DRC-2010-007205 - 0901a0688020f71e

(3/15/2011) Loren Morton - Draft Rd 1A Interrogatories: DUSA Proposed Alternative Covier System for Rec Plan (UDRC. 165^1.
RC-2010-007205 From: <[e-mail]>
To: lmorton(gutah.gov
CC: Jennifer_Kelly(gURSCorp.com; [e-mail]; Robert_D_Bkird@URS„
Date: 10/13/10 9:48 AM
Subject: Draft Rd IA Interrogatories: DUSA Proposed Alternative Cover System for Rec Plan (UDRC.166.301 OUT)
Attachments: ReclPlanR4lntRnd1A-Draft101013.doc
Loren:
Attached please Draft "Round I A" Interrogatories relating to Denison Mines
(USA) Corp's proposed alternative tailings cell cover design for the White
Mesa Facility, for your review/consideration.
We are available If you would like to hold a conference call to further
discuss the draft interrogatories.
In the meantime, please feel free to call If you have any questions.
(See attached file: ReclPlanR4lntRnd1A-Draft 101013:doc)
[e-mail]
Principal Scientist
URS Corporation, Safety Management Solutions
77 Goodell Street
Buffalo, New York 14203
Phone: [phone] Direct Line
1-716-856-5636 General
Fax: [phone]
Cell Phope Number: 1-716-225-3608
Alternate email address: jon.luellen(gwsms.com
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Denison Mines (USA) Corp - Rev. 4.0 Reclamation Plan Round IA Interrogatories WWW%^I^
October 2010 W JPij^
UTAH DIVISION OF RADIATION CONTROL
DENISON MINES (USA) CORPORATION
RECLAMATION PLAN, REVISION 4.0, NOVEMBER 2009;
SUPPLEMENTAL INTERROGATORIES - ROUND 1A
OCTOBER 2010
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TABLE OF CONTENTS
INTRODUCTION 1
EXHIBIT A. PRELIMINARY INFORMATION DEFINING DUSA'S PROPOSED
ALTERNATIVE COVER SYSTEM DESIGN. 2
SYNOPSIS OF INTERROGATORIES 3
INTERROGATORY White Mesa RecPlan 02/01 a: 10CFR40 Appendix A, Criterion 1:
Pennanent Isolation without Ongoing Maintenance 5
INTERROGATORY White Mesa RecPlan 03/01 A: 10CFR40, Appendix A, Criterion 4:
Location and Design Requirements , 9
INTERROGATORY White Mesa RecPlan 05/01 A: 10 CFR PART 40, Appendix A; UAC R317-
3-1; and UAC R317-3: Construction Quality Control and Assurance ....14
INTERROGATORY White Mesa RecPlan 09/01 A: UAC R313-25-7; UAC R313-25-8; UAC
R317-6-1 (6)6.1 : Inflltration through the Final Cover System 18
n
October 2010 URS
ACRONYMS AND ABBREVIATIONS
CFR Code of Federal Regulations
DOE U.S. Department of Energy
DUSA Denison Mines (USA) Corporation
EPA U.S. Environmental Protection Agency
MWH Montgomery Watson Harza
NRC U.S. Nuclear Regulatory Commission
UAC Utah Administrative Code
ni
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INTRODUCTION
The Utah Division of Radiation Control (the Division) is reviewing the license renewal
application submitted by Denison Mines (USA) Corp. (DUSA) for its White Mesa uranium mill.
The Division has mobilized the expertise of URS Corporation (URS) by authorizing the latter to
review Revision 4 of DUSA's Reclamation Plan, submitted in connection with the license
renewal application and to prepare interrogatories that solicit information the Division judges is
necessary to satisfy relevant regulatory requirements.
On October 5, 2010, the Division met with the Division to review RQipft'l Interrogatories that
address Revision 4.0 ofthe Reclamation Plan for the White Mesa^glity. In this meeting,
DUSA proposed to submit details and justification for an ?^^^xxy0^n^QX design that would rely
primarily on evapotranspiration to control and minimize infiltration. DUSA expressed its belief
that such a change could be made in the approach to relic|g§in| and an aii|ptable final
reclamation tailings cell closure cover could be reached more rapidly than by pursuing the
previously proposed cover design and relicensing cpisrse and with no greater ex|j>spre to
criticism from the pubhc. The Division agreed tpAlcp^ ]|^JSA's proposed Si|pges with
the expectation that the license renewal process would not be delayed and might even be
accelerated. ^ '"^B
The Division, with DUSA's approval (reiterated by email sent by Harold Robert to Loren
Morton on October 7, 2010), instructed URS, the Division's contractor, to prepare immediately a
supplement set of interrogatories to the Round 1Interrogatories to address issues that should be
pursued and addressed by DUSA in connection with their proposed altemative cover design;
URS has responded to the Division's instructions and considered current NRC guidance on cover
system design in reviewing the bit of defining information provided by DUSA's contractor,
Montgomery Watson Harza (MWH), reproduced as Exhibit 1 below (MWH 2010); sent as an
attachment to the email transmitted from Harold Roberts to Loren Morton ofthe Division on
October 7,-2010. ' ^ "^^,,^^^^m^......
The result of URS' review is thetbllowing set of four supplemental Round 1 interrogatories,
denoted by the suffix "A" to eacfifisirogatory num^ example, ''INTERROGATORY
WHITE MESA RECPLAN 03/01A ...").
Denison Mines (USA) Corp - Rev, 4.0 Reclamation Plan Round 1A Interrogatories WTIJCI
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EXHIBIT A. PRELIMINARY INFORMATION DEFINING DUSA'S PROPOSED
ALTERNATIVE COVER SYSTEM DESIGN (MWH 2010).
The proposed alternative conceptual^cover design for the White Mesa Mill Tailing Cells will consist of
a monolithic evapotranspiration (ET) cover that will cap the entirety of all tailings cells. The proposed
2.84-meter (9.3-feet) thick monolithic ET cover design (see Figure 1) would consist of (from top to
bottom):
• 15 centimeters (0.5 feet) of a gravel-amended topsoil admixture to promote revegetation and
provide for protection against erosion and frost damage
• 107 centimeters (3.5 feet) of random fill soil (sandy clayey silt) placed at 85 percent of
Standard Proctor dry density to serve as a water storage, biointrusion, and radon attenuation
layer
• 162 centimeters (5,3 feet) of random fill soil (sandy clayey silt) composed of 2.8 feet of
random fill compacted to 95 percent of Standard Proctor dry density over 2.5 feet of random
fill placed at 80 percent of Standard Proctor dry density, lo serve as grading (platform fill) and
radon attenuation layers.
The proposed cover design replaces the top surface of the cover (the slope will remain at 0,2
percent); the side slope design may include rock armoring, as included in the original design. An
alternative monolithic ET cover is the preferred conceptual cover design to minimize infiltration and
meet the radon attenuation standard. The proposed cover design will be sufficient to provide
adequate thickness to protect against frost penetration, provide adequate water storage capacity to
minimize the rale of infiltration into the underlying tailings, and provide iong-term moisture within the
cover to attenuate radon flux.
Figure 1. Altemative tailings cell cover design.
VEGETATICN (PRIMARILY GRASSES)
TOP SGIL WITH GRAVEL FOR EROSION ANO FROST PROTECTIdN
SANDY CL/YEY SILT PUCED AT86% STAMD/vRD PROCTOR DRY DENSITY
FOR WATER STORAGE, 8IOINTRU810N AND RADON ATTENUATION
SANDY CLAYEY SILT UPPER 2 6 fl :
COMPACTED TO WA ST>^NOARD PROCTOR DRY DEtlSITY AND
lOWR 2 5 FEET FUOED AT 80% STA^DARD PROCTOR DRY DENSITY
FORGRAOI^G (PlArPORVt FILLJAND
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SYNOPSIS OF INTERROGATORIES
A summary of the items addressed in the Round 1A interrogatories that comprise this request for
additional information follows below.
Interrogatory White Mesa RecPlan 02/01 A: This interrogatory addresses:
• Information on the specific characteristics of soils proposed for use in constructing the
' proposed altemative cover design to demonstrate that the soil #11 ha^ properties that are
_ compatible with the vegetation community that is propose(|;|Sr establishment in the final .
cover.
Information to demonstrate the capability of the prc)p(l|d altemative cover design for
preventing possible future penetration ofthe tailinfifey plants or iii|c)wing animals
under the no-active maintenance scenario.
• Information regarding the need for incorporating a filter layer at the interface between the
sideslope and the components ofthe topdeck portion of the proposed altemative cover
design to limit possible movement of fine soil particles derived from internal erosion of
the proposed topdeck gravel/topsoil and loosely compacted topdeck soil layers into the
filter and sidelope riprap erosion protection layer in the eover
Interrogatory White Mesa RecPlan OS/OIA:Thi| interrogatory addresses:
• Procedures that will be used to produ8|| and jl gravel/topsoil admixture
layer on the topdeck; i ly
• Key data and material testing results for component materials proposed for use in
constructing the gravel/topsoil admix layer.
• Information on the types of vegetation proposed to be established and subsequent plant
^-••sucqiiillJ^^^^^^^^^^^^^^^^^^^^^ wsgim ' . ;
• Modeling to project rate of soil erosion ofthe gravel/topsoil admix surface layer with
jii|i|gt erosion, ovdij^ and gullying. .i; •
• Construction ofthe proposed altemative cover system.
• Revisions to the ReclaMation Plan necessary to properly describe the proposed
altemative cover system.
Interrogatory White Mesa RecPlan 05/OlA: This interrogatory addresses the revision and
expansion of the Quality Plan for Construction Activities:
• Information regarding DUSA's plans for constructing and monitoring a Test Pad to
quantify parameters used in modeling (short-term and long-term) performance.
• Justification for monitoring approaches and monitoring devices.
• Information on natural analogs that might be used to complement the results ofthe
CQAQC Test Pad testing program/cover performance program.
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Interrogatory White Mesa RecPlan 09/OlA: Although no Round 1 interrogatory exists
(namely, Interrogatory White Mesa Recplan 09/01) this interrogatory is provided to address
issues related to the alternative cover system design that were not germane to the existing
authorized rock cover system design. This supplemental interrogatory addresses:
Information regarding potential long-term conditions in the proposed altemative cover
system considered in developing the cover design.
Information regarding the need to include a low-permeability barrier layer in the
altemative cover system for limiting long-term infiltration rates through the cover.
Information regarding the need for including a capillary hxA. or lateral drainage and/or
cobble layer in the topdeck portion.
Information regarding the need for including a very loVtepermeability^ component (e.g.,
HDPE geomembranes and a geosynthetic clay liner [CrCL]) in the tbp(ieck.
Information on the applicability of publishe(| joint NRC-EPA guidance i^lated to the
conceptual design of LLRW disposal facilittif j^^
components to the'design ofthe cover system.'"^^B,,,:
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INTERROGATORY WHITE MESA RECPLAN 02/01 A: 10eFR40 APPENDIX A,
CRITERION 1: PERMANENT ISOLATION WITHOUT ONGOING MAINTENANCE
REGULATORY BASIS:
UAC R313-24-4 invokes the following requirement from 10CFR40 Appendix A. Criterion 1: "The
general goal or broad objective in siting and design decisions is permanent isolation of tailings
and associated contaminants by minimizing disturbance and dispersion by natural forces, and to
do so without ongoing maintenance. For practical reasons, specific siting decisions and design
standards must involve finite times (e.g., the longevity design standard in Criterion 6), The
following site features which will contribute to such a goal or objective must be considered iri
selecting among alternative tailings disposal sites or judging the adeqtiacy of existing tailings
sites: ^ ' . ' , •' ; ^
• Remoteness from populated areas;
• Hydrologic and other natural conditions m
immobilization and isolation of contamindfi^from gj0tmd-water sources; and
• Potential for minimizing erosion, disturbance,
the long term. • ,
The site selection process must be an optirmzati<m to the maxirn&^g^^nt reasonably achievable
in terms of these features. • ^ - ^'"^ <
In the selection of disposal sites, primary emphasis must hegpmtto isolation of tailings or
wastes, a matter having long-term impacts, as opp6sed to consideration only of short-term
convenience or benefits, such as mmimization of transportation or land acquisition costs. While
isolation of tailings will be a function of both site and engineering design, overriding
consideration must be given to siting features given the long-term nature of the tailings hazards.
Tailings shoiiJ^J^Jis^^ active maintenance is required to preserve .
conditions^i^^^F^^^^
INTEJIIpGATORY S^^JEME^
1. Refer to Sections 3.2.2, 3.3, Section 5 of Attachment A, Figures A-5. Ul through A-5.1-3,
and Table A-5, 3.2.1-1 of the Rev 4.0 Reclamation Plan, and MWH 2010, In addition to the
information requested in Interrogatory V^ite Mesa RecPlan 02/01 (as it remains applicable to
the proposal altemative cover design), please provide the following information for the proposed
altemative tailings cell dover design (MWH 2010):
a. Provide additional information on the specific characteristics of soils (sandy clayey silt
materials) proposed for use in constracting the proposed altemative cover design to
demonstrate that the soil will have properties (e.g., favorable water relations, appropriate
nutrient capacity and Sodium Absorption Ratio, etc...) that are compatible with the
vegetation community that is proposed for establishment in the final cover. Provide
information demonstrating that the soils would be likely to achieve the goal of
establishing ''primarily grasses" (MWH 2010) on the cover in a manner which will allow
Denison Mines (USA) Corp - Rev. 4.0 Reclamation Plan Round lA Interrogatories W\ Hi^S
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the established grasses to competitively preclude the invasion of the vegetated surfaces
by deeper-rooted tress and shrubs.
b. Describe assumptions that have been made, with supporting rationale, with respect to the
degree to which any more shallow-rooted plants (e.g., shallow-rooting trees or sKmbs) could
colonize the proposed altemative cover during the required design life of the cover and that
might be prone to future tip-up/blow-over, resulting in physical damage to the cover system
over the long term, unless they were removed through an active maintenance program.
c. Evaluate and provide information to demonstrate the capability qf |he alternative cover,
design for preventing possible future penetration of the tailig|i Sy plants or burrowing
animals under the no-active maintenance scenario. Please |fty^
• of this evaluation: .
• Information on the potential fof future deep-rog||d plants an| i||p-burrowing
animals to occur at/frequent the site or site yiSiniff^i including any pceurrences that
could result from future climate changes occurring within the required performance
- period for the cover. •
• Information on the possible need for includiij^^l^^^ layer, capillary break layer,
and/or later drainage layer in the cover system W$;^^;di^l^^QT\t penetration of the
cover throughout the required gerformanc period b^ burrowing animals or root
growth, under the no-active m^|||fcice scenario.- '^'^^^^ • ^ • ^ ' •
2. Refer to Sections 3.2.2, 3.3, Section%of^^S^mMntA, Fibres A-5.1-1 through A-5.1-
. 3, and Table A-5.3.2.1-1 ofthe Rev %Re^^^^j^--and MWH 2010: In addition •
to the information liglMted in Interrogltgrf White K|pa RecPlan 02/01 (as it remains
applicable to thg ffopBB|||^ co\% design), please provide the following
information f(^fy^ propoi^|altemative tfl|ings cell cover design (MWH 2010):
• Provide information regarding the need for incorporating a filter layer at the interface
between the sideslc|^eani^ft^ ofthe topdeck portion ofthe proposed
altemative cover design. Evaluate filter requirements for limiting the possible
movement of fine soil particles derived from intemal erosion of the proposed topdeck
gravel/topsoil and loosely compacted topdeck soil layers into the filter and sidelope
)rap erosion protection layer in the cover. Provide filter criteria and supporting
lations utilizing applicable filter design criteria (e.g., as described in NUREG-
1623) and guidancpcontained in NUREG/CR-4620 (Nelson et al. 1986).
Altematiyely, provide detailed information that would clearly justify why such filter
layer would not required. ...
BASIS FOR INTERROGATORY:
As discussed in Interrogatory White Mesa RecPlan 02/01, maximum burrowing depths for
animals at or near the site should be defined and justification provided as to how the proposed
alternative cover design will prevent potential long-term damage/disruption of the buried tailings
by burrowing animals and /or deep plant root penetration. Different pubHshed references
indicate that Big Sagebmsh in the westem U.S. can exhibit typical average rooting depths
between about 114 and 250 cm [between about 3.7 and 8 ft] (e.g., see Waugh et al. 1994; Foxx,
Denison Mines (USA) Corp - Rev. 4,0 Reclamation Plan Round lA Interrogatories WT^J^^T
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et all984; Klepper, et al. 1985, Reynolds 1990b); however, at least one reference suggests that
root depths for Big Sagebrash could be much deeper - possibly extending to up to 914 em [30 ft]
(Foxx etal. 1984).
The proposed altemative cover design (MWH 2010) does not contain a capillary break layer,
lateral drainage layer, or cobble rock layer. Inclusion of a layer of this type (with any required
filter layers also provided to prevent migration of fines into the voids of this layer) could help
provide a barrier to deep root penetration within the cover. For example, in certain
circumstances, established plant species could undergo agrolnomic stress (as a result of
unfavorable water relations and/or insufficient nutrient capalcity in the cover soils; during a dry
weather period). Certain plants could likely extend their roots seeking water and nutrients in -
response to such stresses (e.g, see DOE 1989, Section 4.3.4) - see also Interrogatory RecPlan
09/OlA: UACR313-25-7; UAC R313-25-8; UAC R317-6-1 (6)6.1: Infiltration through the Final
Cover, below. Additional information needs to be provided that demonstrates the ability of the
proposed altemative cover materials will provide and maintain the appropriate nutrient capacity
and favorable water relations required to promote a more on less uninterrapted cover of the
intended/preferred grasses over the cover throughout the required design life of the cover. The
evaluation should take into consideration the future climate,! soil properties and rooting
characteristics of the desired plants on the cover (DOE 1989). j
Although compacted soil layers in final cover system may oiffer some protection against root
penetration, plants vary greatly in their ability to penetrate cpmpacted soils (Waugh and
Richardson 1997). At arid and semi-arid sites, root densities can be higher in buried clayey-type
soils arid plant roots may concentrate in and extract water from buried clayey layers, causing
some seasonal desiccation (Hakonson 1986 and Reynolds 1990a, b). Based on these
considerations, there is likely to be uncertainty as to the degree to which shallower-rooted tress
or shrubs or deeper-rooted plants (e;g.. Big Sagebrush) mi^t eventually become established in
the cover system during the required design life of the eriibaliknient, especially during the future
no-active maintenance period. The potential therefore exists for some degree of penetration of
the cover system by the roots of deeper-rooted plants following final cover constmction. The
range of potential future plant development and animal burrowing conditions for the final cover
environment needs to be adequately defined for use as input in subsequent performance model
assessments.
Inclusion of a rocky layer within the final cover would also provide a deterrent against future
burrowing by animals as the animals would not attempt to move into a rocky, unfavorable layer
in lieu of a more favorable soil medium.
A filter layer should be included at the interface between the sideslope and the components of the
topdeck portion of the proposed altemative cover design. The filter layer should be designed to
limit the possible movement of fine soil particles derived from intemal erosion of the proposed
topdeck gravel/topsoil and loosely compacted topdeck soil layers into the filter and sidelope
riprap erosion protection layer. Without inclusion of an appropriate filter, piping of fines from
the top deck portion of the cover system could occur if seepage gradients or pressures are high
enough to initiate erosive discharge velocities at the baseflow. (U.S. Department of Agriculture
1994).
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REFERENCES:
Foxx, T.S,, G.D. Tiemey, and J.M. Wilhams., 1984. Rooting Depths of Plants Relative to
Biological and Environmental Factors, Los Alamos Report LA-10254-MS, November
1984.
Hakonson, T.E. 1986. Evaluation of Geologic Materials to Limit Biological Intrusion into Low-
Level Radioactive Waste Disposal Sites, LA-10286-MS. Los Alamos National
Laboratory, Los Alamos, New Mexico.
Klepper, E. L., K. A. Gano, and L. L. Cadwell. 1985. Rooting Depth and Distributions ofDeep-
Rooted Plants in the 200 Area Control Zone ofthe Hanford Site, PNL-5247, Battelle
Pacific Northwest Laboratory, Richland, Washington.
MWH 2010. "Proposed Preliminary Altemative CoverDesigh for White Mesa Tailings Cells".
Letter from MHW to Harold Roberts of Denison Mines (USA) Corp. dated October 6,
• 2010., • .^^^ '^lli^^ ' /
NRC (U.S. Nuclear Regulatory Commission). 2003. Standard Review Plan for the Review of a
Reclamation Plan for Mill Tailings Sites under Titie II of the Uranium Mill Tailings
. RadiationControl Act of 1978; \^^gpnDC, June 1^ . ' ; '
Reynolds, T.D. 1990a. Effectiveness of Three Natural Biobarriers in Reducing Root Intmsion
by Four Semi-Arid Plant Species. Health Physics, Vol. 59, pp,. 849-852.
Reynolds, T. D, 1990b. "Root Mass and Vertical Root Distribution of Five Semiarid Plant
Species," \nHealth Physi6^,y6[, 58, No. 2^ pp. 191-197.
U. S Department of Agriculture, 1994>- 'Chapter 26, Gradation Design of Sand and Gravel
. FiltegJ||||j^|3 - N^l^^llip^^|lf andbook, Washington, D.C. October 1994, 47 ''
U.S. Department of Energy (DOE) \ 9S9. ''Technical Approach Document, Revision 2.
li4||LA-D0E/AL 0||425.00i2, Albuquerque, New Mexico. December 1989.
Waugh, W. J., J C Charters, G. V. Last, B. N. Bjomstad, S. O. Link, C. R. Hunter, 1994, Barrier
Analogs: LoHg-Term Performance Issues, Preliminary Studies, and Recommendations,
PNL-9004, Pacific >sforthwest Laboratories, Richland, Washington.
Waugh, W.J., and Richardson, G.N., 1997. "Ecology, Design, and Long-Term Performance of
Surface Barriers: AppHcations at Uranium Mil Tailings Sites", in Earner Ti^c/zA^
for Environmental Management, National Academy Press, 1997.
\
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INTERROGATORY WHITE MESA RECPLAN 03/01 A: 10CFR40, APPENDIX A,
CRITERION 4: LOCATION AND DESIGN REQUIREMENTS
REGULATORY BASIS:
UAC R313-24-4 invokes the following requirement frorii 10CFR40; Appendix A;Criterion 4: ''The
following site and design criteria must be adhered to whether tailings wastes are disposed of
above or below grade.
(a) Upstream rainfall catchment areas must be minimized to decrease erosion potential and the
size ofthe floods which could erode or wash out sections of the tailings disposal area.
(b) Topographic features should provide good wind protection,
(c) Embankment and cover slopes must be relatively flat after final stabilization to minimize
erosion potential and to provide conservative factors of safety assuring long-term stability. The
broad objective should be to contour final slopes to grades which are as close as possible to
those which would be provided if tailings were disposed df below grade; this could, for example,
lead to slopes of about 10 horizontal to 1 vertical (10h:lv) dr less steep. In general, slopes
should not be steeper than about 5h:lv, Where steeper slopes areproposed, reasons why a slope
less steep than 5h:lv would be impracticable shoMd be provided, aridpompensatin cind
conditions which make such slopes acceptable shdtild b^ identified.
(d) A full self-sustaining vegetative cover must be established dr rock cover employed to reduce
wind and water erosion to negligible levels. ; liF .•• • •
Where a full vegetative cover is not likely to be self-sustaining due to climatic or other
conditions, such as in semi-arid and arid regions, rock cover must be employed on slopes ofthe
impoundment system. The Executive Secretary will consider relaxing this requirement for
extremely gentle slopes such as those which may exist on the top ofthe pile.
The following factors must be considered in establishing the final rock cover design to avoid
displacement of rock particles by human and animal traffic or by natural process, and to
preclude undercutting and piping:
• Shape, size, composition, and gradation of rock particles (excepting bedding material
average particles size must be at least cobble size or greater);
• Rock cover thickness and zoning of particles by size; and
• Steepness of underlying slopes.
Individual rock fragments must be dense, sound, and resistant to abrasion, and must be free from
cracks, seams, and other defects that would tend to unduly increase their destruction by water
and frost actions. Weak, friable, or laminated aggregate may not be used.
Rock covering of slopes may be unnecessary where top covers are very thick (or less); bulk cover
materials have inherently favorable erosion resistance characteristics; and, there is negligible
drainage catchment area upstream ofthe pile and good wind protection as described in points
(a) and (b) of this criterion. ,
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Furthermore, all impoundment surfaces must be contoured to avoid areas of concentrated
surface runoff or abrupt or sharp changes in slope gradient. In addition to rock cover on slopes,
areas toward which surface runoff might be directed must be well protected with substantial rock
cover (rip rap). In addition to providing for stability of the impoundment system itself, overall
stability, erosion potential, and geomorphology of surrounding terrain must be evaluated to
assure that there are not ongoing or potential processes, such as gully erosion, which would lead
to impoundment instability,
(e) The impoundment may not be located near a capable fault that could cause a maximum
credible earthquake larger than that which the impoundment could reasonably be expected to
withstand. As used in this criterion, the term "capable fault" has the same meaning as defined in
section 111(g) of Appendix A of 10 CFR Part 100. The term "maximum credible earthquake "
means that earthquake which would cause the maximum vibratory ground motion based upon an
evaluation of earthquake potential considering the regional and local geology and ^ismo
and specific characteristics of local subsurface material,
(f) The impoundment, where feasible, shdpild be designed to incorporate features which will
promote deposition. For example, design features which promote deposition of sediment
suspended in any runoff which flows into the impoundment area might be utilized; the object of
such a design feature would be to enhance the thickness of cover over time.''
INTERROGATORY STATEMENT:
1. Refer to Sectioris 3.2.1, 3.2.2, 3.3, Section 5.1 df Attachment A, Figures A-5.1-1
through A-5.1-3, and Table A-5.3.2.1-1 of the Rev 4, 0 Reclamation Plan, and MWH
2010: In additioiTiJ|tli|i^ requested in Intesttogatory White Mesa RecPlan
03/01 (as it remains applicable to the proposal altemative cover design), please provide
and justify the adequacy ofthe following information for the proposed altemative tailings
cell cover design:. / ••:
• Provide procedures that will be used to produce and install the proposed
gravel/topsoil admixture layer on the topdeck portion of the proposed altemative
cover system. Include descriptions of rock crashing operations (if any); the
expected distribution of particle sizes of the gravel materials of constmction; and
^^^^^ p processes to be used to mix, place, and compact the gravel and topsoil
materials that will constitute the final admix layer.
• Provide key dita and material testing results for component materials proposed
for use in constracting the gravel/topsoil admix layer (e.g., plasticity Index of soil;
dispersive vs. non-dispersive nature and organic content of the topsoil; specific
gravity of gravel materials; gravel particle gradation; and percentage of gravel vs.
topsoil in admixture). Provide separate calculation(s) as needed showing how
parameter values were determined (e.g., void ratio, density, and composite
gradation of the final admix) for the admix layer that are used as input into
erosion calculations.
• Provide information on the types of vegetation proposed to be established (e.g.,
type of rangeland grass and/or other plant species) and the type(s) of plant
10
Denison Mines (USA) Corp - Rev, 4,0 Reclamation Plan Round lA Interrogatories W^WWB^SL
October 2010
communities that are anticipated to evolve in the final altemative cover system
over the long term (i.e., describe likely plant succession scenarios). Assess the
abilities of both planned and successive plants to protect against erosion and
support transpiration.
• Provide an analysis of rate of soil erosion of the gravel/topsoil admix surface
layer due to sheet erosion using USLE or MUSLE (Modified Uniform Soil Loss
Equation based on Utah Water Research Laboratory MUSLE [Apt and Ruff
1978]).
• Provide calculations demonstrating the adequacy of thS proposed gravel/topsoil
admix layer to protect against erosion from overland iow (e.g., a calculation of
allowable effective stress on the admix layer surface usi^^^^
method) expected to occur across the cover surface. AcCliliJ)le analysis methods
include those described in NUREG-1623 |S^^
al. 1987 tractive force (allowable shear stress) method and the '?||cjnissible
velocity" method as discussed by Chow (1959). if the latter metiSlig^^^^^^^^
justify the selection of Manning's "n" l|i^s us§|lri the calculation for a
conservative range of potential vegetatiori|||aplons from an essentially
bare "desert pavement" type condition to a wA yegetated or grassy condition).
• Provide information on and justification for valuds of all parameters used in
erosion calculations for assessing stabihty ofthe gravel/topsoil admix layer.
Demonstrate that such layer properties are representative ofthe expected as-built
gravel/topsoil admix layer, as opposed to simply relying on values estimated in
•ihQ]\XsTdX[^^^^^^ •''IIP" ^'
• Provid#||fbrmati6i||o justify the ^
necessatj^lfl; p of gullying in the topdeck portion of the altemative
cover design. Acceptable analysis methods include those described in NUREG-
1623 (NRC 2002), including the Horton/NRC equation and the Corps of
Engineers Method (NRC 2002). Provide appropriate Manning's "n" values for a
conservative range of potential vegetation conditions that would be
considered/used in the calculation (i.e., an essentially bare "desert pavement" type
condition to a well vegetated or grassy condition).
2. Refer to IS^ction 3.3.3§§[nfiltration Analysis), Section 3.3.7 (Soil Cover-Animal
Intrusion), and Attachment A, Section 5.3.2.1 (Methods) and Table 5.3.2.1-1 of the Rev
4.0 ReclamcMpri J!0t and MWH 2010: ^In addition to the information requested in
Interrogatory White Mesa RecPlan 03/01 (as it remains applicable to the proposal
altemative cover design), please provide the following information for the proposed
altemative tailings cell cover design:
a) Provide additional information regarding how the gravel/topsoil admix layer will
be constmcted in the altemative cover system. Discuss whether the composite
admixture will be prepared away from the disposal unit and then transported to
the topdeck surface with low ground pressure equipment, or, altematively, created
in place as the cover is constmcted. In either case, describe and justify the
constraction process. Also provide additional information regarding the proposed
11
Denison Mines (USA) Corp - Rev, 4,0 Reclamation Plan Round 1A Interrogatories W]nDC[
October 2010 ^"MI
loose-lift thicknesses, moisture conditioning, and placement and compaction
methods (e.g., equipment to be used and number of passes to be made by such
equipment when constracting the sandy clayey silt layers in the altemative cover
system. Demonstrate that installation procedures will result in soil systems that
are compacted to a degree to less than or equal to the estimated"Growth Limiting
Bulk Density" of the soil system, as described by Goldsmith et al. (2001) and
Gray (2002), e.g., less than or equal to approximately 80 to 85 % standard Proctor
density for the soils used, in order to not inhibit vegetative growth in the topdeck
portion of the cover system.
b) Please revise Sections 3.3.3, 3.3.7 ofthe text in the Reclamation Plan, and Section
5.3.2.1 arid Table 5.3.2.1-1 in Attachment A to the Reclamation Plan, to reflect
the final compaction criteria selected for the final proposed topdeck cover system,
e.g., as referenced in the proposed Preliminary Altemative Cover Design for the
White Mesa Tailings Cells (MWH 2010).
BASIS FOR INTERROGATORY
The proposed altemative cover design includes a gravel/topsoil admix layer on the topdeck
portion ofthe cover system, rather than a layer of rock riprap. This layer needs to be evaluated
for adequacy with respect to long-term erosion protection, consistent with NRC guidelines and
recommendations for evaluating erosion protection (e.g., NRC 2002). Erosion protection
calculations provided in Apperidix F of the Reclamation Plan, Rev. 4 need to be revised to
address the proposed new cover system design.
The gravel/topsoil admix layer will be unique in its characteristics, depending on the specific
composition ofthe components used in its constraction and the specific procedures used to mix,
place, and compact the layer. For this reason, specific layer properties for this admix layer (e.g.,
admix layer void space and density), as they are used in erosion protection
evaluations/calculations, should be specifically calculated for the layer (i.e., rather than using
literature-derived or assumed values for these layer properties).
Information that needs to be provided, for review, for the proposed altemative cover design also
includes information on the types of vegetation proposed to be established (e.g., type of
rangeland grass and/or other plant species) and plant communities that are anticipated to develop
in the final altemative cover system over the long term. In other words, plant succession must be
addressed. This information will be used as input in separate modeling simulations and will
support certain erosion analyses, including determination of appropriate Manning's "n"
roughness coefficients for use in design analyses.
Work conducted by Goldsmith and others (2001) and Gray (2002) suggests that a compaction
between 80% and 85% of the standard Proctor maximum dry density provides many of the
stabilizing benefits of higher soil compaction without jeopardizing the viability of vegetation
development and growth. Use of excessive compactive effort and/or ineffective techniques
when installing the gravel/topsoil admix layer and use of too-small loose-lift thicknesses and/or
excessive compactive effort during constraction of the portion of the underlying sandy clayey silt
layers that is intended to serve as the vegetative growth medium could result in excessive
12
October 2010 URS
amounts of compaction in these layers, thus deterring vegetation growth. Additional information
should be provided demonstrating that these potential concems will be adequately addressed in
the design and constraction specifications. \
REFERENCES:
Apt, S.R., and Ruff, J.F. 1978. "Three Procedures for Estimating Erosion from Constraction
ArQdis'\ in Symposium on Uranium Mill Tailings Management, Volume II. Geotechnical
Engineering Program, Civil Engineering Department, Colorado State University,
November 20 and 21, 1978, pp. 87-102.
Chow, V.T. 1959. Open-Channel Hydraulics, McGraw-Hill Coriipariy, Inc., New York, NY.
Goldsmith, W., Silva, M., and Fischenich, C. 2001. DeteSming Optimal Degree of Soil
/ Compaction for Balancing Mechanical Stability and Plant Growth Capacity, Report
ERDC-TN-EMRRP-SR-26., U.S. Army En|iieer Research and Deyelopment Cem
Vicksburg,MS. May200l,9pp. URL: v^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^c^
http://el.erdc.usace.armv.mil/elpubs/pdf7sr26.pdiK; ,
Gray, D. H. 2002. "Optimizing Soil Compaction and Other Sti^ategies," Erosion Control.
Volume 9, No. 5, September-Octa|||ifl^^^^
http://www.erosioncontrol.com/septeriibefeoctober-2002/optimizing-soil-
compaction.aspx . J"'^^^^^^^^^
MWH 2010. "Proposed Preliminary Altemative Cover Design for White Mesa Tailings Cells".
Letter from Melanie Davis of MHW to Harold Roberts of Denison Mines (USA) Corp.
dated October 6,2010. "•j %
Nelson, J.D., Abt, S.R., N.E., and Staub, W.P. 1986. '
. Methg^^^^^r Evaluating Long-T^rfn Stabilization Designs of Uranium Mill Tailings,
- //iglinSmSfB^ Regulatory Commission, Washington, DC.
J|||JREG/CR-4^J||INL1^ QP67; June 1986,151 pp. -,
Temple, D.M,, Robinson, K.M., Ahring, R.M., and Davis, A.G. 1987. Stability Design of Grass-
Lined Channels. U.S. Department of Agriculture, Agricultural Handbook No. 667, U.S.
Govemment Printing Office, Washington, D.C, 167 pp.
Nuclear Regulatory Coriimission (NRC) 2002. Design of Erosion Protection for Long-Term
Stability, NUREG-1623, September 2002.
13
Denison Mines (USA) Corp - Rev, 4,0 Reclamation Plan Round lA Interrogatories W T^B^S
October 2010 - %0K%m9
INTERROGATORY WHITE MESA RECPLAN 05/OlA: 10 CFR PART 40, APPENDIX
A; UAC R317-3-1; AND UAC R317-3: CONSTRUCTION QUALITY CONTROL AND
ASSURANCE
REGULATORY BASIS:
Refer to R313-25-7, Specific Technical Information. The application shall include certain
technical information. The following information is needed to determine whether or not the
applicant can meet the performance objectives and the applicable technical requirements of R313-
25: . • ^ ^ ' -.. • . , .-•
,.,(10) Descriptions of quality assurance programs, tailored to low^lMvel waste disposal, including
audit and managerial controls, for the determination of natural disposalsite characteristics and for
quality control during the design, construction, operation, and closure ofthe land disposal facility
and the receipt, handling, and emplacement of waste.
Refer to R317-3-1(1.7). 1.7. Construction Supervision, The applicant must demonstrate that
adequate and competent inspection will be provided during construction. It is the responsibility
ofthe applicant to provide frequent and comprehensive inspectionof the project.
Refer to R317-3-10(4)(E). E. Construction Quality Control dhd Assurance, A construction
quality control and assurance plan showing frequency and type of testing for materials used in
construction shall be submitted with the designfor review and ctpprpval. Results of such testing,
gradation, compaction, field permeability, etc:p^hall be submitted to the Executive Secretary,
INTERROGATORY STATEMENT: .
I. Refer to Section 7.0 of Attachment A dih0kttachment B to the Rev. 4.0 Reclamation
Plan, and MWH 2010: In addition to the information requested in Interrogatory White
Mesa RecPlan 05/01 (as it remains applicable to the proposed altemative cover design),
please include infomiation in the CQAQC Plan regarding DUSA's plans for constracting
and monitoring a Test Pad to quantify parameters that are specifically pertinent to
demonstrating the (short-term and long-term) performance ofthe altemative tailings cell
cover design. Address, as part of the Test Pad program, testing of parameters (e.g,
1^ Research^ouncil ll|||jii^lbright et al. 2007) including, but not necessarily
limited to: - - '• •-• ''.
In-situ water content testing (e.g., soil moisture profile monitoring) and
monitoring for potential changes in water content according to depth through time
In-situ flux rate testing (e.g., through use of one or more pan lysimeters) and
monitoring to assess potential changes in flux rates through tirrie
Physical sampling and laboratory testing for index properties, including Plasticity
Index and saturated hydraulic conductivity, and other pertinent parameters
(organic matter content, compaction properties, etc...) and monitoring to assess
potential changes in these properties through time
Testing for determining soil water characteristic curves (SWCCs, e.g., according
to ASTM D6836 [ASTM 2008]) and monitoring for potential changes in SWCCs
through time
14
Denison Mines (USA) Corp - Rev, 4,0 Reclamation Plan Round lA Interrogatories W¥l}^S
October 2010
• Relevant climatological parameters (precipitation and evaporation rates, etc..)
2. Provide justification for monitoring approaches and monitoring devices (e.g., use of TDR
probes, heat dissipation probes, pan lysimeters, and/or neutron probe access tubes, etc.)
proposed for use in the cover performance verification monitoring program.
3. Describe how information on natural analogs (existing plant communities and existing
natural soil profiles at the borrow source site(s) or other sites that exhibit characteristics
similar to those of the final cover system at various times in its design life) will be used to
complement the results of the CQAQC Test Pad testing program/cover performance
program discussed above. Describe possible future changes iri climate states arid extreme
precipitation events that were considered as part of the design of the proposed altemative
cover and in selecting analog sites for inspection/investigation.
BASIS FbR INTERROGATORY
A cover system Test Pad capable of assisting in confirming the performance of the proposed
altemative cover system should be constmcted and monitored. The proposed altemative cover
design incorporates more loosely compacted soil layers, and a surficial rock riprap layer is no
longer to be included. The altemative cover system appears to be intended to serve as water
balance cover system (an evapotranspiration [ET]-type cover where the cover is designed to act
not as a barrier, but as a sponge or "reservoir" for storing moisture generated during precipitation
events, for subsequent release back to the atmosphere as ET, with pants established on the cover
surface designed that survive on the naturally-occurring precipitation capable of promoting
vegetation growth to enhance evapotranpiration).
Characteristics ofthe proposed altemative cover will inevitably change in the long term in
response to climate, pedogenesis, and ecological succession (Albright et al. 2007; Benson et al.
2007). Use of a less compacted gravel/topsoil admixture layer and more loosely compacted
underlying soil layers in the cover without the riprap layer could rerider the altemative cover
susceptible to post-constraction changes in certain physical and hydraulic properties ofthe cover.
For example, relatively large changesln moisture content (wetting and drying cycles) in the
cover system and plant root developm^rit would be expected to occur through time during the
post-closure period which could eventrially lead to changes in some hydrauhc properties ofthe
soil cover system. Changes could include creation of larger pore spaces and a broader pore size
distribution as a result of wet-dry cycles and reductions in soil density due to frost heave action,
which could ultimately lead to changes in hydraulic properties. By comparison,Ihe conditions
associated with the cover design presented in the Rev. 4.0 Reclamation Plan could have been
expected to reduce evaporation and enhance water storage in the cover (e.g., Groenevelt et al.
1989; Kemper et al. 1994), and thus provide some degree of buffering (insulating) benefit against
larger moisture fluctuations in the upper portion of the underlying soil layer(s) in the cover.
Comparisons of data collected from a depth of 30 cm (I foot) within water balance covers
constmcted at different field sites in the Altemative Cover Assessment Program at the time of
constraction and data collected 2 to 4 years following constraction of those covers indicate
potentially large changes in saturated hydraulic conductivity (increases by as much as 10,000
times); increases in the van Genuchten parameter a (an increase by as much as 1,000 times was
15
Denison Mines (USA) Corp - Rev, 4,0 Reclamation Plan Round 1A Interrogatories T
October 2010
observed); and increases in the saturated volumetric water content and the van Genuchten
parameter n (e.g., Benson et al. 2007). Results of such studies indicated that, depending on the
specific materials and constraction methods, actual as-built conditions, and actual climatic
conditions present, the largest changes in soil cover properties (at least in the upper I foot zone)
were observed in those water balance covers that are comprised of denser, fine-textured soils that
have more uniform pore space distributions. Less is known about how changes in hydraulic
properties vary with depth in ET cover systems evaluated.
Plasticity Index can be a usefiil indicator for assessing volume changes||ppil Water
Characteristic Curves for soils used iri the cover system could be expected to change with time,
based on post-constraction changes that may occur in the controlling soil parameters ofthe soil
layers.
Monitoring the proposed altemative cover system or monitoring of a Test Pad simulating the .
cover system components and geometry) to assess the long-term performance of the altemative
cover is needed to verify the characteristics and infiltration performance of the constmcted cover
system as well as to gain confidence in understanding long-term changes that may occur in the
physical/hydraulic properties ofthe altemative cover systc^ over time following its constraction.
REFERENCES: " \/
Albright, W.H., Waugh, W.J., and Bon^ov^^fff^^^ ''Altematlv|f overs: Enhanced Soil
Water Storage and Evapotranspiration in the Source Zone", in Enhancements to Natural
Attenuation: Selected Case Studies, Early, T*0. (ed), pp 9-17. Prepared for U.S. Dept. of
Energy by WashingtSiSaya^ River Company, WSRC-STI-2007-00250. URL:
http://www.dri.edu/images/stories/research/programs/acap/acap-publications/10.pdf.
ASTM (American Socii|;|^^^^ Materiaii|i!)06. ASMTD6836 - 02(2008)e2:
Standard Test Met^^^^^^^^me^iga^the Soil Water Characteristic Curve for .
Des^f^^^^a H^^^g Columh Pressure Extractor, Chilled Mirror Hygrometer, -
• and/or Centrifuge, ASTM, West Conshohocken, Pennsylvania.
Benson, G.H., Sawangsuriya, A., Trzebiatowski, B., and Albright, W.H. 2007.
"Postconstraction Changes inthe Hydraulic Properties of Water Balance Cover Soils",
Joumal. of Geotechnical and Geoenvironmental, Engineering, 133:4, pp. 349-359. ^
Groenevelt, P H., P. van Straaten, V. Rasiah, and J. Simpson. "Modification in Evaporation
Parameters by Rock Mulches", Soil Technology 2:279-285 (1989).
Kemper, W.D., A.D. Nicks, and A.T. Corey. "Accumulation of Water in Soils under Gravel and
Sand Mulches", Soil Science Society of America Joumal 58:56-63 (1994);
MWH 2010. "Proposed Preliminary Altemative Cover Design for White Mesa Tailings Cells".
Letter from MHW to Harold Roberts of Denison Mines (USA) Corp. dated October 6,
2010.
16
Denison Mines (USA) Corp - Rev. 4.0 Reclamation Plan Round 1A Interrogatories
October 2010 UJU
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.
17
Denison Mines (USA) Corp -Rev, 4,0 Reclamation Plan Round IA Interrogatories ^ITfE^^IL
October 2010 ^ JWyJ
INTERROGATORY WHITE MESA RECPLAN 09701A: UAC R313-25-7; UAC Rf 13-25-
8; UAC R317-6-l(6)6.1 : INFILTRATION THROUGH THE FINAL COVER SYSTEM
REGULATORY BASIS:
UAC R313-25-7 iSped/?c Technical Information. The application shall include certain technical
information. The following information is needed to determine whether or not the applicant can
meet the performance objectives and the applicable technical requirements of R313-25:
,,.(2) Descriptions of the design features of the land disposal facility and of the disposal units
for near-surface disposal shall include those design features related to infiltration of water/
integrity of covers for disposal units; structural stability of bacilli, wastes, and covers;
contact of wastes with standing impacts and the plan for taking corrective measures if
migration is indicated,
UAC R313-25-8 Technical Analysis,: ''The specific technical information shall also include the
following analyses needed to demonstrate that the performance objectives of R31305 will be
met:
,,.(4) Analyses of the long-term stability of the disposal site shall be based upon analyses of
active natural processes including erosion, mass wasting, slope failure, settlement ofyi^astes
and backfill, infiltration through covers over disposal areas and adjacent soils, and surface
drainage of the disposal site. The analyses shall provide reasonable assurance that there
will not be a need for ongoing active maintenance of the disposal site following closure".
UA C R317-6-1 (6)(6.1}M) Implementation. Unless otherwise determined by the Executive
Secretary, the application for a permit to discharge wastes or pollutants to ground water shall
include the following complete infprfnation:
UA C R317-6-1 (6)(6,1)/G) Implementation. Information which shows that the discharge can be
controlled and will not migrate into orddversely affect the quality of any other waters of the
state, including the applicable surface water quality standards, that the discharge is compatible
with the receiving ground water, and that the discharge will comply with the applicable class
TDS limits, ground water quality standards, class protection levels or an alternate concentration
limit proposed by '^
INTERROGATORfSpiTEMENT: -
Although no Round 1 interrogatory exists (namely. Interrogatory White Mesa Recplan 09/01)
this interrogatory is provided to address issues relater to the altemative cover system design that
were not germane to the existing authorized rock cover system design.
Refer to Sections 3.2.2, 3.3, Section 5 of Attachment A, Figures A-5.1-1 through A-5.1-3, and
Table A-5.3.2d-l of the Rev 4.0 Reclamation Plan, and MWH 2010: Please provide the
following information:
18
Denison Mines (USA) Corp - Rev. 4.0 Reclamation Plan Round lA Interrogatories WTO€5
October 2010 %3W^^
• Provide information regarding potential long-term conditions in the proposed altemative
cover system that has been considered in developing the cover design. Include
information on the saturated hydraulic conductivity values expected to be achieved for
the as-built soil layer components in the proposed alternative cover system. Also provide
information on the estimated range of long-term hydrauhc conductivity values projected
to occur within each of the soil layer components in the cover (e.g., under long-term,
degraded cover conditions). Describe the assumptions that have been made with respect
to key variables that influence the cover design, including, but not limited to: (I) Absence
of ongoing maintenance ofthe cover system and lack of maintenance/removal of leachate
from tailings cell sumps in the future; (2) nature and extent of degraded conditions
projected to occur in the cover (and cell liner systems) over the required design life ofthe
embankment; (3) magnitude of potentially wetter future precipitation conditions that may
occur at the site over the embankment's required design life; (4) presence and
distribution of different plant species/communities arid animal-induced burrowing that
could occur in the cover system over the lon^fen; and (5) other degraded conditions
that could develop within the cover system (md liner system) as a result i|it|pr
degradation mechanisms. Describe and quantify^ to the extent practicable, iuncertainties
that are associated with assumptions made with respect to these variables.
• Evaluate and provide infbrmatiori regarding the need to Include a low-permeability
barrier layer in the altemative covei^l5^terii for limiting long-teim inflltration rates
through the cover. Altematively, provide detailed information that clearly demonstrates
why such a compacted low-permeability barrier layei;, vv^hich NRC recommends be
included in final tailings cell reclamation covers (NRG 2003, Section 2.7), is not
warranted or necessary.
• Evaluate and provide information regarding |he need for including a capillary break or
lateral drainage and/or po|^elapr in the tQpdeck portion ofthe proposed altemative
cover,Jor fiirther limilip|yerticali^|^^ infiltration through the cover system and
in|(^ the tailings, Providel demonstrating that omitting such a design feature -
which could provide a meari^ of virtually precluding "breakthrough" of excess moisture
levels in the cover into the tailings at a semi-arid to arid site as is the case for the White
Mesa Site - will not jeopardize the capacity of the altemative cover for minimizing
term infiltration rates through the cover system throughout the postclosure period. See
dXso Interrogatory Recplan 02/01 A: 10CFR40 Appendix A, Criterion 1: Permanent
Isolation without Ongoing Maintenance, above.
Evaluate and provide information regarding the need for including a very low-
permeability component (e.g., HDPE geomembranes and a geosynthetic clay liner
[GCL]) in the topdeck portion ofthe proposed altemative cover, for further limiting
vertical downward infiltration through the cover system and into the tailings.
Evaluate and provide information on the applicability of published joint NRC-EPA
guidance related to the conceptual design of LLRW disposal facilities that contain low-
permeability liner components to the design of the cover system for the tailings cells at
the White Mesa Mill Facility. Provide information that demonstrates that the proposed
19
Denison Mines (USA) Corp - Rev. 4.0 Reclamation Plan Round lA Interrogatories WnfJ^C
October 2010 - - .
altemative cover system will not lead to potential "bathtubbing " of liquid within the
tailings cell during the postclosure period when no active maintenance would be
performed at the facility and under the scenario irivolving long-term (degraded)
conditions present in the cover system.
BASIS FOR INTEROGATORY:
The proposed altemative cover design does not include a low-permeability barrier layer. The
proposed altemative cover does not appear to be consistent with NRC ||idehnes and
recommendations relating to standard acceptance criteria for evaluating infiltration. NUREG-
1620 <NRC 2003), Section 2.7, specifies that a goal of a tailings |||limation plan
/decommissioning plan is to ensure that the disposal cell covq^s il^ponent having minimal
hydraulic conductivity, to limit radon emissions from, andyvater m/z/^raifiow m/c?, [the] stabilized
mill tailings. The discussion in Section 2.7 of NRC 2003iii||ests that NSl japnte^^ that a
cover system containing a low-permeability compon^irt having a properly ficti|:^aijd laboratory
testing-verified satixrated hydraulic conductivity valii of 1 x lO'^ cm/sec or less w
be considered acceptable. ^ .'
Inclusion of a capillary break or lateral drainage layer and/(ii>&)bble layer (accompanied by
appropriate filter layers as needed) in a final cover would help^i^jjtribute toward achieving the
desired water balance in the cover, i.e., the promotion of evapotranspiration relative to the
downward movement of water into the tailings (e.g., see DOE 1989; Stormont and Morris 1998),
as well as help provide a barrier to deep root penetration and minimize upward movement of
contaminants (within the cover) via capillary forces- See also Interrogatory Interrogatory
RecPlan 02/01 A: 10CFR40 Appendix A, Criterion 1: Permanent Isolation without Ongoing
Maintenance above). These benefits would be achieved by virtue of the incorporated
capillary/drainage/cobble layer only allowing significant quantities of water to drain out of and
move downward from the overlying soil layer component when the overlying soil is completely
saturated.
Some ofthe tailings cells (e.g.. Cells 4 A and 4B) contain composite very low-permeability -
liners, including GCL and geomembrane components (having as-built saturated hydraulic
conductivities less than 1 x 10"^ cm/sec.) Use of a cover system that does not include a very low-
permeability component of equal or lower permeability than the liner components could create
the potential for future buildup of liquids in the within the tailings embankment following
closure due to net infiltration rates through the cover exceeding net leakage rates through the
liner system over the long term. Information needs to be provided that demonstrates that the
selected final cover design will not result in the creation of this bathtub effect within the closed
embankment.
REFERENCES:
DOE (U.S. Department of Energy). 1989. Technical Approach Document, Revision II, UMTRA-
DOE/AL 050425.0002. Albuquerque, New Mexico.
20
Denison Mines (USA) Corp - Rev. 4.0 Reclamation Plan Round lA Interrogatories W TBJ^J
October 2010
MWH 2010. "Proposed Preliminary Altemative Cover Design for White Mesa Taihngs Cells".
Letter from MHW to Harold Roberts of Denison Mines (USA) Corp. dated October 6,
2010.
NRC (U.S. Nuclear Regulatory Commission) 2003. Standard Review Plan for the Review of a
Reclamation Plan for Mill Tailings Sites under Titie II of the Uranium Mill Tailings
Radiation Control Act of 1978, Rev. I. Washington DC, June 2003.
Stormont, J. And Morris, C. 1998. "Method to Estimate Water Storage Capacity of Capillary
Barriers," Joumal of Geotechnical and Geoenvironmental Engineering 124: pp. 297-302.
URL: http://ro.uow.edu.au/engpapers/208/
U.S. EPA (Environmental Protection Agency) 1987. Joint NRC-EPA Guidance on a Conceptual
Design Approach for Commercial Mixed Low-Level Radioactive and Hazardous Waste
Disposal Facilities - Action Memorandum, Uii. EPX, Washington, D.C, August 18,
1987. URL: nepis.epa.gov/Exe/ZyPURL.cg()ockey=W^
21