DRC-2011-001352 - 0901a068801f8a2d

State of Utah
GARY R. HERBERT
Govemor
GREG BELL
Lieutenant Governor
Department of
Environmental Quality
Amanda Smith
Executive Director
DrVISlON OF RADIATION CONTROL
Rusty Lundberg
Director
C- 201 1-00 13
TiLt
1^/25-
January 25, 2011
Mr. David C. Frydenlund
Vice President and General Counsel
Denison Mines (USA) Corp. (DUSA)
1050 Seventeenth Street, Suite 950
Denver, CO 80265
Subject: January 12, 2011 State of Utah Groundwater Discharge Permit No. UW370004 White Mesa
Mill - DUSA Request for Removal of Certain Groundwater Monitoring Parameters at Well
MW-11 from Accelerated Monitoring Status: Request for Information
Dear Mr. Frydenlund:
In a letter dated January 12, 2011 DUSA submitted a request that accelerated monitoring for
Tetrahydrofuran (THF) in well MW-11 be retumed to quarterly monitoring rather than the accelerated
monthly monitoring. The Ground Water Compliance Limit (GWCL) for THF in MW-11 is 11.5 ug/L.. As
evidence to justify this request, DUSA provided analytical reports that showed THF concentrations in well
MW-11 were below 11.5 ^g/L in nine consecutive sampling events since the initial exceedance of 12 |ag/L
in the 1" Quarter, 2010, see below for details.
Well . Gonstituent G\VCL Sample Rbsult:
MW-11 THF 11.5 ug/L 1" Quarter, 2010 12
2"" Quarter, 2010 5.2
May 2010 <1.0
June 2010 <1.0
July 2010 2.17
August 2010 <1.0
S'" Quarter, 2010 <1.0
October 2010 <1.0
4"" Quarter, 2010 <1.0
December 2010 <1.0
Although, the Executive Secretary has previously approved DUSA to retum to normal sample frequency
for parameters in wells that show a minimum of eight consecutive sample results below the GWCL, the
Executive Secretary is not in a position to do so at this time, based on the following findings:
168 North 1950 West • Salt Uke City, UT
Mailing Address: P.O. Box 144850 • Salt Lake City, UT 84114^850
Telephone [phone] • Fax (801-533^097 • T.D.D. [phone]
wYi/w.deq. utah.gov
Primed on 100% recycled paper
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PRC Findings
1. History of THF in Groundwater at the White Mesa Uranium Mill - THF has been detected in
several on-site wells and samples including: MW-1, MW-2, MW-3, MW-5, MW-11, MW-12, MW-23,
MW-24, MW-26, field blanks, and equipment rinse blanks. THF was first identified on site in 1999 at
wells MW-1, MW-3, and MW-12. THF was observed in wells MW-2 and MW-5 in 2001 and wells
MW-23, MW-24, and MW-26 in 2005. THF was first observed in well MW-11 in the 2"" quarter of
2009. THF is an anthropogenic contaminant and the results of the THF Demonstration Study
conducted in December 2007 by DUSA were found to be inconclusive after DRC review (DRC
December 12, 2007 Letter).
2. Presence of THF in Tailings Wastewater - during review of the DUSA 2009 (November 30, 2009)
and 2010 (November 19, 2010) Annual Tailings Wastewater Monitoring reports, the DRC observed
measurable THF concentrations in the wastewater impoundments at the White Mesa Mill. Samples
collected from the Tailings Cell 4A Leak Detection System (LDS) in 2009 and 2010 showed results at
140 and 158 |ag/L, respectively. These results are more than 3 times the state Ground Water Quality
Standard (GWQS), which is 46 ^g/L. The Tailings Cell 2 LDS also showed a THF resuU of 6.13 jxg/L
in the 2010 Tailings Report. THF has also been identified in other wastewater impoundments. Iri
2007, THF was observed in Cell 1 (150 ug/L), Cell 3 (150 ^ig/L), and the Cell 2 slimes drain (15
|ag/L), see November 30, 2009 Report Tab F.
3. Historic DUSA Claims on THF Source Now Suspect - previously, DUSA has claimed that the use of
PVC solvents and glues during construction of wells MW-1, MW-2, MW-3, MW-5, and MW-12 are
the source of the THF concentrations observed in those wells and that the THF concentrations are not
related to the operation of the White Mesa Uranium Mill. DUSA has also speculated that the THF
results observed in samples MW-23, MW-24, MW-26, field blanks, and equipment rinse blanks were
caused by cross contamination. However, with the THF results observed in tailings wastewaters from
the Tailings Cell 4A and Cell 2 leak detecdon systems, the claim that DUSA does not use THF in its
Mill operations appears to be without merit.
4. Groundwater Hydraulic Considerations - accelerated sampling needs to continue for THF in well
MW-11 for the following reasons:
• Average linear velocity of 134 feet/year has been calculated at well MW-11. Water within well
MW-11 travels more than 11 feet a year; therefore, even if monthly sampling continues at well
MW-11 independent groundwater samples will be collected and little or no autocorrelation will
occur.
• Well MW-11 is downgradient of Tailings Cells 2, 3, and the Nitrate/Chloride and Chloroform
plumes, currently under investigation.
Request For Information
Although, DUSA has previously claimed that THF is not used in its mill operations, concentrations of THF
were detected above the Utah GWQS (46 jxg/L) in the Tailing Cell 4A LDS in two consecutive samples.
Since Tailings Cell 4A is the current tailing cell being used by DUSA, it appears that the mill is currently
using THF in its operations. Therefore, please provide additional information as to why the THF
concentrations observed in the on-site wastewater impoundments are not caused by the milling process and
justify why the sampling frequency for THF should be reduced in well MW-11 given this new information.
Thank you for your continued cooperation. Please contact Phil Goble at [phone] with any
questions!
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UTAH WATER QUALITY BOARD
Rusty Lundbefg,
Co-Executive Secretary