2010-01-04_REVISION - M1977285 ‎(7)‎

• Permit No: M1977285
• IBM Index Class Name: REVISION
• Doc Date: 1/4/2010
• 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.
The conceptual design for the ore storage pads, including the use of a geomembrane
liner, is provided below. Denison will submit a complete ore storage pad design (e.g.,
specifications and drawings) to DRMS for review and approval prior to construction
of these EPFs.
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 Conceptual Design
The existing ore stockpile areas will each be replaced with 100-ft by 100-ft ore storage
pads, with the exception of a 100-ft by 50-ft pad at the 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 proposes to use a polyvinyl chloride
(PVC) geomembrane liner for ore pad construction. The conceptual 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 three-foot high berm along the perimeter of the pad and may
also be used as liner backfill. The berm will be constructed to contain surface water
run-off from the pad area. The geomembrane liner will be installed consistent with
the manufacturer's specifications and an anchor trench will be constructed to secure
the liner. Select material, typically with grain size no larger than 0.5-inch in diameter,
will be used as bedding and backfill to prevent puncture damage to the membrane
from the use of heavy equipment on the pad.
6-1
T:\64986-Denison Mines\Task Order 4 - EPP Sunday Mines Group-Van4\Sunday Mines Group\DRMS RTC and Revised EPP\FINAL DRMS Report - EPP Sunday Mines.doc