DRC-2011-006588 - 0901a06880242741

Denison Mines (USA) Corp.
105017th Street, Suite 950
Denver, CO 80265
USA
Tel: [phone]
Fax:[phone]
www.denisonmines.com
June 13, 2011
VIA E-MAIL AND OVERNIGHT DELIVERY
Mr. Rusty Lundberg
Utah Department of Environmental Quality
195 North 1950 West
P.O. Box 144850
Salt Lake City, UT 84114-4850
Re: Transmittal of Plan and Time Schedule under Utah Ground Water Discharge Permit
UGW370004 Part LG.4 (d) White Mesa Mill (the "MiH")
Dear Mr. Lundberg:
This letter transmits Denison Mines (USA) Corp.'s ("Denison's") Plan and Time Schedule pursuant to State of
Utah Groundwater Discharge Permit UGW370004 (the "Permit") Part I.G.4(d) for Violations of Part I.G.2 of the
Permit. Part I.G.2 of the Permit provides that out-of-compliance ("OOC") status exists when the concentration
of a pollutant in two consecutive samples from a compliance monitoring point exceeds a groundwater
compliance limit ("GWCL").
The Executive Secretary issued the above Notice of Violation and Compliance Order on May 9, 2011, based on
's V 2"*^ and S''^ quarter the State of Utah Division of Radiation Control ("DRC") findings from review of the
2010 Groundwater Monitoring Reports. On February 14, 2011, Denison submitted a notice to the Executive
Secretary under Part I.G.1(a) of the Permit providing notice that the concentrations of specific constituents in
groundwater monitoring wells at the Mill exceeded their respective GWCL's for the 4*'^ quarter of 2010 and
indicating which of those constituents had two consecutive exceedances during that quarter. On May 13,
2011, Denison submitted a notice to the Executive Secretary under Part I.G:1(a) of the Permit providing notice
that the concentrations of specific constituents in groundwater monitoring wells at the Mill exceeded their
respective GWCL's for the 1^^ quarter of 2011 and indicating which of those constituents had two consecutive
exceedances during that quarter. This Plan and Time Schedule addresses violations of Part I.G.2 of the
Permit for the 1'*, 2"^ 3 and 4*^ quarters of 2010 and the 1'* quarter of 2011.
Please contact me if you have any questions or require any further information.
Yours very truly,
DENISON MINES (USA) CORP.
N:\Inspections and NOVs\GW NOV May 201 l\06_13_l 1 Tmmtl GW Work Plan and Schedule.doc
Letter to Mr. Rusty Lundberg
May 4, 2011
Page 2
Jo Ann Tischler
Director, Compliance and Permitting
cc: David C. Frydenlund
Harold R. Roberts
David E. Turk
K. Weinel
Central files
DENISON
MINES
WHITE MESA MILL
State of Utah Ground Water Discharge Permit UGW370004
Plan and Time Schedule
Under Part LG.4 (d)
For
Violations of Part I.G.2 for Constituents in the First, Second, Third and Fourth Quarters of
2010 and First Quarter of 2011.
Denison Mines (USA) Corp.
1050 17* St., Suite 950
Denver, CO 80265
June 13,2011
1. INTRODUCTION
Denison Mines (USA) Corp. ("Denison") operates the White Mesa Uranium Mill (the "Mill"),
located near Blanding Utah, under State of Utah Ground Water Discharge Permit UGW370004
(the "Permit").
This is the plan and time schedule (the "Plan") required under Part I.G.4(c) of the Permit relating
to violations of Part I.G.2 ofthe Permit for the V\ 2"^ 3'^^ and 4* quarters of 2010 and the first
quarter of 2011. Part I.G.2 of the Permit provides that out-of-compliance status exists when the
concentration of a pollutant in two consecutive samples fi-om a compliance monitoring point
exceeds a ground water compliance limit ("GWCL") in Table 2 of the Permit.
The Permit was originally issued in March, 2005, at which time GWCLs were set on an interim
basis, based on fractions of State Ground Water Quality Standards or the equivalent, without
reference to natural background at the Mill site. The Permit also required that Denison prepare a
background groundwater quality report to evaluate all historic data for the purposes of
establishing background groundwater quality at the site and developing GWCLs under the
Permit.
As required by then Part I.H.3 of the Permit, DUSA submitted the following to the Co-Executive
Secretary (the "Executive Secretary") of the State of Utah Water Quality Board:
• A Revised Background Groundwater Quality Report: Existing Wells For Denison Mines
(USA) Corp. 's Mill Site, San Juan County, Utah, October 2007, prepared by INTERA,
Inc. (the "Existing Wells Background Report");
• A Revised Addendum: — Evaluation of Available Pre-Operational and Regional
Background Data, Background Groundwater Quality Report: Existing Wells For
Denison Mines (USA) Corp.'s Mill Site, San Juan County, Utah, November 16, 2007,
prepared by INTERA, Inc. (the "Regional Background Report"); and
• A Revised Addendum: — Background Groundwater Quality Report: New Wells For
Denison Mines (USA) Corp. 's Mill Site, San Juan County, Utah, April 30, 2008, prepared
by INTERA, Inc. (the "New Wells Background Report, and together with the Existing
Wells Background Report and the Regional Background Report, the "Background
Reports").
Based on a review of the Background Reports and other information and analyses the Executive
Secretary re-opened the Permit and modified the GWCLs to be equal to the mean concentration
of background for each constituent on an intrawell basis plus two standard deviations or the
equivalent. The modified GWCLs became effective on January 20, 2010.
The Executive Secretary issued a Notice of Violation and Compliance Order, Docket No.
UGWll-02 (the "Notice"), dated May 9, 2011, based on the State of Utah Department of
Environmental Quality ("UDEQ"), Division of Radiafion Control ("DRC") findings from the
review of the Mill's 1^\ 2"'* and 3"^^ quarter 2010 Groundwater Monitoring Reports. The Notice
cited five violations of the Permit, including a violation under Utah Water Quality Act (UC 19-5-
107) and Parts I.C.I of the Permit for failing to protect the waters of the state in that six
contaminants have exceeded their respective GWCLs in Table 2 of the Permit for two
consecutive sampling events.
Section E.4 of the Notice orders Denison to prepare and submit within 30 calendar days of
receipt ofthe Notice, a written plan and time schedule, for Executive Secretary approval, to fiiUy
comply with the requirements of Part I.G.4(c) of the Permit, including, but not limited to:
(i) submittal of a written assessment of the source(s) of the six contaminants and multiple
wells listed in Table 3 of the Notice, including: Cadmium, Manganese, Selenium,
Thallium, Uranium , and Total Dissolved Solids ("TDS");
(ii) submittal of a written evaluation of the extent and potential dispersion of said
groundwater contamination; and
(iii) submittal of a written evaluation of any and all potential remedial actions to restore and
maintain ground water quality at the facility, for the point of compliance wells and
contaminants in question, to ensure that: 1) shallow groundwater quality at the facility
will be restored and 2) the contaminant concentrations in said point of compliance wells
will be returned to and maintained in compliance with their respective GWCLs.
On February 14, 2011 Denison submitted a notice (the "4* Quarter 2010 Exceedance Notice") to
the Executive Secretary under Part I.G.I (a) of the Permit providing notice that the
concentrations of specific constituents in the monitoring wells at the Mill exceeded their
respective GWCLs for the 4* quarter of 2010 and indicating which of those constituents had two
consecutive exceedances during that quarter
On May 13, 2011 Denison submitted a notice (the "1st Quarter 2011 Exceedance Notice") to the
Executive Secretary under Part I.G. 1 (a) of the Permit providing notice that the concentrations of
specific constituents in the monitoring wells at the Mill exceeded their respective GWCLs for the
1^* quarter of 2011 and indicating which of those constituents had two consecutive exceedances
during that quarter. Some constituents had two consecutive exceedances during the 1^^ quarter of
2011 that had not already been properly identified as having had two consecutive exceedances in
the 1^ 2"^* or 3''* quarters of 2010, as identified in the Notice, or in the 4* quarter of 2010, as
identified in the 4* Quarter 2010 Exceedance Notice.
Although not subject to the Notice, this Plan also covers the constituents in violation of Part
I.G.2 ofthe Permit that were identified as being in violation in the 4* Quarter 2010 Exceedance
Notice and/or the 1^^ Quarter 2011 Exceedance Notice.
2. CONSTITUENTS AND WELLS SUBJECT TO THIS PLAN
The following constituents and wells have been identified in the Notice, the 4* Quarter 2010
Exceedance Notice and/or the 1^^ Quarter 2011 Exceedance Notice as being in out-of-compliance
status under Part I.G.2 of the Permit^
Table 1
Constituents and Wells Subject to this Plan
Constituent Monitoring Event POC WeU GWCL Result
Cadmium
2"^ Qtr, 2010(5/6/2010)
3'''Qtr 2010 (9/21/2010)
4'''Qtr 2010 (11/17/2010)
Qtr 2011 (2/10/2011)
MW-24 2.5 \ig/L 4.28 ug/L
5.06 \ig/L
3.22 ug/L
2.78 |ig/L
Manganese
1''Qtr 2010 (2/10/2010)
Qtr 2010 (4/28/2010)
October 2010 (10/20/2010)
4'^ Qtr 2010 (11/11/2010)
December 2010 (12/15/2010)
MW-11 131 \ig/L 134 [ig/L
137 \ig/L
141 )Lig/L
133 \ig/L
158 [ig/L
Selenium
2"^" Qtr 2010 (4/27/2010)
3"* Qtr 2010 (9/20/2010)
4'^ Qtr 2010 (11/19/2010)
1'' Qtr 2011 (2/15/2011)
MW-12 25 \ig/L 25.7 \ig/L
31.9 \ig/L
27.6 \ig/L
39 \ig/L
Selenium
2"^* Qtr 2010 (4/27/2010)
August 2010(8/24/2010)
January 2011 (1/10/2011)
Qtr 2011 (2/1/2011)
MW-30 34 lig/L 35.3 lig/L**
35.6 [ig/L**
36.2 lig/L
34.7 lig/L
Selenium
4'^ Qtr 2010 (11/19/2010)
V' Qtr 2011 (2/15/2011)
MW-3 37 lig/L 38.8 lig/L
40.5 lig/L
Selenium
4'*^ Qtr 2010 (11/22/2010)
Qtr 2011 (2/16/2011)
MW-3A 89 [ig/L 94.8 lig/L
99 lig/L
Thallium
January 2010(1/27/2010)*
March 2010 (3/22/2010)*
2"^^ Qtr 2010 (5/4/2010)
3'"^ Qtr 2010 (9/15/2010)
4''' Qtr 2010(11/18/2010)
1''Qtr 2011 (2/15/2011)
MW-18 1.95 \ig/L 3.32 lig/L*
3.91 lig/L*
3.73 lig/L
3.64 lig/L
3.57 lig/L
3.49 lig/L Thallium
2"^* Qtr 2010 (5/6/2010)
3''^ Qtr 2010(9/21/2010)
4* Qtr 2010 (11/17/2010)
1''Qtr 2011 (2/10/2011)
MW-24 1.0 ug/L 1.3 lig/L
1.57 lig/L
1.09 lig/L
1.42 lig/L
Uranium 1''Qtr 2010 (2/2/2010) MW-26 41.8 ug/L 58.7 lig/L
' Table 1 includes the results mdicated on the Notice for the constituents in question plus any additional consecutive
exceedances generated from the 4*^ quarter 2010 and/or the 1^ quarter 2011 results. It does not include every
exceedance of the GWCLs for those periods.
T'' Qtr 2010 (4/22/2010) 66.7 ug/L
4*'' Qtr 2010 (11/11/2010)
1'' Qtr 2011 (2/14/2011)
MW-5 7.5 ^ig/L 11.6 \igjL
29.5 ^ig/L
TDS
1'' Qtr 2010 (3/15/2010)*
2"^* Qtr 2010 (5/3/2010)
4'^ Qtr 2010 (11/12/2010)
Qtr 2011 (2/9/2011)
MW-27 1,075 mg/L 1,080 mg/L*
1,160 mg/L
1,110 mg/L
1,090 mg/L
Sulfate
4"" Qtr 2010 (11/9/2010)
1''Qtr 2011 (2/1/2011)
MW-31 532 mg/L 539 mg/L
538 mg/L Sulfate 4*'' Qtr 2010 (11/22/2010)
Qtr 2011 (2/16/2011)
MW-3A 3,640 mg/L 3,850 mg/L
3,730 mg/L
Fluoride 4'^ Qtr 2010 (11/19/2010)
1'' Qtr 2011 (2/15/2011)
MW-3 0.68 mg/L 0.77 mg/L
0.69 mg/L
* Samples that were not required to be taken under the Permit and hence were incorrectly relied upon in the
Notice to determine compliance status under Part I.G.2 of the Permit. However, for all of those constituents
and wells, consecutive exceedances in subsequent quarters have resulted in the need to include those
constituents and wells in this Plan.
** The Notice incorrectly states these as two consecutive exceedances. However, there was an intervening
sample result taken in July 2010 of 33.5 ^ig/L that was less than the GWCL. Therefore, the indicated sample
results were incorrectly relied upon in the Notice to determine compliance status under Part I.G.2 of the
Permit. However, consecutive exceedances in subsequent quarters have resulted in the need to include
selenium in MW-30 in this Plan.
It should be noted that the Notice, the 4^^ Quarter 2010 Exceedance Notice and 1'^ Quarter 2011
Exceedance Notice identify a number of wells with consecutive exceedances of Nitrate + Nitrite
and/or Chloride (MW-26, MW-27, MW-28, MW-30 and MW-31), Chloroform and
Dichloromethane (MW-26), and pH (less than the respective GWCLs for pH in a number of
wells). However, none of those constituents are included in this Plan, for the reasons stated in
the Notice. That is. Chloroform and Dichloromethane are associated with the Chloroform
Plume, and the August 23, 1999 DRC Notice of Violation and Groundwater Corrective action
Order. Nitrate + Nitrite and Chloride are associated with the Nitrate/Chloride plume, and are
currently being investigated by Denison pursuant to a January 28, 2009 Stipulated Consent
Agreement. With respect to pH, Denison notified DRC in a letter dated February 1, 2011 that
explained the existing GWCLs for groundwater pH are in error due to reliance on historical
laboratory values instead of field measurements, and proposed a plan to submit revised
descriptive statistics for Field pH to be used as revised GWCLs.
The following observations can be made from Table 1:
• Consecutive exceedances have been observed for Manganese in MW-11, Thallium in
MW-18, Selenium in MW-30 and TDS in MW-27 in the 4^'' Quarter 2010 and/or the 1'^
Quarter 2011. This justifies inclusion of these constituents on Table 1, but at later dates
than indicated by DRC in the Notice, based on later data than the data used by DRC, as
discussed in Denison's June 13, 2011 response to the Notice; and
• The following new constituents and wells have demonstrated consecutive exceedances,
based on the 4^^ Quarter 2010 and/or the 1^^ Quarter 2011 results: Selenium in MW-3 and
MW-3 A, Uranium in MW-5, Sulfate in MW-3 and MW-31 and Fluoride in MW-3.
3. CATEGORIES FOR ANALYSIS
The constituents and wells listed in Table 1 can be separated into a number of different
categories, as follows:
3.1. Constituents in Wells With Previously Identified Rising Trends
The following constituents were identified in the Background Reports as having statistically
significant rising trends, due to natural background infiuences:
Table 2
Constituents with Previously Identified Rising Trends
Constituent WeU Reference
Manganese MW-11 Table 16, Existing Wells
Background Report
Selenium
MW-12 Table 16, Existing Wells
Background Report Selenium MW-3 Table 16, Existing Wells
Background Report
Thallium MW-18 Table 16, Existing Wells
Background Report
Uranium MW-26 Table 16, Existing Wells
Background Report
It is worth noting that, although a rising trend in sulfate has not been previously identified in
MW-3A, a rising trend in Sulfate has previously been identified in MW-3, which is right beside
MW-3A.
3.2. Constituents in Pumping Wells
Of the constituents listed in Table 1 above. Uranium in MW-26 is the only constituent in a
pumping well.
3.3. Constituents Potentiallv Impacted bv Decreasing pH Trends Across the Site
Denison has observed a decreasing trend in pH in a number of monitoring wells across the Mill
site. See the discussion in Section 2.5.6 of the New Wells Background Report, where INTERA
noted that as at the date of that report there were statistically significant decreasing trends in pH
in MW-25, MW-27, MW-28, MW-3A, MW-3, MW-12, MW-14 and MW-17. INTERA also
noted that, while not statistically significant, on a review of the pH time plots in all existing
wells, there appeared to be a general decreasing trend in pH in all wells.
The mobility in groundwater of the following constituents is sensitive to decreases in pH:
Table 3
Constituents Potentially Impacted by Decreasing Trends in pH
Constituent WeU
Cadmium MW-24
Manganese MW-11
Selenium
MW-12
Selenium MW-30 Selenium MW-3 Selenium
MW-3A
Thallium MW-18 Thallium MW-24
Uranium MW-5 Uranium MW-26
3.4. Other Constituents and Wells
The following constituents in Table 1 do not fall within one of the previous three categories:
Table 4
Other Constituents
Constituent Well
TDS MW-27
Sulfate MW-3A Sulfate MW-31
Fluoride MW-3
4. PLAN
4.1. General
This Plan is a plan and time schedule for assessment of the sources, extent and potential
dispersion of the contamination, and an evaluation of potential remedial action to restore and
maintain groundwater quality to ensure that Permit limits will not be exceeded at the compliance
monitoring point and that, to the extent applicable, discharge minimization technology and best
available technology will be reestablished.
Given the recent analyses in the Background Reports and other recent information relating to the
Chloroform and Nitrate/Chloride investigations at the site, Denison believes that all of the
exceedances are likely due to background influences (including a natural decreasing trend in pH
across the site, rising water levels in some wells and other factors), disruption of the aquifer by
pumping and/or the geochemical influences of the existing chloroform and nitrate/chloride
plumes.
Therefore, the first step in the analysis will be to perform an assessment of the potential sources
for each exceedance to determine whether the exceedance is due to background influences or
Mill activities. If an exceedance is determined to be due to background influences then it will
not be necessary to perform any fiirther evaluations on the extent and potential dispersion ofthe
contamination or to perform an evaluation of potential remedial actions. Monitoring will
continue, and where appropriate revised GWCLs will be proposed to reflect changes in
background conditions at the site.
However, if any of the exceedances are determined to be caused by Mill activities, then Denison
will proceed to the next step and will consider the extent and potential dispersion of the
contamination, and will perform an evaluation of potential remedial actions to restore and
maintain groundwater quality to insure that Permit limits will not be exceeded at the compliance
monitoring point.
This two-step approach is necessary, because, in light of the varied background conditions at the
site and previously identified background trends, it can't be assumed that consecutive
exceedances of a constituent in a well represents contamination that has been introduced to the
groundwater. It is first necessary to establish whether or not the exceedances represent
background influences.
4.2. Assessment for each Category
The approach and scope of review for each of the different categories described above, is
described in more detail below.
4.2.1. Constituents With Pre-Existing Rising Trends
It was well known at the time of setting the current GWCLs that certain constituents had rising
trends. On page 3 of the Existing Well Background Report, INTERA concluded:
"There are numerous cases of both increasing and decreasing trends in
constituents in upgradient, far downgradient, and Mill site wells, which provide
evidence that there are natural forces at work that are impacting groundwater
quality across the entire site.
In almost all cases where there are increasing trends in constituents in wells at the
site, there are increasing trends in those constituents in upgradent wells.
Furthermore, and more importantly, in no case is there any evidence in the wells
in question of increasing trends in chloride, which is considered the most mobile
and best indicator of potential tailings cell leakage at the site. We consider the
combination of these factors to be conclusive evidence that all increasing trends at
the site are caused by natural forces and not by Mill activities".
The Groundwater Data Preparation and Statistical Process Flow for Calculating Groundwater
Protection Standards, White Mesa Mill Site, San Juan County, Utah, which was approved by the
Executive Secretary, included as Figure 19 to the Existing Wells Background Report, states in
the final decision box, for circumstances where the data indicated an increasing trend (decreasing
in the case of pH), the following:
"Consider modified Approach to GWCL
(Use Post Second Quarter 2005 Data only?)
(Re-evaluate on Renewal?)"
The rising trends in each of the constituents listed in Table 2 above were analyzed by INTERA
in Section 11 of the Existing Wells Background Report. Additional analysis relating to rising
uranium trends in various wells at the site, which includes a discussion on possible causes of the
trends, is found in Section 12 of the Existing Wells Background Report.
Further, a study entitled Summary of Work Completed, Data Results, Interpretations and
Recommendations For the July 2007 Sampling Event at the Denison Mines, USA, White Mesa
Uranium Mill Near Blanding, Utah was prepared by T. Grant Hurst and D. Kip Solomon,
Department of Geology and Geophysics, University of Utah, May 2008 (the "University of Utah
Study").
On pages (ii) and (iii) of the Executive Summary to the University of Utah Study, Hurst and
Solomon note that:
"Increasing and elevated trace metal concentrations in monitoring wells at a
uranium processing facility near Blanding, UT, may indicate leakage from tailings
cells is occurring. To investigate this potential problem, a groundwater study was
done to characterize groundwater fiow, chemical composition, noble gas
composition, and age.
"The data show that groundwater at the Mill is largely older than 50 years, based
on apparent recharge dates from chlorofluorocarbons and tritium concentrations.
Wells exhibiting groundwater that has recharged within the last 50 years appears
to be a result of recharge from wildlife ponds near the site. Stable isotope
fingerprints do not suggest contamination of groundwater by tailings cell leakage,
evidence that is corroborated by trace metal concentrations similar to historically-
observed concentrations."
Included in the University of Utah Study sampling and analysis were the following wells listed
inTablel above: MW-3, MW-3 A, MW-5, MW-11, MW-18, MW-27, MW-30 and MW-31.
It has been established, then, that continued rising trends in the wells listed in Table 2 above are
not inconsistent with natural background, and in fact were accepted as natural background for
purposes of setting the revised GWCLs in January 2010. The primary focus of the source
assessment for the wells listed in Table 2 above will therefore be to determine whether or not
there is any new information that would suggest that the previous analysis conducted in the
Existing Wells Background Report has changed since the date of that Report. This analysis will
include the following for each constituent listed in Table 2:
(i) A geochemical analysis that will evaluate the behavior of all of the constituents in the
well in question to determine if there are any changes in the behavior of indicator
constituents, such as Chloride, Sulfate, Fluoride and Uranium since the date of the
Existing Wells Background Report that may suggest a change in the behavior of that
well since the date of that Report;
(ii) A mass balance analysis that will evaluate the observed concentrations of the
constituent in light of the concentrations in Mill tailings and the presence or absence of
any mounding at the location of the well in question; and
(iii) In cases where the wells in question are distant from the Mill's tailings cells, a
hydrogeologic analysis will be performed to determine the plausibility of impact from
Mill tailings.
The foregoing analysis will be included in a report (the "Source Assessment Report") to be
prepared by an independent engineering consultant.
If no significant changes are identified that would suggest that the previous analysis conducted in
the Background Reports for the constituents in question has changed, then Denison will propose
changes to the GWCLs for those wells to better reflect background concentrations at the site.
If significant changes are identified that cannot be attributed to background influences, then
Denison will propose to the Executive Secretary further analysis that may be required in order to
identify the source and the extent and potential dispersion of the contamination, as well as
potential remedial actions.
The United States Environmental Protection Agency ("EPA") has recognized the need to update
compliance limits periodically to reflect changes to background conditions.
In 2009 guidance, EPA states:
"We recommend that other reviews of background also take place periodically.
These include the following situations:
• When periodically updating background, say every 1-2 years
• When performing a 5-10 year permit review
During these reviews, all observations designated as background should be evaluated
to ensure that they still adequately reflect current natural or baseline groundwater
conditions. In particular, the background samples should be investigated for
apparent trends or outliers. Statistical outliers may need to be removed, especially if
an error or discrepancy can be identified, so that subsequent compliance tests can be
10
improved. If trends are indicated, a change in the statistical method or approach may
be warranted."
and
"Site-wide changes in the underlying aquifer should be identifiable as similar trends
in both upgradient and compliance wells. In this case, it might be possible to remove
a common trend from both the background and compliance point wells and to
perform interwell testing on the trend residuals."
(EPA 530/R-09-007, March 2009, Statistical Analysis Of Groundwater Monitoring Data At
RCRA Facilities Unified Guidance, Environmental Protection Agency, Office Of Resource
Conservation And Recovery.)
In that Guidance, EPA further states:
"5.3.4 UPDATING WHEN TRENDS ARE APPARENT
An increasing or decreasing trend may be apparent between the existing
background and the newer set of candidate background values, either using a time
series plot or applying Chapter 17 trend analyses. Should such trend data be
added to the existing background sample? Most detection monitoring tests
assume that background is stationary over time, with no discernible trends or
seasonal variation. A mild trend will probably make very little difference,
especially if a Student-? or Wilcoxon rank-sum test between the existing and
candidate background data sets is non-significant. More severe or continuing
trends are likely to be flagged as SSIs by formal intrawell prediction limit or
control chart tests.
With interwell tests, a stronger trend in the common upgradient background may
signify a change in natural groundwater quality across the aquifer or an
incomplete characterization of the fiill range of background variation. If a change
is evident, it may be necessary to delete some of the earlier background values
from the updated background sample, so as to ensure that compliance testing is
based on current groundwater conditions and not on outdated measures of
groundwater quality."
4.2.2. Constituents in Pumping Wells
MW-26 is a pumping well. In Section 7.3.1 of the Existing Wells Background Report, INTERA
concluded that:
". . . chloroform pumping wells are being manipulated and the impact on the
quality of the water in those wells from the pumping is uncertain and cannot be
predicted with enough certainty to establish compliance standards under the
GWDP. For example, pumping wells are intended to pull water in from areas of
11
the perched aquifer that would normally flow into other wells. In fact, the
pumping wells are having the effect of drawing down water levels in other wells
(see for example Figure 2 of Appendix D of the second quarter 2007 Chloroform
Monitoring report). This water may be associated with its own background
quality that will impact the water quality in the pumping well. Any increasing or
decreasing trends in constituent in chloroform pumping wells, such as MW-26,
are therefore not unexpected and should be given little, if any, weight in analyzing
potential impacts to groundwater from Mill activities. These impacts should be
subject to the chloroform NOV and not result in parallel out-of-compliance
situations under the GWDP.
For this reason, we believe that MW-26 should continue to be monitored under
the GWDP, but that DUSA should not be subject to any out of compliance
situation under the GWDP relating to MW-26."
This concern was acknowledged by the Executive Secretary in the September 2009 Statement of
Basis issued in connection with approval of the revised GWCLs. On page 23 of that document,
the Executive Secretary stated that:
"It 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-26 is included on Table 1 above because of consecutive exceedances of the GWCL for
uranium in the 1^* and 2"^^ quarters of 2010. Subsequent data show that the concentrations of
uranium in MW-26 in the sampling events in 2010 and through the first quarter of 2011 range
from 29.6 lig/L to 72.7 lig/L, with eight of the thirteen sample results being less than the GWCL
of 41.8 lig/L. The most recent result was 31.8 lig/L for the March 2011 monthly sampling event.
This erratic behavior is not unexpected for a pumping well such as MW-26, and is not
inconsistent with natural background. The primary focus of the source assessment for uranium
in MW-26 will therefore be to determine whether or not there is any new information that would
suggest that the previous analysis conducted in the Existing Wells Background Report, has
changed since the date of that Report. This analysis will include the following:
(i) A geochemical analysis that will evaluate the behavior of all of the constituents in MW-
26 to determine if there are any changes in the behavior of indicator constituents, such
as Chloride, Sulfate, Fluoride and Uranium since the date of the Existing Wells
Background Report that may suggest a change in the behavior of that well since the date
of that Report. However, it is not expected that this analysis will yield any conclusive
findings, given the dynamic nature of the well; and
(ii) A mass balance analysis that will evaluate the observed concentrations in light of the
concentrations in Mill tailings.
12
The foregoing analysis will be included in the Source Assessment Report.
If no significant changes are identified that would suggest that the previous analysis conducted in
the Background Reports for the constituents in question has changed, then Denison will continue
to pump and monitor that well. Since GWCLs for pumping wells have no meaning, for the
reasons discussed above, Denison does not intend to propose revised GWCLs for MW-26.
If significant changes are identified in the Source Assessment Report, that cannot be attributed to
the pumping itself or to background influences, then Denison will propose to the Executive
Secretary further analysis that may be required in order to identify the source and the extent and
potential dispersion of the contamination. Denison will also evaluate potential remedial actions
that may be appropriate. However, continued pumping is probably the best remedial action at
this time.
4.2.3. Constituents Potentially Impacted by Decreasing Trends in pH across the Site.
As mentioned above, Denison has observed a decreasing trend in pH in a number of monitoring
wells across the Mill site. The mobility in groundwater of a number of constituents listed in
Table 1 is sensitive to decreases in pH. Those constituents are listed in Table 3 above.
It should be noted that a number of the wells listed in Table 3 are also wells that were included in
the University of Utah Study. Those are wells MW-3, MW-3A, MW-5, MW-11, MW-18 and
MW-30. This gives further support to the possibility that increases in concentrations of these
constituents in those wells are due to natural influences, such as natural changes in pH, rather
than to Mill activities.
The primary focus of the source assessment for the wells listed in Table 3 above will be two-
fold. First, Denison will determine whether or not there is any new information that would
suggest that the previous analysis conducted in the Existing Wells Background Report has
changed since the date of that Report. This analysis will include the following for each
constituent listed in Table 3:
(i) A geochemical analysis that will evaluate the behavior of all of the constituents in the
well in question to determine if there are any changes in the behavior of indicator
constituents, such as Chloride, Sulfate, Fluoride and Uranium since the date of the
Existing Wells Background Report that may suggest a change in the behavior of that
well since the date of that Report;
(ii) A mass balance analysis that will evaluate the observed concentrations in light of the
concentrations in Mill tailings and the presence or absence of any mounding at the
location ofthe well in question; and
(iii) In cases where the well in question is distant from the Mill's tailings cells, a
hydrogeologic analysis will be performed to determine the plausibility of impact from
Mill tailings.
13
Second, a pH analysis will be performed for each constituent that will:
(iv) Review the behavior of pH in the well in question to determine if there has been a
significant decrease in pH in the well; and
(v) Analyze the expected impact from any such decrease in pH on the concentration of the
constituent in question in the well, based on currently available information.
The foregoing analyses (both steps) will be included in the Source Assessment Report.
If no significant changes are identified that would suggest that the previous analysis conducted in
the Background Reports for the constituents in question has changed, other than what would be
expected from decreasing trends in pH, then Denison will propose changes to the GWCLs for
those wells to better reflect background concentrations at the site.
If significant changes are identified that cannot be attributed to changes in pH or other natural
phenomena, then Denison will propose to the Executive Secretary fiirther analysis that may be
required in order to identify the source and the extent and potential dispersion of the
contamination, as well as potential remedial actions.
4.2.4. Other Constituents and Wells
Table 4 sets out other constituents that do not fall within the categories considered in Sections
4.2.1, 4.2.2 and 4.2.3 above. However, all of those constituents are in wells that were included in
the University of Utah Study.
The primary focus of the source assessment for the wells listed in Table 4 above will again be to
determine whether or not there is any new information that would suggest that the previous
analysis conducted in the Existing Wells Background Report has changed since the date of that
Report. This analysis will include the following for each constituent listed in Table 4:
(i) A geochemical analysis that will evaluate the behavior of all of the constituents in the
well in question to determine if there are any changes in the behavior of indicator
constituents, such as Chloride, Sulfate, Fluoride and Uranium since the date of the
Existing Wells Background Report that may suggest a change in the behavior of that
well since the date of that Report;
(ii) A mass balance analysis that will evaluate the observed concentrations in light of the
concentrations in Mill tailings and the presence or absence of any mounding at the
location of the well in question;
(iii) In cases where the well in question is distant from the Mill's tailings cells, a
hydrogeologic analysis will be performed to determine the plausibility of impact from
Mill tailings;
14
(iv) An analysis of the extent, if any, to which the constituents listed in Table 4 may be
influenced by geochemical changes caused by migrating nitrate and/or chloride or
chloroform from the existing plumes; and
(v) An analysis of the extent, if any, to which the constituents listed in Table 4 may be
influenced by changes in other constituents in ground water that have resulted from
changes in pH or any other natural phenomenon.
The foregoing analysis will be included in the Source Assessment Report.
If no significant changes are identified that would suggest that the previous analysis conducted in
the Background Reports for the constituents in question has changed, then Denison will propose
changes to the GWCLs for those wells to better reflect background concentrations at the site.
If signiflcant changes are identified that are attributable to geochemical changes caused by either
the nitrate/chloride plume or the chloroform plume, then the constituents in Table 4 should be
considered in connection with the applicable plume.
If significant changes are identified that cannot be attributed to one of the existing plumes, or
other background influences, then Denison will propose to the Executive Secretary fiirther
analysis that may be required in order to identify the source and the extent and potential
dispersion of the contamination, as well as potential remedial actions.
4.3. Experts Reports to be Prepared
The Source Assessment Report will detail the results of all of the analysis to be performed and
the conclusions to be drawn from such analyses, including any proposed revisions to existing
GWCLs. The Source Assessment Report will also identify any further studies that the analysis
indicates should be performed, and will propose, for Executive Secretary review and approval, a
plan and schedule for completion of any such additional studies.
If further analysis is required after completion of the Source Assessment Report, Denison and the
Executive Secretary will agree on the scope of that analysis, based on the findings in the Source
Assessment Report, including any further reports that will need to be prepared.
5. TIME SCHEDULE
The Source Assessment Report will be submitted to the Executive Secretary within 60 days after
approval of this Plan.
Any further studies that are identified in the Source Assessment Report or otherwise identified
by the Executive Secretary as being required in order to fulfill the requirements of Part I.G.4(c)
of the Permit or the Notice, will be prepared and submitted by Denison in accordance with a
schedule to be approved by the Executive Secretary.
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6. CONCLUSION
Background at the Mill site was recently thoroughly studied in the Background Reports and in
the University of Utah Study. Both the Background Reports and the University of Utah Study
concluded that groundwater at the site has not been impacted by Mill operations. Both of those
studies also acknowledged that there are natural influences at play that have given rise to
increasing water trends and general variability of background groundwater at the site.
Given the varied background groundwater quality at the site, previously identified rising trends
in some wells and other factors, it cannot be assumed that consecutive exceedances of a
constituent in a monitoring well means that contamination has been introduced to groundwater in
that well. The exceedances may very well be the result of background influences. The approach
in this Plan therefore is to first determine if the recent exceedances are the result of background
influences. If they are determined to be the result of background infiuences, then no remedial
actions are required. If, however, they are determined to not be the result of natural background
influences, then further analyses will be required.
In determining whether or not an exceedance is the result of background influences, it is not
practicable to redo the Background Reports and University of Utah Study each time a monitoring
well shows consecutive exceedances, particularly where the exceedance is consistent with those
recent analyses. The focus should therefore be on identifying any changes in the circumstances
identified in those studies.
Based on the information available at this time, Denison believes that the exceedances observed
are the result of natural influences and reflect the need to adjust some of the GWCLs for the site.
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SIGNATURE AND CERTIFICATION
This document was prepared by Denison Mines (USA) Corp. on June 13, 2011.
DENISON MINES (USA) CORP.
By:
Da^iid C. Frydenlund
Vice President, Regulatory Affairs and Counsel
Certification:
I certify, under penalty of law, that this document and all attachments were
prepared under my direction or supervision in accordance with a system designed to
assure that qualified personnel properly gather and evaluate the information submitted.
Based on my inquiry of the person or persons who manage the system, or those persons
directly responsible for gathering the information, the information submitted is, to the
best of my knowledge and belief, true, accurate, and complete. I am aware that there are
significant penalties for submitting false information, including the possibility of fine and
imprisonrahint fo/faiowing violations.
David/K. Ffydinlund
Vice president. Regulatory Affairs and Counsel
Denison Mines (USA) Corp.