2010-03-18_REVISION - M1997032

• Permit No: M1997032
• IBM Index Class Name: REVISION
• Doc Date: 3/18/2010
• Doc Name: Response to Technical Adequacy comments
• From: Denison Mines
• To: DRMS
• Type & Sequence: AM1
• 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 HRMNM §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 an ore storage pad as an EPF for the Van 4 Mine.
Production and storage of ore is not currently being conducted at the Van 4 Mine.
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 K.
6.1 Proposed Ore Storage Pad with Geomembrane Liner
Ore is temporarily stored at a stockpile location at the Van 4 Mine 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). An ore storage pad will be constructed at the stockpile area to contain surface
water during future ore storage/stockpiling activities.
6.1.1 Proposed Ore Storage Pad Design
The existing ore stockpile area will be replaced with an 80-ft by 80-ft ore storage pad.
On site soils do not meet the minimum requirements of plasticity (plasticity index of
10 percent) for use as soil liner material. Accordingly, Denison proposes to use a
polyvinyl chloride (PVC) geomembrane liner for ore pad construction. The pad layout
is shown in Figure 2-1. 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.
Additional design information including detail drawings and specifications for the
installation of the PVC geomembrane ore pad liner system at the Van 4 Mine is
provided in Attachment K.
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6-1
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