DRC-2010-002731 - 0901a06880177e83

DENISON
MINES
Oii
DRC-2010-00E73i
^ ••••
Received
APR 20^.0
Diulsion ot
Denison Mines (USA) Corp.
105017thi Street, Suite 950
Denver, CO 80265
USA
Tel : [phone]
Fax:[phone]
www.denisonmineB.com
March 31, 2010
VIA PDF AND UPS
Dane L. Finerfrock,
Executive Secretary
Utah Radiation Control Board
Utah Department ofEnvironmental Qualily
168 North 1950 Wesl
P.O.Box 144810
Salt Lake City. UT 84114-4810
Dear Mr. Finerfrock:
Re: State of Utah Radioactive Materials License No» UT1900479 White Mesa Uranium
Mill - Request for Variance Related to Freeboard Limit for Tailings Cell 3
Reference is made to our previous correspondence of October 9, and December 11, 2008, and
May 26, 2009 requesting variances from and amendments to the freeboard limil requirement for
Cell 3. This letter requests an interim variance to the White Mesa Mill's (the "Mill's")
Radioactive Materials License (the "License") and Groundwater Discharge Permit (the
"pemiit") to waive Uie freeboard limit for Ceil 3, pending Executive Secretary review of the
foregoing License and Pennit amendment requests, for the reasons discussed beiow,
1. Facts and Background Information
a) The tailings impoundment system at the Mill is comprised of four cells. Tailings Cell
K which is an evaporation pond, was completed and put into service m June 1981.
Tailings Cell 2 was completed and put inlo service in May 1980. and is cunently full
and covered wilh interim cover. Tailings Cell 3 was completed and put into service in
September 1982 and is currently active, although it is nearly fUled. Tailings Cell 4A
was constmcted and put into ser\'ice in 1989, and was used for a short period of time to
receive tailings solulions until Mill operations ceased in 1991 due to low commodity
prices. Cell 4A fell into disrepair after lhat time. All of the tailings solutions and
residual crystals were removed from the Cell in 2006. CeU 4A has since been relined
and was authorized by lhe Executive Secretary for use on September 17, 2008. In
2009, the MiU submitled an Application to Amend the License for the incorporation of
an additional tailings cell, CeU 4B;
b) The freeboard limils are set as per the January 10, 1990 Drainage Report for CeU 1 al a
liquid maximum elevalion of 5,615.4 feet above mean sea level ("fmsl");
c) The freeboard limit for Cell 3 is determined annuaUy using a prescribed formula set out
in the Oclober 13, 1999 revision to the Drainage Report. The current freeboard limit
for Cell 3 was previously calculated under this procedure at 5,601.6 fmsl. However, in
State of Ulah Department of Environmental Quality ("UDEQ") conespondence dated
November 20, 2008 an interim variance and limit was eslablished at 5,602.5 fmsl for
CeU 3;
d) In conjunction with the variance established under (ii) above, an inierim maximum
elevalion for Cell 4A was also established at 5,593.74 fmsl;
e) The maximum elevation of 5,593.74 fmsl for CeU 4A has been sel assuming that Uie
total probable maximum precipitation ("PMP") volume for Cells 2, 3 and 4A will be
accommodated in Cell 4A. By letter dated December 11, 2008, Denison applied for an
amendment to the License lo set the freeboard limit for Cell 4A al 5,593.74 fmsl and to
eliminate tlie need to set a freeboard limil for Cell 3, given that the freeboard liniit of
5,593.74 fmsl for Cell 4A is adequate lo accommodate die lotal PMP volume for Cells
2, 3 and 4A;
f) In addition. Part I.D.2 of the Permit provides lhat under no circumstances shall the
freeboard of any tailings cell be less than three feet, as measured from the top of the
flexible membrane liner ("FML"). The lop ofthe FML in Cell 1 is at 5,618.5 fmsl, and
the top of the FML in Cell 3 is at 5,608.5 fmsl. This means Uiat Part I.D.2 of the
Permit provides a secondary requirement that the maximum wastewater pool elevations
in Cells 1 and 3 cannot exceed 5,615.5 and 5,605.5 fmsl, respectively; and
g) During the weekly tailings inspection performed at approximately 10:00am on March
26, 2010, Cell 3 was observed visually to be high in elevalion compared to the previous
week. When the elevalion survey was performed at 10:15am on March 26, 2010, this
observation was confirmed. The survey results indicated a wastewater pool elevation
of 5,602.53 fmsl, compared lo the cunent freeboard limit for Cell 3 of 5,602.50 fmsl,
representing an exceedance of 0.03 feet, or 0.36 inches.
DENISO
MINES
im
2. Problems with Requirement for a Freeboard Limit in Cell 3
As described above, CeU 3 is m the process of being filled to capacily wilh solids in preparation
for closure. Maintaining a freeboard limit for a cell al the end of its operating capacity is
problematic and infeasible. As a tailings cell nears the limit of its solids capacily, the pool area
is continually reduced. As the pool area shrinks, the cell's freeboard capacity for precipitation
capture is limited dramatically. It becomes increasingly difficult, or totally impracticable, to
simultaneously balance both the solids addition rate and the solutions evacuation rate for a
continually-changing pond area, as evidenced by the freeboard exceedence event of March 26,
2010. The exceedence occuned despite the fact thai:
a) Mill personnel had made a proactive attempt to manage the liquid level by transfening
Cell 3 liquid to Cell 4A for over a month in anticipation of the start of die ore run and had
achieved a liquid level 7 inches lower than the freeboard limit;
b) CeU 3 was receiving only CCD solids and solutions from the CeU 2 slimes drain, while
and all other tailings flows were routed to Cell 4A;
c) monitoring and surveying were performed at the required frequency;
d) a new, larger pump had been uistalled lo improve the transfer of liquids from Cell 3 to
Cell 4A;
e) all pumping equipment was operating normally; and
f) the liquid transfer from Cell 3 to Cell 4A was occurring as plamied.
hi addition, since a sufficient freeboard is retained in CeU 4A for the PMP volume for all of Cells
2, 3, and 4A, there is no need to apply a freeboard limit to Cell 3.
3. Variance Requested
As result ofthe issues identified above, Denison proposes the following variance to the existing
license and permit conditions, pending Executive Secretary review of the License and Permit
amendment requests referred lo above:
(a) the freeboard limit in Cell 1 will contmue to be sel at 5,615.4 fmsl, which is Uie level
currently required by the application of License condition 10.3, and which will allow Cell
1 to capture all the PMP volume associated with Cell 1;
DENISO MINES
jya
(b) the freeboard limil for Cell 2 wiil continue to be inapplicable, since Cell 2 is filled with
solids; all of die PMP volume associaied with Cell 2 will continue to be aliribulcd to Cell
4A (and/or any future tailings cells);
(c) die freeboard limit for Cell 3 will be inapplicable, since Cell 3 is close to be being filled
with solids, and all of the PMP flood volume associated with Cells 2 and 3 will be
attributed lo Cell 4A (and/or any future tailings cells); and
(d) the freeboard limit for Cell 4A will continue to be set at 5,593.74 fmsl, which assumes
that the total PMP volume for Cells 2. 3, and 4A of 159.4 acre feel will be accommodated
in Cell 4A.
If you have any questions or require any further information, please contact the undersigned.
Yours truly,
Jo Arm Tischler
Director, Compliance and Permitting
cc: David C, Frydenlund
Ron F. Hochstein
Ryan Palmer
Harold R. Roberts
David E. Turk
DENISO
MINES
JiLL