DRC-2010-005965 - 0901a068801dc582

.DRC- 2010-005965
DENISON
MINES
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Denison Mines (USA) Corp.
1050 17th Street, Suite 950
Denver, CO 80265
USA
Tel: [phone]
Fax : [phone]
www.denisonmines.com
November 12,2010
VIA PDF AND FEDERAL EXPRESS
Rusty Lundberg,
Co-Executive Secretary
Utah Water Quality Board
Utah Department of Environmental Quality
195 North 1950 West
P.O. Box 144850
Sah Lake City, UT 84114-4850
Re: State of Utah Ground Water Discharge Permit No. UGW370004
White Mesa Uranium Mill - Notice Pursuant to Part LG.l (a)
Dear Mr. Lundberg:
The White Mesa Mill (the "Mill") performed third quarter ("Q3") groundwater monitoring
during the period from July 20, to September 27, 2010 under the June 17, 2010 version of the
Mill's Groundwater Discharge Permit (the "GWDP"). All analytical data needed for comparison
to the GWCLs was received during the period ending October 15, 2010.
Pursuant to Part I.G.l.a) of the GWDP, please take notice that the concentrations of specific
constituents in the monitoring wells highlighted in yellow and bold italics in the columns for the
third quarter in the attached Table 1, exceeded their respective GWCLs. For ease of review,
Table 1 has been formatted to simplify the tracking of any continued exceedances from one
monitoring period to the next by charting ongoing monitoring of the same well in the same row,
and by highlighting exceedances (in color and bold italics).
Under the June 17, 2010 revisions ofthe GWDP, GWCLs have been determined on a well-by-
well basis to reflect background groundwater quality, as defined by the mean plus second
standard deviation concentration, or the equivalent. Accordingly, the GWDP requires that
constituent concentrations in each monitoring well shall not exceed the GWCLs set out in Table
2 of the GWDP. It should be noted that, because the GWCLs have been set at the mean plus
second standard deviation, or the equivalent, un-impacted groundwater would normally be
expected to exceed the GWCLs approximately 2.5% of the time. Therefore, exceedances are
expected in approximately 2.5% of all sample results, and do not necessarily represent impacts to
groundwater from Mill operations.
N:\Notices\GW Exceedence noticesM 1.15.10 Notice\Notice_of_Exceedance_GW_Q3_l 1.2010 rev B.docx
The following are items of note relevant to all exceedance data presented herein:
1. Nitrate + nitrite and chloride in monitoring wells at the site are the subject of an ongoing
investigation. In the December 30, 2009 Nitrate Contamination Investigation Report,
prepared by Intera, Inc., Intera has concluded that the elevated nitrate + nitrite and
chloride concentrations observed at the Mill resulted from sources unrelated to the Mill's
operations. Denison is in the process of proposing additional investigations to confirm the
source(s) of these constituents.
2. As discussed in previous quarterly groundwater sampling reports, the background levels
and GWCLs for pH were established based on eight or more quarters of laboratory data,
which are historically higher than field data due to effects from the evolution of carbon
dioxide, and subsequent increase in pH from field to lab. Denison will submit to Utah
Department of Environmental Quality (UDEQ) under separate cover, proposed revised
GWCLs for pH. The proposed revised GWCLs based on a statistical analysis of actual
field data, is expected to result in somewhat lower GWCLs for pH in most wells.
Required Quarterly Sampling Wells
As indicated in the attached Table 1, the analytes discussed below exceeded their respective
GWCLs for two successive sampling periods during the third quarter.
MW-14
Field pH has been slightly outside (slightly lower than) the GWCL in MW-14 for both
the Ql and Q2 sampling events but retumed to within the GWCL range for the May and
June monthly sampling periods. The measured field pH for MW-14 was slightly outside
the GWCL in the July, August and Q3 (September) sampling events.
MW-26
• Uranium in MW-26 has exceeded the GWCL in both the Ql and Q2 monitoring periods
but retumed to below the GWCL for the May, June, and July monthly monitoring
periods. Uranium in MW-26 has exceeded the GWCL in the August monthly sampling
event and the Q3 sampling event in September 2010.
• Chloroform in MW-26 has exceeded its GWCL for all of the monitoring periods for
2010. MW-26 is used as a pumping well for the ongoing chloroform capture program
and is expected to yield increased concentrations of chloroform.
N:\Notices\GW Exceedence noticesM 1.15.10 Notice\Notice_of_Exceedance_GW_Q3_11.2010 rev B.docx
• Chloride in MW-26 exceeded its GWCL in the Ql and Q3 quarterly and the May
monthly sampling events.
• Methylene chloride exceeded its GWCL in the Q2 sampling event. Monthly sampling
was scheduled as required and began in July 2010. Data were inadvertently reported by
the analytical laboratory for methylene chloride during the June monthly event. These
data are included for additional information. As shown, methylene chloride exceeded its
GWCL during the July, August and Q3 sampling events.
MW-26 Note: As stated in the September 2009 Statement of Basis (page 23) in support of the
January 20, 2010 revisions to the GWDP, "[i]t should be noted that, because MW-26 is a
pumping well for chloroform removal, concentrations of all constituents in that well are subject
to potential variation over time as a result of the pumping activity. This will be taken into
account by the Executive Secretary in determining compliance for this well."
MW-30
• Nitrate + nitrite concentrations exceeded its GWCL in all sampling events during the
third quarter 2010.
MW-31
• Nitrate + nitrite concentrations exceeded its GWCL in all sampling events during the
third quarter 2010.
New Exceedances Reported in 03
• Uranium in MW-25 exceeded the GWCL in the Q3 sampling event in September 2010.
• TDS in MW-26 exceeded its GWCL in the Q3 sampling event in September 2010.
• TDS in MW-31 exceeded its GWCL in the Q3 sampling event in September 2010.
Semiannual Sampling Wells Accelerated to Quarterly
As indicated in the attached Table 1, the analytes discussed below exceeded their respective
GWCLs for two successive sampling periods (Q2 and Q3).
MW-3
• Field pH has been slightly outside (slightly lower than) the GWCL for both the Q2
sampling event and the Q3 sampling event.
MW-3A
• Field pH has been slightly outside (slightly lower than) the GWCL for both the Q2
sampling event and the Q3 sampling event.
MW-12
• Selenium has exceeded the GWCL for both the Q2 sampling event and the Q3 sampling
event.
MW-18
N:\Notices\GW Exceedence noticesM 1.15.10 Notice\Notice_of_Exceedance_GW_Q3_l 1.2010_rev B.docx
• Thallium has exceeded the GWCL for both the Q2 sampling event and the Q3 sampling
event.
MW-19
• Field pH has been slightly outside (slightly lower than) the GWCL for both the Q2
sampling event and the Q3 sampling event.
MW-23
• Field pH has been slightly outside (slightly lower than) the GWCL for both the Q2
sampling event and the Q3 sampling event.
MW-24
• Field pH has been slightly outside (slightly lower than) the GWCL for both the Q2
sampling event and the Q3 sampling event.
• Thallium has exceeded the GWCL for both the Q2 sampling event and the Q3 sampling
event.
• Cadmium has exceeded the GWCL for both the Q2 sampling event and the Q3 sampling
event.
MW-27
• Nitrate + Nitrite have exceeded the GWCL for both the Q2 sampling event and the Q3
sampling event.
• Chloride has exceeded the GWCL for both the Q2 sampling event and the Q3 sampling
event.
MW-28
• Field pH has been slightly outside (slightly lower than) the GWCL for both the Q2
sampling event and the Q3 sampling event.
• Chloride has exceeded the GWCL for both the Q2 sampling event and the Q3 sampling
event.
MW-32
• Field pH has been slightly outside (slightly lower than) the GWCL for both the Q2
sampling event and the Q3 sampling event.
If you have any questions or require any further information, please contact the undersigned.
Yours truly.
Jo Ann Tischler
Director, Compliance and Permitting
cc: David C. Frydenlund
Ron Hochstein
Harold Roberts
David Turk
N:\Notices\GW Exceedence noticesM 1.15.10 Notice\Notice_of_Exceedance_GW_Q3J 1.2010_rev B.docx
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