2010-03-18_REVISION - M1977285 ‎(6)‎

• Permit No: M1977285
• IBM Index Class Name: REVISION
• Doc Date: 3/18/2010
• Doc Name: Response to technical adequacy comments
• From: Denison Mines
• To: DRMS
• Type & Sequence: AM3
• Email Name: RCO
• Media Type: D
• Archive: No

6.0 Evaluation of Proposed and Existing Environmental
Protection Facilities
An environmental protection facility (EPF) is defined by HRMMR §1.1(15) as follows:
"Environmental Protection Facility" means a structure which is identified in
the "Environmental Protection Plan" as designed, constructed, and operated
for control and containment of designated chemicals, acid mine drainage, or
toxic or acid-forming materials that will be exposed or disturbed as a result of
mining and reclamation operations."
Although geochemical assessment of ore has indicated that the material is not toxic
forming from a risk management criteria (RMC) perspective, as a best management
practice, Denison has designated ore storage pads as EPFs for the Sunday Mines
Group. Production and storage of ore is not currently being conducted at the Sunday
Mines Group. Prior to resuming these operations, Denison will construct ore pads
that are compliant with DRMS' "General Ore Pad Construction Criteria." Denison is
committed to providing containment of surface water in contact with ore material. A
summary of design for the ore storage pads, including the use of a geomembrane
liner, is provided below. The complete ore storage pad design (e.g., specifications and
drawings) is provided as Attachment S.
6.1 Proposed Ore Storage Pad with Geomembrane Liner
The ore stockpile areas at the Sunday Mines Group are currently located at the St.
Jude, Sunday, Topaz, and West Sunday Mine sites. The construction of an ore storage
pad is not planned for the Carnation Mine; ore is not produced at this mine. Ore is
temporarily stored at these stockpile locations and is routinely transported by truck to
the White Mesa Mill near Blanding, Utah for processing (ore is typically stored for
relatively short time periods of one to two weeks; less than 180 days). Ore storage
pads will be constructed at each of these stockpile areas to contain surface water
during future ore storage/ stockpiling activities.
6.1.1 Proposed Ore Storage Pad Design
The existing ore stockpile areas will each be replaced with an 80-ft by 80-ft proposed
ore storage pad at both the Topaz and Sunday Mine, and an 60-ft by 60-ft at both the
West Sunday and St-Jude Mine. On site soils do not meet the minimum requirements
of plasticity (plasticity index of 10 percent) for use as soil liner material. Accordingly,
Denison will use a polyvinyl chloride (PVC) geomembrane liner for ore pad
construction. The pad layout is shown in Figures 2-2 through 2-5. Soil from the
footprint of each ore storage pad will be used to construct a berm along the perimeter
of the pad. The berm will be constructed to contain surface water run-off from the pad
area and prevent surface water run-on. The geomembrane liner will be installed
consistent with the manufacturer's specifications and an anchor trench will be
constructed to secure the liner. Bedding and cover material, typically with grain size
no larger than 3/8-inch in diameter, will be used to prevent puncture damage to the
membrane from the use of heavy equipment on the pad.

6-1
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