DRC-2010-004083 - 0901a068801ac8a3

DENISO
MINES
DRC 2010-004083
Oanison Minas (USA) Corp.
1050 17th Street, Suits 9S0
Denver, CO 8026S
USA
Tel: [phone]
Fax:303 38«M12S
www.(ienisonmines.com
July 23,2010
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
Salt 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 second quarter ("Q2") groundwater monitoring
during the period fi-om April 20 to June 15, 2010 under the January 20, 2010 version of the
Mill's Groundwater Discharge Permit (the "GWDP"). The Utah Department of Environmental
Quality approved a revision to the GWDP effective June 17, 2010. The revision contained no
changes to Table 2 Groundwater Compliance Limits ("GWCLs") or to the notice provisions set
out in Part l.G.l(a). All groundwater sampling for Q2 2010 was completed prior to June 17,
2010. All analytical data needed for comparison to the GWCLs was received during the period
ending June 24, 2010.
Pursuant to Part l.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
second 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 highlighfing exceedances (in color and bold italics).
Under the January 20, 2010 and June 17, 2010 revisions of the 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 ofthe GWDP.'
As indicated in the attached Table 1, the analytes discussed below exceeded their respective
GWCLs for two successive sampling periods.
• Manganese in MW-11 slightly exceeded its GWCL during both the Ql and Q2, 2010
sampling events. However, this analyte has dropped below the GWCL for the
subsequent May and June, 2010 monthly monitoring periods.
• Field pH has been slightly outside (slightly lower than) the GWCL in MW-14 for both
the Ql and Q2 sampling events. 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 fi-om the evolution of carbon dioxide, and subsequent increase in pH from field
to lab. Denison intends to propose revised GWCLs for pH in the near future, based on a
statistical analysis of actual field data, which is expected to result in somewhat lower
GWCLs for pH in most wells. Although monitored results of field pH fi-om MW-14 were
slightly lower than the GWCL for the Ql and Q2 quarterly monitoring periods, they
retumed to within the GWCL range for the May and June monthly sampling periods.
• Nitrate + nitrite and uranium in MW-26 have exceeded their respective GWCLs in both
the Ql and Q2 monitoring periods but have retumed to within their respecfive GWCLs
for both the May and June monthly monitoring periods. Chloroform in MW-26 has
exceeded its GWCL for the Ql and Q2 quarterly as well as the May and June monthly
monitoring periods. MW-26 is used as a pumping well for the ongoing chloroform
capture program and is expected to yield increased concentrations of chloroform. Also,
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 fime as a result of the pumping activity. This will be
taken into account by the executive Secretary in determining compliance for this well."
• Nitrate + nitrite and chloride in MW-30 and MW-31 and other 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
' It should be noted, however, 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%
ofthe time. Therefore, exceedances are expected in approximately 2.5% of all sample results, and do not
necessarily represent impacts to groundwater from Mill operations.
DENISO
MINES
the elevated nitrate + nitrite and chloride concentrations observed at the Mill resulted
fi-om historic off-site sources unrelated to the Mill's operafions.
If you have any questions or require any further information, please contact the undersigned.
Yours tmly,
^Jo Ann Tischler
Director, Compliance and Permitting
cc: David C. Frydenlund
Ron Hochstein
Harold Roberts
David Turk
DENISO
MINES
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