http://www.pnas.Org/cgi/doi/l0.1073/pnas.0909651107 .
82
TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
Mooers, J.D. and Waller, D.H. 1997. On-Site Wastewater Management in Nova Scotia, Final
Report, On-Site Wastewater Research Program, Phase III 1994-1996, Centre for Water
Resources Studies, Technical University of Nova Scotia, Nova Scotia, Canada.
Morrison-Knudsen Environmental Corporation 1993. UMTRA Naturita, Embankment Design,
Settlement Analysis and Cracking Potential Evaluation. Calc. No. 17-740-02-01. May.
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, 134 pp.
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, OR]<IL/TM-10067. June 1986, 151 pp.
Nigam, S., B. Guan, and A. Ruiz-Barradas, 2011. Key Role of the Atlantic Multidecadal
Oscillation in 20th Century Drought and Wet periods Over the Great Plains. Geophysical
Research Letters, 38, doi:10.1029/ 2011GL048 650.
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.
Petersen, K.L. 1994. A Warm and Wet Little Climatic Optimum and a Cold and Dry Little Ice
Age in the Southem Rocky Mountains, U.S.A. Climatic Change, Vol. 26, pp, 243-269. Kluwer
Academic PubHshers, 1994.
Phoenix, D.A. (1955) Occurrence and chemical character of ground water in the Morrison
formation in southwestem Colorado and southeastem Utah. Retrieved October 2012 from
http://pubs.usgs.gov/tei/320/report.pdf
Reynolds, T.D. and Fraley, L. (1989) Root profiles of some native and exotic plant species in
southeastem Idaho. Environmental and Experimental Botany, v. 29, p. 241-248.
Rogers, V.C, and Nielson, K.K. 1991. "Correlations for Predicting Air Permeabilities and Rn-
222 Diffiision Coefficients of Soils", Health Physics, Vol. 61, No. 2, pp. 225-230.
Scanlon, B.R., K. Keese, R.C Reedy, J. Simunek, and B.J. Andraski, 2003. Variations in flow
and transport in thick desert vadose zones in response to paleoclimatic forcing (0-90 kyr): Field
measurements, modeling, and uncertainties. Water Resources Research, 39(7), 1179,
doi: 10.1029/2002WROO1604.
Scanlon, B.R., K.E. Keese, A.L. Flint, L.E. Flint, CB. Gaye, W.M. Edmunds, and I. Simmers,
2006. Global synthesis of groundwater recharge in semiarid and arid regions, Hydrological
Processes, 20: 3335-3370.
Shantz, H. L., and Zon, R. (1924) Natural vegetation, the physical basis of agriculture, U. S.
Dept. Agr. Atias, Am. Agr. I (E).
83
TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
Schenk, H.J. and Jackson, R.B. (2002) Rooting depths, lateral root spreads and below-
ground/above-ground allometries of plants in water-limited ecosystems, J. of Ecology, v. 90, p.
480-494.
Schwartz, F., and H. Zhang, 2003. Fundamental of Groundwater, John Wiley & Sons, New
York, NY.
Schwinning, S., J. Belnap, D. R. Bowling, and J. R. Ehleringer. 2008. Sensitivity of the Colorado
Plateau to Change: Climate, Ecosystems, and Society, geology and Society 13(2): 28. URL:
http://vyvyw.ecologvandsocietv.org/voll3/iss2/art28/main.html.
Seager R, et al.X2007) Model Projections of an Imminent Transition to a More Arid Climate in
Southwestem North America. Science 316: pp. 1181-1184.
Seager, R., Y. Kushnir, M. Ting, M. A. Cane, N. Naik, and J. Velez 2008. Would Advance
Knowledge of1930s SSTs Have Allowed Prediction of the Dust Bowl Drought! Joumal of
Climate, 21, pp. 3261-3281.
Seager, R. and Vecchi. G.A. 2010. Greenhouse Warming and the 21st Century Hydroclimate of
Southwestem North America. PNAS, December 14, 2010 , Vol. 107, No. 50, pp. 21277-21282.
URL: http://wvyw.pnas.org/cgi/doi/l 0.1073/pnas.0910856107 .
Sims, P.L. and Singh, J.S. (1978) The stmcture and function of ten westem North American
grasslands: II. intra-seasonal dynamics in primary producer compartments, Joumal of Ecology,
V. 66, p. 547-572. Smesmd, J.A., Benson, C.H., Albright, W.H., Richards, J.H., Wright, S., and
Goodrich, K. 2012. Using Pilot Test Data to Refine an Altemative Cover Design in Northem
Califomia. Intemational Joumal of Phytoremediation, Vol. 14, Supplement 1, p.. 76-93.
Sturges, D. L. (1977) Soil water withdrawal and rooting characteristics of individual big
sagebmsh plants, American Midland Naturalist, v. 98, p. 257-274.
Tabler, R.D. (1964) The root system of Artemisia tridentata at 9,500 feet in Wyoming, Ecology,
V. 45, p. 630-636.
Temple, D.M., Robinson, K.M., Aliiing, R.M., and Davis, A.G. 1987. Stability Design uf Giass-^
Lined Channels. U.S. Department of Agriculture, Agricultural Handbook No. 667, U.S.
Government Printing Office, Washington, D.C, 167 pp.
Thomton, C, and Abt, S. 2008. ''Gully Intrusion into Reclaimed Slope: Long-Term Time-
Average Calculation Procedure'', Joumal of Energy Engineering, Vol. 134, No. 1, March 2008,
pp. 15-23.
Tinjum, J., C. Benson, and L. Blotz, 1997. Soil-Water Characteristic Curves for Compacted
Clays, Joumal of Geotechnical and Geoenvironmental Engineering, 123(11): 1060-1070.
USACE 1993. Engineering and Design, Seepage Analysis and Control for Dams, CECW-EG
Engineer Manual 1110-2-1902, EM 1110-2-1902, U.S. Army Corps of Engineers, Department of
the Army, Washington, DC 20314-1000, 30 September 1986 (original), 30 April 1993 (change
1).
84
TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
U.S. Department of Energy (U.S. DOE) 1989. Technical Approach Document, Rev. II. UMTRA-
DOE/AL-050425.0002. U.S DOE, Albuquerque, N.M. December 1989.
U.S. DOE 2007. Study of Factors Affecting Shmb Establishment on the Monticello, Utah,
Disposal Cell Cover," DOE-LM/1387-2007, Office of Legacy Management, Grand Junction,
Colorado.
U.S. DOE 2009. 2009 Annual Inspection ofthe Monticello Mill Tailings (USDOE) and
Monticello Radioactively Contaminated Properties Sites. U.S. Department of Energy, Legacy
Management. Report LMS/MNT/S05949. December 2009.
U.S. Nuclear Regulatory Commission (NRC) 1989. "Calculation of Radon Flux Attenuation by
Earthen Uranium Mill Tailings Covers". Regulatory Guide 3.64. June.
U.S. NRC 1993. "Final Standard Review Plan for the Review and Remedial Action of Inactive
Mill Tailings Sites under Title I of the Uranium Mill Tailings Radiation Control Act," Revision
1,1993.
U.S. NRC 1997. "Issue Resolution Status Report on Methods to Evaluate Climate Change and
Associated Effects at Yucca Mountain." Washington, DC: NRC. 1997.
U.S. NRC 2002. Office of Nuclear Material Safety and Safeguards. 2002. NUREG-1623,
"Design of Erosion Protection for Long-term Stabilization", Final Report. September 2002.
U.S. NRC 2003a. "Standard Review Plan for the Review of a Reclamation Plan for Mill Tailings
Sites under Title II ofthe Uranium Mill Tailings Radiation Control Act of 978". NUREG-1620,
Revision 1, June.
U.S. NRC. 2003b. NUREG-1804. "Yucca Mountain Review Plan." Final Report. Rev. 2.
Washington, DC: NRC. 2003.
U.S. NRC 2008. Final Technical Evaluation Report for the Moab, Utah, Uranium Mill Tailings
Site, Division of Waste Management and Environmental Protection, U.S. NRC July 2008.
Utah Department of Environmental Quality, Division of Radiation Control (DRC), 2012.
Denison Mines (USA) Corp's White Mesa Reclamation Plan, Kev. ^.U; mterrogatones - Kouna
I.March 2012.
Waugh, W.J. and K.L. Peterson, 1995. Paleoclimatic Data Application: Long-Term Performance
of Uranium Mill Tailings Repositories, Paper as Part of a Conference Proceedings, Climate
Change in the Four Comers and Adjacent Regions: Implications for Environmental Restoration
and Land-Use Planning, September 12-14, 1994, Paper published September 1994.
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.
Walser, G.S. Illangasekare, T.H. and Corey, A.T. (1999) Retention of liquid contaminants in
layered soils. Journal of Contaminant Hydrology, v. 39, p. 91-108.
85
TECHNICAL MEMORANDUM
WHITE MESA MILLSITE - REVISED ICTM REPORT REVIEW
Weaver, J. E., and Clements, F. E. (1938) Plant Ecology. McGraw-Hill, New York.
Williams, L.O., Zomberg, J.G., Dwyer, S.F., Hoyt, D.L., and Hargreaves, G.A. 2010. ''Design
Rationale for Construction and Monitoring of Unsaturated Soil Covers at the Rocky Mountain
Arsenal. 6th Intemational Congress on Environmental Geotechnics, New Delhi, India. URL:
http://www.ce.utexas.edu/prof/zomberg/pdfs/CP/Williams_Zomberg_Dwyer_Hoyt_Hargreaves
2010.pdf.
Woodhouse C, Kunkel K, Easterling D, Cook E (2005) The Twentieth Century Pluvial in the
Westem United States. Geophysical Research Letters, 32(7): L07,701.
Woodhouse, C.A., Meko, D.M., MacDonald, G.M., Stable, D.W., and Cook, E.R., 2010. A
1,200-year perspective of 21st century drought in southwestern North America. PNAS,
December 14, 2010 , Vol. 107, No. 50, pp. 21283-21288. URL:
http://www.pnas.0rg/cgi/doi/l 0.1073/pnas.0911197107 .
Zhu, C, 2000. Estimate of Recharge from Radiocarbon Dating of Groundwater and Numerical
Flow and Transport Modeling, Water Resources Research, 36(9):2607-2620.
86