DRC-2011-007118 - 0901a06880257a5c

OEMiSON
MIMES
August 1,2011
Denison Mines (USA) Corp.
1050 17th Street, Suite 950
Denver, CO 80265
USA
Tel: [phone]
Fax:[phone]
www.denisonmines.com
VIA PDF AND FEDERAL EXPRESS
Mr. Rusty Lundberg
Executive Secretary
Utah Division of Radiation Control
Utah Department of Environmental Quality
195 North 1950 West
Salt Lake City, UT 84116-3097
Re: White Mesa Mill Cell 2 Slimes Drain Compliance - Confirmation of Completed
Steps from June 17, 2011 Plan Letter
This letter provides confirmation of the actions committed to during discussions in Denison
Mines (USA) Corp.'s ("Denison's") conference call with Utah Division of Radiation Control
("DRC") on May 25, 2011 and in a in June 17, 2011 Status Update letter regarding Cell 2
Annual Slimes Drain Compliance (the "June Status Update" or the "Status Update Letter") at
White Mesa Mill. The actions are addressed in this letter in the same order as they were
discussed in the Status Update Letter.
Re-grading of Interim Fill on Cell 2
The Status Update Letter committed that Denison would re-grade the interim fill on Cell 2 on or
before August 1, 2011 in order to reduce the potential for the accumulation of stormwater on the
surface of Cell 2, which can potentially infiltrate into Cell 2. Denison believes that the reduction
of infiltration by removal of low areas and filling of potential pooling spots will have a positive
effect on the slimes drain level.
Denison completed filling and regrading of Cell 2 on July 30, 2011. The regrade required
62,000 cubic yards of cut and fill, consisting of alluvial material and/or rock. Drawings of the
cell regrading plan are provided in Attachment 1. Photographs of the completed regrading are
provided in Attachment 2.
N:\Cell 2\08.01.11 Itrto R lundberg Cell 2 completion\08.01.11 Itrto R Lundberg Cell 2 modifications.docx
Letter to Mr. Rusty Lundberg
August 1,2011
Page 2
Installation of Piezometers
As discussed in the Status Update Letter Denison has performed an engineering evaluation of
issues related to the feasibility of installation and use of piezometers in Cell 2 for the above
purpose. Based upon this further evaluation, Denison does not believe that it is feasible to install
and operate peizometers that would provide representative and dependable measure of the slimes
drain level for the following reasons.
For the reasons stated in the letter, including
1. The likelihood that artesian effects will create piezometer levels inconsistent with slimes
drain levels;
2. The fact that no piezometer or collection of piezometers could represent cell-wide
conditions; and
3. The high risk of continual plugging
Denison has determined that piezometer installation is not feasible in Cell 2 and, as stated in the
Status Update Letter, has not installed piezometers.
Engineering Evaluation of Pump in Cell 2
Denison performed an engineering evaluation of the current pump in the Cell 2 access pipe to
determine if any changes can be made to improve its efficiency and output and has made
mechanical changes to the pump configuration and adjustments to the pump operational cycle as
discussed below.
As discussed in the June Status Letter, the sensor settings (which trigger pump startup) were
adjusted from the former 0 feet to 4 feet setting to the current setting of 0 feet to 2 feet. As a
result, the pump rate has been slowed sufficiently to allow the pump to cycle on more frequently
for a longer time at a narrower range of solution levels, in effect, performing like a smaller
pump, as suggested by DRC. This mode of operation has been maintaining as lower slimes drain
level based on the increased frequency of pumping.
Amendment of the Groundwater Discharge Permit for Reduced Monitoring Frequency
Denison has received DRC's June 30, 2011 Draft Statement of Basis Memorandum and Draft
amended Groundwater Discharge permit. As agreed upon in a telephone conversation between
Denison and DRC during the week of July 25, 2011, Denison will provide comments or
proposed markups to the draft documents by August 17, 2011.
Please contact me if you have any questions or require any further information.
DENISO
MINES
Letter to Mr. Rusty Lundberg
August 1,2011
Page 3
Yours very truly,
DENISON MINES (USA) CORP.
(^JX/^ ^^^^^^^^^^
Jo Ann Tischler
Director, Compliance and Permitting
cc: David C. Frydenlund
Ron F. Hochstein
Harold R. Roberts
David E. Turk
Kathy A. Weinel
DENISOrAi
MINES
Letter to Mr. Rusty Lundberg
August 1,2011
Page 4
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Letter to Mr. Rusty Lundberg
Auuust 1.2011
Pages
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DENISO
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Cell 2 - Looking Northeast
Cell 2 - Looking East »2
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