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Sonja Robinson - Cell 4B Design Report Approval memo (UDRC.166.102 OUT)
From: <[e-mail]>
To: [e-mail]
Date: 10/1/2009 10:27 AM
Subject: Cell 4B Design Report Apprpval memo (UDRC. 166.102 OUT)
CC: [e-mail]; [e-mail]
Attachments: Cell4B DR AppvlMemo 091001 .doc
Loren:
We have concluded our review of DUSA's Cell 4B Design Report as revised and supplemented. The attached memorandum
documents the process and our rationale for accepting all but two matters:
1. Solution Monitoring Program: The Division should review the proposed solution monitoring
program in connection with its future review ofthe yet-to-be-submitted Cell 4B BAT Monitoring,
Operations, and Maintenance Plan. This review should be consistent with the process used in the
Division's review and approval ofthe BAT Monitoring, Operations, and Maintenance Plan for
Cell 4A; and
2. Permeant travel time calculation: URS WD recommends that the GCL permeant travel time
calculation that was submitted by DUSA as part of their January 9, 2009 Response to the Round 1
Interrogatories should be excepted from the design approval that the Division would grant to
DUSA for the Cell 4B design. This calculation, furnished to support use ofa non-prehydrated
GCL in Cell 4B, is not applicable to the final design selected for implementation.
Please review and retum any comments in Track Changes mode. Of course, we are available to discuss any question you
have regarding this memo.
(See attached file: Cell4B DR AppvlMemo 091001.doc)
Robert D. Baird, PE Tel: [phone] [e-mail]
756 East Winchester Street, Suite 400 Fax: [phone] [e-mail]
Sah Lake City, Utah 84107 Cell: 801-913-2178 [e-mail]
I his e-mail cmd any auachments contain URS ( nrporation confidential information thai may be proprietar,' or privilegfii. If voii receive iliis message
in error or are not llie iniendetl leeipieiit. you .should not retain, dislrilnite, diselo.so or use aiiy of this inrorination and you should destroy Ihe e-mail and
any attachmenis or copies.
file://C:\Documents and Settings\Sdrobinson\Local Settings\Temp\XPgrpwise\4B601B4F... 1/27/2010
Memo

Page 1 of 31

Washington Safety Management
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Salt Lake City, UT 84107
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To: Loren Morton, Utah Division of Radiation Control
From: Jon Luellen and Robert Baird
Date: October 1, 2009
Subject:
Summary of Review of Denison Mines USA, Corp.’s Cell 4B Design Report
and Responses to Rounds 1, 2, & 3 Interrogatories (UDRC.166.102 OUT)

OBJECTIVE:
The objective of this technical memorandum is to document the rationale upon which URS
Corporation, Washington Division (URS WD) recommends acceptance, subject to two
exceptions as noted herein, of the Revised Cell 4B Design Report and Denison Mines USA
Corp’s (DUSA’s) responses to Round 1, Round 2, and Round 3 Interrogatories for the Cell 4B
Design Report for the White Mesa Mill Facility submitted by DUSA to the Utah Division of
Radiation Control (the Division).

DOCUMENTS REVIEWED:
At the request of the Division, URS WD has reviewed and evaluated the following documents
related to the design of Cell 4B at the White Mesa Mill Facility:

Denison Mines (USA) Corp. 2009a. “Cell 4B Lining System Design Report, Response
to Division of Radiation Control (“DRC”) Request for Additional Information – Round 1
Interrogatory, Cell 4B Design”, Letter dated January 9, 2009, from Harold R. Roberts of,
to Dane L. Finerfrock, Division of Radiation Control.

Denison Mines (USA) Corp. 2009b. “ Re: Cell 4B Lining System Design Report,
Response to DRC Request for Additional Information – Round 2 Interrogatory, Cell 4B
Design”, (including attachments), Letter to Dane L. Finerfrock, dated August 7, 2009.
Denison Mines (USA) Corp. 2009c. “ Re: Cell 4B Lining System Design Report,
Response to DRC Request for Additional Information – Round 3 Interrogatory, Cell 4B
Design”, (including attachments), Letter to Dane L. Finerfrock, dated September 11,
2009.

Geosyntec Consultants 2007. “Cell 4B Design Report, White Mesa Mill, Blanding,
Utah”. December 2007. Prepared for International Uranium (USA) Corporation.

Geosyntec Consultants 2008. “Slope Stability Analysis, White Mesa Mill, Cell 4B,
Blanding, Utah”, July 2008.
Memo

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Geosyntec Consultants 2009a. Revised Section 02200 of the Technical Specifications,
Revised September 2009.

Geosyntec Consultants 2009b. Probable Maximum Precipitation (PMP) Event
Calculation Package, Calculation dated September 10, 2009.

Hansen, E. Marshall, Schwartz, Francis K., Riedel, John T., 1984. “Hydrometeorological
Report No. 49: Probable Maximum Precipitation Estimates, Colorado River and Great
Basin Drainages,” Hydrometeorological Branch Office of Hydrology National Weather
Service, U.S. Department of Commerce, National Oceanic and Atmosphere
Administration, U.S. Department of Army Corps of Engineers, Silver Springs, Md.

State of Utah Division of Water Quality 2008. “Groundwater Discharge Permit, Denison
Mines (USA) Corp.” Permit No. UGW370004. March 17, 2008.

Utah Department of Environmental Quality (UDEQ) 2007. “Revised GCL Hydration
Plan Approval”, Letter from Dane Finerfrock, Utah Department of Environmental
Quality, to Harold Roberts of Denison Mines (USA) Corporation, dated September 28,
2007.

EVALUATION:

URS WD has reviewed DUSA’s initial Cell 4B Design Report (Geosyntec 2007), the complete
revision thereto, subsequent partial revisions thereto, and related documents submitted in
response to Round 1, 2, and 3 Interrogatories. Based on these reviews, URS WD recommends,
with two exceptions as noted below, that the Division accept the revised Cell 4B Design Report
(DUSA 2009b), the revised Section 02200 of the Technical Specification Section (Geosyntec
Consultants 2009a), and responses to the three rounds of interrogatories as being acceptable and
complete. URS WD’s rationales for these recommendations are summarized in the following
pages.

ACCEPTANCE OF DESIGN PROPOSALS AS INITIALLY SUBMITTED
The following elements of the Cell 4B Design Report were deemed acceptable as submitted:
• Base grading plan
• Overall design scheme and materials proposed for use in constructing the Cell 4B
containment system, i.e., layering and interfaces of the slimes drain system, primary liner
and secondary composite liner system, leachate collection and removal system, and leak
detection system.
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• Liner system anchor trench design

ACCEPTANCE OF REVISED DESIGN PROPOSALS
Through subsequently submitted revised design proposals (submitted by DUSA in response to
the Round 1, 2, and 3 Interrogatories transmitted by the Division), the revised design proposals
were determined to be acceptable, with the two exceptions noted below. URS WD’s rationales
for determining acceptability of the revised design proposals are presented in the following
pages.

Exceptions to Recommended Acceptance: URS WD has identified the following two issues that
should be excepted by the Division in conjunction with the Cell 4B design review and approval.
The first issue should be pursued in a subsequent review activity. The second issue should be
excepted by the Division as not being applicable to the final design that was selected for
implementation as an outcome of the Cell 4B design Report review and approval process.
Neither exception is deemed to be an impediment to the acceptance of the Cell 4B design at this
time.

1. Solution Monitoring Program: The Division should review the proposed solution
monitoring program in connection with its future review of the yet-to-be-submitted Cell
4B BAT Monitoring, Operations, and Maintenance Plan. This review should be
consistent with the process used in the Division’s review and approval of the BAT
Monitoring, Operations, and Maintenance Plan for Cell 4A; and
2. Permeant travel time calculation: URS WD recommends that the GCL permeant travel
time calculation that was submitted by DUSA as part of their January 9, 2009 Response
to the Round 1 Interrogatories should be excepted from the design approval that the
Division would grant to DUSA for the Cell 4B design. This calculation, furnished to
support use of a non-prehydrated GCL in Cell 4B, is not applicable to the final design
selected for implementation.

REGULATORY REQUIREMENT/ISSUE No. 1:

R313-24-4, 10 CFR 40 Appendix A, Criterion 4 (e) and R313-24-4, 10
CFR 40 Appendix A, Criterion 5A(5): Dike Integrity

• R313-24-4, 10 CFR 40 Appendix A, Criterion 4 (e): The impoundment may not be
located near a capable fault that could cause a maximum credible earthquake larger than
that which the impoundment could reasonably be expected to withstand. As used in this
criterion, the term “capable fault” has the same meaning as defined in section III(g) of
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Appendix A of 10 CFR Part 100. The term “maximum credible earthquake” means that
earthquake which would cause the maximum vibratory ground motion based upon an
evaluation of earthquake potential considering the regional and local geology and
seismology and specific characteristics of local subsurface material.”

• R313-24-4, 10 CFR 40 Appendix A, Criterion 5A(5) : “When dikes are used to form the
surface impoundment, the dikes must be designed, constructed, and maintained with
sufficient structural integrity to prevent massive failure of the dikes. In ensuring structural
integrity, it must not be presumed that the liner system will function without leakage
during the active life of the impoundment.

Round 1 Interrogatory submitted by the Division: The Division submitted a Round 1
Interrogatory to DUSA on May 29, 2008. The Interrogatory requested that DUSA provide a
revised slope stability evaluation that included the following:
• Identify critical Cell 4B slopes;
• Consider Cell 4B interior slopes of the joint berms between Cells 3 and 4B and 4A and
4B, the potential conditions associated with these berms, and the impacts of Cell 3 and
4A on the berm stability;
• Identify and justify the values of the parameters and conditions used; and
• Address potential impacts from seismic concerns, ground motions resulting from blasting
operations to remove bedrock, potential operational loading, and other conditions that
may impact the stability of the berms during the proposed cut back work to obtain the
desired 2H:1V slopes.

Additional requests made to DUSA included the following:

• Justify the use of factors of safety equal to 1.5 and 1.3.
• Provide additional detail on the construction drawings including the layout of the road, its
materials and means of construction, surface water flow, erosion controls and infiltration
controls to preclude adversely impacting the integrity of the Cell 4B liner system and
berms.

In response to this interrogatory, DUSA provided a calculation entitled “Slope Stability
Analyses, White Mesa Mill, Cell 4B, Blanding Utah” (Geosyntec Consultants 2008), dated July
2008, for review. The calculation was found to contain the following elements requested:

• The slope stability analyses were performed for each of the critical slopes for each of the
four embankments surrounding Cell 4B;
• The parameters and conditions used in the evaluations were identified and justified, and
the resulting assumptions were consistent with those provided in support of Cell 4A;
• The analyses considered the potential conditions associated with Cells 3 and 4A on the
berm stability (liquid/soil levels, etc).
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• The analyses considered the impacts of various other surrounding conditions including
the perimeter haul road and interim stockpiling of material at the top of the berm slope;
• The analyses provided adequate justification for the use of factors of safety of 1.5 and 1.3
for static and operational slope stability.

The analyses evaluated seismic impacts on slope stability.

URS WD Evaluation: Based on review of the DUSA response to the request for a revised
slope stability evaluation, URS WD concluded that:

• The potential for slope instability due to blasting in close proximity to the dike berms had
not been adequately addressed. Interrogatory DUSA R313-24-4-06/01 – Subgrade
Preparation and Earthwork – (Round 1 Interrogatories) had previously requested
information about the extent of construction blasting that DUSA proposing and requested
a drawing or figure representing the limits of proposed blasting. The DUSA response
was judged incomplete;
• Other than several schematics of the geologic cross-sections through Cell 4B, no
technical drawings illustrating the horizontal and vertical extents of blasting were
provided;
• The analyses briefly discussed the ground motions resulting from blasting operations to
remove bedrock. The discussion referred to a peak particle velocity limitation of 5 IPS
(not included in the specifications), but did not provide a reference or basis for the value.
URS WD considered information contained in documents such as “Blasting Guidance
Manual, US Department of Interior, Office of Surface Mining and Reclamation and
Enforcement (1987)”. This guidance indicates that, assuming that measured ground
vibration frequencies caused by the blasting are greater than 30 Hz, a maximum peak
particle velocity of 2 IPS can be allowed or utilized without concern for damage to
structures. Further, if ground vibration frequencies caused by the blast are less than 30 Hz,
maximum peak particle velocities should not exceed the limits published by the U.S. Bureau
of Mines (Report of Investigation #8507; and

• The design and Technical Specification Section 02200 placed a requirement on the
Contractor that blasting shall not cause damage. “Damage” was not defined, by DUSA,
and needed to be fully explained

URS WD prepared a Round 2 interrogatory to address unresolved issues identified above (see
below).

Round 2 Interrogatory submitted by the Division: The Division submitted a Round 2
Interrogatory to DUSA on July 31, 2009. The Interrogatory requested that DUSA provide
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additional information concerning and calculation justifying the locations and magnitudes of
blasting expected to occur during Cell 4B construction, and evaluate the potential impacts from
such construction blasting. Additional requests in the interrogatory included the following:

• Identify the proposed horizontal and vertical limits of blasting during the construction of
Cell 4B.
• Evaluate slope stability issues related to blasting, consistent with the geological
drawings/figures that are provided in the design report.
• Provide technical drawings that support the analysis discussed below in reference to the
distance from blasting to berm slope, buildings, etc.
• Explain and justify the assumption that a Peak Particle Velocity (PPV) of 5 inches per
second (IPS) is appropriate for the site, considering protection of the constructed berms
• Evaluate the potential for slope instability, due to construction blasting that:
9 Demonstrates how the blasting will affect the stability and functionality of the
surrounding berms, that will be cut to serve as the side slopes for Cell 4B, as well as
any other components of Cell 4B and adjacent Cells; and
9 Evaluates what effect blasting will have on the effective permeability and speed of
water travel through underlying material.
• Define “damage” both in terms of nearby dike stability, and foundation permeability
under Cell 4B.

In its response to this Round 2 interrogatory, DUSA provided information (letter dated August 7,
2009) suggesting that a more conservative approach than that which was described in the original
Cell 4B Design Report would be used to design the blasting work. The response cited past
construction practices as well as an alternate reference applicable to open mining in developing
the basis for the revised approach. DUSA suggested in its response that the more conservative
PPV limitations were now included in the revised Technical Specifications. Review of the
Technical Specifications, however, indicated that these limitations had not been included as
stated.
Regarding the inquiry of proposed blasting PPV limitations, DUSA referenced a document “The
Influence and Evaluation of Blasting on Stability” presented in “Stability in Open Mining”,
1971. On the basis of this reference, DUSA identified a more conservative PPV range of
between 2 and 4 inches per second (IPS). Further, DUSA stipulated in its response that a PPV of
2 IPS would be utilized for all blasting within 100 ft of the top of the existing berms. Noting the
absence of these limitations in the revised technical Specifications, the Division requested that
DUSA include these limitations in the Technical Specifications for the Blast Plan requirements
specified under Section 02200, Articles 1.05B, 3.03B5, and 3.03B6.
DUSA also indicated in its response that the entire cell floor will require rock removal, which
involves a significant amount of blasting to achieve design subgrades. The Division considered
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the Blast Plan document required in the Technical Specifications be a critical component of the
design, and therefore requested that DUSA submit a Blasting Plan to the Division for review and
approval prior to blasting at the site.

URS Evaluation: Based on review of the DUSA response, URS determined that the issue of
dike integrity had been satisfactorily addressed in all aspects, except for the concept of Peak
Particle Velocity (PPV) related to construction blasting and how PPV limitations are
incorporated into the project Technical Specifications and the Blast Plan. A Round 3
Interrogatory was prepared and submitted to DUSA to address these remaining issues (see
below)

Round 3 Interrogatory No. 2 submitted by the Division: The Division submitted a Round 3
Interrogatory to DUSA on September 4, 2009. The Interrogatory requested that DUSA provide
the following:

• A revised Technical Specification including the limits to be used for PPV during blasting;
• A requirement that PPV limitation specifications be applied in the Blast Plan that is
required under Technical Specification Section 02200, Articles 1.05B, 3.03B5, and
3.03B6; and
• A Blast Plan for Utah Division of Radiation Control (DRC) review.

In response to the Division’s Round 3 Interrogatory, DUSA submitted the following information:
• A revised Technical Specifications Section 02200 (Earthwork), dated September 2009
(Geosyntec Consultants 2009a) requiring that:

1. The Contractor arrange for a pre-blast survey of nearby buildings, berms, or other
structures that may potentially be at risk from blasting damage, and requiring that the
survey method used be acceptable to the Contractor’s insurance company, and that
the Contractor be responsible for any damage resulting from blasting;
2. The preblast survey be made available for review three weeks before any blasting
begins;
3, The Peak Particle Velocity (PPV) in rock be less than 2 inches per second (IPS) when
blasting within 100 ft of the top of any berm; and
4. The Contractor develop a trial blasting technique that identifies and limits the
vibrations and damage at varying distances from each shot, and requires that this trial
blasting information be collected and recorded by beginning the work at points
farthest from areas to remain without damage.

The response also included a Blast Plan submitted by a blasting contractor that includes a plan
for conducting an initial test blast at a distance greater than 100 ft from the top of any berm that
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is designed to induce PPVs less than 2 IPS. The blasting contractor has acknowledged the
restrictions related to PPVs and has presented a method for monitoring blasting effects that will
help to ensure compliance.

URS Evaluation of the Round 3 Interrogatory Responses: URS WD recommends that the
Division accept the revised Technical Specification Section (02200) and the Blast Plan.

REGULATORY REQUIREMENT/ISSUE No. 2:

R317-6-6.4(A), Refer to R313-24-4, 10 CFR 40 Appendix A, Criterion
5A(4) and 5A(1): Slimes Drain System and Side Slope Risers for
Slime Drain Pipe and Leak Detection Pipe

• Refer to R317-6-6.4(A). The applicant must provide information that allows the
Executive Secretary to determine the applicant is using best available technology to
minimize the discharge of any pollutant.
• Refer to R313-24-4, 10 CFR 40 Appendix A, Criterion 5A(4): A surface impoundment
must be designed, constructed, maintained, and operated to prevent overtopping resulting
from normal or abnormal operations, overfilling, wind and wave actions.
• Refer to R313-24-4, 10 CFR 40 Appendix A, Criterion 5A(1): Surface impoundments
must have a liner that is designed, constructed, and installed to prevent any migration of
wastes out of the impoundment to the adjacent subsurface soil, ground water, or surface
water at any time during the active life (including the closure period) of the
impoundment. The liner may be constructed of materials that may allow wastes to
migrate into the liner (but not into the adjacent subsurface soil, ground water, or surface
water) during the active life of the facility, provided that impoundment closure includes
removal or decontamination of all waste residues, contaminated containment system
components (liners, etc.), contaminated subsoils, and structures and equipment
contaminated with waste and leachate. For impoundments that will be closed with the
liner material left in place, the liner must be constructed of materials that can prevent
wastes from migrating into the liner during the active life of the facility.

Round 1 Interrogatory submitted by the Division: Based on review of the initial Cell 4B
Design Report, the Division submitted a Round 1 Interrogatory to DUSA on May 29, 2008
requesting that DUSA provide the following additional information:
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• Indicate in the Design Report (Section 3.4.1) that the slimes drain system has been
designed to be compliant with the following performance standards which were also
specified in Part 1.D.6 of the Groundwater Discharge Permit) for Cell 4A.
• Modify the design of the PVC pipe used in the slimes drain access pipe on the sideslopes
to include measures to protect against damage of the PVC pipe due to prolonged
exposure to the atmosphere.
• Provide additional information to justify the selection of a maximum flow length (longest
drainage path) of 730 feet
• The use of a textured HDPE splash pad needs to be considered.
• Additional detail is required in Drawings 6 and 7 to illustrate how these components are
finished at the top of the side slope/berm in relationship with the slimes drain pipe and
leak detection pipe penetrations.
• Clarify why the cross-section shows the pipes exiting the ground surface at a slope which
varies, given that the inside slope of the berm is reported to be 2:1.
• Demonstrate how the ropes will be secured around the sand bags such that rope does not
become loose from the sand bag; demonstrate how the ropes are secured at the top of the
berm.
• Insure all Construction Drawings key components are identified.
• Provide additional information/data demonstrating that components of the sideslope
system for the slimes drain system and leak detection system riser pipes (including the tie
down straps for the pipes onto the concrete header).
• Provide the justification for not including cleanouts for both the slimes drain and the leak
detection piping.

In response to this interrogatory, DUSA provided the following discussions/clarifications:
1. A revision to Section 4.4.1 of the Design Report to indicate that the design will comply
with the performance standards contained in Part 1.D.6 of the Groundwater Discharge
Permit related to slimes drain monthly and annual average recovery head criteria. A
revised pipe strength calculation was provided that incorporates an EPA-recommended
methodology for accounting for the effect of pipe perforations in the pipe strength
calculations. The response to Round 1 Interrogatory also changed the maximum flow
path length in the slimes drain system from 730 feet to 780 feet, included a drawing to
justify selection of that value, and included a revised action leakage rate calculation
incorporating this revised flow path length. Revised Construction Drawings were also
provided that showed the change to use of a textured HDPE splash pad, and drawings that
provided added details showing how the slimes drain pipe/header pipes and leak
detection pipes penetrate the liner system and an additional explanation was provided to
demonstrate that water would not migrate into the individual liner components.
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2. Additional information and explanations were provided discussing the termination details
for the leak detection and slimes drain pipes with respect to the concrete header wall
(secured in a U-shaped groove in the concrete header). The response also discussed the
adequacy of the sand bag ropes for the site conditions. A revised construction Drawing
was also provided showing (added) surface elevation information for the Cell 4B
components as requested
3. The Response also provided an explanation indicating that cleaning of the slimes drain
and leak detection piping could be accomplished to a maximum length of about 1,000 ft
through the sump riser piping.

URS WD Evaluation: Based on review of the DUSA response, URS WD determined that the
issues of slimes drain system and side slope risers for slime drain pipe and leak detection pipe
had been satisfactorily addressed in all aspects.

REGULATORY REQUIREMENT/ISSUE No. 3:

R313-24-4, 10 CFR 40 Appendix A, Criteria 4 (d), 5A(4), and 5A(5):
Spillway Capacity Design/Calculation and Surface Water Runoff

• R313-24-4, 10 CFR Appendix A, Criterion 5A(4): A surface impoundment must be
designed, constructed, maintained, and operated to prevent overtopping resulting from
normal or abnormal operations, overfilling, wind and wave actions, rainfall, or run-on.

• R313-24-4, 10 CFR Appendix A, Criterion 4 (d): In addition to providing 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.

• R313-24-4, 10 CFR Appendix A, Criterion 5A(5): When dikes are used to form the
surface impoundment, the dikes must be designed, constructed, and maintained with
sufficient structural integrity to prevent massive failure of the dikes.

Round 1 Interrogatory submitted by the Division: The Division submitted a Round 1
Interrogatory to DUSA on May 29, 2008. The Interrogatory requested that DUSA provide the
following:

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• Include the flows from the mill operation to the spillway capacity design/calculations and
apply the results to design (as needed).
• The discharge inlet/outlet elevations need to be identified on the Construction Drawings
to identify how the flow occurs serially from Cell 2, 3, 4A, to 4B.
• Include a demonstration that if the operational requirements for freeboard in each cell are
maintained the complete cell system has the capacity to contain stormwater from the
PMP combined with the water and tailings from anticipated mill processing.
• Demonstrate how the design, at the point of discharge from Cell 4A into Cell 4B from the
emergency spillway, has incorporated features to prevent damage from occurring to the
liner system and slimes drain piping.
• Section 2.5 of the Design Report states that “surface water at the facility is diverted
around the Cells including Cell 4B.” Please provide a drawing(s) that show how surface
water runoff is diverted around Cell 4B, including runoff from adjacent cells which are
either closed or in the process of being closed such that outside slopes of Cell 4B do not
erode and lead to potential failure. Include the design components which allow the
surface water to divert around Cell 4B. Also show the entire site surface water drainage
flows, and explain how Cell 4B is incorporated into this overall facility drainage. This
needs to include how contact stormwater that is or may be contaminated is discriminated
from uncontaminated or non-contact stormwater.
• Clarity why there are two Sections labeled “K/7” on Construction Drawing 7, Section
10/3.
• Clarify why Construction Drawing 7, Section 10/3 and Section K/7 identify the inside
slope of Cell 4B as 3:1, when other portions of the Design Report states that the inside
slope of Cell 4B is 2:1.
• Resolve the conflict between Design Calculations for the Emergency Spillway (spillway
width is 100 feet) and Construction Drawing 7, Section J/(width as 94 feet).

In response to the above interrogatory, DUSA provided the following:

1. A statement indicating that the freeboard capacity of each of the cells is designed to
handle the PMP storm volumes and that the flows from mill operations are not allowed
to consume any of the freeboard. DUSA also indicated that the Emergency Spillway is
designed to pass the flows from the PMP storm event from one cell to the next, and
that Cell 4B must be operated within the approved freeboard limits during normal mill
operations.
2. A revised Construction Drawing 4, included in Exhibit H to the January 9, 2009
Response, indicating elevations for the emergency spillway between Cells 4A and 4B,
and referring to the O&M Plan and the DMT Plan for Cell 4A which also showed
these elevations (previously approved in a letter from the UDEQ to DUSA dated 17
September 2008).
3. Information indicating that the freeboard limit for Cell 4A was established at 5593.7
feet above mean sea level (“fmsl”) as documented in revised freeboard calculations for
Cell 3 and Cell 4A to DRC on December 11, 2008, and a statement that this provides
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for the PMP events from Cell 2, Cell 3 and Cell 4A areas. DUSA indicated that once
Cell 4B is operational the freeboard limit will initially be set at 3 feet below the top of
liner, which is more than adequate to handle the 10 inches of precipitation from the
PMP event, plus wave runup. At the point the remaining pool area in Cell 4A is
insufficient to handle the PMP runoff from Cell 2, Cell 3 and Cell 4A, then the
freeboard limit in Cell 4B will be revised, with approval from the Executive Secretary,
to store the PMP from Cell 2, Cell 3 and Cell 4A, as well as Cell 4B. The freeboard
calculation is very conservative and Cell 4B is therefore designed as a zero discharge
facility.
4. A description of the proposed tailings discharge program indicating that no debris is
expected to be entrained within the discharge water and tailings consist of silts, sands,
and clays, and that before discharging tailings to Cell 4B, the cell will be filled with
process solution to a level with a minimum level of 2 feet. DUSA’s plan includes then
depositing tailings in the liquid-filled cell and the sand, silt, and clay particles that
comprise the tailings gently falling out of solution in a manner that will not damage the
liner system or its underlying components. In addition, DUSA added a textured
geomembrane splash pad to the liner system below the splash pad to provide an
additional level of protection to the liner system.
5. A drawing, “Figure 1, Mill Site Drainage Basins”, showing the various drainage basins
for the entire mill site and the diversion structures where needed. Shown on the
Drawing are drainage basins “C”, “D” and “E” representing Cells 2, 3 and 4A, with all
of the runoff from those basins contained in Cell 4A, drainage basin “F” is the Cell 4B
area. Basin boundaries are the Cell 3 dike on the north, the Cell 4A dike on the east,
and the Cell 4B dikes on the south and west. Precipitation falling within the drainage
basin boundary is retained within that area, and is considered to be contaminated
water, and precipitation falling outside the boundary is diverted away from the area,
and is considered to be uncontaminated water.
6. A revised cross section (Section 12/3, formerly Section 10/3) on Construction Drawing
8, showing one of the two sections as Section J/8 and the other as Section K/8. This
drawing was presented in Exhibit H of the January 9, 2009 Response. Section 10/3
(formerly Section 10/3) and K/8 (formerly K/7) was also now included on
Construction Drawing 8.
7. To resolve the conflict between Design Calculations for the Emergency Spillway
(spillway width is 100 feet) and Construction Drawing 7, Section J/(width as 94 feet),
DUSA provided (included in Exhibit H) a revised detail (Detail J/8) on Construction
Drawing 8 showing the dimensions described in the Design Calculations.

URS WD Evaluation:

URS WD’s review of the Round 1 Response indicated that DUSA had provided an acceptable
response to the request for mill operations to be factored into the storm capacity of the cells;
adequate spillway dimensions for the Cell 4B spillway (based on the DUSA spillway design
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calculations for Cell 4B), and a design for a discharge apron from the 4A/4B spillway that is
equivalent to that approved for the Cell 3/4A spillway.
DUSA indicated that stormwater flow from Cell 4A and upstream cells into Cell 4B had been
factored into the design. It was understood that the design is intended to achieve zero discharge
from the furthest downstream cell, Cell 4B, which would have eliminated any further questions
regarding discharges from Cell 4B from all sources of water and tributary areas. However, based
on the elevation data provided in the response, URS WD requested additional justification be
provided. URS WD concluded that Cell 4A as designed could not contain the PMP flood.
Further, URS WD noted that the point of compliance for the maximum freeboard must be
defined for each tailings cell in the system, and that the requirements for compliance monitoring
clearly identified.
URS WD developed a Round 2 Interrogatory to address the remaining issues following the
Round 2 Interrogatory Response (see below).
Round 2 Interrogatory submitted by the Division: The Division submitted a Round 2
Interrogatory to DUSA on July 31, 2009 requesting that DUSA provide the following:

• Information demonstrating the capacity of the entire facility cell containment system to
handle the Probable Maximum Precipitation (PMP) event under current conditions and
under planned future build-out scenarios. An estimation of the PMP event was requested,
with the demonstration focusing on water volume from the PMP storm, not only flow rate
between the cells.
• Information (including elevation data) to justify that a zero discharge from the furthest
downstream cell (Cell 4B), would occur in light of all sources of water, wastewater, and
tributary areas.
• Details on the freeboard calculations for Cells 4A and 4B, considering the PMP storm
event and the upstream contributions from Cells 1, 2, 3 and 4A; and
• Information to identify a point of compliance for freeboard monitoring and all equipment,
procedures, and a monitoring frequency to be used to monitor compliance at that Cell 4B
location. Information clarifying whether the Response referred to the top of the liner in
the Cell 4A/4B spillway (elevation 5596.3 ft – liquid level of 5593.3 ft) or to the South
Berm top of liner (elevation 5598 ft – liquid level of 5595 ft), and information clarifying
what the actual maximum freeboard elevation will be, under PMP conditions, and
information demonstrating that there will be no potential for Cell 4B overflow,
considering all potential flow from Cell 4A and elsewhere at the facility, was also
requested.

In its response to this Round 2 interrogatory, DUSA provided the following discussions and
clarifications:
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1. Revised drawings identifying the flow path and invert elevations for the emergency
spillway from Cell 4A to Cell 4B, confirmed the width of the proposed spillway, and
provided a appropriate spillway flow capacity design;
2. An adequate spillway discharge apron, equal to that designed and approved for the
Cell 4A spillway, and;
3. An adequate response to the request that plant flows be factored into the PMP flow
evaluation.

URS Evaluation: Based on review of the DUSA response, URS WD concluded that DUSA
provided:

• An acceptable response to the request for mill operations to be factored into the storm
capacity of the cells.
• Spillway design calculations for Cell 4B for which the spillway dimensions appeared
adequate; and
• A design for a discharge apron from the 4A/4B spillway that is equivalent to that
approved for the Cell 3 / 4A spillway.

The information submitted indicated that stormwater Cell 4A and upstream cells into Cell 4B
had been factored into the design. DUSA acknowledged that the design is intended to achieve
zero discharge from the furthest downstream cell, Cell 4B, which appears to eliminate any
further questions regarding discharges from Cell 4B from all sources of water and tributary
areas. However, based on the elevation data provided in the response, DUSA was requested to
provide additional justification of its conclusion that runoff from the PMP from all tributary
areas would be contained in Cell 4A. URS WD further noted that the point of compliance for the
maximum freeboard must be defined for each tailings cell in the system, and that the
requirements for compliance monitoring must be clearly identified.
URS WD prepared a Round 3 interrogatory to address these remaining issues (see below).

Round 3 Interrogatory submitted by the Division: The Division submitted a Round 3
Interrogatory to DUSA on September 4, 2009 requesting that DUSA:

• Provide an estimate of the Probable Maximum Precipitation (PMP) event for the site, as
well as justification for the use of the 6 hour PMP duration; and
• Identify, specifically, the location for compliance monitoring and all equipment,
procedures, and a monitoring frequency to be used to monitor compliance at Cell 4B.
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In response to the first request in the above Round 3 interrogatory, DUSA submitted the
following information:

DUSA submitted a new calculation package (Geosyntec Consultants 2009b) entitled: “Probable
Maximum Precipitation (PMP) Event Computation White Mesa Mill – Cell 4B”. The Probable
Maximum Precipitation (PMP) event for the site was evaluated using “Hydrometeorological
Report No. 49: Probable Maximum Precipitation Estimates, Colorado River and Great Basin
Drainages” (Hansen, et. al., 1984).

DUSA provided the following response with regard to the second of the Division’s requests:

“Compliance monitoring and equipment, procedures, and monitoring frequency are not included
as part of the Cell 4B design, as they will be covered by the facility’s BAT Monitoring,
Operations and Maintenance Plan. Solution monitoring procedures for Cell 4B will be duplicated
from the approved Cell 4A BAT Monitoring, Operations and Maintenance Plan…”

DUSA’s response cited the approved procedures for the Cell 4A solution monitoring, and
indicated that they will be modified as necessary for application to Cell 4B.

URS WD Evaluation: URS WD recommends that the Division accept the PMP Calculation.
URS WD recommends that the Division address the solution compliance monitoring program for
Cell 4B through review of the forthcoming Cell 4B BAT Monitoring, Operations, and
Maintenance Plan, in a manner consistent with the BAT Monitoring, Operations, and
Maintenance Plan that was previously submitted and approved for Cell 4A.

REGULATORY REQUIREMENT/ ISSUE NO. 4:

R313-24-4, 10 CFR 40 Appendix A, Criterion 5A(1), R313-24-4, 10 CFR
40 Appendix A, Criterion 5A(2), R313-24-4, R317-6-1.13: Best Available
Technology [BAT], R313-24-4, R317-6-6.4(A)(3/112): GCL, Primary
Liner, Secondary Liner, and Leak Detection System

• Refer to R313-24-4, 10 CFR 40 Appendix A, Criterion 5A(1): Surface impoundments
must have a liner that is designed, constructed, and installed to prevent any migration of
wastes out of the impoundment to the adjacent subsurface soil, ground water, or surface
water at any time during the active life (including the closure period) of the
impoundment. The liner may be constructed of materials that may allow wastes to
migrate into the liner (but not into the adjacent subsurface soil, ground water, or surface
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water) during the active life of the facility, provided that impoundment closure includes
removal or decontamination of all waste residues, contaminated containment system
components (liners, etc.), contaminated subsoils, and structures and equipment
contaminated with waste and leachate. For impoundments that will be closed with the
liner material left in place, the liner must be constructed of materials that can prevent
wastes from migrating into the liner during the active life of the facility.

• Refer to R313-24-4, 10 CFR 40 Appendix A, Criterion 5A(2): The liner required by
paragraph 5A(1) above must be: (a) Constructed of materials that have appropriate
chemical properties and sufficient strength and thickness to prevent failure due to
pressure gradients (including static head and external hydrogeologic forces), physical
contact with the waste or leachate to which they are exposed, climatic conditions, the
stress of installation, and the stress of daily operation; (b) Placed upon a foundation or
base capable of providing support to the liner and resistance to pressure gradients above
and below the liner to prevent failure of the liner due to settlement, compression, or
uplift; and (c) Installed to cover all surrounding earth likely to be in contact with the
wastes or leachate.

• Refer to R313-24-4, R317-6-1.13: Best Available Technology [BAT] means the
application of design, equipment, work practice, operation standard or combination
thereof at a facility to effect the maximum reduction of a pollutant achievable by
available processes and methods taking into account energy, public health, environmental
and economic impacts and other costs.

• Refer to R313-24-4, R317-6-6.4(A)(3/112): The Executive Secretary may issue a ground
water discharge permit for a new facility if the Executive Secretary determines, after
reviewing the information provided under R317-6-6.3, that: 1. the applicant demonstrates
that the applicable class TDS limits, ground water quality standards protection levels, and
permit limits established under R317-6-6.4E will be met; 2. the monitoring plan,
sampling and reporting requirements are adequate to determine compliance with
applicable requirements; 3. the applicant is using best available technology to minimize
the discharge of any pollutant; and 4. there is no impairment of present and future
beneficial uses of the ground water.

Round 1 Interrogatory submitted by the Division: The Division submitted a Round 1
Interrogatory to DUSA on May 29, 2008. The Interrogatory requested that DUSA provide the
following:

• Additional information demonstrating that the leak detection system and the slimes drain
system have been designed to meet performance standards that are the same as or
equivalent to applicable specific performance standards contained in the Groundwater
Discharge Permit.
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• Clarifications on Construction Drawings, Technical Specifications, and Construction
Quality Assurance Plan.
• Additional information in the specifications for the drainage aggregate.
• Additional justification for the effectiveness (hydraulic equivalency) of the GCL to a
compacted clay liner during the active cell life and for achieving the minimum
requirements contained in the Groundwater Discharge Permit over the design life of the
cell given the acidic cell environment. This justification would include revision of the
calculation for the flow through the GCL and CCL to incorporate degraded conditions in
the GCL.
• Justification for the longest flow path used in, and low factor of safety (1.1) determined
for, flow in the geonet (Action Leakage Rate calculation); and
• Demonstration that the slotted PVC pipe has the required strength to withstand damage
under the imposed loads.
• Information demonstrating that the base low-permeability liner component in Cell 4B
will be constructed of materials that are hydraulically equivalent to, or hydraulically more
effective than, both a compacted clay liner and the base liner component to be installed in
Cell 4A.
• Additional justification to support the determination of the minimum hydration level that
the GCL material should be brought to prior to placing the primary geomembrane. When
specifying the optimum pre-hydration level for the GCL, DUSA was asked to:
• Refer to the Cell 4A GCL hydraulic conductivity testing data and use that and /or
other available data for justifying the selection of the specified minimum pre-
hydration level;
• Consider the specific type of GCL anticipated to be used in the cell;
• Consider the effects of pre-hydration on the shear strength and bearing capacity of
the GCL, and the possible susceptibility for migration of bentonite to occur within the
CGL during and following GCL; and effects on overall cell stability
• Revision of the Design Report and the technical specifications as needed to include a
description of the measures that need to be taken during installation to ensure the GCL is
properly hydrated
• Revision of Section 02772 of the Technical Specifications (Geosynthetic Clay Liner) and
Section 12 of the Construction Quality Assurance Plan as needed to include applicable
requirements contained in ASTM D 6102 (“Standard Guide for Installation of
Geosynthetic Clay Liners”)

In response to the above interrogatory, DUSA provided the following:

1. Information indicating that the Action Leakage Rate (ALR) calculation shows that the
maximum head on the secondary liner does not exceed 0.15 mm, which is much less than
the maximum allowed 12 inch (1 foot). DUSA also provided a statement that this
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information is already addressed in the second paragraph of Section 3.4.3 of the design
report;

2. The ALR computed for Cell 4B is different from the ALR computed for Cell 4A. An
identical design approach and safety factors were used in the calculation for Cell 4A and
Cell 4B. However, because the cells have different dimensions, the ALR is not the same
for both cells;

3. A revision of the calculation entitled “Revised Comparison of Flow through Compacted
Clay Liner and Geosynthetic Clay Liner Calculation Package” (Exhibit D) incorporates
the correct value of the leak detection system (geonet) thickness, tLCL, of 300 mils. The
revised calculations show that the amount of flow through the secondary liner system
with a CCL is 4.74 times greater than the flow through the secondary liner system with
GCL for a liquid head of 0.20 inches.

4. Information indicating that the overall factor of safety equal to 1.1 for flow in the geonet
is acceptable because it has multiple built-in factors of safety to the calculation. The
response indicated that these safety factors account for the geonet’s reduced flow
capacity due to intrusion, biological clogging, chemical clogging, and creep, resulting in
an overall factor of safety of 3.1, and that the measures and precautions outlined in
Section 13, “Geonet”of the CQA Plan are specified to ensure minimal installation
damage and defects, and that, furthermore, the geonet is comprised of a high density
polyethylene polymer, which is resistant to acidic environments.

5. A report (dated October 28, 2008) of additional GCL hydraulic conductivity testing with
a high pH solution. It was indicated that the acidic solution was created in the laboratory,
as was done for the testing performed previously for Cell 4A. The laboratory used this
solution to perform permeability tests on the GCL at 17% moisture content. The
response stated that the results from this laboratory study demonstrated that a GCL with a
17% moisture content had a lower permeability than GCL samples hydrated to 50%.

6. A new permeant time of travel (through the GCL) analysis using the permeability data
obtained from laboratory permeability testing completed on October 28, 2008.

URS WD Evaluation: Based on review of the DUSA response, URS WD concluded that:

1. The information provided in the response did not adequately support the proposed change
in the GCL placement procedure for Cell 4B (i.e., the proposal to not pre-hydrate the
GCL prior to covering it with the geomembrane in a manner consistent with the
procedure used when constructing Cell 4A). Several published studies of laboratory tests
of GCL samples exposed to acidic permeants under similar testing conditions as those
used by the laboratory as described in the October 28, 2008 laboratory test report, as well
as the previous testing done on behalf of Denison Mines to support construction of Cell
4A were discussed that indicate or suggest different behavior in the pattern of GCL
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permeability values with increased exposure to acidic permeant than was reported in the
October 28, 2008 report. A summary of selected other laboratory GCL permeation
studies involving acidic permeants was provided to DUSA in a new Round 2
interrogatory that was developed to address this issue (see below);

2. Recently issued revised criteria for the design of geotextiles for puncture protection of
geomembranes (Koerner 2008) had not been used in the Cushion Fabric Calculations in
Appendix D of the Design Report. It was concluded that the Cushion Fabric Calculations
should be updated to incorporate thee new criteria to demonstrate that particle size
distribution of the proposed aggregate is compatible with the revised set of criteria; and

3. The permeant travel time analysis was not accepted.

URS WD prepared a Round 2 interrogatory to address the remaining issues described above (see
below).

Round 2 Interrogatory submitted by the Division: The Division submitted a Round 2
Interrogatory to DUSA on July 31, 2009. The Interrogatory requested that DUSA provide the
following:

• Additional information to demonstrate (in Appendix D of the Design Report and Section
02225 of the Technical Specifications if necessary) that the specified particle size
gradation for the drainage aggregate remains compatible with the specified cushion
geotextile, if the recently revised criteria are used in the Cushion Fabric Calculations in
lieu of the criteria currently included.
• Additional information from the testing laboratory that describes and documents that test
criteria specified in ASTM D 6766 were followed in the October 28, 2008 GCL testing
program; and
• A thorough analysis comparing the October 28, 2008 test results to: (1) the previous Cell
4A GCL permeability testing results, and (2) other published reported laboratory test
results from similar GCL permeation tests conducted using acidic permeants that suggest
the following:
o Hydraulic conductivity values of non-prehydrated GCL samples that are subjected
to exposure to an acidic permeant would be expected to generally increase
asymptotically (over pre-exposure levels) in proportion to increasing numbers of
pore volumes of flow-though of the acidic permeant, with the hydraulic
conductivity value typically continuing to rise over a range of permeation
volumes between 1 to approximately 20 pore volumes, with the same findings
sometimes reported to occur for a range between 1 and upwards of 40 or more
pore volumes
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o Other factors being equal, and under similar testing conditions, comparable, GCL
samples that were pre-hydrated and subsequently exposed to an acidic permeant
typically experienced less of an overall increase in hydraulic conductivity
compared to their pre-exposure value than non-prehydrated GCL samples
subjected to exposure to the same acidic permeant.

(As an alternative, it was indicated that Denison could proceed with the design and installation of
the GCL in Cell 4B in the same manner that was previously approved by the Division on
September 28, 2007 (UDEQ 2007) for Cell 4A (provided that the GCL used is of the same type
and made by the same manufacturer as was used for Cell 4A).

In response to the above interrogatory, DUSA agreed to install the GCL in Cell 4B and
prehydrate the GCL prior to covering it with the geomembrane, following the same procedure
that was used during construction of Cell 4A. DUSA submitted revised Technical Specifications
and a revised Construction Quality Assurance Program to reflect the pre-hydration of the GCL.

URS WD Evaluation: URS WD recommends that the Division accept this response, with the
exception of the permeant travel time analysis. The travel time analysis is not applicable to the
final design that was selected for implementation, and therefore should be excepted.

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OTHER REGULATORY REQUIREMENTS/ISSUES
SUCCESSFULLY ADDRESSED:

R317-6-6.4(A) : Monitoring Well WMMW-16

• Refer to R317-6-6.4(A). The applicant must provide information that allows the
Executive Secretary to determine: “3. the applicant is using best available technology to
minimize the discharge of any pollutant;…”. DMC must provide information that site
activities meet the requirements of Ground Water Discharge Permit, Permit No.
UGW370004.

Round 1 Interrogatory submitted by the Division: The Division submitted a Round 1
Interrogatory to DUSA on May 29, 2008. The Interrogatory requested that DUSA provide the
following:

• Identify the location of WMMW-16 on the Construction Drawings.
• provide a well construction diagram for WMMW-16 (append it to Specification Section
02070, Well Abandonment), which is currently missing from that Section; and
• submit a well plugging and abandonment (well decommissioning) plan for Well
WMMW-16.

In response to the above interrogatory, DUSA submitted (January 9, 2009) a revised
Construction Drawing 3 showing the location of the surveyed Monitoring Well WMMW-16.
Also, the well construction diagram was appended to Specification Section 02070. The Round 1
Interrogatory Response also indicated that the Contractor is responsible for the well plugging and
abandonment as stated in Section 02070, Part 1.04, Subpart B and Section 02070, Part 3.01,
Subpart A.

URS WD Evaluation: URS WD recommends that the Division accept this response.

R313-24-4, R317-6-1.1, R313-24-4, R317-6-6.4(A)(3/112): Splash Pads

• Refer to R313-24-4, R317-6-1.13: Best Available Technology means the application of
design, equipment, work practice, operation standard or combination thereof at a facility
to effect the maximum reduction of a pollutant achievable by available processes and
methods taking into account energy, public health, environmental and economic impacts
and other costs.
• Refer to R313-24-4, R317-6-6.4(A)(3/112): The Executive Secretary may issue a ground
water discharge permit for a new facility if the Executive Secretary determines, after
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reviewing the information provided under R317-6-6.3, that: 1.the applicant demonstrates
that the applicable class TDS limits, ground water quality standards protection levels, and
permit limits established under R317-6-6.4E will be met; 2. the monitoring plan,
sampling and reporting requirements are adequate to determine compliance with
applicable requirements; 3. the applicant is using best available technology to minimize
the discharge of any pollutant; and 4. there is no impairment of present and future
beneficial uses of the ground water.

Round 1 Interrogatory submitted by the Division: The Division submitted a Round 1
Interrogatory to DUSA on May 29, 2008. The Interrogatory requested that DUSA provide the
following:

• Description of the operational criteria to be used to determine the selection of the splash
pads locations, and an explanation as to why would these criteria become apparent during
construction, as opposed to during the design phase. Explain how three splash pads
would be an adequate number of splash pads (when it is anticipated that more than three
splash pads could be needed, …for example, more are anticipated to be needed along the
western berm). Describe the locations of splash pads and provide justification for the
splash pads prior to the Division granting approval to utilize the cell;
• Provide an overview how the tailings will be introduced and fed through the pipe (i.e.,
operations related to input of tailings into Cell 4B) such that the liner system is not
damaged by movement/handling of the pipe (Note: Construction Drawing 5, Section D/3
suggests that a pipe located at the upper portion of the splash pad will be the mechanism
by which tailings will be placed into Cell 4B). Demonstrate how the tailings will flow,
settle, and enter Cell 4B at critical time periods over the operational life of Cell 4B and
will not damage components (i.e., movement of sandbags, displacement of gravel and
geotextiles) of slimes drain, strip drains, leak detection system, and liner system present
in the bottom of Cell 4B;
• Demonstrate that the dimension of the protective HDPE geomembrane (20’ wide and 5’
extension from the toe of the berm) will resist the influent pressure and scour flow rate of
the tailings (in all directions, width of the side slope and extension from the toe of the
berm); and
• Update the Project Technical Specifications to include the requirements for the
construction of the protective HDPE geomembrane at splash pad locations and update the
Construction Quality Assurance Plan to include procedures which will be followed to
ensure that the protective HDPE geomembrane at splash pads is properly installed.

DUSA submitted information (January 9, 2009 Round 1 Response submittal) that included an
increased number of locations (ten vs. a value of “approximately 3” locations as were previously
proposed in the original version of the Cell 4B Design Report) for splash pads. The locations of
these ten splash pads are provided on Drawing 3 included in Exhibit H of the January 9, 2009
submittal. The splash pads include the addition of a 100-ft-wide splash pad to be installed
beneath the emergency spillway exit. URS WD understands that the splash pads, consisting of a
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textured HDPE geomembrane sheet, are designed to protect the underlying liner system from the
inlet pipes as described in Section 3.5 of the revised Cell 4B Design Report included in the
January 9, 2009 submittal and to protect the liner system from damage due to potential future
flows onto the liner from the emergency spillway.

URS WD Evaluation: URS WD recommends that the Division accept this response.

R313-24-4, 10 CFR 40 Appendix A, Criterion 5A(1); R313-24-4, 10 CFR
40 Appendix A, Criterion 5A(2); R313-24-4, 10 CFR 40 Appendix A,
Criterion 5A(5); R313-24-4, 10 CFR 40 Appendix A, Criterion 4(d); and
R313-24-4, 10 CFR 40 Appendix A, Criterion 3: Subgrade Preparation
and Earthwork

• Refer to R313-24-4, 10 CFR 40 Appendix A, Criterion 5A(1): Surface impoundments
must have a liner that is designed, constructed, and installed to prevent any migration of
wastes out of the impoundment to the adjacent subsurface soil, ground water, or surface
water at any time during the active life (including the closure period) of the
impoundment. The liner may be constructed of materials that may allow wastes to
migrate into the liner (but not into the adjacent subsurface soil, ground water, or surface
water) during the active life of the facility, provided that impoundment closure includes
removal or decontamination of all waste residues, contaminated containment system
components (liners, etc.), contaminated subsoils, and structures and equipment
contaminated with waste and leachate. For impoundments that will be closed with the
liner material left in place, the liner must be constructed of materials that can prevent
wastes from migrating into the liner during the active life of the facility.
• Refer to R313-24-4, 10 CFR 40 Appendix A, Criterion 5A(2): The liner required by
paragraph 5A(1) above must be: (a) Constructed of materials that have appropriate
chemical properties and sufficient strength and thickness to prevent failure due to
pressure gradients (including static head and external hydrogeologic forces), physical
contact with the waste or leachate to which they are exposed, climatic conditions, the
stress of installation, and the stress of daily operation; (b) Placed upon a foundation or
base capable of providing support to the liner and resistance to pressure gradients above
and below the liner to prevent failure of the liner due to settlement, compression, or
uplift; and (c) Installed to cover all surrounding earth likely to be in contact with the
wastes or leachate.
• Refer to R313-24-4, 10 CFR 40 Appendix A, Criterion 5A(5): When dikes are used to
form the surface impoundment, the dikes must be designed, constructed, and maintained
with sufficient structural integrity to prevent massive failure of the dikes.
• Refer to R313-24-4, 10 CFR 40 Appendix A, Criterion 4(d): A full self-sustaining
vegetative cover must be established or rock cover employed to reduce wind and water
erosion to negligible levels.
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• Refer to R313-24-4, 10 CFR 40 Appendix A, Criterion 3: Where full below grade burial
is not practicable, the size of retention structures, and steepness of slopes associated with
exposed embankments must be minimized by excavation to the maximum extent
reasonably achievable or appropriate given the geologic and hydrologic conditions at a
site. In these cases, it must be demonstrated that an above grade disposal program will
provide reasonably equivalent isolation of the tailings from natural erosional forces.

Round 1 Interrogatory submitted by the Division: The Division submitted a Round 1
Interrogatory to DUSA on May 29, 2009. The Interrogatory requested that DUSA provide the
following:

• Information to demonstrate that the construction process for the earthwork movement of
soil between Cell 4B and Cell 3 will not cause cross-contamination of impacted soil to
clean area. The Division indicated that information needs to be demonstrating that the
levels of radiation (contamination) in Cell 4B subgrade are acceptable before a
construction permit can be issued and the liner system installed;
• Answers to the following questions: How does the height (i.e., weight) of the stockpiled
soil affect slope stability of the cut (i.e., West Berm slope)? Demonstrate that soil
stockpile slopes will be stable under foreseeable future conditions. How does stockpiling
of soils (loading) just west of the West Berm and subsequent removal of that soil affect
the performance of the West Berm? In the interrogatory, it was noted that the Technical
Specification Section 02200, Paragraph 3.05 and Construction Drawing No. 2 detail the
requirements for stockpiling excavated soil; however, no limit was placed on the height
of the stockpiled soil in the Technical Specifications;
• Technical specifications indicating how each of the cut slope surfaces will be completed
(i.e., compacted,) to ensure strength and stability of the slopes for Cell 4B’s operation;
• Information to demonstrate how the outside slope of the south berm of Cell 4B and the
upgradient portion of the west berm of Cell 4B will be completed to prevent excessive
erosion and potential slope failure;
• Specifications for drilling and ripping to support any blasting the Contractor might
perform, and demonstrating what level of blasting will be required to remove rock to the
grades/elevations for Cell 4B as indicated in the Drawings and how the blasting will
effect the stability of the surrounding berms in place, effect the functionality of the
surrounding berms which will be cut to serve as the side slopes for Cell 4B, and effect
any other components of Cell 4B and adjacent Cells;
• Information to demonstrate the effect blasting will have on the effective permeability and
speed of water travel through underlying material. The Design should demonstrate that
removal of the rock by blasting does not compromise the design and functionality of Cell
4B and other Cells. The design and Technical Specification Section 02200 placed a
requirement on the Contractor that blasting shall not cause damage. DUSA was asked to
define “damage” both in terms of nearby dike stability, but also foundation permeability
under Cell 4B;
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• Provide detail what level of blasting is necessary to construct Cell 4B without causing
damage and specific points of compliance the Contractor should be expected to meet
such that damage is not caused;
• Provide a definition of “Project Manager” as used in the Technical Specifications;
• Revise Subsections 2.01 (A through C) and 3.02 (A through F) of Section 02220
(Subgrade Preparation) and Section 7.3.3 of the Construction Quality Assurance Plan to
incorporate applicable requirements contained in ASTM D 6102-06, including, but not
limited to the following ;
9 The subgrade surface shall be firm and unyielding, with no abrupt elevation
changes, voids and cracks, ice, or standing water
9 The subgrade surface shall be smooth and free of vegetation, sharp-edged rock,
stones, sticks, construction debris, and other foreign matter that could contact the
GCL
9 At a minimum, the subgrade surface shall be rolled with a smooth-drum
compactor of sufficient weight to remove any excessive wheel ruts, footprints, or
other abrupt grade changes.
• Additional information to address a number of other issues regarding the Technical
Specifications and the Construction Quality Assurance Plan including:
9 Information demonstrating that desiccation cracks of ¼ inch width or less are
acceptable or remove this permissible crack width value from the specifications.
DUSA was asked to detail in the specifications how any desiccation cracks
observed in the subgrade will be remedied. A requirement that the subgrade
surface be checked for cracks and such cracks be remedied was also requested to
be included in specifications and/or in the Construction Quality Assurance Plan as
applicable.
9 Information demonstrate that maximum particle dimension of 3 inches is
acceptable or revise this requirement to be consistent with typical GCL / FML
manufacturer’s recommendations, and indicating that such soil shall be well
graded material (to be consistent with additional typical GCL / FML
manufacturer’s recommendations for subgrade soil) or provide justification for
not including this requirement in the specifications
9 Definitions/clarifications of “fill” as used in Subsection 2.01 of the Section 02200
(Earthwork) and “subgrade soil” as used in Subsection 2.01 (C) of Section 02220
(Subgrade Preparation) of the Technical Specifications to clearly distinguish
between these two types of fill material, and a clarification as to whether “fill”
refers to the material that is suitable for use in constructing the berms, and
“subgrade soil” is select fill material suitable for use in constructing/developing
the subgrade surface
9 Revision to Subsection 3.04 (D) of Section 02200 (Earthwork) of the
specifications which called for the fill to be compacted in lifts no greater than 12-
inches, to 90% of maximum density and to +/- 4% of optimum moisture content
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(per ASTM 1557). Subsections 3.03 (E) and 3.04 (C) of Section 02220 (Subgrade
Preparation) call for fill to be compacted in lifts no greater than 8-inches, to 90%
of maximum density and to +/- 3% of optimum moisture content (per ASTM
1557). Due the critical nature of the fill placement for the slopes and the subgrade
fill placement for the subgrade, the Division deemed that all the fill placed needs
to be compacted in lifts no greater than 8-inches, to 90% of maximum density and
to +/- 3% of optimum moisture content (per ASTM 1557).
9 A resolution of an inconsistency between the compaction requirements cited in
Section 3.3.4 of the design report and the Technical Specifications that call for 8-
inch lifts and +/- 3% of optimum moisture.

In response to the above interrogatory, DUSA submitted information which provided the
following acceptable responses to this interrogatory:
• An explanation for the process of moving soils between Cell 4B and Cell 3 so as to not
cause cross-contamination;
• A stability analyses, provided in Exhibit A, along with updated Drawings related to
stockpile details;
• Technical specification details were provided regarding cut slope surfaces;
• The term “Project Manager” has been revoked and replaced with appropriate personnel in
the technical specifications (Exhibit F);
• Section 02220 of the Technical Specifications has been revised to include appropriate
ASTM D 6102-06 requirements and is provided in Exhibit F;
• Removal of the crack width from Section 02220 and the revised Section is provided in
Exhibit F;
• A revision to the Technical Specification Section 02220 addressing subgrade soil used for
GCL and FML installation applications as is consistent with manufacturer’s
recommendations;
• Revised Technical Specification Sections 02200 and 02220 describing material and
placement requirements of fill soils and subgrade soils; and
• Revised compaction requirements on soil placement as determined by ASTM D 1557.

In response to the request for additional information on the subgrade preparation and earthwork
specifications, DUSA provided the following discussions and clarifications:
1. Regarding the contamination controls that would be implemented while transferring
excavated material into Cell 3, DUSA described a proposed plan that would
effectively eliminate the potential for cross contamination of earthwork equipment
working within Cell 3.
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2. Regarding the stockpiling of soil adjacent to the West Berm, DUSA presented an
appropriate stockpiling scenario in the calculation “Slope Stability Analyses, White
Mesa Mill, Cell 4B, Blanding Utah”, dated July 2008 by GeoSyntec Consultants.
The scenario contained a maximum stockpile height of 20 ft and an offset distance of
20 ft (both measured from the crest of the West Berm), and a berm slope of 2H:1V.
These parameters are recognized as the limitations on the stockpiling operation
without additional analysis.
3. Regarding the procedures for construction and compaction of cut slopes and berm
erosion controls, DUSA referred to specification Section 02200 (Earthwork) and
Section 02220 (Subgrade Preparation). These specifications provide sufficient details
to establish construction and compaction of slopes.
It was determined that the impact of blasting on the functionality and design of Cell 4B and
the other cells had still not been resolved. In order to facilitate resolution to the blasting
questions, it was decided to consolidate the interrogatories and associated questions
discussed in this section under a Round 2 interrogatory addressing the issue of Dike Integrity.

URS WD Evaluation: URS WD recommends that the Division accept this response.

R313-24-4, 10 CFR 40 Appendix A, Criterion 5A(2)(a): Cell 4B
Aggregates Backfill and Compatibility Of Materials

• Refer to R313-24-4, 10 CFR 40 Appendix A, Criterion 5A(2)(a): The liner must be
constructed of materials that have appropriate chemical properties and sufficient strength
and thickness to prevent failure due to pressure gradients (including static head and
external hydrogeologic forces), physical contact with the waste or leachate to which they
are exposed, climatic conditions, the stress of installation, and the stress of daily
operation.

Round 1 Interrogatory submitted by the Division: The Division submitted a Round 1
Interrogatory to DUSA on May 29, 2009. The Interrogatory requested that DUSA provide the
following:

• Demonstrate how much the specified aggregate and sand will deteriorate under a pH of 1
to 2 over the design life of Cell 4B, including the change in permeability of the aggregate
and sand with time and how the change in permeability will effect the drainage of liquids
in the slimes drain (both the header and strip drains) with time; and how the head on the
primary liner and secondary liner is effected over time due to the change in aggregate and
sand permeability;

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• Provide the basis for determining the requirement of the aggregate and sand (in sand
bags) shall have a carbonate content loss of no more than 10 percent by weight based on
UDOT standard specifications; AND

• Demonstrate how the slope stability (i.e., resistance to sliding) of the aggregate is
affected by the low pH environment (of particular concern if the risers and bedding are
placed on a 2H:1V slope since the side slope riser system for liquid removal from slimes
drain and leak detection includes aggregate bedding).

In response to the above interrogatory, DUSA submitted information (January 9, 2009) that
included an explanation on the selection of the aggregate and sand requirements which were
based on an identical slimes drain system design used in Cell 4A. It was also noted that the use
of these materials had been previously approved by the UDEQ in a design approval letter for
Cell 4A dated June 25, 2007. An explanation was also provided addressing the negligible effect
of carbonate loss on the slimes drain system and the multiple safety factors built into the Slimes
Drain Calculation.

URS WD Evaluation: URS WD recommends that the Division accept this response.

R313-24-1(3); R313-24-4; R313-15-501; R313-15-406; R313-24-3(1);
R313-24-4; 10 CFR 40 Appendix A, Criterion 5A(1): Radiation Survey
to Demonstrate Acceptable Subgrade Conditions Prior to Liner
System Construction

• Refer to R313-24-1(3), R313-24-4, R313-15-501, R313-15-406, and 10 CFR 40
Appendix A, Criterion 5A(1); DRC rules require that a radiation survey be performed to
demonstrate that the requirements of R313-15 are met, including the magnitude and
extent of radiation levels and concentrations or quantities of radioactive material (see
R313-15-501). DRC rules also require the applicant to describe “… how facility design
and procedures for operation will minimize, to the extent practicable, contamination of
the facility and the environment,…” (see R313-15-406). R313-24-4 and 10 CFR 40
Appendix A, Criterion 5A(1) require that for uranium tailings impoundments … the liner
be designed, constructed, and installed to prevent migration of wastes out of the
impoundment to adjacent subsurface soil at any time during the active life of the
impoundment.”
• Refer to UAC R313-24-3(1) UAC R313-24-4, 10 CFR 40 Appendix A, Criterion 7

Round 1 Interrogatory submitted by the Division: The Division submitted a Round 1
Interrogatory to DUSA on May 29, 2008. The Interrogatory requested that DUSA provide an
evaluation that demonstrates that the existing soil subgrade has radiation and contamination
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levels that are acceptable. The applicant was requested to demonstrate and justify that any soil
concentration level proposed as a cleanup standard has both technical and regulatory
justification.

In response to the above interrogatory, DUSA submitted a response (January 9, 2009) which
provided an explanation that no cleanup or justification of residual contamination of the liner
subgrade is necessary because the construction area proposed for Cell 4B has not been
previously used as a location for radioactive materials storage. The Response included an
explanation that Cell 4B is upwind of existing tailings cells and is unlikely to encounter
windblown material that would cause contamination of the base of the liner system.

URS WD Evaluation: URS WD recommends that the Division accept this response.

SUMMARY AND CONCLUSIONS:

As discussed in the preceding pages, DUSA has presented a design for Cell 4B that addresses all
relevant and applicable regulatory requirements, with the exception of two items:
1. Cell 4B Solution Monitoring Program: The proposed solution monitoring program
should be reviewed as part of the future Cell 4B BAT Monitoring, Operations, and
Maintenance Plan, in a manner consistent with the process that was used to review and
approve the BAT Monitoring, Operations, and Maintenance Plan for Cell 4A.
2 Permeant travel time calculation: URS WD recommends that the GCL permeant travel
time calculation that DUSA submitted on January 9, 2009 be excepted from the design
approval that the Division would grant for the Cell 4B design (due to not being applicable
to the final design selected for implementation)..

URS WD recommends that the Division accept the revised Cell 4B Design Report and
subsequent submittals furnished in DUSA’s Reponses to the Round 1, 2, and 3 Interrogatories,
and as described herein. URS WD also recommends that the Division review a future Cell 4B
solution monitoring program to be submitted by DUSA, as part of the future Cell 4B BAT
Monitoring, Operations, and Maintenance Plan, in a manner consistent with that process used to
review and approve the BAT Monitoring, Operations, and Maintenance Plan for Cell 4A.

REFERENCES:

Denison Mines (USA) Corp. 2009a. “Cell 4B Lining System Design Report, Response
to Division of Radiation Control (“DRC”) Request for Additional Information – Round 1
Interrogatory, Cell 4B Design”, Letter dated January 9, 2009, from Harold R. Roberts to
Dane Finerfrock, Division of Radiation Control.
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Washington Safety Management
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Denison Mines (USA) Corp. 2009b. “ Re: Cell 4B Lining System Design Report,
Response to DRC Request for Additional Information – Round 2 Interrogatory, Cell 4B
Design”, (including attachments), Letter to Dane Finerfrock, dated August 7, 2009.
Denison Mines (USA) Corp. 2009c. “ Re: Cell 4B Lining System Design Report,
Response to DRC Request for Additional Information – Round 3 Interrogatory, Cell 4B
Design”, (including attachments), Letter to Dane Finerfrock, dated September 11, 2009.

Geosyntec Consultants 2007. “Cell 4B Design Report, White Mesa Mill, Blanding,
Utah”. December 2007. Prepared for International Uranium (USA) Corporation.

Geosyntec Consultants 2008. “Slope Stability Analysis, White Mesa Mill, Cell 4B,
Blanding, Utah”, July 2008.

Geosyntec Consultants 2009a. Revised Section 02200 of the Technical Specifications,
Revised September 2009.

Geosyntec Consultants 2009b. Probable Maximum Precipitation (PMP) Event
Calculation Package, Calculation dated September 10, 2009.

Hansen, E. Marshall, Schwartz, Francis K., Riedel, John T., 1984. “Hydrometeorological
Report No. 49: Probable Maximum Precipitation Estimates, Colorado River and Great
Basin Drainages,” Hydrometeorological Branch Office of Hydrology National Weather
Service, U.S. Department of Commerce, National Oceanic and Atmosphere
Administration, U.S. Department of Army Corps of Engineers, Silver Springs, Md.

State of Utah Division of Water Quality 2008. “Groundwater Discharge Permit, Denison
Mines (USA) Corp.” Permit No. UGW370004. March 17, 2008.

Utah Department of Environmental Quality (UDEQ) 2007. “Revised GCL Hydration
Plan Approval”, Letter from Dane Finerfrock, Utah Department of Environmental
Quality, to Harold Roberts of Denison Mines (USA) Corporation, dated September 28,
2007.
Utah Division of Radiation Control 2008. Cell 4B Design Report Interrogatories –
Round One. Denison Mines (USA) Corporation White Mesa Mill, Blanding, Utah. May
29, 2008
Utah Division of Radiation Control 2009a. Cell 4B Design Report Interrogatories –
Round Two. Denison Mines (USA) Corporation White Mesa Mill, Blanding, Utah. July
31, 2009
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Utah Division of Radiation Control 2009b. Cell 4B Design Report Interrogatories –
Round Three. Denison Mines (USA) Corporation White Mesa Mill, Blanding, Utah.
September 4, 2009.